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Research Review By Dr. Ceara Higgins©

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Date Posted:

March 2016

Study Title:

Association of hip pain with radiographic evidence of hip osteoarthritis: diagnostic test study

Authors:

Kim C, Nevitt MC, Niu J, et al.

Author's Affiliations:

Boston University, School of Medicine; University of California, San Francisco; University of California, Davis; Tufts Medical Center, Boston; Technische Universitat Munchen, Munich; NIHR Manchester Biomedical Research Unit, Manchester, UK;

Publication Information:

BMJ 2015; 351: h5983.

Background Information:

Osteoarthritis (OA) in the hip is a significant cause of morbidity, pain, gait abnormalities, and functional impairments, with more than 332,000 hip replacements occurring each year in the United States alone (1). Hip pain is often the first symptom that leads patients to seek diagnosis and treatment in these cases. Diagnosis generally involves a combination of clinical pain reports in conjunction with positive radiographic findings of osteoarthritic changes (2). Groin pain with limited internal rotation, or pain with internal rotation are also considered to be clinical findings associated with hip OA (5). While it has been shown that the association between knee OA and positive radiographic findings is weak, less is known about the association between hip OA and radiographic findings (3). Often, individuals with hip pain but no positive radiographic findings are assumed to have other causes of hip pain and treated according to this assumption. This study examined data from two cohort studies to determine concordance between hip pain and radiographic evidence of OA as a diagnostic test.

Pertinent Results:

The Framingham Osteoarthritis Study

24.7% of women and 14.7% of men reported pain in either hip, however, radiographic hip OA was found in 13.6% of women and 24.7% of men studied. Radiographs from 1850 hips showed a sensitivity of 15.6% (the percentage of patients with the clinical gold standard of hip OA with positive radiographic results) and specificity of 90.9% (the percentage of participants with hips without the clinical gold standard of hip OA and negative radiographic results) for hip OA. The positive predictive value was 20.7% (the proportion of hips with radiographic hip OA and the clinical gold standard for hip OA), while the negative predictive value was 87.6% (the proportion of hips without radiographic hip OA and no clinical gold standard).

The sensitivity of definite radiographic hip OA for hip pain located in the groin was 36.7%, specificity 90.5%, positive predictive value 6.0%, and negative predictive value 98.9%. For hip pain located in the anterior leg, sensitivity was 24.4% and specificity was 90.4%. For hip pain localized to the groin or anterior leg, sensitivity was 27.1% and specificity was 90.6%. Adding painful internal rotation to the analysis did not improve the agreements of clinical symptoms and radiographic evidence.

The Osteoarthritis Initiative

A lower prevalence of radiographic hip OA was seen in this study, with definite hip OA found in only 7.9% of women and 11.6% of men. When possible hip OA was included, the rate rose to 20.7% of women and 27.3% of men. Hip pain was reported by 27.5% of women and 18.5% of men. The sensitivity of frequent hip pain for radiographic hip OA was 9.1%, specificity was 94.3%, positive predictive value was 23.8% and negative predictive value was 84.1%.

The sensitivity of definite radiographic hip OA for hip pain located in the groin was 16.5%, specificity 94.0%, positive predictive value 7.1%, and negative predictive value 97.6%. For hip pain located in the anterior leg, sensitivity was 15.3% and specificity was 93.9%. For hip pain localized to the groin or anterior leg, sensitivity was 15.8% and specificity was 94.1%. When possible radiographic hip OA was included sensitivity rose to 30.0% for hip pain located in the groin or anterior leg, but specificity dropped to 81.8%.

Poor agreement was found between frequent hip pain and radiographic OA in the ipsilateral hip. Most patients with frequent hip pain did not have radiographic OA, while most patients with radiographic hip OA did not have frequent hip pain.

Clinical Application & Conclusions:

While it is common for health professionals evaluating patients with hip pain to use a physical exam to rule out other causes of hip pain and radiographs to diagnose hip OA, radiographic findings were found to be poor predictors of hip OA in these studies. In addition, restriction in hip internal rotation was shown to be the strongest predictor of hip OA in a study of hip range of motion (4), but the inclusion of pain with hip internal rotation in this study did not improve the performance of the radiograph as a predictive test.

This discordance of hip pain with radiographic hip OA suggests that many older people with hip OA could be missed if clinicians rely on radiographic evidence to diagnose hip OA. Therefore, health professionals are advised to evaluate and treat patients with pain suggesting OA despite negative radiographic findings.

Study Methods:

The Framingham Osteoarthritis Study

Between 2002 and 2005, 946 participants from the Framingham community were recruited, regardless of symptoms.

Inclusion Criteria:
  • Ambulatory individuals (use of assistive devices such as canes and walkers was allowed)
  • No plans to move away for at least 5 years
  • Aged 50 years or older
Exclusion Criteria:
  • History of bilateral total knee replacement
  • Rheumatoid arthritis or other forms of inflammatory arthritis
  • Dementia
  • Terminal cancer
  • Replacement hips
  • Contraindications to MRI
All participants filled out a questionnaire on the presence and frequency of joint symptoms. Those identified as having frequent joint pain (most days) were then asked to identify the location of the pain (groin, anterior leg, lateral leg, low back, or buttocks), and a standardized hip examination was performed with assessment of pain during passive internal rotation and palpation over the greater trochanter. Standing, long limb radiographs were taken of all participants in the anteroposterior (AP) plane and assessed for hip OA using the Kellgren-Lawrence grading system with a grade of 2 or more (definite joint space narrowing in either superolateral or superomedial sites of the hip joint plus a definite osteophyte) being defined as radiographic hip OA. Grading was performed by an experienced musculoskeletal radiologist and a rheumatologist using the Osteoarthritis Research Society International (OARSI) atlas (6).

