Tendinopathies of the Extensor Carpi Ulnaris

Abstract

To improve its mechanical advantage, the extensor carpi ulnaris (ECU) muscle uses, as if it was a pulley, the 6^th extensor compartment, a dorsal fibro-osseous tunnel formed by the ulnar sulcus and the ECU tendon sub-sheath. Rupture or insufficiency of that sheath may allow anteromedial ECU tendon subluxation and subsequent destabilization of the distal radioulnar and ulnocarpal joints. Sometimes, it is not sheath problem, but excessive friction between the sheath and the tendon what causes a painful degeneration of the tendon (tendinosis) with or without tendon entrapment. The term “ECU tendinopathy” has been chosen to designate all painful ECU anomalies resulting from a dysfunctional 6^th extensor compartment. ECU tendinopathies are frequent among sportsmen using bats, sticks or clubs. There are 2 major types of tendinopathy: 1) constrained tendinopathies, where there is entrapment of a thickened overused tendon, and 2) unconstrained tendinopathies, where a ruptured ECU sub-sheath allows the ECU to sublux in a volar direction, a position precluding all its stabilizing potential. In the first type, the goal of the treatment is to avoid further degeneration and subsequent rupture of the diseased tendon; in the second, to re-establish the normal connections between the ulna and the ECU tendon. This article reviews the management of the most frequent ECU tendinopathies.

Zusammenfassung

Zur Optimierung seines mechanischen Nutzeffektes verwendet der M. extensor carpi ulnaris (ECU) das 6. Strecksehnenfach, einen osteofibrösen Gleitkanal bestehend aus einer Rinne im Ellenkopf (ulnar sulcus) und einer Sehnenscheide (ECU tendon sub-sheath), die unabhängig vom Retinaculum extensorum ist, wie ein Ringband. Bei Insuffizienz und Ruptur dieser Sehnenscheide kann die ECU-Sehne nach anteriormedial subluxieren und es in Folge zur Destabilisation des distalen Radioulnargelenkes und der ulnokapalen Gelenke kommen. Auch bei intakten Sehnenscheide kann es zu schmerzhafter Degeneration der ECU-Sehne kommen, mit und ohne Blockierungen. Der Terminus “ECU-Tendinopathie” beschreibt schmerzhafte Zustände der ECU-Sehne in Folge einer Fehlfunktion des 6. Strecksehnenfaches. ECU-Tendinopathien werden häufig bei Schlagsportarten beobachtet. 2 Hauptformen sind zu unterscheiden: 1) Sehnenscheidenengen bei verdickter ECU-Sehne infolge einer Überbeanspruchung und 2) Rupturen der ECU-Sehnenscheide mit Subluxation der ECU-Sehne nach palmar und Verlust der stabilisierenden Wirkung der Sehne. Im ersteren Falle gilt es die weitere Degeneration und letztlich die Ruptur der Sehne zu verhindern; im zweiten Fall die ECU-Sehne zu reponieren und die normale anatomische Beziehung zwischen ECU-Sehne und Ulnakopf wieder herzustellen. Dieser Artikel gibt einen Überblick über die häufigsten Tendinopathien der ECU-Sehne.

Key words

Dislocation of the ECU tendon - ECU tendon sub-sheath - ECU tendinopathy - Extensor retinaculum - 6^th extensor compartment

Schlüsselwörter

Dislokation der ECU-Sehne - ECU-Sehnenscheide (sub-sheath) - ECU-Tendinopathie - Extensor retinaculum - 6. Strecksehnenfach

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