Clinical parameters and radiographic resorption of a novel magnesium based bone void filler

Bone voids can present challenging problems for the Orthopaedic surgeon, and are often treated with backfilling followed by structural stabilization. Recently, a magnesium based, and presumably resorbable, bone void filler (BVF) has been developed, but has limited longitudinal clinical data. Therefore, the purpose of this study was to investigate clinically relevant parameters and radiographic resorption characteristics of this novel magnesium based BVF (MgBVF) with long-term clinical data.All patients who underwent surgery by a single surgeon in which MgBVF was utilized from 2019 to 2020 were retrospectively reviewed. Clinical parameters including evidence of infection, wound breakdown, and wound drainage were reviewed. Radiographic resorption, evidence of joint extrusion of BVF, heterotopic ossification, and subsidence was assessed at each post-operative visit. Those with less than 6 month follow up were excluded from radiographic analysis of resorption. Postoperative images at two weeks were compared to each subsequent radiograph during follow up, and reviewed by each of the three authors in blinded fashion. Interval radiographs were assigned a grade of radiographic resorption which corresponded to estimated percent resorption: grade 1 (0-25%), grade 2 (25-50%), grade 3 (50-75%), or grade 4 (75-100%). After 2 weeks, this process was repeated, and both inter and intraobserver reliability scores were calculated.Forty-two patients were identified for clinical review, and 18 for radiographic review. Average length of follow up was 209±113 days. Five patients experienced a postoperative complication: two wound infections, one delayed wound healing, one sterile serous drainage, and one catastrophic failure of the fixation construct. Four patients were noted to have postoperative joint subsidence of 2 mm or less. Average grade of resorption was found to be 1.5 ± 0.8, 1.7 ± 0.9, 2.9 ± 0.9, and 3.6 ± 0.6 at 6 weeks, 3 months, 6 months, and 1 year, respectively (p<0.001). Average kappa (intrarater reliability) was found to be 0.61, 0.41, 0.55, and 0.63 for each time interval, respectively. Interrater reliability increased form 0.19 at 6 weeks to 0.42 at 1 year.This novel MgBVF demonstrates clinically relevant resorption, provides structural support in challenging bone voids, and does not appear to significantly increase risk of complications, setting it apart from previously described BVF's.