Pathology Failed back syndrome

1 pathology

1.1 recurrent or persistent disc herniation
1.2 spinal stenosis
1.3 post operative infection
1.4 epidural post-operative fibrosis
1.5 adhesive arachnoiditis
1.6 nerve injury

pathology

before advent of ct scanning, pathology in failed syndrome difficult understand. computerized tomography in conjunction metrizamide myelography in late 1960s , 1970s allowed direct observation of mechanisms involved in post operative failures. 6 distinct pathologic conditions identified:

recurrent or persistent disc herniation
spinal stenosis
post operative infection
epidural post-operative fibrosis
adhesive arachnoiditis
nerve injury

recurrent or persistent disc herniation

ct scan image of large herniated disc in lumbar spine.

removal of disc @ 1 level can lead disc herniation @ different level @ later time. complete surgical excision of disc still leaves 30-40% of disc, cannot safely removed. retained disc can re-herniate sometime after surgery. virtually every major structure in abdomen , posterior retroperitoneal space has been injured, @ point, removing discs using posterior laminectomy/discectomy surgical procedures. prominent of these laceration of left internal iliac vein, lies in close proximity anterior portion of disc. in studies, recurrent pain in same radicular pattern or different pattern can high 50% after disc surgery. many observers have noted common cause of failed syndrome caused recurrent disc herniation @ same level operated. rapid removal in second surgery can curative. clinical picture of recurrent disc herniation involves significant pain-free interval. however, physical findings may lacking, , history necessary. time period emergence of new symptoms can short or long. diagnostic signs such straight leg raise test may negative if real pathology present. presence of positive myelogram may represent new disc herniation, can indicative of post operative scarring situation mimicking new disc. newer mri imaging techniques have clarified dilemma somewhat. conversely, recurrent disc can difficult detect in presence of post op scarring. myelography inadequate evaluate patient recurrent disc disease, , ct or mri scanning necessary. measurement of tissue density can helpful.

even though complications of laminectomy disc herniation can significant, recent series of studies involving thousands of patients published under auspices of dartmouth medical school concluded @ four-year follow-up underwent surgery lumbar disc herniation achieved greater improvement nonoperatively treated patients in primary , secondary outcomes except work status.

spinal stenosis

ct scan of laminectomy showing scar formation (highlighted in red)causing new stenosis.

spinal stenosis can late complication after laminectomy disc herniation or when surgery performed primary pathologic condition of spinal stenosis. in maine study, among patients lumbar spinal stenosis completing 8- 10-year follow-up, low pain relief, predominant symptom improvement, , satisfaction current state similar in patients treated surgically or nonsurgically. however, leg pain relief , greater back-related functional status continued favor receiving surgical treatment.

a large study of spinal stenosis finland found prognostic factors ability work after surgery ability work before surgery, age under 50 years, , no prior surgery. long-term outcome (mean follow-up time of 12.4 years) excellent-to-good in 68% of patients (59% women , 73% men). furthermore, in longitudinal follow-up, result improved between 1985 , 1991. no special complications manifested during long-term follow-up time. patients total or subtotal block in preoperative myelography achieved best result. furthermore, patients block stenosis improved result in longitudinal follow-up. postoperative stenosis seen in computed tomography (ct) scans observed in 65% of 90 patients, , severe in 23 patients (25%). however, successful or unsuccessful surgical decompression did not correlate patients subjective disability, walking capacity or severity of pain. previous surgery had strong worsening effect on surgical results. effect clear in patients total block in preoperative myelography. surgical result of patient previous surgery similar of patient without previous surgery when time interval between last 2 operations more 18 months.

post-operative mri findings of stenosis of limited value compared symptoms experienced patients. patients perception of improvement had stronger correlation long-term surgical outcome structural findings seen on postoperation magnetic resonance imaging. degenerative findings had greater effect on patients walking capacity stenotic findings

postoperative radiologic stenosis common in patients operated on lumbar spinal stenosis, did not correlate clinical outcome. clinician must cautious when reconciling clinical symptoms , signs postoperative computed tomography findings in patients operated on lumbar spinal stenosis.

a study georgetown university reported on one-hundred patients had undergone decompressive surgery lumbar stenosis between 1980 , 1985. 4 patients postfusion stenosis included. 5-year follow-up period achieved in 88 patients. mean age 67 years, , 80% on 60 years of age. there high incidence of coexisting medical diseases, principal disability lumbar stenosis neurological involvement. there high incidence of success, recurrence of neurological involvement , persistence of low-back pain led increasing number of failures. 5 years number had reached 27% of available population pool, suggesting failure rate reach 50% within projected life expectancies of patients. of 26 failures, 16 secondary renewed neurological involvement, occurred @ new levels of stenosis in 8 , recurrence of stenosis @ operative levels in eight. reoperation successful in 12 of these 16 patients, 2 required third operation. incidence of spondylolisthesis @ 5 years higher in surgical failures (12 of 26 patients) in surgical successes (16 of 64). spondylolisthetic stenosis tended recur within few years following decompression. because of age , associated illnesses, fusion may difficult achieve in group.

