Radiographic outcomes of a treatment approach for lower leg deformities in patients with hereditary multiple exostoses

Hereditary multiple exostoses (HME) represent a rare skeletal disorder characterized by multiple osteochondromas, often leading to angular deformities in the lower limbs as well as leg length discrepancy (LLD), managed with tension band plates (TBP) for deformity correction. However, the utility of both angular deformity and LLD in HME has not been comprehensively evaluated. In this study, we retrospectively reviewed 25 pediatric patients with HME who visited our institution and reached skeletal maturity between 2012 and 2024, assessing a total of 50 limbs. Surgical indications included patients aged greater than 10 years with an open growth plate, predicted LLD of greater than or equal to 20 mm at the skeletal maturity, and a mechanical axis zone (MAZ) greater than or equal to Zone 2. We categorized the outcomes into four groups: excellent [LLD < 10 mm; mechanical axis percentage (%MA) ≤ ±25%], good (LLD < 15 mm; %MA ≤ ±50%), fair (LLD < 20 mm or at least one limb classified as %MA ≤ ±100%), and poor (worse than the previous categories). We used paired t-tests for statistical analyses. Among the 17 surgically treated patients, TBP was performed on 27 limbs and 60 physes. In most cases, multisite and staged surgeries were required. Angular deformities improved significantly, with the mean hip-knee-ankle angle reduced from 7.8 to 2.7° (lower extremity < 0.01), and 92% of limbs achieved MAZ Zone 1. LLD was corrected from 17.6 to 5.6 mm (P < 0.01) at an average correction rate of 0.47 mm/month. The final outcomes were excellent, good, and fair or poor in 12, 11, and 2 patients, respectively. Major complications were not observed. TBP treatment is effective in correcting both angular deformity and LLD in patients with HME, offering a minimally invasive strategy for comprehensive correction of this complex skeletal dysplasia. Careful surgical planning and timing are essential and staged multisite procedures are often required.