Four stem fractures in a 12-year follow-up study of 9,135 patients with Exeter hip stems at seven teaching facilities in Japan.

BACKGROUND: Although excellent long-term results have been reported for the Exeter stem, stem fracture is recognized as a rare complication. However, there have been no reports on the incidence and risk factors for stem fractures based on detailed population information. This study aimed to clarify the incidence of Exeter hip stem fracture based on detailed population information from seven Exeter stem teaching centers in Japan and to examine the risk factors for stem fracture. METHODS: A total of 8,499 primary total hip arthroplasties (THA) and 636 revision hip arthroplasties (revisions) performed at seven Exeter teaching hospitals between 1999 and 2021 were included and retrospectively investigated based on medical records. RESULTS: Stem fractures were identified in two primary THA (fracture rate: 0.02%) and two revision THA (fracture rate: 0.21%) cases. The stem length was ≤125 mm in three out of these four cases. Revision and 30 stem were the risk factors for stem fractures. Weight and body mass index (BMI) were not significantly associated with the occurrence of stem fractures. CONCLUSIONS: In Western countries, the incidence of Exeter stem fractures is reportedly 0.017-0.15% for primary THA and 0.99-1.21% for revision THA. In this study, the incidence of primary THA was 0.02%, which is similar to the lowest reported rate, whereas the incidence of revision THA was 0.21%, which is lower than that reported in previous studies. Revision surgery had the same risk factors as those reported in the West-namely, stem length ≤125 mm (except for the 30 stem) and BMI, which were not risk factors in Japanese patients.

[Remarkable improvement of the hip joint lesion in a patient with rheumatoid arthritis by the treatment with anti-TNF-α agents].

22-year old woman who was previously diagnosed as having juvenile idiopathic arthritis (JIA) was treated with anti-TNF-α agents. Her disease activity was assessed as Stage IV and Class III by Steinbrocker's classification and resistant to steroids and methotrexate. Initially clinical findings responded well to infliximab (IFX), but polyarthritis recurred 15 months after the start of the treatment, and IFX was switched to etanercept (ETN) with good response. On the other hand, effects on the osteoarticular lesions were continuously observed through the period of the treatment with these two biologics. It was thought very rare that weight-bearing joint like the hip joint was restored as was seen in this case, while its mechanism is unknown. Because mechanism for inhibition of inflammation or joint destruction might be independent, we should investigate further the relationship between inflammation and joint destruction in the future.

Relationship between bone mineral density and urine level of NTx in rheumatoid arthritis.

We analyzed the relationship between the level of type-I collagen N-telopeptide (NTx) in urine (U-NTx) and bone mineral density (BMD) in patients with rheumatoid arthritis (RA). The subjects were 62 female patients with RA who had experienced the menopause 5 years or more before the study commenced, and who had not been treated for osteoporosis. The mean age of the subjects was 61.6 years and the mean disease duration was 13.3 years. They were classified for global functional status (classes I to IV), and then grouped based on the presence or absence of corticosteroid administration. Bone mineral density (BMD) and U-NTx levels were measured. In the presence of corticosteroid administration (CS group; n = 40), the mean level of U-NTx/creatinine (Cr) was 88.8 nM and the percent young adult mean (%YAM) for BMD was 71.2%. In the no corticosteroid (nCS group; n = 22), the values were 72.1 nM and 78.2%, respectively. The U-NTx/Cr value and %YAM were not significantly different between the CS group and the nCS group. A negative correlation was observed between the U-NTx/Cr value and %YAM in both groups (P = 0.005 and P = 0.0265). No significant difference was observed for the U-NTx/Cr value or %YAM between the CS and nCS groups, in any class. In the CS group, a positive correlation was observed between the U-NTx/Cr value and the total dose of corticosteroid (P = 0.001), and a negative correlation was observed between the %YAM and the total dose of corticosteroid (P = 0.003). These results suggested that preventive medical treatment for osteoporosis is required for RA patients in class III, irrespective of whether they have had corticosteroid administration.

Late dissociation of an alumina-on-alumina bearing modular acetabular component.

Alumina-on-alumina bearings for total hip arthroplasty have been introduced as a promising alternative to reduce wear debris and to increase the life expectancy of the prosthesis. We report a case of a late dissociation of an alumina-on-alumina bearing modular acetabular component, which occurred 2 years, 8 months after surgery. Detailed analysis of the retrieved prosthesis suggested that the cause of the failure may be strong rotational torque developed by a roughening of the bearing's alumina surface caused by edge loading (microseparation). The strong friction torque in articulation may explain the higher reported rate of mechanical loosening of the acetabular component in alumina-on-alumina bearing total hip prostheses.