ACI

 

Healthy cartilage is removed from a relatively unimportant part of the joint and cultured in a laboratory.

A membrane is created by harvesting a bit of the connective tissue covering the bone, and sewn over the defect in the bone. The cultured cells are then injected behind it.

What does autologous chondrocyte implantation (ACI) mean?

In the ACI procedure, a healthy cartilage sample is harvested from a relatively unimportant part of the same joint, and the cells or chondrocytes are separated, expanded in number in a laboratory, and injected back into the knee behind a membrane that has been sewn over the damaged area to contain the new cells.

ACI is a mainstream surgical procedure for localised full-thickness cartilage defects of the knee.

The word 'autologous' means that the implanted cells are derived from the patient into whom they are being re-implanted.

• Quote from peer-reviewed paper:

  ...."ACI is a two-stage procedure, beginning with arthroscopic....biopsy to harvest approximately 200 to 300 mg of cartilage....The cryopreserved cells are thawed and expanded to the cell population needed for the second-stage open ACI technique...."

  Citation: Minas T, Ogura T, Bryant T. Autologous Chondrocyte Implantation. JBJS Essent Surg Tech. 2016 Jun 22;6(2):e24. doi: 10.2106/JBJS.ST.16.00018. PMID: 30237933; PMCID: PMC6145632.

• Quote from peer-reviewed paper:

  Stages include "....identify all associated abnormalities....harvest cartilage tissue from the non-weight-bearing area....parapatellar arthrotomy [to] expose the lesion....Debride all fissured and unstable articular cartilage....sew....the membrane patch....Gently deliver the cells and fill the defect...."

  Citation: Minas T, Ogura T, Bryant T. Autologous Chondrocyte Implantation. JBJS Essent Surg Tech. 2016 Jun 22;6(2):e24. doi: 10.2106/JBJS.ST.16.00018. PMID: 30237933; PMCID: PMC6145632.

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When is ACI indicated in cartilage repair?

ACI is indicated for focal cartilage defects, where most of the rest of the cartilage covering is normal.

Because joint cartilage usually contains only a small number of cartilage cells relative to the large volume of surrounding matrix material, this procedure allows expansion of the relative number of cells proportional to the matrix when the sample is injected back behind the membrane.

• Quote from peer-reviewed paper:

  "....Focal cartilage defects can cause symptoms such as pain, swelling, stiffness, giving way, or locking of the knee affecting quality of life. As cartilage has a very limited ability to repair itself, these defects require surgical treatment. Moreover, if cartilage defects are left untreated, the damage progresses leading to osteoarthritis...."

  Citation: Vonk LA, Roël G, Hernigou J, Kaps C, Hernigou P. Role of Matrix-Associated Autologous Chondrocyte Implantation with Spheroids in the Treatment of Large Chondral Defects in the Knee: A Systematic Review. Int J Mol Sci. 2021 Jul 1;22(13):7149. doi: 10.3390/ijms22137149. PMID: 34281202; PMCID: PMC8267622.

• Quote from peer-reviewed paper:

  Repair tissue ranges "...from predominantly hyaline (22% of biopsy specimens), through mixed (48%), to predominantly fibrocartilage (30% of specimens)...."

  Citation: Roberts S, McCall IW, Darby AJ, Menage J, Evans H, Harrison PE, Richardson JB. Autologous chondrocyte implantation for cartilage repair: monitoring its success by magnetic resonance imaging and histology. Arthritis Res Ther. 2003;5(1):R60-73. doi: 10.1186/ar613. Epub 2002 Nov 13. PMID: 12716454; PMCID: PMC154433.

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Protection of ACI graft area after surgery

Because the graft area and the cells are very fragile for some weeks, the patient has to be extremely careful to keep weight off the graft area until the cells have consolidated into true joint surface.

• Quote from peer-reviewed paper:

  "....most rehabilitation protocols for third-generation ACI initiate CPM within 24 hours postoperatively and allow partial WB immediately following surgery with progression to full WB within 12 weeks. ...."

  Citation: Dhillon J, Fasulo SM, Kraeutler MJ, Belk JW, McCulloch PC, Scillia AJ. The Most Common Rehabilitation Protocol After Matrix-Assisted Autologous Chondrocyte Implantation Is Immediate Partial Weight-Bearing and Continuous Passive Motion. Arthrosc Sports Med Rehabil. 2022 Nov 18;4(6):e2115-e2123. doi: 10.1016/j.asmr.2022.09.007. PMID: 36579035; PMCID: PMC9791827.

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