Abstract:
The present invention relates to a craniotomy fixation device and method for fixing a bone flap to the skull following craniotomoy. The device may comprise two portions, one portion may be associated with the skull and the other portion may be associated with the bone flap. The two portions are connected in a way to accommodate changes in intracranial pressure.

Description:
[0001]    This application is a continuation of patent application Ser. No. 14/269,242, filed on May 5, 2014, which is a continuation of patent application Ser. No. 12/655,280, filed on Dec. 28, 2009, and claims priority thereof. 
     
    
     BACKGROUND 
       [0002]    Neurosurgery routinely involves performing craniotomies for exposure of the brain and intracranial contents for various intracranial pathologies including tumors, head injuries, vascular malformations, aneurysms, infections, hemorrhages, strokes, and brain swelling. A craniotomy involves creation of burr holes and removal of a portion of the skull (bone flap) with subsequent approximation of the bone flap for closure. Several methods and fixation devices are available for re-attaching the bone flap to the skull including small metallic or absorbable plates with screws or wires as demonstrated in U.S. Pat. No. 5,578,036 to Stone et al., U.S. Pat. No. 5,916,200 to Eppley et al, and U.S. Pat. No. 5,916,217 to Manthrop et al. Another method has been the use of cranial clamps consisting of two connected circular elements placed on the inside and outside surfaces of the skull. Various descriptions of cranial clamps in the art include U.S. Pat. No. 5,707,373 to Sevrain, U.S. Pat. No. 5,800,436 to Lerch, U.S. Pat. No. 6,485,493 to Bremer, U.S. Pat. No. 6,379,363 to Herrington et al., U.S. Pat. No. 6,755,834 to Amis, U.S. Pat. No. 7,048,737 to Wellisz et al., U.S. Pat. No. 7,361,178 to Hearn et al., U.S. Pat. No. 7,387,633 to Ahmad et al., and U.S. Pat. No. 6,685,707 to Roman et al. 
         [0003]    All of the aforementioned cranial fixation devices in the prior art provide for a rigid fixation of the bone flap to the skull. In cases of post-operative intracranial hemorrhage and/or brain swelling development, a decompressive craniectomy is performed. Decompressive craniectomy is a neurosurgical procedure used to treat increased intracranial pressure (ICP) from head injury, stroke, brain tumor, infection, cerebral hemorrhage, and space occupying lesions. The technique involves removal of the skull and opening of the dura mater covering the brain, thereby allowing the swollen brain to herniate outwards through the surgical skull defect rather than downwards to compress the brainstem. The procedure improves outcomes by lowering ICP, the pressure within the skull. Increased ICP is very often 
         [0000]    debilitating or fatal because it causes compression of the brain and restricts cerebral blood flow. The aim of decompressive craniectomy is to reduce this pressure. The larger the removed bone-flap is, the more ICP is reduced. Following removal of the bone flap, the dural opening is closed with a patch graft taken from a cow, pig, cadaver, or a synthetic graft. The preferred method is a synthetic collagen matrix since it is capable of expanding. In addition to reducing ICP, studies have found decompressive craniectomy to improve cerebral perfusion pressure and cerebral blood flow in head injured patients. Decompressive craniectomy is used to treat major strokes associated with malignant brain swelling and increased ICP. It is well known that a decompressive craniectomy improves survival and functional outcome in patients with severe brain swelling from head injury or stroke if performed in a timely manner. There usually is an inherent time delay between diagnosing the cause of the increased intracranial pressure and performing the decompressive craniectomy. Typically, once a post-operative increase in ICP is detected, either through a clinical exam or an ICP monitoring device, medical treatment is initiated and aCT or MRI imaging is obtained to identify the underlying cause of the raised intracranial pressure. If the need for a re-operation or decompressive cranlectomy is identified, the anesthesiologist and operating room staff are notified and the surgery is subsequently undertaken. Unfortunately, at times the operating room and/or staff are at full capacity necessitating further delay until the surgery can be performed. Despite the best of attempts by the surgeon, in cases of massive brain swelling or a rapidly developing post-operative hemorrhage, the patient may end up with irreversible brainstem injury with consequent vegetative state or death. 
         [0004]    After a craniectomy, the risk of brain injury is increased because of the removed bone flap, particularly after the patient heals and becomes mobile again. There is also a very obvious cosmetic skin deformity. Therefore, special measures must be taken to protect the brain, such as a helmet or a temporary implant in the skull. Other risks include infection, cerebrospinal fluid leakage, hydrocephalus, encephalomyocele, subdural hygroma and hemorrhage. 
         [0005]    When the patient has healed sufficiently, the craniectomy skull defect is usually closed with a cranioplasty. Cranioplasty is repair of a defect in the vault of the skull. This repair can be carried out by using bone removed at earlier surgery that has been preserved or by using bone from elsewhere as a graft. The iliac bone bounding the pelvis, ribs and even a part of adjacent skull bone can be used. 
         [0006]    If possible, the original bone flap is preserved after the cranlectomy in anticipation of the cranioplasty. The bone flap is usually stored sterilely in a freezer until the patient is ready for implantation of the bone flap into the cranlectomy skull defect. Typically, this time period can last several months since it may take this long to treat the underlying cause of the Increased intracranial pressure. This extended time period not only increases the risk of brain injury but also increases the risk of Infection in the stored bone flap. Another technique of storing the removed bone flap involves placing it under the skin in the abdomen. This requires a surgical procedure to place the bone flap in the abdomen and another one to remove it, thereby also increasing the consequent risks to the patient. In cases where the bone flap cannot be replaced due to infection or any other reason, the skull defect is repaired either with a prosthetic plate or a 
         [0000]    titanium mesh and bone cement. A prosthesis obviously cannot completely replicate the original skull defect and therefore, some cosmetic deformity persists following a prosthetic cranioplasty. The prosthesis also increases the risk of infection. 
         [0007]    The risks associated with cranioplasty include infection, hemorrhage, brain injury, seizures, and death along with other risks inherent to any surgery and general anesthesia. It is also usually necessary for the patient to be in hospital for a week or so after a cranioplasty. 
         [0008]    Other cranial fixation devices in the prior art describe their use for distraction osteogenesis. U.S. Pat. No. 5,902,304 to Walker et al. describes a telescopic bone plate for use in bone lengthening by distraction osteogenesis. The bone plates are attached to osteomically separated mandible or skull sections connected by a thread screw assembly. The extent of the required distraction can be adjusted by an external screwdriver. U.S. Pat. No. 5,993,448 to Daniel J. Remmier describes a skull fixation device for treatment of craniofacial deformities that provides for relative movement of the skull segments by a percutaneously placed external wrench, U.S. Pat. No. 6,187,004 to Jeffrey A. Fearon describes a mandible or skull expansion plate. The extent of the expansion is adjusted by an externally placed device. U.S. Pat. No. 6,355,036 to Nakajima describes skull expansion plates with a hinged plate at one end and a bone adjuster at the other end comprising two plates with a shaft. The shaft has to be operated externally to adjust the distance between the bone flap and skull. 
