Dynamic splint for post-operative treatment of flexible implant arthroplasty of the fingers

An improved splint for post-operative treatment of a patient following flexible implant arthroplasty of the fingers. The splint is sizeable to a patient's hand, and features controls for the degree of flexion and extension of each finger, as well as for the alignment of the splint with the natural pivot axis of the finger joint(s) which have been repaired.

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 fingers. 
BACKGROUND 
The hands of patients suffering from rheumatoid or osteoarthritis 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 fingers. 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 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 regeneration. 
Accordingly, the support should be firm enough to minimize 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-consuming (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. 
Several hand splints are the subject of granted patents. U.S. Pat. No. 
4,602,620 discloses an outrigger splint with pulleys juxta-positioned to 
the fingers 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. Pat. 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. Pat. 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. Pat. 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 finger. 
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 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 pre-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. 
SUMMARY OF INVENTION 
In accordance with the invention, a splint for post-operative treatment of 
a patient following flexible implant arthroplasty of the fingers 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 finger support for engaging at least one 
finger of the patient, wherein the finger support is moveable about a 
pivot axis to permit movement of the finger between extended and flexed 
positions; and an adjustment frame coupling the finger support to the 
brace for adjusting the position of the pivot axis until it intersects the 
finger joint. The splint thereby ensures that the axis of movement of the 
finger support is approximately aligned with the natural pivot axis of the 
finger 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 sidably 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 finger support is preferably pivotally coupled to a forward end of the 
adjustment frame, such as a forward end of a corresponding side bar. The 
finger support may be biased toward the extended position. A flexion lock 
is provided for releasably locking the finger 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 finger 
support in the extended position is also provided. 
The finger support may consist of at least one rigging arm pivotally 
coupled to a side bar and extending inwardly therefrom above a finger of 
the patient in the extended position, and a sling adjustably connectable 
to the rigging arm for supporting the patient's finger. The finger support 
may further include a spar sliding 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 sidable longitudinally on 
the spar. The sling is detachably connectable to the spar. Preferably each 
finger support comprises a pair of rigging arms independently pivotable 
relative to a side bar, wherein the rigging arms extend at different 
elevations above the fingers of the patient in the extended position. The 
splint is ordinarily configured so that it includes a pair of finger 
supports pivotally coupled on opposite sides of the adjustment frame.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
This application relates to a hand splint 10 for the post-operative 
treatment of flexible implant arthroplasty of the fingers, principally 
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 FIGS. 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 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 FIGS. 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 (FIG. 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 FIGS. 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. 
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 sidably 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 (FIG. 6). Each side frame 42 may be releasably locked to 
bar 40 at a selected position using a first cam lock 46 (FIGS. 3 and 4). 
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 sidably 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 (FIG. 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 FIG. 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 FIG. 1 for supporting the patient's MCP joints in an 
extended position. In one embodiment of the invention, 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 FIG. 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 (FIGS. 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 FIG. 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. Flexion locks 64 restrict 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 FIG. 1, thereby allowing rigging arms 56 to pivot 
freely. The bias of extension assist spiral torsion springs 58 returns the 
rigging arms to the extended position of FIG. 1, thereby applying a small 
extension force to each finger. 
As shown best in FIG. 7, each finger support assembly 54 further includes a 
pair of spars 70 which are sidable 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 FIGS. 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 sidable 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 (FIGS. 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 FIG. 7. An alternative design (not shown) for sling holder 78 will 
include a lockable sliding joint (i.e. a fourth cam lock). 
As should be apparent from FIG. 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 (FIG. 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 
palmer 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 80 are positioned for right or left hand use. 
The spacing between opposed side frames 42, which are 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, this pivot axis should be set slightly higher than the axis 
of the patient's relaxed hand to compensate for upwardly directed 
extension forces applied to the patient's fingers when they are fitted 
into splint 10 as described below. 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 holds a respective finger on the ulnar side. Sling 
lower portion 84 supports the finger in extension and positions the finger 
in flexion. 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 the 
shaft of the proximal phalanx as close to the proximal interphalangeal 
joint as comfort allows, as shown best in FIG. 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 
interphalangeal 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 (FIG. 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 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 FIG. 7) 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 minimize 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 (FIG. 1) and flexion 
(FIG. 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. 
Since splint 10 is pre-assembled and each setting of adjustment 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.