What is the Diagnostic Accuracy of Aspirations Performed on Hips With Antibiotic Cement Spacers?

BACKGROUND: Periprosthetic joint infection is a serious complication after THA and commonly is treated with a two-stage revision. Antibiotic-eluting cement spacers are placed for local delivery of antibiotics. Aspirations may be performed before the second-stage reimplantation for identification of persistent infection. However, limited data exist regarding the diagnostic parameters of synovial fluid aspiration with or without saline lavage from a hip with an antibiotic-loaded cement spacer. QUESTIONS/PURPOSES: We asked: (1) For hips with antibiotic cement spacers, does saline lavage influence the diagnostic validity of aspirations? (2) What is the diagnostic accuracy of preoperative aspirations performed on hips with antibiotic cement spacers using the Musculoskeletal Infection Society (MSIS) criteria, stratified by saline and nonlavage? (3) For hips with antibiotic spacers, what are the optimal thresholds for synovial fluid white blood cell (WBC) count and polymorphonuclear neutrophil (PMN) percentage for diagnosing infections? METHODS: One hundred seventy-four hips (155 patients) with antibiotic-eluting cement spacers inserted between October 2012 and July 2015 were reviewed. Of these, 98 hips (80 patients) met the inclusion criteria and were included in the analysis (77 nonlavage, 21 saline lavage aspirations). Laboratory data from the aspiration and preoperative workup and intraoperative details were collected. Infection status of each hip procedure was determined based on a modified MSIS criteria using serologic, histologic, and intraoperative findings (sinus tract communicating with the joint at surgery or two positive intraoperative periprosthetic cultures with the same organism or two of the three following criteria: elevated erythrocyte sedimentation rate [ESR] [> 30 mm/hour] and C-reactive protein [CRP] [> 10 mg/L], a single positive intraoperative periprosthetic tissue culture, or a positive histologic analysis of periprosthetic tissue [> 5 neutrophils per high power field]). The diagnostic parameters were calculated for the MSIS criteria thresholds for synovial fluid (ie, WBC count > 3000 cells/µL and PMN percentage > 80%). Optimal thresholds were calculated for the corrected synovial WBC count and PMN percentage with a receiver operating characteristic curve. Separate analyses were performed for the hips with successful aspirations (nonlavage group) and those with saline lavage aspirations. RESULTS: The WBC count and PMN percentage were higher in hips with infection than in hips without infection when nonlavage aspirations were done (WBC count, 6680 cells/µL ± 6980 cells/µL vs 2001 ± 4825; mean difference, 4679; 95% CI, 923-8436; p = 0.015; PMN percentage, 83% ± 13% vs 44% ± 30%; mean difference, 39%; 95% CI, 39%-49%; p < 0.001) and the findings between infected and noninfected aspirations were not different when saline lavage aspirations were done (WBC count, 782 cells/µL ± 696 vs 307 cells/µL ± 343; mean difference, 475; 95% CI, -253 to 1203; p = 0.161; PMN percentage, 67% ± 15% vs 58% ± 28%; mean difference, 10%; 95% CI, -11% to 30%; p = 0.331). Aspirations performed without lavage yielded good diagnostic accuracy in all parameters (WBC count, 78% [95% CI, 70%-86%]; PMN percentage. 79% [95% CI, 70%-88%]; positive culture: 84% [95% CI, 81%-90%]; at least one of the above: 79% [95% CI, 70%-88%]); but in the saline lavage group, none had WBC counts above the threshold (diagnostic accuracies for WBC count, 0%; PMN percentage, 71% [95% CI, 62%-86%]; positive culture, 76% [95% CI, 76%-86%]; at least one: 71% [95% CI, 57%-91%]). Because saline lavage did not result in differences between aspirations from infected and noninfected hips, we calculated the optimal thresholds in the nonlavage group only; the optimal threshold for synovial WBC count was 1166 cells/µL and for synovial PMN the percentage was 68%, which corresponds to WBC count diagnostic accuracy of 78% (95% CI, 69%-87%) and PMN percentage accuracy of 78% (95% CI, 69%-87%). CONCLUSIONS: Because the MSIS criteria thresholds resulted in suboptimal sensitivities owing to a higher number of false negatives, we recommend considering lower WBC count and PMN percentage thresholds for hip-spacer aspirations. Furthermore, the WBC count and PMN percentage results from aspirations performed with saline lavage are not reliable for treatment decisions. LEVEL OF EVIDENCE: Level III, diagnostic study.

Looking back, moving forward: 1988-2013. The first 25 years of the American Society of Emergency Radiology.

