Roentgen stereophotogrammetric analysis (RSA) is the most accurate radiographic technique for the assessment of three-dimensional micromotion in joints. RSA has been used previously to study the kinematics of the anterior cruciate ligament (ACL)-deficient knee and to measure knee laxity after bone-tendon-bone (BTB) reconstructions. There is no published evidence on its use in assessing hamstring grafts in vivo, in comparing hamstring versus BTB reconstruction, or in-depth analyses of graft performance.

The aim of this project was to use RSA to measure laxity in both BTB and hamstring reconstructions, and to attempt a detailed analysis of graft behaviour in both reconstructions, with particular attention to graft stretching and slippage of the bony attachments.

A prospective study was undertaken on 14 patients who underwent ACL reconstruction. Seven had BTB reconstruction, and seven had four-stranded semitendinosus/gracilis (STG). Tantalum markers were inserted at the time of surgery, into distal femur and proximal tibia, and also directly into the graft itself. Stress radiographs (90N anterior and 90N posterior force) were taken early post-operatively, and then at 6 weeks, and 3, 6 and 12 months.

In addition to measuring total anteroposterior knee laxity, a detailed analysis of the graft itself was possible. The BTB grafts had stretched by an average of 1.54%, and the bone plugs had migrated by 0.50 mm at the femoral end and by 0.61mm at the tibial end. The hamstring grafts had stretched on average 3.94%, and the intraosseous ends had migrated by 3.96mm at the femoral end and by 7.10mm at the tibial end. This is believed to be the most detailed application of RSA in analysing the performance of the two commonly used grafts in ACL reconstruction. Details such as graft stretching and fixation slippage have not been available previously; the data obtained in this study may have implications for clinical practice.

Infection remains a significant and common complication after joint replacement and there is debate about which contributing factors are important. Few studies have investigated the effect of the operating time on infection.

We collected data prospectively from 5277 hip and knee replacements which included the type of procedure, the operating time, the use of drains, the operating theatre, surgeon, age and gender. In a subgroup of 3449 knee replacements further analysis was carried out using the tourniquet time in place of the operating time. These variables were assessed by the use of generalised linear modelling against superficial, deep or joint-space post-operative infection as defined by the Australian Surgical-Site Infection criteria.

The overall infection rate was 0.98%. In the replacement data set both male gender (z = 3.097, p = 0.00195) and prolonged operating time (z = 4.325, p < 0.001) were predictive of infection. In the knee subgroup male gender (z = 2.250, p = 0.02447), a longer tourniquet time (z = 2.867, p = 0.00414) and total knee replacement (versus unicompartmental knee replacement) (z = −2.052, p = 0.0420) were predictive of infection.

These findings support the view that a prolonged operating time and male gender are associated with an increased incidence of infection. Steps to minimise intra-operative delay should be instigated, and care should be exercised when introducing measures which prolong the duration of joint replacement.

Purpose of study: There is a controversy in the surgical treatment of unstable thoracolumbar burst fractures scoring high on the Load Sharing Classification (LSC). We have been treating unstable thoracolumbar fractures with postero-lateral fusion using short segment instrumentation and in this study we investigated our complication rate.

Methods and results: We retrospectively reviewed notes and radiographs of patients presenting with thoracolumbar burst fractures and stabilised with a short-segment instrumented postero-lateral fusion between 1998 and 2007. We identified 31 patients who had adequate documentation and radiographs. Twenty patients had a high (> =7) LSC score and none of these fixations failed. Overall early and late complication rate was low (one wound infection, one dehiscence and four unrelated infections), the one metalwork failure related to infection. Fifty-five percent of patients returned to full-time work. Approximately 50% of correction of kyphosis was lost but the average kyphosis at final follow-up was 11 degrees that we thought was acceptable.

Conclusion: We concluded that treating unstable burst fractures with posterior instrumented fusion alone using a pedicle screw construct does not result in late instrumentation failure, high complication rate or unacceptable final deformity.

Ethics approval: None

Interest Statement: None

A recurrence of objectively measured knee laxity after anterior cruciate ligament (ACL) reconstruction has previously been reported in various papers; the purpose of this study was to accurately measure in vivo knee laxity after both bone-tendon-bone (BTB) and hamstring reconstruction using radiostereometric analysis (RSA), and to differentiate between graft fixation slippage and graft stretching and their relative contributions to any increase in laxity.

Twenty patients were studied prospectively after ACL reconstruction. Ten had been operated on using BTB grafts, and ten using hamstring (four-stranded semitendinosus/gracilis) grafts. Tantalum markers were inserted in the distal femur, proximal tibia and into the graft itself. (RSA) was used to measure sagittal laxity, graft stretching and fixation slippage early post-operatively, and then at intervals up to 1 year.

