Abstract
Background:
Capsule-labrum adhesions are a common complication of hip arthroscopy surgery. However, their effects on patient outcomes are poorly understood.
Purpose:
To examine the effect of capsular adhesions on outcomes in patients undergoing hip arthroscopy for treatment of femoroacetabular impingement with labrum tear.
Study Design:
Cross-sectional study; Level of evidence, 3.
Methods:
We retrospectively examined 65 adult patients (67 hips) with a diagnosis of femoroacetabular impingement syndrome (FAIS) with labral tear (LT) who underwent hip arthroscopy. All were followed for at least 2 years. Patients were divided into symptomatic and asymptomatic groups. All patients underwent physical examination and magnetic resonance imaging of the hip at the last follow-up. Patients were also divided into 3 groups based on capsule-labrum adhesion length to further explore the association between adhesions and patient-reported outcomes (PROs).
Results:
A total of 65 patients (67 hips) were analyzed, with 29 hips allocated to the symptomatic group and 38 to the asymptomatic group. The mean age was 44.39 years, and the mean follow-up time was 56 months. Patient characteristics were mostly similar between the 2 groups (P > .05). The only difference between the 2 groups was sex (P = .027). Symptomatic and asymptomatic patients experienced a high incidence of postoperative adhesions (86.84% vs 96.55%; P = .168). The length of adhesive layers was significantly higher in the symptomatic group (21.66 ± 10.52 mm vs 15.16 ± 9.88 mm; P = .012). With respect to capsule-labrum adhesion length, there was no notable discrepancy in postoperative PROs between patients with a length of <13 mm and those with a length between 13 and 23 mm. However, these groups had significantly higher PROs than the group with a capsule-labrum adhesion length of >23 mm. The length of adhesion was negatively correlated with the degree of external rotation postoperatively (ρ = −0.294, 95% CI −0.504 to −0.051) and the age at the time of surgery (ρ = −0.314; 95% CI −0.515 to −0.080).
Conclusion:
Postoperative capsule-labrum adhesions were highly prevalent among patients treated with hip arthroscopy under interportal capsulotomy without capsular repair for FAIS with LT. In this cohort, more extensive capsule-labrum adhesions were associated with persistent symptoms and worse PROs.
Hip arthroscopy is increasingly becoming the preferred treatment for femoroacetabular impingement syndrome (FAIS) and labral tear (LT) because of its advantages of causing less trauma and allowing for faster postoperative recovery compared with conventional open surgery.6,10 However, adhesions are common after hip arthroscopy5,20 and most occur between the iliopsoas tendon and the capsule or between the capsule and the labrum.5,20
Previous studies have reported that intra-articular adhesions are related to postoperative pain, the need for revision surgery, and poor surgical outcomes.1,15,20,22,23 Beck 1 reported that intra-articular adhesions between the femoral neck and joint capsule may be an additional cause of postoperative groin pain, as they may lead to soft tissue impingement. In a study of 39 patients who underwent arthroscopic hip capsular reconstruction, Ruzbarsky et al 22 reported that 4 patients required revision hip arthroscopy, and all had capsulolabral adhesions at the time of revision. Locks et al 15 reported that adhesions were a common factor in all patients who required revision surgery and concluded that postoperative adhesion formation was the primary indication for revision surgery after labral reconstruction.
Capsule-labrum adhesion is a type of postoperative intra-articular adhesion. It was defined as the obliteration of the paralabral sulcus between the labrum and the joint capsule by Kim et al 12 However, they just qualitatively described this radiology sign without illustrating the clinical implications of this sign.
This study aimed to explore whether the incidence and extent of postoperative capsular adhesions differ between asymptomatic and symptomatic patients, and whether the degree of adhesions is associated with postoperative patient-reported outcomes (PROs). We also explored the effect of adhesions on hip range of motion (ROM) and factors that may lead to adhesion. We hypothesized that the incidence and degree of capsular labral adhesions would be higher in patients with postoperative symptoms, and that the degree of adhesions would be negatively correlated with postoperative PROs and hip ROM.
Methods
Participants
The study was approved by the Health Sciences Institutional Review Board of our hospital. All participants provided written informed consent. All patients with FAIS and LT who underwent arthroscopic surgery between August 2015 and December 2021 were invited to participate in this study with a consecutive sampling method. At the last follow-up, each patient completed a comprehensive questionnaire and underwent a physical examination and magnetic resonance imaging (MRI) scan. FAIS was diagnosed using the Warwick Agreement criteria. 8 LT was diagnosed based on observation during arthroscopic surgery.
