A link for connecting surgical rods to bone comprises a bone connector such as a bone screw or a bone hook, and a head connected to one end of the bone connector. The head defines an outwardly facing first recess for receiving a portion of a surgical rod which extends transversely of the link and occupies the first recess. A cover is proportioned to fit in a position to cover the surgical rod portion occupying the first recess. A hinge member is carried by the cover and head, to permit vertical pivoting retention between the cover and the head on one side of the recess. A closure on the cover and head is provided at a position opposed to the hinge member. Specifically, the closure may comprise aligned holes, plus a set screw to provide locking closure between the cover and head with a surgical rod extending through the first recess.

BACKGROUND OF THE INVENTION 
In the field of orthopedics, spinal rods are often implanted on at least a 
temporary basis to hold and support spines for various medical reasons. 
For example, curvature of the spine may be corrected by means of a rod, 
and severe fractures may be dealt with by providing support through one or 
more rods. 
These rods are connected to the spine by means of known spinal hooks or 
spinal screws, for example, open screws or closed screws. Open screws 
define a head and a separable cap or cover to capture the rod between them 
onto the screws. The head itself defines a U-shape which terminates in 
lipped edges, being attached to the screw. Channels on the cap slide 
laterally onto and along the lipped edges of the U-shaped head of the 
screw to capture the spinal rod between them. Spinal hooks may carry heads 
of similar design, and are included by implication in the further 
discussion of the prior art. 
Disadvantages exist in this construction. First, the spinal screws must be 
placed into various vertebra of the spine, and then the rod is placed into 
recesses defined by the U-shaped heads on the ends of the screws. However, 
typically, the spinal rods must be deeply seated into the U-shaped heads, 
or the cap can be applied with the lateral sliding application only with 
great difficulty. If the rod is not completely seated, but is spaced from 
the bottom of the U-recess of the spinal screw, the surgeon may find it 
nearly impossible to apply the cap by the lateral sliding action 
previously described. 
Also, in the prior art spinal screws, a set screw is provided at the center 
of the cap. This set screw initially projects upwardly, and then is 
screwed to move downwardly into frictionally retentive relation with the 
spinal rod within the U-shaped head and the cap. It is desirable for the 
length of the spinal screws to be at an absolute minimum so they fit into 
the surgical incision without the need to enlarge the incision. The 
positioning of the set screw in the prior art undesirably increases the 
vertical profile of the spinal screws. 
Also, in the conventional, open spinal screws described above, lateral 
retention force is provided to the rod by the set screw, forcing the rod 
deeply into the engagement with the walls of the U-shaped recess of the 
screw head. However, a substantial portion of the periphery of the rod 
within the screw head is not held under compressive contact by either the 
set screw or the recess walls. Thus, the possibility of frictional 
slippage of the spinal rod is substantial with respect to conventional 
spinal screws. 
Another type of spinal screw is the closed screw, where the screw head 
carries a preformed aperture without a removable cap. A set screw, coaxial 
with the bone screw, then presses the rod within the aperture of the screw 
head against an opposed aperture wall for retention of the rod. 
Closed screws exhibit some disadvantages similar to the open screws. Also, 
it is of course impossible to apply a spinal rod laterally into engagement 
with a closed spinal screw. The end of the spinal rod must be threaded 
through the preformed aperture, and, in many surgical situations, that is 
not possible. 
The prior art also utilizes links for connecting surgical rods to bone in 
which a hook rather than a screw is used. Apart from that, a head is 
provided with an aperture which may be a preformed aperture, or may have a 
cap of the type described above. 
Another type of bone screw is disclosed in Vignaud et al. U.S. Pat. No. 
5,176,680. 
In accordance with this invention, a link is provided for connecting 
surgical rods to bone, in which the above disadvantages are effectively 
eliminated, providing substantially improved ease of installation during 
the surgical process, coupled with improved retentive characteristics 
shown by the links of this invention for connecting the surgical rods to 
bone. 
DESCRIPTION OF THE INVENTION 
In accordance with this invention, a link is provided for connecting 
surgical rods to bone, which link comprises a bone connector such as a 
screw. A hook may also be used as the bone connector, in which the hook 
extends around behind the bone, and is retained there by a degree of 
retention force generally provided by the rod to which the link connects. 
A head is connected to one end of the bone connector. The head defines an 
outwardly facing first recess for receiving a portion of a surgical rod. 
A cover or cap is provided, being proportioned to fit on the head in a 
position to cover a surgical rod portion that occupies the first recess. 
