ACETABULAR FX'S: THE ROLE OF ARTHROPLASTY

Fracture of the acetabulum can result in damage to the articular surface that ranges from minimal to catastrophic. Hip arthroplasty may be required for more severe injuries due to marked articular surface damage, post traumatic degenerative changes, persistent malunion or nonunion, or occasionally avascular necrosis and destruction of the femoral head. These problems may be seen following both closed and open fracture treatment, but prior open reduction and internal fixation often makes subsequent THA more difficult due to soft tissue scarring and retained hardware. In select acute acetabular fracture cases with severe initial comminution of the joint, open reduction and fixation can be technically impossible or so clearly destined to early failure that initial fracture treatment with combined limited fixation and simultaneous THA is the best option, especially in osteoporotic elderly fracture patients. Problems which may be encountered during any THA in a patient with a prior acetabular fracture include: difficult exposure due to soft tissue defects and scarring, presence of heterotopic ossification, and nerve palsy from the original fracture or subsequent osteosynthesis. Retained hardware can present significant challenges and frequently is left in place or removed in part or completely, when intraarticular in location or blocking preparation of the acetabular cavity and placement of the cup. Additional potential problems include residual deformity and malunion, persistent pelvic dissociation or nonunion of fracture fragments, cavitary or segmental bone loss from displaced or resorbed bone fragments, and occasionally occult deep infection. Preoperative assessment and planning should include careful consideration of the most appropriate surgical approach, which may be impacted by the need for hardware removal. Screening laboratory studies and aspiration of the hip may prove helpful in excluding associated deep infection. Intraoperative sciatic nerve monitoring may be of assistance in patients with partial residual nerve deficits or where extensive posterior exposure and mobilization of the sciatic nerve is needed for hardware removal or excision of heterotopic ossification. Metal cutting tools to allow partial removal of long plates and adjunctive equipment for removal of broken or stripped screws should be routinely available during these cases. Careful preoperative planning regarding implant and reconstructive options can also ensure availability of proper components and equipment. Often implants and techniques developed for revision surgery for management of major bone deficiencies are needed. Reported results suggest that surgery is frequently prolonged, can be associated with greater blood loss and may result in increased risk of post-arthroplasty heterotopic ossification when compared to routine primary procedures. Bone stock and fracture union may be better in patients with prior internal fixation than in those with nonoperative treatment of major displaced acetabular fractures. Available long-term results document more durable results with lower rates of aseptic loosening with uncemented acetabular fixation compared to cemented acetabular components. These patients are at higher risk of revision and failure than patients undergoing THA for simple osteoarthritis, though initial short-term results are comparable to conventional hip arthroplasty patients, as long as early wound healing problems and deep infection can be avoided, which is a greater risk for acute THA for initial fracture care. The application of newer implant designs, highly porous ingrowth materials, and methods for management of acetabular bone deficiency developed for revision THA have helped improve results in this challenging subset of primary THA patients.