MRI Radiological Predictors of Requiring Microscopic Lumbar Discectomy After Lumbar Disc Herniation.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To investigate radiological differences in lumbar disc herniations (herniated nucleus pulposus [HNP]) between patients receiving microscopic lumbar discectomy (MLD) and nonoperative patients. METHODS: Patients with primary treatment for an HNP at a single academic institution between November 2012 to March 2017 were divided into MLD and nonoperative treatment groups. Using magnetic resonance imaging (MRI), axial HNP area; axial canal area; HNP canal compromise; HNP cephalad/caudal migration and HNP MRI signal (black, gray, or mixed) were measured. T test and chi-square analyses compared differences in the groups, binary logistic regression analysis determined odds ratios (ORs), and decision tree analysis compared the cutoff values for risk factors. RESULTS: A total of 285 patients (78 MLD, 207 nonoperative) were included. Risk factors for MLD treatment included larger axial HNP area (P < .01, OR = 1.01), caudal migration, and migration magnitude (P < .05, OR = 1.90; P < .01, OR = 1.14), and gray HNP MRI signal (P < .01, OR = 5.42). Cutoff values for risks included axial HNP area (70.52 mm2, OR = 2.66, P < .01), HNP canal compromise (20.0%, OR = 3.29, P < .01), and cephalad/caudal migration (6.8 mm, OR = 2.43, P < .01). MLD risk for those with gray HNP MRI signal (67.6% alone) increased when combined with axial HNP area >70.52 mm2 (75.5%, P = .01) and HNP canal compromise >20.0% (71.1%, P = .05) cutoffs. MLD risk in patients with cephalad/caudal migration >6.8 mm (40.5% alone) increased when combined with axial HNP area and HNP canal compromise (52.4%, 50%; P < .01). CONCLUSION: Patients who underwent MLD treatment had significantly different axial HNP area, frequency of caudal migration, magnitude of cephalad/caudal migration, and disc herniation MRI signal compared to patients with nonoperative treatment.

Preoperative MRI predictors of health-related quality of life improvement after microscopic lumbar discectomy.

BACKGROUND: Lumbar herniated nucleus pulposus (HNP) is a common spinal pathology often treated by microscopic lumbar discectomy (MLD), though prior reports have not demonstrated which preoperative MRI factors may contribute to significant clinical improvement after MLD. PURPOSE: To analyze the MRI characteristics in patients with HNP that predict meaningful clinical improvement in health-related quality of life scores (HRQoL) after MLD. STUDY DESIGN/SETTING: Retrospective clinical and radiological study of patients undergoing MLD for HNP at a single institution over a 2-year period. PATIENT SAMPLE: Eighty-eight patients receiving MLD treatment for HNP. OUTCOME MEASURES: Cephalocaudal Canal Migration; Canal & HNP Anterior-Posterior (AP) Lengths and Ratio; Canal & HNP Axial Areas and Ratio; Hemi-Canal & Hemi-HNP Axial Areas and Ratio; Disc appearance (black, gray, or mixed); Baseline (BL); and 3-month (3M) postoperative HRQoL scores. METHODS: Patients >18 years old who received MLD for HNP with BL and 3M HRQoL scores of PROMIS (Physical Function, Pain Interference, and Pain Intensity), ODI, VAS Back, and VAS Leg scores were included. HNP and spinal canal measurements of cephalocaudal migration, AP length, area, hemi-area, and disc appearance were performed using T2 axial and sagittal MRI. HNP measurements were divided by corresponding canal measurements to calculate AP, Area, and Hemi-Area ratios. Using known minimal clinically important differences (MCID) for each ΔHRQoL score, patients were separated into two groups based on whether they reached MCID (MCID+) or did not reach MCID (MCID-). The MCID for PROMIS pain intensity was calculated using a decision tree. A linear regression illustrated correlations between PROMIS vs ODI and VAS Back/Leg scores. Independent t-tests and chi-squared tests were utilized to investigate significant differences in HNP measurements between the MCID+ and MCID- groups. RESULTS: There were 88 MLD patients included in the study (Age=44.6±14.9, 38.6% female). PROMIS pain interference and pain intensity were strongly correlated with ODI and VAS Back/Leg (R≥0.505), and physical function correlated with ODI and VAS Back/Leg (R=-0.349) (all p<.01). The strongest MRI predictors of meeting HRQoL MCID were gray disc appearance, HNP area (>116.6 mm2), and Hemi-Area Ratio (>51.8%). MCID+ patients were 2.7 times more likely to have a gray HNP MRI signal than a mixed or black HNP MRI signal in five out of six HRQoL score comparisons (p<.025). MCID+ patients had larger HNP areas than MCID- patients had in five out of six HRQoL score comparisons (116.6 mm2±46.4 vs 90.0 mm2±43.2, p<.04). MCID+ patients had a greater Hemi-Area Ratio than MCID- patients had in four out of six HRQoL score comparisons (51.8%±14.7 vs 43.9%±14.9, p<.05). CONCLUSIONS: Patients who met MCID after MLD had larger HNP areas and larger Hemi-HNP Areas than those who did not meet MCID. These patients were also 2.7× more likely to have a gray MRI signal than a mixed or black MRI signal. When accounting for HNP area relative to canal area, patients who met MCID had greater Hemi-HNP canal occupation than patients who did not meet MCID. The results of this study suggest that preoperative MRI parameters can be useful in predicting patient-reported improvement after MLD.

