`“?’.e,)‘_-.‘__
`ISSN: 0021—9355
`
`JJ
`The Journal of
`Bone and Joint Surgery
`
`The American Orthopaedic Association
`The British Orthopaedic Association
`
`The American Academy of Orthopaedic Surgeons
`The Australian Orthopaedic Association
`The Canadian Orthopaedic Association
`New Zealand Orthopaedic Association
`South African Orthopaedic Association
`Western Orthopedic Association
`
`October 1977
`
`59 -A/7
`
`Page 1 of 13
`
`ZIMMER EXHIBIT 1016
`
`Page 1 of 13
`
`ZIMMER EXHIBIT 1016
`
`

`

`The Journal of Bone and Joint Surgery
`
`PUBLISHED IN TWO VOLUMES
`
`,JM ERICAN VOLUMJ::
`
`BIUTISII VOLUME
`
`Editor and Cltainl/{m Boa rd of Ed iw r:s: T H O RN T ON B ROWN
`
`R. C. F. C,\' l "l'ERi\1. 1., /~'ditor
`
`American Board of As.wt:iate Editors
`
`J oNA'ri-IAN Co l l EN, Defm ty Editor
`R I CH AR D £ . SENC H ,\ S, Book Revit:ws
`J O l iN P. A DA MS , Washingw n , O. C
`Ro oNEY K. BEAtS, Pon land , O rego n
`ANTH O N Y J. BIANCO, J R. , Rod1este r, Minm:sma
`Mu.::H At.:L Bo NFI G LI O, Io wa City, Io wa
`EDWIN G . Bov n .L, San Francisco. C a lifOrnia
`H . R. BnASII t.:AR, J R., C h apel Hill, No rth C aro lina
`·~.·!·l OMAS D_: Bnowt-:R, Le xingLon, Kcmucky
`E. BURKE EvANS, Galves ton, T exas
`F. j AMJ:::s Fu NK, Jn., Atl:tnta, Geo rgia
`joRGE G ALANTE, Chicago, Illinois
`j oH N J. G ARTLAND, Philadelphia, Pe nn sylva nia
`RoBt: RT B. GJU:t:R, III, He rshey . Pennsy lvan ia
`W. R. H ARR I S , Toronto, Canada
`KIN GS BURY G. I-IEII'LE, C le veland , O hio
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`Cr\RL L. NE l-'iON , L iulc Roc k, Ark;msas
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`Tm: j o U RNA L OF Bo N E AND jOINT Su RGt: llY
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`N. J. Bul C KE Y , Glasgo w, St..ot land
`R. G . fi URWt: L L , No ttjn g harn, En gland
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`Conl lnittccs
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`The llriti.~h Cuwr cil of Manageuu:111
`DAVIJ> L. EVA:-JS , Chairuut11
`Ron N t:Y Sw u.:·J ~ A \1 , Serrt•lm)'
`J. CR,\WFI)RD ,\1),\:'\I S
`.
`G. C. LLoYo-RonERTS, Pri•Jidl'nl B.O.tl.
`
`TJr,. !Jriti.l'lr Orthujm n lir !1 1\Ut iatiun
`G. C. I .I .O YD · ROIIEin s, Pri'Jitli'llt
`J. ~ . W I I.~o:-; . Fditm·iul ,)'t•rn·tmy·
`R. Q. C Rt: I.U ;-..". Su r i'lm)'
`Al th e Royal Co lle ge o f Su r geon s, Lin co ln '" In n Fields,
`London. WC2 r\ 3 P N
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`Tltt• C(ll!(ldia11 Orlh uJJ(/t'dir !1.1\1Jtiotio11
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`Published in the United States by
`The Journal of Bone and Joint
`Surgery, Incorporated
`
`Published in the United Kingdom for
`The British Editorial Society of Bone & Joint Surgery by
`E. & S. Livingstone
`23 Ravelston Terrace, Edinburgh EH4 3TL
`
`THE JOURNAL OF BONE AND JOINT SURGERY
`
`Amniwtl Offru·
`IO S hanu ck S1n.:e 1. Boswn, i\b ssac hu scn s 0~ 1
`Mm/(/gi11~ t.'rlitr1r: I I. Ste p he n Tilton
`
`1 5 , U .S. A.
