The proximal hamstring muscle–tendon–bone unit: A review of the normal anatomy, biomechanics, and pathophysiology

Management of Proximal Hamstring Injuries: Non-operative and Operative Treatment

PURPOSE OF REVIEW

To evaluate the current evidence and literature on treatment options for proximal hamstring injuries.

RECENT FINDINGS

Patients with 3-tendon complete tears with greater than 2 cm of retraction have worse outcomes and higher complication rates compared to those with less severe injuries. Endoscopic and open proximal hamstring repair both have favorable patient reported outcomes at 5-year follow up. Proximal hamstring repair in patients who are male, with isolated semimembranosus injury, and have proximal hamstring free tendon rupture are more likely to have earlier return to sports. The Parisian Hamstring Avulsion Score (PHAS) is a validated patient-reported outcome measure to predict return to sports. Proximal hamstring injuries may occur in both elite and recreational athletes and may present with varying degrees of chronicity and severity. Injuries occur most commonly during forceful eccentric contraction of the hamstrings and often present with ischial tuberosity tenderness, ecchymosis, and hamstring weakness. Treatment decision-making is dictated by the tendons involved and chronicity. Many proximal hamstring injuries can be successfully treated with non-surgical measures. However, operative treatment of appropriately indicated proximal hamstring tendon injuries can result in significantly better functional outcomes and faster and more reliable return to sports compared to nonoperative treatment. Both endoscopic and open surgical repair techniques show high satisfaction levels and excellent patient-reported outcomes at short- and mid-term follow-up. Postoperative rehabilitation protocols vary across the literature and ongoing study is needed to clarify the optimal program, though emphasis on eccentric hamstring strengthening may be beneficial.

Reconstruction of proximal hamstring ruptures restores joint biomechanics during various walking conditions

PURPOSE

We aimed to examine the functional outcome in different walking conditions in elderly adults who underwent surgical repair after a non-contact hamstring injury. Our objective was to compare lower limb kinematics and kinetics over the entire gait cycle between the injured and contralateral leg in overground and level and uphill treadmill walking.

METHODS

12 patients (mean ± SD, age: 65 ± 9 years; body mass index: 30 ± 6 kg/m2) walked at self-selected speed in overground (0% slope) and treadmill conditions (0% and 10% slope). We measured spatiotemporal parameters, joint angles (normalised to gait cycle) and joint moments (normalised to stance phase) of the hip, knee and ankle. Data between sides were compared using paired sample t-tests (p < 0.05) and continuous 95% confidence intervals of the paired difference between trajectories.

RESULTS

Patients walked at an average speed of 1.31 ± 0.26 m/second overground and 0.92 ± 0.31 m/second on the treadmill. Spatiotemporal parameters were comparable between the injured and contralateral leg (p > 0.05). Joint kinematic and joint kinetic trajectories were comparable between sides for all walking conditions.

CONCLUSIONS

Refixation of the proximal hamstring tendons resulted in comparable ambulatory mechanics at least 1 year after surgery in the injured leg and the contralateral leg, which were all within the range of normative values reported in the literature. These results complement our previous findings on hamstring repair in terms of clinical outcomes and muscle strength and support that surgical repair achieves good functional outcomes in terms of ambulation in an elderly population.

TRIAL REGISTRATION

clinicaltrials.gov (NCT04867746).

What Is New about the Semimembranosus Distal Tendon? Ultrasound, Anatomical, and Histological Study with Clinical and Therapeutic Application

The semimembranosus muscle inserts into several tendons that are associated with some pathologies. Although ultrasound is useful for studying, diagnosing, and managing these pathologies, the correct interpretation of any images requires a clear knowledge of the related anatomical structures and the inter-related functions. We studied 38 cryopreserved non-paired knees from adult anatomical specimens and 4 non-paired knees from 29 to 38-week-old fetuses. The semimembranosus muscle and its tendons were located, observed, and injected under ultrasound guidance. The macroscopic anatomy was studied using dissection and anatomical cuts and the tendons were analyzed histologically. Measurements of muscle were taken 10 cm from the medial epicondyle and just before the tendon divided. The ultrasound facilitated the identification of the different divisions of the tendon of semimembranosus muscle and the rotation of the muscle and tendon from medial to posterior. An anatomical study confirmed this rotation and revealed an average width, thickness, and diameter of 38.29 mm, 14.36 mm, and 112.64 mm, respectively. Important relationships were observed between the divisions of the main tendons and the medial collateral ligament, the posterior side of the knee and popliteus muscle. This information can help to explain knee pathologies and facilitate rehabilitation after surgery.

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.

Distal hamstrings tendons mechanical properties at rest and contraction using free-hand 3-D ultrasonography

Tendon properties impact human locomotion, influencing sports performance, and injury prevention. Hamstrings play a crucial role in sprinting, particularly the biceps femoris long head (BFlh), which is prone to frequent injuries. It remains uncertain if BFlh exhibits distinct mechanical properties compared to other hamstring muscles. This study utilized free-hand three-dimensional ultrasound to assess morphological and mechanical properties of distal hamstrings tendons in 15 men. Scans were taken in prone position, with hip and knee extended, at rest and during 20%, 40%, 60%, and 80% of maximal voluntary isometric contraction of the knee flexors. Tendon length, volume, cross-sectional area (CSA), and anteroposterior (AP) and mediolateral (ML) widths were quantified at three locations. Longitudinal and transverse deformations, stiffness, strain, and stress were estimated. The ST had the greatest tendon strain and the lowest stiffness as well as the highest CSA and AP and ML width strain compared to other tendons. Biceps femoris short head (BFsh) exhibited the least strain, AP and ML deformation. Further, BFlh displayed the highest stiffness and stress, and BFsh had the lowest stress. Additionally, deformation varied by region, with the proximal site showing generally the lowest CSA strain. Distal tendon mechanical properties differed among the hamstring muscles during isometric knee flexions. In contrast to other bi-articular hamstrings, the BFlh high stiffness and stress may result in greater energy absorption by its muscle fascicles, rather than the distal tendon, during late swing in sprinting. This could partly account for the increased incidence of hamstring injuries in this muscle.

