Research On Mechanism Of Minimal Invasive Osteosynthesis In Promoting Fracture Healing Process Of Humeral Shaft

OBJECTIVE: Minimal Invasive Plate Osteosynthesis(MIPO)technique minimizes the dissection and stripping to the soft tissue and protects the biological environment of the fracture site.Clinical studies have indicated that MIPO technique might promote the healing process when treating with humeral shaft fractures.The current research aimed to investigate the influence of MIPO technique in humeral shaft regarding the blood supply and fracture healing process and compare the influence on fracture healing process of different implants used in MIPO.METHODS: In the first part,cadavers were dissected and observed to investigate the blood supply of humeral shaft and the anatomic feature of nutrient artery foramina.Foramina index was calculated.Data of both sides were compared.Relationships between transverse and longitudinal locations,diameter and total length,and foramina and landmark indices were analyzed.In the second part,randomly selected upper limbs from same cadaver were undergone either MIPO or open reduction and internal fixation(ORIF).The limbs were injected after surgeries and radiology exam and dissection were conducted to compare the influence on vascular integrity and periosteal filling of humeral shaft.In the third part,fracture models were created on beagle dogs and were treated with either MIPO or ORIF.Postoperatively,radiographic exam,Micro-CT scanning,sequential fluorescent labeling and histological observation were conducted to compared the influence on callus formation and bone mineralization of two techniques.In the forth part,fracture models were created on beagle dogs fixed either by Locking Compression Plate(LCP)or Dynamic Compression Plate(DCP)combined with MIPO technique.Postoperatively,radiographic exam,Micro-CT scanning,sequential fluorescent labeling and histological observation were conducted to compared the influence on callus formation and bone mineralization of two implants.RESULTS: The first part showed that the humerus had one or two main nutrient arteries entering the anteromedial aspect of the distal half of humerus through a restricted area between the insertion of the coracobrachial muscle and the origin of the brachial muscle.There was no reciprocity in humeri with two foramina.There was no correlation between the size and distribution of foramina.There was no correlation between the size of foramina and the length of humerus.Foramina indices could help clinicians located the nutrient artery.The second part showed that neither of the two techniques impaired the main nutrient artery.MIPO was superior to the ORIF in preserving the accessory nutrient arteries and periosteal filling.The third part indicated that all fractures from two groups were healed in form of secondary healing.The callus formation and bone mineralization occurred in an early stage in MIPO group.From 6 weeks postoperatively,the callus area began to reduce in both groups and did not show any significance difference.The forth part showed that with MIPO there was no significant difference between the LCP and the DCP in terms of fracture fixation,bone formation,or mineralization.CONCLUSION: The humeral shaft was supplied by the main nutrient artery located in the anteromedial side and the accessory nutrient arteries located in the posterior side.MIPO technique was superior in preserving the accessory nutrient arteries and periosteal filling.Consequently,it could promote callus formation and bone mineralization in an early stage of healing process.There was no difference between LCP and DCP when treating fractures with MIPO technique.Because the fracture pattern is unpredictable,it is preferable to use MIPO to treat humeral fractures,particularly when the soft tissue is in critical condition.