Central Placement of the Screw in Simulated Fractures of the Scaphoid Waist

McCallister, Wren V.; Knight, Jessica L.; Kaliappan, Robert; Trumble, Thomas E.

doi:10.2106/00004623-200301000-00012

Cited by 184 publications

(190 citation statements)

References 15 publications

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“…18 The implications of central screw placement have been evaluated in biomechanical studies of osteotomized fresh cadaveric scaphoid waist fracture repairs. [19][20][21] In one study, central placement was shown to confer greater stiffness and load at failure, compared with eccentric placement. 21 Although the same screw type was utilized in all three cases, we do not attribute secondary fracture risk to hardware make or model.…”

Section: Discussionmentioning

confidence: 99%

“…[19][20][21] In one study, central placement was shown to confer greater stiffness and load at failure, compared with eccentric placement. 21 Although the same screw type was utilized in all three cases, we do not attribute secondary fracture risk to hardware make or model. As refracture after fixation with other screw types 4 has been detailed, we cannot make this association with any degree of certainty.…”

Section: Discussionmentioning

confidence: 99%

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Scaphoid Proximal Pole Fracture Following Headless Screw Fixation

et al. 2015

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Nondisplaced scaphoid waist fractures may be managed nonoperatively, but require strict and prolonged immobilization. Fracture nonunion is a troublesome complication that leads to prolonged casting or secondary surgery and, if untreated, to carpal collapse and degenerative arthritis. 1,2 Unstable or displaced fractures, fracture-dislocations, and fractures involving the proximal pole require anatomic reduction with rigid fixation. Modern headless compression screws demonstrate high union rates, rapid recovery, and good-to-excellent outcomes in most series. 1,3-8 We were unable to identify reports detailing the potential for secondary proximal pole fracture following scaphoid screw fixation.In this series we describe three young men with scaphoid fracture nonunion that healed after antegrade headless compression screw fixation (Acumed, Hillsboro, OR, USA). Months later, the men presented with secondary fracture of the proximal pole (►Table 1). A consistently proximal and volar fracture pattern was observed that was contiguous with the screw insertion site. The purpose of this case series is to report our experience and raise awareness of a possible risk of retained hardware following antegrade scaphoid nonunion fixation, offer treatment strategies, and report outcomes. Case 1A 15-year-old right-handed lacrosse player presented to our institution after 3.5 months of sport-related left wrist pain had not abated. A scaphoid fracture had been treated as a AbstractBackground Headless screw fixation of scaphoid fractures and nonunions yields predictably excellent outcomes with a relatively low complication profile. However, intramedullary implants affect the load to failure and stress distribution within bone and may be implicated in subsequent fracture. Case Description We describe a posttraumatic fracture pattern of the scaphoid proximal pole originating at the previous headless screw insertion site in three young male patients with healed scaphoid nonunions. Each fracture was remarkably similar in shape and size, comprised the volar proximal pole, and was contiguous with the screw entry point. Treatment was challenging but successful in all cases. Literature Review Previous reports have posited that stress-raisers secondary to screw orientation may be implicated in subsequent peri-implant fracture of the femoral neck. Repeat scaphoid fracture after screw fixation has also been reported. However, the shape and locality of secondary fracture have not been described, nor has the potential role of screw fixation in the production of distinct fracture patterns. Clinical Relevance Hand surgeons must be aware of this difficult complication that may follow antegrade headless screw fixation of scaphoid fracture nonunion, and of available treatment strategies.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Scaphoid Proximal Pole Fracture Following Headless Screw Fixation

et al. 2015

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“…It has been shown in biomechanical and clinical study that central placement of a scaphoid screw improves the healing rate and reduces the immobilisation period of a scaphoid fracture [10,13,18]. Trumble et al [18] reported that the scaphoid screw located in the central scaphoid was associated with shorter union time based on their clinical data of 34 patients.…”

