lumbar spinal stenosis ( lss ) presents with intermittent claudication ( ic ) in the lower extremities as a typical symptom26,28 ) . peripheral arterial disease ( pad ) also presents with similar symptoms as vascular ic17,21 ) . neurogenic ic , on the other hand , caused by narrowing of the neural foramen and spinal canal , is aggravated by standing and relieved by sitting . however , it can be difficult to differentiate vascular and neurogenic ic due to atypical signs and variable symptoms . therefore , when patients report claudication , it is important to correctly identify the accompanying pathology . pad includes many pathologies , such as arteriosclerosis obliterans , buerger 's disease , and acute arterial obstruction . untreated pad is progressive and increases the risk of severe vascular events and even death8,13,24 ) . therefore , early diagnosis and treatment of pad is important to reduce fatal or nonfatal vascular events17,21 ) . in order to diagnose lss accompanied by pad , however , the argument arises as to whether pad can be ruled out only by arterial pulse examination . to establish a screening test for pad , ankle - brachial index ( abi ) , abi has been found to be highly sensitive and specific for pad screening10,18,20,23,24 ) . those reports presented the incidence of and risk factors for pad in patients with lss with atypical symptoms . if a patient has atypical symptoms , and diagnostic imaging shows no significant spinal canal stenosis , spine surgeons are always concerned about accompanying pad . however , spine surgeons tend to overlook the possibility of accompanying pad in patients with lss diagnosed by typical symptoms and diagnostic imaging , such as magnetic resonance imaging ( mri ) . in order to prevent misdiagnosis of vascular disease , it is important to know the incidence of and risk factors for pad in patients with lss . therefore , the aim of our study was to evaluate the incidence of and risk factors for pad in patients with typical and severe lss who underwent spinal surgical treatment . the occurrence of pad was examined retrospectively in 171 consecutive patients with lss and severe ic who underwent surgical treatment at our hospital from june 2012 to june 2013 . three diseases were included in this study : spinal stenosis ( st ) , degenerative spondylolisthesis ( ds ) and isthmic spondylolisthesis ( is ) . abi is the ratio of arm systolic blood pressure at the brachial artery to ankle systolic blood pressure at the posterior tibial or dorsalis pedis artery6,11,16,31 ) . abi < 0.9 was considered abnormal according to transatlantic inter - society consensus ( tasc ) guidelines21 ) ( fig . all patients with abnormal abi underwent computed tomography angiography ( cta ) and consultation with a vascular surgeon ( fig . data were collected on background characteristics ( sex , age ) and known risk factors for pad , such as hypertension , diabetes mellitus , smoking , hyperlipidemia , stroke , and ischemic heart disease . quality of life ( qol ) was evaluated using a visual analog scale ( vas ) and the oswestry disability index ( odi)2,3,7,22 ) . patients with coexisting pad and lss were designated the lsspad group , while those with lss but no pad were denoted the lss group . using the lss group as a control , analyses were conducted to identify the characteristics of the lsspad group . to evaluate clinical characteristics at the time of enrollment , univariate analysis was performed using the student 's t test ( v2 test ) . the mann - whitney u - test was used to compare group means of continuous data . any variable with a p value of < 0.05 on univariate analysis was included in multiple logistic regression models . the study population comprised 79 men and 92 women with a mean age of 64.68.6 years . cta was performed in these patients , and a final diagnosis of pad was established for all 7 patients . six of the 7 patients diagnosed with pad were treated with an endovascular stent , while the remaining 1 patient was recommended observation and regular follow - up . the results of univariate analysis of risk factors for pad , type of disease , and other clinical parameters are shown in table 1 . the lsspad group was significantly older than the lss group ( 72.35.5 years vs 64.28.6 years , p<0.01 ) . stroke and ischemic heart disease were significantly more common in the lsspad group compared with the lss group . the other known risk factors for pad(diabetes mellitus , hypertension , smoking history , hyperlipidemia ) showed no significant differences between groups . of the 171 patients with lss , 37 ( 21.6% ) smoked . among the 164 patients in the lss group , 100 ( 61% ) had st , 53 ( 32.3% ) had ds , and 11 ( 6.7% ) had is . among the 7 patients in the lsspad group , 6 ( 85.7% ) had st and 1 ( 14.3% ) had ds . in multivariate analysis , the entered variables were age , diabetes mellitus , preoperative vas score , stroke and ischemic heart disease ( p<0.2 ) ( table 2 ) . multiple logistic regression analyses with a forced - entry method revealed that the stroke ( p<0.05 ) was independent risk factor for pad . pad is an atherosclerotic syndrome with a high prevalence of approximately 5.8% to 12% in older adults1,15 ) . high incidence of fatal or nonfatal cardiovascular events associated with pad increases mortality . according to tasc guidelines for pad , the mortality rate of patients with ic associated with pad is 2 times that of patients with ic only2,7,22 ) . besides the risk of death , the 10-year incidence of myocardial infarction and cerebral stroke in patients with pad are increased by about 4 and 3 times , respectively , compared with that in patients without pad5,29 ) . however , pad is often misdiagnosed in older patients with lss because it is difficult to distinguish vascular ic from neurogenic ic . therefore , spine surgeons often overlook the possibility of pad in patients with severe lss18 ) . in a previous study , the coincidence of pad with lss was similar to the prevalence of pad in older individuals ( 6.7%)27 ) . therefore , it is very important to understand the risk factors and to evaluate pad in patients with lss . arteriography is considered the gold standard for diagnosis of pad . however , the use of arteriography has some limitations , including complications arising from ionizing radiation , its invasive nature , and nephrotoxic contrast media . among substitutable tests , abi is the simplest and most inexpensive25 ) . abi also has high sensitivity ( 79 - 95% ) and specificity ( 96 - 100% ) for screening pad17 ) . thus , we evaluated the coincidence of pad with lss and risk factors for pad using abi . there have been several studies to evaluate the incidence of pad in patients with lss using abi . their study showed that abi had high sensitivity and specificity for screening pad in cases with atypical claudication . twenty - two of 42 patients in their study were diagnosed with lss and pad , showing a high coincidence ( 54.8% ) between diseases . however , their study did not analyze the risk factors for pad and was limited in that only mild cases of lss , determined by mri , were included . most spine surgeons easily can doubt a hidden disease , such as pad , in these cases . therefore , in our study , we enrolled patients with typical symptoms , severe lss , confirmed by mri , who underwent decompressive surgery . they also showed that comorbidity of diabetes mellitus , history of stroke , and history of ischemic heart disease were characteristics of patients with lss and pad . this was the first nationwide multicenter survey of the prevalence of pad in patients with lss in japan . however , the mean vas score of patients with lss and pad was 53.627.0 , while that of patients with lss was 60.128.4 ( vas 0 - 100 mm ) , indicating that patients with mild ic were included in this study as well as patients with severe ic who required surgical treatment . spine surgeons occasionally make a mistake in performing surgery in patients who have radiographically asymptomatic stenosis and vascular ic arising from pad , since it is difficult to distinguish between neurogenic and vascular ic . therefore , diagnosis of pad is not important for patients with mild ic , but is important for patients with typical neurogenic ic and definite lss who require surgical treatment . we analyzed the incidence of and risk factors for pad in patients with severe lss and intractable ic who underwent surgical treatment . the mean preoperative vas score of all patients was 7.21.9 , and there was no response to conservative treatment , such as medication , physical therapy , and epidural nerve block . although the coincidence of pad with lss was not high ( 7 of 171 patients [ 4.1% ] ) , 6 of 7 patients had severe vascular insufficiency requiring endovascular stent surgery . thus , it can be very dangerous if pad is misdiagnosed in patients with lss . previous studies have presented several risk factors for pad , such as old age , sex , diabetes mellitus , dyslipidemia , hypertension , smoking history , and body mass index15,27,30 ) . in this study , old age and history of stroke was the only significant predisposing factor for pad . according to this result , we propose abi examination in old patients with lss and history of stroke to rule out pad . if pad is diagnosed , spine surgeons may be able to decide whether to perform decompressive surgery for lss . in this decision making process , although imaging studies are often not specific for lss , electrodiagnostic testing is highly specific for diagnosis of lss4,12 ) . the strength of this study is the severe ic of the patient population , which was analyzed by multivariate logistic regression to identify the incidence of and risk factors for pad . diagnosis of pad by abi enables spine surgeons to avoid fatal vascular events and unnecessary surgery in patients with radiographically asymptomatic lss . however , this study is limited by its retrospective nature , relatively small patient population , and short - term duration of follow - up . to further verify the incidence of and risk factors for pad in addition , this study did not reveal the sensitivity and specificity of abi because cta was not performed in all patients . misdiagnosis of pad may increases the risk of severe vascular events and even death . to prevent misdiagnosis of fatal pad and to avoid unnecessary surgery , we propose further evaluation