         [0009]    The aforementioned cranial fixation devices in the prior art provide for treatment of craniofacial defects in particular craniosynostosis. They all require an external screwdriver to control the extent of the skull movement allowed and they do not describe or provide for outward or inward movement of the bone flap relative to the skull in response to a change in the intracranial pressure. These devices are also placed on the outer surface of the skull with a very high profile thereby, increasing the risk of painful scalp irritation and palpable cosmetic deformities. Chronic scalp irritation from high profile cranial fixation devices can risk erosion and exposure of the device through the skin with consequent life threatening infection. 
         [0010]    U.S. patent application Ser. No. 11/749,990 to Kathryn Ko describes a method of performing decompressive craniectomy with the bone flap attached to the skull with a hinged plate. The method describes attaching the hinged plate to one end of the bone flap and attaching the other end to a rigid plate or no plate at all. The described method also requires a re-operation to fixate the unconstrained bone flap at the rigid plate or plate free end to the skull once the brain swelling subsides. U.S. patent application Ser. No. 12/033,815 to Tucci also describes a method similar to the Ko 11fi49,990 application of attaching the bone flap to the skull with a hinged plate at one end of the bone flap and a straight plate at the other end with unconstrained bone flap movement. Tucci also describes a deformable plate which could be used instead of a hinged plate for bone flap attachment. This construct would also require a re-operation to fixate the unconstrained bone flap at the straight plate end. The hinged plate bone flap end would not be able to move outwards and therefore, allow very limited bone flap movement. Tucci also describes a two part sliding device for cranial fixation. The device is not very practical as it very significantly sticks outwards from the skull surface and has a very high profile and obvious painful cosmetic defect with overlying skin irritation and risk of erosion/infection. Due to the high protuberance, this device would also require another operation to remove it once the bone flap approximates to the skull. 
         [0011]    Considering the aforementioned complexities and risks involved in the post-operative management of critically ill patients undergoing a craniotomy, there is a need for a better technique and device which provides for cranial fixation along with immediate treatment of increased intracranial pressure and avoids the need for performing a subsequent cranioplasty. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention relates to a cranial fixation device for fixing a bone flap to the skull following a craniotomy. It also provides for constrained outward movement of the bone flap to immediately accommodate for an increase in intracranial pressure (ICP) and subsequently allowing for the bone flap to move inwards up to the skull once the ICP normalizes. 
         [0013]    In one embodiment, the cranial fixation device comprises of two heads with one head attached to the skull and the other to the bone flap. The plates are attached to the skull and bone flap with screws. The telescopic portion slidably connects the two heads and is positioned in the skull burr hole defect. The telescopic portion allows outward movement of the bone flap as well as inward movement of the bone flap up to the skull level and does not allow the bone flap to move inward inside the cranium below the skull level. 
         [0014]    An increase in ICP can result from several pathologies including traumatic injury, stroke, hypoxia, hypertension, brain tumor, aneurysm, arteriovenous malformation, infection, venous sinus thrombosis, craniosynostosis, and hydrocephalus. Traumatic injury can be either closed head injury from blunt trauma or penetrating head injury from a gunshot wound and usually results in development of brain swelling and hemorrhage comprising of subdural hemorrhage, epidural hemorrhage, subarachnoid hemorrhage, intra-ventricular hemorrhage, brain hemorrhage, and cerebral contusions. Strokes can be ischemic, hemorrhagic or a combination of both and usually result from cerebral vessel occlusion. Vessel occlusion can be from an arterial embolus from carotid or vertebral artery stenosis, atrial fibrillation, heart septal defect, heart valve abnormalities, heart or aortic aneurysm surgery, carotid or vertebral artery dissection/thrombosis, and vasculitis. Larger strokes result in the development of severe cerebral cytotoxic edema and brain swelling. Treatment of the strokes with antiplatelet therapy or anticoagulation can also lead to the development of cerebral hemorrhage in some cases, further worsening the brain swelling. Strokes can also be caused by cerebral vessel occlusion from atherosclerotic disease, vasospasm from aneurysmal or traumatic subarachnoid hemorrhage, vasculitis, and a hypercoaguable state. Cerebral venous sinus occlusion can result in significant diffuse brain swelling as well as hemorrhage. Hypertension is a frequent cause of cerebral hemorrhage particularly deep brain and intraventricular hemorrhage. Severe hypertension can also lead to diffuse brain swelling even without any hemorrhage. Hypoxia from cardiac arrest or apnea can lead to diffuse cerebral cytotoxic injury and consequent brain swelling. Ruptured cerebral aneurysms result in subarachnoid hemorrhage but not infrequently also cerebral and intraventricular hemorrhage with associated hydrocephalus which can result in significant and immediate rise in ICP. Ruptured arteriovenous malformation scan also result in cerebral and intraventricular hemorrhage. Some arteriovenous malformations like Vein of Galen aneurysm can enlarge to a significant size leading to a rise in Intracranial pressure without even rupturing. 
         [0015]    Brain tumors either metastatic or primary like gliomas and meninglomas, often cause brain swelling from vasogenic edema. Infections include brain abscess, subdural empyema, epidural abscess, and cerebritis can also lead to significant brain swelling. Seizures can lead to diffuse brain swelling from increased cerebral blood flow and metabolism. 
         [0016]    When an increase in ICP exceeds the normal range, the bone flap is pushed outwards and places the telescopic portion in an extended position. Once the ICP normalizes, the telescopic portions fall back into a retracted position. The retracted telescopic portion position approximates the two heads and thereby the bone flap and the skull. Typically two more of the cranial fixation devices would be needed to achieve this form of decompressive craniectomy. Alternatively, a cranial fixation device can be placed on one side of the bone flap and a hinge device can be placed on the other side to provide a similar but limited decompressive craniotomy. In another embodiment of the cranial fixation device, the heads are attached to the skull and bone flap with spikes or a combination of screws on one head and spikes on the other. In another embodiment of the cranial fixation device, one or both head comprise of clamps which are attached to the skull and/or bone flap. 
         [0017]    In another embodiment, the cranial fixation device telescopic portion comprises a locking mechanism that engages when the telescopic bone fastener is in a retracted position. The retracted telescopic portion position approximates the bone flap to the skull when the intracranial pressure is in the normal range. With an increase in ICP, the pressure placed on the bone flap disengages the telescopic bone fastener locking mechanism and allows outward movement of 
         [0000]    the bone flap to accommodate the increase in ICP. Subsequently, once the ICP normalizes, the bone flap retracts back to the skull level. The locking mechanism comprises of one or more collapsible balls mounted on one telescopic extension with corresponding sockets on the said second telescopic component. Other locking mechanisms include ratchet teeth, ratchet teeth and pawl mechanism, collapsible ratchet teeth, threads, hook mechanism, and ridges with notches. Several locking mechanisms are described here forth. In one embodiment of the cranial fixation device, the locking mechanism comprises a ridge in one telescopic extension with a corresponding socket or defect in the other telescopic extension. In another embodiment of the cranial fixation device, the locking mechanism comprises of ridges in the telescopic extension with notches in the other telescopic extension. In another embodiment of the cranial fixation device, the locking mechanism comprises of ratchet teeth in the telescopic extensions. In another embodiment of the cranial fixation device, the locking mechanism comprises of ratchet teeth in one telescopic extension with a pawl in the other telescopic extension. The ratchet teeth can be unidirectional or bidirectional. In another embodiment of the cranial fixation device, the locking mechanism comprises of collapsible ratchet teeth in the telescopic extension with an engaging defect or ratchet teeth in the other telescopic extension. In another embodiment of the cranial fixation device, the locking mechanism comprises a hook in one telescopic extension with a corresponding engaging hole in the other telescopic extension. 
