Scott L. Blumenthal

Study Design. This was a retrospective study. Objective. The purpose of the study was to determine the incidence and reasons of intraoperative conversion from planned cervical total disc replacement (TDR) to anterior cervical discectomy and fusion (ACDF). Summary of Background Data. TDR currently offers an alternative treatment with results similar or superior to ACDF. Once individual surgeons become comfortable using a device, they will typically expand indications for its use, however, patient safety must remain at the forefront. In order to reduce reoperations, surgeons must use strict selection criteria to determine which patients are most appropriate to receive TDR. Despite those criteria, situations may arise when surgeons convert from TDR to ACDF intraoperatively. Methods. A comprehensive surgery log was reviewed to identify cases of planned TDR converted intraoperatively to ACDF. All cases were performed at a single institution by 28 attending surgeons beginning with the first case experience in November, 2003 and ending with cases performed in November, 2023. Retrospective chart review was performed to collect demographic data and determine reasons for conversion. Results. During the 20-year period, a total of 2,188 consecutive cases of planned TDR were examined. The total number of planned TDR levels was 2,939. The rate of intraoperative conversion of TDR to ACDF was 0.55% (12/2,188 cases), 95% confidence interval 0.30% - 0.90%. With respect to the number of operated levels, the intraoperative rate of conversion was 0.48% (14/2,939 levels), 95% confidence interval 0.30-0.80%. Conclusion. There was a very low incidence of intra-operative conversion of cervical TDR to ACDF. However, surgeons performing this procedure should be prepared for the possibility of intraoperative conversion from TDR to ACDF and educate patients of this possibility.

Lumbar total disk replacement (TDR) has been in use since the 1980s, yet its adoption has not paralleled that of hip or knee arthroplasty or cervical TDR, which was introduced years after lumbar arthroplasty. If the lack of adoption is related to concerns about the safety and/or effectiveness of these implants, these issues have been extensively addressed in the literature. This narrative review aims to concisely report on the evidence published in the peer-reviewed literature related to lumbar TDR. Literature was identified from online databases such as PubMed, Scopus, and ScienceDirect, supplemented by the authors’ institution’s comprehensive database of TDR articles. By the end of 2023, there were at least 816 articles published on lumbar TDR covering all aspects of this technology, including biomechanics, clinical outcome, radiographic outcome, safety as assessed by re-operations and complications, and the cost related to this treatment intervention. Consistently, the evidence indicates that TDR yields outcomes similar or superior to fusion for treating painful disk degeneration unresponsive to non-operative care in appropriately selected patients.

Purpose To describe modes of failure of cervical TDR, their related treatment strategies, and to describe a management strategy for the treatment of failed cervical TDR. Methods This retrospective study was based on a consecutive series of 53 cervical TDR patients who underwent removal or revision surgery. Chart review was conducted to collect general descriptive data, reasons for TDR removal/revision, duration from index implantation to re-operation, and the subsequent procedure performed. Results Among 53 patients, 36 underwent TDR removal and fusion, 16 underwent TDR removal and replacement with another TDR, and one patient’s TDR was revised by repositioning. The mean duration from index surgery to removal/revision was 40.1 months (range: 3 days–222 months). In all cases, removal/revision surgery was completed without complication. The most common reason for removal was severe osteolysis, often involving C. acnes infection, and was primarily associated with one implant type. TDR removal and fusion were performed for subsidence, device migration, treatment of symptoms arising from posterior anatomy (facet joints, etc.), approach-related complications and pain. TDR replacement was feasible for hypermobility, metal allergy, implant locked in kyphosis, and oversized implant use. In one case of TDR malpositioning, the device was successfully revised into appropriate position. Conclusion After cervical TDR failure, replacing a TDR with another implant can be feasible. Reasons for revision or removal after cervical TDR surgery include biomechanical failure, implant migration, surgeon or technical error, or biological reasons. The type of failure can help the surgeon create a strategy to address these complications.

Study Design.: This was a retrospective study combined with attempted prospective patient contact to collect current data. Objective.: The purpose of this study was to investigate the long-term clinical outcomes of patients undergoing lumbar hybrid surgery (total disk replacement (TDR) at one level and fusion at an adjacent level. Summary of Background Data.: Many patients with symptomatic lumbar disk degeneration are affected at more than one level. Lumbar TDR was introduced as a fusion alternative; however, some disk levels are not amenable to TDR, and fusion is preferable at such levels. Hybrid surgery was introduced as an option to fusing multiple levels. Methods.: A consecutive series of 305 patients undergoing lumbar hybrid surgery was identified, beginning with the first case experience in 2005. Operative and clinical outcome data, including visual analog scales (VAS) assessing back and leg pain, Oswestry Disability Index (ODI), and reoperations, were collected. The mean follow-up duration was 67.1 months. Results.: There were statistically significant improvements (P<0.01) in the mean values of all three clinical outcome measures: VAS back pain scores improved from 6.7 to 3.3; leg pain improved from 4.3 to 2.0; and ODI scores improved from 45.5 to 24.6. There were no significant differences in pain and function scores for patients with a minimum 10-year follow-up versus those with a shorter follow-up duration. Re-operation occurred in 16.1% of patients, many of which involved removal of posterior instrumentation at the fusion level (6.2% of the study group, 38.8% of re-operations). Reoperation involving the TDR level occurred in 9 patients (2.9%), only 3 of which (1.0%) involved TDR removal/revision. Conclusion.: This study supports that for many patients with multilevel symptomatic disk degeneration, hybrid surgery is a viable surgical option. Significant improvements were demonstrated in pain and function scores, with no diminished improvement in scores among patients with more than 10-year follow-up. Level of Evidence.: Level IV

