Background: Proprioception as an outcome for patients with osteosarcoma who have undergone modular endoprosthetic knee reconstruction has not been studied, as far as we know. The primary purpose of the present study was to understand the differences in knee proprioception between this patient population and control subjects. We also compared differences in proprioception between patients with tumors at different sites and between patients who had different proportions of bone length excised.

Methods: We evaluated twenty patients who had undergone a wide resection of a tumor about the knee followed by reconstruction with a modular endoprosthesis. The mean age of the patients was 21.7 years. The patients were grouped according to tumor site, i.e., the distal part of the femur or the proximal part of the tibia; they were also grouped according to the length of resected bone (<40% or =40% of the length of the bone). Another twenty age-matched control subjects were recruited for this study. Knee proprioception was evaluated by comparing active and passive angular repositioning of the involved limb and the normal limb in the patients and the dominant limb in the central subjects.

Results: The absolute matching error of active and passive repositioning was 2.7° ± 2.1° and 2.9° ± 2.2°, respectively, for knees treated operatively and 3.2° ± 2.1° and 2.1° ± 1.3°, respectively, for the dominant knees in the control subjects. The differences between the operatively treated knees and the control knees were not significant (p > 0.05). There was also no significant difference in proprioception between the patients with a distal femoral tumor and those with a proximal tibial tumor (p > 0.05). The proprioception of the patients with a greater length of bone resected was significantly worse in both lower extremities than that of patients with a shorter resected length (p = 0.016 for the normal side and p = 0.025 for the involved side).

Conclusions: The proprioception of the involved knees in the patients with osteosarcoma who had modular endoprosthetic reconstruction was not found to be different from the normal knees or the knees in the control subjects. On the basis of our data, we found that proprioception is probably not influenced by the tumor site. Conversely, resection length appears to be an important factor. These study findings may be used as a reference for knee proprioception in patients with osteosarcoma who have a modular endoprosthetic knee reconstruction.

Level of Evidence: Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.