Session IV Scientific Basis for Fracture Care

Occult Colonization of Orthopaedic Implants

Randall L. Lais, MD, Charles M. Reinert, MD, Alan L. Jones, MD

Parkland Memorial Hospital, Dallas, Texas

Purpose: The incidence of quiescent bacterial colonization of orthopaedic implants is unknown. Infections following reconstructive procedures in patients with retained hardware raises concern about indolent infections around orthopaedic implants. We investigated the incidence of bacterial colonization of orthopaedic implants without clinical signs of infection.

Methods: In Part I of the study we prospectively studied intra-operative cultures from 56 orthopaedic implant locations at the time of implant removal. In Part II (n=31) cultures of the subcutaneous tissues were also obtained prior to implant exposure serving as matched controls. Patients with any history of drainage, previous antibiotic treatment, use of external fixators, or suspected clinical infection were excluded. The Chi-Square test was used to assess statistical significance.

Results: Part I- 27 of 56 (48.2%) of the cultures had bacterial growth. While in Part II 16 of 31 (51.6%) implant site cultures grew bacteria, compared to 4 of 31 (12.9%) controls (p=0.001). Two of 4 positive controls had positive implant cultures. In the positive implant culture sites, bacterial growth was Staph. coag. neg. in 21, Propionibacterium acnes in 9, Staph. aureus in 8, Enterococcus in 2, Corynebacterium in 2, and Enterobacter in 1. There was no association between type of implant, time from implant placement to removal, age of patient, sex of patient, open or closed original injury, and a positive implant culture.

Discussion: We conclude that bacterial colonization of orthopaedic hardware exists in many patients without clinical signs of infection. Forty-three of 87 (49.4%) cultures of implant removal procedures had positive culture results in our series, compared to 4 of 31 (12.9%) of controls. Because of the high incidence of bacterial colonization, we recommend that staged hardware removal be done prior to reconstruction of any major joint that has previously undergone open reduction and internal fixation.