GAIT ANALYSIS BASED ONFIRST MTPJ FTJNCTION:The Functional Hallux

Limitus Concept

Donald Ricbard Dinapoli, DPM

INTRODUCTION

Gait analysis is an objective tool that the podiatricphysician has at his disposal in the assessmentand treatment of a wide range of disorders thataffect not only the foot, but the entire muscu-loskeletal system. The prevailing and traditionaltheory of gait analysis, based on excessive subta-Iar joint pronation, fails in its ability to be easilyapplied and documented by simple conventualmeans. Thus, the demonstration of postural disor-ders through gait analysis has been limited.

A relatively new concept of gait analysis,functional hallux limitus, has proven to be evidentin theory and application. The orrerall concept issimple and easy to apply, clocument, and corre-late to other musculoskeletal conditions. This rep-resents a new understanding of pathologic footfunction.

FLINCTIONAL TIALL[IX LIMITUS (FHL)

Functional hallux limitus is defined as a momen-tary failure of the first metatarsophalangeal jointto undergo dorsiflexion at the time of heel-lift(calcaneal unweighting), resulting in the ineffi-cient transfer of weight in the load-bearing foot.In addition, it results in the failure of the weighrbearing foot to initiate the mechanisms of auto-support, and reverse rotation at the end of singlelimb support.

Clinical ApplicationFunctional haliux limitus (FHL) is an entity thatuntil recently has been largely unrecognized bythe human eye. Dananberg, in 1986, firstdescribed FHL and its relationship to gait efficien-cy through the use of high-resolution video tapeancl vertical load analysis systems (Electrodyno-gram). Identification of this phenomena as a

pathologic entity was thus discovered.FHL is a dynamic condition that can only be

appreciated through the use of these specializedstudies. In the usual clinical setting, a patient willcommonly have full range of motion of their greattoe joint. Evaluation of the patient's first metatar-sophalangeal joint motion is performed with thepatient's foot in a plantarflexed attitude, or withthe foot oriented 90' to the leg. The examinerthen places the hallux throup;h its range of motionwhile holding the first ray stable. (Figure 1) Inreality, during gait, it is the metatarsal that movesover a stable and fixed hallux and sesamoiclcomplex.

The determination of the presence of FHL ina static situation is performed by placing the footal a 90" angle to the leg, loading the firstmetatarsal at the level of the sesamoids or at themetatarsal head, and then attempting to dorsiflexthe hallux. (Figure 2) The lack of motion at thefirst MPJ is thus indicative of FHL. This conditionis present more frequently than once thoughtlo be.

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Figure 1. Clinical examination of normal first metatarsophalangealjoint motion. The patient has full excursion of the hallux. both dor-sall1. and PiantarlY.

A simple dynamic test for the presence ofFHL is to obserwe the patient's gait in the frontalplane. A typical sign of FHL is the abductory twistthat is commonly observed in many patients.Another common clinical finding of FHL is mid-stance pronation. In simpler terms, if the heel is

undergoing lift (the propulsive phase), and themidtarsal and subtalar joint continue to pronate,then the patient is no longer in midstancebecause by definition the midstance phase endswith calcaneal lift. This phenomena is due to thefact that the subtalar and midtarsal joints are actu-a1ly plantarflexing while the calcaneus is lifting offof the ground. This is attributed to the lack of firstMPJ dorsiflexion, as well as the failure of thewindlass mechanism to activate at that moment intime.

Computer As sisted VisualizationThe advent and availability of personal computershas significantly altered our view of simple tasks,such as document preparation, but also morecomplex tasks such as vertical load analysis. Com-puters are used to collect and processes the data,which can then be reorganized and convertedinto useabie information.

Of the three coronai planes, angular rotationin the sagittal plane of joints of the lower extremi-ty is the first in children to take on the normaladult characteristics. This is usually achieved bytwo years of age. Since the body moves forwardand has its greatest angular displacement in thesagittal plane, then a system that analyzes vertical

Figure 2. Demonstration of Functional Hallux Limitus in the patientshol,n in Figure 1. The lirst ray is loaded beneath the sesamoids,u,hile an attempt is made to clorsiflex the hallux. If FHL is present.the hal1ux n'ill not exhibit clotsal erculsion.

forces would provicle insight to normal andabnormal gait.

