Arthroscopic Hip Capsular Repair Improves Patient-Reported Outcome Measures and Is Associated With a Decreased Risk of Revision Surgery and Conversion to Total Hip Arthroplasty

Purpose To perform a systematic review to assess the effect of capsular repair compared with nonrepair on patient-reported outcome measures (PROMs) and conversion to total hip arthroplasty (THA) after hip arthroscopy in patients with femoroacetabular impingement syndrome. Methods We initially searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and PubMed databases, as well as ongoing clinical trials (https://clinicaltrials.gov), on December 15, 2022. The eligibility criteria were randomized controlled trials (Level Ⅰ) and prospective comparative studies (Level II) of patients who underwent capsular repair and nonrepair via hip arthroscopy with a minimum follow-up period of 2 years. We registered this protocol a priori on PROSPERO (identification No. CRD42021239306). We assessed the risk of bias using the Methodological Index for Non-randomized Studies (MINORS) appraisal tool. Results This review included 5 studies with a total of 639 patients (270 with capsular repair [average age, 35.4 years; 41% female patients] and 369 with nonrepair [average age, 37.3 years; 38% female patients]). In the included studies, surgical procedures consisting of labral repair and pincer or cam osteoplasty were performed via hip arthroscopy. The modified Harris Hip Score was measured in all the included studies, and the standardized mean difference in PROMs for capsular repair versus nonrepair in the included studies was 0.42 (95% confidence interval [CI], 0.20 to 0.63). A sensitivity analysis of randomized controlled trials achieved consistent results (standardized mean difference in PROMs, 0.31; 95% CI, 0.02 to 0.60). Capsular repair was not associated with a reduction in revision surgery (risk difference, –0.02; 95% CI, –0.06 to 0.03; 26 of 270 patients with capsular repair vs 42 of 369 with nonrepair) but was associated with a reduction in conversion to THA (risk difference, –0.05; 95% CI –0.09 to –0.01; 12 of 270 patients with capsular repair vs 38 of 369 with nonrepair). The average Methodological Index for Non-randomized Studies (MINORS) score in the included studies was 20. Conclusions Patients who undergo capsular repair in conjunction with other arthroscopic hip preservation techniques have better PROMs and a lower incidence of THA conversion. Level of Evidence Level II, systematic review of Level I and II investigations.

38 of 369 with nonrepair).The average Methodological Index for Non-randomized Studies (MINORS) score in the included studies was 20.Conclusions: Patients who undergo capsular repair in conjunction with other arthroscopic hip preservation techniques have better PROMs and a lower incidence of THA conversion.Level of Evidence: Level II, systematic review of Level I and II investigations.
H ip arthroscopy is a minimally invasive surgical procedure performed to treat intra-articular hip disorders, such as femoroacetabular impingement syndrome (FAIS), and extra-articular pathologies. 1 The vast majority of hip arthroscopists prefer capsulotomy or capsular release to improve visualization and instrument accessibility; however, it is unclear how large the capsular repair should be to be beneficial during hip arthroscopy.The hip capsular ligaments reinforce the stability of the hip 2 ; however, release of these ligaments can facilitate arthroscopic management to treat intraarticular pathologies.A biomechanical study has shown that capsular repair reinforces hip instability. 3revious systematic reviews have shown the benefit of capsular closure in hip arthroscopy [3][4][5][6][7][8][9][10][11][12][13][14] (Appendix Table 1).However, it is inconclusive how much capsular closure with hip arthroscopy has an impact on patient-reported outcome measures (PROMs) among high-level studies (Levels I and II).The complete PICO (Population, Intervention, Comparison, and Outcome)e format research question is shown in Appendix 1.This study aimed to perform a systematic review to assess the effect of capsular repair compared with nonrepair on PROMs and conversion to total hip arthroplasty (THA) after hip arthroscopy in patients with FAIS.We hypothesized that capsular repair would significantly improve PROMs and decrease postoperative complications (e.g., incidence of revision surgery and conversion to THA) compared with capsular nonrepair in hip arthroscopy.

