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. 2018 Sep 25;477(4):838–847. doi: 10.1097/CORR.0000000000000487

Do Spatiotemporal Gait Parameters Improve After Pilon Fracture in Patients Who Use the Intrepid Dynamic Exoskeletal Orthosis?

Michael Quacinella 1,2,3,✉, Ethan Bernstein 1,2,3, Brittney Mazzone 1,2,3, Marilynn Wyatt 1,2,3, Kevin M Kuhn 1,2,3
PMCID: PMC6437376  PMID: 30811361

Abstract

Background

Pilon fractures are high-energy fractures about the ankle observed commonly in both civilian and military trauma populations. Despite surgical management, outcomes are predictably poorly characterized by functional deficits secondary to pain and stiffness. The Intrepid Dynamic Exoskeletal Orthosis (IDEO) and Return-to-Run clinical pathway were initially designed to treat military service members after complex battlefield lower extremity injuries. The IDEO has been used to treat nonbattlefield injuries, but, to our knowledge, it has not been studied specifically among patients with pilon fractures. By studying the use of the IDEO in this patient population, we hope to learn how it might improve ambulation in the community, relieve pain, and return patients to work to better identify patients who might benefit from its use.

Questions/purposes

The purpose of this study was to determine whether the IDEO would improve gait parameters including velocity, cadence, stride length, and single-leg stance duration in patients with pilon fractures. Our secondary endpoints of interest were reductions in pain and return to duty.

Methods

A prospectively collected database of all active-duty IDEO users at a single institution was queried for all patients using the IDEO after a pilon fracture. Patients were included if they were using the IDEO after sustaining a surgically treated pilon fracture and had exhausted all nonoperative therapies. Exclusions were patients with an incomplete gait analysis at the two study time points. Seven patients meeting these criteria were identified. Three-dimensional gait analysis was performed two times: first wearing shoes at a self-selected speed and second after a custom-made IDEO was fabricated for the patient and completion of the Return-to-Run pathway. Patients reported their average pain while ambulating using a numeric rating scale. Gait variables of interest were velocity, cadence, stride length, and single stance time. Return to military service was assessed through the military medical record. To return to duty, a service-specific physical readiness test must be completed.

Results

Median gait velocity improved from 1.1 (interquartile range [IQR], 0.9-1.2) to 1.3 m/s (IQR, 1.2-1.5; p = 0.01). All other variables did not change: cadence 98.4 (IQR, 93.0-107.2) to 104.5 steps/min (IQR, 103.0-109.0; p = 0.13), affected stride length 1.3 (IQR, 1.0-1.4 m) to 1.4 m (IQR, 1.3-1.6 m; p = 0.07), and affected single stance 0.42 (IQR, 0.41-0.47) to 0.43 (IQR, 0.42-0.44; p = 0.80). Pain did not change between time points: 3 (IQR, 2-3) to 2.5 (IQR, 1-3.5; p = 0.90). Three of seven patients returned to duty.

Conclusions

At self-selected walking speeds, we observed no improvements in gait parameters or pain after application of the IDEO that would likely be considered clinically important, and so the device is unlikely to be worth the cost in this setting. It is possible that for higher demand users such as elite athletes, the IDEO could have a role after severe lower extremity trauma; however, this must be considered speculative until or unless proven in future studies.

Level of Evidence

Level III, therapeutic study.

Introduction

Intraarticular distal tibia fractures (pilon fractures) are serious injuries usually sustained in high-energy trauma. Even when surgical management achieves a bony union without soft tissue complications, patients with pilon fractures often develop persistent functional limitations, ongoing pain, and posttraumatic osteoarthritis of the ankle [9, 19, 30]. Even when posttraumatic osteoarthritis is not radiographically apparent, gait abnormalities can be observed when compared with normative gait data suggesting these injuries produce an antalgic gait [7]. Anatomic joint reconstruction improves function, pain, and SF-36 scores when compared with conservative therapy [10, 20, 21, 23, 30], but the risk of developing posttraumatic osteoarthritis is often associated with the severity of the initial injury [5, 31] with more severe, high-energy injuries doing predictably worse. The functional deficits associated with ankle stiffness and pain after pilon fracture pose a substantial burden on the patient. Disregarding the cost of acute management of these injuries, the proportion of patients who remain unemployed after these injuries has been estimated to be between 30% and 66%; this places a financial strain on the patient and society [3]. In the military, these patients are often medically separated from service despite their desire to continue because they cannot meet the physical demands of active-duty military service. Furthermore, patients are only allotted 1 year of limited-duty status to convalesce and rehabilitate. They are often forced to decide early in their rehabilitation to pursue life-changing procedures such as ankle arthrodesis and even below-knee amputations in the hopes of salvaging a military career [17, 25].

