Mechanical Evaluation of Four Internal Fixation Constructs for Scaphoid Fractures

Beutel, Bryan G.; Melamed, Eitan; Hinds, Richard M.; Gottschalk, Michael B.; Capo, John T.

doi:10.1177/1558944715614889

Cited by 15 publications

(21 citation statements)

References 26 publications

(38 reference statements)

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“…13,15 Biomechanically, the plate has a similar load to failure (maximum force a structure can resist) to a headless compression screw 27 but was a less stiff construct (or less resistant to deformation), partly due to the thin 0.8-mm profile, although it has more resistance to rotational deformity. 28 This contributes to a different mode of failure; the plate itself failing at the central section in testing where there are no screws.…”

Section: Discussionmentioning

confidence: 99%

Volar Scaphoid Plating for Nonunion: A Multicenter Case Series Study

et al. 2020

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Background The volar scaphoid plate from Medartis (Medartis AG, Austrasse, Basel, Switzerland) is a variable angle titanium locking plate, preformed for the volar aspect of the scaphoid. It does not have compressive capability, and may act as a bridging device. It may provide an advantage over a compression screw where the pathoanatomy is less favorable to such a device with increased rotational stability. It may act as a buttress plate for correction of humpback deformity for example. It has been used in nonunions and with vascularized grafts. Questions Our study aims to assess the results of our patients with scaphoid nonunion treated with scaphoid volar plating over a larger number of patients. We aim to identify techniques to increase the success of plating. Methods Patients from our cohort were retrospectively reviewed. Operations were performed by three hand fellowship trained surgeons and in two centers. Inclusion involved a scaphoid plate procedure for a nonunion of the scaphoid with a minimum of 6 months of follow-up. Exclusions were those who had less than 6 months of follow-up. Data included demographics, patient-rated wrist evaluation (PRWE), a quick disabilities of the arm, shoulder, and hand (qDASH), visual analogue score, and range and grip. Radiology was reviewed. Results Thirty-two eligible patients were assessed. The mean age was 25 years (range 13–46), 2 were female and 15 were smokers. Mean follow-up postsurgery was 18 months. Twenty-nine of 32 patients united (90.6%) on computed tomography scan. Clinical assessment was performed in the 25 patients. The mean qDASH score was 12.5 (range 0–42) and mean PRWE was 11 (range 0–54). The mean arc of motion was 115 degrees. The mean grip strength was 39 kg compared with 41 kg on the nonoperated side. Conclusion We postulate that the plate acts like an internal bridging device, acting over a small distance, and inherent stability of the construct with structural graft and accurate reduction prior to plating is advantageous. Potential problems include plate impingement on the volar lip of the radius, particularly when trying to plate more proximal fractures. Ideally, it is utilized for mid to distal waist fractures.

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Section: Discussionmentioning

confidence: 99%

Volar Scaphoid Plating for Nonunion: A Multicenter Case Series Study

et al. 2020

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“…Fracture displacement was quantified by a displacement of the materials testing machine crosshead and has been previously utilized as failure criterion in biomechanical studies assessing mechanical properties of fixed scaphoids. 12,14,17 During cyclic loading, stiffness was calculated at the 1000th cycle or was calculated at the last cycle if the specimen failed prior to completion of the 1000th cycle. Stiffness was quantified by the slope from the linear region of the load-displacement curve.…”

Section: Methodsmentioning

confidence: 99%

“…An a priori power analysis was conducted with α ¼ 0.05 and β ¼ 0.20 based on previous literature pertaining to stiffness and ultimate load of fixed scaphoid fractures 12,14,17 . A sample size of n ¼ 6 was determined for each possible screw length.…”

