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

The Cobra sign: A marker for overestimation of tendon retraction in proximal semimembranosus tendon avulsion

PURPOSE

To introduce a new magnetic resonance imaging (MRI) sign, termed the Cobra sign, and identify its diagnostic metrics. The secondary aim was to demonstrate that this sign can be a source of false evaluation of tendon retraction in patients with proximal hamstring avulsion injury.

METHOD

This retrospective cohort study targeted patients surgically treated for proximal hamstring avulsion injury from January 2019 to June 2023. The MRI Cobra sign was defined as a wavy curved T2-hypointense band with the free end folding distally over itself, resembling a cobra head. The primary outcome measure was the characterization of the Cobra sign in patients with proximal hamstring avulsion injury. The secondary outcome was the association of this sign with tendon retraction. The study included 81 proximal hamstring avulsion injury patients (mean age of 45.7, SD = 13.9), with 41 (50.6%) complete avulsions, 33 semimembranosus, and 7 conjoint tendons.

RESULTS

The MRI Cobra sign was found in 25 patients (17 semimembranosus and 8 complete). It was confirmed surgically only in semimembranosus cases. It demonstrated 51.5% sensitivity and 83.3% specificity for isolated semimembranosus avulsions, with a significant positive likelihood ratio of 3.0. MRI retraction was 10.05 cm (±3.0), reducing to 7.9 cm (±2.5) on surgical measurement (mean difference = 2.0 cm, p < 0.001). The regression analysis confirmed MRI retraction's influence on the Cobra sign, with a 1.4 odds increase per unit (p < 0.001). In linear regression analysis, each unit increase in MRI retraction corresponded to a 79% increase in surgical retraction (coefficient 0.7, t = 11.1, p < 0.001).

CONCLUSION

The Cobra sign demonstrated acceptable diagnostic accuracy for isolated semimembranosus avulsion, with a high specificity of 83.3%, a low sensitivity of 51.5%, and a positive likelihood ratio of 3.0. The presence of the Cobra sign indicates an overestimated MRI retraction by approximately 21%.

LEVEL OF EVIDENCE

Level III.

Innervation patterns of hamstring muscles, including morphological descriptions and clinical implication

PURPOSE

The hamstrings muscles are innervated by sciatic nerve branches. However, previous studies assessing which and how many branches innervate each muscle have yielded discrepant results. This study investigated the innervation patterns of hamstrings.

MATERIALS AND METHODS

Thirty-five cadaver limbs were investigated. The average age of subjects was 78.6 ± 17.2 years, with 48.6% male and 51.4% female, while 57.1% were right limbs and 42.9% left. The sciatic nerve, hamstrings and associated structures were dissected. The number of nerve branches for each muscle and the level where they penetrated the muscle were recorded.

RESULTS

The sciatic nerve was connected by a fibrous band to the long head of the biceps femoris. This muscle was innervated by either one or two branches, which penetrated the muscle into its superior or middle third. The short head of the biceps femoris was innervated by a single nerve that usually penetrated its middle third, but sometimes inferiorly or, less commonly, superiorly. The semitendinosus was always innervated by two branches, the superior branch penetrating its upper third, the inferior mostly the middle third. The semimembranosus usually was innervated by a single nerve branch that penetrated the muscle at its middle or lower third. Four specimens revealed common nerves that innervated than one muscle.

CONCLUSIONS

We have characterized hamstring innervation patterns, knowledge that is relevant to neurolysis, surgery of the thigh, and other procedures. Moreover, a mechanical connection between the sciatic nerve and biceps femoris long head was identified that could explain certain neuralgias.

The direct muscular origin of the semitendinosus: a pitfall in categorization of proximal hamstring tendon tears

The ischial origin of the hamstring musculature is complex. While the conjoint tendon and semimembranosus are commonly discussed and understood by radiologists, there is a lesser-known origin of the semitendinosus along the inferior and medial surface of the ischium in the form of a broad direct muscular connection. This secondary origin is infrequently described in the radiology literature and is a potential pitfall during grading of semitendinosus injuries if the interpreting physician is unaware of its presence. In a proximal hamstring tendon tear, the direct muscular origin of the semitendinosus can be spared, torn along with the conjoint tendon, or remain intact and contribute to a vertical shearing injury of the semitendinosus myotendinous junction. Detailed knowledge of this anatomy and its imaging appearance in the setting of injury enables the reader to correctly diagnose these unique hamstring injuries.

