Which is longer ulna or radius

Learning Objectives Discuss the radius and ulna. Key Points The radius and the ulna are long, slightly curved bones that lie parallel from the elbow, where they articulate with the humerus, to the wrist, where they articulate with the carpals. The radius is located laterally, near the thumb, and the ulna medially, near the little finger.

The radius and the ulna have a styloid process at the distal end; they are also attachment sites for many muscles. The radius is smaller than the ulna. Key Terms radius : One of two forearm bones, it is located laterally to the ulna. The Ulna Anatomically, the ulna is located medially to the radius, placing it near the little finger.

Proximally, there are five key regions of the ulna: The olecranon is a projection of bone that extends proximally from the ulna. The triceps brachii muscle attaches to the ulna superiorly. Create a personalised content profile. Measure ad performance. Select basic ads. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors.

The radius is the thicker and shorter of the two long bones in the forearm. It is located on the lateral side of the forearm parallel to the ulna in anatomical position with arms hanging at the sides of the body, palms facing forward between the thumb and the elbow. The radius and ulna pivot around one another to allow rotation of the wrist.

Together, along with the humerus, they create the elbow joint. The radius is often thought of as the larger of the two long bones in the forearm because it is thicker than the ulna at the wrist, but it is thinner at the elbow. The ulna is longer than the radius by about an inch in most people, but lengths vary considerably.

Of the two forearm bones, the radius is more likely to suffer a fracture than the ulna. Men and women have similar instances of radius fractures until the mid 40s when they become much more frequent in women than in men. The radius is a long bone, one of the four types of bone in the body. A long bone is a dense, strong bone characterized as being longer than it is wide. The shaft is known as the diaphysis and the end of a long bone is called an epiphysis.

The diaphysis is hollow, with space inside called the medullary cavity. The medullary cavity contains bone marrow. The radius is between 8 to It averages 9. The proximal epiphysis the end at the elbow is about half as wide. As described above, the radius is a typical long bone with dense, hard bone along the shaft diaphysis. The ends of the radius have spongy bone that hardens with age. The radius is located in the forearm, the part of the arm between the elbow and the wrist.

In the anatomical position with the arms straight and palms held forward at the level of the hips, the radius is positioned parallel and lateral to outside of the ulna. In resting position, such as with your hands on a keyboard, the distal far ends of the radius and ulna cross with the radius lying on top of the ulna.

The proximal end of the radius makes up the lateral outer edge of the elbow joint at the distal end of the humerus. The distal end of the radius attaches to the wrist just before the thumb. The pivoting motion of the radius and ulna allow for rotation of the wrist at the distal radioulnar joint. The radius provides stability for the hinge joint at the elbow and allows for motion at the radiohumeral joint, but the ulna and humerus do most of the work there.

There is some movement between the proximal ends of the radius and the ulna called the proximal radioulnar joint. The radius and ulna are connected by a sheet of thick fibrous tissue called the interosseous ligament or the interosseous membrane. A smaller ligament connects the proximal ends of the radius and ulna. It is known as the oblique cord or the oblique ligament and its fibers run in the opposite direction of the interosseous ligament. In some cases, the radius bone may be short, poorly developed, or absent.

One variation seen in the anatomy of the radius is proximal radio-ulnar synostosis, in which the bones of the radius and ulna are fused, usually in the proximal third the third closest to the elbow. The radius allows for movement of the arms and especially provides for the full range of motion of the hand and wrist. When crawling, the radius also can help to provide mobility.

The radius provides bodyweight support when the arms are used during crawling and lifting the weight of the body, such as during pushups.

The radius has seven muscle insertion points for the supinator, biceps brachii, flexor digitorum superficialis, pronator teres, flexor pollicis longus, brachioradialis, and pronator quadratus. We examined two-tailed t-tests to certify the equivalence of the differences in the bilateral radius and ulna, and the level of significance was 0. All length and volume differences were compared between sexes and sides using independent T-tests.

Shape differences of the radius and ulna were also compared between sides utilizing independent T-tests. To assess the reliability of alignment, registration and landmark point creation methods, we randomly selected 14 cases from the original data and randomly re-aligned the selected bones using the same registration method. Landmark points were re-created on the selected bones.

Length, twisting, bending and regional measurement data were compared with ICC tests. We describe significant shape differences of the forearm bones in the S1 File. Table 1 show the results of paired T-tests comparing length and volume. Mean lengths of the radius and ulna were The average length of the radius in males was The average length of the male ulna was The average volumes of the radius and ulna were Paired T-tests revealed that there were statistical significances of length and volume differences of the both forearm bones between the female and male.

Side differences of length and volume and paired T-tests are presented in Table 2. There were no significant differences in right and left female radius measurements.

The average length of the right radius was 1. The average right-side female ulna was 1. The average right radius and ulna were longer than the left in males by 1. There were no significant differences between bilateral forearm bone measurements in either sex 0.

