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Background: Static anterior tibial translation (SATT) is radiographically measured to show the amount of tibial translation during the single-leg stance, and thus it is representative of the physiological axial load subjected to the anterior cruciate ligament (ACL) during the stance. Increased SATT has been associated with increased posterior tibial slope (PTS) and is also associated with increased graft failure. Purpose: To compare the SATT value in a control population with that in a population with an isolated ACL injury, as well as to compare the effect of tibial slope on SATT between the 2 groups. Study Design: Cohort study; Level of evidence, 3. Methods: A consecutive series of patients without ligamentous or meniscal injuries between 2019 and 2022 was reviewed. A matched consecutive cohort of patients with nonacute ACL injuries (surgery between 6 and 12 weeks after injury) without concomitant pathology was reviewed. Preoperative SATT and PTS were measured with a previously validated technique on lateral weightbearing knee radiographs. The SATT value was determined, and regression analysis was performed to investigate the relationship between SATT and PTS. Results: In total, 101 controls and 115 patients with an ACL injury were included in this study. The mean SATT was 1.31 mm (SD, 2.44 mm) and the mean PTS was 10.61° (SD, 3.28°) in the control cohort. The SATT was larger (mean, 2.27 mm; SD, 3.36 mm) in the ACL-injured cohort despite the tibial slope measurement being less in the ACL-injured cohort (mean, 9.46°; SD, 2.85°; P =.016). Linear regression analysis showed that for every 1° of increase in PTS, there was a 0.34-mm increase in SATT in the control cohort; however, there was a greater increase of 0.5 mm for every 1° of increase in PTS in the ACL-injured cohort. We found no significant differences in SATT when the cohorts were compared by age (P =.26) or sex (P =.10). Conclusion: The present study reports a reference SATT value of 1.31 mm (SD, 2.44 mm) in a non–ACL-injured cohort, which was lower than in the ACL-injured cohort (mean, 2.27 mm; SD, 3.36 mm). The effect of slope on weightbearing anterior tibial translation was greater in the ACL-injured population than in the control cohort. [ABSTRACT FROM AUTHOR]

Background: Anterior cruciate ligament (ACL) tears can either be treated nonoperatively with physical therapy and then treated operatively if persistent instability is present, or be directly treated operatively. Advantages of early ACL reconstruction surgery include shorter time from injury to surgery and potentially fewer meniscal injuries, but performing early ACL reconstruction in all patients results in surgery in patients who might not need ACL reconstruction. It is important to assess in which patients nonoperative treatment is successful and which patients will require ACL reconstruction and thus might be better treated surgically in an earlier phase. Purpose: To identify patient characteristics that predict the success of nonoperative treatment. Study Design: Cohort study (Prognosis); Level of evidence, 2. Methods: All patients with complete ACL injuries who were evaluated between 2014 and 2017 at our clinic were included. The minimum follow-up was 2 years. The initial treatment and ultimate ACL reconstruction were reviewed. Univariate analysis was performed using Mann-Whitney U tests and chi-square tests and multivariate analysis using binary logistic regression. Results: A total of 448 patients were included with a median age of 26 years and median Tegner level of 7 and mean Tegner level of 6.4. At initial consultation, 210 patients (47%) were treated nonoperatively with physical therapy and 126 of these patients (60%) ultimately required ACL reconstruction. Nonoperative treatment failed in 88.9% of patients <25 years of age, 56.0% of patients 25 to 40 years, and 32.9% of patients >40 years (P <.001); and 41.9% of patients with Tegner level 3 to 6, and 82.8% of patients with Tegner level 7 to 10. Age <25 years (odds ratio [OR], 7.4; P <.001) and higher Tegner levels (OR, 4.2; P <.001) were predictive of failing nonoperative treatment in multivariate analysis. Patients in the failed nonoperative group had longer time from diagnosis to surgery than the direct reconstruction group (6.2 vs 2.2 months; P <.001), and more frequently had new meniscal injuries (17.4% vs 3.1%; P <.001) at surgery. Conclusion: Nonoperative treatment of ACL injuries failed in 60% of patients and was highly correlated with age and activity level. In patients aged 25 years or younger or participating in higher-impact sports, early ACL reconstruction should be considered to prevent longer delay between injury and surgery, as well as new meniscal injuries. [ABSTRACT FROM AUTHOR]

