Conversion of Dynamic Hip Screw to Avantage Dual Mobility Cup (Zimmer-Biomet) and Proximal Femoral Replacement (METS, Stanmore)
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The revision of a DHS to a total hip is not a straightforward operation in many cases. The x-rays can reveal the obvious challenges, for example a multiple fragmented femur and eroded acetabulum. However intra-operatively the surgeon should expect additional significant soft tissue issues such as widespread scarring and pericapsular thickening which provide their own issues with safe exposure and the subsequent surgical reconstruction.
Whilst most of the issues can be rectified intra-operatively, soft tissue impingement anteriorly, which predisposes to dislocation, remains a risk. The case demonstrated was specifically at high risk for dislocation due to a combination of scarring, potential articular impingement, external impingement (thigh on a significant “abdominal apron”) and poor muscle function. Therefore for the cup a dual mobility system was chosen which in my practice is the Avantage Dual Mobility Cemented cup (Zimmer-Biomet).
A number of increasingly extensive femoral options were considered ranging from a simple cemented femur, or an uncemented extended revision type stem through to a proximal femoral replacement. Although planning is essential, sometimes it is not possible to predict which option will be needed. X-rays do act as a guide but often it is the intra-operative findings which dictate the correct implant. A Surgeon undertaking this type of procedure in this type of patient should be able to use these three femoral options confidently as the situation dictates. Being rigid in implant choice and failure to change plans intra-operatively as required can lead to sub-optimal surgery.
The patient in this case suffered an extracapsular neck of femur fracture which was treated with a DHS. The initial fracture however was complex with loss of the medial wall and displacement of the lesser trochanter. Reduction of the fracture was not fully achieved, which with time and mobility worsened, leaving this patient with a body mass index of over 50 in extreme pain and unable to mobilise.
The outcome of this type of surgery needs to be as reliable as possible (get it right ‘second time’) and the patient needs to be able to mobilise immediately and full weight bearing.
The following operation details the take down and conversion of a failed DHS to an Avantage Dual Mobility Cup (Zimmer-Biomet) and a Proximal Femoral Replacement (Stanmore).
Related surgical techniques that should be read in conjunction with this on OrthOracle are https://www.orthoracle.com/library/stryker-omega-dynamic-hip-screw-extra-capsular-neck-femur-fracture/
Author:Mr Andrew Gordon FRCS Tr & Orth.
Institution: The Northern general Hospital, Sheffield, UK.