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Purpose: Cervical disc replacement has become an acceptable alternative to anterior cervical fusion for the surgical treatment of cervical spine spondylosis resulting in radiculopathy or myelopathy following anterior discectomy and decompression. This concise overview considers the current state of knowledge regarding the continued debate of the role of cervical disc replacement with an update in light of the latest clinical trial results., Methods: A literature review was performed identifying clinical trials pertaining to the use of cervical disc replacement compared to cervical discectomy and fusion. Single level disease and two level disease were considered. Outcome data from the major clinical trials was reviewed and salient points identified., Results: With lengthier follow-up data becoming available, the equivalence of CDR in appropriately selected cases is becoming clear. This is chiefly manifested by reduced re-operation rates and reduced incidence of adjacent level disease in those treated with arthroplasty., Conclusion: Cervical disc replacement shows emerging equivalence in outcomes compared to the gold standard anterior cervical discectomy and fusion. Further longer term results are anticipated to confirm this trend.

Study Design: A retrospective analysis., Objective: To evaluate the long-term clinical and radiographic outcomes and to investigate who achieved the successful outcomes after lumbar total disc replacement (TDR) using ProDisc II., Summary of Background Data: There are few evidences regarding the long-term efficacy and safety of TDR. Furthermore, it has not been addressed which patients achieved good outcomes in long-term follow-up., Methods: Data at 1-, 2-, 5-, 7-year, and last follow-up were used for the analysis. According to the presence of combined pathologies, patients were categorized as groups A and B (presumed good and bad candidates, respectively). Clinical outcomes were evaluated using visual analog scale, Oswestry Disability Index, clinical success rate, and subjective satisfaction (four-point scale). Radiographic results included segmental range of motion., Results: Total study population was 54 patients with 69 segments with the average follow-up duration of 120.0 months. There were 39 patients in group A and 15 in group B. Visual analog scale and Oswestry Disability Index scores were improved significantly at all follow-up periods, reaching maximal improvement at the postoperative 2 years. Clinical success rate and satisfaction rate were significantly higher in group A (76.9% and 87.2%, respectively) than those in group B (40.0% and 60.0%, respectively) at the last follow-up. Five patients (9.3%) required revision fusion surgeries, and they are all in group B. The final segmental range of motion was well maintained in monosegmental TDR, but not in bisegmental TDR., Conclusion: Lumbar TDR using Prodisc II showed the successful outcomes with the clinical success rate of 76.9% and the satisfaction rate of 87.2% when the patients were presumed as good candidate for TDR. However, the patients who had the combined pathologies showed suboptimal results with high risk of the revision surgeries. Thus, the strict patient selection process is mandatory for the successful outcomes., Level of Evidence: 4.

OBJECTIVE Several large-scale clinical trials demonstrate the efficacy of 1- and 2-level cervical disc arthroplasty (CDA) for degenerative disc disease (DDD) in the subaxial cervical spine, while other studies reveal that during physiological neck flexion, the C4-5 and C5-6 discs account for more motion than the C3-4 level, causing more DDD. This study aimed to compare the results of CDA at different levels. METHODS After a review of the medical records, 94 consecutive patients who underwent single-level CDA were divided into the C3-4 and non-C3-4 CDA groups (i.e., those including C4-5, C5-6, and C6-7). Clinical outcomes were measured using the visual analog scale for neck and arm pain and by the Japanese Orthopaedic Association scores. Postoperative range of motion (ROM) and heterotopic ossification (HO) were determined by radiography and CT, respectively. RESULTS Eighty-eight patients (93.6%; mean age 45.62 ± 10.91 years), including 41 (46.6%) female patients, underwent a mean follow-up of 4.90 ± 1.13 years. There were 11 patients in the C3-4 CDA group and 77 in the non-C3-4 CDA group. Both groups had significantly improved clinical outcomes at each time point after the surgery. The mean preoperative (7.75° vs 7.03°; p = 0.58) and postoperative (8.18° vs 8.45°; p = 0.59) ROMs were similar in both groups. The C3-4 CDA group had significantly greater prevalence (90.9% vs 58.44%; p = 0.02) and higher severity grades (2.27 ± 0.3 vs 0.97 ± 0.99; p = 0.0001) of HO. CONCLUSIONS Although CDA at C3-4 was infrequent, the improved clinical outcomes of CDA were similar at C3-4 to that in the other subaxial levels of the cervical spine at the approximately 5-year follow-ups. In this Asian population, who had a propensity to have ossification of the posterior longitudinal ligament, there was more HO formation in patients who received CDA at the C3-4 level than in other subaxial levels of the cervical spine. While the type of artificial discs could have confounded the issue, future studies with more patients are required to corroborate the phenomenon.

This case report presents a 37-year-old man with clinical signs of myelopathy almost 9 years after implantation of a Bryan disc prosthesis (Medtronic Sofamor Danek, Memphis, TN, USA) for C5/C6 soft disc herniation. As demonstrated on MRI and CT scan, spinal cord compression was caused by bony spurs due to heterotopic ossification posterior to the still moving prosthesis. The device, as well as the ectopic bone deposits, had to be removed because of myelopathy and its imminent aggravation. Conversion to anterior spondylodesis was performed., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Background Context: Numerous studies have been conducted on the importance of radiographic parameters after a total disc replacement (TDR). Most of them have focused on sagittal alignment. There has been no research on what influence the coronal alignment or tilting of device has on radiographic parameters., Purpose: The aim was to investigate the influences of coronal tilting of device on radiographic parameters and degeneration., Study Design/setting: This was a prospective comparative study., Patient Sample: A total of 180 patients with single-level cervical disc disease who underwent TDR were included., Outcome Measures: Overall and functional spinal unit (FSU) sagittal range of motion (ROM), coronal alignment (or tilting) of device, and postoperative radiographic degeneration (RD) were analyzed., Methods: Static anteroposterior, lateral X-rays, and dynamic lateral radiographs were assessed preoperatively, postoperatively, at 1.5, 3, 6, 9, 12, 18, 24 months, and every 6 months thereafter until final follow-up. A correlation with various parameters that could result in RD was investigated, For this, the patients were divided into two groups (Group I, RD; Group II, no RD) and subdivided into Group I-A (<5°; low coronal tilt) and Group I-B (≥5°; high coronal tilt) to analyze whether coronal tilting of device was correlated with RD., Results: No statistical differences were found in preoperative overall and FSU ROM, postoperative overall and FSU ROM between Groups I and II. However, there was significant difference in coronal tilting of device between Groups I (4.50±2.83°) and II (2.04±1.15°; p=.001). There were no significant differences in preoperative overall and FSU ROM, postoperative overall and FSU ROM between Group I-A and I-B. But, RD incidence rate at surgical segment in Group I-A was 23.1%, whereas that in Group I-B was 75.0% (p=.001). The influence level of a difference in the incidence rate was found to be 10.0 of the odds ratio. Radiographic degeneration incidence rate at adjacent levels in Group I-A was 8.33%, whereas that in Group I-B was 25.0% (p=.013). The influence level of a difference in the incidence rate was found to be 3.67 of the odds ratio., Conclusions: It is considered that maintaining appropriate coronal alignment of device is important in long-term success after a cervical TDR., (Copyright © 2016 Elsevier Inc. All rights reserved.)

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.

Study Design: Retrospective analysis., Objective: To examine complications and rates of subsequent surgery following lumbar spinal fusion (LF) and lumbar total disc arthroplasty (TDA) at up to 5-year follow-up., Summary of Background Data: LF is commonly used in the management of degenerative disc disease causing pain refractory to nonoperative management. Lumbar TDA was developed as an alternative to fusion with the theoretical advantage of reducing rates of adjacent segment pathology and reoperation. Most prior reports comparing these 2 interventions have come from industry-sponsored investigational device exemption trials and no large-scale administrative database comparisons exist., Methods: The California Office of Statewide Health Planning and Development discharge database was queried for patients aged 18 to 65 years undergoing lumbar TDA and LF for degenerative disc disease from 2004 to 2010. Patient characteristics were collected, and rates of complications and readmission were identified. Rates of repeat lumbar surgery were calculated at 90-day and 1-, 3-, and 5-year follow-up intervals., Results: A total of 52,877 patients met the inclusion criteria (LF = 50,462, TDA = 2415). Wound infections were more common following LF than TDA (1.03% vs. 0.25%, P < 0.001). Rates of subsequent lumbar surgery at 90-day and 1-year follow-up were lower with lumbar TDA than LF (90-day-TDA: 2.94% vs. LF: 4.01%, P = 0.007; 1-yr-TDA: 3.46% vs. LF: 4.78%, P = 0.009). However, there were no differences in rates of subsequent lumbar surgery between the 2 groups at 3-year and 5-year follow-up., Conclusion: Lumbar TDA was associated with fewer early reoperations, though beyond 1 year, rates of reoperation were similar. Lumbar TDA may be associated with fewer acute infections, though this may be approach related and unrelated to the device itself., Level of Evidence: 3.

