Background: Substantial developments in physeal-sparing surgical techniques for anterior cruciate ligament (ACL) reconstruction (ACLR) have demonstrated safety and efficacy in treating skeletally immature patients. However, outcomes using all–soft tissue quadriceps tendon (QT) autograft in this population are unknown. Purpose: To evaluate outcomes including return to sport (RTS) and reinjury risk in skeletally immature patients ≥2 years after undergoing hybrid transepiphyseal ACLR using QT autograft. Study Design: Case series; Level of evidence, 4. Methods: A consecutive series of skeletally immature patients who underwent primary QT autograft ACLR using a hybrid transepiphyseal technique with ≥2 years of follow-up were retrospectively analyzed. Outcomes included RTS (primary), ability to return to preinjury level of competition, and subsequent ipsilateral/contralateral knee injury (secondary). Results: A total of 50 patients were identified and contacted, of which 40 (80.0%) (35 male; mean age, 12.6 years [range, 9.4-16.0 years]) completed the survey at 5.7 ± 2.8 years (range, 2.0-11.5 years) postoperation. Of those, 26 (65.0%) were competitive middle/high school athletes and 18 (45.0%) competed in ≥2 sports. At a mean of 10.6 ± 2.3 months (range, 6-17 months) postoperatively, 37 patients (92.5%) returned to unrestricted sports participation, and 35 patients (87.5%) resumed competition at their preinjury level. Five patients required subsequent ipsilateral knee surgery for ACL revision (n = 2; 5.0%), meniscal injury (n = 2; 5.0%), or symptomatic hardware (n = 1; 2.5%) after a mean of 4.4 ± 1.7 years (range, 2.8-7.1 years). Three patients (7.5%) sustained a subsequent contralateral ACL injury, and 1 patient sustained a contralateral posterior cruciate ligament sprain. Conclusion: Findings of this study suggest that midterm outcomes of patients treated with hybrid transepiphyseal ACLR using QT autograft are promising, with a high and expedited RTS and relatively low graft tear risk.

Objectives: Substantial developments in physeal-sparing surgical techniques for anterior cruciate ligament reconstruction (ACLR) have demonstrated safety and efficacy in treating skeletally immature patients. However, outcomes using all soft tissue quadriceps tendon (QT) autograft in this population are unknown. The purpose of this study was to evaluate outcomes including return to sport (RTS) and reinjury risk in skeletally immature patients ≥2 years after undergoing hybrid transepiphyseal ACLR using QT autograft. Methods: We retrospectively analyzed a consecutive series of skeletally immature patients who underwent primary QT autograft ACLR using a hybrid transepiphyseal technique with ≥2 years of follow-up. Outcomes included RTS (primary), ability to return to pre-injury level of competition, and subsequent ipsilateral/contralateral knee injury (secondary). Results: We identified and contacted 50 patients, of which 40 (80.0%) [(35 male, mean age: 12.6 (range: 9.4–16.0) years] completed the survey at 5.7 ± 2.8 (range: 2.0 – 11.5) years post-operation. Of those, 26 (65.0%) were competitive middle/high school athletes and 18 (45.0%) competed in 2 or more sports. Thirty-seven (92.3%) patients returned to unrestricted participation in sports and 35 (87.5%) patients returned to pre-injury level of competition at 10.6 ± 2.3 (range: 6–17) months. Five patients required subsequent ipsilateral knee surgery for ACL revision (n = 2; 5.0%), meniscus injury (n = 2; 5.0%), or symptomatic hardware (n = 1; 2.5%) after an average of 4.4 ± 1.7 (range: 2.8–7.1) years. Three patients (7.5%) sustained a subsequent contralateral ACL injury, and one patient sustained a contralateral posterior cruciate ligament sprain. Conclusions: Mid-term outcomes of patients treated with hybrid transepiphyseal ACLR using QT autograft are promising, with a high return to sport and relatively low graft tear risk compared to previous studies reporting on other graft choices. At a mid-term graft failure risk of 5%, the QT autograft is an excellent option in young skeletally immature athletes.

