Mechanistic regulation of planarian shape during growth and degrowth.

Adult planarians can grow when fed and degrow (shrink) when starved while maintaining their whole-body shape. It is unknown how the morphogens patterning the planarian axes are coordinated during feeding and starvation or how they modulate the necessary differential tissue growth or degrowth. Here, we investigate the dynamics of planarian shape together with a theoretical study of the mechanisms regulating whole-body proportions and shape. We found that the planarian body proportions scale isometrically following similar linear rates during growth and degrowth, but that fed worms are significantly wider than starved worms. By combining a descriptive model of planarian shape and size with a mechanistic model of anterior-posterior and medio-lateral signaling calibrated with a novel parameter optimization methodology, we theoretically demonstrate that the feedback loop between these positional information signals and the shape they control can regulate the planarian whole-body shape during growth. Furthermore, the computational model produced the correct shape and size dynamics during degrowth as a result of a predicted increase in apoptosis rate and pole signal during starvation. These results offer mechanistic insights into the dynamic regulation of whole-body morphologies.

Editorial Commentary: Older Patients Without Degenerative Joint Disease Can Have Excellent Outcomes After Hip Arthroscopy.

Early research on hip arthroscopy for femoroacetabular impingement syndrome identified patient age as a risk factor for poor outcomes and heightened revision rates. However, more recent research challenges this dogma. Disparities between chronologic and physiologic age exist among patients. In addition, orthopaedic pathology (such as degenerative chondral or labral pathology) can correlate with age, so the use of age, and using age as a predictor of outcome, may be biased by this confounding effect. Older patients without degenerative joint disease can have excellent outcomes after hip arthroscopy. Recent research shows that patients older than the age of 40 years undergoing hip arthroscopy for femoroacetabular impingement syndrome demonstrate outcomes comparable with younger patients at 10-year follow-up. However, older patients were at greater risk for conversion to total hip arthroplasty. In our experience, in the absence of joint degeneration, patients older than the age of 40 years experience predictable and durable relief following arthroscopic management of femoroacetabular impingement syndrome. These outcomes result from sound surgical indications, appropriate preoperative counseling, and meticulous surgical technique. We ought not replace joints we can preserve, and age is not the most determinative factor regarding outcome of otherwise well-indicated and performed hip arthroscopy.

Secondary Hip Labral Reconstruction Yields Inferior Minimum 2-Year Functional Outcomes to Primary Reconstruction Despite Comparable Intraoperative Labral Characteristics.

PURPOSE: To compare intraoperative labral characteristics and minimum 2-year functional outcomes of allograft labral reconstruction in primary versus revision hip arthroscopy across multiple orthopaedic centers. METHODS: A retrospective multicenter hip arthroscopy registry was queried for patients with completed labral reconstruction surgeries from January 2014 to March 2023 with completed 2-year international Hip Outcome Tool-12 (iHOT-12) reports. Age, sex, and major intraoperative variables also were collected. Patients were placed in cohorts based on whether their arthroscopic allograft labral reconstruction was a primary procedure or secondary procedure (reconstruction following failed hip arthroscopy). One-way analysis of variance was performed on continuous variables. χ2 test was performed on categorical variables. Achievement of minimal clinically important difference (MCID), Patient Acceptable Symptom State (PASS), and Substantial Clinical Benefit (SCB) also was assessed. RESULTS: In total, 77 patients met the inclusion and exclusion criteria and had complete information. The primary reconstruction group (n = 50) was significantly older than the secondary reconstruction group (n = 27) (47.5 ± 10.5 vs 39.1 ± 8.8 years; P = .001). In both cohorts, most patients had labral bruising, advanced labral degeneration, and/or grade III complexity of labral tearing. There was no difference in any recorded intraoperative findings (P = .160, P = .783, P = .357, respectively). Each cohort experienced significant improvement in iHOT-12 scores (P < .0001). However, patients undergoing secondary labral reconstruction reported inferior iHOT-12 scores (60.1 ± 29.2 vs 74.8 ± 27.0; P = .030). Patients undergoing primary reconstruction were more likely to reach MCID, PASS, and nearly normal SCB (92 vs 66.7%, P = .024; 68.0 vs 40.7%, P = .021; 76.0 vs 48.1%, P = .014, respectively). CONCLUSIONS: Primary and secondary allograft labral reconstruction show clinical improvement, but primary reconstruction demonstrates better outcomes and greater percentage of patients reaching MCID, PASS, and nearly normal SCB than reconstruction in the revision setting. LEVEL OF EVIDENCE: Level III, retrospective comparative prognostic case-control study.

Editorial Commentary: The Importance of Capsular Closure Following Hip Arthroscopy-Leave No Trace: An Outdoorsman's Ramblings.

