Persistent or recurrent symptoms after arthroscopic surgery for femoroacetabular impingement: A review of imaging findings

Hip Capsulolabral Complex: Anatomy, Disease, MRI Features, and Postoperative Appearance

The hip is a uniquely constrained joint with critical static stability provided by the labrum, capsule and capsular ligaments, and ligamentum teres. The labrum is a fibrocartilaginous structure along the acetabular rim that encircles most of the femoral head. Labral tears are localized based on the clock-face method, which determines the extent of the tear while providing consistent terminology for reporting. Normal labral variants can mimic labral disease and can be differentiated by assessment of thickness or width, shape, borders, location, and associated abnormalities. The Lage and Czerny classification systems are currently the most well-known arthroscopic and imaging systems, respectively. Femoroacetabular impingement is a risk factor for development of labral tears and is classified according to bone dysmorphisms of the femur ("cam") or acetabulum ("pincer") or combinations of both (mixed). The capsule consists of longitudinal fibers reinforced by ligaments (iliofemoral, pubofemoral, ischiofemoral) and circular fibers. Capsular injuries occur secondary to hip dislocation or iatrogenically after capsulotomy. Capsular repair improves hip stability at the expense of capsular overtightening and inadvertent chondral injury. The ligamentum teres is situated between the acetabular notch and the fovea of the femoral head. Initially considered to be inconsequential, recent studies have recognized its role in hip rotational stability. Existing classification systems of ligamentum teres tears account for injury mechanism, arthroscopic findings, and treatment options. Injuries to the labrum, capsule, and ligamentum teres are implicated in symptoms of hip instability. The authors discuss the labrum, capsule, and ligamentum teres, highlighting their anatomy, pathologic conditions, MRI features, and postoperative appearance. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Magnetic Resonance Imaging Approximates Labral Width at the 9-, 12-, and 3-O'Clock Positions in the Setting of Revision Hip Arthroscopy

PURPOSE

To compare preoperative magnetic resonance imaging (MRI) and intraoperative measurements of labral width and determine whether MRI can reliably predict labral width in the setting of revision surgery.

METHODS

Patients who underwent revision hip arthroscopy with labral repair performed by a single surgeon from January 2008 to December 2015 were identified retrospectively from a prospectively collected database. The width of the labrum was measured intraoperatively at the time of surgery. Two orthopaedic surgeons performed labral width measurements on MRI scans at 3 standardized locations using the clock-face method. Interobserver and intraobserver reliabilities were calculated, and comparisons between intraoperatively measured labral widths and MRI measurements were performed.

RESULTS

Fifty-eight patients who underwent revision hip arthroscopy were enrolled in the study. The average labral width measurements at the 3-, 12-, and 9-o'clock positions were 7.4 mm (standard deviation [SD], 1.2 mm), 7.5 mm (SD, 1.4 mm), and 6.6 mm (SD, 1.2 mm), respectively, on MRI compared with 6.7 mm (SD, 2.1 mm), 6.5 mm (SD, 2.5 mm), and 7.0 mm (SD, 1.9 mm), respectively, when measured intraoperatively. The average intraoperative measurements were smaller than the MRI measurements at the 3-o'clock (P = .03) and 12-o'clock (P = .01) positions. The inter-rater intraclass correlation coefficients between the 2 surgeons exhibited good agreement (0.612) at the 3-o'clock position, fair agreement (0.498) at the 12-o'clock position, and poor agreement (0.171) at the 9-o'clock position. The positive predictive values of the MRI measurements were 72% at the 3-o'clock position, 68% at the 12-o'clock position, and 88% at the 9-o'clock position for identifying a labral width of 6 mm or greater.

CONCLUSIONS

The results of this study show that MRI-measured labral width and actual labral width measured at the time of revision arthroscopy are usually within 1 mm of each other.

LEVEL OF EVIDENCE

Level II, diagnostic study investigating diagnostic test.

The posterior crescent sign on MRI and MR arthrography: is it a marker of hip dysplasia and instability?

