Transient Regional Osteoporosis

Transient Regional Osteoporosis

Transient regional osteoporosis is an often missed diagnosis. It is also known as transient regional osteoporosis and transient osteoporosis of pregnancy. Unlike senile osteoporosis, which is a disease of aging with a strong predilection for postmenopausal women, transient regional osteoporosis is a disease that affects otherwise healthy females in their third trimester of pregnancy and healthy middle-aged males. Transient regional osteoporosis most commonly affects the hip, with the knee, foot, and ankle also affected. The onset of this painful condition is spontaneous and acute, without any obvious predisposing factors. The pain of transient regional osteoporosis is exacerbated by weight bearing and activity. There is rarely a history of antecedent trauma to the affected joint. The vast majority of cases are unilateral, although bilateral cases can occur. A joint effusion is common as is the identification of regional bone loss surrounding the affected joint on plain radiograph as the disease progresses. Magnetic resonance imaging will invariably demonstrate bone marrow edema of the affected joint. In spite of the severity of symptoms, spontaneous recovery is the rule rather than the exception.

Etiopathogenesis of Transient Regional Osteoporosis

  • • Chronic regional pain syndrome I
  • • Chronic regional pain syndrome II
  • • Microvascular injury or compromise
  • • Metabolic abnormalities
  • • Viral infection
  • • Neurogenic causes
  • • Endocrinopathies

What are the Symptoms of Transient Regional Osteoporosis

Physical examination of patients with transient regional osteoporosis reveals pain with active range of motion of the affected joint that is exacerbated with weight bearing. The pain is centered around the affected joint with hip pain radiating to the groin and anterior thigh. Associated soft tissue edema may be identified with deep palpation of the joint. The pain may be so severe that the patient may guard the affected joint to avoid increasing the pain.

How is Transient Regional Osteoporosis diagnosed?

There is no specific laboratory test that will reliably diagnose transient regional osteoporosis. Plain radiographs are indicated in all patients with transient regional osteoporosis to confirm the diagnosis as well as to rule out other underlying occult bony pathological processes that may be responsible for the patient’s symptomatology.

Based on the patient’s clinical presentation, additional tests, including complete blood cell count, uric acid, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated. Pregnancy testing is indicated in all females. Magnetic resonance imaging (MRI) of the hip is indicated in all patients suspected to have transient regional osteoporosis as a characteristic bone marrow edema will be evident early in the course of the disease on T1-weighted, short-tau inversion recovery, and fat-suppressed T2-weighted imaging. If the diagnosis is unclear, administration of gadolinium followed by postcontrast imaging may help delineate the adequacy of blood supply.

Computed tomography (CT) scanning may provide additional information regarding the condition of the hip joint and guide treatment decisions if fracture is present. Bone density testing may also help quantify the extent of osteoporosis.

Electromyography is indicated if coexistent lumbar radiculopathy, plexopathy, or both are suspected. A gentle injection of the hip joint with small volumes of local anesthetic provides immediate improvement of the pain and helps show the nidus of the patient’s pain is, in fact, the hip.

Differential Diagnosis

Arthritis and gout of the hip joints, bursitis, and tendinitis may coexist with transient regional osteoporosis and exacerbate the pain and disability of the patient.

Tears of the labrum, ligament tears, bone cysts, avascular necrosis, bone contusions, bone fractures, reflex sympathetic dystrophy, and occult metastatic disease also may mimic the pain of transient regional osteoporosis.

The early bone marrow edema seen on magnetic resonance testing that is characteristic of transient regional osteoporosis is an uncommon early finding in patients suffering from avascular necrosis. Septic arthritis may occasionally cause regional osteoporosis that may mimic transient regional osteoporosis.

Treatment

Initial treatment of the pain and functional disability associated with transient regional osteoporosis should include a combination of nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and decreased weight bearing of the affected hip or hips. Local application of heat and cold may be beneficial.

Intermittent traction of the affected joint and non-weight bearing rest may provide additional relief. An injection of a local anesthetic into the hip joint may be a reasonable next step to provide palliation of acute pain. Vigorous exercises should be avoided because they would exacerbate the patient’s symptoms.

Consideration of oral or intravenous anti-resorptive bisphosphonates should be considered in all non-pregnant patients.

Anecdotal reports suggest that calcitonin may be considered in pregnant women suffering from transient regional osteoporosis.

Complications and Pitfalls

The major pitfall when caring for patients with transient regional osteoporosis is misdiagnosis.

If the patient’s symptoms and radiographic findings are incorrectly diagnosed as avascular necrosis, the patient may be subjected to major surgical interventions such as joint preservation surgery and total joint arthroplasty.

Conversely, if the regional osteoporosis associated with a septic joint is misdiagnosed as transient regional osteoporosis, delays in the initiation of antibiotic therapy may result in additional joint damage.

Failure to correctly diagnose transient regional diagnosis may lead to unnecessarily treating significant transient regional osteoporosis surgically, which usually results in continued pain and disability and in most patients leads to ongoing damage to the hip.

Injection of the joint with local anesthetic is a relatively safe technique if the clinician is attentive to detail, specifically using small amounts of local anesthetic and avoiding high injection pressures, which may damage the joint further.

Another complication of this injection technique is infection. This complication should be exceedingly rare if the clinician adheres to strict aseptic technique. Approximately 25% of patients report a transient increase in pain after this injection technique and should be warned of such.

Clinical Pearls

Transient regional osteoporosis is a diagnosis that is often missed, leading to much unnecessary pain and disability.

The clinician should include transient regional osteoporosis in the differential diagnosis of all patients with hip pain, especially if any of the predisposing factors listed below are present. Coexistent arthritis, tendinitis, and gout may contribute to the pain and may require additional treatment.

The use of physical modalities, including local heat and cold and decreased weight bearing, may provide symptomatic relief.

Vigorous exercises should be avoided because they would exacerbate the symptoms and may cause further damage to the hip.

Simple analgesics and NSAIDs may be used concurrently with this injection technique.

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