Background: Although the femoral tunnel position is crucial to anatomic single-bundle anterior cruciate ligament (ACL) reconstruction, the recommendations for the ideal femoral footprint position are mostly based on cadaveric studies with small sample sizes, elderly patients with unknown ACL status, and 2-dimensional techniques. Furthermore, a potential difference in the femoral ACL footprint position and ACL orientation between ACL-ruptured and ACL-intact knees has not been reported in the literature. Hypothesis: The femoral ACL footprint position and ACL orientation vary significantly between ACL-ruptured and matched control ACL-intact knees. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Magnetic resonance images of the knees of 90 patients with an ACL rupture and 90 matched control participants who had a noncontact knee injury without an ACL rupture were used to create 3-dimensional models of the femur and tibia. The ACL footprints were outlined on each model, and their positions (normalized to the lateral condyle width) as well as ACL orientations were measured with an anatomic coordinate system. Results: The femoral ACL footprint in patients with an ACL rupture was located at 36.6% posterior and 11.2% distal to the flexion-extension axis (FEA). The ACL orientation was 46.9° in the sagittal plane, 70.3° in the coronal plane, and 20.8° in the transverse plane. The ACL-ruptured group demonstrated a femoral ACL footprint position that was 11.0% more posterior and 7.7% more proximal than that of the control group (all P <.01). The same patients also exhibited 5.7° lower sagittal elevation, 3.1° higher coronal plane elevation, and 7.9° lower transverse plane deviation (all P <.01). The optimal cutoff value of the femoral ACL footprint position to prevent an ACL rupture was at 30% posterior and 12% distal to the FEA. Conclusion: The ACL femoral footprint position might be a predisposing factor to an ACL rupture. Patients with a >30% posterior and <12% distal position of the femoral ACL footprint from the FEA might have a 51.2-times increased risk of an ACL rupture. [ABSTRACT FROM AUTHOR]

Background: Surgical treatment to repair partial anterior cruciate ligament (ACL) injury without reconstruction has demonstrated inconsistent clinical success. Purpose: To examine the long-term clinical outcomes of primary ACL repair combined with biologic healing augmentation in patients with symptomatic partial ACL tears. Study Design: Case series; Level of evidence, 4. Methods: 50 patients (mean age, 29.5 years) with a partial ACL tear and symptomatic knee instability were treated with primary ligament repair in conjunction with marrow stimulation and followed prospectively for a mean duration of 10.2 years (range, 5.3-14.3 years). Comparative analysis of preinjury, preoperative, and postoperative scores using patient-reported assessment instruments was performed to examine clinical outcomes. Correlation of final outcome scores with patient age, type of ACL tear, side-to-side difference in ligamentous laxity, and body mass index (BMI) was performed through use of Spearman rank analysis. Results: 44 patients were available for assessment at final follow-up. The median Tegner Activity Scale score of 7 at final follow-up was the same as the preinjury median score of 7 (P = .128). The mean Marx Activity Scale, International Knee Documentation Committee (IKDC) Subjective, and Lysholm Knee Questionnaire scores were 10.8, 90.4, and 96.2, respectively, at final follow-up. Mean final Knee injury and Osteoarthritis Outcome Score (KOOS) subset assessments of Pain, Symptoms, Activities of Daily Living, Sports, and Quality of Life were 98.6, 97.5, 99.7, 94.3, and 95.6, respectively. Secondary ACL insufficiency occurred in 27% of patients. Clinical outcome scores were similar for all scoring instruments between patients treated for an associated diagnosis of meniscal or articular cartilage injury. No significant correlations of age, BMI, ACL tear type, or laxity and final IKDC Subjective, Lysholm, or KOOS scores were found. Analysis revealed a negative correlation of patient age and Tegner score at preinjury (rs = −0.333, P = .022) and at final follow-up (rs = −0.376, P = .013). The mean side-to-side difference in ligamentous laxity of 3.4 mm at short-term follow-up in those patients who developed secondary ACL insufficiency over the duration of follow-up was significantly greater than the mean of 0.9 mm in those who did not (P = .010). Conclusion: Primary ACL repair combined with biologic healing augmentation to treat select cases of knee instability secondary to incomplete ACL rupture demonstrated good to excellent long-term outcomes in this cohort for those patients who did not experience secondary ACL insufficiency, with high rates of restoration of knee stability and return to preinjury athletic activities. The rate of secondary treatment for recurrent ACL insufficiency over the course of long-term follow-up was greater than would be expected for primary ACL reconstruction. Greater side-to-side differences in objective findings of ligamentous laxity were identified at shorter term follow-up in the patients who later went on to experience symptomatic secondary ACL insufficiency, compared with those who maintained stability long term. [ABSTRACT FROM AUTHOR]

