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7
Percutaneous Mini Screw Fixation of Phalangeal and Metacarpal Fractures
Alan E. Freeland and William B. Geissler
Department of Orthopedic Surgery and Rehabilitation, University of Mississippi Medical Center, Jackson, Mississippi, U.S.A.
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INTRODUCTION
The principles of unstable hand fracturemanagement include anatomic restoration, sufficient stability to prevent displace­ment until callusseals the fracture and allows early progressive functional recovery,and the avoidance of unnecess­ary additional operative trauma (1). Afracture is considered unstable when reduction cannot be achieved and maintained without fixation or when motion cannot be initiated without the loss of reduction. Large (involving O 25% of thearticular surface) articular and oblique diaphyseal hand fracturesare typically inherently unstable.
Hand surgeons have long recognized the consequences of fibroplasia, scar generation, and digital stiffness that may result fromthe open surgical treatment of closed hand fractures, especially those of theproximalphalangesand proximal interphalangeal joints (PIPJs) of the fingers (2–7). Subperiosteal dissection may also devascularize fracture fragments. Conse­quently,hand surgeons have been among the early advocates of minimally invasive surgery(MIS) andhaveadmonished against injudicious open surgical procedures.
“Atraumatic” or MIS with closed reduction and internal fixation(CRIF)allows “biological(minimally undisturbed) fracturehealing” (8). CRIF with percutaneous wires or mini screws is relativelyatraumatic when compared with open operative procedures. CRIF preserves periosteal integrity and circulation at the fracture site and minimizes expansion of the zone of injury.Intraoperative fluoroscopicX-ray capability facilitates CRIF.
Wires splint without compressing fractures. By purchasing the bone cortices and having the option for compression, mini screwfixationprovides greaterfracturestability than do Kirschner(K)-wires,with little more soft tissue damage (1,9,10).Percutaneous mini screwfixation mayrequire a higher level of technical proficiency than that in K-wire fixation. While K-wires must typically be removed four to six weeks after insertion, miniscrewshavethe additional advantageof remaining in place for the duration of fracture healing. Mini screwsare usually removed only if they become symptomatic, a rareoccurrence. The pace and intensity of rehabilitation may be accelerated and morbidity decreased owing to the increased stability of mini screw fixation.
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INDICATIONS
CRIF using percutaneous K-wires has established benchmark clinical outcomesfor themanagementofunstable simple (two-part) long obliqueextraarticular phalangealfractures, articular fractures of the phalanges, and Bennett’s fracturesof the thumb (1–6,11–13). The length of along oblique fracture is
equal to or greater than twice the diameter of the adjacent bone. The length of ashort oblique fractureisless than twice the length of the adjacent bone diameter (1).
Open K-wire or mini screw fixation is typically reservedfor irreducible closed isolated simple fractures or as acontingency for failureofpercutaneous technique. Open treatment may also be appropriate for open, pathologic, or multiple hand fractures; hand fractures accompanied by ipsilateral extremity injuries; and polytraumatized or unreliable patients (1–4,14). Percuta­neous mini screw fixationalone is usually notsuitablefor comminuted fractures. Althoughthere maybeexceptions, fracturesofthe metacarpals are usually not sufficiently acces­sible for percutaneous mini screw fixation.
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PREOPERATIVE PLANNING
Hand fractures are evaluated for local signs, deformity,stability, wounding, complexity,sensation, and tissue viability.Digital block with local anesthesia may relieve pain sufficiently to allow the digital motion necessary to define adeformity.The patient should be assessed for any anesthetic or surgical risk factors.
Good quality routine posteroanterior (PA), lateral, and at least one oblique X-ray views are sufficient to evaluate most hand fractures. Additional oblique or special views may be taken at the physician’s discretion. Gedda has described aspecial view to profile the thumb trapeziometacarpal joint for Bennett’s frac­tures (12,13). Computerized tomograms or magnetic resonance imaging is rarely necessary.
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SURGICAL TECHNIQUE
An extremitytourniquet,hand table, mini or conventional C-armfluoroscopicX-ray machine, aconventional X-ray machine, acannulated power drill, K-wire set, and the appro­priate mini screwset and instruments must be available. A“time out” should be taken to avoid “wrong site surgery.” The procedure may be performed with general anesthesia or an appropriate regional or digital block. The use of atourniquet insures good visibility at theoperative site throughoutthe procedure and minimizes operative time, which may be signi­ficant should difficulties arise that require conversion to an open procedure.
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Mini Screws
Conventional mini screwsmay be conceptualizedassmall straight K-wires with ahead and threads (1). The proximal cortex of the pilot hole may be enlarged to the thread diameter of theintendedminiscrew to produce a“glidinghole.”
