Aims

The aim of this study was to explore parents’ experience of their child’s recovery, and their thoughts about their decision to enrol their child in a randomized controlled trial (RCT) of surgery versus non-surgical casting for a displaced distal radius fracture.

Aims

The aim of this study was to explore clinicians’ experience of a paediatric randomized controlled trial (RCT) comparing surgical reduction with non-surgical casting for displaced distal radius fractures.

Aims

The aim of this study was to explore parents and young people’s experience of having a medial epicondyle fracture, and their thoughts about the uncertainty regarding the optimal treatment.

Introduction Transcranial motor evoked potentials are routinely used at The Children’s Hospital at Westmead to monitor the spinal cord in spinal surgery. This study is a prospective review of all spinal cord monitoring procedures from 1999 to 2004 in patients undergoing elective spinal deformity correction surgery at The Children’s Hospital at Westmead and Westmead Hospital. Spinal cord monitoring with Somatosensory Evoked Potentials (SSEP) and MEP has been widely used in combination during spinal surgery with good sensitivity and specificity. The use of CMAP as the only modality has not been widely used and its efficacy has not been fully elucidated. Using MEP and CMAP only may increase the sensitivity of spinal cord monitoring compared with combined SSEP and MEP monitoring.

Methods The intra-operative monitoring outcomes were compared with patient’s post-operative clinical outcomes. The sensitivity and specificity were calculated and determined for our monitoring protocol.

Results Transcranial MEPs were measured in 146 patients in 175 procedures. In 2 patients (2 procedures) we were unable to record any CMAPS. There were 15 intra-operative monitoring changes (8.7%). There were no new post-operative neurological deficits. Our results compare favourably to the literature with respect to the false-negative rate or new neurological events.

Discussion Using our anaesthetic protocol and spinal monitoring criteria, we were able to successfully monitor patients undergoing elective spinal deformity correction surgery for a variety of diagnoses. The monitoring criteria are sufficiently strict to achieve a sensitivity of 1.0 (95%CI = 0.66–1.00) and a specificity of 0.97 (95%CI = 0.83–0.99). Monitoring of CMAPs alone has been adequate to avoid clinical neurological deficits.

The use of roentgen stereophotogrammetric analysis (RSA) in the assessment of total hip arthroplasty is well recognised as an accurate technique in the measurement of small movements of implants. The technique requires the insertion of tantalum beads into a stable location in the bone at the time of surgery. Failure of bead insertion leads to unstable extra-osseous beads that require to be excluded from the analysis. Previous studies have reported an incidence of extra-osseous beads in the proximal femur of between 2% and 13%. In order to further improve the accuracy of the RSA technique, we have developed a test criterion for exclusion of unstable osseous beads in RSA of total joint replacements.

Using specifically developed software each bead’s movement was determined relative to the rest of the beads in the bone segment. The bead movement was determined for radiologically identified extra-osseous beads, which were assumed loose, and for the remaining intra-osseous beads which were suitable for analysis. Analyses with a condition number greater than 100 were rejected. The rate of motion was calculated from consecutive examinations. Unstable beads were identified as those having a median rate greater than a given threshold. The sensitivity and specificity for detecting extra-osseous beads was calculated for different thresholds of median bead motion.

In 149 RSA hip study patients, 43 extra-osseous beads that could be analysed were identified and a group of 36 osseous beads were selected as a control group. This resulted in an optimum threshold of 0.36mm that gave a sensitivity of 89% and a specificity of 86% for detecting unstable (extra-osseous) beads. The remaining 1428 beads, which were assumed to be osseous, were then tested with this threshold, which gave a sensitivity of 84% and a specificity of 79%.

The median extra-osseous bead rate of movement at 6, 12, 18 and 24 months were 2.24, 0.78, 1.03 and 1.31mm respectively and for osseous beads were 0.27, 0.19, 0.18 and 0.19mm. As both groups of beads appear to show a “bedding in” period, with a higher median bead movement in the first 6 months, the test was repeated with the first 6 month period excluded from the criteria. An optimal threshold of 0.37mm was found to have a sensitivity of 73% and a specificity of 87% for identifying an extra-osseous bead.

While most radiographically classified osseous beads identified as unstable may be false-positives, it is probable that some are extra-osseous but not visibly so on radiographs. The specificity of this technique is likely to be further improved with the increased precision from digital scanning techniques. Tantalum beads in general appear to be relatively unstable in the first 6 months, consistent with the expected osteo-intergration of the bead. This new criterion for bead instability allows automatic exclusion of unstable beads increasing the reliability of the RSA technique both in future studies and retrospectively to existing data.

