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Treatment of distal humeral fractures using conventional implants. Biomechanical evaluation of a new implant configuration.

Windolf M, Maza ER, Gueorguiev B, Braunstein V, Schwieger K - BMC Musculoskelet Disord (2010)

Bottom Line: Compared to the LCP constructs, the "Frame" technique revealed significant higher construct stiffness in extension of the arm (P = 0.01).The stiffness in flexion was not significantly different (P = 0.16).Number of cycles to failure was found significantly larger for the "Frame" technique (P = 0.01).

View Article: PubMed Central - HTML - PubMed

Affiliation: AO Research Institute, AO Foundation, Clavadelerstrasse 8, 7270 Davos, Switzerland. markus.windolf@aofoundation.org

ABSTRACT

Background: In the face of costly fixation hardware with varying performance for treatment of distal humeral fractures, a novel technique (U-Frame) is proposed using conventional implants in a 180 degrees plate arrangement. In this in-vitro study the biomechanical stability of this method was compared with the established technique which utilizes angular stable locking compression plates (LCP) in a 90 degrees configuration.

Methods: An unstable distal 3-part fracture (AO 13-C2.3) was created in eight pairs of human cadaveric humeri. All bone pairs were operated with either the "Frame" technique, where two parallel plates are distally interconnected, or with the LCP technique. The specimens were cyclically loaded in simulated flexion and extension of the arm until failure of the construct occurred. Motion of all fragments was tracked by means of optical motion capturing. Construct stiffness and cycles to failure were identified for all specimens.

Results: Compared to the LCP constructs, the "Frame" technique revealed significant higher construct stiffness in extension of the arm (P = 0.01). The stiffness in flexion was not significantly different (P = 0.16). Number of cycles to failure was found significantly larger for the "Frame" technique (P = 0.01).

Conclusions: In an in-vitro context the proposed method offers enhanced biomechanical stability and at the same time significantly reduces implant costs.

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Related in: MedlinePlus

Testing protocol. First 2500 test-cycles were performed in flexion between 15 and 100 N. Cycles 2500 to 7500 were performed in extension between 15 and 150 N. To provoke fatigue failure, the load was then monotonically increased at 0.1 N/cycle. Stiffness was evaluated from quasi-static ramps at 0, 2500 and 7500 cycles as indicated by yellow bars.
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Figure 3: Testing protocol. First 2500 test-cycles were performed in flexion between 15 and 100 N. Cycles 2500 to 7500 were performed in extension between 15 and 150 N. To provoke fatigue failure, the load was then monotonically increased at 0.1 N/cycle. Stiffness was evaluated from quasi-static ramps at 0, 2500 and 7500 cycles as indicated by yellow bars.

Mentions: All specimens were tested successively in simulated flexion and extension of the arm. For the flexion test the functional axis of the humerus was rotated 75° to the vertical towards posterior (Fig. 2). At the beginning of the test, a quasi-static loading ramp was applied at 15 N/s with a vertical force vector to assess construct stiffness. Sinusoidal loading was then performed between 15 N and 100 N for 2500 cycles. Subsequently, the humeral shaft angle was reduced to 15° simulating extension (Fig. 2). Another quasi-static loading ramp was applied and additional 5000 load cycles of 15 N to 150 N were performed. In case no severe failure of the construct occurred, construct stiffness was again measured with a quasi-static ramp and cyclic loading was continued with monotonically increasing peak force (0.1 N/cycle) [23] until severe failure of the sample became obvious. The load valley was maintained constant at 15 N. All cyclic tests were carried out at 2 Hz. The testing protocol is visualized in Fig. 3.


Treatment of distal humeral fractures using conventional implants. Biomechanical evaluation of a new implant configuration.

Windolf M, Maza ER, Gueorguiev B, Braunstein V, Schwieger K - BMC Musculoskelet Disord (2010)

Testing protocol. First 2500 test-cycles were performed in flexion between 15 and 100 N. Cycles 2500 to 7500 were performed in extension between 15 and 150 N. To provoke fatigue failure, the load was then monotonically increased at 0.1 N/cycle. Stiffness was evaluated from quasi-static ramps at 0, 2500 and 7500 cycles as indicated by yellow bars.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2921352&req=5

Figure 3: Testing protocol. First 2500 test-cycles were performed in flexion between 15 and 100 N. Cycles 2500 to 7500 were performed in extension between 15 and 150 N. To provoke fatigue failure, the load was then monotonically increased at 0.1 N/cycle. Stiffness was evaluated from quasi-static ramps at 0, 2500 and 7500 cycles as indicated by yellow bars.
Mentions: All specimens were tested successively in simulated flexion and extension of the arm. For the flexion test the functional axis of the humerus was rotated 75° to the vertical towards posterior (Fig. 2). At the beginning of the test, a quasi-static loading ramp was applied at 15 N/s with a vertical force vector to assess construct stiffness. Sinusoidal loading was then performed between 15 N and 100 N for 2500 cycles. Subsequently, the humeral shaft angle was reduced to 15° simulating extension (Fig. 2). Another quasi-static loading ramp was applied and additional 5000 load cycles of 15 N to 150 N were performed. In case no severe failure of the construct occurred, construct stiffness was again measured with a quasi-static ramp and cyclic loading was continued with monotonically increasing peak force (0.1 N/cycle) [23] until severe failure of the sample became obvious. The load valley was maintained constant at 15 N. All cyclic tests were carried out at 2 Hz. The testing protocol is visualized in Fig. 3.

Bottom Line: Compared to the LCP constructs, the "Frame" technique revealed significant higher construct stiffness in extension of the arm (P = 0.01).The stiffness in flexion was not significantly different (P = 0.16).Number of cycles to failure was found significantly larger for the "Frame" technique (P = 0.01).

View Article: PubMed Central - HTML - PubMed

Affiliation: AO Research Institute, AO Foundation, Clavadelerstrasse 8, 7270 Davos, Switzerland. markus.windolf@aofoundation.org

ABSTRACT

Background: In the face of costly fixation hardware with varying performance for treatment of distal humeral fractures, a novel technique (U-Frame) is proposed using conventional implants in a 180 degrees plate arrangement. In this in-vitro study the biomechanical stability of this method was compared with the established technique which utilizes angular stable locking compression plates (LCP) in a 90 degrees configuration.

Methods: An unstable distal 3-part fracture (AO 13-C2.3) was created in eight pairs of human cadaveric humeri. All bone pairs were operated with either the "Frame" technique, where two parallel plates are distally interconnected, or with the LCP technique. The specimens were cyclically loaded in simulated flexion and extension of the arm until failure of the construct occurred. Motion of all fragments was tracked by means of optical motion capturing. Construct stiffness and cycles to failure were identified for all specimens.

Results: Compared to the LCP constructs, the "Frame" technique revealed significant higher construct stiffness in extension of the arm (P = 0.01). The stiffness in flexion was not significantly different (P = 0.16). Number of cycles to failure was found significantly larger for the "Frame" technique (P = 0.01).

Conclusions: In an in-vitro context the proposed method offers enhanced biomechanical stability and at the same time significantly reduces implant costs.

Show MeSH
Related in: MedlinePlus