[Tissue engineering in orthopaedic surgery--clinical effectiveness and cost effectiveness of autologous chondrocyte transplantation]

Third-generation autologous chondrocyte implantation versus mosaicplasty for knee cartilage injury: 2-year randomized trial

Numerous surgical techniques have been developed to treat osteochondral defects of the knee. A study reported encouraging outcomes of third-generation autologous chondrocyte implantation achieved using the solid agarose-alginate scaffold Cartipatch®. Whether this scaffold is better than conventional techniques remains unclear. This multicenter randomized controlled trial compared 2-year functional outcomes (IKDC score) after Cartipatch® versus mosaicplasty in patients with isolated symptomatic femoral chondral defects (ICRS III and IV) measuring 2.5-7.5 cm(2) . In addition, a histological evaluation based on the O'Driscoll score was performed after 2 years. We needed 76 patients to demonstrate an at least 10-point subjective IKDC score difference with α = 5% and 90% power. During the enrolment period, we were able to include 55 patients, 30 of them were allocated at random to Cartipatch® and 25 to mosaicplasty. After 2 years, eight patients had been lost to follow-up, six in the Cartipatch® group, and two in the mosaicplasty group. The baseline characteristics of the two groups were not significantly different. The mean IKDC score and score improvement after 2 years were respectively 73.7 ± 20.1 and 31.8 ± 20.8 with Cartipatch® and 81.5 ± 16.4 and 44.4 ± 15.2 with mosaicplasty. The 12.6-point absolute difference in favor of mosaicplasty is statistically significant. Twelve adverse events were recorded in the Cartipatch® group against six in the mosaicplasty group. After 2 years, functional outcomes were significantly worse after Cartipatch® treatment compared to mosaicplasty for isolated focal osteochondral defects of the femur.

Changes in dissipated energy and contact pressure after osteochondral graft transplantation

Osteochondral autologous transplantation is frequently used to repair small cartilage defects. Incongruence between the osteochondral graft surface and the adjacent cartilage leads to changed friction and contact pressure. The present study wanted to analyze the differences between intact and surgically treated cartilage surface in respect to contact pressure and frictional characteristic (dissipated energy). Six ovine carpometacarpal joints were used in the present study. Dissipated energy during instrumentally controlled joint movement as well as static contact pressure were measured in different cartilage states (intact, defect, deep-, flush-, high-implanted osteochondral graft and cartilage failure simulation on a high-implanted graft). The best contact area restoration was observed after the flush implantation. However, the dissipated energy measurements did not reveal an advantage of the flush implantation compared to the defect and deep-implanted graft states. The high-implanted graft was associated with a significant increase of the mean contact pressure and decrease of the contact area but the dissipated energy was on the level of intact cartilage in contrast to other treatments where the dissipated energy was significantly higher as in the intact state. However the cartilage failure simulation on the high-implanted graft showed the highest increase of the dissipated energy.

An in vitro model of biomaterial-augmented microfracture including chondrocyte-progenitor cell interaction

BACKGROUND

Biomaterials, acting as scaffolds for cell migration and differentiation, may be used to improve outcomes after microfracture. Three mechanisms determine the success of such procedures and are tested herein: the general capacity of adult femoral mesenchymal progenitor cells (MPC) to differentiate into cartilage, their capacity to do so in a biomaterial, and finally potential interactions between MPC and autologous chondrocytes.

METHODS

Human adult chondrocytes and MPC were obtained with informed consent and cultured individually or in co-culture on a collagenous biomaterial. Differentiation potential of MPC was assessed using PCR and proliferation and biosynthesis were compared to test for differences between individual cultures and co-cultures. Finally, potential interaction between chondrocytes and MPC was assessed by comparing the observed levels of proliferation and biosynthesis with those expected in independent growth.

RESULTS

We found that adult femoral marrow-derived MPC have the potential to differentiate into multiple lineages, and, seeded in a biomaterial, show similar differentiation when compared with autologous chondrocytes. Finally, there was a strong indication for an interaction between MPC and chondrocytes in biosynthetic activity, which was twice as high as would be expected in independent cell activity. Proliferation rates were unaffected.

CONCLUSION

Our study showed that biomaterial-augmented microfracture is a viable option in cartilage repair from a biological perspective because adult femoral MPC have a strong capacity to differentiate into chondrocytes, which is further enhanced by the surrounding cartilage. Failure in in vivo studies must be explained by other factors of the intra-articular environment, such as cytokines or biomechanics.

