This invention relates to devices and methods used in spine surgery, particularly devices and methods used to attach spinal vertebrae to the paraspinal musculature after spine surgery.
One of the most common surgical procedures in the spine involves a decompression or laminectomy, which removes the muscular attachments of the paraspinal musculature to the spinous process and lamina (the posterior bony elements of the spine), and then the posterior bony elements of the spine, particularly the spinous processes and lamina. See
Upon closure of the wound at the end of spine surgery, the muscle layer is commonly closed with individual sutures that incorporate the muscle and fascia and the two split sides are sewn to each other. This closure technique can lead to muscular atrophy, involution of the overlying skin, cosmetic defects, and the loss of the integrity of the spine-ligament-muscular complex that provides integral stability to the spine. Instability of the spine has been documented to contribute, and in many cases, cause pain, deformity and dysfunction. Therefore, prior to undertaking surgery in the spine, virtually all patients are encouraged to undergo aggressive physical therapy with the goal of strengthening the muscular support and its attachments to the spine, and hopefully reducing pain and averting surgery in the first place.
There is a need for improved surgical devices and methods for spinal surgery which prevent or reduce the severity of deformity, dysfunction and/or pain following spine surgery.
Therefore it is an object of the invention to provide devices and kits for use in surgical procedures in the spine that improve the stability of the spinal column and/or prevent the development of cosmetic deformity following such procedures.
It is a further object of the invention to provide improved methods for increasing the stability of the spine following surgical procedures.
Devices, kits, and methods for stabilizing the spine and effectively replacing spinous processes that are removed during spine surgery are provided. The device has a suitable configuration to attach to hardware that is inserted into the patient's spine during surgery and to the paraspinal muscles and fascia. The device contains at least one muscle attachment portion and one or more connectors, in a preferred embodiment, the device also contains one or more cross connectors. Each connector is configured to attach to a cross connector. Each cross connector contains a pair of connection portions configured to attach to hardware that is implanted in the spine, such as screw heads or rods. The muscle attachment portion, also referred to as the fin portion, contains one or more muscle attachment areas that are suitable for the attachment, such as via suturing, of the paraspinal muscles and fascia. In one embodiment, the muscle attachment area contains a material that allows for suturing, such as a biocompatible textile (e.g. a synthetic polyester fabric, preferably formed from polyethylene terephthalate fibers, such as Dacron®), or a mesh material. In another embodiment, the muscle attachment area is a plurality of openings, such as plurality of holes. Optionally, the muscle attachment portion further comprises one or more drugs that are released following implantation over a period of time ranging from one week to five months, preferably ranging from one week to eight weeks.
Following spine surgery including the step of removing the spinous process in one or more vertebra(e), a surgeon can attach the device to the hardware implanted in the surgical site, and then attach the paraspinal muscles and fascia to the muscle attachment area of the muscle attachment portion, typically via sutures. Thus the device provides a direct attachment to the paraspinal musculature and fascia, and thereby further strengthens and stabilizes the spine. Use of the device also prevents or reduces the formation of cosmetic deformities as the spinal wound heals and prevents or reduces involution of the tissues following healing, which typically create a crater or valley effect in a patient's back following spine surgery. Attachment of the paraspinal muscles and fascia to the device also reduces the likelihood that the paraspinal musculature will attach to dura mater, the spinal cord and/or nerves following the surgery, and reduces the formation of scar tissue and adhesions.
A device for replacement of spinous processes that are removed during spine surgery has been developed. The device may be used in any area of the spine, i.e. the cervical, thoracic and/or lumbar portions of the spine.
The device has a suitable configuration to attach to hardware that is inserted into the patient's spine during surgery and to the paraspinal muscles and fascia. Exemplary fixation devices (10) are illustrated in the figures. In a preferred embodiment, the fixation device (10) contains a muscle attachment portion (20), herein referred to as the “fin portion”, and one or more connectors (40), which attach to one or more cross connectors (50). The cross connectors are configured to attach to each of the fixation rods (80a and 80b) or directly to the screw heads (90a, b, and c) of the pedicle screws (98a, b, and c). When fully assembled, the fixation device, rods and screws form a spinal fixation system (100, 200, 300, 400, 500, or 600), where the muscle attachment portion is superior to the cross connectors and positioned at approximately a 90° angle relative to the upper portion of the connectors.
