Clinical History
The authors present a case of a 55-year-old man complaining of right hip bulge and pain radiating to the lower extremity. There's no history of trauma. This patient underwent previous imaging follow-up due to a renal cell carcinoma with no evidence of recurrence. An old ischiatic heterotopic ossification is known.
Imaging Findings
The imaging findings are described along the five figures of this exhibit and highlighted in the discussion section.
Discussion
A.
Injuries to the origin of the hamstring muscles can result in an avulsion fracture of the ischium, an avulsion of the ischial apophysis or a pure avulsion of the hamstring tendons themselves, depending on the patient's age. The ischial apophysis, a secondary ossification centre, appears at puberty and does not fuse until the early twenties. During this interval a sudden forcible hamstring contraction may cause avulsion of the apophysis itself, at a time when the link between cartilaginous apophysis and bone is weaker than that between tendon and apophysis [1]. In rare instances, a skeletally mature patient may avulse a fragment of ischium.
B.
The clinical presentation implies better evaluation of the known ossification and other related or non-related lesions.
C.
The previous follow-up CT images available (Fig. 1) show an ossification adjacent to the right ischial tuberosity demonstrating medular and bony cortex. Degenerative changes are present indicating chronicity. MR imaging was further obtained (Fig. 2, 3, 4, 5) depicting solely the elongated shaped known ossification that shows attachment of the hamstrings tendons with signal intensity equal to normal bone.
Taking into account the location and absence of previous history of trauma the image findings are suggestive of an old apophyseal avulsion of ischial tuberosity and are less likely due to a soft-tissue tumour-like lesion, such as myositis ossificans, or soft tissue tumour (sarcoma).
Furthermore the apophyseal avulsion induces great narrowing of the right ischiofemoral space (7mm), simulating an ischiofemoral impingement syndrome [2]. Consequently, injury and atrophy of the quadratus femoris muscle occurs [3], as shown in Figure 4.
D
Apophyseal avulsion lesions are rare injuries in the general population and are often initially misdiagnosed as a simple ‘hamstring pull’, leading to the development of chronic pain and disability. Delayed diagnosis can lead to a chronic atrophy of hip muscles and other structures around the hip joint [4].
We prescribed nonsteroidal anti-inflammatory drugs, gabapentin for radiating pain, and exercise programs for stretching of the hip muscles.
Displaced injuries of the ischial apophysis and pure tendon avulsions are probably best treated surgically in the acute setting [5].
E
Injury to the hamstring origin depends on the skeletal maturity of the patient. In rare instances, an avulsion of the ischial apophysis may narrow the ischiofemoral space and induce quadratus femoris damage. This situation leads to potential chronic hip pain and referred pain due to irritation of sciatic nerve caused by the proximity of the oedematous quadratus femoris muscle.
Differential Diagnosis List
Ischial apophyseal avulsion (hamstring avulsion)
Ischial apophyseal avulsion;
Old ischial tuberosity fracture with degenerative changes;
Fratured ischial osteochondroma;
Myositis ossificans;
Sarcoma (extraskeletal chondrosarcoma);
Final Diagnosis
Ischial apophyseal avulsion (hamstring avulsion)
