objective: To observe the variations of stress magnitude in the cervical vertebra exerted by vertical traction force from various angles and different points. Methods: The cervical vertebra model was produced by using elastic material of light (polycarbonate) and silica rubber(1:1). By calculating the arithmetical progression of interference fringe. The author judged the stress magnitude in the posterior edge of the C4-7 vertebral bodies when different kinds of pulling force acted on. Result: The interference pattern was seen clearly on the screen while the force acted on the model. When the pulling force acted on C1 or C2, the force was acting at an angle of 150the maximum of the stress presented in C4-5 and when the force acted at an angle of 25° the maximum stress presented in C5-6 and C6-7. Conclusion: The stress distributed upon the posterior edge of the vertebral joints is closely related to the points that the force aced on and the direction of the force． Appropriate points and direction of the pull should be selected according to the change of the lesion joints when manual manipulation is used for the treatment of cervical vertebral disease.

Objective To investigate the efficacy of medial plantar flaps with cutaneous nerves on fixing palm skin defects for patients injured while working.Methods All cases with palm skin defects who received medial plantar flaps grafting from June 2003 to January 2013,were analyzed retrospectively.The data included 13 males and 10 females,with the mean age of 36 years old (range,18-61 years old).There were 16 cases with right hand injury and 7 cases with left,whose skin defects ranged from 3.6 cm×2.8 cm to 7.0 cru×5.5 cm.All cases had skin and soft tissue injury while 5 cases with vascular and nerve injury,3 cases with tendon involvement and being exposed,6 cases with open metacarpal fractures.15 patients were treated with emergency surgery within 8 hours after injury,while 8 patients were treated 10 days after debridement surgery.Results Altogether,23 patients who received medial plantar flaps grafting operations,with palm skin defects,were included in this study.All cases were followed up for 3 to 36 months with a average period of 18 month.The grafted flaps range from 4.6 cm×3.8 cm to 8.0 cm×6.5 cm.Among the patients,19 of them recovered excellently with healing by first intention,with 7-14 d healing time,fully-retained hand functions and palm appearance,and 4-8 mm for between two points distinguish test.Flaps survived fairly well in 3 patients because partial necrosis happened at plantar skin graft donor site.After being debrided and dressed,the wound healed at second phase with a healing time of 12-21 d and 5-9 mm for between two points distinguish test.The operated hands could flex and extend functionally in the follow-up period.Only one patient did not recovered from medial plantar flap grafting and the flap did not survive operationally.The patient recovered after another operation with groin skin grafting later.According to Gu Yudong et al' evaluation criteria,such as improved hand function,19 cases were scored as excellent recovery,3 cases as good,and 1 as poor.The excellent rate was 95.7％ (22/23).Conclusion Medial plantar flaps with cutaneous nerves are ideal flaps for palm skin defects restoration,which characterized by the advantages of fixed anatomical position,high survival rate and being good to the functional recovery and palm appearance.