Patterns of Hamstring Muscle Tears in the General Population: A Systematic Review

Eccentric Hamstring Strength Imbalance among Football and Soccer Athletes

OBJECTIVES

Hamstring strain injuries (HSI) are common among football and soccer athletes. Eccentric strength imbalance is considered a contributing factor for HSI. There is, however, a paucity of data on hamstring imbalances of soccer and American football athletes as they age and advance in skill level. High school athletes will display greater interlimb discrepancies compared with collegiate and professional athletes. In addition, soccer athletes will exhibit greater hamstring asymmetry than American football athletes.

METHODS

Hamstring testing was performed on soccer and American football athletes using the NordBord Hamstring Testing System (Vald Performance, Albion, Australia). Age, sex, weight, sport specialization, and sport level were recorded. Maximum hamstring forces (N), torque (N · m), and work (N · s) were measured. Hamstring imbalance (%) was calculated by dividing the absolute value of the difference in leg forces divided by their sum. One-way analysis of variance and independent sample t tests compared measurements between athlete groups.

RESULTS

A total of 631 athletes completed measurements, including 88 high school male soccer, 25 college male soccer, 23 professional male soccer, 83 high school female soccer, 28 college female soccer, 288 high school football, and 96 college football athletes. High school soccer players displayed significantly greater imbalances for torque (P = 0.03) and work (P < 0.01) than football athletes. Imbalances for maximum force (P = 0.035), torque (P = 0.018), and work (P = 0.033) were significantly higher for male soccer athletes in high school compared with college- and professional-level athletes. Female high school soccer players had significantly higher imbalance in torque (P = 0.045) and work (P = 0.001) compared with female collegiate soccer players. Football athletes did not experience significant changes in force imbalances between skill levels.

CONCLUSIONS

High school soccer athletes exhibit greater hamstring imbalances than football athletes. Higher levels of play in soccer, for both male and female athletes, correlate with less hamstring asymmetry.

Traumatic muscle injury

Traumatic muscle injury represents a collection of skeletal muscle pathologies caused by trauma to the muscle tissue and is defined as damage to the muscle tissue that can result in a functional deficit. Traumatic muscle injury can affect people across the lifespan and can result from high stresses and strains to skeletal muscle tissue, often due to muscle activation while the muscle is lengthening, resulting in indirect and non-contact muscle injuries (strains or ruptures), or from external impact, resulting in direct muscle injuries (contusion or laceration). At a microscopic level, muscle fibres can repair focal damage but must be completely regenerated after full myofibre necrosis. The diagnosis of muscle injury is based on patient history and physical examination. Imaging may be indicated to eliminate differential diagnoses. The management of muscle injury has changed within the past 5 years from initial rest, immobilization and (over)protection to early activation and progressive loading using an active approach. One challenge of muscle injury management is that numerous medical treatment options, such as medications and injections, are often used or proposed to try to accelerate muscle recovery despite very limited efficacy evidence. Another challenge is the prevention of muscle injury owing to the multifactorial and complex nature of this injury.

Systematic Review of Complications Associated With Proximal Hamstring Tendon Repair

Background

Although several complications of proximal hamstring tendon ruptures have been reported in the literature, few studies have comprehensively analyzed the complication profile of proximal hamstring tendon repair.

Purpose

To identify the overall rate of complications following proximal hamstring tendon repair and to differentiate these complications into categories.

Study Design

Systematic review; Level of evidence, 4.

Methods

Included in this review were studies that examined surgical repair of proximal hamstring tendon ruptures; all studies were in English and had an evidence level of 4 or higher. No restrictions were made regarding publication date or methodological quality. Data regarding complications were extracted to calculate the overall complication rate as well as the rate of major and minor complications. A quantitative data synthesis was conducted using the chi-square test to compare the proportion of patients who experienced complications with the endoscopic versus open approach.

Results

A total of 43 articles including 2833 proximal hamstring tendon repairs were identified. The overall postoperative complication rate was 15.3% (n = 433). The rate of major complications was 4.6%, including a 1.7% rate of sciatic nerve injury, 0.8% rate of venous thromboembolism, 0.8% reoperation rate, 0.8% rerupture rate, and 0.4% rate of deep infection. Minor complications included a 2.4% rate of posterior femoral cutaneous nerve injury, 2.3% rate of persistent hamstring myopathy, 2.2% rate of persistent sitting pain, 1.8% rate of peri-incisional numbness, 1.1% rate of superficial infection, and 0.8% rate of hematoma/seroma.

