Factors That Predict Sagittal Plane Knee Biomechanical Symmetry After Anterior Cruciate Ligament Reconstruction: A Decision Tree Analysis.

BACKGROUND: Biomechanical knee asymmetry is commonly present after anterior cruciate ligament (ACL) reconstruction. Factors that could assist in identification of asymmetrical biomechanics after ACL reconstruction could help clinicians in making return-to-play decisions. The purpose of this study is to determine factors that may contribute to knee biomechanical asymmetry present after ACL reconstruction. HYPOTHESIS: We hypothesized that quadriceps strength and activation and patient-reported function would allow for identification of patients with symmetrical knee biomechanics. STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 3. METHODS: Thirty-one subjects (18 women; time since ACL reconstruction = 284.4 ± 53.6 days) who underwent ACL reconstruction and were to return to activity were recruited. Participants completed bilateral assessments of isokinetic quadriceps strength, quadriceps activation using the superimposed burst technique, and biomechanical function testing during a single-leg forward hop. The International Knee Documentation Committee (IKDC) subjective knee form was also completed. Symmetry values were calculated for each variable. Decision trees were utilized to determine which input factors (quadriceps strength symmetry, quadriceps activation symmetry, IKDC score, age, sex, height, mass, graft type) were able to identify participants who had symmetrical knee flexion angles (KFAs) and extension moments. Angles and moments were considered symmetrical if symmetry values were ≥90%. RESULTS: Quadriceps strength and activation symmetry were able to predict whether a patient landed with symmetrical or asymmetrical KFAs, with thresholds of 77.2% strength symmetry and 91.3% activation symmetry being established. Patient-reported function and quadriceps strength were factors that allowed for classification of participants with symmetrical/asymmetrical knee extension moments, with thresholds of 89.1 for the IKDC and 80.0% for quadriceps strength symmetry. CONCLUSIONS: Quadriceps strength contributed to both models and appears to be a critical factor for achieving symmetrical knee biomechanics. High patient-reported function and quadriceps activation are also important for restoring knee biomechanical symmetry after ACL reconstruction. CLINICAL RELEVANCE: Quadriceps strength and activation and patient-reported function may be able to assist clinicians in identifying ACL patients with symmetrical/asymmetrical knee biomechanics.

A Cross-sectional Examination of Quadriceps Strength, Biomechanical Function, and Functional Performance From 9 to 24 Months After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Patients who undergo anterior cruciate ligament reconstruction (ACLR) have deficiencies in strength, functional performance, and biomechanical function at return to activity. Patients who have abnormal strength and function after ACLR may be at a greater risk for secondary injury and posttraumatic osteoarthritis. PURPOSE: To examine quadriceps strength, functional performance, and knee biomechanics in patients who are 9, 12, 18, and 24 months after ACLR. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: We recruited 82 participants (45 female) who underwent ACLR and were cleared to return to activity . Participants were assigned to 1 of 4 groups based on their time from ACLR: 9 months (285.26 ± 8.16 days), 12 months (373.59 ± 8.81 days), 18 months (557.50 ± 11.96 days), and 24 months postoperative (741.05 ± 11.86 days). Quadriceps strength was measured concentrically at 60 deg/s. Functional performance was assessed by measuring maximal hop distances or heights during dynamic hopping/jumping tests (single-leg hop, triple hop, crossover hop, and single-leg vertical hop). Biomechanical function was evaluated during the dynamic hop tests by using peak sagittal plane knee flexion angles recorded during landings. Strength, performance, and biomechanics data were collected for both limbs and reported as symmetry scores ([injured/uninjured] × 100). Self-perceived function was measured using the International Knee Documentation Committee subjective knee form. RESULTS: Quadriceps strength in the 9-month (77.61 ± 16.73) and 12-month (77.80 ± 13.99) groups was significantly lower (P < .01) compared with the 24-month group (92.40 ± 15.55). Self-perceived function for the 9-month group (79.33 ± 10.40) was significantly lower (P < .01) when compared with 12-month (87.58 ± 10.29), 18-month (89.81 ± 8.36), and 24-month (91.59 ± 5.70) groups. Single-leg hop distance symmetry was significantly lower (P < .01) for the 9-month group (90.01 ± 9.46) when compared with the 18-month (96.24 ± 6.47) and 24-month (96.30 ± 6.46) groups; triple hop symmetry was significantly lower (P < .05) for the 9-month group (90.26 ± 10.03) when compared with the 18-month (96.83 ± 9.60) and 24-month (95.91 ± 6.36) groups; and crossover hop was significantly lower (P < .05) for the 9-month group (88.35 ± 13.53) when compared with the 18-month (95.85 ± 8.63) and 24-month (97.10 ± 4.12) groups. CONCLUSION: Quadriceps strength, self-perceived function, and functional performance improve 9 to 24 months after ACLR, indicating that recovery is ongoing after return to activity. Return-to-activity criteria after ACLR should objectively account for strength and function.