The inclusion criteria were as follows: a diagnosis of FAIS with LT, a patient age between 18 and 70 years, and a minimum follow-up period of 2 years. We excluded patients with hip dysplasia 2 (lateral center edge angle of <25°), hips with a Tonnis grade of >1, Perthes disease, slipped capital femoral epiphysis, avascular necrosis, and those who had a previous ipsilateral hip injury or surgery.
Surgical Technique
All procedures were performed by a single experienced orthopaedic surgeon (J.-W.C.). The affected hip joint was abducted by 20°, internally rotated by 20°, and flexed by 10°. A perineal column was used to protect the perineal area. Guidance was provided by C-arm fluoroscopy. Successful traction was confirmed by opening the hip joint gap at least 10 mm and observing the appearance of a “vacuum sign.” The procedure began with fluoroscopic localization of the anterolateral portal, mid-anterior portal, and the anterior portal, using a 70° arthroscope. An interportal capsulotomy was performed for all patients using an arthroscopic electrothermic device between the anterolateral and anterior portals (from about 10 o'clock to 3 o’clock). Acetabuloplasty was performed as needed based on intraoperative findings. The decision to use absorbable anchors (Arthrex, Inc) to repair the damaged acetabular labrum (typically 2-4 anchors with a diameter of 3.0 mm) was based on the severity of the labral injury. After confirming the stability of the repaired labrum, traction was released, the hip was flexed at 45°, and femoral osteoplasty was performed as needed based on intraoperative findings. The joint capsule was not repaired intraoperatively. Hemostasis was carefully achieved, and the skin incision was closed.
Postoperative Rehabilitation
All patients adhered to a standard postoperative rehabilitation program. The protocol involved initiating the use of crutches and mobility on the second postoperative day. Partial weightbearing commenced at 2 weeks, progressing to full weightbearing at 6 weeks. The recovery process was stratified into 3 phases. Phase 1 (the first 6 weeks) focused on limited ROM exercises. Progressive passive ROM exercises, assisted active ROM exercises, and active ROM exercises were performed at a comfortable level. In phase 2 (6-12 weeks), patients were allowed to increase ROM in all directions as tolerated. Patients were instructed to activate all key hip muscles, building core and lower extremity muscle endurance and strength, to facilitate the restoration of daily activities such as normal gait, stair climbing, and sitting tolerance. During phase 3 (12-24 weeks), specific hip ROM, strength, and flexibility exercises were performed as needed. Additionally, patients were encouraged to gradually return to performing various types of aerobic exercise.
Clinical Function Assessments
All patients were queried regarding the persistence of symptoms on the surgical side. The most common symptoms were pain, soreness, stiffness, and limited mobility of the hip joint. The patients were classified into 2 groups (symptomatic or asymptomatic) based on their responses. The PROs included the modified Harris Hip Score (mHHS), Hip Outcome Score-Activity of Daily Living Scale (HOS-ADL), Hip Outcome Score–Sport Specific Subscale (HOS-SSS), University of California at Los Angeles (UCLA) score, and visual analog scale for pain (VAS). The minimal clinically important difference was calculated by using one-half of the standard deviation to determine meaningful improvements in outcomes. 18 The minimal clinically important difference thresholds for the mHHS, HOS-ADL, HOS-SSS, and UCLA scores were 8.4, 10.3, 13.4, and 3.9, respectively. The patient-acceptable symptom states of the mHHS, HOS-ADL, HOS-SSS, and UCLA scores were determined based on previously reported benchmarks.3,9 Physical examination at last follow-up included the log roll test, mid-groin press test, flexion-abduction-external rotation test, and flexion-adduction-internal rotation test. Additionally, ROM measurements were performed using a goniometer, encompassing flexion, extension, abduction, and 90° hip flexion with internal and external rotation.
Assessment of Capsule-Labrum Adhesions
An MRI of the hip was conducted using a 3.0 T system (uMR790; United Imaging) at the last follow-up. Scans included a fat-suppressed turbo spin-echo proton density-weighted sequence in the axial, oblique coronal, and oblique sagittal planes. Each sequence was 2 mm thick.
