Clinical History, Examination and Blood Test Results

  • Step 7 case 2 74-year-old lady who was unable to walk for years due to failure of a previous implant

  • She had severe osteolysis of her acetabular component due to polyethylene wear


Imaging Results

PRE-OP RADIOGRAPH

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Anteroposterior (AP) radiograph showed massive acetabular bone loss with superior medial migration of the left acetabular cup. The calculated centre of rotation recovery was 30mm to match the right hand side.

 

PRE-OP PELVIC 3D CT RECONSTRUCTION

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Pelvic defect.png

This is a 3D model of the patients left hemipelvis produced from her CT scan. This highlights the anterior column defect and erosion of the medial acetabular wall.


Diagnosis

  • Severe acetabular defect classified as a Paprosky 3B with the anterior column of the left hemipelvis completely bisected due to the erosion. In addition the medial wall of the acetabulum is eroded.


Treatment

IMPLANT DESIGN

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TRABECULAR TITANIUM

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This series of images shows the design of the acetabular implant. The blue areas of the design highlight the trabecular titanium which is pictured to the right. The final image shows the implant in situ in the 3D reconstructed left hemipelvis.

This image shows the Trabecular Titanium used with these implants. In order to manufacture this structure, rapid prototyping, better known as 3D printing is utilised. This is made using electron beam sintering, which means the structure is continuous. The pores within the material have been shown to encourage bony ingrowth. 

 

Key surgical steps

  • Posterior approach to allow extensile exposure of acetabulum and femur.

  • Release of psoas and gluteus maximus from the femur, and abductors from the ilium.

  • Bone preparation with reamers according to 3D computer plan and checking using sterilised plastic 3D-printed models of the acetabular pre and post bony preparation.

  • 3D printed trabecular titanium implant secured with at least 3 good screws.

  • Dual mobility bearings 44mm.

  • Cement-in-cement, small sized stem to allow for adjustment of offset and leg length.

  • Wash.


Imaging Outcomes

POST-OP RADIOGRAPH

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This is the post-operative AP plane film radiograph taken post-operatively. The large custom implant is in situ with its superior and inferior flange.

 

6 MONTH POST-OP EOS IMAGING 

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This series of images were taken at 6 months post-op. These are EOS images, taken in a functional standing and sitting position using low-dose bi-planar x-rays to assess the functional position of the implant.


Clinical Outcomes

  • The patient is very happy with the outcome of her custom designed and manufactured 3D printed titanium implant.

  • At 6-months the patient was mobile and able to straight leg raise to 45 degrees and flex her hip to 80 degrees.

 
 

This video demonstrates the patients functional ability 6-months after her operation.


Learning Points

  • Meticulous pre-operative planning is required, involving CT imaging, bioengineers and surgeons to design and approve the custom implant.

  • Extensive surgical exposure is required during the procedure.

  • Close post operative monitoring is needed.