Can segmental mobility be increased by cervical arthroplasty?

Multilevel cervical disc arthroplasty: a review of optimal surgical management and future directions

OBJECTIVE

Cervical disc arthroplasty (CDA) has been recognized as a popular option for cervical radiculopathy or myelopathy caused by disc problems that require surgery. There have been prospective randomized controlled trials comparing CDA to anterior cervical discectomy and fusion (ACDF) for 1- and 2-level disc herniations. However, the indications for CDA have been extended beyond the strict criteria of these clinical trials after widespread real-world experiences in the past decade. This article provides a bibliometric analysis with a review of the literature to understand the current trends of clinical practice and research on CDA.

METHODS

The PubMed database was searched using the keywords pertaining to CDA in human studies that were published before August 2022. Analyses of the bibliometrics, including the types of papers, levels of evidence, countries, and the number of disc levels involved were conducted. Moreover, a systematic review of the contents with the emphasis on the current practice of multilevel CDA and complex cervical disc problems was performed.

RESULTS

A total of 957 articles published during the span of 22 years were analyzed. Nearly one-quarter of the articles (232, 24.2%) were categorized as level I evidence, and 33.0% were categorized as levels I or II. These studies clearly demonstrated the viability and effectiveness of CDA regarding clinical and radiological outcomes, including neurological improvement, maintenance, and preservation of segmental mobility with relatively low risks for several years postoperation. Also, there have been more papers published during the last decade focusing on multilevel CDA and fewer involving the comparison of ACDF. Overall, there was a clustering of CDA papers published from the US and East Asian countries. Based on substantial clinical data of CDA for 1- and 2-level disc diseases, the practice and research of CDA show a trend toward multilevel and complex disease conditions.

CONCLUSIONS

CDA is an established surgical management procedure for 1- and 2-level cervical disc herniation and spondylosis. The success of motion preservation by CDA-with low rates of complications-has outscored ACDF in patients without deformity. For more than 2-level disc diseases, the surgery shows a trend toward multiple CDA or hybrid ACDF-CDA according to individual evaluation for each level of degeneration.

Cervical disc arthroplasty for Klippel-Feil syndrome

OBJECTIVE

Klippel-Feil syndrome (KFS) is a congenital musculoskeletal condition characterized by improper segmentation of the cervical spine. This study aimed to evaluate outcomes of KFS patients who underwent cervical disc arthroplasty (CDA).

METHODS

Consecutive patients who underwent anterior cervical surgery were retrospectively reviewed. Those patients with KFS who received discectomy adjacent to the congenitally fused vertebral segments were extracted and grouped into either the fusion or the CDA group. Clinical and radiological evaluations included visual analog scales, Neck Disability Index (NDI), Japanese Orthopedic Association (JOA) scores, C2-7 range of motion (ROM), C2-7 Cobb angle, C2-7 sagittal vertical axis (SVA), and T1-slope.

RESULTS

Among 2320 patients, there were 41 with KFS (prevalence = 1.77%), who were younger than the entire cohort (53.3 vs 56.4 years). Thirty KFS patients had adjacent discs and were grouped into the CDA and fusion groups (14 vs 16). Type-I KFS with C3-4 involvement was the most common for both groups (92.8% vs 81.2% with 57% vs 50%, respectively). Post-operation, both groups demonstrated improvement of all the patient reported outcomes. The C2-7 ROM significantly decreased in the fusion group than that of pre-operation (12.8 ± 6° vs 28.1 ± 11.5°). In contrast, the CDA group successfully preserved C2-7 and segmental ROM without additional complications.

CONCLUSIONS

KFS is rare (prevalence = 1.77%) among cervical spine surgery patients, and it rarely affects the overall cervical spinal alignment, except that it decreases segmental mobility. CDA is a feasible option for KFS because it not only avoids long-segment fusion but also preserves segmental and global mobility.

Late complication of cervical disc arthroplasty: heterotopic ossification causing myelopathy after 10 years. Illustrative case

BACKGROUND

Heterotopic ossification (HO) is a well-documented complication of cervical disc arthroplasty (CDA), although it rarely causes adverse clinical effects. Despite high-grade HO possibly limiting segmental mobility, it is reportedly seldom associated with symptoms.

