Bone plate system for opening wedge proximal tibial osteotomy

A system for performing proximal tibial or femoral osteotomies. The system includes a plurality of bone plates of various sizes, and a calibrated wedge tool for opening a resected tibial wedge and determining the size plate to use in the osteotomy.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a system for performing proximal tibial 
osteotomies. 
2. Description of the Related Art 
Tibial osteotomies are performed to correct certain deformities. High 
tibial osteotomies (HTO) are indicated by early, medial joint-space 
narrowing, by early arthritis in patients who have had previous medial 
meniscectomy, or following rupture of the anterior cruciate ligament (ACL) 
in patients with pre-existing varus deformity, for example. 
There are two schools of thought regarding osteotomy methods: the closing 
wedge method, and the opening wedge method. In the closing wedge method, 
removal of a bone wedge creates an angled gap in the bone. Part of the 
bone is left as a hinge at the apex of the angle. The hinge allows the gap 
to narrow, and the bone material on either side of the closed gap joins 
together. 
In the opening wedge method, a cut is made across the bone. Part of the 
bone is left as a hinge, as in the closing wedge method. In contrast to 
the closing wedge method, however, the hinge allows the cut gap to open. 
The open wedge is filled with graft material. 
The two methods are performed on opposite sides of the bone to give 
equivalent results. For example, when a given deformity would be corrected 
by performing the opening-wedge procedure on the medial side of a bone, an 
equivalent closing-wedge correction would be performed laterally. 
The closing wedge method is the current standard, although several 
disadvantages are associated with the technique. The most significant 
disadvantages of the closing wedge method are: (i) disruption of the 
tibial-femoral joint; (ii) possible damage to neurovascular structures; 
and, (iii) disruption of the medial cortex, resulting in instability and 
nonunion between the upper and lower bone because of possible soft tissue 
interference. It is also difficult to compute the correct amount of bone 
to remove, and, therefore, several extra cuts may be required. 
The opening wedge technique avoids or limits many of the disadvantages 
associated with the closing wedge method. Additionally, the medial, 
open-wedge HTO has the following advantages over the closed, lateral-wedge 
HTO: (i) speed; (ii) simplicity; (iii) ability to quickly change angle at 
any time during the procedure; and (iv) no fibular osteotomy is required. 
Nevertheless, only a few surgeons are currently using the opening wedge 
procedure. This is most likely due to a lack of proper instrumentation. 
Thus, a need exists for proper instrumentation to perform the opening 
wedge technique. 
SUMMARY OF THE INVENTION 
The present invention overcomes the disadvantages of the prior art and 
fulfills the above-described need by providing a bone plate system for 
performing the opening wedge osteotomy technique. The bone plate system of 
the present invention includes two basic components: a forked-wedge tool 
for opening the wedge, and a set of bone plates for maintaining the wedge 
opening. The tool and the bone plates are designed to allow bone plate 
insertion while the tool is in place. 
Each bone plate includes a distal projection having a length and a depth. 
The depth of the projection preferably is 4 mm. The system preferably 
includes five bone plates, and the length of the projection on each bone 
plate is 5 mm, 7.5 mm, 10 mm, 12.5 mm and 15 mm, respectively. 
According to a preferred embodiment of the invention, each of the ends of 
the bone plates has a screw hole. The holes are counterbored to receive 
bone screws for securing the plates to the tibia, and the proximal side of 
the plate is curved distally to conform with the tibial surface. 
The wedge tool is forked at a distal end, and has a handle at a proximal 
end. The two ends preferably share a common, longitudinal axis. The fork 
is wedge-shaped and preferably includes two prongs having a 
linearly-tapered thickness. The two prongs are separated from each other 
by a distance greater than the width of the bone plates. Preferably, the 
tapered thickness of the wedge is calibrated in relation to the length of 
the bone plate projections. 
The present invention also provides a method of correcting a deformity by 
performing an osteotomy using the aforementioned bone plates and 
forked-wedge tool. A tibial osteotomy is performed according to a 
preferred method of the present invention by forming an incision over the 
tibia, and resecting the tibia from the medial side toward the lateral 
side so as to leave a bony hinge on the lateral side. 
