Surgical Significance of Popliteal Arterial VariantsA Unified Angiographic Classification

DUCKSOO KIM, M.D.,* DAN E. ORRON, M.D.,* and JOHN J. SKILLMAN, M.D.t

Distal popliteal arterial variations may influence the success offemorodistal popliteal and tibial arterial reconstructions. Twopatients whose bypass procedures were initially unsatisfactorybecause of a poor choice for anastomosis stimulated a review ofvariations in the distal popliteal artery in 1000 femoral arterio-grams. The popliteal arterial anatomy could be assessed in 605extremities and the tibial arterial anatomy in 495 extremities.Seventy-five variant cases were identified. Normal branching ofthe popliteal artery was present in 92.2%. Among the 7.8% in-cidence of variants, the majority (72%) were either high originof the anterior tibial artery or a trifurcation pattern. Of variantpatterns to the foot (5.6%), the most common was that in whichthe supply to the distal posterior tibial artery arose from theperoneal artery. We propose a unified classification of the pop-liteal and tibial arterial variations that encompasses both ana-tomic areas. Variant arterial supply to the foot can be suspectedwhen the infrapopliteal vessels show a hypoplastic or aplasticanterior or posterior tibial artery and compensatory hypertrophyof the peroneal artery. Knowledge of these variants is importantto angiographers and vascular surgeons.

V T ARIATIONS IN THE anatomy of the distal popli-teal artery have an influence on the success offemorodistal popliteal and tibial arterial recon-

structions. Two patients whose initial arterial anastomoseswere unsatisfactory because ofa poor choice for the distalanatomic site ofreconstruction stimulated a review ofthevariations in the distal popliteal and tibial arteries in thefemoral arteriograms of 1000 extremities.

In this study we classify and relate variant patterns ofthe popliteal artery and the tibial arterial distribution tothe lower leg. Seventy-five variant cases were classified,including one type that, to our knowledge, has not beenreported previously in the radiologic or anatomic litera-ture.

From the Departments of Radiology* and Surgery,t theCharles A. Dana Foundation,*,t Harvard Medical School,

and the Beth Israel Hospital, Boston, Massachusetts

We propose a modification ofthe classification of pop-liteal arterial variation suggested by Lippert,' in whichattention to the predictability ofvariations in arterial sup-ply to the foot is based on the appearance of the proximaltibial arterial anatomy.

Materials and Methods

Femoral arteriograms performed on 1000 extremitiesin the period from July 1, 1980 to December 31, 1986were reviewed. The angiograms of 395 patients were ex-cluded from analysis because of insufficient radiologic de-tail in the area of interest. The branching pattern of thepopliteal artery was analyzed in 605 extremities. The ar-terial supply to the foot was analyzed in 495 extremi-ties. The following measurements (based on Lippert'sclassification') were made (Fig. 1). Distance A representsthe vertical distance in centimeters between the medialtibial plateau and the origin of the anterior tibial artery(AT) in 286 extremities. Distance B represents the verticaldistance between the origin of the AT and that of theperoneal artery (PR) in 220 extremities. Distance B rep-resents the length of the tibioperoneal arterial trunk.

Results

The following classification includes variations in boththe branching ofthe popliteal artery and the arterial supplyto the foot. The relative incidences of variants were cal-culated (Figs 1 to 3).

The manuscript was presented at the New England Society for VascularSurgery meeting on September 16, 1988 in Montreal, Canada.

Correspondence and reprint requests: John J. Skillman, M.D., De-partment ofSurgery, Beth Israel Hospital, 330 Brookline Avenue, Boston,MA 02215.

Accepted for publication: April 4, 1989.

I. Normal Level ofPopliteal Arterial Branching (Fig. 1)

(A) Usual pattern: AT is the first arterial branch; tib-ioperoneal artery follows and bifurcates into the peronealand posterior tibial (PT) arteries (560/605 = 92.2%).

776

POPLITEAL ARTERY VARIANTS

I-C1.2%

Il-Al3.0%

PTAT

PR-

FIG. 1. Type IA: the usual pattern of popliteal arterial branching andarterial supply to the foot. Type IB: trifurcation: the anterior, peroneal,and posterior tibial arteries arise at the same point without an interveningtibioperoneal trunk. Type IC: the posterior tibial artery is the first branch.The anterior tibial and peroneal arteries arise from a common trunk.

