Reliability of hip muscle strength measured in principal and intermediate planes of movement

Muscle Morphology Does Not Solely Determine Knee Flexion Weakness After Anterior Cruciate Ligament Reconstruction with a Semitendinosus Tendon Graft: A Combined Experimental and Computational Modeling Study

The distal semitendinosus tendon is commonly harvested for anterior cruciate ligament reconstruction, inducing substantial morbidity at the knee. The aim of this study was to probe how morphological changes of the semitendinosus muscle after harvest of its distal tendon for anterior cruciate ligament reconstruction affects knee flexion strength and whether the knee flexor synergists can compensate for the knee flexion weakness. Ten participants 8-18 months after anterior cruciate ligament reconstruction with an ipsilateral distal semitendinosus tendon autograft performed isometric knee flexion strength testing (15°, 45°, 60°, and 90°; 0° = knee extension) positioned prone on an isokinetic dynamometer. Morphological parameters extracted from magnetic resonance images were used to inform a musculoskeletal model. Knee flexion moments estimated by the model were then compared with those measured experimentally at each knee angle position. A statistically significant between-leg difference in experimentally-measured maximal isometric strength was found at 60° and 90°, but not 15° or 45°, of knee flexion. The musculoskeletal model matched the between-leg differences observed in experimental knee flexion moments at 15° and 45° but did not well estimate between-leg differences with a more flexed knee, particularly at 90°. Further, the knee flexor synergists could not physiologically compensate for weakness in deep knee flexion. These results suggest additional factors other than knee flexor muscle morphology play a role in knee flexion weakness following anterior cruciate ligament reconstruction with a distal semitendinosus tendon graft and thus more work at neural and microscopic levels is required for informing treatment and rehabilitation in this demographic.

Hip Contact Forces During Sprinting in Femoroacetabular Impingement Syndrome

PURPOSE

Sprinting often provokes hip pain in individuals with femoroacetabular impingement syndrome (FAIS). Asphericity of the femoral head-neck junction (cam morphology) characteristic of FAIS can increase the risk of anterior-superior acetabular cartilage damage. This study aimed to 1) compare hip contact forces (magnitude and direction) during sprinting between individuals with FAIS, asymptomatic cam morphology (CAM), and controls without cam morphology, and 2) identify the phases of sprinting with high levels of anteriorly directed hip contact forces.

METHODS

Forty-six recreationally active individuals with comparable levels of physical activity were divided into three groups (FAIS, 14; CAM, 15; control, 17) based on their history of hip/groin pain, results of clinical impingement tests, and presence of cam morphology (alpha angle >55°). Three-dimensional marker trajectories, ground reaction forces, and electromyograms from 12 lower-limb muscles were recorded during 10-m overground sprinting trials. A linearly scaled electromyogram-informed neuromusculoskeletal model was used to calculate hip contact force magnitude (resultant, anterior-posterior, inferior-superior, medio-lateral) and angle (sagittal and frontal planes). Between-group comparisons were made using two-sample t -tests via statistical parametric mapping ( P < 0.05).

RESULTS

No significant differences in magnitude or direction of hip contact forces were observed between FAIS and CAM or between FAIS and control groups during any phase of the sprint cycle. The highest anteriorly directed hip contact forces were observed during the initial swing phase of the sprint cycle.

CONCLUSIONS

Hip contact forces during sprinting do not differentiate recreationally active individuals with FAIS from asymptomatic individuals with and without cam morphology. Hip loading during early swing, where peak anterior loading occurs, may be a potential mechanism for cartilage damage during sprinting-related sports in individuals with FAIS and/or asymptomatic cam morphology.

Can Clinicians Trust Objective Measures of Hip Muscle Strength From Portable Dynamometers? A Systematic Review With Meta-analysis and Evidence Gap Map of 107 Studies of Reliability and Criterion Validity Using the COSMIN Methodology

