Hip Capsulolabral Complex: Anatomy, Disease, MRI Features, and Postoperative Appearance.

The hip is a uniquely constrained joint with critical static stability provided by the labrum, capsule and capsular ligaments, and ligamentum teres. The labrum is a fibrocartilaginous structure along the acetabular rim that encircles most of the femoral head. Labral tears are localized based on the clock-face method, which determines the extent of the tear while providing consistent terminology for reporting. Normal labral variants can mimic labral disease and can be differentiated by assessment of thickness or width, shape, borders, location, and associated abnormalities. The Lage and Czerny classification systems are currently the most well-known arthroscopic and imaging systems, respectively. Femoroacetabular impingement is a risk factor for development of labral tears and is classified according to bone dysmorphisms of the femur ("cam") or acetabulum ("pincer") or combinations of both (mixed). The capsule consists of longitudinal fibers reinforced by ligaments (iliofemoral, pubofemoral, ischiofemoral) and circular fibers. Capsular injuries occur secondary to hip dislocation or iatrogenically after capsulotomy. Capsular repair improves hip stability at the expense of capsular overtightening and inadvertent chondral injury. The ligamentum teres is situated between the acetabular notch and the fovea of the femoral head. Initially considered to be inconsequential, recent studies have recognized its role in hip rotational stability. Existing classification systems of ligamentum teres tears account for injury mechanism, arthroscopic findings, and treatment options. Injuries to the labrum, capsule, and ligamentum teres are implicated in symptoms of hip instability. The authors discuss the labrum, capsule, and ligamentum teres, highlighting their anatomy, pathologic conditions, MRI features, and postoperative appearance. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Ultrasound-guided injection and aspiration of small joints: techniques, pearls, and pitfalls.

Ultrasound (US)-guided musculoskeletal intervention of small joints or joints other than the shoulder, elbow, hip, knee, and ankle can be technically challenging. Small joints produce a narrower landing zone for the needle and a smaller target that may be made even more inaccessible by bulky osteophytes. Sonographic (US) guidance offers important advantages including near-field visualization of the joint and soft tissues, ease of access, portability, ability to compare with the contralateral side, and lack of ionization radiation. This review article focuses on the performance of US-guided injections and aspirations involving small joints (joint capacity < 2 mL and/or typically evaluated or injected with a compact linear transducer). For each joint (temporomandibular, acromioclavicular, sternoclavicular, distal radioulnar, symphysis pubis, and joints of the digits of the hands and feet), a brief overview of the relevant anatomy, indications, procedural description, pearls and pitfalls will be highlighted. This article demonstrates the various approaches to diagnostic or therapeutic injection and aspiration of small joints with the aid of US images, cines and graphic illustrations, emphasizing joint positioning, anatomic landmarks, and needle trajectory for a safe and efficacious procedure. A brief review of available literature for each joint will also be provided.

Novel Homozygous Variant in COQ7 in Siblings With Hereditary Motor Neuropathy.