(B) Trifurcation: AT, PR and PT arise within 0.5 cm;

there is no true tibioperoneal trunk. 12/605 = 2.0%.(C) Anterior tibioperoneal trunk: PT is the first branch,

tibioperoneal trunk follows and bifurcates into the PRand AT. 7/605 = 1.2%.

I. High Division ofPopliteal Artery (Fig. 2)

(A) AT arises at or above the knee joint (22/605= 3.7%).

(1) Normal course of proximal AT (18/605 = 3.0%).(2) Medial initial curve in AT (4/605 = 0.7%).(B) PT arises at or above the knee joint. Common trunk

for PR and AT (5/605 = 0.8%).(C) PR arises at or above the knee joint. Common trunk

for AT and PT (1/605 = 0.16%).

III. Hypoplastic orAplastic Branching with Altered DistalSupply (Fig. 3)

(A) Hypoplastic-aplastic PT. Distal PT replaced to PR(19/495 = 3.8%).

(B) Hypoplastic-aplastic PT and AT. Dorsalis pedis(DP) replaced to PR (8/495 = 1.6%).

(C) Hypoplastic-aplastic PT and AT. PT and DP re-

placed to PR (1/495 = 0.2%).

The mean value for distance A was 6 cm with a range

between 2.5 cm above the knee joint and 10 cm below.The mean value for distance B was 3.9 cm with a range

between 0.4 cm and 13.5 cm.

Discussion

This review ofpopliteal and tibioperoneal arterial vari-ations was stimulated by technical difficulties encounteredduring the performance of arterial reconstruction in two

FIG. 2. Type 11A- 1: the anterior tibial artery arises above the knee jointand has a straight course in its proximal segment. Type I1A-2: the anteriortibial artery arises above the knee joint but takes a medial swing, pre-sumably resulting from its passage anterior to the popliteus muscle. TypeIIB: the posterior tibial artery arises at the level of the knee joint. TypeIIC: the peroneal artery arises above the knee joint.

patients who required femorodistal bypass graft proce-

dures.In the first patient, the distal arterial anastomosis ofan

in situ saphenous vein bypass graft was made to a hypo-plastic posterior tibial artery because it was not recognizedby the surgeon that the posterior tibial distal arterial supplywas from a proximal replaced peroneal artery (Fig. 4).

lll-A3.8%

III-B1.6%

III-C0.2%

FIG. 3. Type IIIA: the posterior tibial artery is hypoplastic and the peronealartery is large. At the ankle, the distal posterior tibial artery is replacedto the peroneal artery. Type IIIB: the anterior tibial artery is hypoplasticand the peroneal artery is large. At the ankle, the dorsalis pedis artery isreplaced to the peroneal artery. Type IIIC: both the anterior tibial arteryand the posterior tibial artery are hypoplastic. At the ankle the dorsalispedis and posterior tibial arteries are replaced to the peroneal artery.

Vol. 2 10 * No. 6

I-A92.2%

I-B2.0%

II-A20.7%

Il-B0.8%

777Il-C<0.2%

KIM, ORRON, AND SKILLMAN

FIG. 4. Diagnostic arteriogram reveals a hypoplastic posterior tibial artery(arrowhead) and a hypertrophied peroneal artery (arrow). At the levelof the ankle, the posterior tibial artery is replaced to the peroneal artery(Type IIIA).

The initial operative arteriogram (Fig. 5) shows extrava-sation because there was no outflow from this anastomoticsite. Faint visualization ofthe peroneal artery can be seenon this film. When this error was recognized, the anas-tomosis was resited to the more medially placed peronealartery, resulting in a strong pulse in the posterior tibialartery at the ankle. A second operative arteriogram showsthis anastomosis (Fig. 5).

In the second patient (type 11-B), the initial distal anas-

tomosis was made erroneously to a common trunk oftheAT-PR whose proximal end was stenotic and whose distaloutflow was occluded at mid calf (Fig. 6). The posteriortibial artery, which supplied solitary run-off to the foot,was thereby excluded from revascularization (Fig. 7). Fivedays later revision to the posterior tibial artery was re-quired because of thrombosis of the graft.