Conclusion

Proximal hamstring tendon repair is associated with an overall complication rate of 15.3%, including a 4.6% rate of major complications.

Increasing incidence of surgically treated hamstring injuries: a nationwide registry study in Sweden between 2001 and 2020

BACKGROUND AND PURPOSE

Data on incidence and on trends in treatment of hamstring injuries, including proximal hamstring tendon avulsions (PHA), is limited. We aimed to investigate the incidence, trends in operative treatment, age, and sex distribution of hamstring injuries in Sweden between 2001 and 2020.

PATIENTS AND METHODS

We obtained data recorded in the National Patient Register between 2001 and 2020 on patients between 18 and 90 years of age, with the ICD-10 code S76.3, to calculate the incidence of patients treated operatively for hamstring injuries in Sweden. Patients with the NOMESCO classification NFL49 were considered as having been treated operatively. Data on quadriceps and Achilles tendon injuries were obtained for comparison. To calculate incidences, adult population data for every year were obtained from the Statistics Sweden website.

RESULTS

The incidence of patients diagnosed with hamstring injuries increased from 2.2 to 7.3 per 100,000 person-years. There was a rising trend of surgical treatment per diagnosed case from 3.0% to 14.2%. Patients diagnosed in units with the highest experience of surgical treatment of hamstring injuries tended to be operated on more often (22.2%) than patients diagnosed in units with limited experience (5.1%), although the fraction of operated patients was increasing in both groups.

CONCLUSION

Between 2001 and 2020 there was an increase in the proportion of operatively treated hamstring injuries.

Relationship between Muscle Flexibility and Characteristics of Muscle Contraction in Healthy Women during Different Menstrual Phases

OBJECTIVE

Skeletal muscle function is vital for preventing injury during exercise. It has been reported that skeletal muscle function fluctuates with the menstrual cycle and is considered one of the causes of injury. This study aimed to clarify the relationship between muscle flexibility and muscle contraction characteristics and their changes with the menstrual cycle.

METHODS

The subjects were healthy women who voluntarily participated in the study through recruitment posters. Muscle flexibility was measured with the passive knee extension (PKE) test, isokinetic knee flexor strength, and the maximum muscle strength exertion angle under two conditions of 60°/s and 120°/s in dominant hamstrings. Additionally, their correlations were analyzed and compared between the menstrual and ovulatory phases.

RESULTS

Sixteen subjects (mean age: 20.56 ± 0.73 years; body mass index: 20.21 ± 1.60) participated in the study. Correlation analysis showed a significant negative correlation between PKE and the maximum muscle strength exertion angle under the condition of 60°/s during the menstrual phase (r = -0.54; p = 0.03). No significant difference was observed in the two-group comparison of the variables measured during the menstrual and ovulatory phases.

CONCLUSION

This study confirmed that the more flexible muscles generate the maximum strength at a more contracted position during the menstrual phase in women. In the future, it is necessary to examine the relationship between the results of this study and exercise performance and injury occurrence.

Microwave Antenna System for Muscle Rupture Imaging with a Lossy Gel to Reduce Multipath Interference

Injuries to the hamstring muscles are an increasing problem in sports. Imaging plays a key role in diagnosing and managing athletes with muscle injuries, but there are several problems with conventional imaging modalities with respect to cost and availability. We hypothesized that microwave imaging could provide improved availability and lower costs and lead to improved and more accurate diagnostics. In this paper, a semicircular microwave imaging array with eight antennae was investigated. A key component in this system is the novel antenna design, which is based on a monopole antenna and a lossy gel. The purpose of the gel is to reduce the effects of multipath signals and improve the imaging quality. Several different gels have been manufactured and evaluated in imaging experiments. For comparison, corresponding simulations were performed. The results showed that the gels can effectively reduce the multipath signals and the imaging experiments resulted in significantly more stable and repeatable reconstructions when a lossy gel was used compared to when an almost non-lossy gel was used.