The cost utility of autologous chondrocytes implantation using ChondroCelect® in symptomatic knee cartilage lesions in Belgium

BACKGROUND

Knee cartilage lesions increase the risk of developing osteoarthritis (OA), and may eventually result in a total knee replacement (TKR). There is currently no consensus on the optimal treatment of cartilage lesions. ChondroCelect® (CC) is a cell-based therapy approved for use in autologous chondrocytes implantation (ACI) to treat symptomatic cartilage defects of the femoral condyle. Its capacity to safely restore good-quality cartilage was demonstrated in a randomized controlled trial (RCT) versus the surgical procedure microfracture (MFX).

OBJECTIVE

This study investigated the cost utility of CC used in ACI compared with MFX to treat symptomatic knee cartilage lesions in Belgium.

METHODS

A decision tree model comparing CC with MFX over a 40-year horizon was developed in TreeAge Pro™. The key timepoints of the model were (i) clinical assessment 5 years after initial intervention (success or no success, with or without re-operation); (ii) development of OA at 15 years (yes/no); (iii) need for TKR at 20 years (yes/no); and (iv) need for prosthesis revision at 35 years (yes/no). Clinical data provided by the RCT of CC versus MFX were the clinical success (response) rate based on the Knee injury and Osteoarthritis Outcome Score (KOOS) at 36 months (82.9% vs 62.0%; p = 0.048) and the proportion of good structural repair/presence of hyaline cartilage based on International Cartilage Repair Society (ICRS II) visual item at 12 months (44.9% vs 23.2%; p = 0.023). Utility scores by surgery outcome were derived from the SF-36 questionnaire responses collected in the RCT. Conservative assumptions related to the incidences of OA, TKR and prosthesis revision relied on a literature search. A patient chart review (n = 82) provided follow-up costs by surgery outcome. National tariffs were applied to direct medical resources used (healthcare payer perspective, year 2008 costs). Annual discounting was applied to costs (3%) and effects (1.5%) as recommended by the Belgian pharmacoeconomic guidelines.

RESULTS

The incremental cost per QALY gained for CC compared with MFX was €16,229, with a difference in costs of €20,802 and 1.282 QALYs gained. Sensitivity analyses indicated that the key model drivers were the proportion of patients with hyaline cartilage and the correlation between hyaline cartilage formation and later avoidance of OA. Probabilistic sensitivity analyses showed robustness of the results, with 80% of the simulations below the usual UK National Institute for Health and Clinical Excellence (NICE) threshold of €22,000 per QALY.

CONCLUSIONS

Assuming a good correlation between high-quality cartilage repair and avoidance of OA at a later stage, the benefits of the cell therapy CC over MFX in terms of QALYs gained and OA-related costs avoided appear real. Further research is required to explore long-term effects of cartilage repair and reduce uncertainty on quality of life of patients with OA before and after joint replacement.

Cartilage repair: past and future--lessons for regenerative medicine

Since the first cell therapeutic study to repair articular cartilage defects in the knee in 1994, several clinical studies have been reported. An overview of the results of clinical studies did not conclusively show improvement over conventional methods, mainly because few studies reach level I of evidence for effects on middle or long term. However, these explorative trials have provided valuable information about study design, mechanisms of repair and clinical outcome and have revealed that much is still unknown and further improvements are required. Furthermore, cellular and molecular studies using new technologies such as cell tracking, gene arrays and proteomics have provided more insight in the cell biology and mechanisms of joint surface regeneration. Besides articular cartilage, cartilage of other anatomical locations as well as progenitor cells are now considered as alternative cell sources. Growth Factor research has revealed some information on optimal conditions to support cartilage repair. Thus, there is hope for improvement. In order to obtain more robust and reproducible results, more detailed information is needed on many aspects including the fate of the cells, choice of cell type and culture parameters. As for the clinical aspects, it becomes clear that careful selection of patient groups is an important input parameter that should be optimized for each application. In addition, the study outcome parameters should be improved. Although reduced pain and improved function are, from the patient's perspective, the most important outcomes, there is a need for more structure/tissue-related outcome measures. Ideally, criteria and/or markers to identify patients at risk and responders to treatment are the ultimate goal for these more sophisticated regenerative approaches in joint surface repair in particular, and regenerative medicine in general.