anatomic approach to preparation and fusion of the interphalangeal ...

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56CHAPTER 12Figure 14. The contoured cup and dome fit.addition, the rongeur instrument will often result inincomplete cartilage removal on the middle phalanx, afunction of the mismatch between the phalangeal surfaceand the tip of the instrument. This incomplete tissue removalwill lead to osseous union problems.ANATOMIC APPROACHTO JOINT RESECTIONJoint preparation is very tedious and more often than notimperfect. The ideal operation would be a rapid jointdisarticulation, rapid and precise cartilage removal as withhand instruments without excessive soft tissue disruption orheat generation seen with powered instruments, and perfectapproximation of the bone ends after cartilage removal.These factors led to the development of a micro-reamingsystem, one that combines the precision and control of handinstrumentation with the rapid tissue removal of a poweredinstrument (Figures 16, 17). The instruments reducedoperating time, completely and uniformly removed articulartissue, increased surface area of the fusion mass, and reducetotal bone loss. The corresponding reamers attach tostandard Kirschner wire (K-wire) drivers which run atvariable speeds, a function that allows for slow or rapidremoval of bone tissue (Figures 18, 19). The devices have aclosed periphery, preventing additional soft tissue damageby enclosing the cutting device and restricting tissue removalto the area within a dome. The amount of bone removedcan be finely adjusted by the number of revolutions of thecutter on the bone, a function of two variables directlycontrolled by the surgeon: the speed of the drill and thepressure delivered to the instrument. The dome-shapedcutter leaves behind a rounded edge, eliminating sharpcorners in the prepared joint. The instrument also generatesvery little heat, a function of variable speed tissue removal,extremely sharp cutting edges, and large openings in theFigure 15. Most digital length is lost in theunnecessarily deep transverse resection of the head ofthe proximal phalanx. Dome resection of the head ofthe phalanx achieves the desired tissue removal whileminimizing shortening, an important considerationin the maintenance of the anatomic digital parabolaand in revision surgery.cutters to reduce surface area contact of noncutting surfaceswith the bone.Anatomic position is critical to the success of thearthrodesis procedure. One of the drawbacks to traditionalpowered saws is that the freehand cut on two adjacent bonesis not connected. It is difficult to visualize the final positionof the fused bones while making the osteotomy withoutapproximating and often fixating the bones together. It iscommon to take the fixation out, and revise the bone cut inorder to gain better approximation of the ends. It is likewisedifficult to appreciate the hills and valleys on adjacentsides of the prepared joint until the ends are broughttogether. The dome reamer eliminates this problem. Thecorresponding cup reamer creates a recess in the middlephalanx with specific geometry for the reamed proximalphalangeal head to seat in. The concavity is just fractionallylarger than the convexity. This permits the surgeon to placethe toe in any position and have direct contact of bone ends.The process of fixation-assessment-revision-refixation is thenavoided, since use of corresponding reamers will alwaysresult in direct and complete apposition of bone ends.The cutting portions of the reamer sit behind a leadingtrocar-pointed segment of wire. This lead serves threepurposes; first, the trocar pointed segment leads the cutterdown the medullary center of the cylindrical bone, thus thedevice is self-centering; second, the lead steadies the boneand the reamer such that when the cutting device actuallycontacts and begins reaming, the assembly is stabilizedagainst bending and slippage; and third, the pointed leadalso predrills for intended fixation, leaving behind centrallylocated corresponding holes in both the proximal andmiddle phalanx for placement of fixation.
CHAPTER 12 57JOINT FIXATIONThe standard technique for interphalangeal joint fixationinvolves the use of K-wires, placed from within the preparedjoint, exiting the toe, then retrograded back into the base ofthe proximal phalanx. Wire fixation is made easier bypredrilling a hole in the proximal phalanx prior toretrograding the wire. This maneuver will centralize themiddle phalanx on the proximal phalanx when the bones areapproximated as stated above.The reamer instruments are affixed to a bore of the samedimensions as a traditional K-wire. This bore is the couplingthat allows the cutter to connect to the myriad ofstandardized power instruments. This bore also provides theuser with a built in fixation device, once the cutting sectionof the wire is removed. The remaining wire is the exactdiameter of the lead that has already predrilled the bones.Consequently, the surgeon has in his hand a singleinstrument for cutting and fixating a digital arthrodesis.CONCLUSIONDigital arthroplasty and arthrodesis are among the mostcommonly performed operations in foot and ankle surgery.The surgical technique has remained relatively unchangedfor many years, despite the fact that the majority of thehealing complications are a direct result of poor jointpreparation. The benefits of contoured resections of theankle, subtalar, talonavicular, first metatarsophalangeal joint,and interphalangeal joints have been described in theliterature. However, given the inherently rapid nature of theoperation on interphalangeal joints contoured resections atthis level are not commonly performed, and when they areperformed they are imperfect due to the inherent nature ofthe instruments utilized. A great deal of attention is directedat fixation methods for this procedure, although the abilityto enhance fusion rates and patient satisfaction may simply liein more careful, anatomic preparation of the joint surfaces.Figure 16.Figure 17.Figure 18.Figure 19.
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Page 3 and 4: CHAPTER 12 53Traditionally, cartila
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