Patent Publication Number: US-2004059194-A1

Title: Method and apparatus for replacing knee-joint

Description:
[0001] The present application is based on and claims the benefit of U.S. provisional patent application Serial No. 60/396,850, filed Jul. 18, 2002, the content of which is hereby incorporated by reference in its entirety. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] The present invention relates to a method for performing knee-joint replacement surgery and apparatus for use in such surgery.  
       [0003] The knee-joint is the largest and the most complex joint in the body. The knee joint has four main parts consisting of the lower femur, the upper tibia, cartilage separating the lower femur and the upper tibia and the patella which is commonly known as the kneecap. When the knee-joint functions properly, the upper end of the tibia and the lower end of the femur glide with respect to each other and allow the knee to bend. The cartilage separates the lower end of the femur and upper end of the tibia and provides cushioning between the tibia and femur similar to a shock absorber. The surfaces which are not in contact with the cartilage are covered by a thin smooth tissue liner called the synovial membrane which releases a special fluid that lubricates the knee and reduces the friction in the knee to nearly zero in a healthy knee.  
       [0004] The most common cause of chronic knee pain is arthritis of which osteoarthritis, rheumatoid arthritis and post traumatic arthritis are the most common forms. Osteoarthritis typically occurs after the age of 50 and is caused by the softening and wearing away of the cartilage. As the cartilage is worn away, the tibia and femur rub against each other which causes pain and stiffness.  
       [0005] The second type of arthritis is rheumatoid arthritis which causes the synovial membrane to become thickened and inflamed, producing excessive amounts of synovial fluid which over-fills the joint space. The chronic inflammation can damage the cartilage and eventually cause cartilage loss, pain and stiffness.  
       [0006] The third type of arthritis is post traumatic arthritis which follows a serious knee injury. A knee fraction or severe tear of the knee ligaments may damage the cartilage over time. The damage to the cartilage causes pain and stiffness in the knee joint.  
       [0007] The arthritis in the knee can become painful to the point of extremely limiting the mobility of the person. When medications such as analgesics cannot eliminate or make the pain manageable, an increasingly popular option is to have a total knee replacement operation where the damaged knee joint is replaced with an artificial knee-joint called a prosthesis.  
       [0008] The current procedure for performing a total knee replacement surgery is very taxing on the surgical personnel. An incision is made from the top of the knee exposing the patella. A retractor is disposed into the incision and to one side of the patella. The surgical personnel manually retract the patella to one side and manually use additional retractors to retract the flesh to expose the femur and tibia.  
       [0009] With the femur and tibia exposed, the joint is separated to gain access to either the end of the femur or tibia typically by adjusting the position of the tibia. The ends of the femur and tibia are precisely cut and inserts are attached to each end of the bones. Typically, a metal piece made of stainless steel or titanium is inserted into the femur and an insert made of a durable, non-wearing plastic, typically polyethylene, is inserted into the tibia. The interface of the metal and the plastic provides a smooth moving joint that does not require lubrication. To gain access to the ends of the bones requires manipulation of the shin portion of the leg and the thigh portion of the leg which requires additional personnel.  
       SUMMARY OF THE INVENTION  
       [0010] The present invention includes a method of performing knee-joint replacement surgery. With the patient lying on a surgical table, the tibia and the femur are positioned to place the knee-joint in a bent position. An incision is made over or adjacent the patella to expose the knee-joint. A retractor support which is mounted onto the surgical table is extended along opposite sides of the knee-joint. Skin and flesh layers proximate the knee-joint are retracted utilizing a plurality of retractors which are attached to the retractor support. At least one of the retractors that is attached to the retractor support has a portion which is flexible such that the knee-joint may be moved from an initial selected position to a second selected position during the procedure without having to reposition the retractor blades from their original engagement of the skin and the flesh layers or reattach the retractors to the retractor support or reposition the retractor support. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011]FIG. 1 is a perspective view of the apparatus used in the surgical procedure of the present invention.  
     [0012]FIG. 2 is a perspective view of an alternative apparatus used in the surgical procedure of the present invention.  
     [0013]FIG. 3 is a side view of a surgical retractor for use in the method of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0014] The present invention includes a method and apparatus for performing knee-joint replacement surgery in a manner that does not require repositioning of the surgical retractors during the knee-joint replacement surgery.  
