NORMAL RANGES OF HIP MOTION OF INFANTS BETWEEN NINE AND 24 MONTHS OF AGE

Elizabeth Phelps Laura Jo Smith Ann Hallum

Measurement of hip-joint range of motion (ROM) has been used clinically since 1865 to evaluate joint disability (Milch 1959). For infants and children with various orthopedic, neurological or musculo- skeletal disorders, evaluation of joint motion is used to assess the response to therapy, as well as in the diagnosis of muscle and joint pathology.

Children with cerebral palsy, for example, often have abnormal, restricted patterns of movement that may lead to hip contracture, subluxation and/or dis- location (Bleck 1979). According to Sharrard (1975), a progressive limitation of hip extension and abduction may precede hip dislocation. Early detection of this limitation through assessment of passive hip-joint motion at regular intervals directly correlates with the prevention of hip dysplasia (Sharrard 1975, Root 1983). Accuracy of such measurements requires knowledge of the range of motion of normal hips.

An assessment of passive joint motion in young children must take into account the differences between children and adults, since several authors have shown age- related changes (see Table I). Infants' lack of complete hip extension is an example: 46.3" at birth, decreasing to 7" by age six months (Haas et at. 1973, Coon et al. 1975). Reade et at. (1984) report a mean

value of 27" for the popliteal angle in newborns, decreasing to 0" by age 11 months. Normal passive joint ROM in the child's hip beyond six months of age, however, has not been clearly documented. The normal values cited have been taken from investigations of lower-extremity pathology (see Table 111), in which the methods for determining the normal values were vague or unreported.

Base-line data for normal hip ROM in infants beyond six months of age are essential. Clearly documented and clini- cally reproducible methods are necessary to establish standard values for normal range of motion. The purpose of this study was to determine the normal range of hip extension limitation, internal rotation, external rotation and abduction in infants and children at nine, 12,18 and 24 months of age.

Method Subjects Eighty-six healthy infants (44 males, 42 females) from nine to 24 months of age were studied. The sample consisted of four groups: (1) nine months (N=25), (2) 12 months (N=25), (3) 18 months (N=18), and (4) 24 months (N=18). The infants were examined within 3 . 5 days of their respective monthly birthdays. Criteria for inclusion in the study were as follows:

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TABLE I Range of motion studies

~ ~ ~~

Values Exrensr on

IR ER ABD limitation Source Population Instrumentation Position Population (degrees) fdegrees) fdenrees) fdqrees )

Haas et al. N = 400 (1973) Newborns

Birth to 3 days 200 Black 200 White

Coon et 01. N=44 ( 1975) 6 wks-

3 mths N = 4 0 6 mths

Boone and Azen. N = 19 (1979) males

18 mths-5 yrs

Hoffer N=50 (1980) 1-3 days

N=20 12 mths N = l l I S mths

Waugh er al. N =40 (1983) newborns

birth-3 days

Goniometer, protractor

Goniometer. bony landmarks for alignment, stabilization

Goniometer, bony landmarks for alignment

7

Goniometer, bony landmarks for alignment

R-S, hip and knee flexion to 90'. A-same, E-Thomas test

R-P. hip extension, knee flexion to 90". E-Thomas test

R-sitting, hip, knees flexion to 90". A-supine, E-P ?

E-Thomas test

0-3 days 62.0 (range) 35-100

6 wks 24 3 mths 26

6 mths 21 18 mths-5 yrs 5 5 . 0

1-3 days 40-80

12 mths 40-80

15 mths 40-80 0-3 days - (range)

89.1 76.4 45-110 50-90

48 - 45 -

46 - 56, I 59.3

-30-0 -

0-50 -

40-70 - - -

27.9 10-75

19 7

7 7

50-80

20-40

10-25 46 .3

21.7-68, 3

~

*Active arcs of movement; E = extension/extension limitation; R=rotation (internal, external); A = abduction; P=prone; S = supine.

