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Idiopathic clubfoot, one of the most common problems in pediatric orthopaedics, is characterized by a complex three-dimensional deformity of the foot. The treatment of clubfoot is controversial and continues to be one of the biggest challenges in pediatric orthopaedics. This controversy is due in part to the difficulty in measuring and evaluating the effectiveness of different treatment methods. We believe the heart of the debate is a lack of understanding of the functional anatomy of the deformity, the biological response of young connective tissue to injury and repair, and their combined effect on the long-term treatment outcomes. The aim of this review is not only to assess the different methods of clubfoot treatment used over the years in light of an evolving understanding of the pathoanatomy of the deformity, but to also clarify factors that allow a safe, logical approach to clubfoot management. Further research will be needed to fully understand the pathogenesis of clubfoot, as well as the long-term results and quality of life for the treated foot.

Triple arthrodesis is used to treat major deformities of the hindfoot and is often performed in young patients. The purpose of this study was to assess the long-term outcomes of triple arthrodesis in young patients.Sixty-seven feet of fifty-seven patients were evaluated at an average of twenty-five and forty-four years after triple arthrodesis. The most common indication for the operation was neuromuscular imbalance of the hindfoot, which was secondary to poliomyelitis in thirty-seven feet (55 percent), Charcot-Marie-Tooth disease in six (9 percent), spinal cord abnormalities in four (6 percent), cerebral palsy in three (4 percent), and Guillain-Barré syndrome in one (1 percent).Fifty-two feet (78 percent) had some residual deformity after the arthrodesis. However, these deformities appeared to be nonprogressive between 1973 and 1994. Pseudarthrosis occurred in thirteen feet. Thirty feet or ankles (45 percent) were painful at the first follow-up evaluation, and thirty-seven feet or ankles (55 percent) were painful at the second follow-up evaluation. Of the thirty feet or ankles that were painful at the first follow-up evaluation, twenty-three were painful at the second follow-up evaluation. Of the thirty-seven feet or ankles that were not painful at the first follow-up evaluation, fourteen were painful at the second follow-up evaluation. Eighteen patients (32 percent) needed walking support at the time of the first follow-up, and thirty-nine patients (68 percent) needed it at the time of the second follow-up. Two of the patients who needed support at the first follow-up evaluation did not need it at the second follow-up evaluation. At the first follow-up evaluation, twenty-one ankles (31 percent) had no radiographic evidence of degenerative changes. However, by the second follow-up evaluation, all of the ankles had some degenerative changes. Similar progressive arthritic findings were noted at the naviculocuneiform and tarsometatarsal joints. According to the system of Angus and Cowell, the overall result at the time of the first follow-up was rated as good in fifty feet (75 percent) and as fair in seventeen feet (25 percent). At the time of the second follow-up, nineteen feet (28 percent) were rated as good, forty-six (69 percent) were rated as fair, and two (3 percent) were rated as poor.Despite progressive symptoms and radiographic degeneration in the joints of the ankle and midfoot, fifty-four patients (95 percent) were satisfied with the result of the operation. The triple arthrodesis was a satisfactory solution for imbalance of the hindfoot in this group of patients.

Two feet with congenital metatarsus adductus from fetuses at early development (16 and 19 weeks of gestation) were studied by making serial histologic sections in the horizontal plane of the foot. It was observed that the shape of the medial cuneiform was altered and the first cuneometatarsal joint tilted toward the medial and dorsal directions. The first metatarsal appeared normal, whereas the other metatarsals were deformed in slight adduction at the metaphyseal level. Subluxation at the other cuneometatarsal joints and naviculocuneiform joint was not observed, and the navicular showed no signs of medial or lateral displacement in relation to the head of the talus. No histologic abnormalities of the joint capsules, ligaments, or tendons were observed. On the basis of these pathologic findings, the possibility of a developmental abnormality of the medial cuneiform as a pathogenic factor for the congenital metatarsus adductus deformity should be considered.

The ligamenta flava of the thoracolumbar spine of mammals with great spinal mobility have a larger content of elastin than in animals with little spinal motion. The elastin content is also higher in the ligamenta flava of mammals with arched backs and prolonged sitting posture than in nonsitting mammals with the vertebral column in the shape of a flat bow. The ligamentum flavum appears to be important; a) in the control of intervertebra movements, b) in providing intrinsic stability to the spine in the sitting and standing postures and c) in maintaining a smooth surface in the posterior wall of the spinal canal and neural foraminae.

