numerous causes have been attributed to low back pain ( lbp ) . a long list exists , but the enlistment of sacralization as one of the causes has resulted in a lot of controversy .
sacralization is a congenital vertebral anomaly of the lumbosacral spine ( fusion between l5 and the first sacral segment ) .
several studies have described the occurrence of this anomaly in a back pain population [ 27 ] .
some authors have stated that sacralization is incidentally diagnosed and has no clinical impact [ 7 , 8 ] , whereas others claim that this anomaly may predispose patients to certain clinical disorders [ 911 ] .
this controversy has been quite intriguing and has been the stimulus for carrying out this present study .
the intention was to examine in detail the incidence of this anomaly in the lbp population .
our study aimed to use the incidence of this congenital anomaly to establish a relationship between it and lbp .
after institution review board approval for this prospective study , 500 lumbosacral radiographs of lbp patients and 500 radiographs of control group were collected over a one - year period .
the ages ranged between 16 years and 73 years , and both sexes were involved .
exclusion criteria consisted of any radiologic evidence of previous lumbosacral surgery that would obstruct our measurements . a total of 1000 lumbosacral films were examined and identified as being adequate for measurement of the desired parameters .
data collection consisted of the subject 's age at the time of imaging , gender , number of lumbar vertebral bodies , and bilateral height measurement of the lowest lumbar transverse process .
three orthopedic spine fellows performed all the measurements , using a systemized approach to decrease variability ; in addition , consultations between reviewers took place .
subjects without transverse process dysplasia were classified as normal ( type 0 ) , and those with dysplastic transverse process were classified according to the castellvi radiographic classification system   ( table 1 ) .
the incidence of sacralizations in the two groups was reported , and the anomaly was compared according to the groups .
statistically significant differences were evaluated by using contingency tables with fisher 's exact test for categorical variables .
this test was used to compare statistically the differences between the two groups according to having sacralization .
in g1 , the average age was 39.03  15.9 years ( 1673 years ) .
of these patients ( 281 women , 219 men ) , 106 were classified as positive for sacralization , with a gender distribution of 54 ( 19.22% ) women and 52 ( 23.74% ) men .
of the total number of patients ( 500 ) seen , 12 ( 2.4% ) had lumbarization . according to sacralization classification ,
the most common anatomical variant was castellvi type ia ( 6.8% ) , followed by type ib ( 5.4% ) , type iia ( 1.6% ) , type iib ( 1.8% ) , type iiia ( 1.4% ) , type iiib ( 3.4% ) , and type iv ( 0.8% ) . in g2 ,
of these cases ( 297 women , 203 men ) , 84 were classified as positive for sacralization , with a gender distribution of 39 ( 13.13% ) women and 45 ( 28.48% ) men .
of the total number of cases ( 500 ) seen , 13 ( 2.6% ) had lumbarization . according to sacralization classification ,
the most common anatomical variant was castellvi type ia ( 6% ) , followed by type ib ( 4.2% ) , type iia ( 2% ) , type iib ( 1% ) , type iiia ( 0.8% ) , type iiib ( 1.6% ) , and type iv ( 0.8% ) .
no statistically significant difference was found between the groups according to the presence of sacralization ( p = 0.09 ) ( table 4 ) .
the incidence of sacralization has been reported as 4% to 36% in the general population [ 1 , 6 , 9 , 1317 ] .
its frequency in the low back pain population ranges from 6% to 37% [ 4 , 5 , 10 , 12 , 1821 ] .
numerous studies have found no significant correlation between sacralization and low back pain [ 3 , 5 , 7 , 13 , 22 ] , while others have [ 912 , 21 , 23 ] .
authors who found no significant correlation [ 7 , 8 , 16 ] have concluded that the incidence of transitional vertebra is equal in those with and without back pain , rendering it only an incidental finding on imaging .
frymoyer et al . have determined similar rates of radiological abnormalities in three groups of patients : no lbp , moderate lbp , and severe lbp .
have reported the incidence of sacralization to be 13% in patients with lbp and 11% in their control group .
our study found an incidence rate of 21.2% for sacralization in patients , 16.8% in control group .
demonstrated that the abnormal vertebra does not constitute a risk factor for spine degenerative changes but , when degeneration occurs , it focused on the suprajacent level of the transitional vertebra .
many of the authors with lower estimations used more stringent criteria to count a vertebra as transitional , while other authors did not clearly state all of the inclusion criteria . while elster   and hsieh et al .   reported prevalence as low as 7% and 5.9% , respectively , and delport et al .   observed a rate of 30% , they were based on articulation or fusion of at least one transverse process and presence of an intervertebral disc caudal to the transitional segment , ultimately failing to recognize our most common subtype 
type i. this leaves the current estimates of those with a transitional vertebra in the range of 6%37% in those seeking healthcare for low back pain , either slightly or significantly higher than the range of 4%36% commonly reported as the number with sacralization in the general population .
this large fluctuation in estimates for the general population amplifies the difficulties in determining the significance of the percentage that we found in our patients .
castellvi et al .   reported a 30% prevalence on his low back pain population .
apazidis et al .   found 35.6% prevalence of sacralization in their studies of 211 lumbar spine subjects who had no pain .
their most commonly found pathology was type ia ( 14.7% ) , as in our study .
a great deal of the controversy surrounding the association of sacralization and lbp is the result of an incomplete understanding of the variation present at the lumbosacral junction , as well as the lack of a comprehensive classification scheme that can be used to differentiate lumbosacral variation according to morphological , developmental , and clinical variants .
therefore , a comprehensive understanding of normal and abnormal variations at the lumbosacral junction and a precise classification system are needed to investigate more thoroughly the association between sacralization and lbp .
differences between the classification systems are likely the cause of much of the disagreement ; small sample size may also contribute .
the controversy in the literature centers on the issue of whether or not sacralization cause low back pain .
first , an understanding of the variation present must be achieved , complete with a standard , convenient way to categorize that variation .
second , the possible connections among the categories and both frequencies and intensities of low back pain must be investigated as thoroughly as possible .
 
 objective . 
 the aim of this study was to determine , by plain radiography , if there is a relationship between sacralization and low back pain . methods . 
 five hundred lumbosacral radiographs of low back pain patients and 500 control groups were examined . 
 data collection consisted of the subject 's age at the time of imaging , gender , number of lumbar vertebral bodies , and bilateral height measurement of the lowest lumbar transverse process . 
 dysplastic transverse processes were classified according to the castellvi radiographic classification system . 
 the incidence of sacralization in patients and the control groups was reported , and the anomaly was compared according to the groups . results . of these patients groups , 
 106 were classified as positive for sacralization , which resulted in an incidence of 21.2% . 
 the most common anatomical variant was castellvi type ia ( 6.8% ) . in the control group , 
 84 were classified as positive for sacralization , which resulted in an incidence of 16.8% . 
 no statistically significant difference was found between the groups for having sacralization ( p = 0.09 ) . 
 discussion . 
 the relationship between sacralization and low back pain is not clear . because of this controversial future studies need to focus on identifying other parameters that are relevant to distinguishing lumbosacral variation , as well as corroborating the results obtained here with data from other samples . 