The Journal of Arthroplasty Vol. 24 No. 5 2009

Magnetic Resonance Imaging in the Diagnosis andManagement of Hip Pain After Total Hip Arthroplasty

H. John Cooper, MD,* Amar S. Ranawat, MD,* Hollis G. Potter, MD,yLi Foong Foo, MD, MRCP, FRCR,y Shari T. Jawetz, MD,y and Chitranjan S. Ranawat, MD*

Abstract: Evaluation of pain following total hip arthroplasty (THA) can bechallenging in the absence of radiographic pathology. This study aimed to examinethe diagnostic utility of magnetic resonance imaging (MRI) in the evaluation ofenigmatic hip pain following THA. We reviewed a series of patients who wereevaluated with MRI after presenting with enigmatic hip pain following THA. MRIwas able to demonstrate pathology in the periprosthetic tissues in all hips withminimal artifact. Patients underwent a range of conservative and operativeinterventions depending on the underlying pathology. If used discriminately insituations where pathology cannot be detected by conventional methods, MRI is ahighly effective modality that can aid in the diagnosis of a wide range of disordersthereby allowing the clinician to determine the most appropriate intervention. Keywords: total hip arthroplasty, magnetic resonance imaging, osteolysis, synovitis,periprosthetic inflammation.© 2009 Elsevier Inc. All rights reserved.

Despite the success of total hip arthroplasty (THA),it is not uncommon for patients to present withpain at some point during the life of the implant[1,2]. The painful THA remains one of the mostdifficult challenges to evaluate and treat effectively[3,4], in large part due to imaging limitations.Conventional radiographs are recommended for allpatients with symptoms after hip arthroplasty [4]and can be effective in the diagnosis of loosening,migration, fracture, and other causes of mechanicalfailure. Radiographs remain, however, a 2-dimen-sional assessment of a 3-dimensional diseaseprocess, and studies have shown that they grossly

From the *Department of Orthopaedic Surgery, Lenox HillHospital, New York, New York; and yDivision of Magnetic ResonanceImaging, Department of Radiology, Hospital for Special Surgery, NewYork, New York.

Submitted December 10, 2007; accepted April 13, 2008.No benefits or funds were received in support of the study.Reprint requests: H. John Cooper, MD, Lenox Hill Hospital,

William Black Hall, 11th Floor, 130 East 77th Street, New York,NY 10021.

© 2009 Elsevier Inc. All rights reserved.0883-5403/08/2405-0001$36.00/0doi:10.1016/j.arth.2008.04.023

661

underestimate the extent of osteolysis, with limitedsensitivity [5-9] and poor interobserver reliability[5-7,10]. Although computed tomography (CT)more precisely quantifies osteolysis as comparedwith radiographs, reduction of the beam-hardeningartifact requires an increase in ionizing radiationexposure, especially as serial studies are oftenneeded [11-13]. In addition, neither CT nor radio-graphs are capable of identifying early intracapsularparticle wear, which is thought to exist before bonyresorption, and they are both of limited value forthe visualization of soft-tissue pathology localizedin the periprosthetic envelope.

Given its multiplanar capabilities, lack of ionizingradiation, and superior soft-tissue contrast, magneticresonance imaging (MRI) offers significant potentialadvantages for evaluating the hip joint after arthro-plasty. Although traditional MRI techniques arelimited by the presence of artifact generated by themetallic components, recent refinement and mod-ifications of pulse sequences have allowed for theevaluation of the bone-implant interface and thesurrounding soft tissues due to reduction of suscept-ibility artifact [12,14,15].

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This technology offers the potential for earlydiagnosis and treatment of hip pathology thatmight not otherwise be appreciated using conven-tional methodology. The purpose of this study is toinvestigate the diagnostic potential and clinical useof optimized MRI in the evaluation and manage-ment of enigmatic hip pain after THA.

Materials and Methods

This study was designed to retrospectively reviewthe records of patients who underwent evaluationby MRI for enigmatic hip pain, to describe the rangeof bony and soft-tissue pathology seen, and to reporthow the MRI findings were used to guide treatment.Patients were identified and data were gatheredfrom a database approved by the hospital's institu-tional review board.

