CA1182961A - Prosthetic devices having coatings of selected porous bioengineering thermoplastics - Google Patents

Abstract

PROSTHETIC DEVICES HAVING COATINGS OF SELECTED
POROUS BIOENGINEERING THERMOPLASTICS

ABSTRACT OF THE INVENTION
Prosthetic devices, such as orthopedic, dental and maxillofacial prostheses, are provided which are composed of an inner load bearing, functional component and an outer foamed or sintered porous coating of selected bioengineering thermoplastics. The bioengineering thermoplastic coating is provided in regions where long-term bone fixation is de-sired by tissue ingrowth. The coatings offer substantial biomechanical advantages over any material system previously reported. Also provided, are anatomically shaped devices comprised totally of bioengineering thermoplastics with select porous areas; these devices include bone gap bridges, bone caps, and alveolar ridge augmentation implants.
S P E C I F I C A T I O N

Description

rentlon relat~ ~n general ~o proathe~ic devlc:e~
havlng co~lng6 of ~,ole~ ted poro~ hermopl~tlcs, ~h~ch provide ~n opei~ blomechanicfll cr~v:lrcn~ent for fi~tion of devlce~ by ~ bone in~ro~ch ~ech~nl~m. In one aBpect~ this ~nvention rel~te~ ~o the ~lse of cert~in l~termedlat~ ~odul~ls the~opl~6elc~ ~nd fiber reinf~rced thermopl~tic6 ~
porous co~t~ng~ foa: region~ of pro~thee~ c device~ where los~g-term ~one fixation 16 de~ired by t~ue ingrowth. In a fureher ~pec:t, hi6 invention 1~ directed to ~ proces6 10 for co~ting pro6thetic devices with ~elected pOrou bio~
engine ering the r~nop l ~ 6 ti c ma ~ e rl~ 16 .
~ rior to ~he pre~en~ i nventisn v~rious method~ h~ve b~n di6closed in the liter~turc for the att~chment of pro~hetic devices ts sehe musculo~keletal By~tem, The~e methods can be catcgorized as lnvolvlng: 1) impaction;

2) nails snd 6crews; 3) cemene; ~nd 4j porou~ ~urf~ce ~naterials. The u~e of porous ~urface lmpl~nes for flxatlon has been recognized ~s po~entially providlng 6igrlifican~
advantage~, however; thi~ technlque ha~ no~ been accepted ~0 by ~he ~rgic~l co~uni~cy ~ec~u~e of problems of early f~ation and long l:erm stabill~y ~6socis~ed wlth prior ~rt device~a Prl~r art lnventlons ~nclude lJ. S~ :Patent 2~o~
39986,212 which ~sued October 19, 1976 to B. W, S~uer de~cr~bing '~mpro~ed"compo~lc~ prosthetic devices con~$n-~ng ~ porou6 polymeric coatlng for bone f~xaeion by ~ ue ~ngrowth, The porous polyme-lc maeerl.qls which ~re lndieated to be useful are ~:ho6e having ~ ~peeifie& den6icy and lsleer-connec~ced pore~ o4 ~I Bpel:if:LC sverage pore dl~meeer. Among ehe poly~neric maeerial~ di6closed are hlgh den~ley pcly 30 eEhylene ~nd polypropylene o- ~ix~ure~ ~hereof hav~ng ce2 'C~iD cr:l~ica'l par~eter~ . It 1~ al~o ind~ c~ed t~

1~ ,313 the c~.qting~ c~n be ~ech~nlo~lly ineerlocl~ed or che~n:Lcally }~n~d ~ ~h~ ~c~. .
U. 5~ P~tent 3~571,134 whlch i~suPd July ~7, 1976 eO
J. Cu ESokro~ rel~ee~ to a deneal pro~,the61~ or pe~nene or pro~onged lmpl~rleation lr~ ~ J ~w~)one of a llving body .
Ihe l~plant c~n be co~ted with ~,uch ~Laeesl~l~ lil6 vlnyl poly-~er~ " ~c~l~c poly~ers, polyethylesle ~nd c~rbon fiber fillet3 Teflon.
J. G~l~nte, et ~1, in J. l~one ancl Joine Surgery, 53A, No. 1,101 ~lg71) de~crlbe6 ~intered flber meeal compo6ite6 B5 a ba~i~, f3r ~ttarhr~ nt of impl ar t8 to bone and U, S .
Paeent 39808,6~ whieh i~ued on M~y 7~ 1974 to R~ymond G.
Tronæo de6crlbe~ ~t~inle~s ~teel ~nd cobalt~chror~um-mslybde-nu~ ~lloy pros~che5i6 po~sesslng porou~ ~urface~ or fixstion by ~ ue lngrow~h.
Al~o, o general intere~ are 1~. S. P tent~ 3,992,725 'Implane~ble Material ~nd Applian e~ ~nd Method of Stabillz-~ng Body Implan~s", wh~ch 1~6ued on ~ovember 23, 1976 to C, A. l~omsy~ U. 5, 3,909~852 "ImFlant~ble Sub6til:ute Structure ~0 for ~e IR~S~ Part of ehe Middle Ear Bony Ch~ " which issued October 7, 1975 to C. A. Hom~y, asld UO S~ 3,971,670 "Im-plsn~ble Str~aceure ~n~ MP~hod Bf aSaklng SELme" w~ ch l~ued 3uly 27 9 lg76 ~o C . A. ~om~y.
In addi~ion to p~tent~ 3 v~riou~ artloles h~ve appeared in ~he 3 iterature relatin~ l:o bone ingrowth into porous msterial~, Typlcal ~r~:icle~ ~nclude, ~n~ong oeher~, S. F.
~3u~bert, "Att~chment of Pros~he~e~ ~o ~he 2~usoulo6kele~al Sy~ce~D by T1l56Ue Ingrowth and Mech~nic~l In~erlockirlg"~
J. Biomed. Plate2.~ }~e50 S~lpo6i~, 4, 1 (1973~ p~ctor, 30 et ~1, "BQne Gro~th ln~o ~orou~ High-~n6ity Polyethylenel', 30 Blomed~ M6ter. Re~. Sympo~i~, 7, 595 ~1976); C~ omsy l-L,313 ~ t~ ~ ~

"1mplant Stabilization - Chemical and Biochernical Considera-tions", Orthopedic Clinics of North Americ~, 4, No. 2,295 (1973) and J. ~. ICent, e-t al, "Proplast in Dental Facial Reconstruction", ()ral Surgery, Oral ~edicine~ Oral Pa~hology, 39, No. 3, 347 (1975).
However, the porous materials disclosed ln t~e 1itera-ture as being useful for prosthetic clevices provide inappro-priate biomechanical environments leading to elther of two wndesirable situations. Yirst, low modu]us-high creep porous coatings such as porous *Teflon/graphite composites, exhibit metastable fibrous -tissues in the pores after extended periods.
This tissue is not suited -to support load bearing joint pros-theses. The fibrous tissue is a metastable precursor to bone and under normal physiological conditions (including physio-logical loading conditions) would remodel to bone. The high loads transmitted through low modulus materials and the excess creep result in fibrous tissue which fail to remodel to bone.
Other low modulus-high creep ma-terials employed for prosthetic devices include polyethylenes and polypropylene.
Secondly, high modulus materials such as ceramics (16 x 106 psi) and metals like titanium (17 x 106 psl) and cobalt-chromium~molybdenum alloy ~34 x 106psi), do not spread suffi-cient load to the ingrown or surrounding bone to prevent resorption. In porous metal and ceramic coated femoral and humeral stems, load is concentrated at the apex of these prosthetic components causing stress concentrations in the surrounding bone and subse~uent resorption. In addition, the bone spicules in the pores of these porous ceramic and metallic implants do not experience loads, thereby resorbing.