Purpose/Introduction: The purpose of this study was to evaluate the ASTQT autograft in revision ACL reconstruction in athletes compared to bone-patellar tendonbone (BTB) autograft.Methods: A retrospective study was performed on all athletes undergoing revision ACL reconstruction between August 2013 and December 2019.Patients participating in high-school or college athletics undergoing first-time revision with either ASTQT or BTB autograft with 2 or more years of follow up were included.Demographic variables, complications, return to sport, and outcome scores including the IKDC and Lysholm were collected and compared between the two cohorts.Results: A total of 58 revision ACL reconstructions were included.Return to sport at the same level occurred in 62.5% of the ASTQT and 53.8% of the BTB group The ASTQT group returned to sport significantly faster than the BTB group (8.9 months vs. 10.3 months, p ¼ 0.020).There was no difference in re-tear rates or other complications between the two groups.Both the IKDC and Lysholm scores were significantly higher at the 6-and 12-month follow-up for the ASTQT autograft group compared to the BTB group.However, IKDC and Lysholm scores were similar between both groups at final follow-up.There was no significant clinical difference in the absolute difference in scores or rate of achieving clinical thresholds between the two cohorts.Conclusion: ASTQT autograft for revision ACL in athletes has similar outcomes as compared to BTB autograft.However, the QT may possibly afford quicker return to sport and better early improvements in patient reported outcomes that normalize by one year.The soft tissue quadriceps autograft should be considered as a viable graft option in revision ACL reconstruction in athletes.Disclosure(s): Dr. Economopoulos

Background: Transient traumatic neuropraxia of either the brachial plexus or cervical nerve root(s) is commonly described as a "stinger" or "burner" by the athlete. Stingers in American Football commonly occur acutely as isolated injuries; however, concomitant injuries, including cervical spine pathologies, have also been reported.Hypothesis: Among National Football League (NFL) athletes, the incidence rate of stingers is higher during the regular season than during the preseason and among positions with high velocity impacts such as running backs, linebackers, defensive backs, and receivers.Study Design: Retrospective epidemiology study.Level of Evidence: Level 4.Methods: Aggregation of all in-game injuries with a clinical impression of "neck brachial plexus stretch" or "neck brachial plexus compression" entered into the NFL injury surveillance database through the centralized league-wide electronic medical record system over 5 years (2015-2019 seasons). Incidence rates per player-play were calculated and reported.Results: A total of 691 in-game stingers occurred during the study period, with a mean of 138.2 per year. Average single-season injury risk for incident stinger was 3.74% (95% CI, 3.46%-4.05%). The incidence rate was higher during regular season games than during preseason games (12.26 per 100,000 player-plays [11.30-13.31] vs 8.87 [7.31-10.76], P < 0.01, respectively). The highest reported stinger incidence rates were among running backs and linebackers (both >15 per 100,000 player-plays). Among stingers, 76.41% did not miss time. Of those that resulted in time lost from football activities, mean time missed due to injury was 4.79 days (range, 3.17-6.41 days). Concomitant injuries were relatively low (7.09%).Conclusion: In-game stinger incidence was stable across the study period and occurred most frequently in running backs and linebackers. Stingers were more common during the regular season, and most players did not miss time. Concomitant injuries were relatively rare.Clinical Relevance: An improved understanding of the expected time loss due to stinger and concomitant injuries may provide insight for medical personnel in managing these injuries.

