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Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_5 | Pages 21 - 21
1 Feb 2016
Volk I Gal J Peleg E Almog G Luria S
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Introduction

Scaphoid fractures are commonly treated with a single headless screw. There are different recommendations regarding the optimal location of this screw. The purpose of this study was to compare the location of screws placed for the treatment of acute scaphoid fractures with theoretical and virtual screw locations.

Materials and Methods

10 patients with acute scaphoid fractures treated surgically and with available pre- and postoperative CT scans were included. The scans were analysed using a 3D software model (Amira Dev 5.3, Mercury Computer Systems, Chelmsford, MA). On the preoperative CTs the displaced fractures were virtually reduced. Possible screw locations for fracture fixation were examined including one along the central third of the proximal fragment (central base screw), the scaphoid longitudinal axis calculated mathematically (PCA screw) and a screw placed perpendicular to the fracture plane (90 degree screw). The angle between the axes and fracture plains were measured. The angle and distance between the actual screw on the postoperative CT and the different virtual screw locations were measured as well.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_28 | Pages 123 - 123
1 Aug 2013
Luria S Schwartz Y Wollstein R Emelif P Zinger G Peleg E
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Purpose

Knowing the morphology of any fracture, including scaphoid fractures, is important in order to determine the fracture stability and the appropriate fixation technique. Scaphoid fractures are classified according to their radiographic appearance, and simple transverse waist fractures are considered the most common. There is no description in the literature of the 3-dimensional morphology of scaphoid fractures. Our hypothesis was that most scaphoid fractures are not perpendicular to its long axis, i.e. they are not simple transverse fractures.

Methods

A 3-dimensional analysis was performed of CT scans of acute scaphoid fractures, conducted at two medical centres during a period of 6 years. A total of 124 scans were analysed (Amira Dev 5.3, Visage Imaging Inc). Thirty of the fractures were displaced and virtually reduced. Anatomical landmarks were marked on the distal radius articular surface in order to orient the scaphoid in the wrist. Shape analysis of the scaphoids and a calculation of the best fitted planes to the fractures were carried out implementing principal component analysis. The angles between the scaphoid's first principal axis to the fracture plane, articular plane and to the palmar-dorsal direction were measured. The fractures were analysed both for location (proximal, waist and distal) and for displacement.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_28 | Pages 85 - 85
1 Aug 2013
Khamaisy S Peleg E Segal G Hamad A Luria S
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Purpose

The surgical treatment of scaphoid fractures consists of reduction of the fracture followed by stable internal fixation using a headless compression screw. Proper positioning of the screw remains technically challenging and therefore computer assisted surgery may have an advantage.

Navigation assisted surgery requires placement and registration of stable reference markers which is technically impossible in a small bone like the scaphoid. Custom made wrist-positioning devices with built-in reference markers have been developed for this purpose. The purpose of this study was to evaluate a different method of navigation assisted scaphoid fracture fixation. Temporary stabilisation with a pin of the scaphoid to the radius enables placement of the reference markers on the radius. Our hypothesis was that this method will achieve precise fracture fixation, superior to the standard free hand technique.

Methods

In 20 identical saw bone models with mobile scaphoids, the scaphoid was stabilised to the radius using one Kirschner wire (KW). An additional KW representing the fixating screw was placed either using the Mazor Renaissance Robotic System (MAZOR Surgical Technologies, Israel) or standard free hand technique. CT scans were performed prior to fixation and after fixation in order to plan the location of the KW and compare this planned location with the final result.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_28 | Pages 86 - 86
1 Aug 2013
Luria S Schwartz Y Wollstein R Emelif P Zinger G Peleg E
Full Access

Purpose

Knowing the morphology of any fracture, including scaphoid fractures, is important in order to determine the fracture stability and the appropriate fixation technique. Scaphoid fractures are classified according to their radiographic appearance, and simple transverse waist fractures are considered the most common. There is no description in the literature of the 3-dimensional morphology of scaphoid fractures. Our hypothesis was that most scaphoid fractures are not perpendicular to its long axis, i.e. they are not simple transverse fractures.

Methods

A 3-dimensional analysis was performed of CT scans of acute scaphoid fractures, conducted at two medical centers during a period of 6 years. A total of 124 scans were analysed (Amira Dev 5.3, Visage Imaging Inc). Thirty of the fractures were displaced and virtually reduced. Anatomical landmarks were marked on the distal radius articular surface in order to orient the scaphoid in the wrist. Shape analysis of the scaphoids and a calculation of the best fitted planes to the fractures were carried out implementing principal component analysis. The angles between the scaphoid's first principal axis to the fracture plane, articular plane and to the palmar-dorsal direction were measured. The fractures were analysed both for location (proximal, waist and distal) and for displacement.


