Paper 31: Quantitative MRI of the Hamstring Muscles Ten Years After Autograft Hamstring ACLR

Objectives: After autograft hamstring harvesting for anterior cruciate ligament reconstruction (ACLR) there are several studies of semitendinosus (ST) and gracilis (G) tendon showing variation in muscle/tendon regeneration, muscle atrophy myotendinous retraction. There remains a gap our knowledge on the extent function more than decade after harvest. is paucity long-term morphology following ACLR. no evaluating fatty infiltration, known indicator decreased function. Likewise, cross-sectional area hamstrings functional strength. Finally, comparative bone-patellar tendon-bone (BTB) autografts. In this study, we aim to determine muscles as measured by quantitative magnetic resonance imaging (MRI) ten years ACLR comparing healthy controls patients who received BTB Methods: The subjects were from Multicenter Orthopaedic Outcome Network (MOON) nested cohort with at least ten-year follow-up include 90 (50 autograft, 40 autograft) 21 control participants. Inclusion criteria age 14-33 old index unilateral ACL tear during sport. Exclusion prior knee injury enrollment or graft rupture follow-up. Axial MR images both legs mid-thigh obtained (CSA) junction position (MTJ) measurement. Six-point Dixon %fat fraction measurement (%FF) acquired same level CSA measurements. (cm 2 ) semimembranosus (SM), (ST), (G), biceps femoris short head (Bshort), long (Blong) axial manual image segmentation. %FF maps generated 6-point each was calculated overlying segmentation masks used ST G MTJ distance (cm) joint line manually using localizer images. For type, generalized linear model first fit where dependent variable biomarker (separate models FF, CSA, MTJ) independent variables type (operated vs non-op), muscle, their interaction. A transformation when not normally distributed, needed. Generalized Estimating Equations account clustered nature data. significance 0.05 test interaction term. If term significant, then comparisons between operated non-operated knees performed combination, Holm’s method I error rate. Results: Patient demographics: 33.5 ± 5.3 years; 45 female; body mass [BMI] 25.8 5.1 kg/m ; Controls 30.3 7.8 14 BMI 24 . Mid-thigh (fat (%)) values significantly higher vs. limbs (15.2%±11.1% 7.6%±5.2%) (13.1%±7.6% 9.1%±4.4%) while SM showed differences (Figure 1). patients, significant (7.3%±2.4% 7.4%±2.5%) (10.1%±3.8% 9.8%±3.9%) overall, left had right limbs. (cross-sectional )) measurements lower (6.7±3 9.6±3.4) (3.7±1.8 4.5±1.6), 2). (10.2±3.7 10.4±4) (5.2±1.7 5.0±1.6) controls, (7.9±2.6 7.9±2.4) (4.3±1.5 4.2±1.4). (myotendinous (cm)) greater retraction (14.2±4.6 7.5±2.3) (9.9±4.4 6.4±1.6) 3). (7.4±2.3 7.4±2) (6.2±1.5 6.2±1.4) also (5.7±2.5 5.6±2) (6.1±1.9 6.7±1.7). Conclusions: over hamstring, harvested undergo infiltration (higher %FF), (lower CSA) distance) patients. Whereas remain symmetric expected No compensatory hypertrophy found within cohort. As result these three measures (%FF, retraction) do resume normal indices. biomechanical consequences would need be evaluated an individual patient basis. One measure harvest morbidity persistence changes parameters