The effect of in situ augmentation on implant anchorage in proximal humeral head fractures

Unger, Stefan; Erhart, Stefanie; Kralinger, Franz; Blauth, M.; Schmoelz, Werner

doi:10.1016/j.injury.2012.07.003

Cited by 92 publications

(91 citation statements)

References 22 publications

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“…In an effort to strengthen plating constructs, screw cement augmentation [15], bony autograft or allograft augmentation [16], and additional calcar screws or blades [17] have shown promising biomechanical and clinical results. However, each of these augmentation methods bears the increased risk of infection or impending difficulties in the potentiality of surgical revision.…”

Section: Discussionmentioning

confidence: 99%

Biomechanical evaluation of straight antegrade nailing in proximal humeral fractures: the rationale of the “proximal anchoring point”

Euler

Petri

Venderley

et al. 2017

International Orthopaedics (SICOT)

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Purpose Varus failure is one of the most common failure modes following surgical treatment of proximal humeral fractures. Straight antegrade nails (SAN) theoretically provide increased stability by anchoring to the densest zone of the proximal humerus (subchondral zone) with the end of the nail. The aim of this study was to biomechanically investigate the characteristics of this Bproximal anchoring point^(PAP). We hypothesized that the PAP would improve stability compared to the same construct without the PAP. Methods Straight antegrade humeral nailing was performed in 20 matched pairs of human cadaveric humeri for a simulated unstable two-part fracture. Results Biomechanical testing, with stepwise increasing cyclic axial loading (50-N increments each 100 cycles) at an angle of 20°abduction revealed significantly higher median loads to failure for SAN constructs with the PAP (median, 450 N; range, 200-1.000 N) compared to those without the PAP (median, 325 N; range, 100-500 N; p = 0.009). SAN constructs with press-fit proximal extensions (endcaps) showed similar median loads to failure (median, 400 N; range, 200-650 N), when compared to the undersized, commercially available SAN endcaps (median, 450 N; range, 200-600 N; p = 0.240). Conclusions The PAP provided significantly increased stability in SAN constructs compared to the same setup without this additional proximal anchoring point. Varus-displacing forces to the humeral head were superiorly reduced in this setting. This study provides biomechanical evidence for the Bproximal anchoring point's^rationale. Straight antegrade humeral nailing may be beneficial for patients undergoing surgical treatment for unstable proximal humeral fractures to decrease secondary varus displacement and thus potentially reduce revision rates.

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Section: Discussionmentioning

confidence: 99%

Biomechanical evaluation of straight antegrade nailing in proximal humeral fractures: the rationale of the “proximal anchoring point”

Euler

Petri

Venderley

et al. 2017

International Orthopaedics (SICOT)

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“…Osseous resistance, loading and in vivo loading of structures can only be approximated. This study's strengths are that its findings underline for the first time, that the time of cement application has an effect on pedicle screw anchorage in the osteoporotic vertebral body under physiologic related cyclic craniocaudal loading [2,[25][26][27][28][29] and it applies a stepwise increasing load protocol designed to investigate implant anchorage in reduced bone quality [30,31].…”

Section: Discussionmentioning

confidence: 99%

Timing of PMMA cement application for pedicle screw augmentation affects screw anchorage

