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Purpose: The anterolateral ligament (ALL) has been defined as a key stabilizer of internal tibial rotation at 35° or more of knee flexion, with a minimal primary or secondary stabilizing role in the AP direction. This study aimed to demonstrate that anatomical reconstruction of the ALL confers rotational stability equal to that of the uninjured knee., Hypothesis: anteroposterior (AP) and rotatory laxity will significantly vary after ALL tenotomy and ALL reconstruction with the author's previously described technique., Methods: After ultrasound (US) ALL identification, different kinematic measurements were performed with an image-less Computer-Assisted Navigation System with dedicated software for Laxity Analysis in 5 knee specimens. Anteroposterior (AP) translations and varus/valgus (VV) and Internal-External (IE) rotations were evaluated by two trained orthopedic surgeons before ALL section, after ALL section, and after ALL anatomical reconstruction with doubled ipsilateral autologous gracilis tendon., Results: ALL resection significantly increased laxity in IE rotations with knee 90° flexed (IE90) and AP translation with tibia internally rotated and the knee 30° flexed (APlat) (p < 0.05). ALL reconstruction significantly reduced laxity in IE90 and APlat (p < 0.05) and reduced VV rotations at 30° of flexion (VV30) (p < 0.05). There were no statistically significant elongation differences between native ALL and reconstructed ALL (graft) during laxity tests. The inter-operator repeatability of the tests was excellent for each measurement., Conclusions: ALL acted as an important internal tibial rotation restrain at 90° and a significant (secondary) AP stabilizer at 30° of knee flexion. The presented ALL reconstruction technique significantly restored the increase of knee laxity produced by the ALL section., Scientific Level: Case-Controlled Laboratory Study, Level III., (© 2022. The Author(s).)

Background and Objective: In orthopedic medical devices, elasto-plastic behavior differences between bone and metallic materials could lead to mechanical issues at the bone-implant interface, as stress shielding. Those issue are mainly related to knee and hip arthroplasty, and they could be responsible for implant failure. To reduce mismatching-related adverse events between bone and prosthesis mechanical properties, modifying the implant's internal geometry varying the bulk stiffness and density could be the right approach. Therefore, this feasibility study aims to assess which in-body gap geometry improves, by reducing, the bulk stiffness., Methods: Using five finite element models, a uniaxial compression test in five cubes with a 20 mm thickness was simulated and analyzed. The displacements, strain and Young Modulus were calculated in four cubes, each containing internal prismatic gaps with different transversal sections (squared, hexagonal, octagonal, and circular). Those were compared with a fifth full-volume cube used as control., Results: The most significant difference have been achieved in displacement values, in cubes containing internal gaps with hexagonal and circular transversal sections (82 µm and 82.5 µm, respectively), when compared to the full-volume cube (69.3 µm)., Conclusions: This study suggests that hexagonal and circular shape of the gaps allows obtaining the lower rigidity in a size range of 4 mm, offering a starting approach to achieve a "close-to-bone" material, with a potential use in prosthetic devices with limited thickness., Competing Interests: Declaration of Competing Interest The authors declare that there is no conflict of interest regarding the publication of this article., (Copyright © 2022. Published by Elsevier B.V.)

