Background: Patients with peripheral arterial disease may be asymptomatic or present with symptoms ranging from intermittent claudication to critical leg ischaemia, which may lead to lower limb amputation. This study aims to investigate the relationship between revascularization procedures and amputations rates in Australia.

Methods: This was a retrospective observational study. Medicare claims via procedure item numbers listed in the Medical Benefits Schedule and available on the Medicare Statistic website were accessed. Population data were extracted from the Australian Bureau of Statistics’ database. Data were expressed in per 100 000 population to better reflect the change in population over time, i.e. population based. Regression analysis was used to analyse the trend and correlate variables.

Results: From 2007 to 2017, across all states, there was a 36.98% decline in below knee amputations (p<0.05), 39.52% decline in above-knee amputations (p<0.05) and a 43.49% rise in revascularization procedures (p<0.05).

Conclusion: The increase in revascularisation procedures has been matched by a reduction in major lower limb amputations in Australia. While it is debatable which revascularization procedures are most effective in preventing amputations, the importance of such preventative measures has likely been underestimated.

•    Amputation
•    Trend analysis
•    Revascularization
•    Australia

Yuan TK, Shan NY, Yingli ST, Walker SR (2021) Trend Analysis of Lower Limb Amputation and Revascularization Procedures in Australia: 2007-2017. Ann Vasc Med Res 8(1): 1126.

Peripheral arterial disease (PAD) refers to a manifestation of systemic atherosclerosis. Whilst many patients may be asymptomatic, symptomatic patients can present with benign intermittent claudication or more sinister limb threatening ischaemia. Multiple national and international guidelines reinforce that treatment of PAD requires a comprehensive treatment programme including lifestyle modification, pharmacotherapy and surgical intervention (revascularisation) with the aims of decreasing the risk of cardiovascular events and death, improving exercise ability and quality of life whilst decreasing progression to limb loss [1-3].

In Australia, the most common reason cited for lower limb amputation is calcified arteries in the limb resulting in inadequate blood flow [4] as a result of various co-morbidities such as diabetes, hypertension, hypercholesterolemia, smoking and kidney failure. As amputations result in serious implications on a person’s daily activities, vascular surgeons reserve amputations as a last resort and offer patients restoration of physical function by restoring blood flow through revascularization procedures [5,6].

While data is available describing the incidence rate of lower limb amputations and revascularization procedures at a national and state level, there are no studies that describe and analyse any trend between the two procedures [7-9]. We aim to analyse the trend of amputation and revascularization in Australia between 2007 and 2017.

Study Design

This was a retrospective study with data on major lower limb amputations and revascularisation procedures performed between the calendar year 2007 and 2017. Given that data was obtained from publicly accessible sources, ethics approval was not sought.

Data Source

In Australia, the Medicare Benefits Schedule (MBS) lists by item number services which can be provided my medical practitioners. The principal function of itemising these services is to enable providers to claim a fee for the service. The frequency of claims for specific item numbers can be obtained by year and state from the Medicare statistics website. Amputation and revascularization data were retrieved from the Medicare Australia Statistics website at both national and state level. All 8 states were included, i.e. New South Wales (NSW), Victoria (VIC), Queensland (QLD), South Australia (SA), Western Australia (WA), Tasmania (TAS), Australian Capital Territory (ACT) and Northern Territory (NT). For amputation procedures, we used the MBS item number 44367 (through the thigh, at knee or below knee amputation). Item number 21232 is the specific item number for initiation of management of anaesthesia for above knee amputations. There is no specific item number for initiation of management of anaesthesia for below knee amputation. Thus, by subtracting the number of 21232 from 44367 we would have the number of through and below knee amputations.

For revascularization procedures, we looked at 22 surgical item numbers as listed in Table 1.

Population data were retrieved from the Australian Demographics Statistics published by the Australian Bureau of Statistics (ABS).

As this study utilised data available online and no personal information from patients were involved, no approval was required from the ethics board.

Data Analysis

Data collected were analysed, and sample characteristics and trends of amputations and revascularization procedure over the years were established. Data were expressed in per 100 000 population to better reflect the change in population over time, i.e. population based. Regression line was established to help analyse the trend and correlate variables. Quantitative data were further visually displayed in figures and tables.

National sample characteristics

The national sample characteristics are summarized in Table 2.

