Continuous passive motion for preventing venous thromboembolism after total knee arthroplasty.

BACKGROUND: Total knee arthroplasty (TKA) is a common form of orthopedic surgery. Venous thromboembolism (VTE), which consists of deep venous thrombosis (DVT) and pulmonary embolism (PE), is a major and potentially fatal complication after TKA. The incidence of DVT after TKA is 40% to 80% and the incidence of PE is approximately 2%. It is generally agreed that thromboprophylaxis should be used in patients who undergo TKA. Both pharmacological and mechanical methods are used in the prevention of DVT. Pharmacological methods alter the blood coagulation profile and may increase the risk of bleeding complications. When pharmacological methods cannot be used, the mechanical methods become crucial for VTE prophylaxis. Continuous passive motion (CPM) is through an external motorised device which enables a joint to move passively throughout a preset arc of motion. Despite the theoretical effectiveness and widespread use of CPM, there are still differing views on the effectiveness of CPM as prophylaxis against thrombosis after TKA.

OBJECTIVES: The aim of this review is to determine the effectiveness of continuous passive motion therapy for preventing thrombosis in patients after total knee arthroplasty (TKA).

SEARCH METHODS: The Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (last searched January 2011), CENTRAL (2011, Issue 1), MEDLINE (1948 to Week 2 January 2011) and EMBASE (1980 to Week 3 January 2011). In addition, the authors searched the reference lists of identified trials.

SELECTION CRITERIA: Randomised controlled trials (RCTs) comparing the use of CPM with control in preventing DVT or PE after TKA. People aged 18 years and older who have undergone TKA were included in this review. We excluded studies of patients who presented with DVT at baseline. Both the experimental and control groups received similar postoperative care and therapy other than the CPM.

DATA COLLECTION AND ANALYSIS: Two review authors independently assessed the citations retrieved by the search strategies for reports of relevant RCTs. They independently selected trials that satisfied the inclusion criteria, extracted data and undertook quality assessment. Effects were estimated as risk ratios (RRs) or mean differences or standardised mean differences with 95% confidence intervals (CI). Meta-analyses were performed using a fixed-effect model for continuous variables. Where heterogeneity existed (determined by the I(2) statistic), a random-effects model was used.

MAIN RESULTS: Ten randomised controlled trials involving 764 participants met the inclusion criteria. Four studies with a total of 361 patients reported the incidence of DVT. In the CPM group (182 patients) 36 developed DVT (20%) compared to 28 (16%) the control group of 179 patients. The meta-analysis result showed no evidence that CPM had any effect on preventing VTE after TKA (RR 1.27, 95% CI 0.87 to 1.86). One trial (150 participants) did not find PE in any of the patients during hospitalisation or in the subsequent three months. None of the trials reported any deaths of the included participants.

AUTHORS' CONCLUSIONS: There is not enough evidence from the available RCTs to conclude that CPM reduces VTE after TKA. We cannot assess the effect of CPM on death because no such events occurred amongst the participants of these trials.