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Psychological readiness to return to sport has been shown to be associated with future play after anterior cruciate ligament (ACL) reconstruction surgery but has not been extensively studied in adolescent athletes. To investigate the psychometric properties of the Anterior Cruciate Ligament-Return to Sport after Injury (ACL-RSI) scale in adolescent athletes at multiple time points after ACL reconstruction surgery and determine whether psychological readiness scores at 6 months predict return to competition sport at 12 months. Case series. Private orthopaedic clinic. A total of 115 adolescent athletes (65 girls, 50 boys) 17 years and younger who had undergone primary unilateral ACL reconstruction. The ACL-RSI scale was administered at 6 and 12 months after surgery, and return-to-sport status was also documented. Factor analysis was undertaken and predictive validity assessed using between-groups comparisons and receiver operating characteristic (ROC) curve statistics. The ACL-RSI scores increased between 6 and 12 months (55 to 71; P < .001, effect size = 0.98). No floor or ceiling effects were present, and the scale had high internal consistency (Cronbach α at 6 months = 0.91 and at 12 months = 0.94). Principal component analysis showed that 2 factors were present: the first represented performance confidence and risk appraisal and the second, emotions. For the full-scale ACL-RSI, scores at 6 months had acceptable predictive ability for a return to play at 12 months (area under the ROC curve = 0.7, P = .03). When the 2 identified factors were analyzed separately, the emotions factor also had acceptable predictive ability (area under the ROC curve = 0.73, P = .009), but the confidence in performance and risk appraisal factors had poor predictive ability (area under the ROC curve = 0.59, P = .09). Greater psychological readiness was associated with return to sport in adolescent athletes after ACL reconstruction, with the athletes' emotional response appearing to be more influential than their confidence in their performance or their appraisal of risk.

Background: The Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI) scale was developed to measure an athlete’s psychological readiness to return to sport after anterior cruciate ligament (ACL) injury and reconstruction surgery. The scale is being used with increasing frequency in both research and clinical settings. Purpose: To generate and validate a short version of the ACL-RSI scale. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: The ACL-RSI scale was administered to 535 patients who had undergone ACL reconstruction surgery. Reliability (Cronbach alpha) was determined and factor analysis of the full scale was undertaken along with a process of item selection and elimination. A second group of 250 patients participated in a predictive validation analysis. This group completed the ACL-RSI scale at 6 months and reported return-to-sport outcomes 12 months following ACL reconstruction surgery. The predictive validity of both scales (full and short versions) was assessed by use of receiver operating characteristic (ROC) curve statistics. Results: The scale was found to have high internal consistency (Cronbach alpha, 0.96), which suggested that item redundancy was present. After an item selection process, the scale was reduced to a 6-item format. Cronbach alpha for the short version was 0.92, and factor analysis confirmed the presence of 1 factor accounting for 71% of the total variance. Scores for the short version were significantly different between patients who had and those who had not returned to sport. Six-month ACL-RSI scores for both the full and short versions had fair to good predictive ability for 12-month return-to-sport outcomes (full version: area under ROC curve, 0.77 [95% CI, 0.7-0.8]; short version: area under ROC curve, 0.75 [95% CI, 0.7-0.8]). Conclusion: A 6-item short version of the ACL-RSI scale was developed from a large cohort of patients undergoing ACL reconstruction. The short version appears to be as robust as the full version for discriminating between and predicting return-to-sport outcomes. The short version of the ACL-RSI may be of use in busy clinical settings to help identify athletes who may find return to sport challenging.

