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J Orthop Sci (2004) 9:440–445 DOI 10.1007/s00776-004-0813-4 Simple screening method for deep vein thrombosis by duplex ultrasonography using patients’ active maximum ankle dorsiflexion Kousuke Sasaki, Hiromasa Miura, Shinichiro Takasugi, Seiya Jingushi, Eiji Suenaga, and Yukihide Iwamoto Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan ment produces significant augmentation of venous outflow from lower limbs in healthy subjects or patients undergoing total hip (THA) or knee (TKA) arthroplasty. 16,18,21 We hypothesized that venous stenosis or obstruction by the presence of deep vein thrombosis (DVT) causes decreased augmentation of venous outflow from lower limbs by active ankle movements. At present, duplex ultrasonography has become a primary modality to look for the presence of DVT because of its noninvasive nature; it is also a popular modality for evaluating venous flow. 9,18,19,21 If our hypothesis is true, we thought that we could develop a new screening method for DVT using duplex ultrasonography. Therefore, using duplex ultrasonography and ascend- ing venography in patients undergoing THA or TKA, we compared the rate at which femoral vein blood flow is increased by active maximum ankle dorsiflexion in lower limbs with and without DVT. In this article, we discuss reasons why ultrasound measurement of femoral vein blood flow using patients’ active maximum ankle dorsiflexion is a useful screening method for DVT. Patients and methods Patients who gave informed consent for bilateral as- cending venography after THA or TKA at our depart- ment from April 1999 to October 2003 were recruited for this study. Patients with ankle pain or limited ankle range of motion, such as those with rheumatoid arthri- tis, ankle osteoarthritis, or severe ankle trauma history, were excluded, as were patients with a history of DVT, pulmonary embolism, or chronic venous insufficiency. Consequently, 22 lower limbs of 11 patients undergoing THA or TKA were studied. The patients consisted of two men and nine women with an average age of 68.0 years (range 59–78 years). All of the patients were Abstract We hypothesized that venous obstruction by deep vein thrombosis (DVT) only slightly augments venous outflow from lower limbs by active ankle movements. If our hypoth- esis is true, we thought that we could develop a new screening method for DVT using duplex ultrasonography. Subjects were 22 lower limbs of 11 patients who gave informed consent for venography after total hip or knee arthroplasty. Around postoperative 19.0 days (range 15–32 days), we measured the ratios, called flow ratios, of the peak flow signal with active maximum ankle dorsiflexion and that at rest using duplex ultrasonography in the bilateral femoral veins. On the same day, we then performed bilateral venography. Thrombosis was detected in 5 of the 22 lower limbs. The mean flow ratios with and without DVT were 1.18 (range 1.0–1.3) and 3.31 (range 1.8–4.8), respectively. The flow ratios with DVT were significantly lower than those without DVT. Pain or difficulty performing active maximum ankle dorsiflexion was not observed in any of the operated or unoperated lower limbs during the ultrasound examination. In conclusion, ultrasonographic measurement of flow ratios may become a simple screening method for DVT in lower limbs without the pain or difficulty of performing active maximum ankle dorsiflexion. Key words Venous thrombi · Femoral vein · Blood flow · Ratio Introduction Active ankle movement is a part of the normal physi- ological mechanism that increases venous outflow from lower limbs; it is called the muscle pump effect. Using duplex ultrasonography or strain-gauge plethysmogra- phy some studies have found that active ankle move- Offprint requests to: H. Miura Received: December 15, 2003 / Accepted: June 28, 2004

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Page 1: Simple screening method for deep vein thrombosis by duplex ultrasonography using patients’ active maximum ankle dorsiflexion

J Orthop Sci (2004) 9:440–445DOI 10.1007/s00776-004-0813-4

Simple screening method for deep vein thrombosis by duplexultrasonography using patients’ active maximum ankle dorsiflexion

Kousuke Sasaki, Hiromasa Miura, Shinichiro Takasugi, Seiya Jingushi, Eiji Suenaga, and Yukihide Iwamoto

Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku,Fukuoka 812-8582, Japan

ment produces significant augmentation of venousoutflow from lower limbs in healthy subjects orpatients undergoing total hip (THA) or knee (TKA)arthroplasty.16,18,21

We hypothesized that venous stenosis or obstructionby the presence of deep vein thrombosis (DVT) causesdecreased augmentation of venous outflow from lowerlimbs by active ankle movements. At present, duplexultrasonography has become a primary modality to lookfor the presence of DVT because of its noninvasivenature; it is also a popular modality for evaluatingvenous flow.9,18,19,21 If our hypothesis is true, we thoughtthat we could develop a new screening method for DVTusing duplex ultrasonography.

