Single stage revision of peri-prosthetic hip fracture with Stanmore femoral endo-prosthesis (Stryker) and Trident constrained acetabulum (Stryker),utilising the Zimmer-Biomet Explant and Stimulan bone substitute(Biocomposites)

This is a radiograph of normal, well functioning hip. It was inserted around 12 years ago. The patient was doing well, with no functional limitations. However the patient did have IgG immunodificiency and had previous problems with an infected left knee which ultimately ended in a fusion.

Unfortunately the patient sustained a simple fall which resulted in this peri-prosthetic fracture. As you can see from the films this is a Vancouver B1 fracture.
The Post-operative Vancouver classification system was first published in 1995 and describes fractures around uncemented hips. It has subsequently been updated. The classification system is one of the few in orthopaedics where classification guides management and it incorporates the location of the fracture, stability of the implant and bone stock.
There is much debate regarding its application to cemented stems. In Sheffield (and many other centres) our policy is that if the cement remains well bonded to the bone and a perfect reduction is possible, in the presence of a tapered polished stem then internal fixation is acceptable. In theory if the bone heals then creep of the cement may be possible and the tapered implant may subside until it again reaches stability.
Currently the Vancouver classification and management recommendations are as follows;
A. Fracture around either trochanter – Open reduction and internal fixation(ORIF) if displaced (I would suggest this is only applied to the acute situation, attempted reduction and fixation of chronically displaced fractures is not rewarding)
B1. Fracture around the level of the stem with a well fixed stem – ORIF with plate, screws and cables.
B2 Fracture around the level of the stem with a loose stem but adequate proximal bone stock – Femoral revision (which must bypass the distal fracture by a length of twice the cortical width)
B3. Fracture around the level of the stem with a loose stem and poor quality or severe commutation – Proximal femoral replacement (although I would note that many fractures should be considered for a revision stem, there is no way back from a proximal femoral revision).
C. Fractures distal to the stem – ORIF
Duncan et al. Fractures of the femur after hip replacement. Instr Course Lect. 1995;44:293–304.

I accept that this plate is long. However not all the distal holes have been used. A combination of screws and wires have been used. Screws are more stable than wires and hold the fracture more rigidly. With more modern plates, locking screws should be used. There have also been advances with screw design and many periprosthetic plates systems have specific screws with a flat tip. These give greater grip and are able to abut the prosthesis directly.

There is no true lagging of this fracture (wires have been placed at the fracture site) and the plate is used in a bridging capacity.
I am not going to show multiple follow-up images of the post-operative recovery however, the patient did very well and bone healing was apparent without complication at a 6 week and 3 month follow-up.

At the one year follow-up it was obvious there was a problem. The stem had migrated significantly.
The most obvious culprit for causing failure was infection. Inflammatory markers were elevated (CRP 45, ESR 31) and an aspirate confirmed a growth of Staph epidermidis.
The patient did not want further surgery and was happy to go onto long term suppressive antibiotic therapy.

Again the patient remained mobile and independent.
She then presented with sepsis and was significantly unwell with septic shock.
Her hip had become increasing painful and she underwent surgery, simply to decrease the infective load as a lifesaving procedure. Obviously necrotic and infected tissues were debrided and Stimulan was added to the operative site as an adjunct to increase local concentration of antibiotics.
Positive microbiology yielded a sensitive Staph epidermidis.
The radiograph shows the pellets of Stimulan in the soft tissues.

The patient remained well and although she remained independent she represented with increasing pain and worsening mobility.
This was a difficult call. She was a frail patient and after much discussion at an MDT we decided that she was at best fit for a single stage operation.
Inflammatory markers remained elevated (CRP 42 and ESR of 37) and a repeat aspirate (two weeks after cessation of antibiotics) revealed growth of the same strain of staphlococcus.

There is an obvious extensive scar. Therefore when prepping it is important to ensure that drapes will not cover it. Both proximal and distal extensions need to be accounted for at this stage.

A marker pen was used to identify the scar prior to application of the Ioban drapes.

The initial incisions were not taxing and the subcutanteous tissues were incised down to the fascia lata.

In my opinion it is not necessary to create a massive exposure above the facia. Doing so produces a dead space, increases the risk of haematoma formation and thus the risk of deep infection. However some mobility of these tissues is required. Once the fascia is seen I use a scalpel to create a small plane above the fascia lata. The blade must almost be horizontal. Do not aim ‘down’ or the fascia will be breached.

The fascia is then incised. If it is really tight then hip abduction can de-tension this tissue which helps the mobilisation. It is important not to cut deeply into the underlying tissues (the abductors and vastus lateralis).

