14.1% of men & 22.8% of women over 45 years show symptoms of osteoarthritis OA of the knee [1]. Knee OA is usually associated with lower limb malalignment [2]; 50 of varus results in 70% −90% increase in compressive loading of the medial tibio-femoral compartment [3] and OA worsening over 18 months [4]. High Tibial Osteotomy (HTO) enables preservation of bone stock and soft tissue structures and could be an attractive option to younger patients who wish to return to high level activity. However, results of HTOs are unpredictable, which could be due to patient selection or surgical techniques. The long-term aim of this work is to develop a predictive tool to aid the surgeon in the selection of optimal HTO geometry for improved and more consistent surgical outcomes. The first step in achieving our longterm goal was to determine whether stress predictions at the tibio-femoral articulation were sensitive to simulated high tibial osteotomy, using finite element (FE) method.

CT and MRI data of a cadaveric knee were used to create geometrically accurate 3D models of the femur, tibia, fibula, menisci and cartilage and tendon of the knee joint, using the Mimics V12.11 commercially-available software (Materialise, Belgium). The Simulation module was used to register the bones and the soft tissues. The resulting STL files were exported to CATIA V5R18 pre-processor to generate surface meshes and create the corresponding 3D solid and FE models of the osseous and soft tissues from the STL cloud of points.

The Young’s moduli for cortical bone, cancellous bone, cartilages, menisci and ligaments were taken from literature as 17 GPa, 500 MPa, 12 MPa, 60 Mpa and 1.72 MPa respectively [5,6,7]. The Poisson’s ratios for osseous and soft tissues were taken as 0.3 and 0.45, respectively [8]. The nodes between the bones and the corresponding cartilages were merged and surface contact was applied between the cartilages. The distal ends of the tibia and fibula were fixed and a load of 2.1 KN, corresponding to 3 x body weight, was applied perpendicularly to the proximal end of the femur. Results of finite element analyses show a reduction of 67 % in principal stresses in the knee joint following an open wedge HTO surgery simulating 100 varus correction.

FE analysis results of this study show that HTO reduces stresses in specific regions of the knee, which are associated with OA progression [4]. Our future works include corroborating our results with controlled cadaveric experiments and implementing optimization techniques to predict optimum HTO geometries for patient-specific FE models.

Cemented total hip replacements (THR) are widely used and are still recognized as the gold standard by which all other methods of hip replacements are compared. [1]. Long-term results of cemented total hip replacements show that the revision rate due to aseptic loosening could be as high as 75.4% [2]. Moreover, high stresses developed in the cement mantle of reconstructed hips can lead to premature failure of the constructs [3]. Surgical fixation techniques vary considerably [4]. The aim of this study was to investigate the performances of different surgical fixation techniques of hip implants for patients with different body mass indices, bone morphology and bone quality, using finite element (FE) methods.

Anatomically correct reconstructed hemi-pelves were created, using CT-Scan data of the Visible Human Data set, downloaded to Mimics V8.1 software, where poly-lines of cancellous and cortical bones were created, and exported to I-Deas 11.0 FE package, where the econstructed hemi-pelvis was simulated. Accurate 3D model of the hemi-pelvis was scaled up and down to create hemi-pelves of acetabular sizes of the following diameters: 46 mm, 52 mm, and 58 mm. Following sensitivity analyses, element sizes ranging from 1–3 mm were used. Material properties of the bones, implants and cement were taken from literature [5–7]. Bones of poor quality were simulated by a reduction in the elastic modulii of the cortical bone by 50%, the cancellous bone by 10 % and the subchondral bone by 50% [5]. The nodes at the sacro-iliac joint areas and the pubic support areas were fixed. A compressive force of 3 times body weight was simulated at the hip joint. The nodes between the cancellous and subchondral bones were merged. Contact elements were used at the subchondral bone and cement mantle interface and between the femoral head implant and acetabular component. Dynamic in vitro tests, simulating forces acting on a hip joint during a gait cycle, were carried out on reconstructed synthetic bones, positioned on an Instron 8874 hydraulic machine, to verify the FE models.

The volume of cement stressed at different levels in groups of 0–1 MPa, 1–2 MPa and up to 11 and above MPa were calculated. Results of FE analyses showed that

an increase in the body mass index from 20 to 30 generated an increase in the tensile stress level in the cement mantle;

Results of in-vitro tests show that an increase in the cement mantle thickness improved fixation, corroborating with the FE results.

Performances of fixation techniques depend on the patient’s bone mass index, bone quality, bone morphology.