Two feet with congenital metatarsus adductus from fetuses at early development (16 and 19 weeks of gestation) were studied by making serial histologic sections in the horizontal plane of the foot. It was observed that the shape of the medial cuneiform was altered and the first cuneometatarsal joint tilted toward the medial and dorsal directions. The first metatarsal appeared normal, whereas the other metatarsals were deformed in slight adduction at the metaphyseal level. Subluxation at the other cuneometatarsal joints and naviculocuneiform joint was not observed, and the navicular showed no signs of medial or lateral displacement in relation to the head of the talus. No histologic abnormalities of the joint capsules, ligaments, or tendons were observed. On the basis of these pathologic findings, the possibility of a developmental abnormality of the medial cuneiform as a pathogenic factor for the congenital metatarsus adductus deformity should be considered.

Histological and histochemical studies of the spine of a sixteen-year-old boy with juvenile kyphosis who was killed in an automobile accident showed abnormal cartilage in extensive areas of the vertebral and growth plates of the involved vertebrae. In these areas the cartilage matrix was loose, strongly positive when stained with alcian blue and weakly positive to periodic acid-Schiff, and it contained numerous chondrocytes. Some chondrocytes were irregularly shaped and others were in clusters. Vertebral bone growth was stunted under the areas of abnormal vertebral and growth plates. The ossification in the ring apophyses was irregular in areas of abnormal cartilage plate, but necrotic bone was not seen. Schmorl nodes had formed where areas of abnormal cartilage plate adjoining the nucleus pulposus had collapsed, allowing the disc material to herniate into the vertebral body. Clinical Relevance: The defective vertebral-bone formation in juvenile kyphosis appears to result from abnormal vertebral and growth-plate cartilage. The kyphosis and presumably also the cartilage abnormality can be improved during the florid stage of the disease by decreasing the postural load on the anterior part of the vertebrae with the use of a proper brace.

A study of acetabular development in 148 patients with 185 congenitally dislocated hips treated by closed reduction from 1940 to 1968 showed that eight years after reduction the acetabular index was normal (less than 20 degrees) in 49.2 per cent, satisfactory (from 20 to 24 degrees) in 34 per cent, and poor (more than 24 degrees) in 16.7 per cent. Early treatment led to the best acetabular development. Significant and continuing improvement of the acetabular index was observed between two and eight years after reduction when the femoral head remained concentrically reduced. Failure to maintain proper reduction and necrosis of the femoral head led to poor results.

Postmortem studies of ten normal full-term infants and of three children, seven, nine, and fourteen years old, showed that the acetabular cartilage complex is a unit that is triradiate medially and cup-shaped laterally and is interposed between the ilium, ischium, and pubis. This complex is composed of epiphyseal growth-plate cartilage adjacent to these bones, of articular cartilage adjacent to these bones, of articular cartilage around the acetabular cavity, and, for the most part, of hyaline carilage. Interstitial growth within the triradiate part of the cartilage complex causes the hip socket to expand during growth. The concavity of the acetabulum develops in response to the presence of the spherical femoral head. The depth of the acetabulum increased during development as the result of interstitial growth in the acetabular cartilage, of appositional growth at the periphery of this cartilage, and of periosteal new-bone formation at the acetabular margin. At puberty, three secondary centers of ossification appear in the hyaline cartilage surrounding the acetabular cavity. These centers are homologous with other epiphyses in the skeleton. The os acetabuli, which is the epiphysis of the os pubis, forms the anterior wall of the acetabulum. The epiphysis of the ilium, which has been called the acetabular epiphysis, forms a good part of the superior wall of the acetabulum. A small epiphysis of the ischium was seen in the oldest patient, who was fourteen years old. The bone in these epiphyses expands toward the periphery of the acetabulum and thus contributes to its increase in depth.

We evaluated 121 patients who had had slipped capital femoral epiphysis (149 involved hips) twenty-one to forty-seven years after the diagnosis was made. The results were very good in most of the eighty-three hips with the slip left unreduced. Fifty-four hips that were treated by procedures designed to improve the alignment of the slipped femoral head had more complications and less favorable results, but in general, these were the more severe slips. However, there were enough slips of comparable severity that were treated unreduced to suggest that the long-term results, even in moderate and severe slips, were better after in situ fixation than after operative and manipulative treatment (as performed between 1915 and 1952). Twelve of the thirteen hips with acute slips were reduced (the thirteenth was one of the eighty-three unreduced hips) and aseptic necrosis developed in three, while nine had good results.

