The Long-Term Outcome After Varus Derotational Osteotomy for Legg-Calvé-Perthes Disease: A Mean Follow-up of 42 Years

Shohat, Noam MD; Copeliovitch, Leonel MD; Smorgick, Yossi MD; Atzmon, Ran MD; Mirovsky, Yigal MD; Shabshin, Nogah MD; Beer, Yiftah MD; Agar, Gabriel MD

Journal of Bone & Joint Surgery - American Volume:
doi: 10.2106/JBJS.15.01349
Scientific Articles
Abstract

Background: Varus derotational osteotomy (VDRO) is one of the most common surgical treatments for Legg-Calvé-Perthes disease, yet its long-term results have not been fully assessed. We aimed to determine the long-term clinical and radiographic outcomes following VDRO.

Methods: Forty patients (43 hips) who underwent VDRO for Legg-Calvé-Perthes disease at our institution from 1959 to 1983, and participated in a follow-up study completed 10 years earlier, were approached for the present study. Clinical examination and radiographs were evaluated. Hip status and well-being were assessed with the Harris hip score and the Short Form-36 (SF-36).

Results: Thirty-five patients (37 hips) participated in the study. Information regarding the need for an arthroplasty was gathered on 4 additional hips from the previous study. The mean follow-up was 42.5 years (range, 32.4 to 56.5 years), with a mean patient age of 50.2 years (range, 35.9 to 67.8 years). In total, 7 patients (7 hips; 17% of 41 hips for which information was available, including 1 hip from the original cohort of 40 patients [43 hips]), underwent a total hip arthroplasty for hip pain. Excluding patients who had undergone an arthroplasty, the mean Harris hip and SF-36 scores were 79.8 points (range, 23.1 to 100 points) and 74.8 (range, 15.1 to 100), respectively. Twenty (64.5%) of the 31 hips that had not been replaced achieved a good or excellent Harris hip score (≥80 points). Sixteen (57.1%) of 28 hips with follow-up radiographs had no, or minimal, signs of osteoarthritis. The Stulberg classification was associated with the Harris hip score, the SF-36 score, hip pain, a Trendelenburg sign, coxa magna, and the Tönnis grade. In a multivariate analysis, the Stulberg classification was the only factor associated with fair or poor outcomes (a Harris hip score of <80 points). Patients with a Stulberg class-III or IV hip had significant deterioration with respect to the Harris hip score and Tönnis grade during the 10-year period since the last follow-up.

Conclusions: A long-term follow-up of patients who were operatively treated for Legg-Calvé-Perthes disease revealed that a low proportion underwent total hip arthroplasty and a relatively high proportion maintained good clinical and radiographic outcomes.

Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Author Information

1Department of Orthopedic Surgery, Assaf Harofeh Medical Center, Zerifin, Israel

2Department of Radiology, Carmel Medical Center, Haifa, Israel

E-mail address for N. Shohat: noam.shohat@gmail.com

* Yiftah Beer, MD, and Gabriel Agar, MD, contributed equally to the writing of this article.

Article Outline

Legg-Calvé-Perthes disease is a juvenile hip disorder of unknown etiology that has the potential to cause disabling pain and early-onset osteoarthritis in later life. Despite continuous advances in knowledge1, Legg-Calvé-Perthes disease remains one of the most controversial conditions in pediatric orthopaedics, particularly with regard to the best method of treatment2.

Long-term outcomes are dictated by the shape of the femoral head at maturity and the loss of hip joint congruity3,4. Although femoral head deformity and incongruence are relatively well tolerated in the short and intermediate term, >50% of patients develop disabling arthritis in the sixth decade of life5. Thus, the overall goal of treatment should be to prevent or minimize these deformities.

The principle of surgical treatment is to protect the weak, fragmented femoral head from deforming forces until it reforms. This is accomplished through containment of the head in the acetabulum2,6,7. Femoral varus derotational osteotomy (VDRO) is one of the most common methods employed to achieve this goal8-10. The concept of containment has been challenged over the years, contributing to the elusiveness regarding the best method of treatment11.