     [0015] The apparatus used in the knee-joint replacement surgery of the present invention is generally indicated at  10  in FIG. 1. The apparatus  10  includes a retractor support apparatus  12  that is rigidly mounted to a rail  11  of a surgical table  13  in a manner that is well known in the art and is described in U.S. Pat. Nos. 4,617,916, 4,718,151, 4,949,707, 5,400,772, 5,741,210, 6,042,541, 6,264,396 and 6,315,718 all of which are herein incorporated by reference. From the mount to the surgical table, the retractor support apparatus  12  includes first and second support arms  18  and  20  that extend over the surgical table. The support arms  18  and  20  are independently adjustable into an infinite number of selected positions through use of a clamping mechanism  22  which is described in U.S. Pat. Nos. 5,899,627 and 6,264,396, which are herein incorporated by reference. The support arms  18  and  20  extend in a generally lateral or horizontal direction on opposite sides of a knee-joint  24 . The clamp  22  secures the adjustable support arms  18  and  20  in selected angular positions with respect to the knee-joint  24 .  
     [0016] The knee-joint  24  is preferably placed in and supported in a bent position as is typically done in knee-joint replacement surgery. The bent position is approximately a 45° angle between the femur  26  and the tibia  28 . The support arms  18  and  20  are disposed on both sides and below the knee-joint  24 . An incision  30  is made on top of the knee to gain access to the joint  24 . The incision is made directly over the patella  32  or on occasion to the left or right of the patella depending on the surgeon&#39;s preference.  
     [0017] Once the incision  30  is made, a plurality of retractors  34 ,  35  and  36  and  37  are positioned to retract skin and flesh layers to expose the knee-joint  24 . Since both surgical retractors  34  and  36  are of the same construction only retractor  34  will be described in detail. As best illustrated in FIG. 3, the surgical retractor  34  includes a retractor blade  40  attached to a flexible connector  42  such as plastic cord. The flexible connector  42  is connected to the support arm  18  by an attaching device  44 .  
     [0018] It should be understood that although a cord is illustrated other types of flexible connectors may be used in the method of the present invention. What is important is that the retractor starting from its attachment to either support arm  18  or  20  to the skin and flesh layers not be rigid. The procedure of the present invention permits the tibia  28  or femur  26  to be moved in relation to each other without necessitating repositioning of the retractor blade, repositioning the attachment of the retractor to the retractor support or moving (adjusting) the retractor support. The flexible connector also needs to have sufficient integrity and strength to retain the retractor blade in a flesh retracted position. Although the flexible connector as shown extends from the retractor blade  40  to the attaching device  44 , the flexible connector does not necessarily have to extend from the blade  40  to the device  44 . For example, only a portion of the flexible connector could be flexible while the remainder could be rigid as long as sufficient flexibility exists between the retractor blade  40  and the support arm  18  or  20  to be able to reposition the tibia  28  in relation to the femur  26 . For example, the flexible connector  42  may also be elastic or be made of resilient material as long as the connector is flexible. By flexible is meant that the surgeon may adjust the position of the knee-joint during surgery without having to reposition the retractor blade, reattach the retractor to the retractor support or adjust the position of the retractor support.  
     [0019] It is preferred that at least one of the retractors includes a flexible connector. As illustrated in FIG. 1, standard rigid retractors  37  without a flexible connector can also be used in the surgical procedure of the present invention. In other words, not all of the retractors used in the method of the present invention need to have a flexible connector. Surgical retractors which are rigid are well known in the art and are secured to the support arm  18  by a clamping mechanism  19  that is also well known. A rigid retractor  37  can be used as long as the surgeon can adjust the position of the knee-joint during surgery without having to reposition the retractor blade, reattach the retractor to the retractor support or adjust the position of the retractor support.  
     [0020] The flexible connector  42  is typically made of a polymeric material in the form of a solid cord. However, the connector  42  may be of any construction such as woven, braided, non-woven material or flexible metal. The flexible connector  42  is frictionally attached to the retractor blade  40  by extending through a series of holes  46 ,  48  and  50  in a serpentine fashion.  
     [0021] Knee-joint replacement surgery due to the unique positioning of the knee and its relatively light weight has posed a problem in terms of retraction of the skin and flesh. Table mounted retractors have been used for surgery on various areas of the torso. However, the torso lies flat on the surgical table and is of sufficient weight that rigid surgical retractors pulling up from an elevated position do not move the torso. However, a knee-joint must be positioned in a bent and elevated position generally supported underneath. The knee-joint also does not have the weight of a torso. Consequently retraction of the knee-joint has required significant manual assistance for proper retraction. Utilizing the procedure of the present invention by securing retractors to a table mounted support eliminates the need for additional surgery personnel to manually assist for proper retraction in holding the incision open.  
     [0022] As best illustrated in FIG. 1, the retractor blade  40  is positioned to engage and retract flesh along the incision  30 . The flexible connector  42  is then pulled to engage the attaching device  44 . As the flexible connector  42  is pulled, the retractor blade retracts the skin and flesh layers, opening the incision. Since the support arms  18  and  20  are positioned below the knee-joint, the force against the retracted skin and flesh is disposed along a downward slope from the point of retraction to either the support  18  or  20 .  
