Polyurethane-based cell-free scaffold for the treatment of painful partial meniscus loss.

PURPOSE: The aim of this study was to document, at mid-term follow-up, the clinical and MRI outcome of a polyurethane-based cell-free scaffold implanted to treat painful partial meniscus loss. METHODS: Eighteen consecutive patients were enrolled and treated with arthroscopic polyurethane meniscal scaffold implantation and, in case of other comorbidities, with concurrent surgical procedures: 16 patients (9 men and 7 women, mean age 45 ± 13 years, mean BMI 25 ± 3, 12 medial and 4 lateral implants) were prospectively evaluated with the subjective and objective IKDC and the Tegner scores at 24, 36, 48, 60, and 72 months of follow-up. Eleven patients were also evaluated by 1.5-T MRI at the final follow-up. RESULTS: The IKDC subjective score showed a significant improvement from baseline to 24 months (45.6 ± 17.5 and 75.3 ± 14.8, respectively; p = 0.02) and subsequent stable results over time for up to 72 months (final score 75.0 ± 16.8). The Tegner score improvement between pre-operative status and final follow-up was also significant (p = 0.039). Nevertheless, the final score remained significantly lower than the pre-injury sports activity level (p = 0.027). High-resolution MRIs documented the presence of abnormal findings in terms of morphology, signal intensity, and interface between the implant and the native meniscus. Implant extrusion and bone oedema at the treated compartment were also observed in most of the cases, even though no correlation was found between imaging findings and clinical outcome. CONCLUSIONS: The present study reports satisfactory clinical outcomes at mid-term follow-up after polyurethane-based meniscal cell-free scaffold implantation. The treatment was effective both in cases of isolated partial meniscal lesions and in complex cases requiring the combination with other surgical procedures. On the other hand, a high rate of altered MRI aspects was documented. However, no correlation was found between the altered imaging parameters and the overall positive clinical findings, thus supporting the use of this procedure to treat painful partial meniscus loss. LEVEL OF EVIDENCE: Case series, Level IV.

Fibrin glue improves osteochondral scaffold fixation: study on the human cadaveric knee exposed to continuous passive motion.

OBJECTIVE: To evaluate stability and integrity of bi-layer and three-layer collagen-hydroxyapatite (C-HA) osteochondral scaffolds in a human cadaveric knee exposed to continuous passive motion (CPM) with and without loading and the role of added fibrin glue to improve the press-fit fixation of C-HA scaffolds. DESIGN: Osteochondral lesions (2.0 × 1.5 cm) were chiseled out on both condyles and trochlea in eight human cadaveric knees. A total of 24 bi-layer (5 mm, four in each condyle) or three-layer C-HA scaffolds (8 mm, eight in the trochlea, four in each condyle) were first press-fit implanted and underwent testing with CPM, 90 cycles, 0°-90°. The second set of 24 scaffolds was implanted in cleaned lesions with the addition of fibrin glue. Two knees with fibrin glue fixation were additionally exposed to 15 kg loading, with 30 cycles of CPM, 0°-30°. Then, the knees were reopened and the scaffolds were evaluated using semi-quantitative Drobnic and modified Bekkers scores. RESULTS: All but two scaffolds remained in the lesions site throughout CPM. Two implants failed: both were bi-layer osteochondral scaffolds, press-fit implanted at the lateral femoral condyle (LFC). A statistically significant difference was obtained between press-fit and fibrin glue implants with both Drobnic (2.9 ± 0.7 vs 4.3 ± 0.1, P < 0.0005) and Bekkers (3.3 ± 1.0 vs 5.0 ± 0.1, P < 0.0005) scores. Additional knee loading did not affect fibrin glue scaffold fixation or integrity. CONCLUSION: This cadaveric study showed fibrin glue notably improved bi-layer or three-layer C-HA scaffold press-fit fixation regardless of lesion location. It is therefore recommended that fibrin glue be used during surgery to improve early post-operative C-HA scaffold stability and integrity.

Osteochondral regeneration using a novel aragonite-hyaluronate bi-phasic scaffold in a goat model.

