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Valgus Slipped Capital Femoral Epiphysis: Pathophysiology of Motion and Results of Intracapsular Realignment

Kalhor, Morteza MD*; Gharanizadeh, Kaveh MD; Rego, Paulo MD; Leunig, Michael MD§; Ganz, Reinhold MD

Author Information
Journal of Orthopaedic Trauma: February 2018 - Volume 32 - Issue - p S5-S11
doi: 10.1097/BOT.0000000000001085

Abstract

INTRODUCTION

Valgus slipped capital femoral epiphysis (valgus SCFE) is an uncommon form of SCFE, with lateral or posterolateral displacement of the epiphysis; Muller first reported it in 1926.1 It may present as acute, acute on chronic, or chronic form. Pain may be due to instability or impingement. Although the etiopathology is not entirely clarified, an association with hip dysplasia and metabolic and endocrine diseases have been reported.2–6 Increased neck-shaft angle, horizontal physis, and increased femoral anteversion have been reported as predisposing factors.6–12

The reported surgical treatment was similar to the classic SCFE, with in situ pinning and/or inter/subtrochanteric osteotomy.4,6,9,10,13–15 Compared with classic SCFE, in situ pinning is technically more difficult because of the lateral and posterior displacement of the epiphysis.7,11,16,17 The altered morphology of the proximal end of the femur cannot be addressed by this technique nor can proximal femoral osteotomy distal to the altered morphology sufficiently decrease the impingement. During the past 2 decades, anatomic realignment of classic SCFE to prevent or treat femoroacetabular impingement has found increasing acceptance.18–31 However, to the best of our knowledge, its application in valgus SCFE has not been previously reported. Therefore, the purpose of this case series was to describe the specific and different pattern of impingement in valgus SCFE and report the technique and results of intracapsular realignment.

MATERIALS AND METHODS

We retrospectively reviewed the clinical, radiological, and intraoperative findings of a series of 8 valgus slips that were referred to our 3 centers (Firoozgar Hospital, Shafa Hospital, Schulthess Clinic, and Hospital da Luz) for treatment between 2008 and 2017. Patients were evaluated with clinical examination, laboratory tests, and standard radiographic evaluations. Clinical examination included the measurement of gait, pain, and hip joint mobility using the modified Merle d'Aubigne and Postel scoring system.32,33 In this system, numerical scores from 1 to 6 points are given to pain, gait, and motion. The outcome is rated excellent, good, fair, and poor based on the total numeric score from 18 to 3. All patients had an anteroposterior pelvic radiograph, with the hips in internal rotation when possible and a lateral radiographic view of both hips. In all hips, the neck-shaft angle and head-neck angle were measured. The epiphyseal-shaft angle (ESA) was used to determine the severity of the deformity and also for postoperative evaluation. For 4 patients, preoperative pelvic magnetic resonance imaging and computed tomography were also obtained. Endocrine and metabolic assessments were done for all patients. The indication for operation was lateral or posterior tilt of the proximal femoral epiphysis associated with pain and limitation of hip motion (Table 2).

Eight hips in 6 patients (3 males and 3 females) were treated with subcapital (5 hips) or femoral neck osteotomy (3 hips) for realignment. Two male patients had bilateral involvement. The mean age of the patients was 13.8 years (range: 9–19 years) and the mean follow-up period was 4.4 years (range: 1–9 years)

Clinical, Radiographic Findings

Pain, limping, and limitation of hip motion were the presenting symptoms in all hips. All patients but 1 (case 3; Table 1) were on crutches before operation. All had more or less limited and or painful internal rotation in full extension and to a lesser degree in 90 degrees flexion. External rotation in extension was reduced but less painful. In all patients, the impingement sign was positive in extension and internal rotation and also in full extension and external rotation. Uniformly, the standard anteroposterior (AP) pelvis and lateral x-rays of hips showed a lateral and more or less posterior tilt of the femoral epiphyses. The neck-shaft angle was measured between 150 and 175 degrees and the epiphyseal-shaft angle between 90 and 125 degrees (Table 1). Three hips showed borderline-to-severe acetabular dysplasia. The physis was closed in 3 male hips.