Hamstring Injuries: A Paradigm for Return to Play

Muscle injuries are the most common sports-related injuries, with hamstring involvement most common in professional athletes. These injuries can lead to significant time lost from play and have a high risk of reinjury. We review the anatomy, mechanisms of injury, diagnostic imaging modalities, and treatment techniques for hamstring injuries. We also present the latest evidence related to return to play (RTP) after hamstring injuries, including a review of articles targeted to RTP in European soccer (Union of European Football Associations), American football (National Football League), and other professional sports. Review of imaging findings in hamstring injury, grading systems for injuries, considerations for RTP, as well as advances in injury prevention, are discussed.

Hamstring muscle injuries in athletics

Hamstring muscle injuries (HMI) are a common and recurrent issue in the sport of athletics, particularly in sprinting and jumping disciplines. This review summarizes the latest literature on hamstring muscle injuries in athletics from a clinical perspective. The considerable heterogeneity in injury definitions and reporting methodologies among studies still needs to be addressed for greater clarity. Expert teams have recently developed evidence-based muscle injury classification systems whose application could guide clinical decision-making; however, no system has been adopted universally in clinical practice, yet.The most common risk factor for HMI is a previously sustained injury, particularly early after return-to-sport. Other modifiable (e.g. weakness of thigh muscles, high-speed running exposure) and non-modifiable (e.g. older age) risk factors have limited evidence linking them to injury. Reducing injury may be achieved through exercise-based programs, but their specific components and their practical applicability remain unclear.Post-injury management follows similar recommendations to other soft tissue injuries, with a graded progression through stages of rehabilitation to full return to training and then competition, based on symptoms and clinical signs to guide the individual speed of the recovery journey. Evidence favoring surgical repair is conflicting and limited to specific injury sub-types (e.g. proximal avulsions). Further research is needed on specific rehabilitation components and progression criteria, where more individualized approaches could address the high rates of recurrent HMI. Prognostically, a combination of physical examination and magnetic resonance imaging (MRI) seems superior to imaging alone when predicting 'recovery duration,' particularly at the individual level.

Pathogenesis and Diagnosis of Proximal Hamstring Tendinopathies

The proximal hamstring complex is a highly vulnerable area that is especially prone to injury. Proximal hamstring tendinopathies (PHTs) remain challenging in diagnosis, treatment, rehabilitation, and prevention due to a large variety of different injuries, slow healing response, persistent symptoms, and functional impairments. PHTs are often misdiagnosed or underdiagnosed, leading to delayed treatment and therapy failure. In addition, many athletes are at a high risk of PHT recurrence, a leading cause of prolonged rehabilitation and impaired individual performance. Until now, there have been no clear criteria for the diagnosis and classification of PHT. Tendinopathies can be graded based on their symptoms and onset. Additionally, radiological characteristics exist that describe the severity of tendinopathies. The diagnosis usually includes a battery of pain provocation tests, functional tests, and imaging to ensure a proper classification. Understanding the specific tasks in the pathogenesis and diagnostic process of PHT requires knowledge of functional anatomy, injury pattern and pathophysiological mechanisms as well as examination and imaging techniques. This work provides a structured overview of the pathogenesis and diagnostic work-up of PHT, emphasizing structured examination and imaging to enable a reliable diagnosis and rapid treatment decisions.

Validation of the Parisian Hamstring Avulsion Score (PHAS) in the Evaluation and Follow-up of Patients Operated for Proximal Hamstring Avulsion

BACKGROUND

No validated score is available for the prediction of return to sport (RTS) after proximal hamstring avulsion (PHA) surgery.

PURPOSE

To validate a new assessment tool for patients after PHA surgery: the Parisian Hamstring Avulsion Score (PHAS).

STUDY DESIGN

Cohort study (Diagnosis); Level of evidence, 3.

METHODS

All patients at our clinic who had surgery for PHA between January 2015 and March 2018 were included in this study. A suspected clinical diagnosis of PHA was confirmed by magnetic resonance imaging. PHA was repaired by surgical reinsertion with suture anchors. Minimum postoperative follow-up was 2 years, and the PHAS, University of California, Los Angeles (UCLA), score, and Tegner score were used. The PHAS is a patient-reported outcome measure, evaluating the effect of PHA injury with 9 items. It was validated by calculating its psychometric properties, and then correlation analysis was performed to determine the relationship between the PHAS, UCLA score, and Tegner score. Cutoff values for the prediction of RTS were determined.

