Second stage revision total hip replacement to proximal femoral endoprosthetic replacement for infection using MUTARS proximal femoral endoprosthesis (Implantcast)

Pre-operative x-ray showing a cemented femoral stem with previous cerclage cabling and trochanteric hook plate following a periprosthetic fracture with a cemented acetabular component that appears to be loose with evidence of previous supra-acetabular impaction bone grafting with mesh and screws.
There is also a PLAD, postero-lateral anti-dislocation, mechanism and there is evidence heterotopic ossification Brooker grade 3. There is some evidence of periosteal reaction on the medial side of the bone and the abductors at the trochanter does not appear to be connected with the femur, despite the previous attempt to fix the trochanter.

AP pelvic x-ray following first stage revision whereby the proximal femur has been excised and a cemented stem inserted and fabricated into a proximal femoral endoprosthetic spacer using additional Kuntscher nail distally and a 32 mm femoral head articulating with a cemented cup in the acetabulum.

AP pelvic and lateral of the proximal femur showing a fracture through the Kuntscher nail at the junction of the cement and residual distal femur. This led to revision of the spacer.

AP radiograph of the proximal left femur and hip showing a revised left proximal femoral endoprosthetic spacer articulating in the native acetabulum without an acetabular component, reinforced with Kuntscher nails internally. The acetabulum appears to have lost superior bone stock judging by the size of the cement femoral head, so augmentation seems likely to reconstruct the hip centre of rotation. Given the initial X-ray showing graft, mesh and screw augmentation of the superior acetabulum, the bone quality may be poor and following reaming to expose healthy bleeding bone to accept a revision acetabular shell, this defect may worsen further. Therefore, we will need a revision acetabular system that can cope with almost any defect.

Patient positioned lateral decubitus with hip props and exclusion drapes. The skin is cleansed with alcoholic chlorhexidine twice before formal draping and incisional Ioban skin drapes are applied as shown.

The skin is incised through the old scar centred over the greater trochanterThe approach is deepened in line with the incision down to the fascia lata, which is shown at the base of the wound.

The fascia lata is opened in line with the skin using cautery through the previous site of multiple incisions through to the deeper layers.This fascial layer is often more adherent to the deeper layers such as the vastus lateralis, so care is taken not to incise too deep to avoid inadvertent injury to the sciatic nerve or devascularisation of muscle. One way to achieve this would be to inserted McIndoe’s scissors or an artery clip under the fascia lata and diathermy onto the instrument.

Once through the fascia lata layer, the (Gmax) gluteus maximus is splitThis reveals the trochanteric portion of the antibiotic loaded cement spacer (ABLCS), just visible at the base of the wound.

Having continued the incision down the thigh distally, the ABLCS is now visible prior to explanting. The Charnley bow retractors are used to retract the wound edges at the level of the trochanter.

Dislocate the spacer by hip flexion and adduction with internal rotation and explant the femoral spacer.The prosthesis is then explanted with gentle taps using a femoral head pusher and a mallet.

The explanted cement spacer on the back table showing the Kuntsher nail re-enforcement distally that was inside the residual distal femur. These cement spacers are hand-made during the first stage procedure as there are no commercially available proximal femoral endoprosthetic spacers available.

Apply cement to the face of the augment before inserting the acetabular shell. Prior to insertion of the definitive acetabular shell a thin rim of quick setting cement is smeared onto the augment to prevent micromotion between the shell and the augment. This helps to create a monolithic construct without concerns of metal debris formation which could cause loosening, bone loss, effusion and a pseudo-tumour.

Implant the definitive acetabular shell.Take the alignment tool and attach it to the straight handle for implanting the acetabular shell to positioning of the shell in anteversion and inclination.
Insert the acetabular shell with sharp blows until it is correctly seated and grips the residual acetabular bone. Assess for primary stability by judging the grip of the acetabulum on the shell.

Following impaction of the uncemented shell into the residual acetabulum, appropriate anteversion and inclination can be seen. It can also be seen that it is sitting just underneath the (A) augment which aids stability and will hopefully prevent it from loosening, migrating and failing. The poster-superior corner of the acetabular shell is uncovered, highlighting the degree of bone loss following multiple revision procedures. This is of no consequence to the success of the procedure.

Radical debridement of the joint cavity.Begin the radical debridement of the effective joint space. Using McIndoe’s dissecting scissors and Kocher’s forceps, the cavity lining of the effective joint space is debrided using dissecting scissors and cautery to healthy bleeding tissue. I prefer to start posteriorly where the (GMax) gluteus maximus enters the thigh. Also shown is the posterior (VL) vastus lateralis anteriorly in the wound.
This serves two purposes; 1) to excise any contracted scar tissue that may limit movement or cause impingement risking dislocation and 2) the radical debridement is considered the most important step in eradication of infection at the first stage, so repeating this step is felt to improve our chances of preventing recurrence.

