40 Allograft Management Osteochondral Lesion of the Talus (OLT): Juvenile Cartilage Abstract Particulated juvenile cartilage allograft transplantation (PJCAT) is a technique of transplantation of multiple fresh juvenile cartilage allograft tissue pieces (1 mm3 cubes), containing live chondrocyte cells within their native extracellular matrix, with fibrin adhesive securing the tissue pieces to the base of the osteochondral lesion of the talus (OLT). PJCAT is viable treatment option for OLTs that have failed prior operative management or primary OLTs that are likely to be unresponsive to marrow stimulation techniques. Reports of early follow-up demonstrate patient improvement. Basic science evidence demonstrates that this technique can restore hyaline cartilage. PJCAT delivery can be performed through all-open, arthroscopically assisted open, and all-arthroscopic techniques. The current evidence, indications, and surgical technique for the use of particulated juvenile cartilage allograft transplantation in the management of osteochondral lesions of the talus will be discussed in this chapter. Keywords: juvenile cartilage, transplantation, osteochondral lesion, talus, allograft • Primary osteochondral lesion of the talus (OLT)1 that is larger than 15 mm in one dimension2 or surface area larger than 107 mm2.3 • Previously failed a marrow stimulation technique with continued symptoms. • Currently, there is no evidence to exclude shoulder and cystic lesions. However, it is difficult to restore the native shoulder anatomy with this technique. • Anterior ankle pain and joint line tenderness. • May present with symptoms of ankle instability, but with a clinically stable ankle. • Weight-bearing anteroposterior (AP), lateral, and mortise views of the ankle: • Magnetic resonance imaging (MRI): • Computed tomography (CT) scan (fine cut)—with axial, coronal, and sagittal cuts: • Activity modification. • Unloading bracing. • Active ankle joint infection. • Large deep cystic lesions without a stable bony base. • Immunocompromised host: • The goal of the procedure is to restore hyaline cartilage (cells plus extracellular matrix) to the OLT. Other methods used to deliver intact hyaline cartilage to an OLT are limited to osteochondral autograft transfer (OAT) and allograft transplantation, yet neither of these options provides juvenile cartilage. • Basic science data support the use of juvenile cartilage. Adkisson et al1 compared the chondrogenic activity of human juvenile and adult chondrocytes. • The surgical procedure is less technically demanding than other cartilage replacement procedure because of the following: • Debride the OLT until a stable cartilaginous rim and stable bony base are obtained. • Penetrate the subchondral plate, but ensure a dry bed before graft insertion. • Fill at least 50% of the base of the lesion with allograft. • Apply prethawed fibrin glue to seal the allograft squares into the OLT. • Before the fibrin glue fully sets, contour the surface to match that of the talar dome articular cartilage. • Determination of the appropriate amount of graft to be preordered is necessary. Per the manufacturer, one pack of DeNovo NT Natural Tissue graft (Zimmer Biomet, Inc., Warsaw, IN) is recommended to treat each 2.5 cm2 of lesion surface area, with a recommended fill ratio of at least 50% of the lesion size (e.g., each pack contains enough graft to solidly fill 1.25 cm2 of surface area). In practice, the author attempts to nearly completely fill the lesion’s surface area to the depth of the surrounding healthy cartilage. Prior to the start of the procedure, inspect the packaging for expiration date. • It is imperative that the patient understands the source of the transplanted tissue and is amenable to the transplantation. Currently, the only graft material available for this procedure is DeNovo NT Natural Tissue graft. The cartilage pieces of this product are obtained, in compliance with Good Tissue Practice, from donors ranging in age from newborn to 13 years; however, it is typically obtained from neomorts under the age of 2 years.2 No stillborn or fetal tissue is used. Standard disease screening is performed on each lot (one lot of tissue comes from a single donor). • Regardless of open or arthroscopic technique (see below), position the patient supine with an ipsilateral proximal thigh bump so that the toes point to the ceiling. • Place an ipsilateral thigh tourniquet. • PJCAT can be performed via arthroscopic or open techniques. The open technique is typically an anterior medial or lateral arthrotomy. Rarely is an osteotomy needed because perpendicular access to the OLT is not needed. An open technique should be performed until the surgeon is experienced with the technique. Both techniques will be described. • Even with an open technique, the author recommends a diagnostic arthroscopy to confirm the lesion location and size and to identify and treat any concomitant pathology. • Use either an anteromedial arthrotomy (medial lesions) or an anterolateral arthrotomy (lateral lesions) based on the lesion location. • Regardless of the approach, place a deep retractor inside the joint capsule. Typically, a Gelpi retractor works best. Plantar-flex the ankle and determine the extent to which the lesion can be visualized. • Perpendicular access is not needed, but access to the posterior portion of the OLT is needed for debridement. If additional access to the posterior OLT is needed, perform a plafondplasty.