Background:There is a lack of published information outlining the use of biologics in National Football League (NFL) athletes and limited data to guide biologic treatment strategies. Purpose:To develop a consensus on the use of biologics among NFL team physicians. Study Design:Consensus statement. Methods:A working group of 6 experts convened a consensus process involving NFL team physicians using validated Delphi methodology. Physicians from 32 NFL teams as well as NFL London were invited to take part. This iterative process was used to define statements on the use of biologics in NFL athletes. A recent scoping review exploring biologics in professional athletes was used to inform the first of 3 rounds of surveys, with statements considered under 7 headings: biologics in general, challenges of treating NFL athletes, terminology/nomenclature, autologous blood products, cell-based therapies, guidance for NFL team physicians, and biologic research in the NFL. In addition to rating agreement, experts were encouraged to propose further items or modifications. Predefined criteria were used to refine item lists after each survey. For a consensus within the final round, defined a priori, items were included in the final information set if a minimum of 75% of respondents agreed and fewer than 10% disagreed. Results:Physicians from 26 NFL teams and NFL London responded to the initial invitation to participate in the Delphi process; 88.9% of participating team physicians completed the round 1 survey, with response rates of 87.5% in round 2 and 95.2% in round 3. After 3 rounds, 47 statements reached a consensus. A consensus was achieved that platelet-rich plasma has a positive impact on patellar tendinopathy and on symptoms in early osteoarthritis but not for other indications. NFL team physicians agreed that while cell therapies have the potential to improve symptoms, the misrepresentation of uncharacterized preparations as "stem cells" has contributed to the widespread use of unproven therapies. Conclusion:This study established an expert consensus on 47 statements relating to the use of biologics in NFL athletes. In addition to providing clinical guidance for the use of biologics in NFL athletes, this study identified key areas for future focus including the development of athlete education materials.

Purpose:To characterize the secondary anterior cruciate ligament (ACL) injury rates after primary allograft anterior cruciate ligament reconstruction (ACLR) and to identify the age cut-score at which the risk of allograft failure decreases.Methods:All patients who underwent primary ACLR within a single orthopaedic department between January 2005 and April 2020 were contacted at a minimum of 2 years post-ACLR to complete a survey regarding complications experienced post-surgery, activity level, and perceptions of knee health. Patients were excluded for incidence of previous ACLR (ipsilateral or contralateral) and/or age younger than 14 years. Relative proportions were calculated, binary regression analysis was performed, and receiver operating characteristic analysis was used to identify the threshold age for maximal sensitivity and specificity to predict high risk of allograft failure, defined as undergoing revision ACLR.Results:Of the 939 surveys completed, 398 patients underwent primary allograft ACLR (mean age 39.5 years; range 16.0-66.1 years; 54.3% female). The secondary ACL injury rate was 11.6% (5.8% ipsilateral revision ACLR, 5.8% contralateral ACL injury). Male and female patients had similar revision (5.5% male, 6.0% female, P = .82) and contralateral ACL injury rates (6.6% male, 5.1% female, P = .52). Receiver operating characteristic analysis indicated that age ≤34 years was threshold for differentiating high risk of allograft failure (area under the curve 0.65, 95% confidence interval 0.55-0.76; P = .014). Patients aged ≤34 years had a greater secondary injury rate than patients >34 years (20.4% (10.2% revision ACLR, 10.2% contralateral ACL injury) versus 6.9% (3.5% revision ACLR, 3.5% contralateral ACL injury; P < .001). Binary regression analysis demonstrated that decreasing age was associated with increased risk of graft failure (χ2 = 7.9, P = .02.).Conclusions:Allograft ACLR showed similar failure rates between sexes but displayed suboptimal graft failure outcomes in younger and active patients. By age 34 years, the increased revision risk for younger patients diminished.Level of Evidence:Level IV, therapeutic case series.

Optimal timing of anterior cruciate ligament reconstruction (ACLR) remains under debate. Prolonging time between injury and ACLR risks damaging the meniscus and chondral surface, as well as delays return to play. Early ACLR may be associated with postoperative stiffness or arthrofibrosis. We emphasize that optimal timing for ACLR depends on criterion-based return of knee range of motion and quadriceps strength, not a quantitative temporal period. The length of time is far less important that the quality of prereconstruction care provided. Prereconstruction care includes “prehabilitation,” including prone hangs focusing on optimizing knee range of motion, postinjury effusion resolution, and mentally preparing the patient for postoperative expectations. Defining preoperative criteria for proceeding with surgery is crucial to decrease the risk of arthrofibrosis. Some patients meet these criteria within 2 weeks, whereas others linger to 10 weeks. Reduction in arthrofibrosis requiring surgical intervention is multifactorial and not solely dependent on the length of time between injury and intervention.