OBSERVATIONS

The authors report a case of a 46-year-old male patient who underwent hybrid CDA and anterior cervical discectomy and fusion for 3-level cervical disc herniation that caused myeloradiculopathy. The surgery was successful; the patient experienced nearly complete recovery postoperatively. The follow-up images, including computed tomography and magnetic resonance imaging scans, showed satisfactory decompression at the indexed levels without residual osteophytes or ossification of the posterior longitudinal ligament. However, 10 years later, the patient presented with symptomatic compressive myelopathy caused by severe HO that prompted a secondary surgery.

LESSONS

Although it is generally reported in the literature that HO is clinically innocuous, in this patient, it gradually and progressively developed and caused myelopathy, requiring a secondary surgery. Symptomatic HO can be expected over time, and patients with a high risk of HO deserve long-term follow-up after CDA. Further investigations are warranted to corroborate these risk factors, including multilevel calcified disc herniation, severe spondylosis, and suboptimal placement of the device during primary CDA surgery.

Risk Factors for High-Grade Heterotopic Ossification After Total Disc Replacement: A Single-Center Experience of 394 Cases

BACKGROUND

Heterotopic ossification (HO) is a common complication following total disc replacement (TDR). High-grade HO is a clinically relevant complication, however, only a few studies have evaluated risk factors for high-grade HO.

OBJECTIVE

To evaluate potential risk factors for HO and high-grade HO and their impact on clinical outcomes.

METHODS

We retrospectively reviewed patients who underwent TDR or hybrid surgery (HS) with Prestige-LP (Medtronic), Discover (Depuy), and Prodisc-C (Synthes). Clinical outcomes were assessed using Japanese Orthopaedic Association, Visual Analogue Scale, and Neck Disability Index scores. Radiological variables, including preoperative ossification, global and segmental range of motion (ROM), HO, and adjacent segment degeneration (ASD) were reviewed.

RESULTS

A total of 394 patients were evaluated. HO and high-grade HO occurred in 67.77% and 11.17% patients, respectively. Preoperative ossification was significantly associated with the occurrence of HO (P < .001, OR: 3.507, 95%CI: 2.211-5.562) and high-grade HO (P = .019, OR: 2.176, 95%CI: 1.137-4.166). The ROM of replacement levels and C2-7 were significantly lower in the high-grade HO group compared to those without high-grade HO: (3.80° vs 10.18°, P < .001) and (42.81° vs 54.00°, P < .001), respectively. The incidence of ASD was significantly higher in patients with high-grade HO than those without high-grade HO (22.73% vs 11.14%, P = .048).

CONCLUSION

Preoperative ossification was identified as a potential risk factor for HO and high-grade HO. Patients with high-grade HO had limited ROM of replacement levels and the cervical spine and had a high incidence of ASD compared to those without high-grade HO.

The Changes in Cervical Biomechanics After CTDR and Its Association With Heterotopic Ossification: A Systematic Review and Meta-analysis

STUDY DESIGN

A systematic review and meta-analysis.

OBJECTIVES

Cervical total disc replacement (CTDR) can preserve range of motion (ROM) of the operated spinal segment in cadaver studies. Evidence is less clear in clinical trials. The present study aims to investigate the differences in cervical biomechanics before and after CTDR and its association with heterotopic ossification (HO) development.

METHOD

Articles that reported the rate of HO and ≥1 difference in cervical biomechanics were included in quantitative analyses. We pooled the mean difference (MD) of cervical biomechanics before and after CTDR. Subgroup analyses and metaregression analyses were conducted to identify potential contributors to heterogeneity.

RESULTS

Of the 599 studies screened, 35 studies were included in the final analysis. In comparison with preoperative values, ROM of the spinal segment inferior (MD: 0.38; 95% CI: 0.02 to 0.74) and superior (MD: 0.43; 95% CI: 0.12 to 0.75) to the surgical spinal segment, functional spinal unit (FSU) angle (MD: 2.23; 95% CI: 1.11 to 3.35), and C2/C7 Cobb angle (MD: 3.49; 95% CI: 1.73 to 5.25) significantly increased after CTDR. In contrast, FSU and cervical ROM at baseline were no different from follow-up. On multivariable meta-regression analyses, HO and ROM-limiting HO were not associated with changes in cervical biomechanics. Single-level CTDR and duration of follow-up were associated with changes in cervical biomechanics.

