Evaluation of the hamstring muscle complex following acute injury

Conservative management of proximal hamstring avulsion: A clinical study

Introduction

The management of proximal hamstring tear (PHT) is debated and consensus regarding recommended measures and individual treatment regimens is lacking. The present investigation evaluated the efficacy of a conservative management of partial and complete PHT.

Methods

The present observational study was conducted following the STROBE statement. In June 2018 the medical databases of the BG Klinikum Bergmannstrost Halle, Germany were accessed. All the patients with PHT were retrieved. The outcomes of interest were to evaluate the clinical examination, PROMs, imaging, and isokinetic muscle strength at the baseline and last follow-up.

Results

31 patients were enrolled in the present study. Nine patients (29 % (9 of 31) described local pain at the ischial tuberosity in sitting situations and also in manual palpation. A persistent gap in the tendon string beneath the tuberosity in manual palpation was reported in 25.8 % (8 of 31). The mean VAS at the last follow-up was 2.3 ± 2.3. The mean LEFS score was 50.9 ± 18.8.Control MRI at follow-up showed scarring restitution in the proximal tendon in all patients in the partial tear group. In the complete tear group, a persisting defect state of the proximal tendon course was found in 45 % (9 of 20). The injured side achieved 81.5 ± 22.2 % of the force of the uninjured side, measured in the flexion movement at 60°/s. At an angular velocity of 240°/s, 83.2 ± 26.3 % of the force of the uninjured side was achieved.

Conclusion

According to the main findings of the present study, conservative therapy of PTH tears is associated with good clinical outcomes. High-quality investigations are required to establish the proper therapeutic algorithm and advantages of conservative management compared to a surgical approach.

Level of evidence

Level III.

Magnetic resonance imaging should be the first-line imaging modality for investigating suspected proximal hamstring avulsion injuries

PURPOSE

The purpose of the study was to evaluate how the initial diagnostic tool used-specifically ultrasound (US) or magnetic resonance imaging (MRI)-for diagnosing proximal hamstring avulsion injury affects the delay before surgery and, secondarily, the outcomes of these injuries.

METHODS

This was a retrospective analysis of prospectively collected data (2012-2020). It targeted patients primarily treated for proximal hamstring avulsion injury. It included all patients with a preoperative US and/or MRI. Patients were divided into two groups based on the initial diagnostic tool used (US-first vs. MRI-first groups). The primary outcomes measure was the time from initial injury to surgical intervention (surgical delay). The secondary outcomes were the Parisien Hamstring Avulsion Score, as well as the activity level as measured by the University of California, Los Angeles (UCLA) Activity Scale and Tegner Activity Scale.

RESULTS

The analysis included 392 patients with a mean age of 43.8 ± 13.6 years for the MRI-first group and 47.6 ± 12.0 years for US-first group. Patients in the MRI-first group had a significantly shorter median time from injury to surgery of 20.0 days (interquartile range [IQR]: 11.0-61.0) compared to 30 days (IQR: 18-74) in the US-first group. At the final follow-up (4.2 ± 2.2 years for the MRI-first group and 5.1 ± 1.9 years for the US-first group), the MRI-first group had significantly higher mean Tegner Activity Scale and UCLA scores than the US-first group: The Tegner Activity Scale was median 5 (IQR: 3-7) for the MRI-first group versus median 4 (IQR: 2-6) for the US-first group (p < 0.05). The UCLA scores were 7.9 ± 2.4 for the MRI-first group compared to 7.3 ± 2.4 for the US-first group (p < 0.05). This difference was more pronounced when comparing the MRI-first group with the patient-false negative initial ultrasound. No difference was found regarding the Parisien Hamstring Avulsion Score.

CONCLUSION

MRI as the initial diagnostic tool for proximal hamstring avulsion injury is associated with a shorter time to surgery and better postoperative outcomes in Tegner Activity Scale and UCLA scores, compared to US.

LEVEL OF EVIDENCE

Level III.

Distinct risk profiles for short-term surgical complications and venous thromboembolism exist among extensor mechanism repair procedures

PURPOSE

Extensor mechanism injuries, which comprise patella fractures, patella tendon tears and quadriceps tendon tears, are severely debilitating injuries and a common cause of traumatic knee pathology that requires surgical intervention. Risk factors for short-term surgical complications and venous thromboembolism (VTE) in this population have not been well characterised. The aim of this study was to identify perioperative risk factors associated with these short-term complications.

METHODS

The National Surgical Quality Improvement Program database was used to identify patients who underwent an isolated, primary extensor mechanism repair from 2015 to 2020. Patients were stratified by injury type. Demographic data were collected and compared. A multivariate logistic regression was used to control for demographic and comorbid factors while assessing risk factors for developing short-term complications.

RESULTS

A total of 8355 patients were identified for inclusion in this study. Overall, 3% of patients sustained short-term surgical complications and 1% were diagnosed with VTE within 30 days of surgery. Patella fracture fixation had a nearly twofold higher risk for surgical complications compared to quadriceps tendon repair (p = 0.004). Patella tendon repair had a twofold higher risk for VTE (p = 0.045), specifically deep vein thrombosis (p = 0.020), compared to patella fracture fixation. Increasing age, smoking and American Society of Anesthesiologists Classifications 3 and 4 were also found to be risk factors for surgical complications (p = 0.012, p = 0.004, p = 0.011 and p = 0.032, respectively).

CONCLUSION

This study used a nationally representative, widely validated, peer-reviewed database to provide valuable insights into risk factors for short-term postoperative complications associated with extensor mechanism repair procedures, revealing notable differences in risk profiles among distinct surgical procedures. The results of this study will inform surgeons and patients in enhancing risk assessment, guiding procedure-specific decision-making, optimising preoperative care, improving postoperative monitoring and contributing to future research of extensor mechanism injuries.

LEVEL OF EVIDENCE

Level III.

Hamstring Injuries: A Current Concepts Review: Evaluation, Nonoperative Treatment, and Surgical Decision Making

The purpose of this current concepts review is to highlight the evaluation and workup of hamstring injuries, nonoperative treatment options, and surgical decision-making based on patient presentation and injury patterns. Hamstring injuries, which are becoming increasingly recognized, affect professional and recreational athletes alike, commonly occurring after forceful eccentric contraction mechanisms. Injuries occur in the proximal tendon at the ischial tuberosity, in the muscle belly substance, or in the distal tendon insertion on the tibia or fibula. Patients may present with ecchymoses, pain, and weakness. Magnetic resonance imaging remains the gold standard for diagnosis and may help guide treatment. Treatment is dictated by the specific tendon(s) injured, tear location, severity, and chronicity. Many hamstring injuries can be successfully managed with nonoperative measures such as activity modification and physical therapy; adjuncts such as platelet-rich plasma injections are currently being investigated. Operative treatment of proximal hamstring injuries, including endoscopic or open approaches, is traditionally reserved for 2-tendon injuries with >2 cm of retraction, 3-tendon injuries, or injuries that do not improve with 6 months of nonoperative management. Acute surgical treatment of proximal hamstring injuries tends to be favorable. Distal hamstring injuries may initially be managed nonoperatively, although biceps femoris injuries are frequently managed surgically, and return to sport may be faster for semitendinosus injuries treated acutely with excision or tendon stripping in high-level athletes.

Hamstring Strain Ultrasound Case Series: Dominant Semitendinosus Injuries in National Collegiate Athletic Association Division I Athletes

Authors of previous studies of patients with acute hamstring strains have reported injury to the biceps femoris and semitendinosus (ST) in 50% to 100% and 0% to 30%, respectively. This retrospective case series of hamstring injuries in National Collegiate Athletic Association Division I collegiate athletes exhibited an injury pattern on ultrasound imaging that differed from what would be expected based on prior literature. We examined ultrasound images of 38 athletes with acute hamstring strains for injury location (proximal muscle, proximal myotendinous junction, midportion of muscle, distal muscle) and affected muscles (biceps femoris, ST, or semimembranosus). Twenty-six athletes (68.4%) injured the ST, and 9 athletes (23.7%) injured the biceps femoris long head. Most athletes (23, 60.5%) injured the proximal portion of the muscle or myotendinous junction. Though this study had many limitations, we demonstrated more frequent involvement of the ST and less frequent involvement of the biceps femoris than reported in the literature.

Systematic Review of Bracing After Proximal Hamstring Repair

Background

Traditionally, postoperative rehabilitation protocols after proximal hamstring repair (PHR) for avulsion of the proximal hamstring tendon from its ischial insertion recommend bracing the hip and/or knee to protect the fixation. However, because of the cumbersome nature of these orthoses, recent studies have investigated outcomes in patients with postoperative protocols that do not include any form of postoperative bracing.

Purpose

To synthesize the current body of evidence concerning bracing versus nonbracing postoperative management of PHR.

Study Design

Systematic review; level of evidence, 4.

