Abstract
PurposeTo compare weight-bearing cone-beam computer tomography (CBCT) and conventional computer tomography (CT)-based measurements of patellofemoral alignment and stability in patients surgically treated for recurrent patellar dislocation. These scans implied respectively single-leg up-right posture, the knee flexed, and lower limb muscles activation, versus supine position with the knee extended.MethodsA total of 17 patients (11 males/6 females) after surgical reconstruction with fascia lata allograft for recurrent patellofemoral dislocation were analyzed at 60-month follow-up. Tilt and congruence angles and tibial tuberosity–trochlear groove (TT-TG) offset were measured on images obtained from CBCT and conventional CT scans by three independent and expert radiologists. Paired t tests were performed to compare measurements obtained from the two scans. Inter-rater reliability was assessed using a two-way mixed-effects model intra-class correlation coefficient (ICC).ResultsOnly TT-TG offset was found significantly smaller (p < 0.001) in CBCT (mean 9.9 ± 5.3 mm) than in conventional CT (mean 15.9 ± 4.9 mm) scans. ICC for tilt and congruence angles and for TT-TG offset ranged between 0.80–0.94 with measurements in CBCT scans, between 0.52 and0.78 in conventional CT.ConclusionIn patients surgically treated for recurrent patellar dislocation, TT-TG offset was found overestimated with conventional CT. All measurements of patellofemoral stability and alignment were found more consistent when obtained with weight-bearing CBCT compared to conventional CT.
Highlights
The occurrence of patellar instability is a common event in orthopedics, where chronic patellar dislocation is estimated to affect 5.8 cases every 100,000 people, becoming even five times larger in the young population, aged between 10 and 17 years [1, 2]
The purpose of the present study was to compare patellofemoral stability and alignment parameters measured with cone-beam computer tomography (CBCT) under weight-bearing and with knee flexion of 30°, with those obtained with conventional computed tomography (CT) in supine position in patients treated with medial patellofemoral ligament (MPFL) reconstruction for recurrent patellar dislocation, at medium-term follow-up
The tuberosity–trochlear groove (TT-TG) offset was significantly less when acquired with the CBCT scan compared to the conventional CT scan (P < 0.001) for all the three raters
Summary
The occurrence of patellar instability is a common event in orthopedics, where chronic patellar dislocation is estimated to affect 5.8 cases every 100,000 people, becoming even five times larger in the young population, aged between 10 and 17 years [1, 2]. Different surgical options are available for the treatment of recurrent patellar dislocation either individually or in combination: medial patellofemoral ligament (MPFL) reconstruction, tibial tubercle distalization, trochleoplasty, and tibial or femoral osteotomy for correction of rotational or coronal plane malalignments [4]. Recent studies have shown that anatomical MPFL reconstruction is the gold standard technique to treat recurrent patellar luxation/instability, this being executed in isolation or in combination with other surgical procedures [5]. The choice for single or combined techniques for this surgical treatment needs to be assessed according to patient-specific patho-anatomy. Medical imaging is fundamental to assess factors predisposing to instability and to determine the best treatment planning for each specific patient [6]. Nowadays, imaging of the patellofemoral joint is performed with conventional radiographs, magnetic resonance imaging (MRI), and conventional computed tomography (CT) scans [7]
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