A dorsal approach to proximal scaphoid nonunions allows easier access for removing the necrotic bone from the proximal pole and applying accurate screw or pin fixation.. Table 1 Preventi
Trang 1Thomas E Trumble, MD, Peter Salas, MD, Traci Barthel, MD, and Kearny Q Robert III, MD
Abstract
Scaphoid nonunions are rarely
symp-tomatic in the early stages, and the
success rate of management
decreas-es with the duration of the nonunion.1-4
Scaphoid nonunions occur when
frac-tures are not diagnosed and managed
initially or when they have not healed
with cast immobilization within 6
months of injury Fractures that do not
show signs of radiographic healing
af-ter 6 to 8 weeks of cast
immobiliza-tion and fractures diagnosed 6 weeks
after injury are less likely to heal
Af-ter an even longer duration,
unman-aged scaphoid nonunions
frequent-ly cause wrist pain and lead to
progressive arthrosis.5,6
Because it is not usually possible
to determine how long a nonunion has
been present or how many patients
with asymptomatic nonunions occur
in a particular population, the
natu-ral history of scaphoid nonunions has
not been clearly delineated.1-3
Conse-quently, the risk for developing wrist
arthrosis from a scaphoid nonunion
cannot be calculated However, a
growing body of data suggests that
most symptomatic nonunions
even-tually develop a collapse deformity, followed by onset of wrist arthrosis.4,6-8 During the last 15 years, major ad-vances have occurred in the ability to diagnose scaphoid nonunions and evaluate collapse deformity using computed tomography (CT) Osteone-crosis can be detected in the proximal pole of the scaphoid with magnetic resonance imaging (MRI), enabling better planning for surgery.9Fracture fixation has improved with the devel-opment of specially designed screws that can stabilize a bone covered by articular surface at both ends with fragile blood supply entering between the two cartilaginous ends
Anatomy and Pathophysiology
The articular surfaces of the proximal and distal poles of the scaphoid are rotated with respect to each other The plane of the scaphoid is tilted both vo-larly and radially with respect to the central axis of the forearm; this obliq-uity adds to the complexity of
surgi-cal management The proximal half
of the scaphoid is covered almost com-pletely with articular surface with few,
if any, perforating vessels Thus, the vascularity of the scaphoid is based primarily on retrograde blood flow Vessels entering the scaphoid through the dorsal ridge supply blood to 70%
to 80% of the bone, and vessels that enter it through the volar branches of the artery supply the remaining 20%
to 30%10(Fig 1)
Because the scaphoid is a vital link between the proximal and distal car-pal rows, a scaphoid fracture can se-verely disrupt carpal mechanics Me-chanical instability allows fracture displacement, which impedes healing
Dr Trumble is Professor and Chief, Hand and Mi-crovascular Surgery Service, University of Wash-ington Medical Center, Seattle, WA Dr Salas is Fellow, Hand Surgery, Department of Orthopaedic Surgery and Sports Medicine, University of Wash-ington, Seattle Dr Barthel is Fellow, Hand Sur-gery, Department of Orthopaedic Surgery and Sports Medicine, University of Washington Dr Robert is Fellow, Hand Surgery, Department of Orthopaedic Surgery and Sports Medicine, Uni-versity of Washington.
None of the following authors or the departments with which they are affiliated has received anything
of value from or owns stock in a commercial com-pany or institution related directly or indirectly
to the subject of this article: Dr Trumble, Dr Salas,
Dr Barthel Dr Robert or the department with which he is affiliated has received research or in-stitutional support from Synthes USA Reprint requests: Dr Trumble, University of Washington Medical Center, Box 356500, 1959
NE Pacific, Seattle, WA 98195.
Copyright 2003 by the American Academy of Orthopaedic Surgeons.
Scaphoid nonunions result in a predictable pattern of wrist arthrosis To minimize
the incidence of arthrosis, the goal of treatment should be consolidation of the
frac-ture with the scaphoid in anatomic alignment Computed tomography and
mag-netic resonance imaging scans can aid evaluation of carpal collapse, scaphoid
col-lapse, scaphoid nonunion, bone loss, and detection of osteonecrosis Nonunion of
the scaphoid waist may result in a humpback deformity, increasing the chances of
further collapse and arthrosis This collapse deformity must be approached volarly
with an intercalary bone graft and internal fixation A dorsal approach to proximal
scaphoid nonunions allows easier access for removing the necrotic bone from the
proximal pole and applying accurate screw or pin fixation Vascularized bone graft
is recommended to manage scaphoid nonunions with osteonecrosis.
