Posterior annular strains during discography.

Discography is commonly used in the workup of back disorders. The clinical utility of the test is controversial, and little is known about mechanical changes that may occur in the disc during this exam. To quantify three-dimensional deformations of the posterior annulus during discography, and to examine some of the covariates that influence the deformations, displacements of the lumbar posterior annulus were measured during discographic injection for three different spinal positions. Disc bulge and annular strains were calculated from the displacements. The combined effect of disc pressurization, spine position, and location on the disc (lateral versus midline) explained much of the variation in the measured bulges and strains (r(2) = 0.56). Disc pressurization or spine position alone did not always have a significant effect on strains, and the strains and bulges were often influenced by the interactions between position of the spine, location of the disc, and pressurization. In clinical studies of discography, these results suggest that patient position during the examination should be standardized.

Sensitivity and specificity of dural sac and herniated disc dimensions in patients with low back-related leg pain.

Narrow spinal canals or herniated discs can be associated with leg pain. However, it is not known whether quantitative measurements of the spinal canal or herniated disc are sensitive and specific for low back-related leg pain. The size and cross-sectional area of the dural sac and any herniated discs were measured from magnetic resonance imaging examinations of 22 asymptomatic individuals and 44 patients with sciatica. The sensitivity and specificity of these measurements were determined. In this small population of patients, a dural sac anteroposterior (AP) diameter of 10.2 mm at the L3-4, L4-5, or L5-S1 vertebral levels was 74% sensitive and 74% specific for leg pain. Based on measurements in symptomatic patients, a herniated disc with an AP diameter of approximately 3 mm was over 95% sensitive and 95% specific. However, if the AP diameters of herniated discs in symptomatic patients were compared with similar measurements in asymptomatic controls, the most sensitive and specific threshold value was 6.8 mm. These findings must be confirmed in a larger population before they are applied clinically. J. Magn. Reson. Imaging 2000;12:439-443.

Thoracolumbar pseudarthrosis.

Pseudarthrosis is the leading cause of failed spine fusion and is of paramount concern to surgeons attempting fusion procedures. Thus, it is essential to understand this complication to direct efficient and intelligent management. A review of various modalities in the identification and diagnosis of a pseudarthrosis is presented. In addition, its histologic features and classification system are discussed. Not all pseudarthroses need treatment. When treatment is considered, however, there are both nonoperative and operative strategies. Operative alternatives include posterolateral, anterior, or anterior-posterior combined fusions.

Long-term functional and radiographic follow-up of surgically treated isthmic spondylolisthesis.

We studied patients treated surgically for isthmic spondylolisthesis since 1968, with special emphasis on a detailed functional assessment. We followed up 22 patients for an average of 15 years, with a mean age at time of surgery of 18 years. All patients underwent a thorough physical examination and were evaluated with radiographs at baseline and at follow-up. The functional status of patients at the time of follow-up was assessed with 2 self-report pain and function instruments. All surgical procedures included spinal fusion, 12 of which included internal fixation by using Harrington distraction rods with sacral bars. At final follow-up, there was no statistically significant difference in mean slip percentage or mean slip angle compared with baseline radiographs. Functional evaluation was compared with a control group consisting of 52 patients. We conclude that the long-term radiographic and functional outcome is excellent for patients treated surgically for isthmic spondylolisthesis.

Use of percutaneous transpedicular external fixation pins to measure intervertebral motion.

