Revision and explantation strategies involving the CHARITE lumbar artificial disc replacement

Lumbar Total Disk Replacement Device Removals and Revisions Performed During a 20-Year Experience with 2141 Patients

STUDY DESIGN

This was a retrospective study with prospective patient contact attempted to collect current data.

OBJECTIVE

The purpose was to investigate the incidence and reasons for lumbar total disk replacement (TDR) removal or revision.

SUMMARY OF BACKGROUND DATA

A concern regarding lumbar TDR was safety, particularly the need for device removal or revision. This may be particularly important considering removal/revision requires repeat anterior exposure with an increased risk of vascular injury.

METHODS

Data were collected for a series of 2141 lumbar TDR patients, beginning with the first case experience in 2000. The mean follow-up was 78.6 months. For each case of device removal/revision, the reason, duration from index surgery, and procedure performed were recorded.

RESULTS

Of 2141 patients, 27 (1.26%) underwent TDR removal or revision. Device removal was performed in 24 patients (1.12%), while three patients underwent revision (0.14%). Of the 24 removals, 12 were due to migration and/or loosening, three developed problems post-trauma, two developed lymphocytic reaction to device materials, two had ongoing pain, and there was one case of each: TDR was too large, vertebral body fracture (osteoporosis), lytic lesion, device subsidence and facet arthrosis, and infection seeded from a chest infection 146 months post-TDR. The three revisions were for Core repositioning (technique error), device repositioning after displacement, and core replacement due to wear/failure. With respect to timing, 37.0% of removals/revisions occurred within one-month postimplantation. Of note, 40.7% of removals/revisions occurred in the first 25 TDR cases performed by individual surgeons. There was one significant vascular complication occurring in a patient whose TDR was removed due to trauma. This was also the only patient among 258 with ≥15-year follow-up who underwent removal/revision.

CONCLUSION

In this large consecutive series, 1.26% of TDRs were removed/revised. The low rate over a 20 year period supports the safety of these devices.

Revision surgery of spinal dynamic implants: a literature review and algorithm proposal

INTRODUCTION

Dynamic stabilization of the spine has been performed since the 1990s with the double purpose of restoring spinal segmental stability and allowing residual movement at the operated level. When we take into account the different motion-preserving devices and the spinal areas where they are applied, we can identify three categories of spinal implants: anterior cervical, anterior lumbar, and posterior lumbar. However, as in all prosthetic procedures performed in orthopedic surgery, the life span of a joint replacement device is a central topic of discussion, and this is true also for spinal dynamic devices, being revision surgery a complex procedure in specific cases.

MATERIALS AND METHODS

We performed a literature review on the different dynamic spinal implants and the most common causes of failure, providing clinical cases as illustrative options for revision surgery.

RESULTS

The review of the literature showed a 11.3% to 22.6% revision rate in posterior lumbar dynamic systems, with a peak of 40.6% in case of adjacent segment disease. In lumbar TDRs, infection and severe dislocations are the most frequent causes of anterior revisions, while posterior pedicle screw fixation could be a suitable option in minimal subsidence or TDR displacement. An algorithm for the planning of revision surgery is proposed.

CONCLUSIONS

Surgical revision of spinal dynamic implants could be a demanding surgery especially in anterior approaches. Anterior cervical revision remains globally safe, but careful preoperative evaluation of vessels and ureter are suggested to avoid intraoperative complications in the lumbar spine. In posterior revision, a proper sagittal alignment of the spine should be restored. These slides can be retrieved under Electronic Supplementary Material.

Long-term clinical outcome of two revision strategies for failed total disc replacements

PURPOSE

To compare the long-term clinical results and complications of two revision strategies for patients with failed total disc replacements (TDRs).

METHODS

In 19 patients, the TDR was removed and the intervertebral defect was filled with a femoral head bone strut graft. In addition, instrumented posterolateral fusion was performed (removal group). In 36 patients, only a posterolateral instrumented fusion was performed (fusion group). Visual Analogue Scale (VAS) for pain and Oswestry Disability Index (ODI) were completed pre- and post-revision surgery. Intra- and post-operative complications of both revision strategies were assessed.

RESULTS

The median follow-up was 12.3 years (range 5.3-24.3). In both the removal and fusion groups, a similar (p = 0.515 and p = 0419, respectively) but significant decrease in VAS (p = 0.001 and p = 0.001, respectively) and ODI score (p = 0.033 and p = 0.013, respectively) at post-revision surgery compared to pre-revision surgery was seen. A clinically relevant improvement in VAS and ODI score was found in 62.5% and 43.8% in the removal group and in 43.5% and 39.1% in the fusion group (p = 0.242 and p = 0.773, respectively). Removal of the TDR was associated with substantial intra-operative complications such as major vessel bleeding and ureter lesion. The percentage of late re-operations for complications such as pseudarthrosis were comparable for both revision strategies.

CONCLUSIONS

Revision of a failed TDR is clinically beneficial in about half of the patients. No clear benefits for additional TDR removal as compared to posterolateral instrumented fusion alone could be identified. In particular, when considering the substantial risks and complications, great caution is warranted with removal of the TDR. These slides can be retrieved under Electronic Supplementary Material.

Lumbar Arthroplasty Core Herniation Presenting With Cauda Equina Syndrome: Case Report of a Rare Complication

BACKGROUND

Treatment failures of artificial disc implantation are well-described, but posterior herniation of the arthroplasty core is rare. We present a case of posterior herniation of the arthroplasty core resulting in cauda equina syndrome in a 36-yr-old woman. Preoperative imaging studies including computed tomography (CT), magnetic resonance imaging (MRI), and CT Myelogram were performed; only the CT Myelogram demonstrated the severe compression well. This report highlights the radiographic findings on multiple imaging modalities, clinical implications, and management considerations of posterior arthroplasty failures.

OBJECTIVE

To demonstrate a rare complication of lumbar arthroplasties. The biomechanical considerations, surgical management, and thorough radiographic work-up demonstrate successful diagnosis and treatment of this unusual complication.

METHODS

The patient's chart was reviewed for medical history, laboratory and radiographic studies, and outpatient clinical follow-up.

