Podiatrists Decrease the Odds of Major Amputation in Patients with Diabetes and/or Peripheral Arterial Disease in All Practice Settings: A Retrospective Administrative Claims Data Analysis

1. Introduction

Diabetes mellitus (DM) is a national and international health crisis that is associated with many comorbidities and complications, such as diabetic foot ulcerations (DFU), frequently leading to non-traumatic lower extremity amputations (NTLEA) [1,2]. Up to 25% of individuals with DM will experience a DFU in their lifetime, and approximately 85% of NTLEA are preceded by a DFU [3]. In 2021, 38.4 million Americans had diabetes, including 8.7 million undiagnosed. Adults from low socio-economic statuses (SES) had a 37% higher prevalence of diabetes compared to high SES individuals [1]. Evidence has suggested that NTLEA is associated with increased mortality particularly among patients with advanced age, diabetes, coronary artery disease (CAD), peripheral arterial disease (PAD), history of proximal amputation and/or end stage renal disease [4,5,6]. PAD, identified as infrapopliteal or tibial artery disease and calcification of vessels especially among patients with DM [8], is another leading cause of NTLEA and affects approximately 10 to 12 million people over the age of 40 in the United States and approximately 113-236 million people worldwide [2]. DM, especially when uncontrolled, increases the risk of PAD, defined as, the progression of chronic arterial occlusive disease of the lower extremities [7]. The incidence of PAD increases with the presence of DM which also has been known to accelerate PAD progression and severity [9]. The true prevalence of both DM and PAD in the same patient is difficult to quantify, however, literature estimates that DM has been associated with a 2- to 4-fold increase in the prevalence of PAD from 1996 to 2011 [6]. Risk factors such as age, tobacco use, hypertension, and diabetes are highly associated with PAD [3]. In the case of advanced PAD, patients often lose their limbs and potentially their lives. Similar to DM, the prevalence of PAD disproportionately affects lower SES communities worldwide [4].

The management of patients who suffer from DM and/or PAD, especially those with non-healing wounds, is complex and costly. Epidemiological studies estimated annual costs for concomitant DM and PAD ranging from $84 billion to $380 billion annually [6]. DM and/or PAD comorbidities and complications require management by multiple specialists, however, the disorganized and fragmented structure of the current healthcare system may lead to increased costs [5]. These increased costs are especially seen among patients with high fragmentation of healthcare with $1,085 more in total adjusted costs per person per year than among patients with low fragmentation of healthcare [5]. Studies from academic medical centers, where care is consolidated and perhaps relatively streamlined, demonstrate improved NTLEA rates owing to a interdisciplinary team approach [10,11,12,13]. A common theme in the current literature on diabetic foot management is the close knit relationship between podiatry and various specialists. Systematic reviews have also shown that a team approach improved NTLEA rates specifically by following international guidelines in which podiatrists are involved in preventive, subacute and acute settings [15,16]. While an interdisciplinary team may be more easily established within a healthcare system and/or academic medical center, such a team is not limited to only those settings.

Referrals between podiatry and other specialists to manage patients with DM and/or PAD are common. Such referral patterns occur in any practice setting. As mentioned prior, literature has underscored the important role of podiatrists as part of the multidisciplinary or interdisciplinary team in healthcare systems and academic medical centers to manage lower extremity wounds and prevent NTLEA among patients with DM and/or PAD [6,7,8]. However, the effect of collaboration between podiatry and surgical specialists to prevent major NTLEAs outside the healthcare systems or academic medical center is not well known. This study used administrative claims data to demonstrate the impact of podiatry on major NTLEA among patients with type 2 diabetes, a foot ulcer and/or patients with PAD, regardless of care setting.

2. Materials and Methods

This study utilized administrative claims from PearlDiver (Pearl-Diver Technologies, Fort Wayne, IN, USA) to conduct a retrospective cohort study. The PearlDiver Mariner10 database is a Health Insurance Portability and Accountability Act–compliant national database between October 2010 and October 2022. The data file contains claims information from all U.S. states and territories from private and public payers. The file also contains demographic characteristics, location (e.g., region, state, and ZIP code), diagnosis, procedure, and provider specialty submitted with each claim.

Inclusion criteria were patients with an International Classification of Diseases, 9th/10th Revision, Clinical Modification (ICD-9/10-CM) for DM AND for a foot wound/ulcer AND a Current Procedural Terminology (CPT) code for debridement and/or people with an ICD-9/10 code for PAD AND a CPT code for either vascular studies or vascular procedures [17,18]. [Appendix A] Patients who were not seen by one of the studied specialties (i.e. podiatry, general surgery, orthopedic surgery, plastic surgery, vascular surgery) within the window of 1 year prior and 2 years after being eligible for the final population were excluded. The studied speciality was a variable that was available in the dataset as a “provider type.” The objective of this study was to investigate the impact of incorporating an interdisciplinary approach on major NTLEA in comparison to patients who were treated by only one type of specialist. We defined the interdisciplinary approach as podiatry in addition to surgical providers that perform major NTLEA. The primary outcome of the study was odds of major NTLEA.

