Collagen fibre implant for tendon and ligament biological augmentation. In vivo study in an ovine model.

PURPOSE: Although most in vitro studies indicate that collagen is a suitable biomaterial for tendon and ligament tissue engineering, in vivo studies of implanted collagen for regeneration of these tissues are still lacking. The objectives of this study were the following: (1) to investigate the regeneration of the central third of the ovine patellar tendon using implants made of an open array of collagen fibres (reconstituted, extruded bovine collagen); and (2) to compare two collagen crosslinking chemistries: carbodiimide and carbodiimide associated with ethyleneglycoldiglycidylether. METHODS: Forty-eight Welsh Mountain sheep were operated on their right hind leg. The central third of patellar tendon was removed and substituted with carbodiimide (n = 16) and carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants (n = 16). In the control group the defect was left empty (n = 16). The central third of contralateral unoperated tendons was used as positive controls. Half of the sheep in each group were killed at 3- and 6-month time points. After proper dissection, tendon sub-units (medial, central and lateral) were tested to failure (n = 6 for each group), whilst 2 non-dissected samples were used for histology. RESULTS: Both the implants had significantly lower stress to failure and modulus with respect to native tendon at both 3- and at 6-month time points. The implants did not statistically differ in stress to failure, whilst carbodiimide-crosslinked implants had significantly higher modulus than carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants both at 3 and at 6 months. Histology showed carbodiimide-crosslinked implants to have a better integration with the native tendon than carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants. Carbodiimide-crosslinked implants appeared partially resorbed and showed increased tissue ingrowth with respect to carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants. CONCLUSIONS: To deliver collagen implants as an open array of fibres allows optimal tendon-implant integration and good ingrowth of regenerated tissue. In the present study the resorption rate of both the examined implants was too low due to the high level of crosslinking. This led to only minor substitution of the implant with regenerated tissue, which in turn produced a low-strength implanted region. Further studies are needed to find the right balance between strength and resorption rate of collagen fibres.

Arthroscopic knee cartilage repair with covered microfracture and bone marrow concentrate.

In recent years several single-stage cartilage repair approaches have been devised to treat focal cartilage lesions. These usually associate microfracture (MFX) and a coverage scaffold. We describe a novel arthroscopic technique that combines MFX, autologous bone marrow concentrate (BMC), and a protective scaffold. Bone marrow aspirate from the iliac crest is centrifuged to obtain BMC. The cartilage defect is debrided, MFX holes are created, and the final defect is measured by use of a bent K-wire. The scaffold is then shaped to match the defect, immersed in BMC, introduced into the joint with a grasper, and fixed in place with a mixture of fibrin glue and BMC. This technique aims to augment the original single-stage procedure with a number of mesenchymal stem cells and growth factors contained in the BMC, to increase the defect filling and the rate of hyaline-like cartilage regeneration. The procedure combining MFX, BMC, and a protective scaffold is inexpensive and reproducible and has already shown the ability to regenerate hyaline-like cartilage. Its use as an alternative to autologous chondrocyte implantation requires further investigation.

Matrix-induced autologous chondrocyte implantation (MACI) in the knee.

PURPOSE: Matrix-induced autologous chondrocyte implantation (MACI) has been in use for chondral defect repair since 2000, but to date, only little is known about its histological outcomes in the repair of knee cartilage defects. This prospective multicentre study aims to evaluate (1) the quality of the repair tissue obtained from biopsies taken during second-look arthroscopy and (2) the relationship between the histological outcome, the macroscopic appearance of the repair and the patients' functional status. METHODS: Thirty-three second-look core biopsies from 30 patients treated with MACI were analysed. At the time of biopsy, the surgeon reported the reason for the second-look arthroscopy, the quality of the repair tissue and the patient's functional status on a standardised form. Biopsies together with patient data were sent to our centre to undergo blind histological evaluation and data analysis. RESULTS: The median overall ICRS II histological score of the examined population was 57 (1st-3rd quartile 41-75). According to the ICRS cartilage repair assessment (CRA) arthroscopic evaluation, 10 biopsies (30%) were classified as normal, 17 (51%) as nearly normal, 4 (12%) as abnormal and 2 (6%) as severely abnormal. The histological outcome was not significantly related either to the macroscopic appearance of the lesion or to the patient's functional status at the time of biopsy. CONCLUSIONS: In the examined population, the macroscopic appearance of the repair tissue gave an overly favourable impression in comparison with the real histological composition of the tissue, which was possibly still maturing in many cases. The healing process after MACI needs to be better understood through a larger histological study, and a longer follow-up is needed to better clarify the relationship between histology and long-term functional status. LEVEL OF EVIDENCE: IV.

Distal realignment and patellar autologous chondrocyte implantation: mid-term results in a selected population.

The aim of this prospective observational study was to assess the 3-year clinical outcome of distal realignment and membrane-seeded autologous chondrocyte implantation (MACI) in selected patients with patellofemoral malalignment and large, isolated, patellar cartilage lesions. Twelve patients (14 knees; 6 females, 6 males; mean age 31 years) with Fulkerson type II patellofemoral malalignment (lateralized and tilted patella) and Outerbridge grade III-IV isolated patellar cartilage lesions were treated. All had tibial tuberosity and trochlear sulcus >20 mm on a preoperative CT scan and a cartilage defect >3 cm2. Patients with Outerbridge grade III-IV trochlear cartilage lesions, those with rheumatic, infective or neoplastic conditions, or ligament instability, diabetes or obesity and those aged >40 years were excluded. Follow-up was at 36 months. Patients were enrolled after diagnostic arthroscopy. Cartilage was harvested and sent for culture. After a mean period of 30 days (range 25-40) patients underwent transfer of the tibial tuberosity according to Fulkerson associated with a MACI procedure. Clinical assessment was performed with the Kujala, Lysholm, Tegner and Modified Cincinnati scores. The Patient Satisfaction Survey was administered at 36 months. Consistently improved knee function and activity levels were reflected by significantly increased Kujala, Lysholm, Tegner and Modified Cincinnati scores at 36 months. The significant clinical improvement support the value of associating distal realignment and autologous chondrocyte implantation in treating large, isolated, patellar cartilage lesions associated with patellofemoral malalignment.