Purpose Restoration of knee muscle strength is associated with better outcomes following anterior cruciate ligament (ACL) reconstruction, but little is known about the outcome of strength following quadriceps tendon autograft (QT) ACL reconstruction in relation to other graft types. The aim of this review was to evaluate strength outcomes of the knee extensors and knee flexors following QT ACL reconstruction compared to (1) the non-reconstructed contralateral limb and (2) alternative ACL graft types. Methods Four electronic databases were searched up until 21st February 2020. Summary meta-analyses were performed comparing knee strength outcomes following QT ACL reconstruction to the contralateral limb by way of limb symmetry index (LSI). Comparative meta-analyses were performed comparing QT ACL reconstruction to alternative ACL grafts for the two most frequently reported strength outcome measures which were peak knee extensor torque LSI, and peak knee flexor torque LSI at the following post-operative periods: 3, 5–8, 9–15, 24, 36–60 months. Results In total, 18 studies met the inclusion criteria. Knee strength outcomes of 952 QT ACL reconstructions were included and compared to either the contralateral limb or 1 of 4 alternative ACL graft types; 245 hamstring tendon autograft (HT), 143 patellar tendon autograft (PT), 45 quadriceps tendon allograft, and 21 tibialis anterior allograft. Knee extensor strength LSI following QT ACL reconstruction did not reach 90% even at 24 months post-operatively. Conversely, knee flexor strength LSI following QT ACL reconstruction exceeded 90% at the 9–15 months post-operative period. Knee extensor strength at 5–8 months following QT ACL reconstruction appears similar to PT but weaker than HT ACL reconstruction. In addition, peak knee flexor LSI was significantly greater at 5–8 months in QT ACL reconstruction patients compared to HT patients. Conclusion The decision to utilize a QT graft for ACL reconstruction should include consideration of strength outcomes. Knee extensor strength recovery following QT ACL reconstruction appears not to be restored before 24 months. Level of evidence Level IV.

Background: Return to sport (RTS) after anterior cruciate ligament (ACL) reconstruction is a topic of current interest. The high reinjury rates reported in younger athletes may be due in part to an early RTS. Purpose: To determine the proportion of athletes who return to level I (jumping, hard pivoting, and cutting) sport at less than 1 year after ACL reconstruction and compare return rates by age and sex. A secondary purpose was to examine whether RTS is associated with some commonly used outcome criteria. Methods: A cohort of 1440 athletes (992 males, 448 females) satisfied criteria for inclusion in this study (primary ACL reconstruction, normal contralateral knee, no additional surgery within the first year after the reconstruction, and participation in level I sport on a weekly basis prior to injury). The proportion of athletes in this sample who had resumed level I sport by 12 months after surgery was recorded, along with measurements of knee function (single-legged hop symmetry), laxity (KT-1000 arthrometer), and self-reported outcomes (International Knee Documentation Committee [IKDC] subjective score). Limb symmetry index scores of 90 or higher, side-to-side difference in anterior knee laxity of 2 mm or less, and IKDC scores of 95 or higher were considered indicators of satisfactory recovery from surgery. Results: Rates of return to level I sport were significantly higher for athletes aged 25 years and younger (48% return rate) compared with older athletes (26-35 years, 32% return rate [P < .0001]; ≥36 years, 19% return rate [P < .001]). Male athletes who were in the ≤25-year and 26- to 35-year age brackets had significantly higher return rates than female athletes (52% vs 39% and 37% vs 18%, respectively), whereas no sex-based differences in RTS were seen after 36 years of age. A significantly higher proportion of younger patients met the selected indicators of a satisfactory recovery. Regardless of age, athletes had twice the odds of RTS if they had limb symmetry index scores of 90 or higher (P ≤ .0001) and 3 times the odds of RTS if they had IKDC scores of 95 or higher (P < .0001). Conclusion: Almost half of younger athletes (aged ≤25 years) in the current cohort returned to level I sports within 12 months after ACL reconstruction. Younger athletes were also more likely to meet criteria that indicate a satisfactory functional recovery and that have been used to indicate readiness to RTS. There may be a role for adjusting thresholds for these criteria based on age.