In the military, a recently developed ankle-foot orthosis (AFO) has shown promising results in returning war-injured limb salvage patients back to full active duty [1, 2]. The Intrepid Dynamic Exoskeletal Orthosis (IDEO) is a ground-force reaction AFO developed during the conflicts in Iraq and Afghanistan that appears to help war-injured limb salvage patients recover, return to military service, and avoid delayed amputation. The IDEO was specifically designed to address gait derangements in patients with functional loss after high-energy lower extremity trauma occurring below the knee. The IDEO is able to function as an energy-storing AFO because of its unique design allowing forces to be redistributed away from an arthritic joint through the posterior strut into the proximal tibial cuff (Fig. 1) [15, 22].

Fig. 1.

Fig. 1

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The IDEO is a custom-fabricated AFO with a carbon fiber cuff connected to a Kevlar/carbon fiber foot plate by carbon fiber posterior struts. Note the modular design allowing the brace to be adaptable and customizable to each patient’s unique body habitus.

The Return-to-Run clinical pathway is a multidisciplinary rehabilitative pathway that cohorts new IDEO users together to train them on the use of the AFO. Patients interested in pursuing IDEO fabrication are required to participate in this 8-week intensive physical therapy program because of previous literature demonstrating its effect on return-to-duty rates; it has been shown that service members completing this pathway were four times more likely to return to duty [2]. This pathway incorporates three phases of therapy: strengthening, agility training, and finally running, helping to train new IDEO users on how to properly load the brace so that it might assist in impact activities.

The use of IDEO in combination with the Return-to-Run clinical pathway has been well studied in high-energy combat injuries [1, 2, 14-17]. Although these studies include patients with pilon fractures, these patients were not specifically studied as an individual cohort and most of the results are in a heterogeneous patient population with a multitude of complex injuries [13]. Furthermore, these patients were studied performing high-functioning activities required of service members to return to active duty and improvements in gait during low-function activities such as walking speed ambulation was ignored in these reports.

This study therefore sought to determine whether the IDEO when used with the Return-to-Run clinical pathway would improve gait at walking speeds. Specifically, we sought to determine whether the IDEO would improve gait parameters including velocity, cadence, stride length, and single-leg stance duration in patients with pilon fractures. Our secondary endpoints of interest were reduction in pain and return to duty.

Patients and Methods

After institutional review board approval, a longitudinally collected data registry of all patients using the IDEO at a single institution was retrospectively studied. In general patients are referred to the IDEO clinic for consideration of prescription by the treating physician when pain and loss of function limit daily activities and the patient’s ability to return to military service after a lower extremity injury. Specifically for the pilon fractures, patients who had pain and functional limitations despite achieving bony union were referred to the IDEO clinic to be evaluated to determine if the IDEO was an appropriate treatment option for them. A multidisciplinary evaluation by a team consisting of an orthopaedic surgeon (KMK), physiatrist (RS, CS), prosthetist (RM), and a physical therapist (BM, MW) determined if an IDEO prescription might benefit the patients in their recovery based on the patient’s injury, symptoms, and limitations. Once it was decided that a patient was a good candidate for IDEO prescription, a custom-fitted IDEO brace was fabricated. After fabrication of the IDEO, the patient works closely with the prosthetist and several minor modifications are made to ensure a proper fit and function of the brace before the patient is referred to the Return-to-Run rehabilitative program. Participation and completion of the Return-to-Run program was mandatory for all patients to be considered for IDEO fabrication given the previous literature demonstrating its importance in returning military members back to service in conjunction with the IDEO [13]. The 6-week-long program consists of three phases of gait retraining, strengthening, and agility utilizing the IDEO for assistance.

