The effect of preoperative varus on tibial cut morphology after total knee arthroplasty

Summary: Total knee arthroplasty is a surgical method for the treatment of knee osteoarthritis. Long term survival of total knee arthroplasty depends on soft tissue balance, correction of lower extremity deformities, proper component alignment and bone implant congruity. While there are papers evaluating the correlation of tibial cut surface mophology with gender, race and morphotype, we couldnt find a literature evaluating preoperative anatomic medial proximal tibial angle (aMPTA). Purpose: Evaluation of the correlation between tibial cut surface morphology and bone implant congruity with aMPTA. Material and Methods: Sixtyfive knees of fourtyfive patients (38 female, 7 male, mean age; 75 years) who undergone total knee arthroplasty for primary knee osteoathritis were evaluated. Knees of the patients were divided into two groups according to preoperative aMPTA values (Group 1; aMPTA≤5°, Group 2; aMPTA>5°) . Two groups were compared based on preoperative and postoperative AP and Lateral X-Rays, morphological measurements made on photographs of tibial cut surface taken during operation with a 90° angle and the increase of postoperative 1st year Knee Injury and Osteoarthritis Outcome Scores (KOOS). Results: Tibial width and lateral tibial condyle length of Group 2 were shorter then Group 1 and more tibial component overhang was seen on AP X-Rays of Group 2. When female and male patients were compared ; tibial width and lateral tibial condyle length of female patients knees were shorter then male patients knees and more tibial component overhang was seen on AP X-Rays of female patients. Mean postoperative 1st year KOOS score of Group 1 was higher then Group 2. Conclusion: Better bone implant congruity of total knee arthroplasty depends on the knowledge about tibial and femoral cut surface morphologies and affecting factors. Total knee arthroplasty designs with different shaped components can help maintaining optimum bone implant congruity for patients with different bone cut mophologies.