Description
Objectives: Arthroscopic reshaping surgery is the first treatment option for a symptomatic discoid lateral meniscus (DLM) to preserve the peripheral rim. However, adequate residual volume of meniscus during surgery is unclear. The purpose of this study was to measure the meniscus just after reshaping surgery, 3 months and 2 years after the surgery for a DLM and divided into three groups; higher, middle and low volume, to verify when the morphological change occurred.
Methods: We retrospectively reviewed the medical records of patients who underwent reshaping surgery for a symptomatic DLM and had undergone follow-up for 2 years. Magnetic resonance imaging (MRI) was routinely performed 0 (just after surgery), 3 and 24 months postoperatively, and the width and extrusion of the residual meniscus were measured. We divided into three groups according to the volume of midbody just after surgery: high volume group (more than 13mm) (H group), middle volume group (9mm or more and less than 13mm) (M group) and low volume group (less than 9mm) (L group).Statistical differences between groups were calculated using a one-way analysis of variance with a post hoc Student’s t-test. p < 0.05 was considered significant.
Results: We included 33 knees of 32 patients in this study. The mean age at the time of surgery was 16.7 years. Overall, the width of the anterior horn, midbody, and posterior horn decreased significantly from 0 to 24 months after surgery (from 10.5 to 8.3 mm [P<.001], from 11.0 to 6.4 mm [P<.001], and from 10.2 to 8.8 mm [P < .001], respectively). Meniscal extrusion of the midbody increased significantly from 0 to 24 months after surgery (from -1.3 to1.1 mm; P < .001). the width of midbody in H group (14.0±0.9mm) was wider than that in M (11.1±1.0mm) and L(7.5±0.9mm) groups at 0 months postoperatively, however, the width of midbody in H group was no difference between M group at 3 (10.5±3.8mm, 9.8±2.3mm) and 24 (6.8±2.0mm, 6.8±1.9mm) months postoperatively. The width of the midbody in L group was 5.7±1.3mm and 5.3±0.8mm at 3 and 24 months after surgery respectively and H and M groups was wider than L groups at 3months postoperatively. Meniscal extrusion of the midbody was no difference between H, M and L groups at 0,3,24 months postoperatively.
Conclusions: More than 13mm residual meniscus (H group) rapidly decreases the width to the same level of M group and there was no difference between H and M group at 24 months after the surgery. However, the residual meniscus in H and M groups trended to be wider than L group. We recommend that the residual meniscus width with the midbody is around 11 mm during surgery.