Three-dimensional gait analyses were conducted as part of the registry protocol for all IDEO users. The available spatiotemporal gait data were captured at two time points: with the patient walking at a self-selected speed in self-selected shoes and then again after fabrication of their IDEO and completion of the Return-to-Run clinical pathway. Three-dimensional gait analysis was completed using a 12-camera motion capture system (Motion Corporation, Santa Rosa, CA, USA) with four floor-embedded force plates (AMTI, Watertown, MA, USA). Data were collected and processed using previously described techniques [8, 22]. At this time of this study, there were 70 patients in the registry with complete data for review. Patients were screened for inclusion into this study based on the anatomic location as either ankle or tibia-fibula injuries. Fourteen patients were identified. Their clinical notes and radiographs were then reviewed to further characterize their injury. Patients were included if their radiographs demonstrated intraarticular distal tibia plafond fractures as described by the Orthopaedic Trauma Association classification [11]. Patients were excluded if they had a contralateral extremity injury or the injury was noted to be a rotational ankle injury or an extraarticular tibial-shaft fracture. Seven patients were excluded based on these criteria. Of the remaining seven patients, all had complete gait data and clinical data available for analysis. These seven patients were active duty at the time of injury. All injuries occurred after high-energy trauma. Two patients were involved in motor vehicle accidents, three were involved in an improvised explosive device (IED) blast, one patient sustained a fall from a height, and one patient fell while skateboarding. One injury was open with superficial fragmentation wounds after an IED blast. Using the Orthopaedic Trauma Association fracture classification systems, the fractures were classified as follows: one 43-C1 and six 43-C3 (Table 1) [11]. All patients were treated definitively with open reduction and internal fixation once the soft tissues were amendable to an open procedure. One patient underwent soft tissue coverage with a free flap. There were two postoperative complications, both of which were infections. All fractures went on to radiographic union. There were no identifiable nerve injuries. Patients underwent a median of three (interquartile range [IQR], 2-4) prior operations before IDEO application. At the first gait analysis, median age was 25 years (IQR, 22-38) and median body mass index was 30 kg/m2 (IQR, 25-31). All patients were men and were active duty at the time of injury. The median time from injury to IDEO prescription was 1 year (IQR, 1-5). Two patients used off-the-shelf AFOs for lower extremity bracing devices and three used other assistive devices before IDEO fabrication. Two patients underwent tibiotalar arthrodeses as a result of the severity of their symptoms. After IDEO fitting and Return to Run, all patients were referred to the gait laboratory for further evaluation.

Table 1.

Patient injury classification, mechanism of injury (MOI), and additional treatments

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The primary study outcome variables were gait velocity, cadence, stride length, and single stance time because these have been previously reported variables in patients with pilon fractures [12, 18, 24, 26, 27]. Pain was assessed before and after IDEO while the patients were ambulating by self-reported scores using a numeric scoring system from 0 to 10 with 0 being zero pain and 10 being the worst pain. Return to active military duty was assessed through the military global electronic medical record.

Statistical Analysis

A paired Wilcoxon rank-sum test was conducted using SPSS Statistics 2010 software (SPSS Inc, Chicago, IL, USA). Medians, IQRs, 95% confidence intervals, and p values were calculated. Pre-IDEO and post-IDEO Return-to-Run differences were evaluated for pain, velocity, cadence, stride length, and single stance time. The uninjured extremity was used as a control to evaluate the difference in stride length and single stance time pre-IDEO and post-IDEO. A p value of < 0.05 was selected to represent statistical significance.

