An artificial limb attached directly to the bone by a quick-disconnect coupling was tested in-place at a California medical rehabilitation center. Its design concept and development, made possible by multiple spinoffs of aerospace technology, are discussed

Owens, L. J.

English

NASA Technical Reports Server

1
; I I !
i ,..
O _
e
N76-1919
: 20. DEVELOPMENT OF A BONE-FIXATION
k PROSTHETIC ATTACHMENT
By Lester J. Owens
NASA Kennedy Space Center
SUMMARY
The first of what promises to be a new generation of prosthetic devices--
an artificial limb attached directly to the bone by a quick-disconnect coupling--
_ is undergoing in-place testing at a California medical rehabilitation center.
This paper describes its design concept and development, made possible by
_ multiple spinoffs of a_rospace technology.
;' INTRODUCTION :
'; Man's experience in the design and fabrication of prostheses dates to
prehistoric times, when some cave-dwelling amputee created the first artificial
leg by binding a piece of tree branch to his stump. Since then, and particularly
within this century, many advances have been made in the state of the art.
However, artificial arms and legs of today still have to be strapped or clamped
on the amputee's stump in a manner not unlike that of the olden days.
_ Thus, it was with a considerable sense of challenge that the writer, a
member of the NASA Kennedy Space Center Design Engineering staff, responded
to a request to help design a qulck-connect, strapless prosthesis. The re-
quest was made by Dr. David B. Hartmann, a member of the staff of Rancho Los
Amigos Hospital in Downey, California, during a visit to KSC in March, 1973.
Over a period of years this Los Angeles County hospital has worked closely with
NASA and the aerospace industry in a continuing technological exchange.
Months ago, the hospital's Amputee and Fracture Service chief, Dr. Vert
Meoney, announced that research at the institution had shown the feasibility
of using aerospace-developed biocompatible carbon for "direct skeletal attach-
i ment of llmb prostheses." Heretofore, direct prosthetic attachment had been
thwarted by the body's tendency to reject foreign materials and the failure
of the skin to form a hygienic seal around otherwise compatible material.
Now, the medical researchers hoped for a workable prosthetic design
utilizing a bone-implanted connector accessible through a biocompatible carbon
collar around which the flesh and skin would heal. This led to Dr. Hartmann's #_
request and the launching of the project described herein. _
281 _
_,_
1976012084-277
https://ntrs.nasa.gov/search.jsp?R=19760012104 2020-03-20T01:56:37+00:00Z
ft
CONCEPT DEVELOPMENT
Development of the new prosthetic attachment concept began with considera-
tion of the basic problem of finding a quick-disconnect method suitable for use
; with a person's bone. Aercspace technology quickly suggested the ball-lock
connector, a familiar item in missile and space programs for several years.
: These quick-disconnect devices have served reliably to hold umbilicals and
even complete space vehicles in place until the desired instant of release.
\
The ball-lock mechanism is simple and effective. In a typical device,i
balls captivated in holes near the point of the locking pin are forced to
i protrude from the shaft surface by a spring-loaded rod inside the pin. When
the pin is inserted into its receiver, the balls encounter and lock into an
annular groove. The pin cannot then be withdrawn until a release is pressed,
moving the rod inside the pin to permit the balls to retract into cavities in
the rod shaft.
Ball-lock devices are made in a variety of styles for aerospace applica-
tions. They normally range in diameter from 3/16 inch to i inch, although
the Saturn V is released by four 3 i/2-inch pins. A four-bail stalnless-steel
: ball lock of i/2-inch pin diameter can carry approximately 102,300 newtons
(23,000 pounds) in shear and 6,670 newtons (1500 pounds) in tension.
The medical researchers quickly accepted the simplicity of a ball-lock
prosthetic disconnect, and the conceptualization of the new prosthesis was
expedited as follows:
The male half of the disconnect device, containing the ball-lock pin and
release mechanism, would be part of the prosthetic limb. The female ha!f--the
receiver--would be implanted surgically in the medullary canal of the bone re-
maining in the amputee's stump. A sleeve or collar of biocompatible carbon
would be bonded around the distal end of the receiver insert to provide a
