Adapting innovative motion-preserving technology to spinal surgical practice: what should we expect to happen?

Impact of Posterior Cervical Foraminotomy Before or After Cervical Disk Replacement: Current Evidence

STUDY DESIGN

Narrative review.

OBJECTIVES

The purpose of this study was to provide a review of the current evidence on the impact of posterior cervical foraminotomy (PCF) performed before or after cervical disk replacement (CDR).

SUMMARY OF BACKGROUND DATA

The impact of PCF on outcomes in the setting of CDR is an evolving field, given the recent widespread adoption of CDR and the relative rarity of patients who have undergone both procedures.

METHODS

A literature search was conducted using PubMed to determine current evidence regarding the indications, outcomes, and biomechanical effects of CDR and PCF when performed alone or in combination.

RESULTS

When radicular symptoms persist following PCF, a CDR can be safely performed to provide further decompression. Conversely, a PCF can be safely performed following CDR for these same indications. The biomechanical effects of these procedures in combination demonstrate maintained stability when the facetectomy is less than 50% of the facet joint. Studies demonstrate that stability is not significantly decreased by the presence, amount, or level of posterior foraminotomies in the setting of CDR.

CONCLUSIONS

A PCF can be safely performed before or after cervical disk arthroplasty for recurrent radicular symptoms.

LEVEL OF EVIDENCE

Level V.

Anterior lumbar fusion techniques: ALIF, OLIF, DLIF, LLIF, IXLIF

An anterior approach to the lumbar spine is increasingly used in performing fusion. Depending on the level to be treated, several approaches have been developed to deal with the anatomic obstacles encountered: pure anterior, oblique anterior or lateral, and trans- or pre-psoas. Conventional techniques incur risk of muscle lesion and severe bleeding, and have been replaced by minimally invasive approaches, often with video assistance after rapid closure of laparoscopic approaches with gas insufflation. There has, in parallel, been great progress in anterior spinal instrumentation systems. Non-existent when these techniques were first developed, they have become increasingly sophisticated, and now employ a variety of stand-alone or not cages and anterior screwed plate that can be associated together or to posterior fixation. Each approach and type of fixation has its specific technical requirements that need to be fully mastered so as to minimize risk, especially regarding vessels, and to enable the patient to enjoy the benefit of their very low morbidity. We shall therefore detail here each step of the pure anterior approach, which is most often used for L5S1, the oblique and lateral approaches, mainly used for L2L5, and also the preparation of the lumbar spine for anterior interbody fusion, with the respective instrumentations. We shall then consider the pros, cons and risks, and also spinal or general contraindications that may sometimes preclude this option. From this, we shall derive the specific optimal and wrong indications for anterior lumbar surgery, to help decision-making when fusion is indicated.

Adverse Event Recording and Reporting in Clinical Trials Comparing Lumbar Disk Replacement with Lumbar Fusion: A Systematic Review

Study Design Systematic review. Objectives (1) To compare the quality of adverse event (AE) methodology and reporting among randomized trials comparing lumbar fusion with lumbar total disk replacement (TDR) using established AE reporting systems; (2) to compare the AEs and reoperations of lumbar spinal fusion with those from lumbar TDR; (3) to make recommendations on how to report AEs in randomized controlled trials (RCTs) so that surgeons and patients have more-detailed and comprehensive information when making treatment decisions. Methods A systematic search of PubMed, the Cochrane collaboration database, and the National Guideline Clearinghouse through May 2015 was conducted. Randomized controlled trials with at least 2 years of follow-up comparing lumbar artificial disk replacement with lumbar fusion were included. Patients were required to have axial or mechanical low back pain of ≥3 months' duration due to degenerative joint disease defined as degenerative disk disease, facet joint disease, or spondylosis. Outcomes included the quality of AE acquisition methodology and results reporting, and AEs were defined as those secondary to the procedure and reoperations. Individual and pooled relative risks and their 95% confidence intervals comparing lumbar TDR with fusion were calculated. Results RCTs demonstrated a generally poor description of methods for assessing AEs. There was a consistent lack of clear definition or grading for these events. Furthermore, there was a high degree of variation in reporting of surgery-related AEs. Most studies lacked adequate reporting of the timing of AEs, and there were no clear distinctions between acute or chronic AEs. Meta-analysis of the pooled data demonstrated a twofold increased risk of AEs in patients having lumbar fusion compared with patients having lumbar TDR at 2-year follow-up, and this relative risk was maintained at 5 years. Furthermore, the pooled data demonstrated a 1.7 times greater relative risk of reoperation in the fusion group compared with lumbar TDR, although this risk decreased to 1.1 at 5-year follow-up. However, given the lack of quality and consistency in the methods of recording and reporting of AEs, we are unable to make a clear recommendation of one treatment over the other. Conclusions Based on the currently available literature, lumbar TDR appears to be comparable in safety to lumbar fusion. However, due to lack of consistency in reporting of AEs, it is difficult to make conclusions regarding the true safety profile of lumbar TDR. Standardization in AE reporting will significantly improve the reliability of the current literature.

