Medial hamstring muscle activation patterns are affected 1-6 years after ACL reconstruction using hamstring autograft

Musculoskeletal ultrasound imaging of proximal and distal hamstrings cross sectional area in individuals with history of anterior cruciate ligament reconstruction

BACKGROUND

Ultrasound (US) imaging is used by physical therapists for diagnosis and assessment of musculoskeletal injury and follow-up.

PURPOSE

The aim was to identify long-term effects of graft harvesting on hamstrings muscle mass among athletes who had undergone anterior cruciate ligament reconstruction (ACLR).

METHODS

Twenty-eight participants (ages 18-55) were recruited: 18 with history of ACLR using semitendinosus (ST) autograft and 10 healthy controls. Images of the cross-sectional area (CSA) of ST and biceps femoris (BF) were captured at 30% and 70% of the distance from the ischial tuberosity to the popliteal crease. A mixed model ANOVA was used to identify inter-limb differences in the CSA of ST and BF at each location, for each group.

RESULTS

Inter-limb differences were found for the CSA of ST but not BF across both locations for the ACLR group, not controls (p < .001). Within the ACLR group, ST atrophy of the injured limb was relatively greater at the distal vs. proximal location (p < .001).

CONCLUSION

US imaging identified selective atrophy of ST on the injured side with no compensatory hypertrophy of BF. Specific rehabilitation may influence muscle mass of medial vs. lateral hamstrings muscle groups after ACLR using a ST graft, and monitored with US imaging.

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.

Study protocol for double-blind, randomised placebo-controlled trial evaluating semitendinosus function and morbidity following tendon harvesting for anterior cruciate ligament reconstruction augmented by platelet-rich plasma

INTRODUCTION

Anterior cruciate ligament (ACL) rupture is debilitating, often requiring surgical reconstruction. An ACL reconstruction (ACLR) using a tendon autograft harvested from the semitendinosus results in substantial injury to the donor muscle. Following ACLR, patients rarely return to their preinjury level of physical activity, are at elevated risk of secondary lower limb injuries and early onset knee osteoarthritis. To date, no randomised controlled trial has evaluated the efficacy of platelet-rich plasma (PRP) in aiding knee function and semitendinosus morphology of following ALCR.

METHODS AND ANALYSIS

This is a multicentre double-blind randomised placebo-controlled trial. Fifty-four ACLR patients aged 18-50 years will be randomised to receive either a single application of PRP (ACLR+) or placebo saline (ACLR) into the semitendinosus harvest zone at the time of surgery. All patients will undergo normal postoperative rehabilitation recommended by the attending orthopaedic surgeon or physiotherapist. The primary outcome measure is between-limb difference (ACLR compared with intact contralateral) in isometric knee flexor strength at 60^o knee flexion, collected 10-12 months postsurgery. This primary outcome measure will be statistically compared between groups (ACLR+ and standard ACLR). Secondary outcome measures include bilateral assessments of hamstring muscle morphology via MRI, biomechanical and electromyographic parameters during an anticipated 45° running side-step cut and multidirectional hopping task and patient-reported outcomes questionaries. Additionally, patient-reported outcomes questionaries will be collected before (baseline) as well as immediately after surgery, and at 2-6 weeks, 3-4 months, 10-12 months and 22-24 months postsurgery 10-12 months following surgery.

ETHICS AND DISSEMINATION

Ethics approval has been granted by Griffith University Human Research Ethics Committee, Greenslopes Research and Ethics Committee, and Royal Brisbane & Women's Hospital Human Research Ethics Committee. Results will be submitted for publication in a peer-reviewed medical journal.

TRIAL REGISTRATION NUMBER

ACTRN12618000762257p.

