1. Intraoperative stability assessment of the first carpometacarpal joint Pascal Behm1,2, Stephen J. Ferguson2, Miriam Marks1, Daniel B. Herren3 1Department of Teaching, Research and Development, Schulthess Klinik, Zurich, Switzerland
2Institute for Biomechanics, ETH Zurich, Zurich, Switzerland 3Department of Hand Surgery, Schulthess Klinik, Zurich, Switzerland
Background
When performing trapeziectomy, alone or in combination with suspension and tendon interposition, the surgeon perceives individual differences in joint stability, which may influence the treatment decision (Figure 1). There are no quantitative data available on the stability of the first carpometacarpal (CMC I)1,2. Our aim was to develop a device for intraoperatively measuring CMC I joint stability.
Results
CMC I joint stability could be successfully measured during the cadaver test (Figure 3a) and indicate proof-of-concept for measuring CMC I stability intraoperatively. Interposition of fabric into the trapezial cavity resulted in a 25 % higher apparent stability. Furthermore, a force displacement curve could be derived from simultaneously recorded fluoroscopy images (Figure 4). ? a b
Figure 3: Measurement system in use during cadaver test
CMC I joint stability assessment of cadaver hand during standardised pinch grip position
Linear displacement of the thumb ray with reposition forceps attached to the base of the MC I.
Figure 1: Individual CMC I joint stability may require different treatment for best outcome.
Material & Methods
A measurement system (Figure 2) was developed to provide continuous force measurement during a 10 mm linear displacement of the CMC I joint. A conventional reposition forceps is attached to the base of the MC I (Figure 3b) and connected to a linear slide with integrated force sensor. The maximal measured force defines the apparent joint stability.
Figure 4: Measured force displacement curve of the thumb ray from the cadaver trial.
Conclusion
The developed system allows the intraoperative assessment of the stability of the first carpometacarpal joint and provides accurate force data. It is planned to use the device in a clinical trial, where the CMC I stability will be measured after each step of trapeziectomy with suspension-interposition arthroplasty.
Figure 2: Measurement system for the intraoperative stability assessment of the first carpometacarpal joint.
References
1Wajon et al. (2015). The Cochrane Library
2Vermeulen et al. (2011). J Hand Surg-Am, 36(1),
Contact
Pascal Behm, MSc. ETH Schulthess Klinik, Lengghalde 2, 8008 Zuerich