The effect of the pneumatic tourniquet on the incidence of postoperative deep venous thrombosis is uncertain. We carried out a controlled study comparing the incidence of deep venous thrombosis when a tourniquet was used with the incidence when a tourniquet was not used. Thrombosis was detected by radioisotope venography. The results of the study showed no difference in incidence and we concluded that the pneumatic tourniquet has no influence on the formation of a thrombus in a deep vein

The aim of this study was to determine the prevalence of deep venous thrombosis (DVT) following lower limb arthroplasty and to assess whether this adversely affected satisfaction, relief from pain, or the level of mobility as perceived by patients. Six hundred and ten consecutive recipients of primary total hip replacement (THR) or total knee replacement (TKR) underwent routine post-operative venography. The functional outcome had already been assessed at one year by using the Regional Arthroplasty Database questionnaire, the results of which were correlated to venographic records. The combined prevalence of DVT after THR and TKR in the patients, who did not receive chemical thromboprophylaxis, was 46.4%. Thrombus was identified in 57.6% of those with a TKR and in 33.5% of patients with a THR. Proximal thrombus was found in 11.0% of TKRs and in 14.8% of THRs. One year after surgery, patients who had a DVT established by venography did not report higher levels of immobility (p = 0.07), discomfort (p = 0.12) or dissatisfaction (p = 0.23) when compared to those with patent venous systems. This suggests that the prevalence of DVT following TKR/THR without chemical thromboprophylaxis is high and these findings are consistent with the literature. However, patients did not perceive thrombosis to compromise their overall outcome. This challenges the belief that DVT is associated with morbidity and calls for further comprehensive research in this area. The low morbidity of the lower limb associated with DVT in these patients does not support the use of chemical thromboprophylaxis

Aims. The optimal management of an infrapopliteal deep venous thrombosis (IDVT) following total knee arthroplasty (TKA) remains unknown. The risk of DVT propagation and symptom progression must be balanced against potential haemorrhagic complications associated with administration of anticoagulation therapy. The current study reports on a cohort of patients diagnosed with IDVT following TKA who were treated with aspirin, followed closely for development of symptoms, and scanned with ultrasound to determine resolution of IDVT. Methods. Among a cohort of 5,078 patients undergoing TKA, 532 patients (695 TKAs, 12.6%) developed an IDVT between 1 January 2014 to 31 December 2019 at a single institution, as diagnosed using Doppler ultrasound at the first postoperative visit. Of the entire cohort of 532 patients with IDVT, 91.4% (486/532) were treated with aspirin (325 mg twice daily) and followed closely. Repeat lower limb ultrasound was performed four weeks later to evaluate the status of IDVT. Results. Follow-up Doppler ultrasound was performed on 459/486 (94.4%) patients and demonstrated resolution of IDVT in 445/459 cases (96.9%). Doppler diagnosed propagation of IDVT to the popliteal vein had occurred in 10/459 (2.2%) cases. One patient with an IDVT developed a pulmonary embolus six weeks postoperatively. Conclusion. The results of this study demonstrate a low rate of IDVT propagation in patients managed with aspirin. Additionally, no significant bleeding episodes, wound-related complications, or other adverse events were noted from aspirin therapy. Cite this article: Bone Joint J 2021;103-B(6 Supple A):18–22

