summary Cervical adjacent segment disease refers to the radiographic degeneration of the disc or facets at the caudal or cephalad segment adjacent to a previous cervical surgical fusion construct Diagnosis can be made with plain radiographs of the cervical spine Treatment consists of observation and medical management for patients with mild symptoms. Surgical management is indicated in patients that have failed conservative treatment Epidemiology Incidence studies have estimated a 1.6-2.4% annual incidence of clinically relevant ASD there is a predicted 25.6% ASD rate at 10 years postoperatively for patients undergoing ACDF Demographics females are at increased risk patients <60 y/o are at increased risk Anatomic location the lowest three segments of the subaxial spine are the most commonly affected (C4-5, C5-6, and C6-7) C5-6 has the highest risk login to view 1 more bullet C2-3 has the lowest risk Risk factors smoking is the strongest associated risk factor female <3 segments included in the fusion construct it is speculated that fewer remaining motion segments reduces the risk of adjacent segment degeneration C5-6 and C6-7 segments are adjacent to the fusion construct these are anatomically the most mobile segments of the cervical spine with the highest rates of degeneration preoperative MRI and myelography demonstrating dura mater indentation and disc protrusion, especially at the C5-6 and C6-7 levels no decrease in risk with fusion vs. nonfusion procedures (i.e. posterior foraminotomy or anterior discectomy) Etiology Forms adjacent segment degeneration radiographic changes of degeneration at levels adjacent to a spinal fusion, with or without clinical symptoms adjacent level ossification development (ALOD) login to view 2 more bullets adjacent segment disease (ASD) development of clinical radiculopathy or myelopathy correlating to a motion segment adjacent to the fusion construct Pathophysiology ASD increased motion at the adjacent disc space to compensate for the rigid fused segment login to view 5 more bullets damage to the anterior longitudinal ligament and longus colli muscle at the time of surgery placement of a needle marker into an incorrect disc space when localizing the operative level ALOD etiology is unclear, but speculated to be an inflammatory reaction that occurs from the increased proximity of an anterior cervical plate to the adjacent disc space login to view 2 more bullets Classification Park and Associates Classification of Adjacent Level Ossification Grade 0 No adjacent level ossification Grade 1 Ossification extending <50% of the disc space Grade 2 Ossification extending >50% of the disc space Grade 3 Complete bridging of the adjacent disc space Presentation Symptoms radiculopathy pain in dermatome corresponding to the motion segment adjacent to a previous fusion construct motor weakness corresponding to the root level adjacent to a previous fusion construct myelopathy gait instability hand clumsiness urinary abnormalities Physical exam inspection examine surgical wound motion assess flexion-extension, side bending, and rotational motion login to view 1 more bullet neurological exam assess fine touch sensation in the dermatomal patterns login to view 1 more bullet assess motor strength assess reflexes login to view 1 more bullet provocative tests Hoffman's test login to view 2 more bullets Spurling's test login to view 2 more bullets shoulder abduction test login to view 1 more bullet Lhermitte sign login to view 1 more bullet Imaging Radiographs recommended views AP lateral flexion-extension views findings disc space narrowing foraminal stenosis posterior osteophytes facet arthropathy anterior marginal osteophyte extending from adjacent vertebral body degenerative changes on radiographs do not always correlate with clinical symptoms CT indications assess for pseudoarthrosis assess for ossification of posterior longitudinal ligament axial and sagittal views are most useful MRI indications determine whether there is foraminal or central canal stenosis at the adjacent segment axial and sagittal views are most useful Differential top 5 differential diagnoses pseudoarthrosis progressive degenerative disc disease indolent infection myelopathy at a segment not adjacent to the fused segment radiculopathy at a segment not adjacent to the fused segment Treatment Nonoperative treatment oral medications, activity modifications, physical therapy, +/- brief period of immobilization indications login to view 1 more bullet modalities login to view 9 more bullets severe myelopathy should be surgically addressed to avoid stepwise deterioration Operative extension of fusion construct to affected levels indications login to view 2 more bullets inclusion of C5-6 and/or C6-7 into the fusion construct login to view 1 more bullet placing the anterior plate >5 mm from the adjacent level reduces the risk of adjacent level ossification including >3 levels is associated with reduced risk of developing further ASD cervical total disc replacement indications login to view 1 more bullet when performed as an index procedure, does not appear to have a protective effect on ASD login to view 1 more bullet for the treatment of ASD, appears equivalent to ACDF reduced risk of adjacent segment ossification compared to anterior cervical plating Technique Oral medications, activity modifications, and physical therapy techniques: NSAIDs, tramadol, tylenol, and gabapentin login to view 1 more bullet activity modification login to view 4 more bullets physical therapy login to view 7 more bullets Extension of fusion construct to affected levels approach anterior vs. posterior login to view 1 more bullet anterior right vs. left login to view 1 more bullet Cervical disc replacement technique single-level disease adjacent to previous fusion construct performed through an anterior approach login to view 1 more bullet Complications Progression of ASD following surgical treatment of ASD by extending the fusion construct to the affected levels, the newly adjacent segment can have further development of symptomatic degeneration treatment revision surgery to include the affected segment Prognosis High incidence of clinically relevant ASD and radiographic cervical spondylosis studies have demonstrated radiographic degenerative findings in >80% of asymptomatic unfused patients >60 y/o prevalence of radiographic adjacent segment degeneration in arthrodesis patients ranges from 25-91% Increased revision surgery rates overall reoperation rate ranges from 6.1-25.6% annual reoperation rate reported to be as high as 0.7-3.7%