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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_574_Библиотеки_им_академика_М_И_Перельмана.pdf
The position of the guidewire and final screw is crucial to the
success of the procedure. For retrograde insertion, we have
found that drilling through the volar corner of the trapezium
usually gives the appropriate starting point. The angle is ulnar
and dorsal approximately 458 and follows the line of the thumb
ray.The guide pin must be in the center of the scaphoid in
all views.
Provisional fixation canbeobtainedwith aK-wire,
however,itshouldnot interferewith the desiredscrew
location. Asmall 3to4mm incision should be made at the
screw starting point. The drill is then inserted and driven by
handorpower. Care should be taken not to overdrill the
proximal fragment. If the fragments are unstable or the drill
is inducing rotation, asecond pin can be placed outside the
center of the scaphoid to stabilize the bone. Next, the screw is
placed to the exact depth desired. Length should be accurate to
ensure that the screw is buried at least 2mmonboth the
proximal and distal ends. The goal is to keep the alignment,
induce bone healing, and stabilize the entire scaphoid. Ty pically,one nylon stitch is all that is needed and athumb spica
splint is placed on the extremity.
Currently Available Implants
Thereare currentlytwo bioabsorbablescrewsfor scaphoid
fixation available on the market. Biocomposites, Inc. (Staffordshire, U.K.) makes aproduct called the Little Grafter and is
available for the fixation of scaphoid and various other small
bone fractures. It is a4-mm screw available in asize range of
17 to 27 mm. It can be inserted in apercutaneous method or
through an open approach. It is osteoconductive and provides a
bioactive scaffold for new bone growth. Arthrex, Inc. (Naples,
Florida, U.S.A.) makes abiocompressionscrew that is also
available for fixation of scaphoid fractures. The screw is headless, absorbable and can be inserted either through an open or
percutaneous technique (Figs. 9–11). The company recommends
inserting the screw from adorsal approach in an antegrade
fashion. The screw is only available in one length with 3.7-mm
proximal diameter and 2.7-mm distal diameter.Itiscomposed
of aPLLA polymer.
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OUTCOMES
Bailey et al. (28) studied the biomechanical properties of anew
composite bioresorbable screw in abone model produced from
rigid polyurethane. These authors used abioresorbable cannulated screw composed of PLLA and hydroxyapatite. The study
evaluatedinterfragmentarycompression generatedbythis
screw comparedwithfour conventionalmetal screws. The
mean maximum compression forces for the resorbablescrew,
theAsnis,and Acutrakscrews werecomparableand no
statistical difference was found. The compression forces of the
(B)
(A)
FIGURE 8 Postoperative X-rays show near anatomic alignment of the
metacarpal fracture in the ( A )anterior–posterior and ( B )lateral views.
Source:Courtesy of John T. Capo, MD.
FIGURE 9 Thebiocompression screw from Arthrex Corporation
(Naples, Florida, U.S.A.). It has aconical shape and avariable pitch
screw thread. Source:Photo courtesy of Arthrex Corporation.
24
&
Kavanaghetal.
Herbert and Herbert-Whipple screws weresignificantly lower
(Herbert 21.8 and Herbert-Whipple 19.9N, Zimmer,Warsaw,
Indiana, U.S.A.). The study showed that these bioresorbable
screwshave good compressive fixation when compared with
commonly used small fragment metallic screws.
Kujala et al.(29)examined thetreatment of scaphoid
fractures and nonunions using bioabsorbable screws. In his
study,there were atotal of six patients with scaphoid waist
fractures(3) or nonunions(3) that wereall treatedusing
bioabsorbable SR-PLLA screws.
Interposition of abone graft from the iliac crest was used in
four cases. Asolid union was achieved in five cases. The single
nonunion was in apreviously operated wrist. No infections
developed in any of the patients. Using the Mayo-modified
Green-O’Brien wrist score, results were graded as excellent
in one case, good in four cases, and poor in the single case
of nonunion.
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REPAIR OF ULNAR COLLATERAL LIGAMENT TEARS
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Surgical Technique
Alazy S-shaped incision is typically used over the dorsal ulnar
aspect of the thumb metacarpophalangeal (MCP) joint. Care
should be taken to protect the terminal branches of the superficial radial nerve. The adductor aponeurosis should be incised
sharplyand theulnar collateral ligament (UCL)shouldbe
identified on or beneath it. Often aStener lesion is present
and the ligament rests superficial to the aponeurosis. Most UCL
ruptures occur distally.Ifthe ligament is ruptured distally,a
tunnel shouldbedrilledinthe proximalphalanxthatis
perpendicular to the axis of the finger.This tunnel should be
approximately 3to4mm from the MCP joint and should be
appropriately sized for the tack being used for repair.
Once the tunnel is drilled a1.1-mm diameter K-wire is used
to create ahole in the ligament approximately 3to4mm from its
torn end. Next, abioabsorbable tack should be placed through
the ruptured ligament. Once this tack is in place and through
the ligament, it should be introduced into the tunnel created
in the proximal phalanx. The top of the tack should be pressed
tightly against the ligament and cortex. Alternatively,asuture
may be attached to the ligament end and then attached to the
anchor which is inserted into the drill hole (Figs. 12 and 13).
