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Iowa Orthop J. 2010; 30: 191–194.
PMCID: PMC2958296

VALGUS SUPPED CAPITAL FEMORAL EPIPHYSIS

Abstract

Valgus slips of the epiphysis are rare, making radiological diagnosis difficult. A high degree of clinical suspicion is required to diagnose the condition.

The patient was a 13-year, 7-month-old girl who had been suffering from pain in the left thigh for ten days. She had a limp and a positive Tren-delenburg sign. Menstrual function had started when she was 12 years and 10 months old. Pain occurred with getting up from a chair.

Hip radiographs revealed symmetrical, bilateral caput valgum, which was a potential cause of confusion given the valgus displacement of the proximal femoral epiphysis. Axial view showed an almost imperceptible posterior slip. The patient was diagnosed as having a valgus slipped capital femoral epiphysis (SCFE). Surgical treatment was performed using in-situ fixation with a cannu-lated, fully threaded percutaneous screw placed through the external cortex of the femoral neck. Non-weight-bearing for six weeks was prescribed.

Although a medial approach is usually used for screw insertion using a more medial entry-point, preventing neurovascular risks, in-situ fixation (through a lateral approach) was performed more safely and distally. This was done through the outer cortex of the femoral neck (and centered in the axial view), to achieve fixation of the femoral head in the center of the femoral neck and head.

INTRODUCTION

Slipped capital femoral epiphysis, SCFE, or proximal femoral epiphysiolysis is an alteration that occurs in adolescence and preadolescence, most frequently affecting patients with an adipose-genital phenotype, hormone imbalances, and other disorders, in the presence of mechanical factors such as excessive weight or trauma.

SCFE is usually idiopathic, but in some cases can be associated with endocrinopathies and hypogonadism. Occurrence can be acute, acute-on-chronic, and chronic.

SCFE has classically been described as a posterior and inferior slip of the proximal femoral epiphysis through the physis. The basic pathological and radiological feature of the lesion is a varus, posteriorly slipped proximal femoral epiphysis. The slip, which is usually progressive, is sometimes not easy to detect on initial radiographs.

Klein et al.1 described the typical ‘Klein line,’ which is a line that can be traced along the superior aspect of the femoral neck, as an early indicator of SCFE. Failure of this line to intersect the superior aspect of the epiphysis is a subtle sign of SCFE.

When the epiphysis has slipped into valgus with minimal or no posterior displacement, radiological signs may go unnoticed. The existence of the laterally displaced femoral head in slipped capital femoral epiphysis has been a subject of debate2 but now there no doubt about the existence of a true valgus SCFE.

Valgus slips of the epiphysis are rare, making radiological diagnosis difficult. A high degree of clinical suspicion is required to diagnose the condition.

PURPOSE

We present a case of valgus slipped capital femoral epiphysis in which atypical displacement made initial radiological diagnosis difficult. We also report a successful nontypical surgical approach.

CASE REPORT

The patient was a 13-year, 7-month-old girl who had been suffering from pain in the left thigh for ten days. She had a limp and a positive Trendelenburg sign. Menstrual function had started when she was 12 years and 10 months old. Pain occurred when getting up from a chair when it was mechanical in nature, and it was worse with weight-bearing and activity. Flexion of the left hip was painful. Internal rotation of the hip was limited (-40°), with the limb adopting an externally rotated posture.

At the age of 12 years and 8 months, the patient underwent a bilateral hemiepiphysiodesis of the proximal tibia for bilateral idiopathic genu valgum (13° and 12° of valgus of the mechanical axis, with an intermalleolar distance of 14 cm when bearing weight). During intubation for anaesthesia, a lump was discovered in the thyroid area. This turned out to be a medullary thyroid carcinoma, which was treated by total thyroidectomy and node excision. The patient required replacement hormone therapy for hypothyroidism.

Hip radiographs revealed symmetrical, bilateral caput valgum, which was a potential cause of confusion given the valgus displacement of the proximal femoral epiphysis. The axial view showed an almost imperceptible posterior slip of the left hip. The patient was diagnosed as having valgus SCFE of the left hip. The cervico-diaphyseal angle was normal (130° bilaterally).

Surgical treatment was performed using in-situ fixation with a cannulated, fully threaded percutaneous screw placed through the external cortex of the femoral neck. During the immediate postoperative period, pain disappeared. Non-weight-bearing for six weeks was prescribed.

Four years later, the patient remained asymptomatic, with no pain or limping, and was leading a normal life. External rotation of the hip was 60° on the right side and 45° on the left side; internal rotation was 45° on the right side and 60° on the left side. Roentgenogram showed physeal fusion, with caput valgum.

DISCUSSION

Valgus SCFE was first described by Muller in 1926.3 Twenty-seven patients, involving a total of 34 hips, have been reported to date. The condition is often not noticeable on AP radiographs. In valgus SCFE, the Klein line will always be normal, emphasizing the need for lateral radiographs in all cases when evaluating children for SCFE.4 Valgus SCFE occurs mostly in girls (76%).4 It is also surprising that many of the cases reported in the literature were recorded between 1940 and 1960, or recently,2,4,5 with a higher male predominance in earlier series. One of the possible explanations of the higher female predominance in valgus SCFE is the increased femoral anteversion in females. Loder et al. found a prevalence of valgus SCFE of 1.9% when reviewing the literature. Thus, 1-2% of children with SCFE will have the valgus-displacement type.

