In children with severely involved Legg-Calvé-Perthes disease (LCPD), abnormal painful hinge movement, so-called “hinge abduction,” may occur during both the early and late stages of the disease.1 This phenomenon is thought to be due to impingement of the protruded epiphyseal segment of the deformed femoral head, abutting against and hinging on the superior lip of the acetabulum.1,2–6 Hinge abduction seems to be a complex manifestation of the hinge movement occurring in the continuum between lateral and anterior impingement.6 If hinge abduction is fixed, abnormal hinge movement results in progressive subluxation, collapse of the lateral pillar, and widening of the femoral head.1,3–6 When the patient presents late with established hinge abduction, pain, restricted hip motion, gait disturbance, and an unpleasant clunking sensation are frequent on examination.3 Patients may present with abnormal gait in the transverse plane, that is, out-toeing and in-toeing gaits.7 It is the intention of this study to provide the treatment guidelines for noncontainable LCPD hips, focusing on valgus osteotomy for the treatment of hinge abduction.
TREATMENT GUIDELINES FOR NONCONTAINABLE LCPD HIP
Figure 1 illustrates the investigator's algorithmic treatment approach to hinge abduction. The first step is to determine whether the subluxated hip showing abnormal hinge movement is “reducible” or “irreducible” using dynamic arthrography under general anesthesia. The degree of reducibility can be determined by the position of the femoral head within the acetabulum in abduction without imposing undue pressure on the lateral edge of the acetabulum.8,9 Aggressive soft tissue release (adductor tenotomy, psoas tenotomy, and medial joint capsular release, if necessary), followed by traction and/or abduction casting is indicated for the hip with “reducible” hinge abduction, which is usually found in the transitional stage. If follow-up arthrograms demonstrate stable movement of the femoral head within the acetabulum, continued hip motion exercises and a bracing program may be implemented. However, we had little experience of such instance. In contrast, when the hip remains unstable due to previously extruded epiphyseal segment of the femoral head, that is, containable in abduction, but subluxatable in adduction, containment surgery (eg, a femoral varus osteotomy,1,10 double-level osteotomy,11,12 triple innominate osteotomy,13,14 and shelf acetabuloplasty8,9,15) should be contemplated, taking into consideration the age, the neck-shaft angle, and the extent of uncoverage of the femoral head.
When the child presents in more advanced stages, that is, in late reossification or healed stages with established hinge abduction, the enlarged, crushed femoral head may remain “irreducible.” In this situation, the surgical treatment modality should be changed from one that depends on remodeling by “containment” of the femoral head to one that improves joint “congruity” and/or acetabular volume. A variety of surgical techniques have been addressed for the management of noncontainable LCPD hips, including a proximal femoral valgus osteotomy,2,3,6,16 shelf acetabuloplasty,8,15,17 Chiari osteotomy,18–20 hip joint distraction,21,22 osteochondroplasty,23 femoral head reshaping procedure,24 and combinations of these procedures, although no long-term follow-up data have been published. Moreover, the optimum indications of each surgical technique are controversial. Our position on articulated hip joint distraction is that this treatment should be used very selectively for noncontainable, severely subluxated hips in adolescents or young adults in whom other conventional methods have proven to be insufficient and the hip remains stiff after adductor and psoas tenotomy (Fig. 2). Shelf acetabuloplasty is known to be effective for remodeling of hips with “reducible subluxation” during the early stage of LCPD in older children, usually over 7 years.8,9,15 For this reason, there is a view that shelf acetabuloplasty is a primary method of containment. However, shelf acetabuloplasty, if performed in the noncontainable hips with “irreducible” hinge abduction, should be considered as a salvage procedure to cover enlarged femoral head. In this situation, shelf acetabuloplasty would not reduce lateral impingement of the femoral head in abduction. “Coxa irregularis” is frequently found in adolescent Perthes' disease, in which segmental collapse or destructive patterns are often observed without radiologic evidence of revasularization and remodeling.25 It is generally agreed that Chiari osteotomy is effective for the treatment of a painful, subluxated hip with “coxa irregularis”.18–20 We, however, think that a Chiari osteotomy should be considered as one of the last resort salvage procedures. It is because a Chiari osteotomy does not necessarily improve lateral impingement in abduction and may exacerbate any existing abductor weakness, although there is theoretical advantage of Chiari osteotomy over shelf acetabulolasty; Chiari osteotomy enables medialization of the hip with a resultant reduction of the load. When “coxa irregularis” is associated with a saddle-shaped epiphysis, it is our experience that a Ganz osteochondroplasty of the femoral head and a valgus osteotomy by surgical dislocation seem to be effective for pain relief and restoration of hip motion in adolescents or young adults with hinge abduction.25 We have no experience of the femoral head-reshaping procedure.