Tables 1 and 2 summarize the frequency of each sub-type of arterial variation in our study and list those re-ported by previous authors using angiography2-4 or limbdissection.5`9 Our classification is a modification of Lip-pert's system.' The two major variants in the poplitealbranching pattern are trifurcation (I-B) and high divisionwith normal branching sequence (II-A). Our proposedclassification includes an additional type of high division(IC). We have excluded variants not involving one of thethree run-off vessels (AT, PR, PT), such as the islandbranch of the popliteal artery described by Adachi6 andincluded in Lippert's system. We have followed Lippert'ssystem of dividing the variants into those with normallevel of division (I) and those involving a high division(II). Variants grouped into category III possess a normalbranching pattern and sequence but involve a criticalvariation in arterial supply to the foot that can be predictedby observing the popliteal region even if visualization ofthe distal run-off is suboptimal. For this reason we in-

FIG. 5. Initial operative arteriogram (left) obtained following distal anas-

tomosis to the hypoplastic posterior tibial artery (arrowhead). The pe-

roneal artery is opacified (arrow). There is extravasation of contrast about

the anastomosis. Second operative arteriogram (right) shows revision to

hypertrophied replaced peroneal artery.

778 Ann. Surg. - December 1989

POPLITEAL ARTERY VARIANTS 779

5.9 and 3.7 cm in his review of246 extremity angiograms.3Bardsley found no correlation between the length of thetibia and the level of branching of the popliteal artery.4The tibioperoneal artery terminates at the point wherethe peroneal artery originates. The latter courses downthe interosseous membrane to end slightly above the anklein a mustache configuration, composed of the commu-nicating branch to the PT and the perforating branch tothe AT. The posterior tibial artery runs down the posteriorcalf and terminates at the level of the calcaneus by bifur-cating into the medial and lateral tarsal arteries. The DPand PT supply the foot arcades, and there are multiplecommunications at these levels, as well as multiple vari-ations.9The reader is referred to the detailed work of Senior'0

for review of the embryologic development of the usualand variant patterns. Briefly, the lower extremity vesselsarise from two sources: the primary limb bud artery (axialor sciatic artery, a branch of the umbilical artery), andthe femoral artery. By the 14-mm embryonic stage, thefemoral artery has grown into the thigh and joined thesciatic artery at the level of the adductor canal. Devel-opment of the run-off vessels is complete by the end ofthe third month. The popliteal and PR arise from thesciatic artery, whereas the AT and PT derive from thefemoral system.

Type I-B: trifurcation. The AT, PR, and PT arise inclose proximity posterior to the inferior border ofthe pop-liteus muscle. We have followed the criteria of Adachiwherein a trifurcation is described only if the common

FIG. 6. Operative arteriogram obtained after the distal anastomosis to acommon trunk of the anterior tibial and peroneal arteries distal to theorigin of the posterior tibial artery.

cluded category III to provide a unified system that webelieve will be of greater clinical relevance to vascularsurgeons. These three categories are described more fullybelow.

Category I

Type I-A: usual pattern. The popliteal artery posteriorlydivides to the inferior border of the popliteus muscle bygiving offthe anterior tibial artery, which courses laterallytoward the fibula before running down the calf to ter-minate as the dorsalis pedis artery. In our study the meandistance between the medial tibial plateau and the originof the AT is 6 cm. The subsequent segment of the mainartery is known as the tibioperoneal trunk, which averaged3.9 cm in our study. Morris determined mean values of

FIG. 7. Diagnostic arteriogram reveals the posterior tibial artery (arrow-head) arising from the popliteal artery at the knee joint (Type IIB). Thereis a significant stenosis ofthe popliteal artery at the origin ofthe posteriortibial artery. The anterior tibial and peroneal arteries are occluded prox-imally.

