Both low and high knee flexion angles during tibial graft fixation yield comparable outcomes following ACL reconstruction with quadriceps tendon autograft: A systematic review

IMPORTANCE: A paucity of clinical evidence surrounds the effect of the knee flexion angle during tibial fixation of the graft during anterior cruciate ligament (ACL) reconstruction. While biomechanical studies have recently sought to revive this area of study in both single- and double-bundle graft populations, they have done so using variants of the hamstring graft. This does not shed light on the optimal fixation of other autograft options, namely, the quadriceps tendon (QT) autograft. OBJECTIVES: To determine the effect of the knee flexion angle during tibial graft fixation on functional and clinical outcomes following ACL reconstruction using single-bundle QT autograft, inclusive of both soft-tissue and bone-plug graft types. EVIDENCE REVIEW: An electronic search of MEDLINE, EMBASE, Web of Science, and the Cochrane Library was carried out from database inception to June 2020. Following study screening, patient demographics and fixation technique as well as both subjective and objective clinical outcomes were abstracted. Studies were divided based on the knee flexion angle during tibial fixation of the graft. The low knee flexion angle (L-KFA) group included patients with a tibial fixation angle of < 30° of flexion, and the high knee flexion (H-KFA) group included those with a tibial fixation of exactly 30° of flexion. The data were qualitatively synthesized due to significant heterogeneity across the included studies. FINDINGS: Sixteen studies (1,169 patients) were included for analysis. There were 675 patients in the L-KFA group (mean age range, 18.7-34.5 years) and 494 patients in the H-KFA group (mean age range, of 23.2-32.1 years). Both groups yielded statistically significant improvements from preoperative to postoperative scores across several functional and clinical outcomes. Return to pre-injury activity levels ranged from 64% to 81% in L-KFA studies and from 73.3% to 86.7% in H-KFA studies. All-cause graft failure rates ranged from 1.4% to 4.3% in L-FKA studies and from 0%-10.7% in H-KFA studies. CONCLUSION: Both low- and high-knee flexion angles during tibial graft fixation produce improved postoperative clinical and functional outcomes with comparable outcomes across groups. There is inconclusive evidence to recommend the ideal knee flexion angle for graft fixation in primary ACLR. LEVEL OF EVIDENCE: Level IV.