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.

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.

Effects of Fatigue Induced by Repeated Sprints on Sprint Biomechanics in Football Players: Should We Look at the Group or the Individual?

The aim of this study was to analyse the influence of fatigue on sprint biomechanics. Fifty-one football players performed twelve maximal 30 m sprints with 20 s recovery between each sprint. Sprint kinetics were computed from running speed data and a high-frequency camera (240 Hz) was used to study kinematic data. A cluster analysis (K-mean clustering) was conducted to classify individual kinematic adaptations. A large decrease in maximal power output and less efficiency in horizontally orienting the ground reaction force were observed in fatigued participants. In addition, individual changes in kinematic components were observed, and, according to the cluster analysis, five clusters were identified. Changes in trunk, knee, and hip angles led to an overall theoretical increase in hamstring strain for some players (Cluster 5, 20/51) but to an overall decrease for some others (Cluster 1, 11/51). This study showed that the repeated sprint ability (RSA) protocol had an impact on both kinetics and kinematics. Moreover, fatigue affected the kinematics in a different way for each player, and these individual changes were associated with either higher or lower hamstring length and thus strain.

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.

Is Myofascial Decompression Effective at Increasing Hamstring Flexibility in the Athletic Population? A Critically Appraised Topic

CLINICAL SCENARIO

There are a variety of therapeutic modalities used to treat flexibility issues in athletes, which can be the main cause of hamstring injuries. Myofascial decompression is one modality used to treat these patients.

FOCUSED CLINICAL QUESTION

Is myofascial decompression effective at increasing hamstring flexibility in the athletic population? Summary of Search, "Best Evidence" Appraised, and Key Findings: The literature was searched for studies of level 2 evidence or higher that investigated the use of myofascial decompression to increase hamstring flexibility, that were published in the last 5 years. Two high-quality randomized controlled trials were included and one cohort study.

CLINICAL BOTTOM LINE

There is not enough consistent, clinically significant, high-level evidence to support the use of myofascial decompression to increase hamstring flexibility.

STRENGTH OF RECOMMENDATION

There is level B evidence to support that myofascial decompression is effective at increasing hamstring flexibility.

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).

The Hamstrings: Anatomic and Physiologic Variations and Their Potential Relationships With Injury Risk

The incidence and recurrence of hamstrings injuries are very high in sports, posing elevated performance and financial-related costs. Attempts to identify the risk factors involved in predicting vulnerability to hamstrings injury is important for designing exercise-based programs that aim to mitigate the rate and severity of hamstrings injuries and improve rehabilitation strategies. However, research has shown that non-modifiable risk factors may play a greater role than modifiable risk factors. Recognizing non-modifiable risk factors and understanding their implications will afford the prescription of better suited exercise programs, i.e., that are more respectful of the individual characteristics. In a nutshell, non-modifiable risk factors can still be acted upon, even if indirectly. In this context, an underexplored topic is how intra and inter- individual anatomic and physiologic variations in hamstrings (e.g., muscle bellies, fiber types, tendon length, aponeurosis width, attachment sites, sex- and age-related differences) concur to alter hamstrings injuries risk. Some anatomic and physiologic variations may be modifiable through exercise interventions (e.g., cross-sectional area), while others may not (e.g., supernumerary muscle bellies). This apparent dichotomy may hide a greater complexity, i.e., there may be risk factors that are partially modifiable. Therefore, we explored the available information on the anatomic variations of the hamstrings, providing a deeper insight into the individual risk factors for hamstrings injuries and contributing with better knowledge and potential applications toward a more individualized exercise prescription.

[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.

Current advances and novel research on minimal invasive techniques for musculoskeletal disorders

The present review summarized the current advances and novel research on minimal invasive techniques for musculoskeletal disorders. Different invasive approaches were proposed in the physical therapy field for the management of musculoskeletal disorders, such as ultrasound-guided percutaneous needle electrolysis, dry needling, acupuncture and other invasive therapy techniques, discussing about their worldwide status, safety and interventional ultrasound imaging. Indeed, dry needling may be one of the most useful and studies invasive physical therapy applications in musculoskeletal disorders of different body regions, such as back, upper limb, shoulder, arm, hand, pelvis, lower limb, neck, head, or temporomandibular joint, and multiple soreness location disorders, such as fibromyalgia. In addition, the assessment and treatment by acupuncture or electro-acupuncture was considered and detailed for different conditions such as plantar fasciitis, osteoarthritis, spasticity, myofascial pain syndrome, osteoporosis and rheumatoid arthritis. As an increasing technique in physical therapy, the use of ultrasound-guided percutaneous needle electrolysis was discussed in injuries of the musculoskeletal system and entrapment neuropathies. Also, ultrasound-guided percutaneous neuromodulation was established as a rising technique combined with ultrasound evaluation of the peripheral nerve system with different clinical applications which need further studies to detail their effectiveness in different musculoskeletal conditions. Thus, invasive physical therapy may be considered as a promising approach with different novel applications in several musculoskeletal disorders and a rising use in the physiotherapy field.

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.

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.

A combined endoscopic and open surgical approach for chronic retracted proximal hamstring avulsion

Proximal hamstring avulsion is an uncommon injury which usually requires surgical intervention. When possible, primary surgical fixation is recommended. In chronic hamstring avulsion with significant retraction of the tendon, hamstring reconstructions using an autograft or allograft are required in order to bridge the gap. This is mainly performed using an open surgical technique. We describe a combined endoscopic and open surgical approach to hamstring reconstruction surgery.