If the ruptured occurred proximally,the previous steps would
FIGURE 10 Anterior–posterior view of aproximalthird scaphoid
fracture with unacceptabledisplacement. Source:Photo courtesy of
Arthrex Corporation.
FIGURE 11 Postoperative radiographofscaphoid fracture stabilized
with aresorbable biocompression screw. Source:Photo courtesy of
Arthrex Corporation.
FIGURE 12 Anonabsorbable suture is used to hold the ligamentend
with agrasping technique.The suture is placed through the anchor
approximately 3mmfrom the ligament end.
Bioabsorbable Implants in Hand and Wrist Surgery
&
25
be reversed and atunnel would be drilled in the metacarpal
head approximately 3to4mm from the joint and the ligament
would be secured with atack into the metacarpal head.
&
Currently Available Implants
Arthrex, Inc. has asystem of bioabsorbable anchors (V-Take
and Mini V-Tak e ,Arthrex, Naples, Florida, U.S.A.) for small
joint ligamentous repair.The anchors are available with 2–0
sized nonresorbable suturesand range in sizes of 2.2 mm!
4mmor2.2 mm! 7mm. The anchors are made from proprietarily prepared poly(
L -lactide-co- D , L -lactide) acid.
&
Outcomes
Vihtonen et al. (24) examined the use of an absorbable SR-PLLA
tack for the repair of ruptured UCLs in first MCP joints. This
study has atotal of 70 patients with total avulsion of UCL. The
authors wereable to achieve good or satisfactory results in 66
of the patients. One patient developed alocal infection at nine
months postoperatively and the tack was removed, and one
patient had persistentpain in the scarand required an
additional surgery.After reoperation, this patient had normal
function without pain.
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COMPLICATIONS
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Adverse Reactions to Self-Absorbable Implants
There are reports in the literatureofinfrequent occurrences of
fluid accumulation and/or sinusformation associatedwith
localpain, redness, and swelling(8,27,30–32).These are
mainly related to older generation of implants made of polyglycolide. Pelto-Vasenius et al. (31) described osteolytic changes
thatoccurred afterPGA fixation in chevron osteotomiesin
metatarsalheads.Postoperative osteolytic changes occurred
in 22% (21 out of 94) of patients. At final follow-up, 16 out
of 21 patients with osteolysis had complete resolution and 4
had partial resolution. In one patient, the osteolytic changes
remained visible at six years. Av ascular necrosis with signs of
collapse in the subchondral bone occurred in one patient and
minor redisplacement (1–2 mm) occurred in another patient.
Foreign body reactions occurred in 6.3% of patients. None of
these reactions were associated with an infection. Superficial
wound infections occurred in 3.2% of patients. These infections
healed completely after treatment with antibiotics and none
occurredinpatients with osteolytic lesions.There wasno
correlationfound betweentransient osteolysisand foreign
body reaction or infection.
Bostman (32) reported on adverse tissue reactionsto
bioabsorbablefixation devices in 2528patientsoperatedon
using pins,rods, bolts, andscrewsmadeofPGA or PLA.
Aclinically significant local inflammatory,sterile soft tissue
reaction was seen in 108 (4.3%) of the cases. In 107 patients,
the reactionwas due to aPGA implant (5.3% of 2037 patients)
occurring at an average of 11 weeks postimplantation. In four
patients, asevere reaction, which caused extensive osteolytic
lesions in the implant tracks, occurred with subsequent arthrodesis of the wrist or ankle due to severe osteoarthritis. Only
one patient had areaction due to aPLA implant (0.2% of 491
patients) 4.3 years after surgery.
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SUMMARY
Using bioabsorbable implants to treat fracturesofthe hand is
of special interestbecause the applied mechanical stresses are
relatively low and subsequent surgical removal of traditional
metallic hardwarecan be avoided. Modern SR manufacturing
techniques allow bioabsorbable devices for osteofixation that
possess high strength, formability with controlled degradation,
and offer auseful option to treat small bone fractures of the
hand. Resorbable pins and screws are being increasingly used
in the treatment of fracturesand osteotomies of the extremities,
including metacarpal, phalangeal, and scaphoid bones. Early
data suggest that bioabsorbable implants have similar clinical
success as metal implants, and can be used effectively to treat
fractures in the hand and wrist.
Bioresorbable implants are ideal as they ensure adequate
bone fixation, transfer increasing load to bone, do not affect
skeletal growth, and do not need to be removed. These implants
also avoid problems associated with metal devices, such as
stress shielding, corrosion, wear and debris formation.
Reported complication rates are low,but include sterile sinus
tract formation, osteolysis, synovitis, and hypertropic fibrous
encapsulation. Currently,further clinical studies are needed in
order to determine in which specific situations these implants
have the best indications.
&
REFERENCES
1. Fitoussi F, Lu W, Ip WY,Chow SP.Biomechanical properties of
absorbable implants in finger fractures. JHand Surg[Br] 1998;
23:79–83.
