Legg-Calve-Perthes disease (LCPD) is a self-limited condition characterized by avascular necrosis (AVN) of epiphysis, followed by subchondral fracture, fragmentation, revascularization, and remodeling.1–3 Age at onset is the most important prognostic factor: children older than 8 or 9 years of age at the time of diagnosis are likely to have a poor outcome compared with children presenting at a younger age.4–7 As there is less potential for bone remodeling in older children, the pathology of later onset LCPD is similar to that of AVN of the femoral head in adults.4,8
The treatment options for late-onset LCPD vary significantly. Conservative treatment includes physical therapy, bracing/casting, and sometimes adductor tenotomy.9,10 Surgical treatment includes femoral11,12 and/or pelvic osteotomy.13,14 Although surgical treatments have been shown to be more effective than conservative treatment, however, uncertainty persists as to the optimal treatment method for children with this condition.
Transtrochanteric rotational osteotomy (TRO) was developed by Sugioka15 as a surgical treatment of AVN. TRO was then applied to selected cases with LCPD and the short-term clinical results for LCPD were reported.16,17 The necrotic lesions are generally located in the anterosuperior aspect of the femoral head, and the intact area often remained at the posterior portion. Even when the necrotic lesions reach the posterior portion of the femoral head, the new bone formation usually starts at the posterior part. The intact or healed posterior surface becomes a new weight-bearing portion by TRO (Fig. 1).18 The purpose of our study was to report the long-term clinical outcomes of TRO for the patients with late-onset LCPD.
The local Institutional Review Board approved this study. Medical charts were retrospectively reviewed for sex, laterality, age, clinical presentation, treatment, complications, and clinical outcomes. The individuals consisted of 14 hips in 13 cases. All the patients had reached skeletal maturity at the time of final radiographs and the average follow-up period was 12 years and 4 months. There were 12 boys and 1 girl. The average age at disease onset was 10 years and 9 months (range, 9 to 15 mo) and the average age at operation was 12 years and 0 month. The average interval between the disease onset and TRO was 1 year and 5 months. All the patients were primarily treated with a nonweight abduction brace and then indicated for TRO when they met the indication criteria. The indications of TRO for LCPD were as follows: (1) children more than 9 years old with large necrotic lesions involving the superolateral portion of the femoral head were primarily indicated; (2) the radiographic appearance includes subluxation and/or hinge abduction; (3) the prerequisite was the evidence of a healed or intact portion in posterior or anterior femoral head.17 The surgical protocol described by Sugioka15 was used in all the patients.19
On the basis of a review of the radiographs, the disease was initially staged according to the Catterall classifications,20 the lateral pillar classification,21,22 and the posterior pillar classification.23 In brief, the Catterall classification specifies 4 different classes according to the extension of AVN: class I—AVN is <25% of the femoral head, class II—approximately 25% to 50%, class —III approximately 50 to 75%, and class IV—more than 75%. The lateral pillar classification included 3 types: type A, where the lateral pillar maintains 100% of the height when compared with the other hip; type B, presenting up to 50% of collapse of the lateral pillar; and type C, where there is over 50% collapse of the lateral pillar. The posterior pillar classification assesses the posterior 15% to 30% of the femoral epiphysis according to the same criteria as those of the lateral pillar classification. Lateral radiographs taken at the fragmentation stage were divided into 3 groups (A, B, and C).
At the review, each patient was clinically examined using the Merle d'Aubigne and the Postel scoring system.24 The final radiographic outcome was based on a modification of the Stulberg criteria.21,25 In brief, the Stulberg classification describes the radiographic appearance of the hip at the time of skeletal maturity and includes 5 types: type I is defined as a completely normal hip; type II indicates hips that have a spherical femoral head that is larger than normal, has a short neck, or has an abnormally steep acetabulum. Sphericity was determined with the protractor technique as described by Herring et al.22 Type III hips have a nonspherical femoral head with an ovoid mushroom or umbrella shape, but was not flat; type IV hips have a flat femoral head that is articulated with a flat acetabulum; and type V hips have a flat femoral head within a round acetabulum.
Statistical analysis included the χ2 test and the Mann-Whiteney U test, where appropriate. The patients were divided into 2 groups according to the Stulberg classes, spherical (class II) versus nonspherical (class III and IV), or congruent (class II and III) versus noncongruent (class IV). The impact of the onset age, age at operation, the interval between the onset and operation, the Catterall classes, lateral, and posterior pillar classes on these groups was examined. The significance level was set at P<0.05.
The details of the patients are shown in Table 1. According to the amount of head involvement, there were 6 hips in Catterall III and 8 hips in Catterall IV. Lateral pillar classification showed 3 hips in group B and 11 hips in group C, indicating the severity of LCPD. Final radiographic outcomes based on the modified Stulberg classification showed that 5 hips were in Stulberg class II, 2 hips in class III, and 7 hips in class IV (Figs. 2–4). There were no hips in class I and V.