Congenital bilateral absence of the semimembranosus muscles

Variations of the anatomy of the hamstring muscle complex are uncommon. In particular, absence of some or all of the hamstring muscles is rarely described in the literature. This report presents a case of absent semimembranosus musculature detected incidentally on knee magnetic resonance imaging (MRI), then found to be bilateral on MRI of both thighs performed shortly thereafter. Imaging also demonstrated atypical morphologies of the semitendinosus and biceps femoris muscles in both thighs.

Validity of an On-Field Readaptation Program Following a Hamstring Injury in Professional Soccer

Context: Despite the presence of various injury prevention programs, the rate of hamstring injuries and reinjuries is increasing in soccer, warranting the need for a soccer-specific rehabilitation program. Objective: To develop and validate a new, functional on-field program for the rehabilitation and readaptation of soccer players after a hamstring strain injury through a panel of experts; and determine the usefulness of the program through its application in professional soccer players. Design: A 13-item program was developed, which was validated by a panel of experts and later applied to professional soccer players. Setting: Soccer training ground. Participants: Fifteen strength and conditioning and rehabilitation fitness coaches with a professional experience of 15.40 (1.57) years in elite clubs and national teams in Europe validated the program. The program was later applied to 19 professional soccer players of the Spanish First Division (La Liga). Interventions: Once a player sustained a clinically diagnosed injury, the player would first be subject to mobilization and strengthening exercises in the gym after undergoing treatment by percutaneous needle electrolysis. The player would then complete an on-field readaptation program consisting of 13 drills arranged in a progressive manner in terms of complexity. The drills integrated various aspects of repeated sprint abilities, retraining and reeducation of biomechanical patterns, and neuromuscular control of the core and lower limbs. Main Outcome Measures: Aiken’s V for each item of the program and number of days taken by the players to return to play. Results: The experts evaluated all items of the program very highly, as seen from Aiken’s V values between 0.78 and 0.98 (0.63–0.99) for all drills, while the return to play was in 22.42 (2.32) days. Conclusion: This program has the potential to help a player suffering from a hamstring strain injury to adapt to real-match conditions in the readaptation phase through the application of sports-specific drills that were very similar to the different injury mechanisms.

A New Option for the Reconstruction of Primary or Recurrent Ischial Pressure Sores: Hamstring-Adductor Magnus Muscle Advancement Flap and Direct Closure

BACKGROUND

Owing to the high recurrence rates of ischial pressure sores, surgeons should consider the possibility of future secondary flap surgery during flap selection. The purpose of this article is to present a new surgical option for the reconstruction of primary or recurrent ischial pressure sores using a simple hamstring-adductor magnus advancement flap and direct closure.

METHODS

After horizontal fusiform skin excision, complete bursa excision and ischiectomy were performed. The tenomuscular origin of the adductor magnus and the conjoined tenomuscular origin of the biceps femoris long head and semitendinosus were isolated and completely detached from the inferior border of the ischial tuberosity. They were then advanced in a cephalad direction without detachment of the distal tendon or muscle and securely affixed to the sacrotuberous ligament. The wound was directly closed without further incision or dissection.

RESULTS

Twelve ischial pressure sores (6 primary and 6 recurrent; 12 patients) were surgically corrected. The follow-up period was 12 to 65 months. All patients healed successfully without early postoperative complications, such as hematoma, seroma, infection, wound dehiscence, or partial necrosis. Late complications included wound disruption 5 weeks after surgery that spontaneously healed in 1 case and recurrence 3 years later in another case.

CONCLUSIONS

The new surgical option presented herein, which involves hamstring-adductor magnus advancement flap and direct closure, is a simple and reliable method for providing sufficient muscle bulk to fill the dead space and proper padding to the bone stump while preserving the main vascular perforators and pedicles as well as future surgical options.

Ultrasound Features of the Proximal Hamstring Muscle-Tendon-Bone Unit

The hamstring muscle complex is made by a group of posterior biarticular thigh muscles, originating at the ischial tuberosity, which extend the hip and flex the knee joint. Proximal hamstring injuries are frequent among athletes, commonly involving their long myotendinous junction during an eccentric contraction. In this pictorial essay, we describe the ultrasound technique to visualize the normal anatomy of the proximal hamstring muscle-tendon-bone complex and present ultrasound findings in patients with traumatic injuries and tendinopathies.

Intra- and Inter-Muscular Variations in Hamstring Architecture and Mechanics and Their Implications for Injury: A Narrative Review

Understanding the architecture, anatomy, and biomechanics of the hamstrings may assist in explaining the mechanisms that affect and improve their function. The aim of this review is to specifically examine intra- and inter-muscular variations in architecture and mechanical properties of the hamstrings. Of the hamstrings, the long head of the biceps femoris shows the shortest and more pennated fibers. The semimembranosus has a similar muscle architecture with a long head of the biceps femoris but it has a different proximal attachment as well as a different moment arm compared with the long head of the biceps femoris. For the same joint motion, the semitendinosus displays less relative strain than the other hamstrings probably owing to a greater length, longer fascicles and, possibly, a longer tendon. Intra-muscular variations in architecture are documented but their implications are currently unclear. Proximally, the long head of the biceps femoris has shorter and more pennated fibers coupled with a narrower aponeurosis than distally, while the semitendinosus is the only muscle that entails a tendinous inscription. In conclusion, some of the identified intra- and inter-muscular variations in architecture may help explain why some muscles sustain injuries more than others. In the same line, exercises designed for the hamstrings may not provide the same stimulus for all components of this muscle group. Future research could examine whether intervention strategies that target specific muscles or specific areas of the hamstrings may offer additional benefits for injury prevention or rehabilitation of their function.

Imaging Characteristics Predict Operative Difficulty Mobilizing the Sciatic Nerve for Proximal Hamstring Repair

BACKGROUND

Repair of proximal hamstring avulsions requires mobilization of the sciatic nerve away from the tendon stump, which can be achieved with varying difficulty depending on the degree of scar formation and adherence. Predicting when a scarred, adherent, difficult-to-mobilize nerve will be encountered has been difficult.