Pickleball: Review and Clinical Recommendations for this Fast-growing Sport

Pickleball is a single or doubles volley sport played with paddles and ball on a hardcourt. Growing in popularity in recent years, injuries can occur similar to racquet sports; however, there is a scarcity of references in the literature for sports medicine providers encountering these athletes and injuries. This review provides clinicians treating pickleball athletes with an overview of the sport, a case study demonstrating the significant injuries that can occur in pickleball, and a review of the available literature. We provide a discussion on common pickleball injuries, injury prevention strategies, and event coverage recommendations to better equip sports medicine providers with a base of knowledge and a clinical approach to treat these athletes, or "picklers," who enjoy this fast-growing sport.

Outcomes of Open and Endoscopic Repairs of Chronic Partial- and Full-Thickness Proximal Hamstring Tendon Tears: A Multicenter Study With Minimum 2-Year Follow-up

BACKGROUND

The preponderance of literature on the repair of proximal hamstring tendon tears focuses on the acute phase (<4 weeks). As such, there is a paucity of data reporting on the outcomes of chronic proximal hamstring tears.

PURPOSE

To report minimum 2-year postoperative patient-reported outcome (PRO) scores, visual analog scale (VAS) for pain, and patient satisfaction from patients who underwent open or endoscopic repair of partial- and full-thickness chronic proximal hamstring tendon tears.

STUDY DESIGN

Case series study; Level of evidence, 4.

METHODS

Between April 2002 and May 2017, prospectively collected data from 3 tertiary care institutions were retrospectively reviewed for patients who underwent open and endoscopic repair of partial- and full-thickness chronic proximal hamstring tendon tears. Patients were included only if they had a chronic proximal hamstring tear (defined as ≥4 weeks from symptom onset to surgery). Patients were excluded if they had a tear treated <4 weeks after injury, underwent hamstring reconstruction, or claimed workers' compensation. Patients who reported minimum 2-year follow-up for VAS, patient satisfaction, and the following PROs had their outcomes analyzed: the modified Hip Harris Score, Non-arthritic Hip Score, iHOT-12 (International Hip Outcome Tool), and Hip Outcome Score-Sports Specific Subscale.

RESULTS

Fifty patients (34 females and 16 males) were included in this study. There were 19 endoscopic repairs and 31 open repairs. Within the cohort, 52.0% had a full-thickness tendon tear on magnetic resonance imaging, and 48.0% had a partial tear. Average follow-up time was 58.07 ± 37.27 months (mean ± SD; range, 24-220 months). The mean age and body mass index of the group were 46.13 ± 13 years and 25.43 ± 5.14. The average time from injury to surgery was 66.73 weeks (range, 5.14-215.14 weeks). Average postoperative PROs were as follows: modified Hip Harris Score, 91.94 ± 9.96; Non-arthritic Hip Score, 91.33 ± 9.99; iHOT-12, 87.17 ± 17.54; Hip Outcome Score-Sports Specific Subscale, 87.15 ± 18.10; and VAS, 1.16 ± 1.92. Patient satisfaction was 8.22 ± 1.20.

CONCLUSION

Patients who underwent open and endoscopic repairs for chronic partial- and full-thickness proximal hamstring tendon tears reported high PROs and satisfaction at a minimum 2-year follow-up with low rates of complications.

Influence of Lumbar Mobilizations During the Nordic Hamstring Exercise on Hamstring Measures of Knee Flexor Strength, Failure Point, and Muscle Activity: A Randomized Crossover Trial

OBJECTIVE

The aims of this study were to quantify the effects of spinal mobilization on force production, failure point, and muscle activity of the hamstrings during the Nordic hamstring exercise (NHE), and to explore individual differences in responses.

METHODS

In a replicated randomized crossover trial, 24 asymptomatic, recreationally active men (age [mean ± standard deviation]: 27 ± 6 years; body mass: 82 ± 17 kg; height: 181 ± 8 cm) completed 2 standardized intervention trials (L4/5 zygapophyseal mobilizations) and 2 control trials. The failure point of the NHE was determined with 3D motion capture. Peak force, knee flexor torque, and electromyography (EMG) of the biceps femoris were measured. Data analyses were undertaken to quantify mean intervention response and explore any individual response heterogeneity.