Subchondral bone marrow lesions (BMLs) are areas of disease within subchondral bone that appear as T1 hypointense and T2 hyperintense ill-defined areas of bone marrow on magnetic resonance imaging. The most common bone marrow lesions include subchondral lesions related to osteoarthritis, osteochondral defects, and avascular necrosis. Emerging therapies include autologous biologic therapeutics, in particular mesenchymal stem cells (MSCs), to maintain and improve cartilage health; MSCs have become a potential treatment option for BMLs given the unmet need for disease modification. Active areas in the preclinical research of bone marrow lesions include the paracrine function of MSCs in pathways of angiogenesis and inflammation, and the use of bioactive scaffolds to optimize the environment for implanted MSCs by facilitating chondrogenesis and higher bone volumes. A review of the clinical data demonstrates improvements in pain and functional outcomes when patients with knee osteoarthritis were treated with MSCs, suggesting that BM-MSCs can be a safe and effective treatment for patients with painful knee osteoarthritis with or without bone marrow lesions. Preliminary data examining MSCs in osteochondral defects suggest they can be beneficial as a subchondral injection alone, or as a surgical augmentation. In patients with hip avascular necrosis, those with earlier stage disease have improved outcomes when core decompression is augmented with MSCs, whereas patients in later stages post-collapse have equivalent outcomes with or without MSC treatment. While the evidence for the use of MSCs in conditions with associated bone marrow lesions seems promising, there remains a need for continued investigation into this treatment as a viable treatment option.

Articular cartilage injuries have a limited healing capacity and, due to inflammatory and catabolic activities, often experience progressive degeneration towards osteoarthritis. Current repair techniques generally provide short-term symptomatic relief; however, the regeneration of hyaline cartilage remains elusive, leaving both the repair tissue and surrounding healthy tissue susceptible to long-term wear. Therefore, methods to preserve cartilage following injury, especially from matrix loss and catabolism, are needed to delay, or even prevent, the deteriorative process. The goal of this study was to develop and evaluate a cartilage-penetrating hyaluronic-acid (HA) hydrogel to improve damaged cartilage biomechanics and prevent tissue degeneration. At time zero, the HA-based hydrogel provided a 46.5% increase in compressive modulus and a decrease in permeability after simulated degeneration of explants (collagenase application). Next, in a degenerative culture model (interleukin-1β [IL-1β] for 2 weeks), hydrogel application prior to or midway through the culture mitigated detrimental changes to compressive modulus and permeability observed in non-treated explants. Furthermore, localized loss of proteoglycan was observed in degenerative culture conditions alone (non-treated), but hydrogel administration significantly improved the retention of matrix elements. Finally, NITEGE staining and gene expression analysis showed the ability of the HA gel to decrease chondrocyte catabolic activity. These results highlight the importance of reinforcing damaged cartilage with a biomaterial system to both preserve tissue content and reduce catabolism associated with injury and inflammation.

ABSTRACT:Musculoskeletal injuries are common in American football, with an incidence ranging from approximately 10 to 35 per 1000 playing hours. Injuries occur more commonly in games than in practice. Although several studies have analyzed specific injury types in football, this review aims to describe the most common knee injuries sustained by American football players and to review the existing literature pertaining to the radiologic findings used in the diagnosis of these injuries.

Background: The COVID-19 pandemic has led to changes to in-office orthopedic care, with a rapid shift to telemedicine. Institutions’ lack of established infrastructure for these types of visits has posed challenges requiring attention to confidentiality, safety, and patient satisfaction. Purpose: The aim of this study was to analyze the feasibility of telemedicine in orthopedics during the pandemic and its effect on efficiency and patient satisfaction. Methods: Patients seen by the Emory University Department of Orthopaedics Sports Medicine and Upper Extremity Divisions via telemedicine from March 23 to April 24, 2020, were contacted by telephone. Each patient was asked to respond to questions on satisfaction, ease of use, and potential future use; satisfaction with telemedicine and previous clinical visits were measured using a modified 5-point Likert scale. Results: Of the 762 patients seen, 346 (45.4%) completed the telemedicine questionnaire. Satisfaction varied by visit type, with average scores of 4.88/5 for in-office clinic visits versus 4.61/5 for telemedicine visits. There was no significant difference among age groups for satisfaction ratings. Patients 65 years old or older reported significantly longer visit times and decreased ease of use with the telemedicine platform. Conclusion: Telemedicine in a large orthopedics department was successfully implemented without compromising patient satisfaction. The use of telemedicine allows many patients to be seen quickly and efficiently without diminishing their musculoskeletal clinical experience.

