Year: 2021
Type: article
Abstract: This Journal of Orthopaedic Research special issue shines a spotlight on anterior cruciate ligament (ACL) injury. This complex structure is so often injured, with young athletes being particularly vulnerable to injury and reinjury. We now understand that this injury is really an interconnected mosaic of injuries that vary considerably from athlete to athlete. The invited reviews and original data articles as well as other papers accepted for inclusion in this issue advance the science and practice of how we care for athletes at risk for or recovering from an ACL injury. Our four invited reviews are from a cadre of the most talented clinician–scientists in this area of study and these reviews provide a cutting edge take on four of the most critical issues surrounding ACL injury. The first updates our readers about arguably the most important issue, primary and secondary prevention of ACL injury, from physical therapist scientists Drs. Amelia Arundale, Holly Silvers-Granelli, and Grete Myklebust. ACL injury has many modifiable risk factors and the evidence for the effectiveness of injury prevention programs is high, yet implementation lags.1-3 The review emphasizes that strategies like coach education, increasing awareness of free programs, identifying barriers, and overcoming implementation obstacles through creative collaboration could help improve both the implementation of and adherence to ACL injury prevention programs which could ultimately decrease the incidence of ACL injury.4 Orthopedic surgeon scientists, Martha Murray, Constance Chu, and Elizaveta Kon all approach the conundrum of ACL reconstruction and graft healing from their own scientific perspectives. Dr. Murray describes and discusses her group's work using a tissue engineering strategy to solve one of the most vexing problems, that the ACL does not heal. Her paper takes us from the concept of biologically enhanced ACL repair to bench, preclinical small and large animal studies, clinical trials, and ultimately FDA 510(k) de Novo approval, providing clinicians and patients with a viable alternative to ACL reconstruction.5 Another topic of high relevance to the recovery, return to sport, and reinjury risk of patients undergoing ACLR is graft maturation. Dr. Chu shines a light on what she calls the “silent” process of ACL graft healing, using cutting edge imaging methods to detail the 2-year long maturation process from an avascular, aneural tendon graft to mature incorporated structure that functions as an ACL.6 Dr. Elisaveta Kon presents a systematic review of whether biologics, a particularly contentious set of interventions, can help facilitate healing after ACL injury and reconstruction. The review underscores that evidence is still lacking to support the use of biologic agents and that no clinical superiority has been demonstrated when using platelet-rich plasma (PRP) in ACL reconstruction. Preliminary work however provides some encouragement for the use of PRP to aid healing in partial ACL tears.7 The eleven invited original data articles, and other articles accepted for this issue, run the gamut from epidemiology8 to imaging9-11 rehabilitation12-15 and biomechanics16, 17 from some of the best and brightest minds in this area. Work from the laboratories of Dr. Elizabeth Wellsandt18 and Dr. Susan Sigward19 add to the growing body of work that cites underloading rather than overloading of the involved limb after ACL injury as problematic.20, 21 Dr. Lindsey Lepley's group shows that even in a preclinical model of ACL injuries it is apparent that an ACL injury dramatically alters joint kinematics that ultimately redistributes joint loading that is associated with subchondral bone plate remodeling.22 Dr. Sigward shows that after ACL reconstruction, the underloading strategies also occur during daily activity. Asymmetrical loading quantified in the laboratory is practiced throughout the day in individuals after ACL reconstruction and reinforces a movement pattern that countermands rehabilitation exercises. Quadriceps weakness was also related to greater underloading.19 Dr. Wellsandt reports that altered knee adduction moment impulse, less knee flexion excursion, and greater daily step counts accounted for a large percentage of the variation in cartilage T2 relaxation times. Gait biomechanics and daily physical activity may therefore be modifiable targets to improve cartilage health acutely after the ACL injury.19 Dr. Riann Palmieri-Smith and colleagues show that a potential simple intervention, walking faster, exacerbates the limb asymmetries. Evaluating faster-walking speeds may identify biomechanical asymmetries in individuals with ACL reconstruction earlier rehabilitative time points when more difficult tasks like hopping and running are not feasible, thus facilitating targeted rehabilitation.23 Dr. Kay Crossley's lab, pioneered the elucidation of patellofemoral PTOA as a significant problem after ACL reconstruction as is