2. Berman KS, Rothkopf DM, Shufflebarger JV,Silverman R. Internal
fixation of phalangeal fractures using titanium miniplates. Ann
Plast Surg 1999; 42:408–10.
3. Stern PJ ,Wieser MJ, Reilly DG. Complications of plate fixation in
the hand skeleton. Clin Orthop Relat Res 1987; 214:59–65.
4. Bostman O, Pihlajamaki H. Clinical biocompatibility of biodegradable orthopaedicimplants for internal fixation: areview.
Biomaterials 2000; 21:2615–21.
5. Tegnander A, Engebretsen L, Bergh K, Eide E, Holen KJ,
Iversen OJ. Activationofthe complement system and adverse
effects of biodegradable pins of polylactic acid (Biofix) in osteochondritis dissecans.Acta OrthopScand 1994; 65:472–5.
FIGURE 13 The anchor is then inserted into the drill hole bringing the
ligament in opposition to the bone surface. The free ends of the sutures
may be used to reinforce the repair.
26
&
Kavanaghetal.
6. Bostman OM, Paivarinta U, Partio E, et al. The tissue–implant
interface during degradation of absorbable polyglycolide fracture
fixation screws in the rabbit femur.Clin Orthop Relat Res 1992;
285:263–72.
7. Bostman O, Paivarinta U, Partio E, et al. Absorbable polyglycolide
screws in internal fixation of femoral osteotomies in rabbits. Acta
Orthop Scand 1991; 62:587–91.
8. Bostman OM, Laitinen OM, Ty nninen O, Salminen ST,
PihlajamakiHK. Tissue restoration after resorption of polyglycolide and poly-laevo-lactic acid screws. JBone Joint Surg Br 2005;
87:1575–80.
9. Partio EK, Bostman O, Hirvensalo E, et al. Self-reinforced absorbable screws in the fixation of displacedankle fractures: aprospective
clinical study of 152 patients. JOrthop Trauma 1992; 6:209–15.
10. Vance RJ, Miller DC, Thapa A, Haberstroh KM, We bster TJ.
Decreased fibroblast cell density on chemically degradedpolylactic-co-glycolic acid, polyurethane, and polycaprolactone. Biomaterials 2004; 25:2095–103.
11.Joukainen A, Pihlajamaki H, Makela EA, et al. Strength retention of
self-reinforced drawn poly-
L / DL-lactide 70/30 (SR-PLA70) rods
and fixation properties of distal femoral osteotomies with these
rods. An experimental study on rats. JBiomater Sci Polym Ed 2000;
11:1411–28.
12. Rubel IF,Seligson D, Lai JL, Vo or MJ, Wang M. Pullout strengths of
self-reinforced poly-
L -lactide (SR-PLLA) rodsversus Kirschner
wiresinbovine femur.JOrthop Tr auma 2001; 15:429–32.
13. Prevel CD, Eppley BL, Ge J, et al. Acomparative biomechanical
analysis of resorbable rigid fixation versus titanium rigid fixation
of metacarpal fractures. Ann Plast Surg1996; 37:377–85.
14. Viljanen J, Kinnunen J, Bondestam S, Majola A, Rokkanen P,
Tormala P. Bone changes after experimental osteotomies fixed
with absorbable self-reinforced poly-
L -lactide screws or metallic
screws studied by plain radiographs,quantitative computed
tomography and magnetic resonance imaging.Biomaterials 1995;
16:1353–8.
15. Viljanen J, Pihlajamaki H, Kinnunen J, BondestamS,Rokkanen P.
Comparison of absorbablepoly-
L -lactide and metallic intramedul-
lary rodsinthe fixation of femoral shaft osteotomies: an
experimentalstudy in rabbits. JOrthop Sci 2001; 6:160–6.
16. Kobayashi H, Shiraki K, Ikada Y. Toxicity test of biodegradable
polymers by implantation in rabbit cornea. JBiomed Mater Res
1992; 26:1463–76.
17. Ekholm M, Helander P, Hietanen J, et al. Ahistological and
immunohistochemical study of tissue reactions to solid poly(ortho
ester) in rabbits. Int JOral MaxillofacSurg 2006; 35:631–5.
18. PihlajamakiH,Bostman O, Hirvensalo E, Tormala P,
Rokkanen P. Absorbable pins of self-reinforced poly-
L -lactic
acid for fixation of fractures and osteotomies. JBone Joint
SurgBr1992; 74:853–7.
19. Vo che P, Merle M, MembreH,Fockens W. Bioabsorbable rodsand
pins for fixation of metacarpophalangeal arthrodesis of the thumb.
JHand Surg [Am] 1995; 20:1032–6.
20. Vo utilainenN,Juutilainen T, Patiala H, Rokkanen P. Arthrodesis of
the wrist with bioabsorbable fixation in patients with rheumatoid
arthritis. JHand Surg[Br] 2002; 27:563–7.
21. Vo utilainenNH, Patiala HV,Juutilainen TJ,Rokkanen PU .Longterm results of wrist arthrodeses fixed with self-reinforced polylevolactic acid implants in patients with rheumatoid arthritis.
Scand JRheumatol 2001; 30:149–53.
