To determine whether measuring pedicle size on CT is accurate and reproducible using the WEBPACS ruler tool

Radiological analysis.

A human cadaveric spine along with 5 geometrical shapes were scanned using a multislice spiral CT scanner with 1mm cuts. The objects and the pedicle diameters for lumbar and thoracic vertebrae in the axial plane were measured independently using the WEBPACS ruler tool by 2 observers (to the nearest 0.1mm). The geometrical shapes and pedicle size on the skeleton were then measured using Vernier callipers by an independent third observer. All measurements were repeated a week later.

Reproducibility of the measurements was assessed using Bland and Altman plots. Accuracy was assessed using the Vernier calliper measurements as the gold standard and comparing the plots.

Perfect reproducibility was achieved when measuring the geometric objects with the Vernier callipers. The error of the measurement associated when measuring the pedicles was 0.5mm. The error of the measurement for the geometric objects for observers 1 and 2 was 0.5 and 0.6mm respectively, and for the pedicles it was 1.0 and 0.6mm respectively.

The WEBPACS ruler on a CT scan is accurate to within 0.5-0.6mm of the true size of an object. The error for pedicle measurements is marginally higher (0.6-1.0mm) and this may reflect the fact that they are ill defined geometric shapes. Measuring pedicle size on CT for surgical planning may have implications for small pedicles when sizing them up for a good screw.

Ethics approval None Interest Statement None

Pedicle screw systems are now the commonest method of achieving posterior spinal fixation. Surgical planning in spinal surgery may include measuring pedicle size to guide screw size on WEBPACS. We performed a study to determine whether measuring pedicle size on CT is accurate and reproducible using the WEBPACS ruler tool.

A human cadaveric spine along with 5 geometrical shapes were scanned using a multislice spiral CT scanner with 1mm cuts. The objects and the pedicle diameters for lumbar and thoracic vertebrae in the axial plane were measured independently using the WEBPACS ruler tool by 2 observers (to the nearest 0.1mm). The geometrical shapes and pedicle size on the skeleton were then measured using Vernier callipers by an independent third observer. All measurements were repeated a week later.

The WEBPACS ruler on a CT scan is accurate to within 0.5-0.6mm of the true size of an object. The error for pedicle measurements is marginally higher (0.6-1.0mm) and this may reflect the fact that they are ill defined geometric shapes. Measuring pedicle size on CT for surgical planning may have implications for small pedicles when sizing them up for a good screw.

Introduction: The role of prophylactic antibiotics in reducing the incidence of infection following hip and knee arthroplasty is well established. The British Orthopaedic Association (BOA) published best practice guidance on the use of prophylactic antibiotics in hip and knee arthroplasty. The guidance stated that all patients should receive prophylactic antibiotics at induction of anaesthesia and that each unit should have a locally agreed policy with advice from microbiologist. The aim of this audit was to compare the practice in our unit with the BOA guidance and implement necessary changes.

Patients and Methods: A prospective audit was conducted over a one month period in 2007 and included all patients undergoing elective primary hip and knee replacements. A similar re-audit was conducted over one month period in 2008 after the initial audit recommendations were implemented.

Results: Forty patients (40) were included in the initial audit. All patients received prophylactic antibiotics at induction but the choice, dose and duration of administration of antibiotics varied widely among surgeons in the unit. After discussion with the local microbiologist, we recommended a departmental policy for prophylactic antibiotics. The policy recommended a single dose of Cefuroxime and Gentamycin for standard cases and a single dose of Teicoplanin and Gentamycin for high-MRSA risk cases. A re-audit was conducted after the new policy was agreed. The re-audit included 33 patients. All patients received prophylactic antibiotics at induction. The choice of antibiotics was concordant with the policy in 79% of cases and duration of administration was appropriate in 85% of cases. Overall, the policy was adhered to in 22 cases (67 %).

Discussion & Conclusions: The closed audit cycle resulted in improvement of our practice but the compliance rate with the new policy was lower than expected. Although it is the primary responsibility of the operating surgeon to ensure the appropriate prophylactic antibiotics are administered, more awareness of other team members is necessary to improve the compliance rate with the new policy.

Introduction: Acetabular loosening can limit long-term success of total hip replacement. There are at least 62 different prosthesis designs available in the UK, many of which have no long term results. Revision surgery is expensive, challenging and potentially dangerous. There is still currently debate about the best method of acetabular fixation, in particular, regarding the use of press fit devices in elderly osteoporotic bone. Our study aims to test the null hypothesis that there is no significant difference in outcome between cemented and non-cemented acetabular fixation in this group of patients.

Methods: Patients over 72 years of age were prospectively randomised to receive either a cemented Exeter cup or a HA coated press fit cementless cup. Both groups received a cemented Exeter stem. The patients were assessed pre-operatively and reviewed at 6 weeks, 6 months and yearly in a research clinic, by an independent observer. Outcome measures were the Merle D’Aubignon Postel, Oxford Hip and Visual analogue pain scores. The implants were also assessed radiographically and all complications were recorded.

Results: To date 151 patients have been recruited into the trial. 2 year data is available for 69 patients. There were no differences in satisfaction, pain or hip scores between the groups.

There have been no major surgical complications. In particular, there have been no failures of acetabular fixation, dislocations or deep infections.

Discussion: There have been no failures in either group. Although there is insufficient data at this stage to reject our null hypothesis, there is no early evidence for concern in using cementless cups in elderly patients.

Introduction: The treatment of end stage hip osteonecrosis in patients with Sickle cell disease presents a unique set of challenges, with patients often needing arthroplasty in young adult life. Traditionally, this group of patients has a high incidence of complications and failure. We report the early results of THR in patients managed by the single hip surgeon working as part of the comprehensive Sickle Cell service.

Methods: Data was collected prospectively on all sickle patients undergoing THR at our institution. 18 patients underwent surgery with a mean age of 37 (range 25–63). There were 16 primary and 2 revisions. All patients were optimised pre-operatively with an exchange transfusion to ensure the HB SS < 30%, and all possible sites of sepsis were treated aggressively. All patients received uncemented implants with hard on hard bearings and broad-spectrum prophylactic intravenous antibiotics for 48 hours.

Results: 18 patients were followed up at a mean of 25 months. Despite technical challenges, all patients had a stable hip with good resolution of pain and radiographic evidence of bony ingrowth of all components. There were 3 minor intra-operative metaphyseal peri-prosthetic fractures, which all healed satisfactorily. There was a single early dislocation that has remained stable after closed reduction. There have been no superficial or deep infections.

Discussion: This study shows that THR can be performed safely in patients with sickle cell disease within the context of a multi-disciplinary team approach. Operative technique involves the use of long drills under image intensifier to prepare the femur safely and use of a modular uncemented system to address the mismatch between the metaphysis and the diaphysis.