Study Group

The study group included all patients with a THAwho were seen in the offices of 2 attendingorthopedic surgeons presenting with complaints ofhip pain over a 3-year period from July 1, 2003,through June 30, 2006, and who were subsequentlyreferred for modified MRI of the postarthroplastyhip. Before MRI, each patient underwent a radio-graphic evaluation in the office, including standardanteroposterior and false profile views of thesymptomatic hip, as well as a standard lowanteroposterior pelvis view, which was read by theattending orthopedic surgeon at the time of the visit.Patients were referred for magnetic resonance (MR)evaluation only if radiographs demonstrated mini-mal wear, with little to no osteolysis. In cases inwhich radiographic evidence of osteolysis wasdocumented, the presenting symptoms weredeemed to be inconsistent with or out of proportionto radiographic findings. In addition, patients werescreened to rule out deep sepsis where clinicallyappropriate by sending blood work for C-reactiveprotein and erythrocyte sedimentation rate.All patients in whom an obvious cause for pain

could be delineated by physical examination, radio-graphic evaluation, or blood work were not sent forMRI and thus were not included in this study.

Plain Radiograph Assessment

The most recent complete series of radiographstaken before the MR evaluation were located andreviewed for all 21 hips. Osteolysis was measured onboth the acetabular side as well as the femoral sideusing previously described techniques [12]. All areas

of periprosthetic radiolucencies were noted andoutlined independently by 2 experienced attendingorthopedic surgeons who were blinded to the MRIfindings. The total area of each radiolucent lesionwas calculated (in square millimeters) by multi-plying the greatest diameter of a lesion to a seconddiameter perpendicular to the first. The totalosteolysis load for each side was calculated byadding the areas of all lesions on that side. Theosteolysis load measured by each of the 2 indepen-dent evaluators was averaged to reach a final areaboth for the acetabulum and for the femur.

Magnetic Resonance Imaging Technique andEvaluation

All MRI were performed on a clinical 1.5-T unit(General Electric Healthcare, Milwaukee, Wis).Initial images were obtained with a body coil usingan initial coronal fast inversion recovery sequencewith field of view 35 cm, repetition time (TR) 4500 to5000 milliseconds/echo time 17 milliseconds (effec-tive), inversion time 150 milliseconds, receiverbandwidth 62.5 kHz (over entire frequency range),and slice thickness 5 mm with no interslice gap.Additional optimized coronal, sagittal, and axial fastspin echo sequences (Fast spin echo XL, GeneralElectric Healthcare)were obtained using a 4-channelphased array receive-only shoulder coil (Med Radphased array, Indianola, Pa), with repetition time3000 to 5000 milliseconds/echo time 30 to 36milliseconds, with a wider receiver bandwidth 62.5to 100 kHz over the entire frequency direction. Fieldof view ranged between 17 and 20 cm, slice thicknesswas 3 to 4 mmwith no gap, matrix was 512 × 320 to384 at 4 to 6 excitations, yielding a maximum inplane resolution of 332 μ. Total imaging time rangedbetween 25 and 40minutes, depending upon patientsize and the need for repetition of pulse sequencesdue to involuntary motion.

After image acquisition, data sets were analyzedfor presence of osteolysis around the acetabular andfemoral components of the arthroplasty, as well asthe presence of synovial reaction. If these werepresent, the volume of bone loss and/or intra-articular burden of synovial disease were manuallysegmented and recorded on a dedicated workstation using commercial software (Functool,Advantage Windows, General Electric Healthcare).In addition, any other periarticular pathology wasnoted and described.

Clinical Interventions

The results of the MRI studies were used by theattending orthopedic surgeon to initiate a treatment

Table 1. Quantification of Osteolysis seen by PlainRadiograph and by MRI

Area of Osteolysison X-Ray (mm2)

Volume of Osteolysison MRI (mm3)

Femoral osteolysis 269 1370

Magnetic Resonance Imaging � Cooper et al 663

algorithm of operative and nonoperative manage-ment aimed at symptomatic pain relief as well astreating the underlying pathology where appropri-ate. The results of these interventions were recordedwhere available.

Periacetabularosteolysis

186 10 999

Results

Clinical Data

Magnetic resonance imaging of 21 hips wasperformed in 19 patients; 2 patients underwent 2independent MRI evaluations for different indica-tions, separated by a minimum of 17 months,and these studies were thus considered indepen-dently. The study group included 11 men and 8women. A total of 14 hips were primary THA; 7had been revised.The indications for primary hip arthroplasty

included degenerative joint disease (12 hips) anddysplasia (1 hip); the diagnosis was unknown in 1patient whose operation was performed at anotherinstitution. The indications for revision arthroplastywere osteolysis (2), pain (2), aseptic loosening (1),and unknown (2).The average age of the patients was 60.1 years at

the time of first complaint (range, 29.4-83.6 years),and the average time from the index procedure tothe time of first complaint was 6.9 years (range,1.1-16.5 years).