RESULTS

After imaging work-up, this patient was found to have a herniation of the arthroplasty core at L5-S1. She was taken emergently to the operating room for a decompression at L5-S1 and arthroplasty core removal. She made some recovery neurological, but over 3 mo time, she developed a spondylolisthesis with new back pain and radiculopathy. This ultimately responded well to an L5-S1 instrumented posterior fusion.

CONCLUSION

Posterior herniation of the lumbar arthroplasty core is a rare complication from implantation of an artificial lumbar disc. Confirmation of the diagnosis is best confirmed with a CT Myelogram. Furthermore, this case underscores the biomechanical importance of the artificial disc given the development of the spondylolisthesis after removal, and fusion after arthroplasty core removal should be considered.

Limitations and complications of minimally invasive spinal surgery in adult deformity

Minimally invasive spine (MIS) surgery has rapidly progressed from simple short segment fusions to large adult deformity corrections, with radiographic and clinical outcomes as good as those of open surgery. Anterior longitudinal ligament release (ALLR) and anterior column realignment (ACR) have been key advancements in the ability to correct deformity using MIS techniques. However, patient selection and appropriate preoperative workup is critical to obtain good outcomes and for complication avoidance. Despite favorable outcomes in spinal deformity surgery, MIS techniques are limited in (I) pronounced cervical or thoracic deformity; (II) patients with prior fusion mass; and (III) severe sagittal imbalance necessitating Schwab 5 osteotomy or higher. Guidelines for proper patient selection are needed to guide MIS spine surgeons in choosing the right candidate.

Transforaminal endoscopic decompression of a postoperative dislocated bone fragment after a 2-level lumbar total disc replacement: case report

The proposed advantages of total disc replacement (TDR) over fusion in the lumbar spine are the preservation of motion and the avoidance of adjacent-level disease. One of the complications inherent in TDR is the possibility of vertebral body fracture due to trauma or a malpositioned implant. The resulting dilemma is that posterior decompression of the displaced bone fragment could then have a destabilizing effect and possibly require fusion, thus obviating the benefit of an arthroplasty procedure. In this study, the authors describe the technical considerations and feasibility of the treatment of a postoperative L-5 paresis that resulted from a dislocated bone fragment at L4–5 during a 2-level lumbar TDR.

Lumbar total disc replacement by less invasive lateral approach: a report of results from two centers in the US IDE clinical trial of the XL TDR® device

PURPOSE

To evaluate the clinical and radiographic outcomes following total disc arthroplasty using the XL TDR(®) Lumbar Disc in the treatment of patients with symptomatic degenerative disc disease at one level between L1-2 and L4-5.

METHODS

Data were compiled from two centers participating in a prospective, multi-center Food and Drug Administration-approved investigational device exemption clinical trial enrolling patients with single-level lumbar degenerative disc disease unresponsive to non-operative treatment. Longitudinal outcomes were evaluated through 3-year follow-up and included patient-reported pain, function, and general health, as well as radiographic measures such as maintenance of disc height and range of motion.

RESULTS

The two-center cohort included 64 treated patients, 42 % female, averaging 45.3 years of age (range 26-67). The majority of procedures were performed at the L4-5 level (75 %), uncomplicated, with minimal blood loss (88 % 0-50 cc), and in an outpatient setting (93.8 %). Postoperative events included 10 patients (15.6 %) with new hip flexion weakness, 7 (10.9 %) with new lower extremity weakness, and 10 (15.6 %) with new lower extremity sensory deficits, all resolved by 3 months in all but two patients whose deficits were prolonged but eventually resolved. Average disc height increased postoperatively from 7.2 to 12.1 mm (69 %), and was 10.7 mm (49 % increase from preoperative) at 3 years. Flexion/extension range of motion averaged 5.9° (SD 4.8°) at 3 years, and was not statistically different from preoperative (p = 0.471). Heterotopic ossification interfering with segmental motion was noted in 3 patients (10.3 %) at 3 years, none ankylosed (Grade IV). Postoperative improvement in patient-reported outcomes was significant (p < 0.01 for all measures) and maintained through 3-year follow-up. Satisfaction with results was reported by 85 % (51/60) of patients at 2 years and 93 % (28/30) at 3 years. There were no revisions through 3 years postoperative.

CONCLUSIONS

The results following XL TDR show good clinical and radiographic outcomes out to 3 years postoperative, with clinically significant improvements in pain, function, and general health, few complications, and high patient satisfaction.

ISASS Policy Statement - Lumbar Artificial Disc

PURPOSE

The primary goal of this Policy Statement is to educate patients, physicians, medical providers, reviewers, adjustors, case managers, insurers, and all others involved or affected by insurance coverage decisions regarding lumbar disc replacement surgery.

PROCEDURES

This Policy Statement was developed by a panel of physicians selected by the Board of Directors of ISASS for their expertise and experience with lumbar TDR. The panel's recommendation was entirely based on the best evidence-based scientific research available regarding the safety and effectiveness of lumbar TDR.

Indications for lumbar total disc replacement: selecting the right patient with the right indication for the right total disc

Summary of Background Data

As with any surgery, care should be taken to determine patient selection criteria for lumbar TDR based on safety and optimizing outcome. These goals may initially be addressed by analyzing biomechanical implant function and early clinical experience, ongoing evaluation is needed to refine indications.

Objective

The purpose of this work was to synthesize information published on general indications for lumbar TDR. A secondary objective was to determine if indications vary for different TDR designs.

Methods

A comprehensive literature search was conducted to identify lumbar TDR articles. Articles were reviewed and patient selection criteria and indications were synthesized.

Results

With respect to safety, there was good agreement in the literature to exclude patients with osteopenia/osteoporosis or fracture. Risk of injury to vascular structures due to the anterior approach was often addressed by excluding patients with previous abdominal surgery in the area of disc pathology or increased age. The literature was very consistent on the primary indication for TDR being painful disc degeneration unresponsive to at least 6 months of nonoperative care. Literature investigating the impact of previous spine surgery was mixed; however, prior surgery was not necessarily a contra-indication, provided the patient otherwise met selection criteria. The literature was mixed on setting a minimum preoperative disc height as a selection criterion. There were no publications investigating whether some patients are better/worse candidates for specific TDR designs. Based on the literature a proposal for patient selection criteria is offered.

