Design and Evaluation of a Percutaneous Fragment Manipulation Device for Minimally Invasive Fracture Surgery.

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.

Robot-Assisted Fracture Surgery: Surgical Requirements and System Design.

The design of medical devices is a complex and crucial process to ensure patient safety. It has been shown that improperly designed devices lead to errors and associated accidents and costs. A key element for a successful design is incorporating the views of the primary and secondary stakeholders early in the development process. They provide insights into current practice and point out specific issues with the current processes and equipment in use. This work presents how information from a user-study conducted in the early stages of the RAFS (Robot Assisted Fracture Surgery) project informed the subsequent development and testing of the system. The user needs were captured using qualitative methods and converted to operational, functional, and non-functional requirements based on the methods derived from product design and development. This work presents how the requirements inform a new workflow for intra-articular joint fracture reduction using a robotic system. It is also shown how the various elements of the system are developed to explicitly address one or more of the requirements identified, and how intermediate verification tests are conducted to ensure conformity. Finally, a validation test in the form of a cadaveric trial confirms the ability of the designed system to satisfy the aims set by the original research question and the needs of the users.

Image-Guided Surgical Robotic System for Percutaneous Reduction of Joint Fractures.

Complex joint fractures often require an open surgical procedure, which is associated with extensive soft tissue damages and longer hospitalization and rehabilitation time. Percutaneous techniques can potentially mitigate these risks but their application to joint fractures is limited by the current sub-optimal 2D intra-operative imaging (fluoroscopy) and by the high forces involved in the fragment manipulation (due to the presence of soft tissue, e.g., muscles) which might result in fracture malreduction. Integration of robotic assistance and 3D image guidance can potentially overcome these issues. The authors propose an image-guided surgical robotic system for the percutaneous treatment of knee joint fractures, i.e., the robot-assisted fracture surgery (RAFS) system. It allows simultaneous manipulation of two bone fragments, safer robot-bone fixation system, and a traction performing robotic manipulator. This system has led to a novel clinical workflow and has been tested both in laboratory and in clinically relevant cadaveric trials. The RAFS system was tested on 9 cadaver specimens and was able to reduce 7 out of 9 distal femur fractures (T- and Y-shape 33-C1) with acceptable accuracy (≈1 mm, ≈5°), demonstrating its applicability to fix knee joint fractures. This study paved the way to develop novel technologies for percutaneous treatment of complex fractures including hip, ankle, and shoulder, thus representing a step toward minimally-invasive fracture surgeries.

Intra-operative fiducial-based CT/fluoroscope image registration framework for image-guided robot-assisted joint fracture surgery.

PURPOSE: Joint fractures must be accurately reduced minimising soft tissue damages to avoid negative surgical outcomes. To this regard, we have developed the RAFS surgical system, which allows the percutaneous reduction of intra-articular fractures and provides intra-operative real-time 3D image guidance to the surgeon. Earlier experiments showed the effectiveness of the RAFS system on phantoms, but also key issues which precluded its use in a clinical application. This work proposes a redesign of the RAFS's navigation system overcoming the earlier version's issues, aiming to move the RAFS system into a surgical environment. METHODS: The navigation system is improved through an image registration framework allowing the intra-operative registration between pre-operative CT images and intra-operative fluoroscopic images of a fractured bone using a custom-made fiducial marker. The objective of the registration is to estimate the relative pose between a bone fragment and an orthopaedic manipulation pin inserted into it intra-operatively. The actual pose of the bone fragment can be updated in real time using an optical tracker, enabling the image guidance. RESULTS: Experiments on phantom and cadavers demonstrated the accuracy and reliability of the registration framework, showing a reduction accuracy (sTRE) of about [Formula: see text] (phantom) and [Formula: see text] (cadavers). Four distal femur fractures were successfully reduced in cadaveric specimens using the improved navigation system and the RAFS system following the new clinical workflow (reduction error [Formula: see text], [Formula: see text]. CONCLUSION: Experiments showed the feasibility of the image registration framework. It was successfully integrated into the navigation system, allowing the use of the RAFS system in a realistic surgical application.