Thescrew head buttressesthe adjacent cortex while the distal threadspurchasethe distalcortex, compressing the fracture as the screw is tightened. Lag screws have the greatest compressive force when inserted perpendicularly to afracture. Mini screws inserted perpendicularly to the bone axis provide maximumresistancetoshear forcesand providesufficient stability for hand fractures(1).
Closed anatomic fracture reduction and provisional K-wire fixationare critical to successful percutaneous mini screw management,especially in articular fractures. Once fracture reduction is assured, the K-wires can be exchanged for mini screws, thus enhancing stability.The exchangeisfacilitated owingtocollinear K-wire andminiscrew core diameters allowing K-wire removal and immediate insertion of aself­tapping bicortical mini screw (“fixation mini screw”) or mini lag screw (Table 1). Roth and Auerbach have reported that bicor­tical fixation is as reliable as lag screw fixation in treating well­reduced oblique phalangeal shaft fractures (9).
Although single mini screw fixation is typically sufficient for securing articular fragments owing to interlocking of the cancellous interstices, two or more mini screws are required for reliable fixation of oblique shaft fractures of the hand. Twoor more mini screws in the shaft of ahand fracture serve to protect each other from shear,rotational, and bending forces during rehabilitation. Larger articular fragments may allow the inser­tion of two mini screws spaced with equal distance between the screws and between each mini screw and the proximal or distal edge of the fracture.
Cannulated headless mini screws are also available. Their conical shape and differential thread pitch (the screw pitch increases as the cone expands) allow them to compress the fracture.Percutaneous headless cannulated mini screw fixation is an excellentoptionfor obliquearticular and diaphyseal fracture fixation in the hand (10). Headless mini screwstypi­cally fit entirelywithinthe bone fragments, minimizing interference with adjacent soft tissues. Mini screw cannulation allowsprecise placementoveraguide wire and may simplify insertion.
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Bennett’s Fracture
Technique
The articular fragment at the base of the thumb metacarpal is securedinanatomic position by theanteriorulnar oblique ligament whilethe remainingmetacarpalbaseissubluxed radially,proximally, and dorsally (Fig.1A,B). Aclosed reduction is performed under fluoroscopic X-ray control using traction and manipulation. Apointed dental pic may be useful in applying pressureatthe base of the thumb metacarpal. A1to 2cmdorsal “buttonhole” or “portal-sized” incision is centered between the abductor pollicis longus and the extensor pollicis longus approximately 1cmfrom the proximal border of the
thumb metacarpal. Afine hemostat is used to spread the sub­cutaneous tissue away from the bone. Adrill guide, tap sleeve, or 14-gauge hypodermic needle is always used with K-wires or drill bits to protect the adjacent soft tissues. The concept of “targeting” is usedtodetermine wire placement(Fig. 1C). The fractureissecuredwith one K-wire directed through the dorsal base of the main metacarpal fragment into the center of thepalmar ulnarfragment(“target”). Asecond peripheral K-wire maintainsthe reductionand prevents rotation of the fragment during mini screw insertion. The central K-wire is removed. Screwlengthmay be determined usinga depth gauge.
Aself-tapping mini screw is inserted (Fig. 1D). The periph­eral K-wire may removed or left undisturbed for two to four weeks at the discretion of the surgeon, depending upon the stability of the fracture(Fig. 1E,F).
TABLE 1 Inches to Millimeter Conversion Tables
K-wire diameter (inches)
Core
diameter (mm)
Corresponding mini screw core diameter
0.028 0.7 1.1
0.035 1.1 1.5
0.045 1.5 2.0
0.62 2.0 2.7
K-wires are named by their diameter. Mini screws are designated by their thread diameter. Abbreviations:K-wire, Kirschner wire.
(F)(E)
(D)(C)
(A) (B)
FIGURE 1 ( A )PAillustration of aBennett’s fracture. ( B )Lateral illustration of aBennett’s fracture. ( C )The concept of centering a “target” on the articular fragment is illustrated. Ascrew head is located in the center of the target. Across-section of aKirschner wire is located on an inner peripheralring to the left of center. ( D )Fracture stabiliza­tion with acentral mini screw and aperipheral K-wire. ( E )PAillustration afterthe K-wire is cutand bent at itsproxima lend.(F )Lateral illustration after theK-wire is cutand bent at its proximal end. Abbreviations:K-wire, Kirschner wire; PA, posteroanterior.
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Freeland and Geissler
Case Example
A31-year-old patient fell while playing tennis and sustained a Bennett’s fracture of his dominant hand (Fig. 2A). Surgery was performed on the day of injury.The fracture was reduced and provisionally fixed with a1.5 mm central K-wire (Fig. 2B). After inserting aperipheral1.5 mm K-wire, the central wire was removed and aself-tapping bicortical 2.0 mm mini screw was inserted (Fig. 2C). The K-wire was removed two weeks after surgery (Fig. 2D,E). The patient resumed administrative duties within one week. The fracture healed and the patient resumed full occupational responsibilities six weeks after surgery.Five yearsafter injury,the patient wasasymptomaticand had full function.