Conclusions

Several TDR indications and contra-indications are widely accepted. No literature addresses particular TDR design being preferable for some patients. As with any spine surgery, ongoing evaluation of TDR outcomes will likely lead to more detailed general and device design specific indications.

Outcome of salvage lumbar fusion after lumbar arthroplasty

Study Design

Retrospective review.

Purpose

This study aims to define the role of lumbar fusion for persistent back pains after the lumbar disc replacement.

Overview of Literature

Little is written about lumbar fusion after optimally placed lumbar arthroplasty in patients with persistent lower back pains.

Methods

Retrospective review of cases of lumbar artificial disc requiring subsequent fusion because of persistent back pains despite optimally placed artificial discs. Outcomes were evaluated using Oswestry Disability Index (ODI) and visual analogue scale (VAS). Clinical improvements indicated 25% improvement in ODI and VAS values.

Results

Five patients met the study criteria. The mean baseline ODI for the five patients was 52. The mean baseline VAS scores for back and leg pains were 76 and 26, respectively. All the five patients had optimally placed prosthesis. The indication for surgery was the constant low back pains found in all the patients. Revision surgery involved disc explantation and fusion in two of the patients and posterolateral fusion without removing the prosthesis in three. None of the patients achieved adequate pain control after the revision surgery despite the solid bony fusion documented by postoperative computed tomography. The mean ODI value after the fusion was 55. The mean values for back and leg pains VAS were 72 and 30, respectively.

Conclusions

Lack of good pain relief after successful lumbar artifical disc replacements may indicate different etiology for the back pains. The spine-treating surgeons should have a high threshold level to perform salvage fusion at that level.

Multilevel extreme lateral interbody fusion (XLIF) and osteotomies for 3-dimensional severe deformity: 25 consecutive cases

Background

This is a retrospective review of 25 patients with severe lumbar nerve root compression undergoing multilevel anterior retroperitoneal lumbar interbody fusion and posterior instrumentation for deformity. The objective is to analyze the outcomes and clinical results from anterior interbody fusions performed through a lateral approach and compare these with traditional surgical procedures.

Methods

A consecutive series of 25 patients (78 extreme lateral interbody fusion [XLIF] levels) was identified to illustrate the primary advantages of XLIF in correcting the most extreme of the 3-dimensional deformities that fulfilled the following criteria: (1) a minimum of 40° of scoliosis; (2) 2 or more levels of translation, anterior spondylolisthesis, and lateral subluxation (subluxation in 2 planes), causing symptomatic neurogenic claudication and severe spinal stenosis; and (3) lumbar hypokyphosis or flat-back syndrome. In addition, the majority had trunks that were out of balance (central sacral vertical line ≥2 cm from vertical plumb line) or had sagittal imbalance, defined by a distance between the sagittal vertical line and S1 of greater than 3 cm. There were 25 patients who had severe enough deformities fulfilling these criteria that required supplementation of the lateral XLIF with posterior osteotomies and pedicle screw instrumentation.

Results

In our database, with a mean follow-up of 24 months, 85% of patients showed evidence of solid arthrodesis and no subsidence on computed tomography and flexion/extension radiographs. The complication rate remained low, with a perioperative rate of 2.4% and postoperative rate of 12.2%. The lateral listhesis and anterior spondylolisthetic subluxation were anatomically reduced with minimally invasive XLIF. The main finding in these 25 cases was our isolation of the major indication for supplemental posterior surgery: truncal decompensation in patients who are out of balance by 2 cm or more, in whom posterior spinal osteotomies and segmental pedicle screw instrumentation were required at follow up. No patients were out of sagittal balance (sagittal vertical line <3 cm from S1) postoperatively. Segmental instrumentation with osteotomies was also more effective for restoration of physiologic lumbar lordosis compared with anterior stand-alone procedures.

Conclusions

This retrospective study supports the finding that clinical outcomes (coronal/sagittal alignment) improve postoperatively after minimally invasive surgery with multilevel XLIF procedures and are improved compared with larger extensile thoracoabdominal anterior scoliosis procedures.

Early postoperative dislocation of the anterior Maverick lumbar disc prosthesis: report of 2 cases

The authors report on 2 cases of anterior dislocation of the Maverick lumbar disc prosthesis, both occurring in the early postoperative period. These cases developed after experience with more than 50 uneventful cases and were therefore thought to be unrelated to the surgeon's learning curve. No similar complications have been previously reported. The anterior Maverick device has a ball-and-socket design made of cobalt-chromium-molybdenum metal plates covered with hydroxyapatite. The superior and inferior endplates have keels to resist translation forces. The patient in Case 1 was a 52-year-old man with severe L4-5 discogenic pain; and in Case 2, a 42-year-old woman with disabling L4-5 and L5-S1 discogenic back pain. Both patients were without medical comorbidities and were nonsmokers with no risk factors for osteoporosis. Both had undergone uneventful retroperitoneal approaches performed by a vascular access surgeon. Computed tomography studies on postoperative Day 2 confirmed excellent prosthesis placement. Initial recoveries were uneventful. Two weeks postoperatively, after stretching (extension or hyperextension) in bed at home, each patient suffered the sudden onset of severe abdominal pain with anterior dislocation of the Maverick prosthesis. The patients were returned to the operating room and underwent surgery performed by the same spinal and vascular surgeons. Removal of the Maverick prosthesis and anterior interbody fusion with a separate cage and plate were performed. Both patients had recovered well with good clinical and radiological recovery at the 6- and 12-month follow-ups. Possible causes of the anterior dislocation of the Maverick prosthesis include the following: 1) surgeon error: In both cases the keel cuts were neat, and early postoperative CT confirmed good placement of the prosthesis; 2) equipment problem: The keel cuts may have been too large because the cutters were worn, which led to an inadequate press fit of the implants; 3) prosthesis fault: Both plates of the dislocated implants looked normal and manufacturer analysis reported no fault; 4) patient factors: Both dislocations happened early in the postoperative period, after hyperextension of the spine while the patient was supine in bed. Bracing would not have reduced hyperextension. Dislocation of a lumbar spinal implant represents a life-threatening complication and should therefore be considered and recognized early. Radiographic and CT studies of both the lumbar spine (for prosthesis) and the abdomen (for hematoma) should be performed, as should CT angiography (for vessel damage or occlusion). Any anterior lumbar revision surgery is hazardous, and it is strongly advisable to have a vascular surgeon scrubbed. In cases of dislocation or extrusion of a lumbar interbody prosthesis, the salvage revision strategy is fusing the segment via the same anterior approach. Surgeons should be aware of the risk of anterior dislocation of the Maverick prosthesis. Keel cutters should be regularly checked for sharpness, as they may be implicated in the loosening of implants. Patients and their physical therapists should also avoid lumbar hyperextension in the early postoperative period.

