Retrograde Blood Supply | AVN Risk | Vascularized Bone Graft | SNAC Progression
HERBERT D CLASSIFICATION (NONUNION)
Critical Must-Knows
- Retrograde blood supply - proximal pole at highest AVN risk (80% from dorsal scaphoid branch)
- Humpback deformity - flexion through nonunion site creates dorsal angulation
- DISI pattern develops - lunate extends as scaphoid flexes (carpal collapse)
- 100% progress to SNAC wrist if untreated - arthritis is inevitable
- VBG (1,2 ICSRA) indicated for AVN or failed previous fixation
Clinical Pearls
- "Lateral intrascaphoid angle greater than 45 degrees = significant humpback requiring wedge graft
- "MRI with gadolinium assesses AVN - lack of enhancement means AVN, requires VBG
- "Non-vascularized graft if viable proximal pole, VBG if AVN or failed surgery
- "Union rates: 90-95% non-VBG viable bone, 80-90% VBG for AVN
Clinical Imaging
Imaging Gallery
Critical Scaphoid Nonunion Exam Points
Humpback Deformity
Nonunion allows flexion through fracture site creating dorsal angulation (convex dorsally like a humpback). Lateral intrascaphoid angle greater than 45 degrees is significant. Must correct with wedge graft for union.
AVN Assessment
MRI with gadolinium is gold standard - lack of proximal pole enhancement indicates AVN. Intraoperative punctate bleeding confirms vascularity. AVN requires vascularized bone graft.
1,2 ICSRA Graft
1,2 Intercompartmental Supraretinacular Artery pedicled graft from dorsal distal radius. Gold standard for AVN nonunion. Described by Zaidemberg 1991.
SNAC Wrist Progression
Untreated nonunion = 100% SNAC wrist. Arthritis progresses: Stage 1 radial styloid, Stage 2 scaphocapitate, Stage 3 capitolunate, Stage 4 pancarpal.
Quick Decision Guide - Scaphoid Nonunion
| Presentation | Assessment | Treatment | Graft Type |
|---|---|---|---|
| Fibrous union (D1) | Minimal motion at nonunion | ORIF alone may suffice | Cancellous graft if needed |
| Pseudarthrosis (D2) | Mobile nonunion, viable bone | ORIF + bone graft | Iliac crest cancellous |
| Humpback, no AVN | ISA greater than 45 degrees, MRI signal intact | Correct deformity + fix | Corticocancellous wedge |
| AVN proximal pole (D4) | No MRI enhancement, no intraop bleeding | Vascularized bone graft | 1,2 ICSRA pedicled graft |
| Failed previous surgery | Prior nonunion repair failed | Revision with VBG | Free vascularized MFC graft |
RETROScaphoid Blood Supply
| R | Radial artery Main supply via dorsal scaphoid branch |
| E | Enters distally Blood enters at dorsal ridge (waist level) |
| T | Travels proximally Retrograde flow toward proximal pole |
| R | Risk to proximal Proximal pole most vulnerable to AVN |
| O | Only 20% Only 20-30% of proximal pole has direct supply |
| R | Radial artery Main supply via dorsal scaphoid branch | R | Risk to proximal Proximal pole most vulnerable to AVN |
| E | Enters distally Blood enters at dorsal ridge (waist level) | O | Only 20% Only 20-30% of proximal pole has direct supply |
| T | Travels proximally Retrograde flow toward proximal pole |
Hook:Blood enters distally and runs RETRO (backwards) up the scaphoid - proximal pole is at highest risk!
SNAPSNonunion Risk Factors
| S | Smoking Major modifiable risk factor for nonunion |
| N | NSAID use Anti-inflammatories inhibit bone healing |
| A | AVN Avascular necrosis prevents healing |
| P | Proximal pole Poor blood supply location |
| S | Significant displacement Displacement greater than 1mm increases nonunion |
| S | Smoking Major modifiable risk factor for nonunion | P | Proximal pole Poor blood supply location |
| N | NSAID use Anti-inflammatories inhibit bone healing | S | Significant displacement Displacement greater than 1mm increases nonunion |
| A | AVN Avascular necrosis prevents healing |
Hook:SNAPS cause nonunion - especially Smoking and proximal pole location!
