Clinical History, Examination and Blood Test Results

  • Step 5 case 1 is a 60-year-old male patient who presented with a painful right hip resurfacing and difficulty putting on shoes and socks. In 2014, he had a right metal-on-metal Birmingham hip resurfacing for osteoarthritis.

  • Examination revealed a negative Trendelenburg test, a stiff right hip and trochanteric tenderness.

  • His oxford hip score was 29/48.

  • He had a raised CRP of 20mg/L. A hip aspirate was negative after 14 days.

  • Blood Cobalt levels were 2.9 ppb and chromium levels were 2.7 ppb.

  • Ultrasound guided injection of local anaesthetic into his right hip relieved his pain for 24 hours.


Imaging Results

PRE-OP RADIOGRAPH

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This is an anteroposterior (AP) radiograph of the pelvis showing a well fixed Birmingham right hip resurfacing. The right component is slightly large and the cup inclination is low at 22 degrees. A CT scan revealed that the cup was anteverted at 40 degrees.

 
  • Cup inclination 22 degrees and anteversion 40 degrees.

  • The low cup inclination angle with a high aversion angle is an issue because it can cause lateral impingement at low levels of abduction. This can effect walking and other normal daily activities. It also causes the shedding of metal ions which can irritate the soft tissue surrounding the hip.


Diagnosis

  • Painful right Birmingham hip resurfacing secondary to metal ion synovitis.

  • Differential diagnosis includes mechanical symptoms due to the cup position: high centre of rotation and low cup inclination (which can cause impingement on femoral neck and psoas tendon).


Treatment

AUGMENT

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This augment allows the surgeon to reconstruct a socket that has poor underlying bone stock.  It is secured to the bone by screws, and acts as a buttress for the acetabular cup to fit in against.

 
  • This patient underwent a revision procedure to convert his Birmingham hip resurfacing to a ceramic-on-polyethylene total hip replacement.

  • The revision procedure required the use of a superior augment with bone graft due to a superior acetabular wall defect


Imaging Outcomes

POST-OP RADIOGRAPH

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ONE-YEAR POST-OP RADIOGRAPH

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LONG LEG FILM

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This post-operative AP of the pelvis shows a Corail stem and Pinnacle Gription acetabular socket with superior augment. The centre of rotation of the and cup angles have been optimised. A ceramic-on-polyethylene bearing surface was used.

This is the one year post-operative radiograph. The augment and cup are still in an adequate position. There has been no rotation of the cup. The Corail stem remains well fixed.

This post-operative long leg radiograph shows that the patients leg length discrepancy has been corrected by the revision surgery


Clinical Outcomes

  • The patient feels as if his legs are now back to the correct lengths confirmed by the post-operative long leg radiograph.

  • One-year post op the hip replacement was functioning well and the patient was able to return to his normal exercises.


Learning Points

  • Augments can be used to restore the centre of rotation of the cup and maintain appropriate cup size to avoid the loss of anterior and posterior columns as seen with jumbo cups.