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Revision Total Hip replacement- Direct exchange Link MP revision stem for periprosthetic fracture

    Overview

    Learn the Revision Total Hip replacement: Direct exchange Link MP revision stem for periprosthetic fracture surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Revision Total Hip replacement: Direct exchange Link MP revision stem for periprosthetic fracture surgical procedure.

    Intra-operative fracture rates during total hip replacement have been reported as high as 7% which is a disappointing figure but simply reflects the strength of implants and instrumentation compared to the relative weakness of adult bone. Some cases are potentially avoidable but even an experienced surgeon following best practices and excercising all his or her skill will inevitably encounter such events and should be in a position to manage them.
    To avoid iatrogenic peri-prosthetic fractures fractures I would strongly suggest always carefully templating pre-surgery as well as being entirely familiar with the implant. If intra-operatively trial sizes are going significantly above those that have been templated or following some resistance to rasping there is a suddenly easy passage of the rasp it is beholdent upon the surgeon to consider the possibility of an iatrogenic fracture and proceed appropriately.
    I would recommend exploring the femur (as detailed in this technique) following the use of intraoperative radiographs if a femoral fracture is confirmed.
    The Vancouver classification for intra-operative fractures is a logical descriptor which reliably guides the management of these complex and technically challenging injuries, though its preferable not to need to refer to it too often during a primary joint replacements.
    The Vancouver Classification for Intraoperative fractures is, like its postoperative counterpart, logical. It classifies the area of fracture as being either proximal metaphysis (A), proximal diaphysis (B) or as being distal to the implant (C). Each of these areas is also subdivided into 1, 2 and 3 representing a cortical perforation, an undisplaced crack or a displaced fracture respectively.
    This technique demonstrates the use of the MP stem (Link) for an acute peri-prosthetic femoral fracture of a total hip replacement. The MP stem is a modular, cementless stem with a porous finish allowing bony on-growth. Leg length, offset and version adjustments are all possible with this versatile system.
    Within this presentation the Vancouver intraoperative periprosthetic fracture classification is discussed in detail along with principles of peri-prosthetic fracture exposure, implant removal, fracture reduction and maintenance of the femoral fracture. I also discuss methods of achieving leg length and stability after direct exchange.

    Indications

    Intra-operative fracture rates during total hip replacement have been reported as high as 7% which is a disappointing figure but simply reflects the strength of implants and instrumentation compared to the relative weakness of adult bone. Some cases are potentially avoidable but even an experienced surgeon following best practices and excercising all his skill will inevitably encounter such events and should be in a position to manage them.
    To avoid iatrogenic peri-prosthetic fractures fractures I would strongly suggest always carefully templating pre-surgery as well as being entirely familiar with the implant. If intra-operatively trial sizes are going significantly above those that have been templated or following some resistance to rasping there is a suddenly easy passage of the rasp it is beholdent upon the surgeon to consider the possibility of an iatrogenic fracture and proceed appropriately.
    I would recommend exploring the femur (as detailed in this technique) following the use of intraoperative radiographs if a femoral fracture is confirmed.
    The Vancouver classification for intra-operative fractures is a logical descriptor which reliably guides the management of these complex and technically challenging injuries, though its preferable not to need to refer to it too often during a primary joint replacements.
    The Vancouver Classification for Intraoperative fractures is, like its postoperative counterpart, logical. It classifies the area of fracture as being either proximal metaphysis (A), proximal diaphysis (B) or as being distal to the implant (C). Each of these areas is also subdivided into 1, 2 and 3 representing a cortical perforation, an undisplaced crack or a displaced fracture respectively.
    This technique demonstrates the use of the MP stem (Link) for an acute peri-prosthetic femoral fracture of a total hip replacement. The MP stem is a modular, cementless stem with a porous finish allowing bony on-growth. Leg length, offset and version adjustments are all possible with this versatile system.
    Within this presentation the Vancouver intraoperative periprosthetic fracture classification is discussed in detail along with principles of peri-prosthetic fracture exposure, implant removal, fracture reduction and maintenance of the femoral fracture. I also discuss methods of achieving leg length and stability after direct exchange.

    Setup

    MP stem and associated trays.
    Basic revision kit (balls, reamers, osteotomes etc.)
    Wiring system (up until very recently I used the Charnley wiring system which is very versatile and cheap, (there is apparently a national shortage).