VIABLESGraft Selection Algorithm
| V | Vascularity Check MRI/intraop bleeding - viable or AVN? |
| I | Intrascaphoid angle Measure humpback - greater than 45 degrees needs wedge |
| A | Articulations check Any arthritic changes (SNAC)? |
| B | Bone quality Sclerosis, cystic changes? |
| L | Length of nonunion Chronic more challenging |
| E | Earlier surgery? Failed previous fixation = VBG |
| S | Select graft Non-VBG vs VBG based on assessment |
| V | Vascularity Check MRI/intraop bleeding - viable or AVN? | B | Bone quality Sclerosis, cystic changes? | S | Select graft Non-VBG vs VBG based on assessment |
| I | Intrascaphoid angle Measure humpback - greater than 45 degrees needs wedge | L | Length of nonunion Chronic more challenging | ||
| A | Articulations check Any arthritic changes (SNAC)? | E | Earlier surgery? Failed previous fixation = VBG |
Hook:Is the bone VIABLE? Use this checklist to decide if patient needs VBG or non-vascularized graft!
RSC-PSNAC Wrist Stages
| R | Radial styloid Stage 1 - Radial styloid to scaphoid arthritis |
| S | Scaphocapitate Stage 2 - Scaphoid to capitate arthritis added |
| C | Capitolunate Stage 3 - Capitate to lunate arthritis added |
| P | Pancarpal Stage 4 - Entire wrist arthritis |
| R | Radial styloid Stage 1 - Radial styloid to scaphoid arthritis | C | Capitolunate Stage 3 - Capitate to lunate arthritis added |
| S | Scaphocapitate Stage 2 - Scaphoid to capitate arthritis added | P | Pancarpal Stage 4 - Entire wrist arthritis |
Hook:SNAC progresses RSC-P: Radial styloid first, then Scaphocapitate, Capitolunate, finally Pancarpal!
Overview and Epidemiology
Definition: Scaphoid nonunion is failure of a scaphoid fracture to heal, typically defined as absence of radiographic union at 6 months despite treatment, or presence of an established nonunion pattern.
Incidence and Risk Factors:
- 5-15% of all scaphoid fractures progress to nonunion
- Higher rates in:
- Proximal pole fractures (up to 30%)
- Displaced fractures (greater than 1mm)
- Delayed presentation (greater than 4 weeks)
- Missed diagnosis
- Smokers (2-3x increased risk)
Risk Factors
- Proximal pole location - poor blood supply
- Displacement greater than 1mm
- Delayed treatment greater than 4 weeks
- Smoking - major modifiable factor
- NSAID use - inhibits healing
- Initial AVN
- Poor immobilization compliance
Natural History
- 100% progress to SNAC wrist if untreated
- Mean time to symptomatic SNAC: 5-10 years
- Even asymptomatic nonunions deteriorate
- Mack et al: 97% radioscaphoid arthritis within 10 years
- Young patients especially vulnerable
Clinical Pearl
Key exam point: Unlike other nonunions where the question is "will it cause problems?", scaphoid nonunion has a 100% certainty of progression to SNAC wrist arthritis. Treatment is almost always indicated.
Anatomy and Blood Supply
Scaphoid Anatomy:
- Largest carpal bone in proximal row
- Spans both carpal rows (proximal and distal)
- 80% covered by articular cartilage - limits periosteal blood supply
- Acts as kinematic link between carpal rows
Blood Supply (Critical for Exam):
Scaphoid Blood Supply
| Vessel | Contribution | Entry Point | Area Supplied |
|---|---|---|---|
| Dorsal scaphoid branch (radial artery) | 70-80% | Dorsal ridge at waist | Majority of bone via retrograde flow |
| Palmar branches (superficial palmar arch) | 20-30% | Scaphoid tubercle | Distal pole and tuberosity |
| Direct proximal supply | Variable (20%) | Variable | Small portion proximal pole |
Clinical Implications:
- Retrograde flow = proximal pole at highest AVN risk
- Waist fractures interrupt main blood supply to proximal pole
- Proximal pole fractures have highest nonunion rate (up to 30%)
- Only 20-30% of proximal pole has any direct blood supply
Proximal Pole Fractures
Proximal pole fractures have the highest nonunion and AVN rates (up to 30%) because they completely disrupt the retrograde blood supply from the main dorsal scaphoid branch. Always consider these high-risk injuries.
