Arthrodiastasis of the Ankle joint: An Alternative to Fusion

CHAPTER 6ARTHRODIASTASIS OF TFIE ANKLE JOINT,AN ALTERNATIVE TO FUSIONGeorge R.Wto, DPMLeomard Talarico, DPMINTRODUCTIONPresently, we know of two major forms ofosteoarthritis, both of which can be severelydisabling. In primary osteoafihritis the cause isgenerally unknown, and in secondary osteoafihdtisthe cause is generally ffaumatic in origin. Both formspresent with similar clinical symptoms, whichinclude pain, decreased range of motion, andswelling. Radiologically, there is a decrease in thejoint space, and presence of osteoph),tes andsubchondral cysts with sclerosis of subchondralbone. Extracel1ularly, afiicular cafiilage has twoprinciple components. Collagen that gives it shapeand tensile strength and proteoglycans, that givearlicular cafiilage its compressive propefties. Inosteoafihritis there is an imbalance between thesynthesis and the release of these two components.This leads to both a disruption of the collagennetwork and a loss of proteoglycans. Thesebiochemical changes that occur appear to have nodiagnostic clinical correlation, especially in the earlystages of the disease process.Treatment of osteoarthritis has includedantiinflammatory medications and exercise. Also,arthroscopic joint lavage coupled with subchondralbone drilling has been used. None of thesemodalities have proven to provide significantimprovement in symptoms, 1et alone a cure. Theultimate end for patients with osteoarthritis iscomplete destmction of the articular cafiilage withresultant need for afihrodesis or arthroplasty of theaffected joint.THE PROCEDURERecently, five patients who were candidates forafihrodesis of the tibiotalar joint as a result of eitherprimary or secondary arthritis were offered anothertreatment option, diastasis of the tibiotalar iointusing external fixation. The goal of the surgery wasto eliminate mechanical stress on the ankle joint bypreventing contact between the tibia and the talus.It should be noted that adjunctively, arthroscopiclavage cor-rld be performed at the same time asframe application.The primary reason that this particularprocedure was chosen is because it has beenreported that when intermittent hydrostatic pressureis applied to human osteoarthritic catilage in tissueculture the result was a significant increase in thesynthesis of proteoglycans. Recall that proteoglycansprovide arlicular cafiilage with its compressivepropefiies. Thus, hypothetically, when intermittentintraarticular hydrostatic pressure is applied tohuman articular cartilage, in the absence of mechanicalstress, the result could be a reparative activity bythe chondroq,tes in the osteoafihritic cartilage. Asecondary reason for making this choice is that thisprocedure is not joint destructive.Under general anesthesia, one of two types ofexternal fkation was applied. These included eitherthe Ilizarov ring apparatus or a mono lateral flxator.Application of the llizarov apparatus involved tw-oleg rings applied to the tibia and attached withscrew-threaded rods. A footplate was then appliedwith two wires in the calcaneus and two wiresthrough the metatarsals. The footplate was thenfked to the 1eg rings with two hinged rods and onescrew-threaded rod posteriorly to initially preventankle motion for the first two weeks postoperatively.The mono Tateral fixator involved placement of halfpins into the tibia, talus and calcaneus. Fixation ofthe ankle joint was also maintained for the first twoweeks postoperatively.Distraction was achieved on the operating tableand was then carried out until approximately 5mmof joint space was achieved. The patients wereencouraged to ambulate to tolerance on the firstpostoperative day. Load bearing on the distractedjoint was essential in order for there to be anincrease in the intraarticular hydrostatic pressure.After two weeks, ankle joint motion was allowedwith the use of hinges. Exercises for range of motionwere performed and ambulation was encouraged.During the treatment period with either fixator there