22. Waris E, Ashammakhi N, Happonen H, et al. Bioabsorbable
miniplating versus metallic fixation for metacarpal fractures. Clin
Orthop Relat Res 2003; 410:310–9.
23. Waris E, Konttinen YT.Onthe use of Lactosorb plate for fixation of
ametacarpal shaft fracture. Ann Plast Surg 2004; 52:111–2.
24. Vihtonen K, Juutilainen T, Patiala H, Rokkanen P, To rmala P.
Reinsertion of the ruptured ulnar collateralligament of the
metacarpophalangeal joint with an absorbable self-reinforced
polylactide tack. JHand Surg[Br] 1993; 18:200–3.
25. Pelto-Vasenius K, Hirvensalo E, Bostman O, Rokkanen P. Fixation
of scaphoid delayedunion and non-union with absorbable polyglycolide pin or Herbert screw. Consolidation and functional
results. Arch Orthop Trauma Surg 1995; 114:347–51.
26. Jensen CH, Jensen CM. Biodegradable pins versus Kirschner wires
in hand surgery.JHand Surg [Br] 1996; 21:507–10.
27. Arata J, Ishikawa K, Soeda H, Kitayama T. Arthrodesis of the
distal interphalangeal joint using abioabsorbable rod as an
intramedullary nail. Scand JPlast Reconstr Surg Hand Surg 2003;
37:228–31.
28. Bailey CA, Kuiper JH, Kelly CP.Biomechanical evaluation of a
new composite bioresorbable screw. JHand Surg [Br] 2006;
31:208–12.
29. Kujala S, Raatikainen T, Kaarela O, Ashammakhi N, Ryhanen J.
Successfultreatment of scaphoid fractures and nonunions using
bioabsorbable screws: report of six cases. JHand Surg[Am] 2004;
29:68–73.
30. Bostman O, Partio E, Hirvensalo E, Rokkanen P. Foreign-body
reactions to polyglycolide screws. Observations in 24/216
malleolar fracturecases. Acta Orthop Scand 1992; 63:173–6.
31. Pelto-Vasenius K, Hirvensalo E, Vasenius J, Rokkanen P. Osteolytic
changes after polyglycolide pin fixation in chevron osteotomy.Foot
Ankle Int 1997; 18:21–5.
32. Bostman OM, Pihlajamaki HK. Adverse tissue reactions to
bioabsorbable fixation devices.Clin Orthop Relat Res 2000;
371:216–27.
Bioabsorbable Implants in Hand and Wrist Surgery
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27
5
Use of Cannulated Screws in Hand and Wrist Surgery
Drew Engles
Summit Hand Center, Crystal Clinic, Inc., Akron, Ohio, U.S.A.
&
INTRODUCTION
Recent advances in instrument and imaging technology have
revolutionized how hand surgeons treat the entire spectrum of
upperextremityailmentsand injuries.Manyofthese previously daunting conditions are now amenable to minimally
invasive techniques.
Minimally invasive surgery has long been the purview of
orthopedic surgeons. Arthroscopic procedures predated most
endoscopic advances in the other surgical disciplines. Additionally,the use of cannulated screws has been prevalent for
decades(1).Morerecentlyupper extremitysurgeonshave
applied thesetechniques,either alone or in combinationto
address injuries and disorders specific to the hand and carpus.
This chapter deals specifically with concepts critical to the
appropriate applicationofcannulatedscrew technology in
upper extremity surgery.Obviously,any technique has specific
indications as well as limitations. At times these limitations are
afunction of the human anatomy and the biological properties
of its components. For instance there are obvious biomechanical
differences between cancellous bone and cortical bone. There
also exist age related constraints when injuries are adjacent to
epiphysealorphysealstructures. Finally theimplant or its
deliverysystemmay preclude its utilizationin
certain situations.
Advances in imaging technology have coincided with these
breakthroughs in upper extremity care. Specifically,small scale
low-intensity fluoroscopy systems, with directdigital conversion capabilitycan provideexcellent osseousimaging.The
availability of this high resolutionfluoroscopyhas helped
support thewidespreadimplementationofthese
orthopedic advances.
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BASICS OF SCREW CONFIGURATION
To optimallyutilize cannulatedscrewsinhandand wrist
surgery, oneshouldhaveaworkingknowledge of screw
design and geometry.Many of the variables in screw geometry
affect their biomechanical properties and influence their clinical
performance and their application. The basic terminology of
screw geometry and configuration are provided here for review
(Fig. 1).
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Major Diameter
Thediameterofthe crests of an external straight thread
measured orthogonal to the screw axis.
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Minor Diameter
Thediameterofthe rootsofanexternal straight thread
measured orthogonal to the screw axis.
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Pitch
The distance betweentwo points on adjacent thread forms
measuredparallel to the screw axis and on the same side of
that axis.
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Thread Length
The distance measured from where the thread pattern begins to
where it terminates measured parallel to the axis of the screw.
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Thread Depth
The distance between the crest of an external straight thread
and the root of an external straight thread measured orthogonal
to the axis of the screw axis and on the same side of that axis.
