Abstract:
A device for correcting the shape of an infant&#39;s abnormally-shaped cranium by applying external forces over time with the growth of an infant to achieve normal shaping of the infant&#39;s head. The device applies inwardly-directed external forces only to areas of bony prominence and minimizes (or altogether eliminates) these forces on the areas of the skull that are less prominent (or flattened). Because the present invention is non-conforming to the shape of an abnormal skull, the exerted forces cause accelerated expansion of the skull in less prominent (flattened) areas coincident with brain and skull growth. This causes the cranium to return to a normal symmetric cranial shape. The material that contacts the infant&#39;s cranium is semi-rigid, relatively non-flexible, and maintains its overall shape under stress. For an infant with an already normally-shaped cranium, the device causes the infant&#39;s cranium to grow evenly and maintain its normal shape, and thus prevents abnormal cranial shaping.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    This is a continuation-in-part application claiming priority to U.S. patent application Ser. No. 11/449,402 filed Jun. 8, 2006, which is incorporated herein by reference. 
     
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to a mattress incorporating a headrest in which an infant&#39;s cranium is positioned while the infant is sleeping to prevent and correct cranial deformities. More specifically, the invention relates to a mattress incorporating a headrest for preventing and correcting any non-synostotic deformity of the side and posterior aspects of an infant&#39;s head. 
         [0004]    2. Description of Related Art 
         [0005]    At birth, the six cranial bones comprising an infant&#39;s skull are spaced far enough apart to allow the skull to rapidly grow during the first months of the infant&#39;s life. This spacing also allows the bones to overlap so the infant&#39;s head can pass through the birth canal without compressing, and thereby damaging, the infant&#39;s brain. Eventually—some time between three and six years of age—the cranial bones will fuse and remain fused for the rest of the child&#39;s life. 
         [0006]    During an infant&#39;s normal growth, forces within the infant&#39;s skull are directed outward and are constant and equally distributed on the inner surface of the growing skull causing the skull to expand. Accordingly, a decrease of the intracranial pressure will cause a reduced head size. Similarly, an increase in intracranial pressure will cause an increased head size. 
         [0007]    Fibrous bands of tissue, called cranial sutures, fill the space between the bones and connect the bones of the skull to each other. These cranial sutures are strong and elastic, providing a flexibility to the skull to allow rapid brain growth during the first months of life. Without the sutures, a child would suffer brain damage due to constriction of the brain during the period of normal growth. 
         [0008]    During the first few months of an infants&#39; life, however, the infant is most susceptible to the formation of synostotic or non-synostotic deformities in the cranium. Synostotic deformities are a result of craniosynostosis, which is a birth defect of the skull characterized by premature closure of one or more of the cranial sutures. Craniosynostosis can be hereditary or the result of a metabolic disease, and is characterized by an abnormally-shaped skull and potential for abnormal intracranial pressure, mental retardation, seizures, and blindness. 
         [0009]    On the other hand, non-synostotic deformities, in which the cranial sutures remain open, are caused by environmental conditions, including premature birth, torticollis (twisting of the neck muscles beyond their normal position), or the preferred sleeping position of the child. In addition, neurological abnormalities, such as paralysis, cerebral palsy, or some sort of developmental delay, may predispose a child to cranial positioning problems. Non-synostotic deformities are also called positional deformities. 
         [0010]    Synostotic and non-synostotic deformities manifest themselves in a variety of ways. Plagiocephaly, for example, is a cranial deformity resulting in an asymmetric head shape. Plagiocephaly consists of a focal area of flattening in the anterior or posterior aspect of one side of the head, which also commonly produces additional compensatory deformities in adjacent areas of the skull, skull base, and face, including the orbital (eye) and mandibular (jaw) structures. This deformity most commonly occurs in the posterior aspect of the head (posterior plagiocephaly), resulting in a focal area of flattening on that side and a compensatory prominence, or bulge, on the other side. In addition, the deformity produces anterior displacement of the ear, ear canal, temporomandibular (jaw) joint, forehead and orbital structures on the same side. Cranial deformities may also be classified, inter alia, as brachycephaly (a short, wide head shape), scaphocephaly (a long, narrow head shape), and turricephaly (a pointed head shape). 