Methods

Using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we conducted a thorough search of the PubMed/Medline, Cochrane, CINAHL (Cumulative Index to Nursing and Allied Health Literature), and Embase (OVID) databases on March 24, 2023. We analyzed complication rates, reoperation rates, patient satisfaction, return to sport, and patient-reported outcomes of studies that used postoperative bracing versus studies that used no postoperative bracing after PHR with at least 12 months of follow-up. A total of 308 articles were identified after initial search.

Results

In total, 25 studies were included in this review: 18 studies (905 patients) on bracing and 7 studies (291 patients) on nonbracing after PHR. The overall complication rate in the braced patients was found to be 10.9%, compared with 12.7% in nonbraced patients. The rate of reoperation due to retear of the proximal hamstring was found to be 0.05% in braced patients and 3.1% in nonbraced patients. Patient-reported outcome measures were found to be higher at the final follow-up in braced versus nonbraced patients, and patient satisfaction was found to be 94.7% in braced studies compared with 88.9% in nonbraced studies. The rate of 12-month return to sport in athletic patients was 88.4% with bracing and 82.7% without bracing.

Conclusion

The findings of this review demonstrated lower complication and reoperation rates, higher patient-reported outcome scores, higher patient satisfaction, and a higher rate of return to sport in braced patients compared with nonbraced patients.

The Effect of the Nordic Hamstring Exercise on Muscle Activity: A Multichannel Electromyography Randomized Controlled Trial

The aim of this study was to evaluate the effect of a Nordic hamstring exercise intervention on biceps femoris long head, semitendinosus, and semimembranosus muscle's activity and relative contributions through multichannel electromyography. Twenty-four injury-free male basketball players (mean age 20 [3] y) were randomly assigned to a 12-week intervention (n = 13) or control group (n = 11). The primary outcome measures were normalized muscle activity (percentage of maximal voluntary isometric contraction, %MVIC) and relative contribution of hamstring muscles over 12 weeks. No effects were found on any of the primary outcome measures. Between-group differences over 12 weeks were 2.7%MVIC (95% confidence interval 95% CI, -0.7 to 6.1) for the biceps femoris long head, 3.4%MVIC (95% CI, -1.4 to 8.2) for the semitendinosus, and 0.8%MVIC (95% CI, -3.0 to 4.6) for the semimembranosus, P = .366. Between-group differences over 12 weeks were 1.0% relative contribution (%con; 95% CI, -3.0 to 5.1) for the biceps femoris long head, 2.2% relative contribution (95% CI, -2.8 to 7.2) for the semitendinosus, and -3.3% relative contribution (95% CI, -6.4 to -0.1) for the semimembranosus P = .258. A positive value implies a higher value for the Nordic group. A Nordic hamstring exercise intervention did not affect the level of muscle activity and relative contribution of hamstring muscles in performance of the Nordic hamstring exercise.

Traumatic Isolated Avulsion Rupture of the Distal Semitendinosus Tendon in a Non-athlete

Isolated distal semitendinosus (ST) injuries remain an uncommon hamstring injury, with avulsion ruptures reported even less frequently. These injuries occur due to eccentric overloading seen in sprinting or jumping injuries. Treatment ranges from conservative management to surgical tenotomy or reattachment to the tibial bone. We present a unique case of a 30-year-old male with an isolated avulsion rupture of the distal ST tendon after a fall. To our knowledge, this is the first case reported in the literature of an isolated distal ST injury in a non-athlete due to trauma.

The effects of hip- vs. knee-dominant hamstring exercise on biceps femoris morphology, strength, and sprint performance: a randomized intervention trial protocol

BACKGROUND

The hamstrings are an important muscle group that contribute to horizontal force during sprint acceleration and are also the most injured muscle group in running-based sports. Given the significant time loss associated with hamstrings injury and impaired sprinting performance following return to sport, identifying exercises that drive adaptations that are both protective of strain injury and beneficial to sprint performance is important for the strength and conditioning professional. This paper describes the study protocol investigating the effects of a 6-week training program using either the hip-dominant Romanian deadlift (RDL) or the knee-dominant Nordic hamstring exercise (NHE) on hamstring strain injury risk factors and sprint performance.

METHODS

A permuted block randomized (1:1 allocation) intervention trial will be conducted involving young, physically-active men and women. A target sample size of 32 will be recruited and enrolled participants will undergo baseline testing involving extended-field-of-view ultrasound imaging and shear wave elastography of the biceps femoris long head muscle, maximal hamstrings strength testing in both the RDL and NHE, and on-field sprint performance and biomechanics. Participants will complete the 6-week training intervention using either the RDL or NHE, according to group allocation. Baseline testing will be repeated at the end of the 6-week intervention followed by 2 weeks of detraining and a final testing session. The primary outcome will be regional changes in fascicle length with secondary outcomes including pennation angle, muscle cross sectional area, hamstring strength, and maximal sprint performance and biomechanics. An exploratory aim will determine changes in shear wave velocity.

DISCUSSION

Despite extensive research showing the benefits of the NHE on reducing hamstring strain injury risk, alternative exercises, such as the RDL, may offer similar or potentially even greater benefits. The findings of this study will aim to inform future researchers and practitioners investigating alternatives to the NHE, such as the RDL, in terms of their effectiveness in reducing rates of hamstring strain injury in larger scale prospective intervention studies.

TRIAL REGISTRATION

The trial is prospectively registered on ClinicalTrials.gov (NCT05455346; July 15, 2022).

Degree of Tendon Retraction and Younger Age Are Associated With Functional Decline Following Nonoperative Management of Complete Proximal Hamstring Ruptures

Purpose

To characterize functional outcomes of patients with complete proximal hamstring tendon ruptures who were treated nonoperatively and determine whether there are patient characteristics associated with unfavorable outcomes.

Methods

We retrospectively identified patients aged 18-80 (treated 1/2000-12/2019) who received nonoperative management of complete rupture of the hamstring tendon origin. Participants completed the Lower Extremity Functional Scale (LEFS), as well as Tegner Activity Scale (TAS), and a chart review was conducted to obtain demographic and medical information. Preinjury and postinjury TAS scores were compared, and additional models quantified associations between LEFS scores or changes in TAS scores (ΔTAS) and patient characteristics.

Results

Twenty-eight subjects (mean age: 61.5 ± 1.5 years; 10 male) were included. The mean follow-up time was 5.8 ± 0.8 years (range: 2-22 years). Mean preinjury and postinjury TAS scores were 5.3 ± 0.4 and 3.7 ± 0.4, respectively, with a change of 1.5 ± 0.3 (P = .0002). Degree of tendon retraction showed a negative correlation with LEFS score (P = .003) and ΔTAS (P = .005). Increased follow-up time (P = .015) and body mass index (P = .018) were associated with lower LEFS scores. Moreover, increased follow-up time (P = .002) and younger age at injury (P = .035) were associated with more negative ΔTAS. Patients classified with an American Society of Anesthesiologists (ASA) score of 2 had a median LEFS score that was 20 points (95% CI: 6.9-33.6) lower than those classified as ASA 1 (P = .015).

Conclusions

In this study, we found that increased degree of tendon retraction, increased follow-up time, and younger age at initial injury were associated with significantly worse self-reported functional outcomes.

Level of Evidence

Level IV, prognostic case series.

London International Consensus and Delphi study on hamstring injuries part 1: classification

Muscle injury classification systems for hamstring injuries have evolved to use anatomy and imaging information to aid management and prognosis. However, classification systems lack reliability and validity data and are not specific to individual hamstring muscles, potentially missing parameters vital for sport-specific and activity-specific decision making. A narrative evidence review was conducted followed by a modified Delphi study to build an international consensus on best-practice decision-making for the classification of hamstring injuries. This comprised a digital information gathering survey to a cohort of 46 international hamstring experts (sports medicine physicians, physiotherapists, surgeons, trainers and sports scientists) who were also invited to a face-to-face consensus group meeting in London . Fifteen of these expert clinicians attended to synthesise and refine statements around the management of hamstring injury. A second digital survey was sent to a wider group of 112 international experts. Acceptance was set at 70% agreement. Rounds 1 and 2 survey response rates were 35/46 (76%) and 99/112 (88.4%) of experts responding. Most commonly, experts used the British Athletics Muscle Injury Classification (BAMIC) (58%), Munich (12%) and Barcelona (6%) classification systems for hamstring injury. Issues identified to advance imaging classifications systems include: detailing individual hamstring muscles, establishing optimal use of imaging in diagnosis and classification, and testing the validity and reliability of classification systems. The most used hamstring injury classification system is the BAMIC. This consensus panel recommends hamstring injury classification systems evolve to integrate imaging and clinical parameters around: individual muscles, injury mechanism, sporting demand, functional criteria and patient-reported outcome measures. More research is needed on surgical referral and effectiveness criteria, and validity and reliability of classification systems to guide management.