TABLE 1.
TABLE 1.:
Pre- and Postoperative Hip Function Scores Based on Merle d' Aubigne Scoring System

Surgical Technique

Using surgical hip dislocation34 and extended retinacular flap technique,18–20 5 hips with open physis were addressed by subcapital reorientation, and 3 hips with closed physis underwent neck osteotomy. The surgical technique is described elsewhere in detail.18–20 In short, with the patient in lateral decubitus, a straight lateral approach was centered over the greater trochanter. The fascia lata was incised along the anterior margin of the gluteus maximus and continued distally in line with skin incision. After a digastric osteotomy of the greater trochanter, the capsule was approached between piriformis tendon and gluteus minimus muscle. The hip capsule was exposed by anterior and superior retraction of the greater trochanter with the attached muscles. This was followed by Z-shaped capsulotomy and anterior hip dislocation.34 To protect the femoral head supplying vessels,35–37 the extended retinacular soft tissue flap was developed along the lateral and medial circumference of the neck as described earlier18–20 (Fig. 1). Separation and mobilization of the pedicled epiphysis was performed step by step and with great patience. In the cases with open physis, the bone was removed from the medial or anteromedial surface of the neck metaphysis until anatomic reorientation of the head fragment was possible without tension of the retinacula. In contrast to a classic SCFE, only little bone apposition had to be resected from the posterior surface of the neck. After subcapital realignment, the head fragment was fixed with 3–4 threaded pins. In the cases with closed physis, an osteotomy of the true neck with an anteromedially based wedge resection was preferred. Again, special care was taken to avoid tension of the retinacula throughout the manipulations. During alignment, attention was paid to achieve circumferential cortex contact, which however was not always possible. For fixation, two 6.5-mm cancellous lag screws were inserted parallel to the neck axis. Tension was also avoided during adaptation of the retinacular fold and during closure of the capsule. The greater trochanter was slightly advanced distally and refixed with two 3.5-mm cortical screws.

FIGURE 1.
FIGURE 1.:
Steps in the development of extended retinacular flap. A, Capsulotomy in the left hip and chipping of the posterior lip of the greater trochanter together with the short external rotators and periosteum. B, Development of anteromedial and posterolateral retinacular flap from the base of epiphysis to the lesser trochanter. C, With the head dislocated, the epiphysis together with the retinacular half tube separated from the femoral neck. The retinacular tube carries adequate blood supply to the epiphysis [reproduced with permission from Leunig et al18]. Reproductions are works protected by copyright. So in order to publish this reproduction, authorization must be obtained from the owner of the copyright in the original work.

Postoperative management was the same as for classic SCFE. The nonweight-bearing period was planned for 12–16 weeks for neck osteotomies and 8–12 weeks for subcapital alignment.19 One case (case 1; Table 1) was previously reported in an article about anteroinferior impingement.38

RESULTS

All 8 hips showed a metaphyseal or neck margin reaching more medial than the epiphyseal margin (Fig. 2). Intraoperatively, inclusive anteromedial impingement could be demonstrated in all hips with damage to the acetabular cartilage and labrum with a maximum at the antero-inferior quadrant (Fig. 3). In all hips, posterior impingement between neck and inferior acetabular rim could be reproduced in extension. Three hips (cases 3 and 4; Table 1) showed severe chondral lesions at the posterior head-neck junction because of this impacting impingement (Fig. 4).

FIGURE 2.
FIGURE 2.:
Preoperative x-rays of case 4. A, AP pelvic x-ray with maximum possible internal rotation shows the prominent metaphysis (white arrows). B, AP pelvic x-ray in patients favored leg position in external rotation shows impingement cysts (white arrows) at the postero-medial metaphysis as a result of chronic impacting impingement with the posteroinferior acetabular rim.
FIGURE 3.
FIGURE 3.:
Intraoperative image shows damage to the inferomedial acetabular labrum and cartilage as well as the prominent medial metaphysis producing the damage (left hip, case 1).
FIGURE 4.
FIGURE 4.:
Chondral damage at the posterior head-neck junction as a consequence of impacting impingement. A, Right proximal femur of case 4 after surgical dislocation during surgery. White arrows pointing to the impaction area produced by the posteroinferior acetabular rim; yellow arrow pointing to the most prominent medial metaphysis responsible for inclusive impingement against the anteroinferior acetabular cartilage. B, Left proximal femur of case 3 (19-year-old male) in slight internal rotation demonstrating the volume of destruction by the impacting forces (white arrow). Reproduced with permission.38 Reproductions are works protected by copyright. So in order to publish this reproduction, authorization must be obtained from the owner of the copyright in the original work.

