October 14, 2009
3 min read
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Smaller mosaicplasty plugs implanted flush with joint surfaces yield best results

Plugs should be handled with care, harvested with manual punches, a mosaicplasty proponent said.

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To achieve hyaline cartilage healing of 2 cm² to 4 cm² focal chondral or osteochondral defects, a sports medicine specialist recommended as one option to master the mosaicplasty technique, an autograft reconstruction procedure indicated for treating these knee injuries in young, active patients.

“Osteochondral transfers have good early clinical results, but it is a technically demanding procedure,” Anthony Miniaci, MD, said.

Performing mosaicplasty arthroscopically, which is Miniaci’s preferred approach for scope-accessible defects, presents a considerable challenge even to those highly skilled with this or similar techniques, he said.

“I think you need to start with an open procedure and then proceed to arthroscopic procedures. The geometry of reconstruction of a curved surface viewed with a 30° angled arthroscope presents technical challenges if you are going to do it arthroscopically,” Miniaci said.

More reproducible

Miniaci discussed research into the effectiveness of resurfacing defects with mosaicplasty plugs and reviewed the steps he has found critical to well planned and executed procedures: harvesting and sizing grafts, defect preparation and graft implantation.

In the literature, there is strong evidence of graft survival using the mosaicplasty technique Laszlo Hangody, MD, described more than a decade ago, Miniaci noted.

“I have adopted this technique of mosaicplasty and the transfer of autogenous cartilage and bone because it heals with type 2 collagen, and the early clinical results are excellent,” Miniaci said.

However, mosaicplasty’s clinical reproducibility has been inconsistent, which may result in suboptimal knee function, he said. Some problems that have been noted include incomplete donor site filling or cyst formation at the implantation site.

Animal study

Attention to detail with this technique is crucial to proper healing and bone incorporation, Miniaci said.

He encouraged harvesting smaller rather than larger plugs based on the detrimental effects he saw when taking larger plugs from the donor area, a practice that some had initially used with mosaicplasty.

A comparative study Miniaci performed of 4.5 mm² and 6.5 mm² plugs in sheep showed differences related to defect filling. After 3 months, he observed better results in the 4.5 mm group without erosion of the patella’s reciprocal surface.

Plug size critical

After 3 months in the 6.5 mm group, “There are already early arthritic changes on the opposite patella where you do not have complete healing of the donor site,” Miniaci said. “Just a 2-mm difference can make that much difference biologically.”

As such, he recommends using a 5 mm² maximum plug size but avoiding really small grafts that can produce unstable repairs and may fracture or collapse.

Flush surface

Miniaci also analyzed the effect of manual punches and power instruments on graft harvesting and found the manual method produced more symmetrical plugs that sustained less cartilage damage.

On histology, 80% of cells were killed with power harvesting; however, even with a manual harvesting technique, 20% of cells on a plug’s periphery were killed using a manual punch. This demonstrates how friable and sensitive the articular cartilage is and needs to be handled carefully, he said.

Another concept involves implanting plugs flush with the remaining knee cartilage, not even 2 mm proud, to ensure they follow the joint surface’s natural contour. This facilitates optimal cartilage regeneration, avoids the formation of cysts and prevents graft collapse, Miniaci said.

“We still have a search for a biologic solution, but I think that this is a valuable tool in your armamentarium of treatment of cartilage lesions,” he said.

For more information:

  • Anthony Miniaci, MD, can be reached at the Cleveland Clinic Sports Health, 9500 Euclid Ave., Desk A41, Cleveland, OH 44195; 216-518-3466; e-mail: miniaca@ccf.org. He is a consultant to, has ownership interest in, does teaching and speaking for and has intellectual property rights with Arthrosurface.

References:

  • Evans PJ, Miniaci A, Hurtig MB. Manual punch versus power harvesting of osteochondral grafts. Arthroscopy. 2004; 20:306-310.
  • Miniaci A. Mosaicplasty: Robbin’ Peter to pay Paul. #67. Presented at the 25th Annual Current Concepts in Joint Replacement Winter Meeting. Dec. 10-13, 2008. Orlando, Fla.