SYNERGISTIC WRIST DYNAMIC SPLINT FOR FLEXOR TENDON REPAIR

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1 APPLICATIONS, BASIS & COMMUNICATIONS SYNERGISTIC WRIST DYNAMIC SPLINT FOR FLEXOR TENDON REPAIR 23^ PEI-HSI CHOU 1, YOU-LI CHOU 2, KAI-NAN AN 3, GAU-TYAN LIN, 1 FONG-CHIN Su, CHING-SHOUNG YANG, GWO-FENG HUANG deprtment of Orthopedic Surgery, Kohsoung Medicl University, Kohsiung 2 lnstitute of Biomedicl Engineering, Ntionl Cheng Kung University, Tinn, Tiwn 3 Biomechnics Lbortory, Deprtment of Orthopedics, Myo Clinic, USA Biomed. Eng. Appl. Bsis Commun : Downloded from ABSTRACT Tendons re frequently injured by direct trum. Tendon dhesions were common sequel of tendon repir nd re one of the most chllenging problems in hnd surgery. The concept of "controlled motion" grdully replced "totl immobiliztion" in the tretment of flexor tendon injuries nd tody represents stndrd of cre for il primry repired flexor tendon injury. Use of controlled motion splints during the erly stges of stges of tendon recovery in crese tendon gliding. However, how best to chieve pssive motion nd the effect of pssive motion on tendon gliding hve remined controversil subjects. Bsed on series of recent experiments, the concept of "dynmic synergistic wrist motion splint" ws estblished nd evluted. It ws found tht this synergistic wrist motion increses the tendon excursion due to eliminting the lxity nd buckling of tendon in the regions between pulleys without introduce excessive mount of tension. The purpose of this study is to design nd fbricte dynmic splint bsed on this concept nd define the nture coordinted motion between the wrist nd finger joints due to the pssive tension of the muscles in vivo. Prmetric nlysis will be conducted to chieve n optimum design with the considertion of ntomic constrints. Clinicl tril of using such dynmic splint will be evluted in the future. Biomed Eng Appl Bsis Comm (October); 13: Keyword: dynmic splint, Flexor Tendon Repir, synergistic wrist motion, optimum design 1. INTRODUCTION Tendons re frequently injured by direct trum. Tendon dhesions were common sequl of tendon repir nd re one of problems needed to fce in hnd surgery; the inbility to restore cceptble function in the finger in which the tendons hve been injured" [1]. The postopertive tretment of injured flexor ten- Received: Aug. 30, 2001; ccepted: Sep. 25, 2001 Correspondence : You-Li Chou, Ph.D. Institute of Biomedicl Engineering, Ntionl Cheng Kung University, 1, T-Hsueh Rod, Tinn, 7014, Tiwn; Emil: ylchou@mil.ncku.edu.tw dons is significnt prt to obtin the good motion nd strength. When the first time, the repir of flexor tendons ws considered by Bunnell, the dvice given ws, "Repired tendons should be protected from breking out by splinting for three weeks nd prtilly so for four week" [1]. Mson nd Allen [2] demonstrted, in fct, tendon strength would loss during the first 5 to 7 dys nd the sitution will improve fter 14 dy. Erly motion cn void tendon dhesions but this would cuse the scr t two ends of the tendons nd it ws discourged. As result, this concept hs been influenced on the improvement of rehbilittion in wrist for mny yers. In 1960, this concept ws first ccepted s n lterntive tretment progrm in fter the suggestion from Hrmon nd Young [3]. They suggested tht ps- -19

