Session IX - Tibia

Perioperative External Fixator Management during Secondary Surgical Procedures

J. Tracy Watson, MD; Michael J. Occhietti, MD; Berton R. Moed, MD; David E. Karges, DO; Kathryn E. Cramer, MD; Vikram S. Parmar, MD, Department of Orthopaedic Surgery, Wayne State University, Detroit, MI

Introduction: External fixation is currently used as a temporizing measure or as definitive treatment for a variety of traumatic and reconstructive indications. At times these patients will require additional secondary operative procedures. Anecdotal recommendations for intraoperative fixator management during secondary procedures range from temporary fixator removal with frame reapplication versus attempting to prep the fixator out of the operative field, or various protocols to prep the fixator into the operative field. It is our protocol to prep the fixator directly into the operative field. The purpose of this study was to investigate the safety and efficacy of this management in patients with pre-existing external fixators undergoing secondary operative procedures.

Materials and Methods: Ninety-six patients (average age, 39; range, 16­63) were entered into this prospective study (30, females; 66, males). The patients underwent a total of 108 secondary procedures between September 1996 and September 1998. Nine patients had two secondary procedures and one patient had three.

Fifty-four patients were in fixators for acute fractures (24, open; 30, closed). Average duration of fixation prior to secondary procedure: 11 days (range, 2­30). Fortytwo patients were in fixators for posttrauma reconstruction (nonunions and malunions). Average frame duration prior to secondary procedure: 132 days (range 31­403 days). Patients with infected fractures and nonunions were excluded from the study. Secondary procedures consisted of open reduction and internal fixation, wound-coverage procedures, or bone grafting in the acute fracture group. Interim irrigation, debridement and open-wound packing procedures were excluded. The post-trauma reconstruction group consisted Ilizarov reconstructions undergoing wound coverage or bone graft procedures. Patients were examined at the time of the secondary procedure for evidence of pin-tract infection. Parameters used to define pin-tract infection were: 1) presence of erythema; 2) presence, degree and type of drainage; and 3) presence of clinical or radiographic pin loosening. Twenty patients (21%) had some evidence of mild pin-tract infection at the time of secondary procedure. Nine patients had serous or serosanguineous drainage. No patient had purulent drainage at the time of surgery. Ten patients had an erythematous border around one or more pin sites, and one patient had frank clinical pin loosening.

Standardized surgical prep consisted of cleansing the entire limb and fixator pins, initially with 95 percent isopropyl alcohol. The external fixator was then prepped using a routine aqueous Betadine prep scrub solution for six minutes, followed by similar prep to the limb. The fixator was then coated with spray Betadine paint solution, as was the extremity. The entire extremity, including the external fixator, was then draped into the operative field. After drying the prep, three routine aerobic cultures were obtained. The first culture was taken at the site of the proposed skin incision site, the second at the Schanz pins or transfixion wires of the fixator (which were in close proximity to the incision), and the third cultured the fixation rings, or bars. Each swab covered approximately nine square centimeters of area on the respective surface. The results of the cultures were blinded and not used in any way to guide the subsequent treatment. Those patients that were undergoing conversion of fixator to internal hardware, had the fixator left in place for the duration of the procedure. When fixation was accomplished, the frame was removed after wound closure. All patients received intravenous antibiotics covering skin flora preoperatively (cephalosporin or vancomycin if the patient was pen-allergic), and the antibiotics were continued prophylactically for 24 hours postoperatively.

Patients had a minimum followup of at least six months from the date of their secondary procedure (average, 9 months; range, 2­26 months). Patients were evaluated at each office visit for the presence of any wound infection, superficial or deep, using the criteria outlined by the Appendix A of the CDC Definitions of Nosocomial Infections. At the conclusion of their treatment, the culture results were unblinded, matched with the patient's clinical outcome, and statistical analysis was carried out (ANOVA).

Results: Eleven patients (11.4%) had at least one positive culture (skin, 54.5%; pins, 54.5%; and bars, 36.9% [not sig.]). Species identification, as well as antibiotic sensitivities, were performed on all of the positive cultures. The most frequent bacterial isolate was Bacillus species, not Anthracis in 12 of 16 (75%), which was significant. The second was MSSA in 16 (18.75%), and one isolate of S.. Epidermitus (1 of 16, 6.25%).

Four patients (4.1%) developed wound complications postoperatively, all with negative precultures [not sig.]. Two patients (2.08%) developed superficial wound infections, and two (2.08%) developed deep-wound infections. One superficial infection was a culturenegative stitch abscess, and the other infection was a partial wound dehiscence with cultures positive for Pseudomonas. Both patients healed uneventfully with local wound care and oral antibiotics. Both deep infections had intraoperative cultures positive for S. Aureus and Pseudomonas, respectively. Both required subsequent irrigation and debridement procedures and healed without sequelae.

Discussion: Only two of 96 patients developed deep postoperative wound infections (2.08%). Both of these patients had initial injuries classified as Grade III-B, open. Fifty-five percent of the patients presented with open fractures, of which 46 percent were Grade III. A postoperative infection rate of two percent, given the severe nature of these injuries, is consistent with the literature for open fractures. Our small number of patients prohibits meaningful statistical analysis to rule out the fixator as the agent for infection in these patients. However, preoperative cultures were not found to be predictive of the occurrence of postoperative infection, nor were they predictive of the organisms that caused the four infections. The most-frequently found bacterial isolates from the preoperative cultures were Bacillus species, not Anthracis. Only two of these species have been found to be of sufficient virulence to cause infections in humans with normal immune status. Bacillus species are a common skin flora and are widespread. It was not surprising to find these species the most-commonly-cultured organism in the study, as the spores of these bacteria are relatively resistant to chemical disinfectants. Duration of the frame prior to the secondary procedure was not significant in predicting infection, nor was the presence of mild clinical pin-tract infection.

Conclusion: The benefits of safely prepping an external fixator into the operative field includes the ability to maintain reduction during secondary conversion procedures, as well as decreasing the time, materials cost and frustration in trying to drape a fixator safely out of the operative field. Following a standardized protocol of pre-cleansing the ex-fix frame followed by alcohol wash, sequential Betadine prep and paint solution and draping the extremity and fixator directly into the operative field does not lead to an increased rate of postoperative wound infection. Routine ex-fix cultures are not indicated, as they were not predictive of developing a postoperative deep-wound infection or identifying an infecting organism.