A. Muscle Attachment Portion
The muscle attachment portion (20) can have any suitable shape that provides attachment areas to which the paraspinal muscles and fascia can connect and is sufficiently long to be placed in the portion of the patient's spine from which the spinous processes were removed from the vertebrae. In one embodiment the muscle attachment portion is a single unified portion. Preferably in this embodiment, the lateral cross section of the muscle attachment portion has a shape comprising at least two long sides having the same length, wherein the long sides are longer than each of the other sides. In another embodiment the muscle attachment portion is formed from two or more smaller segments, which are aligned in the same plane when assembled.
Suitable shapes are illustrated in
a. Muscle Attachment Areas
The muscle attachment portion contains one or more muscle attachment areas (23) that are suitable for the attachment, such as via suturing, of the paraspinal muscles and fascia. The one or more muscle attachment areas (23) allow a surgeon to attach the muscle and/or fascia at multiple points along the muscle attachment portion, thereby reducing the stretch on the muscle and/or fascia and reducing the likelihood of pullout or tearing off of the fin portion. In one embodiment, the muscle attachment area contains a material (25) that allows for suturing, such as a biocompatible textile (e.g. a synthetic polyester fabric, preferably formed from polyethylene terephthalate fibers, such as Dacron®), or a biocompatible mesh material. In another embodiment, the muscle attachment area is a plurality of openings (24a, b, c), such as plurality of holes in the muscle attachment portion.
As shown in
In use, a surgeon typically sutures the paraspinal musculature and/or fascia to the muscle attachment area.
In one embodiment, the muscle attachment portion is formed from a porous material or a material with striations suitable to encourage muscular attachments to the device, thereby further strengthening the patient's spine.
b. Flange In some embodiments, the muscle attachment portion contains a flange (26) at its lower region (30) (see, e.g.
In another embodiment, in place of a flange, a rod (see, e.g.
1. Materials
The muscle attachment portion is formed from any biocompatible material, including biodegradable and non-biodegradable materials. As used herein, “biocompatible materials” are those which do not elicit an acute inflammatory response when implanted into the muscle of an animal such as a mouse. Preferred non-biodegradable polymers include polyesters, polycarbonates, polyethylene, polyamides, and nylon. Ceramics and natural bone materials such as hydroxyapatite can also be used. In one embodiment, the muscle attachment portion is formed from a biodegradable material. Preferably the biodegradable materials degrade over a period of time ranging from two months to three years following implantation in a patient's spine. Examples of biodegradable polymers include polyesters such as poly(lactide-co-glycolide), polyanhydrides, and polyhydroxyalkanoates.
Biodegradable polymers for medical uses must degrade into non-toxic metabolites. Medical devices must also be nonpyrogenic, i.e., the products must not produce fever reactions when administered to patients. The presence of bacterial endotoxin (which is an integral component of the outer cell surface of Gram-negative bacteria), in the product is by far the largest concern of manufacturers in achieving nonpyrogenation. (Weary and Pearson, BioPharm., 1:22-29 (1988)). The U.S. Food and Drug Administration (FDA), for example, requires the endotoxin content of medical devices be less than 20 U.S. Pharmacopeia (USP) endotoxin fluid, where the content must not exceed 2.15 USP endotoxin units per device. U.S. Pat. No. 7,906,135 to Williams, et al. discloses polyhydroxy alkanoates (PHAs) from which pyrogen has been removed for use in numerous biomedical applications, including medical devices.
In one embodiment, the muscle attachment portion is formed from synthetic polymers. Synthetic polymers produce materials that are biocompatible and are not contaminated by biological materials. Additionally, synthetic polymers generally have more reproducible synthesis and degradation both in vitro and in vivo. Synthetic polymers may be modified to produce materials with different properties (e.g. by changing molecular weight and/or functional groups).
Representative synthetic polymers include but are not limited to poly(hydroxy acids) such as poly(lactic acid), poly(glycolic acid), and poly(lactic acid-co-glycolic acid), polyglycolides, polylactides, poly(lactide-co-glycolide) copolymers and blends, polyanhydrides, polyorthoesters, polyamides, polycarbonates, polyalkylenes such as polyethylene and polypropylene, polyalkylene glycols such as poly(ethylene glycol) (PEG), polyalkylene oxides such as poly(ethylene oxide) polyvinyl alcohols, poly(valeric acid), and poly(lactide-co-caprolactone), derivatives, copolymers and blends thereof. As used herein, “derivatives” include polymers having substitutions, additions of chemical groups, for example, alkyl, alkylene, hydroxylations, oxidations, and other modifications routinely made by those skilled in the art.
