Clinical History, Examination and Blood Test Results

  • Workshop case 1 is a 49-year-old lady who presented with pain and stiffness in both hips and her lower back

    • The mean age for a hip replacement in the UK is 67-years old and she was much younger.

  • She had end stage hip osteoarthritis with complex anatomy;

    • Acetabulae protrusio

    • Ring of acetabular osteophytes - Captive joint

    • Coxa vara

  • She was an active patient who enjoyed hiking and running. She was keen to get back to these activities after her operation.


Imaging Results

PRE-OP CT

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PRE-OP EOS

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End stage osteoarthritis is present in both hips, as demonstrated by the CT scan. The pre-operative CT scan is used to plan the procedure and design the patient specific instrumentation used during the operation. This instrumentation guides the surgeon in the femoral neck cut and the reaming angle of the acetabulum.

Pre-operative EOS was ordered to help plan the procedure. This patient has varus femoral necks. Patients with varus femoral necks are at an increased risk of post-operative leg length discrepancy, so understanding their functional anatomy pre-op is vital for surgical planning.


Diagnosis

  • Bilateral end stage osteoarthritis requiring bilateral total hip arthroplasty.

  • Complex anatomy with coxa vara, ring osteophytes and acetabulae protrusio.


Treatment Operation One

  • Left primary total hip replacement using patient specific instrumentation.

  • The instrumentation is designed from the pre-operative CT scan and the surgical plan. The aim of the instrumentation is to guide the surgeon throughout the operation to achieve an optimal position.

  • The jigs (pictured below; from another case demonstrating a right primary THR) are 3D printed and sterilised for intra-operative use.

 

FEMORAL MODEL AND JIG

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ACETABULAR MODEL AND JIG

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This is an image of a PSI femoral jig sat on a 3D printed model of the patient’s proximal femur. This jig is designed for the posterior surgical approach, and is also complementary to the patient’s anatomy. It is used to aid in the cutting of the femoral neck, to ensure the position and the angle of the neck cut is correct. 

This is a photo of a PSI acetabular jig sat in a 3D printed model of the patient’s acetabulum. The jig is custom made to fit into the patient’s own acetabulum. The left hand arrow shows the points where the jig is complimentary to the patient’s anatomy to get an exact fit. The right hand arrow shows the drilling guide. When the jig is sat correctly in the patient’s acetabulum, the drilling guide is used to place two pins onto the pelvic bone. A visual guide (pictured below) is then slid over these pins and aids the surgeon in getting the reaming angle correct. 

INTRAOPERATIVE USE - FEMORAL JIG

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INTRAOPERATIVE USE - ACETABULAR JIG

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This series of three photos shows the intraoperative use of the femoral jig. Image one shows the placement of the femoral jig on the posterior of the proximal femur. Image two shows the jig, pinned in place, being used as a cutting guide to remove the femoral head. Image three shows the femoral head being removed with the jig attached.

This series of three photos shows the intraoperative use of the acetabular jig. Image one demonstrates the acetabular model and jig being used to visualise the positioning of the jig within the acetabulum. Pins are then drilled into the acetabular bone using this jig. Image two shows the visual guidance bar being slid over the two precisely positioned pins. Image three shows the surgeon lining the trajectory of the cup with the visual guidance bar to ensure optimal positioning.


Imaging Outcomes Operation one

POST-OP CT

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This post-operative radiograph demonstrates the left total hip replacement in situ. The position of the implant is good.

 

Treatment operation 2

  • Right primary total hip replacement using patient specific instrumentation (as demonstrated above).


Imaging outcomes operation 2

POST-OP RADIOGRAPHS

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POST-OP CT

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This post-operative radiograph shows both of the hip replacements in situ. Both are in the planned position

This CT scan shows the final position of the implants.


Clinical Outcomes

  • Post-operatively the patient was happy with her bilateral hip replacements. She is undergoing physiotherapy with the aim to return to running.


Learning Points

  • This was a complex primary hip replacement. There were three main challenges;

    • Young patient under 50

      • It is important that this implant lasts for this patient due to her age. This may need to last for up to 50-years, which no one can promise, but using patient specific instrumentation can guide the surgeon in achieving an optimal position in complex cases

    • Reconstructing the medial acetabular wall and the hip COR

      • This is due to the protrusio acetabulae, meaning the native acetabulae are more medial than normal

    • Avoiding leg length discrepancy

      • Coxa vara increases the risk of a post-operative leg length discrepancy

  • Ring osteophytes and protrusio acetabulae can result in a “captive” hip: this risks fracture of the femur or posterior acetabular wall if care not taken during dislocation during hip replacement. This can be avoided if the osteophytes are removed before dislocation or the neck is cut before dislocation.

  • For cases of protrusion, bone graft from the femoral head (autograft) can be used (sliced) to place in the floor of the acetabulum.