A novel radiopaque tissue marker for soft tissue localization and in vivo length and area measurements

Intrinsically radiopaque biomaterial assortments: a short review on the physical principles, X-ray imageability, and state-of-the-art developments

X-ray attenuation ability, otherwise known as radiopacity of a material, could be indisputably tagged as the central and decisive parameter that produces contrast in an X-ray image. Radiopaque biomaterials are vital in the healthcare sector that helps clinicians to track them unambiguously during pre and post interventional radiological procedures. Medical imaging is one of the most powerful resources in the diagnostic sector that aids improved treatment outcomes for patients. Intrinsically radiopaque biomaterials enable themselves for visual targeting/positioning as well as to monitor their fate and further provide the radiologists with critical insights about the surgical site. Moreover, the emergence of advanced real-time imaging modalities is a boon to the contemporary healthcare systems that allow to perform minimally invasive surgical procedures and thereby reduce the healthcare costs and minimize patient trauma. X-ray based imaging is one such technologically upgraded diagnostic tool with many variants like digital X-ray, computed tomography, digital subtraction angiography, and fluoroscopy. In light of these facts, this review is aimed to briefly consolidate the physical principles of X-ray attenuation by a radiopaque material, measurement of radiopacity, classification of radiopaque biomaterials, and their recent advanced applications.

Visualization of implanted mesh in the pelvic reconstructive surgery using an X-ray-detectable thread

PURPOSE

Visualization of the implanted mesh after a pelvic floor repair surgery is important for evaluating mesh-related complications. We made an X-ray-detectable mesh and studied the histocompatibility and toxicity of it.

METHODS

A thin barium sulfate thread was weaved on a traditional polypropylene mesh to make it X-ray detectable. The cytotoxicity of the mesh was tested by the MTT assay on L929 cell line. The histocompatibility and toxicity of mesh were evaluated in rabbits. Meshes were first implanted intraperitoneally. On postoperative day 7, bloods were tested to estimate the acute toxicity of meshes. After 6 months, rabbits were sacrificed and local inflammatory reaction and tissue regeneration at implantation sites were estimated by the HE stain and Masson stain. In addition, CT scans were performed after surgeries to display the location and shape of implanted meshes.

RESULTS

Compared to the polypropylene mesh group, no significant difference was observed in the X-ray-detectable mesh group on both in vitro cytotoxicity and in vivo acute and chronic toxicity. The amounts of extra cellular matrix between two groups did not differ. Through CT scan and 3D remodeling, the barium sulfate thread clearly revealed the position and shape of the X-ray-detectable mesh, whereas the traditional mesh was invisible under CT scan.

CONCLUSION

Adding a thin barium sulfate thread on the polypropylene mesh does not change its histocompatibility or toxicity in rabbit model. The barium sulfate thread can effectively show the location and shape of implanted mesh under CT scan.

Variability of glenohumeral positioning and bone-to-tendon marker length measurements in repaired rotator cuffs from longitudinal computed tomographic imaging

Background

To address the need for more objective and quantitative measures of tendon healing in research studies, we intend to use computed tomography (CT) with implanted radiopaque markers on the repaired tendon to measure tendon retraction following rotator cuff repair. In our small prior study, retraction at 1-year follow-up averaged 16.1± 5.3 mm and exceeded 10.0 mm in 12 of 13 patients, and thus tendon retraction appears to be a common clinical phenomenon. This study's objectives were to assess, using 5 longitudinal CT scans obtained over 1 year following rotator cuff repair, the variability in glenohumeral positioning because of pragmatic variations in achieving perfect arm repositioning and to estimate the associated measurement variability in bone-to-tendon marker length measurements.

Methods

Forty-eight patients underwent rotator cuff repair with intraoperative placement of radiopaque tendon markers at the repair site. All patients had a CT scan with their arms at the side on the day of surgery and at 3, 12, 26, and 52 weeks postoperatively. Glenohumeral position (defined by the orientation and distance of the humerus with respect to the scapula) and bone-to-tendon marker lengths were measured from each scan. Within-patient variation in glenohumeral position measurements was described by their pooled within-patient standard deviations (SDs), and variation in bone-to-tendon marker lengths by their standard errors of measurement (SEMs) and 95% confidence level minimally detectable distances (MDD₉₅) and changes (MDC₉₅).

Results

The mean glenohumeral orientation from the 5 longitudinal CT scans averaged across the 48 patients was 12.6° abduction, 0.4° flexion, and –0.1° internal rotation. Within-patient SDs (95% confidence intervals) of glenohumeral orientation were 3.0° (2.7°-3.4°) in extension/flexion, 5.2° (4.6°-5.8°) in abduction/adduction, and 8.2° (7.3°-9.2°) in internal/external rotation. The SDs of glenohumeral distances were less than 1 mm in any direction. The estimated SEMs of bone-to-tendon lengths were consistent with a common value of 2.4 mm for any of the tendon markers placed across the repair, with MDD₉₅ of 4.7 mm and MDC₉₅ of 6.7 mm.

Conclusion

Apparent tendon retraction of 5 mm or more, when measured as the distance from a tendon marker's day of surgery location to its new location on a volumetrically registered longitudinal CT scan, may be considered above the usual range of measurement variation. Tendon retraction measured using implanted radiopaque tendon markers offers an objective and sufficiently reliable means for quantifying the commonly expected changes in structural healing following rotator cuff repair.