The principal object of the locking nail system for arthrodesis reconstruction of calcaneus fractures is the reconstruction of severe comminuted fractures of the calcaneus in humans and fixation of this bone after reconstructing its principal form, to the talus, in order to attain arthrodesis or fusion with the latter.
Chronic residual pain is the most common sequela following comminuted talar fracture of the calcaneus. There may be multiple causes of this problem: compartment syndrome, reflex-sympathetic dystrophy, plantar cushion syndrome, tarsal and peroneal canal syndrome and subtalar arthritis. This latter cause has been found to be responsible for the majority of poor long-term results of current treatment of these fractures.
Talar fractures account for 8-10% of tarsal tunnel syndrome, particularly in the lateral plantar nerve branch, and for 78% of peroneal nerve entrapment (external submalleolar pain). In 70% of these severe fractures there is chronic pain caused by the posterior subtalar joint, which normally becomes ankylosed after trauma.
Although the latest publications support the results of open reduction and internal fixation of calcaneus fractures, orthopaedic treatment still has many defenders. In other cases, the adoption of an initially conservative philosophy is chosen, treating sequelae if they appear. Like Barnard and Odegard, we believe that perfect restoration of the subtalar joint is impossible.
Numerous arthrodesis techniques have been disclosed for the treatment of post-traumatic subtalar arthritis, including prosthetic replacement. In other cases, triple arthrodesis has been advocated over isolated subtalar fusion, in order to improve foot biomechanics and to prevent degeneration of adjacent joints. According to different reviews conducted in hospitals, isolated arthrodesis of the subtalar joint does not cause degeneration of adjacent joints, even after many years of evolution.
This experience has led to the belief that the old postulations of Stulz and Noble may provide the key to a fracture that has yet to be resolved. Since the subtalar joint cannot be surgically reconstructed in the most severe fractures, and always degenerates, the solution would be to arthrodese it immediately during the acute period in order to prevent the disabling sequelaes that appear during later evolution.
But in addition to fusing the damaged joint, an attempt should be made to reconstruct the form of the hindfoot as far as possible, in order to avoid other associated complications such as compartment syndrome, reflex-sympathetic dystrophy, plantar cushion syndrome and tarsal and peroneal canal syndromes, that would clearly benefit from fracture reduction.
The Spanish patent with publication number
The document
In order to alleviate the aforementioned problems, this new locking nail system is presented for arthrodesis reconstruction of calcaneus fractures, which is the object of the present invention patent.
Hence, the invention relates to a locking nail system for arthrodesis reconstruction of calcaneous structures as defined in appended claim 1, comprising a nail, two calcaneous-talar screws, a guide, an applicator guide and two guide tubes, wherein the nail has a blunt end having a threaded hole in order to incorporate the applicator guide; said nail having two through holes through which the calcaneous-talar screws can be positioned in order to arthrodese the subtalar joint; the calcaneous-talar screws are cannulated in order to be guided by the guide tubes, and they are threaded at the distal end for fixation in the spongy bone of the talus; the guide comprises a principal support that has a guide hole at the top, said guide hole having a geometry mating to the exterior geometry of the nail, in order to introduce the nail by means of the applicator guide, and at the bottom the guide has a wad with two holes through which the guide tubes can be passed to permit the calcaneous-talar screws to be inserted in the calcaneous-talus; wherein the nail is a cylindrical geometrical part with a tapered point, and wherein the guide has a grip that is connected to a jaw adapted to be attached to a guide pin placed in the talus, said guide pin defining a reference axis which is transverse to a plane defined by the axis of the guide hole and the axis of one of the holes of the wad, said guide pin serving as a support to adjust the position of the nail and the calcaneous-talar screws by means of a handle, that is situated at the end of the grip.
Preferred embodiments of the invention are now claimed in the dependent claims 2 to 12.
The system consists of the layout of a cylindrical nail with two stabilising fins, a tapered point and two threaded holes, that is inserted into the greater tuberosity of the calcaneus. Likewise, it consists of two cannulated screws that are screwed into the nail holes, inserting them in the talus until they are locked in the nail, thus stabilising the whole assembly, increasing its rigidity and resistance to loads to which it will be subjected.
The use of cannulated screws for arthrodesis of the subtalar joint is a known and implanted technique that offers amongst the best results for the treatment of this type of fracture. The locking nail system for arthrodesis reconstruction in calcaneus fractures, which is the object of the present invention patent, offers a marked improvement in the technique that is habitually employed, because of the insertion of a nail that both supports and locks the said screws, thus making the system more stable and secure, and preventing failure from screw migration. In this way, the foot recovers its natural anatomy, repairing the relationship between the calcaneus and the talus and thus recovering its biomechanical function.
In order to complement this description, and with the aim of contributing to a greater comprehension of the characteristics of the invention, this specification is accompanied by a series of drawings that form an integral part of the same. These drawings are of an illustrative and not limiting nature, and show the following:
As can be observed in the attached figures, the locking nail system for arthrodesis reconstruction in calcaneus fractures is comprised of the following components: nail (1), screws (2) calcaneus-talar guide (3), guide tubes, bit, depth gauge, cannulated screwdriver, diapason impactor, bit with limiter and reference guide-pin.