Once the facsia is incised the blade is used to re-create the fascial plane. I tend to cut with the blade horizontal / aiming upwards as shown here.

Splitting of the scarred tissues with digital dissection is significantly less risky. Often tight structures are felt above the deeper tissues but below the fascia. Be careful though when breaking these down as they often represent scaring around traversing vessels. Cutting these should be done under direct vision after diathermy.

This image shows the lateral hip following release of the adherent fascia. It is often easier to find an area of normal tissues to identify the correct anatomical planes. However this was not possible in this case.

Wound extensions are made as required.

Once exposed fully the posterior border of vastus lateralis is identified and released from the lateral intermuscular septum.

Vastus lateralis was very scarred in this case and required patient dissection. However once released a ‘ring handle’ Hohmann retractor was placed under the muscle belly. The tip of the retractor was placed anterior to the femur to allow retraction.

Further dissection was required to elevate vastus lateralis (A) proximally. This was a combination of sharp dissection, the use of diathermy and blunt dissection with Bristow and Cobb osteotomes.

The femoral stem was protruding out of the femur and a nibbler was used to remove further soft bone over the lateral aspect of the tip of the femoral implant.

Further exposure revealed more of the plate. You can see the distal end of the femoral stem protruding anterolaterally to the plate. (A)
The profunda femoris (deep femoral artery) supplies the muscles of the thigh. It arises from the lateral side of the femoral artery in the femoral triangle (the borders of femoral triangle are – Superior – Inguinal ligament, Medially – Adductor longus, Laterally – Sartorius). Profunda passes deep to adductor longus, the femoral artery passes anteriorly.
Generally when elevating vastus anteriorly it is safe around the lateral aspect, the terminal ends of the perforators are usually visible but stay close to bone. Posteriorly however the perforators of the thigh present a rather more tricky problem as they pass through the lateral intermuscular septum (and they tend to be larger here too as they have not terminally divided).
There are three classical perforators from the profunda. Dissection around the posterior aspect around the linea aspera should be meticulous. Search for the perforators before cutting them. I use ligaclips to occlude before cutting. Others use ties. Diathermy doesn’t work.
If a perforator is cut inadvertently I release the linea aspera proximally and distally to the bleeder. This releases the lateral intermuscular septum allowing access to the posterior compartment, it is then simpler (but not easy) to control the bleed. Caution is required around the medial side of linea aspera as the profunda artery and vein are close by on the adductors.
The most proximal branches of the profunda are the medial and lateral femoral circumflex arteries. The medial circumflex passes between iliopsoas and pectineus and lies on adductor magnus. It passes between quadratus femoris and adductor magnus and divides into ascending and descending branches. The ascending branch lies on the anterior border of quadratus and is at risk during the posterior approach to the hip.
Regarding the three perforators, the first passes between pectineus and adductor brevis and pierces the adductor magnus posteriorly very close to the linea aspera.
The second pierces adductor brevis and magnus. It is located around mid thigh.
The third arises distal to adductor brevis and pierces adductor magnus. As a rule of thumb it is located one hands breadth above the flare of the metaphysis.

More proximally ectopic bone had covered the plate. Most normal anatomy had gone.

An osteotome was used to remove the ectopic bone. Sometimes is can be daunting to take these sharp tools to areas where the anatomy is a little suspect, however I would say that from a knowledge of anatomy it is clear that no significant structures could be at risk. The sciatic nerve is posteriorly, the adductors more anterior and any major bleeders cannot be in this region.

Further expose of the plate was therefore completed.

As the hip had migrated distally and there did not appear a lot of bone on the radiographs it is easy to get lost. Proximally you can confirm presence of the addutors. These are felt as a muscular pad anteriorly over the neck of the hip.

Further dissection of the plate superiorly was required.

The whole of the plate is now exposed. In order to do this the origin of vastus has had to be compromised. The tendon has been split longitudinally and the two aspects reflected anteriorly and posteriorly respectively. When I find a good plating case to present I will show how this can be repaired. However as a general rule when plating a femur try not to compromise the origin of vastus lateralis.

The screws of the plate were then removed. Remember to plan ahead before starting to ensure that you have all the kit to remove the screws (including a broken screw set).

If screws have no grip, forceps clamped under the head can aid removal. The teeth of the forceps engage the screw threads.

The wires were removed with wire cutters.

“Simple” step though it is it’s always a relief when the plate comes off, you are making progress.

The lateral femur is then seen almost in totality and the state of the femoral bone stock starts to become more evident.

