Sagittal and Axial Posterior Calcaneal Screw Prominence are Independent Risk Factors for Hardware Removal
Authors: Shamrock Alan , Chinnakkannu Karthikeyan , Foreman Cameron , Glass Natalie , Amendola Annunziato , Phisitkul Phinit , Femino John 
Published: October 2019

Category: Hindfoot Introduction/Purpose: Painful hardware requiring removal occurs after the use of posterior calcaneal screws. Reconstructive procedures that rely on screws placed through the posterior calcaneus include calcaneal osteotomy and subtalar arthrodesis. Screw placement is typically percutaneous and relies on the use of fluoroscopy to evaluate screw starting point, length, and trajectory. Screw prominence in the sagittal plane is readily determined with a lateral radiograph, however screw location in the axial plane requires an intraoperative axial hindfoot view. The impact of screw prominence in the isolated axial plane on symptomatic hardware is unknown. The aim of this retrospective review is to determine, by analyzing postoperative radiographs, the association between posterior calcaneal screw type, sagittal and axial prominence, location, and trajectory with painful hardware requiring surgical removal. Methods: A consecutive series of 365 cases of posterior calcaneal screws in 333 patients (163 females: 48.9%) (mean age 47.4 years) was retrospectively reviewed from 2004-2018. Cases were performed by one of three fellowship trained foot and ankle surgeons. Inclusion criteria included the use of at least one posterior calcaneal screw and post-operative radiographs consisting of weight-bearing lateral and axial hindfoot views. Patient charts were retrospectively reviewed to determine the rate of symptomatic hardware removal (HWR). Weight-bearing radiographs were examined to determine screw head prominence in the lateral and axial planes, screw trajectory, and screw location in the calcaneus. Screw trajectory was calculated by subtracting the angle of the screw from the horizontal by the calcaneal pitch. Other variables collected included patient demographic information and screw number, diameter, and type. Statistical analysis was performed using Wilcoxon rank-sum and chi-square tests, with statistical significance defined as p<0.05. Results: The HWR rate was 16.7% (n=61). The HWR group was significantly younger (44 vs 48; p=0.0039) with more females (67.9% vs 45.4%; p=0.0026). Body mass index (BMI) (p=0.4167) and calcaneal pitch (p=0.7651) were not different between groups. Of screws that were flush or buried in the sagittal plane, 9.1% (n=64) were prominent on the hindfoot view. Screws flush/buried on both the lateral and hindfoot views (p<0.0001) were not associated with pain; prominent screws on the lateral radiograph (p=0.0002) and both the lateral and hindfoot radiographs (p=0.0071) were significantly more likely to undergo HWR. Isolated axial plane prominence of the plantar screw was found to be an independent risk factor for HWR (p=0.0060). Screw diameter (p=0.2318), location (p=0.4691) and trajectory (p=0.1077) were not associated with pain. Conclusion: Posterior calcaneal screws that were prominent on the lateral radiograph and both the lateral and hindfoot views were associated with HWR. Additionally, isolated prominence of the plantar screw on the hindfoot radiograph was a significant risk factor for hardware removal. These results emphasize the importance of not leaving screw heads proud. It is important to obtain and carefully analyzing the axial view in addition to a lateral view with intraoperative fluoroscopy. Relying on the lateral fluoroscopy view alone to assess screw head prominence is to be avoided. A weakness of this study is the lack of fluoroscopy images for comparison.