PURPOSE: The objective of this study was to examine whether different mechanical modifications and/or impregnation of hyaluronic acid (HA) might enhance aragonite-based scaffold properties for the regeneration of cartilage and bone in an animal model. METHODS: Bi-phasic osteochondral scaffolds were prepared using coralline aragonite with different modifications, including 1- to 2-mm-deep drilled channels in the cartilage phase (Group 1, n = 7) or in the bone phase (Group 2, n = 8), and compared with unmodified coral cylinders (Group 3, n = 8) as well as empty control defects (Group 4, n = 4). In each group, four of the implants were impregnated with HA to the cartilage phase. Osteochondral defects (6 mm diameter, 8 mm depth) were made in medial and lateral femoral condyles of 14 goats, and the scaffolds were implanted according to a randomization chart. After 6 months, cartilage and bone regeneration were evaluated macroscopically and histologically by an external laboratory. RESULTS: Group 1 implants were replaced by newly formed hyaline cartilage and subchondral bone (combined histological evaluation according to the ICRS II-2010 and O'Driscoll et al. 34 ± 4 n = 7). In this group, the cartilaginous repair tissue showed a smooth contour and was well integrated into the adjacent native cartilage, with morphological evidence of hyaline cartilage as confirmed by the marked presence of proteoglycans, a marked grade of collagen type II and the absence of collagen type I. The average scores in other groups were significantly lower (Group 2 (n = 8) 28.8 ± 11, Group 3 (n = 8) 23 ± 9 and Group 4 (empty control, n = 4) 19.7 ± 15). CONCLUSIONS: The implants with the mechanical modification and HA impregnation in the cartilage phase outperformed all other types of implant. Although native coral is an excellent material for bone repair, as a stand-alone material implant, it does not regenerate hyaline cartilage. Mechanical modification with drilled channels and impregnation of HA within the coral pores enhanced the scaffold's cartilage regenerative potential. The modified implant shows young hyaline cartilage regeneration. This implant might be useful for the treatment of both chondral and osteochondral defects in humans.

3D Patterning of cells in Magnetic Scaffolds for Tissue Engineering.

A three dimensional magnetic patterning of two cell types was realised in vitro inside an additive manufactured magnetic scaffold, as a conceptual precursor for the vascularised tissue. The realisation of separate arrangements of vascular and osteoprogenitor cells, labelled with biocompatible magnetic nanoparticles, was established on the opposite sides of the scaffold fibres under the effect of non-homogeneous magnetic gradients and loading magnetic configuration. The magnetisation of the scaffold amplified the guiding effects by an additional trapping of cells due to short range magnetic forces. The mathematical modelling confirmed the strong enhancement of the magnetic gradients and their particular geometrical distribution near the fibres, defining the preferential cell positioning on the micro-scale. The manipulation of cells inside suitably designed magnetic scaffolds represents a unique solution for the assembling of cellular constructs organised in biologically adequate arrangements.

New cell-based technologies in bone and cartilage tissue engineering. I. Bone reconstruction.

A tissue engineering, cell-based therapeutic approach could be essential for extensive bone or cartilage reconstruction. This article is divided in two chapters and describes new cell-based surgical techniques for cartilage and bone reconstruction. In the first part on bone reconstruction, marrow-derived osteogenic progenitor cells combined with hydroxyapatite were utilized. The validity of this model has been shown for the repair of critical size bone defects in large size animal models. We used this cell-based therapeutic approach to treat 3 patients with large bone defects, achieving bone reconstruction.

A novel nano-composite multi-layered biomaterial for treatment of osteochondral lesions: technique note and an early stability pilot clinical trial.

INTRODUCTION: Osteochondral articular defects are a key concern in orthopaedic surgery. Current surgical techniques to repair osteochondral defects lead to poor subchondral bone regeneration and fibrocartilage formation, which is often associated with joint pain and stiffness. The objective of this pilot clinical study is to evaluate the performance and the intrinsic stability of a newly developed biomimetic osteochondral scaffold and to test the safety and the feasibility of the surgical procedure. METHODS: A gradient composite osteochondral scaffold based on type I collagen-hydroxyapatite was obtained by nucleating collagen fibrils with hydroxyapatite nanoparticles. Thirteen patients (15 defect sites) were treated with scaffold implantation from January 2007 to July 2007: four at the medial femoral condyle, two at the lateral femoral condyles, five at the patellas and four at the trochleas. The mean size of the defects was 2.8 cm(2) (range: 1.5-5.9 cm(2)). All patients were followed up prospectively. High-resolution magnetic resonance imaging (MRI) was used to determine "the early postoperative adherence rate" at 4-5 weeks and 25-26 weeks after scaffold implantation. Moreover, the magnetic resonance observation of cartilage repair tissue (MOCART) score was performed on every MRI. Two second-looks were performed at 6 months; cartilage repair was assessed using the International Cartilage Repair Society (ICRS) visual scoring system and histological and immunohistochemical analysis of the two biopsies was carried out. RESULTS: A completely attached graft and repair tissue were found in 13 of 15 lesions (86.7%). A partial detachment was observed in two patients (13.3%). No detached grafts were found. Complete filling of the cartilage defect and congruency of the articular surface were seen in 10 lesions (66.7%) with MRI evaluation at 6 months. The complete integration of the grafted cartilage was detected in eight lesions (53.3%). Subchondral bone changes (oedema or sclerosis) were found in eight defects (53.3%). Statistical analysis showed a significant improvement in the International Knee Documentation Committee (IKDC) subjective and objective scores from preoperative to 6 months' follow-up (p<0.0005). Visual scoring of the repaired tissue at second-look revealed a normal repair score in one case and a near-normal repair score in the other case. Histological analysis showed the formation of subchondral bone without the presence of biomaterial. The cartilage repair tissue appeared to be engaged in an ongoing maturation process. CONCLUSIONS: The technique is safe and MRI evaluation at short-term follow-up has demonstrated good stability of the scaffold without any other fixation device. The preliminary clinical results at short-term follow-up are encouraging. A clinical and MRI study with longer follow-up and randomised studies will be done to confirm the high potential of this novel osteochondral scaffold.

