Radiologists should use the hip-knee-ankle angle rather than the mechanical axis deviation to describe knee alignment.

OBJECTIVE: Preoperative and postoperative coronal knee alignment is an important predictor of total knee arthroplasty (TKA) failure. Radiologists often report the mechanical axis deviation (MAD) rather than hip-knee-ankle angle (HKAA) to describe coronal knee alignment. The aim of this study is to evaluate (i) how well the MAD predicts the HKAA; (ii) if patient height and sex affect the performance of the MAD; and (iii) if the MAD could be measured faster than the HKAA. MATERIALS AND METHODS: Two hundred patients undergoing hip-to-ankle radiographs for TKA planning were retrospectively reviewed. The MAD and HKAA were measured using previously published methods by the Visage picture archiving and communication systems (PACS) tools. Receiver operator characteristic (ROC) curves were used to evaluate the performance of the MAD to predict HKAA by gender and height. The performance of a linear model was used to predict HKAA from MAD in a prospectively collected cohort of 40 patients. Paired t tests were used for the comparison of time measurement in MAD and HKAA in this cohort. RESULTS: MAD strongly correlated with HKAA (r = 0.99, p < 0.001); however, the performance of MAD differed by height (p = 0.005) and sex (p < 0.001). There was no significant difference in the time taken to measure HKAA versus MAD (p > 0.05). CONCLUSION: HKAA should be used instead of the MAD because it is more clinically relevant and takes the same amount of time to be measured.

Multiple myeloma: a review of atypical imaging features and other distinct plasma cell disorders that demonstrate similar imaging features.

Multiple osteolytic lesions are a well-recognized and typical imaging feature of multiple myeloma as well as several other plasma cell disorders. Given the high volume of imaging studies obtained of multiple myeloma patients, radiologists will likely encounter a subset of multiple myeloma patients with less common or "atypical" findings during their practice. These atypical findings include osteosclerotic lesions, extramedullary lesions, and amyloid deposition. Similar imaging findings that are considered atypical for multiple myeloma can also be detected in other plasma cell disorders that are distinct from multiple myeloma. For instance, POEMS syndrome is a distinct plasma cell disorder from multiple myeloma, but also can present with osteosclerotic lesions. This article reviews the atypical findings associated with multiple myeloma and also reviews other plasma cell disorders that can have a similar spectrum of imaging findings. Special attention is paid to the musculoskeletal imaging findings.

Epithelioid osteoblastoma with secondary aneurysmal bone cyst and FOS gene rearrangement.

Epithelioid osteoblastoma, sometimes equated with aggressive osteoblastoma, is a variant of osteoblastoma that typically demonstrates more worrisome imaging and pathological features compared to conventional osteoblastoma. These more aggressive features can overlap with those seen in osteosarcoma, creating a diagnostic challenge for radiologists and pathologists. Recent identification of FOS and FOSB gene rearrangements in osteoid osteoma and osteoblastoma has allowed for greater diagnostic confidence following biopsy, but careful radiological-pathological correlation remains a key component for guiding appropriate management. Although the imaging features of conventional osteoblastoma have been previously described, there are limited examples in the literature of the imaging appearance of epithelioid osteoblastoma, and none with secondary aneurysmal bone cyst. In this case report, we detail the clinical, imaging, and histological characteristics of a proximal femoral epithelioid osteoblastoma which was pathologically confirmed by FOS and FOSB genetic testing. The initial imaging impression favored a malignancy, but when the biopsy results were correlated in a multidisciplinary fashion with the imaging, epithelioid osteoblastoma became the leading diagnosis which was subsequently genetically confirmed. This case emphasizes the value of multidisciplinary radiology-pathology correlation in routine practice.

Bone health of transgender adults: what the radiologist needs to know.

Sex steroids are important regulators of bone development before puberty and of bone homeostasis throughout adulthood. Gender-affirming therapies with sex steroids are used in transgender and gender diverse persons for treatment of gender dysphoria, which may have profound impacts on their bone metabolism. Many studies have described variable changes in bone density and geometry in transgender cohorts. In order to provide informed guidance on the effect of gender-affirming therapy, the International Society of Clinical Densitometry issued official position statements in 2019 for the performance and interpretation of dual-energy x-ray absorptiometry in transgender and gender-diverse patients. We review the effects of gender-affirming hormone therapy on bone physiology and the changes in bone modulation that have been reported in the literature in transgender patients who have received gender-affirming therapy. We also summarize the recent guidelines for interpretation of dual energy x-ray absorptiometry as an update for the radiologist.

Magnetic Resonance Imaging of the Shoulder: Interpretation of Common Orthopaedic Injuries.

Magnetic resonance imaging (MRI) is frequently obtained to assess for pathology in the setting of shoulder pain and dysfunction. MRI of the shoulder provides diagnostic information that helps optimize patient management and surgical planning. Both general and subspecialized orthopaedic surgeons routinely order and review shoulder MRIs in practice. Therefore, familiarity with the MRI appearance of common shoulder pathologies is important. This document reviews the most common shoulder pathologies using a standardized MRI interpretative approach. Instructional videos demonstrating a musculoskeletal radiologist interpreting normal and abnormal shoulder MRIs are also provided.

Is Heterotopic Ossification Associated With Surgical Approach in Total Hip Arthroplasty?