J Am Acad Orthop Surg 2003;11:380-391
Trang 2and causes abnormal carpal
kinemat-ics and loading, leading to wrist
arthrosis.6,11-14Normally, the
connec-tion of the scaphoid to the lunate via
the scapholunate interosseous
liga-ment draws the lunate into a flexed
position as the wrist moves from
ul-nar to radial deviation Scaphoid
col-lapse with palmar flexion of the
dis-tal pole reduces the carpal height and
allows the lunate to rotate in a
dor-sal intercalated segmental instability
(DISI) pattern A pattern of arthritis
known as scaphoid nonunion
ad-vanced collapse occurs once a DISI
deformity becomes fixed from loss of
mechanical integrity of the scaphoid
This deformity closely resembles the
pattern of arthrosis that results from
chronic disruption of the
scapholu-nate interosseous ligament
Most scaphoid fractures occur as
a result of a fall, sports injury, or
ve-hicular accident When the hand is
out-stretched and the wrist is in ulnar
de-viation, the scaphoid is aligned (and
colinear) with the axis of the radius,
which produces a bending moment
Thus, the distal portion of the scaphoid
is forced into palmar flexion, and an
acute humpback deformity is
creat-ed as the fracture occurs with
com-minution of the volar scaphoid waist
Etiology and Prevention
The most frequently cited factors
in-volved in the development of scaphoid
nonunion are tenuous blood supply
in the scaphoid (especially the prox-imal pole), delay in diagnosis and management, fracture displacement/
comminution, and inadequate immo-bilization or poor patient compliance
These injuries often are perceived to
be simple wrist sprains, an oversight that contributes to delay in diagno-sis Adequate radiographs and care-ful physical examination are helpcare-ful but not foolproof in diagnosing acute scaphoid fracture Acute scaphoid frac-tures with collapse into a malalign-ment or a humpback deformity or with displacement≥1.0 mm, an intra-scaphoid angle >45°, or a height-to-length ratio >0.6515,16have a higher incidence of malunion and non-union.6,17Comminution results in a highly unstable fracture that requires internal fixation to avoid a collapse deformity Patient compliance is dif-ficult to measure at the beginning of
casting Many patients express anx-iety about prolonged cast immobili-zation, especially active individuals aged 18 to 28 years.18Some nonunions may be preventable with earlier sur-gical management in patients with poor prognostic features (Table 1) Spontaneous healing of scaphoid nonunions without specific treatment has been reported, but that outcome
is extremely rare.20Although asymp-tomatic nonunions without evidence
of carpal collapse have been identi-fied, several studies have reported ra-diographic evidence of radiocarpal ar-throsis within 10 years in almost all patients with scaphoid nonunion.1,2,21 These studies may be subject to sam-pling bias in that they have included only patients who presented with symptoms, thus underrepresenting those who were asymptomatic None-theless, they offer strong evidence sup-porting surgical management of scaphoid nonunions to prevent fur-ther carpal collapse and degenerative wrist arthrosis
Evaluation Physical Examination
Scaphoid nonunion can be insid-ious in onset and may not be associ-ated with a definite history of
trau-ma Patients may complain of a vague ache involving the wrist The most common presentation is pain and loss
of wrist motion Some athletes
mod-Figure 1 Radial view The primary blood supply to the scaphoid is through the dorsal branch
of the radial artery MCI = first metacarpal, R = radius, S = scaphoid, Tz = trapezium.