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Shaft Length
The distance from the base of the head to the tip of the screw
measuredparallel to the axis of the screw.
This nomenclature becomes extremely important when
comparing the mechanical properties of different screw designs.
&
MECHANICAL PROPERTIES OF SCREWS
The mechanical properties of screws are adirect function of
both their material composition and their geometric design.
Several reproduciblemethodsare available to studythese
properties. Using this knowledge adesign team can optimize
those characteristics which will be most advantageous for the
intended applicationofthe device.The mechanicalcharacteristics most applicable to the orthopedic clinician are pullout
strength, torsion to failure, stripping torque, bending strength,
and compressive force (2,3).
The first four properties are important in that they quantify
under what applied loads screws fail. Pullout strength quantifiesatwhatmaximum load ascrew dissociatesfrom the
material into which it has beeninserted. Torsiontofailure
typicallyisperformed insertingascrew into amaterialof
greater strength and with afinite depth and then applying a
torque to the screw until it fails. Ty pically the maximum torque
achieved beforefailureand the site of failureare recorded for
comparison (2). Stripping torque refers to the maximum torque
applied prior to the screw stripping out of the material into
which it was inserted (2). Bending measures the deformation of
ascrew as an outside load is applied. Several different types of
bending studies can be performed. They include three point
bending, four point bending, and cantilevered bending. The
data collected yield astress/strain curve. Information garnered
from this curve includes yield point, stiffness, and ultimate
strength. The yield point signifies the point at which permanent
deformation of the material or implant occurs. The ultimate
strength is themaximal load that the screw canwithstand
beforebreakage. Material fatigue can be determined by cyclicallyloading theimplant until failure(or apredetermined
degree of deformation occurs) (4). Compressive force measurements allow for analysis of compression that ascrew is able to
produce with in agiven substance.
Some studies utilize cadaveric bone while others utilize
synthetic bone substitute because of its reproducibility,lower
cost,and availability.Multiple authorshaveshown that
syntheticboneissatisfactoryfor simulatingrealbonein
biomechanical experiments. In some instances, its homogeneity
makes it moresuitable for certain experimental designs.
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BIOMECHANICAL EVALUATION OF CANNULATED
SCREWS
The biomechanical evaluation of screws is of importance in that
it allows the design engineer to study how permutations in
screw geometry and material composition affect screw function.
The following discussion provides areview of biomechanical
analyses regarding various properties of cannulated screws. In
1991, Dr James Shaw studied the biomechanical properties of
four different screws (5). This was actually afollow-up study to
his original paper which evaluated the Herbert screw (6). In this
second paper,hecompared the compressive forces generated
in asimulated bone model using acustom designed load cell.
The four screws studied were the Herbert screw (Zimmer), the
Herbert/Whipple cannulated screw,the Arbeitsgemeinschaft
fiir Osteosynthesfragen/Association for the Study of Internal
Fixation (AO/ASIF) 4-mm cancellous screw (Synthes), and the
AO/ASIF 3.5-mm cannulated screw (Synthes). He found that
theHerbert/Whipplecannulatedscrew andthe AO/ASIF
cancellous screwwereabletogeneratecomparablecompression whichwas almost fivetimes that of theHerbert
screw.The AO/ASIF 3.5-mm cannulated screw was able to
generateacompressiveforce nearly 2.5timesthat of the
Herbert screw.
In additiontothese compression studies, Carter and
colleagues evaluatedbending properties of severalscrews.
Specifically,theystudied thebending rigidity, andthe
bending moment at failure, for experimental scaphoid osteotomies that were fixated with apair of parallel placed 0.045-inch
Kirschner (K) wires, aHerbert screw or an AO/ASIF 3.5-mm
cannulated screw.Theyfoundthat, whencompared to the
K-wires on amatched pair basis, both screws werestatistically
stronger in resisting bending forces (7).
In 1997, Toby and colleagues noted that the Herbert screw
remained apopular choice for scaphoid fixation, despite the
reports that it possessed less compressive force and pull-out
strength than other screws. They therefore elected to study
Herbert screw performance, with respect to ramped intensity
cyclical bending loads, when comparedtofour other commercially available cannulated screws (8). These screws included
the Herbert/Whipple screw,the AO/ASIF 3.5-mm cannulated
screw,the Acutrakcannulated screw (Acumed),and the
Universal compression screw (Howmedica). They found that
the AO/ASIF,Acutrak and Herbert/Whipple screws all fared
better at withstanding ramped cyclical bending forces than did
the Herbert screw.The AO/ASIF and Universal compression
screws providedthe most stable constructs.However,the
Universal compression screw did have apropensity for fracturing bone at the insertion site of the scaphoid (2 out of 6trials).
The test was then extended to evaluate the AO/ASIF screw and
theHerbert screwunder thesame parameters butwitha
segment of the volar cortex removed from the scaphoid. With
this alteration, both screws showed asignificant decrease in
ability to withstand ramped cyclical bending forces.