OBJECTIVE: To summarize the evidence on reliability and criterion validity of hip muscle strength testing using portable dynamometers. DESIGN: Systematic review with meta-analysis. LITERATURE SEARCH: Five databases were searched from inception to March 2023. STUDY SELECTION CRITERIA: We included studies investigating reliability or criterion validity of hip flexor, extensor, abductor, adductor, or internal/external rotator strength testing with portable dynamometers in injury-free individuals or those with pelvic/lower limb musculoskeletal disorders. DATA SYNTHESIS: We performed meta-analyses for each muscle group, position, and method of fixation. We rated pooled results as sufficient (>75% of studies with correlations ≥0.70), insufficient (>75% of studies with correlations <0.70), or inconsistent (sufficient/insufficient results). We assessed the quality of evidence, created evidence gap maps, and made clinical recommendations. RESULTS: We included a total of 107 studies (reliability 103, validity 14). The intrarater and interrater reliability for hip muscle strength testing across different positions and methods of fixation was sufficient (intraclass correlation coefficient = 0.78-0.96) with low- to high-quality evidence. Criterion validity was less investigated and mostly inconsistent (very low-to moderate-quality evidence) with a wide range of correlations (r = 0.40-0.93). CONCLUSION: Hip muscle strength testing using portable dynamometers is reliable. The use of portable dynamometers as clinical surrogates for measuring strength using an isokinetic dynamometer requires further investigation. Clinicians testing hip muscle strength with portable dynamometers should use external fixation seated for hip flexors, prone or supine for hip extensors, side-lying or supine for abductors and adductors, and prone and seated for internal and external rotators. J Orthop Sports Phys Ther 2023;53(11):655-672. Epub 3 October 2023. doi:10.2519/jospt.2023.12045.

Hip Abductor and External Rotator Strengths Correlate With Hop Symmetry in Men Athletes 2 Years After Anterior Cruciate Ligament Reconstruction

CONTEXT

Hip muscle strength and hop performance limb symmetries after anterior cruciate ligament reconstruction (ACLR) are not well studied. This study aimed to determine the differences in hip abductors' (ABD) and external rotators' (ER) muscle strength measures between limbs, and the relationship between hip ABD and ER muscle strengths and hop performance limb symmetry indices (LSIs) 2 years after ACLR.

DESIGN

Cross-sectional study.

METHODS

Forty (level I/II) men athletes 2 years after unilateral ACLR completed 4 single-legged hop tests and involved hip ABD and ER strength testing (maximum voluntary isometric contraction [MVIC]; isokinetic peak torque [PKTQ] at 60°, 180°, and 300°/s; and isotonic peak velocity at 75% of their MVICs). Muscle strength measures were normalized to body mass, and hop performances were reported as LSIs. Paired t test was used to determine strength differences between limbs, and the Pearson correlation coefficient was used to assess the relationship between involved hip muscle strength measures and hop performance LSIs.

RESULTS

Hip ER-MVIC (involved: 60.26 [12.01], uninvolved: 63.68 [13.17] N·m/kg) and ER eccentric PKTQ at 60°/s (involved: 32.59 [9.28]; uninvolved: 35.73 [10.50] N·m/kg) were significantly different between limbs (P ≤ .018). Single-hop LSI correlated with hip ER-PKTQ at 180°/s (r = .354) and 300°/s (r = .324, P ≤ .041), while triple-hop LSI correlated with hip ER-MVIC (r = .320), concentric ER-PKTQ at 180°/s (r = .355), eccentric ER-PKTQ at 60°/s (r = .314), and hip ABD-PKTQ at 60°/s (r = .364) and 300°/s (r = .336, P ≤ .049).

CONCLUSIONS

Men athletes demonstrated symmetrical hop performance and hip muscle strengths, except for ER hip's MVIC and isokinetic eccentric peak torque at 60°/s 2 years after ACLR. Hop performance LSIs had a few, yet positive moderate relationships with involved hip ABDs and ER strength measures. This may indicate that hip ABD and ER muscle strength measures contribute to athletes' hop performances 2 years after ACLR. Post-ACLR rehabilitation programs might incorporate hip muscle strengthening training to improve athletes' functional performances.