The American Society of Emergency Radiology (ASER) was founded in 1988 and is celebrating its 25th Anniversary. ASER is thriving and emergency radiology has never enjoyed greater popularity than at present. This history describes the genesis of the Society, its growth and current state of affairs. It is based on the recollections and personal files of the authors, one Founder and both former ASER Presidents and Gold Medalists, the ASER archives, and interviews and correspondence with many ASER members. It is hoped that this brief review will be interesting to the reader, provide some insight into ASER evolution over the years, and hold some lessons moving forward.

Cases from the Cleveland Clinic: cerebral venous sinus thrombosis presenting to the emergency department with worst headache of life.

A 31 year old woman presented with the worst headache of her life and was diagnosed with cerebral venous sinus thrombosis (CVST) by routine unenhanced computed tomography (CT) scan, subsequently confirmed with magnetic resonance imaging (MRI) and magnetic resonance venography (MRV). Awareness of this less common cause for acute neurological presentation in the Emergency setting is important; the imaging characteristics of CVST are reviewed.

Imaging of lisfranc injury and midfoot sprain.

Injuries to the tarsometatarsal joint and of the Lisfranc ligament present a challenge. They are difficult to diagnose and outcomes worsen as diagnosis is delayed. As a result, radiologists and clinicians must have a clear understanding of the relevant nomenclature, anatomy, injury mechanisms, and imaging findings.

Thyroid acropachy.

Thyroid acropachy is a rare complication of thyroid disease most often occurring in patients with a long history of active Graves' disease with ophthalmopathy and dermopathy already present. It presents with digital clubbing and soft tissue swelling with possible pain in the digits. Plain radiographs show a solid periosteal reaction that tends to be bilateral and generally symmetrical involving the tubular bones of the hands and feet. Treatment is directed at the thyroid dysfunction and the accompanying ophthalmopathy and dermopathy. It is important to recognize the association with a more severe ophthalmopathy. In the absence of Graves' ophthalmopathy and dermopathy, a diligent search for other causes of acropachy is warranted.

Morel-Lavallee lesion.

Morel-Lavallee lesions, or closed internal degloving injuries, are most common in the subcutaneous tissues of the proximal thigh and trochanter. Bilateral lesions are rare. These post-traumatic fluid collections can be isolated or associated with concomitant pelvic fractures. Morel-Lavallee lesions may present as a pseudotumor when not recognized in the early post-traumatic period. Magnetic resonance imaging is the modality of choice in the evaluation of Morel-Lavallee lesions. The identification of a capsule on MRI can have important management implications.

Your diagnosis? Midfoot sprain: Lisfranc ligament disruption.

Suspected midfoot sprains can be a challenge to evaluate when the initial weight-bearing views are normal. In this case, MRI allowed prompt confirmation of the suspected unstable Lisfranc ligament injury and contributed to prompt management with rigid fixation.

Easily Missed Fractures of the Upper Extremity.

Radiographs remain the mainstay for initial imaging of suspected fracture in the emergency setting. Missed fractures potentially have significant negative consequences for patients, referring physicians, and radiologists. Most missed fractures are owing to perceptual errors. In this review, we emphasize knowledge of 3 categories of pitfalls as they pertain to the upper extremity: the common but challenging; the out of mind, out of sight; and those related to satisfaction of search. For specific injuries, emphasis is placed on helpful radiographic signs and important additional radiographic views to obtain.

Extended MRI findings of intersection syndrome.

OBJECTIVE: The symptoms and physical findings of intersection syndrome have been well described in the clinical medical literature. However, the magnetic resonance imaging (MRI) findings in patients with intersection syndrome of the forearm have only recently been described in a small number of patients. We review our experience with imaging of intersection syndrome, describe previously unreported MRI findings, and emphasize modifications to MRI protocols for its evaluation. MATERIALS AND METHODS: Institutional review board approval was obtained for this retrospective review of patients with MRI findings consistent with intersection syndrome of the forearm during the period from January 2004 to September 2006. Six patients were identified, three males and three females, with an average age of 39.3 years. The MRI examinations were reviewed to assess signal abnormalities within and adjacent to the first and second dorsal extensor tendon compartments (DETC): tendinosis, peritendinous edema or fluid, muscle edema, subcutaneous edema, and juxtacortical edema. The overall longitudinal extent of signal alterations was measured as well as the distance from Lister's tubercle to the crossover of the first and second DETC. RESULTS: Review of the MRIs showed increased intrasubstance tendon signal suggesting tendinosis in two of the six patients, peritendinous edema or fluid in all six patients, muscle edema in five of the six patients, and subcutaneous edema in three of the six patients. Juxtacortical edema was seen in one patient. Peritendinous edema or fluid extended distally beyond the radiocarpal joint in three of the six patients. The average distance from Lister's tubercle to the crossover of the first and second DETC was 3.95 cm, in keeping with recently published data. CONCLUSION: Intersection syndrome is an uncommon MRI diagnosis. In addition to the previously described MRI findings of edema adjacent to the first or second DETC, possibly with proximal extension and subcutaneous edema, we have identified additional abnormalities: tendinosis, muscle edema, and juxtacortical edema. In addition, our review shows that first and second DETC signal abnormalities in patients with intersection syndrome are not necessarily limited to the site of crossover but can extend distally beyond the radiocarpal joint. As standard wrist protocols may not include the area of intersection between the first and second DETC, coverage may need to be extended to the mid-forearm.