         [0018]    Rather than providing a fixed locked position once implanted as described in all the cranial fixation devices in the prior art, the current invention allows for constrained outward movement of the bone flap relative to the skull in cases of cerebral swelling and subsequently retracts the bone flap against the skull once the swelling subsides. 
         [0019]    In the various embodiments described herein the preferred head configuration is circular or semi-circular so as to cover the burr hole or skull opening. Other plate configurations could be rectangular, square, straight, X-shaped, Y-shaped, fan shaped, or any other configuration able to connect the skull to the bone flap. Similarly, the telescopic configurations described are either cylindrical or rectangular and designed to fit into the skull defect or burr hole. Other telescopic configurations could be partially solid, tapered, V-shaped or any other configuration that fits the skull opening. The positioning of the telescopic portion in the burr hole skull defect provides for a very low profile cranial fixation with no scalp irritation or risk of skin erosion. The cranial fixation device can be made of titanium or titanium alloy for MRI imaging compatibility. They could also be made of a bio-absorbable material (polyesters, poly amino acids, polyanhydrides, polyorthoesters, polyurethanes, polycarbonates, homopolymers, copolymers of poly lactic acid and poly glycolic acid, copolyesters of e-caprolactone, trimethylene carbonate, and para-dioxanone), or allograft or xenograft bone that is absorbed by the body over time once the bone flap has fused with the skull. Alternatively, it could made of a radiolucent material (polyetheretherketone), plastic, or a combination of plastic and metal to reduce CT and MRI imaging artifact. 
         [0020]    Although the application for the cranial fixation device described in the various embodiments is for fixation of the bone flap to the skull following a craniotomy and provide for a method of decompressive cranlectomy for treatment of Increased intracranial pressure, it can also be used to cover a burr hole or skull fracture and treat congenital cranial skull defects like craniosynostosis Various embodiments and advantages of the current invention are set forth in the following detailed description and claims which will be readily apparent to one skilled in the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a perspective diagram of one embodiment of the cranial fixation device in a retracted position. 
           [0022]      FIG. 2  is a perspective diagram of the device seen in  FIG. 1  in an extended position. 
           [0023]      FIG. 3  is a perspective diagram of another embodiment of the cranial fixation device in an extended position. 
           [0024]      FIG. 4  is a schematic diagram of the cranial fixation device seen in  FIG. 1  in a retracted position attached to the skull and bone flap. 
           [0025]      FIG. 5  is a schematic diagram of the device as seen in  FIG. 2  in an extended position attached to the skull and bone flap. 
           [0026]      FIG. 6  is a cross-sectional side view of the device seen in  FIG. 3  in a retracted position. 
           [0027]      FIG. 7  is a cross-sectional side view of the device seen in  FIG. 3  in a partially extended position. 
           [0028]      FIG. 8  is a cross-sectional side view of the device seen in  FIG. 3  in a completely extended position. 
           [0029]      FIG. 9  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0030]      FIG. 10  is a perspective diagram of the device seen in  FIG. 9  in an extended position. 
           [0031]      FIG. 11  is a cross-sectional side view of the device seen in  FIG. 9 . 
           [0032]      FIG. 12  is a cross-sectional side view of the device seen in  FIG. 10 . 
           [0033]      FIG. 13  a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0034]      FIG. 14  is a perspective diagram of the device seen in  FIG. 13  in an extended position. 
           [0035]      FIG. 15  is a cross-sectional side view of the device seen in  FIG. 13 . 
           [0036]      FIG. 16  is a cross-sectional view of the device seen in  FIG. 14 . 
           [0037]      FIG. 17  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0038]      FIG. 18  is a perspective diagram of the device seen in  FIG. 17  in an extended position. 
           [0039]      FIG. 19  is a cross-sectional view of the device seen in  FIG. 17 . 
           [0040]      FIG. 20  is a cross-sectional view of the device seen in  FIG. 18 . 
           [0041]      FIG. 21  a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0042]      FIG. 22  is a perspective diagram of the device seen in  FIG. 21  in an extended position. 
           [0043]      FIG. 23  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0044]      FIG. 24  is a cross-sectional view of the device seen in  FIG. 23  in an extended position. 
           [0045]      FIG. 25  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0046]      FIG. 26  is a cross-sectional view of the device seen in  FIG. 25  in an extended position. 
           [0047]      FIG. 27  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0048]      FIG. 28  is a cross-sectional view of the device seen in  FIG. 27  in an extended position. 
           [0049]      FIG. 29  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0050]      FIG. 30  is a cross-sectional view of the device seen in  FIG. 29  in an extended position. 
           [0051]      FIG. 31  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0052]      FIG. 32  is a cross-sectional view of the device seen in  FIG. 31  in an extended position. 
           [0053]      FIG. 33  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0054]      FIG. 34  is a cross-sectional view of the device seen in  FIG. 23  in an extended position. 
           [0055]      FIG. 35  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0056]      FIG. 36  is a cross-sectional view of the device seen in  FIG. 35  in an extended position. 
           [0057]      FIG. 37  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0058]      FIG. 38  is a perspective diagram of the device seen in  FIG. 31  in a partially extended position. 
           [0059]      FIG. 39  is a perspective diagram of the device seen in  FIG. 31  in a completely extended position. 
           [0060]      FIG. 40  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0061]      FIG. 41  is a perspective diagram of the device seen in  FIG. 40  in an extended position. 
           [0062]      FIG. 42  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0063]      FIG. 43  is a perspective diagram of the device seen in  FIG. 42  in an extended position. 
           [0064]      FIG. 44  is a schematic diagram of the cranial fixation device seen in  FIG. 42  in a retracted position attached to the skull and bone flap. 
           [0065]      FIG. 45  is a schematic diagram of the device as seen in  FIG. 43  in an extended position attached to the skull and bone flap. 
           [0066]      FIG. 46  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0067]      FIG. 47  is a perspective diagram of the device seen in  FIG. 46  in an extended position. 
           [0068]      FIG. 48  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0069]      FIG. 49  is a perspective diagram of the device seen in  FIG. 48  in an extended position. 
           [0070]      FIG. 50  is a schematic diagram of the cranial fixation device seen in  FIG. 48  in a retracted position attached to the skull and bone flap. 
           [0071]      FIG. 51  is a schematic diagram of the device as seen in  FIG. 49  in an extended position attached to the skull and bone flap. 