`
`Hriti 1h Of/ir,•
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`;\ 1 the Ro y;tl C ollege..: of' S urgco11 S
`;s:>..:l;\ l .inwln 's 11111 Fidd s. l.111Hio11 W C~ A :\PN . Enf.{l ~tl H I
`J·:rlito ri(/1 M rlllflgi'l': .J ean Bames
`
`Page 2 of 13
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`

`

`The Journal of
`Bone and Joint Surgery
`
`American Volume
`
`TABLE OF CONTENTS
`OCTOBER 1977
`
`Deep Wound Sepsis following Total Hip Art hroplasty.
`Cy Robert fl . Fit;:Me mld. Jr .. M.D .. Dec/an R. Nolan, M.B., B. Ch., Duane M . 1/stmp, M.S .. Rubert'"·· VanScoy, M . D .. John A. Washington, 11.
`M.D .. and Mark IJ . Col't•ntr v. M . D .. Rochcs rcr. Minncsora
`The Penetration C haract eristics of Ccfazolin, Cep halothin, and Cephradine into Bone in Patients undc•·going Total Hip Replacement.
`By Burke t f . C tllllw, M . D .. Hanford . // anT A. Goss /ing , M.D., Farminglon, Herbert S. Pasternak. M.D . . Hanford. Charles H. Nightingale . Ph.D ..
`Buffalo. New York. and Richard Q ui111iliani. M.D .. Hanford, Connee1icu1 .
`Polymeric Dchris in Syno\'ium al'tcr Total Joint Replacement: Histological Identification.
`By A/do C m gnula , Ph . D .. Lowell , A lan Schiller, M.D .. and Eric Radin, M.D .. Boston , Massachusens
`Meta l Sensiti\'ity hefm·e and al'tcr Total Hip Arthroplasty.
`By R . DeWIItan. M . D .. '/ h. .1 . Mulder. M . D .. R . Brian, M.D., and./. P. Nater, M.D ., Groningcn , The Netherlands
`Mcthylmet hacrylate as an Adjunct in Spinal Inst rumentation.
`By Lany D . llerro11, M .D .. and t:'dgar G. Da wson , M.D., Los Ange les, California
`Scintigraphic Find ings in Stress Fractures.
`By J erry L . Pr<llher, M . D .. M arr in L . Nusynowitz. M . D .. Harry A. Snuwdy, M . D .. Alan D. Hughes. M.D .. Williwn H . McCarrner, M . D .. and
`Raymond .1 . /Jagg . M.D .. El Paso. Texas
`Roentgenographic E\'aluation of the Tibiotalar Joint.
`By Th oma.\· G. Cuergcn. M.D . Lat'l'\' A. Danzig. M.D. , Donald Resnick , M . D .. and Ciwr/e.1· A. Owen, M . D .. San Diego. Californ ia
`Blood Alcohol :md Fat Embolism Sy ndrome.
`By Ram Myers, F .R .C.S .E .. and} . ./. F. Taljaard, M.D .. Johannesburg, Soulh Africa
`Allogeneic Segmental Fibular Transplants in Azathioprine-Immunosuppressed Dogs.
`By H . Burclumlt , Ph . D .. F . P . Glo 11·c:ewskie. B .S .. and W. F. Enneking, M . D., Gainesv ille , Florida
`Abductor Digiti Quinti Opponensplasty.
`By 1-1. Andre11· Wiss inger. M . D .. and L'dwin G. Singsen, M.D., Pinsburgh , Pennsylvania
`Kienhiick's Disease: The Role of Silicone Replacement Arthroplasty.
`By Co11unwuln Da• ·id M. Lichtmo11 . Medical Corps, Unired Srares Navy, Lit'lltl'llmtt Commw1der Gregon · R . Mack, Medical Corps. Unir cd S!ales Nava l
`Rese rve, Co pill in Rodnt'\' I. MacDonald, Medi cal Corps, Unilcd S1a1es Navy , Stephen F. Gunther. M.D. , Washingron. D.C .. and James N . Wilson,
`M.D .. San Diego . Ca lifornia . . .
`. . . . . . . . . . . . . . .
`. . . . . .
`.
`.
`. . . . . . . . . . .
`The Usc of Paratenon, Polyethylene Film , or Silastic Sheeting to Prevent Restricting Adhesions to Tendons in the Hand.
`By Herbert /-1 . Swrk, M . D .. .loseplt H . IJoves, M .D .. Los Angeles , Lanny Johnson, M . D .. Easl Lansi ng, Mi chi gan. and Charles R . A.l'hll'orth, M.D ..
`Los Angeles , Ca lifo rnia
`Percutaneous Fixation of Supracond ylar Fntctures of the Humerus in Children.
