Srinivasan US and Radhi Lawrence
Introduction: In cervical disc disease, the exact location of the posterior osteophyte with relationship to the bodies of the adjacent cervical vertebra at each disc space level, as observed during surgery under operating microscope and correlating it with the histopathological development of the posterior osteophyte has not been documented in literature. A detailed review of literature on the development of posterior osteophytes and its impact on cervical spinal cord is also being reviewed.
Materials and Methods: 1st Phase: In a prospective study conducted over first 5 years (2007-2012), intraoperative observations of 294 disc spaces in 201 patients who were operated for cervical disc disease using the standard anterior cervical microdiscectomy were analyzed. We observed under operating microscope 32 C3-C4 disc spaces, 62 C4-C5, 123 C5- C6, 74 C6-C7, 2 C7- D1 and 1 C2- C3 disc space during the study period.
2nd Phase: The above prospective study was extended into the 2nd phase over next 3 1/2 years (2009-2012), and clinico-radiological (MRI findings) - intraoperative observations of 118 disc spaces in 70 patients who were operated for cervical disc disease were analyzed. These observations were correlated with the histopathological characteristics of the excised disc material.
Results: 1st Phase study: At C3-C4 disc space, posterior osteophyte originates from the upper vertebral body of C3 in 78.13% [25/32] disc spaces. In mobile segments of C4-C5 in 70.96% [44/62] and C5-C6 in 84.55% [104/123] disc spaces, the osteophyte arises from posterior margins of both the vertebral bodies. At C6 –C7, it arises from lower vertebral body of C7 in 71.62% [53/74]) disc spaces.
2nd Phase: It was observed histopathologically and intraoperatively, that posterior osteophytes formation goes through three stages. Posterior osteophyte formation is of Fibrocartilage in 10.17% (12/118), Mixed variety 7.62% (9/118) and Bony type in 82.20% [97/118]. In patients who had Bony type, 89.4% had myelopathy, 75 % had radiculopathy while 89.4% patients had hyperintense signal within the spinal cord.
Discussion: Our results show that there is a definite pattern in the formation of the posterior osteophyte within the cervical disc spaces. At junctional areas like C3-C4 and C6 –C7 the posterior osteophyte originates from the relatively fixed vertebra like C3 and C7. In mobile segments like C4-C5 and C5- C6 the posterior osteophyte originates from both the bodies of adjacent vertebra. We also observed that the posterior osteophyte formation in cervical disc disease goes through the following three stages. 1st stage: Fibrocartilage, 2nd stage: Mixed type consisting of both the fibrocartilage and partially bony and 3rd stage: Bony type. These stages we feel evolve over a span of few years. Patients presenting with myeloradiculopathy and hyperintense signal within the spinal cord are likely to harbor bony posterior osteophytes compressing the thecal sac and requires surgical intervention. This is the first document of its kind in literature.
Detailed reviews of literature on experimental models showing the development of posterior osteophyte supporting our observations, the pathological and radiological impact of the posterior osteophytes on cervical spinal cord, natural history of cervical spondylotic myelopathy and fate of the posterior osteophytes after anterior fusion surgery are being dealt upon in this paper.
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