An evaluation of the clinical utility of the modified FABER’s test: Can it discriminate for low back pain of sacroiliac joint origin?

Abstract

Background: Innominate kinematic anomalies resulting in non-specific low back pain (LBP) of sacroiliac joints (SIJ) origin have been well recognized in the literature. While the complex anatomical orientation and position of the SIJs renders evaluation of innominate kinematic anomalies difficult, recent techniques of palpation-digitization of pelvic landmarks (in the modified FABER’s test positions) using electromagnetic tracking device have been able to accurately and non-invasively quantify subtle innominate kinematics (in healthy individuals). The aim of this thesis is to determine if the modified FABER’s test positions and the electromagnetic palpation-digitization technique are capable of discriminating for subjective (pain provocation) and objective (innominate kinematics) clinical parameters respectively, that would allow differentiation and identification of individuals clinically diagnosed with LBP of SIJ origin (SIJ-positive) when compared to individuals clinically diagnosed with LBP of Non-SIJ origin (SIJ-negative).

Methods and results: This thesis comprises of three studies. The first two studies were conducted to evaluate the psychometric properties (validity and reliability) of the palpation-digitization technique, and the third study was conducted to determine the use of the palpation-digitization technique for identifying and differentiating between two clinical groups. Study 1 systematically reviewed the literature, in order to determine the level of evidence for the validity and reliability of the electromagnetic palpation-digitization technique for measurement of joint kinematics. The results of this (PRISMA guided) systematic review demonstrated an overall strong level of evidence for validity [n (3 high quality studies)] and intra-rater reliability [n (5 high & 2 low quality studies)] of palpation-digitization technique for measurement of joint kinematics. Evidence for inter-rater reliability of electromagnetic palpation-digitization technique was limited [n (1 study)] and was deemed essential for use of this procedure in the clinical utility. Study 2 evaluated the inter-tester reliability of the palpation-digitization technique for measurement of innominate kinematics. Four musculoskeletal testers, using electromagnetic tracking device, palpated and digitized the pelvic landmarks in fourteen healthy participants. The innominate vector length was calculated from the 3D co-ordinates of the palpated and digitized landmarks, in two modified FABER’s test positions. The results of this reliability study demonstrated very high inter-tester reliability [Intraclass correlation coefficient (≥ 0.97), and Standard error of measurement (≤ 1%)] of the palpation-digitization technique for non-invasive innominate kinematics measurement. This results thus demonstrate that the palpation-digitization technique satisfies the psychometric properties essential for its further research and clinical use. The next step was to explore the use of the palpation-digitization technique and the modified FABER’s test positions for determining innominate kinematics in a clinical population. Study 3 evaluated the subjective (pain reproduction) and objective (innominate movement pattern, range of motion and trend of rotation) clinical parameters of modified FABER’s test positions and the palpation-digitization technique respectively, in two clinical groups of chronic non-specific LBP individuals [SIJ-positive: n (45), and SIJ-negative: n (77)], to determine if these clinical parameters would allow differentiation and identification of SIJ-positive LBP individuals. The results of this kinematic study demonstrated that both the subjective and objective clinical parameters were capable of differentiating and identifying SIJ-positive LBP individuals. The modified FABER’s test positions reproduced familiar pain in SIJ-positive LBP individuals compared with SIJ-negative LBP individuals [p (0.001)], and had moderate levels of sensitivity (67% to 78%) and specificity (63% to 66%) for identifying SIJ-positive LBP individuals. The innominate kinematics of movement pattern and trends of rotation were significantly different [p (< 0.017)] in SIJ-positive LBP individual compared with SIJ-negative LBP individuals, but the innominate ranges of motion did not demonstrate a significant between-group difference [p (> 0.300)]. Conclusion: These between-group differences in pain reproduction and innominate kinematics in the modified FABER’s test positions, demonstrate significant associations between innominate kinematic anomalies and the SIJ pain. However, it is unknown if the innominate kinematic patterns observed in SIJ-positive LBP individuals are a cause or an effect of SIJ pain. Nevertheless, the discriminative results for palpation-digitization examination of non-invasive innominate kinematic measurement in a clinical LBP population is an important step toward a greater understanding of normative, aberrant and pathological SIJ kinematics. This thesis thus has set the groundwork for further exploration of clinical measurement, clinical relevance, and clinical management of these potentially important movement observations.