Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02233933 1998-04-03
DYNAMIC SPLINT FOR POST-OPERATIVE TREATMENT
OF FLEXIBLE IMPLANT ARTHROPLASTY OF THE DIGITS
Technical Field
This application relates to an improved hand splint. The
splint is particularly suited for the treatment of patients following flexible
implant arthroplasty of the digits.
Background
The hands of patients suffering from rheumatoid or osteoar-
thritis are often deformed by the disease process. Deterioration of the
metacarpophalangeal (MCP) joints may cause loss of range, ulnar drift and
subluxation, resulting in pain and partial to total dysfunction of the digits.
These conditions can be treated surgically. Implant arthroplasty of the
damaged joints involves the insertion of silicone implants which act as
spacers between the bones of the reconstructed joint to maintain their
internal alignment. Arthroplasty restores some degree of function to the
damaged joints and helps alleviate joint pain.
Arthroplasty is most commonly used to reconstruct the MCP
joints of arthritic patients. However, the same techniques may be used to
repair the distal and proximal interphalangeal joints of the fingers and
thumb. This type of MCP joint arthroplasty was pioneered by Dr. Alfred
Swanson in the 1960s. The operation involves excision of the metacarpal
heads and reaming of the intramedullary canals. A flexible silicone
implant with titanium circumferential grommets is then inserted into the
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canals. Finally, the ligaments and tendons around the implant are
reattached to achieve a balanced joint.
The use of splinting in the post-operative management of
MCP joint arthroplasty is imperative to the success of the procedure.
During recovery, the reconstructed joints must be supported to prevent
stretching of reconstructed tendons and ligaments during tissue regenera-
tion. Accordingly, the support should be firm enough to minsmise any
lateral movement of the fingers. At the same time, the splint should be
dynamic enough to allow movement in the desired plane and range. As
part of the post-operative regimen, the finger must be allowed to
reciprocate between a flexed and an extended position, with the degree of
flexion and extension increasing in the course of the regimen. Because the
patient has an active role in the post-operative period, the design of the
splint should be simple enough to encourage patient participation. . The
splint should also be as unobstructive as possible, and light enough to
prevent fatigue.
In most prior art hand splints, the dynamic force required for
finger extension is generated by springs or rubber bands attached to
rigging which operates in conjunction with a dorsal outrigger structure.
Such splints suffer from several serious drawbacks. Custom fabrication
and fitting of outrigger splints is time-conswning (typically 4 - 8 hours per
splint) and requires professional expertise. Moreover, such splints lose
accuracy of fit due to exaggerated ulnar directed extension lift and cause
resistance to flexion.
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Several hand splints are the subject of granted patents. U.S.
Patent No. 4,602,620 discloses an outrigger splint with pulleys juxta-
positioned to the digits of the hand, mounted to the outrigger structure,
and guiding a rigging line attached to a fixed-length spring. The dynamic
force is controlled by the choice of a colour-coded spring used to anchor
the rigging line.
U.S. Patent No. 4,765,320 discloses an outrigger splint with an
elongated, laterally adjustable rigging guide operating as a pulley for
changing the direction and the force applied by a rigging. The dynamic
force is controlled by an elastic band used to anchor the rigging line.
U.S. Patent No. 4,949,711 discloses an outrigger splint which
uses a single extensible coil spring to generate variable tension force in the
rigging. The tension force is adjusted by the choice of attachment point for
the coil spring securable on the base of the splint by use of releasable hook
and loop fasteners.
U.S. Patent No. 4,772,012 discloses a dynamic splint with a
work arm tensioned by a torsion spring, and a band connected at one end
to the work arm and at the other to a connecting member on the digit.
In all of these prior art examples, the dynamic force always
pulls the fingers toward an extension position. Some devices allow control
of the amount of the dynamic force exerted, either by interchanging the
flexible elements which create the force, or by altering their anchorage
position. No means is provided for training the fingers in a flexion or
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partial flexion position or ensuring that the joint will flex relative to a
natural pivot axis.
'The need has therefore arisen for a dynamic hand splint which
overcomes the various shortcomings of the prior art. The applicant's
splint described herein is pxe-assembled for easier and faster fitting, is
readily adjustable while being worn by the patient for optimum joint
alignment, and does not apply radial or protractive/retractive forces to the
joint during function which can interfere with post-operative tissue
healing.