The Osteoarthritis Initiative

Between 2003 and 2005, 4796 people aged 45-79, considered to be at risk for knee OA, were recruited from four centers (Columbus, OH; Providence, RI; Baltimore, MD; and Pittsburgh, PA). Inclusion Criteria:
  • Ambulatory individuals (use of assistive devices such as canes and walkers was allowed)
  • No plans to move away for at least 3 years
Exclusion Criteria:
  • History of bilateral total knee replacement
  • Rheumatoid arthritis
  • Bilateral bone-on-bone knee OA
  • Comorbidities that might interfere with the ability to participate in the study for four years
  • Replacement hips
  • Contraindications to MRI
Participants were shown a visual representation of the hip region and asked if they had pain, aching, or stiffness in the hip on most days of the month during the past year. Participants who answered yes were defined as having frequent hip pain and asked to use the diagram to indicate the location of this discomfort (groin, anterior leg, lateral leg, low back, or buttocks) in each hip, separately. All participants had standard anteroposterior pelvic radiographs taken, weight bearing with their feet internally rotated using a V-shaped foot angulation frame. Radiographs were assessed by two musculoskeletal radiologists and a rheumatologist for hip OA, specifically the presence of hip osteophytes or joint space narrowing, using the OARSI atlas. Hips were classified as showing definite hip OA based on the presence of any of the following:
  1. A modified Croft grade of 2 or more (greater than or equal to definite osteophytes; definite joint space narrowing; sclerosis, cysts, or deformity);
  2. joint space narrowing plus grade 1 or more femoral osteophytes or grade 2 or more acetabular osteophytes;
  3. grade 2 or more femoral osteophytes regardless of other features;
  4. superolateral joint space narrowing grade 2 or more or superomedial joint space narrowing grade 3 or more, regardless of other features.
Hips were classified as showing possible radiographic hip OA when other individual or combinations of indefinite radiographic features were present.

For the statistical analysis, radiographs were used as the diagnostic test and the clinical gold standard method as the diagnosis. Sensitivity was calculated as the percentage of patients with the clinical gold standard of hip OA with positive radiographic results, specificity as the percentage of participants with hips without the clinical gold standard of hip OA and negative radiographic results, the positive predictive value as the proportion of hips with radiographic hip OA and the clinical gold standard for hip OA, and the negative predictive value as the proportion of hips without radiographic hip OA and no clinical gold standard.

Study Strengths / Weaknesses:

Strengths:
  • In the Osteoarthritis Initiative study, test-retest reliability of the reading method was evaluated in 189 patients and found to be good for: medial and lateral joint space narrowing superior and inferior femoral osteophytes; acetabular osteophytes; cysts, sclerosis, or deformity; the three level summary classification; and presence or absence of definite radiographic hip OA.
  • The Framingham Osteoarthritis study was community based and participants were recruited without reference to joint problems and, while participants in the Osteoarthritis Initiative were recruited based on possibly having knee OA, the findings in the two studies both showed similarly poor concordance between hip pain and radiographic hip OA.
  • The reproducibility of the discordance between hip pain and radiographic hip OA in two different cohort studies adds robustness to the findings.
Weaknesses:
  • The lack of a validated gold standard for determining if hip pain is due to OA makes OA more difficult to study.
  • The questionnaires used in these studies did not asses the severity of hip pain or response to treatment for OA.
  • Plain radiographs may lack the sensitivity needed to detect hip OA. Therefore, MRI may be a better choice of imaging modality.
  • Participants recruited in the Osteoarthritis Initiative had, or were at risk for, knee OA and may therefore have an increased risk of hip OA. Thus both the positive and negative predictive values in this study may be biased.
  • Most participants in the Framingham Osteoarthritis Study were white, making it difficult to apply their results to other ethnicities, however, this is not true of the Osteoarthritis Initiative study.

Additional References:

  1. Kim C, Linsenmeyer KD, Vlad SC et al. Prevalence of radiographic and symptomatic hip osteoarthritis in an urban United States community: the Framingham osteoarthritis study. Arthritis Rheumatol 2014; 66: 3013-3017.
  2. Nevitt MC. Definition of hip osteoarthritis for epidemiological studies. Ann Rheum Dis 1996; 55: 652-655.
  3. Hannan MT, Felson DT, Pincus T. Analysis of the discordance between radiographic changes and knee pain in osteoarthritis of the knee. J Rheumatol 2000; 27: 1513-1517.
  4. Birrell F, Croft P, Cooper C, et al. Predicting radiographic hip osteoarthritis from range of movement. Rheumatology (Oxford) 2001; 40: 506-512.
  5. Altman R, Alarcon G, Appelrouth D, et al. The American College of Rheumatology criteria for the classification and reporting of osteoarthritis of the hip. Arthritis Rheum 1991; 34: 505-514.
  6. Altman RD, Gold GE. Atlas of individual radiographic features in osteoarthritis, revised. Osteoarthr Cartil 2007; 15(Suppl A): A1-56.
  7. Birrell F, Lunt M, Macfarlance G, et al. Association between pain in the hip region and radiographic changes of osteoarthritis: results fro a population-based study. Rheumatology (Oxford) 2005; 44: 337-341.
  8. Guermazi A, Niu J, Hayashi D, et al. Prevalence of abnormalities in knees detected by MRI in adults without knee osteoarthritis: population based observational study (Framingham Osteoarthritis Study). BMJ 2012; 345: e5339.

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