Arthroscopically Assisted Ulnar Shortening

Published on 11/04/2015 by admin

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Last modified 11/04/2015

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CHAPTER 3 Arthroscopically Assisted Ulnar Shortening

Daniel J. Nagle

To my son, Peter

Basic Science and Anatomy

Ulnocarpal Joint Anatomy

The base of the triangular fibrocartilage attaches to the distal radius at the distal edge of the sigmoid notch. Its distal surface blends imperceptibly with the hyalin cartilage of the lunate fossa of the distal radius. The triangular fibrocartilage narrows as it passes from radial to ulnar to insert in the fovea at the base of the ulnar styloid. Dorsally and palmarly, the TFCC thickens to form the distal radioulnar ligaments. The integrity of these two ligaments is critical to the stability of the distal radioulnar joint. The triangular fibrocartilage meniscal homologue passes distally to attach at the ulnar aspect of the triquetrum. The interval between the ulnotriquetral ligament and the meniscal homologue and ulnar collateral ligament is known as the pre-styloid recess (or the pisotriquetral recess).1

Biomechanics

Palmer and others have demonstrated an inverse relationship between the thickness of the triangular fibrocartilage and ulnar variance.2 That is, the more positive the ulnar variance the thinner the triangular fibrocartilage. This relationship explains the observed coincidence of ulnar plus variance and TFCC tears (ulnar abutment syndrome). The ulnar abutment syndrome is characterized by an ulnar plus variance, central tears of the triangular fibrocartilage, and chondromalacia of the adjacent articular surfaces of the lunate, triquetrum, and ulnar head.

Werner et al.3 have studied the effect of ulnar length on load transmission across the triangular fibrocartilage. They demonstrated a direct relationship between the length of the ulna and the amount of force transmitted across the TFCC. As the ulna gets longer, the force transmitted across the TFCC increases. The opposite occurs with ulnar shortening.

The vascular supply of the triangular fibrocartilage is characterized by a peripheral vascular zone and a central avascular zone.4 The lack of central blood supply precludes any healing of central TFCC tears and dictates the choice of debridement as the treatment for such tears.

Indications

Patients presenting with a symptomatic triangular fibrocartilage complex (TFCC) tear, either acute or chronic, in combination with an ulnar zero or ulnar plus variance are unlikely to respond to a simple debridement of the TFCC. These patients are suffering from an ulnar abutment syndrome in which the TFCC is “pinched” between the ulnar head and the proximal surface of the lunate. Such patients are candidates for arthroscopic debridement of the TFCC combined with an arthroscopic ulnar shortening.

Contraindications

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