Safe zone for retractor placement to the lumbar spine via the transpsoas approach

PURPOSE

To measure anatomic variations of the lumbar plexus within the psoas in relation to the L2/3, L3/4, and L4/5 disc spaces and to delineate a safe zone to avoid nerve injury during retractor placement via the transpsoas approach.

METHODS

Six male and 6 female cadavers (24 psoas/ lumbar plexuses) aged 35 to 74 years were dissected. The lumbar plexus was isolated bilaterally. The L2, L3, and L4 nerve roots were identified and isolated without disturbing their natural anatomic course. The anteroposterior (AP) diameter of each intervertebral disc at L2/3, L3/4, and L4/5 was used as a reference. Four measurements were made using a caliper: the AP and mediolateral (ML) diameters of the psoas and AP and ML excursions of each nerve root. Percentages were calculated for the 4 measurements using the reference of the AP diameter of the intervertebral disc at each level. Comparison between left and right sides, between males and females, and between excursions of nerve roots were made.

RESULTS

The AP diameter of the psoas increased from L2 to L4, with a mean vertebral body coverage of 80%, 86%, and 85% at L2/3, L3/4, and L4/5, respectively. Both the L2 and L3 nerve roots demonstrated substantial anterior trajectories as they coursed distally in the lumbar spine. No nerve root encroached anteriorly beyond 33% of the intervertebral disc space at L2 to L5.

CONCLUSION

The lumbar plexus area corresponding to the anterior half of the intervertebral disc was the safe zone. Procedures to the lumbar spine via the transpsoas approach should be performed within the safe zone to avoid nerve injury.

Reducing subsidence risk by using rapid manufactured patient-specific intervertebral disc implants

BACKGROUND CONTEXT

Intervertebral disc implant size, shape, and position during total disc replacement have been shown to affect the risk of implant subsidence or vertebral fracture. Rapid manufacturing has been successfully applied to produce patient-specific implants for craniomaxillofacial, dental, hip, and knee requirements, but very little has been published on its application for spinal implants.

PURPOSE

This research was undertaken to investigate the improved load distribution and stiffness that can be achieved when using implants with matching bone interface geometry as opposed to implants with flat end plate geometries.

STUDY DESIGN

The study design comprises a biomechanical investigation and comparison of compressive loads applied to cadaveric vertebrae when using two different end plate designs.

METHODS

Four spines from male cadavers (ages 45-65 years, average 52 years), which had a total of n=88 vertebrae (C3-L5), were considered during this study. Bone mineral density scans on each spine revealed only one to be eligible for this study. Twenty remaining vertebrae (C3-L3) were potted and subjected to nondestructive compression tests followed by destructive compression tests. Custom-made nonfunctional implants were designed for this experiment. Ten implants were designed with matching end plate-to-bone interface geometry, whereas the other 10 were designed with flat end plates. Testing did not incorporate the use of a keel in either design type. I-Scan pressure sensors (Tekscan, Inc., MA, USA) were used during the nondestructive tests to assess the load distribution and percentage surface contact.

RESULTS

Average percent contact area measured during nondestructive tests was 45.27% and 10.49% for conformal and flat implants, respectively-a difference that is statistically significant (p<.001). A higher percent contact area was especially observed for cervical vertebrae because of their pronounced end plate concavity. During destructive compression tests, conformal implants achieved higher failure loads than flat implants. Conformal implants also performed significantly better when stiffness values were compared (p<.0001).

CONCLUSIONS

One of the main expected benefits from customizing the end plate geometry of disc implants is the reduced risk and potential for subsidence into the vertebral bone end plate. Subsidence depends in part on the stiffness of the implant-bone construct, and with a 137% increase in stiffness, the results of this study show that there are indeed significant potential benefits that can be achieved through the use of customization during the design and manufacture of intervertebral disc implants.

Analysis of intraoperative difficulties and management of operative complications in revision anterior exposure of the lumbar spine: a report of 25 consecutive cases

PURPOSE

After a first anterior approach to the lumbar spine, formation of adhesions of soft tissues to the spine increases the surgical difficulties and potential for iatrogenic injury during the revision exposure. The objective of this study was to identify the intraoperative difficulties and postoperative complications associated with revision anterior lumbar spine procedures in a single institution.

METHODS

This is a retrospective review of 25 consecutive anterior revision lumbar surgeries in 22 patients (7 men and 15 women) operated on between 1998 and 2011. Patients with trauma or malignancies were excluded. The mean age of the patients at the time of revision surgery was 56 years (range 20-80 years). The complications were analyzed depending on the operative level and the time between the index surgery and the revision.

RESULTS

Six major complications (five intraoperatively and one postoperatively) occurred in five patients (20 %): three vein lacerations (12 %) and two ureteral injuries (8 %), despite the presence of a double-J ureteral stent. The three vein damages were repaired or ligated by a vascular surgeon. One of the two ureteral injuries led to a secondary nephrectomy after end-to-end anastomosis failure; the other necessitated secondary laparotomy for small bowel obstruction.

CONCLUSIONS

Anterior revision of the lumbar spine is technically challenging and is associated with a high rate of vascular or urologic complications. Therefore, the potential complications of the procedure must be weighted against its benefits. When iterative anterior lumbar approach is mandatory, exposure should be performed by an access surgeon in specialized centers that have ready access to vascular and urologic surgeons.