There were a total of 3 894 claims for below and through knee amputations (BKA), 1,327 for above knee amputations (AKA) and 43,759 for revascularization procedures (RP) performed in Australia from 2007 - 2017. Of those undergoing a BKA, 65.69% were male 74.88% were aged 65 years or older. Of those undergoing an AKA, 62.25% were male and 82.82% were aged 65 years or older. For RP, 62.87% were male and 77.12% were aged 65 years or older.

National population-based amputation and revascularization rate

The breakdown of the national population-based amputation and RP is seen in Table 3.

From 2007 to 2017, we observe a change in the population-based BKA from 2.08 amputations per 100 000 population to 1.31 amputations per 100 000 population (-36.98%; p < .05). In the same period, the population-based AKA rate changed from 0.77 amputations per 100 000 population to 0.47 amputations per 100 000 population (-39.52%; p < .05). For the population-based lower limb amputations (LLA), it changed from 2.86 per 100 000 population to 1.78 per 100 000 population (-37.67%; p = .05).

For the population-based RP rate, we observed an increase from 44.56 procedures per 100 000 population to 63.94 procedures per 100 000 population (+43.49%; p < .05). For population-based open RP rate, we observed a decrease from 8.18 procedures per 100 000 population to 6.02 procedures per 100 000 population (-26.39%; p < .05) and for populationbased endovascular RP rate, there is an increase from 36.39 procedures per 100 000 population to 57.92 procedures per 100 000 population (+59.19%; p < .05).

The trendlines for amputations and revascularization procedures are shown in Figure 1.

Figure 1: Trendline of various procedures per 100000 population over the period 2007 - 2017.

Figure 2

Figure 2: Regression line of various amputation procedures against the total number of revascularizations per 100,000 population

depicts the regression line plotted with the population-based revascularization rate against population based below knee amputation rate which shows an inverse relationship between the two (p < .05; r2 = .74) as well as the population-based revascularization rate against population based above knee amputation rate (p < .05; r2 = .58); the regression line plotted with the population-based revascularization rate against population based total number of lower limb amputation rate, which shows an inverse relationship between the two (p < .05; r2 = .57)

Sample characteristics, by state

In general, proportion of patients who are male, and had BKA ranged from 62.59% (VIC) to 80.00% (NT); had AKA ranged from 55.98% (VIC) to 100% (ACT & NT) and had revascularization procedures ranged from 56.95% (NT) to 67.07% (WA). Proportion of patients who are ≥ 65 years old and had BKA ranged from 50.00% (NT) to 80.60% (VIC); had AKA ranged from 50% (NT) to 86.41% (QLD); and had RP ranged from 41.72% (NT) to 79.00% (VIC).

Population-based amputation and revascularization rates, by state

The sample characteristics of individual states are summarized in Table 4.

In general, proportion of patients who are male, and had BKB ranged from 62.59% (VIC) to 80.00% (NT); had AKA ranged from 55.98% (VIC) to 100% (ACT & NT) and had RP ranged from 57.02% (NT) to 66.15% (WA).

Proportion of patients who are ≥ 65 years old and had BKA ranged from 50.00% (NT) to 80.60% (VIC); had AKA ranged from 50% (NT) to 86.41% (QLD); and had RP ranged from 44.74% (NT) to 79.64% (VIC).

Figure 3

Figure 3: Revascularizations, below knee amputations, above knee amputations and lower limb amputations per 100,000 population, by states, from 2007 to 2017.

shows the revascularisation rates per 100 000 population by each state.

Interpretation

This study analyses the trend of the treatment for PAD in Australia over 11-year period from 2007 to 2017. We observed an inverse relationship between the amputation rate and the revascularization procedures. The BKA rate per 100 000 population has decreased by 7.09% while the AKA rate per 100 000 population has decreased by 18.97% over the last 11 years. We also noticed a significant decrease in total number of LLA per 100 000 population - a drop of 37.67%. During the same time-period, there has been an increase of 43.49% in the use of revascularisation procedures. This relationship is statically strong with a moderate to high r2 value. We have shown that patients who receive revascularisation procedures are more likely to be male and above the age of 65, thus reinforcing strong risk factors for atherosclerosis. This is coherent with a study done in 2018 [10], attributing sex and age as strong risk factors of PAD [11,12]. For revascularization procedure, we also observe a fall in open procedures and a rise in endovascular procedures. Some studies have suggested that endovascular procedures are likely to confer improved amputation-free survival over long term when compared to open procedures [13], and incur a lower healthcare cost [14]. Several other studies have reported on the pattern of treatment for peripheral artery disease. Tunis et al. studied the pattern of treatment of PAD in Maryland from 1979 to 1989 and found that while there was an increase in RP rate, there was no significant changes in the rate of amputation [15]. Other studies performed in a similar time-periods also demonstrated an increasing trend in the usage of endovascular and open endovascular revascularization procedures but variable amputation rates [16-21].

