Toshinori Masaoka

Study of hip joint dislocation after total hip arthroplasty

The present study was undertaken to identify the factors responsible for hip joint dislocation after total hip arthroplasty, laying emphasis on analysis of the background variables of the patients. Of the 317 hips included in the study, ten (3.2%) dislocated. Only the anteversion angle of the cup differed significantly between the dislocation group and the dislocation-free group. The safe zone of the anteversion angle seems to be between 20 and 30 degrees. but it is also essential to set the antetorsion angle of the stem to match the shape of individual bones to create a more stable hip joint. This safe zone may be expanded by the additive effect of antetorsion angle of the stem.RésuméLe but de cette étude a été d’identifier les facteurs responsables d’uneluxation de la hanche après arthroplastie totale en insistant sur l’analysedes différents paramètres de chaque patient. Sur les 317 hanches inclusesdans cette étude, 10 (3,2%) ont présenté une luxation. La seule différencesignificative entre le groupe des sujets ayant présenté une luxation et ceuxn’en ayant pas présenté est l’angle d’antéversion de la cupule. L’angleoptimum d’antéversion de la cupule semble être compris entre 20 et 30 degrésmais il est également essentiel de lier l’angle d’antéversion avec l’angled’antétorsion de la pièce fémorale, celles-ci ayant été manufacturées surmesure et adaptées à la géométrie osseuse de chaque individu de façon àcréer une hanche parfaitement stable. Cette zone de sécurité peut êtreaméliorée par l’addition, à l’angle d’antéversion de la cupule de l’angled’antétorsion de la pièce fémorale.

Highly crosslinked polyethylenes in hip replacements : Improved wear performance or paradox?

The lubrication and wear of artificial joints are important issues for their longevity. Bone loss caused by the biological response (osteolysis) to the wear debris leads to implant loosening and eventual failure of the device. Various studies have shown that the size, shape, and the number of particles are important factors in the osteolytic response to wear debris. It has been demonstrated that both submicron-size particles and long fibrils can stimulate macrophage responses. This paper examines the clinical and laboratory data on highly crosslinked polyethylene (XLPE) regarding implant wear and particulate debris. In simulator studies, total hip replacements have shown greatly reduced wear with XLPE cups compared with conventional polyethylene (PE) and short-term clinical studies of XLPE have now also shown reduced levels of wear. However, simulator studies have also demonstrated that adverse wear conditions can partially or completely negate the wear advantage of XLPE. Additionally, it has been shown that the XLPE debris particles are smaller than conventional PE. In a paradoxical manner, the decreased wear rate of XLPE should decrease the osteolytic potential, but the decreased debris size may have the potential to increase the biological activity. Therefore, the long-term clinical performance of XLPE is not clear at this time. Long-term clinical follow-ups will be needed to determine the actual benefit of XLPE in patients.

Morphological studies on the ageing and osteoarthritis of the articular cartilage in C57 black mice.

Purpose. To study the cause and mechanism of joint degeneration in osteoarthritis, through histopathological and ultrastructural-histochemical experiments on the articular cartilage of the knees of the C57 black mouse. Methods. 192 C57 black mice and a control group of 64 C57BL/6J mice were used in this study. The left and right knee articular capsules of the joints were removed and stained. Each articular cartilage sample was examined and osteoarthritic changes were assessed using a transmission electron microscope. The severity of osteoarthritis in the knee joint cartilage of C57 black mice was histologically assessed using a classification system described by Okabe, based on Maiers system. Results. The incidence and the severity of osteoarthritis gradually increased with age; the incidence increased from 20% at 2 months to 80% at 16 months. Irreversible changes appeared at an advanced stage, and the process of degeneration was quite similar to that in human osteoarthritis. Through transmission electron microscopy, we observed poorly developed Golgi apparatus, markedly increased intracellular microfilaments, decreased proteoglycan granules, and broken collagen networks in all stages of osteoarthritis. By contrast, Golgi apparatus and other organelles were well developed in histologically normal mice of all ages. Proteoglycan granules, which mainly consisted of keratan sulphate, were observed; collagen networks were maintained. Conclusion. Disturbed protein transport and sugar synthesis in chondrocytes, caused by the deficient development of the Golgi apparatus, could result in degenerative changes in articular cartilage. The structure and function of the matrix were maintained mainly because of the continued presence of keratan sulphate.

Postoperative clinical results in cubital tunnel syndrome.

