A study of radiographs from 50 males and 50 females was undertaken
to determine whether a relationship existed between the proximal articular
set angle and the hallux abductus angle. Gender differences in the
relationship were also investigated. The normal range for the proximal
articular set angle was –2.6° to 8.6°, with a mean of 5°. There was no
significant difference in the mean values between males and females. A
positive linear correlation between the proximal articular set angle and
hallux abducto valgus deformity was found (R2 = 0.52), suggesting that
an increased lateral tilt of the metatarsal head is one of the factors that
lead to hallux abducto valgus deformity. The relationship between proximal
articular set angle and hallux abducto valgus deformity was similar
in males and females and did not account for the increased hallux deformity
seen in females

Ferrari, J.

Malone-Lee, James

UEL Research Repository at University of East London

  University of East London Institutional Repository: http://roar.uel.ac.uk   This paper is made available online in accordance with publisher policies. Please scroll down to view the document itself. Please refer to the repository record for this item and our policy information available from the repository home page for further information.  Author(s): Ferrari, Jill; Malone-Lee, James Article title: Relationship Between Proximal Articular Set Angle and Hallux Abducto Valgus Year of publication: 2002 Citation: Ferrari, J. and Malone-Lee, J. (2002) ‘Relationship Between Proximal Articular Set Angle and Hallux Abducto Valgus’ Journal of the American Podiatric Medical Association 92 (6) 331-335 Link to published version: http://www.japmaonline.org/cgi/content/full/92/6/331  Journal of the American Podiatric Medical Association • Vol 92 • No 6 • June 2002 331The proximal articular set angle is described as “theangle formed between a line representing the effec-tive articular surface of the first metatarsal head anda perpendicular to a line representing the bisectionof the shaft of the first metatarsal” (Fig. 1).1Laporta et al1 describe the relationship betweenhallux abducto valgus and the proximal articular setangle, stating that in the normal adult foot the proxi-mal articular set angle is 0° to 8° and is tilted laterallyto account for the 0° to 8° adduction of the first meta-tarsal. The source of the normal range of angles quot-ed and whether the relationship between the angleshas been tested are unclear from the study. Despitethis, the authors describe various types of operationsthat address these abnormal angles when found witha hallux abducto valgus deformity. Other authorshave also measured the angle in adult feet. In onestudy of 41 radiographs of women,2 the proximal ar-ticular set angle ranged from 0° to 15°. Another study3found a mean proximal articular set angle of 6°(range, –3° to 26°) in 100 cadavers.The reliability of the proximal articular set anglemeasurement has been studied frequently. The radio-graphic measurement of the proximal articular setangle has been found to differ in value from the intra-operative measurement,4, 5 although a significant pos-itive correlation existed between the measurements(r = 0.6, P < .05).5 A difference between the radio-graphic and intraoperative measurements is not sur-prising, as the radiograph does not show the sagittalplane deviation of the metatarsal and phalanx, and,therefore, the curve of the metatarsal seen may rep-resent the curve across any part of the metatarsalhead. For example, if the metatarsal is in a plan-tarflexed position, the dorsal edge of the metatarsalhead will be seen in the anteroposterior radiograph.If the metatarsal is dorsiflexed, the curve across thecentral area or the plantar edge of the head will beseen. When measuring the curve intraoperatively, theobserver can take the reading at any chosen point,which will not necessarily correspond to the samepoint on the radiograph. It has been found that thesagittal plane deviation does not influence the radio-Relationship Between ProximalArticular Set Angle and HalluxAbducto ValgusJill Ferrari, BSc(Hons), MChS, SRCh*James Malone-Lee, MD, FRCP†A study of radiographs from 50 males and 50 females was undertakento determine whether a relationship existed between the proximal artic-ular set angle and the hallux abductus