permanent passage through the skin.
This connection concept would be usable wherever stump size permitted a
receiver implant, including arm and leg locations above and below the elbow
and knee. Hopefully, it would benefit many amputees with stumps too short
for conventional strap-on or clamp-on prosthetic limbs.
DESIGN DEVELOPMENT
The announcement early this spring that an amputee at Rancho Los Amigos
Hospital had volunteered for implant surgery spurred the development of a
working prototype of the quick-disconnect prosthesis. Work was concentrated
at KSC to provide a suitable ball-lock receiver and subsequently the a_socl-
ated hardware for a lower-leg prosthesis. A basic design was standardized
using ball locks of three pin sizes: 1/4-, 5/16-, and 3/8-inch.
282
1976012084-278
" 1 r
°:l
[ !...... ' I I
O
:, The receiver design (Figure 1) was influenced by consideration of Young's
' modulus of bone elasticity and corresponding modull for the steel implant and
an acrylic plastic, methylmethacrylate, which would be used as an insulator
_: and bond between the implant and the _rrounding bone. These modull were .
_ calculated to be approximately 2 x i0 IO, 2 x i0II, and 4 x 109 newto_s/mete_ 2
_ respectively. The lower modulus of the methylmethacrylate allows a transfer
_ of bearing loads between the implant and the bone; the oglval contouring of the
receiver was designed to provide decreasing load transfer toward the bone end
_ and to avoid stress concentrations. The toothed, grooved shaft of the receiver
_:_ enhances its seating in the bone canal with optimum distribution of the semi-
i fluid methylmethacrylate and gives mechanical interference with the plastic
against pull-out and rotation within the bone.
_: Type 316-L stainless steel, previously proven biocompatlble, was selected
as the receiver material. Implant dimensions were determined by the writer
[ through reference to gray's Anatomy; they were subsequently approved by
_ hospital personnel. The interior design provides a second ball-locklng groove
against the possibility that wear or future adjustments might require this
backup feature, as the receiver could not easily be reolaced The unused
groove would be filled in with an epoxy that could be removed cleanly with a
dental pick when required. The epoxy would prevent wearing of the groove and
_- facilitate cleaning of the receiver, which could be done simply with a swab
and alcohol.
t
The finished implant device, complete with its blocompatlble carbon collar
L and plastic plug, is shown in Figure 2. The protective plug would be used
during the implant operation and recovery period and could be used afterwards
during periods of prosthetic disconnection. The carbon collar was manufactured
_; by Gulf General Atomic Corporation. Hospital experts developed the collar
design to provide optimum healing and implant support. The circumferential
holes are intended to promote tissue growth about the stump end.
_r
_ The remaining design work was encouraged by the initial success of the
. implant operation, which was undertaken in March of this year. Figure 3 is a
view of the healing leg stump showing the receiver in place.
Development of the prosthetic attachment involved the writer in a design
effort to produce a mounting assembly containing not only the male portion of
!i the ball-lock mechanism but also adequate shock-isolatlon provisions. The
i importance of the latter was emphasized by the belief that rejection of pre-
vlously attempted implants may have resulted from shocks and stresses to the
bone at the implan_ interface. It was decided to provide a coaxial shock ;
absorber mount extending from Just below the connection point into the main _
i, support column of the prosthesis. ,
l_ Experimentation with various techniques and materials led to the develop- '
ment of the shear-radial isolation mount shown in Figure 4. This is formed
_" by bonding an elastomer (silastlc rubber) between aluminum cylinders that are !
threaded to provide adjustment capability.
283
t
] 9760] 2084-279
tI 1 ' *t I
'| I . i
. o',. . . ,. t
I " I
t l_' ' '!
L(! .....
• _ 3.47 >
_ 1.00 _ 101,4 "
GIVE __
l" ,4.. r T*.GENTI ._0DI,4
N,,::,,,,o:L,,o= i i
_"; r-f i-l-rT'-,-ra-n-8 u-u-,--rn-e-e-8"-: ........ _ 1 <i
_o li I t 9 I I I I -- -- -- _ -- -- -- . -- -- _ _m, _'-. .r.J ---- -i
-5.00 R OGIVE
RECEIVER ,)
.06 WIDE, 12 GROOVES
EQUALLY SPACE 15° (TYP) i
,i
,7
_ .045 (TYP) i
SECTION A-,4
NOTE: ALL'DIMENSIONS IN INCHES
Figure I, Receiver Zmplant 1)eslgn (Extracted
from Hanufacturln8 DrawlnS)
284 ,
1976012084-280

