Shea, Cooper

Background: An increased posterior tibial slope (PTS) results in greater force on the anterior cruciate ligament (ACL) and is a risk factor for ACL injuries. Biomechanical studies have suggested that a reduction in the PTS angle may lower the risk of ACL injuries. However, the majority of these investigations have been in the adult population. Purpose: To assess the mean medial and lateral PTS on pediatric cadaveric specimens without known knee injuries. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 39 pediatric knee specimens with computed tomography scans were analyzed. Specimens analyzed were between the ages of 2 and 12 years. The PTS of each specimen was measured on sagittal computed tomography slices at 2 locations for the medial and lateral angles. The measurements were plotted graphically by age to account for the variability in development within age groups. The anterior medial and lateral tibial plateau widths were measured. The distance between the top of the tibial plateau and the physis was measured. The independent-samples t test and analysis of variance were used to analyze the measurements. Results: The mean PTS angle for the medial and lateral tibial plateaus was 5.53° ± 4.17° and 5.95° ± 3.96°, respectively. The difference between the PTS angles of the medial and lateral tibial plateaus was not statistically significant ( P > .05). When plotted graphically by age, no trend between age and PTS was identified. Conclusion: This data set offers values for the PTS in skeletally immature specimens without a history of ACL injury and suggests that age may not be an accurate predictive factor for PTS.

Background: Recent research has identified posterior tibial slope as a risk factor for anterior cruciate ligament (ACL) injury, due to increased forces on the ACL with this tibial anatomy. Biomechanical studies suggest that altering a patient’s posterior tibial slope may lower the risk of ACL injury. Due to the presence of an open physis, guided growth may be used to reduce the posterior tibia slope in this high risk skeletally immature population. The primary purpose of this study was to quantify and measure the posterior tibial slope in pediatric knees. Methods: Forty-four pediatric knee CT scans were analyzed using OsiriX, an imaging software. Specimens analyzed were between the ages of 2 and 12 years of age. The proximal tibial slope for each specimen was measured on CT scan sagittal slices at 2 locations: 1) At the medial tibial plateau at the mid region of the medial femoral condyle, as determined on a coronal slice through the femoral condyle; 2) At the lateral tibial plateau at the mid region of the lateral femoral condyle, as determined on the coronal slice through the femoral condyle. The measurement of the posterior tibial slope was determined by placing two lines parallel to the diaphysis of the tibia, one located in the middle of the diaphysis and one located at the most posterior aspect of the diaphysis. The most proximal aspect of both the medial and lateral tibial plateau were then identified and angle measurements were taken in reference to the parallel lines. The angle measurements were plotted graphically by age in order to account for variability in development within age groups. The anterior medial and lateral tibia plateau widths were measured by identifying the mid region of the respective plateaus. From this point, the distance between the top of the tibial plate and the physis was measured. Results: The average posterior tibial slope angle for the medial and lateral tibial plateau were (5.53° ± 4.17°) and (5.95° ± 3.96°) respectively. Independent samples t-test and ANOVA indicate the difference between the posterior tibial slope angle of the medial and lateral tibial plateau were not statistically significant (p < 0.05). When plotted graphically by age, a slight negative trend between age and posterior tibial slope was identified. As age increases, the medial and lateral posterior tibial slope decreases. The mean anterior medial tibial plateau width and lateral tibial plateau width were .99 cm and 1.19 cm respectively. Discussion/Conclusion: ACL primary and secondary injury occur at very high rates in the skeletally immature, especially in females at age 11 and older, and in males at age 13 and older. This data set offers some preliminary values for posterior tibial slope in patients without a history of ACL injury, allowing for comparisons to patients with ACL Injury. Increased tibial slope is a risk factor for ACL injury. In the skeletally immature, one option to alter the tibial slope is the use of guided growth with implants to slow the anterior growth of the proximal tibia, reducing the posterior slope of the tibia, and possibly lower the risk of ACL injury in this high-risk population. [Figure: see text][Figure: see text][Figure: see text][Figure: see text][Figure: see text][Table: see text][Table: see text]

Background: In skeletally immature patients, the MPFL femoral origin as near or below the physis in most age groups. Although MPFL reconstruction procedures that employ patella drill holes facilitate graft tension adjustment, recent research demonstrates significant risk of patella fractures if patella drill holes are utilized. For this reason, the use of patella drill holes may be best avoided, but this technical alteration makes graft tension fixation more challenging during MPFL reconstruction in the skeletally immature. The purpose of this study was to evaluate the feasibility of developing a physeal respecting femoral drill for the MPFL origin with surgical model simulation, which allows for graft tensioning during MPFL reconstruction. Methods: Pediatric cadaveric specimens (n=5) were dissected by a group of fellowship trained pediatric and/or sports orthopaedic surgeons, and these specimens were then subject to CT Scans for the creation of 3D models. Specimens, aged 7, 9, 10, 11 and 11 years, were used to develop surgical simulations. CT Scans were loaded into Osyrix, converted to appropriate file structure, and then 3D models were loaded into Blender (Stichting Blender Foundation, Buikslotermeerplein 161, 1025 ETAmsterdam, the Netherlands). These models were used to evaluate 3D models of the knee, with placement of medial femoral condyle drill holes starting at the MPFL femoral origin, and entering the joint just anterior to the PCL femoral origin. The anatomic goals of the surgical simulation include: 1. Place drill hole at the MPFL origin on the femur. 2 Enter the intercondylar notch region of the femur anterior to the PCL origin allowing for arthroscopic visualization. 3. avoiding the articular cartilage on the medial femoral condyle. 4. Avoid the femoral physis throughout the course of drilling from the femoral MPFL Origin point to the entry location into the intercondylar notch. In the specimens, a full length drill hole was placed with either a 4 or 5 mm drill hole. Results: All specimens were subject to the surgical modeling and simulated drill hole placement. In each case, a drill hole was successfully placed meeting all the goals of the simulation: 1. Starting Point at MPFL, 2. Exit point anterior the PCL origin, 3. Exit point posterior to the articular cartilage, and 4. Avoidance of direct physeal injury. Figures 1 and 2. Conclusion: Setting graft tension during MPFL reconstruction is one of the significant technical challenges during MPFL reconstruction, and appropriate graft position and tension may be the most critical elements of successful MPFL reconstruction. Historically, graft tension has been set on the patella, using drill holes for the MPFL attachment point on the patella, but this technique has been associated with patella fractures. In order to allow for adjustment of graft tension on the femoral side of the MPFL graft during surgical reconstruction, a surgical simulation was developed to confirm the anatomic appropriateness and safety of placement of femoral drill holes which allow for adjustment of graft tension. This surgical simulation model confirms that MPFL femoral origin anatomy can be reproduced with injury to the physis, the PCL, or the articular cartilage of the femoral condyle. This drill hole and graft can be visualized arthroscopically and allow for appropriate graft tensioning during the procedure. [Figure: see text][Figure: see text]