A comprehensive subaxial cervical spine injury severity assessment model using numeric scores and its predictive value for surgical intervention.

Multiple factors contribute to the determination for surgical intervention in the setting of cervical spinal injury, yet to date no unified classification system exists that predicts this need. The goals of this study were twofold: to create a comprehensive subaxial cervical spine injury severity numeric scoring model, and to determine the predictive value of this model for the probability of surgical intervention. In a retrospective cohort study of 333 patients, neural impairment, patho-morphology, and available spinal canal sagittal diameter post-injury were selected as injury severity determinants. A common numeric scoring trend was created; smaller values indicated less favorable clinical conditions. Neural impairment was graded from 2-10, patho-morphology scoring ranged from 2-15, and post-injury available canal sagittal diameter (SD) was measured in millimeters at the narrowest point of injury. Logistic regression analysis was performed using the numeric scores to predict the probability for surgical intervention. Complete neurologic deficit was found in 39 patients, partial deficits in 108, root injuries in 19, and 167 were neurologically intact. The pre-injury mean canal SD was 14.6 mm; the post-injury measurement mean was 12.3 mm. The mean patho-morphology score for all patients was 10.9 and the mean neurologic function score was 7.6. There was a statistically significant difference in mean scores for neural impairment, canal SD, and patho-morphology for surgical compared to nonsurgical patients. At the lowest clinical score for each determinant, the probability for surgery was 0.949 for neural impairment, 0.989 for post-injury available canal SD, and 0.971 for patho-morphology. The unit odds ratio for each determinant was 1.73, 1.61, and 1.45, for neural impairment, patho-morphology, and canal SD scores, respectively. The subaxial cervical spine injury severity determinants of neural impairment, patho-morphology, and post-injury available canal SD have well defined probability for surgical intervention when scored separately. Our data showed that each determinant alone could act as a primary predictor for surgical intervention.

A novel application of high-dose (50kGy) gamma irradiation for demineralized bone matrix: effects on fusion rate in a rat spinal fusion model.

BACKGROUND CONTEXT: The safety of allograft material has come under scrutiny because of recent reports of allograft-associated bacterial and viral infections in tissue recipients. Gamma irradiation, although being one of the most effective ways of terminal sterilization, has been shown to affect the biomechanical properties of allograft bone. It may also have detrimental effects on the osteoinductivity of allograft material such as demineralized bone matrix (DBM) by the denaturation of proteins because of heat generated by irradiation. Sterilization of DBM material is an important variable in processing graft materials. This is considered to be one of the factors leading to different fusion rates observed with different commercially available DBM products, as the sterilization procedure itself may affect the osteoinductivity of the material. Currently, there is no ideal sterilization technique that limits the detrimental effect on osteoinductivity and fusion rates. PURPOSE: To evaluate the effects of a range of hydrogen peroxide exposures with or without the controlled high-dose gamma irradiation after processing with radioprotectant solutions (Clearant radiation sterilization procedure) on the fusion rates of human DBM. STUDY DESIGN: A prospective in vivo animal study. METHODS: Eighty mature athymic nude female rats were used for this study, which formed 10 equal groups. Human DBM exposed to hydrogen peroxide for different time periods (0, 1, 6, and 24 hours) was divided into two major subgroups. One group was further treated with controlled high-dose radiation using radioprotectants (radiation treated), whereas the other group was frozen immediately without specific treatment (non-radiation treated). Both radiation-treated and non-radiation-treated DBM material from each group of hydrogen peroxide exposure times were implanted between L4 and L5 transverse processes of the rats forming eight test groups including eight animals in each. The remaining 16 rats were divided into two additional groups to form negative (only decortication, n=8) and positive (bone morphogenetic protein [BMP]-2, n=8) control groups. The rats were evaluated for fusion by radiographs (2, 4, and 8 weeks), manual palpation (8 weeks), and histological analysis after sacrificing. Comparison of fusion rate among all groups was made using these three evaluation methods. RESULTS: Increasing the time period of hydrogen peroxide (0, 1, 6, or 24 hours) exposure for preparation of DBM from bone allograft did not affect the fusion rates significantly (p<.05), although there was a trend toward decreasing fusion rates with longer exposure times. When the hydrogen peroxide washed DBM preparations were also radiation treated, the resulting fusion rates were again not significantly different (p<.05). Agreement among fusion detection methods was found to be high. CONCLUSIONS: Hydrogen peroxide processing was not detrimental to fusion rates. The additional terminal sterilization technique with special gamma irradiation protocols (Clearant process) also did not decrease the fusion rates but could provide an additional margin of safety.

