Det er ikke længe siden, min nabo havde gips på det samme håndled efter et uheld.

It is a very common Danish expression meaning It wasn’t long ago that... or more literally It is not long since...

So the whole structure is:

• Det er ikke længe siden ... = It wasn’t long ago that ...
• Det er længe siden ... = It’s been a long time since ...

Even though English often uses ago, Danish uses this since-type structure very naturally.

Because the sentence is measured from now.

Danish is saying: From the present moment, not much time has passed since that event happened.

So:

• Det er ikke længe siden ... = from now, it has not been long
• Det var ikke længe siden ... = from some point in the past, it had not been long

Using var would shift the reference point into the past.

Because længe is an adverb, while lang is an adjective.

• lang = long
• længe = for a long time / long

In ikke længe siden, Danish needs the adverb længe.

Compare:

• en lang dag = a long day
• jeg ventede længe = I waited a long time
• det er ikke længe siden = it wasn’t long ago

Because in a normal Danish main clause, the finite verb usually comes before sentence adverbs like ikke.

So the pattern is:

• Det er ikke ...
• Han kommer ikke ...
• Vi har ikke ...

This is standard Danish word order in main clauses.

Yes, it can often be omitted, depending on comma style.

The sentence after siden is a subordinate clause, and Danish has two common comma practices:

• traditional comma: Det er ikke længe siden, min nabo havde ...
• new comma: Det er ikke længe siden min nabo havde ...

Both are seen.

You may also see at added:

• Det er ikke længe siden, at min nabo havde ...
• Det er ikke længe siden at min nabo havde ...
  depending on comma style

So the comma here is not about meaning; it is mainly about writing convention.

Because the clause after siden is not an independent main clause in the same way as a normal statement. It keeps the usual subject + verb order:

• min nabo havde gips ...

You would not normally invert it to havde min nabo here.

So:

• main structure: Det er ikke længe siden ...
• following clause: min nabo havde gips ...

Because havde (simple past) is the normal choice for a finished event in this kind of sentence.

• havde = had
• har haft = has had
• havde haft = had had

In this sentence, the neighbor’s having a cast is presented as a completed past situation, so havde is the natural choice.

Havde haft would only be used if you were placing that situation further back relative to another past event.

Gips here means a cast.

In Danish, have gips på is a natural medical expression meaning to have a cast on.

So:

• have gips på håndleddet = have a cast on the wrist
• have gips på benet = have a cast on the leg

Danish often leaves out the article in this kind of expression. It is treated more like a material/state expression than a simple countable noun phrase.

You may also hear expressions like:

• være i gips = be in plaster / be in a cast

There are two useful things to notice here.

1. Why det? Because håndled is a neuter noun:

• et håndled = a wrist

So with samme, the form is:

• det samme håndled = the same wrist

Compare:

• den samme arm = the same arm
• det samme håndled = the same wrist
• de samme fingre = the same fingers

2. Why not håndleddet? Because when Danish uses a determiner like det plus an adjective-like word such as samme, the noun normally stays in its basic form:

• det samme håndled
• not det samme håndleddet

Also, the same wrist depends on context. It means the wrist is the same one as something already known from the conversation.

It means after an accident or following an accident.

• efter = after
• et uheld = an accident / a mishap

Here efter suggests that the accident happened first, and the cast came as a result of it.

A small vocabulary note:

• uheld often means a mishap or accident
• ulykke can sound more serious, though the line is not always strict

Yes, but the structure is a little different.

• For ikke længe siden = Not long ago
• Det er ikke længe siden ... = It wasn’t long ago that ...

So you could say:

• For ikke længe siden havde min nabo gips på det samme håndled efter et uheld.

That is also correct.

The difference is mostly stylistic:

• For ikke længe siden is a time phrase at the start of the sentence
• Det er ikke længe siden ... emphasizes that only a short time has passed since the event

Mostly yes, but det samme håndled sounds a bit context-dependent.

The same wrist usually refers back to something already mentioned or understood. For example, maybe the speaker or someone else had injured that wrist before, and now the speaker is comparing it with the neighbor’s injury.

So grammatically it is fine, but in isolation a learner may feel that it points to missing context. That is normal.