Blood Flow Restriction Training Applied With High-Intensity Exercise Does Not Improve Quadriceps Muscle Function After Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial.

BACKGROUND: A major goal of rehabilitation after anterior cruciate ligament reconstruction (ACLR) is restoring quadriceps muscle strength. Unfortunately, current rehabilitation paradigms fall short of this goal, such that substantial quadriceps muscle strength deficits can limit return to play and increase the risk of recurrent injuries. Blood flow restriction training (BFRT) involves the obstruction of venous return to working muscles during exercise and may lead to better recovery of quadriceps muscle strength after ACLR. PURPOSE: To examine the efficacy of BFRT with high-intensity exercise on the recovery of quadriceps muscle function in patients undergoing ACLR. STUDY DESIGN: Randomized controlled trial; Level of evidence, 2. METHODS: A total of 34 patients (19 female, 15 male; mean age, 16.5 ± 2.7 years; mean height, 169.0 ± 19.7 cm; mean weight, 73.2 ± 17.7 kg) scheduled to undergo ACLR were randomly assigned to 1 of 4 groups: concentric (n = 8), eccentric (n = 8), concentric with BFRT (n = 9), and eccentric with BFRT (n = 9). The exercise component of the intervention consisted of patients performing a single-leg isokinetic leg press, at an intensity of 70% of the patients' 1-repetition maximum during either the concentric or eccentric action, for 4 sets of 10 repetitions 2 times per week for 8 weeks beginning at 10 weeks postoperatively. Patients randomized to the BFRT groups performed the leg-press exercise with a cuff applied to the thigh, set to a limb occlusion pressure of 80%. Isometric and isokinetic (60 deg/s) quadriceps peak torque, quadriceps muscle activation, and rectus femoris muscle volume were assessed before ACLR, after BFRT, and at the time that patients returned to activity and were converted to the change in values from baseline for analysis. Also, 1-way analyses of covariance were used to compare the change in values for each dependent variable between groups after BFRT and at return to activity (P ≤ .05). RESULTS: No significant differences were found between groups for any outcome measures at either time point (P > .05). CONCLUSION: An 8-week BFRT plus high-intensity exercise intervention did not significantly improve quadriceps muscle strength, activation, or volume. On the basis of our findings, the use of BFRT in conjunction with high-intensity resistance exercise in patients undergoing ACLR to improve quadriceps muscle function may not be warranted. REGISTRATION: NCT03141801 ( ClinicalTrials.gov identifier).

Longitudinal Assessment of Quadriceps Muscle Morphology Before and After Anterior Cruciate Ligament Reconstruction and Its Associations With Patient-Reported Outcomes.

