James J. Yue

Results of the prospective, randomized, multicenter Food and Drug Administration investigational device exemption study of the ProDisc-L total disc replacement versus circumferential fusion for the treatment of 1-level degenerative disc disease.

Study Design. A prospective, randomized, multicenter, Food and Drug Administration-regulated Investigational Device Exemption clinical trial. Objective. To evaluate the safety and effectiveness of the ProDisc®-L (Synthes Spine, West Chester, PA) lumbar total disc replacement compared to circumferential spinal fusion for the treatment of discogenic pain at 1 vertebral level between L3 and S1. Summary of Background Data. As part of the Investigational Device Exemption clinical trial, favorable single center results of lumbar total disc replacement with the ProDisc®-L have been reported previously. Methods. Two hundred eighty-six (286) patients were treated on protocol. Patients were evaluated before and after surgery, at 6 weeks, 3, 6, 12, 18, and 24 months. Evaluation at each visit included patient self-assessments, physical and neurologic examinations, and radiographic evaluation. Results. Safety of ProDisc®-L implantation was demonstrated with 0% major complications. At 24 months, 91.8% of investigational and 84.5% of control patients reported improvement in the Oswestry Low Back Pain Disability Questionnaire (Oswestry Disability Index [ODI]) from preoperative levels, and 77.2% of investigational and 64.8% of control patients met the ≥15% Oswestry Disability Index improvement criteria. Overall neurologic success in the investigational group was superior to the control group (91.2% investigational and 81.4% control; P = 0.0341). At 6 weeks and 3 months follow-up time points, the ProDisc®-L patients recorded SF-36 Health Survey scores significantly higher than the control group (P = 0.018, P = 0.0036, respectively). The visual analog scale pain assessment showed statistically significant improvement from preoperative levels regardless of treatment (P < 0.0001). Visual analog scale patient satisfaction at 24 months showed a statistically significant difference favoring investigational patients over the control group (P = 0.015). Radiographic range of motion was maintained within a normal functional range in 93.7% of investigational patients and averaged 7.7°. Conclusions. ProDisc®-L has been found to be safe and efficacious. In properly chosen patients, ProDisc®-L has been shown to be superior to circumferential fusion by multiple clinical criteria.

The treatment of disabling single-level lumbar discogenic low back pain with total disc arthroplasty utilizing the Prodisc prosthesis: a prospective study with 2-year minimum follow-up.

Study Design. Prospective, longitudinal minimum 2-year follow-up. Objective. To assess the efficacy and safety of the Prodisc implant in patients with disabling multilevel discogenic low back pain (LBP). Summary of Background Data. Few, if any, alternatives have been proposed to treat recalcitrant and debilitating multilevel lumbar discogenic low back pain. To date, a prospective study specifically examining the use of multilevel Prodisc total disc arthroplasty has not been described Methods. A prospective analysis was performed on 25 patients (63 prostheses) treated with multilevel lumbar ProDisc total disc arthroplasty. Minimum follow-up was 2 years. Patients 18 to 60 years of age with disabling discogenic low back pain and minimal radicular pain secondary to multiple level lumbar spondylosis from L1 to S1 were included. Preoperative and postoperative disability and pain scores were measured using Oswestry and visual analog scores. Preoperative and postoperative neurologic, radiographic, and pain medication assessments were also performed at similar postoperative intervals. Results. A total of 29 patients (72 prostheses) were enrolled in the prospective analysis. Twenty-five patients (63 prostheses) fulfilled all follow-up criteria and are included for final analysis. Fifteen bisegmental and 10 trisegmental level cases were performed. Visual analog pain, Oswestry, and patient satisfaction scores were significantly reduced at the 3-month as well as at 48-month follow-up. Radiographic analysis revealed an affected disc height increases from 5 mm to 12 mm (P < 0.05) and affected disc motions from 3° to 7° (P < 0.05). No change in adjacent level disc heights was seen. Complications included a single case of subsidence of the inferior endplate of the L4–L5 segment in a bisegmental L4–L5/L5–S1 case. We also report a delayed case of anterior extrusionof a polyethylene component in a patient who had sustained a fall of a bicycle. Conclusions. Our preliminary data on multisegmental ProDisc lumbar total disc arthroplasty appear to be a safe and efficacious treatment method for debilitating lumbar spondylosis without significant facet arthropathy. In our select (non-Workers Compensation and/or medical legal) cohort of patients, we demonstrate a patient satisfaction rate of 93%. Careful and appropriate patient selection is essential in ensuring optimal surgical outcomes.

