Sensitivity of Magnetic Resonance Imaging in Evaluation of Patients with Hip Joint Pain

Introduction

The hip is a stable, major weight-bearing joint with significant mobility. Magnetic resonance imaging, with its development of techniques, particularly for the hip, has opened a new horizon regarding clinical approach to pathologies leading to hip joint pain. Modern MRI has a great sensitivity in detecting hip joint abnormalities, and because of its property of excellent visualization of soft tissue and nonionizing radiation, it is the modality of choice these days in not only adults but also pediatric musculoskeletal pathologies.^1,2

Evaluation of the patient with hip pain is still a diagnostic dilemma for physicians. The differential diagnosis is diverse including common entities such as osteoarthritis, fracture, and avascular necrosis (AVN), as well as less common entities including pigmented villonodular synovitis, synovial osteochondromatosis, snapping hip syndrome, and hemorrhage into the ligamentum teres.^3,4

With the use of dynamic contrast-enhanced MRI, abnormal femoral head perfusion (common complication associate with femoral neck fracture internal fixation) can be detected before the development of femoral head osteonecrosis, subchondral collapse, and secondary osteoarthritis.⁵

Despite the vast literature supporting the role of imaging of the hip with MRI, its role as a diagnostic imaging modality continues to evolve. This study emphasizes the role of MRI in the evaluation of hip joint pain.

Material and Methods

This prospective study was conducted on 64 patients with painful hip joint; males and females with age ranging between 10 and 70 years, referred to Department of Radiodiagnosis, for MRI from Department of Orthopaedics. The study period was from June 2016 to September 2018. Detailed history was taken of patients who then underwent local examination of the diseased hip. MRI of the hip joint was performed on all suspected patients sent to Department of Radiodiagnosis. Patients were followed up for final diagnosis that was done on the basis of X-ray correlation, laboratory tests (complete blood count [CBC], erythrocyte sedimentation rate [ESR], liver function test [LFT], kidney function test [KFT], C-reactive protein [CRP], rheumatoid arthritis [RA] factor, human leukocyte antigen B27 [HLA B27], sickling, uric acid test, etc.) and clinical correlation.

Patients with congenital hip pathologies, with metallic implants and cardiac pacemakers, and postoperative patients were excluded from the study. Standard imaging protocol was used, and in patients with AVN of the femoral head, Ficat and Arlet staging system was used.⁶

Results

This study was conducted on 64 patients at a tertiary care institute. Age of patients ranged from 10 to 70 years. Maximum number of patients were in the age group of 21 to 30 years (27 cases–42%). Male-to-female ratio was approximately 47:17. Affection was unilateral in 32 (50%) cases, whereas it was bilateral in 29 (45.3%) cases. Contrast agent was used whenever necessary to evaluate the extent of the disease and the pattern of involvement. Various pathologies detected on MRI are shown in ►Table 1. The most common pathology encountered was AVN comprising 28 of the 64 cases. AVN was unilateral in 10 of the 28 cases and bilateral in 18 cases. In patients with AVN of the femoral head, the most common finding was double-line sign, seen in 23 (95%) patients, which was followed by subchondral signal abnormality in 20 (83.3%) patients, as depicted in ►Table 2. Maximum patients had stage II AVN followed by stages III and I AVN, as shown in ►Table 3.

The next most common abnormality detected was infective arthritis, found in 10 cases. It was mainly bacterial in origin in most cases. In infective arthritis of the hip, MRI helps particularly in detecting soft tissue lesions that are not well seen on other modalities. There are some features that support discrimination between tuberculous arthritis and pyogenic arthritis such as the presence of bone erosion and absence of subchondral marrow signal intensity abnormality, favoring a diagnosis of tuberculous arthritis.

Two patients from the pediatric age group had Perthes' disease. In cases of Perthes' disease, there were marrow edema and contour abnormality with unilateral involvement. There was no bilateral joint involvement or effusion noted.

Three patients diagnosed with carcinoma of the breast/colon/kidney demonstrated metastatic focus with MRI findings of postcontrast enhancement (100%), hyperintensity in the adjacent bones (100%), adjacent muscle involvement (66.67%) with unilateral involvement in (66.67%), and bilateral involvement in 33.3% patients. Two cases of stress fractures were detected using MRI.