`By Vicente L. A ritio, M.D., Ph . D .. Eugenio L' . Lluch , M .D ., A lberto M . Ramire z, M .D ., Jose Ferra. M.D .. Luis Rodrigue: . M . D .. and .Fmn cisco
`IJaixau/i. M .D .. Va lencia . Spain
`C ast-Bracing filr Fractures of' the Femur. A Preliminary Report of a Modified Device.
`By Benjamin C. Lesin. 1'vi . D .. Vert Mooney, M . D .. and Milton E. Ashbv. M . D .. Downey , Californ ia
`The Popliteus Muscle.
`By Roger A. M ann, iV/.0 .. and John L . /-logy. O. R.E .. San Francisco, California
`Tibial Rotation-Piasty for Proximal Femoral Focal Deficiency .
`By A/ji'ed '"·· Krilter. M .D .. Waukes ha, Wisconsin
`Fragmentation of the Distal Pole of the P:ttella in Spastic Cerebral Palsy .
`By Rol>ert K . Rosl'lltlllll. M . D .. Boslon, Massachusells, and Da vid B. Levin e, M .D .. New York , N.Y.
`Fractures of the Atlas Associa ted with Fractures of the Odontoid Process and Transverse Ligament Ruptures.
`lly S teph en .1 . Lir>.lmt. M.D .. lloslon . Massachusens
`Fracture of the Odontoid Process in Young C hildren.
`By Leonardi'. S imon, M .Ch .Orth .. F .R .C.S. r:·. Durban. Soulh Afri ca
`Roentgenographic Measurements after Miillcr Total !-lip Rcphtccment. Correlations among Roentgenographic Measurements and Hip Strength and
`Mobility .
`By Donald R . Gore, M.IJ .. M . 1'. Murrm·. Ph.D .. Gena M . Gardner, B .S .. andSusilltiJ . Sepic , B .S .. Milwaukee, Wisco nsin
`.
`f he Co mpressive lleha\'ior of' Hone as a Two-Phase l'orous Structure.
`lly D ennis R . Carta, Ph .D .. Scank. Was hingron, and Wilson C. Haye.l', Ph .D., Philadelphia, Penn sy lvania
`A \'Uision Fracture of the Coracoid Epiphysis with Acromioclavicular Separation. Report of Two C ases in Adolescents and Review of the Literature.
`BySter>h l'll 1'. M rmtgomnr. M . D .. and R. Daniel Loyd, M . D ., Dallas, Texas
`Peronea l- Ner ve Palsy Complicating Ankle Sprain. Report of Two Cases and Review of the Literature.
`By Rov A. Meal.\'. M.D .. Balli more. Maryland
`
`PA(jE
`
`847
`
`856
`
`860
`
`862
`
`866
`
`869
`
`874
`
`878
`
`88 1
`
`895
`
`899
`
`908
`
`9 14
`
`917
`
`924
`
`927
`
`934
`
`940
`
`94J
`
`<)48
`
`954
`
`963
`
`966
`
`I ht' loun.~tl !if /Ju,!c ' 11111/ Jou!t.;\'tlr~o" (1\ n.H:rit·om Vohu~H: ) ! ~ issued e ight tim es 11 yea r -
`i~1 Jan uary , March. April. Jun e. Jul y . Scp~c.:mhcr . O ctobe r , <and Dt·t·~.:mbcr. The 11J7H !<>Uhsn iption prilc, payabk in adv;tnlr:. i ~
`'S 20. 00. Smg k cupzc:-. 'S5.0: l. I"~" .lou mal ~~1 llo11c ' ami lomt .~ u rgt'l)' , sccontl -d;lss poswgc pa1d at Bosto n, Mass . . am.! at addi tion;ll mailing o lli l·cs. lilitorial <trx.l bus iness ofli n:~. t 0 Shauud S trCl'l. B11Ston. Ma ss. 0 2 11 ) .
`Copyright 1977 hy The• Jmmwl of Bm11' and J oim Stl r~ay, / m ·ortWrtlfc•d
`
`(Comin11ed on page J)
`
`Page 3 of 13
`
`

`

`T ABLE OF CO NT ENTS
`(Cominued fro m page I )
`
`Postradiation Osteosarcoma of the Cervical Spine in Childhood. A Case Report.
`By John A . Do 11:dle. J r .. M .D .. Roberr B. Wimer, M. D ., and Louis P. Delmer. M .D ., Minn eapolis, Minnesota
`Immobilization Hypercalcemia. Report of Two Cases Treat ed with Calcitonin.
