The pathology of the posterior acetabular legion in femoroacetabular impingement (FAI) syndrome, so called “contre-coup region”, is still unclear. ¹⁸F-fluoride positron emission tomography (PET) is a functional imaging modality, which reflects the osteoblast activity. Recent technological advances in PET combined with computed tomography (CT) imaging allowed us to obtain detailed 3-dimensional (3D) morphological information. We evaluated the abnormal uptake of ¹⁸F-fluoride PET/CT on posterior acetabular lesion in FAI syndrome cases. We enrolled forty-one hips from 41 patients who were diagnosed as FAI syndrome and were performed ¹⁸F-fluoride PET/CT between October 2014 and October 2016. In each hip, the maximum standardized uptake value (SUV_max) on the posterior acetabular was measured. The cases were divided into 4 groups; cam-type (11 cases), pincer-type (7), combined-type (11), dysplastic developmental hip (DDH) with cam morphology (12). The average SUV_max of the pincer-type was significantly smaller than that of the other 3 groups (p < .05). The percentage of the cases with SUV_max ≥ 6 was 81.8% in cam-type, 28.6% in pincer-type, 90.9% in combined-type, 91.7% in DDH with cam morphology. Furthermore, the average degree of α angle of the cases of SUV_max ≥ 6 was significantly higher than that of the cases of SUV_max < 6 (p = .005). Although actual biomechanical mechanism in contre-coup region is still controversial, this result indicated that the cam morphology related to the posterior acetabular lesion with accelerated bone metabolism.

In this study, we evaluated the labrum tear using radial sequence 3D Multiple Echo Recombined Gradient Echo (MERGE) MRI without arthrography based on modified Czerny's classification, comparing with actual arthroscopic findings. A total of 61 hips including 27 hips of femoroacetabular impingement (FAI), 19 hips of borderline development dysplasia of the hip (BDDH) and 15 hips of early stage osteoarthritis (OA) were enrolled this retrospective study. MRI findings evaluated in each three regions of interest; anterior region, anterolateral region, and lateral region. The cases with severe degeneration that is not concordant with any original Czerny's classification is defined as stage4. We compared MRI findings with arthroscopic findings and calculated the sensitivity, specificity, and likelihood ratio in terms of the existence of labrum tear. MRI findings revealed labrum tear more frequently in anterolateral than lateral (p<0.001). Especially in FAI group, labrum tear was more frequently observed by MRI in anterolateral than lateral (p=0.006). In comparison with MRI findings and arthroscopic findings, the sensitivity was 97%, specificity was 79% and likelihood ratio was 4.59 as average of all regions in terms of the existence of labrum tear. In each region, sensitivity and specificity was 97% and 50% in anterior, 97% and 100% specificity in anterolateral, 94% and 81% in lateral, respectively. Thus, MERGE MRI revealed excellent sensitivity and specificity for diagnosis of labrum tear, especially in anterolateral region. The cases with severely degenerated labrum were classified as newly defined stage 4, which was recognized frequently in OA cases.

Minimally invasive surgery (MIS) for total hip arthroplasty and hemiarthroplasty is performed through anterior or anterolateral approach from April 2006.

Appropriate stem insertion is often difficult by conventional approach.

Retractor for MIS stem insertion is used from February 2007 and initial stem position is measured.

Forty-four hemiarthroplasty and 20 total hip arthroplasty were performed from April 2006 until December 2007 with mean age of 79.7.

Retractor for MIS stem insertion has been used for 36 hips from February 2007.

Stem was cemented for more than 13mm at femoral isthmus.

Stem position was measured in rentogenographs of hip after operation about adduction or abduction, extension or flexion, and anteversion of stem in proximal femur.

The average abduction/adduction was 1.75 degree abduction in conventional method and 1.38 degree abduction from February 2007.

The average extension/flexion was 1.10 degree flexion in conventional method and 0.25 degree flexion from February 2007.

The average anteversion was 30.3 degree in conventional method and 28.4 degree from February 2007.

Two cases in conventional method and one case from February 2007 complicated femoral fracture during operation.

In conventional method, cement cap in one case was undersized and proximal major trochanteric fracture was happened in one case.

Ectopic ossification at medial gluteal muscle in one case was observed and one case was dislocated among conventionally operated cases during follow-up period.

Care of femoral exposure though gluteal muscles is needed in anterior and anterolateral MIS. More exact and safe stem insertion procedure is available by using retractor for MIS of the hip.