Fractures and dislocations: tip-apex distance after a sliding hip screw: practice question

A Orthopaedics question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

Orthopaedics · Fractures and dislocations: tip-apex distance after a sliding hip screw

Sample item

A surgeon fixes an unstable intertrochanteric fracture with a sliding hip screw. Intra-operative films show the lag screw tip lying 35 mm from the apex of the femoral head after correcting for magnification. Which complication is this positioning most likely to predict?

AFat embolism syndromeBInjury to the lateral femoral cutaneous nerveCAvascular necrosis of the femoral headDCut-out of the lag screw through the femoral head

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Cut-out of the lag screw through the femoral head

The tip-apex distance is the sum of the distances from the screw tip to the femoral head apex on AP and lateral views. Values above about 25 mm are associated with cut-out, so the screw should be placed centrally and deep in the head. Poor placement is a more important cause of failure than the choice of implant.

Option by option

A. Fat embolism syndrome
Fat embolism relates to the fracture and canal instrumentation, not to the tip-apex distance.
B. Injury to the lateral femoral cutaneous nerve
That nerve is at risk from surgical approaches around the anterior superior iliac spine, not from screw depth.
C. Avascular necrosis of the femoral head
The head of an extracapsular fracture keeps its blood supply, so osteonecrosis is not the expected consequence of screw position.
D. Cut-out of the lag screw through the femoral head (correct)
Correct. A tip-apex distance above about 25 mm predicts cut-out of the lag screw.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Orthopaedics question

What is the answer to this Orthopaedics question?

The best answer is D, Cut-out of the lag screw through the femoral head. The tip-apex distance is the sum of the distances from the screw tip to the femoral head apex on AP and lateral views.

Why is "Fat embolism syndrome" not the answer?

Fat embolism relates to the fracture and canal instrumentation, not to the tip-apex distance.

Why is "Injury to the lateral femoral cutaneous nerve" not the answer?

That nerve is at risk from surgical approaches around the anterior superior iliac spine, not from screw depth.

Why is "Avascular necrosis of the femoral head" not the answer?

The head of an extracapsular fracture keeps its blood supply, so osteonecrosis is not the expected consequence of screw position.

What concept does this question test?

It tests Fractures and dislocations: tip-apex distance after a sliding hip screw in Orthopaedics. Values above about 25 mm are associated with cut-out, so the screw should be placed centrally and deep in the head. Poor placement is a more important cause of failure than the choice of implant.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Fractures and dislocations: tip-apex distance after a sliding hip screw?

Pair each fracture with its classic complication and nerve injured. Then use the flashcards and the other Orthopaedics questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.