What is Spherox?: A Revolutionary Autologous Cartilage Repair Therapy

October 11, 2025 •

4 min read

Cartilage defects in the knee are a common orthopedic problem, and what is Spherox? It is a breakthrough advanced therapy medicinal product (ATMP) designed to address this issue by using a patient's own cells to regenerate damaged cartilage. This innovative, two-stage procedure offers a promising alternative to traditional repair methods for specific defects.

Quick Summary

An advanced cell therapy, Spherox uses spherical aggregates of a patient's own cartilage cells to repair symptomatic defects in the knee through arthroscopic implantation.

Key Points

Autologous Therapy: Spherox uses the patient's own cartilage cells to regenerate damaged tissue, minimizing immune rejection risks associated with foreign materials.
Minimally Invasive Implantation: The spherical cell aggregates can be delivered arthroscopically, reducing the need for large incisions and potentially shortening hospital stays compared to older ACI methods.
Effective for Mid-to-Large Defects: Spherox is indicated for cartilage defects up to 10 cm², making it a viable option for larger lesions where microfracture is less effective.
Two-Part Surgical Process: The treatment requires two surgical interventions: an initial biopsy to harvest cartilage cells, and a second procedure to implant the cultured spheroids.
Self-Adhering Implants: The chondrocyte spheroids self-adhere to the defect site within minutes, removing the need for external fixation materials like fibrin glue or membranes.
Post-Operative Rehabilitation: A specific and structured rehabilitation program is crucial for successful outcomes and the long-term integration of the newly formed cartilage.
EU-Approved ATMP: Spherox is classified as an Advanced Therapy Medicinal Product (ATMP) with marketing authorization across the European Union.

The Science Behind Spherox

Spherox is a state-of-the-art form of autologous chondrocyte implantation (ACI), a therapeutic approach that has evolved significantly since its introduction in the 1990s. Unlike earlier ACI techniques that required larger surgeries and additional membranes, Spherox uses a minimally invasive, scaffold-free method. The core of the therapy is the use of chondrocyte spheroids, which are spherical aggregates of a patient's own cartilage cells.

The Spherox Procedure: A Two-Stage Process

The Spherox treatment involves a multi-step process that is performed in a medical facility by a specialized orthopedic surgeon.

Biopsy: In the first stage, a small cartilage sample is collected from a healthy, non-weight-bearing area of the patient's knee using arthroscopy (keyhole surgery). This minimizes the initial surgical impact.
Cell Culture: The collected cells are then sent to a laboratory, where they are isolated and cultured over a period of 6 to 8 weeks. During this time, they multiply and form the three-dimensional cell aggregates known as spheroids.
Implantation: In the second, also arthroscopic, surgical procedure, the spheroids are delivered as a suspension directly into the prepared cartilage defect.
Adherence: The spheroids are designed to self-adhere to the defect site within approximately 20 minutes, eliminating the need for an external fixation method like a periosteal flap or glue.

How the Therapy Repairs Cartilage

The spheroids' mechanism of action relies on the natural regenerative capabilities of chondrocytes. Once implanted, the chondrocytes within the spheroids begin to synthesize extracellular matrix, which gradually fills the defect with new, hyaline-like cartilage tissue. This process is gradual and requires a subsequent rehabilitation program to ensure proper integration and maturation of the new cartilage.

Spherox vs. Traditional Repair Methods

Spherox is one of several treatment options for cartilage damage, each with its own advantages and limitations. Traditional methods like microfracture rely on stimulating a repair response from the patient's bone marrow. The following table highlights key differences:


Feature	Spherox (ACI with Spheroids)	Microfracture	Matrix-associated ACI (MACI)	Osteochondral Autograft Transfer System (OATS)
Technique	Two-stage, arthroscopic implantation of autologous chondrocyte spheroids.	One-stage, creates microfractures in the bone to stimulate clot formation.	Two-stage, implants cells within a biomaterial membrane.	One-stage, grafts healthy cartilage and bone from another area.
Invasiveness	Minimally invasive, uses two arthroscopies.	Minimally invasive, one arthroscopy.	Can be less invasive than traditional ACI, arthroscopic or mini-arthrotomy.	More invasive, requires a donor site.
Defect Size	Suitable for defects up to 10 cm².	Typically for smaller defects (< 4 cm²).	Effective for similar or larger defects than microfracture.	Best for small, well-contained defects.
Tissue Quality	Encourages the formation of hyaline-like cartilage.	Primarily forms fibrocartilage, which is less durable.	Aims to produce hyaline-like repair tissue.	Transplanted hyaline cartilage retains its original structure.
Rehabilitation	Follows a specific, phased program lasting up to a year.	Requires a rehabilitation protocol, but less complex.	Similar post-operative rehabilitation required.	Rehabilitation is required and depends on the size of the defect.

