Friedrich Boettner1, Bernhard Springer2, Reinhard Windhager2, Wenzel Waldstein2. 1. Adult Reconstruction and Joint Replacement Division, Hospital for Special Surgery, New York, NY, 10021, USA. boettnerf@hss.edu. 2. Department of Orthopaedic and Trauma Surgery, Vienna General Hospital, Medical University of Vienna, Vienna, Austria.
Abstract
PURPOSE: A radiographic overlap of the lateral femoral condyle and the lateral tibial spine ('tibial spine sign') might indicate lateral compartment cartilage damage and might be considered a contraindication for unicompartmental knee arthroplasty (UKA). Therefore, the following research questions were asked: (1) does the presence of a 'tibial spine sign' on radiographs correlate with cartilage lesions on the medial aspect of the lateral femoral condyle on corresponding MRIs?; (2) do cartilage lesions on the medial aspect of the lateral femoral condyle indicate cartilage damage in the central area of the distal lateral femur?; and 3) is the 'tibial spine sign' impacted by the degree of varus deformity, the amount of coronal tibiofemoral subluxation or the functional status of the ACL? METHODS: One hundred consecutive knees with varus OA in 84 patients were prospectively included. The relationship of the lateral femoral condyle and the tibial spine was graded from 0 to 2 based on the degree of overlap on AP standing knee radiographs. On MRI, cartilage on the medial aspect of the lateral femoral condyle was assessed. Cartilage in the weight-bearing area of the distal lateral femur was analysed according to the OARSI system. RESULTS: The 'tibial spine sign' assessment correlated well with the degree of cartilage damage on the medial aspect of the lateral condyle (rs = 0.7, p < 0.001) but did not impact histological OARSI grades in the central weight bearing area of the lateral condyle (n.s.). Mechanical varus and tibiofemoral subluxation were not associated (n.s.) with a positive tibial spine sign. Knees with suggestive ACL insufficiency on MRI had more often a positive tibial spine sign; however, this difference was not statistically significant (n.s.). CONCLUSION: A positive tibial spine sign does not indicate histologic cartilage damage in the central area of the distal lateral femur and may not be considered a contraindication for medial UKA. LEVEL OF EVIDENCE: Level III, diagnostic study.
PURPOSE: A radiographic overlap of the lateral femoral condyle and the lateral tibial spine ('tibial spine sign') might indicate lateral compartment cartilage damage and might be considered a contraindication for unicompartmental knee arthroplasty (UKA). Therefore, the following research questions were asked: (1) does the presence of a 'tibial spine sign' on radiographs correlate with cartilage lesions on the medial aspect of the lateral femoral condyle on corresponding MRIs?; (2) do cartilage lesions on the medial aspect of the lateral femoral condyle indicate cartilage damage in the central area of the distal lateral femur?; and 3) is the 'tibial spine sign' impacted by the degree of varus deformity, the amount of coronal tibiofemoral subluxation or the functional status of the ACL? METHODS: One hundred consecutive knees with varus OA in 84 patients were prospectively included. The relationship of the lateral femoral condyle and the tibial spine was graded from 0 to 2 based on the degree of overlap on AP standing knee radiographs. On MRI, cartilage on the medial aspect of the lateral femoral condyle was assessed. Cartilage in the weight-bearing area of the distal lateral femur was analysed according to the OARSI system. RESULTS: The 'tibial spine sign' assessment correlated well with the degree of cartilage damage on the medial aspect of the lateral condyle (rs = 0.7, p < 0.001) but did not impact histological OARSI grades in the central weight bearing area of the lateral condyle (n.s.). Mechanical varus and tibiofemoral subluxation were not associated (n.s.) with a positive tibial spine sign. Knees with suggestive ACL insufficiency on MRI had more often a positive tibial spine sign; however, this difference was not statistically significant (n.s.). CONCLUSION: A positive tibial spine sign does not indicate histologic cartilage damage in the central area of the distal lateral femur and may not be considered a contraindication for medial UKA. LEVEL OF EVIDENCE: Level III, diagnostic study.