2 Biomed. Eng. Appl. Bsis Commun : Downloded from live motion with protective splinting would increse tendon gliding nd improve functionl results. The concept of "controlled motion" grdully replced totl immobiliztion hs been supported by numerous niml studies performed in the pst ten yers [7,]. However, how best to chieve pssive motion nd the effect of pssive motion on subjects [4,5,6], series of in vitro experiments hve been crried to evlute nd compre the differences in tendon excursion between flexor digitorium profundus nd superficilis using severl mobiliztion techniques [9-14]. In these experiments, "the dynmic splint" ws estblished nd evluted. We found tht this synergistic wrist motion will increse the tendon excursion by eliminting the lxity nd buckling of tendon in the regions between pulleys without introduce excessive mount of tension. Bsed on the concept of dynmic synergistic wrist motion, it is possible to design nd fbricte dynmic hnd splint of controlled movement. However, with little vilble numericl dt describing the nture coordinted motion mong the wrist nd finger joints up to the present, systemtic study of the hnd coordinted motion is necessry. In the study, the three-dimensionl motion nlysis system ws employed to mesure the reltive motion mong the wrist nd finger joints due to the pssive tension of the muscles. Then, the nture coordinted motion cn be quntittively ddressed through sttistic regression nlysis. The results not only id to chieve n optimum design on synergistic wrist dynmic splint with the considertion of ntomicl constrints, but lso provide the useful informtion bout keeping inherent condition of wrist flexors nd extensors for clinicl dignosis. 2. METHOD Fifty norml subjects, 25 mles nd 25 femles, ge from 20 to 40 with no previous history of injury Vol. 13 No. 5 October 2001 ssocited with the upper extremity were recruited for the experiment. They were clssified into two groups by sex with equl number of subjects. The reltive joint positions of the hnd nd wrist were mesured by using three-dimensionl motion nlysis system with externl retroflective mrker plced on the dorsl surfce of the subjects' hnd. Six video cmers surrounded by the on-xis ring-lights (Mc-Lite) were djusted so tht ll the mrkers could be viewed t lest by two cmers throughout the rnge of joint motion. 19 pssive retroflected mrkers were mde of plstic spheres which dimeter is 2mm nd covered with 3M retroreflective mteril. Clibrtion frme ws mnufctured so tht the ccurcy of.1% ws chieved for the field of view including forerm nd hnd. In order to esily trce the positions of retroflextive mrkers esily by expertvison, two combintions were used in the mesurement, one is for the index nd ring fingers nd the other is for the middle nd little fingers (Fig. 1). During experiment, the subject ws in sitting posture with the elbow plced on the tble nd the forerm ws in the upright position. Subject ws instructed to relx the hnd muscle. During the test, 1.wrist movement: first the wrist joint ws instructed to move the wrist ctively, but with the hnd muscle be relxed, 2.utonomic coordintion movement: the subject moved the wrist without the hnd muscle be relxed. The motion cycle : wrist flexion nd phlnges extension, then wrist extension nd phlnges flexion. The ngle needed be found. B, BPIF nd Dt nlysis Hypothesis 1. Distl interphlngel () nd Proximl interphlngel () joint re single xis hinge joint. 2. Metcrpl phlngel () nd Wrist joint re three-xis rotting o using Euler Angle to description the chnge of movement. = Flexion - Extension 0 = Ddioulnr - Devition 0 = Prontion-Supintion 3. The ngle between nd is instneous ngle. 4. The ngle between nd Wrist ngle is Euler ngle. 2.2 Formul 1. nd ngle: 0 - COS -1 IP12 P23 P 12 lip23 Fig. 1 : Mrker set of the hnd motion nlysis -20-

3 APPLICATIONS, BASIS & COMMUNICATIONS INDEX- regression ng le so [ e B -se so Wrist ngle (Jg.) INDEX- regression-nle 12r- 12 INDEX- regression ngle Biomed. Eng. Appl. Bsis Commun : Downloded from N. e 'd ze s 5 1ZINDEX- reg ression ngle...:... s FAB -5e 5e 12 INDEX- re gression ng le AAA. to. 6 o _...: "no -5 5 Fig. 2 The motion reltionship of wrist joint nd index finger joints -21-

4 Biomed. Eng. Appl. Bsis Commun : Downloded from 234, P 7 P 9 BP,P = COS P7 II P 9 coc soc0 -so socj' + cososv c/cy) + sososip COsyI SOS V + cosocip - cosy) + $Sfc1V c0c7p c=cos,s=sin [A] = [R] [B],,,2,3 [R] = 2, nd WRIST euler ngle: [A]=components of vector mesured with respect to the distl system [B]=components of vector mesured with respect to the proximl system 2.3 Sttistics nlysis In the study, It is very importnt tht how to indicte the reltionship between wrist joint nd ech finger joint. So we tke the wrist joint s x, nd ech finger joints s Y. nd then we hve done sttistic nlysis s flowing steps: 1.normliztion experimentl dt. 2.men, stndrd devition nd vrince of,, nd WRIST joints. 3.correltion nlysis. 4.regression nlysis. 3. RESULTS 3.1 Movement of - joint nd wrist joint: = tn-' 12 k,, Vol. 13 No. 5 October 2001 nd wrist joint lso the mximum nd minimum ngle of the motion. The detils re ddressed s follows: 1. There re no significnt differences on the joint motions between mle nd femle (Tble 1). 2. The motion reltionship between ' nd wrist joint motion is liner. Our experiment indicted tht the synergistic wrist motion coordinted well significntly (Tble 2). 3.2 The motion reltionship of,, nd wrist joint: The motion reltionship of wrist joint nd finger joints cn be defined quntittively with the two order regression nlysis of ll finger joint ssuming the ngle of wrist joint rotted s x nd the ngle of ech finger joints rotted s Y. A. The motion reltionship of wrist joint nd index finger joints for regression nlysis (Tble 3, Fig. 2). Y=x?+bx+c X degree of wrist joint rotted Y degree of finger joint rotted,b,c, coefficients R2 determinte coefficients corr correltion coefficients B. The reltionship of wrist joint nd middle finger joints for regression nlysis (Tble 4, Fig. 3). C. The reltionship of wrist joint nd ring finger joints for regression nlysis (Tble 5, Fig.4). D. The reltionship of wrist joint nd little finger joints for regression nlysis (Tble 6, Fig.5). 3.3 Splint design Our experiment found out tht the synergistic wrist motion coordinted well significntly. Quntittive description is possible defined by the sttistics nd regression nlysis. Then the design of splint is bsed on the mesurement of coordinted motion pttern. In the current stge, the proto-type of four-br (Fig.6), six-br (Fig.7) nd eight-br (Fig.) linkge mechnism of splint hve been designed completely. Further theoretic nlysis nd prcticl fit is processing. Prmetric nlysis will be used to chieve n optimum design under the considertion of ntomic constrints. Functionl test of dynmic splint in clinicl is needed to evluted in the future. 4. CONCLUSION 33 By momentum estimtion nd sttistic nlysis, we cn find out the rnge of motion of,,, 1. The motion reltionships between the wrist nd finger joints due to the pssive nd ctive tension of the muscles hve been systemticlly documented. 2. The coordintion between the wrist joint, nd joints, is more importnt thn tht between the wrist joint nd joint. 3. Quntittive description is then possible through the -22-

