Biomedical subjects

David Ip

Publications and source records attributed to David Ip.

3 recordsLinked to original sources

PubMed2005

The role of intraoperative frozen section in decision making in revision hip and knee arthroplasties in a local community hospital.

There is little information in the literature regarding the reliability of intraoperative frozen section to predict infection in revision arthroplasties performed in community hospitals as most reports are from specialized centers or academic institutes. Between November 1997 and May 2001, we performed intraoperative frozen sections in 40 revision hip and knee arthroplasties. We used Mirra's criteria of more than 5 polymorphs per high power field to constitute a positive result. We found a sensitivity of 67% and a specificity of 97%. The positive and negative predictive values were 86% and 91%, respectively, with an accuracy of 90%. We conclude that intraoperative frozen section is a reasonably sensitive and specific adjunct investigation in the differentiation between septic and aseptic loosening.

Aged↗

PubMed2003

REML and ML estimation for clustered grouped survival data.

Clustered grouped survival data arise naturally in clinical medicine and biological research. For example, in a randomized clinical trial, the variable of interest is the time to occurrence of a certain event with or without a new treatment and the data are collected from possibly correlated subjects from independent clusters. However it is sometimes impossible or too expensive to monitor the experimental subjects continuously. The subjects are examined regularly and the continuous survival data are thus grouped into a discrete time scale. With such a design, researchers are mainly interested in the effectiveness of the new treatment as well as the correlation among subjects from the same cluster, namely the intracluster correlation. This paper suggests a random effects approach to the estimation of the regression parameter with various choices of regression model and also the dependence parameter which characterizes the intracluster correlation. Time dependent covariates can be accommodated in the proposed model, and the estimation procedure will not be further complicated with large cluster sizes. The proposed method is applied to the data from the Diabetic Retinopathy Study, the objective of which is to evaluate the effectiveness of laser photocoagulation in delaying or preventing the onset of blindness in the left and right eyes of individuals with diabetes-associated retinopathy. The intracluster correlation using a grouped proportional hazards regression model can be estimated and the relationship between the regression parameter estimates based on the random effects approach and the marginal approach using a dynamic logistic regression model are discussed. Results from a simulation study of the proposed method are also presented.

Cluster Analysis↗

PubMed2003

Reconstruction of forearm deformities in multiple cartilaginous exostoses.

The management of complex forearm deformities in patients with multiple cartilaginous exostoses is controversial. The objective of this study is to look into the outcome of treatment with the combined use of ulna lengthening, radial osteotomy, and excision of exostosis in our six patients, who all had Masada type 1 deformity of the forearm. Clinical assessment was performed using the pre- and postoperative range of motion of the wrist, forearm and elbow. The chief symptom each patient had was noted as well as the demographic data of all patients. Radiological assessment was performed by checking the degree of negative ulna variance, the radial articular angle, and the degree of carpal slip. The degree of satisfaction of the patients and their parents were noted. Good clinical and radiological results were obtained at a mean follow-up of 2.5 years. All patients and parents were satisfied and there was no recurrence of deformity in the latest follow-up. The authors believe in early and aggressive treatment of Masada type 1 deformity of the wrist and forearm for multiple cartilaginous exostoses with a combination of excision of exostosis, ulna lengthening and radial osteotomy.

Bone Lengthening↗