Biography

Dr. Ledoux's research has been devoted to preventing limb loss, either functionally or anatomically. He has used CT, MRI, motion analysis, and more recently, a custom developed biplane fluoroscope, to quantify reduced lower limb function (i.e., functional limb loss) in different foot types (flat feet and high arched) compared to neutrally aligned feet. He has studied the functional aspects of various orthopedic foot maladies using the custom developed Robotic Gait Simulator. Additionally, he has explored functional differences between ankle fusion and ankle joint replacement for end-stage ankle arthritis. Anatomical limb loss prevention has involved quantifying the mechanical, histological and biochemical differences between normal and diabetic plantar soft tissue and foot ligaments. Dr. Ledoux has also developed a patient-specific finite element foot model, including customized anatomy and tissue properties, for the purpose of quantifying the effects of increased tissue stiffness and foot deformity on internal tissue stresses. Finally, Dr. Ledoux has explored the complex relationship between foot type and diabetic ulceration.

Education

• PhD in Bioengineering, University of Pennsylvania, 1999
• MS in Bioengineering, University of Pennsylvania, 1993
• BS in Biomedical Engineering, Rensselaer Polytechnic Institute, 1992

Current projects

Quantitative Prescription of Foot Orthoses: A Dose-Response Study of Kinematics in Patients with Foot and Ankle Pain using Biplane Fluoroscopy

Our aim with this proposal is to better understand how in-shoe foot orthoses achieve improvements in foot and ankle function for people with ankle osteoarthritis (OA) and/or adult acquired flatfoot resulting from posterior tibial tendon dysfunction (PTTD). We also aim to be able to predict what the optimal, personalized orthotic device is for each patient is. These are common, painful, and often highly debilitating conditions, with ankle OA estimated to affect around 6% of the adult population and adult acquired flat foot around 3.3% percent of females. It has been shown that foot orthoses can be an effective conservative intervention for these conditions, and can help to postpone or negate surgery. However, for a significant proportion of patients foot orthoses are unsuccessful, and there is evidence that this may be a result of significant inter-individual variability in joint movement and loading response to the intervention. This may be due to a number of factors, including foot bone shape, muscle strength, and/or joint range of motion. In addition, the design of foot orthoses is often inconsistent between suppliers, largely because of the manual approach that is used to design and manufacture them. A further complicating factor is that prescriptions for foot orthoses are often vaguely written. Improving our understanding of different foot and ankle responses to variation in foot orthotic design is essential if we are to improve how these devices function at the level of the individual patient. To measure how the individual bones of the foot move using traditional techniques is, however, very difficult. Such methods rely on skin-mounted markers that are tracked in space to determine foot and ankle kinematics. However the size and position of the foot and ankle bones means that it is not possible to measure them all of them individually. Moreover, the movement between the skin and the underlying bones, known as soft tissue artifact, introduces significant errors into the measurements. This is further complicated by the need to wear shoes for orthoses to function properly. Our group has developed a biplane fluoroscopy system that is tailored to address the unique issues of measuring foot kinematics. This system has the additional advantage of being able to measure the effects of foot orthotics in unmodified shoes. To achieve our objective of understanding and being able to predict the effects of orthoses, our specific aims are: [1]: To collect, via biplane fluoroscopy, kinematic data describing the effect of varying the angle of hindfoot posting in foot orthotics. These data will be obtained from 90 participants: 30 with ankle OA; 30 with symptomatic PTTD; and 30 healthy controls. [2]: Using the data from SA1, carry out a regression analysis to identify factors obtained from biplane fluoroscopy and clinical exam that significantly influence an individual’s response (i.e., hindfoot kinematics) to the orthotic intervention. These factors include: foot type, bone geometry, static foot posture, joint axis location, range of motion, and muscle strength. [3]: Using the data from SA1, generate a musculoskeletal model of the foot that allows detailed analysis of the muscles and ligaments controlling ankle movement. This will be developed in the OpenSim modeling platform and made freely available upon project completion. [4]: To compare the kinematic responses to orthotic devices prescribed using standard methods and those prescribed using algorithms and insight from SA2 and SA3 in a separate group of participants. Biplane fluoroscopy will be used to collect kinematic data from 10 patients with ankle OA and 10 with PTTD to compare the performance of the three pairs (one traditional, one from SA2 and one from SA3) of orthotics. This data will also be used to validate the predictions resulting from SA2 and SA3. This proposed research project will improve our understanding of how foot orthotics work and will help us to prescribe more effective devices to patients. This will benefit the large number of people in the population with ankle osteoarthritis and adult acquired flat foot.