Quo Vadis Nordic Hamstring Exercise-Related Research?-A Scoping Review Revealing the Need for Improved Methodology and Reporting

The objective of this scoping review is to assess Nordic Hamstring Exercise quality (ANHEQ) of assessments and interventions according to the ANHEQ rating scales and to present practical recommendations for the expedient design and reporting of future studies. A total of 71 Nordic Hamstring Exercise (NHE) assessments and 83 NHE interventions were selected from the data sources PubMed, Scopus, and SPORTDiscus. Research studies which were presented in peer-reviewed academic journals and implemented the NHE during laboratory-based assessments or multi-week interventions met the eligibility criteria. NHE assessments analyzed force (51%), muscle activation (41%), knee angle kinematics (38%), and bilateral symmetry (37%). NHE interventions lasted 4-8 weeks (56%) and implied an exercise volume of two sessions per week (66%) with two sets per session (41%) and ≥8 repetitions per set (39%). The total ANHEQ scores of the included NHE assessments and interventions were 5.0 ± 2.0 and 2.0 ± 2.0 (median ± interquartile range), respectively. The largest deficits became apparent for consequences of impaired technique (87% 0-point-scores for assessments) and kneeling height (94% 0-point-scores for interventions). The 0-point-scores were generally higher for interventions compared to assessments for rigid fixation (87% vs. 34%), knee position (83% vs. 48%), kneeling height (94% vs. 63%), and separate familiarization (75% vs. 61%). The single ANHEQ criteria, which received the highest score most frequently, were rigid fixation (66% of assessments) and compliance (33% of interventions). The quality of NHE assessments and interventions was generally 'below average' or rather 'poor'. Both NHE assessments and interventions suffered from imprecise reporting or lacking information regarding NHE execution modalities and subsequent analyses. Based on the findings, this scoping review aggregates practical guidelines how to improve the design and reporting of future NHE-related research.

Can Increased Locomotor Task Difficulty Differentiate Knee Muscle Forces After Anterior Cruciate Ligament Reconstruction?

Changes in knee mechanics following anterior cruciate ligament (ACL) reconstruction are known to be magnified during more difficult locomotor tasks, such as when descending stairs. However, it is unclear if increased task difficulty could distinguish differences in forces generated by the muscles surrounding the knee. This study examined how knee muscle forces differ between individuals with ACL reconstruction with different graft types (hamstring tendon and patellar tendon autograft) and "healthy" controls when performing tasks with increasing difficulty. Dynamic simulations were used to identify knee muscle forces in 15 participants when walking overground and descending stairs. The analysis was restricted to the stance phase (foot contact through toe-off), yielding 162 separate simulations of locomotion in increasing difficulty: overground walking, step-to-floor stair descent, and step-to-step stair descent. Results indicated that knee muscle forces were significantly reduced after ACL reconstruction, and stair descent tasks better discriminated changes in the quadriceps and gastrocnemii muscle forces in the reconstructed knees. Changes in quadriceps forces after a patellar tendon graft and changes in gastrocnemii forces after a hamstring tendon graft were only revealed during stair descent. These results emphasize the importance of incorporating sufficiently difficult tasks to detect residual deficits in muscle forces after ACL reconstruction.

The relationship between eccentric hamstring strength and dynamic stability in elite academy footballers

OBJECTIVES

Previous research describes dynamic stability and functional strength as key aetiological risk factors associated with lower limb non-contact musculoskeletal injury. Due to the multifactorial nature of injury risk, relationships between the two factors will inform injury management and training design.

METHODS

A total of 59 elite academy footballers from two English premier league category 1-status academies completed the study. All players completed measures of eccentric hamstring strength and dynamic stability. Relationships between directional stability (Anteroposterior (Ant), Posteromedial (PM) and Posterolateral (PL)) and eccentric strength metrics (PkT, AvT, PkF, AvF and Ɵ) bilaterally were identified for analysis.

RESULTS

Significant correlations were identified bilaterally for functional hamstring strength metrics and PM and PL stability (P ≤. 0.05). No significant relationships were identified between anterior stability and eccentric hamstring strength parameters (P > 0.05).