         [0011]    Non-synostotic posterior plagiocephaly is a very common problem for which parents seek evaluation and recommendations from their family physician or pediatrician. The incidence of this abnormality has increased significantly since publication of recommendations by the American Academy of Pediatrics that neonates (infants) should be put to sleep on their back rather than face down. These recommendations were made to reduce the incidence of Sudden Infant Death Syndrome (SIDS) by eliminating airway and respiratory compromise in the prone (face-down) position, which the Academy considered a possible contributor to the SIDS problem. 
         [0012]    The usual method of attempting to treat these deformities involves trying to reposition the child during sleep. The most common adjuncts available to assist with this treatment are flat- and wedge-shaped foam pads. For example, U.S. Pat. No. 6,473,923 (filed Nov. 22, 2000) (issued Nov. 5, 2002) discloses a body pillow and head positioner attached to a mat. The device is intended to maintain the infant&#39;s supine position while reducing the risk of positional plagiocephaly by causing the head to rotate to the side while maintaining the infant&#39;s supine position. 
         [0013]    Simply put, repositioning, even with foam padding, is ineffective for treating or preventing these deformities, and even after treatment most children do not obtain a perfectly normal head shape. Repositioning merely distributes or disperses the forces over a larger area of the head. The foam padding remains in contact with the skin and conforms the head to an abnormal shape. Due to this ineffectiveness, a large number of these children require additional treatment from five to ten months of age due to persistent or progressive deformities. 
         [0014]    The additional treatment most often is by application of a custom-made external orthosis, or helmet. See, e.g., Corrective Infant Helmet, U.S. Pat. No. 6,592,536 (filed Jan. 7, 2000) (issued Jul. 15, 2003); Therapeutic and Protective Infant Helmets, U.S. Pat. No. 4,776,324 (filed Apr. 17, 1998) (issued Oct. 11, 1998). Such devices provide an expanded area over the site of the deformity, thereby allowing for correction of the deformity over a three- to six-month period of time related to brain and skull growth and subsequent reshaping. This prolonged time of use is necessary because of the reduced rate of brain and skull growth during the six- to twelve-month time frame. Due to a decrease in the rate of brain and skull growth to approximate fifty percent of the rate from birth to six months and increased stiffness of bones and cranial sutures, the recommendation is to wear the helmet continuously for twenty-three hours each day for up to twelve months. But despite extended use of these helmets, deformities rarely return to a normal shape. In addition, many health insurance companies and programs refuse to pay for these devices, leaving a large number of infants with no available treatment because of the relatively high cost of the helmets. 
         [0015]    Another approach to correcting cranial deformities is to soften the material on which the infant&#39;s head rests by using a foam pad or memory foam pillow. This method allows the redistribution of inwardly directed forces over a slightly larger surface area, but fails to adequately correct cranial deformities because the softened material conforms to the head shape. The material still contacts, and therefore applies forces to, flattened areas instead of only the abnormal cranial bulges. Preventing cranial deformities with this approach is also ineffective because forces continue to act directly on a focused area of the head. Forces acting on a smaller area of the head results in cranial flattening, and therefore an abnormal head shape, because the head conforms to the shape of the material at the point of contact. 
         [0016]    Still another approach is to suspend the infant&#39;s head on a flexible material, which, for example, may be a net with an open weave that keeps the infant&#39;s head slightly elevated over the resting surface. See Method and Apparatus to Prevent Positional Plagiocephaly in Infants, U.S. Pat. No. 6,052,849 (filed Mar. 18, 1999) (issued Apr. 25, 2000). Although the use of an elastic stretchable material or netting may be slightly better than regular foam for preventing the development of flattened areas, these devices do not promote normal shaping due to the continuous application of external forces directed at a smaller posterior aspect of the infant&#39;s head. As with the “softened material” approach previously described, forces acting on a smaller area of the head results in cranial flattening because the head conforms to the shape of the stretched material, thus resulting in an abnormal head shape in which the frontal areas are wider than the posterior aspect of the head. 
         [0017]    After ten to twelve months of age, little, if any, correction of a cranial deformity can be accomplished with non-operative treatment because of reduced velocity of brain and skull growth, increased thickness of bone, and reduced flexibility of the cranial sutures. Surgical intervention is typically the only effective treatment for moderate to severe deformities in children over twelve months of age. 