Section: Discussionmentioning

confidence: 99%

“…The optimal position of this screw has been discussed frequently in recent years [3,9] Central placement, as supported by biomechanical studies that have examined scaphoid fractures in a cadaveric model, is accepted as one of the preferred methods of internal fixation [10,18]. Central placement of the screw could be determined either by Trumble et al's [18] central one-third proximal-pole criterion on anteroposterior (AP) and lateral X-rays or roughly follow the overall scaphoid central axis as reported by some authors [11,16].…”

Section: Introductionmentioning

confidence: 99%

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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“…The properties of the model lunate and scaphoid (provided by the manufacturer) showed that the model was $5 times stiffer than actual lunate and scaphoid bones, 42 but the density (1.06 vs. 1.67 g/cm 3 ) and shore hardness (80 vs. 85) compared well. 43,44 Our repeated impact methodology may have induced nonvisible cumulative micro-traumas that could have changed the bones' material properties and altered their failure characteristics. The comparison of the force data to previous work 40 suggests that the cumulative damage between the pre-fracture and crack events was minimal and had little effect on the outcome.…”

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confidence: 99%

Failure characteristics of the isolated distal radius in response to dynamic impact loading

Burkhart

Andrews

Dunning

2011

Journal Orthopaedic Research

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We examined the mechanical response of the distal radius pre-fracture and at fracture under dynamic impact loads. The distal third of eight human cadaveric radii were potted and placed in a custom designed pneumatic impact system. The distal intraarticular surface of the radius rested against a model scaphoid and lunate, simulating 458 of wrist extension. The scaphoid and lunate were attached to a load cell that in turn was attached to an impact plate. Impulsive impacts were applied at increasing energy levels, in 10 J increments, until fracture occurred. Three 458 stacked strain gauge rosettes were affixed along the length of the radius quantifying the bone strains. The mean (SD) fracture energy was 45.5 (16) J. The mean (SD) resultant impact reaction force (IRFr) at failure was 2,142 (1,229) N, resulting in high compressive strains at the distal (2,718 (1,698) me) and proximal radius (3,664 (1,890) me). We successfully reproduced consistent fracture patterns in response to dynamic loads. The fracture energy and forces reported here are lower and the strains are higher than those previously reported and can likely be attributed to the controlled, incremental, dynamic nature of the applied loads. Keywords: radius; impact; fracture; forward fall; injury criteriaThe distal radius is a common fracture site, often resulting from a forward fall. Nevitt and Cummings 1 reported that, of 337 forward falls, 39% resulted in a wrist fracture, with more than 60% requiring some form of surgical intervention. 2,3 This has lead to these injuries being identified as a major health problem, 4 and the World Health Organization has listed fracture prevention among healthcare priorities. 5 Nonetheless, fracture frequency remains high ($164,000 emergency room visits/year from 1991 to 2009 in the US alone 6 ), and researchers have been unable to determine optimal treatment strategies for various patterns and severities of wrist fractures. 7 Although general consensus exists regarding risk factors for distal radius fractures, 8 prevention of these injuries requires a more thorough understanding of the injury mechanisms. The injury mechanism is one of the most important elements of the history, 7 as this information can help discern the degree of damage to the bone and the surrounding soft tissues. Beardley et al. 9 identified the importance of understanding the energy involved in a fracture as it generally determines the degree of comminution, thus affecting the treatment protocol.An accurate understanding of the injury mechanisms (e.g., kinetic energy involved and direction of loading) can be accomplished by improving our knowledge of the input parameters and the bones' response to dynamic loading through valid laboratory studies. 10 Many researchers mechanically loaded human cadaver specimens to determine the maximal strength of the distal radius, 10-22 but methodological inconsistencies have led to variability in results. Researchers studied the response to dynamic impact loads 10,[17][18][19] to better simulate real-worl...

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Central Placement of the Screw in Simulated Fractures of the Scaphoid Waist

Cited by 184 publications

References 15 publications

Scaphoid Proximal Pole Fracture Following Headless Screw Fixation

Scaphoid Proximal Pole Fracture Following Headless Screw Fixation

Establishing a central zone in scaphoid surgery: a computational approach

Failure characteristics of the isolated distal radius in response to dynamic impact loading

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