angle. Gender differences in therelationship were also investigated. The normal range for the proximalarticular set angle was –2.6° to 8.6°, with a mean of 5°. There was nosignificant difference in the mean values between males and females. Apositive linear correlation between the proximal articular set angle andhallux abducto valgus deformity was found (R 2 = 0.52), suggesting thatan increased lateral tilt of the metatarsal head is one of the factors thatlead to hallux abducto valgus deformity. The relationship between prox-imal articular set angle and hallux abducto valgus deformity was similarin males and females and did not account for the increased hallux de-formity seen in females. (J Am Podiatr Med Assoc 92(6): 331-335, 2002)*Research Fellow/Lecturer, Department of Podiatry, Uni-versity College London, 33 Fitzroy Square, London W1T 6AY,England.†Professor, Department of Medicine, Whittington Hospi-tal, London, England.332 June 2002 • Vol 92 • No 6 • Journal of the American Podiatric Medical Associationgraphic findings as much as the varus or valgus rota-tion of the metatarsal.6 In a cadaver study,6 it wasfound that the usual method of measuring radio-graphs was not sensitive to the rotation of the meta-tarsal, although the radiographic measurement had a95% probability of being within 5° of the true mea-surement. When measuring intraoperatively, the ob-server can identify the medial and lateral borders ofthe bone and therefore can measure the true trans-verse curvature. On radiographs, the medial and lat-eral borders may be incorrectly identified becausethe rotation of the bone is difficult to assess, and thecurvature measured will be different. One study3 hasreported that the typical method of measuring theproximal articular set angle produces angles that arewithin 5° of those produced by a method that addsmetal beads to aid identification of the medial andlateral edges of the articular surface on x-rays.The intraobserver and interobserver reproducibili-ty of the measurements has been tested, with varyingresults. There seems to be difficulty in establishingwhich part of the joint surface represents the effec-tive articular surface for some observers but not forothers.7 There is particular difficulty in measuring anarticular surface on radiographs, because these showonly bone and not articular cartilage. Vittetoe et al6found that differences in identifying the articular sur-face led to good intraobserver reliability but poor in-terobserver results. Conversely, another study4 re-ported good interobserver measures. In one of thelargest interobserver tests, 300 practitioners mea-sured a single x-ray.8 A wide variation in measuringcapabilities was reported, but the data were not ana-lyzed in such a way as to prove or disprove a null hy-pothesis; only trends in the results were considered.Despite the considerable work undertaken to testthe reliability of the measurement technique, the re-lationship between the proximal articular set angleand the hallux abductus angle has not been studied,to the authors’ knowledge. This experiment aimed toidentify whether a relationship exists between theproximal articular set angle and hallux abducto val-gus deformity and to investigate gender differencesin this relationship. Because the interobserver mea-surement of the angle seems to be suboptimal, onlyintraobserver data were used.Materials and MethodsOne hundred radiographs were selected from thecollection held at the London Foot Hospital in Lon-don, England. All radiographs had been taken at theRoyal National Orthopaedic Hospital in London,which uses a standard procedure of placing the beamat 15° to the navicular, 100 cm from the foot. Weight-bearing views from 50 males and 50 females were se-lected. All patients were younger than 40 years andwere in good general health to reduce the likelihoodof distortion of the image by arthritic changes. Eachradiograph was then digitized and analyzed usingOSIRIS software (University Hospital of Geneva, Ge-neva, Switzerland).On the digitized image, a line was drawn from themedial to the lateral side of the articular surface ofthe metatarsal head, establishing the parameters ofthe effective articular surfaces. A second line wasdrawn from the medial to the lateral side of the baseof the metatarsal. The center of this line was foundand used to anchor a line