The Application Value Of X-ray And Color Doppler Ultrasound~1 During Limb Lengthening

Objective To establish rabbit models of tibia diaphyseal lengthening.To observe and analysis the blood circulation and the new callus at the osteotomy site with X-ray and color doppler ultrasound.To investigate the changed information of the new callus at the lengthening area in the early stage.To compare the advantage and disadvantage between the two methods during limb lengthening.To discuss the Monitoring value of the two evaluated methods.Methods The average age of the fifteen healthy rabbits was 5.0±0.5 months and their mean weight was 2.5-2.8 Kg.The rabbit models were established under general anaesthesia by means of the upper third of tibia osteotomy and slow traction for lengthening.Lengthening was commenced traction seven days after surgery at a rate of 1mm twice a day.Lengthening was continued to increase 30%over initial bone length and stopped to be mineralized for 5 weeks.With the color doppler ultrasound to observe and analyse the blood circulation and the new callus at the osteotomy site at different stages during limb lengthening,we compare the the outcome between ultrasound and X-ray.In addition,we need to examine the active range of the knee and ankle joint before and after surgery.With the X-ray to measure the length and diameter of the tibia before surgery,we make sure the length needed to lengthen and the diameter of the half pins.Also,we could observe the length and the new callus at the lengthening area and the limb alignment with the X-ray after surgery.Results 1 Common observation:All animals passed the operative period,no one was infected,even osteomylitis during limb lengthening.When the limb was lengthened to a increase of 10%over initial bone length,the active range of the knee and ankle joint was not obviously different(p＞0.05).When the limb was increased 20%and 30%over initial bone length,the dorsal flexion range of ankle joint was serious limited(P＜0.01),the outcome was significant.After 5 weeks mineralized,the function of the joints was improved,but was not recovered to be normal(P＜0.05). 2 X-ray:When the limb is lengthened to 10%increased,there was no clear evidence of new bone formation within the traction sites.When the limb is lengthened to 20%, we can see small amount callus at the osteotomy site.When lengthened to 30%,there is much more callus at the lengthening area,and the cortical bone appeared at both ends.Three weeks mineralized later,the cortical bone of the both ends get in touch with each other and the medullary cavity has appeared.After 5 weeks mineralized, the amount of callus at the traction site is larger than before,and cortical bone and medullary cavity are classified,but the mid-part is thin.After 7 weeks mineralized, the callus is union.We remove the external frame with no deformity and good alignment of the limb.3 Ultrasound:In the early stage(3-5 days after surgery),the amount of the micrangium and the rate of blood flow increased and then decreased gradually.After 1 week,we can see some speckled echogenic at the traction site that means new bone has formed.When the limb is lengthened to 30%,the ultrasound islands coalesce and the accuracy of gap measurement is reduced.Serial longitudinal ultrasound scans showed the traction gap as an echolucent window.New bone appeared as echogenic islands which became aligned longitudinally and progressively increased to fill the window.From the transverse ultrasound images,the proximal and distal segments of bone were seen as hyper-reflecting lines.At the site of the traction gap,these lines broke up into speckled echogenic areas corresponding to the presence of immature new bone.Conclusions Limb lengthening usually results in the function of the joint limited, especially dorsal flexion range of ankle joint.With X-ray,we can measure the length and diameter of the tibia before surgery,and then make sure the length needed to lengthen and the diameter of the half pins.After operation,we can observe the limb alignment.During limb lengthening,we can make sure the length of the traction site and the amount of the new callus.In addition,we can see whether the external frame is loosed and the limb is infected or not.Ultrasound can discover the new callus at early stage.The time is earlier than X-ray.We can forecast the outcome and change the rate of lengthening through the ultrasound image.It can discover the cyst.More important,it is a way without any invasion.In brief,the two ways have their advantage and disadvantage.If we combine them,they will give us much more accurate information during limb lengthening.