tips and “pearls” for the surgeon

The technique is not as much challenging as it is detail oriented. There are several “pearls” that help speed the procedure along.

  1. When taking the biopsy, several Tylenol sized pieces of cartilage are placed into the transfer medium. If you do not have a biopsy kit and therefore no transfer medium, place the cartilage in normal saline and refrigerate until the kit becomes available.
  2. Enter the knee thru an anterior approach; be sure to have adequate exposure.
  3. Do all osteotomy work or other ancillary procedures before the ACI.
    1. In the case of an HTO, do it first and fix its position
    2. In the case of an AMZ, do it first and then fix the osteotomy as part of the final closure.
    3. In the case of a Meniscal Allograft, complete the meniscal procedure completely before doing the ACI. Note, for exposure sake, a concurrent tibial tubercle osteotomy may be used.
  4. The capsular approach for a tibial tubercle osteotomy, when needed (courtesy of Tom Minas, MD)
    1. On the medial side: start at the medial retinaculum/VMO interval and come anterior to the patella then distal to the medial side of the tibial tubercle
    2. On the lateral side: start at the interval between the Ilio-tibial band and the Vastus Lateralis Obliqus, come anterior to the patella then distal to the lateral side of tibial tubercle
    3. Then do the osteotomy and evert the bone fragment to expose the entire joint
  5. When cleaning the injured sites:
    1. Be sure all injured cartilage is removed even if this increases the size of the lesion
    2. Have a stable perimeter to which to sew and graft
    3. Clean the base of the lesion well
      1. All calcified or cornified tissue
      2. Create vertical walls
      3. If there is a central osteophyte, use a high speed burr to gently remove to base level without invading the subchondral plate
    4. If patient has had a microfracture or other marrow stimulating procedure, the subchondral plate may be thickened – take the burr and thin the plate so that the yellow fatty morrow cancellous layer can be seen to blush thru the thinned plate before implant.
  6. Control bleeding
    1. Most surgeons use epinephrine or thrombin
    2. But for problem lesions try a spot of fibrin glue and push it into the bleeding area
  7. If the lesion is uncontained, consider using the 1.7 mm bio-absorbable mini anchors (Mitek). Place them around the uncontained perimeter about every 3-4 mm in order to tie down the tissue covering
    1. The anchors are double armed with 4-0 Ethibon suture. Some surgeons opt to re-load with a 6-0 Vicryl suture. However, I use the suture as packaged. The sutures are usually at the periphery of a lesion and do not interfere with articulation.
    2. The sutures are placed through the BioGuide in a mattress like configuration which creates a firm water tight seal
  8. Although the original protocols call for periosteum as the covering to the defect, most surgeons in the USA are currently using BioGuide (Geistlich, Inc, Germany) – a bipolar porcine based tissue graft. It is easier to use, has the same flexible qualities of periosteum, but is more durable and does not have the morbidity or problems of periosteal harvest.
    1. Cut the graft dry based on the template made – cut “inside the line” which makes the graft slightly smaller than the template
    2. Then take some of the cells and pre-seed the coarse, “down side”, of the graft which will allow the graft to enlarge now that it is slightly moist
    3. Sew the graft in place as usual; be sure the graft lies inside the edge of the lesion
  9. If the procedure involves the patella or trochlea, be sure to start at the apices.
    1. In the patella start at the center at the central ridge and work by making opposite sutures rotating like the spokes of a wheel. The goal is to recreate the ridge and convexity of the patella.
    2. In the trochlea start in the center of the concavity and work by making opposite sutures rotating like the spokes of a wheel. The goal is to recreate the concavity of the trochlea.
  10. If there seems to be a shortage of cells either because the lesions are too large or because cells were used to seed the graft, then the volume of cells can be expanded by adding 0.3cc of normal saline to each vial of cells. The cells are usually 0.3cc after being mixed in a colloid. I usually place 0.3 cc normal saline in a tuberculin syringe and then add the colloid so the combination equals 0.6cc.

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