Intervertebral Disc Space Height Research Articles

The Results of β-tricalcium Phosphate Coated Hydroxyapatite (β-TCP/HA) Grafts for Interbody Fusion After Anterior Cervical Discectomy

The efficacy of tricalcium phosphate and hydroxyapatite (beta-TCP/HA) grafts was studied after anterior cervical discectomy (ACD). This study presents our observations about the efficacy of beta-TCP/HA grafts after ACD. Especially in the last 2 decades, fusion materials such as autograft and allograft, as well as different kind of cages were used to maintain fusion after ACD. beta-TCP/HA grafts after ACD were used in 17 patients. The cervical and radicular pain was evaluated via visual analog scale (VAS) score preoperatively, at postoperative third week, and after 20 months (range: 18 to 24 mo) after the operation. The radiologic evaluations were done preoperatively, at postoperative first day and at the latest follow-up. The VAS, intervertebral space ratio, height of intervertebral disc space and neural foramen, and cervical and segmental lordosis angles were recorded preoperatively and during the postoperative follow-up period. The presence of fusion was controlled in computed tomography scans taken at the latest follow-up. Both clinical and radiologic evaluations yielded satisfactory results. VAS scores decreased significantly in all patients. The intervertebral space and neural foramen and intervertebral disc heights increased at postoperative day 1 but were found to be decreased at the latest follow-up (P<0.05). On the contrary the cervical and segmental lordosis angles decreased at postoperative day 1 but were found to be increased at the latest follow-up (P<0.05). There was a solid fusion in 16 out of 17 patients (94.11%). Although there was a loss of the initially obtained neural foraminal and disc height, the application of beta-TCP/HA graft after ACD resulted in a high rate of fusion and patient satisfaction. Additionally, the cervical and segmental lordosis was preserved. We concluded that it is a good alternative to current methods to maintain cervical alignment and fusion after ACD.

Subsidence of Cylindrical Cage (AMSLU™Cage) : Postoperative 1 Year Follow-up of the Cervical Anterior Interbody Fusion

There are numerous reports on the primary stabilizing effects of the different cervical cages for cervical radiculopathy. But, little is known about the subsidence which may be clinical problem postoperatively. The goal of this study is to evaluate subsidence of cage and investigate the correlation between radiologic subsidence and clinical outcome. To assess possible subsidence, the authors investigated clinical and radiological results of the one-hundred patients who underwent anterior cervical fusion by using AMSLUtrade mark cage during the period between January 2003 and June 2005. Preoperative and postoperative lateral radiographs were measured for height of intervertebral disc space where cages were placed. Intervertebral disc space was measured by dividing the sum of anterior, posterior, and midpoint interbody distance by 3. Follow-up time was 6 to 12 months. Subsidence was defined as any change in at least one of our parameters of at least 3 mm. Subsidence was found in 22 patients (22%). The mean value of subsidence was 2.21 mm, and mean subsidence rate was 22%. There were no cases of the clinical status deterioration during the follow-up period. No posterior or anterior migration was observed. The phenomenon of subsidence is seen in substantial number of patients. Nevertheless, clinical and radiological results of the surgery were favorable. An excessive subsidence may result in hardware failure. Endplate preservation may enables us to control subsidence and reduce the number of complications.

Minimum 5 Year Results of Posterior Lumbar Interbody Fusion with Cages in Lumbar Spondylolisthesis

Study Design: A retrospective study Objectives: To examine the mid term clinical and radiologic findings of patients treated by Posterior Lumbar Interbody Fusion (PLIF) with cages in spondylolisthesis. Literature Review: The clinical result of PLIF with cages is satisfactory. PLIF with cages is a useful treatment for spondylolisthesis. Materials and Methods: Forty-two patients were followed up for more than 5 years. Their mean age was 53 years and the mean follow-up period was 68 months. Twenty-one cases were the isthmic type, and 21 cases were the degenerative type. The low back pain score, Lin s clinical result, perioperative value of slippage, anterior intervertebral disc space height, radiological change in the adjacent level and complications were evaluated. Results: The preoperative lower back pain score improved from 46.7 to 86.4 points at the last follow-up (p�0.05). Thirty-eight patients (91%) showed excellent or good results. The preoperative value of slippage improved from 17.5% to 5.7% (p�0.05). The anterior intervertebral disc space height increased from 10.0 to 14.5 mm (p�0.05). There were changes in the above and lower adjacent segments in 12 cases (28%). Two of these cases required surgery. Conclusions: PLIF with cages might be an effective method in spondylolisthesis. However, the long-term follow-up showed changes in the adjacent segment.