         [0018]    The prior art for treating this condition does not directly address the cause of the problem, and therefore does not effectively treat the condition. All other products and devices, including foam, elastic (and therefore flexible) material or netting, merely distribute or disperse forces over a larger area of the head. Because these products and devices remain in contact with the skin, they therefore conform the cranium to the abnormal shape. Thus, the prior art does not remove or eliminate the external forces at flattened areas of the cranium, but rather maintains an abnormal cranial shape and promotes a static deformity. 
         [0019]    Currently there is no specific apparatus available to provide effective corrective and preventative treatment for non-synostotic cranial deformities in the age range of birth to five months. To avoid the difficulties and pitfalls associated with currently available devices aimed at treating non-synostotic cranial deformities, the present invention discloses a corrective headrest for use at the very first recognition of development of a deformity. The headrest and method allow effective treatment during the rapid period of brain and skull growth (birth to six months), thereby providing rapid correction of the deformity. Children with predisposing conditions possibly require prolonged treatment. Early effective treatment is the key to providing complete correction of these deformities. 
       BRIEF SUMMARY OF THE INVENTION 
       [0020]    The present invention discloses a mattress incorporating a headrest for correcting and preventing the shape of an infant&#39;s abnormally-shaped cranium by applying external forces over time with the growth of an infant to achieve normal shaping of the infant&#39;s head. Unlike the prior art, the present invention both 1) prevents abnormal shaping of an infant&#39;s cranium by causing even growth of the infant&#39;s normally shaped head and 2) provides forces that act unevenly across an abnormally shaped cranium to correct existing cranial deformities. The embodiments of the present invention include a mattress incorporating a headrest having a depression that approximates the posterior and side aspects of the skull and head, with cervical, or neck, support. The headrest can be formed as part of the mattress or as a separate piece that fits and is received into a cavity in the mattress. The headrest material that contacts the infant&#39;s cranium is semi-rigid and relatively non-flexible, maintains its overall shape under stress, and demonstrates minimal superficial focal elasticity only at the site of cutaneous contact. 
         [0021]    The mattress is concave with raised sides and maintains the infant in a supine position. A raised leg rest supports the infant&#39;s knees and helps position the infant so that the infant&#39;s head rests within the depression in the headrest. 
         [0022]    To correct existing cranial deformities, the headrest of the present invention applies inwardly-directed external forces only to areas of bony prominence and minimizes (or altogether eliminates) these forces on the areas of the skull that are less prominent (or flattened). The present invention is non-conforming to the shape of an abnormal skull. The forces exerted allow for accelerated expansion of the skull in the less prominent (flattened) areas coincident with brain and skull growth, allowing for return to a normal symmetric cranial shape. 
         [0023]    The headrest prevents development of abnormal cranial shaping by providing a round, normally-shaped contour for the posterior and side aspects of the head, even if the head is turned slightly to one side or the other. Because the contour is normally shaped, substantially the entire surface area of the normally-shaped cranium that rests in the depression continuously contacts the surface of the headrest. Moreover, because the contacting surface is semi-rigid, the surface will allow for even cranial growth over this area of contact, thereby maintaining the infant&#39;s normal head shape. 
         [0024]    The preferred embodiment of the headrest of the present invention is made from a self-skinning foam, which provides ease of cleaning as well as flame retardant properties. Other embodiments of the present invention are made from other foam variants and/or materials, including closed cell foam and closed cell foam layered over or applied to more rigid solid or hollow plastic (e.g., PVC or nylon). In addition, the present invention may be made from open cell foam to which has been applied a surface treatment, such as a vinyl or other coating, impregnating paint into the surface during the molding process, or painting the surface. 
