Introduction

“Von Luschka” in 1858 was first one to give accurate and detailed description of the uncovertebral joint. Different authors like Girudi, Trolard, Turner, Frykholam have described this joint under different names (1,3)

Uncus is the bony projection on the lateral margin of upper surface of the bodies of lower five cervical vertebra (2,3,5) The lateral part of inferior surface of the body facing the medial surface of the uncus is slightly concave (2,3) and is covered by cartilage. Articulations between these two surface is called Luschka's joint. This prominence is also present in the upper surface of the body of first thoracic vertebrae (2,6) (Figures: 1,2,3)

These joints are located anteromedial to mixed nerve root and posteromedial to vertebral vessels and sympathetic nerve fibers.(1) Well developed larger joints are observed in the mid to lower cervical (C3- C7) regions and smaller joints appear in the most cranial and caudal (C2-C3, C7-T1)levels.(6)

These uncinate processes are easily seen in anteroposterior roentgenogram of typical cervical vertebra (3) (Figure: 4)

Three ossification centers appear for each vertebra: one for the vertebral body and two for the neural arch. Uncus ossifies from ossification center for neural arch. In cervical region part of the neural arch forming uncus is not on the same transverse plane as the body but is cephalad to it. In other regions of the vertebra, ossification centers for body and arch are at same transverse plane. (2,7)

Uncinate processes guide and control the anteroposterior translation which occurs during sagittal motion (4)

Like other joints osteophytes and osteochondrosis can develop in this joint. Clinicians keep in mind about this less studied joint while diagnosing (3)

Materials and methods

We have selected 40 number of adult cervical vertebra of unknown sex which are available in our practical laboratory (excluding damaged ones). We have observed both superior and inferior surface of the body and noted those articular facets.

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Figure 1

Superior surface of cervical vertebra showing A- Uncus. B- Articular facet.

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Figure 2

Superior surface of cervical vertebra showing A-Beveled inferolateral surface.

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Figure 3

Anterior surface of cervical vertebra showing A-Uncus, B- Articulating facet.

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Observation

Among 40 vertebra studied we found articular facets on the medial surface of uncus in 18 vertebrae among these 9 of them had the facet on right, 5 had on left & 4 had facets on both sides.

Out of the 40 vertebra studied articular facets were found on the infero lateral part of the body in 11 vertebrae among these 6 of them had the facet on right, 3 had on left & 2 had facets on both sides.

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Figure 4

Anteroposterior view of x-ray of neck showing A- Uncus, B- Uncovertebral joint.

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Discussion

Frykholm and Hall proposed their theories about the function of uncus , but none of them are able to explain the formation of uncus. According to Tonduny as well as Sherk and Parke described the uncus belonging to the neural arch, but they were not clear about its origin. Hayashi K, Yabuki T. in 1985 studied a specimen of fourth cervical vertebra from seven year old boy. They found that junction between developing body and neural arch gives raise to uncus. (2) We also observed bony projection uncus is located between body and pedicle of cervical vertebrae.

Payne and Spillane, Onofino et al., and Hirsch et al., thought this joint as a degenerative change. Boreadis and Gershon Cohen, stated it to be a true joint, but did not describe how it is formed. Frykholm said that this joint is part of the intervertebral disc. But Orofino et al., Hall, and Tonduny stated that, some of the loose fibrous tissues present at birth or during the fetal period that has different character than the disc tissue is found in the area is absorbed and develops into Luschka's joint. Hayashi K, Yabuki T. described this by microscopic study of sliced fetal spine. (2)

Turner described typical cervical vertebra with two well marked lateral lips on the upper surface and beveled inferior surface laterally. Both these surfaces rest against each other to form a joint. These lateral lips or uncus is easily seen in antero-posterior roentgenogram of typical cervical vertebra (3). Turner proceeds to describe the superior vertebral notch is deeper than inferior because of this joint located antero-medially, which can be seen in oblique roentgenogram. (3)

Uncovertebral joints are small synovial joints measuring 2x4 to 3x6 mm., situated between the bodies lower five cervical vertebra. These are related to mixed nerve roots antero-medially and postero-medially to vertebral artery, vein and sympathetics. (1)

Three dimensional study of joint is done by obtaining sequential cryo-sectioning of the specimens in all three axes and measuring them by obtaining good quality of magnified images by Kumaresan S and his colleague. They found that these synovial joints are located between C2- T1 vertebrae bilaterally. They found no any statistically significant difference between right and left side. Joint is located more ventrally in mid and lower (C3- C7) cervical region compared to cranial (C2- C3) and caudal (C7- T1) (6).

Uncovertebral joints control the anteroposterior translation which occurs during sagittal motion in the neck confirmed by five linear and two angular measurements on each cervical vertebra. (4)