Two different posterior-stabilized mobile-bearing TKA designs: navigator evaluation of intraoperative kinematic differences.

PURPOSE: The purpose of this study was to compare two types of posterior-stabilized (PS) mobile-bearing (MB) total knee arthroplasties (TKAs). The hypothesis was that no major differences were going to be found among the two TKA designs. METHODS: Two cohorts of patients who were divided according to implant design (Cohort A, new design gradually reducing radius PS MB TKA; Cohort B, traditional dual-radius PS MB TKA) were analyzed by means of intraoperative navigation. All operations were guided by a non-image-based navigation system that recorded relative femoral and tibial positions in native and implanted knees during the following kinematic tests: passive range of motion (PROM), varus-valgus stress test at 0° and 30° (VV0, VV30) and anterior/posterior drawer test at 90° of flexion (AP90). RESULTS: There were no significative differences in kinematic tests between the two implants. Cohort A, however, showed a different post-implant trend for VV0 and VV30 that were lower than the pre-implant ones, as expected, while for Cohort B, the trend is opposite. However, the gradually reducing radius prosthesis (Cohort A) showed a trend of improving stability (29% compared to the preoperative status) in mid-flexion (VV30) which the traditional dual-radius design (Cohort B) would not. Moreover, we found no differences among postoperative results of the two TKA designs. CONCLUSION: Despite design variations, no difference has been found among the prostheses in terms of PROM, rotations and translations. Both design kinematics did not show paradoxical external rotations, but an increase in femoral translation in mid-flexion without affecting the functioning of the prosthesis. LEVEL OF EVIDENCE: II.

Anterior cruciate ligament revision with Achilles tendon allograft in young athletes.

BACKGROUND: Return to sport after revision ACL reconstruction is a controversial topic, several studies reported the results of different techniques and graft in sportsman, presenting an incredibly wide range of return to the same pre-injury activity level, from 0% to 100%. The purpose of this study was to evaluate the clinical outcomes and return to sport rate in young athletes after non anatomic double-bundle revision ACL reconstruction with Achilles allograft. HYPOTHESIS: The present revision technique was effective in terms of stability, return to sport and functional outcomes. MATERIAL AND METHODS: All the athletes undergone Revision ACL reconstruction with non-irradiated Achilles tendon allograft with a non-anatomical double-bundle technique were included in the study. A split Achilles tendon allograft was used to reproduce the anteromedial (AM) bundle using the over-the-top position, while the posterolateral (PL) bundle was reconstructed through a femoral tunnel located in the anatomical PL footprint. Sport activity, knee function with Lysholm score, knee laxity and re-injury or re-operations were evaluated. RESULTS: Twenty-six athletes (23 males, three females) with a mean age of 23.4±3.6 years were evaluated at a mean follow-up of 6.0±1.6 years. Overall 69% of patients returned to sport both at elite (44%) or county level (56%) after a mean 6.7±1.5 (3-9 range) months. The mean Lysholm score showed a significant improvement from 64.4±8.1 at pre-operative status to 83.8±11.3 at final follow-up (P<.0001). Seven patients (30%) were rated as excellent, nine (39%) as good, five (22%) as fair and 2 (9%) as poor. Three patients (12%) experienced a further graft rupture after a mean 2.6 years, (3.5 months-48 months range) and two had >5mm side-to-side difference at KT-1000. Therefore, the overall survival rate at mean six years follow-up was 81%. CONCLUSION: The ACL revision with a double-bundle technique using Achilles tendon allograft was successful in 81% of athletes at six years mean follow-up. TYPE OF STUDY AND LEVEL OF EVIDENCE: Retrospective case series, level IV.

Technical variables of ACL surgical reconstruction: effect on post-operative static laxity and clinical implication.

PURPOSE: The hypothesis was that an alteration of different surgical variables of ACL reconstruction would produce significant changes in post-operative static laxity of knee joint. METHODS: Joint laxity was acquired by a surgical navigation system for 17 patients just after graft fixation during single-bundle reconstruction with extra-articular lateral tenodesis. The analysed laxity parameters were: internal/external rotation at 30° (IE30) and 90° (IE90) of flexion, varus/valgus rotation at 0° (VV0) and 30° (VV30) of flexion and anterior/posterior displacement at 30° (AP30) and 90° (AP90) of flexion. As surgical variables, the angles between the tibial tunnel and the three planes were defined as well as the lengths of the tunnel and the relationship between native footprints and tunnels. The same analysis was performed for the femoral side. All surgical variables were combined in a multivariate analysis to assess for predictive factors between them and post-operative laxities values. To quantify the performance of each multivariate model, the correlation ratio (η 2) and the corresponding P value (*P < 0.050) have been evaluated. RESULTS: Multivariate analysis underlined statistically significant models for the estimation of: AP30 (η 2 = 0.987; P = 0.014), IE30 (η 2 = 0.995; P = 0.005), IE90 (η 2 = 0.568; P = 0.010), VV0 (η 2 = 0.932; P = 0.003). The parameters that greatly affected the identified models were the orientation of the tibial tunnel with respect to the three anatomical planes. The estimation of AP30, IE30 and IE90 got lower value as the orientation of the tibial tunnel with respect to transverse plane decreases. Considering the orientation to sagittal ([Formula: see text]) and coronal ([Formula: see text]) plane, we found that their reduction provoked a decrease in the estimation of AP30, IE30 and IE90 (except [Formula: see text] that did not appear in the estimation of AP30). The estimation of VV0 got an increase of [Formula: see text], and [Formula: see text] which led to a laxity reduction. CONCLUSION: The main finding of the present in vivo study was the possibility to determine significant effects on post-operative static laxity level of different surgical variables of ACL reconstruction. In particular, the present study defined the conditions that minimize the different aspects of post-operative laxity at time-zero after surgery.