Jess H. Lonner

Recognizing persistent infection after resection arthroplasty and implantation of cement spacers in the infected total knee arthroplasty is often difficult. The purpose of this study was to determine whether aspiration of the knee after resection arthroplasty is valuable for determining the presence of ongoing infection. Thirty-four previously infected knees that were aspirated and cultured after resection arthroplasty, implantation of cement spacers, and intravenous antibiotics for an average of 6.3 weeks were identified. There were 8 cases of persistent infection-none identified on preoperative aspiration. Two preoperative cultures were false positive for Staphylococcus epidermidis. Preoperative cultures were negative in 32 knees, with 8 false-negative results. The antibiotic-free interval among all cases averaged 20 days; the cases with false-negative results from aspiration had an antibiotic-free interval averaging 11.5 days, compared with an average of 26 days among all other cases. Aspiration of knees after resection arthroplasty had sensitivity of 0%, positive predictive value of 0%, and accuracy of 71%. Specificity was 92%, and negative predictive value was 75%. A negative result from joint aspiration after resection arthroplasty does not necessarily rule out the presence of ongoing infection. False-negative results may be observed if joint aspiration is not delayed more than 2 to 3 weeks.

Spontaneous osteonecrosis of the tibial plateau involves a continuum of change observed in the subchondral zone that is commonly associated with early and mid stages of osteoarthritis. The typical patient is an elderly woman who experiences a sudden onset of pain in the medial aspect of the knee. The diagnosis of this under-appreciated clinical entity may be difficult, but careful examination and judicious use of imaging studies, as well as a high index of suspicion, may facilitate the accurate diagnosis. Although the radiographs may initially be normal (with the exception of mild arthrosis), radionuclide scans and MRI can be of great value. The MRI studies usually show a decreased signal intensity on a T1-weighted image, but may be normal in the early course of the disease. The T2-weighted images and fat suppression views are helpful in establishing a diagnosis and determining the extent of involvement. Recognition of this problem may help to avoid unnecessary intra-articular surgery. Many of these patients have complete or partial resolution of symptoms by 1 year, after a period of protected weight bearing. Nonetheless, surgery may be necessary for more advanced lesions and in those patients with progressive arthrosis.

With simultaneous corrective osteotomy and total knee arthroplasty for the treatment of severe extra-articular femoral deformity associated with ipsilateral osteoarthritis of the knee....

Eighteen patients with nonunions of the proximal tibial metaphysis were treated at one institution. Nine patients had a history of osteomyelitis. There was an average of 4 prior surgical procedures to achieve fracture union, obtain soft-tissue coverage, or eradicate infection. Stable internal fixation with bone grafting was performed in 13 patients, with a fixed angle blade plate in 10 and standard compression plate in 3. Three patients were treated with hybrid circular external fixators, and one patient was placed in a cast. An additional patient underwent long-stem total knee arthroplasty with structural allografting. Follow-up averaged 45 months. Osseous union was achieved in 100% of patients. Alignment was within 5 degrees of neutral in 94% of patients. Forty-four percent of patients continue to require the assistance of a cane for ambulation. Twelve patients have some pain with activity, primarily related to ipsilateral knee arthrosis. No infections have recurred. Knee motion improved an average of 28 degrees. Healing of nonunions of the proximal tibial metaphysis may be achieved with meticulous soft-tissue care and appropriate stabilization of small, osteoporotic, periarticular fragments.