Long-term outcomes after intrepid dynamic exoskeletal orthosis treatment coupled with advanced rehabilitation

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Abstract

Objective:

To measure Intrepid Dynamic Exoskeletal Orthosis (IDEO) use patterns, return to work or return to duty, and amputation rate among patients undergoing limb salvage ≥2 years after discharge.

Design:

Telephone survey and retrospective medical chart review.

Setting:

Military tertiary care hospital and rehabilitation center.

Patients/Participants:

A total of 190 active duty or retired service members, military health care beneficiaries, and civilians aged 22 to 64 years old with traumatic lower limb injuries treated with an IDEO were invited to participate in a telephone survey. A total of 145 individuals (76.3% of those contacted) completed the survey.

Main Outcome Measurements:

IDEO use patterns, participation in the Return to Run (RTR) rehabilitation program, return to work or active duty, and elective amputation rate.

Results:

The most common initial diagnosis was lower limb fracture (54.5% of participants). The most common mechanism of injury was from explosive devices (22.8%). After IDEO prescription, 86.9% of respondents participated in the RTR program. Approximately 77.9% of patients returned to work; 67.3% of active duty IDEO users returned to active duty. At final follow-up (mean 90.3 ± 32.9 months, range 24.0–157.0 months), 80 patients (55.2%) still use their IDEO, whereas 14 patients (9.7%) had elected for amputation.

Conclusions:

Long-term IDEO use combined with the RTR rehabilitation program was associated with positive long-term outcomes as evidenced by a high self-reported activity level, high rate of return to work or duty, and low elective amputation rate among patients with severe lower limb injuries.

1. Introduction

Lower extremity limb salvage outcomes were historically poor; thus, many surgeons advocated for amputation in favor of prolonged limb salvage.^1,2 These studies were performed at a time when neither advanced orthoses nor functional rehabilitation was available to patients undergoing limb salvage.^2–5

Twenty-first century US military operations saw an increase in survivability from combat-related trauma and an increase in injury complexity, particularly as it pertained to extremity injuries.^6–8 The influx of wounded service members undergoing complex orthopedic reconstruction, limb salvage operations, limb optimization, and advanced physical therapy necessitated the development of orthotic devices and rehabilitation programs that permitted highly functional limb salvage. The Center for the Intrepid (CFI) at Brooke Army Medical Center developed an interdisciplinary rehabilitation model that collaborated in the development and optimization of the Intrepid Dynamic Exoskeletal Orthosis (IDEO) and the Return to Run rehabilitation (RTR) program around 2009.^2,9 The RTR program seeks to return IDEO patients to high-level activity, including active duty. During this 4-week program, patients are taught a mid-foot strike pattern that maximizes the IDEO's energy-storing capacity and increases strength and multidirectional agility.

The IDEO is a custom-made energy storage-and-return carbon-fiber device that increases ankle joint power in late stance using a dynamic strut placed parallel to the tibia. This flexible strut is attached to a rigid footplate and is secured to the leg by a proximal cuff (Fig. 1).^2,3,10–13 The design is informed by the principle that the rigid footplate transfers the energy absorbed from collision with the ground during loading response to the posterior strut, where it is stored through deformation (like a spring) and then returned at the end of stance for increased propulsion during walking and running.^10–13 The IDEO has been reported to offload injured tissues and reduce peak pressures on the forefoot and hindfoot by as much as 60% and 12%, respectfully, with a mean of 26% reduction.¹⁴ The energy storage and return properties of the IDEO combined with a capacity to reduce loads in the lower leg, ankle, and hindfoot has enabled service members to resume high-level activities after complex limb salvage operations.^3,14 In a 2012 study of 16 patients with post-traumatic osteoarthritis in the ankle, the provision of an IDEO combined with the RTR program enabled patients with extremity trauma to run (81%), jump (75%), return to active duty (44%), and redeploy (13%).¹⁵ Despite best efforts, some injuries were too severe to ensure successful IDEO use; 121 of 624 (19%) CFI patients provisioned with an IDEO between 2009 and 2014 had a subsequent amputation within 1 year of IDEO delivery.¹⁶ It is not clear if or how many of the 81% who did not acquire an amputation retained their limbs long term or if an amputation was ultimately acquired.¹⁶ Patient records from the CFI and from within the Military Health System allow for unique research into the effectiveness of this advanced orthotic device plus focused rehabilitation, which has the potential to inform future treatment decisions.

Figure 1.

Energy absorption and return mechanism of the IDEO. The IDEO uses a rigid foot plate that absorbs energy during midstance, transmits it to the posterior strut during loading response, and stores it for return at the end of stance.