     
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0025]    The present invention, as well as further objects and features thereof, are more clearly and fully set forth in the following description of the preferred embodiments, which should be read with reference to the accompanying drawings, wherein: 
           [0026]      FIG. 1  shows a perspective view of the preferred embodiment of the present invention; 
           [0027]      FIG. 2  illustrates a sectional view of the preferred embodiment along section line  2 - 2  of  FIG. 1 ; 
           [0028]      FIG. 3  shows a perspective view of an infant positioned in the preferred embodiment of the present invention; 
           [0029]      FIG. 4  is a perspective view of an alternative embodiment of the present invention that incorporates a harness and leg rest; 
           [0030]      FIG. 5  illustrates a sectional view of the preferred embodiment along section line  5 - 5  of  FIG. 4 ; 
           [0031]      FIG. 6A  and  FIG. 6B  depict the leg rest of the alternative embodiment; 
           [0032]      FIG. 7  illustrates an exploded view of the alternative embodiment of the present invention; 
           [0033]      FIG. 8  is a perspective view of an infant positioned in the alternative embodiment of  FIG. 4 ; 
           [0034]      FIG. 9  shows a perspective view of a second alternative embodiment of the mattress wherein a headrest portion of the top surface is inclined relative to a body portion of the mattress; 
           [0035]      FIG. 10  is a sectional view of the second alternative embodiment along section line  10 - 10  of  FIG. 9 ; 
           [0036]      FIG. 11  discloses a perspective view of a third alternative embodiment of the present invention having a removable headrest; 
           [0037]      FIG. 12  illustrates a sectional view of the third alternative embodiment along section line  12 - 12  of  FIG. 11 ; 
           [0038]      FIG. 13  shows a partially exploded view of the third alternative embodiment; and 
           [0039]      FIG. 14  depicts a perspective view of the removable headrest of the third embodiment in greater detail. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0040]      FIGS. 1 ,  2  and  3  depict the preferred embodiment of present invention, which is a mattress incorporating a headrest for preventing and correcting non-synostotic cranial deformities in infants. 
         [0041]      FIGS. 1 and 3  show a perspective view of the mattress  20 .  FIG. 2  illustrates a sectional view of the preferred embodiment along section line  2 - 2  of  FIG. 1 . 
         [0042]    As shown in  FIGS. 1 ,  2  and  3 , the mattress  20  comprises a bottom surface  22  and a top surface  24 . A body portion  26  of the top surface  24  of the mattress  20  is concave and has raised sides  28  to prevent an infant lying on the mattress  20  from rolling or moving from the infant&#39;s sleeping or resting position, as shown in  FIG. 3 . A headrest portion  30  of the mattress  20  further comprises a generally hemi-ellipsoidal depression  32  in the top surface  24  that corresponds to the shape of a normal infantile cranium. A semi-rigid surface  34  of the depression  32  is resilient, and preferably made of self-skinning foam. A ridge  36  is adjacent to one end of the depression  32 , and a curved intermediate surface  38  positioned between the ridge  36  and the body portion  26  of the mattress  20 . A rim  40  defines a substantial portion of the outer edge of the depression  32 . 
         [0043]    The mattress  20  is preferably a single body molded from a self-skinning foam material. Alternatively, the mattress  20  may be made from a number of foam variants, including closed cell foam layered over higher density foam or layered over a more rigid solid or hollow plastic. In addition, the mattress  20  may be made from open cell foam to which has been applied a surface treatment such as, for example, using a vinyl or other coating, impregnating paint into the surface during the molding process, or painting the surface. 
         [0044]      FIG. 3  depicts the preferred embodiment of the present invention in normal operation for the correction of an abnormally shaped infant cranium  42 . The mattress  20  is placed on a resting surface (not shown) so that the bottom surface  22  is in contact therewith. The infant&#39;s cranium  42  is placed in the depression  32  with the infant&#39;s cranium  42  resting on the semi-rigid surface  34  of the depression  32  and the infant&#39;s neck  44  being supported by the ridge  36 . The infant&#39;s body  46  is positioned in the body portion  26  of the mattress  20 , where the raised sides  28  aid in preventing the infant  48  from rolling or moving from a sleeping or resting position. Initially the posterior and part of the side aspects of the infant&#39;s cranium  42  contact the semi-rigid surface  34  in the depression  32 , although during the sleep period the infant&#39;s cranium  42  may roll to one side or the other. Throughout the sleep period, the infant&#39;s neck  44  is supported by the ridge  36 . The infant&#39;s shoulders  50  are aligned in and cradled by the curved intermediate surface  38 . 
         [0045]    As the infant&#39;s cranium  42  makes contact with the semi-rigid surface  34  in the depression  32 , the semi-rigid surface  34  provides external forces acting on any abnormal bulges of the infant&#39;s cranium  42  and diminishes or eliminates external forces that act on abnormal depressions of the infant&#39;s cranium  42 . This contact reduces the net outward forces from brain and skull growth at these bulges, and redirects the growth to areas of depression in the cranium  42  which are lightly touching or not in contact with the semi-rigid surface  34 . 
