Medial patellofemoral ligament is a part of the vastus medialis obliquus and vastus intermedius aponeuroses attaching to the medial epicondyle

Abstract

Purpose: This study aimed to investigate the bony surface characteristic of the femoral attachment of the medial patellofemoral ligament (MPFL) and the correlation between the relevant layered structures, including muscular aponeurosis and the joint capsule, which contribute to patellofemoral joint (PFJ) stability.

Methods: The morphology of the medial aspect of the medial condyle using micro-computed tomography and analysed cortical bone thickening in 24 knees was observed. For the macroscopic and histological analyses, 21 and 3 knees were allocated, respectively. The Kruskal-Wallis one-way analysis of variance test with Dunn post hoc testing was performed for statistical analysis.

Results: At the level of the adductor tubercle, there were no significant differences in cortical bone thickness. At the level of the medial epicondyle (MEC), cortical bone thickness was considerably greater than that in other areas of the medial condyle (mean ± standard deviation, 0.60 ± 0.20 mm; p < 0.0001). Macroscopic analysis revealed that the deep aponeurosis of the vastus medialis obliquus and the tendinous arch of the vastus intermedius distally formed the composite membrane and adjoined to the joint capsule to firmly attach to MEC, which was located at 41.3 ± 5.7 mm posterior and 14.2 ± 3.1 mm superior to the joint cartilage. Histological analysis showed a composite membrane and adjoining capsule attached to MEC via fibrocartilage.

Conclusion: MPFL could be interpreted as part of the deep aponeurosis of the vastus medialis obliquus (VMO) and the tendinous arch of the vastus intermedius, which combined with the joint capsule to attach to MEC. The cortical bone thickening indicated that the tensile stresses were loaded on MEC in aged cadavers. Involvement of VMO and vastus intermedius aponeuroses in restored graft of MPFL could utilise the dynamic stability of surrounding muscles to mimic a native structure.

Keywords: Adductor tubercle; Aponeurosis; Cortical bone thickness; Joint capsule; Medial epicondyle; Medial patellofemoral ligament; Vastus intermedius; Vastus medialis obliquus.

Fig. 1

Flow diagram of the study enrolment process. Micro-CT micro-computed tomography, VMO vastus medialis obliquus, VI vastus intermedius

Fig. 2

Morphology of the adductor tubercle and medial epicondyle. The medial aspect of the medial condyle of the right femur. The medial epicondyle (MEC; white circle) is located distal to the adductor tubercle (asterisk). The anterior margin of the MEC (dotted line) was remarkable in comparison with the posterior and inferior margins. A The medial condyle was examined using micro-computed tomography (micro-CT). B In the same specimen as A, soft tissues were chemically removed to assess correlations with the micro-CT image. Ant, anterior; Prox, proximal

Fig. 3

Evaluation of cortical bone thickening in the medial condyle of the femur. The cortical thickening maps on the right medial condyle were visualised after processing the micro-computed tomography (micro-CT) images. The thicker the cortical bone of the point, the brighter the colour of the point. A Three-dimensional image of the medial condyle surface. Levels of axial slices are shown as white dotted lines. B Axial image at the middle level of the adductor tubercle (asterisk). The mean cortical bone thickness was measured in each rectangle from the anterior to posterior part of the adductor tubercle (from AT1 to AT5). C Axial image at the level of the apex of the medial epicondyle (white circle). The mean cortical bone thickness was measured in each rectangle from the anterior to posterior part of the medial epicondyle (from ME1 to ME3). The cortical thickness distribution (mm) is shown as the spectrum from black to marine blue, violet, red, orange, yellow, and white. Ant, anterior; Med, medial; Prox, proximal

Fig. 4

Layered relationships between the fibrous structures attached to the medial epicondyle. A The medial aspect of the right femur. The superficial fascia was removed, and the vastus medialis oblique (VMO) muscle is shown. B After removing the muscular portion of the VMO, the sartorius (Sa), gracilis (Gr), and semitendinosus (St) muscles are reflected to the anterior. The deep aponeurosis of the VMO (VMO-da) and posterior part of the composite membrane are exposed. C The VMO-da is reflected anteriorly. The tendinous arch of the vastus intermedius (VI) posterodistally continues to the composite membrane. The dashed line indicates the posterior margin of the tendinous arch of the VI. D The VI is reflected anteriorly. The composite membrane comprising the VMO-da and tendinous arch of the VI attaches to the MEC (black circle). AM, adductor magnus; Ga-m, medial head of the gastrocnemius; RF, rectus femoris; SM, semimembranosus; TCL, tibial collateral ligament; Ant, anterior; Prox, proximal

Fig. 5

Attachment of the compositive membrane on the medial condyle of the femur. The tibia was removed from Fig. 3. A The medial half of the patellar bone and composite membrane, comprising the deep aponeurosis of the vastus medialis obliquus (VMO-da), tendinous arch of the vastus intermedius (VI), and joint capsule, are detached en bloc from the medial condyle of the femur and posteriorly reflected. Black solid lines indicate the proximal edge of the joint cartilage and corresponding part of the joint capsule. B The composite membrane is detached more posteriorly than A, and the adductor tubercle (asterisk) and medial epicondyle (MEC; black circle) are shown. C The composite membrane was detached more posteriorly than B to expose the firmly attached area to the MEC. Black dotted lines indicate the anterior margin of the firmly attached area of the composite membrane and the corresponding part of the membrane. The location of the firmly attached area on the MEC was measured from the medial (X) and proximal (Y) edges of the joint cartilage. D Distally reflecting the joint capsule, the connection between the joint capsule and tendinous arch of the VI is shown. AM, adductor magnus; Ga-m, medial head of the gastrocnemius; SM, semimembranosus; VI, vastus intermedius; Ant, anterior; Prox, proximal

Fig. 6

Histological analyses of the fibrous structures on the medial condyle of the femur. A Illustration of the medial aspect of the right medial condyle showing levels of the histological sections using Masson trichrome stain in B and C with dotted lines. B Axial section at the middle level of the adductor tubercle (asterisk). The deep aponeurosis of the vastus medialis obliquus (VMO-da), tendinous arch of the vastus intermedius (VI), and joint capsule are separated to form each layer. C The axial section at the middle level of the medial epicondyle (black circle in A). The composite membrane, comprising the VMO-da, tendinous arch of the VI, and joint capsule, is attached to the medial epicondyle via fibrocartilage. Ant, anterior; Prox, proximal; Med, medial. Scale, 5 mm