Hamstrings Ultrasound

Assessment of muscle injury is a routine part of the daily workload for the musculoskeletal sonographers. The hamstring muscle complex (HMC) is by far the most frequently injured muscle and is often recalcitrant to even the most meticulous rehabilitation, making HMC injury a significant contributor to athletic morbidity.

Clinicians are now turning to imaging tests to confirm injury as well as to provide information about a proposed period of convalescence. Minimizing the amount of time spent out of training and competition is not only critical for the professional athlete but also important for an active general population in whom injury can often limit leisure activity.

 The goals of imaging are to confirm injury, provide a comprehensive assessment of the nature of the injury, and identify which patients may benefit from surgery. Imaging may not be necessary in all cases, and clinical data can provide valuable information about the nature of an injury;

 Start from the insertion points of the Biceps femoris, semitendinosus and semitmembranosus tendons , image in a sagittal and transverse sections . Then scan distally 1 cm increment until you reach the knee for each tendon in both plans, use the proper probe depending on the thigh thickness and patient size.use panoramic scan if you have in your us machine. cine lope. Record any hematoma, tears, abscess, the distant from hip insertions or knee insertions. the size of the hematoma, use color flow and r/o hypermia.

hence, a close working relationship with the sports medicine physician or orthopedic surgeon is advantageous.

 Tendon avulsion generally requires surgical reattachment, whereas strain patterns of injury are managed conservatively. A detailed knowledge of the anatomic, biomechanical, and Pathophysiology features of the HMC and of the various imaging manifestations of hamstring injuries is therefore necessary for providing the referring clinician with an accurate diagnosis and report.

History and clinical examination will help diagnose a hamstring strain in most cases.

The patient typically describes sudden excruciating pain in the posterior thigh, resulting in the immediate cessation of competitive activity. However, not all posterior thigh pain is the result of hamstring strain or, indeed, of hamstring disease . Furthermore, not all strain injuries of the HMC manifest with this classic history.

Differentiating between injury and muscle soreness, identifying recurrent tears in the rehabilitating athlete, or diagnosing an acute injury against a background of prior chronic strain can be difficult clinically. The latter situation is often clouded by the presence of scar tissue within the muscle. Furthermore, an acute intramuscular hemorrhage following direct impact, which is not uncommon in contact sports, can be difficult to differentiate from a muscle tear on the basis of imaging findings alone.

Referred pain, most commonly from the lumbar spine and sacroiliac joint, may further complicate the clinical picture and commonly coexists with HMC strain injury in the highly trained athlete.

Overall, the prognosis for HMC injury is good, even in the setting of avulsion injury, provided the injury is diagnosed and treated early.

Many athletes return to professional competition following tendon reattachment; however, a few may have chronic disabling symptoms or recurrence of avulsion .

Normal Anatomy

The three muscles that constitute the HMC are the biceps femoris, semitendinosus, and semimembranosus muscles. Some anatomists consider the adductor magnus muscle to be a hamstring muscle, but for the purposes of this review it will not be considered as such.

Biceps Femoris Muscle

The biceps femoris muscle is considered to be a double muscle, with the long head arising from the medial facet of the ischial tuberosity and the short head arising from the lateral linea aspera, lateral supracondylar line, and intramuscular septum.

The short head is the only component of the HMC that does not span two joints; consequently, it has been postulated that the short head is not a true hamstring . Occasionally, the short head may be absent .The origin of the biceps femoris muscle on the femur has been used as a consistent landmark in distinguishing between proximal and distal injuries.

 The distal biceps femoris tendon inserts onto the head of the fibula, the lateral condyle of the tibia, and the fascia of the leg, a rather extensive attachment that is thought to predispose it to tears. The proximal and distal tendons with the corresponding musculo tendinous junction (MTJ) span the entire length of the biceps femoris muscle, with both the short and long heads contributing to the formation of the distal tendon.

 The long head is innervated by the tibial portion of the sciatic nerve and the short head by the peroneal division. The dual innervation of the biceps femoris muscle may result in asynchrony in the coordination or intensity of stimulation of the two heads, which is also postulated as a cause for this muscle having the highest frequency of tears of the HMC.

Semitendinosus Muscle

The semitendinosus muscle is a single muscle but is best considered physiologically as a digastric muscle, given that it possesses an intervening raphe onto which the proximal fibers insert. These fibers arise from the inferomedial impression of the upper portion of the ischial tuberosity by way of a conjoint tendon with the long head of the biceps femoris muscle .

 Caudal to the ischial tuberosity, the semitendinosus muscle becomes bulbous, with the semimembranosus tendon lying anterior to it. The semimembranosus muscle is often mistaken for the semitendinosus muscle because the proximal tendon of the latter is not always a distinct structure. More distally, the semitendinosus muscle forms a long tendon. This elongated distal tendon may predispose the muscle to rupture .

( Hamstring insertion sagittal).

The muscle fibers distal to the raphe insert onto the tibia with the gracilis muscle at the Gerdy tubercle. Nerve supply is from two distinct branches from the tibial nerve, the lower branch arising in common with the nerve to the semimembranosus muscle.

( Hamstring insertion sagittal).

Semimembranosus Muscle

The semimembranosus muscle originates on the superolateral aspect of the ischial tuberosity, beneath the proximal half of the semitendinosus muscle. The semimembranosus tendon runs medial and anterior to the other hamstring tendons.

( Hamstring insertion transverse).

The proximal tendon is an elongated structure, with connections to the adductor magnus tendon and the origin of the long head of the biceps femoris muscle.

( Hamstring insertion transverse).