Mid- to long-term results of total lumbar disc replacement: a prospective analysis with 5- to 10-year follow-up

BACKGROUND CONTEXT

The role of fusion of lumbar motion segments for the treatment of intractable low back pain (LBP) from degenerative disc disease (DDD) without deformities or instabilities remains controversially debated. Total lumbar disc replacement (TDR) has been used as an alternative in a highly selected patient cohort. However, the amount of long-term follow-up (FU) data on TDR is limited. In the United States, insurers have refused to reimburse surgeons for TDRs for fear of delayed complications, revisions, and unknown secondary costs, leading to a drastic decline in TDR numbers.

PURPOSE

To assess the mid- and long-term clinical efficacy as well as patient safety of TDR in terms of perioperative complication and reoperation rates.

STUDY DESIGN/SETTING

Prospective, single-center clinical investigation of TDR with ProDisc II (Synthes, Paoli, PA, USA) for the treatment of LBP from lumbar DDD that has proven unresponsive to conservative therapy.

PATIENT SAMPLE

Patients with a minimum of 5-year FU after TDR, performed for the treatment of intractable and predominant (≥80%) axial LBP resulting from DDD without any deformities or instabilities.

OUTCOME MEASURES

Visual analog scale (VAS), Oswestry Disability Index (ODI), and patient satisfaction rates (three-scale outcome rating); complication and reoperation rates as well as elapsed time until revision surgery; patient's professional activity/employment status.

METHODS

Clinical outcome scores were acquired within the framework of an ongoing prospective clinical trial. Patients were examined preoperatively, 3, 6, and 12 months postoperatively, annually from then onward. The data acquisition was performed by members of the clinic's spine unit including medical staff, research assistants, and research nurses who were not involved in the process of pre- or postoperative decision-making.

RESULTS

The initial cohort consisted of 201 patients; 181 patients were available for final FU, resembling a 90.0% FU rate after a mean FU of 7.4 years (range 5.0-10.8 years). The overall results revealed a highly significant improvement from baseline VAS and ODI levels at all postoperative FU stages (p<.0001). VAS scores demonstrated a slight (from VAS 2.6 to 3.3) but statistically significant deterioration from 48 months onward (p<.05). Patient satisfaction rates remained stable throughout the entire postoperative course, with 63.6% of patients reporting a highly satisfactory or a satisfactory (22.7%) outcome, whereas 13.7% of patients were not satisfied. The overall complication rate was 14.4% (N=26/181). The incidence of revision surgeries for general and/or device-related complications was 7.2% (N=13/181). Two-level TDRs demonstrated a significant improvement of VAS and ODI scores in comparison to baseline levels (p<.05). Nevertheless, the results were significantly inferior in comparison to one-level cases and were associated with higher complication (11.9% vs. 27.6%; p=.03) and inferior satisfaction rates (p<.003).

CONCLUSIONS

Despite the fact that the current data comprises the early experiences and learning curve associated with a new surgical technique, the results demonstrate satisfactory and maintained mid- to long-term clinical results after a mean FU of 7.4 years. Patient safety was proven with acceptable complication and reoperation rates. Fear of excessive late complications or reoperations following the primary TDR procedure cannot be substantiated with the present data. In carefully selected cases, TDR can be considered a viable treatment alternative to lumbar fusion for which spine communities around the world seem to have accepted mediocre clinical results as well as obvious and significant drawbacks.

