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Preliminary biomechanical study of different acetabular reinforcement devices for acetabular reconstruction.

Tai CL, Lee PY, Hsieh PH - PLoS ONE (2015)

Bottom Line: Initial stability was compared among the groups.In both compression and torsion experiments, the monoaxial interlocking construct demonstrated the highest construct stiffness (672.6 ± 84.1 N/mm in compression and 13.3 ± 1.0 N · m/degree in torsion), whereas the non-locked construct had the lowest construct stiffness (381.4 ± 117.2 N/mm in compression and 6.9 ± 2.1 N · m/degree in torsion) (P < 0.05).Our study demonstrates the potential benefit of adding a locking mechanism to an ARD.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Medical Mechatronics, Department of Mechanical Engineering, Chang Gung University, Kweishan, Taoyuan, Taiwan.

ABSTRACT

Background: Acetabular reinforcement devices (ARDs) are frequently used as load-sharing devices to allow allograft incorporation in revision hip arthroplasty with massive acetabular bone loss. The key to a successful reconstruction is robust fixation of the device to the host acetabulum. Interlocking fixation is expected to improve the initial stability of the postoperative construct. However, all commercially available ARDs are designed with non-locking fixation. This study investigates the efficacy of standard ARDs modified with locking screw mechanisms for improving stability in acetabular reconstruction.

Methods: Three types of ARDs were examined to evaluate the postoperative compression and angular stability: i) standard commercial ARDs, ii) standard ARDs modified with monoaxial and iii) standard ARDs modified with polyaxial locking screw mechanisms. All ARDs were implanted into osteomized synthetic pelvis with pelvic discontinuity. Axial compression and torsion tests were then performed using a servohydraulic material testing machine that measured load (angle) versus displacement (torque). Initial stability was compared among the groups.

Results: Equipping ARDs with interlocking mechanisms effectively improved the initial stability at the device/bone interface compared to standard non-locked ARDs. In both compression and torsion experiments, the monoaxial interlocking construct demonstrated the highest construct stiffness (672.6 ± 84.1 N/mm in compression and 13.3 ± 1.0 N · m/degree in torsion), whereas the non-locked construct had the lowest construct stiffness (381.4 ± 117.2 N/mm in compression and 6.9 ± 2.1 N · m/degree in torsion) (P < 0.05).

Conclusions: Our study demonstrates the potential benefit of adding a locking mechanism to an ARD. Polyaxial ARDs provide the surgeon with more flexibility in placing the screws at the cost of reduced mechanical performance. This in vitro study provides a preliminary evaluation of biomechanical performance for ARDs with or without interlocking mechanisms, actual clinical trial deserves to be further investigated in future studies.

No MeSH data available.


Related in: MedlinePlus

A schematic drawing (left) and a photograph (right) showing (A) a standard ARD and (B) a 5.0-mm compression screw.The screw hole in the ARD is smooth (without threads) and it can be fixed with standard compression screws.
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pone.0121588.g003: A schematic drawing (left) and a photograph (right) showing (A) a standard ARD and (B) a 5.0-mm compression screw.The screw hole in the ARD is smooth (without threads) and it can be fixed with standard compression screws.

Mentions: Three types of stainless ARDs with a uniform thickness of 3 mm were custom-manufactured using a computer numerically controlled (CNC) machine based on ZCA Acetabular Reconstruction Cages (EDI Code: E1141004, Zimmer Inc., Warsaw, Indiana, USA). The ARDs made of 316L stainless-steel were manufactured with different fixation mechanisms: standard (non-locked), monoaxial, and polyaxial locking. The screw holes of standard ARDs were smooth without threads (Fig. 3A) and fixed with standard compression screws (Fig. 3B). To create the monoaxial locking ARD, the standard ARD was modified with a monoaxial locking mechanism: the head of the locking screw was equipped with a thread, and a matching thread was made in the ARD in a unidirectional manner (Fig. 4). To create the polyaxial locking ARD, the standard ARD was modified with a polyaxial locking mechanism based on the non-contact bridging plate (NCB plate, Zimmer Inc., Warsaw, Indiana, USA). The head of the polyaxial locking screw was contoured to fit congruently into the reciprocal hole, and screw locking was achieved through the use of a locking cap that was threaded into the screw holes (Fig. 5).


