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Original Article
18 (); 204-208
doi:
10.1016/j.jor.2019.11.003

Validity of direct magnetic resonance arthrogram in patients with femoroacetabular impingement and their outcome post hip arthroscopy

, ,
a Department of Trauma and Orthopaedics, St Helens and Knowsley NHS Trust, Whiston Hospital, Warrington Road, L35 5DR, United Kingdom
b The Robert Jones and Agnes Hunt Orthopaedic Hospital NHS Foundation Trust, Oswestry, SY10 7AG, United Kingdom

∗Corresponding author: Rahul Mohan. rahul.mohan@sthk.nhs.uk

Received: , Accepted: ,
Professor P K Surendran Memorial Education Foundation
Disclaimer:
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.

Abstract

Abstract

Femoroacetabular Impingement is an established cause of labral tears and chondral delamination. The aim was to test the validity of direct magnetic resonance arthrogram [dMRA] in the diagnosis of the same. We also looked at the short term functional outcome in these patients post hip arthroscopy. The dMRA is valuable in diagnosing labral tears nevertheless poor in detecting cartilage delamination. Hip arthroscopic intervention provided a good short-term functional outcome; however, should be offered with caution in patients over 40 years. To our knowledge, this is the single largest series published with similar methodology.

Keywords

Young adults
Femoroacetabular impingement
Direct MR arthrogram
Hip arthroscopy
Functional outcome
1

1 Introduction

The femoroacetabular impingement [FAI] is a major cause for the labral tear and cartilage delamination.1 Among the athlete and nonathlete population 22% and 66% respectively present with groin pain and mechanical symptoms proven to have a labral tear.2,3 According to Beck et al., labral tear is an important cause for the early age osteoarthritis.4 Early diagnosis and management of FAI influence in preventing premature osteoarthrosis and subsequent total hip arthroplasty.5,6 Given the increasing number of young age hip arthroplasty surgeries, the approach is shifting towards preventive arthroscopic procedures in patients with femoroacetabular impingement.7,8

Arthroscopy of the hip is the gold standard in diagnosing labral tears and chondral delamination. Unlike knee arthroscopy, only a few studies reported the outcome of hip arthroscopy.9 Hip arthroscopy in all patients with femoroacetabular impingement may not be ideal, especially in the absence of reliable evidence of its validity. If a successful, less invasive diagnostic tool is identified, hip arthroscopy can be reserved as a definitive therapeutic option.10

Direct Magnetic Resonance Arthrogram [dMRA] with intraarticular injection of gadolinium is proved to have high sensitivity and specificity in diagnosing labral tears. However, the detection of chondral delamination is poor in MRA.11,12 Direct MRA occasionally reports false-positive labral tear for normal sub labral sulcus.13 Hence it is vital to know the validity of the direct MR arthrogram in diagnosing intraarticular pathologies.

The primary aim of this study was to assess the validity of dMRA in diagnosing labral tears and cartilage delamination. The secondary objective was to study the effects of the arthroscopic intervention on the functional outcome.

2

2 Methods

It is a retrospective, single surgeon case series study between 2013 and 2016 in one of the NHS hospitals at the North West of England. We follow our in-house protocol for the young patients presenting to the outpatient clinic with hip pain and mechanical symptoms. These patients are first evaluated clinically and radiologically to rule out arthritis and non-mechanical aetiologies of hip pain. The patients were then scored using the non-arthritic hip score in the clinic and were referred for direct magnetic resonance arthrogram of the involved hip.

Hip arthroscopy was performed in patients whome the direct MR arthrogram and their clinical examination was consistent with FAI. In patients in whome there was non correlation between clinical examination and dMRA proceeded with diagnostic intraarticular hip injection. 8 mls 0.5% levobupivacaine and 2 ml of 80 mg depomedrone was used for hip injection in theatre under fluroscopy control. In patients who responded positively to diagnostic injection were listed for hip arthroscopy. Non-responders were evaluated for other causes of hip pain. Hip arthroscopy was performed not only to confirm the MR arthrogram findings but also for the management of intra and extra-articular hip pathologies.

