You are in: eMedicine Specialties > Orthopedic Surgery > PEDIATRICS Congenital Coxa VaraArticle Last Updated: Mar 20, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Robert Mervyn Letts, MD, FRCS(C), FACSC, Chief, Department of Surgery, Division of Pediatric Orthopedics, Children's Hospital of Eastern Ontario, University of Ottawa Coauthor(s): Ken K Kontio, MD, FRCSC, Assistant Professor, Department of Surgery, University of Ottawa; Consulting Surgeon, Department of Surgery, Division of Orthopedics, Children's Hospital of Eastern Ontario, Ottawa Children's Treatment Centre Editors: Mininder S Kocher, MD, MPH, Associate Professor of Orthopedic Surgery, Harvard Medical School/Harvard School of Public Health; Associate Director, Division of Sports Medicine, Department of Orthopedic Surgery, Children's Hospital Boston; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; George H Thompson, MD, Professor of Orthopedic Surgery and Pediatrics, Department of Pediatric Orthopedic Surgery, Case Western Reserve University; Director, Rainbow Babies and Children's Hospital; Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; Dennis P Grogan, MD, Clinical Professor, Department of Orthopedic Surgery, University of South Florida College of Medicine; Chief of Staff, Department of Orthopedic Surgery, Shriners Hospital for Children of Tampa Author and Editor Disclosure Synonyms and related keywords: CCV, developmental coxa vara, infantile coxa vara, cervical coxa vara, childhood coxa vara, proximal femoral varus, proximal femoral focal deficiency, PFFD, congenital short femur, congenital bowed femur INTRODUCTIONSection 2 of 12
  Coxa vara includes all forms of decrease of the femoral neck shaft angle to less than 120-135°. This condition has many etiologies: congenital, acquired, and developmental. Congenital coxa vara (CCV), also referred to as infantile or cervical coxa vara, is a condition in which a varus deformity exists that is assumed to be caused by either an embryonic limb bud abnormality or an intrauterine condition causing significant proximal femoral varus. CCV is, by definition, present at birth but manifests clinically during early childhood and commonly follows a clinical course that is progressive with growth. As a specific entity, CCV has characteristic clinical and radiographic features that help differentiate it from other forms of coxa vara. It is commonly associated with a significant limb-length discrepancy, segmental shortening of the femur, or other abnormalities of the bony femur. Associated diagnoses include proximal femoral focal deficiency (PFFD), congenital short femur, and congenital bowed femur. Acquired forms of coxa vara are varus deformities of the proximal femur that develop secondary to metabolic, neoplastic, or traumatic conditions. This group includes ricketic coxa vara, fibrous dysplasia, proximal physeal injury, and premature closure. Also included in this category are secondary varus changes due to generalized skeletal conditions or dysplasias such as Morquio disease, cleidocranial dysostosis, metaphyseal diaphyseal dysplasia, and metaphyseal dysostosis. History of the ProcedureFiorani first clinically described CCV in 1881. Hofmeister, in 1894, first coined the term coxa vara and was the first to show radiographic evidence of a decreased neck shaft angle. In 1905, Hoffa was the first to report on the histologic changes associated with coxa vara, and in 1928, Fairbank described the progressive tendency of the proximal femoral deformity during growth in coxa vara observed in childhood. Duncan proposed in 1938 that progressive childhood coxa vara represented a deformity that appeared during the early years of growth, rather than being congenital, thus coining the term developmental coxa vara. This proposal, although not generally accepted initially, was supported by the work of Amstutz in 1970. Amstutz documented 2 patients who had normal findings on radiographs of the hips at birth but had radiographic evidence of coxa vara by age 2-3 years. ProblemAbnormal development of the proximal femoral cartilaginous physis and defective ossification of the adjacent metaphysis are responsible for the progressive decrease of the neck shaft angle. In severe cases, a separate triangular fragment involving the inferior-medial aspect of the femoral neck may also be found. These anatomic and biologic factors underlying the biomechanical loading characteristics of the varus hip lead to a progressive inclination of the proximal epiphyseal plate with shortening of the femoral neck and concomitant relative trochanteric overgrowth. A serious hip deformity, both clinically and radiographically, often results, for which the course is not always clear and the treatment is not always successful. FrequencyCCV is believed to be a relatively rare condition, with a reported incidence ranging from 1 per 13,000 population to 1 per 25,000 population. Relative to developmental dysplasia of the hip (DDH), it is estimated to occur less frequently, with the CCV-to-DDH ratio ranging from 1:13 to 1:20. No sex predilection appears to exist, and reported rates of right and left side involvement are essentially equal. Bilateral involvement seems to occur only half as often as unilateral involvement. Although some authors propose that no racial predilection exists, there is some suggestion that incidence is higher in persons of African descent than in whites. No clear pattern of inheritance has been elucidated, but familial involvement in a number of cases has suggested an