Background There is some evidence that functional performance and validated outcome scores differ according to the gender, age, and sport participation status of a patient after anterior cruciate ligament (ACL) reconstruction. However, the impact of these three factors, and interaction among them, has not been studied across a large relatively homogeneous group of patients to better elucidate their impact. Questions/purposes We reviewed a large cohort of patients who had undergone ACL reconstruction to determine if ROM, knee laxity, objective performance measures, and validated outcome scores differed according to (1) gender; (2) age; and (3) sport participation status. Methods This was a retrospective analysis of prospectively collected data. Between 2007 and 2016, we performed 3452 single-bundle ACL reconstructions in patients who participated in sport before ACL injury. Of those, complete followup (including preoperative scores and scores at 1 year after surgery; mean, 14 months; range, 12–20 months) was available on 2672 (77%) of patients. Those lost to followup and those accounted for were not different in terms of age, gender, and sports participation at baseline. The study group consisted of 1726 (65%) men and 946 (35%) women with a mean ± SD age of 28 ± 10 years. For these patients, the following measures were obtained: knee ROM (flexion and extension deficit), instrumented knee laxity, single and triple hop for distance limb symmetry index (LSI), International Knee Documentation Committee (IKDC) subjective evaluation, and Single Assessment Numeric Evaluation score. Mean scores and measures of variability were calculated for each outcome measure. Comparisons were made among gender, age, and sport status. Results Men had less knee laxity after reconstruction (men 1.1 ± 2.2 mm, women 1.3 ± 2.4 mm; mean difference 0.2 mm [0.1–0.4], p < 0.001), greater limb symmetry (single limb hop men: 94% ± 12%, women 91% ± 13%, mean difference 3% [2%–4%], p < 0.001), and higher IKDC scores than did women (men 84 ± 12, women 82 ± 12, mean difference 2 [1–3], p < 0.001). With the exception of instrumented laxity, all outcome measures showed reduced deficits and higher scores in younger patients. This was most marked for LSI scores between the youngest and oldest aged patient groups (crossover hop: < 16 years 99% ± 10%, > 45 years 90% ± 16%, mean difference: 9 [5–11], p < 0.001). Patients who had returned to their preinjury sport also scored higher and had smaller deficits for all outcomes except ROM compared with patients who had not returned to sport at the time of followup (IKDC subjective: returned 90 ± 9, no sport 79 ± 12, mean difference 11 points [9–12], p < 0.001; single limb hop: returned 97 ± 10, no sport 91 ± 14, mean difference 6% [5%–7%], p < 0.001). Conclusions This study showed that some of the most commonly used functional performance and validated clinical scores for ACL reconstruction are superior for patients who are younger, male, and have returned to preinjury sport. Reference to these data allows clinicians to more effectively evaluate a patient based on their age, gender, and sport status when making return to sport and rehabilitation decisions. Level of Evidence Level III, therapeutic study.

Many causal questions involve interactions between units, also known as interference, for example between individuals in households, students in schools, or firms in markets. In this paper we formalize the concept of a conditioning mechanism, which provides a framework for constructing valid and powerful randomization tests under general forms of interference. We describe our framework in the context of two-stage randomized designs and apply our approach to a randomized evaluation of an intervention targeting student absenteeism in the school district of Philadelphia. We show improvements over existing methods in terms of computational and statistical power.

The purpose of this study was to develop a scale to measure the psychological impact of returning to sport after anterior cruciate ligament (ACL) reconstruction surgery. Three types of psychological responses believed to be associated with resumption of sport following athletic injury—emotions, confidence in performance, and risk appraisal—were incorporated into a 12-item ACL-Return to Sport after Injury (ACL-RSI) scale. Two hundred and twenty participants who had undergone ACL reconstruction completed the scale between 8 and 22 months following surgery. The scale was shown to have acceptable reliability (Cronbach's alpha=0.92). Participants who had given up sport scored significantly lower on the scale (reflecting a more negative psychological response) than those who had returned or were planning to return to sport ( p<0.001). It was concluded that the decision to return to sport after ACL reconstruction is associated with a significant psychological response. Preliminary reliability and validity was found for the ACL-RSI scale. This scale may help to identify athletes who will find sport resumption difficult.

