gms | German Medical Science

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2013)

22.10. - 25.10.2013, Berlin

Automated quantitative fit assessment of tibial nail designs during insertion using 3D computer modelling

Meeting Abstract

  • presenting/speaker Jayani Amarathunga Arachchige - Queensland University of Technology, Kelvin Grove, Australia
  • Michael Schütz - Queensland University of Technology, Princess Alexandra Hospital, Department of Orthopaedics and Traumatology, Brisbane, Australia
  • Prasad Yarlagadda - Queensland University of Technology, Brisbane, Australia
  • Beat Schmutz - Queensland University of Technology, Kelvin Grove, Australia

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2013). Berlin, 22.-25.10.2013. Düsseldorf: German Medical Science GMS Publishing House; 2013. DocIN22-615

doi: 10.3205/13dkou015, urn:nbn:de:0183-13dkou0153

Veröffentlicht: 23. Oktober 2013

© 2013 Amarathunga Arachchige et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Objective: Intramedullary nailing is the standard fixation method for displaced diaphyseal fractures of the tibia in adults. The optimal nail design should be easy to insert and anatomically fit the bone geometry at its final position.

In a previous study, through a virtual manual fit quantification method, the authors have shown that the modified Expert Tibia Nail (ETN) fits better at its final position inside Japanese tibiae models compared to the ETN.

Therefore, the aim of this study was to, first develop a customised software tool to enable quantifying the anatomical fit during the insertion process, and second to determine whether the optimised ETN design is also easier to insert.

Methods: We used 3D models of two tibial nail designs (ETN and ETN-Proximal-Bend, Synthes), and fifteen CT based 3D cortex models of Japanese cadaver tibiae.

The fitting was quantified in terms of the total surface area, and the maximum distance (in axial plane) by which the nail was protruding from the medullary cavity of the virtual model.

The fit analysis tool was programmed (Matlab, The Mathworks) to automatically insert the nail model into the inner cortex surface at 15 mm increments until fully inserted. At each increment level, the optimal nail position (least area of protrusion) was obtained and quantified while keeping the proximal part of the nail centred at the nail entry point on the bone model.

The sums of protrusions, calculated at each increment level, were used to quantify the overall fitting of each design for a particular tibia model.

Results and conclusion: In all 15 bone models, the sums of total surface areas and maximum distances of the nail protruding from the medullary cavity were smaller for the ETN-Proximal-Bend (average: 2038 mm2, 6.3 mm) compared to the ETN (average: 2704 mm2, 8.9 mm). On average, the maximum protruding distance during insertion was 1.5 mm for the modified ETN versus 2.4 mm for the ETN. All the differences were statistically significant (p < 0.05). With the exception of one tibia, both nail desings could be inserted for at least the first half of the nail lenght without generating protrusions.

By developing a customised software tool we were able to conduct a quantitative anatomical 3D fit assessment of different nail designs during the insertion process.

The results clearly demonstrate that the modified ETN does not only fit significantly better at the final position, but is indeed overall also significantly easier to insert compared to the original ETN. Moreover, if at all, stress fractures are more likely to occur during the insertion of the second half of the nail for both designs.

The clinical implications of an improved anatomical fitting are: a reduction in malalignments of the fractured bone; less pain, a lower likelihood of stress fractures, and easier nail insertion. Additionally, this tool could potentially be suitable for pre-operative planning enabling the surgeon to choose the most appropriate nail design for the anatomy of a particular patient.