Background: Anterior cruciate ligament (ACL) reconstruction with remnant preservation has been described and related to potential advantages. Literature is lacking regarding gene expression of potential factors related to ligament healing in the ACL remnant and its relation to time from injury. Hypothesis: The mRNA expression of ligament healing factors in the ACL remnant would be higher in acute tears (<3 months from injury) than in intermediate (3-12 months) and chronic (>12 months) injuries. Study Design: Controlled laboratory study. Methods: Gene expression of 21 genes related to ligament healing factors was analyzed in 46 ACL remnants biopsied during surgical reconstruction with quantitative real-time polymerase chain reaction technique. Specimens were divided into 3 groups according to time from injury: acute (<3 months from injury; n = 19), intermediate (3-12 months; n = 12), and chronic (>12 months; n = 15). Histological and immunohistochemical evaluation was performed by analysis of hematoxylin and eosin, CD-34, and S-100 staining. Results: Expression of COL1A1, COL1A2, COL3A1, COL5A1, COL5A2, COL12A1, LOX, PLOD1, and TNC genes in ACL remnant was greater in acute compared with chronic injuries. COL1A1, COL5A1, COL12A1, and TNC genes were also expressed more in the acute group compared with the intermediate group. Furthermore, expression of the genes COL1A1 and COL5A2 was significantly higher in female than in male patients. No difference in the number of blood vessels and mechanoreceptors among groups was observed in the microscopic evaluation. Conclusion: The present study demonstrates that expression of COL1A1, COL1A2, COL3A1, COL5A1, COL5A2, COL12A1, LOX, PLOD1, and TNC genes in ACL remnant is greater in acute (<3 months from injury) compared with chronic (>12 months) injuries. Furthermore, COL1A1, COL5A1, COL12A1, and TNC genes were expressed more in the acute group compared with the intermediate group (3-12 months from injury). Clinical Relevance: ACL reconstructions with remnant preservation should be performed in patients with acute injuries, as in these cases the ACL remnant may present the greatest healing potential. [ABSTRACT FROM AUTHOR]

Background: Biomechanical studies indicate that the tibia shifts medially and has a more valgus orientation in the anterior cruciate ligament (ACL)–deficient knee. However, it is not known whether these differences can be detected on standing radiographs. Purpose: To determine whether medial subluxation and more changes in coronal alignment of the tibia are detectable in both weightbearing radiographs and a cadaveric model simulating quiet standing. Study Design: Case series; Level of evidence, 4, and Descriptive laboratory study. Methods: Radiographic data were available for a cross-section of 74 patients with unilateral ACL tears. Tibial subluxation and coronal limb alignment were measured on hip-to-ankle weightbearing radiographs. Eight cadaveric knees were mounted on a 6 degree of freedom robot. Mediolateral position and varus-valgus alignment of the tibia relative to the femur were measured in response to 300-N axial compression simulating quiet standing at 5° and 15° of flexion with the ACL intact and sectioned. Results: Across all 74 patients included in the clinical study, the ACL-injured knee experienced 1.6 ± 2.3 mm (mean ± SD) of medial tibial subluxation compared with the contralateral uninjured knee (P < .001). The 24 patients with isolated ACL rupture exhibited 2.0 ± 1.8 mm of medial subluxation (P < .001). The mean coronal alignment of all 74 patients in the study was 0.7° ± 2.8° varus in the injured limb and 1.3° ± 2.6° varus in the uninjured contralateral limb (P = .0187). In the cadaveric model, the tibia translated 0.4 ± 0.5 mm more medially after sectioning of the ACL at 15° of flexion (P = .0485); however, no changes in coronal alignment were detected. Conclusion: The tibia shifts medially and is less varus in the ACL-deficient knee on standing radiographs. The medial tibial shift is reproduced in an axially loaded cadaveric model. Clinical Relevance: Medial tibiofemoral subluxation seen on frontal plane standing radiograph is an underappreciated sequela of isolated ACL rupture. The ability of ACL reconstruction to restore this aspect of ACL injury is not well understood and should be investigated further. Cadaveric models may be used to directly measure the mechanical effect of subtle changes in mediolateral position on articular contact stress as an indicator of the importance of this finding. [ABSTRACT FROM AUTHOR]