MRI was most sensitive in cases with stress fracture, synovitis, metastasis, Perthes' disease, sacroiliitis, and migratory osteoporosis, that is, 100% followed by AVN of the femoral head (85.7%), osteoarthritis (80%), septic arthritis (71.4%), tumors (66.6%), osteomyelitis (66.6%), inflammatory arthritis (50%), and least sensitive in patients with tubercular arthritis (33.3%) (►Fig. 1).

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Fig. 1

Sensitivity of magnetic resonance imaging (MRI) in patients with hip pain.

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Discussion

Our study comprised patients belonging to age groups between 11 and 70 years with mean ± standard deviation (SD) of 36.40 ± 14.80 years. Maximum patients belonged to the age group between 21 and 30 years followed by 41 and 50 years, which is similar to study done by Ragab et al,⁷ Drar et al,⁸ and Tripathi et al.⁹ However, age does not have any significant role in determining the onset of hip pain. In our study, there was male preponderance, that is, out of 64 patients, 47 (73.44%) were male and 17 (26.5%) were female, which can be compared with study done by Ragab et al⁷ and Tripathi et al⁹ that also showed male predominance. However, in study done by Drar et al,⁸ female preponderance was seen. There were 50% patients with bilateral hip involvement and 45.3% patients with unilateral hip involvement, and 4.7% had sacroiliitis in our study, which was comparable with study by Tripathi et al⁹ that showed 48% bilateral hip involvement and 52% unilateral involvement.

According to our study, the most common MRI finding in AVN is double-line sign (95.83%) that is similar to the finding by Ragab et al⁷ (100%); however, Drar et al⁸ and Tripathi et al⁹ have found subchondral signal abnormality to be more common. In our study, maximum AVN cases were detected in during stage II (39.29%), which is similar to the finding by Beltran et al¹⁰ who in their study detected 62% cases in stage II of AVN. There were six (21.43%) patients who came with hip joint pain whose X-ray was normal but on MRI was detected with stage I AVN. Our finding was supported with the findings by Beltran et al¹⁰ who found MRI signs of stage I AVN in 21.6% of hips with normal X-ray. Hence MRI is the most sensitive modality for early detection of AVN. Patients with sickle cell anemia usually presented in late stage of AVN, that is, stages III and IV, which is similar to the findings by Sartoris and Resnick¹¹ and Coleman et al.¹²

Out of five patients, the most common finding in patients with osteoarthritis was marginal osteophytes (100%), followed by joint space narrowing (80%) and subchondral cyst (60%), and others were joint effusion (20%), marrow edema (20%), and adjacent soft tissue edema (20%). Boutry et al¹³ also reported most cases of marginal osteophytes (83%). Ragab et al⁷ studied joint space narrowing in 78.1% cases of osteoarthritis, which was similar to our study.

In our study, there was only one case showing migratory osteoporosis in which marrow edema and joint effusion were observed in MRI, which was comparable to study by Drar et al,⁸ which reported marrow edema in 100% cases and joint effusion in 50% cases and study done by Ragab et al,⁷ in which marrow edema was present in 100% cases, but joint effusion was seen in 33.3% cases.

In seven patients with septic arthritis, the most significant MRI findings were marrow edema (100%), synovial thickening (100%), joint effusion (71.4%), and bone destruction (71%), and least common was involvement of adjacent muscles (57.14%). These results were comparable to the study by Ragab et al,⁷ which showed marrow edema (100%), synovial thickening (68.8%), joint effusion (50%), and bone destruction (62.5%). Kwack et al¹⁴ reported synovial thickening (55.5%), joint effusion (100%), and marrow edema (33.3%) as the characteristic findings in septic arthritis.

In three patients with tubercular arthritis, maximum patients had marrow edema (100%), joint effusion (100%), and involvement of adjacent muscle (100%), and others had synovial thickening (33.3%), and bone erosion (33.3%). Similar findings were done in study of Ragab et al.⁷

Out of two patients with Perthes' disease, both had marrow edema (100%) and contour abnormality (100%) with unilateral involvement. There was no case of bilateral joint involvement. Drar et al⁸ also reported similar findings in their study; that is, 80% cases showed unilateral affection and contour abnormality and marrow edema was observed in maximum cases.

The most sensitive MRI finding in patients with stress fracture is marrow edema that was found in all patients with stress fracture. Our study is comparable with studies done by Ragab et al⁷ and Drar et al⁸ who reported similar findings. The second most common finding is subchondral linear hypointensity. Joint effusion was least found in any of the studies.

