INTRODUCTION
Treatment for Legg-Calvé-Perthes (LCP) disease remains controversial.1 A survey of the European Pediatric Orthopedic Society, with the respondents averaging 20 yr of clinical experience, showed tremendous variations in treatment when presented a series of four clinical scenarios.2 The only long-term prospective study in the literature recommends surgical containment early in the course of disease for children over age 8 yr with lateral pillar B or B/C border hips.3,4 Proximal femoral varus osteotomy (PVFO) or Salter innominate osteotomy gave similar results in that study.3,5
The most popular reconstructive strategies for containment early in the course of LCP disease are PVFO3,6,7 and Salter innominate osteotomy.3,6,8–10 Combined femoral and pelvic osteotomies,11–13 Sugioka osteotomy,14 and triple innominate osteotomies15–18 have their proponents as well.
When containment is not possible, salvage procedures have been used to treat symptomatic LCP disease. Proximal femoral valgus osteotomy has been successfully used in later stage disease with hinge abduction.19 Chiari osteotomy20–22 also has been done when containment was not possible.23–27
Shelf acetabuloplasty has been performed both in early stages of LCP for containment23,28–30 and later in the course of the disease as a salvage coverage procedure,23–25 or for treatment of hinge abduction.26,27 Concerns about disruption of the lateral acetabular growth after SA have been raised. Two recent reports show that lateral acetabular growth persists or even is stimulated after SA in patients with LCP disease.30,31
Given the referral nature of our practice, we treat patients during any phase of the disease process. The initial favorable results seen by Bowen and Catterall32–35 led us to perform SA for the treatment of symptomatic LCP disease. This study reflects our intermediate term results.
MATERIALS AND METHODS
An Institutional Review Board approved a retrospective chart and radiographic review study of all patients treated with a shelf acetabuloplasty (SA) for LCP disease. This review included a final follow-up visit consisting of a physical examination, range of motion, and radiographic studies. An initial cohort of 48 patients who had undergone SA was identified. All of these were further reviewed. Of these, 12 were excluded because they had a reconstructive procedure before SA. This yielded 36 patients to contact for study participation. The last recorded contact information was used, and we attempted to reach patients or their parents by phone on multiple occasions. In addition, patients were asked to participate during a clinic follow-up appointment. Patients with varus or valgus proximal femoral osteotomy at the time of the index SA also were included in the study.
Seventeen patients responded and consented to participate. Each participant returned to clinic for a follow-up appointment that included radiographs, range of motion (ROM) measurements of the affected hip, completion of the Pediatric (Adolescent – parent report) Outcomes Data Collection Instrument (PODCI) and a question about whether or not they would recommend this procedure to others. An extensive chart review was undertaken, and initial symptoms, age at presentation and at diagnosis, preoperative treatments including physical therapy, surgeries, medications, and bracing were documented. Additional ROM data were collected from the chart review of the clinic visit preceding the SA procedure.
Radiographs consisted of both an anteroposterior pelvis and a lateral frog-leg view. The images were placed in picture archiving and communication system (PACS), McKesson Radiology™ (McKesson Radiology, San Francisco, CA), and Horizon Medical Imaging™ (McKesson Radiology, San Francisco, CA). The Orthoview software (Orthoview LLC by materialise, Jacksonville, FL) was utilized for the angular distance and percentage head subluxation measurements. Preoperative and final follow-up radiographs were reviewed for center-edge angle (CEA), lateral acetabular shape (LAS), percentage of femoral head subluxation (A/B), acetabular angle of Sharp (AAS), and articulotrochanteric distance (ATD). The images were measured by the primary author (AP) then reviewed and confirmed by the second author (CM). The lateral acetabular shape (LAS) was defined as type I, normal, concave lateral acetabular margin; type II, flat, horizontal acetabular margin; and type III, as convex acetabular margin.4 The preoperative radiographs were classified using the lateral pillar classification as described by Herring et al.36,37 and final radiographs were graded using the Stulberg et al. classification.38
The shelf acetabuloplasty performed was a variation of the technique described by Staheli and Chew.39 The sartorius and tensor fascia lata interval was developed. The inner and outer wall of the ilium was exposed, and the reflected head of the rectus femoris was preserved. Multiple drill holes were placed on the outer ilium at the junction of the capsular attachment with the assistance of intraoperative C-arm imaging. The drill holes were connected to form a slot. Cortical bone from either the inner or outer ilium was harvested and placed in the slot. The space between the cortical bone and outer ilium was back-filled with allograft cancellous bone chips with the reflected head sewn over the bone graft.