The athlete's hip is complex when it comes to the surrounding musculature-approximately 21 different muscles can cross the hip and pelvis region, all synchronously working to maintain pelvic stability and functional hip activities. Commonly injured muscle groups for high-level athletes include flexors, adductors, abductors, and/or proximal hamstring musculotendinous complex. These muscle groups work in harmony; however, each has an independent function and propensity for injury. Rehabilitation phases for each injury group can be broken down into 3 phases: acute management, strengthening, and return-to-sport or return-to-competition phase. Specific rehabilitation principles and modalities are described for each injury group.

We aimed to objectively compare the effects of wearing newer, higher-ranked football helmets (HRank) vs. wearing older, lower-ranked helmets (LRank) on pre- to post-season alterations to neuroimaging-derived metrics of athletes’ white matter. Fifty-four high-school athletes wore an HRank helmet, and 62 athletes wore an LRank helmet during their competitive football season and completed pre- and post-season diffusion tensor imaging (DTI). Longitudinal within- and between-group DTI metrics [fractional anisotropy (FA) and mean/axial/radial diffusivity (MD, AD, RD)] were analyzed using tract-based spatial statistics. The LRank helmet group exhibited significant pre- to post-season reductions in MD, AD, and RD, the HRank helmet group displayed significant pre- to post-season increases in FA, and both groups showed significant pre- to post-season increases in AD ( p ’s < .05 [corrected]). Between-group analyses revealed the pre- to post-season increase in AD was significantly less for athletes wearing HRank compared to LRank ( p < .05 [corrected]). These data provide in vivo evidence that wearing an HRank helmet may be efficacious for preserving white matter from head impact exposure during high school football. Future prospective longitudinal investigations with complimentary imaging and behavioral outcomes are warranted to corroborate these initial in vivo findings.

Background: The Patient Protection Affordable Care Act has expanded Medicaid eligibility in recent years. However, the provisions of the act have not translated to improved Medicaid payments for specialists such as orthopaedic surgeons. The number of health care practitioners who accept Medicaid is already decreasing, with low reimbursement rates being cited as the primary reason for the trend. Hypothesis: Private practice orthopaedic groups will see patients with Medicaid or Medicare at lower rates than academic orthopaedic practices, and business days until appointment availability will be higher for patients with Medicaid and Medicare than those with private insurance. Study Design: Cross-sectional study. Methods: Researchers made calls to 2 regular-sized orthopaedic practices, 1 small orthopaedic practice, and 1 academic orthopaedic practice in each of the 50 states in the United States. Callers described a scenario of a recent injury resulting in a bucket-handle meniscal tear and an anterior cruciate ligament tear seen on magnetic resonance imaging at an outside emergency department. For a total of 194 practices, 3 separate telephone calls were made, each with a different insurance type. Data regarding insurance acceptance and business days until appointment were tabulated. Student t tests or analysis of variance for continuous data and χ2 or Fisher exact tests for categorical data were utilized. Results: After completing 582 telephone calls, it was determined that 31.4% (n = 59) did not accept Medicaid, compared with 2.2% (n = 4) not accepting Medicare and 1% (n = 1) not accepting private insurance (P < .001). There was no significant association between type of practice and Medicaid refusal (P = 0.12). Mean business days until appointment for Medicaid, Medicare, and private insurance were 5.3, 4.1, and 2.9, respectively (P < .001). Conclusions: Access to care remains a significant burden for the Medicaid population, given a rate of Medicaid refusal of 32.2% across regular-sized orthopaedic practices. If Medicaid is accepted, time until appointment was significantly longer when compared with private insurance.