SummarX of Invention
In accordance with the invention, a splint for post-operative
treatment of a patient following flexible implant arthroplasty of the digits
is disclosed. The splint is primarily designed to allow function by
controlling movement and assisting the extensor muscles following
arthroplasty of the metacarpophalangeal joint, but may also be used
following surgical replacement of the distal interphalangeal or proximal
interphalangeal joints, or to control the thumb following MCP joint
arthroplasty. The splint includes a brace securable to a limb of the
patient, such as a forearm; a digit support for engaging at least one digit
of the patient, wherein the digit support is moveable about a pivot axis to
permit movement of the digit between extended and flexed positions; and
an adjustment frame coupling the digit support to the brace for adjusting
the position of the pivot axis until it intersects the digit joint. The splint
thereby ensures that the axis of movement of the digit support is
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approximately aligned with the natural pivot axis of the digit-joint in
question.
Preferably the width, height and length of the adjustment
frame are independently adjustable. The adjustment frame may be
pivotally coupled to the brace to enable adjustment of the height and
inclination of the pivot axis. More particularly, the adjustment frame may
include a rod pivotally coupled to the brace and extending transversely
between opposite sides of the splint; and at least one (and preferably a
pair) of side frames slidably coupled to the rod for varying the width of
the adjustment frame. The side frames are releasably lockable at a selected
transverse position and extend upwardly and outwardly from the rod to
a respective side of the splint. The adjustment frame may further include
at least one side bar extending longitudinally, preferably alongside the
patient's hand, which is slidably coupled to an upper end of a respective
side frame and is lockable at a selected longitudinal position. The side bar
may be adjusted to vary the longitudinal position of the pivot axis and the
overall length of the splint.
The digit support is preferably pivotally coupled to a forward
end of the adjustment frame, such as a forward end of a corresponding
side bar. The digit support may be biased toward the extended position.
A flexion lock is provided for releasably locking the digit support against
the bias at a selected angular position between the extended and flexed
positions. An adjustable stop for restraining rearward pivoting motion of
the digit support in the extended position is also provided.
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The digit support may consist of at least one rigging arm
pivotally coupled to a side bar and extending inwardly therefrom above
a digit of the patient in the extended position, and a sling adjustably
connectable to the rigging arm for supporting the patient's digit. The
digit support may further include a spar slidably transversely on the
rigging arm and lockable at a selected transverse position, the spar having
a support rod which extends longitudinally; and a sling holder slidable
longitudinally on the spar. The sling is detachably connectable to the
spar. Preferably each digit support comprises a pair of rigging arms
independently pivotable relative to a side bar, wherein the rigging arms
extend at different elevations above the digits of the patient in the
extended position. The splint is ordinarily configured so that it includes
a pair of digit supports pivotally coupled on opposite sides of the
adjustment frame.
Brief Description of Drawings
In drawings which illustrate the preferred embodiment of the
invention, but which should not be construed as restricting the spirit or
scope of the invention in any way:
Figure 1 is a front isometric view of the applicant's splint
supporting the patient's fingers in an extended position;
Figure 2 is a right side elevational view of the splint of Figure
1 showing the patient's fingers in a flexed or partially flexed position;
Figure 3 is a front isometric view of the splint of Figure 1;
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Figure 4 is a rear isometric view of the splint of Figure 1;
Figure 5 is a top plan view of the splint of Figure 1;
Figure 6 is a bottom plan view of a rear portion of the splint
of Figure 1; and
Figure 7 is an exploded isometric view of a finger support
assembly.
Description of the Preferred Embodiment
This application relates to a hand splint 10 for the post-
operative treatment of flexible implant arthroplasty of the digits, princi-
pally metacarpophalangeal joint ("MCP") arthroplasty. Effective splinting
of the patient's hand following such surgery is critical to a successful
outcome. In order to heal properly, the reconstructed joint must be
supported in the proper alignment while permitting the fingers to
periodically articulate between extended and flexed positions. Since the
anatomy and functional range of motion of each patient's hand is different,
it is important that the splint be optimally adjusted to suit each individual.
The applicant's splint 10 is specially adapted for this purpose.