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Condylar Fracture of the Proximal Phalanx
Technique
Condylar fractures typically displace proximally (Figs. 3and 4). A“bicondylar sign” may be present on lateral Xray owing to rotationofthe condylar fragment.Aclosed reductionis performedunder fluoroscopic X-raycontrol usingtraction and afine-pointed reduction forceps(Fig. 3B,C and Fig. 4B) (17). The condyles should align concentrically on lateral Xray following reduction. A1to 2cm“buttonhole” or “portal-sized” midlateral incision is centered over thecondylar fragment (“target”). (Fig. 4C,D) Afine hemostat is used to spread the subcutaneous tissue away from the collateral ligament over­lying the condylar fragment.Adrill guide or tap sleeve is always used with K-wires or drill bits to protect the adjacent soft tissues. AK-wireisinserted into the distal periphery of the subchondral bone of the condylar fragment just beneath and parallel to the articular surface of the proximal phalanx at the PIPJ and advanced through the opposing cortex (Fig. 3D). TheperipheralK-wiremaintains the reductionand pre-
ventsrotation of thefragmentduringthe remainderof the procedure.
Theproximal originofthe collateralligamentmay be reflected distally or acruciate incision made at the mid-origin of theconjointcollateraland accessorycollateralligaments adjacent to the center of the fragment (Fig. 4E,F). AK-wire or drill bit is directed through the center of the condylar fragment and into the opposing condylar cortex. The central K-wire is exchanged for amini screw (Fig. 3E). The peripheral K-wire may be removed or left undisturbed for two to four weeks at the discretion of thesurgeon, depending upon thestabilityof the fracture.
(E)
(D)
(A) (C)(B)
FIGURE2 ( A )Displaced Bennett’s fracture. ( B ) Bennett’s fracture, reduced and stabilized with asingle central K-wire. ( C )Aperipheral K-wire has been added. Amini screw has been inserted in place of the central K­wire. ( D )The small, minimally invasive incision is demon­strated one week after surgery. ( E )The K-wire has been removed. The central mini screw remains in position. Abbreviation:K-wire, Kirschner wire.
(A) (B) (C) (D) (E)
FIGURE 3 ( A )Displaced unicondylar fracture, PA view. ( B )Digital traction restores finger length. ( C )The fracture reduction is completed by direct application of apointed reduction forceps. ( D )AK-wire is inserted parallel to and just beneath the articular surface. ( E )Amini screw is inserted through the central portion of the condylar fragment. Abbrevi- ations:K-wire,Kirschnerwire; PA,posteroanterior. Source:From Ref. 15; (Fig. 1).
Percutaneous Mini Screw Fixation of Phalangeal and Metacarpal Fractures
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Case Example
A19-year-old patient jammed the index finger of his dominant hand while playing basketball. He sustainedadisplaced fracture of theulnar condyleofthe proximal phalanx (Fig. 5A). Aclosed reduction was performed and temporarily securedwith acannulated pointed reduction forceps(Fig. 5B). Aperipheral 1.5 mm K-wireand acentral 1.5 mm mini screw wereinserted (Fig. 5C). The wirewas removed two weeks after surgery.The mini screw was left in place (Fig. 5D). The fracture healed and the patient had 178 to 858 of PIPJ flexion six weeks after surgery (Fig. 5E,F).
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Long Oblique Fractures of the Phalangeal Shaft
Technique
Oblique proximal phalangeal shaft fractures tend to shorten and rotate (Fig. 6A). Aclosed reduction is performed under fluoroscopicX-ray controlusing traction and oneortwo fine-pointed reduction forceps(Fig. 6B,C). Approximately 1to
2cmmidlateral incisions are centered over the junctures of the proximal third and middle thirdand the middle and distal third of asagittal uniplanar fracture. Uniplanar oblique fractures may vary slightly from the true sagittal plane, but are rarely found in the coronal plane. Wire and mini screw application are easier in uniplanar oblique than in spiral fractureswhich require adjust­mentsinthe positionselected forminiscrew insertionin relation to the rotating plane of the fracturefor each wire or screw that is inserted.
