Waist Fractures & Nonunion | FCR-Based Interval | Corrects Humpback Deformity
Surgical Imaging
Indications & Rationale
Scaphoid waist and distal-pole fractures requiring open reduction/fixation; waist nonunion, especially with volar resorption and humpback (flexion) deformity needing a volar opening-wedge corticocancellous graft; correction of carpal collapse (DISI) associated with scaphoid nonunion; concurrent volar carpal procedures.
Preserves the dorsally entering, retrograde blood supply to the scaphoid; gives direct access to the volar surface where resorption and flexion deformity occur; allows length restoration and deformity correction with a volar wedge graft — the superior route for humpback deformity.
Proximal-pole fractures and nonunions, and many percutaneous/arthroscopically assisted central-screw placements, are better served by a dorsal approach that gives a straighter central axis to the proximal pole and direct access to that fragment.
Established SNAC-wrist arthritis (consider salvage rather than reconstruction); avascular proximal pole (may need vascularised graft, often dorsal); the need to securely repair the radioscaphocapitate ligament.
Surgical Anatomy
- Flexor carpi radialis (FCR): The approach is centred on FCR — open the sheath and incise its floor to reach the volar capsule and scaphoid. Staying radial to FCR keeps the median nerve safe.
- Radial artery: Lies just radial to FCR at the wrist; identify, protect and retract it. A superficial palmar branch may need ligation.
- Palmar cutaneous branch of the median nerve: Arises ~5 cm proximal to the wrist crease and runs on the radial side of the median nerve/ulnar side of FCR — at risk if the incision strays ulnar to FCR; injury causes a painful neuroma over the thenar base.
- Radioscaphocapitate (RSC) ligament: A volar extrinsic ligament crossing the scaphoid waist; incised for exposure and repaired at closure.
- The scaphoid's dominant blood supply enters dorsally (dorsal ridge vessels from the radial artery), supplying the proximal pole retrogradely — hence proximal-pole fractures are prone to avascular necrosis and slow union.
- A volar approach spares these dorsal vessels, making it the vascularity-friendly route for waist and distal pathology and for grafting; the distal pole also receives volar branches.
The Approach — Step by Step
- Supine with the arm on a hand table, wrist extended over a bolster; tourniquet and image intensifier available. The wrist may be radially/ulnarly deviated to open the scaphotrapezial region.
- Landmarks: the FCR tendon, the scaphoid tubercle (palpable at the radial wrist crease, accentuated by radial deviation) and the radial styloid.
Dangers & How to Avoid Them
Structures at risk
The radioscaphocapitate ligament is divided to reach the scaphoid waist and MUST be repaired at closure. An unrepaired RSC ligament is a recognised cause of post-operative carpal (ulnar translation) instability — a classic viva 'gotcha'. Likewise, keep the dissection radial to FCR to protect the radial artery and the palmar cutaneous branch of the median nerve.
Volar vs Dorsal Approach to the Scaphoid
Choosing the approach
Outcomes & Evidence
Volar (Russe-type) cancellous grafting for scaphoid nonunion — high union
Volar percutaneous screw fixation for scaphoid nonunion
Volar percutaneous screw fixation for scaphoid waist delayed union
Based on articles retrieved from PubMed: Yasuda et al. (DOI), Gurger et al. (DOI) and Kim et al. (DOI). The FCR-based interval, the dorsal/retrograde scaphoid blood supply, the radioscaphocapitate ligament and the volar humpback-correction principle reflect standard, well-established surgical-anatomy teaching.
Viva Scenarios
Practise clinical reasoning and management decisions out loud
“You plan to graft a scaphoid waist nonunion with a humpback deformity. The examiner asks: 'Which approach and why, and what is your interval?'”
“During the volar approach the examiner asks which structures you must protect and what happens if the radioscaphocapitate ligament is not repaired.”
Viva & Exam Focus
RAREVolar scaphoid safety
Hook:The volar scaphoid approach is RARE-ly forgiving of a missed RSC ligament — protect the Radial artery, go radial to FCR, Repair the RSC ligament, and Extend the scaphoid with a volar graft.
- Volar = waist/distal pole & humpback correction; dorsal = proximal pole (driven by the dorsal retrograde blood supply).
- FCR-based interval; radial to FCR protects the median nerve and palmar cutaneous branch; protect the radial artery.
- The radioscaphocapitate ligament is incised and MUST be repaired.