Permanent growth arrest of the longer bone is an option in the treatment of minor leg-length discrepancies. The use of a tension band plating technique to produce a temporary epiphysiodesis is appealing as it avoids the need for accurate timing of the procedure in relation to remaining growth. We performed an animal study to establish if control of growth in a long bone is possible with tension band plating. Animals (pigs) were randomised to temporary epiphysiodesis on either the right or left tibia. Implants were removed after ten weeks. Both tibiae were examined using MRI at baseline, and after ten and 15 weeks. The median interphyseal distance was significantly shorter on the treated tibiae after both ten weeks (p = 0.04) and 15 weeks (p = 0.04). On T₁-weighted images the metaphyseal water content was significantly reduced after ten weeks on the treated side (p = 0.04) but returned to values comparable with the untreated side at 15 weeks (p = 0.14). Return of growth was observed in all animals after removal of implants.

Temporary epiphysiodesis can be obtained using tension band plating. The technique is not yet in common clinical practice but might avoid the need for the accurate timing of epiphysiodesis.

Cite this article: Bone Joint J 2013;95-B:855–60.

Introduction: Implantation of a THA changes the strain distribution pattern in the proximal femur, with a massive loss of stress in the proximal part of the femur and an increase in stress at the distal part of the femoral component.

Aim: The purpose of this study was to quantify the changes in BMD during long-term follow-up, i.e. five years, after insertion of the collarless, two-side conical, cemented Exeter stem.

Material & Methods: Eighteen patients (all women), aged 55 to 80 years, undergoing THA were included in the study after informed consent. BMD was measured in 7 regions of interest according to Gruen et al., using Dual Energy X-ray Absorptiometry postoperatively, after 18 and 60 months of follow-up. At the same time, the contra lateral hip and spine were scanned. Results were tested using Wilcoxon matched-pairs signed-rank test. P values below 0.05 were considered significant.

Results: During the first 18 months, a significant decrease in BMD was present in Gruen zones 2, 3, 6, and 7. No significant changes were seen in BMD of the zones 4, and 5 in the contra lateral hip, nor at the spine. In zone 1 there was a small but significant rise in BMD.

From 18 to 60 months of follow up we observed a significant rise in BMD in all Gruen zones but zone 4 and 7. Despite this the total periprostetic BMD decreased during the study periode. There was no significant decrease in BMD in the contra lateral hip. In the spine, we observed a significant rise in BMD.

Conclusion: During short-term follow-up (i.e. 18 months) after THA, BMD decreased in Gruen zones 2, 3, 6 and 7. The bone loss is similar to findings in other implants and seems to be related to the changes in stress pattern within the proximal femur. During long-term follow-up (i.e. 5 years) BMD increased again in these zones, however, BMD remained lower than baseline.