     [0023] The attaching device  44  is secured to the support arm  18  through aperture  52  through which the support arm  18  extends. To prevent the attaching device from rotating about the support arm  18 , the support arm  18  includes a flat section  54  that cooperates with or acts against a flat or straight section  56  of the aperture  52 . The support arm  20  also has a like flat section (not shown) for the same purpose. It should be understood by those skilled in the art that other methods of preventing rotation of the attaching device  44  about the arm  18  are included within the scope of the present invention. Such other methods of retaining the attaching device  44  may include clamps, set screws, pins and the like.  
     [0024] The attaching device  44  extends in a direction generally away from the incision  30  and has a distal end  58  that includes a V-shaped notch  60 . When the flexible connector  42  is pulled back, a free end  43  of the connector is inserted between opposing sides of the V-shaped notch  60  for engagement. The V-shaped notch  60  pinches the flexible connector  42 , thereby holding or retaining the flexible connector  42  in a pinched or frictional engagement.  
     [0025] The surgical procedure of the present invention can be performed entirely using the retractor with flexible connectors of the present invention as illustrated in FIG. 2, where like reference characters will be used to indicate like elements of FIG. 1. The apparatus generally indicated at  68  includes retractors  68 ,  70 ,  72  and  73 , all which have flexible connectors  42 . All are mounted to either one of the support arms  18  and  20  which in turn is mounted to the rail  11  of the surgical table  13 .  
     [0026] The flexible connector  42  of the surgical retractor  68 ,  70 ,  72  and  73  is attached to the support arms  18  and  20  by an attaching device  74  that has a different configuration than the attaching device  44  illustrated in FIG. 1. However, the attaching device  74  is secured to the support arms  18  and  20  in a similar fashion, and that is by an aperture  76  having a flat section  78  that cooperates or acts against the flat section  54  of the support arm  18 . Similarly, the flexible connector  42  is engaged in a V-shaped notch  80  similar to the V-shaped notch  60  of the attaching device  44 . The primary difference between the attaching device  74  and the attaching device  44  illustrated in FIG. 1 is that the attaching device  74  is made of flat sheet metal wherein the mid-section  82  of the device  74  is twisted approximately 90° to provide rigidity to the attaching device. Rigidity is provided to the attaching device  44  by virtue of its arcuate cross-section.  
     [0027] A lower leg hold down device  90  is attached to distal end portions  92  and  94  of the support arms  18  and  20 , respectively. The hold down device  90  includes a pair of downwardly extending rigid legs  96  and  98  that project downwardly from the distal end portions  92  and  94 . A flexible strap  100  is attached at both ends to lower portions  102  and  104  of the downwardly extending legs  96  and  98 , respectively. The legs  96  and  98  are secured in a rigid fashion to the distal end portions  92  and  94  of the support arms  18  and  20 . The flexible strap  100  is attached to the downwardly extending legs at a position below the point at which the strap engages the lower leg so that a force is applied to the lower leg to retain the lower leg in position. Holding the lower leg down in position eliminates the need for manual retention of the lower leg during surgery or the use of other additional devices that may be secured to the working surface of the surgical table.  
     [0028] After the retractors  68 ,  70 ,  72  and  73  are positioned to retract skin and flesh, the patella  32  is either removed or moved aside thereby exposing the ends of the femur and the tibia. Since the knee-joint  24  is in a bent position, the end of the femur is accessible to the surgeon through the incision. Due to the flexible connector of the retractors, the knee-joint can be repositioned without having to adjust the position of the support arm  18  or  20  or readjusting the retractor blade or reattaching the retractor blade to either support arm or both,  18  and  20 . The end of the femur is then cut, and prepared to accept a prosthetic insert made of metal such as stainless steel or titanium as is standard in knee-joint replacement.  
     [0029] After the end of the femur has been prepared to accept the prosthetic insert (not shown), the tibia must then also be prepared to accept a prosthetic insert typically made of polyethylene which interacts with the first prosthetic insert of the femur. To prepare the tibia to accept the second prosthetic insert, the tibia must be pushed away from the femur and lifted to gain access to the end of the femur. Since the retractors of the present invention have flexible connectors, the tibia may be moved with respect to the femur without the need to reposition retractor blades or reattach the retractors to the support arms  18  or  20  or adjust the support arms  18  or  20 . Once the surgeon cuts the end of the tibia and secures the second prosthetic insert to the tibia, the tibia with prosthetic insert is then maneuvered to engage the prosthetic insert on the femur.  
     [0030] Once the two prosthetic inserts are engaged, the surgical retractor of the present invention are disengaged from their retracted position. The patella is then moved back in position or a new prosthetic patella is substituted and the surgery is then completed.  
     [0031] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.