Stress fractures of the pars interarticularis of the lumbar spine in professional fast bowlers have become commonplace in modern times with a recently reported prevalence of 16.1%. We report 25 years of experience in the management of this patient group.

Between 1982 and 2007, we diagnosed pars defects in 21 professional cricketers. 8 were managed conservatively by a combination of rest, supervised rehabilitation, bowling action analysis and re-training to a ‘safe’ action. Surgery was considered in those players who did not respond to these conservative measures and this group essentially compromised of the fast bowlers. Surgery was by Buck’s direct repair of the pars lesion.

This treatment regime has given very good results enabling all of these players to return to professional sport with an average follow-up of over 5 years. Two of the surgical group have over 10 years follow-up and 4 have played to international level subsequent to their surgery.

We recommend treatment of this group of sportsmen in a unit consisting of a specialist physiotherapist, a bowling coach and a spinal surgeon. Should conservative measures fail, we recommend Buck’s repair as the operation of choice.

Stress fractures of the pars interarticularis of the lumbar spine in professional fast bowlers have become commonplace in recent times. Should conservative measures in their treatment fail, surgery can give good results. Postoperative rehabilitation is of the utmost importance following surgery and a suggested programme is outlined.

Post operatively, exercises and rehabilitation should proceed at a rate that is proportional to graft incorporation at the surgical site. Our rehabilitation programme has been fine tuned over several years giving much clearer guidance regarding that bowlers’ progress.

We have rehabilitated 12 fast bowlers subsequent to Bucks repair of the pars interarticularis stress fracture in the lumbar spine. We have identified 7 stages in this process to rehabilitate the bowler to the highest level. We emphasise that the process of rehabilitation involves a team approach, the most important members being surgeon, physiotherapist, bowling coach and trainer.

Surgery to the fast bowler with a stress fracture of the pars interarticularis can give good results. However it is necessary to have a multidisciplinary rehabilitation programme that proceeds in a stepwise manner to enable a return to full sport.

We present the results of 228 consecutive Charnley low friction arthroplasties, inserted in 193 patients between July 1972 and December 1976. All hips were inserted by the posterior approach without trochanteric osteotomy. All patients were enrolled into a prospective study and pre-and post-operative findings recorded. This series was reviewed in 1985 and once again in 2002.

The pre-and peri-operative findings are similar to contemporary series. Due to our stable population only two patients were lost to follow-up. Our survivorship results show a 10-year survival of 93%, 20-year survivorship of 84% deteriorating to a 30-year survival of 73%.

Of the 26 hips revised 6 were for recurrent dislocations and these were satisfactorily stabilised using acetabular augments. There were 8 revisions for fracture of the femoral component (all flatbacks), 8 revisions for aseptic loosening of the femoral component and 6 revisions for aseptic loosening of the acetabulum. There was one revision for deep infection and the remaining 3 were for periprosthetic fractures.

The survivors were scored clinically using the Merle d’Aubign-Postel score with a mean value of 12. None of the survivors were on the waiting list for revision arthroplasty or felt that it was indicated.

Overall our results are comparable to other studies and vindicate the choice of approach, which at the time was a source of some controversy

Introduction and Aims: We present the results of 228 consecutive Charnley low-friction arthroplasties, inserted in 193 patients between July 1972 and December 1976. Unusually for this time, all hips were inserted by the posterior approach without trochanteric osteotomy.

Method: All patients were enrolled into a prospective study and pre- and post-operative findings recorded. This series was reviewed in 1985 and once again in 2002. The survivors were scored clinically using the Merle d’Aubigné-Postel score with a mean value of 12. The reason for revision was also recorded and analysed.

Results: The pre- and peri-operative findings are similar to contemporary series. Due to our stable population, only two patients were lost to follow-up. Our survivor-ship results show a 10-year survival of 93%, deteriorating to a 30-year survival of 73%.

Conclusion: Overall our results are comparable to other studies and really vindicate the choice of approach, which at the time was a source of some controversy.

The purpose of the study was to reduce peak cement mantle stresses occurring at the tip of the keel for an all-polyethylene cemented glenoid component using finite element (FE) techniques.

Loosening of the glenoid component remains to be one of the most determinant factors in the outcome of total shoulder arthroplasty. Due to the off-centre loading that occurs, there is bending of the glenoid component with high shearing forces. These forces are transmitted to the underlying cement mantle and bone. It has been reported in previous FE studies that high cement mantle stresses occurs at the tip of the keel and at the edges of the cement flange. These stresses at the bone-cement interface can exceed the fatigue life of the cement, therefore initiating crack formation and damage accumulation. This results in loosening of the component and thus failure.

