ACI

brane such as Chondro-Gide(r) in place of periosteum, resulting in a less invasive procedure that has been shown to reduce or even eliminate graft hypertrophy (16).

The general indications for ACI and the exclusion criteria are shown in Table 1. In line with NICE guidelines ACI is not cur- rently recommended for ‘routine primary treatment of articular cartilage defects of the knee joint’ in the NHS (17). However there has been increasing evidence in recent years to support the use of ACI as a primary treatment for high demand individ- uals - generally the young and active (18).

COLLAGEN MEMBRANE ACI PROCEDURE Stage 1 The first stage is arthroscopic and involves assessment of the defect. If the defect is suitable for ACI, a biopsy of cartilage is taken from a non weight-bearing area (Figure 1). The cartilage sample is sent to a specialist laboratory where the chondro- cyte cells from the sample are multiplied until there is sufficient number for the size of the defect (average of 1 million cells per cm defect area).

Stage 2 The second stage is via an open arthroto- my. The defect is first cleaned and pre- pared. The Chondro-Gide(r) membrane is then sutured onto the defect to produce a water tight pocket (Figure 2) into which the cultured autologous cells are implant- ed back into the defect (Figure 3).

TABLE 1. GENERAL INDICATIONS FOR ACI TREATMENT AND EXCLUSION CRITERIA

General indications for ACI ■ Chondral/osteochondral defect >1 cm ■ Focal lesion ■ Age 15-55 years Inclusion criteria ■ Symptomatic ■ Willing and able to commit to and complete the rehabilitation programme Exclusion criteria ■ Advanced asteoarthritis ■ Rheumatoid arthritis ■ Total menisectomy ■ Ligament instability, malalign- ment and patellofemoral instability if not corrected prior to, or concomit- tant with, the ACI procedure.

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ACI OUTCOMES There are an increasing number of ACI out- come studies including an 11 year follow up study (19,20). A variety of outcome measures are in use but studies commonly use a combination of arthroscopy, MRI, clinical assessment and histology. New studies are looking at correlations between different outcome scoring systems and clinical results. Advanced magnetic reso- nance imaging (MRI) technologies have been developed using special articular car- tilage scanning protocols and MRI is becoming an increasingly effective, non- invasive method of assessing articular car- tilage defects and repairs (21-23).

Reported outcomes range between 65% to 96% excellent or good ratings dependent on location, number and size of defects. The lower success rates generally tend to be the earlier procedures where a technical learning curve was taking place and in the last few years good or excellent patient sat- isfaction ratings have been in the 80% to 90% range. Initially outcomes for patella and trochlea lesions weren’t as promising as those for the medial femoral condyle, how- ever recent studies have shown high patient satisfaction with 71% excellent or good results for patellofemoral ACIs (24).

Incidence of treatment failure is low with the most widely reported causes due to either post-implantation trauma, non-com- pliance with rehabilitation, too early return to high impact sports, progressive osteoarthritis or graft delamination. As with any surgery there are associated risks and recognised complications following ACI. These include infection, swelling, deep vein thrombosis, adhesions, graft delamination and hypertrophy. Recent research has shown that age, duration of symptoms and the number of prior surgical procedures are the most significant adverse prognostic factors and that traumatic lesions tend to do better than chronic (18).

REHABILITATION AND RETURN TO SPORT Successful ACI procedures can be attrib- uted to a number of factors including patient selection, quality assurance of chondrocytes and surgical technical exper- tise. Rehabilitation is also accepted as a critical factor (25-27). Rehabilitation fol- lowing ACI is a long and demanding process that requires an understanding of both the procedure and the healing

Figure 1: During arthroscopy a biopsy of articular cartilage is taken from a non weight bearing area.

Figure 2: The Chondro-Gide(r) membrane is sutured to the chondral defect

Figure 3: The cultured autologous cells are implanted back into the defect.

process. Graft remodeling and maturation can continue for up to 24 months follow- ing ACI surgery and therefore patient edu- cation and management of patient expec- tations and goals is important.

The general principle of ACI rehabilitation is to optimise local adaptation and modifi- cation of the repair in a manner that is functional, progressive and safe. This is reliant on a collaborative environment with good communication between the surgeon, therapist and patient. There are three main components of the rehabilita- tion programme - progressive weight-bear- ing, restoration of range of motion and muscle strengthening. Modifications to the rehabilitation programme may be neces- sary based on defect size, location (28), age, previous activity level, concomittant surgical procedures and individual patient demands. For the first 12 weeks after ACI the graft is at its most vunerable and dur- ing this time it is important to avoid

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