The Journal of bone and joint surgery. American volume.
1983 Oct; 65(8): 1116-1124
Postacchini F, Massobrio M
More information extracted from the paper by Jon Miles
Postacchini and Massobrio studied x-rays of 120 coccyxes of people without pain and 51 coccyxes of people with unexplained coccyx pain. They looked at how many segments people had in their coccyxes, which joints were fused together, and how they curved. These are their results:
| Percent of subjects without pain | Percent of subjects with unexplained coccydynia | ||
| Number of coccyx segments |
1 |
7 |
8 |
|
2 |
54 |
41 |
|
|
3 |
34 |
49 |
|
|
4 |
5 |
2 |
|
| Joint fused | Sacrum/coccyx joint |
37 |
51 |
| First coccyx joint |
10 |
12 |
|
| Second coccyx joint |
43 |
49 |
|
| Configuration of coccyx | 1. Curving slightly forward |
68 |
31 |
| 2. Curving strongly, tip straight forward |
17 |
23 |
|
| 3. Angled sharply forward |
6 |
23 |
|
| 4. Partly dislocated forward at one of the joints |
9 |
22 |
|
Configuration 1, curving slightly forward, was the most common in the general public, with two thirds of people having this type. But less than one third of people with coccyx pain of unknown origin had a type 1 coccyx. Therefore if you happen to have a coccyx that points forward more than down, you are more likely to get coccyx pain even if you don't have an accident.
Postacchini and Massobrio found that 8% of the people without pain had a coccyx that pointed partly left or right. In people with pain of unknown origin, more than 16% had a coccyx that went to one side.