Study Design: This was a prospective, randomized, controlled, multicenter study., Objective: The purpose of this study was to compare outcomes of two lumbar total disc replacements (TDRs) at 5-year follow-up and report results of serum ion level analysis in a subgroup of patients receiving a metal-on-metal implant., Summary of Background Data: Lumbar TDR has been compared with fusion in several randomized studies, finding TDR noninferior to fusion and superior on some measures. Receiving less attention has been comparing TDR devices. Additionally, there is concern about metal-on-metal implants, with little data available for spine devices., Methods: The study included 204 patients receiving Kineflex-L (investigational) and 190 receiving CHARITÉ (control). Outcome measure included Oswestry Disability Index, visual analog pain scales (VAS), patient satisfaction, neurological status, complications, reoperations, and a composite success score. Radiographic assessment included range of motion, subsidence, and heterotrophic ossification. In 32 investigational patients, serum ion analysis was performed for cobalt and chromium. These values were compared with Medicines and Healthcare Products Regulatory Agency values to merit monitoring total hip replacement patients for potential wear problems., Results: Mean Oswestry and VAS scores in both groups improved significantly by 6 weeks and remained improved during 5-year follow-up (Oswestry Disability Index, scores in both groups were approximately 60 preoperatively vs. 20 at 2- and 5-year follow-up; P < 0.01; VAS scores improved >50% by 6 weeks and remained significantly improved; P < 0.05). Approximately 11% of both groups underwent reoperation. Radiographic analysis found segmental range of motion decreased at 3 month, then increased through 24 months, and was maintained thereafter. Serum ion level analysis found the greatest mean value at any follow-up point was less than 20% of Medicines and Healthcare Products Regulatory Agency recommended minimum value to merit monitoring hip replacement patients., Conclusion: This prospective, randomized study comparing two TDRs found no significant differences in outcomes during 5-year follow-up. Both provided statistically significant improvements by 6 weeks that were maintained. This results support other studies. Serum ion levels in TDR patients were well below the recommended threshold levels to merit monitoring.

Study Design: Retrospective study., Objective: The aims of this study were to evaluate the radiographic and clinical outcomes of Bryan cervical disc arthroplasty at 10-year follow-up., Summary of Background Data: Cervical arthroplasty is a new technique for treating degenerative cervical disease. Previous reports have shown that cervical arthroplasty with Bryan disc gained good clinical outcomes at 4- to 6-year follow-up., Methods: Clinical outcomes and dynamic x-ray examination were evaluated at baseline and at final follow-up., Results: Thirty-three patients with complete clinical and radiographic data were included in this study. The mean follow-up period was 120.5 months (116-130 months). Twenty-five patients underwent single-level arthroplasty and 7 underwent arthroplasty at 2 levels. One patient underwent arthroplasty at 3 levels. Eight of the 33 patients presented with radiculopathy and 25 patients with myelopathy. The 42 levels of surgery included C3/4 (3 levels), C4/5 (7 levels), C5/6 (26 levels) and C6/7 (6 level). The mJOA score of the 25 patients with myelopathy was 11.8 at the baseline and 15.9 at the final follow-up. No patient suffered from adjacent segment disease. Two patients received revision surgeries at the index level for recurrent radiculopathy caused by osteophyte formation and heterotopic ossification. On x-ray examination, the range of motion at the operated level was 7.8 degree at the baseline and 4.7 degree at the final follow-up. Heterotopic ossification was observed in 29 (69.0%) levels and heterotopic ossification of Grade 4 was observed in 14 levels. Adjacent segment degeneration was observed in 30 (47.6%) levels., Conclusion: Cervical arthroplasty using Bryan cervical disc prosthesis resulted in fine clinical outcomes in this study. Heterotopic ossification was common after Bryan disc arthroplasty, which decreased the range of motion., Level of Evidence: 4.

Purpose: The purpose of this study is to assess safety and feasibility of intradiscal bone marrow concentrate (BMC) injections to treat discogenic pain as an alternative to surgery., Methods: A total of 26 patients (11 male, 15 female, aged 18-61 years, 13 single level, 13 two level) that met inclusion criteria of chronic (> 6 months) discogenic low back pain, degenerative disc pathology assessed by magnetic resonance imaging (MRI) with modified Pfirrmann grade of IV-VII at one or two levels, candidate for surgical intervention (failed conservative treatment and radiologic findings) and a visual analogue scale (VAS) pain score of 40 mm or more at initial visit. Initial Oswestry Disability Index (ODI) and VAS pain score average was 56.5 % and 80.1 mm (0-100), respectively. Adverse event reporting, ODI score, VAS pain score, MRI radiographic changes, progression to surgery and cellular analysis of BMC were noted. Retrospective cell analysis by flow cytometry and colony forming unit-fibroblast (CFU-F) assays were performed to characterise each patient's BMC and compare with clinical outcomes. The BMC was injected into the nucleus pulposus of the symptomatic disc(s) under fluoroscopic guidance. Patients were evaluated clinically prior to treatment and at three, six, 12 and 24 months and radiographically prior to treatment and at 12 months., Results: There were no complications from the percutaneous bone marrow aspiration or disc injection. Of 26 patients, 24 (92 %) avoided surgery through 12 months, while 21 (81 %) avoided surgery through two years. Of the 21 surviving patients, the average ODI and VAS scores were reduced to 19.9 and 27.0 at three months and sustained to 18.3 and 22.9 at 24 months, respectively (p ≤ 0.001). Twenty patients had follow-up MRI at 12 months, of whom eight had improved by at least one Pfirrmann grade, while none of the discs worsened. Total and rate of pain reduction were linked to mesenchymal stem cell concentration through 12 months. Only five of the 26 patients elected to undergo surgical intervention (fusion or artificial disc replacement) by the two year milestone., Conclusions: This study provides evidence of safety and feasibility in the non-surgical treatment of discogenic pain with autologous BMC, with durable pain relief (71 % VAS reduction) and ODI improvements (> 64 %) through two years.

Background: No previous reports have mentioned bone loss of the superior adjacent vertebra immediately posterior to the anterior flange of Bryan cervical disc (Medtronic Sofamor Danek, Memphis, TN, USA), which plays a central role to prevent posterior migration of the device. The purpose of this study is to describe a new potential complication, bone loss immediately posterior to the anterior total disc replacement (TDR) flange on the superior adjacent vertebra following the Bryan cervical TDR and to discuss the possible mechanism., Methods: The authors retrospectively reviewed 37 patients undergoing cervical TDR with the Bryan cervical disc. The clinical and radiological outcome data were collected at 1, 3, 6, 12, 24, and 36 months postoperatively, and at last follow-up, which ranged from 42 to 113 moths (average, 60.1 months). Clinical evaluation included the visual analog scale and neck disability index, and the radiographic evaluation included measurements of the functional spinal unit range of motion on flexion and extension and identification of radiographic changes such as bone loss., Results: The Bryan TDR showed good mid-term clinical and radiological outcomes. Interestingly, however, bone loss was noted immediately posterior to the TDR flange on superior adjacent vertebra in 3 total patients; at 3 months (n = 2) and 6 months (n = 1). Although the bone loss was increased up to 6 months, this did not progress and no degradation of clinical and radiological outcomes occurred at last follow-up., Conclusions: Bone loss immediately posterior to the anterior TDR flange on the superior adjacent vertebra can occur in the early postoperative period due to possibly stress shielding effect. However, it did not result in clinical changes or increased rates of graft failure at last follow-up. A long-term follow-up study is mandatory to evaluate the long-term effects of the bone loss.

Purpose: To evaluate the incidence and risk factors for adjacent segment pathology (ASP) after anterior cervical spinal surgery., Methods: Fourteen patients (12 male, mean age 47.1 years) who underwent single-level cervical disk arthroplasty (CDA group) and 28 case-matched patients (24 male, mean age 53.6 years) who underwent single-level anterior cervical discectomy and fusion (ACDF group) were included. Presence of radiologic ASP (RASP) was based on observed changes in anterior osteophytes, disks, and calcification of the anterior longitudinal ligament on lateral radiographs., Results: The mean follow-up period was 43.4 months in the CDA group and 44.6 months in the ACDF group. At final follow-up, ASP was observed in 5 (35.7%) CDA patients and 16 (57.1%) ACDF patients (p = 0.272). The interval between surgery and ASP development was 33.8 months in the CDA group and 16.3 months in the ACDF group (p = 0.046). The ASP risk factor analysis indicated postoperative cervical angle at C3-7 being more lordotic in non-ASP patients in both groups. Restoration of lordosis occurred in the CDA group regardless of the presence of ASP, but heterotopic ossification development was associated with the presence of ASP in the CDA group. And the CDA group had significantly greater clinical improvements than those in the ACDF group when ASP was present., Conclusion: In both CDA and ACDF patients, RASP developed, but CDA was associated with a delay in ASP development. A good clinical outcome was expected in CDA group, even when ASP developed. Restoration of cervical lordosis was an important factor in anterior cervical spine surgery.