Asubsequent study,comparing the Acutrak cannulated
screw,anAO/ASIF 4-mm cancellous screw,and the Herbert
screw was performed (9). This study once again showed both
the Acutrak and the AO/ASIF screws to have superior characteristics than theHerbert screw with respect to fragment
compression in both synthetic andcadaveric bone.When
compared to theAO/ASIF screw, theAcutrak screwwas
able to maintain better compression after cyclical loading and
it was able to maintain fragment contact at higher levels of
torque.
In 2000, Brownand colleagues published astudy evaluating solid andcannulated screws(3).Theymeasured the
mechanical characteristics of five screws from three separate
manufacturers. Theirfindings supported theprior work of
Chapmanwhere thread length, major diameter,and thread
shape factor werecorrelated to pull-out strength (10). In fact,
their predicted pull-out strength correlated to observed pull-out
strength with an r
2
valueof0.90. They usedthe equation
developed by Shigley for their stripping torque calculations
(11). Furthermore,they reportedthat, in both theoretical models
and in actual mechanical testing, cannulation alone did not
inherently impair 4.0-mm screw mechanical function.
The adjunctive use of athreaded washer with the AO/ASIF
3-mm cannulated screw was studied by Lo and colleagues in
2001 (12).Theyfeltthatthe 3-mm cannulatedscrew,used
in conjunction with the threaded washer,provided compression
similar to that previously described by Rankinfor 3.5-mm
cannulated and solid screws (6).
Morerecently several authors have looked into the biomechanicalpropertiesofsmaller diameter(2and 3mm)
cannulated screws. Kissel and colleagues studied the pull-out
strength of 2-, 2.4-, and 3-mm Osteomed cannulated and solid
screws as well as 2-, 2.5-, 3-mm Vilex cannulated screws (13). In
the 2-mm group, there werenostatistical differences in the pullout strength comparing cannulated and solid devices. In the
2.4/2.5-mm subset,the cannulated screws hadsignificantly
( P ! .05) higher pull-out strengths than their noncannulated
counterparts. The cannulated Osteomedscrew revealed a
Shaft length
Major
dia
Pitch
Minor
dia
Thread
length
FIGURE 1 Computer Aided Design (CAD) diagram of acannulated
screw. Source:Courtesy of OrthoHelix Surgical Designs, Inc.
30
&
Engles
significantly ( P ! .05) greater pull-out strength than the other
two 3-mm devices.
The most recent analysis of smaller diameter cannulated
screwsevaluated the AO/ASIF 3-mm cannulated cancellous
screw (in conjunction with athreaded washer), the AO/ASIF
2-mm cortical screw, theMini-Acutrakscrew andthe
Herbert/Whipplescrew (14).Compressive forceswere
measured in asynthetic bone model. The 3-mm AO/ASIF
screw generated the most compression, nearly twice that of the
2-mm screws. The Mini-Acutrak(Acumed) andHerbert/
Whipple screws were found to generate similar compression,
which was approximately 70% of that of the 3-mm cancellous
cannulated screw.The authors pointed out that, despite its
small diameter, theMini-Acutrak screw wasequivalent in
compressionstrengthtothe Herbert/Whippleand within
30% of that of the 3-mm cannulated cancellous screw and
threaded washer combination.
Careful review of these studies provides sufficient scientific
evidence for the use of thelatestgenerationofcannulated
screwswith the confidencethat they possess sufficient
strength and provide adequate compression for hand surgery
applications.
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TECHNICAL CONSIDERATIONS IN CANNULATED
SCREW PLACEMENT
The use of cannulated screws has several advantages over solid
screws. First, guide pins can be inserted and then their position
verified by fluoroscopic techniques before drilling (Fig. 2). This
then allows for moreprecision in the use of the drill, typically
with asingle pass and thus with less chance for errant passes
and potential loss of bone stock. Secondly,the screw is then
placed over theguide pinand thepotential for angular
mismatch between the implant and the far cortex or subchondral restingsiteisobviated. Thirdly, screw length canbe
determined by measuring offofthe guide wire whose length
and position have already been fluoroscopically determined.
Additionally, the guide pin offers aprecise fit betweenthe
screwdriver andscrew head even in deeper tissueswhere
visualization may be limited.
From aphysiologic stand point, cannulated screws can
often be placed percutaneously or through alimited incision.
This decreases tissue trauma, periosteal stripping, and potential
dead space creation. One would hypothesize that this decreases
the degree of scar formation, preserves blood supply to fracture
fragments, and reduces the potential for hematoma formation.
With respect to fracture reduction, the guide pin itself can
provide provisional fixation. Additional dissection for clamp or
tenaculum placement may be avoided. With the placement of a
second guide pin, rotational control can be obtained. If the
fracture fragment is too small to accommodate asecond screw,
the guide pin can be left in place as either atemporary or
potentially permanent implant. This concept is often used in the
treatment of radial styloid fractures(15).
In using cannulated screws several concepts are important
to maintain. It is imperative that reduction be obtained prior to
guidewireplacement.The addition of asecondpin,even
temporarily,toaugment reductionand preventrotation, is
often required for optimal management of the fracture. When
measuring offofthe guide pin, for screw length, it is important
to take into account not only counter sinking of the head, when
necessary,but also anticipated compression. If the screw size
selected abuts subchondral bone on the distal side of the far
fragment and then significant fragment compression is
achieved, thescrew tip mayeventually rest in either the
articular cartilage or within the joint space.
