The outcome following arthroscopic anterior cruciate (ACL) reconstruction is dependant on a combination of surgical and non-surgical factors. Technical error is the commonest cause for graft failure, with poor tunnel placement accounting for over 80% of those errors.

A routine audit of femoral and tibial tunnel positions following single bundle hamstring arthroscopic ACL reconstruction identified apparent inconsistent positioning of the tibial tunnel in the sagittal plane. Intra-operative fluoroscopy was therefore introduced (when available) to verify tibial guide wire position prior to tunnel reaming. This paper reports a comparison of tibial interference screw position measured on post-operative radiographs with known tunnel position as shown on intra-operative fluoroscopic images in 20 patients undergoing routine primary ACL reconstruction between January and June 2009.

Surgery took a mean of 5 minutes longer when intra-operative fluoroscopy was used. In 3/20 patients, fluoroscopy led to re-positioning of the tibial guide wire prior to tunnel reaming. The mean tibial tunnel position as indicated by the tunnel reamer was 41 +/− 2.7 % of the total plateau depth (range 37% to 47%). The mean position projected from the tibial screw on post operative radiographs was 46 +/− 9.2% (range 38% to 76%). A paired t-test showed a significant difference (p = 0.022) between true tunnel position and tibial screw position. 6/20 patients had post operative screw positions that were > 5% more posterior than the known position of the tibial tunnel.

The position of the tunnel should be measured at its mid-point where this is evident. On most early radiographic images, the margins of the tunnel are not clear and therefore a line projected from the centre of the screw is used. This audit demonstrates the potential inaccuracy associated with this.

Introduction: Inadequate cementation of the acetabular component in hip replacement surgery leads to early aseptic loosening, the most common cause of revision. The optimum method of cementation has not been fully evaluated. This study aimed to determine the effect of the acetabular component flange on mean and peak pressure during component insertion.

Method: A 53mm deepened hemisphere was machined from aluminium. Pressure transducers were positioned at the rim, at 45 degrees, and at the base. Polyethelene acetabular components of different sizes and flange designs were mounted onto a materials testing machine and inserted at a constant rate into Palacos R cement within the aluminium hemisphere. Insertion was stopped at a pre-determined point when an even cement mantle was achieved. The same components were then tested without a flange. Each test was repeated six times. Output data from the transducers was analysed.

Results: Components with a flange create a mean pressure 6–18 times higher at the rim than those without a flange. At the base pressures are 2–4 times higher. A stiffer flange generates higher peak and mean pressures than a more malleable flange. Delaying insertion by one minute does not increase the pressures achieved unless a flange is used.

Discussion: These results strongly support the use of a flange to contain cement during insertion of the acetabular component. Unflanged components fail to achieve satisfactory mean or peak pressures, even if insertion is delayed. This is likely to result in poor cement penetration into bone and reduced longevity of interface fixation.

From a search of MRI reports on knees, 20 patients were identified with evidence of early anteromedial osteoarthritis without any erosion of bone and a control group of patients had an acute rupture of the anterior cruciate ligament. The angle formed between the extension and flexion facets of the tibia, which is known as the extension facet angle, was measured on a sagittal image at the middle of the medial femoral condyle.

The mean extension facet angle in the control group was 14° (3° to 25°) and was unrelated to age (Spearman’s rank coefficient, p = 0.30, r = 0.13). The mean extension facet angle in individuals with MRI evidence of early anteromedial osteoarthritis was 19° (13° to 26°, SD 4°). This difference was significant (Mann-Whitney U test, p < 0.001).

A wide variation in the extension facet angle was found in the normal control knees and an association between an increased extension facet angle and MRI evidence of early anteromedial osteoarthritis. Although a causal link has not been demonstrated, we postulate that a steeper extension facet angle might increase the duration of loading on the extension facet during the stance phase of gait, and that this might initiate failure of the articular cartilage.

