9.4.1 Response Rate
In total, two hundred and fifty-eight surgeons responded to the invitation letters, however some responses could not be included in the analysis (Table 28). The final response rate was 49.2% (221, N=449). Most completed responses were submitted as hard copies; however 9 respondents (4.1%) completed the survey online.
Table 28. Break down of responses (N=258).
n %
Uncertain if respondent conducted hip or knee arthroplasty 4 1.6
Respondent did not conduct hip or knee arthroplasty 7 2.7
Invitation letter returned because surgeon left country, no longer practising,
terminally ill or deceased 25 9.6
Responded 8 months after the close of the survey 1 0.4
Responded with completed survey 221 85.7
9.4.2 Demographics
Most respondents were males (217, 98.2%, N=220), with an average of 17.8 years practising as orthopaedic surgeons (SD 9.0). Most participants practised in Queensland, New South Wales and Victoria (Table 29) and predominantly in the private sector (155, 70.7%), followed by both sectors equally (55, 25.1%, N=220).
Table 29. Break up of responses from each state and territory (N=221).
n Overall %
Australian Capital Territory 1 0.5
New South Wales 59 26.7
Northern Territory 3 1.4 Queensland 49 22.2 South Australia 21 9.5 Tasmania 12 5.4 Victoria 61 27.6 Western Australia 15 6.8
Participants conducted an average of 14.6 arthroplasties each month; with a slight preponderance for knee arthroplasties (6.0 hips vs. 8.9 knees, SD 14.6), which is reflective of the national trend. There was no correlation between the number of years practising and the number of arthroplasties participants conducted monthly.
Forty-eight participants (23.0%, n=209) identified themselves as ASA members. There was no significant demographic difference between members and non-members, however ASA members reported conducting significantly more arthroplasties each month (21 vs. 13, p<0.001).
9.4.3 Prescribing Practices 9.4.3.1 Agent Preference
Most surgeons (213, 95.9%) reported routinely prescribing pharmacological prophylaxis for their patients following surgery, and most (210) shared their preferred prescribing regimen. The regimens described included the following:
LMWH
LMWH / rivaroxaban
Aspirin if one knee, LMWH if two knees
Apixaban
Rivaroxaban
Warfarin
LMWH during inpatient stay, rivaroxaban at home
Unfractionated heparin during inpatient stay, LMWH at home
LMWH during inpatient stay, apixaban at home
LMWH during the inpatient stay, aspirin at home
Aspirin if low risk, LMWH if high risk
Aspirin if low risk, rivaroxaban if high risk
Anticoagulants were the most popular choice (154, 75.1%), followed by a combination of an anticoagulant + aspirin (28, 13.7%, Table 30). LMWH was the most popular anticoagulant; however as noted above, a range of anticoagulants were regularly used by respondents.
Table 30. Primary pharmacological preferences (%) between ASA and non-ASA members (N=205).
Overall ASA member Non-ASA member p
Aspirin 11.2 17.0 9.5
0.12
Anticoagulant 75.1 63.8 78.5
Aspirin + anticoagulant 13.7 19.2 12.0
NB: Eleven people did not indicate if they were an ASA member or not, and a further five people did not indicate their prescribing preference.
There was no statistically significant difference in agent choice between ASA members and non-members; however there was a trend towards more members favouring aspirin (± an anticoagulant) compared to non-members. There was no significant correlation between agent preference and surgeon demographics.
9.4.3.2 Duration Preference
Most participants preferred continuing pharmacological prophylaxis post-discharge; and knee arthroplasty patients were more likely to receive shorter courses of thromboprophylaxis than hip arthroplasty patients (p<0.001, Table 31).
Table 31. Preferred duration of thromboprophylaxis (%).
Hip Arthroplasty (n=176) Knee Arthroplasty (n=190)
3-4 days 1.7 1.6 5-7 days 8.5 10.5 8-14 days 9.7 32.1 15-21 days 10.2 18.4 22-28 days 21.0 11.1 29-35 days 25.6 7.9 36-42 days 21.6 16.8 90 days 1.7 1.6 Median number of days 28.0 (SD 14.1) 15.0 (SD 14.7)
Surgeons who preferred anticoagulants prescribed significantly shorter courses of thromboprophylaxis than surgeons who preferred aspirin ± an anticoagulant (-14 days for hip arthroplasties and -21 days for knee arthroplasties, p<0.05). There was no correlation between duration preference and ASA membership or surgeon demographics.
