Ryan Zarzycki

Gait mechanics and second ACL rupture: Implications for delaying return-to-sport

Second anterior cruciate ligament rupture is a common and devastating injury among young women who return to sport after ACL reconstruction, but it is inadequately understood. The purpose of this study was to compare gait biomechanics and return‐to‐sport time frames in a matched cohort of young female athletes who, after primary ACLR, returned to sport without re‐injury or sustained a second ACL injury. Approximately 6 months after primary reconstruction, 14 young women (age 16 ± 2 years) involved in jumping, cutting, and pivoting sports underwent motion analysis testing after physical therapy and impairment resolution. Following objective return‐to‐sport clearance, seven athletes sustained a second ACL rupture within 20 months of surgery (13.4 ± 4.9 months). We matched them by age, sex, and sport‐level to seven athletes who returned to sports without re‐injury. Data were analyzed using a previously validated, EMG‐informed, patient‐specific musculoskeletal model. Compared to athletes without re‐injury, athletes who sustained a second ACL injury received surgery sooner (p = 0.023), had post‐operative impairments resolved earlier (p = 0.022), reached criterion‐based return‐to‐sport benchmarks earlier (p = 0.024), had higher body mass index (p = 0.039), and walked with lower peak knee flexor muscle forces bilaterally (p = 0.021). Athletes who sustained a second injury also tended to walk with larger (p = 0.089) and more symmetrical peak knee flexion angles and less co‐contraction, all indicative of a more normal gait pattern. Statement of Clinical Significance: Delayed return‐to‐sport clearance even in the absence of gait or clinical impairments following primary ACL reconstruction may be necessary to mitigate second ACL injury risk in young women.

Report of the Clinical and Functional Primary Outcomes in Men of the ACL-SPORTS Trial: Similar Outcomes in Men Receiving Secondary Prevention With and Without Perturbation Training 1 and 2 Years After ACL Reconstruction

BackgroundAthletes often are cleared to return to activities 6 months after anterior cruciate ligament (ACL) reconstruction; however, knee function measures continue to improve up to 2 years after surgery. Interventions beyond standard care may facilitate successful return to preinjury activities and improve functional outcomes. Perturbation training has been used in nonoperative ACL injury and preoperative ACL reconstruction rehabilitation, but has not been examined in postoperative ACL reconstruction rehabilitation, specifically return to sport rehabilitation.Questions/PurposesThe purpose of this study was to determine whether there were differences at 1 and 2 years after ACL reconstruction between the male SAP (strengthening, agility, and secondary prevention) and SAP+PERT (SAP protocol with the addition of perturbation training) groups with respect to (1) quadriceps strength and single-legged hop limb symmetry; (2) patient-reported knee outcome scores; (3) the proportion who achieve self-reported normal knee function; and (4) the time from surgery to passing return to sport criteria.MethodsForty men who had completed ACL reconstruction rehabilitation and met enrollment criteria (3–9 months after ACL reconstruction, > 80% quadriceps strength limb symmetry, no pain, full ROM, minimal effusion) were randomized into the SAP or SAP+PERT groups of the Anterior Cruciate Ligament-Specialised Post-Operative Return to Sports trial (ACL-SPORTS), a single-blind randomized clinical study of secondary prevention and return to sport. Quadriceps strength, single-legged hopping, the International Knee Documentation Committee (IKDC) 2000 subjective knee form, Knee Injury and Osteoarthritis Outcome Score (KOOS)-sports and recreation, and KOOS-quality-of-life subscales were collected 1 and 2 years after surgery by investigators blind to group. Athletes were categorized as having normal or abnormal knee function at each time point based on IKDC score, and the time until athletes passed strict return-to-sport criteria was also recorded. T-tests, chi square tests, and analyses of variance were used to identify differences between the treatment groups over time.ResultsThere were no differences between groups for quadriceps symmetry (1 year: SAP = 101% ± 14%, SAP+PERT = 101% ± 14%; 2 years: SAP = 103% ± 11%, SAP+PERT = 98% ± 14%; mean differences between groups at 1 year: 0.4 [−9.0 to 9.8], 2 years = 4.5 [−4.3 to 13.1]; mean difference between 1 and 2 years: SAP = −1.0 [−8.6 to 6.6], SAP+PERT = 3.0 [−4.3 to 10.3], p = 0.45) or single-legged hop test limb symmetry. There were no clinically meaningful differences for any patient-reported outcome measures. There was no difference in the proportion of athletes in each group who achieved normal knee function at 1 year (SAP 14 of 19, SAP+PERT 18 of 20, odds ratio 0.31 [0.5–19.0]; p = 0.18); however, the SAP+PERT group had fewer athletes with normal knee function at 2 years (SAP 17 of 17, SAP+PERT 14 of 19, p = 0.03). There were no differences between groups in the time to pass return to sport criteria (SAP = 325 ± 199 days, SAP+PERT = 233 ± 77 days; mean difference 92 [−9 to 192], p = 0.09).ConclusionsThis randomized trial found few differences between an ACL rehabilitation program consisting of strengthening, agility, and secondary prevention and one consisting of those elements as well as perturbation training. In the absence of clinically meaningful differences between groups in knee function and self-reported outcomes measures, the results indicate that perturbation training may not contribute additional benefit to the strengthening, agility, and secondary prevention base of the ACL-SPORTS training program.Level of EvidenceLevel II, therapeutic study.