         [0046]    The mattress  20  works similarly to prevent cranial deformities. With the infant&#39;s cranium  42  placed in the depression  32 , the semi-rigid surface  34  of the depression  32  matches the round, normally-shaped contour of the posterior and side aspects of the infant&#39;s cranium  42 . Thus, the semi-rigid surface  34  substantially and continuously contacts the entire surface area of the cranium  42  within the depression  32 . Forces from the semi-rigid surface  34  act on the area of the cranium  42  in contact with the semi-rigid surface  34 . The resulting pressure causes the infant&#39;s cranium  42  to grow evenly and maintain its normal shape. In other words, the contour of the normally-shaped semi-rigid surface  34  allows for the development of normal cranial shaping regardless of the cranium&#39;s  42  resting position by preventing abnormal growth (i.e., cranial bulges and cranial depressions) in the area of contact with the semi-rigid surface  34 . The pressure caused by the forces acting on the cranium from the semi-rigid surface  34  is preferably substantially isometric. 
         [0047]      FIG. 4  through  FIG. 8  depict a first alternative embodiment of the present invention. As shown in  FIGS. 4 ,  5 , and  7 , the mattress  60  comprises a bottom surface  62  and a top surface  64 . A body portion  66  of the top surface  64  of the mattress  60  is concave and has raised sides  68  to prevent an infant lying on the mattress  60  from rolling or moving from the infant&#39;s resting or sleeping position. The mattress  60  further comprises a generally hemi-ellipsoidal depression  70  in the top surface  64  that corresponds to the shape of a normal infantile cranium. A semi-rigid surface  72  of the depression  70  is resilient, and preferably made of self-skinning foam. A ridge  74  is adjacent to one end of the depression  70 , and a curved intermediate surface  76  is positioned between the ridge  74  and concave body portion  66  of the mattress  60 . A rim  78  defines a substantial portion of the outer edge of the depression  70 . 
         [0048]    The mattress  60  of this alternative embodiment includes a leg rest  80  for positioning an infant&#39;s legs thereon to increase the infant&#39;s comfort and to more effectively immobilize the infant during use, as will be described hereinafter. The leg rest  80  is preferably made from foam, although any material that comfortably supports the infant&#39;s legs may be used. Flame retardant materials and water-resistant materials may also be preferred over other materials. 
         [0049]    As shown by  FIG. 6A  and  FIG. 6B , the bottom surface  86  of the leg rest  80  conforms to the shape of the top surface  64  of the concave body portion  66  of the mattress  60  so that when the leg rest  80  is placed on the top surface  64 , the bottom surface  86  of the leg rest  80  is flush with the top surface  64  of the body portion  66  of the mattress  60  (see  FIGS. 4 &amp; 5 ). The leg rest  80  further comprises a first side  88  and a second side  90  on which the infant&#39;s legs rest, the first side  88  supporting the legs  82  above the knees  92  and the second side  90  supporting the legs  82  below the knees  92  (see  FIG. 8 ). The first side  88  and second side  90  meet at an apex  93  and are each adjacent to the bottom surface  86  of the leg rest  80 . 
         [0050]    A positioning tab  94  protrudes from the bottom surface  86  of the leg rest  80  and is preferably formed from the same material as the rest of the leg rest  80 . As shown in  FIG. 5  and  FIG. 7 , a plurality of positioning slots  96  are longitudinally aligned in the top surface  64  of the concave body  66  portion of the mattress  60  and positioned to receive the positioning tab  94 . The positioning slots  96  are spaced to accommodate the leg position of infants of different lengths. By inserting the positioning tab  94  into one of the plurality of slots  96 , the leg rest  80  may be longitudinally positioned for an infant&#39;s length and relatively immobilized. 
