Particulated Juvenile Cartilage Allograft Transplantation for Osteochondral Lesions of the Talus

Samuel B. Adams Jr.

Mark E. Easley

DEFINITION

The term osteochondral lesion of the talus (OLT) refers to any pathology of the talar articular cartilage and corresponding subchondral bone. A variety of names have been given to these lesions, including osteochondritis dissecans, osteochondral fracture, transchondral fracture, and osteochondral defect, but currently, OLT is the preferred nomenclature.
Particulated juvenile cartilage allograft transplantation (PJCAT) is a new technique of transplantation of multiple fresh juvenile cartilage allograft tissue pieces, containing live cells within their native extracellular matrix, with fibrin adhesive securing the tissue pieces firmly inside the OLT.
This technique is in many ways similar to the osteochondral autograft transfer with the following differences: transplantation of particulated cartilage pieces instead of osteochondral plugs, the use of juvenile cartilage instead of adult cartilage, and graft fixation with fibrin adhesive instead of bony press-fit.
The advantages of this technique are that it is a surgically simple procedure without the need for graft press-fitting/contouring (as needed for osteochondral autograft or allograft transplantation), it does not require osteotomy in most cases (as often needed for osteochondral autograft transfer or allograft transplantation), it is a single-stage procedure, there is no donor site morbidity, and there is a minimal chance for immunologic reaction (cartilage is considered immune privileged).
The disadvantages of this technique are the fact that it is a relatively new procedure with limited patient data, there is a limited supply of juvenile donor cartilage, it is a relatively expensive treatment option compared to other techniques, and as with any allograft tissue, disease transmission concerns exist.
Currently, the only graft material available for this procedure is DeNovo NT Natural Tissue Graft (Zimmer, Inc., Warsaw, IN). The cartilage pieces of this product are obtained, in compliance with Good Tissue Practice, from donors ranging in age from newborn to age 13 years; however, it is typically obtained from neomorts younger than the age of 2 years.¹ No stillborn or fetal tissue is used. Standard disease screening is performed on each lot (one lot of tissue comes from a single donor).

ANATOMY

Tol et al¹⁵ reported that 56% of OLTs were located medially and 44% were located laterally. Of the medial lesions, trauma was implicated in only 62%, whereas trauma was implicated in 94% of the laterally located lesions.
Elias et al⁶ reported similar results regarding location in a magnetic resonance imaging (MRI) examination of 424 OLTs. The talar dome was divided into nine equal sizes zones. Sixty-two percent of lesions were located medially, whereas 34% were located laterally. In the sagittal plane, 80% of lesions were located centrally. The medial-central zone was the most common location for lesions (53%). The authors also reported that medial lesions were significantly larger and deeper.

PATHOGENESIS

Kappis⁷ initially described this pathology as osteochondritis dissecans, suggesting spontaneous necrosis of bone as the primary etiology.
However, contemporary data support trauma as the cause of most OLTs, with repetitive microtrauma, avascular necrosis, and congenital factors as the remaining etiologies.⁴

NATURAL HISTORY

There is debate as to whether a symptomatic OLT will increase in size or progress to ankle arthritis.

PATIENT HISTORY AND PHYSICAL FINDINGS

An OLT should be suspected in anyone presenting after acute traumatic injury to the ankle, chronic ankle sprains, or chronic instability. Patients may complain of pain, stiffness, catching, and swelling of the ankle.¹¹ However, none of these complaints are specific to OLTs.
Often, in the acute setting, a detailed examination is limited secondary to pain and swelling.
In chronic cases, the ankle should be palpated for areas of tenderness. Specifically, the ankle should be plantarflexed, partially uncovering the talar dome, and deep palpation of the anteromedial and anterolateral corners can elicit pain in the presence of an OLT.
Ankle range of motion (ROM) should be recorded and compared to the contralateral extremity. Ankle stability, including the anterior drawer and talar tilt tests should be performed and compared to the contralateral extremity.

IMAGING AND OTHER DIAGNOSTIC STUDIES

Every patient should have weight-bearing anteroposterior (AP), lateral, and mortise radiographic views of the ankle joint.
A debate exists as to the choice of MRI or computed tomography (CT) following negative plain radiographs in a patient with a suspected OLT. We routinely perform an MRI first, as this modality has been shown to be more accurate² in
diagnosing OLTs in the setting of negative plain radiograph and an MRI may identify other bony or soft tissue pathology involved in a painful ankle.
Stroud and Marks¹⁴ proposed an algorithm regarding OLTs diagnosed on plain radiographs. If the OLT is nondisplaced, an MRI is recommended to evaluate the integrity of the articular cartilage and assess the true stability of the lesion. If the lesion appears displaced on plain radiographs, a CT scan is preferred to accurately assess the lesion size and location.
In some cases in which an OLT is diagnosed on MRI, a CT scan can be beneficial for determining the treatment modality, as estimation of the size and stage of the lesion can be obscured by bone marrow edema on MRI.⁹ We routinely obtain both an MRI and a CT scan in large or cystic lesions to aid in treatment decision making.