    Operation – 1

    Review pre-op imaging
    This patient had sustained an intra-capsular neck of femur fracture abroad which was treated with an uncemented total hip replacement before repatriation to the UK.
    It was noted at the time of surgery that there was a minor crack around the calcar area and my understanding was that weight bearing was to be limited. However language communication between the patient, her surgeon and the physiotherapists broke down secondary to language barriers. The patient walked on her prosthesis, the implant migrated and she was transferred to our care as an emergency.
    As can be noted the fracture is seen to extend from the femoral neck cut (A) and propagate distally(B). The full extent of the fracture is not seen on this image however it propagated to a level above the isthmus. The classification falls down a little here as we do not know if this was the initial fracture configuration or a resultant of weight bearing. However if present at the time of surgery, following the classification system, this is a B3 fracture. One of the advantages of the classification system is that it aids treatment. These are listed below. You may need to refresh your memory looking at the introduction slide to remind yourself what each code stands for, however to save you a few clicks;
    The classification ‘divides the bone into the proximal metaphysis (A), the proximal diaphysis (B) and fractures of the cortex distal to the implant (C). Each area is subdivided into 1, 2 and 3 representing a cortical perforation, undisplaced crack and displaced fracture respectively.’
    Metaphysis.
    A1 – Bone graft the defect – this can be autograft from the acetabulum or femoral head.
    A2 – Cerclage wire before inserting stem, reducing the risk of crack propagation. I use simple Charnley wires (when available).
    A3 – The recommendation is to use a fully porous or taper fluted stem. In practise a cemented stem can be used if anatomical reduction of the fracture is obtained and the cerclage wires are tight enough. I would not use Charnley wires here but Dall Mills or equivalent.
    Proximal Diaphysis.
    B1 – Bypass the defect by 2 cortical diameters with a fully porous stem. The use of strut allograft has significantly decreased.
    B2 – Cerclage wires. The B2 are most frequently missed which can be disastrous. The stem needs to bypass the fracture. If noted post operatively then the patient should be partial weight bearing (I personally use 1/6th body weight)
    B3 – Fully porous coated stem to bypass defect
    Distal to the Stem Tip.
    C1 – Morcellised bone graft and fully porous coated stem to bypass defect
    C2 – The classical teaching is that as the fracture is distal to stem tip, cerclage wiring is satisfactory. My assumption is that the majority of these are rotational injuries associated with dislocation of the hip. I would personally plate these fractures if bone strength is anything but good.
    C3 – Open reduction and internal fixation.
    Therefore if a fracture is suspected and then confirmed on table, a treatment plan based on its location and extent can be put into place.

    Review pre-op imagingThe lateral radiograph adds little except to show that the fracture has not significantly displaced. The cup orientation looks satisfactory.

    Pre-operative templating of the fracture.This patient underwent lower limb dopplers to excluded a DVT. Risk factors here would be both the fracture, the surgery and air travel. If a DVT had been found, local policy would have been to insert an IVC filter.
    I also templated the fracture. If the fracture, or the tip of the revision stem, would have passed the isthmus (2 cortical distances below the distal end of the fracture) strong consideration would need to be made for a locking revision stem. It doesn’t always follow that a distally fixed stem however needs to be used. For example strong, thick bone, an anatomical reduction, excellent fracture stability and a sensible patient who could partial weight bear might .
    Templating is important. It can be done on the contralateral hip if the fracture is significantly comminuted. LINK place significant emphasis on this in their op-tech.

    This is the kit for the MP (LINK). We have trimmed it down somewhat and in keeping with most of our kit this is the basic, no frills kit.
    They are shown here as a reference and their use will be explained fully as we go along.
    It consists of;
    A – Stem Inserter
    B – 3.5mm screwdriver
    C – Tapered reamer handle
    D – Inserters (implant holders)
    E – (2 parts) Threaded rod and slap hammer
    F – Trial heads

    The second tray consists of;
    A – Hollow Reamer (for the neck of the implant)
    B – Driver (head reducer)
    C – Large Hex screwdriver
    D – Screwdriver (to secure trial implant to inserter)
    E&F Long and short trial locking bolts
    G – Reamer guide
    H – Caliper
    I – Trial necks (we only stock 35mm and 65mm standard and XXL offsets)
    J – Trial proximal spacers
    K – Guide rod

    The final tray has consists of;
    A – 3.5mm screwdriver
    B – ‘Insertion Forceps’ -Neck holder), neck holder sheath
    C – Screwdriver
    D – Torque wrench

    Patient positioning and preparationThe patient was placed in the lateral position and the old scar marked before application of the ioban dressing.