et al. 2017

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Introduction Cement augmentation is an established method to increase the pedicle screw (PS) anchorage in osteoporotic vertebral bodies. The ideal timing for augmentation when a reposition maneuver is necessary is controversial. While augmentation of the PS before reposition maneuver may increase the force applied it on the vertebrae, it bears the risk to impair PS anchorage, whereas augmenting the PS after the maneuver may restore this anchorage and prevent early screw loosening. The purpose of the present study was to evaluate the effect of cement application timing on PS anchorage in the osteoporotic vertebral body. Methods Ten lumbar vertebrae (L1-L5) were used for testing. The left and right pedicles of each vertebra were instrumented with the same PS size and used for pairwise comparison of the two timing points for augmentation. For the reposition maneuver, the left PS was loaded axially under displacement control (2 9 ±2 mm, 3 9 ±6 mm, 3 9 ±10 mm) to simulate a reposition maneuver.Subsequently, both PS were augmented with 2 ml PMMA cement. The same force as measured during the left PS maneuver was applied to the previously augmented right hand side PS [2 9 F (±2 mm), 3 9 F (±6 mm), 3 9 F (±10 mm)]. Both PS were cyclically loaded with initial forces of ?50 and -50 N, while the lower force was increased by 5 N every 100 cycles until total failure of the PS. The PS motion was measured with a 3D motion analysis system. After cyclic loading stress, X-rays were taken to identify the PS loosening mechanism. Results In comparison with PS augmented prior to the reposition maneuver, PS augmented after the reposition maneuver showed a significant higher number of load cycles until failure (5930 ± 1899 vs 3830 ± 1706, p = 0.015). The predominant loosening mechanism for PS augmented after the reposition maneuver was PS toggling with the attached cement cloud within the trabecular bone. While PS augmented prior to the reposition, maneuver showed a motion of the screw within the cement cloud. Conclusion The time of cement application has an effect on PS anchorage in the osteoporotic vertebral body if a reposition maneuver of the instrumented vertebrae is carried out. PS augmented after the reposition maneuver showed a significant higher number of load cycles until screw loosening.

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“…In order to have a failure or loosening of the implant system before these 100,000 cycles the loads were increased every 5000 cycles. Other groups have suggested already similar protocols for dynamic testing of single screws with increasing load [45][46][47].…”

Section: Discussionmentioning

confidence: 99%

A pedicle screw system and a lamina hook system provide similar primary and long-term stability: a biomechanical in vitro study with quasi-static and dynamic loading conditions

et al. 2016

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Purpose For the stabilization of the thoracolumbar spine area, various stabilization techniques have been developed in recent decades. The aim of these techniques is to immobilize the treated segment to repositioning or correct the spine and guaranty long-term stability to achieve a reliable fusion. The aim of this study was to simulate in an in vitro experiment the postoperative long-term situation in elderly osteoporotic patients to compare two different stabilization principles; a pedicle screw system and a lamina hook system. Methods Two comparable groups with respect to age and bone mineral density with each n = 6 fresh-frozen human, bi-segmental thoracolumbar spine specimens (T11-L1) were used. Antero-posterior and lateral radiographs were taken before the test, to assess the spinal status. Then the intact specimens were biomechanically characterized with pure moments in the three anatomical planes in different states in terms of range of motion and neutral zone. After implantation of either, a pedicle screw system or a lamina hook system, the primary stability was determined under the same conditions. Subsequently the specimens were cyclically loaded under complex loading, using a custommade set-up in a dynamic materials testing machine with increasing moments from 3 to 66 Nm until 100,000 cycles or until one of the three defined ''failure'' criteria was reached.(1) A failure of a bony structure. (2) Exceeding of the threefold ROM of the primary stability after implantation in flexion plus extension. (3) Reaching of the ROM based on the intact state before implantation both in flexion plus extension.Results The results showed that the ROM was strongly reduced after instrumentation similar for both implant systems in all motion planes. The highest stabilization was found in flexion/extension. During cyclic loading with increasing moments, the ROM increased continuously for both systems. The number of load cycles until one of the failure criteria was reached varied only slightly between the two groups. In the pedicle screw group 30,000 (median) loading cycles (range 5000-80,000) with a corresponding moment of 24 Nm (range 9-54) could be reached. In the lamina hook group 32,500 load cycles (range 20,000-45,000) could be achieved with a corresponding moment of 25.5 Nm (range 18-33). There was a slight trend that the pedicle screw system is influenced more by bone mineral density. Conclusion Both implant systems provide similar primary stability and similar long-term stability. In the pedicle screw group, there was a stronger correlation between bone mineral density and the reached number of load cycles.

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The effect of in situ augmentation on implant anchorage in proximal humeral head fractures

Cited by 92 publications

References 22 publications

Biomechanical evaluation of straight antegrade nailing in proximal humeral fractures: the rationale of the “proximal anchoring point”

Biomechanical evaluation of straight antegrade nailing in proximal humeral fractures: the rationale of the “proximal anchoring point”

Timing of PMMA cement application for pedicle screw augmentation affects screw anchorage

A pedicle screw system and a lamina hook system provide similar primary and long-term stability: a biomechanical in vitro study with quasi-static and dynamic loading conditions

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