The wires were removed with wire cutters.

A final check was made to ensure there was no bony overgrowth or excessive scaring over the plate and the plate was then levered off the lateral femur.

Lateral bone was removed with osteotomes to expose the femoral component further.

Once exposed the femoral implant was pulled posteriorly and laterally out of the femoral shaft. I was then able to make my first cut across the femur.

The cut was completed with osteotomes to prevent damage to structures posterior to the femur.

Even when complete there was not a great deal of movement of the femoral implant.

Further release of soft tissue posterior to the femur was then started to improve the mobility.

I actually repeated the bony cut 2cm proximally and removed a segment of bone as access was proving difficult.

The proximal femur was then placed under traction and soft tissue dissection was completed.

A significant perforating bleeding vessel was encountered and the Ligaclip applied.

In keeping with my previous advice on dealing with bleeding, the lateral inter-muscular septum was released more proximally and a clip placed on the perforator.

Further dissection around the proximal femur allows the femoral head to become evident.

The abductors were released last and their position noted(they can be tagged with suture to aid this).

Finally the proximal femur (containing the implant) was removed.

It is apparent how far the implant had migrated. This was obviously a slow migration in soft bone as it hadn’t fractured proximally.

Not a lot of normal anatomy remains. The main bed of the wound is made of the adductors (A), anteriorly is vastus (B) and the cup (C).

The polyethylene was removed with an osteotome. It needed to be removed intact as it needed to go back into the shell once the shell screws had been removed (more later).

The screws were removed. Luckily there was no bony overgrowth over the screw heads. I find the tip of the ball pusher useful to breakup any bony overgrowth without damaging the head.

The acetabular shell was removed with an Explant device (Zimmer-Biomet). This consists of three main parts.
The centralling head – A. This is interchangable and needs to be the same size as the internal diameter of the acetabular component. (22,28 32 etc).
The blade – B. These come in two lengths, truncated (short) and full radius (long). The short is used first. There are multiple blades corresponding to the outer diameter of the shell, a 52mm offset blade is used for a 52mm shell etc.
The shaft – C. This is used to both impact the blade and also to twist the blade.

The head of the Explant is placed in the “poly” of the cup. The blade should just be lateral to the metal shell. Full exposure of the shell is therefore important. In significantly worn cups (or offset cups) the poly should be removed and a trial liner inserted to ensure excessive bone is not removed.

The head of the shaft is then impacted with a hammer and the blade is inserted into the bone surrounding the shell. I repeat this many times around the shell. Once complete I then insert the Explant for the final time and it is twisted ensuring it travels 360 degrees around the shell. There should now not be any bony attachments left.

The truncated blade is then swapped for the full radius blade.

Again this is impacted circumferentially around the shell and then twisted. Eventually the cup will come out with the Explant. When impacting is very important the the head remains firmly in the cup. If it lifts out the blade will not cut accurately and there may be excessive bone loss. Excessive torque forces in sclerotic bone will twist the blade, if significant resistance if felt, stop and repeat the impaction steps again.

This cup was removed with out bone loss.

Finally all potential soft tissue pockets were opened with diathermy.

All obviously necrotic tissue and infected tissue was removed.

A pilot hole was made with a drill to expand the deformed femoral canal and then corkscrews were introduced. A slap hammer removed the corkscrew and fibrinous tissue. Up-cutting osteotomes completed the debridement.

The acetabular bed is reamed to remove all fibrinous tissue. Healthy bleeding bone should be seen. Stryker recommend a 2mm cement mantle for their constrained cup.
Care is required to preserve all the acetabular walls. If they are becoming thin you need to stop and reconsider surgical options. The common scenarios are for example sclerotic bone, in which case will multiple drill holes or a reciprocating saw assist fixation of a cemented cup. Consider whether the bone bleeding enough for an uncemented shell. If there are bony defects do augments need to be used.
In an dirty to clean operation I always aim to use a cemented cup if bone stock is adequate. Cement can incorporate heat stable antibiotics. If sensitivities are appropriate Copal cement with 1g of Vancomycin per mix is our workhorse. 1g of Vancomycin will not effect cement strength. Its use at higher concentrations does.

Sclerotic areas and the old screw tracts were overdrilled.

Stage 1 is now complete.
This wasn’t quick and needed a fair bit of concentration.
How to prep for the second stage varies between surgeons.
Some centres (including the Endo Klinik, Hamburg) will now close the wound, and fully redrape and prep. We do not do this. Instead we pack the wound and personnel and dirty trays etc are removed from the tent.
The clean part of the operation is performed with new trays and a re-scrubbed team. We use a new leg-bag, reprep the ioban area with chlorhexadine and fully redrape. However I am considering whether to change to the Endo Klinik method.