Prosthetic total disk replacement--can we learn from total hip replacement?

Total lumbar disk replacement has become a routine procedure in many countries. However, discussions regarding its use are ongoing. Issues focus on patient selection, technical limitations, and avoidance or management of complications or long-term outcomes. A review of the development of this technology, since the development of the first successful implantation of a total lumbar disk prosthesis in 1984, shows an amazing analogy to the history of total hip replacement. This article is a one-to-one comparison of the evolution of total hip and total lumbar disk replacement from "skunk works" to scientific evidence.

In situ contact analysis of the prosthesis components of Prodisc-L in lumbar spine following total disc replacement

STUDY DESIGN

A three-dimensional, nonlinear finite element analysis was performed to predict the in situ contact interaction of prosthesis components of the Prodisc-L in a multisegmental lumbar model following total disc replacement (TDR).

OBJECTIVE

Efforts were made to investigate how the TDR implant contact characteristics could affect the 3-dimensional kinematics, facet loads of the lumbar spine following TDR.

SUMMARY OF BACKGROUND DATA

Although spinal motion analyses of human lumbar cadaveric models after Prodisc TDR have been widely studied, the interaction of the disc prosthesis, particularly its in situ contact mechanics, is never known.

METHODS

A validated intact multisegmental lumbar finite element model L2-L4 was altered to accommodate the TDR prosthesis through anterior approach. At L3-L4 disc space, the Prodisc-L of 6 degrees lordosis angle was implanted centrally. The model was subjected to compressive preload and pure moments to create flexion, extension, lateral bending, and axial rotation motion in physiologic range. The contact interaction between the superior component of Prodisc-L and the UHMWPE inlay were assessed in terms of contact region (CR), contact area (CA), and contact pressure (CP). Parameters of range of motion (ROM) and facet loading transfer were simultaneously analyzed and compared with those of the intact model.

RESULTS

The predicted contact area was 3.5 times larger in flexion than that observed in extension, whereas the maximum contact pressure in the disc articulation was very similar with 15.1 MPa for flexion and 14.5 MPa for extension. Joint surface incongruence was developed in extension motion. The implanted model exhibited a 91.4% increase in ROM accompanied by a 150.6% rising in facet force during extension, while the flexion motion showed the least effects of TDR. In lateral bending and axial rotation, the abnormal joint "lift off" was not seen.

CONCLUSION

The in situ function of the TDR prosthesis was highly dependent on how well the device could incorporate itself into the mechanical environment in the disc space, which has been determined by the rest of the spinal structures, including the retained disc anulus, articular facets, ligaments, vertebrae, and muscular stabilizers. The different contact interaction of the artificial disc components revealed here could be attributed to the violation of this mechanical environment which, in turn, may bring adverse effects to those spinal elements.

Analysis of post-operative pain patterns following total lumbar disc replacement: results from fluoroscopically guided spine infiltrations