Open Proximal Hamstring Repair

Background:

Proximal hamstring ruptures meeting operative criteria may be treated through endoscopic, open, or combined techniques. Open techniques allow for facilitated tendon visualization and mobilization with ease of suture passage.

Indications:

Proximal hamstring repairs are indicated for complete 3 tendon avulsions; partial avulsions with 2 or more tendons involved with more than 2 cm of retraction in young, active patients; and partial avulsion injuries or chronic tears that remain refractory to conservative treatment.

Technique Description:

Through an incision along the gluteal crease, the tendon stump is identified and mobilized. Anchors are placed in the prepped ischium and sutures are passed through the tendon in a running fashion. The tendon is secured to its origin in a docking technique.

Results:

Patients undergoing hamstring repair have high satisfaction rates and patient-reported outcome scores. Competitive and elite athletes have demonstrated reliable return-to-sport rates at presurgical levels.

Discussion:

Open proximal hamstring repairs produce reliable results. The open technique is advantageous for its ease of tendon mobilization, direct visualization, and suture passage.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Proximal Hamstring Ruptures: Treatment, Rehabilitation, and Return to Play

PURPOSE OF REVIEW

To assess the current literature surrounding the treatment and rehabilitation strategies surrounding proximal hamstring rupture injuries, along with comparative return to sport and patient-reported outcomes.

RECENT FINDINGS

A high degree of variability exists in protective and rehabilitation strategies after both operative and non-operative proximal hamstring rupture management. Acceptable outcomes after both operative and non-operative management have been observed but may vary greatly with injury chronicity, severity, and surgical technique. The high complication rates observed after surgical treatment, along with poor functional outcomes that may occur in the setting of non-operative treatment or delayed surgery, highlight the importance of early injury evaluation and careful patient selection. Further high-quality research elucidating clearer indications for early operative management and an optimized and standardized rehabilitation protocols may improve outcomes and return to sport experience and metrics for individuals sustaining proximal hamstring ruptures.

The Evaluation of Asymmetry in Isokinetic and Electromyographic Activity (sEMG) of the Knee Flexor and Extensor Muscles in Football Players after ACL Rupture Reconstruction and in the Athletes following Mild Lower-Limb Injuries

This study was aimed at evaluating knee stabilizer (quadriceps and hamstring) muscle strength and the medio-lateral symmetry of hamstring fatigue in football players after ACL reconstruction and with mild lower extremity injuries. The study comprised 65 professional football players who were divided into three groups: Group 1 (n = 24; 22.7 ± 3.6 years; 175 ± 4 cm; 77.3 ± 7.6 kg) after ACL reconstruction, Group 2 (n = 21; 20.5 ± 3.7 years; 177 ± 6 cm; 74.3 ± 9.1 kg) with mild lower-limb injuries (grade 1 muscle strains) and Group 3 (n = 20; 23.1 ± 2.8 years; 178 ± 6 cm; 75.8 ± 8.8 kg) without injuries in the past 3 years. The concentric isokinetic test (10 knee flexions and extensions at 60, 180 and 300°/s with a 30 s interval for rest) was performed on both limbs. Fatigue symmetry between the medial and lateral hamstrings was measured with sEMG during 60 s of isometric contractions. In comparison to the other groups, the injured leg demonstrated significantly lower values of peak torque for the quadriceps (G1-G2 = 48%, 38%, 14%; G1-G3 = 49%, 25%, 14%) and hamstring muscles (G1-G2 = 36%, 35%, 18%; G1-G3 = 64%, 28%, 17%) as well as lower values of hamstring muscle work (G1-G2 = 262 J, 157 J; G1-G3 = 219 J, 179 J) and power (G1-G2 = 34 W; 11 W; G1-G3 = 29 W, 12 W). No significant differences were noted in strength between Groups 2 and 3. The significantly higher fatigue of the BF compared to the SEM muscle was seen in Group 1 for the involved (mean difference = 0.12) and uninvolved limbs (mean difference = -0.10), but in Group 2, a non-significant trend towards asymmetry was also noted. No asymmetry in hamstring muscle fatigue was determined in Group 3. The results of our study allow us to indicate that active football players who previously met the RTS criteria, had deficits in lower-limb muscle performance 2-3 years after reconstruction, which could lead to ACL re-injury. This observation is potentially of importance because these deficits may not be subjectively reported by such athletes and also may not be visible in regular orthopedic and physiotherapeutic assessment.

Differences in the Contractile Properties of the Biceps Femoris and Semitendinosus Muscles Throughout a Season in Professional Soccer Players

The aim of this study was to monitor seasonal changes in the mechanical and neuromuscular characteristics of the knee flexor muscles with tensiomyography, the biceps femoris (BF) and semitendinosus (ST) muscles, of 27 soccer players. All male professional soccer players (age 25 ± 4 years) were measured at the beginning of the preseason (second week) and in the competitive season (10 weeks later). The variables contraction time (Tc) and muscle displacement (Dm) showed significant differences in some muscles, and in others they indicated a tendency to change. In general, the BF improved (more explosive and better muscle tone) and the ST worsened (slower and worse muscle tone) its values during the season. The findings of this study suggest that usual daily soccer training and weekly competition might produce antagonistic changes between the knee flexor muscles.

Evaluation of muscle strain injury severity in active human body models

Even though significant efforts in the field of injury detection with finite element active human body models (FE AHBMs) have been made, injuries of the muscle-tendon unit (MTU) have not yet been taken into consideration. Therefore, the goal of this study was to define a muscle strain injury criterion (MSIC) to evaluate the damage sustained by the musculature during muscle driven movement scenarios. The MSIC was derived from biomechanical tests found in the literature and the proposed threshold values were substantiated through a comparison to an estimate of the ultimate tensile strength of human skeletal muscle and the forces acting on the biceps femoris long head muscle during one sprinting gait cycle. The application of the MSIC to state-of-the-art FE AHBMs was demonstrated by evaluating the strain injury severity of selected neck muscles of a full-body AHBM during two seat rotation load cases. The results of the MSIC substantiation suggest that all three injury threshold values proposed in this work fall in a plausible corridor of forces acting on the MTU. The combined results of the AHBM simulations indicate that neither of the two examined seat rotations are likely to cause strain injury to the neck muscles and that the proposed MSIC can easily be applied to current AHBMs without further modification of the model architecture or the muscle parameters. The MSIC was also used to formulate a hypothesis on the aetiology of muscle strain injuries, through which it was demonstrated that material inhomogeneities in the MTU might be the cause for strain injuries sustained during otherwise physiological movements. This work is a first step in the direction of the definition of a wholistic injury criterion for the human skeletal muscle fibre.

Hamstrings force-length relationships and their implications for angle-specific joint torques: a narrative review

Temporal biomechanical and physiological responses to physical activity vary between individual hamstrings components as well as between exercises, suggesting that hamstring muscles operate differently, and over different lengths, between tasks. Nevertheless, the force-length properties of these muscles have not been thoroughly investigated. The present review examines the factors influencing the hamstrings’ force-length properties and relates them to in vivo function. A search in four databases was performed for studies that examined relations between muscle length and force, torque, activation, or moment arm of hamstring muscles. Evidence was collated in relation to force-length relationships at a sarcomere/fiber level and then moment arm-length, activation-length, and torque-joint angle relations. Five forward simulation models were also used to predict force-length and torque-length relations of hamstring muscles. The results show that, due to architectural differences alone, semitendinosus (ST) produces less peak force and has a flatter active (contractile) fiber force-length relation than both biceps femoris long head (BFlh) and semimembranosus (SM), however BFlh and SM contribute greater forces through much of the hip and knee joint ranges of motion. The hamstrings’ maximum moment arms are greater at the hip than knee, so the muscles tend to act more as force producers at the hip but generate greater joint rotation and angular velocity at the knee for a given muscle shortening length and speed. However, SM moment arm is longer than SM and BFlh, partially alleviating its reduced force capacity but also reducing its otherwise substantial excursion potential. The current evidence, bound by the limitations of electromyography techniques, suggests that joint angle-dependent activation variations have minimal impact on force-length or torque-angle relations. During daily activities such as walking or sitting down, the hamstrings appear to operate on the ascending limbs of their force-length relations while knee flexion exercises performed with hip angles 45–90° promote more optimal force generation. Exercises requiring hip flexion at 45–120° and knee extension 45–0° (e.g. sprint running) may therefore evoke greater muscle forces and, speculatively, provide a more optimum adaptive stimulus. Finally, increases in resistance to stretch during hip flexion beyond 45° result mainly from SM and BFlh muscles.

Open Repair of Complete Proximal Hamstring Avulsions in Workers’ Compensation Patients

Background:

Several studies have reported excellent results after surgical repair of proximal hamstring avulsions. However, the effect on these patients of receiving workers’ compensation has not yet been explored.