CONCLUSION

Our study reported the pooled mean of biomechanics at baseline and final follow-up and their differences. The changes in biomechanics were not associated with the rates of HO and ROM-limiting HO.

The Effect of T1-Slope in Spinal Parameters After Cervical Disc Arthroplasty

BACKGROUND

Although patients with cervical kyphosis are not ideal candidates for cervical disc arthroplasty (CDA), there is a paucity of data on patients with a straight or slightly lordotic neck.

OBJECTIVE

To correlate cervical lordosis, T1-slope, and clinical outcomes of CDA.

METHODS

The study retrospectively analyzed 95 patients who underwent 1-level CDA and had 2-yr follow-up. They were divided into a high T1-slope (≥28°) group (HTSG, n = 45) and a low T1-slope (<28°) group (LTSG, n = 50). Cervical spinal alignment parameters, including T1-slope, cervical lordosis (C2-7 Cobb angle), and segmental mobility (range of motion [ROM]) at the indexed level, were compared. The clinical outcomes were also assessed.

RESULTS

The mean T1-slope was 28.1 ± 7.0°. After CDA, the pre- and postoperative segmental motility remained similar and cervical lordosis was preserved. All the clinical outcomes improved after CDA. The HTSG were similar to the LTSG in age, sex, segmental mobility, and clinical outcomes. However, the HTSG had higher cervical lordosis than the LTSG. Furthermore, the LTSG had increased cervical lordosis (ΔC2-7 Cobb angle), whereas the HTSG had decreased lordosis after CDA. Patients of the LTSG, who had more improvement in cervical lordosis, had a trend toward increasing segmental mobility at the index level (ΔROM) than the HTSG.

CONCLUSION

In this series, T1-slope correlated well with global cervical lordosis but did not affect the segmental mobility. After CDA, the changes in cervical lordosis correlated with changes in segmental mobility. Therefore, segmental lordosis should be cautiously preserved during CDA as it could determine the mobility of the disc.

Financial Aspects of Cervical Disc Arthroplasty: A Narrative Review of Recent Literature

Recently, there has been significant interest in understanding the cost-effectiveness of treatments in spine surgery as health care systems in the United States move toward value-based care and alternative payment models. Previous studies have shown comparable outcomes of cervical disc arthroplasty (CDA) and anterior cervical discectomy fusion; however, there is a lack of consensus on the cost-effectiveness of CDA to support full adoption. Evidence of the limitations of these cost-analysis studies also exists in the literature, including industry funding, potential selection bias, and varying methods of calculating value. The goal of this narrative review is to provide an overview of the cost-effectiveness of CDA compared with anterior cervical discectomy and fusion, and potential limitations with cost-analysis studies in spine surgery.

Cervical Total Disc Replacement and Heterotopic Ossification: A Review of Literature Outcomes and Biomechanics

Anterior cervical discectomy and fusion (ACDF) immobilizes surgical segments and can lead to the development of adjacent segment degeneration and adjacent segment disease. Thus, cervical total disc replacement (CTDR) has been developed with the aim to preserve the biomechanics of spine. However, heterotopic ossification (HO), a complication following CTDR, can reduce the segmental range of motion (ROM) and defects the motion-preservation benefit of CTDR. The pathological process of HO in CTDR remains unknown. HO has been suggested to be a self-defense mechanism in response to the non-physiological biomechanics of the cervical spine following CTDR. The current literature review is concerned with the association between the biomechanical factors and HO formation and the clinical significance of HO in CTDR. Endplate coverage, disc height, segmental angle, and center of rotation may be associated with the development of HO. The longer the follow-up, the higher the rate of ROM-limiting HO. Regardless of the loss of motion-preservation benefit of CTDR in patients with HO, CTDR confers patients with a motion-preservation period before the development of ROM-limiting HO. This may delay the development of adjacent segment degeneration compared with ACDF. Future clinical studies should explore the association between HO and changes in biomechanical factors of the cervical spine.

