Outcome following subluxation of mobile articulating spacers in two-stage revision total knee arthroplasty.
BACKGROUND
Infection after total knee arthroplasty (TKA) is a severe complication. It is usually treated with two-stage revision and implantation of a cement spacer. Few studies describe the complications associated with a mobile articulating spacer. This study examined the subluxation of articulating antibiotic spacers in knees and correlated it with prospectively collected early outcome scores after implantation of a revision prosthesis.


METHODS
Staged revisions for 72 infected primary total knee arthroplasties between 2004 and 2012 were examined. The mean age of the patients was 70.2 ± 10.8 years, with 40 right and 32 left knees. Sagittal and coronal subluxation was measured using radiographs prior to second-stage revision and grouped to be within (Group 1) or outside (Group 2) one standard deviation from the mean. Medical Outcomes Study Short Form-12 (SF-12), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Society Score (KSS) were obtained via patient-administered questionnaire. Statistical analysis was carried out to look at the correlation between subluxation and outcome.


RESULTS
Significant improvements were observed between the interim outcome scores prior to implantation of a revision prosthesis and scores obtained after second-stage revision. Debonding occurred in 5.6%, and one dislocation was found. Mean coronal subluxation was 4.8 ± 5.5% of the tibia width, in the lateral direction. Coronal subluxation did not affect SF12, WOMAC or KSS outcome scores. Mean sagittal subluxation was 6.1 ± 16.4% posteriorly. However, sagittal subluxation had a significant influence on Knee Society Scores, with Group 2 having a lower mean Knee Society Function Score of 39.3 than Group 1 (60.2) (p = 0.045). Sagittal subluxation did not affect SF12 or WOMAC scores.


CONCLUSIONS
Sagittal subluxation of the knee may influence the early to midterm outcome scores following a staged revision TKA for infection.
Division of Orthopaedic Surgery, Department of Surgery, Schulich School of Medicine and Dentistry, The University of Western Ontario, 339 Windermere Road, London, ON, N6A 5A5, Canada. Brent.Lanting@lhsc.on.ca.
Brent A
BA
Lanting
Changi General Hospital, Singapore, Singapore.
Adrian
A
Lau
Division of Orthopaedic Surgery, Department of Surgery, Schulich School of Medicine and Dentistry, The University of Western Ontario, 339 Windermere Road, London, ON, N6A 5A5, Canada.|Department of Medical Biophysics, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Canada.|Surgical Innovation Program, Lawson Health Research Institute, London, Canada.
Matthew G
MG
Teeter
Division of Orthopaedic Surgery, Department of Surgery, Schulich School of Medicine and Dentistry, The University of Western Ontario, 339 Windermere Road, London, ON, N6A 5A5, Canada.
James L
JL
Howard
D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005548:Foreign-Body Migration / Q000000981:diagnostic imaging*; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D016459:Prosthesis-Related Infections / Q000628:therapy*; D011859:Radiography; D012086:Reoperation / Q000379:methods; D012189:Retrospective Studies; D011795:Surveys and Questionnaires; D013977:Tibia / Q000000981:diagnostic imaging; D016896:Treatment Outcome
D000900:Anti-Bacterial Agents
Articulating spacer; Revision knee arthroplasty; Subluxation; Two stage