Scapholunate instability treatment: Importance of the dorsal intercarpal ligament and robot portrait of an ideal tailored procedure

The biomechanics of post-traumatic scapholunate instability (PTSLI) remains incompletely understood . Despite numerous surgical techniques already described, mid and long-term outcome are insufficient. The increased use of arthroscopy and crucial anatomical descriptions of the Dorsal-Capsulo-Scapholunate-Septum (DCSS) and the Dorsal Intercarpal Ligament (DICL) have radically changed the approach to treatment .  

Based on a dynamic anatomical study carried out by 2 of the co-authors, and a review of the literature, we described the ligamentous structures that should ideally be targeted in any scapholunate stabilization surgery. Dynamic scapholunate (SL) instability was graded according to the European Wrist Arthroscopy Society ( EWAS) after sequential sectioning of the different parts of the SL ligament and DICL. Specifications applicable to any surgical scapholunate stabilization technique are described. An evidence-based treatment algorithm, according to the instability grade, is developed. 

Sequential sectioning of the dorsal intrinsic and extrinsic ligaments showed, in high grade PTSLI (greater than EWAS IIIB ):

 -the secondary and minor role of the dorsal scapholunate interosseous ligament (SLIOL).

 -the major role of the DIC and mainly its proximal portion, the scapholunotriquetral ligament. 

A review of the literature shows not only the importance of the scapholunate complex in SL stability but also that of the proprioceptive mechanoreceptors of the DCSS. Finally, the distal palmar ligaments (DPL) and the palmar portion of the SIOSL do not have an established and consensual biomechanical role. 

Various open or arthroscopic techniques are regularly described, making consensus difficult. A specification that the optimal surgical technique must meet therefore seems necessary.

 This technique should:

 -ideally be arthroscopic (preservation of the proprioceptive mechanoreceptors of the DCSS). 

-allow stabilization or reconstruction of the DIC in high grades greater than EWAS III B.

 -in all cases allow the stabilization of the DCSS and to a lesser extent the dorsal portion of the LIOSL. 

The need to stabilize or reconstruct the palmar ligaments is not established. 

The following treatment algorithm is proposed with a tailored choice of technique depending on the EWAS stage. In EWAS stages I to IIIB, classic arthroscopic capsulo-ligament repair techniques (ADCLR) are sufficient, with or without intercarpal pinning. Isolated scapholunate pinning can be used in acute cases. In EWAS stages IIIC and IV, techniques targeting the DIC are necessary (modified ADCLR, plication of the DICL, “super capsuloplasty”, ligamentoplasties, etc.) In more advanced stages (EWAS IV+), the extrinsic radiocarpal ligaments should be reconstructed in addition to the DIC (targeted ligamentoplasties). 

Keywords: Scapholunate instability, dorsal intercarpal ligament, DCSS, scapholunate complex, extrinsic ligaments, DIC plication, supercapsuloplasty