A novel approach for posterior acetabular fractures: Surgical technique.

This article describes a novel approach, the Direct Posterior Approach (DPA) for the treatment of posterior acetabular fractures (posterior column, posterior wall, or both posterior column and wall). This technique allows direct visualization of the entire posterior wall, part of the hip capsule and the posterior column between the space of the gluteus medius and the piriformis superiorly. The approach spares the division of short external rotators, abductors, and hip capsule, thus preventing iatrogenic damage to the medial femoral circumflex artery, sciatic nerve, and superior and inferior gluteal neurovascular bundles, as well as protecting the vascularity of the fracture fragments. In addition to the low blood loss, short operative time and low risk of iatrogenic injury, patients who are treated by the DPA approach exhibit positive functional recovery in follow-up. DPA is an effective, safe and minimally-invasive technique for the treatment of posterior acetabular fractures.

[Establishment of a rabbit model of lumbar intervertebral disc degeneration via the paraspinal approach].

OBJECTIVE: To establish a rabbit model of intervertebral disc degeneration by puncturing the anulus fibrosus through an approach between the longissimus dorsi muscle and obliquus externus abdominis. METHODS: The L(4/5) and L(5/6) intervetebral discs of 6 New Zealand white rabbits were punctured by an 18-gauge pin in the anterolateral annular fibrosus through an approach between the longissimus dorsi muscle and the obliquus externus abdominis with the right transverse processes of L(5) and L(6) resected; the L(2/3) discs were used as the control without exposure or needle stab, and the L(3/4) discs were subjected to sham operation with the discs exposed but not punctured after resecting the right transverse process of L(4). X-ray and magnetic resonance imaging (MRI) were performed preoperatively and at the 4th week after puncture. At 4 weeks after the operation, histological and immunohistochemical analyses of the discs were carried out. RESULTS: X-ray of the punctured discs at 4 weeks after the operation presented a significant decrease of disc height, osteophytosis formation, and end-plate stiffness; an obvious decrease of signal intensity on T(2)-weighted images was found in the puncture group but not in the control or sham-operated groups. Gross morphological inspection showed atrophy of the nucleus pulposus, which became loose, soft, and fragile with a light yellow color. Histological and immunohistochemical analyses showed a significant decrease of notochordal cells and type II collagen in the nucleus pulposus in the puncture group as compared to the control and sham-operated groups. CONCLUSION: Puncture through the approach between the longissimus dorsi muscle and the obliquus externus abdominis allows the establishment of a reliable animal model for studying intervertebral disc degeneration.

Metformin stimulates osteoprotegerin and reduces RANKL expression in osteoblasts and ovariectomized rats.

Anti-diabetic drug metformin has been shown to enhance osteoblasts differentiation and inhibit osteoclast differentiation in vitro and prevent bone loss in ovariectomized (OVX) rats. But the mechanisms through which metformin regulates osteoclastogensis are not known. Osteoprotegerin (OPG) and receptor activator of nuclear factor κB ligand (RANKL) are cytokines predominantly secreted by osteoblasts and play critical roles in the differentiation and function of osteoclasts. In this study, we demonstrated that metformin dose-dependently stimulated OPG and reduced RANKL mRNA and protein expression in mouse calvarial osteoblasts and osteoblastic cell line MC3T3-E1. Inhibition of AMP-activated protein kinase (AMPK) and CaM kinase kinase (CaMKK), two targets of metformin, suppressed endogenous and metformin-induced OPG secretion in osteoblasts. Moreover, supernatant of osteoblasts treated with metformin reduced formation of tartrate resistant acid phosphatase (TRAP)-positive multi-nucleated cells in Raw264.7 cells. Most importantly, metformin significantly increased total body bone mineral density, prevented bone loss and decreased TRAP-positive cells in OVX rats proximal tibiae, accompanied with an increase of OPG and decrease of RANKL expression. These in vivo and in vitro studies suggest that metformin reduces RANKL and stimulates OPG expression in osteoblasts, further inhibits osteoclast differentiation and prevents bone loss in OVX rats.