Articular cartilage (AC) and subchondral bone (SB) are intimately intertwined, forming a complex unit called the AC-SB interface. Our recent studies have shown that cartilage and bone marrow are connected by a three-dimensional network of microchannels (i.e. cartilage-bone marrow microchannel connector; CMMC), which differ microarchitecturally in number, size and morphology depending on the maturation stage of the bone and the region of the joint. However, the pathological significance of CMMC is largely unknown. Here, we quantitatively assessed how CMMC microarchitecture relates to cartilage condition and regional differences in early idiopathic osteoarthritis (OA). Two groups of cadaveric female human femoral heads (intact cartilage vs early cartilage lesions) were identified and biopsy-based high-resolution micro-CT imaging was used. Subchondral bone (SB) thickness, CMMC number, maximum and minimum CMMC size, and CMMC morphology were quantified and compared between the two groups. The effect of joint region and cartilage condition on each dependent variable was examined. The number and morphology of CMMCs were influenced by the region of the joint, but not by the cartilage condition. On the other hand, the minimum and maximum CMMC size was modified by both joint location and cartilage condition. The smallest CMMCs were consistently found in the load bearing region (LBR) of the joint. Compared to healthy subjects, the size of the microchannels was increased in early OA, most notably in the non-load bearing region (NLBR) and the peripheral rim (PR) of the femoral head. In addition, subchondral bone thinning was observed in early OA as a localized event associated with areas of partial chondral defect. Our data suggest an enlargement of the SB microchannel network and a collective structural deterioration of the SB in early idiopathic OA.
Loosening of pedicle screws is a major complication of posterior
spinal stabilisation, especially in the osteoporotic spine. Our
aim was to evaluate the effect of cement augmentation compared with
extended dorsal instrumentation on the stability of posterior spinal
fixation. A total of 12 osteoporotic human cadaveric spines (T11-L3) were
randomised by bone mineral density into two groups and instrumented
with pedicle screws: group I (SHORT) separated T12 or L2 and group
II (EXTENDED) specimen consisting of T11/12 to L2/3. Screws were
augmented with cement unilaterally in each vertebra. Fatigue testing
was performed using a cranial-caudal sinusoidal, cyclic (1.0 Hz)
load with stepwise increasing peak force.Aims
Materials and Methods
It is becoming increasingly common for a patient
to have ipsilateral hip and knee replacements. The inter-prosthetic (IP)
distance, the distance between the tips of hip and knee prostheses,
has been thought to be associated with an increased risk of IP fracture.
Small gap distances are generally assumed to act as stress risers,
although there is no real biomechanical evidence to support this. The purpose of this study was to evaluate the influence of IP
distance, cortical thickness and bone mineral density on the likelihood
of an IP femoral fracture. A total of 18 human femur specimens were randomised into three
groups by bone density and cortical thickness. For each group, a
defined IP distance of 35 mm, 80 mm or 160 mm was created by choosing
the appropriate lengths of component. The maximum fracture strength
was determined using a four-point bending test. The fracture force of all three groups was similar (p = 0.498).
There was a highly significant correlation between the cortical
area and the fracture strength (r = 0.804, p <
0.001), whereas
bone density showed no influence. This study suggests that the IP distance has little influence
on fracture strength in IP femoral fractures: the thickness of the
cortex seems to be the decisive factor. Cite this article:
From a mechanical point of view, the clinical use of pedicle screws in the atlas is a promising alternative to lateral mass screws due to an increased biomechanical fixation. The most established surgical technique for posterior screw fixation in the atlas (C1) is realised by screw placement through the lateral mass [1]. This surgical placement may lead to extended bleeding from the paravertebral venous plexus as well as a violation of the axis (C2) nerve roots [1]. Using pedicle screws is an emerging technique which utilises the canal passing through the posterior arch enabling the use of longer screws with a greater contact area while avoiding the venous plexus and axis nerve roots. The aim of this Summary Statement
Introduction