           [0072]      FIG. 52  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0073]      FIG. 53  is a perspective diagram of the device seen in  FIG. 52  in an extended position. 
           [0074]      FIG. 54  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0075]      FIG. 55  is a perspective diagram of the device seen in  FIG. 54  in an extended position. 
           [0076]      FIG. 56  is a schematic diagram of the cranial fixation device seen in  FIG. 54  in a retracted position attached to the skull and bone flap. 
           [0077]      FIG. 57  is a schematic diagram of the device as seen in  FIG. 55  in an extended position attached to the skull and bone flap. 
           [0078]      FIG. 58  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0079]      FIG. 59  is a perspective diagram of the device seen in  FIG. 58  in an extended position. 
           [0080]      FIG. 60  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0081]      FIG. 61  is a perspective diagram of the device seen in  FIG. 60  in an extended position. 
           [0082]      FIG. 62  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0083]      FIG. 63  is a perspective diagram of the device seen in  FIG. 62  in an extended position. 
           [0084]      FIG. 64  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0085]      FIG. 65  is a perspective diagram of the device seen in  FIG. 64  in an extended position. 
           [0086]      FIG. 66  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0087]      FIG. 67  is a perspective diagram of the device seen in  FIG. 66  in an extended position. 
           [0088]      FIG. 68  is a schematic diagram of the cranial fixation device seen in  FIG. 66  in a retracted position attached to the skull and bone flap. 
           [0089]      FIG. 69  is a schematic diagram of the device as seen in  FIG. 67  in an extended position attached to the skull and bone flap. 
           [0090]      FIG. 70  is a perspective diagram of another embodiment of the cranial fixation device in a retracted position. 
           [0091]      FIG. 71  is a perspective diagram of the device seen in  FIG. 70  in a partially extended position. 
           [0092]      FIG. 72  is a perspective diagram of the device seen in  FIG. 70  in a completely extended position. 
           [0093]      FIG. 73  is a partial schematic view of the cranial fixation device seen in  FIG. 70  attached to the bone flap and skull in a retracted position. 
           [0094]      FIG. 74  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0095]      FIG. 75  is a cross-sectional view of the device seen in  FIG. 74  in an extended position. 
           [0096]      FIG. 76  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0097]      FIG. 77  is a cross-sectional view of the device seen in  FIG. 76  in an extended position. 
           [0098]      FIG. 78  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0099]      FIG. 79  is a cross-sectional view of the device seen in  FIG. 78  in a partially extended position. 
           [0100]      FIG. 80  is a cross-sectional view of the device seen in  FIG. 78  in a completely extended position. 
           [0101]      FIG. 81  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0102]      FIG. 82  is a cross-sectional view of the device seen in  FIG. 81  in an extended position. 
           [0103]      FIG. 83  is a perspective side view of another embodiment of the cranial fixation device with a removable superior head extension. 
           [0104]      FIG. 84  is a perspective side of the device seen in  FIG. 84  with the head extension removed. 
           [0105]      FIG. 85  is a cross-sectional side view of another embodiment of the cranial fixation device in a retracted position. 
           [0106]      FIG. 86  is a cross-sectional view of the device in  FIG. 85  in an extended position. 
           [0107]      FIG. 87  is a cross-sectional view of another embodiment of the cranial fixation device in a retracted position. 
           [0108]      FIG. 88  is a cross-sectional view of the device in  FIG. 87  in an extended position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0109]    The present invention describes a method for cranial fixation following a craniotomy with the fixation device allowing for constrained movement of the bone flap to accommodate an Increase in Intracranial pressure. The cranial fixation device as shown in  FIGS. 1 and 2  comprises of a head  1  with an extension  5  and a head  2  with an extension  7 . The extensions  5  and  7  are telescopic and allow for inward or outward movement of the heads relative to each other. The medial edges of the heads  1  and  2  are sloped  6  and overlap each other when the heads are approximated, thereby not allowing the head  2  to move inward beyond the head  1 . The head  1  has holes  3  which allows placement of screws attaching the head to the outer surface of the skull. Head  2  has holes  4  through which screws can be placed for attachment of the head to the outer surface of the bone flap.  FIG. 1  shows the telescopic extensions in a compressed position whereby extension  5  is contained in the extension  7  and  FIG. 2  shows the extensions  5  and  7  in a distracted position.  FIG. 3  illustrates another embodiment of the cranial fixation device with an intermediate telescopic component  8  which allows the two heads attached to their respective bone flap and skull to move outwards further if needed to accommodate an increase in intracranial pressure. The method for cranial bone flap fixation with the device in  FIGS. 1 and 2  is illustrated in  FIGS. 4 and 5 .  FIG. 4  illustrates the cranial fixation device in place attached to the bone flap  14  with screw  10  and attached to the skull  11  with screw  9 . The brain  13  and dura  12  are shown in their normal position. Typically two or more of the cranial fixation devices would be placed to fixate the bone flap  14  to the skull  11  with the cranial fixation device telescopes in a retracted position approximating the bone flap to the skull. As shown in  FIG. 5 , with the development of brain swelling or an increase in intracranial pressure from a hemorrhage, the brain  15  pushes against the bone flap  14 . The pressure on the bone flap places the cranial fixation device telescopes  7  in an extended position thereby allowing the head  2  attached to the bone flap to move outwards relative to the head  1  attached to the skull and accommodate the brain swelling. The dural closure material is preferably a collagen matrix that allows expansion but is not necessary. The dura can be left open or other dural substitutes made from autograft, allograft, or xenograft material can also be used. Once the brain swelling subsides, the bone flap moves back in towards the skull but the overlap of the cranial fixation heads prevents the bone flap from moving inside the skull.  FIGS. 6-8  illustrate a cross-sectional view of the cranial fixation device shown in  FIG. 3 . The head  1  contains a hole  3  for a screw to be placed to secure the head to the skull and a telescopic housing compartment  5  which typically would reside in the skull opening or burr hole defect. The head  2  contains a hole  4  for a screw to be placed into the bone flap and a telescopic extension  7 . The intermediate telescopic component  8  resides between the telescopic portions  5  and  7 .  FIG. 6  shows the cranial fixation device in a retracted position.  FIG. 7  shows the device in a partially extended position. The intermediate telescopic component  8  comprises of extension  18  at one end which prevents it from pulling completely out of the housing compartment  5 . The housing compartment  5  comprises of a recess  17  at one end which engages with the extension  18  of the telescopic portion  8  in a retracted position to lock these two telescopic portions as illustrated in  FIG. 6 .  FIG. 8  illustrates the device in a completely extended position. The telescopic portion  7  comprises of extension  20  at the end which prevents it from pulling completely out of the telescopic component  8 . The telescopic component  8  also comprises of a recess  19  at one end which engages with the extension  20  of the telescopic portion  7  in a retracted position to lock these two telescopic portions as shown in  FIG. 6 . 
