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Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_6 | Pages 62 - 62
1 Mar 2017
van der List J Chawla H Joskowicz L Pearle A
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INTRODUCTION

There is a growing interest in surgical variables that are controlled by the orthopaedic surgeon, including lower leg alignment and soft tissue balancing. Since more tight control over these factors is associated with improved outcomes of total knee arthroplasty (TKA), several computer navigation systems have been developed. Many meta-analyses showed that mechanical axis accuracy and component positioning are improved using computer navigation and one may therefore expect better outcomes with computer navigation but studies showing this are lacking. Therefore, a systematic review with meta-analysis was performed on studies comparing functional outcomes of computer-navigated and conventional TKA. Goals of this study were to (I) assess outcomes of computer-navigated versus conventional TKA and (II) to stratify these results by the surgical variables the systems aim to control.

METHODS

A systematic search in PubMed, Embase and Cochrane Library was performed for comparative studies reporting functional outcomes of computer-navigated versus conventional TKA. Knee Society Scores (KSS) Total were most often reported and studies reporting this outcome score were included. Outcomes of computer-navigated and conventional TKA were compared (I) in all studies and (II) stratified by navigation systems that only controlled for lower leg alignment or systems that controlled for lower leg alignment and soft tissue balancing. Level of evidence was determined using the adjusted Oxford Centre for Evidence-Based Medicine tool and methodological quality was assessed using Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) tool. Outcomes were reported in mean difference (MD) with 95% confidence intervals [Lower Bound 95%, Upper Bound 95%].


Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_16 | Pages 26 - 26
1 Oct 2014
Kovler I Weil Y Salavarrieta J Joskowicz L
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Trauma surgeries in the pelvic area are often difficult and prolonged processes that require comprehensive preoperative planning based on a CT scan. Preoperative planning is essential for the appreciation and spatial visualisation of the bone fragments, for planning the reduction strategy, and for determining the optimal type, size, and location of the fixation hardware.

We have developed a novel haptic-based patient specific preoperative planning system for pelvic bone fractures surgery planning. The system provides a virtual environment in which 3D bone fragments and fixation hardware models are interactively manipulated with full spatial depth and tactile perception. It supports the choice of the surgical approach and the planning of the two mains steps of bone fracture surgery: reduction and fixation. The purpose of the tool is to provide an intuitive haptic spatial interface for the manipulation of bone fracture 3D models extracted from CT images, to support the selection of bone fragments, the annotation of the fracture surface, the selection and placement of fixation screws, and the creation and placement of fixation plates with an anatomically fit shape.

The system incorporates ligament models that constrain the bone fragments motions and provides a realistic interactive fracture reduction support feeling to the surgeon. It allows the surgeon to view the fracture from various directions, thereby allowing fast and accurate fracture reduction planning. Two haptic devices, one for each hand, provide tactile feedback when objects touch without interpenetrating. To facilitate the reduction, the system provides an interactive, haptic fracture surface annotation tool and a fracture reduction algorithm that automatically minimises the pairwise distance between the fracture surfaces. For fracture fixation, the system provides a screw creation and placement capability as well as custom anatomical-fit fixation plate creation and placement. The screw placement is facilitated by the transparent viewing mode that allows the surgeon to navigate the screws inside the bone fragments while constraining them to remain within the bone fragments with haptic forces.

Our experimental results with five surgeons show that the method allows highly accurate reduction planning to within 1 mm or less. To evaluate the alignment in terms of quantity, we created a model of an artificial fracture in a healthy pelvis bone. The created model is placed in its anatomic location thus allowing us to measure the error in relation to its initial position. We calculate the anatomic alignment error by measuring the Hausdorff distance in mm between the fragment positioned in the desired location and the fragment placed by the surgeon. The new haptic-based system also supports patient-specific training of pelvic fracture surgeries.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XLIV | Pages 37 - 37
1 Oct 2012
Lamdan R Simanovsky N Joskowicz L Liebergall M Gefen A Peleg E
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Supra-condylar humerus fractures (SCHF) are amongst the most common fractures requiring surgical stabilisation in the pediatric age group (1). Closed reduction and percutaneous fixation with Kirschner wires (KW) is currently the standard of care (2). The number of KW used and their configuration has been the subject of much research (3, 4). The failure modes leading to loss of fracture reduction are not clear and have not been quantified. The aim of this study is to compare the mechanical stability of the opt-used configurations for various loading modes and contact interactions at the KW/bone interface.

