Image-Based Robotic System for Enhanced Minimally Invasive Intra-Articular Fracture Surgeries

Abstract: Robotic assistance can bring significant improvements to orthopedic fracture surgery: facilitate more accurate fracture fragment repositioning without open access and obviate problems related to the current minimally invasive fracture surgery techniques by providing a better clinical outcome, reduced recovery time, and health-related costs. This paper presents a new design of the robot-assisted fracture surgery (RAFS) system developed at Bristol Robotics Laboratory, featuring a new robotic architecture, and real-time 3D imaging of the fractured anatomy. The technology presented in this paper focuses on distal femur fractures, but can be adapted to the larger domain of fracture surgeries, improving the state-of-the-art in robot assistance in orthopedics. To demonstrate the enhanced performance of the RAFS system, 10 reductions of a distal femur fracture are performed using the system on a bone model. The experimental results clearly demonstrate the accuracy, effectiveness, and safety of the new RAFS system. The system allows the surgeon to precisely reduce the fractures with a reduction accuracy of 1.15 mm and 1.3°, meeting the clinical requirements for this procedure

The Effect of Fixation Plate Length on Spinal Instability Following Anterior Cervical Plate Fixation for the Repair of in Vitro Flexion-Distraction Injuries

Abstract: The Effect of Fixation Plate Length on Spinal Instability Following Anterior Cervical Plate Fixation for the Repair of in Vitro Flexion-Distraction Injuries Introduction: Anterior cervical decompression and fusion with a plate (ACDFP) is a commonly performed treatment following a traumatic injury to the subaxial cervical spine. The purpose of the presented work was to determine the biomechanical effect of plate length on cervical spine kinematic stability following ACDFP stabilization for a simulated traumatic injury. Methods: Eleven fresh-frozen cadaveric C5-C6 and C6-C7 motion segments were examined in this study. To assess kinematics, flexibility testing was performed on each specimen using a spinal loading simulator. A testing protocol was designed to assess the kinematics of the following conditions: i) preinjury, ii) simulated soft tissue injury (both facet capsules, ½ of the ligamentum flavum, and 2/3 of the annulus were sectioned along with an induced rotation to a unilateral facet perch), iii) ACDFP with 22.5mm plate fixation, and iv) ACDFP with 32.5mm fixation. Kinematic range of motion (ROM) data was collected and analyzed for motions of flexion-extension, axial rotation, and lateral bending. Results: The injury produced significantly greater motion than the pre-injury state; with the greatest increase in motion occurring for axial rotation. Both plates were successful in significantly reducing the ROM (for all motion types) below the injured condition and there were no significant differences in the change in ROM between the two plate sizes. Furthermore, in flexion-extension, both plates also significantly reduced the ROM below that of the intact condition. Discussion and Conclusions: The results would suggest that the simulated injury was successful in generating spinal instability consistent with the intended injury. The position of the plate in the frontal plane is responsible for impeding the flexion-extension ROM below the motions experienced by the intact condition. Finally, there were no differences between plate sizes for any of the measured motions. Therefore, we advise the use of smallest plates suitable to avoid the theoretical risk of adjacent level degeneration

Vision-based real-time position control of a semi-automated system for robot-assisted joint fracture surgery

Purpose: Joint fracture surgery quality can be improved by robotic system with high-accuracy and high-repeatability fracture fragment manipulation. A new real-time vision-based system for fragment manipulation during robot-assisted fracture surgery was developed and tested. Methods: The control strategy was accomplished by merging fast open-loop control with vision-based control. This two-phase process is designed to eliminate the open-loop positioning errors by closing the control loop using visual feedback provided by an optical tracking system. Evaluation of the control system accuracy was performed using robot positioning trials, and fracture reduction accuracy was tested in trials on ex vivo porcine model.Results: The system resulted in high fracture reduction reliability with a reduction accuracy of 0.09mm (translations) and of (Formula presented.) (rotations), maximum observed errors in the order of 0.12mm (translations) and of (Formula presented.) (rotations), and a reduction repeatability of 0.02mm and (Formula presented.). Conclusions: The proposed vision-based system was shown to be effective and suitable for real joint fracture surgical procedures, contributing a potential improvement of their quality