TABLE I1 Normal ranges of hip joint motion for infants from birth to 24 months of age

Age Source Range of motion (degrees)

Extension Internal External limitation rotation rotation Abduction

Newborn 6 wks 3 mths 6 mths 9 mths

12 mths 18 mths 24 mths

Haas et 01. 30 62 89 Coon et al. 19 24 48 Coon et a/. 7 26 45 Coon et al. 7 21 46 Phelps el al. 10 41 56 Phelps et al. 9 44 58 Phelps et al. 4 45 52 Phelps et al. 3 52 47

76 -

- 59 54 59 60

Testing positions: Extension limitation: Thomas test (Coon et al. 1975, Haas el a/. 1973); Staheli test (Phelps et a/. 1985). Internal and external rotation: supine, hi and knee flexion to 90" (Haas et a/. 1973); prone, hips extended, knee &xion to 90" (Coon et a/. 1975, Phelps el a/. 1985). Abduction: supine, hip and knee extensions (Coon et al. 1975, Haas et at. 1973, Phelps et al. 1985). 786

TABLE 111 Range of motion from related studies

Values Extension

IR ER ABD limitation Source Popularion Instrumentation Position Population (dqrees) (degrees) (degrees) (degrees)

Somerville (1957)

Crane (1959)

Alvik (1962)

Engel and Staheli (1974)

Pitcow (1975)

Staheli (1980)

N-50 Estimation adults N=SO children

B = 174 total Roentgenogram 6 mths-9 yrs Estimation N - 1 6 6 m t h s N = l O I yr N = 3X 4 yrs

N = ? ? Younger children Older children

N 7 160 total Gravity, N = 10 0-6 mths goniometer N = 10 6-12 mths N - I 0 I yr N = 10 2 yrs

N =500 total ? 0-10 yrs Suspected LE abnormality and/or gait deviation 0-3 mths 3-6 mths 6-12 mths 12-18 mths 18-24 mths 2-3 yrs N .. '! Goniometer Normal 0-14 yrs

? Adults

Children

R-hip extension

R-Pin hipextension, Younger hip flexion children

R-P in hip extension. knee flexion to 90"

Older

R-S hip and knee flexion to 90" R-P, hip extension, knee flexion to 90"

R-P, hip extension. knee flexion to 90"

No values reported for adults

- - 45 45

Specific values at each age not given. Line graph shows trend from 6 mths t o 9 yrs

- - 65-70 - - - - 60

Specific values of hip rotations not given for each age. Line graph shows trend from 0-14 yrs

Specific values of hip rotations not given for each age. Line graph shows trend from 0- I0 yrs

Mean values for hip rotations in line graph show trend from 0-14 yrs

E = extension/extension limitation; R =rotation (internal. external); A =abduction; P= prone; S =supine.

TABLE IV Ranee of motion test soecifications

Name Po5ition Motion Fulcrum Movable arm Stationary arm

HIP extension limitation

Internal rotation

External rotation

Abduction

Staheli position'. neutral rotation

Prone, hip extended, knee llexed to 90" tibia perpendicular to floor

Same as internal rotation

Supine. hip and knee extended. neutral rotation

Passive movement of LE** superiorly. posteriorly in sagittal plane, until pelvis begins to rotate Passive movement of tibia laterally in transverse plane with knee kept stationary

Passive movement of tibia medially in transverse plane with knee kept stationary

Passive movement of LE laterally in frontal plane

Summet of greater trochanter shaft offemur through

Parallel with lateral

lateral femoral epicondyle

Tibia1 tuberosity Parallel with anterior shaft of tibia through middle of ankle joint

Same as internal rotation rotation

Same as internal

Anterior aspect of hip joint femur through patella

Anterior shaft of

Perpendicular to line between ASIS and PSIS

Perpendicular to floor

Same as internal rotation

Parallel with line between ASlSs

*Prone. both hips flexed comfortably o v e r the end of the examining table with the contralateral limb supported (Staheli 1977). **LE = lower extremity. 78 7

TABLE V Means and standard deviations for hip range of motion

Range of motion 9 mths 12 mths 18 mths 24 mths (degrees) (N = 2s) (N = 2s) (N= It?) (N= 18)

Mean SD Mean SD Mean SD Mean SD Extension limitation 10 2 . 6 9 4 . 8 4 3 . 2 3 3 . 0 Internal rotation 41 7 . 8 44 9 . 1 45 7 . 6 52 10.1

External rotation 56 6 . 6 58 8 . 8 52 8 . 8 47 8 . 5

Abduction 59 7 . 3 54 7 . 5 59 5 . 4 60 7 . 1

TABLE VI Analysis of variance results by agegroup

Source of variation

Extension limitation Between groups Within groups

Internal rotation Between groups Within groups

External rotation Between groups Within groups

Between groups Within groups

Abduction

DF SS F

3 774.76 20.32' 82 1042'22 -

3 1306.67 5.79* 82 6163.94 -

3 1452.34 7.28* 82 5448'90 -

3 510.22 3.50 82 3981.92 -

*p<o.o1

fullterm gestation (37 to 42 weeks); uncomplicated delivery; cephalad presen- tation; no history of trauma to the hip joint; and no known orthopedic, neurological or developmental abnor- malities involving the lower extremities. Infants born by caesarean section were included if no associated complications were reported.