    Initial approach, excising skin edges.As the wound was not fully healed (and therefore potentially contaminated) the skin edges were excised as part of the approach. This entailed removing a 2mm skin edge.

    Deeper exposure, old wound explored.It can be seen from this image that the wound had not fully healed. Additionally there was presence of haematoma in the superficiail tissues.

    Deeper exposure onto vastus lateralis and visualisation of the femurAll of the sutures from fascia lata were removed and the partially healed fascia was incised. The deeper structures were all intact. (GT- greater trochanter, VL – vastus lateralis, Ab – abductors)

    Wound edge protection with gauze before muscle mobilisation.Saline soaked gauze was sutured onto the fascia lata, isolating the fat and skin. The Charnley initial retractor was used to expose the operating field.

    Proximal femoral implant exposure through old posterior approach.The initial approach had been posterior and this was taken down without further surgical incisions. Fortunately there had not been been pull off of the posterior structures – from top to bottom – piriformis, superior gemelus, obturator internus, inferior gemelus and quadratus femoris. Release of the posterior sutures resulted in the external rotators retracting back allowing visualisation of the prosthesis. You can see evidence of clot and haematoma in the joint cavity.
    If the external rotators had pulled off they would have been identified, mobilised and tagged with sutures.
    Remember in 95% of cases the sciatic nerve will exit the pelvis below piriformis and pass deep (anterior) to the short external rotators. It needs, at a minimum, to be palpated along its course to avoid damage.

    Exposure of the metaphysis and diaphysis of the femur by elevation of the vastus lateralis.The posterior border of vastus was identified (the most reliable landmark is where it originates distal to the greater trochanter).
    My preference is to elevate the posterior border. The terminal branches of the perforating profunda vessels should be sought and either tied or occluded with ligaclips.
    It is theoretically acceptable to split the vastus in the approach to the femur, the innervation of vastus is proximal and splitting the muscle does not denervate it but in my opinion this is a ‘messy’ and destructive approach.

    Exposure of the metaphysis and diaphysis of the femur by elevation of the vastus lateralis.The posterior muscle fibres (A) are elevated anteriorly from the lateral intermuscular septum

    Once vastus lateralis is mobilised the fracture can be identified.Vastus is then displaced anteriorly (A) using either a Bristow or Cobb’s elevator. It can be seen in this image that the origin of the muscle is kept intact and not disturbed (B).
    What is apparent is the fracture line extending distally along a substantive area of the femur (C)

    Once vastus lateralis is mobilised the fracture can be identified.Further blunt dissection, lavage and gentle controlled levering with osteotomes reveals the fracture. The implant can be seen in the base of the fracture (A)

    Femoral implant removal from fractured femurThe implant was very loose and could simply be pulled out of the femur.
    However extraction can be difficult with well fixed implants and osteotomes, saws and an extraction device (which pulls in the line of the femur) are often used.
    With cemented stems, the stem usually comes out easily. However the cement requires removal. I use cement osteotomes, burrs and chisels. Others use ultrasonic cement removal devices, however this is a topic in itself.

    Femoral implant removal from fractured femurThis image reveals that the implant was a proximally coasted uncemented implant. It is obvious that there in no bony ingrowth.

    Exploring the extent of the femoral fracture to identify two cortical diameters beneath the fracture.The bone bed was lavaged to identify the extent to the fracture and the exposure extended to identify distal propagation of the fracture. You should be able to palpate or be able to measure 2 cortical diameters below the most distal extent of the fracture. It however is not the case that this has be fully exposed.