STUDY DESIGN: Direct measurement of intervertebral motion was compared to motion determined by measuring the position of the exposed ends of the external fixation pins. OBJECTIVES: To verify the accuracy of this technique, so that this protocol can be used to study intervertebral motion in the clinical setting. SUMMARY OF BACKGROUND DATA: The transpedicular external fixation test has been shown to be a test that can predict the outcome of spinal fusion. In patients who are candidates for this test, intervertebral motion can be calculated from motion at the external ends of these pins. METHODS: Six fresh cadaveric spinal segments from L2 to L5 were instrumented with titanium Schanz screws. Reflective markers were placed on the tips of the pins, and intervertebral motion was measured using a noncontacting camera system. Computed tomography data were used to determine the position of the vertebra relative to the reflective markers. Intervertebral distances were calculated and compared with direct measurements obtained using a three-dimensional digitizing arm. RESULTS: There was an excellent correlation (r2 = 0.931) between the directly measured intervertebral motions and those that were indirectly calculated from measurements of motion at the end of the Schanz screws. CONCLUSIONS: Intervertebral motion can be measured by monitoring motion of the ends of transpedicular external fixation pins. Motion of anatomic landmarks on the vertebrae can be calculated from the pin end's motion if computed tomography data are used to determine the geometric relation between the vertebrae and the external fixation pins. This validation study supports the use of this method in clinical investigations of intervertebral motion in patients with low back pain and external fixation.

Femoral ring versus fibular strut allografts in anterior lumbar interbody arthrodesis. A biomechanical analysis.

STUDY DESIGN: A comparison between femoral ring and fibular strut allografts in anterior lumbar interbody arthrodesis, as assessed by biomechanical analysis. OBJECTIVES: To assess the difference in stability and rigidity provided by the femoral ring allograft versus that provided by fibular strut allograft. SUMMARY OF BACKGROUND DATA: Two commonly used techniques for spinal arthrodesis at L4-L5 include the femoral ring allograft and the fibular strut allograft. The postoperative stability has not been evaluated biomechanically. METHODS: An anterior lumbar interbody fusion on seven cadaveric specimens was performed using femoral ring and fibular strut allografts. Biplanar radiography was used to measure the 6 degrees of motion of L4 with respect to L5 during a range of loading maneuvers. RESULTS: When an extension moment was applied, the femoral ring allograft extended 4.2 degrees more than the intact specimen, compared with 1.6 degrees with the fibular strut allograft (P = 0.18). When the flexion moment was imposed, lateral bending increased by 2.2 degrees with the femoral ring, compared with 0.7 degree with the fibular strut allograft (P = 0.06). During lateral bending, increased lateral translation was observed to be 0.9 mm with the fibular strut allograft compared with 1.4 mm with the femoral ring allograft (P = 0.06). CONCLUSIONS: Although not statistically significant, the fibular strut allograft creates a more rigid construct immediately after surgery during flexion-extension, lateral bending angulations, and lateral translation. One should consider using the fibular strut allograft over the femoral ring allograft, as it is more stable and rigid construct in the immediate postoperative period.

Radiographic verification of pedicle screw pilot hole placement using Kirshner wires versus beaded wires.

STUDY DESIGN: Kappa statistics were used to compare the accuracy of two different techniques for verifying pedicle screw pilot hole placement in cadaveric vertebrae. OBJECTIVE: To determine whether clinicians radiographically detect misplaced pedicle screw holes with greater sensitivity and specificity when beaded wires rather than straight Kirschner wires are used. SUMMARY OF BACKGROUND DATA: Pedicle screws commonly are used in orthopedic surgery to obtain and maintain spinal stability. Pedicle screws are reportedly misplaced at a rate of 20% to 40%. Radiographic verification is commonly used to place pedicle screw pilot holes, but this technique is known to be less than 100% accurate. Computer-assisted techniques may allow more accurate screw placement, but these techniques require expensive equipment. METHODS: Pedicle screw pilot holes were drilled into 12 human lumbar and thoracic vertebrae. Some of the holes were misplaced deliberately so that they violated the pedicle walls. Lateral and posteroanterior radiographs of the vertebrae were evaluated by 13 experienced orthopedic spine surgeons and 3 inexperienced observers. At different times, the observers were shown radiographs depicting Kirschner wires or beaded wires placed in the pilot holes. Observers indicated whether they thought the pedicle screw pilot hole violated the pedicle. RESULTS: The sensitivity and specificity of using posteroanterior or lateral radiographs to detect misplaced pedicle screws were increased when beaded wires were placed in the pilot holes. CONCLUSIONS: Radiographic evaluation of beaded wires placed in pedicle screw pilot holes can be both sensitive and specific for misplaced screws. The highest sensitivity and specificity were found using posteroanterior radiographs.