Study Design.: Retrospective cohort study. Objective.: The purpose of this study was to investigate the rate of cervical total disc replacement (TDR) device removal or revision. Background.: Cervical TDR has gained acceptance as an alternative to anterior cervical discectomy and fusion in appropriately selected patients. There have been concerns over device safety, one measure of which is subsequent surgery related to device problems. Patients and Methods.: A consecutive series of 1626 patients undergoing cervical TDR from 2003 to June 2021 were included, consisting of TDRs up to 3 levels and hybrids (TDR and fusion). TDR removal or revision surgeries and reasons for these surgeries, procedures performed, and duration from index procedure were recorded. Data were analyzed to determine the removal/revision rate and factors possibly related to these events. Results.: There were 24 removals/revisions (1.48%) in the 1626 patients. Removal was performed in 23 cases (1.41%) and revision in 1 (0.06%). Among removal cases, anterior cervical discectomy and fusion was performed in 18 and TDR was replaced with another TDR in 5. Removals with fusion included 5 cases of osteolysis with/without Cutibacterium acnes, 4 device displacement/migration, 4 posterior spinal pathology, and one for each of the following: metal allergy, approach-related complications, malpositioning, subsidence, and hypermobility. The revision involved TDR repositioning 3 days after index surgery. There were 66 patients for whom a minimum of 10-year follow-up was confirmed, and none had removal/revision surgery 10 or more years after index surgery. There was no relationship between the occurrence of removal/revision and age, sex, body mass index, or physician experience (learning curve). The removal/revision rate was significantly higher in FDA trials versus postapproval (4.1% vs. 1.3%, P < 0.05). Conclusion.: In this large consecutive series of patients, 1.48% of cervical TDRs were removed/revised. The low rate of removals/revisions over a long period of time provides support for the devices’ safety. Level of Evidence.: Level IV.

Background Intraoperative neuromonitoring (IONM) became widely used in spine surgery to reduce the risk of iatrogenic nerve injury. However, the proliferation of IONM has fallen into question based on effectiveness and costs, with a lack of evidence supporting its benefit for specific spine surgery procedures. The purpose of this study was to evaluate the use of IONM and the rate of neurological injury associated with anterior lumbar spinal surgery. Methods This was a retrospective study on a consecutive series of 359 patients undergoing lumbar anterior approach surgery for anterior lumbar interbody fusion (ALIF), total disc replacement (TDR), or hybrid (ALIF with TDR) for the treatment of symptomatic disc degeneration. Patients undergoing any posterior spine surgery were excluded. Operative notes were reviewed to identify any changes in IONM and the surgeon’s response. Clinic notes were reviewed up to 3 months postoperatively for indications of iatrogenic nerve injury. Results There were 3 aberrant results with respect to IONM. Changes in IONM of a lower extremity occurred for 1 patient (0.3%). The surgeon evaluated the situation and there was no observable reason for the IONM change. Upon waking, the patient was found to have no neurological deficit. There were 2 cases of neurologic deficits in this population, which were classified as false-negatives of IONM (0.56%, 95% CI: 0.1% to 1.8%). In both cases, the patients were found to have a foot drop after the anterior approach surgery. Conclusion In this study, there was 1 false-positive and 2 false-negative results of IONM. These data suggest that IONM is not beneficial in this population. However, many surgeons may feel obligated to use IONM for medicolegal reasons. There is a need for future studies to delineate cases in which IONM is beneficial and the type of monitoring to use, if any, for specific spine surgery types. Clinical Relevance This study questions the routine use of IONM in anterior lumbar approach surgery for the treatment of symptomatic disc degeneration. This has significant implications related to the cost of this practice. Level of Evidence 4.

Purpose It is sometimes anticipated that patients with prior spine surgery will have a compromised outcome from future procedures. The purpose of this study was to compare TDR outcomes in patients with prior lumbar spine surgery to those with no previous surgery. Methods Post hoc analysis was performed on 5-year follow-up data collected prospectively in the multi-centre FDA-regulated trial for the activL® Artificial Disc which involved 376 patients treated for single-level symptomatic disc degeneration. Clinical outcome measures included the Oswestry Disability Index (ODI), visual analog scales (VAS) assessing back and leg pain, SF-36, adverse events, and re-operations. Radiographic outcomes included flexion/extension range of motion (ROM) and translation of the operated segment. Patients were divided into two groups: Prior Lumbar Surgery (PLS, n = 92) and No Prior Lumbar Surgery (NPLS, n = 284). Results Baseline demographics were similar in the two groups. ODI, VAS, and SF-36 Physical Component Scale scores improved significantly (p < 0.05) from baseline in both groups with improvements maintained through 5-year post-TDR with no significant differences between groups. There were no statistically significant differences in rates of serious device-related events, procedure-related events, or re-operations. While ROM was significantly less prior to TDR surgery in the PLS group, there was no significant difference in ROM at post-operative points. Conclusion Prior lumbar spine surgery was not associated with compromised outcomes following TDR. These results are in line with reports from earlier studies with shorter follow-up, finding that non-destabilizing prior surgery is not a contra-indication for TDR provided that selection criteria are met. Level of Evidence I Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.