Proximal Hamstring Avulsion Injuries: Injury Mechanism, Diagnosis and Disease Course

Proximal Hamstring Avulsion Injuries: Injury Mechanism, Diagnosis and Disease Course Ermias S. Abebe, BS, Claude T. Moorman, MD, and William E. Garrett Jr, MD, PhD The hamstrings group is made up of three two-joint muscles whose unique anatomy and functional properties during movement make this group particularly susceptible to muscle stain injury along the extensive muscle-tendon junctions, particularly during high-speed activities like sprinting. Proximal strains injury to the hamstring can also occur from unopposed stretch that can lead to a possible avulsion injury. An office examination will identify numerous clinical signs and symptoms of strain injury, but an MR image is helpful for defining the extent of a proximal injury. The common strain injury is treated with RICE while the choice of treatment for a proximal injury is dependent upon the number of tendons involved and the amount of tissue retraction. Early surgical intervention is advocated to avoid complications from a chronic injury. Oper Tech Sports Med 20:2-6 © 2012 Elsevier Inc. All rights reserved. KEYWORDS avulsion, hamstrings, mechanism, proximal muscle injury

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amstring injuries are very common in sports.1-4 These injuries usually occur within the substance of the muscle near the muscle-tendon junction with stretch or eccentric activation, and are easily recognized clinically and radiologically.4-6 Disruption of the proximal hamstring occurs by a unique mechanism, can be much more debilitating acutely, and lead to permanent athletic disability if not recognized and treated early.7 The more severe injury is a complete or nearly complete avulsion of the proximal tendons from the ischial tuberosity. The hamstring muscles attaching to the ischium then lose their function, while the short head of the biceps femoris which originates from the posterior surface of the femur remains functionally intact.

Anatomy The hamstring group consists of the biceps femoris (long and short heads), semitendinosus, and semimembranosus muscle bellies. All the muscles are innervated by the tibial branch Reprinted with permission from Abebe ES, Moorman CT, Garrett WE Jr: Proximal Hamstring Avulsion Injuries: Injury Mechanism, Diagnosis and Disease Course. Oper Tech Sports Med 17:205-209, 2009 (© 2009 Elsevier Inc.). Department of Orthopaedics, Duke University Medical Center, Durham, NC. Address reprint requests to William E. Garrett Jr, MD, PhD, Department of Orthopaedics, Duke University Medical Center, Box 3338, Durham, NC 27710. E-mail: [email protected]

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1060-1872/12/$-see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1053/j.otsm.2012.03.001

of the sciatic nerve, except for the short head of the biceps femoris, which is also dually innervated by the peroneal portion of the sciatic nerve.6 With the exception of the short head of the biceps femoris, all hamstring muscles originate as a common dense tendinous mass from the lateral aspect of the ischial tuberosity of the pelvis.8 This myotendinous junction extends through nearly 60% of the total length of the bicep femoris muscle, and the individual muscle bellies split into distinguishable bodies along this tendon within 10 cm of the tuberosity, with the semimembranosus splitting off first.6,9 The semimembranosus originates lateral to the common tendon of the semitendinosus and biceps femoris on the lateral aspect of ischial tuberosity.9 It is also important to note that the semitendinosus muscle fibers uniquely come directly off the tuberosity and proximal musculotendinous junction, whereas the short head of the biceps femoris originates just medial to the linea aspera in the distal femur.10,11 The hamstring muscles trace unique courses along the femur as they descend to their respective attachments. On the lateral aspect, the long head of the biceps femoris attaches to the fibular head and lateral condyle of the tibia. The short head of the biceps femoris descends at an angle from its origin on the femur and inserts into the tendon of the long head of the bicep femoris, and forms insertions to the posterolateral capsule, iliotibial tract, the fibular head, and proximal lateral tibia. On the medial side, the semimembranosus inserts into the posteromedial tibia, while the semitendinosus joins the sartorius and gracilis tendons

Proximal hamstring avulsion injuries to form the pes anserinus attachment on the proximal medial tibia.8,10,11