Pathophysiology of Nonunion
Humpback Deformity:
The scaphoid normally acts as a strut connecting the proximal and distal carpal rows. When nonunion develops:
- Loss of structural integrity at nonunion site
- Flexion force from scaphotrapezial ligament pulls distal fragment into flexion
- Dorsal angulation develops at nonunion site
- Dorsal convexity creates "humpback" appearance
Measuring Humpback:
- Lateral intrascaphoid angle measured on lateral radiograph or sagittal CT
- Lines drawn along proximal and distal pole axes
- Normal: less than 35 degrees
- Significant humpback: greater than 45 degrees
- Must correct with wedge graft for successful union
DISI Pattern Development:
Normal Carpal Mechanics
- Scaphoid links proximal and distal rows
- Flexion tendency balanced by lunate
- Lunate in neutral position
- Normal scapholunate angle: 30-60 degrees
DISI in Nonunion
- Scaphoid collapses into flexion
- Lunate (attached to proximal fragment) extends
- Dorsal intercalated segment instability (DISI)
- Scapholunate angle increases (greater than 60 degrees)
- Leads to abnormal load distribution
Carpal Collapse Cascade
DISI pattern from scaphoid nonunion leads to abnormal carpal mechanics, altered load distribution, and ultimately SNAC wrist (Scaphoid Nonunion Advanced Collapse). This is the inevitable endpoint without treatment.
Classification Systems
Herbert Nonunion Classification (Type D):
| Type | Description | Characteristics | Treatment |
|---|---|---|---|
| D1 | Fibrous union | Minimal motion, may heal with prolonged immobilization | ORIF, may not need graft |
| D2 | Pseudarthrosis | Established nonunion, mobile but viable | ORIF + bone graft |
| D3 | Sclerotic | Dense sclerosis at nonunion margins | Debride + extensive graft |
| D4 | Avascular necrosis | No proximal pole vascularity | Vascularized bone graft |
Clinical Pearl
Herbert D classification is the exam standard. D4 (AVN) is the critical type - requires vascularized bone graft. D1-D3 may be treated with non-vascularized graft if bone is viable.
Clinical Assessment
History:
- Often delayed presentation with chronic wrist pain
- May have history of wrist injury (sometimes remote, forgotten)
- Pain with gripping, loading wrist
- Weakness, reduced grip strength
- Decreased range of motion
Physical Examination:
Inspection
- Swelling often minimal in chronic cases
- Dorsal wrist fullness may be present
- Compare with contralateral side
- Assess overall wrist posture
Palpation
- Anatomical snuffbox tenderness
- Scaphoid tubercle tenderness (volar)
- Dorsal scaphoid tenderness
- Check for crepitus
Provocative Tests:
- Scaphoid shift test (Watson test): Painful clunk with radial deviation
- Thumb compression: Pain with axial load through thumb
- Grip strength: Compare to contralateral side
Range of Motion:
- Decreased wrist flexion/extension
- Decreased radial deviation
- May have relatively preserved ulnar deviation
Clinical Pearl
Many scaphoid nonunions are "forgotten fractures" - patients may not recall injury. Always have high index of suspicion for nonunion in chronic wrist pain with snuffbox tenderness.
Differential Diagnosis of Radial-Sided Wrist Pain
Differential Diagnosis - Chronic Radial Wrist Pain
| Condition | Key features | Distinguishing finding |
|---|---|---|
| Scaphoid nonunion | Snuffbox tenderness, prior injury (often forgotten), reduced grip | CT shows nonunion gap/sclerosis; MRI assesses proximal pole AVN |
| Acute / occult scaphoid fracture | Recent fall on outstretched hand, snuffbox tenderness | Fracture line without sclerosis; MRI positive within days |
| Scapholunate (SLAC) instability | Dorsal SL tenderness, positive Watson scaphoid shift | Widened SL interval (Terry Thomas sign), no scaphoid fracture line |
| Preiser disease (idiopathic scaphoid AVN) | Insidious radial wrist pain, no fracture history | MRI AVN of intact (non-fractured) scaphoid |
| De Quervain tenosynovitis | Pain over 1st dorsal compartment, positive Finkelstein | Tenderness/swelling over APL-EPB, normal scaphoid imaging |
| Thumb CMC (basal) osteoarthritis | Pain at thumb base, positive CMC grind | Trapeziometacarpal joint changes, not scaphoid |
| Radial styloid / intersection syndrome | Tenderness more proximal/dorsal, crepitus | Soft-tissue, normal bony scaphoid imaging |
Investigations
Plain Radiographs:
Radiographic Views for Scaphoid Nonunion
| View | Assessment | Key Findings |
|---|---|---|
| PA wrist | Overall alignment, DISI | Signet ring sign, widened SL interval |
| Lateral wrist | Humpback measurement, DISI | Intrascaphoid angle, SL angle greater than 60 degrees |
| Scaphoid PA (ulnar deviation, tube angled) | Nonunion site detail | Gap, sclerosis, cystic changes |
| 45 degree pronation oblique | Scaphoid length | Additional nonunion detail |
X-ray Findings in Nonunion:
- Gap at fracture site
- Sclerotic margins
- Cystic changes
- Bone resorption
- Humpback deformity on lateral
- DISI pattern (scapholunate angle greater than 60 degrees)
- SNAC changes if advanced
CT Scan:
- Gold standard for assessing bony union/nonunion
- Sagittal reconstructions for humpback measurement
- Identifies cystic changes, sclerosis
- Essential for surgical planning
- Assesses arthritic changes (SNAC staging)
MRI:
- Essential for AVN assessment - determines graft choice
- T1 sequences show marrow signal
- Gadolinium enhancement confirms vascularity
- No proximal pole enhancement = AVN = VBG required
MRI with Gadolinium
MRI with gadolinium is mandatory before scaphoid nonunion surgery to assess proximal pole vascularity. Lack of enhancement indicates AVN and mandates vascularized bone graft. Non-vascularized graft in AVN has high failure rate.