OBJECTIVE

To identify clinical and/or radiological factors predictive of a difficult intraoperative dissection of the sciatic nerve during proximal hamstring repair.

METHODS

We retrospectively reviewed the medical records and preoperative magnetic resonance imaging of consecutive patients undergoing proximal hamstring repair. We compared the groups with and without a difficult sciatic nerve dissection.

RESULTS

The total cohort consisted of 67 patients. Factors found to increase the likelihood of a difficult sciatic nerve dissection included complete conjoint tendon avulsion, higher maximal amount of tendon retraction, higher degree of imaging abnormality in the sciatic nerve, and higher degree of circumferential relationship of hematoma to the sciatic nerve. At a threshold of 23 for the Sciatic Nerve Dissection Score, the positive and negative predictive values were 53% and 88%, respectively. For the decision tree, the positive and negative predictive values were 75% and 87%, respectively.

CONCLUSION

We have identified imaging factors associated with a scarred, adherent sciatic nerve that predict a difficult dissection during proximal hamstring repair. We have developed 2 novel methods-the Sciatic Nerve Dissection Score and a decision tree-that can be applied to predict the probability of a difficult sciatic nerve dissection at the time of surgical repair.

US Assessment of Sports-related Hip Injuries

Traumatic and overuse hip injuries occur frequently in amateur and professional athletes. After clinical assessment, imaging plays an important role in diagnosis and in defining care management of these injuries. Ultrasonography (US) is being increasingly used in assessment of hip injuries because of the wide availability of US machines, the lower cost, and the unique real-time imaging capability, which allows both static and dynamic evaluation as well as guidance of point-of-care interventions such as fluid aspiration and steroid injection. Accurate diagnosis of hip injuries is often challenging, given the complex soft-tissue anatomy of the hip and the wide spectrum of injuries that can occur. To conduct a skillful US evaluation of hip injuries, physicians must have pertinent knowledge of the normal anatomy and should make judicious use of surface anatomy landmarks while using a compartmentalized diagnostic approach. In this article, common sports-related injuries of the anterior, lateral, and posterior hip compartments are discussed. This review includes assessment of joint effusion, acetabular labral tear, acute and chronic tendon injuries including tendinopathy, partial and full-thickness tears, snapping hip syndromes, relevant US-guided procedures, and some other conditions such as Morel-Lavallée lesion and perineal nodular induration. Principles of care management and current knowledge on imaging findings that may affect return to activity are also presented. Using an oriented US examination technique and having knowledge of the normal hip anatomy will help physicians characterize US findings of common sports-related hip injuries and make accurate diagnoses. Online supplemental material is available for this article. ^©RSNA, 2018.

A previous hamstring injury affects kicking mechanics in soccer players

BACKGROUND

Although the kicking skill is influenced by limb dominance and sex, how a previous hamstring injury affects kicking has not been studied in detail. Thus, the objective of this study was to evaluate the effect of sex and limb dominance on kicking in limbs with and without a previous hamstring injury.

METHODS

Forty-five professional players (males: N.=19, previously injured players=4, age=21.16±2.00 years; females: N.=19, previously injured players =10, age= 22.15±4.50 years) performed 5 kicks each with their preferred and non-preferred limb at a target 7m away, which were recorded with a three-dimensional motion capture system. Kinematic and kinetic variables were extracted for the backswing, leg cocking, leg acceleration and follow through phases.

RESULTS

A shorter backswing (20.20±3.49% vs. 25.64±4.57%), and differences in knee flexion angle (58±10º vs. 72±14º) and hip flexion velocity (8±0 rad/s vs. 10±2 rad/s) were observed in previously injured, non-preferred limb kicks for females. A lower peak hip linear velocity (3.50±0.84 m/s vs. 4.10±0.45 m/s) was observed in previously injured, preferred limb kicks of females. These differences occurred in the backswing and leg-cocking phases where the hamstring muscles were the most active. A variation in the functioning of the hamstring muscles and that of the gluteus maximus and iliopsoas in the case of a previous injury could account for the differences observed in the kicking pattern.

CONCLUSIONS

Therefore, the effects of a previous hamstring injury must be considered while designing rehabilitation programs to re-educate kicking movement.

Hip Imaging in Athletes: Sports Imaging Series

Hip or groin pain in athletes is common and clinical presentation is often nonspecific. Imaging is a very important diagnostic step in the work-up of athletes with hip pain. This review article provides an overview on hip biomechanics and discusses strategies for hip imaging modalities such as radiography, ultrasonography, computed tomography, and magnetic resonance (MR) imaging (MR arthrography and traction MR arthrography). The authors explain current concepts of femoroacetabular impingement and the problem of high prevalence of cam- and pincer-type morphology in asymptomatic persons. With the main focus on MR imaging, the authors present abnormalities of the hip joint and the surrounding soft tissues that can occur in athletes: intraarticular and extraarticular hip impingement syndromes, labral and cartilage disease, microinstability of the hip, myotendinous injuries, and athletic pubalgia. (©) RSNA, 2016.

Repair of Proximal Hamstring Tears: A Surgical Technique

Proximal hamstring tears are among the most common sports-related injuries. These injuries often occur as strains or partial tears at the proximal muscle belly or the musculotendinous junction, with avulsion injuries of the proximal attachment occurring less frequently. Regardless of the mechanism, they produce functional impairment and negatively affect an athlete's performance. Various classifications for these injuries are reported in the literature. Early surgical treatment is recommended for patients with either a 2-tendon tear/avulsion with more than 2 cm retraction or those with complete 3-tendon tears. Surgery can be performed in the chronic phase but it is technically demanding because of scar formation and tendon retraction. This Technical Note describes a biomechanically validated surgical technique for repair of the proximal hamstring tears.

