Background: Meniscal function after repair of radial/flap tears of the posterior horn of the lateral meniscus (LM) with anterior cruciate ligament reconstruction (ACLR) has not been comprehensively investigated. Purpose: To evaluate not only the clinical and radiographic outcomes of patients with repair of radial/flap tears of the posterior LM with ACLR but also the healing status of the repaired meniscus and changes of chondral status with second-look arthroscopy. Study Design: Case series; Level of evidence, 4. Methods: From January 2008 to April 2016, 41 patients of a consecutive series of 505 primary anatomic ACLR cases had a concomitant radial/flap tear of the posterior horn of the LM and underwent side-to-side repair with an inside-out or all-inside technique. All patients were followed for >2 years, evaluated clinically and radiologically (radiograph and magnetic resonance imaging [MRI]), and compared with a control group without any concomitant injuries that underwent ACLR. Of the 41 patients, 30 were assessed by second-look arthroscopy 2 years postoperatively. Results: The mean follow-up times of the study and control groups were 3.4 and 3.9 years, respectively. The study group showed no significant differences in clinical findings, lateral joint space narrowing on radiograph, and coronal extrusion on MRI as compared with the control group, whereas sagittal extrusion on MRI progressed significantly in the study group (1.2 ± 1.5 mm vs 0.32 ± 1.0 mm, P < .001). Eighteen patients (60%) obtained complete healing; 9 (30%) showed partial healing; and 3 (10%) failed to heal on second-look arthroscopy. Changes of chondral status in the femoral condyle showed no significant difference between the groups ( P = .29). However, chondral status of the lateral tibial plateau worsened significantly in the study group ( P = .0011). Conclusion: The clinical and radiographic outcomes after repair of radial/flap tears of the posterior horn of the LM as combined with anatomic ACLR were successful and comparable with those after isolated ACLR without any other injuries at a mean postoperative follow-up of 3.4 years, except for sagittal extrusion on MRI. Chondral lesions of the lateral tibial plateau deteriorated regardless of meniscal healing at 2 years postoperatively. Surgeons should keep in mind that chondral injuries might progress over the midterm.

A radial tear of 100% width involving the rim significantly decreased the in situ force of the lateral meniscus and caused medial shift and valgus rotation of the tibia, whereas a radial tear of up to 66% width produced only little change. The clinical relevance is that loss of meniscal functions due to complete radial tear can lead to abnormal stress concentration in a focal area of cartilage and can increase the risk of osteoarthritis in the future.

Internal rotation of the hip at rest and lateral patellar tilt increase after THA.

IV.

Purpose To compare the efect of the lateral meniscus (LM) complete radial tear at diferent tear sites on the load distribution and transmission functions. Methods A compressive load of 300 N was applied to the intact porcine knees (n = 30) at 15°, 30°, 60°, 90°, and 120° of lexion. The LM complete radial tears were created at the middle portion (group M), the posterior portion (group P), or the posterior root (group R) (n = 10, each group), and the same loading procedure was followed. Finally, the recorded three-dimensional paths were reproduced on the LM-removed knees. The peak contact pressure (contact area) in the lateral compartment and the calculated in situ force of the LM under the principle of superposition were compared among the four groups (intact, group M, group P, and group R). Results At all the lexion angles, the peak contact pressure (contact area) was signiicantly higher (lower) after creating the LM complete radial tear as compared to that in the intact state (p < 0.01). At 120° of lexion, group R represented the highest peak contact pressure (lowest contact area), followed by group P and group M (p < 0.05). The results of the in situ force carried by the LM were similar to those of the tibiofemoral contact mechanics. ConclusionThe detrimental efect of the LM complete radial tear on the load distribution and transmission functions was greatest in the posterior root tear, followed by the posterior portion tear and the middle portion tear in the deep-lexed position. Complete radial tars of the meniscus, especially at the posterior root, should be repaired to restore the biomechanical function.