Aims

Cervical spondylosis is often accompanied by dizziness. It has recently been shown that the ingrowth of Ruffini corpuscles into diseased cervical discs may be related to cervicogenic dizziness. In order to evaluate whether cervicogenic dizziness stems from the diseased cervical disc, we performed a prospective cohort study to assess the effectiveness of anterior cervical discectomy and fusion on the relief of dizziness.

Purpose: Cervical arthroplasty is an emerging technology with the potential of motion preservation and reduced adjacent level disease. However, the factors that influence postoperative range of motion (ROM) and patient satisfaction is not fully understood. The aim of this study was to evaluate the influence of disk height on the postoperative motion as well as clinical outcomes.

Method: 167 patients from a multi-center prospective randomized FDA trial with single level ProDisc-C arthroplasty performed were evaluated radiographically utilizing Medical Metrics (QMATM, Medical Metrics, Inc.). Preoperative and postoperative disk height and ROM were measured from standing lateral and flexion-extension radiographs. Of these 167 patients, 19 patients from a single center had clinical outcomes based on ODI and VAS scores evaluated pre and postoperation with a mean follow-up of 22 months. Two-tailed student’s T-test and Spearman’s Rho tests were performed in order to find out if there was any correlation or “threshold” effect between the disk height and ROM.

Results: Patients with less than 4 mm of preoperative disc height had a 1.8° increase in their flexion-extension ROM after TDA as compared to no change in ROM in patients with more than 4 mm of preoperative disc height (p=0.04). Patients with more than 5mm of postoperative disc height have significantly higher postoperative flexion-extension ROM (10.1°) than those with less than 5mm disc height (8.3°, p=0.014). However, patients with more than 7mm of postoperative disc height have significantly lower postoperative lateral bending ROM (4.1°) than those with less than 7mm disc height (5.7°, p=0.04). It appears that the optimal postoperative disc height is between 5 to 7 mm for increased ROM on flexion-extension and lateral bending. No correlation could be found between clinical outcomes and disc height. Similarly, no threshold effect could be found between any specific disc height and ODI or VAS.

Conclusion: Patients with greater disc collapse benefit more in ROM from a TDR. The optimal range to maximize ROM for postoperative disc height is between 5 to 7mm. This optimal range did not translate into better clinical outcome at 2 year follow-up. A longer follow-up will yield if less ROM ultimately leads to worse clinical outcomes.

Discogenic low back pain is a common cause of disability, but its pathogenesis is poorly understood. We collected 19 specimens of lumbar intervertebral discs from 17 patients with discogenic low back pain during posterior lumbar interbody fusion, 12 from physiologically ageing discs and ten from normal control discs. We investigated the histological features and assessed the immunoreactive activity of neurofilament (NF200) and neuropeptides such as substance P (SP) and vasoactive-intestinal peptide (VIP) in the nerve fibres.

The distinct histological characteristic of the painful disc was the formation of a zone of vascularised granulation tissue from the nucleus pulposus to the outer part of the annulus fibrosus along the edges of the fissures. SP-, NF- and VIP-immunoreactive nerve fibres in the painful discs were more extensive than in the control discs. Growth of nerves deep into the annulus fibrosus and nucleus pulposus was observed mainly along the zone of granulation tissue in the painful discs. This suggests that the zone of granulation tissue with extensive innervation along the tears in the posterior part of the painful disc may be responsible for causing the pain of discography and of discogenic low back pain.

We examined the pathogenesis of Schmorl’s nodes, correlating the histological findings from 12 lumbar vertebrae with the corresponding conventional radiographs, tomographs, MR images and CT scans. The last revealed round, often multiple cystic lesions with indistinct sclerotic margins beneath the cartilaginous endplate. The appearances are similar to the typical CT changes of osteonecrosis. Histological examination of en-bloc slices through Schmorl’s nodes gave clear evidence of subchondral osteonecrosis. Beneath the cartilage endplate, we found fibrosis within the marrow cavities with the disappearance of fat cells. Osteocytes within bone trabeculae were either dead or had disappeared. We suggest that Schmorl’s nodes are the end result of ischaemic necrosis beneath the cartilaginous endplate and that herniation into the body of the vertebra is secondary.