Children’s orthopaedics
Obstructive sleep apnoea syndrome in
morbidly obese children with tibia vara
J. E. Gordon,
M. S. Hughes,
K. Shepherd,
D. A. Szymanski,
P. L. Schoenecker,
L. Parker,
E. C. Uong
From St Louis
Shriners Hospital for
Children and St Louis
Children’s Hospital,
St Louis, USA
J. E. Gordon, MD,
Associate Professor
M. S. Hughes, BS
K. Shepherd, MD,
Associate Professor
D. A. Szymanski, RN,
Nurse
P. L. Schoenecker, MD,
Professor, Chief Paediatric
Orthopaedics
Washington School of
Medicine, St. Louis Shriners
Hospital for Children, 2001 S.
Lindbergh Boulevard, St.
Louis, Missouri 63131, USA.
L. Parker, RPSGT
E. C. Uong, MD, Director of
Sleep Diagnostics Lab
St. Louis Children’s Hospital,
One Children’s Place, St.
Louis, Missouri 63110, USA.
Correspondence should be
sent to Dr J. E. Gordon;
e-mail: Gordone@
msnotes.wustl.edu
©2006 British Editorial
Society of Bone and
Joint Surgery
doi:10.1302/0301-620X.88B1.
16918 $2.00
J Bone Joint Surg [Br]
2006;88-B:100-3.
Received 1 July 2005;
Accepted 9 August 2005
100
Morbid obesity and its association with obstructive sleep apnoea syndrome have been
increasingly recognised in children. Orthopaedic surgeons are often the primary medical
contact for older children with tibia vara, which has long been associated with obesity, but
are unfamiliar with the evaluation and treatment of sleep apnoea in children.
We reviewed all children with tibia vara treated surgically at one of our institutions over a
period of five years. Thirty-seven patients were identified; 18 were nine years of age or
older and 13 of these (72%) had morbid obesity and a history of snoring.
Eleven children were diagnosed as having sleep apnoea on polysomnography. The
incidence of this syndrome in the 18 children aged nine years or older with tibia vara, was
61%. All these patients required pre-operative non-invasive positive-pressure ventilation;
tonsillectomy and adenoidectomy were necessary in five (45%). No peri-operative
complications related to the airway occurred.
There is a high incidence of sleep apnoea in morbidly obese patients with tibia vara.
These patients should be screened for snoring and, if present, should be further evaluated
for sleep apnoea before corrective surgery is undertaken.
The prevalence of obesity in childhood (body
mass index (BMI) greater than the 95th percentile) has more than tripled in the past 30
years and now affects one in five.1 Comorbid
conditions include type-2 diabetes, hypertension, hyperlipidaemia, neurocognitive deficits and psychosocial dysfunction.1-3 Tibia
vara is associated with obesity in childhood
and adolescence4-14 and may lead to progressive genu varum and ultimately to degenerative
changes.15-17 Pain associated with tibia vara
can cause problems in the design of regimens
for weight loss. Tibia vara is strongly correlated with morbid obesity in African-American children with a prevalence of 2.5% in that
population.10,18
Obstructive sleep apnoea syndrome is characterised by nocturnal obstruction of the upper
airway leading to snoring, hypoxia and hypercarbia. It has only recently been recognised as a
complication of obesity in children in whom it
has a prevalence of 2%.19-30 When untreated,
sleep apnoea has significant health complications including systemic and pulmonary hypertension,31,32 attention-deficit hyperactivity disorder, behavioural disorders33-35 and stunting
of growth.36 It is also associated with increased
peri-operative anaesthetic complications including difficulty with intubation and acute respi-
ratory failure during the induction of anaesthesia. Post-operative complications include
hypoxia, airway oedema, obstruction of the
upper airway, pulmonary oedema and respiratory failure.31,37-47 Diagnosis may be difficult
and polysomnography remains the technique
of choice.37 The severe complications of sleep
apnoea in childhood require physicians to have
a high index of suspicion. Few orthopaedic
surgeons have formal training in the diagnosis
of sleep disorders in children.
Our aim was to report the incidence and
symptoms, and discuss the management of
sleep apnoea in a series of obese children with
tibia vara.
Patients and Methods
We reviewed 37 consecutive patients with tibia
vara who had undergone surgical treatment
between 1 January 1998 and 31 December
2002. This included 18 patients who were nine
years of age or older at the time of evaluation.