Radiological and clinical outcomes of 3-level cervical disc arthroplasty

OBJECTIVE

One- and two-level cervical disc arthroplasty (CDA) has been compared to anterior cervical discectomy and fusion (ACDF) in several large-scale, prospective, randomized trials that have demonstrated similar clinical outcomes. However, whether these results would be similar when treating 3-level disc herniation and/or spondylosis has remained unanswered. This study aimed to investigate the differences between 3-level CDA and ACDF.

METHODS

A series of 50 patients who underwent 3-level CDA at C3-7 was retrospectively reviewed and compared with another series of 50 patients (age- and sex-matched controls) who underwent ACDF at C3-7. Clinical outcomes were measured using the visual analog scale (VAS) for neck and arm pain, the modified Japanese Orthopaedic Association (mJOA) scale, and the Neck Disability Index (NDI). Radiological outcomes included range of motion (ROM) at the index levels. Every patient was evaluated by CT for the presence of fusion in the ACDF group. Also, complication profiles were investigated.

RESULTS

The demographics and levels of distribution in both groups were very similar. During the follow-up period of 24 months, clinical outcomes improved (overall and respectively in each group) for both the CDA and ACDF patients when compared with the patients' preoperative condition. There were essentially few differences between the two groups in terms of neck and arm pain VAS scores, mJOA scores, and NDI scores preoperatively and at 3, 6, 12, and 24 months postoperatively. After the 3-level surgery, the CDA group had an increased mean ROM of approximately 3.4°, at 25.2° ± 8.84°, compared to their preoperative ROM (21.8° ± 7.20°) (p = 0.001), whereas the ACDF group had little mobility (22.8° ± 5.90° before and 1.0° ± 1.28° after surgery; p < 0.001). The mean operative time, estimated blood loss, and complication profiles were similar for both groups.

CONCLUSIONS

In this selectively matched retrospective study, clinical outcomes after 3-level CDA and ACDF were similar during the 2-year follow-up period. CDA not only successfully preserved but slightly increased the mobility at the 3 index levels. However, the safety and efficacy of 3-level CDA requires more long-term data for validatation.

Sagittal Reconstruction and Clinical Outcome Using Traditional ACDF, Versus Stand-alone ACDF Versus TDR: A Systematic Review and Quantitative Analysis

STUDY DESIGN

Systematic review.

OBJECTIVE

To determine the difference in postoperative sagittal alignment when single level cervical radiculopathy or myelopathy is treated with an anterior cervical discectomy and fusion (ACDF) using a structural graft and plate, a stand-alone ACDF, or a total disc arthroplasty (TDR). We also wanted to determine if postoperative sagittal alignment impacted clinical outcomes in this patient population.

SUMMARY OF BACKGROUND DATA

Although there are several accepted techniques for interbody reconstruction during single level anterior cervical surgery, little is known on the impact of any of them on segmental and regional sagittal alignment.

METHODS

A systematic review of the literature was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines of the PubMed, Embase, and Cochrane databases. Only studies which contained pre and postoperative C2-7 Cobb angles as well as Neck Disability Index (NDI) scores following single level traditional ACDF with plate and cage, stand-alone ACDF, or TDR with at least 1 year follow up were included.

RESULTS

There were 12 publications that fulfilled the inclusion criteria with a total of 658 patients. Cluster regression analysis showed no difference between treatment arms at each respective time-point or in the overall change in NDI from preoperative to postoperative (P = 0.88). Cluster regression analysis showed no difference between treatment arms at each respective time point or in the overall change in lordosis from pre-op to post-op (P = 0.93).

CONCLUSION

This review provides evidence that while NDI scores improved across all devices, there was no significant difference in NDI improvement or C2-7 Cobb angle change between single level traditional ACDF, stand-alone ACDF, or TDR. Although TDR has not been considered a lordosis producing operation, our investigation shows it does not differ significantly in sagittal profile from other cervical fusion techniques. Moreover, we show that the NDI score improved, regardless of device implanted.

LEVEL OF EVIDENCE

1.