`By Cym s Pe:e.l'hki. M .D .. and Andre\\' F . Brooker. Jr .. M .D .. Balti more. Ma ryland
`Hydatid Disease of the Femur. Report of a Case.
`· B y Jonmhan Hooper. F. R .C .S .. F.R .C.S .E. , F.R .A.C.S. , and lain McLean. M .B ., B .S., Melbourne, Australia
`Pseudart hr·osis of the Radius Associated with Neurofibroma tosis. A Case Report.
`By Masilnt:- l.aman . M .B .. B .S .. F .R .C.S.E .. Newcastle-upon-Tyne, England
`Pent:rzocinc Injections as a Causati ve Factor in Dislocation of th e Shoulder. A C:1sc Report .
`By Le\llis N . Co;:en . M .D .. Los Angeles , Cali forni a
`Compression of the Ulnar Ne r ve in the Hand by a Ganglion. Report of a Case.
`By Charles L. McDo\\le/1 . M .D .. and William D . Henceroth. M .D .. Richmond , Vi rginia
`Follow-up Notes on Articles Previously Published in The Journal.
`Lymphocyte and Serum-Mediated Immunity in Murine Osteosarcoma.
`By C . W. Miller. M .D ., and S. J . Fisher. M .S .. Charl o!tesville, Virginia
`Brief Notes.
`Apparatus to Position Knees for Varus-Valgus Stress Roentgenograms.
`By Tillman M. Moore . M .D .. and Marvin H . Myers. M.D .. Los Angele , Cali forn ia
`Ne ws Notes
`Book Reviews
`Books Received
`List of Ad vertisers
`
`I' AGE
`
`969
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`97 1
`
`974
`
`977
`
`979
`
`980
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`981
`
`984
`985
`988
`990
`. Adv. 129
`
`1978 Subscription Rates
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`C hecks should be made payable to Th e J oum a / of Bone and Join! Surgery. Inc.
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`Ann Arb01·, Michigan .
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`Page 4 of 13
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`

`

`The Compressive Behavior of Bone
`as a Two-Phase Porous S tructure*t
`BY DEN NI S R. CA RT E R, PH.D.:i:, SE ATTL E, WASHINGTON AND WIL SO N C. HAYES, PH.D. S, PHI LA D ELPH IA, PENNSYLVANIA
`
`From the Departm ent of Orthopaedics. Uni vers ity of Washin gton. Seaule, and
`th e Deparrment of Orthopa edic Surgery, University of Penm y vlania , Philadelphia
`
`A BSTRACT: Compression tests of human and bovine
`trabecular bone specimens with and without marrow in
`situ were conducted at strain rates of from 0.001 to
`I 0.0 per second. A porous platen above the specimens
`allowed the escape of marrow during testing. The pres(cid:173)
`ence of marrow increased the strength, modulus, and
`energy absorption of specimens only at the highest
`strain rate of 10.0 per second. This enhancement of
`material properties at the highest strain rate was due
`primarily to the restricted viscous flow of marrow
`through the platen rather than the flow through the
`pores of the trabecular bone. In specimens without
`marrow, the strength was proportional to the square of
`the apparent density and the modulus was proportional
`to the cube of the apparent density.
`Both strength and modulus were approximately
`proportional to the strain rate raised to the 0.06 power.
`These power relationships, which were shown to hold
`for all bone in the skeleton, allow meaningful predic(cid:173)
`tions of bone tissue strength and stiffness based on in
`vivo density measurements.
`
`Whole bones of the skeleto n are composed of bone
`tissue ex hibitin g two form s of structural organization.
`Com pac t bone ti ssue form s the structural she ll of most
`bone s and nearly all of the diaphyses of long bones .
`Trabec ular bone is continuous with the inner surface of the
`cortica l shell and ex ists as a three-dimensional lattice
`composed of plates and columns of bone. Th e trabec ulae
`di vid e th e interi or volume o f bone into inte rcommunicat(cid:173)
`in g po res or diffe rent dimensions , produc in g a structure of
`20
`va ria b le poros it y and apparent de ns ity 10
`. Th e
`'
`c lass ifi ca ti o n o r bone ti ss ue as compac t o r trabec ular is
`based on bo ne porosity, which is the proportion of the vol(cid:173)
`ume occu pied by no n-mine rali zed ti ss ue . Compact bone
`to 30 pe r ce nt;
`ha s a po ros it y of approx imate ly 5
`trabec ular-bone porosity may range from approximately
`30 to mo re than 90 per cent. Howeve r, the di stinction be(cid:173)
`tw ee n ve ry po rou s compact bone and very dense trabecu lar
`bone is somewhat arbitrary 2 1 . The porosity of normal
`bone ti ss ue shows a n approximately linea r re lation ship to
`
`~ Thi s res~a rc h was s upported by NIH Grant A M 18376- 01.