None had previously been diagnosed with a
disorder of sleep or breathing. A total of 13
patients (eight boys and five girls) were morbidly obese with a BMI greater than the 95th
percentile for age and had a history of snoring.
Of the 13, 12 were of African-American origin
and their mean age at presentation was 12.7
THE JOURNAL OF BONE AND JOINT SURGERY
OBSTRUCTIVE SLEEP APNOEA SYNDROME IN MORBIDLY OBESE CHILDREN WITH TIBIA VARA
years (10 to 16). Their mean weight was 142 kg (102 to
188). Eleven had juvenile tibia vara (age of onset 3 to 10
years) and two had adolescent tibia vara (age of onset 11
years or older).12,48 Each underwent a detailed sleep history, with questions to both the children and their parents
regarding snoring, mouth breathing, enuresis, daytime
somnolence and witnessed apnoeic events. Physical examination included measurement of the circumference of the
neck, oropharyngeal examination for tonsillar enlargement
and lateral neck radiography to evaluate the adenoids.
Height, weight and BMI measurements were also obtained.
Polysomnographic assessment. A standard overnight multichannel polysomnographic evaluation was performed.
No drugs were used to induce sleep. Variables determined
include measurement of the movement of the chest and
abdominal wall by piezoelectric respiratory belts (Respironics, Murrysville, Pennsylvania), the heart rate by electrocardiogram, airflow by sidestream end-tidal capnography,
which provided breath-by-breath assessment of end-tidal
levels of CO2 (Capnocheck Plus, BCI International, Waukesha, Wisconsin) and temperature using an oronasal thermistor (Respironics). Arterial oxygen saturation was
assessed using pulse oximetry (BCI International) with
simultaneous recording of the pulse waveform. Bilateral
electro-oculography, an eight-channel electroencephalogram, and analysis of a body position sensor were also
monitored. Tracheal sound was monitored using a microphone sensor (Respironics) and a synchronised video
recording was performed. All recordings were digitised
using a commercially-available polysomnography system
(Alice 3; Respironics) in which data were acquired,
recorded and stored. Raw data were scored manually.
Sleep variables. The sleep pattern was assessed using standard techniques.49 The apnoea index was defined as the
number of periods of apnoea per hour of total sleep time.
Episodes of central, obstructive and mixed apnoea were
counted. Obstructive apnoea was defined as the absence of
airflow with continued movement of the chest and abdominal wall for at least two breath cycles.23 Hypopnoea was
defined as a decrease in nasal airflow of ≤ 50% with a corresponding decrease in arterial oxygen saturation ≥ 4%
and/or arousal.50 The respiratory disturbance index was
defined as the number of periods of apnoea and hypopnoea
per hour of total sleep time. The mean oxygen saturation
and arterial oxygen saturation nadir were determined.
Arousals were defined as recommended by the American
Sleep Disorders Task Force report.51 The arousal index
included the total number of arousals per hour of total
sleep time.
Results
All of the patients were above the 99th percentile on the
paediatric BMI for age scale and the mean adult BMI was
57.5 kg/m2 (44.1 to 114.8).52 All were in good health with
only one (8%) child on medication for hypertension and
two (15%) for seasonal allergies. All had nightly snoring,
VOL. 88-B, No. 1, JANUARY 2006
101
Table I. Details of the 13 patients and physical findings
Mean age in yrs (range)
Mean weight in kg (range)
Mean BMI* (kg/m2)
Mean neck size in cm (range)
Mouth breathing (%)
Enuresis (%)
Daytime somnolence (%)
Dyspnoea during sleep (%)
Enlarged adenoids and/or tonsils
Snoring
12.7
142
57.5
45.5
23
31
38
54
69
100
(10 to 16)
(102 to 188)
(44 to 115)
(38 to 53)
* BMI, body mass index
Table II. Polysomnographic data in the 13 patients
Respiratory disturbance index
Sleep efficiency (sleep time per
hour in bed) (%)
REM* total sleep time (%)
Oxygen saturation nadir (%)
Arousal index per hour
Mean (range)
Normal
17.4 (0.4 to 69)
83 (73 to 98)
< 5 events per hour
> 90
18.5 (5 to 29)
82.7 (62 to 93)
16.5 (5 to 28)
> 20
> 90
< 5 hour
* REM, rapid eye movement
six (46%) having restless sleep and four (31%) with episodes of enuresis. Five (38%) had daytime somnolence and
five (38%) had difficulty with schoolwork or behavioural
problems. Seven (54%) had difficulty of breathing during
sleep and three (23%) had mouth breathing during the day.
