Date Published: August 25, 2012
Publisher: Informa Healthcare
Author(s): Bert Boonen, Martijn G M Schotanus, Nanne P Kort.
Patient-specific templating total knee arthroplasty (TKA) is a new method for alignment of a total knee arthroplasty that uses disposable guides. We present the results of the first 40 consecutive patients who were operated on using this technique.
In this case-control study, we compared blood loss, operation time, and alignment of 40 TKAs performed using a patient-specific templating alignment technique with values from a matched control group of patients who were operated on by conventional intramedullary alignment technique. Alignment of the mechanical axis of the leg and flexion/extension and varus/valgus of the individual prosthesis components were measured on standing, long-leg, and standard lateral digital radiographs. The fraction of outliers (> 3˚) was determined.
Mean mechanical axis of templating TKAs was 181° with a fraction of outliers of 0.3, and mean mechanical axis of conventional TKAs was 179˚ (outlier fraction 0.5). Fraction of outliers in the frontal plane for femoral components was 0.05 in the templating TKAs and 0.4 in the conventional TKAs, and for tibial components the corresponding values were 0.2 and 0.2. In the templating TKAs and conventional TKAs, fraction of outliers in the sagittal plane was 0.4 and 0.9, respectively, for femoral components and 0.4 and 0.6 for tibial components. Mean operation time was 10 min shorter and blood loss was 60 mL less for templating TKA than for intramedullary-aligned TKAs.
Patient-specific templating TKA showed improved accuracy of alignment and a small reduction in blood loss and operating time compared to intramedullary-aligned TKA, but the fraction of outliers was relatively high. Larger RCTs are needed for further evaluation of the technique and to define the future role of patient-specific template alignment techniques for TKA.
40 knees in 39 patients (25 women) with osteoarthritis were operated on by means of the SPPC procedure between December 2009 and March 2010, and were eligible for inclusion in this case-control study. We excluded patients with a BMI above 35, patients with a history of osteotomy, and patients with metal near the knee joint.
Patients in the SPPC group (n = 40) were adequately matched to a control group (n = 40) with respect to age, sex, and operative procedure. Mean age was 68 years in both groups, and there were 25 women in each group. Mean BMI indices for both groups indicated an overall overweight (non-obese) classification of patients. Mean preoperative mechanical axis in the SPPC group was 175° (range 162–188, SD 6.4). 31 of 40 had varus mechanical axis (range 162–178°) and 9 of the 40 had valgus mechanical axis (range 180–188°). No preoperative long-leg radiographs were taken in the control group.