Radiographic and clinical comparisons between loose-fit and press-fit stems in monopolar radial head arthroplasty for comminuted radial head fractures.

PURPOSE: Few clinical studies have compared the operative outcomes between loose- and press-fit stems in radial head arthroplasty (RHA). We aimed to evaluate the radiographic and clinical results of the two radial head implant concepts. METHODS: In this retrospective multicenter study, 32 patients (24 women and 8 men) with a mean age of 63.1 years who underwent RHA for comminuted radial head fractures were reviewed between 2005 and 2021. Seventeen patients underwent RHA with a loose-fit stem (L-group), whereas the remaining fifteen patients underwent RHA with a press-fit stem (P-group). The mean follow-up period was 40.1 ± 9.9 months, with the minimum follow-up duration of 12 months. The radiographic findings were evaluated for periprosthetic osteolysis; furthermore, clinical outcomes were analyzed to measure the range of motion of the elbow. The rate of reoperations and prosthesis removal were also reviewed. RESULTS: The general characteristics of the patients were similar in the two groups. The rate of periprosthetic osteolysis was 17.6% in the L-group, whereas it was 53.3% in the P-group. The mean elbow flexions were 128° and 133° in the L- and P-groups, respectively. The mean elbow extensions were -12° and -9° in the L- and P-groups, respectively. The rate of reoperation was 23.5% in the L-group and 15.2% in the P-group. One patient in the L-group had the prosthesis removed because of surgical site infection, whereas one patient in the P-group had the prosthesis removed owing to painful loosening. CONCLUSIONS: No significant differences in the clinical outcomes and reoperation rate were observed between the two radial head implant concepts in this study. However, osteolysis occurred more frequently in the P-group. Although patients with periprosthetic osteolysis are currently asymptomatic, they should be carefully followed up for the symptoms in the long term.

Surface Replacement Arthroplasty Using a Volar Approach for Osteoarthritis of Proximal Interphalangeal Joint: Results After a Minimum 5-Year Follow-up.

Background: Surface replacement arthroplasty (SRA) through a volar approach for the proximal interphalangeal (PIP) joint can preserve the integrity of the extensor tendon, which allows early range of motion (ROM) exercise postoperatively. However, a few reports have shown that the PIP ROM tends to decline with longer follow-up. The goal of this study is to assess the results of at least 5 years of follow-up of SRA through a volar approach and also to investigate the cause of deterioration of ROM with time after SRA through this approach. Methods: Eleven fingers with degenerative osteoarthritis that underwent SRA through the volar approach were examined. ROM of the PIP joint preoperation, 1 year after the surgery, and at final follow-up was measured and statistically analyzed. Also, the relationship between PIP ROM and the osteophyte developed postoperatively was examined. Results: The average follow-up period was 7.3 years. The average PIP ROM of the PIP joints was 52.3° preoperatively, 54.1° at 1 year postoperatively, and 31.1° at the final follow-up. PIP ROM at the final follow-up was significantly decreased compared with that preoperatively or at 1 year postoperatively. Also, the development of an osteophyte was negatively correlated with the ROM of the PIP joint at the final follow-up. Conclusions: PIP ROM after SRA through a volar approach has the tendency to deteriorate with a longer follow-up. Development of an osteophyte is considered to be a main risk factor of deterioration in the cases of SRA through a volar approach.

Post-Operative Contracture of the Proximal Interphalangeal Joint after Surface Replacement Arthroplasty Using a Volar Approach.

