Does the Inion OTPS^TM absorbable plating system induce higher foreign-body reaction than titanium implants? An experimental randomized comparative study in rabbits

Abstract

Hardware removal after complete fracture healing is a laborious and traumatic procedure that bears the risks of refracture, infection, and soft tissue damage. Absorbable materials for fracture fixation have the advantage of eliminating the need for removal; however, they may stimulate a considerable inflammatory response. For that reason, we compared in a prospective randomized experimental animal model study the incidence of foreign-body reactions between Inion OTPSTM absorbable plate implants, consisting of carbon trimethylene, L-polylactic acid, and D, L-polylactic acid, and conventional titanium plates. Seventy rabbits were equally divided into two groups. Titanium (Group A) or absorbable (Group B) plates and screws were implanted in the femoral shaft of the rabbits. Wound reaction and laboratory tests including white blood cell count (WBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) values were measured and compared at different time points. Radiographs and histological analysis of tissue samples from all animals were also used to identify potential foreign-body reactions. WBC showed normal values in both groups. In Group A, ESR levels were higher at all time points but CRP values were normalized at 3 weeks postoperatively. In Group B, ESR and CRP levels reached a peak at 3 weeks and were above normal values throughout the whole experiment (p < 0.001). Radiologic examination revealed periosteal thickening and surrounding sclerosis in 23 out of 35 animals of Group B (66%). All Group A animals had normal radiographic findings. Histopathology showed a typical non-specific foreign-body reaction in all animals in Group B (100%) but none in Group A. However, only four of them (11.8%) developed non-infected wound complications and showed significantly elevated CRP and ESR values (p = 0.054). Although Inion OTPSTM Biodegradable Plating System stimulates a foreign-body reaction, only a small but not negligible percentage of almost 12% may lead to wound problems. However, this difference compared to titanium plates was of borderline not statistically significant. Future studies should focus on the development of absorbable implants with improved biocompatibility aiming to further decrease the potential of foreign-body reaction and eliminate the need for additional reoperative procedures.

Stereochemistry Determines Immune Cellular Responses to Polylactide Implants

“…There have been numerous in vivo studies characterizing the host immune cellular response to polylactide (PLA). − While being highly informative, the complexity of the in vivo microenvironment where PLA is implanted could preclude a thorough understanding of mechanistic events therein. To deconvolute in vivo events, several in vitro studies have been undertaken. − However, many prior in vitro models on PLA biocompatibility focused on acidity, based on prior correlation between reduced pH and the adverse immune responses elicited by PLA. , Instead, this study builds on observed alterations in bioenergetics as well as metabolic reprogramming as drivers of adverse immune responses to polyethylene wear particles , after total joint replacements and PLA biomaterials .…”

“…While different immune outcomes occur following surgical implantation of various types of PLA, − this observation has not been previously modeled in vitro. Not only do we model this phenomenon, but we also reveal the biological mechanisms that explain the complex relationships among material stereochemistry, immune responses, bioenergetics, and metabolic reprogramming.…”

Polylactide Degradation Activates Immune Cells by Metabolic Reprogramming

“…However, after surgical implantation, PLA elicits adverse immune responses in up to 44% of human patients, often requiring further interventions 2,3 . In animals, a 66% incidence of excessive fibrosis with capsules from long-term inflammation which significantly limit implant-tissue integration has been reported 4 . PLA degrades by hydrolysis into D- or L-lactic acid, with semi-crystalline PLA degrading slower and tending to contain less D-content than amorphous PLA 1,5 .…”

Breast implant causes allergic contact dermatitis or foreign body reaction?

“…In this specific case there were no clinical (or systemic) signs of infection. However the ESR was slightly increased this can be seen in any inflammatory process, for example a foreign body reaction [ 8 ]. Whenever there would be an acute infection one would expect increased leukocytes, lowered Hb and increased ALAT.…”