         [0110]    In another embodiment of the cranial fixation device as shown in  FIGS. 9-12 , the head  22  comprises an extension  25  and the head  21  comprises an extension  27 . The extensions  25  and  27  are telescopic and allow for inward or outward movement of the heads relative to each other. The medial edges of the heads  22  and  24  are sloped  29  and overlap each other when the heads are approximated, thereby not allowing the head  21  to move inward beyond the head  22 . The head  22  has holes  23  which allows placement of screws attaching the head to the skull. Head  21  has holes  23  through which screws can be placed for attachment of the head to the bone flap.  FIGS. 9 and 11  show the telescopic extensions in a compressed position whereby extension  27  is contained inside the extension  25  and  FIGS. 10 and 12  show the extensions  27  and  25  in a distracted position. The telescopic extension  25  also comprises recess  26  and  28  which engage with a ridge  30  on the telescopic extension  27 . The recess  26  engages with ridge on the telescopic extension  27  in a completely retracted position and the recess  28  engages with the ridge on the telescopic extension  27  in a completely extended position and therefore prevents the extension  27  from completely pulling out of the extension  25 . 
         [0111]    In another embodiment of the cranial fixation device as shown in  FIGS. 13-16 , the head  31  comprises an extension  35  and the head  33  comprises an extension  37 . An intermediate telescopic extension  38  connects the extensions  35  and  37 . The telescopic extensions allow for inward or outward movement of the heads relative to each other. The head  31  has holes  32  which allows placement of screws attaching the head to the skull. Head  33  has holes  34  through which screws can be placed for attachment of the head to the bone flap.  FIGS. 13 and 15  show the telescopic extensions in a compressed position whereby extensions  37  and  38  are contained inside the extension  35  and  FIGS. 14 and 16  show the extensions  37  and  38  in a distracted position. The telescopic extension  35  also comprises recesses  36  and  41  which engage with a ridge  40  on the telescopic extension  38 . The recess  36  engages with ridge  40  on the telescopic extension  35  in a completely retracted position and the recess  41  engages with the ridge  40  on the telescopic extension  38  in an extended position and prevents the extension  38  from completely pulling out of the extension  35 . The telescopic extension  38  also comprises of a recess which engages a ridge  39  on the telescopic extension  37  in an extended position as shown in  FIG. 16 . In a retracted position as seen in  FIG. 15  the ridge  39  engages with the ridge  40  and maintains the telescopes in that position. 
         [0112]    In another embodiment of the cranial fixation device as shown in  FIGS. 17-20 , the head  42  comprises an extension  44  and the head  43  comprises an extension  46 . The extensions  44  and  46  are telescopic and allow for inward or outward movement of the heads relative to each other. The head  42  has holes  47  which allows placement of screws attaching the head to the skull. Head  43  has holes  48  through which screws can be placed for attachment of the head to the bone flap.  FIGS. 17 and 19  show the telescopic extensions in a compressed position whereby extension  46  is contained inside the extension  44  and  FIGS. 18 and 20  show the extensions  46  and  44  in a distracted position. The telescopic extension  44  also comprises recesses  45  which engage with a ridge  49  on the telescopic extension  46 . 
         [0113]    In another embodiment of the cranial fixation device as shown in  FIGS. 21 and 22 , the head  51  comprises an extension  52  and the head  50  comprises an extension  55 . The extensions  52  and  55  are telescopic and allow for inward or outward movement of the heads relative to each other.  FIG. 21  shows the telescopic extensions in a compressed position whereby extension  55  is contained inside the extension  52  and  FIG. 21  shows the extensions  52  and  55  in a distracted position. The telescopic extension  52  also comprises multiple recesses  53  which engage with ridges  54  on the telescopic extension  55 . 
         [0114]    In another embodiment of the cranial fixation device as shown in  FIGS. 23 and 24 , the head  62  comprises an extension  59  and the head  56  comprises an extension  58 . The head  62  has holes  61  which allows placement of screws attaching the head to the skull. Head  56  has holes  57  through which screws can be placed for attachment of the head to the bone flap. The extensions  58  and  59  are telescopic and allow for inward or outward movement of the heads relative to each other.  FIG. 23  shows the telescopic extensions in a compressed position whereby extension  58  is contained inside the extension  59  and  FIG. 24  shows the extensions  58  and  59  in a distracted position. The telescopic extension  58  also comprises multiple ridges which engage with ridges  60  in the telescopic extension  59 . 
         [0115]    In another embodiment of the cranial fixation device as shown in  FIGS. 25 and 26 , the head  63  comprises an extension  68  and the head  64  comprises an extension  67 . The head  64  has holes  66  which allows placement of screws attaching the head to the skull. Head  63  has holes  65  through which screws can be placed for attachment of the head to the bone flap. The extensions  67  and  68  are telescopic and allow for inward or outward movement of the heads relative to each other.  FIG. 25  shows the telescopic extensions in a compressed position whereby extension  68  is contained inside the extension  67  and  FIG. 26  shows the extensions  67  and  68  in a distracted position. The telescopic extension  68  also comprises multiple ratchet teeth recesses  69  which engage with the ratchet teeth  70  in the telescopic extension  67 . 
         [0116]    In another embodiment of the cranial fixation device as shown in  FIGS. 27 and 28 , the head  71  comprises an extension  75  and the head  73  comprises an extension  76 . The head  73  has holes  74  which allows placement of screws attaching the head to the skull. Head  71  has holes  72  through which screws can be placed for attachment of the head to the bone flap. The extensions  75  and  76  are telescopic and allow for inward or outward movement of the heads relative to each other. The telescopic extension  75  also comprises sockets  78  and  79  which engage with the collapsible ball mechanism  77  in the telescopic extension  78 .  FIG. 27  shows the telescopic extensions in a compressed position with ball  77  engaged with the socket  78  and extension  75  contained inside the extension  76 .  FIG. 28  shows the extensions  75  and  76  in a distracted position with the ball  77  engaged with socket  79 . 
         [0117]    In another embodiment of the cranial fixation device as shown in  FIGS. 29 and 30 , the head  80  comprises an extension  85  and the head  83  comprises an extension  84 . The head  83  has holes  82  which allows placement of screws attaching the head to the skull. Head  80  has holes  81  through which screws can be placed for attachment of the head to the bone flap. The extensions  84  and  85  are telescopic and allow for inward or outward movement of the heads relative to each other. The telescopic extension  85  also comprises sockets  86  which engage with the ridges  87  in the telescopic extension  84 .  FIG. 29  shows the telescopic extensions in a compressed position with the ridges  87  engaged with the sockets  86  and extension  85  contained inside the extension  84 .  FIG. 30  shows the extensions  85  and  86  in a distracted position. 
         [0118]    In another embodiment of the cranial fixation device as shown in  FIGS. 31 and 32 , the head  88  comprises an extension  93  and the head  90  comprises an extension  92 . The head  90  has holes  91  which allows placement of screws attaching the head to the skull. Head  88  has holes  89  through which screws can be placed for attachment of the head to the bone flap. The extensions  92  and  93  are telescopic and allow for inward or outward movement of the heads relative to each other. The telescopic extension  93  also comprises an extension  94  at one end. The telescopic component  92  has an extension  95  at one end.  FIG. 31  shows the telescopic extensions  92  and  93  in a compressed position with their respective extensions  95  and  94  engaged.  FIG. 32  shows the extensions  92  and  93  in a distracted position with the extension  94  preventing the head  88  and extension  93  from pulling out of the telescopic component  92 . 
