Yonsei Med J.  2015 Jan;56(1):154-158. 10.3349/ymj.2015.56.1.154.

Effect of the Starting Point of Half-Pin Insertion on the Insertional Torque of the Pin at the Tibia

• Kim SJ
• Kim SH
• Kim YH
• Chun YM

• KMID: 2352801
• DOI: http://doi.org/10.3349/ymj.2015.56.1.154

Abstract

PURPOSE
The authors have observed a failure to achieve secure fixation in elderly patients when inserting a half-pin at the anteromedial surface of the tibia. The purpose of this study was to compare two methods for inserting a half-pin at tibia diaphysis in elderly patients.
MATERIALS AND METHODS
Twenty cadaveric tibias were divided into Group C or V. A half-pin was inserted into the tibias of Group C via the conventional method, from the anteromedial surface to the interosseous border of the tibia diaphysis, and into the tibias of Group V via the vertical method, from the anterior border to the posterior surface at the same level. The maximum insertion torque was measured during the bicortical insertion with a torque driver. The thickness of the cortex was measured by micro-computed tomography. The relationship between the thickness of the cortex engaged and the insertion torque was investigated.
RESULTS
The maximum insertion torque and the thickness of the cortex were significantly higher in Group V than Group C. Both groups exhibited a statistically significant linear correlation between torque and thickness by Spearman's rank correlation analysis.
CONCLUSION
Half-pins inserted by the vertical method achieved purchase of more cortex than those inserted by the conventional method. Considering that cortical thickness and insertion torque in Group V were significantly greater than those in Group C, we suggest that the vertical method of half-pin insertion may be an alternative to the conventional method in elderly patients.

Keyword

Fracture; tibia; diaphysis; external fixation

MeSH Terms

Aged
Aged, 80 and over
*Bone Nails
Bone Screws
Diaphyses/radiography/surgery
*External Fixators
Female
Humans
Male
Tibia/radiography/*surgery
*Torque
X-Ray Microtomography

Figure

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  Fig. 1 Cross-section of the right tibia diaphysis. A, anterior border; I, interosseous border; M, medial border.

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  Fig. 2 Schanz screw (5.0×120-mm; thread length=40 mm).

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  Fig. 3 Orientation of Schanz screws inserted by the conventional method and vertical method. C, conventional method, from the anteromedial surface to the interosseous border; V, vertical method, from the anterior border to the posterior surface.

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  Fig. 4 Torque driver for measuring the insertion torque of the Schanz screws.

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  Fig. 5 Cortical thickness at the cross-section of the tibia diaphysis. A, anterior border of the tibia; M, medial border; I, interosseous border. Blue arrow: cortical thickness in Group C. Red arrow: cortical thickness in Group V.

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