After a decade-long paradigm shift and an evidence-based enormous increase in the prevalence of hip arthroscopic procedures, hip capsular closure following arthroscopy, once a rare procedure, is now performed in the majority of surgical cases. This results from improved surgeon experience, refined surgical technologies and techniques and an explosion of research regarding stability of the hip joint. Once viewed as inherently stable, it is become clear that meticulous capsular management and closure can not only maintain joint stability but is a treatment for and/or prevents micro-instability. Recent research shows that hip capsular closure can improve outcomes and return to sport rates in the highest demand athletes having hip arthroscopy. Close the capsule!

Labral Degeneration Predicts Inferior Mid-Term Outcomes in Hip Labral Repair: A Multicenter Comparative Analysis.

PURPOSE: To analyze and compare the mid-term outcomes of hip arthroscopy for patients with and without labral degeneration from multiple orthopaedic centers. The purpose of this research is to develop an understanding of the impacts of labral degeneration on patient outcomes following arthroscopic treatment of labral tears. METHODS: A prospective multicenter hip arthroscopy registry was queried for primary surgeries from January 2014 to October 2017 with completed 2-year International Hip Outcome Tool-12 (iHOT-12) reports. Patients were placed into cohorts based on the presence or absence of labral degeneration noted intraoperatively during hip arthroscopy. Degeneration was defined as yellowing, ossification, or calcification present in at least 50% of the labrum. Differences in baseline variation between groups were assessed with a Wilcoxon rank-sum test or χ2 test. Two-year outcomes were assessed with iHOT-12. Multivariate logistic regression models were fitted while controlling for age, body mass index, sex, and preoperative iHOT-12 scores to identify significant predictors of achieving the clinically significant thresholds of minimal clinically important difference, substantial clinical benefit, and patient-acceptable symptom scale. RESULTS: In total, 735 patients met inclusion criteria, of whom 613 had complete outcomes information. Relative to the control group, the labral degeneration group was significantly older (mean age 44 ± 11 years vs 33 ± 12 years; P < .01). Both groups experienced statistically significant improvement in iHOT-12 scores from baseline to final follow-up (P < .001); however, patients with labral degeneration reported inferior 2-year iHOT-12 scores when compared with patients without degeneration (P < .001). In the logistic regression models, labral degeneration was a significant negative predictor of achieving iHOT-12 minimal clinically important difference (odds ratio [OR] 0.47; 95% confidence interval [95% CI] 0.28-0.79), patient acceptable symptom state (OR 0.50; 95 CI 0.32-0.77), and substantial clinical benefit (OR 0.58; 95% CI 0.37-0.89). CONCLUSIONS: The results of our study conclude that patients with nondegenerative labral tissue at the time of repair have superior patient-reported outcomes at mid-term follow-up. The presence of labral degeneration was a negative predictor of achieving clinically significant thresholds after controlling for patient age, body mass index, sex, and baseline iHOT-12 scores. LEVEL OF EVIDENCE: III, retrospective comparative prognostic trial.

Acetabular Cartilage Lesions Predict Inferior Mid-Term Outcomes for Arthroscopic Labral Repair and Treatment of Femoroacetabular Impingement Syndrome.

PURPOSE: To analyze the effect of acetabular chondrosis at a minimum of 2 years following hip arthroscopy in patients undergoing labral repair and treatment of femoroacetabular impingement. METHODS: From 2014 to 2017, patients undergoing arthroscopic labral repair were prospectively enrolled in a multicenter hip arthroscopy registry. The registry was retrospectively queried for primary labral repair patients with complete 2-year outcomes and a Tonnis grade of less than 2. Patients were grouped according to severity of articular cartilage damage noted intraoperatively using the Beck classification system: none, low-grade (Grade 1 or 2), or high-grade (Grade 3 or 4) damage. A Kruskal-Wallis test and post hoc Dunn's test with Holm correction compared 2-year postoperative outcome scores of the iHOT-12 scale between groups. The proportion of patients in each cohort who achieved the clinically significant thresholds of the minimum clinically important difference (MCID), patient-acceptable symptom scale, and substantial clinical benefit (SCB) were analyzed. Multivariate logistic regression models identified predictors of achieving clinical thresholds while controlling for demographic variation. RESULTS: 422 patients met inclusion criteria, from which 347 completed 2-year outcomes. All groups experienced improvement in iHOT-12 scores from baseline to follow-up (P < .001). iHOT-12 scores at follow-up were inferior for Low-Grade Damage and High-Grade Damage Groups relative to the No Damage Group (P = .04; P = .03). When accounting for age, body mass index, gender, and preoperative iHOT-12 scores in logistic regression models, the presence of high-grade lesions was a negative predictor for achieving SCB (OR [95% CI], 0.54 [0.29-0.96]) and low-grade lesions a negative predictor for achieving MCID (0.50 [0.27-0.92]. Among patients with high-grade lesions, there was no significant difference in 2-year iHOT-12 scores between those undergoing chondroplasty (n = 50) and those undergoing microfracture (n = 14) (P = .14). CONCLUSIONS: Acetabular cartilage damage portends inferior patient-reported outcomes 2 years after primary labral repair and treatment of femoroacetabular impingement. The presence of cartilage lesions was a negative predictor of individual achievement of several clinical thresholds. LEVEL OF EVIDENCE: III, Retrospective comparative cohort.

