Clinical assessment of generalized ligamentous laxity using a single test: is thumb-to-forearm apposition enough?

The complete Beighton criteria, commonly used to establish the diagnosis of generalized ligamentous laxity (GLL), include nine discrete examination maneuvers. However, busy examiners may perform only a single maneuver (e.g. passive apposition of the thumb to the forearm) as a rapid method of assessment. We hypothesize that the use of a single-joint hypermobility test does not reliably identify the presence of GLL. Healthy patients 2-18 years old presenting to a general pediatric orthopaedic clinic were screened for participation. Exclusion criteria included the presence of a systemic illness, neuromuscular disease, and inability to complete the examination. Subjects were assessed for GLL according to the Beighton criteria, using a cutoff score of 5. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and likelihood ratio were calculated for the thumb-to-forearm apposition test with the composite Beighton score used as the gold standard. Two hundred and four patients were included in the study, 111 females and 93 males, with an average age of 10.7 years. The prevalence of GLL was 13.3%. When thumb-to-forearm apposition was performed unilaterally, the PPV was poor (34%). Conversely, the NPV was excellent (99%). Sensitivity of thumb-to-forearm motion was extremely high (99%), although the specificity of this test was modest (67%). The likelihood ratio was fair (+3.3). Performing the test bilaterally did not significantly change its utility. Thumb-to-forearm apposition testing was equally effective in identifying the presence of GLL in males and females. When performed in isolation, assessment of thumb-to-forearm apposition has a poor PPV, excellent NPV, and modest likelihood ratio. It is an extremely sensitive test, with only fair specificity. Other upper extremity tests of GLL perform similarly. Therefore, while single tests like thumb-to-forearm apposition may be helpful for 'ruling out' GLL, they are less reliable at identifying it correctly. When single tests are used to identify GLL in either clinical or research settings, the results should be interpreted with caution. Level of evidence Level I (diagnostic).