Chi-square analysis was performed initially for population characteristics and demographics in relationship to amputations status. Multivariable regression models were then conducted with major or no major NTLEA as the outcome with the exposure to podiatric surgery while controlling for age, gender, Charlson Comorbidity Index (CCI), obesity, tobacco use, chronic kidney disease (CKD), peripheral neuropathy, heart disease, presence of an ulcer, and presence of PAD. Since PAD and DM are known independent risk factors for NTLEA, we performed a sensitivity analysis including PAD patients only which was defined as people with diagnosis of PAD + vascular study on record, and then controlled for DM/DFU in the multivariable analysis. Significant difference is defined as a P-value <0.025. The presented study follows STROBE reporting guidelines [9].

3. Results

3.1. Population Characteristics and Demographics

A total of 269,022 people met inclusion criteria (Table 1). A majority of the population (93%; n=249,593) were patients with PAD whereas 36,460 patients had diabetes and foot ulcer that was confirmed by at least one debridement. Approximately 2% of the population experienced a major amputation (n=5,493). The mean age of those who underwent major amputation was 63.8 years and 67.3 years for those who did not undergo major amputation (P<0.01) (Table 1). A majority of patients who underwent major amputation were male (66%, P<0.01) and used tobacco (66%, P<0.01). Several comorbidities were significantly associated with major amputation including heart disease (98%, P<0.01), CKD (65%, P<0.01), PAD (89%, P<0.01), foot ulcer and peripheral neuropathy (62%, P<0.01).. Podiatry was involved in the care of 7% of the NTLEA group and 4% in the no major NTLEA group. Patients who were cared for by vascular surgery had the highest NTLEA counts (n=3,313) followed by general surgery (n=1,530) then orthopedic surgery (n=620) and plastic surgery (n=158).

3.2. Multivariable Analysis

The multivariable analysis demonstrated that patients seen by vascular surgery without the addition of podiatry had the highest odds of NTLEA at 3.82 (97.5% CI, [3.61-4.06]) followed by orthopedic surgery at 2.78 (97.5% CI, [2.52-3.05]), general surgery at 2.59 (97.5% CI, [2.42-2.77]), and plastic surgery at 1.60 (97.5% CI, [1.34-1.90]). When the interdisciplinary approach included podiatry in addition to vascular or general surgery, the odds of NTLEA reduced to 1.38 (97.5% CI, [1.21-1.57]) and 1.10 (97.5% CI, [0.90-1.33]) for vascular and general surgery, respectively. (Table 2) There were not enough patients seen by podiatry in addition to orthopedic or plastic surgery to perform multivariable analysis. Adjusted OR in podiatric surgery (97.5%, CI, [0.61-0.76]) suggested that podiatric surgery was protective for major amputation.

3.3. Sensitivity Analysis

The sensitivity analysis revealed similar results, demonstrating our primary analysis was robust to these population differences (Vascular Alone: OR 5.84, p-value <0.01, DPM Alone: OR 1.00, p-value 0.67, Vascular + DPM: OR 1.86, p-value <0.01).

4. Discussion

Our findings support that podiatrists play a crucial role in the interdisciplinary approach to reduce major NTLEA in patients with DM and/or PAD. Most notably, the odds of major NTLEA was reduced when podiatrists were involved in care along with either vascular or general surgeons. While this finding coincides with prior studies in the academic medical center setting, to our knowledge this was the first study utilizing administrative claims data to demonstrate that the addition of podiatry in an interdisciplinary approach in any healthcare setting can reduce the odds of major NTLEA, a health status that is associated with increased mortality.

NTLEA has long been a marker to track the health of a population. HealthyPeople, a US federal government initiative to track the population’s health, includes the trend of amputation rate [10]. NTLEA has been an essential indication for the health of the population because it is closely related to mortality [11]. Complications of DM such as angiopathy, neuropathy, and nephropathy can further compound the effect of PAD among the aging population and increase the risk of NTLEA. [12,13] NTLEA is also thought to be a reflection of overall cardiovascular condition. Individuals who have had NTLEA often have a history of CAD, stroke or CKD[13]. As a result, the management of such a population requires a team approach and different specialists at different levels of care. Podiatry, a specialty that focuses on diabetic foot prevention, management and surgery plays an unique and essential role in this population. Based on previous research, the inclusion of podiatry contributes to better outcomes and cost-savings. Skrepnek et al. found that excluding podiatrists from Medicaid in Arizona cost the system $48 for every $1 the payer thought they would save [14]. Poor outcomes and increased costs were the result of podiatrists being excluded from providing care for Medicaid patients in Arizona [14]. As a result, podiatrists are no longer excluded from Medicaid in Arizona. Additionally, the professional relationship between vascular surgery and podiatry has been proven to be an economic value in limb salvage efforts [15].

