Tibio-femoral and patello-femoral joint kinematics during navigated total knee arthroplasty with patellar resurfacing.

PURPOSE: In total knee arthroplasty, surgical navigation systems provide tibio-femoral joint (TFJ) tracking for relevant bone preparation, disregarding the patello-femoral joint (PFJ). Therefore, the important intra-operative assessment of the effect of component positioning, including the patella, on the kinematics of these two joints is not available. The objective of this study is to explore in vivo whether accurate tracking of the patella can result in a more physiological TFJ and PFJ kinematics during surgery. METHODS: Ten patients underwent navigated knee replacement with patellar resurfacing. A secondary system was used to track patellar motion and PFJ kinematics using a special tracker. Patellar resection plane position and orientation were recorded using an instrumented probe. During all surgical steps, PFJ kinematics was measured in addition to TFJ kinematics. RESULTS: Abnormal PFJ motion patterns were observed pre-operatively at the impaired knee. Patellar resection plane orientation on sagittal and transverse planes of 3.9° ± 9.0° and 0.4° ± 4.1° was found. A good restoration of both TFJ and PFJ kinematics was observed in all replaced knees after resurfacing, in particular the rotations in the three anatomical planes and medio-lateral patellar translation. CONCLUSIONS: Patella tracking results in nearly physiological TFJ and PFJ kinematics in navigated knee arthroplasty with resurfacing. The intra-operative availability also of PFJ kinematics can support the positioning not only of the patellar component in case of resurfacing, but also of femoral and tibial components.

Tibial component alignment and risk of loosening in unicompartmental knee arthroplasty: a radiographic and radiostereometric study.

PURPOSE: Unicompartmental knee arthroplasty (UKA) has shown a higher rate of revision compared with total knee arthroplasty. The success of UKA depends on prosthesis component alignment, fixation and soft tissue integrity. The tibial cut is the crucial surgical step. The hypothesis of the present study is that tibial component malalignment is correlated with its risk of loosening in UKA. METHODS: This study was performed in twenty-three patients undergoing primary cemented unicompartmental knee arthroplasties. Translations and rotations of the tibial component and the maximum total point motion (MTPM) were measured using radiostereometric analysis at 3, 6, 12 and 24 months. Standard radiological evaluations were also performed immediately before and after surgery. Varus/valgus and posterior slope of the tibial component and tibial-femoral axes were correlated with radiostereometric micro-motion. A survival analysis was also performed at an average of 5.9 years by contacting patients by phone. RESULTS: Varus alignment of the tibial component was significantly correlated with MTPM, anterior tibial sinking, varus rotation and anterior and medial translations from radiostereometry. The posterior slope of the tibial component was correlated with external rotation. The survival rate at an average of 5.9 years was 89%. The two patients who underwent revision presented a tibial component varus angle of 10° for both. CONCLUSIONS: There is correlation between varus orientation of the tibial component and MTPM from radiostereometry in unicompartmental knee arthroplasties. Particularly, a misalignment in varus larger than 5° could lead to risk of loosening the tibial component. LEVEL OF EVIDENCE: Prognostic studies-retrospective study, Level II.

Cartilage repair procedures associated with high tibial osteotomy in varus knees: clinical results at 11 years' follow-up.

BACKGROUND AND AIM: In this study, the authors retrospectively compared the clinical outcome of middle-aged active patients affected by a varus knee with medial unicompartmental osteoarthritis: the treatment was isolated high tibial osteotomy (HTO) for one group or HTO associated with a cartilage repair procedure, that was autologous chondrocyte implantation (ACI) for one group (HTO+ACI) and microfracture (MFX) for the other group (HTO+MFX). The purpose of this study was to analyse the clinical outcomes at long-term follow-up. The hypothesis was that a cartilage repair procedure may add some benefit to isolated axial correction. METHODS: 56 patients affected by medial osteoarthcritis in a varus knee were retrospectively investigated: 20 patients were treated by HTO, 18 by HTO+ACI and 18 by HTO+MFX. All patients underwent clinical assessment following HSS and WOMAC rating scores and a radiographic study was performed preoperatively and at follow-up. The statistical analysis confirmed that the three groups of patients were homogeneous regarding clinical, radiographical and anatomopathological patterns; differences have been reported in body mass index (BMI). RESULTS: At final follow-up, improvements in clinical and radiographical results were obtained in all patients. HTO and HTO+ACI series showed significantly higher scores compared to the HTO+MFX series. CONCLUSIONS: At more than 11 years of follow-up, isolated HTO and HTO+ACI treatments showed satisfactory results similar to those reported in the literature with no evidence of superiority of the addition of ACI to isolated HTO. MFX associated with HTO provided the worst results in the series.