Material and method: Computer-assisted total knee arthroplasty (TKA) or primary osteoarthritis of the knee was performed in 51 knees in 36 patients with a mean age of 69.51 years. All procedures were performed by a single surgeon using the same implant design. The intraclass correlation coefficient (ICC) was used to compare the intra-operative CAN-FRA with the post-operative CT-FRA. The angle between the anatomical epicondylar axis and the posterior condylar axis of the implant (CT-FRA) was measured at two separate timepoints by three observers who were blinded to the intra-operative CAN-FRA. Internal rotation was defined as rotation in the negative direction, while external rotation was defined as positive.
Results: The mean intra-operative CAN-FRA was 0.1° ± 2.8° (range -5.0° to 5.5°). The mean post-operative CT-FRA was -1.3° ± 2.1° (range -4.6° to 4.4°). The mean difference between the CAN-FRA and the CT-FRA was -1.3° ± 2.2° (range -7.9° to 2.4°). The respective ICC values for the three observers were 0.92, 0.94, and 0.93, while the respective intra-observer coefficients were 0.91, 0.85, and 0.90. The ICC for the intra-operative CAN-FRA versus the post-operative CT-FRA was 0.71.
Conclusion: This study shows that using a computer-assisted navigation system in TKA achieves reliable results and helps to achieve optimal positioning of the femoral component and rotation alignment correction.
Materials and Methods: This is a retrospective study, including 48 patients from a single institution who underwent MUA for stiffness, separated into objective and subjective knee stiffness. Patients with subjective knee stiffness who underwent MUA had failed conservative management. ROM, Oxford Knee Scores (OKS), Knee Society Scores (KSS) and Short Form 36 (SF36) scores were compared at two years post MUA.
Results: The demographics of the two patient groups were similar. The time interval between index TKA and MUA was higher in the subjective knee stiffness group. Pre-MUA OKS, KS Function Score, KSS and SF36 scores were similar in both patient subgroups. There was no significant difference in the OKS, KSS or SF36 at two year follow-up. The proportion of patients in each group who achieved the Minimum Clinically Important Difference (MCID) improvement in the scores was also similar.
Conclusions: Patients with subjective knee stiffness can achieve similar functional outcome improvements in Oxford and Knee Society Scores with MUA at two years follow-up.
METHODS: Three different cams (triangle, ellipse, and circle) and three different posts (straight, convex, concave) geometries were considered in this study and were analysed using kinematic analyses. Femoral rollback did not occur until reaching 50° of knee flexion. Beyond this angle, two of the nine combinations demonstrate poor knee flexion and were eliminated from the study.
RESULTS: The combination of circle cam with concave post, straight post and convex post showed 15.6, 15.9 and 16.1 mm posterior translation of the femur, respectively. The use of ellipse cam with convex post and straight post demonstrated a 15.3 and 14.9 mm femoral rollback, whilst the combination of triangle cam with convex post and straight post showed 16.1 and 15.8 mm femoral rollback, respectively.
CONCLUSION: The present study demonstrates that the use of circle cam and convex post created the best femoral rollback effect which in turn produces the highest amount of knee flexion. The findings of the study suggest that if the design is applied for knee implants, superior knee flexion may be possible for future patients.
LEVEL OF EVIDENCE: IV.