Nowygrod et al. found that from 1998 to 2003, there was a substantial decrease in the national amputation rate and a shar increase in lower limb revascularization procedures [22]. This was further complemented by Rowe et al. who found that there is a significant increase in the use of endovascular procedures with a corresponding decrease in major amputation rates from 1996 to 2005 [23]. As postulated by Rowe et al., the decrease in amputation rate as observed by Nowygrod et al. and Rowe et al. and ourselves may associate with the time period where the benefits of revascularization procedures positively impacted the outcome of patients with PAD and is further fuelled by the rapid improvement in endovascular technology [23]. Despite the general trend of rising revascularization procedures across a national level, when we take a closer look at state levels, it is not hard to find that the trend of revascularization procedures has declined over the years with the exception of SA, QLD, TAS and NT. Conversely, while the general trend of decline in lower limb amputations was observed across the national level, we observe a rising trend for NT and ACT. Dillion et al. also conducted a similar study in regards to the geographic variation of the incidence of LLA in Australia from 2007 - 2012 and found that while the rates are similar across various states, it was higher in NT [24]. Goodney et al. suggested that for areas with poor healthcare access, patients with peripheral arterial disease often present late, resulting in irreversible damage [25]. Interestingly, while NT has been reported to have a disadvantageous local government area given its rural and remote nature, ACT has been reported to have an be an advantageous local government area [26]. There are likely to be other underlying factors that affect the rate of amputation procedures-patient characteristics, ethnicity, co-morbidities and social-economical statuses, which are not examined in this study [27,28].

Given the observational and retrospective nature of this study, the study findings do not imply causation, and we recognise that our study does not present any direct causative experimental evidence to explain the decrease in amputation rate but correlation. The data presented here are based on claims data and this might account for an under representation of procedures performed.

Our data is also not able to identify the clinical indications for procedures done and hence not able to explain the variation in incidence rate across various states. Be that as it may, it is evident that with the increase in utilisation of revascularization procedures has been associated with lower rates of major amputation [25].

While it is debatable which revascularization procedures are most effective in preventing amputations, the importance of such preventative measures has likely been underestimated and should be closely examined. Future works examining relationships between preventative measures, revascularization, and amputation are necessary to help clinician’s better outline the best treatment for decreasing the risk for amputation [29,30]. Future works should also aim to analyse and explain the trend of amputation rates due to other factors- patient characteristics, comorbidities and socio-economical statuses

1. Au T, Golledge J, Walker P, Kate Haigh, Mark Nelson. Peripheral arterial disease Diagnosis and management in general practice. Aust Fam Physician. 2013; 42: 397-400.

2. Hirsch AT, Criqui MH, Treat-Jacobson D. Peripheral Arterial Disease Detection, Awareness, and Treatment in Primary Care. JAMA. 2001; 286: 1317-1324.

3. Hiatt WR. Medical Treatment of Peripheral Arterial Disease and Claudication. N Engl J Med. 2001; 344: 1608-1621.

4. Lazzarini PA, Clark D, Derhy PH. What are the major causes of lower limb amputations in a major Australian teaching hospital? The Queensland Diabetic Foot Innovation Project, 2006 - 2007. Journal of Foot and Ankle Research 2011; 4: O24-O24.

5. Paudel B, Shrestha B and Banskota AK. Two faces of major lower limb amputations. Kathmandu University medical journal (KUMJ). 2004; 3: 212-216.

6. Sabzi Sarvestani A, Taheri Azam A. Amputation: a ten-year survey. Trauma monthly. 2013; 18: 126-129. 2013/10/14. DOI: 10.5812/ traumamon.11693.

7. Medicare Item Statistics Reports. In: Services DoH, (ed.). 25 March 2019 ed.: Australian Government 2019.

8. Australian Demographic Statistics. In: Statistics ABo, (ed.). Canberra, Australia: Australian Bureau of Statistics. 2012.

9. Australian Demographic Statistics. In: Statistics ABo, (ed.). Canberra. 2018.

10. Behrendt C-A, Sigvant B, Szeberin Z, et al. International Variations in Amputation Practice: A VASCUNET Report. European Journal of Vascular and Endovascular Surgery. 2018; 56: 391-399.