In this cohort of 17 patients, surgery took place on the left hip in 11 and the right hip in six. An intraoperative arthrogram was performed prior to shelf acetabuloplasty in 13 out of 17 patients. Of the 13 patients with arthrogram, three showed hinged abduction. Those three patients had a valgus osteotomy of the proximal femur performed at the time of the index procedure.
Additional procedures performed during SA included two greater trochanteric transfers, three greater trochanteric apophyseodeses, three adductor longus tenotomies, three proximal femoral valgus osteotomies, two proximal femoral varus osteotomies, and one distal femoral epiphysiodesis. Five patients had SA alone; nine patients had one additional procedure; and three patients had two additional procedures done at the time of SA.
Postoperatively, ten of the patients had a 1.5 spica cast for 6 wk, one had a 1.5 spica cast for 4 wk, two had broomstick casts for 6 wk, and four had bilateral short leg casts with a bar and knee immobilizers for 6 wk.
The mean age at final follow-up was 14.25 yr (range 10–19). The mean time after SA to follow-up was 5.66 yr (range 2.0–10.75). In addition to the radiographic evaluation, the hip passive ROM measurements were completed for the affected hip by a physical therapist using an articulated double-arm goniometer. The PODCI questionnaire and the follow-up question also were completed. Final radiographs were reviewed for CEA, LAS, A/B, AAS, ATD, and were graded using the Stulberg Classification.38 Preoperative values and final follow-up values were statistically compared. A P value<0.05 was considered to be significant. Analysis was undertaken using a two-tailed paired t test on GraphPad Prism version 5.0d for Mac OS X, GraphPad Software, San Diego California USA, http://www.graphpad.com.
RESULTS
Clinical Cohort
There were 12 boys and five girls. For these 17 patients, an SA was the initial bony surgical procedure. The mean age of this population at diagnosis was 7.49 yr (range 3–11 yr). These patients had a mean of 4.11 mo (range 0-12 mo) of symptoms before diagnosis. Pain was cited in 11 of 17 patients, and limping was seen in 10 of 17 patients. The mean age at surgery was 8.65 yr (range 4-13 yr). Based on radiographic assessment, 10 hips were graded Herring B, two were Herring B/C border, and five were Herring C. Before surgery, 13 of 17 underwent formal physical therapy, 14 used anti-inflammatory medications, six underwent Petrie abduction casting, four tried the Atlanta-Scottish-Rite abduction brace, eight used crutches, two were nonweightbearing in a wheelchair, one was placed on bed rest, five underwent an adductor longus tenotomy, one underwent a hip aspiration, one had a cortisone injection, and one underwent traction.
Clinical Evaluation
When comparing the range of motion preoperatively and at final follow-up, the only significant improvement was with internal rotation (P=0.0033); with a mean of 8.08 degrees preoperatively and 24.3 degrees at final follow-up (Figure 1A). Data sets were incomplete and based on 13 of 17 patients. If a data point was missing for the preoperative range of motion or at final follow-up, then that patient’s data were not used in the mean calculation. Abduction was not significantly affected (P=0.0981) with a mean of 21.5 degrees preoperatively and 29.5 degrees at final follow-up, as measured for 13 of 17 patients (Figure 1B). Flexion also was not significantly affected (P=0.2419) with a mean of 79.5 degrees preoperatively and 93.6 degrees at final follow-up, as measured for 10 of 17 patients (Figure 1C). Lastly, extension was not significantly affected (P=0.7264), with a mean of 13.3 degrees preoperatively and 8.1 degrees at final follow-up, as measured for nine of 17 patients.
