Polymer Ceramic Hybrid Acetabular Liner: Bench to Bedside Translation

 

Dr. Bikramjit Basu Professor at the Materials Research Center IISc, Bangalore

According to a published report of the World Health Organization (WHO), about 190 million adults suffer from osteoarthritis and related disabilities worldwide. This is commensurate with the fact that the number of revision surgeries has increased at about the same rate as the number of primary surgeries of joint replacement due to prostheses failures. Currently, there are more than 100,000 cases every year of Total Hip Arthroplasty (THA) procedures in India. The available articulating joint-implants generally offer a trouble free life for about 10-15 years, which is inadequate, considering the increased lifespan for humans in many developing nations. Therefore, a search for ideal prosthetic materials together with treatment methods, reconstructive solutions and surface designs is currently being pursued in the field of orthopedic biomaterials.

The global orthopedic market was approximately 30% of the total implants market and the market shares of segments in 2020. The growth rate of the need for orthopedic implants is estimated to be more than 25% per annum for the next five to six years. The global hip replacement implant market is expected to grow at a Compound Annual Growth Rate (CAGR) of 3.0% during the forecast period 2017–2023 to an aggregate of $7,150.0 million by 2023. The overall trend therefore shows a steady, yet slow expected market growth in the THR application domain. The THR market is further sub-divided into three sectors: total hip replacement, partial hip replacement and revision and hip resurfacing. Although several hip implant options are available commercially, these are currently imported and there are no affordable indigenous alternatives.

In a decade-long research program, Prof. Bikramjit Basu’s research group at Indian Institute of Science, Bangalore, made

important breakthroughs in developing three different generations of polymer-ceramic hybrid acetabular sockets, namely HDPE-HA-Al2O3 hybrid composites, polyethylene grafted graphene oxide (GO) reinforced high density polyethylene (HDPE) composites and lately, a UHMWPE-HDPE blend with surface modified GO reinforcement. For example, a new synthesis approach was developed to chemically couple GO in polymer blends, which resulted in high mechanical strength (~65 MPa) and wear resistance properties with acceptable biocompatibility. Research on this technology has also been conducted at IIT Kanpur.

Gamma irradiation of the acetabular liner was shown to help in improving wear resistance, hardness and coefficient of friction, without compromising on biocompatibility. Improved wettability and surface polarity after gamma-ray sterilization further supported cell adhesion and stability of coefficient of friction. The resulting wear debris were found to be non-toxic. Optimum implant design was determined using Finite Element Analysis and theoretical wear analysis, and was customized according to the bone condition and body weight of the patient. It was shown that implant stiffness could be optimized to be close to the natural strain profile within bone.

The scalability for manufacturing of acetabular liners (44, 46 or 48 mm outer diameter with 8 mm wall thickness) with acceptable surface finish has been established at the prototype level. The new implant design was accomplished by biomechanical analysis of principal stresses in periprosthetic bone around the acetabular joint, and current efforts are underway to adopt machine learning algorithms to accelerate the implant design. The augmented bone tissue regeneration around the variants of hybrid composite were demonstrated in both cylindrical and segmental defect models in femurs of experimental rabbits for a period of up to 26 weeks.