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Mosaicplasty

What is Mosaicplasty?

Mosaicplasty, also called Autologous Osteochondral Grafting, is a technique for transplantation of bone and hyaline cartilage to a site where a chondral or osteochondral defect is found or in layman’s terms, knee cartilage damage. In Mosaicplasty, transfer of numerous minor osteochondral plugs is done to a region of chondral or osteochondral defects. The use of multiple tiny grafts permits regulation of the donor-site integrity while new surface contouring occurs.

In a study by Lane et al., it has been shown that the hyaline cartilage can remain sustainable for 12 weeks post-transfer. Though, dual issues were faced with one osteochondral plug transfer, including surface inaptness at the receiver site and donor-site morbidity. Mosaicplasty was thus established as an endeavor to lessen these issues.

knee pain before mosaicplasty

What History Shows?

Several procedures have introduced using huge osteochondral grafts from the posterior femoral condyle, medial trochlea, and patella. These methods don’t provide a consistent graft, are invasive, and may disrupt articular biomechanics. However, utilizing multiple osteochondral cylinders may reimburse for these shortcomings.

  • The first case study was issued in 1993 byMatsusue et al. on the femoral condyle defect of 15 mm diameter related to an anterior cruciate ligament tear.
  • In 1996, the outcomes were published by Bobic.
  • The multiple graft procedure was developed byHangody in 1992 and was termed “Mosaicplasty,” the results of which were reported in 1997.

How Is Mosaicplasty Performed?

In Autologous Osteochondral Grafting (OAG) or Mosaicplasty grafting, one or more cylindrical autografts are transferred from the knees’ low weight-bearing area to the site of defect such as the femoral condyle.

Several histological, biomechanical, animal, and clinical research have explored the various procedural facets of this technique. Surgically, the procedure involves harvesting the grafts with the help of medial or lateral trochlea’s mini-arthrotomy with a phase of arthroscopic graft insertion. The defect is categorized as per the ICRS classification (area, depth, location) pre-and post-debridement.

Harvesting of a small number of large diameter grafts is done from the trochlea over the defect. The transplantation of the graft plugs is performed by press-fit in the recipient plugs across a convergent plane of the same precise depth. Harvesting, drilling, and insertion are performed repetitively until coverage occurs over the entire full-thickness gap.

Typically, the steps in the procedure involve the following.

  1. Installation – the patient is installed and positioned with the tools.
  2. Surgery – the equipment is set and prepared.
  3. Arthroscopic Evaluation – assessment of the condylar defect is done. This involves curettage and debridement of the defect, followed by determining whether arthrotomy or arthroscopy is to be done depending on the surgeon’s expertise.
  4. Planning – the diameter and number of grafts to be used is determined as per the defect size.
  5. Harvesting the graft – a harvester, such as a tubular chisel, is used to harvest the graft from the donor.
  6. Graft implantation – the harvester is then placed in position, drilling and insertion then follow.

Preoperatively, the workup comprises:

  • Assessment of functional instabilities
  • Alignment
  • Knee stability and imaging (CT arthrography/MRI with cartilage sequences)

Free movement is allowed after the procedure. However, weight-bearing must be postponed for 2-4 weeks. This procedure is indicated in younger individuals below 50, including those with symptomatic osteochondral or chondral defects of size 3 cm or less in the femoral condyle’s weight-bearing region. One condition in which Mosaicplasty is absolutely contraindicated is pre-osteoarthritis.

Merits And Demerits of The Mosaicplasty Procedure

Merits

The merits of the procedure include:

  • The osteochondral graft serves as a sustainable functioning unit that runs hyaline cartilage on a bony base.
  • The size of the graft can be adjusted to the recipient site within specific limits.
  • Mosaicplasty is a single-stage process that does not need a lab nor cell rehabilitation.
  • Infection risk is minimal, and the risk of rejection is negligible.

Demerits

  • This procedure requires careful harvesting and implantation in order to achieve maximum coverage (more than or equal to 80%) with well-integrated and stabilized grafts.
  • Harvesting of multiple grafts can cause postoperative pain.

a mosaicplasty candidate

Frequently Asked Questions (FAQS)

What Is the Smallest Size Of Defect Indicated For Chondral Graft?

A study on cadaveric knees has reported that there is the highest pressure on the peripheries of the defects of diameter more than 10 mm. A minor defect doesn’t impact peripheral pressure. Convery et al. have described 9mm as a threshold in research on the horse. Several authors have embraced a threshold of 10 mm indicative for chondral repair over a weight-bearing area.

What Are the Results of Transplanting Grafts?

The study conducted by Lane et al. reported that transplanting two trochlear grafts over the condyle of 6 adult goats showed a normal surface of 10 out of 12 grafts at three months. Only 2 cases of surface fibrillation were seen. Complete consolidation of the plug’s bony interface into the recipient area was noted, though no healing of the surface of the cartilage was found. 95% grafts were reported to be viable while also synthesizing glycosaminoglycans, as seen through a confocal microscope. Overall, the results of the procedure are found to be extremely promising. However, further research is warranted.

What Is the Aftermath at The Donor Site?

In general, the donor site remains empty. The secondary arthroscopic follow-up has reported surface depressions with fibrous tissue in deeper regions. Some authors have also attempted to fill this region by means of an osteoperiosteal plug coming from the tibia. However, these trials have not caused superior quality bone filling.

Subsequently, the Mosaicplasty procedure is reliable and acceptable for treating small-sized full-thickness chondral defects and preventing the development of initial arthritis in patients. It is a minimally invasive, single-stage procedure with minimal risk of complications and economical price.

References:

  1. Oztürk A, Ozdemir MR, Ozkan Y. Osteochondral autografting (mosaicplasty) in grade IV cartilage defects in the knee joint: 2- to 7-year results. Int Orthop. 2006;30(3):200-204. doi:10.1007/s00264-005-0068-5
  2. Robert. Chondral repair of the knee joint using Mosaicplasty. Orthopaedics & Traumatology: Surgery & Research. 2011;97(4):418-429. ISSN 1877-0568,https://doi.org/10.1016/j.otsr.2011.04.001.
  3. Lane J G. et al. A morphologic, biochemical, and biomechanical assessment of short-term effects of osteochondral autograft plug transfer in an animal model, Arthroscopy: The Jr. of Arthros. & Rel. Sur. 2001;17(8):856-863.ISSN 0749-8063.https://doi.org/10.1016/S0749-8063(01)90010-6.
  4. Van Susante, J.L.C., Wymenga, A.B. & Buma, P. Potential healing benefit of an osteoperiosteal bone plug from the proximal tibia on a mosaicplasty donor-site defect in the knee. Arch Orthop Trauma Surg 123, 466–470 (2003).https://doi.org/10.1007/s00402-003-0577-x
  5. Curl WW, Krome J, Gordon ES, Rushing J, Smith BP, Poehling GG. Cartilage injuries: a review of 31,516 knee arthroscopies. Arthroscopy. 1997;13(4):456-460. doi:10.1016/s0749-8063(97)90124-9

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