Table 1 Prevention of Scaphoid Nonunions 6,15,19
To prevent scaphoid nonunions and malunions, surgical treatment is recom-mended with any of the following:
Fracture displacement≥1.0 mm Fracture comminution
Any proximal pole fracture Delay in diagnosis and initial treatment Fracture angulation in the sagittal plane with a lateral intrascaphoid angle
>45° or a height-to-length ratio >0.65 Poor patient compliance as evaluated from the patient interview
Trang 3ify their activities, such as doing
knuckle pushups rather than using
their palms Such adaptive behaviors
may indicate the necessity of
radio-graphs and appropriate diagnostic
tests Pain to palpation in the
anatom-ic snuffbox is a less reliable way of
di-agnosing scaphoid nonunion
Radiographic Evaluation
Standard radiographs of a patient
with a suspected scaphoid nonunion
should include the following views:
posteroanterior, lateral wrist,
scaph-oid (posteroanterior in ulnar
devia-tion), and oblique with 45° to 60° of
pronation These radiographs also may
reveal evidence of arthritis, including
scaphoid sclerosis, cyst formation, and
bone resorption Careful examination
of the lateral radiographs will help
de-termine whether DISI with dorsal
ro-tation of the lunate is present A
scapholunate angle >60° or a
radiolu-nate angle >30° indicates a DISI
de-formity.4,22If a DISI deformity is
pres-ent, it can be difficult to correct both
the alignment of the scaphoid and the
normal scaphoid-lunate relationship
When radiographs are equivocal,
CT scans are useful in detecting
scaphoid nonunions or incomplete
unions They also aid surgical
plan-ning (ie, bone graft type and location)
in patients with extensive areas of
col-lapse and/or bone resorption In
ad-dition, CT scans provide more precise
definition of the osseous anatomy and
measurement of intrascaphoid angles
When definitive evaluation of fracture
healing is needed, such as before
re-turning to heavy work or contact
sports, CT scans of the sagittal plane
of the scaphoid (not the wrist) are done
to quantify cortical bridging.4
Carpal collapse in the sagittal
plane of the scaphoid can be
deter-mined by measuring the lateral
in-trascaphoid angle6(Fig 2, A) or the
height-to-length ratio15,16(Fig 2, B) on
sagittal CT scans.23The mean lateral
intrascaphoid angle is 24° in patients
with a normal scaphoid.6An angle
>45° is associated with an increased
incidence of arthrosis even in frac-tures that have healed.6Bain and col-leagues15,16reported greater
observ-er reliability with the height-to-length ratio than with intrascaphoid angles
A height-to-length ratio >0.65 corre-sponded to significant scaphoid col-lapse; however, clinical correlation with management options was not evaluated
MRI scans can be used to detect oc-cult acute scaphoid fractures,24 eval-uate scaphoid nonunions, and assess viability of the fracture fragments Be-cause the vascularity of the proximal pole can be difficult to assess on plain radiographs, MRI should be
strong-ly considered in cases of scaphoid waist nonunions However, if plain radiographs clearly show osteonecro-sis, MRI is not necessary Proximal pole scaphoid nonunions may be as-sumed to be dysvascular, and
empir-ic management can be initiated with
vascularized bone grafting
Howev-er, it is important to accurately eval-uate nonunions of the waist and prox-imal one third of the scaphoid (Fig 3) The more proximal the initial in-jury, the greater the likelihood of de-veloping osteonecrosis Additionally, MRI is indicated in patients with non-unions refractory to previous surgery
to determine the extent of necrotic bone
Fractures/nonunions with low signal on both T1- and T2-weighted sequences seem to be associated with the greatest compromise of vascular supply and have suboptimal healing rates after nonvascularized grafts9 (Fig 3, B) Proximal fragments with hypointense T1-weighted marrow signal have demonstrated osteone-crosis, empty bone lacunae, and poor uptake of fluorescent bone labels on biopsy.9In contrast, retention of some proximal pole signal has been
asso-Figure 2 A,Sagittal CT scan of a displaced fracture with a lateral intrascaphoid angle of 66° The lateral intrascaphoid angle (normal, ≤30°) is formed by lines (a and d) perpendicular
to the diameters of the proximal and distal poles (b and c) B, Sagittal CT scan of an intact
scaphoid The height-to-length ratio should average <0.65 A greater ratio indicates collapse
of the scaphoid (Reprinted with permission from Trumble TE, Gilbert M, Murray LW, Smith
J, Rafijah G, McCallister WV: Displaced scaphoid fractures treated with open reduction and
internal fixation with a cannulated screw J Bone Joint Surg Am 2000;82:633-641.)
