Summary

Aims: to determine the incidence, anatomical distribution and extentof deep vein thrombosis (DVT) in limbs undergoing elective unilateralknee arthroscopy without active prophylaxis, to evaluate its effect onvenous function following early diagnosis, and to quantify the impactof risk factors on its incidence. Methods: 102 consecutive patients undergoing unilateral kneearthroscopy without prophylaxis were studied. A history was obtainedwith emphasis on the risk factors for thromboembolism, and physicalexamination and colour duplex were performed prior to and within aweek after surgery. Patients who developed calf DVT were givenaspirin (150 mg) and compression stockings; those with proximal DVTwere admitted for anticoagulation (heparin followed by warfarin).Follow-up (mean 118 [range 84-168] days) entailed weekly physicaland duplex examinations during the first month and monthly thereafter. Results: 8 patients developed calf DVT in the operated leg (incidence7.84% [95% Cl: 2.7%-13.2%]); thrombosis was asymptomatic in4 of those (50%), caused calf tenderness in 4 (50%) and a positiveHoman’s sign in one (12.5%). DVT occurred in the following veins:peroneal 4 subjects (50%), soleal 4 (50%), gastrocnemial 2 (25%) andtibial 2 (25%). Propagation of a calf DVT to the popliteal vein wasidentified in 1 patient (12.5%). After a median period of 118 days, totalclot lysis was found in 50% of DVTs, with partial thrombus resorptionin the rest; reflux in the thrombosed veins was present in 75% of limbswith DVT. 43% of patients had 1 risk factor for DVT and 20% had =2.The incidence of DVT was higher amongst those with two or more riskfactors for thromboembolism (p <.05) or those with previous thrombosisalone (p <.005). Symptoms or signs of pulmonary embolismwere not documented. Conclusions: Elective unilateral knee arthroscopy performedwithout prophylaxis is complicated by ipsilateral calf DVT in 7.8%(95% CI: 2.7%-13.2%) of cases. The risk is higher in the presence ofprevious thrombosis (relative risk: 8.2) and two or more risk factors forDVT (relative risk: 2.94). Thrombosis may propagate to the proximalveins, despite early diagnosis. 50% of calf clots totally lyse in 4 months,yet reflux develops in at least 75% of limbs with DVT. Further studiesto determine optimal prophylaxis are warranted.