RESULTS

A prospective case series study was performed. A total of 156 patients were included. Median age (first quartile; third quartile) was 54.2 years (44.7 years; 61.3 years), and the mean ± SD time of the final follow-up was 69 ± 11.6 months. Two years after surgery, 66.7% (n = 104) of patients were able to RTS. A strong correlation was noted between all 3 scores at 1 year postoperatively. Overall internal consistency was high, with a Cronbach alpha coefficient of 0.86. The intraclass correlation coefficient was 0.96, showing excellent reliability. The minimal detectable change was 12.9. No patients reached the maximum score at 2 years. Analysis of the receiver operating characteristic curves of the 3 scores at postoperative 9 months in relation to the RTS at 1 and 2 years showed area under the curve values of >0.7, indicating significant discriminant capacity for the RTS. A PHAS cutoff value of 86 at 9 months for the prediction of RTS at postoperative 1 year had a sensitivity of 65.6% (95% CI, 53.7%-77.5%) and a specificity of 81.4% (95% CI, 69.8%-93%).

CONCLUSION

PHAS is a valid and reliable tool for follow-up after PHA surgery. It also offers a simple way to predict RTS.

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.

Managing Lower Limb Muscle Reinjuries in Athletes: From Risk Factors to Return-to-Play Strategies

Muscle injuries and subsequent reinjuries significantly impact athletes, especially in football. These injuries lead to time loss, performance impairment, and long-term health concerns. This review aims to provide a comprehensive overview of the current understanding of muscle reinjuries, delving into their epidemiology, risk factors, clinical management, and prevention strategies. Despite advancements in rehabilitation programs and return-to-play criteria, reinjury rates remain alarmingly high. Age and previous muscle injuries are nonmodifiable risk factors contributing to a high reinjury rate. Clinical management, which involves accurate diagnosis, individualized rehabilitation plans, and the establishment of return-to-training and return-to-play criteria, plays a pivotal role during the sports season. Eccentric exercises, optimal loading, and training load monitoring are key elements in preventing reinjuries. The potential of artificial intelligence (AI) in predicting and preventing reinjuries offers a promising avenue, emphasizing the need for a multidisciplinary approach to managing these injuries. While current strategies offer some mitigation, there is a pressing need for innovative solutions, possibly leveraging AI, to reduce the incidence of muscle reinjuries in football players. Future research should focus on this direction, aiming to enhance athletes' well-being and performance.

Endoscopic Proximal Hamstring Tendon Repair With Knotless Suture-Bridge Technique

Symptomatic proximal hamstring tendon tears are typically repaired surgically, with open incision and knot-tying technique. An endoscopic, knotless, suture-bridge repair technique is presented. Potential advantages include knotless simplicity, compression over a broad zone to improve tendon-bone healing, and decreased pain secondary to elimination of knots and the open incision and approach.

Effects of 4-Aminopyridine on Combined Nerve and Muscle Injury and Bone Loss

PURPOSE

Musculoskeletal injuries are common, and peripheral nerve injury (PNI) causes significant muscle and bone loss within weeks. After PNI, 4-aminopyridine (4-AP) improves functional recovery and muscle atrophy. However, it is unknown whether 4-AP has any effect on isolated traumatic muscle injury and PNI-induced bone loss.

METHODS

A standardized crush injury was performed on the sciatic nerve and muscles in mice, and the mice were assigned to receive normal saline or 4-AP treatment daily for 21 days. The postinjury motor and sensory function recovery was assessed, injured muscles were processed for histomorphometry, and the tibial bone was scanned for bone density.

RESULTS

4-Aminopyridine significantly accelerated the postinjury motor and sensory function recovery, improved muscle histomorphometry, increased muscle satellite cell numbers, and shifted muscle fiber types after combined nerve and muscle injury. Importantly, the 4-AP treatment significantly reduced PNI-induced bone loss. In contrast, in the case of isolated muscle injury, 4-AP had no effect on functional recovery and bone density, but it improved muscle-specific histomorphometry to a limited extent.

CONCLUSIONS

These findings demonstrate the potential beneficial effects of 4-AP on the recovery of muscle morphology and bone density after combined muscle and nerve injury.

CLINICAL RELEVANCE

Nerve injuries frequently involve muscle and result in rapid muscle and bone atrophy. In this scenario, 4-AP, in addition to accelerating nerve functional recovery, might work as an adjunctive agent to improve the recovery of injured muscle and attenuate PNI-induced bone loss.

Preoperative ultrasound can accurately predict the diameter of double-stranded peroneus longus tendon autografts

PURPOSE

This study aimed to determine the correlation between the intraoperative diameter of double-stranded peroneus longus tendon (2PLT) and length of the PLT autograft and preoperative ultrasound (US) measurements, as well as radiographic and anthropometric measurements. The hypothesis was that US can accurately predict the diameter of 2PLT autografts during operation.

