Radiographic classification and treatment of fibrous dysplasia of the proximal femur: 227 femurs with a mean follow-up of 6 years

In reviewing the literature on fibrous dysplasia of the proximal femur, we found that the descriptions, treatments, and outcomes of similar lesions could substantially differ across studies. For example, when treating a femur without fracture and deformity, one can use conservative treatment, curettage and bone grafting, or internal fixation [12, 13]. Therefore, it is difficult for readers to compare the various treatments and choose the appropriate one because there is no such classification system to help standardize the description of this disease. Furthermore, there are no specific treatments based on the different disease types. In this study, we classified fibrous dysplasia of the proximal femur into five reproducible types by retrospectively reviewing AP X-ray and axial CT images of 227 femurs in 206 patients. We also assessed the repeatability of this classification system with the kappa test. Finally, we propose different treatments according to these different types and report the effectiveness of these treatments through mid-term follow-up. We treated 75 type 1 femurs conservatively, and only three type 1 femurs progressed to type 2. Therefore, we believe that conservative treatment may be sufficient for type 1 femurs. DiCaprio and Enneking drew a similar conclusion in a study published in 2005, which was the most comprehensive publication on fibrous dysplasia to date [14]. For type 2 femurs without fracture, internal fixation alone may be sufficient. For type 2 femurs with fracture, open reduction and internal fixation should be performed [15]. For type 3–5 femurs, valgus osteotomy and internal fixation are necessary [5, 6, 8]. For type 5 femurs, double-level osteotomy should be performed to correct the coxa vara and the varus deformity in the proximal femoral shaft. The double-level osteotomy can be performed in a one-stage or two-stage operation [16]. The one-stage valgus osteotomy has several advantages compared with two-stage osteotomy, including shortened treatment time, reduced number of operations, and lower medical costs. Therefore, we treated the 32 type 5 femurs with one-stage double-level valgus osteotomy. All alignments of the lower extremity were corrected to normal. This result is consistent with that of the 2009 report of Liu, who treated five type 5 femurs with double-level valgus osteotomy in a one-stage operation and observed good healing at all osteotomy sites [17].

Finally, type 4 and type 5 femurs may have valgus deformity in the juxtaarticular area, and there may be secondary genu valgum deformity after correcting the varus deformity in the proximal femoral shaft. If the secondary valgus angle was more than 10°, we performed a varus supracondylar osteotomy (Fig. 6). We planned the varus supracondylar osteotomy in the distal femur and the valgus osteotomy in the proximal femur simultaneously before the operation. We performed the varus supracondylar osteotomy just after union of the osteotomy site in the proximal femur. To our knowledge, this study is the first to report the correction of the secondary genu valgum deformity. Our proposed surgical method may help in treating fibrous dysplasia with total femur involvement.

There are several limitations in our study. First, the lesions are described only in the coronal plane. Therefore, the recurrence or progression of the deformity in the sagittal plane could have been underestimated. Further analyses should be based on three-dimensional CT. Second, this study was a retrospective analysis without a control group. These conclusions should be tested with a prospective clinical controlled study in the future. Third, the classification and the treatments are more suitable for adult patients, as the majority of our patients were adults.