Implantation of a bone-anchored annular closure device in conjunction with tubular minimally invasive discectomy for lumbar disc herniation: a retrospective study.

BACKGROUND: Minimally invasive techniques for lumbar discectomy have been recommended as superior to open techniques due to lower blood loss, lower rates of infection and shorter recovery. There are, however, concerns that this approach does not sufficiently remove the herniated nuclear material, thus leaving the patient susceptible to reherniation requiring reoperation. The purpose of this study was to examine the safety and viability of an annular closure device in limiting reherniation and reoperation in a cohort of patients undergoing minimally invasive lumbar discectomy with the assistance of an annular closure device. METHODS: We retrospectively analysed the results from patients treated by a single surgeon between March 2011 and December 2017. All patients had been diagnosed with a large (≥ 5 mm) defect and were treated via minimally invasive surgical techniques. Outcomes included demographic data, the procedural duration and the rates of symptomatic reherniation and reoperation. RESULTS: 60 patients were included in the study. The mean age was 42 years (range: 19-66); mean BMI was 24.1 (range: 16.7-36.3). Mean surgical duration was 29 min (range: 16-50). Reoperation was required in 5% (3/60) of patients, although only 3% (2/60) experienced symptomatic reherniation at the index level. No other complications were reported. CONCLUSIONS: In our study, the use of an annular closure device during minimally invasive lumbar discectomy in a population of patients with large herniations was associated with low rates of reherniation and reoperation at the index level. While more research is required, the results of this study demonstrate the safety and viability of the annular closure device as an adjunct to minimally invasive discectomy.

The facet joint loading profile of a cervical intervertebral disc replacement incorporating a novel saddle-shaped articulation.

STUDY DESIGN: Biomechanical study. OBJECTIVE: To evaluate the cervical facet loading profile of an intervertebral cervical disc prosthesis incorporating a unique saddle-shaped articulation and to determine the effect of implantation of the prosthesis on both the loading curve and area distribution of facet loading, when compared with that of an intact specimen. SUMMARY OF BACKGROUND DATA: This is the first study that examines the effect of implantation of a cervical disc replacement on the loading of the facet joints. METHODS: Fresh-frozen ovine cervical spine specimens were used. Specimens were prepared and disarticulated to yield 6 functional spinal units, which were secured and mounted in a custom fixture on a material testing apparatus. A novel pressure sensor was constructed by combining a resistive ink thin film sensor with Fuji pressure-sensitive film. The sensor was calibrated before unilateral insertion into the cervical facet joint via a small arthrotomy. Specimens were tested in both intact condition and after surgical intervention consisting of discectomy and implantation of an intervertebral cervical disc prosthesis (CerviCore, Stryker Spine, Allendale, NJ). Specimens were tested in flexion, extension, and lateral bending to 3 Nm and in torsion to 2.5 Nm. At the termination of each loading profile, the load was maintained for 30 seconds to permit full exposure of the Fuji film. For each configuration, the maximum resultant load, load rate, and contact area pressure at the endpoint of the loading profile were determined. A paired Student t test was used to determine the differences between the intact specimen and the specimen with an implanted intervertebral disc prosthesis. RESULTS: There were no statistically significant differences in mean or maximum pressures between the intact specimen and the specimen with an intervertebral disc in all loading configurations. Similarly, there was no significant difference in the total measured force between the groups in all loading configurations. There was no significant difference in contact areas between the groups in flexion, lateral bending, and torsion. When evaluated in extension, the intact specimen had a mean contact area of 0.8 cm compared with 0.5 cm for the intervertebral disc (P<0.02). CONCLUSIONS: Biomechanical testing in an ovine model demonstrated no significant difference in measured facet pressures and forces between an intact native cervical disc specimen and a cervical intervertebral disc prosthesis using a saddle-shaped articulation. Peak and mean pressures were not demonstrated to be significantly different between the implanted and intact disc conditions. Implantation of the prosthesis resulted in a significant reduction of contact area under extension moments.