The second part of the study was to assess the short-term effects of hip arthroscopic treatment and the functional outcome. As a part of the postoperative protocol, all patients who underwent hip arthroscopy were given a clinic appointment at six weeks, six months and one year. Patients scored the non arthritic hip score on their final visit. All patients who came to the clinic via the protocol were included and patients who had pre operative arthritic changes on the Xrays and BMI >35 kg/m2 were excluded.

The researcher was not involved in the treatment of any of these patients. A data collection proforma was used for systematic data collection. We divided the acetabulum into four quadrants to explain the labral tear and chondral delamination as anterior, anterosuperior, posterior and posterosuperior. Descriptive statistics were used to describe patient demography. Patient characteristics were reported using mean, percentage and range. The sensitivity, specificity, positive predictive value and negative predictive value tests were used to assess the validity of dMRA in comparison with hip arthroscopy. SPSS software was utilised for the statistical analyses. The agreement between dMRA and hip arthroscopy was calculated using Kendall's tau-b test.

The paired t-test was used to compare and analyse the pre and post operative non-arthritic hip scores. The relation between gender, age and cartilage status and postoperative scores were calculated using the inferential statistics and the level of significance was set at a P-value of <0.05.

Ethical clearance was obtained from the trust ethical committee and governance approval obtained from the “Health Research Authority”. All patients signed a consent form before undergoing hip arthroscopy and MR arthrogram, which was checked and confirmed as per NHS trust guidelines. The confidentiality of patients’ details was strictly maintained throughout, according to the "Data protection act".

3

3 Results

One hundred thirty-one patients were identified with an average duration of symptoms of 23.8 months. There were 88 females and 43 males. Of the 131 patients, 51 were involved in contact sports. Majority of the operated patients (76%) had no history of trauma. Arthroscopic findings were taken as the standard to assess the validity of dMRA.

Table 1 illustrates the cross-tabulation between dMRA and Hip arthroscopy findings of labral tear. Of the total 23 anterior labral tears identified in the hip arthroscopy, only 9 were reported as anterior in dMRA, the remaining 8 reported as anterosuperior and the rest 6 as the normal labrum. Similarly, of the total 101 patients diagnosed with an anterosuperior labral tear on hip arthroscopy, 74 correlated with the findings on dMRA. dMRA suggested normal labrum in 15 and anterior labral tears in the remaining. Of the seven normal labrum confirmed on hip arthroscopy, dMRA suggested on 5 and on the remaining falsly reported as an anterosuperior labral tear.

Table 1 Cross tabulation of dMRA and hip arthroscope findings for labral tears.
Direct MR Arthrogram and Hip arthroscopy cross tabulation for labral tear
Labral tear in Hip arthroscope
Anterior Anterosuperior Normal Total
Labral tear in Direct MRA Anterior 9 12 0 21
Anterosuperior 8 74 2 84
Normal 6 15 5 26
Total 23 101 7 131

Consequently, 43 out of the 131 patients have a discrepancy in findings between the hip arthroscopy and dMRA. The misclassification rate between the two for the labral tear was 32%. The agreement between the dMRA and hip arthroscopy in the diagnosis of labral tear was assessed using Kendall's tau-b test. This test showed a value of 0.218 with a significance of 0.009 suggesting a direct MR Arthrogram is useful in diagnosing labral tears. Another way to assess the validity of dMRA in diagnosing labral tears can be estimated by calculating the sensitivity and specificity of the dMRA compared with the hip arthroscopy.

The anterior or anterosuperior labral tear does not make any difference in the treatment patient was going to receive. Thus both these are considered together as labral tear for the calculation of sensitivity and specificity. The sensitivity and specificity of dMRA in diagnosing labral tear were 83.06% and 71.43% respectively, while the Positive predictive value [PPV] and the negative predictive value calculated was 98.1% and 19.23% respectively.

Table 2 illustrates the cross-tabulation results between dMRA and hip arthroscopy in diagnosing chondral delamination. A total of 9 patients were confirmed with anterior chondral delamination on the hip arthroscopy. dMRA identified this rightly only in 1 patient. Similarly of the 84 patients with anterosuperior chondral delamination, 67 were reported as normal which is a significant number of wrong reports. 16 patients reported correctly as anterosuperior and 1 as anterior.

