Intervertebral disc abnormalities are common in the population and cause considerable pain, particularly if they affect adjacent nerves. Disc abnormalities result from trauma, wear, metabolic disorders and the aging process and include degenerative discs, localized tears or fissures in the annulus fibrosus, localized disc herniations with contained or escaped extrusions, and chronic, circumferential bulging discs. Disc fissures occur as a degeneration of fibrous components of the annulus fibrosus. Rather minor activities such as sneezing, bending or simple attrition can tear degenerated annulus fibers and create a fissure. The fissures may be further complicated by extrusion of nucleus pulposus material into or beyond the annulus fibrosus. Difficulties can still present even when there is no visible extrusion, due to biochemicals within the disc irritating surrounding structures and nerves.
A contained disc herniation is not associated with free nucleus fragments migrating to the spinal canal. However, a contained disc herniation can still protrude and irritate surrounding structures, for example by applying pressure to spinal nerves. Escaped nucleus pulposus can chemically irritate neural structures. Current treatment methods include reduction of pressure on the annulus by removing some of the interior nucleus pulposus material by percutaneous nucleotomy. See, for example, Kambin U.S. Pat. No. 4,573,448. Complications include disc space infection, nerve root injury, hematoma formation, instability of the adjacent vertebrae and collapse of the disc from decrease in height. It has been proposed to treat weakening due to nucleus pulposus deficiency by inserting preformed hydrogel implants. See, Ray U.S. Pat. Nos. 4,772,287; 4,904,260 and, 5,562,736 and Bao U.S. Pat. No. 5,192,326.
More recently, delivery of in situ curing liquids to form a solid prosthetic in the nucleus of a disc have been disclosed. The fluid form of these implants enables access to the spine in a minimally invasive manner, and includes procedures for restoring structural integrity to vertebral bodies. See Scribner U.S. Pat. Nos. 6,241,734 and 6,280,456; Reiley U.S. Pat. Nos. 6,248,110 and 6,235,043; Boucher U.S. Pat. No. 6,607,554 and Bhatnagar U.S. Pat. No. 6,395,007. Methods of repairing the spinal disc or portions thereof are disclosed in Cauthern U.S. Pat. No. 6,592,625, Haldimann U.S. Pat. No. 6,428,576, Trieu U.S. Pat. No. 6,620,196 and Milner U.S. Pat. No. 6,187,048.
There are a variety of injectable biomaterials disclosed in issued patents including: cross-linkable silk elastin copolymer disclosed in Stedronsky U.S. Pat. No. 6,423,333, Capello U.S. Pat. No. 6,380,154, Ferrari U.S. Pat. No. 6,355,776, Stedronsky U.S. Pat. No. 6,258,872, Ferrari U.S. Pat. No. 6,184,348, Ferrari U.S. Pat. No. 6,140,072; Stedronsky U.S. Pat. No. 6,033,654; Ferrari U.S. Pat. No. 6,018,030; Stedronsky U.S. Pat. No. 6,015,474; Ferrari U.S. Pat. No. 5,830,713; Stedronsky U.S. Pat. No. 5,817,303; Donofrio U.S. Pat. No. 5,808,012; Capello U.S. Pat. No. 5,773,577; Capello U.S. Pat. No. 5,773,249; Ferrari U.S. Pat. No. 5,770,697; Stedronsky U.S. Pat. No. 5,760,004; Donofrio U.S. Pat. No. 5,723,588; Ferrari U.S. Pat. No. 5,641,648; Capello U.S. Pat. No. 5,235,041; protein hydrogel described in Morse U.S. Pat. No. 5,318,524; Morse U.S. Pat. No. 5,259,971; Morse U.S. Pat. No. 5,219,328; polyurethane-filled balloons disclosed in Bao U.S. Pat. No. 7,077,865; Bao U.S. Pat. No. 7,001,431; Felt U.S. Pat. No. 6,306,177; Felt U.S. Pat. No. 6,248,131; Bao U.S. Pat. No. 6,224,630; collagen-PEG disclosed in Olsen U.S. Pat. No. 6,428,978; Olsen U.S. Pat. No. 6,413,742; Rhee U.S. Pat. No. 6,323,278; Wallace U.S. Pat. No. 6,312,725; Sierra U.S. Pat. No. 6,277,394; Rhee U.S. Pat. No. 6,166,130; Berg U.S. Pat. No. 6,165,489; Simonyi U.S. Pat. No. 6,123,687; Berg U.S. Pat. No. 6,111,165; Sierra U.S. Pat. No. 6,110,484; Prior U.S. Pat. No. 6,096,309; Rhee U.S. Pat. No. 6,051,648; Esposito U.S. Pat. No. 5,997,811; Berg U.S. Pat. No. 5,962,648; Rhee U.S. Pat. No. 5,936,035; Rhee U.S. Pat. No. 5,874,500; chitosan disclosed in Chemte U.S. Pat. No. 6,344,488; other polymers discussed in Boyd U.S. Pat. No. 7,004,945; Collins U.S. publication 2006/0004326; Collins U.S. publication 2006/0009851; Milner U.S. Pat. No. 6,187,048; Daniell U.S. Pat. No. 6,004,782; Urry U.S. Pat. No. 5,064,430; Urry U.S. Pat. No. 4,898,962; Urry U.S. Pat. No. 4,870,055; Urry U.S. Pat. No. 4,783,523; Urry U.S. Pat. No. 4,589,882; Urry U.S. Pat. No. 4,500,700; Urry U.S. Pat. No. 4,474,851; Urry U.S. Pat. No. 4,187,852; Urry U.S. Pat. No. 4,132,746.
Delivery of an in situ forming prosthetic to the nuclear space requires constructing a passageway into the nucleus and removal of the nucleus fibrosus, in total or in part. The passageway is usually made through the annulus, especially when part of the annulus should be removed to correct a pathological condition. Whether the passageway is through the annulus or elsewhere, for example, through the vertebral body, there is a risk of the formed nucleus prosthetic extruding through the passageway. Nucleus prosthetic extrusion can affect the surrounding nerves adversely. Methods of blocking a passageway made through the annulus are disclosed in Lambrecht U.S. Pat. No. 6,425,919, Lambrecht, et al. U.S. Pat. No. 6,482,235, Lambrecht, et al. U.S. Pat. No. 6,508,839, Cauthen U.S. Pat. No. 6,592,625, Lambrecht, et al. U.S. Pat. No. 6,821,276 and Lambrecht et al. U.S. Pat. No. 6,883,520. Other methods of preventing nucleus prosthetic extrusion include enclosing the prosthetic entirely inside of an enveloping sheath and are disclosed in Ray, et al. U.S. Pat. No. 4,904,260, Bao, et al. U.S. Pat. No. 5,192,326, Kuslich U.S. Pat. No. 5,549,679, Stalcup, et al. U.S. Pat. No. 6,332,894, Wardlaw U.S. Pat. No. 6,402,784, Weber, et al. U.S. Pat. No. 6,533,818, and Reuter, et al. U.S. Pat. No. 6,805,715. Still other methods of preventing nuclear prosthetic extrusion include delivering a preformed prosthetic in a reduced state, which when introduced into the body increases in volume. These methods and devices are disclosed in Ray, et al. U.S. Pat. No. 6,602,291, Stoy, et al. U.S. Pat. No. 6,726,721, and Li, et al. U.S. Pat. No. 6,764,514.
None of the techniques or devices and associated methods of their use described above are entirely satisfactory from either a biocompatibility or efficacy perspective, for localization of an in situ curing liquid nucleus implant. Accordingly, there remains a need for the development of treatment methods and devices for implanting spinal disc prostheses.