The effects of core stabilization exercises on the neuromuscular function of athletes with ACL reconstruction

Athletes who have undergone anterior cruciate ligament reconstruction (ACLR) often exhibit persistently impaired kinematics and strength. Core stability training appears to be effective for reducing high-risk landing mechanics and preventing primary anterior cruciate ligament (ACL) injuries; however, there have been few attempts to examine their effects in athletes who have undergone ACLR. This study aimed to investigate the effect of eight weeks of simple core stability training on core endurance, hip strength, and knee kinematics in ACLR athletes. Twenty-six male athletes (20-30 years old) with a history of ACL surgery with hamstring tendon autograft were randomly divided into training (n = 13) and control groups (n = 13). The training group performed core stability exercises for eight weeks before starting their team training; the control group did not receive any intervention. Both groups continued their regular team schedule. The core endurance, hip muscle strength, and knee kinematics were assessed by the McGill test, a hand-held dynamometer, and video-taping, respectively. Analysis of covariance test was used for data analysis. The training group showed a significant increase in core endurance, hip abductor and external rotator strength, knee flexion angle, and a significant decrease in the knee valgus angle during single-leg landing in post-training tests compared to their baseline tests (P < 0.05). Our results demonstrated that core stability exercise alters neuromuscular function to a level that is clinically acceptable and statistically significant. Because of the high incidence rate of secondary ACL injury after ACLR, it is recommended that athletes with a history of ACLR benefit from adding core stability exercises to warm-up routines or tertiary prevention programs even after completing post-operative rehabilitation. It is fast and not time-consuming to perform for athletes to reduce the risk factors of re-injury. Trial registration: This study was registered in the Iranian Registry of Clinical Trials with the number IRCT20190224042827N2, registered on 19 December 2019.

Semitendinosus muscle morphology in relation to surface electrode placement in anterior cruciate ligament reconstructed and contralateral legs

The semitendinosus tendon is commonly harvested as graft tissue for anterior cruciate ligament reconstruction (ACLR). Although the semitendinosus tendon can regenerate following harvesting, ACLR results in substantial reductions in semitendinosus muscle size and length, potentially complicating electrode placement for electromyography. The purpose of this study was to assess whether the most commonly used electrode placement [recommended by the “Surface Electromyography for Non-Invasive Assessment of Muscles” (SENIAM) project] is appropriate for measuring semitendinosus electromyograms after ACLR. In nine participants (unilateral ACLR with a semitendinosus graft), B-mode ultrasonography was used to bilaterally determine (i) the semitendinosus muscle-tendon junction position and the state of tendon regeneration (latter for the ACLR leg only) and (ii) the anatomical cross-sectional area (ACSA) of the semitendinosus muscle at the SENIAM-recommended electrode placement site at rest and during isometric maximal voluntary contraction (MVC) at two knee joint angles. Depending on the contraction state and joint angle, the semitendinosus muscle had retracted past the recommended placement site in 33–78% of ACLR legs, but not in any contralateral legs. The ACSA of semitendinosus was smaller both at rest and MVC in the ACLR compared to contralateral leg. The ACSA for both legs decreased at MVC compared to rest and at deep compared to shallow knee flexion angles, likely due to sliding of the muscle under the skin. These results suggest SENIAM guidelines are likely unsuitable for recording surface electromyograms from the semitendinosus muscle after tendon harvesting for ACLR as the muscle of interest may not be within the electrode detection volume.

Electromyography measurements of the deep hip muscles do not improve estimates of hip contact force

The deep hip muscles are often omitted in studies investigating hip contact forces using neuromusculoskeletal modelling methods. However, recent evidence indicates the deep hip muscles have potential to change the direction of hip contact force and could have relevance for hip contact loading estimates. Further, it is not known whether deep hip muscle excitation patterns can be accurately estimated using neuromusculoskeletal modelling or require measurement (through invasive and time-consuming methods) to inform models used to estimate hip contact forces. We calculated hip contact forces during walking, squatting, and squat-jumping for 17 participants using electromyography (EMG)-informed neuromusculoskeletal modelling with (informed) and without (synthesized) intramuscular EMG for the deep hip muscles (piriformis, obturator internus, quadratus femoris). Hip contact force magnitude and direction, calculated as the angle between hip contact force and vector from femoral head to acetabular center, were compared between configurations using a paired t-test deployed through statistical parametric mapping (P < 0.05). Additionally, root mean square error, correlation coefficients (R²), and timing accuracy between measured and modelled deep hip muscle excitation patterns were computed. No significant between-configuration differences in hip contact force magnitude or direction were found for any task. However, the synthesized method poorly predicted (R²-range 0.02-0.3) deep hip muscle excitation patterns for all tasks. Consequently, intramuscular EMG of the deep hip muscles may be unnecessary when estimating hip contact force magnitude or direction using EMG-informed neuromusculoskeletal modelling, though is likely essential for investigations of deep hip muscle function.