Criticism of Current Ultrasound Guidelines Regarding Causes of DVT
Why is it that the standardised way of assessing the popliteal vein is carried out in the standing position when general understanding and observation demonstrate DVT occurs in the recumbent position?
Popliteal Vein compression has been reported by others in France, Italy and the USA in examinations in the erect standing position in small numbers but in our observations and those by Huber in Australia have demonstrated a very high incidence of total popliteal vein compression in recumbent positions. Sitting with the legs up extended, the favourite recommendation to treat leg swelling, heart failure etc., Patients in hospital sit with the legs extended in bed. The favourite lounges now being sold encourage this position to be assumed for hours in the new home Cinemas. On long flights in economy the sleep position forces the legs into extension under the seat in front, there is no room to get comfortable otherwise. The new development and fashion of flat beds for flying now adds a dimension where first class passengers can experience long periods recumbent with their legs extended.
In hospitals plaster casts are applied with the legs extended and patients are encouraged to spend most of their time with the legs up while recumbent.
In the operating theatre supine patients are positioned with their legs hyperextended on achilles rests designed to prevent decubitus ulcers of the heel. Huber has demonstrated 40% of these patients have total occlusion of the main deep vein of the leg in the Popliteal region. DVT would therefore be a much higher risk than a heel ulcer.
We have been scanning all patients who present with venous problems for this condition and have found many hundreds in the last 30 months. It is very common. Marzo in Rome has reported an incidence of at least 25% in his community studies.
The major cause appears to be the anatomical arrangement at the back of the knee where the vein can be compressed by the overarching muscle the gastrocnemius, as it gets stretched taught by extension.
This has been demonstrated in sporadic studies, often just case reports since the 1960s. Division of the muscle can resolve the problem but this is not a sensible solution for such a common problem unless there are major complicating factors with venous stasis, ulcers, recurrent DVT, which are generally associated with the condition being expressed whilst standing also. We have found prolonged recumbency can produce these same problems. One recent patient developed such a swollen leg after knee surgery he had been confined to bed with leg elevation in extension for 7 months before he was referred with a massively swollen, red, hot lower leg. This cured within 2 weeks after he was told to keep the knee bent and to mobilise normally.
When patients with DVT are analysed for the likely cause, the current assessment is the in over 50% no underlying cause is recognised.
This problem of Popliteal Vein Compression however is common, fits the condition of recumbency which is associated with the large numbers of DVT and may become an increasing problem as fashion dictates lounges and recliners which will put those that sit back with their legs up for prolonged periods at risk.
It is difficult to display evidence of popliteal vein occlusion in the acute situation if clot extends through the popliteal vein. However it is usually evident in the contralateral limb. This is not always the case as there are individuals who are affected only unilaterally.
Over 50% of the patients we have cared for in the last 30 months with DVT have this condition as the most likely cause.
According to current Medical opinion the cause for the majority of DVTs is unknown.
Recurrent DVTs occur in 20% of this unknown category within 24 months. Another 10% show similar recurrence if associated with plaster casts, travel etc. That is 30% recurrence with no real explanation within 2 years. This lack of knowledge has allowed current recommendations for treatment to be haphazard and illogical, based on probable haematological factors which have been proven as unfounded.
Popliteal Vein Compression with the Knee Extended in the sitting or recumbent position is the factor most able to explain the cause of DVT. Prevention of Vein Occlusion by this functional problem with our anatomy should offer major assistance in the Prevention of DVT.
Modification of all human activities that cause prolonged Popliteal Compression Occlusion are necessary.
Hospital beds, Home beds, Lounges, Recliners, Airline seats and Flat beds need Modification.
Individual factors that increase the Gastrocnemius muscle mass, weight lifting, extreme sports, cycling and obesity may increase the risk. Obesity stands out for the likelihood of associated extended recumbency, in addition the common finding of genu recurvatum or hyperextension of the knee associated with ligament stretch is very common in the obese and usually is found with Popliteal Vein Compression even in the standing position.
Ultrasound assessment of venous conditions needs to have new standards and guidelines, the current guidelines prevent this condition from being recognised.
The youngest patient we have found with this to be associated with Varicose Veins is 17 years old.
Guidelines for drug therapy require total reassessment . Current Guidelines are not geared to assess rapidity of clot resolution, comparative effects on long term stasis problems or appropriate protection against the high incidence of recurrence in the main group of DVT.