Date Published: June 6, 2012
Publisher: Hindawi Publishing Corporation
Author(s): Gregor Nemschak, Michael L. Pretterklieber.
Even though the vascular supply of the human patella has been object of numerous studies until now, none of them has described in detail the rich arterial supply provided via the infrapatellar fat pad (of Hoffa). Therefore, we aimed to complete the knowledge about this interesting and clinically relevant topic. Five human patellae taken from voluntary body donators were studied at the Department of Applied Anatomy of the Medical University of Vienna. One was dissected under the operation microscope, a second was made translucent by Sihlers-solution, and three underwent angiography using a 3D X-ray unit. The results revealed that the patella to a considerable amount is supplied by arteries coursing through the surrounding parts of the infrapatellar fat pad. The latter were found to branch off from the medial and lateral superior and inferior genicular arteries. Within the infrapatellar fat pad, these arteries formed a dense network of anastomoses which are all contributing to the viability of the patellar bone. Due to the rich arterial supply reaching the patella via the infrapatellar fat pad, it seems advisable to preserve the fat pad during surgery of the knee in order to reduce the risk of vascular impairment of the patella.
The infrapatellar fat pad (of Hoffa) is located in the anterior compartment of the knee joint and is bordered by the inferior pole of the patella, the patellar retinacula, the patellar tendon, the anterior part of the tibia, the anterior horns of the menisci, and the femoral condyles. Further, it is attached to the intercondylar notch of the femur by the infrapatellar synovial plica also referred to as ligamentum mucosum . Because of its high amount of nerve endings, the infrapatellar fat pad may become source of anterior knee pain. As reported by Bennell et al., the application of hypertonic saline into the fat pad led to pain experience in healthy volunteers . In rare cases, tumour-like lesions of the infrapatellar fat pad such as osteochondroma, pigmented villonodular synovitis, synovial cysts , and vascular malformation  may lead to anterior knee pain. Furthermore, the infrapatellar fat pad may be affected by postarthroscopic alterations, postsurgery fibrosis, and shear injuries .
For the presentation of the vascular course within the infrapatellar fat pad of Hoffa, five isolated corpora adiposa were studied at the Department of Applied Anatomy of the Medical University of Vienna. These specimens were taken from two female and three male voluntary body donators which had died at a mean age of 75 years. All parts of this study have been approved by the local ethical board (registration number 919/2010). The first two knee joints were taken from anatomic specimens that had been used in the student dissection courses and, therefore, were perfusion fixed with a mixture of 1.6% formaldehyde solution and 5% phenol solution. One specimen taken from a 79-year-old male individual was dissected layer by layer by means of a surgical microscope (Zeiss OPMI 11; Carl Zeiss GmbH, Vienna); during this procedure, for better visibility, the vessels were injected with Wright’s eosin methylene blue solution (Merck, Art 1383). The injection was carried out with Insulin Syringes (BD Micro-Fine, 1 mL of 0.33 mm (29) × 12.7 mm. BD Medical-Diabetes Care Becton Dickinson France SAS, Le Pont de Claix, France). Microanatomical preparation was carried out by microsurgical forceps and scalpel blade number 15 (Aesculap, Aesculap AG, et. Co. KG.).
After careful removal of the synovial membrane covering the inner aspect of the infrapatellar fat pad, a dense network of superficial vascular anastomoses appeared. These anastomoses were especially concentrated in the central parts of the fat pad including the distal portions adjacent to the patellar tendon. The superficial vascular plexus was formed by afferent vessels entering the fat pad from deep within the knee joint (intercondylar fossa); additional supply was received by branches of the inferior genicular arteries. The superficial vascular plexus only appeared to supply the fat pad itself and its synovial membrane, respectively, since no direct vascular connections to the bone could be detected. After removal of the superficial vascular plexus and careful microdissection of the remaining adipose tissue, a second layer of blood vessels appeared in the intermediate level of the fat pad (Figures 1 and 3). The vessels of the intermediate vascular layer themselves received their supply from the inferior genicular arteries, and laterally also from a branch of the anterior tibial recurrent artery. From within the intercondylar fossa, numerous vessels reached the dense anastomotic network in the central parts of the fat pad ((1) in Figure 2 and (c) in Figure 15(a)).
The main findings of our study revealed that within the central mass of the infrapatellar fat pad, the vessels showed an arrangement of three layers, with the caliber of the vessels increasing from posterior to anterior, that is, towards the patellar tendon. Interconnections between these layers were established by numerous vascular channels. Together, they thus formed a functional unit. Except for the most superficial level, which was only found in the central portions of the infrapatellar fat pad or in the dorsodistal areas of the patellar tendon, both the intermediate and the deep vascular level provided vascular supply to the distal half of the patellar bone.
Until now, the arterial blood supply reaching the patella via the infrapatellar fat pad (of Hoffa) has not been subject of any detailed anatomical dissection, although radiographic presentations have been previously published [7, 11, 13]. Using microanatomical dissection techniques and a sophisticated morphological method to generate translucent specimens as well as multiplanar reconstructed angiograms, we were able to demonstrate the course of anastomoses in the peripatellar portions of the fat pad, especially in its superior aspect, which have obviously been overlooked in previous articles.