Diabetic muscle infarction: a rare complication of advanced diabetes mellitus.

Diabetic muscle infarction is a rare complication of diabetes mellitus first described in 1965. It typically arises in patients with long-standing diabetes mellitus who have complications of the disease, including nephropathy, retinopathy, and neuropathy. It typically presents with acute onset of thigh pain with an associated palpable tender mass. Recurrent episodes in the same or opposite limb are common. Laboratory evaluation does not generally show any consistent abnormality except for poor glucose control. Histologic features of diabetic muscle infarction consist of large areas of muscle necrosis and edema. Magnetic resonance imaging (MRI) findings in patients without clinical evidence of infection may be typical enough to make tissue biopsy unnecessary. In the appropriate clinical setting, MRI may obviate invasive testing and is the preferred imaging modality. Treatment is supportive with analgesics, rest, and immobilization.

Radiographic detection of perflubron fluoromediastinum and fluororetroperitoneum 9 years after partial liquid ventilation.

A 17-year-old patient presented, after a motor vehicle collision, with right hip pain and unusual radiographs of the chest and pelvis. Multiple radiopacities obscured detail. These partly obscured and distracted attention from a right acetabular fracture. The etiology was persistent perflubron 9 years after partial liquid ventilation for acute respiratory distress syndrome. Persistence of perflubron beyond 138 days has not been previously reported. We review the imaging appearance of perflubron and the mechanism likely related to its distribution and persistence in this case, and emphasize the importance of obtaining clinical history and avoiding distraction when faced with unusual radiographic findings.

Renal medullary carcinoma: unsuspected diagnosis at stone protocol CT.

Renal medullary carcinoma (RMC) is an aggressive neoplasm occurring almost exclusively in adolescents and young adults with sickle cell (SC) hemoglobinopathies, usually sickle cell trait (SCT) or hemoglobin SC disease. The most common presentations are hematuria and flank or abdominal pain. It is a highly malignant tumor, and responses to chemotherapy are rare and transient resulting in a dismal prognosis. A high level of suspicion is necessary when evaluating at risk patients presenting with hematuria or flank pain, as currently it appears that only early diagnosis could potentially alter the outcome of this disease. We report a case of RMC in a young male patient with SCT, who presented to the emergency department with low back pain and microscopic hematuria, clinically mimicking acute obstructing urolithiasis. Our case emphasizes the need to consider alternate diagnoses when evaluating computed tomography scans for acute flank pain.

Charcot spine.

Identification of a destructive spinal process in the acute setting most commonly is related to infection or neoplasm. In the appropriate clinical setting, Charcot spine, also known as neuropathic spinal arthropathy or spinal neuroarthropathy, should be considered. We present a case of spinal destruction due to spinal neuroarthropathy in a 51-year-old man who had been paraplegic for 13 years, and review the characteristic and potentially differentiating imaging findings of this uncommon process.

Segmental omental infarction.

Acute right-sided abdominal pain is a common presenting symptom in the emergency department. Acute cholecystitis and acute appendicitis are the most likely etiologies for right upper and lower quadrant pain, respectively. However, other differential possibilities include right-sided diverticulitis and perforated colon carcinoma. This case report of an 18-year-old man with segmental omental infarction highlights a much less frequent, self-limited cause of right-sided abdominal pain, which is increasingly identified on computed tomography scans.

MRI of Little Leaguer's shoulder.

The MRI appearance of 'Little Leaguer's shoulder' has not been previously reported in the radiology literature. Purported etiologies include proximal humeral epiphyseolysis, osteochondrosis of the proximal humeral epiphysis, stress fracture of the proximal humeral epiphyseal plate, and rotational stress fracture of the proximal humeral epiphyseal plate. We describe magnetic resonance imaging findings in four patients and review the literature.