Present knowledge regarding surgical and nonsurgical treatment for Legg-Calvé-Perthes disease is based predominantly on relatively short-term follow-up studies. The Stulberg class at maturity is the main criterion for long-term prognosis9,12. Few studies have examined long-term outcomes of Legg-Calvé-Perthes disease5,11,13-15, and even fewer have focused on surgical treatment in the management of this disease16-18.

Beer et al.19 presented the long-term outcome for 40 patients (43 hips) at a mean follow-up of 33 years after VDRO. In the present study, we reevaluated the clinical and radiographic outcomes of these patients 42.5 years after surgery.

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Materials and Methods

Patient Population

Forty patients (43 hips) who had undergone VDRO for Legg-Calvé-Perthes disease, and who had participated in the long-term follow-up study a decade earlier19, were approached to participate in the present study. All patients were treated with proximal VDRO at our institution from 1959 to 1983. The purpose of the surgery was to relocate the protruded, deformed femoral head from its lateral position back to the acetabulum to achieve containment. The indications for surgery were Catterall group-III and IV involvement with the so-called head-at-risk sign20. Surgery was preceded by hip arthrography with a dynamic examination to identify the suitable containment position, in which there was full coverage of the femoral head, and to plan the correct osteotomy angles accordingly. When extreme abduction was necessary for containment, leaving <20° for active abduction, patients did not undergo surgery. A subtrochanteric osteotomy was performed with an open or closed-wedge technique, with fixation in an angle that afforded best coverage21. In 10 patients, VDRO was followed by greater trochanteric transfer a few years later to improve a Trendelenburg limp.

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Data Collection

Study participants were invited for a medical interview and a physical examination. They had standing anteroposterior pelvic and lateral hip radiographs made during the visit, or they provided radiographs made shortly before the visit. Questionnaires assessed information regarding daily function, physical activity, work status, and family history. All participants completed the Harris hip score instrument22 (maximum score, 100 points), with a higher score indicating less dysfunction, and the Short Form-36 (SF-36)23 (maximum score, 100), a questionnaire with 8 sections, with a higher score indicating less disability. We collected data on comorbidity, which showed that most patients were healthy. Six had hypertension, two had hypothyroidism, and one had type-2 diabetes mellitus. One patient had a meniscal tear a few months earlier and had a low result on the SF-36, but he had a good Harris hip score and no hip pain. No patient had had surgery in the previous six months. The physical examination included assessment of the hip range of motion, limb-length discrepancy, and the presence of a Trendelenburg sign. All examinations were done by a single examiner (N. Shohat).

The radiographic parameters evaluated were the Tönnis grade, head size ratio, and center-edge (CE) angle. The head size ratio was calculated as the size of the unaffected femoral head divided by that of the affected femoral head, with a ratio of <0.9 representing coxa magna. This could therefore not be calculated for patients with bilateral involvement. When the femoral head was substantially deformed, the radius was determined by its circular portion, and calculations were made accordingly. All radiographs were evaluated by an experienced musculoskeletal radiologist (N. Shabshin). The Tönnis grade was also evaluated by a senior orthopaedic surgeon. The physicians who reviewed the data were blinded to current or past clinical information about the study participants.

The Stulberg classification was applied to all hip radiographs made at maturity by 2 orthopaedic surgeons who reached consensus regarding the class. Classifications were compared with those assigned to the same patients 10 years earlier. Interobserver agreement was 81%, with 94% agreement between low classes (I and II) and high classes (III, IV, and V). We were able to assess the lateral pillar classification, with the use of the criteria described by Herring et al.24, for only 16 patients, according to radiographs made preoperatively, close to the fragmentation stage. Unfortunately, all other preoperative radiographs were destroyed. Those who assessed lateral pillar classification were blinded to current or past clinical information about the study participants.