Characterizing differential poststroke corticomotor drive to the dorsi- and plantarflexor muscles during resting and volitional muscle activation

Imbalance of corticomotor excitability between the paretic and nonparetic limbs has been associated with the extent of upper extremity motor recovery poststroke, is greatly influenced by specific testing conditions such as the presence or absence of volitional muscle activation, and may vary across muscle groups. However, despite its clinical importance, poststroke corticomotor drive to lower extremity muscles has not been thoroughly investigated. Additionally, whereas conventional gait rehabilitation strategies for stroke survivors focus on paretic limb foot drop and dorsiflexion impairments, most contemporary literature has indicated that paretic limb propulsion and plantarflexion impairments are the most significant limiters to poststroke walking function. The purpose of this study was to compare corticomotor excitability of the dorsi- and plantarflexor muscles during resting and active conditions in individuals with good and poor poststroke walking recovery and in neurologically intact controls. We found that plantarflexor muscles showed reduced corticomotor symmetry between paretic and nonparetic limbs compared with dorsiflexor muscles in individuals with poor poststroke walking recovery during active muscle contraction but not during rest. Reduced plantarflexor corticomotor symmetry during active muscle contraction was a result of reduced corticomotor drive to the paretic muscles and enhanced corticomotor drive to the nonparetic muscles compared with the neurologically intact controls. These results demonstrate that atypical corticomotor drive exists in both the paretic and nonparetic lower limbs and implicate greater severity of corticomotor impairments to plantarflexor vs. dorsiflexor muscles during muscle activation in stroke survivors with poor walking recovery.NEW & NOTEWORTHY The present study observed that lower-limb corticomotor asymmetry resulted from both reduced paretic and enhanced nonparetic limb corticomotor excitability compared with neurologically intact controls. The most asymmetrical corticomotor drive was observed in the plantarflexor muscles of individuals with poor poststroke walking recovery. This suggests that neural function of dorsi- and plantarflexor muscles in both paretic and nonparetic limbs may play a role in poststroke walking function, which may have important implications when developing targeted poststroke rehabilitation programs to improve walking ability.

Functional and Patient-Reported Outcomes Improve Over the Course of Rehabilitation: A Secondary Analysis of the ACL-SPORTS Trial:

Background: The Anterior Cruciate Ligament–Specialized Post-Operative Return to Sports (ACL-SPORTS) randomized controlled trial was designed to address deficits in functional and patient-reported outcomes. The trial examined the effects of a secondary ACL prevention program that included progressive strengthening, agility training, plyometrics (SAP), and other components of current primary prevention protocols, with perturbation training (SAP + PERT group) and without PERT (SAP group). A secondary purpose of this study was to examine whether study outcomes differed between men and women. Hypotheses: (1) Athletes in both the SAP and SAP + PERT groups will have improved knee function and patient-reported outcome measures from pre- to posttraining, (2) the SAP + PERT group would have higher outcome scores than the SAP group, and (3) outcomes will differ by sex. Study Design: Randomized controlled trial (NCT01773317). Level of Evidence: Level 2. Methods: A total of 79 athletes (39 women) were randomized into the SAP and SAP + PERT groups. All athletes had undergone primary ACL reconstruction and achieved 80% quadriceps strength limb symmetry (QI), full range of motion, had minimal effusion, and had no pain. Additionally, all had begun running again. Prior to and after the training program, athletes’ QI, hopping, and patient-reported outcomes were assessed. Repeated-measures analyses of variance were used to determine whether there were differences between groups. Subsequently, the SAP and SAP + PERT groups were collapsed to analyze differences between sexes. Results: There were significant increases for all variables, with the exception of QI. There were no differences between the SAP and SAP + PERT groups. Both men and women made significant improvements in all knee function and patient-reported outcome measures except QI. Men made significant improvements in QI, whereas women did not. Conclusion: The common elements of the training program that all athletes received (10 sessions of progressive strengthening, agility training, plyometrics, and secondary prevention) may be a beneficial addition to the return-to-sport phase of ACL reconstruction rehabilitation. The results suggest that women may require further quadriceps strengthening to maintain and improve QI, an important focus given the relationship between QI and risk for reinjury. Clinical Relevance: During the return-to-sport phase of ACL reconstruction rehabilitation, clinicians tend to shift their focus away from strengthening toward more advanced sports-related tasks. These results indicate that women in particular need continued focus on quadriceps strengthening.

