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

C H A P T E R 1 2ANATOMIC APPROACH TO PREPARATIONAND FUSION OF THE INTERPHALANGEAL JOINTRobert B. Weinstein, DPMINTRODUCTIONThe complex combination of deformities grouped under theumbrella “hammertoes” is a very common complaint seen infoot and ankle clinics across the world. The prevalence of thismalady is a function of the number of conditions that canimpact either development or function of the lowerextremity musculature. Certain genetic disorders can result indigital contracture, as can trauma, infection, arthritis, andneuropathy. While not uncommon, collectively these causeslikely contribute to a very low percentage of the overallprevalence of the condition when compared to biomechanicalabnormalities of the leg and foot. Despite a more proximalcause, it is the dysfunctional interphalangeal joint that oftenbecomes symptomatic, and therefore is generally addressed inthe treatment of the disorder.Dozens of conservative treatment options are availableto those who report the symptoms associated with thesedigital contractures, including splinting, taping, padding,and modifications of shoegear or activities. However, a largenumber of individuals fail these measures and eventually seekprofessional treatment. Very often definitive treatment restswith surgical intervention that is designed to alleviate thecontractures and prevent recurrence.PATHOLOGY DEVELOPMENTCONSIDERATIONSUpon clinical evaluation, the appearance of “hammered” toesrange from mild, fully reducible and only functionallysymptomatic to rigidly dislocated, multiple-joint deformities.The compound hammertoe deformity generally begins withsoft tissue imbalance of the flexor and extensor tendons asthey cross over the metatarsophalangeal and interphalangealjoints dorsally and plantarly. The force exerted by thesestructures creates a sagittal plane buckling, generally towardsplantarflexion at the proximal interphalangeal joint level. Thedistal interphalangeal joint may either contract intoplantarflexion or remain neutral, depending on the longflexor influence. Over long periods of time and afterprolonged or sustained contraction of the tendons, otherperiarticular structures either stretch (dorsally) or contract(plantarly) under this influence. This process of jointadaptation leads to the rigidity seen in many situations. Atthis point the joint has little movement, and the likelihood ofreverting back to normal joint architecture and function evenwith removal of the deforming influence of the tendons isneglible. This is the basis for functional orthotic failure intreating hammered digits.SURGICAL MANAGEMENTThe fundamental procedures for addressing hammered toesinclude arthroplasty and arthrodesis. Generally the choicefor one type of procedure over the other rests with theextent of deformity, likelihood of recurrence, patientexpectation, and other perioperative factors. Arthrodesisrequires more time, dexterity, instrumentation, andmanipulation, and that generally translates to a morecomplicated postoperative course. It is important to knowthat the joint approach is essentially the same for both, andsometimes a surgical plan is for one procedure and the otheris carried out instead, given the common disarticulationtechnique. Between the two interphalangeal joints of eachtoe, the proximal joint is more often addressed surgically andtherefore the discussion will center on this joint.The interphalangeal joints are characterized as synovialhinge joints. Structurally, the head of the proximal phalanxis saddle shaped, having a medial and lateral flare to thecondyles (Figure 1). The base of the middle phalanx has aFigure 1. Representation of the head of the proximalphalanx. Note the flare of the condyles and centraldepression characteristic of a saddle joint.

52CHAPTER 12Figure 2. Representation of the base of the middlephalanx. Lateral depressions with central crista forcentering the phalanx at the articulation.Figure 3A. Collateral ligaments assist in maintainingtransverse plane alignment and normal sagittal planejoint tracking.Figure 3B. Collateral ligaments help maintain transverse plane alignment.central projection that tracks within the groove formedby the proximal phalangeal condyles (Figure 2). Thisarrangement, along with the presence of a pair of collateralligaments that run on either side of the joint restrictsmovement to just the sagittal plane (Figure 3).Anatomic access to the joint begins with transversesectioning of the extensor tendon and capsule over thedorsum of the joint. This palpable landmark translates to theproximal ridge of the bone-cartilage junction on the head ofthe proximal phalanx. The medial and lateral collateralligaments are then divided, completing the disarticulationand exposing the head of the proximal phalanx. A smallamount of further dissection of the capsular attachments andadjacent periosteum may be required for full degloving inpreparation for joint ressection. This leaves a small flap oftissue over both the head of the proximal phalanx and baseof the middle phalanx. These are usually clamped andretracted with a mosquito hemostat.Arthrodesis requires cartilage removal from adjacentsides of the joint, removal of the subchondral bone plate,and approximation and rigid fixation throughout the phasesof bone healing. When performing an arthrodesis there area few general principles to follow. First, exposure of thecancellous bone material is critical to fusion. Incompletetissue removal during the operation is possibly the leadingcause of nonunion. However, aggressive bone resection canFigure 4. The typical resection includes the entiretyof articular cartilage back to the flare of themetaphysis on the respective sides of the proximaland middle phalanges as depicted by the red lines.leave a digit short or render the tendinous structures unableto move the toe, resulting in a flail toe. The digital lengthshould represent a parabola, or unbroken arc with respectto adjacent digits. Second, joint apposition is critical tosuccessful osseous bridging. The prepared joint ends must bein contact, preferably along the entire surface of the boneends, to achieve fusion. Third, anatomic alignment isimportant for both function and cosmesis. The fusion shouldleave the toe neutral on the frontal plane, neutral to slightlyflexed on the sagittal plane, and parallel with adjacent digitson the transverse plane. Finally, the choice of fixation mustmake sound biomechanical sense, maintaining the bone endsin alignment against the two main deleterious forces:distraction and plantarflexion. Use of poor fixation methodsor failure to maintain bone apposition for long enough willlikely result in postoperative complications.