         [0119]    In another embodiment of the cranial fixation device as shown in  FIGS. 33 and 34 , the head  98  comprises an extension  101  and the head  96  comprises an extension  100 . The head  98  has holes  99  which allows placement of screws attaching the head to the skull. Head  96  has holes  97  through which screws can be placed for attachment of the head to the bone flap. The extensions  100  and  101  are telescopic and allow for inward or outward movement of the heads relative to each other. The telescopic extension  100  also comprises an extension  261  at one end and sockets  103  along the body. The telescopic component  101  has an extension  104  at one end and ridges  102  along the body.  FIG. 33  shows the telescopic extensions  100  and  101  in a compressed position with their respective extensions  104  and  261  engaged. The ridges  102  are also shown engaged with the recesses  103 .  FIG. 34  shows the extensions  100  and  101  in a distracted position with the extension  261  preventing the head  96  and extension  100  from pulling out of the telescopic component  101 . 
         [0120]    In another embodiment of the cranial fixation device as shown in  FIGS. 35 and 36 , the head  108  comprises an extension  1 . 10  and the head  105  comprises an extension  107 . The head  108  has holes  109  which allows placement of screws attaching the head to the skull. Head  105  has holes  106  through which screws can be placed for attachment of the head to the bone flap. The extensions  107  and  110  are telescopic and allow for inward or outward movement of the heads relative to each other. The telescopic extension  107  also comprises an extension  262  at one end and ratchet teeth recesses  111  along the body. The telescopic component  110  has an extension  263  at one end and ratchet teeth  112  along the body.  FIG. 35  shows the telescopic extensions  107  and  110  in a compressed position with their respective extensions  262  and  263  engaged.  FIG. 35  shows the extensions  107  and  110  in a distracted position with the extension  262  preventing the extension  107  from pulling out of the telescopic component  110 . 
         [0121]    In another embodiment, the cranial fixation device as shown in  FIGS. 37 and 38  comprises a head  113  with an extension  116  and a head  114  with an extension  117 . The extensions  116  and  117  are telescopic and allow for inward or outward movement of the heads relative to each other. The medial edges of the heads  113  and  114  are sloped  119  and overlap each other when the heads are approximated, thereby not allowing the head  114  to move inward beyond the head  113 . The head  114  has holes  115  which allow placement of screws attaching the head to the bone flap and the head  113  rests on the outer surface of the skull.  FIG. 37  shows the telescopic extensions in a compressed position whereby extension  117  is contained inside the extension  116  and  FIG. 38  shows the extensions  116  and  117  in a distracted position.  FIG. 39  illustrates another embodiment of the cranial fixation device with an intermediate telescopic component  118  which allows the two heads attached to their respective bone flap and skull to move outwards further if needed to accommodate an increase in intracranial pressure or brain swelling. 
         [0122]    In another embodiment, the cranial fixation device as shown in  FIGS. 40 and 41  comprises a head  120  with an extension  124  and a head  122  with an extension  125 . The extensions  124  and  125  are telescopic and allow for inward or outward movement of the heads relative to each other. The head  120  has holes  121  which allow placement of screws attaching the head to the skull and the head  122  has a clamp  123  that attaches to the dipole of the bone flap and the head  122  rests on the outer surface of the bone flap.  FIG. 40  shows the telescopic extensions in a compressed position whereby extension  125  is contained inside the extension  124  and  FIG. 41  shows the extensions  124  and  125  in a distracted position. 
         [0123]    In another embodiment, the cranial fixation device as shown in  FIGS. 42 and 43  comprises a head  126  with an extension  130  and a head  128  with an extension  131 . The extensions  130  and  131  are telescopic and allow for inward or outward movement of the heads relative to each other. The head  126  has a clamp  127  that secures the head to the skull and the head  128  has spikes  129  that attach to the bone flap.  FIG. 42  shows the telescopic extensions in a compressed position whereby extension  131  is contained inside the extension  130  and  FIG. 43  shows the extensions  131  and  130  in a distracted position. The method for cranial bone flap fixation with the device in  FIGS. 42 and 43  is illustrated in  FIGS. 44 and 45 .  FIG. 44  illustrates the cranial fixation devices  137  and  138  in place attached to the outer surface of the bone flap  133  and the skull  132  and  134 . The brain  135  and dura  136  are shown in their normal position. Typically two or more of the cranial fixation devices would be placed to fixate the bone flap  133  to the skull  132  and  134  with the cranial fixation device telescopes in a retracted position approximating the bone flap to the skull. As shown in  FIG. 45 , with the development of brain swelling or an increase in intracranial pressure from a hemorrhage, the brain  155  and dura  156  push against the bone flap  133 . The pressure on the bone flap places the cranial fixation device  139  and  140  telescopes in an extended position thereby allowing the bone flap to move outwards and accommodate the brain swelling. 
         [0124]    In another embodiment of the cranial fixation device as shown in  FIGS. 46 and 47 , the head  141  comprises an extension  145  and the head  142  comprises an extension  146 . The extensions  145  and  146  are telescopic and allow for inward or outward movement of the heads relative to each other. The heads  141  and  142  also comprise of spikes  143  and  144  that attach to the skull and bone flap respectively.  FIG. 46  shows the telescopic extensions in a compressed position whereby extension  146  is contained inside the extension  145  and  FIG. 47  shows the extensions  145  and  146  in a distracted position. 
         [0125]    While the abovementioned cranial fixation device heads are positioned on the outer surface of the skull and bone flap, in other embodiments one head is positioned on the outer surface of the skull and/or bone flap and the other head is positioned on the inner surface. The head shapes can be rectangular or circular. As shown in  FIGS. 48 and 49  the head  147  rests on the outer surface of the bone flap and comprises a hole  188  for placement of a screw and a telescopic extension  151 . The head  150  is positioned on the inner surface of the skull and comprises a telescopic housing extension  149 .  FIG. 48  shows the telescopic extensions in a compressed position whereby extension  151  is contained inside the extension  149  and  FIG. 47  shows the extensions  149  and  151  in a distracted position. The method for cranial bone flap fixation with the device in  FIGS. 48 and 49  is illustrated in  FIGS. 50 and 51 .  FIG. 50  illustrates the cranial fixation devices  159  and  160  in place attached to the outer surface of the bone flap  153  with screws and the inner surface of the skull  152  and  154 . The brain  158  and dura  157  are shown in their normal position. Typically two or more of the cranial fixation devices would be placed to fixate the bone flap  153  to the skull  152  and  154  with the cranial fixation device telescopes in a retracted position approximating the bone flap to the skull. As shown in  FIG. 51 , with the development of brain swelling or an increase in intracranial pressure from a hemorrhage, the swollen brain  164  and dura  163  push against the bone flap  153 . The pressure on the bone flap places the cranial fixation device  161  and  162  telescopes in an extended position thereby allowing the bone flap to move outwards and accommodate the brain swelling. 