Bone Scan:
- Less commonly used now
- Decreased uptake suggests AVN
- Non-specific
Management Algorithm
Management Decision Tree
Goals of Treatment:
- Achieve union - primary goal
- Restore anatomy - correct humpback, length
- Prevent SNAC progression - all nonunions lead to arthritis
- Maintain/restore function - motion, grip strength
Assessment Steps:
- History and examination - symptom duration, prior treatment
- Plain radiographs (4 views) - confirm nonunion
- CT scan - nonunion detail, bone quality
- MRI with gadolinium - AVN assessment (critical)
- Check for SNAC changes - determines if salvage needed
Classification:
- Herbert D type (D1-D4)
- Location (proximal/waist/distal)
- SNAC stage if arthritis present
- Degree of humpback (ISA measurement)
Complete assessment guides appropriate treatment selection.
Bone Graft Selection
Indications:
- Viable proximal pole (MRI enhancement, intraop bleeding)
- Herbert D1, D2, D3 with vascularity
- Primary nonunion surgery
Types:
| Graft Type | Source | Indication |
|---|---|---|
| Cancellous | Distal radius, iliac crest | Minimal deformity, fill defect |
| Corticocancellous | Iliac crest | Moderate defect, some stability |
| Wedge (Fisk-Fernandez) | Iliac crest | Humpback correction |
| Russe inlay | Iliac crest | Classic corticocancellous inlay |
Technique Principles:
- Debride sclerotic bone to punctate bleeding
- Size graft to correct deformity
- Pack cancellous around cortical strut
- Fix with headless compression screw
Union Rates: 85-95% with appropriate patient selection
Surgical Technique
Modified Russe Volar Approach
Indications:
- Waist nonunions
- Humpback deformity requiring correction
- Non-vascularized bone graft
Steps:
-
Incision: Longitudinal over scaphoid tubercle, between FCR and radial artery. Protect palmar cutaneous branch of median nerve.
-
Exposure: Incise joint capsule, identify nonunion site. Wrist flexion improves access.
-
Debridement: Remove fibrous tissue, debride sclerotic bone margins. Continue until punctate bleeding seen. Preserve periosteum where possible.
-
Graft Insertion: Size wedge graft to correct humpback. Insert graft into prepared slot. Pack cancellous around. Confirm correction on fluoroscopy.
-
Fixation: Headless compression screw (Acutrak, Herbert). Guidewire placement checked fluoroscopically. Screw should cross nonunion and engage proximal pole.
The volar approach provides excellent access for waist nonunions and humpback correction.
