lumbar spondylolysis , a defect in the pars interarticularis , is a common cause of low back pain in adolescents and young adults . it occurs in 6% of the general population and has been reported more commonly in men . spondylolysis commonly occurs at the fourth and fifth lumbar vertebrae , accounting for more than 95% of total cases of spondylolysis . symptomatic pars lesions appear to be particularly a clinical problem in adolescents , especially adolescent athletes . conservative treatment is commonly considered first in most patients , but those who remain symptomatic may benefit from operative treatment . when the source of back pain is the pars defect itself , direct repair of spondylolysis seems to be most effective and appears to be more logical than posterior spinal fusion in the patients without disc degeneration or spondylolisthesis . multilevel spondylolyses are rare , varying between 1.2% and 5.6% of lumbar spondylolysis cases , and majority involve 2 levels , l4 and l5 . so for , to our knowledge , only 11 cases of 3-level lumbar spondylolyses have been reported in the existing english literature . in this paper , we reported 3 cases of 3-level lumbar spondylolyses in young adults and review the management choices made in these cases . this study obtained the approval of the medical ethics committee of our hospital ( general hospital of armed police force , beijing , china ) . case 1 , a 22-year - old male , presented with low back pain for 2 years . he did not complain of radicular pain , numbness , and concomitant claudication in his lower extremities . he had a history of lumbar injury dropped down from 2 meters high 2 years ago . motor , sensory , and tendon reflex were all normal in his 2 lower limbs . lumbar radiography and computed tomography ( ct ) scan showed left l3 and bilateral l4 and l5 spondylolyses without any slippage . before admission to our hospital , the patient had underwent a 3-month course of conservative treatment with physiotherapy and nonsteroidal anti - inflammatory drugs in a local clinic , but these therapies did not relieve his low back pain . because ct scans have showed terminal - stage findings in the isthmic lysis areas , no abnormality of the posterior arches such as dysplasia and spina bfida was found , surgical indication for left l3 and bilateral l4 and l5 direct isthmic repair via a pedicle screw case 2 , a 22-year - old male , was admitted with low back pain for 14 months . pain was originated from an acute lumbar heavy blow 14 months ago , and increased gradually . one month ago , he felt numbness in his right hip and right lateral thigh . motor , sensory , and tendon reflex were all normal in his 2 lower limbs . radiographs and ct scans showed bilateral l3l5 spondylolyses without any slippage ( figures 1 and 2 ) . after his lumbar injury , he was sent to a local hospital , and was diagnosed with l3l5 bilateral spondylolyses by plain radiography . since then , he has undergone conservative treatment with bracing to protect lumbar spine , physiotherapy , and oral nonsteroidal anti - inflammatory drugs in a local clinic , but these therapies did not relieve his low back pain . after he underwent a 4-month course of conservative treatment , further ct scan showed terminal - stage findings in the l3l5 bilateral isthmic lysis areas . surgical indication for bilateral l3l5 direct isthmic repair via a screw  hook technique was recommended . case 3 , a 23-year - old man , was admitted with low back pain for 6 months . in the beginning a month ago , he sprained his waist carelessly , which aggravated his back pain . since then , he has undergone conservative treatment in a local hospital , but conservative treatment did not relieve his back pain motor , sensory , and tendon reflex were all normal in his 2 lower limbs . because mri showed l5/s1 disc degeneration , we needed to identify whether this disc was a pain - generating disc . the result of discography showed l5/s1 disc disruption with pain reproduction , which indicated the l5/s1 disc as the one of the back pain sources . because ct scan had shown terminal - stage findings in the l3l5 bilateral isthmic lysis areas , accordingly , surgical indication for bilateral l3 and l4 direct isthmic repair and l5/s1 interbody fusion was recommended . three cases of 3-level lumbar spondylolyses were diagnosed and subsequently direct isthmic repair in 2 cases and a combined surgery of isthmic repair and interbody fusion in 1 case were recommended for the 3 patients preoperatively based on clinical findings consistent with imaging study . case 1 underwent a surgery of direct isthmic repair in 5 lytic defects . under general anesthesia , conventional posterior midline approach to lumbar spine was used to exposure l3l5 spinous processes , vertebral laminae , and facet joints . first , a 6.0    45  mm pedicle screw was inserted to involved vertebra under fluoroscopic guidance . second , the involved lysis area was curetted , freshened , and grafted with autologous iliac bone . finally , sublaminar hook was placed , and connected through a short rod under compression with corresponding pedicle screw . the total surgical time was 3  hours with 300  ml of blood loss . a lumbar - sacral brace was used for 3 months after surgery . surgical procedure in case 2 was the same as case 1 . the total surgical time was 3  hours with 500  ml of blood loss . postoperatively , the symptoms of low back pain and numbness in right hip and right lateral thigh disappeared . four pedicle screws were placed in l5 and s1 vertebrae bilaterally , then left laminectomy was performed to allow a cage placement ( 10    26  mm ) filled with autogenous local bone derived from laminectomy between the decorticated endplates of l5 and s1 , and finally 2 rods were connected with 4 pedicle screws under compression . the total surgical time was 3.5  hours with 400  ml of blood loss . after surgery , a brace was placed for 3 months , and symptom of low back pain was almost completely disappeared . case 1 has undergone a follow - up of 2  years , and his low back pain was almost completely disappeared . at 6 months after surgery , bone healing was found in all 5 lytic defects . at 8 months after surgery in case 2 , bone healing was found in all 6 lytic defects . during a 1-year follow - up period , he was pain - free . at 2-year follow - up in case 3 , his low back pain had not recurred , and bone fusion was found between l5 and s1 vertebral bodies and in all 4 isthmi of l3 and l4 according to the evaluation of lumbar radiographs and ct scans . the surgery for the 3 patients was successfully performed and their symptoms were obviously relieved and lumbar function was markedly improved . the alleviation of back pain and improvement of lumbar function was assessed by the change in the degree of pain with a self - assessment of pain by an 11-point visual analog scale ( vas , 010 ) pain scale and the oswestry disabiligy index ( odi , version 1.0 , 0100 ) . lumbar spondylolysis is a common disease , in more than 90% of cases located in l5 . a pars defect develops into a chronic nonunion , and becomes bridged by tissue composed of a combination of fibrous , cartilaginous , or osseous material . in this circumstance , the origin of chronic low back pain could be in the scar and connective tissue rich in nociceptive nerve endings that bridges the gap of a pars defect . extra load exerted on the motion segment may cause disc degeneration , which is therefore an accompanying disorder of spondylolysis . the prevalence of progressive disc degeneration in the involved level is markedly increased in the adult spondylolytic patients who often appear low back pain later in life , after an asymptomatic childhood . the pathology of lumbar spondylosis was considered being congenital failure of fusion of 2 ossification centers or a hyperflexion injury at birth , but spondylolysis had never been founded in embryos , fetus and at birth . following wiltse 's proposal in 1957 , the pathology of spondylolysis was shifted to a consensus of fatigue fracture of the pars interarticularis with a strong hereditary basis . for now , 2 factors can explain isthmic lysis , both genetic and mechanical . no specific genetic variation was identified , but it would seem that a genetic predisposition to this pathology may exist . yamada et al reported 3 cases of lumbar spondylolysis in juveniles from the same family . the highest incidence was reported in native residents in greenland up to 54% . from a mechanical point of view , heavy work and repeated injuries seem to favor the appearance of lumbar spondylolysis . a number of studies have described the association of sports activities with spondylolysis , and all of them support the stress fracture theory . traumatic spondylolysis can be diagnosed early with the use of isotope bone scan or single photon emission computed tomography scan . preoperative ct scan is very important to evaluate the degree of sclerosis in the bony margins of the isthmic defect . the obvious osteosclerosis was shown in all the isthmic defect margins in the 3 patients by ct scan , which indicated that direct isthmic repair was necessary . preoperative lumbar mri is imperative to evaluate the state of intervertebral disc . in our case 3 , due to l5/s1 disc degeneration , an additional lumbar discography was used to indicate this disc as a painful disc . this result finally determined the indication for fusion surgery at the l5/s1 segment instead of a direct isthmic repair in l5 . there are many types of direct repair methods , including scott 's wiring , buck 's screwing , louis butterfly plate , and screw  hook technique ( pedicle screw and hook  rod system ) . from clinical aspects , screw  hook technique allows for fixation of the defects in the pars interarticularis with rigid implants and exerts force along the lamina to effectively suppress the defect motion , which is critical for better bone healing . the precondition of direct defect repair is normal signal intensity in the involved disc shown in t2-weighted mri . if not , lumbar fusion should be considered . in the present cases 1 and 2 , the patients were young with normal discs and normal posterior arches , so l3l5 direct isthmic pair was reasonable . in the case 3 , because mri showed both the l3/4 and l4/5 discs normal and the l5/s1 disc degeneration with disruption and pain reproduction in discography , accordingly a combined surgery of bilateral l3 and l4 direct isthmic repair and l5/s1 interbody fusion was performed for the young patient . surgical treatment varies between fusion , direct isthmic repair , and combined management associating 2 procedures at different levels . success of management of multilevel spondylolyses depends on the choice of appropriate treatment for every patient . we reported here 3 cases of 3-level lumbar spondylolyses with good clinical and radiological results . hook technique is a simple and safe procedure for the motion segment with normal disc . although our clinical results are satisfactory , all 3 patients are young and the duration of their follow - up periods has not been long . therefore , further observation of these patients clinical course and radiological results at the segments treated as well as adjacent segments is needed .