CHAPTER 12 53Traditionally, cartilage resection is carried out with apowered saw or side cutting bone forceps and possibly arongeur. High speed oscillating and sagittal saws are morecommonly used for this procedure. Their use requirescareful retraction of neurovascular structures. Since there isno jig or guide to aid the surgeon, the instrumentationdemands meticulous positioning of the saw blade in all threecardinal planes when sectioning both sides of the joint(Figures 4- 8). This will ensure precise apposition of the jointends to achieve fusion. Hand instrumentation is also usedto remove the cartilage from the proximal phalanx, as well asthe middle phalanx in the case of arthrodesis. A side cuttingforceps is used in this instance, and the cartilage andsubchondral plate of the phalangeal head is removedpiecemeal until the head is fully denuded of cartilage.A rongeur is used on the base of the middle phalanx, in ascraping or gouging motion. Use of this method eliminatesthe problem of frictional heat generated with high speedsaws. The surgeon also has precise control over how muchbone is removed, which is especially important in cases ofrevision and nonunion, where substantial length problemscan arise. Hand instruments permit very precise adjustmentsFigure 5A The resection is ideally 90 degrees to thelong axis of the phalanx, or to the long axis of thefoot if correcting for malunion.Figure 5B. The resection angle is the same for eachphalanx to achieve uniform joint apposition and arectus digit upon approximation.Figures 6A. Often, the level of resection is anestimate of the depth of subchondral plate on themiddle phalanx. This is due to incomplete visualizationof the metaphyseal flare.Figure 6B. The resultant apposition after theresection depth of Figure 6A. The intact subchondralplate or remaining articular cartilage will impedefull bridging.

54CHAPTER 12Figure 7A. Deviation of resection angle in thetransverse plane can occur on one side as depicted, orto varying degrees on both resection surfaces.Figure 7B. Apposition of the joint after this type ofresection will need revision to achieve uniform jointapposition.Figure 8A. Deviation of resection angle in the sagittal plane can occur onone side as depicted, or to varying degrees on both resection surfaces.Figure 8B.Apposition of the joint after this type of resection will needrevision to achieve uniform joint apposition.to high and low areas of bone ends that may not beadequately apposed when the joint is fixated (Figures 9-15).In addition to the technical problems with their use,there are certain deficiencies with these set-ups. Care mustbe taken with high speed powered saws to minimizeprolonged contact with the bone ends and avoid excessiveheat generation. This is a function of the relatively largesurface area of the side of the blade rapidly moving againstthe bone surface and generating friction. It is widely knownthat excessive heat generation can result in bone cell death,and consequently can compromise the intended outcome ofthe operation. Saw blade depth can also be problematic inthe sense that the oscillations carry the square cutting surfacethrough an arc, and consequently the blade edges escapeinto the soft tissues when cutting the small cylindrical bone.Hand instrumentation is not without its owndeficiencies; the method can be extremely slow due tomultiple passes back and forth between the surgical site anda sponge to remove the material from the instrument. InFigure 9. Complete removal of joint surfaces usingmicrosaws leaves uniformly flat surfaces. These candrift, in either the transverse or sagittal planes, orrotate in the frontal plane.

CHAPTER 12 55Figure 10A. Anatomic, contoured joint resection ofthe head of the proximal phalanx.Figure 10B. This technique minimizes boneshortening and increases the surface area available tocontact the middle phalanx.Figure 11A. Anatomic, contoured joint resection ofthe base of the middle phalanx.Figure 11B. This technique minimizes boneshortening and increases the surface area available tocontact the proximal phalanx.Figure 13. The contoured cup and dome fit allows fine tuning final toeplacement on the three cardinal planes, including the sagittal plane foranatomic, flexed fusions.Figure 12. The resultant approximation of thecorresponding head and base when the contours areexactly fitted.

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.