- Pre Op Planning:
- exam for THR loosening:
- radiology of press fit stems
- note degree of porous coating around the stem;
- note any migration or subsidence of component which may indicate presence of fibrous membrane and poor osseous fixation;
- as noted by Glassman and Engh 1992, radiographically stable stems are usually resistant to attempts at extraction;
- in contrast, when cementless stems are painful and appear unstable on x-rays, they will often be easily removed;
- note however, stable fibrous ingrowth can make extraction difficult;
- finally, cementless stems that were initially stable, do not usually become unstable in the presence of infection;
- attempt to plan ahead of time as to whether trochanteric osteotomy is required;
- Removal of Cementless Stems:
- products for component removal;
- if stem collar is not present, then there must be a variety of sturdy vice grip pliers, which can be applied to the trunion, and impacted with heavy maul;
- if there is extreme difficulty in dislocating the hip, attempt to perform a wide capsulotomy or perform a trochanteric osteotomy;
- it is essential to avoid a proximal femoral frx while extracting the stem;
- before attempting prosthesis removal, remove granulation tissue and capsule around the neck of the prosthesis;
- direct extraction of a femoral stem can be blocked by excessive cement or proximal bony overgrowth medial to the greater trochanter;
- if the femoral head is modular w/ Morris taper, then remove it;
- usually an ingrowth implant requires cutting of the ingrowth sites on all sides of the prosthesis;
- area of ingrowth, whether fibrous or bone is first cut as far distally as possible by flexible osteotomes or a small power burr;
- although power burr necessarily sacrifices some bone, this loss is better than fracturing proximal femur becuase bond was not broken adequately;
- if the porous coating is only proximal, the femoral component can be extracted after the interface has been adequately cut;
- remove all soft tissue and fibrous tissue from the bone stem interface, anteriorly, posteriorly, and laterally;
- access to proximal fixation points anteriorly and posteriorly is easy;
- access to posterior edge can be achieved w/ curved flexible osteotomes;
- always direct the osteotome slight toward the prosthesis inorder to avoid cutting bone;
- thin burr or thin flexible osteotomes will allow bone & fibrous tissue to be divided;
- as long as flexible osteotomes are used in the proximal femur (where metaphyseal bone is present), the risk of fracture is minimal;
- it is also important to clear the medial trochanter;
- if large collar is present and there is an ingrowth area on the medial side of implant, this collar may have to be removed with a metal cutting burr;
- curved thin osteotomes can then be slid down along the interface;
- consider extended lateral trochanteric osteotomy:
- one option is to create only one longitudinal limb of the osteotomy at a time;
- by using an osteotome to created a single longitudinal split down the femur, enough osseous disruption may occur to allow the prosthesis to be removed;
- if the prosthesis cannot be removed the other limb of the osteotomy is created;
- use of curved microsaggital saw blade
- Removal of a well-fixed cementless femoral stem using a microsagittal saw.
- Distal Porous Coating:
- if the porous coating extends well distally or if the prosthesis has a roughened surface distally esp titanium alloy stems, interface between
prosthesis and bone must be cut throughout most of or all of the stem length before the stem can be removed;
- note that there is a significant chance of femoral fracture, when flexible osteotomes are used in areas where cortical bone has ingrown into prosthesis;
- this is especially the case w/ oversized femoral stems;
- it may be safer in these areas to use a high speed burr;
- it is also important to not only divide the ingrowth material, but remove it in order to allow further room for the burr to advance;
- even small area of well ingrown porous coating may prevent removal;
- safest method is to create an anterior cortical window about 1 cm wide throughout entire length of stem, saving removed cortical bone for later repair;
- the interface around the rest of stem circumference is cut with flexible osteotomes;
- during reconstruction, the window is replaced and fixed with cerclage wires
The Removal of Porous Coated Femoral Hip Stems
A technique of extensile exposure for total hip arthroplasty.
Removal of cementless hip implants. Rubash HE et al. Instructional Course Lectures. 1991;40:171-176.
Technical Notes. Removal of a well-fixed cementless femoral stem using a microsagittal saw.
The removal of porous-coated femoral hip stems.
Cold Saline Lavage for Removal of Incarcerated Porous Ingrowth Stems