Examples of preferred biodegradable polymers include polymers of hydroxy acids such as lactic acid and glycolic acid, polylactide, polyglycolide, poly(lactide-co-glycolide), and copolymers with PEG, PHAs, polyanhydrides, poly(ortho)esters, polyurethanes, poly(butyric acid), poly(valeric acid), poly(lactide-co-caprolactone), blends and copolymers thereof.
In one embodiment, the muscle attachment portion is formed from a biocompatible, non-biodegradable material, such as polyaryletherketones (PAEKs), preferably poly(aryl-ether-ether-ketone) (PEEK), titanium or stainless steel. These materials are typically used in the hardware that is inserted into the spine. Titanium is strong, lightweight, weighing 56% as much as steel, and it is one of the few materials that bone grows into and on. However, titanium, like all metals, has the drawback in that it is not translucent to X-rays or MRI scans. So once installed, it can blur or hide anatomical changes. But unlike steel, titanium is non-ferrous, so magnets used in MRI machines will not exert a force on them. have been increasingly employed as biomaterials for orthopedic, trauma, and spinal implants.
PAEK is a family of high temperature thermoplastic polymers, consisting of an aromatic backbone molecular chain, interconnected by ketone and ether functional groups. These polymers are strong, inert, and biocompatible. Due to its strength and relative inertness, PEEK is broadly accepted as a radiolucent alternative to metallic biomaterials in the spine community. Preferably the muscle attachment portion is formed from PEEK.
c. Therapeutic or Diagnostic Agents
Optionally, the muscle attachment portion contains one or more therapeutic and/or diagnostic agents, which are released from the device following its implantation in the patient. A variety of agents can be incorporated into and released from the muscle attachment portion. Suitable agents include, but are not limited to, analgesics, anesthetics, antibiotics, steroids, antibodies against vascular endothelial growth factor (VEGF), such as bevacizumab. The agents may be released in an effective amount to reduce pain, such as for a period of time ranging from two to eight weeks following surgery. For agents that inhibit or reduce scar formation, the agent may be released in an effective amount for a time period, such as ranging from two to eight weeks following surgery.
Drugs for use in the devices include the following categories and examples of drugs and alternative forms of these drugs such as alternative salt forms, free acid forms, free base forms, and hydrates: analgesics/antipyretics (e.g., aspirin, acetaminophen, ibuprofen, naproxen sodium, buprenorphine, propoxyphene hydrochloride, propoxyphene napsylate, meperidine hydrochloride, hydromorphone hydrochloride, morphine, oxycodone, codeine, dihydrocodeine bitartrate, pentazocine, hydrocodone bitartrate, levorphanol, diflunisal, trolamine salicylate, nalbuphine hydrochloride, mefenamic acid, butorphanol, choline salicylate, butalbital, phenyltoloxamine citrate, diphenhydramine citrate, methotrimeprazine, cinnamedrine hydrochloride, and meprobamate); antibiotics (e.g., vancomycin, neomycin, streptomycin, chloramphenicol, cephalosporin, ampicillin, penicillin, tetracycline, and ciprofloxacin); and anti-inflammatories (e.g., non-steroidal such as indomethacin, ketoprofen, flurbiprofen, naproxen, ibuprofen, ramifenazone, and piroxicam, steroidal anti-inflammatories such as cortisone, dexamethasone, fluazacort, celecoxib, rofecoxib, hydrocortisone, prednisolone, and prednisone.
B. Connectors
At least one connector (40) attaches the lower region (30) of the muscle attachment portion (20) to the one or more cross-connectors (50).
In some embodiments, such as illustrated in
Each connector (40) includes an upper portion (42) and a lower portion (44). The upper portion (42) contains a threaded shaft in its center into which a screw or a nut (46) fits. The lower portion (44) contains a slot (45) which has a suitable size and shape to fit around and in slidable relation with the cross-connector (50). The side of the lower portion (44) proximal to the muscle attachment portion (20) contains a groove (32) which has a suitable size and shape to receive the flange (26) of the muscle attachment portion. The screw/nut(s) are tightened to attach the muscle attachment portion to the one or more cross connectors.
The device may contain more than one pair of connectors, and preferably contains at least two pairs of connectors, more preferably at least three pairs of connectors. The number of pairs of connectors depends on the size (e.g. length) of the muscle attachment portion; the longer the muscle attachment portion, the greater the number of connectors.