Function of Hamstrings The hamstrings are 2-joint muscles spanning the hip and knee joint with multiple attachments that allow it to affect function throughout the pelvis and lower extremities.8 This biarcticular structure provides it the ability to localize contraction to one joint by allowing movement to occur at the other, if either of its antagonists contract.10 The muscle group provides knee support during the early stance phase, propulsion during the late-stance, and controls knee momentum of the limb during mid-swing. The principle activities of the hamstring group are hip extension and knee flexion.10 They function more to slow or control hip flexion and knee extension, emphasizing their eccentric action. Gait analysis has shown that hamstrings are primarily active during the late swing and early stance phases of walking. With running, the hamstring muscles are active for a longer portion of the swing phase and early stance.12 Hamstring flexibility also controls passive and active range of motion in the body. Thus, flexibility is very important for athletic and artistic performance.6 Past gait analysis studies have tried to isolate the time of hamstring muscle injury during sprinting. Some investigators found that the greatest knee flexion and hip extension moment occurs during the stance phase of treadmill running, and predicted that the potential for hamstring muscle strain injury exists during the stance phase of running.8,13 Others have shown that maximal lengthening of the hamstrings occurs at the end of swing phase of treadmill running, and suggested that the potential for injury exists during late phase swing before foot contact, when hip is flexed and the knee flexion moment is reducing.8,14-16 More recent overground running studies have demonstrated that maximum muscle lengthening was similar during the late stance and the late swing phase, whereas muscle activation occurred at higher velocity during the late swing phase.17 These combined findings suggest that the hamstring muscles have the necessary condition and potential for strain injuries during both the late stance phase and late swing phase of sprinting.17

Mechanisms of Injury A few recent studies have postulated that different sporting activities recruit the hamstring in different ways and can lead to different injury mechanisms as well as lesions.8,18-21 As seen in other muscles, strain injuries to the hamstrings are thought to occur as the group resists a powerful eccentric load when contraction combined with lengthening of the muscle takes place and the applied force to the contracted muscle exceeds the biomechanical strength of the muscle-tendon unit.22,23 As biarticular muscles, which are rarely stretched during activities of daily living, the hamstrings are especially vulnerable to injury in eccentric loading.8,16,20,24,25 The published data suggest that hamstring muscles strains involve at least 2 different injury mechanisms: the predominant type occurring during

3 high-speed running and the other when stretching is carried out to extreme joint position.18,21,26-28 Hamstring injury is believed to occur when a sudden forcible contraction of the muscles takes place against resistance causing excessive eccentric overload, as noted in high-speed sporting activities such as sprinting.29 The reported injuries occur in a variety of sports and all involve a common mechanism, such as forced hip flexion and maintained extension of the knee combined with eccentric contraction of hamstring.3,4,7,11,20,21,30,31 The motion of the hip and knee in the stated mechanism likely subjects the hamstrings to increased stretch and force production extrinsically.12,19 It is now postulated that the collective high levels of tension in the hamstrings produced by the combined muscles’ intrinsic force production and extrinsic stretch of this mechanism potentially stretches the contracting hamstring muscle beyond its elastic capabilities, leading to its failure.12,32 Although proximal hamstring avulsions can potentially occur during the same actions as the localized hamstring strains, most appear in association with activities such as water skiing with stretch applied to the muscle and not due to unopposed muscle activity.4,29,32,33 It is believed that an awkward stance is achieved, as water skiers are being pulled out of the water during skiing, where the knees remain extended and the back and hips are forcibly hyperflexed over the lower extremity.33 The exaggerated hip flexion and knee extension can create incredible strain in the hamstrings and lead to avulsions at the origin.33 This can occur in other conditions, such as when an American football player is tackled to the ground while sitting with hips flexed and knees extended, and another player lands on his back forcing hyperflexion of the back and hips. It has also been observed in sprinters as they lose balance or when athletes do a split on wet grass, pushing the forward extremity in forced knee extension and hip flexion. These proposed mechanisms can create tremendous stretch-induced strain in the hamstrings and may lead to avulsion of the common origin.4,33

Diagnosis On visual inspection, there may be extensive ecchymosis, swelling, and dramatic bruising in the thigh, as this injury causes a persistent and remarkable intramuscular hematoma and edema.7,8,10,34 Examination with the patient lying in prone position is ideal, and allows for easy identification of the characteristic knee flexion weakness observed with this injury.6 In the supine position, there often is an appreciable increase in flexibility of the injured side. With complete avulsions, an appreciable increase in knee extension with hip flexed at 90° in the injured knee is found when compared with the contralateral extremity. The injured may have decreased tone or tension in the cords as palpated distally at the knee. Decreased but not absent hamstring strength is often noted during examination with complete avulsions,4-6,10,35 as about 25% of the total hamstring force can remain with an intact short head of biceps femoris. A palpable gap in the proximal hamstring attachment and a prominence of the retracted muscle bells may be apparent in some cases.4,29 According to clinical reports, efforts to detect this gap during

E.S. Abebe, C.T. Moorman, and W.E. Garrett Jr

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focal T2-signal hyperintensity, especially between the tendon edge and ischial tuberosity (Fig. 1).4 Chronic avulsions can show lightened color of injured muscles, indicating changes of muscle atrophy (Fig. 2).