Multicenter Outcomes After Primary Hip Arthroscopy: A Comparative Analysis of Two-Year Outcomes After Labral Repair, Segmental Labral Reconstruction, or Circumferential Labral Reconstruction.

PURPOSE: (1) To report minimum 2-year follow-up patient-reported outcome measures in patients undergoing labral repair (LR), segmental labral reconstruction (SLR), or circumferential labral reconstruction (CLR) in the primary setting; and (2) to compare minimum 2-year follow-up patient-reported outcome measures among these groups. METHODS: A retrospective review of a prospectively maintained multicenter database of patients undergoing hip arthroscopy was performed. Inclusion criteria were patients undergoing hip arthroscopy for treatment of labral tear and femoroacetabular impingement syndrome between January 2014 and October 2017, and completion of minimum 2-year postoperative outcome scores. Exclusion criteria were patients undergoing revision hip surgery, labral treatment limited to debridement, lateral center-edge angle <20°, osteoarthritis (Tönnis grade > 1), slipped capital femoral epiphysis, workers compensation status, and patients undergoing concomitant gluteus medius and/or minimus repair. Labral reconstruction patients were matched (1:3) with labral repair patients on age, sex, and body mass index. The labral reconstruction group was further stratified into SLR, and CLR groups. Patient demographic characteristics and clinical outcomes including Hip Outcome Score - Activities of Daily Living, Hip Outcome Score - Sport Subscale, modified Harris Hip Score, international Hip Outcome Tool, and visual analog scale for pain were analyzed, as well as achievement of the minimal clinical improvement difference (MCID). A P-value less than .05 indicated statistical significance. RESULTS: A total of 416 patients were included (LR, n = 312; SLR, n = 53; CLR, n = 51). The age, body mass index, and sex of the matched cohort were 42.3 ± 11.2 years, 24.7 ± 3.7, and 55.0% female. At a minimum of 2-year after hip arthroscopic surgery, no differences were found in preoperative, postoperative, or the delta visual analog scale for pain, modified Harris Hip Score, Hip Outcome Score - Activities of Daily Living, Hip Outcome Score - Sport Subscale, or international Hip Outcome Tool. Subsequently, the proportion of patients achieving the MCID and the PASS at latest follow-up were analyzed. This analysis revealed that no significant differences in the rate of MCID or PASS achievement for any outcome measure existed based on labral treatment. CONCLUSIONS: In this multicenter study on labral treatment in the primary setting, patients undergoing LR, SLR, and CLR demonstrated no difference in preoperative or postoperative scores, nor the proportion of patients achieving clinically significant outcome improvement. LEVEL OF EVIDENCE: III; therapeutic outcome study with controls.

Symptom duration predicts inferior mid-term outcomes following hip arthroscopy.

INTRODUCTION: Studies have demonstrated a negative relationship between the length of time with symptoms and patient-reported outcome measures in primary hip arthroscopy. Our aim was to expand the generalizability of this finding with a multi-center cohort. METHODS: A multi-center hip arthroscopy registry was queried for patients undergoing primary hip arthroscopy from 2014 to 2017. Patients were stratified according to whether pre-operative symptom duration exceeded two years or did not exceed two years. A Wilcoxon rank sum test was performed for differences in two year post-operative outcome scores. Logistic regression models analyzed the influence of symptom duration on achieving clinically meaningful thresholds (minimum clinically important difference, patient-acceptable symptom state, substantial clinical benefit) when controlling for baseline scores, age, BMI, and sex. RESULTS: Seven hundred forty-four patients met the inclusion criteria, from which 620 had complete outcomes information. The mean ± SD 2-year iHOT-12 scores of patients with symptom duration greater than two years (69 ± 26) were significantly lower than patients with symptom duration less than two years (77 ± 23) (Dunn test, p < 0.001). Chronic duration of pain was a negative predictor of achieving iHOT-12 MCID (0.47 [0.31-0.72]), PASS (0.53 [0.37-0.76]), and SCB (0.67 [0.47-0.94]). CONCLUSION: When controlling for differences in baseline demographic factors and pre-operative iHOT-12 scores, patients with chronic pain report poorer functional outcomes at mid-term follow-up. These results suggest that chronic pain predicts inferior outcomes from primary hip arthroscopy and that surgical intervention at earlier time points may be beneficial in achieving better outcomes.