Multidirectional testing of one- and two-level ProDisc-L versus simulated fusions

Study Design. An in vitro human cadaveric biomechanical study. Objectives. To evaluate intervertebral rotation changes due to lumbar ProDisc-L compared with simulated fusion, using follower load and multidirectional testing. Summary of Background Data. Artificial discs, as opposed to the fusions, are thought to decrease the long-term accelerated degeneration at adjacent levels. A biomechanical assessment can be helpful, as the long-term clinical evaluation is impractical. Methods. Six fresh human cadaveric lumbar specimens (T12–S1) underwent multidirectional testing in flexion-extension, bilateral lateral bending, and bilateral torsion using the Hybrid test method. First, intact specimen total range of rotation (T12–S1) was determined. Second, using pure moments again, this range of rotation was achieved in each of the 5 constructs: A) ProDisc-L at L5–S1; B) fusion at L5–S1; C) ProDisc-L at L4–L5 and fusion at L5-S1; D) ProDisc-L at L4–L5 and L5–S1; and E) 2-level fusion at L4–L5 to L5–S1. Significant changes in the intervertebral rotations due to each construct were determined at the operated and nonoperated levels using repeated measures single factor ANOVA and Bonferroni statistical tests (P < 0.05). Adjacent-level effects (ALEs) were defined as the percentage changes in intervertebral rotations at the nonoperated levels due to the constructs. Results. One- and 2-level ProDisc-L constructs showed only small ALE in any of the 3 rotations. In contrast, 1- and 2-level fusions showed increased ALE in all 3 directions (average, 7.8% and 35.3%, respectively, for 1 and 2 levels). In the disc plus fusion combination (construct C), the ALEs were similar to the 1-level fusion alone. Conclusions. In general, ProDisc-L preserved physiologic motions at all spinal levels, while the fusion simulations resulted in significant ALE.

Auricular acupuncture as a treatment for pregnant women who have low back and posterior pelvic pain: a pilot study.

OBJECTIVE The primary aim of this study was to examine whether 1 week of continuous auricular acupuncture could reduce low back and posterior pelvic pain associated with pregnancy. STUDY DESIGN A randomized controlled trial was conducted on pregnant women who have lower back and posterior pelvic pain. These women were randomly assigned into an acupuncture group, a sham acupuncture group, or a waiting list control group. All participants were monitored for 2 weeks. RESULTS Baseline and day 7 showed significant group differences in pain (F = 15; P < .0001) and in the disability rating index score (F = 7; P < .0001). The participants in the acupuncture group reported a significant reduction of pain and improvement of functional status as compared with those in the sham acupuncture and control groups. CONCLUSION One week of continuous auricular acupuncture decreases the pain and disability experienced by women with pregnancy-related low back and posterior pelvic pain.

Lumbar total disc arthroplasty utilizing the prodisc prosthesis in smokers Versus nonsmokers : A prospective study with 2-year minimum follow-up

Study Design. Prospective nonrandomized clinical series. Objectives. To evaluate the efficacy of ProDisc lumbar artificial disc replacement (ADR) in smokers versus nonsmokers. Summary of Background Data. Smoking is a negative predictor in fusion surgery. To date, a prospective study of the treatment of incapacitating discogenic low back pain using ADR in smokers versus nonsmokers has not been described. Methods. A prospective analysis was performed on 104 patients with disabling discogenic low back pain treated with single-level lumbar ProDisc total disc arthroplasty. Smokers and nonsmokers were assessed before surgery and after surgery using patient satisfaction, Oswestry, and Visual Analog Scores. Additionally, preoperative and postoperative neurologic, radiographic, and pain medication assessments were performed at similar postoperative intervals. Results. Oswestry, Visual Analog Scores, and patient satisfaction scores revealed statistical improvement beginning 3 months after surgery and were maintained at minimum 2-year follow-up. Patient satisfaction scores were higher in smokers (94%) than in nonsmokers (87%) at 2-year follow-up (P = 0.07). Radiographic analysis revealed an affected disc height increase from 4 mm to 13 mm (P < 0.05) and an affected disc motion from 3° to 7° (P < 0.05). No cases of loosening, dislodgment, mechanical failure, infection, or fusion of the affected segment occurred. Conclusions. The results of our study indicate that smokers do equally well compared with nonsmokers when ProDisc ADR is used in the treatment of debilitating lumbar spondylosis. Patient outcome and radiographic scores showed significant improvement compared with preoperative levels. Although not evident in our series, additional surveillance for intraoperative and postoperative vascular spasm and occlusion may be warranted in smokers.