The purpose of this study was to evaluate the long-term outcomes of patients who had received an IDEO at least 2 years prior, with an emphasis on understanding patterns of continued device use, return to work and duty, and delayed amputation rate. This information would be helpful to define the effectiveness of limb salvage when coupled with an advanced orthotic device and focused rehabilitation. This study provides foundational work for larger studies aimed toward helping clinicians predict who will most benefit from an IDEO combined with a focused rehabilitation program.

2. Methods

After Institutional Review Board approval, a list of patients who received an IDEO between 2010 and 2021 was created from institutional records. The subset of IDEO users who had had their device for at least 2 years was identified. This patient list was randomized. Patients were invited to participate in the study via phone (Fig. 2). If they agreed to participate, a member of the research team administered the phone survey after receiving both informed consent and Health Insurance Portability and Accountability Act (HIPAA) authorization from the participant. Military Health System Genesis, the military's electronic health record system, was used to review patients' medical records to determine age, race, ethnicity, sex, the cause of and characteristics of their limb injury, the date they received their first IDEO, the number of devices prescribed, and rehabilitation history. The survey consisted of questions relating to the patient's IDEO use (or lack thereof), reason(s) for ongoing or discontinued use, whether the patient was able to return to duty or to their previous job, mobility aids used in addition to or in lieu of the IDEO, and, if applicable, a history of amputation (Appendix A, http://links.lww.com/OTAI/A133). Data were coded and combined in a spreadsheet to generate descriptive statistics. The dataset supporting the findings of this study is not available for public access due to restrictions imposed by military regulations and institutional security policies governing sensitive defense-related data. Requests for access may be considered on a case-by-case basis through appropriate military channels in accordance with applicable policies.

Figure 2.

Participant enrollment flowchart. The diagram summarizes participant selection for the study. Of the total patient list (n = 1100), 1093 were deemed eligible for follow-up regarding device use. Of these, 190 patients with IDEO use of at least 2 years were contacted. A total of 145 patients were enrolled in the study, whereas 45 declined to participate.

3. Results

A total of 1100 patients were identified from CFI prosthetic records as having received an IDEO (Fig. 2). Of these, 1093 had been prescribed their IDEO at least 2 years prior. A random sample of 190 patients was contacted. A total of 145 patients (76.3%) consented to participate in the telephone survey. Survey respondents were primarily male and had a mean age of 42.5 ± 8.7 years (range, 22.4–64.4 years) (Table 1). Three-quarters of respondents (75.9%) were still on active duty when provided their IDEO, whereas an additional 19.3% had separated or retired, and an additional 4.8% were dependents, military beneficiaries, or affiliated civilians (Table 1). Surveys were administered a mean of 90.3 ± 32.9 months (24.0–157.0 months) after patients' IDEOs were provisioned.

Table 1.

Demographic characteristics.

Demographics	Number (n)	Percent (%)
Age (y)
18–29	6	4.1
30–39	57	39.3
40–49	49	33.8
50–59	32	22.1
60–65	1	0.7
Sex
Male	125	86.2
Female	20	13.8
Race
White	113	77.9
Black/African American	19	13.1
Native American (American Indian or Alaskan Native)	1	0.7
Pacific Islander	1	0.7
Other	7	4.8
Unanswered	4	2.8
Ethnicity
Not Hispanic	127	87.6
Hispanic/Latino	16	11.0
Did not identify	2	1.4
Military status
IDEO provision
Active duty	110	75.9
Separated or retired	28	19.3
Dependent, civilian, or beneficiary	7	4.8
Survey completion
Active duty	74	51.0
Separated or retired	64	44.1
Dependent, civilian, or beneficiary	7	4.8

The demographics of the study participants are presented as counts and percentages of the cohort. Age was categorized into 5 groups, and sex was classified as male or female. Race and ethnicity followed US military classifications, including Hispanic/non-Hispanic and racial groups including White, Black/African American, Native American/American Indian or Alaskan Native, and Pacific Islander. Military status was reported both for the IDEO provision and at the time of survey completion classified as active duty, beneficiary, or civilian.

Over half of respondents (54.5%) were prescribed their device after experiencing injuries involving the tibia, ankle, and hindfoot. Respondents' injuries were commonly sustained due to blasts (22.8%), motor vehicle or motorcycle injuries (15.9%), falls (10.3%), and ballistic injuries (8.3%). Injuries sustained during training or deployment activities represented 22.1% of injuries. Associated injury characteristics included post-traumatic osteoarthritis (45.5%), chronic regional pain syndrome (40.7%), chronic wounds (21.4%), and osteomyelitis (17.2%). Other patients experienced stiffness, neuropathic pain, foot drop, nonunion, malunion, soft tissue infection, and avascular necrosis. Patients were provided a median of 3 IDEOs (range, 1–18) during the course of their treatment. Fifteen patients (10.3% of respondents) were prescribed an IDEO for both limbs.

