Renal osteodystrophy: neurosurgical considerations and challenges

A Review of Strategies to Improve Biomechanical Fixation in the Cervical Spine

STUDY DESIGN

Systematic review.

OBJECTIVES

Review the surgical techniques and construct options aimed at improving the biomechanical strength of cervical constructs.

METHODS

A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A search of the MEDLINE, Embase, and Cochrane Library databases was performed to identify all studies examining biomechanical strategies utilized in the osteoporotic cervical spine. Screening was performed in duplicate for all stages of the review process.

RESULTS

An initial search returned 3887 articles. After deletion of duplications and review of abstracts and full text, 39 articles met inclusion criteria. Overall, the surgical techniques reviewed aimed at obtaining rigid fixation in the setting of poor bone quality, or dispersing the forces at the bone-implant interface. We identified 6 key techniques to improve biomechanical fixation. These include bicortical fixation, appropriate screw selection (size and trajectory), PMMA augmentation, load sharing techniques, consideration of ancillary fixation around the occipitocervical junction, and supplementing the construct with post-operative collar or halo.

CONCLUSION

The summation of the literature highlights a framework of modalities available to surgeons to improve biomechanical fixation in the cervical spine. While these may improve construct strength in the setting of osteoporosis, there is a paucity of evidence available to make recommendations in this patient population.

Complex Revision Surgery for Cervical Deformity or Implant Failure

Postoperative cervical deformity sometimes occurs in the short or long term after primary surgery for cervical disorders related to the degenerative aging spine, neoplastic etiologies, hemodialysis, infection, inflammation, trauma, etc. Cervical kyphosis after posterior decompression surgery, such as laminectomy or laminoplasty, is a common problem for spine surgeons. However, revision surgery for cervical deformity is definitely one of the most challenging areas for spine surgeons. There is no doubt that surgery for cervical deformity carries a high risk of surgery-related complications that might result in aggravation of health-related quality of life. Revision surgery is even more challenging. Hence, spine surgeons need to assess carefully the overall severity of the underlying condition before revision surgery, and try to refine the surgical strategy to secure safe surgery. Needless to say, spine surgeons are now facing great challenges in making spine surgery a much more reliable and convincing entity.

Inpatient Outcomes in Dialysis Dependent Patients Undergoing Elective Cervical Spine Surgery for Degenerative Cervical Conditions

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To evaluate inpatient outcomes in dialysis dependent patients undergoing elective cervical spine surgery.

METHODS

A total of 1605 dialysis dependent patients undergoing elective primary or revision cervical spine surgery for degenerative conditions were identified from the National Inpatient sample from 2002 to 2012 and compared to 1 450 642 nondialysis-dependent patients undergoing the same procedures. The National Inpatient Sample is a de-identified database; thus, no institutional review board approval was needed.

RESULTS

Dialysis dependence was associated with higher inpatient mortality rates (7.5% vs 1.9%; P < .001) as well as both major (17.3% vs 0.6%; P < .001) and minor (36.8% vs 10.5%; P < .001) complication rates as compared with nondialysis-dependent patients. Dialysis-dependent patients had substantially increased mean lengths of stay (9.8 days compared with 2.0 days; P < .001) and total hospital charges ($141 790 compared with $46 562; P < .001).

CONCLUSION

Dialysis-dependence is associated with drastically increased complication rates, risk of mortality, and represent a significant financial and psychosocial burden to patients undergoing elective cervical spine surgery. Both surgeons and patients should be aware of these risks while planning elective surgeries.

Clinical comparison between simple laminectomy and laminectomy plus posterior instrumentation in surgical treatment of cervical myelopathy

BACKGROUND

Posterior stabilization in patients treated with laminectomy for spondylotic cervical myelopathy is still a debate. Despite both being reported in literature by several authors, some controversies still exist. The aim of this study is to compare clinical and radiological outcomes in patients treated with laminectomy or laminectomy with posterior stabilization.

MATERIAL AND METHODS

We retrospectively evaluated 42 patients affected by cervical myelopathy (mean age 70.43 ± 5.03 years), 19 treated with laminectomy (group A) and 23 with laminectomy and posterior instrumentation (group B). Neurological status was assessed with Nurick scale, pain with VAS and radiological parameters with C2-C7 SVA, T1 slope and C2-C7 lordosis, clinical function with modified Japanese Orthopaedic Association score (JOA). Also, surgery time and blood loss were recorded. Student's t test was used for continuous variables, while Kruskal-Wallis test was used for categorical values.