CONCLUSIONS

Eccentric hamstring strength has a positive influence on directional stability through two planes, PM and PL. The lack of influence of eccentric hamstring strength on Ant directional stability could be attributed to increased ACL risk. Careful consideration of the significance of the relationships between eccentric hamstring strength and directional stability must be given when quantifying injury risk in elite academy footballers.

Which assessments are used to analyze neuromuscular control by electromyography after an anterior cruciate ligament injury to determine readiness to return to sports? A systematic review

BACKGROUND

Adequate neuromuscular control of the knee could be one element to prevent secondary injuries after an anterior cruciate ligament (ACL) injury. To assess neuromuscular control in terms of time, amplitude and activity, electromyography (EMG) is used. However, it is unclear which assessments using EMG could be used for a safe return to sports (RTS). Therefore, we aimed to summarize EMG-related assessments for neuromuscular control of the knee in adult patients after an ACL injury to decide upon readiness for RTS.

METHODS

This systematic review followed guidelines of Preferred Reporting of Items for Systematic Reviews and Meta-Analyses (PRISMA) and Cochrane recommendations. MEDLINE/PubMed, EMBASE, CINAHL, Cochrane Library, Physiotherapy Evidence Database (PEDro), SPORTDiscus and the Web of Science were searched from inception to March 2019 and updated in November 2020. Studies identifying electromyographic assessments for neuromuscular control during dynamic tasks in adult, physically active patients with an anterior cruciate ligament injury were eligible and qualitatively synthesized. Two independent reviewers used a modified Downs and Black checklist to assess risk of bias of included studies.

RESULTS

From initially 1388 hits, 38 mainly cross-sectional, case-controlled studies were included for qualitative analysis. Most studies provided EMG outcomes of thigh muscles during jumping, running or squatting. Outcomes measures described neuromuscular control of the knee in domains of time, amplitude or activity. Risk of bias was medium to high due to an unclear description of participants and prior interventions, confounding factors and incompletely reported results.

CONCLUSIONS

Despite a wide range of EMG outcome measures for neuromuscular control, none was used to decide upon return to sports in these patients. Additional studies are needed to define readiness towards RTS by assessing neuromuscular control in adult ACL patients with EMG. Further research should aim at finding reliable and valid, EMG-related variables to be used as diagnostic tool for neuromuscular control. Moreover, future studies should aim at more homogenous groups including adequately matched healthy subjects, evaluate gender separately and use sport-specific tasks. Registration The protocol for this systematic review was indexed beforehand in the International Prospective Register of Systematic Reviews (PROSPERO) and registered as CRD42019122188.

Anterior Cruciate Ligament Reconstruction Increases the Risk of Hamstring Strain Injury Across Football Codes in Australia

OBJECTIVE

The aim of this study was to determine the impacts of anterior cruciate ligament reconstruction (ACLR) and recent (< 12 months) hamstring strain injury (HSI) on (1) future HSI risk, and (2) eccentric knee flexor strength and between-limb imbalance during the Nordic hamstring exercise. A secondary goal was to examine whether eccentric knee flexor strength was a risk factor for future HSI in athletes with prior ACLR and/or HSI.

METHODS

In this prospective cohort study, 531 male athletes had preseason eccentric knee flexor strength tests. Injury history was also collected. The main outcome was HSI occurrence in the subsequent competitive season.

RESULTS

Overall, 74 athletes suffered at least one prospective HSI. Compared with control athletes, those with a lifetime history of ACLR and no recent HSI had 2.2 (95% confidence interval [CI] 1.1-4.4; p = 0.029) times greater odds of subsequent HSI while those with at least one HSI in the previous 12 months and no history of ACLR had 3.1 (95% CI 1.8-5.4; p < 0.001) times greater odds for subsequent HSI. Only athletes with a combined history of ACLR and recent HSI had weaker injured limbs (p = 0.001) and larger between-limb imbalances (p < 0.001) than uninjured players. An exploratory decision tree analysis suggested eccentric strength may protect against HSI after ACLR.