The semimembranosus muscle is recognized by its sharp medial border and cord-like appearance . More distally, it is mostly composed of muscle, with numerous short unipennate and multipennate fibers, maximizing the number of muscle fibrils per unit area. In contrast, the semitendinosus muscle is a largely thin, bandlike tendinous structure after its origin and for most of its course through the thigh. The semimembranosus muscle has multiple insertions by way of five tendinous arms, or expansions, to the medial tibial condyle (anterior, direct, and inferior arms), the posterior oblique ligament (capsular arm), and the posterior joint capsule and arcuate ligament (oblique popliteal ligament).

The first three arms are closely related to the tibial collateral ligament, coursing deep to it .U- or J-shaped bursa exists between this ligament and the semimembranosus attachments, which have characteristic morphologic features when pathologically inflamed.

Variations in anatomy may predispose certain patients to injury that may lead to a decrease in the normal glide and flexibility of the muscles. This is true for the short and long heads of the biceps femoris muscle, whose myofascial interface is a common site for injury. For example, slips between the hamstring muscles may be given off and can be quite large, resulting in variations in the extent of origin and insertion points and causing a decrease in flexibility by way of tethering.

The muscles of the HMC are important hip extensors and flexors of the knee in the gait cycle. They become active in the last 25% of the swing phase just as hip extension begins and continue for 50% of the swing phase to actively produce extension at the hip and actively resist extension of the knee.

As the thigh is swung forward, flexion at the knee is largely passive, accounting for the paucity of strains at this stage. With heel strike, the HMC also functions to decelerate the forward translation of the tibia during knee extension when foot strike occurs and the weight of the body is shifted forward.The HMC is thus a dynamic stabilizer of anterior tibial translation, working alongside the corresponding static stabilizer, the anterior cruciate ligament (ACL). This occurs particularly when the knee is flexed at 30° and the foot reaches its greatest distance forward from the body.

 

The prime function of the HMC is to contract eccentrically, thereby absorbing kinetic energy so as to protect the knee and hip joints. Eccentric contraction occurs when a muscle contracts while being passively stretched.

Injury is more likely to occur during eccentric contraction than during concentric contraction, since the tension contributed by stretch is superimposed on that brought about by contraction.

Hamstring muscle injury typically occurs in the region of the MTJ, which, as opposed to being a distinct point, is really a 10–12-cm transition zone in which myofibrils contribute to form the tendon.

The most serious acute injury of the HMC is avulsion, which in adults usually involves the tendon but not the bone . Tendon avulsion is important to identify because it necessitates prompt surgical repair. This pattern of injury occurs more commonly at the ischial tuberosity than at the distal ligamentous insertion. In such a case, avulsion almost always involves the conjoint tendon (biceps femoris and semitendinosus muscles) and often results in either complete or incomplete tearing of the semimembranosus. This is the most common form of proximal avulsion. The biceps femoris can arise as a separate and distinct tendon from the semitendinosus as an anatomic variant. In this case, avulsion of the biceps femoris alone carries a better chance of successful surgical repair.

Partial tearing of the HMC is often referred to as a strain. Most strains occur in the region of the MTJ, which is the weakest link in the muscle complex .

However, the MTJ is not a distinct area but a 10–12-cm zone of transition in which muscle fibrils intersect with the tendon origin or ligamentous insertion.

The proximal MTJ is more commonly strained than the distal MTJ, with the biceps femoris disproportionately represented. Injury rates to the semimembranosus and semitendinosus vary. In the largest study to date on the prevalence of HMC strain, semimembranosus injury exceeded semitendinosus injury, a finding that has been supported by other studies.

Muscle belly injury can occur anywhere within the muscle. This is a rare injury whose pathogenesis is poorly understood. Hematomas arising from such injury usually remain localized within the deep substance of the muscle belly and are easily recognized .

For examination of the posterior hip, the patient lies prone with the feet hanging out of the bed. Lower US frequencies may be required to image thick thighs or obese patients. The gluteus maximus muscle is first evaluated by means of transverse and coronal oblique planes oriented according to its long- and short-axis.

Hamstring and sciatic nerve.

Posterior axial planes are the most useful to recognize the proximal origin of the ischiocrural (semimembranosus, semitendinosus, long head of the biceps femoris) muscles. The ischial tuberosity is the main landmark: once detected, the most cranial portion of the ischiocrural tendons can be demonstrated as they insert on its lateral aspect. At this level, the semimembranosus tendon and the conjoined tendon of the semitendinosus and the long head of the biceps femoris cannot be separated. Lateral to them, the sciatic nerve is seen as a flattened structure with fascicular echotexture emerging from under the piriformis muscle. 6 Hip Shifting the probe downward on axial planes, the conjoined tendon of semitendinosus and biceps femoris can be distinguished from the tendon of semimembranosus due to its more superficial and lateral position.

The conjoined tendon of the semitendinosus and biceps femoris appears as a sagittal hyperechoic image separating the muscle bellies of the semitendinosus (medial) and the biceps (lateral). The semimembranosus has a large aponeurosis connected to the medial side of the tendon: its muscle belly arises from the medial end of this aponeurosis.

Legend: asterisk, ischiatic tuberosity; arrows, common tendon origin of the semitendinosuslong head of biceps femoris. Legend: large void arrow, sciatic nerve; narrow void arrow, conjoined tendon of the semitendinosus-long head of the biceps; 1, long-head of the biceps muscle; 2, semitendinosus muscle; 3, adductor magnus muscle; white arrow, semimemb.

https://www.youtube.com/watch?v=AN_FqPWd69o

Thank you for reading.

Steve Ramsey, PhD.

Calgary, Alberta- Canada.