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Singapore Med J 2011; 52(9) : 674
Table I. Quantitative analysis of various parameters of the distal end of the ulnae.
Component Measurement Mean ± SD (mm)
Right-sided ulna
Left-sided ulna
Pole Maximum width 5.40 ± 0.99 6.10 ± 0.67
Seat Maximum height 5.90 ± 0.69 6.90 ± 0.87
Fovea Maximum width 4.50 ± 0.47 4.90 ± 1.10
Styloid process Length 5.20 ± 0.82 5.00 ± 0.67
SD: standard deviation
radius rotates through a 150° arc; further lateral movement
of the radius of around 30° in the direction of rotation
enables this movement to go through approximately 180°
for hand rotation. (4) At the extremes of the movement of
pronation and supination, the ulnar head has little contact
with the articulating sigmoid notch, making the joint
vulnerable. Since the distal part of the ulna is a stable
anatomical point of reference for rotation of the forearm,
the distal part of the radius dislocates volarly or dorsally
with respect to the ulna.
There is general agreement that the mechanism
of injury in an ulnar dorsal dislocation of the DRUJ is
hyperpronation, while the mechanism of injury in ulnar
volar dislocation is hypersupination. Galeazzi-fracture
dislocations can also be associated with fracture of the
ulnar shaft and styloid process in high-energy trauma.
During sporting activities, forceful impact loading on the
thenar side of the hand causes the wrist to be progressively
levered into hyperextension, with ulnar deviation and
intercarpal supination. (5)
Many reports on the diagnosis and treatment of
injuries of the DRUJ under-emphasised the role of
the lower end of the ulna. Many of these irreducible
dislocations commonly have displaced fracture of the
ulnar styloid process as an associated feature. (6) Although
instability of the DRUJ after radius end fracture did not
receive much attention, the residual symptoms related to
DRUJ instability are common. Our anatomical studies
revealed the detailed structural anatomy of the lower
end of the ulna. This study is one of the few to present the
morphometric data of configurations of the lower end of the
ulna. The detailed morphometric data on regular anatomy
in this study would be helpful to the design of ulnar head
prosthesis. Irreparable fracture dislocation of the ulnar
head with concomitant fracture of the radius (Galeazzi
lesion) had been treated by implantation of a Herbert Ulnar
Head Prosthesis, which had yielded good results. (7)
METHODS
The present study, which was conducted over a period of
one year, involved 50 right- and 50 left-sided dry adult
human ulnae of unknown gender belonging to an Indian
population. Approval for the study was obtained from
the institutional ethics committee. A selected number
of specimens were collected from the bone bank of the
anatomy department at our institution, depending on the
availability and time planned to conduct the study. Only
bones that were intact and free from any pathological
or congenital anomalies were selected. Anatomic
measurements were taken using a vernier caliper
(accurate to 0.1 mm). Appropriate statistical analysis
was done wherever applicable. Each ulna was studied for
different features, such as the shape of the pole (articular
surface for articulation with TFCC), maximum width
of the pole along the transverse axis (mm), slope of the
seat (articular surface on the head of ulna for articulation
with radius), maximum vertical height of the seat (mm),
maximum width of the fovea (roughened depression at
the base of the styloid process) along the transverse axis
(mm) (Fig. 1). Also noted were the presence or absence of
vascular foramina in the fovea, the presence or absence
of styloid process, the shape and length (base to apex) of
the styloid process, if any, and the presence or absence of
grooves for extensor carpi ulnaris (ECU).
RESULTS
All quantitative measurements of the pole, seat, fovea
and styloid process of the 50 right- and 50 left-sided
ulnae were taken and tabulated. The mean and standard
deviation of each parameter was calculated (Table I), and
the various shapes of the poles and styloid processes were
noted. The ulna seat (sloping or non-sloping surfaces),
the presence or absence of vascular foramina of the fovea
and that of ECU groove were also observed and their
percentages tabulated (Table II).
DISCUSSION
DRUJ injury can occur in association with fracture of
the forearm or as an isolated phenomenon. A dislocation
of this joint may be simple or complex. The possibility
of DRUJ injury should be kept in mind when treating
wrist, forearm and elbow injuries. The distal end of the