Femoral acetabular impingement

Three-Dimensional CT and 3D MRI of Hip- Important Aids to Hip Preservation Surgery

Common hip internal derangements include femoroacetabular impingement (FAI), developmental dysplasia of hip (DDH) dysplasia, and avascular necrosis (AVN) of the femoral head. These are initially screened by radiographs. For preoperative planning of hip preservation, 3-dimensional (3D) CT is commonly performed to assess bony anatomy and its alterations. Magnetic resonance imaging (MRI) is used to evaluate labrum, hyaline cartilage, tendons, synovium, and loose bodies, and provides vital information for surgical decision-making. However, conventional 2D MRI techniques are limited by lack of isotropic multiplanar reconstructions and partial volume artifacts. With advancements in hardware and software, novel isotropic 3D MR Proton Density images are acquired with acceptable acquisition times leading to improved visualization of soft tissue and osseous structures for various hip conditions. Three-Dimensional MRI allows multiplanar non-gap reconstructions along the structures of interest. It results in detection of small, otherwise inconspicuous labral tears without the need for MR arthrogram, which can be subsequently measured. In addition, radial reconstructions of the femoral head can be performed from original 3D volume MR imaging and CT imaging without the need for individual different plane acquisitions. Three-Dimensional MRI thus impacts surgical decision-making for the important common hip derangement conditions. For example, femoral head hyaline cartilage loss may make hip preservation difficult or impossible. In this review, we discuss the advantages and technical details of 3D CT and MRI and their significant role in aiding hip preservation surgery for common hip conditions. The conditions discussed in this article include FAI, DDH, AVN, synovial disorders, cartilaginous tumors, and hip fractures.

Surgical Technique of the "Up-The-Neck" View During Hip Arthroscopy for Femoroacetabular Impingement

In the setting of femoroacetabular impingement, arthroscopy versus open surgery confers many advantages. However, inadequate bony resection remains a concern and is the leading cause of revision surgery. Several strategies have been described to ensure a more-complete resection during hip arthroscopy. In this current technique article, the authors describe a modified anterior portal site view called the "up-the-neck" view. This view allows for greater visualization of the femoral head-neck junction and alleviates challenges faced when assessing resection intraoperatively. The "up-the-neck" view is achieved by placing a 70° arthroscope in the anterior lateral portal and subsequently rotating the camera 90°. The head-neck junction will appear horizontally, rather than vertically, on this view, which allows for the easy identification of missed imperfections. This may reduce the need for revision surgery and future investigation is necessary to determine the reoperation rates following this technique.

Does 3DMR provide equivalent information as 3DCT for the pre-operative evaluation of adult Hip pain conditions of femoroacetabular impingement and Hip dysplasia?

OBJECTIVE:

Femoroacetabular impingement (FAI) and hip dysplasia (HD) are frequently evaluated by isotropic CT (3DCT) for preoperative planning at the expense of radiation. The aim was to determine if isotropic MRI (3DMR) imaging can provide similar quantitative and qualitative morphological information as 3DCT.

METHODS:

25 consecutive patients with a final diagnosis of FAI or HD were retrospectively selected from December 2016-December 2017. Two readers (R1, R2) performed quantitative angular measurements on 3DCT and 3DMR, blinded to the diagnosis and each other's measurements. 3DMR and 3DCT of the hips were qualitatively and independently evaluated by a radiologist (R3), surgeon (R4), and fellow (R5). Interobserver and intermodality comparisons were performed.

RESULTS:

The ICC was good to excellent for all measurements between R1 and R2 (ICC:0.60-0.98) and the majority of intermodality measurements for R1 and R2. Average inter-reader and inter-modality PABAK showed good to excellent agreement for qualitative reads. On CT, all alpha angles (AA) were significantly lower in dysplasia patients than in cam patients (p < 0.05). All lateral center-edge angle (LCEA) were significantly lower in dysplasia than in cam patients (p < 0.05). On MR, AA at 12, 1, and 2 o'clock, and LCEA at center were significantly lower in dysplasia patients than in cam patients (p < 0.05).

CONCLUSION:

3DMR offers similar qualitative and quantitative analysis as 3DCT in adult painful hip conditions.

ADVANCES IN KNOWLEDGE:

3DMR has good potential to replace 3DCT and serve as a one-stop modality for bone and soft tissue characterizations in the pre-operative evaluation of FAI and HD.