Afine hemostat is used to spread the subcutaneous tissue away from the lateral band or oblique fibers of the metacarpo­phalangealjoint dorsal expansionproximally or thelateral surface of the proximal phalanx distally.The lateral band may be retracted, divided, or excised to approach the proximal mini screw insertion site (19–21). Cortical bone surfaces of metacar­pals and phalanges are hard and round, and the medullary canal is narrow. Adrill guide, tap sleeve, or 14-gauge hypo­dermic needle is always usedwith K-wires or drill bitsto control the wire or drill, prevent slippage, and protect the soft tissuesatthe insertionsite. Instrument compression of the
(A)
(B)
(C)
(D)
(E)
(F)
1–2 cm
FIGURE 4 ( A )Displaced unicondylar fracture, lateral view. ( B )The fracturereduction is completedbydirect applicationofapointed reduction forceps. ( C )The conceptofcentering a“target” on the articular fragmentisillustrated. Ascrew head is located in the center of the target. Across-sectionofaKirschner wire is located on an inner peripheral ring to the right of center. ( D )The midlateral line is illustrated for placement of the mini incision. ( E )Acruciate incision is illustratedatthe center of rotation of the PIPJ. ( F )Partial reflection of the origin of the collateral ligament is illustrated. Abbreviations :PIPJ, proximal interphalangeal joint. Source:From Ref. 15; (Fig. 1).
(A) (B)
(F)
(C) (D)
(E)
FIGURE5 ( A )Displaced unicondylar fracture, PA view.(B )The fracture reduction is completed by direct application of acannulated pointed reduction forceps. ( C )AK-wire has been inserted parallel to and just beneath the articularsurface. Amini screw has been inserted through the central portion of the condylar fragment. ( D )The K-wire has been removed. The fracture remains stabilized by the central mini screw. ( E )Finger extension at six weeks. ( F )Fingerflexionatsix weeks. Abbreviations:K-wire, Ki rschner wire;PA, posteroanterior. Source : From Ref. 16; (Fig. 2).
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Freeland and Geissler
fracture with afine-pointed small bone reductionforceps prevents distraction at the fracture site during wire insertion and the mini screw for K-wireexchange. Long oblique diaphy­seal phalangeal fractures may be stabilized by two or more mini screwsspaced with equal distance between the screws and between each mini screw and the proximal or distal edge of the fracture.
The fracture is secured with two K-wires directed through both cortices of the reduced fractureatthe selected sites that divide the fracture into thirds (Fig. 6D). One K-wire is removed (Fig. 6E). Screw length may be measureddirectly by depth gauge or indirectly determined by holding the mini screw over the fracture and imaging with the fluoroscope (Fig. 6F). Indirect measurement by imagingavoidsthe smallbut real risk of displacing thefracturethat accompanies thedepth gauge measurement maneuver. Aself-tapping bicortical “fixation” mini screw is inserted distally (Fig. 6G). The proximal K-wire is removed(Fig. 6H). Theproximal cortexisenlargedto correspond to the thread diameter of the selected mini screw (Fig. 6I). Aself-tapping mini lag screw is inserted (Fig. 6J). Athirdmini screw may be inserted at the discretion of the surgeon.Three miniscrewsmay be inserted,dividingthe
fracture into quarters, when the fracture length is three times the bone diameter (1).
Headless mini screws areinsertedsothat thewidest parts of the screws are frequently positioned opposite each other to allow maximum bone purchase. Headless screws are usually not placed in the middle thirdofthe phalangeal shaft owing to the risk of fragmentingthe hard cortical surfaces in thenarrow area of theisthmus of thephalanx.Supple­mentary K-wire fixation may be used in the midshaft area, if necessary.
Case Example
A38-year-old patient felland sustained aclosedoblique fracture of the shaft of the proximal phalanx of her nondomi­nant small finger (Fig. 7A,B). Small “stab” skin incisions were made to facilitate K-wire and mini screw insertion (Fig. 7C). Two1.1 mm K-wires were inserted, dividing the fractureinto thirds. Indirect screw measurement was performed (Fig. 7D). Two1.5 mm mini screws wereinserted (Fig. 7E,F). The fracture healed.Six weeksafter surgery,the patienthad recovered flexion of 128 to 808 of PIPJ and returned to work (Fig. 7G,H).
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Articular Fracture—Phalangeal Base
Technique and Case Example
A34-year-old patient jammed his finger at work. He sustained a closed articular fracture of thebaseofthe middle phalanx (Fig. 8A). Aclosed reduction was performed under fluoroscopic X-raycontrol using traction andafine-pointed cannulated reduction forceps (Fig. 8B). One guide wire was placed centrally into the condylar fragment parallel to the articular surface and just distal to the insertion of the collateral ligament (Fig. 8B,C). This site should be selected so as to assurethat the mini screw threads do not penetrate the adjacent joint surface. The guide wire is advanced through the reduced fracturefragments and through the skin on the opposite side of the digit so that it can be removed easily should it break. Asecond guide wire is inserted eccentrically into the condylar and major phalangeal fragments to prevent fragment rotation during reaming and mini screw insertion (Fig. 8D,E). A1to 2cmmidlateral incision is centered over the condylar fragment (“target”) (Fig. 8F). Blunt dissection is continued with ahemostat to the level of the bone surface. Acannulatedreamerslides over thecentral guide wire (Fig. 8G). The bone is then reamed across both bone cortices. Recently,aself-drilling headless cannulatedminiscrew (variable pitchminiAcutrak screw, Acumed,Hillsboro, Oregon, U.S.A.) has been introduced. With this new self-drilling cannulated headless mini screw,only the near cortex has to be reamed, and the self-drilling screw is then inserted over the guide wire(Fig. 8H). The screw is inserted over the guide wire so that it fits entirely inside the bone on both the PA and lateral X-ray views. The final mini screw position is fluoroscopically confirmed by both PA and lateral views. The guide wires are then removed(Fig.8I,J).Asingleminiscrew may provide adequatestability.The fracturehealedand thepatienthad recovered full finger motion six weeks after surgery (Fig. 8K,L).