Hypothesis:

Workers’ compensation patients undergoing proximal hamstring repair of complete tears will have similar outcomes when compared with a matched control group of non–workers’ compensation patients.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Workers’ compensation patients who underwent complete proximal hamstring avulsion open repair between 2010 and 2019 were identified (WC group). A control group was matched by age (±3 years), sex, and body mass index (BMI; ±3). Demographics and patient-reported outcome measures were compared, including standard and custom Marx activity rating scale (MARS), standard and custom lower extremity functional scale (LEFS), and visual analog scale (VAS) for pain. Rate and time to return to work were recorded.

Results:

The WC group was composed of 20 patients (8 men, 12 women) with a mean age of 52.3 years and BMI of 32.4. The 20 matched controls (8 men, 12 women) who underwent repair had a mean age of 50.6 years and a mean BMI of 31.2. There was no difference between the groups regarding age (P = .924), sex (P > .999), or BMI (P = .330). The WC group reported similar mean MARS (3.3 vs 5.4; P = .174), custom MARS (87.5 vs 97.0; P = .215), and VAS pain (3.3 vs 3.8; P = .698) scores compared with controls. However, the WC group had significantly lower standard LEFS (69.1 vs 94.1; P < .001) and custom LEFS (62.3 vs 87.9; P < .001) scores, returned to work at a lower rate (70.0% vs 94.1%; P = .039), and required more time to return to work after repair (4.3 vs 3.5 months; P = .029) compared with controls.

Conclusion:

Workers’ compensation patients who underwent open proximal hamstring repair for complete avulsions experienced inferior patient-reported outcomes, required more time to return to work, and returned to work at a lower rate than a matched control group.

US and MRI of Pelvic Tendon Anatomy and Pathologic Conditions

The bony pelvis serves as the attachment site for a large number of powerful muscles and tendons that drive lower extremity movement. Organizing the pelvic tendons into groups that share a common function and anatomic location helps the radiologist systematically evaluate these structures for injury, which can be caused by repetitive stress, acute trauma, or failure of degenerated tissues. Tears of the anteromedial adductors around the pubic symphysis and anterior flexors traversing anterior to the hip principally affect younger male athletes. Tears of the lateral abductors and posterior extensors are more common in older individuals with senescent tendinosis. The deep external rotators are protected and rarely injured, although they can be impinged. Imaging of the pelvic tendons relies primarily on US and MRI; both provide high spatial and contrast resolution for soft tissues. US offers affordable point-of-care service and dynamic assessment, while MRI allows simultaneous osseous and articular evaluation and is less operator dependent. While the imaging findings of pelvic tendon injury mirror those at appendicular body sites, radiologists may be less familiar with tendon anatomy and pathologic conditions at the pelvis. The authors review pertinent anatomy and imaging considerations and illustrate common injuries affecting the pelvic tendons. Online supplemental material is available for this article. ^©RSNA, 2022.

Effect of hip and knee joint angles on resting hamstring muscles rigidity in men and women

PURPOSE

Hamstring muscle strains are one of the most common injuries in sports practice, for both men and women. However, sex disparities in the rate of muscle injuries have been observed. As these muscular injuries usually occur at long muscle length, this study aimed to determine the effect of sex on hamstring muscles' resting rigidity under different stretching conditions.

METHODS

The shear wave speed (SWS) of resting hamstring muscles was measured in 12 men and 12 women in different hip and knee positions (hip extended with knee flexed, hip flexed with knee extended, both joints extended and both joints flexed).

RESULTS

Combining all the positions, the SWS of the semitendinosus was higher in men than in women (2.96 vs. 2.71 m.s^-1). Regardless of sex, a significant rise in SWS was systematically observed when the semimembranosus was stretched (1.86, 2.37, 2.76 and 4.39 m.s^-1) but it was neither the case for the semitendinosus (p = 0.82) nor for the biceps femoris (p = 0.50). Finally, differences in SWS among the hamstring muscles were only observed at the longest muscle length, with greater SWS values for the semimembranosus and semitendinosus in comparison with the biceps femoris (4.39 and 4.12 vs. 3.38 m.s^-1 respectively).

CONCLUSION

In conclusion, a sex difference was only observed in the resting semitendinosus rigidity. Independently of sex, the increase in resting hamstring muscles SWS with stretch was muscle specific.

Early Changes of Hamstrings Morphology and Contractile Properties during 10 d of Complete Inactivity

PURPOSE

The hamstrings (HS) muscle group plays a fundamental role in maintaining knee stability, thus contributing to the prevention and rehabilitation of lower limb musculoskeletal injuries. However, little is known about HS structural and functional adaptations after periods of prolonged inactivity. Our purpose was to investigate the HS morphological and contractile properties changes during 10 d of bed rest (BR).

METHODS

Ten young healthy males underwent a 10-d BR. HS cross-sectional area (CSA) (at 30%, 50%, and 70% of femur length) and biceps femoris long head (BFlh) architecture were assessed by ultrasound imaging after 0 d (BR0), 2 d (BR2), 4 d (BR4), 6 d (BR6), and 10 d (BR10) of BR, whereas BFlh contractile properties (radial twitch displacement [Dm] and contraction time [Tc]) were evaluated at the same time points by tensiomyography. HS muscle volume was assessed by magnetic resonance imaging at BR0 and BR10.

RESULTS

A reduction in muscle volume was observed in BFlh ( P = 0.002; Δ = -3.53%), biceps femoris short head ( P = 0.002; Δ = -3.54%), semitendinosus ( P = 0.002; Δ = -2.63%), semimembranosus ( P = 0.002; Δ = -2.01%), and HS pooled together ( P < 0.001; Δ = -2.78%). Early changes in CSA were detected at 30% femur length already at BR6 for BFlh ( P = 0.009; Δ = -2.66%) and biceps femoris short head ( P = 0.049; Δ = -1.96%). We also found a reduction in fascicle length at BR6 ( P = 0.035; Δ = -2.44%) and BR10 ( P < 0.001; Δ = -2.84%). Dm and Tc increased at BR2 ( P = 0.010; Δ = 30.0%) and B10 ( P = 0.019; Δ = 19.7%), respectively.

CONCLUSIONS

Despite being a nonpostural muscle group, HS exhibited a moderate reduction in muscle dimensions in response to a short unloading period. Small changes in BFlh fascicle length were also observed, accompanied by alterations in BFLh contractile properties. These HS modifications should not be ignored from a clinical perspective.

Comparative Analysis of Patient-Reported Outcome Measures for Proximal Hamstring Injuries: A Systematic Review

Background

There is controversy regarding which patient-reported outcome measures (PROMs) should be used for proximal hamstring tendon injuries.

Hypothesis

It was hypothesized that (1) most (>50%) of the questions on the 13 most common PROMs for proximal hamstring injuries would demonstrate extensive overlap in the health domains and question categories and (2) each of the PROMs would contain a variable distribution of questions within each health domain.

Study Design

Systematic review.

Methods

We conducted a literature review through PubMed, Scopus, and CINAHL and identified the 13 most common PROMs for proximal hamstring injuries: Lower Extremity Functional Scale (LEFS), Marx activity rating scale (MARS), 12-item Short Form Survey (SF-12), Tegner activity scale (TAS), Single Assessment Numeric Evaluation (SANE), Perth Hamstring Assessment Tool (PHAT), Proximal Hamstring Injury Questionnaire (PHIQ), modified Harris Hip Score (mHHS), University of California, Los Angeles activity score (UCLA), International Hip Outcome Tool (iHOT-12), Hip Outcome Score (HOS), Sydney Hamstring Origin Rupture Evaluation (SHORE), and Non-Arthritic Hip Score (NAHS). All PROM questions were sorted into 5 health domains (pain, symptoms, activities of daily living, sports, and mindset) and further divided into question categories if they referred to similar tasks or aspects of health. Questions in the same health domain and question category were considered overlapping, and those within a health domain that did not fit into a question category were considered unique. For each PROM, we analyzed the distribution of questions within particular health domains and question categories as well as the amount of overlapping and unique questions.

Results

Of the 165 questions evaluated, 116 (70.3%) were overlapping, and 49 (29.7%) were unique. The SF-12 contained the most unique questions (9/12 [75.0%]). The MARS, TAS, SANE, and UCLA had 0 unique questions. The PHIQ and iHOT-12 contained questions in all 5 health domains. The PHAT, SHORE, and NAHS contained questions in every health domain except mindset. The LEFS, MARS, SF-12, TAS, mHHS, SANE, UCLA, and HOS contained questions in ≤3 health domains.

Conclusion

The evaluated PROMs had a high degree of overlapping questions (≥50%) and demonstrated a statistically significant variance in the distribution of questions within each health domain.