Morphology of the lumbar vertebral endplates.

STUDY DESIGN: The dimensions and shapes of vertebral body endplates of inferior L4, inferior and superior L5, and superior S1 were analyzed. Computed tomographic scans parallel to each endplate were used to develop a standardized geometric model of the boundaries of each vertebral body. OBJECTIVES: To provide a detailed analytic and geometric model of the vertebral endplates from the inferior surface of L4 to the superior surface of S1. SUMMARY OF BACKGROUND DATA: Although measurements of the sagittal and maximum transverse diameters of the vertebral bodies have been well documented, no study offers a complete geometric description of the shape of the endplates. Also, information acquired using the techniques of previous published reports may not provide measurements as accurate as those of the current investigation. METHODS: Twenty-five men and 21 women were studied. Computed tomographic scans of the endplates were digitized. The data were interpolated, and multivariate regression equations were derived to devise a standardized model. Measurements were taken, and the data were curve fitted to give best-fit equations for the standardized models. RESULTS: The endplates resembled a cardioid at the inferior L4 level and became more elliptical toward the superior S1 level. The sagittal and transverse diameters of the endplates of inferior L4, superior and inferior L5, and superior S1 are provided and compared with those reported in previous studies. CONCLUSION: Although the female endplates are smaller than their male counterparts, the overall shapes are similar.

Neuroaugmentation in the management of sacroiliac joint pain. Report of two cases.

STUDY DESIGN: A report of two cases of severe sacroiliac pain that were resistant to conventional management techniques. Both patients had undergone lumbar fusion. This appeared to be a predisposing factor. OBJECTIVE: To define the source of pain in these patients by performing a series of diagnostic blocks under fluoroscopic guidance to determine if these patients were candidates for neuroaugmentation. SUMMARY OF BACKGROUND DATA: Mild to moderate sacroiliac joint pain can be managed conservatively with analgesics, anti-inflammatory drugs, and physical therapy. Severe sacroiliac joint pain can be incapacitating and more challenging to manage. Fluoroscopically guided intra-articular local anesthetic-steroid injections, followed by joint manipulation, can be effective, intracapsular injections of glycerin, glucose, and phenol also may be beneficial in some patients. The use of neuroaugmentation to manage pain of synovial origin has not been reported previously. Sacral nerve root stimulation in particular has been used to manage urinary bladder dysfunction and pain, but not sacroiliac joint pain. METHODS: Two patients with severe sacroiliac joint pain were treated by implanting a neuroprosthesis at the third sacral nerve roots. The patients had undergone lumbar fusion for back pain that developed as a result of work-related injuries. Stimulation was tried for 1 week with bilateral, percutaneously implanted, cardiac pacing wires at the third sacral nerve roots. RESULTS: Both patients experienced relief of approximately 60% of their pain during the trial period. Therefore, a neuroprosthesis (Medtronics, MN) was implanted permanently bilaterally at the third sacral nerve root in both patients. The use of analgesics was reportedly the same after implantation, but significantly more effective, and the patients' daily living activities were more tolerable. CONCLUSIONS: Two cases of refractory sacroiliac joint pain are reported that were managed with permanently implanted neuroprostheses at the third sacral nerve roots. The authors suggest that neuroaugmentation can be a reasonable option in selected patients with refractory sacroiliac pain.

Anterior cervical fusion: outcome analysis of patients fused with and without anterior cervical plates.

