Loss to follow-up after arthroplasty: a new use for registry data

We assessed the outcome of patients who were lost to follow-up after arthroplasty by a single surgeon. The aim was to validate the surgeon's data set with the Australian Orthopaedic Association National Joint Replacement Registry and determine the outcome of those patients lost to follow-up. Prospective data on patient demographics, operative details and outcomes of the surgeon's 1192 primary unicompartmental knee arthroplasty (UKA) procedures were analysed. There were 69 knees in patients who were lost to follow-up, among whom the Registry identified 31 deaths and eight revisions. The cumulative percentage revision (CPR) at seven years using the additional Registry data was 8.8% (95% confidence interval (CI) 7 to 11). Using the surgeon's data, the CPR at seven years was 8% (95% CI 6.3 to 10.1) for the best-case scenario where loss to follow-up was excluded, and 16% (95% CI 13.8 to 19.4) for the worst-case scenario, where all patients lost to follow-up were deemed to have been revised. There was a significantly higher mortality rate in those patients lost to follow-up. This study demonstrates that a national joint registry can be used by individual surgeons to establish more accurate revision rates in their arthroplasty patients. This is expected to facilitate a more rigorous audit of surgical outcomes by surgeons and lead to more accurate and uniform reporting of the results of arthroplasty in general.

Anterior cruciate ligament graft fixation. Initial comparison of patellar tendon and semitendinosus autografts in young fresh cadavers

The initial biomechanical properties of semitendinosus and patellar tendon autografts and their fixation strengths were investigated. Twenty fresh cadaveric knees from donors under 42 years of age were used in the study. After removing all soft tissues other than the anterior cruciate ligament, we determined the ultimate tensile strength (2195 +/- 427 N) and stiffness (306 +/- 80 N/mm) of the anterior cruciate ligament in nine knees. In six knees, anterior cruciate ligaments were reconstructed using an autologous patellar tendon graft with proximal and distal interference fit screws; this resulted in an ultimate tensile strength of 416 +/- 66 N. Five knees were reconstructed with quadruple-stranded (double-looped) semitendinosus tendons fixed proximally by a titanium button and braided tape and distally by tibial post screw. This resulted in an ultimate tensile strength of 612 +/- 73 N, which was significantly higher than the strength in the patellar tendon group. Graft stiffness did not differ between the groups and was 47 +/- 19 N/mm (N = 11). This study demonstrates that the reconstructed knees had only 20% to 30% of the ultimate tensile strength of the normal anterior cruciate ligament. In summary, the semitendinosus reconstruction using a button for proximal fixation is, at the time of surgery, approximately 50% stronger than patellar tendon reconstructions with similar stiffness.