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Recurrent lumber disc herniation

Tuesday, February 5, 2008




Recurrent Lumbar Disc Herniations





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There are numerous risk factors for recurrent disc herniation. In patients with diabetes, hospitalization is prolonged and there is a higher risk of postoperative infection as well as poorer long-term results. Simpson, et al.,[22] reported excellent/good outcomes in 39% of their patients with diabetes and 95% of those without diabetes, inAlthough work type and profession were not found to be risk factors, patients filing Workers' Compensation claims experienced poorer outcomes than thoscases in which an initial discectomy was performed. In their retrospective analysis, Mobbs, et al.,[17] noted a slightly higher rate of excellent/good outcome; whereas it was 60% in their diabetic group, it remained significantly lower (86%) in the nondiabetic group. This may be attributable to lower quality of life indicators in diabetic compared with nondiabetic individuals. Robinson, et al.,[18] analyzed the proteoglycan profile in the intervertebral discs of diabetic and nondiabetic patients, and determined that there were fewer proteoglycans in the former group, which may increase susceptibility to disc prolapse in patients with diabetes.One controversial risk factor for recurrence is the shape of the disc itself. Grane, et al.,[13] and Suk, et al.,[24] have asserted that disc shape plays no part in recurrence. Carragee, et al.,[7] prospectively evaluated disc herniation types, rate of reherniation, and rate of reoperation. They divided disc herniations into four shape-based groups: 1) fragment–fissure herniations (disc fragment and small anular defect); 2) fragment–defect herniations (large disc fragment with massive posterior anular tear); 3) fragmentcontained discs (incomplete anular tear); and 4) absence of fragment-contained herniations (anular prolapse). Of the four groups, the fragment–fissure type herniations were associated with the best outcomes, lowest rate of reherniation (1%), and required the fewest reoperative procedures (1%). Those with anular prolapse were associated with the worst outcomes, with 38% of patients experiencing recurrent or persistent symptoms.e not making claims.[7] Sex, age, smoking status, level of herniation, and duration of symptoms were not associated with higher rates of recurrence.[7,8,14,17,24]Minimizing Risks of RecurrenceIn an attempt to minimize postoperative complications in general, early postoperative mobilization of patients is strongly recommended. Many proposed risk factors have not been substantiated—neither the act of anular incision nor extent of discectomy, for example, has been shown to influence recurrence.[8,14,17,24] Not only higher recurrence rates but also poorer outcomes have been documented in patients with diabetes;[17] it has not yet been shown if close control of diabetes has any effect.Evaluation of RecurrenceMany modalities have been used to evaluate the lumbar spine after surgery. The current neuroimaging tool of choice is Gd-enhanced MR imaging to investigate postdiscecetomy recurrent symptoms.[2] Variations, including fat saturation, T2-weighted turbo–spin echo, turbo fluidalternated inversion recovery, short-tall inversion recovery, and differing contrast media have been suggested to increase sensitivity and specificity of MR imaging.[2,3,11,15] Most practitioners agree that optimal evaluation requires that the patient undergo neuroimaging immediately after contrast administration because the enhancement pattern is best within the first 5 minutes; beyond that, enhancement in the disc can be seen if imaging is delayed (2)Figure 1. Representative MR images. Upper Left: Sagittal T1-weighted image demonstrating recurrent L4–5 disc herniation. Upper Right: Axial T1-weighted image without contrast of recurrent disc herniation. It is difficult to differentiate between scar and disc fragment in this image. Lower Left: Image revealing recurrent disc herniation with caudal migration. Similarly there is no differentiation between scar, nerve root, and disc herniation. Lower Right: Contrastenhanced image demonstrating lack of enhancement of soft-tissue suggestive of recurrent disc herniation.Figure 2. Representative MR images. Upper: Contrast-enhanced image demonstrating an extruded fragment. Lower Left: Lack of enhancement of material in continuity with the disc space strongly suggests a disc herniation. Contrast enhancement can be seen adjacent to the disc material. Lower Right: Contrast (scar) surrounds the extruded fragment of disc.To recognize postoperative pathological changes, one must be familiar with changes appropriate to early and late phases. Normal postdiscectomy appearances can be mistaken for recurrent or retained disc. In the early (0 to 6–month) postoperative period, MR imaging reveals an interspace high signal intensity band extending from the nucleus pulposus to the site of anular disruption (especially noticeable at 0–2 months). The anulus is typically hyperintense and the nucleus hypointense. There is loss of disc space height. The endplates and marrow can exhibit changes as well, often low signal on T1-weighted and high signal on T2-weighted images suggesting inflammation and edema. The anterior epidural space initially reveals an increase in soft-tissue mass, evidence of tissue disruption, edema, and hemorrhage, with the appearance of mass effect.