Several authors have reported that Computer-Assisted Surgery (CAS) can improve limb and prosthesis alignment and ligament balancing in total knee arthroplasty (TKA) and permit the use of a less invasive surgical procedure. This can have a positive impact on the time of recovery of patients. In order to evaluate the real impact on the final outcome of CAS in TKA, we conducted a prospective control study comparing the outcome of computer-assisted and conventional TKAs. We analyzed 60 primary TKAs, randomly divided into two cohorts -group 1 = STD (standard instrumentation) and group 2 = CAS -over three consecutive years. Both cohorts included 30 cases, all affected by primary knee osteoarthritis. The same model of prosthesis was implanted in all cases, by one surgeon, using the same surgical technique. Two patients were bilateral: in both cases one side was treated with standard instrumentation and the other with CAS. We conducted a clinical evaluation at the pre-operative moment and at the consecutive Follow-Up (FU), using the American Knee Society Score (AKSS). We scored patient satisfaction using the Oxford and the Ranawat Center questionnaire. We also recorded the main intra-operative data, such as total blood loss, surgical time, tourniquet time, Range of Motion (ROM). Finally, we performed a radiological study analyzing the pre-operative and consecutive FU radiographs to obtain a quantitative evaluation of limb and prosthesis alignment. The intra-operative blood loss was higher in patients of group STD, with an average difference of 127 ml, statistically significant (p = 0.0283). Component position was acceptable for all implants, but the mechanical axe error of the CAS group was (1.00 +/−0.20) degrees, significantly less than that of the STD group (2.10 +/−0.50) degrees. The mean coronal femoral alignment was 90.00 degrees (range, 89 −92 degrees) in the CAS group, and 91.00 degrees (range, 88 −93 degrees) in the STD group. The operating time of the CAS group was longer than that of the STD group, with an average time difference of 26 minutes, statistically significant [ P = 0.005]. The AKSS and the Oxford and the Ranawat Center questionnaire analysis revealed a faster rehabilitation and an earlier return to daily life activities in the CAS group, independent of the preoperative level of disability. We conclude that the use of navigation in TKA increases accuracy in limb and implant alignment and improves the rehabilitation phase. By achieving more reliable artificial joint implantation, CAS can improve prosthesis duration and joint function. It, however, needs more operating time.
In the past, the clinical outcome of earlier types of resurfacing hip arthroplasty was often characterised by a high percentage of failures and early mobilisations. An implant retrieval of a Co-Cr head and UHMWPE cup cemented resurfacing hip prosthesis was analysed. The implant was in place 11 years, without any clinical problem for nearly 10 years. The cup was highly worn. There was a complete fracture of the interface between cement and bone at the base of the femural neck. A significant hyperplastic reaction was present at the level of the synovial membrane, with fibrin deposits, hyperplasia of lining cells and a cellular infiltrate formed mostly by macrophages, with occasional giant cells and localised groups of perivascular lymphocytes. Immunohistochemical analysis showed that all lymphocytes were of the T type and that the largest part of macrophages containing debris were not activated. Inside the prosthetic head there were only traces of ossified tissue. This picture indicated that for a long time no viable bone tissue had been in contact with the cement and bone rarefaction was massive. The study shows an important cause of the failure of earlier types of hip resurfacing arthroplasty, namely the abnormal stress distribution that caused the complete bone rarefaction.