Asecond headless cannulated screw may be inserted into larger condylar fragments at the discretion of the surgeon. The second mini screw is usually inserted in the opposite direction of the first screw,owing to the obliquity of the fracture line. This allows the smaller diameter lead portion of the screw to cross the fracture site and engage the smaller remaining cortical area of thecondylarfragment, thus decreasing therisk of fragmentation.
(A) (B) (C) (D) (E)
(F)
(G) (H) (I) (J)
FIGURE 6 ( A )Aclosed long oblique fracture of aproximal phalanx is shortened and rotated. ( B )Length is restored and alignment improved with traction and manipulation.(C )Reductioniscompleted by the direct application of apointed reduction forceps. ( D )The reduced fracture is secured with two K-wires that divide the fracture into thirds. ( E )The distal K-wire is removed. ( F )Mini screw length is measured indirectly. ( G )Abicortical“fixation” mini screw is inserted distally. ( H )The proximal K-wire is removed. ( I )The proximal cortex is drilled to correspond to the mini screw thread diameter. ( J )Amini lag screw is inserted proximally. Abbreviations:K-wire, Kirschner wire. Source:From Ref. 18; (Fig. 3).
Percutaneous Mini Screw Fixation of Phalangeal and Metacarpal Fractures
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Postoperative Care and Rehabilitation
Functional recovery is the fundamental goal of rehabilitation (22,23). Early digital motion and differential superficialis and profundus tendon gliding exercises are prioritized. Elevation augments digital motion by diminishing and resolvingrestric­tiveswellingand edema. Progress is guidedbysofttissue response, fracture stability,and the patient’s pain tolerance. Rehabilitation must be stopped short of generating additional inflammatory or fibroblastic response, signaled by increased pain, swelling, tenderness, redness, or heat at the fracture site. Fracturestability limits pain and allows morerapid implemen­tation of exercises. There may be less morbidity if exercises can be started early (within 21 days), although final outcome is usually not adversely affected in patients who require as much
as four weeks of continuous static splinting provided motion is initiated at that time (24,25).
Protective splints maybeworn betweenexercise sessions until pain, swelling, and tenderness subside. Splints that hold the wrist in slight flexion and all four finger meta­carpophalangealjointsinfullflexionallowthe extrinsic extensors to supplement the intrinsic extensors in recovering interphalangealjoint (IPJ) extensionwithoutimpedingthe recovery of finger flexion, especially in patients with proximal phalangeal fractures. An attachment to hold the PIPJ’s fully extended may be added to the splint at night to decrease the risks of PIPJ extensor lag and contracture.
Therecoveryof4to 5mmofflexor tendon excursion during the first four weeks following flexor tendon repair in
(G)
(H)
(A) (B) (C)
(D) (E) (F)
FIGURE 7 ( A )Aclosed long oblique fracture of aproximal phalanx is shortened and rotated. The amount of rotation corresponds to the size of the gap between the fragments. ( B )Alateral x-ray demonstratesthat the tip of the proximal fragmentwill block PIPJ flexion unless it is reduced. ( C )The incision site is guided by fluoroscopic x­ray. ( D )Two K-wires stabilize the fracture. Mini screw length is measured indirectly.(E )Mini screw fixation, PA view. ( F )Mini screw fixation, lateral view. ( G )Finger extension six weeks after surgery. ( H )Finger flexion six weeks after surgery. Abbreviations:PIPJ, proximal interphalangeal joint; K-wire, Kirschner wire; PA, posteroanterior.
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Freeland and Geissler
zone 2reliably preventsthe formation of permanent adhesions between bone and tendon, and correlates with good to excellent final digital motion in most patients(26).Amore modest recovery during thefourweeksfollowing surgery predicts less favorable results. Extrapolation of these findings to prox­imal phalangeal fractures and allowance for 4to5mm of both adjacent flexor and extensor tendon excursion would requirea 408 to 508 partial arc of PIPJ or total active integrated finger motion (27).