Comparison of Sagittal Contour and Posterior Disc Height Following Interbody Fusion

Segmental restoration of sagittal contour is recognized as critical for improved long-term success following instrumented lumbar fusions. As such, the use of wedged implants has become more popular. Few studies exist to assess the postoperative lordotic and disc height changes following these varied techniques in spinal fusion. An observational radiographic study examining lumbar sagittal contour and posterior intervertebral disc space height following posterior lumbar interbody fusion (PLIF) or transforaminal lumbar interbody fusion (TLIF) was conducted using vertical cages (VCs), wedged structural allograft (WSA), and threaded cylindrical cages (TCCs). Forty-nine consecutive patients (59 spinal segments) were evaluated following single- or two-level interbody fusion with either stand-alone TCCs (n = 18 levels), WSA with posterior transpedicular compression instrumentation (n = 25 levels), or VCs with posterior transpedicular compression instrumentation (n = 16 levels). Standing lumbar radiographs were measured by two independent observers preoperatively, immediately postoperatively (within 1 week), at 6-week follow-up (range 4-8 weeks), and postoperatively (at 1-year follow-up) for segmental lordosis at each level undergoing posterior interbody arthrodesis and posterior intervertebral disc space height to assess indirect nerve root decompression. At the 1-year follow-up, postoperative lordosis was improved in the VC group (+5.3 degrees ; P < 0.005), whereas it decreased in the WSA group (-0.9 degrees ; P = 0.407) and TCC group (-3.5 degrees ; P < 0.005). The posterior disc space height decreased in the VC group (-0.5 mm; P = 0.109), whereas it increased for both the WSA group (+1.2 mm; P = 0.05) and the TCC group (+0.8 mm; P = 0.219). PLIF with stand-alone TCC and PLIF (or TLIF) with WSA and posterior transpedicular instrumentation results in an increased posterior disc height and thus improved indirect nerve root decompression. PLIF (or TLIF) with VC and posterior transpedicular instrumentation results in an overall decrease in posterior disc height. However, TCC and WSA resulted in a loss of lumbar lordosis, whereas VC resulted in an increase in lumbar lordosis.

Answer to the ?Letter to the editor? of Dr. Wolfgang B�rm

Dear Dr Borm, We would like to thank you for your comments that show you took great interest in our paper. When the first report on stand-alone lumbar cages came out, this method was obviously hailed as the answer to treatment of axial low back pain. However, further follow-ups and critical analyses showed that stand-alone lumbar interbody cages subsided, did not restore anatomic lumbar lordosis and had pseudarthroses. Some authors recommended that lumbar cages should not be inserted into the lumbar spine in a stand-alone fashion. However improved cage technology and further refinements to the surgical techniques have ensured that lumbar cages are here to stay. The biomechanics in the cervical spine are somewhat different and one would expect to see fusion more easily in the cervical spine than in the lumbar spine as simple cervical discectomy leads to fusion in a significant number of cases. Artificial discs that are supposed to maintain motion in the cervical spine have also been associated with spontaneous fusion in a number of cases. You criticise our paper because we do not give any clear conclusions as to the use of stand-alone cages in the cervical spine. As we have already written, our series was small and specifically studied subsidence of the cervical cages inserted in a stand-alone fashion even though the outcome of our patients was favourable in most cases. At the time of writing the paper, we did not have any of the most recently available literature on cage subsidence. A review of the most recent literature on the subject (including the two papers you quote) shows that it is recognized that cage subsidence may occur after the insertion of stand-alone cervical cages, and we are happy to have been the first ones to have brought this up in the form of a warning (20% rate of cage subsidence in the Payer series, 35% rate in the Thome series, 50% rate in the Kanayama series, 62% rate in our series) [1, 2, 3]. Payer is currently changing the size of its cage and its design because of the high rate of subsidence. The available literature on anterior cervical discectomy with or without fusion mostly reports excellent clinical results with resolution of the symptoms. The purpose of adding an instrumentation or interbody cage after anterior discectomy is threefold: to achieve a better fusion rate, restore anatomic segmental lordosis and restore intervertebral disc height. The findings of all the available literature and our series showed that no segmental motion was present on the flexion-extension X-rays after the use of stand-alone cervical cages. So we can therefore assume that stand-alone cervical cages fuse in the large majority of cases, as we were able to assume in our series. As far as segmental lordosis is concerned, there is obviously not enough information in the literature, and it is possible to debate the value of cylindrical or rectangular cages that do not restore anatomic lordosis. Lastly, subsidence of stand-alone cervical cages is now a well recognized problem in the literature. This rate of subsidence does not seem to affect the initial clinical result although one of the targets of the cage (restoration of disc space height) is not achieved in a large number of cases. However, all these clinical results are short-term follow-up results, and anterior discectomy alone or non-instrumented anterior fusion with dowel graft led to segmental kyphosis and loss of height in a significant number of cases. Such adverse effects were sometimes only observed after one or two decades after the initial surgery. Therefore we do not condemn cage technology in the cervical spine, but maintain our initial warning that many available stand-alone cervical cages may be associated with subsidence, as is now well documented in the literature. Long-term follow-up of such subsidence should determine whether this has a clinical impact on the patient’s symptoms and adjacent segments of the cervical spine. Lastly, I would like to urge you not to feel guilty about your previous use of anterior cervical cages. I suggest you document your cases and look at the clinical outcome of your patients, as well as the radiographic anatomic parameters of segmental lordosis, intervertebral disc space height and cage subsidence.