Results

Only gait velocity improved after application of the IDEO and completion of the Return-to-Run pathway (Table 2). Median gait velocity improved (Fig. 2) from 1.1 m/s (IQR, 0.9-1.2) to 1.3 m/s (IQR, 1.2-1.4; p = 0.01). However, the effect sizes of this observation were small and unlikely to have clinical importance. There was no change to the remaining gait variables (Table 2). Cadence (Fig. 3) of the injured leg did not change with 98.4 steps/min (IQR, 93.0-107.2) initially to 104.5 steps/min (IQR, 103.0-109.0) after treatment (p = 0.13). Affected limb stride length (Fig. 4) did not improve with 1.3 m (IQR, 1.1-1.4) initially to 1.4 m (IQR, 1.4-1.6) after treatment (p = 0.07). Percent of affected limb single stance time (Fig. 5) was unchanged from 0.42 (IQR, 0.41-0.47) to 0.43 (IQR, 0.42-0.44; p = 0.8). There was no difference between affected single stance time and unaffected single-leg stance time pre- and post-IDEO bracing, 0.032 (IQR, 0.024-0.082) to 0.041 (IQR, 0.034-0.048; p = 0.9). There was also no difference between the uninjured contralateral extremity and the injured extremity stride length pre- and post-IDEO, -0.0004 (IQR, -0.008 to 0.003) to 0.0007 (IQR, -0.017 to 0.002; p = 0.9).

Table 2.

Spatiotemporal gait data measured before IDEO and after IDEO application and completion of the Return to Run program and results of Wilcoxon rank-sum scores

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Fig. 2.

Fig. 2

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Distribution of velocity (meters/sec) pre- and post-IDEO and Return-to-Run pathway are shown.

Fig. 3.

Fig. 3

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Distribution of cadence (steps/min) pre-and post-IDEO and Return-to-Run pathway are shown.

Fig. 4.

Fig. 4

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Distribution of affected limb stride length (meters) pre- and post-IDEO and Return-to-Run pathway are shown.

Fig. 5.

Fig. 5

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Distribution of single stance time of the affected extremity as a percentage of the gait cycle pre- and post-IDEO and Return-to-Run Pathway are shown.

Patient self-reported pain scores (Fig. 6) did not change between the two time points: 3 (IQR, 2-3) to 2.5 (IQR, 1-3.5; p = 0.9). Three of the seven patients were able to return to full active duty and continue their military careers.

Fig. 6.

Fig. 6

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Distribution of self-assessed pain scores while ambulating pre- and post-IDEO and Return-to-Run pathway are shown.

Discussion

Pilon fractures are not uncommon both in civilian trauma and in combat injuries. Before this study, most studies on using the IDEO in this patient population have focused on return to military service and focused on functional outcomes while performing demanding activities such as running, jumping, and cutting activities [14-17]. These studies demonstrate improvements in function while performing these types of activities; however, they do not evaluate the patient’s ability to ambulate at walking speeds. As the IDEO becomes commercially available in the civilian sector, it will become important to further validate its use for specific injuries and patient populations that might benefit from its use. By using gait analysis to look at gait changes pre- and post-IDEO during walking speeds, this study gives us a better understanding about where the IDEO should be utilized in the treatment algorithm for the deficits associated with high-energy lower extremity injuries. This study found no clinically important differences in measurable gait parameters after application of the IDEO and Return-to-Run clinical pathway. The IDEO and Return-to-Run clinical pathway were also not associated with improvements in pain scores. Although three of seven study participants returned to full duty, it is impossible to know to what degree the IDEO influenced that endpoint in the absence of a control group. This study found no compelling benefit to the IDEO and Return-to-Run clinical pathway in military service members who had high-energy pilon fractures ambulating at walking speeds.

There are several limitations of this study and the IDEO itself. This study is small, and the patient cohort is relatively homogeneous. The brace was studied in an all-male cohort; however, there was little concern that these results would not be applicable to a female population. This study is at risk for selection bias because the number of patients who were treated for pilon fracture but did not receive an IDEO is unknown and the referral to the IDEO clinic was driven by each treating surgeon’s preference; those preferences could not be defined in the context of this study. Transfer bias (loss to followup and incomplete followup) is an issue here as well, because to be included into the registry of prospectively collected data, all gait studies and completion of the Return-to-Run pathway had to be completed. Validated functional outcome scores were not collected and using return to duty as a proxy for a good functional outcome has never been validated. Therefore, although a few of the patients were able to return to active duty, which suggests that the IDEO is most effective when utilized in high-demand activities, these findings are only speculative and in no way conclusive. The use of the IDEO is limited by its cost, availability to service members and civilians, need for lifetime maintenance, and the need for a multidisciplinary team approach of surgeons, physiatrists, and prosthetists to appropriately prescribe the brace. Because the IDEO is a custom-fitted orthosis, any fluctuations in patient weight, body build, or calf size can negatively affect the fit and function of the brace. Like any orthosis, the components are at risk for malfunction or failure and need frequent maintenance and even replacement.