Capsule-labrum adhesion was defined as the absence of the paralabral sulcus between the capsule and labrum. 11 The location of adhesions was evaluated primarily between 10 and 3 o’clock, which was the primary site for surgical management of the joint capsule, acetabular margin, and labrum. The coronal plane was reviewed from 10 o’clock to approximately 1 o’clock to evaluate the presence of adhesions. Subsequently, from approximately 1 o’clock to 3 o’clock, an oblique sagittal plane was used for the same purpose. The transverse plane was employed to facilitate positioning and guarantee that the assessment of adhesions was neither repeated nor overlooked. The clock-face method was based on the previous studies.14,19 We evaluated the range of adhesion by the number of scanning layers of MRI. The total number of layers of adhesion was superimposed by the adhesion layers of the anterior capsule and the adhesion layers of the superior capsule. The capsule-labrum adhesion length was calculated as the total number of adhesion layers multiplied by the MRI scan thickness (2 mm).
One fellowship-trained sports physician (L.-Y.S.) and one senior radiologist (L.S.) independently reviewed and analyzed the MRI images in a random order to assess interrater reliability. In addition, author A assessed the images twice at 1-week intervals to assess intrarater reliability. In cases of discordant results, the senior surgeon (H-Y.L.) made the final determination. Both readers were blinded to the patients’ clinical histories. Evaluation of the healing of the capsule,7,25 labrum, 26 acetabular cartilage lesion, 27 femoral head cartilage lesion, 27 , and the residual Cam deformity was conducted via postoperative MRI.
Statistics
Normality of data was examined using the Shapiro-Wilk test, and P < .05 was considered significant. The F-test was employed to ascertain whether the compared datasets exhibited equal variances. The intraclass correlation coefficient and its 95% CI were calculated to assess inter- and intrarater reliability. Continuous variables were compared using the 2-tailed t test or the Mann-Whitney U test as appropriate. Analysis of covariance or its nonparametric equivalent was used to determine the effect of covariates. For categorical data with 2 categories, statistical significance was analyzed using the χ2 test or the Fisher exact test. Correlation analyses were performed using the Pearson method or its nonparametric equivalent. Receiver operating characteristic (ROC) curve analysis was used to determine optimal cutoff values. As adhesion length is a continuous variable, patients were divided into 3 groups based on the means plus or minus one-half standard deviation of the postoperative adhesion length. All calculations were conducted using SPSS software Version 29.0 (IBM Corp). Sample size calculations were based on a similar previous radiology study involving a total of 34 patients. 11
Results
Patient Characteristics
As shown in Figure 1, of the 239 patients with FAIS who underwent arthroscopic hip surgery during the study period, 65 (67 hips) met the criteria and were included in the analysis: 29 hips were allocated to the symptomatic group and 38 to the asymptomatic group. A total of 29 hips were in men and 38 in women. The mean patient age was 44.39 years, and the mean follow-up was 56 months. Characteristics of the hips according to group are shown in Table 1. Body mass index, follow-up duration, affected side, alpha angle, lateral center edge angle, FAI type, Tonnis grade, number of anchors, arthroscopic procedures, and preoperative PROs did not significantly differ between the groups; however, the proportion of male hips was significantly higher in the symptomatic group (P = .027). Figure 2 shows examples of hips with and without postoperative adhesions as visualized on MRI.
Study flowchart. FAIS, femoroacetabular impingement syndrome.
Characteristics of the Analyzed Hips According to Group a
Data are presented as mean ± SD or n (%). The bold P value indicates statistical significance (P < .05). BMI, body mass index; FAI, femoroacetabular impingement; HOS-ADL, Hip Outcome Score-Activity of Daily Living Scale; HOS-SSS, Hip Outcome Score-Sport Specific Subscale; LCEA, lateral central edge angle; mHHS, modified Harris Hip Score; Postop, postoperative; PROs, patient-reported outcomes; UCLA, University of California at Los Angeles; VAS, visual analog scale.
Fat-suppressed turbo spin-echo proton density-weighted imaging of the hip in the oblique sagittal (A and B) and oblique coronal planes (C and D). (A) The paralabral sulcus is absent, indicating an anterior capsule-labrum adhesion (red arrow).
Postoperative Evaluation and Clinical Outcomes
Postoperative MRI data showed that 61 hips (91.04%) exhibited adhesions with a mean length of 17.97 ± 10.59 mm. The intraclass correlation values for inter- and intrarater reliability were 0.909 (95% CI, 0.857-0.943) and 0.912 (95% CI, 0.861-0.945), respectively. These results indicated substantial agreement.