5 APPLICATIONS, BASIS & COMMUNICATIONS 235 WRIST -ngle 120PIDDLE- re ressionngje N Biomed. Eng. Appl. Bsis Commun : Downloded from '......:: to Be... :.....:... Be ^ ,:..::... c 6 -s 5 12o r DLg se -5 MAI regression p lt regression ngle 12^IDDL ^ regres sion ngle 1e se s ngle Be so FA1 Fig 3. The reltionship of wrist joint nd middle finger joints -23-

6 236 Vol. 13 No. 5 October 2001 WRIST ngle regression ngl so -so Biomed. Eng. Appl. Bsis Commun : Downloded from -5 so 12 RAMC- regression n gl, 12 ^ R.INC-NP lee Be 60 4e 2 se e' e -se -so so wrist ngle (deg.) -se se 120 RING regression ngle NAe regression ngle 12 RING- regression ngle tee Be se se -se se RING-NP regression ngle Wrist ngle (deq.) rao -se 0 se Fig 4. The reltionship of wrist joint nd ring finger joints -24-

7 APPLICATIONS, BASIS & COMMUNICATIONS 237 ITTLE relresslo" ngle -se e se wrist ngle (deg.) lee Be 6 4e 2 e -se se Biomed. Eng. Appl. Bsis Commun : Downloded from 12J.IttLE- regression. ngle 1 Be 6 4 2e 5e e -50 -s so -50 5e regression ngle -s se NAt wrist ngle (deg.) 12^',ITTLT- re^ressionrng ^e lee s S s FA1 Fig 5. The reltionship of wrist joint nd little finger joints -25-

8 23 Vol. 13 No. 5 October 2001 sttistics nd regression nlysis. 4. The prototypes of splints hve been designed completely. 5. Motion nlysis system is good choice to mesure the motion of hnd. REFERENCES Biomed. Eng. Appl. Bsis Commun : Downloded from Fig.6 Four-br linkge mechnism Fig.7 Six-br linkge mechnism: Fig. Eight-br linkge mechnism: 1. Bunnell S: Surgery of the hnd. Phildephi. J.B. Lippincott, 1994; Mson ML nd Allen HS: The rte of heiling of tendons-sexperimentl study of tensile strength. Ann Surg, 1941; Young RES nd Hrmon JM: Repir of tendon injuries of the hnd. Ann Surg, 1960; Gelbermn RH, Woo SLY, et l.: Effects of erly intermittent pssive mobiliztion on heling cnine flexor tendons. J. Hnd Surgery 192;7: Hitchcock TF, Light TR, Bunch WH, et l.: the effect of immedite controlled obiliztion on the strength of flexor tendon repir. Trns Orthopedic Reserch Society 196;11: Kleinert HE, Kutz JE, Cohen MJ: Prim repir of zone II flexor tendon lcertion In AAOS Symposium on tendon Surgery in the Hnd. St.louis, C.V. Mosby, 1975;97: Lister GD, Klieinert HE, Kutz JE nd Atsoy E: Primry flexor repir by immedite controlled mobiliztion. J. Hnd Surg 1977;2:441.. Chow JA, Thoms LJ, Provost JM, et l.: A commbined regimen of controlled motion following flexor tendon repirof hnd. Plst Reconstr Surg 197;79: cooney WP, Lin GT nd An KN: Improved tendon excursion following flexor tendon repit. J. Hnd Therpy 199;2: Peter OTR, Mildenberger A, Amdic C nd An KN: Dynmic Splinting : A systemtic pproch to the selection of elstic trction. Arch Phys Med Rehbil 19;67: Linden PWV, Crlson SJ nd Hubbrd RL: Reproducibility nd ccurncy of ngle mesurements obtined under sttic conditions with the motion nlysis video system. Physicl Therpy 1992;72: Philips F: Hnd Splinting principles nd methods. St. Louis, the C.V. Mosby Co An KN, Cho EYS, Cooney WP III nd Linscheid RL: Biomechnics of the hnd. world Scientific Publishing Co. PO Box 123, Frrer Rod, Singpore 912, Buchhlz B nd Armstrong JT: A kinemtic model of the humn hnd to evlute it prehnsile cpbilities. J. Biomechnics 1992;25:

9 APPLICATIONS, BASIS & COMMUNICATIONS 239 Tble 1. The mximl nd minimus ngle rnge of motion of, nd joints by utonomic coordintion movement., Distl interphlngel;, Proximl interphlngel;, Metcrpl phlngel. (degree) Biomed. Eng. Appl. Bsis Commun : Downloded from Mx Min Rnge WRIST 57.2(6.7) (10.24) (7.54) 11.27(10.6) index 99.47(6.33) 16.97(12.12) (.26) 23.10(.47) (11.07) 12.51(30.5) Mle middle 110.(11.17) 22.76(10.26) (7.73) 26.49(11.21) (4.9) 11.12(19.01) 39.6 ring (11.79) 20.47(12,57) (10.67) 21.65(10.00) (6.60) 14.99(1.3) little (12.51) 21.50(9.4) (.44) 20.19(14.0) WRIST 61.40(6.50) (13.39) (4.21) 9.26(21.1) index 9.97(6.90) 20.54(9.2) (9.59) 21.54(.05) (10.90) 10.36(17.10) middle (9.79) 19.31(17.55) 3.19 femle 74.46(10.43) 22.53(14.27) (7.24) 11.1(15.30) ring 114.0(10.39) 23.6(7.62) (.95) 19.63(9.56) (.95) 11.79(23.44) little (12.4) 24.95(15.2) (9.41) 14.7(13.91) Tble 2. The mximl nd minimus ngle rnge of motion of, nd joints by wrist control movement, Distl interphlngel ;, Proximl interphlngel;, Metcrpl phlngel. (degree) Mx Min Rnge WRIST 55.0(7.15) (10.52) (.6) 12.00(13.70) 1.70 index 70.4(6.72) 1.5(10.70) (7.24) 26.61(10.21) (20.3) 13.3(12.07) middle 90.44(11.42) 20.32(11.79) mle 66.70(10.16) 2.36(14.66) (7.7) 14.15(13.62) 1.11 ring 93.07(11.06) 2.79(15.2)

10 240 Vol. 13 No. 5 October 2001 Biomed. Eng. Appl. Bsis Commun : Downloded from femle little WRIST index middle ring little 65.09(.05) 39.60(.77) 0.37(10.49) 64.21(.97) 62.51(7.10) 34.35(3.77) 0.02(6.26) 57.73(7.44) 34.49(4.04) 4.93(6.06) 65.(12.50) 35.26(9.99) 96.09(2.17) 69.14(12.22) 40.20(29.10) 6.02(10.17) 69.41(10.97) 27.55(15.04) 15.46(13.37) 24.7(13.4) 22.13(15.40) (9.64).47(13.29) 21.07(16.73) 22.14(9.95) 9.0(12.61) 29.40(11.72) 25.46(9.74) 14.0(15.90) 34.17(12.06) 16.37(13.3) 13.14(11.) 27.22(15.99) 21.2(12.7)?4fl Tble 3. The motion reltionship of wrist joint nd index finger joints for regression nlysis b c R2 corr Mle femle Tble 4. The reltionship of wrist joint nd middle finger joints for regression nlysis b c R2 corr Mle femle

11 APPLICATIONS, BASIS & COMMUNICATIONS 241 Tble 5. The reltionship of wrist joint ndringfingerjoints for regression nlysis Mle femle A B C R corr Biomed. Eng. Appl. Bsis Commun : Downloded from Tble 6. The reltionship of wrist joint nd littlefingerjoints for regression nlysis Mle femle A B C R2 corr