The current study did not demonstrate improvement in gait at walking speeds after pilon fracture utilizing the IDEO and Return-to-Run pathway. Although velocity was found to be improved, cadence, affected single stance time, and stride length were not changed when compared with the uninjured contralateral extremity. Although these patients were able to walk faster, it was only slightly so, calling into question the utility of utilizing the IDEO in low-demand patients who do not desire to or are incapable of returning to high-level functional activities such as running or jumping. Although these patients’ velocity improved to 1.3 m/s after IDEO and Return to Run, they barely meet the 1.2 m/s needed to safely cross a street as defined by the US Departments of Transportation [28]. Wilken et al. [29] reported military-aged individuals’ normal gait data. In that study, men of average age 25 years old ambulated at a median of 1.52 m/s (IQR, 1.41-1.64) on level ground, which, when compared with this study’s population, further highlights the deficits these patients were left with despite intervention with IDEO and Return to Run.

Posttraumatic osteoarthritis leading to pain and stiffness commonly limits function after pilon fracture. Although this study did not specifically look at the radiographic grade of arthritis before IDEO application, this diagnosis can be made through analysis of the patient’s gait data. Jansen et al. [6] demonstrated that high Orthopaedic Trauma Association fracture classification predicted poor motion and function after pilon fracture and was associated with high-grade radiographic posttraumatic osteoarthritis. Posttraumatic ankle arthritis has been further characterized using gait data in other studies where it was demonstrated that radiographic posttraumatic osteoarthritis was correlated with decreased cadence, stride length, velocity, and percent of stance phase spent on the affected extremity [7, 27]. Given the high Orthopaedic Trauma Association fracture classification and pre-IDEO gait data in this cohort, which demonstrated decreased velocity, cadence, and stride length, it is reasonable to assume that their functional limitations were in part the result of the posttraumatic osteoarthritis they developed after their injury. Because of the unique design of the IDEO, it was believed the brace would be effective in offloading the tibiotalar joint by bypassing the joint as the foot plate dynamically loads the posterior strut connected to the proximal tibial cuff. This small series did not demonstrate the IDEO’s utility in improving patient-reported pain scores before and after fabrication. Future stratification of IDEO intervention before and after arthrodesis may clarify any temporal associations between the brace and functional outcomes over the course of surgical management.

This study failed to demonstrate a potential for an improvement in gait in patients using the brace for community ambulation; however, the three of seven patients who returned to military duty suggest that there may be some utility of the IDEO as an adjunct in the rehabilitative process of servicemen and women. For these military members to return to duty, they must complete a service-specific physical readiness test to include activities such as running. Patzkowski et al. [17] have previously described the use of the IDEO to treat posttraumatic osteoarthritis primarily in the combat-injured patient population. In their series, they demonstrated improved function when compared with traditional AFOs and a return to duty rate of 44%. This current study replicates these findings demonstrating a similar return to duty rate. These findings suggest that the clinical effect of the IDEO may be more substantial for high-level activities that are demanded of active-duty personnel; however, this is speculative and the gait data in this study cannot be extrapolated to support this.

In summary, this study does not demonstrate a clinical benefit in patients with gait derangements after pilon fracture at walking speeds. The IDEO has an important place in the treatment paradigm for patients experiencing debilitating posttraumatic arthritis, paresis, and volumetric muscle loss after high-energy lower extremity injuries such as combat injuries [1, 4, 14-17]. The findings of the current study demonstrate that patients and clinicians should not expect similar improvements in function for patients desiring to use the IDEO for activities of community ambulation only.

Acknowledgments

We thank Robert Sheu MD, and Carter Sigmond MD, for their expertise as physiatrists and contributions to the IDEO clinic. We also thank Richard Miltenberger CPO, for his specialties in IDEO fabrication.

Footnotes

Each author certifies that neither he or she, nor any member of his or her immediate family, has funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.

All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request.

Clinical Orthopaedics and Related Research® neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA approval status, of any drug or device before clinical use.

Each author certifies that his or her institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.

The views expressed herein are those of the author(s) and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the US Government.

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