Trang 4ciated with viable bone on histologic
examination and normal uptake of
fluorescent labels.9
Management
Surgical management of established
scaphoid nonunions is necessary
giv-en the strong likelihood of evgiv-entual
development of radiocarpal arthrosis
with a persistent nonunion Patients
younger than 40 years with a short
duration of nonunion (<2 years) have
the best prognosis in the absence of
osteonecrosis of the proximal pole CT
and MRI scans can help evaluate
non-union in patients with minimal
ar-throsis present on plain radiographs
If a significant collapse exists, the
ex-tent of bone resorption and the
loca-tion of the fracture can be difficult to
ascertain A CT scan will help in
plan-ning the surgical reconstruction If
os-teonecrosis is suspected, an MRI scan
should be obtained to plan the type
of graft to be used
Most hand surgeons recommend
open reduction and internal fixation
of the nonunion combined with bone
graft.19,24-28 Cast immobilization for
scaphoid nonunion is not as effective
as surgical intervention Electrical
stimulation cannot be used as the sole
treatment, but it can be used in con-junction with either casting or sur-gery Overall success rates for heal-ing with the combination of cast immobilization and pulsed electro-magnetic fields is 69%.29Previously, stimulation required an invasive tech-nique for proper electrode position-ing, but the advent of pulsed ultra-sound or electromagnetic fields has eliminated this difficulty.30 Concom-itant long arm casting has been asso-ciated with a higher likelihood of healing when bone stimulators are used Patients with nonunions of more than 5 years’ duration or with proximal pole nonunions have less fa-vorable outcomes.22 Because union rates with pulsed electromagnetic fields are inferior to those with sur-gery, it should be used as an adjunct
to surgery or in cases in which sur-gery is not feasible and cast immo-bilization is the only option
Management hinges on whether os-teonecrosis of the proximal pole is present When a scaphoid nonunion
is present with normal vascularity of the proximal pole, internal fixation and nonvascularized grafting is recom-mended, with the approach directed
by the site of the fracture Initially, af-ter excision of the sclerotic bone, can-cellous autograft was packed into the
nonunion defect through a dorsal ap-proach Russe31modified this
meth-od by advocating a volar approach and use of an oblong-shaped graft Russe also reported another modification in which two matching corticocancellous iliac crest grafts were implanted with their cancellous sides facing each
oth-er.31However, one study, following
a technique advocated by Russe, dem-onstrated only a 71% union rate Heal-ing was less likely with proximal pole nonunions and in the presence of os-teonecrosis.32
The location of the nonunion helps
to determine the surgical approach
A dorsal approach is used for prox-imal pole nonunions and a volar ap-proach for scaphoid waist non-unions.33,34 Studies by Inoue and Shionoya35and Robbins et al36have demonstrated that proximal pole nonunions can heal with stable inter-nal fixation and bone grafting How-ever, Green32showed that the rate of healing correlated directly with the vascularity of the proximal pole Un-fortunately, fibrous unions and per-sistent nonunions tend to develop when osteonecrosis of the proximal pole is present Such conditions often are refractory to traditional grafting methods, even when augmented with internal fixation
Vascularized bone grafts are used for proximal pole nonunions and oc-casionally for scaphoid waist fractures with osteonecrosis, or when
tradition-al bone grafting has failed to achieve union Intercarpal instability requires careful attention to correct any hump-back deformity at the nonunion site, usually through placement of a vo-larly based wedge graft Early vascu-larized grafts often were based on a pedicle from the pronator quadratus muscle insertion on the distal radius, but this graft was difficult to place be-cause of the short, bulky pedicle More recent reports have advocated the use
of a variety of sources, including the ulnar artery, the first dorsal metacar-pal artery, and even a free vascular-ized graft from the iliac crest.37,38
Figure 3 A,T1-weighted coronal MRI scan showing normal signal intensity from the
prox-imal pole to the scaphoid despite fracture, indicating normal vascularity of the proxprox-imal pole.
B,T1-weighted MRI scan showing the loss of signal from the proximal pole of the scaphoid
(arrow), consistent with osteonecrosis (Reprinted with permission from Trumble TE:
Avas-cular necrosis after scaphoid fracture: A correlation of magnetic resonance imaging and
his-tology J Hand Surg [Am] 1990;15:757-764.)
Trang 5Fernandez and Eggli39modified the
Hori technique40of implanting the
vas-cular bundle from the second dorsal
intermetacarpal artery into the
non-union site, in addition to a wedge bone
graft Although the vascular pedicle
lacked an osseous component, union
was achieved in 10 of 11 patients at
a mean of 10 weeks after surgery The
most frequently used donor sites
in-clude the dorsoradial aspect of the
dis-tal radius and the index metacarpal
(based on the first dorsal metacarpal
artery).41-43When osteonecrosis of the
proximal pole is present, a dorsal
ap-proach can be used with either a
vas-cularized bone graft from the distal
radius41or, in selected cases
requir-ing a very small graft, a second
meta-carpal bone graft.42The unsolved
re-constructive problem is the scaphoid
nonunion with osteonecrosis and
col-lapse requiring a volar wedge with a
vascularized graft Possible solutions
include (1) a dorsal approach with a
radial styloidectomy to facilitate
plac-ing the Zaidemberg graft volarly, (2)
a dorsal approach with a vascularized
second metacarpal bone graft that has
a pedicle allowing it to be rotated
vo-larly, and (3) two separate
approach-es using a standard Fernandez39,44,45
volar bone graft and a second dorsal
approach for a Zaidemberg
vascular-ized bone graft or second metacarpal
vascularized bone graft.22
One criticism of the use of bone
graft alone is the long period of
post-operative immobilization that often
is required (usually >6 months) For
this reason, the addition of
supple-mental internal fixation recently has
gained favor, with a gratifying