9.4.4 Thromboprophylaxis Efficacy
Almost one third of surgeons (29.1%) indicated that they did not believe pharmacological prophylaxis prevented fatal PE, 44.1% indicated it may potentially reduce fatal PE, and 26.8% responded that it definitely decreased fatal PE. There was a trend towards non-members being more confident in the ability of pharmacological agents to prevent fatal PE than ASA members; however this did not reach statistical significance (Table 32).
Table 32. Opinions on efficacy of pharmacological prophylaxis (%, N=208).
Pharmacological agents… ASA member
(n=48)
Non-ASA member
(n=160) p
Do not decrease fatal PE 27.1 29.4
0.08
Potentially decrease fatal PE 56.2 40.0
Definitely decrease fatal PE 16.7 30.6
9.4.5 Factors that Influence Thromboprophylaxis Prescribing
Previous VTE, prolonged preoperative immobility and morbid obesity were the top three factors surgeons indicated would prompt them to prescribe pharmacological prophylaxis following surgery (Table 33). The only statistically significant difference between ASA members and non-members was that ASA members were more likely to select prolonged surgery as a factor that would prompt them to prescribe pharmacological agents (55.1% vs. 36.1% p<0.05). In addition to the factors laid out in the original question, 6 surgeons (2.7%) indicated malignancy and/or family history of VTE would also prompt them to prescribe prophylaxis.
Table 33. Patient factors that prompt surgeons to prescribe pharmacological prophylaxis (n=170). %
Previous VTE 96.5
Prolonged preoperative immobility 78.2
Morbid obesity (BMI >40) 75.3
HRT 65.3
Previous thrombophlebitis 57.1
Moderate obesity (BMI >30) 54.7
Current smoker 53.5
Surgery > 2 hours 50.6
Previous vein surgery 40.6
Age ≥ 70 years 35.9
Age < 70 years 32.9
General anaesthesia 30.0
Preoperative Infection 17.6
None of these factors 17.1
None of the above (I routinely prescribe chemoprophylaxis for all of my patients) 1.8
The top two factors reported to limit participants’ prescribing of pharmacological prophylaxis for arthroplasty patients were the conviction that it increases the risk of infection at the operation site, and the belief that patients would not be compliant (Table 34). Furthermore, bleeding risk was a concern for almost half of the respondents (44.3%), particularly during the inpatient period. Aspirin users were more likely be concerned with bleeding complications than anticoagulant users (88.0% vs. 37.7%, p<0.001).
Table 34. Factors that limit pharmacological prophylaxis use ((n=221).
Inpatient (%) Discharge (%)
It increases the risk of infection at the operation site 40.3 22.2
It is not safe as it causes too much bleeding 39.8 22.2
It is not superior to mechanical methods 24.0 13.6
It is too expensive 1.8 4.1
It is too inconvenient 4.1 18.1
Patients will not be compliant 2.3 17.2
Poor continuation of care from hospital to community 3.2 9.0
Study evidence isn't applicable to real-world populations 14.5 15.4
The risks of VTE are low 11.3 14.0
None of the above 28.1 23.1
A further 18.1% of participants felt that the inconvenience associated with thromboprophylaxis limited its prescribing at discharge. Notably, these participants prescribed significantly shorter courses of prophylaxis for their patients on average. This reached statistical
significance following knee arthroplasty (17 days vs. 23 days, p=0.04). There were no significant differences between any of the ASA members’ and non-members’ responses.
9.4.6 Familiarity with Contemporary Guidelines
Between 169 and 191 surgeons answered different parts of the question regarding contemporary guideline familiarity. Those participants who did respond indicated greatest familiarity with the ASA, AAOS and NHMRC guidelines (Figure 28).
Figure 28. Surgeon familiarity with contemporary guidelines.
I have not come across it before I have heard of it in passing I am very familiar with it
ASA members were significantly more likely to be familiar with the ASA Guideline than non- members (92.8% vs. 53.6%, p<0.001). Furthermore, there was a trend towards those who had practised longer as orthopaedic surgeons being more familiar with the contemporary guidelines. This finding reached statistical significance with the ANZWP, AAOS and ASA guidelines; surgeons who were very familiar with these guidelines had been practising for 5 to 8 years longer than surgeons who had only heard of them in passing (p<0.05).