We present the first known case of bilateral, acute ruptures of the subscapularis tendons following a bicycle accident in a 43-year-old male. He underwent right shoulder arthroscopic, anatomic subscapularis tendon repair two weeks postinjury, with the left side staged for surgical treatment six weeks after the index procedure. Postoperatively, the patient remained in a sling for 6 weeks before advancing with therapy protocols. The interval between arthroscopic treatments allowed for independence with activities of daily living and focused, early therapy for each shoulder. This approach yielded a right-sided constant score of 89 and subjective shoulder value of 90%; the left side was 87 and 90%, respectively, at 33 months postoperatively. The patient’s only postoperative complaint was slightly diminished external rotation, a near-universal limitation after unilateral repair. This represents a successful outcome that balances functional independence, concentrated rehabilitation, and adherence to safe indications for primary repair. While bilateral traumatic shoulder injuries in a young person is a rare clinical entity, early and staged treatment can lead to good patient outcomes.

The National Football League's (NFL) 2011 collective bargaining agreement (CBA) with its players placed a number of contact and quantity limitations on practices and workouts. Some coaches and others have expressed a concern that this has led to poor conditioning and a subsequent increase in injuries. We sought to assess whether the 2011 CBA's practice restrictions affected the number of overall, conditioning-dependent, and/or non-conditioning-dependent injuries in the NFL or the number of games missed due to those injuries. The study population was player-seasons from 2007-2016. We included regular season, non-illness, non-head, game-loss injuries. Injuries were identified using a database from Football Outsiders. The primary outcomes were overall, conditioning-dependent and non-conditioning-dependent injury counts by season. We examined time trends in injury counts before (2007-2010) and after (2011-2016) the CBA using a Poisson interrupted time series model. The number of game-loss regular season, non-head, non-illness injuries grew from 701 in 2007 to 804 in 2016 (15% increase). The number of regular season weeks missed exhibited a similar increase. Conditioning-dependent injuries increased from 197 in 2007 to 271 in 2011 (38% rise), but were lower and remained relatively unchanged at 220-240 injuries per season thereafter. Non-conditioning injuries decreased by 37% in the first three years of the new CBA before returning to historic levels in 2014-2016. Poisson models for all, conditioning-dependent, and non-conditioning-dependent game-loss injury counts did not show statistically significant or meaningful detrimental changes associated with the CBA. We did not observe an increase in injuries following the 2011 CBA. Other concurrent injury-related rule and regulation changes limit specific causal inferences about the practice restrictions, however.

Background: In the currently published literature, a higher risk for developing arthrofibrosis after anterior cruciate ligament (ACL) reconstruction has been reported for female patients, adolescents, early surgery or concomitant procedures, and the use of a patellar tendon autograft. There is a lack of evidence regarding other graft choices or factors. Hypothesis: Multiple risk factors will play a significant role in the development of arthrofibrosis after ACL reconstruction. Specifically, we hypothesized that the risk of manipulation under anesthesia (MUA) and/or lysis of adhesions (LOA) would be affected by graft choice and patient demographic factors. Study Design: Case-control study; Level of evidence, 3. Methods: The charts of all patients who underwent ACL reconstruction over a 10-year period at a single academic institution were queried from an electronic medical record database and reviewed at a minimum of 6 months after ACL reconstruction, with the collection of demographic and surgical data. The relative risk for undergoing MUA and/or LOA was calculated for each analyzed risk factor. Results: A total of 2424 ACL reconstructions were included, with a chart review at a mean of 56.7 months after surgery (range, 7.6-124.0 months). The rate of MUA and/or LOA for arthrofibrosis was 4.5%. A statistically significantly increased relative risk was found for infection (5.45), hematoma requiring evacuation (3.55), ACL reconstruction with meniscal repair (2.83), use of a quadriceps tendon autograft (2.68), age <18 years (2.39), multiple concomitant procedures (1.69), contact injury (1.62), female sex (1.60), and surgery within 28 days of injury (1.53), and a statistically significantly decreased relative risk was found for revision ACL reconstruction (0.30), age >25 years (0.34), and use of a tibialis anterior allograft (0.36). In the multivariate regression model, the use of a quadriceps tendon autograft (P = .00007), infection (P = .00126), and concomitant meniscal repair (P = .00194) were independent risk factors, whereas revision ACL reconstruction (P = .0024) was an independent protective factor. Conclusion: Graft type, infection, concomitant meniscal repair, and primary reconstruction are significant risk factors for undergoing MUA or LOA after ACL reconstruction.