Two hundred and nineteen patients with untreated adolescent idiopathic scoliosis who were seen at the University of Iowa between 1932 and 1948 were studied, and recent information was available on 194 of the patients. The mortality rate was 15 per cent. Backache was somewhat more common in these patients than in the general population, although it was never disabling. The backache was unrelated to the presence of osteoarthritic changes on roentgenograms. Many curves continued to progress slightly in adult life, particularly thoracic curves that had reached between 50 and 80 degrees at skeletal maturity. The lumbar components of combined curves between 50 and 74 degrees also tended to progress. Pulmonary function was affected only in patients with thoracic curves.

Forty-two patients with congenital dislocation of the hip demonstrated good correlation between the arthrograms and the operative findings of a large ligamentum teres, an hourglass constriction of the capsule, a prominent transverse ligament and an acetabular bulge. The number of hips found at operation to have an inturned labrum was smaller than had been predicted on arthrogram. Larger percentages of hips with inturned labrum found at operation have been reported by other authors. We noted an acetabular bulge in a sizeable number of our patients. On arthrogram an inturned labrum has to be differentiated from the acetabular bulge and from an hourglass constriction. Open reduction is indicated when arthrogram indicates an interposition of a large ligamentum teres, an hourglass constriction, or a prominent transverse ligament. Isolated findings of an acetabular bulge or an inturned labrum on arthrogram are not indications for open reduction.

Thirty-two patients with treated unilateral clubfoot deformity were followed for a period of 13 to 30 years. The functional results were satisfactory in 28 feet. A comparison of the skeletal features of the normal and the clubfeet was made on roentgenographs. Many clubfeet had small, slightly flattened talar heads, decreased talocalcaneal angles, undersized or misshapen facets of the subtalar joint, and medially displaced navicular. The residual deformity of the hindfoot was compensated by the lateral displacement and lateral angulation of the cuneiforms with respect to the navicular resulting in a normal alignment of the forefoot in relation to the hindfoot. The range of ankle dorsiflexion, subtalar and midtarsal joint motion was restricted in the clubfeet.

An 8-year-old boy was diagnosed as having unilateral aseptic necrosis of the humeral trochlea on the basis of: loss of elbow carrying angle and decreased range of motion, radiographic demonstration of trochlear collapse and sclerosis. Partial resolution of the radiographic changes occurred within 17 months. In the absence of marked functional impairement, the treatment is conservative clinical observation.

Eight to 29 year follow-up investigation of the results of closed reduction in 40 completely dislocated hips in children, treated under one year of age, show that 92.5% of the hips had good functional results and 77.5% had good anatomical results. The slant and depth of the acetabular roof rapidly improved during the first year after reduction and slowly during the following 8 years. Femoral head necrosis occurred in 12 hips (30%). The necrosis was mild in 4 hips and severe in 8. The 8 hips with severe femoral head necrosis had poor anatomical results. Surprisingly, the development of the acetabulum was not influenced by femoral head necrosis. Femoral head necrosis was frequently observed when the head was in a high position in relation with the acetabulum prior to reduction. Closed reduction should not be attempted unless the head can be brought down below the level of the acetabulum.

A study of acetabular development in 148 patients with 185 congenitally dislocated hips treated by closed reduction from 1940 to 1968 showed that eight years after reduction the acetabular index was normal (less than 20 degrees) in 49.2 per cent, satisfactory (from 20 to 24 degrees) in 34 per cent, and poor (more than 24 degrees) in 16.7 per cent. Early treatment led to the best acetabular development. Significant and continuing improvement of the acetabular index was observed between two and eight years after reduction when the femoral head remained concentrically reduced. Failure to maintain proper reduction and necrosis of the femoral head led to poor results.