The osteoinductive properties of Nell-1 in a rat spinal fusion model.

BACKGROUND CONTEXT: Recombinant growth factors bone morphogenetic protein-2 (BMP-2) and BMP-7 are currently approved for human use but are associated with various adverse effects including ectopic bone formation and local inflammatory reaction. The development of alternative growth factors may help minimize the adverse effects of current osteoinductive therapeutics. Nell-1 (Nel-like molecule-1; Nel [a protein strongly expressed in neural tissue encoding epidermal growth factor like domain]) is a novel secretory molecule that appears to act more specifically on osteoblasts than the BMPs, which can act on multiple cell types. From a molecular point of view, Nell-1 is directly regulated by runt-related transcription factor 2 (Runx2/Cbfa1), a master regulatory gene controlling bone formation. Previous studies showed that Nell-1 accelerates osteogenic differentiation in vitro and calvarial bone formation in vivo. We hypothesize that Nell-1 may also effectively form bone in spinal fusion. PURPOSE: Our primary aim was to assess if direct adenoviral gene delivery with Nell-1 in a demineralized bone matrix (DBM) carrier can improve spinal fusion in a rat model. Because adenoviral vectors allow for sustained growth factor delivery, they were used for initial feasibility testing before protein studies. STUDY DESIGN/SETTING: Two groups of 20 athymic rats underwent posterolateral intertransverse process spinal fusion at L4-L5 with implanted DBM carrier containing either adenovirus coding for Nell-1 (AdNell-1) or control, Lac Z (AdLacZ). No cells were implanted. The 20 rats were sacrificed at 6 weeks for evaluation of spinal fusion. METHODS: All animals underwent Faxitron radiographs at 2, 4, and 6 weeks, manual spine palpation at 6 weeks, and high-resolution micro computerized tomography (microCT) at 6 weeks. Spinal fusion rate was assessed by: 1) 6-week Faxitron images; 2) manual palpation by three independent observers; 3) microCT; and 4) histology. New bone formation was assessed by hematoxylin-eosin and Masson trichrome staining on decalcified, coronally sectioned spine segments. RESULTS: All differences achieved statistical significance. After 6 weeks, direct application of adenoviral Nell-1 in a DBM carrier achieved significantly higher rates of spinal fusion over Lac Z controls: 60% Nell-1 versus 20% Lac Z by manual palpation and 70% Nell-1 versus 20% Lac Z by microCT and histology. Histological assessment of bone quality and maturity revealed more mature, higher quality bone in all the Nell-1 treated specimens relative to Lac Z at 6 weeks. CONCLUSIONS: Spinal fusion is more accurately assessed by microCT and histology than manual palpation. Direct application of adenoviral Nell-1 in a DBM carrier achieved significantly higher rates of spinal fusion over Lac Z controls at 6 weeks. Direct application of adenoviral Nell-1 in a DBM carrier also achieved significantly higher rates of spinal fusion over other reports in the literature using direct adenoviral BMP application. Direct application of adenoviral BMP in an allograft carrier achieved 8% fusion for BMP-2 and 16% fusion for BMP-7 at 8 weeks. These results indicate that Nell-1 may be a potent osteoinductive molecule. In addition, the regulation of Nell-1 by the master bone regulatory gene, Runx2 suggests that Nell-1 may exert its effects more specifically in osteoblastic cells than BMPs which affect multiple cell types. Overall, Nell-1 may fulfil a current need for an osteoinductive factor.

A thoracic and lumbar spine injury severity classification based on neurologic function grade, spinal canal deformity, and spinal biomechanical stability.

