McAfee-Mehren classification
Grade 0 No Heterotopic ossification (HO) present
Grade I HO is detectable in front of the vertebral body but not in the anatomic interdiscal space
Grade II HO is growing into the disc space. Possible affection of the function of the prosthesis
Grade III Bridging ossifications which still allow movement of the prosthesis
Grade IV Complete fusion of the treated segment without movement in flexion/extension 1).
Heterotopic ossification occurs in three-fourths of the patients after anterior cervical disc arthroplasty at two years after surgery, but does not necessarily correspond to clinical outcome, nor loss or preservation of ROM. The McAfee-Mehren classification should be combined with ROM evaluation to properly study HO 2).
1)
Mehren C, Suchomel P, Grochulla F, Barsa P, Sourkova P, Hradil J, Korge A,
Mayer HM. Heterotopic ossification in total cervical artificial disc replacement.
Spine (Phila Pa 1976). 2006 Nov 15;31(24):2802-6. PubMed PMID: 17108833.
2)
Yang X, Bartels RHMA, Donk R, Depreitere B, Walraevens J, Zhai Z,
Vleggeert-Lankamp CLA. Does Heterotopic Ossification in Cervical Arthroplasty
Affect Clinical Outcome? World Neurosurg. 2019 Jul 31. pii:
S1878-8750(19)32103-5. doi: 10.1016/j.wneu.2019.07.187. [Epub ahead of print]
PubMed PMID: 31376560.