At autopsy, the hips of six infants who died soon after birth and had unilateral congenital hip dysplasia were found to have a cartilaginous ridge in the acetabulum which separated the hip socket into two sections. In two of the hips with a moderate degree of dysplasia and in one completely dislocated hip the ridge was formed exclusively by a bulge of acetabular cartilage. In three completely dislocated hips the ridge was formed by a bulge of acetabular cartilage covered by the inverted labrum. The acetabular cartilage showed signs of degeneration whereas the triradiate cartilage was normal. Examination of many newborn infants indicated that hip "clicks" are common and are not diagnostic of hip dysplasia. This diagnosis should be made only when the femoral head slides with a jolt over the acetabular ridge, causing a true positive Ortolani sign. Scattered ossification centers in the acetabular cartilage were seen on the roentgenograms of nearly half of fifty-nine hips with congenital dislocation reduced after the child was two years old, but less frequently in hips reduced at an earlier age.

We evaluated 121 patients who had had slipped capital femoral epiphysis (149 involved hips) twenty-one to forty-seven years after the diagnosis was made. The results were very good in most of the eighty-three hips with the slip left unreduced. Fifty-four hips that were treated by procedures designed to improve the alignment of the slipped femoral head had more complications and less favorable results, but in general, these were the more severe slips. However, there were enough slips of comparable severity that were treated unreduced to suggest that the long-term results, even in moderate and severe slips, were better after in situ fixation than after operative and manipulative treatment (as performed between 1915 and 1952). Twelve of the thirteen hips with acute slips were reduced (the thirteenth was one of the eighty-three unreduced hips) and aseptic necrosis developed in three, while nine had good results.

Histological and histochemical studies of the spine of a sixteen-year-old boy with juvenile kyphosis who was killed in an automobile accident showed abnormal cartilage in extensive areas of the vertebral and growth plates of the involved vertebrae. In these areas the cartilage matrix was loose, strongly positive when stained with alcian blue and weakly positive to periodic acid-Schiff, and it contained numerous chondrocytes. Some chondrocytes were irregularly shaped and others were in clusters. Vertebral bone growth was stunted under the areas of abnormal vertebral and growth plates. The ossification in the ring apophyses was irregular in areas of abnormal cartilage plate, but necrotic bone was not seen. Schmorl nodes had formed where areas of abnormal cartilage plate adjoining the nucleus pulposus had collapsed, allowing the disc material to herniate into the vertebral body.The defective vertebral-bone formation in juvenile kyphosis appears to result from abnormal vertebral and growth-plate cartilage. The kyphosis and presumably also the cartilage abnormality can be improved during the florid stage of the disease by decreasing the postural load on the anterior part of the vertebrae with the use of a proper brace.

Core biopsy specimens of the proximal femoral growth plate from three patients with slipped capital femoral epiphysis were studied by light and electron microscopy. In the resting zone, the cartilage matrix was composed of large, densely packed collagen fibrils. The cartilage matrix in the zones of chondrocyte hypertrophy where the slippage occurred contained only scattered fine collagen fibrils in a homogeneous ground substance. The change in composition of cartilage matrix in the distal region of the epiphyseal plate may predispose that region to slippage.

Sixteen patients with pseudarthrosis of the tibia and one of the radius were evaluated clinically, radiograpically, and microscopically and separated into 3 groups; 8 had neurofibromatosis clinically, 3 had fibrous dysplasia histologically, and 6 had no evidence of either neurofibromatosis or fibrous dysplasia. Prognosis and therapy were determined by correlated clinical, radiographic, and histological observations. Fracture before age 2 years carried a poor prognosis. Electron microscopy allowed neither differentiation among these fibrous lesions, nor any clue to their origin, nor did it support the concept of a neural or vascular derivation.

From January 1970 to December 1976, seventeen patients with twenty-two congenital hip dislocations were treated by open reduction through a medial approach. The average follow-up was 42.2 months. The patients were evaluated for acetabular development, aseptic necrosis, and intraoperative findings. The incidence of aseptic necrosis was 10 per cent. The acetabular index improved rapidly during the first year after reduction. After the first year the rate of development was decreased, but the acetabular index continued to improve throughout the period of study. The medial approach provides a safe, effective way to reduce a dislocated hip in infancy. This procedure is advocated when closed reduction cannot be obtained by gentle manipulation or maintained by positioning once reduction is done.