Instrumented Footwear to Measure Plantar Tissue Properties

For most individuals, each and every day the plantar tissues of the foot experience thousands of cycles of loading, with each cycle equivalent to their entire bodyweight or more. These tissues cushion and protect the rest of the foot from damage and subsequent problems. In diseases such as diabetes or rheumatoid arthritis, displacement or stiffening of the material properties is common, and this puts these individuals at an increased risk of foot ulceration and related problems. In people with diabetes in particular, foot ulceration is highly prevalent, and leads to almost two thirds of the non-traumatic amputations that occur in the US each year. Our ability to identify feet at-risk of these problems at an early stage, and to protect the tissues using optimized interventions such as therapeutic footwear, is restricted by the lack of tools available to measure the material properties of these tissues in dynamic situations representative of the activities of daily living. The behavior of these tissues is complex, with non-linear and viscoelastic components to their loading response. Current approaches for measuring the material properties of the plantar tissues have tended to involve static indentation rigs, and do not accurately reflect the dynamic behavior of the tissues in the in-shoe environment where the viscoelastic nature of the tissue and the effects of factors including the dynamic stiffness of the nearby muscles play an important role. The proposed experimental work intends to address these problems through the  following: Specific Aim 1 - Develop an instrumented shoe that can provide detailed measurements of the dynamic behavior of the plantar tissues of the foot. An ultrasound probe will be embedded within the sole of the shoe to measure tissue strain, and combined with a force transducer to allow simultaneous collection of the forces being imparted onto the probe by the foot. Specific Aim 2 - Validate the instrumented shoe against biplane fluoroscopy. In ten healthy participants and ten participants with diabetes and peripheral neuropathy, measurements of tissue strain beneath the metatarsal heads and calcaneal tuberosity obtained with the prototype footwear will be compared against those from a biplane fluoroscopy system, which is the current gold standard for measuring the dynamic behavior of the bones of the foot. Our group is uniquely positioned to carry out this work, given our experience in using in-shoe ultrasound, and our established biplane fluoroscopy laboratory. The impact of a validated, instrumented shoe for measuring plantar tissue properties could ultimately lead to a step change in our ability to screen for problems, model interventions, and could initiate new treatment strategies aimed at preventing or treating these disorders. The results from this project will motivate and inform the submission of a R01 application to reach these long term goals.

Characterizing and Restoring Joint Motion in Patients with Hallux Rigidus

The first metatarsophalangeal joint (MTPJ1) is one of the sites most often affected by osteoarthritis, leading to a condition called hallux rigidus (HR). This is very common, estimated to affect 25% of the adult population and increasing in prevalence with age. The number of patients seen by the Veterans Health Administration (VHA) for HR has more than doubled over the last decade. In contrast to degenerative osteoarthritis at the hip and knee, which is commonly treated with joint replacement arthroplasties, the most common surgical treatment for severe HR is arthrodesis, which eliminates joint function. This approach does not allow modification of footwear, interferes with some activities (e.g., yoga, Pilates) and may lead to secondary complications such as metatarsalgia and mobility restrictions. To date, various designs for MTPJ1 arthroplasties have been proposed, but none have been particularly successful, with high failure rates due to loosening and regular reports of migration of the implant. This may be in part because of the relatively small amount of cortical bone in the metatarsal head and proximal phalanx regions, making it difficult to achieve adequate fixation of the prosthetic components. Development of new implants aimed at addressing these problems has been limited by the sparseness of the literature regarding the mechanical environment of the MTPJ1. Similarly, there is very little detailed information on the typical 3D movement of the MTPJ1 required during activities of daily living. Our recent work has established the groundwork for a computational-based modeling workflow that is intended to optimize the design of a novel MTPJ1 implant, and we have had some initial success in generating new, evidence-based implant concepts. In this project, we intend to advance this work, increasing our ability to further MTPJ1 implant technology through computational and robotic gait simulation-based testing. This will ultimately lead to improved patient outcomes. We intend to achieve these aims by: 1) characterizing pathological and healthy MTPJ1 function during different activities of daily living; 2) using a robotic gait simulator to measure the effectiveness of existing and novel MTPJ1 implants at restoring joint function; and 3) further refining our musculoskeletal and finite element models of MTPJ1 to improve their accuracy and provide further validation of their ability to generate useful results. We believe this work has the potential to reinvigorate the study of MTPJ1 arthroplasty, which at present is primarily driven by ideas and not data. The knowledge disseminated from this research will allow surgeons and patients to make better decisions regarding surgical treatments for HR. Specifically, these data will help better understand the disease process of HR and lead to more physiologic MTPJ1 replacements, that will ultimately result in an improvement in mobility and quality of life for Americans with HR. Upon completion, our group will have obtained the expertise to undertake a large clinical trial investigating surgical treatment of HR with the goals of developing a more rigorous classification of HR, and better insight into the various causes of MTPJ1 pain (e.g., dorsal first metatarsal osteophytes or MTPJ1 cartilage damage or sesamoid arthropathy).