An uncommon case of Mycoplasma hominis infection after total disc replacement

PURPOSE

Beside mechanical complications, the majority of adverse events after total disc arthroplasty (TDA) are related to the surgical approach. Septic complications are very uncommon and only one previous case has been published. The objective of this article is to describe the clinical circumstances, treatment, and outcomes of septic complication after TDA at L4-L5, involving an uncommon pathogen (Mycoplasma hominis).

METHODS

A 38-year-old woman underwent a MobiDisc(®) TDA at L4-L5 level for discogenic pain. One month postoperatively, she complained of acute low back and abdominal pain associated with fever (39 °C). C-reactive protein level was elevated (197 mg/L; normal <5 mg/L) and the white blood cell count was normal (7 × 10(9)/L; normal 4-10 × 10(9)/L). A computerized tomography (CT) showed a left psoas-based retroperitoneal abscess. Treatment consisted of open debridement, drainage and empirical antibiotic therapy. Intraoperative cultures yielded M. hominis after 7 days incubation. Antibiotic therapy was adapted and discontinued after 2 months. The patient had failed to mention earlier that she had been suffering from abnormal vaginal discharge for some time and was using an intrauterine contraceptive device.

RESULTS

At 1.5-year follow-up, review confirmed healing of the infection with biological normalization without residual collection, radiolucent lines or osteolysis around the prosthesis at radiographs, CT and MRI.

CONCLUSIONS

Mycoplasma hominis can be involved as an extragenital pathogen in musculoskeletal infections. Because its culture and identification are difficult, special media and real-time PCR are required in case of postoperative deep wound infection after anterior lumbar spine surgery, especially in the case of previous genitourinary infections, to decrease the delay in diagnosis and treatment.

Clinical outcomes of two revision strategies for failed total disc replacements

PURPOSE

To compare mid-term clinical outcomes of two revision strategies for patients with failed SB Charité III total disc replacements (TDRs).

METHODS

Eighteen patients with a failed TDR underwent posterolateral instrumented fusion (fusion group); in 21 patients, the TDR was removed and the intervertebral defect was filled with a bone strut graft, followed by an instrumented posterolateral fusion (removal group). Visual analogue scale (VAS) for pain and Oswestry Disability Index (ODI) were completed pre- and post-revision surgery. Intra- and post-operative complications of both revision strategies were assessed.

RESULTS

Mean follow-up was 3.7 years (range 1.0-6.4) in the removal group and 4.4 years (range 0.7-11.0) in the fusion group. Although the removal group showed a significantly lower VAS and ODI score post-revision surgery as compared to preoperative (P < 0.01 and P = 0.01, respectively), no significant differences were found between the removal and fusion groups before and after revision surgery in VAS and ODI. A clinical relevant improvement in VAS and ODI was found in 47 and 21 % respectively in the removal group, and in 22 and 27 % respectively in the fusion group. Substantial complications were observed only in the removal group.

CONCLUSIONS

Both procedures showed improvement clinically. There were no significant additional benefits of removing the TDR as compared to fusion alone at mid-term follow-up. The clinical decision to remove the TDR should be carefully weighed up against potential risks and complications of this procedure.

Cervical myelopathy after cervical total disc arthroplasty: case report and literature review

STUDY DESIGN

Case report and literature review.

OBJECTIVE

This article reports 2 cases in which the patients accepted revision surgery after cervical total disc arthroplasty (CTDA) because of iatrogenic neurological injury.

SUMMARY OF BACKGROUND DATA

CTDA has been increasingly investigated to treat cervical degenerative disc disease. However, there are limited reports focused on its complications, especially the neurological complications after the procedure.

METHODS

A 52-year-old man underwent total disc arthroplasty for C5-C6, but immediately after surgery, he experienced paralysis of his upper and lower limbs. Radiographical images indicated residual compression to the spinal cord in the level of C5-C6. Another patient, a 60-year-old man, underwent total disc arthroplasty for C4-C5. Afterward, he experienced severe neck pain and paralysis of upper and lower limbs. He was unresponsive to conservative treatments; thus, a laminectomy was performed 3 months later. However, little improvement was observed. Radiographical images indicated kyphosis and spinal cord compression at the level of C4-C5. Furthermore, both cases showed a high signal in the spinal cord by T2-weighted magnetic resonance image, suggestive of spinal cord injuries.

RESULTS

Revision surgeries were performed in both cases. Cervical implants were first removed by the anterior approach, and fusion was then performed after a complete decompression. Motor examination of the patient in case 1 showed grade 3 strength in both of his hands and feet 6 months after revision surgery. In case 2, the patient's severe neck pain was resolved at the early postoperative stage. Motor examination showed grade 1 strength in both of his hands and feet 3 months after revision surgery.

CONCLUSION

On the basis of presented cases and other reports, the surgical goals in these patients were prioritized as follows: (1) safe and adequate neurological decompression and (2) establishment and maintenance of cervical sagittal balance. Moreover, a criterion for selecting patients undergoing CTDA needs to be established in order to reduce the occurrence of neurological complications associated with the procedure.

Infection and revision strategies in total disc arthroplasty

PURPOSE

Our aim was to revise the different strategies for treating an infected disc arthroplasty.

METHODS

Despite recognition that disc replacement may reduce the incidence of adjacent-segment disease, the risk of potential complications associated with primary and revision total disc arthroplasty has diminished surgeon enthusiasm for the procedure. We performed a literature review of the different revision strategies for an infected disc arthroplasty.

RESULTS

The need for revision of lumbar total disc arthroplasty has been reported in a number of prospective, randomised trials (level I or II evidence). Suboptimal patient selection and/or surgical technique accounted for the majority of failed disc arthroplasties. Revision procedures include posterior stabilisation or anterior extraction and conversion to arthrodesis. The risk of injury to the great vessels and retroperitoneal structures is greater during revision than primary procedures. The use of a distant lateral, or transpsoas, approach to the anterior column may reduce these adverse events. Also, the use of adhesion barriers has been shown to reduce adhesions in abdominal and pelvic surgery and may be of benefit in revision disc arthroplasty.

CONCLUSION

This review article provides an update on the various treatments for infected lumbar disc prosthesis and the different surgical approaches used in these difficult cases. It also describes potential options to avoid complications associated with the revision surgical approach.