Isotonic and Isometric Exercise Interventions Improve the Hamstring Muscles’ Strength and Flexibility: A Narrative Review

Background: Hamstring weakness has been associated with an increased risk of hamstring strain, a common sports injury that occurs when athletes perform actions such as quick sprints. The hamstring complex comprises three distinct muscles: the long and short heads of the bicep femoris, the semimembranosus, and the semitendinosus. Methods: The researchers collected the data from different electronic databases: PubMed, Google Scholar, and the Web of Science. Results: Many studies have been conducted on the numerous benefits of hamstring strength, in terms of athletic performance and injury prevention. Isotonic and isometric exercises are commonly used to improve hamstring strength, with each exercise type having a unique effect on the hamstring muscles. Isotonic exercise improves the muscles’ strength, increasing their ability to resist any force, while isometric training increases strength and the muscles’ ability to produce power by changing the muscle length. Conclusions: These exercises, when performed at low intensity, but with high repetition, can be used by the healthy general population to prepare for training and daily exercise. This can improve hamstring muscle strength and flexibility, leading to enhanced performance and reduced injury risk.

Endoscopic Repair of Proximal Hamstring Insertion With Sciatic Nerve Neurolysis

Open surgical repair of proximal hamstring avulsions has been the standard of care for a long time, when surgery is needed. Endoscopic repair is a relatively new surgery, and its popularity increased in the last 10 years. This technique allows the surgeon an anatomic repair and a safe sciatic nerve exploration with small incisions and dissection. As a new technique, it has its limitations, mostly in chronic retracted tears, and long follow-up series are needed to assess long-term outcomes. We present an endoscopic repair of a right proximal hamstring avulsion performed along with a sciatic nerve neurolysis.

Acute Surgical Repair of Simultaneous Bilateral Proximal Hamstring Tendon Avulsion: A Case Report

CASE

Proximal hamstring tendon avulsions are rare injuries that can be successfully treated with surgical intervention. However, there are limited reports on the surgical and postoperative management of patients with bilateral avulsions. We report a 54-year-old male gym teacher with acute bilateral proximal hamstring 3-tendon nonbony avulsions who underwent simultaneous surgical repairs and a unique postoperative rehabilitation course. At 1-year clinical follow-up, the patient demonstrated significant improvements in activity levels and functionality, with no complications.

CONCLUSION

Bilateral proximal hamstring 3-tendon nonbony avulsions can be successfully treated with a simultaneous surgical repair and a modified postoperative rehabilitation course.

Distal Hamstring Muscle Injuries

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Distal hamstring muscle injuries, although relatively uncommon, can potentially lead to substantial morbidity in athletes; prolonged rehabilitation times and high rates of reoccurrence have been documented.

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Overall, magnetic resonance imaging is considered the "gold standard" for evaluation of hamstring injuries because it allows assessment for concomitant pathology and can clarify return-to-sport timelines.

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Complete tears of the distal biceps femoris and semimembranosus muscles respond well to surgical repair, whereas complete tears of the distal semitendinosus can be successfully treated nonoperatively or with surgical resection.

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Future research may be necessary to further optimize treatment of these injuries and to determine the efficacy of biologic adjuvant therapy.

Ultrasound assessment of the hamstrings complex of athletes with MRI correlation

Due to anatomical complexity, ultrasound examination of the hamstring muscles is challenging, resulting in potential diagnostic uncertainty and under-confidence in the technique. This leads to a subsequent tendency to favour magnetic resonance imaging (MRI) evaluation, which can delay diagnosis and potential intervention. This article describes a comprehensive technique of ultrasound evaluation of the hamstrings complex, using key anatomical landmarks. A direct comparison of the sonographic landmarks with corresponding MRI appearances is also provided. If these landmarks can be identified successfully, the complex anatomy can be unlocked, thus improving the time and sensitivity of diagnosis of acute injuries, as well as providing a reliable framework for monitoring injury progress and helping to identify candidates for potential intervention. Many of the anatomical landmarks discussed are common areas of injury in elite athletes, encountered frequently in clinical practice.

Is Muscle Architecture Different in Athletes with a Previous Hamstring Strain? A Systematic Review and Meta-Analysis

Hamstring strains are a frequent injury in sports and are characterized by a high recurrence rate. The aim of this review was to examine the muscle and tendon architecture in individuals with hamstring injury. A systematic literature search in four databases yielded eleven studies on architecture following injury. Differences in the fascicle length (FL), pennation angle (PA) and muscle size measures (volume, thickness and physiological cross-sectional area) at rest were not significantly different between the previously injured limb and the contralateral limb (p > 0.05). There was moderate evidence that biceps femoris long head (BFlh) FL shortening was greater during contraction in the injured compared to the contralateral limb. The BFlh FL was smaller in athletes with a previous injury compared to uninjured individuals (p = 0.0015) but no differences in the FL and PA of other muscles as well as in the aponeurosis/tendon size were observed (p > 0.05). An examination of the FL of both leg muscles in individuals with a previous hamstring strain may be necessary before and after return to sport. Exercises that promote fascicle lengthening of both injured and uninjured leg muscles may be beneficial for athletes who recover from a hamstring injury.

Endoscopic Proximal Hamstring Repair Is Safe and Efficacious With High Patient Satisfaction at a Minimum of 2-Year Follow-Up

PURPOSE

To evaluate the short-term outcomes of endoscopic proximal hamstring repair including clinical outcomes, patient-reported outcomes, and complications.

METHODS

A retrospective analysis was performed on consecutive patients who underwent endoscopic proximal hamstring repair from 2013-2018 by a senior sports medicine orthopaedic surgeon. Demographic, operative, clinical data, complications, and patient-reported outcomes were collected and analyzed including the International Hip Outcome Tool-12 (iHOT-12), Single Assessment Numeric Evaluation (SANE), modified Harris Hip Score (mHHS), and the Hip Outcome Score activities of daily living scale (HOS-ADL).

RESULTS

Thirty patients were included with a minimum 24.0- and average 44.0-month follow-up. The average age was 52.0 years (standard deviation [SD], 14.2), and 80.0% (n = 24) were women. Most patients presented with a history of refractory insertional tendinosis (83.3%, n = 25) and an average of 34.0 months of symptoms prior to surgical intervention. Two-year patient-reported outcomes were clinically acceptable with a postoperative iHOT-12 of 81.9 (SD, 21.1), SANE 78.8% (SD, 20.0), mHHS 89.6 (SD 13.4), and HOS-ADLs 87.2% function (SD, 15.9). Nine patients (30%) had available preoperative iHOT-12 scores. Among these patients, the mean increase in iHOT-12 was 46.3 (P = .0005; n = 9). Eighty percent (n = 24) of patients achieved the iHOT-12 patient acceptability symptomatic state. Complications (3%) included 1 atraumatic rerupture. Four patients participated in an organized sport and 18 in recreational sport with a return to play of 100% and 72.2%, respectively. All patients returned to work. Some 76.7% (n = 23) of patients reported return to their baseline level of physical activity, and 73.3% (n=22) of patients reported complete resolution of pain at last follow-up. There was a 90.0% (n=27) satisfaction rate.

CONCLUSIONS

Short-term follow-up for endoscopic proximal hamstring repair shows high patient satisfaction (90.0%) and clinically significant patient-reported outcomes with minimal residual pain and a low complication rate (3%).

LEVEL OF EVIDENCE

IV, retrospective case series.

Achievement of the minimal clinically important difference following open proximal hamstring repair

There is a paucity of literature on patient-reported outcome measures (PROMs) following proximal hamstring repair beyond return to play, patient satisfaction and pain improvement. The minimal clinically important difference (MCID) defines the minimum degree of quantifiable improvement that a patient can perceive, but the MCID and predictors of this measure have not been defined for this patient population. This study aimed to define the MCID and determine the efficacy of open proximal hamstring repair through achievement of MCID and identify characteristics predictive of achieving MCID. A retrospective cohort review of an institutional hip registry was conducted, analyzing the modified Harris Hip Score (mHHS) and International Hip Outcome Tool (iHOT-33). MCID was calculated using a distribution-based method. Demographic and clinical variables predictive of achieving MCID were analyzed using univariable and multivariate logistic regression analyses. Thirty-nine patients who underwent open proximal hamstring repair were included. The mean patient age was 48.5 ± 12.4 years, with a mean follow-up of 37.1 ± 28 months. The MCID was determined for each PROM (mHHS—11.8; iHOT-33—12.6). A high percentage of patients achieved MCID for both PROMs (mHHS—85.7%; iHOT-33—91.4%). Univariate logistical regression demonstrated increased age (P = 0.163), increased body mass index (BMI; P = 0.072), requirement for inpatient admission (P = 0.088) and pre-operative iHOT-33 (P = 0.104) trended towards clinically significant predictors of not achieving MCID. A high percentage of patients achieved MCID while age, BMI, inpatient admission and pre-operative iHOT-33 appear to influence the achievement of clinically significant outcome in patients undergoing open proximal hamstring repair.

