Abstract
Reduction of fractures in the minimally invasive (MI) manner can avoid risks associated with open fracture surgery. The MI approach requires specialized tools called percutaneous fragment manipulation devices (PFMD) to enable surgeons to safely grasp and manipulate fragments. PFMDs developed for long-bone manipulation are not suitable for intra-articular fractures where small bone fragments are involved. With this study, we offer a solution to potentially move the current fracture management practice closer to the use of a MI approach. We investigate the design and testing of a new PFMD design for manual as well as robot-assisted manipulation of small bone fragments. This new PFMD design is simulated using FEA in three loading scenarios (force/torque: 0 N/2.6 Nm, 75.7 N/3.5 N, 147 N/6.8 Nm) assessing structural properties, breaking points, and maximum bending deformations. The PFMD is tested in a laboratory setting on Sawbones models (0 N/2.6 Nm), and on ex-vivo swine samples (F = 80 N ± 8 N, F = 150 ± 15 N). A commercial optical tracking system was used for measuring PFMD deformations under external loading and the results were verified with an electromagnetic tracking system. The average error difference between the tracking systems was 0.5 mm, being within their accuracy limits. Final results from reduction maneuvers performed both manually and with the robot assistance are obtained from 7 human cadavers with reduction forces in the range of (F = 80 N ± 8 N, F = 150 ± 15 N, respectively). The results show that structurally, the system performs as predicted by the simulation results. The PFMD did not break during ex-vivo and cadaveric trials. Simulation, laboratory, and cadaveric tests produced similar results regarding the PFMD bending. Specifically, for forces applied perpendicularly to the axis of the PFMD of 80 N ± 8 N deformations of 2.8, 2.97, and 3.06 mm are measured on the PFMD, while forces of 150 ± 15 N produced deformations of 5.8, 4.44, and 5.19 mm. This study has demonstrated that the proposed PFMD undergoes predictable deformations under typical bone manipulation loads. Testing of the device on human cadavers proved that these deformations do not affect the anatomic reduction quality. The PFMD is, therefore, suitable to reliably achieve and maintain fracture reductions, and to, consequently, allow external fracture fixation.
Highlights
The incidence of fractures of the lower limb, especially osteoporotic, is increasing and their surgical treatment accounts for a large proportion of orthopedic operations (Hernlund et al, 2013)
Similar observation was made during the experimental process (Sawbones model, wood) and cadaveric tests where the K-wires bent on the interface with the bone
At the laboratory testing the displacement at the interface point of K-wire and Drilling Template (DT) was measured at 0.23 mm, standard deviation (SD) 0.03 mm, CI50% 0.02 mm
Summary
The incidence of fractures of the lower limb, especially osteoporotic, is increasing and their surgical treatment accounts for a large proportion of orthopedic operations (Hernlund et al, 2013). These type of fractures bear considerable health costs and if managed sub-optimally could have a detrimental effect to patient’s quality of life (Joubair et al, 2015). The standard fracture procedure can be summarized in two steps: (1) fracture reduction, and (2) fixation of bone fragments with a stable mechanical construct such as an intramedullary nail or using plates and screws. Percutaneous techniques have been developed to mitigate these problems (Gaston et al, 2005)
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