    Distal femur preparation with the MP hand reamers, to twice the cortical thickness beneath the fracture.Once found distal preparation for the MP stem is started. The first step is to insert the distal reamers. This must progress twice the cortical thicknesses beyond the fracture.
    The length of the reamer is determined both from the template and from direct assessment on table.
    The reamer lengths / diameters correspond directly to the stem proportions. The stem lengths range from 160 to 330mm with diameters ranging from 12 to 25mm

    Distal femur preparation with the MP hand reamers, to twice the cortical thickness beneath the fracture.The depth of reaming is approximated using a bony landmark. As a rule, the bottom ring mark on the reamer is at the level of the original neck resection, if the neck is absent (revision for osteolysis, infection etc) the level is a thumbs width above the lesser trochanter. The fourth ring should be at the level of the greater trochanter.
    In this case the ring markings on the reamer aligned to the inferior femoral neck resection (i.e the lower ring on the reamer was advanced until it was parallel to the original inferior neck resection)
    Getting the exact length is challenging in significantly comminuted fractures. Therefore some ‘play’ can be built into the system. It is relatively easy to lengthen the prosthesis in situ, but not always so easy to shorten.
    Therefore if the length is in doubt I set my reaming based around the second ring mark. This may leave the leg a little short (by 1cm) but it is then easy to build up using the proximal spacers.
    This all sounds rather complicated but I will explain how to do this with some ex-vivo examples later.
    It is important to not keep advancing the reamers. The idea is to build up a conical space in the femur with the reamers, the reamers should all be advanced to the same bony landmark and then the diameters expanded. In this way there will be significant bone / implant pressfit.

    The body of the new femoral implant must have a firm grip within the femur. If this is not the case the stem will migrate as the patient weight bears. A simple guide as to whether good bony hold is going to be achieved is to examine the reamer. It should have bone in the cutting flutes.

    Distal femur preparation to allow for a distal fix as an initial step in most cases around which further reconstruction then occurs.This fracture was very simple and in two parts.
    As a principle with periprosthetic fractures it is important to obtain distal fix first and then reconstruct the proximal bone around the stable implant. With complex periprosthetic fractures I often reconstruct multiple fragments with the hip reduced. In this way most of the soft tissue tension is reduced as the tissues are close to their anatomical positions.
    However, there are some exceptions and this was one of them.
    My concern was that if we obtained distal fix and then simply tried to wrap the proximal fractured femur around the implant we would not obtain perfect reduction. There would be gaps as the size / bulk of the implant would be too great. We then would have spent ages with burrs trying thin down parts of the proximal femur to get fracture reduction.
    In some fractures (especially those with very thin femoral bone) perfect reduction does not always matter, however as can be seen in these images, the bone stock is very good and I wanted to achieve perfect reduction.
    I therefore decided to reduce the fracture, ream through the proximal femur and still achieve good distal hold.
    This image shows the Charnley wire passer(A). It is slid from posterior to anterior (this lessens the risk of catching the sciatic nerve). The Charnley wire is passed into the the tip of the passer (B).
    The sciatic nerve is formed from the the lumbosacral plexus (L4-S3) and exits the pelvis with the internal iliac vessel through the greater sciatic notch deep to pirifomis (which arises from the ventral sacrum and inserts onto the trochanter in the piriformis fossa). The sciatic nerve travels superficial to the short external rotators of the hip (superior gemellus, obturator internus, inferior gemellus and quadratus femoris) and enters the posterior compartment of the thigh deep to the tendon of gluteus maximus. In the posterior thigh the nerve lies between the medial hamstrings (semitendinosus, semimembranosus) and lateral hamstrings (long and short head of biceps femoris) and divides into the tibial, common peroneal and sural nerves.
    However, in summary stay on bone and you will be OK!

    Proximal femoral fracture reduction using reduction forcepsThe fracture was reduced with Haygrove’s reduction forceps and the reduction is near perfect (A).
    The Charnley wire can be seen (B) prior to tensioning. Other cables or cabling systems can be used.
    To aid the initial passing of the wire around the femur I use the diathermy to form a space in the lateral intermuscular septum. This is performed under direct vision to avoid the perforators.

    Proximal femoral fracture wire stabilisationThe Charnley wires are then tightened. There is a knack to this. The two ends of each wire are crossed and then twisted together loosely at first. The wire grabber than grabs this crossing point in the tip of its jaws. The knot is pulled upwards and then twisted around once. This is repeated for each turn that is added to the knot, the slack in the wire being taken up as the knot is pulled and twisted. It is important not to have the knot kink around itself or it will snap.

    Operation – 2

    Femoral fracture stability testingThe leg is moved to ensure that the hold is secure and that the fracture does not displace.

    Further preparation of the femur with hand reamers after wiring.The hand reamers were then passed again.

    Further preparation of the femur with hand reamers after wiring.In hard bone this can be physical work. I start with reamers 2-3 mm less than the templated image and slowly build up.

