Lymphocyte Subset Ratio Cannot Diagnose Immune Failure of a TKA.

BACKGROUND

Up to 20% of patients are dissatisfied following total knee arthroplasty (TKA), most often due to pain and/or stiffness. The differential diagnosis includes immune reaction to the prosthesis. However, there is no consensus on diagnostic criteria for immune failure, an allergic reaction, to a TKA. Histologic evaluation could provide evidence as to whether an allergic reaction caused TKA failure. A recent study showed an increase in CD4+ lymphocytes compared to CD8+ lymphocytes in patients lymphocyte transformation testing (LTT) + for Ni. This finding is consistent with Ni sensitization, but can lymphocyte subsets be used to diagnose immune failure on a case-by-case basis?

METHODS

Periprosthetic tissues from 18 revision cases of well-fixed, aseptic, but painful and/or stiff primary TKAs were analyzed. Six patients LTT- for Ni were matched as a cohort for age, sex, and body mass index (BMI), to 12 patients LTT + for Ni. Periprosthetic tissue biopsies underwent immunohistochemical IHC staining for CD4+ and CD8+ lymphocyte subsets and were compared by LTT status. The immunohistochemicalIHC results were also compared with periprosthetic histology.

RESULTS

There was no relationship between LTT status and mean CD4+ cells/hpf or CD4+:CD8+ lymphocyte ratio. No relationship was found between LTT stimulation index (continuous or categorical) and CD4+:CD8+ ratio or aseptic lymphocyte-dominant vasculitis-associated lesion ALVAL score.

CONCLUSION

Lymphocytes in periprosthetic tissue are highly variable in number, subtype ratio, and location, and have no relationship to LTT result or ALVAL score on a case-by-case basis. Based on these results, lymphocyte subsets cannot diagnose immune failure. Further work is needed to determine criteria for the diagnosis of immune failure of a TKA.