OBJECTIVE

To evaluate the prevalence of the 'posterior crescent sign' in symptomatic patients referred for MRI/MR arthrogram of the hip and identify any correlation with imaging features of joint pathology.

MATERIALS AND METHODS

Retrospective imaging assessment of a cohort of 1462 hips, from 1380 included MR examinations (82 bilateral) retrieved from a search of all examinations in patients 16-50 years old from June 2018 to June 2021, with median age 45.8 years (range 17.8-50.0) and 936 hips (64%) in women. Radiographic and MR findings related to hip dysplasia, femoroacetabular impingement and osteoarthritis were assessed.

RESULTS

Fifty-one hips (3.5%) were positive for the posterior crescent sign, median age of 45.8 years (range 17.8-50.0) and 29 (58%) in women. Radiographic findings included the following: mean lateral centre edge angle (LCEA) 22.2° (± 7.8°) with LCEA < 20° in 15 (31%) and LCEA 20-25° in 17 (35%) and mean acetabular index (AI) of 13.1° (± 5.8°) with AI > 13° in 22 (45%). MR findings included the following: mean anterior acetabular sector angle (AASA) 54.3° (± 9.8°), mean posterior acetabular sector angle (PASA) 92.7° (± 7.0°), labral tear at 3-4 o'clock in 20 (39%), high-grade acetabular chondral loss in 42 (83%) and ligamentum teres abnormality in 20 (39%).

CONCLUSION

The posterior crescent sign occurs in 3.5% of symptomatic young and middle-aged adults on MR. It is associated with overt and borderline hip dysplasia and other findings of hip instability. It is also associated with osteoarthritis in some cases and should be interpreted with caution in these patients.

[Persistent or recurrent symptoms after surgery for femoroacetabular impingement syndrome (FAIS) : Pathology, diagnostics and therapy]

BACKGROUND

Femoroacetabular impingement syndrome (FAIS) has gained vast importance in the last two decades. Multiple studies have shown that if untreated, early osteoarthritis of the hip joint may result. Hip arthroscopy is one of the fastest growing procedures in the orthopedic cosmos, having already replaced the majority of (mini) open techniques in FAIS surgery. However, with the recent remarkable increase in the volume of hip arthroscopies performed worldwide, the number of patients with persistent or recurrent symptoms after FAIS surgery is also growing.

PATHOLOGY

Potential underlying pathologies are misresection of the bony deformity, insufficiency fracture of the femoral head neck junction or the femoral subchondral head itself (SIFFH), adhesions, failed chondrolabral or capsular treatment, septic arthritis, heterotopic ossification or a wrong indication in the case of osteoarthritis that is already too advanced. Most of these occur more often during the extensive learning curve for hip arthroscopy.

DIAGNOSTICS

High-quality imaging plays a key role in determining the need for revision surgery vs. further conservative treatment. Therapeutical avenues are shown with the common goal of proper detection and correction of the underlying pathology to address unsatisfactory FAIS treatment outcomes and ensure long-term survival of the native hip joint.

Assessment of the iliocapsularis muscle on magnetic resonance imaging

INTRODUCTION

Morphologic features of Iliocapsularis (IC) may aid clinical decision-making in the symptomatic hip. The relationship between IC muscle size and underlying hip pathology is emerging; however, research is limited in the imaging literature. The purpose of this study was to determine the reliability and reproducibility of measurements of the IC muscle and its MRI appearances. It also looked for any association between IC dimension and axial levels, side, gender and bony features of hip instability.

METHODS

Retrospective study of 37 MRI scans were assessed by four observers. MRI axial T1 images were used to define the IC anatomy, measure the IC and rectus femoris at the femoral head centre (FHC) and adjacent levels and calculate the iliocapsularis-to-rectus femoris (IR) ratio. Measurements were repeated at least 2 weeks later. Radiographic assessment of the lateral centre edge angle, acetabular index and femoral neck-shaft angle were also conducted.