The Electrodynogram is a system by whichsagittal plane angular displacement is assessed. Itis beyond the scope of this text to discuss al1 ofthe features and fi:nctions of computerized gaitanalysis, however, if there is motion taking placeacross a joint, then vertical load sensors placedabout that joint should reflect vertical displace-ment changes. If the motion is actually blockedfor a period of time, then a wave form wouldindicate a flat line as opposed to a sinusoidal typecurYe. (Figure 3)

PRINCIPLES OF FLINICTIONALTIALLTIX LIMITUS

The principles of FHL provide a new perspectiveor perception of how we actually walk. Due tothis fundamental change in the view of humanwalking, there is a new foundation for communi-cation which utilizes commonly used terms thatare at best vaguely defined. The principlesinvolve the process of energy generation and stor-age as well as the concept of auto-suppofi.

Perspective

Historically, gait analysis has been confined tomajor research institutions and applied to themost severe cases of abnormalities. Research thenmoved into the busy clinical setting where it is

often performed as an afterthought. The usualapproach from a podiatric perspective is to view

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Figure 3. EDG rvavefbrm demonstratrng fnnc-tional hallux limitus. The X and 1 sensor zrle flarcluling this period of gait. Nonnal first IIPJ func-tion is iclentified as a smooth curve with anincreasing slope.

Figure 5. A similar position in step. but from a posterior attitude.The first NITPJ becomes the pivot point in gait.

the patient from a frontal or posterior view. Thepatient most often ambulates with their pantsrolled up to their knees. This process results inonly one degree of information. If the patient'sgait is viewed from the sagittal piane perspective,then a whole new appreciation for the angularrelationship changes. (Figures 4, 5)

Sagittal Plane BlockadeIf each joint of the lower extremity is examined,and its ranges of motion reviewed, it will befound that the ratio of sagittal plane motion to

Figure 4. Different perspectives of foot function yield differentreslrlts. X4edial view of FHL: notice that the first MPJ is locked as theheel has risen off the ground. The arch has flattened as the toe jointhas locked.

either of the other planes is approximately four toone. This is significant in terms of overall analysisbecause the prevailing theory of gait analysisfocuses on the frontal plane abnormalities of therearfoot only. Functional hallux limitus has beendescribed as a locking of the great toe joint. Thisis essentially a block in normal sagittal planemotion. As a result of the block of sagittal planemotion at the great toe joint, there will be com-pensation at some level more proximal to themetatarsophalangeal joint. The leve1 of compensa-tion in the foot is usually a combination of medialcolumn plantarflexion, generally exhibited at themetatarsal-cuneiform ioint, as well as talonavicularand talocalcaneal joint subluxation. In addition,there is often a marked delay in ankle joint plan-tarflexion at the point of heel-off.

Terminology Foundation andPhysical PrinciplesNew concepts are much like foreign languages.Many of the same words are utilized, but theirdefinitions will vary based on the context. It isimportant to establish a new foundation as a start-ing point to facilitate communication. Thisrequires a redefining of the terms. Force is anyaction that tends to maintain or alter the positionof a body, or to distort the body. Vector describesa force, and requires a magnitude and direction.Moment is the tendency of a force acting on a

body, causing it to rotate about an axis or point.Motion is a change of position. Pressure is theaction of a force against an opposing force.

)o

Weight TransferThe principles of weight transfer are described inone of two ways. The most common type ofweight transfer is that which occurs between twolimbs. The critical aspect of weight transfer is thatit occurs within the weight bearing foot itself, as

the center of mass moves over the foot. It is thisphenomena of weight transfer that permits theuse of vertical load analysis. The critical factor tounderstand is that the waveform reflects theforces acting about a point as body weight istransferred across that axis. If there is motionabout a joint, the waveforrn will change to reflectnot only the motion, but also the change inpressure.

Pivot PointIf the foot is viewed as a simple lever system,then in the process of weight transfer and motionduring walking, the great toe joint becomes thelimiting factor about which the entire body movesas it progresses forward. In essence, the firstmetatarsophalangeal joint becomes the pivotpoint in gait. If motion is inhibited at this pointcluring the peak moment of weight transfer (the

time when potential energy is converted to kineticenergy), then not only is the step altered but so isthe process of energy expenditure.