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Statistical Analysis

Patients with a Stulberg class-I or II hip were compared with those with a Stulberg class-III, IV, or V hip. Patients who were ≤8 years old at the time of diagnosis were compared with those who were >8 years old. The Tönnis grades were grouped into 2 categories. Grades 0 and 1 were considered “no or minimal osteoarthritis,” and grades 2 and 3 were considered “moderate or severe osteoarthritis.” The Harris hip score was categorized into 2 groups. A score of ≥80 points was considered excellent or good, and a score of <80 points was considered fair or poor. Categorical variables were analyzed with the chi-square test, and continuous variables were analyzed with the Student t test. A p value of <0.05 was considered significant. Factors that were significantly associated with a Harris hip score of <80 points in the univariate analysis were evaluated in a multiple logistic regression model. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

The categories for the Harris hip score outcome and Tönnis grade were compared with the results for the same patients at the last follow-up 10 years earlier using the McNemar test. The continuous variables for the Harris hip score and the SF-36 were compared between the two time points using analysis of variance (ANOVA) with repeated measures.

The study was approved by the institutional review board of Assaf Harofeh Medical Center, and all participants signed informed consent.

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Results

Of the 40 patients (43 hips) who participated in the study 10 years earlier, 2 patients (3 hips) could not be located, 2 declined to participate, and 1 had died. Thirty-five patients (37 hips) agreed to participate in the follow-up study. Of those, 4 completed the study questionnaires but declined to have radiographs made. Table I summarizes the demographic characteristics of the study participants and their Stulberg and lateral pillar classifications. The mean age was 50.2 years (range, 36 to 68 years), and the mean duration of follow-up was 42.5 years (range, 32 to 56 years). Six patients (6 hips; 16.2%) had undergone an arthroplasty for hip pain. Information regarding hip replacement was available for 4 of the 5 patients who had participated in the previous study but not in the present one. One of the 4 had undergone an arthroplasty for hip pain; thus, a total of 7 (17%) of a total of 41 hips for which information was available underwent hip replacement.

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Clinical and Radiographic Outcomes

Of the 31 hips (29 patients) included in the present study that had not undergone an arthroplasty, 20 (64.5%) had no or slight occasional pain without limitation in activity, 7 (22.6%) had moderate pain, and 4 (12.9%) had marked pain with serious limitation in activities. Two patients required analgesic medications daily or weekly. Seventeen patients (58.6%) performed physical activity at least once a week, and 6 patients (20.7%) worked in physically demanding occupations. Physical examination revealed 13 patients, including two with bilateral involvement (41.9% of 31 hips), who had a positive Trendelenburg sign and 8 patients (27.6%) with a leg-length discrepancy of >1 cm.

The mean Harris hip score for the native hips was 79.8 points (range, 23.1 to 100 points). Twenty hips (64.5%) achieved a good or excellent score (≥80 points); 4 hips (12.9%), a fair score (70 to 79 points); and 7 hips (22.6%), a poor score (<70 points). The mean SF-36 score was 74.8 (range, 15.1 to 100). The mean scores for the 8 sections of the SF-36 were 63.3 for vitality, 78.0 for physical functioning, 65.8 for bodily pain, 74.8 for general health perceptions, 76.2 for physical role functioning, 81.5 for emotional role functioning, 79.0 for social role functioning, and 76.8 for mental health.

Follow-up radiographs (Figs. 1-A through 1-D) were analyzed for 26 patients (28 hips). This excluded the 6 patients who had required reconstructive surgery (1 of whom declined to undergo radiographic examination) and 3 who declined to undergo radiographic examination. Five hips (17.8%) had no degenerative changes, 11 hips (39.3%) had mild changes (Tönnis grade 1), 5 (17.8%) had moderate changes (grade 2), and 7 (25%) had severe changes (grade 3). Eleven hips (39.3%) had a CE angle of >25°. The presence of coxa magna could be assessed in only 23 hips (2 other hips were in the same patient and 3 had a deformity of the femoral head that did not enable proper measurement), and 11 (47.8%) of them had coxa magna.

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Association Between Head Deformity and Outcomes

The Stulberg classification was significantly associated with the Harris hip score, SF-36 score, and subjective hip pain. Patients with a higher Stulberg class more often had a positive Trendelenburg sign (81.8% compared with 20.0%) and coxa magna (100% compared with 33.3%), as well as higher Tönnis grades as revealed by radiographic evaluation (80.0% compared with 22.2%), than those with a lower Stulberg sign (Tables II and III).