Five club feet and three normal feet of fetuses aborted at sixteen to twenty weeks of gestation were studied by making serial histological sections cut in the sagittal, frontal, and transverse planes. In the club feet we found gradations in the severity of the following abnormalities: 1. Altered shape, size, and relationships of the tarsal bones. 2. Decrease in the size and number of fibers in the distal third of the muscles of the posterior and medial aspect of the leg; increased fibrous connective tissue in these muscles, their tendon sheaths, and the adjacent fasciae; and shortening of the triceps surae. 3. Thickening of the distal parts of the tendo archillis and of the posterior tibial tendon. 4. Ligaments on the posterior and medial aspects of the ankle joint pulled into the joint by the severe plantar flexion and varus displacement of the talus, and marked shortening and thickening of the tibionavicular and plantar calcaneonavicular ligaments. On the basis of these pathological findings, the possibility of a retracting fibrosis as the primary etiological factor of the club-foot deformity should be considered.

Core biopsies of the proximal femoral growth plate from three patients with slipped capital femoral epiphysis were compared with three normal growth plates from patients of similar ages. The growth plates of patients with slipped capital femoral epiphysis had a normal resting zone, a loose and fibrillated proliferative zone, and a very disarranged and thickened hypertrophic zone. The proliferative zone stained strongly with alcian blue, suggesting the presence of abundant proteoglycans in the cartilage matrix. The thickened hypertrophic zone was strongly positive to periodic acid-Schiff stain, indicating the presence of abundant structural glycoproteins. Enchondral ossification was scanty and irregular, and there were large clusters of cartilage in the metaphysis. Slippage occurred through the thickened proliferative and hypertrophic zones.The proximal femoral growth plate in slipped capital femoral epiphysis is histochemically abnormal and histologically disarranged. These features contribute to abnormal widening of the growth plate and to further slippage.

One hundred and thirty-three curves in 102 patients who were followed for an average of 40.5 years were evaluated to quantitate curve progression after skeletal maturity and for prognostic factors leading to curve progression. Sixty-eight per cent of the curves progressed after skeletal maturity. In general, curves that were less than 30 degrees at skeletal maturity tended not to progress regardless of curve pattern. In thoracic curves the Cobb angle, apical vertebral rotation, and the Mehta angle were important prognostic factors. In lumbar curves the degree of apical vertebral rotation, the Cobb angle, the direction of the curve, and the relationship of the fifth lumbar vertebra to the intercrest line were of prognostic value. Translatory shifts played an important role in curve progression. Curves that measured between 50 and 75 degrees at skeletal maturity, particularly thoracic curves, progressed the most.

A review of the literature on Ehlers-Danlos syndrome with particular attention to vascular complications enabled us to outline an orderly diagnostic and therapeutic plan which has allowed salvage of an individual with a popliteal false aneurysm. In patients with Ehlers-Danlos syndrome and brachial, superficial femoral, or popliteal arterial disruption, the use of proximal tourniquet control to allow ligation of the disrupted artery under a no-flow, no-pressure situation is recommended. The ligations should be carried out with a large ligature or possibly with large hemoclips and/or reinforced with multiple fine atraumatic vascular sutures distally. These patients may be treated successfully for flexion contractures because of the laxness of their tissues.

In seventy patients with 104 club feet that were treated at our hospital and followed for ten to twenty-seven years after treatment, the functional results were satisfactory according to our rating system in 88.5 per cent of the feet, and 90 per cent of the patients were satisfied with both the appearance and function of the club foot. However, in the majority of the patients, foot and ankle motion was limited and the talocalcaneal angles as seen on the anteroposterior and lateral roentgenograms were not fully corrected. The amount of motion in the joints of the foot and ankle and the correction of the lateral talocalcaneal angle correlated with the degree of patient satisfaction and the functional rating of the club foot. Transfer of the anterior tibial tendon to the third cuneiform appeared to prevent relapse.