Therefore, using duplex ultrasonography and ascend-ing venography in patients undergoing THA or TKA,we compared the rate at which femoral vein blood flowis increased by active maximum ankle dorsiflexionin lower limbs with and without DVT. In this article,we discuss reasons why ultrasound measurement offemoral vein blood flow using patients’ active maximumankle dorsiflexion is a useful screening method forDVT.

Patients and methods

Patients who gave informed consent for bilateral as-cending venography after THA or TKA at our depart-ment from April 1999 to October 2003 were recruitedfor this study. Patients with ankle pain or limited anklerange of motion, such as those with rheumatoid arthri-tis, ankle osteoarthritis, or severe ankle trauma history,were excluded, as were patients with a history of DVT,pulmonary embolism, or chronic venous insufficiency.Consequently, 22 lower limbs of 11 patients undergoingTHA or TKA were studied. The patients consisted oftwo men and nine women with an average age of 68.0years (range 59–78 years). All of the patients were

Abstract We hypothesized that venous obstruction by deepvein thrombosis (DVT) only slightly augments venous outflowfrom lower limbs by active ankle movements. If our hypoth-esis is true, we thought that we could develop a new screeningmethod for DVT using duplex ultrasonography. Subjects were22 lower limbs of 11 patients who gave informed consentfor venography after total hip or knee arthroplasty. Aroundpostoperative 19.0 days (range 15–32 days), we measured theratios, called flow ratios, of the peak flow signal with activemaximum ankle dorsiflexion and that at rest using duplexultrasonography in the bilateral femoral veins. On the sameday, we then performed bilateral venography. Thrombosiswas detected in 5 of the 22 lower limbs. The mean flowratios with and without DVT were 1.18 (range 1.0–1.3) and3.31 (range 1.8–4.8), respectively. The flow ratios with DVTwere significantly lower than those without DVT. Pain ordifficulty performing active maximum ankle dorsiflexion wasnot observed in any of the operated or unoperated lowerlimbs during the ultrasound examination. In conclusion,ultrasonographic measurement of flow ratios may becomea simple screening method for DVT in lower limbs withoutthe pain or difficulty of performing active maximum ankledorsiflexion.

Key words Venous thrombi · Femoral vein · Blood flow ·Ratio

Introduction

Active ankle movement is a part of the normal physi-ological mechanism that increases venous outflow fromlower limbs; it is called the muscle pump effect. Usingduplex ultrasonography or strain-gauge plethysmogra-phy some studies have found that active ankle move-

Offprint requests to: H. MiuraReceived: December 15, 2003 / Accepted: June 28, 2004

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441K. Sasaki et al.: Simple screening method for thrombosis

instructed about the procedure, the purpose of thestudy, and any known risks. Informed consent was ob-tained from all of the patients.

Of the 11 patients, 7 underwent primary THA for hiposteoarthritis, and 4 underwent primary unilateral TKAusing a tourniquet for knee osteoarthritis. Epidural andspinal anesthesia were used for all of the operations.After THA, a foot-pump system was used for 5 days.Movement using a wheelchair and gait with partialweight-bearing were started on the fifth and seventhpostoperative days, respectively. After TKA, a foot-pump system was used until the third postoperative day.Use of a wheelchair and continuous passive motionwere started on the third postoperative day, and gaitwith partial weight-bearing was started on the fifthpostoperative day. None of the patients underwentanticoagulant prophylaxis.

Ultrasound measurements of the bilateral femoralvein blood flow were performed an average of 19.0 daysafter operation (range 15–32 days). All of the measure-ments were started after resting on a bed with quietrespiration for 3min. During the measurements, thepatients were on a bed in a supine position. Venous flowwas measured in the common femoral vein approxi-mately 2cm above the junction of the greater saphenousand femoral veins using duplex ultrasonography withcomputed sonography and a 7.5-MHz linear-arraytransducer (SSD-2000; Aloka, Tokyo, Japan).