The manubrium as an external guide for centralizing anterior cervical plates: technique tips and initial experience.

STUDY DESIGN: Technique tips and retrospective review of prospectively collected data. OBJECTIVE: To describe a technique for centralizing cervical plates using the center of the manubrium as a primary external guide and its alignment with the mandible as a secondary guide. SUMMARY OF BACKGROUND DATA: Proper alignment of cervical plates is desirable to avoid improper placement of screws and possibly altered biomechanical performance. Large body habitus may portend suboptimal exposure, a limited utility of skin surface landmarks for level determination, and may make it difficult to reliably centralize plates in the coronal plane during anterior cervical surgery. METHODS: We describe a technique that uses the center of the manubrium to determine the midline of the cervical spine and align a line drawn through the manubrium with the center of the mandible to provide a central axis for placing cervical plates along the entire cervical spine. We used anteroposterior fluoroscopy to validate that a line from the middle of the manubrium to the mandible bisected the spinous processes and midline of the vertebral bodies. We prospectively collected data on 39 consecutive patients undergoing anterior cervical discectomy and fusion with cervical plates using this technique. RESULTS: The mean amount of angulation and translation about a midline axis were 2.24 degrees +/- 1.49 degrees and 1.04 +/- 0.86 mm, respectively. There were no statistical differences among 1-level, 2-level, and 3-level fusions (P > 0.05). The intraobserver correlation coefficient for the measurement technique was R = 0.90 (P = 0.0016). CONCLUSION: We validated that the midline of the cervical spine is in line with a straight bovie cord connecting the midline of the manubrium to the midline of the mandible using anteroposterior fluoroscopy. Using this line, we prospectively centered cervical plates with no significant difference between levels. These data may also serve as a benchmark for assessing cervical plate alignment.

Early failure of lumbar disc replacement: case report and review of the literature.

We report a case of a patient who underwent two-level lumbar total disc replacement at L4-L5 and L5-S1 with the ProDisc II prosthesis, who was diagnosed with early anterior migration of the caudally placed device with partial occlusion of the left common iliac vein. The device was explanted and revised to an anterior lumbar interbody fusion with posterior instrumented fusion. Despite the substantial experience with lumbar disc arthroplasty in Europe and the United States, there exist few reports of device explantation or revision. To our knowledge, early postoperative vascular complications, while discussed hypothetically, have not been reported. With implantation of the total disc replacement in proximity to the great vessels, the potential for vascular complications is clearly substantial. The technical aspects of the device explantation are discussed as well as issues pertinent to early failure. A literature review of device complications associated with lumbar total disc replacement is also presented.

Anterior cervical decompression and fusion with plate fixation as an outpatient procedure.

BACKGROUND CONTEXT: Outpatient cervical spine surgery has previously been described for posterior laminoforaminotomy and anterior microdiscectomy with allograft fusion. Anterior cervical discectomy and fusion (ACDF) with plate fixation has not, to our knowledge, been described as an outpatient procedure. PURPOSE: The objective of this study was to evaluate the safety and feasibility of ACDF with instrumentation when performed as an outpatient in a free-standing ambulatory surgical center. Additionally, the authors sought to determine any patient selection bias and its effect on outcome. STUDY DESIGN: This study is a retrospective medical record review. PATIENT SAMPLE: The sample included all patients who underwent one or two level ACDF with plate fixation at levels C4-5 or below as an adjunct to autogenous iliac crest bone graft or structural allograft from 1998 to 2002 by the two senior authors. OUTCOME MEASURES: Complications were assessed clinically with special attention to dysphagia and respiratory complications. Inpatient lengths of stay and postoperative hospital admission or readmission were also measured. METHODS: Thirty consecutive patients were treated at a free-standing ambulatory surgery center, whereas two control groups, each of 30 consecutive patients, had surgery performed in the hospital and were admitted overnight for observation. The first control group consisted of admitted patients before the commencement of patient selection for the outpatient group; the second control group was comprised of admitted patients who had surgery performed concurrently with the outpatient group. The study group was evaluated on the first postoperative day and 3 weeks after surgery. RESULTS: Ninety patients underwent ACDF plate fixation at 140 different levels. Forty patients were treated at one level, and 50 were treated at two levels. The three groups were comparable in age, sex, and body mass index. There were no major complications. Seven patients (13%) had minor postoperative complications among the controls: transient dysphagia in three (5%) and graft donor site pain in four (14%). Three patients (10%) in the outpatient group had minor complications (all had dysphagia). Among the controls, four patients (7%) had increased length of stay owing to complications. Four patients (7%) in the combined control group were readmitted for early complications; no patient was admitted for a complication after outpatient surgery. CONCLUSIONS: In the present study, selection criteria for outpatient surgery included one or two level involvement C4-5 or lower, absence of myelopathy, subjective neck size, and estimated operative time. The data did not otherwise suggest a difference in the surgical populations. The outpatient group had a lower complication rate compared with the controls. This was likely the result of selection bias. Transient dysphagia was the most prevalent complication in the outpatient group.