[20] Nerve root enhancement with Gd is normal, reflecting breakdown of the blood–nerve barrier, but should resolve by 6 months. Adhesions within the thecal sac at the operative level usually resolve within several weeks. Postoperative changes at the laminectomy site depend on the extent of surgery, ligamentum flavum removal, and whether fat graft was placed in the epidural space. Facet joint enhancement occurs as a local response to dissection and persists long (> 6 months) after surgery in more than half of the patients in whom imaging is performed.[2,6,25]Normal late (> 6 months) postdiscectomy changes are those of healing. The now low-intensity signal band in the disc space represents a healing anular defect. The mass effect seen earlier in the anterior epidural space may have resolved[25] or may persist as a masslike scar.[9] Scarring is most pronounced before 9 months[12] and primarily involves the anulus fibrosus. The nerve root should not enhance after 6 months.[6] The laminectomy space exhibits matured scar with peripheral enhancement identifying granulation tissue. Facet joint enhancement is visible after contrast administration in approximately half of the patients 6 months postoperatively.[2]Pathological changes of the anterior epidural space can reflect mass effect due to scarring or the disc.[2,9] Differentiation between these is central in choosing the best treatment option because the former will not benefit from surgery but the latter may. Both are demonstrated to have similar signal intensities on unenhanced T1-weighted MR images.[15] Scarring often displays intermediate signal intensity; beyond 2 years, it may be hypointense. Scarring enhances heterogeneously because of its vascular supply. The disc usually appears as a polypoid mass of low signal on T1- and T2-weighted sequences. It is usually contiguous with the parent disc unless sequestrated. There is often a hypointense rim of the posterior longitudinal ligament and outer anular fibers outlining the herniation, enhancing after contrast administration. The disc itself does not enhance because it has no blood supply.[2,15] Retraction of the thecal sac toward a soft-tissue lesion is suggestive of scar;[20] displacement away from such a mass is suggestive of a herniated disc. Although a pseudomeningocele may also be seen as mass, its signal characteristics are different, identifying them as such: cerebrospinal fluid intensity on T1- and T2-weighted images and often an enhancing fibrous capsule.[2]What constitutes identifiable differences between symptomatic and asymptomatic postoperative MR imaging changes is not well understood; a mass lesion at the level of previous surgery is a common finding, especially in the early postoperative period.[13] Recurrent pain prompting postoperative neuroimaging is poorly specific in nature and is difficult to interpret.[21] Discordance between neuroimaging and intraoperative findings is more common than anticipated, occurring in 18 to 33% of the cases proven surgically.[10]Treatment of RecurrenceDifferentiation of recurrent disc hemiation from scar formation will allow for improved treatment choices and selection of patients who may benefit from a second surgery. Gadolinium-enhanced MR imaging is thought to be the best modality to differentiate between the two.[2,3,11,20,25] Computerized tomography discography may also provide additional information.[4] The scar may surround the nerve roots and cause symptoms by means of neural tension, decreased axoplasmic transport, restriction of blood flow, or of venous return.[2] In classical teaching, a scar does not benefit from reoperation and in fact may result in worse outcomes.[13]Treatment options include observation and aggressive medical management (pharmacological therapy and physical therapy for rehabilitation) or operative intervention. Revision laminectomy and discectomy are the most commonly performed surgical therapies, starting at an area known to be intact, finding landmarks, beginning medially, and working out laterally to locate the pathological entity. In creating the surgical exposure, the surgeon should concentrate on removing scar from the lamina to make a clear identification of the previous laminotomy edges. Curettes are then used to dissect the scar from the osseous margins. Care must taken to delineate meticulously the bone from scar to avoid violating the dura mater. It is generally easier to dissect laterally in the canal and work medially. Identification of pedicles allows for clean separation of the scar tissue from bone as well as identification of the disc space. The use of an operative microscope greatly improves identification and separation of tissues. Chymopapain, intradiscal electrothermal coagulation therapy, and laser-assisted decompression are not options because the anulus is no longer intact in revision disc surgery. Fusion is not routinely needed, unless spinal instability is demonstrated.In an analysis of recurrent herniated disc surgery in the setting of conventional open discectomy, Suk, et al.,[24] found no significant differences in factors influencing the outcomes of repeated discectomy, in terms of sex, age, smoking status, trauma status, degree of degenerative disease, and whether the anulus was incised during surgery. Cinotti, et al.,[8] reported no difference in recurrence rates when comparing cases of partial and complete discectomy. There is no significant reported effect related to the original surgery and revision surgery on hospital stay and clinical improvement rates; reoperation for recurrent disc herniation has been associated with good outcome, comparable with that achieved after initial surgery

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