It is often of benefit to advance the guide pin slightly after
the screw length measurement has been taken. This will prevent
drilling beyond the guide pin and accidentally extracting it
upon removal of the drill. In some cannulated screw systems, a
stylet is provided which is help to prevent inadvertent guide
pin removal during removal of the cannulated drill bit. It is also
important that the drill be passed parallel to the guide pin, if too
much cantilevering occurs during drilling there is the risk of pin
breakage deep within the bone. These pin fragments are often
difficult to retrieve. There is also the risk of pin bending or
breakage during manipulation. The potentialfor this is
discussed by Shin andHofmeister in theirdescriptionof
percutaneousscaphoidfixationvia avolar approach(16).
They specifically recommended the standard Acutrak screw
because of its stouter guide wire.
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CLINICAL APPLICATIONS
The developments in cannulated screw technology,especially
those of smalldiameter screws, have allowed for agreater
applicationoftheir use in hand and wristsurgery.While
initiallyutilizedprimarily in scaphoidfixation, cannulated
screws are now usedatthe digital, metacarpal, and carpal
levels.Percutaneous and limited open techniques,often
combined with arthroscopic technology,have revolutionized
how many traumatic conditions are now treated (17,18).
Thefollowing discussionisanoverview of techniques
utilizing cannulated screws for minimally invasive surgery of
the hand and wrist. As many of these techniques are described
in moreexhaustive detail in the following chapters, the nuances
will be left for discussion by other authors, many who are
experts and pioneers in these very procedures.
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Interphalangeal Arthrodesis
In the distal phalanx, cannulated screws can be utilized for
arthrodesisofthe distal interphalangeal(DIP)joint (19).
However,because of the small diameter of both the middle
and distal phalanges and the relativelytight softtissue
envelope, caremust be employed in both patient and implant
selection. Specifically,other techniques may be better suited for
patients with diminutive hands or when the small digit is being
Cannulated
screw
Guide wire/
k-wire
FIGURE 2 Computer Aid ed Design (CAD)diagram of cannulated
screwand guide wire relationship. Source:CourtesyofOrthoHelix
Surgical Designs, Inc.
Use of Cannulated Screws in Hand and Wrist Surgery
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fused. Brutus and colleagues found a15% nonunion rate and
37% complication rate (20). All nail bed injuries were seen in the
small digit. This compares to a12% nonunion rate and 20%
major complication rate published by Stern and Fulton for DIP
arthrodesis using noncannulated techniques (20). With these
findingsinmind, carefulpatientand implant selectionis
required to optimize results.Assmaller implants continue to
be developed, it will be interesting to see if outcomes improve.
In larger caliber digits, this author has used the AO/ASIF
3-mm cannulated screw with good results (Fig. 3). The interphalangeal joint of the thumb is particularly amenable to this
technique. The typically greater ratio of the middle phalanx to
distal phalanx intramedullary diameter of the thumb makes this
implant, with its increased major diameter to minor diameter
ratio, well suited for this application.
Afew technical considerations are worthy of discussion.
First, screw fixation limits the amount of flexion that can be
imparted on the distal joint. Ty pically,joints are fused in neutral
posture and it is difficult to achieve much morethan 108 to 158 of
flexion due to the geometric constraints of screw diameter and
length within the intramedullary cavity.Second, care must be
taken not to violate the dorsal cortex of the distal phalanx as this
may lead to nail bed injury.Finally,ifaheadless screw is not
utilized, the head must be countersunk into the tuft to avoid
symptomatic hardware.
To date, no authors have published their results regarding
proximal interphalangeal(PIP)arthrodesis with cannulated
screws. Leibovic and Strickland comparedtheir results with
Herbert screws to other fixation methods (21). They found a
more favorable outcome with Herbert compression screwsas
opposed to K-wires or tension band techniques. It remains to be
seen if cannulated screws can provide similar results.
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Metacarpophalangeal Joint Arthrodesis
Several authors have published their experiences and result
with cannulated screw fixation for metacarpophalangeal (MCP)
joint arthrodesis. In 2002, Messer and colleagues reportedtheir
experience with thumb MCP arthrodesis using the AO/ASIF
3-mm cannulated screw (22). Atotal of 18 thumbs weretreated
with this technique. Their union rate was an impressive 100%.
The also had no major complications. Twopatients underwent
screw removal for hardware discomfort. Alater study of 26
patients utilizingthe same implant in conjunctionwitha
threaded washer revealed a96% union rate (23). Other than
thesinglenonunion, no othermajorcomplicationswere
reported. Both studiesfound cannulatedscrew fixationfor
thumbMCP arthrodesis asatisfactoryalternative to
other techniques.
