Cadaveric, MRI assessment of the hallucal metatarso-phalangeal joint: implications for fusion surgery

B. Jamal, S. Spence, W. Holmes, Q. Fogg, A. Pillai

Introduction: Non union following hallucal Metatarso-Phalangeal (MTP) joint fusion has been reported to be as high as 15% following preparation of the articular surfaces with a dome shaped reamer and fixation with a dorsal plate. Flat cuts to prepare the articular surface are, arguably, more likely to help achieve union at the fusion site. However, they are more likely to lead to rotational or axial malalignment at the fusion site.

Methods: We wished to identify, via cadaveric specimens, the normal thickness of articular cartilage at the hallucal MTP joint. We did this by amputating the first ray from a fresh, frozen cadaver. This specimen was then scanned using a 7 tesla MRI scanner. This is the first scan that we have performed. We have funding, via a BOFAS research grant, to perform further scans.

Results: We have identified the articular cartilage thickness within 9 zones of both the metatarsal head and the proximal phalanx at the MTP joint. We also describe the cartilage thickness of the sesamoid articular surface.

Conclusion: Such information is of use to the forefoot surgeon who performs fusion surgery. An understanding of the thickness of the articular cartilage thickness at the MTP joint will aid in the adequate preparation of the joint surface. This will improve the incidence of successful fusion. Our finding are also likely to be of interest to the basic scientist who wishes to utilise MRI scanning technology to orthopaedics - ours is the first report, as far as we are aware, of the use of a 7 tesla MRI scanner in orthopaedic research.