Computer Hexapod-Assisted Orthopaedic Surgery for the Correction of Tibial Deformities.

We describe the intraoperative use of the Taylor Spatial Frame to correct complex multiplanar deformities of the tibia before definitive internal stabilization using minimally invasive techniques. Thirteen consecutive procedures were performed in 12 patients. All deformities of the tibia were assessed with standardized radiographs allowing estimation of the center of rotation of angulation (CORA) or multiple CORA for multiplanar deformities. The cause of the deformity included both posttraumatic and metabolic conditions. A wide range of deformities was deemed appropriate for correction with this technique. All underwent acute intraoperative correction through single or multiple osteotomies mediated by the Taylor Spatial Frame before definitive internal stabilization using a locked intramedullary nail. Deformity correction and restoration of the tibial mechanical axis was achieved in all cases. There were no cases of nonunion. There was only one superficial infection necessitating removal of implants following union of the osteotomies. Two patients developed a common peroneal nerve palsy, 1 had full recovery at 18 months and 1 had partial recovery. Another patient developed a tibial artery pseudoaneurysm treated successfully with a percutaneous stent. This series demonstrates the use of the Taylor Spatial Frame for acute intraoperative correction of complex tibial deformities and definitive internal stabilization.

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 [Formula: see text] (translational) and [Formula: see text] (rotational). Correspondent physical reductions resulted in an accuracy of 1.03 ± 0.2 mm and [Formula: see text], 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 [Formula: see text], and meeting the clinical requirements for distal femur fracture reduction procedures.

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 0.09 mm (translations) and of [Formula: see text] (rotations), maximum observed errors in the order of 0.12 mm (translations) and of [Formula: see text] (rotations), and a reduction repeatability of 0.02 mm and [Formula: see text]. 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.

Preliminary analysis of force-torque measurements for robot-assisted fracture surgery.

Our group at Bristol Robotics Laboratory has been working on a new robotic system for fracture surgery that has been previously reported [1]. The robotic system is being developed for distal femur fractures and features a robot that manipulates the small fracture fragments through small percutaneous incisions and a robot that re-aligns the long bones. The robots controller design relies on accurate and bounded force and position parameters for which we require real surgical data. This paper reports preliminary findings of forces and torques applied during bone and soft tissue manipulation in typical orthopaedic surgery procedures. Using customised orthopaedic surgical tools we have collected data from a range of orthopaedic surgical procedures at Bristol Royal Infirmary, UK. Maximum forces and torques encountered during fracture manipulation which involved proximal femur and soft tissue distraction around it and reduction of neck of femur fractures have been recorded and further analysed in conjunction with accompanying image recordings. Using this data we are establishing a set of technical requirements for creating safe and dynamically stable minimally invasive robot-assisted fracture surgery (RAFS) systems.

The treatment of calcaneal malunion.

The surgical treatment of calcaneal malunion is technically very demanding and requires a careful assessment of the exact cause of the problem. A number of different surgeries are available depending on the precise cause of symptoms. The results are reasonable and justify surgery in an otherwise disabled group of patients. Calcaneal malunion surgery should not be performed by the occasional surgeon, as the price of error is usually amputation.

Interobserver and intraobserver reliability assessment of calcaneal fracture classification systems.