METHODS

Twenty-six patients underwent ligament reconstruction with 2PLT autografts were included. Preoperative US was used to calculate the in situ PLT cross-sectional area (CSA) at seven levels (0, 1, 2, 3, 4, 5, 10 cm proximal to the harvest start point). Femoral width, notch width, notch height, maximum patellar length, and patellar tendon length were determined on preoperative radiographs. Intraoperative measurements of PLT were made, including all fiber lengths of PLT and diameters of 2PLT using sizing tubes calibrated to 0.5 mm.

RESULTS

CSA at 1 cm proximal to the harvest site had the highest correlation with the diameter of 2PLT (r = 0.84, P < 0.001). Calf length had the highest correlation with PLT length (r = 0.65, P < 0.001). The diameter of the 2PLT autografts could be predicted by the following formula: 4.6 + 0.2 × [sonographic CSA of PLT at 1 cm level]; the length of PLT could be predicted by the following formula: 5.6 + 0.5 × Calf length.

CONCLUSION

The diameter of 2PLT and length of PLT autografts can be accurately predicted by preoperative US and calf length measurements, respectively. Accurate preoperative prediction of the diameter and length of autologous grafts can provide the most suitable and individualized graft for patients.

LEVEL OF EVIDENCE

IV.

Instabilität des Kniegelenks – medial oder anteromedial?

Hintergrund

Verletzungen des medialen Bandkomplexes gehören zu den häufigsten Knieverletzungen. Sie heilen zwar meist mit konservativer Therapie problemlos aus, persistierende Instabilitäten erhöhen aber die Belastung der Kreuzbänder und benötigen speziell bei deren Beteiligung eine adäquate Therapie.

Anatomie und Biomechanik

Der mediale Seitenbandkomplex besteht im Wesentlichen aus dem oberflächlichen Seitenband (sMCL), welches der primäre Stabilisator gegen Valgus ist, dem tiefen Seitenband (dMCL) mit dessen schräg verlaufendem ventralem Anteil (AML), die nur sekundäre Stabilisatoren gegen Valgus darstellen, aber primär gegen Außenrotation stabilisieren, und dem hinteren Schrägband (POL), das in vollständiger Streckung gegen Valgus sowie gegen Innenrotation stabilisiert.

Therapie

Chronische Instabilitäten bzw. höhergradige Verletzungen mit Dislokation der Bandstümpfe oder multiligamentäre Verletzungen bedürfen einer operativen Versorgung. Im Akutstadium zeigen Avulsionsverletzungen bei anatomischer Refixation gutes Heilungspotenzial, während bei intraligamentären Verletzungen zusätzlich zur Naht der Bandanteile eine Augmentation mit Sehnenmaterial empfohlen wird. Bei chronischen Instabilitäten ist die Differenzierung des Instabilitätsmusters ausschlaggebend für die Wahl der Rekonstruktionstechnik (reine sMCL-Rekonstruktion oder kombinierte Rekonstruktion von sMCL und AML). In beiden Fällen kommt die hier beschriebene Technik mit flachem Transplantat der Anatomie näher als bei konventionellen Verfahren.

Diskussion

Rekonstruktionstechniken unter Verwendung flacher Sehnentransplantate, die alle betroffenen Bandanteile adressieren, haben sich biomechanisch als sehr effektiv erwiesen, komplexe mediale Instabilitäten suffizient zu behandeln. Ob diese auch klinisch überlegen sind, werden zukünftige klinische Studien zeigen müssen.

Angle-specific analysis of knee strength deficits after ACL reconstruction with patellar and hamstring tendon autografts

After anterior cruciate ligament reconstruction (ACLR) there are differences in the neuromuscular deficits observed in patients with bone-patellar tendon-bone (BPTB) and with hamstring tendon (HT) autografts. Differences in knee extensor and flexor strength are commonly reported, but analyses have largely focused on peak torque metrics despite the requirement to generate torque through range when returning to sport. The aim of this study was to investigate the angle-specific strength and strength asymmetry differences between BPTB and HT around the time of return to play after ACLR. A total of 357 male field sport athletes with either a BPTB (n=297) or an HT (n=60) autograft underwent concentric knee flexor and extensor isokinetic strength testing nine months post-ACLR. Angle-specific torques were compared between grafts and limbs using 1D Statistical Parametric Mapping and discrete-point variables. Inter-limb extensor torque asymmetry was greater in BTPB than HT at knee angles of >30° (p=0.001, peak d=5.53), with flexor torque asymmetry lower in BPTB than HT at flexion angles of >25° (p=0.001, peak d=2.68). Angle of maximum asymmetry and angle of operated limb peak torque differed in knee extension for BPTB (p<0.001, d=0.32) but not HT, whereas knee flexion angle of maximum asymmetry and operated limb peak torque differed in both BTPB (p<0.001, d=0.75) and HT (p<0.001, d=0.43). Graft type affected extensor torque at knee angles of 67-85° and flexor torque at knee angles of 27-85°. Angle-specific strength analysis may inform the rehabilitation process and improve rehabilitation and return-to-play decision making strategies in comparison to the use of peak torque values alone.