This article reports on factors affecting the postoperative results in cubital tunnel syndrome. We evaluated 111 limbs of 107 patients who had been surgically treated for cubital tunnel syndrome. Average patient age was 43.9 years (range: 11-77 years). Postoperative follow-up ranged from 1 to 17 years (mean: 5.2 years). Causal diseases included cubitus valgus following fractures in childhood in 43 limbs, osteoarthritis in 45 limbs, and others in 23 limbs. Surgical treatment involved Kings method for 66 limbs, anterior transposition for 41 limbs, and Osbornes method for 4 limbs. Preoperative severity and postoperative results were evaluated according to the critera for evaluation of ulnar nerve palsy of Yokohama City University. Preoperative severity was stage I in 19 limbs, stage II in 12 limbs, stage III in 41 limbs, and stage IV in 39 limbs. Postoperative results at final evaluation were excellent in 37 limbs, good in 39 limbs, fair in 26 limbs, and poor in 9 limbs. Age at surgery, duration of cubital tunnel syndrome, preoperative severity, and clinical symptom score and motor nerve conduction velocity in the early postoperative stage (one month after surgery) were found to be important prognostic factors of the syndrome.

RETRACTED: Cement Spacer Loaded With Antibiotics for Infected Implants of the Hip Joint

It is difficult to treat infected implants of the hip joints. Such treatment involves immeasurable physical and psychological suffering of the patients. We used antibiotic-impregnated cement spacers in 17 cases of infection after total hip arthroplasty and bipolar arthroplasty with good clinical results. We thoroughly removed any foreign material and formed an antibiotic-impregnated cement spacer into a similar shape as that of the implants. A cement spacer enables high-concentration antibiotics to act on infected sites. Also, it can prevent leg length discrepancy and atrophy of bones or muscles. Although cement spacers have been reported to have problems regarding shape and strength, we achieved good results with a cement spacer mold in the present study. No recurring infection has been found at a mean follow-up period of 3 years and 2 months.

Failure of ceramic THR with liner dislocation--a case report.

In September 1998, an all-alumina total hip replacement was performed in a 57-year-old woman using an ABS Cup System THR (Kyocera Ltd. Kyoto, Japan) (ABS HA Shell (CH 46)/ABS Liner (28-46)/Ball Head (28N: -4)/Perfi x Stem #12-M) for left traumatic femoral head necrosis (Figure 1a). The liner had an alumina inlay packed with polyethylene.In May 2002 discomfort appeared in the hip, with crepitation when walking. 3 weeks later, dis-location of the liner was confi rmed on radiographs. The liner had rotated about 90° in the metal shell and the ball head had been displaced in superolat-eral direction (Figure 1b). At the revision opera-tion, we observed pale gray color contamination in the synovia surrounding the neck and pseudocap-sule. The inlay had been dislocated in the liner and the stem neck had been impinged against the rim of the inlay. The ball head was in contact with the metal shell in the superolateral area. We found no distraction of ceramic parts. The liner, metal shell and alumina ball were revised into a polyethylene liner, metal shell and metal ball (Figure 1c).For the revised implant, we confi rmed the lesion and degree of injury of the implants by the naked eye and light microscopy, and observed the wear pattern of the ball head and the inlay. We used scanning electron microscopy (SEM) to examine the microstructure of the bearing surface. Based on macroscopic observation, about two-thirds of the circumference of the marginal part of the liner polyethylene had suffered a loss around the notch, to lock the liner between the shell. Metal contamination was observed on the rim of the alu-mina inlay, which had been dislocated in the liner (Figure 2).The SEM fi ndings in the normal load-bearing area suggested a very low wear rate, because the machine marks had just been smoothed out (grade II) (Shishido et al. 2002). On the other hand, in the rim of the bearing surface of the inlay and in the peripheral area of the ball head, the grain of the surface had been pulled out (grade V), so the wear was considered to be more severe (Figure 3).

Mechanisms of plastic deformation in highly cross-linked UHMWPE for total hip components--the molecular physics viewpoint.