Introduction. Deep venous thrombosis (DVT) is a potentially serious complication after total hip (THA) and knee (TKA) arthroplasty, traditionally justifying aggressive prophylaxis with low molecular weight heparin (LMWH) or direct oral anticoagulants (DOA) at the cost of an increased risk of bleeding. However, fast-track procedures might reduce the DVT risk and decrease the cost-benefit ratio of the current recommendations. The objective of this study was to compare thrombotic and bleeding risk in an unselected population of elective THA and TKA with a fast-track procedure. MATERIAL - METHODS. A series of 1,949 patients were analyzed prospectively. There were 1,136 women and 813 men, with a mean age of 70 years. In particular, 16% were previously treated by antiplatelet agents and 8% by anticoagulants. All patients followed a fast-track procedure including early walking within 24 hours of surgery, and 80% of patients returned home after surgery, with a mean length of stay of 3 days (THA) or 4 days (TKA). The occurrence of a thromboembolic event or hemorrhagic complication has been identified. Results. Out of the 1,110 THAs, 5 thromboembolic events were identified (0.4%): 2 non-fatal pulmonary embolism and 3 DVTs. There was no impact of these complications on the final result. 19 hemorrhagic complications were identified (1.7%): 10 significant haematomas (3 of which were complicated by infection), 9 anemias (with 4 transfusions). Out of the 839 TKAs, 9 thromboembolic events were identified (1.0%): 4 non-fatal pulmonary embolism and 5 DVTs. There was no impact of these complications on the final result. 14 hemorrhagic complications were identified (1.7%): 8 haematomas including 4 reoperations, 6 anemias (with 5 transfusions). Discussion. Thromboembolic complications after elective THA and TKA have virtually disappeared, with a rate of 0.7%. On the other hand, bleeding complications are now more frequent, with a rate of 1.7%. This suggests that the cost-benefit ratio of preventive treatments with LMWH or DOA should be reassessed. Prescribing LMWH or DOA after elective THA and TKA with fast-track procedures exposes the patient to a much higher risk of bleeding than thrombotic risk. The use of aspirin may represent an acceptable compromise in these patients

A wide variety of hospital data is reported to and published by national groups intending to compare quality of care between institutions. The rate of deep venous thrombosis and pulmonary embolism (DVT/PE) after orthopaedic surgery is among those reported. In an effort to examine the validity of hospital data reported to these national groups, we looked deeper into the cases of DVT reported by our hospital to the University Health Services Consortium (UHC). The rate of DVT/PE after orthopaedic surgical procedures reported to UHC for 2007 was 2.6% (33 cases). This rate is over twice the UHC mean for this same time period. Review of the 33 reported cases of DVT/PE revealed that only 12 were appropriately coded; if appropriately coded and reported, the DVT/PE rate would have been 0.95%. The rates of DVT/PE reported by this institution to UHC result in that institution being characterised as having comparatively high rates of this complication. However, the validity of this characterisation should be questioned, based on inconsistencies seen in the institution's diagnostic coding. This investigation raises concerns that coding variations between institutions may prohibit accurate quantification of hospital complications and ought not be used for the purpose of benchmarking

Background. Post-operative deep venous thrombosis (DVT) and subsequent pulmonary embolism (PE) remain a serious complication after total joint replacement. Although with modern chemical and mechanical prophylaxis and rapid rehabilitation the rate of symptomatic DVT and PE has reduced, isolation of pre-operative DVT, specially in patients with prior history of DVT remains a challenge. The aim of this study was to assess the use of pre-operative dopplers as a tool to detect and identify prior DVT in patients undergoing total joint replacement. Methods. Between January 2014 and December 2014, 211 elective primary and revision hip and knee arthroplasty were identified from our prospective institutional database. All cases were performed by two adult reconstruction specialists. All primary total hip arthroplasties (THA) were non-cemented and all primary total knee arthroplasties (TKA) were cemented with similar implant and technique. Prior to July 2014, only patients with prior history of DVT or PE underwent pre-operative dopplers. From July 2014, all cases underwent routine pre-operative doppler screening. All patients with clinical symptoms of calf pain underwent post-operative dopplers. Patients were followed for a minimum of 3 month post-operatively. All emergency room (ER) visits for role out DVT were identified. No patient was lost to follow. Results. 115 patients patient underwent pre-operative dopplers. Three patients had a history of prior popliteal DVT, none of which had post-operative DVT or PE. In the remaining 112 patients, none of the pre-operative dopplers were positive for DVT. 34 patients in this group (29%) underwent post-operative dopplers, either during the hospital stay or in the ER within 3 month after index surgery. Only one patient developed symptomatic PE (0.8%) after total knee arthroplasty. 96 patients did not have pre-operative dopplers, 3 of which (3%) had symptomatic DVT and PE during hospital stay, all after total knee arthroplasty. There was no statistical difference for rate of symptomatic DVT/PE between the two groups (p=0.3). There was no correlation between DVT and obesity, age, or revision versus primary cases. Discussion and Conclusions. Routine pre-operative dopplers do not significantly lower rate of symptomatic DVT/PE and are not helpful in early detection and prevention in asymptomatic patients prior to routine total joint replacement

