Incidence and management of secondary deformities after megaendoprosthetic proximal femur replacement in skeletally immature bone sarcoma patients

TL;DR

This study examines hip and knee deformities in children after a specific type of bone replacement surgery and suggests management strategies based on remaining growth.

Contribution

The study identifies and analyzes the incidence and management of secondary hip dysplasia and genu valgum in skeletally immature patients after proximal femur replacement.

Findings

Hip dysplasia occurred in 58.3% of intraarticular resections and led to dislocation in 71.4% of those cases.

Genu valgum was observed in 41.6% of patients, with a combined incidence of 42.9% for both deformities.

Stress shielding was observed in 71.4% of patients, and management strategies varied based on patient age and growth potential.

Abstract

Megaendoprosthetic reconstruction of bone defects in skeletally immature patients has led to the development of unique complications and secondary deformities not observed in adult patient cohorts. With an increasing number of megaendoprosthetic replacements performed, orthopedic oncologists still gain experience in the incidence and type of secondary deformities caused. In this study, we report the incidence, probable cause and management outcome of two secondary deformities after megaendoprosthetic reconstruction of the proximal femur: hip dysplasia and genu valgum.

Retrospective analysis of 14 patients who underwent primary and/or repeat reconstruction/surgery with a megaendoprosthetic proximal femur replacement between 2018 and 2022.

Mean patient age was 9.1 years (range 4–17 years). Stress shielding was observed in 71.4%. Hip dislocation was the most frequent complication (50%). While four dislocations occurred without an underlying deformity, secondary hip dysplasia was identified in 58.3% (n = 7/12) of intraarticular resections and reconstructions, leading to dislocation in 71.4% (n = 5/7). A genu valgum deformity was observed in 41.6% (n = 5/12). The incidence of secondary hip dysplasia and concomitant genu valgum was 42.9% (n = 3/7). Triple pelvic osteotomy led to rebound hip dysplasia in two cases (patients aged < 10 years), whereas acetabular socket replacement led to stable hip joints over the course of follow-up. Temporary hemiepiphyseodesis was applied to address secondary genu valgum.

Patients aged < 10 years were prone to develop secondary hip dysplasia and genu valgum following proximal femur replacement in this study. Management of secondary deformities should depend on remaining skeletal growth. Stress shielding was observed in almost all skeletally immature patients.

The online version contains supplementary material available at 10.1007/s00402-024-05334-1.

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