11. Hussain MA, Lindsay TF, Mamdani M. Sex differences in the outcomes of peripheral arterial disease: a population-based cohort study. CMAJ open. 2016; 4: E124-E131.

12. Muir RL. Peripheral arterial disease: Pathophysiology, risk factors, diagnosis, treatment, and prevention. J Vasc Nurs. 2009; 27: 26-30.

13. Wiseman JT, Fernandes-Taylor S, Saha S, Havlena J, Rathouz PJ, Smith MA, et al. Endovascular Versus Open Revascularization for Peripheral Arterial Disease. Ann Surg. 2017; 265: 424-430.

14. Tang L, Paravastu SCV, Thomas SD. Cost Analysis of Initial Treatment with Endovascular Revascularization, Open Surgery, or Primary Major Amputation in Patients with Peripheral Artery Disease. Journal of Endovascular Therapy. 2018; 25: 504-511.

15. Tunis SR, Bass EB and Steinberg EP. The Use of Angioplasty, Bypass Surgery, and Amputation in the Management of Peripheral Vascular Disease. N Engl J Med. 1991; 325: 556-562.

16. Ebskov LB, Schroeder TV, Holstein PE. Epidemiology of leg amputation: The influence of vascular surgery. Br J Surg. 1994; 81: 1600-1603.

17. Mattes E, Norman PE, Jamrozik K. Falling incidence of amputations for peripheral occlusive arterial disease in Western Australia between 1980 and 1992. Eur J Vasc Endovasc Surg. 1997; 13: 14-22.

18. Sayers RD, Thompson MM, Varty K, et al. Changing trends in the management of lower-limb ischaemia: A 17-year review. Br J Surg. 1993; 80: 1269-1273.

19. Simunovic M, To T, W Johnston K. Trends and variations in the use of vascular surgery in Ontario. 1996; 12: 249-253.

20. Pell JP, Fowkes FGR, Ruckley CV. Declining incidence of amputation for arterial disease in Scotland. European Journal of Vascular Surgery 1994; 8: 602-606.

21. Hallett JW, Byrne J, Gayari MM. Impact of arterial surgery and balloon angioplasty on amputation: A population-based study of 1155 procedures between 1973 and 1992. Journal of Vascular Surgery. 1997; 25: 29-38.

22. Nowygrod R, Egorova N, Greco G. Trends, complications, and mortality in peripheral vascular surgery. J Vasc Surg. 2006; 43: 205-216.

23. Rowe VL, Lee W, Weaver FA. Patterns of treatment for peripheral arterial disease in the United States: 1996-2005. Journal of Vascular Surgery. 2009; 49: 910-917

24. Dillon MP, Fortington LV, Akram M, Erbas B, Kohler F. Geographic Variation of the Incidence Rate of Lower Limb Amputation in Australia from 2007-12. Plos One. 2017; 12: e0170705.

25. Goodney PP, Holman K, Henke PK. Regional intensity of vascular care and lower extremity amputation rates. Journal of Vascular Surgery. 2013; 57: 1471-1480.e1473

26. Statistics ABo. Census of Population and Housing: Reflecting Australia - Stories from the Census, 2016. In: Statistics ABo, (ed.). Canberra: Australian Bureau of Statistics, 2018.

27. Jones WS, Patel MR, Dai D, Subherwal S, Stafford J, Calhoun S, et al. Temporal Trends and Geographic Variation of Lower-Extremity Amputation in Patients With Peripheral Artery Disease: Results From U.S. Medicare 2000-2008. J Am Coll Cardiol. 2012; 60: 2230-2236.

28. Moxey PW, Hofman D, Hinchliffe RJ, Jones K, Thompson MM, Holt PJE, et al. Epidemiological study of lower limb amputation in England between 2003 and 2008. Br J Surg. 2010; 97: 1348-1353.

29. Bradbury AW, Adam DJ, Bell J, Forbes JF, Fowkes FGR, Gillespie I, et al. Bypass versus Angioplasty in Severe Ischaemia of the Leg (BASIL) trial: An intention-to-treat analysis of amputation-free and overall survival in patients randomized to a bypass surgery-first or a balloon angioplasty-first revascularization strategy. J Vasc Surg. 2010; 51: 5S-17S.

30. Conte MS. Diabetic Revascularization: Endovascular Versus Open Bypass-Do We Have the Answer? Semin Vasc Surg. 2012; 25: 108-114.