Deep learning and conventional hip MRI for the detection of labral and cartilage abnormalities using arthroscopy as standard of reference

Abstract

Objectives: To evaluate the performance of high-resolution deep learning-based hip MR imaging (CSAI) compared to standard-resolution compressed sense (CS) sequences using hip arthroscopy as standard of reference.

Methods: Thirty-two patients (mean age, 37.5 years (± 11.7), 24 men) with femoroacetabular impingement syndrome underwent 3-T MR imaging prior to hip arthroscopy. Coronal and sagittal intermediate-weighted TSE sequences with fat saturation were obtained using CS (0.6 × 0.8 mm) and high-resolution CSAI (0.3 × 0.4 mm), with 3 mm slice thickness and similar acquisition times (3:55-4:12 min). MR scans were independently assessed by three radiologists and a hip arthroscopy specialist for labral and cartilage abnormalities. Sensitivity, specificity, and accuracy were calculated using arthroscopy as reference standard. Statistical comparisons between CS and CSAI were performed using McNemar's test.

Results: Labral abnormality detection showed excellent sensitivity for radiologists (CS and CSAI: 97-100%) and the surgeon (CS: 81%, CSAI: 90%, p = 0.08), with 100% specificity. Overall cartilage lesion sensitivity was significantly higher with CSAI versus CS (42% vs. 37%, p < 0.001). Highest sensitivity was observed in superolateral acetabular cartilage (CS: 81%, CSAI: 88%, p < 0.001), while highest specificity was found for the anteroinferior acetabular cartilage (CS and CSAI: 99%). Sensitivity was lowest for the assessment of the anteroinferior and posterior acetabular zones, and inferior and posterior femoral zones (CS and CSAI < 6%).

Conclusion: CS and CSAI MR imaging showed excellent diagnostic performance for labral abnormalities. Despite CSAI's improved cartilage lesion detection, overall diagnostic performance for cartilage assessment remained suboptimal.

Key points: Question Accurate preoperative detection of labral and cartilage lesions in femoroacetabular impingement remains challenging, with current MRI protocols showing variable diagnostic performance. Findings High-resolution deep learning-based and standard-resolution compressed sense MRI demonstrate comparable diagnostic performance, with high accuracy for labral defects but limited sensitivity for cartilage lesions. Clinical relevance Current MRI protocols, regardless of resolution optimization, show persistent limitations in cartilage evaluation, indicating the need for further technical advancement to improve diagnostic confidence in presurgical planning.

Keywords: Arthroscopy; Deep learning; Femoracetabular impingement; Hip joint; Magnetic resonance imaging.

Fig. 1

Sagittal diagram (left) and high-resolution sagittal (middle) and coronal (right) IM-weighted TSE sequences with SPIR of acetabular (top row) and femoral (bottom row) cartilage zones adapted from the Geographic Zone Method by Ilizaliturri et al [21], modified by Griffin et al [22, 23]. For the acetabulum, anterior-inferior is zone E, anterior-superior is zone D, mid-superior is zone C, posterior-superior is zone B, and posterior-inferior is zone A. For the Femur, central is zone A, posterior is zone B, superolateral is zone C, anterior is zone D, and inferior is zone E. Zone F is the acetabular notch as well as the fovea capitis femoris that contains the ligamentum capitis femoris. IM, intermediate-weighted; TSE, turbo spin echo; SPIR, spectral presaturation with inversion recovery

Fig. 2

True positive (left hip). MR: Coronal IM-weighted TSE images of the left hip show a labral lesion (arrow) in the CS (a) and CSAI (b) sequences. Arthroscopy: c A full-thickness labral tear (thick arrow) with chondrolabral separation at the junctional zone. d Arthroscopic probing confirms an unstable labral tear (thick arrow)

Fig. 3

True positive (right hip). MR: CS (a—sagittal, b—coronal) and CSAI (c—sagittal, d—coronal) IM-weighted TSE images both demonstrate a chondrolabral defect in acetabular zone C (arrows). Arthroscopy: e Delamination of the articular cartilage with macroscopic debonding (thick arrows) and (f) exposure of the acetabular bone (arrows), confirmed by arthroscopic probing (Haddad grade 4)

Fig. 4

False negative (right hip). MR: IM-weighted TSE images with CS (a—sagittal, b—coronal) and CSAI (c—sagittal, d—coronal). There is no detectable pathology in acetabular zone C. The arrows are pointing to acetabular zone C. Arthroscopy: e Cleavage tear (thick arrow) with separation at the chondrolabral junction, surface roughening, and fibrillation of the cartilage. f Arthroscopic probing reveals adherence of the articular cartilage to the subchondral bone, with no delamination detected (Haddad grade 2)

Fig. 5

False positive for femur zone C (left hip). MR: IM-weighted TSE images with CS (a—sagittal, b—coronal) and CSAI (c—sagittal, d—coronal). Readers detected a chondrolabral defect on acetabular zone C (arrows) with a ‘kissing-lesion’ on femoral cartilage zone C (arrow heads). Arthroscopy: e Separation at the chondrolabral junction with cartilage delamination (thick arrow), confirmed by probing (Haddad grade 3). f No arthroscopic evidence of femoral head cartilage damage (thick arrow)