`. T Reau 1n part at the A nnua l Meeting o f the Orthopaedi c Resea rc h
`.
`Soc 1ety~ New O rleans. Lou isia na. Jan uary 28. 1976.
`T Schoo l o f Medicine. U ni vers it y o f Was hingto n . Seattle, Washing(cid:173)
`ton 9X 195.
`
`* Sc hoo l of Medi c ine. U ni ve rs ity o f Penn sy lvan ia . Philade lphia,
`
`Pc nn s ylva ni" 191 74 .
`
`954
`
`the apparent den s ity (mineralized ti ssue mass pe r to ta l ti s (cid:173)
`sue vo lume) and ash de nsi ty (ash we ig ht pe r to ta l ti ss ue
`volume) zo.n. Therefore porosity, as h den s it y, a nd app a r (cid:173)
`e nt de ns ity are al l reaso nabl e meas ures o r the a m o unt of
`mine ra li zed tiss ue.
`Weaver and C ha lme rs :H in ves ti gated the influe nce of
`ash dens ity and age on the ultim ate compress ive st re ng th of
`trabecular bone specime ns fro m ve rtebral bodies. They
`found
`that co mpress iv e stre ng th s
`ran ged from 3.81
`meganewtons per sq uare me te r in an e ig hty-one-year-o ld
`man to 8.25 meganewton s per sq uare meter in a thirty(cid:173)
`yea r- o ld woman, an d de ri ved posit i ve corre la tion
`coe ffi c ie nts re lating stren gth to as h den s ity. S imi lar res ults
`were obtained by Bartley and assoc iates 1
`. Bell and co(cid:173)
`workers 2 tested intact hum an ve rtebrae in compress ion a nd
`noted ultim ate co mpress ive stre ng th s o f from 1. 37 to 13 .7
`megane wtons per square me te r. Vertebra l ash de ns ity was
`show n to dec line with age and appeared to be non- linearl y
`related to the vertebral compress ive streng th.
`Ga lante and co-workers 10 examined the influe nce of
`apparent den sity and trabecul a r orie ntatio n on the compres(cid:173)
`s ive strength of vertebral bo ne spec ime ns . They and othe r
`workers Hi.l !J fo und a pos iti ve corre latio n between apparent
`de ns ity and compress ive streng th. Spec im ens loaded in th e
`supe rio r- inferior direction were mo re than twice as strong as
`those loaded in the late ral -medi al direction . In addition,
`spec imen s loaded at a rate of 0. I centimeter per minute
`were approximately 30 per ce nt stronge r than those tested at
`0.01 centimeter per minute.
`1 observed pos itive corre(cid:173)
`McElh aney and assoc iates 1
`!
`lati o ns between the a pparen t de ns ity o f vertebral bone
`spec ime ns and compress ive stre ng th and modulu s of e las (cid:173)
`tic it y. U s in g a porous block model for bone.
`they
`hypothes ized that the co mpressive modulus was propor (cid:173)
`tiona l to the c ube of the apparent den s ity and that the com(cid:173)
`press ive strength was propo rtional to the fourth power of th e
`apparent de nsity nl .zo
`
`Bon e as o Two -Phose Porous Murerial
`
`The compos ition s and tru e ti ss ue de nsiti es (mass o f
`mine ra lized ti ssue per vo lume of mine rali zed ti ss ue) o f
`normal trabec ular and co mpact bone ti ssue 10 ' 1 ~ are s imilar.
`In addition , rece nt work has suggested that the microscopi c
`mate rial properties o r trabecular bone are simil ar to those of
`compact bone 20 · 2 J. ZUK.:l~. These observations suggest that
`who le bo nes can be mode led as com pos ite structures con(cid:173)
`s istin g o r both a so lid and a tluid pha se . The solid phase is
`the minerali zed bone ti ssue. and th e lhtid phase is composed
`
`THE JO URNAL O F !lON E AN IJ JOINT SURGERY
`
`Page 5 of 13
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`

`CO MPRESS IVE BEH AV IO R OF BONE
`
`95 5
`
`of blood vessels, b lood. red and ye llow marrow, ne rve tis(cid:173)
`sue , mi sce ll aneou s ce lls, and inte rst iti a l tluid l !l. 20 The di s(cid:173)
`tribution o r pores throughout the who le bo ne co ntribute s to
`the apparent de nsit y d istri b utio ns w hi c h are observed roent (cid:173)
`genographica ll y. T he pore geomet ry and orie ntation con(cid:173)
`tribute to th e stru ctura l ani sotropy. w hi ch is ev ide nt in both
`trabecul ar and compact bone.