Power of Movement and Mechanisms of Auto-supportThe power of movement and the mechanisms ofauto support are complex issues, which will bediscussecl in brief terms. The power of movementrepresents the overall mechanics of gait initiation.It involves four major areas from which power isgenerated, as well as maintained. The primarysource of motion is generatecl from the swinglimb and axial skeletal muscles. The rernainingaspects include momentum, gravity, and the elas-tic energy or tissue response. In the simplestterms, it is not the weight bearing limb that pro-pels us for-ward, rather, it acts as a lever and pivotpoint. One must think in terms of a man walkingon stilts, or an amputee, and how they generatethe energy to wa1k.

The mechanisms of auto support represent a

series of actions that take place in the foot duringsingle limb support, which permit the foot to sup-port itself. These actions, which occur almost

simultaneously, are: the closed pack effect andthe high and low gear push-off originallydescribed by Bosen-Moller, the windlass mecha-nism as described by Hicks, and the osseous andligamentous support as described by Basmajian.

NEW MODEL CLOSEDCIIAIN KINETICS

A new concept of viewing gait, based on the prin-ciples of Functional Hallux Limitus, have beenclescribed. In addition, some simple definitionshave been reviewed. In the past, the phases ofgait have been broken down into two major cate-gories, stance and swing. Each of these two cate-gories are further subdivided. Swing phase isdivided into an early and late stage, and this willnot change or be affected in the FHL concept.However, the phases of stance phase will bedescribed in new terms. These descriptions reflectthe input of computer analysis on foot functionduring gait.

Stance phase can be dividecl into three majorperiods: the first is heel contact and forefoot load-ing, the second is midstance, and the third is thepropulsive period. (Figure 6) Heel contact is

defined as the period from the strike of the heel

Figure 6. EDG n'ave form clepicting the variousphases of gait: heel contact, folefbot loading andfoot flat. midstance including calcanealunr,veighting and heel-lift, ancl propuision t'ithterminal dor.rble support.

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to the contact of the forefoot on the weight bear-ing surface. This is followed by forefoot loading,as the remainder of the foot bears weight. Themost critical phase of gait is the period of singlelimb support, or midstance. This is the periodwhen all of the body weight is on the contactlimb. It is during this portion of the step when allof the joint rotations mllst take place. It is duringthis period of single limb support that the bodymoyes over the foot, and weight is transferredfrom the heel to the forefoot.

Critical to understanding the FHL concept isthat as the weight is transferred forward on thefoot, the calcaneus unweights, as the heel pre-pares for lift. It is during this phase that the loadon the forefoot increases. Heel-lift follows cal-caneal unweighting, and is easily detected as thesensors stop firing. It is this period of heel-1ift thatcorresponds to early propulsion. If the mecha-nisms of auto-suppofi are not initiated as the heellifts, then locking of the first MPJ occurs . This isexhibited as a flat line on an EDG printout. Thisrepresents the sagittal blockade and the "NewPathologic Foot Function."

The propulsive phase is divided into earlyancl late stages, and we have identifiecl the eadypropulsive phase as heel-lift. This phase endswith heel contact of the opposite limb, inirieting a

new double limb support again. This period hasbeen termed "passive propulsion," but is moreappropriately termed terminal dor-rble limbsuppofi.

Normal MechanicsIn terms of mechanics and timing, the sequenceof events can be described as follows: Heel con-tact with forefoot loading, in which there is subta-lar joint pronation. This is followed by midstance,with calcaneal unweighting. The mechanisms ofautosupport initiate great toe joint dorsiflexion,creating arch raising (midtarsal and subtalar jointsretllrn to the normal and locked position), exter-nal leg rotation and ankle joint plantarflexion, andknee and hip extension with lumbar lordosis.Simply stated: heel-lift, first MPJ dorsiflexion, archraising, external leg rotation, and ankie joint dor-siflexion, are the normal stages of gait.