Comprehensive Literature Search
We registered this protocol a priori on PROSPERO (identification No. CRD42021239306) in April 2021.In April 2021 and again in December 2022, we conducted a comprehensive literature search for all relevant articles using 4 electronic databases: Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library, 2022), MEDLINE (1946 to December 15,  2022), EMBASE (1974 to December 15, 2022) and PubMed (1990 to December 15, 2022).The PubMed search was limited to the period after 1989 because hip arthroscopy has only been widely adopted since the 1990s. 15We also examined ongoing trials using a database of clinical trials (https://clinicaltrials.gov).
Each search strategy is shown in Appendix 2. In the manual search, we screened the reference lists of previous meta-analyses and relevant studies for additional articles not identified through the electronic search.We chose the following key search terms: (Hip*) AND (arthroscopy OR arthroscopic OR arthroscop*) AND (capsule OR capsular OR capsul*).
We adopted a 3-step screening process (title screening, abstract screening, and full-text screening) to select eligible articles.After the duplicate articles were removed, 2 board-certified orthopaedic surgeons (K.Kizaki and Y.M.) independently performed the title and abstract screenings.If either reviewer included an article during title or abstract screening, the article was moved to the next stage for screening.During the fulltext screening, discrepancies were resolved through discussion and consensus with the senior author (S.U.).For each study, 2 reviewers (K.Kizaki and Y.M.) independently extracted the following data: article type, journal, authors, publication year, country, study design, number of patients, number of female patients, age, follow-up period, PROMs, surgery time, and complications.

Criteria for Study Inclusion
In this review, we included studies that compared capsular repair and nonrepair in hip arthroscopy.Capsular repair was considered present when complete capsular repair was performed using any surgical procedure.Studies were not excluded based on patient age or disease resulting in a surgical indication.The eligibility criteria were as follows: Level I and II studies comparing capsular repair versus nonrepair, patients treated with hip arthroscopic surgery for conditions including FAIS, and studies presenting at least 1 primary outcome (i.e., PROM) (Appendix Table 2).The exclusion criteria were cadaveric studies, patients with hip dysplasia, noncomparative studies, studies with no description of capsular procedures, studies including the same cohort as another study (studies including more patients were prioritized), and studies with less than 2 years of follow-up data.
The primary outcome was PROMs (e.g., modified Harris Hip Score [mHHS] and Hip Outcome Score).The secondary outcome was complications such as surgicalsite infection, symptomatic deep vein thrombosis, or pulmonary embolism; revision surgery; and conversion to THA.

Risk-of-Bias Assessment
Two epidemiologists with expertise in systematic reviews (K.Kizaki and M.A.) independently evaluated the risk of bias using the Methodological Index for Nonrandomized Studies (MINORS) appraisal tool. 16

Synthesis of Results
Dichotomous outcomes (i.e., complications) were expressed as risk differences with 95% confidence intervals (CIs).Continuous outcomes (i.e., PROMs) were expressed as mean differences between the capsular repair and nonrepair groups.We preferred to calculate effect size measures (standardized mean difference [SMD]) when studies used different instruments to assess the primary outcome (i.e., PROMs).When multiple measurement scales were used in a study, we adopted the most commonly used measurement scale in the included studies in a quantitative data synthesis (meta-analysis).
We analyzed outcomes according to the modified intention-to-treat method without imputation.When data were not expressed as mean and standard deviation but were expressed as median, minimummaximum range, or interquartile range, we estimated the mean and standard deviation in accordance with Wan et al. 17 We pooled the included studies using the generic inverse variance method for continuous outcomes and the Mantel-Haenszel method for dichotomous outcomes in Review Manager (RevMan 5, The Nordic Cochrane Centre, Copenhagen, Denmark).Either a fixed-effect or random-effect model was used depending on heterogeneity.The heterogeneity among pooled studies was assessed using the c 2 test, with the level of statistical significance set at P < .10,and the I 2 statistic.The I 2 value was assessed as follows: 0% to 40%, not important; 30% to 60%, moderate; 50% to 90%, substantial; and 75% to 100%, considerable. 18In addition, we considered the variance in the point estimate and overlap in the CIs.We prespecified and conducted sensitivity analyses based on the PROMs of randomized controlled trials (RCTs).We also prespecified and performed subgroup analysis according to the 2 most common capsular repair techniques.For the primary outcome measures (PROMs), we evaluated the degree of the effect size in reference to Cohen et al., 5 with an SMD of 0.2 to 0.5 defined as small; 0.5 to 0.8, medium; and greater than 0.8, large.