Aims: To develop a threshold criteria for exclusion of unstable osseous beads in radiostereometric analysis (RSA) of total joint replacements. Methods: Bead movement was determined for radiologically identified extra-osseous beads which were assumed loose, and for intra-osseous beads as a stable control group. Analyses with a condition number greater than 100 were considered unreliable and rejected. The median rate of total motion over 2 years was used to identify a threshold that identifies unstable beads. Results: In 149 RSA hip study patients 44 extra-osseous beads that could be analysed were identified and 36 osseous control beads were randomly selected. The sensitivity and specificity for detecting extra-osseous beads was calculated for different thresholds of median bead motion (see ROC curve). An optimal threshold of 0.36mm was found to have a sensitivity of 89% and a specificity of 86% for identifying an extra-osseous bead.

Conclusions: Extra-osseous beads are more unstable than osseous beads and are should be removed from RSA analysis series. This new criteria allows automatic exclusion of unstable beads increasing the reliability of the RSA study.

Aims Intro: Radiostereometry (RSA) is a powerful tool for assessment of prosthesis migration in total hip replacement. Typically marker beads are inserted into the bone and into turrets inserted into the prosthesis. Where the prosthesis can not be beaded valuable information may be lost. We present two methods that determine the three-dimensional prosthesis position using geometric models. Method: The þrst method approximates the stem of the prosthesis to an axially symmetric cylinder and spherical head. The method is fast but may lead to errors due to the cylinder approximation. The second uses accurate three-dimensional surface models of each implant model. Clinical precision was determined from repeat same day RSA examinations. Results: Given as 99% precision limit rotation ranged from 0.4 degrees (sagittal) to 2.5 degrees (axial) for the cylinder method (n = 38), compared to 0.2 degrees (sagittal) to 0.6 degrees (axial) for the 3d model (n = 6). Translations were similar ranging from 0.2mm axial to 0.7mm sagittal. Conclusion: Model based RSA can give useful results where beads can not be implanted into the prosthesis. Although the primary method gives good results these are less precise than that for beaded RSA. Simulations infer a potential accuracy for the method of a few microns, however this is currently limited by the closeness of correspondence of an individual stem to its model. The method here is applicable to any implant type. Accurate 3D models are required, however for new designs these should be available.

Aims: To study prospectively the characteristic migration of four different cemented femoral stems using Radiostereometry. Methods: 96 patients undergoing cemented femoral hip replacement for osteoarthritis were randomised to receive an Exeter (Howmedica Stryker), Ultima Tapered Polished Stem [TPS], Ultima straight stem [USS] (Johnson and Johnson) or Charnley Elite (Depuy/Johnson and Johnson) stem. RSA migration measurements were performed postoperatively and at 6,12,18 and 24 months post surgery using the UMRSA system. Results: Two signiþcantly distinct patterns of distal migration in the y direction (subsidence) were seen, compatible with previous studies. Tapered stems subsided rapidly by six months, Exeter 0.85mm (±0.15) UTPS 0.85mm (±0.15), stabilising by 2 years, Exeter 1.3mm (±0.35), UTPS 1.2mm (±0.25). The USS and Elite designs showed lower migrations of 0.1mm (±0.1) and 0.15 (±0.15) mm at six and 0.25mm (±0.15) and 0.35mm (±0.15) at 24 months. For migrations and rotations in other directions, differences were seen between prostheses with the same design concept. Whilst both the UTPS and Exeter exhibited posterior migration of the head, by 24 months this was expressed as a rotation about the transverse axis for the TPS and the axial axis for the Exeter. The Elite and USS differed in rates of posterior migration and varus tilt. Conclusions: Patterns of migration for stems with the same design concept may vary due to subtle differences in prosthesis shape. These variations produce a distinct migration Ç signature È for each stem.

Aims: To study prospectively the characteristic migration of four different cemented femoral stems using Radiostereometry.

Methods: 96 patients undergoing cemented femoral hip replacement for osteoarthritis were randomised to receive an Exeter (Howmedica Stryker), Ultima Tapered Polished Stem [TPS], Ultima straight stem [USS] (Johnson and Johnson) or Charnley Elite (Depuy/Johnson and Johnson) stem. RSA migration measurements were performed at postoperatively and at 6,12,18 and 24 months post surgery using the UMRSA system enhanced with locally developed software.

Results: Two significantly distinct patterns of distal migration in the y direction (subsidence) were seen compatible with previous studies. Tapered stems subsided rapidly by six months Exeter 0.85mm (+/−0.15) UTPS 0.85mm (+/−0.15) stabilising by 2 years Exeter 1.3mm(+/−0.35), UTPS 1.2mm(+/−0.25). The USS and Elite designs showed lower migrations of 0.1mm (+/−0.1) and 0.15 (+/−0.15) mm at six and 0.25mm(+/−0.15) and 0.35mm (+/−0.15) 24 months. For migrations and rotations in other directions differences were seen between prostheses with the same design concept. Whilst both the UTPS and Exeter exhibited posterior migration of the head, by 24 months this was expressed as a rotation about the transverse axis for the TPS and the axial axis for the Exeter. The Elite and USS differed in rates of posterior migration and varus tilt.

Conclusions: Patterns of migration for stems with the same design concept may vary due to subtle differences in prosthesis shape. These variations produce a distinct migration “signature” for each stem.