We first obtained a full longitudinal image of thecommon femoral vein by color flow mode (Fig. 1). Wemade sure that no thrombus was visualized in the meas-urement area. We adjusted the angle between the direc-tion of the ultrasound beam and that of venous flow toapproximately 60° by steered beam function, placed ascreen cursor at the center of the lumen, and made thedirection of the cursor parallel to that of the venousflow. We then obtained real-time venous flow signals atrest by Doppler mode. Next, we told the patient toperform active maximum ankle dorsiflexion as rapidlyas possible and to keep a position of maximum dorsi-flexion for 2 s. We then obtained real-time venous flowsignals with active maximum ankle dorsiflexion. Aftertracing the obtained venous flow signals using anautotracing function, we measured the peak signal atrest for 2 s immediately before the patient performedactive maximum ankle dorsiflexion; we then measuredthe peak signal with active maximum ankle dorsiflexion.We calculated a ratio of the peak signal with activemaximum ankle dorsiflexion to that at rest. The ratiousing the patient’s active maximum ankle dorsiflexionwas measured three times in each lower limb. We calcu-lated a mean value for the three obtained ratios andcalled it flow ratio in each lower limb. Each intervalbetween active maximum ankle dorsiflexion was 3min.During each interval between active maximum ankle

dorsiflexion, the patient was resting on a bed with quietrespiration.

On the same day as the ultrasound measurement anddirectly following it, bilateral ascending venographywas performed to confirm the diagnosis of DVT. Allvenographies were done using a modification of thetechnique described by Rabinov and Paulin17 and wereinterpreted independently by an experienced radiolo-gist who was blinded to our study. Thrombosis wasdiagnosed when venograms revealed a constant intralu-minal filling defect in the deep veins. Patients with aDVT were treated with an oral anticoagulant. Thethrombosis was defined as a proximal DVT if thethrombi were in the popliteal or more proximal veins; itwas a distal DVT if the thrombus was in a calf vein. Ifboth areas were involved, it was categorized as a proxi-mal DVT.

Clinical details of the 11 patients (age, gender, height,weight, operating time, intraoperative and postopera-tive blood loss, and interval between operation and theultrasound examination or venography) are summa-rized in Table 1.

Statistical comparison between 2 groups was per-formed by a Mann-Whitney U-test. The two-tailed P

Fig. 1. Full longitudinal image of the common femoral veinwhere venous flow is measured. Angle between the directionof the ultrasound beam and that of venous flow is adjusted toapproximately 60°. A screen cursor (arrow) is located at thecenter of the lumen, and its direction is parallel to that ofvenous flow

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442 K. Sasaki et al.: Simple screening method for thrombosis

value was reported. The level of significance was set atP � 0.05.

Results

The number of lower limbs with DVT and locations ofthe thrombi are shown in Table 2. Thrombosis was de-tected by venography in five lower limbs of five patients,all of whom were women. All of the thrombi weredetected in the operated lower limbs. Of the five lowerlimbs with DVT, three lower limbs had undergoneTHA and two had undergone TKA. Proximal DVTwas observed in one lower limb undergoing THA andone lower limb undergoing TKA. Distal DVT was ob-served in two lower limbs undergoing THA and onelower limb undergoing TKA. All of the five lower limbswith DVT were clinically asymptomatic. All of thethrombi were nonocclusive because the venogramsshowed that contrast medium was passing around anintraluminal filling defect. No symptomatic pulmonaryembolisms were observed in any patients with DVTuntil the latest follow-up.

The results of the three measured ratios and the flowratio in each lower limb are shown in Table 3. The meancoefficient of variation (CV) of the three measured ra-tios in the lower limbs with DVT and that of the limbs

without DVT were 6.5% (range 4.7%–12.4%; n � 5)and 4.8% (range 1.8%–9.4%; n � 17), respectively. TheCV values of the three measured ratios with DVT andthose without DVT were both small. The flow ratioswith DVT and those without DVT are shown in Table 4.The mean flow ratios with and without DVT were 1.18and 3.31, respectively. The flow ratios with DVT weresignificantly lower than those without DVT (P �0.0010). The mean flow ratio with proximal DVT andthat with distal DVT were 1.05 and 1.27, respectively.The number of subjects was small in our study, and sowe could not statistically compare the flow ratios be-tween the lower limbs with proximal DVT and thosewith distal DVT. However, the difference in the flowratios between the two groups was small. A typicalDoppler signal waveform of femoral vein blood flowwithout DVT and a typical waveform with DVT areshown in Fig. 2.

Pain or difficulty performing active maximum ankledorsiflexion was observed in all of the operated lowerlimbs after TKA until approximately 1 week after op-eration. However, they were not observed in any oper-ated or unoperated lower limbs during the ultrasoundexamination after THA or TKA.

