Abstract
Introduction
The aim of this study is to investigate the accuracy and reliability of a Magnetic Resonance Imaging (MRI) based Patient Match Technology (PMT) system (VISIONAIRE, Smith & Nephew, Inc, Memphis, Tenn) by intraoperative use of VectorVision knee navigation software from BrainLAB (Redwood City, California, USA).
Methods
Between February 2011 and May 2011, 15 patients with primary gonarthrosis were selected for unilateral Total Knee Arthroplasty (TKA). The first three patients were excluded from this study, as they were considered as a warm up to set up the procedure. Therefore 12 patients entered the study. Preoperatively all patient underwent a full-length weight-bearing radiograph in antero-posterior (AP) and a MRI according to the protocol suggested and approved by the manufacturer. All patients were operated with cemented posterior stabilised prosthesis cruciate ligament sacrificing (Journey BCS, Smith & Nephew, Inc, Memphis, Tennessee, USA) by the same surgeon using the VISIONAIRE patient matched cutting jigs. During surgery, once the guides were placed and fixed, the orientation was checked by the navigator. The following parameters were evaluated: size of the implant, alignment in coronal and sagittal plane. An unsatisfactory result was considered an error ≥ 2° in both plane for each component as a possible error of 4° could result in aggregate.
Results
On the coronal plane the mean deviation of the tibial guide from the ideal alignment was 1.2°±1.5 (range 0–5°) with 2 cases > 2°, while in the sagittal plane was 3.8°±2.4 (range 0–7.5°) with 7 cases exceeding 2°. On the coronal plane the mean deviation of the femoral guide from the ideal alignment was 1.2°±0.6 with 1 case > 2°, while in the sagittal was 3.7°±2.0 with 3 cases exceeding 2°. The size of the custom cutting blocks were correct in all the patients.
Conclusions
The results of this preliminary study documented a only fair accuracy of the method with a consistent risk of error of more than 2°, especially in the sagittal plane.
We could speculate that the great error found in the tibial slope and femoral flexion is due to the lack of a preoperative radiological study of the overall lower limb in lateral view as only a MRI imaging with a lateral view extending 8 cm below joint line is acquired preoperatively. On the basis of this preliminary experience, the PMT system based only on data acquisition with AP radiograms and MRI cannot be defined as accurate. In cases using custom-made cutting jigs, we recommend performing an accurate control of the alignment before making the cuts in any step of the procedure.
