A Novel Semi-Cannulated Screw Enhanced Bone Cement Augmentation and Pullout Strength in Posterior Cervical Lateral Mass Screw Fixations: An In Vitro Biomechanical and Morphological Study.

OBJECTIVE: To develop a novel semi-cannulated lateral mass screw (SC-LMS) for cervical posterior fixations and compare the fixation stability and safety of SC-LMS with regular solid lateral mass screw (S-LMS) in bone cement augmentation and pullout strength using fresh cadaveric cervical vertebrae. METHODS: The conventional multiaxial screw for cervical lateral mass fixation was modified to a cannulated screw with two lateral holes, used for bone cement injection in situ. Eight fresh human cervical vertebrae (C3, C4, and C5) were collected and used. µCT scan was performed to evaluate the bone quality of the lateral masses, including bone mineral density (BMD), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp). SCLMS or S-LMS were randomly inserted into the paired cervical vertebrae and pulled out as a screw loosening model. These screws were reinserted in with bone cement augmentation, scanned by µCT to obtain the bone cement distribution along the screws, and pulled out to test the screw purchase strength. RESULTS: Fmax values exhibited strong positive correlations with the local BMD (𝑟 = 0.8640, p < 0.0001) and Tb.Th (𝑟 = 0.6795, p = 0.0038), whereas a negative correlation with Tb.Sp (𝑟 = -0.5567, p = 0.0251). A significant difference was observed between the Fmax before and after PMMA injection on the SC-LMS side (p = 0.019). The SC-LMS exhibited lower risk of cement leakage than S-LMS after PMMA injection, and a positive correlation was observed between 𝐹max and the distribution volumes on the SC-LMS side. CONCLUSION: The novel SC-LMS provides more robust fixation stability and is safer than the S-LMS for PMMA augmentation, which may be related to the cement-screw-cement-bone complex formation.

Effect of persistence and protophase motor nerve baby-sitting on nerve function recovery in nerve root re-implantation for brachial plexus avulsion injury / 中华创伤杂志

Objective To observe the effect of motor nerve baby-sitting and different babysitting stages on nerve regeneration in nerve root re-implantation for brachial plexus avulsion injury.Methods Twenty-four SD rats were used to induce the brachial plexus avulsion injury.C5-7 roots were avulsed and C6 anterior root was re-implanted to the spine cord via a posterior approach.Branches erupting from C6 and the branches affiliated to the musculocutaneous nerve were cut away via an anterior approach.Re-implanted C6 anterior root was connected singly with musculocutaneous nerve.After that,the end of one branch of medial pectoral nerve was sutured to the lateral musculocutaneous nerve.The animal was divided into persistence motor nerve baby-sitting group (Group A,n =12) and protophase motor nerve baby-sitting group (Group B,n =12) according to the random number table.Electrophysiological evoked potential,muscle wet weight and muscle fiber cross-sectional area were measured at postoperative 2 and 3 months.Results At postoperative 2 and 3 months,the restoration rates of motor evoked potential in Group A [(12.2 ± 3.3) ％ and (15.1 ± 3.5) ％] revealed significant differences from these in Group B [(30.1 ±4.2)％ and (54.8 ±9.6)％] (P ＜0.01),the restoration rates of muscle wet weight in Group A [(75.9 ± 5.3) ％ and (92.7 ± 8.6) ％] were similar with (76.4 ± 7.3) ％ and (94.3 ± 4.4) ％ in Group B (P ＞ 0.05),and the restoration rates of muscle fibrin cross section area in GroupA [(74.4±5.5)％ and (88.5±7.5)％] were similar with (76.9±6.7)％ and (92.9± 3.5) ％ in Group B (P ＞ 0.05).Conclusions Motor nerve end-lateral baby-sitting can improve functional restoration of the skeletal muscle in the early stage after nerve root re-implantation,but prevent functional restoration of skeletal muscle in the late stge.On the contrary,protophase motor nerve babysitting avoid the inhibitory effect in the late stage,which gains better restoration rate of muscle motion evoked potential.