`T he struc ture o f trabecular bone is similar to th at of
`open-ce ll ed r ig id p last ic foa ms and aerated (porou s) co n(cid:173)
`crete . In such materi a ls the apparent densit y is gene ra ll y the
`mo st impo rtant factor affec tin g the mate ri a l pro pe rties 2
`" .
`Empiri ca ll y de ri ved express ion s for re latin g the e lastic co n(cid:173)
`stants or strength o f these po rou s material s to the ir apparent
`de nsiti es arc powe r re lati o ns o f the fo rm 20 · 2·;
`
`y= /\pi\
`
`(I)
`
`where y = mate ri a l prope rt y Uo r e xamp le, stre ngth, mod(cid:173)
`ulu s), p = app are nt dens it y (mass/ bulk vo lume), and A a nd
`B = expe rime nt a ll y der ived constant s . This equati o n co uld
`also be w ritte n as
`
`log y =
`
`log A + B log p
`
`The rel at io ns hip betwee n y and p is thu s li nea r o n log -log
`plots . The reg ress io n s lo pe o f data pre sented in thi s manne r
`is the va lue o f B and the inte rce pt is log A.
`Addition a l fa cto rs a ffe ctin g the mate ria l prope rties in(cid:173)
`c lude structural ani sot ropy (direc tion o f so -c a lled foa m rise
`or trabecula r o rie ntation in the case of bone), the material
`pro pe rti es o r the so li d p hase, and the s ize o r the test spec i(cid:173)
`men s .
`Th e objec tives of th is in ves ti gatio n we re to exp lo re
`further th e mode l of bone as a two- phase compos ite mate(cid:173)
`rial. Compress io n tes ts o f human and bo vine trabec u lar
`bone w hi c h spanned a w ide ra nge o f appare nt densiti es we re
`conducted ove r a w ide ran ge o f strain rates . By analy z ing
`these data w it h rcl'c rcnce to the va lues for th e mechanical
`behav io r o f compact bone re pon ed in the li te rature, we
`hoped to obta in e mpirica l re lat io nships betwee n the appar(cid:173)
`ent de nsit y and the compress ive strength, modulus . and
`strain rate or bo ne .
`
`Materials and Methods
`
`One hun dred cy lin dri ca l spec ime ns of human trabecu(cid:173)
`lar bon e and twent y- four spec imen s o r bov ine trabecular
`bone we re machined under continuo us
`irri gation. The
`spec ime ns, whic h we re approx imate ly fi ve mi llime te rs thic k
`w ith a radiu s o r 10 .3 millime te rs, we re removed from
`human tibial p lateau s and bo vine fe mora l condy les and were
`oriented w ith the ir a xes para lle l to the lo ng ax is oft he bone.
`A fte r th e machining, the s pec im ens we re sto red at - 20 de (cid:173)
`g rees ce nti g rade until testing :w Prio r to testing , they were
`thawed and ke pt full y mo ist.
`Seve ra l additiona l s pec imens prepared in an identica l
`manne r were sectio ned . c mbedoed in acry li c res in , and ex(cid:173)
`amined in a rc fkcted li g ht mi croscope for ev ide nce o f dam(cid:173)
`age durin g pre parat io n. Frac ture and te aring o f trabec ulae
`we re occas iona ll y observed o n the ex posed surfaces . How-
`
`VOL. 59-A, NO.7. OCT OBER 1 ~ 77
`
`ever, the spec imens appeared to be undamaged througho ut
`most of their volume .
`
`TAB L E I
`
`EX PER IMENTAL D ES IGN
`
`Speci men Type
`
`-
`H uman with marrow in s;w
`Human w ithout marrow
`Bovine w ithout marrow
`
`0.00 1
`- - --
`10
`10
`
`~-a in Rate pe r Second*
`0.0 1
`0. 1
`1.0
`
`10
`10
`12
`
`10
`10
`12
`
`10
`10
`
`10.0
`
`10
`10
`
`)j: Number of spec imens at ~ a c h strain rate.