The safe zones for endoscopic proximal hamstring repair: a cadaveric assessment of standard portal placement and their relationship to major neurovascular structures

PURPOSE

To define the anatomical relationship of the major neurovascular structures to the standard endoscopic portals used in endoscopic hamstring repair. A secondary outcome was to determine the safest angle of insertion from each standard portal.

METHODS

Endoscopic portals were established in the 3 standard locations (lateral, medial, and inferior) and Steinmann pins inserted at various angles. Each hip was dissected and the distance between the pins and the pertinent anatomy measured.

RESULTS

The lateral portal placed the sciatic and posterior femoral cutaneous (PFC) nerves at greatest risk: direct injury to the sciatic nerve was seen in 11/30 (37%) of the lateral portals sited. A lateral portal with an approach at 60° was the most dangerous orientation with a mean distance of 0.36 ± 0.49 mm and 4.30 ± 2.69 mm from the sciatic and PFC nerves, respectively (p < 0.001). The 60° medial portal was the safest of all portals measured, at a mean distance of 67.37 ± 11.06mm (range, 47-78 mm) from the sciatic nerve and 58.90 ± 10.57 mm (range 40-70 mm) from the PFC nerve.

CONCLUSIONS

While currently described techniques recommend establishing the standard lateral portal first, this study shows that it carries the highest risk of injury if used blind. We recommend that the standard medial endoscopic portal is established first to identify the neurovascular structures and minimise iatrogenic neurovascular injury. The inferior and lateral portals can then be established created under direct vision. The lateral portal should be inserted in a more horizontal orientation to decrease the risk of nerve injury.

[Avulsion of the hamstring muscles]

BACKGROUND

Avulsion injuries of the proximal hamstring muscles are rare but very severe injuries to the dorsal thigh musculature.

OBJECTIVE

Due to improved diagnostics and experience in treatment, the decision for surgical treatment is becoming more and more frequent. Presentation of the surgical method, follow-up treatment and outcome.

MATERIAL AND METHODS

Description of the anatomy, origin, diagnostics and treatment of avulsions of the hamstring musculature.

RESULTS

Due to improvement of knowledge and diagnostics, avulsion injuries of the hamstring muscles are identified more frequently. The rapid expansion of the diagnostics, including magnetic resonance imaging (MRI) is decisive for a better identification of the extent and severity of the injury. Even if the differences in long-term results between surgical and conservative treatment are not significant in the literature, there is a clear improvement in function and resilience after surgical treatment of avulsion injuries of the hamstring muscles.

CONCLUSION

In view of the poor results of nonsurgical treatment and the clearly positive reports of surgical success, open refixation is recommended for recent proximal hamstring ruptures.

Classifying Ischial Tuberosity Avulsion Fractures by Ossification Stage and Tendon Attachment

BACKGROUND

We propose a new classification system for ischial tuberosity fractures in adolescents that is based on the ossification pattern of the apophysis.

METHODS

We performed a retrospective review of patients who were diagnosed with ischial tuberosity avulsion fractures at a single institution from 2008 to 2018. Skeletal maturity and fracture location, size, and displacement were recorded based on initial injury radiographs. The fractures were classified by location as being lateral (type 1) or complete (type 2). Pelvic computed tomography (CT) review demonstrated 5 stages of ossification. We then reviewed pelvic CT and magnetic resonance imaging scans to assess the tendinous insertions at the ischial tuberosity apophysis. Reliability analysis was performed.

RESULTS

We identified 45 ischial tuberosity fractures. The mean patient age was 14.4 years (range, 10.3 to 18.0 years). Boys accounted for 82% of the cohort. Forty-seven percent of the fractures were classified as type 1, and 53% were classified as type 2. Type-1 fractures were associated with younger age (p = 0.001), lower Risser score (p = 0.002), lower modified Oxford score (p = 0.002), less displacement (p = 0.001), and smaller size (p < 0.001) when compared with type-2 fractures. Of the 45 patients, 18 had follow-up of >6 months, with 56% going on to nonunion. Nonunion was associated with greater displacement (p = 0.016) and size (p = 0.027). When comparing union rates by fracture type, 33% of type-1 fractures progressed to nonunion, while 78% percent of type-2 fractures progressed to nonunion; however, this difference was not significant (p = 0.153). A review of the advanced imaging indicated that type-1 fractures involved the semimembranosus and conjoined tendons, whereas type-2 fractures also involved the adductor magnus tendon.

CONCLUSIONS

We propose a new classification system based on the ossification pattern of the ischial tuberosity apophysis that reflects the skeletal maturity of the patient, the size and location of the fracture, and the amount of displacement, and likely predicts the probability of subsequent nonunion. The ischial tuberosity ossifies in a pattern similar to the iliac crest as described by Risser, and this pattern of ossification dictates the size of the ischial tuberosity avulsion fracture fragments and the involved tendons.

Distal avulsion of reconstituted hamstring tendons

PURPOSE

Hamstring tendon autograft (semitendinosus and gracilis) is the most commonly used graft in anterior cruciate ligament (ACL) reconstruction. Distal hamstring tendons avulsion is a rare condition, and this paper describes a previously unreported injury, local management of this rare injury pattern, and the existing literature regarding treatment options.

METHODS

Two cases are presented of distal hamstring avulsion from the tibia of reconstituted tendons, together with additional 12 cases of distal hamstrings tendon avulsion. Functional outcomes following treatment of this injury are presented, together with a literature review of management options.

RESULTS

Early surgical reattachment using suture anchor fixation was performed and excellent results were achieved in 93% of cases (13 out of 14 patients). Patient-reported outcome measures demonstrated a median Marx score 14.5 (IQR 4) and median SHORE score 34.5 (IQR 4). The mean time to surgery was 22 days (range 5-60), with mean time to return to sport at pre-injury level 5.5 months (range 2.5-12).

CONCLUSIONS

Distal hamstring tendon avulsion is a rare condition, with no consensus regarding optimal management options. Acute surgical repair leads to excellent results, with a return to pre-injury level of sporting activity.

LEVEL OF EVIDENCE

IV.

Hamstrings load bearing in different contraction types and intensities: A shear-wave and B-mode ultrasonographic study

The main aim was to examine the load bearing of individual hamstring muscles in different contraction types and intensities, through local stiffness measurement by shear wave elastography (SWE). A secondary aim was to examine the relationship between the SWE stiffness measure and hamstrings morphology. Ten healthy males (age 22.1±4.1 years; height 173.7±5.9 cm; body mass 68.6±12.4 kg; mean ± SD) performed knee flexions on an isokinetic dynamometer at different intensities (20–70%MVC, random order) in three separate, randomized conditions: isometric (ISO), concentric (CON) and eccentric (ECC). SWE was used to measure muscle shear wave velocity (SWV) in biceps femoris long head (BFlh), semitendinosus (ST) and semimembranosus (SM) during contraction. Muscle anatomical cross-sectional area (ACSA) was measured with magnetic resonance imaging and muscle architecture with B-mode ultrasonography. Muscle SWV increased linearly with contraction intensity, but at a varying rate among muscles and contraction types. ST exhibited greater SWV than BFlh and SM in all contraction types, however, there was an upward shift in the SM SWV–torque relationship in ECC compared to ISO and CON. Strong negative correlations were found between peak ISO SWV and ST ACSA (r = -0.81, p = 0.005) and BFlh pennation angle (r = -0.75, p = 0.012). These results suggest that ST has a primary role in hamstrings load bearing in all contraction types, likely due to its morphology; however, there is evidence of increased contribution from SM in eccentric muscle actions.

Site-specific features of active muscle stiffness and proximal aponeurosis strain in biceps femoris long head

Limited information is available on site-specific features of muscle stiffness and aponeurosis strain of the biceps femoris long head (BFlh) during contractions. Therefore, understanding of the mechanics and etiology of hamstring strain injuries remains difficult. As a first step to gain further insight into them, the present study aimed to identify whether active muscle stiffness and proximal aponeurosis strain during contractions are varied along the long axis of the BFlh. The BFlh muscle shear wave speed (proxy for stiffness) was measured in the proximal, central, and distal sites during 20%, 50%, and 80% of maximal voluntary isometric contraction (MVC) of knee flexion exerted with the hip and knee joints flexed at 40° and 30°, respectively, using ultrasound shear wave elastography. Further, a segmental strain of the BFlh proximal aponeurosis was assessed in the proximal, central, and distal sites during isometric knee flexion, using B-mode ultrasonography. The shear wave speed was significantly higher in the distal site than the proximal and central sites at 20% MVC (p ≤ .002, with a large effect size), whereas no significant difference was found between the three sites at 50% and 80% MVC. The BFlh proximal aponeurosis strain showed no significant difference between the proximal, central, and distal sites at any contraction intensity. These findings indicate that site-specific differences in muscle stiffness and proximal aponeurosis strain are substantially small and that muscle stiffness and proximal aponeurosis strain of the BFlh at moderate-to-high contraction intensity is not exceptional in the site where a sprinting-type hamstring strain typically occurs.