Plain Radiographic Assessment

None of the films revealed radiographic evidenceof fracture, loosening, or mechanical failure.Femoral osteolysis was detected in 3 hips by eachevaluator; the average area of osteolysis seen byradiographs in the subset of patients who haddefinitive femoral osteolysis by MRI was 269 mm2.Acetabular osteolysis was detected in 2 hips by 1evaluator and in 4 hips by the other; the averagearea of osteolysis seen by plain film in the subset ofpatients who had definitive acetabular osteolysis byMRI was 186 mm2 (Table 1).

Magnetic Resonance Imaging

The average time between the radiographic eva-luation and the MRI evaluation was 39 days (range,1-241). In all 21 hips, MRI allowed for consistentvisualization of the bone-implant interface and thesurrounding periprosthetic soft tissues with minimalsusceptibility artifact. A wide range of pathology wasvisualized (Table 2). Osteolysis (Fig. 1) was demon-strated by areas of marrow replacement, of inter-mediate to increased intraosseous signal intensity,

with or without a peripheral rim of lower signalintensity, which is consistent with previous descrip-tions [12]. These focal areas of intermediate signalintensity contrast with the high signal intensity of themedullary fat on moderate echo time sequences andthe low signal of suppressed fatty marrow on the fastshort tau inversion recovery sequences. Decreasedsignal intensity throughout the synovial lining withdistension of the joint capsule was indicative ofparticle-induced synovitis caused by an extensivedebris load (Fig. 2). These patients showed distensionof the normally thin, hypointense pseudocapsule byparticulate synovitis. The intracapsular debris typi-cally had signal characteristics similar to those of theosteolytic material replacing the bone. Iliopsoasbursitis (Fig. 3) and trochanteric bursitis (Fig. 4)were evidenced by the presence of a discrete, well-defined, characteristic fluid collection at theserespective sites, as has been described in previousstudies [12-16]. Abductor tendinosis (Fig. 5) andiliopsoas tendinosis (Fig. 6) were characterized byincreased signal intensity within the tendon near itsinsertion. Scarring of the pseudocapsule was visua-lized on MRI as intermediate signal intensity liningthe normally thin, hypointense capsule. Soft-tissueganglia had an appearance characterized by well-defined foci of cystic hyperintense signal.

Femoral osteolysis was detected by MRI in 7 hips;in these, the mean volume of osteolysis was 1370mm3. Periacetabular osteolysis was detected in 10hips, and in these, the mean volume of periacetab-ular osteolysis was 10 999 mm3 (Table 1).

Clinical Interventions

Eight patients were advised to modify theiractivity levels, including rest and a stretchingprogram to help alleviate symptoms. Sevenpatients were prescribed nonsteroidal anti-inflam-matory medications for treatment of bursitis ortendinosis. Four patients were prescribed bispho-sphonates for moderate periacetabular osteolysiswith the goal of reducing further osteolysis andperiprosthetic bone loss. One patient underwent atherapeutic aspiration for massive iliopsoas bursitis(Fig. 3). Four patients underwent revision surgery

Table 2. Periprosthetic Soft-Tissue Pathology Visualizedon MRI

Pathology No. of Patients

Abductor tendinosis 17Periacetabular osteolysis 10Femoral osteolysis 7Particle-induced synovitis 7Iliopsoas bursitis 6Iliopsoas tendinosis 5Scarring of the pseudocapsule 3Trochanteric bursitis 2Soft-tissue ganglia 2

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for severe, extensive osteolysis detected by MRI,the extent of which was not appreciated on theradiographs, and the imaging findings were con-firmed on intraoperative inspection.In addition, 4 patients in whom revision surgery

was being strongly considered before obtaining theMRI were subsequently managed conservatively,after the MR examination disclosed relativelybenign findings including iliopsoas bursitis (1),iliopsoas tendinosis (1), mild periacetabular osteo-lysis (1), and moderate periacetabular osteolysis (1).It should be noted that the 1 patient with moderateperiacetabular osteolysis who was initially managedconservatively later required revision of the acet-abular component for progressive osteolysis andpain 27 months later.Of the 17 hips that were initially managed

conservatively, clinical follow-up in the office wasavailable in 13. Two patients did not return to theoffice but were able to be contacted by telephone.The remaining 2 patients were lost to follow-upafter the MRI was performed and were unable tobe contacted. At an average follow-up of 17.3months, 11 of the 15 patients were asymptomaticwith complete resolution of pain, 3 patientsreported intermittent recurrence of symptoms,and the final patient underwent revision surgeryas descried previously.

ig. 1. (A) Periacetabular osteolysis. Coronal MR image ofhip arthroplasty shows a considerable amount of boneesorption around the acetabular component (arrow-eads), extending into the posterior column of thecetabulum, without cortical penetration into the pelvis.B) Femoral osteolysis. Coronal MR image of a hiprthroplasty shows a focal of area of bone resorption inhe proximal femur (arrowheads) at the lateral bone-plant interface.

