Ultrasonography after hip arthroplasty

Value of ultrasound-guided aspiration of hip arthroplasties performed in an orthopedic clinic by orthopedic surgeons

Background: Total joint arthroplasties continue to increase as do periprosthetic joint infections (PJIs). Ultrasound-guided aspiration can yield useful synovial fluid for analysis while avoiding radiation exposure. This study presents a high-yield, ultrasound-guided technique with analysis of aspiration results. Methods: All consecutive ultrasound-guided aspirations of hip arthroplasties performed from May 2016 through to April 2019 were retrospectively reviewed. Patient demographic information, component specifics, presence of draining sinus, and inflammatory markers were recorded. Results of aspiration including volume, appearance, lavage use, synovial fluid differential leukocyte count, synovial neutrophil percent, and culture results were recorded. Surgical results, specimen cultures, and surgeon description of purulence were recorded. Aspiration results were compared to the surgical specimen results in all patients who underwent reoperations. Results: Review of 349 hip aspirations demonstrated accuracy of 87 %, sensitivity of 83 %, specificity of 89 %, positive predictive value of 79 %, and negative predictive value 91 %. Surgical and aspiration cultures matched in 81 % of cases. Bloody aspirates and aspirates obtained after lavage had less accuracy at 69 % and 60 %, respectively. Specificity was 100 % for cultures obtained with lavage and 91 % for bloody aspirates. Synovial leukocyte count and neutrophil percentage was obtained in 85 % of aspirations, and cultures were obtained in 98 % of aspirates. Contamination rate was 2 %. Conclusion: Ultrasound-guided aspirations aid in the diagnosis of PJI. The use of lavage to obtain fluid is helpful when aspiration cultures are positive. Bloody aspirates are less accurate but have high specificity. A low contamination rate and 88 % accuracy results with this meticulous technique.

The Accuracy of Imaging Techniques in the Assessment of Periprosthetic Hip Infection: A Systematic Review and Meta-Analysis

BACKGROUND

Various imaging techniques are used for excluding or confirming periprosthetic hip infection, but there is no consensus regarding the most accurate technique. The objective of this study was to determine the accuracy of current imaging modalities in diagnosing periprosthetic hip infection.

METHODS

A systematic review and meta-analysis of the literature was conducted with a comprehensive search of MEDLINE and Embase to identify clinical studies in which periprosthetic hip infection was investigated with different imaging modalities. The sensitivity and specificity of each imaging technique were determined and compared with the results of microbiological and histological analysis, intraoperative findings, and clinical follow-up of >6 months.

RESULTS

A total of 31 studies, published between 1988 and 2014, were included for meta-analysis, representing 1,753 hip prostheses. Quality assessment of the included studies identified low concerns with regard to external validity but more concerns with regard to internal validity including risk of bias (>50% of studies had insufficient information). No meta-analysis was performed for radiography, ultrasonography, computed tomography, and magnetic resonance imaging because of insufficient available clinical data. The pooled sensitivity and specificity were 88% (95% confidence interval [CI], 81% to 94%) and 92% (95% CI, 88% to 96%), respectively, for leukocyte scintigraphy; 86% (95% CI, 80% to 90%) and 93% (95% CI, 90% to 95%) for fluorodeoxyglucose positron emission tomography (FDG PET); 69% (95% CI, 58% to 79%) and 96% (95% CI, 93% to 98%) for combined leukocyte and bone marrow scintigraphy; 84% (95% CI, 70% to 93%) and 75% (95% CI, 66% to 82%) for antigranulocyte scintigraphy; and 80% (95% CI, 72% to 86%) and 69% (95% CI, 64% to 73%) for bone scintigraphy.

CONCLUSIONS

Of the currently used imaging techniques, leukocyte scintigraphy has satisfactory accuracy in confirming or excluding periprosthetic hip infection. Although not significantly different, combined leukocyte and bone marrow scintigraphy was the most specific imaging technique. FDG PET has an appropriate accuracy in confirming or excluding periprosthetic hip infection, but may not yet be the preferred imaging modality because of limited availability and relatively higher cost.

