Scaphoid Fractures/ Non union/ AVN/ SNAC

• It has a dual blood supply, both from radial artery

• 80% is retrograde from the dorsal carpal branch which supplies the proximal pole (also from radial artery)
• 20% is antegrade from the superficial palmar branch from Radial artery

• Articular cartilage 75%
• Retrograde blood supply

• Waist > Proximal pole > distal pole

• Proximal pole 100%, proximal 1/3 30%, waist 20%, distal 10%

• due to intact SL ligament extending proximal pole as the lunate moves with the triquetrium (LT ligament extends)

• PA, Obliques (supinated + pronated), Ulnar deviated PA, Lateral

• No consensus on the best imaging modality - MRI, CT, Bone scan,
• personally, I will use MRI as my institution can obtain it rather quickly, and it has no risks of radiation.
• Options are CT, MRI or Bone scan. I will do CT scan if concerned about costs and speed. MRI if concerns about radiation, no issue on availability and costs.
• Recent Cochrane review in 2015 compared the 3 modalities in 11 studies. All three imaging tests were found to be highly accurate for definitive diagnosis. CT and MRI were comparable in diagnostic accuracy (the correct diagnosis is made). Although BS had significantly better accuracy than CT and MRI, it could lead to more people receiving unnecessary treatment.https://www.cochrane.org/CD010023/MUSKINJ_comparing-different-types-of-scan-ct-mri-bone-scan-for-diagnosis-of-clinically-suspected-scaphoid-fractures-when-initial-radiographs-are-negative
• Mallett et al. JBJS 2011 Both CT and MRI comparable. Both better at excluding scaphoid fractures.

• Herbert
• A = Stable Fractures =
• A1 Tubercle or
• A2 Incomplete waist
• B = Unstable Fractures
• B1 = distal oblique
• B2 = complete Waist
• B3 = proximal pole - as long as proximal pole (displaced or undisplaced) = unstable!
• B4 = transscaphoid perilunate
• C = Delayed union
• D = Established non union

• Not essential.
• JBJS 1991 RCT by Clay et al. 392 patients allocated to either standard Colles cast or thumb spica casted to IPJ. No difference in non union after 6 months

• Treatment for undisplaced scaphoid fracture is controversial and depends on Patient factors
• Elderly, low function ➔ Cast total 12 weeks (3 months!)
• Young, working, wants to RTW earlier ➔ Percutaneous screw
• SWIFFT study - Lancet 2020 Joseph Diaz et al.
• Bicortical waist fracture displaced < 2mm
• No difference in op vs no op in functional outcomes at 52 weeks
• More patients had complications from surgery.
10.1016@S0140-67362030931-4.pdf409.4KB
• Based on McQueen et al. 2008 RCT in JBJS. RCT of 60 patients with undisplaced WAIST fractures into 2 groups 30 screw, 30 Colles cast.
• Trend towards higher rate of nonuion in non op group (but not statistically significant)
• Surgery had more rapid return of function, sport and work.

• Patient and Injury factors
• P - well, high function
• Reccomendation will be ORIF to reduce the risk of non union
• Singh et al. Injury 2012 Meta-analysis of 1400 scaphoids. Displaced WAIST fractures 4 x higher risk of nonunion if treated in cast.

• “balance between cartilage damage (more in dorsal) vs trajectory for screw (better for dorsal) - mostly 75% is done palmar…
• 1. Volar – Trans FCR tendon down

• 2. Dorsal approach – Incision centered on Lister’s tubercle between 3rd and 4th extensor compartments. Beware SRN! [same approach as dorsal approach for perilunate]
• 3. Dorsolateral aka dorsoradial approach - between 1st and 3rd extensor compartments. [same as the approach used to approach base of thumb]

• I - scaphoid tubercle, along FCR tendon

• Ligate the superficial palmar branch of radial artery, retract FCR tendon ulnarly ➔ incise capsule and RSC ligament obliquely

• Because the scaphoid flexes forward
• Only makes sense that proximal pole ➔ dorsal
• Distal pole ➔ Volar

• Defined as fractures not uniting by 6 months
• 5-10% of scaphoid fractures

• Osseous resorption ➔ Pseudocysts ➔ Osteosclerosis ➔ Osteoarthritis (SNAC)

• CT scan - look at morphology of humpback
• MRI with contrast - look for AVN

• XR would show sclerosis, not radiolucency!

• Gold standard is Intraoperative assessment where by perfusion to the scaphoid is assessed by puncturing the proximal pole to visually inspect for signs of bleeding; this serves as the gold standard to which imaging modalities are then compared.
• Pre op,
• MRI with contrast found to have higher sensitivity and specificity
• CT scans found not to correlate with vascularity
• MRI more reliable

• Hypointensity on T1 + T2
• Lack of enhancement on fat-suppressed T1-weighted post-gadolinium sequences
• T1 post contrast ➔ showing enhancement ➔ no AVN
• T1 post contrast ➔ no enhancement ➔ AVN

• Traditionally, presence of AVN will indicate the need for a vascularized bone graft. As such, if there is AVN, …
• AVN = need vascularized graft
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Dorsal VBG - Zaidemberg graft (1,2 Intercomparmental Supraretinacular artery ICSRA) [cf. kien bock is 2,3 ICSRA]

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Volar VBG - from radial branch of palmar radiocarpal arch

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Free VBG - Medial femoral condyle
• No AVN = no need vascularized graft ➔ can be either Fisk interpositional or Ruse inlay. Choose depending on the need to correct deformity
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Unstable or need to correct deformity = need structural support = Fisk interpositional iliac crest graft

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If Stable = Ruse inlay graft

• “I will cast to union”

• No. Recent studies show that even with NVBG, union rates can be expected to be 80-90%

• Because the scaphoid flexes forward
• Only makes sense that proximal pole ➔ dorsal
• Distal pole ➔ Volar

“SNACK Vendor”

• Vender's Classification - 3 stages + 1

• 1 = Radial styloid Scaphoid arthritis
• 2 = + Scaphocapitate OA (due to humpback deformity, affects the SC joint first; proximal RS joint is still relatively congruent)
• 3 = + Capitolunate Arthritis
• Finally = pan arthritis and end stage collapse

• Dependant on the stage (non op always an option)
• 1 = Radial styloidectomy
• 2 = 4CF or PRC
• 3 = 4CF since CL joint is affected [if PRC then the arthritis capitate joint will articulate with the radius]
• 4 = Wrist Arthrodesis

• Wrist denervation can be done
• Original techniques uses 8 approaches to resect all 10 articular nerve branches, Now, it is done via 2 or 3 incisions
• Some of the nerves including the terminal branch of PIN between 3 and 4th EC, terminal branches of AIN, terminal branches of SRN.

• PRC - expect poorer weak strength due to shortening of tendons (theoretical)
• But overall minimal difference - expect ROM 60%, grip strength 80%

• Limited intercarpal fusions
• e.g. Lunate capitate fusion - after excision of scaphoid and KIV triquetrium.

• Fusion of Capitate, Hamate, Triquetrium and Lunate [HTCL]. usually w scaphoid excision

• Capitate will articulate with the radius; so not reccomended if capitolunate joint is already arthritic

• Eventual OA changes
• Incongruity of the radial lunate fossa with the capitate

• Mulford JHS 2009 systematic review – no difference in grip strength, function and pain relief
• Theoretically, PRC does produce an incongruent joint as capitate head has smaller curvature than lunate (try to avoid in younger)
• Also, PRC should only be done if no Lunocapitate arthritis ➔ if not the new radiocapitate joint will be arthritic and painful as well.