Lapidus 2007a.

Methods	Study design: randomized, controlled, double‐blind trial Method of randomization: by computer Concealment of allocation: not specifically reported Losses to follow‐up: 4 (withdrawal of consent treatment group 2, control group 2) and excluded from efficacy analysis
Participants	Country: Sweden Number randomized: 105; treatment group 52; control group 53 Number reported, included in analysis 1 (all participants with negative color duplex sonography, and all participants with DVT verified by phlebography): 91; treatment group 47; control group 44 Number reported, included in analysis 2 (all participants with color duplex sonography for patients with multiple distal DVT or proximal DVT, and all participants with DVT verified by phlebography): 96; treatment group 49; control group 47 Age mean (SD): treatment group 37 years (8); control group 42 years (9) Sex (male/female): treatment group 41/11; control group 42/11 Inclusion criteria: age 18 to 75 years, admitted for an acute (0 to 72 hours) Achilles tendon rupture, accepted for surgery Exclusion criteria: inability or refusal to give informed consent, ongoing treatment with anticoagulant therapy, known allergy for contrast media, kidney disorder, recent thromboembolic event, recent surgery, known malignancy, current bleeding disorder, pregnancy, treatment with platelet inhibitors
Interventions	Treatment group: LMWH dalteparin 5000 units sc once daily until removal of the plaster cast Control group: placebo
Outcomes	Diagnosis of DVT by means of ultrasound and confirmation by venography
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomization by computer, no further information provided. However, patients were not included when study personnel were off duty
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Study described as double‐blind. Each patient received a box containing 45 prefilled syringes with either Dalteparin or placebo. Syringes of both groups were identical. Blinding of personnel was not explicitly described.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	"evaluation was carried out by an experienced independent radiologist blinded to the randomization and previous phlebographic findings"
Incomplete outcome data (attrition bias) All outcomes	Low risk	4 patients were lost to follow‐up, evenly divided between the two groups.
Selective reporting (reporting bias)	Low risk	Outcome measures were reported, as well as any adverse event.
Other bias	Low risk	No other bias was detected.