A Comparison of the Inflammatory Host Response to Particulate Debris Adjacent to Unlocked and Locked Screws of a Growth Guidance System for Early Onset Scoliosis

Authors

Jeffrey M. Toth, Marquette UniversityFollow
Felix Ankomah, Medical College of Wisconsin
Noriaki Kawakami, Ichinomiya Nishi Hospital
Koki Uno, Kobe Medical Center

Document Type

Article

Publication Date

9-2022

Publisher

Springer

Source Publication

European Spine Journal

Source ISSN

0940-6719

Abstract

Purpose

The SHILLA™ Growth Guidance system is a stainless-steel rod and screw system used for Early Onset Scoliosis which incorporates a unique flanged set screw designed to capture the rod, while allowing it to slide as the patient grows. Concomitant with this design is the potential for generation of wear debris and for an inflammatory host response. We hypothesized that the magnitude of the host response adjacent to the unlocked screws and rods would be greater than the host response to the locked rod/screws.

Methods

Seven tissue samples adjacent to locked (3) and unlocked screws (4) from three SHILLA patients (mean implantation time of 19 post-operative months) with infantile idiopathic scoliosis were obtained as part of an explant analysis protocol during a PMDA-approved clinical trial in Japan. Gross appearance, high-resolution radiographs, and histology were assessed. ISO Standard 10993 Part 6 was used to assess the host response.

Results

All three locked screw had no metallosis. In contrast, metallosis for unlocked screw tissue samples were rated as “ubiquitous” (2/4), “focal” (1/4), or “absent” (1/4). Microscopic metallic debris was found intracellularly and within interstices of fibrous connective tissues more frequently adjacent to unlocked screws compared to locked screws. Cell type and population scoring consistently showed a modestly larger inflammatory response (macrophages) in the unlocked tissue samples.

Conclusions

The peri-prosthetic [sic] tissue response to the unlocked rods/screws had a higher reactivity grade (slight reaction, Δ = 4.0) per ISO 10993 Part 6 compared to the locked screws in three patients with the SHILLA™ Growth Guidance scoliosis system.

Comments

European Spine Journal, Vol. 31, No. 9 (September 2022): 2301-2310. DOI.

Recommended Citation

Toth, Jeffrey M.; Ankomah, Felix; Kawakami, Noriaki; and Uno, Koki, "A Comparison of the Inflammatory Host Response to Particulate Debris Adjacent to Unlocked and Locked Screws of a Growth Guidance System for Early Onset Scoliosis" (2022). Biomedical Engineering Faculty Research and Publications. 666.
https://epublications.marquette.edu/bioengin_fac/666