RESULTS

The IC was always present, but was well-defined in only 4% of cases with fair agreement. The intraclass correlation coefficient for reliability and reproducibility was the highest for IC width 0.94 (0.91-0.96). No significant correlation was identified between the IR ratio and radiographic parameters.

CONCLUSION

Iliocapsularis is visible and reliably measured on MRI despite observers considering the muscle to be not well-defined. Despite gender differences in muscle size, the IR ratio was unchanged. There is a significant difference in the IR ratio above and below the FHC; therefore, clinicians need to be aware of how this may impact the clinical use when utilising the IR ratio.

Three-Dimensional Magnetic Resonance Arthrography of Post-Arthroscopy Hip Instability Demonstrates Increased Effective Intracapsular Volume and Anterosuperior Capsular Changes

Purpose

To quantify the magnetic resonance arthrography (MRA) capsular morphologic findings associated with postarthroscopy hip instability.

Methods

Among patients with clinically significant iatrogenic hip instability at a single center, patients with preindex and postindex surgery MRAs were identified. These MRAs were compared regarding effective intracapsular volume calculated by semi-automated 3-dimensional pixel intensity region segmentation, 2-dimensional anterior proximal intracapsular area in the femoral neck axial plane reconstruction, maximal anterior fluid pocket depth, capsule retraction distance, and capsular instability grade. Morphological measurements were conducted using Horos image processing software. Paired t-test, paired Wilcoxon signed rank test, and the McNemar test were used for identifying statistical significance.

Results

In 42 patients, mean effective intracapsular volume was significantly greater in the postindex surgery MRAs (19.44 cm³ vs 17.26 cm³; P = .006). Proximal anterosuperior (12-3 o'clock) intracapsular area was also significantly greater after index surgery (2.84 cm² vs 1.43 cm²; P < .001. Proximal anteroinferior (3-6 o'clock) intracapsular area (1.34 cm² vs 0.97 cm²; P = .002), capsule deficiency grade (P < .001), anterior capsule retraction distance (4.83 mm vs 0.34 mm; P < .001), and maximum anterior fluid depth (8.33 mm vs 4.90 mm; P <.001) were also significantly increased after index surgery.

Conclusion

In comparison to the preoperative state, iatrogenic hip instability is associated with MRA findings that include increases in total effective intracapsular volume, proximal anterosuperior and anteroinferior intracapsular cross-sectional area, maximum proximal anterosuperior fluid depth, and capsule retraction distance.

Level of Evidence

Level IV, diagnostic case series.

Salvage Revision Hip Arthroscopy Including Remplissage Improves Patient-Reported Outcomes After Cam Over-Resection

PURPOSE

To evaluate outcomes of arthroscopic hip remplissage with folded iliotibial band allograft to treat cam over-resection.

METHODS

Patients who underwent arthroscopic iliotibial band hip remplissage from May 2013 to April 2018 were prospectively evaluated. Pre- and postoperative patient-reported outcome scores were compared and included the 12-Item Short Form Survey (SF12) Physical Health Composite Score (PCS), SF12 Mental Health Composite Score (MCS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), modified Harris Hip Score (mHHS), and Hip Outcome Score (HOS) (Activities of Daily Living [ADL] and Sport). Postoperative Tegner Activity Scale and patient satisfaction (1-10) were also evaluated.

RESULTS

Thirteen patients (2 men, 11 women) with an average age of 39.8 ± 9 years underwent arthroscopic hip remplissage with minimum 2-year and mean 3.1-year follow-up (range, 2.1-4.1 years). One hundred percent follow-up was achieved. The average number of previous surgeries was 1.38 (range, 1-3). One patient underwent total hip arthroplasty 2 years after remplissage. All 12 patients who did not undergo total hip arthroplasty had improved patient-reported outcomes after remplissage (mean scores: SF12 PCS 36 vs 42, P = .02; SF12 MCS 45 vs 51, P = .14; mHHS 45 vs 66, P < .001; minimal clinically important difference [MCID] 83%; WOMAC 42 vs 28, P < .001; HOS ADL 52 vs 69, P = .003; MCID, 67%; HOS Sport 27 vs 46, P = .015; MCID, 67%). All improvements met statistical significance, besides the SF12 MCS. Median postoperative Tegner score was 2.9. Median postoperative patient satisfaction was 7 out of 10 (range, 5-10).