Metacarpal and phalangeal fracturesare usually clinically stable at four weeks after injury even in the absence of the appearance of callus on Xray (1). Fracture fragments may be considered “locked” whenthey are joined by callus that is visualized on Xray,usually at five to six weeks after fixation. At four to six weeks after injury,patients may be weaned from their splints as fracture stability and healing, pain, and tender­ness allow.Whenadequatefracturehealingisassured, movement may be intensified, and static joint blocking and strengthening and conditioning exercises may be initiated with
minimalriskoffracturedisruption. Passive stretchingand dynamic splints designed to overcome tendon and joint adhe­sions may usually be initiated safely at five to six weeks after injury (22,23).
Patients are instructed and checked out so that they can perform daily therapy at home. If monitoring demonstrates that progress is unsatisfactory,outpatient therapy is initiated. Wo rk hardening may be added if needed. Therapy is continued until the patient reaches apoint of maximum recovery. Patients may continue to regain PIPJ motion for as long as one year following injury (7).
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COMPLICATIONS AND THEIR MANAGEMENT
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Intraoperative Complications
Percutaneous fixation sacrifices direct visual confirmation of fracture reduction. The fracture may be opened if direct visual­ization becomes necessary during the procedure in order to
(J) (K) (L)
(G) (H) (I)
(D) (E)
(F)
(A)
(B) (C)
FIGURE 8 ( A )Displaced large articular fracture of the condylar base of amiddle phalanx. ( B )AK-wire has been inserted through acannulated pointed reduction forceps. ( C )The K-wire is parallel and distal to the proximal joint surface. ( D )Asecond K-wire is being inserted through the fracture distal to the first K-wire. ( E )The reduction and K-wire fixation have been completed. ( F )Asmall incision is made in the skin at the insertionsite of the proximal K-wire. ( G )The cannulated drill has been inserted over the proximal K-wire. ( H )The cannulated headless mini screw is ready to be inserted over the proximal K-wire. ( I )The reduced fracture has been secured with the headless mini screw. The headless mini screw is entirely contained within the bone. ( J )The reduced fracture has been secured with the headless mini screw, lateral view. The patient has regained full finger extension ( K )and full finger flexion ( L )six weeks after surgery. Abbreviations:K-wire, Kirschner wire.
Percutaneous Mini Screw Fixation of Phalangeal and Metacarpal Fractures
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51
assure proper fracture reduction. Unambiguously,irreducible fracturesrequire open reduction. Percutaneous or open K-wire or open mini screw fixation may be used as acontingency when technical difficulties necessitate abandonment of percutaneous mini screw fixation. Physicians and patients should be prepared for conversion of apercutaneous to an open procedure. Mini screw breakage, loosening, or pull-out is arare occurrence.
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Long-Term Complications
Residual stiffness is the most common complication following articular and phalangeal fractures of the hand (2–4,7). Patients with residual finger stiffness typically adapt well and rarely desireremedial surgery (7,28,29). Approximately 25% of patients with articular fractures suffer long-term cold intolerance and aching pain, typically managed nonoperatively (7,28–30). Symp­tomatic arthritis is more frequent in poorly reduced articular fractures, emphasizing the importance of accurate reduction and reliablestabilization. Occasional joint reconstruction maybe necessary. Malunion and nonunionare rare occurrences. Fambrough and Greenreported aflexor tendon rupture owing to attrition from aprotruding mini screw tip (31).
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OUTCOMES
Initial efforts at mini screw fixation of hand fracturesin1958 werediscouraging (32). However,in1976, Crawford reported typically successful results and no complications following mini screwfixationin21various articular fractureswithlarge fragmentsand obliquephalangeal shaftfractures,reviving interestinthe technique (33).
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Bennett’s Fracture
CRIF with percutaneous K-wires has previously been acknowl­edgedasthe treatment of choice forBennett’s fracture (3,4,11–13). K-wire or screw fixation has been successfully used for those Bennett’s fractures requiring open reduction (34–37). Lutz et al. reported no difference in outcome or posttraumatic arthritis between patients treated with percutaneous Kirschner wire fixation or open mini screw fixation followed for amean of seven years (37). Meyer et al. reported uniform fracture healing, 13 good to excellent results, one fair result, and two poor results in 16 Bennett’s fractures treated with cannulated screw osteo­synthesis and followed for an average of 17 weeks (38).