Average Merle d'Aubigne Postel score at the final follow-up was 16.2 points ranging from 12 to 18 points. Seven hips in 7 patients (1 in class II, 1 in class III, and 5 in class IV) had restriction of hip motion in several degrees. There were no cases with the iatrogenic AVN caused by the surgical treatment. All the patients did not have additional treatment except nail removal by the final follow-up. Three hips (1 in class III and 2 in class IV) showed slight joint space narrowing and none of them showed severe osteoarthritic changes.
When spherical hips (class II) and nonspherical hips (class III and IV) were compared, the amount of head involvement (Catterall class) and the remaining posterior pillar had significant influences on the final radiographic outcomes (P=0.036 and 0.0073). When congruent hips (class II and III) and noncongruent hips (class IV) were compared, the more preserved lateral pillar tended to have better congruency, but was not significant (P=0.0507). Age at onset, age at operation, and the interval between the onset and operation did not have significant effects on these comparisons.
Age at disease onset has been an important prognostic factor in LCPD. As there is a shorter period remaining for remodeling of the femoral head, the clinical presentation was similar in part to that with AVN in adults.4,8,26 TRO is an established treatment for adult AVN; therefore, it was applied to the treatment of late-onset LCPD. TRO for LCPD was firstly reported by Sugioka describing 7 hips in 6 cases of those who were more than 10 years old at onset.16 He reported the accelerated repair process of the necrotic bone and the excellent radiographic results at minimum 1-year follow-up. However, the evaluation was somewhat subjective. Hotokebuchi et al17 have reported the 7-year clinical results of TRO performed for 20 severe LCPD hips in 19 cases. Using the Stulberg classification, they showed 1 hip in class I, 4 hips in class II, and 15 hips in class III, demonstrating the difficulty to have both spherical and congruent hips for late-onset LCPD. On the basis of the modified Stulberg classification, average 12-year results of TRO in this study were 5 hips of class II, 2 hips of class III, and 7 hips of class IV. As a result, 36% of the hips obtained spherical and congruent hips and 50% of the hips obtained congruent hips. We thought that this was acceptable for this severe condition. Treatment of LCPD aims to obtain a spherical and congruent hip at skeletal maturity; however, in cases with late onset and poor lateral pillar, the realistic goal might be to salvage the hip to have congruent hip, which is usually classified as “fair,” even when nonspherical.
Ippolito et al4 described that the majority of older patients developed early degenerative arthritis with the conservative treatment. They recommended a more aggressive approach for this age group.6 As a surgical treatment, varus osteotomy (VO) is often indicated for late-onset LCPD. In cases with better lateral pillar, we agree to choose VO as the first choice. In fact, we indicated VO to the patients with LCPD more often than TRO (data not shown). However, in cases with collapsed lateral pillar, the superolateral portion of the femoral head will be a new weight-bearing area by VO. In adult AVN, VO without sufficient intact area in the lateral weight-bearing area was reported to have unsatisfactory results.27 Therefore, locating the intact or healed surface at this portion by the rotation of the femoral head is thought to be reasonable. The intact or healed surface tended to locate at the posterior portion of the femoral head in LCPD; therefore, more preserved posterior pillar significantly led to better radiographic results. Atsumi et al28 also tried to locate the viable portion at the weight-bearing area. They reported the rotational open-wedge osteotomy for the patients with LCPD with an extensive lesion. By this osteotomy, the femoral head was rotated anteriorly, and the posterolateral viable segment was moved below the lateral acetabular roof. The mean rotational angle was 33 degrees, with a mean of 18 degrees of varus. Although it was only 1-year follow-up, they mentioned that the repair of the femoral head was accelerated.
Compared with the VO or the rotational open-wedge osteotomy described above, TRO was a more complicated surgical procedure due to the circumferential capsulotomy coupled with the careful preservation of the nutrition vessel of the femoral head. Therefore, one of the disadvantages of TRO is being technically demanding and the long learning curve is recommended to be performed. In contrast, circumferential capsulotomy made it possible to obtain large rotation of the femoral head, which is the advantage of TRO. Rotation of the femoral head could change the weight-bearing surface from the collapsed one to the intact or healed one.
TRO was performed at the various time points from the initial pain onset. As we tried the conservative treatment using the abduction brace for most patients, the interval between the pain onset and TRO ranged from 3 months to 2 years. Some patients were treated at the necrotic phase and the others were treated at the fragmentation phase, although the effect of the interval on the final radiographic results was not statistically significant. However, our study had limited statistical power because of the small number of the patients. The optimal timing of TRO needs further clarification with more number of the patients.
In conclusion, 36% of the hips obtained spherical and congruent hips and 50% of the hips obtained congruent hips. TRO is an effective salvage procedure for the late-onset LCPD. Amount of head involvement, posterior, and lateral pillar had influences on the surgical outcomes.
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