BACKGROUND: Although risk factors for heterotopic ossification (HO) have been defined, the effect from surgical approach is not fully understood. The primary objective of our study was to evaluate the effect that surgical approach has on the risk for developing severe HO after total hip arthroplasty (THA) and compare this with other known risk factors. We hypothesized that there would be no difference in HO formation based on the surgical approach. METHODS: We retrospectively reviewed all patients who underwent primary THA at our hospital between March 2011 and March 2021. Patients with HO documented in the radiology reports were cross-referenced with our THA data set and manually reviewed to determine Brooker classification. Patient demographics, medical comorbidities, surgical details, and medication information were collected from the electronic medical record and compared. RESULTS: Of 3,427 patients who underwent THA, 677 (19.8%) developed HO postoperatively. A multivariable analysis confirmed that surgical approach was independently associated with increased odds for HO development. The anterolateral (odds ratio [OR], 3.43; P < 0.001) and posterior (OR, 2.24; P < 0.001) approaches had increased odds for developing HO compared with the direct anterior approach. However, only the anterolateral approach (OR, 1.85; P = 0.033) demonstrated an increased association with the development of severe HO (Brooker 3, 4) postoperatively. CONCLUSION: Although the use of the direct anterior approach had the lowest overall OR for developing HO after THA, this is likely only clinically notable when compared with the anterolateral approach. LEVEL OF EVIDENCE: III.

Direct anterior approach associated with lower dislocation risk after primary total hip arthroplasty in patients with prior lumbar spine fusion.

BACKGROUND: While there has been much interest in the increased dislocation rate in total hip arthroplasty (THA) patients with a lumbar spine fusion (LSF), there is minimal literature comparing the risk based on surgical approach. The purpose of this study was to determine if a direct anterior (DA) approach was protective against dislocation when compared to the anterolateral and posterior approaches in this high-risk patient population. METHODS: A retrospective review was performed of 6554 THAs performed at our institution from January 2011 to May 2021. 294 (4.5%) patients had a prior LSF and were included in the analysis. The surgical approach, timing of LSF in relation to THA, vertebral levels fused, timing of THA dislocation, and the need for revision surgery were recorded for statistical analysis. RESULTS: In total, 39.7.3% of patients underwent a DA approach (n = 117), 25.9% underwent an anterolateral approach (n = 76), and 34.3% underwent a posterior approach (n = 101). There was no difference in number of vertebral levels fused between groups (mean 2.5, all p > 0.05). There was a total of 13 (4.4%) THA dislocation events, with an average time from surgery to dislocation of 5.6 months (0.3-30.5 months). There were fewer dislocations in the DA cohort (0.9%) in comparison to both the anterolateral (6.6%, p = 0.036) and posterior groups (6.9%, p = 0.026). CONCLUSIONS: The DA approach demonstrated a significantly lower THA dislocation rate compared to both the anterolateral and posterior approaches in patients with a concomitant LSF.

Shoulder Osteoarthritis.

Glenohumeral osteoarthritis has proven to be a major contributor to shoulder joint pain and dysfunction in the elderly. There are several conditions about the shoulder that contribute to the development of glenohumeral osteoarthritis, which includes traumatic injuries, rotator cuff pathology, glenohumeral instability, glenoid dysplasia, and osteonecrosis. When glenohumeral osteoarthritis pain is refractory to conservative treatment, intra-articular injections and surgery can be performed. The radiologist should be aware of the varying types of shoulder arthroplasties, what preoperative findings influence that decision and the expected postoperative appearance of the differing components.

Bone and Soft Tissue Tumors: Interventional Techniques for Diagnosis and Treatment.

Radiologists have an integral role in the diagnosis of bone and soft-tissue tumors beyond image interpretation. Image-guided biopsies are used to diagnose and stage musculoskeletal tumors. This article reviews the steps of minimally invasive image-guided biopsies, from prebiopsy planning through postbiopsy pathology follow-up. Helpful techniques to perform and troubleshoot these procedures adequately and safely are detailed. Radiologists are also expanding the treatment options available for many benign and malignant bone and soft-tissue tumors. Some of these more frequently performed procedures include percutaneous thermal ablation and cementoplasty. The evidence, indications, and basic principles of these interventional procedures are also discussed.

Diagnostic Imaging Approach to Solitary Bone Lesions.

Radiologists frequently encounter solitary bone lesions in daily practice. The interpreting radiologist has the onus to determine the level of suspicion and appropriate next-step recommendations to aid in timely healthcare decisions. Lesion imaging characteristics in conjunction with patient history and demographics ultimately determine if a bone lesion is benign. Lesions that cannot be confidently disregarded as benign and clinically insignificant require further evaluation through additional imaging, tissue sampling, or both. We review a diagnostic imaging approach to solitary bone lesions with case examples that detail real-world thought processes for interpretations and practical next-step recommendations.

MRI of the Elbow: Interpretation of Common Orthopaedic Injuries.

MRI is a valuable diagnostic tool that has become an essential part of an orthopaedic surgeon's practice. When acquired in the appropriate clinical setting, an MRI can direct patient management as surgical versus nonsurgical, guide surgical decision making, and even predict patient outcomes. The quality of MRI obtained and quality of the radiology report received varies. Ultimately, the orthopaedic surgeon must interpret the available imaging and apply these findings to treat the patient. The current day practicing orthopaedic surgeon should be familiar with interpreting common MRIs. Although subspecialized orthopaedic surgeons usually have experience and understanding of MRIs in their field, the general orthopaedic surgeon and those in-training will encounter the gamut of musculoskeletal MRIs. This review focuses on common injuries that can occur in the elbow and provides an approach to minimize missed findings.