    Further preparation of the femur with hand reamers after wiring.I also ream by hand as on power thermal damage can occur.

    Preparation of the femur with hand reamers finishes once the diameter of the definitive implant has been reamed to.Again I confirmed that we were into bone by checking the cutting flutes on the reamer.
    The Link op-tech states that levels should be confirmed by radiography on table. When first starting I do not think this is unreasonable. It can confirm not only the depth of reaming but also that there is good endosteal contact with bone along the reamer.
    The last reamer diameter determines the diameter of the implant. The reamer diameters are identical to the stem diameters in other words a 16mm reamer equates to a 16mm stem.

    Assembling the stem inserter and the MP femoral stemThe stem inserter is then screwed onto the definitive stem using the 8mm screwdriver.

    Assembling the stem inserter and the MP stemAs can be seen the introducer has ring markings at exactly the same levels as those of the reamers.

    Commencing insertion of the MP femoral stem, which has a 3 degree bow.All implants have a 3 degree angle corresponding to the normal bow of the femur.
    The implant has to be inserted with the 3 degrees aimed posteriorly to match the femur (as with any simple nailing).

    Careful advancement of the femoral stem using a mallet.The stem is then advanced using a mallet. Frequent and light impactions with control are required.
    I tell all my juniors to place their index finger on the counter surface of the mallet head, it is difficult to ‘overhit’ with the mallet held in this way.

    Appropriate depth of femoral implant is indicated by the proximal markings on the inserter.As the stem approaches full depth, as indicated by the markings visible, more resistance will be felt.
    If this doesn’t happen then something is wrong. Check the implant was the correct size and check that you haven’t propagated the fracture. If both of these are ok try gentle tapping again. It maybe that the implant will bed in a few mm distally. This is OK as you can build up the stem (lengthen it) using the proximal spacers.
    If none of these work you’ve got it wrong. I would then advocate checking with fluoroscopy, simply opening the next size implant can get costly.

    Prepare the proximal femur for the MP neck component.To do this the reamer guide is used.
    There are actually two of these. A short guide is used when a long neck segment is used, the long guide is used when a short neck is used.
    The 160mm stem must be used with a short neck. All other stem lengths can use the long or short neck segment. The 160mm stem and short body are not much longer than a normal implant therefore I personally cannot see much use for it.
    The guide is screwed into the stem using the hex-drive

    Either the short or the long neck guide is chosen and then screwed into the proximal end of the femoral stem.The hex drive is tightened. It is important that there is no soft tissue blocking the final screw home. If this happens the hollow reamer will not advance far enough and the neck segment will not sit down correctly on the stem.

    The neck is reamed using the neck reamer over the previously selected guide.The hollow reamer was placed over the reamer guide. It was apparent that soft tissue was in the way.

    The neck is reamed using the neck reamer over the previously selected guide.It was apparent that soft tissue was in the way.
    Therefore the reamer guide was removed and soft tissue was cleared.

    The neck is reamed using the neck reamer over the previously selected guide.The reamer guide was re-inserted into the proximal femur.

    The neck reamer is always used with careful reference to its effect, in particular avoiding removal of any of the proximal femoral “wall”.The hollow reamer was then advanced.
    It is a sharp and destructive tool. I would advise caution if it appears that the reamer is going to take out a femoral wall. Check fracture reduction and the stem alignment again if it this appears to be the case.
    Irrigation is used if the bone is hard.

    Reaming ceases, the reamer guide is removed and the guide rod is then screwed into the stem. The neck segment is threaded over this.

    MP neck segment trialling-selection of inserterThe trial neck segment can be loaded onto these inserters. There are differing inserters (in our kit) for different angled necks. In practice I rarely use these, however they hold the implant tightly and if in a tight spot, can rotate and angle the neck segments accurately.
    These inserters are shown without the neck trial attached.

    MP neck segment trialling-insertion of the neck trial to the femoral stem.I simply thread the trial neck segment over the guide rod.

    MP neck segment trialling-insertion of the neck trial to the femoral stem.When pushed home the teeth of the trial segment interlock with the teeth of the stem.