Plastic deformation is an unavoidable event in biomedical polymeric implants for load-bearing application during long-term in-vivo service life, which involves a mass transfer process, irreversible chain motion, and molecular reorganization. Deformation-induced microstructural alterations greatly affect mechanical properties and durability of implant devices. The present research focused on evaluating, from a molecular physics viewpoint, the impact of externally applied strain (or stress) in ultra-high molecular weight polyethylene (UHMWPE) prostheses, subjected to radiation cross-linking and subsequent remelting for application in total hip arthroplasty (THA). Two different types of commercial acetabular liners, which belong to the first-generation highly cross-linked UHMWPE (HXLPE), were investigated by means of confocal/polarized Raman microprobe spectroscopy. The amount of crystalline region and the spatial distribution of molecular chain orientation were quantitatively analyzed according to a combined theory including Raman selection rules for the polyethylene orthorhombic structure and the orientation distribution function (ODF) statistical approach. The structurally important finding was that pronounced recrystallization and molecular reorientation increasingly appeared in the near-surface regions of HXLPE liners with increasing the amount of plastic (compressive) deformation stored in the microstructure. Such molecular rearrangements, occurred in response to external strains, locally increase surface cross-shear (CS) stresses, which in turn trigger microscopic wear processes in HXLPE acetabular liners. Thus, on the basis of the results obtained at the molecular scale, we emphasize here the importance of minimizing the development of irrecoverable deformation strain in order to retain the pristine and intrinsically high wear performance of HXLPE components.

Traumatic anterior dislocation of the hip associated with ipsilateral femoral shaft fracture in a child: A case report

Traumatic anterior dislocation of the hip joint in children is rare, and only one case with ipsilateral femoral fracture has been reported in Japan. We report a case of such dislocation and a review of the literature. The patient was a 31-month-old girl who was injured in a car accident while asleep on a tilted front passenger seat. Radiographic examination showed dislocation of the right obturator foramen and transverse fracture of the ipsilateral femoral shaft. The dislocation of the right hip was easily reduced without anaesthesia during radiography. We applied Bryant traction after reduction for 4 weeks, followed by cast application for 3 weeks. Walking with support and full weightbearing were permitted 14 weeks and 16 weeks after the injury, respectively. Radiography at 4.5 years after the injury showed a mildly enlarged right femoral head and femur overgrowth of approximately 8 mm. Magnetic resonance imaging showed no evidence of suspected avascular necrosis of the femoral head. The patient has no subjective or objective symptoms, and is able to engage in all usual activities. The detailed mechanism of the injury is unknown. We assume that the lower leg was dislocated through abduction during flexion, or abducent, external flexion, considering that the child was sleeping at the time of the accident. Since she was hurled to the back seat, it was assumed that strong external force was vertically added to the femur, which caused the abducent force.

Micro-wear features on unique 100-Mrad cups : two retrieved cups compared to hip simulator wear study

We studied the micro-wear phenomena of unique, extensively cross-linked polyethylene cups (cross-linked with 1,000 kGy-irradiation) that had been used briefly in Japan. Two retrievals (at 15 years) came from the Japanese “SOM” hip system (implanted 1971–78). These were compared to a set of 0kGy and 500–1,500 kGy cups run in our hip simulator. The polyethylene cups that had not been cross-linked had the greatest wear. The worn areas had a burnished appearance and were clearly separated from the unworn region by a distinct ridge-line. The worn areas had lost all machine tracks, showed a large amount of UHMWPE ‘flow’, and long PE fibrils. The associated surface rippling was degraded. These features were considered synonymous with severe polyethylene wear. In contrast, the worn areas in the very cross-linked cups had a visibly matte surface and no ridge-line. Micro-examination showed that the machine tracks were still present. Ripple formations were less obvious than in the cups that were not cross-linked, polyethylene surface fibrils were scarcer and all the fibrils were much smaller than in the cups that were not crosslinked. Our two retrieved cups and the simulator cups confirmed the greater wearresistance of very cross-linked polyethylene. It should also be noted that the SOM cup design and processing were unique and differed greatly from that of modern polyethylene cups.

Clinical results of arthrolysis using postero-lateral approach for post-traumatic contracture of the elbow joint.

We evaluated clinical results and postoperative problems associated with arthrolysis for post-traumatic contracture of the elbow joint. Arthrolysis was carried out in 47 elbows in 46 patients. Age at the time of arthroplasty ranged from 12 to 64 years (average 33 years). The period from time of injury to arthrolysis ranged from six months to six years (average 16 months). It was notable that scarring of the anterior capsule was pronounced in cases of long-term contracture. No apparent differences were observed in causes or age at operation, but the duration of preoperative symptoms and period of postoperative external fixation tended to affect the outcome. We conclude that arthrolysis is indicated irrespective of preoperative range of motion (ROM) and age, and that the surgery should be carried out before degeneration of cartilage and muscle atrophy progress. It was considered that long-term postoperative observation is also necessary, because in some cases there was postoperative progression of joint deformities, while in others there was decreased muscle strength after surgery.