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					                        RADIOGRAPHIC                                                     FEATURES                                        OF NEONATAL                                                              CONGENITAL
                                                                                       DISLOCATION                                         OF THE HIP

                                                                                  P. BERTOL.                       M.     F. MACNICOL.                         G.      P. MITCHELL

         Frotn           the      Departnent                     of     Orthopaedic                      Surgery,             Princess               Margaret                   Rose            Ort/iopaedic                             Hospital,                         Edinburgh

                    Over                 the 10-year     period                        1969 to 1978,                    271 consecutive                   cases           of congenital                          dislocation       of the hip were
             diagnosed                    at birth.  Standard                          anteroposterior                     radiographs                   ofthe            pelvis were                          obtained      routinely    and were
             analysed                retrospectively.                       The medial                  gap,       a measure             ofthe          separation                      between                  the proximal                                   femur           and the
             pelvic            wall,        was found                 to be significantly                            increased           in    cases with                   unilateral                        or bilateral                          dislocation                        when
             compared    to normal.      A medial      gap greater   than five millimetres        is indicative       offemoral     head displacement
             and is of value where        the clinical     diagnosis    is uncertain.
                   The rate of missed      dislocation     at birth was 0.6 cases per thousand.                 Treatment       with the Malmo      splint
             was the normal     routine.    The Pavlik       harness   was applied    ifsplintage        was poorly tolerated          by the infant,     or
             in the rare                 instance             oflimited             hip abduction.                       Failure         to maintain                  reduction                       by splintage                        occurred                  in 3.3 per
             cent. The                 incidence            of pressure    deformities     ofthe   femoral                                              head         was 2.95                      per cent and there                                          was a residual
             deformity                  in later         childhood      of 1 . 1 per cent. It is presumed                                                that       this lesion                     can be attributed                                           to the effect                   of
             splintage                 and  it was notably                               avoided              in the         latter       period               of the             review                 when             greater                         mobility                   of the
             abducted                  hips was encouraged.

        The         successful  outcome     of conservatively                                                        managed                  equivocal                  the         presence     of a hip    standing    out” laterally  “

dislocation              of the   hip   depends       upon                                                an         accurate                 is accepted                       as     an indication       to splint   the infant.     The
screening                 of       all       infants            and          appropriate                      splintage             if        Malmo                splint             is employed                            in the                   majority                      (von              Rosen
instability               of the            hip       can       be      demonstrated                          (von        Rosen               1962,            1970;             Mitchell                     1972)           and                 is retained                      for       a total             of
1962,     1970;     Barlow     1962;                                   Mitchell    1972).                       The initial                   three     months.                         The             Pavlik             harness                              is used                in the few
detection       of the dislocatable                                     or dislocated                         hip is often                    instances      when                        the           infant            or mother                                tolerate               the splint
the        responsibility                      of       the      paediatrician.                        All       suspected                    poorly,              or in the                  occasional                       case                 were            abduction                         of the
cases should                    however               be reported       to and examined                                    by an              hips       is found                 to be limited.                          Rarely                      is the              harness                applied
orthopaedic                      surgeon               with     special     experience                                   in this              after          the      initial               three             months                 of splintage.
condition.             Radiographs have been        considered      by some                                                                                                           MATERIALS                              AND                  METHOD
authors             to be of use    in establishing           the diagnosis                                                                   All      27 1 cases           of clinically                 diagnosed                congenital                      dislocation                  of the           hip
(Andren              and von Rosen    1958;     Fell#{228}nder, Gladnikoff                                                                    were        reviewed                   over          the         period              1969                   to       1978            inclusive,                  thus
and        Jacobsson                      1970;     Fredensborg                           1976)   but others                                  complementing                      an earlier              study         of consecutive                            cases       over         a seven-year
have         felt    that                 the   radiograph                         offered      no precision                                  period         (Mitchell               1972).           During           the      10 ears                        of this      later         review         there
                                                                                                                                              were      44 953           live     births,           all infants              being            subjected                   to routine                neonatal
(Barlow               1962;              MacKenzie                    1972;            Smaill           1968).
                                                                                                                                              examination                of the         hips.         The        presence               of an exit                  clunk.          representing                       a
        In        Edinburgh          the policy      has been     to obtain      a                                                            dislocatable               hip.        or an entrance                     clunk.            representing                        a dislocated                     hip.
standard             anteroposterior          radiograph      of     the  pelvis                                                              was      noted        and         was         used         as the         criterion                   for        inclusion             in this          study.
whenever              the hip is considered           to be unstable     by the                                                                        Neonatal                 radiographs                    (233)           were                 reviewed                 and          two         specific
paediatric               resident.                The         film     is obtained                    using        a 40-inch                  measurements                      made:           the           medial          gap”            .    representing                     the      distance                 in
                                                                                                                                              millimetres             between                the      calcar       of the            femur                and       the      lateral          pelvic           wall
focal distance,                    with the machine                               centred             over the             pelvis
                                                                                                                                              at that level           (Fig.    I): and the “superior                                     gap” representing                                 the distance
and the legs                     held parallel   and                             in slight            traction             by an              in millimetres              between     the uppermost                                     edge of the proximal                                  femur    and
experienced                     radiographer.                         An      abduction              radiograph                     is        a horizontal               line        passing             through             the        triradiate                  cartilage               (Fig.        I).
not obtained.                    The orthopaedic                             surgeon             is called    upon                 to                  Thirty-eight                   radiographs                   were            excluded                      because                 rotation             was
review           all suspicious                     hips       and         the     radiograph                   is assessed                   evident     from    asymmetry        of the obturator                                                    foramina.                    but in none      of
                                                                                                                                              these   cases    was there    a later dislocation                                                   after splintage.                    Hence  a total
only after clinical     examination.                                          Lateral             displacement                     of
                                                                                                                                              of 233         radiographs                were           reviewed.               Similar                 measurements                          were        taken
the proximal     femur,     while    not                                    diagnostic               of dislocation,                          from           120      radiographs                        of      newborn                  infants                   examined                    for      other
is nevertheless                   considered       to be an indication                                       of possible                      conditions            or where          evidencefl()     of hip                                     instability              could           be detected.
instability.                   In cases      where     the  clinical                                      findings       are                  The results             were   compared        statistically.

