Orthopedic surgeons frequently encounter short statured patients. A systematic approach is needed for proper evaluation of these children. The differential diagnosis includes both proportionate and disproportionate short stature types. A proper history and physical examination and judicious use of plain film radiography will establish the diagnosis in most cases. In addition to the orthopedic surgeon, most of these patients will also be evaluated by other specialists, including endocrinologists and geneticists. This article provides an overview of the evaluation of the child with short stature and offers several illustrative examples.
Key points
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Orthopedic surgeons frequently encounter short statured patients. A systematic approach is needed for proper evaluation of these children.
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The differential diagnosis includes both proportionate and disproportionate short stature types.
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A proper history and physical examination and judicious use of plain film radiography will establish the diagnosis in most cases.
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In addition to the orthopedic surgeon, most of these patients will also be evaluated by other specialists, including endocrinologists and geneticists.
Introduction
Normal growth and development usually proceed quite smoothly from single-celled zygote all the way to an approximately one hundred trillion–celled adult human being. Three discernable growth spurts occur, with the first being intrauterine (and arguably the most dramatic), the second involving the first 2 years of life (with about a 100% increase in size of the child), and the third is the adolescent (also known as pubescent) growth spurt. The amazing thing may not be that growth aberrations occur, but that they do not occur more frequently. When a child falls 2 standard deviations or more below the average height for age, sex, and ethnic group established norms, they are considered to have short stature.
Short statured humans have been well-recognized by others within society all the way back to antiquity. For instance, the ancient Egyptian sarcophagus carving of Djeho offers a detailed picture of a prominent citizen with achondroplasia ( Fig. 1 ). Djeho lived around 360 BC and worked with the chief financial officer of Upper Egypt. There also were powerful short statured Egyptian gods with the god Bes (god of music and warfare) and the god Ptah (a god of creation and master architect of the universe) serving as excellent examples.
In 1951 when Sir Harold Arthur Thomas Fairbank (at 75 years of age) published his classic Atlas of General Affections of the Skeleton , he helped bring order to the chaos of this complex mixture of musculoskeletal entities. This article focuses on important orthopedic aspects in the evaluation of short stature in children with a particular focus on skeletal dysplasia. It does not focus on each and every diagnostic entity, but rather the options that must be considered and the process one may undertake to arrive at the most precise diagnosis.
Introduction
Normal growth and development usually proceed quite smoothly from single-celled zygote all the way to an approximately one hundred trillion–celled adult human being. Three discernable growth spurts occur, with the first being intrauterine (and arguably the most dramatic), the second involving the first 2 years of life (with about a 100% increase in size of the child), and the third is the adolescent (also known as pubescent) growth spurt. The amazing thing may not be that growth aberrations occur, but that they do not occur more frequently. When a child falls 2 standard deviations or more below the average height for age, sex, and ethnic group established norms, they are considered to have short stature.
Short statured humans have been well-recognized by others within society all the way back to antiquity. For instance, the ancient Egyptian sarcophagus carving of Djeho offers a detailed picture of a prominent citizen with achondroplasia ( Fig. 1 ). Djeho lived around 360 BC and worked with the chief financial officer of Upper Egypt. There also were powerful short statured Egyptian gods with the god Bes (god of music and warfare) and the god Ptah (a god of creation and master architect of the universe) serving as excellent examples.
In 1951 when Sir Harold Arthur Thomas Fairbank (at 75 years of age) published his classic Atlas of General Affections of the Skeleton , he helped bring order to the chaos of this complex mixture of musculoskeletal entities. This article focuses on important orthopedic aspects in the evaluation of short stature in children with a particular focus on skeletal dysplasia. It does not focus on each and every diagnostic entity, but rather the options that must be considered and the process one may undertake to arrive at the most precise diagnosis.
Differential diagnosis
The differential diagnosis for short stature is exhaustive and includes what have been referred to as proportionate and disproportionate types. Comprehensive evaluation often includes referrals to pediatric subspecialists like endocrinology and genetics. Proportionate short stature may be owing to familial short stature, intrauterine growth retardation (commonly owing to smoking), constitutional delay of growth, occult medical diseases (including endocrinopathy), and idiopathic short stature. Multiple evaluations over time may be quite valuable, because skeletal dysplasia may be later confirmed in up to 20% of patients previously labeled as idiopathic short stature or small for gestational age. This paper does not focus on these proportionate short stature types because it is extremely rare for such patients to present undiagnosed to the orthopedic surgeon.