MRI is the modality of choice for early detection of inflammatory arthritis. The most sensitive feature in diagnosing rheumatoid arthritis is synovial thickening that we found in all our patients (100%). Uneven and degree of synovial thickening also helps in distinguishing infective and inflammatory arthritis. Our study and finding are comparable those by Choi et al.¹⁵ The other most common MRI feature is bone erosion (100%). There are studies by Narváez et al¹⁶ and Tehranzadeh et al¹⁷ in the literature, which have shown persistence and progression of bone erosions on MRI in cases of inflammatory arthritis.

We had three patients complaining of hip joint pain, who were previously diagnosed with carcinoma (CA) prostate (two patients) and CA stomach (one patient). In our study, the MRI finding comprised postcontrast enhancement and hyperintensity in the adjacent bones in all patients with adjacent muscle involvement in two patients. Two out of three patients had unilateral involvement and one had bilateral hip joint involvement. The MRI features in our study are similar to those explained in the literature such as Heindel et al¹⁸ and Yang et al.¹⁹

Sensitivity of Magnetic Resonance Imaging in Patients with Hip Joint Pain

We found that MRI is the modality of choice for early detection of AVN, even in stage I in which X-rays are normal. Our study is comparable with many studies in the literature like Stoica et al,²⁰ Rupp et al,²¹ and Pierce et al.²² Accurate localization and knowledge of the extent of the necrosis by means of MRI make it possible to plan an osteotomy accurately.

We found MRI to be highly sensitive (80%) in diagnosis of osteoarthritis of the hip joint. This was comparable with study done by Drar et al⁸ who found MRI sensitivity to be 80% in case of osteoarthritis of the hip joint. Boutry et al¹³ also discussed the widespread application MRI as a modality of choice for evaluation of painful hip joint due to rapidly destructive osteoarthritis of the hip joint.

MRI facilitates early diagnosis of stress fracture. In this study, two patients were diagnosed with stress fracture and MRI findings were true positive in both patients, hence making MRI 100% sensitive to cases of stress fracture, as the dominant finding in cases of stress fracture is bone marrow edema that is very well appreciated on STIR sequences. Our finding is comparable with those by Kiuru et al²³ and Mammoto et al.²⁴

Out of 64 patients, 7 were diagnosed with septic arthritis on MRI with 5 of them being true positive; hence, we found MRI to be 71.43% sensitive in cases of septic arthritis that is comparable with study by Kwack et al¹⁴ who found the sensitivity to be 82%.

Three patients were diagnosed with tubercular arthritis on MRI; however, only one of them who had bone erosions and synovial thickening came out to be true positive. Hence the sensitivity of MRI for tubercular arthritis was 33.33%. Concluding, the most sensitive MRI findings for diagnosis of tubercular arthritis are synovial thickening and bone erosions, which is also quoted by Ragab et al.⁷

The sensitivity for tumors and metastasis on MRI is high in our study, which is 100% in case of metastasis and 66.7% in case of bone tumor (two out of three patients were true positive) which comparable with study by Tripathi et al⁹ who also found similar results.

We found MRI to be 100% sensitive in cases of Perthes' disease that is contradicted by Tiwari et al²⁵ who found low sensitivity and high specificity of MRI. However, our study is comparable with Drar et al⁸ who found MRI to be 80% sensitive in patients with Perthes' disease.

Conclusion

MRI has high sensitivity of 85.71% in patients with AVN of the femoral head. It also helps in early diagnosis of AVN stages, which prevents late complications. MRI has high sensitivity in patients with osteoarthritis, stress fracture, septic arthritis, metastasis, Perthes' disease, sacroiliitis, and migratory osteoporosis. On the basis of MRI findings, it is moderately sensitive in patients with tumor, inflammatory arthritis, and osteomyelitis. MRI was found to be least sensitive in patients with tubercular arthritis.

Hence, MRI is the modality of choice for characterization of the various disorders. It helps in assessing the entire extent of osseous, chondral, and soft tissue involvement in patients with hip pain. It can also accurately demonstrate marrow edema, joint effusions, synovial thickening, articular cartilage abnormalities, subchondral bone, ligaments, muscles, juxta-articular soft tissues, and adjacent bones.