In another embodiment, such as illustrated in
As shown in
The connectors are formed from any suitable biocompatible material, and may be formed from the same material or a different material than the muscle attachment portion. Preferably the connector is formed from titanium or stainless steel.
C. Cross Connectors
The fixation device can attach to standard hardware used in spinal surgery, including, but not limited to, pedicle screws, lateral mass screws, and rod constructs using one or more cross connectors. Preferably the cross connectors are formed from titanium or stainless steel.
Cross connectors are placed in a generally transverse direction relative to the spinal rods and link adjacent spinal rods across the spinal midline to provide a rigid and stable construct. Any suitable cross connector can be used, including both fixed and adjustable, or multi-axial, cross connectors. Examples of suitable cross connectors include, but are not limited to, the EXPEDIUM™ SFX™ Cross Connector System by DePuy Spine™, the Spinal Fixation System (SFS) by Orthofix® (typically intended for non-cervical use). Exemplary cross connectors, particularly their systems for attachment to screw heads or rods, are also described in the literature, such as in U.S. Pat. No. 7,645,294 to Kalfas et al. and U.S. Pat. No. 7,628,799 to Richelsoph et al., the disclosures of which are incorporated herein by reference.
The lamina and spinous processes are removed from the vertebrae in the area of spine in which a laminectomy and/or foraminotomy (decompression of the spine) is performed. Attachments to the fascia and muscular attachments of the paraspinal musculature to the spinous process and lamina are also removed.
Paraspinal muscles refer collectively to the band of muscles next to the spine. For example, in the thoracic spine, the paraspinal muscles consist of five sets of muscles: longissimus thoracis muscles, which connect the transverse processes of adjacent vertebrae and help extend and laterally flex the vertebral column and help rotate the ribs; iliocostalis thoracis, which are small muscles that connect the ribs; spinalis thoracis, which connect the spinous processes of adjacent vertebrae and help extend the vertebral column; spinalis thoracis connect the spinous process of one vertebra to the transverse processes of an adjacent vertebra and extend and rotate the vertebral column; and rotatores thoracis which connect the spinous process of one vertebra to the transverse process of an adjacent vertebra (short rotatores) or the vertebra two away (long rotatores) and extend and rotate the vertebral column. The lumbar paraspinal muscles are a set of three muscle groups: multifidus muscle, longissimus muscle and iliocostalis muscle fascicles.
After the surgeon places the lateral mass or pedicle screws and rods to stabilizes the patient's spine, optionally following the placement of any cross connectors to further stabilize the patient's spine, the surgeon attaches one or more fixation device(s) described herein.
For surgery in which a relatively small muscle attachment portion is needed, then the muscle attachment portion may be preassembled to the cross connector prior to insertion into the patient.
For surgery, in which longer muscle attachment portions are required, then the fixation device is attached via its connectors to the cross connectors in situ, after the cross connectors are attached to the rods or pedicle screws.
The surgeon then sutures the paraspinal muscles and fascia that were previously separated from the spine to the muscle attachment portion by attaching the sutures through the muscle attachment area, particularly along the length of the muscle attachment area.
Then the surgeon closes the wound by sewing the two split sides to each other.
The device provides a substrate for attachment of the paraspinal musculature and fascia, thereby reestablishing the natural interaction between the spine and the paraspinal muscles following a laminectomy and providing support in this portion of the spine.
The use of the fixation device following surgery not only provides greater support to the spine, it also prevents or reduces the likelihood that the paraspinal musculature will attach to the dura mater, spinal cord and/or nerves. It also reduces the likelihood of a tissue reaction, such as the formation of scar tissue and/or adhesions.
The fixation device may be provided as part of a kit for a spinal fixation system. Optionally the kit contains a plurality of lateral mass screws or pedicle screws, at least two rods and optionally more than two rods, at least one fixation device. If the fixation device is formed only of one or more muscle attachment portions and one or more connectors, then the kit will also typically contain one or more cross connectors. The kit also contains instructions for care and insertion of the spinal fixation system.
The kit may also include tool(s) for placement of the screws, rods, cross connectors and fixation device, such as drills, taps and drivers.
Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.
This application claims priority to U.S. Provisional application Ser. No. 61/682,039, filed on Aug. 10, 2102. The disclosure of U.S. Ser. No. 61/682,039 is herein incorporated by reference.
Number | Date | Country | |
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61682039 | Aug 2012 | US |