High Risk of Venous Thromboembolism With Aspirin Prophylaxis After THA for High-riding Developmental Dysplasia of the Hip: A Retrospective, Comparative Study.

BACKGROUND Despite advancements, THA is still associated with risks, particularly venous thromboembolism (VTE). THA in patients with high-riding developmental dysplasia of the hip (DDH) could potentially be associated with an elevated risk of VTE. We conducted a study to evaluate whether patients with high-riding DDH undergoing THA and receiving aspirin have an increased risk of symptomatic VTE compared with patients undergoing primary THA for other diagnoses. Additionally, we investigated possible risk factors for VTE within this specific patient group. QUESTIONS/PURPOSES (1) Is the risk of symptomatic VTE (all deep vein thrombosis [DVT] plus pulmonary embolism, or proximal DVT plus pulmonary embolism) increased in patients undergoing THA for severe DDH, defined as Crowe type III or IV, compared with patients undergoing THA for other reasons when aspirin is used for prophylaxis? (2) In patients with severe DDH undergoing THA, are there specific identifiable risk factors associated with an increased risk of symptomatic VTE? METHODS Between June and November 2021, an arthroplasty surgeon performed 153 consecutive primary THAs on 146 patients across two arthroplasty centers. All patients except those with a history of prior VTE or those on chronic anticoagulation received aspirin as pharmacologic prophylaxis for VTE. No routine surveillance for VTE was used. To be eligible for this retrospective comparative study, a chart note documenting any signs or symptoms of symptomatic VTE had to be present at least 3 months postoperatively. Patients were excluded for the following reasons: they had a personal history of VTE (1% [2 of 146]), they were receiving ongoing anticoagulant therapy (2% [3 of 146]), they were out of the age criteria range (2% [3 of 146]), they had undergone same-setting bilateral THAs or the second side of staged bilateral THAs (3% [4 of 146]), or they were lost to follow-up within 90 days after surgery (0% [0]). After exclusions, 134 patients (134 hips) remained. Patients were divided into two groups based on their preoperative diagnosis: (1) high-riding DDH of Crowe type III or IV (35% [47 of 134] of hips) and (2) all other diagnoses, including primary or inflammatory arthritis, Crowe type I or II DDH, fracture, and osteonecrosis (65% [87 of 134] of hips). A comprehensive records review was conducted to determine the incidence of symptomatic VTE, including distal DVT, proximal DVT, or pulmonary embolism. Patients' demographics, surgical details, and outcomes were compared between the groups. The high-riding group had longer operations and a higher percentage of patients having general anesthesia, acetabular bone grafting, transfusions, or restricted weightbearing postoperatively. Univariable analysis was performed to compare the high-riding DDH group with the control group and to evaluate associations between potential risk factors and symptomatic VTE. Subsequently, multivariable logistic regression was conducted to identify independent risk factors among the variables identified in the univariable analysis. RESULTS Patients undergoing THA for DDH had higher odds of experiencing symptomatic VTE compared with the control group (17% [8 of 47] versus 1% [1 of 87], OR 18 [95% confidence interval (CI) 2 to 146]; p = 0.001). After adjusting for confounding variables such as age, sex, American Society of Anesthesiologists grading, anesthesia type, operation duration, shortening osteotomy, shelf/impaction grafting, and blood transfusion, patients undergoing THA for high-riding DDH still had higher adjusted odds of symptomatic VTE compared with the other group (adjusted OR 67 [95% CI 3 to 151]; p = 0.008). When considering only proximal DVT or pulmonary embolism events (excluding distal DVT), the odds of experiencing a VTE event remained higher in patients with high-riding DDH compared with the other group (11% [5 of 47] versus 1% [1 of 87], OR 10 [95% CI 1 to 90]; p = 0.02). In patients undergoing THA for high-riding DDH, after controlling for potential confounding variables, limb lengthening was identified as the only factor associated with an increased likelihood of symptomatic VTE (median [range] lengthening 38 mm [25 to 60] versus 25 mm [15 to 50]; p = 0.002). CONCLUSION Our findings showed that patients undergoing THA for high-riding developmental DDH and receiving aspirin for VTE prophylaxis had a higher likelihood of experiencing symptomatic VTE, including DVT and pulmonary embolism, compared with patients undergoing primary THA for other indications. Additionally, greater intraoperative limb lengthening in this group appeared to further increase the risk of VTE. While DDH may be a risk factor for symptomatic VTE after THA, this association could also be attributed to the increased complexity of the procedure in hips with high-riding DDH. Until larger studies with multivariable analyses of potential risk factors are conducted to clarify this issue, we recommend that surgeons consider using thromboprophylaxis agents more potent than aspirin for patients undergoing THA for high-riding DDH and remain particularly vigilant in the postoperative period for signs and symptoms of VTE. LEVEL OF EVIDENCE Level III, therapeutic study.