**3. Evaluation**

Apart from the history and the classic clinical symptoms and examination findings of pain, tenderness, and swelling of the leg, different techniques are employed to detect even small thrombi in the venous system.

**4. DVT prophylaxis guidelines**

**Figure 2.** Highlights of the recent ACCP guidelines for thromboprophylaxis.

ACCP 2012 guidelines recommend thromboprophylaxis for patients undergoing TJA for a minimum of 10–14 days. They prefer agents like low molecular weight heparin (LMWH), vitamin K antagonist, aspirin, fondaparinux, apixaban, dabigatran, or rivaroxaban. Regular Doppler screening during postoperative period is not recommended. But, prophylaxis is advocated as it is recognized that asymptomatic DVT can produce a fatal PE [6] (**Figure 2**).

Methods of DVT Prophylaxis after Total Knee Arthroplasty

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*Ultrasound Doppler*: it is the most common test used for diagnosing deep-vein thrombosis. It is quick, noninvasive, cheap and patient-friendly.

*D-dimer test*: the level of D dimer will be elevated in the presence of a blood thrombus.

*Venography*: this test is indicated if ultrasound does not provide a clear diagnosis. It is an invasive technique whereby a radio-opaque dye is injected into a vein, and then, a radiograph is taken of the leg. The entire pathway of the vein can be identified from the X-ray, and any obstruction somewhere indicates a thrombus.

*Impedance plethysmography*: changes in venous filling are produced by inflating and deflating the thigh cuff, and electrodes sense the change in blood volume by electrical impedance in the calf veins. A delay indicates that an occlusive thrombus is present in the popliteal or more proximal veins. But this modality is not useful in detecting more proximal DVTs.

*Ventilation–Perfusion Scan (V/Q scan)*: a lung V/Q scan uses a ventilation (V) scan to measure air flow in the lungs and a perfusion (Q) scan to assess the blood flow in the lungs. This will detect even an occult event of pulmonary embolism.

*Pulmonary CT angiography*: currently, the most commonly used first-choice imaging examination in patients with suspected PE is pulmonary CT angiography [4]. This recommendation is based on high sensitivity and specificity for PE and other clinically important conditions that mimic PE.

But the point of interest is to prevent the occurrence of DVT rather than its detection. All these modalities are used to detect even a minute thrombus occurring in the system. Apart from the identification of high-risk patients, it would be better to screen all these patients for DVT preoperatively. So many studies have been done in this regard in different population using preoperative Doppler screening studies. According to the Scottish Arthroplasty Registry, the incidence of clinically significant VTE within 3 months of TKA is 1.79%, whereas that of fatal PE is 0.15% [5] and the asymptomatic DVT rates are much higher. Therefore, thromboprophylaxis use has been recommended for all patients undergoing TJA in Western population. Many other regional studies have shown that the incidence of DVT in patients undergoing TKA is so less to warrant a regular preoperative Doppler screening. However, it is said that a better modality to detect thrombi would be venography, which is not an appealing invasive procedure.

Numerous guidelines and recommendations suggest the use of various methods of thromboprophylaxis and methods to reduce the risk of development of modifiable factors. Pharmacological and mechanical prophylaxis methods are used, either in isolation or in combination, to reduce the risk of postoperative VTE.