This is the kit for the Trident Captive cup. It is pretty basic but consists of;
A – Trial Insert (there is a central screw hole for use with a metal shell (if used)
B- Impactor
C – Impactor Tip
D- Head Removal Keys (when inserted into the inner bearing area of the cup these can release the head)
E – Femoral Head Reduction tool (we’ve added this to the tray)
F – Impactor (alternative version)

The Constrained cup is a bulky implant and in my opinion slightly lateralises the centre of rotation. I use it only as a last resort. If I can get away with a large diameter head or dual mobility cup I will. We do not use the uncemented versions of this cup as they are usually used in salvage cases where bone quality and bone stock is poor. Therefore reaming to a perfect hemisphere for the uncemented shell is often not possible.
By default these implants will cause impingement and forces will be transferred to the cement / bone interface. They can then fail. We have also had cases where the implant has disassembled.
To try and reduce failure it is important to insert the cup in a position where impingement is as limited as possible, try to preserve some abductor muscles and ensure that offset is correct.
The All-Poly captive cup consists of an outer UHMPE shell (A), a cobalt chrome bipolar femoral head which has polyethylene fused to its inner surface (B) and a polyethylene locking ring. (C)

Articulation therefore occures between the outer UHWPE and the CoCr bipolar head and the CoCr head and the head on the femoral stem. It is essentially a cemented bipolar.
The locking mechanism a split locking ring. As the femoral head is inserted through the ring it expands allowing passage. As the femoral head ‘equator’ passes through the ring it contracts but as the femoral head enters, the locking ring is pushed laterally into a more constrained space where it can no longer expand.

The impactor handle actually consists of two parts. The shaft of the handle (A) and a metal adaptor (B). The adaptor is threaded onto the handle.

The adaptor tip is simply a pushed / snapped into the adaptor on the handle.

The constrained shell is then mounted onto the shell. It does not lock home, do not let it fall off! To my knowledge there are no alignment rods.

Now to the Stimulan, an absorbable calcium sulphate product. The kit consists of the following components:
A. Calcium sulphate
B. Mixing pot
C. Sterile water
D. Bead mat
E. Paste applicator and spatula

Currently Stimulan is licensed to have 1g of sterile vancomycin powder and sterile liquid gentamycin added to it. We replace the sterile water with an equivalent amount of gentamycin (80mg / 2ml) therefore for a 20CC pack, 12ml of water is replaced with 480mg of gentamycin.

Vancomycin powder may clump so larger lumps are broken down in a separate pot (A) before being added to the mixing bowl.

Stimulan is then added to the vancomycin.

The gentamycin is added.

The mixture is stirred for 30 seconds until it forms a smooth paste.

The paste is then smeared onto the bead mat ensuring that the pellet cavities are completely filled. Differing volumetric bead mats are available.

Stimulan sets in 5 minutes.

The bead mat is then flexed to release the beads. These are captured in the mixing bowl.

The beads are firm and do not crumble.
Data from Biocomposites Ltd states that pin on plate testing (weighted pin dragged across a block of poly) does not lead to increased wear (which would lead to “third body” production and wear). Nor does it lead to heterotopic ossification.
Elution of antibiotics (>MIC) occurs for at least 40 days.

The cup is inserted as per any normal standard cemented polyethylene cup.
The cup chosen is 4mm smaller than the last reamer to ensure an even 2mm cement mantle. The cement is pressurised and the cup inserted. Standard fashion, medialise then correct for version and inclination. Remember there is no alignment device.
In this slide I am maintaining pressure with the impactor handle covered with a swab. This is only done after the cup is seated as it allows better visualisation of the whole cup and it is easier to remove surplus cement.

As noted earlier, this was a long operation and the kit used for the proximal femoral replacement had been expertly demonstrated on this site already :
https://www.orthoracle.com/library/endoprosthetic-proximal-femoral-replacement-trochanteric-reattachment-pathological-femoral-fracture/
The steps we undertook were exactly the same. The only difference here was that we did not perform a trochanteric osteotomy and therefore I did not use a body with the hydroxyappetite coated trochanteric attachment plate.
My reasoning behind not using the HA body was that the patients trochanter may not have had complete vascularisation and could have acted a nidus for infection and we were using a constrained captive cup.
The resection was also greater than that already demonstrated and we used a ‘principle shaft’ as part of the reconstruction.
We trailed in a similar way to the earlier group however with a captive cup it is not possible to trial fully as I did not want to reduce a trial head into the captive cup. I could have used the unlocking device (slide – 64) however my confidence with them is not great and I did not want to have to take out the cemented captive cup if we got the trial head stuck. Leg length was therefore a calculated estimate (I believe is the common paraphrase)