         [0126]    In another embodiment of the cranial fixation device as shown in  FIGS. 52 and 53  the head  165  rests on the outer surface of the bone flap and comprises a hole  166  for placement of a screw and a telescopic extension  170 . The head  168  is attached to the Inner surface of the skull with spikes  169  and comprises a telescopic housing extension  167 .  FIG. 52  shows the telescopic extensions in a compressed position whereby extension  170  is contained inside the extension  167  and  FIG. 53  shows the extensions  167  and  170  in a distracted position. 
         [0127]    In another embodiment of the cranial fixation device as shown in  FIGS. 54 and 55  the head  171  is attached to the outer surface of the bone flap with spikes  172  and comprises a telescopic extension  176 . The head  174  is attached to the Inner surface of the skull with spikes  175  and comprises a telescopic housing extension  173 .  FIG. 54  shows the telescopic extensions in a compressed position whereby extension  176  is contained inside the extension  173  and  FIG. 55  shows the extensions  173  and  176  in a distracted position. The method for cranial bone flap fixation with the device in  FIGS. 54 and 55  is illustrated in  FIGS. 56 and 57 .  FIG. 56  illustrates the cranial fixation devices  181  and  182  in place attached to the outer surface of the bone flap  178  and the inner surface of the skull  77  and  179 . The brain  180  is shown in its normal position. Typically two or more of the cranial fixation devices would be placed to fixate the bone flap  178  to the skull  177  and  179  with the cranial fixation device telescopes in a retracted position approximating the bone flap to the skull. As shown in  FIG. 57 , with the development of brain swelling or an increase in Intracranial pressure from a hemorrhage, the swollen brain  185  pushes against the bone flap  178 . The pressure on the bone flap places the cranial fixation device  183  and  184  telescopes in an extended position thereby allowing the bone flap to move outwards and accommodate the brain swelling. 
         [0128]    In another embodiment of the cranial fixation device as shown in  FIGS. 58 and 59 , the head  186  rests on the outer surface of the bone flap and skull. The head  186  has a clamp  188  at one end and a telescopic extension  187  in the center that resides in the burr hole defect. The clamp end of the head attaches to the bone flap and the other head end rests on the outer surface of the skull.  FIG. 58  shows the telescopic extensions in a compressed position whereby extension  189  is contained inside the extension  187  and  FIG. 59  shows the extensions  187  and  189  in a distracted position. 
         [0129]    In another embodiment of the cranial fixation device as shown in  FIGS. 60 and 61 , the head  190  rests on the outer surface of the bone flap and skull. The head  190  has a hole  191  at one end and a telescopic extension  192  in the center that resides in the burr hole defect. The screw hole  191  end of the head attaches to the bone flap and the other head end rests on the outer surface of the skull.  FIG. 60  shows the telescopic extensions in a compressed position whereby extension  193  is contained inside the extension  192  and  FIG. 61  shows the extensions  192  and  193  in a distracted position. 
         [0130]    In another embodiment of the cranial fixation device as shown in  FIGS. 62 and 63 , the device comprises of a head  194  and a head  195  connected with a telescopic portion  196 . The head  194  resting on the outer surface of the bone flap and skull also comprising of holes  197  for screw placement. The side of the head  194  with screw holes  197  is secured to the bone flap and the opposing side of the head  194  rests on the skull. The head  195  rests on the inner surface of the skull and bone flap and the telescopic portion  196  is positioned in the skull defect. The telescopic portion  196  also comprises of extensions  199  and  198  that allow outward movement of the head  194  secured at one end to the bone flap as shown in  FIG. 63 . 
         [0131]    In another embodiment of the cranial fixation device as shown in  FIGS. 64 and 66 , the device comprises of a head  200  and a head  203  connected with a telescopic portion  202 . The head  200  resting on the outer surface of the bone flap and skull also comprising of holes  201  for screw placement. The side of the head  200  with screw holes  201  is secured to the bone flap and the opposing side of the head  200  rests on the skull. The head  203  rests on the inner surface of the skull and bone flap and the telescopic portion  196  is positioned in the skull burr hole opening. The side of the head  203  towards the skull comprises of spikes  204  for attachment to the inner surface of the skull. The telescopic portion  202  also comprises of extension  205  that allows outward movement of the head  200  secured at one end to the bone flap as shown in  FIG. 65 . 
         [0132]    In another embodiment of the cranial fixation device as shown in  FIGS. 66 and 67 , the device comprises of a head  206  and a head  207  connected with a telescopic portion  208 . The head  200  resting on the outer surface of the bone flap and skull also comprising of spikes  210  on the side of the head secured to the bone flap and the opposing side of the head  200  rests on the skull. The head  207  rests on the inner surface of the skull and bone flap and the telescopic portion  196  is positioned in the skull defect. The side of the head  207  towards the skull comprises of spikes  211 . The telescopic portion  208  also comprises of extension  209  that allows outward movement of the head  206  as shown in  FIG. 67 . The method for cranial bone flap fixation with the device in  FIGS. 66 and 67  is illustrated in  FIGS. 68 and 69 .  FIG. 68  illustrates the cranial fixation devices  216  and  217  in place attached to the outer and inner surface of the bone flap  213  and the skull  212  and  214  respectively. The brain  215  is shown in its normal position. Typically two or more of the cranial fixation devices would be placed to fixate the bone flap  213  to the skull  212  and  214  with the cranial fixation device telescopes in a retracted position approximating the bone flap to the skull. As shown in  FIG. 69 , with the development of brain swelling or an increase in intracranial pressure from a hemorrhage, the swollen, brain  220  pushes against the bone flap  213 . The pressure on the bone flap places the cranial fixation device  218  and  219  telescopes in, an extended position thereby allowing the bone flap to move outwards and accommodate the brain swelling. 
         [0133]    In another embodiment of the cranial fixation device as shown in  FIGS. 70-72 , the head  221  rests on the outer surface of the bone flap and skull and comprises an extension  222 . The head  225  rests on the inner surface of the bone flap and skull and comprises a hollow extension  224 . The extensions  222  and  224  are telescopically connected by an intermediary hollow extension  223 .  FIG. 72  illustrates the device in a distracted position with telescopic extensions  222 ,  223 , and  224 .  FIG. 71  illustrates the device in a partially distracted position with the telescopic extensions  222  and  224 . The intermediate extension  223  has telescoped inside the extension  224 .  FIG. 70  illustrates the device in a completely retracted position with the intermediate extension  223  and head extension  222  telescoped inside extension  224 , thereby bringing the heads  221  and  225  closer together.  FIG. 73  illustrates the cranial fixation device in place with head  226  resting on the outer surface of the bone flap  228  and skull  229 . The head  227  rests on the inner surface of the bone flap  228  and skull  229 . The two heads  226  and  227  are connected by the telescopic extension  230  residing in the burr hole defect between the bone flap  228  and skull  229 . Various telescopic extension locking mechanisms are illustrated in  FIGS. 74-82 . 