Results of Search
We screened a total of 2,048 articles (MEDLINE, 582; EMBASE, 902; PubMed, 517; and CENTRAL, 47).After the removal of duplicates, we screened the titles of 1,458 articles and the abstracts of 487 articles.We identified 5 articles from the reference lists of previous meta-analyses and implemented a full-text screening process.As shown in Appendix Table 2, we also performed critical appraisal of the previous systematic reviews answering the following clinical question: Does capsular repair yield preferable outcomes compared with capsule nonrepair in hip arthroscopy?From the database of clinical trials, we found 4 studies in progress; however, the results were not presented.The ongoing trials are shown in Appendix Table 3.
0][21][22][23] Details regarding the screening process are illustrated in the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) flowchart 24 in Figure 1.

Included and Excluded Studies
We ultimately included 5 studies with a total of 639 patients (270 in capsular repair group and 369 in nonrepair group) (Appendix Fig 1).6][27][28] Details of the included studies are provided in Table 1.The most common surgical indication in the included studies was FAIS resistant to conservative treatment.In the included studies, the surgical indications were no advanced arthritis (Tönnis grade 0 or 1) with younger age (average, 36.5 years).Postoperative clinical outcomes in each study are presented in Appendix Table 2.

Risk of Bias in Included Studies
In the included studies, the mean MINORS score was 20.MINORS scores are presented in Appendix Table 4.All of the included studies followed up the patients for 2 years or more.

Patient-Reported Outcome Measures
The most common PROM was the mHHS (5 studies), followed by the Hip Outcome ScoreeActivities of Daily Living (HOS-ADL) scale (4 studies).On qualitative synthesis, the study of Ashberg et al. 19 showed the superiority of capsular repair according to PROMs (Appendix Table 2).In the meta-analysis of studies reporting at least 1 PROM, the SMD (0.42; 95% CI, 0.20 to 0.63) indicated that capsular repair yielded favorable PROMs compared with nonrepair in hip arthroscopy, as shown in Figure 2. When we limited the analysis to RCTs, 2 studies were included, 21,22 and the SMD was again significant (0.31; 95% CI, 0.02 to 0.60) 5 (Fig 3).The mean difference in the mHHS showed the superiority of capsular repair over nonrepair in hip arthroscopy (mean difference, 4.64; 95% CI, 1.14 to 8.14) (Fig 4).

Subgroup Analysis of PROMs Between Interportal and T-Shaped Capsulotomy
We prepared a subgroup analysis based on the surgical techniques of capsulotomy a priori (i.e., T-   shaped capsulotomy vs interportal capsulotomy); however, there was no pooled study on T-shaped capsulotomy.Therefore, we did not perform subgroup analysis of PROMs between interportal and T-shaped capsulotomy.

Complications
The most frequently monitored complication was the number of revision surgical procedures and conversions to THA.Regarding revision surgery, 5 studies with 639 patients were included.The incidence of revision surgery was not associated with capsular repair in hip arthroscopy (risk difference, e0.02; 95% CI, e0.06 to 0.03; 26 of 270 patients with capsular repair vs 42 of 369 with nonrepair), as shown in Figure 5. Regarding conversion to THA, 5 studies with 639 patients were included with surgical indication (nonarthritis; Tönnis grade 0 or 1).The incidence of conversion to THA was significantly associated with capsular repair (pooled mean follow-up, 47.3 months) when compared with nonrepair (pooled mean follow-up, 47.8 months) (risk difference e0.05; 95% CI, e0.09 to e0.01; 12 of 270 patients with capsular repair vs 38 of 369 with nonrepair), as shown in Figure 6.In the pooled populations, no severe complications such as symptomatic deep venous thrombosis, pulmonary embolism, or deep surgical-site infection were reported. 29