Treatment of proximal hamstring tendinopathy-related sciatic nerve entrapment: presentation of an ultrasound-guided "Intratissue Percutaneous Electrolysis" application

BACKGROUND

Proximal Hamstring Tendinopathy-related Sciatic Nerve Entrapment (PHTrSNE) is a neuropathy caused by fibrosis interposed between the semimembranosus tendon and the sciatic nerve, at the level of the ischial tuberosity.

METHODS

Ultrasound-guided Intratissue Percutaneous Electrolysis (US-guided EPI) involves galvanic current transfer within the treatment target tissue (fibrosis) via a needle 0.30 to 0.33 mm in diameter. The galvanic current in a saline solution instantly develops the chemical process of electrolysis, which in turn induces electrochemical ablation of fibrosis. In this article, the interventional procedure is presented in detail, and both the strengths and limits of the technique are discussed.

RESULTS

US-guided EPI eliminates the fibrotic accumulation that causes PHTrSNE, without the semimembranosus tendon or the sciatic nerve being directly involved during the procedure. The technique is however of limited use in cases of compression neuropathy.

CONCLUSION

US-guided EPI is a technique that is quick to perform, minimally invasive and does not force the patient to suspend their activities (work or sports) to make the treatment effective. This, coupled to the fact that the technique is generally well-tolerated by patients, supports use of US-guided EPI in the treatment of PHTrSNE.

Evaluation and management of ischiofemoral impingement: a pathophysiologic, radiologic, and therapeutic approach to a complex diagnosis

Ischiofemoral impingement syndrome (IFI) is an underrecognized form of atypical, extra-articular hip impingement defined by hip pain related to narrowing of the space between the ischial tuberosity and the femur. The etiology of IFI is multifactorial and potential sources of ischiofemoral engagement include anatomic variants of the proximal femur or pelvis, functional disorders as hip instability, pelvic/spinal instability, or abductor/adductor imbalance, ischial tuberosity enthesopathies, trauma/overuse or extreme hip motion, iatrogenic conditions, tumors and other pathologies. Magnetic resonance imaging (MRI) is the diagnostic procedure of choice for assessing IFI and may substantially influence patient management. The injection test of the ischiofemoral space (IFS) has both a diagnostic and therapeutic function. Endoscopic decompression of the IFS appears useful in improving function and diminishing hip pain in patients with IFI but conservative treatment is always the first step in the treatment algorithm. Because of the ever-increasing use of advanced MRI techniques, the frequent response to conservative treatment, and the excellent outcomes of new endoscopic treatment, radiologists must be aware of factors that predispose or cause IFI. In addition, focused treatment in these conditions is often more important than in secondary impingement. In this article, we briefly describe the anatomy of the IFS, review the clinical examination and symptoms, assess the diagnostic imaging criteria and pathophysiological mechanisms, and develop an understandable classification of IFI, with particular focus on its etiology, predisposing factors, and associated musculoskeletal abnormalities. We also assess the role of the radiologist in the diagnosis, treatment, and preoperative evaluation of both primary and secondary IFI.

Ischiofemoral Impingement and Hamstring Syndrome as Causes of Posterior Hip Pain: Where Do We Go Next?

Recent advances in understanding hip joint anatomy and biomechanics have contributed to improvement of diagnosis and treatment decisions for distal causes of deep gluteal syndrome (DGS). Ischiofemoral impingement and hamstrings syndrome are sources of posterior hip pain that can simulate symptoms of DGS. The combination of a comprehensive history and physical examination with imaging and ancillary testing are critical for diagnosis. Six key physical examination tests are described to differentiate distal versus proximal sources of extrapelvic posterior hip pain. Outcomes depend on patient compliance and the understanding of the entire anatomy, biomechanics, clinical presentation, and open versus endoscopic treatment options.

The adductor magnus "mini-hamstring": MRI appearance and potential pitfalls

OBJECTIVE

To examine the anatomic MRI characteristics of the adductor magnus mini hamstring (AMMH) and explore its involvement in cases of hamstring avulsion.

MATERIALS AND METHODS

An IRB-approved retrospective review of patients undergoing "hamstring protocol" MRI between March 2009 and June 2014 was performed. Two musculoskeletal radiologists recorded multiple AMMH anatomic characteristics and involvement in cases of hamstring avulsion.

RESULTS

Seventy-six AMMHs were analyzed in 66 patients [35 females and 31 males, mean age 49.3 ± 15.2 years (range 17-81)]. Eleven percent of AMMHs were poorly visualized, 51 % visualized, and 37 % well visualized. Seven percent demonstrated round, 73 % ovoid, and 21 % flat/lenticular tendon morphologies. Most (88 %) demonstrated typical origins. Average cross-sectional area (CSA) was 22.4 ± 10.6 mm² (range 6-56), diameter was 7.2 ± 2.5 mm (range 2.9-15), medial distance from the semimembranosus tendon was 7.5 ± 2.5 mm (range 3-14), and tendon length was 6.8 ± 3.3 cm (range 1.2-14.1). There was no gender difference in AMMH anatomic measurements or correlation between age and CSA or diameter. Of 17 complete hamstring avulsion cases, the AMMH was intact in 13, partially torn in 3, and completely torn in 1.

CONCLUSION

The AMMH is a constant finding with variable anatomic characteristics. It is visualized or well visualized by MRI in 88 % of cases and is a sizable tendon located in close proximity to the semimembranosus tendon. Because it is uncommonly completely torn (6 %) in cases of complete hamstring avulsion, radiologists should be aware of its presence and appearance to avoid diagnostic confusion.

Anatomy of the Adductor Magnus Origin: Implications for Proximal Hamstring Injuries

Background:

The adductor magnus (AM) has historically been a potential source of confusion in patients with suspected proximal hamstring avulsion injuries.

Purpose:

To investigate the anatomic characteristics of the AM, including its osseous origin, anatomic dimensions, and relationship to the proximal hamstring tendons.

Study Design:

Descriptive laboratory study.

