gms | German Medical Science

54. Jahrestagung der Norddeutschen Orthopädenvereinigung e. V.

Norddeutsche Orthopädenvereinigung

16.06. bis 18.06.2005, Hamburg

The biomechanics of the metacarpophalangeal joint after surface replacement arthroplasty

Meeting Abstract

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  • corresponding author H.C. Fayaz - Johanna-Etienne-Krankenhaus, Klinik für Orthopädie und Orthopädische Chirurgie, Neuss

Norddeutsche Orthopädenvereinigung. 54. Jahrestagung der Norddeutschen Orthopädenvereinigung e.V.. Hamburg, 16.-18.06.2005. Düsseldorf, Köln: German Medical Science; 2005. Doc05novFJW4

The electronic version of this article is the complete one and can be found online at:

Published: June 13, 2005

© 2005 Fayaz.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.




Prosthetic replacement of the MCP joint is selected for functional restoration of the affected hand in cases of joint destruction and soft tissue imbalance. Arthrodesis is generally not satisfactory in MCP joint reconstruction. The MCP joint arthroplasty will benefit from a total joint replacement, which can be used to treat the entire range of patient needs. The goal is to provide a total MCP prosthesis, which allows for stable fixation and durability, and accurately mimics the anatomy of the joint. The pyrolytic carbon implant (Ascension Orthopedics, Austin, TX) is designed to simulate the normal anatomy of the finger MCP joint. It is an unlinked MCP joint implant. A number of different implants and techniques have been described in literatur. Purpose: We examined the hypothesis that a resurfacing arthroplasty of the metacarpophalangeal (MCP) joint simulates normal anatomy, motion, and stability equal to the normal intact joint.

Material and Methods

We used eight fresh-frozen normal human cadaveric hands disarticulated through the carpometacarpal joints to measure stability of intact joint versus pyrolytic carbon MCP prosthesis as a resurfacing MCP joint prosthesis. A Magnetic Isotrak system was used to record motion and translation of the long finger MCP joint. Two plastic rods are cemented into the proximal second and fourth metacarpals fixing the hand to a testing frame which supports the hand unit. We transfixed the interphalangeal joints of the long finger using a plastic plate on the dorsum. We balanced the finger by respectively loading the FDP, FDS, EDC, and intrinsic tendons to the third finger, as well as the EDC tendons to the second and fourth fingers. One Isotrak sensor was fixed distally on the finger, the other to the mounting device. The source or reference sensor was fixed to the loading platform. In the first testing setup, we placed the hand with the dorsum side up, followed by radial and ulnar side up respectively. Passive then active flexion-extension movement of the MCP joint was performed first by moving the finger and then by changing the tendon loading. We tested for lateral and rotational stability of the MCP joint by increasing loads to 100, 200, and 300 gm placed at the end of the long finger. We tested the intact joint first, then repeated the procedure with a pyrolytic carbon implant, and followed by cutting the collateral ligament and repairment.


Translational and rotational stability following implant arthroplasty was similar following both pyrolytic carbon implant arthroplasty and collateral repairment. The mean of the maximum lateral angulation with 300 g of stress (9 N-cm) was 34° in intact specimens, 37° for the implants, 60° after undermining the collateral ligament and 42° for the collateral ligament repair, respectively. While the mean of the maximum rotational angulation with 300 g of stress (9 N-cm) was 13° in intact specimens, 33° for the implants, 48° after undermining the collateral ligament and 46° for the collateral ligament repair, respectively.


The study demonstrates that the resurfacing ascension implant was capable of duplicating normal joint motion and maintaining joint stability. In particular the amount of lateral stability was well maintained after both MCP replacement and following ligament repair. The results also indicate that the collateral ligament provides the primary stability of the MCP joint. Preservation or repair of the collateral ligament is essential to assist the prosthesis to resist volar subluxation during flexion.