         [0051]    Referring again to  FIGS. 4 and 5 , a three-point restraint harness  102  with a leg strap  100  and two shoulder straps  104  is affixed to the mattress  60 . The non-buckling end of the leg strap  100  is stitched into the top surface  64  of the mattress  60  adjacent to the end of the mattress  60  opposite the headrest portion  106 . Preferably the non-buckling end of each of the shoulder straps  104  is stitched to the rim  78  of the depression  70 , although it is anticipated that the shoulder straps  104  could be secured to the ridge  74 , the intermediate surface  76 , or the top surface  64  of the headrest portion  106  instead. It is also contemplated that other means of securing the harness  102  to the mattress  60 , such as fastening or adhesively securing the harness  102  to the top surface  64 , may be used. Alternatively the leg strap  100  and shoulder straps  104  may be disposed through the mattress and secured to the bottom surface  62  using hook-and-loop materials or other securing means. Similarly, a single shoulder strap  104  could be looped through securing slots (not shown) disposed through the headrest portion  106  of the mattress  60 , as described with reference to  FIG. 12 . Moreover, other alternative embodiments of the mattress  60  contemplate the use of other restraint harnesses, such as a five-point restraint harness. 
         [0052]      FIG. 8  is a perspective view of the first alternative embodiment of the present invention in normal operation with an infant  84  positioned on the mattress  60 . For correction of an abnormally shaped infant cranium  105 , the mattress  60  is placed on a resting surface (not shown) so that the bottom surface  62  is in contact therewith. Prior to placing the infant  84  on the mattress  60 , the leg rest  80  is moved to a position accommodating the size of the infant  84  such that when the infant&#39;s cranium  105  is placed in the depression  70 , the infant&#39;s knees  92  will be located over the apex  93  of the leg rest  80 . In this position, the portion of the infant&#39;s legs  82  above the knees  92  is supported by the first side  88  of the leg rest  80 , and the portion of the infant&#39;s legs  82  below the knees  92  is supported by the second side  90  of the leg rest  80 . 
         [0053]    The infant  84  is then placed in the mattress  60  in a supine position where the infant&#39;s cranium  105  rests in the depression  70 . When in this position, the infant&#39;s neck  108  rests on the ridge  74 , which provides support for the infant&#39;s neck  108  and makes sleeping and resting more comfortable. The infant&#39;s body  110  rests on the concave body portion  66  of the mattress  60 . Should the infant  84  try to roll or move from a supine the position, the raised sides  68  of the top surface  64  impede the rolling or moving action, thus helping to prevent the infant  84  from inadvertently repositioning to a sideways or prone position on the mattress  60 . Initially the posterior and part of the side aspects of the infant&#39;s cranium  105  contact the semi-rigid surface  72  of the depression  70 , although during the sleep period the infant&#39;s cranium  105  may roll to one side or the other. In addition, the leg rest  80  aids in immobilizing the infant  84  while providing greater comfort by allowing a bend in the infant&#39;s legs  82 . The infant&#39;s shoulders  112  are aligned in and cradled by the curved intermediate surface  76 . The leg strap  100  and shoulder straps  104  of the restraint harness  102  are thereafter fastened at the buckle  114 . The leg strap  100  is placed across the leg strap guide  98  at the apex  93  of the leg rest  80 , which helps to prohibit agitating contact between the leg strap  100  and the infant  84 . After fastening the leg strap  100  to the shoulder straps  104 , the harness  102  is adjustable to the size of the infant&#39;s body  110 , and the shoulder straps  104  and leg strap  100  may be tightened to fit snugly but comfortably therebout. 
         [0054]    As the infant&#39;s cranium  105  makes contact with the semi-rigid surface  72 , the semi-rigid surface  72  provides external forces acting on any abnormal bulges of the infant&#39;s cranium  105  and diminishes or eliminates external forces that act on abnormal depressions of the infant&#39;s cranium  105 . This contact reduces the net outward forces from brain and skull growth at the bulges, and redirects the growth to areas of depression in the cranium that are lightly touching or not in contact with the semi-rigid surface  72 . 
         [0055]    The mattress  60  works similarly to prevent cranial deformities. With the infant&#39;s cranium  105  placed in the depression  70 , the semi-rigid surface  72  of the depression  70  matches the round, normally-shaped contour of the posterior and side aspects of the infant&#39;s cranium  105 . Thus, the semi-rigid surface  72  substantially and continuously contacts the entire surface area of the cranium  105  within the depression  70 . Forces from the semi-rigid surface  72  act on the area of the cranium  105  in contact with the semi-rigid surface  72 . The resulting pressure causes the infant&#39;s cranium  105  to grow evenly and maintain its normal shape. In other words, the contour of the normally-shaped semi-rigid surface  72  allows for the development of normal cranial shaping regardless of the cranium&#39;s  105  resting position by preventing abnormal growth (i.e., cranial bulges and cranial depressions) in the area of contact with the semi-rigid surface  72 . The pressure caused by the forces acting on the cranium from the semi-rigid surface  72  is preferably substantially isometric. 
