Patients who experience dislocations, fractures, infections, or pain usually maintain close orthopedic follow-up. Significant wear of the prosthesis damages the socket; osteolysis can cause irreversible bone loss, fracture, and loosening. Massive acetabular bone loss is very difficult to reverse and creates major reconstruction challenges.
Figure 1A is a 2009 X-ray of a woman aged 44 years who underwent a THA after a motor vehicle accident in 1997 and who was advised to have a revision THA when seen in 2009.
Figure 3A is an X-ray of a man aged 71 years who had undergone THA 21 years earlier and had complied with routine follow-up. When his X-rays showed significant wear of the liner and some osteolysis, he was able to undergo a simple revision (Figure 3B).
Three-dimensional CT is useful for quantifying the presence and severity of osteolytic lesions, because plain radiographs may underestimate the amount of bone loss that is present.25 The CT in Figure 3C shows the magnitude of osteolysis that was underestimated by the preoperative plain X-rays (Figure 3A). Computed tomography scans are crucial for surgical planning in the setting of severe acetabular bone loss.
There is a wide spectrum of signs and symptoms that can occur in the setting of acetabular component failure. Pain is a common presenting symptom. Groin pain can represent acetabular failure; thigh pain may be correlated to femoral component failure.25 The clinical patient presentation ultimately depends on the underlying cause: an infection, polyethylene wear, instability, or aseptic loosening.25 Leg-length discrepancy, joint deformity, location of prior incisions, functional status, and baseline neurologic status should be evaluated and documented during the preoperative evaluation as well.25
Case Study Revision Options
The X-rays and CT scans for this case study patient showed that he was a possible candidate for the simplest revision surgery; an isolated liner exchange and replacement of the femoral head. When the original surgery was performed (1997), the only FDA approved PE liner was UHMWPE. To justify isolated liner exchange, the modular acetabular metallic shell also should be well-fixed and appropriately oriented.26 This is evaluated both preoperatively and intraoperatively.
If found to be well fixed with an appropriate orientation and locking mechanism, the UHMWPE liner could be replaced with a HXLPE liner and a larger metal femoral head for improved wear and stability. Acetabular revision is indicted for an asymptomatic patient who has progressive osteolysis, severe wear, or bone loss that would compromise future reconstruction.
Conclusions
Over the past several decades, THA has become recognized as an effective treatment option for the reduction of pain and disability associated with hip joint disease and is associated with successful clinical outcomes. The most frequently noted recommendations for trying to increase the life expectancy of an artificial hip replacement include maintaining a normal weight, keeping leg muscles strong, and avoiding repetitive squatting and kneeling.
As the number of primary THAs has increased and the average age of those undergoing a primary THA has decreased, the need for revisions has risen. Reviews have demonstrated that the most common causes for early total hip revision, regardless of component, included infection, instability/dislocation, and fracture, whereas wear is the most common reason for mid to late revisions.
The wear of all materials used has been shown to be greatest in the most active patients.
Studies continue to identify ways to potentially prevent or reverse osteolysis from wear debris. Alendronate therapy has been shown to prevent and treat PE debris-induced periprosthetic bone loss in rats.27 It also was successfully used in a case report of an asymptomatic woman aged 39 years who had rapid PE wear and aggressive periprosthetic osteolysis within just 2 years of a bilateral THA.28 Other areas of research on decreasing osteolysis in THA recipients include trials with mesenchymal stem cells, bone morphogenic proteins, and gene therapy.6
In the U.S., 46,000 revisions were performed in 2004 and this number is expected to more than double by 2030.4 Primary care providers are sure to encounter patients who will be in need of a hip revision procedure. It’s important for them to make sure that their patients who have undergone a THA are periodically seen for orthopedic follow-up. Despite the long history of primary THAs, there is still not a single technique and material to suit all patient characteristics.1 Unfortunately, the same currently applies to hip revision procedures.