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14th Triennial Congress of the International Federation of Societies for Surgery of the Hand (IFSSH), 11th Triennial Congress of the International Federation of Societies for Hand Therapy (IFSHT)

17.06. - 21.06.2019, Berlin

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Ideal cup position in trapeziometacarpal joint arthroplasty: a biomechanical cadaver study

Meeting Abstract

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  • presenting/speaker Annelien Brauns - ZOL Genk, Genk, Belgium
  • Pieter Caekebeke - ZOL Genk, Genk, Belgium
  • Joris Duerinckx - ZOL Genk, Genk, Belgium

International Federation of Societies for Surgery of the Hand. International Federation of Societies for Hand Therapy. 14th Triennial Congress of the International Federation of Societies for Surgery of the Hand (IFSSH), 11th Triennial Congress of the International Federation of Societies for Hand Therapy (IFSHT), 11th Triennial Congress of the International Federation of Societies for Hand Therapy (IFSHT). Berlin, 17.-21.06.2019. Düsseldorf: German Medical Science GMS Publishing House; 2020. DocIFSSH19-698

doi: 10.3205/19ifssh1133, urn:nbn:de:0183-19ifssh11336

Published: February 6, 2020

© 2020 Brauns et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.

Outline

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Objectives/Interrogation: It has been suggested that in trapeziometacarpal total joint arthroplasty, the trapezial cup should be positioned parallel to the proximal articular surface of the trapezium (PAST). This suggestion was based on radiographic measurement of the range of motion of healthy joints. The goal of this study was to biomechanically test this statement.

Methods: 7 fresh frozen cadaver hands were mounted in a test jig and the different thumb musculotendinous units were loaded. An Arpe metacarpal stem was implanted and combined with 3D-printed trapezium cups. These cups were available in 17 different inclinations relative to the PAST (neutral and 10°, 20°, 30° or 40° of palmar, dorsal, lateral or medial inclination). For every cup inclination, stability of the prosthesis was assessed through its entire passive range of motion (flexion, extension, abduction, adduction, retropulsion and opposition). Outcome was dislocation or not. All these measurements were performed with both 15° offset and straight necks. Logistic regression was used to determine the odds ratio for dislocation and its significance for the different oblique cup inclinations compared with neutral cup placement.

Results and Conclusions: With the cup in neutral position relative to the PAST, no dislocations were observed in any direction of thumb motion. In flexion, a significantly higher dislocation rate was observed when an offset neck was combined with the cup in 30° or more of dorsal inclination. Using a straight neck increased the risk of dislocation, starting at 10° of dorsal cup inclination. In opposition, the number of dislocations was significantly higher when a straight neck was combined with the cup in 10° or more of dorsal inclination, an offset neck with the cup in 20° or more of dorsal inclination, or both stem types with the cup in 30° or more of medial inclination. In adduction and retropulsion the prosthetic joint dislocated with the cup in 30° or more of lateral inclination.

Cup inclination is an important factor in prosthetic joint stability. Ideally the cup should be placed parallel to the PAST. Flexion and opposition are the motions that are most prone for dislocation. We recommend the use of an offset neck and to avoid placement of the cup in dorsal inclination relative to the PAST.