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.

Location of Hamstring Injuries Based on Magnetic Resonance Imaging: A Systematic Review

CONTEXT

Hamstring muscle injury location using magnetic resonance imaging (MRI) is not so well described in the literature.

OBJECTIVE

To describe the location of hamstring injuries using MRI.

DATA SOURCES

PubMed, Web of Science, Scopus, SPORTDiscus, Cochrane Library.

STUDY SELECTION

The full text of studies, in English, had to be available. Case reports and reviews were excluded. Included studies must report the location of hamstring injuries using MRI within 8 days of the acute injury.

STUDY DESIGN

Systematic review.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

A first screening was conducted based on title and abstract of the articles. In the second screening, the full text of the remaining articles was evaluated for the fulfillment of the inclusion criteria.

RESULTS

From the 2788 references initially found in 5 databases, we included 34 studies, reporting a total of 2761 acute hamstring injuries. The most frequent muscle head involved was the long head of the biceps femoris (BFLH) (70%), followed by the semitendinosus (ST) (15%), generally associated with BFLH. The most frequent tissue affected was the myotendinous junction (MTJ) accounting for half the cases (52%). Among all lesions, the distribution between proximal, central, and distal lesions looked homogenous, with 34.0%, 33.4% and 32.6%, respectively. The stretching mechanism, while only reported in 2 articles, represented 3% of all reported mechanisms, appears responsible for a specific lesion involving the proximal tendon of the semimembranosus (SM), and leading to a longer time out from sport.

CONCLUSION

BFLH was the most often affected hamstring injuries and MTJ was the most affected tissue. In addition, the distal, central, and proximal locations were homogeneously distributed. We also noted that MRI descriptions of hamstring injuries are often poor and did not take full advantage of the MRI strengths.

SYSTEMATIC REVIEW REGISTRATION

Before study initiation, the study was registered in the PROSPERO International prospective register of systematic reviews (registration number CRD42018107580).

Deep Gluteal Pain in Orthopaedics: A Challenging Diagnosis

Identifying the specific source of gluteal pain can elude the most seasoned orthopaedic diagnosticians. Patients will often present with a protracted course of symptoms, and failure to successfully identify and treat the underlying etiology leads to frustration for both patient and clinician. Pain deep in the buttocks can arise from compression, inflammation, or injury of one or more of the structures in this anatomically dense area. Although sacroiliitis, hip arthritis, and trochanteric bursitis may also masquerade as gluteal pain, sciatic nerve irritation in its various presentations causes a substantial percentage of cases. Deep gluteal syndrome, hamstring syndrome, and ischiofemoral impingement can have overlapping presentations but can be differentiated by clinical examination and judiciously placed diagnostic corticosteroid injections. Although nonsurgical management, including physical therapy, relative rest, and injections represent the mainstay of treatment, open and endoscopic surgical approaches have yielded encouraging success rates in refractory cases.

[Clinical results after refixation of proximal hamstring tendon ruptures comparing different anchor systems]

BACKGROUND

Injuries to the hamstring muscles and tendon complex are among the most frequent muscular injuries with proximal hamstring tendon avulsion being a particularly severe form. The surgical treatment of these injuries is superior to conservative management with respect to patient satisfaction, recovery of muscle strength and function as well as return to sport rates. It is therefore the method of choice.

OBJECTIVE

Presentation and comparison of the surgical results after treatment with titanium, polyether ether ketone (PEEK) and all suture anchors.

MATERIAL AND METHODS

A systematic search was carried out in the PubMed medical database and the results are summarized.

RESULTS

All systems exhibit comparable biomechanical properties regarding elongation and ultimate failure load. Tendon repair with these anchors results in good to excellent clinical outcomes and shows high return to sport and low complication rates. Patient satisfaction after hamstring tendon repair is reported to be over 90% and return to sport rate is 80-100%. The muscle strength recovers to 80-90% in comparison to the contralateral side.