CONCLUSIONS

Arthroscopic hip remplissage is a successful salvage treatment option for hip instability caused by previous cam over-resection. Care must be taken during primary surgery not to over-resect the cam as patient-reported outcomes after remplissage are inferior to those undergoing primary hip arthroscopy.

LEVEL OF EVIDENCE

Level IV, case series.

Arthroscopic labral repair for femoroacetabular impingement: A systematic review

BACKGROUND

The present systematic review investigated return to sport, patient reported outcome measures (PROMs), complications and subsequent progression to total hip arthroplasty (THA) in patients undergoing arthroscopic labral repair for FAI.

MATERIAL AND METHODS

Following the PRISMA statement, the literature search was performed in February 2021. The outcomes of interest were: rate of return to sport, modified Harris Hip Score (mHHS), the subscales Activities of Daily Living and Sport-Specific Subscale of the Hip Outcome Score (HOS-ADL and HOS-SSS, respectively). Complications, revision surgeries and progression to total hip arthroplasty were recorded.

RESULTS

Data from 210 procedures were retrieved. The mean follow-up was 34.0 (24.0-42.5) months. The mean age of the patients was 32.0 (20.0-47.0) years, while the mean BMI was 20.9 (20.1-21.7) kg/m². 52.8% (111 of 210 patients) were women. At 24-month follow-up, 100% of the patients had returned to sport. At a mean of 34 months follow-up, the mean mHHS increased by 25.5% (P = 0.02), the mean HOS-ADL by 23.0% (P = 0.03), the mean HOS-SSS by 32.8% (P = 0.001). No complications were observed. The rate of revision was 4.3% (9 of 210 procedures). At a mean of 37.9 ± 7.5 months, 1.9% of patients (4/210) underwent THA.

CONCLUSION

Arthroscopic labral refixation for FAI yields reliably positive clinical outcomes, with a low rate of revision and conversion to THA.

Ultrasound-guided release of post-arthroscopy extra-articular hip adhesions in femoroacetabular impingement: a novel technique

OBJECTIVE

To explore a novel ultrasound-guided injection technique of releasing extra-articular anterior hip adhesions in arthroscopically treated femoroacetabular impingement patients.

MATERIALS AND METHODS

IRB-approved pilot study included 24 consecutive patients referred for ultrasound-guided injection (Jan 1, 2017-Mar 31, 2018) with anterior hip pain and/or limited hip flexion following arthroscopic treatment for femoroacetabular impingement. They underwent ultrasound-guided pressure injection, releasing post-operative extra-articular adhesions between the joint capsule and flexor tendons along the arthroscopic portal followed by steroid instillation. A visual analogue pain score of 0-10 and standard Hip Outcome Score was used to record treatment response pre-injection, at 6 weeks and at 6 months following injection.

RESULTS

Nine out of 11 patients (complete data group) who answered all questionnaires showed response to injection with improvement in Hip Outcome Scores at 6 weeks and 6 months. Three out of 10 patients (incomplete data group) showed significant response to injection from clinical follow-up records. No records were available in 3 patients. In total, 12 (57.14%) out of 21 patients showed response to injection. No post-procedure complications.

CONCLUSION

Ultrasound-guided pressure injection is a novel, safe, and effective procedure providing pain relief and improved hip movement as evaluated in our small sample study. The limitations of this pilot project include small sample size, lack of control group, short 6-month follow-up, and single institution study. This minimally invasive technique could be a cost-effective alternative to surgical adhesiolysis and can potentially be extended for extra-articular adhesions at other peripheral joints, amenable to ultrasound.

Pain Scores and Activity Tolerance in the Early Postoperative Period After Hip Arthroscopy

Background:

Despite the rapid growth in the use of hip arthroscopy, standardized data on postoperative pain scores and activity level are lacking.

