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.
The imaging findings are described along the five figures of this exhibit and highlighted in the discussion section.
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.
Ischial apophyseal avulsion (hamstring avulsion)
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1. From the provided pelvic CT cross-section (Figure 1), a mature heterotopic ossification can be observed near the right ischial tuberosity. It presents as a bony shadow with cortical and medullary structures, indicating that it is not a newly formed ossification but a chronic bony change.
2. MRI (Figures 2, 3, 4, 5) shows that this ossified lesion is spindle-shaped, with signal characteristics similar to normal bone, and is connected to the hamstring tendon attachment site. There is no evident soft tissue mass or indication of any new lesion.
3. The right ischiofemoral space is markedly narrowed, with the narrowest portion measuring about 7 mm, suggesting a potential risk of ischiofemoral impingement.
4. In the region of the right quadratus femoris, there is a certain degree of muscle atrophy and abnormal signal, potentially related to long-term chronic impingement or post-injury changes at the tendon-bone attachment site.
Based on the current imaging findings and the patient’s medical history, the following diagnoses or differential diagnoses should be considered:
1. Chronic Ischial Tuberosity Apophyseal Avulsion: During adolescence, before the apophysis fuses with the main bone, sudden violent pulling can cause an avulsion. If left unnoticed or untreated at the time, heterotopic bone may form over the long term, leading to chronic pain and structural changes.
2. Myositis Ossificans: Although heterotopic ossification can also develop in soft tissues, it often appears after trauma with characteristic calcification patterns in different stages. In this case, the lesion is mature, well-defined, and closely related to the muscle attachment, making this diagnosis less likely.
3. Soft Tissue Tumor or Sarcoma: This possibility arises when there is an abnormal soft tissue mass, bone destruction, or destructive bony changes. However, given the lesion’s distinct bony structure, smooth borders, and lack of obvious infiltration or bone destruction, malignancy is relatively unlikely.
Considering the patient is 55 years old, has no significant history of trauma, exhibits stable imaging findings of tendon attachment around the lesion, along with associated narrowing of the ischiofemoral space and quadratus femoris atrophy as chronic changes, the most likely diagnosis is:
“Chronic Ischial Tuberosity Apophyseal Avulsion with Secondary Ischiofemoral Impingement Syndrome”.
Currently, there are no evident signs of malignancy, nor are there findings consistent with an acute avulsive fracture or acute muscle injury.
1. Conservative Treatment:
- Medications: Consider using non-steroidal anti-inflammatory drugs (NSAIDs) to relieve pain and reduce inflammation. For sciatic nerve radicular pain, adjunct nerve modulators (such as gabapentin) may be employed.
- Physical Therapy and Rehabilitation Exercises: Focus on alleviating discomfort associated with the narrowed ischiofemoral space. Modalities such as heat therapy, ultrasound therapy, or shockwave therapy can be used to promote local blood circulation and tissue repair.
- Exercise Prescription:
• Begin with low-intensity, short-duration hip and lower-limb exercises, such as seated leg extensions and supine leg lifts, at a frequency of 3-4 times per week for 15-20 minutes per session.
• As symptoms improve, progressively increase both the difficulty and intensity of exercises, including hip extension, external rotation training, and more sets of core and lower-limb strengthening exercises.
• Follow the “FITT-VP” principle: gradually increase Frequency and Intensity, manage Time and Type of each session, and monitor your Volume/Progression.
• Monitor symptoms and soft tissue response closely. Reduce intensity or pause specific exercises if marked pain or discomfort occurs.
2. Surgical Treatment:
- In cases of significantly displaced bony fragments, soft tissue or tendon rupture, or severe ischiofemoral impingement symptoms unresponsive to conservative management, surgical intervention such as reduction, repair, or removal of large bony fragments may be considered to improve structural relationships.
- Postoperative care should include systematic rehabilitation, with close attention to wound healing and the functional restoration of local muscles.
Disclaimer:
This report is based on existing data and medical experience for clinical reference only and cannot replace face-to-face consultation or professional medical advice. Hospitals or specialists should integrate the patient’s actual condition, further examination results, or pathologic evidence for final diagnostic and therapeutic decisions.
Ischial apophyseal avulsion (hamstring avulsion)