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KIM, ORRON, AND SKILLMAN Ann. Surg. . December 1989

TABLE 1. Frequency of Type I and Type II Popliteal Arterial Variations (Figs. 1 and 2)

Extremities IA IB IC IIA- I IIA-2 IIB IICAuthor Source Examined (%) (%) (%) (%) (%) (%) (%)

Kim, Orron Angiography 605 92.6 2 1.2 3 0.7 0.8 <0.2Mauro, 1988 Angiography 343 88 4.1 1.2 2.3 0.9Morris, 1961 Angiography 246 88.6 2.9 1.2 3.6 - 0.8Bardsley, 1970 Angiography 235 92.8 0.4 4.2 1.7Quain, 1844 Dissection 258 90.3 2.3 6.6 0.8Adachi, 1928 Dissection 770 96 0.8 0.5 0.9 1 0.8Trotter, 1940 Dissection 1168 93.4 0.5 1.3 1.5 2.4 1.4Keen, 1961 Dissection 280 90.7 4.3 0.4 3.6 0.4 1.1Lippert, 1985 Dissection 90 4 1 3 1 1

-, no information available.

trunk following the origin of the first branch is less thanor equal to 0.5 cm in length.6 Morris found an incidenceof 2.9% using these criteria.3 However they also found an

incidence of 2.9% of common trunks measuring more

than 0.5 cm but less than 1 cm. Although the criteria ofAdachi are anatomically more precise, it may well be thatMorris' notion presents greater practical clinical use tothe surgeon pondering potential sites for distal anasto-mosis.

Type I-C. anterior tibial-peroneal trunk. The PT is thefirst branch. The anterior tibioperoneal trunk bifurcatesinto the PR and PT. An incident reflecting the clinicalsignificance of this variation was described above.

Category II: High Division ofthe Popliteal ArteryAnatomists consider division to be high if it occurs

proximal to the inferior border of the popliteus muscle(PM). Because this level can not be determined angio-graphically, we used the superior edge ofthe medial tibialplateau as our cut-off point. In Table 1 we have excludedthe cases reported in the anatomic studies in which di-vision occurred between the superior and inferior bordersof the PM. We have, therefore, assumed an equivalenceof the superior border of the PM and the superior borderof the medial tibial plateau because the anatomists didnot consider the latter in their determinations.

Type II-A: AT arises at or above the knee joint. This isconsistently the most frequent type of high division.

TABLE 2. Frequency of Type III Popliteal Arterial Variations (Fig. 3)

Extremities IIIA IIIB IIICAuthor Source Examined (%) (%) (%)

Kim, Orron Angiography 495 3.8 1.6 0.2Mauro, 1988 Angiography 343 2.3Bardsley, 1970 Angiography 235 0.9 -

Adachi, 1928 Dissection 1239 - 7.1Huber, 1940 Dissection 200 - 3Keen, 1961 Dissection 280 2.5 5Lippert, 1985 Dissection 5 6

-, no information available.

Anatomists have described two subtypes. In the first (II-Al), the AT courses posteriorly to the PM; in the second(II-A2), the AT courses anteriorly to the PM. A review ofsketches by Adachi reveals that in II-A2 the initial courseof the AT takes a medial swing before crossing anteriorlyto the pM.6 We postulate this medial swing to be theresult ofthe anterior course, and we found four such cases

in our series.

Type IH-B: PT arises at or above the knee joint. This isthe correlative ofType I-C, differing in that the PT ariseshigh. As in Type I-C, an anterior tibioperoneal trunk isformed.

Type IH-C: PR arises at or above the knee joint. Thispattern was observed in a single case. The PR arose abovethe knee. A short (1.3 cm) anterior-posterior tibial trunkensued. To our knowledge this variant has not been pre-viously reported (Fig. 8).

