Radiocarpal Instability

Fig. 1

(a, b) Extrinsic ligaments form a double pronosupinator helix. This helix is particularly apparent on pronosupination against resistance

The pronator helix is activated by active pronation against resistance or passive carpal supination. It originates on the posterior border of the radius and joins the posterior border of the triquetrum ulnarly and is composed mainly of the dorsal radiotriquetral ligament. It is prolonged palmarly by the triquetrocapitate ligament then by the thick capitotrapeziotrapezoidal complex. The supinator helix is activated by active supination against resistance or passive carpal pronation. It originates on the anterolateral border of the radius with the radioscaphocapitate ligament, prolonged by the palmar capitotriquetral ligament. On the dorsal aspect of the carpus, it is continuous with the transverse dorsal carpal ligament by a ligament band that joins the triquetrum to the trapezoid. This band is more apparent on active supination against resistance.

In a 1995 cadaveric study, Ritt et al. [7] resumed the previous work to study the rotational carpal stability with respect to the radius. He released the anatomic structures activated by a rotational radiocarpal moment arm. When a pronatory moment arm is exerted at the carpal condyle, the radioscaphocapitate ligament is the first to be solicited.

The long and short radiolunate ligaments play a secondary role.

The dorsal radiocarpal ligament is the principal ligament to oppose carpal supination.

Ritt emphasizes that the action of these ligaments depends on the position of the forearm in pronosupination. The ligaments originating from the ulna can be activated by radiocarpal rotation depending on the position of the forearm in pronosupination.

Such is the case for the palmar ulnolunate ligament which essentially resists carpal supination but its action varies according to the pronosupination of the forearm.

The work of Ritt [7, 8] and ours [4–6] show the adaptation of the entire radiocarpal and intracarpal ligamentous structure to the pronosupinator forces the wrist is subjected to.

3 Clinical Test

Since 1992, we use a simple clinical test that activates the previously described ligaments [4–6]. It consists of exerting a distal passive pronosupination force while maintaining midpronation of both forearm bones (Fig. 2).

Fig. 2

The test for evaluation of radiometacarpal rotation is a systematic part of our clinical wrist examination, particularly useful if an extrinsic capsular ligament sprain is suspected. (a) The forearm is held in midpronation with one hand while the other hand is used to rotate the carpal condyle longitudinally into pronation. (b) In supination

This test has become systematic for clinical examination of wrist ‘sprains’. Palmar pain provoked by passive pronation of the carpus suggests a radioscaphoid ligament lesion. This test is also positive in scaphoid fractures. Verdan used a similar test holding the hand while the patient tries to actively supinate the forearm. Palmar and palmar radial wrist pain evoked corresponds to the radioscaphocapitate ligament pressing on the fracture site. It suggests a scaphoid fracture.

The passive carpal supination activates dorsal radiotriquetral ligament and is positive in case of radiotriquetral sprain.

Clinical experience led us to consider results of this test during wrist immobilization [9]. In function of results of this test, we suggest immobilization in slight carpal supination or pronation. This position is independent of the pronosupination of the forearm. We have used this principle for the orthopaedic/closed treatment of dorsal flake triquetral fractures. These fractures are the equivalent of sprain of the dorsal radiotriquetral ligament when this test is positive – this is almost always the case in our experience. For scaphoid fractures and palmar sprains painful in carpal pronation, we place the wrist in mild supination.

4 Radiocarpal Rotatory Instability in Supination

Radiocarpal rotatory instability in supination is defined by increased rotation of the carpal condyle over the distal radius compared to the other side. The clinical test is done symmetrically with one hand holding the forearm in midpronation while the other hand exerts longitudinal rotation in supination at the carpal condyle. In certain cases, simple observation of the wrist shows carpal supination on the distal radius (Fig. 3).

Fig. 3

(a) Carpal supination is difficult to observe in case of isolated rupture of the dorsal radiotriquetral ligament. This patient presents with a mild carpal supination of the right wrist following radiotriquetral ligament rupture. (b) The carpal supination deformity is apparent in rheumatoid affection or when rupture of ulnocarpal ligaments is associated. Palmar dislocation of the radius with respect to the ulna exacerbates the supination deformity of the carpus

5 Anatomical Reminder

The dorsal radiotriquetral ligament inserts onto the dorsal distal surface of the radius (Fig. 4). Exactly at the dorsal border of the articular surface of the radius, extending from the tubercle of Lister to the sigmoid fossa. It has an oblique pathway passing ulnarly over the posterior horn of the lunate where its deep fibres are attached. These fibres are the reason why the name dorsal radiocarpal ligament is preferred to radiotriquetral. They strengthen the dorsal portion of the lunotriquetral ligament and insert distally on the dorsum of the triquetrum where the ligament merges with the insertion of the dorsal intercarpal ligament. Viegas et al. [10] described the anatomic variations of this ligament but the radiotriquetral fibres are constant.

Fig. 4

Dorsal radiotriquetral ligament resists carpal supination. According to Viegas, the radiotriquetral fibres are constant, and in 99 % of cases some fibres terminate on the lunate

6 Clinical Experience

Since 1998, we have operated four patients for rotatory radiocarpal instability in supination. To us, this is synonymous with dorsal radiotriquetral ligament insufficiency. We have treated this instability by reconstructing this ligament using extensor retinaculum.

The series includes four men with wrist trauma after a fall. In three cases, the fall was backwards with torsion and supination of the carpus in one case. All cases had posttraumatic oedema. Three patients had radiograms and immobilization, two in a plaster for 3 weeks and one in resin for 1 month. One patient had ignored his initial trauma.

The four patients presented with ulnar wrist pain and acute tenderness on the posterior triquetrum. The radiometacarpal rotation test was positive with pain which increased on carpal supination. In three cases, there was increased radiocarpal rotation in supination compared to the contralateral side. In one case the test was equivocal but the pain sharp. There was no lunotriquetral instability clinically. The radiolunate joint was free with complete pronosupination of the wrist, and normal ROM in other planes with tenderness at extremes of range of motion being the reason for consultation. Patients also complained of a loss of grip strength, measured at 65 % of the contralateral side.

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