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Research Papers

Comparative Evaluation of a Positive-Locking Antirotation Mechanism in the Design of Telescopic Nails for Patients in the Growth Phase

[+] Author and Article Information
Jens Rolf Franz Lakomy

Department of Orthopedics
and Tumor Orthopedics,
Muenster University Hospital,
Albert-Schweitzer-Campus 1,
Muenster 48149, Germany
e-mail: jens.lakomy@t-online.de

Bjoern Vogt

Department of Orthopedics
and Tumor Orthopedics,
Muenster University Hospital,
Albert-Schweitzer-Campus 1,
Muenster 48149, Germany
e-mail: bjoern.vogt@ukmuenster.de

Georg Gosheger

Department of Orthopedics
and Tumor Orthopedics,
Muenster University Hospital,
Albert-Schweitzer-Campus 1,
Muenster 48149, Germany
e-mail: ortho@ukmuenster.de

Robert Rödl

Muenster University Hospital,
Albert-Schweitzer-Campus 1,
Muenster 48149, Germany
e-mail: kinderorthopaedie@uni-muenster.de

Dirk Wähnert

Muenster University Hospital,
Albert-Schweitzer-Campus 1,
Muenster 48149, Germany
e-mail: Dirk.waehnert@ukmuenster.de

Frank Schiedel

Department of Pediatric Orthopedics
and Deformity Correction,
Clemenshospital Muenster,
Duesbergweg 124,
Muenster 48153, Germany
e-mail: frank.schiedel@t-online.de

Manuscript received September 15, 2016; final manuscript received April 7, 2017; published online June 27, 2017. Assoc. Editor: Chris Rylander.

J. Med. Devices 11(3), 031008 (Jun 27, 2017) (7 pages) Paper No: MED-16-1320; doi: 10.1115/1.4036650 History: Received September 15, 2016; Revised April 07, 2017

The aim of this study is to develop an intramedullary telescopic nail that—in contrast to the current standard—is rotationally stable and firmly anchored in the bone proximally and distally, without containing any extraosseous components that may alter the surrounding soft tissue. Three prototypes for a positive-locking adapted telescopic intramedullary nail (PLATIN) were developed. In a series of biomechanical tests, the prototypes were compared with two Fassier–Duval telescopic nails, which represent the clinical standard. Axial pressure, torsion, and four-point bending measurements were carried out in a materials testing machine, with the telescopic nails implanted into composite bone. Tests were conducted without failure and up to failure. Specifically, the force required for telescoping, as well as torsional stiffness and bending stiffness, was investigated. Taking into account differences that were inherent in the materials, the prototypes showed similar results in the four-point bending tests. In the pressure tests, the prototypes required greater forces than the Fassier–Duval nails. The torsional stiffness was between 0.020 N·m/deg and 0.135 N·m/deg, depending on the diameter of the nail. Positive-locking effect was achieved by a hexagonal shape of an inner rod part and a hexagonal form-fitting outer tube part. Proximal and distal locking of the telescopic nail in the bone was performed by usage of K-Wires in specific arranged drill holes at the end of both parts. Based on these satisfactory results, the future clinical application of positive-locking irrotational telescopic nails can be expected. Furthermore, redesign or development of new designs for existing telescopic nails is recommended.

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References

Figures

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Fig. 1

The cross section of PR3

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Fig. 2

The thread on the female part of the PR5 prototype, with a K-wire for transverse locking

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Fig. 3

The male end of the PR5

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Fig. 4

Sawbone with central osteotomy, showing the connections to the materials testing machine and supports for the four-point bending test

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Fig. 5

Experimental setup for the four-point bending test

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Fig. 6

Anteroposterior radiograph of the untested PR50 with transverse locking

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Fig. 7

Comparison of means in the axial compression tests for test nails PR30, FD32, PR50, FD48, and PR50, with standard deviation. The asterisks (*) indicate the testing of the values for PR30 and DF32 (left) and of PR50 and FD48 (right) for significant differences, using the Mann–Whitney U test. Highly significant differences were found in both cases, at P < 0.0001.

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Fig. 8

Means for torsional stiffness (bars) and bending stiffness (points) for test nails PR30, FD32, PR50, FD48, and PR60. The two brackets indicate the statistical test for differences between PR30 and FD32 and between PR50 and FD48 using the Mann–Whitney U test. No significant differences were found.

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Fig. 9

Bent 1 mm and 2 mm K-wire of PR 60 after torsion test up to failure

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