Dynamic ultrasound-based determination of the optimal knee position for pullout fixation of medial meniscus posterior root tears.

PURPOSE: A larger medial meniscus extrusion (MME) predicts a poorer prognosis after arthroscopic pullout fixation for medial meniscus posterior root tears (MMPRT). However, the optimal knee position in surgery for MMPRT to reduce MME is unclear. We evaluated the MME at various knee positions used for medial fixation.

METHODS

We enrolled 20 patients who underwent MMPRT repair and performed ultrasonography preoperatively under anaesthesia, before fixation (both with or without traction), and post-fixation. MMEs were measured in positions A, B, C, and D (supine with the leg dropped from the bed with the knee flexed; valgus stress knee; figure-of-four; and supine with the injured knee flexed over the bed, respectively) at different time points and compared. Surgical fixation was performed in Position B.

RESULTS

The preoperative mean MMEs at positions A, B, C, and D were 1.5, 1.4, 5.8, and 3.6 mm, respectively, and MMEs at A and B were significantly smaller than those at C and D, whereas the MME at C was significantly larger than that at D. The intraoperative mean MMEs, at positions B and C, before traction, with traction, and post-fixation were 1.2 and 5.5 mm, 0.7 and 4.3 mm, and 0.9 and 2.3 mm, respectively.

CONCLUSION

During MMPRT repair, MMEs increased in the figure-of-four position, but decreased with pullout fixation in the valgus stress knee position. Therefore, the valgus stress knee position is suitable for pullout fixation in MMPRT repair.

LEVEL OF EVIDENCE: IV.