BACKGROUND CONTEXT: Current well regarded thoracic and lumbar spine injury classifications use mechanistic and anatomical categories, which do not directly rely on quantifiable management parameters. Their clinical usefulness is not optimal. PURPOSE: Formulate an injury severity based classification. STUDY DESIGN/SETTING: This retrospective investigation studied patients who suffered thoracic and lumbar spine injuries, and examined the following three quantifiable parameters: 1) neurologic function grade; 2) spinal canal deformity; 3) biomechanical stability. These parameters are the primary clinical indications for management decisions. PATIENT SAMPLE: One hundred twenty-six consecutive patients with spinal trauma admitted to a level 1 tertiary trauma center from January 1997 to November 2005 were enrolled in this study. OUTCOME MEASURES: Spine injury severity was independently scored on three parameters: 1) neurologic function impairment grade according to the modified Frankel grading method and the American Spinal Injury Association (ASIA) function scale; 2) spinal canal deformity from translation and intrusion, measured as percent canal cross-sectional area compromise; 3) failure of five possible biomechanical functions in Denis's three anatomic columns, and a sixth group of unstable deformities. All three columns contribute to tensile function. Only the anterior and middle columns provide compression load-bearing function. A combination of three or more column biomechanical function failure or an unstable deformity renders the injury unstable. METHODS: Five fellowship-trained spine surgeons from one institution took part in the study. Hospital medical records, including admission history and physical examination, discharge summary, and operative report (if surgery was performed), were examined for neurologic deficit. Plain radiographs, computed tomographic scans and magnetic resonance imaging were assessed for canal compromise and biomechanical function status. RESULTS: Injuries were located from T3 to L5, 58% of which were at the thoracolumbar junction (T11-L2). Neurologic impairment occurred in 45% (57/126) of patients, with 19 complete paraplegias (Frankel grade A). The average spinal canal cross-sectional area compromise was 56.1% in neurologically impaired and 14.2% for patients who where neurologically intact. The number of tensile element failure patients in neurologically impaired versus intact are as follow: tri-columns 22/4; two columns 16/8; one column 11/17; all columns intact 8/40. Load-bearing element failed in 55/57 neurologically impaired and 63/69 intact patients. Sixty-seven patients had spinal reconstructive surgery. Their average instability profile score was 4.4 out of 6, and canal compromise score was 3.3 out of 5. CONCLUSIONS: A clinically useful thoracic and lumbar spine injury classification should be based on parameters that are the primary indications for management decisions. The same parameters should be injury severity quantifiable as to guide treatment. In this study we introduced spinal canal deformity and column biomechanical functions as quantifiable parameters in thoracic and lumbar injury severity classification. Validation of this method is beyond the scope of this preliminary study.

Percent spinal canal compromise on MRI utilized for predicting the need for surgical treatment in single-level lumbar intervertebral disc herniation.

BACKGROUND CONTEXT: There is limited information describing the correlation between the initial quantitative measurements on magnetic resonance imaging (MRI) scans of disc herniation area, canal cross-section areas, percent canal compromise, and disc herniation location to the need for surgery. PURPOSE: Our aim is to determine if the size of disc herniation area, canal cross-section area, percent canal compromise, and disc herniation location taken from MRI images of patients with symptomatic single-level lumbar herniated intervertebral discs upon initial presentation to a spine surgeon, were predictive of the need for surgical treatment. STUDY DESIGN/SETTING: This is a retrospective case matched study of patient MRI images in the senior author's private practice. PATIENT SAMPLE: From a pool of 332 patients with sciatica caused by lumbar intervertebral disc herniations at our institution, 65 patients had surgery, of which MRI images were available and analyzed on 44 patients. Forty-four additional patients were randomly selected from the remaining 267 original group as nonoperative controls. METHODS: The axial MRI image showing the largest canal compromise by the herniated disc was selected for measurements. Using T1- and T2-weighted images, the areas of interest were digitally scanned at high resolution. The canal area and disc herniation area measurement were calculated from the total number of pixels per cross-sectional area, multiplied by a scan correction factor, mm(2) /pixel. Disc herniation locations were classified into either central or paracentral. The percent canal compromise was obtained by disc herniation area divided by canal cross-section area and multiplied by 100. RESULTS: The surgical group's overall mean herniated disc area was 219.6 square millimeter (mm(2)), 179.8 at L4-5, and 267.4 at L5-S1. The nonoperative group's overall mean herniated disc area was 178.4 mm(2), 135.1 at L2-3, 160.3 at L4-5, and 207.4 at L5-S1. The surgical group's overall mean canal cross-sectional area was 471.8 mm(2), 418.6 at L4-5, and 535.6 at L5-S1. The nonoperative group's overall mean canal cross-sectional area was 541.3 mm(2), 518.1 at L2-3, 446.8 at L4-5, and 669.9 at L5-S1. The overall percent canal compromise ratio in the surgery group was 46.7%, 44.1% at L4-5, and 49.8% at L5-S1. The overall percent canal compromise in the nonoperative group was 34.2%, 34.1% at L2-3, 36.1% at L4-5, and 31.8% at L5-S1. The percent canal compromise in central herniations at L4-5 level was 53.0% in the surgical group, and 32.8% in the nonoperative group; at the L5-S1 level surgical group percent canal compromise was 64.1% and in the nonoperative group canal compromise was 27%. L4-L5 level paracentral herniations canal compromise was 36.7% in the surgical group compared with 42.5% canal compromise in the nonoperative group. At the L5-S1 level the canal compromise was 45% in the surgical group and 34.8% in the nonoperative group. CONCLUSIONS: Our findings show a trend for patients treated with surgery to have larger disc herniation areas and smaller canal cross-section areas, corresponding to larger percent canal compromise than the nonoperative group. Centrally located herniations followed this trend closely at all levels studied. However, the paracentral herniation at the L4-5 level does not follow this trend, possibly because paracentral disc herniation clinical course is determined more by herniation location rather than the overall herniation size.

