Typically, implant removal and reconstruction are performed in a single procedure, unless difficulties are encountered during implant removal or infection is present. No literature exists to support routine staging of conversion hip arthroplasties.
If implant records are available preoperatively, proprietary extraction instruments may aid implant removal. Otherwise, for retained femoral implants, a universal extraction set with a slap hammer and vise grip may be used.
A metal cutting burr, trephines, and broken screw removal sets are necessary for taking out old screws and plates. Cerclage cables and trochanteric fixation devices should be available. For previous femoral trauma, flexible reamers may be necessary for canal preparation. Intraoperative fluoroscopy is routinely used to assist implant removal, bone preparation, and subsequent implant positioning.
A variety of techniques including the anterior, anterolateral, and posterior approaches may be used depending on what exposure is needed. The patient is positioned in the lateral decubitus or supine position on a specialized radiolucent table to facilitate intraoperative imaging. Prior surgical incisions are incorporated if they do not compromise exposure, and the approach is extended as necessary. If a history of posterior column fixation or notable acetabular deformity exists, a posterior approach offers the most extensile acetabular exposure. The posterior capsule is taken down as a sleeve, tagged, and repaired at the procedure conclusion to enhance postoperative stability. Care is taken to protect the sciatic nerve throughout surgery. For isolated anterior column fixation or femoral implants, an anterolateral approach may be preferred depending on surgeon familiarity. This approach may enhance postoperative stability[10,11] by preserving the posterior structures and is easily extended along the femoral shaft. The anterolateral approach also reduces the risk of direct injury to the sciatic nerve. In cases where the surgeon plans to retain previous implants, the direct anterior Smith-Peterson approach may also be considered. Use of this interval would provide a pristine tissue plane to operate in. This practice would also reduce the risk of injury to the sciatic nerve by avoiding previously scarred posterior tissue planes. In settings of trochanteric nonunion, the fragment may be mobilized as if it were a traditional trochanteric osteotomy.
Prior Acetabular Trauma
The hip is dislocated and a femoral neck osteotomy is performed. In cases of ankylosis, the femoral neck may be osteotomized in situ or constrictive osteophytes may be removed before hip dislocation. A snake retractor over the anterior column and a posterior paddle retractor usually provide adequate exposure. Obscuring soft tissues are removed to define the bone anatomy, while preserving the transverse acetabular ligament as a guide to cup anteversion. The acetabulum is then prepared with stepwise reaming, using larger reamers to engage the rim and avoid overmedialization. Care is taken during reaming because the bone quality is often poor from disuse osteopenia.
Prior fixation implants are selectively removed as necessary. Posterior column screws will often be encountered during reaming, and these screws may either be removed if easily accessible or burred away from inside to allow proper acetabular component seating. Anterior column screws are usually not an issue during acetabular preparation (Figure 4). Bone defects may be grafted using femoral head autograft or allograft, and reverse reaming is performed to compact the bone graft into place. Once adequate reamer engagement is observed, a trial implant is used to check stability of rim fit.
Radiographs showing acetabular reconstruction. A, Prior posterior column acetabular fracture and severe posttraumatic arthritis. B, Accessible portions of the plate were removed as necessary for acetabular preparation and cup placement. A standard primary wedge tapered femoral stem was used. C, Prior anterior column acetabular fracture. D, Fracture fixation was essentially disregarded at the time of reconstruction. Routine primary noncemented components were used.
Noncemented acetabular reconstruction is generally performed using a porous metal implant with multiple screw holes for additional fixation. Intraoperative fluoroscopy is useful to assess cup position to ensure proper medialization, abduction, and anteversion. When possible, larger inner diameter highly crosslinked polyethylene liner options are used for optimal stability. Recently, more centers have used dual mobility cups for high-risk patients and revision surgeries.[12,13] This approach may be appealing for patients with trochanteric or abductor deficiency, but evidence for routine usage is not well defined.
In cases of acetabular nonunion, revision plating, cages, or triflange constructs may be necessary. When adequate bone stock remains, revision plating may be undertaken to support the acetabular component. Alternatively, if moderate bone loss and medialization of the head through the medial wall are present, a cage or triflange implant can be used.