The nail (1) is a cylindrical geometrical part with a tapered point, in order to facilitate insertion. Its blunt end has a threaded hole (12) and a groove (13) in order to incorporate an insertion guide (33). Likewise, it has two lateral fins (14) to stabilise the implant and prevent it from rotating. The nail (1) has two through holes (15 and 16) that are partially threaded and set at an angle of 10° to the horizontal shaft, in order to arthrodese the subtalar joint by means of the screws (2).
The calcaneus-talar screws (2) are cannulated (22) in order to insert them with the guide tubes. They are threaded (21) at the distal end for fixation in the spongy bone of the talus. The tip is self-perforating and self-threading in order to facilitate its insertion by means of an optimum torque. The head has a metal thread for fixing it in the nail (1) and it has a hexalobe-type connection that guarantees a more efficient turning action. Preferential length of the screws (2) is not less than 60 mm and not greater than 90 mm.
The guide (3) is an instrument that is used to place the different components in the system in situ, and it is comprised of a principal support (31), that has a guide hole (32) at the top, with the exterior geometry of the nail (1), in order to introduce the same by means of an applicator guide (33), which has a projection (34) at the end that fits into the recess (13) of the nail (1), such that its fixation is guaranteed, preventing rotation movements. Furthermore, the applicator guide (33) has a longitudinal cotter (35) that permits placing the nail (1) at a good angle in the calcaneus, through the guide hole (32).
The lower part of the guide (3) has a wad with two holes (36) that are placed at a 10° angle with respect to the horizontal shaft, in order to pass through the whole system of cannulas and instruments that permit the screws (2) to be placed in the calcaneus-talus.
The guide (3) has a grip (38) that, in addition to serving as such, is connected to the jaw (37) that is attached to a pin that has been previously placed in the talus and that serves as a reference axis and as a support to adjust the position of the nail (1), by means of a handle (39) that is situated at the end of the grip (38).
The guide tubes must be embodied in duplicate except for the trocar tip, permitting suitable guidance and direction of the different instruments used to prepare the bed and position the screws (2). The instruments used to prepare the bed are the guide-pin, the cannulated bit with a diameter corresponding to the nucleus of the screws (2), and the screws themselves (2). Therefore, three guide tubes of different diameters are necessary, and the trocar tip. Other elements used by the system are the depth gauge to determine the length of the screws (2), the cannulated screwdriver to insert the screws (2), the diapason impactor to strike the nail (1), the bit with limiter to work the nail bed (1) and the reference pin for the guide support (3).
The implantation of the locking nail system for arthrodesis reconstruction in calcaneus fractures, object of the present invention patent, is embodied as follows:
First, and after opportune surgical procedures, the guide-pin is placed in the centre of the talar head. The guide-pin is the spatial reference for the nail instrumentation (1). It is placed from the internal face of the foot, locating the centre of talar head by radiological means. The guide-pin should be positioned on the frontal plane parallel to the ankle joint interline, and on the axial plane, perpendicular to the foot shaft. Surgery should not be continued until it is verified that the guide-pin is in the correct position.
The guide (3) is initially supported by the guide-pin situated in the talar head, and then the guide (3) is initially adjusted to the greater tuberosity using the handle (39) situated at the end of the grip (38).
A radiological control is performed on the position, using guide-pins to simulate the direction of the screws (2) by inserting them in the holes (36) made for this purpose in the guide arms (3). These pin-guides will indicate the position of the definite screws (2). If they do not sit appropriately in the talar head, the guide (3) will have to be re-positioned.
At this stage, the guide permits the calcaneus axis to be distracted using the handle (39) and grip (38) and it also permits flexion-extension movements to be applied to the same, by mobilising the guide (3), using the guide-pin placed in the talar head as an axis. Then, a hole is drilled to house the nail (1) in the greater tuberosity. If the guide (3) is in the correct position, drilling of the greater tuberosity is not a problem. Drilling should continue as far as the bit limiter. The only precaution to take is to protect the Achiles tendon adequately.
In some cases, the severity of the comminuted fracture means that drilling will be effected on fractured bone. This situation does not pose any disadvantage for inserting the implant as the latter does not require intact bone for correct functioning. When the bit is removed, it should continue to revolve in order to extract bone dislodged during drilling. The drilling direction should not be inverted. In the majority of cases, this bone will be sufficient for the graft in the subtalar arthrodesis.
The nail (1) is held by the guide (3) and is placed in the previously marked channel. The nail (1) is inserted by hammering. The guide (3) will direct the nail towards the lower zone in the greater tuberosity where it will be inserted in the plantar fascia. The nail (1) must be completely inserted up to the applicator limiter, thus attaining correct alignment of the holes of the screws (2) and the guide (3) that applies the same.
With the guide tubes in position on the guide (3), the surgeon makes a small incision reaching the bone. The guide-pin is inserted. The length of the screws (2) is measured with the depth gauge. After the guide-pin, the 4.5 mm cannulated bit is inserted. The screws (2) are then positioned. When the system is in position, the bone extracted from drilling the nail (1) is applied.
Having sufficiently disclosed the nature of the present invention, as well as the practical embodiment of the same, the only thing to add is that said invention may undergo certain variations with respect to form and materials, provided that such alterations do not substantially change the characteristics that are claimed below.
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