The effect of uniform heating on the biomechanical properties of the intervertebral disc in a porcine model.

BACKGROUND CONTEXT: The use of minimally invasive lumbar intradiscal heating techniques, including intradiscal electro-thermal therapy (IDET), endoscopic radio-frequency annuloplasty, nucleoplasty and laser discectomy, for chronic lumbar discogenic pain and contained disc herniation has recently gained popularity. The purported therapeutic mechanisms of these interventions include subtotal nuclectomy, annular nociceptor ablation, and stabilization of the annular fibers. Basic science data elucidating the biomechanical and histomorphologic alterations of heat treatments on disc remain sparse. PURPOSE: The purpose of this study is to examine the effects of uniform heating on biomechanical properties and histomorphology of intervertebral disc tissues using a porcine model. STUDY DESIGN/SETTING: In a laboratory setting, porcine functional spinal units consisting of vertebra-nucleus pulposus-vertebra core and porcine hamstring tendons were harvested. Studies were performed on these tissue samples by uniformly heating the specimens in a constant temperature water bath. Ten porcine lumbar disc core and twenty-five porcine hamstring tendons were utilized as the subjects for this study. The effects of uniform heat treatments on disc core and hamstring tendon were measured for shrinkage, stiffness, and load to failure strength. Histomorphological study was also carried on the same specimen. METHODS: The porcine vertebra-nucleus pulposus-vertebra segments were cored to a uniform 1-cm diameter. The hamstring tendons were cut to uniform 1.2-inch lengths. The tendon specimens were divided into groups of five each and heated in constant temperature water baths of 60 degrees C, 65 degrees C, 70 degrees C, or 75 degrees C for 10 min. Unheated specimens served as controls. The disc core specimens were divided in two group of five each, and tested at room temperature or after immersion in a 70 degrees C bath. The shrinkage was monitored during immersion in the water bath. Biomechanical testing to failure was carried out using mechanical loading on an MTS servohydraulic testing machine operating under stroke control. Strength and stiffness of the tissue was determined. Histomorphology was studied by staining the specimen with hematoxylin and eosin (H&E), and examined under 200 times magnification. Non-heated controls were used for comparisons. RESULTS: The porcine hamstring tendons had no measurable shrinkage in specimens heated up to 65 degrees C. At temperatures above 65 degrees C, the shrinkage was concluded within 2 min of immersion and 70 degrees C appeared to be the optimal temperature, as temperatures higher than this did not demonstrate incremental effects. The disc core samples were heated to 70 degrees C (optimum temperature), and there appeared to be gross contraction of the disc core circumference to visual inspection, but no measurable lengthwise shrinkage could be appreciated. Histologically, the specimens demonstrated progressive loss of individual collagen fiber outline as the temperature increased. In the tendons, at 75 degrees C all of the fibers appear to be fused together, and the voids between individual collagen fibers were no longer present. Biomechanical testing revealed that the tendons undergo a substantial reduction in stiffness after heating. The mean tendon stiffness for the unheated specimens was 19,356 psi, while the corresponding value for the heated tendons was 1023 psi. These were significantly different using the paired t-test at p=0.0043. For the disc core samples, there was no significant difference in either stiffness (p=0.182) or failure strength (p=0.998) after heating. All failures occurred in mid-substance of the specimen. CONCLUSIONS: The application of uniform heating to nucleus pulposus disc core caused visible contraction of its circumference but not lengthwise shrinkage. The same heating shrinks the hamstring tendon and reduces its stiffness. Ultimate failure strength of the disc core specimen remains unchanged. The failure data was not obtainable for the tendon due to premature slippage from the fixation apparatus before failure. The results of this study fail to support a biomechanical justification for the application of uniform heat treatment to the whole intervertebral disc. Heating annulus fibrosus and nucleus pulposus separately to specific temperatures may have potential clinical benefits.