Tenotomy for Iliopsoas Pathology is Infrequently Performed and Associated with Poorer Outcomes in Hips Undergoing Arthroscopy for Femoroacetabular Impingement.

PURPOSE: The purpose of this article was to report prevalence of iliopsoas pathology in patients undergoing hip arthroscopy for femoroacetabular impingement (FAI), incidence of rendered tenotomy, and outcomes of hips with iliopsoas involvement compared with those with primary FAI. METHODS: A cohort study from a hip arthroscopy study group using a prospectively-collected multicenter database was performed. Patients who underwent isolated hip arthroscopy for FAI from January 2016 to March 2017 were assigned to the Iliopsoas group (defined as preoperative diagnosis of coxa saltans internus, intraoperative anteroinferior labral bruising or tear, and preoperative positive psoas injection) or control group. The prevalence of iliopsoas pathology, radiographic and intraoperative findings, and rendered procedures between groups were compared. Mean 2-year (minimum 1.8 year) outcomes of iliopsoas groups with and without rendered tenotomy and a control group were compared. RESULTS: There were 1393 subjects, of which 92 (7%) comprised the iliopsoas study group with 1301 subjects control subjects. Sixteen subjects in the iliopsoas group received tenotomy (17% of iliopsoas group, 1% of all subjects), whereas 76 subjects (83% of iliopsoas group) with iliopsoas involvement did not. There was significant effect on postoperative International Hip Outcome Tool-12 (iHOT-12) scores based on iliopsoas involvement and treatment, F(2,1390) = 3.74, P = .02. Compared with the control group (M = 73, standard deviation [SD] = 24), the non-tenotomized iliopsoas group (M = 69, SD = 32) had similar postoperative scores (P = .46), whereas the tenotomized iliopsoas group (M = 57, SD = 28) averaged lower postoperative scores (P = .03). In the tenotomy group, 25% achieved the iHOT-12 substantial clinical benefit and patient acceptable symptomatic state value for normal function and 100% satisfaction, compared to 49% and 41% for the without tenotomy and control groups. CONCLUSIONS: Tenotomy in patients with iliopsoas pathology undergoing arthroscopic surgery for FAI is infrequently performed and is associated with poorer outcomes. Co-afflicted patients treated without tenotomy have similar successful outcomes to patients with primary FAI. Indiscriminate tenotomy for iliopsoas pathology in this setting should be cautiously considered. LEVEL OF EVIDENCE: Level III, cohort study.

Arthroscopic classification of intra-articular hip pathology demonstrates at best moderate interrater reliability.

PURPOSE: The purpose of this study was to report several novel classification systems for intra-articular lesions observed during hip arthroscopy, and to quantify the interrater reliability of both these novel systems and existing classifications of intra-articular lesions when tested by a group of high-volume hip arthroscopists. METHODS: Five hip arthroscopists deliberated over shortcomings in current classification systems and developed several novel grading systems with particular effort made to capture factors important to the treatment and outcomes of hip arthroscopy for labral injury. A video learning module describing the classifications was then developed from the video archive of surgeries performed by the senior author and reviewed by study participants. Following review of the module, a pilot study was completed using five randomly selected videos, after which participating surgeons met once more to discuss points of disagreement and to seek clarification. The final video collection for testing reliability was composed of 29 videos selected with the intent of capturing all sublevels of each classification scheme. Study participants recorded their assessments using each classification scheme, and interrater reliability was calculated by a study participant not involved in grading. RESULTS: The average kappa coefficients for the classification schemes ranged from 0.38 to 0.54, with the interrater reliability of all classification schemes except labral degeneration qualifying as moderate. The percent of cases with absolute agreement ranged from 17.2% to 51.7% across the classification systems. CONCLUSIONS: Even among a group of high-volume hip arthroscopists who engaged in several discussions about the proposed classification schemes, grades were found to have at best moderate interrater reliability. Moderate interrater reliability is demonstrated for novel grading systems for describing labral tear complexity, labral bruising, labral size, and extent of synovitis, and fair reliability is demonstrated for labral degeneration. Further development and refinement of multifactorial grading systems for describing labral injury are indicated. Evaluating the multifactorial nature of intra-articular lesions in the hip is an important part of intraoperative decision-making and defining reliable classifications for intra-articular lesions is a critical first step towards developing generalizable criteria for guiding treatment type. LEVEL OF EVIDENCE: Level III.

Primary and Revision Circumferential Labral Reconstruction for Femoroacetabular Impingement in Athletes: Return to Sport and Technique.