Morphometric comparison of the pedicle rib unit to pedicles in the thoracic spine

Study Design. A radiographic study of the pedicle rib unit morphology as compared with measurements of the pedicle in cadaveric thoracic spines. Objective. To evaluate the morphology of pedicle rib units in the thoracic spine in normal thoracic human spines, with particular attention to T4–T9, and to compare the dimensions of the pedicle rib unit with corresponding dimensions of the adjacent pedicles. Summary of Background Data. Despite the clinical successes reported with thoracic pedicle screw-rod constructs, controversy exists as to the safety of this technique in pedicles that are anatomically too small for transpedicular fixation. An alternative method of extrapedicular screw fixation within the pedicle rib unit was evaluated in a previous study and found to be anatomically feasible. Although the morphology of the pedicle rib unit was described in two previous studies, the measurements were obtained in scoliotic spines. Therefore, no study has sought to define the transverse dimension and chord length of the pedicle rib unit, and compare it with the corresponding pedicle dimensions. Material and Methods. Six fresh unfixed adult cadavers were obtained randomly. No history of spine disease was noted, and cause of death was unrelated to spinal disorder or trauma. The mean age was 84, with a range of 76 to 90. There were two females and four males. Computerized tomographic (CT) images of the thoracic spine were obtained. For cadavers in which the gantry resulted in oblique axial sections, reformatting was performed for more accurate measurements. Measurements of the transverse diameter and chord length of the pedicle rib unit were obtained and compared with measurements of the transverse pedicle width and chord length. Results. The transverse width and chord length of the pedicle rib unit were significantly larger than corresponding pedicle measurements at all levels, a consistent finding when comparing the mean of all levels, the mean of T4–T9, and the mean of each individual level T4–T7. Conclusion. This study confirms the marked difference in size of the pedicle rib unit as compared with the pediclein both transverse width and chord length. This allows for a space that accommodates much larger major screw diameters, longer screw lengths, and because of the nature of screw placement, a greater screw convergence. Thus, there is anatomic potential for extrapedicular vertebral body fixation in the thoracic spine. However, care must be taken in placement of screws following precisely our previously described method of extrapedicular screw insertion. Penetration of surrounding structures, most notably the aorta on the left, is a potential risk when deviating from the method. Biomechanical evaluations are presently being conducted to evaluate the use of extrapedicular thoracic screw fixation.

Mechanism of cervical spinal cord injury during bilateral facet dislocation.

Study Design. An in vitro biomechanical study. Objectives. The objectives were to: quantify dynamic canal pinch diameter (CPD) narrowing during simulated bilateral facet dislocation of a cervical functional spinal unit model with muscle force replication, determine if peak dynamic CPD narrowing exceeded that observed post-trauma, and evaluate dynamic cord compression. Summary of Background Data. Previous biomechanical models are limited to quasi-static loading or manual ligament transection. No studies have comprehensively analyzed dynamic CPD narrowing during simulated dislocation. Methods. Bilateral facet dislocation was simulated using 10 cervical functional spinal units (C3–C4: n = 4; C5–C6: n = 3; C7–T1: n = 3) with muscle force replication by frontal impact of the lower vertebra. Rigid body transformation of kinematic data recorded optically was used to compute the CPD in neutral posture (before dislocation), during dynamic impact (peak during dislocation), and post-impact (flexion rotation = 0°). Peak dynamic impact and post-impact CPD narrowing were statistically compared. Results. Average peak dynamic impact CPD narrowing significantly exceeded (P < 0.05) post-impact narrowing and occurred as early as 71.0 ms following impact. The greatest dynamic impact narrowing of 7.2 mm was observed at C3–C4, followed by 6.4 mm at C5–C6, and 5.1 mm at C7–T1, with average occurrence times ranging between 71.0 ms at C7–T1 and 97.0 ms at C5–C6. Conclusion. Extrapolation of the present results indicated dynamic spinal cord compression of up to 88% in those with stenotic canals and 35% in those with normal canal diameters. These results are consistent with the wide range of neurologic injury severity observed clinically due to bilateral facet dislocation.

