Elevated Patellofemoral and Tibiofemoral T1ρ Relaxation Times Following a First Time Patellar Dislocation

Abstract

Objective The study was performed to evaluate cartilage within the knee following a first-time patellar dislocation, using elevated MRI-based T1ρ relaxation times as an indicator of low proteoglycan concentration. The hypothesis is that MRI-based T1ρ relaxation times for patellofemoral and tibiofemoral cartilage are significantly longer for knees being treated for patellar dislocation than for healthy control knees. Design Twenty-one subjects being treated for a first-time, unilateral dislocation of the patella and 16 healthy controls participated in MRI-based T1ρ relaxation time mapping. Mean relaxation times were quantified for patellofemoral and tibiofemoral regions for injured knees, the contralateral knees, and healthy controls. T1ρ values for each region were compared between the 3 groups with generalized estimating equations. Linear regressions were also performed to correlate T1ρ relaxation times with time from injury. Results The knees with a disloction had longer T1ρ relaxation times than the contralateral knees and control group at the medial patella and longer relaxation times than the control group at the lateral tibia ( P < 0.05). T1ρ relaxation times at the medial patella also decreased with time from injury (r2 = 0.21, P = 0.037). Conclusions Compositional changes to cartilage on the medial patella are related to traumatic impact during a dislocation. Potential exists for cartilage properties at the medial patella to improve with time. Cartilage degradation at the lateral tibia is not directly related to traumatic impact. The current baseline data are a starting point to characterize the pathway from a first-time dislocation to progressive cartilage degradation and osteoarthritis.

T2 Mapping of Patellar Cartilage After a Single First‐Time Episode of Traumatic Lateral Patellar Dislocation

“…On the other hand, according to recent data, 5 the clinical course of the first episode of LPD causes longer T 1 ρ relaxation times due to the proteoglycan loss immediately after trauma, whereas beyond 2 months after LPD, T 1 ρ diminishes down to normal values. The subsequent process of T 1 ρ restoration in the medial patella indicates the ability of cartilage to recover from the initial injury.…”

“…trochlear articular surfaces, which occurs in $85% and 65% of cases, respectively. 4 The primary traumatic impact along with altered biomechanics in the patellofemoral joint may initiate short-term 5 and long-term gradual degeneration of patellar cartilage and can raise the risk of patellofemoral osteoarthritis (OA). 6,7 Recurrent LPD increases the risk of cartilage degeneration.…”

“…Complications of first‐time LPD include 1) redislocation risk (up to 44% of cases 3 ), 2) medial patellofemoral ligament injury (in ~98% of cases 4 ), and 3) chondral damage to patellar and trochlear articular surfaces, which occurs in ~85% and 65% of cases, respectively 4 . The primary traumatic impact along with altered biomechanics in the patellofemoral joint may initiate short‐term 5 and long‐term gradual degeneration of patellar cartilage and can raise the risk of patellofemoral osteoarthritis (OA) 6,7 . Recurrent LPD increases the risk of cartilage degeneration 7 …”

Patellar Dislocation in Adolescent Patients: Influence on Cartilage Properties Based on T1ρ Relaxation Times

“…11,37 The current study adds elevated T1ρ relaxation times for the central trochlear groove. 11 Multiple studies have also used T2 relaxation times to evaluate cartilage beyond the acute phase of injury. After ≥3 dislocations, T2 relaxation times were elevated for cartilage at the medial and central patella, as compared with healthy controls.…”

“…The sample size was designed to achieve a power of 0.8 for an effect size of 1.3, and statistical significance was set at P \ .05 based on effect sizes from previous studies that compared knees with 1 or multiple dislocations with healthy controls. 9,11,14 T1r relaxation times were related to time from most recent dislocation and parameters of alignment and anatomy for the single-and multiple-dislocation groups. Pearson correlations were used if the data met assumptions of normally distributed residuals based on a probability-probability (P-P) plot and homoscedasticity based on a scatterplot of the residuals.…”