Cartiform | Brian Gilmer M.D., Knee & Sports Medicine Specialist, Mammoth Lakes, CA, Reno, NV

Ricardo Garcia-Inguanzo, MS 3, Brian Gilmer, MD

Cartiform Cartilage

Introduction

Cartiform cartilage is a surface graft of cryopreserved osteochondral allograft, constructed with chondrogenic growth factors, chondrocytes, and extracellular matrix proteins (1). It is structured with a thicker superficial cartilage (with intact superficial, transitional, and radial cartilage zones) and a thinner bony portion (1). Cartiform is produced in various sizes that can be cut to size, including 10 mm diameter disc, 20 mm diameter disc, 12x19 mm rectangle, and 20x25 mm rectangle (2). The graft is designed with pores that penetrate the entirety of the system. This arrangement of pores combined with the limited size of the bony portion allow for increased surface area for the cryopreservative solution to maintain the validity of the chondrocytes, increased flexibility for maneuvering and embedding the allograft, and permits for the release of growth factor and migration of progenitor cells into the graft (1). Chondrocytes in type II collagen matrix are preserved at -80C and remain valid for use for 2 years (3).

Advantages

The cryopreservation of Cartiform cartilage allows for a longer shelf life and storage compared to current fresh stored osteochondral allografts, which currently are stored at 4C for 14 days and must be used within 30 days (4). The perforated structure of the Cartiform graft provides more flexibility allowing it to be placed arthroscopically, and can be trimmed to match the size and contour of the defect. Additionally, when used with marrow stimulation, mesenchymal stem cells from bone marrow will aid in the formation of hyaline cartilage within the pores of the graft for improved cartilage regrowth.

Indications

Cartiform cartilage is an excellent option for isolated, full-thickness cartilage defects that have incurred minimal bone loss (3). It is used for defects that are 1-2cm2 in size, allowing for a single procedure, ideally on the patella or femur, as well as the foot and ankle. Cartiform can not be used in defects with more than 5mm bone loss, or defects in which malalignment, laxity, or meniscal insufficiency is not previously managed.

Preparation

The Cartiform graft is stored in a sterile jar at -80C. The jar is transferred into a sterile basin where saline solution is added to a level below the lid, and is allowed to thaw for 10 minutes or until ice crystals are no longer visible (5). Sterile forceps are used to remove the Cartiform from its jar, and rinsed in sterile saline at room temeprature for at least one minute and up to two hours (1). Thawing solution should not exceed temperatures of 39C, and the Cartiform should not be thawed for more than 30 minutes.

Operative Technique (Patellar) and Rehabilitation

A diagnostic arthroscopy is performed followed by debridement (6). Abrasion chondroplasty using rotary burr and a ring curette is then implemented for removal of peripheral articular cartilage to expose the underlying bone, until bleeding is noted in the subchondral bone. The graft site is prepared by making an incision in the patellar tendon, and placing bone wax for evaluating the size and contour of the area of defect. Once the Cartiform cartilage is appropriately trimmed, and after careful identification of the bony portion, the graft is implanted with the bony portion making contact with the defect. Depending on the size of the defect, a single Vicryl or 2-0 suture (<1cm2) or two to four sutures (>1cm2) is used along with suture anchors for proper fixation of the graft. Fibrin glue is applied to the perimeter of the graft repair. The knee is placed in a brace and fixed in full extension, with rehabilitation focused on gradual improvement of weight-bearing and knee flexion while avoiding damage to the graft.

References

Ricardo Garcia-Inguanzo, MS3 is a third year medical student at the University of Nevada, Reno.