Normal and Abnormal Imaging Findings in Lumbar Total Disk Replacement: Devices and Complications

Fusion, with or without laminectomy, is the standard treatment for symptomatic lumbar degenerative disk disease when conservative management has failed. Yet even radiographically verified solid fusion may be accompanied by considerable long-term problems, including recurrent low back pain, spinal stenosis, hypertrophic facet disease, pseudarthrosis, and spondylolysis and spondylolisthesis at adjacent levels. Several studies have shown a relationship between solid fusion and the development of adjacent-level disk disease, which is thought to result from increased stress on, or hypermobility of, adjacent segments. Total disk replacement (TDR) was developed as a way to restore normal mobility of the diseased segments and improve clinical outcomes by decreasing the risk of adjacent-level degenerative disease and related complications. However, like fusion, TDR is associated with various complications; some of these (eg, migration, subsidence) may occur regardless of the device used, whereas others (eg, extrusion of the polyethylene inlay, vertical fractures) are device specific. Facet arthrosis, device wear, particle disease, adjacent-level degeneration, and heterotopic ossification also have been observed after TDR, but the frequency and importance of these findings remain uncertain. Given the increasing use of lumbar TDR to treat degenerative disk disease, it is important that radiologists be familiar with the most commonly used devices and the potential complications of their use.

An extrapedicular approach to the placement of screws in the thoracic spine: an anatomic and radiographic assessment.

Study Design. A radiographic and anatomic study of an extrapedicular method of screw placement in cadaveric thoracic spines. Objective. To evaluate an alternative method of thoracic vertebral body screw fixation using an extrapedicular screw technique. To evaluate the anatomic safe zones and proper starting point for this alternative approach to the placement of screw fixation in the thoracic spine. Summary of Background Data. Despite the clinical successes reported with thoracic pedicle screw-rod constructs, controversy exists about the safety of this technique in pedicles that are anatomically too small for transpedicular fixation. An alternative method of extrapedicular screw fixation was evaluated in this present study. Materials and Methods. Two fresh, unfixed, adult cadavers were obtained randomly; 6.0-mm AO Synthes pedicle screws were placed using an extrapedicular approach bilaterally from T3 to T10. The screws were placed according to one defined method described later. Computerized tomographic (CT) images were obtained. The position of each screw was analyzed. The cadavers were then dissected with the screw pathway exposed and the relation of the screw to surrounding anatomy documented. Results. All screws did not penetrate the spinal canal. All screws were within the pedicle rib unit and did not penetrate the neural foramen or pleura. Conclusion. This study, although only introductory, indicates the potential for extrapedicular vertebral body fixation in the thoracic spine. Biomechanical evaluations are presently being conducted to evaluate the use of extrapedicular thoracic screw fixation.

New Techniques in Lumbar Spinal Instrumentation: What the Radiologist Needs to Know

Lumbar spinal fusion is a commonly performed procedure, and, despite changes in cage types and fixation hardware, radiologists have, over the years, become familiar with the imaging features of typical spinal fusion and many of the complications seen in patients after surgery, including pseudoarthrosis, hardware loosening, and recurrent or residual disk herniation. Recently, however, novel approaches and devices have been developed, including advances in minimally invasive surgery, the increasing use of osteoinductive materials, and a wide variety of motion-preserving devices. These new approaches and devices manifest with characteristic imaging features and the potential for unusual and unexpected complications. Several of these devices and approaches are experimental, but many, including those devices used in lateral approaches to fusion, as well as the use of bone morphogenic protein, disk arthroplasty, and interspinous spacers, are seen with increasing frequency in daily clinical practice. Given the recent advances in spinal fusion surgery, it is important that radiologists have a basic understanding of the rationale behind these procedures, the common imaging features of the devices, and the complications associated with their use.