Procedure The range of motion evaluation procedure was conducted in one session at a convenient place for the parents and/or guardians. The infant was undressed from below the waist and depending on the test, was positioned either prone or supine on a firmly padded examination table. The following ROMs were measured: hip extension limitation, internal rotation, external rotation and abduction (see Table IV for the specific infant position, passive 788

movement, and bony landmarks used for each motion assessed).

The right lower-extremity was randomly selected for assessment because there is no significant difference in range of motion between left and right extremities (Haas et al. 1973, Boone and Azen 1979). A hypoallergenic skin pencil was used to denote bony landmarks (see Table IV). All range of motion measurements were taken with a clear plastic goniometer with 180" dial marked in 5" increments.

Examiner A palpated and marked the appropriate bony landmarks to aid in the alignment of the goniometer. Examiner B held the infant in place by placing a hand on the pelvis and/or sacrum and then moved the right lower-extremity through the specific motion until firm resistance was met. The position was held for several seconds to allow the muscles to accommodate to the stretch, and then examiner B gently attempted to move the extremity farther to reach the end-point of the range of motion. Examiner A measured the range and recorded the values. Each motion was measured three times and the mean was calculated.

For each measurement the examiner attempted to maintain the infant's head in mid-line to minimize any possible influence of the asymmetrical tonic neck reflex. Measurements were taken with the infant in a relaxed, awake state-if distress was noted the procedure was suspended until the infant was calmed.

Results Of the 93 infants tested, usable data were obtained from 86 (72 Caucasian, six Black, three Asian and five others). The other seven were eliminated because they did not

meet the inclusion criteria or were too irritable to be evaluated. 44 males and 42 females were tested. The means and standard deviations for hip extension limitation, internal rotation, external rotation and abduction are given in Table V.

Statistical analysis revealed no signifi- cant difference between males and females. Pearson product moment correlation analysis was used to determine any relationship between each of the four hip- motions tested. Results indicated that the infants with the greatest hip extension limitation tended to have more external rotation (r=+0*325, ~ ~ 0 . 0 1 ) and that those with the least hip extension limitation had more abduction range motion (r = -0.23 I , p<O. 05).

The results of a one-way analysis of variance (ANOVA) are given in Table VI. A significant F ratio (pG0.01) was deter- mined for mean ROM values between age- groups for hip extension limitation, internal rotation and external rotation. No significant difference was obtained between the age-groups for mean values of abduction ROM.

Hip extension limitation diminished with age. 100 per cent of the nine- and 12- month-old groups had some degree of hip extension limitation. The percentage of infants with limitation in extension range declined to 89 per cent a t 18 months and to 72 per cent a t 24 months.

Mean values for internal rotation increased with age from 41" at nine months to 52" at 24 months of age. External rotation slightly increased from a mean of 56" at nine months to 58" at 12 months, and decreased to a mean of 47" by 24 months.

All nine-month-olds tested had greater mean values for external rotation than internal rotation, but the percentage decreased with age to 92 per cent a t 12 months, 62 per cent a t 18 months and 39 per cent at 24 months (Fig. 1).

Mean values for abduction changed only 1" from 59" at nine months to 60" at 24 months. The mean value for abduction ROM at 12 months was 54" (Fig. 2).

Discussion The purpose of the study was to report normal values for hip-joint motion in infants which would be accurate and

mean internal rotation 0 mean external

9 12 18 24 Age (months)

Fig. 1. Mean hip internal rotation and external rotation range of motion values in relation to age.

mean abduction

9 1 2 18 24

Age (months)

Fig. 2. Mean hip abduction and extension limitation range of motion values in relation to age.

clinically reproducible. Although one clinician could take the measurement effectively, two investigators were used in this study t o ensure preciseness of measurement.

Given the brief time available for data collection, this study documented normal hip ROM values from a cross-section of infants and children at nine, 12, 18 and 24 months of age. The authors acknowledge that when feasible a longitudinal study is preferred. Individual changes over time in joint ROM may be analyzed as well as documentation for normal values a t particular ages.

