Pigs Going Out on a Limb: Proof of concept of a video fluoroscopy method for measuring trans-radial socket-residuum coupling

Pickard, Nicolaas; Harthikote Nagaraja, Vikranth; Kenney, Laurence

Abstract

Background
Complaints about comfort and function are consistently associated with prosthetic non-use and abandonment, and the design of sockets likely impacts both aspects [1]. Socket fit can be considered the compromise between socket function and comfort. Mechanical coupling (stiffness) of the socket-residuum interface offers a quantifiable measure of socket fit. Previous methods for measuring socket-residuum coupling have used marker-based motion capture (MOCAP) [2] [3] [4], but socket occlusion of skin-mounted markers represents a major limitation. Sensinger and Weir showed the potential to use video fluoroscopy (X-ray) to capture socket-limb coupling, but the 2D planar X-ray system used only provided data on anterior/posterior rotation of the socket relative to the limb [5]. Biplanar video fluoroscopy combined with scientific rotoscoping (X-ROMM [6]) could be used to estimate the 3D pose of the socket relative to underlying bony anatomy. This study reports on preliminary work to assess the feasibility of this approach with a pig limb.
Methods
This study used a biplanar X-ray set-up at the University of Liverpool combined with 3D bone models acquired using MRI. Since the biplanar capture volume is small (approximately basketball size), a three-camera marker-based MOCAP system (V120 trio by Optitrack [7]) was used to expand the capture volume. By utilising “doped” reflective markers (containing metal beads), which could be detected by both systems, X-ray and MOCAP data could be spatially synchronised.
We used a pig limb (shoulder joint to trotter), to avoid exposing human participants to ionising radiation, oriented in four positions to induce skin-bone movement. “Doped” markers were attached to key anatomical landmarks, with a cluster consisting of standard retro-reflective markers used to simulate a prosthetic socket (Figure 1).
Results and Discussion
Spatial synchronisation was achieved between the MOCAP and VF systems, enabling the position and pose of the cluster (tracked using MOCAP) to be established relative to the VF system (and the rotoscoped skeletal model captured using MRI to reduce ionising dosage). Analysis, currently in progress, focuses on calibrating the VF system, and will describe the relative cluster (socket)-ulna pose, which should vary depending on the limb orientation (and skin-bone movement). Further processing will follow, attempting to utilise scientific rotoscoping to obtain the most accurate possible bone orientation.

Figure 1: Pig limb with attached markers and cluster simulating a socket (left), an X-ray image of the pig limb with markers (markers with black dots are “doped”; right).
Conclusion
This work demonstrates the viability of combining scientific rotoscoping with MOCAP to measure socket-limb coupling with a pig limb. Future work will involve applying this to participants with intact forearm anatomy and a bypass socket, as well as trans-radial prosthesis users, to better understand socket fit and how this relates to socket function and comfort.
Acknowledgements
We would like to acknowledge and thank the team at the University of Liverpool (Dr. Kris D’Aout and Dr. Roger Kissane) for their support and expertise in the use of their MRI and Biplanar Xray systems throughout this work and also Dr. Jamie Gardener from Manchester Metropolitan University for his input and support.

• Presentation Conference Type: Presentation / Talk
• Conference Name: Trent International Prosthetics Symposium
• Start Date: Mar 19, 2025
• Deposit Date: Apr 1, 2025
• Peer Reviewed: Not Peer Reviewed