Methods:

Dissection of the AM origin was performed in 11 (8 cadavers) fresh-frozen hip-to-foot cadaveric hemipelvis specimens. The gross anatomy and architecture of the proximal hamstring and AM tendons were studied. After dissecting the hamstring tendons away from their origin, the dimension, shape, and orientation of the tendon footprints on the ischial tuberosity were determined.

Results:

The AM was identified in all cadaveric specimens. The mean tendon thickness (anterior to posterior [AP]) was 5.7 ± 2.9 mm. The mean tendon width (medial to lateral [ML]) was 7.1 ± 2.2 mm. The mean tendon length was 13.1 ± 8.7 cm. The mean footprint height (AP dimension) was 12.1 ± 2.9 mm, and mean footprint width (ML dimension) was 17.3 ± 7.1 mm. The mean distance between the AM footprint and the most medial aspect of the conjoint tendon footprint was 8.5 ± 4.2 mm. Tendon measurements demonstrated a considerable degree of both intra- and interspecimen variability.

Conclusion:

The AM tendon is consistently present just medial to the conjoint tendon at the ischial tuberosity, representing the lateral-most portion of the AM muscle. This study found wide variation in the dimensional characteristics of the AM tendon between specimens. Its shape and location can mimic the appearance of an intact hamstring (conjoint or semimembranosus) tendon intraoperatively or on diagnostic imaging, potentially misleading surgeons and radiologists. Therefore, detailed knowledge of the AM tendon anatomy, footprint anatomy, and its relationship to the hamstring muscle complex is paramount when planning surgical approach and technique.

Clinical Relevance:

The reported data may aid surgeons in more accurate recognition, diagnosis, and repair of proximal hamstring avulsion injuries.

A qualitative and quantitative analysis of the attachment sites of the proximal hamstrings

PURPOSE

Proximal hamstring tears represent a challenge. Surgical repair of such tears has been reported utilizing both open and endoscopic techniques. It was hypothesized that the proximal attachments of the hamstring muscle group could be reproducibly and consistently measured from pertinent bony anatomical reference landmarks.

METHODS

Fourteen fresh-frozen, human cadaveric specimens were dissected, and measurements were taken regarding the proximal attachments of the hamstring muscle group in reference to bony landmarks. A highly precise coordinate measuring device was used for three-dimensional measurements of tendon footprints and bony landmarks, and relevant distances between structures were calculated.

RESULTS

The semitendinosus and long head of the biceps femoris shared a proximal origin (conjoined tendon), having an oval footprint with an average area of 567.0 mm(2) [95 % CI 481.0-652.9]. The semimembranosus (SM) footprint was crescent-shaped and located anterolateral to the conjoined tendon, with an average area of 412.4 mm(2) [95 % CI 371.0-453.8]. The SM footprint had an accessory tendinous extension that extended anteromedially forming a distinct footprint. A consistent bony landmark was found at the medial ischial margin, 14.6 mm [95 % CI 12.7-16.5] from the centre of the conjoined tendon footprint, which coincided with the distal insertion of the sacrotuberous ligament.

CONCLUSION

The conjoined tendon was the largest attachment of the proximal hamstring group. Two other distinct attachment footprints were identified as the SM footprint and the accessory tendinous extension. The sacrotuberous ligament insertion served as a bony landmark. The anatomical data established in this study may aid in better restoring the anatomy during repair of proximal hamstring tears.

Gross anatomical and dimensional characteristics of the proximal hamstring origin

PURPOSE

The current study was undertaken to better define the gross anatomical and dimensional characteristics of the proximal hamstring origin.

METHODS

Twelve paired whole-lower extremities from six embalmed cadavers were dissected. The gross anatomy of the proximal hamstrings was studied. With the tendons attached to the ischial tuberosity, the width and thickness of each tendon was measured 1 cm distally to their origin, and the distance from the most proximal border of the common origin of the semitendinosus (ST) and long head of the biceps (LB) to their distal junction was assessed. After removal of the hamstring group, the shape, orientation, and dimension of the tendon footprints were determined.

RESULTS

One cadaver demonstrated unique anatomy, which was considered as an anatomic variant and was therefore excluded from the study group. The ST and LB had a common origin on the posterolateral aspect of the ischial tuberosity (ST/LB), whereas the semimembranosus (SM) had a separated origin at the anterolateral aspect. The mean distance from the most proximal border of the ST/LB origin to the distal junction was 10.0 ± 1.3 cm. The shape of both footprints was longitudinal-oval, with the longitudinal axes of the SM and ST/LB footprints parallel aligned. Mean tendon width was 3.4 ± 0.5 cm for the common ST/LB complex and 4.2 ± 0.9 cm for the SM (p = 0.009). The corresponding values for tendon thickness were 1.0 ± 0.3 cm (ST/LB) and 0.8 ± 0.2 cm (SM), respectively (n.s.). Mean footprint length was 3.9 ± 0.4 cm for ST/LB and 4.5 ± 0.5 cm for SM (p = 0.002). The corresponding values for footprint height were 1.4 ± 0.5 cm (ST/LB) and 1.2 ± 0.3 cm (SM), respectively (n.s.).

CONCLUSION

The ST and LB had a common origin, whereas the SM originated separately. The site of origin of both tendons was the lateral aspect of the ischial tuberosity, with the SM footprint lying directly anterior to the footprint of the ST/LB complex. The footprint of the SM was significantly wider than the footprint of the ST/LB. The reported gross anatomic findings and dimensions may aid surgeons in anchor placement at the anatomical attachment site, thereby facilitating anatomic hamstring repair. In addition, the provided data may improve diagnosis and conservative treatment of proximal hamstring tendinopathy, since detailed knowledge about the normal anatomy is crucial for recognizing tendon abnormalities and for several conservative treatment modalities such as shockwave application or ultrasound-guided injections.