*Trademark ~ li,3l3 The loss o~: borle ~ro[n the pores in areas of por()us imylantc;
which experience no load has been demonstrated histologicall.y.
This type of bone loss leads to a decrease in composlte strength (e.g. interfacial shear strength~ and a subsequent decrease in "in ~Ise'' performance in these high modul~s porous materials.
The above-cited patents and literature describe t'he use of porous coatings on pros-theses and describe acceptab'Le pore size range requi.rements. However, it has been found that metals, ceramics and polymers sllch as the vinyl polymers, polyethylene, polypropylene, carbon filled *Teflon and others disclosed as being useful. for coating prosthe-tic devices do not establish the proper biomechanical. enviromnent to achi.eve appropriate early fixation, long-term sta'billty and strength at the bone-prosthes:is interface. Previ.ously described poly-meric materials can also lack the toughness, creep resistance tensile and impact strength and steam sterilizability -to be acceptable as the polymer of choice for coating prosthetic devices. Even select high density polyethylene and polypro-pylene porous compositions~ sta-ted to possess the right amount of flexibility and strength i.n ~. S~ Patent 3,986,212 are deficient as will be.discussed be]ow.
The bone ingrowth in porous orthopedic implants can be considered as a two stage phenomenon. Each s-tage is i.nfluenced by the pore characteristics and biomechanical characteristics of the implant. In the first stage and immediately after implan-ta-tion the porous component fills with a blood clot which subsequently becomes ~'organized".
Fibroblasts appear in the clot region and fibrogenesis occurs. The clot is replaced by loose connec-tive tissue ~Trademark ~ a 11,31~

ancl capillaries. At this point preosteob:lasts begin to appear in the peripheral pores of implant. These cells can become osteoblasts or chondroblasts depending upon the environment. If the original pore size of the implant is too small or if the pore structure 'has been distorted by the initial applied loads as will occur with *Teflon, high density polyet'hylene and polypropylene porous materia'ls, one or rnore of the above sequence of events car- be in-terrupted. For example, it is generally believed that a smaller pore size (~90~) 1eads to the ultimate for~lation of fibrous tissue, not bone, in the implant. If the modulus of the materia'L is too low, micromotion occurs with loading. This would lead to an environment tha-t is conducive to fibrous or cartilage tissue, not bone, formation.
For example, excessive motion can lead -to disruption of vascularity and a decrease in oxygen, a condition which favors cartilage formation.
After bone has filled the pores of the implant, in the second stage it undergoes remodeling which is influenced prim~rily by its biomechanical environment~ Spicules in the implant which experience uniform stress will thicken while those spicules which experience no stress or excessive stress (stress concentration) are resorbed. The modulus of metals and ceramics is so high that the implants do not deform under the applied loads. The bone spicules in these porous im-plants thus do not experience sufficient load to thicken.
Bone trabeculae in these higher modulus porous materials tend to resorb, becoming thinner than the spicules in the porous implants which are the subJect of this invention.
The above discussion indicates that the biomechanical environmen-t established by the implant material and the geometry of the porous substrate have a profound effect on the biological fate of implants. I-t has now been found ~Trademark -5 ~1, 313 ~hae cereain ther~Doplastics, here~ter described AS a class as bioengineering ther~Doplast:Lc~, provide the delicate balance whlch rnu6t be schieved between para.r~eters affec~ing lo~d trans~
miss~on, ~n:Lcro mo~ion, dimention~l ~tability, Bnd ~trengthO
Bioengineer~ng thermoplastics, us~ally prepared by conder)sat:icn poly~slerizations ~ ~lso show low metal contamlnation levels (io e., I,ow tr~nsl~ior- snetal catalysts levels) and exllibit e~cellent ch~r~cterlstics in biotoxlci~y 6tudies ~uch a6 ~he U0 S, Ph~rmacopi~ ClaBS VI St~nd~rd6. ~ey 10 represent an up~i~ ma~eriAl~ c~tegory for or~hopedic, dental and ma~illof~cial ~pplications. The tran~ sion of ~tre~s to b~one in the pore~ of bloengineerin~ thermo-~l~s6~ic~ mimic~ ~he phy~iologic~1 b~omecharlical emriron-men~ ~ evi deneed by ~he replication of th~ norm~ one repair proce~e~. Bone 1~ porous bioengineerlng thermo-pla~tlc ~mplant remL)delled ~fter a cl~nically appropriace per~ od to r2'fl ect the rn~gn1tude ~s~d direction of the pre-~alling ~tres~e~ the ~ tt)mlcal ~l~e. Thi~ occurrence per~it~ ~e lngrown ~one 'co be a ~tructur~lly eficlent 20 ~ember for ghe lo,sd envlronmen~ ts:) whlch a pro~the~
~ub~ ec ~ d, It t~, therefore, an ob,~ec~ of the inventlon to pro-~ide ~fficaciou~ prosthetic device~ cc>mpri3ed of sn inner lo~d bearin~ functlonal componen~ and ~ outer foa~e~ or ~ tPred porou~ co~e~ng over at leA~ 8 p~r~lon ~hereof, of seleel~ed ~ic~engineertng ~hermopla6eic~, ~no~her ob~ ec~
0 f ~rli6 invent~os~ o proYide co~ted pro6~heeic devices which sf~r ~plan~ion achieve & long~term bone fixa~lon by ~nE;ro~th of ~ 9 into and through ~ ~lee~ porous 30 bioen~:LDeer~ng ~her~pl ~tlc coating ~h ~ubsequen~

. 6 7t~ , 313 rams:idell~ng to ~ozle . A further ob~ ec t ~.~ to provide proae}l~tle deY~ce h~ving ~ coating of a apeciied poro~ity ~hich provide~ the opti~ ub~t:raee for ~ Bue ingrow~h, Aslother ob~ec~ o provide pro~the~ic de~rice~ reln ~he c~e~ng ~xhlbie8 ~u~flclene tor ~ile and 1mPACt ~tren~th during ~nd ~~:er bone form~tion to ~ccoc~od~ee ~pplied loeds durlng ln~ertion ~nd ~Isfter ~urgery. ~ f~rther ob~ect i~ to prov.Lde co~ted pro6thetic device~ whlch can und~rgo &tC~2 at~rlliz~tion wlthout a~er~e ~fecta on ~he co~ing. A
' 10 ~111 f u -ther ob.~ect of thl~ lnvent~on 1~ to pro~de An~o~-ically ~haped porou~ ~tructures of select bioenglneering chermopls6l:lcs which are u~eful for reconatruct:ive procedure6.
Asloeher ob~ec~ of 'chl~ invent~on 16 ~:o pravlde porou~ bio-engineerlng thermopla~tic coating~ ~r senlct:ures coneaisling ~d~ es fc~r enhancemen~ of ~chelr biological arld/or mech-~nical propertie~. A fur~her ob~ ec~ of ~:hl6 lnventl~n 16 ~o pro~ide porou~ bioengineering ~her~Dopl~eic coa~lngs or ~tnuc~ures containing ~ddi~ive~ for lncreasing wear and ~bra~ion resistance. ~no~her ob~ect i6 to pro~de one or ~ore proces~es for preparing coated prosthe~lc tevices or ~natom~cally ~haped ~tructures eompo~ed of bioengineerln~
then~opls~tlc6~ The importa~ce of the~e ~nd other ob~ec~
will readily become Qpparent to eho6e &killed ~n ;he art ln ~he ligh~ of ~he ~eachlng~ herein ~e~ fortn.
1~ it~ br~ad ~pece ehe pre~ent in~en~ion is direc~ed to pro~hetic dev~ce6 compri~ed o or coated wieh porous bioengineerlng thermopla~tic materi~ lch en~bles ~uch de~ice~ ~o becom~ firmly ~nd perm2ne~ly ~nehored into ~he mu~culoskel~tal ~y~tem by ti66ue ~ngrcw~h iD~o ~he coaeed ~terl~l.. In one embodiment ehe pro~thetic ~ev~ce~ are c~prl~ed o ~ loat be~rlng funct~on~l com~onent ~nd o~er ~ 7 -ï1,313 ~e l~a~e ~ por~ion eh~reof, ~ porolu~ oo~ting of fro~ about 0,5 i:o ~bout 10 ~llll~eters ln ehicl~ne~ vf a blo~nglneer~
~ng ehermop~ t~Lc ~ter~al whlch i~ comp~tlbl~ h, ~nd conduclve :for, the ~ngrowth of c~nceïlou6 and cortlcsl bone ~picule~, ~he coat~rlg h~ring ~he iFollo~ng propere~e~:
n ~verage pore dl~meter oiE iErom about 90 eo ~bou~ 600 ~icron~;
(b~ pore ln~:erconnection6 hsving average dla~zeer6 of gre~er ~h~n ~boS?t 50 ~aicrons;
~c~ Ea modulus of ela~t~c~ey from sboue 250,000 ~co ~bout 3,000,000 pounds per ~quare lnch for the neat thermoplastic material or ~hf~ ~ein Eorred thermoplastic snaterial;
(d) ~ porosity of Breater than aboue 50 per cent; and9 (c) ~ ~ot~l creep strain ~f less eh2n one percent at constar~t litress of 1, 000 pounds per 6quare inch at ambient temperat~lre ~