Preferably, a pin is inserted into the tibia prior to the resection, from 
the medial side to the lateral side, to guide the tibial resectioning. 
Insertion of the pin is performed under fluoroscopic control. The pin 
preferably is a 4 mm Steinmann pin that is placed from the medial side to 
the lateral side following a path beginning approximately 3 to 5 
centimeters below a tibial-femoral joint line on the medial side of the 
tibia, and ending at a point approximately 1 to 2 centimeters below the 
joint line laterally on the tibia. 
The resection is wedged open with the tool by inserting the tapered prongs 
to a depth at which the deformity is corrected. The calibrated wedge 
enables the surgeon to determine what size spacer is needed and to pick 
the appropriate bone plate. This helps to prevent disruption of the 
tibial-femoral joint. 
Once the correct opening is established by insertion of the wedge tool, a 
bone plate is selected which has a projection length equal to the 
thickness of the tool at the deformity-correcting depth. The selected bone 
plate is then placed between the two prongs of the tool, and the 
projection of the bone plate is inserted distally into the resection 
opening. 
With the bone plate projection inserted in the resection opening, the screw 
holes are located above and below the resection opening. Bone screws are 
inserted through the screw holes to secure the plate to the tibia. The 
forked tool is removed, and autologous bone is packed into the resection. 
The bone plate, in conjunction with the autologous-bone graft filler, 
provides an effective means of eliminating the deformity. Further, the 
procedure is performed on the medial side, thus making it easier, faster 
and more reproducible than previous methods. 
Other features and advantages of the present invention will become apparent 
from the following description of the invention with reference to the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIGS. 1 and 2, the bone plate system of the present 
invention consists of a set of five stainless steel plates 2 each 
including two holes 4 at opposite ends for receiving AO cortical or 
cancellous screws, and a projection 6. The plates have projections of 
various lengths A (5 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm). The correct 
plate is selected such that projection 6 interposes into the osteotomy in 
accordance with the degree of axial correction desired by the surgeon. The 
height B of the projection is preferably 4 mm. Once the plate is 
synthesized at the site, the projection prevents the osteotomy from losing 
the obtained correction. 
The bone plate has a proximal surface 8 which preferably is curved as shown 
in FIG. 1 to conform generally with the surface of the tibia. Each of the 
two holes 4 has a tapered counterbore 10 for receiving the head of a bone 
screw. Preferably, a cancellous screw is used in the proximal hole, and a 
cortical screw is used in the distal hole. Bone plate 2 has a width C that 
is sized to be accommodated by an insertion tool, described below. 
Referring now to FIGS. 3 and 4, the system further includes a forked, 
wedge-shaped insertion tool 12. Tool 12 includes a head 14 and a handle 
16, preferably made of stainless steel or other surgically acceptable 
material. 
Tool head 14 includes two prongs 18 having smooth, linearly-tapered faces. 
Prongs 18 define an opening having a width D which is greater than the 
width C of bone plate 2. The opening extends into recess 20 which is 
disposed proximally to the end of the inclined faces. Prongs 18 are 
calibrated in millimetric graduations 22, which allows the surgeon to 
obtain the desired correction and easily determine the correct size bone 
plate. 
Surgical Technique 
The method of performing an opening wedge osteotomy in accordance with the 
present invention will now be described. Prior to the surgery, full length 
standing AP and lateral x-rays are obtained and correction angles are 
measured and marked on the x-rays to determine the appropriate size plate 
needed. A routine arthroscopy is performed and general joint debridement 
is carried out. Any osteochondral defects are penetrated using Arthrex 
Chondro picks (available from Arthrex, Inc. of Naples, Fla.) and a 
standard micro-fracture technique. A 4 cm. skin incision is made over the 
pes anserinus insertion and the medial collateral ligament is incised. 
The following surgical steps are then performed: 
1. The patient is prepped and draped in the usual fashion, keeping in mind 
that intra-operative fluoroscopy will be used on the lower extremity. 
Prophylactic antibiotics are given at the surgeon's discretion. 
2. An antero-medial incision is made over the tibia 3 to 5 centimeters 
below the joint line. 