Changes in biomechanical knee injury risk factors across two collegiate soccer seasons using the 11+ prevention program

The 11+ injury prevention program effectively reduces injuries in high school‐aged female soccer player, but the mechanism of the 11+ is unknown, particularly whether it impacts biomechanical risk factors associated with knee injuries. The purpose of this study was to report the changes in hip and knee biomechanics with use of the 11+ over two soccer seasons. Two collegiate womens soccer teams performed the 11+ for two soccer seasons. A control team was followed for one season. Athletes performed motion analysis of a drop vertical jump during preseason and postseason. Both groups had meaningful increases in peak knee abduction angle over the first season, and there were no meaningful changes in peak knee abduction moment over either season. The control group had bilateral decreases in knee flexion angle. The program did not seem to systematically impact biomechanical risk factors associated with knee injuries, with increases in peak knee abduction angle and no bilateral changes in frontal or transverse hip motion. The 11+ may have mitigated clinically meaningful decreases in knee flexion; however, as ACL injuries do not occur purely in the sagittal plane, it is unclear the impact of these changes. The results of this study indicate that the 11+ may require some modifications to impact landing biomechanics and potentially risky movement patterns, particularly when used in collegiate women over multiple seasons.

Gait mechanics and tibiofemoral loading in men of the ACL-SPORTS randomized control trial: ACL-SPORTS TRAINING AND GAIT MECHANICS

The risk for post‐traumatic osteoarthritis is elevated after anterior cruciate ligament reconstruction (ACLR), and may be especially high among individuals with aberrant walking mechanics, such as medial tibiofemoral joint underloading 6 months postoperatively. Rehabilitation training programs have been proposed as one strategy to address aberrant gait mechanics. We developed the anterior cruciate ligament specialized post‐operative return‐to‐sports (ACL‐SPORTS) randomized control trial to test the effect of 10 post‐operative training sessions consisting of strength, agility, plyometric, and secondary prevention exercises (SAPP) or SAPP plus perturbation (SAPP + PERT) training on gait mechanics after ACLR. A total of 40 male athletes (age 23 ± 7 years) after primary ACLR were randomized to SAPP or SAPP + PERT training and tested at three distinct, post‐operative time points: 1) after impairment resolution (Pre‐training); 2) following 10 training sessions (Post‐training); and 3) 2 years after ACLR. Knee kinematic and kinetic variables as well as muscle and joint contact forces were calculated via inverse dynamics and a validated electromyography‐informed musculoskeletal model. There were no significant improvements from Pre‐training to Post‐training in either intervention group. Smaller peak knee flexion angles, extension moments, extensor muscle forces, medial compartment contact forces, and tibiofemoral contact forces were present across group and time, however the magnitude of interlimb differences were generally smaller and likely not meaningful 2 years postoperatively. Neither SAPP nor SAPP + PERT training appears effective at altering gait mechanics in men in the short‐term; however, meaningful gait asymmetries mostly resolved between post‐training and 2 years after ACLR regardless of intervention group.