LEVEL OF EVIDENCE

Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

A comparison of the diagnostic accuracy of MARS MRI and ultrasound of the painful metal-on-metal hip arthroplasty

BACKGROUND AND PURPOSE

Metal artifact reduction sequence (MARS) MRI and ultrasound scanning (USS) can both be used to detect pseudotumors, abductor muscle atrophy, and tendinous pathology in patients with painful metal-on-metal (MOM) hip arthroplasty. We wanted to determine the diagnostic test characteristics of USS using MARS MRI as a reference for detection of pseudotumors and muscle atrophy. PatienTS AND METHODS: We performed a prospective cohort study to compare MARS MRI and USS findings in 19 consecutive patients with unilateral MOM hips. Protocolized USS was performed by consultant musculoskeletal radiologists who were blinded regarding clinical details. Reports were independently compared with MARS MRI, the imaging gold standard, to calculate predictive values.

RESULTS

The prevalence of pseudotumors on MARS MRI was 68% (95% CI: 43-87) and on USS it was 53% (CI: 29-76). The sensitivity of USS in detecting pseudotumors was 69% (CI 39-91) and the specificity was 83% (CI: 36-97). The sensitivity of detection of abductor muscle atrophy was 47% (CI: 24-71). In addition, joint effusion was detected in 10 cases by USS and none were seen by MARS MRI.

INTERPRETATION

We found a poor agreement between USS and MARS MRI. USS was inferior to MARS MRI for detection of pseudotumors and muscle atrophy, but it was superior for detection of joint effusion and tendinous pathologies. MARS MRI is more advantageous than USS for practical reasons, including preoperative planning and longitudinal comparison.

Size of cup affects the anterior capsular distance in total hip arthroplasty, as measured with ultrasound

Background

Previously was found that sonography is a reliable method to measure a capsular distance in total hip arthroplasty hips. The aim of our current study was to investigate the relation between the implanted size of the cup and the anterior capsular distance, as measured with ultrasound one year after THA.

Methods

50 osteoarthritis (OA) patients operated on with total hip arthroplasty one year before were included in the study and the anterior capsular distance was measured sonographically. Patients were grouped with respect to cup size. The correlation between the implanted cup size and capsular distance was determined.

Results

The mean capsular distance in the whole group was 1.37 (SD 0.19) cm. The mean capsular distance in the group with small cups was 1.27 (SD 0.13) cm, in large cups it was 1.45 (SD 0.20) cm, p = 0.02. Spearman correlation analysis showed a statistically significant correlation between a greater capsular distance and the larger size of the cup (r = 0.5, p < 0.0001).

Conclusion

The greater capsular distance in successful THA hips is affected by cup size. We propose that this should be considered when evaluating sonography of the anterior capsular distance after THA.

Review article: Joint aspiration for diagnosis of periprosthetic infection

Joint aspiration is a reliable tool for diagnosis of periprosthetic infection. There are different indications, techniques, and approaches for joint aspiration. We recommend that it be performed selectively when infection is suspected clinically. The specimens should be interpreted based on the results of the culture as well as the white cell count and differential. Specimen collection, transport, and analysis should be prompt to ensure yield accuracy.

MR imaging and ultrasound correlation of hip pathologic conditions

Magnetic resonance (MR) imaging has become the workhorse in the imaging evaluation of the painful or clinically abnormal hip. It provides an excellent anatomic overview and demonstration of the bony structures, articular surfaces, and surrounding soft tissues. Conversely, sonography can also demonstrate superficial intraarticular structures and the periarticular soft tissues, is quickly performed, allows dynamic evaluation of tendons and muscles, and can guide percutaneous procedures. These two modalities are complementary, and this article concentrates on the MR imaging-sonographic correlations of several entities about the hip.

The role of ultrasound in the assessment of post-operative complications following hip arthroplasty

Hip arthroplasty is one of the most commonly performed orthopedic procedures. Clinicians can be faced with the diagnostic dilemma of the patient presenting with a painful hip following arthroplasty and satisfactory post-operative radiographs. Identifying the cause of symptoms can be challenging and ultrasound is increasingly being utilized in the evaluation of potential soft tissue complications following hip surgery. In this article, we describe the common surgical approaches used during hip arthroplasty as this can influence the nature and location of subsequent complications. A review of the literature is presented along with the imaging appearances frequently encountered when imaging this patient population.