The purpose of this study was to assess the role of the anterior cervical plate in the treatment of cervical spondylosis. Forty-three patients surgically treated for cervical spondylosis were reviewed. The technique for discectomy and fusion was the same for both groups (Smith-Robinson with autologous iliac crest bone graft). Group I consisted of 25 consecutive patients treated with anterior cervical discectomy, autograft fusion, and anterior cervical plate fixation (Morscher titanium hollow screw plate system). Group II consisted of 18 consecutive patients treated without plate fixation. The overall clinical results in this study were not improved with the use of anterior cervical plate fixation (Fisher's exact test, p > 0.05). The fusion rate of one-level cervical fusions was not improved with anterior cervical plate fixation (Fisher's exact test, p > 0.05). The overall graft complication rate (pseudoarthrosis plus delayed union plus graft collapse) in multilevel fusions was decreased with anterior cervical plate fixation (Fisher's exact test, p < 0.01). The cost effectiveness and risk versus benefit of anterior cervical plate fixation in the surgical treatment of cervical spondylosis require further investigation.

Kinematic evaluation of lumbar fusion techniques.

STUDY DESIGN: Eight human cadaveric lumbosacral spines were biomechanically and kinematically tested in torsion and compression-flexion. They were retested after simulated posterolateral fusion, anterior lumbar interbody fusion, and circumferential fusion. OBJECTIVES: To analyze stiffness and motion in the anterior and posterior columns of the index and contiguous spinal motion units of anterior, posterolateral, and circumferential fusions. SUMMARY OF BACKGROUND DATA: Previous biomechanical studies have not incorporated analysis of motion with six degrees of freedom, consideration of contiguous levels, and comparisons of anterior and posterior column motion. METHODS: Eight human cadaveric lumbosacral spines were biomechanically tested in compression-flexion and torsion using an advanced biplanar radiography technique. Each specimen underwent either a simulated posterolateral fusion or anterior fusion followed by a circumferential fusion. Motion and stiffness at the level of the fusion and at contiguous levels were analyzed independently in the anterior and posterior columns of the spine. RESULTS: At the level of fusion, the simulated posterolateral and anterior fusions prevented more motion in torsion compared with compression-flexion. With all specimens, it was shown that circumferential fusions were stiffer than the intact specimen. Our comparison of motion in the anterior and posterior columns found no significant differences within the columns of a single vertebral motion segment. Compared with posterolateral fusions, anterior fusions were found to have the greatest effect in increasing motion at contiguous levels. The effect of circumferential fusions on adjacent level kinematics was not significantly greater than that of anterior fusions. CONCLUSION: There are major biomechanical differences between different fusion techniques. This information should be considered in patients undergoing lumbar spinal fusion.

Conservative options in the management of spinal disorders, Part II. Exercise, education, and manual therapies.

At this time, evidence supports exercise as an efficacious form of treatment for individuals suffering from back pain. The incorporation of education regarding posture, body mechanics, and ergonomics as part of a progressive exercise program appears justified. While there is empirical evidence available for the use of biofeedback, there are no specific studies supporting its efficacy in the treatment of the spine. Manual therapies such as mobilization and/or manipulation appear to shorten the course of subacute back pain, but do not alter the natural history and do not appear to be efficacious as monotherapy for chronic back pain.

Posterior interbody arthrodesis with a fibular strut graft in spondylolisthesis.

We reviewed the results of posterior interbody arthrodesis of the fifth lumbar and first sacral vertebrae with the use of a fibular strut graft in nine patients who had had a grade-III, IV, or V spondylolisthesis. The average age of the patients at the time of the operation was twenty-seven years (range, seventeen to thirty-two years). The average duration of the symptoms preoperatively was three years (range, nine months to eleven years), and the average duration of follow-up was three years (range, two to five years). The most common preoperative symptom was back pain, which was rated an average of 8.3 points (7, 8, or 9 points) on a visual-analog scale of 1 to 10 points. The average angle of the slip was 45 degrees (range, 15 to 70 degrees). Four of the slips were grade III, four were grade IV, and one was grade V. Postoperatively, the average pain score was 1.4 points (1, 2, or 3 points). This improvement was significant (p < 0.05, Student t test). All nine patients had roentgenographic evidence of osseous fusion at the one-year follow-up examination. Complications included a dural tear in one patient, a superficial wound infection in two patients, temporary weakness of the evertors of the foot in six patients, and transient decreased sensation along the dorsum of the foot of the donor leg in two patients.