P. Bertol,         MD.           Hospital      S Vincente       Dc Paulo.      Passo     Fundo.       Brazil.
M. F. Macnicol.                    BSc. MChOrth.          FRCSEd(Orth).             Senior      Lecturer                                  Princess      Margaret       Rose                           Orthopaedic                    Hospital.
G. P. Mitchell.                 ,l(,      FRCSEd.      Consultant       Orthopaedic         Surgeon                                       Fairmilehead.          Edinburgh                              EHIO      7ED.                Scotland.
Requests          for     reprints           should         he sent         to    Mr     M.     F. Macnicol.
01982          British          Editorial           Society          of Bone           and    Joint      Surgery          03()l-620Xi82/2025-0176                                     S2.00

176                                                                                                                                                                                      THE           JOURNAL                     OF         BONE               AND         JOINT              SURGERY
                                                RADIOGRAPHIC                    FEATURES                 OF     NEONATAL                       CONGENITAL                       DISLOCATION                                OF      THE               HIP                                                  177

                                                                                                                                                          Later         radiographs                      (271)         were         taken                 up     to      an       average           of    28.4
                                                                                                                                                months            (range:          16-      108          months)            and       this       allowed                 an assessment                   of hip
                                                                                                                                                development.                  The         age        at which              the     ossific            nucleus             became             visible       was
                                                                                                                                                estimated            by using            radiographs                    taken        immediately                         before        and       after      the
                                                                                                                                                appearance                  of the         femoral               capital           epiphysis.                    the      mean         age      between
                                                                                                                                                these       two      recorded              dates           being        assumed              to be the                  time       of radiographic
                                                                                                                                                opacification.                Any         asymmetry                    in the       size         or quality                of the epiphysis,                   or
                                                                                                                                                evidence            of growth               plate           arrest,          was       noted.

                                                                                                                                                Table              I lists          the          number                      of live                  births                  in consecutive
                                                                                                                                                years           from          1 969            to 1 978.                The          rate             of clinical                    diagnosis               of
                                                                                                                                                congenital                 dislocation                              made    within   the                                first        week     of life
                                                                                                                                                was 6.02                per thousand                                live births,   while                                 the        incidence       of
                                                                                                                                                missed              dislocation       over this period                                                         was            0.60          cases          per
                                                                                                                                                thousand.                  Unilateral      dislocation                                                         was             six          times            as
                                                             Fig. I                                                                             common                   on        the          left        side           as on             the               right.
The medial          gap is a measure             of the distance        between       the most medial                                                       The         medial       gap (Fig.    1) was found       to be approxi-
portion      of the proximal           femur       and a line drawn         perpendicularly            to the
                                                                                                                                                mately               four      millimetres     on the left or right          sides  in
lateral     edge of the ischium.               The superior         gap is the distance            between
the most superior              portion      of the proximal          femur    and a horizontal             line                                 normal                 infants        (Table   II).   By   contrast,      values    of
passing       through        the triradiate         cartilages.     A right-sided         dislocation          is
illustrated        with     an increased           medial       gap of eight      millimetres          and a
                                                                                                                                                5.9±1.5,                      5.5±1.5                        and           6.2±1.4                               millimetres                           were
                       decreased        superior         gap of six millimetres.                                                                obtained                    in left-sided,                            right-sided                              and bilateral                           cases

