Assessing the Intraarticular Pressure During Single Versus Double Staple Naviculocuneiform Joint Arthrodesis: A Biomechanical Study

Category: Midfoot/Forefoot, Other Keywords: Midfoot arthrodesis, Biomechanics, Fusion Introduction/Purpose: Naviculocuneiform joint (NC) arthrodesis is commonly indicated for midfoot arthritis and other pathologies, however it is associated with a high rate of nonunion. Recent studies have identified a higher nonunion rate when fusing just the medial NC joint (NC1) compared to fusion of the medial and middle (NC2) NC joint. This study aims to evaluate if there is any increase in the contact forces and contact area at NC1 after NC2 undergoes compression in a cadaveric model. We hypothesized that joint preparation and compression of both NC1 and NC2 will achieve greater compression across NC1 than when NC1 is fused alone. Methods: A static foot model using 13 fresh-frozen cadaveric feet measured intra-articular peak forces at NC1with Tekscan electronic pressure sensors after preparation and compression with a 20mm nitinol staple. Using the same foot models, NC2 was then prepped and fused with another nitinol staple. The difference between contact forces, contact area, and peak pressures at the NC1 joint after single vs double NC compression was measured and analyzed. Results: There was a statistically significant increase in mean force recorded at NC1 between the single (8.94 ± 3.05 N) and double joint compression (11.33 ± 2.93 N) groups (p < 0.01). The total contact force across both joints was significantly higher in the double compression group versus the single compression group (35.39 ± 13.29 N vs. 19.36 ± 9.17 N, p < 0.01). Peak pressure (measured in pounds per square inch, PSI) was markedly increased in the double compression group (348.15 ± 38.48 vs. 268.00 ± 91.95, p < 0.001). Contact area at NC1 increased with the addition of compression of NC2 (50.69 ± 16.23 mm² vs. 44.62 ± 18.44 mm², p = 0.041). Conclusion: When compared to single joint compression, compression of both NC1 and NC2 resulted in a statistically significant increase in the mean force, contact force and peak contact forces observed at NC1. Greater compression across NC1 may correlate with an increased likelihood of successful arthrodesis in vivo.