After realignment, the epiphyseal perfusion was tested with 2-mm drill holes, showing brisk bleeding in all cases.39,40 The ESA could be reduced from 107.5 to 60 degrees (Table 1). Intraoperative range of motion after correction was free of impingement in all but 1 case (see below). Time to union and unprotected weight bearing in the group with subcapital realignment occurred within 8–12 week of the postoperative period. One of the 3 neck osteotomies healed after 16 weeks, and 1 was fully consolidated at 32 weeks. In the third hip (right hip of case 4; Table 2), 3 revisions for screw failure were needed to get consolidation. This hip finally had to be replaced by prosthesis for painful osteoarthritis.

TABLE 2.
TABLE 2.:
ESA and NSA Measurements

For 2 of the 3 hips with additional acetabular dysplasia (cases 3, 5, and 6; Table 2), joint instability became evident intraoperatively after realignment and periacetabular osteotomy was required to regain hip stability. One periacetabular osteotomy was performed immediately after the index surgery (case 5; Table 2), and 1 had to be postponed for 3 months (case 6; Table 2).

Realignment of the femoral epiphysis using intra-articular techniques in this study resulted in 5 excellent, 3 good, and 1 poor result after a follow-up ranging from 1 to 9 years (mean 4.4 years) (Table 2). There was no necrosis of the epiphysis. At the last follow-up, in all hips but 1, motion was pain-free and within normal range.41,42 All patients except 1 (case 4) could walk without aids. Two patients (case 5 and 6) had slight limping due to mild abductor weakness.

Illustrative Clinical Case

A 12-year-old female (case 5; Tables 1 and 2) was unable to walk without crutches after she felt sudden pain in the left hip. X-rays showed bilateral high neck-shaft angles and borderline acetabular dysplasia on the right side more than the left. The SCFE configuration confirmed the clinical impression of an unstable classic SCFE (Fig. 5A). Subcapital realignment was performed as an emergency procedure. After definitive fixation of the epiphysis, joint stability was insufficient because of residual posterior impingement of the slightly anteverted and high valgus neck. A derotation osteotomy at the subtrochanteric level resolved the problem by reducing the anteversion to about 10 degrees (Fig. 5B). Full recovery of signs and symptoms was achieved after 12 weeks. Over the following year, the slight pain in the opposite hip increased and a new pelvic radiograph at that time showed a slip of the left epiphysis, however this time into the valgus (Figs. 6A, B). Clinical evaluation revealed a positive anterior and posterior impingement sign. Epiphyseal realignment was achieved through the physis using the extended retinacular dissection.18–20 At final testing, joint stability was again insufficient, however this time posterior impingement could not be identified and stability was achievable only with substantial internal rotation of the femur. Because such high derotation would lead to unacceptable femoral retroversion and acetabular coverage was clearly insufficient, periacetabular osteotomy was performed at the same sitting as the procedure of choice to regain stability43 (Fig. 7A). One year after surgery, the patient is free of pain, has symmetrical joint motion, but is still limping on the right side from abductor weakness (Fig. 7B).

FIGURE 5.
FIGURE 5.:
Preoperative and postoperative pelvic x-rays of case 5 that shows bilateral coxa valga which is associated with classic slip in the left hip (A). The deformity was corrected by subcapital realignment. Subtrochanteric derotation was necessary to treat anterior subluxation developing after correction of the slip (B).
FIGURE 6.
FIGURE 6.:
AP pelvis (A) and lateral (B) hip x-ray of the same patient after 1 year to demonstrate reverse slippage in the right side. The lateral view shows the posterior component of this slip.
FIGURE 7.
FIGURE 7.:
Postoperative x-ray of the same patient as in Figure 5. A, after surgical treatment of the right hip by subcapital reorientation to address the valgus slip and periacetabular osteotomy for dysplastic acetabulum and joint instability. B, Results 1 year after surgery of the right hip and 2 years after surgery of the left hip. The patient has painless, symmetrical range of motion. The abductor force on the right side is still M4 of 5.