~11 of the propereie6 belng ~ufficlent to enable ~tre~ses applied on ~he muscul~kele~al ~yst~ to be tran~ferred to bone ~picule~ wiehln the pore~ and malneain ~ufflcient load as-d pore ~t2bility t~ promote lrreverslble 06~;~ ficatlon~
~/ Hence, it hs~ been ob~erved that he ~n~eerial~ used ,, i~ co~eing ehe load bear~ng ~nct~onal co~ponen~: o pro6ehet-ic de ~ri c e 8 ~u~ t pO 6 6e 815 l~p~C 1 f iC prope r ~i e ~ ~ f long - eerm Ibone fi~aeion ~ ~G be ~chieved. Prosthe~lc devices pre-pared in ~ceordance wi~h the teachi~g o ehi~ ~nvention h~ve been fGuDd ~o prov~de ~he b~omechanic~l envlroF~ent nece~6~ry to u:elifos~ly tg~an~}~lt the proper magnitu~e of applied lo~d~ proE~t~ng the ~esired rem~delllng of bon2 tsabecul~e .

i5 ~1 ,313 ~ p:cev:lou~ly indioated, ~he ~ter:lal3 ~ployed i21 ~he pr~p~rEItion o~ the pro~chetlc de~ce~ o:~ thl~ :Invent~on ~re c1~6~ fled ~ a '9bloen&ineerislg ehermopl~t lc~o One impor~ne feature of these ~naterial~ 1~ thst theis perfor;~ance ean be pred~c~ed ~y the u~e of ~aeeal de~ign englneering equ~tion~
for boeh long and hort-term, mc~e ~ngineering de~ign ~qu~elor~6 only ~pply up eo t~e llnear vi.Dcoel~tic limit of ~he materi~l, Algh desl~ity polyethylerae h~6 ~ llnear ~is-cc)elastie llmit of lc~6 than 0.1 percent ~nd wlth thl~ limit 10 on ~he amo~t of ~er~L n,the ~llowable str~R~ 1B mln:l~l, In con~ra~c, the linear Yi~coela~eic llmi~ o~ ~loengin~er~Tlg therpl~tic~ hin the definition of thi~ dl~clo~ure, i8 Bt le8@,t 1 percen~ ~rair10 For e~ample, one o the preferred englneerirlg ~hermopla~tic maeerl~l~ found to be suieable for the coating~ of thi~ invention i6 a poly~ulfone whlch hs~ a 2 pcrGent atr~lrl limi~. Henoe, the me~al engineerin~ de61~1 eq.lat;ons or both long ~t 6hort ~::erm can apply up ~co ~his li~it O
Th~ unique ch~raeterl~tlo~ of the bioengineer~xlg ther~-pla6tie materi~l~ are s~re cle~rly e~ider~c ~en ~heir per-fonnaalce ~6 compared to polymeric ~teri~l~ prev~ou~ly di6-clo~ed as be~ng u~eful or porous fixation device~ If ~he creep ~dulu6 ~xtensively varies ~ith tlme, e~2fles~ion ~ncrea~es ~rkedly, c~u~lng micro di~lacemerlt of a pros~hesis ~der lo~B snd pore di~tort~o~. Cseep 'ce~ h~ve already beeTl reported ~n ~:he litcral:ure o~ porou~ hl~h den~ y poly-ethylent? and a polytetrafluorbethylene-graphlt2 ~mpo~te, bo~h of ~hich have been lnd~o ted ln the pre~ou~ly ei~ed ~atent~ beerl ~b~erveà th~t d gniflc~nt change~ ln pore structure oceurred upon ccmpress~ve ~resses ~s low as 80 p~i fos the por~w polytetraflllor~e~hylene~graphl~e com-po~ite~ ~d ~t 300 p~l fo~ t~ ~rou~ h den~ poly~
~et~l5Sle, ~p~ 0 fa~lure ~ 1U8 19~re!~g~1!; for ~h~ ~wo _ 9 _ ll 9313 reported high d~n~lty polyethylene ~brlc~t~on~ were u:nder flvc ~ ee~ when ~tre3~ level~ gre~ter than 300 pcl were ~pplied. Ie ~ahould be noeed th~t this repre~er~ta the ~re~
le~els th~t ~ill be experiencPd in ~me orthopedlc ~olr~t ~nd de~.rlce ~ppllcuelo~ ne ~pore~nc e o ~ir~t~inlng pore geometrle~ und~r lo~ding envlroTu;pents W~8 indic~ted e~rLier where it wa~ obse~ed ~h~t fibrou6 t~ s~ue i~ created in ~mall pore~. Thl6 11~ par~lcul~rly cr:L~lcal ln e~rly po~t-operative period~ prior to the ingrowth of bone ~en ~he porou~ poly-lQ ~neric coat~ng on ~oint pros~he~e~ m-uBt h~ve ~ufficient ~tren~ch ~nd rigidity to i2ldependently ~uppor~ ~pplied load wichout ~si6tance from ingrown bon~. ~he ~trength of prior polymeric matcrl~ls con:e~ from the ingro~rn bone. Bioeng~ neer-lng the~opla~tlc porou~ coatlng h~e ~trength llke bone, Xllu~trstive prosthetic dev1ce~ which are wi~hln the ~oope of ~che ~eachlng& o ~i6 ir~ventlon arc readily apparen~
from the followirlg descr~p~c~ on and from the ~coompanying drawings ~?herein:
F~E~,ure 1 1B ~a plan vie~ Gf the ~tem and ball porticn 20 of ~ ~o~al hlp pro~he~i6 havlng a co~cing of 8 porou~ blo-engineerlT~g ~hepla ~tic materia~
F~gure 2 iB a pî~n vlew o an endo6teal blsd~o implas hsving .q co~ing of ~ porou6 bioeng~neering the~oplas~ic m~teri~l on ~he blade portlo~s therecr.
Flgure 3 i~ ide plan view of ~noeher endo~eal plfin~ hsvirl~ the bl~de portion coated ~th ~he porou~ bio engineering, the:rmopl&~tio rn~terialO
Figure 4 i;s a ~ide plan ~ew of a ~elf~broachlng ~nera-~ medullary nail hsving a coatlDg over :1~ en~:ire len~'sh of 30 the porou6 bioengiTleer~slg thermoplastic material.

1,313 ~ igurc 5 ~ ~ p7 an vlew of ~ pro~ the~lc clevlc2 c~mpri~ed ~entlrely of a porotl6 bioengin~er-ing ther~nopl~t~c m~eeri~l.
F~gure 6 la ~ ~raph deplct~ng the rel~tion6h~p of ln~er-faciAl she~s strenB~h VerBu6 i~pl~nt~tion t~e of severAl porous ~ma~erl~