Table 2 Cross tabulation between the findings in dMRA and hip arthroscope in patients regarding chondral delamination.
Direct MR Arthrogram and Hip arthroscopy cross tabulation for chondral delamination
Chondral delamination in Hip arthroscope
Anterior Antero-superior Grade 3/4 changes in the hip Normal Total
Chondral delamination in Direct MRA Anterior 1 1 0 0 2
Antero- superior 1 16 4 4 25
Grade 3/4 changes in the hip 0 0 1 0 1
Normal 7 67 4 25 103
Total 9 84 9 29 131

In cases confirmed as advanced arthritis, 8 out of the 9 [88.89%] patients were reported as normal cartilage on dMRA. However in diagnosing normal cartilage, 25 out of the 29 were diagnosed correctly by dMRA while 4 reported as anterosuperior delamination (Table 2).

The Kendall's tau-b test was used to detect the agreement between dMRA and hip arthroscopy in detecting cartilage delamination. This test result was 0.015, with a weak significance of 0.860 questioning the validity of dMRA in identifying cartilage delamination. For the purpose of calculating the validity of dMRA in detecting cartilage changes, the anterior, anterosuperior and global changes were grouped as a single entity. The sensitivity, specificity, positive predictive value and negative predictive value are 23.53%, 86.21%, 85.71% and 24.27% respectively.

Non-arthritic hip scores were used to assess the outcome of the arthroscopic intervention in hip impingement patients. The average preoperative non-arthritic hip score was 36.53, and the average postoperative score was 70.49. The hip arthroscopic intervention improved the mean difference of 33.653, which is statistically significant. Majority of the patients [105 out of 131] showed good improvement in the score. However, 26 patients [19.85%] had a poor postoperative outcome score. The average score of this group was 48.23, which might have caused a high standard deviation [13.295] of the postoperative scores.

It is noted that as the age increases the outcome scores becomes poor.14 Hence, the 131 subjects were sub-grouped according to age and sex [Table 3]. Those less than 20 years had the best average postoperative score of 73.24 with female patients having a better score (76.31) compared to males (63.25). However, the average score decreased to 68 in those aged more than 40. In this group, male patients scored better (71.51) compared to females (69.99).

Table 3 Table illustrating the age and sex wise distribution of post-operative non-arthritic hip scores.
Post-operative score at Discharge
Age Sex Mean Number Standard deviation Minimum Maximum
Less than 20 yrs F 76.31 13 8.548 60 88
M 63.25 4 14.930 49 81
Total 73.24 17 11.366 49 88
20–40 yrs F 70.46 46 13.505 32 87
M 73.64 22 11.875 40 85
Total 71.49 68 12.998 32 87
More than 40 yrs F 66.41 29 14.613 35 87
M 70.71 17 13.541 49 86
Total 68.00 46 14.228 35 87
Total F 69.99 88 13.546 32 88
M 71.51 43 12.861 40 86
Total 70.49 131 13.295 32 88

Twenty-six patients among the 131 (19.84%) continued to have the symptoms after the operation scoring a poor average postoperative score of 48.23. Among the 26, 16 patients (61.5%) were over age 40 years out of which females had a poor average postoperative score (46) compared to males. Of the 131, 9 patients (7%) ended up with a total hip replacement due to the grade 3/4 osteoarthritic changes found in the hip arthroscopy. 8 of them were more than 40 years of age and 5 were females. Four out of these eight patients (44.44%) were reported having normal cartilage in the dMRA and another three reported as anterosuperior focal involvement before the operation. The hip arthroscopy in all these seven patients could have been avoided if direct MR Arthrogram diagnosed the advanced cartilage degenerative changes.

4

4 Discussion

Femoroacetabular impingement [FAI] is a important atraumatic cause for the labral tear and chondral delamination.Early diagnosis and management of FAI are crucial in preventing early age total hip arthroplasty. Imaging in hip impingement patients aims to identify the abnormal bone morphology, labral tears as well as chondral delamination.15 Anteroposterior and lateral X-ray views are the common radiological investigation for any symptomatic hip, but it is difficult to quantify the findings on the X-ray.

Beaulé, Zaragoza et al. conducted a study on 36 patients about the use of three-dimensional computed tomography (CT) scan to assess the FAI.16 They compared patients with radiographs, MRI with gadolinium contrast enhancement and three-dimensional CT scan. They recommend CT scan for head-neck junction abnormalities of the femoral head, though not much useful to diagnose the labral and cartilage pathologies.

