Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Utility Patent
1997-08-29
2001-01-02
Milano, Michael J (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S017110, C623S018110, C623S021110
Utility Patent
active
06168631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods and devices for correcting foot disorders, and more particularly to methods and devices for correction of pediatric pes valgus and adult posterior tibial dysfunction deformity by reducing calcaneal eversion.
2. Description of Related Art
As early as 1946, surgeons have been attempting to apply the arthroereisis concept to the subtalar joint to correct severe collapsing pes valgo planus. One early method was to remedy abnormal excursion of the talus on the calcaneus with the talus contacting the floor of the sinus tarsi by using an “abduction block” procedure. During the abduction block procedure, a wedge-shaped bone graft was impacted into the anterior leading edge of the posterior facet of the calcaneus. Impacting such a bone graft prevented excessive inferior displacement of the talus upon the calcaneus, thus limiting the amount of excess pronation of the subtalar joint.
A pronation limiting osteotomy inter form of a lateral opening wedge of the posterior facet was developed for treatment of “flatfoot” in cereal palsy patients in 1964. In order to prevent interfering with subtalar joint motion, a wedge-like bone graft was used to improve the weight-bearing alignment of the calcaneus. In 1970, an accessory bone graft placed in the sinus tarsi was developed as a corrective procedure. Later, the bone graft was replaced with a silastic plug. As early as 1976, a high molecular weight polyethylene plug was developed. The plug is cemented into the calcaneal sulcus against a resected portion of the posterior calcaneal facet. This procedure, known as “STA-peg” (subtalar arthroereisis-peg), is today a commonly used subtalar joint arthroereisis procedure. STA-peg does not block excessive pronation, but rather alters the axis of motion of the subtalar joint.
Also in 1976, a high-molecular-weight, polyethylene, threaded device known as a “Valenti Sinus Tarsi Arthroereises Device” was invented. The procedure used implant the Valenti device is commonly referred to as the “Valenti” procedure. Unlike the STA-peg procedure, the Valenti procedure is an extra-articular procedure that involves placing the Valenti device into the sinus tarsi to block the anterior and inferior displacement of the talus. Such placement of the Valenti device does not restrict normal subtalar joint motion, but does block excessive pronation and resulting sequelae. The Valenti device has a frusto-conical shape and threads on the outer surface of the device which allow it to be screwed into the sinus tarsi. As a consequence of the shape of the Valenti device, the greater the penetration of the device into the sinus tarsi, the more the sinus is dilated and the more calcaneal eversion is eliminated.
However, several problems reduce the desirability of the Valenti procedure and device. For example, the Valenti device is manufactured from polyethylene which must be gas-sterilized prior to use and which allows the device to deform under the compressive pressure to which it is subjected under normal post-operative conditions. Furthermore, because of its fresto-conical shape and the manner in which it is inserted, it is difficult to precisely locate the device and ensure that the proper amount of calcaneal eversion has been eliminated. Still further, it is generally difficult to locate the device properly within the tarsal canal because the implant must be threaded at least 3 to 5 millimeters medial to the most lateral aspect of the posterior facet for correct placement. Because of its polyethylene construction, the device cannot be imaged using radiography (X-ray) to determine whether the proper position has been achieved.
Accordingly, it is an object of the present invention to provide an implant which can be easily located within the tarsal canal, which would not deform under post-operative compressive forces, which would ensure the proper amount of calcaneal eversion has been eliminated after insertion of the implant, and which can be imaged using radiography to determine whether the implant has been properly positioned during the procedure.
SUMMARY OF THE INVENTION
The present invention is a system including a subtalar arthroereisis implant for use in reducing calcaneal eversion, blocking anterior and inferior displacement of the talus, and blocking excessive pronation and the resulting sequelae, while allowing normal subtalar joint motion. The present invention also includes instruments and a method for inserting the implant.
The implant is preferably a generally cylindrical, or barrel shaped device having threads on the exterior surface. In addition, the implant preferably has slots formed in the threaded surface. The slots make the implant resilient and allow the implant to dissipate forces impacted upon the implant. Accordingly, stresses encountered by the implant are reduced. Another benefit of the slots and threads is that fibrous tissue will readily attach to the implant, thus aiding in securing the implant within the sinus tarsi. The implant is preferably fabricated from a titanium based alloy. Thus, the implant can be imaged in radiographs, making proper placement of the implant more discernable. Furthermore, the use of a titanium based alloy reduces the likelihood that the implant will deform under normal post-operative compressive forces.
In accordance with the preferred embodiment, the implant generally has a uniform radius along a central longitudinal axis. This allows strict control over the amount of calcaneal eversion to be eliminated and is not directly related to the location of the implant within the tarsal canal. That is, if the implant is properly located within the sinus tarsi, then the exact number of rotations of the implant will not affect the amount of dilation that occurs as a result of the implant. In addition, the implant is preferably cannulated to allow the implant to be mounted upon a guide device for positioning.
In the preferred system, most of the instruments which must be inserted into the tarsal canal are cannulated, such that the instruments, and the implant itself, can be guided through the canal by a guide device. A selection of differently sized implants are available to the surgeon performing the implantation. To begin the procedure, the tarsal canal is exposed by applying a scalpel or laser to the site, or by any other technique which allows access to the tarsal canal. A probe is used to slightly dilate the tarsal canal. Once the tarsal canal has been dilated by insertion of the probe, a first cannulated “sizer” is inserted into the sinus tarsi. Sizers preferably range from approximately 6 mm to approximately 12 mm, but other sized sizers may be used. The sizers are used to estimate the proper size implant. A guide device is inserted through the tarsal canal. The device is preferably relatively thin and thus may be inserted through the tarsal canal relatively easily. The guide device is placed into the cannulated sizer and inserted into the sinus tarsi together with the sizer. The sizer is removed, leaving the guide device in the patient.
Once the proper size implant has been estimated, a trial implant is preferably inserted into the sinus tarsi. In accordance with the preferred embodiment, the trial implant is not slotted in order to allow for ease of cleaning and resterilization. In addition, the trial implant may be manufactured from a material which is less costly than the titanium alloy which is preferably used for the actual implant.
To insert the trial implant, a generally conical shaped “nose cone” is preferably placed on the guide device to clear the sinus tarsi ahead of the implant. The trial implant is placed on the guide device directly behind the nose cone. A cannulated hex head driver, which mates to the trial implant, is preferably used to bring the cone and the insert into contact with the sinus tarsi, allowing the surgeon to screw the trial implant into place within the sinus tarsi.
Once the trial implant is in place, a determination can be made as to whether the implant is
Brancheau Steven P.
Maxwell Jerry R.
Baker & Maxham
Kinetikos Medical, Inc.
Milano Michael J
LandOfFree
Subtalar implant system and method for insertion and removal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Subtalar implant system and method for insertion and removal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Subtalar implant system and method for insertion and removal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2483210