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FIGURE 1: Standard box plots of the range of motion data. The centerline through the box is the median or 50th percentile of the sample, the upper edge of the box is the 75th percentile, and the lower edge is the 25th percentile. The top whisker is the sample maximum and the lower whisker is the sample minimum. (A) Internal rotation. (B) Abduction. (C) Flexion. *signifies statistical significance with a P value <0.05.
Radiographs
Statistical analysis of the radiographic evaluation showed a significant improvement in all radiographic parameters (P values 0.0001 to 0.04993) with the exception of ATD (P=0.5648). The ATD initially had a mean of 13.9 mm and at final follow-up was 25.2 mm (Figure 2A). The percent subluxation of the femoral head (A/B) decreased from a mean of 14.2% to a mean of 5.58% (P=0.0323) (Figure 2B). The acetabular angle of Sharp (AAS) improved from a mean of 43.7 degrees to a mean of 36.5 degrees (P=0.0006) (Figure 2C). The CEA improved from a mean of 23.8 degrees to a mean of 34.7 degrees (P=0.0499) (Figure 2D). At final follow-up, two hips (11.8%) were classified as Stulberg grade 1, four (23.5%) as grade 2, six (35.3%) as grade 3, two (11.8%) as grade 4, and two (11.8%) as grade 5. One of the hips graded as a 5 went on to a total hip arthroplasty. Initially ten hips (58.8%) were graded with a lateral acetabular shape of 1, three (17.6%) graded as a 2, and four (23.5%) graded as a 3. At final follow-up eleven hips (64.7%) were graded with a lateral acetabular shape of 1, three (17.6%) graded as a 2, and three (17.6%) graded as a 3.
FIGURE 2: Standard box plots of the radiographic data. The centerline through the box is the median or 50th percentile of the sample, the upper edge of the box is the 75th percentile and the lower edge is the 25th percentile. The top whisker is the sample maximum and the lower whisker is the sample minimum. (A) Articulotrochanteric distance (ATD). (B) Percent subluxation of the femoral head (A/B). (C) Acetabular angle of Sharp (AAS). (D) Wilberg center edge angle (CEA). *signifies statistical significance with a P value <0.05.
Figure 3 shows the radiographic result of an 8-year-old girl with a Herring B/C border hip treated with SA that ended up with a Stulberg 5 result. Figure 4 demonstrates the radiographic result of a 6-year old-boy with a Herring B hip treated with SA that resulted in a Stulberg 2 hip.
FIGURE 3: (A–C) Herring group B/C Perthes disease in an 8-year-old girl prior to lateral shelf acetabuloplasty with narrowing and shortening of the lateral pillar. (B) Worsening of the femoral head deformity 2.9 yr after surgery. (C) Stulberg group V, 2.9 yr after surgery showing collapse of the femoral head.
FIGURE 4: (A) Herring group B Perthes disease prior to lateral shelf acetabuloplasty with a lateral pillar with less than 50% of the original height maintained in a 6-year-old boy. (B) Coxa magna, 7.9 yr after surgery with an aspherically congruent acetabulum. (C) Stulberg group II, 7.9 yr after surgery with some loss of head height but conforming within 2 mm to a concentric circle.
PODCI Scoring
The completion of the PODCI was the final component to the study. The PODCI is a validated tool, whereby the data are analyzed and then normative scores are reported for six outcome measures. Each outcome is scored on a scale that has a mean normative score of 50. The mean normative score for the upper extremity scale in the study cohort was 51.8 (SD 3.07) and a range of 44-53. The mean normative score for the transfer and basic mobility scale was 48.6 (SD 5.49; range of 34-52); for the sports and physical functioning scale 44.4 (SD 11.69; range of 20-56); for the pain/comfort scale 45.5 (SD 12.75; range of 19-57); for the happiness scale 55.4 (SD 5.32; range of 41-60); and for the global functioning scale 45.3 (SD 11.12; range of 26-57).