Complications
Complications of Scaphoid Nonunion Surgery
| Complication | Incidence | Prevention | Management |
|---|---|---|---|
| Persistent nonunion | 5-20% | Appropriate graft selection, technique | Revision with VBG if AVN |
| AVN progression | Variable | VBG for at-risk cases | Free vascularized graft |
| SNAC progression | If nonunion persists | Achieve union | Salvage procedure |
| Stiffness | 10-20% | Early motion when healed | Physiotherapy |
| Hardware issues | 5-10% | Appropriate screw sizing | Hardware removal if symptomatic |
| Donor site morbidity | 5-10% | Minimize graft size | Symptomatic treatment |
| Infection | less than 2% | Sterile technique, prophylaxis | Antibiotics, debridement |
Persistent Nonunion Management:
- Identify cause (inadequate graft, AVN, poor fixation, smoking)
- Address modifiable factors
- Revision with vascularized graft if non-VBG failed
- Consider free vascularized (MFC) if pedicled VBG failed
- If SNAC advanced, salvage procedures
SNAC Wrist Salvage:
- If arthritis too advanced for nonunion repair:
- Stage 1-2: Scaphoid excision + 4-corner fusion
- Stage 2-3: Proximal row carpectomy (if capitolunate preserved)
- Stage 3-4: Total wrist fusion or arthroplasty
Postoperative Care and Rehabilitation
Rehabilitation Protocol
- Thumb spica cast or splint
- Immobilize wrist and thumb IP joint
- Allow finger motion
- Serial radiographs at 4, 6, 8 weeks
- No loading, gripping
- CT scan at 8 weeks to assess union
- If signs of healing, transition to removable splint
- Gentle active ROM exercises
- Continue night splinting
- No resistance activities
- Progressive strengthening if union confirmed
- Grip exercises, putty
- Proprioception work
- Gradually increase resistance
- Return to manual work when pain-free, strong
- Contact sports delayed until 6 months
- Monitor for complications
CT Monitoring:
- Serial CT scans best for union assessment
- Bridging trabeculae indicate healing
- Complete bridging = union
- May take 12+ weeks for VBG cases
Union Rates by Graft Type:
Expected Union Rates
| Graft Type | Indication | Union Rate | Time to Union |
|---|---|---|---|
| Non-vascularized (viable) | D1-D3, no AVN | 85-95% | 8-12 weeks |
| Wedge graft (viable) | Humpback correction | 85-95% | 10-14 weeks |
| 1,2 ICSRA (AVN) | D4, AVN | 80-90% | 12-16 weeks |
| Free MFC (salvage) | Failed VBG | 70-85% | 14-20 weeks |
Outcomes and Prognosis
Factors Affecting Outcome:
- Vascularity - AVN has lower union rates
- Time from injury - chronic worse than acute
- Deformity correction - humpback must be addressed
- Graft choice - appropriate graft selection critical
- Smoking cessation - major modifiable factor
Functional Outcomes:
- Most patients achieve pain relief with union
- Grip strength 70-85% of contralateral
- Range of motion 70-85% of contralateral
- Return to work/sport in 4-6 months if union achieved
Clinical Pearl
Exam key: Prognosis is excellent if union achieved - most patients return to normal function. The key is selecting the right graft (VBG for AVN) and correcting deformity (wedge graft for humpback).
Evidence Base
1,2 ICSRA Vascularized Bone Graft (Zaidemberg)
- Cadaveric study (10 dissections) defined a consistent vascularised bone graft from the distal dorsoradial radius (later termed the 1,2 ICSRA graft)
- Used in 11 patients with long-standing scaphoid nonunion with good results
- Described as technically easy, offering shorter immobilisation and a higher union rate than conventional inlay grafting
- Pedicled graft avoids the microsurgical anastomosis needed for free transfers
Natural History of Scaphoid Nonunion (Mack)
- 47 nonunions in 46 symptomatic patients; duration of nonunion 5 to 53 years
- Three radiographic stages: changes confined to scaphoid (8.2 years), radioscaphoid arthritis (17.0 years), generalised wrist arthritis (31.6 years)
- Fracture displacement and carpal instability (lunate dorsiflexion 10 degrees or more) correlated with severity of degeneration
- Few nonunions remained undisplaced, stable or arthritis-free beyond 10 years
Scaphoid Malunion and Humpback Deformity (Amadio)
- 45 patients with 46 healed scaphoid fractures assessed by trispiral tomography after union
- Normal lateral intrascaphoid angle defined as less than 35 degrees; humpback malunion ranged up to 60 degrees
- Normal alignment gave 83% satisfactory outcomes and only 22% post-traumatic arthritis
- Lateral intrascaphoid angulation greater than 45 degrees gave just 27% satisfactory outcomes and 54% arthritis
Treatment of Scaphoid Nonunions: Quantitative Meta-analysis (Merrell)
- Meta-analysis of 36 eligible studies addressing scaphoid nonunion treatment
- Unstable nonunions: screw fixation with grafting 94% union versus K-wires and wedge grafting 77%
- Avascular proximal pole: vascularised graft 88% union versus 47% with screw and wedge fixation
- Solid screw fixation showed no clear benefit from prolonged postoperative casting
Medial Femoral Condyle vs Distal Radial Pedicle Graft for Avascular Nonunion (Jones)
- 22 scaphoid waist nonunions with an avascular proximal pole and carpal collapse, treated at two institutions
- Free vascularised medial femoral condyle (MFC) graft: 12 of 12 united (100%) at a median 13 weeks
- Distal radial pedicled graft: only 4 of 10 united (40%) at a median 19 weeks
- Union rate significantly higher and time to union shorter with the MFC graft (p = 0.005)
Vascularised vs Non-vascularised Grafting: Systematic Review (Duncumb)
- 78 studies, 7,671 patients (mean age 27.9 years, 87.8% male) pooled for scaphoid nonunion union rates
- Mean union 88.7% for non-vascularised versus 87.5% for vascularised grafts, with no significant difference (p = 0.685)
- No significant difference between fixation techniques, or between distal radius and iliac crest graft sources
- Studies excluding both proximal pole fractures and AVN achieved 96.5% union, significantly higher than the rest (86.8%, p less than 0.001)
Viva Scenarios
Clinical Decision Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scenario 1: Scaphoid Nonunion with AVN
"A 28-year-old male presents with wrist pain 2 years after a fall. He recalls being told he fractured his wrist but didn't follow up after initial casting. CT shows a waist nonunion with humpback deformity (intrascaphoid angle 55 degrees). MRI shows no gadolinium enhancement of the proximal pole."