Posterolateral transforaminal selective endoscopic discectomy and thermal annuloplasty for chronic lumbar discogenic pain: a minimal access visualized intradiscal surgical procedure.

BACKGROUND CONTEXT: Chronic lumbar discogenic pain (CLDP) impairs the patient's physical abilities to function within the normal physiologic loading ranges of activities of daily living. The pathogenesis of CLDP is multifactorial and not well understood. Conservative therapeutic regimens often fail to achieve sufficient pain relief. Surgical options vary greatly in surgical invasiveness as well as outcome. Definitive surgical treatment is often 360-degree fusion. The morbidity associated with this approach is significant, considering that only 65% to 80% of patients obtain satisfactory clinical results. This has spawned interest in minimally invasive surgical options, such as intradiscal electrothermal therapy (IDET; ORATEC Interventions, Inc., Menlo Park, CA), but results are conflicting. PURPOSE: The authors describe their surgical technique of minimal access posterolateral transforaminal selective endoscopic discectomy (SED) and bipolar radiofrequency thermal annuloplasty to treat CLDP. The procedure's rationale is based on the hypothesis that annular defects are the focal points of chronic exposure between neural sensory receptors in the defect and the inflammatogenic nucleus pulposus. In contrast to other percutaneous procedures, this technique allows direct visualization and targeting of the disc nucleus and annular fissures. Our 2-year clinical result is reported. STUDY DESIGN/SETTING: This is a retrospective review of consecutive surgical cases performed by one surgeon (ATY). The procedures were carried out from January 1997 to December 1999. Each patient has a minimum postoperative follow-up of 2 years. PATIENT SAMPLE: A total of 113 patients met the generally accepted clinical criteria for chronic lumbar discogenic pain and were selected for the procedure. OUTCOME MEASURES: Two outcome measures were used for clinical assessment: a surgeon-based modified MacNab method and a patient-based questionnaire. A mandatory poor result was given to any patient who had repeat spine surgery at the same level or has indicated dissatisfaction with the surgical result on the questionnaire response. METHOD: After meeting CLDP selection criteria, provocation contrast/indigo carmine dye discography was performed. This test was used to confirm the suspected discs as pain generators. The subject surgery then followed. Only cases with one and two levels of confirmed painful discs were entered into the study. The nonoperating author (PMT) analyzed the data. RESULTS: Using the surgeon assessment method, 17 patients (15%) had excellent results, 32 patients (28.3%) had good results, 34 patients (30.1%) had fair results and 30 patients (26.5%) had poor results. Of the 30 patients in the poor result group, 12 reported either no improvement or worsening, and refused further surgical treatment. Of the remaining 18 patients in the poor group, 8 had spinal fusion, 3 had laminectomy and 7 had repeat spinal endoscopic surgery. The patient-based questionnaire yielded similar percentages in each category. However, only 73.5% of the 113 patients returned the survey questionnaire. There were no aborted procedures, unexpected hemorrhage, device-related complications, neurologic deficits, perioperative deaths or late instability. CONCLUSIONS: Posterolateral transforaminal SED and radiofrequency thermal annuloplasty were used to interrupt the purported annular defect pain sensitization process, thought to be necessary in the genesis of chronic lumbar discogenic pain. Lack of clinical benefit from the subject procedure did not degrade any subsequent surgical or nonsurgical treatment options. The experience gained from this study warrants further investigation into the cellular and molecular processes that provided back pain relief in these patients.

