The Mechanism Of Radiographic Parameters In Adult Spondylolysis And Spondylolisthesis

Objectives: To evaluate four radiographic parameters highly correlated withspondyloysis in distinguished groups to explore the mechanism in the process oflysis.Methods: A retrospective study of spondylolysis was initiated in 1992 withradiographic study of four sex,age-matched groups(L4 Nonslip group,L5 Nonslipgroup,L5 Slip group,Control group).The following four parameters were measuredand analyzed:Interfacet distance index ID,Sacral endplate angle STA,Iliac crest hightHIC,Relative thickness of the L5 transverse process RT.A one-way analysis ofvariance followed by Student-Newman,SNK and LSD comparisons were performed.Results:1. The interfacet distance index of L4 in L5 Nonslip groups was significantly greaterthan in the control group (p<0.01),but no significant difference was observedbetween the control and L4 Nonslip groups (p>0.01).2.The Sacral endplate angle STA was significantly smaller in L5 Slip group than inthe control group and L4 Nonslip group (p<0.01).3.The Iliac crest hight HIC was significantly greater in L4 Nonslip groups than in L5Slip group and control group (p<0.01).4.The Relative thickness of the L5 transverse process RT was significantly smaller inL5 Slip group than in control group and L4 Nonslip group(p<0.01).Conclusions:1. Marked increases in interfacet distances of L4 results in subjacent(L4) andsuprajacent(Sl) articular processes contact in the same cross-section of theintervening pars(L5),resulting in direct contact pressure. That mechanism do not support L4 lysis.2. A steeper sacral table acts as a dangerous factor to L5 spondyloysis andspondylolisthesis.3.To some extent,Iliac crest hight and relative thickness of L5 transverse processescan alter the location of the mechanical stress. A greater HIC and RT served as aprotective role by providing stability of L5/S1 segments and resulted degeneration ofL4/5.