Quads or quins? Atraumatic restricted knee flexion due to accessory quadriceps bands in children

Incidence of the tensor of the vastus intermedius: A cadaveric study

INTRODUCTION

The quadriceps femoris muscle is present in the anterior region of the thigh and is classically described as a muscle with four heads: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. A few years ago, a "fifth head" was described and named the tensor of the vastus intermedius (TVI). The TVI belly is in line with the belly of the vastus lateralis, and its aponeurosis imposes considerable tension on the vastus intermedius, medializing its action, to play a significant role in knee extension.

OBJECTIVE

To perform a study of the TVI incidence in a Brazilian population and describe its variations.

MATERIAL AND METHODS

We dissected lower limbs from cadavers previously fixed in 10% formaldehyde, belonging to the Laboratory of Anatomy of the Department of Morphology of the Biosciences Center of the Federal University of Rio Grande do Norte.

RESULTS

Eighty-one lower limbs were analyzed with only 33 (40.74%) of them presenting TVI. All four types of TVI described by the literature were present in our sample with the following distribution: type 1 with 15.15%; type 2 with 9.1%; type 3 with 33.33%; type 4 with 42.42%.

DISCUSSION

Although the literature points to the TVI as a normal belly of the quadriceps, making it a "quinticeps", our analysis points to the TVI as a variation and probably a matter of regionality. However, the presence of TVI is not a rare case and cannot be disregarded, which makes this study important for anatomists, physiotherapists, physicians, and surgeons.

Anatomy, Morphology and Function of the Tensor of Vastus Intermedius: A Systematic Review

The tensor of vastus intermedius is a newly discovered muscle that is located at the anterior compartment of the thigh. The aim of the present study is to report, assess and synthetize the existing evidence on the anatomy, variation and morphological characteristics of the TVI as well as to examine its clinical importance. A systematic review was performed evaluating both anatomical and medical imaging studies which provided information about TVI anatomy, prevalence, variations and morphological characteristics. The search strategy was conducted in major electronic databases. Two reviewers worked independently to screen all possible references via a title/abstract examination. Methodological quality was examined with the Anatomical Quality Assurance checklist. A total of 295 cadaveric knees were included in the nine studies where in 244 (82.7%) cases the TVI was identified. Based on this evidence, it appears that the TVI is located between the vastus lateralis and vastus intermedius. The muscle belly is located proximally, and it is combined with a broad and flat aponeurosis before forming a tendinous structure that is attached at the medial aspect of the patella. The TVI presented some morphological variations and complex muscle architecture that varied along its length. There is insufficient good quality evidence as more than half of the included studies were ranked as having a "High" risk of bias with various methodological issues. Higher quality studies are recommended to evaluate the TVI morphology to better understand its functional and clinical importance.