CONCLUSION

ACLR and recent HSI were similarly predictive of future HSI. Lower levels of eccentric knee flexor strength and larger between-limb imbalances were found in athletes with combined histories of ACLR and recent HSI. These findings may have implications for injury rehabilitation.

sEMG Activity in Superimposed Vibration on Suspended Supine Bridge and Hamstring Curl

Traditionally in strength and conditioning environments, vibration has been transmitted using platforms, barbells, dumbbells, or cables but not suspension devices. This study aimed to examine the effects on the lower limb of applying superimposed vibration on a suspension device. Twenty-one physically active men and women performed supine bridge and hamstring curl exercises in three suspended conditions (non-vibration, vibration at 25 Hz, and vibration at 40 Hz). In each exercise condition, the perceived exertion scale for resistance exercise (OMNI-Res) was registered, and the electromyographic signal was assessed for gastrocnemius (medialis and lateralis), biceps femoris, semitendinosus, gluteus maximus, and rectus femoris. A linear mixed model indicated a significant fixed effect for vibration at 25 Hz and 40 Hz on muscle activity in suspended supine bridge (p < 0.05), but no effect for suspended hamstring curl (p > 0.05). Likewise, the Friedman test showed a significant main effect for vibration at 25 Hz and 40 Hz in suspended supine bridge (p < 0.05) but not for suspended hamstring curl (p > 0.05) on OMNI-Res. Post hoc analysis for suspended supine bridge with vibration at 25 Hz showed a significant activation increase in gastrocnemius lateralis (p = 0.008), gastrocnemius medialis (p = 0.000), semitendinosus (p = 0.003) activity, and for semitendinosus under 40 Hz condition (p = 0.001) compared to the non-vibration condition. Furthermore, OMNI-Res was significantly higher for the suspended supine bridge at 25 Hz (p = 0.003) and 40 Hz (p = 0.000) than for the non-vibration condition. Superimposed vibration at 25 Hz elicits a higher neuromuscular response during the suspended supine bridge, and the increase in vibration frequency also raises the OMNI-Res value.

The Temporal Pattern of Recovery in Directional Dynamic Stability Post Football-Specific Fatigue

BACKGROUND

Rising injury rates within football require further understanding of the etiological risk factors associated with lower-limb injury.

AIM

To examine the temporal pattern of recovery of directional dynamic stability measures post football-specific fatigue.

METHODS

Eighteen male elite footballers completed baseline assessments of directional dynamic stability measures (Overall Stability Index, anterior-posterior stability [A-P], medial-lateral stability [M-L] on level 1 of the Biodex Stability System). Post Soccer-Specific Aerobic Field Test90 measures were repeated immediately, +24 hours, +48 hours, and +72 hours. The main effects for the recovery time and direction of stability were supplemented by regression modeling to describe the temporal pattern of recovery.

RESULTS

Significant main effects for time were identified for all directions of stability (Overall Stability Index, A-P, and M-L) up to +48 hours postexercise (P ≤ .05). The quadratic pattern of temporal recovery highlights a minimum of 37.55 to 38.67 hours and maximum of 75.09 to 77.33 hours. Additionally, a main effect for direction of stability was observed, with significant differences identified between A-P and M-L stability at all time points (P ≤ .001).

CONCLUSIONS

Reductions in directional dynamic stability +48 hours postfatigue highlight implications for training design, recovery strategies, and injury management for performance practitioners. Interestingly, A-P stability has been highlighted as being significantly reduced compared with M-L stability at all time points, regardless of the fatigue exposure. Practitioners should consider the reduction of stability in this plane in relation to common mechanisms of injury in the knee to inform injury-risk-reduction strategies.

