Answer to the Letter to the Editor of Shen YW, et al. concerning “Complications of cervical total disc replacement and their associations with heterotopic ossification: a systematic review and meta-analysis” by N. Hui, et al. [Eur Spine J; 2020; 29(11):2688–2700]

Study Design: A systematic review and meta-analysis. Objectives: The results from previous meta-analyses are limited by the small number of included studies. Moreover, the risk factors of heterotopic ossification (HO) have not been well studied. Therefore, this study aims to estimate the prevalence of HO after cervical total disc replacement (CTDR) at different follow-up time points and explore potential risk factors for HO. Methods: We searched databases to identify eligible studies that reported the rate of HO after CTDR. The pooled prevalence of HO, according to different grades of HO, length of follow-up and types of prosthesis, and 95% confidence intervals (CIs) were calculated. Multivariable meta-regression analyses were performed to identify factors that may contribute to the heterogeneity between estimates. Results: Of the 94 studies included, 82 studies reported an overall rate of HO, encompassing a total of 5861 cervical spinal levels that underwent CTDR. The overall pooled prevalence of HO was 32.5% (95% CI 26.7% to 38.4%). Single-level CTDR was associated with a higher overall rate of HO. When the rate of HO was stratified by McAfee/Mehren classification, the pooled prevalence of range of motion (ROM)–limiting HO was 11.0% (95% CI 9.2% to 12.8%). Latest publication, single-level CTDR, longer follow-up period, and studies published outside were associated with a higher rate of ROM-limiting HO. Conclusions: We provide a comprehensive overview of the prevalence of different grades of HO. This meta-analysis also identifies and rules out some risk factors for HO after CTDR.

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Does Heterotopic Ossification Affect the Outcomes of Cervical Total Disc Replacement? A Meta-analysis

Spine ◽

10.1097/brs.0000000000000776 ◽

2015 ◽

Vol 40 (6) ◽

pp. E332-E340 ◽

Cited By ~ 23

Author(s):

Hao-han Zhou ◽

Yang Qu ◽

Rong-peng Dong ◽

Ming-yang Kang ◽

Jian-wu Zhao

Keyword(s):

Heterotopic Ossification ◽

Meta Analysis ◽

Total Disc Replacement ◽

Disc Replacement ◽

Cervical Total Disc Replacement

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Early Development and Progression of Heterotopic Ossification in Cervical Total Disc Replacement

The Spine Journal ◽

10.1016/j.spinee.2011.08.210 ◽

2011 ◽

Vol 11 (10) ◽

pp. S84

Author(s):

Soo Eon Lee

Keyword(s):

Heterotopic Ossification ◽

Early Development ◽

Total Disc Replacement ◽

Disc Replacement ◽

Cervical Total Disc Replacement

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Early development and progression of heterotopic ossification in cervical total disc replacement

Journal of Neurosurgery Spine ◽

10.3171/2011.8.spine11303 ◽

2012 ◽

Vol 16 (1) ◽

pp. 31-36 ◽

Cited By ~ 38

Author(s):

Soo Eon Lee ◽

Chun Kee Chung ◽

Tae Ahn Jahng

Keyword(s):

Clinical Outcome ◽

Heterotopic Ossification ◽

Total Disc Replacement ◽

Disc Replacement ◽

Adjacent Segment ◽

Segmental Motion ◽

Cervical Total Disc Replacement ◽

The Mean ◽

Grade Iii

Object The purpose of cervical total disc replacement (TDR) is to decrease the incidence of adjacent segment disease through motion preservation. Heterotopic ossification (HO) is a well-known complication after hip and knee arthroplasties. There are few reports regarding HO in patients undergoing cervical TDR, however; and the occurrence of HO and its effects on cervical motion have rarely been reported. Moreover, temporal progression of HO has not been fully addressed. One goal of this study involved determining the incidence of HO following cervical TDR, as identified from plain radiographs, and demonstrating the progression of HO during the follow-up period. A second goal consisted of determining whether segmental motion could be preserved and identifying the relationship between HO and clinical outcomes. Methods The authors conducted a retrospective clinical and radiological study of 28 consecutive patients who underwent cervical TDR with Mobi-C prostheses (LDR Medical) between September 2006 and October 2008. Radiological outcomes were evaluated using lateral dynamic radiographs obtained preoperatively and at 1, 3, 6, 12, and 24 months postoperatively. The occurrence of HO was interpreted on lateral radiographs using the McAfee classification. Cervical range of motion (ROM) was also measured. The visual analog scale (VAS) and Neck Disability Index (NDI) were used to evaluate clinical outcome. Results The mean follow-up period was 21.6 ± 7.0 months, and the mean occurrence of HO was at 8.0 ± 6.6 months postoperatively. At the last follow-up, 18 (64.3%) of 28 patients had HO: Grade I, 6 patients; Grade II, 8 patients; Grade III, 3 patients; and Grade IV, 1 patient. Heterotopic ossification progression was proportional to the duration of follow-up; HO was present in 3 (10.7%) of 28 patients at 1 month; 7 (25.0%) of 28 patients at 3 months; 11 (42.3%) of 26 patients at 6 months; 15 (62.5%) of 24 patients at 12 months; and 17 (77.3%) of 22 patients at 24 months. Cervical ROM was preserved in Grades I and II HO but was restricted in Grades III and IV HO. Clinical improvement according to the VAS and NDI was not significantly correlated with the occurrence of HO. Conclusions The overall incidence of HO after cervical TDR was relatively high. Moreover, HO began unexpectedly to appear early after surgery. Heterotopic ossification progression was proportional to the time that had elapsed postoperatively. Grade III or IV HO can restrict the cervical ROM and may lead to spontaneous fusion; however, the occurrence of HO did not affect clinical outcome. The results of this study indicate that a high incidence of HO with the possibility of spontaneous fusion is to be expected during long-term follow-up and should be considered before performing cervical TDR.

