| BACKGROUNDLumbar spondylolysis is referred to as discontinuity in the pars interarticularis of vertebra.Its etiology is known as fatigue fracture caused by repeated stress.Patients with spondylolysis suffer low-back pain and/or lower extremity pain.Some patients remain stable after conservative treatments,and some patients may develop vertebral slippage or slip further.Early surgery can reconstruct spinal stability,enabling patients to start a new life and work as soon as possible.Surgical treatments mainly include direct repair of the pars defect and lumbar fusion.The most important factors influencing the operation method choice are the degree of vertebral slippage and disc degeneration.The degree of disc degeneration below the level of the pars defects is much greater than that of normal anatomical structures.The progression of spondylolisthesis is related to intervertebral disc degeneration.The fifth lumbar vertebra is generally below the intercrestal line and connects pelvis through the iliolumbar ligament,so the L5/S1 segmental stability may be superior to other segments.Recent anatomical research indicated that L4 spondylolysis had a greater degree of degenerative disc disease than that of spondylolysis at L5.Whether different segments clinically affect the degree of disc degeneration is unclearLumbar sacralization is defined as L5 vertebrae with broadened elongated transverse,and/or the formation of an anomalous articulation or complete fusion to the sacrum.Lumbar sacralization may increase the stress of the level above a transition,thus lead to early degeneration or aggravating degree of intervertebral disc degeneration.Few studies have showed the relations between lumbar sacralization and spondylolisthesis and disc degeneration.The L5/S1 may be relatively stable after sacralization,so spondylolysis is difficult to occur at L5.Additionally,L5 spondylolysis can lead to anterior slip of the vertebral body,articular process and transverse process,therefore it is difficult to determine whether L5 transverse has an anomalous articulation or osseous union to the sacrum.Owing to the majority of pars lesions occurring at L5,it appears that the effect of sacralization to lumbar spondylolysis has been overlooked.L4 spondylolysis is often accompanied by sacralization,and whether the slippage and disc degeneration associated with sacralization is unclear.AIM1.To evaluate the influence of different segments to the degree of vertebral slippage and disc degeneration in lumbar spondylolysis.2.To investigate the prevalence of sacralization in L4 spondylolysis,and to evaluate the effect of sacralization to the slippage and disc degeneration.METHODS1.204 patients with lumbar single-level spondylolysis were retrospectively reviewed.Of these patients,74 were diagnosed as L4 spondylolysis(19 males and 55 females;mean age:51.2 years,range,27?72 years),and 130 were diagnosed as L5 spondylolysis(47 males and 83 females;mean age:49.9 years,range,22?76 years).No significant difference was found in sex(x2=2.37,P=0.12)and age(t=1.55,P=0.12)between two groups.The degree of disc degeneration was evaluated using modified Pfirrmmann grading system from Grade 1 to Grade 8 on MRI.The status of end plate degeneration was assessed by Modic changes from normal to type ?,from score 0 to score 3.Radiographic measurements were compared between groups in the severity and distribution of the percentage of slipping,modified Pfirrmann grades,and the Modic changes.2.74 patients with L4 spondylolysis were retrospectively reviewed.Of these patients,28 were diagnosed as lumbar sacralization simultaneously(4 males and 24 females;mean age:52.2 years,range,40-69 years),and 46 were normal(15 males and 31 females;mean age:52.0 years,range,27?72 years).No significant difference was found in sex(?2=3.06,P=0.08)and age(t=0.13,P=0.90)between two groups.Radiographic measurements were compared between groups in the severity and distribution of the percentage of slipping,modified Pfirrmann grades,and Modic changes.RESULTS1.The severity of vertebral slippage between different lesions:the percentage of slipping was(27.8±14.0)%in L4 spondylolysis and(18.9±14.3)%in L5 spondylolysis,respectively.There was significant difference in the percentage of slipping between groups(t=4.34,P<0.01).Significant difference was found in the distribution of the degree of slip(?2=14.618,P=0.002).L4 spondylolysis showed greater amounts of disc degeneration compared with that of L5 spondylolysis(L4:6.92±1.20;L5:5.78±1.70;Z=-4.951,P<0.01).Significant difference was found in the distribution of the degree of disc degeneration(?2=28.247,P<0.01).L4 spondylolysis showed greater amounts of Modic changes compared with that of L5 spondylolysis(L4:1.45±0.36;L5:0.74±1.09;Z=-3.897,P<0.01).Significant difference was found in the distribution of the degree of Modic changes(?2=21.472,P<0.01).2.The severity of L4 slippage between the sacralization group and normal group:the percentage of slipping was(36.0±13.8)%in the sacralization group and(22.9±11.7)%in the normal group,respectively.There was significant difference in the percentage of slipping between groups(t=4.394,P<0.01).Significant difference was found in the distribution of the degree of slip(x2=13.070,P=0.004).The sacralization group showed greater amounts of disc degeneration compared with that of the normal group(sacralization group:7.39±0.92;normal group:6.63±1.27;Z=2.689,P=0.007).Significant difference was found in the distribution of the degree of disc degeneration(?2=10.416,P=0.034).There was no significant difference in the severity of Modic changes(sacralization group:1.75±1.30;normal group:1.26±1.37;Z=1.404,P=0.160)and the distribution of the degree of Modic changes(?2=2.976,P=0.226)between groups.CONCLUSION1.Although not as common as L5 spondylolysis,both the degree of spondylolisthesis and the severity of disc degeneration in L4 spondylolysis were greater.Special attention should be given to patients with bilateral pars defects of L4 in order to avoid extensive surgery due to severe degeneration in the future.2.Patients with L4 spondylolysis had a high prevalence of lumbar sacralization,which may result in a greater degree of anterior slip and degenerative disc disease at the corresponding level of the pars defect.It is of vital importance to obtain the early diagnosis of lumbar sacralization in patients with L4 spondylolysis. |
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