Summary

In cases of symptomatic discoid meniscus, preserving as much of the meniscus structure as possible is important for achieving successful long-term functional and radiological outcomes

Abstract

Discoid lateral meniscus (DLM) is the most common congenital anomaly of the lateral meniscus. The differences in morphological structure and disorganized arrangement of collagen fibrils histologically make the meniscus more prone to degeneration. Furthermore, rates of healing after repair and, consequently, the chances of success are also reduced.

Total of 79 patients who were registered in our patient system between 1996-2019, underwent surgical treatment for discoid meniscus were identified. 35 patients were not included as we were unable to reach them to obtain their 5-year results. Among the remaining 44 patients, VAS, Lysholm, and IKDC scores were obtained via phone for 13 patients whose 5-year or longer follow-up results were not available on the system. Seven of the patients had undergone bilateral surgery. Therefore, total of 51 knees were included in the study.

According to the Watanabe classification, 24 were type 1, 25 were type 2, and 2 were type 3. There were 49 discoid lateral menisci and 2 discoid medial menisci. Among the presenting complaints, 37 patients had pain (72%), 8 had locking (15%), 9 had snapping (17%), 8 had extension deficit (15%), and 8 had effusion (15%). Tears were present in 36 out of 51 knees (70%). These tears included 15 horizontal, 8 complex, 6 bucket-handle, 5 radial, and 2 flap tears. Partial meniscectomy was performed on 30 patients, partial meniscectomy plus repair on 3 patients, subtotal meniscectomy on 11 patients, and total meniscectomy on 7 patients.

The average follow-up duration is 13.5 years (range: 5-27 years). In their last follow-up, 25 patients were found to have grade 0 osteoarthritis, 7 patients had grade 1, 10 patients had grade 2, 7 patients had grade 3, and 2 patients had grade 4 osteoarthritis. Two patients underwent total knee arthroplasty in the 24th and 25th years post-surgery, respectively. Patient who had undergone bilateral surgery received meniscus transplantation in both knees in the 4th and 5th years, respectively.

VAS, Lysholm, and IKDC scores at the final follow-up showed significantly better results compared to preoperative values (p<0.01). VAS scores were 6 (5.5-7) preoperatively and 2 (0-2) postoperatively. Lysholm score was 70 (66-76) preoperatively and 90 (88-100) postoperatively. IKDC score was 70.8±6.4 preoperatively and 90.5±8.4 postoperatively.

When subtotal and total meniscectomy were considered as one group and partial meniscectomy and partial meniscectomy + repair were considered as another group, it was shown that 41% (7/17) of the patients in the subtotal and total meniscectomy group developed grade 3-4 osteoarthritis. In contrast, in other group, 75% (21/28) of the patients did not show any findings suggestive of osteoarthritis at the final follow-up. In the initial surgeries of two patients who developed grade 4 osteoarthritis, subtotal and total meniscectomy were performed due to a horizontal tear in one and a complex tear in the other, respectively.

Saucerization or saucerization + repair appear to be clinically successful in patients with symptomatic and torn discoid meniscus. Moreover, preserving the meniscus structure significantly slows the progression to radiological osteoarthritis. Therefore, subtotal meniscectomy and total meniscectomy should be avoided.