Final answer:
The most common complication post-THA for AVN of the femoral head is thrombophlebitis, which can result in serious conditions like pulmonary embolism.
Step-by-step explanation:
The most common complication in total hip arthroplasty (THA) performed for avascular necrosis (AVN) of the femoral head, regardless of etiology, involves postoperative issues such as thrombophlebitis (deep vein thrombosis or DVT) and the potential for pulmonary embolism (PE). AVN itself is a result of disrupted blood supply leading to the death of bone and cartilage. THA is a significant surgical intervention and, while it helps alleviate the pain and loss of mobility due to AVN or osteoarthritis, it comes with risks. These include infection, dislocation of the new joint, and blood clot formation. Deep vein thrombosis is particularly concerning because it can break loose and cause a pulmonary embolism, a critical and potentially life-threatening condition.