Editorial Commentary: Double-Sling Transfer of Both the Conjoined Tendons and Long Head Biceps Tendon for Glenoid Bone Loss in Patients With Shoulder Instability Shows Biomechanical Benefit in Shoulder Abduction and External Rotation But May Be Insufficient in Mid-Range Arm Positions.

Recurrence of shoulder glenohumeral instability is exacerbated in cases of glenoid bone loss. Surgical bone transfer techniques well address the issue. Innovative soft-tissue tendon transfers may fill the defect plus provide a sling effect. Double-sling transfer of both the conjoined tendons and long head biceps tendon for glenoid bone loss in patients with shoulder instability shows biomechanical benefit in shoulder abduction and external rotation. However, as the sling effect is less pronounced in mid-range arm position, the benefit of double-sling transfer may be insufficient. Moreover, the biomechanical models are limited relative to the complexity of clinical glenohumeral function, and obviously limited to time-zero analysis. We should be careful before we abandon bony augmentation procedures.

Effect of Slope and Varus Correction High Tibial Osteotomy in the ACL-Deficient and ACL-Reconstructed Knee on Kinematics and ACL Graft Force: A Biomechanical Analysis.

BACKGROUND: Correction of high posterior tibial slope is an important treatment option for revision of anterior cruciate ligament (ACL) failure as seen in clinical and biomechanical studies. In cases with moderate to severe medial compartment arthritis, an additional varus correction osteotomy may be added to improve alignment. PURPOSE: To investigate the influence of coronal and sagittal correction high tibial osteotomy in ACL-deficient and ACL-reconstructed knees on knee kinematics and ACL graft load. STUDY DESIGN: Controlled laboratory study. METHODS: Ten cadaveric knees were selected according to previous computed tomography measurements with increased native slope and slight varus tibial alignment (mean ± SD): slope, 9.9°± 1.4°; medial proximal tibia angle, 86.5°± 2.1°; age, 47.7 ± 5.8 years. A 10° anterior closing-wedge osteotomy, as well as an additional 5° of simulated varus correction osteotomy, were created and fixed using an external fixator. Four alignment conditions-native, varus correction, slope correction, and combined varus and slope correction-were randomly tested in 2 states: ACL-deficient and ACL-reconstructed. Compressive axial loads were applied to the tibia while mounted on a free-moving X-Y table and free-rotating tibia in a knee testing fixture. Three-dimensional motion tracking captured anterior tibial translation (ATT) and internal tibial rotation. Change of tensile forces on the reconstructed ACL graft were recorded. RESULTS: In the ACL-deficient knee, an isolated varus correction led to a significant increase of ATT by 4.3 ± 4.0 mm (P = .04). Isolated slope reduction resulted in the greatest decrease of ATT by 6.2 ± 4.3 mm (P < .001). In the ACL-reconstructed knee, ATT showed comparable changes, while combined varus and slope correction led to lower ATT by 3.7 ± 2.6 mm (P = .01) than ATT in the native alignment. Internal tibial rotation was not significantly altered by varus correction but significantly increased after isolated slope correction by 4.0°± 4.1° (P < .01). Each isolated or combined osteotomy showed decreased forces on the graft as compared with the native state. The combined varus and slope osteotomy led to a mean decrease of ACL graft force by 33% at 200 N and by 58% at 400 N as compared with the native condition (P < .001). CONCLUSION: A combined varus and slope correction led to a relevant decrease of ATT in the ACL-deficient and ACL-reconstructed cadaveric knee. ACL graft forces were significantly decreased after combined varus and slope correction. Thus, our biomechanical findings support the treatment goal of a perpendicular-aligned tibial plateau for ACL insufficiencies, especially in cases of revision surgery. CLINICAL RELEVANCE: This study shows the beneficial knee kinematics and reduced forces on the ACL graft after combined varus and slope correction.

Posteromedial Ligament Repair of the Knee With Suture Tape Augmentation: A Biomechanical Study.

BACKGROUND: In cases of acute combined posteromedial and anterior cruciate ligament (ACL) injuries, primary repair of the superficial medial collateral ligament (sMCL) and posterior oblique ligament (POL) with suture tape augmentation may be a reasonable alternative to standard tendon reconstruction techniques. PURPOSE/HYPOTHESIS: The purpose was to examine the rotational and valgus laxity with ACL strain following sMCL and POL repair with suture tape augmentation at various degrees of knee flexion. It was hypothesized that this technique would restore knee laxity and kinematics comparable with those of the intact state. STUDY DESIGN: Controlled laboratory study. METHODS: Ten cadaveric knee specimens (mean ± SD, 57.9 ± 5.9 years) were obtained. Specimens were tested with the tibia fixed and the femur mobile on an X-Y table. Each specimen was tested in 4 conditions according to the state of the sMCL and POL: native, deficient, repaired with suture tape augmentation, and reconstructed with tendon allografts. Valgus laxity was tested with 40-N force applied in the lateral direction of the femur, and rotational motion was tested with 5-N torque applied to the tibia. ACL strain during valgus stress was also measured. Each condition was tested in 0°, 15°, 30°, 45°, and 60° of knee flexion. RESULTS: Dissection of the sMCL and POL led to significantly increased valgus laxity in all flexion angles, with a significant increase in ACL strain at 30° (P < .001) and 45° (P < .001). Ligament repair with suture tape augmentation demonstrated similar valgus and rotational laxity as compared with intact specimens, with the exception of increased internal rotation at 30° (P = .005). Ligament reconstruction resulted in significantly increased valgus opening at 45° (P = .048) and significantly increased internal rotation at 30° (P < .001) as compared with the native state. Direct comparison between surgical techniques showed no significant differences. CONCLUSION: At time zero, ligament repair of the posteromedial knee with suture tape augmentation restored close-to-native valgus and rotatory laxity, as well as native ACL strain for cases of complete sMCL and POL avulsion. CLINICAL RELEVANCE: Ligament repair of the sMCL and POL with suture tape augmentation may be a reasonable alternative to tendon reconstruction techniques in cases of acute combined posteromedial and ACL injuries with valgus and rotatory instability.