Abstract
Reconstruction of the extensor mechanism is essential for good extremity function after endoprosthetic knee replacement following tumor resection. Only a few biological methods have been able to reliably restore a functional extensor mechanism, but they are often associated with significant complication rates. Reattachment of the patellar tendon to the prosthesis using an alloplastic patellar ligament (Trevira cord) can be an appropriate alternative. In vivo and in vitro studies have already shown that complete fibrous ingrowth in polyethylene chords can be seen after a period of six months. However, until now, no biomechanical study has shown the efficacy of an alloplastic cord and its fixation device in providing sufficient stability and endurance in daily life-activity until newly formed scar tissue can take over this function. In a special test bench developed for this study, different loading regimes were applied to simulate loads during everyday life. Failure loads and failure modes were evaluated. The properties of the cord were compared before and after physiological conditioning. It was shown that rubbing was the mode of failure under dynamic loading. Tensile forces up to 2558 N did not result in material failure. Thus, using an artificial cord together with this fixation device, temporary sufficient stable fixation can be expected.
Highlights
Until the early 1970s, amputation was the only alternative in the treatment of malignant musculoskeletal tumors
Reconstruction of the extensor mechanism is essential for good extremity function after endoprosthetic knee replacement following tumor resection
The load to failure was statistically significantly reduced by approximately 12% to 2248 N (SD = 88 N) when Trevira cords were kept for 25 days in saline at 37◦C before testing (P = .007) (Figure 5)
Summary
Until the early 1970s, amputation was the only alternative in the treatment of malignant musculoskeletal tumors. Even the five-year survival rates of patients with osteosarcoma reached only 20 percent. Since the introduction of chemotherapy and radiotherapy, survival rates have increased significantly, that is, up to 70 percent in osteosarcoma. The number of patients eligible for limb salvage procedures after wide resection of tumors has been increased continuously [4]. For reconstruction of skeletal defects after local tumor resection, both biological techniques (e.g., autografts, allografts, rotation plasty) and megaprostheses are used. These procedures, mainly allograft reconstruction and endoprostheses, are well established and have been well described in the literature [5,6,7,8]. A few biological methods, have been able to reliably restore a functional extensor mechanism [22]
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