Biomedical subjects

P B M Thomas

Publications and source records attributed to P B M Thomas.

4 recordsLinked to original sources

PubMed2007

Fracture healing assessment comparing stiffness measurements using radiographs.

Based on published reports, we presumed radiographs would be unreliable as a sole measure of fracture healing. To confirm this presumption we correlated radiographic fracture healing assessments with fracture stiffness measurements. We showed 100 plain radiographs of fractures with corresponding fracture stiffness measurements to 92 observers. The radiographs were shown twice to assess intraobserver variation. Observers were divided into three groups and asked to determine whether each fracture had healed (union corresponded to a fracture stiffness greater than 15 nm/degrees). Group 1 based fracture healing on the general appearance of healing. Groups 2 and 3 assessed fracture healing based on the number of cortices bridged by callus. In Group 2, the fracture was considered healed if two or more cortices were bridged on both radiographic views and in Group 3 if three or more cortices were bridged by callus. All groups performed poorly. There was no difference in terms of correct prediction of healing between methods, although there was a trend toward more reliability with cortical callus bridging assessment. We found substantial intraobserver variability, which improved using cortical bridging methods. Observers were less reliable at predicting healing when there was a metaphyseal extension to a diaphyseal fracture.

Bony Callus↗

PubMed2004

Reliability of radiographs in defining union of internally fixed fractures.

We assessed whether radiographs can predict union of internally fixed fractures, and therefore be used as end-points in studies of fracture healing. Forty-seven radiographic series of forearm, femoral and tibial fractures treated by internal fixation over a 3-year period were reviewed. All forearm fractures were treated with dynamic compression plates (DCP), and all tibial and femoral fractures with intra-medullary nails. Callus formation and fracture line filling with time were measured on each radiograph. The ability of five orthopaedic surgeons to chronologically rank the blinded radiographs and to agree on the point of union was assessed. Correlation between callus formation, fracture line filling and union was noted. The ability of surgeons to correctly rank the radiographs and to agree on the point of union was in the order of 70%. Callus formation and union progression was significant in femoral fractures (P<0.05). Fracture line filling and union progression showed significance in the forearm (P<0.01) and femoral groups (P<0.05). Taking serial radiographs to assess healing would have led to only one early intervention. Radiographs do not define union in internally fixed fractures with sufficient accuracy to enable their use as end-points of fracture healing. Studies quoting radiographic end-points should be interpreted with care.

Femoral Fractures↗

PubMed2003

The current management of tibial fractures: are clinical guidelines effective?

BACKGROUND: The production of clinical guidelines is increasing and will continue to do so with the introduction of clinical governance. In 1997, the British Orthopaedic Association (BOA) and the British Association of Plastic Surgeons (BAPS) published joint guidelines on the management of open tibial fractures. It is not known whether these guidelines reached their target audience, or indeed influenced clinical practice. METHODS: We determined the effectiveness of these guidelines by sending a postal questionnaire survey to 172 orthopaedic surgeons. RESULTS: Only 57% of consultants were aware of the guidelines, 70% of registrars and 25% of staff grades. Less than 29% of orthopaedic consultants would choose to consult the plastic surgical team pre-operatively in the management of an open tibial fracture and only 43% would seek plastic surgical involvement at all. The primary aim of increasing multidisciplinary communication has not been achieved. CONCLUSIONS: The awareness of, and adherence to, these guidelines is sub-optimal. This clearly has implications for both the future management of open tibial fractures and the further production of guidelines.

Compartment Syndromes↗

PubMedDate not supplied

Modelling the Rayleigh match.

We use the photopigment template of Baylor et al. (1987) to define the set of Rayleigh matches that would be satisfied by a photopigment having a given wavelength of peak sensitivity (lambda(max)) and a given optical density (OD). For an observer with two photopigments in the region of the Rayleigh primaries, the observer's unique match is defined by the intersection of the sets of matches that satisfy the individual pigments. The use of a template allows us to illustrate the general behavior of Rayleigh matches as the absorption spectra of the underlying spectra are altered. In a plot of the Y setting against the red-green ratio (R), both an increase in lambda(max) and an increase in optical density lead to an anticlockwise rotation of the locus of the matches satisfied by a given pigment. Since both these factors affect the match, it is not possible to reverse the analysis and define uniquely the photopigments corresponding to a specific Rayleigh match. However, a way to constrain the set of candidate photopigments would be to determine the trajectory of the change of match as the effective optical density is altered (by, say, bleaching or field size).

Color Perception Tests↗