Cervical disc arthroplasty for less-mobile discs

OBJECTIVE

The published clinical trials of cervical disc arthroplasty (CDA) have unanimously demonstrated the success of preservation of motion (average 7°-9°) at the index level for up to 10 years postoperatively. The inclusion criteria in these trials usually required patients to have evident mobility at the level to be treated (≥ 2° on lateral flexion-extension radiographs) prior to the surgery. Although the mean range of motion (ROM) remained similar after CDA, it was unclear in these trials if patients with less preoperative ROM would have different outcomes than patients with more ROM.

METHODS

A series of consecutive patients who underwent CDA at the level of C5-6 were followed up and retrospectively reviewed. The indications for surgery were medically refractory cervical radiculopathy, myelopathy, or both, caused by cervical disc herniation or spondylosis. All patients were assigned to 1 of 2 groups: a less-mobile group, which consisted of those patients who had an ROM of ≤ 5° at C5-6 preoperatively, or a more-mobile group, which consisted of patients whose ROM at C5-6 was > 5° preoperatively. Clinical outcomes, including visual analog scale, Neck Disability Index, and Japanese Orthopaedic Association Scale scores, were evaluated at each time point. Radiological outcomes were also assessed.

RESULTS

A total of 60 patients who had follow-up for more than 2 years were analyzed. There were 27 patients in the less-mobile group (mean preoperative ROM 3.0°) and 33 in the more-mobile group (mean ROM 11.7°). The 2 groups were similar in demographics, including age, sex, diabetes, and cigarette smoking. Both groups had significant improvements in clinical outcomes, with no significant differences between the 2 groups. However, the radiological evaluations demonstrated remarkable differences. The less-mobile group had a greater increase in ΔROM than the more-mobile group (ΔROM 5.5° vs 0.1°, p = 0.001), though the less-mobile group still had less segmental mobility (ROM 8.5° vs 11.7°, p = 0.04). The rates of complications were similar in both groups.

CONCLUSIONS

Preoperative segmental mobility did not alter the clinical outcomes of CDA. The preoperatively less-mobile (ROM ≤ 5°) discs had similar clinical improvements and greater increase of segmental mobility (ΔROM), but remained less mobile, than the preoperatively more-mobile (ROM > 5°) discs at 2 years postoperatively.

Radiological and clinical outcomes of cervical disc arthroplasty for the elderly: a comparison with young patients

Background

This study aimed to investigate whether cervical disc arthroplasty (CDA) would be equally effective in elderly patients as in the young. The inclusion criteria of published clinical trials for CDA-enrolled patients covered the ages from 18 to 78 years. However, there was a paucity of data addressing the differences of outcomes between older and the younger patients.

Methods

A series of consecutive patients who underwent one- or two-level CDA were retrospectively reviewed. Patients at the two extreme ends of the age distribution (≥65 and ≤ 40 years) were selected for comparison. Clinical outcome parameters included visual analog scale (VAS) of neck and arm pain, neck disability index (NDI), and Japanese Orthopaedic Association (JOA) scores. Radiographic outcomes included range of motion (ROM) at the indexed level and evaluation of heterotopic ossification (HO) by computed tomography (CT). Complication profiles were also investigated.

Results

There were 24 patients in the elderly group (≥65 years old) and 47 patients in the young group (≤40 years old) with an overall mean follow-up of 28.0 ± 21.97 months. The elderly group had more two-level CDA, and thus the mean operative time was longer (239 vs. 179 min, p < 0.05) than the young group. Both groups had similarly significant improvement in clinical outcomes at the final follow-up. All the replaced disc segments remained mobile on post-operative lateral flexion and extension radiographs. However, the elderly group had a slight decrease in mean ROM (− 0.32° ± 3.93°) at the index level after CDA when compared to that of pre-operation. In contrast, the young group had an increase in mean ROM (+ 0.68° ± 3.60°). The complication profiles were not different, though a trend toward dysphagia was noted in the elderly group (p = 0.073). The incidence or severity (grading) of HO was similar between the two groups.