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Unicondylar Fractures
Weissand Hastings reportedtheir results in 38 consecutive patients withunicondylar fractures of the proximal phalanx followed for an average of 3years (39). PIPJ motion in their series averaged from 138 (range: 0–358 )to85 8 (range: 60–1158 )of flexion. Clinical outcomes measured by total active PIP joint motion were slightly better when two or more K-wires wereused (898 G 188 )than with open mini screw fixation (798 G 8 8 )(30,40). No differences were detected between percutaneous and open wiring techniques. None of the fracturesstabilized with multiple K-wiresorminiscrewslostreduction for theduration of treatment. Five out of seven undisplaced fracturesand four out of ten fractures treated with asingle K-wire lost reduction during the course of treatment, required secondary fixation, and had greater PIP joint stiffness than those managed with multiple K-wire or mini screw fixation. These investigators did not use percutaneous mini screws. Irreducible condylar fractures were approached in the capsular interval between the central slip and the ipsilateral lateral band. Full recovery of PIP joint motion was
theexceptionratherthanthe rule,typically owingtosome residualextensorlag or flexioncontracture or some loss of flexion. They concluded that all unicondylar phalangeal frac­tures requireinitial fixation with two or moreK-wires, one or more mini screws,orawire and amini screw.
Ford, et al.detailedtheir results treatingten condylar fractures of theproximalphalanges and four of themiddle phalangeswithopenminiscrew fixation(30). No excellent results werereported. Four patients with unicondylar proximal phalangealfractures hadgoodresults and sixhad poor outcomes. There was an average residual loss of 208 to 308 of extension. PIPJflexion was more reliablyrestored. Dynamic splints seldom improved results. Twopatients with condylar fractures of the middle phalanx had good results and two had poor results.
Geissler andFreelandreportedon12patients with intra-articular fracturesofthe digits (10).Ten patients had unicondylar fractures of the fingers and two patients had intra­articular thumb fractures. The average age was 22 years (range: 16–35 years). Nine patients were males and three were females. Nine patients underwent stabilization with asingle headless cannulated mini screw and three patients had two headless mini screws inserted. All patients healed clinically and radiographi­cally within six weeks following surgery.There was no loss of reduction in any of the patients. Out of the 10 patients with unicondylar fracturesofthe phalanges, the average loss of PIPJ extension was 3 8 (range: 0–78 )and the average PIPJ flexion was 858 (range:80–958 ). Twopatientswithintra-articular thumb fractures averaged 168 of IPJhyperextension(range: 12–208 ) and 608 of IPJ flexion (range: 55–658 ). There was no fracture displacement or malunion. No patients required mini screw removal. Although this series is small, the results were uniform and suggest that headless mini screw fixation may be superior to open mini screw fixation and at least equivalent to multiple wirefixations. More data and replication of these results are needed.
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Long Oblique Proximal Phalangeal Shaft Fractures
Green and Anderson reported that 18 out of 21 (87%) oblique proximal phalangeal shaft fractures treated with two or more transfixing K-wires healed and achieved afull range of motion at eight weeks after injury (6). Belsky et al. reported fracture healingand 29 good [total active motion (TAM)180–2208 ] and 61 excellent (TAM O 2208 )motion in 90 out of 100 consecu­tiveclosedsimple phalangealshaftfractures treatedwith percutaneous K-wireCRIF (5). Out of the total, 55 fractures were oblique.
Using open K-wire fixation on avariety of closed phalan­geal fracture configurations, Widgerow,etal. reported results nearly equivalent to those of Green and Anderson and Belski, et al. (5,6,40) Dabeziesand Schutte reported excellent results (TAM O 2208 )inall 29 proximal phalangeal fractures stabilized with miniscrewsalone, or with miniplatesplacedonthe dorsolateral side of the phalanx (19). They advocated amidlat­eral approach dividingthe lateralband, if necessary, and avoiding the gliding tissue between the periosteum and the extensor apparatus. Ford, et al. reported13excellent results, four good results,and one poor result in 18 proximal phalangeal fractures treated by open reduction and internal fixation using
1.5 and 2mmAOmini screws (30).
Diwaker and Stothard reported better results with open mini screw fixation than with percutaneous K-wires in their retrospective review of metacarpal and phalangeal fractures (41). Horton et al. conducted arandomized prospective study of 22 patientswithobliqueextraarticular proximal phalangeal
52&Freeland and Geissler
fractures treated with percutaneous K-wireoropen mini screw fixation (21). Fractures were approached through amidlateral incision and, if necessary,the lateral band was excised. There werenodifferences between the two groups in outcomes for fractureunion, functional recovery,orresidual deformity.All fractures united and the patients returned to their previous jobs. Case reportsoffractureunion with excellent functional recovery using percutaneous or limited open incision of 1to2 cm and internal mini screw fixation of oblique phalangeal shaft fractures have been published (42,43). More data and report replications are needed to determine the efficacy of percuta­neous mini screw application as compared to percutaneous K-wireoropen K-wire or mini screw fixation.
