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Findings and Management of the Rare Caput Flexum Deformity of the Hip

A Case Report

Leunig, M. MD1; Fickert, S. MD2,3; Ganz, R. MD4

doi: 10.2106/JBJS.CC.18.00321
Case Reports
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Disclosures

Case: A 10-year-old girl presented after possible occult hip trauma, with shortening of the leg being the initial clinical symptom, followed by motion-dependent pain. She had limited external rotation in extension with anterior apprehension. Radiographically, the deformity was an anterior tilt of the epiphysis with coxa vara. Surgery included surgical dislocation using a retinacular flap for the anterior open wedge femoral neck osteotomy for extension and posterior translation, with an excellent 4.5-year clinical outcome.

Conclusions: Caput flexum is a rare deformity with localized premature closure of the anterior growth plate of the hip. To avoid secondary impingement, an osteotomy was successfully placed close to the deformity.

1Department of Orthopedics, Schulthess Clinic, Zurich, Switzerland

2Hüftchirurgie, Sportorthopaedicum Straubing, Straubing, Germany

3Department of Orthopedics, University Medical Centre Mannheim, University of Heidelberg, Heidelberg, Germany

4Faculty of Medicine, University of Bern, Bern, Switzerland

E-mail address for M. Leunig: Michael.leunig@kws.ch

Investigtaion performed at the Department of Orthopedics, Schulthess Clinic, Zürich, Switzerland

Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSCC/A820).

The shape and spatial orientation of the proximal end of the femur may be affected by various insults during its development and maturation, including diseases, trauma, and surgical interventions. A well-known proximal femoral deformity is retrotilt of the femoral epiphysis in slipped capital femoral epiphysis (SCFE) frequently, combined with varus and rarely with valgus1. Another pathology is the head in the neck deformity, also called caput valgum, resulting from a retardation of the lateral growth plate. It is a possible consequence of cerebral palsy2 but has been seen after conservative and operative treatment of development dysplasia of the hip3 or after septic arthritis4. It is nevertheless distinct from coxa valga or valgus SCFE5. Until now, it has been unclear whether the opposite, caput varum, exists and whether this is distinct from inherent postinfectious or posttraumatic coxa vara4,6,7. Until now, caput flexum has been described and named “caput antetortum” in 4 cases only, all after septic arthritis4.

We present here a case of caput flexum in which septic origin is very unlikely. Most likely, unrecognized trauma was causative and the developing deformity substantially contributed to limited hip range of motion, function, pain, and early hip degeneration. For these reasons, it was corrected with a femoral neck osteotomy.

The patient and her parents were informed that data concerning the case would be submitted for publication, and they provided consent.

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Case Report

A 10-year-old physically very active girl developed pain after an accident while skiing when she was 8 years old. Pain subsided with reduction of activities over time, but her parents observed her slowly increasing limping. When she regained her former activity level 1 year after the initial symptoms, she experienced pain in the right groin, especially after playing soccer. There was no history suggesting previous infection. Given her altered activity pattern after the skiing accident, her parents suspected the possibility of occult trauma. Clinical evaluation revealed shortening of the right leg of 1.5 cm. Whereas adduction, abduction, and flexion were symmetrical, hip rotation was altered with reduced external rotation in extension (external rotation (ER) and internal rotation (IR) 30°/0°/80° compared with 80°/0°/30° for the left side) and pain at the extreme of external rotation.

Imaging showed a complex deformity of the proximal end of the femur. The anteroposterior (AP) pelvic radiograph showed varus of the neck (coxa vara) combined with a substantially decreased height of the epiphysis and a sagging rope sign (Fig. 1-A). Lateral views showed an anterior tilt and translation of the epiphysis (Figs. 1-B and 1-C). Magnetic resonance imaging and computed tomography (not shown) revealed fusion of the head-neck physis in its anterior one third (Fig. 1-D).