Manifestations of hereditary multiple exostoses.

The solitary osteochondroma, a common pediatric bone tumor, is a cartilage-capped exostosis. Hereditary multiple exostosis is an autosomal dominant disorder manifested by the presence of multiple osteochondromas. Linkage analysis has implicated mutations in the EXT gene family, resulting in an error in the regulation of normal chondrocyte proliferation and maturation that leads to abnormal bone growth. Although exostoses are benign lesions, they are often associated with characteristic progressive skeletal deformities and may cause clinical symptoms. The most common deformities include short stature, limb-length discrepancies, valgus deformities of the knee and ankle, asymmetry of the pectoral and pelvic girdles, bowing of the radius with ulnar deviation of the wrist, and subluxation of the radiocapitellar joint. For certain deformities, surgery can prevent progression and provide correction. Patients with hereditary multiple exostosis have a slight risk of sarcomatous transformation of the cartilaginous portion of the exostosis.

Intradiscal pressure monitoring in the cervical spine.

BACKGROUND: Discography has been widely used in the lumbar and cervical spine as a diagnostic tool to identify sources of discogenic pain that may be amenable to surgical treatment. Discography in the cervical spine is currently performed without the benefit of pressure monitoring, and corresponding pressure parameters have not been determined. OBJECTIVE: The purpose of this study was to develop the framework for intradiscal pressure monitoring in the cervical spine and the basis for a pressure curve that will reflect clinically significant cervical internal disc disruption. We also sought to determine whether there is any pressure increase in adjacent discs during cervical discography that might result in false-positive diagnosis during in-vivo discography. An additional goal was to establish safe upper parameters for infusion volume and intradiscal pressure in the cervical spine. DESIGN: Investigation of fresh-frozen discs in the cervical spine. METHODS: Investigated were 26 discs in 5 fresh-frozen cadaveric cervical spines aged 45 to 68 with no prior history of cervical spine disease. A T2 MRI was performed on each specimen and radiographically abnormal discs were noted. Pressure-controlled, fluoroscopically guided discography was performed on each level using a right lateral approach. Opening pressure, rupture pressure, volume infused, and location of rupture were recorded. Pressures were simultaneously recorded at each adjacent disc level using additional pressure monitors and identical needle placement. Immediately following discography, CT was performed on each specimen according to the discography protocol. RESULTS: Twenty-six discs C2-3 to C7-T1 were grossly intact for evaluation. The median opening pressure was 30 psi (range 14-101 psi). Two discs did not rupture and were pressurized to 367 psi. In 24 discs, the median intradiscal rupture pressure was 40 psi (range 14-171 psi). The median volume infused at rupture was 0.5 ml (range 0.25-1.0 ml). When grouped, the median intradiscal rupture pressure in the C2-3, C3-4, and C7-T1 discs was 53 psi (range 16-171 psi) compared to 36.5 psi (range 14-150 psi) in the C4-5, C5-6, and C6-7 discs (p=0.18). There was no measurable pressure change in any of the 30 adjacent disc levels evaluated. CONCLUSION: In the cervical spine, iatrogenic disc injury may be caused at significantly lower pressures and volumes infused than in the lumbar spine. There was no measurable pressure change in any of the adjacent disc levels evaluated at maximum intradiscal pressurization. Further cadaveric testing will be necessary to develop parameters for intradiscal pressure monitoring in the cervical spine.