There were enlarged tonsils and/or adenoids in nine (69%)
patients. The mean circumference of the neck was larger
than the mean adult neck measurement at 45.5 cm (38 to
53; Table I).
Eleven (85%) children had sleep apnoea documented by
polysomnography. The incidence of sleep apnoea in the
total series of children requiring surgical treatment for tibia
vara was 30% (11 of 37). When only children nine years of
age or older at the time of evaluation were considered, 11
of 18 patients (61%) had sleep apnoea. The 13 children in
this series had a mean respiratory distress index of 17.4
events per hour (0.4 to 69). The mean nadir desaturation
(normal greater than 90%) was 82.7% (62% to 93%).
These apnoea-hypopnoeic events often culminated in cortical awakenings with a mean arousal index of 16.5 awakenings per hour (5 to 28). The normal is less than five
awakenings per hour in adults. Sleep patterns showed
diminished time spent in the recuperative rapid eye movement stage of sleep, with a mean of 18.5% of rapid eye
movement sleep (5% to 29%). The normal value is a total
time of rapid eye movement sleep of > 20% (Table II).
All 11 with sleep apnoea were treated by non-invasive
positive-pressure ventilation either in the form of continuous positive airway pressure or bilevel positive airway pressure. Five (45%) required tonsillectomy and adenoidectomy to decrease obstruction of the airway in addition to
non-invasive positive-pressure ventilation. After treatment
for obstructive sleep apnoea surgical correction of the tibia
102
J. E. GORDON, M. S. HUGHES, K. SHEPHERD, D. A. SZYMANSKI, P. L. SCHOENECKER, L. PARKER, E. C. UONG
vara was performed. All 13 patients, 22 affected limbs, had
tibial osteotomies with gradual correction using circular
external fixation. There were no perioperative pulmonary
or anaesthetic complications. Patients with obstructive
sleep apnoea have continued follow-up visits at the sleep
clinic.
3. Sinha R, Fisch G, Teague B, et al. Prevalence of impaired glucose tolerance among
children and adolescents with marked obesity. N Engl J Med 2002;346:802-10.
Discussion
7. Henderson RC, Kemp GJ Jr, Greene WB. Adolescent tibia vara: alternatives for
operative treatment. J Bone Joint Surg [Am] 1992;74-A:342-50.
Tibia vara and sleep apnoea have each been positively correlated with obesity and African-American race.7,18,53
However, the incidence of sleep apnoea in patients with
tibia vara has not been established. In our series 30% of
children requiring surgical treatment for tibia vara had
sleep apnoea. This is higher than the estimated prevalence
of 2%. When only children aged nine years and over were
considered, 61% had sleep apnoea. Identification of
patients with morbid obesity and the identification of a history of snoring allowed us to identify a group of children
with an extremely high risk (85%) of having sleep apnoea.
Sleep apnoea is probably under-diagnosed and when unrecognised there may be significant complications in relation
to anaesthesia.39,42,47,54-59 The importance of this disorder
to orthopaedic surgeons cannot be overemphasised.
A clinical history and physical examination are poor
indicators of sleep apnoea.22,34,60 While daytime somnolence may be a cardinal feature of this condition in adults,
it only occurred in 38% of our series. Another 38% had
behavioural problems. Only half of the patients presented
with difficulty in breathing during sleep and only 23% had
mouth breathing while awake. Recognising this growing
challenge, the American Academy of Pediatrics has recently
set out guidelines to increase awareness of sleep apnoea and
to decrease delays in diagnosis and treatment.37
Our protocol has included paediatric advice and polysomnography. An electrocardiogram and evaluation for
pulmonary hypertension may be considered. Careful preoperative anaesthetic assessment is required. Appropriate
supervised weight-reduction programmes are also required.
Tonsillectomy and/or adenoidectomy remain the first line
of treatment and have a cumulative cure rate of approximately 80%.61 In our series, although five (45%) of 11 children with sleep apnoea required tonsillectomy and adenoidectomy, follow-up polysomnography showed improvement
but some persistent apnoea. All 11 children required positive-pressure ventilation. The timely diagnosis and treatment of sleep apnoea in patients with tibia vara allow
proper precautionary measures to be taken and ensure
maintenance of the airway, administration of drugs, and
cardiorespiratory monitoring.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
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