Patient selection
This study was approved by the medical research ethics committee of our institution. Diagnosis of patients with MMPRT primarily relied on clinical evidence and knee magnetic resonance imaging (MRI) findings [9] (including cleft, giraffe neck, and ghost signs). Indications for surgery included MMPRT (type II), no changes or 1–2 stages of knee osteoarthritis. Patients undergoing surgery for other indications (cartilage resurfacing, osteotomy or ligament reconstruction), previous surgery of the same knee (such as: previous tibia or femur fracture treated with surgically; osteotomy), obvious knee deformity (valgus or varus > 5°), other types of root tear, concomitant anterior cruciate ligament (ACL) injury or other associated knee joint lesions were excluded from the study.
Of the 82 MMPRT patients (type II), patients associated with ligamentous injuries (5 cases) and varus malalignment > 5° (5 cases), and concomitant high tibial osteotomy (2 cases) were excluded from the study. 70 MMPRT patients received treatment of posterior meniscus root attachment point through the tibial tunnel between January 2018 and April 2019. However, 6 patients were not evaluated because they were lost to follow-up. Ultimately, 64 MMPRT patients were included in this study. Patients were divided into 2 groups (arthroscopically assisted meniscus root reconstruction with gracilis autograft: 29 cases; transtibial pull-out technique group: 35 cases) according to the different MMPRT treatment methods. Participants were followed up for 2 years with a total of six follow-ups at directly postoperative, 1 month, 3 months, 6 months, 12 months, and 24 months.
Data collection
The following parameters were recorded: age, gender, body mass index (BMI), comorbidities, stages OA of the knee joint evaluated according to Kellgren and Lawrence (K-L), treatment for medial meniscus posterior root tears, hospitalization time, side of injury, complications, preoperation and the final follow-up VAS (a visual analogue scale from 0 to 10 was used to assess pain), Lysholm score (the Lysholm score is a functional score designed for knee ligament injuries, which has also been validated for other knee injuries) and IKDC score of the affected knee, and radiologic outcomes of the repaired meniscus root healing status were assessed using knee MRI at the latest follow-up.
Surgical techniques
Patients were placed in a supine position with knee flexion of 90°, and a pneumatic tourniquet was used after spinal anesthesia. In the pullout repair techniques group, arthroscopic evaluation of the MMPRT (Fig. 1) and other intraarticular lesions,a limited refreshment was applied to the torn edge of the meniscus with a motorized shaver, and a 2.0 mm guide pin was drilled from a small incision over the anterior proximal tibia and advanced to the posterior horn root of the knee assisted by the special guide system (Smith & Nephew, Andover, Massachusetts, USA). Then, the suture shuttle was used to place a No. 0 fiber wire suture (Smith & Nephew) through the posterior meniscus and shuttled into the tibial tunnel and the meniscus root down into the posterior horn root attachment under arthroscopic visual control (Fig. 2). The fiber wire sutures were tightened to the cortical button (Smith & Nephew, Andover, Massachusetts, USA) to ensure appropriate position and tension of the construct with knee flexion of 90°. In the arthroscopically assisted meniscus root reconstruction with gracilis autograft group, the gracilis tendon was harvested via a 2-cm longitudinal incision over the pes anserinus. The tendon was dissected and harvested with a tendon stripper. The graft was prepared and the ends were whipstitched with a No. 0 fiber wire. A 2.0 mm guide pin was drilled from a small incision over the anterior proximal tibia and advanced to the meniscus root attachment point of the knee under the special guide system (Smith & Nephew, Andover, Massachusetts, USA) assisted, then the guide pins were over-drilled with a cannulated 6-mm drill. The suture shuttle was used to place a No. 0 fiber wire suture through the posterior meniscus (Fig. 3), then the soft tissue tunnel was dilated with multiple passes of No. 0 fiber wire (Fig. 4) followed by the gracilis tendon passes through the medial meniscus posterior root (Fig. 5) and shuttled into the tibial tunnel (Fig. 6). The tails of the gracilis tendon were fixed to a 6 mm PEEK (polyether ether ketone) knotless suture anchor (Biosure RG, Smith & Nephew) to the tibial (Fig. 7), and arthroscopic visualization was used to maintain the appropriate position and tension of the graft.
Postoperative management
Passive knee flexion and quadriceps strengthening exercises were started on the first postoperative day and were gradually increased to reach 90° of flexion after 2 weeks. Moreover, patients were allowed non-weight-bearing with two crutches for six weeks, and weight bearing was progressed as tolerated starting at 6 weeks postoperatively, a rehabilitation of 12 weeks was recommended before starting with weight-resisted exercise and half squat exercise. Return to athletic activity occurred at a minimum of 6 months postoperatively, if indicated.
Outcome assessment
Clinical examinations were performed directly postoperative, 1 month, 3 months, 6 months, 12 months, and 24 months, and knee functional assessment was performed according to the Lysholm score, IKDC score, and VAS score. Patients and the staff collecting questionnaire data were blinded to the surgical procedure.
To assess the accuracy of the measurements, a second MRI reading of these factors was performed 24 months later. The imaging outcomes were evaluated by 2 trained and experienced senior orthopedic surgeons and radiologists who were blinded to pre- and postoperative status and imaging. Radiologic outcomes of the repaired meniscus root healing status were assessed using knee 3.0 T MRI (The slice thickness was 4 mm with a 0 mm gap) (Fig. 8). Meniscal root healing status was assessed according to the criteria of previous studies [10,11,12] and was classified as complete healing (continuity in sagittal, coronal, and axial MRI views), lax healing (loss of continuity in any 1 view), and failed healing (no continuity and no evidence of meniscal healing at the repair site).
Statistical analysis
Quantitative variables were presented as mean value ± standard deviation (SD), and the two groups were compared using the Student’s t-test. Count variables were expressed as numbers and percentages and were assessed by the Chi-square test. Statistical significance was set as a P value less than 0.05. All analysis was performed by IBM SPSS Version 22.