CONCLUSION

All available anchors systems provide good to excellent clinical outcomes and an explicit advantage for one anchor system could so far not be shown.

Superimposing hip extension on knee flexion evokes higher activation in biceps femoris than knee flexion alone

Hamstring muscle function during knee flexion has been linked to hamstring injury and performance. However, it is unclear whether knee flexion alone (KF) requires similar hamstring electromyography (EMG) activity pattern to simultaneous hip extension and knee flexion (HE-KF), a combination that occurs in the late swing phase of sprinting. This study examined whether HE-KF maximal voluntary isometric contraction (MVIC) evokes higher (EMG) activity in biceps femoris long head (BFlh) and semitendinosus (ST) than KF alone. Effects of shank rotation angles were also tested. Twenty-one males performed the above-mentioned MVICs while EMG activity was measured along ST and BFlh. Conditions were compared using a one-way mixed functional ANOVA model under a fully Bayesian framework. Higher EMG activity was found in HE-KF in all shank rotation positions than in KF in the middle region of BFlh (highest in the 9th channel, by 0.022 mV [95%CrI 0.014 to 0.030] in neutral shank position). For ST, this was only observed in the neutral shank position and in the most proximal channel (by 0.013 mV [95%CrI 0.001 to 0.025]). We observed muscle- and region-specific responses to HE-KF. Future studies should examine whether hamstring activation in this task is related to injury risk and sprint performance.

A single session with a roller massager improves hamstring flexibility in healthy athletes: a randomized placebo-controlled crossover study

Purpose

The aim of this randomized placebo-controlled crossover study was to compare the acute effect on young athletes of a single session of roller massager (RM) with that obtained from passive static stretching (PSS) and a placebo intervention (PL) on hamstring flexibility and on strength.

Methods

Twenty-nine (23 male, 6 female) young athletes completed the study. Maximal voluntary contraction (MVC) and two-leg sit-and-reach test were performed before and immediately after PL, PSS and RM on three different days.

Results

Results showed that all three interventions increased the flexibility of the hamstring muscles compared to the pre-test measurements (Wilcoxon signed-rank test, p < 0.05). Only the RM intervention was significantly higher than the PL intervention (sham ultrasound). Stretching intervention was not significantly different from either of the other two interventions. None of the three interventions significantly changed the muscle strength in the short term.

Conclusions

RM can be considered as an effective alternative to stretching to increase the flexibility of the hamstring. This could be meaningful when stretching is contraindicated or evokes pain.

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.

Acute Hamstring Muscle Tears in Climbers-Current Rehabilitation Concepts

Acute hamstring injuries are often caused by the heel hook technique. This technique is unique to climbing and causes injury to muscular and inert tissues of the posterior thigh. The heel hook is used by climbers during strenuous ascent on overhanging walls and when crossing difficult terrain. The technique reduces the amount of upper body strength required during strenuous climbing because the climber's center of mass is retained within the base of support. The heel hook is stressful collectively for the hamstring muscle group and musculotendinous junction. Depending on injury severity, both conservative and surgical methods exist for the management of hamstring injuries. Contemporary approaches to rehabilitation primarily advocate the use of eccentric muscle strengthening strategies because of high rates of elongation stress associated with sprinting and team sports. However, there is reason to doubt whether this alone is sufficient to rehabilitate the climbing athlete in light of the high degree of concentric muscle strength required in the heel hook maneuver. This review examines the contemporary rehabilitation and strength and conditioning literature in relation to the management of acute hamstring musculotendinous injuries for the climbing athlete. The review provides a comprehensive approach for the rehabilitation and athletic preparation of the climbing athlete from the initial injury to full return to sports participation.

Sports-related lower limb muscle injuries: pattern recognition approach and MRI review

Muscle injuries of the lower limbs are currently the most common sport-related injuries, the impact of which is particularly significant in elite athletes. MRI is the imaging modality of choice in assessing acute muscle injuries and radiologists play a key role in the current scenario of multidisciplinary health care teams involved in the care of elite athletes with muscle injuries. Despite the frequency and clinical relevance of muscle injuries, there is still a lack of uniformity in the description, diagnosis, and classification of lesions. The characteristics of the connective tissues (distribution and thickness) differ among muscles, being of high variability in the lower limb. This variability is of great clinical importance in determining the prognosis of muscle injuries. Recently, three classification systems, the Munich consensus statement, the British Athletics Muscle Injury classification, and the FC Barcelona-Aspetar-Duke classification, have been proposed to assess the severity of muscle injuries. A protocolized approach to the evaluation of MRI findings is essential to accurately assess the severity of acute lesions and to evaluate the progression of reparative changes. Certain MRI findings which are seen during recovery may suggest muscle overload or adaptative changes and appear to be clinically useful for sport physicians and physiotherapists.