bisection that was placedalong the shaft of the metatarsal (Fig. 2). The shaft ofthe proximal phalanx was also bisected.The angle between the articular surface and themetatarsal bisection line was calculated as the proxi-mal articular set angle. The angle between the meta-tarsal and phalanx bisection lines was the hallux ab-ductus angle. Each radiograph was measured fivetimes, and the mean of the measurements was usedin the analysis of results. A pilot study had been un-dertaken initially to test the reproducibility of themeasurements and the accuracy of using the five re-peated measurements.ResultsThe characteristics of the male and female sub-groups are given in Table 1. The normal distributionFigure 1. Radiograph showing the line representingthe effective articular surface and the metatarsal bi-section.Journal of the American Podiatric Medical Association • Vol 92 • No 6 • June 2002 333of the data was tested using a one-sample Kolmogo-rov-Smirnov test. Because all data were normally dis-tributed, parametric analysis was applied.The mean proximal articular set angle was 4.52°for males and 5.47° for females. A two-tailed t-testshowed that there was no significant difference inthe proximal articular set angle between males andfemales (P = .27). The hallux abductus angle was sig-nificantly different between the sexes, with the meanangle being 12.95° for males and 18.28° for females(P = .001). The mean proximal articular set angle forsubjects without hallux abducto valgus (ie, with ahallux abductus angle of less than 16°) was 5° (range,–2.6° to 8.6°).Examination of the data shown in Figure 3 sug-gested that a positive correlation existed betweenthe proximal articular set angle and the hallux ab-ductus angle. Regression analysis demonstrated asignificant correlation for the 100 subjects (R 2 = 0.52).There seemed to be little difference in the relation-ship between males and females, and this was con-firmed by the regression coefficients for males (R2 =0.52) and females (R2 = 0.55) (Table 2). Examinationof the raw data suggested a threshold for the proxi-mal articular set angle of 7.6°. In the 27 subjects witha proximal articular set angle greater than 7.6°, only1 had a normal hallux abductus angle. The residualline fit plot suggested that the application of a linearregression plot was suitable (Fig. 4).The relationship between the proximal articularset angle and age was also considered. The scatter-plot shown in Figure 5 suggests that no linear rela-tionship exists. The proximal articular set angle doesnot seem to change with age.DiscussionThe findings from this study agree with those fromearlier studies regarding the normal range for theproximal articular set angle. Laporta et al1 had sug-gested a normal range of 0° to 8°. This study found arange of –2.6° to 8.6° in subjects without hallux ab-ducto valgus deformity. Steel et al2 found values from0° to 15° in their population, which closely mirrorsthe range of –2.6° to 19° found across the group usedin this study. The wide range of –3° to 26° found inthe cadaver study3 was not found here, although themean was similar to that in the present study (6° ver-sus 5°).It was initially hypothesized that if a correlationbetween the proximal articular set angle and halluxabducto valgus deformity did exist, a large hallux ab-ductus angle may cause increased lateral forces onthe metatarsal head and lead to a change in the prox-imal articular set angle over time. This study did notinvestigate progression of the angle over time, but itwas found that the proximal articular set angle andpatient age were not related. However, patient ageFigure 2. Digitized image of a radiograph with line bi-section of the metatarsal shaft and lines across themedial and lateral edges of the articular surface ofthe metatarsal head, creating the proximal articularset angle (92° – 90° = 2°).Table 1. Characteristics of the Male and Female SubgroupsMean (SE) and RangeTotal Number Age (years) Hallux Abductus Angle (°) Proximal Articular Set Angle (°)Males 50 30 (1.00) 12.95 (1.06) 4.52 (0.54)13 to 40 –3 to 28 –2 to 18Females 50 29 (1.19) 18.28 (1.15) 5.47 (0.67)12 to 40 4 to 40 –2 to 19Abbreviation: SE, standard error.334 June 2002 • Vol 92 • No 6 • Journal of the American Podiatric Medical Associationwas limited to 40 years and younger, and any changesin the proximal articular