Study Design: A prospective, multicenter, randomized, controlled, investigational device exemption (IDE) noninferiority trial., Objective: The aim of this study was to evaluate the comparative safety and effectiveness of lumbar total disc replacement (TDR) in the treatment of patients with symptomatic degenerative disc disease (DDD) who are unresponsive to nonsurgical therapy., Summary of Background Data: Lumbar TDR has been used to alleviate discogenic pain and dysfunction while preserving segmental range of motion and restoring stability. There is a paucity of data available regarding the comparative performance of lumbar TDR., Methods: Patients presenting with symptomatic single-level lumbar DDD who failed at least 6 months of nonsurgical management were randomly allocated (2:1) to treatment with an investigational TDR device (activL, n = 218) or FDA-approved control TDR devices (ProDisc-L or Charité, n = 106). The hypothesis of this study was that a composite effectiveness outcome at 2 years in patients treated with activL would be noninferior (15% delta) to that in controls., Results: The primary composite endpoint of this study was met, which demonstrated that the activL TDR was noninferior to control TDR (P < 0.001). A protocol-defined analysis of the primary composite endpoint also confirmed that activL was superior to controls (P = 0.02). Radiographic success was higher with activL versus controls (59% vs. 43%; P < 0.01). Mean back pain severity improved by 74% with activL and 68% with controls. Oswestry Disability Index scores decreased by 67% and 61% with activL and controls, respectively. Patient satisfaction with treatment was over 90% in both groups at 2 years. Return to work was approximately 1 month shorter (P = 0.08) with activL versus controls. The rate of device-related serious adverse events was lower in patients treated with activL versus controls (12% vs. 19%; P = 0.13). Surgical reintervention rates at the index level were comparable (activL 2.3%, control 1.9%)., Conclusion: The single-level activL TDR is safe and effective for the treatment of symptomatic lumbar DDD through 2 years., Level of Evidence: 2.

Chronic low back pain is extremelyfrequent and its management is still con troversial among spine physicians. For decades, intervertebral fusion has been considered as the gold- standard. However, non fusion techniques have been developed in order to avoid fusion's complications. Numerous studies have reported satisfactory results of total disc arthro- plasty in the management of lumbar degenerative disc disease. So far it is still dificult to prove the superiority of disc replacement over fusion due to a lack of high level studies. The aim of this work was to try to answers various questions related to that technique which was described twenty years ago.

Cervical artificial disc replacement (CADR) as a new method for the treatment of cervical spondylosis, is becoming a basic and clinical research. Compared with the anterior cervical discectomy and fusion (ACDF), the biggest difference of CADR lies in the reconstruction of the cervical vertebra height and physiological curvature, retaining the spinal physiological function maximally and reducing the degenerative changes in adjacent segments. A large number of clinical investigation have suggested that ACDR can become an operation method to replace the ACDF. However, the complications and the problems of prosthesis itself are gradually exposed, such as that the prosthesis, can't completely simulate the biological effects of human intervertebral disc, the other factors and including the operation methods and prosthesis itself. At the same time, the problem that how to prevent complications and problems is required to be solved. Whether, the effect of CADR on the activity of the operation segment, and the prevention of adjacent segment degeneration can be guaranteed for a long time has drawn more and more attention from scholars.

Purpose: Accelerated degenerative changes at intervertebral levels adjacent to a spinal fusion, the so-called adjacent segment degeneration (ASD), have been reported in many clinical studies. Even though the pathogenesis of ASD is still widely unknown, biomechanical in vitro approaches have often been used to investigate the impact of spinal instrumentation on the adjacent segments. The goal of this review is (1) to summarize the results of these studies with respect to the applied protocol and loads and (2) to discuss if the assumptions made for the different protocols match the patients' postoperative situation., Methods: A systematic MEDLINE search was performed using the keywords "adjacent", "in vitro" and "spine" in combination. This revealed a total of 247 articles of which 33 met the inclusion criteria. In addition, a mechanical model was developed to evaluate the effects of the current in vitro biomechanical test protocols on the changes in the adjacent segments resulting from different stiffnesses of the "treated" segment., Results: The surgical treatments reported in biomechanical in vitro studies investigating ASD can be categorized into fusion procedures, total disc replacement (TDR), and dynamic implants. Three different test protocols (i.e. flexibility, stiffness, hybrid) with different loading scenarios (e.g. pure moment or eccentric load) are used in current biomechanical in vitro studies investigating ASD. According to the findings with the mechanical model, we found that the results for fusion procedures highly depend on the test protocol and method of load application, whereas for TDR and dynamic implants, most studies did not find significant changes in the adjacent segments, independent of which test protocol was used., Conclusions: The three test protocols mainly differ in the assumption on the postoperative motion behavior of the patients, which is the main reason for the conflicting findings. However, the protocols have never been validated using in vivo kinematic data. In a parallel review on in vivo kinematics by Malakoutian et al., it was found that the assumption that the patients move exactly the same after fusion implemented with the stiffness- and hybrid protocol does not match the patients' behavior. They showed that the motion of the whole lumbar spine rather tends to decrease in most studies, which could be predicted by the flexibility protocol. However, when the flexibility protocol is used with the "gold standard" pure moment, the difference in the kinematic changes between the cranial and caudal adjacent segment cannot be reproduced, putting the validity of current in vitro protocols into question.

Object: The anterior approach to the lumbar spine may be associated with iliac artery thrombosis. Intraoperative heparin can be administered to prevent thrombosis; however, there is a concern that this will increase the procedural blood loss. The aim of this study was to examine whether intraoperative heparin can be administered without increasing blood loss in anterior lumbar spine surgery., Methods: A prospective study of consecutive anterior approaches for lumbar spine surgery was performed between January 2009 and June 2014 by a single vascular surgeon and a single spine surgeon. Patients underwent an anterior lumbar interbody fusion (ALIF) at L4-5 and/or L5-S1, a total disc replacement (TDR) at L4-5 and/or L5-S1, or a hybrid procedure with a TDR at L4-5 and an ALIF at L5-S1. Heparin was administered intravenously when arterial flow to the lower limbs was interrupted during the procedure. Heparin was usually reversed on removal of the causative retraction., Results: The cohort consisted of 188 patients with a mean age of 41.7 years; 96 (51.1%) were male. Eighty-four patients (44.7%) had an ALIF, 57 (30.3%) had a TDR, and 47 (25.0%) had a hybrid operation with a TDR at L4-5 and an ALIF at L5-S1. One hundred thirty-four patients (71.3%) underwent a single-level procedure (26.9% L4-5 and 73.1% L5-S1) and 54 (28.7%) underwent a 2-level procedure (L4-5 and L5-S1). Seventy-two patients (38.3%) received heparinization intraoperatively. Heparin was predominantly administered during hybrid operations (68.1%), 2-level procedures (70.4%), and procedures involving the L4-5 level (80.6%). There were no intraoperative ischemic vascular complications reported in this series. There was 1 postoperative deep venous thrombosis. The overall mean estimated blood loss (EBL) for the heparin group (389.7 ml) was significantly higher than for the nonheparin group (160.5 ml) (p < 0.0001). However, when all variables were analyzed with multiple linear regression, only the prosthesis used and level treated were found to be significant in blood loss (p < 0.05). The highest blood loss occurred in hybrid procedures (448.1 ml), followed by TDR (302.5 ml) and ALIF (99.7 ml). There were statistically significant differences between the EBL during ALIF compared with TDR and hybrid (p < 0.0001), but not between TDR and hybrid. The L4-5 level was associated with significantly higher blood loss (384.9 ml) compared with L5-S1 (111.4 ml) (p < 0.0001)., Conclusions: During an anterior exposure for lumbar spine surgery, the administration of heparin does not significantly increase blood loss. The prosthesis used and level treated were found to significantly increase blood loss, with TDR and the L4-5 level having greater blood loss compared with ALIF and L5-S1, respectively. Heparin can be administered safely to help prevent thrombotic intraoperative vascular complications without increasing blood loss.

Purpose: While much evidence suggests that adjacent segment degeneration is merely a manifestation of the natural degenerative process unrelated to any spine fusion, a significant body of literature supports the notion that it is a process due in part to the altered biomechanics adjacent to fused spine segments. The purpose of this study was to review and critically analyze the published literature that investigated the in vivo kinematics of the adjacent segments and entire lumbar spine in patients receiving spinal fusion or motion-preserving devices., Methods: A systematic review of the PubMed database was conducted, initially identifying 697 studies of which 39 addressed the in vivo kinematics of the segments adjacent to spinal implants or non-instrumented fusion of the lumbar spine., Results: Twenty-nine articles studied fusion, of which three reported a decrease in range of motion of the caudal adjacent segment post-fusion. Examining the rostral adjacent segment, twelve studies observed no change, nine studies found a significant increase, and three studies reported a significant decrease in sagittal plane range of motion. Of the six studies that analyzed motion for the entire lumbar spine as a unit, five studies showed a significant decrease and one study reported no change in global lumbar spine motion. Kinematics of the segment rostral to a total disc replacement was investigated in six studies: four found no change and the results for the other two showed dependence on treatment level. Fifteen studies of non-fusion posterior implants analyzed the motion of the adjacent segment with two studies noting an increase in motion at the rostral level., Conclusions: There appears to be no overall kinematic changes at the rostral or caudal levels adjacent to a fusion, but some patients (~20-30%) develop excessive kinematic changes (i.e., instability) at the rostral adjacent level. The overall lumbar ROM after fusion appears to decrease after a spinal fusion.

