Aims

The aim of this study was to identify the optimal lip position for total hip arthroplasties (THAs) using a lipped liner. There is a lack of consensus on the optimal position, with substantial variability in surgeon practice.

We have previously reported on the improved all-cause revision and improved revision for instability risk in lipped liner THAs using the NJR dataset. These findings corroborate studies from the Australian (AOANJRR) and New Zealand (NZOA) joint registries. The optimal orientation of the lip in THAs utilising a lipped liner remains unclear to many surgeons. The aim of this study was to identify impingement-free optimal liner orientations whilst considering femoral stem version, cup inclination and cup version.

A cementless THA kinematic model was developed using a 20 degree XLPE liner. Physiological ROM and provocative dislocation manoeuvre analyses were performed. A total of 9 cup positions were analysed (inclination 30–40–50 degrees, anteversion 5-15-25 degrees) and combined with 3 stem positions (anteversion 0-15-30 degrees) and 5 lip orientations (right hip 11 to 7 o'clock).

Some lip orientation/component position combinations lead to impingement within the physiological ROM range. Using a lipped liner increases the femoral head travel distance prior to dislocation when impingement occurs in the plane of the lip. In THAs with a cup inclination of 30 and 40 degrees, inferior lip orientations (7–8 o'clock for a right hip) performed best. Superior lip orientation performed best with a cup inclination of 50 degrees. Femoral stem version has a significant effect on the range of movement prior to impingement and hence the preferred lip orientation.

The optimal orientation of the lip in lipped liner THA is dependent on the position of both the acetabular and femoral components. In the common component orientation combination of stem anteversion 15, cup inclination 40 and cup anteversion 15, the optimal lip orientation was postero-inferiorly (8 o'clock for a right hip). Preventing impingement during physiological ROM is possible with appropriate lip liner orientation.

Aims

The aim of our study was to investigate the effect of asymmetric crosslinked polyethylene liner use on the risk of revision of cementless and hybrid total hip arthroplasties (THAs).

Our previous work presented at BHS revealed a reduced risk of revision for all reasons in THAs using lipped (asymmetric) liners. Some audience members felt that this finding may be due to unaccounted confounders and the hip surgery community remains sceptical.

A fully adjusted Cox model was built after exploratory Kaplan-Meier analyses. The following surgical approaches were included in the analysis: Posterior, Hardinge/anterolateral, Other. The variables included in the final Cox model included: Gender, liner asymmetry, age, head composition, stem fixation method, head diameter, indication for implantation and surgical approach. An additional analysis of the 3 most commonly used polyethylene liners with both a flat and asymmetric version was performed.

In the fully adjusted Cox model, the use of a flat liner was associated with increased risk of revision for instability (HR: 1.79, 95%CI: 1.52–2.10) and increased risk of revision for all reasons (HR 1.195, 95%CI: 1.104 – 1.293) when compared to THAs utilising flat liners. This finding was upheld in the product specific analysis.

When utilising flat liners, the Hardinge/anterolateral approach was associated with a reduced risk of revision for instability compared to the posterior approach (HR 0.56, 95%CI: 0.446 to 0.706). When an asymmetric liner was used, there was no significant difference in the risk of revision for instability between the Hardinge/anterolateral approach and the posterior approach (HR 0.838, 95%CI: 0.633 – 1.110).

The use of polyethylene-based bearings gives the surgeon the option to use asymmetric liners. The reduced risk of revision in THAs with asymmetric liners was seen in the analysis of the complete dataset and in the product specific analysis. Our results demonstrate that the posterior approach, when used with asymmetric XLPE liners, is not associated with a higher risk of revision for instability as historical data suggested.

Computer aided Total Hip Arthroplasty (THA) surgery is known to improve implantation precision, but clinical trials have failed to demonstrate an improvement in survivorship or patient reported outcome measures (PROMs). Our aim was to compare the risk of revision, PROMs and satisfaction rates between computer guided and THA implanted without computer guidance.