Reerr~ng now to Flgure 1 o the! ~ccomp~nying dr~wing~, the toeal h~ p prosthe~ls 10 1~ c~mprl~ed of b~ll and ~tem ~ber 12 ~nd cup member 14. ~he ~tem portioal of the b~ll ~nd ~S~em ~emb~ r 12 iB soated over ~ entire surface wlth porou~ bioeng~neering the~pla2~tlc co~ting 16 of thi6 lTrv~ntion, ~lehough the ~em por~on 1~ depic ted ~n Figure 1 a~ æ a3olld ~tem ~eh ~ groo~e 18 long Bt lea6~ por~lon of lt~ length, lt can have openlng~, rldge~ or o~her con-flgura~lon~ ~o provide coaeed ~lte~ for tl~ue growth ~o flrrrlly ~nchor ~e ~o ~he ~lceletal ~y~eeDl. Cup ~Lember 14 1 likewi~e ~oated on its exterlor ~urace ~ieh the porous engineering eher~pla~tic 16 . The ~eck 20 9 ball 22 ~nd lnner ~ur~ce of the cup 24 do rlot3 of courj, contais any coaei~g O
F$gurec 2 and 3 o the drawlngs depict c~mmerclally ~vailable implan~ 26 as~d 28 w~ich can be f~bricsted ~n ~ varlety of 20 ~hape~ and ~re de~igned for ~upporelng grc~up6 o ~r~:Lficg~al teeth The6e d~vices are u~ually ~ ri~ed of cob~lt or tltanl~n ~lloys and ase ~Ln6ereed irlto ~loe~ cu~ ~D~O ~he alveolar sidge.
~e pvst~ 30 and 32 proerude ineQ ehe OTal e~ y and are u~ed for anchc)rlng ~he art~flcal teeth. A~ ~ho~ :in ~he drawlng, the ~tem p~or~l ons 34 snd 36 ~n be coaeed wlth the porGus biQengineering eh2~pla~tic maeerial and ps~de for ~one ~ row~h ~ flrmly aff~x the pro~ehesi ln ~he ~l~eolar r~dge O
~n ~tr~dullarg 2~il 38 1~ ~llustr~ted lr. Figure 4 30 ~d h~ ~ coating 40 of ~he pOrOUJ ~ioer~ineering ~her~-11,3'L'' plastic material over its entire length. 'rhese nails areplaced in the medullary canal of long bones, such as femurs, and are usually limited to the ~iddle one-third section o-f such bones. These nails are wed,~ed lengthwise into the medullary canal and press a~ainst the interior of the cortex. Finally, Fi~,ure 5 provides a pl,an view of a porous implant 42 which can be used for alveolar ridge re-construction. Thus, ridge reconstnlctions can be rnade by using a poro~ls or solid interior bioen~ineering therrnoplastic implant~ without a load-bearing functional cornponent, carbed or molded to the desired anatomica'L shape.
Figure 6 is a ~raph depicting the relationship of inter-facial shear stren,~th in pounds per square inch versus time in weeks for trochanteric implanted intramedullary rods of porous polysulfone, porous titanium and porous polyethylene.
The porous polysulfone was prepared in accordance with the teachings of this invention and exhibited the physical charac-teristics previously described for bioen~ineering thermo-plastics. The data for the porous titanlum and polyethylene implants was reported by other investigators. In each case, the rods were implanted in do~s in accordance with accepted surgical techniques.
While each of the tests was performed in a sirnilar Eashion in dogs, there is the possibility that the results could vary somewhat because of differences in implantation and mechanical testing procedures used by the different in-vestigators. However, these variations are not great enou~h to prevent comparison. Of particular interest is the fact that ~he interfacial sheer strength of porous polysulfone is hi~h enou~h after only two weeks (~150 psi) ,12-~ ~ ~7~ 3 11,313 to support the static load and most dynamic loads that might be placed upon a hip prosthesis by a pa~ient immediately after surgery. This type of data thus evidences the possi-bility of eaxly weight-bearing postoperatively for polysul-fone, whereas the porous high density polyethylene exhibits an inter~acial shear strength value only one-third that of polysulfone. Indeed, only after extended implant periods, did the high density polyethylene come up to the two week value ~or polysulfone, and it fell short of the ultimate shear s~renR~h value for polysulfone.
As hereinbefore indicated, the materials which are employed in the present invention are designated as bio-engineering thermoplastics. These materials are unique in that they combine melt processability with structural strength, rigidity, creep resistance, toughness, and steam sterilizibility. In corporation of glass, carbon or organic based fibers into the bioengineering thermoplastics extends the load-bearing and structural characteristics. Bioen-gineering thermoplastics exhibit bulk tensile or flexural modulus values in the range of 250,000-500,000 psi. Fiber relnforced products exhibit modu'lus values up to 3.0 million depending on the fiber type and loading. These values of modulus provide the intermediate range required for initial post-operative support and long-term s~abili~y of implanted prostheses in high load areas anchored by bone ingrowth.

1.1,313 Each of these materials when prepared in accordance with the teachings of this invention provides coatings or free standing articles having the physical properties herein-before enumerated. Illustrative of these materials are the polysulfones, such as, polyphenylsulfone, polyethersulfone, polyarylsulfones, and the like; polyphenylenesulfide, poly-acetal, thermoplastic polyes~ers such as the aromatic poly-esters polycarbonates; aromatic polyamides, aromati.c poly amideimides, thermoplastic polyimides and the polyaryletherke tones, polyarylethernitriles, aromatic polyhydroxyethers, and the like. The most preferred materials for use in the in-vention are the aromatic polysulfones. These polysulfones contain repeatin~ units havin~ the formula:
~Ar-S02]

wherein Ar is a divalent aromatic radical containing at least one unit having the structure:

~-Y-~

> 3 ~h ~`

~ 11,313-C~l in which Y is oxygen, sulrur or the rad;ical residuum of an aromatie diol, such a~ 4,4'-bis(p hydroxyphenyl)-alkane. Particularly preferred polyary:Lene polyether polysulfone thermoplastic resins are those composed of repeating units having the structure shown below:
_ ~_ _~SO~O ~C ._<~0 __ -wherein n equals 10 to about 500. These are commercially available from Union Carbide Corporation as UDEL*
Polysulfones P~1700 and P-3703. These materials differ in that P-3703 has a lower molecular weight. Also useful are Astrel*360 a polysulfone sold by 3M Corporation and Polysulfone 200 P sold by ICI and Radel polyphenyl-sulfone sold by Union Carbide Corporation. Certain crystalline bioengineering thermoplasties like Stilan from Raychem Corporation, Polyarylene and Phenoxy A
from Union Carbid~ Corporation, are also useful.

*Trademarks.

.. ...

11,313 In practice, the prosthetic devices of- ~his invencion having an inner load-bearing functional component or those existing as free standing anatomically shaped devices are conveniently prepared by one or more methods. In one method the coating or article can be formed by a sintering technique whereby particles of the bioengineering thermoplastic material are heated for a period of time ancl at a temperature suffi-cient to cause sintering that is, the particles fuse together at one or more contact points to provide a porous continuous composite material of the bioengineering thermoplastic. In a second method, the coating or article can be formed by a process which involves the formation of a low density foam of the normally solid thermoplastic material. This second method which can be described as the dough foam technique is particularly useful for the preparation of the porous materials. However, its use is limited to the aforementioned polysulfones and phenoxy A aromatic polyhydroxyethers.
Porous bioen~ineering thermoplastic coatinv,s and blocks prepared by these methods exhibit intermediate modulus values, high strength and high creep resistance. They can uniquely be fabricated with high total porosities and pore sizes, while still meeting the strength and biomechanical criteria observed to be necessary for bone repair and prosthesis fixa-tion/stabilization. For example, sintered polysulfone having an average pore size of 200 and a 53 per cent porosity, had a flexual strength of 2000 psi and flexural modulus of 60,000 psi.
Foamed specimens with a 70 percent porosity had a flexural modulus of about 105 psi. This value increased to 8 x 105 psi with the introduction o~ 30 weight percent carbon fibers.

~-16-11, 313 Wieh r~pect ~o the flrst ~ethod, lt h~ ~eerl ob62rved tha~ through eareful contxol of t~nper~ture, tlme and pre~ure, ~11 b~engineerlng thermopl~6tics c~n be ~lntered ~or ~xa~ple, UI~EL~P~1700 poly~ulfor)e can be ~atisf~ctor$1y sineered glt ~ppr~xl~ely 24S~C and R~del poly~ulfone i~
gener~lly ~ln~red ~t approximately 285C. At 8ppropr~ate temperatur~s, t~oes ~nd pre6~ure~ ~clle other thermoplastic m~eri~ls c~n al50 be ~in~ered ~co provide a porous pr~duct ~ultable for the irleended u~e. It has been obsP2ved, however, and particul~rly for u~e in pseparlng the c~atings and ~rticles of Phis islv~ntlon, ~3aat optim~ proper~ies can be obtsined i~ a unique and facile manner by proper choice of both (s)particle sixe ~nt (b) molecular weight distr$but~
~ s indic3ted previously, ~he des~sed propert~es are exh~bi~ed ~y ~he prosthe~ic device when the bi3engineering ~hermoplastic ~a~erial has a porosl.ty of a~u~ 50 per cerlt ~d more preferably frolD about 4Q eo sbout 70 per CeRt. Po20sl~y i~ ~nfluenced by the p~rticle ~ize ~nployed ~ri the ~interlng operationO Particle ~lze ~lso ~nflueslce~ the ~trength of the porous 6irltered maeerials.
Large particles result in large pore 6izes 5 while mall pareicles lmprove ~;erengeh by ~ncreasing ~he fusion area o ~he part$cles.
It has ~een observed th~e the modulus ~f ~ porous materl~1 can be pr~dle~ted l:hrough the ~e~nes equ~tion ~r ~hrough a mod~fied Ralpin-T6si equatlo~ ~e~ce3 ~n order ~o ~chieve ~ aterial ~th a poro~lty, fL~r ~xample, of 55 per cen~, and an elastic ~dulu~ gseaeer ~han 40,000 p~i,the ~30dulus o~ che 11~313 ~eart~8 polymer s~st ~xceed 200,000 p81. Thu~;, ~0. t polyprGpylene, ~nd ~ll high den6~ty polyethylenes are ~nc~pable o be~ng fab2~c~ed in ~ m~eri~l of 55 pe:r cent porosity with ~ IDodul~s of 40,000 psi. I:n ~h~ o~eher hsnd 3~nce the modulus of ~ol~d poly~ulfone exceeds 34~;000 p6i,1~ snat~rial of 55 per c2nt poro~ty who~e ~odulus axt:eeds 70,000 p~i can be cbe~ined .
Even though lt was po~sible to predlct ~he ~nodulus of ~
therrsopl~stle h~ving ~ deslred poro61ty there ~s no ~imple ~nethod available to abrie~e a materiAl ~ppro~hing these predictions which would ~e u eful for the device~ of thls inverl~ion. It was unexpeetedly ~ound, howe~er, thAt the desired degree of poro~icy could ~e obtained wi~hout ~aeri~icing meohanioal proper~cies b; the proper choice of particle ~ize, ~oleeular ~e~gh~c distr~bu~ion nd ~int~ring condit~ons. ~11 thr2e are lnter~related and neccssary to aeh~ eve ~ coating or srtiele haY~ng the neoes~ary oharacter-istic~ . ~or example ~ the ~!;intering time and tempers~ure which resul~cs ln ~ des~sed pore ~ize distri~u~on ~ay ~ot produce the desired modulus o elas~:ieity and/or tensile 6trengthO S~arting partiele ~ize dis~cribu~clon, 6intering, time and temperature muse ~e ~d~u&ted co aehieve the de~ired ~alance of pore ~ize, porosi~y, snd mechanieal properti~s .

