Muscle Strength Characteristics Following Megaprosthetic Knee Reconstruction for Bone Sarcoma

Objective: To assess muscle strength characteristics in patients with resection and megaprosthetic reconstruction of the knee for bone sarcoma compared to age- and sex-matched controls. Methods: This was a cross-sectional, case-control study. Muscle strength characteristics for knee extension and -flexion were assessed isokinetically at three different joint velocities: 60, 120 and 180 degrees/s, and by the rate of force development (RDFmax) in knee extension. The Toronto Extremity Salvage Score (TESS) was used in patients. Results: Eighteen patients (91.6 months postop.) and 18 controls were included. Relative to controls, patients generated maximal torques of 19%, 23% and 23% in knee extension at 60, 120 and 180 degrees/s, respectively. For knee flexion, patients generated maximal torques of 58%, 53% and 60% at 60, 120, and 180 degrees/s, relative to the controls. RDFmax of the operated leg was 2.75 +/- 2.13 N/ms, 7.16 +/- 4.78 N/ms for the non-operated leg, and 7.95 +/- 4.29 N/ms for the controls. The mean TESS score was 84.0. Conclusion: Patients reached approximately 20% of the maximal knee extension torque. In isometric assessments, they used double the amount of time to generate one-third of the maximal force compared to the controls despite good TESS scores.