Purpose The principal aim of this study was to report the outcomes of medial patellofemoral ligament (MPFL) reconstruction, used as either an isolated procedure or in combination with another stabilization procedure, for the primary treatment of recurrent patellar instability. Methods Between 2007 and 2012, 45 patients with recurrent patellar instability and no prior stabilization surgery had an MPFL reconstruction by a single surgeon, either as an isolated procedure or in combination with another stabilization procedure. Questionnaires detailing patellar instability since surgery, knee pain, ability to negotiate stairs, and sports participation were completed, and data regarding examination and radiological findings were collected from the medical record. Results A total of 36 (80 %) patients completed the questionnaire at a mean of 3.1 years (minimum 1 year), whilst a further 11 % had clinical follow-up of greater than 1 year. Four patients were excluded due to lack of adequate follow-up. Thirty-one patients had an isolated MPFL reconstruction and none had further patellar instability. Of the ten patients who had a combined procedure, one experienced recurrent instability. Return to sport rates were 81 and 57 % for the isolated and combined groups, respectively, with the majority returning to strenuous sport (81 and 57 %, respectively). Most patients (96 and 80 %) could negotiate stairs without difficulty, whilst 38 and 40 % reported some degree of anterior knee pain. Conclusions This study shows that satisfactory results can be obtained using MPFL reconstruction either in isolation or in combination to treat recurrent patellar instability. Whether the indications for an isolated MPFL can be extended further remains unclear. Level of evidence III.

Background: Return-to-sport (RTS) testing after anterior cruciate ligament (ACL) reconstruction (ACLR) surgery has become popular. It has been recommended that such testing should incorporate several domains, or set of tests, but it is unclear which are most associated with a successful RTS. Purpose: To determine (1) the proportion of patients who can pass a set of self-report and functional tests at 6 months after ACLR; (2) age, sex, and activity level differences between patients who pass and those who do not; and (3) whether specific types of tests are associated with a return to competitive sport at 12 months. Study Design: Cohort study; Level of evidence, 2. Methods: This was a prospective longitudinal study of 450 patients who had primary ACLR. At 6 months postoperatively, patients completed 2 self-report measures, the International Knee Documentation Committee (IKDC) subjective knee form and ACL–Return to Sport after Injury (ACL-RSI) scale, and 3 functional measures: single hop and triple crossover hop for distance and isokinetic quadriceps strength. Limb symmetry index scores of ≥90 for functional tests, IKDC scores ≥85, and ACL-RSI scores ≥65 were considered indicators of satisfactory recovery. Proportional statistics and contingency analysis were used to determine associations between age, sex, preinjury sports level, and (1) meeting test thresholds and (2) RTS at 12 months. Results: Only 17 (3.8%) patients met all 5 test criteria at 6 months, and 95 (21%) patients did not pass any test. More of the younger patients (<21 years) passed all of the functional tests (P < .01), and more male patients met the IKDC threshold (P = .03). Patients who played level I sports before injury had the same pass rates as those who played level II/III sports. Patients who passed the thresholds for the ACL-RSI and IKDC scales had 4 and 3 times the odds, respectively, of RTS at 12 months (both P < .0001). Meeting the threshold for quadriceps strength or either of the hop tests at 6 months was not associated with RTS. Conclusion: At 6 months after ACLR, few patients met all of the thresholds of the common tests used to assess RTS ability, although younger patients had higher rates of passing the functional tests. Self-perceived symptoms/function and psychological readiness were associated with a return at 12 months.

To examine fear of re-injury in athletes who had returned to regular sports participation following anterior cruciate ligament reconstruction surgery. Cross-sectional case series. A self-report questionnaire was used to collect data 2–7 years following surgery. Key inclusion criteria were regular participation in sport prior to injury and participation in sport at the time of the study. A sample of 209 (88 females, 121 males) at a mean of 39.6±13.8 months post surgery participated. Overall, participants did not express fear of re-injury, scoring >6/10 (where 10 was the most positive response) on all questions. In terms of the total score and for six out of eight questions, participants who returned to their pre-injury sports level had significantly less fear of re-injury than those who had not returned to their pre-injury level. Females had significantly more concern than males about the environmental conditions experienced while playing (mean 6.1 compared to 7.5). On three out of eight questions, individuals who had surgery more than 3 months after injury had a greater fear of re-injury than those who had their surgery closer to the time of injury. Athletes participating in sport 2–7 years following their anterior cruciate ligament reconstruction generally appear to do so without fear of re-injury. However, gender, the timing of surgery following injury and the level of sport the athletes returned to may be associated with fear of re-injury following surgery.