DISCUSSION

The incidence of valgus SCFE varies between 1.9% and 8.6%.7,10,11 All cases presented here are referrals from other orthopaedic surgeons. Like in most reported cases,7,8,11,13,16,17 our 8 hips showed a typical coxa valga of varying degrees (Table 1). The valgus position of the epiphysis without coxa valga has also been reported.6,10 However, the horizontal or even reverse orientation of the physis in these cases may rather be the result of a lateral growth plate closure than of a SCFE.42–46 None of our patients had signs of endocrine, metabolic, or neurogenic diseases that have been reported as predisposing factors.2,5,6,12 However, 1 patient (case 3) had thoracic kyphosis. Associated acetabular dysplasia was seen in 3 hips (cases 3, 5, and 6), resulting in a prevalence of more than 30%.

To the best of our knowledge, this is the first study reporting the complex mechanism of impingement in valgus SCFE, which differs substantially from the impingement in classic varus SCFE. In all hips, anterior impingement was noticeable in extension-internal rotation, whereas posterior impacting impingement was seen in extension. The posterior impingement may also produce anterior subluxation47 that can become more symptomatic than the posterior impact. Although epiphyseal realignment resulted in all cases in a normal head-neck relation, residual posterior impingement may persist as a result of the coax valga deformity.43,47 Therefore, it is important to test the achieved clearance intraoperatively. If not sufficient, additional femoral derotation may be taken into consideration; periacetabular osteotomy can also increase the posterior clearance. Besides impingement-free motion, joint stability has to be tested at the end of the correction and when insufficient, as to be expected in hips with additional acetabular dysplasia, periacetabular reorientation is the method of choice. ESA is a good parameter to measure the severity of a valgus slip and is not very sensitive to leg rotation.48 Normalization of ESA was, except in extreme valgus neck, equivalent with impingement-free motion. The left hip in case 6 is a rare example of varus slip in a hip involved with coxa valga deformity.

Avascular necrosis did not occur in this small series. In the literature, information about surgical results is anecdotal and unspecific.7,14 Prevention of further slipping of the SCFE is usually the treatment goal, and these results cannot be compared with the results of our patient group. Short- and mid-term results in our group were remarkably good, both radiologically and clinically.

Intracapsular correction is certainly a more demanding technique than pinning in situ and has a distinct learning curve. However, pinning in situ for valgus slips is more difficult than for varus slips7,11,16,17 and does not address the existing pathomorphology and physiology. The techniques of intracapsular reorientation have proven to be safe in classic SCFE18–30 and have led to good clinical results.7,11,16,17 In valgus SCFE, the surgical technique is somewhat less demanding. Detachment of the epiphysis is easier because anteromedial bone resection at the surface of the metaphysis can be executed under visual control; in addition, posterior callus is nearly absent. The longer healing time of neck osteotomy has been previously reported.19 It may be related to the retinacular dissection, which reduces the perfusion of the metaphyseal part attached to the epiphysis. Another reason may be incomplete cortical contact between the two fragments that results in sub-optimal mechanical stability. Both of these factors may have contributed to the delayed union of the left side and serial failure of the fixation of the right hip of case 4. As a consequence, optimal cortical contact must be an important surgical objective and nonweight bearing has to be strictly observed for a longer period than the 8–12 weeks recommended for subcapital realignment, which was consistent with the findings in the treatment of the classic SCFE.20

The study has some limitations. The number of cases is small and the follow-up period is somewhat short for this type of reconstructive hip procedure. Nevertheless, this is the largest number of cases treated with a uniform technique. In addition, the procedures were done in different centers by different surgeons (the authors). However, each of the treating surgeons has had similar training in doing these procedures and used a similar technique, as described.

CONCLUSIONS

Valgus SCFE deformity creates a specific pattern of complex impingement. Anatomical realignment, although technically demanding, can lead to favorable results by the restoration of normal morphology and impingement-free range of motion.

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Keywords:

hip; femur; valgus slipped capital femoral epiphysis; impingement; epiphyseal realignment

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