Excellent clinical outcome and low complication rate after proximal hamstring tendon repair at mid-term follow up

PURPOSE

Proximal hamstring tendon avulsions lead to a significant loss of strength and a functional deficit of the respective lower limb and surgery is the recommended treatment. Only little is known about the clinical outcomes and complications when comparing acute and chronic management as well as partial and complete tears. Therefore, the purpose of this study was to investigate the clinical results and the complication rate of patients after surgical treatment of proximal hamstring tendon injuries. It was hypothesized that surgical treatment of an acute proximal hamstring avulsion would lead to a superior clinical outcome with a low complication rate and high return to sports rate compared to chronic cases and partial avulsions.

METHODS

Patients who underwent proximal hamstring tendon repair between 2008 and 2015 were retrospectively evaluated with a minimum follow up of 2 years. Outcome measurements were obtained by means of Lysholm score, Harris Hip Score, Visual Analog Scale, and Tegner Activity Scale. Return to sports (RTS) rate was determined. Postoperative adverse events were recorded and complications reported. Patients' outcomes were compared between acute/chronic repair and partial/complete injury patterns.

RESULTS

Ninety-four of 120 (78.3%) were available for final assessment at a mean follow-up of 56.2 ± 27.2 months. Clinical outcome measures were excellent and did not differ between the treatment groups or between the different injury patterns. RTS was achieved by 86.2% of the patients and was significantly superior after acute treatment (p < 0.05). The overall complication rate was 8.5% and significantly higher in complete tears compared to partial tears and in delay compared to acute surgery (p < 0.05).

CONCLUSION

Surgical treatment of proximal hamstring tendon avulsions results in excellent clinical outcome scores and a high RTS rate. Open surgical treatment has shown to be a safe procedure with a low complication rate. Surgical timing is important, as early surgical intervention provides a higher RTS rate and a lower complication rate than delayed surgery and should therefore be preferred in clinical practice. Repair of partial and complete tears lead to similar clinical outcome, but a higher complication rate in complete avulsions.

LEVEL OF EVIDENCE

Level IV.

A Longitudinal Investigation of Muscle Injuries in an Elite Spanish Male Academy Soccer Club: A Hamstring Injuries Approach

The aims of this study were to analyze the muscle injury incidence in an elite Spanish soccer academy during three consecutive seasons attending to different chronological age groups (i.e., U14, U16, U19 and senior) and to examine the hamstring injury incidence in this elite soccer academy. Elite male youth soccer players (227) participated in this study. A total of 207 time-loss injuries (i.e., injuries that involve at least one absence day) were observed during this study period. The overall incidence rate of muscle injury was 1.74 muscle injuries/1000 h. In addition, higher muscle injury incidence was observed during match play in comparison to training sessions (6.78 vs. 3.20 muscle injuries/1000 h, p < 0.05). The oldest age group presented the highest injury rate (2.73 muscle injuries/1000 h, p < 0.05), with the burden (i.e., number of absence days per 1000 h of exposure) peak values recorded in the U16 age group (26.45 absence days/1000 h). In addition, muscle tears accounted for the greatest percentage of muscle injuries (43.5%), and the most frequent anatomical site of injury was the hamstring (30.4%). Muscle tear was the most common type of hamstring injury (49.2%), with the biceps femoris the most commonly injured muscle of the hamstring complex (39.7%). Fullbacks (FB), wide midfielders (WM) and forwards (F) suffered a greater number of hamstring injuries. Hamstring injury incidence showed a seasonal variation, as indicated by peaks in August and October. Specifically, the highest injury incidence was observed in the final part of each period during match play. These results reinforce the necessity to implement individual preventive strategies according to each specific injury profile across the youth soccer development phase.