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Associations Between Age at Diagnosis and Outcomes

Patients who were ≤8 years old at the time of diagnosis were more likely to have a lower Stulberg class and better long-term outcomes; however, the differences were not significant (Table IV). An opposite trend was observed regarding the need for an arthroplasty; 21.7% of patients who were ≤8 years old at the time of diagnosis underwent an arthroplasty compared with only 7.1% of those who were >8 years old.

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Factors Associated with a Harris Hip Score of <80 Points

Patients with fair and poor outcomes according to the Harris hip score had significantly more osteoarthritis (p < 0.005) and more often a Trendelenburg sign (p < 0.002). Older age at the time of diagnosis and at the time of surgery were associated with fair or poor outcomes, but this did not reach significance (p < 0.13 and p = 0.11, respectively). In a multiple logistic regression analysis, we examined the association between fair or poor outcomes on the Harris hip score and the age at diagnosis, age at surgery, number of years since surgery, a positive Trendelenburg sign, and Stulberg class. Stulberg class was the only significant variable associated with a fair or poor outcome utilizing this statistical technique (OR, 190.0; 95% CI, 10.71 to 3369.95).

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Comparison with Findings from 10 Years Earlier

Since the last follow-up (1 decade earlier), 6 patients (6 hips) underwent total hip arthroplasty. The mean age at the time of replacement was 47.2 years (range, 42.1 to 59.2 years), with a mean time from VDRO of 46.5 years. One hip was classified as Stulberg class V; 2 hips, as class IV; 2 hips, as class III; and 1 hip, as class II. Ten years earlier, the mean Harris hip score for the six hips was 69.78 points, the mean SF-36 score was 61.09, and 2 hips had no pain at all. At that time, 2 hips had Tönnis grade-2 osteoarthritis, 3 hips had Tönnis grade 1, and 1 hip had no sign of osteoarthritis.

With the hips that had an arthroplasty excluded, the mean Harris hip score deteriorated significantly during the last decade (from 85.4 to 79.8; p < 0.02). While hips with a Stulberg class-I or II femoral head maintained similar Harris hip scores (from a mean of 92.3 to 93.2 points), the Harris hip score for Stulberg class-III and IV hips deteriorated by a mean of 17.4 points (from 72.9 to 55.5 points) (p < 0.01) (Fig. 2). The mean SF-36 score was 78.1 and had not changed significantly from a decade earlier. However, the SF-36 for Stulberg class-III and IV hips showed an 11.1-point decrease, which reached significance (p < 0.05). Of the patients who were assessed radiographically in the current study, only 2 patients had Tönnis grade-2 or 3 osteoarthritis ten years earlier, and both had a Stulberg class-III femoral head. In the present study, the Tönnis grade changed from 0 or 1 (no or minimal osteoarthritis) to 2 or 3 (moderate or severe osteoarthritis) for 6 of 10 patients with a Stulberg class-III or IV hip and for only 4 of 18 with a Stulberg class-I or II hip (p < 0.03) (Fig. 3).

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Discussion

To our knowledge, the present study has the longest reported follow-up for patients who underwent VDRO for Legg-Calvé-Perthes disease. The most important findings were the low percentage of patients who underwent reconstructive surgery, the relatively high percentage of patients who were found to maintain good functional outcomes, a positive association between the Stulberg class and the clinical and radiographic outcomes in adulthood, and a marked deterioration during the fourth decade of follow-up for patients with a Stulberg class-III or IV hip.