RESULTS

Mean (95% confidence interval) left-limb force was higher in intervention than in control trials by 18.7 (4.6-32) N. Similarly, right-limb force was higher by 22.0 (3.4-40.6) N, left peak torque by 0.14 (0.06-0.22) N • m, and right peak torque by 0.14 (0.05-0.23) N • m/kg. Downward force angle was decreased in intervention vs control trials by 4.1° (0.5°-7.6°) on the side of application. Both peak EMG activity (P = .002), and EMG at the downward force (right; P = .020) increased in the intervention condition by 16.8 (7.1-26.4) and 8.8 (1.5-16.1) mV, respectively. Mean downward acceleration angle changed by only 0.3° (-8.9° to 9.4°) in intervention vs control trials. A clear response heterogeneity was indicated only for right force (Participant × Intervention interaction: P = .044; response heterogeneity standard deviation = 34.5 [5.7-48.4] N). Individual response heterogeneity was small for all other outcomes.

CONCLUSION

After spinal mobilization, immediate changes in bilateral hamstring force production and peak torque occurred during the NHE. The effect on the NHE failure point was unclear. Electromyographic activity increased on the ipsilateral side. Response heterogeneity was generally similar to the random trial-to-trial variability inherent in the measurement of the outcomes.

Proximal Hamstring Tendon Avulsion Resulting in Acute Posterior Thigh Compartment Syndrome: A Case Report

CASE

A healthy 36-year-old man developed compartment syndrome of the posterior thigh with an associated sciatic nerve palsy secondary to an acute proximal hamstring tendon avulsion injury.

CONCLUSION

Compartment syndrome of the thigh is rare and is usually associated with high-energy trauma. Atraumatic causes have been described, typically involving the anterior compartment. Posterior thigh compartment syndrome is especially uncommon. This case highlights the potential occurrence of posterior thigh compartment syndrome after proximal hamstring tendon rupture. Given the morbidity associated with compartment syndrome, it is important to recognize the risk factors and injury patterns that can cause thigh compartment syndrome.

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.

Reconstruction of chronic proximal hamstring avulsion injuries using ipsilateral distal hamstring tendons results in good clinical outcomes and patient satisfaction

PURPOSE

To report outcomes following proximal hamstring reconstruction employing an ipsilateral distal hamstring tendon autograft, in patients with chronic proximal ruptures.

METHODS

Six patients presenting with a chronic proximal hamstring avulsion and a medial time from injury of 11.0 months (range 7-18), confirmed via magnetic resonance imaging, underwent proximal hamstring repair using a free graft harvested from the ipsilateral distal hamstrings. Patients were evaluated at 6, 12 and 24 months post-surgery, via the Perth Hamstring Assessment Tool, the Short Form Health Survey, the Lower Extremity Functional Scale, a Patient Satisfaction Questionnaire, the Active Knee Extension and 6 min walk tests, the single and triple hop tests for distance, and isokinetic knee extensor and flexor strength. Knee strength was assessed at 180° and 240°/s (total work, peak and average torque), and both mean absolute scores and limb symmetry indices (LSIs) comparing the operated and non-operated limbs were presented.

RESULTS

Patients demonstrated good clinical improvement throughout the post-operative timeline in all subjective and objective outcomes. Mean knee extensor LSIs had recovered by 12 and 24 months. At 24 months post-surgery, while mean LSIs for knee flexor peak and average torque were at (or above) 90%, a significant difference still existed between the operated and non-operated limbs in knee flexor total work. At 24 months, five patients (83%) were satisfied with the results of the surgery, as well as their ability to return to recreational and sporting activities. There were two adverse events including an early deep vein thrombosis and a secondary surgery to remove a loosened staple.

CONCLUSIONS

While isokinetic hamstring strength had not fully recovered by 24 months, this surgical technique demonstrated a high level of patient satisfaction and return to function, in patients with chronic proximal hamstring ruptures. As the clinical relevance, this surgical technique provides a viable option with good post-operative outcomes for patients with chronic proximal hamstring tears that cannot be approximated back to the ischium.