Conclusions

During the follow-up of two years, CDA was equally effective for patients over 65 years old and those under 40 years in clinical improvement. Although the elderly group demonstrated a small reduction of mean ROM after CDA, in contrast to the young group which had a small increase, the segmental mobility was well preserved at every indexed level for each group.

Postoperative Heterotopic Ossification After Cervical Disc Replacement Is Likely a Reflection of the Degeneration Process

BACKGROUND

The cause of postoperative heterotopic ossification (HO) after cervical disc replacement (CDR) is unclear. The aim of the present study was to investigate the incidence of HO, its clinical significance, and whether the degree of preoperative degeneration was associated with its occurrence.

METHODS

Patients who had undergone CDR using the Prestige-LP disc with a minimum of 48 months of follow-up were included. The patients were divided into 2 groups stratified by the presence of HO. The clinical outcomes (visual analog scale for neck and arm pain, neck disability index, and Japanese Orthopaedic Association scores) and radiographic parameters were collected and analyzed pre- and postoperatively and compared between the 2 groups. The preoperative degeneration at the operated levels was evaluated using the Kellgren-Lawrence scale and Miyazaki magnetic resonance imaging grading system.

RESULTS

A total of 69 patients (89 levels) were identified, and the average age at surgery was 45.8 years. The overall incidence of HO at the final follow-up visit was 37.7% (26 of 69 of patients), and an increasing incidence and severity of HO was observed during the follow-up period. Significant and maintained improvements for all clinical outcome measures were observed, and the presence of HO did not influence these improvements. Segments with greater severe preoperative degeneration had a greater incidence of HO (P < 0.01). However, no statistical significant correlation between the degree of preoperative degeneration and the grade of HO was observed.

CONCLUSION

The presence of HO after CDR was a relatively frequent finding at the final follow-up visit but did not influence patients' improvements. Segments with higher grades of preoperative degeneration had a greater incidence of HO; thus, HO is likely a reflection of the degeneration process.

Effects of smoking on cervical disc arthroplasty

Objective

Cigarette smoking can adversely affect bone fusion in patients who undergo anterior cervical discectomy and fusion. However, there is a paucity of data on smoking among patients who have undergone cervical disc arthroplasty (CDA). The present study aimed to compare the clinical and radiological outcomes of smokers to those of nonsmokers following CDA.

Methods

The authors retrospectively reviewed the records of consecutive patients who had undergone 1- or 2-level CDA for cervical disc herniation or spondylosis and had a minimum 2-year follow-up. All patients were grouped into a smoking group, which consisted of those who had consumed cigarettes within 6 months prior to the CDA surgery, or a nonsmoking group, which consisted of those who had not consumed cigarettes at all or within 6 months of the CDA. Clinical outcomes were evaluated according to the visual analog scale for neck and arm pain, Neck Disability Index, Japanese Orthopaedic Association Scale, and Nurick Scale at each time point of evaluation. Radiological outcomes were assessed using radiographs and CT for multiple parameters, including segmental range of motion (ROM), neutral lordotic curve, and presence of heterotopic ossification (HO).

Results

A total of 109 patients completed at least 2 years of follow-up and were analyzed (mean follow-up 42.3 months). There were 89 patients in the nonsmoking group and 20 in the smoking group. The latter group was younger and predominantly male (both p < 0.05) compared to the nonsmoking group. The two groups had similar improvements in all clinical outcomes after CDA compared to preoperatively. Radiological evaluations were also very similar between the two groups, except for two factors. The smoking group had well-preserved segmental ROM after CDA at an average of 8.1° (both pre- and postoperation). However, while the nonsmoking group remained mobile, segmental ROM decreased significantly (8.2° to 6.9°, p < 0.05) after CDA. There was a trend toward more HO development in the nonsmoking group than in the smoking group, but the difference was without significance (59.6% vs 50.0%, p = 0.43).

Conclusions

During an average 3.5 years of follow-up after 1- and 2-level CDA, cigarette smokers and nonsmokers had similar improvements in clinical outcomes. Moreover, segmental mobility was slightly better preserved in smokers. Since smoking status did not negatively impact outcomes, CDA may be a reasonable option for selected patients who have smoked.