Zlatkin, Pevsner et al. assessed the validity of MRI and indirect MRA to diagnose labral tears.1 Of the 14 patients with proven labral lesions, only 85% were detected by the conventional MRI scan, while the indirect MR arthrogram diagnosed 100% of the labral tears. However, the detection rate for chondral delamination was the same (82%) for MRI scan and MR arthrogram. Saied, Redant et al. conducted a meta-analysis on the validity of conventional MRI [cMRI], direct MR arthrogram [dMRA] and indirect MR arthrogram [iMRA] in detecting the labral and cartilage delamination associated with FAI.17 They reported dMRA as the best investigation for diagnosing labral tears and cartilage lesions with an overall 91% sensitivity compared to cMRI (76%) and iMRA (72%).

A similar meta-analysis by Smith, Hilton et al. reported 87% sensitivity and 64% specificity for dMRA in diagnosing labral tears compared to cMRI values of 66 and 79, respectively.18 In a study by Sutter, Zubler et al., one radiologist found dMRA better than cMRI for diagnosing labral tear while another radiologist reported both are same, which suggests that MRI interpretation might be operator dependent.19

The delayed Gadolinium-Enhanced MRI of Cartilage (dGEMRIC) is a method of indirect MR arthrogram with delayed T1 relaxation time is a promising new MR investigation, which is shown to improve the sensitivity for detecting cartilage delamination. Bittersohl et al. studied 16 patients with a mean age of 31, which showed a sensitivity of 75 and specificity of 33.20 Similarly, another study by Lattanzi, R.Petchprapa, C.Glaser, C. et al. with ten patients with an average age of 19.9 reported a sensitivity of 71 and specificity of 36.21 A multicentre study is required to confirm the benefits of the dGEMRIC scan. Of the different MRI sequences, direct MR Arthrogram is the choice investigation because of the high sensitivity and specificity reported in many studies.

It is proven knowledge that the early arthroscopic management of femoroacetabular impingement [FAI] could possibly prevent subsequent osteoarthritis. Our study showed that the prompt diagnosis of hip impingement is a challenge as most of the patients presented with insidious onset of hip pain. This finding agrees with Clohisy et al., that the onset of symptoms in this group was insidious in the majority (65%) of the patients.22

Table 4 below is a comparison of all the recent studies performed with a similar methodology as ours.17 These studies, in general, prove that direct MR Arthrogram has good sensitivity in diagnosing labral tears and good specificity in detecting chondral delamination, which is consistent with our results. In our study, the sensitivity and specificity of direct MR Arthrogram in diagnosing labral tear was 83.06 and 71.43, respectively. dMRA have a positive predictive value of 98.1 in diagnosing true labral tear and negative predictive value of 19.23 in reporting a true normal labrum. To the best of our knowledge, this study has the largest number of patients ever published addressing the aims of this paper.

Table 4 Comparison of the results of all the recent studies performed with a similar methodology with our study.
Study [Year] No of cases Mean age Pathology studied Labral tear Chondral delamination
Sensitivity Specificity Sensitivity Specificity
Crespo R et al.23 [2014] 51 43 ±9 Combined chondral and labral tear 95 100 92 54
Sahin et al.24 [2014] 14 35 Acetabular chondral lesion 89 40
Femoral chondral lesion 100 90
Sutter et al.19 [2014] 28 31.8 Acetabular chondral lesion 91 25
Femoral chondral lesion 50 90
Labral lesion 89 50
Tian et al.25 [2014] 90 35.1 Labral lesion 95 84
Aprato et al.26 [2013] 41 24 Acetabular chondral lesion 69 88
Femoral chondral lesion 46 81
Labral lesion 91 86
McGuire et al.27[2012] 61 32 Acetabular chondral lesion 86 50
Femoral chondral lesion 85 44
Labral lesion 96 33
Reurink et al.28 [2012] 95 41.3 Labral lesion 86 75
Banks et al.29 [2012] 69 Combined chondral and labral lesions 81 51 17 100
Perdikakis et al.30 [2011] 14 43 Combined chondral and labral lesions 100 50 63 33
Zaragoza et al.31 [2009] 48 38.8 Acetabular chondral lesions 79 84
Anderson et al.32 [2009] 27 Acetabular chondral lesions 22 100
Pfirrmann et al.33 [2008] 44 30.7 Acetabular chondral lesions 74 90
Studler et al.34 [2008] 57 35 Labral lesion 97 53
Schmid et al.35 [2003] 42 37 Combined chondral lesion 79 77
OUR STUDY [2018] 131 33.2 Combined chondral and labral lesion 83.06 71.4 23.5 86.2