While collaboration between vascular and podiatric providers to prevent amputation has been well demonstrated in recent literature, the evidence behind such a team approach often occurs in a healthcare system or an academic medical center in the United States. As an example, the UCSF Center for Limb Preservation makes use of vascular and podiatric surgery co-directorship to provide interdisciplinary care that leads to better outcomes and minimization of hospital readmissions in high risk populations. [7] A 2020 systematic review found that ninety-four percent of studies reported a reduction in major amputations after the implementation of a team approach.[6] The “toe and flow” model where podiatrists and vascular specialists see patients with diabetes and/or PAD in one clinical setting has been advocated for a number of years in the US.[16] The partnership between vascular and podiatry has shown to reduce foot complications and major amputations due to better communication and organization between the specialties.[6] Furthermore, across 10 United States Department of Veteran Affairs (VAs), a special care unit designed to prevent NTLEA was also proven to be successful, with the use of the Foot Systems Assessment tool. [17] There was a significant association between facility-level foot care program coordination and rates of diabetes-related amputations.[17] Such collaboration was further advocated by various medical and nursing associations and published in a recent clinical practice guideline.[18] [2] These guidelines support the interdisciplinary approach for the management of PAD-related lower extremity complications.[2]

Our findings suggested that the interdisciplinary approach, although potentially easier to foster in a hospital-based or academic medical center setting, is still possible in the community. Nonetheless, despite sustained advocacy to include podiatry in the interdisciplinary approach to reduce NTLEA, our analysis indicated that only 7% of major NTLEA patients and 4% of no major NTLEA patients had a podiatrist as part of their care team. There are several factors that may contribute to the low rates of having a podiatrist as part of a patient’s care team. There could be a lack of podiatrists, patient-specific factors related to transportation or financial constraints, unaware of the condition by the patients and/or referring providers or challenges associated with the referral process.[19] Recent qualitative studies interviewing patients with DFU history continued to raise similar concerns and complaints. At the individual level, lack of knowledge of diabetic foot and insurance coverage as well as wound care supplies seemed to hinder the outcome.[20,21] Fragmented communication between providers including the lack of timely referral. Participants identified that “improved access often came too late to alter their course.”[21] Another group of participants further stressed that “insufficient preventative foot care and education before DFU onset.”[20] Some respondents even experienced initial misdiagnoses which delayed care.” [20] The qualitative and quantitative findings indicated the need for improvement to increase access to podiatric care in a timely manner so disease processes may be intervened earlier and amputations may be prevented. .

A number of limitations exist in this study. First, we only included claims in the United States. Second, the study relied on administrative claims data, including ICD-9, ICD-10, and CPT codes, which can have misclassifications, coding errors, limited anatomical and clinical detail, specifically DFU severity. Third, our analysis did not include DFU referrals from primary care physicians as our primary interest of the study was to investigate the impact of podiatrists on major NTLEA. Fourth, the unique role of podiatrists in the US may explain the support of the “toe-and-flow” model, whereas podiatrists may not be able to provide surgical intervention in other countries. Therefore, the findings of this study may only apply to the healthcare environment in the United States. Fifth, the low percentage of podiatry involvement could be a result of categorization of podiatrists that was not accurately classified during some of the years within the dataset. Furthermore, due to the inherent limitations of retrospective cohort studies, our findings can only suggest, and not prove, causality. Nonetheless, our findings support an interdisciplinary approach to manage high risk patients with diabetes and/or PAD so NTLEA can be mitigated and patient outcomes can be optimized.

5. Conclusions

Managing multimorbidity, which is often seen in patients with DFU, can be challenging. The benefits of multidisciplinary DM care teams are well-documented. Our findings highlighted the importance of the inclusion of podiatry within an interdisciplinary approach in the management of patients with DM and/or PAD regardless of practice setting. The inclusion of podiatry is an essential part of the “Toe and Flow” model which is shown to be effective in NTLEA prevention. Further research aims at investigating potential barriers that limit this crucial interdisciplinary approach in the care of patients with DM and/or PAD outside of structured healthcare systems such as academic medical centers is warranted and may provide insight on how to further improve patient outcomes.