LEVEL OF EVIDENCE

IV.

Surgical Approach Impacts Posterior Femoral Cutaneous Nerve Outcomes After Proximal Hamstring Repair

OBJECTIVE

The goal of this study was to characterize the risk of intraoperative injury to the posterior femoral cutaneous nerve and to evaluate potential risk factors for injury during surgical repair of proximal hamstring injuries.

DESIGN

Retrospective cohort study.

SETTING

Single tertiary referral center.

PATIENTS

The cohort consisted of all patients presenting to a single institution with a proximal hamstring avulsion injury who were managed with surgical repair between January 1, 2000 and August 1, 2016. A total of 67 patients were included in the cohort.

INDEPENDENT VARIABLES

Variables assessed for their association with postoperative numbness in the distribution of the posterior femoral cutaneous nerve included age, sex, body mass index, mechanism of injury, time to surgical repair, and incision used.

MAIN OUTCOME MEASURES

The primary outcome of interest was neurologic symptoms referable to the posterior femoral cutaneous nerve.

RESULTS

Postoperatively, 13 patients (19%) developed new numbness in the distribution of the posterior femoral cutaneous nerve. One patient reported neuropathic pain and paresthesias associated with the numbness. The use of a gluteal crease incision was the only predictive factor for postoperative numbness in the posterior femoral cutaneous nerve distribution (odds ratio 8.67; 95% confidence interval, 2.30-42.80; P = 0.001).

CONCLUSIONS

The current study provides data that can be used in discussing the risks and benefits of surgical repair with patients and when weighing the pros and cons of using a gluteal crease versus longitudinal incision.

Time-course changes associated with PA lumbar mobilizations on lumbar and hamstring range of motion: a randomized controlled crossover trial

OBJECTIVE

We aimed to compare the post-intervention time-course changes in active knee extension (AKE) and active lumbar flexion (ALF) range of motion in response to unilateral posterior-anterior (UPA) mobilizations of the lumbar spine (L4/5 zygapophyseal).

METHODS

Twenty-four asymptomatic participants (maleness: 0.58, age [mean ± standard deviation]: 32 ± 8 years, body mass index 25.9 ± 2.6 kg m2) were recruited to a fully controlled crossover trial. Following either the intervention (L4/5 zygapophyseal mobilizations) or control, participants immediately performed the AKE and ALF tests, which were also performed at baseline. Subsequent tests were made at intervals of 5, 10, 15, 20, 25, 30, 45 and 60 min.

RESULTS

After adjustment for baseline (mean AKE: 37.2° from full extension, mean ALF: 14.37 cm), sex and age, UPA lumbar mobilizations had a most likely moderate effect on AKE (9.8° closer to full extension; ±1.9) and a likely moderate effect on ALF (1.34 cm; ±90% confidence limits 0.43). The magnitude of the AKE effect became most likely small 20-min posttreatment (5.3; ±1.7) and possibly small/possibly trivial 60-min posttreatment (2.1; ±1.4). For ALF, the magnitude of the effect became most likely small 15-min posttreatment (0.76; ±0.25), possibly small/possibly trivial 25-min posttreatment (0.38; ±0.18) and likely trivial 60-min posttreatment (0.26; ±1.8).

DISCUSSION

UPA lumbar mobilizations increased lumbar Range of Motion and hamstring extensibility by a moderate magnitude, with the effect reducing after 10-20-min posttreatment. Clinicians should consider these time-course changes when applying UPA lumbar mobilizations. Clinical Trials Registry: NCT03273400 Evidence Level: 2b.

Anatomy of proximal attachment, course, and innervation of hamstring muscles: a pictorial essay

Hamstring injuries are very common in sports medicine. Knowing their anatomy, morphology, innervation, and function is important to provide a proper diagnosis, treatment as well as appropriate prevention strategies. In this pictorial essay, based on anatomical dissection, the detailed anatomy of muscle-tendon complex is reviewed, including their proximal attachment, muscle course, and innervation. To illustrate hamstrings' role in the rotational control of the tibia, the essay also includes the analysis of their biomechanical function.Level of evidence V (expert opinion based on laboratory study).