Thank you. This is a scaphoid nonunion with humpback deformity and avascular necrosis of the proximal pole - a Herbert D4 nonunion requiring vascularized bone graft.
Assessment summary: The humpback deformity (ISA 55 degrees, greater than 45 degree threshold) indicates significant collapse requiring correction. The lack of MRI enhancement confirms proximal pole AVN, which mandates a vascularized bone graft rather than a standard non-vascularized graft.
Classification: Herbert D4 (AVN nonunion) with significant humpback deformity.
Management: I would recommend surgical treatment with a 1,2 ICSRA vascularized bone graft via a dorsal approach. The key steps would be: (1) Expose the nonunion dorsally, (2) Identify and raise the 1,2 ICSRA pedicled graft from the dorsal distal radius, (3) Debride the nonunion site - I would expect no punctate bleeding confirming AVN, (4) Correct the humpback deformity, (5) Insert the vascularized graft maintaining pedicle integrity, (6) Fix with K-wires or a small headless screw.
Postoperative care: Thumb spica immobilization for 10-12 weeks minimum, serial CT scans to assess union. Expected union rate is 80-90% with VBG for AVN.
Rationale for VBG: Non-vascularized grafts in AVN have unacceptably low union rates (less than 60%). The 1,2 ICSRA graft provides vascularized bone to revascularize the proximal pole while avoiding the need for microsurgical anastomosis.
Scenario 2: Simple Scaphoid Nonunion - Viable Bone
"A 22-year-old female presents with 1 year of wrist ache after a fall playing netball. She was initially treated in a cast for 6 weeks. CT shows a waist nonunion with minimal deformity (intrascaphoid angle 35 degrees). MRI shows normal proximal pole signal with good gadolinium enhancement."
Thank you. This is a scaphoid nonunion with viable proximal pole and minimal deformity - a Herbert D2/D3 nonunion suitable for non-vascularized bone grafting.
Assessment: The preserved MRI signal and gadolinium enhancement confirm the proximal pole is vascularized. The intrascaphoid angle of 35 degrees is within normal limits, so a wedge graft for deformity correction is not mandatory. This is a favorable situation for non-vascularized grafting.
Classification: Herbert D2 (pseudarthrosis) or D3 (sclerotic) based on CT appearance, with viable proximal pole.
Management: I would perform surgery via a volar approach (modified Russe). The steps would be: (1) Expose the nonunion through FCR/radial artery interval, (2) Debride the nonunion to punctate bleeding - I expect bleeding confirming vascularity, (3) Harvest cancellous or corticocancellous graft from the distal radius or iliac crest, (4) Insert graft into the prepared nonunion site, (5) Fix with a headless compression screw (e.g., Acutrak or Acutwist).
Postoperative: Thumb spica cast for 8-10 weeks, CT at 8 weeks to assess union. Expected union rate is 90-95% with viable bone and non-VBG.
Why non-VBG is appropriate: With confirmed vascularity on MRI and intraoperative punctate bleeding, a non-vascularized graft will incorporate successfully. VBG would be over-treatment and add unnecessary donor site morbidity.
Scenario 3: Scaphoid Nonunion with SNAC Changes
"A 45-year-old manual laborer presents with progressive wrist pain and stiffness. Radiographs show a long-standing scaphoid nonunion with arthritic changes at the radial styloid and scaphocapitate joint. The capitolunate joint appears preserved."
Thank you. This patient has a scaphoid nonunion with established SNAC wrist - specifically SNAC Stage 2 with radial styloid and scaphocapitate arthritis, but preserved capitolunate joint.
Assessment: The presence of established SNAC changes indicates the nonunion is longstanding. The key finding is that the capitolunate joint is preserved, which opens salvage options. At Stage 2, simple nonunion repair is unlikely to address the existing arthritis.