    MP neck segment trialling – Anterversion settingWith the leg held vertical, anterversion can be dialled in.
    There is an additional check that can be made with a caliper (see later). However in practice, if the neck segment is seated correctly it will not move.
    Finally the trial neck segment is secured with a locking bolt (this can be seen on the next slide)

    MP neck segment trialling – Securing the neck segment with the locking bolt.Locking bolt (A) shown locked into place.
    A trial head is also inserted. This head diameter obviously had to match the unrevised cup but they come in both ceramic and CoCr, 28, 32 and 36mm diameters and four potential neck lengths.

    Trial reduction and stability assessment. The hip is then reduced.
    The checks that occur now are imperative and must be rigorous.
    Firstly check for stability. This is simply flexion and internal rotation. I would expect at least 80 degrees of flexion and 30 of internal rotation. I would also expect 30 degrees of external rotation in full extension.
    Revisions are more complex with regard to tissue tension. I would not expect significant laxity with longitudinal traction. The abductors should be moderately tight and there should be no kick back when the tibia is released from a flexed position with the thigh in neutral.
    If there is instability, assessment of why is very important. ‘Jacking it out’ (or increasing the head size) is never the next step.
    I will run through my thought processes, there will be others but this is how I attempt to get stability and optimise hip biomechanics. Remember in this case the centre of rotation is fixed as the cup is not being revised.
    Assuming instability is present the first step should be to check the leg length is correct ?
    If it is short it can be built up with spacers with the Link system.
    If leg length is correct, is there impingement?
    If impingement is present, is it secondary to poor offset or soft tissue interposition or abnormal femoral version.
    Firstly check the version to ensure this is ‘normal’ (15-30 degrees)
    Then check for impingment, remove soft tissue if present. Revision surgery is associated with scarring from the primary surgery. Often when going in from the back the posterior structures are released / thinned leaving an imbalance and anterior scaring can cause impingement. This needs thinning out. I use diathermy. It is important to stop when the scar tissue is replaced with fatty tissue. Further dissection of this can bring you into close contact with the femoral vessels.
    Finally I check offset. Getting this right can be difficult. Increasing offset by increasing the head size increases both offset and leg length. Going from a 0 to +8 in a 135 degree angled neck increases offset by 4mm and length by 4mm. If leg length is perfect shortening the L/L by 4mm is optimal but not often possible in the revision setting.
    Decreasing the neck / shaft angle of the body from 135 to 126 increases the offset but also decreases L/L, here length needs to be added.
    Although I have placed these checks in an order, in reality many happen at the same time and there is interplay between them.
    If all remains unstable, dialling in abnormal version may reduce dislocation. If anterior impingement, increasing version decreases posterior dislocation and visa versa.
    Finally if all fails consider changing the cup. But remember, going from a 28mm to a 32 mm head only increases the ROM by 3 degrees before impingement recurs.
    Alternatives include a dual mobility or worst case scenario, a captive cup.

    As noted in the last slide, it is important to know how to lengthen the implant. To show this I present a series of ex-vivo examples.
    This slide shows the guide rod inserted into the stem. There are two proximal spacers, a 10mm and 20 mm spacer that can be used in isolation or in combination gaining 30mm in length.

    When no spacer is inserted, the caliper will show “0”. If the reading on the caliper is not flush with the reading lines the teeth of the neck segment is not engaged with the stem.

    Operation – 3

    A 10mm spacer can be added, it has teeth to engage with the body and teeth to engage with those of the neck segment.

    To ensure that all teeth are engaged the caliper again can used to confirm correct seating.

    Up to 30mm can be added to the implant using these spacers.

    The caliper again is used to confirm seating. The 30 mark is just visible.

    Ex-vivo examples of adjusting the MP construct lengthNote with increasing spacers the distance between the stem and neck segment increases (A)

    Ex-vivo examples of adjusting the MP construct lengthWhilst that is pretty simple there are a few rules when constructing the MP.
    With the long neck segment, with no proximal spacer or a 10mm spacer the SHORT screw is used.
    For 20mm or 30mm spacers the long screw is used.
    With a short neck segment (body) no spacers can be used and the screw is always short. Remember though that the reamer guide is long.

    Definitive choice of MP neck constructTherefore in this case, no spacers were used and the screw was therefore short.

    Securing the definitive MP neck construct-insert over guide wire and confirm with caliperIf inserted by the book, the neck segment would be inserted over the guide rod and seating confirmed by the caliper. However I find that with increasing familiarity this does not always need to be done. You will have an idea of the angle of insertion from all the trialling and you will know from the trials how far down the neck segment should go (from bony landmarks), you can judge therefore when it is engaged.
    If however the locking bolt doesn’t engage (perhaps 2 or 3%) I will use the rod and caliper.