Mechanical factors have been cited in connection with the appearance of SCFE but the etiology of this pattern of SCFE remains uncertain or not clear. Ogden6 postulated that the valgus slip can occur in an older child with an acute SCFE, where a thin remnant of cartilage along the posterior femoral neck is present, enabling the epiphysis to be pushed laterally as it is slipping posteriorly.

A marked coxa valga orients the physis to a relative horizontal position.2,7,8 Griffith, in 1976,9 and later Morris-Sy(io)m 1990, believed that the direction of displacement in SCFE was strictly posterior as defined by the femoral neck and no true medial or lateral displacement of the capital femoral epiphysis occurs. The typical appearance of varus and exceptionally valgus, on AP radiographs of the hip was thought to be attributable to the effect of parallax. External rotation of the lower extremity results in varus appearance and internal rotation results in apparent valgus displacement of the epiphysis.

But Segal2 reported two cases of true valgus SCFE, confirmed by CT scan and MRI with posterolateral epiphyseal displacement. Increased femoral anteversion will lead to the appearance of an increased neck-shaft angle on AP radiograph of the hip. Increased femoral anteversion, in addition to exaggerating the degree of coxa valga and contributing to the projectional phenomena of parallax, may play a role in the mechanical etiology of valgus SCFE. These are patients with coxa valga3,7 whose hips exhibit a previously increased cervico-diaphyseal angle (20°) and an increased lateral tilt (27°), which are the cause of greater loads during weight-bearing, and facilitate the development of deformity in the same direction during gait.7,11,12,13 A slip may frequently occur in the coronal plane only, without posterior displacement.5 Our patient did not have coxa valga, but her hips displayed a rare case of bilateral, idiopathic caput valgum; although no such instances have as yet been described in the literature, this could clearly represent a mechanical predisposing factor. Only Rothermel8 described a patient with valgus SCFE secondary to acute trauma, but with one month of hip pain. He believed that lateral epiphyseal displacement may have occurred secondary to forced femoral abduction on a horizontal physis. Meyer et al.,14 and Fahey and O'Brien15 described valgus SCFE in children after traumatic events. Pritchett and Perdue,16 through a 3-dimensional force analysis, support that the relationship of femoral retroversion 10° more than normal increases the shear stress that the femoral growth plate will experience by 20%.

Yngve et al.13 have shown that valgus SCFE can occur on a biomechanical basis. A transphyseal shear force of 2.7 times body weight is seen in a child with valgus neck-shaft angle and lateral tilt of the capital femoral physis, which is greater than the 2.2-times body weight needed to cause physeal slip in slowly walking obese children. Thus, a valgus SCFE can occur because of biomechanical factors alone.

It is important to detect the above variant, since surgical treatment demands in-situ fixation. Medial approach is usually performed in valgus SCFE. This medial approach will require open surgery to protect the neu-rovascular structures (Segal). Loder4 and Segal2 warned that the valgus SCFE needs a much more medial entry point for a single central-screw fixation than the typical ‘varus’ SCFE. Therefore, the proximity of the femoral neurovascular bundle makes this approach risky.

An external approach is difficult because of the minimal space available. In order to avoid screw insertion using a more medial entry point to prevent neurovascular risks, Shea5 performed in-situ fixation through the external femoral metaphysis. In our patient, due to the greater epiphysis displacement and the lack of space available, percutaneous in-situ fixation with one cannulated screw was also performed more safely and distally, from the metaphysis through the outer cortex of the femoral neck (and centered in the axial view). This situation made it necessary to pass screw threads through the outer cortex of the femoral neck to achieve fixation of the femoral head in the center of the femoral neck and head. We recommend keeping in mind this possibility when facing a valgus SCFE.

CONCLUSIONS

Idiopathic caput valgum is an infrequent morphological alteration of the femoral head which produces a mechanical predisposition to valgus displacement of the latter.

Diagnosis of SCFE requires a high degree of suspicion.

When in-situ fixation is attempted we recommend lateral osteosynthesis even, if necessary, through the outer cortex of the femoral neck. This approach helps to avoid a medial entry-point, thus preventing the risk of injuring the neurovascular structures.

Figure 1
A) Anteroposterior roentgenogram of both hips. Horizontal proximal physis can be seen of both hips with idiopathic caput valgum. B) Bilateral axial view showing valgus slipped proximal femoral epiphysis of the left hip.
Figure 2
More detailed view on A) AP view and B) axial view. Note the difference in Klein's line.
Figure 3
A) Four years after the surgery. Anteroposterior view after “in situ” fixation. Due to the minimal space available, the screw threads pass through the outer cortex of the femoral neck. B) Axial view showing the screw centered in the neck ...

REFERENCES

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Articles from The Iowa Orthopaedic Journal are provided here courtesy of The University of Iowa