`
`A rando m all ocation scheme was used to divide the
`specim ens into twe lve test groups (Table 1) . Groups of
`twenty human bone specim ens were tes ted at constant strain
`rat esofO .OOI ,O.Ol ,O . I , I .O,and IO.Oper second . Ha lf o f
`th e human spec imens were tested w ith marrow in situ , and
`half were tested aft er the marrow bad bee n removed w ith an
`air jet and running water. The bovi ne specim ens were tested
`primari ly to stud y bone w ith greate r appare nt de ns ities than
`th ose nonn all y found in human tibial metaph ysea l bone. A ll
`of the bov ine spec im ens were tes ted w ithout mm-row in situ.
`Twe lve bov ine spec ime ns were com pressed at a strain rate
`of 0. 0 I per second , and twe lve were compressed at a rate of
`0. I per second.
`T es tin g was done in uniax ial stra in by con fin ing the
`spec im ens in a ri gid stainle ss-steel annu lus a nd compress in g
`them by more than 50 per cent of the or ig in al spec im en
`thi ckness in an e lectrohyd rau li c materials testing mach me
`( MTS System s). A porou s compress io n plate n above the
`spec imen al lowed the escape of marrow fro m the specimens
`during testing . A lo ad-deformation curve for eac h specime n
`was recorded on a storage osc illo scope and photographed
`fo r later data analys is . Load was measured by the ca librated
`load ce ll o f the test system. and deform ation was measured
`by the bu ilt -in line ar va ri ab le differenti al tran sforme r of the
`loadi ng p iston . The stiffness of the test system was a lso re(cid:173)
`corded durin g the appli cation o f direct platen-to-platen load(cid:173)
`ing . Thi s mach ine stiffness was late r used to adjust the
`load-de formation data for each spec imen based o n a correc(cid:173)
`tio n fo r the loadin g sys te m compliance 21
`;.
`Aft er testin g , the marrow was rem oved from those
`spec im ens tested w ith th e marrow in situ by an air jet and
`running wate r. A ll spec imens were degreased w ith ethano l.
`A ti er innners io n in di still ed water and vac uum degass ing,
`the spec imens were we ighed suspe nded fro m an analytical
`balance to determine sulm!e1-ged \\'eig ht . They were the n
`centrifuged at 8,000g on blo tting paper for fift een minutes
`to remove res idual water from th e pores and weig hed in air
`to obta in hrdulled tissue ll'cight. T he vo lume o f bone ti ssue
`in c ubi c centimeters (excludin g pores) was ca lcul ated as the
`difte re nce between the hydrated ti ssue we ig ht and sub(cid:173)
`merged weight expressed in grams 10
`. Tissu e dcnsit\' o f the
`spec im en was found by di v iding hydrated ti ssue we ight by
`bone tiss ue vo lume. Apparmt demitr o f the spec imen was
`calc ul ated by divid in g hydrated tissue weight by bu lk vol-
`
`/ -
`
`Page 6 of 13
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`

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`

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`

`960
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`D . R . CA RTE R A N D W . C . H AYES
`
`a much more important factor than strain rate.
`
`Th e Influence of Strain Rate on
`Specimens with Marrow in S itu
`T he loadin g config uratio n in this study imposed uni (cid:173)
`axial compress ive strains on the test specimens, allowin g
`restricted fl ow of marrow out through the porous platen .
`Since the charac te ristic dimensions of the platen po res
`we re much smaller than those o f trabecul ar bone, the
`influence of marrow on the recorded mechanica l properties
`is due to marrow flow out through the pl aten rather than
`through the pores o f the trabecul ar bone spec imens . In
`spite of these restri cti ve boundary conditions durin g test(cid:173)
`in g, the spec imens tested at stra in rates between 0 .001 and
`I .0 pe r second showed no enhance ment of strength , stiff(cid:173)
`ness, or ene rgy absorption . Spec imens tested at a stra in
`rate of I 0.0 per second , however, demo nstrated a marked
`increase in stren gth , stiffness, and energy absorptio n.
`T hese results are co nsistent with the findin g of Swan(cid:173)
`son and Freeman :ll th at trabecul ar bone is not hydrauli (cid:173)
`call y strengthened by the presence of marro w under mod(cid:173)
`erate, phys io logical loading conditions such as norm al
`walking. The findings in thi s stud y are also consistent with
`th ose of Pugh and co-worke rs 27 , who found that the pres(cid:173)
`ence o f marrow in unconfined spec imens did not influence
`the viscoe lastic behavior o f trabecul ar bo ne . The results
`from spec imens te sted at a strain rate o f I 0. 0 per seco nd ,
`howeve r, suggest that the presence of marrow during se(cid:173)
`vere, traum atic , co mpressive loading in vivo may serve to
`absorb considerable energy.
