Preliminary validity study comparing the prone lumbar hypermobility test against the prone instability test*

Abstract: Objective: The Prone Instability Test (PIT) is an established orthopaedic test that predicts the probability of low back pain patients responding positively to a spinal stabilization program (.71 sensitivity, .57 specificity for PIT). This preliminary study suggests the Prone Lumbar Hypermobility Test (PLHT) as an effective alternative to the PIT that is more suitable for a wider population due to the modified patient positioning. In contrast to the PIT, the PLHT has the patient's entire body supported by the examination table. This is hypothesized to maximize patient comfort while still maintaining clinical effectiveness for the chronic low back pain population. The purpose of this preliminary study is to determine whether the PLHT is comparable to the PIT in diagnostic effectiveness when predicting the benefits of stabilization interventions. Methods: To compare the clinical effectiveness of the PLHT to the PIT, each subject underwent parts I and II (relaxed and contracted) of each test (PIT and PLHT). 36 subjects received both parts of PIT and PLHT (in a randomized order). Subjects assumed each of the four positions and 4 kg/cm2 of pressure was applied directly on the skin over the L4 spinous process, using an algometer. The subjects verbally indicated perceived pain following each of the 4 positions. Results: Of the 36 participants included in the study, 23 participants had a negative PIT and a negative PLHT and six had a positive PIT and a positive PLHT. Three participants had a positive PIT and negative PLHT and four had a positive PLHT and negative PIT. This indicates that the PIT and PLHT have a statistically significant level of agreement. Conclusions: This study found that the PLHT is valid in identifying negative results in the predicted negative population, as well as positive results in the predicted positive population. For future investigations, a larger sample size is advantageous - particularly with an evenly distributed and accurate sample of positive and negative participants. This will more accurately determine the validity of the PLHT and broaden the application of the PLHT to the population for which the test is aimed to identify in clinical practice.