Systematic literature review. To categorize published evidence systematically for lumbar fusion for chronic low back pain (LBP) in order to provide an updated and comprehensive analysis of the clinical outcomes. Despite a large number of publications of outcomes of spinal fusion surgery for chronic LBP, there is little consensus on efficacy. A MEDLINE and Cochrane database search was performed to identify published articles reporting on validated patient-reported clinical outcomes measures (2 or more of visual analogue scale, Oswestry Disability Index, Short Form [36] Health Survey [SF-36] PCS, and patient satisfaction) with minimum 12 months of follow-up after lumbar fusion surgery in adult patients with LBP due to degenerative disc disease. Twenty-six total articles were identified and stratified by level of evidence: 18 level 1 (6 studies of surgery vs. nonoperative treatment, 12 studies of alternative surgical procedures), 2 level 2, 2 level 3, and 4 level 4 (2 prospective, 2 retrospective). Weighted averages of each outcomes measure were computed and compared with established minimal clinically important difference values. Fusion cohorts included a total of 3060 patients. The weighted average improvement in visual analogue scale back pain was 36.8/100 (standard deviation [SD], 14.8); in Oswestry Disability Index 22.2 (SD, 14.1); in SF-36 Physical Component Scale 12.5 (SD, 4.3). Patient satisfaction averaged 71.1% (SD, 5.2%) across studies. Radiographical fusion rates averaged 89.1% (SD, 13.5%), and reoperation rates 12.5% (SD, 12.4%) overall, 9.2% (SD, 7.5%) at the index level. The results of the collective studies did not differ statistically in any of the outcome measures based on level of evidence (analysis of variance, P > 0.05). The body of literature supports fusion surgery as a viable treatment option for reducing pain and improving function in patients with chronic LBP refractory to nonsurgical care when a diagnosis of disc degeneration can be made.

Review article. To critically review the state of the emerging field of cervical disc replacement. Although anterior cervical decompression and fusion (ACDF) has been used successfully in the treatment of symptomatic radiculopathy and/or myelopathy, biomechanical studies have reported the deleterious effects of cervical fusion on adjacent level kinematics. Proponents of cervical disc replacement claim that maintenance of motion at the operated level will reduce the incidence of adjacent level degeneration and improve long-term clinical outcomes when compared with ACDF. A systematic review of the literature dealing with cervical disc replacement and technologies of arthroplasty design that may have relevance to the cervical spine. A review of the design characteristics and published clinical data for cervical prostheses undergoing Investigational Device Exemption (IDE) study in the United States is provided. Current cervical disc replacement designs include one-piece implants and implants with single- or double-gliding articulations with either metal-on-metal or metal-on-polymer bearing surfaces. Reports of in vitro wear testing have claimed substantially less wear for cervical implants than that seen with prosthetic hips and knees. Short-term clinical results after decompression and cervical disc replacement for the treatment of cervical radiculopathy and/or myelopathy are encouraging. Prospective, randomized trials are lacking. Cervical disc replacement is an innovative technology that preserves motion at the instrumented level/s and will potentially improve load transfer to the adjacent levels compared with fusion. Clinical reports of success of cervical total disc replacement are encouraging but are also quite preliminary. As the U.S. IDE studies are completed, a clearer role for the place of cervical disc replacement in the spine surgeon’s armamentarium should emerge.

Prospective 6-center study. To evaluate outcomes of cervical disc replacement performed adjacent to a prior cervical fusion. The use of disc replacement adjacent to a prior anterior cervical decompression and fusion (ACDF) is an attractive reconstructive option, obviating the need for a multilevel fusion. This study reports outcomes from patients with and without previous ACDF receiving the porous coated motion (PCM) artificial cervical disc in a United States Federal Drug Administration Investigational Device Exemption trials. Patients between ages of 18 and 65 with single-level cervical radiculopathy and/or myelopathy, unresponsive to at least 6 weeks of nonsurgical therapy, or experiencing progressive neurologic symptoms were enrolled. Clinical outcomes are compared for patients receiving a PCM disc at a level adjacent to a prior ACDF (“adjacent”) and those without having previously had fusion (“primary”). 126 PCM patients were primary (mean age: 44.4 years.) and 26 patients had previous “adjacent level” fusion surgery (mean age: 46.4 years). Surgery time was similar in both groups (96 minutes and 98 minutes, respectively; P = 0.761), and mean blood loss was 76 mL and 66 mL in the 2 groups, respectively (P = 0.491). Clinical outcomes using Neck Disability Index and Visual Analog Scores neck and arm scores showed significant improvement after surgery and were similar between groups at all time points. Revision surgery occurred in 2 of 126 primary patients, and in 2 of 26 patients in the adjacent-to-fusion group. Although the level adjacent to a prior cervical fusion is subject to increased biomechanical forces, potentially leading to a higher risk of failure, the PCM disc was well tolerated in the short term. The early clinical results of disc replacement adjacent to a prior fusion are good and comparable to the outcomes after primary disc replacement surgery. However, in view of the small study population and short-term follow-up, continued study is mandatory.

Various designs of total disc replacement (TDR) devices have been compared to anterior cervical discectomy and fusion (ACDF) with favorable outcomes in FDA-approved investigational device exemption trials. The design of M6-C with a compressible viscoelastic nuclear core and an annular structure is substantially different than prior designs and has previously demonstrated favorable kinematics and clinical outcomes in small case series. To evaluate the safety and effectiveness of the novel M6-C compressible artificial cervical disc compared with ACDF for subjects with single-level degenerative cervical radiculopathy. Prospective, multicenter, concurrently and historically controlled, FDA-approved investigational device exemption clinical trial. Subjects with one-level symptomatic degenerative cervical radiculopathy were enrolled and assigned to receive M6-C or ACDF. Pain and function (Neck Disability Index, VAS), quality of life (SF-36), safety, neurologic, and radiographic assessments of motion (both flexion extension and lateral bending) were performed. The primary clinical endpoint was composite clinical success (CCS) at 24 months. Using propensity score subclassification to control for selection bias, 160 M6-C subjects were compared to a matched subset of 189 ACDF controls (46 concurrent and 143 historical controls). Both ACDF and M6-C subjects reported significant improvements in patient-reported outcomes at all time points over baseline. Overall SF-36 Physical Component Score and neck and arm pain scores were significantly improved for M6-C as compared to ACDF treatment. CCS and mean Neck Disability Index improvements were similar between M6-C and ACDF. Correspondingly, there were significantly fewer subjects that utilized pain medication or opioids following M6-C treatment at 24 months relative to baseline. Range of motion was maintained in subjects treated with M6-C. Subsequent surgical interventions, dysphagia rates, and serious adverse events were comparable between groups. M6-C treatment demonstrated both safety and effectiveness for the treatment of degenerative cervical radiculopathy. Treatment with M6-C demonstrated noninferiority for the primary endpoint, indicating a similar ability to achieve CCS at 24 months. However, for the secondary endpoints, M6-C subjects demonstrated significantly improved pain and function compared to ACDF subjects, while maintaining range of motion, improving quality of life, and decreasing analgesic and opioid usage at 2 years postoperatively relative to baseline.