The Navicular Prosthesis Template: A Cadaveric Study of the Talonavicular Morphometric Profiles and Side-to-side Differences

CATEGORY: Hindfoot, Midfoot/Forefoot, Trauma INTRODUCTION/PURPOSE: The navicular bone destruction is a challenging condition in the foot surgery. This can be occurred from severe comminuted fracture, avascular necrosis from steroid used or Mueller-Weiss Syndrome, etc. However, little is known about the treatment option which can spare the talonavicular or naviculocuneiform joint regarding this condition. The navicular prosthesis replacement may be the promising option in the future. This study is to present the talonavicular (TN) ratio, other morphometric profiles, and side-to-side differences for the template of customized navicular prosthesis manufacturing. METHODS: A total of eight matched pairs of the ankle (16 ankles) were collected in this study. The measurements were performed regarding the morphometric profiles of navicular and talar head. All data were recorded and analyzed to determine the TN ratio to be the template of navicular prosthesis manufacturing. The TN width ratio was calculated as talar head width was divided by navicular width in axial view. The TN height ratios were calculated as talar head height was divided by navicular height at the central arc in sagittal view. Medial and lateral navicular heights were also recorded in sagittal view. The medial, lateral, and central arc lengths of navicular were recorded from the cadaveric specimens. RESULTS: The average talar head width was 28.5 +/- 3.2 mm. The average talar head height at central arc was 26.6 +/- 2.2 mm. The average navicular heights at medial, lateral rims, and central arc were 16.8, 21.4, and 24.5 mm respectively. The average navicular lengths at medial, lateral rims, and central arc were 18.6, 15.3, and 18.4 mm respectively. The average navicular width was 40.4 +/-2.7 mm. The average TN width ratio was 0.7 +/- 0.1. The average TN height ratio at central arc was 1.2 +/- 0.2. The side-to-side differences were insignificantly found on all talonavicular morphometric profiles (P>0.05). CONCLUSION: Based on this study, the talonavicular ratios and the morphometric profiles were demonstrated in the cadaveric specimens. The contralateral side of navicular can be the template for the manufacturing of the customized navicular prosthesis for the pathologic side due to the insignificant differences of side-to-side morphometric profiles. These data may help develop the customized navicular prosthesis to replace in the challenging pathologic condition of navicular.