[Keel-implants: Activ-L]

Due to its modular design, the Activ-L total disc replacement (B. Braun/Aesculap, Tuttlingen, Germany) allows for a flexible anchoring concept either with spikes or one or two keels. It has a semiconstraint design which allows for some movement of a UHMWPE inlay. The minimal invasive surgical technique is highly standardized. Early clinical results are comparable to established disc-replacement devices.

OBJECTIVE

Aim of the surgery is lasting pain relief and complete restauration of segmental mobility without affection of adjacent motion segments.

INDICATIONS

Mono- or multisegmental lumbar disc degeneration leading to low-back pain, refractory to conservative treatment.

CONTRAINDICATIONS

Infections of vertebra or disc-space, fractures, prior fusion surgery of the affected motion segments, malignancy, osteoporosis, metabolic bone disease, severe conditions affecting general health, conditions prohibitive for anterior abdominal surgery, unclear or non-discogenic low-back-pain.

SURGICAL TECHNIQUE

Minimal-invasive anterior approach to the lumbar spine, removal of nucleus and cartilagenous endplates, sizing with trial implant, decision about spike or keel anchoring concept, implantation of prosthesis, x ray-control, wound closure.

POSTOPERATIVE MANAGEMENT

Bed-rest for 6 hours, stabilizing physiotherapy 3 weeks postoperative.

RESULTS

Level-3 evidence shows early clinical results comparable with published data from previous implants, particle wear of inlay is significantly lower, possibly due to different testing protocols.

[Revision strategies for ventral implant failure in the lumbar spine exemplified by stand-alone cages]

This article gives a review of the possible revision strategies after repeated operative treatment of degenerative spinal diseases using stand-alone cages. Own clinical experiences and reports from the literature were taken into consideration. Dorsal stabilization is the main consideration for all access routes even if it can be discussed, albeit controversially, whether ventral removal of an installed cage is justified, because this contains a significantly higher perioperative risk. The increased risk of neurological complications by dorsal revision and for vascular complications by ventral access, especially at the L4/5 level must be particularly considered. Clinical data and own experience have shown that in the majority of cases an additional dorsal stabilization should be favored for revision surgery. Currently large clinical studies which deal with the revision problematic of stand-alone cages with respect to the access route are still lacking.

Total disc replacement surgery for symptomatic degenerative lumbar disc disease: a systematic review of the literature

The objective of this study is to evaluate the effectiveness and safety of total disc replacement surgery compared with spinal fusion in patients with symptomatic lumbar disc degeneration. Low back pain (LBP), a major health problem in Western countries, can be caused by a variety of pathologies, one of which is degenerative disc disease (DDD). When conservative treatment fails, surgery might be considered. For a long time, lumbar fusion has been the “gold standard” of surgical treatment for DDD. Total disc replacement (TDR) has increased in popularity as an alternative for lumbar fusion. A comprehensive systematic literature search was performed up to October 2008. Two reviewers independently checked all retrieved titles and abstracts, and relevant full text articles for inclusion. Two reviewers independently assessed the risk of bias of included studies and extracted relevant data and outcomes. Three randomized controlled trials and 16 prospective cohort studies were identified. In all three trials, the total disc replacement was compared with lumbar fusion techniques. The Charité trial (designed as a non-inferiority trail) was considered to have a low risk of bias for the 2-year follow up, but a high risk of bias for the 5-year follow up. The Charité artificial disc was non-inferior to the BAK^® Interbody Fusion System on a composite outcome of “clinical success” (57.1 vs. 46.5%, for the 2-year follow up; 57.8 vs. 51.2% for the 5-year follow up). There were no statistically significant differences in mean pain and physical function scores. The Prodisc artificial disc (also designed as a non-inferiority trail) was found to be statistically significant more effective when compared with the lumbar circumferential fusion on the composite outcome of “clinical success” (53.4 vs. 40.8%), but the risk of bias of this study was high. Moreover, there were no statistically significant differences in mean pain and physical function scores. The Flexicore trial, with a high risk of bias, found no clinical relevant differences on pain and physical function when compared with circumferential spinal fusion at 2-year follow up. Because these are preliminary results, in addition to the high risk of bias, no conclusions can be drawn based on this study. In general, these results suggest that no clinical relevant differences between the total disc replacement and fusion techniques. The overall success rates in both treatment groups were small. Complications related to the surgical approach ranged from 2.1 to 18.7%, prosthesis related complications from 2.0 to 39.3%, treatment related complications from 1.9 to 62.0% and general complications from 1.0 to 14.0%. Reoperation at the index level was reported in 1.0 to 28.6% of the patients. In the three trials published, overall complication rates ranged from 7.3 to 29.1% in the TDR group and from 6.3 to 50.2% in the fusion group. The overall reoperation rate at index-level ranged from 3.7 to 11.4% in the TDR group and from 5.4 to 26.1% in the fusion group. In conclusion, there is low quality evidence that the Charité is non-inferior to the BAK cage at the 2-year follow up on the primary outcome measures. For the 5-year follow up, the same conclusion is supported only by very low quality evidence. For the ProDisc, there is very low quality evidence for contradictory results on the primary outcome measures when compared with anterior lumbar circumferential fusion. High quality randomized controlled trials with relevant control group and long-term follow-up is needed to evaluate the effectiveness and safety of TDR.

The effect of implant size and device keel on vertebral compression properties in lumbar total disc replacement

BACKGROUND CONTEXT

Vertebral end plate support is necessary for successful lumbar total disc replacement (TDR) surgery. Failure to achieve anterior column support as a result of lumbar TDR device undersizing could lead to implant subsidence and fracture.

PURPOSE

The purpose of the study was to examine the compressive biomechanical behavior of the vertebral end plate with varying sizes of disc replacement implants.

STUDY DESIGN

The study design comprises a biomechanical investigation using a human cadaveric lumbar spine model.

METHODS

Fifty-six vertebrae with intact posterior elements were prepared from 13 fresh frozen lumbar spines. Peripheral quantitative computed tomography was performed to assess regional bone density. Vertebrae were potted and subjected to nondestructive compression testing with a small, medium, and large custom-made implants with the footplate geometry of the ProDisc-L TDR (Synthes Spine, West Chester, PA, USA) system and having no keel. Failure testing was performed using the ProDisc-L implant with an intact keel. Pressure sensor film was used to assess contact pressure and distribution.