Although a variety of biomechanical laboratory investigations and radiological studies have highlighted the potential problems associated with total lumbar disc replacement (TDR), no previous study has performed a systematic clinical failure analysis. The aim of this study was to identify the post-operative pain sources, establish the incidence of post-operative pain patterns and investigate the effect on post-operative outcome with the help of fluoroscopically guided spine infiltrations in patients from an ongoing prospective study with ProDisc II. Patients who reported unsatisfactory results at any of the FU-examinations received fluoroscopically guided spine infiltrations as part of a semi-invasive diagnostic and conservative treatment program. Pain sources were identified in patients with reproducible (> or =2x) significant (50-75%) or highly significant (75-100%) pain relief. Results were correlated with outcome parameters visual analogue scale (VAS), Oswestry disability index (ODI) and the subjective patient satisfaction rate. From a total of 175 operated patients with a mean follow-up (FU) of 29.3 months (range 12.2-74.9 months), n = 342 infiltrations were performed in n = 58 patients (33.1%) overall. Facet joint pain, predominantly at the index level (86.4%), was identified in n = 22 patients (12.6%). The sacroiliac joint was a similarly frequent cause of post-operative pain (n = 21, 12.0%). Pain from both structures influenced all outcome parameters negatively (P < 0.05). Patients with an early onset of pain (< or =6 months) were 2-5x higher at risk of developing persisting complaints and unsatisfactory outcome at later FU-stages in comparison to the entire study cohort (P < 0.05). The level of TDR significantly influenced post-operative outcome. Best results were achieved for the TDRs above the lumbosacral junction at L4/5 (incidence of posterior joint pain 14.8%). Inferior outcome and a significantly higher incidence of posterior joint pain were observed for TDR at L5/S1 (21.6%) and bisegmental TDR at L4/5/S1 (33.3%), respectively. Lumbar facet and/or ISJ-pain are a frequent and currently underestimated source of post-operative pain and the most common reasons for unsatisfactory results following TDR. Further failure-analysis studies are required and adequate salvage treatment options need to be established with respect to the underlying pathology of post-operative pain. The question as to whether or not TDR will reduce the incidence of posterior joint pain, which has been previously attributed to lumbar fusion procedures, remains unanswered. Additional studies will have to investigate whether TDR compromises the index-segment in an attempt to avoid adjacent segment degeneration.

Polyethylene wear debris and long-term clinical failure of the Charité disc prosthesis: a study of 4 patients

STUDY DESIGN

A clinical case series of 4 patients undergoing anterior lumbar revision due to failure of total disc replacement surgery.

OBJECTIVES

To assess the clinical significance of polyethylene wear debris in salvage surgery after initial total disc replacement, the pattern and the mechanisms of polyethylene wear in the retrieved cores, and the extent of polyethylene debris in the periprosthetic tissues obtained from 4 patients.

SUMMARY OF BACKGROUND DATA

Previous in vitro wear tests have demonstrated low wear rates for lumbar artificial discs, suggesting that implant wear may not be a clinically relevant issue with total disc replacement. However, only long-term clinical investigations with analysis of retrieved implants and periprosthetic tissue can ultimately establish the significance of polyethylene wear debris for total disc arthroplasty.

METHODS

Starting in 2004, we began routinely performing salvage procedures in patients with failed total disc replacements. We report on the short-term outcomes of 4 patients at our institution who were revised with a Charité prosthesis (DePuy Spine, Raynham, MA). Wear analysis of the retrieved prosthesis and histologic examination of the periprosthetic tissue were also performed.

RESULTS

All of the retrieved polyethylene cores showed evidence of wear, but the extent and severity varied among the 4 patients. Wear and fracture of the core were associated with osteolysis of the underlying sacrum in 1 patient. Histologic examination of the periprosthetic tissues confirmed the presence of wear debris lying in inflammatory fibrous tissue. In 3 of the 4 patients, implant wear was associated with an unfavorable biomechanical environment (e.g., subsidence, migration, undersizing, and adjacent fusion). The mechanisms of wear included adhesive/abrasive wear of the central domed region of the polyethylene core, as well as chronic rim impingement, resulting in rim fatigue and fracture.

CONCLUSIONS

This study demonstrates the clinical significance of polyethylene wear debris and the potential for osteolysis with total disc replacements. The authors recommend that patients undergoing lumbar disc arthroplasty receive long-term follow-up to monitor the wear and functional status of their implants.

Total lumbar disc replacement in athletes: clinical results, return to sport and athletic performance

