Hewett, Timothy E.

Purpose To perform a systematic review to determine if there is (1) an association between decreased hip internal rotation and anterior cruciate ligament (ACL) tear rates; (2) an association between radiographic femoroacetabular impingement (FAI) and ACL tear rates; and (3) biomechanical evidence demonstrating increased strain in the ACL of patients with decreased hip internal rotation. Methods A systematic review was performed using Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines. Studies investigating relationships between hip motion, hip radiographs, and ACL tear were sought. Studies with Levels of evidence I‐IV were eligible for inclusion. Study methodology/evidence were evaluated using Methodological Index for Non‐Randomized Studies (MINORS), Strengthening the Reporting of Observational Studies in Epidemiology (STROBE), and Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria. Results Eleven studies were analyzed (2 cadaveric in vitro models, 8 clinical studies measuring hip internal rotation (2 concurrently assessing radiographic FAI), and 1 clinical study assessing radiographic FAI alone). Mean MINORS, STROBE, and GRADE for the studies was 82.4%, 20.9 out of 22, and “low,” respectively. A total of 959 subjects (84.8% male; mean age 23.6 ± 3.8 years) were analyzed. Overall, 378 subjects sustained 427 ACL tears (399 primary ACL ruptures, 28 reruptures). Six of 8 clinical studies identified a significant association between limited rotation (internal rotation [IR; loss greater than 10°‐20°], external rotation [ER], or combined IR + ER [loss greater than 20°]) and ACL tears. Two studies found an association between ACL ruptures and radiographic cam/pincer impingement. Two cadaveric models found a significant association between ACL strain and limited hip internal rotation. Conclusions This systematic review identified a significant association between ACL tear and both limited hip rotation and radiographic FAI. Level of Evidence Level IV, systematic review of Levels II‐IV studies.

Purpose The purpose of this meta‐analysis was to determine overall objective graft failure rate, failure rate by graft type (allograft vs autograft reconstruction), instrumented laxity, and patient outcome scores following revision anterior cruciate ligament (ACL) reconstruction. Outcomes of interest were collected for all studies meeting the study inclusion criteria, but lower‐level studies (level III/IV) were not pooled for quantitative synthesis due to high levels of heterogeneity in these study populations. Methods A comprehensive search strategy was performed to identify studies reporting outcomes of revision ACL reconstruction. The primary outcome reported was graft failure. A meta‐analysis comparing rate of failure by graft type was conducted using a random effects model. Studies also reported patient clinical outcome scores, including International Knee Documentation Committee (IKDC), Lysholm, and knee injury and osteoarthritis outcome scores (KOOS) and graft laxity. Results Eight studies with 3,021 patients (56% male, 44% female) with an average age of 30 ± 4 years and mean follow‐up time of 57 months were included. The overall objective failure rate was 6% (95% confidence interval [CI], 1.8%‐12.3%). Mean instrumented laxity as side‐to‐side difference was 2.5 mm (95% CI, 1.9‐3.1 mm). Mean IKDC subjective score was 76.99 (95% CI, 76.64‐77.34), mean KOOS symptoms score was 76.73 (95% CI, 75.85‐77.61), and mean Lysholm score was 86.18 (95% CI, 79.08‐93.28). The proportion of patients with IKDC grade A or B was 85% (95% CI, 77%‐91%). When the available data for failure rate were analyzed by graft type, autograft reconstruction had a failure rate of 4.1% (95% CI, 2.0%‐6.9%), similar to allograft reconstruction at 3.6% (95% CI, 1.4%‐6.7%). Conclusions In this meta‐analysis, revision ACL reconstruction had failure rates similar to autograft or allograft reconstruction. Overall outcome scores for revision reconstruction have improved but appear modest when compared with primary ACL reconstruction surgery. Level of Evidence Meta‐analysis of Level II studies, Level II.