Partial semitendinosus tendon tear in a young athlete: a case report and review of the distal semitendinosus anatomy

Distal semitendinosus tears have been infrequently reported in the radiology literature, and a detailed description of the anatomy and imaging features of these injuries is lacking. The semitendinosus tendon is clinically relevant, as it is frequently grafted in knee ligament reconstructions and plays an important role in performing competitive activities. We present a case of a 31-year-old man who developed a partial semitendinosus tear during competitive training. This case highlights the common clinical and imaging findings found with distal semitendinosus tears, and explores the various modalities available to treat this injury. We also review the clinically pertinent anatomy of the distal semitendinosus tendon and discuss the pitfalls that musculoskeletal radiologists may encounter, to avoid misdiagnosing these rare injuries.

The hamstring muscle complex

PURPOSE

The anatomical appearance of the hamstring muscle complex was studied to provide hypotheses for the hamstring injury pattern and to provide reference values of origin dimensions, muscle length, tendon length, musculotendinous junction (MTJ) length as well as width and length of a tendinous inscription in the semitendinosus muscle known as the raphe.

METHODS

Fifty-six hamstring muscle groups were dissected in prone position from 29 human cadaveric specimens with a median age of 71.5 (range 45-98).

RESULTS

Data pertaining to origin dimensions, muscle length, tendon length, MTJ length and length as well as width of the raphe were collected. Besides these data, we also encountered interesting findings that might lead to a better understanding of the hamstring injury pattern. These include overlapping proximal and distal tendons of both the long head of the biceps femoris muscle and the semimembranosus muscle (SM), a twist in the proximal SM tendon and a tendinous inscription (raphe) in the semitendinosus muscle present in 96 % of specimens.

CONCLUSION

No obvious hypothesis can be provided purely based on either muscle length, tendon length or MTJ length. However, it is possible that overlapping proximal and distal tendons as well as muscle architecture leading to a resultant force not in line with the tendon predispose to muscle injury, whereas the presence of a raphe might plays a role in protecting the muscle against gross injury. Apart from these architectural characteristics that may contribute to a better understanding of the hamstring injury pattern, the provided reference values complement current knowledge on surgically relevant hamstring anatomy.

LEVEL OF EVIDENCE

IV.

Platelet-rich plasma in the treatment of skeletal muscle injuries

INTRODUCTION

Every year recreational and professional sports cause thousands of lesions to muscle, ligament and tendon. Critical progress in biological interventions could meet a pressing health need to help athletes resume their activity levels.

AREAS COVERED

We perform a narrative review on platelet-rich plasma (PRP) therapies and muscle injuries. The field is eminently translational, thus besides clinical data we summarize experimental studies that bring meaningful biological insights on PRP effects. Some concepts regarding healing mechanisms are reviewed including innate immune response, myogenesis and fibrosis. It is commonly thought that PRPs are not uniform and cannot be assessed against each other, thus current PRP classifications are addressed. PRP effects also depend on the characteristics of the host tissue; therefore we focus on clinical muscle injury classifications. Controversial clinical findings are attributed to both the variability in PRP formulations and variability in the application protocols, so we discuss current clinical data in this basis.

EXPERT OPINION

Currently, there is little clinical evidence to support the use of PRP in skeletal muscle injuries. The future of PRP therapies relies not only in finding the best products, most appropriate indications and application protocols, but also in conceiving combination products. Moreover, as our understanding of healing mechanisms progresses, off-the-shelf allogenic PRP products could be part of the solution for sport injuries.

Effects of low-level laser therapy on skeletal muscle repair: a systematic review

A review of the literature was performed to demonstrate the most current applicability of low-level laser therapy (LLLT) for the treatment of skeletal muscle injuries, addressing different lasers, irradiation parameters, and treatment results in animal models. Searches were performed in the PubMed/MEDLINE, SCOPUS, and SPIE Digital Library databases for studies published from January 2006 to August 2013 on the use of LLLT for the repair of skeletal muscle in any animal model. All selected articles were critically appraised by two independent raters. Seventeen of the 36 original articles on LLLT and muscle injuries met the inclusion criteria and were critically evaluated. The main effects of LLLT were a reduction in the inflammatory process, the modulation of growth factors and myogenic regulatory factors, and increased angiogenesis. The studies analyzed demonstrate the positive effects of LLLT on the muscle repair process, which are dependent on irradiation and treatment parameters. The findings suggest that LLLT is an excellent therapeutic resource for the treatment of skeletal muscle injuries in the short-term.

Structural properties of the intact proximal hamstring origin and evaluation of varying avulsion repair techniques: an in vitro biomechanical analysis

BACKGROUND

Although surgical repair has been reported to provide improved outcomes compared with nonoperative treatment in the management of complete proximal hamstring origin avulsions, no intact or avulsion repair biomechanical data exist to support various repair strategies or guide postoperative rehabilitation.

PURPOSE

To compare failure load among 4 proximal hamstring tendon conditions: (1) intact, (2) repair with 2 small anchors (2S), (3) repair with 2 large anchors (2L), and (4) repair with 5 small anchors (5S).

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty-four human cadaveric hemipelvises were randomly allocated to 1 of the 4 testing groups. Intact and repaired specimens were subjected to cyclic loading at 1 Hz between 25 N and a progressively increasing maximum load that was incremented by 200 N every 50 cycles, beginning at 200 N and increasing to 1600 N. Displacement, maximum load, stiffness, number of cycles to failure, and mode of failure during cyclic loading were recorded and analyzed.

RESULTS

The intact proximal hamstring tendons failed at the highest cyclic force of all tested groups, yet no significant differences existed between the intact (1405 ± 157 N) and 5S repair (1164 ± 294 N) conditions. Both the 2S and the 2L repair groups failed at a level significantly lower than the intact hamstring (474 ± 145 N [P < .001] and 543 ± 245 N [P < .001], respectively). The maximum load attained by the 5S repairs was significantly greater than the loads attained by the 2S (P = .005) and 2L (P = .013) repairs.