Discussion

This failure of the routine radiographic evaluationto detect early pathology around the THA [17,18]represents a missed opportunity to prevent moreserious sequelae in these patients. Revision arthro-plasty is more costly and is associated with a highercomplication rate than primary THA [19] becausemost patients requiring revision surgery are at leasta decade older than their age at the primaryoperation, with decreased physiologic reserve [13].As a result, early diagnosis can spare many patientsincreased cost, morbidity, and potential mortality

from delayed revision surgery [19-21]. Early detec-tion and noninvasive longitudinal monitoring ofparticle disease will enable assessment of treatmentsdesigned to delay or prevent revision surgery. Inaddition, correct diagnosis can also avoid unneces-sary interventions such as revision surgery alto-gether, as was demonstrated in our study.

Although MRI has proven useful in evaluationof the native hip, it has not traditionally beenused for patients after arthroplasty because of thesusceptibility artifact induced by the implant. In

Farha(atim

Fig. 2. Particle-induced synovitis. Coronal MR image of ahip arthroplasty shows intermediate signal intensitysynovial debris within the distended inferior recess ofthe hip joint (arrowheads), consistent with intracapsularsynovial burden of particle disease.

ig. 4. Trochanteric bursitis. Axial MR image of a hiprthroplasty shows distension of the greater trochantericursa (arrow).

Magnetic Resonance Imaging � Cooper et al 665

addition, despite significant advances in techniqueover recent years, there has been a continuingand prevailing notion that MRI is not appropriatefor the assessment of potential complications ofTHA [22]. However, with appropriate modificationof pulse sequence parameters, MRI is able togenerate superior soft-tissue contrast, more sensi-tive detection of osteolysis, and improved depic-tion of the periprosthetic soft tissues. It also allowsfor the detection of synovitis within the pseudo-capsule, which may be present before there is

Fig. 3. Iliopsoas bursitis. Axial MR image of a hiparthroplasty shows marked distension of the iliopsoasbursa (arrowheads).

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evidence of osteoclastic bone resorption on radio-graphs or MRI [12].

There have been several prior studies examiningthe use of optimized MRI for THA [12,13,20,22-24]. Two recent studies used MRI to assess latecomplications of THA in patients already scheduledto undergo revision surgery. In these, the authorswere able to identify periprosthetic abnormalities,such as mechanical loosening, granulomatosis,infection, and periprosthetic fracture [22], andcorrelate MRI findings to radiographic, surgical,and pathologic findings for various failure modesof the primary implant [23]. Another studyevaluated 28 hips for a variety of indications,most commonly to assess the extent of osteolysis

ig. 5. Abductor tendinosis. Coronal MR image of a hiprthroplasty shows mild insertional gluteus minimusndinosis without tear (arrow).

Fate

Fig. 6. Iliopsoas tendinosis. Axial MR image after a hiparthroplasty shows mild insertional iliopsoas tendinosiswithout tear (arrow).

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that had been previously detected on plain radio-graphs [12]. A later study demonstrated that thesensitivity of MRI for detection of lesions in acadaveric model (95%) was significantly betterthan that offered by conventional radiographicanalysis (52%) or optimized CT (75%) and alsodemonstrated that sensitivity increased for all 3imaging modalities as the lesion size increased butthat lesion detection was independent of locationonly with MRI [24].The current study is novel with respect to the

aforementioned work in that it demonstrates theuse of this technology to detect early complicationsof THA in patients presenting with enigmatic painand therefore without a known diagnosis. This studyalso examines the diagnostic use of MRI in a clinicaltreatment algorithm.Limitations of this work include the relatively

small number of arthroplasties imaged, as well asits retrospective nature. One of the reasons for thesmall number of patients is the relatively narrowindication for use of this technology: only thosepatients without an obvious source of pain afterphysical examination, radiographic evaluation,and laboratory testing were subsequently referredfor an MRI evaluation. This allowed imaging ofearly stages of disease and THA complicationbefore the pathology became obvious on routineradiographic examination.In conclusion, this study was able to demonstrate

that MRI, with modification of pulse sequenceparameters to reduce metallic susceptibility artifactand improve image quality, is an extremely power-ful tool in the evaluation of patients with enigmatic

pain after hip arthroplasty, allowing for detailedassessment of the arthroplasty-bone interface andthe surrounding soft-tissue envelope. The use ofMRI in the assessment of patients with possiblecomplications related to THA is an evolving area,and additional refinement and clinical correlationwill further elucidate the optimal applications of thistechnique. Although not indicated in all patients,selective use of MRI could be invaluable in directingthe care of patients after hip arthroplasty.

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