46yo male presents with T 98.4 P 74 BP 138/80 chief complaint of left O2 100% wrist pain. Patient Gen NAD slipped on side walk on MSK pain to dorsum of sheet of ice and fell left wrist just proximal to forward, landing on 3rd metacarpal. 2+ distal outstretched hand. Pain pulses. Pain with wrist has been lingering for rotation past two days, and pt endorses “clicking” Neuro: motor 5/5 nl sound with certain wrist sensation movements
scapholunate dissociation scaphoid impaction syndrome (SIS) occult ganglion cyst posterior interosseous nerve neuroma physiologic scapholunate (compare to other hand) perilunate dislocation non-displaced scaphoid fx
White arrow: "Terry Thomas"sign gap between scaphoid and lunate, normal 1-2 mm(abnormal 3mm) Progressive flexion and foreshortening of the scaphoid leads to the scaphoidring sign, seeing scaphoid end on.Black arrow: Signet Ring sign- seen with abnormal palmar flexion of scaphoid.Right Image: Scapholunate angle nl 30-60 degrees, >80 degrees diagnostic of DISI (dorsalintercalated segment instability) signifying carpal instability
Orthopedic follow up, for most cases will need operative repair of interosseous ligament. Can place patient in thumb spica splint and have patient f/u with ortho within one week. Untreated, SLD can lead to DISI, defined by SL angle >80 degrees due to abnormal flexion of scaphoid, indicating wrist instability, and if further untreated, can lead to severe arthritis; thus prompt ortho f/u necessary
MCC of carpal instability Assoc. injuries: simultaneous radial styloid fx is relatively common w/ carpal dislocation; also always consider non- displaced scaphoid fx. Mechanism is similar to that of scaphoid fx, w/ stress loading of extended carpus, except it is usually in ulnar rather than radial deviation SL angle greater than 80 degrees indicative of DISI, which can occur with SLD left untreated, and is indicative of worsened carpal instability. DISI can lead to scapholunate advance collapse (SLAC), a specific pattern of osteoarthritis and subluxation which results from untreated chronic SLD.