CONCLUSION

Repairs using 5 small anchors were similar to the intact tendon and were significantly stronger than repairs using only 2 large or 2 small anchors in the repair of complete avulsions of the proximal hamstring tendons. Additionally, no significant differences in strength were observed when only anchor size differed.

CLINICAL RELEVANCE

This finding supports the clinical investigation of postoperative range of motion rehabilitation protocols that permit full flexion and extension of the hip and knee when a 5-anchor repair construct is used.

An anatomical and histological study of the structures surrounding the proximal attachment of the hamstring muscles

INTRODUCTION

The proximal attachment of hamstring muscles has a very high incidence of injuries due to a wide number of factors and its morphology may be one of the underlying factors as scientific literature points out. The connective tissue component of the attachment of hamstring muscles is not well known. For this reason the aim of this study is to describe the anatomy and histology surrounding the proximal attachment of the hamstring muscles (PAHM) and its direct anatomic relations.

METHODS

Forty-eight cryopreserved lower limbs have sequentially been studied by means of dissection, anatomical sections and histology.

RESULTS

All specimens studied presented an annular connective tissue structure that resembles a retinaculum, which covers and adapts to the attachment of hamstring muscles on the ischial tuberosity.

CONCLUSION

The results show how this retinaculum is continuous with the long head of biceps femoris muscle, however there is a layer of loose connective tissue between the retinaculum and the semitendinosus muscle. Furthermore, this structure receives expansions of the anterior epimysium of the gluteus maximus muscle (GIM).

A qualitative and quantitative analysis of the attachment sites of the proximal hamstrings

PURPOSE

Proximal hamstring tears represent a challenge. Surgical repair of such tears has been reported utilizing both open and endoscopic techniques. It was hypothesized that the proximal attachments of the hamstring muscle group could be reproducibly and consistently measured from pertinent bony anatomical reference landmarks.

METHODS

Fourteen fresh-frozen, human cadaveric specimens were dissected, and measurements were taken regarding the proximal attachments of the hamstring muscle group in reference to bony landmarks. A highly precise coordinate measuring device was used for three-dimensional measurements of tendon footprints and bony landmarks, and relevant distances between structures were calculated.

RESULTS

The semitendinosus and long head of the biceps femoris shared a proximal origin (conjoined tendon), having an oval footprint with an average area of 567.0 mm(2) [95 % CI 481.0-652.9]. The semimembranosus (SM) footprint was crescent-shaped and located anterolateral to the conjoined tendon, with an average area of 412.4 mm(2) [95 % CI 371.0-453.8]. The SM footprint had an accessory tendinous extension that extended anteromedially forming a distinct footprint. A consistent bony landmark was found at the medial ischial margin, 14.6 mm [95 % CI 12.7-16.5] from the centre of the conjoined tendon footprint, which coincided with the distal insertion of the sacrotuberous ligament.

CONCLUSION

The conjoined tendon was the largest attachment of the proximal hamstring group. Two other distinct attachment footprints were identified as the SM footprint and the accessory tendinous extension. The sacrotuberous ligament insertion served as a bony landmark. The anatomical data established in this study may aid in better restoring the anatomy during repair of proximal hamstring tears.

Sacrotuberous ligament: relationship to normal, torn, and retracted hamstring tendons on MR images

PURPOSE

To evaluate continuity of the sacrotuberous ligament (STL) in normal and abnormal hamstring (HS) tendons on magnetic resonance (MR) images and to test the hypothesis that greater degrees of HS retraction are correlated with STL discontinuity.

MATERIALS AND METHODS

The institutional review board approved this retrospective HIPAA-compliant study and waived informed consent. Control cohort comprised 33 patients (mean age, 54.1 years) without HS abnormalities at hip MR arthrography. Study cohort comprised 100 patients (mean age, 55.3 years) with HS abnormalities at pelvic or hip MR imaging. Two musculoskeletal radiologists independently assessed STL continuity with the ischium and semimembranosus (SM) and conjoined biceps femoris and semitendinosus (BF-ST) tendons and evaluated these tendons for tendinopathy, partial tear, or rupture. A third musculoskeletal radiologist measured retraction of ruptured tendons. Inter- and intraobserver agreement was calculated with weighted κ or intraclass correlation coefficients. HS abnormalities in the cohorts were compared with Mann-Whitney test. In patients with tendon rupture, relationships between qualitative (STL and HS attachments) and quantitative (tendon retraction measurements) data were analyzed with analysis of variance and linear regression with Bonferroni correction.

RESULTS

STL was continuous with ischium in all patients. In control patients, STL was always continuous with BF-ST but never continuous with SM. In study patients, BF-ST tendon alone, SM tendon alone, and both BF-ST and SM tendons showed abnormalities in 17, six, and 77 patients, respectively. HS rupture occurred in 24 patients; it involved BF-ST tendon alone in 13 patients and both BF-ST and SM tendons in 11. STL was continuous with BF-ST tendon in 12 patients and discontinuous in 12 patients. Retraction of BF-ST tendon (mean, 33 mm; range, 5-81 mm) was independently correlated with STL continuity with BF-ST (P = .0001) and SM (P = .0004) tendon rupture. Retraction was significantly greater (P ≤ 0.01) when STL was discontinuous and SM tendon was ruptured. Inter- and intraobserver agreement was very good or excellent in categorization of HS abnormalities and measurement of retraction.

CONCLUSION

STL showed continuity with both ischium and BF-ST tendon but not SM tendon. In HS rupture, tendon retraction was significantly less when STL remained attached to BF-ST tendon.

Peri-articular diseases of the hip: emerging frontiers in arthroscopic and endoscopic treatments

The precise diagnosis of both intra and extra-capsular disease of the hip is now possible because of commonly available advanced diagnostic imaging techniques. An increasing number of reports in the orthopedic literature describe new endoscopic and arthroscopic techniques to address peri-articular pathology of the hip. The purpose of this paper is to review current techniques in the management of extra-articular hip conditions.