Ipsilateral patellofemoral morphological abnormalities are more severe than those of contralateral joints in patients with unilateral patellar dislocation

Abstract

PurposeTo determine the differences in anatomic parameters between ipsilateral dislocated knees and contralateral non‐dislocated knees in patients with unilateral patellar dislocation and to identify any variations in ipsilateral knees contributing to contralateral anatomic abnormalities. MethodsA total of 82 patients with unilateral patellar dislocation from 2016 to 2019 were retrospectively evaluated. Bilateral anatomic factors, including the tibial tubercle to trochlear groove (TT‐TG) distance, lower limb rotational deformities, trochlear dysplasia, patella tilt, and patellar height, were assessed by CT. ResultsThe study included 46 patients (32 females and 14 males, mean age ± SD 20.5 ± 6.8). The interobserver reliability of each parameter showed excellent agreement. The ipsilateral TT‐TG distance (P = 0.004), patella tilt (P = 0.001), and patellar height (P = 0.01) were greater in the ipsilateral knees than in the contralateral knees. The lateral trochlea inclination (LTI) in the contralateral knees was larger than that in the ipsilateral knees (P = 0.022). There was a significant difference in the distribution of trochlear dysplasia of Dejour between the ipsilateral knees (dislocated side) and the contralateral knees (P = 0.036). However, bilateral femoral and/or tibial torsion, and bilateral knee joint rotation did not differ significantly. Binary logistic regression showed that only ipsilateral LTI revealed significant ORs of 8.83 (P = 0.016) and 7.64 (P = 0.018) with regard to contralateral abnormal tibial torsion and LTI, respectively. ConclusionIn patients with unilateral patellar dislocation, the ipsilateral TT‐TG distance, patella tilt, and patellar height values were larger in the ipsilateral knees than in the contralateral knees, and trochlear dysplasia was more severe in the ipsilateral joints. The risks of contralateral pathological tibial torsion and LTI were 8.8‐ and 7.6‐fold higher, respectively, in patients with abnormal ipsilateral LTI. Level of evidenceLevel IV.

Femoral Anteversion Measured by the Surgical Transepicondylar Axis Is Correlated with the Tibial Tubercle–Roman Arch Distance in Patients with Lateral Patellar Dislocation

“…Trochlear dysplasia has been accepted as the most significant predisposing factor for LPD, and the Dejour classification and LTI are commonly used to evaluate trochlear dysplasia [ 15 ]. P-dAV showed a significant correlation with Dejour classification [ 11 ].…”

“…Patella alta was also considered an important risk factor for LPD [ 15 ]. Research regarding the relation between patellar height and femoral anteversion is scarce.…”

“…Sixth, the anatomical features of the femoral anteversion and the TT-RA distance in patients with growth potential are unclear. Seventh, intra-observer agreements of the parameters were not determined, while we assumed the intra-observer bias to be minimal because both the orthopedist and the radiologist were well trained on the measuring methods, and the parameters included in this study were found to have excellent reliability values by recent studies [ 10 , 15 ].…”

“…Trochlear dysplasia includes four subtypes identified by axial CT slice according to the Dejour classification [ 15 ]. Type A (mild) shows a relatively shallow trochlea; type B shows a flat or convex trochlea; type C has a convex medial trochlear wall and asymmetric facets; type D (severe) presents asymmetric trochlear facets with a cliff.…”

Pathological Thresholds of Segmental Femoral Torsion in Patients With Patellar Dislocation: Influence on Patellofemoral Malalignment

“…Excessive femoral torsion is reported as a risk factor for patellar dislocation. 3 , 10 , 15 Therefore, increased femoral torsion warrants the consideration of FDO in patients with patellar dislocation. 8 , 11 , 17 , 32 – 34 Although the measurements of femoral torsion have proven to be helpful in treating these kinds of patients, the pathological threshold for these measurements has remained controversial for decades.…”