With respe~t to p~rtlcle ~ize di~eribueion~ ~ ~lend of ~wo or ~ore differen~ ~izes ~f i:he bi~engineering ~hermo-plastic lDsterisl ~Ira~ found tv pro~ride ~ 6~ntered material ~hich be6t ~ec the poro~ity ~d Dechanical requlr2menes needed for a ~ucces~ful prosthet~c device., l ~

lL,313 In practice, a mixture oE particle sizes wherein the ratio o particle diameters ranges from about 7:1 to about 5:1 has been found to be acceptable. Particle sizes of from abou~ 300 microns to about 50 microns are particularly preferred. For example, a mixture of particles which are retained on a 50 mesh screen (~.S. Standard Sieve) and pass through a 270 mesh screen have provided coatings and articles having the desired porosit:y and biomechanical features. I~ has also been observed that optimun results are achieved when the particle size distribution ranges from abou~ 40 to about 60 weight per cent.
As indicated, the sintering conditions are also im portant to achieve the desired properties. Sintering has been accomplished by charging a metal mold with powder and heating the mold to a prescribed sintering temperature, Ts, greater than the glass transition temperature, Tg, and less than the melting or melt processin~ temperature, Tm, (i.e.
T~ cTS cTm). The sintering temperature is held constant for a given time, t. Essentially, no pressure, other than that induced by differential thermal expansion, is applied.
The application o~ pressure at Ts leads to fluxing of the mat.rial. This indicates that if pressure is applied, lower temperatures and shorter time cycles must be employed to retain porosity in the sintered parts. Experiments were run and set forth in the examples to delineate the effects of the sintering conditions on the pore size, porosity, and tensile properties of the porous sintered plastic for various powder size and molecular weight distributions.

~ 3 11, ~13 Xn ~ 0ec~:l ~Dethod lt h~ been fo~d that ~lnce ~ome ~bioen~lneering thenDopl~tlc~ slre ~oluble in low-boillng organ~c ~olvent3 ~ llolven~ fo~ming t~c~lque ean be utllized ~or ~olding open cell porou~ fo~m co~t~ngs orlto protheses or for the preparation of foa~ed articles. Porous fo~ed coatings ~d ar~lcles o~er advant~ge6 over sintered porous coatings ~nd articles in that higher porosltle~ can be l~chieved at hi&,her ~creng~hs, due eo the thin conti~uous pore walli obe~lned in the ft~ing pr.ocesses. FurthPr, low f~brica~ion eemperaeures are experienced due to the plAsti-c~zing effect~ of the ~olvent on the ~hermvpla~tic. This tecl.nique is not ~men~ble to Teflon, polyethylene or polypropylene being desoribed as preferred materials ~n prior art paten s.
This solvent foaming technlque for fabr~ca~ng low density~ oEmed artisles c~prises the ~eeps o:
(a) ~lend~ng at least ~ne nor~ally ~olid bioe~gineering thenmoplastic with about 25 to about 80 parts, per 100 par~s by weight~ of ~ normally liquid orRanic ~ol~ene having a 601ubili~y parameter~S ~ withln (1.3 calories per co) of that of ~he thermoplastio~ or a ~ixeure of normally liquid ~rga~ic solvents havln~ the ~ame Rolu~ility psrameter;
(b) ~lending the ~ixture obtalned ~n ~tep (a) with at les~t about 1 par~ by weighe 7 per hundred par~s of then~o-plas~ic, of wa~er whereby a non-tacky hydrogel dough is ob~ned;
(c) ~h~p~ng ~he hydrogel do~gh obtained in step ~b);
(d) vsporizing the ~ol~ent and water a~d (e~ ~eco~ering a f~Emed re~n article, It ha~ ~e n foun~ tb~t foam preparet i~ ~his ~anner posseses ~he de~ired degree~ of ~oth poro~i~y ~d b~amechan~oal proper-eie~ .

en observed, however, ~ha~ the ~alues of ~he -20~

11,313 ~olubility p~r~meeer~ of the ~or~lly llquld organlc ~olven~ u~od ~r~ ~alrly cr1~1c~1 ~6 ~ enced by the fact ~hat wieh ~ preerred ther~opl~st~c ~2sin ~uch ~8 the polysulfone depicted ~bove there is a tlstinct diference ~etween struct~rally ~$mil,~r ~o~v~nt isomers.
Thus, ~or ~xample, the ~bove-de~cribe~d polyaulfone, which has ~ solubility parameter calculated to be 10.55, i~ ~olu~le ln 1,1,2-trichloroethane h~ving a solubility parameter of 10.1~ but lnsoluble in l,l,l-trichloroethane ha~ing a solubility p~rameter of B.S7. ~owever, a mix~ure of organic ~olvents which indi~idu~lly i~ unsAti~factory can be used as lo~g as the average solubillty par2meter of the mixtur~ is w~hin ~1.3 calories per cc) / of the re6in being blown.
In addi~icn, i ehe Tg of ~he poly~er ~hat i~ ~o be p~astici~ed is exoeptionally high ~n value, plasticity of the gel can be prolanged during the ~oaming 6tep by fosming ~ ~ixture of ~olven~s, one of wh~ hould h~ve a much higher boiling point value. Thus for example while ~thanolor l,l,l~trichloroethane ca~not ~e used ~ndividually wlth the polysulfone depic~ed ~bove a ~ixture compri~ng equal parts by volume of ethanol ~nd l,l,l-trich~Droethane c~ be u~ed. Other c~mb~n-ations ~h~ch funct:lon a6 organic ~olvents for poly~ulfone are:
95Z chloroform ~nd 5Z water, R5% methylene chloride, cthanol 2~% ~nd w~er 5%, '3S7. tetrahytrofursn ~d wat2r 5~, ~ 5Z ~e~hylene chlor~de, 10% ~oetone, 10% ethanol, An~ 5Z w~ter, ~nd 8QZ cyclohexanone, ~hanol 15~ ~nd ~ter 5~.

11,3~3 The ~mo~t of water ~Ddted ~ mot crlt:Lc~l ~ut gener~lly 8~ lesst 1 p~rt ia r~quired per 100 p~rt6 by weight of resill. There $~ no ~axim~D ~mount becau~e excess lda~r ~ep~rates frc7m ~he dough-llke ~8~ ~S ~1 ~eparaee ph~s2~ ~3ecau~e of ehe ptia'se ~eparat$on, where the ~olvent esnployed ls for the mos~ p~rt not ~iscible wi~h the waePr phase, the exces~ w~ter ~ct~ ~s ~ proteetive ~lanke~ whlch prevents rapld ~olvent 10~i6 rom the pla~
~ized polymer. Thi6 e~ture ~llows the plastir~2ed poly-eric gel to be exposed ~ sn open ve~sel dur$ng handl~g and trans~er wLthout ~ealed eontainment. In this :Eorm the poly~ae~ blend can be easily transfeEred frclm one ve6sel ~r container 1:0 another asld can be ~haped ~nd ~olded or other-~se worked without the necessity ~or using coneamina~lng release agents. Simple mixing equipment known to those ~killed in 'che art ~ ~11 that is required to blend the wa~er ~ c ehe ~nixture of ther;aoplastic res~n a:nd liquid organic 601vesll:. The resultant hydrogels can ~e u~ed immedistely or ~f desired s~Q2ed indefinitely under water End then recoYeret and u~ed without urthe~ tre~tment.
l~e c~rganic solvent orlce ~t diffuses lnto polymer resisl, 6erves two purpo~es, namely, ehe formatio~ of ~ gel retain~g R finite ~olven~ concentration 1~ ~ plasticized fOD and secondly ~he ~ol~ en~ ~erve~ a6 ~ ~lowing or fo~ming agent at ~ much lower eempera~ure ~nd vl~coslty thasl tha~ which would be required ~o foam the orlginal r~on-pl~stlc$2ed polym~r resin ~th 8 convcn~:iono~ ;a51!0U6 type l~lowing or fo~ing ~gent, ~t ~low~g ~emper~ures ~f ~rc~ 165-200C. nece~sary for ~2 ~

