Introduction: The purpose of this study is to evaluate the long-term effects of repeat cervical fusion after development of adjacent segment disease (ASD).

Methods: We collected 888 patients who underwent ACDF for cervical degenerative disease over a 20-year period at a single institution. Patients were followed for an average of 94.0 ± 78.1 months after the first ACDF.

Results: Of 888 patients who underwent ACDF, 108 (12.2%) patients developed ASD, necessitating a second cervical fusion. Among these 108 patients, 27 (25%) patients later developed recurrent ASD, requiring a third cervical fusion. A 12.2% incidence of ASD after the first ACDF significantly increased to 25% after the second ACDF (p=0.0002). ASD developed significantly faster after the second ACDF (30.3 ± 24.9 months) versus the first ACDF (47.0 ± 44.9 months) [Student’s t-test (p=0.01); Kaplan-Meier analysis (p<0.0001)]. Out of 77 patients who underwent a second cervical fusion via an anterior approach, 23 developed recurrent ASD requiring a third cervical fusion. In contrast, of 31 patients who had a posteriorly approached second cervical fusion, only 4 developed recurrent ASD requiring a third cervical fusion (p>0.05). Overall, patients who underwent a second anterior cervical fusion benefited neurologically via a decrease in Nurick score. However, patients who had a third anterior cervical fusion exhibited a post-operative decrease in ability to ambulate (p=0.02).

Conclusions: The pathophysiology of adjacent segment disease after ACDF has yet to be fully established. The incidence of ASD development is lowest after the first ACDF. Patients who undergo a second cervical fusion develop ASD at both higher and faster rates. Moreover, ASD is more likely to occur after a second cervical fusion with an anterior approach versus posterior approach. While patients with ASD improved neurologically after their second cervical fusion, a third cervical fusion resulted in worse neurologic function for patients approached anteriorly.

Patient Care: The topic of this abstract is adjacent segment disease, a major cause of morbidity for patients after ACDF. Here, we focus on the select group of patients that undergo a second and third cervical fusion for adjacent segment disease. We hope that our research will lead to a greater understanding of this challenging patient population.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Discuss the impact of repeat cervical fusion on the development of adjacent segment disease, 2) Identify the rate of adjacent segment disease for second and third repeat cervical fusions.

References: 1. Hilibrand AS, Carlson GD, Palumbo MA, Jones PK, Bohlman HH: Radiculopathy and myelopathy at segments adjacent to the site of a previous anterior cervical arthrodesis. J Bone Joint Surg Am 81:519-528, 1999 2. Hilibrand AS, Robbins M: Adjacent segment degeneration and adjacent segment disease: the consequences of spinal fusion? Spine J 4:190S-194S, 2004 3. Javedan SP, Dickman CA: Cause of adjacent-segment disease after spinal fusion. Lancet 354:530-531, 1999 4. Kowalczyk I, Lazaro BC, Fink M, Rabin D, Duggal N: Analysis of in vivo kinematics of 3 different cervical devices: Bryan disc, ProDisc-C, and Prestige LP disc. J Neurosurg Spine 15:630-635 5. Lee MJ, Dumonski M, Phillips FM, Voronov LI, Renner SM, Carandang G, et al: Disc replacement adjacent to cervical fusion: a biomechanical comparison of hybrid construct versus two-level fusion. Spine (Phila Pa 1976) 36:1932-1939 6. Matsunaga S, Kabayama S, Yamamoto T, Yone K, Sakou T, Nakanishi K: Strain on intervertebral discs after anterior cervical decompression and fusion. Spine (Phila Pa 1976) 24:670-675, 1999 7. McAfee PC, Cunningham BW, Hayes V, Sidiqi F, Dabbah M, Sefter JC, et al: Biomechanical analysis of rotational motions after disc arthroplasty: implications for patients with adult deformities. Spine (Phila Pa 1976) 31:S152-160, 2006