Anterior bone loss after cervical disc replacement: A systematic review

Table 3 Summarized data of incidence and identification of anterior bone loss

Ref.	Prevalence	Notification time	Course of ABL	Grading system
Ren et al[22]	Bryan: 5.88% more cases were noted from the figures	Within 6 mo postop	Stopped after 6 mo postop	Not reported; ABL distance: < 2 mm in 2 patients, > 2 mm in 1 patient
Hacker et al[23]	Total: 1.96%, Bryan: 3.13%; Prestige-LP: 0	6 wk postop	Not reported	Not reported
Kim et al[24]	Bryan: 8.11%	3-6 mo postop	Progressed within 6 mo postop; Self-limited	Not reported; Mean ABL distance: 2.57 mm (range 2.0-3.0 mm)
Heo et al[25]	Baguera-C: 60.42%	6 mo postop	Progressed within 12 mo postop; Self-limited	Grade 1, Minor, disappearance of the anterior osteophyte or small minor bone loss: 31.25%; Grade 2, Minor, bone loss of the anterior portion of the vertebral bodies at the operated segment without exposure of the implant: 12.5%; Grade 3, Major, significant bone loss with exposure of the anterior portion of the implant: 16.67%
Kieser et al[26]	Total: 63.73%; Cranial: 62.11%; Caudal: 48.7%; Bryan: 57.14%; Discocerv: 47.73%; Baguera-C: 64.29%; Mobi-C: 91.89%	Not reported	Self-limited within 12 mo postop	Mild, ABL ≤ 5%: 48.7%; Moderate, 5% < ABL ≤ 10%: 11.92%; Severe, ABL > 10%: 3.11%
Kieser et al[27]	Total: 57.05%; Cranial: 54.9%; Caudal: 42.31%; Bryan: 57.14%; Discocerv: 47.73%; Baguera-C: 64.29%	Within 3 mo postop	Benign course; progressed within 12 mo postop then stopped; self-healing in several cases	Grade 1, Mild, ABL ≤ 5%: 45.51%; Grade 2, Moderate, 5% < ABL ≤ 10%: 8.33%; Grade 3, Severe, ABL > 10% without endplate collapse: 0.64%; Grade 4, Severe, ABL > 10% with endplate collapse: 2.56%

ABL: Anterior bone loss; postop: Postoperatively.