3. Referring to FIG. 5, a 4 mm Steinmann pin 26, which will act as an 
orientation marker, is drilled from medial to lateral starting at 
approximately 5 mm superior and 2.5-3.0 cm medial to the tibial tubercle 
and exiting approximately 1 cm inferior to the lateral tibial plateau. 
4. Using a wide, thin osteotome 28, as shown schematically in FIG. 6, the 
tibia is resected along the same plane as the previously placed Steinmann 
pin, using the pin as a guide, taking care to leave a bony hinge on the 
lateral side. An oscillating saw may be used to resect the tibial cortex 
superior to the marking guide pin in the tibial tubercle. The wedge is 
then completed using the osteotome. The lateral cortical wall is not 
resected but is left intact to act as a hinge for the medial osteotomy. 
Pin 26 is removed after completing the osteotomy. 
5. The osteotomy site is then carefully opened using the calibrated forked 
wedge tool 12. See FIG. 7. The medial open wedge is created by inserting 
the calibrated wedge tool in the opening to the desired depth to create 
the required medial opening. The forked wedge tool 12 is inserted into the 
osteotomy until the deformity is corrected. Calibrations on the side of 
the tool make measuring the width of the osteotomy quick and easy. Once 
the necessary correction angle has been obtained, the osteotomy plate 
containing the appropriate spacer is selected from the implant tray. 
6. Referring to FIG. 8, bone plate 2, of appropriate thickness, is then 
placed in the opening of the fork with one screw hole 4 above the 
osteotomy site, and the other below. The plate is then secured to the bone 
with bone screws, using standard AO technique. Once the plate is 
positioned and the bone graft is inserted, fixation is obtained by 
inserting a cancellous screw in the proximal hole and a cortical screw in 
the distal hole. 
7. The forked wedge tool is then removed and autologous bone is packed into 
the defect. See FIG. 9. If the gap in the corrected tibia is 7.5 mm or 
less, autograft bone is taken from the tibia. If the gap is wider than 7.5 
mm, the bone graft is taken from the iliac crest. This provides a good 
osteosynthesis and a correction that does not reduce in time. 
8. The wound is closed in the usual manner. The medial collateral ligament 
is then repaired and the skin incision is closed. 
Limited weight bearing for six weeks, or until adequate callous formation 
can be determined, is advised. 
Post-operative Rehabilitation 
The patient is placed in either a cast or full leg brace (non-weight 
bearing) based on surgeon preference and rehab is carried out for about 30 
days with patient progress determined by bone-healing times indicated by 
progressive x-ray follow up. 
A combination ACL reconstruction and open wedge HTO is not contraindicated 
and may be performed when necessary. The arthroscopy is performed as 
previously described and the remnants of the ACL are completely resected 
followed by a standard notchplasty. Either a patellar tendon or 
semitendinosus autograft technique may be used. Positioning and fixation 
of the HTO plate is carried out more posterior in these cases to allow 
room for the tibial tunnel. Tibial tunnel creation can be carried out 
using a coring reamer as disclosed in U.S. Pat. No. 5,423,823 (the 
disclosure of which is herein incorporated by reference), and the bone 
core is used as osteotomy autograft material if not used to build a 
bone-hamstring construct. Interference screw fixation of the graft in the 
tibia can be performed, but placement of the screw should be made opposite 
the osteotomy incision line in the anterior medial tibia to prevent 
conflict with placement and fixation of the HTO plate. Rehab is as 
previously indicated with non-weight bearing for 30 days and range of 
motion as dictated by the ACL reconstruction. 
The above-described technique and bone plate system can also be used to 
perform femoral osteotomy. Post-op rehab requires a minimum 45 days 
non-weight bearing in these cases, however. 
The present invention is unique in that it uses a calibrated wedge to 
determine what size spacer is necessary to eliminate the previous 
deformity. No other known device uses spacers. Not only is the method easy 
to perform, but it more accurate than other known methods. 
Although the present invention has been described in relation to particular 
embodiments thereof, many other variations and modifications and other 
uses will become apparent to those skilled in the art. It is preferred, 
therefore, that the present invention be limited not by the specific 
disclosure herein, but only by the appended claims.