Purpose To determine and compare the frequency of imaging abnormalities in asymptomatic and symptomatic patients after arthroscopic hip surgery. Materials and Methods This study was approved by the institutional review board. Informed consent was obtained from all patients. Thirty-four patients (17 asymptomatic and 17 symptomatic patients) underwent 1.5-T magnetic resonance (MR) arthrography of the hip 1 year after arthroscopic treatment of femoroacetabular impingement. Two readers independently analyzed all MR arthrographic images for the presence of abnormal imaging findings, including capsular adhesions at the femoral neck, obliteration of the paralabral sulcus, labral defects, and defects of the hip capsule in several anatomic positions (anterior to posterior). Postoperative findings were compared with linear and generalized linear mixed-effects regression models. Results Capsular adhesions at the anterior femoral neck were present in 12 of the 34 patients (35%), and there were no differences between the groups or readers (P = .99). The paralabral sulcus was obliterated in at least one anatomic location in 94% (reader 1, 32 of 34 patients) and 100% (reader 2, 34 of 34 patients) of patients (P = .99). Residual labral tears were detected in 35% of asymptomatic patients (six of 17 patients) and 41% of symptomatic patients (seven of 17 patients) by reader 1 and in 53% of asymptomatic and symptomatic patients (nine of 17 patients in each group) by reader 2, without significant differences between the groups (P = .81). Defects of the hip capsule were more common in asymptomatic patients (77% [13 of 17 patients] for reader 1 and 53% [nine of 17 patients] for reader 2) than in symptomatic patients (59% [10 of 17 patients] for reader 1 and 47% [eight of 17 patients] for reader 2), but without significant differences (P = .33). Conclusion Obliteration of the paralabral sulcus was the most frequent finding after arthroscopic hip surgery in both asymptomatic and symptomatic patients, and capsular adhesions at the anterior femoral neck were present in 35% of patients in both groups. RSNA, 2016.

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Background Diagnosis of osteomyelitis by imaging can be challenging. The feasibility of diffusion‐weighted imaging (DWI) as ancillary sequence was evaluated in this study. Purpose To evaluate DWI for differentiation between osteomyelitis, bone marrow edema, and healthy bone on forefoot magnetic resonance imaging (MRI). Study type Prospective. Subjects A total of 60 consecutive patients undergoing forefoot MRI divided into three study groups (20 subjects each): osteomyelitis, bone marrow edema, and healthy bone. Field strength/Sequence A 1.5T and 3T MRI scanners; readout‐segmented multishot echo planar DWI. Assessment Two independent radiologists measured apparent diffusion coefficient (ADC) values within abnormal or healthy bone. Statistical Tests ADC values were compared between groups (pairwise t‐test with Bonferroni‐Holm correction for multiple testing). Intraclass correlation coefficient (ICC) was calculated to assess inter‐reader agreement. Threshold ADC values were determined as the cutoffs that maximized the sum of sensitivity and specificity. Receiver operating characteristic (ROC) analysis was performed with statistical threshold of P < 0.05. Results Inter‐reader agreement was 0.92 in the healthy bone group and 0.78 in both the edema and osteomyelitis groups. Average ADC values were significantly different between groups: 1432 ± 222 × 10−6 mm2/sec (osteomyelitis), 1071 ± 196 × 10−6 mm2/sec (bone marrow edema), and 277 ± 89 × 10−6 mm2/sec (healthy bone). A threshold ADC value of 534 × 10−6 mm2/sec distinguishes between healthy and abnormal bone with specificity and sensitivity of 100% each. For distinction between osteomyelitis and bone marrow edema, two cutoff values were determined: a 95%‐specificity cutoff indicating osteomyelitis (>1320 × 10−6 mm2/sec) and a 95%‐sensitivity cutoff indicating bone marrow edema (<1155 × 10−6 mm2/sec). Diagnostic accuracy of 95% was achieved for 73% (29/40) of the subjects. Data Conclusion DWI with ADC maps distinguishes between healthy and abnormal bone on forefoot MRI. Calculated cutoff values allow confirmation or exclusion of osteomyelitis in a high proportion of subjects. Evidence Level 2 Technical Efficacy Stage 2

The open-face design of the Leksell Vantage frame provides many advantages. However, its more rigid, contoured design offers less flexibility than other frames. This is especially true for posterior fossa approaches. This study explores whether these limitations can be overcome by tailored frame placement using a virtual planning approach. The posterior fossa was accessed in ten patients using the Leksell Vantage frame. Frame placement was planned with the Brainlab Elements software, including a phantom-based (virtual) pre-operative planning approach. A biopsy was performed in all patients; in four, additional laser ablation surgery was performed. The accuracy of virtual frame placement was compared to actual frame placement. The posterior approach was feasible in all patients. In one case, the trajectory had to be adjusted; in another, the trajectory was switched from a right- to a left-sided approach. Both cases showed large deviations from the initially planned frame placement. A histopathological diagnosis was achieved in all patients. The new Leksell Vantage frame can be used to safely target the posterior fossa with a high diagnostic success rate and accuracy. Frame placement needs to be well-planned and executed. This can be facilitated using specific software solutions as demonstrated.

In addition to the patient's medical history and clinical evaluation, conventional radiographs and magnetic resonance imaging (MRI) are important tools to indicate appropriate conservative treatment or even revision surgery in patients with symptoms after surgical management of femoroacetabular impingement (FAI). We present an overview of current evidence in postoperative imaging after impingement surgery. Undercorrection of the underlying osseous FAI configuration is the most frequent indication for revision surgery within the first 2 years after index FAI surgery. Femoral neck fractures, iatrogenic chondral injuries, early conversion to total hip arthroplasty, loose bodies, and heterotopic ossifications are rare but typical early complications after surgical treatment of FAI. Abnormal MRI findings after FAI surgery such as intra-articular adhesions, labral tears, cartilage defects, and anterior capsular defects are common findings in both asymptomatic and symptomatic postoperative patients. Avascular necrosis of the femoral head is an extremely rare complication after surgical treatment of FAI.