Purpose:

To quantify narcotic consumption and use of the stationary bicycle in the early postoperative period after hip arthroscopy.

Study Design:

Case series; Level of evidence, 4.

Methods:

In this prospective case series, patients undergoing a primary hip arthroscopy procedure by a single surgeon were asked to fill out a daily survey for 9 days postoperatively. Patients were asked to report their pain level each day on a visual analog scale from 1 to 10, along with the amount of narcotic pain pills they used during those postoperative days (PODs). Narcotic usage was converted to a morphine-equivalent dosage (MED) for each patient. Patients were also instructed to cycle daily starting on the night of surgery for a minimum of 3 minutes twice per day and were asked to rate their pain as a percentage of their preoperative pain level and the number of minutes spent cycling on a stationary bicycle per day.

Results:

A total of 212 patients were enrolled in this study. Pain levels (POD1, 5.5; POD4, 3.8; POD9, 2.9; P < .0001) and the percentage of preoperative pain (POD1, 51.6%; POD4, 31.8%; POD9, 29.5%; P < .01) significantly decreased over the study period. The amount of narcotics used per day (reported in MED) also significantly decreased (POD1, 27.3; POD4, 22.3; POD9, 8.5; P < .0001). By POD4, 41% of patients had discontinued all narcotics, and by POD9, 65% of patients were completely off narcotic medication. Patients were able to significantly increase the number of minutes spent cycling each day (POD1, 7.6 minutes; POD4, 13.8 minutes; POD9, 19.0 minutes; P < .0001). Patients who received a preoperative narcotic prescription for the affected hip were significantly more likely to require an additional postoperative narcotic prescription (P < .001).

Conclusion:

Patients can expect a rapid decrease in narcotic consumption along with a high degree of activity tolerance in the early postoperative period after hip arthroscopy.

Approach to a Failed Hip Arthroscopy

PURPOSE OF REVIEW

Hip arthroscopy has seen increasing utilization over the last decade. This is largely related to increased recognition and improved techniques for treating femoroacetabilar impingement (FAI). Though hip arthroscopy generally yields favorable outcomes, there are a subset of patients who have residual or recurrent symptoms that require reoperation. The current review discusses an algorithmic approach to evaluating patients following a failed hip arthroscopy including a framework for clinical and radiographic assessment, available treatment options, and associated outcomes in revision surgery.

RECENT FINDINGS

Residual FAI has been demonstrated to be the most common indication for revision arthroscopy. Other indications include residual or recurrent labral pathology, gross instability, microinstability, or adhesions. Appropriate history and imaging are important to determine the cause for residual symptoms. Novel techniques including labral and capsular reconstruction, and modified remplissage procedures have been developed to deal with complex revision cases. Though studies have shown improved outcomes after revision surgery, they have been shown to result in inferior outcomes compared to a matched cohort following primary hip arthroscopy. Management of a failed hip arthroscopy remains a complex problem. Focused history, cross-sectional imaging, and revision hip arthroscopy with novel techniques can improve outcomes, albeit to a lesser extent than patients undergoing successful primary hip arthroscopy. The information provided here can help guide treatment and set appropriate patient expectations for revision surgery.

Prediction of intra-articular pathology and arthroscopic outcomes for femoroacetabular impingement and labral tear based on the response to preoperative anaesthetic hip joint injections

OBJECTIVE

This study investigated whether the preoperative response to intra-articular injections is associated with intra-articular pathological findings and arthroscopy outcomes.

METHODS

This study included 49 patients who underwent arthroscopic hip surgery for femoroacetabular impingement and labral tear after receiving preoperative hip joint injections. The response to anaesthetic injections was categorized as poor (0-50%) or good (51-100%). With respect to anatomical indices, we evaluated the lateral centre-edge angle (LCEA), acetabular roof obliquity (ARO), vertical-centre-anterior angle (VCA), and the alpha angle (on a lateral view). We evaluated the association between these indices (including the types of hip labral tears and cartilage damage) and the effectiveness of intra-articular injections.

