Thromboembolism following orthopaedic surgery : outcome and diagnostic procedures after prophylaxis in lower limb injuries

Abstract

Deep vein thrombosis (DVT) and pulmonary embolism (PE) frequently occur after major orthopaedic surgery. The clinical assessment of DVT and PE is unreliable and most cases are asymptomatic. However, even in asymptomatic DVTs, the risk for a PE is considerable. Low-molecular-weight heparins (LMWHs) have been shown to be safe and effective for this purpose and are used especially in patients undergoing major orthopaedic surgery. Whether prophylaxis is necessary after minor surgery and plaster cast immobilization of the lower limb still remains an issue of debate. Available techniques for the objective diagnosis of DVT include both invasive and non-invasive methods. Technical advances and increased experience have improved the accuracy of non-invasive methods such as colour duplex sonography (CDS).

In an observational study of 30 816 consecutive patients (Paper I) undergoing orthopaedic surgery the mortality and incidence of DVT and PE was recorded prospectively during a 6-week follow-up. After major joint surgery of the lower extremity, after spinal surgery and after lower limb fracture surgery, thromboprophylaxis (LMWHs) was administered during 7 to 10 days. The overall DVT and PE incidence was 1.0% and 0.3%, respectively, and the 6-week mortality was 2.3%. The highest incidence of venous thromboembolism (VTE) with the LMWH prophylaxis was seen after pelvic fracture surgery (13.0%) and knee replacement (3.5%). The highest incidence without prophylaxis was found after Achilles tendon repair (7.0%).

The sensitivity and specificity of CDS were compared with that of phlebography in a prospective trial (Paper II) with 180 consecutive patients surgically treated for ankle fracture. With a sensitivity of 96% and a negative predictive value of 99%, the results showed that CDS is highly reliable for ruling out DVT for screening purposes.

In a randomized placebo-controlled double-blind study (Paper III) on patients surgically treated for an ankle fracture, one week of open-labeled treatment with dalteparin was followed by 5 weeks of dalteparin prophylaxis or placebo. The phlebography verified a DVT incidence of 21% in the dalteparin group and 28% in the placebo group. This difference was not statistically significant and the results do not support the use of prolonged thromboprophylaxis after ankle fracture surgery.

In another randomized placebo-controlled study (Paper IV), thromboprophylaxis with dalteparin during 6 weeks was compared with placebo during immobilization after Achilles tendon repair. DVT screening was performed with CDS and all DVTs were confirmed with phlebography. The phlebography verified that the DVT incidence was 34% in the treatment group and 36% in the placebo group. This difference was not statistically significant and thromboprophylaxis after Achilles tendon repair cannot be recommended on the basis of these results.

In summary, despite prophylaxis VTE remains an important cause of morbidity and mortality after orthopaedic surgery. Adequate thromboprophylaxis is essential after major procedures although prolonged prophylaxis after ankle fracture surgery and Achilles tendon repair did not reduce the risk of DVT.