Articulating Versus Static Antibiotic Loaded Spacers for the Treatment of Prosthetic Knee Infection
Condition: Osteoarthritis; Knee Infection; Prosthetic Joint Infection; Complications; Arthroplasty, Infection or Inflammation; Complications; Arthroplasty
MeSH terms: Infections; Communicable Diseases; Osteoarthritis; Inflammation
Study type: Interventional

Summary: 
      Infection remains a difficult-to-treat complication of total knee arthroplasty. The gold
      standard treatment is two-stage removal of the prosthesis with later replacement of permanent
      implants. The first stage consists of removal of the infected arthroplasty components and the
      surrounding devitalized tissue, copious pulsed irrigation, and placement of a temporary
      antibiotic-impregnated cement spacer. This spacer typically is left in place six weeks,
      during which time the patient receives intravenous antibiotics. After the surgeon feels that
      the infection has been eradicated, or if the patient requires repeat debridement, a second
      operative procedure is performed. While the use of an antibiotic-loaded spacer is well
      accepted, whether the spacer should immobilize the knee (a so-called "static" spacer) or
      allow for range of motion (a so-called "articulating" spacer) is controversial. Proponents of
      articulating spacers argue that they prevent scarring of the musculature surrounding the knee
      resulting in easier reimplantation, improved long-term knee function, and improved range of
      motion. Proponents of static spacers argue that immobilization of the periarticular soft
      tissues aids in clearance of the infection and is simpler to fashion intraoperatively. While
      good results have been described with both methods, comparative trials have been conflicting
      as to whether spacer design alters knee function, operative time, and range of motion.
      Equipoise exists within the literature, and no randomized clinical trial has been conducted
      to evaluate this issue.

      The purpose of this study is to compare articulating and static antibiotic-impregnated
      spacers for the treatment of chronic periprosthetic infection complicating total knee
      arthroplasty through a prospective, randomized clinical trial. The goals of this trial are to
      determine the effect of spacer design upon eradication of infection, knee function, ease of
      reimplantation, and range of motion. The investigators hypothesize that articulating spacers
      will provide shorter operative times at reimplantation, while improving knee function and
      range of motion.
    

Detailed description: 
      After diagnosis of infection and informed consent, patients will be taken to the operating
      room. After anesthetization, patients will be randomized to either an articulating spacer or
      a static spacer. Randomization will be performed by prepared opaque envelopes administered by
      a nonparticipant in the study. After a complete debridement of devitalized tissue,
      explantation of the infected components and any associated cement, either an articulating or
      static spacer will be placed. All spacers will be formed of 3 g of Vancomycin and 1 g of
      Tobramycin for each 40 g packet of cement. Articulating spacers will be formed of antibiotic
      impregnated cement using the Stage One system (Biomet, Warsaw, IN). Static spacers will be
      hand-made to fit the femoral and tibial exposed metaphyses as a solid block with associated
      antibiotic cement coated tibial and femoral intramedullary rod, such that knee motion will be
      minimized.

      Post-operatively, all patients will be made touch-down weight bearing protected with a walker
      or crutches. If a static spacer is placed, patients will be immobilized using with a knee
      immobilizer. If an articulating spacer is utilized, range of motion will be allowed to the
      limits of stability as determined in the operating room and protected with a hinged knee
      brace. At the time of reoperation, the joint will be aspirated and multiple cultures obtained
      along with intraoperative histopathological analysis to evaluate for persistent infection.

      Data collected preoperatively will include age, gender, laterality, etiology of knee
      degeneration, comorbidities, Knee Society score, and infecting organisms. The Knee Society
      score has been used extensively in the study of revision knee arthroplasty and has been found
      to be reliable and valid and will be determined pre-operatively and at all follow-up visits.

      Data collected at the time of implant removal and reimplantation will include operative time,
      blood loss, and need for an extensile exposure. Radiographs performed immediately following
      and just prior to reimplantation will be reviewed to determine if the spacer utilized has
      caused bone loss; bone loss to the cut bony surfaces will be confirmed intraoperatively. At
      each follow-up visit radiographic appearance, the Knee Society Score, knee range of motion,
      recurrence of infection, and the need for revision or reoperation of any kind on the knee
      will be determined.

      All portions of this study will be part of conventional care except for randomization to
      either a static or articulating spacer. Which type of spacer is used currently depends upon
      the judgment of the attending surgeons and both are used routinely.

      The primary outcome variable will be range of motion. A power analysis was conducted with the
      assistance of Dr. Mario Moric at Rush using range of motion as our primary outcome variable,
      with standard deviations culled from two of the largest series to date -Van Thiel and
      colleagues (2010) and Fehring and colleagues (2000). For an 80% chance of detecting a
      predetermined clinically significant difference of 10 degrees, 53 patients per group, 106
      patients total, will be needed. To account for attrition, our target sample size will be 140
      patients.
    

Intervention name(s): Static Spacer; Articulating Spacer
Intervention type(s): Procedure; Procedure
Intervention description(s): After diagnosis of infection and informed consent, patients will be taken to the operating room. After anesthetization, patients will be randomized to either an articulating spacer or a static spacer. Randomization will be performed by prepared opaque envelopes administered by a nonparticipant in the study. After a complete debridement of devitalized tissue, explantation of the infected components and any associated cement, either an articulating or static spacer will be placed. All spacers will be formed of 3 g of Vancomycin and 1 g of Tobramycin for each 40 g packet of cement. Static spacers will be hand-made to fit the femoral and tibial exposed metaphyses as a solid block with associated antibiotic cement coated tibial and femoral intramedullary rod, such that knee motion will be minimized.; After diagnosis of infection and informed consent, patients will be taken to the operating room. After anesthetization, patients will be randomized to either an articulating spacer or a static spacer. Randomization will be performed by prepared opaque envelopes administered by a nonparticipant in the study. After a complete debridement of devitalized tissue, explantation of the infected components and any associated cement, either an articulating or static spacer will be placed. All spacers will be formed of 3 g of Vancomycin and 1 g of Tobramycin for each 40 g packet of cement. Articulating spacers will be formed of antibiotic impregnated cement using the Stage One system (Biomet, Warsaw, IN).
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: arthroplasty; knee replacement; Osteoarthritis; knee Infection; Prosthetic Joint Infection; Complications; Arthroplasty, Infection or Inflammation; Complications; Arthroplasty