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

Global Spine Journal ◽

10.1177/2192568220922949 ◽

2020 ◽

pp. 219256822092294

Author(s):

Nicholas Hui ◽

Kevin Phan ◽

Mei-Yi Lee ◽

Jack Kerferd ◽

Telvinderjit Singh ◽

...

Keyword(s):

Systematic Review ◽

Heterotopic Ossification ◽

Meta Analysis ◽

Total Disc Replacement ◽

Final Analysis ◽

Spinal Segment ◽

Functional Spinal Unit ◽

Before And After ◽

Cadaver Studies

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.

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Heterotopic ossification after cervical total disc replacement: determination by CT and effects on clinical outcomes

Journal of Neurosurgery Spine ◽

10.3171/2010.11.spine10444 ◽

2011 ◽

Vol 14 (4) ◽

pp. 457-465 ◽

Cited By ~ 61

Author(s):

Tsung-Hsi Tu ◽

Jau-Ching Wu ◽

Wen-Cheng Huang ◽

Wan-Yuo Guo ◽

Ching-Lan Wu ◽

...

Keyword(s):

Ct Scan ◽

Heterotopic Ossification ◽

Total Disc Replacement ◽

Disc Replacement ◽

Segmental Motion ◽

Cervical Total Disc Replacement ◽

Plain Radiographs ◽

Bryan Disc ◽

The Mean

Object Heterotopic ossification (HO) after cervical total disc replacement (TDR) has been reported to impede artificial disc motion. In all previously reported cases of HO, assessment was based on plain radiographs. The authors hypothesized that CT scan is a more sensitive and accurate detector. The aims of this study were to assess the actual incidence of HO and its effect on outcome in a cohort of patients undergoing cervical TDR with the Bryan disc and to compare HO detection by means of plain radiographs and CT. Methods The authors retrospectively assessed data from medical records, radiological studies, and clinical evaluations of patients who underwent 1- or 2-level cervical TDR with the Bryan disc and were followed up for more than 12 months. The presence and grading of HO according to the McAfee classification were assessed by CT scan, and these findings were compared with findings on plain radiographs. Thirty-six patients (mean age 46.61 ± 7.24 years; range 29–60 years; 21 men and 15 women) who underwent Bryan TDR at 52 levels were included in the study. The mean duration of CT follow-up was 19.03 ± 4.64 months; the mean duration of clinical follow-up was 26.78 ± 7.20 months. Results On the basis of CT, HO was identified in 18 (50%) of 36 patients and 25 (48.1%) of 52 levels treated. Grade 1 HO was present in 9 of the levels treated (17.3%), Grade 2 in 13 levels (25.0%), Grade 3 in 2 levels (3.8%), and Grade 4 in 1 level (1.9%). Nineteen (76%) of the 25 affected levels were in patients who had undergone 2-level TDR. There was no significant association with patient sex or disc pathology. There was a tendency for HO development among older patients, but this finding was not statistically significant (mean age 48.8 ± 6.8 in patients with HO vs 44.4 ± 7.2 in those without HO, p = 0.065). Although HO was found in 25 levels, 96.2% of the treated levels (50 of 52) had segmental range of motion on dynamic (flexion and extension) radiographs. The concordance between HO grading by CT and radiography was high, with an intraclass correlation coefficient of 0.822 (lower limit of 95% CI: 0.710, p < 0.001). Patients who had HO had the same clinical success rate as those who did not (94.4% vs 94.4%, p = 1.00). The visual analog scale scores for neck and arm pain were significantly improved in both the HO and the non-HO group. Conclusions The rate of HO detected by CT scan in this cohort of patients undergoing cervical TDR with a Bryan disc was 48.1% per level treated and 50% per patient with minimal limitation of segmental motion (96.2% of levels remained mobile), but plain radiograph is an acceptable detection tool. Two-level surgery has a higher risk of HO, although development of HO does not affect clinical outcome.

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