The proportion of patients who developed postoperative adhesions was high in both the asymptomatic and symptomatic groups (86.8% and 96.6%, respectively; P = .168). However, the adhesion length was significantly higher in the symptomatic group (21.66 ± 10.52 mm vs 15.16 ± 9.88 mm; P = .012). The majority of postoperative PROs were significantly lower in the symptomatic group. However, MRI findings, physical examination findings, and other indicators did not differ significantly between the groups (Table 2).
Clinical Outcomes in the Asymptomatic and Symptomatic Groups a
Data are presented as mean ± SD or n (%). Bold P values indicate statistical significance (P < .05). FABER, flexion-abduction-external rotation; FADIR, flexion-adduction-internal rotation; HOS-ADL, Hip Outcome Score-Activity of Daily Living Scale; HOS-SSS, Hip Outcome Score-Sport Specific Subscale; mHHS, modified Harris Hip Score; MRI, magnetic resonance imaging; Postop, postoperative; PROs, patient-reported outcomes; UCLA, University of California at Los Angeles; VAS, visual analog scale.
The hips were divided into 3 groups based on the length of capsule-labrum adhesion, using the following cutoffs: <13 mm (group 1), 13-23 mm (group 2), and >23 mm (group 3). Postoperative PROs did not differ notably between the groups with lengths of <13 mm and 13 to 23 mm. However, the mHHS, HOS-ADL, HOS-SSS, VAS for pain scores, and VAS for satisfaction scores were higher in the 2 groups with a length of ≤23 mm than in the group with a length of >23 mm (Table 3).
Patient-Reported Outcomes With Patients Grouped According to Degree of Postoperative Adhesions a
Data are presented as mean ± SD or n (%). Bold P values indicate statistical significance (P < .05). HOS-ADL, Hip Outcome Score-Activity of Daily Living Scale; HOS-SSS, Hip Outcome Score-Sport Specific Subscale; mHHS, modified Harris Hip Score; MCID, minimal clinically important difference; PASS, patient-acceptable symptom state; Postop, postoperative; PROs, patient-reported outcomes; UCLA, University of California at Los Angeles; VAS, visual analog scale.
Correlation Analysis
When exploring the effect of adhesion length on ROM, external rotation was found to be inversely proportional to adhesion length (ρ = −0.296; P = .016). However, no significant correlation was found for other ROM (Table 4).
Correlation Between Capsule-Labrum Adhesion Length and ROM a
The bold P value indicates statistical significance (P < .05). ROM, range of motion.
When evaluating potential factors that may influence the development of postoperative adhesions, patient age was negatively correlated with adhesion length (ρ = −.314; P = .010). No significant correlation was found for other potential influencing factors (Table 5).
Correlation Between Potential Influencing Factors and Extent of Capsule-Labrum Adhesions a
The bold P values indicate statistical significance (P < .05). BMI, body mass index; LCEA, lateral central edge angle.
ROC Analysis
To evaluate the efficacy of adhesion length in predicting persistent symptoms after hip arthroscopy, ROC analysis was performed using adhesion length as the continuous predictor variable and postoperative symptomatic status as the binary outcome variable. The optimal cutoff value for adhesion length was 27 mm, at which the Youden index reached its maximum, yielding a sensitivity of 0.379, specificity of 0.895, and an area under the curve of 0.661 (95% CI, 0.529-0.793; P = .017). This indicated that adhesion length had moderate diagnostic accuracy in distinguishing between symptomatic and asymptomatic patients (Figure 3).
ROC curve analysis. ROC, receiver operating characteristic.
Discussion
In this study, among patients undergoing hip arthroscopy with interportal capsulotomy without capsular repair for FAIS with LT, postoperative capsule-labrum adhesions were highly prevalent. The adhesion length was significantly higher in the symptomatic group than in the asymptomatic group. In addition, more extensive capsule-labrum adhesions were associated with poorer PROs. Furthermore, an inverse relationship was observed between external rotation and the length of adhesions. Additionally, age at surgery was found to be negatively correlated with the extent of adhesions.
Postoperative hip adhesions developed in 86.8% of asymptomatic hips and 96.6% of symptomatic hips. Kim et al 11 conducted a study using magnetic resonance arthrography (MRA) and found that the percentage of anterosuperior capsule-labrum adhesions was 82% in the symptomatic group and 94% in the asymptomatic group. Clearly, the rate of postoperative capsule-labrum adhesions is high after hip arthroscopy, as indicated by these 2 studies. Nonetheless, the extent of these adhesions varies considerably. Currently, there is a paucity of studies examining the range of adhesion. Our study highlighted the effect of adhesion length on persistent symptoms and postoperative outcomes, suggesting that patients with a wide range of capsule-labrum adhesions may be more likely to experience residual symptoms and exhibit worse postoperative PROs.
