John Goetschius

Reposition Acuity and Postural Control after Exercise in Anterior Cruciate Ligament Reconstructed Knees

PURPOSE This study aimed to compare the effects of 36 min of continuous exercise on postural control and joint reposition acuity in patients with anterior cruciate ligament reconstruction (ACL-R) and healthy controls. METHODS Twenty patients (10 women and 10 men; mean ± SD; age = 25.5 ± 5.5 yr, height = 1.75 ± 0.10 m, weight = 76.7 ± 14.4 kg) with a history of primary, uncomplicated ACL-R (5.0 ± 4.3 yr postsurgery) were matched to 20 healthy controls (10 women and 10 men, 24.6 ± 5.0 yr, 1.70 ± 0.09 m, 65.2 ± 12.1 kg). The center of pressure (COP) excursions in the medial-lateral (COP(ML-SD)) and anterior-posterior (COP(AP-SD)) directions and the velocity (COP(Vel)) and area (COP(Area)) were calculated during static, unipedal stance. Open-chain knee joint reposition acuity measures (absolute angular error [AAE] and relative angular error [RAE]) at 45° (AAE₄₅ and RAE₄₅) and 15° of knee flexion (AAE₁₅ and RAE₁₅) were recorded. Measures were recorded at baseline and after a 36-min exercise protocol. Exercise consisted of six repeating cycles of inclined treadmill walking (5 min) and jumping exercises (1 min). RESULTS At baseline, the ACL-R group exhibited higher magnitude AAE₄₅ compared with controls. AAE₄₅ and COP(ML-SD) significantly increased after exercise in the control group; however, the ACL-R group did not experience a change in these measures. CONCLUSIONS In a rested state, patients with a history of ACL-R have greater impairment in joint reposition acuity than healthy control. Exercise increased COP measurements and impaired joint reposition acuity. Healthy controls experienced impaired joint reposition acuity after exercise, whereas patients with a history of ACL-R did not.

Knee extension torque variability after exercise in ACL reconstructed knees

The purpose of this study was to compare knee extension torque variability in patients with ACL reconstructed knees before and after exercise. Thirty two patients with an ACL reconstructed knee (ACL‐R group) and 32 healthy controls (control group) completed measures of maximal isometric knee extension torque (90° flexion) at baseline and following a 30‐min exercise protocol (post‐exercise). Exercise included 30‐min of repeated cycles of inclined treadmill walking and hopping tasks. Dependent variables were the coefficient of variation (CV) and raw‐change in CV (ΔCV): CV = (torque standard deviation/torque mean x 100), ΔCV = (post‐exercise – baseline). There was a group‐by‐time interaction (p = 0.03) on CV. The ACL‐R group demonstrated greater CV than the control group at baseline (ACL‐R = 1.07 ± 0.55, control = 0.79 ± 0.42, p = 0.03) and post‐exercise (ACL‐R = 1.60 ± 0.91, control = 0.94 ± 0.41, p = 0.001). ΔCV was greater (p = 0.03) in the ACL‐R group (0.52 ± 0.82) than control group (0.15 ± 0.46). CV significantly increased from baseline to post‐exercise (p = 0.001) in the ACL‐R group, while the control group did not (p = 0.06). The ACL‐R group demonstrated greater knee extension torque variability than the control group. Exercise increased torque variability more in the ACL‐R group than control group.

Knee-Extension Torque Variability and Subjective Knee Function in Patients With a History of Anterior Cruciate Ligament Reconstruction

CONTEXT When returning to physical activity, patients with a history of anterior cruciate ligament reconstruction (ACL-R) often experience limitations in knee-joint function that may be due to chronic impairments in quadriceps motor control. Assessment of knee-extension torque variability may demonstrate underlying impairments in quadriceps motor control in patients with a history of ACL-R. OBJECTIVE To identify differences in maximal isometric knee-extension torque variability between knees that have undergone ACL-R and healthy knees and to determine the relationship between knee-extension torque variability and self-reported knee function in patients with a history of ACL-R. DESIGN Descriptive laboratory study. SETTING Laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 53 individuals with primary, unilateral ACL-R (age = 23.4 ± 4.9 years, height = 1.7 ± 0.1 m, mass = 74.6 ± 14.8 kg) and 50 individuals with no history of substantial lower extremity injury or surgery who served as controls (age = 23.3 ± 4.4 years, height = 1.7 ± 0.1 m, mass = 67.4 ± 13.2 kg). MAIN OUTCOME MEASURE(S) Torque variability, strength, and central activation ratio (CAR) were calculated from 3-second maximal knee-extension contraction trials (90° of flexion) with a superimposed electrical stimulus. All participants completed the International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, and we determined the number of months after surgery. Group differences were assessed using independent-samples t tests. Correlation coefficients were calculated among torque variability, strength, CAR, months after surgery, and IKDC scores. Torque variability, strength, CAR, and months after surgery were regressed on IKDC scores using stepwise, multiple linear regression. RESULTS Torque variability was greater and strength, CAR, and IKDC scores were lower in the ACL-R group than in the control group (P < .05). Torque variability and strength were correlated with IKDC scores (P < .05). Torque variability, strength, and CAR were correlated with each other (P < .05). Torque variability alone accounted for 14.3% of the variance in IKDC scores. The combination of torque variability and number of months after surgery accounted for 21% of the variance in IKDC scores. Strength and CAR were excluded from the regression model. CONCLUSIONS Knee-extension torque variability was moderately associated with IKDC scores in patients with a history of ACL-R. Torque variability combined with months after surgery predicted 21% of the variance in IKDC scores in these patients.

