Introduction

Periprosthetic fractures of the femur are potentially catastrophic injuries associated with significant morbidity and mortality. Surgical treatment comprises revision arthroplasty or internal fixation. It is well established that a delay in treating patients with hip fracture leads to higher mortality rates, however there is limited evidence regarding mortality rates and the time to surgery in patients with lower limb periprosthetic fractures.

Bone and joint infections of the lower limbs cause significant morbidity for patients. Infection is a devastating complication for prosthetic joint replacements. In this large case series from a single centre in the NE of England, we present our experience of using antibiotic impregnated dissolvable synthetic pure calcium sulphate beads [Stimulan R]1 for local elution of antibiotics at the site of infection.

At our centre, from August 2012 to Jan 2015, antibiotic impregnated dissolvable synthetic pure calcium sulphate beads [Stimulan R]1 was used for local elution of antibiotics in 45 patients with lower limb bone or joint infections. Tailored plans were made by Orthopedic surgeon and Microbiologist MDTs based on bacteria and sensitivities.

Cases included 20 THR, 13 TKR, 5 Hemiarthroplasties, 4 tibial nonunions, 1 infected femoral plate and 2 paediatric osteomyelitis.

Organisms isolated – Coagulase negative Staphs, Staph aureus, MRSA, E coli, Enterococcus, Enterobacter cloacae, Serratia and 1 Salmonella typhimurium!!

In our cases, a combination of Vancomycin and Gentamicin was added to Stimulan beads following manufacturer's mixing guide. In 2 cases, we added Ceftazidime to the beads and Daptomycin in 1 case.

In bone infections, surgical debridement and systemic antibiotics were also needed. All arthroplasty infections underwent explantation with addition of antibiotic impregnated beads either at single stage or both stages of 2 stage revisions and systemic antibiotics.

Follow up (ranging 9months to 2 years) indicates no failure so far. The beads caused no excessive wound drainage. There was no need to remove beads as they dissolve. In the cases where a staged revision was performed, the beads were inserted at first stage and there was microbiological clearance of infection at 2nd stage. Our series includes some experince in paediatric cases too.

As far as we are aware, this is the largest series in the UK from a single centre reporting experience with Stimulan in infected bone and joints of the lower limbs. Our experience suggests use of dissolvable pure Calcium sulphate beads impregnated with carefully selected antibiotics, works as an effective adjunct to current treatments and offers flexibility with choice of antiobiotics that can be added locally.

Instability is reported to account for around 20% of early TKR revisions. The concept of restoring the “Envelope of Laxity” (EoL) mandates a balanced knee through a continuous arc of functional movement. We therefore hypothesised that a single radius (SR) design should confer this stability since it has been proposed that the SR promotes normal medial collateral ligament (MCL) function with isometric stability throughout the full arc of motion.

Our aim was to characterise the EoL and stability offered by a SR cruciate retaining (CR)-TKR, which maintains a SR from 10–110° flexion. This was compared with that of the native knee throughout the arc of flexion in terms of anterior, varus/valgus and internal/ external laxity to assess whether a SR CR-TKR design can mimic normal knee joint kinematics and stability.

Eight fresh frozen cadaveric lower limbs were physiologically loaded on a custom jig. The operating surgeon performed anterior drawer, varus/ valgus and internal/external rotation tests to determine ‘maximum’ displacements in 1) native knee and 2) single radius CR-TKR (Stryker Triathlon) at 0°, 30°, 60°, 90° and 110° flexion. Displacements were recorded using computer navigation. Significance was determined by linear modelling (p≤0.05).

The key finding of this work was that the EoL offered by the SR CR-TKR was largely equivalent to that of the native knee from 0–110°. The EoL increased significantly with flexion angle for both native and replaced knees. Overall, after TKR anterior laxity was comparable with the native knee, whilst total varus-valgus and internal-external rotational laxities reduced by only 1°. However, separated varus and valgus laxities at 110° significantly increased after TKR as did anterior laxity at 30° flexion.

In conclusion, the overall EoL offered by the SR CR-TKR is comparable to that of the native knee. In the absence of soft tissue deficiency, the implant appears to offer reliable and reproducible stability throughout the functional range of movement, with exception of anterior laxity at 30° and varus and valgus laxity when the knee approaches high flexion. These shortcomings should offer scope for future work.