         [0056]      FIG. 9  and  FIG. 10  (in combination with  FIGS. 6A  &amp;  FIG. 6B ) depict a second alternative embodiment of the present invention.  FIG. 9  shows this embodiment of the mattress  120  wherein a headrest portion  122  of the mattress  120  is angled relative to a body portion  124  of the mattress  120 . 
         [0057]    As shown in  FIGS. 9 and 10 , the mattress  120  comprises a bottom surface  126  and a top surface  128 . A body portion  124  of the top surface  128  of the mattress  120  is concave and has raised sides  130  to prevent an infant (not shown) lying on the mattress  120  from rolling or moving from the infant&#39;s resting or sleeping position. The top surface  128  of the headrest portion  122  of the mattress  120  is inclined relative to the body portion  124  of the mattress  120 . The headrest portion  122  of the mattress  120  further comprises a generally hemi-ellipsoidal depression  132  in the top surface  128  of the headrest portion  122 . The depression  132  corresponds to the shape of a normal infantile cranium. A semi-rigid surface  135  of the depression  132  is resilient, and preferably made of self-skinning foam. A ridge  134  is adjacent to one end of the depression  132 , and a curved intermediate surface  136  is positioned between the ridge  134  and the concave body portion  124  of the top surface  128 . A rim  138  defines a substantial portion of the depression  132 . 
         [0058]    This alternative embodiment includes a leg rest  80  for positioning an infant&#39;s legs thereon to increase the infant&#39;s comfort and to more effectively immobilize the infant during use, as is described with reference to  FIGS. 6A and 6B . This alternative embodiment also contemplates a three-point restraint harness  102  with a leg strap  100  and two shoulder straps  104  affixed to the mattress  120 , as has been previously described with reference to the first alternative embodiment. Moreover, other alternative embodiments of the invention contemplate the use of other restraint harnesses, such as a five-point restraint harness. Use of the harness  102  is as described with reference to  FIG. 4  through  FIG. 8 . 
         [0059]    The mattress  120  is preferably a single body molded from a self-skinning foam material. The mattress  120 , however, may alternatively be made from a number of other materials, including closed cell foam layered over higher density foam or layered over a more rigid solid or hollow plastic. In addition, the mattress  120  may be made from open cell foam to which has been applied a surface treatment such as, for example, a vinyl or other coating, impregnating paint into the surface during the molding process, or painting the surface. 
         [0060]    The embodiment disclosed by  FIG. 9  and  FIG. 10  is used in the same manner as the previously-described embodiments to correct and prevent abnormal cranial bulges and depressions in an infant&#39;s cranium. Because the headrest portion  122  of this is embodiment is angled relative to the body portion  124  of the mattress, the infant&#39;s head will be supported at an angle relative to the infant&#39;s body. In combination with the support provided to the infant&#39;s neck from the ridge  134  and to the infant&#39;s shoulders from the curved intermediate surface  136 , this embodiment may provide a more comfortable resting position by elevating the infant&#39;s head. 
         [0061]      FIGS. 11 through 14  depict a third alternative embodiment of the present invention that incorporates a removable headrest  170 . As shown in  FIGS. 11 through 13 , and as shown in the embodiments previously described, a mattress  160  has a top surface  164  having a body portion  162  that is concave and has raised sides  166  to prevent an infant lying on the mattress  160  from rolling or moving from the infant&#39;s sleeping or resting position. A leg rest  80  as has been previously described and shown in  FIGS. 6A and 6B  is placed on the top surface  164  for positioning an infant&#39;s legs thereon to increase the infant&#39;s comfort and to more effectively immobilize the infant during use. A three-point restraint harness  102  with a leg strap  100  and two shoulder straps  104  (or a five-point restraint harness) is also affixed to the mattress  160 , as has been previously described with reference to  FIG. 4  through  FIG. 10 . The headrest portion  168  of the top surface  164  of the mattress  160  includes a cavity  169  that is positioned, shaped, and sized to receive the removable headrest  170 . 