Study Question
Each study participant was asked to answer a question about whether or not they would recommend this procedure to others. Sixteen of the 17 participants responded to the question, and all 16 stated they would recommend SA to others for the treatment of symptomatic LCP disease.
DISCUSSION
The management of Legg-Calvé-Perthes disease continues to be difficult. Nonoperative treatment of LCP disease is problematic. Maintaining hip ROM, especially hip abduction, is well accepted. Physiotherapy and judicious use of nonsteroidal antiinflammatory medications are commonly recommended.40 Hip abduction bracing has been tried, but most studies have demonstrated lack of containment with bracing alone.41 Adductor tenotomy and Petrie casting can also play a role in treatment, usually to decrease inflammation and maintain hip ROM.42
Achieving a relatively spherical femoral head and a congruent hip joint at skeletal maturity are goals of any treatment for LCP disease. Age at the onset of disease is a known risk factor in the ultimate prognosis for hip development. Children ages 8 yr or older are a higher risk group. Containment by PVFO or Salter osteotomy prior to the stage of late fragmentation in Herring B or B/C border hips in children ages 8 yr or older is supported in the literature.3
SA done early in the course of LCP disease may be analogous to a Salter osteotomy, and will provide containment for these at-risk hips. The decision to perform additional procedures in this retrospective study was at the discretion of the treating surgeon. Valgus osteotomy was done in three patients in whom hinge abduction was documented by arthrogram. We would expect the valgus osteotomy to eliminate hinged abduction but worsen the coverage of the femoral head. The SA was used to improve femoral head coverage. The indication for a varus proximal osteotomy typically would be made for “hypercontainment” or for large femoral heads where SA alone may not lead to full femoral head coverage; thus improving coverage by providing additional containment. This is analogous to the combination of Salter and PVFO to “hypercontain” the femoral head.5,13,43 This was performed in only two patients in our study with good overall results.
A PFVO does have some potential drawbacks. It leads to a shortened limb, an adducted hip, genu valgus, and a lurching gait pattern. Additional future surgeries are more common after PFVO. These can include hardware removal, valgus osteotomy or trochanteric advancement for lever arm dysfunction, and opposite limb epiphysiodesis for leg-length discrepancy. Trochanteric overgrowth after SA is less likely since the proximal femoral anatomy is not altered.
Femoral acetabular impingement (FAI) is nearly universal after healing of LCP disease. Coxa brevis and coxa magna that are seen as a result of the disease, lead to femoral head and neck offset problems and cam impingement. Acetabular procedures like a Salter osteotomy or SA lead to increased femoral head coverage and likely predispose to pincer impingement. Long-term studies are needed to assess whether more aggressive treatment of FAI lesions in adolescence or early adulthood will lead to less end-stage hip arthritis.
Limitations of this study include its retrospective nature, small sample size, and use of historical controls. Despite numerous attempts to contact subjects, only 47% (17 of 36) of patients were located and participated in the study.
Seventy percent of our patients had good or fair results and 30% had poor results in this nonselective group of patients with LCP disease. We found SA to be useful in the treatment of symptomatic LCP disease during any stage of the disease process.
Our results for containment compare favorably with previous studies using proximal femoral varus osteotomies or Salter procedures for containment.3,6–10 This study supports other studies23–26,28,29 that SA is useful for late stage disease or for hinge abduction.
All measurements for coverage of the femoral head were improved. The SA did not affect lateral acetabular shape and ATD. Outcome measures as determined by PODCI show a modest decrease in mobility, physical functioning, and comfort with a slight increase in happiness as compared to normative data. Sixteen out of 17 would recommend SA to others for the treatment of their LCP disease.
In conclusion, SA is a versatile procedure that can effectively treat symptomatic LCP disease early for containment or later to provide femoral head coverage or to treat hinge abduction.
ACKNOWLEDGMENTS
The authors would like to express our gratitude to Gabriela Ferski, RN, MPH, MS and Sarah Werner, PAc for their assistance with this manuscript. There are no conflicts of interest to disclose by the authors.
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