Kaeding, Christopher C.

Background: Anterior cruciate ligament reconstruction (ACLR) using a hamstring tendon autograft often results in hamstring muscle strength asymmetry. However, the effect of hamstring muscle strength asymmetry on knee mechanics has not been reported. Hypothesis: Participants with hamstring strength asymmetry would demonstrate altered involved limb knee mechanics during walking and jogging compared with those with more symmetric hamstring strength at least 2 years after ACLR with a hamstring tendon autograft. Study Design: Controlled laboratory study. Methods: There were a total of 45 participants at least 2 years after ACLR (22 male, 23 female; mean time after ACLR, 34.6 months). A limb symmetry index (LSI) was calculated for isometric hamstring strength to subdivide the sample into symmetric hamstring (SH) (LSI ≥90%; n = 18) and asymmetric hamstring (AH) (LSI <85%; n = 18) groups. Involved knee kinematic and kinetic data were collected using 3-dimensional motion analysis during gait and jogging. Peak sagittal-, frontal-, and transverse-plane knee angles and sagittal-plane knee moments and knee powers were calculated. Independent-samples t tests and analyses of covariance were used to compare involved knee kinematic and kinetic variables between the groups. Results: There were no differences in sagittal- and frontal-plane knee angles between the groups ( P > .05 for all). The AH group demonstrated decreased tibial internal rotation during weight acceptance during gait ( P = .01) and increased tibial external rotation during jogging at initial contact ( P = .03) and during weight acceptance ( P = .02) compared with the SH group. In addition, the AH group demonstrated decreased peak negative knee power during midstance ( P = .01) during gait compared with the SH group, after controlling for gait speed, which differed between groups. Conclusion: Participants with hamstring strength asymmetry showed altered involved knee mechanics in the sagittal plane during gait and in the transverse plane during gait and jogging compared with those with more symmetric hamstring strength. Clinical Relevance: Hamstring strength asymmetry is common at 3 years after ACLR with a hamstring tendon autograft and affects involved knee mechanics during gait and jogging. Additional research is warranted to further investigate the longitudinal effect of these alterations on knee function and joint health after ACLR.

Background: Knee laxity in the setting of suspected anterior cruciate ligament (ACL) injury is frequently assessed through physical examination using the Lachman, pivot-shift, and anterior drawer tests. The degree of laxity noted on these examinations may influence treatment decisions and prognosis. Hypothesis: Increased preoperative knee laxity would be associated with increased risk of subsequent revision ACL reconstruction and worse patient-reported outcomes 2 years postoperatively. Study Design: Cohort study; Level of evidence, 2. Methods: From an ongoing prospective cohort study, 2333 patients who underwent primary isolated ACL reconstruction without collateral or posterior cruciate ligament injury were identified. Patients reported by the operating surgeons as having an International Knee Documentation Committee (IKDC) grade D for Lachman, anterior drawer, or pivot-shift examination were classified as having high-grade laxity. Multiple logistic regression modeling was used to evaluate whether having high-grade preoperative laxity was associated with increased odds of undergoing revision ACL reconstruction within 2 years of the index procedure, controlling for patient age, sex, Marx activity level, level of competition, and graft type. Multiple linear regression modeling was used to evaluate whether having high-grade preoperative laxity was associated with worse IKDC score or Knee injury and Osteoarthritis Outcome Score Knee-Related Quality of Life subscale (KOOS-QOL) scores at a minimum 2 years postoperatively, controlling for baseline score, patient age, ethnicity, sex, body mass index, marital status, smoking status, sport participation, competition level, Marx activity rating score, graft type, and articular cartilage and meniscus status. Results: Pre-reconstruction laxity data were available for 2325 patients (99.7%). Two-year revision data were available for 2259 patients (96.8%), and patient-reported outcomes were available for 1979 patients (84.8%). High-grade preoperative laxity was noted in 743 patients (31.9%). The mean postoperative IKDC score was 81.8 ± 15.9, and the mean KOOS-QOL score was 72.0 ± 22.0. The presence of high-grade pre-reconstruction laxity was associated with significantly increased odds of ACL graft revision (odds ratio [OR] = 1.87 [95% CI, 1.19-2.95]; P = .007). The presence of high-grade pre-reconstruction laxity was not associated with any difference in postoperative IKDC (β = −0.56, P = .44) or KOOS-QOL (β = 0.04, P = .97). Conclusion: The presence of high-grade pre-reconstruction knee laxity as assessed by manual physical examination under anesthesia is associated with significantly increased odds of revision ACL surgery but has no association with patient-reported outcome scores at 2 years after ACL reconstruction.

Background: American football and rugby players are at substantial risk of injury because of the full-contact nature of these sports. Methodological differences between previous epidemiological studies hamper an accurate comparison of injury rates between American football and rugby. Purpose: To directly compare injury rates in American collegiate football and rugby, specified by location, type, mechanism, and severity of injury, as reported by licensed medical professionals. Study Design: Cohort study; Level of evidence, 2. Methods: Licensed medical professionals (athletic trainer or physician) associated with the football and rugby teams of a National Collegiate Athletic Association Division I university reported attendance and injury details over 3 autumn seasons. Injuries were categorized by the location, type, mechanism, and severity of injury, and the injury rate was calculated per 1000 athlete-exposures (AEs). Injury rate ratios (IRRs) were calculated to compare overall, game, and practice injury rates within and between sports. Results: The overall injury rate was 4.9/1000 AEs in football versus 15.2/1000 AEs in rugby: IRR = 3.1 (95% CI, 2.3-4.2). Game injury rates were higher than practice injury rates: IRR = 6.5 (95% CI, 4.5-9.3) in football and IRR = 5.1 (95% CI, 3.0-8.6) in rugby. Injury rates for the shoulder, wrist/hand, and lower leg and for sprains, fractures, and contusions in rugby were >4 times as high as those in football (all P ≤ 0.006). Concussion rates were 1.0/1000 AEs in football versus 2.5/1000 AEs in rugby. Most injuries occurred via direct player contact, especially during games. The rate of season-ending injuries (>3 months of time loss) was 0.8/1000 AEs in football versus 1.0/1000 AEs in rugby: IRR = 1.3 (95% CI, 0.4-3.4). Conclusion: Overall injury rates were substantially higher in collegiate rugby compared with football. Similarities between sports were observed in the most common injury types (sprains and concussions), locations (lower extremity and head), and mechanisms (direct player contact). Upper extremity injuries were more common in rugby, and the rate of season-ending injuries was similar between sports.