Study Design: Decision analysis from prior randomized controlled trial (RCT) data., Objective: To describe the importance of developing baseline utility indices while identifying effective treatment options for cervical spine disease., Summary of Background Data: Cervical total disc replacement (CTDR) was developed to treat cervical spondylosis while preserving motion. Although anterior cervical discectomy and fusion (ACDF) has been the standard of care, a recent RCT suggested similar outcomes for 2-level disease. The quality-of-life benefit afforded by both CTDR and ACDF has never been fully elucidated. The purpose of our investigation was to better define the changes in utility and perceived value for patients undergoing these procedures., Methods: Data were derived from LDR's RCT comparing CTDR and ACDF for 2-level cervical disc disease. Using linear regression, we constructed health states on the basis of the stratification of clinical outcomes used in the RCT, namely, neck disability index and visual analogue scale. Data from SF-12 questionnaires, completed preoperatively and at each follow-up visit, were transformed into utilities using the SF-6D mapping algorithm. SAS v.9.3 was used for the analyses., Results: A strong correlation (R = 0.6864, P < 0.0001) was found between neck disability index and visual analogue scale. We constructed 5 distinct health states by projecting neck disability index intervals onto visual analogue scale. A poorer health state was associated with a lower mean utility value whereas a higher health state was associated with a higher mean utility value (P < 0.0001). The difference in preoperative utility between 2-level ACDF and CTDR was not significant (P = 0.1982), and yet, the difference in the postoperative utility between the cohorts was significant (P < 0.05) at every time point collected from 6 to 60 months., Conclusion: This is the first instance in which distinct utility values have been derived for validated health states related to cervical spine disease. There is substantial potential for these to become baseline future indices for cost-utility analyses in similar populations., Level of Evidence: 1.

Purpose: The aim of the study was to evaluate whether there is a superior clinical effect of artificial cervical arthroplasty compared with anterior cervical discectomy and fusion (ACDF) for the treatment of one-level cervical degenerative disc disease (CDDD)., Methods: A comprehensive literature search of multiple databases, including PubMed, ScienceDirect, Scopus, Embase, Cochrane Central Register of Controlled Trials, was conducted to identify studies that met the inclusion criteria. Methodological quality was assessed and relevant data were extracted, and if appropriate, meta-analysis was performed., Results: Thirteen randomized controlled trials were identified. At 24 months post-operatively, total disc replacement (TDR) was demonstrated to be more beneficial for patients compared with ACDF for the following outcomes: neurological success [odds ratio (OR) 1.92; 95% confidence interval (CI) 1.47-2.49; p < 0.00001], range of motion [mean differences (MD), 6.67; 95% CI 4.82-8.53; p < 0.00001], secondary surgical procedures (OR 0.50; 95% CI 0.37-0.68; p < 0.00001), and visual analogue scale neck pain scores (MD -5.99; 95% CI -10.54 to -1.45; p = 0.001) and visual analogue scale arm pain scores (MD -3.23; 95% CI -6.48 to 0.02; p = 0.004). Other outcomes, including length of the hospital stay (MD -0.03; 95% CI -0.18 to 0.12; p = 0.68), blood loss (MD 6.92 mL; 95% CI -3.09 to 16.92 mL; p = 0.18), Neck Disability Index scores (MD -1.00; 95% CI -5.28 to 3.28; p = 0.65) and rate of adverse events [risk ratio (RR), 0.93; 95% CI 0.76-1.15; p = 0.52] demonstrated no differences between the 2 groups. Although the TDR group had a significantly longer operation time than the ACDF group, it was not considered clinically important., Conclusions: For patients with one-level CDDD, TDR was found to be more superior than ACDF in terms of neurological success, secondary surgical procedures, visual analogue scale pain scores and range of motion at 24 months post-operatively. Therefore, cervical arthroplasty is a safe and effective surgical procedure for treating one-level CDDD. We suggest adopting TDR on a large scale; with failure of TDR, ACDF would be performed.

Study Design: A prospective, randomized, multicenter Food and Drug Administration Investigation Device Exemption study using total disc replacement as surgical treatment of degenerative disc disease at 1 or 2 contiguous levels of the cervical spine., Objective: To evaluate the safety and effectiveness of total disc replacement at single or 2 contiguous levels through 48 months of follow-up., Summary of Background Data: Cervical total disc replacement has been shown to be a safe and effective alternative to anterior cervical discectomy and fusion at 24 months. Its motion-preserving capabilities may avoid accelerating adjacent segment pathology and thereby lower the rate of associated complications., Methods: Patients were randomized in a 2:1 ratio (total disc replacement [TDR]: anterior cervical discectomy and fusion [ACDF]) at 24 sites. Ultimately, 164 patients received TDR at 1 level and 225 patients received TDR at 2 contiguous levels. An additional 24 patients (15 one-level, 9 two-level) were treated with TDR as training cases.Outcome measures included neck disability index, visual analogue scale neck and arm pain, Short Form 12-item Health Survey (SF-12) Mental Composite Score (MCS) and Physical Composite Score (PCS), range of motion, major complication rates, and secondary surgery rates. Patients received follow-up examinations at regular intervals through 4 years after surgery., Results: Preoperative characteristics were statistically similar for the 1- and 2-level patient groups. Four-year follow-up rates were 83.1% (1-level) and 89.0% (2-level). There was no statistically significant difference between 1- and 2-level TDR groups for all clinical outcome measures. Both TDR groups experienced significant improvement at each follow-up when compared with preoperative scores. One case of migration was reported in the 2-level TDR group., Conclusion: A 4-year post hoc comparison of 1- and 2-level TDR patients concurrently enrolled in a 24-center, Food and Drug Administration Investigation Device Exemption clinical trial indicated no statistical differences between groups in clinical outcomes, overall complication rates, and subsequent surgery rates., Level of Evidence: 1.

OBJECT The purpose of this study was to evaluate the failure risk of cervical vertebrae after total disc replacement with a keel-design prosthesis (ProDisc-C), taking into consideration the effects of vertebral body height, multilevel replacement, and the association with an adjacent fusion cage. Although promising clinical results have been reported for the ProDisc-C, some clinical studies have reported vertebral body-splitting fractures at single- and multilevel arthroplasty sites. This implant has central keels to provide solid initial stability, and some authors associate the potential risk of vertebral body failure with the keel design, especially in patients with small vertebral body height or when the implant is used at multiple levels. METHODS The study was performed using a specimen-specific C4-6 cervical-segment finite-element model to assess the compressive strains on the C-5 vertebral body for each cervical segment configuration, and synthetic polyurethane models to experimentally predict the compressive load at failure for 3 vertebral body heights. RESULTS The use of a keeled ProDisc-C prosthesis at multiple levels or in combination with a fusion cage increases by a factor of 2-3 the compressive strains at the C-5 vertebral body relative to single-level arthroplasty. All implanted segment configurations tested demonstrated a continuum of the load at failure and the vertebral body height, but no significant differences were found between the 3 vertebral body heights in each segment configuration. CONCLUSIONS The use of a keeled ProDisc-C prosthesis at 2 adjacent levels or combined with a fusion cage presented the lowest load-at-failure values, 2 times higher on average than the ones occurring during physiological tasks. This fact indicates an identical and limited risk of vertebral body failure for these 2 segment configurations, whereas vertebral body height appears to slightly affect this risk. However, for some tasks that place higher physical demands on the neck, beyond what was represented by our models, there may also be risk of microdamage initiation, which is not present in the single-level arthroplasty.

Study Design: Prospective, multicenter, randomized clinical trial., Objective: To evaluate the long-term safety and effectiveness of the PCM Cervical Disc compared with anterior cervical discectomy and fusion (ACDF) in treatment of patients with symptomatic single-level degenerative spondylosis between C3-C4 and C7-T1 with or without prior cervical fusion., Summary of Background Data: The 2-year results of the PCM Cervical Disc trial have been reported previously. The current study reports the long-term results of the same trial., Methods: Patients with single-level cervical spondylosis and radiculopathy with or without myelopathy unresponsive to nonoperative treatment were enrolled. The per protocol patient sample at 5 years included 293 patients (163 PCM, 130 ACDF). Adverse events and secondary surgical procedures are reported on the cohorts through current follow-up, which include 110 patients (68 PCM, 42 ACDF) at 7 years., Results: At 5 years postoperative, all patient-reported outcomes-neck and arm pain visual analogue scale score, neck disability index, and general health (36-Item Short Form Health Survey physical and mental component scores: physical component summary, mental component summary)-were significantly improved from baselines in both groups, and mean scores were significantly better in the PCM group for neck disability index (P=0.001), neck pain (P=0.002), general health (Pphysical component summary=0.014; Pmental component summary=0.004), and patient satisfaction (P=0.005). PCM patients trended toward fewer 2- to 7-year device-related serious adverse events (1/214, 0.5% PCM; 2/190, 1.1% ACDF) and secondary surgical procedures (7/211, 3.3% PCM; 14/290, 7.6% ACDF). Adjacent-level degeneration was radiographically more frequent after ACDF (33.1% PCM, 50.9% ACDF; P=0.006) and was the primary indication for the increase in late-term secondary surgical procedures after ACDF., Conclusion: The long-term results show good clinical outcomes after ACDF and PCM arthroplasty. PCM patients showed greater improvement in neck disability index and neck pain scores with a lower rate of radiographical adjacent-level degeneration and a trend toward fewer secondary surgical procedures. These data support PCM arthroplasty to be a viable and sustainable alternative to ACDF., Level of Evidence: 1.

