Radial Wrist Extensors as a Dynamic Stabilizers of Scapholunate Complex

Abstract

Wrist stabilization is ensured by the complex of stabilizers, both static (intrinsic and extrinsic ligaments) and dynamic ones (flexor and extensor sinews of the wrist). Extrinsic carpal ligaments link both carpal rows with forearm, while the intrinsic ones connect individual carpal bones. From among intrinsic ligaments, the most significant from clinical point of view is scapholunate ligament (scapholunate lig. -SL). Instability of the SL resulting from SL ligament tear is the most frequent type of carpal instability. If untreated or undiagnosed, it may lead to destabilization of the carpal rows, and in the final stage to massive degenerative changes with SLAC (scapholunate advanced collapse). the aim of the study was to present a hypothesis of a possible influence of radial extensors of the wrist as dynamic stabilizers for SL complex, based on which it is possible to discern the partial ligament tear with accompanying damage of static stabilizers of the complex. material and methods. This hypothesis was based on radiological tests carried out on 5 patients, with acute partial SL ligament tear, which was confirmed during wrist arthroscopy. The outcome was presented as well, with its visualization in radiological tests. Results. The picture of rotary subluxation of the scaphoid -signet ring sign in PA view and strengthening in stress position (clenched fist) was demonstrated in all 5 patients. In 2 patients who had wrist arthroscopy performed it was observed that the palmar and proximal part of SL ligament were injured, yet no damage of dorsal part was reported. In MRI tests of these patients, an additional injury of dorsal intercarpal ligament was revealed. Conclusions. Correction of the scaphoid reduction in position of clenched fist may result from influence of radial extensors of the wrist (both short and long) as dynamic stabilizers of SL complex. This imagining is a completion of the radiological symptoms so far occurring in this SL instability. In case of acute, partial scapholunate ligament tear, reduction of scapholunate subluxation and its internal fixation with the lunate and capitate for a 6-week period may be an optional procedure.

Face to Face with Scapholunate Instability

“…In our study we have found that rotatory subluxation of the scaphoid can also occur with incomplete SLIL lesion. In the new classification this injury can be present at both I b and III a (Garcia-Elias stage IV) stages, depending on the ability of primary repair of SLIL lesion [3,[10][11][12]20,21,[24][25][26].…”

“…That is the reason why in numerous cases of SL instability SL angle will exceed 80° [3,10,11]. For rotatory subluxation of the scaphoid the radio scaphoid angle (≤45°) will be more typical [20,21]. Finally, we speak about the last stage (IV°) when any degenerative changes occur.…”

“…One of the discussed above intercarpal arthrodesis shall be done. [3,5,6,[8][9][10][11][12]20,21]as dynamic -with incomplete SL lesion (I b°), complete lesion to SL ligament (II b°) or as static deformity (III b°). The cortical ring sign will not always be a pathologic, an additional X-ray of the opposite wristin PA projection and in clenched fist of the injured wrist must be taken to ensure that this sign is pathologic.…”

“…Another significant point is the increase of SL angle (30°-60°). It shall increase not only in the situation with rotatory subluxation of the scaphoid, but also in DISI deformity [3,20,21 ]. SL ligament balances flexion of scaphoid and lunate extension.…”

Sports-related wrist and hand injuries: a review

“…2a ). A PA clenched fist view may show greater than 5 mm of widening between the scaphoid and lunate (Terry Thomas sign) is diagnostic of a complete SL ligament tear [ 13 ]. Chronic tears may demonstrate a static SL gap on the PA film and an increased SL angle on the lateral consistent with dorsal intercalated segmental instability (DISI).…”