Background

Treating fractures is expensive and includes a long post-operative care. Intra-articular fractures are often treated with open surgery that require massive soft tissue incisions, long healing time and are often accompanied by deep wound infections. Minimally invasive surgery (MIS) is an alternative to this but when performed by surgeons and supported by X-rays does not achieve the required accuracy of surgical treatment.

One of the more difficult tasks in surgery is to apply the optimal instrument forces and torques necessary to conduct an operation without damaging the tissue of the patient. This is especially problematic in surgical robotics, where force-feedback is totally eliminated. Thus, force sensing instruments emerge as a critical need for improving safety and surgical outcome. We propose a new measurement system that can be used in real fracture surgeries to generate quantitative knowledge of forces/torques applied by surgeon on tissues.

We instrumented a periosteal elevator with a 6-DOF load-cell in order to measure forces/torques applied by the surgeons on live tissues during fracture surgeries. Acquisition software was developed in LabView to acquire force/torque data together with synchronised visual information (USB camera) of the tip interacting with the tissue, and surgeon voice recording (microphone) describing the actual procedure. Measurement system and surgical protocol were designed according to patient safety and sterilisation standards.

The developed technology was tested in a pilot study during real orthopaedic surgery (consisting of removing a metal plate from the femur shaft of a patient) resulting reliable and usable. As demonstrated by subsequent data analysis, coupling force/torque data with video and audio information produced quantitative knowledge of forces/torques applied by the surgeon during the surgery. The outlined approach will be used to perform intensive force measurements during orthopaedic surgeries. The generated quantitative knowledge will be used to design a force controller and optimised actuators for a robot-assisted fracture surgery system under development at the Bristol Robotics Laboratory.

Purpose

To compare the early medial open approach (MO) with the anterior approach (AO) performed after the appearance of the ossific nucleus for DDH that has failed closed reduction or presented late.

Enhanced Orthopaedic Recovery (EOR) is an evidence-based, integrated, multi-modal approach to improving recovery following elective orthopaedic surgery. The principles of EOR are to reduce time to functional recovery of postoperative patients safely with subsequent benefits to their length of stay in hospitals, their quality of life and health economics and outcomes. The combination of interventions used has been shown to be effective following major gastro-intestinal surgery but have not been tested in Orthopaedics until now. They aim to reduce the stress response provoked by surgery and the peri-operative catabolic state by optimally managing patient metabolism, post-operative pain, mobility and expectations.

Simple interventions along the patients’ journey include pre-operative educational classes, pre-operative carbohydrate loading, a (short) two hour fast ensuring surgery performed on anabolic patients, post operative pain and metabolic optimisation, empowering patients with ownership of their post-operative recovery and proactive post-discharge management. We found that these simple interventions translate well into elective orthopaedic arthroplasty surgery, can be achieved without additional cost and have little impact on intra-operative practice.

We conducted a single surgeon, consecutive patient, interventional, cohort study of lower limb primary joint arthroplasty surgery (primary total knee and primary total hip arthroplasty) in a busy district general hospital, 30 bed orthopaedic department. We reviewed the preceding 141 primary joint replacements (75 total hip and 66 total knee arthroplasties) before prospectively assessing the next 50 total hip and 32 total knee arthroplasties. A Mann-Whitney test between the two periods showed a highly statistically significant fall in time to discharge (median hospital stay 6.5 - 4 nights, p< 0.001). We noted no adverse effects as a result implementing EOR.

We have shown that by implementing EOR, reduced time to functional recovery and subsequent hospital discharge can be safely achieved with consequent quality of life and health economic benefits.

Introduction and aim: We have previously shown an association between whole blood metal ions and reduced CD8+ T cells in patients with unilateral metal on metal (MOM) hip resurfacings. Our aim was to substantiate this controversial finding with a follow up cohort of larger numbers of patients before further immunological investigation.

Method: We measured lymphocyte subset counts and whole blood Cobalt and Chromium in 2 groups of patients: a Birmingham hip resurfacing group (n=100); and a metal on polyethylene MOP hip arthroplasty group (n=34). Metal ions were measured using inductively-coupled mass spectrometry (ICP-MS) with a Dynamic Reaction Cell (DRC). The detection limit was 10 parts per trillion. All hip components were well fixed, clinically and radiologically.

Results: Cobalt and chromium levels were significantly elevated in the MOM resurfacing group compared to the MOP group (p< 0.0001). There was a statistically significant decrease in the MOM resurfacing groups’ level of CD8+cells (T cytotoxic) (p=0.005) when analysed by a Mann-Whitney U test. There was no significant difference between levels of CD4+ (T helper cells), CD19+ (B cells) and CD16/56+ (Natural Killer cells). A threshold level of blood cobalt and chromium ions for depression of total numbers CD8+ T cells was observed.

Conclusions: This follow up cohort of 100 MOM hip resurfacing patients has replicated the association of reduced CD8+ T cells and raised metal ion levels observed in our founder cohort. This was specific to CD8+ T cells. We are now more certain that this association needs further detailed immunological investigation.

Background: Metal-on-metal bearing hip replacements release between three and nine times more cobalt and chromium ions than a metal on polyethylene bearing hip replacement. We do not fully understand the cause for the variability of ion levels after metal on metal hip replacement. The factors that determine an individual’s levels of metal ions include: firstly, patient factors (renal failure, patient weight, high activity); secondly, manufacture factors (head size (and fluid film lubrication), carbide density, surface finish) and lastly study factors (bilateral implants, time from operation). Biomechanical studies suggest that component position, in particular acetabular inclination, is important for wear rate but there is no published correlation from clinical studies.

Aim: To investigate the relationship between acetabular inclination angle and metal ion levels of patients with Birmingham Hip resurfacings.

Methods: Using standardised radiographs, we measured the inclination angle (using UTHSCSA image tool) of the acetabular components in thirty-one patients (mean age 54 years) who underwent unilateral Birmingham hip resurfacing (mean time post operation of 22 months). We also measured peripheral whole blood chromium and cobalt ion concentrations using inductively coupled mass spectrometry. All components were well fixed.

Results: There was a positive correlation between the inclination angle (range 28 degrees – 55 degrees) of the acetabular component and whole blood concentration of Cobalt (range 2.3 – 7 mcg/L), Chromium (range 0.56 – 4.3 mcg/L) and total metal ion levels (range 3.1 – 10.3 mcg/L). This finding was statistically significant, with a Pearson correlation coefficient of 0.46 (95% CI 0.13-0.70) and a p-value of 0.00398.

Conclusion: Acetabular inclination angle is likely to be a factor in determining an individual’s metal ion levels in patients with metal on metal resurfacing. We also iden-tified a threshold level of 50 degrees inclination, after which the metal ion levels rise dramatically. We describe the possible biomechanical mechanisms to explain these results. We recommend surgeons implant the metal socket at an inclination angle of less than 50 degrees.