Implant alignment and rotation is important in total knee arthroplasty (TKA). If incorrect it leads to abnormal wear and premature loosening. However, little is known with regard to how these factors influences rehabilitation. Our aim was to identify which aspects of alignment affect functional outcome and Length of Stay. This is an ongoing study with 300 patients results expected by september 2008. Currently 159 patients underwent TKA between May 2003 and July 2004 at Royal Perth Hospital. A Duracon TKA (Stryker Corp) was implanted by multiple surgeons using either computer navigation or conventional jiging. A WOMAC and knee society score (KSS) were calculated on each patient by a physiotherapist at 6 months, 1 year and 2 years. Implant alignment was measured using the Perth CT protocol. A statistician used a combination of independent t-tests and one way analysis of variance to determine significance between groups.

Two groups of alignment were created to allow comparison. These were termed good alignment (< = 2 degrees of mechanical axis) and outlier group (> 2 degrees of mechanical axis). There were no difference between the two groups in terms of age, BMI and preop function. This suggest no confounding variables between the groups. Coronal femoral alignment as well as cumulative error (additive error in all planes of both components) were statistically significant. The p-values are 0.031 and 0.011 respectively. Cumulative error also had an impact on hospital stay, increasing it by 2 days when greater than 6(p=0.006). Trends towards better function at 1 year were seen with regards to sagittal alignment in both the femur and tibia, as well as coronal tibial alignment. It is expected by september 2008 that patient numbers will be double. This should provide the most comprehensive analysis of alignment versus function in the literature to date.

Functional outcome following TKA is multifactorial. However certain aspects of alignment, especially the cumulative error of alignment appear to have significant effects on function.

Femoral component malrotation is a major cause of patello-femoral complications in total knee arthroplasty. In addition, it can affect varus/valgus stability during flexion which can lead to increased tibiofemoral wear.

Debate exists on where exactly to rotate the femoral component. The three principal methods utilise different anatomical landmarks: the posterior condylar axis, the transepicondylar axis and the antero-posterior axis (Whiteside’s line).

A prospective randomised controlled trial was undertaken. Sixty consecutive patients undergoing total knee arthroplasty by a single surgeon (LML) at the Royal Perth Hospital were randomised into 3 groups based on the intra-operative method for measuring femoral rotation using the PFC sigma prosthesis (Depuy) with computer navigation (Depuy/Brainlab). All patients received the usual post-operative treatment, rehabilitation and JRAC (Joint Replacement Assessment Clinic) follow up. All underwent a CT scan according to the Perth CT protocol designed specifically to accurately measure component alignment and rotation.

No significant difference in femoral rotation was found between the three groups using a one-way analysis of variance (p=0.67). However, Whiteside’s line had a significantly greater variability than the posterior condylar or transepicondylar axis using the F Test for variances (p=0.02, p=0.03). In conclusion, whilst there was no significant difference in femoral rotation, Whiteside’s line did show greater variability (−6° to 3°), and therefore we recommend the use of either the transepicondylar or posterior condylar axis in Total Knee Replacement.

The aim of this study was to identify what aspects of implant alignment and rotation affect functional outcome after total knee arthroplasty (TKA). 159 TKAs were performed at the Royal Perth Hospital between May 2003 and July 2004. All patients underwent an objective and independent clinical and radiological assessment before and after surgery. A CT scan was performed at six months. The alignment parameters that were measured included: sagital femoral, coronal femoral, rotational femoral, sagital tibial, coronal tibial and femoro-tibial mismatch. The cumulative error score, which represents the sum of the individual errors, was calculated. Functional outcome was measured using the Knee Society Score (KSS).

Good coronal femoral alignment was associated with better function at 1 year (p=0.013). Trends were identified for better function with good sagital and rotational femoral alignment and good sagital and coronal tibial alignment. Patients with a low cumulative error score had a better functional outcome (p=0.015). These patients rehabilitated more quickly and their length of stay in hospital was 2 days shorter.

We have investigated whether the thigh tourniquet used during total knee replacement (TKR) influenced the development of postoperative wound hypoxia and was a cause of delayed wound healing.

We allocated randomly 31 patients (31 TKRs) to one of three groups: 1) no tourniquet; 2) tourniquet inflated at low pressure (about 225 mmHg); and 3) tourniquet inflated to high pressure of about 350 mmHg. Wound oxygenation was measured using transcutaneous oxygen electrodes.

In the first week after surgery, patients with a tourniquet inflated to a high pressure had greater wound hypoxia than those with a low pressure. Those without a tourniquet also had wound hypoxia, but the degree and duration were less pronounced than in either of the groups with a tourniquet.

Use of a tourniquet during TKR can increase postoperative wound hypoxia, especially when inflated to high pressures. Our findings may be relevant to wound healing and the development of wound infection.