A Gartland type-III SCHF was introduced to a fourth generation composite saw bone (Sawbones®, Vashon, Washington, USA). The model was CT scanned with a slice spacing of 0.5mm and pixel size 0.3×0.3mm. The CT data set was imported into AmiraDev (AmiraDev 5.2 Visage Imaging, Inc). A uniaxial mechanical test was conducted in order to measure the KW pullout forces from the distal humerus.

A model of the fractured humerus was constructed with the following steps: 1) manual segmentation; 2) surface generation of each fragment, and; 3) automatic volumetric grid generation for each fragment. The fracture was then virtually reduced and KWs were placed at the desired configurations (Fig 1a-b). For each configuration, a separate model was generated. Material properties were assigned to the bone-model elements according to the manufacturer's data sheet; Young's modulus E = 16GPa and E = 150MPa for the cortical and cancellous bone respectively. The KW were assigned a Young's modulus of 200GPa. Each of the models created in Amira was imported to a finite element application (Abaqus 6.9, DS-Simula) for structural analysis. For each of KW configuration four different torque forces load types were simulated (Fig 1c left): 1) a clockwise and counterclockwise torque with a magnitude of 1.5 NM (Newton/Meters); 2) a translational force with a magnitude of 30 N (Newtons) in the direction of the humerus shaft, and; 3) a shear force with a magnitude of 30 N in the direction parallel to the fracture plane. The results were normalised such that the maximum displacement for the crossed pin configuration with a coefficient of friction equal to zero (μ = 0) was used as unity for each load configuration. Similarly, for each of KW configuration four different translational forces load types were simulated (Fig 1c right): 1) a clockwise and counter clock-wise torque with a magnitude of 1.5 NM (Newton/Meters); 2) a translational force with a magnitude of 30N in the direction of the humerus shaft, and; 3) a shear force with a magnitude of 30N in the direction parallel to the fracture plane. The results were normalised as described above.

Results

Torque forces: the crossed configuration was found to be almost independent of the bone-implant friction and was symmetric in terms of direction of the applied torque. The diverging configuration exhibited larger dependency on the bone-implant interface. This is especially noticed as the coefficient of friction (COF) reduced to values below μ = 0.2. Translational forces: the diverging configuration exhibited high sensitivity to reduction of the COF μ = 0. Displacement of the fracture for μ = 0 was substantially larger for the diverging configuration relative to the crossed configuration: 13.5 times and 19 times for the transverse and pullout directions, respectively. As the COF increased to values above μ = 0.5, both fixation configurations performed in a similar manner.

Stabilisation of SCHF has been the subject of numerous studies. Relative stability of the different configurations and the risk for iatrogenic ulnar nerve injury has been in the center of the debate. Crossed KW configuration was shown in some clinical studies to be more stable than two lateral KW while others demonstrated no significant difference in stability. As ulnar nerve injury may occur in up to 15.4% of surgeries even if insertion of a medial KW is performed under direct vision, utilisation of two lateral KW configurations offers the advantage of reducing this risk significantly. The main finding of this study is that for a COF exceeding a threshold level (µ = 0.2) the crossed KW configuration did not offer any mechanical advantage over the diverging lateral KW configuration. However, for very low COF values (µ<0.2) the crossed configuration exhibited improved performance when compared with divergent lateral KW (figure 1d). The data demonstrates that the KW-bone bonding has a profound effect on the stability of the fixated bone construct. This is mostly evident when distraction forces are applied but also occurs, to a lesser degree, with rotational or translational forces. This may be a clinically important consideration in the rare SCHF in children with abnormal bones and possibly more commonly, when the KW-bone bonding was compromised after multiple attempts of passing the KW through the same entry point.