Disproportionate short stature relates to an improper balance between standing height and sitting height. In normal populations, the sitting height/standing height ratio has been shown to be approximately 0.7 at birth and closer to 0.5 at skeletal maturity. Standing height has contributions from both limb length as well as trunk length, whereas sitting height is effectively all about trunk length. One broad (and imperfect) generalization is that disproportionate short stature can be divided into those characterized mainly by shortened limbs and those mainly characterized by a shortened trunk. In the past, these have been referred to as short limb dwarfism and short trunk dwarfism. Fig. 2 illustrates the striking contrast that can be seen when assessing standing height and sitting height. The sitting height/standing height ratio has been shown to be of significant clinical value. In addition to many other more sophisticated methods, the relative femoral and tibial contributions to lower limb length discrepancy can be determined by instantaneous limb length assessment ( Fig. 3 ).
Prenatal evaluation
Various imaging techniques (most commonly ultrasonography) may be used to assess the unborn child suspected of having skeletal dysplasia. It should be remembered that as many as 80% of prenatally detected skeletal dysplasias are lethal, and thus the prenatal cohort and the live birth cohort are epidemiologically distinct. Understanding this allows one to properly interpret the differential prevalence between live births and still births (3.0 per 10,000 vs 20.0 per 10,000). A powerful rule of thumb is that until proven otherwise, age-adjusted fetal femoral length of less than 40% indicates achondrogenesis, 40% to 60% is consistent with osteogenesis imperfecta type II or thanotophoric dysplasia, and greater than 80% of femoral length points to osteogenesis imperfecta type III or achondroplasia. Additional prenatal cytogenetic and molecular genetic analysis may also be undertaken as indicated. Situations where such studies are felt to be appropriate include a parent with a known skeletal dysplasia, significant family history, and micomelic or hypoplastic thorax ultrasound findings.
Although more firmly established for congenital central nervous system and cardiac anomalies, the role of fetal MRI continues to evolve in the setting of prenatal evaluation of skeletal dysplasias. It should also be remembered that ultrasound remains the only recommended imaging in the first trimester. Information from fetal MRI may be considered complementary to that obtained from ultrasound, adding additional findings in about 30% of cases and changing the diagnosis more than 50% of the time when considering all fetal diagnoses. However, when focusing on musculoskeletal system fetal MRI, it is less likely to show diagnostic advantages over ultrasound. Researchers from the Cincinnati Children’s Hospital have recently shown that fetal MRI can play a significant role in predicting lethal skeletal dysplasias based on fetal lung volume. Until these various applications mature and clinical utility becomes clear, the overall indications for fetal MRI for suspected skeletal dysplasia remain limited.
Physical examination
Of the more than 450 known skeletal dysplasias, only about 100 are discernable at birth. The remainder may not manifest until after 2 to 3 years of age. Height, weight, head circumference, and growth velocity are all important parameters that must be measured. There are significant rates of hearing impairment among skeletal dysplasia patients and it is reasonable for the orthopedist to ask about prior hearing assessment. Airway and pulmonary compromise are also common in these patients and at times require sophisticated assessment.
The impact on health-related quality of life caused by pain and decreased physical function can be substantial in skeletal dysplasia patients. Many validated instruments are available to measure this in the clinical setting. In the most common skeletal dysplasia, achondroplasia, low back pain and lower extremity pain have been shown to be brutally progressive over time. An increased rate of sleep apnea and sudden infant death syndrome have also been identified in newborns with achondroplasia. Multidisciplinary evaluation may include pediatric otolaryngology as well as pediatric pulmonology and sleep studies of even very young children are often indicated.
There are several important points regarding the history and physical examination of short statured patients during the newborn and early childhood periods. The craniofacial region should be inspected for a wide variety of abnormalities including clouding of the cornea (eg, mucopolysaccharidoses), calcification of or overall thickening of the ears (eg, diastrophic dwarfism), and midface hypoplasia (eg, achondroplasia). Nasal depression may be a prominent feature of achondroplasia, whereas broadening of the same nasal region is characteristic of mucopolysaccharidoses, like Hunter and Hurler syndromes. Abnormalities of the teeth and gums are common in Ellis van Crevald syndromes and cleft palate has been associated with diastrophic dysplasia and many other skeletal dysplasias.
In addition to anthropomorphic measurements of the trunk and extremities, particular attention should be paid to several other areas. A markedly abducted thumb (hitchhiker’s thumb) is consistent with disastrohic dysplasia. Exceptionally well-formed polydactyly is strongly associated with Ellis van Crevald syndrome ( Fig. 4 ). A trident hand (relatively abducted index and long finger one way and abducted ring and small finger the other way) is one of the hallmarks of achondroplasia.