Elevate this layer of thickened fibrotic scar tissue which is formed in reaction to the cement spacer lying between (GMax) gluteus maximus and (VL) vastus lateralis. Care is required not to inadvertently damage the profunda femoris artery and vein, branches of the femoral nerve and the sciatic nerve. Once the correct plane is identified, maintaining firm traction (as shown) helps to stay in the correct layer to avoid damaging any structures. It is always wise to palpate for the pulse of the profunda anteriorly and to palate for the sciatic nerve posteriorly to help to identify vital structures. However, in reality it is often impossible to convincingly identify the anatomy with this degree of fibrotic tissue and you must rely on your familiarity with the anatomy from previous primary excisions of the proximal femur.

Continue to excise from proximal to distal the scar tissue. For orientation the (Gmax) posteriorly and the (VL) vastus lateralis anteriorly are annotated.

The dissection continues anteriorly under the deep surface of the (V) vastus muscles. the residual (F) femoral shaft is just visualised distally.

The radical dissection from the cavity is now complete and can be seen were the tissue has been excised with cautery from the gluteus maximus (GMax), deep surface of the vastus lateralis (V). The residual distal (F) femur is also visible in the base of the wound.

Debride the acetabulum.Dissection now turns to around the acetabulum using cautery to identify the cotyloid fossa (the acetabular fossa and medial wall previously containing the ligamentum teres); again the scar tissue that has formed in reaction to the cement spacer is excised using cautery to leave healthy bleeding tissue.

Expose the acetabulum.Having cleared the (A) acetabulum, the hemispherical shape is now more easily identified and the floor of the acetabulum can be visualised. Norfolk and Norwich self-retaining retractors are inserted to aid exposure. These are placed carefully onto the split gluteus maximus (GMax) seen posteriorly. The Charnley retractors are also seen retracting gluteus maximus posteriorly and vastus lateralis (VL) anteriorly.

Identify the transverse acetabular ligament (TAL)Place a Hohmann’s retractor underneath the transverse acetabular ligament (TAL), this is useful not only for retraction but also for identifying the orientation of the native acetabulum for reaming.
Often it is visible, but after multiple revisions may have been excised, in which case place the tip of the Hohmann’s deep to the inferior rim (A) acetabulum at the apex of the cotyloid fossa to protect the obturator vessels and nerve. The obturator canal lies in the superolateral aspect of the obturator foramen and this is closely related to this retractor; as described by Rue et al., obturator vessel injuries may occur through inadvertent positioning of this retractor
(Rue J.P., Inoue N., Mont M.A. Current overview of neurovascular structures in hip arthroplasty: anatomy, preoperative evaluation, approaches, and operative techniques to avoid complications. Orthopedics. 2004;27(1):73–81.).

Skeletonise the residual distal femur.Returning to the (F) femur, the residual distal femur skeletonised from the soft tissues sub-periosteally using cautery as shown. Sub-periosteal dissection is safe and allows the femur to be mobilised from scar tissue on the deep surface of (VL) vastus lateralis for the next few steps.

A Cobb elevator is used to aid the sub-periosteal dissection to mobilise the (VL) vastus lateralis off the residual (F) femur .

A Hey-Groves bone holding forceps are used to grasp the now skeletonised residual distal femur as shown. The medullary cavity can now be reamed and broached.

Osteotomise the distal femur.Using a 1.27 mm oscillating saw the end of the femur is freshened up to accept a new proximal femoral endoprosthesis. I place a Langenbeck retractor around the femur to protect the soft-tissues and in particular the peroneal and tibial sciatic nerve divisions and femoral artery and vein from injury at this step.

Curette the medullary cavity then ream the distal femur.Having freshened-up the residual femur, a curette is used to remove any soft-tissue from inside the medullary cavity as can be seen being removed to start the debridement endosteally.

Having removed any soft-tissue using a curette to prevent any potentially infected tissue being pushed distally deep into the distal femur, sequential flexible reamers are now used to ream up the medullary cavity until cortical chatter is achieved. These reamers increase in 1mm increments. Ream the femoral medullary cavity preferably up to a depth of 130mm and to at least 12mm as the smallest rasp on the set is 12mm in diameter.

Ream the acetabulum.Sequential acetabular reaming is undertaken attempting not to migrate the reamer and therefore hip centre of rotation superiorly by keeping close to the transverse acetabular ligament and Hohmann’s retractor. Using acetabular hemispherical reamers from the Zimmer Biomet TMARS set, the acetabulum is prepared until scratch fit is achieved.
This is a feeling developed with practice, but essentially is the point at which the reamers catch on the residual bone stock to indicate that an uncemented hemispherical shell might achieve primary stability. This can be judged by stopping reaming and assessing whether the reamer is gripped by the acetabulum.
As you may be able to see in the photograph the bone stock superiorly is deficient i.e. no superior lip, and this will need augmentation.