Abnormal Mechanics

The pathomechanics of FHL are centered aroundthe failure of the great toe joint to dorsiflex at the

time of heel-lift. \[ith the failure of great toe clor-siflexion, the arch actually drops (midtarsal joint,subtalar joint plantarflexion), and the ankle jointfails to plantarflex and actually dorsiflexes, ailwhile the heel continues to rise. There is a failureof the leg to externally rotate, followed by hipand spine flexion. This is the basic pathomechan-ic process of FHL. The result of this pathologicfoot function is symptomatology from toe to head.

CLINICAL IMPLICATIONS OF FHL

Foot and Leg ManifestationsFunctional Hallux Limitus is manifested in the footand leg as a wide variety of symptoms. It may beas simpie as callous formation at the medialaspect of the hallux, chronic heloma dura forma-tion on the fifth toe, plantar fascitis, hammefioes,hursitis. tendonitis. or neuroma pain.

Postural ManifestationsAs stated previously, FHL results in a sagittalblockade of motion. Compensation also occllrsprimarily in the sagittal plane as well. The usualpostural symptoms include: shin splints, patellatendonitis, sciatica, hamstring tendonitis, musculo-genic low back pain, increased bulging of verte-bral disks, temporomandibular joint dysfunction,and chronic headaches.

TREATMENT: AN OYERVIEW OFMOTION ENHANCEMENT

The treatment of Functional Hallux Limitusclepends on restoration of the normal timing andsagittal plane function of the first metatarsopha-langeal joint. It is well known that if a body partis braced or casted, the musculature atrophies,weakens, and the function is reduced. This is con-trasted by stimulating a part through exercise,increasing its strength and performance. The con-cept of motion enhancement employs the use ofan orthotic that will function during the criticalmoment of gait. This critical moment is the periodof increased forefoot loading during the heel-1iftphase. The orthotic must permit the firstmetatarsal to plantarflex as the heel lifts. The firstmetatarsophalangeal joint undergoes dorsiflexionas the foot raises, and the metatarsals move into avertical position in relationship to the ground.

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This is accomplished through a series of firstray cutouts on the ofihotics device itself. In addi-tion, the first ray cutouts are combined with anaperture pad know as a "kinetic wedge," whichfurther facilitates first MPJ function.

STTMMARY

A new concept of gait pathomechanics, Function-al Hallux Limitus, has been introduced. In addi-tion, many symptomatic conditions appear sec-ondary to this new biomechanical phenomena.FHL is an easily recognized and teatable condi-tion, Recognition of this disorder as the underly-ing pathology in many gait-related problemsplaces the podiatrist in a position as the primarycare specialist for w-alking and postural disordersrelated to gait.

BIBLIOGRAPTIYBasmajian JV, Deluca Cl: Muscles Aliue 5th ed, Baltimore, MD,

\X/illiamr & \X ilkins, 1985.

Bojsen-Moller F: Calcaneocuboid joint stability of the longitudinalarch of the foot at high and low gear push off. J Anat 129:765-176,1979.

Dananberg HJ: Functional Hallux Limitus and Its Relationship to GaitEfficiency. J Am Podidtr Med Assoc 7 6:648-652, 1986.

DiNapoli DR, Dananberg HJ, Lawton M; Hallux Limitus and Non-Specific Gait Related Bodily Trauma. In DiNapoli DR (.ed) Recon-structiue Surgery of tbe Foot and Leg UpdLTte 9O Tucker, GA, Podi-atry Institute Publishing, 1990.

Hicks JH: The mechanics of the foot, Part II: The plantar aponeurosisand the arch. J Anat 88:25, 1954,

Langer S, Polchainoff M, Hoemer EF, Wernick J: A Practical Manualof Clinical Electod))nogrdph)) Deer Park, NY, Langer Biomechan-ics Institute. 1989.

Sutherland DH, Olshen R, Cooper L, \fi/oo SLY: The Development ofmat1re gait. J Bone Joint Surg 62At336, 1980.