Study Design: Retrospective review of prospectively collective administrative data., Objective: The purpose of this study was to determine the reoperation rates, adverse event rate, as well as the direct and follow-on costs of cervical disc arthroplasty (CDA) compared with anterior cervical discectomy and fusion (ACDF) in a "real-world" population of patients with single-level symptomatic cervical disc disease., Summary of Background Data: Until very recently, there was a paucity of human clinical data to demonstrate that CDA lowers the rate of adjacent segment disease over ACDF., Methods: This was a retrospective, matched cohort analysis of a prospectively collected database of costs and outcomes for patients aged 18 to 60 years, who were continuously enrolled in a Blue Cross Plan contributing data to a claims database. Inclusion criteria were as follows: all patients who were treated surgically with either CDA or ACDF between January 2008 and December 2009, with single-level cervical pathology and claims reflecting at least 6 weeks of nonsurgical preoperative care without claims history of prior surgery., Results: There were 6635 ACDF patients and 327 CDA patients. There were no significant differences in the incidence of comorbidities or mean follow-up time (ACDF 25.7 mo vs. CDA 26.1 mo) between groups. By 36 months postoperatively, the reoperation rate was significantly increased in the ACDF group (10.5%) versus the CDA group (5.7%) (hazard ratio, P = 0.0214). The index surgery and 90-day global window costs were significantly lower in the CDA groups. At final follow-up, there was a statistically significant reduction in total costs paid by insurer in CDA patients (CDA $34,979 vs. ACDF $39,820)., Conclusion: Patients who underwent CDA for single-level degenerative disease had lower readmission rates, lower reoperation rates, and reduced index and total costs than those treated with ACDF. CDA was effective in reducing the monthly cost of care compared with ACDF., Level of Evidence: 2.

The prevalence of cervical disc disease is high, and the traditional surgical method of anterior cervical discectomy and fusion (ACDF) carries with it the disadvantages of motion loss at the operated level, and accelerated adjacent level disc degeneration. Preliminary results of the efficacy and reoperative rate comparing TDA versus ACDF have been reported; however, the long-term outcomes of TDA versus ACDF still remain a topic of debate. This review was prepared following the standard procedures set forth by the Cochrane Collaboration organization, and preferred reporting items for systematic reviews and meta-analyses (PRISMA). The only studies included were randomized controlled trials with a minimum of 4 years of follow-up data. The meta-analysis included the neck disability index (NDI), visual analog scale (VAS) of neck and arm pain, SF-36 physical component scores (SF-36 PCS), over success, neurological success, work status, implant-related complications, and secondary surgery events. Four randomized controlled trials meet the inclusion criteria. The long-term improvement of NDI, VAS of neck and arm pain, SF-36 PCS, over success, and neurological success favored the TDA group. The TDA group also had a lower incidence of secondary surgery for both the index level (RR: 0.45 [0.28, 0.72]) and adjacent level (RR: 0.53 [0.33, 0.88]). In this meta-analysis of 4 included RCTs with a minimum 4 years of follow-ups, total disc arthroplasty showed improvements over ACDF as measured by the NDI, VAS of neck and arm pain, and SF-36 PCS.

Background: Despite being considered the standard surgical procedure for symptomatic cervical disc disease, anterior cervical decompression and fusion invariably accelerates adjacent segment degeneration. Cervical total disc replacement is a motion-preserving procedure developed as a substitute to fusion. Whether cervical total disc replacement is superior to fusion remains unclear., Methods: We comprehensively searched PubMed, EMBASE, Medline, and the Cochrane Library in accordance with the inclusion criteria to identify possible studies. The retrieved results were last updated on December 12, 2014. We classified the studies as short-term and midterm follow-up., Results: Nineteen randomized controlled trials involving 4516 cases were identified. Compared with anterior cervical decompression and fusion, cervical total disc replacement had better functional outcomes (neck disability index [NDI], NDI success, neurological success, neck pain scores reported on a numerical rating scale [NRS], visual analog scales scores and overall success), greater segmental motion at the index level, fewer adverse events and fewer secondary surgical procedures at the index and adjacent levels in short-term follow-up (P < 0.05). With midterm follow-up, the cervical total disc replacement group indicated superiority in the NDI, neurological success, pain assessment (NRS), and secondary surgical procedures at the index level (P < 0.05). The Short Form 36 (SF-36) and segmental motion at the adjacent level in the short-term follow-up showed no significant difference between the two procedures, as did the secondary surgical procedure rates at the adjacent level with midterm follow-up (P > 0.05)., Conclusions: Cervical total disc replacement presented favorable functional outcomes, fewer adverse events, and fewer secondary surgical procedures. The efficacy and safety of cervical total disc replacement are superior to those of fusion. Longer-term, multicenter studies are required for a better evaluation of the long-term efficacy and safety of the two procedures.

Study Design: Meta-analysis., Objective: The purpose of this study was to answer the following questions: (1) Does heterotopic ossification (HO) negatively influence clinical outcomes after cervical total disc replacement (CTDR)? (2) Should patients be classified into HO and non-HO groups? (3) Is there a more rational classification?, Summary of Background Data: Heterotopic ossification has emerged as a common complication after CTDR and has been an important reason for reoperation, thus limiting the use of the surgery. However, the influence of HO on clinical outcomes after CTDR has not been well established., Methods: A meta-analysis was conducted with studies identified by searches of MEDLINE, EMBASE, and the Cochrane Library. We calculated the weighted mean differences of the visual analogue scale pain score, Neck Disability Index, and range of motion (ROM). Patients were classified into 2 groups under 3 classifications on the basis of the grade of HO. Results were pooled using a fixed effect model or a random effects model, according to the heterogeneity., Results: There were significant differences in ROM under all 3 classifications. The visual analogue scale pain score and the Neck Disability Index between the patients with and without HO showed no significant difference after CTDR. Significant differences in visual analogue scale pain score were observed when patients were classified into a "high-grade HO" group (McAfee grades 3 or 4 HO) and a "low-grade HO" group (McAfee grade 0, 1, or 2 HO)., Conclusions: The presence of HO is not associated with clinical outcomes after CTDR. However, the severity of HO actually impacts clinical outcomes in an inverse manner, which needs further investigation. It is inappropriate to classify patients on the basis of the presence of HO; further studies of the classifications (ROM-affecting HO vs. ROM-preserving HO; high-grade HO vs. low-grade HO) and cervical stability after CTDR are needed., Level of Evidence: 2.

Background: When surgically treating cervical degenerative disc disease, the most commonly performed procedure is anterior cervical discectomy. This procedure is performed with, or without fusion promoting methods. For both options the rate of fusion is high and there is much debate whether fusion of the treated segment is a contributing factor to accelerated degeneration of adjacent motion segments. In an effort to prevent degeneration of adjacent segments (ASDeg) due to loss of mobility at the operated level, cervical disc arthroplasty (CDA) was introduced. To evaluate the effectiveness of CDA in preventing ASDeg long term studies are necessary. However, prevention of ASDeg is based on the premise that mobile disc prostheses preserve cervical spine motion in a physiological way. In this article the authors describe a short term protocol for a study that aims to investigate whether CDA reaches the intended goal: restoration or preservation of physiological cervical spine motion. To this end, a technique is used to establish the sequence of contributions of cervical motion segments to flexion/extension of the spine., Methods: 24 subjects between 18 and 55 years old, with radicular symptoms due to a herniated disc between C5 and C7, refractory to conservative therapy are randomized to simple discectomy, or CDA. These groups are preceded by a pilot group of three subjects receiving CDA. Fluoroscopic flexion-extension recordings are acquired preoperatively, and at three and 12 months postoperative. At these same time points, patient reported outcomes are collected, and a neurological examination is performed by and independent physician., Discussion: Studies investigating arthroplasty determine mobility by measuring segmental range of motion (sROM), which gives no information other than presence, and quantity, of mobility. SROM suffer from high variability. The authors therefore chose to use a method previously used in healthy controls, to describe the dynamic process of cervical spine motion in more detail. Determining cervical spine motion patterns has been reported to be more consistent than sROM. If a physiological motion pattern is absent after surgery in the CDA group, prevention of future ASDeg is less likely. Radiological outcomes will be correlated to clinical outcomes., Trial Registration: NCT00868335.

Purpose: To evaluate the incidence of adjacent segment disease (ASD) requiring surgical intervention between anterior cervical decompression and fusion (ACDF) and total disc replacement (TDR)., Background: The concern for ASD has led to the development of motion-preserving technologies such as TDR. However, whether replacement arthroplasty in the spine achieves its primary patient-centered objective of lowering the frequency of adjacent segment degeneration is not verified yet., Methods: A comprehensive literature search was performed using PubMed, Cochrane Central Register of Controlled Trials and Embase. These databases were thoroughly searched for prospective randomized studies comparing ACDF and TDR. Eight studies met the inclusion criteria for a meta-analysis and were used to report an overall rate of ASD for both ACDF and TDR., Results: Pooling data from 8 prospective studies, the overall sample size at baseline was 1,726 patients (889 in the TDR group and 837 in the ACDF group). The ACDF group had significantly more ASDs compared with the TDR group at 24 months postoperatively [odds ratios (OR), 1.31; 95 % confidence interval (CI), 1.04-1.64; p = 0.02]. The TDR group had significantly fewer adjacent segment reoperations compared with the ACDF group at 24 months postoperatively (OR, 0.49; 95 % CI, 0.25-0.96; p = 0.04)., Conclusions: For patients with one-level cervical degenerative disc disease (CDDD), total disc replacement was found to have significantly fewer ASDs and reoperations compared with the ACDF. Cervical replacement arthroplasty may be superior to ACDF in ASD. Therefore, cervical arthroplasty is a safe and effective surgical procedure for treating CDDD. We suggest adopting TDR on a large scale.

