Session VI - Reconstruction

·*The Use of an Antibiotic-Impregnated, Bioabsorbable Bone Substitute in the Treatment of Infected Long Bone Defects: Results of a Prospective Trial

Michael McKee, MD, FRCS (b-Wright Medical, Inc.); Emil H. Schemitsch, MD, FRCS (b-Wright Medical, Inc.); Lisa Wild, RN, BSCN (b-Wright Medical, Inc.); James P. Waddell, MD, FRCS (b-Wright Medical, Inc.), St. Michael's Hospital ­ University of Toronto, Toronto, Ontario, Canada

Purpose: In a prospective clinical trial, we sought to evaluate the use of a bioabsorbable, tobramycin-impregnated bone graft substitute (calcium sulfate alphahemihydrate pellets) in the treatment of patients with infected bony defects and nonunions. Outcome parameters studied included eradication of infection, promotion of bony union and conversion to host bone.

Method and Results: Twenty-four patients (15 males and 9 females, mean age 43.7 years, range 30 to 73 years) requiring surgical debridement of long bone infection were entered into a consecutive, prospective clinical trial. Involved bones included the tibia (13), femur (6), ulna (3), clavicle (1) and humerus (1). All patients had positive bone cultures and/or active draining sinuses (S. aureus - 12, S. epidermidis - 6, Pseudomonas - 3, other / polymicrobial - 3). All defects were post-traumatic in origin, and all patients had had previous surgery at the involved site (mean 3.7, range 1-11). The bony defect in each patient resulted from a combination of active infection and surgical debridement. Sixteen patients had associated nonunion. The duration of infection ranged from 4 months to 18 years (mean 17.5 months). According to the Cierny-Mader classification system, there were 4 stage I, 15 stage III, and 5 stage 4 lesions. There were 7 normal (A) hosts and 17 locally or systemically compromised (B) hosts. There were 13 smokers and 11 nonsmokers. Mean bone defect / void was 18.6 cm3 with a range >from 2 cm3 to 45 cm3. In all cases, use of the bone graft substitute was an integral part of a protocol that included radical debridement, irrigation, stable fixation (prn), adequate soft-tissue coverage and adjuvant systemic antibiotics. Radiographically, pellets were resorbed by 2 to 3 months in the majority of patients, and gradually replaced by host bone. Mean follow-up was 9.6 months with a range from 6 to 22 months. Infection was eradicated in 23 of 24 patients, and union achieved in 10 of 16 patients. Complications included refracture (1- casted), recurrence of infection (1), superficial wound necrosis (1) and persistent nonunion requiring autogenous bone grafting (6). Seven patients developed sterile draining sinuses that healed upon radiographic resorption of pellets.

Discussion/Conclusion: In comparison to previous patients from our institution, this bone graft substitute has lowered infection recurrence rates, eliminated the need for routine autogenous bone grafting and reduced the requirement for secondary procedures to remove biologically inert cement beads and add bone graft. Antibiotic-impregnated bone graft substitute is very effective in eradicating deep infection and serves an osteoconductive role in bony defects. In certain situations it can also aid in promoting bony union. This material appears to be ideal for infected bony defects and nonunions by virtue of its antibacterial action, osteoconductive nature and ability to aid in union.