Background: The pivot-shift test has become more consistent and reliable and is a meaningful outcome measurement after anterior cruciate ligament reconstruction (ACLR)., Purpose/hypothesis: The purpose of this investigation was to assess patient-reported outcomes (PROs) and the quantitative pivot shift (QPS) preoperatively, at time zero immediately after anatomic ACLR, and after 24 months as well as the relationship between PROs and the QPS. It was hypothesized that anatomic ACLR would restore rotatory stability measured by the pivot-shift test and that QPS measurements would be positively correlated with PROs., Study Design: Cohort study; Level of evidence, 2., Methods: The ACL-injured and contralateral uninjured knees from 89 of 107 (83.2%) enrolled patients at 4 international centers were evaluated using a standardized pivot-shift test. Tibial acceleration was assessed with an inertial sensor, and lateral compartment translation was measured using an image analysis system preoperatively, at time zero immediately postoperatively, and at follow-up after 2 years. PROs were assessed at 12 and 24 months postoperatively with the International Knee Documentation Committee (IKDC) subjective knee form, Cincinnati Knee Rating System (CKRS), Marx activity rating scale, and activity of daily living score (ADLS)., Results: The mean patient age at surgery was 27 years (range, 15-45 years). A positive pivot shift preoperatively (side-to-side difference in tibial acceleration, 2.6 ± 4.0 m/s 2 ; side-to-side difference in anterior tibial translation, 2.0 ± 2.0 mm) was reduced at time zero postoperatively (side-to-side difference in tibial acceleration, -0.5 ± 1.3 m/s 2 ; side-to-side difference in anterior tibial translation, -0.1 ± 1.0 mm). All PROs improved from preoperatively to final follow-up at 24 months: from 56.5 to 85.5 points for the IKDC ( P = .0001), from 28.8 to 32.4 points for the CKRS ( P = .04), from 11.2 to 7.9 points for the Marx ( P < .0001), and from 75.7 to 91.6 points for the ADLS ( P < .0001). Neither preoperative nor time zero postoperative rotatory laxity assessed by the pivot-shift test correlated with PROs at 24-month follow-up. A graft retear was observed in 4 patients (4.5%) within 2 years of follow-up., Conclusion: Anatomic ACLR resulted in significantly improved and acceptable PROs at 2-year follow-up and a low failure rate. Anatomic ACLR restored QPS measurements of anterior tibial translation and tibial acceleration to those of the contralateral knee immediately after surgery while still under anesthesia, but there was no correlation between the QPS preoperatively or at time zero after ACLR and PROs at 2-year follow-up., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: This study was funded by an International Society for Arthoscopy, Knee Surgery and Orthopedic Sports Medicine/Orthopedic Research and Eduction Foundation research grant (No. 708661). J.J.I., Y.H., and V.M. are codevelopers of the image analysis system used in this study; at the moment, the system is not on the market and not producing revenue. R.K. has received grants from Smith & Nephew, Zimmer Biomet, Stryker, and Johnson & Johnson; consulting fees from Medacta, Arthrex, Japan Tissue Engineering, and Hirosaki Life Science Innovation; and speaking fees from Arthrex, Smith & Nephew, Zimmer Biomet, Johnson & Johnson, and Japan Tissue Engineering. V.M. has received consulting fees and speaking fees from Smith & Nephew. A.S. has received grant support from Arthrex and Stryker; educational support from Arthrex, Mid-Atlantic Surgical Systems, and Smith & Nephew; and hospitality payments from Stryker. J.M.B. has received grant support from Arthrex and educational support from Arthrex, Smith & Nephew, and Mid-Atlantic Surgical Systems. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto., (© The Author(s) 2020.)

Purpose: To determine the medium-term implant survivorship, the clinical results and the failure mechanisms of a novel unicompartmental arthroplasty for uncemented resurfacing of the medial tibio-femoral compartment., Methods: Seventy-six consecutive patients were prospectively evaluated with a mean final follow-up of 6 years (SD 5.3 months). In 44 patients, the diagnosis was osteoarthritis, and in 32 patients, it was avascular necrosis of the medial femoral condyle. The Hospital for Special Surgery Score was used for objective clinical evaluation, and a self-administered visual analogue scale was used to quantify residual pain at each observation point. Implant survivorship was determined assuming revision for any reason as endpoint., Results: Nineteen patients were revised (6 with osteoarthritis and 13 with avascular necrosis of the medial femoral condyle). The mean interval time from index surgery to revision was 11.2 months (SD 4.66 months). Implant survivorship was higher in patients with osteoarthritis with respect to those with avascular necrosis of the medial femoral condyle (p = 0.018). Aseptic loosening was the most frequent failure mechanism. Femoral component loosening was reported in five patients and tibial component loosening was reported in other six patients. Assuming revision for any reason as endpoint, an implant survivorship of 74.3 % at 6-year follow-up was determined. In the remaining 57 patients, satisfactory clinical results were obtained. Hospital for Special Surgery Score and visual analogue scale for residual pain showed significant improvements (p < 0.03 and p < 0.045, respectively)., Conclusions: At the present time, the standard cemented implants and the conventional designs for unicompartmental knee replacement still represent the optimal solution. The authors do not recommend the widespread use of this technique., Level of Evidence: IV.