Background. Post-operative deep venous thrombosis (DVT) and subsequent pulmonary embolism (PE) remain a serious complication after total joint replacement. Although with modern chemical and mechanical prophylaxis and rapid rehabilitation the rate of symptomatic DVT and PE has reduced, isolation of pre-operative DVT, especially in patients with prior history of DVT remains a challenge. The aim of this study was to assess the utility of pre-operative dopplers as a tool to screen and reduce DVT/PE rate in patients undergoing total joint replacement. Methods. Between January 2014 and December 2014, 211 elective primary hip and knee arthroplasty were identified from our prospective institutional database as two consecutive cohorts (115 cases had pre-operative dopplers and 96 did not). All cases were performed by two adult reconstruction specialists. All primary total hip arthroplasties (THA) were non-cemented and all primary total knee arthroplasties (TKA) were cemented with similar implant and technique. In the first cohort, all cases underwent routine pre-operative doppler screening and in the control cohort, only patients with prior history of DVT or PE underwent pre-operative dopplers. All patients with clinical symptoms of calf pain underwent post-operative dopplers. Patients were followed for a minimum of 3 month post-operatively. All emergency room (ER) visits for role out DVT were identified. No patient was lost to follow. Results. In the cohort with pre-operative dopplers, none of the pre-operative dopplers were positive for DVT, including three patients that had a history of prior DVT. 34 patients in this group (29%) underwent post-operative dopplers, either during the hospital stay or in the ER within 3 month after index surgery. Only one patient (no prior history of DVT) developed symptomatic DVT/PE (0.8%) after total knee arthroplasty. In the control cohort, 3 of which (3%) had symptomatic DVT, one of which had PE (1%) during hospital stay, all after total knee arthroplasty. There was no statistical difference for rate of symptomatic DVT/PE between the two groups (p=0.3). There was no correlation between DVT and age, gender or BMI. Discussion and Conclusions. Utilization of routine pre-operative dopplers for all patients did not lower the rate of symptomatic DVT/PE and are not helpful in early detection and prevention in asymptomatic patients prior to routine total joint replacement. Pre-operative dopplers should be used in selected patients with high risk of DVT

Patients with a thrombotic history are thought to be at greater risk for developing blood clots following total hip arthroplasty (THA) or total knee arthroplasty (TKA). The incidence of venous thromboembolism and risk factors associated with clot development in this population of patients, however, are not well defined. From the years 2002 to 2008, 547 patients undergoing elective joint arthroplasty with a history of thrombotic disease, defined by prior history of deep venous thrombosis (DVT) or pulmonary embolism (PE), were followed prospectively for a minimum of one month after TKA or THA. Patients received prophylactic anticoagulation with coumadin starting on POD 1 with or without bridge therapy with low molecular weight heparin (LMWH). Patients were compared for the following risk factors: advanced age (> 70 years old), inherited or acquired thrombophilia, time elapsed since prior episode, association of prior episode with surgery, and method of anticoagulation. Of the 547 patients, 72 (13.2%) developed symptoms consistent with DVT or PE. Thirty-two thromboembolic events (5.9%, 26 DVT, 6 PE) were confirmed by lower extremity Doppler ultrasound, spiral computerized tomography or ventilation-perfusion scanning. 60% of events occurred before POD 3, and the average INR at the time of diagnosis was 1.67. The incidence of thromboembolism was 14.6% and 9.9% for unilateral TKA and THA, respectively and 27.6% and 25% for bilateral TKA and THA, respectively. The institutional rate of DVT during that same time frame is 1.9%. History of inherited or acquired thrombophilia (p< 0.01), time elapse since prior thrmoboembolic event (p=0.04), and association of prior events with surgery (p=0.02) significantly increase the risk of thromboembolism in this population. Bridge therapy with LMWH of any dose did not significantly reduce the risk of DVT or PE, however, there was a trend towards significance (p=0.17). Eight patients (1.5%) experienced bleeding complications; 6 were major in nature (gastrointestinal bleeding and joint hematoma). Patients with a thrombotic history are at increased risk for developing DVTs after joint arthroplasty. These patients share the same risk factors for development of DVT or PE then patients without a history of prior events. Furthermore, thromboembolic events tend to occur early following surgery in these patients and treatment with LMWH may help reduce the risk of developing clots when used in combination with coumadin

