Background: The measurement facility on PACS is used to aid decision making. This facility is inaccurate and does not reflect clinical parameters, rendering its use ineffectual. Previous works utilised only a single prostheses type, were under-powered and not statistically robust.

Aim: To establish and statistically analyse the reliability of PACS software for the measurement of orthopaedic parameters at a university teaching hospital.

Methods: Retrospective analysis of radiographs of 100 patients (50 hip hemi-arthroplasty, 50 intra-medullary nailing) was performed to provide a wide base and allow a comparison of the spherical implant and a nail.

Implant sizing from theatre records was compared with the post-operative films. The size of the implant on radiograph, the magnification of the exposure and the effect of further magnification was noted. Analysis of the results was by paired student’s t testing incorporating inter-observer error into the test statistic.

Results: The hip prostheses were found to be oversized (range: 7–16mm; mean: 10.9mm). This is highly significant (p=< 0.01). The nails were similarly oversized (range: 0–6mm; mean: 1.87mm). This result was significant (p=< 0.05) although the error was less than for the spherical prosthesis. This is presumed due to the nature of the implant size and the distance of the implant from the cassette during exposure.

Discussion: This study demonstrates with statistical significance the unreliability of PACS measurement software. The manufacturer was contacted and has confirmed that accurate imaging can only be obtained on a named case, calibrated image. This has implications for all orthopaedic surgeons.

Introduction: Electrolyte imbalance in the elderly is a clinical problem faced by both elderly care physicians and orthopaedic surgeons alike. The abnormalities in homeostatic mechanisms that manifest with age can have dramatic consequences for the unwary clinician. This study aims to establish the incidence of hyponatraemia within an orthopaedic population and to determine whether this is different to a control group of elderly care patients.

Methods: Retrospective, consecutive analysis of serum sodium levels of 200 patients (100 hip fracture patients and a control group of 100 elderly care patients). Serum sodium levels on admission and during the inpatient stay were recorded and analysed using student’s t-tests to establish the incidence of hyponatraemia, changes in serum sodium level during admission and differences between the two groups.

Results: Hyponatraemia was evident in a third of all admissions (Orthopaedic: 29%; Elderly Care: 33%). The admission sodium level for both groups was not statistically different (t (198) =0.70, p=0.49). There was no significant difference in the observed hyponatraemia between the two populations throughout their care in hospital (t (198) =0.64, p=0.52).

Discussion: While there is a high incidence of hyponatraemia within the elderly population, there is no difference in its incidence between the aged orthopaedic population and the general elderly population. This is seen on admission and is also shown to be independent of operative procedures and fluid management as in-patients. Clinicians must be aware of the innocuous symptoms that may herald the catastrophic and avoidable consequences of this condition.