autosomal dominant genetic pattern of transmission. EtiologyThe exact cause of CCV remains unknown. Many hypotheses have been proposed, including the following: mechanical intrauterine stresses affecting hip development, avascular necrosis involving selected areas of the proximal femoral physis/head and neck, and metabolic abnormalities causing deficient production of, or a delay in, the normal ossification process of the proximal end of the femur. Pylkkanen (1960) proposed what remains to be the most widely accepted theory regarding the cause of CCV. He postulated that the proximal femoral deformity is the result of a primary ossification defect in the inferior femoral neck, on which physiologic shearing stresses (applied during weightbearing) cause fatigue of the local dystrophic bone, resulting in progressive varus deformity. PathophysiologyHistologic investigations by Chung and Riser (1978) and Bos et al (1989) have revealed abnormalities in the proximal femoral physeal chondrocyte maturation, with disruption of the normal columnar architecture and abnormal calcification of the cartilaginous matrix. This abnormal enchondral ossification resulted in decreased production of metaphyseal bone, leading to a relative osteoporosis and subsequent weakness in this area. Notably, no evidence exists in these studies or others of an avascular-type process occurring or of any pathologic or radiologic signs suggesting slippage of the proximal physeal plate as an underlying cause of the observed coxa vara. Biomechanically, the sheer effect causing progressive varus deformity is best understood in relation to the resultant force (R) at the femoral/acetabular articulation (see Image 1). In the normal hip, this resultant force would be perpendicular and compressive (C) in nature with respect to the physis. The force transmitted to the proximal femoral neck would include a net tension force (T) at the superior or lateral cortex and a net compressive force (C) at the inferior or medial cortex. In the case of CCV, the more vertical position of the proximal femoral physis would increase not only the sheer component (S) of the hip articulation resultant force but also the net medial compressive force (C) on the metaphyseal bone of the femoral neck. These forces overwhelm the mechanical strength of the abnormally ossified bone in this area (see Image 1). This may lead to a relentless and progressive cycle of deformity that often continues unless these forces are corrected with surgical intervention. ClinicalPatients with CCV usually present with gait abnormalities. Affected children generally present between the time they begin ambulation and age 6 years. In most patients, the gait abnormality is progressive and, notably, pain free. Unilateral involvement with an associated relative limb-length discrepancy and Trendelenburg limp may be noted. This discrepancy in limb lengths usually is mild, ranging from 1.5 to 4.0 cm. Patients with bilateral involvement commonly present with a waddling gait abnormality, similar to that of patients with bilateral DDH. The Trendelenburg sign is commonly elicited in the affected hip or hips. A tabletop examination may reveal weak abductors, a prominent greater trochanter, decreased abduction due to a decreased articulo-trochanteric distance, and coxa vara. A decrease in internal rotation also is often noted, caused by decreased femoral anteversion or true retroversion associated with this condition. INDICATIONSSection 3 of 12
Weinstein et al (1984) proposed a radiological means of quantifying CCV. This measure, the Hilgenreiner epiphyseal angle (HEA), is the angle subtended by the horizontal Hilgenreiner line through the triradiate cartilages and an oblique line through the proximal femoral capital physes (see Image 3). A study of normal values of the HEA found that the angle in children younger than 7 years averages 20°, with a wide variation of 4-35°. The mean value for those aged 8 years to maturity is 23°. Using this measurement, patients in whom surgery is indicated include the following:
If left untreated, CCV historically was believed to be a relentless and progressive deformity leading to pain and a loss of hip function with the development of premature degenerative changes (see Image 4). Some authors have shown, however, that not all patients with the diagnosis of CCV necessarily follow this course. On the basis of the HEA, 3 relatively distinct groups have emerged:
RELEVANT ANATOMYSection 4 of 12
See Pathophysiology. CONTRAINDICATIONSSection 5 of 12
Treatment of CCV is contraindicated in children who demonstrate any of the following:
In such situations, close clinical and radiographic follow-up is warranted. WORKUPSection 6 of 12
Imaging Studies
Histologic FindingsSee Pathophysiology. TREATMENTSection 7 of 12
Medical therapyMany forms of nonoperative treatment have been proposed, including spica cast immobilization and skeletal pin traction with bed rest, with generally unsatisfactory results. It is generally accepted that no place remains for conservative nonoperative measures for individuals requiring treatment for either symptomatic or progressive CCV. Surgical therapyAs surgical intervention is required in a large percentage of those with CCV, remembering the indications for surgery and also clearly defining the goals of treatment are important in an attempt to ensure the best possible outcome and to minimize the number of surgical procedures for the patient. The goals of surgical intervention are as follows:
The treatment of choice for CCV has followed the recommendations of early works by Amstutz, Freiberger, and Wilson in use of either subtrochanteric or intertrochanteric osteotomies. Among the intertrochanteric osteotomies (see Image 5), the Pauwels Y-shaped and Langenskiöld valgus-producing osteotomies have been shown to provide good results. Note, however, that these osteotomies have a somewhat limited ability to correct the associated femoral neck retroversion. The subtrochanteric valgus-producing osteotomies used by many authors also have provided good and lasting clinical results (see Image 6). More important, perhaps, is not the actual type of osteotomy performed but, rather, that the goals of surgical correction, as outlined above, are achieved. Many issues have been raised surrounding surgical intervention, including the amount of correction needed, associated procedures at the time of surgery to aid in the osteotomy and decrease hip joint forces, and the optimum age for operation. Postoperatively, good results have been achieved consistently when the HEA has been corrected to less than 35-40°. Although some have suggested the need to correct the neck shaft angle to more than 130-135°, Carroll et al (1997) found no strong correlation between the postoperative neck shaft angle and lasting good clinical outcomes. They suggested that the most consistent and reliable predictor of outcome was the HEA. Weighill (1976) emphasized the use of an adductor tenotomy in association with osteotomy, with adductor release removing the deforming force during reduction of the femoral bone fragments and aiding in postoperative stability of the osteotomy. If required, a segment of proximal femur may be removed to facilitate reduction and reduce joint reactive forces at the hip joint. Unfortunately, this may further shorten an already short limb. Many investigators have also considered the optimal age for surgical intervention. Weighill has suggested the best time for correction to be in patients as young as 18 months. Weinstein found that patients treated when older than, rather than younger than, 5 years maintained correction better. Serafin and Szulc (1991) suggest that correction in children younger than 9 years maximizes the remodeling potential of both the proximal femur and the acetabulum. It is generally accepted that more important than the age at correction is the ability to correct the hip to meet the goals of surgery. Once the diagnosis is clear and progression is evident, few reasons remain to delay surgery beyond an age at which stable fixation can be reliably achieved. Preoperative detailsAs with many surgical procedures, preoperative planning is essential to a favorable outcome. Up-to-date imaging is necessary to decide on the amount of bone to be resected and the size of implants to be used. Templating the operative plan is often invaluable to ensure that the proposed result will meet the surgical goals. Having hardware of various angles available is helpful if intraoperative measurements lead to the size of bone resection being altered. Intraoperative detailsPosition the patient supine on a radiolucent table and ensure that adequate quality images are available before beginning surgery. Rotate the affected hip under fluoroscopy to compensate for hip (femoral head) version, defining the maximal varus deformity. From this view, determine the size of the bone wedge to be resected. Use clinical rotation of the hip to decide if derotation will be combined with wedge resection. Free draping of the hip allows for better intraoperative control. The proximal-lateral femur is routinely exposed. Image intensification is used in implant insertion and bone resection. Confirm correct positioning once provisional fixation is achieved. Postoperative detailsAfter skin closure in the usual fashion, with the use of wound suction as required, apply a 1.5 hip spica cast. Obtain postoperative radiographs through the spica cast for later comparison. Maintain a non-weightbearing status for the patient until early bone healing is demonstrated radiographically, at approximately 6-10 weeks after surgery. Follow-upPerform an initial postoperative check 1 week after surgery, with radiographs to ensure maintenance of position and integrity of fixation. The patient should be seen every 2 weeks until early healing is present (approximately 6-8 wk after surgery). At that time, the spica cast is removed and physiotherapy is begun for mobilization and range-of-motion instruction. Close follow-up every 3-6 months is required to ensure that the deformity is resolving. Assess for greater trochanteric overgrowth and commonly encountered proximal femoral physeal closure. Carry out trochanteric apophysiodesis if indicated (see Complications). Perform a careful serial examination for a relative limb-length discrepancy and treat as appropriate. COMPLICATIONSSection 8 of 12