,313 polysulfone~, ~nost of the co~nonly u~ed organic ~olverlts difuse out of the polymer blend oo quickly to provide sdequate ~lowing of the resin. Durlrlg the blowlng operatlon the waeer in the Ihydrogel ls also r~ ved wieh ~lle normslly liquid F:~rganic ~ol~nt, ~hus ~h~le the ~econt order er~n~it~or~ t~perature (Tg) o ~he polymer ~esin ~eing ~reated in this ~anner i~ 10WeÆeà~
enh~ncing the pr~ce~sing of the poly~er ~t lower ~emperature, the llquid or~n~e solvent and the water being fugitive in na~ure ~ w~en removed fr~ ~he polymer resin leave ~he foa:med ~r~lcle with ~he physic~l pr~perties of the or~ginal resln prior eo processing. Th~6 i~ extremely i~portant ln the case of pol~ers which are difficult to process ~ecau~e of thelr ~i5eoelastic snd rheolog~cal propereies or hea~ ~nstability, T~e wlde latltude o~ condltlons under ~hioh the foaming operation c~n ~e carriet o~lt in th$s process was al~o ~uite surpri~ing. Thus for example, while ~ c~n prac_ice ~he foaming ~ep at higher temperatures, one can ~l~o oper~te at: ~h~ other end oiF the ~pect~, that is, ag room te$pera~ure or ~y placing the hydroge~ in ~ Yacuum de~iee, 6u~h a~, ~ vacuu;~ o~ven ~nd ~ith organie ~olvents o low vol~
~tility9 ~uch s/ me~hylene ~hlor~de, re~d~ly remoYe ~he ~olvent ~nd water in a relatlvely ~horl: time.

~ 11,313 As previously indicated, another embodiment of this inventiorl is directed to prosthe~ic devices which do not contain a separate inner load-bearing functional component but rely on the s~ructural integrity of the bioengineering thermoplastic material itself. For example, a porous block can be carved to an anatomically appropriate shape, and used to augment atrophic mandibular alveolar ridges and deficient facial contours in the mental, mandibular border, and zygomatic areas. Other devices, can include bone gap bridges and bone caps ~used to control bone overgrowth in amputees) which are either totally porous bioengineerino therm~plastics, or bioengineering thermoplastic coated metals or bulk polymers (relnforced and unreinforced). The alveolar ridge recon-struction au~,mentation device shown in Fi,gure 5 is prepared fr,om a porous bioengîneerin~ thermoplastic composite by moldino and/or carving a block of the composite to the de-sired shape.
The porous bioengineering thermoplastics can also be carved to anatomical shapes without destruction or collapse of ~he surface porosity. Bone gap bridges, bone caps and other pre-sized implants can be machined without destroyin~
the porosity and surface of the porous engineering thermo-plastics. Porous high density polyethylene, polypropylene, and the polytetrafluoroethylene creep and "feather" durin~
carving and machining operations.
The ~igh stren~th-low creep o the bioen~ineerin,o, thermoplastics and reinforced bioen,~ineering the,rmoplastics also translate to the load-bearing components of prosthetic devices and implants. For this reason, prostheses can be

3 313 ~eveloped ~cQrpora~lng ~ co~Dpo~te ~yst~m of bloengine~rlng eher~opla~eic load-be~rin~ c~mponents ~nd srtl~ul~tlng ~urfaoes, ~ith porou~ 'bloeng:Lneering, thermopls6tlc coatings ln areQs ~here ~laetachm2nt to ehe ~ 60ulo6kelet~1 ~yBtem iL6 tesired. Ttle blo-engineering thermoplastlos remaln tough af~er be~rlg filled with reinforcillg fillers, where polyolef~s auch A8 high density polyethylene become brittle ~t hlgh fiber loadir:~gs.
Bone gap bridges and joint prostheses demons~rate this prlnciple, Such impl~ntable~ ~e rendered more useful beoau~e ~f the ability to achieve high ~neerfacial ~trengeh~ between the ~ulk lo~d-bearing component and the porous coat~ng when the iden~clcal ~aterials ~re co~n~iDed ~ thc oonstruc~cion.
These comblnatiorls are not achievable with polyol2fins due ~co the poor 6tructural char~c~erl6t~c~ vf these m~teril~s, nor ~ith cer~ics o!r ~netals because of the ~iomech~ cal unsuit~biliey of the respective porous co~:ingsO
In ~o~t pro~heses where the bioengineering thermo-pla~tic ~st also form the ~ri:iculating ~urface, ~ is of cen de~ able ~o ~nc~rporate adti~ives ~lch increase ~he ~dear ~Lnd ~rasi~ re5i~;t~1rlCe of ~he composite. C~rbon fib~r, graphite f~ber~ tefl~l molybdenum disulfide are useul ~ddiei~res which ~fford wear re6ilstance engineer~ng thermopla~l:ic~ ~qual or 3uper~0r l:o ~elf~lubricated materials typ~e~lly u ed ln co~erci~lly ava:~lable ~D~n~ pros~che~s.
In ~ou~nal ~earin~, wear 'cests*, the fci~Low~r~g comparative re~ults were ob~ed:

*C~ndi~lon6 ~T?I-D1242 - 1400 hours, 110 ppm, 5 lbs. ~n level a~

ll, 313 ~ ~e~b~ L~
C~n~crol Hl)E'E 0 . 0806 C~trol polypropylene û. 0404 UDEL poly~ulone 0 ~ 2 794 UDEL br~th 20% c~ n fiber û.~362 WEL wi~h 20% graphite ~ . 0324 C:csmpos~eions with esrbon fiber ~re pref~rred for the ~ n~ec~ion s~olding ~r ~achin~ng of articul~tirlg pr~thes~ ~uch as acetsbulsr cup~, t~bi~, snd gleno~d co~npe~ents of ~o~al kn~e and ~houlder repl~cements, In ~other embo~meTIt of this invention ~ilyl re~ctlve polymers like ~llyl reaetion poly6ulfone ~re utilized for bond~ng porous polymerlc c~atings to ~etal ~ubstrates.
Silyl re~ctlve polysulfone (PSFSR) resins possess th~e~ ~portaT~c features. First, the presence of hydr~lyzable s~l~ne end grsups provld~s an inherent coupling abiligy ~o metaLlic ~urfaces. Secorld, the PSF-SR resins have a low r~el~
(or ~olution) vi cosity whlch ~reatly ~acilitates ~Iwetting~
turirlg t'ne fonnatiorl of ~dhesive ~onds. Third, they are polymer~c adhesiv~ which exhibit no ~olubility ~n physlological fluids ant hence have no biologic~ oxicolog~ cal effects when ~nplanted .

The lo~d he~rlng $us~ctlon~1 c~ponent o 'che pr~thetlc d~vicc~ of thi~ ~nvention can l~e c~prised of a variety of etals ~snd ~allDy~ knOwn 1S~ ~he ~rt. Whlle Eltsnium and tantslu~ ~re, l~or the 2no~t part, the only p~re meeal6 con-~idered as ~a~e ~or ~neernsl use, ~ v~rleey o alloy6 h~ve fo~d general ~cceptance. 5tainles6 ~teel~ ~ cobal~ base ~lloys ~nd titanlum baseJ~lloy~ all ~re tolerated by the body 85 well as be~ng corro~ion re~istant ~nd ~abriea~ed ~to de61sed ~hape.

