Predictors of Persistent Limp Following Proximal Femoral Varus Osteotomy for Perthes Disease.

INTRODUCTION: One of the most popular containment procedures for Legg-Calvé-Perthes disease (LCPD) is proximal femur varus osteotomy (PFO). While generally successful in achieving containment, PFO can cause limb length discrepancy, abductor weakness, and (of most concern for families) a persistent limp. While many studies have focused on radiographic outcomes following containment surgery, none have analyzed predictors of this persistent limp. The aim of this study was to determine clinical, radiographic, and surgical risk factors for persistent limp 2 years after PFO in children with LCPD.

METHODS: A retrospective review of a prospectively collected multicenter database was conducted for patients aged 6 to 11 years at disease onset with unilateral early-stage LCPD (Waldenström I) who underwent PFO. Limp status (no, mild, and severe), age, BMI, and pain scores were obtained at initial presentation, 3-month, and 2-year postoperative visits. Preoperative and follow-up radiographs were used to measure traditional morphologic hip metrics including acetabular index (AI), lateral center-edge angle (LCEA), and femoral neck-shaft angle (NSA). Univariate analysis as well as multivariate logistic regression models were used to analyze factors associated with mild and severe limp at the 2-year visit.

RESULTS: A total of 95 patients met the inclusion criteria, and of these 50 patients underwent concomitant greater trochanter apophysiodesis (GTA) at the time of PFO. At the 2-year visit, there were 38 patients (40%) with a mild or severe limp. Multivariate logistic regression revealed no significant radiographic factors associated with a persistent limp. However, lower 2-year BMI and undergoing GTA were associated with decreased rates of persistent limp regardless of age (P<0.05). When stratifying by age of disease onset, apophysiodesis appeared to be protective against any severity of limp in patients aged 6 to 8 years old (P= 0.03), but not in patients 8 years or older (P= 0.49).

CONCLUSIONS: Persistent limp following PFO is a frustrating problem that was seen in 40% of patients at 2 years. However, lower follow-up BMI and performing a greater trochanter apophysiodesis, particularly in patients younger than 8 years of age, correlated with a lower risk of postoperative limp.