Posterolateral endoscopic excision for lumbar disc herniation: Surgical technique, outcome, and complications in 307 consecutive cases.

STUDY DESIGN: A retrospective review involving 307 consecutive cases of lumbar disc herniation managed by posterolateral endoscopic discectomy was conducted. OBJECTIVES: To describe a contemporary posterolateral endoscopic decompression technique for radiculopathy secondary to lumbar disc herniation; to evaluate the efficacy of the technique as it is applied to lumbar disc herniation including primary herniation, reherniation, intracanal herniation, and extracanal herniation; and to report outcome and complications. SUMMARY OF BACKGROUND DATA: The concept of percutaneous posterolateral nucleotomy was introduced in 1973. The development of the related equipment and technique had witnessed a slow and lengthy evolution. METHOD: A retrospective assessment of 307 patients was performed at least 1 year after their index operation. The outcome was graded according to a modified MacNab method. A patient-based outcome questionnaire also was incorporated into the study. RESULTS: The surgeon-performed assessment showed satisfactory results in 89.3% of the cases. The rate of response to the questionnaire was 91%. The responses indicated that 90.7% of the respondents were satisfied with their surgical outcome and would undergo the same endoscopic procedure again if faced with a similar herniation in the future. The poor outcome occurred in 10.7% of the primary group and 9.7% of the questionnaire group. The combined major and minor complication rate was 3.5%. CONCLUSIONS: The surgical outcome of posterolateral endoscopic discectomy for lumbar disc herniation is comparable with that for the traditional open transcanal microdiscectomy. Intracanal and extracanal herniations, reherniations, and incidental lateral recess stenosis can be addressed by the same approach.

Transforaminal endoscopic decompression for radiculopathy secondary to intracanal noncontained lumbar disc herniations: outcome and technique.

BACKGROUND CONTEXT: In 1973 Kambin and Gellman introduced the concept of percutaneous posterolateral extracanal approach in the management of radiculopathy secondary to lumbar disc herniation (LDH). This new surgical approach was recognized as potentially even less invasive compared with the microscope-assisted transcanal technique. However, the development of the posterolateral extracanal approach has witnessed a slow and complicated technique and equipment evolution. PURPOSE: To report the surgical outcome, complications and technique of decompressing radiculopathy secondary to noncontained intracanal LDH using percutaneous extracanal access, the transforaminal endoscopic approach. STUDY DESIGN/SETTING: Consecutive cases of LDHs from L3-S1 who had at least 1-year postoperative follow-up were included in this retrospective review. PATIENT SAMPLE: Two hundred nineteen patients met inclusion criteria. There were 136 (62.1%) male patients, average age 41.5 years, and 83 (37.9%) female patients, average age 42.5 years. The age range was 17 to 71 years. METHODS: Two outcome measures were used. The first part was a surgeon-performed assessment. The second used a patient-based outcome questionnaire. OUTCOME MEASURES: The surgeon's retrospective assessment of excellent, good, fair and poor is a modified MacNab classification. The same terminology is used in the patient-based outcome questionnaire. Poor outcome resulting from technique failure is identified. RESULTS: Two hundred nineteen patients met the inclusion criteria. One hundred ninety-three patients also send back their completed questionnaire. The surgeon graded 88% percent of the 219 patients had a good or excellent result and the questionnaire subgroup 91.2%. The fair results were 5% of the 219 patients, 3.6% for the questionnaire patients. The poor results were 6.8% of the 219 patients and 5.2% for the questionnaire subgroup. The overall complication rate was 2.7% and missed fragment rate 0.9%. CONCLUSIONS: Noncontained intracanal LDH fragments are accessible using the transforaminal endoscopic technique and equipment described. Retrospective outcome reviews of our clinical material showed results comparable to the reported findings in the literature for both the endoscopic and open transcanal decompression techniques.