Select publications

1. Kimura T, Thorhauer ED, Kindig MW, Shofer JB, Sangeorzan BJ, Ledoux WR. Neuropathy, claw toes, intrinsic muscle volume, and plantar aponeurosis thickness in diabetic feet. BMC Musculoskelet Disord. 2020 Jul 23;21(1):485. doi: 10.1186/s12891-020-03503-y.PMID: 32703177
2. Buckner BC, Stender CJ, Baron MD, Hornbuckle JHT, Ledoux WR, Sangeorzan BJ. Does Coronal Plane Malalignment of the Tibial Insert in Total Ankle Arthroplasty Alter Distal Foot Bone Mechanics? A Cadaveric Gait Study. Clin Orthop Relat Res. 2020 Jul;478(7):1683-1695. doi: 10.1097/CORR.0000000000001294.PMID: 32574472
3. Martin JA, Kindig MW, Stender CJ, Ledoux WR, Thelen DG. Calibration of the shear wave speed-stress relationship in in situ Achilles tendons using cadaveric simulations of gait and isometric contraction. J Biomech. 2020 Jun 9;106:109799. doi: 10.1016/j.jbiomech.2020.109799. Epub 2020 Apr 20.PMID: 32517985
4. Imsdahl SI, Stender CJ, Cook BK, Pangrazzi G, Patthanacharoenphon C, Sangeorzan BJ, Ledoux WR. Anteroposterior translational malalignment of ankle arthrodesis alters foot biomechanics in cadaveric gait simulation. J Orthop Res. 2019 Sep 10. doi: 10.1002/jor.24464. [Epub ahead of print] PMID: 31502697
5. McKearney DA, Stender CJ, Cook BK, Moore ES, Gunnell LM, Monier BC, Sangeorzan BJ, Ledoux WR. Altered range of motion and plantar pressure in anterior and posterior malaligned total ankle arthroplasty: A cadaveric gait study. J Bone Joint Surg Am. 2019 Sep 18;101(18):e93. doi: 10.2106/JBJS.18.00867. PMID: 31567808
6. Norvell DC, Ledoux WR, Shofer JB, Hansen ST, Davitt J, Anderson JG, Bohay D, Coetzee JC, Maskill J, Brage M, Houghton M, Sangeorzan BJ. Effectiveness and safety of ankle arthrodesis versus arthroplasty: A prospective multicenter study. J Bone Joint Surg Am. 2019 Aug 21;101(16):1485-1494. doi: 10.2106/JBJS.18.01257. PMID: 31436657
7. Shofer JB, Ledoux WR, Orendurff MS, Hansen ST, Davitt J, Anderson JG, Bohay D, Coetzee JC, Houghton M, Norvell DC, Sangeorzan BJ. Step activity after surgical treatment of ankle arthritis. J Bone Joint Surg Am. 2019 Jul 3;101(13):1177-1184. doi: 10.2106/JBJS.18.00511. PMID: 31274719
8. Moore ES, Kindig MW, McKearney DA, Telfer S, Sangeorzan BJ, Ledoux WR. Hind- and Midfoot Bone Morphology Varies with Foot Type and Sex. J Orthop Res. 2018 Dec 11. doi: 10.1002/jor.24197. [Epub ahead of print] PMID: 30537297
9. Johnson L, Richburg C, Lew M, Ledoux W, Aubin P, Rombokas E. 3D Printed lattice microstructures to mimic soft biological materials, Bioinspir Biomim. 2018 Sep 13. doi: 10.1088/1748-3190/aae10a. [Epub ahead of print] PMID: 30210061
10. Pihl CM, Stender CJ, Balasubramanian R, Edinger KM, Sangeorzan BJ, Ledoux WR. Passive engineering mechanism enhancement of a flexor digitorum longus tendon transfer procedure. J Orthop Res. 2018 May 18. doi: 10.1002/jor.24051. [Epub ahead of print] PMID: 29774947