PURPOSE: To determine return-to-play rates and hip-specific outcomes in athlete hips with femoroacetabular impingement syndrome treated with circumferential labral reconstruction (CLR). METHODS: All consecutive patients who underwent CLR from January through December 2016 performed by the senior surgeon with complete 2-year outcome scores were identified. The hips of 57 non-athletes who underwent CLR were excluded from analysis, as were 165 patients who underwent labral repair and 4 patients who underwent labral debridement. Outcome measures were completed by patients within 1 week prior to surgery and between 22 and 26 months postoperatively. Thirty patients met the inclusion criteria for this study. All 30 participated in regular, competitive athletic events and had magnetic resonance arthrogram-confirmed labral tears, and nonsurgical measures had failed. Of the 30 patients, 5 (16.7%) participated in cutting sports; 5 (16.7%), asymmetrical or overhead sports; 4 (13.3%), contact sports; 13 (43.3%), endurance sports; and 3 (10.0%), flexibility sports. Moreover, 25 of 30 (83.3%) were high-level athletes. Both primary (n = 23) and revision (n = 7) procedures were included. RESULTS: As determined by the International Hip Outcome Tool 12 score, 28 of 30 patients (93.3%) met the patient acceptable symptomatic state whereas 30 of 30 (100%) achieved substantial clinical benefit and exceeded the minimal clinically important difference for their operative hip. In addition, 23 of 30 patients (76.6%) met the patient acceptable symptomatic state whereas 30 of 30 (100%) achieved substantial clinical benefit and exceeded the minimal clinically important difference for the operative hip as determined by the visual analog scale pain score. Of 30 patients, 26 (86.7%) were able to return to play. The mean time to return to play was 6.6 months (standard deviation, 2.4 months). CONCLUSIONS: Two-year outcomes in this population of athletes undergoing CLR for femoroacetabular impingement syndrome show a statistically and clinically significant improvement in patient-reported outcomes, a statistically and clinically significant decrease in pain, and an overall return-to-play rate of 86.7%. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Unique Substantial Clinical Benefit Values for the 12-Item International Hip Outcome Tool Based on Preoperative Level of Function.

PURPOSE: To define unique substantial clinical benefit (SCB) values for improvement on the 12-item International Hip Outcome Tool (iHOT-12) based on a preoperative self-rating of function in patients undergoing hip arthroscopy for intra-articular pathology. METHODS: This was a retrospective review of prospective collected data on patients having hip arthroscopy for labral and chondral pathology and femoroacetabular impingement. On preoperative assessment and 1-year (+/-1 month) follow-up, subjects completed the iHOT-12 and a self-categorical rating of function ("severely abnormal," "abnormal," "nearly normal," or "normal"). Separate receiver operator characteristic analyses were performed for each preoperative categorical self-rating of function to determine unique SCB values for improvement-based changes in self-rating of function. RESULTS: Of 1034 eligible patients, 733 (71%) subjects met the inclusion criteria. Subjects consisted of 537 (73%) female and 196 (27%) male subjects with a mean age of 35.3 years (standard deviation 13). At a mean of 352 (standard deviation 21) days postsurgery, changes in iHOT-12 scores of 22, 28, and 27 points were associated with acceptable accuracy in identifying those who had an improved function rating when reporting a "severely abnormal," abnormal," and "nearly normal" rating on preoperative assessment, respectively. The accuracy of these SCB values in predicting improvement was different depending on the patient's preoperative rating of function. The accuracy of the SCB values in predicting improvement in those who had a "nearly normal" rating of function was not as accurate (area under the curve = 0.73) compared with those who had a "severely abnormal" or "abnormal" rating of function on preoperative assessment (area under the curve = 0.89; 0.89). CONCLUSIONS: This study provides surgeons with unique SCB values for the iHOT-12 based on a preoperative rating function and may allow for a more precise interpretation of score changes. SCB values of 22, 28, and 27 points on the iHOT-12 at 1-year (+/-1 month) follow-up identified those who had an improved function rating, when reporting a "severely abnormal," abnormal," and "nearly normal" rating on preoperative assessment, respectively. LEVEL OF EVIDENCE: III, retrospective comparative study.

Analysis of sea star larval regeneration reveals conserved processes of whole-body regeneration across the metazoa.