`
`N- 5000 A
`E
`' z
`::;:
`w 2000
`(f)
`:::)
`_J
`:::) 1000
`0
`0
`::;:
`w 500
`~
`(f)
`(f)
`w
`0::
`u. 200
`::;:
`0
`u
`
`0
`
`8
`
`0
`
`o &o
`
`O&
`{}
`0
`
`0
`0
`
`a#
`
`0
`
`0
`
`€ =.0 1 SEC 1
`
`0
`
`€=0 .1 SEC 1
`
`00
`I
`
`2
`
`)
`
`1.0
`.5
`.3
`.2
`1.0
`.5
`.3
`APPARENT DEN SITY p(gm /c m3
`F IG. 6
`Com pressive modulus ve rsus appa re nt de nsity of bov ine tra be c ula r
`bo ne tested a t strain rates of 0 .0 1 a nd 0. I pe r seco nd .
`
`It is imp ortant to recogni ze that the observed en(cid:173)
`hancement of the properties of trabec ular bone by the pres (cid:173)
`ence of marrow is de pendent primarily o n the flow o f mar(cid:173)
`row throug h restri ct ive boundari es rather than through the
`trabecul ar pores th emse lves . Trabecul ar bone in the skele(cid:173)
`to n (for exampl e, in th e vertebral bodies or in the end s of
`lo ng bones) is norm all y surrounded by a shell of comp act
`bone. When traumatic co mpress ion fractures of trabec ul ar
`
`bo ne occur, th e surrounding compac t bone itself pre se nts
`very restricti ve bound ari es li mitin g the o utfl ow of m a rrow .
`T he boundar y conditio ns used in the tests in thi s stud y im (cid:173)
`posed si milar restri cti ons on the outfl ow of marrow. A
`more rigorous anal ytical or experime nta l stud y w hic h at(cid:173)
`tempts to simulate in vivo who le-bone geome try is needed
`to quanti fy th e pract ical significance o f marrow fl ow in
`high- strain-rate compress ion fractures.
`
`Th e Influence of Apparent Density
`on Strength and Modulus
`
`Be ll and assoc iates 2 fo und th at the total ash de ns ity
`(and the refore the apparent bo ne de ns ity) of hum an verte(cid:173)
`brae decreased with age . Compress io n tests of w ho le ver(cid:173)
`tebrae resulted in a pos iti ve . non-linea r corre la ti o n be(cid:173)
`twee n total ash density and co mpress ive strength , w hich
`ranged from 1. 37 to 13.7 meg anew to ns per squ are me ter.
`A s implifi ed mathe matica l ana lys is based on E ul e r buck(cid:173)
`lin g of trabecul ae suggested that the compress ive strength
`o f the vertebrae was approx im ate ly propo rtio na l to th e
`squ are o f the as h co ntent. The semi-empirica l mo de l of
`bone as a poro us mate ri al deve loped by McElh a ney and
`assoc iates 2 0 predic ted that the compress ive stre ng th of
`bone ti ss ue was proportio na l to th e fo urth powe r o f the ap(cid:173)
`parent density.
`In the prese nt investi gation the compress ive strength
`of bone was fo und to be appro ximate ly propo rti o nal to th e
`app arent density squ ared (Fig . 4-B). The most striking fea(cid:173)
`ture of thi s findin g is that th e re la tio nship is va li d fo r the
`entire range o f bo ne density in the ske leto n , fro m comp ac t
`bone to the most porous trabec ul ar bo ne. Th e sq uared re(cid:173)
`latio nship be twee n compress ive stre ngt h and apparent
`densit y is consistent with theore tica l and ex pe rime nta l
`work on ri gid ce llular pl asti cs 25
`. Th e bas ic ass ump tio n of
`the theoretica l analys is is that the ce llul ar struts and walls
`(trabecul ae in bone) fail by buck lin g and bendin g . Pre vi (cid:173)
`o us studi es o f the compress ive beha vio r of trabecul a r bo ne
`indicate that bucklin g and bendin g o f trabec ulae are indeed
`2
`32
`major fa ilure mode s 13
`•
`M·
`•
`The compress ive mod ulus o f bone ti ss ue was approx(cid:173)
`imate ly propo rtional to the cube of th e bo ne de nsity (Fig .
`7-B). S igni fica nt scatter o f the data was present , howe ver ,
`suggestin g th at other fac to rs may play an important role in
`establ ishing bone stiffness . S uch fac tors may include th e
`ultrastructure o f bo ne ti ssue and mi