Category III

The peroneal artery normally terminates into smallbranches that communicate with the AT and PT at thelevel ofthe ankle joint. In instances in which the proximalsegments of the AT or PT are congenitally absent or hy-poplastic, the respective branch of the PR will directlysupply the distal distribution of the AT (the DP) or PT,which can, therefore, be considered replaced to the PR.In all our cases in this category, the pattern at the footcould be predicted by observing the area of the poplitealbifurcation because the hypoplastic or absent vessel was

evident along with a concomitant increased caliber oftheproximal PR. In the presence of this finding it is essentialthat the distal run-off is adequately demonstrated withparticular attention paid to the nature of supply to theDP and PT at the ankle. Caution must be used to differ-entiate this phenomenon from atherosclerotic occlusivedisease of the AT or PT, with the hypertrophied PR col-lateralizing the distal AT or PT. The presence of gradualtapering of the hypoplastic artery, the lack of collateralreconstitution distally, and a straight, nonundulating ap-pearance ofthe distal segment of the PR reaching the DP

780

Vol. 210 . No.6 POPLITEAL ARTERY VARIANTS 781

4.~..

-I d

FIG. 8. Type IIC. The peroneal artery arises from the popliteal artery atthe knee joint.

or distal PT favor against atherosclerosis. In instances ofcollateral reconstitution, there will be a transitional ta-pering at the junction between the PR and the DP or PT.

Type III-A: hypoplastic-absent PT, distal PT replacedto PR. A clinical example of this variation has been de-tailed above. Bardsley proposed that this variant "repre-sents disappearance ofthe normally retained distal femoralartery with the sciatica persisting as an enlarged peronealbranch."'

Type Ill-B: hypoplastic-absent AT, DP replaced to PR.Our frequency of 1.6% is the lowest of the reported series

(3.0% to 7.1%). Cases of these variants have been re-ported. "

Type III-C. hypoplastic-absent AT and PT, both re-placed to PR. In this case, the distal distribution of bothvessels is supplied by the PR. We found a single previousreport of this variant in the radiologic literature.'2 Seniordescribed it as the Artery Saphena Magna, or the PeroneaMagna.'°

In Keen's study there was no right-left predominanceof variants.8 He did find bilaterality in 27.5% of his vari-ants. These factors were not considered in our study be-cause in too many cases either a single extremity wasstudied or only one provided adequate opacification ofthe areas of interest. Trotter demonstrated a slight racialbut no sexual variation.7Our statistical findings agree with those of the other

angiographic studies.2'3'4 There appears to be greater vari-ation described in the anatomic studies in comparison tothose that analyze angiographic data. Authors of otherangiographic studies did not include incidence figures forsubtypes we found in Type III, but either grouped themtogether2 or included only one of the three types.3'4 Webelieve that the completeness offered by our system isjustified clinically by the increasing number of distal an-gioplasties and femorotibial arterial bypass grafts beingperformed.

Awareness of these popliteal arterial variants is impor-tant for those performing surgical or percutaneous vas-cular reconstruction in the lower extremity. We proposethe modification of Lippert's system as a more practicalguide to the clinically significant arterial variants in thisfrequently studied anatomic area.

References1. Lippert H, Pabst R. Arterial variations in man: classification and

frequency. Munchen: J.F. Bergmann Verlag, 1985.2. Mauro MA, Jacques PF, Moore M. The popliteal artery and its

branches: embryological basis of normal and variant anatomy.AJR 1988; 150:435-37.

3. Morris GC, Beall AC, Berry WB, et al. Anatomical studies of thedistal popliteal artery and its branches. Surg Forum 1961; 10:498-502.

4. Bardsley JL, Staple TW. Variations in branching of the poplitealartery. Radiology 1970; 94:581-87.

5. Quain R. The anatomy of the arteries of the human body. London:Taylor & Walter, 1844.

6. Adachi B. Das arteriensystem der Japaner, Vol. II, Kyoto: Maruzen1928.

7. Trotter M. The level of termination of the popliteal artery in thewhite and the negro. Am J Phys Anthropol 1940; 27:109-18.

8. Keen JA. A study of the arterial variations in the limbs with specialreference to symmetry of vascular patterns. Am J Anat 1961;108:245-61.

9. Huber JF. The arterial network supplying the dorsum of the foot.Anat Rec 1941; 80:373-91.

10. Senior HD. The development of the arteries of the human lowerextremity. Am J Anat 1919; 25:55-94.

11. Sackler JP, Abrams RM, Beranbaum ER. Congenital absence oftheanterior tibial artery. Angiology 1968; 19(2):67-74.

12. Zwass A. A case report of anomalous branching of the poplitealartery. Angiology 1986; 37:132-35.