Forces During Limb Lengthening with Different Distraction Rhythms

1
Forces During Limb Lengthening with Different
Distraction Rhythms

• Horn J., Aarnes G.T., Steen H., Ludvigsen P.,
• Kristiansen L.P.

2
Background Facts
Introduction Materials Methods
Results Discussion
Conclusion

• Optimal daily distraction rate in callotasis
  lengthening 0.75 1.0 mm
• Tensile forces across the callotasis zone depend
  on
• distraction frequency
• time interval between each distraction increment

Hypothesis

• Too high tensile forces must be unfavourable
• Tissue damage may contribute to
• Increased pain
• Slow bone healing
• Distraction rhythms with longer intervals without
  distraction may be advantageous by generating
  overall lower tensile forces

3
Present study
Introduction Materials Methods
Results Discussion Conclusion

• 17 year old female
• Constitutional shortness
• Standing height 139 cm
• Simultaneous bilateral bifocal lengthening
• Different distraction rhythms at prox. callotasis
  zones
• Continuous force measurements
• Unique model to test our hypothesis

4
Introduction Materials Methods
Results Discussion Conclusion
Left Leg Standard regime
Right Leg 4th-day-off regime
Prox. 0.25 mm x 4/d
Prox. 0.25 mm x 3/d
Dist. 0.25 mm x 3/d
Dist.0.25 mm x 3/d
5
Forces
Introduction Materials Methods
Results Discussion
Conclusion
Kleinbaums test of slope and force difference
p lt 0.001
6
70 mm lengthening - Consolidation
Introduction Materials Methods
Results Discussion
Conclusion
4th-day-off-regime
Standard regime
Lengthening Index 4th Day Off
Regime Leg 1.6 months/cm Standard Regime Leg
1.1 months/cm
7
Axial stiffness measurements of regenerate
(Load-share tests) Aarnes GT et al., J Orth
Research 2005
Introduction Materials Methods
Results Discussion
Conclusion

• Confirmed x-ray findings with lower stiffness
  values
• across the callotasis zone in 4th-day-off regime

8
Pain registration (VAS)
Introduction Materials Methods
Results Discussion
Conclusion
Standard regime
4th-day-off-regime
Pain Area 1616
Pain Area 2284
Paired t-test p lt 0.001
9
Introduction Materials Methods
Results Discussion
Conclusions

• Healing was faster in the leg with highest force
  values
• Tensile forces may be important contributor to
  stiffness, stability and stimulation of
  osteogenesis
• Upper and lower limits of tensile forces may
  exist for optimal bone healing
• Pain may be dominated by local conditions related
  more to pin placement etc. than to moderate
  tensile forces ( max. 250-300 N)

10
Introduction Materials Methods
Results Discussion
Conclusions

• Pre-planned regular rest periods in distraction
  resulted in
• reduced tensile forces across the callotasis zone
• increased lengthening index
• increased pain
• Tensile forces of 300 N (vs 250 N) may be
  closer to the optimal value for stimulation of
  osteogenesis