BACKGROUND: Metazoan lineages exhibit a wide range of regenerative capabilities that vary among developmental stage and tissue type. The most robust regenerative abilities are apparent in the phyla Cnidaria, Platyhelminthes, and Echinodermata, whose members are capable of whole-body regeneration (WBR). This phenomenon has been well characterized in planarian and hydra models, but the molecular mechanisms of WBR are less established within echinoderms, or any other deuterostome system. Thus, it is not clear to what degree aspects of this regenerative ability are shared among metazoa. RESULTS: We characterize regeneration in the larval stage of the Bat Star (Patiria miniata). Following bisection along the anterior-posterior axis, larvae progress through phases of wound healing and re-proportioning of larval tissues. The overall number of proliferating cells is reduced following bisection, and we find evidence for a re-deployment of genes with known roles in embryonic axial patterning. Following axial respecification, we observe a significant localization of proliferating cells to the wound region. Analyses of transcriptome data highlight the molecular signatures of functions that are common to regeneration, including specific signaling pathways and cell cycle controls. Notably, we find evidence for temporal similarities among orthologous genes involved in regeneration from published Platyhelminth and Cnidarian regeneration datasets. CONCLUSIONS: These analyses show that sea star larval regeneration includes phases of wound response, axis respecification, and wound-proximal proliferation. Commonalities of the overall process of regeneration, as well as gene usage between this deuterostome and other species with divergent evolutionary origins reveal a deep similarity of whole-body regeneration among the metazoa.

Risk of intra-articular hip injury in adolescent athletes: a five-year multicentre cohort study.

PURPOSE: The purpose of the current study was to establish a risk stratification for hip injury by presenting the classification of sports among adolescent athletes undergoing hip arthroscopy. METHODS: A multicentre registry was queried to examine the incidence of adolescent athletes undergoing hip arthroscopy. Patients were identified and grouped according to their sport-specific risk classification (level I-III). Chi-square analysis was performed to determine the relationship of classification of sport and gender in adolescent athletes to hip arthroscopy. A second chi-square analysis was performed to determine the relationship of classification of sport and number of sports the adolescent athlete was participating in prior to arthroscopic hip surgery. RESULTS: A total of 297 adolescent athletes were included in the study with 129 (43.4%) participating in level I sports compared with 84 (28.3%) in level II and 84(28.3%) in level III sports. Chi-square testing demonstrated a significant effect on gender and sport classification, X2 (2, N = 297) = 31.18, p < 0.01. There was a greater percentage of athletes participating in a single sport (65.3%) compared with multiple sports (34.6%), but was not statistically significant, X2 (1, N = 297) = 1.88, p = 0.17. CONCLUSION: The current study was successful in stratifying a large, multicentre cohort of adolescent athletes requiring hip arthroscopy based on classification levels of sport. There were more male athletes participating in level I sports, while more female athletes participated in level II and level III sports.

Minimal Clinically Important Difference and Substantial Clinical Benefit Values for a Pain Visual Analog Scale After Hip Arthroscopy.

PURPOSE: To define minimal clinically important difference (MCID) and substantial clinical benefit (SCB) values for a pain visual analog scale (VAS) in patients undergoing hip arthroscopy for femoroacetabular impingement or chondrolabral pathology. METHODS: This was a retrospective review of prospective collected data on patients having hip arthroscopy for femoroacetabular impingement and/or chondrolabral pathology. On initial assessment and follow-up between 335 and 395 days postsurgery, subjects completed a pain VAS and categorical self-rating of function. MCID was calculated using one-half the standard deviation (SD) of the change in 1-year pain VAS values. Receiver operator characteristic analysis was performed to determine SCB values. A change in SCB value was determined based on change in categorical self-rating of function to create "improved" and "not improved" groups. Absolute postoperative SCB scores were calculated to determine scores that would be associated with "normal" or "abnormal" function ratings. RESULTS: Of 1,034 eligible patients, 733 (71%) met the inclusion criteria, with 537 (73%) women and 196 (27%) men having a mean age of 35.3 years (SD 13). At a mean of 352 (SD 21) days postsurgery, 536 (73%) were in the improved group and 197 (27%) in the not improved group. MCID was -15.0 mm. A change of -22.7 mm on the pain VAS was able to identify those that improved with high sensitivity (0.74) and specificity (0.63). Values of ≤10.4 mm and ≥29.0 mm were cutoffs identifying subjects that rated their function as normal or abnormal, respectively, with high sensitivity (0.79 and 0.76) and specificity (0.88 and 0.76). CONCLUSIONS: This study provides surgeons with information to help interpret pain VAS values at a follow-up period ranging from 335 to 395 days with MCID and SCB values of -15.0 mm and -22.7 mm, respectively. Additionally, a patient who assesses a pain level at ≤10.4 mm is likely to have a normal rating of function, whereas a patient who assesses a pain level at ≥29.0 mm is likely to have an abnormal rating of function. LEVEL OF EVIDENCE: III, retrospective comparative study.

Arthroscopic Outcomes as a Function of Acetabular Coverage From a Large Hip Arthroscopy Study Group.