Background and Objectives: Coenzyme Q10 (CoQ10) is an important electron carrier and antioxidant. The COQ7 enzyme catalyzes the hydroxylation of 5-demethoxyubiquinone-10 (DMQ10), the second-to-last step in the CoQ10 biosynthesis pathway. We report a consanguineous family presenting with a hereditary motor neuropathy associated with a homozygous c.1A > G p.? variant of COQ7 with abnormal CoQ10 biosynthesis. Methods: Affected family members underwent clinical assessments that included nerve conduction testing, histologic analysis, and MRI. Pathogenicity of the COQ7 variant was assessed in cultured fibroblasts and skeletal muscle using a combination of immunoblots, respirometry, and quinone analysis. Results: Three affected siblings, ranging from 12 to 24 years of age, presented with a severe length-dependent motor neuropathy with marked symmetric distal weakness and atrophy with normal sensation. Muscle biopsy of the quadriceps revealed chronic denervation pattern. An MRI examination identified moderate to severe fat infiltration in distal muscles. Exome sequencing demonstrated the homozygous COQ7 c.1A > G p.? variant that is expected to bypass the first 38 amino acid residues at the n-terminus, initiating instead with methionine at position 39. This is predicted to cause the loss of the cleavable mitochondrial targeting sequence and 2 additional amino acids, thereby preventing the incorporation and subsequent folding of COQ7 into the inner mitochondrial membrane. Pathogenicity of the COQ7 variant was demonstrated by diminished COQ7 and CoQ10 levels in muscle and fibroblast samples of affected siblings but not in the father, unaffected sibling, or unrelated controls. In addition, fibroblasts from affected siblings had substantial accumulation of DMQ10, and maximal mitochondrial respiration was impaired in both fibroblasts and muscle. Discussion: This report describes a new neurologic phenotype of COQ7-related primary CoQ10 deficiency. Novel aspects of the phenotype presented by this family include pure distal motor neuropathy involvement, as well as the lack of upper motor neuron features, cognitive delay, or sensory involvement in comparison with cases of COQ7-related CoQ10 deficiency previously reported in the literature.

Biallelic SOX8 Variants Associated With Novel Syndrome With Myopathy, Skeletal Deformities, Intellectual Disability, and Ovarian Dysfunction.

Background and Objectives: The human genome contains ∼20,000 genes, each of which has its own set of complex regulatory systems to govern precise expression in each developmental stage and cell type. Here, we report a female patient with congenital weakness, respiratory failure, skeletal dysplasia, contractures, short stature, intellectual delay, respiratory failure, and amenorrhea who presented to Medical Genetics service with no known cause for her condition. Methods: Whole-exome and whole-genome sequencing were conducted, as well as investigational functional studies to assess the effect of SOX8 variant. Results: The patient was found to have biallelic SOX8 variants (NM_014587.3:c.422+5G>C; c.583dup p.(His195ProfsTer11)). SOX8 is a transcriptional regulator, which is predicted to be imprinted (expressed from only one parental allele), but this has not yet been confirmed. We provide evidence that while SOX8 was maternally expressed in adult-derived fibroblasts and lymphoblasts, it was biallelically expressed in other cell types and therefore suggest that biallelic variants are associated with this recessive condition. Functionally, we showed that the paternal variant had the capacity to affect mRNA splicing while the maternal variant resulted in low levels of a truncated protein, which showed decreased binding at and altered expression of SOX8 targets. Discussion: Our findings associate SOX8 variants with this novel condition, highlight how complex genome regulation can complicate novel disease-gene identification, and provide insight into the molecular pathogenesis of this disease.

US and MRI of Pelvic Tendon Anatomy and Pathologic Conditions.

The bony pelvis serves as the attachment site for a large number of powerful muscles and tendons that drive lower extremity movement. Organizing the pelvic tendons into groups that share a common function and anatomic location helps the radiologist systematically evaluate these structures for injury, which can be caused by repetitive stress, acute trauma, or failure of degenerated tissues. Tears of the anteromedial adductors around the pubic symphysis and anterior flexors traversing anterior to the hip principally affect younger male athletes. Tears of the lateral abductors and posterior extensors are more common in older individuals with senescent tendinosis. The deep external rotators are protected and rarely injured, although they can be impinged. Imaging of the pelvic tendons relies primarily on US and MRI; both provide high spatial and contrast resolution for soft tissues. US offers affordable point-of-care service and dynamic assessment, while MRI allows simultaneous osseous and articular evaluation and is less operator dependent. While the imaging findings of pelvic tendon injury mirror those at appendicular body sites, radiologists may be less familiar with tendon anatomy and pathologic conditions at the pelvis. The authors review pertinent anatomy and imaging considerations and illustrate common injuries affecting the pelvic tendons. Online supplemental material is available for this article. ©RSNA, 2022.

Neurolymphomatosis of the lumbosacral plexus and its branches: case series and literature review.

