Associations between Anterior Cruciate Ligament Injuries and Patella Alta and Trochlear Dysplasia in Adults Using Magnetic Resonance Imaging

Abstract

The aim of this study was to research the associations between anterior cruciate ligament (ACL) injuries and patella alta and trochlear dysplasia in adult patients using magnetic resonance imaging (MRI). This retrospective study included 221 adult patients: 110 with acute complete noncontact ACL tears and 111 without ACL injuries who underwent knee MRI procedures between May 2016 and July 2018. After the ACL injuries were verified using the sagittal proton density images, the patellar height and patellar tendon length were measured on the sagittal T1-weighted images, and the Insall–Salvati ratio (ISR) was calculated. In the axial proton density MRI scans, according to the Dejour and Le Coultre classification of trochlear dysplasia, the knees were classified as normal or as types A, B, C, or D. The patellar length was not significantly different between the patient and control groups (41.5 ± 3.3 vs. 41.0 ± 2.9 mm, respectively). An increased patellar tendon length (46.1 ± 3.9 vs. 44.5 ± 3.4 mm, respectively) and an increased ISR (1.11 ± 0.08 vs. 1.08 ± 0.06, respectively) were measured in the patient group (with the ACL tears). In the group with the ACL tears, the rate of trochlear dysplasia was higher (15.45%) than that in the healthy group (4.5%). Of the 17 trochlear dysplasia patients in the ACL group, 11 were type A (10%), 2 were type B (1.82%), 3 were type C (2.73%), and 1 was type D (0.91%). Results showed increased patellar tendon lengths, ISRs, and trochlear dysplasia in the patients with the ACL injuries when compared with the healthy control group. Although the causative relationship has not yet been clearly elucidated, one should keep in mind that these variations may be risk factors for ACL tears.

Correlation of Femoral Trochlear Dysplasia With Anterior Cruciate Ligament Injury in Skeletally Immature Patients

“…In the literature, only 2 studies have examined the relationship between ACL injury and the 2 aforementioned anatomical phenomena. 1 , 18 Ntagiopoulos et al 18 reported increased prevalence of trochlear dysplasia and patella alta in patients with ACL injury relative to the incidence of femoral trochlear dysplasia and patella alta in the general population. However, there was no significant correlation between femoral trochlear dysplasia and ACL injury in adult patients.…”

Knee biomechanics during squat rising with patella alta and after distal transfer of tibial tubercular surgery

“…Our findings support the theory that the surgery attempted to equalize the quadriceps moment arm and patellar tendon moment arm as it is seen in the intact knee, 2 but the quadriceps leverage remained dominant even after the surgery. The increased anterior directed force is resisted by enlarged ACL tension at higher flexion angles 19,20 as it was illustrated in Figure 10. As ACL load increases, external rotation of the tibia 3 increases (Figure 15).…”

“…In Ecamilla's work (2000), it was argued no ACL force during squatting, however several studies stated the existence of tensional force on ACL during squatting. 16,19,21 The reason of the existence of ACL load in our study might be the absence of the primary muscles that produce posterior directed force during squatting such as hamstrings and gastrocnemius. 21 On the other hand, most of these muscles are tight for children with cerebral palsy and can generate excessive posterior directed force on tibia.…”

“…With distal tubercular transfer, the angle of the patellar tendon relative to the tibia (β) decreases (a), therefore patellofemoral contact force (Fr) diminishes and transferred force from quadriceps (Fq) to patellar tendon (Fpl) increases. 19 Although the tibial rotations became closer to normal as a result of DTTTS, the internal rotation was found as lower and the excursion of the valgus-varus rotations were still slightly higher than normal for high knee flexion angles (Figure 15, 17). The new distal attachment of the patellar tendon may be the reason for the rotational instability (internal-external and valgusvarus) of the knee because it alters the normal loading pattern of the ligaments.…”

“…The PCL force progressively increased for higher flexion angles for normal knee as reviled in literature. 19,21 (Figure 11). Increased tensional load on pPCL in lower flexion angles and earlier initiation of loading pattern on aPCL could be due to induced valgus rotation which is primarily resisted by medial collateral ligaments and PCL.…”