After their IDEO prescription, 126 patients (86.9% of respondents) participated in the RTR rehabilitation program for a mean of 4.9 weeks. Of these, 100 patients (79.4%) in the RTR program reported an increase in activity level after receiving their IDEO. Seven patients (5.6%) reported a decrease in activity level, and 19 patients (15.1%) reported no change in activity level.

More than half of respondents (55.2%, 80 patients) continued to use the IDEO at the time they completed the survey. Forty patients (27.6%) report using their device daily or almost daily and an equal number use their device only for specific activities such as hiking, weightlifting, and running. Seventy-four of the 110 IDEO users on active duty (67.3%) returned to active duty; all except for 6 service members were able to return to their previous military occupation (Table 1). Overall, 113 patients (77.9%) returned to active duty or employment.

Sixty-five respondents (44.8%) do not currently use their IDEO. Of these patients, 36 (24.8% of respondents) no longer use any orthotic device, 14 (9.7%) currently use a non-IDEO orthosis, 1 (0.7%) uses a similar orthosis, and 14 (9.7%) electively underwent amputation (Fig. 3). Of the 14 patients who elected amputation, 8 (47%) were battlefield injuries (7 due to an improvised explosive device and 1 due to a ballistic injury) and 7 (50.0%) had complex injuries characterized by multiple fractures. In this cohort, 12 (85.7%) reported chronic regional pain syndrome, 9 (64.3%) had injuries complicated by osteomyelitis, and 6 (42.9%) had post-traumatic osteoarthritis. The cohort of patients electing for amputation used the IDEO for a mean of 2.4 ± 2.1 years (range, 3 months to 7.0 years), with 3 patients opting for amputation less than 1 year after receiving the IDEO, 8 patients undergoing amputation between 1 and 3 years, and 3 patients electing for amputation greater than 3 years after IDEO provision.

Figure 3.

Use of mobility aids. Most patients (55.2%) fitted with an IDEO continue to use their IDEO, whereas 24.8% of the total cohort no longer uses any device; an additional 9.7% use a non-IDEO orthosis and 0.7% use another orthosis. Approximately 9.7% of the cohort underwent amputation and use a prosthesis.

4. Discussion

Patients with high energy lower limb trauma involving the tibia, hindfoot, and foot can have devastating outcomes.^17–19 Early studies denigrated limb salvage in favor of amputation^4,5,20–22; however, modern orthotics and advanced rehabilitation programs have provided new functional opportunities for patients choosing limb salvage. Prior studies of one such device, the IDEO, described amputation rates nearing 20% 1 year after it was prescribed for severe lower extremity limb injuries¹⁶; however, the outcome of patients using the device for longer periods is unknown. This study evaluated the self-reported rate of IDEO use among service members a mean of 7.5 years after the device was provisioned, with an emphasis on understanding patterns of continued device use, return to work and duty, and delayed amputation rate.

Given the data available for analysis, more than half of individuals were still using their device either full-time or for specific (usually high-demand) activities and less than 10% of the cohort elected for amputation. Although previous studies described IDEO users return to high level activities early in their rehabilitation process,^12,23 the current study demonstrates that these trends continue well after the initial rehabilitation phase.^12,23 These data demonstrate the important role of advanced orthoses and functional rehabilitation in active patients with complex lower extremity injuries and help clinicians counsel patients and manage expectations regarding limb salvage long term.

The impact on a patient's ability to return to work, duty, or sport has been one of the defining characteristics of the IDEO and the RTR program. Data from recent conflicts showed that patients with a grade III open tibia fracture or combat-related hindfoot injury were about as likely to return to duty as a patient with a unilateral transtibial amputation (20% vs 18%).^24,25 Our study supports findings by several authors that some IDEO users can return to their previous military occupations, including deployment in a combat role.^2,26,27 In the current study, nearly two-thirds of patients surveyed report successfully returning to their previous military occupation. This has implications for returning to work among individuals working in the civilian sector, even those with active jobs requiring high levels of physical function.

When specific diagnoses were evaluated among a cohort of IDEO users with post-traumatic osteoarthritis, 44% were able to return to active duty.¹⁵ The additive effect of the IDEO and RTR on patients' ability to return to high levels of function is supported in the literature. Blair et al²⁶ report that service members that participated in the RTR program with the IDEO were 4 times as likely to return to active duty than those that did not. That study demonstrated that the proportion of patients who returned to duty increased to 51.3% when IDEO use was combined with the RTR program (or equivalent) compared with just 12.9% of patients who returned to duty with an IDEO without having completed a dedicated functional rehabilitation program. However, the authors defined neither the follow-up period nor the patients' level of activity or return to occupational specialty. A recent study highlights the importance of the IDEO when combined with the RTR program using the 2-minute walk test as an objective measure of physical performance.²⁸ The study evaluated individuals with no IDEO, with the IDEO alone, and with the IDEO after completion of the RTR program. Participants demonstrated improvement in 2-minute walk distance using the IDEO alone when compared with no IDEO; however, use of the IDEO after completion of the RTR program normalized their function (walking distance) comparable with uninjured individuals.²⁸