Prior Femoral Trauma
After soft-tissue dissection and exposure, the hip is dislocated. Prior implants are left in place until the hip is dislocated, to avoid fracture during hip dislocation. At this point, the vastus lateralis is elevated and all implants that require extraction are identified before removal. A high-speed burr may be necessary if implants are overgrown.
In the case of cannulated screws, the appropriate screwdriver is used to back out the screws. Occasionally, if screws cannot be extracted in this manner, a neck osteotomy is made around the screws and they are removed from within, once the femoral head is removed. If the distal-most screw hole is below the level of the lesser trochanter, a cerclage cable may be used for prophylactic fixation at this level.
For intramedullary rods, an anterolateral approach may be in line with the nail entry site and provide optimum postoperative stability. If the tip of the rod is overgrown, fluoroscopy can be used to localize the entry site and selectively burr away overlying bone. The extraction device can then be placed onto the nail. This method will help avoid more iatrogenic damage to the trochanter. An extractor is attached to the top of the nail before all locking screws are removed, to ensure that the rod remains rotationally stable for this step.
For screw and sideplate devices, screws in the shaft portion of the plate are removed first. If the plate is long, selective screw removal may be feasible in some cases, leaving distal screws in place. In this case, a metal cutting burr will be used to cut the plate at the appropriate level. Next, the hip screw and sideplate are removed. If the bone quality is poor, cerclage cables may be placed around empty screw holes.
After implant removal, the femoral neck osteotomy is performed according to preoperative templating and referencing the lesser trochanter. At this point, acetabular exposure and preparation is performed in standard fashion. Care is taken to not overream the acetabulum, because there may be disuse osteopenia.
To commence femoral preparation, the canal is first reestablished. Given that the medullary bone may be sclerotic and lateral defects are present from failed implants, care is taken to avoid femoral cortical perforation and eccentric bone preparation. A high-speed burr, canal finder awl, and fluoroscopic guidance are useful for this step to ensure in-line preparation. After the canal is entered, the medullary cavity may be further opened by using a ball-tipped guidewire and flexible reamers. During the process, care is taken to protect the greater trochanter to avoid iatrogenic fracture.
On the femoral side, preoperative templating and planning will determine which implants will be used for reconstruction. Intraoperative assessment after implant removal serves to confirm the bone defects and deformities which were previously anticipated. In most cases, noncemented reconstruction is undertaken. With prior intramedullary fixation, the endosteal surface is sclerotic and forms a weaker bone-cement interface. Furthermore, screw holes allow for cement extrusion and make cement technique more demanding. A variety of stem options can be used, including proximally porous coated, fully porous coated diaphyseal fitting, and modular revision systems. For prior cannulated screw fixation of the neck, a primary stem will usually suffice. For lateral plate or intramedullary fixation, a longer stem is generally used bypassing the distal-most site of implant removal by two cortical diameters (Figure 5). After bone preparation, notable bone defects may be grafted using the resected femoral head or allograft. In some instances, a cortical strut allograft may be appropriate to supplement proximal femoral bone loss.
A, Prior proximal femoral trauma and severe posttraumatic arthritis, heterotopic ossification, and a nearly ankylosed joint. B, Along with removal of some of the heterotopic bone, an in situ femoral neck osteotomy was needed to dislocate the joint. A monolithic diaphyseal engaging stem was used, bypassing the distal-most site of implant removal by two cortical diameters.
Trochanteric osteotomies or nonunions can be secured using a variety of fixation options including wires, cable grips, or claw plates depending on the size of the fragment and amount of bone available for obtaining fixation.
Intraoperative cultures are routinely obtained in the presence of prior implants, even when preoperative infectious workup is negative, because occult infections can occur. Routine drain usage is controversial.[15–17] A deep drain may be placed if extensive soft-tissue dissection and dead space are present, especially in the setting of therapeutic-level anticoagulation postoperatively.
Arthroplasty for posttraumatic sequelae is associated with greater intraoperative blood loss than routine primary hip arthroplasty. One measure taken to decrease intraoperative blood loss is the use of antifibrinolytic agents such as tranexamic acid. In cases where estimated blood loss is likely to be high, intraoperative cell salvage systems should be available. This condition allows transfusion of autologous blood and decreases the likelihood of needing postoperative allogeneic blood transfusion.
J Am Acad Orthop Surg. 2019;27(8):275-285. © 2019 American Academy of Orthopaedic Surgeons