The aim of the present study was to assess the reliability of commonly used intra-articular calcaneal fracture classification systems and to compare them with the newer AO Integral Classification of Injuries (ICI) system. Forty computed tomography and radiographic images of 40 intra-articular calcaneal fractures were reviewed independently by 3 reviewers on 2 separate occasions and classified according to the Essex-Lopresti, Atkins, Zwipp and Tscherne, Sanders, and AO-ICI classification systems. The reviewers were unaware of the patients' identity and all aspects of clinical care. The data were analyzed using kappa (κ) statistics to assess the intra- and interobserver reliability. The κ values were calculated for Essex-Lopresti (κ = 0.85 intraobserver, κ = 0.78 interobserver), Atkins (κ = 0.42 intraobserver, κ = 0.73 interobserver), Zwipp and Tscherne (κ = 0.40 intraobserver, κ = 0.47 interobserver), Sanders (κ = 0.31 intraobserver, κ = 0.35 interobserver), and AO-ICI (κ = 0.41 intraobserver, κ = 0.33 interobserver). The AO-ICI classification system had levels of reproducibility similar to that of the Sanders classification, currently the most widely used system. The Essex-Lopresti classification demonstrated improved reliability compared with that reported in previous studies. This can be attributed to using sagittal computed tomography images, in addition to the originally described plain radiographs, for assessment. This improvement is relevant because of its accepted prognostic predictability.

Intra-operative correction of Taylor Spatial Frame without a computer.

The Taylor Spatial Frame (TSF) is a circular external fixator used to treat complex fractures and skeletal deformities. The device consists of 2 rings attached to bone by wires or half pins, connected by universal hinge joints to 6 independent telescopic struts, creating a hexapod. The output piece is defined as the movable ring, which has 6 degree of freedom relative to the other ring, which is the base. With 6 degree of freedom, the movable platform is capable of moving in 3 linear directions and 3 angular directions singularly or in any combination. These hexapod devices require complex mathematical software programs to accurately control the output piece. In the case of the TSF, the deformity and positional frame parameters can be indentified on postoperative radiographs. They are then input into internet-based software to calculate strut adjustments required to achieve deformity correction. When treating fractures with the TSF, the rings can be connected using FastFx struts. These struts can be locked in position or left in a sliding mode (unlocked) allowing manual manipulation of the frame to acutely correct the position of the fracture fragments. This reduction is rarely perfect however and often requires further postoperative frame adjustments using software calculations. We describe an intra-operative method for accurately adjusting the frame in its locked mode without the need for software input.

Complications of definitive open reduction and internal fixation of pilon fractures of the distal tibia.

A series of 49 pilon fractures in a tertiary referral centre treated definitively by open reduction and internal fixation have been assessed and the complications of such injuries examined. A retrospective analysis of case notes, radiographs and computerised tomographs over a seven-year period from 1999-2006 was performed. Infection was the most common postoperative problem. There were seven cases of superficial infection. There was a single case of deep infection requiring intravenous antibiotics and removal of metalwork. Other notable complications were those of secondary osteoarthritis (three cases) and malunion (one case). The key finding of this paper is the 2% incidence of deep infection following the direct operative approach to these fractures. The traditional operative approach to such injuries (initially advocated by Rüedi and Allgöwer in Injury 2:92-99, 1969) consisted of extensive soft tissue dissection to gain access to the distal tibia. Our preferred method is to access the tibia via the "direct approach" which involves direct access to the fracture site with minimal disturbance of the soft tissue envelope. We therefore believe that open reduction and internal fixation of pilon fractures via the direct approach to be a safe technique in the treatment of such devastating injuries.

Posttraumatic proximal tibial growth arrest: a rare injury managed successfully with ring fixators.

A ring fixator was used in the treatment of five patients (ages 11 to 16 years) with proximal tibial growth arrest after trauma. The mean corrections were 14.2 degrees (maximum 28 degrees , minimum 0 degrees ) in the saggital plane and 14 degrees (maximum 38 degrees , minimum 2 degrees ) in the coronal plane. Leg length discrepancy was also corrected (max 1 cm). The average time in frame was 17.8 weeks, with an average correction time of 29.8 days. Knee Society Clinical Rating System scores post operatively ranged from 95-100. All patients returned to full activity, and would accept the same treatment if offered again. The circular fixator is an effective, minimally invasive method for treating the complex deformities arising from this rare injury. Patients remain active during treatment, encouraging a rapid return to school/work activities.

Complex regional pain syndrome (type 1): a comparison of 2 diagnostic criteria methods.

