Operations
Hip & Pelvis

What is a triple reamer?

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• Specialist part of the DHS kit that is able to ream three separate components of the proximal femur at the same time:

  • For the DHS screw

  • For the DHS Barrel

  • For the DHS plate-barrel junction

• It is adjustable in 5mm depths

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What do you understand by the term Tip-to-Apex Distance?

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• Summation of the distance of the tip of the lag screw to the apex of the femoral head on AP + Lateral radiographs

• First defined by Baumgaertner [1] in 1995

  • Examined factors leading to the failure of sliding hip screws in 198 patients with intertrochanteric fractures

  • Found that a Tip-to-Apex Distance of <25mm has been shown to minimise the fixation cut out

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What are the diameters of the DHS lag screw and guidewire?

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The diameters of the DHS guidewire can help to estimate the Tip-to-Apex Distance intraoperatively:

• DHS guide wire = 2.5mm

• DHS lag screw = 12.5mm

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How would you manage spinning of the femoral head during lag screw insertion?

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Spinning of Femoral Head

• Increased likelihood with left sided basi-cervical fractures

• Femoral head can spin around guidewire during lag screw insertion

• Options to counteract this include:

  • Reverse lag screw (reducing displacement)

  • Insertion of de-rotation wire

  • Tapping prior to DHS screw insertion

  • Manually holding neck to prevent displacement (e.g. with Heygroves clamp)

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Describe how you would perform a DHS

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“In an appropriately consented and marked patient I would perform a WHO sign in and time out, prior to proceeding…”

 

Positioning

• Supine on radiolucent TRACTION table

• Padded post in groin 

• Contralateral leg padded placed in leg holder

  • Hip flexed/abducted so C-Arm can gain access from contralateral side

• Secure ipsilateral leg in traction boot.

• Traction

  • Confirm reduction with traction + internal rotation

  • Confirm with image intensifier

  • Aiming for anatomic reduction - medial and posterior cortices should be aligned at fracture site

  • Ensure lateral II image was at 90 - to groin post to aid anteversion of guidewire

• Scrub, prep + drape patient

 

Incision

• Identify level of lesser trochanter on AP with guidewire

• 8cm lateral incision starting at level of greater trochanter

 

Superficial dissection

• Dissect down to fascia lata

  • (Keeping in line with femur)

• Divide fascia lata with scalpel/scissor

• Then extend proximally and distally with dissecting scissor

 

Deep dissection

• Expose lateral femoral cortex with vastus splitting approach

• Insert self-retaining retractor (Norfolk and Norwich) to bone

• Use periosteal elevator to clear muscle fibres from lateral cortex

 

Guidewire placement

• Place 135-guide and position a 2.5mm guide wire in the centre of femoral head on AP+Lateral views

• Aiming for a Tip-to-Apex distance of <25mm

  • Aim to put the guidewire into subchondral bone to ensure doesn’t come loose

• Second guidewire? - If fracture was basi-cervical, consider placing second guidewire to prevent head spin

 

Reaming + Screw insertion

• Measure guidewire - then use triple reamer to 5-10mm below measured length

• Insert DHS screw on T-handle

  • Using II throughout to ensure tip-apex distance + head not spinning

  • Final position of T-handle has to be parallel to femoral shaft

• Attach 4-hole DHS plate

• 4x4.5mm Bi-cortical screws

  • Using 3.2mm drill

  • Inserted from distal - proximal

• Confirm final images on II

 

Closure

• Closure in layers:

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References

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[1] Baumgaertner MR, Curtin SL, Lindskog DM, Keggi JM. The value of the tip-apex distance in predicting failure of fixation of peritrochanteric fractures of the hip. J Bone Joint Surg Am. 1995 Jul;77(7):1058-64.