The Achilles tendon is the largest, and most commonly torn tendon in the body. The Achilles is usually torn at a region of relative hypo-vascularity proximal to its insertion. However, partial thickness tears and other pathologies often occur at its insertion on the calcaneus. Anatomically, the insertion is a confluence of the gastrocnemius and soleus muscles that fuse to form a myotendinous unit on the posterosuperior aspect of the calcaneus. This review aims to reveal the insertional footprint as individual fascicular components attaching to facets of calcaneal tuberosity. Understanding this anatomy is essential for interpreting tear patterns and surgical implications.

Introduction: To our knowledge, no previous study has evaluated the use of MRI to diagnose posterior capsule dehiscence after posterior approach total hip arthroplasty (THA) with capsular repair and its association with postoperative posterior hip dislocation. Methods: A retrospective chart review of patients who underwent posterior approach THA with capsulotomy repair was performed. Patients were identified who subsequently underwent MRI, and these studies were evaluated for signs of posterior capsular disruption. Each chart was then evaluated for episodes of postoperative hip dislocation. Results: Six hundred seventy-five patients were included in the retrospective review. Thirty-two patients (17 women [aged 37 to 78 years] and 15 men [aged 34 to 80 years]) met the inclusion criteria. Fifteen patients of 32 (48.4%) developed posterior capsule dehiscence after repair (group 1). Seventeen patients of 32 (51.6%) did not have MRI evidence of posterior capsule dehiscence (group 2). In group 1, 2 patients of 15 (13.3%) experienced a posterior hip dislocation. No group 2 patients experienced a posterior hip dislocation. Overall, only 2 patients of 32 (6.3%) developed posterior hip dislocations. In group 1, 12 patients of 15 (80%) developed dehiscence at the lateral capsule margin at the greater trochanter suture repair site. The two patients in group 1 with posterior hip dislocations displayed MRI evidence of capsular dehiscence in this region. Two patients of 15 (13.3%) in group 1 demonstrated dehiscence at the central third of the posterior capsule, whereas 1 patient of 15 (6.6%) in group 1 demonstrated dehiscence at the medial/acetabular margin. No significant difference was found between the dislocation rates between groups 1 and 2 (P = 0.212). The distribution of capsular dehiscence (lateral, middle, and medial capsule) in group 1 was significant (P = 0.0006). Discussion: MRI can effectively diagnose capsular dehiscence in patients who have undergone posterior THA. Most repaired capsules failed in the lateral repair region. MRI offers the potential to identify patients with a higher risk of implant dislocation. Level of Evidence: Therapeutic level III

Ectopic gas is defined as the presence of gas in abnormal locations, that is, outside the aerodigestive tract. It constitutes a common radiologic finding associated with a wide range of disorders. Although it is usually an innocuous and self-limited condition, it should prompt a search for the underlying cause, given that the clinical significance of ectopic gas varies from benign to life threatening, depending on the site involved and the rate of accumulation. To ensure optimal management of each case, the origin of ectopic gas should be determined. The search for its exact location and underlying cause often represents a challenge, as air can be depicted distant from its point of origin because of fascial interconnectivity. Thorough knowledge of anatomic compartments facilitates quick identification of the cause and contributes to a prompt diagnosis. Likewise, radiologists should be familiar with the alarm signs associated with severe conditions. Imaging studies are essential to help the radiologist confirm the diagnosis of ectopic gas, determine its precise location and extension, identify severe cases, exclude associated complications, and monitor evolution. CT is the modality of choice in the imaging assessment of ectopic gas. In this review, the authors discuss the different causes of ectopic gas with an etiopathogenic approach to describe the myriad processes that might give rise to this condition. In addition, alarm signs associated with potentially fatal ectopic gas are described and depicted.© RSNA, 2020 • radiographics.rsna.org

Massive irreparable rotator cuff tears can be a challenging problem for arthroscopists in the perioperative setting because the typical treatment, reverse total shoulder arthroplasty, may not be the best option for all patients. Superior capsular reconstruction (SCR) is an advancing treatment option for patients with rotator cuff tears that are neither amenable to primary repair nor ideal for arthroplasty. Patient selection, which is strongly dependent on preoperative imaging findings, is an important step in obtaining favorable surgical outcomes. The tissue quality and tear type are particularly important when considering SCR for a patient. When unsuccessful SCR is suspected, postoperative MRI of the shoulder offers the surgeon and radiologist a means of evaluating the integrity and fixation of the graft. Fluid-sensitive MRI sequences are best for examining the final SCR construct, with high-signal-intensity fluid interruptions within the graft and the presence or worsening of shoulder arthropathy indicating graft failure. The indications for SCR are discussed, and the normal postoperative MRI findings after SCR are described in this review. In addition, the common types of SCR graft failure and associated imaging findings are described and illustrated.© RSNA, 2020 • radiographics.rsna.org

Background: Given the high prevalence of musculoskeletal conditions in the USA, it is important for orthopedic surgeons to promptly identify patients who may be at risk for opioid misuse. Questions/Purposes: The aim of this literature review was to elucidate various musculoskeletal pathologies and complications, as seen on imaging, that may indicate opioid misuse or opioid use disorder. Methods: A literature search was conducted using the PubMed, Scopus, and Cochrane Library databases for articles related to imaging findings associated with chronic opioid use or misuse in orthopedic patients. Two independent reviewers conducted the search utilizing pertinent Boolean operations. Results: We reviewed 36 full-text articles and categorized the radiographic evidence of opioid misuse as follows: soft-tissue radiologic findings, cellulitis, necrotizing fasciitis, abscess formation, retained needles, discitis, myopathy and rhabdomyolysis, osteomyelitis, septic arthritis, and septic thrombophlebitis. Conclusion: Knowledge of the radiologic findings of opioid misuse will assist orthopedic surgeons in making timely diagnoses that may alter therapeutic regimens for their patients.