Containment and stabilization of bone graft in anterior lumbar interbody fusion: the role of the Hartshill Horseshoe cage.

The Hartshill Horseshoe cage is a titanium implant that is inserted after removal of the disc in anterior lumbar interbody fusion. The authors use corticocancellous iliac crest graft, which is contained within the confines of the implant. The cage and the motion segment are stabilized by inserting screws into the adjacent vertebral bodies through holes in the implant. Between 1995 and 1997, 27 patients had this implant inserted. Minimum follow-up was 2.1 years (mean: 2.9 years). Patients were assessed using the Oswestry disability index, a core set of six questions, a pain drawing, and psychometrically using the Zung Depression Scale and the Modified Somatic Perception Questionnaire. The patients' subjective assessment was also obtained. Twenty-one patients (77.8%) improved significantly on the Oswestry disability index and 22 patients (81.5%) improved by subjective assessment using the "core set" of six questions. There was no evidence of pseudarthrosis, loosening, or osteolysis around the implant or the screws. The cage prevents graft extrusion, collapse, or sinkage through the endplates. The normal lumbar lordosis is restored and, by restoring normal intervertebral disc space height, the Horseshoe opens up the neural foraminae. This cage stabilizes the motion segments and secures the graft, preventing micromotion at the graft vertebral body interface and providing a conducive environment for fusion.

A Pathologic Study of Discs in the Elderly

Eighty-eight autopsy specimens from L4-5 lumbar discs of cadavers with an average age of 77.6 years were examined radiologically and histopathologically. They were classified into three groups by the height of intervertebral disc space: slightly degenerated (57 cases), moderately degenerated (25 cases), and severely degenerated (6 cases). Cartilaginous end-plate rupture was found most commonly in the severely degenerated group. Reverse orientation of the anulus fibrosus was found in one third of all specimens. End-plate was separated from vertebral body in 45 cases (51.1%) of 88 specimens. From the findings it is suggested that the end-plate is avulsed from the vertebral body under the precondition of separation and then herniated with anchoring anulus fibrosus. This type of herniation occurs more often than herniation of the nucleus pulposus in the elderly.

A Pathologic Study of Discs in the Elderly

Eighty-eight autopsy specimens from L4-5 lumbar discs of cadavers with an average age of 77.6 years were examined radiologically and histopathologically. They were classified into three groups by the height of intervertebral disc space: slightly degenerated (57 cases), moderately degenerated (25 cases), and severely degenerated (6 cases). Cartilaginous end-plate rupture was found most commonly in the severely degenerated group. Reverse orientation of the anulus fibrosus was found in one third of all specimens. End-plate was separated from vertebral body in 45 cases (51.1%) of 88 specimens. From the findings it is suggested that the end-plate is avulsed from the vertebral body under the precondition of separation and then herniated with anchoring anulus fibrosus. This type of herniation occurs more often than herniation of the nucleus pulposus in the elderly.

Disc Degeneration in the Thoracolumbar Junctional Region

Disc dimensions and lengths of spondylophytes in the thoracolumbar junctional region (T 10-L 1) of 37 male cadaveric spines were measured from conventional radiographs. The disc degeneration was assessed by discography. The surface areas of the spondylophytes at vertebral body margins were recorded directly from the bones of 24 of the spines. Disc degeneration and the largest spondylophytes at corresponding levels measured from radiographs were related at T10-11 and at T11-12 (r = 0.41 and r = 0.43; p less than 0.01), but not at T12-L1 (r = 0.14). In the individual discs, however, only large spondylophytes in radiographs (actual length over 4 mm) were related to signs of disc degeneration. In addition, 'traction spurs' and Scheuermann's changes were more often associated with severe disc degeneration than 'claw-type' spondylophytes. The intervertebral disc space height correlated poorly with disc degeneration except, to some extent, at T11-12. Thus, the assessment of disc degeneration from conventional radiographs seems unreliable at this region of the spine.