Conservative options in the management of spinal disorders, Part I. Bed rest, mechanical and energy-transfer therapies.

Current literature does not support the efficacy of solitary use of energy-transfer therapies, such as ice or heat treatments, or electrotherapy, for the treatment of idiopathic back pain. Bed rest does not alter the natural history of back pain, and in fact can be detrimental to optimal recovery. Mechanical therapies, such as traction and orthoses, have limited usefulness. Although orthoses do not appear to weaken the trunk, they also do not appear to alter posture out of the brace, do not consistently diminish back muscle action during activities, and do not immobilize the spine. There have been no conclusive studies to substantiate the solitary use of any of these forms of treatment, although some may be beneficial at times in an adjunctive role.

Biomechanical testing of pars defect repairs.

STUDY DESIGN: Human lumbar vertebral bodies were used to biomechanically test three different pars interarticularis defect repair techniques. A posteriorly directed force was applied to the inferior facets so that a bending moment was created across the pars. OBJECTIVES: The stiffness and strength of each type of repair was measured and compared with the intact values. SUMMARY OF BACKGROUND DATA: The Buck screw provided both the stiffest and strongest repair overall and within each group of cadaveric specimens. This was followed by the Morscher hook screw. Both the screw and hook repair were statistically significantly stronger and stiffer than the wire repair. There was no statistical difference between the screw and hook repairs regarding strength or stiffness. METHODS: Using the intact L1 vertebral body as a control for each cadaver, the three surgical techniques for pars repair could be evaluated. RESULTS: The screw repair provided 64% of the intact stiffness and 58% of the intact strength. The hook repair provided an average of 52% of the intact stiffness and 40% of the intact strength. The wire provided only 3.5% of the intact stiffness and 12% of the intact strength. CONCLUSIONS: The screw repair technique is the stiffest and strongest pars repair method. The wire technique restores the least stiffness and strength.

Indications for pedicle fixation. Results of NASS/SRS faculty questionnaire. North American Spine Society and Scoliosis Research Society.

STUDY DESIGN: The faculty of the North American Spine Society and Scoliosis Research Society pedicle fixation workshop were questioned about their use of pedicle screw implants for fixation of the spine. OBJECTIVES: This study ascertained which faculty members used pedicle implants given specific clinical scenarios and analyzed the data for trends and consensus. SUMMARY OF BACKGROUND DATA: For the past 4 years, the North American Spine Society in conjunction with the Scoliosis Research Society has sponsored a course on pedicle fixation of the spine. During these courses, techniques of pedicle fixation have been discussed. The indications, however, for pedicle fixation have remained controversial, even among the course faculty. METHODS: A questionnaire was developed with 20 clinical scenarios, and the faculty were asked whether they would use pedicle implants as part of their surgical treatment. RESULTS: Thirty-eight of 45 (84%) questionnaires have been received and analyzed. For most scenarios, there was statistically significant consensus among the faculty that they would use a pedicle implant. There was statistically significant consensus that the faculty would not use pedicle implants for thoracic fractures or adolescent idiopathic scoliosis. DISCUSSION: This study is useful in assessing pedicle implant usage in our community but should not be used as a guide for their indications and contraindications.

A comparative analysis of spondylolysis repair.

STUDY DESIGN: This retrospective study compared patient outcome after two surgical techniques for pars interarticularis repair: 1) buck screw fixation and 2) the modified Morscher-designed spondylolysis distraction hook. OBJECTIVES: To determine whether one technique was associated with higher radiographic, clinical, or implant failure. SUMMARY OF BACKGROUND DATA: Both techniques have been reported as giving good clinical results. METHODS: Twenty patients were included in this study. All patients had Type IIA spondylolytic defects with either a Grade 0 or Grade I spondylolisthesis. Nine patients were treated with the Morscher hook implant, and 11 patients were treated with the Buck technique. RESULTS: Radiographic follow-up of the Morscher implants demonstrated loosening in three and breakage in one. Radiographic analysis of the Buck technique demonstrated implant failure in one. Failure of healing occurred in four instances with the Morscher implant compared with two instances with the Buck technique. Clinical outcome was assessed using the modified Prolo score. The mean outcomes were 6.33 in the Morscher group and 6.09 in the Buck group. CONCLUSIONS: In these patients, the Morscher implant had a high failure rate. Furthermore, the clinical outcome in this group of patients was poor using either technique.

