Mechanical properties of morcellised bone graft with the addition of hydroxyapatite

Alternating Layers of Morselized Allograft and Injectable Ceramic Bone Graft Substitute in Acetabular Reconstruction: A Novel 'Sandwich' Technique

Background

Impaction of morselized allograft is an appealing procedure for addressing the bone defects. However, concerns remain about its suitability for massive defects. We used a novel "sandwich" technique by impacting the morselized allograft in layers with an intervening layer of injectable bone graft substitute for restoring bone defects during acetabular reconstruction in total hip arthroplasties.

Methods

From August 2015 to June 2017, 17 revisions, 4 rerevisions, and 3 complex primary total hip arthroplasties were operated by this novel technique. Postoperatively, serial X-rays were evaluated at regular intervals. Clinical and functional outcomes were assessed by the Harris hip score. To examine if introducing an injectable bone substitute into allograft stock increased its load-bearing capability, simulated mechanical testing using Synbone samples was conducted in the laboratory.

Results

The mean Harris hip score significantly improved from 54.6 preoperatively to 86.8 at the latest follow-up. Graft incorporation was seen in all the cases. There was no evidence of component migration or loosening as compared to the X-rays at 3 weeks and 3 months in all the cases. With revision of component as end point, the survivorship was 100% at 82 months. The mechanical testing reported a higher capability of allograft samples when compared to those without bone substitutes.

Conclusions

Our data confirms that the use of the "sandwich" technique is a reliable option for major acetabular reconstruction. Early weight bearing is a significant value addition, and short-term results confirm good clinical and functional outcome. Longer follow-up is necessary to assess the status of the construct in the long term.

Anabolic and antiresorptive actions of locally delivered bisphosphonates for bone repair: A review

During the last decades, several research groups have used bisphosphonates for local application to counteract secondary bone resorption after bone grafting, to improve implant fixation or to control bone resorption caused by bone morphogenetic proteins (BMPs). We focused on zoledronate (a bisphosphonate) due to its greater antiresorptive potential over other bisphosphonates. Recently, it has become obvious that the carrier is of importance to modulate the concentration and elution profile of the zoledronic acid locally. Incorporating one fifth of the recommended systemic dose of zoledronate with different apatite matrices and types of bone defects has been shown to enhance bone regeneration significantly in vivo. We expect the local delivery of zoledronate to overcome the limitations and side effects associated with systemic usage; however, we need to know more about the bioavailability and the biological effects. The local use of BMP-2 and zoledronate as a combination has a proven additional effect on bone regeneration. This review focuses primarily on the local use of zoledronate alone, or in combination with bone anabolic factors, in various preclinical models mimicking different orthopaedic conditions.

Cite this article: I. Qayoom, D. B. Raina, A. Širka, Š. Tarasevičius, M. Tägil, A. Kumar, L. Lidgren. Anabolic and antiresorptive actions of locally delivered bisphosphonates for bone repair: A review. Bone Joint Res 2018;7:548–560. DOI: 10.1302/2046-3758.710.BJR-2018-0015.R2.

The Influence of Liquids on the Mechanical Properties of Allografts in Bone Impaction Grafting

Allografts are used to compensate for bone defects resulting from revision surgery, tumor surgery, and reconstructive bone surgery. Although it is well known that the reduction of fat content of allografts increases mechanical properties, the content of liquids with a known grain size distribution has not been assessed so far. The aim of the study was to compare the mechanical properties of dried allografts (DA) with allografts mixed with a saline solution (ASS) and with allografts mixed with blood (AB) having a similar grain size distribution. Fresh-frozen morselized bone chips were cleaned chemically, sieved, and reassembled in specific portions with a known grain size distribution. A uniaxial compression was used to assess the yield limit, initial density, density at yield limit, and flowability of the three groups before and after compaction with a fall hammer apparatus. No statistically significant difference could be found for the yield limit between DA and ASS (p = 0.339) and between ASS and AB (p = 0.554). DA showed a statistically significant higher yield limit than AB (p = 0.022). Excluding the effect of the grain size distribution on the mechanical properties, it was shown that allografts have a lower yield limit when lipids are present. The liquid content of allografts seems to play an inferior role as no statistically significant difference could be found between DA and ASS. It is suggested, in accordance with other studies, to chemically clean allografts before implantation to reduce the contamination risk and the fat content.

Fabrication and in vitro biological properties of piezoelectric bioceramics for bone regeneration

The piezoelectric effect of biological piezoelectric materials promotes bone growth. However, the material should be subjected to stress before it can produce an electric charge that promotes bone repair and reconstruction conducive to fracture healing. A novel method for in vitro experimentation of biological piezoelectric materials with physiological load is presented. A dynamic loading device that can simulate the force of human motion and provide periodic load to piezoelectric materials when co-cultured with cells was designed to obtain a realistic expression of piezoelectric effect on bone repair. Hydroxyapatite (HA)/barium titanate (BaTiO₃) composite materials were fabricated by slip casting, and their piezoelectric properties were obtained by polarization. The d₃₃ of HA/BaTiO₃ piezoelectric ceramics after polarization was 1.3 pC/N to 6.8 pC/N with BaTiO₃ content ranging from 80% to 100%. The in vitro biological properties of piezoelectric bioceramics with and without cycle loading were investigated. When HA/BaTiO₃ piezoelectric bioceramics were affected by cycle loading, the piezoelectric effect of BaTiO₃ promoted the growth of osteoblasts and interaction with HA, which was better than the effect of HA alone. The best biocompatibility and bone-inducing activity were demonstrated by the 10%HA/90%BaTiO₃ piezoelectric ceramics.