Hamstrings Neuromuscular Function After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-Analysis

BACKGROUND

Hamstrings neuromuscular function is a crucial component of functional movement, and changes after anterior cruciate ligament (ACL) injury contribute to risk factors for secondary injury and long-term sequelae. To effectively treat muscular impairments, an accurate understanding of hamstrings neuromuscular function in patients with ACL reconstruction (ACLR) is needed.

OBJECTIVE

A systematic review and meta-analysis were undertaken to describe and quantify hamstrings neuromuscular function in individuals with ACLR compared to controls.

METHODS

We searched PubMed, Web of Science, SPORTDiscus, CINAHL, and EBSCOhost databases in October of 2020 for studies evaluating the difference between hamstrings electromyography (EMG) between individuals with ACLR and controls. Two independent reviewers assessed each paper for inclusion and quality. Means and standard deviations were extracted from each included study to allow random-effect size (ES) meta-analysis calculations for comparison of results.

RESULTS

Thirty-four studies were included for final review. From these, 5 categories of neuromuscular outcomes were identified, and studies were grouped accordingly: (1) muscle activation levels (EMG amplitude), (2) co-activation, (3) onset timing, (4) electromechanical delay, and (5) time-to-peak activity. Moderate to strong evidence indicates that individuals with ACLR demonstrate higher hamstrings EMG amplitude (normalized to % maximum voluntary isometric contraction) and hamstrings-to-quadriceps co-activation during gait and stair ambulation compared to controls. In addition, there was moderate evidence of longer electromechanical delay during knee flexion and greater hamstrings-to-quadriceps co-activation during knee extension compared to controls.

CONCLUSIONS

Greater hamstrings EMG amplitude and co-activation during gait and ambulation tasks and longer electromechanical delay of the hamstrings in individuals with ACLR align with clinical impairments following ACLR and have implications for re-injury risk and long-term joint health, thus warranting attention in rehabilitation.

Hamstring muscle activation and morphology are significantly altered 1-6 years after anterior cruciate ligament reconstruction with semitendinosus graft

PURPOSE

Harvest of the semitendinosus (ST) tendon for anterior cruciate ligament reconstruction (ACLR) causes persistent hypotrophy of this muscle even after a return to sport, although it is unclear if hamstring activation patterns are altered during eccentric exercise. It was hypothesised that in comparison with contralateral control limbs, limbs with previous ACLR involving ST grafts would display (i) deficits in ST activation during maximal eccentric exercise; (ii) smaller ST muscle volumes and anatomical cross-sectional areas (ACSAs); and (iii) lower eccentric knee flexor strength.

METHODS

Fourteen athletes who had successfully returned to sport after unilateral ACLR involving ST tendon graft were recruited. Median time since surgery was 49 months (range 12-78 months). Participants underwent functional magnetic resonance imaging (MRI) of their thighs before and after the Nordic hamstring exercise (NHE) and percentage change in transverse (T2) relaxation time was used as an index of hamstring activation. Muscle volumes and ACSAs were determined from MRI and distal ST tendons were evaluated via ultrasound. Eccentric knee flexor strength was determined during the NHE.

RESULTS

Exercise-induced T2 change was lower for ST muscles in surgical than control limbs (95% CI - 3.8 to - 16.0%). Both ST muscle volume (95% CI - 57.1 to - 104.7 cm³) and ACSA (95% CI - 1.9 to - 5.0 cm²) were markedly lower in surgical limbs. Semimembranosus (95% CI 5.5-14.0 cm³) and biceps femoris short head (95% CI 0.6-11.0 cm³) volumes were slightly higher in surgical limbs. No between-limb difference in eccentric knee flexor strength was observed (95% CI 33 N to - 74 N).

CONCLUSION

ST activation is significantly lower in surgical than control limbs during eccentric knee flexor exercise 1-6 years after ACLR with ST graft. Lower levels of ST activation may partially explain this muscle's persistent hypotrophy post ACLR and have implications for the design of more effective rehabilitation programs.