Splint 10 includes a brace 12 for supporting the patient's
forearm. As shown best in Figures 5 and 6, brace 12 includes a metal stay
14, preferably made from light-weight, flexible aluminum, which is
generally aligned with the patient's ulnar axis. Stay 14 fits within a sleeve
formed in a central, longitudinal portion of an armlet 16. Stay 14 may be
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contoured to conform to the patient's forearm. For example, the forward
end of stay 14 may be curved to support the patient's palm and maintain
a normal hand arch. The rear end of stay 14 includes wings 17 which curve
upwardly on either side of the patient's forearm. Armlet 16 is preferably
made of neoprene or some other material and which will conform to the
user's forearm. Armlet 16 includes an aperture 18 in the lower, forward
end thereof to accommodate the patient's thumb. An extension of stay 14
may optionally be added here to support a thumb fusion. As shown in
Figures 1 and 2, armlet 16 also includes a pair of straps 20 securable to
fasteners for wrapping armlet 16 snugly around the patient's forearm.
Alternative strapping arrangements may include two rows of eyelets laced
together with a continuous lace which finishes in one or more pull straps.
In a another alternative embodiment of the invention, brace 12 may be
moulded from a thermoplastic material.
Stay 14 further includes a first ball joint coupler 32 projecting
downwardly from a central portion thereof (Figure 2). A hole (not shown)
is cut in the fabric of armlet 16 to accommodate the stem of ball joint
coupler 32. The rounded end of coupler 32 is captured at the rear end of
a clamp 26 which extends underneath brace 12. Clamp 26 comprises
matching halves 28 which are releasably coupled together with a fastener
30.
An adjustment frame generally designated 34 is pivotally
coupled to a forward end of clamp 26. As shown best in Figures 5 and 6,
frame 34 includes a transverse bar 40 having a second ball joint coupler 36
projecting downwardly from a central portion thereof. Coupler 36 has a
rounded end captured by clamp 26.
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Adjustment frame 34 also includes a pair of side frames 42
which curve upwardly and outwardly on opposite sides of splint 10. The
lower end 44 of each side frame 42 is slidably coupled to bar 40 to enable
adjustment of the distance between side frames 42 to accommodate hands
of varying widths. For example, each side frame 42 may comprise a slot
sized to receive bar 40 (Figure 6). Each side frame 42 may be releasably
locked to bar 40 at a selected position using a first cam lock 46.
Adjustment frame 34 further includes a pair of side bars 48
which extend longitudinally on opposite sides of splint 10. A rear end 50
of each side bar 48 is slidably coupled to an upper end 45 of a respective
side frame 42. For example, side frame upper end 45 may comprise a slot
sized to receive side bar 48 (Figure 7). A second cam lock 52 is provided
to releasably lock side bar 48 at a selected longitudinal position.
Splint 10 further includes a pair of finger support assemblies
54 which are each pivotally coupled to adjustment frame 34. As shown
best in Figure 7, each assembly 54 comprises a pair of L-shaped rigging
arms 56 each having a rounded end 57 pivotally coupled to an enlarged
forward end 51 of a respective side bar 48. Each rigging arm 56 is coupled
to either an inner or an outer surface of side bar 48 with fasteners 61
together with an extension assist spiral torsion spring 58 and a spring
retainer cap 60. Spiral torsion spring 58 has an end which fits into a
corresponding hole formed in side bar end 51 and is tensioned when the
corresponding rigging arm 56 is pivoted forwardly to a flexed position as
discussed further below. Thus, spring 58 biases a respective rigging arm
56 to a vertical orientation shown in Figure 1 for supporting the patient's
MCP joints in an extended position. In one embodiment of the invention,
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the tension of springs 58 is adjustable to provide greater or lesser
resistance to flexion.
A stop 62 is mounted on each side bar 48 for restricting
rearward pivoting motion of rigging arms 56 beyond the vertical
orientation of Figure 1, thereby preventing hyper-extension of the patient's
MCP joints. Each stop 62 may consist of an extension governor screw 63
rotatable to adjust the extension limit of a corresponding rigging arm 56.
Each rigging arm 56 is bent at an elbow to provide a mounting
platform 59 which extends over the patient's hand toward the mid-line of
splint 10. The inner rigging arm 56 of each finger support assembly 54 is
shorter in height and has a longer mounting platform 59 than the adjacent
outer rigging arm 56 (Figures 1 and 3). As discussed further below, this
ensures that the path of the inner rigging arm 56 will not be obstructed by
the adjacent outer rigging arm 56 when the finger support assembly 54 is
articulated to a flexed position.