RESULTS

There was a linear correlation between percent coverage of the end plate and implant-end plate stiffness (p=.0001) and an inverse correlation with displacement (p=.01). The difference in implant-end plate stiffness between small-medium, medium-large, and small-large implants was 10.5% (p=.03), 10.2% (p=.02), and 19.6% (p<.0001), respectively. Failure analysis revealed similar trends for implant sizing, but only bone density was found to significantly correlate with failure properties (r=0.76, p<.0001). There was a significant reduction in implant-end plate stiffness of 18% when the keel was intact compared to without the keel (range 6-27%, p=.0008). Pressure film analysis revealed that the implant was loaded peripherally and did not have central contact during nondestructive loading. There was a trend toward greater contact pressure with the small implant when compared with the medium implant (p=.06) and the large implant (p=.06).

CONCLUSIONS

Although larger implants reduce end plate displacement, increase apparent implant-end plate stiffness, increase the implant-end plate contact area, and decrease the peak contact pressures, low bone density reduces failure properties. The keel introduces a reduction in stiffness to the implant-end plate interface, the clinical significance of which is currently unknown.

National revision burden for lumbar total disc replacement in the United States: epidemiologic and economic perspectives

STUDY DESIGN

Retrospective cohort study using a nationally representative inpatient database.

OBJECTIVE

To quantify the national revision burden for lumbar total disc replacements (TDRs) in the United States following Food and Drug Administration approval, for comparison with lumbar fusion and other common orthopedic procedures, including hip and knee replacement.

SUMMARY OF BACKGROUND DATA

Previous studies of revision lumbar TDR surgery have been based on IDE studies. The epidemiology and costs of TDR revision surgery from a national perspective have not yet been reported.

METHODS

The Nationwide Inpatient Sample was used to identify primary and revision TDR and anterior fusion procedures in 2005 and 2006. Surgeries were identified in the Nationwide Inpatient Sample using ICD9-CM codes. The prevalence of TDR and fusion surgery was calculated as a function of age, gender, race, census region, primary payer class, and type of hospital. Average length of stay and total hospitalization costs were also computed for each type of procedure.

RESULTS

During the study period, there was a national total of 7172 TDR and 62,731 anterior fusion surgeries, including both primary and revisions. Overall, TDR patients were younger and had less comorbidity than fusion surgery patients. The average revision burden for lumbar TDR and anterior fusion was 11.2% and 5.8%, respectively. The average length of stay for primary lumbar TDR was significantly shorter compared to revision TDR, primary anterior fusion, and revision anterior fusion (P < 0.0001). Both the primary and the revision surgery using the TDR surgery involved significantly lower total hospital costs relative to anterior fusion surgery (P < 0.0001). Including revision, the average costs per TDR procedure were lower than anterior and posterior lumbar fusion.

CONCLUSION

Although the revision burden for TDR was significantly higher than fusion surgery, the TDR revision burden fell within the revision burden range of hip and knee replacement, which are generally considered successful and cost-effective procedures. Economically, the higher revision burden for TDRs was offset by lower costs for both the primary as well as the revision procedures relative to fusion.

Current trends in spinal arthroplasty: an assessment of surgeon practices and attitudes regarding cervical and lumbar disk replacement

STUDY DESIGN

Survey study involving orthopedic and neurosurgical spine surgeons.

OBJECTIVE

To report the current practices and opinions of spine surgeons regarding cervical and lumbar total disk arthroplasty (TDA) as alternatives to arthrodesis for the treatment of degenerative conditions of the spine.

SUMMARY OF BACKGROUND DATA

TDA represents an alternative surgical treatment for degenerative spinal conditions that may avoid the deleterious effects associated with fusion. Unfortunately, the prevailing opinions of surgeons about TDA have not been well characterized and the patterns of its utilization have not been documented previously in the literature.

METHODS

A questionnaire was developed to record the attitudes of spine surgeons regarding cervical and lumbar TDA and to assess their utilization of this technology. This survey was distributed to all of the surgeons attending the 2007 "Contemporary Update on Disorders of the Spine" meeting in Whistler, British Columbia.

RESULTS

One hundred thirteen of the 133 surgeons present at the meeting completed the questionnaire, corresponding to a return rate of 85%. The percentage of surgeons who had performed lumbar TDA was significantly higher than that for cervical TDA (42% vs. 30%, P=0.05). However, 81% of respondents stated that they were more likely to perform cervical TDA now compared with 1 year ago, whereas 64% indicated that they were less likely to perform lumbar TDA. The most frequently cited reasons for not performing both cervical and lumbar TDA were questions concerning long-term outcomes and perceived difficulties with obtaining financial compensation from insurance companies; in addition, surgeons were also concerned about revising lumbar TDA cases.

CONCLUSIONS

Although the results of this study confirm that the enthusiasm for TDA was shared by many of these respondents, it is clear that additional long-term, prospective, comparative data are required before this technology may be considered as a replacement for more traditional spinal fusion procedures.

Revision of a lumbar disc arthroplasty following late infection

Anterior removal of a lumbar total disc replacement implant is often a very technically demanding procedure. The anterior retroperitoneal anatomy is prone to scarring, limiting remobilization and making a direct anterior exposure above the L5-S1 level difficult if not impossible to achieve safely. Anterolateral approach strategies can be more safely achieved at L4-L5 and above, but may require vertebral osteotomy in order to remove a keeled prosthesis. Successful conversion to a fusion with implant removal can be achieved, even when osteotomy is needed for implant removal. This Grand Rounds case presentation involves an unusual late retroperitoneal abscess following two-level TDR with direct extension to one of the implants, and the subsequent nonoperative and operative management. Removal of a well-fixed keeled implant at the L4-L5 level following nonoperative treatment of a surrounding retroperitoneal abscess and conversion to fusion represents close to, if not a 'worst-case' scenario for revision TDR. However, with proper preoperative planning and surgical experience, a safe and successful procedure can be the end result.

Spine imaging after lumbar disc replacement: pitfalls and current recommendations

Background

Most lumbar artificial discs are still composed of stainless steel alloys, which prevents adequate postoperative diagnostic imaging of the operated region when using magnetic resonance imaging (MRI). Thus patients with postoperative radicular symptoms or claudication after stainless steel implants often require alternative diagnostic procedures.