Discussion
The most important finding of this study was that capsular repair in hip arthroscopy was statistically significantly superior to nonrepair in terms of PROMs, a finding that was maintained when the analysis was limited to RCTs; however, the effect size was small.The incidence of revision surgery was not higher with nonrepair than with capsular repair during hip arthroscopy, but the incidence of conversion to THA was lower with capsular repair.0][11] In our comprehensive search, we covered all the comparative studies included in the previous meta-analyses.
Riff et al. 13 found that interportal capsulotomy and Tshaped capsulotomy are the most common techniques for capsular repair.Various types of suture techniques for capsular repair have recently been introduced. 30,31o identify the superiority of interportal versus T-shaped capsulotomy, we prepared a subgroup analysis; however, because there was no pooled study on Tshaped capsulotomy, this analysis was not completed.Recently, arthroscopic capsular reconstruction has been developed. 32Further studies are required to evaluate clinical differences between interportal capsulotomy, Tshaped capsulotomy, and capsular reconstruction. 33apsular repair is rational in the stabilization of hip joints.Our meta-analysis showed the positive impact on PROMs and the association with a reduction in the incidence of conversion to THA; these results support the practical application of capsular repair in hip arthroscopy.Hip arthroscopy is associated with small risks of symptomatic deep venous thrombosis (0.09%) and deep surgical-site infection (0.02%) 34 ; therefore, severe complications were not present in the pooled populations.
The most noteworthy strength of our review is its robust methodology: This review's protocol was registered on PROSPERO prior to searching and data collection.This review followed the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions.Two board-certified orthopaedic surgeons specializing in hip surgery and arthroscopy conducted the searches, and 2 epidemiologists with educational backgrounds in health research methodologies performed the data synthesis (meta-analysis) and evidence assessment according to the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach.Another strength is the generalizability to the target population treated with hip arthroscopy.In the pooled analysis, the most common surgical indication was FAIS resistant to conservative treatment, which is the main surgical indication for hip arthroscopy.

Limitations
Several limitations are present in this review.First, our review only included 2 RCTs.RCTs are the gold-standard study design because this design prevents selection bias.Second, we encountered limitations in accessing the gray literature.To ensure a broad search, we completed searches in 4 databases and 1 online clinical trials platform, but a residual risk of reporting bias may be present.Third, the surgical procedure of capsular repair has potential risk of performance bias: therefore, capsular repair may be a surrogate procedure with skillful procedures.Fourth, capsular nonrepair is applicable in several situations.In cases with hip joint stiffness, capsular release may be intentionally selected to avoid postoperative stiffness.Therefore, whether capsular repair versus nonrepair should be performed in hip arthroscopy may not be a simple issue; rather, it depends on each case.Finally, this systematic review has revised and modified the original search methodology, which may have influenced our results.

Conclusions
Patients who undergo capsular repair in conjunction with other arthroscopic hip preservation techniques have better PROMs and a lower incidence of THA conversion.

Fig 1 .
Fig 1. PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) flowchart.(CENTRAL, Cochrane Central Register of Controlled Trials; PROMs, patient-reported outcome measures.)

Fig 2 .Fig 3 .
Fig 2. Standardized (Std) mean differences in patient-reported outcome measures for capsular repair versus nonrepair in hip arthroscopy among Level I and II studies.(CI, confidence interval; IV, inverse variance; SD, standard deviation.)

Fig 4 .Fig 5 .
Fig 4. Mean differences in modified Harris Hip Score for capsular repair versus nonrepair in hip arthroscopy among Level I and II studies.(CI, confidence interval; IV, inverse variance; SD, standard deviation.)

Table 1 .
Characteristics of Included Studies