CHAPTER 53tinstances the author Llses a Jones compressiondressing. This type of cast is usecl during rhe initialpostoperative phase as it provides a measure ofprotection for the external frame. Although this isnot a necessity, it does generally provide a certainlevel of comfofi and security for the patient tintilthey can become adfusted to the presence of theframe. The cast is usually discontinued within thefirst week or so after the surgery.In some patients the distraction process willresr-r1t in deviation of the toe due to the tension thatis placecl on the flexor or extensor tendons. Anumber of authors have described inserting aKirschner-wire into the associated digit, and at timesacross the metatarsophalangeal joint as it is believedby some that the use of the wire will tend tcrmediate this effect. The author has not found that thisis a problem, and a pin is not used routinely in theassociated toe. However, there have been somepatients where the toe required some additionalsplintage with tape during the lengthening process toovefcome this type of problem.Postoperative CareAs noted above, the patient is usually placed into aJones compression cast initially. The patient is maintainednonweightbearing until it is deemed thatsufficient lengthening and healing have occurred. Attwo weeks after surgery the patient will begin thedistraction process, turning the apparatLls onequaftertllrn every six hours. Racliographs are thenmade periodically to assess the amount of lengtheningwhich has been achieved, and once this is felt tobe sufficient, the patient is instructed to discontinuethe distraction process. Should the metatarsal beovedengthenecl, the reverse process can beemployed, that being shofiening of the metatarsaluntil a sufficient length has been achieved.Afterwards, the patient is evaluated periodicallywith radiographs to cletermine when there has beensufficient healing for initial weightbearing. Once thisinterval has been achieved. the author will allow thepatient to begin initial weightbearing with rhe pinsand frame in place. It is felt that this provides somemeasure of protection against excessive weightbearingforces on the newly lengthened area ofbone. The author has seen some patients wheresagittal plane deformity has developed in themetatarsal once weightbezrring was instituted. Inthose circumstances, it was usually due to the factthat the frame was removed prior to the institutionof weightbearing.The patient is then re-evaluated two weeks later,at which time the distal and proximal pins areremoved from the erlernal fkator. Weightbearingcontinues for an additional two weeks with only twoof the remaining pins in p1ace. At that time, theremaining pins and exlernal fxator are removed. Thisallows the osseous tissues to adapt to weight-bearingstress over time, reducing the likelihood of plasticdeformation of the more immature bone substance.The greatest drawback to this type of procedureis the lengthy period of nonweightbearing thatmay be required in some patients. On average, ittakes abor-rt three months before patients are readyto begin ful1 weight-bearing without the externalfixator when a lesser metatarsal has been addressed.How-ever, patients undergoing surgery on the firstmetatarsal generally require a much more lengthyinterval of nonweightbearing, sometimes extendingup to sk months.ComplicationsPotential complications with this approach are generallyminor and usually will consist of some type ofdigital deformity due to the altered tension on thetendons. Mild cases of dorsal nelve entrapment havealso been encountered, but these have respondedwell to locai injections of corticosteroid.Fufihermore, in some patients the degree of scarringin the skin can be objectionable. This is due to thefact that linear tension is being applied to the scarduring the initial healing interva1. Therefore, theauthor attempts to warn all patients prior to undergoingthe procedure that this may be a factor aftersurgery. This may be particularly important whenpatients are undergoing the procedure primarily forcosmetic reasons. However, the scar can ceflainlybe excised and primarily closed at a later time,rendering a more appealing scar for the foot.ConclusionOverali callous distraction is a viable alternative in aselect patient group to address shofiening of ametatarsal. However, the author's preference in mostsituations is to employ a sagittal Z osteotomy, iffeasible. This approach is simple, effective, andinvolves less recovery time than if callous distractionor bone grafting is required. Nonetheless, callousdistraction is effective, and may be preferable inmost situations where previous infection has beena problem.

CHAPTER 6 33was radiographic evidence of increased joint spacewith the patient fuli weight bearing. The assumptionwas made that the weight bearing surfaces of thetibia and the talus did not come into contact duringthe time of distraction. Total time of distraction wasbetween five and sk weeks. The frame was thenremoved and the patients continued with physicaltherapy and ambulation to tolerance.The resultant effect of diastasis of the tibiotalarjoint is an elimination of normal mechanical stressplaced on the articular cartilage due to the absenceof contact between the joint surfaces and aLintermittent increase in intraarticular hydrostaticpressure. As previously mentioned, in tissue culture,cartilage displays reparative activity when placed inthese conditions. The primary reparative activitynoted was that of increased proteoglycan productionby more than 50%. It can be speculated that thisincrease in synthesis of proteoglycans may be thereason for the increase in joint space. It has alsobeen suggested that by distraction of the joint thereis a subsequent increase in the circulation ofsynovial fluid that provides nutrition to the afiicularcartilage. For whatever reason, diastasis of the anklejoint, with elimination of mechanical stress, leadsto improvement in the articular cafiilage and areduction of the symptoms of osteoarthritis.The purpose of performing diastasis of thetibiotalar joint in patients with severe osteoarthritiswas to delay the need for arthrodesis. Thus far, fivepatients have been treated in this manner. Clinicallyall patients continlle to experience a recluction inpain, an increase in joint range of motion, andradiographic appearance of joint space. \[ith thispositive clinical evidence it appears that ankle iointdiastasis, with either the Ilizarov apparatus or amonolateral fixator, may deiay the need forarthroclesis in patients with primary or secondaryosteoarthritis.Figure 1. Preoperative AP radiograph of theankleFigure 2lramePost distraction AP racliograph srith

CHAPTER 6Figllre .1. Postoperatile latcral vie\\. of extcrnal fkatorFignle J. PostopcrlLtive clinical At, r-ies of crter.nal flrator.Figue 6. Postoperative latelal vics- of ankle at 1 ve.LrFigure 5. Postoperati\.e A1) r':rcliograph of ..rnkle :rt1 ycar'.