Infection after Constrained Condylar Knee Arthroplasty: Incidence and microbiological findings in 100 consecutive complex primary and revision total knee arthroplasties

Low implantation volume, comorbidities, male sex and implantation of constrained TKA identified as risk factors for septic revision in knee arthroplasty: A register-based study from the German Arthroplasty Registry

PURPOSE

Periprosthetic joint infection (PJI) is a major cause of revision surgery after total knee arthroplasty (TKA) and unicondylar knee arthroplasty (UKA). Patient- and hospital-related risk factors need to be assessed to prevent PJI. This study identifies influential factors and differences in infection rates between different implant types.

METHODS

Data were obtained from the German Arthroplasty Registry. Septic revisions were calculated using Kaplan-Meier estimates with septic revision surgery as the primary endpoint. Patients with constrained and unconstrained TKA or UKA were analysed using Holm's multiple log-rank test and Cox's proportional hazards ratio. The 300,998 cases of knee arthroplasty analysed included 254,144 (84.4%) unconstrained TKA, 9993 (3.3%) constrained TKA and 36,861 (12.3%) UKA with a maximum follow-up of 7 years.

RESULTS

At 1 year, the PJI rate was 0.5% for UKA and 2.8% for TKA, whereas at 7 years, the PJI rate was 4.5% for UKA and 0.9% for TKA (p < 0.0001). The PJI rate significantly increased for constrained TKA compared to unconstrained TKA (p < 0.0001). The PJI rate was 2.0% for constrained TKA and 0.8% for unconstrained TKA at 1 year and 3.1% and 1.4% at 7 years. Implantation of a constrained TKA (hazard ratio [HR] = 2.55), male sex (HR = 1.84), increased Elixhauser score (HR = 1.18-1.56) and implant volume of less than 25 UKA per year (HR = 2.15) were identified as risk factors for revision surgery; an Elixhauser score of 0 (HR = 0.80) was found to be a preventive factor.

CONCLUSIONS

Reduced implant volume and constrained knee arthroplasty are associated with a higher risk of PJI. Comorbidities (elevated Elixhauser score), male sex and low UKA implant volume have been identified as risk factors for PJI. Patients who meet these criteria require specific measures to prevent infection. Further research is required on the potential impact of prevention and risk factor modification.

LEVEL OF EVIDENCE

Level III.

Difficult primary total knee arthroplasty requiring a varus-valgus constrained implant is at higher risk of periprosthetic infection

PURPOSE

The goal of this study was to compare the risk of periprosthetic infection of a consecutive cohort of primary varus-valgus constrained (VVC) total knee arthroplasties (TKAs), with a matched 1:1 cohort of primary posterior-stabilized (PS) TKAs.

METHODS

74 primary VVC TKAs performed in 66 patients were identified and matched 1:1 with a cohort of 74 primary PS TKAs performed in 73 patients. At last follow up, patients were clinically evaluated using the Knee Society Score (KSS). Kaplan-Meier survival curves were generated to analyze survivorship using as endpoints revision for any reason, revision for periprosthetic infection and revision for mechanical failure after excluding periprosthetic infection. A multivariate logistic regression analysis was constructed to determine whether revision surgery for periprosthetic infection was influenced by patients' gender, age, surgical time and reasons for TKA (primary vs secondary osteoarthritis).

RESULTS

Demographic data were not significantly different between the two groups as regard patients' age, gender, body mass index, Charlson Comorbidity Index, reasons for replacement, and length of follow-up. Surgical time was greater in the VVC group (95.7 ± 22.5 min vs 88.6 ± 17.1 min, respectively, p = 0.032). Postoperative KSS, range of motion and radiographic data did not differ significantly between the two groups. Overall revision rate and revision rate for mechanical failure after 5 years of follow-up was not statistically different between the two groups. Considering only the revision rate due to periprosthetic infection, the risk was higher in patients with primary VVC implants (p = 0.013). The surgical time was the only factor that significantly affected the risk of revision for periprosthetic infection (OR 1.0636, CI 95% 1.0209-1.1081, p = 0.0032), whereas patients' gender, age and reason for TKA had no influence.

CONCLUSIONS

Patients and surgeons should be aware of the higher risk of periprosthetic knee infection using a VVC prosthesis. However, the present study supports the use of VVC implants in cases of difficult knee replacements, since comparable clinical outcomes and overall revision rate was found after at least 5 years of follow up.

LEVEL OF EVIDENCE

Retrospective cohort study, Level III.

Reinfection and re-revision rates of 113 two-stage revisions in infected TKA

Introduction: Two-stage revision is the most frequently performed revision procedure of a (suspected) periprosthetic joint infection (PJI) after total knee arthroplasty (TKA). The reported results of this treatment show large variability between studies, ranging between 0 - 40 percent failure. The purposes of this study were to determine long term (1) reinfection rate, (2) re-revision rates for any reason, and (3) the reinfection rate of patients with positive cultures at reimplantation.

Methods: We prospectively followed and retrospectively reviewed 113 consecutive two-stage revision TKAs, performed between 2003 and 2013 in our clinic with a minimum follow-up of 2 years. Diagnosis of PJI was based on the major Musculoskeletal Infection Society criteria for PJI.

Results: After a mean follow-up of 94 months (range 24-172 months), infection recurred in 23 cases (23%). Of these, nine cases (9%) were defined as relapse (same micro-organism as index revision) and in 14 cases another causative was found (14%). In 11 patients debridement, antibiotics and retention of the prosthesis successfully eradicated the reinfection. After overall follow-up 17 patients (17%) underwent re-revision surgery, 11 patients (11%) due to an infection and 6 patients (6%) for aseptic reasons.

Conclusions: Treatment of a (suspected) infection of a TKA by a two-stage revision had acceptable results based on re-revision and re-infection rates in the long term (>5 years), resembling the short-term results (<2 years). Focussing on the cultures at the index two-stage revision, episodes of relapse and new infections during follow-up were almost equally divided. Reinfection rates were higher in cases with positive cultures at reimplantation. Patients should be counselled appropriately in this particular situation.