Table 1. Clinical details of patients in this study

Clinical characteristic THA (n � 7) TKA (n � 4) Total (n � 11)

Age (years) 69.4 (59–78) 65.5 (59–74) 68.0 (59–78)Sex (male/female) 1/6 1/3 2/9Height (cm) 153.7 (147–165) 155.5 (148–166) 154.4 (147–166)Weight (kg) 58.4 (51–68) 61.5 (57–64) 59.5 (51–68)Operating time (min) 106.0 (85–132) 98.3 (88–120) 103.2 (85–132)Total blood loss (ml) 887.1 (645–1005) 665.0 (530–750) 806.4 (530–1005)Interval between operation 17.1 (15–21) 22.3 (17–32) 19.0 (15–32)

and US or venography (days)

Values are expressed as mean with the range in parenthesesTHA, total hip arthroplasty; TKA, total knee arthroplasty; Total blood loss, amount of intraoperative and postoperative blood loss; US,ultrasonography

Table 2. Number of lower limbs with DVTs and locations of the thrombi

THA TKA

Operated side Unoperated side Operated side Unoperated side TotalParameter (n � 7) (n � 7) (n � 4) (n � 4) (n � 22)

Lower limbs with DVTs (no.) 3 — 2 — 5Proximal DVTs 1 — 1 — 2Distal DVTs 2 — 1 — 3

Lower limbs without DVTs (no.) 4 7 2 4 17

DVT, deep vein thrombosis; Operated side, operated lower limbs; Unoperated side, unoperated lower limbs

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443K. Sasaki et al.: Simple screening method for thrombosis

Table 3. Results of three measured ratios and flow ratio in each lower limb

PatientThree measured ratios Flow ratioa

no. Operated side Unoperated side Operated side Unoperated side

THA1 3.20 � 0.17 (5.3%) 2.87 � 0.15 (5.2%) 3.2 2.92 4.23 � 0.21 (5.0%) 4.77 � 0.15 (3.1%) 4.2 4.83 1.83 � 0.12 (6.6%) 2.23 � 0.21 (9.4%) 1.8 2.24 4.37 � 0.21 (4.8%) 4.73 � 0.21 (4.4%) 4.4 4.75 0.97 � 0.12 (12.4%)b 2.93 � 0.12 (4.1%) 1.0b 2.96 1.27 � 0.06 (4.7%)c 2.43 � 0.06 (2.5%) 1.3c 2.47 1.17 � 0.06 (5.1%)c 2.83 � 0.12 (4.2%) 1.2c 2.8

TKA8 3.37 � 0.06 (1.8%) 3.80 � 0.10 (2.6%) 3.4 3.89 2.70 � 0.20 (7.4%) 3.23 � 0.12 (3.7%) 2.7 3.210 1.07 � 0.06 (5.6%)b 3.83 � 0.21 (5.5%) 1.1b 3.811 1.27 � 0.06 (4.7%)c 3.07 � 0.21 (6.8%) 1.3c 3.1

Data values of three measured ratios are expressed as the mean � standard deviation (SD), with the coefficient of variation (CV) in parenthesesa Mean value of three measured ratiosb Lower limbs with a proximal DVTc Lower limbs with a distal DVT

Fig. 2. Typical Doppler signal waveform of femoral veinblood flow without a deep vein thrombosis (DVT) (A) andtypical waveform with a DVT (B). Solid and broken straightlines show peak venous flow signals with active maximum

ankle dorsiflexion and the peak signals at rest, respectively.Arrows indicate the beginning of active maximum ankledorsiflexion. Flow ratios are 2.4 and 1.0 in cases A and B,respectively

A B

Discussion

In lower limbs with pain or that have difficulty per-forming active maximum ankle dorsiflexion, whetherthrombi are present or absent, flow ratios are probablylow because the muscle pumping power of active maxi-mum ankle dorsiflexion is weak. In our study, however,pain or difficulty performing active maximum ankledorsiflexion was not observed in any operated or un-operated lower limbs during the ultrasound examina-tion after THA or TKA. We believe, therefore, thatvenous stenosis or obstruction due to the presence ofDVT caused the low flow ratios in our study, and that

the ultrasound measurement of flow ratios may becomea screening method for DVT in lower limbs withoutpain or difficulty performing active maximum ankledorsiflexion. Also, we believe that the ultrasound mea-surement of flow ratios can be used as a reliable screen-ing method because the CVs of the three measuredratios using the patients’ active maximum ankle dorsi-flexion were low in our study, although the number ofsubjects is small. Determining whether the ultrasoundmeasurement of flow ratios is a true screening methodfor DVT requires a large number of flow ratios forpatients with and without DVT. Therefore, a futurestudy will require much larger patient populations.