LEVEL OF EVIDENCE

IV.

The significant effect of the medial hamstrings on dynamic knee stability

PURPOSE

While hamstring autograft is a popular option for the general population, BTB autograft is still significantly more popular among professional athletes due to concerns of altering knee kinematics with hamstring harvest. This study seeks to quantify the contribution of the medial hamstrings to knee stability.

METHODS

Valgus knee laxity, anterior tibial translation, and rotational motion were measured in eight fresh-frozen cadaveric knees after forces were applied on the tibia in each plane (coronal, sagittal, and axial). Four muscle loading conditions were tested: (1) physiologic fully loaded pes anserinus, (2) semitendinosus only loaded, (3) gracilis only loaded, and (4) unloaded pes anserinus. The protocol was then repeated with the ACL transected.

RESULTS

In the ACL intact knee, the neutral position of the tibia with an unloaded pes anserinus was significantly more externally rotated (p < 0.01) and anteriorly translated (p < 0.05) at all knee flexion angles than a tibia with a physiologic loaded pes anserinus. Applying an external rotation torque significantly increased external rotation for the fully unloaded (p < 0.001), gracilis only loaded (p < 0.001), and semitendinosus only loaded (p < 0.01) conditions at all flexion angles. Applying a valgus torque resulted in a significant increase in laxity for the fully unloaded condition only at 30° of flexion (p < 0.05). Applying an anterior tibial force resulted in significant increase in anterior translation for the fully unloaded condition at all flexion angles (p < 0.01), and for the gracilis only loaded condition in 30° and 60° of flexion (p < 0.05). Similar results were seen in the ACL deficient model.

CONCLUSION

The medial hamstrings are involved in rotational, translational, and varus/valgus control of the knee. Applying anterior, external rotation, and valgus forces on the hamstring deficient knee significantly increases motion in those planes. Harvesting the gracilis and semitendinosus tendons alters native knee kinematics and stability. This is clinically relevant and should be a consideration when choosing graft source for ACL reconstruction, especially in the elite athlete population.

Eccentric knee flexor weakness in elite female footballers 1-10 years following anterior cruciate ligament reconstruction

OBJECTIVES

To determine eccentric knee flexor strength in elite female Australian Rules Football (ARF) players with and without a history of unilateral anterior cruciate ligament reconstruction (ACLR) using an ipsilateral semitendinosus graft.

DESIGN

Case-control.

SETTING

Elite ARF Women's competition.

PARTICIPANTS

Eighty-four elite female ARF players (mean age, 25 ± 4.9 years; height, 1.71 ± 0.73 m; weight, 67 kg ± 7.4 kg) with (n = 12) and without (n = 72) a history of unilateral ACLR in the previous 10 years.

MAIN OUTCOME MEASURES

Peak eccentric knee flexor force during the Nordic hamstring exercise (NHE).

RESULTS

Players with a history of unilateral ACLR displayed lower levels of eccentric knee flexor strength in their surgically reconstructed limb than their uninjured contralateral limb (mean difference -53.77 N, 95% CI = -85.06 to -24.27, d = -0.51) and compared to the limbs of players with no history of injury (mean difference = -46.32 N, 95% CI = -86.65 to -11.13, d = -0.73).

CONCLUSION

Elite female ARF players with a history of unilateral ACLR display deficits in eccentric knee flexor strength in their surgically reconstructed limb for up to 10 years following surgery.