Aim of Study: To assess the efficacy of Computerised Strain Gauge Plethysmography (CSGP) to screen for proximal Deep Venous Thrombosis (DVT) following Total Knee Replacement (TKR). Introduction: CSGP is a non invasive, bedside screening tool, used to detect the presence of proximal lower limb DVT. CSGP uses a low pressure thigh cuff to first occlude venous outflow. When the cuff is released the device is used to measure changes in calf dimensions (by means of strain gauges tied around a standardised point of the calf of the patient’s operated limb) thereby giving a measure of venous outflow. Obstruction to outflow (producing a positive result with the device) is seen with occlusion of proximal veins. Patients & Methods: A retrospective analysis of 184 consecutive patients who had undergone primary TKR was performed. Foot pumps were used for thrombophylaxis during the erioperative period. On the fifth post operative day all patients were screened for proximal DVT using CSGP. Those with a negative result who were ambulating safely were discharged. Those with a positive test had further imaging to confirm or refute the diagnosis of proximal DVT in the operated limb. The patients’ medical notes were scrutinised for evidence of re attendances and evidence of whether proximal DVT was diagnosed following discharge from the ward. Results: The negative predictive value of CSGP was found to be 99%. The sensitivity of CSGP for detecting proximal DVT was 83 %. The specificity was found to be 69%. The false positive rate was 92%. Conclusion: CSGP allows the safe and prompt discharge of TKR patients who testnegative with CSGP with some degree of confidence. Patients who test positive with CSGP however require further imaging to select out those individuals who have clinically significant proximal DVT meriting full anticoagulation post operatively

Aims

The aim of this study was to investigate the incidence, risk factors, and outcome of venous thromboembolism (VTE) following anterior cruciate ligament (ACL) reconstruction in a nationwide cohort.

The selection of a prophylaxis agent is a balance between efficacy and safety. Total knee arthroplasty patients receive DVT prophylaxis because orthopaedic surgeons are concerned about the morbidity and mortality associated with pulmonary embolism. However, at the same time there is great concern about excessive bleeding. The goal is to provide the appropriate anticoagulation to prevent symptomatic pulmonary embolism (PE) and DVT but at the same time avoid over anticoagulation which can be associated with bleeding and other wound problems. Therefore, risk stratification is necessary.

Although risk stratification is the ideal way to determine the appropriate prophylaxis agent to use for a specific patient, there is no validated risk stratification strategy available today. There is general agreement at this time that patients who have had a prior PE or symptomatic DVT are at higher risk for development of a pulmonary embolism. In addition, there is a general belief that patients who have coagulation abnormalities (i.e. Factor V Leiden, Protein C and S deficiency) have an increased risk of developing a pulmonary embolism. Other factors that have been mentioned as associated with PE after total hip arthroplasty include age, female gender, and higher body mass index. The selection of a prophylaxis regimen should be influenced by the ability to mobilise the patient after surgery.

Over a 13-year period we studied all patients who underwent major hip and knee surgery and were diagnosed with objectively confirmed symptomatic venous thromboembolism, either deep venous thrombosis or non-fatal pulmonary embolism, within six months after surgery. Low-molecular-weight heparin had been given while the patients were in hospital. There were 5607 patients. The cumulative incidence of symptomatic venous thromboembolism was 2.7% (150 of 5607), of which 1.1% had developed pulmonary embolism, 1.5% had deep venous thrombosis and 0.6% had both. Patients presented with deep venous thrombosis at a median of 24 days and pulmonary embolism at 17 days after surgery for hip fracture. After total hip replacement, deep venous thrombosis and pulmonary embolism occurred at a median of 21 and 34 days respectively. After total knee replacement, the median time to the presentation of deep venous thrombosis and pulmonary embolism was 20 and 12 days respectively. The cumulative risk of venous thromboembolism lasted for up to three months after hip surgery and for one month after total knee replacement. Venous thromboembolism was diagnosed after discharge from hospital in 70% of patients who developed this complication. Despite hospital-based thromboprophylaxis, most cases of clinical venous thromboembolism occur after discharge and at different times according to the operation performed

The December 2022 Spine Roundup. 360. looks at: Deep venous thrombosis prophylaxis protocol on a Level 1 trauma centre patient database; Non-specific spondylodiscitis: a new perspective for surgical treatment; Disc degeneration could be recovered after chemonucleolysis; Three-level anterior cervical discectomy and fusion versus corpectomy- anterior cervical discectomy and fusion “hybrid” procedures: how does the alignment look?; Rivaroxaban or enoxaparin for venous thromboembolism prophylaxis; Surgical site infection: when do we have to remove the implants?; Determination of a neurologic safe zone for bicortical S1 pedicle placement; Do you need to operate on unstable spine fractures in the elderly: outcomes and mortality; Degeneration to deformity: when does the patient need both?