We retrospectively analysed the MR scans of 25 patients with patellofemoral dysplasia and ten control subjects, to assess whether there was any change in the morphology of the patella along its vertical length. Ratios were calculated comparing the size of the cartilaginous and subchondral osseous surfaces of the lateral and medial facets. We also classified the morphology using the scoring systems of Baumgartl and Wiberg. There were 18 females and seven males with a mean age of 20.2 years (10 to 29) with dysplasia and two females and eight males with a mean age of 20.4 years (10 to 29) in the control group.

In the patient group there was a significant difference in morphology from proximal to distal for the cartilaginous (Analysis of variance (ANOVA) p = 0.004) and subchondral osseous surfaces (ANOVA, p = 0.002). In the control group there was no significant difference for either the cartilaginous (ANOVA, p = 0.391) or the subchondral osseous surface (ANOVA, p = 0.526).

Our study has shown that in the dysplastic patellofemoral articulation the medial facet of the patella becomes smaller in relation to the lateral facet from proximal to distal. MRI is needed to define clearly the cartilaginous and osseous morphology of the patella before surgery is considered for patients with patellofemoral dysplasia.

Introduction: Aseptic loosening is the main cause of revision in hip replacement surgery. Improved cementation techniques have reduced the rate of loosening of the femoral component, leaving the cemented acetabular cup as the major problem, with reported loosening rates as high as 25% at 12 – 15 years. The ideal method of acetabular cementation has not been fully evaluated.

Aim: To determine the ideal thickness of cement mantle to resist torsional forces.

Method: Mahogany blocks with a 54mm hemispherical hole were used to simulate an acetabular socket. Machined aluminium cups were created in 5 sizes (52mm to 44mm) to give a cement mantle that varied in size from 1mm to 5mm. Three 10mm keyholes were drilled in the blocks and appropriate-sized spacers were inserted to ensure the mantle was accurate and even. Silicone grease was used to prevent any micro-interlock between cement and wood. The cups were then cemented into the wooden blocks using vacuum-mixed Palacos R cement and left to cure in air for 7 days at 37 °C. The constructs were tested to failure using a servo-hydraulic testing machine. Each experiment was repeated six times.

Results: The stiffness of the cement mantle varied according to thickness as follows:

Discussion: A stiffer cement mantle will transfer more torque to the bone-cement interface, possibly leading to earlier loosening of the prosthesis. This biomechanical analysis suggests that surgeons should aim to achieve a mantle at least 2mm thick. There appears to be little further mechanical advantage gained if the mantle is increased in thickness beyond 4mm.

Introduction: The CPS-Plus cemented, collarless, polished stem, is a double-taper design with rectangular cross section. An additional proximal stem centraliser ensures optimal alignment of the stem and an even cement mantle and has been shown to increase cement pressurisation during insertion.

Guidelines from the National Institute of Clinical Excellence (NICE) recommend comparative clinical evaluation for prostheses without long-term follow-up data and set an initial ‘benchmark’ for performance at 3 years.

Data collection for the CPS-Plus stem is on-going as part of a multi-centre prospective clinical trial. 227 patients have been recruited to the trial and 70 of these have reached 3 years follow-up.

Method: Patients were recruited to the study by surgeons working at three centres in the UK and two in Norway. Patients were fully evaluated pre-operatively. Operative details, post-operative course and follow-up visits at 3, 6, 12, 24, and 36 months were recorded. Postoperative clinical progress was monitored using recognised scoring systems and radiographic assessment.

Results: The mean Harris hip score (0 – 100) improved from 42.7 pre-op to 91.6 at 6 months and 95.8 at 3 years. The mean Merle d’Aubigne and Postel score (0 – 18) improved from 8.55 pre-op to 16.09 at 6 months and 17.08 at 3 years. The mean Oxford hip score (60 – 12) improved from 41.6 pre-op to 14.1 at 3 years. Radiological subsidence at 3 years is less that 1.5mm in 97% of patients and less than 3mm in the remainder. From all 227 implants, there has been one revision for deep infection. There have been no cases of aseptic loosening. Other significant complications include one peri-prosthetic fracture and 4 dislocations, but these were not thought to be related to the design of the implant.

