Date Published: May 13, 2012
Publisher: Hindawi Publishing Corporation
Author(s): A. R. Memon, J. F. Quinlan.
Articular cartilage (AC) injury is a common disorder. Numerous techniques have been employed to repair or regenerate the cartilage defects with varying degrees of success. Three commonly performed techniques include bone marrow stimulation, cartilage repair, and cartilage regeneration. This paper focuses on current level of evidence paying particular attention to cartilage regeneration techniques.
AC injury is a common disorder of the knee. It affects people of all ages and sexes. With the ever-increasing population and the active lifestyle of the older generation, incidence of AC injuries is on the rise. In the USA more than 500,000 procedures are performed for cartilage-related injuries and majority represent repeat procedures suggesting an ineffectiveness of surgical treatment . The incidence of cartilage defects has been reported to be as high as 65% in routine knee arthroscopies [2–5]; however, the relevance of these defects to symptomatology is not yet clear. Hunter reported the inability of articular cartilage to regenerate in 1743 . Early chondral lesions are often not detected due to lack of nerve supply, and the absence of vascularity limits the repair potential.
ACI is a two-staged procedure. An initial arthroscopy is performed to evaluate the lesion. 3 to 4 chondral biopsies of AC are taken from non-weight-bearing surfaces of the joint (intercondylar notch, peripheral edges of femoral condyles). The specimen is then transported to the laboratory where the chondrocytes are isolated with an enzymatic process. The chondrocytes are then cultured for 3 to 4 weeks until volume increases by 30-fold for implantation (12 million chondrocytes approx.). Usually at 6 weeks from the initial surgery a second stage operation is carried out. Depending upon the location of the lesion, a medial or lateral patellar arthrotomy is performed. The defect is debrided and fashioned. A periosteal flap is then harvested from proximal tibia (medial femoral condyle can also be used). The flap is then secured to the defect (with its cambium layer facing the bone) on all sides except superiorly. The cultured chondrocytes are then injected under the flap and finally the flap is then attached superiorly as well. Fibrin glue may be used to seal the edges of the flap.
Success of cartilage regeneration is based on its clinical, radiological, and histological outcome. In a number of observational studies, good to excellent clinical results have been obtained at short-to-medium-term followup [31–33]. When comparing ACI to OATS, Horas showed similar outcomes with both procedures; however, the speed of recovery was slower with ACI . Bentley showed good to excellent results in 89% patients following ACI compared to 69% following mosaicplasty . Dozin, on the other hand, observed improvement in 88% patients after mosaicplasty versus only 68% in ACI group . Saris compared chondrocyte implantation with microfracture technique and found better cartilage histomorphometry at 12 months after chondrocyte implantation; however, no difference was observed in clinical outcome (KIIS, Knee Injury and Osteoarthritis Outcome score) at 12–18 months . In another randomized controlled trial (RCT), Knutsen found no difference in clinical and radiological outcome between ACI and microfracture technique . Comparing classical ACI using a periosteal flap with newer generation type I/III collagen membranes, Gooding et al. observed no difference in functional outcome at two years . A similar RCT comparing ACI with matrix-induced ACI by Bartlett et al. also found no significant difference between the two techniques .
MACI is a newer technique and data regarding its efficacy is at best scarce. Several case series have described its efficacy and good short-term results; however, the long-term followup is lacking. Behrens, Elbert, Ventura, and Schneider et al. have described significant improvement in International Knee Documentation Committee (IKDC) Tegner Activity Score and Lysholm and Gillquist scores [46, 49–51]. However, randomised trials by Bartlett, Zeifang, and Manfredini comparing the outcome following MACI versus standard ACI using periosteal flap failed to show superiority of the MACI technique [38, 52, 53]. Zeifang et al. noted no difference in IKDC, Tegner Activity Score, and Short Form-36 at 12 and 24 months whereas better efficacy was observed with ACI technique on Lysholm and Gillquist scoring . Bartlett et al. also observed no difference in the outcome following the two procedures . Graft hypertrophy has been reported at almost 25% in MACI; however, it has not been associated with worse clinical outcome . New experimental studies have been carried out in sheep models to replace the articular chondrocytes with predifferentiated mesenchymal stem cells. Initial results have shown good histological repair with less degradation at 1 year compared to classical articular chondrocyte . This, if proved successful in humans, may substitute the need for the primary procedure to harvest the chondrocytes.
In conclusion, the search for ideal cartilage repair technique continues. The newer generation repair techniques have shown some promise, but long-term outcome is still unknown. Genetic modulation of mesenchymal stem cells and chondrocytes with viral and nonviral vectors has also shown potential but needs further evaluation. Long-term data is required to prove the real benefit of these costly interventions. While MACI has shown good early results, its long-term efficacy is unknown. Microfracture and abrasion arthroplasty are cheap and easier to do but do not provide a durable repair. OAT and mosaicplasty are extremely technically demanding with variable outcomes. Therefore articular cartilage repair remains under intense investigation and an ideal cure is yet to be defined.
The authors declare no conflict of interests.