A Computational Approach to the “Optimal” Screw Axis Location and Orientation in the Scaphoid Bone

Leventhal, Evan L.; Wolfe, Scott W.; Walsh, Eric; Crisco, Joseph J.

doi:10.1016/j.jhsa.2009.01.011

Cited by 60 publications

(45 citation statements)

References 28 publications

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“…This is not the first time that investigators have attempted to use radiographic images to identify the central position for scaphoid screw placement [7][8][9]18]. The purpose of this study Fig.…”

Section: Discussionmentioning

confidence: 99%

“…During the last decade, the continued developments in computed tomography (CT) and computer technology has enabled a generation of 3D models allowing a more accurate demonstration of scaphoid geometry [5,7]. We borrowed the concept of a central one third of the scaphoid and developed a computer programme to establish an entire central third zone within the entire scaphoid reconstruction model.…”

Section: Introductionmentioning

confidence: 99%

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Establishing a central zone in scaphoid surgery: a computational approach

Guo

Tian

Chen

et al. 2013

International Orthopaedics (SICOT)

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Purpose Scaphoid fractures are commonly fixed with headless cannulated screws positioned centrally in the scaphoid. Judgement of central placement of the screw may be difficult. We generated a central zone using computer analysis of 3D reconstructions of computed tomography (CT) images. As long as the screw axis is completely contained within this central zone, the screw would be considered as centrally placed. Methods Thirty cases of 3D CT reconstructions of normal scaphoids in a computerised operation planning and simulation system (Vxwork software) were obtained. The central zone was established after some distance shrinkage of the original scaphoid surface reconstruction model using the function "erode" in the software. The shape of the central zone was evaluated, and the width of the central zone in the proximal pole, waist portion and distal pole was measured. We also established the long axis of the scaphoid to see whether it stays in the central zone. Results All central zones could be divided into distal, waist and proximal portions according to the corresponding irregular shape of the scaphoid. As the geometry of the central zone was so irregular and its width very narrow, it was possible to completely contain the screw axis either in the proximal portion alone, waist alone or distal central zone alone. Conclusions Establishing the central zone of scaphoid 3D CT images provided a baseline for discussion of central placement of a scaphoid screw. The geometry of the scaphoid central zone determined that the screw could hardly be inserted through entire scaphoid central area during surgery.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Establishing a central zone in scaphoid surgery: a computational approach

Guo

Tian

Chen

et al. 2013

International Orthopaedics (SICOT)

View full text Add to dashboard Cite

show abstract

“…Placement of a screw along this axis can be technically demanding. In vitro or in vivo direction of the guide wire may vary from the long axis resulting in different screw length if directed obliquely away from the axis [26]. The approach can influence positioning of the screw and previous studies have shown that screws are placed more parallel to the long axis when using a dorsal approach [11,22].…”

Section: Discussionmentioning

confidence: 99%

“…1). A coordinate system for each scaphoid was computed using its inertial properties [26]. To compare scaphoids between the sexes, we determined the sagittal and coronal planes by creating planes with the x-and y-axes and x-and z-axes, respectively.…”

Section: Methodsmentioning

confidence: 99%

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Influence of Screw Design, Sex, and Approach in Scaphoid Fracture Fixation

Meermans¹,

Verstreken²

2012

Clinical Orthopaedics &Amp; Related Research

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Background Screw fixation of scaphoid fractures has gained popularity. A long central screw has been shown to be biomechanically advantageous. Questions/purposes We compared the ability of different screw designs to obtain this goal and determined the influence of sex and approach on screw length. Methods We performed all measurements on threedimensional reconstructions of 20 CT scans of normal scaphoids (10 men and 10 women) with the use of software. The three-dimensional computer models were analyzed, the central axis was defined, and the screws were placed along this axis. We compared 15 different available screw designs and volar and dorsal screw placement. Results The length of the scaphoid along its central axis was longer in men (mean, 27.14 mm; standard error of the mean, 0.97 mm) than in women (mean, 23.86 mm; standard error of the mean, 0.37 mm). The screw length that can be used was longer in the volar approach (mean, 23.72 mm; standard error of the mean, 0.19 mm) than in the dorsal approach (mean, 23.31 mm; standard error of the mean, 0.19 mm) regardless of the screw design. Screws with a trailing thread diameter greater than 3.9 mm and leading thread diameter greater than 3.0 mm were shorter. Conclusions Scaphoids in women are smaller than in men. Theoretically, fixation of scaphoid fractures through a volar approach will allow the surgeon to use longer screws. The screw design has a significant influence on the screw length that can be used in scaphoid fracture fixation. We recommend using a differential pitch screw with a thread diameter of 3.9 mm or less.

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Osseous microarchitecture of the scaphoid: Cadaveric study of regional variations and clinical implications

et al. 2011

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Bone strength and structure are closely associated with fracture and screw fixation, however osseous micro architecture on scaphoid has not been clearly addressed. We conducted histomorphometric study of the scaphoid using micro CT to find regional variations and differences in the scaphoid to provide better understanding of fracture mechanism and suggest optimal screw position. We divided scaphoid into eight regions and collected regional data from eleven different cadaveric scaphoids. A computer program was used to measure parameters, which includes mean subchondral bone thickness, bone mineral density for bone density parameters, and tissue mineral density, trabecular thickness, trabecular spacing, trabecular number and bone volume fraction for bone quality parameters. All bone strength parameters were measured the maximum value in the regions where scaphoid articulates with radius. Articular regions presented higher bone strength parameters and thicker subchondral bone. The minimum value of trabecular number was in midcarpal side of waist portion. There was trend of higher subchondral bone thickness in the scaphoid which articulates with capitate and radius. This histomorphometric study showed regional variation of the scaphoid in terms of bone density and quality parameters. Waist portion presented thick subchondral and trabecular bone for high cross section moment of inertia against bending. Three point bending for scaphoid fracture and vertical screw placement are suggested based on these variations.

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A Computational Approach to the “Optimal” Screw Axis Location and Orientation in the Scaphoid Bone

Cited by 60 publications

References 28 publications

Establishing a central zone in scaphoid surgery: a computational approach

Establishing a central zone in scaphoid surgery: a computational approach

Influence of Screw Design, Sex, and Approach in Scaphoid Fracture Fixation

Osseous microarchitecture of the scaphoid: Cadaveric study of regional variations and clinical implications

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