Introduction: Hip simulator tests, analyses of retrieved components as well as radiostereometric measurements revealed that cups made of highly linked polyethylene show a much better wear performance than cups of conventional polyethylene. However, to the best of our knowledge, histomorphological studies of tissues from the surrounding of highly cross – linked polyethylene components have not been reported yet. The aim of this study was to examine such tissues for particles, released from highly cross – linked polyethylene cups and to compare the findings with those of conventional polyethylene.

Material and methods: So far, periprosthetic tissues retrieved at revisions of 11 total hip endoprostheses with highly cross – linked polyethylene cups could be analysed. The revisions became necessary 3 to 50 months after implantation because of cup loosening (4), stem loosening (1), infection (3), periprosthetic fracture of the femur (1), multiple dislocations (1) and periarticular ossification (1). The findings were compared with those of 5 artificial joints (2 ABG, 2 Müller Cup older design, 1 Metalback pressfit) with conventional polyethylene cups and 54 to 231 months of function. 5 μm sections were made from the tissues and conventionally stained with HE and van Gieson. Morphometric measurements were done using objectives 10 and 40 of an Olympus microscope and the ‘Analysis’ program of Soft Ware Imaging GmbH. In the Durasul TM – cases, the total amount and the total area of particles were ascertained while in the cases used for comparison only random CX 40 samples could be measured because of the much higher content of particles.

Results: The DurasulTM cases showed in contrast to the cases with conventional polyethylene cups, no distinct foreign body reaction. In four of the DurasulTM cases no particles could be detected at all and in the remaining seven particles could be found only in a few areas. Their number per section was between 6 and 1208, their total area per mm² section ranged between 0,03 and 6,99 × 10 5.mm² In the conventional polyethylene cases the number of particles per section was between 2832 and 71447, their total area per mm² section ranged between 1,06 and 25,91 × 10 3mm²! The average size of the DurasulTM particles was clearly bigger than the size of the conventional Polyethylene.

Discussion: The measurements in tissues of early revisions show that DurasulTM releases much less particles into the surrounding than PE and cause rather no foreign body reaction. Accordingly, the burden of the tissue with polyethylene debris is much lower while the particle size is bigger with DurasulTM than with PE.

Metal-on-metal bearing surfaces have been reintroduced for use in total hip replacement, despite concerns regarding the potential risks posed by metallic by-products. We have compared periprosthetic tissues from metal-on-metal and metal-on-polyethylene hip replacements at revision surgery with control tissues at primary arthroplasty.

Tissues were obtained from 9 control, 25 contemporary metal-on-metal, 9 CoCr-on-polyethylene and 10 titanium-on-polyethylene hip replacement arthroplasties. Each was processed for routine histology with Haematoxylin and Eosin. Quantitative stereological analysis was performed at the light microscopic level.

Metal-on-metal sections showed more surface ulceration and this was correlated with the density of inflammation in the deeper tissues layers. Metal-on-metal tissues displayed a pattern of well-demarcated tissue layers, which were rarely seen in metal-on-polyethylene cases. In metal-on-polyethylene cases, the inflammation was predominantly histiocytic. Metal-on-metal cases by contrast showed a lymphocytic infiltrate with abundant plasma cells. Metal-on-metal tissues showed a striking pattern of peri-vascular inflammation with prominent lymphocytic cuffs especially deep to areas of surface ulceration. Levels of inflammation were higher in cases revised for failure than in those retrieved at autopsy or exploratory surgery. Total replacement and surface replacement designs of metal-on-metal arthroplasty showed similar histological changes. Plasma cells were not seen in any of the metal-on-polyethylene cases. The differences between the patterns of inflammation and cellular infiltration seen in metal-on-metal and metal-on-polyethylene tissues were highly statistically significant.

The pattern and type of inflammation in periprosthetic tissues from metal-on-metal and metal-on-poly-ethylene arthroplasties is very different. Our findings support the conclusion that metal-on-metal articulations are capable of generating a form of immunological response to metallic wear debris that has not been described previously. The incidence and clinical implications of these immunological responses in failed metal-on-metal joints are unknown.

A six-year-old girl with congenital sensory neuropathy with anhidrosis (CSNA) presented with bilateral hip dysplasia and subluxation on the right side.

Conservative treatment of the hips by closed reduction and a plaster cast was unsuccessful. When aged seven years the patient had an intertrochanteric varus rotation osteotomy on the right side, but subluxation was again evident after five months. A Salter-type pelvic osteotomy was carried out followed by immobilisation, but one year later subluxation was present in the right hip and dislocation in the left. At the age of nine years, the right femoral head resembled a Charcot joint, although walking ability was preserved.

In patients with CSNA, surgery may not always be advisable.

The pathogenesis of longitudinal reduction deformities of the limbs, or dysmelia, is still a matter of debate. Their morphological pattern was defined from a large collection of radiographs of children with dysmelia following the thalidomide disaster.

We compared radiographs of 378 of these limbs with the sclerotomes which are areas of segmental sensory innervation of the limb skeleton defined by the radiation of referred pain. The pattern of dysmelia matched the sclerotomes closely in 279 limbs (73.5%).

The principles of skeletal reduction in dysmelia are explained by the arrangement of the sclerotomes. The congruence between two separate and independent data sets shows that both patterns are expressions of the underlying segmental sensory innervation of the skeleton, and that the sensory nervous system is involved in the process of limb morphogenesis and teratogenesis.

A classification of a group of malformations of the extremities is given and an underlying common pattern is developed from a survey of 693 deformed limbs. It is characterised by a certain reduction tendency of the affected bones and the malformed extremity, an axis of malformation and an interdependence between the proximal and peripheral parts of the deformed limbs. The group, called dysmelia, has a common morphology, but morphologically identical types have been seen caused by thalidomide and as hereditary or sporadic cases. An attempt has been made not only to name and classify these deformities but also to clarify the underlying principles of their morphology. This will enable the teratologist to see the pattern of these malformations in comparison with that of normal development of the limbs and of experimentally induced limb defects.