Patient outcomes and surgical strategies in revision cervical arthroplasty following M6-C™ disc-related osteolysis

PURPOSE:
Periprosthetic osteolysis from the M6-C™ Artificial Cervical Disc (Orthofix, Lewisville, Texas) has become a significant issue, sometimes requiring revision spine surgery (RSS). This study evaluates patient-reported outcome measures (PROMs) and revision strategies for managing device-related wear and osteolysis.

METHODS:
PROMs, including the Visual Analogue Scale (VAS) for neck/arm pain and the Neck Disability Index (NDI), were analyzed at pre-index surgery (T1), pre-RSS (T2), and final follow-up (T3). Osteolysis severity was graded radiographically. A control group who underwent primary M6-C cervical total disc replacement (CTDR) without RSS was included for comparison.

RESULTS:
Of 53 patients with M6-C CTDR, 19 (35.9%) required RSS due to osteolysis. Osteolysis grades included Grade 1 (4 patients), Grade 2 (7 patients), Grade 3 (3 patients), and Grade 4 (5 patients). Revision strategies included removal and anterior fusion, requiring vertebrectomy for Grade 4 cases; revisions to a different CTDR prosthesis were reserved for Grades 1-3. The RSS group showed significant VAS neck pain improvement at T3 (mean = 36.2 points, p < 0.001), exceeding the minimum clinically important difference (MCID). However, VAS arm pain and NDI did not meet MCID thresholds. The control group showed clinically significant improvements across all PROMs. At T2, the RSS group had a higher disability (NDI, p = 0.027) than the controls.

CONCLUSION:
Revision surgery for M6-C osteolysis improves neck pain, not arm pain or disability. Early detection and tailored revision strategies are crucial to optimize patient outcomes and mitigate osteolysis-related disability.