Deep Infections after Endoprosthetic Replacement Operations in Orthopedic Oncology Patients

Numerous studies have described various complications after endoprosthetic reconstructive operations. However, there are limited reports that focus specifically on deep infections (e.g., deep incisional surgical site infections), which remain one of the most dreaded complications of these operations, with rates ranging from 10% to 17%. Thus, this study was undertaken to determine the deep infection rates and to analyze possible risk factors, clinico-pathologic characteristics, and treatment modalities of endoprosthetic infections.

We reviewed retrospectively the records of 105 consecutive patients who underwent endoprosthesis replacements from January 2007 to September 2011, with a minimal follow-up period of 32 mo. Comparison was made between patients with and without endoprosthetic infections.

Thirteen of the 150 patients (12.38%) who underwent endoprosthetic operations developed deep infections. Ninety-seven (92.4%) patients presented with a primary bone/soft tissue tumor, 5 (4.8%) with bone metastasis, and 3 (2.9%) with non-tumor conditions. Distal femoral was the most common implant location (42%). The majority of the infections (6/13) occurred within 3 mo post-operation. An elevated C-reactive protein concentration or erythrocyte sedimentation rate were present consistently in all patients at time of diagnosis, whereas clinical presentations and leukocytosis were inconsistent in determining infection. Staphylococcus aureus and coagulase-negative staphylococci (CoNS) were the most common organisms isolated, with high numbers demonstrating methicillin-resistance. Overall, multi-drug resistance was noted in 52.6% of the isolated strains. Four risk factors were associated independently with deep infection by multivariable analysis (p<0.05) and these were proximal tibia endoprosthesis, pelvic endoprosthesis, pre-operative duration of hospitalization of more than 48 h, and additional surgical procedures performed after the initial endoprosthetic insertion. Overall, infection was eradicated successfully in 53.8% (7/13) of the patients. Two-stage revision successfully treated the infection in 80% (4/5) of the patients, whereas surgical debridement without a change of implant was successful in only 42.8% (3/7) of patients. Amputation was performed in three patients.

Patients undergoing endoprosthetic replacement for various orthopedic oncologic conditions have high infection rates. The present study allows early identification of such patients in view of the high morbidity associated with this condition. This report also highlights the high rate of multi-drug-resistant infections, especially methicillin-resistant strains of S. aureus and CoNS encountered, which complicates further the management of these patients.