An Investigation of Subaxial Cervical Spine Trauma and Surgical Treatment through Biomechanical Simulation and Kinematic Analysis

In vitro biomechanical investigations can help to identify changes in subaxial cervical spine (C3-C7) stability following injury, and determine the efficacy of surgical treatments through controlled joint simulation experiments and kinematic analyses. However, with the large spectrum of cervical spine trauma, a large fraction of the potential injuries have not been examined biomechanically. This includes a lack of studies investigating prevalent flexion-distraction injuries. Therefore, the overall objective of this thesis was to investigate the changes in subaxial cervical spine kinematic stability with simulated flexion-distraction injuries and current surgical instrumentation approaches using both established and novel biomechanical techniques. Three in vitro experiments were performed with a custom-designed spinal loading simulator. The first evaluated sequential disruption of the posterior ligaments with and without a simulated facet fracture (n=7). In these specimens, posterior lateral mass screw fixation provided more stability than anterior cervical discectomy and fusion with plating (ACDFP). A second study examined a unilateral facet perch injury by reproducing a flexion-distraction injury mechanism with the simulator (n=9). The resulting soft tissue damage was quantified through meticulous dissection of each specimen, which identified the most commonly injured structures across all specimens as both facet capsules, ¾ of the annulus, and ½ of the ligamentum flavum. This information was used to develop and validate a standardized injury model (SIM) in new specimens (n=10). A final study examined the ACDFP surgical factor of graft size height (bony spacer replacing the intervertebral disc to promote fusion) for the SIM and two other injuries (n=7). Results were motion and injury dependent, which suggests that both these factors must be considered in the surgical decision. Two additional investigations were completed. The first examined mathematical techniques to generate a large number of accurate finite helical axes from six-DOF rigid body tracker output to describe changes in cervical spine kinematic stability. The second explored the effect of boundary conditions and PID control settings on the ability of the current simulator design to reproduce desired loading techniques. Ultimately, it is hoped that these results, and the protocols developed for future investigations, will provide valuable biomechanical evidence for standardized treatment algorithms

RAFS: A computer-assisted robotic system for minimally invasive joint fracture surgery, based on pre- and intra-operative imaging

The integration of minimally invasive robotic assistance and image-guidance can have positive impact on joint fracture surgery, providing a better clinical outcome with respect to the current open procedure. In this paper, a new design of the RAFS surgical system is presented. The redesign of the robotic system and its integration with a novel 3D navigation system through a new clinical workflow, overcomes the drawbacks of the earlier prototype. This makes the RAFS surgical system more suitable to clinical scenarios in the operating theatre. System accuracy and effectiveness are successfully demonstrated through laboratory trials and preliminary cadaveric trials. The experimental results demonstrate that the system allows the surgeon to reduce a 2-fragment distal femur fracture in a cadaveric specimen, with a reduction accuracy of up to 0.85 mm and 2.2°. Preliminary cadaveric trials also provided a positive and favorable outcome pointing to the usability and safety of the RAFS system in the operating theatre, potentially enhancing the capacity of joint fracture surgeries