Biopsy specimens of the lateral aspect of the femoral head and neck were obtained from five children with Legg-Calvé-Perthes disease and were studied using histochemistry and electron microscopy. Beneath the normal articular cartilage there was a thick zone of hyaline (epiphyseal) cartilage containing sharply demarcated areas of hypercellular and fibrillated cartilage with prominent blood vessels. The fibrillated cartilage was strongly positive to alcian blue, weakly positive to periodic acid-Schiff, and positive to aniline blue. The interterritorial matrix in the hypercellular areas was weakly positive to both alcian blue and periodic acid-Schiff. Ultrastructural examination of these areas revealed many irregularly oriented large collagen fibrils and variable amounts of proteoglycan granules. These results suggest that in the fibrillar areas there are: (1) a high proteoglycan content, (2) a decrease in structural glycoproteins, and (3) a different size of collagen fibrils from that of normal epiphyseal cartilage. The hypercellular areas had a decrease in proteoglycans, glycoproteins, and collagen. The lateral physeal margin was often irregular, with a marked reduction of collagen and proteoglycan granules, and contained numerous large lipid inclusions.The abnormal areas in the epiphyseal cartilage of patients with Legg-Calvé-Perthes disease have different histochemical and structural properties from normal cartilage and from fibrocartilage. This suggests that the disease could be a localized expression of a generalized, transient disorder of epiphyseal cartilage that is responsible for delayed skeletal maturation. The cartilage lesions are similar to those seen in the vertebral plates in patients with juvenile kyphosis. Whether the epiphyseal cartilage abnormalities are primary or are secondary to ischemia remains uncertain; however, it appears that the collapse and necrosis of the femoral head could result from the breakdown and disorganization of the matrix of the epiphyseal cartilage, followed by abnormal ossification.

The center of pressure paths of foot-floor contact were examined in detail in normal subjects and a group of 44 patients with treated clubfeet. The foot-floor contact areas were wide and the center of pressure paths more variable in clubfeet patients. The center of pressure paths did not always distinguish between normal and abnormal subjects nor between abnormal subjects with varying functional ratings. Foot prints are not sensitive enough to be a diagnostic aid and are of only limited application to the problem of evaluation of treatment of clubfoot deformity.

Biopsy specimens of the spine, including intervertebral disc, vertebral plate, growth plate, and part of the vertebral body, were obtained from seven patients with juvenile kyphosis treated by anterior spinal arthrodesis. Histological and histochemical studies showed abnormal loose-appearing cartilage in both the vertebral plate and the growth plate. Both plates were missing in some vertebrae. Ultrastructurally the abnormal cartilage had a matrix rich in proteoglycans and very thin collagen fibrils. The mineralization and ossification of the vertebral plates were irregular. Vertebral bone growth was stunted under the areas of abnormal growth plates.

Postmortem studies of ten normal full-term infants and of three children, seven, nine, and fourteen years old, showed that the acetabular cartilage complex is a unit that is triradiate medially and cup-shaped laterally and is interposed between the ilium, ischium, and pubis. This complex is composed of epiphyseal growth-plate cartilage adjacent to these bones, of articular cartilage adjacent to these bones, of articular cartilage around the acetabular cavity, and, for the most part, of hyaline carilage. Interstitial growth within the triradiate part of the cartilage complex causes the hip socket to expand during growth. The concavity of the acetabulum develops in response to the presence of the spherical femoral head. The depth of the acetabulum increased during development as the result of interstitial growth in the acetabular cartilage, of appositional growth at the periphery of this cartilage, and of periosteal new-bone formation at the acetabular margin. At puberty, three secondary centers of ossification appear in the hyaline cartilage surrounding the acetabular cavity. These centers are homologous with other epiphyses in the skeleton. The os acetabuli, which is the epiphysis of the os pubis, forms the anterior wall of the acetabulum. The epiphysis of the ilium, which has been called the acetabular epiphysis, forms a good part of the superior wall of the acetabulum. A small epiphysis of the ischium was seen in the oldest patient, who was fourteen years old. The bone in these epiphyses expands toward the periphery of the acetabulum and thus contributes to its increase in depth.

Scoliosis often occurs in otherwise normal individuals or it may be associated with many widely differing diseases. The curve patterns are fairly uniform and the vertebrae always rotate in the frontal and horizontal planes producing convex side rotation with little displacement of the spinuous processes. Many small curves do not increase. Progressive scoliosis increases linearly and the rate of increase accelerates at puberty. No endocrine abnormalities have been observed in these patients. Usually the deformity is not caused by abnormal vertebral growth nor by abnormal collagen in verterbral ligaments. The glycosaminoglycans of nucleus pulposus are decreased in patients with idiopathic scoliosis. We speculate that loss of proteoglycans will affect the viscoelastic properties of the intervertebral discs which may result in permanent deformation. The etiology of scoliosis appears to be multifactorial with a genetic tendency to the deformity which is triggered in different individuals by different factors, some medical, some mechanical and some genetic.