Tranexamic acid (TXA) has been used to reduce blood loss during total hip arthroplasty (THA), but its use could increase the risk of venous thromboembolic disease (VTE). Several studies have reported that TXA does not increase the prevalence of deep vein thrombosis (DVT), but most of those used routine chemical thromboprophylaxis, thereby masking the potential increased risk of TXA on VTE. We wished to ascertain whether TXA increases the prevalence of VTE in patients undergoing THA without routine chemical thromboprophylaxis. We carried out a retrospective case-control study in 254 patients who underwent a primary THA, 127 of whom received TXA (1 g given pre-operatively) and a control group of 127 who did not. All patients had mechanical but no chemical thomboprophylaxis. Each patient was examined for DVT by bilateral ultrasonography pre-operatively and on post-operative days 1 and 7. TXA was found to statistically significantly increase the incidence of total DVT on post-operative day 7 compared with the control group (24 (18.9%) and 12 (9.4%), respectively; p < 0.05) but most cases of DVT were isolated distal DVT, with the exception of one patient with proximal DVT in each group. One patient in the control group developed a non-fatal symptomatic pulmonary embolism (PE). The use of TXA did not appear to affect the prevalence of either proximal DVT or PE.

Cite this article: Bone Joint J 2015; 97-B:458–62.

Introduction: Risk-profiling of patients in knee arthroplasty to prepare for postoperative complications is becoming more important. Materials and Methods: Major complications (hematoma, cardio-vascular complication, deep venous thrombosis, pulmonary embolism, joint infection and pneumonia) following 17644 knee arthroplasties occurring within the postoperative hospitalization period have been documented based on a standardized protocol used for external quality assessment in Germany. Using logistic regression, the influence of potential risk factors were assessed for their significance on postoperative complications and uni-variate analysis used to assess this influence on every single major complication. The influence of patient age and the surgery time on major complications were calculated using ANOVA. Results: Major postoperative complications occurred in 7.22 per cent with hematoma in 2.89, cardio-vascular complications in 1.79, deep venous thrombosis in 1.23, pulmonary embolism in 0.23, joint infection in 0.82 and pneumonia in 0.25 per cent. Patient age, surgery time, gender, high classification according to the American Association of Anesthesiologists, allogeneic blood transfusion and lateral release significantly increased the rate of postoperative complications. Males are more prone to suffer from hematoma, joint infection and pneumonia in the immediate postoperative course. Females are more endangered for deep venous thrombosis. Extended surgery time increased the rate of hematoma and infection, increased patient age elevated the rate of hematoma, cardiovascular complication and pneumonia. Alloge-neic blood transfusion increased the risk of all major complications except deep venous thrombosis. Conclusions Male gender, allogeneic blood transfusion, increased age and surgery time elevate immediate postoperative complications following knee arthroplasty

Purpose: The purpose of this study was to determine the rate of clinically detected deep venous thrombosis and pulmonary embolism in patients with trunk or extremity bone or soft tissue sarcomas. Patients and methods: The clinical records of patients with a confirmed diagnosis of primary bone or soft tissue sarcoma presenting between 1998 and 2003 were reviewed. Data relating to clinical features, risk factors for thromboembolism and clinical thromboembolic events were retrieved. Results: 252 patients were identified. 94 had a diagnosis of primary bone sarcoma and 158 a diagnosis of primary soft tissue sarcoma. The mean age was 53 (range 15 to 94); 137 (54%) were male. 37 patients were suspected clinically of having a deep venous thrombosis, 10 of which were confirmed radiologically, giving a rate of 4%. Nine patients had a suspected pulmonary embolism, 2 of which were confirmed radiologically and one of whom died of pulmonary embolism, giving an overall rate of fatal pulmonary embolism of 0.4%. All patients with thromboembolic events had lower extremity tumours and all were surgical patients. However, the majority of thromboembolic events (6 of 10 deep venous thromboses and 2 of 3 pulmonary embolisms) occurred prior to surgery. Discussion: The risk of a clinically apparent thromboembolic event in patients with bone or soft tissue sarcomas is comparable to that in other orthopaedic patients. Risk factors for venous thromboembolism include lower extremity sarcomas and mechanical obstruction of the venous system. Consideration should be given to excluding deep venous thrombosis before surgery