In the current cohort, fewer than 10% of patients treated with an IDEO elected for amputation in favor of ongoing limb salvage. With the data available for analysis, we were unable to identify specific variables that correlated with delayed amputation due to the small sample size in this cohort. Anecdotally, indications for amputation include having a nonreconstructable limb injury (usually involving multiple systems and often complicated by infection and/or soft tissue loss), significantly limited function including inability to ambulate (either due to limb injury or pain), rest pain, or unrelenting nerve pain. In the study cohort, three-quarters of patients had a history of fractures complicated by issues such as osteomyelitis, soft tissue infections, osteoarthritis, and chronic or complex regional pain syndrome. Other factors that contribute to the decision to proceed with amputation include function (perceived, anticipated, and actual), patient preference, surgeon experience and bias, context (culture and peer support), and local resources. These findings align with prior research on patients' decision to pursue amputation.²⁹ Previous analyses of IDEO users give insight into how this orthosis has affected amputation rates after lower extremity limb salvage. In one study, a 63.6% decrease in desire for amputation was seen at a medium follow-up of 35 months after IDEO provision.³ Others evaluated separate groups of IDEO users who completed the RTR pathway and determined that 15% to 23% of patients wished to proceed with amputation.^12,27 An in-depth prospective study or more comprehensive survey may be able to inform this discussion in a manner that the preliminary findings of this pilot study cannot.

The temporal relationship between injury and amputation differs dramatically between studies based on the study cohort and its injury characteristics (for example, how “limb salvage” is defined). Among a cohort of individuals with service-related amputations, 17.0% of individuals undergoing “late” amputation (defined as more than 3 months after injury) opted for amputation more than 2 years postinjury.³⁰ In a study of 624 IDEO users, 19% of patients proceeded with amputation within 1 year of receiving their device.¹⁶ Even midterm analyses of limb salvage outcomes can be misleading; among a cohort of military members with lower limb injuries, patients opted for amputation a mean of 5 ± 3 years after injury.³¹ Patients in our study elected for amputation a mean of 2.4 ± 2.1 years (range, 3 months to 6.9 years) after being prescribed an IDEO, with 3 patients opting for amputation less than 1 year after receiving the IDEO, 8 patients undergoing amputation between 1 and 3 years, and 3 patients electing for amputation greater than 3 years after IDEO provision. This is similar to another recent study on IDEO use³ but does not give information on the timeliness of amputation relative to injury. The importance of the current study is the long duration of follow-up (mean 90 months, range 24–157 months) relative to prior studies.

A limitation of this retrospective study is the risk of self-selection to participate. As with other survey studies, we suspect that patients with positive responses (ongoing IDEO users) were more likely to participate than those with neutral or negative responses. Similar suspicions have been noted in studies with similar study designs.³ Participants' recall bias may also affect data accuracy. Another limitation is the modest sample size that may not accurately represent the broader population. Last, this study lacks a control group due to the relative scarcity of having IDEO users that did not participate in RTR. It is difficult to ascertain the relative importance of the IDEO versus functional rehabilitation (the Return to Run program or a similar program) alongside an interdisciplinary team, as prior studies underline the importance of rehabilitation in returning patients to duty.^26,28 Among patients with severe lower extremity trauma, nonmedical factors such as self-efficacy, support, mental health, and access to social services can affect functional outcomes.⁴ This support network likely improves treatment adherence and addresses confounding nonmedical drivers of negative outcomes among patients with severe lower extremity trauma. Unfortunately, due to cost constraints and other considerations, these services are often less available to civilian trauma patients than they are to active and prior military members.

In this study, service members and beneficiaries provisioned with an IDEO were to some degree (and, for many, broadly) integrated in a comprehensive support network, with nearly 90% participating in the RTR program as well. This study offers insight into long-term outcomes of limb salvage patients using the IDEO. Understanding factors such as design features that limit IDEO wear, why the IDEO is discontinued, factors leading to amputation, and the timing of amputation will help surgeons and rehabilitation professionals define the role of this device. Further insight into the continued use of the IDEO may be gained from technology such as a novel robotic surrogate that monitors muscle activation related to pain and mobility.³² Future prospective studies or a more comprehensive survey may increase clinicians' understanding of how advanced orthotics such as the IDEO may optimize limb salvage patients perceived and actual function. In addition, it may inform strategies for the optimization of IDEO use to reduce pain and increase function as new advanced therapies are developed.

Data Availability Statement

The datasets generated during and/or analyzed during the current study are not available.