The dimensions of the hip labrum can be reliably measured using magnetic resonance and computed tomography which can be used to develop a standardized definition of the hypoplastic labrum

Abstract

PurposeThe purpose of this study was to examine the existing literature to determine the dimensions of the acetabular labrum, with a focus on hypotrophic labra, including the modalities and accuracy of measurement, factors associated with smaller labra, and any impacts on surgical management. MethodsFour databases (PubMed, Ovid [MEDLINE], Cochrane Database, and EMBASE) were searched from database inception to January 2020. Two reviewers screened the literature independently and in duplicate. Methodological quality of included papers was assessed using the Methodological Index for Non‐Randomized Studies (MINORS) criteria. Where possible, data on labral size were combined using a random effects model. ResultsTwenty‐one studies (5 level II, 9 level III, 7 level IV) were identified. This resulted in 6,159 patients (6,436 hips) with a mean age of 34.3 years (range 8.4–85). The patients were 67.3% female with an average follow‐up of 57.3 months. There was no consistent definition of labral size quoted throughout the literature. The mean width on MRI/MRA was 7.3 mm (95% CI 6.9–7.8 mm), on computed tomography arthrography was 8.7 mm (95% CI 8.0–9.3), and during arthroscopy was 5.0 mm (95% CI 4.9–5.2). Inter‐observer reliability was good to excellent in all modalities. Labral hypotrophy may be associated with increased acetabular coverage. Hypertrophic labra were highly associated with acetabular dysplasia (r = − 0.706, − 0.596, − 0.504, respectively; P < 0.001). ConclusionLabral width can reliably be measured utilizing imaging techniques including magnetic resonance and computed tomography. The pooled mean labral width was 6.2 mm, and height 4.6 mm. The establishment of a gold‐standard of measurement on arthroscopy and advanced imaging would aid in clinical decision‐making regarding treatment options for patients presenting with a painful hip, particularly those with hypoplastic labra, and provide radiological guidelines for standardized labrum size classifications. Level of evidenceLevel IV.

Preoperative Magnetic Resonance Imaging Predicts Intraoperative Labral Width at the 9-O’clock and 12-O’clock Positions in Primary Hip Arthroscopy

“…Other investigators have previously aimed to measure the dimensions of the acetabular labrum on imaging; however, there is a lack of consensus regarding nomenclature and measurement methodology when reporting labral size and distinguishing between normal and hypotrophic labra. 11 In a systematic review, Walker et al 11 reported on 21 studies describing measurements of the labral dimensions and found the length of the labrum from the chondrolabral junction to be measured from the capsular facet, articular facet, or midsubstance using various anatomic landmarks such as the acetabular rim or labral free edge and the clock-face method on MRI, magnetic resonance arthrography (MRA), computed tomographic arthrography, ultrasound, or arthroscopic assessment. 11 The terms "labral height" and "labral width" were used interchangeably among the studies.…”

“…11 In a systematic review, Walker et al 11 reported on 21 studies describing measurements of the labral dimensions and found the length of the labrum from the chondrolabral junction to be measured from the capsular facet, articular facet, or midsubstance using various anatomic landmarks such as the acetabular rim or labral free edge and the clock-face method on MRI, magnetic resonance arthrography (MRA), computed tomographic arthrography, ultrasound, or arthroscopic assessment. 11 The terms "labral height" and "labral width" were used interchangeably among the studies. Average widths on imaging and arthroscopy were pooled, and the data suggested that the labral width is largest in the superior aspect and smallest in the posterosuperior aspect, which was similar to the differences in labral size by location observed in this study and previously described by the senior author.…”

“…Average widths on imaging and arthroscopy were pooled, and the data suggested that the labral width is largest in the superior aspect and smallest in the posterosuperior aspect, which was similar to the differences in labral size by location observed in this study and previously described by the senior author. 9,11 The accuracy of preoperative prediction of labral size has been assessed previously, with mixed results. Hartwell et al 8 compared MRA versus intraoperative labral width measurements in 117 patients and found strong inter-rater reliability between readers in MRA-based hip labrum measurements but poor correlation between MRA and intraoperative measurements at the 3-, 12-, and 9-o'clock positions.…”

“… 11 In a systematic review, Walker et al. 11 reported on 21 studies describing measurements of the labral dimensions and found the length of the labrum from the chondrolabral junction to be measured from the capsular facet, articular facet, or midsubstance using various anatomic landmarks such as the acetabular rim or labral free edge and the clock-face method on MRI, magnetic resonance arthrography (MRA), computed tomographic arthrography, ultrasound, or arthroscopic assessment. 11 The terms “labral height” and “labral width” were used interchangeably among the studies.…”

“…Average widths on imaging and arthroscopy were pooled, and the data suggested that the labral width is largest in the superior aspect and smallest in the posterosuperior aspect, which was similar to the differences in labral size by location observed in this study and previously described by the senior author. 9 , 11 …”