Abstract
BackgroundThe shape of the patella has been considered to be a predisposing factor resulting in patellar instability, but the effects of abnormal patella position during its development are unclear. The present study evaluated patellar morphological changes after patella instability and evaluated the influence of patellar instability on the patella shape.MethodsTwenty rabbits that were 2 months old were included in the study. The left knee of each rabbit, defined as the experimental group (N = 20 knees/group), underwent a medial soft tissue restraint release. The right knee of each rabbit, defined as the control group (N = 20 knees/group), did not undergo any surgical procedures. A CT scan was performed on each knee before surgery and 6 months post-surgery to measure the transverse diameter, thickness, Wiberg index, and Wiberg angle for analysis of the patellar morphological changes. Cross-specimen examination was conducted to evaluate the differences between the experimental group and the control group.ResultsThe four indices remained the same between the two groups before surgery. However, 6 months after surgery, the mean transverse diameter of the patellae in the experimental group was significantly longer than that in the control group (P < 0.001), while the mean thickness in the experimental group was not significantly greater than that in the control group (P = 0.314), resulting in a flattened shape. The Wiberg indices were not significantly different between the two groups. However, the mean Wiberg angle was higher in the experimental group than in the control group (P < 0.001), which resulted in a flattened articular surface of the patella.ConclusionThe sectional shape and articular surface of the patella became more flattened after patella instability in this study, which indicates that patella dysplasia could be caused by patella instability. Clinically, early intervention for adolescent patients with patella instability is important.
Highlights
The shape of the patella has been considered to be a predisposing factor resulting in patellar instability, but the effects of abnormal patella position during its development are unclear
The mean thickness of the patella in the experimental group (4.83 ± 0.55 mm) was not significantly greater than that in the control group (4.66 ± 0.51 mm) (P = 0.314), which resulted in a flattened shape
The mean Wiberg angle was larger in the experimental group than in the control group (P < 0.001), which resulted in a flattened articular surface of the patella (Table 2)
Summary
The shape of the patella has been considered to be a predisposing factor resulting in patellar instability, but the effects of abnormal patella position during its development are unclear. The present study evaluated patellar morphological changes after patella instability and evaluated the influence of patellar instability on the patella shape. The patellofemoral joint is formed by the articulation between the patella and the trochlear groove. The patella is shaped like an upside-down triangle [1]. The patella anatomy reveals a median crest traversing in the articular part of the patella, defining a medial and a lateral facet, and the shape-based classification has been proposed by Wibeeg [2]. The patella plays an essential role in knee functions. It acts as a biomechanical lever arm and improves the effective extension capacity of the
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