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Indications for revision hip arthroplasty are septic or aseptic loosening of one or both components of a hip arthroplasty. For revision THA the DAA allows for keeping the incision small if only the cup has to be revised or in cases of stem revision; the femoral preparation can be performed strictly endofemorally from the proximal direction. Gluteal muscles can be preserved whether the approach can be limited to the original interval between the TFL and the rectus or it must be extended.

If preservation of the gluteal muscles is desired, the DAA and its extension are the approaches of choice. For endofemoral revision other than detachment of the TFL, hyperextension and sufficient adduction of the operated leg are important. If these cannot be achieved, an alternative operative strategy or a different approach should be considered. As this approach allows for extensions proximally and distally along the femur, it competes with lateral approaches to the hip joint and femur and does not have additional specific contraindications. The availability of specific curved, angulated, or offset instruments is mandatory.
Templating is indicated for every revision hip arthroplasty, whether it is a straightforward or a complicated case.

Revision THA is a complex procedure with a higher risk of complications and unforeseen circumstances. Templating is an essential part of preoperative planning that is more important and sophisticated for revision than for primary arthroplasty.


Preoperative planning is required for the type of implants to be used, the method of fixation (cemented, uncemented, or hybrid), and the need for bone grafting and/or special instruments or devices.

Larger femoral heads or constrained cups may be required if a higher risk of dislocation is expected.


In revision surgery, bone stock is usually deficient, and metal or allograft augmentation may be required. It is useful to know in advance the cup size and the level of femoral neck cut to facilitate minimal bone removal.


The anatomy is usually distorted in revision surgery, and planning is required to restore the center of rotation, offset, and leg length and to obtain optimal alignment of the implants.



Templating may allow the surgeon to predict intraoperative difficulties and possible complications.


Implant inventory is another concern. Revision implants and instrumentation are not usually stored at the hospital site. Surgeons, nurses, and manufacturers need to be aware long in advance about unusual implants or instruments.


The value of preoperative planning for revision THA has been reported by several authors (Barrack and Burnett, 2006; Bono, 2004; Knight and Atwater, 1992; Morrey, 1992; Seel et al., 2006).

PITFALLS


External rotation gives a false impression of valgus leading to underestimation of the femoral offset.


Internal rotation gives a false impression of varus leading to overestimation of the femoral offset.


Abduction may alter the leg length (apparent lengthening).


Adduction may alter the leg length (apparent shortening).


Pelvic tilting or asymmetry may alter the leg length.
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