An in vivo study to investigate an original intramedullary bone graft harvesting technology

Abstract

Background: Harvesting bone graft (BG) from the intramedullary canal to treat bone defects is largely conducted using the Reamer-Irrigator-Aspirator (RIA) system. The RIA system uses irrigation fluid during harvesting, which may result in washout of osteoinductive factors. Here, we propose a new harvesting technology dedicated to improving BG collection without the potential washout effect of osteoinductive factors associated with irrigation fluid. This novel technology involves the conceptual approach of first aspirating the bone marrow (BM) with a novel aspirator prototype, followed by reaming with standard reamers and collecting the bone chips with the aspirator (reaming-aspiration method, R-A method). The aim of this study was to assess the harvesting efficacy and osteoinductive profile of the BG harvested with RIA 2 system (RIA 2 group) compared to the novel harvesting concept (aspirator + R-A method, ARA group).

Methods: Pre-planning computed tomography (CT) imaging was conducted on 16 sheep to determine the femoral isthmus canal diameter. In this non-recovery study, sheep were divided into two groups: RIA 2 group (n = 8) and ARA group (n = 8). We measured BG weight collected from left femur and determined femoral cortical bone volume reduction in postoperative CT imaging. Growth factor and inflammatory cytokine amounts of the BGs were quantified using enzyme-linked immunosorbent assay (ELISA) methods.

Results: The use of the stand-alone novel aspirator in BM collection, and in harvesting BG when the aspirator is used in conjunction with sequential reaming (R-A method) was proven feasible. ELISA results showed that the collected BG contained relevant amounts of growth factors and inflammatory cytokines in both the RIA 2 and the ARA group.

Conclusions: Here, we present the first results of an innovative concept for harvesting intramedullary BG. It is a prototype of a novel aspirator technology that enables the stepwise harvesting of first BM and subsequent bone chips from the intramedullary canal of long bones. Both the BG collected with the RIA 2 system and the aspirator prototype had the capacity to preserve the BG's osteoinductive microenvironment. Future in vivo studies are required to confirm the bone regenerative capacity of BG harvested with the innovative harvesting technology.

Keywords: Bone graft; Cytokines; Growth factors; Harvesting.

Fig. 1

Depiction of the RIA 2 system for harvesting intramedullary BG (mixture of BM and bone chips) and the novel aspirator prototype for BM harvesting as well as for the R–A method (harvesting bone chips). The RIA 2 system is comprised of a reamer head connected to a drive shaft, which is located in a tube assembly. This construct is connected to an aspiration port, which is connected to the operating room wall vacuum over a graft filter to capture the BG. BG harvesting with the RIA 2 device is a one-step procedure with continuous flow of irrigation fluid during reaming, which allows for evacuation of diluted BM and bone chips. The novel aspirator prototype allows for harvesting BM after opening the bone by intruding the intramedullary canal with a specific cannula under continuous suction. Optionally, after emptying the medullary canal of BM, bone chips can be harvested applying iterative intramedullary reaming and aspiration (R–A method). Partially created with BioRender.com

Fig. 2

Representative images of the BG and bar chart with the determined weight of the harvested BG. Illustrative pictures of the harvested BG after aspiration of the aqueous BG components A. Weight of the harvested BG B. Means ± SD, n = 8

Fig. 3

Reduction of femoral cortical bone volume after BG harvesting based on a comparison of preoperative and postoperative CT scans. Reaming volume was determined to be between + 20% and − 20% from the middle of the bone A. Representative images of cylinder volume, i.e., volume difference due to reaming, indicated by dashed lines, measured as increase in intramedullary volume in pre- and postoperative comparison B. Similar to slightly higher bone volume reduction for the RIA 2 compared to the ARA group C. Means ± SD, n = 8

Fig. 4

Boxplots of BG growth factor amount by harvesting method. Relevant amounts of GFs were detected in BG hard tissue components A and aqueous BG components B in all three harvesting methods. Please note that if less than eight dots per group are shown, missing measurements were below the detection range

Fig. 5

Boxplots of BG total protein amount by harvesting method. In the ARA group with BG harvested by either the aspirator prototype or the R–A method, there was a tendency for higher total protein in the BG hard tissue components A and the aqueous BG components B compared with the BG harvested by the RIA 2 system

Fig. 6

Boxplots of BG inflammatory cytokine amount by harvesting method. In the BG hard tissue components A and aqueous BG components B, a similar tendency toward higher inflammatory cytokine amounts was observed for the ARA group, which includes both the aspirator prototype and the R–A method, compared to the BG harvest obtained with the RIA 2 system. Please note that if less than eight dots per group are shown, missing measurements were above the detection range