BACKGROUND: Neurolymphomatosis (NL) is a direct process of invasion of peripheral nerves by lymphoma. It occurs in roughly 5% of patients with lymphoma and represents a particularly difficult diagnostic dilemma when it is the presenting focal manifestation of occult lymphoma. CASE PRESENTATION: We present 3 examples of invasion of the lumbosacral plexus and its branches. These cases demonstrate a protean clinical picture with regards to the time relationship to the clinical course of lymphoma and the neuroanatomical extent of lumbosacral plexus invasion. We demonstrate the complementary role of different imaging modalities. A review of the literature summarizes 23 reports where lumbosacral plexus invasion was the index manifestation, at the time of first diagnosis or recurrence of lymphoma. This series confirms the strong preponderance of B-cell type (92%). There is a marked predilection for involvement of the sciatic nerve (74%), either focally or in a longitudinally extensive fashion, from the ischium to the popliteal fossa. There can also be restricted and discrete involvement of tibial and fibular branches. In recent years, ultrasound and CT have been given a more limited role, as screening tools or as a guide for biopsy. MRI neurography and PET-CT have become leading diagnostic modalities for diagnosis, staging and assessment of treatment response. CONCLUSION: The diagnosis of NL may be challenging, and it was once only reached at autopsy. Improved diagnostic imaging of focal or even asymptomatic disease offers new hope for earlier diagnosis and successful targeted therapy.

Relationship between radiologist training level and radiation exposure for therapeutic hip injections.

OBJECTIVE: The aim of this study was to determine the relationship between the level of training of the performing radiologist and patient radiation exposure, as measured by fluoroscopy time (FT) and dose area product (DAP), during fluoroscopic guided hip injections. MATERIALS AND METHODS: This IRB-approved retrospective review of our institutional radiology report database identified all fluoroscopic guided hip injections performed between August 1st, 2012 and May 30th, 2015. Performing radiologists were divided into groups based on their level of training at the time of the procedure: first-year residents (R1), second-year residents (R2), third-year residents (R3), fourth-year residents (R4), staff fellowship trained musculoskeletal radiologists, and non-musculoskeletal radiologists. A mixed effects model was applied, using level of training as an independent predictor to model FT and DAP separately. RESULTS: There were 20, 19, 18 and 20 residents in the R1, R2, R3 and R4 groups, respectively. There were 5 performers in the non-MSK radiologist group, and 7 in the MSK radiologist group. A total of 1362 hip injection procedures met the inclusion criteria and were included in the analysis. The overall average FT was 26s (±17SD) and overall average DAP was 20.4uGy*m2 (±22.3SD). The mixed effects model showed no statistically significant difference between the groups, for FT (p=0.31) and for DAP (p=0.82). CONCLUSION: There is no association between radiologist level of training and patient radiation exposure for fluoroscopic hip injections. Resident trainees maintain radiation exposure to patients at levels comparable to their more experienced colleagues.

MR imaging of osseous lesions of the hip.

MR imaging, because of its multiplanar capability and superior soft tissue contrast resolution, is the preferred modality to assess osseous and soft tissue structures around the hip joint. This article reviews the clinical presentation, disease process, and imaging findings of important congenital and acquired osseous disorders of the pediatric and adult hip.

Elbow magnetic resonance imaging variants and pitfalls.

Imaging variants of the elbow and pitfalls can be disconcerting and can lead to diagnostic mistakes. Inhomogeneities in the magnetic field and coil position can result in signal changes that may simulate abnormality. Bone signal and morphology variants, such as the islands of red marrow and the pseudodefect of the capitellum and intraarticular inclusions such as plicae, may be mistaken for abnormal findings. Variations of the distal biceps and triceps tendons and different aspects of the ligaments and their insertions, as well as nonpathologic signal and width changes in the ulnar nerve, are other examples of common pitfalls in magnetic resonance imaging of the elbow.