         [0062]      FIG. 13  illustrates an exploded view of the embodiment shown in  FIGS. 11 and 12 . The cavity  169  is positioned, shaped, and sized to receive the removable headrest  170  such that a sidewall  167  of the cavity  169  contacts a side surface  183  of the headrest  170  so that the headrest  170  fits snugly in the cavity  169 . The two shoulder straps  104  of the restraint harness  102  extend through strap holes  171  disposed through the headrest portion  168  of the mattress  160  to the bottom surface  126 . An opening of each of the strap holes  171  is positioned in the cavity surface  165  such that it will align with one of the strap slots  184  in the removable headrest  170  when the headrest  170  is placed into the cavity  169  (see  FIG. 12 ). The ends of the shoulder straps  104  are secured to the bottom surface  126  using a hook-and-loop material, although it is anticipated that other means of securing the shoulder straps  104  to the bottom surface  126 , such as adhesively securing or stitching, may be used. The shoulder straps  104  may thereafter be positioned in the strap slots  184  of the removable headrest  170  as the headrest  170  is received by the cavity  169 . 
         [0063]    Alternatively, instead of two shoulder straps  104  as shown in  FIGS. 11 through 13 , a single strap  104  may be used by threading the strap  104  downwardly through one strap hole  171  to the bottom surface  126 , across the bottom surface  126  of the mattress  160 , upwardly through another strap hole  171 , and outwardly from the cavity surface  165 . Thus, a single strap  104  may be looped through the headrest portion  168  of the mattress  160 . 
         [0064]    As shown in  FIG. 11 , prior to placing the infant on the mattress  160 , the removable headrest  170  is inserted into the cavity  169 , which includes positioning the shoulder straps  104  through strap slots  184  in the headrest  170 . The headrest&#39;s bottom surface  182  contacts the cavity surface  165 , while the headrest&#39;s side surface  183  contacts the sidewall  167  of the cavity  169  to aid in immobilizing the headrest  170  relative to the headrest portion  168  of the mattress  160 . In alternative embodiments, the headrest  170  may additionally be secured to the cavity surface  165  using a hook-and-loop material or other fastening means. 
         [0065]    Also prior to placing the infant on the mattress  160 , the leg rest  80  is moved to a position accommodating the size of the infant such that when the infant&#39;s cranium is placed in the depression  172 , the infant&#39;s knees will be located over the apex  93  of the leg rest  80 . The restraint harness  102  is secured about the infant as described hereinabove with reference to the other disclosed embodiments. Thereafter, the infant is placed in the mattress  160  in a supine position where the infant&#39;s cranium rests in the depression  172 . 
         [0066]      FIG. 14  depicts the removable headrest  170  in greater detail. The removable headrest  170  includes the bottom surface  182 , the side surface  183 , and a semi-rigid top surface  174  having a generally hemi-ellipsoidal depression  172  that corresponds to the shape of a normal infantile cranium. An outer rim  180  defines a substantial portion of the depression  172 . The two strap slots  184  are disposed in the rim  180  and extend through the headrest  170  to its bottom surface  182 . While the removable headrest  170  is itself preferably self-skinning foam, it may alternatively be made from a number of foam variants or other materials, including closed cell foam layered over higher density foam or layered over a more rigid solid or hollow plastic. In addition, the removable headrest  170  may be made from open cell foam to which has been applied a surface treatment such as a vinyl or other coating, impregnating paint into the surface during the molding process, or painting the surface. Use of this third alternative embodiment to correct and/or prevent cranial deformities in infants is thereafter the same as described with reference to the other embodiments. 
         [0067]    The present invention is described above in terms of a preferred illustrative embodiment of a specifically described mattress incorporating a headrest, as well as alternative embodiments of the present invention. Those skilled in the art will recognize that alternative constructions of such a mattress can be used in carrying out the present invention. For example, although some of the embodiments described herein include a leg rest, other embodiments may not include a leg rest. Similarly, although some of the embodiments described herein include a three-point restraint harness, other embodiments may omit such a harness or include an alternative type of harness (e.g., a five-point restraint harness). Accordingly, other aspects, features, and advantages of the present invention may be obtained from a study of this disclosure and the drawings, along with the appended claims.