Articulating Versus Static Antibiotic Loaded Spacers for the Treatment of Prosthetic Knee Infection

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.

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.

Osteoarthritis, Knee Infection, Prosthetic Joint Infection, Complications; Arthroplasty, Infection or Inflammation, Complications; Arthroplasty

arthroplasty, knee replacement, Osteoarthritis, knee Infection, Prosthetic Joint Infection, Complications; Arthroplasty, Infection or Inflammation, Complications; Arthroplasty

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).

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).

Inclusion Criteria: 1) Diagnosis of a periprosthetic joint infection of a primary total knee arthroplasty with a planned two-stage exchange procedure. Exclusion Criteria: Infection of a revision as opposed to a primary total knee arthroplasty Medically unfit for operative intervention Extensive bone loss preventing the use of an articulating spacer Soft tissue defects that prevent the use of an articulating spacer Known allergy to polymethylmethacrylate, tobramycin or vancomycin.

Gooding CR, Masri BA, Duncan CP, Greidanus NV, Garbuz DS. Durable infection control and function with the PROSTALAC spacer in two-stage revision for infected knee arthroplasty. Clin Orthop Relat Res. 2011 Apr;469(4):985-93. doi: 10.1007/s11999-010-1579-y.

Haleem AA, Berry DJ, Hanssen AD. Mid-term to long-term followup of two-stage reimplantation for infected total knee arthroplasty. Clin Orthop Relat Res. 2004 Nov;(428):35-9. doi: 10.1097/01.blo.0000147713.64235.73.

Van Thiel GS, Berend KR, Klein GR, Gordon AC, Lombardi AV, Della Valle CJ. Intraoperative molds to create an articulating spacer for the infected knee arthroplasty. Clin Orthop Relat Res. 2011 Apr;469(4):994-1001. doi: 10.1007/s11999-010-1644-6.

Cuckler JM. The infected total knee: management options. J Arthroplasty. 2005 Jun;20(4 Suppl 2):33-6. doi: 10.1016/j.arth.2005.03.004.

Goldman RT, Scuderi GR, Insall JN. 2-stage reimplantation for infected total knee replacement. Clin Orthop Relat Res. 1996 Oct;(331):118-24. doi: 10.1097/00003086-199610000-00016.

Hirakawa K, Stulberg BN, Wilde AH, Bauer TW, Secic M. Results of 2-stage reimplantation for infected total knee arthroplasty. J Arthroplasty. 1998 Jan;13(1):22-8. doi: 10.1016/s0883-5403(98)90071-7.

Emerson RH Jr, Muncie M, Tarbox TR, Higgins LL. Comparison of a static with a mobile spacer in total knee infection. Clin Orthop Relat Res. 2002 Nov;(404):132-8. doi: 10.1097/00003086-200211000-00023.

Fehring TK, Odum S, Calton TF, Mason JB. Articulating versus static spacers in revision total knee arthroplasty for sepsis. The Ranawat Award. Clin Orthop Relat Res. 2000 Nov;(380):9-16. doi: 10.1097/00003086-200011000-00003.

Freeman MG, Fehring TK, Odum SM, Fehring K, Griffin WL, Mason JB. Functional advantage of articulating versus static spacers in 2-stage revision for total knee arthroplasty infection. J Arthroplasty. 2007 Dec;22(8):1116-21. doi: 10.1016/j.arth.2007.04.009.

Hsu YC, Cheng HC, Ng TP, Chiu KY. Antibiotic-loaded cement articulating spacer for 2-stage reimplantation in infected total knee arthroplasty: a simple and economic method. J Arthroplasty. 2007 Oct;22(7):1060-6. doi: 10.1016/j.arth.2007.04.028.

Jamsen E, Sheng P, Halonen P, Lehto MU, Moilanen T, Pajamaki J, Puolakka T, Konttinen YT. Spacer prostheses in two-stage revision of infected knee arthroplasty. Int Orthop. 2006 Aug;30(4):257-61. doi: 10.1007/s00264-006-0102-2. Epub 2006 Mar 25.

Haddad FS, Masri BA, Campbell D, McGraw RW, Beauchamp CP, Duncan CP. The PROSTALAC functional spacer in two-stage revision for infected knee replacements. Prosthesis of antibiotic-loaded acrylic cement. J Bone Joint Surg Br. 2000 Aug;82(6):807-12. doi: 10.1302/0301-620x.82b6.10486.

Hart WJ, Jones RS. Two-stage revision of infected total knee replacements using articulating cement spacers and short-term antibiotic therapy. J Bone Joint Surg Br. 2006 Aug;88(8):1011-5. doi: 10.1302/0301-620X.88B8.17445.

Hofmann AA, Kane KR, Tkach TK, Plaster RL, Camargo MP. Treatment of infected total knee arthroplasty using an articulating spacer. Clin Orthop Relat Res. 1995 Dec;(321):45-54.

Meek RM, Dunlop D, Garbuz DS, McGraw R, Greidanus NV, Masri BA. Patient satisfaction and functional status after aseptic versus septic revision total knee arthroplasty using the PROSTALAC articulating spacer. J Arthroplasty. 2004 Oct;19(7):874-9. doi: 10.1016/j.arth.2004.06.028.

Calton TF, Fehring TK, Griffin WL. Bone loss associated with the use of spacer blocks in infected total knee arthroplasty. Clin Orthop Relat Res. 1997 Dec;(345):148-54.

Fehring TK, Calton TF, Griffin WL. Cementless fixation in 2-stage reimplantation for periprosthetic sepsis. J Arthroplasty. 1999 Feb;14(2):175-81. doi: 10.1016/s0883-5403(99)90122-5.

Asif S, Choon DS. Midterm results of cemented Press Fit Condylar Sigma total knee arthroplasty system. J Orthop Surg (Hong Kong). 2005 Dec;13(3):280-4. doi: 10.1177/230949900501300311.

Ghanem E, Pawasarat I, Lindsay A, May L, Azzam K, Joshi A, Parvizi J. Limitations of the Knee Society Score in evaluating outcomes following revision total knee arthroplasty. J Bone Joint Surg Am. 2010 Oct 20;92(14):2445-51. doi: 10.2106/JBJS.I.00252.

Insall JN, Dorr LD, Scott RD, Scott WN. Rationale of the Knee Society clinical rating system. Clin Orthop Relat Res. 1989 Nov;(248):13-4.

Liow RY, Walker K, Wajid MA, Bedi G, Lennox CM. The reliability of the American Knee Society Score. Acta Orthop Scand. 2000 Dec;71(6):603-8. doi: 10.1080/000164700317362244.