ABSTRACT
Background: Postoperative infection can be a devastating complication of ankle replacement and arthrodesis surgery. Management consists of eradication of the infection and either, revision of the initial surgery or some form of salvage procedure. There are instances however when the patient is asymptomatic, medically unfit, or the local tissue is too tenuous to warrant performing additional surgery. We conducted a retrospective review of the outcome of the use of an antibiotic impregnated cement spacer as the definitive procedure in this kind of patient. Methods: There were nine patients with post operative deep ankle infection following surgery who did not undergo subsequent revision surgery. The initial surgeries were either total ankle replacement (TAR) (n = 6) or ankle arthrodesis (n = 3). The indications for the retention of the cement spacer were patients who were asymptomatic following insertion of the cement spacer, did not desire further surgery, or were medically unfit for further surgery. The patients all underwent removal of hardware or implants, debridement, and insertion of an antibiotic impregnated cement spacer. Six weeks of intravenous antibiotics were administered according to culture sensitivity results. Patients were followed up closely for complications (wound dehiscence, spacer migration, bone loss), resolution of infection, functionality, and satisfaction. Results: The average time of cement spacer retention was 20.1 months, ranging from 6 to 62 months. The most common infecting organisms were Staph. Aureus (n = 3) and Staph. Epidermidis (n = 3). One patient had wound complications, possibly due to the proximity of the cement spacer to the anterior skin surface. One patient had a repeat infection at 52 months. The most common co-morbidities were rheumatoid arthritis (n = 3) and diabetes (n = 2). At final followup, seven patients still had a retained cement spacer and two had subsequent below knee amputations (BKA) performed as a result of delayed complications. Review of the X-rays revealed two patients with loosening and migration of the cement spacer. No patients had signs of excessive bone loss. All patients with a retained antibiotic cement spacer were mobile and able to perform basic activities of daily living with minimal discomfort. Conclusion: The long-term use of antibiotic impregnated cement spacers following postoperative ankle infection is a reasonable option in the low demand patient with surgical or medical co-morbidities.
Level of Evidence: IV, Retrospective Case Series
Key Words: Infection; Total Ankle Replacement; Ankle Arthrodesis; Salvage
INTRODUCTION
Postoperative deep ankle infection is a relatively uncommon and difficult problem to manage. Unlike the hip joint, the ankle has a frail soft tissue envelope, making infection following surgery a difficult problem to manage. The goals in treating the infection is first to eradicate the infection, and then to restore a painless functional limb. Surgical options for the treatment of postoperative infection include debridement of the joint with retention of hardware (as in fractures and early TAR infection), aggressive debridement of the joint with removal of all hardware, one- or twostage exchange procedure, one- or two-stage arthrodesis, or amputation.15
The two stage procedure involves the use of an antibioticimpregnated cement spacer or beads at the first surgery. The cement spacer has a two-fold function of preventing soft tissue contracture and delivery of antibiotics locally to the bone and soft tissue by elution. The prevention of soft tissue contracture is important for future revision surgery. The importance of local antibiotics is that infected bone often has poor blood supply, potentially making systemic antibiotics less effective. Calhoun et al. showed that antibiotic impregnated cement beads are beneficial in managing foot infections in the presence of vascular compromise, such as in patients with diabetes and/or renal failure. Patients with renal failure are especially difficult to treat as parenteral antibiotics like gentamycin are toxic due to the patients reduced clearance capacity.4 This elution of antibiotics from the acrylic cement, however, has the disadvantage of uncontrollable pharmacokinetics.15
Although there have been reports on the long term use of cement spacers in infected total hip replacements7,18 and total shoulder replacements,17,24 there is no similar study on the use of antibiotic impregnated cement spacers as a permanent solution for postoperative ankle infection. We retrospectively reviewed nine patients at two foot and ankle centers. All the patients underwent debridement and antibiotic impregnated cement spacer insertion as the definitive management for postoperative ankle infection.
MATERIALS AND METHODS
This is a retrospective, Institutional Review Board approved study examining patients who underwent treatment for post operative ankle infection using an antibiotic impregnated cement spacer as the definitive procedure. We identified nine patients at two institutions from 2004 until 2009. The group consisted of six men and three women. The average age was 63.3 (range, 51 to 75) years. The primary surgical procedure was either a total ankle replacement (TAR) in six patients or an ankle arthrodesis in three patients. All ankle arthrodeses were done through an anterior approach, preserving the medial and lateral malleolus. The ankle arthrodeses were fixed using three cannulated 6.5-mm screws. Time from index procedure to diagnosis of infection ranged from 33 days to 6 years.
Preoperative diagnosis of infection was made with a detailed clinical history, physical examination, radiographic evaluation, and laboratory workup. Laboratory workup consisted of a white blood cell count (WBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). A history of sudden onset of pain, swelling, or wound drainage with or without fever and clinical findings of tenderness, increased local temperature and effusion, were indicative of infection.26 An ESR of 30 mm/h or greater together with a CRP of 10 mg/L or greater highly suggestive of infection.21 In cases where an effusion was palpable, the joint was aspirated under sterile conditions. The fluid was then sent for gram staining and microscopy (cell count), culture, and sensitivity (MC&S). This helped with making a definitive diagnosis as well as deciding on the appropriate antibiotic to mix with the cement at the time of surgery.
No antibiotics were given prior to surgery so as not to affect intraoperative culture specimens. Previous incisions were used for exposure. Most approaches were through an anterior incision. Three intraoperative culture specimens were obtained. These being synovial fluid, inflamed synovial tissue, and tissue from the prosthesis-bone or arthrodesis interface. All specimens were sent for MC&S. In cases where the diagnosis of infection was equivocal, because of either not obtaining fluid on initial aspiration or fluid aspiration preoperative culture and sensitivity results were inconclusive, tissue was sent during surgery for immediate pathologic examination. If the white cell count was greater than five per high power field or gram stain positive, a presumptive diagnosis of infection was made.16 If present, synovial fluid was also sent for STAT cell count and gram stain. A cell count was positive for infection if there were more than 50,000 leukocytes per ml and more than 80% neutrophils present under high power field.21 All hardware was then removed. All devitalized tissue was meticulously debrided down to healthy, well perfused tissue. The bony surfaces were debrided of all dead bone to bleeding bone. This is important for systemic antibiotics to be effective. Cement was then mixed with the appropriate culture sensitive antibiotic powder. If no culture was available, two grams of Vancomycin and 1.9 g of Gentamycin were mixed into the cement. This gave good gram negative and positive antibacterial coverage. Time was taken when molding the cement block, making sure not to overstuff the joint or cause protrusion of the cement into the soft tissue envelope (Figure 1). All wounds were then closed primarily.
Following surgery all patients were placed on intravenous antibiotics according to the organism and sensitivity obtained from the cultures, in consultation with an infectious disease specialist. Antibiotics were given through a peripherally inserted central catheter (PICC) for 6 weeks as an outpatient. ESR and CRP were measured on a weekly basis to assess response to therapy. Normalization of blood markers and clinical assessment were used to assess eradication of infection. Patients were allowed to bear full weight, as tolerated, on the affected side once the wound had healed. Patients were kept in a boot for 6 weeks.
Despite resolution of the infection, the patients in this study were either medically unfit (n = 7) or they themselves...
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