Aims

This study investigates head-neck taper corrosion with varying head size in a novel hip simulator instrumented to measure corrosion related electrical activity under torsional loads.

Objectives

This study aimed to characterise and qualitatively grade the severity of the corrosion particles released into the hip joint following taper corrosion.

Summary Statement

Combination of sorafenib with irradiation achieved synergistic effect with dose reduction in both 143B and HOS cell lines. This demonstrated the potential application of sorafenib in the treatment of osteosarcoma metastasis and radiation resistance.

We analysed 54 alumina ceramic-on-ceramic bearings from total hip replacements retrieved at one centre after a mean duration of 3.5 years (0.2 to 10.6) in situ. These implants were obtained from 54 patients (16 men and 38 women) with a mean age of 67 years (33 to 88) who underwent revision for a variety of reasons. Posterior edge loading was found in the majority of these retrievals (32 out of 54). Anterosuperior edge loading occurred less often but produced a higher rate of wear. Stripe wear on the femoral heads had a median volumetric wear rate of 0.2 mm³/year (0 to 7.2). The wear volume on the femoral heads corresponded to the width of edge wear on the matching liner. Anteversion of the acetabular component was found to be a more important determinant than inclination for wear in ceramic bearings. Posterior edge loading may be considered to be a normal occurrence in ceramic-on-ceramic bearings, with minimal clinical consequences. Edge loading should be defined as either anterosuperior or posterior, as each edge loading mechanism may result in different clinical implications.

Infrapatellar Contracture Syndrome describes a postoperative complication characterised by a vertical migration of the patella due to Patella Tendon (PT) shortening and/or PT adhesion (PTA) formation. We investigated how removal of the central one-third of the PT influences both PT length (LP) and in vitro knee kinematics in 18 sheep divided into 3, 6, 12 and 24 week groups. At time of sacrifice the pelvis-lower extremities complexes were left in a supine position until rigor mortis set in. Limbs were CT-scanned (0.5mm) whilst frozen and LP measured (ProEngineer, PTC, MA). Specimens were fixed into a loading frame with 50N applied to the rectus femoris and knee kinematics obtained (Polhemus, VT). Bones and associated registration block portions of the receiver assemblies were CT-scanned (0.5mm), reconstructed, and imported into ProEngineer where coordinate systems were created in accordance with the Joint Coordinate System (JCS). Registration was accomplished by aligning models of the receiver assemblies with the reconstructed surfaces. Post-processing and statistical analysis (ANOVA) was performed using Matlab (MathWorks, MA) and data referenced to the contralateral controls.

No significant changes in LP were observed. The mean PT length ratio (LP/LC) in the 3 week group was 1.0028±0.004 (mean±SD). In the 6 week group this ratio had increased to 1.0282±0.0246, returning to 1.005±0.0035 at 12 weeks and back to 1.0159±0.0217 at 24 weeks. No PTA’s were observed. A significant proximal shift of the patella reflecting the increase in LP was observed which correlated well with a retardation of patellar flexion (r = 0.880, p< 0.001). A significant decrease in medial patellar tilt was also observed but was not coupled with changes in tibial rotation. Proximal and lateral tibial shifts were also detected.

The results of this study seem to suggest that the changes in knee kinematics and LP induced by removal of the central one-third of the PT do not recover 24 weeks post-operatively.

This prospective study presents the ten-year (5 to 16) clinical and radiological results of 55 primary total hip replacements (THR) using a cementless modular femoral component (S-ROM). All patients had a significant anatomical abnormality which rendered the primary THR difficult.

The mean Harris hip score was 36 (12 to 72) pre-operatively, 83 (44 to 100) at five years, and 85 (45 to 99) at ten years. The Western Ontario and McMaster Universities osteoarthritis index (WOMAC) and short-form (SF)-12 scores were recorded from the year 2000. The mean SF-12 score at five years after surgery was 45.24 (22.74 to 56.58) for the physical component and 54.14 (29.20 to 66.61) for the mental component. By ten years the SF-12 scores were 42.86 (21.59 to 58.95) and 51.03 (33.78 to 61.40), respectively. The mean WOMAC score at five years post-operatively was 25 (0 to 59), and at ten years was 27 (2 to 70).

No femoral components were radiologically loose, although five had osteolysis in Gruen zone 1, three had osteolysis in zone 7, and two showed osteolysis in both zones 1 and 7. No osteolysis was observed around or distal to the prosthetic sleeve. No femoral components were revised, although three hips underwent an acetabular revision and two required a liner exchange. At a mean of ten years’ follow-up the S-ROM femoral component implanted for an anatomically difficult primary THR has excellent clinical and radiological results.

Introduction: The delivery of regional antibiotic prophylaxis has been described in reconstructive knee surgery as well as in the management of hand injuries. In this study, we describe a technique for the delivery of regional antibiotic prophylaxis to the upper extremity in patients undergoing elbow surgery, and compare tissue antibiotic concentrations achieved with this technique to those achieved with standard systemic intravenous antibiotic prophylaxis.

