Background: Coccyx is named as resemblance to curved beak of the cuckoo. The coccyx is a triangular bone
consisting of three to five segments: the first is the largest, it articulates with the sacrum. The last three segments are smaller
and form a single bony piece. The anterior surface presents three transverse grooves indicating site of fusion of these segments.
Aim of the Work: To study the normal variations of coccyx in number of segments, shape, size, curves, in different age groups
by plain X-ray, MRI scan. Patients and Methods: Study was carried out on 200 normal Egyptian individuals, and were divided
into 4 groups:- First group from the age of 1 up to ˂ 6 years. Second group from the age of 6 years up to ˂ 12 years. Third
group from the age of 12 years up to ˂ 20 years. Fourth group from 20 years up to 40 years. Each one of these groups
comprises 50 persons (25 males & 25 females). A full medical history was taken and each individual was subjected for plain
X-ray on the pelvis (Anteroposterior & Lateral View) to study the variations of the coccyx, forty individuals were subjected to
MRI scan as ten from each group. Results: Three coccygeal segments were present in 138 (68.3%) of individuals. Most of the
subjects had coccyx type I (82; 41.0%) Fig.(2) , II (63; 31.5%), Fig.(3) III (25;12.5%) Fig.(4)IV(19; 9.5%) Fig.(5) and V(11;
5.5%), Fig.(6) Type I being more common among males. Joint subluxation was significantly more present among females. The
sacrococcygeal structures were longer in men than women. However the coccyx was more ventrally angulated among females.
Conclusion: Most of the Egyptian adults have a gently curved forward, or straight, coccyx composed of 3 segments.
Sacrococcygeal morphologic findings that are associated with coccydynia, such as joint subluxation, spicule, and lateral
deviation of coccygeal tip, commonly present in adult persons.