The principle shaft used in this case is coated with a silver compound (Agluna in Strykers case). Some studies have shown this does decrease in incidence of post-operative infections, however these results are not universal.
Ref: Silver-Coated Megaprosthesis of the Proximal Tibia in Patients With Sarcoma. Hardes et al. Journal of Arthoroplasty. 2017. 32 (7) 2208-2213.
Silver-coated (Agluna®) tumour prostheses can be a protective factor against infection in high risk failure patients. Parry et al. Eur J Surg Oncol 2018. Dec S0748-7983.

The trochanter (body) is impacted onto the principle shaft. I try to keep the plastic covering on the implant for as long as possible.
Note the collar impactor (A) in the background, this is used later.

The collar is then placed onto the distal end of the principle shaft.

The collar impactor slots into the collar.

Finally the stem is impacted.

A hardinge restrictor was placed down the femoral canal and the canal was lavaged and aspirated.
Bone cement was inserted in a retrograde fashion.

Without dragging the implant across the skin, the implant was inserted. The leg at this time was in the the leg bag and vertical. The implant was inserted with 15 degrees of anteversion.

Once impacted home, excess cement was removed.

A femoral head is ready to be impacted onto the proximal femur.

The femoral head was then pushed through the locking ring into the Cobalt Chrome bipolar head.

A trial range of movement showed no soft tissue or bony impingement. You can see however in this image that the neck of the femur impacts against the rim of the cup. This occurs in this design of cup. There are others which have recessed areas where impingement occurs commonly (posteriorly in extension and anteriorly with flexion and internal rotation)
These implants however are only available in an uncemented version. I have however in extreme cases roughened the posterior surface of the polyethylene and cemented these in. The reason for this is that the smallest diameter cemented constrained cup is 54mm. Most manufacturers do not go below this for cemented versions. The uncemented constrained cups do go a little smaller but not small enough for DDH cases. This use is clearly off licence.

The wound is thoroughly rinsed and soaked in chlorhexadine solution.
There has been work both in-vitro and in-vivo directly comparing the effects of chlorhexadine soaks versus a saline and povido-iodine solution. Studies are only small but chlorhexadine is as effective (better in-vitro) , cheaper, and has fewer complications and contraindications.
Intraoperative chlorhexadine irrigation to prevent infection in total hip and knee replacement. Frisch et al. Arthroplasty Today. 2007. 3, 294-297
Effects of antiseptics, ultraviolet light and lavage on airborne bacteria in a model wound. Taylor et al. JBJS (Br) 1993;75(5):724-30

The wound is dryed and haemostasis ensured before the Stimulan is added.

Stimulan is spread liberally along the whole wound. Although stated to cause less drainage issues than other calcium based products Stimulan can cause an increase in wound drainage. I know that some surgeons place drains in situ for 24 hours (which seems a little counter-intuitive). I however ensure that Stimulan is only placed in the sub-fascial layer. I also use glue on the wounds. Wound leakage has not been a problem in the cases in which I have used it.
It has however (at the higher doses) resulted in a transient hypercalcemia. Not at a level that needs treatment but calcium levels do need monitoring after its usage.

Stimulan does tend to collect posteriorly in the wound but I am not convinced that this is of any clinical significance.

During closure the vastus is repaired and the capsule closed (this sometimes requires mobilisation or fashioning). I then repair the abductors to vastus. In cases where I use a captive cup I have not always repaired the abductors onto the implant. It heals and the abductors and vastus act as a sleeve. The fascia lata is repaired.
I finish with a two layer fat closure, ensuring minimising of dead space, subcuticular monocryl, glue and Aquacell dressings.
A suture line VAC dressing or PICO type dressing is not used. I want the antibiotics to elute and remain high within the hip.

The post operative radiograph reveals that the bone cement is acceptable within the femur. The collar is sitting flush on the bone. The captive cup is well cemented with no ‘bottoming out’ however there has been a medial wall breach with cement protrusion. This usually is of no consequence.

The lateral radiograph shows adequate anteversion of the cemented polyetheylene componenent. It also shows that most of the Stimulan is posterior along the shaft of the femur.

By three months there has been resorption of the Stimulan. No other changes of significance are noted. The ligaclips are at the levels of the 1st and 2nd perforators.