Thorsten Ernstberger

Artifacts in spine magnetic resonance imaging due to different intervertebral test spacers: an in vitro evaluation of magnesium versus titanium and carbon-fiber-reinforced polymers as biomaterials.

IntroductionIntervertebral spacers are made of different materials, which can affect the postfusion magnetic imaging (MRI) scans. Susceptibility artifacts especially for metallic implants can decrease the image quality. This study aimed to determine whether magnesium as a lightweight and biocompatible metal is suitable as a biomaterial for spinal implants based on its MRI artifacting behavior.Materials and methodsTo compare artifacting behaviors, we implanted into one porcine cadaveric spine different test spacers made of magnesium, titanium, and carbon-fiber-reinforced polymers (CFRP). All test spacers were scanned using two T1-TSE MRI sequences. The artifact dimensions were traced on all scans and statistically analyzed.ResultsThe total artifact volume and median artifact area of the titanium spacers were statistically significantly larger than magnesium spacers (p < 0.001), while magnesium and CFRP spacers produced almost identical artifacting behaviors (p > 0.05).ConclusionOur results suggest that spinal implants made with magnesium alloys will behave more like CFRP devices in MRI scans. Given its osseoconductive potential as a metal, implant alloys made with magnesium would combine the advantages to the two principal spacer materials currently used but without their limitations, at least in terms of MRI artifacting.

The interobserver-validated relevance of intervertebral spacer materials in MRI artifacting

Intervertebral spacers for anterior spine fusion are made of different materials, such as titanium, carbon or cobalt-chrome, which can affect the post-fusion MRI scans. Implant-related susceptibility artifacts can decrease the quality of MRI scans, thwarting proper evaluation. This cadaver study aimed to demonstrate the extent that implant-related MRI artifacting affects the post-fusion evaluation of intervertebral spacers. In a cadaveric porcine spine, we evaluated the post-implantation MRI scans of three intervertebral spacers that differed in shape, material, surface qualities and implantation technique. A spacer made of human cortical bone was used as a control. The median sagittal MRI slice was divided into 12 regions of interest (ROI). No significant differences were found on 15 different MRI sequences read independently by an interobserver-validated team of specialists (P>0.05). Artifact-affected image quality was rated on a score of 0-1-2. A maximum score of 24 points (100%) was possible. Turbo spin echo sequences produced the best scores for all spacers and the control. Only the control achieved a score of 100%. The carbon, titanium and cobalt-chrome spacers scored 83.3, 62.5 and 50%, respectively. Our scoring system allowed us to create an implant-related ranking of MRI scan quality in reference to the control that was independent of artifact dimensions. The carbon spacer had the lowest percentage of susceptibility artifacts. Even with turbo spin echo sequences, the susceptibility artifacts produced by the metallic spacers showed a high degree of variability. Despite optimum sequencing, implant design and material are relevant factors in MRI artifacting.

Implant detectibility of intervertebral disc spacers in post fusion MRI: evaluation of the MRI scan quality by using a scoring system—an in vitro study

IntroductionIntervertebral spacers for anterior spine fusion are made of different materials, such as titanium and cobalt chromium alloys and carbon fiber-reinforced polymers. Implant-related susceptibility artifacts can decrease the quality of MRI scans. The aim of this cadaveric study was to demonstrate the extent that implant-related MRI artifacting affects the postfusion differentiation of determined regions of interest (ROIs).MethodsIn six cadaveric porcine spines, we evaluated the postimplantation MRI scans of a titanium, cobalt-chromium and carbon spacer that differed in shape and surface qualities. A spacer made of human cortical bone was used as a control. A defined evaluation unit was divided into ROIs to characterize the spinal canal as well as the intervertebral disc space. Considering 15 different MRI sequences read independently by an interobserver-validated team of specialists the artifact-affected image quality of the median MRI slice was rated on a score of 0–3. A maximum score of 18 points (100%) for the determined ROIs was possible.ResultsTurbo spin echo sequences produced the best scores for all spacers and the control. Only the control achieved a score of 100%. For the determined ROI maximum scores for the cobalt-chromium, titanium and carbon spacers were 24%, 32% and 84%, respectively.ConclusionBy using favored T1 TSE sequences the carbon spacer showed a clear advantage in postfusion spinal imaging. Independent of artifact dimensions, the scoring system used allowed us to create an implant-related ranking of MRI scan quality in reference to the bone control.