We have conducted a combined in-vitro mechanical test and finite element-based simulations of a fixated SCHF with different KW configurations, under various friction conditions. Under normal bone-implant interface bonding conditions, the two diverging lateral KW configuration offers adequate mechanical stability and may be the preferred choice of SCHF fixation.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 514 - 515
1 Aug 2008
Ilsar I Joskowicz L Kandel L Liebergall M
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Introduction: The common belief is that navigation-assisted TKR improves the surgical accuracy and reduces outliers, albeit increasing the operating time. We conducted a detailed study of the published studies with four main criteria:

Reduction of outliers in the placement of implants.

Increased operating time.

Reduction of blood loss.

Higher post-operative score.

Methods: We performed a computerized search of the PubMed repository and a manual search of the proceedings of the International Society for Computer Assisted Orthopaedic Surgery (CAOS, 2001–05) to include all studies that presented clinical data of the results of this procedure. A total of 139 clinical studies were found, a total of 7,158 patients who underwent navigation-assisted TKR.

Results: Of the 139 studies, 39 studies presented data showing a reduction of outliers of the post-operative mechanical axis in the 180±3° range. 2,130 out of 2,401 (89%) patients operated with navigation were within this range. 27 out of the 39 studies compared the postoperative alignment of the navigated technique to that of the non-navigated technique. In the non-navigated technique, only 1,325 out of 1,880 (71%) patients were in that range, close to the published 74–75% for conventional TKR studies.

Regarding the operating time with navigation, 32 studies report an average increase of 21 min. (range 6– 48 min.), or about 20% than conventional TKR.

One of the perceived benefits of using extramedullary jigs in navigation-assisted TKR is thought to be reduction of blood loss. However, of the 15 studies that address this issue, 10 (67%) found no significant difference compared to the conventional technique. Regarding post-operative functional and/or pain scoring, 12 (80%) out of 15 studies found no statistically significant differences between navigated and non-navigated techniques.

Conclusions: The published clinical data so far shows that navigated-assisted TKR provides good alignment of the implants and a reduction of outliers from one in four to at most one in ten at the expense of 15–20 min. (about 20%) increase in operating time. No significant advantage was found for blood loss or functional/pain scoring. From a public health viewpoint, the increased cost of the navigated procedure may very well be compensated by the reduction of future revisions.


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_II | Pages 337 - 338
1 May 2006
Ilsar I Weil Y Mosheiff R Joskowicz L Peyser A Liebergall M
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Introduction: To enable navigated-assisted orthopedic surgery, a reference frame must be rigidly fixed to a stable bony structure. This may create technical obstacles and wound complications. Instead, we propose to attach the reference frame to the fracture table.

Methods: The study population consisted of 10 patients who underwent fixation of subcapital femoral neck fracture with three cannulated screws, using fluoroscopy-based navigation. Step 1 – the patient was positioned on a fracture table and the reference frame was attached to the iliac crest. Three guide wires were inserted under fluoroscopy-based navigation. 2 – New fluoroscopic images were acquired. 3 – Navigated drill guide placed over each guide wire to record final navigated drill guide position – these images include actual guide wire positions and the trajectories of the navigated drill guide. Navigation accuracy was validated, measuring translational and angular deviations of the virtual trajectory from the implant on the same fluoroscopic image in anteroposterior and lateral views. 4 – The reference frame was removed from the iliac crest and attached to the fracture table. Step 3 was then repeated.

Results: The translational deviation of the virtual trajectory from the inserted guide wire when the reference frame was attached to the iliac crest was not statistically significant from the deviation when it was attached to the fracture table. Angular differences were also not statistically significant.

Conclusions: In our experience, attaching the reference frame to the fracture table instead of to the iliac crest allows for similar accuracy of the navigation process with the possible benefit of reducing patient morbidity.