Purpose: Total cervical artificial disc replacement (TDR) simulates normal disc structure, thus avoiding the drawbacks of anterior cervical decompression and fusion (ACDF). This prospective, randomized, controlled and multicentre study aimed to evaluate clinical and radiographic outcomes by comparing cervical disc replacement using Mobi-C disc prostheses with ACDF., Methods: This prospective, randomized, controlled and multicentre study consisted of 111 patients undergoing single-level Mobi-C disc prosthesis replacement (TDR group, n = 55) or ACDF (n = 56) from February 2008 to November 2009 at 11 medical centres across China. Patients were assessed before surgery, at seven days postoperation and one, three, six, 12, 24, 36 and 48 months postoperation. Clinical and neurological outcome was determined by measuring the Japanese Orthopaedic Association (JOA) scores, visual analogue scale (VAS) and Neck Disability Index (NDI). Static and dynamic radiographs were obtained of the cervical curvature, the functional spinal unit (FSU) angle and range of motion (ROM) of the cervical spine, FSU angle and treated and adjacent segments., Results: A total of 111 patients were included and randomly assigned to either Mobi-C disc prosthesis replacement or ACDF. JOA, VAS and NDI showed statistically significant improvements 48 months after surgery (P < 0.05). ROM, FSU angle, treated segment and adjacent segments in the Mobi-C group were not significantly different before and after replacement (p > 0.05). ROM in the ACDF group was significantly reduced at one month and remained so throughout the follow-up. By 48-months, more ACDF patients required secondary surgery (four of 56 patients)., Conclusions: Although ACDF may increase the risk of additional surgery, clinical outcomes indicated that both Mobi-C artificial cervical disc replacement and ACDF were reliable. Radiographic data showed that ROM of the cervical spine, FSU angle and treated and adjacent segments were relatively better reconstructed and maintained in the Mobi-C group compared with those in the ACDF group.

Background: Total disc replacement was clinically introduced to reduce pain and preserve segmental motion of the lumbar and cervical spine. Previous case studies have reported on the wear and adverse local tissue reactions around artificial prostheses, but it is unclear how design and biomaterials affect clinical outcomes., Questions/purposes: Which design and material factors are associated with differences in clinical wear performance (implant wear and periprosthetic tissue response) of (1) lumbar and (2) cervical total disc replacements?, Methods: We performed a systematic review on the topics of implant wear and periprosthetic tissue response using an advanced search in MEDLINE and Scopus electronic databases. Of the 340 references identified, 33 were retrieved for full-text evaluation, from which 16 papers met the inclusion criteria (12 on lumbar disc replacement and five on cervical disc replacement; one of the included studies reported on both lumbar and cervical disc replacement), which involved semiquantitative analysis of wear and adverse local tissue reactions along with a description of the device used. An additional three papers were located by searching bibliographies of key articles. There were seven case reports, three case series, two case-control studies, and seven analytical studies. The Methodological Index for Non-randomized Studies (MINORS) Scale was used to score case series and case-control studies, which yielded mean scores of 10.3 of 16 and 17.5 of 24, respectively. In general, the case series (three) and case-control (two) studies were of good quality., Results: In lumbar regions, metal-on-polymer devices with mobile-bearing designs consistently generated small and large polymeric wear debris, triggering periprosthetic tissue activation of macrophages and giant cells, respectively. In the cervical regions, metal-on-polymer devices with fixed-bearing designs had similar outcomes. All metal-on-metal constructs tended to generate small metallic wear debris, which typically triggered an adaptive immune response of predominantly activated lymphocytes. There were no retrieval studies on one-piece prostheses., Conclusions: This review provides evidence that design and biomaterials affect the type of wear and inflammation. However, clinical study design, followup, and analytical techniques differ among investigations, preventing us from drawing firm conclusions about the relationship between implant design and wear performance for both cervical and lumbar total disc replacement.

Background Context: Cervical total disc replacement (TDR) and anterior cervical discectomy and fusion (ACDF) provide comparable outcomes for degenerative cervical pathology. However, revisions of these procedures are not well characterized., Purpose: The purpose of this study is to examine the rates, epidemiology, perioperative complications, and costs between the revision procedures and to compare these outcomes with those of primary cases., Study Design: This study is a retrospective database analysis., Patient Sample: A total of 3,792 revision and 183,430 primary cases from the Nationwide Inpatient Sample (NIS) database from 2002 to 2011 were included., Outcome Measures: Incidence of revision cases, patient demographics, length of stay (LOS), in-hospital costs, mortality, and perioperative complications., Methods: Patients who underwent revision for either one- to two-level cervical TDR or ACDF were identified. SPSS v.20 was used for statistical analysis with χ(2) test for categorical data and independent sample t test for continuous data. The relative risk for perioperative complications with revisions was calculated in comparison with primary cases using a 95% confidence interval. An alpha level of less than 0.05 denoted statistical significance., Results: There were 3,536 revision one- to two-level ACDFs and 256 revision cervical TDRs recorded in the NIS database from 2002 to 2011. The revision cervical TDR cohort demonstrated a significantly greater LOS (3.18 vs. 2.25, p<.001), cost ($16,998 vs. $15,222, p=.03), and incidence of perioperative wound infections (13.6 vs. 5.3 per 1,000, p<.001) compared with the ACDF revision cohort (p<.001). There were no differences in mortality between the revision surgical cohorts. Compared with primary cases, both revision cohorts demonstrated a significantly greater LOS and cost. Furthermore, patients who underwent revision demonstrated a greater incidence and risk for perioperative wound infections, hematomas, dysphagia, and neurologic complications relative to the primary procedures., Conclusions: This study demonstrated a significantly greater incidence of perioperative wound infection, LOS, and costs associated with a TDR revision compared with a revision ACDF. We propose that these differences are by virtue of the inherently more invasive nature of revising TDRs. In addition, compared with primary cases, revision procedures are associated with greater costs, LOS, and complications including wound infections, dysphagia, hematomas, and neurologic events. These additional risks must be considered before opting for a revision procedure., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Study Design: Measurement of zygapophyseal joint pressure and displacement was performed after placement of a semiconstrained integrated artificial disc (SIAD) in a cadaver model., Objective: To understand the likelihood of accelerated zygapophyseal joints degeneration as a result of the implant., Summary of Background Data: A SIAD has been developed to treat lumbar spondylosis secondary to segmental disc degeneration and spinal stenosis. The SIAD replaces the stenotic segment's disc. Previous studies have demonstrated that nonconstrained artificial disc (NAD) replacements fail to achieve their optimal long-term outcomes likely because of significantly increased zygapophyseal joint pressure and displacement at the implanted level. Moreover, clinical studies have reported an increased incidence of zygapophyseal joint degeneration after lumbar disc replacement., Methods: Eight cadaver lumbar specimens (L2-L5) were loaded in flexion, neutral, extension, left bend, and right rotation. Zygapophyseal joint pressure and displacement were measured during each of the 5 positions at each of the 3 levels with the ratio of deformation calculated under the different loads. An artificial disc was placed at the L3-L4 level, and the measurements were repeated., Results: After L3-L4 segment implantation, the pressure in the zygapophyseal joint at operative segment was not significantly changed by SIAD and NAD implantation in axial compression and flexion, compared with physiological disc. Notable differences in zygapophyseal joint pressure between the SIAD and NAD were identified at the operative level in extension, left bend, and right rotation. The adjacent-level effect of NAD was significantly greater than that of SIAD. The ratio of deformation difference between the 2 discs was increased by load experienced in extension, flexion, left bend, and right rotation., Conclusion: The SIAD provided a superior biomechanical milieu for zygapophyseal joints at the implanted and adjacent levels compared with NAD, which may avoid the acceleration of postoperative zygapophyseal joint degeneration., Level of Evidence: 1.

Cervical disc arthroplasty (CDA) has been gaining popularity as a surgical alternative to anterior cervical discectomy and fusion. Spontaneous fusion following a CDA is uncommon. A few anecdotal reports of heterotrophic ossification around the implant sites have been noted for the BRYAN, ProDisc-C, Mobi-C, PRESTIGE, and PCM devices. All CDA fusions reported to date have been in devices that are semiconstrained. The authors reported the case of a 56-year-old man who presented with left C-7 radiculopathy and neck pain for 10 weeks after an assault injury. There was evidence of disc herniation at the C6-7 level. He was otherwise healthy with functional scores on the visual analog scale (VAS, 4.2); neck disability index (NDI, 16); and the 36-item short form health survey (SF-36; physical component summary [PSC] score 43 and mental component summary [MCS] score 47). The patient underwent total disc replacement in which the DISCOVER Artificial Cervical Disc (DePuy Spine, Inc.) was used. The patient was seen at regular follow-up visits up to 60 months. At his 60-month follow-up visit, he had complete radiographic fusion at the C6-7 level with bridging trabecular bone and no motion at the index site on dynamic imaging. He was pain free, with a VAS score of 0, NDI score of 0, and SF-36 PCS and MCS scores of 61 and 55, respectively. Conclusions This is the first case report that identifies the phenomenon of fusion around a nonconstrained cervical prosthesis. Despite this unwanted radiographic outcome, the patient's clinical outcome was excellent.