         [0134]    In another embodiment of the cranial fixation device as shown in  FIGS. 74 and 75 , the head  231  comprises a telescopic extension  235  and the head  232  comprises a telescopic extension  236 . The extension  236  contains ridges  234  that engage with corresponding recesses  233  in extension  235 .  FIG. 74  shows the telescopic extensions  235  and  236  in a partially retracted position and  FIG. 75  shows the telescopic extensions in an extended position. 
         [0135]    In another embodiment of the cranial fixation device as shown in  FIGS. 76 and 77 , the head  237  comprises a telescopic extension  239  and the head  242  comprises a telescopic extension  241 . The extension  241  contains a collapsible ball  240  that engage with corresponding recesses  238  and  264  in extension  239 . 
         [0136]      FIG. 76  shows the telescopic extensions  239  and  241  in a partially retracted position and  FIG. 77  shows the telescopic extensions in an extended position. In another embodiment of the cranial fixation device as shown in  FIGS. 78-80 , the head  243  comprises a telescopic extension  247  and the head  244  comprises a telescopic extension  245 . The extension  247  contains a collapsible hook  248  that engages with corresponding recesses  246  and  249  in extension  245 .  FIG. 78  shows the telescopic extensions  245  and  247  in a retracted position with the hook  248  engaged with the recess  249 .  FIG. 79  shows the telescopic extensions in a partially retracted position and  FIG. 80  shows the telescopic extensions in an extended position with the hook  248  engaged with the recess  246 . 
         [0137]    In another embodiment of the cranial fixation device as shown in  FIGS. 81 and 82 , the head  250  comprises a telescopic extension  252  and the head  251  comprises a telescopic extension  255 . The extension  255  contains ratchet teeth  254  that engage with corresponding recesses  253  in extension  252 .  FIG. 81  shows the telescopic extensions  252  and  255  in a retracted position and  FIG. 82  shows the telescopic extensions in an extended position. 
         [0138]    Although several telescopic extension engaging mechanisms are described in the various embodiments, it is obvious that any variations made to the embodiments by those skilled in the art maintain the broad incentive concepts described herein. 
         [0139]    The head on the outer surface of the skull can also contain a removable extension to assist in holding and placement of the cranial fixation devices described herein. As shown in  FIG. 84  the head  257  comprises a telescopic extension  258  as well as an extension  256 . The head  260  comprises a telescopic extension  259 . The extension  256  can be used to hold the cranial fixation device and position the head  260  under the inner surface of the bone flap and skull following the craniotomy. Once the head  257  is positioned on the outer surface of the skull and bone flap, the extension  256  can be snapped off either manually or with a cutting instrument. The cranial fixation device of  FIG. 4  with the extension  256  removed is shown in  FIG. 83 . 
         [0140]    In alternate embodiments, the heads or telescopic components can be connected with a flexible material like a spring or an elastomer which retracts the telescopic extensions thereby positioning the bone flap down towards the skull once the ICP has reduced to a normal level. As shown in  FIGS. 85 and 86 , the two heads  264  and  265  contain telescopic extensions  270  and  282  with bone screw holes  268  and  269 . The head  264  is attached to a spring  281  that is housed in the hollow component  280  of the telescopic extension and is also attached to the telescopic extension  270 . In the current embodiment the spring is shown residing inside the telescopic extensions but in other embodiments it can be placed outside the telescopic extensions. With normalization of the 
         [0000]    intracranial pressure the spring  281  retracts the heads and telescopic extensions to approximate the two heads together as shown in  FIG. 85 . With an increase in intracranial pressure the head  264  connected to the bone flap is pushed outwards and places the telescopic extensions in an extended position as shown in  FIG. 86 .  FIGS. 87 and 88  illustrate another embodiment of the fixation device with heads  283  and  288  and telescopic extensions  284  and  286  with an elastomeric band  287  that is housed in the hollow portion  285  of the telescopic extensions.  FIG. 87  shows the retracted position of the telescopes with heads approximated and  FIG. 88  shows the extended position of the telescopic extensions. 
         [0141]    The normal intracranial pressure is less than 20 mm-Hg and with any brain swelling or hemorrhage the intracranial pressure can increase to greater than 20 mm Hg. With an increase in the intracranial pressure above the normal range, the cranial fixation devices are designed to disengage the locking mechanism and place the telescopic extensions into an extended position from a retracted position and therefore place the two heads apart, thereby allowing the bone flap to move outwards from the skull in a constrained manner and accommodate the higher intracranial pressure. Once the intracranial pressure reaches below 20 mm Hg again the telescopic extensions retract and position the bone flap downwards to the skull level. 
         [0142]    In the various embodiments described herein the preferred head configuration is either circular or semi-circular coming together in a circular shape when the telescopic extensions are in a compressed position. The circular shape covers the burr hole skull defect. Other head shapes can include oval, rectangular, square, semi-oval, C-shape, L-shape, T-shape, X-shape, Y-shape, Z-shape, fan shaped or any other configuration able to connect the skull to the bone flap. Similarly, the telescopic configurations described are either cylindrical or rectangular and hollow designed to fit into the burr hole or skull opening. Other telescopic configurations could be partially solid, tapered. V-shaped or any other configuration that fit&#39;s the skull opening. The cranial fixation device can be made of titanium or titanium alloy for MRI imaging compatibility. It could also be made of a bioresorbable (polyesters, poly amino adds, polyanhydrides, polyorthoesters, polyurethanes, polycarbonates, homopolymers, copolymers of poly lactic acid and poly glycolic acid, copolyesters of e-caprolactone, 
         [0000]    trimethylene carbonate, and para-dioxanone), or allograft, or xenograft bone that is absorbed by the body over time once the bone flap has fused with the skull. Alternatively, it could made of a radiolucent material like polyetheretherketone (PEEK) or polyaryletherketone (PEAK), high molecular weight polyethylene, carbon fiber, polyurethane, plastic, or a combination of plastic and metal to reduce CT and MRI imaging artifact. The cranial fixation device discussed herein can be of unitary construction, such that the heads and telescopic portions can be integral or formed from a single piece material. Alternative embodiments contemplate that the components of the cranial fixation device can be non-Integral, and can be attached to and/or coupled to other components of the device. The thickness of the heads can range from 3 mm to 20 mm. The size of the head can range from 6 mm to 40 mm. The length of the telescopic portion in a retracted position can range from 5 mm to 20 mm and in an extended position can range from 10 mm to 60 mm. The length of the screws can range from 4 mm to 20 mm. While the above-mentioned size range of the device components reflects the preferred embodiments, other embodiments can comprise of head, telescope, and screw sizes outside of the aforementioned ranges. The angulations of the telescopic component in the preferred embodiment are 90 degrees relative to the heads but could any other angle from perpendicular to parallel to the head. 
         [0143]    While the invention and methodology described herein along with the illustrations is specific, it is understood that the invention is not limited to the embodiments disclosed. Numerous modifications, rearrangements, and substitutions can be made with those skilled in the art without departing from the spirit of the invention as set forth and defined herein.