The Thomas test* to assess the degree of hip extension limitation has been used in

*For hip flexion contracture: infant is supine and the contralateral hip and knee are flexed to the chest while the evaluated hip is extended in neutral rotation.

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California. (M.A. candidate at Stanford University School of Medicine at time of study.) Laura J o Smith, Physical Therapist, California Stanford, California. Children's Services, Santa Clara County, California. (M.A. candidate at Stanford University School of Medicine at time of study.)

SUMMARY The means and standard deviations were obtained for hip extension limitation, internal rotation, external rotation and abduction at nine, 12, 18 and 24 months of age from a sample of 86 normal, healthy children Statistically significant changes were found for three of the four motions tested. Hip extension limitation decreased from 10' at nine months to 3" at 24 months. At nine months external rotation was greater than internal rotation in all cases, but with increasing age the mean values for the two motions began to approximate each other. There was a statistically significant positive correlation between infants with the greatest hip extension limitation and the degree of external rotation. There was also a significant negative correlation between the least hip extension limitation and greater abduction.

Ann Hallum, Senior Lecturer, Division of Physical Therapy, Stanford University School of Medicine,

*Correspondence to first author at 361 Mendocino Street, Brisbane, CA 94005.

RESUME Variations normales des mouvements de hanche chez le nourrisson, entre neuf et 24 mois d i g e Les moyennes et tcarts-types ont Ctt obtenus pour la limitation des mouvements de hanche concernant I'extension, la rotation interne, la rotation externe et I'abduction, neuf mois, 12, 18 et 24 mois a partir d'un Cchantillon de 86 nourrissons normaux, en bonne santt. Des modifications statistiquement significatives ont Ctt trouvtes pour trois des quatre mouvernents explorts. La limitation de I'extension de hanche dtcroit de 10" i neuf mois, jusqu'a 3" 24 mois. A neuf mois, la rotation externe ttait plus importante que la rotation interne dans tous les cas mais avec I'lge croissant, les moyennes pour les deux mouvements se rapprochent. II y a une corrtlation positive statistiquement significative chez les divers nourrissons entre I'importance de la limitation de I'extension de hanche et le degrC de rotation externe. II y a aussi une corrtlation ntgative significative entre une moindre limitation d'extension de hanche et une plus grande abduction.

ZUSAMMENFASSUNG Normalwerre der Huftbeweglichkeit bei neun und 24 Monate alien Sauglingen Im Alter von neun, 12, 18 und 24 Monaten wurden bei 86 gesunden Kindern die Mittelwerte und Standardabweichungen fur die rnaximale Hiiftstreckung, die Innenrotation, die Aupenrotation und die Abduktion bestimmt. Bei drei der vier getesteten Bewegungen fanden sich signifikante Unterschiede. Die maximale Hiiftstreckung ging von 10" im Alter von neun Monaten auf 3" im Alter von 24 Monaten zuriick. Bei allen Kindern war mit neun Monaten die Aupenrotation groper als die Innenrotation, aber mit zunehmendem Alter glichen sich die Mittelwerte fur diese beiden Bewegungen mehr und mehr einander an. Es fand sich eine statistisch signifikante positive Korrelation zwischen den Kindern mit der gropten maximalen Hiiftstreckung und dem Grad der Aupenrotation. AuPerdem fand sich eine signifikante negative Korrelation zwischen der geringsten maximalen Hiiftstreckung und der groperen Abduktion.

RESUMEN Amplitudes normales de 10s movimientos de la cadera en nifios entre nueve y 24 meses de edad Las desviaciones media y estandar se obtuvieron para la extension limite, rotaci6n interna, rotaci6n externa y abducci6n a 10s nueve, 12, 18 y 24 meses de edad en una muestra de 86 nifios normales y sanos. Estadisticamente se hallaron cambios significativos en tres de 10s cuatro movimientos estudiados. La extension limite de la cadera disminuia de 10" a 10s nueve m e s a a 3" a 10s 24 meses. A 10s nueve meses la rotacidn externa era mayor que la interna en todos 10s casos, pero con la edad 10s valores medios para 10s dos movimientos empezaron a aproximarse entre si. llabia una correlaci6n estadisticamente positiva entre lactantes con la extension limite de la cadera y el grado de rotaci6n externa. Habia tambitn una correlaci6n negativa entre la menor extensi6n limite de la cadera y la abduccibn mayor.

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