Nonunion of the scaphoid could be an incidental finding
after re-injury to the wrist. Risk fractures for nonunion include fractures
with displacement more than 1mm, fractures that have inadequate treatment,
fractures with instability, fractures that are displaced in a cast, proximal
pole fractures, and delayed immobilization more than 4 weeks increases the rate
of nonunion. An untreated scaphoid nonunion will have a high incidence of wrist
arthritis. Early arthritis will start at five years. At 10 years, the patient
will have significant arthritis. Arthritis will develop in stages: SNAC wrist
(Scaphoid Nonunion Advanced Collapse). The three stages of arthritis: stage I
arthritis is between the radial styloid and the scaphoid, stage II
scaphocapitate arthritis in addition to stage I, and stage III periscaphoid
arthritis including capitolunate arthritis. Scaphoid fractures that are left
untreated will have carpal collapse and 100% development of degenerative
arthritis. There is tendency for the fracture to gap open dorsally. Up to 35%
of the patients have a humpback deformity and 40% have a DISI deformity. A CT
scan along the scaphoid axis is the best test to check for nonunion of the
scaphoid bone. Treat scaphoid fracture nonunion early (before 5 years) because
the healing rate is much better. Correct the deformity and restore the scaphoid
length and alignment. Use bone graft and do rigid internal fixation. Volar
approach is used for waist fractures and fracture in the distal third of the
scaphoid. You may want to remove the edge of the trapezium to place the screw
in the volar approach. The humpback deformity is better corrected through the
volar approach. The dorsal approach is better for proximal nonunion because of
direct visualization of the nonunion. It helps reduction and also bone grafting
can be done through the same incision from the distal radius if necessary. For
a nonunion without AVN and no humpback deformity, do ORIF and bone graft or
percutaneous technique. The Russe procedure is used for distal or waist
fractures, patients with minimal deformity and no collapse, no excessive
humpback deformity, and over 90% union rate. The dorsal approach can also be
used for waist scaphoid fracture nonunion in addition to proximal nonunion. If
the patient has a nonunion and no AVN, but there is a significant humpback
deformity, there is a tendency of the fracture to pen dorsally. A significant
number of patients will have a DISI deformity (there is association between a
humpback deformity and DISI deformity). This patient will need an opening wedge
interposition graft to restore the scaphoid length and alignment. The humpback
deformity is best corrected from a volar approach (use interposition bone
graft). Nonunion that is associated with AVN, but there is no humpback
deformity, do ORIF and vascularized bone graft (1,2 ICSRA vascularized graft
from the dorsal aspect of the distal radius). This technique can also be used
for nonunion of the proximal pole. If the nonunion has an associated AVN and a
major humpback deformity, because it is an AVN, you will use a vascularized
graft, and because you have a humpback deformity, you will need a larger graft,
so you will use a vascularized bone graft from the medial femoral condyle (use
this technique if there is no arthritis, it utilizes the descending genicular
artery pedicle). Punctate bleeding of bone during surgery may indicate good
prognosis for healing of the nonunion. To treat a stage I SNAC wrist, do radial
styloid excision plus bone graft for the nonunion. Do not remove more than 4mm
of the radial styloid; avoid injury of the radioscaphocapitate ligament. To
treat stage II & III SNAC wrist, do scaphoid excision and four corner
fusion in younger patients; do proximal row carpectomy. Do not do proximal row
carpectomy if the capitolunate joint is involved with arthritis. Preservation
of the radioscaphocapitate ligament will prevent ulnar subluxation of the
carpus (it is the primary stabilizer of the wrist following proximal row
carpectomy). You can do arthrodesis for pancarpal arthritis.