PROXIMAL FEMORAL VALGUS OSTEOTOMY
If the femoral head and acetabulum become congruent when the joint is adducted, but remain incongruent in a neutral or abducted position, a valgus osteotomy is preferred for restoration of joint congruity and alleviation of femoroacetabular impingement by reducing nonphysiologic forces through the hip joint.2,3,6,16 The concept of realignment of the leg with the hip in the position of the “best fit” by redirecting the more congruent, round, posteromedial aspect of the femoral head to the neutral position of weight bearing has been popularized by Bombelli26 and Quain and Catterall.3 This procedure is contraindicated if the “irreducible” hip is very stiff.
The advantages of valgus osteotomy2,3,6,16 are as follows: (a) correction of abnormal hinge movement by repositioning the hinge segment away from the acetabular margin, and thereby pain is relieved by unloading the lateral parts of the femoral head; (b) increasing the effective weight-bearing contact surface area with a resultant decrease in peak contact pressure and a decrease in the potential for degenerative arthritis; (c) correction of the shortening by increasing the femoral neck-shaft angle; (d) improvement in the abductor mechanism by increasing the abductor muscle length and redirecting the abductor muscle pull; and (e) producing favorable remodeling of the hip with a resultant improvement in lateral acetabular coverage, particularly in younger children. Remodeling may be further enhanced if a valgus osteotomy is combined with a shelf acetabuloplasty, which provides additional molding effect.16 Moreover, a valgus osteotomy can safely and effectively be repeated if the deformity recurs. The reported positive results after valgus osteotomy include improvement in gait and hip motion, reduced pain, and improved superior joint space, overall shape of the femoral head, bicompartmentalized acetabulum, and leg length inequality. Other reported positive results include a decrease in lateral femoral subluxation, and healing of a central osteochondral defect of the femoral head.3,4 However, these positive clinical and radiologic observations do not preclude the possibility of the future development of degenerative arthritis in adulthood. The theoretical disadvantage of a valgus osteotomy is that by making the femoral neck more vertical, increased contact pressures on the femoral head may occur, and it will alter forces passing vertically through the knee, unless the shaft is laterally displaced on the proximal fragment.17
Technical Considerations and Pitfalls of Valgus Osteotomy
In cases of advanced osteoarthritis, Bombelli26,27 reported that a valgus osteotomy at an angle of 30 degrees or more made the capital drop a fulcrum, redirecting the axis of abnormal hinge movement toward the medial side of the femoral head along with a decreased compression force at the lateral margin of the joint. This concept may not apply to children with hinge abduction, because most children with hinge abduction do not present with capital drop osteophyte. Therefore, the degree of valgization should be better determined by the “best fit” joint congruity position in adduction using intraoperative dynamic arthrograms.
