The role of ultrasonography in the assessment of peri-prosthetic hip complications.
OBJECTIVE
Total hip arthroplasty (THA) is a widespread option for treating hip osteoarthritis. Peri-prosthetic complications after THA represent a common event influencing patient outcome and costs. The purpose of this paper is to report the use of ultrasonography (US) to detect peri-prosthetic complications in symptomatic patients who underwent THA.


METHODS
We retrospectively reviewed the records of patients with THA who underwent imaging evaluation between January 2009 and December 2012 at two different institutions. We evaluated the presence/absence of superficial and/or deep peri-prosthetic collections as well as the presence/absence of a cutaneous sinus tract. For patients who underwent both MRI and US, a concordance correlation analysis between US and MR findings was performed.


RESULTS
In the reference period, 532 symptomatic patients (mean age ± standard deviation 74 ± 12 years) underwent X-ray and MRI examinations for suspected peri-prosthetic complications. Among them, 111 (20.9 %) underwent also US. Overall, 108 patients underwent both US and MRI. US findings included 67 superficial collections, 48 subcutaneous fistulas, 74 deep peri-prosthetic collections. Twenty-four patients had solid, mass-like peri-prosthetic collections. In 11 patients, no peri-prosthetic complications were seen. MRI findings included 68 superficial collections, 49 subcutaneous fistulas, 79 deep peri-prosthetic collections. Twenty-four patients had solid, mass-like peri-prosthetic collections. In four patients, no peri-prosthetic complications were seen. Concordance analysis between US and MRI findings showed almost perfect agreement (k ≥ 0.89).


CONCLUSIONS
US is an efficient and practical imaging modality to evaluate peri-prosthetic complications in patients with THA, being almost comparable to MRI in detecting and characterizing these complications.
Scuola di Specializzazione in Radiodiagnostica, Università degli Studi di Milano, Piazza Malan 1, San Donato Milanese, 20097 Milan, Italy.
Silvana
S
Sdao
Scuola di Specializzazione in Radiodiagnostica, Università degli Studi di Genova, Via Alberti 4, 16132 Genoa, Italy.
Davide
D
Orlandi
Servizio di Radiologia, IRCCS Policlinico San Donato, Piazza Malan 1, San Donato Milanese, 20097 Milan, Italy.
Alberto
A
Aliprandi
Dipartimento di Radiologia, Ospedale Santa Corona, ASL 2 Savonese, Via XXV Aprile 38, 17027 Pietra Ligure, SV Italy.
Francesca
F
Lacelli
Servizio di Radiologia, IRCCS Policlinico San Donato, Piazza Malan 1, San Donato Milanese, 20097 Milan, Italy ; Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Piazza Malan 1, San Donato Milanese, 20097 Milan, Italy.
Luca Maria
LM
Sconfienza
Unità di Chirurgia dell'anca, IRCCS Policlinico San Donato, Piazza Malan 1, San Donato Milanese, 20097 Milan, Italy.
Filippo
F
Randelli
Servizio di Radiologia, IRCCS Policlinico San Donato, Piazza Malan 1, San Donato Milanese, 20097 Milan, Italy ; Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Piazza Malan 1, San Donato Milanese, 20097 Milan, Italy.
Francesco
F
Sardanelli
Dipartimento di Radiologia, Ospedale Santa Corona, ASL 2 Savonese, Via XXV Aprile 38, 17027 Pietra Ligure, SV Italy.
Giovanni
G
Serafini
Hip infection; Magnetic resonance imaging; Total hip arthroplasty; Ultrasound