Linear and nonlinear measures of gait variability after anterior cruciate ligament reconstruction

The objective of this study was to assess gait variability after anterior cruciate ligament reconstruction (ACLR), as an indicative of possible altered gait pattern and a measure of recovery compared to control subjects. Forty subjects (32 male), divided into 4 groups of 10 participants, were enrolled in the study: a control group (CG), and observational groups OG-I (90 days), OG-II (180 days), and OG-III (360 days) after ACLR. All subjects underwent the same rehabilitation program for six months. For kinematic recording, each subject walked on a treadmill for 4 min at a preferred walking speed. Linear gait variability was assessed using average standard deviation (VAR) and normalized root mean square of medial-lateral (ML) trunk acceleration (RMS_ratio). Gait stability was assessed using the margin of stability (MoS) and local dynamic stability (LDS), and nonlinear variability was assessed using sample entropy (SEn). Compared to the CG, the VAR ML increased significantly in the OG-I group and decreased incrementally in OG-II and OG-III. MoS increased significantly in the OG-I group and tends to maintain in OG-II and OG-III, while LDS was greater in the CG and decreased incrementally in the OG groups. The SEn was higher in the OG groups than in the CG and increased in OG-II and OG-III. The results indicated that ACL reconstruction was followed by a progressive increase in stability and a progressive increase in variability over the postoperative rehabilitation period. In terms of stability and gait variability, six months of physiotherapy for rehabilitation after ACL reconstruction appears to be effective, but it is insufficient for a complete recovery as compared to healthy individuals.

Hamstring Injuries in Major League Baseball Pitchers: Implications in Graft Selection for Ulnar Collateral Ligament Reconstruction

BACKGROUND

Hamstring tendons are commonly harvested as autograft for ulnar collateral ligament reconstruction. There is no consensus in the literature whether the hamstring tendon should be harvested from the ipsilateral (drive) leg or contralateral (landing) leg of baseball pitchers undergoing ulnar collateral ligament reconstruction. Hamstring injuries commonly occur in baseball players, but there are no reports on their incidence specifically among Major League Baseball (MLB) pitchers, nor are there reports on whether they occur more commonly in the drive leg or the landing leg.

HYPOTHESIS

Hamstring injuries occur more commonly in the landing legs of MLB pitchers.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

MLB pitchers who sustained hamstring injuries requiring time spent on the disabled list were identified from publicly available sources over 10 seasons. Demographics of the pitchers and injury and return-to-sport data were collected. Hamstring injuries to the drive leg were compared with injuries to the landing leg.

RESULTS

Sixty-five pitchers had 78 disabled list stints due to hamstring injuries over 10 seasons. The landing leg was injured in 67.9% of cases, and the most common mechanism of injury was pitching. There were no significant differences in demographics between pitchers who sustained drive leg and landing leg injuries. There was no significant difference in mechanism of injury or time to return to sport between pitchers who sustained drive leg and landing leg injuries.

CONCLUSION

The landing leg is more commonly injured than the drive leg among MLB pitchers who sustain hamstring injuries. There is no difference in time to return to sport between pitchers who sustain drive leg and landing leg injuries. More research is required to determine whether there is a difference in performance or future injury between hamstring tendons harvested from the drive leg and the landing leg for ulnar collateral ligament reconstruction among pitchers.

The Effect of Tibial Rotation on the Contribution of Medial and Lateral Hamstrings During Isometric Knee Flexion

Background:

Selective atrophy of hamstring components may result from muscle strain or graft harvesting for anterior cruciate ligament reconstruction. Assessment and rehabilitation that specifically targets medial (MH) or lateral (LH) hamstring components may improve patient outcomes. The purpose of this study was to evaluate effects of volitional tibial rotation medially (MR) versus laterally (LR) on activation levels of MH versus LH and strength measures during isometric testing of knee flexors.

Hypothesis:

Muscle activation of MH and LH during knee flexor strength testing will be augmented when coupled with MR and LR of the tibia, respectively, without affecting knee flexor strength measures.

Study Design:

Cross-sectional laboratory study.

Level of Evidence:

Level 3.

Methods:

Surface electrodes were used to record neuromuscular activity from MH and LH of the right lower limb in 40 healthy young men and women during isometric knee flexor strength testing at 40° of knee flexion, where participants maintained concurrent volitional MR or LR of the tibia. Statistical analyses of variance included general linear models for repeated measures.