A steady increase in total anteroposterior laxity was found in both groups over the year. For the BTB group, total mean slippage of the bone plugs increased to 1.28 mm at 1 year. For the hamstring group, the tunnel attachments had slipped by a total of 6.82 mm. More stretching was found for the hamstrings grafts than for the BTB grafts and the amount of stretching increased significantly with time post-surgery. The hamstring grafts stretched by a mean of 4.18%, the BTB grafts by 1.18%.

This is believed to be the most detailed application of RSA in analysing the performance of the two commonly used grafts in ACL reconstruction. Details such as graft stretching and fixation slippage have not been available previously; the data obtained in this study may have implications for clinical practice.

In 90 patients undergoing primary THA, leg length discrepancy (LLD) and hip function were assessed pre-operatively and 3 and 12 months postoperatively. Hip function was measured by the Oxford hip score (OHS).

Postoperatively the mean OHS improved by 26 points out of a possible 48 at 3 months and by 30 points at 12 months. Postoperatively 62% of patients’ limbs were lengthened by a mean of 9 mm. The LLD was perceived by 43% of the affected patients at 3 months and by 33% at 12 months. The OHS in patients who perceived true lengthening was 27% worse than in the other patients at 3 months and 18% worse at 12 months. In 98%, lengthening occurred in the femoral component.

The problem of LLD after THA is lengthening. Appropriate placement of the femoral component could reduce patients’ perception of this.

Introduction Roentgen stereophotogrammetric analysis (RSA) is the most accurate radiographic technique for measuring three-dimensional micromotion in joints, and is now being developed for the study of anterior cruciate ligament (ACL) injury and outcome after surgical reconstruction. Using RSA a prospective study of ACL reconstruction is being undertaken. The aim is to obtain accurate information on the performance of both bone-patellar tendon-bone (BPTB) and hamstring grafts post-operatively.

Materials and methods 14 patients with a unilateral ACL tear who underwent ACL reconstruction have been studied prospectively. Seven had BPTB grafts, and seven had four-stranded semitendinosus/gracilis. Tantalum markers were inserted at the time of surgery, 4 each into the femur and tibia, and 8 into the graft, at regular intervals along the length. Stress stereo radiographs (90N anterior and posterior draw forces) were taken at 1, 6, 12 and 24 weeks post-operatively. They were analysed using Medis RSA software.

Results Initial results suggest that in addition to measuring total anteroposterior knee laxity, detailed analysis of the graft itself is possible. Beads placed in the bone blocks of the BPTB grafts, and in the intraosseous ends of the hamstrings, enable calculation of slippage of the fixation. The BPTB bone plugs moved 0.6 to 1.2mm by 12 weeks, the Hamstrings fixation was more variable. Beads placed in the intraarticular graft may enable measurement of any post-operative stretching, but are also somewhat erratic. Identification of the site of stretching – around the tunnel entrances, or intraarticularly, should be possible.

Conclusions We believe that this detailed application of RSA in analysing the performance of the two commonly used grafts in ACL reconstruction has not been previously described. We hope to gain valuable insight into the behaviour of both graft types and reasons for graft failure. This presentation will demonstrate the methods developed and include the technical difficulties encountered in this on-going study.

Introduction and aims: Leg length discrepancy (LLD) after total hip arthroplasty (THA) has been associated with a number of complications. The aim of this study was to assess the influence of LLD on the outcome of THA by comparing patients’ perception and their Oxford Hip Score with their anatomical leg length. A secondary aim was to identify the site at which LLD was created intraoperatively.

Methods: LLD and hip function were assessed in 90 patients undergoing primary total hip arthroplasty before and 3 months after surgery. Hip function was measured by the Oxford Hip Score (OHS). We measured leg length on pre- and postoperative radiographs and the position of the centre of rotation and the stem length on the postoperative radiographs.

Results: Post operatively 62% of patients’ limbs were lengthened by a mean of 9 mm. This was perceived by 43% of the lengthened patients. The OHS in patients who perceived true lengthening was 27% worse than the rest of the population. In 98%, lengthening occurred in the femoral component. 20% perceived true shortening and their OHS was not affected.

Conclusion: The problem of LLD after THA is lengthening. Accurate placement of the femoral component and especially avoiding overlengthening could significantly reduce patients’ perception of this.

We assessed leg length discrepancy and hip function in 90 patients undergoing primary total hip arthroplasty before surgery and at three and 12 months after. Function was measured using the Oxford hip score (OHS). After surgery the mean OHS improved by 26 points after three months and by 30 points after 12.

After operation 56 (62%) limbs were long by a mean of 9 mm and this was perceived by 24 (43%) patients after three months and by 18 (33%) after 12. The mean OHS in patients who perceived true lengthening was 27% worse than the rest of the population after three months and 18% worse after 12. In 55 (98%) patients, lengthening occurred in the femoral component. Appropriate placement of the femoral component could significantly reduce a patient’s perception of discrepancy of length.