Six Degrees of Freedom: Kinematics of the Healthy Ankle Syndesmosis Joint

Syndesmotic injury, more commonly known as a high ankle sprain , accounts for over 12% of all ankle sprain incidents in the US; of which, over 25% occur during a sporting activity. Typically, harm to the syndesmosis occurs in sports such as football, soccer, lacrosse, and hockey where it is common for an athlete to experience rapid and extreme dorsiflexion-external rotations of the foot. Severe syndesmotic sprains have been noted by clinicians as the most difficult ankle injury to accurately diagnose and treat, require the most recuperation time, and often results in life-long dysfunction. Even more problematic, 40% of patients suffering from a high ankle sprain also report joint instability 6 months after the initial injury. The distal tibiofibular syndesmosis joint consists of a fibrous interosseous membrane and four stabilizing ligaments, allowing for only slight movements of the fibula about the tibia. These distal bone surfaces closely articulate with the talus to form a stable mortise joint, giving the ankle joint complex its hinge-like range of motion (ROM). In the case of severe ankle sprains, excessive external rotation, dorsiflexion, and eversion of the foot can cause tearing of these stabilizing ligaments, distraction of the bones, or even fracture. A rigid screw fixation method is the standard practice for repair in these severe cases, although new dynamic fixation techniques using sutures and buttons instead of a screw are thought to allow for a more natural motion of the joint during healing and better post-operative results. However, most research of the ankle joint complex has primarily been dedicated to the talocrural joint formed between the talus and tibia, where the fibula is treated as single segment with the tibia. Very little research has been dedicated towards understanding the unique role the fibula plays in dynamic weight-bearing tasks to overall ankle joint strength, stability, and mobility. This gap in knowledge of fibular articulation and load bearing, lends to the difficulty and inaccuracy in properly reducing the bones during syndesmotic fixation. There also lacks a clear and consistent method for syndesmotic fixation with minimal validation that dynamic fixation heeds superior post-operative results. Gaining insight on healthy syndesmosis joint motion could provide baseline measures for more realistic loading conditions of cadaveric testing various fixation devices, serve as design parameters for new device design, set a gold standard for normal range of motion (ROM) in rehabilitation, and ultimately improve diagnostic and treatment modalities for syndesmotic injury. The goals of the project were to establish a standard for the six degree of freedom (DOF) kinematics in the syndesmosis and talocrural joints in healthy active adults, as well as define the normal ROM. This was done using a high speed stereo radiography (HSSR) system to capture dual plane in-vivo motion of the bones with sub-millimeter and sub-degree accuracy. Changes in bone positioning during static and dynamic weight bearing activities were compared to a non-weight bearing neutral pose of the foot. The second scope of this work defines average values of medial and lateral clear space widening between the bones. Both are current clinical measures used to gauge the degree of ankle injury and instability present. Knowing the kinematics of the bones primarily responsible for stability of the ankle joint complex, along with their expected distraction between each other could help bridge the gap in the diagnosis and treatment of severe high ankle sprains, as well as reduce the risk of incorrect healing and chronic ankle instability

Developments in circular external fixators: a review

Circular external fixators (CEFs) are successfully used in orthopedics owing to their highly favorable stiffness characteristics which promote distraction osteogenesis. Although there are different designs of external fixators, how these features produce optimal biomechanics through structural and component designs is not well known. Therefore, the aim of this study was to conduct a review on CEFs following the PRISMA statement. A search for relevant research articles was performed on Scopus and PubMed databases providing the related keywords. Furthermore, a patent search was conducted on the Google Patent database. 126 records were found to be eligible for the review. Different designs of CEFs were summarized and tabulated based on their specific features. A bibliometric analysis was also performed on the eligible research papers. Based on the findings, the developments of CEFs in terms of materials, automation, adjustment methods, component designs, wire-clamping, and performance evaluation have been extensively discussed. The trends of the CEF design and future directions are also discussed in this review. Significant research gaps include a lack of consideration towards ease of assembly, effective wire-clamping methods, and CEFs embedded with online patient-monitoring systems, among others. An apparent lack of research interest from low-middle and low-income countries was also identified

BIOMECHANICS OF THE DISTAL RADIOULNAR JOINT WITH A MALALIGNED DISTAL RADIUS

Distal radius fractures are the most common fractures in humans and frequently have suboptimal outcomes, fostering considerable discussion with regard to treatment. This body of work was based on the postulate that quantifying the biomechanics, specifically the kinematics and loading of the distal radial ulnar joint (DRUJ) before and after simulated distal radius malalignment would provide important new information to the treatment of these fractures. Furthermore, an investigation into the effect of soft- tissues would further the biomechanical understanding of these disorders. In light of the foregoing, a distal radial implant to simulate malalignment in vitro was designed and developed. An instrumented ulnar load cell was also employed to measure the load transfer at the distal ulna. A series of in vitro studies employing simulated muscle loading to produce forearm rotation were conducted using an upper extremity joint simulator. The distal radial implant and ulnar load cell were implanted and an electromagnetic tracking device was used to record the motion of the radius and ulna. The kinematics and joint loading of the native forearm were measured at the beginning of each testing and compared with simulated distal radial deformities. As the severity of distal radial deformities worsened, a gradual loss of forearm rotation, a progressive change in kinematic patterns and an increasing alteration in the load transfer at the distal ulna was quantified. No absolute threshold in distal radial deformity was noted before joint dysfunction was markedly disturbed. This is in agreement with clinical findings as patients with malunited Colles’ fractures often present iii with reduced range of motion, joint stiffness and pain, suggesting that this pain may be in part be due to the increase in joint loading required to generate forearm rotation. Sectioning the triangular fibrocartilage complex, which is commonly injured in association with distal radial fractures, restored rotation and reduced the loading on the joint; however, this resulted in greater alteration of DRUJ kinematics. In conclusion, this work has provided valuable information to assist biomechanists and clinicians in understanding the implication of both osseous and soft tissue disorders of the distal radius and provides better evidence to improve patient outcomes