Intervertebral total disc replacements (TDR) are used in the treatment of degenerative spinal disc disease. There are, however, concerns that they may be subject to long-term failure due to wear. The adverse effects of TDR wear have the potential to manifest in the dura mater and surrounding tissues. The aim of this study was to investigate the physiological structure of the dura mater, isolate the resident dural epithelial and stromal cells and analyse the capacity of these cells to internalise model polymer particles. The porcine dura mater was a collagen-rich structure encompassing regularly arranged fibroblastic cells within an outermost epithelial cell layer. The isolated dural epithelial cells had endothelial cell characteristics (positive for von Willebrand factor, CD31, E-cadherin and desmoplakin) and barrier functionality whereas the fibroblastic cells were positive for collagen I and III, tenascin and actin. The capacity of the dural cells to take up model particles was dependent on particle size. Nanometer sized particles readily penetrated both types of cells. However, dural fibroblasts engulfed micron-sized particles at a much higher rate than dural epithelial cells. The study suggested that dural epithelial cells may offer some barrier to the penetration of micron-sized particles but not nanometer sized particles., (© 2014 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc.)

Background Context: Surgical treatment of degenerative disc disease remains a controversial subject. Lumbar fusion has been associated with a potential risk of segmental junctional disease and sagittal balance misalignment. Motion preservation devices have been developed as an alternative to fusion. The LP-ESP disc is a one-piece deformable device achieving 6 df, including shock absorption and elastic return. This is the first clinical report on its use., Purpose: To assess clinical outcomes and radiologic kinematics in the first 2 years after implantation., Study Design: Prospective cohort of patients with LP-ESP total disc replacement (TDR) at the lumbar spine., Patient Sample: Forty-six consecutive patients., Outcome Measures: Clinical outcomes were the visual analog scale (VAS) for pain, the Oswestry disability index (ODI), and the GHQ28 (General Health Questionnaire) psychological score. Radiologic data were the range of motion (ROM), sagittal balance parameters, and mean center of rotation (MCR)., Methods: Patients had single-level TDR at L4-L5 or L5-S1. Outcomes were prospectively recorded for 2 years (before and at 3, 6, 12, and 24 months after surgery). The SpineView software was used for computed analysis of the radiographic data. Paired t tests were used for statistical comparisons., Results: No intraoperative complication occurred. All clinical scores improved significantly at 24 months: the back pain VAS scores by a mean of 4.1 points and the ODI by 33 points. The average ROM of the instrumented level was 5.4°±4.8° at 2 years and more than 2° for 76% of prostheses. The MCR was in a physiological area in 73% of cases. The sagittal balance (pelvic tilt, sacral slope, and segmental lordosis) did not change significantly at any point of the follow-up., Conclusions: Results from the 2-year follow-up indicate that LP-ESP prosthesis recreates lumbar spine function similar to that of the healthy disc in terms of ROM, quality of movement, effect on sagittal balance, and absence of modification in the kinematics of the upper adjacent level., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Anterior lumbar surgery for degenerative disc disease (DDD) is a relatively novel technique that can prevent damage to posterior osseous, muscular and ligamentous spinal elements. This study reports the outcomes and complications in 286 patients who underwent fusion - with artificial disc implants or combined fusion and artificial disc implants - by a single-operator neurosurgeon, with up to 24 months of follow-up. The visual analogue scale (VAS), Oswestry Disability Index (ODI), Short Form 36 (SF36) and prospective log of adverse events were used to assess the clinical outcome. Radiographic assessments of implant position and bony fusion were analysed. Intraoperative and postoperative complications were also recorded. Irrespective of pre-surgical symptoms (back pain alone or back and leg pain combined), workers' compensation status and type of surgical implant, clinically significant improvements in VAS, ODI and SF36 were primarily observed at 3 and/or 6 month follow-up, and improvements were maintained at 24 months after surgery. A 94% fusion rate was obtained; the overall complication was 9.8% which included 3.5% with vascular complications. The anterior lumbar approach can be used for treating DDD for both back pain and back and leg pain with low complication rates. With appropriate training, single-operator neurosurgeons can safely perform these surgeries., (Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.)

Background: Anterior cervical discectomy and fusion (ACDF) was one of the preferred treatments for degenerative cervical spondylosis. However, the motion of adjacent segment was significantly increased after operation. So cervical disc arthroplasty have been suggested to keep the motion of adjacent segment. A new implant named dynamic cervical implant (DCI) has been developed to keep the motion of adjacent segment., Methods: We retrospectively reviewed 91 patients treated for single level cervical spondylotic myelopathy with anterior cervical discectomy and fusion (ACDF), dynamic cervical implant (DCI) and cervical total disc replacement (CTDR) between sep 2009 and Mar 2011 in our hospital. They were divided into three groups by surgical methods: ACDF group (group A, 34 cases), DCI group (group B, 25 cases), CTDR group (group C, 32 cases). Operation time, intraoperative blood loss, preoperative and postoperative JOA score and JOA recovery rate were compared among the three groups. Pre-and postoperative hyperextension and hyperflexion radiograms were observed to measure range of motion (ROM) of C2-7, operative and adjacent levels., Results: There was no statistical difference in operative time, intraoperative blood loss, and JOA recovery rate (P > 0.05) among three groups. But the differences of their postoperative JOA scores and preoperative JOA scores were of statistical significance (P < 0.05). Compared the pre-and postoperative ROM of C2-7, operative, upper and lower levels of each group respectively, the difference between preoperative ROM and postoperative ROM of group A were of statistically significant (P < 0.05), while was no statistically significant of group C (P > 0.05). There was no statistically significant difference between preoperative ROM and postoperative ROM of upper and lower levels in group B (P > 0.05), but had statistically significance of C2-7 and operative levels (P < 0.05)., Conclusions: Three operations are effective therapies for single level cervical spondylotic myelopathy. But each group has respective advantages and disadvantages.

Study Design: Retrospective clinical and radiographic assessment of 21 levels of 18 consecutive patients treated using total lumbar disk replacement (TDR) for degenerative disk disease., Objectives: To report clinical and radiographic outcomes after TDR using the Mobidisc prosthesis. In addition, to determine whether there is a correlation between clinical and radiologic outcomes and prosthesis positioning., Summary of Background Data: TDR for lumbar degenerative disk disease is reported to provide good clinical and radiographic outcomes. However, TDR can alter the kinematics of the facet joint during flexion and extension. If prosthesis positioning is poor, the facet joint loading is increased upto 2.5-fold. No study has examined whether differences between the prosthesis center of rotation (COR) and the individual's COR have an effect on the clinical or radiographic outcomes after TDR., Methods: A retrospective study of 21 levels from 18 consecutive degenerative disk disease patients who underwent lumbar TDR. The Mobidisc prosthesis was used in all cases. Clinical parameters measured were lower back and leg pain [both assessed using the Oswestry Disability Index (ODI)]. These parameters were measured preoperatively and at the last follow-up. Radiographic assessment involved examining standard lateral flexion/extension views taken at the preoperative, postoperative 6-month, and the last follow-up assessments to determine disk space height (DSH) and range of motion (ROM). Patient satisfaction (subjective outcome) was determined by telephone questioning. For analysis, TDR cases were categorized into 3 groups on the basis of the size of the "COR index," which represented the difference between an individual's inherent COR and the inherent prosthesis COR. Group 1, COR index <5 mm, consisted of 13 levels; group 2, COR index >5 mm, and <10 mm, consisted of 5 levels; and group 3, COR index >10 mm, consisted of 3 levels., Results: Overall, 77.8% of patients stated that they were highly satisfied with their surgical outcome. Low back pain visual analogue scale scores decreased from 7.61±2.17 (mean±SD) preoperatively to 2.33±2.679 at the last follow-up (P<0.001). The function increased postoperatively (ODI: 25.89±7.77 preoperative vs. 5.89±7.21 at last follow-up; P<0.001). The difference between preoperative and the last follow-up ODI was greater in group 1 than in groups 2 and 3 (P=0.034). Radiographic findings showed that TDR resulted in improved disk space height and segmental ROM (P<0.05). Analysis of the 3 groups showed that ROM preservation decreased as the COR index increased., Conclusions: The present study found that lumbar TDR using the Mobidisc prosthesis resulted in good clinical and radiologic outcomes and good patient satisfaction. Furthermore, we found that patient satisfaction, function, and ROM preservation correlated with correct COR positioning of the prosthesis.

