Chapter 67

Defects of articular cartilage are a relatively common problem encountered by the sports medicine physician. Isolated cartilage defects can occur secondary to acute trauma or can be atraumatic in nature. The latter often occur in the form of osteochondritis dissecans, the cause of which is not fully understood, and can be found in juveniles and in adults. The distinction is important, because patients with open physes have a much better prognosis with nonoperative treatment.¹

Patients with symptomatic focal cartilage defects are candidates for operative treatment to relieve symptoms and also to potentially prevent subsequent arthritic changes.² Surgical treatment options include arthroscopic debridement, microfracture, autologous chondrocyte implantation (ACI), matrix-induced chondrocyte transplantation, osteochondral autograft transplant surgery (OATS), and osteochondral allograft transplantation. OATS may be the best option in appropriately selected patients. There are several different transplant systems available, but the concept remains the same: the transplantation of full-thickness osteochondral bone plugs from an area of the knee that is non–weight-bearing or has low contact pressures to the osteochondral defect of the ipsilateral knee.

Preoperative Considerations

History

Patients with focal osteochondral lesions typically have pain and swelling that is intermittent in nature. The history may mimic that of mensical pathology.

Typical History

• Patient age—varies from adolescence to middle age

• Intermittent pain

• Pain elicited by low- or high-impact activities (tibiofemoral disease) or stair climbing and prolonged sitting (patellofemoral disease)

• Recurrent swelling

• Frequently a history of acute or distant trauma, including patellar dislocation

• Mechanical symptoms common

• Symptoms referable to an associated loose body

Physical Examination

Typical Physical Examination Findings

• Effusion

• Relatively preserved range of motion (ROM)

• Possible joint line tenderness

• Possible patellar instability, apprehension

Physical examination findings may be unimpressive; patient history and radiographs or magnetic resonance imaging (MRI) scans are often more telling.

Physical Factors Affecting Surgical Planning

• Limb malalignment (may compromise repair, require realignment procedure)

• Concomitant ligamentous injury (may require prior or concomitant reconstruction)

Imaging

Radiography

• Standard anteroposterior (AP) and lateral knee views.

• Sunrise patellofemoral view to visualize patellar and trochlear lesions.

• Notch view may be best to visualize lateral aspect of medial femoral condyle (typical location of osteochondral defects [OCDs]).³

• A mechanical axis view is obtained if malaligment is suspected.

Additional Imaging

• MRI is necessary to best evaluate location and size of articular cartilage lesions. MRI is also important for evaluation of menisci, ligaments, and remainder of articular cartilage.

• Bone scans, computed tomography, and tomograms are not as useful as MRI for evaluation of OCDs and the remainder of the knee.

• Contrast arthrography (intra-articular or intravenous) may prove to be more sensitive than MRI alone, which can have a high false-negative rate.⁴

• Arthroscopy remains the gold standard for evaluation of articular cartilage lesions.

Indications

The indications for OATS are narrow. The patient generally has a small, isolated lesion in an otherwise healthy knee. However, concomitant ligament, meniscus, or alignment pathology may be present and can be addressed simultaneously or with a staged procedure.

Typically during concomitant procedures the surgeon performs autologous osteochondral grafting and anterior cruciate ligament (ACL) reconstruction or high-tibial osteotomy. During ACL reconstruction the osteochondral grafting should proceed after meniscal or other cartilage pathology has been addressed and notchplasty has been performed, but before ACL graft fixation. This is to avoid damage to the newly implanted osteochondral plugs. Osteotomy is typically performed after the OATS procedure.

We prefer to perform single-plug autograft transplants on defects 1 cm² in diameter or smaller, with allograft transplants used for larger defects. However, some authors perform autograft transplants on defects as large as 4 cm², with good results⁵ with use of multiple plugs of varying size (aka “mosaicplasty”).

Contraindications

• Generalized arthritis

• Inflammatory arthritis

• Lesions smaller than 1 cm² for single plugs

• Lesion larger than 3 cm² for multiple plugs

• Uncorrected malalignment or knee instability

Surgical Planning

Osteochondral defects are frequently diagnosed in the office after history and physical examination and interpretation of radiographs and MRI scans. The patient and surgeon might then plan for single-stage surgery with arthroscopic examination of the knee to assess the defect. If applicable, an autograft transplant with single or multiple plugs can be performed. The number and size of osteochondral plugs required cannot be determined until the defect has been thoroughly examined via arthroscopy. Defects that are discovered to be excessively large may require allograft transplant, which must be anticipated and planned for. Typically this is performed as a second procedure.

At times, OCDs are not appreciated preoperatively and are discovered during routine knee arthroscopy. The morbidity of the procedure and its rehabilitation process is quite different from that of a standard knee arthroscopy. These patients usually require a second procedure for definitive treatment at a later date unless the surgeon and patient have discussed this possibility preoperatively.

Surgical Steps

See Box 67-1 for a summary of the surgical steps.

Box 67-1   Surgical Steps for Osteochondral Autograft Transfer

1. Diagnostic arthroscopy to debride and measure defect. Plan number, size and placement of specific grafts. Remainder of procedure can be performed as mini-open if desired.

2. Place donor harvester perpendicular to donor site and tamp harvester to required depth. View measurement on outside of harvester.

3. Disengage graft from local bed. Method of disengaging the graft varies with system.

4. Remove graft donor assembly from knee with autograft plug and measure depth of plug.

5. Tamp recipient harvester into defect to desired depth (1 to 2 mm deeper than plug). Keep recipient harvesting tools perpendicular to articular surface.

6. Insert graft under direct visualization through optional clear tube. Be careful to keep tube on articular surface during implantation.

7. Remove clear tube and gently seat graft with plastic tamp until graft is flush with articular surface.

Expanded Surgical Technique

Three different systems are commercially available in the United States. All three are very similar and differ in the available graft sizes and minor variations of technique. A comparison is shown in Table 67-1. An example of the necessary equipment is shown in Figure 67-1.

TABLE 67-1

Specific Aspects of the Three Different Commercially Available Osteochondral Autograft Systems

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