Trial augments available on the tray.The hemispherical trial augments available with the TMARS include four different thicknesses (10-30mm) and six diameter sizes to match the shell outer diameter (50 to 70mm).

Trial the acetabulum.Having reamed to the point at which the reamer starts to bite into the residual bone, reamers are explanted and a matching sized trial tapped into the acetabulum to assess for primary stability.
If this grips the acetabulum then the correct size has been achieved and the definitive component is selected. The TMARS shells range from 48 to 80mm outer diameter.

Select the acetabular augment. The photograph shows a trabecular metal curved augment in the surgeon’s hands, which has two holes which are used for screws to fix the augment onto the bone but are also used to grasp the augment for trialling. The trabecular metal is highly porous tantalum with structural pores properties similar to that of bone to support bony in-growth to achieve secondary stability. The low modulus of elasticity of trabecular metal allows supposedly reduces stress shielding.

Insert augment and drill screw holes through the augment. Having determined the correct size of the augment, this is fixed to the bone with screws. The process for this involves taking a drill and drilling through the augment into the residual supra-acetabular bone to gain fixation.
The screw hole directions must be judged to be in the safe zone for acetabular screws to avoid inadvertent vascular or visceral damage anteriorly or neurovascular damage of structures exiting the sciatic notch posteriorly.
Use minimal pressure on the drill to try to remain within cancellous bone, if the feedback from the drill suggests your have reached cortical bone and further drilling risks perforation and therefore vascular injury (Tavares, R., Arcenio Neto, E., & Taki, W. (2018). Total hip revision arthroplasty of high-risk pelvic vascular injury associated with an endovascular approach: a case report. Revista brasileira de ortopedia, 53(5), 626–631. https://doi.org/10.1016/j.rboe.2018.07.002).

Measure drill holes.Having drilled, measured the depth of the screws, assessing whether the deepest part of the hole has perforated through to the other side of the ileum (and therefore potentially into vital structures) or remains within bone.

Insert screws through the augment.Insert two screws into the supra-acetabulum to fix the augment to the bone. They are self tapping screws.

Following the insertion of two screws, the augment can be seen to have reconstructed the superior rim of the acetabulum to aid stability of the uncemented acetabular shell. I would then take the trial acetabular shell and double check it will fit under the reconstructed superior rim before opening and implanting the definitive acetabular shell in the next step.

Insert screws into the acetabular shell. The primary stability of the shell is augmented with some additional screws. The same procedure for the augment screws is repeated by drilling, measuring and inserting self-tapping screws.
Again, the surgeon should be conscious of the ‘safe zone’ – described by Wasielewski from the centre of the acetabulum, imagine two lines to the anterior-inferior iliac spine to the sciatic notch posteriorly. This safe zone ‘should’ avoid penetration of screws into the pelvis. (Wasielewski R.C., Cooperstein L.A., Kruger M.P., Rubash H.E. Acetabular anatomy and the transacetabular fixation of screws in total hip arthroplasty. J Bone Joint Surg Am. 1990;72(4):501–508.).
Should you suspect an inadvertent vascular injury, my advice would be inform your anaesthetist and scrub staff of your concern and to prepare equipment and personal to deal with haemorrhage, to assess whether you can extend your approach to deal with the bleeding e.g. superior gluteal branch, but if not, pack the wound and request senior vascular surgical support and whilst waiting think about what approach (e.g. extra-abdominal intrapelvic approach) a vascular surgeon may require to achieve haemostasis.

Three screws are inserted into the acetabular shell to aid primary stability. Again these are self-tapping screws.

Insert trial acetabular liner. A trial liner is placed into the acetabular shell for trailing of the reconstructed hip later. Definitive liner options include neutral and lipped polyethylene liners, fully constrained liners or you can use the shell as a cage and cement a liner inside the shell if you wish to optimise host bone contact and maximise correct liner positioning.

On the back table the tray for the Implantcast proximal femoral endoprosthesis is shown.
On the right-hand side are the rasps which are hexagonal, which are inserted into the femur following reaming.
The hexagonal shape cuts channels into the endosteal bone to provide rotational stability.

Rasp the distal femur.The size of the last flexible reamer correlates to the size of the rasp in its diameter, which is inserted into the femur. The femoral rasp has a slight bow on it to match the bow of the curvature of the femur and this is attached to a handle which is struck using the mallet as shown, ensuring that you rotationally orientate the curvature of the rasp with the curvature of the femur. There is a collar on the rasp to replicate the collar of the endoprosthesis and the rasp is impacted until the collar sits flush with the freshened up end of the residual femur. Using the rasps is essential for the optional cementless femoral stem, but given the previous surgery and infection a cemented stem with antibiotics in the cement is preferable.