Purpose To analyze failure rate in 2‐year increments to determine if graft choice changed over time and graft failure rate. Methods A prospective 2002‐2008 database was used to identify risk factors for anterior cruciate ligament (ACL) retear. Subjects who had primary ACL retear with no history of contralateral surgery and 2‐year follow‐up were included. Subjects who underwent a multiligament reconstruction were excluded. Graft type, age, sex, smoking status, body mass index, Marx activity level at index surgery, medial and lateral meniscus status at time of ACL retear, sport played after ACL reconstruction, and clinical site were evaluated. Analysis was repeated using 2002‐2003 (early) and 2007‐2008 (late) 2‐year databases. Analysis of variance with post hoc analysis was performed to detect significant differences in age and Marx score by graft type over time. Results Two‐year follow‐up for graft failure was obtained on 2,497 of 2,692 (93%) subjects. There were 112 of 2,497 (4.5%) ACL retears identified at 2‐year follow‐up. The only predictor that changed between early/late periods was allograft use. Allograft odds ratio decreased from 13.1 to 9.5 ( P < .01). Allografts were used in older patients (31‐40 years) and with lower Marx scores (10‐8) from early to late periods. The mean age of subjects who received bone–patellar tendon–bone autografts did not significantly change over time (22.8‐23.5). The mean age of subjects who received hamstring autografts fell (27.9‐25.5). The mean age of subjects who received allografts rose significantly (31.3‐39.8, P < .01). The mean Marx score of subjects who received bone–patellar tendon–bone and hamstring autografts did not significantly change over time. The mean Marx score of subjects who received allografts decreased significantly ( P < .01). Conclusions After early recognition, allograft use in young active patients was a risk factor for retear; graft choice by surgeons changed in the late period to use of allografts in older and less‐active patients, which correlated with a significant decrease in retear risk. Level of Evidence Level III, case control study.

Background: The reported rate of second anterior cruciate ligament (ACL) injuries (20%-30%), including graft failure and contralateral ACL tears, after ACL reconstruction (ACLR) or nonoperative therapy indicates that multiple factors may predispose patients to subsequent ACL injuries. Purpose: To determine the incidence of second ACL injuries in a population-based cohort over a 10-year observation period (2001-2010) and to identify factors that contribute to the risk of second injuries. Study Design: Descriptive epidemiological study. Methods: International Classification of Diseases, 9th Revision (ICD-9) codes relevant to the diagnosis of an ACL tear and the procedure code for ACLR were utilized to search the Rochester Epidemiology Project, a multidisciplinary county database, between the years of 2001 and 2010. The complete medical records for all cases were reviewed to confirm diagnosis and treatment details. A total of 914 unique patients with 1019 acute, isolated ACL tears were identified. These patients were stratified by primary and secondary tears, sex, age, activity level, side of injury, sex × side of injury, and graft type of reconstruction. Results: Second ACL tears were recorded in 141 (13.8%) of the 914 patients diagnosed with an ACL tear in Olmsted County, Minnesota, USA, from 2001 to 2010; 50.4% of these occurred in the contralateral knee. A noncontact mechanism was responsible for 76.4% of all ACL injuries. A second ACL injury was influenced by factors of sex × age group, treatment type × age group, and treatment type × activity level. Nonparametric analysis of graft disruption × graft type demonstrated that a higher prevalence of second ACL tears occurred with allografts compared with hamstring autografts ( P = .0054) and patellar tendon autografts ( P = .0001). Conclusion: The incidence of second ACL tears in this population-based cohort was 13.8%, and half occurred to the ACL of the contralateral knee. Statistically, second ACL injuries differed by sex, occurring in female patients younger than 25 years and male patients aged 26 to 45 years. Allografts continued to be associated with a greater risk of second ACL injuries compared with hamstring and patellar tendon autografts. Nonoperative treatment carried more risk of contralateral tears than ACLR.

General and Critical Review Format: The evolution of clinical practice and medical technology has yielded an increasing number of clinical measures and tests to assess a patient's progression and return to sport readiness after injury. The plethora of available tests may be burdensome to clinicians in the absence of evidence that demonstrates the utility of a given measurement. Objective: Thus, there is a critical need to identify a discrete number of metrics to capture during clinical assessment to effectively and concisely guide patient care. Data Sources: The data sources included Pubmed and PMC Pubmed Central articles on the topic. Therefore, we present a systematic approach to injury risk analyses and how this concept may be used in algorithms for risk analyses for primary anterior cruciate ligament (ACL) injury in healthy athletes and patients after ACL reconstruction. Main Results: In this article, we present the five-factor maximum model, which states that in any predictive model, a maximum of 5 variables will contribute in a meaningful manner to any risk factor analysis. Conclusions: We demonstrate how this model already exists for prevention of primary ACL injury, how this model may guide development of the second ACL injury risk analysis, and how the five-factor maximum model may be applied across the injury spectrum for development of the injury risk analysis.