Postfusion magnetic resonance imaging artifacts caused by a titanium, cobalt-chromium-molybdenum, and carbon intervertebral disc spacer.

Intervertebral spacers for anterior spine fusion are made of different materials, such as titanium and CoCrMo-alloys or carbon fiber reinforced polymers (CFRP). Implant-related susceptibility artifacts can decrease the quality of magnetic resonance imaging (MRI) scans. This cadaveric study aimed to demonstrate the extent that implant-related MRI artifacting affects the postfusion differentiation of the spinal canal (SC) and intervertebral disc space (IDS). In 6 cadaveric porcine spines, we evaluated the postimplantation MRI scans of a titanium, CoCrMo-spacer and CFRP-spacer that differed in shape and surface qualities. A spacer made of human cortical bone was used as a control. A defined evaluation unit was divided into regions of interest (ROI) to characterize the SC and IDS. Considering 15 different MRI sequences read independently by an interobserver-validated team of specialists artifact-affected image quality of the median MRI slice was rated on a score of 0-1-2-3. A maximum score of 15 points for the SC and 9 points for the IDS (100%) was possible. Turbo spin echo sequences produced the best scores for both spacers and the control. Only the control achieved a score of 100%. For the IDS the CoCrMo-spacer, titanium and CFRP-spacer maximally scored 0%, 0% and 74%, for the SC 60%, 80% and 99%, respectively. By using favored T1 TSE sequences the CFRP-spacer represented clear advantages in postfusion spinal imaging. Independent of artifact dimensions the used scoring system allowed us to create an implant-related ranking of MRI scan quality in reference to the bone control.

Centralization of the femoral component in cemented hip arthroplasty using guided stem insertion

Abstract In order to improve the positioning of the stem within the femur, to centralize it within the cement and to achieve a complete and homogeneous cement mantle, a new hip endoprosthesis with guided stem insertion was developed. The femoral component has a longitudinal channel that takes up a guidewire which directs it during insertion into the centre. The guidewire is attached to the cement stopper which is positioned in the marrow cavity before applying the bone cement. The first 100 endoprostheses of this type with an observation period of at least 6 years were assessed radiologically and clinically. The clinical evaluation according to the hip scores of Merle d’Aubigne and Harris revealed a marked improvement between preoperative and postoperative values for all criteria. On radiological assessment 94% of the stems had a neutral position within the femur; 98% of the stems were found to be ideally centred within the cement distally, 80% distally and proximally; 74% of the cement cuffs had a complete and homogeneous cement layer between 2 and 5 mm medially and laterally, while 25% had partially a dimension of more than 5 mm, predominantly proximally. In only 3 cases was one part of the cement mantle found to be less than 2 mm. The radiological follow-up was also documented according to the delineated zones of Gruen. It revealed zonal radiolucent lines in 15 cases, combined in 11 cases with reactive lines, never extending up to 4 zones out of 14. Five prostheses had subsided moderately between 2 and 3 mm, and only one 8 mm. None of these radiological signs was associated with clinical symptoms. There were five cement fractures. Two stems were symptomatic, radiologically loose and revised. Beside these two cases of aseptic loosening there was one septic case, so that in total 97% of the implants are still functioning well.

Intervertebral test spacers and postfusion MRI artifacting: A comparative in vitro study of magnesium versus titanium and carbon fiber reinforced polymers as biomaterials

Intervertebral spacers are made of different materials, which can effect the postfusion magnetic imaging (MRI) scans. Susceptibility artifacts specially for metallic implants can decrease the image quality. This study aimed to determine whether magnesium as a lightweight and biocompatible metal is suitable as a biomaterial for spinal implants based on its MRI artifacting behavior. To compare artifacting behaviors, we implanted into one porcine cadaveric spine different test spacers made of magnesium, titanium and CFRP. All test spacers were scanned using 2 T1-TSE MRI sequences. The artifact dimensions were traced on all scans and statistically analyzed. The total artifact volume and median artifact area of the titanium spacers were statistically significantly larger than magnesium spacers (p < 0.001), while magnesium and CFRP spacers produced almost identical artifacting behaviors (p > 0.05). Our results suggest that spinal implants made with magnesium alloys will behave more like CFRP devices in MRI scans.