A pair of spring-loaded flexion locks 64 each having a handle
66 and a stop 68 are provided to lock each pair of rigging arms 56 in a
selected flexed position against the bias of springs 58. As shown best in
Figure 2, when each lock 64 is deployed, a serrated edge of stop 68 engages
the rounded end 57 of a corresponding rigging arm 56 to restrict pivoting
motion thereof. This motion is restricted in extension only, as the
serrations are so designed to allow the rigging arm to follow the finger as
it moves into flexion. Lock 64 may be disengaged by pushing lock handle
66 rearwardly to the unlocked position of Figure 1, thereby allowing
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rigging arms 56 to pivot freely. The bias of extension assist spiral torsion
springs 58 returns the rigging arms to the extended position of Figure 1.
As shown best in Figure 7, each finger support assembly 54
further includes a pair of spars 70 which are slidable transversely along a
mounting platform 59 of a respective rigging arm 56. Each spar 70 has a
sleeve 72 for receiving a mounting platform 59. Each spar sleeve 72 may
be locked at a selected transverse position by means of a third cam lock 74.
Each spar 70 also includes an elongate member 76 extending
forwardly from sleeve 72 parallel to the longitudinal axis of splint 10. In
the extended position of Figures 1 and 3, the elongate members 76 of splint
10 preferably extend in a common horizontal plane. Since mounting
platforms 59 of rigging arms 56 are staggered at different elevations, the
orientation of spars 70 is adjusted accordingly (i.e. spar sleeves 72
connected to the outer rigging arms 56 extend downwardly whereas spar
sleeves 72 connected to the inner rigging arms 56 extend upwardly).
A sling holder 78 is slidable along the length of each member
76 for detachably supporting a respective sling 80. Sling 80 has an upper
portion 82 which is securable to holder 78 and a C-shaped lower portion
84 for supporting a finger of the patient (Figures 1 and 2). Slings 80 may
be of the same or varying lengths to suit the requirements of the patient.
In one embodiment, the sling upper portion may comprise a leaf spring
which releasably snaps into place on a respective sling holder 78 as shown
best in Figure 7. An alternative design (not shown) for sling holder 78 will
include a lockable sliding joint (i.e. a fourth cam lock).
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As should be apparent from Figure 1, splint 10 ordinarily
consists of two finger support assemblies 54 mounted on opposite sides of
splint 10, each supporting two adjacent fingers of the patient. Each
assembly 54 is a structurally identical, mirror-image of the opposite
assembly. MCP joint arthroplasty typically involves the reconstruction of
all of the MCP joints of a patient's hand. However, if only one or two of
the finger joints are fitted with a prosthesis, then only one finger support
assembly 54 would be required.
Splint 10 is essentially bilaterally symmetrical and may be
used on either a left or right hand with relatively few modifications. The
embodiment shown in the drawings is adapted for right-hand use. In the
case of left-hand use, thumb aperture 18 formed in armlet 16 (Figure 5) is
located on the opposite side of splint 10.
In use, splint 10 may be quickly and precisely adjusted to suit
the hand anatomy of a particular patient. Splint 10 is preferably provided
to therapists fully assembled. In order to fit a particular patient, the
armlet
16 is first detached from frame 34 by loosening ball joint clamp 26. The
aluminum stay 14 within armlet 16 is bent to fit the patient's pa1mer arch,
forearm diameter and wrist extension. In some cases it is necessary to trim
excess fabric from armlet 16 and enlarge thumb aperture 18. Straps 20, or
alternative lace style straps, are then adjusted to secure armlet 16 snugly
to the patient's forearm.
The therapist then removes finger slings 80 from their
respective sling holders 78. Sling holders 78 are positioned for right or left
hand use. The spacing between opposed side frames 42, which are
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slidable on bar 40, is temporarily preset at an excess width. The armlet 16
is pivotably reconnected to frame 34 by tightening ball joint clamp 26.
Clamp 26 is sufficiently tightened to allow pivoting of ball joints 32, 36
upon the application of a moderate force (clamp 26 is fully tightened after
correct alignment has been obtained).
The next step in the fitting procedure is for the therapist to
adjust side frames 42, side bars 48 and ball joints 32, 36 repeatedly as
described above until the pivot axis passing through all four rigging arms
56 is approximately in line with the mean axis through the patient's MCP
joints. In practice, the pivot axis should be set slightly higher than desired
since the extension assist will pull it down when the patient's fingers are
hooked up. It is important that the left and right side bars 48 be in
approximately the same position relative to their respective side frames 42.
If the alignment is only acceptable on one side of splint 10, then it may be
necessary to further adjust ball joints 32 and 36.
