[Cell-based and future therapeutic strategies for femoral head necrosis]

BACKGROUND

The application of cell- and growth factor-based techniques in conjunction with conventional surgical approaches has great therapeutic potential for the treatment of avascular necrosis of the femoral head (AVNFH).

OBJECTIVES

This review provides an overview of new strategies for the treatment of AVNFH, with emphasis on cell and growth factor-based approaches.

MATERIALS AND METHODS

The results of a literature search are summarised, the most relevant publications are presented and discussed by the authors.

RESULTS

In the focus of new strategies for treatment of AVNFH are bone marrow-derived cell concentrates and ex vivo-expanded mesenchymal stem cells. Besides local application during core decompression, the systemic administration of cells via blood vessels supplying the femoral head is an interesting approach. The application of osteogenic and angiogenic growth factor-laden scaffold materials has also been clinically tested. Initial results of randomised clinical trials using cell- and growth factor-based approaches underline the potential of these innovative therapeutic strategies. Cell-based therapies are governed by EU law and generally require a manufacturing authorization.

CONCLUSION

To date, only few randomized controlled clinical trials are available which additionally display a considerable diversity concerning cell parameters, cell processing, adjuvant surgical techniques and the quality outcome parameters. Therefore, a final statement about the effectiveness of new cell and growth factor-based strategies is currently not possible.

[Patellar tendon injuries after total knee arthroplasty : Classification and management]

BACKGROUND

Ruptures of the patellar tendon after total knee arthroplasty represent a rare but severe complication, which in general requires surgical therapy.

OBJECTIVES

To implement a classification and correspondent therapy algorithm in consideration of the current literature for the treatment of patellar tendon ruptures after TKA.

MATERIAL AND METHODS

A review of the recent literature and the author's experience are summarized in a classification and correspondent therapy algorithm for the treatment of patellar tendon ruptures after TKA.

RESULTS

Ruptures of the patella tendon can be classified as avulsions (Type I), acute (Type II) and chronic ruptures (Type III). Avulsions are often of iatrogenic nature and can be sufficiently treated by transosseous refixation prior to implantation of the revision TKA. Acute ruptures of the patellar tendon can originate from trauma or intraoperative injury. The rupture can be restored by primary suture in combination with a wire cerclage in the case of good tendon quality and the absence of patient comorbidities (Type IIA). In the case of poor tendon quality or existing comorbidities (Type IIB) additional augmentation of the ruptured tendon, utilizing the autologous semitendinosus/gracilis tendon, is recommended. Chronic ruptures revealing a good patellar bone stock (Type IIIA) can be treated by a combination of a semitendinosus augmentation and a turndown quadriceps tendon flap. In the case of a poor patellar bone stock (Type IIIB) transpatellar fixation of the semitendinosus tendon is virtually impossible, so that an allograft augmentation or the use of a soft tissue muscle flap (i. e. the gastrocnemius flap) has to be considered. A failed complex reconstruction with or without infection (Type IIIC) is an invidious surgical task and needs to be addressed by the utilization of a muscle flap, an allograft or a patellectomy with or without arthrodesis.

Scaffold-cell bone engineering in a validated preclinical animal model: precursors vs differentiated cell source

The properties of osteoblasts (OBs) isolated from the axial skeleton (tOBs) differ from OBs of the orofacial skeleton (mOBs) due to the different embryological origins of the bones. The aim of the study was to assess and compare the regenerative potential of allogenic bone marrow-derived mesenchymal progenitor cells with allogenic tOBs and allogenic mOBs in combination with a mPCL-TCP scaffold in critical-sized segmental bone defects in sheep tibiae. After 6 months, the tibiae were explanted and underwent biomechanical testing, micro-computed tomography (microCT) and histological and immunohistochemical analyses. Allogenic MPCs demonstrated a trend towards a better outcome in biomechanical testing and the mean values of newly formed bone. Biomechanical, microCT and histological analysis showed no significant differences in the bone regeneration potential of tOBs and mOBs in our in vitro study, as well as in the bone regeneration potential of different cell types in vivo. Copyright © 2015 John Wiley & Sons, Ltd.

[Bone tissue engineering. Reconstruction of critical sized segmental bone defects in the ovine tibia]

Well-established therapies for bone defects are restricted to bone grafts which face significant disadvantages (limited availability, donor site morbidity, insufficient integration). Therefore, the objective was to develop an alternative approach investigating the regenerative potential of medical grade polycaprolactone-tricalcium phosphate (mPCL-TCP) and silk-hydroxyapatite (silk-HA) scaffolds.Critical sized ovine tibial defects were created and stabilized. Defects were left untreated, reconstructed with autologous bone grafts (ABG) and mPCL-TCP or silk-HA scaffolds. Animals were observed for 12 weeks. X-ray analysis, torsion testing and quantitative computed tomography (CT) analyses were performed. Radiological analysis confirmed the critical nature of the defects. Full defect bridging occurred in the autograft and partial bridging in the mPCL-TCP group. Only little bone formation was observed with silk-HA scaffolds. Biomechanical testing revealed a higher torsional moment/stiffness (p < 0.05) and CT analysis a significantly higher amount of bone formation for the ABG group when compared to the silk-HA group. No significant difference was determined between the ABG and mPCL-TCP groups. The results of this study suggest that mPCL-TCP scaffolds combined can serve as an alternative to autologous bone grafting in long bone defect regeneration. The combination of mPCL-TCP with osteogenic cells or growth factors represents an attractive means to further enhance bone formation.

[Reconstruction of osteochondral defects with a stem cell-based cartilage-polymer construct in a small animal model]

AIM

Mesenchymal stem cells have a high therapeutic potential for the reconstruction of articular cartilage defects. In this study, a cartilage-polymer construct using mesenchymal stem cells from trabecular bone and a polylactic acid polymer was fabricated with a press-coating technique. We investigated whether cells from human trabecular bone fragments have the same chondrogenic differentiation potential as mesenchymal stem cells derived from bone marrow and whether it is possible to reconstruct an osteochondral lesion in the nude rat with the fabricated construct.

METHOD

Cells were obtained from the femoral head of patients undergoing total hip arthroplasty. The fabrication of the constructs was performed by centrifugation of 1.5x10(6) cells to a cell pellet which was then placed in a polymer block. The fabricated cell constructs were cultivated for 3 weeks in a serum-free medium, supplemented with transforming growth factor beta1. Every third day, the chondrogenic differentiation was analysed using chondrogenic and osteogenic marker genes. After three weeks the constructs were implanted into 5 mm osteochondral defects of the knee joint of nude rats. After 4 and 12 weeks histochemical and immunohistochemical analyses were performed.

RESULTS

At the end of the culture period the constructs showed a proteoglycan-rich extracellular matrix with the expression of collagen types II, IX and X as well as aggrecan und COMP (cartilage oligomeric matrix protein). No osteogenic markers except collagen type I could be detected. The analysis of the in vivo experiment showed a good defect filling with a reconstructed cartilage surface along with increasing resorption of the polymer.

CONCLUSION

We have shown that it is possible to fabricate cartilage-polymer constructs from trabecular bone-derived cells, and that the cells have the same chondrogenic differentiation potential as mesenchymal stem cells derived from bone marrow. With the fabricated cartilage-polymer construct it is possible to reconstruct an osteochondral defect in the knee joint of the nude rat.