Femoral Resurfacing with an Osteochondral Allograft for Osteochondritis Dissecans
Table of Contents
- Femoral nerve block given in the preoperative holding area
- General anesthesia given in the operating room
- This procedure is performed on an outpatient basis and can be done under general or regional anesthesia.
- Before induction, the surgeon must assess the allograft tissue to ensure that it is of the appropriate size and side matched.
- The patient is then placed supine on a standard operating room table. A well-padded proximal thigh tourniquet is placed on the patient and is inflated before the arthrotomy. A foot holder device is especially useful to maintain high degrees of flexion needed for accessing more posterior lesions.
- An anterior skin incision is made from the proximal pole of the patella to the level of the joint surface. Although a midline incision is used most commonly, it can be moved medially or laterally toward the involved compartment.
- Once the capsule is exposed, a limited peri-patellar arthrotomy is made over the involved compartment. This is made laterally for lateral defects and medially for medial or bicondylar defects.
- The incision can be extended proximally using a sub-vastus or mid-vastus approach as needed for greater exposure.
- The patella is retracted by placing a z- or bent Hohman retractor in the notch. It can be helpful to release the fat pad and dissect the capsule off of the anterior horn of the meniscus to improve exposure. The knee can be flexed, extended, or rotated to place the defect in the center of the incision.
- Once the defect has been confirmed, the allograft can be opened and placed on the back table allowing it to gradually re warm at room temperature.
- The allograft is maintained at room temperature in medium.
Size and Remove Defect
- Once the defect has been identified, the surrounding damaged cartilage and bone is debrided. This allows for more accurate sizing of the lesion.
- For most contained defects, a press-fit technique can be performed using a commercial system (Arthrex, Naples, FL).
- A cannulated, cylindrical sizing guide is positioned such that it completely encompasses the defect. This determines the optimal plug diameter. It must sit flush with the surrounding normal cartilage to properly restore the geometry of the articular surface.
- A guide pin is driven into the base of the defect, thereby setting the center and perpendicular axis.
- The sizing tube is then removed and taken to the back table where it is positioned on the donor graft to ensure that the size and location can be properly matched.
- Score the cartilage with cylinder device.
- A cannulated counter bore reamer is advanced over the guide pin to a depth of 6 to 8 mm.
- Multiple perforations are made in the base of the defect using a k-wire to allow for vascular inflow.
- A skin marker is used to mark the 12 o’clock position for reference. A depth gauge is used to measure and record the socket depth at the 3, 6, 9, and 12 o’clock positions. The recipient socket is now complete.
- For uncontained or large structural lesions, a free- hand technique is used. A skin marker is used to outline a geometrical shape that encompasses the defect.
- A 15- blade knife is used to incise the remaining cartilage, which is then removed using sharp curettes.
- Graft preparation is performed on the back table. For the press-fit technique, it is helpful to use a graft work station.
- The donor graft is positioned in the workstation and a bushing of the chosen diameter is placed in the platform.
- The sizing tube is again used to confirm that the selected angle will match the contour of the defect. The 12 o’clock position is marked.
- A donor harvester is passed through the housing and advanced through the entire depth of the donor graft.
- The plug is then extracted from the harvester.
- The chosen depths are then marked for each of the 4 quadrants.
- An allograft forceps is used to hold the plug, whereas a sagittal saw is used to trim the excess bone.
- For the free-hand technique, the donor graft is fashioned using a sagittal saw. It is advisable to make these cuts slightly wider than measured to allow for trial fittings.
- Once the graft has been prepared, pulsatile lavage is used to remove any remaining marrow elements, which are felt to be the most immunogenic part of the graft.
- By aligning the 12 o’clock markings, the graft is pressed into place by hand.
- If it does not pass easily, the dilator can be used to provide an additional 0.5 mm of dilation.
- Occasionally, on oversized tamp is used to ensure that the graft is flush with the surrounding articular surface.
- This step should be minimized to preserve maximal chondrocyte viability. For the press-fit technique, additional fixation is usually not necessary.
- For the larger structural grafts, fixation can be achieved using compression screws or bioabsorbable polydioxanone pins.
- Release the tourniquet and ensure hemostasis.
- Close the patellar retinaculum with interrupted 0 Vicryl sutures.
- Close the skin incision with interrupted non-absorbable sutures.
- Apply compressive dressing and ice therapy device.