Candidate Eligibility and Restrictions

To be eligible for Spherox, a patient must meet specific clinical criteria. The therapy is indicated for symptomatic articular cartilage defects of the femoral condyle and the patella of the knee, with defect sizes not exceeding 10 cm². It is intended for adults and adolescents with closed epiphyseal growth plates in the affected joint.

Several conditions preclude a patient from undergoing Spherox treatment:

Active Infection: Patients with hepatitis B, C, or HIV I/II cannot receive the therapy.
Advanced Osteoarthritis: Primary generalized or advanced osteoarthritis is a contraindication.
Skeletal Immaturity: Individuals whose bones are still growing cannot be treated.
Joint Instability: Significant joint instability or malalignment must be corrected before treatment.
Obesity: A body mass index (BMI) over 30 kg/m² is an exclusion criterion.

Potential Risks and Side Effects

While Spherox offers significant benefits, there are associated risks and potential side effects, many of which are related to the surgical procedures. Common side effects observed in clinical trials include:

Bone marrow oedema (fluid accumulation in the bone marrow)
Arthralgia (joint pain)
Joint effusion (fluid accumulation in the knee)
Joint swelling
Delayed wound healing
Gait disturbance

Less common but more serious risks can include venous thrombosis and pulmonary embolism, which are general risks associated with knee surgery. Patient screening and post-operative monitoring are essential for mitigating these risks.

Post-Operative Rehabilitation and Recovery

A structured rehabilitation program is a critical component of successful Spherox treatment. Immediately following implantation, a patient must adhere to a strict schedule of limited weight-bearing, physical therapy, and restricted movement. The rehabilitation plan typically progresses in phases over several months, with a gradual increase in weight-bearing and range of motion. High-impact sports are usually restricted for at least one year. Adherence to the rehabilitation protocol is crucial for the long-term integration and durability of the new cartilage tissue.

Conclusion

As a sophisticated advanced therapy medicinal product, Spherox represents a significant evolution in the treatment of symptomatic knee cartilage defects. By harnessing the body's own regenerative potential in a minimally invasive, two-stage process, it offers a durable repair solution for a specific patient population. While careful patient selection and adherence to a strict rehabilitation protocol are necessary, clinical studies and real-world results have demonstrated its efficacy in improving knee function and quality of life for many individuals. For qualifying patients, Spherox provides a compelling, state-of-the-art option for restoring joint health and mobility. More information can be found on the European Medicines Agency website, which authorized the product.

Frequently Asked Questions

Spherox is administered in a two-stage process. First, a cartilage biopsy is taken from the patient. The cells are then cultured in a lab to form spheroids. In a second, minimally invasive, arthroscopic surgery, these spheroids are implanted into the knee's cartilage defect.

The overall process takes several weeks. After the initial biopsy, the cell culture phase in the laboratory takes approximately 6 to 8 weeks. The subsequent implantation surgery is performed after the spheroids are ready.

Spherox is indicated for repairing symptomatic articular cartilage defects of the femoral condyle and patella of the knee, specifically for defects up to 10 cm² in size.

Contraindications include patients with active infections (e.g., hepatitis B/C, HIV), advanced osteoarthritis, or those with still-open epiphyseal growth plates. Severe joint instability or malalignment are also disqualifying factors.

Common side effects include swelling, pain, and effusion in the treated joint. These are often related to the surgical procedure itself. Bone marrow oedema is also a reported side effect.

Spherox uses autologous chondrocyte spheroids to produce hyaline-like cartilage, while microfracture stimulates the formation of less durable fibrocartilage. Spherox is also effective for larger defects and offers potentially better long-term results.

After Spherox implantation, patients follow a specific, structured rehabilitation program, including physiotherapy. This program dictates a gradual increase in weight-bearing and activity and can last up to a year, with high-impact sports resuming much later.

Spherox was originally developed by Co. Don AG. In 2023, ReLive Biotechnologies, Ltd. completed the acquisition of Co. Don AG's assets, taking over the global patent rights for Spherox.