Rapid ultrathin slice plastination of embalmed specimens with minimal tissue loss

Development of an ultrathin sheet plastination technique in rat humeral joints with osteoarthritis induced by monosodium iodoacetate for neovascularization study

Injection with monosodium iodoacetate (MIA) is widely used to produce osteoarthritis (OA). Ultrathin sheet plastination has been used to study the morphology of structures, with strong application in anatomical education and research. Our aim was to carry out, for the first time, ultrathin sheet plastination of rat humeral joints to observe the neovascularization provoked by OA. We injected 0.1 mL of MIA into the left humeral joints of ten Sprague-Dawley rats. The right shoulders of the same rats were used as control. Sixteen weeks after the injection, the animals were euthanized and were given an immediate red epoxy resin injection through the thoracic aorta. The samples were fixed in 10% formalin, prior to the plastination process, without decalcification. Samples were dehydrated with acetone (100%) at - 25 °C, for 10 days. Later, for degreasing, samples were immersed in methylene chloride at room temperature during 1 week. Forced impregnation was performed inside a stove within a vacuum chamber. The plastinated blocks obtained were cut with a slow velocity diamond blade saw. Slices were placed in curing chambers to achieve curing and final tissue transparentation. 230 μm thickness slices were obtained. The slices were analyzed under magnifying glass and microscope, achieving visualization of OA neovascularization. The cartilage affected by OA loses its ability to remain avascular, and blood vessels invade it from the subchondral bone to the calcified and uncalcified cartilage. Ultra-thin sheet plastination is useful to observe articular cartilage neovascularization, caused by OA induced with MIA in humeral rat joint.

Learning anatomy of the foot and ankle using sagittal plastinates: A prospective randomized educational trial

BACKGROUND

Foot and ankle anatomy is highly complex and presents a considerable educational challenge for the medical student or junior doctor. The successful interpretation of cross-sectional radiological images requires a detailed knowledge of anatomy and spatial relationships. Plastic-impregnated cadaveric prosection slices, known as 'sagittal plastinated slices', or 'SPS', are becoming popular as an adjunct to traditional anatomical teaching methods.

OBJECTIVES

To compare the impact of SPS versus conventional anatomy teaching resources (dry bones and whole cadaveric feet) on learners' ability to correctly identify structures of the foot and ankle on sagittal MRI images.

METHODS

Randomized educational study using sequential exploratory mixed-methods.

RESULTS

The intervention group anatomy test scores were a mean of 1.2 higher after the educational intervention, compared to 0.7 for the control group (scores out of 14), but this was not statistically significant (p=0.41). Learners reported that the SPS intervention was most useful to augment and refine their knowledge after a teaching session using conventional resources.

CONCLUSION

The qualitative results showed that SPS provide a valuable adjunct to traditional teaching methods in both anatomy and radiology of the foot and ankle, which should be used after teaching with traditional methods.

The oblique popliteal ligament: an anatomic and MRI investigation

PURPOSE

Despite being the largest ligament on the posterior aspect of the knee, relatively little is known about the normal morphology of the oblique popliteal ligament (OPL). The aim of this study was to investigate the detailed anatomy of the OPL in cadavers and healthy volunteers.

METHODS

The posterior knee was investigated in 25 cadaver lower limbs (mean age 76 ± 9.5 years; 7 men) by dissection, histology, and serial plastination and in 14 healthy individuals (mean age 23 ± 3.2 years; 11 men) using magnetic resonance (MR) imaging. OPL morphology, attachments sites, ligament length and width, relationship to surrounding structures and histological composition were recorded. Intraobserver reliability was assessed using intraclass correlation coefficients.

RESULTS

The OPL is a distinct expansion of the semimembranosus (SM) tendon and sheath, which courses superolaterally to attach to the posterolateral joint capsule or fabella (when present), at the medial margin of the lateral femoral condyle. The ligament blends with the joint capsule medially and laterally, serves as an attachment site for plantaris, and has connections with popliteus. In 70% of dissections, the OPL divided into two bands, separated by small branches of the middle genicular neurovascular bundle that pierced the posterior joint capsule. Differences in mediolateral length were noted between dissection and MR imaging (43.6 ± 6.2 vs. 57.6 ± 4.4 mm; p < 0.001). At its medial and lateral attachments, the OPL was 23.2 ± 6.9 and 17.4 ± 8.7 mm wide (proximodistal), respectively. The OPL was predominantly composed of transverse collagen layers, with little elastin. While visible on axial MR scans, delineation of its most lateral extent was difficult. Repeatability of selected measurements ranged from good to almost perfect.

CONCLUSIONS

The OPL is a distinct ligament with identifiable anatomical limits. Based on its morphological characteristics, it appears more tendinous than ligamentous in nature. A better understanding of the OPL may help define its importance in the assessment and treatment of posterior knee injuries.

Oblique sectional planes of block plastinates eased by Sac Plastination

To find an oblique cutting plane of a plastinate, e.g. to cut gamma-nails in the femur, the Block Plastination technique was modified. After CT and MRI examination, the specimens were plastinated with the standard resin mixture E6/E12/E600. Instead of using a box to form a block during the casting and curing stage, we embedded the specimen in a sac made of polyester foil. A polymerized wooden block was attached to the specimen. The sac was wrapped with tape to the embedded specimen with the block. This approach limited the amount of required resin to the inner volume of the plastinate. Then, the plastination sac was put in the incubator for further polymerization and curing. When the foil was removed from the plastinated specimen, the wooden block served as a socket for the grip when sawing. The outer shape of the specimen remained visible. Doing so, the adequate cutting plane could be determined easily.