Classification: SNAC Stage 2 - arthritis involves radial styloid-scaphoid and scaphoid-capitate articulations, with preserved capitolunate joint.
Management options: Given SNAC Stage 2, I would discuss two main options with the patient:
1. Scaphoid excision and 4-corner fusion (SLAC/SNAC procedure): This involves excising the scaphoid (the source of abnormal mechanics), and fusing the lunate, capitate, hamate, and triquetrum. This converts the wrist to a single functional unit while preserving the radiolunate articulation for motion. Expected motion is approximately 50% of normal, with good pain relief.
2. Proximal row carpectomy (PRC): This involves removing the scaphoid, lunate, and triquetrum, creating a new "joint" between the capitate head and lunate fossa of the radius. This requires an intact capitate head and lunate fossa, which would need to be confirmed on imaging. Simpler procedure but dependent on cartilage quality.
My preference for this manual laborer would be 4-corner fusion as it provides better grip strength and durability for heavy use.
MCQ Practice Points
Blood Supply Question
Q: What is the primary blood supply to the scaphoid and why is the proximal pole at risk for AVN?
A: The dorsal scaphoid branch of the radial artery provides 70-80% of the blood supply. It enters the scaphoid at the dorsal ridge (waist level) and supplies the bone via retrograde flow. The proximal pole receives only 20-30% of its supply directly, making it highly vulnerable to AVN when the waist is fractured.
Humpback Question
Q: What lateral intrascaphoid angle indicates significant humpback deformity requiring wedge graft correction?
A: A lateral intrascaphoid angle greater than 45 degrees indicates significant humpback deformity. Normal is less than 35 degrees. Angles between 35-45 degrees are borderline. Significant humpback must be corrected with a wedge graft (e.g., Fisk-Fernandez) to restore scaphoid length and allow union.
Graft Selection Question
Q: When is a vascularized bone graft indicated for scaphoid nonunion?
A: Vascularized bone graft (typically 1,2 ICSRA) is indicated for:
- AVN of the proximal pole (no MRI gadolinium enhancement)
- Failed previous non-vascularized graft
- Prolonged nonunion (greater than 5 years)
Non-vascularized graft in AVN has unacceptably low union rates (less than 60%). VBG achieves 80-90% union in AVN.
1,2 ICSRA Question
Q: Where is the 1,2 ICSRA located and how is it harvested?
A: The 1,2 ICSRA (1,2 Intercompartmental Supraretinacular Artery) runs between the 1st extensor compartment (APL, EPB) and the 2nd extensor compartment (ECRL, ECRB) in the supraretinacular plane (above the extensor retinaculum). It is harvested from the dorsal distal radius as a pedicled bone flap, maintaining the vascular pedicle for transfer to the scaphoid nonunion site.
SNAC Progression Question
Q: What is the sequence of joint involvement in SNAC wrist?
A: SNAC wrist progresses through 4 stages:
- Stage 1: Radial styloid to scaphoid
- Stage 2: + Scaphocapitate joint
- Stage 3: + Capitolunate joint
- Stage 4: Pancarpal (including radiolunate)
Key difference from SLAC: In SNAC, radiolunate is preserved until Stage 4, allowing salvage procedures (4-corner fusion, PRC) in earlier stages.
Natural History Question
Q: What percentage of untreated scaphoid nonunions develop arthritis?
A: 100% of untreated scaphoid nonunions will eventually develop SNAC wrist arthritis. Mack et al (1984) showed 97% had radioscaphoid arthritis within 10 years. This makes observation inappropriate - all symptomatic nonunions should be treated surgically.
Guidelines, Registries & Global Practice
Global Epidemiology
The scaphoid is the most commonly fractured carpal bone, and nonunion is the dominant late complication that drives carpal collapse and arthritis worldwide.
| Measure | Figure | Source population |
|---|---|---|
| Scaphoid fracture incidence | approximately 12.4 in 100,000 per year | UK regional cohort (Garala 2016) |
| Peak demographic | Young men, highest aged 15-19 years | UK regional cohort (Garala 2016) |
| Fracture location | Waist 64%, tubercle 18.1% | UK regional cohort (Garala 2016) |
| Nonunion rate of all scaphoid fractures | approximately 5-15% (up to 30% proximal pole) | Pooled clinical series |
| Mean age at grafting for nonunion | approximately 27.9 years (87.8% male) | Systematic review, 7,671 patients (Duncumb 2022) |
Incidence rises with social deprivation and shows summer seasonality, reflecting the high-energy sporting and occupational mechanisms typical of the young male population at risk (Garala 2016).
