Outcomes after Customized Individually Made Total Knee Arthroplasty
Huber, B; Tait, R; Kurtz, W; Swanson, T; Martin, G; Dickey I; Mack, D; Burkhardt, J; Clyburn, T
Introduction
Customized Individually Made (CIM) TKA implants with patient customized femoral components, customized tibial trays, and customized inserts are available as an alternative to traditional, off-the-shelf implants. Data obtained in studies with this implant are encouraging. Hence, the objective of this multicenter study was to prospectively analyze adverse events and outcomes scores on a larger series of patients implanted with a CIM TKA.
Methods
At 9 centers across the United States a cohort of 326 patients have been prospectively recruited and implanted with a CIM TKA (iTotal CR, ConforMIS, Inc., Bedford, MA) to date. Institutional Review Board approval was obtained at all sites and all patients were consented prior to participating in the study. Consistent with the indications for cruciate retaining TKA, patients with compromised posterior cruciate or collateral ligaments or having a varus/valgus deformity >15° were excluded from the study. Patients were assessed for Range of Motion, the 2011 Knee Society Score (KSS), the Knee Injury and Osteoarthritis Outcome Score (KOOS) pre-operatively, at 6-weeks (309 patients), 6-months (253), 1-year (179), and 2 years (42) post-operatively. In addition, post-operative adverse events such as manipulations under anesthesia (MUA), transfusions and revision rates were tracked.
Results
Average age of the patient population was 65 yrs (range: 40-84), while the average BMI was 30 (range: 18.5- 41). 53.5% of the enrolled patients were female. Range of motion was improved from an average of 110° preoperatively to 123° at 2 years post-op (110° at 6 wks, and 120° at 6 months, 122° at 1 year) (figure 1). By the 6 week time-point, patients demonstrated significant improvement from baseline scores across all 5 domains of the KOOS (p<0.05) and 3 out of 4 domains of the KSS (p<0.05), with continued improvement at the one year follow up visit (figure 2). Post-operative analysis revealed 9 (2.8%) reported MUAs for stiffness or reduced range of motion. Five (1.53%) patients received transfusions post-surgery. There have been 3 (0.9%) poly-swap reoperations in patients who continue to be enrolled in the study, in addition to 2 (0.6%) complete revisions to OTS TKA to date (1 due to traumatic fracture after patient fall, 1 due to nickel allergy).
Discussion
The 2-year follow up data collected on CIM TKA compares favorably to adverse event rates, as well as patient outcome scores, when compared to multicenter studies published on off-the-shelf implants. Manipulation rates are consistent with published studies of 4.6%3. Results from this study support previous findings that patients implanted with the CIM TKA experience significant improvements in outcome scores for the KSS, KOOS, and higher range of motion from baseline post-surgery. The CIM TKA also demonstrated an excellent safety profile, with a low transfusion rate (1.5%), low manipulation rate (2.8%), and favorable complete revision (0.6%) and poly-swap rates (0.9%).
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