ABSTRACT
Objective:To evaluate the clinical application of virtual and simulation techniques to aid pre-operative design for precise screw placement into the sustentaculum tali in the treatment of intra-articular calcaneal fractures.Methods:From January 2016 to January 2019, 68 patients were treated at Department of Orthopaedics, Suqian Hospital Affiliated to Xuzhou Medical University for intra-articular calcaneal fractures of Sanders types Ⅱ-Ⅳ. According to different designs of screw placement into the sustentaculum tali, they were assigned into a control group (38 cases and 42 feet) and an observation group (30 cases and 33 feet). There were 24 males and 14 females with an age of 39.3 years±8.8 years in the control group. There were 17 males and 13 females with an age of 42.0 years ± 7.6 years in the observation group. The control group was given a routine placement design based on the X-ray and MSCT scanning images of the injured feet. In the observation group, a Mimics model was first constructed using the X-ray and MSCT scanning images of the normal or less injured feet for further virtual screw placement into the sustentaculum tali on a 3D printed model. The disparity was investigated between the parameters designed and the actual values in both groups. The 2 groups were compared in terms of average placements, screw distribution, placement accuracy, placement time and Maryland scores of foot function one year after operation.Results:There were no significant differences in the preoperative general data between the 2 groups, showing comparability ( P>0.05). The design parameters and actual values in the control group were respectively as follows: 17.7°±3.2° versus 15.1°±5.9° in upward oblique angle, 20.3°±2.1° versus 16.2°±6.8° in backward oblique angle, and 47.9 mm ± 3.8 mm versus 45.4 mm ± 4.2 mm in length of screw path, showing significant differences ( P< 0.05). The design parameters and actual values in the observation group were as follows: 16.5°±3.5° versus 17.1°±3.9° in upward oblique angle, 20.9°±4.3° and 19.6°±3.8° in backward oblique angle, and 48.1 mm ± 3.1 mm versus 47.3 mm ± 3.8 mm in length of screw path, showing insignificant differences ( P>0.05). The average screw placements into the sustenta culum tali in the observation group (1.6±0.5) were significantly more than those in the control group (1.2±0.4). Compared with the control group, the observation group had a higher rate of placement of 2 screws[60.6 % (20/23) versus 16.7% (7/42)], higher accuracy of placement [94.3% (50/53) versus 77.6% (38/49)], less placement time for each screw (9.6 mm±3.9 min versus 13.2 mm±4.7 mm), less placement time for each foot (15.6 mm±4.8 min versus 20.5 mm±3.8 mm), and higher Maryland scores at one year after operation (94.2±6.5 versus 89.7±6.9). All the above comparisons were statistically significant ( P<0.05). Conclusions:Application of virtual and simulation techniques to aid pre-operative design for precise screw placement into the sustentaculum tali can improve the outcomes of intra-articular calcaneal fractures, because it increases the number of screws placed, enhances quality of screw placement, shortens operation time, and thus facilitates functional recovery of the injured foot.