Figure 1. Anteroposterior radiograph of the pelvis.
Figure 2. Sagittal STIR magnetic resonance imaging of the pelvis.
A 42-year-old man presents to the office with severe left buttock pain after lifting a heavy object in his garage 3 days ago. He has developed bruising in the left buttock area over the last day. On physical examination, he is very tender over the ischial tuberosity on the left and has very weak hamstring strength. Imaging of the pelvis shows no evidence of a bony avulsion fracture (Figure 1). Sagittal short-TI inversion recovery (STIR) magnetic resonance imaging (MRI) of the pelvis (Figure 2) shows an avulsion tear of the conjoined tendon of the biceps femoris, semitendinosus, and semimembranosus with 5 cm of distal retraction.
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The 3 hamstring muscles — semimembranosus, semitendinosus, and biceps femoris — attach to the pelvis at the ischial tuberosity. The biceps femoris has a long head that attaches to the ischial tuberosity and a short head that attaches to the mid-femur.
The hamstring muscles can tear with a sudden extension of the knee in a flexed position or a sudden contraction of the hamstrings. Most tears are muscular (better described as a strain) and occur near the midpoint of the hamstrings. Proximal avulsion injuries, where the hamstring tendons avulse off the ischial tuberosity, represent a more severe injury. Patients with proximal injuries have trouble sitting, ecchymosis in the buttocks a few days after the injury, and severe hamstring weakness.1,2
Radiographs should be taken in all patients with a suspected proximal rupture to rule out bony avulsion fracture, which is common in the pediatric population. MRI is the study of choice to determine the extent of proximal avulsion injuries.1 Nonoperative treatment is indicated with hamstring strains, single tendon proximal tears, and 2 tendon proximal tears with less than 2 mm of retraction. Surgical repair is indicated when all 3 tendons are torn off the ischial tuberosity or if there is more than 2 mm retraction from 2 tendons.1,2
Acute repair should be performed within 4 weeks of the injury or the tendon begins to retract and becomes difficult to repair.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopaedics for Physician Assistants.
1. Alzahrani M, Aldebeyan S, Abduljabbar F, Martineau PA. Hamstring injuries in athletes: diagnosis and treatment. JBJS Rev. 2015;3(6):e5. doi:10.2106/JBJS.RVW.N.00108
2. Cohen S, Bradley J. Acute proximal hamstring rupture. J Am Acad Orthop Surg. 2007;15(6):350-355. doi:10.5435/00124635-200706000-00004