Dynamics of hip joint effusion after posterior soft tissue repair in total hip arthroplasty

Dislocation after total hip replacement is more common in the early, postoperative period. Postoperative intraarticular haematoma and remaining seroma fluid and/or weakened posterior soft tissue wall may be contributing factors. Our purpose was to compare and follow with sonography the resorption of the postoperative volume of intraarticular fluid/synovial oedema after total hip arthroplasty (THA) with or without posterior soft tissue repair. Thirty-three consecutive patients with hip osteoarthritis were admitted for THA. All of them received the same type of cemented implant. Patients were randomised for posterior soft tissue repair or not. Sonography, measuring the anterior capsular distension, indicating the volume of intraarticular fluid/synovial oedema in the prosthetic hip joints, was performed after six and 12 months in all patients. At six months postoperatively greater capsular distension, i.e., remaining volume of intraarticular fluid/synovial oedema, was observed in the group with posterior soft tissue repair than in the group without. After one year the capsular distension had decreased in both groups and there was no significant difference between the groups. Our results show that posterior soft tissue repair after THA is associated with increased capsular distension during the first six months. After 12 months the volume of intraarticular fluid/synovial oedema is the same with or without posterior soft tissue repair.

Limited effectiveness of sonography in revealing hip joint effusion: preliminary results in 21 adult patients with native and postoperative hips

OBJECTIVE

The object of this study was to determine the effectiveness of sonography in the detection of hip joint effusions in both native and postoperative adult hips using arthrocentesis as a gold standard.

MATERIALS AND METHODS

Twenty-one consecutive patients with clinical suspicion of hip joint effusion were examined on sonography by one of five musculoskeletal radiologists with experience in musculoskeletal sonography. All 21 patients underwent diagnostic arthrocentesis (fluoroscopic in 16, sonographic in five) to confirm the presence or absence of joint effusion. A retrospective analysis of the sonograms was made to assess the size of the distention of the anterior joint recess (anteroposterior dimension) and the echogenicity (anechoic or other relative to muscle), and correlation was made to the presence or absence of joint effusion.

RESULTS

Joint effusion was seen on diagnostic arthrocentesis in 10 (48%) of the 21 patients. Seven of the 21 patients had native hips and 14 had prior hip surgery. Retrospectively, no significant difference was found with regard to the size of the anterior recess distention (p = 0.34) or echogenicity (p = 0.2) when comparing the patients with and without joint effusion.

CONCLUSION

Anterior recess distention and echogenicity could not reliably be used as an indicator of adult hip joint effusion, either in native or postoperative hips. Diagnostic arthrocentesis was necessary to establish or exclude the presence of hip joint effusion.

Sonography of polyethylene liners used in total knee arthroplasty

OBJECTIVE

We investigated the ability of sonography to reveal the polyethylene liner used in total knee arthroplasty with the hopes of establishing a possible relationship between the sonographic measurement of the actual thickness of the polyethylene liner and the estimated thickness based on conventional radiography.

MATERIALS AND METHODS

Twenty-four consecutive patients who were referred for Doppler screening for deep venous thrombosis after total knee arthroplasty were evaluated. The polyethylene liner was identified on sonography, and three measurements were obtained from four locations: anteromedial joint line (just medial to the midline incision), along the medial joint line, anterolateral joint line (just lateral to the midline incision), and along the lateral joint line. These sonographic measurements were compared with radiographic measurements of the radiolucent polyethylene liner and with the manufacturers' stated size of the polyethylene liner. Linear regression analyses were then performed.

RESULTS

The polyethylene liner is seen on sonography as a strong linear echogenic interface with posterior acoustic shadowing. Linear regression analyses showed a high correlation (r = 0.8) between the sonographic measurements and the radiographic measurements. A relatively poor correlation (r = 0.2) was noted between the manufacturers' stated size of the liner and the sonographic measurements.

CONCLUSION

We found that the polyethylene liner used in total knee arthroplasty can be clearly identified during sonographic evaluation of the knee. We also found a high correlation between the longitudinal measurement of the polyethylene liner with the thickness of the radiolucent polyethylene as measured on conventional radiographs. We propose that sonography could potentially be a useful noninvasive imaging modality to screen for subtle cases of polyethylene wear.

Magnetic resonance imaging-guided focused ultrasound synovectomy

OBJECTIVE

To investigate the feasibility of magnetic resonance imaging (MRI)-guided high power focused ultrasound (FUS) to perform synovectomy noninvasively.

METHODS

Five New Zealand white male rabbit knees with experimentally induced arthritis underwent MRI-guided thermal surgery by high power (60 W/10 s) sonication. Evidence of tissue coagulation was monitored during the procedure and confirmed by gross and microscopic evaluation and MRI.