Corticospinal and intracortical excitability differ between athletes early after ACLR and matched controls: EXCITABILITY DIFFERS EARLY AFTER ACLR

Neuromuscular impairments, such as quadriceps weakness and activation deficits, persist after anterior cruciate ligament reconstruction (ACLR). Recent research demonstrating changes in the function of the primary motor cortex after ACLR posits that quadriceps impairments may be influenced by reduced corticospinal excitability. The purpose of this study was to investigate whether the integrity of the neuromotor axis of the vastus medialis is altered in subjects 2 weeks post‐ACLR compared to uninjured control subjects. Eighteen athletes 2 weeks post‐ACLR and 18 age and sex matched uninjured control subjects participated in this cross‐sectional study. We quantified corticospinal (resting motor threshold, RMT; motor evoked potential amplitudes at 120% RMT, MEP120) and intracortical (inhibition and facilitation) excitability using single and paired pulse transcranial magnetic stimulation (TMS), respectively. We assessed spinal‐reflex excitability (H‐reflex amplitude normalized to maximal M‐wave, H/M ratio) using peripheral stimulation. Subjects post‐ACLR had higher RMTs (p = 0.001), greater MEP120 amplitudes (p = 0.001), and more asymmetric facilitation (p = 0.041) than the uninjured control subjects. No significant group differences were found for intracortical inhibition (p = 0.289) and H/M ratio (p = 0.332). Our findings indicate that both intracortical and corticospinal excitability of vastus medialis are bilaterally altered in subjects 2 weeks after ACLR. Given persistent neuromuscular deficits seen after ACLR, rehabilitation strategies targeting intracortical and corticospinal deficits may potentially improve clinical outcomes.

Psychological Readiness to Return to Sport Is Associated With Knee Kinematic Asymmetry During Gait Following ACL Reconstruction

• BACKGROUND: Gait asymmetry is frequently observed following anterior cruciate ligament reconstruction (ACLR). Psychological readiness to return to sport is associated with functional and activity‐related outcomes after ACLR. However, the association between gait asymmetry and psychological readiness to return to sport is unknown. • OBJECTIVES: To determine the relationship between kinematic and kinetic measures of knee symmetry during gait and psychological readiness to return to sport following ACLR. • METHODS: In this controlled laboratory, cross‐sectional study, 79 athletes (39 women) underwent gait analysis following impairment resolution after ACLR (ie, full range of motion, minimal or no effusion, quadriceps strength index of 80% or greater). Interlimb differences during gait were calculated for sagittal plane knee angles at initial contact, peak knee flexion, and peak knee extension, as well as for peak knee flexion moment and peak knee adduction moment. Athletes completed the Anterior Cruciate Ligament‐Return to Sport after Injury scale (ACL‐RSI) to assess psychological readiness to return to sport. Pearson correlations were used to examine the association between ACL‐RSI score and each gait symmetry variable. • RESULTS: Significant negative correlations were observed between the ACL‐RSI and 2 kinematic variables: knee flexion angle at initial contact (r = ‐0.281, P = .012) and peak knee flexion (r = ‐0.248, P = .027). In general, lower scores on the ACL‐RSI were associated with greater interlimb asymmetry. • CONCLUSION: There was a weak association between psychological readiness to return to sport and knee kinematic asymmetry during gait.

Hop Test Symmetry Scores Early after Rehab Predict Successful 2 Year Outcomes of ACLR

Objectives: Return to pre-injury function, return to pre-injury activity, and avoiding repeated knee joint instability are common goals of anterior cruciate ligament reconstruction (ACLR). None of these goals, however, are guaranteed through surgical intervention. Clinical test batteries are able to differentiate between those with good and poor knee function after ACL injury, but the usefulness of this battery after reconstruction to predict longer-term outcomes is unknown. The purpose of this study is to determine if a test battery consisting of clinical, functional, and patient-reported measures 6 months after surgery is predictive of a successful outcome 2 years after ACLR. Methods: This is a secondary analysis of prospectively collected data. Seventy-three athletes after acute, isolated, unilateral ACL rupture were included in this analysis. All subjects underwent ACLR, and returned for follow-up testing at 6 and 24 months after reconstruction. A test battery consisting of quadriceps strength symmetry (QI), 6-meter timed hop test symmetry (TimHP), the Knee Outcome Survey Activities of Daily living (KOS), and the Global Rating (GLO) was administered 6 months after reconstruction. At 2 year follow-up, all athletes completed the International Knee Documentation Committee Subjective Knee Form 2000 (IKDC) and self-reported whether they had returned to their pre-injury sports and if they had a second ACL injury to the ipsilateral or contralateral knee. A successful outcome was considered achieving at least the 15th percentile of age and sex matched IKDC normative values, returning to pre-injury sports, and not having a second ACL injury at 2 years. Logistic regression was used to predict a successful outcome 2 years after ACLR. Receiver operating characteristic curve (ROC), positive and negative likelihood ratios were calculated for any statistically significant individual predictors. Significance was set at .05 a priori. Results: Fifty-five (75%) of the 73 athletes had a successful outcome. There were no differences between groups in age, sex, graft type or body mass index (p >.05). The test battery performed 6 months after ACLR was predictive of 2 year success (r2=.307;p=.005). The TimHP (p=.018; exp(b)=1.11) was the only significant individual predictor in the test battery. Maximizing sensitivity and specificity (Table 1), a cutoff score of 96% symmetry for the TimHP had a positive likelihood ratio of 1.95 and a negative likelihood ratio of 0.4. Conclusion: A test battery of clinical, functional, and patient-reported measures was predictive of success 2 years after ACLR. Achieving 96% symmetry on the 6-meter timed hop test 6 months after ACLR was associated with almost twice the probability of a successful outcome while not achieving that cutoff was associated with 2.5 times less likely of having a successful outcome. Return to sport criteria have typically suggested 85-90% symmetry cutoffs, and this work suggests those cutoffs might be too low. While delaying return to sport for high risk athletes is warranted, clinical and functional measures should still be maximized early after ACLR to optimize outcomes. Table 1: Discriminate and ROC Curve Analysis of 6-Meter Timed Hop Symmetry Scores TimHP Successful Unsuccessful Total Pass 41 4 45 Fail 14 14 28 Total 55 18 73 Optimum Cutoff Sensitivity Specificity Positive Likelihood Ratio Negative Likelihood Ratio TimHP 96 .750 .615 1.95 0.40