PURPOSE: To report comparative hip arthroscopic outcomes of patients with low (borderline dysplasia), normal, and high (global pincer femoroacetabular impingement [FAI]) lateral acetabular coverage. METHODS: A retrospective analysis of prospectively collected data from a multicenter registry was performed. Primary hip arthroscopy patients were assigned to 1 of 3 groups based on preoperative lateral center-edge angle: borderline dysplasia (≤25°), normal (25.1°-38.9°), and pincer (≥39°). Repeated-measures analysis of variance compared preoperative with 2-year minimum postoperative International Hip Outcome Tool (iHOT-12) scores. Subsequent analysis of variance determined the effect of acetabular coverage on magnitude of change in scores. RESULTS: Of 437 patients, the only statistical difference between groups was a lower prevalence of acetabuloplasty in the borderline dysplasia group (P = .001). A significant improvement in the preoperative to postoperative iHOT-12 scores for patients with normal acetabular coverage, acetabular undercoverage, and acetabular overcoverage was observed: F(1, 339) = 311.06; P <.001, with no statistical differences in preoperative (P = .505) and postoperative (P <.488) iHOT-12 scores when comparing the groups based on acetabular coverage. Mean iHOT-12 scores increased from 37.3 preoperatively to 68.7 postoperatively (P <.001) in the borderline dysplasia group, from 34.4 to 72 (P <.001) in the normal coverage group, and from 35.3 to 69.4 (P <.001) in the pincer group. These preoperative scores increased by 31.4, 37.8, and 34.1, respectively, with no effect for acetabular coverage on the magnitude of change from preoperative to postoperative iHOT-12 scores: F(2,339) = 1.18; P = .310. Ten patients (2.3%) underwent conversion arthroplasty, and 19 patients (4.4%) underwent revision arthroscopy with no significant effect of acetabular coverage on the incidence of revision or conversion surgery: χ2 (6,433) = 11.535; P = .073. CONCLUSIONS: Lateral acetabular coverage did not influence outcomes from primary hip arthroscopy when performed in patients with low (borderline dysplasia), normal, and high (global pincer FAI) lateral center-edge angle. Borderline dysplasia and moderate global pincer FAI with no or minimal osteoarthritis do not compromise successful 2-year minimum outcomes or survivorship following primary hip arthroscopy when performed by experienced surgeons. LEVEL OF EVIDENCE: Level III, retrospective therapeutic trial.

Minimal Clinically Important Difference and Substantial Clinical Benefit Values for the 12-Item International Hip Outcome Tool.

PURPOSE: To define minimal clinically important difference (MCID) and substantial clinical benefit (SCB) values for the 12-item International Hip Outcome Tool (iHOT-12) in patients undergoing hip arthroscopy for intra-articular pathology. METHODS: This was a retrospective review of prospectively collected data on patients who underwent hip arthroscopy. On initial assessment and follow-up between 335 and 395 days after surgery, subjects completed the iHOT-12 and a categorical self-rating of function (severely abnormal, abnormal, nearly normal, or normal). One-half the standard deviation (SD) of the change in 1-year iHOT-12 scores was used to calculate the MCID. Receiver operator characteristic analysis was performed to determine SCB values. A change in SCB value was determined based on an improvement in the categorical rating of function. Absolute postoperative SCB scores were calculated to determine scores that would be associated with normal function ratings or with abnormal or severely abnormal function ratings. RESULTS: Of 1,034 eligible patients, 733 (71%) met the inclusion criteria. The subjects consisted of 537 female patients (73%) and 196 male patients (27%), with a mean age of 35.3 years (SD, 13 years). At a mean of 352 days (SD, 21 days) after surgery, 536 patients (73%) were in the "improved" group and 197 (27%) were in the "not improved" group. The MCID was 13 points. An SCB change score of 28 points was able to identify patients who improved with high sensitivity (0.79) and specificity (0.72). Scores of 86 points or greater and 56 points or less were the cutoff values found to identify subjects who rated their function as normal and abnormal, respectively, with high sensitivity (0.74 and 0.90, respectively) and specificity (0.82 and 0.86, respectively). CONCLUSIONS: This study provides information to help interpret iHOT-12 scores for a follow-up period ranging between 335 and 395 days with MCID and SCB values of 13 and 28 points, respectively. In addition, a vpatient who scored 86 points or better was likely to have a normal rating of function, whereas a patient with a score of 56 points or less was likely to have an abnormal rating of function. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

The Patient Acceptable Symptomatic State of the 12-Item International Hip Outcome Tool at 1-Year Follow-Up of Hip-Preservation Surgery.

