Transient Osteoporosis of the Hip - An Overview

What Is Transient Osteoporosis of the Hip?

Transient osteoporosis of the hip (TOH) is an uncommon disorder marked by temporary bone depletion and weakening, particularly in the upper femur. Those afflicted often encounter abrupt onset of pain that intensifies with weight-bearing activities involving the affected hip, such as walking or standing.

This discomfort typically progresses and may eventually become severely limiting. Although transient osteoporosis of the hip can be debilitating, it generally follows a self-limiting course, resolving spontaneously within a specified timeframe. Typically, throughout six to 12 months, the distressing symptoms diminish gradually, and the bone integrity in the hip usually restores to baseline for most patients.

While transient osteoporosis primarily impacts the hip, it can also manifest in the ankle, foot, or knee. This condition typically afflicts otherwise healthy individuals aged 30 to 60, with a higher prevalence observed in men. This condition is also seen in women during the final trimester of pregnancy or shortly after childbirth.

What Is the Cause of Transient Osteoporosis of the Hip?

The exact etiology remains elusive, though researchers have posited various hypotheses to elucidate its onset.

• Fluctuations in hormones during pregnancy can impact bone metabolism and contribute to hip bone demineralization.

• Vascular occlusion around the hip can result in transient bone demineralization and subsequent discomfort.

• Atypical mechanical strains or loading on the hip bone.

• Non-traumatic reflex sympathetic dystrophy is a persistent limb disorder characterized by severe pain and inflammation.

• Viral infections that enhance bone resorption.

• Dysregulation of bone metabolism.

• Neurological factors impact bone health and vascular function.

What Are the Phases of Transient Osteoporosis of the Hip?

The progression of transient osteoporosis of the hip is typically divided into three distinct phases:

• Initial Phase: This phase is marked by a sudden onset of pain accompanied by limited movements, lasting approximately one month from symptom onset.

• Middle Phase: During this phase, the signs and symptoms stabilize without worsening. It typically lasts one to two months. X-rays in this phase may reveal osteopenia, indicating a decrease in bone density.

• Final Phase: In the final phase, symptoms spontaneously regression, with gradual improvement in pain and functional limitations. This phase can extend for a longer duration, up to approximately four months from the initial onset of symptoms.

What Are the Symptoms of Transient Osteoporosis of the Hip?

The symptoms of transient osteoporosis of the hip are distinct and include:

• The condition is characterized by an abrupt onset of pain near the hip joint, buttocks, or groin.

• Increased pain with weight-bearing activities.

• Gradual worsening of pain over weeks or months as the condition advances.

• Relief or reduction of pain when the affected hip joint is rested.

• Absence of any history of hip trauma.

• Restricted range of motion in the affected joint.

• Development of a limp or gait alteration to reduce pressure on the affected hip joint.

What Is the Diagnosis of Transient Osteoporosis of the Hip?

The diagnosis requires a comprehensive evaluation of symptoms and a thorough medical history review, including the onset of symptoms, the identification of triggers, and any prior hip injuries. The physician will evaluate the hip joint through specific movements during the physical assessment. In cases of transient hip osteoporosis, patients typically report heightened discomfort during active movements (self-initiated hip movements) in contrast to passive movements (movements conducted by the physician).

Imaging studies, such as X-rays, may be requested to confirm the diagnosis and exclude other potential causes of hip pain. In X-rays, during the early phases of transient osteoporosis, typically within the initial six weeks of symptom onset, subtle changes in bone density of the femoral head may be observed, albeit challenging to discern due to their slight nature. As the condition advances over several months, X-ray findings become more evident, showing significant and pronounced loss of bone density. Nevertheless, the joint space is generally maintained. This gradual bone loss can ultimately result in a nearly complete disappearance of the femoral head on X-ray images.

Alternative imaging techniques, such as computed tomography (CT) scans and magnetic resonance imaging (MRI), can offer more detailed visualization and early detection of bone changes. MRI, particularly, is highly adept at identifying soft tissue injuries around the hip and can reveal bone marrow edema—a key characteristic of transient osteoporosis—wherein the bone marrow within the bone’s central region becomes inflamed and fluid-filled. Furthermore, in nuclear medicine, bone scans or bone scintigraphy involve injecting a radioactive tracer into the bloodstream, which accumulates in areas of bone loss. Specialized gamma cameras then detect radioactive emissions from the bones, providing valuable information about bone metabolism and areas affected by osteoporosis.

Although blood tests may not directly aid in diagnosing the disease, they can be instrumental in ruling out alternative causes such as vitamin deficiencies, underlying systemic conditions, or endocrine disorders. For pregnant women, caution is warranted with imaging modalities involving radiation due to potential risks to the developing fetus. However, MRI can be considered a safer alternative. Pregnant individuals should always engage in thorough discussions with healthcare providers to make informed decisions about their care and imaging options.

What Is the Management of Transient Osteoporosis of the Hip?

Given the self-limiting nature of transient osteoporosis of the hip, management primarily revolves around symptom relief and prevention of additional bone loss.

Strategies for managing transient osteoporosis of the hip encompass:

• Utilizing non-steroidal anti-inflammatory drugs (NSAIDs) such as Naproxen or Ibuprofen can effectively mitigate inflammation and alleviate pain associated with transient osteoporosis of the hip.

• To mitigate stress and the risk of potential fracture in weakened bones affected by transient osteoporosis of the hip, healthcare providers frequently advise restricting weight-bearing activities on the affected hip. Using a walker or cane can provide additional support and stability, reducing stress during walking.

• Engaging in physical therapy plays a pivotal role in maintaining strength, enhancing flexibility, improving joint function, and easing movements.

• Ensuring adequate calcium and vitamin D intake is paramount for maintaining optimal bone health.

Conclusion:

Transient osteoporosis of the hip presents as a painful hip joint condition, but the outlook is usually optimistic, as symptoms tend to improve, and bone strength recovers naturally with time. When managed effectively, this condition commonly resolves within a timeframe of two to nine months. Nonetheless, in a minority of instances, typically a small proportion, there is a potential for the condition to recur later in life.