Bilateral differences in hamstring coordination in previously injured elite athletes

Hamstring strain injuries (HSIs) involve tissue disruption and pain, which can trigger long-term adaptations of muscle coordination. However, little is known about the effect of previous HSIs on muscle coordination and in particular, after the completion of rehabilitation and in the absence of symptoms. This study aimed to determine if elite athletes with a prior unilateral HSI have bilateral differences in coordination between the hamstring muscle heads after returning to sport. Seventeen athletes with a unilateral history of biceps femoris (BF) injury participated in the experiment. Surface electromyography was recorded from three hamstring muscles [BF, semimembranosus (SM), and semitendinosus] during submaximal isometric torque-matched tasks at 20% and 50% of maximal voluntary contraction. The product of normalized electromyographic amplitude with functional physiological cross-sectional area (PCSA) and moment arm was considered as an index of individual muscle torque. The contribution of the injured muscle to total knee flexion torque was lower in the injured than the uninjured limb (-5.6 ± 10.2%, P = 0.038). This reduced contribution of BF was compensated by a higher contribution of the SM muscle in the injured limb (+5.6 ± 7.5%, P = 0.007). These changes resulted from a lower contribution of PCSA from the injured muscle (BF) and a larger contribution of activation from an uninjured synergist muscle (SM). In conclusion, bilateral differences in coordination were observed in previously injured athletes despite the completion of rehabilitation. Whether these bilateral differences in hamstring coordination could constitute an intrinsic risk factor that contributes to the high rate of hamstring injury recurrence remains to be investigated.NEW & NOTEWORTHY We used an experimental approach, combining the assessment of muscle activation, physiological cross-sectional area, and moment arm to estimate force-sharing strategies among hamstring muscles during isometric knee flexions. We tested athletes with a history of hamstring injury. We observed a lower contribution of the injured biceps femoris to the total knee flexor torque in the injured limb than in the contralateral limb. This decreased contribution was mainly due to selective atrophy of the injured biceps femoris muscle and was compensated by an increased activation of the semimembranosus muscle.

Hamstring Injuries in Athletes: Evidence-based Treatment

Hamstring injuries are common in athletes and can cause notable disability. They can be separated based on proximal, muscle belly, and distal injuries, with proximal and distal injuries more commonly requiring surgical intervention. Most injuries do not require acute MRI; however, MRI is useful in proximal and distal injuries as well as muscle belly tears that fail to respond to nonsurgical treatment. Acute repair of proximal avulsions, both partial and complete, result in successful outcomes, whereas chronic complete repairs are more difficult and less reliable. Muscle belly injuries have predictable outcomes but recurrence is common. Nonsurgical treatments focus on eccentric strengthening with the possible addition of low WBC platelet-rich plasma, which may have the potential to hasten recovery and decrease re-rupture. Distal injuries are relatively rare but may require surgical intervention. Hamstring reinjury is common, making continuation of preventive therapies after return to sport essential. Future research with larger sample sizes are required to determine how to decrease injury and reinjury rates, to evaluate the efficacy of platelet-rich plasma and to determine other treatments that may accelerate recovery after injury.

Proximal hamstring tendon avulsion treatment choice depends on a combination of clinical and imaging-related factors: a worldwide survey on current clinical practice and decision-making

Objectives

To evaluate current practice in the treatment of proximal hamstring tendon avulsions and identify decision-making preferences.

Methods

An invitation to an anonymous e-survey containing 32 questions was sent to 3475 members of the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS) and the European College of Sports and Exercise Physicians (ECOSEP).

Results

We received 403 (12%) unique responses with a completion rate of 79%. Participants were orthopaedic/trauma surgeons (90%), sports medicine physicians (7%) or physical therapists (2%). For 83% of the participants, the preferred treatment (ie, surgical or non-operative) depends on the individual case. Participants base their decision-making process on patient- and injury-related factors (decision modifiers). The five most frequently selected decision modifiers that support the choice for surgical treatment were diminished function (84%), neurological symptoms (74%), involved tendons (82%), tendon retraction on MRI (84%) and patient preference for surgery (78%). The majority prefer early surgical repair (<2 weeks after injury) to achieve highest functional outcome (63%) and ensure a low complication risk (61%). Suture anchors are used by 93% of the participants for tendon reattachment. Estimated recovery duration (ie, time to return to sports) was a median 12 weeks (IQR: 12–20) for non-operative treatment and 17 weeks (IQR: 12–24) for surgical treatment. Estimated reinjury risk was a median 25% (IQR: 10–31.5) and 10% (IQR: 5–20), respectively.

Conclusion

This survey among experienced medical professionals has summarised current practice and identified treatment decision-making preferences. The typical surgical patient has a retracted (>2 cm) two-tendon avulsion (ie, common tendon and semimembranosus tendon), is unable to engage in sports or activities of daily life, reports sciatic symptoms and prefers surgical treatment. Surgery is thought to prolong recovery and decrease reinjury risk compared with non-operative treatment and is preferably performed early.

Level of evidence

Level V.