Objectives

Pulsed electromagnetic field (PEMF) stimulation was evaluated after anterior cervical discectomy and fusion (ACDF) procedures in a randomized, controlled clinical study performed for United States Food and Drug Administration (FDA) approval. PEMF significantly increased fusion rates at six months, but 12-month fusion outcomes for subjects at elevated risk for pseudoarthrosis were not thoroughly reported. The objective of the current study was to evaluate the effect of PEMF treatment on subjects at increased risk for pseudoarthrosis after ACDF procedures.

The aim of this study was to validate the use of three models of fracture fixation in the assessment of technical skills. We recruited 21 subjects (six experts, seven intermediates, and eight novices) to perform three procedures: application of a dynamic compression plate on a cadaver porcine model, insertion of an unreamed tibial intramedullary nail, and application of a forearm external fixator, both on synthetic bone models. The primary outcome measures were the Objective Structural Assessment of technical skills global rating scale on video recordings of the procedures which were scored by two independent expert observers, and the hand movements of the surgeons which were analysed using the Imperial College Surgical Assessment Device.

The video scores were significantly different for the three groups in all three procedures (p < 0.05), with excellent inter-rater reliability (α = 0.88). The novice and intermediate groups specifically were significantly different in their performance with dynamic compression plate and intramedullary nails (p < 0.05). Movement analysis distinguished between the three groups in the dynamic compression plate model, but a ceiling effect was demonstrated in the intramedullary nail and external fixator procedures, where intermediates and experts performed to comparable standards (p > 0.6). A total of 85% (18 of 21) of the subjects found the dynamic compression model and 57% (12 of 21) found all the models acceptable tools of assessment.

This study has validated a low-cost, high-fidelity porcine dynamic compression plate model using video rating scores for skills assessment and movement analysis. It has also demonstrated that Synbone models for the application of and intramedullary nail and an external fixator are less sensitive and should be improved for further assessment of surgical skills in trauma. The availability of valid objective tools of assessment of surgical skills allows further studies into improving methods of training.

We studied the origin of extensor carpi radialis brevis using 40 fresh frozen human cadaver specimens. Ten were stained with haematoxylin and eosin and trichrome which showed the collagenous structure of the extensor tendons at their origin. Gross anatomical observation showed that there was no definitive separation between brevis and communis at the osseotendinous junction. The histological findings confirmed the lack of separation between the two tendons. The extensor tendons were in close proximity to the joint capsule but trichrome staining showed no interdigitation of the tendon with the capsule. The validity of ascribing the pain of lateral epicondylitis to extensor carpi radialis brevis must be questioned. It appears to arise more from the ‘common extensor’ origin.

We examined 59 cemented high density polyethylene sockets removed at revision hip arthroplasty. Of these 19 showed areas of wear between the outside of the socket and the acetabular bone. This was associated with lack of acrylic cement in those areas and was also related to the depth of the wear on the articulating surface of the socket. It is suggested that, in some cases, changes at the bone-cement junction are secondary to socket loosening and abrasion against the bone of the acetabulum, rather than to particles migrating from the metal-polyethylene interface. It is therefore important that impingement of the neck of the femoral stem on the edge of the cup be avoided and that, when the socket is inserted, it is not in direct contact with the bone.

In laboratory tests, the ultra-high molecular weight polyethylene used for the acetabular cups of Charnley hip prostheses has a very low wear rate against steel. In the body radiographic measurements indicate that the polyethylene wears more rapidly. In order to investigate this higher wear rate, the sockets of acetabular cups removed at post-mortem have been examined using optical and electron microscopy. It has been shown that a socket wears predominantly on its superior part and that this is a direct consequence of the orientation of the cup in the body and the direction of loading of the hip. In the worn region the femoral head in effect bores out a new socket for itself, a process which is visible with the naked eye after approximately eight years. Electron microscopy shows that the predominant wear mechanism is adhesion, but after about eight years the appearance of surface cracks suggests that surface fatigue is taking place in addition to this. Laboratory wear tests have shown that pure surface fatigue is not sufficient to account for the high clinical wear rate. Other deformation processes are suggested and discussed with regard to the higher clinical wear rate.

1. A detailed study of density variations with age in cortical bone samples from different areas of the femoral diaphysis has been carried out.

2. Bone of relatively high density and, conversely, of low density was found to have a spiral pattern along the bone shaft.

3. Moving distally along the femoral shaft there was a transposition of the greatest density from the anterior to the posterior aspect.

4. In the erect body posture the femoral inclination is such that areas of denser bone might be expected to be aligned vertically because of the weight-bearing characteristics of the femur.

5. Most areas of the cortex tended to decrease in density after the age of fifty, the less dense areas changing more than those with an initial high density. Thus, osteoporosis tended not only to maintain but to accentuate the spiral pattern of density distribution by increasing the difference between dense and less dense bone.

6. In the distal region of the diaphysis bone resorption was greatest anteriorly but hardly affected the posterior aspect. A densitometric comparison between these two sites provided a clear indication of the effect of osteoporosis.

1. Discs of bone from two fixed sites on the front of the femur were taken from ninety-one necropsy subjects and the density, width and histological appearance of the cortical bone were examined.

2. Cortical thickness, and the density of the femoralcortex, decreased with increasingage of bone.

3. There was an increase in the rate of resorption of the bone cortex from both sexes after the fifth decade.

4. The difference between the density of the metaphysial cortex and that from the diaphysis increased for both sexes after the age of fifty, because of the greater metaphysial resorption.

5. There was no change in the degree of mineralisation of the cortical bone with age. The decrease in density with age is, therefore, accounted for by resorption.