Bone defects are repaired by enhanced osteogenic activity of the induced membrane: a case report and literature review

Background The induced membrane technique (IMT) is an effective strategy to repair bone defects and involves a two-stage set of surgical procedures. Although the IM has osteogenic activity, bone grafting is necessary in standard IMT. Bone defects repaired completely by osteogenic activity of the IM alone without bone grafts are rare. Case presentation We present a case of infected fractures and bone defects of the ulna and radius treated with IMT. After the first stage using polymethylmethacrylate (PMMA) beads, X-rays showed that new callus developed after 2 to 4 months, and the defects were repaired completely by 5 months. We also present a literature review on spontaneous osteogenesis of the IM in patients. Conclusions We present a case of infected ulnar and radial bone defects that healed by 5 months after the first stage of the IMT using a PMMA spacer. This finding suggests that local associated inflammatory reactions and bone tissue might enhance the osteogenic activity of the IM, causing spontaneous healing of bone defects. This appears to be the first such case reported in the literature.

PROPERTIES OF THE HAND MIXED PMMA BASED CEMENT FOR BIOMEDICAL APPLICATIONS

This paper presents insights into the recent trends in development of PMMA bone cements considering their improvements for applications in clinical practice. Experimental investigation of hand mixed PMMA bone cement was realized, aiming to determine mechanical behavior of the material during nanoindentation. Standard multi-cycle indentation tests were applied, with maximum load of 15 N and immediate load relaxation down to 5 N, with sharp Vickers indenter. Indentation curves were obtained and analyzed as the function of the normal load vs penetration depth, for three different numbers of cycles (100, 200 and 300 cycles) and different indentation positions on the sample surface. Resulting indents were analyses from the aspect of the final material structure and its subsequent mechanical behavior. Agglomeration of PMMA beads was observed in the final hardened cement in some surface zones, thus indicating non-homogenous material structure. Changes in the number of cycles did not show significant influence on the mechanical response of the sample. However, sites with agglomerated PMMA beads showed significantly different indentation curves, thus indicating that hand-mixing of PMMA bone cement can produce non-homogenous final material structure.

THE EFFECTS OF GENTAMICIN-IMPREGNATED COLLAGEN SPONGE VERSUS GENTAMICIN-IMPREGNATED POLYMETHYLMETHACRYLATE BEADS IN PATIENTS WITH OSTEOMYELITIS

Objective: The usage of antibiotic-impregnated polymethylmethacrylate (PMMA) beads is regarded as the gold standard for local antibiotic delivery. However, the relatively new antibiotic-impregnated collagen sponge has multiple advantages over it. The objective of this study is to compare the measurable effects between gentamicin-impregnated collagen sponge and gentamicin-impregnated (PMMA) beads in patients with osteomyelitis.Methods: This is a case–control study which involved 60 patients who were diagnosed with osteomyelitis between January 2014 and June 2015, and underwent first surgical debridement with application of either gentamicin-impregnated collagen sponge (n=28) or gentamicin-impregnated PMMA beads (n=32). The numbers of debridement, trend of blood parameters, duration of hospitalization, and total duration of systemic antibiotic therapy needed to be completed were reviewed from the patients’ file.Results: A total of 53 patients of 60 were diagnosed with osteomyelitis of the lower limbs, while the remaining seven were involving the upper limbs. The gentamicin-impregnated collagen sponge group has significant lower reoperative rate (p<0.05) and also significant reduction of total white cell count in 6 weeks (p<0.05). The two groups showed no statistical difference in regard of duration of hospital admission, duration of systemic antibiotic therapy completed, and the reduction of C-reactive protein at 6 weeks post-debridement.Conclusion: This study reiterates the efficacy of gentamicin-impregnated collagen sponge that results in lower reoperative rate as compared to conventional gentamicin-impregnated PMMA beads.

Image-based high strain rate testing of orthopaedic bone cement

Bone cement is widely used for the fixation of orthopaedic implants. It is a multi-component material that consists of a PMMA base with a small proportion of (usually ceramic) radiopacifier to enable the cement to be observed by X-ray. Bone cement is formed through an exothermic reaction in which a powder of pre-polymerised beads of PMMA reacts with MMA monomer. The resulting polymer microstructure consists of PMMA beads in a matrix of newly formed PMMA containing radiopacifier particles. In service, bone cement can experience deformation over a range of strain rates, from the lower end in normal gait to 100s of s-1 in the case of falls or impacts. In the current study, it is hypothesised that the response of homogeneous (clear) PMMA to high strain rates will be different to that of bone cement due to the microstructural differences. There have been very few studies on this topic in the past, mostly because of the difficulty involved in adapting the Hopkinson bar protocol to this material, particularly for dynamic tension. The objective of this paper is to present new results on the stiffness and damping of bone cement at strain rates in the range of 100 s-1, and to compare the data with that obtained on clear PMMA. The technique employed here to measure the mechanical properties of both commercial grade PMMA and bone cement is a new image-based DMTA method recently proposed by Seghir and Pierron (Seghir, Pierron, Exp. Mech., 2018). This allows for the measurement of the complex modulus over a range of temperatures and strain rates (100s of s-1). The method relies on imaging the deformation of the specimen bearing a printed grid using a Shimadzu HPV-X camera at up to 5 million frames per second. This allows for the time-resolved displacements to be measured, leading to fields of strain and acceleration, the latter being used to derive stress information to build up stress-strain curves. The methodology is described in more details in www.photodyn.org.