Davids J R, Blackhurst D W, Allen B L
Motion Analysis Laboratory, Shriners Hospital for Children, 950 West Faris Road, Greenville, South Carolina 29605, USA.
J Pediatr Orthop B. 2000 Oct;9(4):278-84. doi: 10.1097/01202412-200010000-00012.
Early radiographic screening and/or referral to a clinical specialist are often used to distinguish between physiologic bow leg deformity and infantile tibia vara disease in young children. These practices are a consequence of the clinician's inability (based upon the clinical examination) to distinguish between the deformities associated with physiologic and pathologic bow legs. Because the great majority of these children have physiologic bowing, routine radiographic screening and referral are not cost effective and expose children to unnecessary radiation. This study describes and evaluates the efficacy of a simple clinical examination technique, the 'cover up' test, to identify young children with bow legs who are at high risk for having infantile tibia vara. The 'cover up' test qualitatively assesses the alignment of the proximal portion of the shank or lower leg relative to the thigh or upper leg. Obvious valgus alignment is considered a negative test and is indicative of physiologic bowing. Neutral or varus alignment is considered a positive test and suggests that the child is at greater risk for having infantile tibia vara. Eighteen children with infantile tibia vara, evaluated initially prior to 3 years of age, and followed to the time of surgical correction, were compared with 50 children with physiologic bowing, also evaluated initially prior to 3 years of age and followed to resolution (mean follow-up 3 years and 10 months). All of the children with infantile tibia vara had a positive 'cover up' test (sensitivity = 1.00). Eighteen of 25 children with a positive 'cover up' test actually had or developed infantile tibia vara (positive predictive value = 0.72). Forty-three of 50 children with physiologic bowing had a negative 'cover up' test (specificity = 0.86). All of the children with a negative 'cover up' test actually had physiologic bowing (negative predictive value = 1.00). We conclude that the 'cover up' test is an effective screening tool for the assessment of bow legs in children between 1 and 3 years of age. Children with a negative 'cover up' test do not require radiographic evaluation and should be followed clinically for resolution of the bowing. Children with a positive 'cover up' test should have radiographic evaluation of the lower extremities or be referred to a specialist for further evaluation and treatment.
早期影像学筛查和/或将患儿转诊给临床专科医生，常用于区分幼儿生理性膝内翻畸形和婴儿型胫骨内翻疾病。这些做法是由于临床医生（基于临床检查）无法区分生理性和病理性膝内翻相关的畸形。由于这些儿童中绝大多数是生理性膝内翻，常规影像学筛查和转诊不具有成本效益，且会使儿童暴露于不必要的辐射中。本研究描述并评估了一种简单的临床检查技术——“遮盖”试验，以识别有婴儿型胫骨内翻高风险的膝内翻幼儿。“遮盖”试验定性评估小腿近端相对于大腿的对线情况。明显的外翻对线被视为阴性试验，提示生理性膝内翻。中立或内翻对线被视为阳性试验，表明患儿患婴儿型胫骨内翻的风险更高。将18例最初在3岁前接受评估并随访至手术矫正时的婴儿型胫骨内翻患儿，与50例同样最初在3岁前接受评估并随访至畸形消退（平均随访3年10个月）的生理性膝内翻患儿进行比较。所有婴儿型胫骨内翻患儿的“遮盖”试验均为阳性（敏感性 = 1.00）。25例“遮盖”试验阳性的患儿中有18例实际患有或发展为婴儿型胫骨内翻（阳性预测值 = 0.72）。50例生理性膝内翻患儿中有43例“遮盖”试验为阴性（特异性 = 0.86）。所有“遮盖”试验阴性的患儿实际均为生理性膝内翻（阴性预测值 = 1.00）。我们得出结论，“遮盖”试验是评估1至3岁儿童膝内翻的有效筛查工具。“遮盖”试验阴性的儿童无需进行影像学评估，应进行临床随访以观察膝内翻畸形的消退情况。“遮盖”试验阳性的儿童应进行下肢影像学评估，或转诊给专科医生进行进一步评估和治疗。