Surgical Repair of Distal Biceps Femoris Avulsion Injuries in Professional Athletes

Background

Understanding the optimal management of distal biceps femoris avulsion injuries is critical for restoring preinjury function, restoring hamstring muscle strength, increasing range of motion, and minimizing risk of complications and recurrence. Due to the rarity of these injuries, prognosis and outcomes within the literature are limited to case reports and small case series.

Purpose

To assess the effect of surgical repair for acute distal avulsion injuries of the biceps femoris tendon on (1) return to preinjury level of sporting function and (2) time to return to preinjury level of sporting function, patient satisfaction, and complications.

Study Design

Case series; Level of evidence, 4.

Methods

This prospective single-surgeon study included 22 elite athletes (18 men [82%], 4 women [18%]; mean age, 26 years; age range, 17-35 years; mean body mass index, 25.3 ± 4.1 kg/m²) undergoing primary suture anchor repair of avulsion injuries of the distal biceps femoris confirmed on preoperative magnetic resonance imaging. Predefined outcomes relating to time for return to sporting activity, patient satisfaction, complications, and injury recurrence were recorded at regular intervals after surgery. Minimum follow-up time was 12 months (range, 12.0-26.0 months) from the date of surgery.

Results

The mean time from injury to surgical intervention was 12 days (range, 2-28 days). All study patients returned to their preinjury level of sporting activity, predominately professional soccer or rugby. Mean time from surgical intervention to return to full sporting activity was 16.7 ± 8.7 weeks. At 1- and 2-year follow-up, all study patients were still participating at their preinjury level of sporting activity. There was no incidence of primary injury recurrence, and no patients required further operation to the biceps origin.

Conclusion

Surgical repair of acute avulsion injuries of the distal biceps femoris facilitated early return to preinjury level of function with low risk of recurrence, low complication rate, and high patient satisfaction in elite athletes. Suture anchor repair of these injuries should be considered a reliable treatment option in athletes with high functional demands to permit an early return to sport with restoration of hamstring strength.

Combining the Copenhagen Adduction Exercise and Nordic Hamstring Exercise Improves Dynamic Balance Among Male Athletes: A Randomized Controlled Trial

BACKGROUND

Copenhagen adduction exercise (CAE) and Nordic hamstring exercise (NHE) reduce the incidence of groin and hamstring injuries. Efficient dynamic balance can improve motor performance and reduce the risk of injuries in athletes. However, the effects of these exercises on dynamic balance have not been investigated.

HYPOTHESIS

CAE and NHE, as well as a combination of both exercises, would improve dynamic balance among amateur male athletes.

STUDY DESIGN

Randomized controlled trial.

LEVEL OF EVIDENCE

Level 1.

METHODS

A total of 200 male athletes aged 21.9 ± 2.4 years were included in the study and randomly assigned to 4 groups: CAE group (n = 50), NHE group (n = 50), CAE and NHE group (n = 50), and a control group (n = 50). A total of 177 male athletes completed the study. The primary outcome measure was the limit of stability (LoS), which was measured using the Biodex Stability System to assess the performance of the dynamic balance. The LoS of the athletes' performance was measured pre- and postintervention after 6 weeks.

RESULTS

The LoS significantly improved in all treatment groups, including CAE (44.5% ± 5.3%), NHE (43.2% ± 5.3%), and CAE + NHE (48.4% ± 5.1%) groups when compared with the control group (28.3% ± 4.8%) after 6 weeks (all Ps < 0.01). The improvement of LoS was significantly greater in the CAE + NHE group compared with other groups (CAE, NHE, and control groups).

CONCLUSION

There was a significant increase in dynamic balance performance postintervention among male athletes. CAE and NHE may improve injury prevention programs.

CLINICAL RELEVANCE

The results of this study provide evidence for athlete trainers and coaches to consider including the CAE and NHE as components of injury prevention programs to improve balance capacity and performance in athletes. Such improvements in balance may prevent injury risk and decrease absenteeism and injury-related financial burdens.

The task dependent differences in electromyography activity of hamstring muscles during leg curls and hip extensions

This study aimed to investigate the influence of the task type on the relative electromyography (EMG) activity of biceps femoris long head (BFlh) to semitendinosus (ST) muscles, and of proximal to distal regions during isometric leg-curl (LC) and hip-extension (HE). Twenty male volunteers performed isometric LC with the knee flexed to 30° (LC30) and 90° (LC90), as well as isometric HE with the knee extended (HE0) and flexed to 90° (HE90), at 40% and 100% maximal voluntary contraction (MVIC). Hip position was neutral in all conditions. EMG activity was recorded from the proximal and distal region of the BFlh and ST muscles. BFlh/ST was calculated from the raw root-mean-square (RMS) amplitudes. The RMS of 40% MVIC was normalized using MVIC data and the proximal/distal (P/D) ratio of normalized EMG (NEMG) was calculated. The BFlh/ST ratio was higher in HE0 than in LC90 during MVIC and 40% MVIC (p<0.05), and was higher in HE90 than in LC90 (p<0.05) during 40% MVIC at the proximal region, whereas no difference was observed between HE0 and LC30. There was no inter-task difference in BFlh/ST ratio in the distal region. Furthermore, the P/D ratio was higher in LC90 than in LC30 and HE0 (p<0.05) in BFlh and ST muscles, and was higher in HE90 than in LC30 and HE0 (p<0.05) in BFlh during 40% MVIC. However, there was no difference in P/D ratio between LC30 and LC90, and HE0 and HE90. This showed that there was no task-dependent difference in the EMG activity of the BFlh muscle relative to the ST muscle between prone hip extension and prone knee flexion when the knee joint was set at an equivalent angle. Similarly, there was no task-dependent difference in the NEMG of the proximal region relative to the distal region in BFlh and ST muscles during 40% MVIC.

Proximal Hamstring Injuries

Proximal hamstring injuries can present as chronic tendinosis, acute strain, partial tendinous avulsions, or complete 3-tendon rupture. Nonoperative management for chronic insertional tendinosis and low-grade tears includes activity modification, anti-inflammatories, and physical therapy. Platelet-rich plasma injections, corticosteroid injections, dry needling, and shock wave therapy are newer therapies that also may provide benefit. Surgical indications include complete, proximal avulsions; partial avulsions with least 2 tendons injured with more than 2 cm of retraction in young, active patients; and partial avulsion injuries or chronic tendinosis that have failed nonoperative management. Surgical management entails open primary repair, endoscopic primary repair, or augmentation/reconstruction.

Endoscopic Implantation of Bioinductive Patch for Chronic Partial Retearing After Hamstring Repair

Proximal hamstring tendon avulsions are a relatively rare type of hamstring injury associated with persistent morbidity, including pain, weakness, and functional limitations. Open or endoscopic surgical repair is the standard treatment for complete tendon avulsions or partial tears that remain symptomatic despite conservative management in relatively young, healthy, and active patients. However, complications known to occur include retearing of the hamstring, infection, nerve injury, inability to return to work or sport, subjective persistent weakness, and subjective persistent pain. In the case of persistent pain where the repair is partially retorn, a careful history, physical examination, and scrutiny of radiologic studies can help guide management. We describe a technique for using revision endoscopy and augmentation with a bovine bioinductive patch in a case of chronic persistently painful partial retear after a proximal hamstring repair.

Does Muscle-Tendon Unit Structure Predispose to Hamstring Strain Injury During Running? A Critical Review

Hamstring strain injury (HSI) remains the most common muscle injury in high-intensity running in humans. The majority of acute HSI occur specifically within the proximal region of the long head of biceps femoris and there is a sustained interest among researchers in understanding the factors that predispose to HSI. The present critical review describes the current understanding of biceps femoris long head (BFlh) structural features that might influence strain injury risk. Inter-individual differences in muscle-tendon architecture and interactions, muscle fiber type and region-specific innervation are likely to influence biceps femoris long head injury risk and might inform why some individuals are at an increased risk of sustaining a HSI during running. However, more research is needed, with future studies focusing on prospective data acquisition, improved computer simulations and direct imaging techniques to better understand the relationship between structural features, hamstring muscle function, and injury risk.

Proximal hamstring tendon avulsion: state of the art

Complete proximal hamstring tendon avulsions from the ischial tuberosity, though infrequent, are the most severe type of hamstring muscle injury in the field of sport medicine. These serious injuries are commonly associated with a delayed or even misdiagnosis, despite obvious clinical findings. The published literature favours surgical repair even though the studies represent lower levels of evidence. Non-surgical treatment is a viable option for lower physical demand patients. This state-of-the-art article reviews the relevant anatomy, the clinical assessment including specific physical examination signs and diagnostic testing in patients suspected of a proximal hamstring avulsion. Up-to-date evidence is reviewed to address surgical and non-surgical treatment options and outcome assessment. The authors provide a detailed description of what would be considered the current worldwide standard of care; an open, suture-anchor-based repair of the avulsed tendon complex (semitendinosus, long head of biceps femoris and semimembranosus) securely to the ischial tuberosity. Also included are surgical tips and tricks, with advice on postsurgical management and rehabilitation. Future perspectives should involve higher quality, prospective research to better define the indications for surgery, evaluate the emerging role of endoscopic repair and disclose complications along with measuring patient-reported outcomes.

