This study reported an overall prevalence of DVT of 6.2% in patients undergoing UKA using 10 mg rivaroxaban (3 days) for chemical DVT prophylaxis after the surgery during hospitalization. The prevalence of DVT was 7.4% in patients undergoing UKA 3 months after discharge without any specific DVT prophylaxis treatment. No symptomatic DVT or PE was detected during the whole length of hospital stay or the whole 3-month follow-up. No proximal DVT was observed in the present study.
The ninth ACCP guideline recommends pharmacologic DVT prophylaxis for Total hip arthroplasty (THA) and TKA for a minimum of 10–14 days and up to 35 days, respectively (8). However, no recommendation was made for the duration of chemical prophylaxis in patients undergoing UKA. It is desirable to reduce the pharmacologic administration period because chemical prophylaxis is associated with several complications such as infection, wound problems, and hematoma formation (9, 15). A study published in 2016 explored whether routine thromboprophylaxis was necessary for Korean patients undergoing UKA by determining the prevalence of VTE without chemical prophylaxis (16). Their results showed that the overall prevalence of VTE was 26%, although no symptomatic DVT or PE was detected (16). The prevalence of VTE of 26% was higher than the prevalence of VTE of 0–5% following UKA in the present study and some other previous studies (17–19). However, only with symptomatic VTE who received routine pharmacological prophylaxis were evaluated in previous studies (17–19). In this study, the prevalence of VTE was examined among asymptomatic patients. Hence, it was believed that the prevalence of 6.2% and 7.4% in the present study was really low. This study suggested that 3-day chemical thromboprophylaxis was sufficient in patients undergoing UKA.
The results showed that six of nine DVTs (66.7%) dissolved 3 months postoperatively after discharge. Previous studies showed the complete resolution of VTEs without thrombolysis in patients after TKA, regardless of size or location (3, 20). The aforementioned study conducted by Korean scholars demonstrated the complete resolution of all VTEs during the postoperative 6-month follow-up (16). Therefore, it was suggested that therapeutic thrombolytic treatment might not be necessary for patients undergoing UKA who had only asymptomatic DVTs. Six of 108 patients (5.6%) were detected with newly formed DVTs 3 months after discharge in the present study. Several studies suggested that VTEs might occur in people without surgery (21, 22). In 2017, a study evaluated 322 patients admitted for TKA and found that 56 patients (17.4%) were diagnosed with preoperative DVT (21). Another study showed that the prevalence of DVT was 8% before TKA (22). The results of the present study suggested that abandoning specific DVT prophylaxis after discharge did not increase the prevalence of VTEs.
The pneumatic leg compression, effective pain management, and rehabilitation exercises, including ankle pump movement, ambulation, range-of-motion exercises, and muscle strength development, also played a pivotal role in DVT prophylaxis after UKA. Several studies emphasized the importance of pneumatic compression (23–25). A study showed that intermittent pneumatic compression might be an effective and safe method for preventing VTE after total hip arthroplasty (23). Another study demonstrated that intermittent compression applied during exercise could result in increased limb blood flow (24), contributing to DVT prophylaxis. A meta-analysis study including 22 trials revealed that the combination of pneumatic compression and pharmacological prophylaxis could reduce the incidence of symptomatic PE from 2.92–1.20%, compared with pharmacological prophylaxis alone (25). The duration of chemical prophylaxis administration and pneumatic leg compression in the present study was supported by a previous study comprising a large cohort of patients undergoing total joint arthroplasty, which demonstrated that 81% of symptomatic PE cases occurred within the first three postoperative days (26). It was also presumed that rehabilitation played a positive role toward DVT prophylaxis, as vein circulation in the lower limb could be promoted. A study showed that active ankle movements might prevent the formation of lower-extremity DVT after orthopedic surgery (27). One study showed that active movement of the ankle joint yielded better results in DVT prevention compared with passive movement (28). Effective pain management was essential for active rehabilitation exercise.
The present study had several limitations. First was the use of ultrasound in majority of patients to detect DVT. The sensitivity of using ultrasound to detect DVT was between 88% and 100%, although venography was considered the gold standard to detect DVT (29, 30). Ultrasound is technician dependent, which might affect the sensitivity to detect DVT. Both the sonographers in the present study had experience of handling about 2000 cases of DVT each year at the institution. Also, the use of duplex ultrasound was less expensive, less invasive, and more convenient compared with venography. Second was the relatively small sample size. Only 146 patients were enrolled in this study, and all participants were Chinese. A multi-ethnic study enrolling a large number of patients is still needed. Third, a risk screening approach for patient stratification was not used to further diverge the duration of chemical prophylaxis. Further, only one kind of pharmacological thromboprophylaxis agent was used in the present study.