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Scaphoid Fracture Fixation
Aplethora of studies exist detailing cannulated screw fixation
of scaphoid fractures. One study of particular interest is that of
Trumble and colleagues (24). In this reportHerbert/Whipple
screws were compared to AO/ASIF 3-mm cannulated screws in
thetreatmentofacute displaced fractures. Theyfound no
statistical diff erence in clinical andradiographic results
between thetwo groups. Additionally,scaphoidalignment
was improved and carpal collapse was decreased by either
technique. They also evaluated screw placement with computerizedtomographyscans in both thesagittaland coronal
planes. They noted that both techniques allowed for placement
of the implant into the proximal fragment with satisfactory
accuracy.
Morerecent studies have evaluated percutaneous screw
fixation of scaphoid fractures either alone or in conjunction with
arthroscopicassistance (17,18,25). This can be performed either
via adorsal or volar approach (Fig. 4). While the personality of
the fracture may dictate the approach chosen, the bulk of these
injuries are mid-waistfractures andare amenable to either
anterogradeorretrograde insertion. Thus oftenphysician
preference determines the technique employed.
In agroundbreaking study,Bond and colleagues evaluated
percutaneous screw fixation as an alternative to cast immobilizationfor nondisplacedscaphoidfractures (26).Their
prospective, randomized study of twenty-five active military
patients evaluated with aminimum of two years follow-up
found that the surgically treatedgroupachieved radiographic
union in ashorter period of time and amore rapid return to
military duty.The average time to fracture union was seven
weeks in those patients treated with cannulated screw fixation
as opposed to 12 weeks in the cast immobilization cohort. At the
two-yearfollowup, therewas no statisticallysignificant
difference in range of motion or grip strength.
Slade and Moore have extended the use of percutaneous
cannulated screw fixation for scaphoid fracturestonow include
unstable fractures, displaced fracturesand fibrous unions (25).
They reported a100% union rate, confirmed by computerized
tomography,in50scaphoid fractures. No complications were
reported.Capoand Tanhavealsoreported percutaneous
(A)
(B)
FIGURE 3 ( A )Aposteroanterior radiograph of athumb IP joint fusion
utilizing an AO/ASIF 3-mm cannulated screw. ( B )Lateral radiographic
image of athumb IP joint fusion. Abbreviation:IP, interphalangeal.
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Engles
cannulated screw fixation of selected scaphoid nonunions (27).
This author has had similar experience utilizing the Acutrak
screw for scaphoid fractureswith delayed union or nonunion.
Healing timesare, however, typically longer than those of
acute injuries.
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Carpal Injuries
In addition to isolated scaphoid injuries, Slade has championed
thepercutaneous treatment of transscaphoid, transcapitate
perilunate fracture dislocations (28). The rationale behind this
approach is the desire to stabilize the carpal fractureswith
minimally invasive technology thus limiting soft tissue stripping, preserving carpal blood flow,and allowing for amore
rapid initiation of postoperative motion. In his technique, the
scaphoid fractureisaddressed with adorsally placed headless
compression screw and then the capitate is repaired with an
identical implant using apercutaneous approach procedure
from either thesecondorthird web space. Anterograde
placement of acannulated screw in the scaphoid can be utilized
in conjunction with lunotriquetral ligament repair or dorsal
capsulodesis in transscaphoid perilunate fracture dislocations
(Fig. 5).
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Intercarpal Arthrodesis
Several authors have described the use of cannulated screws in
intercarpalarthrodesis.Bothpercutaneousand open
approaches have been utilized. Calandruccio and colleagues
performedcapitolunate arthrodesis in combinationwith
scaphoid and triquetrum excision as treatment for scapholunate
advanced collapse (SLAC) arthritis.Bothcannulated and
noncannulatedscrews wereemployedfor fixation of the
capitolunate interface (29). These included Herbert, Herbert/
Whipple and AO/ASIF 3-mm cannulated screws. They did not
specify which implant was used in each patient. They found
their results similar to other procedures described for SLAC
wrist arthritis but utilizing atechnique necessitating fusion at
only one site. Slade and Bomback have described percutaneous
capitolunate arthrodesis using either an arthroscopicorlimited
open approach (30). He reported the use of aheadless compression screw (Acutrak) across the lunocapitate interval for
fixation. In his study,ten patients were treated via this technique; Five had an arthroscopic resection while the remainder
had alimited open incision. At aminimum of 38-months follow
up, all patients had satisfactory fusion based on computerized
tomography scans. Nine patients were reported to be pain free
and onehad mildpain. Allreturned to theirprior work
and avocations.
Thisauthorhas utilized AO/ASIF 3-mm cannulated
screws in conjunction with acorticocancellous bone graft for
lunotriquetral fusion with satisfactory results. The screw can be
placed percutaneously via an ulnar approach in combination
with alimited open dorsal exposure.
(A) (B)
FIGURE 4 ( A )Scaphoid fixation utilizing avolar percutaneousretrograde fixation technique.(B )Asimilar
fracture treated via adorsal approach and anterograde screw placement.
FIGURE 5 Aposteroanterior radiographofatransscaphoid perilunate
fracture dislocation repaired utilizing an anterograde cannulatedscrew
for scaphoid fixation and supplemental Kirschner (K) wire fixation of the
lunotriquetral ligament repair.
Use of Cannulated Screws in Hand and Wrist Surgery
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