title: Popliteal vein compression with the limb extended.
abstract: BACKGROUND
  The aim of this study was to assess the haemodynamic significance of popliteal vein compression by full knee extension.
  
  
  METHODS
  We examined patients without a history of previous deep vein thrombosis with the knee slightly flexed and then fully extended. The popliteal vein diameters and venous pressures in 61 subjects (116 limbs) were examined using duplex ultrasonography and photoplethysmography. The venous outflow in 50 patients was assessed using photoplethysmography.
  
  
  RESULTS
  The diameter of the popliteal vein in semiflexion was 7.7 (+ 1,5) mm, in extension it was reduced to 4.3 (+ 1,7) mm (p < 0.001). Venous pressure in the big toe rose from 12.3 (+ 6,1) mmHg to 15.5 (+ 7,4) (p < 0.001). We have demonstrated the reduction of maximum venous outflow in 50 patients from 65.8 (+ 24) %/min to 60.1 (+ 23) %/min (p < 0.01) immediately after loosening the 2-minute venous occlusion, as well as outflow reduction during subsequent seconds.
  
  
  CONCLUSIONS
  Our results provide evidence of haemodynamically significant popliteal vein compression in full extension of the limb. Clinically, the compression may play a role as a risk factor for venous thrombosis in immobilized patients, particularly during operations.
authors.affiliation: 3rd Department of Internal Medicine, General University Hospital, Praha. jiri.spacil@vfn.cz
authors.forename: Jiří
authors.initials: J
authors.lastname: Spáčil
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D002908:Chronic Disease; D003251:Constriction, Pathologic; D005260:Female; D006439:Hemodynamics; D006801:Humans; D035002:Lower Extremity / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D056888:Patient Positioning; D017156:Photoplethysmography; D011152:Popliteal Vein / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011237:Predictive Value of Tests; D012039:Regional Blood Flow; D012307:Risk Factors; D018616:Ultrasonography, Doppler, Duplex; D014652:Vascular Diseases / Q000175:diagnosis / Q000503:physiopathology*; D014690:Venous Pressure; D020246:Venous Thrombosis / Q000209:etiology / Q000503:physiopathology; D055815:Young Adult