Total knee arthroplasty is a well established treatment modality for knee osteoarthritis with an 82% satisfactory outcome as reported by the Swedish Knee Arthroplasty Register. Overall revision rate is 15% at 10 years with aseptic loosening and instability being the most common indication for revision. Axial alignment of limb with restoration of mechanical axis within a range of +/− 3° varus/valgus is thought to be associated with a better outcome. Although short term outcome results show no significant differences in CAS TKR versus traditional TKR, we expect long term clinical outcome to be better. The primary aim is to investigate the benefits and pitfalls of using CAS TKR such as improved component alignment and restoration of mechanical axis. In addition, we also share our experience of the current PiGalileo™ Computer Navigated System (ENDOPLUS®). Since October 2002 we have performed over 80 CAS TKR. We have prospectively collected pre and post operative data of patients undergoing CAS TKR and analysed the operative details, as well as evaluated their WOMAC and Knee Society Scores. We looked in particular at the performance of PiGalileo™ Computer Navigated System (ENDOPLUS®). We have positive experience with PiGalileo™ Navigation System. We have had no computer related complications. We recognize although the system is user friendly, it naturally involves a learning curve. Surgeries done with PiGalileo™ are still performed by a surgeon, with navigation and mechanized technologies aiding the surgeon in instrument positioning. Surgeons are provided with critical real-time intra-operative feedback to help improve precision, leading to better implant alignment and positioning of the implants to a degree of accuracy not possible with the naked eye. The achievable accuracy of implant positioning is less than 1 mm, and less than 1°. Data is currently being collected to prove the superior long term clinical outcome of such accuracy.
We analysed in-vivo migration and wear over a long period of all-polyethylene acetabular cups which had not been affected by mechanical loosening. The selection criteria of regular radiological follow-up, good clinical outcome (Charnley score of 5 or 6), continued walking without crutches and no radiological signs of loosening of the acetabular cups were fulfilled by 25 Charnley total hip arthroplasties. Mean migration, measured by the Nunn method, was 0.6 mm in the medial and 0.2 mm in the cranial direction. The mean yearly rate of wear was 0.05 mm and 0.04 mm, with six and two cups having no detectable wear, as measured by the Livermore and Charnley-Cupic methods, respectively. The maximal detected wear was 3.7 mm. There were no changes in the rate of wear with time. Computerised We conclude that long-term successful cups do not migrate and have a very low rate of wear which was not affected by ageing of the polyethylene. There was no evidence that polyethylene wear alone caused mechanical loosening of the cup but high rates of wear seem to have an adverse prognostic value in terms of the long-term survival of the prosthesis.
We compared the outcome of total knee arthroplasty in 19 patients who had had previous patellectomy with the results in a matched series of arthroplasties performed on knees in which the patella was intact. The mean follow-up was 63 months (21 to 114). In the study group, the outcome was poor in five patients. There was instability in the coronal plane in three patients and persistent pain in four. Three supracondylar fractures occurred. The overall complication rate was 36%. In the control group, pain was relieved in every case and there were no complications. Total knee arthroplasty has a higher complication rate and inferior results if the knee has undergone prior patellectomy.