Fig. 1-A

Fig. 1-A

Fig. 1-B

Fig. 1-B

Fig. 1-C

Fig. 1-C

Fig. 1-D

Fig. 1-D

Fig. 1-E

Fig. 1-E

Due to her clinical and radiographic deterioration over 2 years with a reaction of the acetabular cartilage due to posterior impingement of the neck at the rim in external rotation and the failure of conservative treatment to alleviate her symptoms, a surgical correction of the deformity was indicated. Our surgical treatment was based on the anatomic deformity. To address the flexed position of the femoral epiphysis, a femoral-sided osteotomy was proposed. Although an intertrochanteric osteotomy could address this situation, the amount of deformity induced by the rather distant correction site would have been significant. Therefore, we considered a neck osteotomy as the optimal surgical correction to avoid new impingement. Exposing the hip through posterolateral trochanteric osteotomy, capsular exposure between the gluteus minimus and piriformis muscles, and z-shaped capsulotomy8, the anterior head-neck area appeared similar to an anterior SCFE (Fig. 2-A). Bringing the hip into extension led to contact and inclusive impingement of the posterior metaphysis and the posteroinferior acetabulum. Slight hyperextension and external rotation produced anterior subluxation. After anterior dislocation of the femoral head with transsection of the round ligament, the pink color of the posteroinferior acetabular cartilage became visible, indicating chronic irritation at this location. To avoid adverse stretching of the retinaculum during mobilization of the epiphysis, an extended retinacular flap was undertaken9. In brief, for the retinacular flap, the soft tissues close to the posterior trochanter consisting of the retinaculum and the short external rotator muscles are developed subperiosteally containing the medial femoral circumflex artery (MFCA). The obturator externus protects the MFCA during dislocation of the femoral head. This flap allows mobilization of the epiphysis within the growth plate and access to the posterior femoral neck. As parts of the anterior physis have already been fused (Fig. 1-E), with the head dislocated, a slightly oblique osteotomy of the neck somewhat distal to the growth plate was performed using an oscillating saw with protection of the retinaculum by blunt retractors. The curved neck was superiorly straightened (Fig. 1-E). A 2.0-mm Kirschner wire placed through the fovea in the epiphysis was used as a joy stick to open the osteotomy anteriorly approximately 60°, to shift the head posteriorly to overcome the antecurvatum of the neck (Fig. 2-B) and to recreate the posterior head-neck offset. Intraoperative fluoro images in extension and in 45° and 90° of flexion and abduction demonstrated the anterior opening wedge osteotomy and posterior translation of the osteotomized fragment (Fig. 3). After provisional fixation of this position using a Kirschner wire from the lateral subtrochanteric cortex, the range of motion (ROM) was assessed for impingement, and fluoroscopy was used to confirm the correction achieved. To maintain joint congruity, a mild head in the neck position had to be accepted (Fig. 4-A), due to previous acetabular adaptation to the pathologic condition. Three additional 3.0 mm fully threaded Kirschner wires were inserted to stabilize the osteotomy passing the partially fused growth plate to ensure physeal stabilization. The anterior osseous gap resulting from the osteotomy was filled with metaphyseal cancellous bone from the area of the trochanteric osteotomy. Drill holes of 2 mm revealed prompt bleeding from the epiphyseal fragment, suggesting maintained epiphyseal blood flow. The trochanter was advanced distally and stabilized using two 3.5 mm screws. The osteotomies healed uneventfully within 10 weeks. The hardware was removed 15 months postoperatively. At this time, the growth plate as a whole was consolidated with normal epimetaphyseal alignment. The AP view shows the caput valgum that was accepted during surgery but with good acetabular coverage and joint congruency. There were no signs of disturbed perfusion of the epiphysis, and the ROM was equal for both sides. The girl fully regained her demanding activity, except for soccer, and has so far experienced no pain (Figs. 4-B and 4-C). Leg length discrepancy due to the premature closure of the growth plate had reached slightly more than 2 cm and was addressed by an epiphysiodesis at the contralateral knee 2.5 years postoperatively. At the most recent follow-up 4.5 years postoperatively, she had an excellent clinical outcome with a symmetric leg length (Fig. 5), a straight leg axis, and internal and external rotation without any pain. Nevertheless, although the lateral view showed near normal head-neck proximal femoral relationship, the most recent follow-up whole leg view suggests some coxa magna and a mildly upsloping and short acetabular rood with a crossover sign (Perthes-like deformity). The affected hip showed in 90° flexion an external and internal rotation of 40°/0°/30° (contralateral hip 60°/0°/20°). In prone was the ER and IR 30°/0°/35° (contralateral 30°/0°/20°). Adduction, abduction, and flexion were symmetrical. Her Oxford hip score reached the maximum score; the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) subscales and the global WOMAC index were also excellent with the lowest score. Also, the Core Outcome Measure Index (COMI) score showed the maximum achievable score. The muscular strength of the gluteus was symmetric. Impingement tests were negative.

Intraoperative view of the anterior tilted epiphysis before (Fig. 2-A) and after (Fig. 2-B) correction with subcapital open wedge osteotomy and posterior shifting of the proximal fragment.

Fig. 2-A

Fig. 2-A

Fig. 2-B

Fig. 2-B

Fig. 3

Fig. 3

Postoperative anteroposterior (AP) radiograph of the corrected epiphysis. An additional varization was discussed but not performed for stability reasons. Fig. 4-B AP and (Fig. 4-C) lateral radiographs after hardware removal 28 months after surgery. The head is vital and reasonably covered. A leg length discrepancy of 2 cm is planned to be treated with epiphysiodesis at the distal femur.

Fig. 4-A

Fig. 4-A

Fig. 4-B

Fig. 4-B

Fig. 4-C

Fig. 4-C

Fig. 5

Fig. 5

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Discussion

The caput flexum, an anterior tilt of the epiphysis within the physis, reported here was most likely as a consequence of premature closure of an anterior portion of the growth plate. While caput flexum, valgum, and varum are deformities of the head in relation to the neck, are coxa valga or vara rather deformities of the neck-head against the femur reflected in the neck shaft angle. So far, caput flexum has been observed only after septic arthritis4. For the case presented here, no septic history has been reported.

The young girl had a history of impact physical activities (soccer and a ski accident) which might have affected the hip. Intraoperatively, the findings were similar to partial necrosis; however, necrosis near the vessel entrance with a normal rest of the head is hardly conceivable. The pathomechanism of impingement with external rotation in full extension combined with anterior subluxation could be verified by intraoperative trial motion. It may be speculated whether additional antecurvatum and varus of the neck as well as the valgus tilt were related to the amount and localization of the growth plate injury.

The osteotomy technique used in this case is demanding, and some orthopaedic surgeons might have preferred an intertrochanteric or even subtrochanteric correction, being less demanding and less risky. However, the more distant osteotomies may have addressed only the deformities in one, the coronal plan (visible on AP pelvic radiograph) but have added new impingement between anterior neck and acetabulum in the sagittal plane10. Residual posterior impingement would have been the consequence when the anterior open wedge osteotomy of the neck would have been executed without posterior shift of the epiphysis. The perfusion of the epiphysis during correction was respected with establishment of an extended medial and lateral retinacular flap9 after surgical hip dislocation8. Both techniques have meanwhile proven to be safe and successful when performed with the required accuracy and adhere to their technical description11,12. The mild Perthes-like deformity that occurred at the last follow-up warrants clinical and radiographic long-term surveillance.

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References

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