Abbreviations

ACDF = anterior cervical discectomy and fusion; ASD = adjacent-segment degeneration; CDA = cervical disc arthroplasty; FDA = Food and Drug Administration; HO = heterotopic ossification; JOA = Japanese Orthopaedic Association; NDI = Neck Disability Index; ROM = range of motion; VAS = visual analog scale.

The Option of Motion Preservation in Cervical Spondylosis: Cervical Disc Arthroplasty Update

Cervical disc arthroplasty (CDA), or total disc replacement, has emerged as an option in the past two decades for the management of 1- and 2-level cervical disc herniation and spondylosis causing radiculopathy, myelopathy, or both. Multiple prospective randomized controlled trials have demonstrated CDA to be as safe and effective as anterior cervical discectomy and fusion, which has been the standard of care for decades. Moreover, CDA successfully preserved segmental mobility in the majority of surgical levels for 5–10 years. Although CDA has been suggested to have long-term efficacy for the reduction of adjacent segment disease in some studies, more data are needed on this topic. Surgery for CDA is more demanding for decompression, because indirect decompression by placement of a tall bone graft is not possible in CDA. The artificial discs should be properly sized, centered, and installed to allow movement of the vertebrae, and are commonly 6 mm high or less in most patients. The key to successful CDA surgery includes strict patient selection, generous decompression of the neural elements, accurate sizing of the device, and appropriately centered implant placement.

[Interest of robotic stereotactic radiosurgery in the management of brain metastases: Results of a retrospective, single center analysis]

PURPOSE

The management of malignant brain metastases becomes a main issue for the treatment of patients, because of the survival extension related to the improvement in systemic treatments. Robotic stereotactic radiosurgery (RSR) is a new approach in this indication. The purpose of this analysis was to define the efficacy of RSR, in order to determine prognostic factors of survival and factors of response.

PATIENTS AND METHODS

It was a retrospective, single center (polyclinique de Bordeaux Nord Aquitaine) analysis performed from 2012 to 2015, involving patients with malignant brain metastases treated by RSR using the Cyberknife^® technique. We analyzed the following parameters: response to RSR, prognostic and predictive factors of response, and survival.

RESULTS

A total of 72 RSRs were performed among 55 analyzed patients; 62 treatments were assessable with a median follow-up of 9.4 months. The main delivered dose on the 80%-isodose was 20Gy. A complete response was achieved in 40.3% of patients (stability or regression=83.9%). The overall survival was 13 months. The risk of failure was significantly correlated with the increase in metastasis size and non-adenocarcinoma histology. A performance status<2 was the main prognostic factor of survival.

CONCLUSIONS

The RSR allowed treating 3 to 5 brain metastases, avoiding an entire brain irradiation, and maintaining survival and quality of life.

Detection of brain micrometastases by high-resolution stereotactic magnetic resonance imaging and its impact on the timing of and risk for distant recurrences

Object

The aim of this study was to assess the order of micrometastases that can be detected with high-resolution MR imaging at the time of Gamma Knife surgery (GKS), and to estimate the impact this has on the time until and incidence of distant recurrences.

Methods

A consecutive series of 835 patients with brain metastases treated with GKS in a 7-year period, excluding patients in whom earlier brain metastases were treated with other modalities, were retrospectively analyzed. In all patients GKS was based on high Gd–dose (0.3 mmol/kg), high-resolution stereotactic MR imaging. These images were compared with the standard pretreatment MR images, and the difference in number of metastases found was analyzed. The distant recurrence rate following GKS was compared with that found in a prospective randomized study (Aoyama et al.) comparing radiosurgery to radiosurgery plus prophylactic whole-brain radiation therapy.

Results

New tumors were diagnosed in 40% (95% CI 36%–43%) of all patients as well as in the majority of patients with multiple lesions found on the diagnostic scan. The more tumors there were on the diagnostic scan, the higher the likelihood of detecting additional lesions with high-resolution imaging. It was calculated that approximately 50% of the micrometastases present at the time of GKS could be diagnosed with high-resolution imaging, which decreased the incidence of and delayed the time for the development of distant recurrences.

Conclusions

Additional brain metastases can be diagnosed in 40% of patients by using high-resolution imaging. Thus, radiosurgical treatments based on high-resolution stereotactic MR imaging decrease the incidence of and lengthen the time to distant recurrences.

