Autologous Osteochondral Transplantation

39 Autologous Osteochondral Transplantation

Yoshiharu Shimozono, Youichi Yasui, Andrew W. Ross, and John G. Kennedy

Abstract

Autologous osteochondral transplantation (AOT) is an osteochondral replacement technique to restore the biologic and anatomic function of the articular cartilage and subchondral bone. This procedure is typically indicated for large (>100–150 mm ²) or cystic lesions. The surgical approach is determined by the location of the lesions, and adequate exposure of the lesions is essential for optimal results. Both medial and lateral tibial osteotomies have been utilized to obtain exposure of the lesions for perpendicular insertion of grafts. The osteochondral graft is typically harvested from the non-weight-bearing portion of the ipsilateral femoral condyle. Graft implantation should be flush with the adjacent native cartilage surface. Concentrated bone marrow aspirate may be utilized to promote bone healing and integration between the graft and host tissue cartilage. The clinical outcomes after AOT are promising in the short to medium term. In the athletic population, 90% of professional athletes returned to preinjury sports activity. Donor-site morbidity and postoperative cyst formation have been reported in several studies. However, donor-site knee pain does not appear to be a significant issue and its incidence is reported to be less than 5%, and most cysts are asymptomatic and resolve over time.

Keywords: osteochondral lesion, ankle, talus, autograft, malleolar osteotomy

39.1 Indications

• Osteochondral lesions of the talus (OLTs) with persistent ankle pain following 3 months of conservative treatment.

• Operative techniques can be broadly divided into two procedures: reparative, including bone marrow stimulation (BMS), and replacement procedures, including autologous osteochondral transplantation (AOT).

• The clinical criteria to decide which operative technique should be indicated are the following:

Lesion size:
Large OLTs, traditionally characterized as lesions greater than 150 mm² in area or 15 mm in diameter, are candidates for AOT.¹^,² However, a recent systematic review study demonstrated that lesions greater than 107.4 mm² in area and/or 10.2 mm in diameter are the optimal for AOT.³

Previously failed BMS.⁴^,⁵

Cystic lesions:
OLTs with large cystic subchondral defects may be optimal candidates for AOT, although there are no clearly established criteria regarding cyst depth or size.⁶

39.1.1 Pathology

• Damage to the cartilage and underlying bone in the talar dome.

• Most commonly traumatic in nature.

• Most commonly seen in younger adult athletes.

39.1.2 Clinical Evaluation

• Patient usually complains of pain on weight-bearing on the ankle:

Usually pain-free when not weight-bearing.

• May have symptoms of ankle instability with clinically stable ligamentous complex.

• Tenderness at the ankle joint line:

Tenderness and location of reported pain does not always correspond with location of the lesion.

39.1.3 Radiographic Evaluation

• Weight-bearing anteroposterior, lateral, and mortise views of the ankle:

A shadowing or defect may be seen in the bone in the region of the lesion.

Loose body or fragment may be seen within or separate from the lesion base.

• Magnetic resonance imaging (MRI):

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.

• CT scan (fine cut)—with axial, coronal, and sagittal cuts:

Best study to determine the size and configuration of the bony lesion.

Accurate in determining presence of cysts and microcysts adjacent to the OLT.

39.1.4 Contraindications

• Rheumatoid disease.

• Posttraumatic ankle osteoarthritis with grade II or greater lesions.

• Uncorrected ankle malalignment.

• Moderate to severe medical comorbidities (e.g., diabetes, autoimmune disease, active infection).

39.2 Goals of Surgical Procedure

The goal of AOT is to restore the biologic and anatomic function of talar articular cartilage and subchondral bone. To achieve this, AOT includes replacement of the damaged cartilage and subchondral bone with one or more autologous grafts that have similar mechanical, structural, and biochemical properties of native hyaline articular cartilage.

39.3 Advantages of Surgical Procedure

The advantage of AOT is that this technique can replace the lesions with viable hyaline cartilage and subchondral bone without the need for two-staged procedure. Intraoperative damage of subchondral bone during BMS procedure is of growing concern. The role of the local subchondral environment has been shown to be integral to cartilage repair, and failed functional outcomes following BMS may be due to impairment of subchondral bone. Unlike BMS, AOT replaces local subchondral bone and may result in the restoration of the native biological environment leading to better functional outcomes.

AOT has several potential disadvantages, including donor-site morbidity, the possible need for an osteotomy while accessing the talar dome, differences of cartilage biology between the host and graft tissues, and poor potential for integration at the cartilage interface.

39.4 Key Principles

AOT involves cylindrical osteochondral grafts harvested from a donor site, typically a non-weight-bearing portion of the ipsilateral knee. These are transplanted into a recipient site at the location of the cartilage defect on the talus. The procedure is typically carried out in the following steps:

1. Tibial osteotomy.

2. Preparation of the recipient site for the insertion of the osteochondral graft.

3. Harvesting of osteochondral graft from ipsilateral lateral femoral condyle.

4. Insertion of osteochondral graft into the created recipient site of the talus.

5. Fixation of tibial osteotomy fragment.

39.5 Preoperative Preparation and Patient Positioning

Numerous commercial instruments are available for AOT of the talus. While several instruments are available, the authors utilize the Osteochondral Autograft Transplant System (OATS; Arthrex, Naples, FL). The utilized core sizes are 6, 8, and 10 mm. A recipient sizer, recipient harvester, donor harvester, and tamp are basic instruments for AOT. Standard surgical instruments for the tibial osteotomy and exposure of the ankle joint are also required. Kirschner wires (K-wires), cannulated drill set and screws (3.5/4.0 mm), and fluoroscopy are used for fixation of the osteotomy site. Titanium screws are optimal for fixation of the osteotomy to allow for potential postoperative MRI evaluation with minimal metallic interference.

Under general or spinal anesthesia, the patient is placed in the supine position. The authors prefer to use a thigh tourniquet.

39.6 Operative Technique

39.6.1 Tibial Osteotomy

It is imperative to create a direct path for perpendicular insertion of the osteochondral graft in order to construct a congruent articular surface. The acceptable range between graft surface and native articular surface is only 1.0 mm sunken to 0.4 mm proud.⁷

Due to the majority of medial OLTs being located in the central or posterior position in talus, a medial malleolar chevron osteotomy is often required to provide adequate exposure. First, a longitudinal skin incision is made over the medial malleolus. The posterior tibial tendon is then retracted with extra care taken to avoid iatrogenic neurovascular damage. The medial corner of the anterior aspect of tibia is exposed in order to establish the anatomical landmark for the osteotomy line. Caution is taken to minimize periosteum stripping of the medial malleolus. A provisional K-wire is then inserted under fluoroscopy to determine a precise osteotomy line (Fig. 39.1). After the decision of the osteotomy line is complete, two parallel fixation holes in the medial malleolus are predrilled for later anatomic fixation with 4.0-mm titanium screws. A medial malleolar chevron osteotomy is then performed using an oscillating saw. A chevron-type osteotomy is preferred in order to provide appropriate anatomic alignment, stability after fixation, and a large surface area for greater healing and visualization. At the level of the subchondral bone, the saw is stopped and the osteotomy is completed with an osteotome. The osteomized medial malleolus is reflected in the plantar direction on the deltoid ligament hinge to allow exposure of the medial aspect of the talar dome. The authors employ a retractor to maintain visualization (Fig. 39.2).