                              Table       I. Details            of hips       notified          at the      Simpson                Maternity             Unit       from        1969            to       1978         inclusive

                                                           Number                                                                                  Deformity                             proximal                          Surgkal        reduction
                                                               of                                                     Missed                             of                               frmoral                           required         despite
                                      Year                  births              Dislocations                    dislocations                       epiphysis                             deformity                                 splintage

                                      1969                     4544                        27                                 6                                                                      1                                           1

                                      1970                     4902                        19                                 1                              1*

                                      1971                     5071                        54                                 3                              1                                       1                                           I

                                      1972                     4470                        14                                 5                             1

                                      1973                     4478                        32                                 3                             3’                                       1

                                      1974                     4357                        26                                 4                              1                                                                                   4

                                      1975                     4377                        25                                 2                             1                                                                                    1

                                      1976                     4288                        32                                 1                                                                                                                  2

                                      1977                     4128                        13                                 1

                                      1978                     4338                        29                                 2

                                  Total                     44953                        271                             28                                  8                                       3                                           9

                               Incidence                                                 0.60                           0.06                               2.95                                1.10                                        3.32
                                                                                   per      cent                  per      cent                      per      cent                       per      cent                               per      cent

                              *Associated                 metaphysial          change           in one        case.

                           Table          II.     Value     for medial      and             superior          gaps       in normal                and       dislocated              hips        (expressed                  as mean                   ±        one       standard
                                                  deviation     in millimetres)

                                                                              Control                                             Left   CDH                                                                                            Bilateral                    CDH
                                                                                                                                                                                   Right             CDH
                                                                          L                        R                      L                         R                                                                                        L                                R
                                                                                                                                                                               L                                R
                               Medial            gap                4.1±1.1               4.0±1.2                 5.9±1.5                      4.8±1.3             J    4.8±1.3                          5.5±1.5                   6.2±1.5                            6.2±1.4

                                                                    9.5±0.7                9.5±0.9                7.9±1.7                      8.4±1.8j                 8.6±1.3                          8.0±1.3                   7.0±1.8                             7.2±1.7
                               peri                 gap

                           Figures              derived        from     233      technically             satisfactory               neonatal             radiographs.

VOL.     64-B,     No.   2,     1982
178                                                          P. BERTOL,            M.    F. MACNICOL,           G.   P. MITCHELL

                                                                                                                                                             -         ,   ‘Normal’   ‘    cantralateral           hip
                                                                                                                                                             - -   -   Unilateral          C D H
                                                                                                                                                             -         BiIateralCDH

                                              UI.                                                                                                   Fig.
This   radiograph       was obtained        from an infant     with   bilateral   dislocatable     These     approximation            curves    show the age of appearance         of the capital
hips    and     shows    clearly     widened          medial gaps     of eight     millimetres     epiphysis      radiographically.           The incidence   is expressed      as a percentage
                                           bilaterally.                                            of the total       number        of infants     reviewed, being      I 58 for the unilateral
                                                                                                                            cases     and 1 1 3 for the bilateral      cases.

                                                                                                   Figure       4-A         mild pressure       lesion        of the     left   proximal     femoral
                                                                                                   epiphysis,      with a temporary        epiphysial         cyst evident     on the right.   Figure
                                                                                                                    5-Eight      years    later    left    coxa plana       is evident.

                                                                                                    Figure      6-Epiphysial         and      metaphysial         abnormalities                    of     the    right
                                                                                                    proximal       femur     in a six-month-old           infant.     Figure              7-The            pressure
                                                                                                    lesions    of the right hip are still evident          one year later.                Figure        8-By        the
                                                                                                    age     of six years       the  epiphysis        and     growth      plate              have        recovered

                                                                                                                                 THE     JOURNAL           OF BONE             AND        JOINT         SURGERY
                                                           RADIOGRAPHIC                               FEATURES                     OF      NEONATAL                         CONGENITAL                         DISLOCATION                       OF THE               HIP                                                   179

