The details of all patients with a proximal femoral fracture presenting at a single institution (Peterborough District Hospital, U.K.) between January 1989 and January 2007 were recorded at the time of admission. The collection of data had been approved by the Hospital Review Board. Patients over the age of 16 years were included, including those with fractures secondary to tumors or with localized bone pathology—such as Paget's disease.
Preoperative data included the patient demographics, patient's residence preoperatively, mobility (including the use of walking aids), mental test score, and smoking status. In addition, the hemoglobin (g/L) on admission was recorded. The length of time from fracture to admission and from fracture to surgery was also documented.
Mobility was assessed using a mobility score rated from 0 to 9. A score of 9 represented full mobility without the use of walking aids, while a score of 0 signified that the patient was bed-bound (Parker and Palmer 1993
). The mental test score was a series of 10 questions on recall, scored from 0 to 10 (Qureshi and Hodkinson 1974
Operative details regarding the type of procedure performed, the length of surgery, and length of anesthesia were collected. Patients who were treated nonoperatively were excluded from any analysis involving operative timing. The type of anesthetic was documented, as was any co-morbidity (as assessed by ASA grade).
Fractures were classified into intracapsular, inter-trochanteric, and sub-trochanteric (Parker 2001
). Intracapsular hip fractures were treated either with fixation with multiple screws or with a hemiarthroplasty. Extracapsular fractures were treated by internal fixation with a sliding hip screw or an intramedullary nail.
All symptomatic VTE cases were recorded, defined as any case of symptomatic deep vein thrombosis or pulmonary embolism. Deep vein thrombosis was defined as any thrombosis diagnosed by ultrasound, venography, or at autopsy. Pulmonary embolism was diagnosed by computer tomography pulmonary angiography (CTPA), nuclear medicine isotope scanning, or at autopsy. All patients presenting with symptoms of VTE were subject to investigation.
After discharge from hospital, at least 1 follow-up assessment was undertaken in a hip-fracture clinic after 6 weeks. Subsequent follow-up was by telephone with a final follow-up at 1 year after admission. Any patient who had been diagnosed with a VTE in the community was identified at the follow-up points.
All patients received thromboprophylaxis, which was given from the day of admission. From 1989 until 1992, unfractionated calcium heparin was used (5,000 units twice daily). In 1992, the thromboprophylaxis regime was changed to low-molecular-weight heparin (Enoxaparin, 40 mg once a day). The thromboprophylaxis regime was continued for 14 days after surgery. Graduated compression stockings and mechanical calf or foot pumps were not used. After surgery, all patients were mobilized as soon as possible.
Initially, the baseline characteristics of the group that presented with VTE were compared with the baseline characteristics of the group without VTE. The methods of analysis were chi-squared test for categorical variables, the Mann-Whitney test for variables involving length of time, and t-test for other continuous variables. Statistically significant risk factors for VTE were assessed together by multivariate analysis in a logistic regression model, adjusting for sex and age. Effects are presented as odds ratios, which approximate to relative risk due to the low incidence rates.
The VTE group was subdivided into the subcategories of deep vein thrombosis and pulmonary embolism, and compared with the group with no thrombosis using similar methods. All tests were two-sided, and were assessed both at the 5% level of significance—and also at the stricter 1% level. Analyses were done using SPSS version 12.0.1.