Introduction: Risk-profiling of patients in hip arthroplasty to prepare for perioperative complications is becoming more important. Materials and Methods Major complications (haematoma, cardiovascular complication, deep venous thrombosis, pulmonary embolism, joint infection, injuries of neurovascular structures and pneumonia) following 29994 hip arthroplasties occurring within the postoperative hospitalisation period have been documented based on a standardised protocol used for external quality assessment in Germany. Using logistic regression, the influence of potential risk factors was assessed for their significance on postoperative complications and univariate analysis was used to assess this influence on every single major complication. The influence of patient age and the surgery time on major complications were calculated using ANOVA. Results: Major perioperative complications occurred in 7,26 per cent. Haematomas were reported in 3.22, cardiovascular complications in 1.55, joint infections in 0.94, injuries of neuro-vascular structures in 0,63, deep venous thrombosis in 0.37, pulmonary embolism in 0.26 and pneumonia in 0.28 per cent of all cases. Patient age, length of surgery and allogeneic blood transfusion significantly increased the rate of major perioperative complications. Increased patient age increased the risk for all major complications but neuro-vascular injuries. Increased surgery time elevated the risk for all major complications except haematoma. Allogeneic blood transfusions were associated with an elevated risk for all major postoperative complications except deep venous thrombosis. In contrast, autologous blood transfusions did not increase the risk for suffering a postoperative complication. Surprisingly, gender did not have a significant influence on the occurrence of immediate postoperative complications. Conclusions Allogeneic blood transfusion, increased age and surgery time contribute to an elevated incidence of perioperative complications following hip arthroplasty

Venous thromboembolic events, either deep vein thromboses or pulmonary emboli, are important complications in patients undergoing knee or hip arthroplasty. The purpose of this study was to evaluate the effectiveness of a mobile compression device (ActiveCare+S.F.T.®; Medical Compression Systems, Inc., Or Akiva, Israel) with or without aspirin compared with current pharmacology protocols for venous thromboembolism prophylaxis in patients undergoing elective primary unilateral lower extremity joint arthroplasty. A multicenter registry was established to capture the rate of symptomatic venous thromboemboli following primary lower extremity joint arthroplasty in 3,060 patients from ten sites including knee arthroplasty (1,551) or hip arthroplasty (1,509). All patients were 18 years of age or older with no known history of venous thromboembolism, coagulation disorder, or solid tumor. Use of the compression device began peri-operatively and continued for a minimum of ten days. Patients with symptoms of deep venous thrombosis or pulmonary embolism underwent duplex ultrasonography and/or spiral computed tomography. All patients were evaluated at three months post-operatively to document any evidence of deep venous thrombosis or pulmonary embolism. Of 3,060 patients, twenty-eight (0.92%) had venous thromboembolism (20 distal deep venous thromboses, 3 proximal deep venous thromboses, and 5 pulmonary emboli). One death occurred with no autopsy performed. Symptomatic venous thromboembolic rates observed in lower extremity joint arthroplasty patients using the mobile compression device were non-inferior (not worse than) at a margin of 1.0% to rates reported for pharmacological prophylaxis, including warfarin, enoxaparin, rivaroxaban, and dabigatran except in the knee arthroplasty group where the mobile compression device fell short of rivaroxaban by 0.06%. Use of the mobile compression device with or without aspirin for patients undergoing lower extremity joint arthroplasty provide a non-inferior risk for developing venous thromboembolism compared with current pharmacological protocols reported in the literature

1. One hundred patients with fractures of the upper end of the femur were investigated clinically and radiographically to ascertain the incidence and site of deep venous thrombosis during convalescence. 2. The technique of phlebography used has its own inherent dangers, but we believe that familiarity with the technique reduces the risk of complications. 3. The investigation revealed thrombi that were clinically unsuspected and indicates a need for further investigation of factors such as manipulation and retraction that may promote deep thrombosis. 4. The study has provided a control series for an investigation of the effect of prophylactic anticoagulants upon the incidence of deep venous thrombosis and pulmonary embolism after fractures about the hip