~ 11,313 EXA~LE I
ErFEcr l~r sln~~ c cD~~ ON PORE SIZE

For this ~xper~ment ~imple molds were abr~c~ted from 3/8 inch outer t~ameter s~eel tubin~z. The tublng w~s cut to a 6 ~nch lengeh ~nd fi~ted wlth t~rleaded end plugs. Wall thickness of the tubing was ~pproximaeely 0 038 ~nch. The lesulting ~ln~ered pl~s~ic part had ~ dismeter of 0.300 inch and w~s 6 inches long. Thi~ proved to be a cont~enient s~mple size for tensile proper~y characterization.
PSF-3703 powder with the part~cle ~ize distributio~
~hown in T~ble I below was u~ed This material was sintered according ~o ~he following ~ehedule: pack powder in ~ molt;
immerso ~old ~n an oll bath at 220C or various t~mes ranging fr~m 10 to 30 ~in. The resul~ing rod of 0.300 inch diameter was then cu~ ~o ~ample lengehs of 2.5 inches.
Interconnecti~g pore ~i~e distribution was then tetermined through mercury ~ntrusion poroslmetFy. Daea are repor~ed in Table I ~ Characeerist~c pore siæe is 6hown as t~e percen~sge of pores larger than or equal to 132f~. ~s the time a~ temper-~ture ~s increased fr~m 10 to 30 min~tes, the number of pores 132~ in diameter lnereasesO However, i he ~ateria~ is held at 220C for times greater than 30 m~nutes~ ~he resulting sample would no longer be porous. On ~he ~ther hand, if ~he ~aterial were expo~ed ~o ~:emperaeure for le~s than 10 minute , litele or no s~tering would have occurred. Thus, ~here i an opeimum time st temperature~nd t~mperature for a ~l~e~ part~cle ~ize ~nd ~olecular welght fii~tsl~ueion to aehie~e a desired pore ~ize.

6'~
11, 313 _AE~LE I

U S SCREEN DISTRIBUTION

~, on 35 ~~
Oil 40Trace on 50 __ on 6014.0 on 8050,0 on 10018 . 0 th~u 10 0 ~~
on 14010.0 on 2 30 4 . 0 thr~ 230 4.0 Sinterin~ Time% Pore Volume 1~ 49.~
12 52.6 14 56. 5 16 58.1 18 ~1.8 69.5 ?5.4 -2~

ll,313 EXAMPLE II
EFFECT OF MOLECULAR WEIGHT ON SINTERING
_ _ _ The following experiment was conducted to demon-strate the efect of a low molecular weight tail upon sintering conditions and resultin~ mechanical properties.
PSF-3703 was "plasticized" via the addition of 0.5 and 1.0 weight percent of diphenysulfone. Blendin~ was accomplished in an E~an 1 inch labora~ory extruder. The "plasticized"
PSF was then ground into powder on a laboratory WEDCO
grinder. The resulting powder was sintered into porous rods 0.300 inch diameter and 6 inches long, Tensile properties of the rods were measured.
Table II presents the mechanical properties or the porous materials after sintering for 20 minutes at various tempera~ures. The material containing 1 wt. % diphenylsul fone was weakly sintered at 200C while the o~her materials did not sinter at this temperature. In all cases, as the sintering temperature is increased, the "plasticized"
material possesses superior mechanical properties in the porous sintered form. It is evident ~hat addition of dipl~enylsulfone, (or similar low molecular weight species) pro~ide a method to control sinterin,~ conditions. Speci-fically, shorter sinterin~ time cycles at a given tempera-ture or lower temperatures at a given time may be possible.

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_ /t / ~ / '3 - 3 1 -11 ,313 EXAMPLE I I I

_e~ t ic Co~ed _Prosthes is The ~ter~ ~ectlon of ~ Ric~rds MQnufacturlng c~snine f~moral c~mponene was dlp co~ted ~n a lO percent ~olu~lon ~f PSF-SR./n~ethylene chlor~de, air dried ~nd baked at 110C
for 1 hour. The ~tesn ~3ection of the prosthesls was ~hen dip coatet wlth ~ 15 percent ~olution of P-3703/te~ra-hyàro~r~n ~nd while tac3cy, dusted with powdered ~-3703.
The prlmed prosthes~s w~s pl~ced ln 9 eapered sluminum ~old whose c~vi~y repl~cated ~che ~tem section of the emoral cosnporlent, ~th a tolerance of lO0 mil. The cavity was loo~ely plicked with powdered P-3?03, ~ealed st ~he bot~om and pl~ced ~n ~n oil ba h at 215C for ~4 minutes.
After cooling, ehe prosthesis was removed. The ~tem sec-tion h~d a tigh~ly ~dherarl~ coatis~ of porous polysulfone.

~32-6 1 11,313 EXAMPLE IV
__._ _ ~3~
~T~_3:#LJUo~5L~5:~Cl~
.
To 400 ~ms. of UDEL polysulfone Pol700 re~in ln 8 one g~llon wide mouth ~r WAS added 31~.2 gms. of ~eehy-lene chlorlde wleh ~gitatlon. The ~ar W8S sealed ~nd ~ wed to ~tand at room temper~ture for 16 hours. A
polysulfone/m~ehylene ~hloride brown gel w~s obt~ined to which 558 gms of water were added with mixing. The brown ~el turned white i~ col~r. These proportions formed a 6tandard dough mix (SDM). A 30 g. port~on of ehe SDM was shaped t room temperature ~y h~nd compres-~ion into ~ l/8l' aluminum met~l pl~te 8" x 8" ha~ing a circular hole ~easuring 4 7/B" in diameter. The result-~n~ dough preform was then insertet ~t 155C. islto ~ heated t~lescoping ~ype ~luminum mold eonsisting of an upper 5"
~luminum disc, fastened to the upper pl~ten of a F)ress, which ~lides ~to a ring ~nd ~eets asloeher 5" ~l~in~
disc within the ring. The ring and bott~3 disc were not astened to ~he bottom plae~n of the press.
Vpon insertion of the dough preform the press was closet all~wing both disc mold ~urf~ces ~o campress ~he preformed dough wi~h a pressure of 50 psi. During the following 15~25 ~econts 8 pressure build up ~ccurs due ~o the volatillzat~on of ~he solvents. The pressure ~uilds up to ~52 psl at which poine the press was released clowly ~o main~in 3 pres~ure ~f 125 to 150 ps~. The rele~se of the pres&ure all~ws movemen~ o the mold sur-faces sctivatlng 8n exp~n~ion of the ~old with ~ubsequent ~ele~se of ~olvent snd ~ater vapor from the mold ~nd _33-11 ,313 poly~aer exp~n~on. D~ring the dwell time ln the ~Dold continuous ~olvene and w~ter vapor 108E; further reduces ehe pressure to ~boue 50 p~i or :Le~ feer ~ tot~l of ~our ~in~ee6 ehe ~old was cpened and he fD~med disc w s removed. The di~c h~d ~mo~eh ~urface6 orl both IYides ~nd had ~ ~erts~ty of 0.19 g. cc. ~che ~urf~ces when s~achinet ~eve~led ~n open pore nl~twork and the dlsc eould be cut to desired ~h~pesO

11,313 ., LE Y

S~men ~ 6 o f P ous Bioen~lnee~ Ther~

St~nle~s steel p~tes 0.0625" x 1" x 4" (type 304) were ~ip co~ted ln ~ 10 wt. percent of PSF-SR solutlon uslng methylerle chlorite ~s A ~olvent. The PSF-SR h~d ~n R.V. of 0.45. A~ter a~r drylng for 1 hour ~nd oven ~rying for lû minutes at 110C l:he ~amples were subsequen~-ly dlp coated a~ain ~n a 15 wt. percen~ ~olution of P-37 03, a lower ~nol. wt. polysulfone, ln r~eehyiene chloride, air dri~d 1 hour, oven dried 110C for 15 minutes. The ~amples were then b~ked in ~ hoe alr oven for 5 minutes at 24S C
- removed ~nd immedia~ly were powder co~ted with 40 mesh powdered P-3703 polysulone, u~ing a e~pped ~ieve. The s~mples ~ere ~hen clamped together to form lap-shear tes~
speciDlesls ~nd placed i~ ~ 240 C hot ~ir ~erl or 1/2 hotlr to fuse. The same procedure was repe~ted only P~1700 powdered (40 mesh) resir~ was ~ifted c~ver the pr~ed, hot ~mple plates. The ~amples were then tested ~n lap ~he~r followirlg ASTM D11:02-72 method. In eable XII below Che results ob~ ained are set forth:
Table III
___ _ ~o3703 1596 ~ohesive P-37û3 1435 Collesive P~1700 1407 ~ohesive P~1700 1340 Cohe5ive ,313 ~LE VI
ah~L~y~t ~ of h e n ~

Stainlgss ~teel ~trlps (type 304) .0625" x 1" x 4"
were ~shed ~n hexnne f~llowed by i ~oprop~nol ~nd dried .
~he str~ps were the~ dlp co~ted ln a 10~ y wt. polysulfone SR ~R.V. 0~ 517) methylene chîoride solut~on u~ing a ~echanic~ dlpping motor which provided ~ uni~orru r~te of withdr~wal from ehe ~;olution of the ~t~inle~s ~trip of

