Collagen fibre and fibril ultrastructural arrangement of the superficial medial collateral ligament in the human knee.

PURPOSE: The aim of the study was to investigate the collagen fibre ultrastructural arrangement and collagen fibril diameters in the superficial medial collateral ligament (sMCL) in the human knee. Considering sMCL's distinctive functions at different angles of knee flexion, it was hypothesized a significant difference between the collagen fibril diameters of each portion of the sMCL. METHODS: Fourteen sMCL from seven fresh males (by chance because of the availability) cadavers (median age 40 years, range 34-59 years) were harvested within 12 h of death. sMCLs were separated into two orders of regions for analysis. The first order (divisions) was anterior, central and posterior. Thereafter, each division was split into three regions (femoral, intermediate and tibial), generating nine portions. One sMCL from each cadaver was used for transmission electron microscopy (TEM) and morphometric analyses, whereas the contralateral sMCL was processed for light microscopy (LM) or scanning electron microscopy (SEM). RESULTS: LM and SEM analyses showed a complex tridimensional architecture, with the presence of wavy collagen fibres or crimps. TEM analysis showed significant differences in median collagen fibril diameter among portions inside the anterior, central and posterior division of the sMCL (p < 0.0001 within each division). Significant differences were also present among the median [interquartile range] collagen fibril diameters of anterior (39.4 [47.8-32.9]), central (38.5 [44.4-34.0]) and posterior (41.7 [52.2-35.4]) division (p = 0.0001); femoral (38.2 [45.0-32.7]), intermediate (40.3 [47.3-36.1]) and tibial (40.7 [55.0-32.2]) region (p = 0.0001). CONCLUSIONS: Human sMCL showed a complex architecture that allows restraining different knee motions at different angles of knee flexion. The posterior division of sMCL accounted for the largest median collagen fibril diameter. The femoral region of sMCL accounted for the smallest median collagen fibril diameter. The presence of crimps in the medial collateral ligament, previously identified in the rat, was confirmed in humans (taking into consideration differences between these two species).

Early healing events around titanium implant devices with different surface microtopography: a pilot study in an in vivo rabbit model.

In the present pilot study, the authors morphologically investigated sandblasted, acid-etched surfaces (SLA) at very early experimental times. The tested devices were titanium plate-like implants with flattened wide lateral sides and jagged narrow sides. Because of these implant shape and placement site, the device gained a firm mechanical stability but the largest portion of the implant surface lacked direct contact with host bone and faced a wide peri-implant space rich in marrow tissue, intentionally created in order to study the interfacial interaction between metal surface and biological microenvironment. The insertion of titanium devices into the proximal tibia elicited a sequence of healing events. Newly formed bone proceeded through an early distance osteogenesis, common to both surfaces, and a delayed contact osteogenesis which seemed to follow different patterns at the two surfaces. In fact, SLA devices showed a more osteoconductive behavior retaining a less dense blood clot, which might be earlier and more easily replaced, and leading to a surface-conditioning layer which promotes osteogenic cell differentiation and appositional new bone deposition at the titanium surface. This model system is expected to provide a starting point for further investigations which clarify the early cellular and biomolecular events occurring at the metal surface.

Electron microscopy of the remodelling process in hamstring tendon used as ACL graft.

The purpose of the present study was to make a histological analysis of the remodelling process of hamstring tendon graft used as Anterior Cruciate Ligament (ACL). The hamstring graft of eight patients was biopsied at different follow-up times from 1 to 10 years. The specimens were analysed with transmission electron microscopy (TEM) at ultrastructural level comparing them with a native ACL and a native hamstring graft. The hamstring graft was found to undergo ultrastructural changes in terms of number and diameter of fibrils with the major changes occurring in the first 2 years. At longer times after surgery (48 and 120 months) no important further changes were evident and the ultrastructure did not vary substantially from 2 to 10 years. In conclusion, the hamstring tendon used as ACL graft undergoes a transformation process but does not match the ultrastructure pattern of a normal ACL up to 10 years.

Correlative microscopy of bone in implant osteointegration studies.

Routine morphological analyses usually include investigations by light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Each of these techniques provides specific information on tissue morphology and all the obtained results are then combined to give an in-depth morphological overview of the examined sample. The limitations of this traditional comparative microscopy lie in the fact that each technique requires a different experimental sample, so that many specimens are necessary and the combined results come from different samples. The present study describes a technical procedure of correlative microscopy, which allows us to examine the same bone section first by LM and then, after appropriate processing, by SEM or TEM. Thanks to the possibility of analyzing the same undecalcified bone sections both by LM and SEM, the approach described in the present study allows us to make very accurate evaluations of old/new bone morphology at the bone-implant interface.

