Introduction

Osteonecrosis of the femoral head (ONFH) is a progressive, degenerative disease of the hip characterized by microfractures of the subchondral bone and collapse of the femoral head, which ultimately leads to hip dysfunction [1]. It predominantly affects young or middle-aged individuals. Epidemiological studies have demonstrated that steroid intake, trauma, and chronic alcohol intake are common etiologies of ONFH; however, in nearly 20-30% of cases, the cause of ONFH is idiopathic [2,3].

At the cellular level, osteoblasts and osteocytes play a critical role in osteogenesis. However, in ONFH, osteocyte apoptosis, lipid accumulation in osteoblasts and osteocytes, and decreased osteoblastic differentiation potential of mesenchymal stem cells (MSCs) near the ONFH lesion led to inadequate bone repair [4-8]. Additionally, prolonged ischemia during the course of the disease further reduces osteoblast concentration. Together, these processes lead to further disease progression, loss of structural integrity, and subchondral fracture of the femoral head [9].

Treatment for ONFH aims to relieve pain, retard disease progression, prevent joint collapse, and restore hip biomechanics. In the early stages of ONFH, non-surgical treatment approaches such as restricted weight bearing, pharmacological therapy, and non-invasive biophysical modalities (electromagnetic stimulation, extracorporeal shock-wave therapy, and hyperbaric oxygen) are often recommended [2,10]. However, in patients with advanced disease, surgical interventions become necessary. Repair and reconstruction methods such as core decompression, osteotomy, and non-vascularized bone transplantation aim to preserve the femoral head. If these methods are ineffective, total hip arthroplasty (THA) may be considered [11].

Core decompression is a widely used and safe surgical treatment for early-stage ONFH. This procedure decreases intra-osseous pressure, improves vascularity to the necrotic area, and augments new bone formation before mechanical failure of the femoral head [12,13]. However, core decompression alone may not provide structural support, likely due to a lack of osteoprogenitor cells in the femoral head. This limitation increases the risk of femoral head collapse and leads to clinical failure in about 30% of patients with ONFH [14,15]. The implantation of orthobiologics such as platelet-rich plasma, bone marrow aspirate concentrate, stromal vascular fraction, and autologous cultured osteoblast cells, along with core decompression, is an innovative strategy for the treatment of ONFH [10,14,16]. Osteoblast cell therapy involves ex vivo processing of the autologous bone marrow to isolate and differentiate MSCs into osteoblast cells and further expand them before implantation [16]. Various clinical studies have demonstrated delayed progression to subchondral fracture and reduced pain in patients with ONFH treated with combined core decompression and osteoblast cell therapy [16,17].

Although previous studies have demonstrated the safety and efficacy of this approach for the treatment of ONFH, these had small patient populations and short follow-up durations [16,17]. Hence, the present study was conducted to assess clinical outcomes (pain intensity, functional capacity, and the need for other surgical treatments) in patients who underwent osteoblast cell therapy with core decompression for the treatment of ONFH at different clinical centers across India. The study was carried out following the market authorization of OSSGROW® (Regrow Biosciences Pvt. Ltd., Mumbai, Maharashtra), which comprises autologous adult live-cultured osteoblasts (AALCO), referred to as osteoblast cell therapy, by the Drugs Controller General of India, Ministry of Health and Family Welfare, Government of India, in 2017 [18].