4"/lol/2 o~inutes. The 6trips were air dried ae room temper~ture ~or 2 hours and ehen hot ~ir oven baked ~t various temperseures for 1/2 hour. ~fter dryin~, the spec~mens were ~p~ced 3/16" ~par~ with shlms, clamped eoge~her ~nd ~ 15% by we. carbon fiber filled polysulfone/
CH2C12~H~0 dough was inserted between the stainless pla~es.
The ~ssembly was pl~ced in a hot ~ir oven ~ 150C for 15 minute~ to oam the "dough" and ho~d it to the me~al plaees. The ~ampl s were ehen tested ln lap ~hear ollow-lng th~ ASTM ~1002-72 method. The results obtalned are 8e~ forth ~n ~ble IV below:
Table IV
C :~ c She~r S~ ~e ~f F~ c R.T. a$r dry 245.2 Adh~sive 190JC 10 min. 428.5 A~heslve 25%
Cohesive 757 240C 10 ~in. 444 Co~esive ~6-3~ 13 The ~a~ae procedure w~s repeat~d to cO~e lden~ic~l ~ lnl~ss ~teel 3t~ip6 ~IBing ~ lO wt. percerlt 801ution of P-l~00 polysulfone ~n ~ethylene chloride. ~he result~ 4bts~ned ~re ~et orth ~n Tsble V below:
Tab le V
Co a t i~ _r e r ~ c S~he 2 r S t ren~ ~ 3 ~l ~ r~
R.T. ~ir dry (coatlng peeled of) 190C lO minO 113~1 ~dhesive ~40~C 10 ~nin. 340 Cohe~ve 320C lO Dlln. 410 Cohesive 11>313 ~LE StII

' ~E~ulu~
D- n T~5!Lc 6 Ir~ order to de~Donseraee the ~lfference~ creep o~odulu~ ~t ~5~ ~or the ~ioen~ eeslng ther~opl~s~lc6 of ~hi~ ~nv~ntlon ~nd other ~teri~l~, d~ta w~ compil~d 16 ~et forth ~n T~bl2 VI ~e15JW:

T~b le V I
Y4t~ri~ 1t~1 Appl:led C:ree~ (apparene~ dulus _ss L~ t ous~nd p. ~.1.
1 hr. 100 hr. 1000 hr.
ENGINEERING
PLASTICS
@l 360 * ~00 2~30 1365 ~C:I 3~ ~ * 40~ 35~ 320 310 P-1700 * 4000 345 3~0 325 41~111** 3000 345 ~0 310 OIXER
~TERIA~
Dlaken P~G 3.02*** 1450 386 ~69 ~. A.
~,EX 6050~* 3500 30 ~ . 5 N. A.
St~nyl~n 930~**** 1~75 ~70 80 31 ~rofuc 6423***** 1500 104 58 37 Propathe~e GWM
201*~*** 72S ~4 ~6 e-l -*P o ly~ul f one ****~IDPE
*~Polycarbonat:e ****~Polypropylene 3'l ~ .

~ lthc)ugh the ~nven~ion has beerl ~llustratecl by ehe pre~
cedin~ exs~ples, ~e i6 ~ot to be cons t~led ~6 ~e!~lg limlted ~
the materlal~ e~ployed there~n, ~ut r~her the is~vention relates . . .
t~ the ,~eneri~ ~re~ a~ here~nbefore di~closet. V~r~0~l6 d:Li-~atio~s and esDl)QdiDents can ~e mate without departing from the ~pirit ~d ~cop~ thereof.

Claims (9)

WHAT IS CLAIMED IS:

1. A process for the preparation of a prosthetic device comprised of a porous, bioengineering thermoplastic material which is compatible with, and conducive for, the ingrowth of bone spicules, said material being selected from the group consisting of polysulfones, polyphenylenesulfides, polyacetals, thermoplastic polyesters, polycarbonates, aromatic polyamides, aromatic polyamideimides, thermoplastic polyimides, polyaryl-etherketones, polyarylethernitriles and aromatic polyhydroxy-ethers, and having the following properties:
(a) an average pore diameter of from about 90 to about 600 microns;
(b) pore interconnections having average diameters of greater than about 50 microns;
(c) a modulus of elasticity from about 250,000 to about 3,000,000 pounds per square inch for the thermoplastic material;
(d) a porosity of greater than about 40 percent; and (e) a total creep strain of less than one percent at a constant stress of 1,000 pounds per square inch at ambient temperature;
all of the properties being sufficient to enable stresses applied on a musculoskeletal system to be transferred to bone spicules within the pores of said material and maintain suffi-cient load and pore stability to promote irreversible ossi-fication, which process comprises the steps of:
(a) forming a mixture of at least one bioengineering thermoplastic material in particulate form and having at least one fraction of a biomodal distribution of average particle diameters of from about 7:1 to about 5:1;
(b) heating said mixture at a temperature and time sufficient to sinter said particulate bioengineering thermo-plastic material to provide said porous material 40.

having said properties, and (c) shaping the surface of said sintered material to form an anatomically shaped prosthetic device.

2. The process of claim 1 wherein said average particle diameters are from about 50 to about 300 microns.

3. The process of claim 1 wherein said biomodal distri-bution of particle sizes is within the range of from about 40:60 to about 60:40.

4. A process for the preparation of a sintered bioengi-neering thermoplastic material which is compatible with, and conducive for, the ingrowth of bone spicules, wherein both porosity and mechanical strength are optimized, said material being selected from the group consisting of polysulfones, poly-phenylenesulfides, polyacetals, thermoplastic polyesters, poly-carbonates, aromatic polyamides, aromatic polyamideimides, thermoplastic polyimides, polyaryletherketones, polyarylether-nitriles, and aromatic polyhydroxyethers, and said process comprising the steps of:
(a) forming a mixture of at least one sinterable mate-rial in particulate form, said mixture having at least one fraction of a biomodal distribution of average particle diameters of from about 7:1 to about 5:1, (b) heating said mixture at a temperature and time sufficient to sinter the components of said mixture, and (c) recovering said sintered material.

5. The process of claim 4 wherein said sintered material has a porosity of at least about 40 percent.

6. The process of claim 4 wherein said sintered material has a porosity of from about 40 to about 70 percent and a modulus of elasticity of from about 250,000 to about 3,000,000 pounds per square inch for said sinterable material.

41.

7. The process of claim 4 wherein said mixture contains a sintering additive in an amount sufficient to lower said temperature and/or shorten said time necessary to prepare said sintered material.

8. A process for the preparation of a prosthetic device comprised of a porous, bioengineering thermoplastic material which is compatible with, and conducive for, the ingrowth of bone spicules, said material being selected from the group consisting of polysulfones, polyphenylenesulfides, polyacetals, thermoplastic polyesters, polycarbonates, aromatic polyamides, aromatic polyamideimides, thermoplastic polyimides, polyaryl-etherketones, polyarylethernitriles and aromatic polyhydroxy-ethers, and said material having an average pore diameter, pore interconnections a modulus of elasticity, a porosity, and a total creep strain which enables such device to become firmly and permanently anchored into a musculoskeletal system in which it is employed by tissue ingrowth into the device, which process comprises the steps of:
(a) forming a mixture of at least one bioengineering thermoplastic material in particulate form and having at least one fraction of a biomodal distribution of average particle diameters of from about 7:1 to about 5:1;
(b) heating said mixture at a temperature and time suf-ficient to sinter said particulate bioengineering thermoplastic material to provide said porous material having said properties, and (c) shaping the surface of said sintered material to form an anatomically shaped prosthetic device.

9. A process for the preparation of a sintered material having an average pore diameter, pore interconnections, a modulus of elasticity, a porosity, and a total creep strain which enables such material to become firmly and permanently 42.

anchored into a musculoskeletal system in which it is employed in the form of an anatomically shaped prosthetic device by tissue ingrowth into the material, said material being selected from the group consisting of polysulfones, polyphenyl-enesulfides, polyacetals, thermoplastic polyesters, polycar-bonates, aromatic polyamides, aromatic polyamideimides, thermo-plastic polyimides, polyaryletherketones, polyarylethernitriles and aromatic polyhydroxyethers, and said process comprising the steps of:
(a) forming a mixture of at least one sinterable material in particulate form, said mixture having at least one fraction of a biomodal distribution of average particle diameters of from about 7:1 to about 5:1.
(b) heating said mixture at a temperature and time sufficient to sinter the components of said mixture, and (c) recovering said sintered material.

43.