Outcome & Survival Analysis of Conventional Measured Resection, Neutral Alignment Attune TKA vs CAS Anatomic Tibia, Balanced Femur, Constitutional Alignment Attune TKA

OBJECTIVES: Arthroplasty knee surgeons have traditionally performed a measured resection technique with a neutral mechanical axis. We have recently developed a new total knee arthroplasty technique whereby the tibia is cut anatomically and the femoral component position is determined using a balanced approach utilizing a computer assisted ligament tension device with aim of restoring constitutional alignment. This study compares the Oxford scores and survival of these two techniques for Attune TKA’s. METHOD: The New Zealand Joint Registry has requested Oxford Knee Scores at six months on all Attune Total Knee Replacements performed. 1088 scores have been returned. 716 have been performed using a conventional measured resection technique aiming for a neutral mechanical axis. 362 have been performed using the CAS anatomic tibia, balanced femur (ATBF) technique aiming for constitutional alignment. Oxford scores are compared alone and with a multivariate analysis including age, sex, surgeon level, fixed vs mobile, public vs private, operative time and cruciate retaining vs cruciate substituting RESULTS: Mean Oxford Conventional TKA univariate Oxford Score is 38.1 Mean Oxford CAS ATBF TKA univariate Oxford Score is 40.7 p=<0.001 Mean Oxford Conventional TKA multivariate Oxford Score is 36.9 Mean Oxford CAS ATBF TKA multivariate Oxford Score is 39.1 p=<0.001 The CAS ATBF had 10% less poor and fair scores and 15% more excellent scores Non infection conventional TKA has 0.71 failures per 100 component years Non infection CAS ATBF TKA has 0.25 failures per 100 component years. CONCLUSION: The CAS assisted anatomic tibia balanced femur TKA has a significantly higher Oxford score with a three times lower non infection failure rate at three years