The length of right coronal bowing of females was The location of bowing in the coronal plane was The coronal bowing depth of the right female radius was In males, the length of the right radial bowing was The coronal bowing location of the right male radius was The coronal bowing depth of the right male radius was The measured length of sagittal bowing in females was Sagittal bowing in females was located at The bowing location in the sagittal plane of females was 7.

In males, right sagittal bowing was located at The bowing location in the sagittal plane of male was located in Sagittal depth was 9. The length of the right coronal ulnar bowing in females was Coronal bowing depth of the right female ulna was 7. In males, the length of right coronal ulnar bowing was The coronal bowing location of the right male ulna was located at The coronal bowing depth of the right male ulna was 9.

Ulnar bowing length in the sagittal plane was The location of sagittal bowing for females was The depth of sagittal bowing for females was 6. Bowing location in the sagittal plane of males was located at Sagittal depth was 7. The twisting angle of the female radius was In the male radius, the twisting angle was The ulnar twisting angle of females was Male ulnar twisting angle was Angles with significant shape differences between bilateral bones are marked with dotted red lines on each cross-sectional image.

P , proximal; C , central; D , distal; Pu , upper section of the proximal part; Pm , middle section of the proximal part; Pl , lower section of the proximal part; Cu , upper section of the central part, Cm , middle section of the central part, Cl , lower section of the central part, Du ; upper section of the distal part, Dm ; middle section of the distal part, Dl ; lower section of the distal part.

Our results might be affected by factors related to registration and alignment. To assess the inter-rater reliability of our measures, we performed intraclass correlation coefficient ICC tests. First, we compared the lengths, twisting, and bowing of bilateral radii and ulnae and found that the ICCs were greater than 0.

Then, we compared all measurement values of each section for both forearm bones and found that ICCs ranged from 0. All ICCs therefore satisfy criteria for reproducibility and data reliability. The radius and ulna have a unique anatomical arrangement and complicated anatomical structure that enable the forearm bones to perform supination and pronation.

Due to these distinct movements, complications after severe fracture such as posttraumatic malunion may occur. Despite that symptomatic malunion or pseudarthrosis can occur without symptoms or pain in some cases, posttraumatic malunion of the forearm bones needs to be addressed in many cases [ 21 ].

Malunited forearm bones can limit pronation and supination movement ranges, and result in unstable and painful DRUJ as well as cosmetic deformities. Because of these complications, forearm bone fractures must be restored to proper length and rotational alignment. However, corrections of comminuted forearm bone fractures are not simple. Several researchers have described bilateral asymmetry of the forearm bones.

Auerbach et al. These studies concentrated on only one bone or only on the distal parts of the forearm bones. Malunion can occur if bilateral forearm to the overall shape is not considered, and that leads to dysfunction of forearm bone movement [ 30 , 31 ]. Furthermore, there is few information on regional asymmetry of the forearm bones. In this study, we suggested differences in whole bone parameters and regional shape analysis of the forearm bones.

Length, volume, bowing and twisting differences of the bilateral forearm bones were investigated first, then regional shape differences were analyzed. In particular, many researchers have reported that the radius and ulna have characteristic natural bowing and twisting [ 28 , 32 — 36 ]. According to Dumont et al. In our study, there were no statistically significant differences in bowing or twisting values between the two sides.

In the results of regional shape difference analysis, the proximal and distal sections of both forearms show large differences. The average bilateral difference of the proximal upper section of the radius was 1. In the distal lower section of the radius, the mean bilateral difference was 0. The average bilateral difference of the proximal upper section of the ulna was 0. The minimum and maximum bilateral distances of the proximal upper section of the ulna were 0.

The mean bilateral difference of the distal lower section of the ulna was 0. The bilateral distance values at the ends of forearm bones had large standard deviations, but the differences were not significant. There was a large bilateral difference in the proximal ulna of This difference in the right and left ulna of this sample indicated a rapid change in the shape of the proximal articular portion, especially in the coronoid process.

We observed the same phenomenon in other samples; there were seven of samples with large gaps in the bilateral coronoid process, and this may be a characteristic feature of these samples. None of the samples had deformities associated with fractures or osteophytes that would exclude them from analysis.

However, these samples did not show statistically significant differences between sides. Bilateral radii and ulnae were aligned and registered by the whole bone standard in this study. Whole bone registration can result in findings of differences in the ends of bones, because asymmetry of the left and right forearm bones frequently occurs in terms of length.

Besides, proximal and distal articulations of the radius and ulna have complex shapes. For these reasons, large bilateral differences were detected in the proximal and distal ends of both bones. Bilateral forearm bones should be aligned and registered by proximal or distal ends in studies of asymmetry of articulation shape. On the anterior surface of the radius, significant shape differences were found in the upper section of the central part to the upper section of the distal part.

On the anterior surface of the ulna, proximal lower to central lower sections show significant shape differences Fig 1.