We used the National Joint Registry dataset and linked PROMs data. Our sample included THAs implanted for osteoarthritis using cementless acetabular components from a single manufacturer (cementless and hybrid). An additional analysis was performed limiting the sample size to THAs using cementless stems (fully cementless). The primary endpoint was revision (of any component) for any reason. Kaplan Meier survivorship analysis and an adjusted Cox Proportional Hazards model were used.

41683 non computer guided, and 871 (2%) computer guided cases were included in our cementless and hybrid analysis. 943 revisions were recorded in the non-guided and 7 in the computer guided group (adjusted Log-rank test, p= 0.028). Cumulative revision rate at 10 years was 3.88% (95%CI: 3.59 – 4.18) and 1.06% (95%CI: 0.45 – 2.76) respectively. Cox Proportional Hazards adjusted HR: 0.45 (95%CI: 0.21 – 0.96, p=0.038). In the fully cementless group, cumulative revision rate at 10 years was 3.99% (95%CI: 3.62 – 4.38) and 1.20% (95%CI: 0.52 – 3.12) respectively. Cox Proportional Hazards adjusted HR: 0.47 (95%CI: 0.22 – 1.01, p=0.053). There was no statistically significant difference in the 6-month Oxford Hip Score, EQ-5D, EQ-VAS and success rates. Patient Satisfaction (single-item satisfaction outcome measure) was improved in the computer guided group but this finding was limited by a reduced number of responses.

In this single manufacturer acetabular component analysis, the use of computer guided surgery was associated with a significant reduction in the early risk of revision. Causality cannot be inferred in view of the observational nature of the study, and further database and prospective studies are recommended to validate these findings.

Aims

To investigate the effect of polyethylene manufacturing characteristics and irradiation dose on the survival of cemented and reverse hybrid total hip arthroplasties (THAs).

Aim

To assess the effect of different polyethylene modifications on Total Hip Replacement survival.

Aim

To assess the effect of the bearing surface and head size on the survival of total hip replacements with modern bearing surface combinations.

Aims

The aim of this study was to identify the effect of the manufacturing characteristics of polyethylene acetabular liners on the survival of cementless and hybrid total hip arthroplasty (THA).

Introduction

Early identification and conservative management of paediatric Monteggia fractures has been shown to correlate with good results. Nevertheless, several authors advocate more aggressive management with open reduction and internal fixation (ORIF) for unstable fractures. We herein present the experience of a tertiary paediatric hospital in the management of Monteggia fractures.

Introduction

Lateral humeral condyle fractures account for 17% of the distal humeral condyle fractures. They affect children between 5 and 10 years of age. Recent reports advocate closed reduction and internal fixation for the less displaced fractures.

Implant alignment in knee arthroplasty has been identified as critical factor for a successful outcome. Human error during the registration process for imageless computer navigation knee arthroplasty directly affects component alignment. This cadaveric study aims to define the error in the registration of the landmarks and the resulting error in component alignment.

Five fresh frozen cadaveric limbs including the hemipelvis were used for the study. Five surgeons performed the registration process via a medial parapatellar approach five times. In order to identify the gold standard point, the soft tissues were stripped and the registration was repeated by the senior author. Errors are presented as mm or degrees from the gold standard registration.

The error range in the registration of the femoral centre in the coronal plane was 6.5mm laterally to 5.0mm medially (mean: −0.1, SD: 2.7). This resulted in a mechanical axis error of 5.2 degrees valgus to 2.9 degrees varus (mean: 0.1, SD: 1.1). In the sagittal plane this error was between −1.8 degrees (extension) and 2.7 degrees (flexion). The error in the calculation of the tibial mechanical axis ranged from −1.0 (valgus) to 2.3 (varus) degrees in the coronal plane and −3.2 degrees of extension to 1.3 degrees of flexion. Finally the error in calculating the transepicondylar axis was −11.2 to 6.3 degrees of internal rotation (mean: −3.2, SD: 3.9).

The error in the registration process of the anatomical landmarks can result in significant malalignment of the components. The error range for the mechanical axis of the femur alone can exceed the 3 degree margin that has been previously been associated with implant longevity. The technique during the registration process is of paramount importance for image free computer navigation. Future research should be directed towards simplifying this process and minimizing the effect of human error.

