Post-total knee arthroplasty herpes zoster activation

Herpes Zoster Risk After Total Knee Replacement: a multicenter, propensity-score-matched cohort study in the United States

Background: Total knee replacement (TKR) is a common surgical procedure for osteoarthritis (OA) patients. TKR may increase susceptibility to herpes zoster (HZ) by inducing immunosuppression, surgical stress, and nerve injury. However, limited data exist on the relationship between TKR and HZ. This study examined the risk of HZ over time among OA patients who underwent TKR and those who did not, using a large population-based cohort. Method: Utilizing the TriNetX research network, people with OA and underwent TKR were recruited as case group. After 1:1 propensity score matching, OA patients who never experienced TKR were included as control group. Covariates, including demographics, comorbidities, and laboratory data, were balanced using propensity score matching. A 5-year follow-up assessed the hazard ratio of incident HZ and related complications. Results: Compared to the control group, a significantly elevated risk of HZ was observed in the TKR cohort across 5-year follow-up period, with the hazard ratio of 1.223 (95% CI: 1.089-1.373). Zoster without complications presented 1.173-fold risk in TKR patients while comparing with non-TKR controls. However, most other secondary outcomes related to HZ complications-such as encephalitis, neurological involvement, ocular disease, and disseminated zoster-did not show a significant increase in risk. The risk of HZ was statistically significant for females and older adults in the TKR cohort than in the control cohort. Conclusions: OA patients who underwent TKR had an increased risk of HZ compared to those who did not receive the procedure, especially females and older adults. These findings highlight the need for HZ monitoring/prevention protocols and further research on mitigating viral reactivation after major joint surgery.

Periprosthetic Joint Infection Diagnosis: A Narrative Review

Replacement of native joints aims to restore patients' quality of life by relieving pain and improving joint function. While periprosthetic joint infection (PJI) affects a small percentage of patients, with an estimated incidence of 1-9% following primary total joint replacement, this postoperative complication necessitates a lengthy hospitalisation, extended antibiotic treatment and further surgery. It is highlighted that establishing the correct diagnosis of periprosthetic infections is critical in order for clinicians to avoid unnecessary treatments in patients with aseptic failure. Of note, the PJI diagnosis could not purely rely upon clinical manifestations given the fact that heterogeneity in host factors (e.g., age and comorbidities), variability in infection period, difference in anatomical location of the involved joint and discrepancies in pathogenicity/virulence of the causative organisms may confound the clinical picture. Furthermore, intra-operative contamination is considered to be the main culprit that can result in early or delayed infection, with the hematogenous spread being the most prevalent mode. To elaborate, early and hematogenous infections often start suddenly, whereas chronic late infections are induced by less virulent bacteria and tend to manifest in a more quiescent manner. Last but not least, viruses and fungal microorganisms exert a role in PJI pathogenesis.

[Reactivation of latent viruses in Neurology]

After establishing latent infection, some viruses can be reactivated by the alteration of host immunological conditions. First, we reviewed viruses that can cause neuronal damage by reactivation. Then we focused on the herpes simplex virus (HSV). The reactivation leads to neuronal damages through two possible mechanisms; "reactivation of a latent herpes virus" by which viruses can cause direct virus neurotoxicity, and "post-infectious immune inflammatory response" by which a focal reactivation of HSV leads to an inflammatory reaction. The former is radiologically characterized by cortical lesions, the latter is characterized by subcortical white matter lesions. We experienced a female, who underwent the right posterior quadrantectomy and then developed recurrent herpes encephalitis caused by herpes simplex reactivation, which pathologically demonstrated inflammation in the white matter, suggesting a post-infectious immune inflammatory response. The patient was successfully treated with immunosuppressants. The reactivation of the HSV is extremely rare in Japan. Neurologists should recognize this condition because this disorder will increase as epilepsy surgery gains more popularity.