To assess the construct validity of the flip test as a sign of nerve root tension.
The flip test is commonly performed in patients with sciatica to confirm or otherwise nerve root tension evidenced by a restricted supine straight leg raise (SLR). Passive extension of the knee with the patient in the erect position and the hip flexed is reported to cause a sudden falling or flipping back of the trunk. Although widely known there are no research articles validating this test.
Sixty-seven patients with sciatica and magnetic resonance imaging scans confirming disc protrusion and nerve root compression underwent the flip test. The response of the patient was recorded, compared with the supine SLR, and subjected to statistical analysis.
Thirty-three percent of patients felt no pain, 39% felt pain on full extension of the knee, and 28% resisted full extension of the knee due to pain. Only one-third of patients demonstrated a “flip.” The response was related to the supine SLR, such that patients with high SLRs tended not to show a painful reaction whereas all patients with a supine SLR below 45° showed a painful response.
We consider that the flip test has been substantially misinterpreted in the past. However, it remains a useful check of nerve root tension but only for patients with supine SLRs below 45°. The most reliable response was not a flip but the demonstration of pain on extension of the knee. We would recommend the term “sitting SLR test,” as a more accurate and less misleading name.
The flip test is a well known historical test for confirming nerve root tension in patients with sciatica, but it has never been validated. Our study indicated that only one-third of patients with clinical and magnetic resonance imaging evidence of sciatica demonstrated a “flip.” The test is reevaluated, redefined, and renamed.
From the *Department of Orthopaedics, The Princess Royal Hospital, Telford, Shropshire, United Kingdom; †Castle Hill Hospital, Cottingham, East Yorkshire, United Kingdom; and ‡Department of Mathematics, Keele University, Keele, Staffordshire, United Kingdom.
Acknowledgment date: June 27, 2008. First revision date: November 11, 2008. Second revision date: January 19, 2009. Acceptance date: January 20, 2009.
The manuscript submitted does not contain information about medical device(s)/drug(s).
No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.
Address correspondence and reprint requests to Bruce Summers, FRCS, Department of Orthopaedics, The Princess Royal Hospital, Telford, Shropshire TF1 6TF, United Kingdom; E-mail: firstname.lastname@example.org