Premature closure of the proximal femoral physis has been very consistently noted and occurs along with or shortly after healing of the inferomedial fragment of metaphyseal bone. Carroll et al (1997) reported that all of their patients had premature closure of the proximal femoral physis, as did Desai and Johnson (1993). This closure occurred their series at an average of 3 years after surgical correction. Pylkkanen (1960) reported a 90% rate of premature closure. This, along with any residual shortening due to the osteotomy, requires follow-up with an aim of a contralateral physeal arrest or ipsilateral lengthening at the appropriate time should a clinically significant limb-length discrepancy exist near maturity. Associated with the premature closure of the proximal femoral physis is the often-encountered overgrowth of the greater trochanter (see Image 7). Desai and Johnson reported that this occurred in 60% of their series, with just under half of these patients having abductor weakness at final follow-up. They noted no overgrowth in the cases in which successful greater trochanteric apophysiodesis was achieved. All of these patents had a good clinical outcome. Undertake surgical epiphysiodesis or distal transfer if overgrowth of the greater trochanter is noted both radiographically and clinically on follow-up. OUTCOME AND PROGNOSISSection 9 of 12
Serafin and Szulc (1991) retrospectively reviewed 130 hips with CCV at a mean follow-up of about 9 years. Their indication for surgery was a neck shaft angle of less than 110°, and they suggested correction of the HEA to less than 35-40°. They reported good results in 80% of 2- to 9-year-olds, 62% in 10- to 11-year-olds, and 52% in 12- to 16-year-olds at surgical treatment. Growth disturbances noted were a decrease in femoral head size (87%), flattening (43%), shallowness and underdevelopment of the acetabulum (76%), and shortening of the femoral neck. Interestingly, they suggested that most of these changes were to some extent reversible if surgical correction was undertaken in children aged 2-9 years. Desai and Johnson reported their experience with valgus subtrochanteric osteotomies in 20 hips. Age of patient at evaluation averaged 7 years, with surgery at an average age of 8 years and 20-year follow-up. Preoperative HEAs averaged 66°, and postoperative HEAs averaged 30°. Five also had greater trochanteric apophysiodesis at the discretion of the surgeon. Good radiographic outcomes were noted in 89% of these patients, with Iowa hip scores of more than 90 points in all but one patient. They reported a recurrence rate of 16%, citing inadequate correction (mean HEA >43°), and there was eventual healing with repeat osteotomies. Trochanteric overgrowth was noted in 63% of their patients, and adductor weakness was noted in 41%. No patients had a limb-length discrepancy of more than 2 cm, although 2 patients had undergone epiphysiodesis prior to maturity with projected discrepancies of 2 cm and 4.2 cm respectively. Weinstein et al reviewed 20 patients with 25 hips affected with CCV. Average age at diagnosis was 5.75 years, age at treatment averaged 6.6 years, and mean follow-up was 15.3 years. Average HEA preoperatively measured 82.1°, and the preoperative mean head-shaft angle was 89.9°, corrected to 132.4°. Postoperative HEAs were not reported. The authors noted that 85.3% of initial correction was maintained at final follow-up. In patients older than 5 years at the time of surgery, 75% maintained better than 80% correction, whereas in patients younger than 5 years, only 37% maintained 80% correction or better. A possible reason for this rate of correction, as well as whether it was related to greater trochanteric overgrowth, expected to be more of an issue in the younger patient, was not elucidated. This was the landmark article introducing the concept of the HEA as a predictor of progression in developmental coxa vara. As with any treatment, long-term results remain the mainstay of evaluation of utility and effectiveness. Available long-term evaluations of CCV show that with the proper diagnosis and indications for surgery and, most importantly, adequate correction of the deformity of the proximal femur, an optimistic outlook can be adopted for most patients affected by this condition. FUTURE AND CONTROVERSIESSection 10 of 12
Does congenital coxa vara represent a variant of slipped capital femoral epiphysis with chronic changes? A few studies in the literature do consider CCV a variant of a chronic slip with the continued varus biomechanically predisposing to increased shear stresses across the proximal femoral physis. The changes found in the cartilage of this physis are suggested to resemble those found in SCFE. Other studies suggest that imaging (eg, MRI) results are not similar to those of SCFE and that a chronic slip theory does not explain the bone changes found in the metaphyseal bone of the proximal femur. The authors believe that a more generalized bone abnormality is present that predisposes these patients to deformity. Hopefully, future investigations will shed further light on this topic. When is the best patient age at which to operate on hips affected by this condition? Most patients seem to present for evaluation and are considered for treatment when aged 5-10 years. Femoral osteotomy procedures are technically easier in the older child, as more bone stock is present. Earlier surgical intervention may allow the hip, including the acetabulum, to remodel more completely. Interestingly, however, this remodeling potential in very young children has been suggested to possibly lead to higher recurrence rates after surgical correction. In the young surgical patient, the incidence of greater trochanteric overgrowth is also higher. Most agree, however, that the milder the deformity, the easier the correction. Long-term outcomes would suggest that a good adequate realignment of the deformity is most important. The authors tend to operate as soon as patients meet radiographic and clinical criteria (see Treatment), regardless of patient age or size. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
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