RESULTS

No differences were found in postoperative Nurick scale (p = 0.587), VAS (p = 0.62), mJOA (p = 0.197) and T1 slope (p = 0.559), while laminectomy with fusion showed better postoperative cervical lordosis (p = 0.007) and C2-C7 SVA (p < 0.00001), but higher blood loss (p < 0.00001) and surgical time (p < 0.00001). Both groups showed better Nurick scale (p = 0.00017 for group A and p = 0.00081 for group B), VAS (p = 0.02 for group A and p = 0.046 for group B) and mJOA (p < 0.00001 for both groups) than preoperative values.

CONCLUSIONS

Both treatments are a valuable choice, offering some benefits and disadvantages against each other. Each procedure must be carefully evaluated on the basis of patients' general status, preoperative pain, signs of instability and potential benefits from cervical alignment correction.

Inpatient Outcomes in Dialysis-dependent Patients Undergoing Elective Lumbar Surgery for Degenerative Lumbar Disease

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To evaluate hospital outcomes in dialysis-dependent patients undergoing elective lumbar surgeries.

SUMMARY OF BACKGROUND DATA

Because of their overall poor health status and concomitant comorbidity burden, spinal surgery in dialysis-dependent patients represents a significant challenge to spine surgeons. Large studies evaluating their immediate postoperative outcomes in elective lumbar surgery are lacking.

METHODS

Utilizing the National Inpatient Sample, an estimated 1834 dialysis-dependent patients undergoing elective lumbar spine surgery for degenerative lumbar conditions were compared to an estimated 2,522,594 non-dialysis-dependent patients undergoing the same procedures between 2002 and 2012. Our primary outcomes measures included postoperative complication rates, hospital length of stay, and total hospital costs.

RESULTS

Mean age of dialysis-dependent patients was 64.2 years compared to 59.9 in the non-dialysis-dependent cohort (P < 0.001). Dialysis-dependent patients had substantially higher inpatient mortality rates (1.8% vs 0.1%; P < 0.001), major complication rates (8.1% vs 1.1%; P < 0.001), and an increased need for blood transfusion (18.3% vs 12.5%; P < 0.001). Multivariate analysis revealed that dialysis dependence independently increased odds of in-hospital mortality (odds ratio = 8.30; 95% confidence interval 5.78-11.93; P < 0.001) and odds of a major postoperative complication (odds ratio = 3.63; 95% confidence interval 3.49-3.89; P < 0.001). Dialysis dependence was associated with an increased mean length of stay of 3.3 days (P < 0.001) and a significant increase in hospital costs when stratified by procedure type.

CONCLUSION

Dialysis dependence is associated with poorer immediate postoperative outcomes and increased hospital costs when compared to non-dialysis-dependent patients. In addition, an increased need for postoperative transfusion should be anticipated in this patient population. Further studies are warranted to confirm these findings.

LEVEL OF EVIDENCE

3.

Neurosurgical aspects of dialysis-related spinal amyloidosis: Report of three cases and a review of the literature

BACKGROUND AND PURPOSE

Osteoarticular manifestations of beta-2 microglobulin amyloidosis are often diagnosed in long-term dialyzed patients. However, spinal involvement is rare (10-25% of patients), and generally not associated with neurological deterioration. Compression of the spinal cord or roots is extremely rare, and probably under-recognized.

METHODS

The authors describe three cases of spinal stenosis presenting with neurological signs in long-term dialyzed patients, prospectively collected over 2 years in two different institutions and treated by surgical decompression. In all three cases, the main cause of neural compression was amyloid deposition in the spine, either extradurally in the ligamentum flavum or intradurally.

RESULTS

All patients improved after surgery and did not present any postoperative complications. However, two out of three patients with amyloid in the cervical spine required surgical revision to obtain a satisfactory decompression of the spinal cord.

DISCUSSION

The authors discuss spinal amyloidosis which is a well-known complication of long-term dialysis. However, neurological complications such as spinal cord or radicular symptoms have been rarely reported and, when present in dialyzed patients, are symptoms that are often attributed to other causes. To our knowledge, this is the first case series that demonstrates the relationship between neurological deterioration and amyloid depositions in the spinal canal that occur in long-term dialyzed patients. The prevalence of spinal stenosis related to the presence of amyloid in this specific subgroup of patients is probably underestimated.