1)

SAGITTAL PLANECONSIDERATIONS IN THE

KALISH-AI-]STINBT]NIONECTOMY:

Q u antttatrv e and Q u ahtativeAnalysis of the Kalish-Austin

Bunionectomy

Donald R. Dinapoli, DPM

A.l. Pbillips, DPM

ABSTRACT

Sagittal plane shift of the first metatarsophalangealjoint by axis guide manipulation of the Austinbunionectomy has been popularized recently inPodiatry Institute literature. The purpose of thispaper is to exam sagittal plane changes in thosepatients who have undergone hallux valgus cor-rection via the Kalish-Austin bunionectomy. It isthe authors' opinion that sagittal plane correctionof the first ray will be reflected not only in theangular alignment of the first ray, but also in theentire forefoot and rearfoot complex.

Each patient was objectively assessed preop-eratively with a test orthotic system utilizing theElectrodynogram for dynamic evaluation andgreater understanding of the first ray function. Inaddition, each patient was assessed postopera-tively to determine outcome analysis. Static evalu-ation was performed by examining the preopera-tive and postoperative radiographs anddocumenting the sagittal plane changes.

INTRODUCTION

Preoperative analysis of transverse plane defor-mity and anlicipated correction of hallux abductovalgus is routinely performed by examining pre-operative weight-bearing radiographs. In addition,there is usually significant input from the clinicalexam. Radiographs are purely two dimensional.Procedure selection and surgical goals are basedupon combined clinical and radioeraphic exami-nation and findings.

At the present, the consideration for concur-rent sagittal plane correction is based upon a

number of factors that include the presence ofhyperkeratotic lesions beneath the secondmetatarsal head, along the medial aspect of thehallux interphalangeal joint, or the MPJ itself.Biomechanical exam and intra-operative evalua-tion may also reveal a significant degree of hyper-mobility of the first ray. In those obvious cases offirst metatarsal elevatus, the surgeon may deter-mine that plantarflexion of the capital fragment

.))

will be necessary, in addition to recluction of theintermetatarsal angle. This adclitional plane of cor-rection has often been discnssed, but no concreteparameters hzrve yet been described. It is theattempt of the authors to preoperatively deter-mine the specific amount of plantarflexion thatwill be neecled in conjunction with the transverseplane correction.

METHODS AND MATERIALS

The authors selected 17 cases (25 feet) of patientsthat had undergone hallux valgus correction viathe Kalish-Austin bunionectomy between July,1989 and December, 7992, Al]r procedures wereperformed by one surgeon. The patients selectedunderwent the same surgical procedure and pre-operative testing via the test orthotic system, andhad a minimum of six months of postoperativefo1low-up at the time of this writing. In addition,the patients were free of postoperative complica-tions such as fixation failure, second surgeries,and infections requiring incision and clrainage.The patients also had preoperative and postopera-tive weightbearing radiographs available for angu-lar assessment and measurements of the firstintermetatarsal angie, first metatarsal declinationangle, talar declination ang1e, and the calcanealinclination angle. These were only angles consid-ered in the initial study, but the includement ofother angles and methods of static assessment willbe considered in future studies. Angular measure-ments were performed using standard techniques,by one of the authors. A summary of the resultsczrn be for-rnd in Table 1.

Table L

SUMMARY OF RADIOGRAPHICANALYSIS (25 FEET)

PREOPERATIVE POSTOPERATIVEIM FMD TDA CIA IM FDX{ TDA CIA

Mean 1,4.2 22.6 30.1 22.1 i.6 22.8 30.2 23.8

Standard 4.6 3.9 4.2 5.6 1.7 4.1 3.5 5.9Deviation

Range 7-25 73-30 23-40 t3-31 7-8 20-35 24-40 76 40

IM: First lntenr-retatalsal Ang1e, FMD: First Metatarsal Declina-tion Ang1e. TDA: Talar Declination Angle, CIA: CalcanealInclination Angle

Preoperative Test Orthotic System

The test orthotic system was designed for thisstudy by one of the authors. Patients were exam-ined preoperatively with a high resolution, bi-directional video tape system. In addition, theywor-rld undergo computerized gait evaluation uti-lizing the Electrodynogram System. In this testsystem, the sensors were distributed as recom-mended by the manufacturer: M & L were placedunder the tuberosity of the heel, 1 and X wereplaced over the tibial ancl fibular sesamoidsrespectively, the 2, 5 and H sensors were placedproximal to the metatarsal heads and over theinterphalangeal joint of the hallux. (Figure 1) Theauthors' variation from the manufacturers recom-mendation placed the X and 1 sensors at the 1eve1

of the first MTPJ. This simple change revealed a

number of unusual findings.

