Van der Post A, Noorduyn J C A, Scholtes V A B, Mutsaerts E L A R
Universiteit van Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
Onze Lieve Vrouwe Gasthuis, Amsterdam, The Netherlands.
Clin Orthop Relat Res. 2017 Dec;475(12):2963-2969. doi: 10.1007/s11999-017-5475-6. Epub 2017 Aug 14.
Clinical weightbearing provocation tests, like the duck walk test, may be of value in diagnosing or screening for medial meniscal tears. However, evidence of the diagnostic accuracy of the duck walk test is lacking.
QUESTIONS/PURPOSES: (1) To determine the sensitivity and specificity of the duck walk test in diagnosing medial meniscal tears. (2) To determine whether tear location, tear cause (traumatic versus degenerative), and ACL insufficiency were associated with differences in the sensitivity and specificity of the test.
A convenience sample of 136 patients of all ages was retrospectively analyzed by evaluating the outpatient knee clinic appointment list of one orthopaedic surgeon for patients with a broad range of knee injuries who had a prior MRI before (24%) or after (76%) physical examination and had a duck walk test stated in their patient records. Of 230 patients with MRI requested by one orthopaedic surgeon attributable to knee complaints, 136 (59%) fulfilled the inclusion criteria; 70 (52%) patients were male and 66 (49%) were female, with a mean age of 42 (± SD 14) years. The duck walk test was performed in case of suspected meniscal injury, based on mechanism of injury, general joint line pain, and/or mechanical complaints (ie, locking, giving away). The test is performed by squatting and "waddling" before rising and is positive in case of general joint line pain or painful "clicking". Interobserver repeatability was not evaluated, but the test is well defined and leaves little room for difference in interpretation. Diagnostic accuracy measures were evaluated. Since the convenience sample in this study consisted of patients who had a duck walk test and MRI, and a positive result of the duck walk test almost certainly increased the probability that MRI would be ordered in the majority (76%) of the patients, the test properties calculated here-especially sensitivity-should be considered inflated.
The calculated sensitivity of the duck walk test was 71% (95% CI, 59%-81%) and there was low specificity of 39% (95% CI, 27%-52%). We found no difference in sensitivity between medial (67%; 95% CI, 51%-80%) and lateral (76%; 95% CI, 50%-92%; p = 0.492) meniscal tears. With the numbers available, we compared these patients with patients without a history of trauma and with an intact ACL. We found no difference among patients with traumatic tears (79%; 95% CI, 59%-91%; p = 0.253) and in patients with ACL tears (77%; 95% CI, 46%-94%; p = 0.742).
Because of the issue of verification bias, the actual sensitivity of this test in practice is likely much lower than the calculated sensitivity we observed. In addition, the test did not seem to perform better in patients with trauma or ACL insufficiency, nor was it more effective in detecting medial than lateral tears, although the numbers on some of those comparisons were rather small. Based on these results, we conclude that used alone, the duck walk test likely has little value in practice as a screening test. However, it is conceivable that it could be used in combination with other provocative tests for screening purposes. Future studies might consider using it as a means to best identify which patients should undergo MRI for the possibility of a meniscal tear.
Level III, diagnostic study.
临床负重激发试验，如鸭步试验，可能对诊断或筛查内侧半月板撕裂有价值。然而，缺乏鸭步试验诊断准确性的证据。
问题/目的：（1）确定鸭步试验诊断内侧半月板撕裂的敏感性和特异性。（2）确定撕裂部位、撕裂原因（创伤性与退变性）以及前交叉韧带功能不全是否与该试验的敏感性和特异性差异相关。
通过评估一位骨科医生的门诊膝关节诊所预约名单，对136名各年龄段患者的便利样本进行回顾性分析，这些患者有广泛的膝关节损伤，在体格检查之前（24%）或之后（76%）进行过MRI检查，并且患者记录中有鸭步试验。在一位骨科医生因膝关节不适而要求进行MRI检查的230名患者中，136名（59%）符合纳入标准；70名（52%）患者为男性，66名（49%）为女性，平均年龄为42（±标准差14）岁。根据损伤机制、关节线普遍疼痛和/或机械性症状（如锁定、打软腿）怀疑半月板损伤时进行鸭步试验。该试验通过在起身前蹲下并“摇摆”来进行，如果出现关节线普遍疼痛或疼痛性“咔嗒声”则为阳性。未评估观察者间的重复性，但该试验定义明确，解释差异的空间很小。评估诊断准确性指标。由于本研究中的便利样本由进行了鸭步试验和MRI检查的患者组成，并且鸭步试验阳性结果几乎肯定会增加大多数（76%）患者进行MRI检查的可能性，因此此处计算的试验特性——尤其是敏感性——应被视为夸大了。
计算得出鸭步试验的敏感性为71%（95%可信区间，59%-81%），特异性较低，为39%（95%可信区间，27%-52%）。我们发现内侧半月板撕裂（67%；95%可信区间，51%-80%）和外侧半月板撕裂（76%；95%可信区间，50%-92%；p = 0.492）之间的敏感性没有差异。根据现有数据，我们将这些患者与没有创伤史且前交叉韧带完整的患者进行了比较。我们发现创伤性撕裂患者（79%；95%可信区间，59%-91%；p = 0.253）和前交叉韧带撕裂患者（77%；95%可信区间，46%-94%；p = 0.742）之间没有差异。
由于验证偏倚问题，该试验在实际中的实际敏感性可能远低于我们观察到的计算敏感性。此外，该试验在创伤患者或前交叉韧带功能不全患者中似乎表现也不佳，在检测内侧撕裂方面也不比外侧撕裂更有效，尽管其中一些比较的样本量相当小。基于这些结果，我们得出结论，单独使用时，鸭步试验在实际中作为筛查试验可能价值不大。然而，可以想象它可以与其他激发试验联合用于筛查目的。未来的研究可能会考虑将其作为最佳手段来确定哪些患者因半月板撕裂的可能性而应接受MRI检查。
III级，诊断性研究。
