History (Signs and Symptoms)

An adequate history is the initial step in determining whether ACI is the appropriate treatment for a suspected chondral defect. Patients with femoral condylar lesions commonly have pain with weight bearing or increased loading and mechanical symptoms such as catching, locking, or giving way. Persistent or intermittent swelling is also a common complaint. Often patients are able to localize the area of pain or tenderness. The presence of a patellofemoral defect will produce similar complaints, but with symptoms exacerbated by stairs, getting into and out of a chair or car, and anterior knee pain. Patellar subluxation symptoms are often present as well. It is prudent to match the patient’s complaints to the location of the chondral defect to determine that the symptoms are originating from the defect and are not caused by other, coexisting pathology. Finally, individual patient characteristics must be considered in the treatment planning; these include age, body mass index, concomitant knee pathology, smoking, compliance, and expectations. With known chondral defects, additional information is frequently available through previous operative reports and intraoperative images. This will give some indication of the size, location, and number of defects present within the knee. Taking advantage of any available information will help in determining the suitability of the defect for ACI.

Physical Examination

Physical examination is helpful to match the patient’s symptoms to the location of the actual defect. Basic observation of gait and gross alignment provide information about the patient’s level of function. A thorough evaluation of the knee can quickly establish the presence of an effusion, determine any ligamentous instability or motion deficits, and reveal areas of tenderness with palpation or provocative testing. Should there be questions regarding the examination findings, MRI can provide additional information. Evaluation of the menisci includes provocative meniscal tests and an assessment of radiographs and possibly MRI scans.

Imaging

To adequately evaluate a patient for any cartilage treatment including ACI, it is imperative that weight-bearing anteroposterior (AP) and 45-degree posteroanterior (PA) views be obtained. In addition, patellar alignment radiographs should be obtained with lateral and sunrise views. This allows evaluation of the alignment of the tibiofemoral and patellofemoral portions of the knee and gives an indication of any underlying bone involvement associated with the defect. A long-leg limb alignment radiographic view should be used to assess the mechanical axis and determine the potential need for realignment (Fig. 69-1). The greater availability of office-based digital imaging has made obtaining these long-limb alignment views very practical. As mentioned, MRI can then be used to assess for the presence of both ligamentous injury and damage to the menisci, as well as to define the degree of subchondral bone involvement. Increased signal and edema of a chronic nature in the subchondral bone may indicate persistent overload of the involved compartment and may indicate the need for a realignment procedure in addition to ACI. Bone loss of more than 7 to 8 mm in depth necessitates bone grafting before or at the time of cell implantation. Although MRI is helpful to evaluate subchondral bone loss and the soft tissues of the knee, owing to the wide variations in magnetic resonance field strengths and imaging protocols, at present it does not have consistent sensitivity or specificity to evaluate the full extent of chondral injury or other, more subtle changes to the cartilage.

Indications and Contraindications4,5,8,14,15

ACI is indicated for symptomatic, full-thickness chondral lesions and osteochondritis dissecans (OCD) lesions of the femoral condyles and trochlea in physiologically young patients (aged 15 to 55 years) who can be compliant with the rehabilitation protocol (Fig. 69-2). Results of treatment of chondral injuries of the patella with ACI have become much more consistently favorable with realignment and appropriate patellar tracking. ACI is not indicated as a treatment for advanced osteoarthritis or in the presence of bipolar sclerotic bone-on-bone lesions (Fig. 69-3). ACI is also contraindicated in active inflammatory arthritis or infection. In summary, the prerequisites for a successful outcome in treatment of a full-thickness focal chondral defect with ACI include appropriate bony alignment, ligamentous stability, meniscal function, adequate motion and muscle strength, and patient compliance without significant arthritic changes.

Anesthesia and Positioning

Typically ACI is performed with general anesthesia augmented by use of peripheral nerve blocks for postoperative pain management. In general, we prefer to have the peripheral block in place before initiation of the procedure. The peripheral block is either a femoral or sciatic block or both. Depending on the complexity of the procedure (multiple lesions or concomitant bony procedures), we have had high patient satisfaction with use of a catheter pain pump for the peripheral block for 2 to 3 days postoperatively.

The patient is placed on the operating table in the supine position. The involved lower extremity is positioned so that the knee may be placed into maximum flexion if necessary, and rests with the foot on a sandbag or other positioning device so that the knee is at 90 degrees of flexion. Prophylactic antibiotics are routinely used. After preparation and draping, a midline incision is generally recommended, followed by a medial or lateral parapatellar arthrotomy, exposing the corresponding chondral injury for condyle defects. For patellar defects and many trochlear defects, the patella is generally reflected superiorly through a tibial tubercle osteotomy that is commonly performed for purposes of patellofemoral realignment. As with any surgical procedure, good exposure is critical for performance of the intended technique and good outcome. The approach must allow the surgeon access to properly suture the covering membrane to the chondral defect with 6-0 Vicryl suture. The end result should never be compromised for the sake of an ill-advised concern for keeping the approach small.