11. Norvell DC, Shofer JB, Hansen ST, Davitt J, Anderson JG, Bohay D, Coetzee JC, Maskill J, Brage M, Houghton M, Ledoux WR, Sangeorzan BJ. Frequency and impact of adverse events in patients undergoing surgery for end stage ankle arthritis. Foot Ankle Int. 2018 Sep;39(9):1028-1038. doi: 10.1177/1071100718776021. Epub 2018 May 31. PMID: 29852755
12. Segal AD, Cyr KM, Stender CJ, Whittaker EC, Hahn ME, Orendurff MS, Ledoux WR, Sangeorzan BJ. A three-year prospective comparative gait study between patients with ankle arthrodesis and arthroplasty. Clin Biomech (Bristol, Avon). 2018 May;54:42-53. doi: 10.1016/j.clinbiomech.2018.02.018. Epub 2018 Mar 5. PMID: 29550642
13. Iaquinto JM, Kindig MW, Haynor DR, Vu Q, Pepin N, Tsai R, Sangeorzan BJ, Ledoux WR. Model-based tracking of the bones of the foot: A biplane fluoroscopy validation study. Comput Biol Med. 2018 Jan 1;92:118-127. doi: 10.1016/j.compbiomed.2017.11.006. Epub 2017 Nov 8. PMID: 29175098
14. Wang YN, Lee K, Shofer JB, Ledoux WR. Histomorphological and biochemical properties of plantar soft tissue in diabetes. Foot (Edinb). 2017 Dec;33:1-6. doi: 10.1016/j.foot.2017.06.001. Epub 2017 Jun 7. PMID: 29126035
15. Benich MR, Ledoux WR, Orendurff MS, Shofer JB, Hansen ST, Davitt J, Anderson JG, Bohay D, Coetzee JC, Maskill J, Brage M, Houghton M, Sangeorzan BJ. Comparison of treatment outcomes of arthrodesis and two generations of ankle replacement implants. J Bone Joint Surg Am. 2017 Nov 1;99(21):1792-1800. doi: 10.2106/JBJS.16.01471. PMID: 29088033
16. Vander Griend RA, Younger ASE, Buedts K, Chiodo CP, Coetzee JC, Ledoux WR, Pinzur MS, Prasad KSRK, Queen RM, Saltzman CL, Thordarson DB. Total ankle arthroplasty: Minimum follow-up policy for reporting results and guidelines for reporting problems and complications resulting in reoperations. Foot Ankle Int. 2017 Jul;38(7):703-704. doi: 10.1177/1071100717716110. No abstract available. PMID: 28682140
17. Williams ED, Stebbins MJ, Cavanagh PR, Haynor DR, Chu B, Fassbind MJ, Isvilanonda V, Ledoux WR. A preliminary study of patient-specific mechanical properties of diabetic and healthy plantar soft tissue from gated MRI. Proc Inst Mech Eng H. 2017 Jul;231(7):625-633. doi: 10.1177/0954411917695849. Epub 2017 Mar 17. PMID: 28661227
18. Telfer S, Kindig M, Sangeorzan BJ, Ledoux WR. Metatarsal shape and foot type: A geometric morphometric analysis. J Biomech Eng. 2017 Mar 1;139(3). doi: 10.1115/1.4035077. PMID: 27802481
19. Ledoux WR, Pai S, Shofer JB, Wang Y-N. The association between mechanical and biochemical/histological characteristics in diabetic and non-diabetic plantar soft tissue. J Biomech. 2016 Aug 24. pii: S0021-9290(16)30931-9. doi: 10.1016/j.jbiomech.2016.08.021. Epub 2016 Aug 24. PMID: 27623704
20. Isvilanonda V, Iaquinto JM, Pai S, Mackenzie-Helnwein P, Ledoux WR. Hyperelastic compressive mechanical properties of the subcalcaneal soft tissue: An inverse finite element analysis. J Biomech. 2016 May 3;49(7):1186-91. doi: 10.1016/j.jbiomech.2016.03.003. Epub 2016 Mar 8. PMID: 27040391