“Rose is a 57-year old female who presented with an interesting but complicated orthopaedic history. As a young child, she had been diagnosed with developmental dysplasia of the hip. Throughout her early years, she had received multiple operations to try and maintain an acetabulum on the right side.
At the time of presentation, she had received two previous hip replacements. These had led to a massive right sided pelvic defect, with superior migration of the acetabular cup and complete loss of the medial acetabular wall.
The defect was too large to correct with an off the shelf component. The only way forward was to use a custom implant to fill the defect and correct the position of her right hip joint.”
Rob to complete
Anteroposterior plain radiograph showing right sided acetabular bone loss with superior migration of the right acetabular cup. This left the patient with a severe leg length discrepancy which is not quantifiable from this radiograph.
Sitting EOS which highlights the superior migration of the implant.
Standing EOS -The red lines in the picture on the right highlight the leg length discrepancy Rose had been living with while she is standing.
Axial CT - This scan was used to create a 3D model of the patients hemipelvis in order to design the custom implant. Note the positioning of the implanted femoral heads as you scroll through the images.
Hemipelvis defect - This is a 3D reconstruction (from a CT scan) of this patients right hemipelvis. This highlights the extent of her acetabular defect. The medial wall is completely missing however the anterior and posterior columns are still intact.
Rose had a Paprosky 3B acetabular defect with considerable superior migration of the existing acetabular cup. The acetabulum was flattened and the medial acetabular wall was almost entirely missing.
We planned to reconstruct Rose’s hip using a custom implant. This implant was designed using the pre-operative CT imaging to fit the large acetabular defect left in Rose’s pelvis after two failed total hip replacements. The implant is manufactured from 3D printed trabecular titanium to improve osseointergration of the implant.
Please check Prof —> I think it would be interesting to add how you planned her centre of rotation due to the large defect
Implant design - This series of images shows the design of the acetabular implant. The blue areas of the design highlight the trabecular titanium. Scroll through to see the implant in-situ. These images are produced as part of the planning and designing stage of the procedure.
3D Printed Trabecular Titanium - 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.
We used a posterior approach to allow extensile exposure of the acetabulum and the femur. We progressed to release psoas and gluteus maximus from the femur, and the abductors from the ilium.
The acetabular bone was prepared with reamers according to the 3D computer plan. We used the sterilised plastic 3D-printed models of the acetabulum to guide us. Two models were used, one demonstrating the pre-operative anatomy, and one demonstrating the preparation we were aiming to achieve.
A trial 3D printed model of the acetabular cup was introduced to assess the bony preparation. When we had achieved the plan, we introduced the 3D printed trabecular titanium implant. This was secured with 3 good screws. Dual mobility bearings were used in the cup (44mm in size).
Finally we used a cement-in-cement small sized stem on the femoral side, which allowed us to adjust for femoral offset and the leg length. We then washed the operative site and closed after a series of thorough checks assessing the stability of the joint and the length of the leg.
Anteroposterior plain radiograph taken post operatively. The large custom implant is in situ filling the defect made by the superior migration of the old implant.
Sitting EOS - This is a post operative sitting EOS image with the implant in situ.
Standing EOS - The leg length discrepancy has been corrected using the 3D printed trabecular titanium implant
Axial CT scan taken 10 days post-operatively to assess the position of the component.
Axial CT scan taken one year later at follow-up demonstrated there was no component migration.
Anteroposterior plain radiograph taken one year after the operation demonstrating no implant migration. The function of the new hip joint was very good and Rose was able to walk without a leg length discrepancy.
Eight weeks after the operation, Rose was pain free and her right hip had a full range of movement. There was some evidence of foot and ankle weakness. At her one year review, clinically her leg lengths were almost equal, a massive improvement on the pre-operative discrepancy. Her pre-operative antalgic gait was no longer present. Rose was attending the gym and continuing her physiotherapy. She was very happy with the outcome of her procedure.
Video of Rose walking at her one-year post operative follow up appointment. An amazing result!
Prof —> Can we incorporate these learning points into the verdict?
The use of pre-operative and post-operative EOS scanning allows for accurate measurement of the change in leg length discrepancy
Custom implants can be used to achieve an initial strong primary fixation in huge acetabular defects. This patient at 8-weeks post-op was pain free with a good range of movement
Evidence for this treatment
In closer detail