The second part of the test system was a test

orthotic that was fabricated at the time of preop-erative testing. It consisted of a neutral positionimpression taken semi-weight bearing. The mate-rials used were aliplast and plastizote. The devicewas shaped into a neutral position orthotic with aforefoot post that was neutral positioned in rela-tion to the rearfoot. It was modified to not influ-ence the forefoot in function with the exceptionof its thickness.

Figure 1. Electrodyne sensor distribution

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A series of tests were then performecl withvariations in a first ray cLrtout. The cutouts wereas fbllows: standard clltout, bidirectional cutont,metatarsal cuneiform cutout. (Figure 2A-D) Eachof these cutollts allowed a certain degree of plan-tar displacement of the first metatarsai duringforefoot loading and subsequent lift phase of gait.

Figures 2A-D. Test ofthotic system with a seriesof first ray cutouts (medial margin of device).A. Neutral shell without first rav cutout.

Each patient was tested by the same techni-cian, using the previously described techniques.The overall testing process included a series oftests beginning with a barefoot test followed by ashoe test. This sequence was foilowed by at leastthree tests utilizing the test orthotics with varia-tions in the first ray cutout.

Figure 28. Standard Cutolrt.

Figure 2C. Bidirectional Cutout Figufe 2D. Metatarsal Cuneifonn Cutout

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The important data that was examined fromthe Electrodynogram printout consisted of theratio of the total pressure of the X and 1 sensors.(Figure 3) It is postulated that as the ratio of thetotal pressure reflected by the X and 1 sensors

approached one (1) during the gait cycle ancl thatit represented uniform loading of the metatar-sophalangeal joint. (Figures 4A-4D)

RESULTS

A summary of the results are found in Tables 1

and 2. A full repofi of each angular measurementof the patients used is beyond the scope of thiscurrent paper and will be reserued for future pub-lication. The radiographic results report on allcases initially examined. However, in reviewingthe data, there were 9 feet involving 6 cases thathad incomplete EDG data. They were subse-quently discarded from the second half of theanalysis.

There were a number of variables that wereencountered. The first has already been notedand includes a number of the cases reviewed forthis initial retrospective study that had incompleteElectrodynogram data, either preoperatively as a

result of technical error (one case) or as a resultof not undergoing testing (two cases) or data notobtarned postoperatively at the time of this writ-ing (6 cases). As a result, the overall sampling sizemay not be large enough for adequate statisticalanalysis. The authors will attempt to eliminate allof these variables in the future for a more defini-tive report.

Figure 48.

ls.mr ar..or. I rt- or P..k rrc..l&r.r... I of x./cr: ll!tr. er.rtoi lMi .r... or xtl.n2

...t iP..lrie i ...11P..rI'. l16. 3r.*.1 .. . r lror.l Pr...l I lof 5r.rc.1 .. . r lrotrt Pr..sI lor 3r.rc. i --- ll iot strrc.iltiI lerull:.d iI ro 1

'.cotull I I

i-l-i-il--i--rlii

L I r- I 2r i ro-2 ll L 16r | 23r..o ll (!o- 62 R.@ 12- 23)l

tlle31..ii.2o.o

r I rD I 21 i 1o-2 li . i,6 I 22 | 1o.?

l13:ro.2l.i-o)i 2..,r ii ( o- o..r. o- o)i !r..

i t,e., li i , 1,,a.7

5 | .o i 7. | 1o.2 il 3 i & | ,a I ro2

,1"' | ". i ;"..'.,'- 1.,.3O!-. 11 (7o-.! r.6 rr-..)_ii_i*"li_l_i_*'

t | 7a i 7. ro,2 ii I i .2 ir7o- 35 i.E.70-.o) .1o,. ii (ro-.5 i.E 70- $)li i *'r ii | |

^i.rz i & ro.:iiri,s I

2&.. it (ro. .r r.8..!- e.)i ,rr.6 it i I

Figure 3. Typical EDG printor-rt of pressures

Figure 4A-D. Preoperative dorsal plantar, andlateral views of one patient in the study. Herpreoperati\re angular relationships n'ere as fol-lows: I&I 10. FMD 24, TDA 33, CIA 33. Postoper-ative angr:lar relationshrps: IM 1, FX,ID 27, TDA25, CIA 40, The EDG X:1 ratios \\,ere as follou.s:preoperative 0.64, postoperalive 0.45.