BACKGROUND: Complex regional pain syndrome (CRPS) is a common problem presenting to orthopedic surgeons or pain therapists, most frequently encountered after trauma or surgery to a limb. Because of a lack of a simple objective diagnostic test, diagnosis is reliant on clinical assessment. Prospective studies have repeatedly demonstrated a higher incidence than retrospective studies, an observation that has been challenged owing to the lack of uniformity of diagnostic criteria across specialties and workers researching the condition. METHODS: A series of 262 adult patients presenting to the Bristol Royal Infirmary with a closed unilateral distal radial fracture were assessed at a mean of 9.47 weeks after their injury by a single clinician (J.A.L.). Each assessment made allowed comparison of the modified International Association for the Study of Pain (Bruehl) criteria for the presence of CRPS with the criteria described by Atkins. FINDINGS: The incidence of CRPS was similar using either criteria (Bruehl 20.61% vs. Atkins 22.52%). Using the Bruehl criteria as a gold standard, there was strong diagnostic agreement (kappa=0.79, sensitivity=0.87, specificity=0.94). Disagreements between the 2 criteria methods were found in 19 patients. The majority of these discordances were due to differences in pain and sensory abnormality assessment. INTERPRETATION: These findings show that the Bruehl and Atkins criteria are basically concordant. The differences reflect only minor variations in the assessment of pain. Agreement between researchers in the orthopedic and pain therapy communities will allow improved understanding of CRPS.

Computer hexapod assisted orthopaedic surgery (CHAOS) in the correction of long bone fracture and deformity.

SUMMARY: We describe a surgical technique using the Taylor Spatial Frame intraoperatively to correct complex multiplanar deformities of the distal femur prior to definitive internal fixation using minimally invasive stabilization techniques. Eight procedures were done in 7 patients. All deformities were complex oblique plane deformities, often with a rotational component, and ranged from 10 degrees valgus to 35 degrees varus; up to 45 degrees of external rotation; 10 mm of translation and in 1 case, 100 mm of shortening. All patients underwent acute intraoperative deformity correction mediated by the Taylor Spatial Frame prior to definitive internal fixation using either a percutaneous locking plate or locked intramedullary nail. Deformity correction and restoration of the mechanical axis were achieved in all cases. There were no cases of wound breakdown, infection, nerve palsy or compartment syndrome. We believe the Taylor Spatial Frame can be effectively and safely used to assist the acute correction and subsequent internal fixation of limb deformity.

Dermal traction on the Ilizarov frame.

We report a technique of skin traction, which harnesses the biological and mechanical properties of skin. We have used this technique in open fractures to close or reduce the size of the wound, thereby avoiding the use of split skin grafts or free flaps and their resultant additional morbidity. This report summarises our early experience with this technique in seven patients. We describe the technique and the results so far.

Calcaneal fractures in adolescents. CT classification and results of operative treatment.

The morphology of calcaneal fractures in 9 adolescents (mean age 13.4 years) with 10 fractures were classified using plain films and computed tomography scans. The patterns were found to be similar to those in adults. All except one of the fractures (which was not significantly displaced) were treated with open reduction and internal fixation. In all cases it was possible to achieve anatomic reduction and rigid internal fixation. Seven patients had 'excellent' long-term clinical results. One patient with pending litigation scored 'good', and one patient with an ipsilateral fracture of the talar neck scored 'fair'. This patient had mild limitation of ankle movement, all others had full ankle movement. Five had unrestricted subtalar movement, in two it was mildly limited and in three it was moderately limited (50-80%). There was no evidence of abnormality of the physes on follow up X-rays. We conclude that operative treatment of this fracture yields good results.

Fine wire frame-assisted intramedullary nailing of the tibia.

Intramedullary nailing is accepted as the technique of choice for treatment of unstable tibial diaphyseal fractures. Indirect closed reduction must first be obtained to allow passage of the guide wire and reamers. We describe the use of a simple frame that allows precise reduction, control of rotation and easy imaging access, without increasing operating or screening time.