Intact PCL is a potential predictor of ACL graft size in the skeletally immature knee and other anatomic considerations for ACL reconstruction

Purpose To develop a method for using an intact posterior cruciate ligament (PCL) as a predictor of anterior cruciate ligament (ACL) graft size and examine possible differences in tunnel length based on all-epiphyseal drilling method. Methods One hundred one patients 5–18 years of age with magnetic resonance imaging (MRI) of the knee at an outpatient pediatric orthopaedic clinic from 2008 to 2020 were included. ACL and PCL coronal, sagittal, and length measurements were made in all patients. Tunnel length measurements were made in patients with open physes. Statistical analyses were performed to evaluate potential associations in patient bony or ligamentous measurements. Results PCL sagittal width and PCL coronal width were statistically significant predictors of ACL sagittal width and ACL coronal width, respectively (p = 0.002, R = 0.304; p = 0.008, R = 0.264). The following equations were developed to calculate ACL coronal and sagittal width measurements from the corresponding measurement on an intact PCL; ACL Coronal Width (mm) = 6.23 + (0.16 x PCL Coronal Width); ACL Sagittal Width (mm) = 5.85 + (0.53 x PCL Sagittal Width). Mean tibial maximum oblique length (27.8 mm) was longer than mean tibial physeal sparing length (24.9 mm). Mean femoral maximum oblique length (36.9 mm) was comparable to mean femoral physeal sparing length (36.1 mm). Both were longer than mean femoral straight lateral length (32.7 mm). Conclusion An intact PCL is a predictor of native ACL size. Tunnel length differs based on chosen drilling method in all-epiphyseal technique. Level of evidence Diagnostic Level III.

Mineralized Tissue Changes Within the Anterior Cruciate Ligament Entheses Following a Tear

Background: Thirty-percent of patients under 20 years of age suffer a primary ACL graft failure. Young patients show significant bone loss at the femoral ACL-bone insertion site (enthesis). We hypothesize that active bone resorption during ACL graft fixation contributes to poor graft survival in the young. We investigated distal femoral and entheseal bone morphology changes after injury in a novel mouse model to determine if previously reported post-injury patient condition anti-translates to the mouse. Confirmation of a similar condition across species will allow us to use this model to spatially and temporally track physiologic processes within this critical region. Methods: We induced an in vivo ACL rupture in 24 10-week C57BL/6J female mice and sacrificed them at 7 and 28 post-injury. Both loaded ipsilateral and non-loaded contralateral knees were 3D imaged and distal femoral and ACL entheseal cortical regions have begun being analyzed. Traits analyzed include 1) cortical (Ct.) mean gray-value density, area (Ar.), thickness (Th.), and bone volume fraction (BV/TV) Statistics: two-way ANOVA and Tukey posthoc. Results: So far, mice are temporally demonstrating bone differences between injured and non-injured knees similar to that of patients at the time of ACL reconstructive surgery. By 7 days there is a steep decline in whole distal femoral epiphysis and ACL femoral entheseal Ct.Ar (-19.84% and -11.46%, respectively) and Ct.Th (-8.09% and -3.52%, respectively). The trend in Ct.Ar loss holds at 28 days (-40.95% and -8.32%, respectively), but not in Ct.Th, which substantially increases (6.26% and 11.05%, respectively). Conclusion: It appears bone loss is rapid following injury, and that by 28 days there is increased porosity within the cortex with new periosteal/endosteal bone formation counteracting this. If true, particularly within the entheseal region, this may prove problematic for long-term graft outcomes when surgery is performed at the time of significant macrophagic activity.

Graft Survivorship After Anterior Cruciate Ligament Reconstruction Based on Tibial Slope

Background: Increased tibial slope (TS) is believed to be a risk factor for anterior cruciate ligament (ACL) tears. Increased TS may also promote graft insufficiency after ACL reconstruction. Purpose: To delineate the relationship between TS and single as well as multiple graft insufficiencies after ACL reconstruction. Study Design: Cohort study; Level of evidence 3. Methods: We retrospectively identified 519 patients who had sustained ACL graft insufficiency after primary or revision ACL reconstruction (1 graft insufficiency, group A; 2 graft insufficiencies, group B; and ≥3 graft insufficiencies, group C). In addition, a subgroup analysis was conducted in 63 patients who received all surgical interventions by 2 specialized high-volume, single-center ACL surgeons. TS was measured by an observer with >10 years of training using lateral knee radiographs, and intrarater reliability was performed. Multiple logistic and univariate Cox regression was used to assess the contribution of covariates (TS, age, sex, and bilateral ACL injury) on repeated graft insufficiency and graft survival. Results: The study included 347 patients, 119 female and 228 male, who were 24 ± 9 years of age at their first surgery (group A, n = 260; group B, n = 62; group C, n = 25). Mean TS was 9.8°± 2.7° (range, 3°-18°). TS produced the highest adjusted odds ratio (1.73) of all covariates for repeated graft insufficiency. A significant correlation was found between TS and the number of graft insufficiencies ( r = 0.48; P < .0001). TS was significantly lower in group A (9.0°± 2.3°) compared with group B (12.1°± 2.5°; P < .0001) and group C (12.0°± 2.6°; P < .0001). A significant correlation was seen between the TS and age at index ACL tear ( r = −0.12; P = .02) as well as time to graft insufficiency ( r = −0.12; P = .02). A TS ≥12° had an odds ratio of 11.6 for repeated ACL graft insufficiency. Conclusion: The current results indicate that patients with a markedly increased TS were at risk of early and repeated graft insufficiency after ACL reconstruction. Because the TS is rarely accounted for in primary and revision ACLR, isolated soft tissue procedures only incompletely address recurrent graft insufficiency in this subset of patients.

Anterior Closing Wedge Proximal Tibial Osteotomy and Revision Anterior Cruciate Ligament Reconstruction With Quadriceps Tendon Autograft

Background: Anterior cruciate ligament (ACL) ruptures are among the most common injuries in young athletes and active adults. Reconstruction of the ACL most often leads to good functional outcomes and return to full activities. However, a number of patients experience ACL graft failures requiring revision surgery. The reasons for ACL graft failure are often multifactorial, though recent attention has been given to elevated posterior tibial slope (PTS) as a risk factor for recurrent ACL injuries. Indications: In patients with 2 or more ACL reconstruction failures with a PTS ≥12 degrees, anterior closing wedge proximal tibia osteotomy (ACWPTO) may be indicated to reduce the risk of recurrent ACL graft failure and allow return to full activities. Technique Description: This surgical technique video demonstrates the ACWPTO using a case example in a young athlete. Preoperative templating on lateral radiograph is used to determine the amount of correction for the closing wedge. The osteotomy is completed using K-wires and a free hand biplanar cutting technique with the tibial tubercle left in place. This is performed with a concomitant revision ACL reconstruction using quadriceps tendon autograft. Results: There are 2 small cases series published with good clinical outcomes and return to sport activities. No ACL graft failures were reported in either study with short-term follow-up. Discussion: In this surgical technique video, we review the literature indicating elevated PTS as a risk factor in ACL injuries and recurrent ACL graft failures. We highlight important technique pearls and pitfalls to avoid complications during the surgical demonstration. Finally, we review postoperative rehabilitation guidelines and clinical outcomes within the existing literature. In patients with recurrent ACL graft failures, ACWPTO provides a safe and reliable technique to correct an elevated PTS and return patients back to full activities with reduced risk of ACL graft re-tear.