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Note added at 14 mins (2014-11-07 23:34:36 GMT)
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The sacral vertebra is typically fused, and the last fully formed disc is at L5-S1...
For purposes of this report, the lowest fully formed disc space was referred to as L5-S1.
http://tinyurl.com/njoumgk

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Note added at 20 mins (2014-11-07 23:41:16 GMT)
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The most inferior fully formed disc space is labeled as L5-S1...
There are presumed to be five lumbar-type vertebrae with last fully formed disc space at L5-S1.
http://tinyurl.com/p66glqm

Nieco rzadziej przez "k" (disk):

For the purpose of this dictation the last fully formed disk space will be designated as L5-S1...
The L5-S1 level is assigned to the lowest fully formed disk level.
http://tinyurl.com/k9jhgsd

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Note added at 26 mins (2014-11-07 23:47:17 GMT)
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Gwoli wyjaśnienia, skąd wziął się ten "problem anatomiczny":

In some cases the sacrum will consist of six pieces or be reduced in number to four. The bodies of the first and second vertebrae may fail to unite.
https://en.wikipedia.org/wiki/Sacrum