Beier Luo1, Ming Yan2, Jinghui Huang2, Wei Duan2, Zhiping Huang3, Jianting Chen3, Zhuojing Luo4, Qingan Zhu5, Ming Li6. 1. Department of Orthopaedics, Changhai Hospital, The Second Military Medical University, Shanghai 200433, China. 2. Department of Orthopaedics, Xijing Hospital, The Fourth Military Medical University, Xi'an 710032, China. 3. Department of Orthopaedic and Spinal Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China. 4. Department of Orthopaedics, Xijing Hospital, The Fourth Military Medical University, Xi'an 710032, China. Electronic address: zjluo@fmmu.edu.cn. 5. Department of Orthopaedic and Spinal Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China. Electronic address: qinanzhu@gmail.com. 6. Department of Orthopaedics, Changhai Hospital, The Second Military Medical University, Shanghai 200433, China. Electronic address: limingch@21cn.com.
Abstract
BACKGROUND: The biomechanical stability of unilateral pedicle screw (UPS) combined with contralateral translaminar facet screw (TLFS), especially long-term stability, still needs to be compared to traditional UPS or bilateral pedicle screws (BPSs) in details. METHODS: Twenty-four porcine spines (L2-L5) were tested for flexibility with pure moments of 5Nm under intact status and transforaminal lumbar interbody fusion status using UPS+TLFS, UPS or BPS at L3-L4. After short-term (3cycles) and long-term cyclic loading (18,000cycles), the range of motion was obtained and analyzed for single-level constructs in flexion/extension, lateral bending and axial rotation modes. In addition, the relative displacement of contralateral articular processes was recorded in a real time fashion. FINDINGS: The range of motion was significantly reduced in all instrumented constructs. In all movement directions, UPS+TLFS achieved similar range of motion to BPS after short and long-term loading, which were significantly lower than that in UPS. A significantly larger displacement of contralateral articular process was recorded in UPS than UPS+TLFS and BPS during extension/flexion, lateral bending and axial rotation, suggesting its compromised stability. INTERPRETATION: The hybrid construct of UPS+TLFS showed instant and long-term equivalent biomechanical ability to that of traditional BPS, making it an alternative option to BPS that could be less invasive while maintains a stable and effective instrumentation.
BACKGROUND: The biomechanical stability of unilateral pedicle screw (UPS) combined with contralateral translaminar facet screw (TLFS), especially long-term stability, still needs to be compared to traditional UPS or bilateral pedicle screws (BPSs) in details. METHODS: Twenty-four porcine spines (L2-L5) were tested for flexibility with pure moments of 5Nm under intact status and transforaminal lumbar interbody fusion status using UPS+TLFS, UPS or BPS at L3-L4. After short-term (3cycles) and long-term cyclic loading (18,000cycles), the range of motion was obtained and analyzed for single-level constructs in flexion/extension, lateral bending and axial rotation modes. In addition, the relative displacement of contralateral articular processes was recorded in a real time fashion. FINDINGS: The range of motion was significantly reduced in all instrumented constructs. In all movement directions, UPS+TLFS achieved similar range of motion to BPS after short and long-term loading, which were significantly lower than that in UPS. A significantly larger displacement of contralateral articular process was recorded in UPS than UPS+TLFS and BPS during extension/flexion, lateral bending and axial rotation, suggesting its compromised stability. INTERPRETATION: The hybrid construct of UPS+TLFS showed instant and long-term equivalent biomechanical ability to that of traditional BPS, making it an alternative option to BPS that could be less invasive while maintains a stable and effective instrumentation.