DIFFERENTIAL DIAGNOSIS

Occult fracture of the talus
Syndesmosis injury
Synovitis
Degenerative arthrosis
Peroneal tendonitis
Soft tissue or bony impingement
Ankle instability
Subtalar arthritis

NONOPERATIVE MANAGEMENT

The initial treatment for a newly diagnosed OLT should be based on the patient’s age, symptoms, chronicity, and stage of the lesion.
Incidentally found asymptomatic lesions do not need treatment but should be followed with serial radiographs.
For symptomatic, nondisplaced lesions, some authors recommend a trial of conservative management for a period of 3 to 6 months.³,¹⁰,¹³
Nonoperative modalities include protected weight bearing, physical therapy, and nonsteroidal anti-inflammatory drugs (NSAIDs). Protected weight bearing can range from cast immobilization and non-weight-bearing status to weight bearing as tolerated in a walking boot.

SURGICAL MANAGEMENT

Arthrotomy

Indications for PJCAT include a primary OLT that is larger than 15 mm in one dimension and/or that has previous failed a marrow stimulation technique with continued symptoms and an OLT as evidenced on MRI. Shoulder and cystic lesions are not excluded.
Contraindications to surgical management of OLTs include infection, medical comorbidities that preclude a surgical procedure, diffuse ankle arthritis, or uncorrected ankle malalignment.
- Specific recommended contraindications to PJCAT include large cystic or necrotic bony defects. Small cystic lesions with bony defects can be managed with concomitant bone grafting with PJCAT. In these instances, the authors have performed local bone grafting from the calcaneus, tibia, or iliac crest with application of the PJCAT graft in the same surgical setting.
PJCAT delivers 1 mm³ of fresh juvenile cartilage, containing live cells in their native extracellular matrix, that are secured into the osteochondral defect with the use of a fibrin adhesive. Because of the particulated nature, perpendicular access to the OLT is not needed. Therefore, an osteotomy is often not necessary. Here, we will discuss the use of an anterior arthrotomy.

Arthroscopic

Performing all-arthroscopic PJCAT can be challenging.
The diagnostic arthroscopy serves to ensure that complete access to the OLT can be obtained.
We have a low threshold to move to an extended portal approach or arthrotomy if OLT access or instrument working room is limited.

Preoperative Planning

Preoperative planning is the same for open or arthroscopic surgery.
Confirmation of the location and size of the OLT is absolutely necessary.
Determination of the appropriate amount of graft to be preordered is necessary. Per the manufacturer, one pack of DeNovo NT Natural Tissue graft (Zimmer) 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 (eg, each pack of tissue graft will cover 1.25 cm² of surface area). In practice, attempts are made to completely fill the lesion’s surface area to the depth of the surrounding healthy cartilage while allowing fibrin adhesive to interpose between cartilage pieces for good tissue fixation.
Fibrin glue (5 to 10 mL) will be needed. Typically, this is stored frozen. It has been our experience that rapid thawing alters the workability of the fibrin glue. Therefore, the fibrin glue should be opened at the start of the case and placed in a warm saline bath according to the manufacturer’s recommendations.
Inspect the PJCAT product for the expiration date prior to starting the procedure.

Positioning

Arthrotomy

The patient is positioned supine. An ipsilateral proximal thigh bump is used to point the toes to the ceiling.
Often, even for the open approach, we perform a diagnostic arthroscopy to confirm the size and location of the lesion. The location of the lesion is assessed while the ankle joint is ranged. This allows a better assessment as to whether the lesion can be approached through an arthrotomy with or without plafondplasty versus a medial or lateral malleolar osteotomy. The technique for standard arthroscopy is beyond the scope of this chapter but is detailed elsewhere.

Arthroscopy

The patient is placed supine on the operating room table with the foot at the end of the bed. The operative leg is placed in a leg holder to keep the hip and knee flexed.
We recommend using noninvasive destraction to allow working room for graft application.

Approach

Arthrotomy