Relationships of Muscle Function and Subjective Knee Function in Patients After ACL Reconstruction

Background: After anterior cruciate ligament reconstruction (ACLR), relationships between objective measures of muscle function and patient-reported outcomes may change over time. Examining these measures at different time frames after surgery may help develop individualized approaches to improve post-ALCR analysis. Purpose: To examine the associations between subjective knee function and lower-extremity muscle function in individual patients at various time points after ACLR. Study Design: Descriptive laboratory study. Methods: Fifty-one participants who underwent primary, unilateral ACLR (15 males, 36 females; mean age, 22.9 ± 4.5 years; mean height, 172.4 ± 10.1 cm; mean weight, 68.7 ± 13.1 kg) were separated into 3 groups depending on time since surgery (early, <2 years; middle, 2-5 years; late, >5 years). Subjective knee function was quantified using the International Knee Documentation Committee (IKDC) subjective knee form and the Knee injury and Osteoarthritis Outcome Score (KOOS). Isometric knee extension and flexion strength were collected at 90 deg/s. Single-leg hop performance was measured using the single hop, triple hop, cross-over hop, and 6-m timed hop. Coefficient correlations were calculated between subjective knee function and objective measures of muscle function for each group. Results: The early group demonstrated moderate correlations between the KOOS and unilateral measures of flexion peak torque (r = 0.514, P = .035) and flexion power (r = 0.54, P = .027). The middle group demonstrated the strongest correlations between the KOOS and symmetry measures of the single hop (r = 0.69, P = .002) and extension work (r = 0.71, P = .002) as well as unilateral measures of the triple hop (r = 0.52, P = .034) and extension work (r = 0.66, P = .004). The late group demonstrated strong correlations between the 6-m timed hop symmetry and the IKDC (r = 0.716, P = .001) and KOOS (r = 0.71, P = .001). Conclusion: Patients with a post-ACLR status of less than 2 years exhibited stronger relationships with unilateral strength measures to subjective function; graft type was found to change these relationships. Patients at 2 to 5 years postsurgery demonstrated relationships with both unilateral and symmetry measures of muscle function to subjective function. Patients who were more than 5 years after ACLR exhibited strong associations between hopping symmetry and subjective function. Clinical Relevance: Future clinical guidelines for patients after ACLR may need to consider time since surgery as a potential factor.

The Utility of Objective Strength and Functional Performance to Predict Subjective Outcomes After Anterior Cruciate Ligament Reconstruction

Background: Many clinicians release patients to return to activity after anterior cruciate ligament reconstruction (ACLR) based on time from surgery despite deficits in muscle strength and function. It is unclear whether symmetry or unilateral performance is the best predictor of subjective outcomes after ACLR. Purpose: To determine physical performance predictors of patient-reported outcomes after reconstruction. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 88 participants (49 males, 39 females; mean ± SD height, 174.0 ± 9.6 cm; weight, 76.1 ± 18.5 kg; age, 19.4 ± 3.7 years) who underwent primary, unilateral ACLR volunteered for this study. Participants had undergone reconstruction a mean of 6.9 ± 1.8 months (range, 5.0-14.1 months) before the study. All participants underwent strength testing as well as hop testing and then completed the International Knee Documentation Committee (IKDC) and Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaires. Stepwise linear regression models were used for symmetry and unilateral performance to identify the proportion of variance explained in the IKDC score, KOOS total score, KOOS-sport subscale, and time from surgery, as well as receiver operating characteristic (ROC) curve analyses on those variables that explained the most variance in patient-reported outcomes to determine cutoff thresholds. Results: No significant correlations were found between time from surgery and objective performance. The only significant predictors of IKDC score were single-hop limb symmetry index (LSI) and age (R 2 = 0.177) and unilateral triple-hop performance and age (R 2 = 0.228). The cutoff for single-hop symmetry was 0.92 (area under the curve [AUC], 0.703; P = .012), and the cutoff for normalized triple-hop distance was 3.93 (AUC, 0.726; P = .005). When stratified by age, the cutoff for single-hop symmetry was 0.81 (AUC, 0.721; P = .051) for younger patients (age <19.1 years) and was not significant for older patients (age ≥19.1 years). The cutoff for normalized triple-hop distance was 3.85 (AUC, 0.832; P = .005) in older patients and was not significant for younger patients. The only significant predictors of KOOS-sport subscale were single-hop LSI (R 2 = 0.140) and normalized knee extensor power at 180 deg/s (R 2 = 0.096). When subjective outcomes were predicted based on KOOS-sport subscale, the cutoff for single-hop symmetry was 0.85 (AUC, 0.692; P = .018). Conclusion: Hopping performance is the most predictive functional variable of subjective outcomes after reconstruction. Single-hop symmetry was most important for younger patients and unilateral triple-hop distance was most important for older patients. Clinicians should consider hopping performance when making return-to-activity decisions after ACLR.