Spine imaging after lumbar disc replacement: pitfalls and current recommendations

Effect of patient-specific factors on regeneration in lumbar spine at healthy disc and total disc replacement. Computer simulation

BACKGROUND AND OBJECTIVE

Degenerative diseases of the spine have a negative impact on the quality of life of patients. This study presents the results of numerical modelling of the mechanical behaviour of the lumbar spine with patient-specific conditions at physiological loads. This paper aims to numerically study the influence of degenerative changes in the spine and the presence of an endoprosthesis on the creation of conditions for tissue regeneration.

METHODS

A numerical model of the mechanical behaviour of lumbar spine at healthy and after total disc replacement under low-energy impacts equivalent to physiological loads is presented. The model is based on the movable cellular automaton method (discrete elements), where the mechanical behaviour of bone tissue is described using the Biot poroelasticity accounting for the presence and transfer of interstitial biological fluid. The nutritional pathways of the intervertebral disc in cases of healthy and osteoporotic bone tissues were predicted based on the analysis of the simulation results according to the mechanobiological principles.

RESULTS

Simulation of total disc replacement showed that osseointegration of the artificial disc plates occurs only in healthy bone tissue. With total disc replacement in a patient with osteoporosis, there is an area of increased risk of bone resorption in the near-contact area, approximately 1 mm wide, around the fixators. Dynamic loads may improve the osseointegration of the implant in pathological conditions of the bone tissue.

CONCLUSIONS

The results obtained in the case of healthy spine and osteoporotic bone tissues correspond to the experimental data on biomechanics and possible methods of IVD regeneration from the position of mechanobiological principles. The results obtained with an artificial disc (with keel-type fixation) showed that the use of this type of endoprosthesis in healthy bone tissues allows to reproduce the function of the natural intervertebral disc and does not contribute to the development of neoplastic processes. In the case of an artificial disc with osteoporosis of bone tissues, there is a zone with increased risk of tissue resorption and development of neoplastic processes in the area near the contact of the implant attachment. This circumstance can be compensated by increasing the loading level.

A cross-sectional analysis of 284 complications for lumbar disc replacements from medical device reports maintained by the United States Food and Drug Administration

BACKGROUND CONTEXT

Lumbar disc replacement (LDR) is a motion sparing procedure for degenerative disc disease. When compared to lumbar fusion, this procedure may reduce complications, reoperations, operative time, and length of stay. However, the extent of overall complications related to LDR has not been well defined in the literature.

PURPOSE

Demonstrate the complication profile of popular LDR implants reported to the Food and Drug Administration (FDA).

STUDY DESIGN

Retrospective database review.

PATIENT SAMPLE

Nationwide database of reported complications related to LDR products from patients throughout the country.

OUTCOME MEASURES

Complications related to LDR.

METHODS

Data files from January 1, 2004 to April 1, 2021 were queried using the publicly accessible Manufacturer and User Facility Device Experience (MAUDE) database and Alternative Summary Reporting program. Three LDR ("Charité," "Prodisc-L," and "Activ L") products were analyzed for complications. Data collected included the date the reports were received by the FDA, the type of complication, complication event description, and the source of the report. The complication event description was utilized to determine the completion of the investigation. Entries with insufficient information were excluded. Complications were further divided into two categories, device and non-device related.

RESULTS

A total of 431 complication entries were found between January 1, 2004, and April 1, 2021. After screening for duplicates and events with insufficient information there were 284 total complications. The total complications were then further divided into implant and non-implant related. The five most common overall complications were lumbar pain (49 entries, 17.25%), migration of implant (42 entries, 14.78%), polyethylene dislodged (37 entries, 13.0%), insertion of device problem (37 entries, 13.0%), device handling problem (12 entries, 4.22%). The most common implant related complication, along with the number of MAUDE entries for each implant was migration of implant for Charité (n=6); Migration of implant for ActivL (n=24); Polyethylene dislodged for ProdiscL (n=32). Of the 284 total complications analyzed, 86 (30.28%) of the entries were deemed "investigation completed." The majority of reports were submitted from the manufacturer and company representative (66.2%, 14.8 % respectively). There were no entries related to LDR within the Alternative Summary Reporting search.

CONCLUSIONS

This study outlined the complications of LDR implants from the MAUDE database which have not always been highlighted in previously published studies. The findings of this study provide insight into the potential targets for improvement in future LDR design and surgical techniques to reduce complications and ensure the safe utilization of these implants.