Compared with earlier long-term studies on nonoperative treatments, our study found better clinical outcomes4,14. McAndrew and Weinstein5 described the natural history of the disease in 37 patients with a mean follow-up of 47.7 years. The mean age was 8.2 years at diagnosis and 55.5 years at the time of follow-up. Forty percent had undergone an arthroplasty, another 10% had disabling pain, and 10% had an Iowa hip score of <80. In a prospective study with a shorter duration of follow-up, Larson et al. reported worse outcomes than in previous studies25. The 56 patients in that cohort, with a mean age of 7.7 years at diagnosis, were treated with bracing or range-of-motion exercises. The patients were all >6 years old, and most were categorized as having lateral pillar class B. At 20 years of follow-up, the mean age was 28.7 years, 76% reported having at least occasional pain, and more than half had an Iowa hip score of <80. In our follow-up, 7 patients (18%) had undergone reconstructive surgery, and >65% of the 40 patients had a good or excellent outcome (a Harris hip score of ≥80 points). The differences in age at diagnosis and the length of follow-up preclude a comparison of surgery and the natural history or conservative treatment. Nevertheless, these results suggest a relatively good prognosis for patients who had a VDRO from 30 to 50 years earlier.

Stulberg et al. classified the shape of the femoral head according to 5 classes of deformity, with higher classes associated with more degenerative hip changes 40 years later3. The validity of this classification system has been questioned because of the low interobserver reliability noted in some studies24,26, although not in others27. We found a 94% interobserver agreement when simplifying the classification system into 2 groups (classes I and II compared with classes III, IV, and V). We showed a significant association between clinical and radiographic outcomes and the Stulberg classification. The Stulberg class was the only examined variable found to be associated with a fair or poor outcome in a logistic regression model. These results support the reliability of the Stulberg classification in operatively treated hips.

A drawback of evaluating hips in the short term is that it does not necessarily predict functional outcomes in the future. The current study provides evidence that the good short-term results observed in patients who underwent VDRO9,12 are valid in the long term. Our results are comparable with those reported by Herring et al.9, who showed good outcomes in patients who underwent VDRO at an age of >8 years; 62% had a Stulberg class-I or II hip at maturity compared with 50% in this age group in our study. These patients maintained good functional outcomes during long-term follow-up, as indicated by the Harris hip score and the low proportion who required arthroplasty.

Noticeable deterioration in hip function has been reported in studies examining the natural history of the disease with a follow-up of >40 years5,11. Our study design enabled us to examine the impact of surgical treatment throughout the fourth decade of life. We found that for patients with a higher Stulberg class, the fourth decade of life is a turning point in the disease; there was a marked deterioration in the Harris hip score and in osteoarthritic changes in patients with Stulberg class III or IV. Furthermore, most patients who underwent arthroplasty during the last decade showed minimal signs of osteoarthritis at the earlier follow-up, suggesting that they rapidly developed osteoarthritis. It is important to adjust patients’ expectations while counseling them and making them aware of the possibility that they may develop rapid symptoms in the fourth decade. The physician should counsel these patients to maintain low weight and to participate in nontraumatic sports activities to reduce the risk of osteoarthritis.

The main limitation of the present study is the lack of a control group. Thus, we cannot attribute the positive outcomes to surgery alone or compare the technique implemented with other surgical treatments. Furthermore, we did not take into account possible comorbidities that could have influenced the results. The retrospective design and the long-term follow-up resulted in missing data, such as for lateral pillar classification, which is known to be a prognostic factor. The study reflects the common practice 40 years ago with regard to surgery on young patients. Some of the patients were <6 years old and presumably would not have undergone surgery on the basis of the current criteria. Although we reached most of the patients included in the previous follow-up, a selection bias may have arisen. For example, patients who were symptomatic may have been more likely to return for follow-up in order to seek medical advice. Finally, while this is the longest follow-up to date as far as we know, it would be interesting to reexamine the patients in another 10 years.

In conclusion, for decades, VDRO has been commonly used to treat Legg-Calvé-Perthes disease, without evidence of its long-term outcomes. In this study, we show good clinical and radiographic outcomes in a cohort of patients at a mean of 42 years after surgery. This is important information to be relayed in patient consultations regarding the expected long-term prognosis.

Investigation performed at the Department of Orthopedic Surgery, Assaf Harofeh Medical Center, Zerifin, Israel

Disclosure: There was no external funding source. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article.

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