(Fig.            2)         respectively.                             These                  results                 are       significantly
different                   from             the          normal                   value             (P<0.001)                           and          were
also        statistically                         different                   from             the       contralateral                            “     nor-
mal”     hip                      of infants                     with    unilateral          dislocating                                                hips
(P<0.001                          using   the                  permutation          1-test).      Superior                                               gap
measurements                             are also                    shown             in Table                  II and once                          again
significant                       differences                        were             encountered                     between                            un-
stable         and control                           hips.
            The   age at                            which                  the          upper                 femoral                    epiphysis
appeared                      radiographically                            was                       four     months      for the
clinically                  normal       side                    in unilateral                         cases   of dislocation,
five  months    for the contralateral         dislocated    side,                                                                              and six
months      for the bilateral      cases   (Fig. 3). Normal                                                                                     values
could    not be obtained        since    only      the neonatal                                                                                 radio-
graph             was             available                    for     review.
                                                                                                                                                                            The       Malmo           splint        applied      in a manner                       that permits               movement                of the
            An           epiphysial                       irregularity                        of ossification,                             or pres-                                                                 hips.   avoiding    forced                       abduction.
sure        deformity                        of the              epiphysis,                     occurred                     in eight                 cases
(2.95            per cent)                      that           had         been          splinted.                     In five of these                                     there           is a trend                towards                  delay          in the              appearance                    of the
infants               the         radiographic                             abnormality                         was          transient,                   but                epiphysial                    ossific       centre              on the clinically      abnormal                                           side,
in the remaining                                  three          (1 1 per cent)
                                                                       .                                 mild              coxa          plana          was                 and     hence                    the        centre               is smaller       than    that                                    on         the
still       evident                   on          current                  radiographs                          at the               eight-year                             contralateral                       side           for      some     months                            after              it becomes
follow-up                   (Figs  4 and 5). An associated                                                                     metaphysial                                  visible.      In               clinically                overt   bilateral                           cases              the delay                     is
reaction                 was observed    in two of the cases                                                                with transient                                  somewhat                      greater.
epiphysial                          irregularity                           (Fig.              6).        In           both               instances                                     Treatment                      with          the           Malmo               splint   has                     been        free
recovery                     of        the          growth                    plate            was             considered                         to       be               from         complications                            since           1976              when     a less                    restrictive
complete                    with           little         evidence                   of coxa              vara             or broadening                                    application                     of the splint                  was          ensured.                 The          lower          struts           of
of the femoral                               neck           on the                 current               radiographs                           (Figs           7            the splint should     be loosely     applied     so that the thighs                                                                             are
and 8).                                                                                                                                                                     free to move     forwards      through       an arc of approximately
                                                                                                                                                                            30 degrees                 from the fully abducted                                         position                   (Fig. 9). The
                                                           DISCUSSION                                                                                                       incidence                of pressure  deformities                                        secondary                     to the splint
The      use of radiographs         as an aid in the diagnosis      of                                                                                                      was        approximately                             three            per         cent,              and         of      these          eight
neonatal      congenital    dislocation      of the hip is contro-                                                                                                          cases, five showed        complete                                               recovery.                 In three    cases
versial.    We have found        that a standard    anteroposterior                                                                                                         mild coxa plana    persisted       but                                          in none                of these   cases did
view         of the                  pelvis              with          the          legs            parallel                is of value                     in              arrest          of the           growth               plate          occur.             The            relative            rigidity               of
those         cases where                            the clinical                      diagnosis       is in doubt,     and                                                 the       splint          presumably                         accounts                  for       the        damage                (Salter,
helps         to confirm                           the diagnosis                         in clinically      overt   insta-                                                  Kostuik                 and           Dallas   1969;   Kalamchi                                              and   MacEwen
bility.    A media)     gap                                    of over five                         millimetres   should                                  be                1 980).              In only          nine (3.3 per cent) cases                                            did the splint  fail
considered     suspicious                                       and a value                         of over six millimetres                                                 to reduce    a dislocated      hip after a three-month         period     of
is indicative                       of dislocation                            (Fig.           2). The                 difference                      from                  use. The Pavlik        harness    has been  used where        limitation
the        normal                   value           of approximately                                      four              millimetres                        is           of abduction      of the hip at birth makes       application        of the
highly             significant                      when              analysed                      retrospectively.                                                        Malmo                 splint           hazardous,                    or where                    the splint     is poorly
           Subsequent                          radiographic                          examination   of the infants                                                           tolerated                 by         the child                on       account                   of hyperactivity         or
with       congenital                        dislocation                         of the hip has confirmed      that                                                         rapid           growth.
Our       thanks            are      due        to Dr          Robin             Prescott,            Department                    of Medical                 Computing.                  for     statistical         advice.            Mr     Michael             Devlin            for    the     photographic

reproductions                      and       to     Miss        Elizabeth               Dunn            for      typing            the     manuscript.


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VOL.       64-B,         No.        2. 1982

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