in-crease in union rates (consistently
>90%) and a reduction in duration of
immobilization.4,35,46-49Internal
fixa-tion in conjuncfixa-tion with bone
graft-ing can be done with staples, wires,
and screws However, staples may
cause distraction of the fracture site
and rarely are used Multiple
Kirsch-ner wires (K-wires) can provide
fix-ation but not the compressive effect
that is achieved with screw fixation
The wires must be removed eventu-ally, but they may have to be removed before union if they migrate or be-come prominent Although K-wires initially were used to stabilize the scaphoid, screws with threads at their ends or along their entire course can
be buried beneath the articular sur-faces to prevent impingement Sev-eral screws have been specifically de-signed for use in the scaphoid The Herbert screw is a double-threaded noncannulated screw with a differen-tial pitch that allows for compression
at the fracture site Its insertion can
be facilitated with a positioning jig
The Herbert-Whipple screw, its can-nulated counterpart, may allow more optimal positioning via placement of
an initial guidewire.4 The Acutrak screw (Acumed, Hillsboro, OR)50,51is cannulated and has a tapered diam-eter Regardless of the type of screw used, accurate centering of the im-plant is critical Trumble and col-leagues4,17,52found that successful po-sitioning of screws within the central third of the proximal pole was
signif-icantly (P < 0.05) more likely with
can-nulated implants, and time to union was reduced more than 50% Salvage procedures, such as ra-dial styloidectomy, proximal row carpectomy, limited intercarpal ar-throdesis, and complete wrist fusion, are reserved for cases of severe de-generative arthrosis
Surgical Techniques Scaphoid Waist Nonunions With
a Viable Proximal Pole
Scaphoid waist fractures with a vi-able proximal pole should be ap-proached volarly to preserve the re-maining dorsal blood supply Unlike the acute fractures that can be ap-proached using a small incision over the scaphotrapezial joint, the Russe technique is used, with an incision made along the course of the flexor carpi radialis (FCR) longus muscle, extending distally along the border of the glabrous skin of the thenar em-inence (Fig 4, A) Splitting the sheath
Figure 4 A,The sheath of the flexor carpi radialis (as noted by the pen) is incised to expose
the capsule overlying the scaphoid B, The scaphoid nonunion is exposed by incising the
floor of the flexor carpi radialis sheath that forms the volar capsule of the radioscaphoid ar-ticulation If possible, the radioscaphocapitate ligament is preserved FCR = flexor carpi ra-dialis, PQ = pronator quadratus muscle, R = radius, S = scaphoid, Tz = trapezium.
Trang 6of the FCR allows it to be retracted
ulnarly to protect the palmar
cutane-ous branch of the median nerve The
floor of the FCR sheath is incised
lon-gitudinally to expose the distal pole
and waist of the scaphoid (Fig 4, B)
Preservation of as much of the
radio-scaphocapitate ligament as possible
is important because it helps to
con-tain the proximal pole and prevent
it from subluxating volarly.4,17If
can-nulated screws are used, it is not
necessary to completely divide the
ra-dioscaphocapitate to facilitate
place-ment of the guide The humpback
de-formity must be corrected to allow
stable fixation with the screw in the
long axis of the scaphoid4,6(Fig 5)
Small osteotomes are used to wedge
the collapsed scaphoid into its correct
alignment (Fig 6) Care must be
tak-en not to disrupt the dorsal cortex of
the scaphoid, which can damage any
remaining blood supply to the
prox-imal pole and make the fracture
high-ly unstable Full excavation of the
nonunion site is accomplished with
fine curettes and a high-speed burr
with saline irrigation The burr is
re-quired largely to remove sclerotic
por-tions of the proximal pole Dental
picks or K-wire joysticks can help
re-duce the scaphoid nonunion
With a volar approach, the inner
wall of the dorsal cortex can be notched
to accommodate the wedge graft The
dorsal cortex serves as a hinge around
which the distal fragment can be
ro-tated as it is reduced with wrist
dor-siflexion Because the screw fixation
offers significant stability, a cancellous
rather than corticocancellous bone graft
can be used; the guidewire prevents scaphoid collapse as the screw com-presses the fracture site When large segments of the volar cortex are miss-ing, the corticocancellous graft aids stability, especially if it can be com-pressed with the scaphoid screw To provide the best access for insertion
of a screw into the long axis of the scaphoid, it is important to remove the small volar lip of the trapezium with a rongeur Failure to do so can result in a screw that is placed too dor-sal and too close to the fracture line
in the proximal pole (Fig 7)
The guidewire is inserted with a power drill up to the limits of the sub-chondral bone to measure the length
of the screw With an unstable non-union, a second wire is placed into the scaphoid to prevent rotation of the fragments during screw insertion
This derotation wire helps stabilize scaphoid alignment while the screw
is placed into the center of the prox-imal pole When large bone grafts are needed, rendering the screw fixation
less stable, the derotation wire can be left in place for approximately 3 months53(Fig 7) The guidewire then
is driven into the radius to prevent
it from dislodging The cannulated drill and tap prepare the path for the screw, and progress is monitored with fluoroscopy After the screw is
insert-ed, the guidewire is removed and plain radiographs are made to con-firm the position of the screw (Fig 8) Inlay grafting does not achieve ad-equate correction of deformity in scaphoid nonunions with palmar flex-ion of the distal fragment This defor-mity must be corrected to allow for stable screw fixation in the long axis
of the scaphoid These humpback scaphoids may be associated with the DISI pattern of carpal collapse, in which the lunate assumes a
relative-ly fixed dorsiflexed position Fisk54 noted that the position of the lunate can be corrected by filling the defect
of the scaphoid nonunion with a trap-ezoidal bone graft Because the broad base of the defect faces volarly, the
Figure 5 A wedge of bone graft used to
cor-rect the humpback deformity Axial placement
of the screw stabilizes the correction.
