The Ketogenic Diet and Its Effect on Bone Mineral Density: A Retrospective Observational Cohort Study.

BACKGROUND: During long-term follow-up of children treated with the ketogenic diet therapy (KDT) have an increased incidence of bone fractures. However, the exact contribution of KDT to a decreased bone mineral density (BMD) remains unclear. OBJECTIVE: This study aimed to evaluate (changes in) BMD in children treated with KDT and to evaluate whether intravenous bisphosphonate therapy may be effective. DESIGN: In this retrospective, observational cohort study, all children treated with KDT from 2010 until 2018 at the Radboudumc Amalia Children's hospital were included. Patients who were on KDT for more than 6 months and who had at least two dual-energy X-ray (DXA)-scans were eligible for inclusion for longitudinal analysis. Z-scores of DXA-scans were compared over the course of time. RESULTS: In 34 out of 68 patients, one or more lumbar DXA-scans were performed, with a mean lumbar Z-score of -1.32 ± 1.74. Of these 68 patients, 8.8% got a fracture during KDT, and also 8.8% got kidney stones. In 20 patients, more than one DXA-scan was performed. A statistically not significant decrease in BMD (0.22 Z-score/year) was found. However, there was an increase in BMD in the five patients treated with intravenous bisphosphonate therapy. This was statistically significant in comparison to the nonbisphosphonate treated group (p = 0.034). CONCLUSION: Children on KDT have low normal BMD which may decrease further during KDT. For this reason monitoring of BMD is crucial, as is monitoring of kidney stones and hypercalciuria. Intravenous bisphosphonate therapy may have a positive effect, when other therapies have failed.

Can digital X-ray radiogrammetry be an alternative for dual-energy X-ray absorptiometry in the diagnosis of secondary low bone quality in children?

Bone quality in children is generally measured with dual-energy X-ray absorptiometry (DXA). Digital X-ray radiogrammetry (DXR) uses BoneXpert to measure cortical bone quality on hand radiographs. This prospective study compared DXR and DXA results in children with high probability of secondary low bone quality, defined as DXA of the lumbar spine (DXALS) Z-score ≤ - 2.0. One hundred one children underwent both DXA and DXR assessment. DXALSZ-scores were also adjusted for bone age. DXR Z-scores were compared with both DXALSZ-scores, using Pearson correlations, Bland-Altman analysis, and sensitivity-specificity analysis. Mean bone age, DXR, and both DXA Z-scores were significantly impaired. Pearson correlation coefficients were significant between DXR Z-scores and both DXALSZ-scores 0.507-0.564 (p < 0.001). Bland-Altman analysis showed a mean difference of 0.05-0.48 between DXR and both DXA Z-scores and showed more than 90% similarity for both DXALSZ-scores ≤ - 2.0. DXR had a sensitivity of 67-71% and specificity of 77-83% compared to both DXALSZ-scores.Conclusion: DXR correlates well with as well DXALS as bone age-adjusted DXALSZ-scores and shows good agreement with as well DXALS as bone age-adjusted DXALSZ-scores ≤ - 2.0. DXR shows best results when compared with DXALSZ-scores. What is Known: • Digital X-ray radiogrammetry (DXR) may correlate well with dual-energy X-ray absorptiometry (DXA) in pediatric, adolescent, and adult patients. • DXR is a feasible method for assessment of bone quality in children. What is New: • This is the first prospective study in children with suspected secondary low bone quality that illustrates correlation between DXR and bone age-adjusted DXA Z-scores and that shows good agreement between DXR and DXA as bone age-adjusted DXA Z-scores ≤ -2.0. • Our results suggest DXR to be a good alternative for DXA for determining low bone quality.

Valgus bracing in patients with medial compartment osteoarthritis of the knee. A gait analysis study of a new brace.

A new valgus brace was evaluated in 15 patients with medial osteoarthritis of the knee and a varus leg axis. Significant improvement of pain and function were found after 6 weeks of brace treatment. Gait analysis showed that the brace had a tendency of lowering the peak varus moment about the knee. This effect was more profound in the presence of higher initial varus deformity angle of the knee. Furthermore, bracing led to a small decrease of knee extension at the end of the swing phase and an increase of walking velocity. The mechanisms identified by gait analysis in this study may be of clinical importance for future developments in brace treatment.