Methods: We collected bone and fat samples from eight patients undergoing elective elbow surgery who had received regional antibiotic prophylaxis, and measured tissue antibiotic concentration by high performance liquid chromatography. In these patients, prior to the surgical incision, we exsanguinated the arm, inflated the tourniquet, and delivered a standard dose of Cephazolin into a dorsal hand vein. For comparison, we measured antibiotic concentrations in bone and fat samples taken from eight patients undergoing elective shoulder surgery who had received standard systemic antibiotic prophylaxis.

Results: Mean tissue antibiotic concentrations were significantly higher in the patients who received regional antibiotic prophylaxis compared with those who received standard systemic prophylaxis (Bone: 1060 mcg/gm versus 41 mcg/gm; Fat: 649 mcg/gm versus 10 mcg/gm; p < 0.05.)

Discussion/conclusions: The delivery of regional antibiotic prophylaxis in elbow surgery achieved higher tissue antibiotic concentrations than those achieved with standard systemic delivery. This technique may help reduce the risk of acute infection in elbow surgery, and may be especially valuable in elective surgery in predisposed patients (e.g. rheumatoid arthritis), in the management of open fractures, as well as in protection against particularly virulent organisms.

Introduction: Although a variety of fixation techniques have been reported for fixation of oblique or spiral metacarpal fractures, lag screw fixation has been reported to be the most biomechanically stable method. Lag screws are inserted following over-drilling of the proximal cortex, which provides compression at the fracture site. We believe the compression provided by the Leibinger Bow system makes over-drilling unnecessary.

Methods: Twenty fresh-frozen human cadaveric metacarpal bones (index, ring and middle) were utilised. Bones were cleared of soft tissue and the proximal ends were embedded in Wood’s metal using a Teflon mould. Long oblique osteotomies were performed with a fine oscillating saw. Bones were randomly allocated to lagged and non-lagged groups. All bones were held in the Leibinger Bow and fixed with two screws at right-angles across the fracture site. The proximal cortex of the lagged specimens was over-drilled and the non-lagged specimens were not. The bones were subjected to cantilevered bending to failure in a mechanical testing machine. The axial stress was calculated from results for load to failure and the moment of inertia for each specimen.

Results: All specimens failed through the proximal screw. Analysis of variance statistical analysis revealed no significant difference in axial stress between the two groups.

Conclusions: Minute errors during over-drilling of the proximal cortex can easily lead to inadequate fixation. These data suggest that the use of the Leibinger Bow System may eliminate the need for this over-drilling. This not only shortens the procedure, but also reduces the chance of errors leading to poor fixation.

Introduction: New flexor tendon repair techniques have been proposed to withstand the increased loads of active mobilisation. Most reports on the biomechanics of tendon repair are based on static testing. Cyclic testing more closely replicates the clinical situation and leads to gap formation at lower loads than in static testing.

Aim: To examine three types of tendon repair using a new cyclic testing protocol.

Methods: Thirty fresh-frozen cadaveric tendons were randomly assigned to three groups; Kessler repair with simple or cross-stitch epitendinous suture or Savage repair with simple epitendinous suture. All repairs were performed in situ in Verdan’s zone 2. Samples underwent tensile cyclic testing in a saline bath at a rate of 0.1Hz. Each specimen was subjected to two phases of testing replicating passive and active motion. Gap formation, stiffness and the mode of failure were recorded for each.

Results: The Savage repairs were stiffer and more resistant to gap formation than the Kessler repairs. The simple epitendinous suture seemed to be more resistant to gap formation than the cross-stitch suture although there was no significant difference in ultimate strength.

Conclusions: Cyclic testing is a more rigorous testing protocol that more closely replicates the clinical situation. This study showed that some repairs formed significant gaps at lower loads than the reported ultimate load-to-failure seen with static testing. Although cyclic testing has its limitations, we believe it is essential to assess fully tendon repair techniques, especially those considered for active mobilisation post-operatively. This study suggests the Savage repair may be a better option for active mobilisation protocols.

In severe forearm injuries, the diagnosis of disruption of the interosseous membrane is frequently delayed and sometimes missed, giving difficulties in the salvage of forearm stability.

We studied the structure and function of the interosseous membrane in 11 cadaver preparations, using mechanical and histological analysis. Seven of the specimens tested in uniaxial tension sustained a mid-substance tear of the central band of the membrane at a mean peak load of 1038 ± 308 N. The axial stiffness was 190 ± 44 N/mm with elongation to failure of 10.34 ± 2.46 mm. These results provide criteria for the evaluation of reconstructive methods.

A preliminary clinical investigation of the use of ultrasound suggests that this may be of value in the screening of patients with complex fractures of the forearm, and for investigating the natural history of tears of the interosseous membrane.