Figure 6 A,Small osteotomes can be used to correct the humpback deformity of the scaphoid
nonunion B and C, Cancellous or tricortical bone graft can be harvested from the iliac crest
or distal radius to help maintain the corrected position of the scaphoid Supplemental in-ternal fixation is recommended S = scaphoid, Tz = trapezium.
Trang 7wedge autograft is inserted so its apex
is positioned dorsally, thus
abolish-ing the humpback deformity Fisk used
a radial approach to the scaphoid and
radial styloid bone graft without
in-ternal fixation Fernandez44modified
this technique by using graft from the
iliac crest and a volar incision with
internal fixation (Fig 6) Recent reports
on the Fisk-Fernandez technique show
union rates that consistently exceed
90%, with fairly rapid healing (in the
absence of osteonecrosis) that
obvi-ates the need for prolonged
immobili-zation.4,35,46-49Cannulated screw
fix-ation improves the accuracy of screw
placement in these difficult
non-unions.4Better functional scores,
in-cluding range-of-motion arcs, were
ob-tained when DISI collapse was corrected with adequate restoration
of scaphoid height.55One report sug-gests that the correction is more pre-dictably obtained with proper lunate reduction and temporary radiolu-nate pinning done before placement
of the scaphoid graft.56The radiolu-nate pin is removed at the conclusion
of the procedure However, the lu-nate may remain in a dorsally
rotat-ed position despite correction of the humpback deformity, especially in long-standing nonunions
Proximal Pole Nonunions With
an Avascular Proximal Pole
The dorsal approach is preferred for proximal pole fractures because the small proximal fragment often can
be difficult to target from the volar ap-proach Also, placing the screw vo-larly can displace the proximal pole.36Usually the fracture line of a nonunion occurs from distal volar to proximal dorsal Thus, a screw may not cross the nonunion if a volar ap-proach is used (Fig 9, A) The dorsal approach allows screw placement in the central portion of the proximal pole fragment (Fig 9, B) Realizing that the vascular supply of the prox-imal fragment already has been sig-nificantly compromised by a fracture mitigates concerns that a dorsal ap-proach might further threaten
vascu-larity Implants can be inserted either freehand or with the use of a guidewire advanced from proximal
to distal toward the trapezium Im-plants must be countersunk ade-quately because insertion is per-formed in the center of the articular surface of the proximal pole The dorsal approach is performed using a small longitudinal incision made in the midline of the wrist cen-tered over the radiocarpal joint The sheath of the extensor pollicis longus (EPL) muscle is released, and a lon-gitudinal incision is made in the sule of the radiocarpal joint The cap-sule and fourth dorsal compartment are sharply dissected off the dorsal lip
of the radius to expose the scapho-lunate articulation (Fig 10) Because the nonunion site can be difficult to identify, a needle often is used under fluoroscopy as a guide pin to help lo-cate the correct plane of the nonunion Small curettes are used to remove the necrotic bone without disrupting sig-nificant amounts of the articular car-tilage Occasionally, a high-speed burr is necessary to remove the dense necrotic bone It is important to pro-tect the vessels entering the distal dor-sal ridge of the scaphoid
The entry site for the screw just ad-jacent to the scapholunate interos-seous ligament can be visualized by flexing the wrist The noncannulated Herbert screw can be inserted free-hand, or a cannulated screw can be used The guide pin position is con-firmed with fluoroscopy and then driven up to the subchondral bone of the distal pole The length of the screw is measured with a depth gauge Frequently, placement of a sec-ond derotational K-wire will prevent the screw insertion from displacing the proximal pole fragment The guide pin then is driven into the tra-pezium to prevent it from dislodging The hole is drilled and tapped before inserting the screw In small proximal pole fragments, the guide pin is re-moved and a noncannulated Herbert screw is inserted because it leaves a
Figure 7 The volar lip of the trapezium is removed and the cannulated scaphoid screw is
inserted into the long axis of the scaphoid to obtain excellent purchase in the proximal pole.
