Matrix-Assisted Autologous Chondrocyte Transplantation in the Knee: A Systematic Review of Mid- to Long-Term Clinical Outcomes

[Regeneration - A New Therapeutic Dimension in Otorhinolaryngology]

Regeneration as a therapeutic priniciple and regenerative medicine in general are promising new strategies to add new therapeutic dimensions to our current treatment options. Today, reconstructive surgery, drugs and implants such as the cochlear implant can replace the functions of damaged tissues. In contrast, regenerative therapies aim at the replacement of the damaged tissues themselves while at the same time replacing their lost tissue function. In this review article new technologies such as 3D-bioprinting and the application of decellularised tissues as biomaterials are introduced and explained. A summary of current preclinical and clinical regenerative studies in otorhinolaryngology is complementing these basic aspects.

Electron microscopic observation of human auricular chondrocytes transplanted into peritoneal cavity of nude mice for cartilage regeneration

Restoration of damaged cartilage tissue has been deemed futile with current treatments. Although there have been many studies on cartilage regeneration thus far, there is no report that chondrocytes were completely re-differentiated in vitro. The clarification of cellular composition and matrix production during cartilage regeneration must be elucidated to fabricate viable mature cartilage in vitro. In order to achieve this aim, the chondrocytes cultured on coverslips were transplanted into the peritoneal cavities of mice. At different time points post-transplantation, the cartilage maturation progression and cells composing the regeneration were examined. Cartilage regeneration was confirmed by hematoxylin & eosin (HE) and toluidine blue staining. The maturation progression was carefully examined further by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). At the first and second week time points, various cell shapes were observed using SEM. Chronologically, by the third week, the number of fibers increased, suggesting the progression of extracellular matrix (ECM) maturation. Observation through TEM revealed the chondrocytes located in close proximity to various cells including macrophage-like cells. On the second week, infiltration of lymphocytes and capillary vessels were observed, and after the third week, the chondrocytes had matured and were abundantly releasing extracellular matrix. Chronological observation of transplanted chondrocytes by electron microscopy revealed maturation of chondrocytes and accumulation of matrix during the re-differentiation process. Emerging patterns of host-derived cells such as macrophage-like cells and subsequent appearance of lymphocytes-like cells and angiogenesis were documented, providing crucial context for the identification of the cells responsible for in vivo cartilage regeneration.

Patellofemoral Cartilage Repair

Purpose of Review

This review provides an overview of well-established and newly developed cartilage repair techniques for cartilage defects in the patellofemoral joint (PFJ). An algorithm will be presented for approaching cartilage defects considering the distinct anatomy of both the patellar and trochlear articular surfaces.

Recent Findings

Recent studies on cartilage repair in the PFJ have demonstrated improved outcomes in an attempt to delay or obviate the need for arthroplasty, and improve symptoms in young patients. While autologous chondrocyte implantation shows good and excellent outcomes for chondral lesions, osteochondral defects are adequately addressed with osteochondral allograft transplantation. In case of patellar malalignment, concomitant tibial tubercle osteotomy can significantly improve outcomes. Particulated cartilage and bone marrow aspirate concentrate are potential new alternative treatments for cartilage repair, currently in early clinical studies.

Summary

Due to the frequency of concomitant anatomic abnormalities in the PFJ, a thorough clinical examination combined with careful indication for each procedure in each individual patient combined with meticulous surgical technique is central to achieve satisfying outcomes. Additional comparative studies of cartilage repair procedures, as well as investigation of newer techniques, are needed.

Is Delayed Weightbearing After Matrix-Associated Autologous Chondrocyte Implantation in the Knee Associated With Better Outcomes? A Systematic Review of Randomized Controlled Trials

Background:

Proper rehabilitation after matrix-associated autologous chondrocyte implantation (MACI) is essential to restore a patient’s normal function without overloading the repair site.

Purpose:

To evaluate the current literature to assess clinical outcomes of MACI in the knee based on postoperative rehabilitation protocols, namely, the time to return to full weightbearing (WB).

Study Design:

Systematic review; Level of evidence, 1.

Methods:

A systematic review was performed to locate studies of level 1 evidence comparing the outcomes of patients who underwent MACI with a 6-week, 8-week, or 10/11-week time period to return to full WB. Patient-reported outcomes assessed included the Knee injury and Osteoarthritis Outcome Score (KOOS), Tegner activity scale, Short Form Health Survey–36 (SF-36), and visual analog scale (VAS) for pain frequency and severity.

Results:

Seven studies met the inclusion criteria, including a total of 136 patients (138 lesions) who underwent MACI. Treatment failure had occurred in 0.0% of patients in the 6-week group, 7.5% in the 8-week group, and 8.3% in the 10/11-week group at a mean follow-up of 2.5 years (P = .46). KOOS, SF-36, and VAS scores in each group improved significantly from preoperatively to follow-up (P < .001).

Conclusion:

Patients undergoing MACI in the knee can be expected to experience improvement in clinical outcomes with the rehabilitation protocols outlined in this work. No significant differences were seen in failure rates based on the time to return to full WB.