of Wrist Arthroscopy to the Study of the Intrinsic Ligaments

Fig. 1

Localisation of the scapholunate interosseous ligament thanks to palpation. The ligament is found during the exam of the radiocarpal interval: tonus in the interval between the scaphoid and semilunate is diminished. S scaphoid, L lunate

Fig. 2

Breach of the scapholunate interosseous ligament: the hook is introduced in the breach inside the ligament. S scaphoid, L lunate

3.2.3 The Pyramido-Lunate Interosseous Ligament

It is more difficult to locate than the previous one as there is no topographic reference. To locate it, the arthroscope has to be reintroduced by the 4/5 portal, and once again, palpation with the hook is often necessary.

3.3 Practice of Arthroscopic Dynamic Tests [13]

3.3.1 Dissociative Scapholunate Instabilities

Before any dynamic test, it is necessary to reduce the tension on the finger traps so as not to distort the interpretation by the artificial tension impressed on the extrinsic ligamentous structures induced by distraction. At the beginning of our experiment, we systematically used dynamic tests in the radiocarpal joint. The examining hook was introduced in a ligamentous breach and moved axially to try and separate the scaphoid from the semilunate, or the lunate from the triquetrum. In the same way, we made an ‘arthroscopic test of Watson’ as we dorsally pushed on the tubercle of the scaphoid to try and put forward a rotatory subluxation of the proximal pole of the scaphoid. Retrospectively, it becomes obvious that the analysis of these tests’ results is difficult, especially when the interval contains post-traumatic ligament remnants. Thus, these tests have now been abandoned and replaced by the midcarpal dynamic tests which interpretation is far easier.

In the midcarpal space, it is also possible to use the hook to estimate the stability of the scapholunate or the pyramido-lunate couples. To make these tests, the arthroscope is introduced by one of the midcarpal portals (RMC or UMC), and it visualises the junction of the scapholunate or pyramido-lunate distal facets. Normally, it is impossible to slip the hook in the interosseous scapholunate and pyramido-lunate intervals. When there is no instability, the hook can definitely not penetrate into the interosseous interval. If there is an instability, the hook can be pushed into the interosseous interval, towards the midcarpal. The axial movements that are impressed on it manage to move both osseous pieces apart (Figs. 3 and 4). The interosseous interval opens and makes the remnants of the interosseous ligament visible at the floor.

Figs. 3 and 4

Practice of dissociative dynamic tests in the scapholunate interval: the hook is introduced by the UMC portal and pushed towards the scapholunate interval. Axial movements are created to try and create a diastasis in the scapholunate interval. In the case of dissociative instability, the opening of the interval becomes clearly visible (see text)

At a further stage of instability, these dynamic manoeuvres with the hook even allow an opening which is wide enough to let the arthroscope go from the radiocarpal to the midcarpal space, through the ligamentous breach (Figs. 5, 6 and 7). However, this is only possible when the instability is further in the spectrum of injuries and can usually be established by a radiographic diagnosis.

Figs. 5, 6 and 7

Midcarpal view of the scapholunate base during dissociative tests: (Fig. 5) The scapholunate interval is perfectly congruent and ‘continent’. If there is a breach in the SLIOL, there is no instability. (Fig. 6) Moderate opening of the interval under the twisting motion applied to the hook. (Fig. 7) The interval is clearly opened and leaves the remnants of the SLIOL visible at the floor. The arthroscope easily goes from the midcarpal to the radiocarpal joint, through the ligamentous breach (see text). S scaphoid, L lunate, T triquetrum, H hamate, RSCL radioscaphocapitate ligament

3.4 Meaning of the Dynamic Arthroscopic Tests in the Dissociative Scapholunate Instabilities

These manoeuvres and dynamic tests thus enable to put forward a deficiency in the ligamentous devices. The surgeon indirectly analyses the effects of intrinsic and/or extrinsic possible ligamentous injuries on the carpal stability. Throughout our experiment, thanks to these dynamic arthroscopic tests, it has been made possible to point out an early instability before it creates abnormalities in the dynamic or a fortiori static radiographic results [14, 15]. It is easy to understand the higher ‘sensitiveness’ of arthroscopy as far as dissociative instabilities are concerned since this exam enables to make a test of direct dissociation and impress constraints on the bones (under the effect of the twisting motion applied to the hook). On the contrary, in a dynamic radiographic study, the component of dissociation is indirectly induced under the effect of axial compression which is itself induced by fist clenching. Scapholunate dissociative instability is probably an entity with various declinations following a vast spectrum of injuries. The distinction between a static and a dynamic instability only is not sufficient to make the vastness of this spectrum clear. If the conditions in which radiographic images are made are perfectly standardised, correlations can be established between the severity of ligamentous injuries seen in arthroscopy and their radiographic interpretation [16].

3.5 Dynamic Arthroscopic Tests in Pyramido-Lunate Dissociative Instabilities

The practice of these tests has been deduced from what was observed in the scapholunate interval. In that case, the absence of ligamentous injury does not let the hook penetrate into the triquetrolunate interosseous interval. Instability is established after an abnormal opening of the interosseous interval impressed by the twisting motion applied to the hook (Fig. 8).