Section: Methodsmentioning

confidence: 99%

Impact of Screw Length on Proximal Scaphoid Fracture Biomechanics

et al. 2019

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Background Proximal scaphoid fractures display high nonunion rates and increased revision cases. Waist fracture fixation involves maximizing screw length within the cortex; however, the optimal screw length for proximal scaphoid fractures remains unknown. Purpose The main purpose of this article is to compare stiffness and ultimate load for proximal scaphoid fracture fixation of various headless compression screw lengths. Methods Eighteen scaphoids underwent an osteotomy simulating a 7 mm oblique proximal fracture. Screws of three lengths (10, 18, and 24 mm) were randomly assigned for fixation. Each specimen underwent cyclic loading with stiffness calculated during the last loading cycle. Specimens that withstood cyclic loading were loaded to failure. Results No significant difference in stiffness between screw lengths was found. Ultimate load was significantly impacted by the screw length. A significant difference in ultimate load between a 10 and 24 mm screw was found; however, no significant difference occurred in ultimate load between an 18 and 24 mm screw. Conclusions No significant difference in stiffness between all groups could be due to similarities in purchase in the proximal aspect. The 10 mm screw withstanding less ultimate load compared to the 24 mm screw could be due to the 10 mm screw gaining less purchase on either side of the fracture site compared to the 24 mm screw. Lack of significant difference in ultimate load between the 18 and 24 mm screw could be occurring because the fracture site is closer to the 18 mm screw midpoint, as distal threads are engaged closer to the fracture. Clinical Relevance Maximizing screw length may not provide superior fixation biomechanically compared with fixation utilizing a 6 mm shorter screw for proximal scaphoid fractures.

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“…There are few biomechanical studies comparing the stability of single versus double screw fixation with conflicting results. [8,9] Similarly, there are only two clinical studies that reported higher union rates in double screw fixation compared to single screw fixation in the current literature. [11,12] We hypothesized that double screw fixation would provide greater rotational stability regarding biomechanical analysis and nonunion rates would be reduced.…”

mentioning

confidence: 92%

“…Biomechanical and clinical studies have shown that newly-developed scaphoid plates provide more stable fixation. [8,9] In addition, Erhart et al [10] have developed new anti-rotational screws particularly designed for scaphoid fractures.…”

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confidence: 99%

Single versus double screw fixation for the treatment of scaphoid waist fractures: Finite element analysis and preliminary clinical results in scaphoid nonunion

et al. 2020

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This study aims to compare the single versus double screw fixation of scaphoid waist fractures using finite element analysis, and to present the preliminary clinical results of double screw fixation in a consecutive series of patients with scaphoid nonunion. Patients and methods: A transverse scaphoid waist fracture (Herbert type B2) model was fixed with either single or double cannulated compression screws. Displacement and rotation of the fragments were performed using three-dimensional finite element analysis in three different wrist positions. A retrospective review was performed on 13 male patients (mean age 31.6±12.8 years; range, 17 to 64 years) who underwent double screw fixation for an established scaphoid nonunion in our clinic between January 2015 and December 2017. Assessment of union was established with serial plain radiographs in eight patients and with wrist computed tomography in five patients. Clinical evaluation was performed using the Mayo wrist score and visual analog scale (VAS). Results: In all wrist positions, the displacement of the fracture gap in double screw fixation in all planes (x, y, and z) was less than in single screw fixation. Similarly, rotation of the fracture fragments around the longitudinal axis of the scaphoid was lower in double screw fixation. Complete union was obtained in all patients. The mean time to union was 5±0.75 months (range, 4 to 6 months). The mean VAS was 0.8±0.9 (range, 0 to 3). Mayo wrist score was 91±6.9 (range, 80 to 100) at the final follow-up. Conclusion: Double-screw fixation technique may be a solution to reduce the rate of scaphoid nonunion in unstable type B2 scaphoid fractures or nonunion.

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Mechanical Evaluation of Four Internal Fixation Constructs for Scaphoid Fractures

Cited by 15 publications

References 26 publications

Volar Scaphoid Plating for Nonunion: A Multicenter Case Series Study

Volar Scaphoid Plating for Nonunion: A Multicenter Case Series Study

Impact of Screw Length on Proximal Scaphoid Fracture Biomechanics

Single versus double screw fixation for the treatment of scaphoid waist fractures: Finite element analysis and preliminary clinical results in scaphoid nonunion

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