Despite the increasing popularity of total lumbar disc replacement (TDR) in predominantly young and active patients, no previous study has addressed possibilities, limitations and potential risks regarding athletic performance following TDR. Mechanical concerns remain and the implant's resilience as regards its load-bearing capacity during sporting activities is unknown. Thirty-nine athletic patients fulfilled the inclusion criteria for this study. These patients participated in a large variety of different types of sport. Significant and lasting pain-relief was attained following TDR with a mean follow-up of 26.3 months (range 9-50.7 months; FU rate 97.4%). Sporting activity was resumed within the first 3 months (38.5%) to 6 months (30.7%) with peak performance being reached after 5.2 months. Thirty-seven patients (94.9%) achieved resumption of sporting activity. Athletic performance improved significantly in 33 patients (84.6%). Minor subsidence was observed in 13 patients (30%) within the first 3 months with no further implant migration thereafter in 12 patients. Participation in all types of sport recorded in this study was accessible for a high rate of patients up to the level of professional athletes as well as those participating in extreme sports. Preoperative participation in sport proved to be a strong positive predictor for highly satisfactory postoperative outcome following TDR. In a selected group of patients, however, preoperative inability to participate in sporting activities did not impair postoperative physical activity. Due to the young age of the patients and significant load increase exerted during athletic activities, persisting concerns regarding the future behaviour of the implant remain and will require longer follow-up, modified investigation techniques and larger patient cohorts.

Radiologic landmark accuracy for optimum coronal placement of total disc arthroplasty in the lumbar spine

OBJECTIVE

This study was performed to determine which of the radiographic markers visible on an anteroposterior (AP) radiograph of the spine-the vertebral body, the pedicles, and the spinous process-provided the most accurate guide to correctly placing an intervertebral disc replacement in the coronal midline.

METHOD

The coronal midline was defined as the perpendicular bisector of a line drawn between the midpoints of the two facet joints. Axial CT images were reconstructed from 35 abdominal and renal computed tomograms to compare how consistently the midpoints of the above structures fell on the coronal midline.

RESULTS

The mean distance (SD) from the vertebral body midpoint, the interpedicular midpoint, and the spinous process midpoint from the coronal midline, respectively, were 0.55 mm (SD 0.45 mm), 0.19 mm (SD 0.40 mm), and 1.30 mm (SD 1.30 mm). Sixteen percent of the distances from the coronal midline to the spinous process midpoint were greater than or equal to 3 mm compared with 0% of the distances to the interpedicular midpoint or the vertebral body midpoint.

CONCLUSIONS

We concluded that the interpedicular midpoint is the most accurate guide to the coronal midline. We recommend that this landmark be used in preference to the spinous processes or the midpoint of the vertebral bodies when placing the implant in intervertebral disc arthroplasty.

Clinical results of total lumbar disc replacement with ProDisc II: three-year results for different indications

STUDY DESIGN

Prospective study analyzing midterm clinical results of total lumbar disc replacement (ProDisc II) for different indications.

OBJECTIVES

To assess functional outcome after total lumbar disc replacement (TDR) treated for varying indications.

SUMMARY OF BACKGROUND DATA

Despite its frequent use and increasing popularity, indications and contraindications for TDR have not been defined precisely at this stage and remain a matter of debate, leading to disc replacement procedures in a variety of pathologies that have not yet been evaluated and compared separately.

METHODS

Patients meeting inclusion criteria were evaluated prospectively according to Visual Analogue Scale (VAS), Oswestry Questionnaire, SF-36, and numerous clinical parameters. Indications included degenerative disc disease (DDD), DDD with accompanying soft disc herniation (nucleus pulposus prolapse, NPP), osteochondrosis following previous discectomy, and DDD with presence of Modic changes. Postoperative improvement was recorded and analyzed for influence of preoperative diagnosis.

RESULTS

Overall, 92 patients from four groups with a mean follow-up of 34.2 months (minimum, 24 months) achieved significant and maintained improvement from preoperative levels (P < 0001). Patients with DDD + NPP achieved results significantly better than patients from the other groups (P < 0.05). Presence of Modic changes or previous discectomy did not influence outcome negatively. Improvement was achieved for both monosegmental and bisegmental disc replacements (P < 0.05), nevertheless with significantly inferior results for bisegmental interventions at 12- and 24-month follow-up and considerably higher complication rate. While older patients were still highly satisfied with postoperative outcome, better functional outcome was observed in younger patients.

