Spinal Biomechanics Lab, Baylor College of Medicine, Houston, Texas, USA

Documenting the patterns and frequency of collapse in non-operatively managed spine fractures, using a motion analysis software.

Retrospective analysis of prospective case series

105 patients with thoracic or lumbar fractures, were neurologically intact, and treated non-operatively for the ‘stable’ injury at our unit between June 2003 and May 2006. The mean age of the cohort was 46.9 yrs

Serial radiographs (mean 4 radiographs/patient; range 2 – 9) were analysed using motion analysis software for collapse at the fracture site. We defined collapse as a reduction of anterior or posterior vertebral body height greater than 15% of the endplate AP width, or a change in the angle between the inferior and superior endplates > 5°.

The changes were assessed on serial radiographs performed at a mean of 5.6 mo (95% CI 4.1 – 7.1 mo) after the initial injury. 11% showed anterior collapse, 7.6% had posterior collapse, 14% had collapse apparent as vertebral body wedging, and 17% had any form of collapse. ODI scores were obtained in 35 patients at the time of the last available radiograph. There were no significant differences in ODI scores that could be associated with the presence of any form of collapse (p > 0.8 for anterior collapse; and p = 0.18 for posterior collapse).

This pilot study with the motion analysis software demonstrates that some fractures are more likely to collapse with time. We hope to carry this work forward by way of a prospective study with a control on other variables that are likely to affect the pattern and probability of post-fracture collapse, including age, bone density, vertebral level, activity level, fracture type.

Background: Thoraco-lumbar fractures without a neurological deficit are usually suitable for non-operative treatment. The main area of clinical interest is the deformity at the injured levels. The deformity may be evident at the time of presentation, though could be expected to progress in time.

Objective: Accurate assessment of the temporal behaviour in the geometry of the injured segments in non-operatively treated thoracolumbar fractures with normal neurology.

Materials: 102 patients with thoracolumbar fractures without a neurological deficit were treated non-operatively at our unit between June 2003 and May 2006. The mean age of our patient cohort was 46.9 yrs (16–90 yrs). Strict criteria were followed to determine suitability for non-operative treatment. Supine radiographs were performed at the initial assessment. Erect radiographs were performed when trunk control was achieved and at follow-up assessments thereafter.

Methods: Quality Motion Analysis (QMA) software (Medical Metrics Inc, Houston, Tx) was used to measure rotational and translation changes between the end plates using a validated protocol. The radiographs were standardised for magnification and superimposed from different time points. Transformation matrices were used to track the changes. The AO classification was used to classify the fractures by 2 independent observers.

Results: A median of 4 radiographs were analysed for each patient (range 2–9), at a mean follow-up of 5.6 mo (95% CI 4.1–7.1 mo). 92% of the cohort had sustained a 1 level injury. 76% of the injuries were between T12 and L2; 19% were in the thoracic spine. An inter-observer rating of 0.58 was obtained for the classification of the primary fracture type. The mean rotational change was −1.4855° ± 0.248° (95% CI: −0.994° to–1.976°). The mean anterior vertebral body height collapse was −4.3444° ± 0.6938 (95% CI: −2.695 to −5.724). The mean posterior vertebral height collapse was −0.7987 ± 0.259 (95% CI: −0.284 to −1.313).

Conclusions: We report the use of QMA software to track changes in the vertebral body geometry accurately. This has implications on the clinical aspects of management of thoracolumbar fractures based to progression of deformity that could be explored in future studies.

Aim: To investigate the outcome following revision total hip arthroplasty (THA) using 36 mm and 40 mm modular femoral heads.

Methods: Details were retrieved from our arthroplasty database regarding all revision THAs done in our unit using 36 mm and 40 mm femoral heads. Follow-up information was obtained from patient records and telephone conversation.

Results: The cohort considered totalled 107 revision THAs, 93 using a 36 mm head and 14 using a 40 mm head. All received either highly cross-linked UHMWPE liners or metal on metal liners. The indications for revisions were recurrent instability in eight, periprosthetic fracture in 11, second stage revision in 24, fracture of the femoral stem in one and aseptic loosening in the remaining 63. At a minimum follow up of one year, information was not available for five but they did not have any record of dislocation. Out of the remaining 102 patients, dislocation occurred in 4 hips (3.9%). None of the revisions done with 40 mm head dislocated. In two of the dislocations, the initial indication for revision THA was recurrent instability and if they are excluded, the dislocation rate was 1.96%.

Discussion: Dislocation and the sequalae of recurrent instability remains a significant problem following revision THA and the existing literature varies greatly in the quoted dislocation rates. We believe that the use of 36 mm and 40 mm femoral heads in our unit has been a major factor in low (3.6%) dislocation rate following revision THA. To date there have been no problems encountered resulting from the use of highly cross-linked UHMWPE.