PURPOSE: To determine the patient acceptable symptomatic state (PASS) cutoff score for the 12-item International Hip Outcome Tool (iHOT-12) for patients after hip-preservation surgery. METHODS: A multicenter hip arthroscopy registry containing deidentified patient data was analyzed to discriminate patients who achieved satisfactory results from patients who did not. Patients eligible for inclusion in the study were between 18 and 75 years of age, consented to undergo elective hip arthroscopy, and completed preoperative patient-reported outcome questionnaires. A receiver operating characteristic analysis was performed to determine the PASS cutoff score for the iHOT-12 at 1 year after surgery based on the sensitivity and specificity of achieving satisfaction with surgery. A visual analog scale rating patient satisfaction 1 year after surgery was documented and compared between subjects who achieved the PASS score for the iHOT-12 and those who did not achieve it through an independent t test with an a priori α set at .05. RESULTS: A total of 647 subjects (66% women) aged between 18 and 73 years (mean, 36.5 years; standard deviation [SD], 12.0 years) were included in the study. A cutoff score of 75.2 for the iHOT-12 yielded a sensitivity of 0.91 and specificity of 0.81. Satisfaction averaged 89.5% (SD, 18.0%) for the patients with iHOT-12 scores greater than the PASS cutoff score versus 60.9% (SD, 30.61%) for those who did not achieve the PASS iHOT-12 score. CONCLUSIONS: The PASS cutoff score of 75.2 for the iHOT-12 establishes a "minimal" target score at which the patient is highly likely to be satisfied with the physical state of his or her hip joint at 1 year after hip arthroscopy. LEVEL OF EVIDENCE: Level III, case-control study.

CK-2127107 amplifies skeletal muscle response to nerve activation in humans.

INTRODUCTION: Three studies evaluated safety, tolerability, pharmacokinetics, and pharmacodynamics of CK-2127107 (CK-107), a next-generation fast skeletal muscle troponin activator (FSTA), in healthy participants. We tested the hypothesis that CK-107 would amplify the force-frequency response of muscle in humans. METHODS: To assess the force-frequency response, participants received single doses of CK-107 and placebo in a randomized, double-blind, 4-period, crossover study. The force-frequency response of foot dorsiflexion following stimulation of the deep fibular nerve to activate the tibialis anterior muscle was assessed. RESULTS: CK-107 significantly increased tibialis anterior muscle response with increasing dose and plasma concentration in a frequency-dependent manner; the largest increase in peak force was ∼60% at 10 Hz. DISCUSSION: CK-107 appears more potent and produced larger increases in force than tirasemtiv-a first-generation FSTA-in a similar pharmacodynamic study, thereby supporting its development for improvement of muscle function of patients. Muscle Nerve 57: 729-734, 2018.

Hip Dysplasia: Prevalence, Associated Findings, and Procedures From Large Multicenter Arthroscopy Study Group.

PURPOSE: To report observational findings of patients with acetabular dysplasia undergoing hip arthroscopy. METHODS: We performed a comparative case series of multicenter registry patients from January 2014 to April 2016 meeting the inclusion criteria of isolated hip arthroscopy, a documented lateral center-edge angle (LCEA), and completion of preoperative patient-reported outcome measures. A retrospective analysis compared range of motion, intra-articular pathology, and procedures of patients with dysplasia (LCEA ≤25°) and patients without dysplasia (LCEA >25°). RESULTS: Of 1,053 patients meeting the inclusion criteria, 133 (13%) had dysplasia with a mean LCEA of 22.8° (standard deviation, 2.4°) versus 34.6° (standard deviation, 6.3°) for non-dysplasia patients. There were no statistically significant differences in preoperative modified Harris Hip Score, International Hip Outcome Tool-12 score, or visual analog scale score (pain). Cam deformity occurred in 80% of dysplasia patients. There was a significant difference in internal rotation between the dysplasia (21°) and non-dysplasia groups (16°, P < .001). Mean internal rotation (33.5°; standard deviation, 15.6°) of the dysplastic subjects without cam morphology was greater than that of the dysplastic patients with cam morphology (18.5°; standard deviation, 11.6°; P < .001). Hypertrophic labra were found more commonly in dysplastic (33%) than non-dysplastic hips (11%, P < .001). Labral tears in patients with dysplasia were treated by repair (76%), reconstruction (13%), and selective debridement (11%); labral treatments were not significantly different between cohorts. The most common nonlabral procedures included femoroplasty (76%) and synovectomy (73%). There was no significant difference between the dysplasia and non-dysplasia groups regarding capsulotomy types and capsular closure rates (96% and 92%, respectively). CONCLUSIONS: Dysplasia, typically of borderline to mild severity, comprises a significant incidence of surgical cases (13%) by surgeons performing high-volume hip arthroscopy. Despite having similar preoperative pain and functional profiles to patients without dysplasia, dysplasia patients may have increased flexed-hip internal rotation. Commonly associated cam morphology significantly decreases internal rotation. Arthroscopic labral repair, femoroplasty, and closure of interportal capsulotomy are the most commonly performed procedures. LEVEL OF EVIDENCE: Level III, therapeutic comparative case series.