Coexistence of heterotopic ossification and anterior bone loss after multilevel cervical disc arthroplasty: illustrative case.

backgroundMultilevel (≥ 2) cervical disc arthroplasty (CDA) has become increasingly popular over the past decade. The authors report the first case of three-level CDA demonstrating divergent bone remodeling, heterotopic ossification (HO), and anterior bone loss (ABL) at separate operative levels, with preserved segmental motion. OBSERVATIONS: A 45-year-old man underwent three-level CDA (C4-5, C5-6, C6-7) with the ROTAIO prosthesis for medically refractory cervical myeloradiculopathy secondary to multilevel disc herniation superimposed on congenital stenosis. Surveillance imaging identified grade 2 ABL at C4-5 at 6 months and McAfee class II HO at C6-7 at 18 months; the intervening C5-6 remained unaffected. At the 2-year follow-up, the patient was asymptomatic with mobility preserved across all three levels. LESSONS: The coexistence of HO and ABL at different operative levels within a single patient, despite identical implants and uniform perioperative conditions, implicates level-specific mechanical factors-rather than implant design, material properties, or patient-intrinsic variables-as the principal drivers of bone remodeling after multilevel CDA. Close radiological surveillance is warranted even in asymptomatic patients. https://thejns.org/doi/10.3171/CASE26368.