Finger slings 80 are sized to fit the patient's fingers. The
lower portion 84 of each sling 80 supports a respective finger on the ulnar
side whereas he lower portion of the sling supports the finger in extension
and the top portion supports the finger in flexion In extension (Figure 1)
there must be adequate finger clearance for comfort and easy access. Once
the necessary adjustments have been made, each finger sling 80 is then
snapped into place on a respective sling holder 78.
The preferred position of the finger sling 80 depends upon
which of the patient's finger joints have been fitted with a prosthesis. In
the case of MCP joint arthroplasty, the finger sling 80 is typically fitted on
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the shaft of the proximal phalanx as close to the proximal interphalangeal
joint as comfort allows, as shown best in Figure 1. This allows for flexion
of the proximal and distal phalangeal joints so that the patient can
maintain a relatively normal range of motion in the end portions of his or
her fingers while wearing splint 10. In the case of proximal interphalan-
geal and distal interphalangeal arthroplasty, finger slings 80 may be
positioned at any other suitable position on the patient's finger and the
MCP joints would need to be stabilized. The longitudinal position of the
finger sling 80 may be adjusted by sliding a sling holder 78 along the
length of a respective spar 70. The transverse position of the finger sling
80 may be adjusted by sliding the spar 70 along the length of a respective
rigging arm 56 and locking it in place at the desired position with a third
cam lock 74.
As discussed above, an important feature of the applicant's
invention is that the height, inclination, width and length of adjustment
frame 34 may be independently varied to ensure that the pivot axis of
rigging arms 56 approximates the natural pivot axis of the finger joints in
question. The height and inclination of adjustment frame 34 may be
modified by pivoting transverse bar 40 relative to clamp 26 about ball joint
coupler 36; and by pivoting clamp 26 about coupler 32 relative to stay 14
(Figure 2). The width adjustment is achieved by sliding side frames 42
transversely along the length of bar 40 and locking the side bars 48 in
place at the desired position with first cam locks 46. The longitudinal
adjustment is achieved by sliding side bars 48 forwardly or rearwardly
relative to side frames 42 and locking them in the desired position with
second cam locks 52. Unlike some prior art designs, all adjustments may
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be made while splint 10 is worn by the patient, ensuring a more accurate
fit.
As indicated above, frame 34 is preferably adjusted so that the
pivot axis of rigging arms 56 (i.e. the transverse axis passing through
fasteners 61 as shown in Figure ~ very closely approximates the natural
pivot axis of the finger joint fitted with a prosthetic implant. This ensures
that the joint will move through a natural range of motion when splint 10
is adjusted between extended and flexed or semi-flexed positions. By
ensuring that the joint is fully supported but may move through a natural
range of motion, splint 10 helps rr~inimi~e the unwanted radial, protractive
and retractive forces to the joint which are commonplace in conventional
splints and which may disrupt the post-operative healing process.
Movement of the patient's fingers between extension (Figure
1) and flexion (Figure 2) is critical to successful recovery. Splint 10 is
designed to support each finger while it moves between extension and
flexion. Spiral torsion spring 58 provides assistance for weak extensor
muscles when movement is from flexion to extension. When a passive
flexion force is desired each rigging arm 56 is pivoted downwardly and a
corresponding flexion lock 64 is engaged as discussed above to lock the
rigging arm 56 in place. When the flexion locks 64 are disengaged,
springs 58 assist in returning the patient's fingers to a fully extended
position. As discussed above, the elevation of the rigging arms 56 is
staggered so that an inner arm will not obstruct pivoting motion of an
adjacent outer arm, or vice versa, when the rigging arms are moved
between the extended and flexed positions.
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Since splint 10 is pre-assembled and each setting of adjust-
went frame 34 is independently adjustable, splint 10 may be quickly and
precisely adjusted or readjusted to suit the needs of a particular patient,
or to fit on to a new patient. Prior art splints typically require a very high
degree of time-consuming custom fitting and suffer from the drawback
that a change in one setting (for example, the position of an elastic finger
sling) necessitates a change in many other interrelated settings of the splint
(for example, the position of an outrigger platform).
As will be apparent to those skilled in the art in the light of
the foregoing disclosure, many alterations and modifications are possible
in the practice of this invention without departing from the spirit or scope
thereof. Accordingly, the scope of the invention is to be construed in
accordance with the substance defined by the following claims.
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