CONCLUSION

Present data suggest beneficial clinical results of TDR for treatment of DDD in a highly selected group of patients. Better functional outcome was obtained in younger patients under 40 years of age and patients with degenerative disc disease in association with disc herniation. Multilevel disc replacement had significantly higher complication rate and inferior outcome. Results are significantly dependent on preoperative diagnosis and patient selection, number of replaced segments, and age of the patient at the time of operation. Because of significantly varying outcomes, indications for disc replacement must be defined precisely.

Cervical arthroplasty after previous surgery: results of treating 24 discs in 15 patients

OBJECT

The potential role of cervical arthroplasty in patients who have undergone previous cervical surgery is unknown. The authors performed a prospective study involving nonrandomized clinical and radiological assessment in patients who had undergone either previous posterior cervical foraminotomy or anterior interbody fusion and who suffered new or persistent arm/neck symptoms related to neural compression.

METHODS

During a 30-month period, 15 patients who had previously undergone cervical spinal surgery underwent cervical arthroplasty that involved placement of the Bryan disc for neck or arm symptoms related to cervical disc disease. A total of 24 devices were implanted. Six of the 15 patients had undergone a previous posterior foraminotomy, and in nine cases an anterior interbody fusion had been perfomed at some stage prior to surgery. Clinical and radiological evaluations were performed preoperatively and after surgery to assess outcomes. A total of 24 arthroplasties were performed encompassing between one and three levels. There were no major perioperative complications or immediate device-related failures. Two patients were lost to follow up. The follow-up period ranged from 12 to 43 months (mean 24.2 +/- 10.5 months). Good results were obtained in all cases as reflected by an increase in the visual analog scale score of 6.4 in terms of neck/arm pain (p < 0.05). There was no difference in Oswestry Disability Index scores for neck pain (p > 0.05) and no patient required surgery at the same level. In one patient hypermobility developed with internal subluxation of the device, which suggested a compromise adjacent to a two-level fusion at 21 months. The segment was hypermobile preoperatively. The patient has experienced recurrent neck pain but otherwise remains clinically well and has not required revision surgery to date.

CONCLUSIONS

Insertion of the Bryan artificial cervical disc in patients who have previously undergone cervical fusion or posterior foraminotomy, in general, appears to be safe. It provided encouraging early clinical results, although patients with preoperative hypermobility should be treated with caution. Issues such as accelerated device-related wear and the use of arthroplasty after aggressive facetectomy resection will need further study; however, in carefully selected patients who have undergone previous surgery cervical arthroplasty may provide an additional tool in the management of cervical disc disease.

General Considerations for Cervical Arthroplasty with Technique for Prodisc-C

Motion-preserving spinal arthroplasty is a triumph of modern biomechanics, material sciences, and surgical technique. The ability to remove entire intervertebral discs and re-place them with prostheses that preserve height and alignment as well as motion and stability, all the while alleviating the pain and spinal cord compression, is the result of nearly 50 years of progress in joint arthroplasty. Although the clear benefit or danger of artificial cervical discs is still unknown, they are already fundamentally changing the field of cervical spine surgery and are undoubtedly going to establish their place in the armamentarium for spinal surgeons. Short-term follow-up studies indicate that cervical arthroplasty is as safe and effective as traditional fusion surgery, but follow-up studies are no longer needed.

History of spinal surgery: one neurosurgeon's perspective

Spinal surgery has advanced from decompression procedures to complex spinal reconstruction and internal stabilization within the last 25 years, as a result of a broad-based technological boom that began in the 1970s with the advent of spinal computerized tomography and magnetic resonance imaging. These technological advances have coincided with, and developed as a result of, the concomitant rise of a complex, economically driven consortium of innovative surgeons and researchers, academic institutions, government agencies, and private industry, to form a Medical–Industrial Complex (MeIC). A major growth industry has formed, resulting in an overall societal benefit. Nevertheless, it has impacted graduate medical education and has significantly increased the cost of treating spinal disorders. Back pain and spinal disorders are a major societal health problem that is associated with a high demand for treatment services. There is a potential for abuse as well as a benefit in offering these services. The MeIC has contributed to the overall rise in the cost of health care insurance and in the migration of manufacturing jobs abroad as a solution for lowering production costs. The increased cost has had a negative impact on local and regional economies.