Previous studies have found that intra-articular adhesions may be related to postoperative pain, the need for revision surgery, and poor surgical outcomes.1,15,20,22,23 However, the precise mechanism by which adhesions are responsible for poor surgical outcomes or result in the persistence of symptoms remains uncertain. The labrum seals the hip joint and preserves negative pressure within the joint, fostering a suction effect.4,13 However, adhesions between the capsule and labrum can lead to pathological eversion of the labrum. This can disrupt the suction seal function of the labrum, 24 which in turn can lead to worse clinical outcomes.
Our study also revealed a negative correlation between the adhesion length and the external rotation angle. This finding may be related to adhesion location—most were located in the anterior-superior aspect of the joint, where the iliofemoral ligament is predominantly situated. This ligament is primarily responsible for limiting external rotation of the hip joint. 17 However, it is important to acknowledge that the correlation coefficients were relatively weak, which may be attributed to the fact that hip ROM can be influenced by numerous factors, including the flexibility of the surrounding muscles and fascia, as well as the thickness of the hip capsule. 27 In addition, we measured active ROM instead of passive ROM. Passive ROM is often used to reflect a joint's maximum ROM. Adhesions between the hip labrum and the capsule may only manifest as a functional impairment at the extremes of hip motion.
The cause of adhesions remains unclear. Willimon et al 26 reported that age <30 years is a risk factor for adhesion formation after hip arthroscopy, and that patients who did not receive circumduction therapy were 4.1 times more likely to have adhesions than those who did. In our study, patient age was negatively correlated with the extent of adhesions, which means that adhesions may be more extensive in younger patients. Ruzbarsky et al 21 proposed that joint capsule-labrum adhesion is mainly caused by the fresh wound after acetabuloplasty. In our study, 92.57% of patients underwent acetabuloplasty.
Hip circumduction exercises and continuous passive motion (CPM) are 2 physical interventions used to prevent adhesions.5,20 Both Willimon et al 26 and Menge et al 16 found reduced development of postoperative capsulolabral adhesions after implementation of a rehabilitation protocol that included early use of CPM and circumduction exercises. We did not use CPM in this study's rehabilitation protocol—patients were only required to complete specific passive ROM exercises with limited ROM during their early rehabilitation. Reducing postoperative hip labrum adhesions may require a greater amount of passive motion exercises in the early postoperative period. However, more research is needed.
Ruzbarsky et al 21 used a spacer autograft or allograft to prevent postoperative capsule-labrum adhesions in 53 patients (56 hips) undergoing revision surgery. Six hips underwent another revision surgery at a mean of 2.4 years, of which 5 still exhibited adhesions at the time of reoperation; 4 hips underwent total hip arthroplasty. For the hips that did not require another operation, there was a significant improvement in postoperative PROs. Although most patients showed improvement after revision surgery using a spacer, postoperative adhesions remained inevitable. The mechanisms underlying the improved efficacy associated with spacer use are not clear.
Limitations
This study has several limitations. First, we used MRI rather than MRA to assess joint adhesion. MRA might have offered greater precision in determining the presence of adhesions, as contrast agents could potentially separate some capsular-labral structures that were otherwise adherent, whereas MRI might have misinterpreted such adherences as adhesions. However, we used a 3T scanner and imaged joints using 2-mm slices, which provided us with high-resolution images. Second, the study was retrospective; thus, selection bias was almost certainly present. Third, the sample size was relatively small, resulting in low statistical power. Finally, capsulotomy was not performed in any patient, which may have influenced postoperative outcomes.
Conclusion
Postoperative capsule-labrum adhesions were highly prevalent among patients treated with hip arthroscopy under interportal capsulotomy without capsular repair for FAIS with LT. In this cohort, more extensive capsule-labrum adhesions were associated with persistent symptoms and worse PROs.
Footnotes
Final revision submitted June 12, 2025; accepted July 16, 2025.
One or more of the authors has declared the following potential conflict of interest or source of funding: This work was supported by a grant awarded to Hong-Yun Li from the National Key Research and Development Program of China (2023YFC2410705). AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
Ethical approval for this study was obtained from Huashan Hospital.