Effects of Calcaneo-Stop Arthroreisis on Joint Kinematics during Simulated Walking: A Cadaver Study

Research Type: Level 5 - Case report, Expert opinion, Personal observation Introduction/Purpose: The calcaneo-stop procedure is a variation of arthroreisis used to treat progressive collapsing foot deformity (PCFD), primarily in pediatric patients outside the United States. In this procedure, a screw is inserted into the sinus tarsi to block valgus motion at the subtalar joint to prevent further collapse and impingement. Although the use of the calcaneo-stop procedure is uncommon in adults, some clinicians elect to perform the procedure despite little biomechanical evidence to support its use. The objective of this study was to evaluate the effects of the calcaneo-stop procedure on hindfoot kinematics during simulations of level walking in a simulated PCFD model (sPCFD). We hypothesized that using the procedure to treat sPCFD would alter joint kinematics of the subtalar and talonavicular joint toward intact values. Methods: Eight cadaveric distal tibia and foot specimens (age: 64±8 years, 6 males, 2 females) were used in this study. A six-degree-of-freedom robot, which operates by rotating a force platform around a stationary tibia, was used to simulate the stance phase of level walking. Specimens were tested during four conditions: (1) intact, (2) sPCFD, (3) calcaneo-stop procedure with the screw head at joint line (STL) and (4) calcaneo-stop procedure with the screw head raised above the joint line (STR). Eight infrared cameras were used to track the motion of reflective markers inserted into the talus, calcaneus, and navicular bones. Joint rotational kinematics of the subtalar and talonavicular joints were calculated for each condition. Bias-corrected bootstrapped 95% confidence intervals were calculated to evaluate the kinematic differences between the two calcaneo-stop procedure conditions and both the intact and sPCFD conditions. Results: Joint rotational kinematics of the sPCFD condition were corrected towards intact after the STL, while slightly overcorrecting intact values with the STR procedure. In the subtalar joint, the STL procedure decreased eversion by an average of 3.8° resulting in an undercorrection by 1.5° [95% CI: 0.4°, 3.6°] relative to intact in early stance. The STR procedure decreased eversion by 6.2°, resulting in an average overcorrection of 2.4° [95%CIs: 1.7°,3.5°] during early stance relative to the intact condition. In the talonavicular joint, STL decreased talonavicular abduction by an average of 4.9°, resulting in an undercorrection by 1.4° [95% CI 0.2°, 3.2°] during early stance. . The STR procedure decreased talonavicular abduction by 6.9°, resulting in a 2.5° [95%CIs: 1.2°,3.7°] overcorrection during mid-stance relative to intact. Conclusion: The results of our study demonstrate that the calcaneo-stop procedure can change joint kinematic toward intact values in a simulated PCFD cadaver model. Additionally, our study suggests that an overcorrection of kinematics can occur when the screw head is placed superior to the joint line of the subtalar joint. We advise surgeons to carefully evaluate the position of the screw intraoperatively. More clinical studies are needed to confirm our data and to address potential complications, such as sinus tarsi pain due to screw related impingement and lateral foot pain.