40.1 Indications and Pathology
40.1.1 Clinical Evaluation
Plantarflex the ankle to expose the OLT during deep palpation.
Usually, but not always, located over the region of the OLT.
40.1.2 Radiographic Evaluation
A shadowing or defect may be seen in the talar dome in the region of the lesion.
Bone fragments may be seen within the base or separate from the OLT, especially in acute osteochondral fractures.
Useful in screening for OLTs.
Presence of associate bone marrow edema confirms bioactivity of the lesion.
Not reliable for determining the true size or anatomic configuration of the lesion.
Best study to determine the size and configuration of the osseous aspect of the lesion.
Accurate in determining presence of cysts and microcysts adjacent to the OLT.
40.1.3 Nonoperative Options
40.1.4 Contraindications
Immune-deficient disease.
Medications cause immune compromise.
40.2 Goals of Surgical Procedure
Chondrocytes from juvenile (<10 years) donors showed significantly greater extracellular matrix synthesis (sulfated glycosaminoglycan [S-GAG]) than chondrocytes from mature donors.
Moreover, the rate of S-GAG synthesis was greater than 100-fold for the juvenile chondrocytes. The authors also demonstrated 100and 700-fold decreased amounts of mRNA (messenger ribonucleic acid) for type and type IX collagen, respectively, in mature chondrocytes compared to the juvenile chondrocytes. They speculate that the decreased gene expression directly affects the ability of adult chondrocytes to form neocartilage in vivo.
Likewise, they demonstrated a significantly increased growth rate for juvenile chondrocytes and that this cell population did not illicit an immunogenic reaction when transplanted into a xenogeneic goat model, indicating immunoprivilege for juvenile chondrocytes.
40.3 Advantages of Surgical Procedure
Particulated juvenile cartilage allograft transplantation (PJCAT) does not need graft press-fitting/contouring (as needed for osteochondral autograft or allograft transplantation).
It does not require perpendicular access to the base of the OLT. Therefore, it does not require an osteotomy (as often needed for OAT or allograft transplantation) and can be performed arthroscopically or through a minimally invasive anterior ankle arthrotomy.
It is a single-stage procedure unlike autologous chondrocyte implantation (ACI).
There is no donor site morbidity unlike OAT.
The graft is readily available; therefore, there is no donor wait time as is the case for allograft transplantation.
There is minimal theoretical and no clinically documented chance for immunological reaction (cartilage is considered immune privileged) or disease transmission.
40.4 Key Principles
40.5 Preoperative Preparation and Patient Positioning
40.6 Operative Technique
40.6.1 Open Technique
Anteromedial arthrotomy:
Make a longitudinal incision over the ankle joint and just medial to the tibialis anterior tendon. Incise the extensor retinaculum in line with the incision.
Retract the tibialis anterior tendon laterally and incise the joint capsule in line with the skin incision.
Place a deep retractor, typically a Gelpi retractor is best suited.
Plantarflex the ankle to identify the lesion.
Anterolateral arthrotomy:
Make a longitudinal incision just lateral to the peroneus tertius tendon and medial to the anterior border of the fibula.
Carefully identify and protect any branches of the superficial peroneal nerve.
Incise the extensor retinaculum, retract the peroneus tertius medially, and incise the ankle joint capsule longitudinally.
Plafondplasty:
Use a curved 0.25-inch osteotome to remove the superior and medial or lateral aspect of the anterior tibial plafond. Place a Joker or Freer retractor into the joint space to protect against further damage to the talar cartilage. Careful attention should be paid not to remove more than 1 cm of the nonarticular tibia in any dimension.
Smaller plafondplasties are generally not repaired. If the plafondplasty approaches 1 cm in any dimension or loss of structural integrity is a concern, use a small fragmentary screw for fixation.
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