[Dosimetric stereotactic radiosurgical accident: Study of 33 patients treated for brain metastases]

The consequences of a dosimetric radiosurgery accident are not the same as a conventional radiotherapy accident. The objective of this study was to estimate the clinical and radiological outcome of patients treated by radiosurgery for metastasis during the period of the overexposure accident that occurred in the Toulouse Radiosurgery Unit. Between April 2006 and March 2007, 33 patients with 57 metastases were treated in the Toulouse Radiosurgery Unit (Novalis(®), BrainLab). An initial error in the estimation of the scatter factors led to an overexposure to radiation. The median age was 55 years [range, 35-85]. Twenty-one patients (64%) harbored a single metastasis. The primary tumor location was lung (16 cases), kidney (nine cases), breast (four cases), and others (four cases). The mean tumoral volume was 3.2cm(3) [0.04-14.07]. The mean prescribed dose at the isocenter was 20 Gy [range, 10-23], the mean delivered dose was 31.5 Gy [range, 13-52], and the mean overdose was 61.2% [range, 5.6-226.8]. In order to evaluate the consequences of the overdose, three parameters were analyzed: a risk index using dose and volume, the volume of parenchyma that received more than 12 Gy, and the mean dose in a sphere of 20cm(3) surrounding the target volume. Median actuarial survival was 14.1 months, the survival rate was 79.4 % at six months, 59.1% at 12 months, and 27.2% at 24 months. The rate of tumor control was 80.7%. No morbidity was observed. There was no correlation between death and the parameters studied. The survival rates and times observed in our study of the patients treated for brain metastases by radiosurgery and overexposed were among the good results of the international literature. Deaths were not related to the overdose and no side effect was noted. This dosimetric accident has not had worse consequences in this population.

Helical TomoTherapy versus sterotactic Gamma Knife radiosurgery in the treatment of single and multiple brain tumors: a dosimetric comparison

The objective was to compare the dosimetry of Helical TomoTherapy (TOMO) and Gamma Knife (GK) treatment plans for tumor and normal brain in the treatment of single and multiple brain tumors. An anthropomorphic Rando Head phantom was used to compare the dosimetry of TOMO and GK. Eight brain tumors of various shapes, sizes and locations were used to generate 10 plans. The radiation dose was 20 Gy prescribed to the 100% isodose line for TOMO plans and to the 50% for the GK plans. Dose Volume Histograms for tumor and brain were compared. Equivalent Uniform Dose (gEUD), Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) were performed and used for plan comparisons. Average minimum, mean, median and maximum tumor doses were 19.93, 27.83, 27.38, 39.60 Gy for GK and 20.17, 20.60, 20.59, 20.90 Gy for TOMO. Average gEUD values for tumor and normal brain were 25.0 and 7.2 Gy for GK and 20.7 and 8.1 Gy for TOMO. Conformity indices (CI) were similar for both modalities. Gradient indices (GI) were greater for TOMO. A combination plan was also generated using all eight tumors. TOMO was able to target all eight tumors simultaneously resulting in mean tumor and brain doses of 20.5 and 9.35 Gy, respectively. Due to the maximum limit of 50 beams per plan, GK was unable to provide a treatment plan for all eight tumors. GK provides an advantage for all tumor sizes with respect to tumor and normal brain dose. Clinical studies are needed to correlate these dosimetric findings with patient outcomes.

PACS number: 87.55‐x

Surgery of brain metastases – Is there still a place for it?

The role of surgery in the treatment of metastatic brain tumors has always been a source of controversy. It was only in the early 1990s that two randomized prospective trials demonstrated that surgery plus radiation therapy improved survival in patients with single metastatic brain tumors vs. radiation therapy alone. This paper reviews these articles as well as other evidence outlining management options for multiple brain metastases. An attempt has been made to better define the role of surgery in brain metastases. The prognostic factors for brain metastases after surgery are also reviewed and the data comparing stereotactic radiosurgery to surgery is examined. A short description of surgical planning, operative techniques and tools, followed by a discussion on complication avoidance before, during, and after surgery is included.