Although most ACL injury prevention programmes encourage greater hip and knee flexion during landing, it remains unknown how this technique influences tibiofemoral joint forces. We examined whether a landing strategy utilising greater hip and knee flexion decreases tibiofemoral anterior shear and compression. Twelve healthy women (25.9 +/- 3.5 years) performed a drop-jump task before and after a training session (10-15 min) that emphasised greater hip and knee flexion. Peak tibiofemoral anterior shear and compressive forces were calculated using an electromyography (EMG)-driven knee model that incorporated joint kinematics, EMG and participant-specific muscle volumes and patella tendon orientation measured using magnetic resonance imaging (MRI). Participants demonstrated a decrease in peak anterior tibial shear forces (11.1 +/- 3.3 vs. 9.6 +/- 2.7 N . kg(-1); P = 0.008) and peak tibiofemoral compressive forces (68.4 7.6 vs. 62.0 +/- 5.5 N . kg(-1); P = 0.015) post-training. The decreased peak anterior tibial shear was accompanied by a decrease in the quadriceps anterior shear force, while the decreased peak compressive force was accompanied by decreased ground reaction force and hamstring forces. Our data provide justification for injury prevention programmes that encourage greater hip and knee flexion during landing to reduce tibiofemoral joint loading.

Impaired muscle function of the quadriceps and hamstring muscles is commonly observed following anterior cruciate ligament reconstruction (ACLR), which makes these muscles primary targets during post-ACLR rehabilitation. The changes in quadriceps and hamstrings muscle morphology, however, have not been investigated following ACLR using an allograft in which the donor site morbidity accompanied with autografts is avoided. PURPOSE: To examine muscle volume of the quadriceps and hamstring muscles in females following ACLR using an allograft. METHODS: Seven females (mean age: 25.1 ± 2.6 years) with unilateral ACLR using an allograft participated. The average time from surgery was 30.3 ± 18.7 months. All subjects had completed rehabilitation and had been cleared to return to full activity by their orthopaedic surgeons. Magnetic resonance images were used to quantify volumes of the quadriceps, hamstrings, and subcutaneous fat for the distal two-thirds of both thighs, starting from the base of the patella. Differences between the injured and uninjured limbs were examined using Wilcoxon signed-rank tests. RESULTS: The overall quadriceps muscle volume of the reconstructed limb was 7.3 ± 6.4 % (p = 0.043) smaller when compared to the uninjured limb. The lower quadriceps volume of the reconstructed limb was a result of a smaller volume of the vastus lateralis (smaller by 7.9 ± 8.2 %, p = 0.043) and vastus medialis (smaller by 10.3 ± 9.1 %, p = 0.043) when compared to the uninjured limb. No differences between the two limbs were observed for the entire or individual hamstring muscles. While subcutaneous fat volume of the reconstructed limb was 2.7 ± 3.6 % greater compared to the uninjured limb, this difference was not statically significant (p = 0.063). CONCLUSION: Females who have undergone ACLR using an allograft do not demonstrate a change in the hamstring muscle volume as previously reported in individuals with ACLR using a semitendinosus-gracilis autograft. However, our findings of selective atrophy in the vastus lateralis and vastus medialis suggest that factors other than donor tissue integrity (e.g., unloading, muscle inhibition, etc.) may be responsible for the impaired quadriceps muscle function following ACLR using an allograft.