Unicompartmental knee arthroplasties in Hong Kong: 15 years of experience in a teaching hospital

Metformin use and the risk of total knee replacement among diabetic patients: a propensity-score-matched retrospective cohort study

Metformin has been shown to modulate meta-inflammation, an important pathogenesis in knee osteoarthritis (OA). The study aimed to test the association between regular metformin use with total knee replacement (TKR) in patients with diabetes. This is a retrospective study with electronic records retrieved in Hong Kong public primary care. Patients with diabetes aged ≥ 45 who visited during 2007 to 2010, were followed up for a four-year period from 2011 to 2014 to determine the incidence of TKR. Propensity score matching based on age, sex, co-medications and chronic conditions was conducted to adjust for confounding. Cox regression was implemented to examine the association between metformin use and TKR. In total, 196,930 patients were eligible and 93,330 regular metformin users (defined as ≥ 4 prescriptions over the previous year) and non-users were matched. Among 46,665 regular users, 184 TKRs were conducted, 17.1% fewer than that among non-users. Cox regression showed that regular metformin users had a 19%-lower hazard of TKR [hazard ratio (HR) = 0.81, 95% confidence interval: 0.67 to 0.98, P = 0.033], with a dose–response relationship. Findings suggest a potential protective effect of metformin on knee OA progression and later TKR incidence among diabetic patients.

Plain Radiographs Can Safely Be Used to Measure and Follow Up on Tibial Component Alignment in Unicondylar Knee Replacement: A Correlation Study With CT Scans

Background and objective

Unicondylar knee replacement (UKR) is one of the most frequently performed arthroplastic operations worldwide. Migration and subsidence regarding the tibial component of UKR is a well-known phenomenon. In this study, we aimed to analyze whether plain radiographs are a reliable means to measure the true coronal and sagittal alignment of the UKR’s tibial component.

Methods

Patients undergoing a UKR procedure at our center between December 2020 and March 2011 were eligible for this study. Inclusion criteria were as follows: the presence of well-aligned standard and reproducible anteroposterior and lateral X-rays taken one week before or after a low-radiation artifact-reduced CT scan. Sixty-six knees were included in the study. Coronal and sagittal alignment of the tibial component was measured in a standard manner by two observers on both X-rays and CT scans. A correlation analysis was performed, and the margin of error was established.

Results

Intra-observer reliability was high among the two observers whether for X-ray or CT scan measurements [intraclass correlation coefficient (ICC): >0.900]. On the other hand, coronal plane measurements had lower inter-observer ICC values on both X-rays and CT scans while reliability on the sagittal plane was higher. There was a high correlation between radiographic measurements on X-rays and CT scans on both planes.

Conclusion

Even though the measurements on plain radiographs were slightly different from the ones obtained from CT scans, the correlation between them was very strong. Caution should be exercised when measuring the coronal alignment of the tibial implant on X-rays since it is more frequently affected by rotational misalignment.