Discussion: The early results of the CPS-Plus femoral stem are encouraging and the prosthesis achieves the 3-year benchmark set out in the NICE guidelines, with a zero revision rate in the first 70 patients recruited to the trial. The prosthesis shares many design features with other well-established collarless, polished, tapered stems. The ease of accurate insertion and improved cement pressurisation resulting from its unique design features should ensure excellent medium to long-term outcome. The multi-centre clinical trial will continue to monitor progress.

The rate of deep infection following primary joint replacement has reduced to below 1%, but the cost remains high. The surgical team is the most important source of bacteria causing infection. All surgical gowns are susceptible to penetration by these organisms, which may then spread to the wound via the surgeon’s hands or contact with wet drapes without ever being airborne.

There is insufficient clinical data on the penetration of bacteria through surgical gowns, in part due to the difficulty of in vivo measurement. A simple new method was developed, using petri dishes filled with horse blood agar that were attached to the outside of the gown material. This was used to assess bacterial penetration through disposable spun-bonded polyester gowns and re-usable woven polyester gowns during normal use.

There was a significant difference between the two gown types when tested in the axilla (p < 0. 05), the groin (p < 0. 05) and the peri-anal region (p < 0. 01), with the disposable gowns performing to a higher standard.

Re-usable gowns demonstrated significant variation in penetrability. This is most likely to be due to the number of laundering and sterilisation cycles that they had undergone. Unless the continued satisfactory performance of multiple-use gowns can be guaranteed, they may be unsuitable for use in orthopaedic implant surgery.

Twelve patients undergoing total hip replacements were given 600mg linezolid as a 20min intravenous infusion along with conventional prophylaxis of 1gm cefamandole immediately before surgery. Routine total hip arthroplasty was performed and at timed intervals during surgery, samples of bone, fat, muscle and blood were collected for assay by HPLC analysis. Samples of haematoma fluid that formed around the operation site and further blood samples were also collected at timed intervals following the operation for assay. The penetration of linezolid into bone was rapid with mean levels of 9.1mg/L (95% CI: 7.7–10.6mg/L) achieved at 10min after the infusion, decreasing to 6.3mg/L (95% CI: 3.9–8.6mg/L) at 30min. Correcting for the simultaneous blood concentrations gave values for bone penetration of 51% at 10min, 60% at 20min and 47% at 30min. although the penetration of linezolid into fat was also rapid, mean levels and degree of penetration were approximately 60% of those seen in bone at 10min: 4.5mg/L (95%CI:3–6.1mg/L; penetration 27%) 20min: 5.2mg/L (95% CI:4–6.4mg/L; penetration 37%) and 30min:4.1mg/L (95% CI:3.3–4.8mg/L; penetration 31%). For muscle, the corresponding values were 10min: 10.4mg/L (95%CI:8.1–12.7mg/L; penetration 58%), 20min 13.4mg/L (95%:10.2–16.5mg/L; penetration 94%) and 30min 12mg/L (95% CI:9.2–14.8mg/L; penetration 93%). Mean concentration of linezolid in the haematoma around the operation site were 8.2mg/L at 6–8h and 5.6mg/L at 8–10h after the infusion and 7mg/L at 2–4h following a second 600mg infusion given 12h postoperatively.

We conclude that linezolid exhibits rapid penetration in bone, fat and muscle of patients undergoing hip arthroplasty to achieve levels in excess of the MIC for sensitive organisms (MIC of < _ 4mg/L); with therapeutic levels maintained in the drainage which surrounds the operation site for more than 16h. This pharmaco-kinetic profile is similar to those of agents currently used for the treatment of bone and associated soft tissue infections and suggests a role for linezolid in the management of such patients