RESULTS

The study included 22 men and 27 women, and the mean age of patients was 36.4 years. No statistically significant association was observed between the response to preoperative anaesthetic hip joint injections and patient demographics (age, sex) and anatomical indices (LCEA, ARO, VCA, and alpha angle) (p > 0.05). All patients showed labral damage; however, labral tear classification or cartilage damage was not significantly associated with the effectiveness of joint injections. At the 1-year post-operative follow-up, patients with a good response to anaesthetic hip joint injections showed a significantly better outcome than patients with a poor response to these injections (p < 0.01).

CONCLUSION

The response to preoperative anaesthetic hip joint injections may indicate the presence of intra-articular pathology. Furthermore, this association may have predictive value in determining post-operative outcomes following hip arthroscopy.

The CU PAO: A Minimally Invasive, 2-Incision, Interlocking Periacetabular Osteotomy: Technique and Early Results

BACKGROUND

The aims of this study were to describe a novel minimally invasive, interlocking periacetabular osteotomy (PAO) for the treatment of hip dysplasia that was developed at our institution and to report on its safety, complications, and early clinical outcomes.

METHODS

This was a prospective longitudinal study of the first 200 consecutive hips that underwent the CU (University of Colorado) PAO, an interlocking osteotomy combining the benefits of the Birmingham interlocking pelvic osteotomy (BIPO) and the Ganz PAO. The technique provides direct visualization of the sciatic nerve during the ischial osteotomy and allows for immediate weight-bearing postoperatively. Demographic characteristics, intraoperative and perioperative parameters, and functional outcomes were documented. All patients underwent hip arthroscopy 3 to 10 days prior to the PAO to address concomitant intra-articular pathology. Mechanical deep venous thrombosis (DVT) prophylaxis was used for 2 weeks postoperatively. Results were stratified to compare the first 100 and the second 100 cases.

RESULTS

A total of 161 patients (200 hips) underwent primary PAO; mean follow-up was 20 months (range, 3 to 33 months). The mean patient age at the time of surgery was 29.4 years (range, 13 to 55 years). Females accounted for 89% of the patients included in this study. The average length of stay was 4 days. A concomitant proximal femoral derotational osteotomy was performed in 19 hips. The lateral center-edge angle (LCEA) improved from a mean of 18.8° preoperatively to 31.5° postoperatively (p < 0.001). The mean Non-Arthritic Hip Score (NAHS) improved from 56.0 preoperatively to 89.4 at the 24-month follow-up (p < 0.0001). Paresthesias in the distribution of the lateral femoral cutaneous nerve were common (65% at 2 weeks postoperatively) but resolved in 85% of the patients within the first 6 months. There were no sciatic nerve-related complications, deep infections, or DVTs.

CONCLUSIONS

The CU PAO enables corrective realignment of symptomatic acetabular dysplasia with direct visualization of the sciatic nerve, early weight-bearing, cosmetic incisions, and good short-term outcomes.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Surgical Treatment for FAI: Arthroscopic and Open Techniques for Osteoplasty

PURPOSE OF REVIEW

To review the relevant literature and techniques regarding arthroscopic and open treatment of femoroacetabular impingement (FAI). To discuss both the senior authors' preferred method of arthroscopic and open treatment of FAI.

RECENT FINDINGS

Routine treatment of FAI has moved away from open techniques and is more focused arthroscopic methods. Arthroscopic treatment of FAI has more recently focused on differing techniques of hip access and capsular management. Open techniques still have a role in FAI, but indications for open management are focused on cases with more severe pathology. While arthroscopic techniques have shown better outcomes in the short term and higher return to play, it is not without risk and is a procedure with a steep learning curve. In cases of complex joint pathology, such as FAI coupled with dysplasia or Legg-Calve-Perthes, arthroscopy may be not indicated and an open approach preferred. We outline various techniques for both arthroscopic and open treatment of FAI and their outcomes when possible.