Guideline and Society Guidance, Side by Side
There is no single high-level (Level I) guideline dedicated to scaphoid nonunion; recommendations are drawn from society resources and pooled evidence, which broadly agree.
| Body / region | Core guidance on scaphoid nonunion | Evidence basis |
|---|---|---|
| AO Foundation (global) | CT to confirm nonunion and assess deformity; debride to bleeding bone, restore length/alignment, structural graft plus stable internal fixation (headless compression screw) | Expert consensus / surgical reference |
| BOA / BSSH (UK) | Refer suspected nonunion to a hand unit; image with CT (union/deformity) and MRI (proximal pole viability); graft and fix; counsel that untreated nonunion risks collapse and arthritis | Society best-practice / narrative |
| AAOS / ASSH (US) | Operative reconstruction for symptomatic nonunion; vascularised graft considered for avascular proximal pole or failed prior surgery; salvage (4-corner fusion, PRC) once SNAC arthritis established | Society resources / pooled series |
| EFORT / European | Consistent with AO: address vascularity, deformity and stability; reserve vascularised grafts for avascular or revision cases | Instructional / consensus |
Points of genuine agreement: confirm nonunion and deformity on CT; assess proximal pole vascularity (MRI plus intra-operative bleeding); debride, correct humpback and stabilise; salvage rather than reconstruct once SNAC arthritis is established.
Points of genuine controversy:
- Vascularised versus non-vascularised graft. Classic series and the Merrell meta-analysis favour vascularised grafts for avascular proximal poles, but the larger Duncumb 2022 systematic review found no significant difference in pooled union (88.7% versus 87.5%), and called for randomised trials.
- Open versus arthroscopic-assisted grafting for nonunion without major humpback, where union rates appear comparable.
Registry Evidence
Unlike arthroplasty, scaphoid nonunion is not tracked by national joint registries (NJR, AJRR, AOANJRR, SHAR, NZJR), which capture hip, knee and other joint replacements rather than carpal reconstruction. The best population-level evidence therefore comes from epidemiological cohorts (Garala 2016) and large pooled systematic reviews (Duncumb 2022) rather than implant registries.
Global Practice Variation
High-resource settings
- Routine CT for union/deformity and MRI for proximal pole viability
- Access to headless compression screws and vascularised graft (1,2 ICSRA, free MFC) techniques
- Microsurgical capability concentrated in tertiary hand units
Limited-resource settings
- Reliance on plain radiographs; delayed or missed initial diagnosis more common
- K-wire fixation and non-vascularised iliac crest/distal radius grafts predominate
- Later presentation increases the proportion presenting with established SNAC
Clinical Pearl
Exam framing: scaphoid nonunion has no Level I guideline, so candidates should reason from principles - confirm nonunion and deformity (CT), assess vascularity (MRI plus intra-operative bleeding), debride, correct humpback, stabilise, and salvage once SNAC arthritis is established - and be able to cite the controversy that pooled data (Duncumb 2022) question the assumed superiority of vascularised grafts.
SCAPHOID NONUNION
Clinical summary
Key Statistics
- •5-15% nonunion rate (30% proximal pole)
- •100% progress to SNAC wrist if untreated
- •80% blood from dorsal scaphoid branch (retrograde)
- •Only 20-30% of proximal pole has direct supply
Herbert D Classification
- •D1: Fibrous union - ORIF, may not need graft
- •D2: Pseudarthrosis - ORIF + bone graft
- •D3: Sclerotic - Debride + extensive graft
- •D4: AVN - VASCULARIZED bone graft required
Humpback Deformity
- •Flexion through nonunion site
- •Creates dorsal convexity (humpback)
- •Measure lateral intrascaphoid angle
- •Greater than 45 degrees = significant = wedge graft needed
Graft Selection
- •Viable bone (MRI signal+) = Non-vascularized graft
- •AVN (no MRI enhancement) = VBG (1,2 ICSRA)
- •Failed surgery = Free vascularized (MFC)
- •1,2 ICSRA: between 1st and 2nd compartments, supraretinacular
SNAC Stages
- •Stage 1: Radial styloid-scaphoid
- •Stage 2: + Scaphocapitate
- •Stage 3: + Capitolunate
- •Stage 4: Pancarpal (including radiolunate)
Must Know for Exam
- •Retrograde blood supply - proximal pole at risk
- •MRI with gadolinium for AVN assessment
- •VBG (1,2 ICSRA) for AVN - gold standard
- •Correct humpback with wedge graft
- •All untreated nonunions become SNAC