Avascular necrosis (AVN), also known as osteonecrosis, occurs when bone tissue dies due to an interruption of its blood supply, most commonly affecting the femoral head of the hip joint. This loss of blood flow causes the bone structure to weaken and eventually collapse, leading to severe pain and disability. Total hip replacement (THR) is often proposed as a treatment for advanced disease, leading many patients to question if this major surgery serves as a definitive cure for avascular necrosis. This analysis explores the pathology of AVN and the role of hip replacement in managing this bone disease.
Understanding Avascular Necrosis
Avascular necrosis begins when the blood vessels supplying a section of bone become compromised, initiating localized bone death, or ischemia. The precarious circulation to the femoral head—the “ball” of the hip joint—makes it particularly vulnerable to this interruption. Without a constant supply of blood, the bone marrow and structural cells die, weakening the bone over time.
This process often progresses silently in the early stages, without significant pain or symptoms. As the necrotic bone tissue is no longer able to support the body’s weight, microfractures accumulate in the bone just beneath the joint surface. This eventually leads to a collapse of the joint surface, often visible on imaging as a “crescent sign,” which is the hallmark of advanced AVN. The collapse of the femoral head results in an irregular joint surface, leading to rapid cartilage breakdown, severe pain, and the development of osteoarthritis.
Non-Surgical and Joint-Preserving Interventions
In the earliest stages of avascular necrosis, before significant bone collapse has occurred, the focus of treatment is on preserving the native hip joint. Non-surgical options include lifestyle modifications, such as reducing or eliminating alcohol consumption and steroid use, which are common risk factors for the disease. Physicians may prescribe medications, including bisphosphonates to slow bone breakdown or blood thinners to improve blood flow. Reduced weight-bearing through the use of crutches is also frequently recommended.
When non-surgical management is insufficient, joint-preserving surgical interventions may be utilized to delay or prevent the need for total hip replacement. One common procedure is core decompression, where a surgeon drills channels into the necrotic area of the femoral head. This relieves pressure within the bone and creates pathways for new blood vessel growth. Core decompression is often combined with bone grafting or the injection of concentrated cells, such as stem cells, to fill the defect and promote bone healing. These joint-sparing methods are effective only for small lesions diagnosed before the joint surface has collapsed.
Total Hip Arthroplasty for Necrotic Bone
Once the femoral head has undergone structural collapse (Ficat-Arlet Stages III or IV), the damage to the joint is considered irreparable, and Total Hip Arthroplasty (THA) is the definitive treatment for advanced AVN. The procedure is necessary because the necrotic bone is structurally unsound and causes mechanical failure of the joint. The goal of the surgery is to eliminate the source of pain and dysfunction by removing the damaged tissue entirely.
During the THA procedure, the surgeon removes the destroyed femoral head and the damaged cartilage lining the hip socket (acetabulum). These natural components are then replaced with prosthetic implants, typically made of metal, ceramic, or plastic. The new components form a smooth, functional ball-and-socket joint that mimics the mechanics of the original hip. For AVN patients, cementless fixation is frequently used, allowing the patient’s natural bone to grow directly onto the implant surface to promote long-term stability. The surgery provides a mechanical solution to a biological problem, restoring the hip’s stability and function.
Patient Outcomes and Defining Success
Total hip replacement is effective in addressing the localized damage caused by avascular necrosis, but the term “cure” requires careful definition in this context. THR does not eliminate the underlying systemic conditions (such as steroid use or alcoholism) that may have caused the AVN. However, it effectively removes the necrotic bone and resolves the associated pain and functional limitation in that specific joint. Success is measured by significant pain relief and restoration of mobility.
Patient outcomes following THR for AVN are positive, showing marked improvements in functional scores and pain levels. Patients often experience significant pain reduction within the first year after surgery. Functional mobility, measured by scales like the Harris Hip Score, routinely shows substantial improvement from pre-operative levels. High patient satisfaction rates are common, allowing many to return to daily activities without restriction.
Despite positive short-term and mid-term results, the prosthetic joint is a mechanical device with a finite lifespan; thus, it is not a biological cure for the disease itself. Modern implants typically have a survival rate of 90% or higher at 10 years. Success is defined as eliminating pain and restoring function for the expected 15 to 25-year lifespan of the implant, after which a revision surgery may be necessary.