In one aspect of this invention, a hinge member is carried by the cover and 
head to permit vertical pivoting retention (assuming that the longitudinal 
axis of the link is vertical) between said cover and head, the hinge being 
positioned on one side of the first recess. A closure on the cover and 
head is provided at a position opposed to the hinge member to lock the 
cover and head together. Thus, the rod may be placed in the first recess, 
and the cover or cap brought vertically downward onto the rod by vertical 
pivoting action from the hinge as the cover is closed into retained 
relation on the head of the link. In so doing, the cover can press 
downwardly on the rod portion positioned in the first recess, more easily 
forcing the rod downwardly into fully seated relation with the recess. 
Thus, the cover is more easily closed and locked into position. 
Corresponding covers or caps of prior art bone screws must slide laterally 
along a track into their closed relation, possibly fighting a portion of 
surgical rod occupying the recess all the way, if the surgical rod is not 
well seated in the screw head. This is often the case in actual surgical 
experience, since it is difficult to perfectly align the various prior art 
bone screws in the patient so that the surgical rod is naturally well 
seated in all of them. 
The closure of the link of this invention may comprise aligned holes in 
each of the cover and head on a side opposed to the hinge member, to 
receive a screw of other connecting member to provide locking closure 
between the cover and head, with a surgical rod extending through the 
recess. 
The hinge member used in this invention may be a permanently connected 
hinge, or a hinge with separable components. It may preferably comprise a 
hook member carried by each of the head and cover. The hook members may 
then be separably engaged by the surgeon to define and form the hinge 
member, which then may be closed to lock the surgical rod in place. By 
such a technique, a smaller surgical incision may be possible, since there 
is no need to place the cover in a completely lateral position beside the 
head to slide it into locked position. Instead, one can simply engage the 
respective hooks of the head and cover at about a 45 degree angle or so, 
and then pivot the cover by the resulting hinge into the closed 
relationship. Also, the head and cover can laterally slide together into 
position in parallel relation if that is appropriate. 
Preferably, the cover may define a second recess which is proportioned to 
form a substantially cylindrical space with the first recess, when the 
cover occupies the position covering the first recess. Typically, both the 
first and second recesses may be substantially semi-cylindrical. Also, it 
is preferred for the first and second recesses to be sized so that the 
specific surgical rod used to occupy the recesses is held with compression 
about substantially the entire outer surface of the surgical rod portion 
which is within the first and second recesses. Thus, a larger area of the 
outer surface of the surgical rod is in frictionally retainer contact with 
the walls of the first and second recess and also the set screw, 
approximating 360 degree retention of the surgical rod. Accordingly, the 
force retired to cause either longitudinal or rotational slippage of the 
surgical rod in the link of this invention can be higher than the 
corresponding slippage force of the prior art links, where substantially 
less than 360 degree retention of the surgical rod is provided. 
As an important feature of the invention, the cap or cover comes down upon 
the surgical rod occupying the first recess in a longitudinal (vertical) 
manner, i.e., more or less parallel to the axis of the screw when screw 
threaded links of this invention are used, and in a corresponding 
direction when a link having a bone hook or another bone connector is 
used. This vertical application of the cover to the head of the link can 
force incompletely seated rods into complete seating. This can be done 
with much greater ease on the part of a surgeon, when compared with the 
closing motion of the prior art in which a spinal screw cap laterally 
slides along a pair of U-shaped prongs of the head, since the incompletely 
seated spinal rod will seriously interfere with the sliding action. 
However, preferred embodiments of the connecting links of this invention 
can still have their caps or covers also applied from a lateral rather 
than a vertical direction, if the surgeon desires to do that for any 
reason.

DESCRIPTION OF SPECIFIC EMBODIMENTS 
Referring to FIGS. 1-3, a spinal screw 10 is shown having a U-shaped head 
12, a bone-connecting, screw-threaded shank 14, and a cover 16. Head 12 
defines an outwardly facing, semi-cylindrical first recess 18 for 
receiving a portion of surgical rod 20. Cover 16 is proportioned to fit in 
a position to cover the portion of the surgical rod 20 which occupies 
first recess 18, as shown in FIG. 2. 
