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Thromboprophylaxis in Trauma & Orthopaedic Surgery

  Len Funk, Chris Lewis, Sherif Awad, Jas Daurka - 1999

  Why? - Pathophysiology; Incidences; Cost Benefit

Who? - Which Patients?; Which Procedures?

How? - Efficacy; Complications; Cost

1. WHY ?

A. Pathophysiology [Lieberman, 1994]

A total hip or knee arthroplasty is a potent stimulus for the formation of thrombi. The triad of venous stasis, hypercoagulability, and endothelial injury is associated with the formation of thrombi and is present perioperatively in patients being managed with an arthroplasty of the lower extremity. A large proportion of thrombi have been shown to begin intraoperatively. Venous stasis results from the positioning of the limb during the procedure, localised postoperative swelling, sand reduced mobility after the operation. McNally and Mollan confirmed dramatic reductions in the venous capacitance of the lower limbs and in the venous outflow after hip arthroplasty. Torsion and complete occlusion of the femoral vein during dislocation of the hip joint and insertion of the prosthesis have also been demonstrated with the use of intraoperative venography. Finally, knee arthroplasty involves the use of a tourniquet on the thigh and flexion of the knee for a prolonged time.

      Injury to the venous endothelium as a result of operative positioning and manipulation, thermal injury from bone cement, and the use of a tourniquet on the thigh may result in foci of vascular damage that provide a nidus for thrombosis. The trauma of the procedure itself results in a sustained activation of tissue factor and other clotting factors, which then localise at the sites of vascular injury and in the areas of venous stasis. Postoperative reduction in the levels of antithrombin III and inhibition of the endogenous fibrinolytic system may allow continued growth of the thrombus.

 Following femoral neck fractures the combination of trauma to a lower extremity, forced immobilisation that often lasts several hours or even days, and an operative procedure places elderly patients at especially high risk for the development of venous thrombosis.

B. Incidences

 i. Lower Limb Arthroplasty Surgery:

  The historical rate of venous thromboembolic complications in unprotected hip and knee arthroplasty was well documented in the 1970s and '80s with large clinical series using venography, pulmonary angiography, and autopsy as diagnostic endpoints [Bergqvist, 1983; McNally, 1993].

 They have described the following incidences:

 .         Without prophylaxis -

.         40 to 80% DVT incidence overall

.         15 to 25% proximal DVTs

.         0.5 to 2% PE incidence.

.         0.1 to 0.2% Fatal PE rate (Murray, Britton et al. 1996)[Murray et al, JBJS, 1996]

.         PE is the most common cause of death after a hip or knee arthroplasty when thromboprophylaxis is not used.

.         With prophylaxis -

.         10 to 15% DVT

.         3 to 7% Proximal DVT following THR [Paiemont, Schutzer, J Arthroplasty, 1992]

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