Athletes with a Positive Psychological Response to Return to Sport Training Have Better Outcomes One and Two Years after ACL Reconstruction

Objectives: Fear of re-injury and psychological readiness to return to sport have emerged as important factors affecting outcomes following anterior cruciate ligament reconstruction (ACLR). The time when athletes transition from rehabilitation to return to sport can be especially fearful. Psychological factors are potentially modifiable at this time, and improving them may lead to better outcomes. The purpose of this study was to evaluate whether athletes who showed a positive psychological response to a return to sport training program have better self-reported function and activity outcomes compared to athletes who do not have a clinically meaningful change in their psychological response. Methods: Following ACLR and completion of formal rehabilitation, 67 level I/II athletes (27 female) completed the following self-report measures at enrollment: Anterior Cruciate Ligament Return to Sport after Injury scale (ACL-RSI), International Knee Documentation Committee Subjective Knee Form (IKDC), and global rating scale (GRS). Subjects then underwent ten additional sessions, including injury prevention exercises, progressive strength training, agility training, and plyometric training, to transition the athlete to sport-specific activities. All self-report measures were repeated after training (post). Subjects subsequently completed the IKDC, a GRS, and indicated whether they had returned to the same level of sport one and two years after ACLR. Subjects were dichotomized into 2 groups based on their ACL-RSI scores. Subjects who displayed an increase in ACL-RSI score from enrollment to post that exceeded the MCID (≥1.9) were defined as having a positive psychological response (responder) to training while those who did not were defined as non-responders. Independent t-tests and chi-square tests were used to measure group differences with all outcome measures at all time points (alpha = 0.05). Results: Fourteen of sixty-seven athletes (21%) demonstrated a positive psychological response to treatment. Significant group differences were found with the IKDC one year, and two years after ACLR(Table 1). Ninety-two percent of the responder group returned to their preinjury level of sport at one year while only sixty-nine percent of the non-responder group returned (Figure 1) (Pearson chi-square=2.93, p=.087). Ninety-two percent of the responder group and eighty-eight percent of the non-responder group had returned at 2 years (Pearson chi-square=.074, p=.785). There were no group differences in time from surgery to enrollment (mean ± SD, responder: 22.6 ± 8.0 weeks, non-responder: 23.0 ±8.1 weeks, p=.882) or age (responder: 20.9 ± 6.1 years, non-responder: 22.1 ± 8.5 years, p=.624). Conclusion: Athletes who experienced a positive psychological response to return to sport training demonstrated better self-reported knee function following treatment and one and two years after ACLR. At one year, while non-responders were similar to published mean return to sport level rates (sixty-five percent in a recent meta-analysis), responders demonstrated return rates far exceeding these mean rates. The findings of this study suggest that in some athletes, return to sport training improved psychological readiness. These changes may be related to better functional and return to sport outcomes. Additional strategies may need to be added to this training program so that more athletes see improvements in their psychological response.