To evaluate the postoperative clinical efficacy and meniscus healing of knee anterior cruciate ligament(ACL) injury with lateral meniscus posterior horn tear by different treatment methods with different tear lengths, and to provide basis and reference for clinical decision-making of knee ACL injury with lateral meniscus posterior horn tear.

A retrospective analysis was carried out on 113 patients with ACL injury accompanied with lateral meniscus posterior angle tear who were admitted to the Sports Medicine Department of Qingdao University Affiliated Hospital from 2010 to 2019. Inclusion criteria: ACL injury with lateral meniscus posterior angle tear; the distance between the tear edge of the meniscus and the synovial margin was within 5 mm during surgery; the postoperative follow-up time was 12 months. Exclusion criteria: multiple ligament injuries in the knee joint; inner meniscus injury; accompanying knee joint fractures; the duration was more than six months after trauma. According to the posterior horn tear length of the lateral meniscus and whether it had been sutured for repair, the patients were divided into two groups: the small tear group in which the posterior horn tear length was less than 15 mm and no popliteal tendon involved (33 cases were not sutured for repair in the small tear group A; 27 cases were fully sutured in the small tear group B); the moderate tear group in which the posterior horn tear length was larger than 15 mm but less than 20 mm, and no popliteal tendon involved (28 cases were not sutured for repair in the moderate tear group A, while 25 cases were fully sutured in the moderate tear group B). Lysholm score, International Knee Joint Documentation Committee (IKDC) score, and imaging MRI examination before surgery and at 12 months follow-up after surgery were recorded. The data were analyzed by repeated measurement analysis of variance, chi square test, and histogram format.

All the patients were followed up and showed improvement in their clinical functional scores at the last follow-up compared to the scores before surgery. For patients with lateral meniscus tear length less than 15 mm, there was no statistically significant difference in postoperative Lysholm functional score and IKDC score between suture repair and non-suture repair (F=0.49, 2.21, all P>0.05). For lateral meniscus tear-length of 15 to 20 mm, the postoperative Lysholm functional score and IKDC score of the suture repair group were significantly improved compared to the non-suture repair group (F=189.21, 41.08, all P <0.05). MRI results at follow-up showed that all patients in small tear group achieved satisfactory healing; the healing rates of the two subgroups in the moderate group was 96.4% and 96.0% respectively, which showed no statistically significant difference(χ²=0.94, P>0.05).

For patients with ACL injury accompanied with posterior horn tear of lateral meniscus, if the popliteal tendon is not involved and the tear length is less than 15 mm, the posterior horn of lateral meniscus can be healed without repair, which may achieve the equal clinical efficacy as suture repair of meniscus and simple ACL reconstruction. If the popliteal tendon is not involved and the tear length is larger than 15 mm and less than 20 mm, suture repair of the posterior horn of the lateral meniscus tear is stronly recommended.