+;L :'+6 OntGm,_Pj,,+mm
OF POOR QUALITY
J.............. 1976012084-282

_o °.
O _
• C I
! C _
View A of Figure 4 shows the shock moun_ with full elaetomer content
while View B shows it partially filled, with elastomer only at the ends. The
accompanying graphs give load-deflection and torque charaaterlstizs for both
conditions shown. The amount of elastomer used may be adjusted to produce
: design variations as required for individual appiicatio_,s. For heavy, active '_
individuals, even larger mounts may be required. ,_
Metal and nylon parts for the shock isolator were fabricated by the
Development Testing Branch and the elastomer was _;ucessed by the Materials
Testing Branch of the Laboratory Division of NASA's KSC Support Opezations _
_! Directo.?ate. Avibank Manufactdring, Inc., contributed the ball-lock h_a4 4_ign. i
Figure 5 shows the ball-lock pin and shock mount along with a matching receiver _o
_[ end mounting accessories•
• Remaining design details were completed with the results shown in the : ;
pictorial and detailed views of the below-knee attachment (Figures 6 and 7 •
! respectively). The molded plastic stump socket, designed by hospital staff
members and made from a cast of the actual stump, assures custom-fitting
and maximum support, it is designed to impart natural feeling by assistin_
the wearer in sensing minute pressure variations. Tension adjustments on
the KSC-engineered portion also contribute toward this end, and to patient
r comfort, by allowing adjustment of the ratio of load carried by the socket
and the connection.
Overall comfort and safety were carefully considered in the design to
achieve an integration of components with a progressive ±allure scheme provi-
: ding maximum protection to the amputee and the surgical implant.
The yoke-shaped support column of the prosthesis is one of the design
' variables Most leg prostheses would require this feature for structural
, strength, whereas artificial arms hopefully would derive meat of their strength
{ from the structural properties of the prcsthesis proper. In general, however,
• _ the conceptual design developed for the in_tlal qulck-dlsconnect llmb would be
"usable.
Exact design, including cosmetic treatment and dimensioning, would
necessarily follow consideration of various characterlstlcs of the individual
i amputee, including age, sex, build, and degree of activity. The modularity _
i of the basic design would provide for ease of changes and adjustments necessi-
! tared by such factors as growth, weight changes, and activity changes in theindividual user, Figure 8 shows an attached prosthesis.
I CONCLUDING REMARKS
i It is the privilege to report completion the first phase of
writer's of
i the qulck-disconnect prosthetic design project with the shipment of the leg
! mechanism in late June, 1974. While it is still too early to assess the im-
pact of this development on the prosthetic state of the art, the hope is great
1 and the hospital reports are enthusiastic. The designers would like to f_el
that their work, with a major boost from the technology development to help man
i walk on the moon, is destined to help many more walk, and perform, on earth. _.
288
I
] 9760] 2084-284
!l
t0
C
1,4 !I
I I
LJ
Figure 6. Below the Knee Prosthetic Attachment (Pictcrlal View)
290
1976012084-286
TIBIA
I4SUU.alW
CANAL
RECEIVER
CAEIQI4SLEEV|
|Q_IDED TO RECEIVER
RETAINING
ISOLATOR
YOK|
_ Fi$ure 7. Below the Knee Prosthetic Attachment (Detail View)t ,
_i_;_ A.L I)._G_
1
]9760]2084-287
! ]1 1 I
n _ . o:. . .
1 ! i
0
C
(
Figure 8. First User
_'L:i;_NALPAGE i_
292
1976012084-288
! CREDITS
The success of the design effort must be credited to the efforts and
contributions of several individuals, including Drs. Hartmann and Mooney, .
already mentioned. Others who contributed significantly were Dr. Michael
Eaklewlcz_ who performed the first KSC implant, and Dr. James Reswlck_
Director of the Rehabilitation Engineering Center, both of Rancho Los Amigos
Hospital; John Duran, Avlbank Manufacturlng_ Inc. ; Jack Bokros, Ph.D., Medical
Device Divlslon_ Gulf General Atomic Corporation; James Harrell_ Miles
Ho11ingsworthp Charles Bright, Frank Markley, William Jones, Glenn Roberts,
: and Otto Fedor, all of Kennedy Space Center; members of the Logistics Section
of the KSC Systems Engineering Division; and Walter Parsons and Donald Buchanan
of KSC Design Engineering management. Thanks must also go to Larry McGrath
of Planning Research Corporation for assistance in preparing this paper.
i
293
| j
1976012084-289


Development of a bone-fixation prosthetic attachment

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server