“Inflammation–Thrombosis Dissociation”: a retrospective study of early DVT differences after UKA between Han Chinese and Tibetan patients at high altitude

Objective To compare the incidence of early lower-extremity deep vein thrombosis (DVT) after unicompartmental knee arthroplasty (UKA) between Han Chinese and Tibetan patients at high altitude, to analyze the relationships of inflammatory, hematologic, and coagulation indices with DVT, and to explore whether an “inflammation–thrombosis dissociation” phenomenon exists across ethnic groups. Methods We retrospectively analyzed 147 patients who underwent primary medial UKA at the Affiliated Hospital of Qinghai University (altitude 2,261 m) between March 2024 and June 2026, including 93 Tibetan and 54 Han Chinese patients. All patients received a standardized perioperative management protocol, including postoperative aspirin 100 mg once daily for venous thrombosis prophylaxis, and underwent bilateral lower-extremity venous color Doppler ultrasonography on postoperative days 2–3. Demographic characteristics, platelet count, hemoglobin, D-dimer, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, systemic immune-inflammation index, systemic inflammation response index, and aggregate index of systemic inflammation were collected. Propensity score matching was used to control differences in age, sex, and body mass index, and Firth logistic regression was used to analyze factors associated with DVT. Results Among the 147 patients, 14 developed postoperative DVT, for an overall incidence of 9.52%. The DVT incidence was 4.30% (4/93) in Tibetan patients, lower than the 18.52% (10/54) observed in Han Chinese patients ( P = 0.007). Platelet count, D-dimer, platelet-to-lymphocyte ratio, systemic immune-inflammation index, and aggregate index of systemic inflammation were all higher in Tibetan than in Han Chinese patients; however, these higher values did not correspond to a higher DVT incidence. After 1:1 matching for age, sex, and body mass index, 16 matched pairs were obtained; DVT incidences were 18.8% in Han Chinese patients and 0% in Tibetan patients. The difference was not statistically significant ( P = 0.250), although the direction of the association was consistent with that before matching. Firth penalized-likelihood logistic regression showed that increasing age was associated with higher odds of DVT in Model 2 (OR = 1.110, 95% CI: 1.028–1.211, P = 0.007). In the primary model adjusted for age and BMI (Model 3), Tibetan ethnicity was associated with lower odds of DVT than Han Chinese ethnicity (OR = 0.206, 95% CI: 0.038–0.948, P = 0.042). However, this association was no longer statistically significant after further adjustment for sex (Model 4: OR = 0.243, 95% CI: 0.040–1.376, P = 0.109). In exploratory models separately incorporating postoperative platelet count, D-dimer, systemic immune-inflammation index, or aggregate index of systemic inflammation (Models 5–8), the association between ethnicity and DVT remained statistically significant (all P < 0.05), whereas none of these laboratory indices showed a statistically significant association with DVT (all P > 0.05). Conclusion Among high-altitude UKA patients receiving a uniform aspirin prophylaxis regimen, Han Chinese patients had a higher incidence of early postoperative DVT than Tibetan patients. Although Tibetan patients had higher platelet counts and composite inflammatory indices, these measures did not increase in parallel with DVT events, suggesting a possible dissociation between inflammatory phenotype and clinical thrombotic risk among different ethnic groups at high altitude. Age and ethnicity were relatively stable DVT-associated factors in this cohort, whereas platelet count, D-dimer, and platelet–inflammation composite indices were insufficient to explain the between-ethnicity difference in risk. Given the single-center retrospective design and the limited number of outcome events and matched patients, these findings require further validation in multicenter, large-sample prospective studies.