Preliminary biomechanical study of different acetabular reinforcement devices for acetabular reconstruction.

Tai CL, Lee PY, Hsieh PH - PLoS ONE (2015)

A schematic drawing (left) and a photograph (right) showing (A) a standard ARD and (B) a 5.0-mm compression screw.The screw hole in the ARD is smooth (without threads) and it can be fixed with standard compression screws.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4370390&req=5

pone.0121588.g003: A schematic drawing (left) and a photograph (right) showing (A) a standard ARD and (B) a 5.0-mm compression screw.The screw hole in the ARD is smooth (without threads) and it can be fixed with standard compression screws.
Mentions: Three types of stainless ARDs with a uniform thickness of 3 mm were custom-manufactured using a computer numerically controlled (CNC) machine based on ZCA Acetabular Reconstruction Cages (EDI Code: E1141004, Zimmer Inc., Warsaw, Indiana, USA). The ARDs made of 316L stainless-steel were manufactured with different fixation mechanisms: standard (non-locked), monoaxial, and polyaxial locking. The screw holes of standard ARDs were smooth without threads (Fig. 3A) and fixed with standard compression screws (Fig. 3B). To create the monoaxial locking ARD, the standard ARD was modified with a monoaxial locking mechanism: the head of the locking screw was equipped with a thread, and a matching thread was made in the ARD in a unidirectional manner (Fig. 4). To create the polyaxial locking ARD, the standard ARD was modified with a polyaxial locking mechanism based on the non-contact bridging plate (NCB plate, Zimmer Inc., Warsaw, Indiana, USA). The head of the polyaxial locking screw was contoured to fit congruently into the reciprocal hole, and screw locking was achieved through the use of a locking cap that was threaded into the screw holes (Fig. 5).

Bottom Line: Initial stability was compared among the groups.In both compression and torsion experiments, the monoaxial interlocking construct demonstrated the highest construct stiffness (672.6 ± 84.1 N/mm in compression and 13.3 ± 1.0 N · m/degree in torsion), whereas the non-locked construct had the lowest construct stiffness (381.4 ± 117.2 N/mm in compression and 6.9 ± 2.1 N · m/degree in torsion) (P < 0.05).Our study demonstrates the potential benefit of adding a locking mechanism to an ARD.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Medical Mechatronics, Department of Mechanical Engineering, Chang Gung University, Kweishan, Taoyuan, Taiwan.

ABSTRACT

Background: Acetabular reinforcement devices (ARDs) are frequently used as load-sharing devices to allow allograft incorporation in revision hip arthroplasty with massive acetabular bone loss. The key to a successful reconstruction is robust fixation of the device to the host acetabulum. Interlocking fixation is expected to improve the initial stability of the postoperative construct. However, all commercially available ARDs are designed with non-locking fixation. This study investigates the efficacy of standard ARDs modified with locking screw mechanisms for improving stability in acetabular reconstruction.

Methods: Three types of ARDs were examined to evaluate the postoperative compression and angular stability: i) standard commercial ARDs, ii) standard ARDs modified with monoaxial and iii) standard ARDs modified with polyaxial locking screw mechanisms. All ARDs were implanted into osteomized synthetic pelvis with pelvic discontinuity. Axial compression and torsion tests were then performed using a servohydraulic material testing machine that measured load (angle) versus displacement (torque). Initial stability was compared among the groups.

Results: Equipping ARDs with interlocking mechanisms effectively improved the initial stability at the device/bone interface compared to standard non-locked ARDs. In both compression and torsion experiments, the monoaxial interlocking construct demonstrated the highest construct stiffness (672.6 ± 84.1 N/mm in compression and 13.3 ± 1.0 N · m/degree in torsion), whereas the non-locked construct had the lowest construct stiffness (381.4 ± 117.2 N/mm in compression and 6.9 ± 2.1 N · m/degree in torsion) (P < 0.05).

Conclusions: Our study demonstrates the potential benefit of adding a locking mechanism to an ARD. Polyaxial ARDs provide the surgeon with more flexibility in placing the screws at the cost of reduced mechanical performance. This in vitro study provides a preliminary evaluation of biomechanical performance for ARDs with or without interlocking mechanisms, actual clinical trial deserves to be further investigated in future studies.

No MeSH data available.


Related in: MedlinePlus