Methods

Possible complications of lumbar total disc replacement (TDR) are reviewed from the available literature and imaging recommendations given with regard to implant type. Two illustrative cases are presented in figures.

Results

Access-related complications, infections, implant wear, loosening or fracture, polyethylene inlay dislodgement, facet joint hypertrophy, central stenosis, and ankylosis of the operated segment can be visualised both in titanium and stainless steel implants, but require different imaging modalities due to magnetic artifacts in MRI.

Conclusion

Alternative radiographic procedures should be considered when evaluating patients following TDR. Postoperative complications following lumbar TDR including spinal stenosis causing radiculopathy and implant loosening can be visualised by myelography and radionucleotide techniques as an adjunct to plain film radiographs. Even in the presence of massive stainless steel TDR implants lumbar radicular stenosis and implant loosening can be visualised if myelography and radionuclide techniques are applied.

Perioperative complications in revision anterior lumbar spine surgery: incidence and risk factors

STUDY DESIGN

This is a retrospective review of 129 consecutive anterior lumbar revision surgeries in 108 patients. It is a single-center, multi-surgeon study.

OBJECTIVE

To determine occurrence rates and risk factors for perioperative complications in revision anterior lumbar fusion surgery.

SUMMARY OF BACKGROUND DATA

Although complication rates from large series of primary anterior fusion procedures have been reported, reports of complication rates for revision anterior fusion procedures are relatively rare. Concern exists chiefly about the risk to vascular and visceral structures because of scar tissue formation from the original anterior exposure.

METHODS

This was a retrospective review of 129 consecutive anterior revision lumbar surgeries in 108 patients operated between 1998 and 2003. There were 40 men and 68 women. The age of patients ranged from 25 to 83 (average 50.6 years). Patients were excluded if surgery was for tumor or infection. Patients were divided into 2 groups; those with revision surgery at the same level and those with revision surgery at an adjacent level. Outcome measures included all perioperative complications. Statistical analysis included Student t test and nonparametric sign-rank.

RESULTS

The number of surgical levels treated for revision was similar between the 2 groups (1 level 69%; 2 levels 19%; 3 or more levels 12%). Revision cases at the same operative level had a higher overall complication rate (42%) compared with extensions (20%; P = 0.007). This difference was primarily because of vein lacerations (23.7% vs. 3.6%, P = 0.002). There were 2 ureteral problems, both successfully salvaged. There were no arterial injuries or deaths.

CONCLUSION

Complication rates for revision lumbar surgery in this series were 3 to 5 times higher than reported for primary lumbar exposures. Complication rates were significantly higher for revision anterior lumbar fusions at the same segment, which were typically in the lower lumbar spine, compared with cases involving extensions, which were typically in the upper lumbar spine.

Footprint mismatch in lumbar total disc arthroplasty

Lumbar disc arthroplasty has become a popular modality for the treatment of degenerative disc disease. The dimensions of the implants are based on early published geometrical measurements of vertebrae; the majority of these were cadaver studies. The fit of the prosthesis in the intervertebral space is of utmost importance. An undersized implant may lead to subsidence, loosening and biomechanical failure due to an incorrect center of rotation. The aim of the present study was to measure the dimensions of lumbar vertebrae based on CT scans and assess the accuracy of match in currently available lumbar disc prostheses. A total of 240 endplates of 120 vertebrae were included in the study. The sagittal and mediolateral diameter of the upper and lower endplates were measured using a digital measuring system. For the levels L4/L5 and L5/S1, an inappropriate size match was noted in 98.8% (Prodisc L) and 97.6% (Charite) with regard to the anteroposterior diameter. Mismatch in the anterior mediolateral diameter was noted in 79.3% (Prodisc L) and 51.2% (Charite) while mismatch in the posterior mediolateral diameter was observed in 91.5% (Prodisc L) and 78% (Charite) of the endplates. Surgeons and manufacturers should be aware of the size mismatch of currently available lumbar disc prostheses, which may endanger the safety and efficacy of the procedure. Larger footprints of currently available total disc arthroplasties are required.

Implications of lumbar plexus anatomy for removal of total disc replacements through a posterior approach

STUDY DESIGN

An anatomic study in which the lumbar plexuses of 14 embalmed cadavers were dissected bilaterally and measured using a posterior approach.

OBJECTIVE

To determine the cephalocaudal (root-to-root) distances and the mediolateral (root-to-tether) distances within the lumbar plexus and determine the feasibility for removal of a lumbar total disc replacement (TDR) through these anatomic spaces using a posterior approach.

SUMMARY OF BACKGROUND DATA

Currently, lumbar TDRs are implanted primarily through an anterior retroperitoneal or transperitoneal approach. However, revision surgeries through these approaches can be complicated by significant adhesions, with potential injuries to intra- and retroperitoneal contents. Advancements in accessing anterior column structures through a posterior lumbar extracavitary approach suggest that posterior removal of TDRs may be an alternative. Unlike the thoracic extracavitary approach in which ligation of the thoracic nerve rarely leaves significant morbidity, the lumbar extracavitary approach cannot rely on the analogous ligation of the lumbar root to achieve access. Therefore, feasibility of the lumbar extracavitary approach depends on the presence of sufficient anatomic space between the tethered nerves of the lumbar plexus.

METHODS

Fourteen adult cadavers (5 M/9F) were dissected through a posterior approach to expose the lumbar plexus bilaterally. The root-to-root distances at levels L2-S1 and corresponding root-to-tether distances at levels L3-L5 were measured bilaterally.

RESULTS

Root-to-root distance was smallest at the male L5-S1 interval (11.7 +/- standard deviations 4.1 mm). Root-to-tether distance was smallest at the female L5 (43.1 +/- standard deviations 8.4 mm). These plexus measurements compare favorably with the CHARITE TDR components, in which the thickest sliding core is 11.0 mm in height and the largest endplate is 42.0 mm in width.

CONCLUSION

This anatomic study suggests that posterior TDR removal is possible in the lumbar spine without undue risk to the surrounding nervous structures.