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444 K. Sasaki et al.: Simple screening method for thrombosis

Deep vein thrombosis is a serious complication ofTHA and TKA. Without prophylaxis against thrombo-sis, the reported prevalence of DVT has ranged from23% to 42% after THA and from 58% to 76% afterTKA in Western countries.12 In Japan the reportedprevalence of DVT is 22.6% after THA and 48.6%after TKA.10 Early diagnosis and treatment of DVTsare necessary, as they can cause fatal pulmonaryembolisms.

Although ascending venography is accepted as thegold standard for diagnosing DVTs, the procedure isinvasive, lacks repeatability, causes discomfort and localulceration, and exposes the patient to the potential riskof an allergic reaction to the contrast medium andpostvenographic DVT.1,3–5 It is therefore not an idealscreening procedure for DVT. Ultrasonography hasmajor advantages over venography, including the factthat it is noninvasive, is painless, requires no radiationexposure, and can be done at the bedside if necessary; ithas become a popular primary modality for surveillanceregarding the presence of DVT.

Compression ultrasonography has been used as thestandard procedure for detection of DVTs; andnoncompressibility of the vein, when gentle pressure isapplied with the transducer, has been used as the diag-nostic criterion.2,7,14 With the compression ultrasoundprocedure, the entire venous trajectory in a lower limbshould be visualized; however, visualizing the calf veinsis difficult because of the variable anatomical positionsof the veins and the small size of the vessels.7,14 Thecompression ultrasound procedure therefore requiressufficient experience and expertise by the opera-tor.11,14,15,22 We believe that our measurement procedureusing patients’ active maximum ankle dorsiflexion issimple in contrast to the compression ultrasound proce-dure because the area examined for measuring theflow ratios involves only the common femoral vein inthe groin. Because of its simplicity, we suggest thatour measurement procedure is probably operator-independent in contrast to the compression ultrasoundprocedure. However, it is unknown whether accuracy inthe detection of DVT using our measurement proce-dure can bear comparison with that when using thecompression ultrasound procedure. In a future study,we need to compare the sensitivity and specificity fordetecting DVT directly between our measurement pro-cedure and the compression ultrasound procedure inmuch larger patient populations.

Compression ultrasonography is an accurate methodfor detecting a symptomatic proximal DVT,2,7,14,15,22

but it is unreliable for detecting the asymptomatic ornonocclusive DVT.6,8,13,14,20 Incidentally, in our study, allof the thrombi were asymptomatic and nonocclusive.We therefore suggest that our measurement procedureusing patients’ active maximum ankle dorsiflexion mayT

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Page 6: Simple screening method for deep vein thrombosis by duplex ultrasonography using patients’ active maximum ankle dorsiflexion

445K. Sasaki et al.: Simple screening method for thrombosis

become a useful screening method for asymptomatic ornonocclusive DVT. Determining whether our measure-ment procedure is a truly useful screening methodfor the asymptomatic or nonocclusive DVT, however,requires future assessment of the sensitivity andspecificity of detecting asymptomatic or nonocclusiveDVTs using our measurement procedure in much largerpatient populations.

During TKA, leg skeletal muscles are damaged tosome degree. We believe, therefore, that low flow ratiosof lower limbs undergoing TKA cannot always indicatethe presence of a DVT when pain or difficulty perform-ing active maximum ankle dorsiflexion is observed. Wealso believe that ultrasound measurement of flow ratiosprobably cannot be a screening method for DVTs inpatients with rheumatoid arthritis, ankle osteoarthritis,or severe ankle trauma history because these patientsoften experience pain or difficulty when performingactive maximum ankle dorsiflexion.

In our study, the range of the flow ratios in patientswithout a DVT was relatively wide (range 1.8–4.8). Webelieve that flow ratios of normal lower limbs probablydepend on leg muscle strength. In a future study, weneed to measure flow ratios in much larger patientpopulations to determine a cutoff value for the flowratio for detecting DVTs.

We suggest that flow ratios probably do not dependon the location of the thrombi because the difference inthe flow ratio between the lower limbs with proximalDVT and those with distal DVT was small. However,the number of subjects in our study was small. In afuture study, therefore, we need to compare flow ratiosstatistically between lower limbs with a proximal DVTand those with a distal DVT by measuring flow ratios inmuch larger patient populations.

Conclusions

The ultrasound measurement of flow ratios may be-come a simple screening method for DVT in lowerlimbs without pain or difficulty performing active maxi-mum ankle dorsiflexion. However, additional data arenecessary to claim a priority for using the ultrasoundmeasurement of flow ratios as a potential screeningmethod for DVTs.

Acknowledgments. The authors thank Yasuo Noguchi M.D.,Ph.D. at the Department of Orthopaedic Surgery, Saga Pre-fectural Hospital Koseikan, Saga, Japan.

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