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Non‑inferiority study of autologous minced cartilage and autologous cultured chondrocytes in adults with large full‑thickness knee cartilage defects

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

The study focuses on people who have Full-thickness cartilage defects of the knee, a condition where the smooth covering on the joint surface is worn away in a deep area. Two types of surgery are being compared: one that uses tiny pieces of the patient’s own cartilage, called AMCI, and another that places a special matrix containing the patient’s own grown‑up cartilage cells, known as M ACI. Both procedures rely on the patient’s own cells, referred to as autologous cultured chondrocytes and matrix-associated autologous chondrocytes.

The purpose of the study is to determine whether the AMCI approach is at least as effective as the M ACI approach in improving knee function and symptoms, as measured by the KOOS score after two years.

Participants will be randomly assigned to receive one of the two surgeries and will be monitored for about two years. Follow‑up visits will occur at several intervals, such as three, six, twelve and twenty‑four months, during which questionnaires about pain, daily activities, sports, quality of life and any additional surgeries will be completed. The collected information will be used to compare the outcomes of the two treatments.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization and treatment assignment

    After you join the study you will be randomly assigned to one of two surgical options: the minced cartilage method (amci) or the matrix‑associated chondrocyte method (maci or spherox).

    The assignment is done by the study team and you will be informed which procedure you will receive.

  2. Step 2

    Surgical implantation

    The chosen procedure is performed during a single knee surgery.

    If you are assigned to the maci group, a 5 ml implantation matrix containing your own cultured chondrocytes is injected into the cartilage defect.

    If you are assigned to the spherox group, a suspension of spheroids covering 10 cm² of the defect is implanted.

    Both products are autologous, meaning they are made from your own cartilage cells.

  3. Step 3

    Immediate postoperative care

    After surgery you will stay in the hospital for monitoring and receive standard wound care.

    You will be advised to keep weight off the operated leg for a period defined by the surgeon, usually several weeks.

    Pain medication may be prescribed as needed; instructions will be given by the medical staff.

  4. Step 4

    First follow‑up visit (3 months)

    Approximately three months after surgery you will attend a clinic visit.

    You will complete questionnaires that include the koos score, ikdc assessment, lysholm score, and the sf‑12 quality‑of‑life survey.

    The doctor will check the knee for signs of healing or any problems.

  5. Step 5

    Second follow‑up visit (6 months)

    At about six months you will return for another assessment.

    The same set of questionnaires (koos, ikdc, lysholm, sf‑12) will be completed.

    The clinician will evaluate knee function and record any adverse events.

  6. Step 6

    Third follow‑up visit (12 months)

    One year after the operation you will have a further clinic visit.

    You will again fill out the koos subscales, the ikdc score, lysholm, and sf‑12 questionnaire.

    The surgeon will document your knee status and note any additional surgeries if they occurred.

  7. Step 7

    Final follow‑up visit (24 months)

    Twenty‑four months after randomisation is the primary outcome time point.

    You will complete the composite koos5 score, which is the main measure of the study, together with the other questionnaires used at earlier visits.

    Information on work absence, any revision surgeries, and overall quality of life will be collected.

    The results will be used to compare the effectiveness of the two surgical methods.

Who can join the trial?

4 criteria

  • Must have a single (isolated) cartilage injury in the knee that is classified as ICRS grade III or IV (a grading system that shows the damage is deep and reaches the bone), while the surrounding cartilage is still healthy (graded I‑II).
  • The damaged area must be between 3 cm² and 6 cm² in size, and the cartilage around it and the bone underneath must be healthy; this must be confirmed before joining the study using an MRI (a detailed picture of the inside of the knee) or arthroscopy (a small camera inserted into the joint).
  • You must be a man or woman who is older than 18 years and no older than 55 years, and the growth plate (the part of bone that grows in younger people) in the knee must be fully closed.
  • You must already have a confirmed diagnosis that matches each of the treatment methods being tested in the trial before you are assigned to a treatment group (randomisation).

Who cannot join the trial?

8 criteria

  • Any signs of knee instability (the knee feels loose or moves unusually, either reported by you or observed by a doctor).
  • Having a bow‑legged (valgus) or knock‑kneed (varus) alignment that is more than 3 degrees off and not corrected at the time of the procedure.
  • Removal of more than one‑third of the meniscus (the cartilage “cushion” in the knee) or complete removal of the meniscus in the same knee.
  • Having rheumatoid arthritis, an infection‑related arthritis, or any condition that follows these diseases.
  • Having cartilage defects in both knees at the same time, or a second cartilage defect in the same knee.
  • X‑ray findings that show osteoarthritis (joint wear) worse than the very mild stage (grade I) on the Kellgren‑Lawrence scale.
  • Any past or current major problems with important organs such as the heart, liver, or kidneys.
  • Any past or current reasons that make surgery, anesthesia, or the imaging tests used in the study unsafe for you.
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Investigated drugs

  • MACI

    is a treatment where a small piece of the patient’s own cartilage is taken, the cells are grown in a lab, and then placed into the knee on a special matrix. This matrix acts like a scaffold that holds the cells in place, helping them grow and repair the damaged cartilage. The procedure is done during surgery, and the goal is to restore the smooth surface of the knee joint so it can move more comfortably.

  • Spherox

    uses tiny clusters, called spheroids, made from the patient’s own cartilage cells. These spheroids are placed directly into the knee defect during surgery. The clusters contain cells that can produce new cartilage, and because they are delivered in a suspension, they can fill irregularly shaped defects more easily. This therapy aims to rebuild the cartilage layer and improve knee function.

What is already known about the treatment

  • MACI 500,000 to 1,000,000 cells/cm2 implantation matrix

    The product is injected as a 5 ml implantation matrix directly into the knee cartilage defect. It is an approved autologous cultured chondrocyte therapy that is widely reported in medical literature for cartilage repair. It is used to treat full‑thickness cartilage defects of the knee by providing living cartilage cells that produce new cartilage tissue within a supportive scaffold. Pharmacologically it is classified as an autologous cell‑based advanced therapy medicinal product (ATC code M09AX02).

  • Spherox 10-70 spheroids/cm2 implantation suspension

    This suspension contains tiny spheroids of the patient’s own matrix‑associated chondrocytes that are implanted onto the defect area (about 10 spheroids per cm²). It is a commercially available cell‑therapy product with extensive clinical trial data supporting its safety and efficacy. It treats full‑thickness knee cartilage defects by allowing the spheroids to fuse, produce cartilage matrix, and restore the joint surface. It is classified as an autologous matrix‑associated chondrocyte implant, an advanced therapy medicinal product (ATC code M09AX02).

Investigated diseases

Full-thickness cartilage defect of the knee - It is a loss of the entire cartilage layer covering the ends of the femur, tibia, or patella within the knee joint. The damage exposes the underlying bone and creates irregularities on the joint surface. Over time the defect may enlarge as normal walking stresses the joint, causing surrounding cartilage to wear down. The condition often leads to increasing pain and stiffness during activities such as climbing stairs or squatting. It can progress to early signs of osteoarthritis if left unchecked.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-526179-49-00Protocol codeP00094Estimated enrolment166 patientsSponsorMedical Center - University Of Freiburg

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