set angle caused by the hal-lux abductus angle may be obvious only in patientswho have had hallux abducto valgus deformity for agreater length of time. A longitudinal study of halluxabducto valgus deformity and the proximal articularset angle is required to study this. The age of the ca-davers used by Richardson et al3 was not given, but,if typical, they were likely to be elderly subjects witha greater range of hallux abducto valgus deformity orlong-standing deformity, which may account for theincreased proximal articular set angles found.ConclusionA significant correlation was found between theproximal articular set angle and the hallux abductusangle. It seems from this study that as the angle of themetatarsal head tilts increasingly to the lateral side,the hallux abductus angle increases. In theory, thiswould not be surprising, as the head of the metatarsalis dictating the direction of the hallux. With lateral de-viation of the hallux, the frequently cited soft-tissueimbalances, such as bowstringing of the long ten-dons, will then bring about further drift of the hallux.9There is no difference in the proximal articular setangle between males and females, and the correla-tion between the proximal articular set angle and thehallux abductus angle does not vary by gender. Theproximal articular set angle may therefore be consid-ered to be associated with hallux abducto valgus de-formity, but it does not account for the high preva-lence of the deformity in females.10 Hallux abductovalgus has frequently been thought to be multifacto-rial, and this study supports such a hypothesis.References1. LAPORTA G, MELILLO T, OLINSKY D: X-ray evaluation ofhallux abducto valgus deformity. JAPA 64: 544, 1974.2. STEEL MW, JOHNSON KA, DEWITZ MA, ET AL: Radiographicmeasurements of the normal adult foot. Foot Ankle 1:151, 1980.3. RICHARDSON EG, GRAVES SC, MCCLURE JT, ET AL: Firstmetatarsal head-shaft angle: a method of determina-Figure 3. Scatterplot showing the correlation betweenthe hallux abductus angle and the proximal articularset angle for males and females.Table 2. Regression Analysis DataAll 100 Subjects 50 Females 50 MalesR 0.72 0.74 0.72R 2 0.52 0.55 0.52R 2 adjusted 0.52 0.54 0.51SE 5.68 5.48 5.25P value <.05 <.05 <.05Abbreviation: SE, standard error.Figure 4. Residual plot for the proximal articular setangle correlation.Figure 5. Scatterplot showing the relationship be-tween the proximal articular set angle and age for all100 subjects.Hallux Abductus Angle (°)45 -40 -35 -30 -25 -20 -15 -10 -5 -0 -–5 -–10 -–5              0                5              10              15              20Proximal Articular Set Angle (°)Males         FemalesResidual (°)20 -15 -10 -5 -0 -–5 -–10 -–15 -–20 -–5              0                5              10              15              20Proximal Articular Set Angle (°)Age (years)45 -40 -35 -30 -25 -20 -15 -10 -5 -0 -–5         0           5          10         15        20       25       30Proximal Articular Set Angle (°)R 2 = 0.0003R 2 = 0.52R 2 = 0.011Journal of the American Podiatric Medical Association • Vol 92 • No 6 • June 2002 335tion. Foot Ankle 14: 181, 1993.4. EVANS RDL, LILE LN: Proximal articular set angle: ra-diographic versus intraoperative measurement. JAPMA90: 199, 2000.5. AMARNEK DL, MOLLICA A, JACOBS AM, ET AL: A statisticalanalysis on the reliability of the proximal articular setangle. J Foot Surg 25: 39, 1986.6. VITTETOE DA, SALTZMAN CL, KREIG JC, ET AL: Validity andreliability of the distal metatarsal articular angle. FootAnkle Int 15: 541, 1994.7. PALLADINO SJ, TOWFIGH A: Intra-evaluator variability inthe measurement of proximal articular set angle. J FootSurg 31: 120, 1992.8. FOX HR, FIRSHEIN DB: Variation in practitioner-mea-sured x-ray angles in hallux abductovalgus evaluation.J Foot Surg 28: 33, 1989.9. PHILLIPS D: “Biomechanics,” in Hallux Valgus and Fore-foot Surgery, ed by VJ Hetherington, p 39, Churchill Living-stone, New York, 1994.10. GOULD N, SCHNEIDER W, ASHIKAGA T: Epidemiologicalsurvey of foot problems in the continental United States1978-1979. Foot Ankle 1: 8, 1980.

Relationship Between Proximal Articular Set Angle and Hallux Abducto Valgus

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Relationship Between Proximal Articular Set Angle and Hallux Abducto Valgus

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