A tissue engineering approach to meniscus regeneration in a sheep model.

OBJECTIVE: Regeneration of the meniscal tissue occurs to a limited extent, and the loss of meniscal tissue leads to osteoarthritis. A new biomaterial consisting of hyaluronic acid and polycaprolactone was used as a meniscus substitute in sheep to evaluate the properties of the implant material with regard to size, biomechanical stability, tissue ingrowth, and integration. METHODS: Eight sheep (right stifle joints) were treated with three total and three partial meniscus replacements while two meniscectomies served as empty controls. The animals were euthanized after 6 weeks. The specimens were assessed by gross inspection and histology, and compared with the nonoperated left joints. RESULTS: The surgical technique was found to be feasible. The implants remained in position, did not tear, and showed excellent tissue ingrowth to the capsule. Tissue integration was also observed between the original meniscus and the implant. However, graft compression and extrusion occurred. The histological investigation revealed tissue formation, cellular infiltration and vascularization. Cartilage degeneration was more severe in the operated joints. CONCLUSION: The present study shows promising results concerning the qualities of this biomaterial with regard to implantation technique, stability and tissue ingrowth.

Arthroscopic autologous chondrocyte transplantation: technical note.

We describe an arthroscopic surgical technique for tissue engineered cartilage grafting. A three-dimensional hyaluronic acid support is used for autologous chondrocyte culturing. The technique reduces morbidity of classic autologous implant and avoids open surgery and the use of a periosteal flap. The procedure includes the advantages of arthroscopic osteochondral grafting without donor site morbidity. With this technique is possible to reduce the patient morbidity, time and cost of surgery.

Reconstruction of extensive long-bone defects in sheep using porous hydroxyapatite sponges.

The capacity of hydroxyapatite (HA) implants to support large defect repair in weight-bearing long bones of large size animals was investigated. Diaphyseal resections 3.5 cm of the tibia were performed in five adult sheep. They were substituted with HA macroporous ceramic cylinders anatomically shaped, and an external fixator was assembled. The sheep were sacrificed at 20, 40, 60, 120, and 270 days after surgery, respectively. Histology and micro X-ray study of resected implants and adjacent tissues showed proper integration of ceramic with newly formed periosteal bone as early as 20 days after surgery. In one sheep, the external fixator was removed 5 months after surgery. The animal gained the ability to walk with no functional impairment until it was sacrificed 4 months later. At this time, extensive integration of ceramic with bone was detected radiographically and confirmed by a morphological study of the resected sample. Our data indicate that large defects in a weight-bearing long bone can be repaired to the extent necessary for full functional recovery in large animals. These data set the stage for further intervention on material properties as well as for preliminary attempts to use ceramic prostheses for reconstruction of large bone defects in humans.

Autologous bone marrow stromal cells loaded onto porous hydroxyapatite ceramic accelerate bone repair in critical-size defects of sheep long bones.

The ability of marrow-derived osteoprogenitor cells to promote repair of critical-size tibial gaps upon autologous transplantation on a hydroxyapatite ceramic (HAC) carrier was tested in a sheep model. Conditions for in vitro expansion of sheep bone marrow stromal cells (BMSC) were established and the osteogenic potential of the expanded cells was validated. Ectopic implantation of sheep BMSC in immunocompromised mice led to extensive bone formation. When used to repair tibial gaps in sheep, cell-loaded implants (n = 2) conducted a far more extensive bone formation than did cell-free HAC cylinders (n = 2) over a 2-month period. In cell-loaded implants, bone formation was found to occur both within the internal macropore space and around the HAC cylinder while in control cell-free implants, bone formation was limited mostly to the outer surface and was not observed in most of the inner pores. As tested in an indentation assay, the stiffness of the complex HAC-bone material was found to be higher in cell-loaded implants compared to controls. Our pilot study on a limited number of large-sized animals suggests that the use of autologous BMSC in conjunction with HAC-based carriers results in faster bone repair compared to HAC alone. Potentially this combination could be used clinically in the treatment of extensive long bone defects.