Controversy still remains as to whether patella resurfacing in total knee arthroplasty (TKA) should be conducted as a matter of routine. Some authors recommend routine resurfacing of the patella and advocate this due to the reduction in post-operative anterior knee pain and the reduction in requirement for revision surgery.

A database search was conducted to identify prospective randomized controlled studies only. Eighteen prospective randomized trials were identified and found eligible for inclusion. A cumulative sample of 8006 knees were involved, 3418 undergoing resurfacing and 4588 undergoing no resurfacing. Primary outcome data extracted was incidence of secondary operations, incidence of anterior knee pain and functional outcome scores including subgroup analysis of the type of prosthesis used in each study. Der Simonian Laird metanalysis was conducted if studies were found to be homogenous where statistical significance was defined as an overall alpha error of < 0.05.

No statistically significant differences were found to exist between patients undergoing patella resurfacing as a primary total knee replacement and those who preserved the native patella. No differences could be found between specific prosthetic design when subgroup analysis was conducted.

The study does not offer evidence to suggest any advantage of resurfacing versus non-resurfacing. Furthermore, no significant discrepancy existed when comparing different types of total knee prosthesis. This may be due that all the knees analysed are designed to be patella friendly and allow conformity of articulation of both a native and patella button equally

Simvastatin is a 3-Hydroxy-3-methylglutaryl Co-enzyme inhibitor, widely used to reduce lipid levels. Recent studies have demonstrated pleiotropic beneficial effects the skeleton. We aim to demonstrate the effect of Simvastatin on the osteogenic differentiation and proliferation of murine embryonic stem cells.

Tg2a cells were cultured in maintenance medium until confluence and passaged twice into tissue culture flasks. They were then seeded into 6 well and 24 well plates at a density of 10.000 cells/cm2 and cultured for 3 days in maintenance medium mixed at 1:1 with HepG2 conditioned medium. The culture then continued using osteogenic medium with different concentrations of simvastatin for another 16 days. Measurements included Alizarin Red quantification for calcified matrix, ALP assay, RT-PCR for genes expressed during osteogenic differentiation (osteocalcin, Runx2, osterix, Col1a1).

Simvastatin has dose dependent effect on mineralized matrix formation. Alizarin Red quantification assays demonstrated that simvastatin (all dose groups) induced a statistically significant increase in calcified matrix formation on day 11 (P< 0.05) and 16 (P< 0.01) compared to the control group. ALP activity was significantly higher on day 8 in the groups that had a simvastatin concentration of 1nM, 10nM and 100nM (P< 0.05). RT-PCR has demonstrated that simvastatin caused increased expression of all genes measured on differentiation. Statins can induce bone formation when combined with embryonic stem cells.

During hip revision removal of old cement mantle is a major problem. In cases of satisfactory bond between cement mantle and the underlying bone, cementing the revision stem into the old mantle is regarded as a highly attractive option. The aim was the analysis of the shearing strength of the interface between two layers of poly-methylmethacrylate cement in the presence of fluid.

A laboratory, two-dimensional model of the interface was used. Effect of different viscosity fluids and volumes on its strength was checked. 6 variants (control monoblock, dry surface, surface stained with small or large volume of water or highly viscous fluid) containing 7 repeats were exposed to a single shearing stress to failure.

Large volume of viscous fluid prevented bonding completely in two cases and significantly weakened the other samples showing mean failure stress of 5.53 MPa. This was significantly lower compared with control monoblock (19.8MPa), dry surface variant (16.9MPa) and the stain with small amount high viscosity fluid (16.01MPa). Interestingly, presence of a large volume of low viscosity fluid did not significantly reduce resistance to shear stress (17.05MPa).

In all but large volume of viscous fluid variants, the failure occurred away from the interface between two cement layers. Large amount of viscous fluid weakened significantly this interface. If such a viscous fluid could be eliminated by copious water irrigation it is likely that strength of the cement-cement bond will be maintained. Our observations suggest that cement-in-cement technique seems to be biomechanically acceptable