Background: Patients generally choose to undergo anterior cruciate ligament reconstruction (ACLR) to return to their active lifestyles. However, returning to their previous activity level may result in a retear of their reconstructed knee or an injury to their contralateral anterior cruciate ligament (CACL). Purpose: To determine the risk factors associated with revision ACLR and contralateral ACLR (CACLR), compare the survival of the reconstructed ACL with the CACL, and determine how the risk factors associated with revision ACLR compare with those for CACLR. Study Design: Cohort study; Level of evidence, 3. Methods: A retrospective cohort study of prospectively collected data from the Kaiser Permanente ACLR registry between February 1, 2005, and September 30, 2012, was conducted. Primary ACLR cases without history of contralateral knee ACL injury were included. The study endpoints included revision ACLR and CACLR. Graft type (bone–patellar tendon–bone [BPTB] autograft, hamstring autograft, and allograft) was the main exposure of interest, and patient characteristics were evaluated as risk factors for revision ACLR and CACLR. Survival analyses were conducted. Results: A total of 17,436 ACLRs were evaluated. The median age was 27.2 years (interquartile range, 18.7-37.7 years), and 64% were males. The 5-year survival for index ACLR was 95.1% (95% CI, 94.5%-95.6%), and for CACL it was 95.8% (95% CI, 95.2%- 96.3%). Overall, the cohort had a mean of 2.4 ± 1.7 years of follow-up; 18.2% were lost to follow-up. There were fewer CACLRs per 100 years of observation (0.83) than there were revision ACLRs (1.05) during the study period (P<.001). There was a statistically significant difference in the density of revision ACLR and CACL in BPTB autografts (0.74 vs 1.06, respectively; P = .010), hamstring autografts (1.07 vs 0.81; P = .042), and allografts (1.26 vs 0.67; P<.001). The risk factors for revision ACLR and contralateral surgery were different (P<.05). After adjusting for covariates, factors associated with higher risk of revision ACLR were as follows: allografts, hamstring autografts, male sex, younger age, lower body mass index (BMI), and being white as opposed to black. Factors associated with higher risk of CACLR were as follows: younger age, female sex, and lower BMI. Conclusion: The 5-year revision-free and CACLR-free survival rate in this study was 95.1% and 95.8%, respectively. Allografts and hamstring autografts had a higher risk of revision ACLR surgery, and BPTB autografts had a higher risk of CACLR. Males were found to have a higher risk of revision ACLR, and females had a higher risk of CACLR. Increasing age and increasing BMI decreased the risk of both revision and CACLR. [ABSTRACT FROM AUTHOR]

Background: Identifying predictors of contralateral anterior cruciate ligament (ACL) reconstruction is important to focus preventivestrategies and related research on high-risk groups.Purpose: To investigate predictors of contralateral ACL reconstruction in patients who have already undergone a primary ipsilateralreconstruction.Study Design: Cohort study; Level of evidence, 2.Methods: This study was based on data from the Swedish National Knee Ligament Register from January 1, 2005, to December31, 2013. Patients aged 13 to 59 years who underwent primary ipsilateral (index) ACL reconstruction with hamstring tendon orbone–patellar tendon–bone autografts were included. Follow-up started on date of index ACL reconstruction and ended eitherwith primary contralateral ACL reconstruction, after 5 years of follow-up, or on December 31, 2013, whichever occurred first.The investigated variables were patient sex, age at index reconstruction, activity at the time of index injury, timing of surgery, graftselection, graft harvest site, and meniscal and chondral injury. The study end point was primary contralateral ACL reconstruction.Relative risks (RRs) and 95% CIs were calculated and adjusted for confounding factors using multivariate statistics.Results: A total of 9061 participants were included (n = 5196 males [57.3%] and 3865 females [42.7%]), of which 270 participants(3.0%) underwent primary contralateral ACL reconstruction during the 5-year follow-up. There was no difference in contralateralreconstruction rates between males and females (3.0% vs 2.9%, P = .695). Age \20 years significantly increased the risk of contralateralreconstruction (males: RR = 2.4 [95% CI, 1.7-3.4] and females: RR = 2.9 [95% CI, 1.9-4.5]; P \ .001). Among femalepatients undergoing reconstruction using autograft hamstring, harvest of a contralateral hamstring tendon significantly increasedthis risk (RR = 3.4 [95% CI, 1.4-7.9]; P = .006).Conclusion: In both male and female participants, age \20 years predicted an almost 3 times higher 5-year risk of contralateralACL reconstruction. Among female participants undergoing reconstruction with autograft hamstring, a contralateral harvest predicteda more than 3 times higher 5-year risk of contralateral ACL reconstruction. Patient sex, activity at the time of index injury,graft selection, meniscal injury, and chondral injury were not predictors of contralateral ACL reconstruction. [ABSTRACT FROM AUTHOR]

The article explores the contribution of limited internal femoral rotation to anterior cruciate ligament (ACL) strain during a simulated pivot landing. Topics discussed include the methodology used by the authors in performing their controlled laboratory study, the results of the study that showed peak anteromedial bundle of the ACL (AM-ACL) was inversely proportional to available range of internal femoral rotation.