Management of hamstring injuries: current concepts review

Injuries to the hamstring muscle complex are common in athletes, accounting for between 12% and 26% of all injuries sustained during sporting activities. Acute hamstring injuries often occur during sports that involve repetitive kicking or high-speed sprinting, such as American football, soccer, rugby, and athletics. They are also common in watersports, including waterskiing and surfing. Hamstring injuries can be career-threatening in elite athletes and are associated with an estimated risk of recurrence in between 14% and 63% of patients. The variability in prognosis and treatment of the different injury patterns highlights the importance of prompt diagnosis with magnetic resonance imaging (MRI) in order to classify injuries accurately and plan the appropriate management. Low-grade hamstring injuries may be treated with nonoperative measures including pain relief, eccentric lengthening exercises, and a graduated return to sport-specific activities. Nonoperative management is associated with highly variable times for convalescence and return to a pre-injury level of sporting function. Nonoperative management of high-grade hamstring injuries is associated with poor return to baseline function, residual muscle weakness and a high-risk of recurrence. Proximal hamstring avulsion injuries, high-grade musculotendinous tears, and chronic injuries with persistent weakness or functional compromise require surgical repair to enable return to a pre-injury level of sporting function and minimize the risk of recurrent injury. This article reviews the optimal diagnostic imaging methods and common classification systems used to guide the treatment of hamstring injuries. In addition, the indications and outcomes for both nonoperative and operative treatment are analyzed to provide an evidence-based management framework for these patients. Cite this article: Bone Joint J 2020;102-B(10):1281-1288.

Evidence-based Risk Stratification for Sport Medicine Procedures During the COVID-19 Pandemic

Orthopaedic practices have been markedly affected by the emergence of the COVID-19 pandemic. Despite the ban on elective procedures, it is impossible to define the medical urgency of a case solely on whether a case is on an elective surgery schedule. Orthopaedic surgical procedures should consider COVID-19-associated risks and an assimilation of all available disease dependent, disease independent, and logistical information that is tailored to each patient, institution, and region. Using an evidence-based risk stratification of clinical urgency, we provide a framework for prioritization of orthopaedic sport medicine procedures that encompasses such factors. This can be used to facilitate the risk-benefit assessment of the timing and setting of a procedure during the COVID-19 pandemic.

Imaging of chronic male pelvic pain: what the abdominal imager should know

Chronic pelvic pain is an important but underrecognized cause of morbidity in men. While there is abundant literature discussing female pelvic pain and the diagnostic role of imaging, much less attention has been given to imaging of non-gynecologic causes of chronic pelvic pain. Chronic pelvic pain in men can be a challenge to diagnose as pain may arise from visceral, musculoskeletal, or neurovascular pathology. Imaging of the pelvic viscera has been covered in detail elsewhere in this edition and therefore will not be reviewed here. We will focus upon topics less familiar to the abdominal radiologist, including imaging of pelvic floor, musculoskeletal, and neurovascular pathology.

Hamstring Injuries Prevention in Soccer: A Narrative Review of Current Literature

Hamstring injuries and reinjuries are one of the most important sport lesions in several sport activities including soccer, Australian football, track and field, rugby, and in general in all sport activities requiring sprinting and acceleration. However, it is important to distinguish between the lesions of the biceps femoris and semitendinosus and semimembranosus. Indeed, three muscles representing the hamstring complex have a very different injury etiology and consequently require different prevention strategies. This fact may explain, at least in part, the high incidence of reinjuries. In soccer, hamstring injuries cause an important rate of time loss (i.e., in average 15–21 matches missed per club per season). The hamstring injury risk factors may be subdivided in three categories: “primary injury risk factors” (i.e., the risk factors mainly causing a first lesion), “recurrent injury risk factors” (i.e., the risk that can cause a reinjury), and bivalent injury risk factors” (i.e., the risk factors that can cause both primary injuries and reinjuries). The high incidence of hamstring lesions caused consequently an important increase in hamstring injury research. However, although the prevention has increased paradoxically, epidemiological data do not show a loss in injuries and/or reinjuries but, on the contrary, they show an increase in hamstring injuries. This apparent paradox highlights the importance both of the improvement in the prevention programs quality and the criteria for return to play after hamstring injury.

Mechanisms of Hamstring Strain Injury: Interactions between Fatigue, Muscle Activation and Function

Isolated injury to the long head of biceps femoris is the most common type of acute hamstring strain injury (HSI). However, the precise hamstring injury mechanism (i.e., sprint-type) is still not well understood, and research is inconclusive as to which phase in the running cycle HSI risk is the greatest. Since detailed information relating to hamstring muscle function during sprint running cannot be obtained in vivo in humans, the findings of studies investigating HSI mechanisms are based on modeling that requires assumptions to be made based on extrapolations from anatomical and biomechanical investigations. As it is extremely difficult to account for all aspects of muscle-tendon tissues that influence function during high-intensity running actions, much of this complexity is not included in these models. Furthermore, the majority of analyses do not consider the influence of prior activity or muscular fatigue on kinematics, kinetics and muscle activation during sprinting. Yet, it has been shown that fatigue can lead to alterations in neuromuscular coordination patterns that could potentially increase injury risk. The present critical review will evaluate the current evidence on hamstring injury mechanism(s) during high-intensity running and discuss the interactions between fatigue and hamstring muscle activation and function.

Short-Term Outcomes Following Endoscopic Proximal Hamstring Repair

PURPOSE

The purpose of this study was to evaluate the outcomes of endoscopic proximal hamstring repair (ePHR), specifically: (1) functional and subjective outcomes, (2) effectiveness of treatment (preoperative-to-postoperative change), (3) complications, (4) acute versus chronic tears, and (5) partial versus complete tears.

METHODS

A retrospective case series of a single-surgeon database for all patients who underwent ePHR between November 2014 and January 2019 with a minimum 1-year follow-up (range, 12 to 48 months) was performed. Charts were analyzed for preoperative and postoperative passive range of motion (PROM), strength, VAS pain, UCLA activity, and modified Harris Hip Score (mHHS). Manual muscle strength testing based on standard grading scale of 0 to 5 was performed. Complications including re-tear of the repair site, infection, iatrogenic nerve injury, inability to return to work/sport at the same level as preinjury, persistent hamstring weakness, pain with sitting, and subsequent surgery were recorded.

RESULTS

We identified 20 ePHR (6 males, 14 females) with a mean age of 46 years (range, 18 to 63 years). At most recent follow-up, mean VAS pain was 1.85 (SD 2), UCLA activity was 8 (SD 2), mHHS was 90.6 (SD 10.5), and PROM hip flexion of 121.7° (SD 14.5°). Effectiveness of treatment demonstrated significant improvement in objective hamstring strength, hip flexion PROM by 17.3°, UCLA activity by 3, and VAS pain by 3 points. Subjective hamstring weakness was reported in 8 (42.1%) and persistent pain with sitting in 3 (15.8%). Return to work and sport were 100% and 95%, respectively. mHHS was significantly higher postoperatively in patients with complete versus partial tears (95.5 versus 85.7).

CONCLUSION

Endoscopic proximal hamstring repair is an effective approach that provides patients significant improvement in pain and function.

LEVEL OF EVIDENCE

IV, Case Series.

Acute effects of wearable thigh and shank loading on spatiotemporal and kinematic variables during maximum velocity sprinting

Light wearable resistance is used in sprint training but the scientific evidence to guide its implementation is limited. This study investigated thigh and shank loading protocols which were matched based on the average increase in moment of inertia about the hip over a stride cycle. Seven university-level sprinters completed three counterbalanced conditions (unloaded, shank-loaded, thigh-loaded), and kinematic variables were measured between 30 and 40 m. Both thigh and shank loading led to small reductions in step velocity (mean change = -1.4% and -1.2%, respectively). This was due to small reductions in step frequency (-1.8%; -1.7%) because of small increases in contact time (+2.7%; +1.5%) in both conditions and a small increase in flight time (+2.0%) in the shank-loaded condition. Both conditions led to moderate increases in hip extension at toe-off (+2.7°; +1.4°), whilst thigh loading led to a small reduction in peak hip flexion angle during swing (-2.5°) and shank loading led to a small increase in peak biceps femoris muscle-tendon unit length (+0.4%). Thigh and shank loading can both be used to provide small reductions in sprint velocity, and each has specific overload effects which must be considered in the rationale for their implementation.