Scaphoid Fractures and Carpal Instability — DISI, VISI, SLAC, SNAC, and Perilunate Injuries

This episode reviews the core principles of scaphoid fractures and carpal instability, focusing on wrist biomechanics, diagnosis, fixation strategy, and collapse patterns.Topics include the scaphoid as the key link between the proximal and distal carpal rows, its retrograde blood supply, and why waist and proximal pole fractures are at risk for nonunion and avascular necrosis. The episode also reviews exam and imaging strategies, including snuffbox tenderness, scaphoid tubercle tenderness, thumb spica immobilization, dedicated scaphoid views, MRI for occult fractures, and CT for surgical planning.Carpal instability is discussed through CID, CIND, CIC, and CIA, with emphasis on DISI from scapholunate ligament injury and VISI from lunotriquetral ligament injury. Key diagnostic concepts include the Watson shift test, Terry Thomas sign, signet ring sign, clenched fist views, scapholunate angle, and the Geissler arthroscopic classification.Surgical strategy includes headless compression screw fixation, volar versus dorsal approaches, management of humpback deformity, nonunion repair with structural bone grafting, and vascularized bone grafts such as the 1,2 ICSRA. The episode also covers SLAC vs SNAC wrist, the radiolunate “sanctuary” joint, proximal row carpectomy, four-corner fusion, total wrist arthrodesis, and emergency management of perilunate dislocations using Mayfield staging, reduction, carpal tunnel release, and ligament repair. Part of Dr. Lara’s Plastic Surgery Compendium — a high-yield audio reference for plastic surgery trainees and surgeons.Disclaimer:This podcast is intended for educational purposes only and is designed for medical students, residents, fellows, and practicing healthcare professionals. It is not intended to provide medical advice, diagnosis, or treatment for any individual patient. The content presented reflects general surgical principles and should not be used as a substitute for formal medical training, clinical judgment, or consultation with qualified healthcare professionals. Listening to this podcast does not establish a physician–patient relationship.SEO / Topic Keywordsscaphoid fracture, carpal instability, scaphoid nonunion, scaphoid AVN, retrograde blood supply scaphoid, snuffbox tenderness, scaphoid tubercle tenderness, thumb spica splint, Herbert classification, headless compression screw, humpback deformity, Matti-Russe procedure, vascularized bone graft, 1,2 ICSRA, DISI deformity, VISI deformity, scapholunate ligament tear, lunotriquetral ligament tear, Watson shift test, Terry Thomas sign, signet ring sign, Geissler classification, SLAC wrist, SNAC wrist, proximal row carpectomy, four-corner fusion, perilunate dislocation, Mayfield classification, spilled teacup sign, piece of pie sign