If the lip of the trapezium is not removed, the starting point for the screw is too volar and
the proximal end of the screw is placed too dorsal The guidewire prevents rotation of the
small fracture fragment during screw placement.
Figure 8 Anteroposterior radiograph The
cannulated screw is placed in the center of
the scaphoid proximal pole (arrows), which
will ensure the best compression of the
non-union and the most stable configuration.
Trang 8smaller defect or footprint in the
car-tilage of the proximal pole A
mini-Acutrak screw can also be used
Vascularized Bone Grafting for
Proximal Pole Nonunions With
Osteonecrosis
The vascularized bone graft
de-scribed by Zaidemberg et al41relies
on the arterial branch of the radial
ar-tery that courses between the first and
second dorsal compartments27(1,2
in-tracompartmental supraretinacular
artery [1,2 ICSRA]) (Fig 11) This graft
provides blood supply as well as the
bone graft to fill the bone void in the
nonunion The 1,2 ICSRA lies deep to
the tendons of the first dorsal
com-partment and travels in a
distal-to-proximal direction between the two
compartments.Adorsoradial approach
allows for harvesting of the graft as
well as exposure of the scaphoid
non-union as an extension of the dorsal
approach for the viable proximal pole
The incision begins over the midline
of the dorsal region of the wrist and
curves proximal and radial over the
interval between the first and second
dorsal compartments The third
dor-sal compartment, which contains the
EPL muscle, is released, and the EPL
muscle is retracted radially The
sen-sory branch of the radial nerve is
iden-tified exiting from between the
bra-chioradialis and the extensor carpi
radialis longus muscles The extensor
carpi radialis longus is retracted
ul-narly, and the capsule of the wrist is
incised longitudinally to expose the scaphoid
The vascularized bone graft is har-vested with an elliptical paddle of cor-ticocancellous bone, periosteum, and retinaculum supplied by the recur-rent vessel from the radial artery The 1,2 ICSRA is visible as a thin red line
in the groove between the first and second dorsal compartments The vessel originates distally from the ra-dius and pierces the volar wall of the first dorsal compartment The first dorsal compartment is released along its palmar surface and the tendons re-tracted The artery is mobilized by making parallel incisions in the peri-osteum between the two
compart-ments, tracing the course of the artery from distal to proximal Once a
2.0-to 2.5-cm pedicle has been prepared, the periosteum around the planned donor site is incised as an ellipse or rectangle A fine oscillating saw with constant irrigation is used to cut three sides of the graft Small osteotomes then are used to complete the eleva-tion of the graft After preparaeleva-tion of the scaphoid nonunion site, the vas-cularized graft is rotated into the de-fect and secured with either K-wires
or a scaphoid screw The capsule is closed loosely to avoid strangulation
of the vascular pedicle
Union was achieved in all 11 pa-tients included in the original article
Figure 9 A,Volar screw insertion in a proximal pole fracture The proximal threads of the cannulated screw do not cross the nonunion
site B, Dorsal screw placement results in stable fixation of the proximal pole fracture.
Figure 10 A,The proximal pole nonunion is approached dorsally by incising the third
dor-sal compartment and sharply elevating the fourth dordor-sal compartment off the capsule B, A
screw and derotational K-wire in the scaphoid for fixation of a proximal pole fragment.
C = capitate, L = lunate, S = scaphoid.