Many dMRA studies reported poor sensitivity for diagnosing chondral delamination. Our study agrees with a low sensitivity of 23.5%. Pfirrmann, Duc, Zanetti et al. specifically investigated this and explained that the hip joint cartilage is quite thin, and the delamination of the cartilage is very difficult to identify due to the narrow hip joint.33 Moreover, the femoral head pushes the delaminated portion into the subchondral bone obliterating the cleft, which is difficult to detect by MR Arthrogram. Anderson et al. reiterated this saying that the limited distensibility of the hip joint makes the cartilage delamination difficult to identify.32 These might be the reasons for the poor sensitivity of dMRA in detecting chondral delamination. This is significant because out of the eight patients who ended up with a total hip replacement, it was reported as either normal or insignificant cartilage delamination in dMRA.

A relevant study by Sansone, Ahldén et al. assessed the outcome of hip arthroscopic treatment on hip impingement.36 It was a prospective study of 394 patients. The average age of the study cohort was 37 years, and the mean follow-up period was 25.4 months. They have used valid outcome scores like web-based patient-reported outcomes (PROMs), the Copenhagen Hip and Groin Outcome Score (HAGOS), the International Hip Outcome Tool (iHOT-12), the Hip Sports Activity Scale (HSAS), a standardised instrument (EQ-5D) and a Visual Analogue Score for assessing the overall hip function. The preoperative scores compared statistically with the two years follow up scores and concluded that overall, 82% of the patients [286 patients] were satisfied with the arthroscopic procedure.

Very few outcome measures developed to use in hip arthroscopic patients.37 Christensen, Althausen, Mittleman et al. conducted a study to assess the validity, consistency, reliability and reproducibility of Non-Arthritic Hip Score [NAHS] in comparison with Harris Hip Score and Short Form −12.38 They concluded that NAHS is valid, reliable, consistent and reproducible. Similarly, Domb, Martin, Gui et al. also suggested using Non-Arthritic Hip Score in assessing young patients with hip pathologies.39 We have used Non-Arthritic Hip Score to determine the functional outcome of hip arthroscopic treatment.

In our study, the hip arthroscopic intervention made a significant improvement in nonarthritic hip score. Domb, Martin, Gui et al. reported a similar clinically significant improvement in the NAHS following hip arthroscopy.39 They also stated that as the age advances the postoperative score becomes poor. They demonstrated a decrease in the score of 0.208 per year. McCormick et al. shown poor score for patients more than 40 years having hip arthroscopy with an odds ratio of 3.6 for conversion to THR.40

Our study reported poor NAHS score in patients more than 40 years with an average score of 68 compared to the score in those less than 20 years (73.24) and 20–40 years (71.49). Like the finding of Domb, Martin, Gui et al., the postoperative NAHS score of our patients deteriorated with advanced age.39 Another interesting result of their study was the better postoperative score for females compared to males irrespective of age. However, our study demonstrated a better score for females only in less than 20 year age group and males performed better in all other age group. Consistent with our findings, Lindner et al. demonstrated poor outcome scores for females.41 There was a high incidence of total hip arthroplasty among females more than 40 years of age in our study. Our study is not free from limitations. It is a case series study. Only articles in English language were used towards referencing. The risk of selection bias cannot be excluded.

5

5 Conclusions

In summary, the dMRA is a valuable investigation to detect labral tears however poor in diagnosing chondral delamination. The hip arthroscopic intervention in patinets under 40 years provided good short-term functional outcome with a mean difference in the postoperative nonarthritic hip score by 33.65. Female patients generaly had a poor outcome, particularly over 40 years of age. Caution should be maintained if planning hip arthroscopy in FAI patients above 40 years with a normal or focal cartilage damage on dMRA.

Author contributions

Rahul Mohan: Academic Writing, Literature search, Statistics, Editing. PN Unnikrishnan: Literature search, Statistics, Editing. Ravindra Gudena: Concept, Literature search, Editing.

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