Although Bombelli26 and Quain and Catterall3 recommended a valgus-extension osteotomy, we believe that the decision-making as to whether or not the rotational/sagittal components would be combined with valgization should be based on careful determination of the spatial features of the hump of the femoral head.6 Valgus-extension osteotomy is an effective procedure, particularly when hinge abduction is combined with flexion deformity of the hip in association with a small, soft anterior hinge segment that can be contained within the acetabular socket. However, when the “hump” on the femoral head is formed relatively anteriorly and is large enough not to be able to be contained within the acetabulum, a valgus-extension osteotomy may not be indicated because with the extension component of the osteotomy, the anterior hump can cause further impingement against the anterior acetabular rim during an attempted full flexion. In the same context, those hips that show optimal congruity in adduction and internal rotation position of the extended lower limb on dynamic arthrograms can be treated by a valgus-external rotation osteotomy. Similarly, those hips that had the most congruent relationship in the adduction-external rotation position of the extended lower limb can be treated by a valgus-flexion-internal rotation osteotomy. When the flexion component is combined with a valgus-internal rotation osteotomy, anterior capsulotomy of the hip may be combined to prevent possible residual flexion deformity of the hip.28 Preoperative planning and selection of a suitable fixation of the osteotomy is essential. We have used AO 130 degrees-angled blade plate for the fixation of the osteotomy. The ideal position of the blade plate can be determined by adjusting the angle between the direction of chisel and the shaft of femur. Recently, locking compression plates (Synthes, West Chester, PA) are available with a screw angle of 150 degrees.
There is controversy as to whether or not the acetabular procedure, including an innominate osteotomy, shelf acetabuloplasty, or Chiari osteotomy, should be performed to cover the extruded femoral head as a combined procedure at the time of a valgus osteotomy or as a second-stage procedure. We have a strong view that acetabular procedures should be delayed in the younger patient after a valgus osteotomy, because lateral acetabular growth often improves once the hinging pressure is relieved. Bankes et al16 also reported favorable remodeling of the femoral head with disappearance of the prominent lateral ridge of the femoral head 10 years after a valgus-extension osteotomy without a simultaneous acetabular procedure in hinge abduction. We also observed that the impinging hump can regress in size with time after operation in accordance with remodeling of the hip (Fig. 3). The other benefit of a selective, secondary acetabular procedure is that a “hyaline cartilage-to-hyaline cartilage” redirectional acetabular osteotomy (eg, triple innominate osteotomy or periacetabular osteotomy) becomes possible instead of a “hyaline cartilage-to-fibrocartilage” covering salvage procedure (eg, shelf acetabuloplasty or Chiari osteotomy), depending on the degree of roundness of the femoral head. However, we agree with others that if there is a substantial increase in subluxation and the hip remains unstable after a valgus osteotomy, a concomitant acetabular procedure is necessary to obtain adequate acetabular coverage, and thus decrease the unit load on the articular cartilage and prevent the “potential incongruity” that might develop.
There are some technical pitfalls associated with a valgus osteotomy. First, a valgus osteotomy makes the position of the femoral neck more vertical. As a result, abduction contracture with or without pelvic obliquity may occur after a valgus osteotomy in the case of greater valgization, which contributes to a substantial increase in the length of the abductor muscles. If the abduction contracture does not resolve with physiotherapy, an abductor faciotomy may be helpful. Little study has systematically examined how much valgization is too much. It has been known that severe valgus deformation or the lateral displacement of the head or both provides less favorable milieu contributory to earlier degeneration in the hips. From the biomechanical viewpoint, optimum degree of valgus correction can be determined by the degree of adduction to lower the tip of greater trochanter to the level of the center of the femoral head while restoring the joint congruity in neutral position of weight bearing.29 However, practical limits of valgization can be confounded by a variety of anatomic factors before surgery, including the configuration of the femoral head, the neck-shaft angle, uncoverage of the head, position of the greater trochanter relative to the head, and the steepness of acetabular roof. It has been our empiric observation that valgization >160 degrees to 165 degrees tends to cause abduction contracture or lateralization of the femoral head. Thus, we feel that the maximum magnitude of valgus correction in LCPD may be around 35 degrees to 40 degrees.