Navigation system for robot-assisted intra-articular lower-limb fracture surgery

Purpose In the surgical treatment for lower-leg intra-articular fractures, the fragments have to be positioned and aligned to reconstruct the fractured bone as precisely as possible, to allow the joint to function correctly again. Standard procedures use 2D radiographs to estimate the desired reduction position of bone fragments. However, optimal correction in a 3D space requires 3D imaging. This paper introduces a new navigation system that uses pre-operative planning based on 3D CT data and intra-operative 3D guidance to virtually reduce lower-limb intra-articular fractures. Physical reduction in the fractures is then performed by our robotic system based on the virtual reduction. Methods 3D models of bone fragments are segmented from CT scan. Fragments are pre-operatively visualized on the screen and virtually manipulated by the surgeon through a dedicated GUI to achieve the virtual reduction in the fracture. Intra-operatively, the actual position of the bone fragments is provided by an optical tracker enabling real-time 3D guidance. The motion commands for the robot connected to the bone fragment are generated, and the fracture physically reduced based on the surgeon’s virtual reduction. To test the system, four femur models were fractured to obtain four different distal femur fracture types. Each one of them was subsequently reduced 20 times by a surgeon using our system. Results The navigation system allowed an orthopaedic surgeon to virtually reduce the fracture with a maximum residual positioning error of 0.95±0.3mm (translational) and 1.4∘±0.5∘ (rotational). Correspondent physical reductions resulted in an accuracy of 1.03 ± 0.2 mm and 1.56∘±0.1∘, when the robot reduced the fracture. Conclusions Experimental outcome demonstrates the accuracy and effectiveness of the proposed navigation system, presenting a fracture reduction accuracy of about 1 mm and 1.5∘, and meeting the clinical requirements for distal femur fracture reduction procedures

Development of an In-Vitro Passive and Active Motion Simulator for the Investigation of Shoulder Function and Kinematics

Injuries and degenerative diseases of the shoulder are common and may relate to the joint’s complex biomechanics, which rely primarily on soft tissues to achieve stability. Despite the prevalence of these disorders, there is little information about their effects on the biomechanics of the shoulder, and a lack of evidence with which to guide clinical practice. Insight into these disorders and their treatments can be gained through in-vitro biomechanical experiments where the achieved physiologic accuracy and repeatability directly influence their efficacy and impact. This work’s rationale was that developing a simulator with greater physiologic accuracy and testing capabilities would improve the quantification of biomechanical parameters. This dissertation describes the development and validation of a simulator capable of performing passive assessments, which use experimenter manipulation, and active assessments – produced through muscle loading. Respectively, these allow the assessment of functional parameters such as stability, and kinematic/kinetic parameters including joint loading. The passive functionality enables specimen motion to be precisely controlled through independent manipulation of each rotational degree of freedom (DOF). Compared to unassisted manipulation, the system improved accuracy and repeatability of positioning the specimen (by 205% & 163%, respectively), decreased variation in DOF that are to remain constant (by 6.8°), and improved achievement of predefined endpoints (by 21%). Additionally, implementing a scapular rotation mechanism improved the physiologic accuracy of simulation. This enabled the clarification of the effect of secondary musculature on shoulder function, and the comparison of two competing clinical reconstructive procedures for shoulder instability. This was the first shoulder system to use real time kinematic feedback and PID control to produce active motion, which achieved unmatched accuracy ( These developments can be a powerful tool for increasing our understanding of the shoulder and also to provide information which can assist surgeons and improve patient outcomes