By: Peter Sallay MD
Anyone watching John McEnroe playing Michael Chang in last year’s Roger’s Legends Cup match understands the potential severity of hamstring injuries. Forced to stretch wide to return a baseline shot Johnny Mac went down in a heap with an anguished grimace on his face. His hamstring injury sidelined him from playing in senior events for months prompting him to say “It is hell to get old!” Hamstring injury is quite common in a variety of sports especially those requiring sprinting and sudden changes in direction such as soccer, rugby, football, and track and field. There have been numerous studies analyzing the incidence, cause, and possible prevention in these sports. The incidence and prevalence of hamstring muscle injuries in tennis has not been adequately studied. Several studies have examined the occurrence of aggregate injury with muscle strain injuries lumped together in a subcategory of injury. Pluim et al (1) reviewed the literature and found that there was a great variation in the method of reporting tennis injuries which made it difficult to compare studies. They found that most acute injuries occurred in the lower extremities whereas upper extremity injury dominated chronic conditions. Presumably a subset of lower extremity injuries included hamstring strains. Presently the incidence (injury/player hr) remains unknown.
The mechanism of injury typically involves the act of sprinting or being forced to assume a “hurdlers stretch” or “splits” position. Visualize Kim Clijsters stretching wide to retrieve on the baseline and you get the picture. The injury results from simultaneous eccentric contraction of the muscle while the muscle is lengthening. Because the hamstring muscle crosses two joints it is believed that there is increased excursion of the muscle due the hip being flexed while the knee is relatively extending. The resultant overload causes injury to the muscle-tendon junction or less frequently the tendons themselves.
Hamstring injuries are classified by anatomical location and severity. The vast majority of hamstring injuries occur at the level of the proximal muscle-tendon junction (MTJ) (2). The muscle tendon junctions of the hamstring muscles are several centimeters in length typically extending one third the distance of the entire muscle. Histological and MRI studies have shown that a muscle-tendon strain injury is a physical disruption of the muscle fibers at the level of attachment to the tendon. The extent of the injury determines the severity of the strain. Grade 1 strains involve a small portion of the MTJ and clinically result in minimal swelling and loss of motion and strength. Grade 2 injuries involve a larger amount of stripping of the MTJ and are associated with swelling, bruising, and varying degrees of loss of strength and motion. Grade 3 injuries involve most if not complete discontinuity of the MTJ with severe swelling, bruising and profound loss of strength. Less frequent injuries occur at the proximal and distal tendon insertions. In growing adolescents ischial apophyseal fracture can occur effectively disconnecting the proximal common hamstring origin. Proximal avulsion of the hamstring tendon is most common in adults in the fourth decade of life. These injuries are never associated with a bony injury and typically are the result of a higher energy external force. Waterskiing injuries are the most common sport associated with proximal tendon tears (3). These tears can be partial or complete rendering the muscle essentially non-functional.
The clinical presentation includes antalgic protective gait, varying degrees of swelling and bruising. Bruising typically is present no sooner than 3-4 days post injury. With higher grades of injury one may see bruising which has extended into the lower leg and foot. Examination of the acutely injured patient can be hampered by pain, spasm and induration from swelling. Patients with high grade strains and tendon avulsions will have a defect and slack tendons indicating complete discontinuity. These injuries should be further investigated and carefully classified as the treatment may require surgery.
Imaging studies are typically not required for low grade strains. In cases of suspected high grade strain or tendon avulsion an MRI is advised. The scan is useful for both treatment decision as well as prognosis.
Treatment for strain injuries is divided into phases. The acute phase (1-7 days) involves rest, ice, and a compressive wrap. Early motion is advised to prevent adhesion formation. During the subacute phase (1-3 weeks) treatment progresses to include submaximal muscle contractions. More robust concentric strengthening can be added when range of motion and pain are minimal. The remodeling phase (up to 6 weeks) adds eccentric training and more vigorous stretching. The final phase (6 weeks-6 months) includes functional sports specific exercise and a gradual progression back to unrestricted sports. Complete proximal tendon avulsions in athletically active individuals require surgical repair in order to increase the chance of returning to pre-injury competition (3). Failure to diagnose and appropriately treat this injury can lead to marked functional impairment. Surgical repair of acute tears has been demonstrated to have a high percentage of satisfactory results with a majority of athletes returning to sports. Chronic tears are often difficult to repair and can lead to suboptimal results due to muscle contracture, scarring and atrophy.
Numerous factors are thought to predispose to injury including advancing age, previous injury, flexibility, strength, fatigue, core stability, and muscle architecture(4,5). Of these factors prospective studies have implicated age and previous injury as statistically significant factors (3,5). Some authors have shown that a preseason focused prevention programs in soccer can reduce the risk of injury during the following season (4). Advancing age leads to tendon inflexibility and degenerative change which lowers the threshold for injury. This is the one factor that is currently not preventable. Sorry Johnny Mac. There is no cure for what ails you and the rest of us over 50!
References:
Pluim BM, Staal JB Tennis injuries: occurrence, aetiiology, and prevention. Br J Sports Med. 2010; 40:415-423.
Garrett WE, Rich FR, Nikoloau PK Computer tomography of hamstring muscle strains. Med Sci Sports Exerc. 1989;21:506-514.
Sallay PI Diagnosis, classification, and management of acute proximal hamstring avulsion injuries. Op Tech Sports Med. 2009;17(4):196-204.
Mendiguchia J, Alentorn-Geli E, Brughelli M Hamstring strain injuries: are we heading in the right direction? Br J Sport Med. 2012;46(2):81-85.
Petersen J, Holmich P Evidence based prevention of hamstring injuries in sport. Br J Sports Med. 2005;39:319-323.
Dr. Sallay has been practicing orthopedic surgery in Indianapolis, Indiana for 18 years. He completed his orthopedic surgery residency at Indiana University Medical School and his sports medicine fellowship at Duke University Medical School. He served as the ATP orthopedic consultant for the RCA tennis championships, later known as the Indy tennis championships, for 13 years. He is currently serving as president of Methodist Sports Medicine in Indianapolis.
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