Bilateral femoral neck fractures after an epileptic attack: A case report

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Bilateral femoral neck fractures may occur following grand mal epilepsy attack in young patients.

Introduction

Bilateral femoral neck fractures can occur due to high- or low-energy trauma, in the presence of various predisposing factors, such as osteoporosis, renal osteodystrophy, hypocalcemic seizures, primary or metastatic tumors, electroconvulsive therapy, epileptic seizures, and hormonal disorders.

Presentation of case

This report presents a case of bilateral femoral neck fractures that occurred during an epileptic attack in a 24-year-old male with mental retardation. His complaints had started after a grand mal epileptic attack 10 days earlier. Bilateral displaced femoral neck fractures (Garden type 4) were seen in lateral radiographs of both hips. The patient was operated on urgently, with closed reduction, three stainless steel cannulated screws, and internal fixation applied to both hips. At postoperative week 12, solid joining was achieved and active walking with complete loading was started.

Discussion

Bilateral femoral neck fractures can occur following a grand mal epilepsy attack in young patients. The use of antiepileptic drugs can also lead to the development of pathological fractures by reducing bone mineral density.

Conclusion

Femoral neck fractures should be suspected in patients with epilepsy who present with severe pain in both hips and an inability to walk. Stainless steel implants can be used for treatment. The viability of the femoral head should be evaluated by scintigraphy. Bone mineral density should be monitored in patients who use anti-epileptic drugs, and internal fixation is preferred in the treatment of femoral neck fractures.

Biomechanical effects of semi-constrained integrated artificial discs on zygapophysial joints of implanted lumbar segments

This study aimed to optimize the design and application of semi-constrained integrated artificial discs (SIADs) using a finite element (FE) analysis following implantation, wherein the zygapophysial joints of the segment were biomechanically reconstructed. An FE model of the L4-L5 segment was constructed. Variations in the stresses on the discs and zygapophysial joints were observed during 5° anteflexion, 5° extension and 5° rotation under the 400-N applied axial load. Stresses and load translation analyses of the discs and zygapophysial joints were conducted during anteflexion, extension and rotation under the 400-N applied axial load. Following implantation of the lumbar segments, the stresses on the SIAD zygapophysial joints were not significantly different from those of physiological discs during anteflexion, and these were both marginally greater compared with those of non-constrained artificial discs (NADs). During extension, the increase in the stress on the SIAD zygapophysial joints was less than that on NAD zygapophysial joints. Stresses on the NAD zygapophysial joints were higher than those on SIAD and physiological discs during rotation. The stress on the SIAD zygapophysial joints was not significantly different from that on physiological discs during rotation. For SIADs and NADs, the stresses on the zygapophysial joints and the displacements of the discs were greater compared with those of the physiological discs during extension. The SIADs affected the variations in the stresses on the implanted segment more than the NADs, and the SIADs protected the zygapophysial joints of the implanted segment to a higher degree than the NADs.

Magnetic resonance imaging evaluation after implantation of a titanium cervical disc prosthesis: a comparison of 1.5 and 3 Tesla magnet strength

Purpose

Cervical disc prostheses induce significant amount of artifact in magnetic resonance imaging which may complicate radiologic follow-up after surgery. The purpose of this study was to investigate as to what extent the artifact, induced by the frequently used Discover^® cervical disc prosthesis, impedes interpretation of the MR images at operated and adjacent levels in 1.5 and 3 Tesla MR.

Methods

Ten subsequent patients were investigated in both 1.5 and 3 Tesla MR with standard image sequences one year following anterior cervical discectomy with arthroplasty.

Outcome measures

Two neuroradiologists evaluated the images by consensus. Emphasis was made on signal changes in medulla at all levels and visualization of root canals at operated and adjacent levels. A “blur artifact ratio” was calculated and defined as the height of the artifact on T1 sagittal images related to the operated level.

Results

The artifacts induced in 1.5 and 3 Tesla MR were of entirely different character and evaluation of the spinal cord at operated level was impossible in both magnets. Artifacts also made the root canals difficult to assess at operated level and more pronounced in the 3 Tesla MR. At the adjacent levels however, the spinal cord and root canals were completely visualized in all patients. The “blur artifact” induced at operated level was also more pronounced in the 3 Tesla MR.

Conclusions

The artifact induced by the Discover^® titanium disc prosthesis in both 1.5 and 3 Tesla MR, makes interpretation of the spinal cord impossible and visualization of the root canals difficult at operated level. Adjusting the MR sequences to produce the least amount of artifact is important.