A histologic study of soft-tissue reactions to spinal implants.

OBJECTIVES: The biologic reactions to orthopedic spinal implants were determined. METHODS: Biopsies of soft tissue immediately adjacent to spinal implants were done in 36 consecutive patients undergoing elective lumbar spinal hardware removal and was studied histologically. RESULTS: A fibrous tissue matrix was noted in all specimens. In 11 of 36 specimens, a discrete layer of cells with epithelial characteristics was noted on the surface immediately opposed to the metal implant. Results of immunohistochemical staining were negative using antibodies to markers, which suggests that these unique cell layers are probably of histiocytic origin. Black amorphous metallic debris was seen in nine of the specimens. In seven of these specimens, this material was associated with an inflammatory foreign-body reaction. Refractile non-biorefringent crystalline bodies were noted in five specimens. These crystalline deposits provoked a local foreign-body reaction in all cases. CONCLUSION: The role of soft-tissue inflammatory reactions in the production of clinical symptoms of pain is discussed.

In vivo diurnal variation in intervertebral disc volume and morphology.

STUDY DESIGN: Three-dimensional reconstructions of MRI scans measured volume, height, and diameter of intervertebral discs. These measurements were made in vivo. OBJECTIVES: This study documented diurnal change in lumbar disc volume and morphology. The authors studied the pattern of this change over the disc levels that were examined and documented individual differences. SUMMARY OF BACKGROUND DATA: There is a diurnal pattern of standing heights. The majority of this diurnal height change can be accounted for by height loss within the intervertebral disc, which bulges radially with loading. These studies have been performed in vivo. METHODS: Eight normal males were studied using two protocols. In one, the volunteers were in the supine position for 6 hours before MRI scanning. In the other, volunteers spent 4 hours standing and 3 hours sitting before MRI scanning. Three-dimensional MRI scanning was carried out on the L3-4, L4-5, and L5-S1 discs. RESULTS: Volume height and AP diameter of the lumbar intervertebral discs decreased significantly after the protocol of a day's activity. The mean decrease in disc volume at the L3-4 level after standing was 21.1%. At the L4-5 level, it decreased a mean of 18.7%, whereas at the L5-S1 level, there was a 21.6% mean decrease. CONCLUSIONS: The mean simulated diurnal volume decrease in the lower three lumbar discs is 16.2%. Most of the diurnal loss in disc height is due to volume loss. The effect of radial bulging is minimal.

Complications associated with the technique of pedicle screw fixation. A selected survey of ABS members.

A limited survey analysis of 617 surgical cases in which pedicle screw implants were used was undertaken to ascertain the incidence and variety of associated complications. The different implant systems used included variable spinal plating (n = 249), Edwards (n = 143), and AO fixateur interne (n = 101). The most common intraoperative problem was unrecognized screw misplacement (5.2%). Fracturing of the pedicle during screw insertion and iatrogenic cerebrospinal fluid leak occurred in 4.2% of cases. The postoperative deep infection rate was 4.2%. Transient neuropraxia occurred in 2.4% of cases, and permanent nerve root injury occurred in 2.3% of cases. Previously unreported injury to nerve roots occurred late in the postoperative course in three cases. Screw breakage occurred in 2.9% of cases. All other complications had an incidence of less than 2%. The authors conclude that pedicle screw placement may be associated with significant intraoperative and postoperative complications. This information is of value to surgeons using pedicle implant systems as well as to their patients. Repeat surgery is associated with greater numbers of complications.