A three-dimensional (3D) model of the scapula was developed using CT data. Surfaces of the inner and outer contours of the cortical shell were created within commercially available software, using a threshold algorithm. The glenoid bone geometry was then produced. Material properties for the reconstructed glenoid were taken from literature, using four differing material properties. The articulating surface of the keeled glenoid component was modelled with a 3mm radial mismatch. This was positioned in the glenoid bone with a uniform cement mantle thickness of 2mm. The resulting FE mesh consisted of solid parabolic tetrahedral elements.

The effect of varying the angle on the keel of the component in the superior/inferior (S/I) direction was studied with uniform cement mantle thickness. The S/I length of the keel at the lateral end where it meets the back face of the component was maintained (juncture with flange), whilst the S/I length of the keel at the medial end (tip of the keel) was reduced as the change in angle increased. Two load cases were studied, involving a physiological load for 90 degrees of abduction and a central load of same magnitude.

It was found that by increasing the angle of the keel, where the S/I length at the tip of the keel was reduced, resulted in lower cement mantle stresses in this area of interest. This can be attributed to it being further away from the stiffer cortical bone where high tensile stresses exist due to inherent bending of the glenoid construct under loading. Therefore by reducing these high cement mantle stresses at the tip of the keel, fatigue failure of the cement mantle could be reduced.

Aims: Pressure sores are potentially serious complications caused by capillary closure due to extended periods of immobilization such as during surgery. Jellypads are available to reduce this risk but are costly and have been shown to harbour bacteria, thereby posing as an infective risk in implant surgery. The aim of this study is to investigate the potential use of more cost effective, clean, disposable product, without compromising on efficacy. Methods: Currently marketed (jellypad) and novel (bubblewrap) pressure relief products were used in this study to compare pressures generated when a subject sat on the different products. Varying diameter bubblewrap in differing layer structure was used to assess whether (a) the novel material offered better pressure relief and if so, (b) which configuration provided the best pressure dispersion. Results: Our results show that bubblewrap seems to offer better relief of pressure than jellypad. Two to four layers of 10 mm diameter bubblewrap used in opposite directions was the optimum configuration. Conclusion: Based on our investigations, we believe that bubblewrap is a better product for the prevention of pressure sores. Bubble-wrap results in lower peak and average pressure values than jellypad. Moreover, bubblewrap is cheap, disposable and is less likely to transmit infections.

Aim: We present our experience with 20 periprosthetic femoral fractures which were treated with a Biomet plate. Aim of the current study is to clarify the indications of the method and emphasize on the importance of fracture classification in the preoperative planning.

Material-methods: Retrospective study of 20 patients treated between 1999 and 2001. Ten of the patients sustained a periprosthetic fracture around a total hip replacement, 8 around a hemiarthroplasty and 2 around a revised total hip replacement.

Fractures were classified according to the Vancouver classification system. The mechanism of injury, the ambulatory status prior to the fracture and the loosening zones (according to Gruen) were studied.

Results: In 14 patients the results were satisfactory and in 3 poor. Three patients died during follow up. There were marked differences in the outcome depending on the fracture type. In B1 and C fractures the results were satisfactory. Patients with a B3 fracture had a worse outcome.

Patients with a periprosthetic fracture around a hemiarthroplasty had better results compared to those with a fracture around a total hip replacement. Poorer outcomes were noticed in patients with a periprosthetic fracture around a revised total hip replacement.

Conclusion: A careful patient selection is important for the success of the method. The accurate classification of the periprosthetic fractures helps in the preoperative planning.

The physical demand of the modern game of cricket on the fast bowler is known to cause stress fractures of the lumbar spine.

Between 1983 and 2001, we diagnosed pars interarticularis defects in 18 professional cricketers contracted to a single English county cricket club. Initial management was conservative based on a combination of rest, supervised rehabilitation, bowling action analysis and re-education if indicated. Re-deployment (for example an all rounder to concentrate on batting alone) was also considered. 8 of the patient group responded to these measures. The remaining 10 were treated surgically, 9 by Buck’s repair of the spondylolytic lesion. All 9 returned to professional sport with an average follow-up of 5 years 8 months and a maximum follow-up of 10 years.

We recommend treatment of this group of sportsmen in a unit consisting of a specialist physiotherapist, a bowling coach and a spinal surgeon. Should conservative measures fail, we recommend Buck’s repair as the operation of choice. Whether treated conservatively or surgically, we believe the vast majority of this patient group should be able to return to full professional sport