BACKGROUND: Postoperative contracture as a major complication of surface replacement arthroplasty (SRA) remains an unresolved problem. Contracture after SRA can occur early in the postoperative period due to mechanical dysfunction, and tardy contracture where ROM declines with time postoperatively is also reported. METHODS: 13 fingers with degenerative osteoarthritis and two fingers with post-traumatic arthritis where SRA was performed using volar approach were involved. Contracture was defined as limited ROM of less than 35 degrees. Cases were then categorized into two groups according to time of onset of contracture; early contracture and tardy contracture. Characteristic findings of postoperative X-rays in each contracture group were examined. Required procedures and efficacy of any further surgery was also reviewed. RESULTS: Early contracture was observed in three cases, all of which suffered intra-operative fracture or fragility of the central slip insertion on the dorsal rim of the middle phalanx. This was observed in a further two cases, both of which deteriorated to tardy contracture. Tardy contracture was observed in five cases, and the average ROM was 63 degrees preoperatively, 48 degrees one year postoperatively and 21 degrees at the most recent follow-up, or at the time of the second surgery. In the three cases, development of osteophyte formation on the volar aspect of the proximal head component was observed on the follow-up X-rays. Required further surgeries were resection of the volar plate in two cases, resection of ossification in one and resection of the osteophyte in two. The results of further surgeries were mediocre in all but one case. CONCLUSIONS: This study showed that intra-operative fracture or fragility of the central slip insertion was a risk factor for postoperative contracture after SRA, and that development of osteophyte formation can be a cause of deterioration in ROM of the PIP joint.

T.A.C.' pin fixation for basal ulnar styloid fractures associated with distal radius fractures.

Distal radius fractures often accompany ulnar styloid fractures. As basal ulnar styloid fractures sometimes result in symptomatic nonunion causing distal radioulnar joint instability, surgical intervention should be considered as a method of treatment. However, conventional methods of internal fixation for ulnar styloid involving tension band wiring and pinning often causes irritation of hardware, and required further surgery. We performed T.A.C.' pin fixation for basal ulnar styloid fractures associated with distal radius fractures in 24 patients. X-rays showed union at an average of 6.8 weeks postoperatively in all but 1 case, which resulted in asymptomatic fibrous nonunion. Irritation from the hardware was recognized in 3 cases, but soon disappeared after recutting or removal of the pin. At the final follow-up, no symptoms involving ulnar wrist pain or distal radioulnar instability were noted. T.A.C.' pin fixation for basal ulnar styloid is a useful method and rarely requires further surgery compared with conventional methods.

CCAAT/enhancer-binding protein homologous protein (CHOP) regulates osteoblast differentiation.

Differentiation of committed osteoblasts is controlled by complex activities involving signal transduction and gene expression, and Runx2 and Osterix function as master regulators for this process. Recently, CCAAT/enhancer-binding proteins (C/EBPs) have been reported to regulate osteogenesis in addition to adipogenesis. However, the roles of C/EBP transcription factors in the control of osteoblast differentiation have yet to be fully elucidated. Here we show that C/EBP homologous protein (CHOP; also known as C/EBPzeta) is expressed in bone as well as in mesenchymal progenitors and primary osteoblasts. Overexpression of CHOP reduces alkaline phosphatase activity in primary osteoblasts and suppresses the formation of calcified bone nodules. CHOP-deficient osteoblasts differentiate more strongly than their wild-type counterparts, suggesting that endogenous CHOP plays an important role in the inhibition of osteoblast differentiation. Furthermore, endogenous CHOP induces differentiation of calvarial osteoblasts upon bone morphogenetic protein (BMP) treatment. CHOP forms heterodimers with C/EBPbeta and inhibits the DNA-binding activity as well as Runx2-binding activity of C/EBPbeta, leading to inhibition of osteocalcin gene transcription. These findings indicate that CHOP acts as a dominant-negative inhibitor of C/EBPbeta and prevents osteoblast differentiation but promotes BMP signaling in a cell-type-dependent manner. Thus, endogenous CHOP may have dual roles in regulating osteoblast differentiation and bone formation.

Pole and global shape of 25143 Itokawa.

The locations of the pole and rotation axis of asteroid 25143 Itokawa were derived from Asteroid Multiband Imaging Camera data on the Hayabusa spacecraft. The retrograde pole orientation had a right ascension of 90.53 degrees and a declination of -66.30 degrees (52000 equinox) or equivalently 128.5 degrees and -89.66 degrees in ecliptic coordinates with a 3.9 degrees margin of error. The surface area is 0.393 square kilometers, the volume is 0.018378 cubic kilometers with a 5% margin of error, and the three axis lengths are 535 meters by 294 meters by 209 meters. The global Itokawa revealed a boomerang-shaped appearance composed of two distinct parts with partly faceted regions and a constricted ring structure.