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- Title
Intra-operative femoral condylar stress during arthroscopy: an in vivo biomechanical assessment.
- Authors
Schmid, Rahel B.; Wirz, Dieter; Göpfert, Beat; Arnold, Markus P.; Friederich, Niklaus F.; Hirschmann, Michael T.
- Abstract
Purpose: Excessive varus and valgus stress forces during arthroscopy might exceed minimal compressive strength of cancellous bone. In extreme cases, this could lead to post-arthroscopic osteonecrosis. It was our purpose to measure the valgus and varus stress forces during arthroscopy and draw conclusions on the development of osteonecrosis. Methods: On 24 consecutive patients undergoing arthroscopy, the maximum varus and valgus stress forces ( N) were measured in vivo using a strain gauge mounted to a leg holder. The forces ( N) and contact stresses (kPa) on the femoral condyles were calculated based on the measured acting lateral force at the femur fixation based on the lever principle. Results: The maximum contact stress during varus on the medial condyle was significantly lower in patients with intact meniscus (mean ± standard error of the mean: 243 ± 29 kPa) than in patients with meniscus-deficient knees (520 ± 61 kPa; P < 0.01). A similar finding was obtained for the maximum contact stress during valgus on the lateral condyle: 630 ± 72 kPa in patients with intact meniscus compared to 2,173 ± 159 kPa in patients with meniscus-deficient knees ( P < 0.01). In 19 patients (79%), the maximum contact stress was higher during valgus than during varus. The maximum contact stress on the lateral condyle during valgus was significantly higher for more experienced surgeons ( P = 0.01). Conclusion: The maximum contact stresses in knees with intact menisci did not exceed the critical threshold of the compressive strength in cancellous bone. However, the maximum contact stresses in meniscus-deficient knees were frequently higher than the threshold. However, these stresses were much lower than those during daily activities and therefore unlikely to lead to post-arthroscopic osteonecrosis. Level of evidence: Diagnostic study, Level II.
- Subjects
ARTHROSCOPY; FEMUR surgery; OSTEONECROSIS; KNEE surgery; BIOMECHANICS
- Publication
Knee Surgery, Sports Traumatology, Arthroscopy, 2011, Vol 19, Issue 5, p747
- ISSN
0942-2056
- Publication type
Article
- DOI
10.1007/s00167-010-1346-3