Mysql Complex Sort

Hello everyone,

Sorting strings and numbers in SQL.
I have the following:

mysql> SELECT product_article_number, product_details_size FROM product ORDER BY product_details_size;
+------------------------+----------------------+
| product_article_number | product_details_size |
+------------------------+----------------------+
| 2310104115010010R38    | 10R38                |
| 2310104115010012R40    | 12R40                |
| 2310104115010014R42    | 14R42                |
| 2310104115010016R44    | 16R44                |
| 2310104115010018R46    | 18R46                |
| 2310104115010020R48    | 20R48                |
| 2310104115010022R50    | 22R50                |
| 2310104115010024R52    | 24R52                |
| 231010411501006R34     | 6R34                 |
| 231010411501008R36     | 8R36                 |
+------------------------+----------------------+

And as you can see it is not sorted correctly.
What i' m looking for is the following:

+------------------------+----------------------+
| product_article_number | product_details_size |
+------------------------+----------------------+
| 231010411501006R34     | 6R34                 |
| 231010411501008R36     | 8R36                 |
| 2310104115010010R38    | 10R38                |
| 2310104115010012R40    | 12R40                |
| 2310104115010014R42    | 14R42                |
| 2310104115010016R44    | 16R44                |
| 2310104115010018R46    | 18R46                |
| 2310104115010020R48    | 20R48                |
| 2310104115010022R50    | 22R50                |
| 2310104115010024R52    | 24R52                |
+------------------------+----------------------+

Maybe with the function LPAD ? But I cant isolate the first digits.
Any idea.
Maybe with Regex to take out the digit and perform LPAD?
And ofcourse, i don' t want to use an index table ;)

Kind regards,
Django