Abstract
Introduction
The utilization of lymphocyte transformation testing (LTT) has increased for diagnosing metal sensitivity associated with TKA, but its validity for the diagnosis of TKA failure due to an immune reaction has not been established.
Methods
We performed a retrospective study of 27 well-fixed, aseptic primary TKAs with persistent pain and/or stiffness, revised by a single, experienced surgeon for suspected metal allergy to nickel based on a positive LTT. Periprosthetic tissue samples obtained at the time of revision surgery were scored using the aseptic lymphocytic vasculitis-associated lesion (ALVAL) scoring system.
Results
Eight patients were categorized as mildly reactive, 8 reactive, and 11 highly reactive to nickel by LTT. The predominant findings on routine histology were fibrosis and varying degrees of lymphocytic infiltration in 17/27 (63%) of the cases. The average ALVAL score of the cohort was 3.1 ± 1.9, out of a maximum score of 10. Average Knee Society Scores (KSS) improved post-revision, as did range of motion (all p<0.01). Neither LTT stimulation index as a continuous variable nor as a categorical variable (mild, moderate, high) was correlated with ALVAL score, pre-operative function, or change in function at last follow-up (0.015 < r < 0.30, 0.13 < p < 0.95) as measured by KSS. In addition, the ALVAL score did not correlate significantly with either pre-operative or post-operative KSS or range of motion (0.061 < r < 0.365, 0.09 < p < 0.88).
Conclusions
Based on this analysis including histopathology, LTT results alone are insufficient for the diagnosis of TKA failure due to an immune reaction. A positive LTT may not indicate that an immune reaction is the cause of pain and stiffness post-TKA. The role of LTT in assessing immune failure of TKA needs further investigation. Diagnostic criteria for immune failure of a TKA need to be established.