.10

Mean 0.65Standard 0.29

DeviationRange 0.24-7.2

Table 2

SUMMARY OF EDG X SENSOR TO 1.

SENSOR RATrO (16 FEET, 11 CASES)

PREOPERATTVE POSTOPERATIVE

Figure 4D.

metatarsal cuneiform/(.75-20"). These values wereinitially obtained through trial and error and thenbecame rather predictable as the number of casesincreased over a three-year period. However, thestatement that a bidirectional cutout can producea similar overall angular change in the sagittalplane can not be made at this time. In reviewingthe summary data, it can be noted that there wasan overall increase in the total pressure ratio ofthe X:1 in the postoperative test, 0.65 to 0.71. Athorough statistical analysis has not been per-formed, yet the authors believe that this doesshow a trend.

The overall angular changes reveal that theKalish-Ar-rstin bunionectomy can achieve a widerange of correction in both the transverse plane as

well as the sagittal plane. The average change inthe transverse plane (first intermelalarsal angle)was 8.6" degrees. If the authors' overall conceptholds true, there should be corresponding sagittalplane changes as we11. These changes should bereflected as an increased first metatarsal declina-tion angle, a decrease in the talar declinationangle and an increase in the calcaneal inclinationangle. In examining the data summary, it doesreflect a significant change in the first metatarsaldeclination angle, 5.6', hou,ever the changes inthe talar declination angle (0.1') and the calcanealinclination angle (1.4') were not nearly as significant.

It has been the authors' attempt to quantifyand qualify the sagittal plane changes in theKalish-Austin bunionectomy through a retrospec-tive study. It cannot be stated at this time that thecllrrent model in use can predict and determine

0.770.27

0.20-1.23

DISCUSSION

The purpose of this paper was to examine thesagittal plane changes that occur with the use ofthe Kalish-Austin bunionectomy by utilizing a pre-operative dynamic testing model. It was theauthors' assumption that sagittal plane correctionneeds to be obtained in coniunction with trans-verse plane correction and that it can be predict-ed based upon dynamic function utilizing a testmodel. The best ratio of total pressure betweenthe X and 1 sensor utilizing the preoperative testorthotic system was selected. The cutouts coffe-spond to certain degrees of plantar flexion of theapical axis guide during the surgical procedtire:standard/(0-5'), bi<lirectio nal/ (5-1.0" ) , and

Figure 4C.

37

both the needed amount of sagittal plane correc- cain TD, Boyd D: Defining the Limits of the Modified Austin

tion via the apical axis guicle as well as iher"r.,i i;:;";;;'nL,j"i;ilT":;r\:iil2f:{#ffii::f;?"'frfftant sagittal plane change seen postoperatively. Iishing, 1990, p.728-734. . .

Testing will continue nnd u more in depth paper '"TL"J.X\3',?J,1'Hffi;ffiI^;:ir:tr:;:;:il:,':"r\il\will be published.

ff!:rfr'*,rucker, GA, Pocliatry in"stiiute Publishing, 1992, p

BrBLrocRApHy '""2,i';i'Jili2i'il'i,#;I"3lllil,"i;YlTl'!,!":d;{,"K:y:&[Foundation of Biomechanicsincl Sports Medicine Research, 1989.

Boc SF, D Angelantonio A, Grant S: The Triplane Austin Bunionec-tomy: A Review and Retrospective Analysis. J Foot Surg 30:375-382.1991.

Cain TD, Chang TJ: Manipulations of the First Metatarsal in HalluxValgus Surgery (Revisited). In Ruch JR, Vickers NS (eds) Recoz-sttuctiue Surgery of the Foot and Leg, Updarc '92 Tucker, GA,Podiatry Institute Publishing, 1992, p. 244-247.

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