To accomplish this, a separable hinge member 22 is provided between head 12 
and cover 16 at one side of recess 18. Hinge member 22, in this 
embodiment, defines a separable hinge comprising a first hook member 24 
carried by cover 16 and extending substantially the length of cover 16 
(parallel to the axis of recess 18 and spinal rod 20 and perpendicular to 
screw shank 14). A second hook member 26 is defined by head 12, with hook 
26 also extending substantially the length of head 12, parallel to hook 
member 24. As shown in FIG. 2, the respective hooks 24, 26 interlock with 
each other to provide hinged retention when cover 16 is in or approaching 
closed position over head 12, and for a range of pivoting positions, so 
that cover 16 can be swung open or closed in hinged manner, as illustrated 
by FIG. 3. Nevertheless, cover 16 can be separated from head 12 as the 
bone screw 10 is being advanced into a bone 27 or the like. Then cover 16 
can be added to the system by connecting the respective hooks 24, 26 and 
closing the cover to the configuration of FIG. 2. 
Thus, cover 16 can be applied substantially vertically to the screw and 
head, the term "vertically", referring to the axial direction of the screw 
14. However, if desired, cover 16 can be applied from horizontal 
directions as well, so that the link of this invention is easily assembled 
while placed deep in a surgical incision, after the screw 14 has been 
inserted into a bone. 
Head 12 defines a threaded hole 28 on a side of the recess 18, which is on 
a side of head 12 opposed to hinge 22, spaced from recess 18. Cover 16 
defines an unthreaded hole 30, which is positioned to engage hole 28 when 
the cover 16 is in the desired, closed position as shown in FIG. 2, 
covering surgical rod 20. A set screw 32 may be initially carried in hole 
30, being blocked from falling through hole 30 by annular shoulder 33 
(FIG. 3) of hole 30 that engages head 35 of the set screw. Set screw 30 
may then advanced into threaded hole 28 to lock cover 16 into the position 
of FIG. 2. 
As a further advantage, it can be seen that set screw 30 is laterally 
positioned from outermost end 31 of link 10, and thus is longitudinally 
spaced from that end also because of the convex shape of the top of cover 
16. Set screw 30 thus is spaced from both ends of the link of this 
invention so that the vertical profile of the link can be reduced. In some 
links of the prior art, a set screw occupies a central, endmost position 
on the cover or cap of the link, being in coaxial relation with the screw. 
Here, the set screw is laterally displaced, and also spaced from the end 
31 of the link connector of this invention. 
Cover 16 also defines a second recess 34, which may be of substantially 
semi-cylindrical shape. As shown in FIG. 3, the first recess 18 and second 
recess 34 are brought together to form a substantially cylindrical space 
together with each other in the closed relationship between the cover and 
head. It is preferred for the dimensions of surgical rod 20 (which is 
typically a spinal rod) and recesses 18, 34 to be proportioned so that 
surgical rod 20 is held in the recesses 18, 34 with compression about most 
or all of the entire outer rod surface within the recesses. Because of 
this, a larger surface area of frictional retention is provided than in 
prior art bone-rod links, so that less slippage of the spinal rod either 
longitudinally or rotationally takes place in this present invention. 
Also, as cover 16 is pivoted into its closed relationship with head 12 as 
shown in FIG. 3, a substantial downward pressure can be easily exerted on 
spinal rod 20 to fully seat it into recess 18. This can be easily 
accomplished. Cover 16 is pulled into place by advancing set screw 32, 
even if there is some resistance provided by the spinal rod to closure. To 
the contrary, in many situations of the prior art where horizontal sliding 
of the head into locked position is required, the locking of the head into 
place can be a difficult proposition if the spinal rod 20 is not fully 
seated. 
Referring to FIG. 4, another embodiment of this invention is shown, 
specifically a spinal hook 40 which carries a head 12a which may be of a 
design similar to head 12 of the previous embodiment. A cover 16a may be 
placed on head 12a, with cover 16a being identical in design to cover 16, 
so that the advantages of this invention can be achieved with a spinal 
hook as well as a spinal screw or, for that matter, with any design of 
bone connector for retaining a head on a bone to receive and hold a rod. 
Recesses 18, 34 may be off center in head 12, 12a and cover 16, 16a to 
provide room for set screw 32 and the holes 28, 30. 
Accordingly, by this invention a link is provided for connecting surgical 
rods to bone, in which the attachable cover may be applied with 
significant advantages over the prior art surgical rods. Specifically, the 
substantially axial (vertical) direction of application of the cover 
provides significant advantages as described above, and may be a valuable 
feature, particularly since the cover is being applied to the head in the 
highly constrained environment of a surgical incision. However, if 
desired, the cover can be applied laterally if desired in the manner of 
some prior art bone screws, if circumstances dictate the need for that, 
but with much greater ease. 
The above has been offered for illustrative purposes only, and is not 
intended to limit the scope of the invention of this application, which is 
as defined in the claims below.