RESULTS

Partial synovectomy was performed in five animals. Necrotized synovial tissue was observed on gross and microscopic evaluation. Visible signal intensity alterations including high signal intensity on T2-weighted (T2W) images and lack of contrast-enhancement on T1-weighted (T1W) post-contrast, post-sonication images were characteristic and reproducible.

CONCLUSION

Our results demonstrate the ability of high power sonication to destroy synovial tissue in vivo.

Ultrasound in inflammatory disease

US may be used effectively to diagnose and treat a wide range of musculoskeletal inflammatory conditions. It is likely that its usage will increase with regards to such conditions especially in the management of rheumatology clinic patients.

Musculoskeletal sonography and MR imaging. A role for both imaging methods

Sonography is currently being applied to many areas of the musculoskeletal system. Although some areas are in the experimental stage, there exist several indications in which sonography can produce results at least equal to what is possible with MR imaging. Examples include evaluation for shoulder and ankle tendon abnormalities; soft tissue infection and joint effusion; soft tissue foreign bodies; soft tissue masses, such as Baker's cyst and wrist ganglion cyst; carpal tunnel syndrome; developmental dysplasia of the hip; and other indications where MR imaging is contraindicated. The role of sonography in evaluation of the musculoskeletal system is evolving. With continued experience and research, newer applications for musculoskeletal sonography will likely become established further defining the roles of sonography and MR imaging in evaluation of the musculoskeletal system.

Polyethylene wear and synovitis in total hip arthroplasty: a sonographic study of 48 hips

Forty-six patients (48 hips), operated on with cemented total hip arthroplasty (THA) because of arthrosis, were examined radiographically and sonographically at 10-year follow-up. Polyethylene wear of acetabular cups was measured on conventional non-weight-bearing pelvic radiographs, and the volume of polyethylene debris was calculated. Radiographic signs of loosening were identified. The capsular distance (ie, thickness of the synovium or synovial contents) was measured sonographically. We found a significant correlation between increased volumetric wear and increased capsular distance. Hips with radiographically loose acetabular components had significantly greater volumetric wear and capsular distance than those without signs of acetabular loosening. This relationship was not observed in hips with radiographically loose femoral components. In cemented THA, the volume of polyethylene wear debris and the thickness of the synovium and the synovial contents are related. In the event of radiographic loosening of the acetabular component, they are both increased.

Musculoskeletal ultrasonography

This article introduces ultrasound in the evaluation of the musculoskeletal system. An emphasis is placed on currently accepted applications, and examples are included to illustrate pathologic conditions. Topics of current investigations are also presented. The efficacy of ultrasound, combined with its inaccessibility and low cost, has earned it an important role in musculoskeletal imaging.

Therapy with pulsed electromagnetic fields in aseptic loosening of total hip protheses: a prospective study

Aseptic loosening is the most common problem of hip arthroplasties, limiting its long term success. We report a study of pulsed electromagnetic field (PEMF) treatment in 24 patients with this complication. At the end of treatment, six months and one year later, pain and hip movements improved significantly with the exception of flexion and extension. There was significant improvement in both isotope scans and ultrasonography, but not in plain X-ray. The decreased pain and improved function suggest that PEMF is effective in improving symptoms of patients with loose hip replacement. No improvement, however, can be expected in patients with severe pain due to gross loosening.

Ultrasound-guided aspiration in suspected sepsis of resection arthroplasty of the hip joint

The authors described 17 patients who had had resection arthroplasty of the hip and who were suspected of having an infection. The resection arthroplasties had been performed for previous infection. All the patients were studied by ultrasonography to detect effusion in the pseudoarticular space. Thirteen of the 17 patients were found to have an effusion by ultrasonography. Fluid was obtained in 9 of the 13 patients by ultrasonographic-guided aspiration. The mean aspirated volume was 3 ml (range 1-25 ml). Five of the 9 aspirates proved to be septic. The echopattern in all but one of those five with sepsis was nonechofree. Of four other patients in whom it was not possible to aspirate fluid lavage of the pseudoarticular space one yielded a positive culture. The role of ultrasonography in the diagnosis and management of patients who have undergone resection arthroplasty of the hip and who are suspected of having an infected pseudoarticular space is discussed.