Trang 9by Zaidemberg et al.41 Although
union rates associated with the
var-ious vascularized bone grafts appear
to be high, the infrequent use of these
grafts makes it difficult to determine
the superiority of this technique over
others Nonetheless, vascularized
bone grafting clearly has a role in the
treatment of scaphoid nonunions
Scaphoid Waist Nonunions With
an Avascular Proximal Fragment
Scaphoid waist fractures with
os-teonecrosis of the proximal fragment can be managed with a vascularized bone graft through a dorsal approach, using internal fixation with a scaphoid screw, as described for prox-imal pole fractures The deformity is best corrected with a volar bone graft
In cases with a severe humpback de-formity, the graft can be placed vo-larly by rotating the graft under the radial artery Often, additional non-vascularized bone graft is required to help fill the void left by the removal
of necrotic bone The radial styloid can be removed to improve the ex-posure and to avoid later impinge-ment when the scaphoid deformity cannot be corrected
Salvage Procedures for Scaphoid Nonunions With Arthritis
Once significant radiocarpal or inter-carpal arthrosis has developed be-cause of a scaphoid nonunion, bone grafting and/or internal fixation is unlikely to produce a successful re-sult A different armamentarium of salvage procedures is needed to treat scaphoid nonunion advanced col-lapse (SNAC)
As the scaphoid collapses, the car-pus rotates into a fixed DISI pattern with progression of arthritis that re-sembles the four stages of the arthri-tis from a scapholunate ligament dis-ruption.11,57-61Stage I shows beaking
of the radial styloid Stage II is marked by arthrosis of the radio-scaphoid joint Stage III occurs when the arthrosis extends to involve the capitolunate articulation Stage IV is the presence of pancarpal arthrosis
In stage I, a radial styloidectomy can
be done along with internal fixation and bone grafting of the scaphoid nonunion (Fig 12) For stage II arthro-sis, several options are available Malerich et al62described excision of the distal pole as the site of impinge-ment (Fig 13) The proximal pole was maintained to prevent migration of the capitate Ruch et al63performed arthroscopic excision of the radial sty-loid and the distal pole of the scaphoid Proximal row carpectomy and ulnar four-bone arthrodesis (cap-itate-lunate-triquetrum-hamate) with scaphoid excision also has been rec-ommended.64,65Advantages of prox-imal row carpectomy include relative ease of the procedure, a shorter pe-riod of postoperative immobilization, and elimination of concerns about nonunion at the fusion site.64A
pro-Figure 11 A through C, The vascular bone graft described by Zaidemberg is based on an
artery that runs in a retrograde fashion between the first and second dorsal compartments.
(Adapted with permission from Zaidemberg C, Siebert JW, Angrigiani C: A new
vascular-ized bone graft for scaphoid nonunion J Hand Surg [Am] 1991;16:474-478.)
Trang 10gression of the arthrosis between the
lunate and capitate has been
report-ed, although the patients remained
asymptomatic.63A four-bone
arthro-desis combined with scaphoid exci-sion is preferred for stage III SNAC
The development of advanced radio-lunate arthrosis (stage IV) usually is
an indication for complete wrist fu-sion Silicone carpal implants have a poor record because of problems of silicone synovitis, loosening, dislo-cation, and even breakage.66,67Their use after partial or complete exci-sion of the scaphoid is not recom-mended
Summary
Scaphoid nonunions are challenging because they may not always be symptomatic in their early stages; therefore, at delayed presentation, they can have greater bone loss, car-pal collapse, and loss of blood sup-ply The natural history of nonunions
is that eventual carpal collapse and degenerative arthrosis will ensue, usually within 10 years When non-unions are recognized in stable po-sition, bone grafting with use of sup-plemental fixation (typically, screws) yield union in almost all cases as long
as the proximal pole of the scaphoid
is free of osteonecrosis A volar ap-proach is appropriate for waist non-unions, whereas a dorsal approach is required for proximal pole nonunions
to allow for proper implant position-ing Restoration of scaphoid length and correction of existing humpback deformity should be achieved to op-timize results Proximal pole non-unions accompanied by osteone-crosis require the addition of a vascularized bone graft Vascularized grafts also may be useful for non-unions that fail to heal after adequate fixation and traditional grafting methods Salvage procedures, such as radial styloidectomy, scaphoid exci-sion with or without limited midcar-pal fusion, proximal row carpectomy, and total wrist fusion, are reserved for cases with severe carpal collapse and arthrosis
Figure 12 A,Anteroposterior radiograph demonstrating a painful stage I SNAC arthrosis
with beaking of the radial styloid (asterisk) and a “kissing” osteophyte on the scaphoid
(ar-row) B, Anteroposterior radiograph showing excision of the osteophytes, coupled with bone
grafting and internal fixation of the scaphoid The patient’s symptoms resolved.
Figure 13 A,Anteroposterior radiograph demonstrating stage II SNAC arthrosis, with
nar-rowing of the radioscaphoid articulation in addition to the beaking of the radial styloid The
capitolunate articulation (1) and the articulation between the proximal pole of the scaphoid
and the capitate (2) are spared of arthritis The arthritic changes occur between the distal
pole of the scaphoid and the capitate (3) and between the radial styloid and the scaphoid (4).
B,Excision of the distal pole of the scaphoid avoids impingement between the scaphoid and
radius and preserves the midcarpal articular surface (arrowheads) (Reprinted with
permis-sion from Malerich MM, Clifford J, Eaton B, Eaton R, Littler JW: Distal scaphoid resection
arthroplasty for the treatment of degenerative arthritis secondary to scaphoid nonunion.
J Hand Surg [Am] 1999;24:1196-1205.)