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Articular Fractures—Phalangeal Base
CRIF with percutaneous K-wires are widely used to stabilize articular fracturesofthe phalangealbase. Larger fractures involving greater than 25% of the articular surface are typically quite accessible for percutaneous mini screw insertion, but few specific data are available for this specific fracture.
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SUMMARY
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General Conclusions
Clinical results for oblique phalangeal fracturestreated with open mini screw fixation compare favorably with those using percutaneous Kirchnerwires (5,6,16,18,30,41).Amidlateral approach avoiding incision of the dorsal apparatus, sparing of thegliding tissuebetween theperiosteum andthe extensor mechanism, increasedstability,and earlier and more intensive therapy are among the factors that may explain these somewhat paradoxical equivalenciesbetween percutaneousK-wire and open mini screw fixation.Two case reportsofpercutaneous mini screw fixation yielded excellent digital motion.
Reports suggest that percutaneous mini screw fixation may have an advantage over percutaneous K-wire or open K-wire or mini screw fixation for treatment of undisplaced or adequately reduced closed simple oblique Bennett’s, phalangeal unicon­dylar,and articular phalangeal base articular fractures with largefragments ( O 25%ofthe articular surface), butthose reports are not conclusive (44,45). Spiral fractures or smaller ( ! 25% of the articular surface) articular fragments may be more challenging than uniplanar fracturesorfractureswith larger fragments. Cannulated headless mini screws may provide an advantage over conventional mini screwapplication. The surgeon should not hesitate to convert to an open procedure to assureanadequate fracture reduction or if technical difficul­ties arisewithfixationthat cannotbesalvaged with percutaneous K-wire fixation.
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Future Direction of the Technique
The validity of conclusions based upon the material cited in this chapter are confounded by avariety of shortcomings in study design;statisticalpower;enrollment; randomization; effect sizes; uniformity of selection, outcome criteria, and compli­cationcategories; failure to sortspecific fracture configurations; blinding; bias; confidence intervals; and replica­tion (44–46). Greater enrollment is needed to detect beta errors (complications) reflectingminor,intermediate, andmajor trends (47,48). We need to know how many cases are converted to open procedures owing to failureofreduction or technical difficulties. Follow-up of ayear or moreisneeded to attain an accurate assessment of the recovery of motion. The occurrence
of arthritis is related to the accuracy of reduction and its severity may be time-related (7,28,29). Long-term follow-up is needed to assess these parameters. Subjective patient outcome and cost analyses would be helpful.
Logic would dictate that percutaneous procedures would be less likely to cause stiffness than open procedures and that fracturestreated with mini screws might recover more motion andhavelessmorbidity than thosemanaged with K-wire fixation. What are the absolute and relativeoverallspecific complication ratesamong theproceduresdiscussed?More data, improved study design, longer follow-up, higher levels of evidence, and unconflicted replication studies are needed to support or refute the relative risks and benefits of percutaneous and open wire and mini screw techniques (44–49).
At thehighest level, aprospective double-blinded, randomized, controlled trial (RCT) could be initiated between or among methods currently considered equivalent or nearly equivalent. Asingle research question should be addressed, e.g. “Does percutaneous mini screw fixation provide any advantage over percutaneous Kirchner wire fixation in oblique proximal phalangeal shaft fractures as determined by total active range of digital motion at one year after injury?” Apre-study power analysisshouldbedonetoassure adequateenrollment for statistical validity.Amulti-center study may be necessary to assureadequate enrollment, with the caveat that multi-center studieshaveuniqueinherent deficiencies (44,45). Uniform selection and evaluation criteria and comprehensive compli­cation reports are essential. RCTsmay not be practical owing to issues of enrollment, time, and cost. Alternatively,morecare­fullydesignedprospectiveconsecutive case series with adequate enrollment, blindedevaluation of results, and at least 1yearoffollow-up wouldimprove uponour current level of evidence.
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SUMMATION POINTS
Indications
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Bennett’s fractureswithlarge fragments(O 25% of the articular surface).
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Unicondylarphalangealfractures with largefragments ( O 25% of the articular surface).
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Oblique phalangeal shaft fractures.
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Articular phalangeal base fractureswith largefragments ( O 25% of the articular surface).
Outcomes
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No nonunions to date.
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No loss of reduction to date.
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Slightly less residual PIPJ and digital stiffness.
Complications: Reported to Date
(Key: None; Rare, ! 5%; Occasional, 5–10%, Frequent, O 10%)
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Inadequate reduction: none.
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Conversion to an open procedure: none.
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Loss of reduction: none.
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Technical problems with implant insertion: none.
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Stiffness: frequent.
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Cold intolerance: none.
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Nonunion: none.
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Malunion: none.
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Dystrophy: none.
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Arthritis: none.
Percutaneous Mini Screw Fixation of Phalangeal and Metacarpal Fractures&53
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