The implementation of standards for deformity correction planning of axial deformities and leg length discrepancy in paediatric orthopaedics and posttraumatic cases have improved the results of postoperative alignment and joint orientation. A variety of externally and internally applicable devices have been developed for limb lengthening and deformity correction. One of the most recent developments is the Taylor Spatial Frame Fixator based on a hexapod system and a computer software for deformity correction. But little is published about clinical results using this sophisticated technique and its possible advantages over other traditional unilateral fixators or ring systems. In times of difficulties financing our health care systems, a surgeons choice for a comparatively costly system should be based on qualified data. The aim of the present study was to compare the results of deformity correction and limb lengthening using a Taylor Spatial Frame with those of other ring fixators or unilateral systems. Between 1996 and 2004, 72 deformity corrections and/or limb lenghtenings have been performed on 52 patients with the unilateral Orthofix system (n=32), the Ilizarov system (n=22) and the TSF device (n=18). Statistical analysis showed a direct correlation between the healing index and the age at operation, as well as between the lengthening distance and the rate of complications. There were no significant differences of the healing index between all three fixators and the number of complications between the Ilizarov and TSF device, but the unilateral Orthofix fixator showed significantly more axial deviations during distraction osteogenesis. The Taylor Spatial Frame is easier to handle than the Ilizarov fixator but did not show superior results in clinical use.
Studies on the migration of an implant may be the only way of monitoring the early performance of metal-on-metal prostheses. The Ein Bild Roentgen Analyse - femoral component analysis (EBRA-FCA) method was adapted to measure migration of the femoral component in a metal-on-metal surface arthroplasty of the hip using standard antero-posterior radiographs. In order to determine the accuracy and precision of this method a prosthesis was implanted into cadaver bones. Eleven series of radiographs were used to perform a zero-migration study. After adjustment of the femoral component to simulate migration of 3 mm the radiographs were repeated. All were measured independently by three different observers. The accuracy of the method was found to be ± 1.6 mm for the x-direction and ± 2 mm for the y-direction (95% percentile). The method was validated using 28 hips with a minimum follow-up of 3.5 years after arthroplasty. Seventeen were sound, but 11 had failed because of loosening of the femoral component. The normal (control) group had a different pattern of migration compared with that of the loose group. At 29.2 months, the control group showed a mean migration of 1.62 mm and 1.05 mm compared with 4.39 mm and 4.05 mm in the failed group, for the centre of the head and the tip of the stem, respectively (p = 0.001). In the failed group, the mean time to migration greater than 2 mm was earlier than the onset of clinical symptoms or radiological evidence of failure, 19.1 EBRA-FCA is a reliable and valid tool for measuring migration of the femoral component after surface arthroplasty and can be used to predict early failure of the implant. It may be of value in determining the long-term performance of surface arthroplasty.
