The Effect of Impact Location on Force Transmission to the Modular Junctions of Dual-Taper Modular Hip Implants

Frisch, Nicholas B.; Lynch, Jonathan R.; Banglmaier, Richard F.; Silverton, Craig D.

doi:10.1016/j.arth.2016.02.026

Cited by 7 publications

(10 citation statements)

References 10 publications

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“…Trigonometric decomposition of force vectors suggest that 95% of the impact force would be delivered to the 15° NS taper and 97.5% would be delivered to the 8° NS junction. However, the impact results of this and previous work have shown an increase in the impact force delivered to the 15° NS taper [10]. Based on the reported impact forces, this should result in the 15° NS taper junction having the largest distraction force, even greater than the axially impacted 0° neck.…”

Section: Discussionmentioning

confidence: 43%

“…Impact configurations were chosen based on previous research, which showed the impact force delivered to a 0° neck was greater than an off-axis impacted 8° neck but less than an off-axis impacted 15° neck [10]. Thus, a low to high range of impact forces were expected to provide a range of implant stabilities.…”

Section: Methodsmentioning

confidence: 99%

“…However, the ability to direct an ideal impaction along the axis of the mating components is exacerbated by implant neck angulation. Prior work in our laboratory has shown significant changes in the impact forces transmitted to the taper junctions for various impact locations and neck angles [10]. Under similar impact conditions (same mass and drop height), the resultant impact force and force measured at the head neck (HN) or neck stem (NS) were affected by the configuration of impact location and neck angle.…”

Section: Introductionmentioning

confidence: 96%

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The stability of dual-taper modular hip implants: a biomechanical analysis examining the effect of impact location on component stability

et al. 2017

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BackgroundThe purpose of this study was to investigate the stability of dual-taper modular implants following impaction forces delivered at varying locations as measured by the distraction forces required to disassemble the components.MethodsDistraction of the head-neck and neck-stem (NS) tapers of dual-taper modular implants with 0°, 8°, and 15° neck angles were measured utilizing a custom-made distraction fixture attached to a servohydraulic materials test machine. Distraction was measured after hand pressing the components as well as following a simulated firm hammer blow impaction. Impacts to the 0°, 8°, 15° necks were directed axially in line with the neck, 10° anterior, and 10° proximal to the axis of the neck, respectively.ResultsImpaction increased the range of NS component distraction forces when compared to hand pressed components (1125-1743 N vs 248-302 N, respectively). Off-axis impacts resulted in significantly reduced mean (±95% confidence interval) distraction forces (8° neck, 1125 ± 117 N; 15° neck, 1212 ± 73 N), which were up to 35% lower than the mean distraction force for axial impacts to the 0° neck (1743 ± 138 N).ConclusionsDirection of impaction influences stability of the modular interface. The greatest stability was achieved with impaction directed in line with the longitudinal axis of the taper junction. Off-axis impaction of the 8° and 15° neck led to significantly reduced stability at the NS. Improving stability of dual-taper modular hip prostheses with appropriately directed impaction may help to minimize micromotion, component settling, fretting corrosion, and subsequent failure.

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Section: Discussionmentioning

confidence: 43%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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The stability of dual-taper modular hip implants: a biomechanical analysis examining the effect of impact location on component stability

et al. 2017

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“…Furthermore, medical device manufacturers seldom offer standardised recommendations on the surgical technique used to assemble stem and head pairs. Previous studies have investigated the effect of assembly conditions on taper contact mechanics [1,24,[29][30][31][32][33]. An increase in assembly force has been implicated with an improvement in taper interlock, reduction in fretting corrosion [29], and an increase in microgroove deformation [24].…”

Section: Introductionmentioning

confidence: 99%

Changes in the morphology of microgrooved stem tapers with differing assembly conditions

et al. 2019

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Background Fretting and corrosion at the head-stem taper junction has been cited as a potential clinical concern. Material loss measurement is a vital tool for quantifying changes due to in vitro, in vivo, and/or ex-vivo implant experience. Material loss measurement requires reconstruction of pre-implantation geometry to delineate damage. This is straightforward in principle for plain machined tapers, integrating between a fitted interpolated cone and the measured data. Mathematical filtration methods have been developed to remove this texture and facilitate measurement. The extent to which the assembly process could influence filtration accuracy is not currently known. Methods An engagement/ disengagement study was performed on 27 head/ stem pairs using 2, 4, and 8kN impact loads. Impact was delivered in three locations; axial, 10 o anterior, and 10 o anteroproximal. Pull-off force was measured, and stems were measured pre and post assembly using a Talyrond 365 roundness measurement machine. Results An increase in the plastic deformation of microgrooves and pull-off force was noted with increasing assembly loads. Off-axis impaction resulted in reduced pull-off strength and reduced uniform microgroove distortion. Volumetric change between pre and post assembly was below the noise threshold on stem and head surfaces. Discussion The measurement method was shown to be capable of capturing linear microgroove deformation of 1 µm peak-peak and volume loss above 0.1mm 3. Lower peak load was noted when impacting a seated head when compared with engagement of discrete heads and stems, under the same assembly conditions.

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“…We further acknowledge that the methodology of component assembly could affect the surface proximity results but again would not affect the surface contour. There have been a variety studies comparing component assembly and suggest that variation can exist based on hand vs mallet assembly, force of impaction, and direction of impaction [9], [26], [27], [28]. For the purpose of this study, hand assembly was used, but we believe that further study could be warranted to compare different assembly methods.…”

Section: Discussionmentioning

confidence: 99%

Dual-taper modular hip implant: Investigation of 3-dimensional surface scans for component contact, shape, and fit

Frisch¹,

Lynch²,

Pourzal³

et al. 2018

Arthroplasty Today

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BackgroundThe etiology of wear particle generation and subsequent corrosion in modular total hip arthroplasty implants likely begins with mechanical fretting. The purpose of this study was to determine geometric features of the male and female taper surfaces that drive stability within the neck-stem junction.MethodsEighteen modular hip components received 3-dimensional surface scans to examine the neck-stem taper junction using an optical scanner. The normal distance between the surfaces of the neck taper as seated in the stem slot was measured and produced a color map of the contact proximity. Contour plots identified surface shape variation and contact. Angle measurements and neck seated depth were analyzed by regression.ResultsThe typical features observed were (1) a vertical line of contact at one end of the transition from the flat surface to the radius surface; (2) a vertical line of contact in the radius surface just past the centerline; (3) a concavity along the flat surface between the neck and stem components; and (4) one of the neck flat surfaces was closer to its mating surface on the stem. The seated depth of the neck was dependent on the taper angles in the flat section of the neck (R2 = 0.5000, P = .0332).ConclusionsThe shape of the neck and stem tapers deviate from ideal design dimensions, contributing to relative motions between the neck and stem. While these processes are not proven to directly cause implant failure, they may place the implants at higher risk for failure.

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The Effect of Impact Location on Force Transmission to the Modular Junctions of Dual-Taper Modular Hip Implants

Cited by 7 publications

References 10 publications

The stability of dual-taper modular hip implants: a biomechanical analysis examining the effect of impact location on component stability

The stability of dual-taper modular hip implants: a biomechanical analysis examining the effect of impact location on component stability

Changes in the morphology of microgrooved stem tapers with differing assembly conditions

Dual-taper modular hip implant: Investigation of 3-dimensional surface scans for component contact, shape, and fit

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