A 39-year-old man had a right total hip arthroplasty (THA) in 1996 at the age of 26 for degenerative changes of the hip caused by osteomyelitis he had as a child. Pain developed over the course of a week and was localized to the right buttock. He had no history of trauma. There were no constitutional symptoms to suggest an underlying infection. Other than having bilateral osteomyelitis of the hip as a child and the eventual THA, his medical history was unremarkable.
Physical examination identified an incision from a previous posterior approach. He walked with a limp and required the assistance of a cane. Hip range of motion with internal and external rotation re-created the right buttock and groin pain. The right leg was approximately 2.5 cm shorter than the left. Results of his neurovascular examination were normal.
Radiographic examination revealed a noncemented, right THA with asymmetric positioning of the femoral head within the acetabular cup ( Fig. 42.1 ), which was consistent with polyethylene wear. The femoral stem was in slight varus, and there was evidence of osteolysis around the cup. At least one of the acetabular screws was broken. Dysplastic changes were seen within the left femoral head along with secondary, severe degenerative changes.
A 72-year-old woman underwent a primary right THA in 1978, followed by multiple revisions. She was seen on a yearly basis because serial radiographs revealed excessive wear of the polyethylene insert, but there was no associated osteolysis, and she was not symptomatic. Eventually, the patient developed pain in the right groin. Radiographs ( Fig. 42.2 ) demonstrated severe, asymmetric polyethylene wear, with the femoral head articulating with the acetabular cup. Osteolysis was seen around the central and inferior portions of the acetabular cup. The patient also had an uncemented THA on the left with a minor column structural allograft.
A 68-year-old woman had a medical history of malignant melanoma and radiation therapy to the pelvis. She was cured of her cancer but suffered a right hip fracture as a result of the radiation treatment. A THA was performed at an outside hospital 5 years before she presented to our academic hospital with a pelvic discontinuity and a loose cup that protruded into the pelvis. The patient stated that she had an incision and drainage to address a possible infection shortly after her primary THA. Hip aspiration was performed, which was positive for a coagulase-negative Staphylococcus infection.
Radiographs revealed an obvious pelvic discontinuity, fracture of the medial wall, and central displacement of the acetabular component. There was also evidence of osteolysis of the proximal femur ( Fig. 42.3 ).
The evaluation and management of acetabular bone loss in revision total hip arthroplasty (THA) present challenges for the orthopedic surgeon. Detailed preoperative planning requires thorough patient evaluation, radiographs for assessing bone loss, and classification systems to guide the choice of treatment options and ensure good clinical results.
Indications for Revision
In Case 1, results of the laboratory investigations, including a complete blood cell count (CBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) level, were normal. Repeat radiographs of the right hip revealed progressive osteolysis surrounding the acetabular component, with bone loss likely occurring superior to and involving the posterior column. According to the Gross classification for acetabular bone loss, this was a type III defect. For young and active individuals requiring revision THA, the goal is to improve bone stock for future revision operations. An uncemented, porous (trabecular) metal cup (Trabecular Metal Acetabular System, Zimmer, Warsaw, Ind.) with a minor column structural graft using morselized autograft from acetabular reamings or morselized allograft was indicated for this type III defect.
In Case 2, the patient’s CBC, ESR, and CRP values were normal. The woman had a malpositioned, loose acetabular component with severe polyethylene wear. According to the Gross classification for acetabular bone loss, it was a type III defect. For older and less active individuals requiring revision THA, the goal is to stabilize and reconstruct the acetabulum at the correct level so that it will last a lifetime. An uncemented, porous metal cup with a metal augment was indicated for the type III defect.
In Case 3, a two-stage revision THA was required to eradicate the infection and reconstruct the pelvic discontinuity at a later date. In the first-stage revision, the patient received an antibiotic-loaded cement femoral spacer and an acetabular cage ( Fig. 42.4 ) and continued on intravenous antibiotics until infectious markers returned to normal. Most likely, the pelvic discontinuity was a result of previously irradiated bone.