How to Report: Hip MRI

Writing a good magnetic resonance imaging (MRI) hip report requires a sound understanding of hip anatomy, imaging, and related pathologies. The structures of the hip most prone to pathology are the articular surfaces, labrum, subchondral bone, and gluteal tendons. Particular attention should be paid to abnormal hip morphology that is relatively common and can manifest as internal or external hip derangement. It is essential to appreciate and report the specific features of each pathology that carry clinical significance to aid patient management. This article is aimed at trainee radiologists and those less experienced with reporting hip MRI, focusing on the essential features to comment on and providing examples of terminology to use and MR images to illustrate these features.

Consideration of pelvic tilt at the time of preoperative planning improves standing acetabular position after robotic-arm assisted total hip arthroplasty

Introduction: Approximately half of dislocating total hip arthroplasties (THAs) demonstrate acetabular component position within traditional safe zones. It is unclear if postoperative functional acetabular position can be reliably improved by considering preoperative pelvic tilt. We investigated whether standing cup position targets could be more accurately achieved by considering preoperative standing pelvic tilt in addition to bone landmarks when planning for robot-assisted THA. Methods: We reviewed 146 THAs performed by a single surgeon using computed tomography-based 3-dimensional planning and robotic technology to guide acetabular reaming and component insertion. Planning for 73 consecutive cases started at 40° of inclination and 22° of anteversion relative to the supine functional plane and was adjusted to better match native hip anatomy. Planning for the next 73 cases was modified to consider standing pelvic position based on standing preoperative radiographs. We compared groups to determine the rate when cups were placed outside our standing targets of 15–30° anteversion and 35–50° inclination. Results: Cup position proved to be reliable in both groups, with 83% of cups in the anatomic planning cohort and 90% of cups in the functional planning cohort achieving standing targets for both anteversion and inclination ( p = 0.227). Variances were lower in the functional planning group: 9.4° versus 15.8° of inclination ( p = 0.079) and 18.3° versus 26.1° of anteversion ( p = 0.352). The range of functional positions was narrower in the functional planning group: 35.7–47.5° versus 31.8–54.9° of inclination and 16.7–35.0° versus 10.1–35.9° of anteversion. Discussion: Our results suggest enhanced planning that considers pelvic tilt, when coupled to a precision tool to achieve the plan, can reliably achieve target standing component positions. Considering preoperative functional pelvic position may improve postoperative functional acetabular component placement in THA, but the clinical benefit of this has yet to be confirmed.

Innervation of the Posterior Hip Capsule: A Cadaveric Study

Objective Recent studies of hip anatomy have turned to the posterior hip capsule to better understand the anatomic location of the posterior capsular sensory branches and identify nerves with potential for neural blockade. Current literature has shown the posterior hip capsule is primarily supplied by branches from the sciatic nerve, nerve to quadratus femoris, and superior gluteal nerve (1, 2). This cadaveric study investigated the gross anatomy of the posterior hip, while also identifying potential targets for hip analgesia, with emphasis on the superior gluteal nerve and nerve to quadratus femoris. Design Cadaveric study. Setting University of Texas Health San Antonio Anatomy Lab Methods 10 total cadavers (18 hips total), were posteriorly dissected identifying nerve to quadratus femoris, superior gluteal nerve, and sciatic nerve. Nerves were labeled with radio-opaque markers. Following the dissections, fluoroscopic images were obtained as sequential angles to identify neural anatomy and help expand anatomic knowledge for interventional pain procedures. Results The posterior hip capsule was supplied by the sciatic nerve in 1/16 hips, the nerve to quadratus femoris in 15/18 hips, and the superior gluteal nerve in 6/18 hips. Conclusions The nerve to quadratus femoris reliably innervates the posterior hip joint. Both the sciatic nerve and superior gluteal nerve may have small articular branches that may be involved in posterior hip innervation, but not this is not seen commonly. The results of this study may elucidate novel therapeutic targets for treatment of chronic refractory hip pain (i.e., the nerve to quadratus femoris).

Anterior hip ultrasound: A useful technique in developmental dysplasia of the hips

Introduction: Infant developmental dysplasia of the hips arises when there is an interruption to normal joint development, usually present at birth but may be a later development. It has a wide spectrum of severity with potentially disastrous long-term complications if left untreated. Incidence is highly variable, often being attributed to differences of opinion in definition and diagnosis; however, there is consensus that ultrasound be used in screening and management. Topic Description: The anterior hip ultrasound technique is underutilised but is of value due to the additional confidence it provides regarding joint stability. Discussion: The ability to relate the acquired ultrasound image to hip anatomy and a technical appreciation of the technique are crucial to successful use. The method is described and its use within previous literature briefly outlined. Using pictorial ultrasound imaging examples to demonstrate the technique, we aim to highlight the anterior approach as a useful addition to ultrasound assessment of infant developmental dysplasia of the hips. Conclusion: Knowledge and understanding of different techniques is essential for practitioners involved in the diagnosis and management of this multifaceted and vigorously debated condition.

An Evaluation of Sensing Technologies to Measure Intraoperative Leg Length for Total Hip Arthroplasty

Total hip arthroplasty (THA) procedures have been identified as high-volume procedures with growing prevalence. During the procedure, orthopedic surgeons largely rely solely on qualitative assessment to ensure an excessive limb length discrepancy (LLD) is not introduced from the implant selection. LLD can result in back pain and gait complications, with some cases of LLD requiring a revision procedure to mitigate. To address this issue, we evaluated several methods of sensing distance intraoperatively to determine the best approach to measure leg length during the THA procedure. A testing setup using a sawbones model of hip anatomy in the decubitus position was used as a simulation of the THA procedure to test the accuracy of each of the sensing modalities.

The Use of Tinkertoys® for Teaching Hip Anatomy and Alignment

Background: Health education can require an emphasis on potentially difficult concepts in anatomy and alignment. Purpose: The purpose of this study is to describe the effect of active use of Tinkertoys® to promote understanding of alignment and to report its effectiveness for knowledge acquisition among students according to spatial ability. Methods: Two cohorts of physical therapy (PT) students (n=70) participated in this project over two years. Thirty-four students (second cohort) rated their math and spatial abilities on a survey. Following a traditional lecture on femoral torsion and angle of inclination, all participants took a pre-test. Then, a Tinkertoys® model of the lower limb was used along with a pelvic bone to simulate the hip anatomy and alignment. Only students in the second cohort received the opportunity to simultaneously manipulate similar models at their desks. At the end of the class period, a post-test was given. Four days later, a similar quiz was given. Descriptive statistics and repeated measures with pairwise comparisons were used to analyze the data. Results: Quiz means improved from pre-test (32.1%) to post-test (74.6%, p=0.023). Differences were not evident between people who self-reported stronger versus weaker spatial abilities (p=0.186). Conclusions: Tinkertoys® model use, with or without simultaneous model manipulation, facilitated learning, regardless of self-reported spatial ability.