Second, a significant amount of femoral anteversion can ensue after a “pure” valgus osteotomy. Liu et al30 insisted that femoral version and neck-shaft angle alone are not sufficient for a complete understanding of the version of the neck, as the version is dependent on the neck-shaft angle and does not represent the true anatomic inclination of the femoral neck. Third, it is necessary to understand that ground mechanical axis can pass through the lateral compartment of the knee, unless lateral translational of the shaft is not conducted at the time of valgus angulation. Therefore, we advocate preoperative simulating surgery to calculate the amount of lateral displacement of the shaft on the proximal fragment, and thereby unacceptable mechanical axis deviation of the lower extremity can be prevented. This is particularly important for skeletally mature or skeletally maturing patients in whom a valgus osteotomy is contemplated for treatment of hinge abduction. However, in younger children, the subsequent remodeling will usually correct this malalignment spontaneously. If there is any preexisting associated knee deformity, that is, a genu valgum, it should be simultaneously corrected at the time of valgus osteotomy. Guided-growth control by medial hemiepiphysiodesis of the distal femur or supracondylar osteotomy is effective to treat a genu valgum.
Results of Valgus Osteotomy
Raney et al2 reviewed 31 hips, with an average of 5.2 years after valgus osteotomy for hinge abduction. They reported that the Iowa hip scores at follow-up averaged 93 points. Combined clinical and radiographic review for 21 patients yielded 6 (29%) excellent (Stulberg I or II and Iowa hips scores >95), 7 (33%) good (Stulberg III or less and hips scores >90), 5 (24%) fair (Stulberg IV and score >85), and 3 (14%) poor (Stulberg V and hip score <85) results. Bankes at al16 reported similar results with valgus-extension osteotomy for hinge abduction in 48 children (51 hips) with a 10-year follow-up. They reported that the average Iowa hip score of the 46 hips, excluding 5 patients who underwent total hip arthroplasty or hip fusion, was 86. They found that favorable remodeling of the hip was associated with the following 3 factors at surgery: younger age, the phase of reossification, and an open triradiate cartilage.
We also studied the growth and remodeling of 35 hips after valgus osteotomy combined with rotational and/or sagittal correction for hinge abduction in 35 consecutive patients (27 boys and 8 girls) with Perthes' disease between 1984 and 2007. The mean age at surgery was 9.4 years (range, 3.5 to 15 y), and the mean follow-up after surgery was 9.4 years (range, 3.0 to 18.0 y). Of the 35 patients, 31 were skeletally mature and 4 were near skeletal maturity at the latest follow-up. All hips were classified as Catterall group III (15 hips) or IV (20 hips). Surgery was carried out during the stage of fragmentation in 14.3% (5 hips), at healing in 71.4% (25 hips), and for residual deformity of the femoral head in healed disease in 14.3% (5 hips). A valgus osteotomy resulted in postoperative improvement of function and symptoms, and radiographic parameters, particularly in younger age groups. Postoperatively, pain relief, improvement in limping, and an increase in range of hip motion (abduction, internal rotation, and external rotation) were conspicuous findings. Although all patients complained of pain or discomfort before surgery, at the latest follow-up, pain disappeared in all except 9 patients, who nevertheless reported decreased pain severity. Limping also disappeared in all except 11 patients. Overall, the Iowa hip score significantly increased from 71.2 (range, 30 to 91) before surgery to 95.2 (range, 76 to 100) at the latest follow-up. Radiologic observations also revealed sustained remodeling of the femoral head and acetabulum with time after the osteotomy. The neck-shaft angle decreased gradually with remodeling; specifically, the mean neck-shaft angle was 127.7 degrees before surgery, 142.8 degrees immediately after surgery, and 132.9 degrees at the latest follow-up. There was no increase in lateral subluxation after surgery, whereas increased superior joint space and decreased medial joint space were maintained. The mean Mose sphericity index was 3.97 mm (range, 1 to 13 mm) at the latest follow-up. The final Stulberg classification of the radiographs was class II in 4 (11.4%), class III in 22 (62.9%), and class IV in 9 hips (25.7%).
When the patient presents late with established hinge abduction, the hip may remain “noncontainable.” In this situation, valgus osteotomy should first be contemplated if the femoral head and acetabulum become congruent when the joint is adducted but remain incongruent in a neutral or abducted position. Favorable remodeling can be anticipated after a valgus osteotomy, especially when it is performed before late reossification/healed stage and in younger age (<8 to 10 y). A concomitant acetabular procedure is necessary to obtain adequate acetabular coverage, if there is a substantial increase in subluxation and the hip remains unstable after surgery.
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