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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

Test setup. The specimen is placed on a seesaw for physiological force transmission. Marker-sets for optical motion tracking are attached to all fragments. Left and middle: Setup for flexion test with angulation of the shaft of 75° to the vertical. Right: Setup for extension test with 15° angulation to the vertical. The vertical reaction force of the seesaw is indicated by F.
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Figure 2: Test setup. The specimen is placed on a seesaw for physiological force transmission. Marker-sets for optical motion tracking are attached to all fragments. Left and middle: Setup for flexion test with angulation of the shaft of 75° to the vertical. Right: Setup for extension test with 15° angulation to the vertical. The vertical reaction force of the seesaw is indicated by F.

Mentions: Generally, the methodology for biomechanical testing was based on an earlier publication with certain modifications [11]. The specimens were cut proximally to a total length of 160 mm. 60 mm of the proximal end were embedded in Polymethylmethacrylate (Beracryl, W. Troller AG, Fulenbach, Switzerland) to fix the specimen to the actuator of a servo-hydraulic testing machine (MTS 858 Minibionix II, MTS Systems, Minneapolis, MN, USA, 4 kN loadcell). Distally, the Capitellum and Trochlea notch rested on a seesaw with two anatomically shaped supports covered with a layer of silicone to avoid peak stress at the contact points. Eccentric positioning of the supports with respect to the rotational axis of the seesaw enabled physiological force distribution of 60% at the Capitellum and 40% at the Trochlea [11,21,22] (Fig. 2). A cross-table was positioned below the seesaw to eliminate shear forces.


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)

Test setup. The specimen is placed on a seesaw for physiological force transmission. Marker-sets for optical motion tracking are attached to all fragments. Left and middle: Setup for flexion test with angulation of the shaft of 75° to the vertical. Right: Setup for extension test with 15° angulation to the vertical. The vertical reaction force of the seesaw is indicated by F.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Test setup. The specimen is placed on a seesaw for physiological force transmission. Marker-sets for optical motion tracking are attached to all fragments. Left and middle: Setup for flexion test with angulation of the shaft of 75° to the vertical. Right: Setup for extension test with 15° angulation to the vertical. The vertical reaction force of the seesaw is indicated by F.
Mentions: Generally, the methodology for biomechanical testing was based on an earlier publication with certain modifications [11]. The specimens were cut proximally to a total length of 160 mm. 60 mm of the proximal end were embedded in Polymethylmethacrylate (Beracryl, W. Troller AG, Fulenbach, Switzerland) to fix the specimen to the actuator of a servo-hydraulic testing machine (MTS 858 Minibionix II, MTS Systems, Minneapolis, MN, USA, 4 kN loadcell). Distally, the Capitellum and Trochlea notch rested on a seesaw with two anatomically shaped supports covered with a layer of silicone to avoid peak stress at the contact points. Eccentric positioning of the supports with respect to the rotational axis of the seesaw enabled physiological force distribution of 60% at the Capitellum and 40% at the Trochlea [11,21,22] (Fig. 2). A cross-table was positioned below the seesaw to eliminate shear forces.

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