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. 94-B, Issue SUPP_XLIV | Pages 26 - 26
1 Oct 2012
Lubovsky O Safran O Axelrod D Peleg E Whyne C
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Fractures of the clavicle are relatively common, occurring mostly in younger patients and have historically been managed non-operatively. Recent studies have shown an advantage to surgical reduction and stabilisation of clavicle fractures with significant displacement. Currently, fracture displacement is measured using simple anterior-posterior two-dimensional x-rays of the clavicle. Since displacement can occur in all three-dimensions, however, evaluation of the amount displacement can be difficult and inaccurate. The purpose of this study was to determine the view that provides the most accurate assessment.

Nine CT scans of acute displaced clavicle fractures were analysed with AmiraDEV5.2.2 Imaging software. Measurements for degrees of shortening and fracture displacement of the fracture clavicle were taken. Using a segmentation and manipulation module (ITK toolkit), five digitally reconstructed radiographs (DRRs) mimicking antero-posterior x-rays were created for every CT, with each differing by projection angle (ranging from 20° upwards tilt to 20° downwards tilt). Measurements were taken on each DRR using landmarks of entire clavicle length, distance from vertebrae to fracture (medial fragment length), distance from fracture to acromium (lateral fragment length), and horizontal shortening, and then compared to the true measurement obtained from the original CT.

For all 9 samples, after comparing the measurements of clavicle fracture displacement in each 2D image, we found that an AP view with a 20° downward tilt yielded displacement measurements closest to the 3D (“gold standard”) measurements. The results agree with previous data collected from cadaveric specimens using physical X-ray film images. DDRs enable creation of multiple standard AP radiographs from which accurate tilt can be measured. The large deviation in measurements on different DRR projections motivates consideration of standardising X-ray projections. A uniform procedure would allow one to correctly evaluate the displacement of clavicular fractures if fracture displacement information is to be utilized in motivating surgical decision-making.


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_II | Pages 338 - 338
1 May 2006
Atesok K Kallur A Peleg E Weil Y Liebergall M Mosheiff R
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Background: The purpose of this study is to evaluate the applicability and advantages of the intraoperative use of a mobile isocentric C-arm with 3-dimensional imaging (SIREMOBIL ISO-C-3D) in trauma surgery.

Patients & Methods: Between November, 2004 and September, 2005, the ISO-C-3D was used at our institution for intraoperative CT-quality visualization of 33 trauma cases with the fractures of calcaneus (13), tibial plateau (7), tibial plafond (6), acetabulum (4), distal radius (2) and talus (1). The mean patient age was 42 and male to female ratio 25 to 8. In 30 cases ISO-C-3D was used during the surgery after the reduction and fixation of the fracture to assess the accuracy of reduction and implant position prior to wound closure and in 3 cases the device was used before starting the operation to obtain real-time CT images which were transferred to a navigation system to perform computer navigated procedures.

Results: This novel technique was highly beneficial from 4 aspects; intraoperative diagnosis, proper reduction, correct implant placement and feasibility in combining the CT images to computer navigation. In 40% of the cases (13/33) who had no regular CT scan before the surgery, intraoperative three dimensional imaging with ISO-C-3D has been a superior modality in diagnosis. In one case the reduction and implant position was corrected during the surgery after the ISO-C-3D scan. In all the procedures with ISO-C-3D navigation, satisfactory reconstruction of the articular surfaces with precise fixation was achieved.

Conclusion: Intraoperative 3-dimensional visualization with ISO-C-3D provides useful information in trauma surgery which enables the surgeon to re-evaluate the injury diagnostically and to judge the reduction and implant position before wound closure. Combining the ISO-C-3D images with computer navigation makes the reduction and implant placement highly accurate.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 390 - 390
1 Sep 2005
Peleg E Mattan Y Liebergall M Mosheiff R
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Introduction: Decreasing the length of the side plate of the dynamic hip screw (DHS) would theoretically allow a smaller surgical incision, a shorter surgical time, decreased operative blood loss and minimal periosteal stripping. A new design of a very short plate (VSP) dynamic hip screw based on two diagonal screws has been developed. The new design was compared with the four hole side plate regarding its mechanical properties and bio-mechanical outcomes.

Methods: Four pairs of fresh frozen cadaveric femora were extracted from male corpses aged 25–43 (mean 34.8), mechanical loading was applied to four pairs of cadaveric femora which were fixated using the new system on one side and the conventional design on the other. The decline during the periodical loading and the breakage load of the fixated bones were measured. In addition, mechanical performance and probability for failure was assessed by conducting a mathematical analysis using the finite element method.

Results: The average deflection under excessive cyclic loading was 33% higher in bones with the VSP-DHS device than those with regular DHS. The average load failure during the collapse loading test was 312 kg for the VSP-DHS compared to 416 kg for the regular device. The mathematical analysis performed indicated that the maximal stress in the VSP-DHS reached values 3–4 fold higher than in the regular DHS.

Conclusions: Bio-mechanical evaluation was performed both by mechanical testing and theoretically. Although the new design offers a minimally invasive approach to subtrochanteric femur fracture fixation, it was found to have insufficient biomechanical performance resulting in high probability for mechanical failure.