We report on 69 retrospectively reviewed patients who received 73 Bryan (Medtronic Sofamor Danek, Memphis, TN, USA) total disc arthroplasties for recent soft cervical disc herniations over a 9.3year period. Three patients returned with radiculopathy due to the redevelopment of uncoforaminal stenosis at the Bryan segment and later underwent posterior decompression of the uncoforaminal area without modification to the prosthesis. They recovered from the radiculopathy after decompression; however, one patient later required adjacent segment fusion to recover from concomitant cervicalgia. After posterior decompression, all prostheses continued to function normally. In one patient, however, bony bridging of the prosthesis is imminent, despite being currently asymptomatic. We normally exclude patients with uncoforaminal stenosis from Bryan arthroplasty. Analysis of three of these patients (4.3% of patients, 4.1% of prostheses) revealed that they received a prosthesis despite slight uncoforaminal stenosis (slight stenosis was known prior to surgery in one instance, two others were only discovered intra-operatively). Our observation raises the suspicion that slight uncoforaminal stenosis could also recur in physiologically working arthroplasty segments, and that in some instances this spur formation may progress into prosthesis bridging. However, more research is required to confirm the significance of uncoforaminal stenosis discovered pre- or intra-operatively in arthroplasty patients. Posterior minimally invasive decompression using the Frykholm-Scoville keyhole approach successfully treats uncoforaminal stenosis without revising the prosthesis., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The primary goal of motion preservation surgery in the spine is to maintain normal or near normal motion in an attempt to prevent adverse outcomes commonly seen with conventional spinal fusion, most notably the development of adjacent-level degenerative disc disease. Several different surgical approaches have been developed to preserve motion in the lumbar spine, including total disc replacement, partial disc (nucleus) replacement, interspinous spacers, dynamic stabilization devices, and total facet replacement devices. The design of devices varies greatly. The devices are created using a similar rationale but are unique in design relative to their lumbar counterparts., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: Low back pain represents a significant disease burden in Australia. Lumbar artificial intervertebral disc replacement (AIDR) has emerged as an alternative surgical option to lumbar fusion for patients suffering from axial low back pain as a result of degenerative disc disease., Objectives: The aim of this review was to assess the safety and effectiveness of lumbar AIDR for patients suffering from significant axial back pain and/or radicular (nerve root) pain, secondary to disc degeneration or prolapse, who have failed non-operative treatment., Methods: A systematic search of several electronic databases was conducted between January 2005 and April 2012 to identify relevant randomized controlled trials and non-randomized comparative studies. Inclusion of studies was established through the application of a predetermined protocol by two independent reviewers., Results: Six randomized controlled trials (comprising nine studies) and one non-randomized comparative study comparing lumbar AIDR with lumbar fusion were included in this review. For the majority of adverse events reported, there were no obvious differences in incidence rates between the two treatment groups, and serious adverse events were rare in both groups. Following lumbar AIDR, effectiveness outcomes including Oswestry Disability Index scores, procedural success rates, pain scores, narcotic medication use and patient satisfaction were generally significantly better than, or equivalent to, outcomes achieved following lumbar fusion., Conclusions: In the short to medium term, the safety and effectiveness of lumbar AIDR appears to be comparable to that of lumbar fusion., (© 2013 Royal Australasian College of Surgeons.)

Heterotopic ossification is one of the possible complications following cervical total disk replacement. Although there are numerous hypotheses regarding the etiology of heterotopic ossification, the main causes of heterotopic ossification remain unknown. In this study, we hypothesize that heterotopic ossification formation is related to external loading in the cervical vertebrae after total disk replacement. A two-dimensional finite element model of a cervical vertebra treated by total disk replacement in the sagittal plane was developed. The bone adaptation process of heterotopic ossification was simulated based on strain energy density under both compressive and shear forces. Different types of heterotopic ossification formation were analyzed according to the directions of forces. Two distinct types of heterotopic ossification following cervical total disk replacement were predicted, which was consistent with previous clinical studies. Type 1 heterotopic ossification was observed in the posterior upper part of the vertebra under compressive forces, while type 2 heterotopic ossification was detected mostly in the anterior upper part under shear forces. In addition, heterotopic ossification formation enhanced the strain energy distribution, which is known to be related to bone remodeling. This article presents the effects of different mechanical loading conditions on the occurrence of heterotopic ossification following cervical total disk replacement, and the results may be useful for the design of artificial disks that minimize heterotopic ossification.

Study Design: Retrospective database analysis., Objective: To compare the perioperative patient characteristics, early postoperative outcomes, and costs between anterior cervical discectomy and fusion (ACDF) and cervical total disc replacement (TDR) in the United States., Summary of Background Data: Cervical TDR and ACDF are indicated to treat symptomatic cervical degenerative pathology. The epidemiology, complication rates, and the cost differences between the 2 surgical approaches are not well characterized., Methods: Data from the Nationwide Inpatient Sample of the Healthcare Cost and Utilization Project was queried from 2002 to 2009. Patients undergoing cervical TDR or ACDF of 1 to 2 levels were identified. Patient demographics, comorbidities, length of stay, costs, and the in-hospital complications were assessed. SPSS (version 20) was used for statistical analysis with χ test for categorical data and independent-samples t test for continuous data. A value of P ≤ 0.001 denoted statistical significance. Multinomial regression analysis was used to identify the independent risk for complications in the TDR cohort compared with the ACDF cohort., Results: There were 141,230 ACDF cases of 1 to 2 levels and 1830 cervical TDR cases identified in the Nationwide Inpatient Sample database. The ACDF cohort was older and demonstrated a greater comorbidity burden than the TDR group (P < 0.001). The ACDF-treated patients demonstrated a significantly greater length of stay than the TDR group (P < 0.001). In contrast, there were no significant differences in the incidence of postoperative complications, mortality, or hospital costs between the surgical cohorts. Multinomial regression did not demonstrate significant differences in the risk for postoperative complications between the surgical techniques., Conclusion: The ACDF cohort was significantly older and demonstrated a greater comorbidity burden that likely contributed to the greater length of stay when than the TDR cohort. Both cohorts demonstrated comparable incidences of early postoperative complications and costs. There were no significant differences in the risks for postoperative complications between the surgical cohorts. Further studies are warranted to characterize the long-term complications, costs, and patient outcomes between the 2 surgical techniques., Level of Evidence: 3.

Adverse events reporting in pivotal trials of new technologies, such as cervical total disk replacement, are essential to determine safety. Important questions concerning the adequacy of reporting about such new technologies in peer-reviewed publications have prompted this analysis to assess the safety of cervical disk replacement compared with fusion as presented in peer-reviewed publications and FDA summary reports. Identifying differences among these reports highlight the poor quality of adverse event reporting in the peer-reviewed literature. Nine peer-reviewed studies and five FDA summary reports documented excellent safety for both cervical fusion and disk arthroplasty. No differences in rates of adverse events were found to exist between the two treatments. The methods of recording and the actual reporting of adverse events were poor in peer-reviewed manuscripts, whereas they were comprehensive but difficult to clinically apply in the FDA summaries. Recommendations to improve documentation and reporting of adverse events are presented.

Background: Cervical disc replacement (CDR) as a substitute for traditional fusion surgery has been widely used in treating degenerative cervical disc diseases. The objectives of this study were to assess the clinical and radiological findings for patients with heterotopic ossification (HO) following CDR and to detect the risk factors of HO after CDR., Methods: A total of 125 patients with symptomatic cervical single- or double-level disc diseases, who underwent CDR procedure with Discover prosthesis in Department of Spine Surgery, Changzheng Orthopedics Hospital from March 2009 to March 2011, were enrolled in this retrospective study. Occurrence of HO was defined by the McAfee classification on cervical lateral X-rays in this study. Prosthesis vertebral ratio (PVR) was used to determine the matching degree between the cervical disc prosthesis and cervical vertebra. Logistic regression analyses were performed to determine the risk factors of HO. Variables evaluated for their association with HO occurrence included age, gender, high-intensity signal in spinal cord, preoperative range of motion (ROM), postoperative ROM, operation level number, and PVR., Results: Mean follow-up time was (26.4±5.8) months. All the patients had significant symptoms and neurological function improvements during the follow-up period. The ROM of the operated segment from the preoperative period to the last follow-up was relatively well maintained. The rate of HO in this cohort of patients, who underwent Discover disc, was 27.92% per surgical level and 24.8% per patient by the last follow-up. There were 19 patients (19.79%) with HO in the single-level group while 12 patients (41.38%) in the double-level group., Conclusions: We identified preoperative high-intensity signal in spinal cord, postoperative ROM of surgical level, number of operation level, and PVR as significant risk factors for postoperative HO occurrence.

We report a rare case of double-level adjacent segment disease (ASD), occurring ten years later an anterior cervical discectomy (ACD) without fusion, treated by cervical arthroplasty, highlighting the outcome at long-term follow-up and focusing on heterotopic ossification. In 1995 a 25-year-old man satisfactorily underwent ACD at C4/C5. At that time MRI also showed signs of degenerative disc disease (DDD) at C3/C4 and C5/C6. Ten years later, a new MRI scan showed a large C3/C4 and a smaller C5/C6 soft disc hernia together with spondylotic changes at the level above and below the site of the first surgery. At C4/C5 imaging revealed a kyphotic stable "pseudoarthrosis" with anterior bridging osteophyte. The patient underwent double-level arthroplasty with ProDisc-C. Clinical and radiological outcome was satisfactory. 3 and 5 years after surgery, X-rays and CT scan documented the progressive development of heterotopic ossification, with gradual reduction of range of motion. A late onset heterotopic ossification can neutralize the theoretical advantages of cervical arthroplasty, which should be considered an effective surgical option only in selected cases. ACDF and restoration of normal lordosis can be a viable alternative in cervical revision surgery, as motion preservation can not be always mantained for a long time.