The residual femur following reaming and rasping and preparation ready for trialling.

The MUTARS trial tray on the back table, showing the multiple modular options for reconstruction of any segmental defect from 80 up to 340mm.

Insert the trial femoral endoprosthesis. A trial MUTARS proximal femoral endoprosthesis is then inserted into the femur and appropriate anteversion on the prosthesis is applied. The length of the shaft is planned pre-operatively by measuring the segmental defect from the radiographs and confirmed intra-operatively by exchanging different lengths of the modular shafts on the set until limb-length is approximated.

Lock the prosthesis anteversion for trialling.Once the femoral prosthesis has been rotated to achieve the correct anteversion the bolt shown in the photograph entering the shoulder of the prosthesis is tightened using the ‘T’ handle. This locks the anteversion for trialling, without which you cannot assess stability properly. The rotation can be changed in 5 degree intervals.

Add the trial femoral headA trial femoral head is placed onto the femoral neck prior to trial reduction. There is no dual mobility trial so we simply use a monpolar head for this step of the procedure. Definitive head sizes are dictated by the acetabular prosthesis, and specifically by the inner diameter of the dual mobility liner, usually a 22 or a 28mm head is compatible with most dual mobility liners.

Trial reduction of the hip replacement.Reduce the femoral trial into the acetabulum. The trial head will articulate with the trial liner in the TMARs acetabular shell.
I now assess the reconstruction for stability and limb-length in the same way as for a hip replacement by moving the hip through a range of motion into flexion, adduction and into internal rotation whilst also checking that the limb-length is not too short or too long by comparing to the other leg by palpating the patellar tendons through the surgical drapes.

Femoral canal preparation prior to cementation.Having removed the trial endoprosthesis, the femoral canal is washed with pulsed lavage and dried using packed ribbon gauze as shown. A cement restrictor may be placed distal to the tip of the prosthetic stem.

Attach the definitive cemented stem to the handleThe cemented stems range from 11 to 17mm in 2mm increments and we downsize the definitive stem by 2mm from the last rasp to allow for an adequate cement mantle.

Assemble to definitive prosthesis.The definitive part of the prosthesis are assembled on the back table, here we can see a silver coated shaft on the left with a silver coated proximal femur and trochanter and trinium which is covered with plastic for protection and the appropriate bolt which connects the two together. This bolt can be untightened to change rotation of the trochanter on the shaft.

The components are assembled by placing the bolt through the trochanteric portion of the proximal femur to engage with the shaft distally.

Assemble the dual mobility head and liner components.The dual-mobility polyethylene liner is produced onto the Co-Cr femoral head using this compress. The handle is turned until the head is forced inside the polyethylene liner normally with two audible ‘pops’.

The femoral head inside the liner, this should spin freely to ensure that it has been reduced inside correctly to prevent interprosthetic dislocation.

Retrograde cementation of the femoral canal.The femoral canal is now filled with cement with high viscosity cement in a retrograde fashion as shown. This has additional gentamicin in the cement to prevent recurrent infection.

Insert the cemented femoral stem.Once the canal has been filled with cement the femoral stem is inserted using the same impactor for the trial until the white hydroxyapatite collar engages flush with the cut surface of the residual femur. A McDonald’s forceps is used to remove any excess bone from the bone-implant junction.

Assemble the proximal femoral endoprosthesis onto the implanted femoral stem.Once the cement has cured, the assembled shaft and trochanter are attached onto the femoral stem recreating the anteversion determined during the trialling.

Bolt the femur and stem together. Once the anteversion is satisfactory an anti-torque device is held in the left hand and a torque wrench is used to tighten the screw going through the trochanter shaft and into the cemented femoral stem to maintain that level of rotation of the prosthesis. The pre-assembled dual mobility head and liner are inserted onto the clean trunnion of the prosthesis.

Assemble the dual mobility femoral head. The pre-assembled femoral head and dual-mobility liner are placed onto the trunnion.

Engage the femoral head onto the implant trunnion and then finally reduce.Using a femoral head pusher 3 blows are used to engage the femoral head onto the trunnion of the femoral neck.

The prosthesis is now reduced into the acetabulum as shown with gentle axial traction by the assistant.

The layered closure of the gluteus maximus and tensor fascia lata using No. 1 vicryl to approximate the wound edges.

The wound is then closed in layers with a drain exiting distally and clips are applied to the skin before dressings.

Post-operative x-ray showing satisfactory positioning of the acetabular component the augment and the proximal femur.

AP radiograph showing the cemented femoral stem inside the residual distal femur.