Results:

A significant interaction was found for tibial rotation and hamstring component variables (P < 0.01). When isometric knee flexion was coupled with LR, normalized activation levels were similar for MH and LH. When performed with MR, a significant drop in LH activation led to dissimilar activation levels of the 2 components. Significantly greater strength measures were found when isometric knee flexion was performed with concurrent LR of the tibia (P < 0.01). Both sexes demonstrated the same rotation-dependent differences.

Conclusion:

Coupling tibial rotation with knee flexor activities primarily affects the LH component.

Clinical Relevance:

Strategies involving volitional tibial rotation may be considered for specific assessment/rehabilitation of the MH or LH component.

Immersive virtual reality improves movement patterns in patients after ACL reconstruction: implications for enhanced criteria-based return-to-sport rehabilitation

PURPOSE

The purpose of this study was to evaluate the influence of immersion in a virtual reality environment on knee biomechanics in patients after ACL reconstruction (ACLR). It was hypothesized that virtual reality techniques aimed to change attentional focus would influence altered knee flexion angle, knee extension moment and peak vertical ground reaction force (vGRF) in patients following ACLR.

METHODS

Twenty athletes following ACLR and 20 healthy controls (CTRL) performed a step-down task in both a non-virtual reality environment and a virtual reality environment displaying a pedestrian traffic scene. A motion analysis system and force plates were used to measure kinematics and kinetics during a step-down task to analyse each single-leg landing.

RESULTS

A significant main effect was found for environment for knee flexion excursion (P = n.s.). Significant interaction differences were found between environment and groups for vGRF (P = 0.004), knee moment (P < 0.001), knee angle at peak vGRF (P = 0.01) and knee flexion excursion (P = 0.03). There was larger effect of virtual reality environment on knee biomechanics in patients after ACLR compared with controls.

CONCLUSION

Patients after ACLR immersed in virtual reality environment demonstrated knee joint biomechanics that approximate those of CTRL. The results of this study indicate that a realistic virtual reality scenario may distract patients after ACLR from conscious motor control. Application of clinically available technology may aid in current rehabilitation programmes to target altered movement patterns after ACLR.

LEVEL OF EVIDENCE

Diagnostic study, Level III.

Altered medial versus lateral hamstring muscle activity during hop testing in female athletes 1-6 years after anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to assess activation patterns of medial (MH) versus lateral (LH) hamstrings in female athletes who had undergone ACL reconstruction (ACLR) using a hamstrings-graft during single-limb functional testing.

METHODS

Eighteen athletes (1-6 years since ACLR) and 18 healthy controls were recruited from the Icelandic women's top divisions in football, handball, and basketball. Activation of the MH and LH was monitored bilaterally using surface electromyography. Peak activation of the normalized signal was identified for two phases of the single-limb crossover (SLC) hop test and performance (distance jumped) registered. Self-reported knee symptoms and function were evaluated with the Knee injury and Osteoarthritis Outcome Score (KOOS). A repeated measures general linear model was used for main statistical data analyses, comparing variables of interests between limbs (within-subjects factor) and between groups.

RESULTS

ACLR athletes had worse KOOS-symptoms scores (p < 0.05) than controls, while hop distance was equal. Overall, MH and LH muscle activation levels differed between the two phases of the SLC hop test (p < 0.05). Moreover, inter-limb differences in MH and LH activity were identified between groups (p < 0.05), mainly explained by greater LH than MH activation in the uninjured limb of ACLR athletes.

CONCLUSION

One to 6 years after ACLR, female athletes performed on par with uninjured controls, but demonstrated inter-limb differences in muscle activation patterns of the hamstrings that were not evident in controls. This may be an important factor to consider during postsurgical rehabilitation in order to lower the risk of a second injury.

LEVEL OF EVIDENCE

III.