Introduction
Computer assisted Total Knee Arthroplasty (TKA) has been in existence for a number of years. It has however been associated with increased surgical time and financial costs. Shape matching reduces the time associated with peri-operative computer navigation. The use of 3D imaging allows identification of the patient specific dynamic axes of the knee.
Purpose
The purpose of this study was to analyse the outcomes in patients undergoing total knee arthroplasty using 2 different alignment methods: Kinematic alignment using patient specific cutting blocks, and mechanical alignment using conventional methods. Our aim was to establish if using patient specific cutting blocks restored a greater level of functioning post operatively and if this method improved patient satisfaction.
Methods
Eleven patients (12 knees) referred for a total knee replacement were offered the option of having a Custom-fit TKA using OtisMed Shape Matched Technology (Group A). In these patients Magnetic Resonance Imaging (MRI) and weight bearing long leg radiographs were used to make patient specific cutting blocks, which aimed to restore pre-arthritic alignment to the patients knee. Eleven age, gender and functional status matched patients who underwent a TKA using the conventional method were also included (Group B). Both groups were assessed for range of motion (ROM) at 3 weeks and 6 weeks post op, SF-12 health outcome survey and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were used pre-operatively and post operatively. A phone questionnaire was devised to further assess functioning and to look specifically at patient satisfaction. Tourniquet time for both groups was also recorded.
Results
The mean age of group A was 63 years (range 50-74 years). The mean age of group B was 64 years (range 53-71 years). Both groups consisted of 5 males (42%) and 6 females (58%). One female in both groups had two TKAs. Both groups had similar KOOS and SF-12 Physical Health scores. Pre-operative Mental Health score was lower in Group B. Group B had slightly less pre op ROM, 114 degrees compared to 123 degrees. At 3 weeks post op, group A had maintained slightly more ROM 101 degrees compared to 96 degrees. ROM at week 6 was 110 degrees in group A and 107 in group B. Patients in Group A perceived greater post-operative ROM in year 2 post-op. There was no difference in KOOS scores, SF-12 scores or in patient satisfaction levels at this time.
Discussion
In this cohort study comparing the outcomes of 2 groups, one receiving a TKR using OtisMed Shape-Match technology and one the conventional method of TKR, we found no difference between groups. This study was intended to be a larger cohort study however since the study began the OtisMed product has been put on hold.
Conclusion
The benefits of OtisMed ShapeMatch technology in TKR cannot be concluded from this study. Our experience is that the outcome of this technology is engineer dependent.