tibiofemoral PTOA.24 Their contribution demonstrates the interplay of intra- and extra-articular structures in the development of early posttraumatic osteoarthritis features after ACL reconstruction. Greater infrapatellar fat pad volume and Hoffa-synovitis appear to be associated with the presence and worsening of some early patellofemoral PTOA features after ACLR. Persistent quadriceps dysfunction is a hallmark of ACL injury.25 Dr. Sandra Shultz has focused her work on morphological and other risk factors for ACL injury.26, 27 Her study demonstrated a positive relationship between quadriceps volume and the volume of the ACL suggesting that ACL size may in part be modifiable. The training focused on muscle hypertrophy may increase ACL size and potentially reduce ACL injury.28 Exercise and activity compliance are significant problems in rehabilitation. Dr. Jackie Whittaker and Linda Troung examined attitudes, priorities, and perceptions of exercise-based activities in young athletes after a sport-related ACL injury. Three overarching themes were identified. Reframing exercise-based activities in a positive light and leveraging motivation for return-to-sport and life-long knee health may be important strategies for encouraging ongoing exercise therapy and physical activity following a youth ACL injury.29 Neuromuscular interventions have great evidence to support their efficacy in the treatment of ACL injury. Dr. Meredith Chaput and her mentor evaluated the relationship between visual cognitive function and measurements of neuromuscular control. They suggest that the neural strategy used after ACL reconstruction to maintain proprioception and stability varies and may depend on visual cognition and sensory integration neural activity.30 ACL injury results in psychological distress, and this distress has become an area of high interest. Dr. Terese Chmielewski and colleagues' studies have added advanced training consisting of plyometric, strengthening, and agility exercises after the end of traditional rehabilitation on a comprehensive battery of psychological measures assessing risk, self-efficacy, kinesiophobia, and fear intensity as well as hop testing. Advanced training after ACLR facilitated readiness for sports participation by improving confidence and hop performance, but not fear or return-to-sport.31 While we believe less fear and more confidence foretell better outcomes, Dr. Laura Schmitt, Staci Thomas, and the group demonstrate that confident, young athletes at the time of return to sports after ACLR are more likely to meet all return to sports (RTS) criteria and more likely to sustain a second ACL injury after RTS. The biggest risk factor for reinjury after ACL reconstruction is a return to play cutting and pivoting sports. How psychological readiness and confidence moderate that relationship is undoubtedly a rich area for future study in secondary prevention.32 Dr. Robin Queen's lab also attacked primary and secondary prevention and return to play, but from a biomechanical perspective. They assessed movements patterns (landing biomechanics) in a nonresearch setting, demonstrating equivalence to laboratory measures. This study is an important step toward providing quantitative injury risk metrics in a clinical setting that can be used for return to sport decision-making.33 It was a pleasure to serve as both editors of, and contributors to this ACL Special Issue of the Journal of Orthopaedic Research. The authors of the articles in this issue are a cross-section of the community of researchers and clinicians who devote their professional lives to bettering the lives of athletes with an ACL injury. Experienced and young investigators have brought their expertise to bear on important questions about how injury occurs, primary prevention, prevention of subsequent ACL injury and PTOA, as well as treatment, and safe return to activity. We have come a long way in our understanding of ACL injury and recovery; these reviews and original data papers show how far we have come while also illuminating work that still needs to be done: questions unanswered. And, is not that what the best research does? As we write this, we invoke the memory of Dr. Freddie Fu, who left us much too soon on September 24, 2021. Dr. Fu spent his professional life of research, service, and practice, in the pursuit of the best outcomes for patients after the ACL injury. Also apropos of this issue, Freddie was a champion for diversity and gender equity in orthopedic surgery and has mentored countless women including many of the authors of articles in this issue. The Ruth Jackson Society's “He for She” Award, has been renamed in his honor. This issue and the work contained in it is the first of many to carry on Dr. Fu's legacy.
Source: Journal of Orthopaedic Research®
DOI: 10.1002/jor.25220
Authors: Lynn Snyder‐Mackler, Robin M. Queen
Institutions: University of Delaware, Virginia Tech
Language: English
Open Access status: bronze
OpenAlex ID: W3215582129