BACKGROUND: Reductions in muscle size are common after anterior cruciate ligament reconstruction (ACLR) and may contribute to suboptimal patient outcomes. However, few studies have quantified postoperative alterations in muscle quality and evaluated its associations with patient-reported function. HYPOTHESES: Rectus femoris cross-sectional area (CSA) will decrease postoperatively but improve at return to activity (RTA), rectus femoris muscle quality (percentage fat [PF]) will increase postoperatively and be greater at RTA compared with preoperative values, and rectus femoris CSA and PF will be associated with International Knee Documentation Committee (IKDC) scores at both postoperative time points. STUDY DESIGN: Case series. LEVEL OF EVIDENCE: Level 4. METHODS: A total of 26 individuals who sustained an ACL injury and underwent reconstructive surgery were evaluated preoperatively (T0), 9 weeks post-ACLR (T1), and at RTA. Rectus femoris CSA and PF were evaluated bilaterally via ultrasound imaging, and patient-reported function was assessed using the IKDC score. RESULTS: Bilateral reductions in rectus femoris CSA were noted from T0 to T1 (P < 0.01). Only the uninvolved limb returned to preoperative CSA (P = 0.80), as the involved limb failed to return to preoperative levels at RTA (P = 0.04). No significant changes in rectus femoris PF were observed across time points (P > 0.05). Lesser PF (P < 0.01) but not CSA (P = 0.75) was associated with higher IKDC score at T1. Lesser PF (P = 0.04) and greater CSA (P = 0.05) was associated with higher IKDC score at RTA. CONCLUSION: Substantial atrophy occurs bilaterally after ACLR, and the involved limb does not return to preoperative muscle size despite the patient completing rehabilitation. Quadriceps muscle morphology is associated with patient-reported function and may be an important rehabilitation target after ACLR. CLINICAL RELEVANCE: Quadriceps atrophy and poor muscle quality may contribute to suboptimal patient functioning and quadriceps dysfunction and may be important in RTA decision making. Assessing muscle morphology using ultrasound may be a feasible and clinically beneficial tool in patients after ACLR.

Continued Improvements in Quadriceps Strength and Biomechanical Symmetry of the Knee After Postoperative Anterior Cruciate Ligament Reconstruction Rehabilitation: Is It Time to Reconsider the 6-Month Return-to-Activity Criteria?

CONTEXT: Patients who undergo anterior cruciate ligament reconstruction (ACLR) present with strength and biomechanical deficits at return to activity (RTA). Deficits in strength and biomechanical symmetry impair function during activity and may predispose patients to subsequent injury. OBJECTIVE: To compare strength and biomechanical function in patients with ACLR at RTA and more than 12 months post-ACLR. DESIGN: Descriptive laboratory study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 20 participants (12 females, 8 males; age = 21.40 ± 5.60 years, height = 171.3 ± 10.2 cm, mass = 73.21 ± 19.41 kg) who had undergone ACLR and were cleared to RTA were recruited. INTERVENTION(S): Strength was measured during knee extension and evaluated by the isometric and isokinetic quadriceps index. Biomechanical function was evaluated using symmetry values for sagittal-plane knee-joint rotations, changes in sagittal-plane knee-joint rotation, knee-extension moments, and changes in knee-extension moment that were recorded during a single-legged forward hop. MAIN OUTCOME MEASURE(S): Self-reported function was measured using the International Knee Documentation Committee Subjective Knee Evaluation Form. Participants were assessed at RTA (212.25 ± 28.11 days) and more than 12 months post-ACLR (556.25 ± 230.89 days). RESULTS: At RTA, strength and biomechanical values were less than 80% symmetric. We observed improvements from RTA to more than 12 months post-ACLR for the isometric quadriceps index ( F1,18 = 29.22, P < .001), isokinetic quadriceps index ( F1,18 = 10.88, P = .004), sagittal-plane knee-joint rotations ( F1,19 = 9.58, P = .006), change in sagittal-plane knee-joint rotations ( F1,19 = 7.83, P = .01), knee-extension moments ( F1,19 = 5.73, P = .03), change in knee-extension moments ( F1,19 = 21.10, P < .001), and self-perceived function ( F1,19 = 11.50, P = .003). Of the 7 variables that showed improvement at more than 12 months post-ACLR, only 3 met the recommended criteria (≥90%). CONCLUSIONS: Patients with ACLR showed asymmetry in strength and biomechanics at RTA. These asymmetries, along with self-perceived function, improved over time. However, despite improvements in strength and biomechanics at RTA, asymmetries of more than 10% were still present more than 12 months post-ACLR.