Background: First-time lateral patellar dislocation is a common orthopaedic injury. The purposes of this study were to (1) evaluate the incidence of first-time lateral patellar dislocation in a geographically-determined population, (2) report trends over time in the incidence of dislocation, and (3) describe the rate of surgical treatment. Hypothesis: The rate of patellar dislocation is highest among adolescent patients. Study Design: Cohort study. Level of Evidence: Level 3. Methods: The study population included 609 individuals identified through a multidisciplinary geographic cohort county database who were diagnosed with first-episode lateral patellar dislocation between 1990 and 2010. The complete medical records were reviewed to confirm the diagnosis and to evaluate details of injury and treatment. Age- and sex-specific incidence rates were calculated and adjusted to the 2010 US population. Poisson regression analyses were performed to examine incidence trends by age, sex, and calendar period. Results: The overall age- and sex-adjusted annual incidence of patellar dislocation was 23.2 (95% CI, 21.2-24.9) per 100,000 person-years. The annual incidence was similar between male and female patients and highest among adolescents aged 14 to 18 years (147.7/100,000 person-years). The mean age at dislocation was 21.4 ± 9.9 years, and 331 patients (54.4%) were female. During the study period, there was a significant decline in the incidence of patellar dislocation among men aged 19 to 25 years ( P = 0.002) and girls aged 14 to 18 years ( P = 0.025). Eighty patients received surgical treatment during the study period, including 66 patients (10.8%) for recurrent instability and 14 patients (2.3%) for acute osteochondral injury. Conclusion: With an annual incidence of 23.2 per 100,000 person-years, lateral patellar dislocation is a frequently encountered orthopaedic injury. The incidence of dislocation among adolescent patients in this cohort is higher than previously reported. Despite a decrease in the annual incidence of dislocation in adolescent girls, the overall incidence of patellar dislocation remained relatively constant over a 21-year observation period. Clinical Relevance: This study demonstrates that the incidence of patellar dislocation in adolescents is greater than previously reported.

Background: Multi-planar proximal tibial slopes may be associated with increased likelihood of osteoarthritis and anterior cruciate ligament injury, due in part to their role in checking the anterior-posterior stability of the knee. Established methods suffer repeatability limitations and lack computational efficiency for intuitive clinical adoption. The aims of this study were to develop a novel automated approach and to compare the repeatability and computational efficiency of the approach against previously established methods. Methods: Tibial slope geometries were obtained via MRI and measured using an automated Matlab-based approach. Data were compared for repeatability and evaluated for computational efficiency. Results: Mean lateral tibial slope (LTS) for females (7.2°) was greater than for males (1.66°). Mean LTS in the lateral concavity zone was greater for females (7.8° for females, 4.2° for males). Mean medial tibial slope (MTS) for females was greater (9.3° vs. 4.6°). Along the medial concavity zone, female subjects demonstrated greater MTS. Conclusion: The automated method was more repeatable and computationally efficient than previously identified methods and may aid in the clinical assessment of knee injury risk, inform surgical planning, and implant design efforts.

Background: Anterior cruciate ligament (ACL) tear is a common injury in sports and often occurs during landing from a jump. Purpose: To synthesize the evidence on the effects of injury prevention programs (IPPs) on landing biomechanics as they relate to the ligament, quadriceps, trunk, and leg dominance theories associated with ACL injury risk. Study Design: Meta-analysis. Methods: Six electronic databases were searched for studies that investigated the effect of IPPs on landing task biomechanics. Prospective studies that reported landing biomechanics at baseline and post-IPP were included. Results from trunk, hip, and knee kinematics and kinetics related to the ACL injury theories were extracted, and meta-analyses were performed when possible. Results: The criteria were met by 28 studies with a total of 466 participants. Most studies evaluated young females, bilateral landing tasks, and recreational athletes, while most variables were related to the ligament and quadriceps dominance theories. An important predictor of ACL injury, peak knee abduction moment, decreased ( P = .01) after the IPPs while other variables related to the ligament dominance theory did not change. Regarding the quadriceps dominance theory, after the IPPs, angles of hip flexion at initial contact ( P = .009), peak hip flexion ( P = .002), and peak knee flexion ( P = .007) increased, while knee flexion at initial contact did not change ( P = .18). Moreover, peak knee flexion moment decreased ( P = .005) and peak vertical ground-reaction force did not change ( P = .10). Conclusion: The exercises used in IPPs might have the potential to improve landing task biomechanics related to the quadriceps dominance theory, especially increasing peak knee and hip flexion angles. Importantly, peak knee abduction moment decreased, which indicates that IPPs influence a desired movement strategy to help athletes overcome dangerous ligament dominance loads arising from lack of frontal plane control during dynamic tasks. The lack of findings for some biomechanical variables suggests that future IPPs may be enhanced by targeting participants’ baseline profile deficits, highlighting the need to deliver an individualized and task-specific IPP.