Disabilities

Figure 1 T2-weighted coronal MR image showing complex avulsion of the hamstring origin from left ischium. The arrow indicates the ischial surface and arrowhead marks retracted tendon fragment.

physical examinations maybe impeded by the prominent hematoma in the infragluteal rim.2,10,30 It may also be too painful to the patient to demonstrate these findings during examination in the acute cases of this injury. Although both magnetic resonance (MR) imaging or ultrasound can help confirm the diagnosis,4-6,10,20 MR is considered the most accurate tool for diagnosis of proximal hamstring injuries.4,6,10 Normal hamstring origin has homogeneously low signal on all pulse sequences, including at the interface of the tendon and cortical bone of the ischial tuberosity. In the acute setting, MR images of proximal avulsion injuries can display

Patients typically report a sensing pop or snap during the tear, with an immediate disabling posterior thigh pain.4,21 This pain is often in the region from the buttock to mid-thigh and accompanied with weakness or giving away of the affected lower extremity.11 Injury may cause mild hip extension and knee flexion weakness,3 and disallow patients to participate in sporting activities that involve running.7,9,30 Sitting on the affected side is very painful, and the injured may shift to sit on the contralateral buttock to alleviate this discomfort.3,4,10 Other commonly documented symptoms include poor leg control and instability of knee joint while walking due to lowered hamstring– quadriceps strength ratio.11 Patients may be asymptomatic during jogging exercises, but frequently sense poor knee control during swing phase and are often unable to decelerate knee to extension in sprinting activities.11 In the chronic setting, the hematoma accompanying this injury maybe slow to resolve and potentially act as an inflammatory irritant to the injured tissue affecting both scarring and healing.10 The scar pattern associated with this injury is also thought to compress the sciatic nerve and lead to the development of hamstring syndrome or pain in the sciatic distribution, such as local posterior buttock pain and discomfort over the ischial tuberosity.3,36,37 This pain is believed to prolong functional impairment and disability seen in pa-

Figure 2 (A) T2 Coronal MR image of chronic complete hamstring avulsion 14 months from injury. The arrowhead shows distally retracted hamstring muscle bellies. (B) Axial MR image of same patient showing obvious lightened color of injured muscles indicating changes in muscle atrophy.

Proximal hamstring avulsion injuries tients.4,7,10 Atrophy of the hamstring muscles4 (Fig. 2 ) and recurrent tightness are also frequently documented in chronic injuries.11 For these reasons, nonoperative treatment of patients who engage in athletic activities with proximal hamstring avulsion is believed to have poor prognosis and many favor early surgical intervention.4,6,7,29,32,35

Treatment Although operative management is rarely considered in the setting of most muscle strains, the dense collagenous proximal attachment of the hamstring makes surgery a realistic consideration with some proximal hamstring muscle avulsions.3,6 Currently, the treatment for all muscle strains in the acute setting involves the use of the RICE mnemonic device (Rest, Ice, Compression, and Elevation).3,6 The available published data calls for the nonsurgical management of single tendon avulsion with ⬍2 cm of retraction because such tendon ruptures can scar to intact structures and allow return to full strength.3 Thus, they are managed with nonsteroidal anti-inflammatory drugs, therapeutic stretches, and exercises, and patients gradually return to athletic activities.3,6,8 Proximal hamstring ruptures involving 2 or more tendons are managed surgically to avoid long-term hamstring disability and the technical difficulties of delayed surgical intervention. Nonoperative management of proximal avulsions has poor prognosis and may result in failed rehabilitation for active patients.4,30 Recent evidence suggests that while acute repair allows easier mobilization of tendons and permits repair to the ischial tuberosity, chronic rupture repairs are frequently complicated by difficulty involved in sciatic nerve identification and by retracted tendons.3,4,30 In general, the published data seem to advocate early surgical intervention with proximal hamstring strains.4,30

Conclusions The hamstring muscle group control motion at 2 joints and are recruited in unique ways during various activities. These muscles generate great forces for lower limb motion and are subjected to many stressful intrinsic and extrinsic loads that can lead to different lesions. Proximal avulsions from the origin on the ischium are an important subset of these lesions that need to be recognized early and respond well to operative management. Complete ruptures involving 2 or more tendons can be very disabling, cause persistent hematomas, and lead to painful sciatic pain if left untreated. Early operative treatment may help avoid the complications of chronic injury, and the unique dense collagenous tendon of the hamstring at the proximal site of injury makes surgical repair a realistic option with such injuries. In this article, we attempted to summarize the anatomy, function, clinical features, and course of these hamstring avulsions. More extensive treatment options will be discussed in detail later in this edition.

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