    Securing the definitive MP neck construct-tighten the locking bolt.The locking bolt is tightened but not fully.

    Securing the definitive MP neck construct – Final tightening with torque limiting wrench.To achieve the correct tension the wrench and ‘insertion forceps’ are used.
    This is different on the more modern kit where the wrench with a torque indicator has been replaced by a wrench that emits a loud snap when the correct torsion is achieved.

    Securing the definitive MP neck construct – Final tightening with torque limiting wrench.The insertion forceps and its mortice sleeve (A) are placed over the mortice, the wrench (B) is placed over the expansion (locking) bolt.
    The wrench is tightened until the correct tension is achieved (a line indicates this, although I note that some centres now use the snapping wrench).

    Securing the definitive MP neck construct – Trial heads once neck construct completedThe insertion forceps and wrench are removed. Trial heads can be used again to confirm stability and length.

    Definitive femoral head impaction followed by reduction of the joint.The definitive head is then impacted and reduced.

    Closure is then obtained. I start by repairing the posterior capsule and external rotators.
    If in chronically retracted cases, the external rotators may require dissecting free from scar. This can be a delicate task with the sciatic nerve in close proximity. Palpating the location of the nerve is often possible. If not dissection is even more painstaking. Usually the presence of the nerve is heralded by its surrounding fat. Be careful and patient.
    Occasionally in cases with multiple revisions, no anatomy is visible. If the muscles cannot be located I personally fashion a pseudocapsule to close the joint space and bring up what muscle I can find. In my experience, quadratus femoris is the most constant muscle and can usually be located.

    Deep tissue closureVastus lateralis is repaired back to its scar on the lateral intermuscular septum and quadratus is repaired.

    Superficial layer closuresFascia, fat, skin closure follow and finally skin glue and aquacell dressing

    The post operative image reveals that leg length has been achieved. The right leg is slightly abducted and the left adducted however there is a suggestion that offset has increased.

    Distally, there is good implant / bone fit. This film is inadequate as the tip of the implant was not shown but the implant does extend 2 cortical diameters below the fracture.

    The lateral confirms good bony reduction of the fracture.

    The 3 month image reveals excellent bony healing. There are no lucent lines around the implant which would indicate loosening. There has been no migration of the implant.

    Similar excellent healing is shown on the lateral image.

    Post Operative

    Old frail patients rarely partial weight bear. Surgery should be robust enough to allow full weight bearing.
    Standard thromboprophylaxis regimen.
    Checking Hb and U&E the evening of surgery and in the morning is mandatory. These patients can bleed significantly and fluid shifts can occur. Keep an eye on the sodium levels in particular.
    A check x-ray is required before weight-bearing.
    Extended antibiotic prophylaxis is not required unless clinically indicated.

    Recommended Reading

    Periprosthetic fractures evaluation and treatment. Masri et al. Clin Orthop Relat Res. 2004;420:80-95
    Intraoperative Periprosthetic Fractures During Total Hip Arthroplasty. Davidson et al. JBJS (Am) 2008;90:2000-1012.
    Periprosthetic, interprosthetic, and refractures after interprosthetic femoral fractures – Extension of the currently used Vancouver, Rorabeck and Platzer classification.Velickovic M, Hockertz T. J Ortho Rehab Surg. 2018;2(1):1-8
    Intraoperative periprosthetic hip fractures. ElSerwi et al Menoufia Medical Journal. 2015
    Medium-term follow-up of a modular tapered noncemented titanium stem in revision total hip arthroplasty: a single surgeon experience. Klaus et al . J Arthroplasty 2013;28:84-89.
    Results using the MP stem have been good. In my hands the main complications include subsidence and dislocation. There is certainly a learning curve and the use of intra-operative fluoroscopy can be useful when starting. The main reason for subsidence is failure to achieve good bony interface along the implant. However reaming to a set distance and then expanding using increasing diameter reamers is perhaps a key take home point.
    I spend a long time checking for offset, leg length and impingement. Failure to address these can lead to poor results.
    The new implantation kit certainly helps with fluidity and efficiency but it is no substitute for experience.

    Reference

    • orthoracle.com

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