Hip osteoarthritis (OA) is a common condition that often leads people to total hip arthroplasty (THA), also known as hip replacement.
When people think about arthritis, they often focus only on cartilage – the smooth tissue that cushions the ends of bones, or the joint space itself. But just beneath that cartilage is another critical structure: the subchondral bone.
The subchondral bone acts like the foundation of a house. It supports the overlying cartilage, absorbs mechanical forces during movement, and helps distribute weight evenly across the joint. When this bone becomes weakened, inflamed, or damaged, it can contribute directly to joint pain and accelerate cartilage breakdown.
Research has shown that in hip osteoarthritis, changes in the subchondral bone often occur early in the disease process. These changes can include microscopic cracks, altered blood supply, and stiffening of the bone. Over time, this environment makes it harder for cartilage to repair itself, leading to further degeneration.
This is why treatments that address not just cartilage or joint space, but also the underlying bone, may play an important role in managing hip arthritis. A recent long-term study by Hernigou looked at whether bone marrow aspirate concentrate (BMAC), which contains mesenchymal stem cells (MSCs), injected into the subchondral bone could help reduce pain, protect the hip, and delay or even help avoid the need for hip replacement. The significance of this particular study is that the majority of earlier studies focused on injections only into the joint space (intra-articular). Another significant piece of this study is that it followed 217 adults over the course of 14 years (2).
Study Design & Methods
The study followed 217 adults between 2000 and 2014. In these patients, one hip received a subchondral injection of BMAC taken from their own bone marrow (autologous). The other hip did not receive BMAC and was allowed to progress naturally.
Researchers then followed all hips with X-rays and clinical assessments at 6 years and 14 years to compare the outcomes.
Key Findings
At 14 years, only 16% of BMAC-treated hips needed hip replacement, compared with 40% in the control group.
At 6 years, the difference was even more dramatic. Only 6% of hips treated with BMAC required THA, while 30% of untreated hips did. This shows that BMAC-treated hips were about four times less likely to need replacement within six years.
Pain results also favored BMAC. After 14 years, 84% of BMAC-treated hips had pain that was stable or improved, while 40% of control hips had worsening pain.
The number of MSCs mattered too, higher cell counts above a threshold gave better protection.
Severity of arthritis also played a role. Patients with moderate OA (Kellgren-Lawrence grades 2-3) did the best, but even those with more advanced disease showed real improvement and often delayed or avoided hip replacement.
Discussion & Conclusion
This study suggests that subchondral BMAC injections can:
- Reduce hip pain
- Extend the life of the natural hip joint
- Lower the chances of needing hip replacement, even in patients with advanced OA
- Show better results when higher cell numbers are used
Because this treatment targets the subchondral bone instead of just the joint space, it may directly affect one of the main causes of OA progression.
Clinical Expertise
At Regenexx at New Regeneration Orthopedics of Florida, our physicians specialize in precise, image-guided subchondral hip injections. These procedures are performed safely and accurately, using the highest quality orthobiologic (BMAC) preparations and protocols to give patients the best possible outcomes.
References:
- Grynpas MD, Alpert B, Katz I, Lieberman I, Pritzker KP: Subchondral bone in osteoarthritis. Calcif Tissue Int. 1991, 49: 20-26. 10.1007/BF02555898.
- Hernigou, Philippe et al. “Mesenchymal Stem Cell Therapy for Bone Repair of Human Hip Osteonecrosis with Bilateral Match-Control Evaluation: Impact of Tissue Source, Cell Count, Disease Stage, and Volume Size on 908 Hips.” Cells vol. 13,9 776. 1 May. 2024, doi:10.3390/cells13090776