Influence of different implant surfaces on peri-implant osteogenesis: histomorphometric analysis in sheep.

BACKGROUND: The present study investigated peri-implant osteogenesis and implant biologic fixation in different zirconia sandblasted endosseous titanium surfaces (SLA-60 and SLA-120) and a turned titanium surface (T) 2 and 4 weeks after surgery. METHODS: Seventy-two implant screws were implanted in tibia of six sheep. Histologic sections of implants (2 and 4 weeks after surgery) were analyzed with light microscopy for histomorphometric analysis of bone-to-implant contact (BIC), bone ingrowth (BI), and bone surface (BS/BV). Histologic blocks were used to perform bone microhardness studies next to the implants. Some implants were also observed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). RESULTS: In general, the highest values of BIC, BI, BS/BV, and Vickers hardness number (HV) were measured in SLA-60 samples, followed by SLA-120 and T implants. Two weeks after surgery, all the implants appeared biologically fixed by a newly formed woven bone arranged in thin bone trabeculae and filling the gap between implant and host bone. Four weeks after implantation, the thickness of the woven bone trabeculae had increased, especially around the SLA-60 and SLA-120 implants by a gradual deposition of parallel-fiber bone. CONCLUSIONS: Our results suggest that, in the early period of peri-implant healing, the implant surface morphology that seemed to influence the increase of peri-implant osteogenesis, bone turnover, and peri-implant bone maturation was SLA-60. We suggest that this surface, characterized by moderately deep titanium cavities very similar to the osteocyte lacunae, could act as a microscopic scaffold for mesenchymal and/or osteoblast-like cells adhesion.

Influence of a zirconia sandblasting treated surface on peri-implant bone healing: An experimental study in sheep.

A sandblasting process with round zirconia (ZrO(2)) particles might be an alternative surface treatment to enhance the osseointegration of titanium dental implants. Our previous study on sheep compared smooth surface titanium implants (control) with implant surfaces sandblasted with two different granulations of ZrO(2). As the sandblasted surfaces proved superior, the present study further compared the ZrO(2) surface implant with other surface treatments currently employed: machined titanium (control), titanium oxide plasma sprayed (TPS) and alumina sandblasted (Al-SL) at different times after insertion (2, 4 and 12weeks). Twelve sheep were divided into three groups of four animals each and underwent implant insertion in tibia cortical bone under general anaesthesia. The implants with surrounding tissues were subjected to histology, histomorphometry, scanning electron microscopy and microhardness tests. The experimentation indicated that at 2weeks Zr-SL implants had the highest significant bone ingrowth (p<0.05) compared to the other implant surfaces, and a microhardness of newly formed bone inside the threads significantly higher than that of Ti. The present work shows that the ZrO(2) treatment produces better results in peri-implant newly formed bone than Ti and TPS processing, whereas its performance is similar to the Al-SL surface treatment.

Histological and ultrastructural evaluation of Leeds-Keio ligament 20 years after implant: a case report.

We were capable of undertaking a histological and ultrastructural evaluation of an intact Leeds-Keio ligament implanted 20 years ago to assess the neoligamentization process inside this artificial ligament. The histological evaluation disclosed a collagen fibrils orientation very close to the structure of a normal anterior cruciate ligament (ACL) where the collagen fibres are multidirectional [Strocchi et al. in J Anat 180(3):515-519, 1992]. On the other hand we found an unimodal distribution of collagen fibrils in the reconstructed ACL. This suggests that even at long-term follow-up stress exerts a variable influence. The multidirectional arrangement of collagen fibres resembles a normal ACL, but the unimodal distribution of fibrils is quite different from those seen in normal tendon and ligaments which tend to have a bimodal peak [Decker et al. in J Submicrosc Cytol Pathol 23:9-21, 1991; Strocchi et al. in J Anat 180(3):515-519, 1992]. Studies based on biopsy suffer from the potential weakness that the specimen may not have been representative of the entire prosthesis. Further long-term studies, possibly with the entire prosthesis and not only a biopsy, would highlight the behaviour and remodelling of this artificial ligament in greater detail and could be important for the development of future generations of artificial ligaments or tissue engineering ACL reconstruction.