post operative infection

a small minority of lumbar surgical patients develop post operative infection. in cases, bad complication , not bode eventual improvement or future employability. reports surgical literature indicate infection rate anywhere 0% 12%. incidence of infection tends increase complexity of procedure , operating time increase. usage of metal implants (instrumentation) tends increase risk of infection. factors associated increased infection include diabetes mellitus, obesity, malnutrition, smoking, previous infection, rheumatoid arthritis, , immunodeficiency. previous wound infection should considered contraindication further spinal surgery, since likelihood of improving such patients more surgery small. antimicrobial prophylaxis (giving antibiotics during or after surgery before infection begins) reduces rate of surgical site infection in lumbar spine surgery, great deal of variation exists regarding use. in japanese study, utilizing centers disease control recommendations antibiotic prophylaxis, overall rate of 0.7% infection noted, single dose antibiotic group having 0.4% infection rate , multiple dosage antibiotic infection rate of 0.8%. authors had used prophylactic antibiotics 5 7 postoperative days. based on centers disease control , prevention guideline, antibiotic prophylaxis changed day of surgery only. concluded there no statistical difference in rate of infection between 2 different antibiotic protocols. based on cdc guideline, single dose of prophylactic antibiotic proven efficacious prevention of infection in lumbar spine surgeries.

epidural post-operative fibrosis

epidural scarring following laminectomy disc excision common feature when re-operating recurrent sciatica or radiculopathy. when scarring associated disc herniation and/or recurrent spinal stenosis, relatively common, occurring in more 60% of cases. time, theorized placing fat graft on dural prevent post operative scarring. however, initial enthusiasm has waned in recent years. in extensive laminectomy involving 2 or more vertebra, post operative scarring norm. seen around l5 , s1 nerve roots.

adhesive arachnoiditis


myelogram showing typical findings of arachnoiditis in lumbar spine.

fibrous scarring can complication within subarachnoid space. notoriously difficult detect , evaluate. prior development of magnetic resonance imaging, way ascertain presence of arachnoiditis opening dura. in days of ct scanning , pantopaque , later, metrizamide myelography, presence of arachnoiditis speculated based on radiographic findings. often, myelography prior introduction of metrizamide cause of arachnoiditis. can caused long term pressure brought either severe disc herniation or spinal stenosis. presence of both epidural scarring , arachnoiditis in same patient quite common. arachnoiditis broad term denoting inflammation of meninges , subarachnoid space. variety of causes exist, including infectious, inflammatory, , neoplastic processes. infectious causes include bacterial, viral, fungal, , parasitic agents. noninfectious inflammatory processes include surgery, intrathecal hemorrhage, , administration of intrathecal (inside dural canal) agents such myelographic contrast media, anesthetics (e.g. chloroprocaine), , steroids (e.g. depo-medrol, kenalog). lately iatrogenic arachnoiditis has been attributed misplaced epidural steroid injection therapy when accidentally administered intrathecally. preservatives , suspension agents found in steroid injectates, aren t indicated epidural administration u.s. food & drug administration due reports of severe adverse events including arachnoiditis, paralysis , death, have been directly linked onset of disease following initial stage of chemical meningitis. neoplasia includes hematogenous spread of systemic tumors, such breast , lung carcinoma, melanoma, , non-hodgkin lymphoma. neoplasia includes direct seeding of cerebrospinal fluid (csf) primary central nervous system (cns) tumors such glioblastoma multiforme, medulloblastoma, ependymoma, , choroid plexus carcinoma. strictly speaking, common cause of arachnoiditis in failed syndrome not infectious or cancer. due non-specific scarring secondary surgery or underlying pathology.

nerve injury

laceration of nerve root, or damage cautery or traction can lead chronic pain, can difficult determine. chronic compression of nerve root persistent agent such disc, bone (osteophyte) or scarring can permanently damage nerve root. epidural scarring caused initial pathology or occurring after surgery can contribute nerve damage. in 1 study of failed patients, presence of pathology noted @ same site level of surgery performed in 57% of cases. remaining cases developed pathology @ different level, or on opposite side, @ same level surgery performed. in theory, failed patients have sort of nerve injury or damage leads persistence of symptoms after reasonable healing time.