Determination of Incidence of Soft Tissue Reactions after Total Hip Replacement using Elastography and Role of Elastography in Screening of Periprosthetic Soft Tissue: A Prospective Observational Study.

Introduction: Adverse local tissue reactions after Total Hip Replacement (THR) have been widely described in literature recently as a course of aseptic loosening. Evaluation for any adverse soft tissue reactions is challenging with traditional imaging techniques like Magnetic Resonance Imaging (MRI), and are limited, due to production of metallic artifact. Ultrasound, specifically its refined form elastography, has emerged recently as a useful tool for assessing the soft tissues. Aim: To determine the incidence of soft tissue reactions in cases of THR and to evaluate role of elastography in assessment of periprosthetic soft tissue. Materials and Methods: This prospective observational study was conducted in the Department of Orthopaedics, Dr. Hardas Singh Orthopaedic Hospital, Amritsar, Punjab, India, from May 2013 to April 2014. Study comprises of consecutively followedup 66 hips which were evaluated and assessed clinically and radiologically using ultrasound elastography for periprosthetic soft tissue and degree of fibrosis. The MRI was done in patients with positive findings only. Diagnosis was then confirmed with biopsy in patients who underwent revision surgery. Incidence of clinical symptoms, implant loosening, stability of implant, various types of soft tissue reactions, pseudotumour formation and synovial hypertrophy were determined and association between clinical and radiological findings was done. Chi-square test was determined to see the statistical significance. Results: Total of 66 hips were studied in 60 patients with mean age of 56.08±16.55 years (26-95 years). The incidence of soft tissue reactions observed in the study was 83.3% (n=55), of all 66 hips 36 were symptomatic, Implant loosening was seen in 29 hips, pseudotumours were detected in 3 (4.5%) hips, cystic nodules in 2 (3.0%) hips, enlarged lymph nodes in one (1.5%) hip, fibrogranuloma in 2 (3%) hips and synovial thickening was seen in 12 hips. Association of Harris Hip Score with capsular thickness, implant stability and acetabular loosening was found to be statistically significant. Conclusion: The study shows a substantially higher incidence of soft tissue reaction and capsular hypertrophy following THR. Ultrasound elastography is a good screening tool to detect early soft tissue changes in periprosthetic tissue. [ABSTRACT FROM AUTHOR]