Objectives: The incidence of second anterior cruciate ligament (ACL) injury after ACL reconstruction (ACLR) and return to sport (RTS) in a young, active population is likely between 25-33% with the greatest risk in the first 12 months after RTS. Although the use of allograft tissue in young athletes has been reported to result in increased risk of graft failure, differences in graft and contralateral ACL injury risk between patients who receive a hamstrings (HS) autograft and bone-patellar tendon- bone (BTB) autograft has yet to be reported in a young, athletic population. The tested hypothesis was that the relative risk (RR) of ipsilateral graft failure would be higher in young, active patients who receive an ACLR with a hamstrings graft, while the RR of contralateral ACL injury would be higher in patients who receive and ACLR with a BTB autograft. Methods: One hundred thirty-nine subjects (99 female/40 male) with a mean age of 16.9±2.0 years old (range: 13-25 y/o) underwent ACLR with either a HS autograft (n=79) or a BTB autograft (n=60) and were released to return to pivoting/cutting sport. These patients were enrolled in a prospective, observational cohort study and were tracked for incidence of 2 nd ACL after ACLR for a median of 73 months. Thirty-four (24.5%) suffered a 2 nd ACL injury. Fisher’s exact tests were used to determine whether graft choice (HS vs. BTB) was associated with risk of either ipsilateral graft failure or contralateral ACL injury. Sub-group analyses by sex were also conducted. Results: Patients who underwent ACLR with HS graft (n=79) sustained 14 ipsilateral tears and 6 contralateral ACL injuries. Patients who received an ACLR with BTB (n=62) sustained 2 ipsilateral tears and 12 contralateral ACL injuries (Table 1). Patients who received an ACLR with HS graft were 6 times more likely (RR=6.2; 95% CI: 1.4-28.7) to suffer a graft failure after RTS than the BTB group. In the first 12 months after RTS, the HS graft patients were nearly 10 times (RR=9.5; 95% CI: 1.2-76.1) more likely to suffer an ipsilateral graft failure. Patients with a HS graft were 3 times less likely (RR=0.33; 95%CI: 0.12-0.935) to suffer a contralateral ACL injury and nearly 7 times less likely (RR=0.15, 95%CI: 0.031-0.709) to suffer a contralateral ACL injury in the first 12 months after RTS compared to the BTB group. When the cohort was divided by sex, females with HS grafts were significantly more likely to sustain a graft failure in the first 12 months after RTS (p=0.008) and by final follow-up (p=0.002) compared to females with BTB graft. Females with HS grafts were 3 times less likely (RR=0.30; 95%CI: 0.095-0.943) to suffer a contralateral ACL injury than females with BTB graft and 6 times less likely (RR=0.17; 95%CI: 0.034-0.846) to suffer contralateral ACL injury in the first year after RTS. Males demonstrated no significant difference in ipsilateral or contralateral injury risk based on graft type. Conclusion: Young, active females who return to pivoting and cutting sports after ACLR with HS autograft are at greater risk to suffer a graft failure and reduced risk to suffer a contralateral ACL injury compared to females who undergo ACLR with BTB graft tissue. No significant differences in 2 nd ACL injury risk based on graft type were observed in the male patients. [Table: see text]

Objectives: Patellar dislocation can occur in isolation or be associated with chronicinstability. The goals of this study are to describe the rate and factors associated with additional patellar instability events (ipsilateral recurrence and contralateral dislocation), as well as the incidence of patellofemoral arthritis among skeletally immature patients following patellar dislocation. Methods: The study included a population-based cohort of 232 skeletally immature patients who experienced a first-time lateral patellar dislocation between 1990 and 2010. A chart review was performed to collect information related to the initial injury, treatment, and outcomes. Subjects were followed for a mean of 12.1 years to determine the rate of subsequent patellar dislocation (ipsilateral recurrence or contralateral dislocation) as well as clinically significant patellofemoral arthritis. Results: 104 patients had ipsilateral recurrent patellar dislocation. The cumulative incidence of recurrent dislocation was 11% at 1 year, 21.1% at 2 years, 37.0% at 5 years, 45.1% at 10 years, 54.0 % at 15 years, and 54.0% at 20 years. Patella alta (HR: 10.6, 95% CI: 3.6, 36.1), increased TT-TG distance (HR 18.7, 95% CI: 1.7, 228.2), and trochlear dysplasia (HR 23.7, 95% CI: 1.0, 105.2) were associated with recurrence. Similarly, 18 patients (7.8%) had contralateral patellar dislocation. The cumulative incidence of patellofemoral arthritis was 0% at 2 years, 1.0% at 5 years,2.0% at 10 years, 10.1% at 15 years, 17%% at 20 years, and 39.0% at 25 years. Osteochondral injury was associated with arthritis (HR 25.7, 95% CI: 6.2, 143.8). Conclusion: Skeletally immature patients have a high rate of recurrent patellarinstability that is associated with structural abnormalities such as patella alta and trochlear dysplasia. In contrast, the rate of subsequent contralateral dislocation is low. Osteochondral injury is associated with arthritis after patellar dislocation, but the overall incidence of symptomatic arthritis with advanced radiographic changes in pediatric patients is low at 12-year follow-up.