Abstract
The blood supply to the proximal patella is provided primarily via intraosseous vessels
from the inferior patella. Two vascular systems within the patella are distinguished:
Tiny arteries penetrate the middle third of the anterior patellar surface via vascular
foramina and continue in a proximal direction. Additional vessels enter the patella
at its distal pole, between the patellar ligament and the articular surface, and also
run proximally. As a result of the double vascular supply to the distal portion and
the vulnerable blood supply to the proximal part, localized osteonecroses subsequent
to fracture may occur within the patella and nearly exclusively affect the upper portion
of the patella. Such focal regions of osteonecrosis may appear radiographically as
localized regions of hyperdensity within the patella. The aim of this study was to
investigate the extent to which radiologically hyperdense areas, possibly representing
localized osteonecrosis, may occur subsequent to surgical treatment of a patella fracture
and the influence that they have on the outcome of the fracture. Retrospective analysis
of 100 patients who had been treated operatively for a patella fracture from January
1998 to December 2008 was conducted. The subjective pain rating, clinical scores,
and patient satisfaction scores were recorded. Existing X-rays were assessed with
regard to possible increased radiological dense areas. After an average of 60.61 ( ± 33.88)
months, it was possible to perform a clinical follow-up on 60 patients aged 45.48
( ± 18.51) years. Radiographic follow-up of all patients revealed that nine patients
(9%) exhibited a hyperdense area in the proximal patella portion. X-rays showed radiopaque
areas between 1 and 2 months after surgery. In seven cases, the radiological finding
disappeared after six months. In two patients with persisting radiologically dense
areas, bone necrosis was verified by means of magnetic resonance imaging (MRI) examination
and a histological assessment, respectively. The clinical outcome of these patients
with a hyperdense area on the patella, in this small series, was not shown to be worse
than those who demonstrated normal healing. Radiologically hyperdense areas subsequent
to patella fracture may represent partial osteonecrosis caused by localized vascular
compromise. This was confirmed by MRI and histological examinations in two patients
with persistent hyperdense lesions. The clinical outcome of patients with hyperdense
zones seems to be poorer than that of patients without such findings, but no statistical
difference was shown in this small series. It is possible that earlier surgical treatment
and thus a shorter ischemic period as well as tissue-conserving operative techniques
could prevent the occurrence of partial necroses. This hypothesis would require further
study.
Keywords
patella fracture - blood supply - osteonecrosis
