Stryker MAKO Express Workflow total hip replacement (using Accolade II and Tritanium implants)

From the preoperative CT, the patients leg lengths and femoral offset are calculated. Comparisons/differences are then calculated between the two hips. This is prepared well in advance of the case, currently this is prepared by MPS technician. The MPS technician manages the case during the procedure from their computer terminal. Ensure you are happy with the plan before proceeding to theatre.

The ideal cup placement is then considered. The coloured dots on the screen represent the centre of rotation on the femur and acetabular component.

Planned acetabular component position. The cup positioned is planned to the inclination angle and version you prefer. typically cup inclination of 40-45 degrees and version 20-25 degrees. Type in the angles you wish and the computer superimposes the cup position on the patients anatomy. You can then visualise in 3-D the cup position and decide if you are happy. Look if the cup is covered by bone, its not too proud especially in the psoas tendon area where it could be irritated by a proud cup rim.

Planned femoral stem position and neck resection line (green) calculated. Once you are happy with the plan, proceed to the operating room!

Computer generated component position from planning. The plan is an accurate reflection of the final component positions on the post-operative x-ray.

For positioning of the patient for the posterior approach refer to:
Total Hip replacement: C stem AMT/Elite (Depuy) cemented hip (femur first)
For the MAKO THR prior to preparing the patient’s leg with antibacterial solution place an ECG dot on the inferior pole of the patella. The metal dot on the ECG sticker acts as a marker during point capturing during the MAKO set up later.

Prior to surgery it is prudent to check the patient’s leg lengths in the “floppy lateral” position.
Make sure to abduct the leg to get a true reflection of the leg length (not shown). Remember this length for comparison later in the case. In this picture the upper most leg is adducted, for true leg length comparison abduct the leg until it is neutral position (adduction/abduction) and then compare the leg lengths.
Prior to positioning it is important to check the patient’s leg lengths when they are supine as this will identify if the leg is shorter/longer or equal relate the clinical picture to pelvic radiograph to plan your operation. In the supine position apparent leg length descepancies secondary to the spine or pathology in the limbs can be appreciated more fully.
However as you are using MAKO the leg length measurements will be calculated for you. It is prudent though to clinically check in case there has been an intra-operative error.

Pre-operatively test the stiffness of the hip.
The hip here has been put in to internal rotation. Rotate the leg internally until it reaches its maximal rotation. If the angle of internal rotation is low (<30 degrees) the chances of dislocation are much less. In essence the stiffer the hip pre-operatively a lower range of motion will be achieved by the patient post-operatively and so the range of motion of the hip construct is subjected to is less. Therefore when testing intra-operative stability of the hip implants a lower range of internal rotation before dislocation occurs can be accepted in the stiffer hip.

A lower leg calf pump has been applied to provide intermittent pneumatic compression during the procedure to decrease the risk of thrombosis formation.

This is the MAKO camera (c) and computer screen (s). This should be placed at the “head” end of the patient. Unfortunately this may not be possible due to the position of the anaesthetist. It can be placed anywhere between 11 o’clock and 1 o’clock i.e either side of the patient’s head.
This position allows the camera optimal chance of array capture and allows the surgeon good visualisation of the screen.

The patient is prepped and draped.
Prior to this 2% Chlorhexidine prep has been applied to the skin. An Ioban preparatory skin drape (Iodine impregnated) has been applied to the thigh.

Make stab incisions for the pelvic array into the iliac wing.This is a fixed reference point for the computer to know where it is in space. The pelvic array is clamped to threaded pins which go into the ileum.
The threaded pins need to be placed into the iliac wing to hold the pelvic array. Three pins are recommended, two can be used as a minimum.
Insert the first pin through a stab incision into the iliac wing 2cm proximal to the anterior superior iliac spine. Make the stab incision in an oblique direction perpendicular to the iliac crest.

Once the stab incision has been made use blunt dissection through the fat layer to identify the inner and outer margins of the iliac crest.

Drill the first bone pin into the iliac crest. Aim to have sound fixation by placing through both the inner and outer ilium table.

Use the pin clamp to plan the subsequent stab incisions and bone pin placements.
Perform a stab incision aligned with the hole.

Apply and tighten the pin clamp block to the three iliac crest pins.Three bone pins have now been passed into the iliac wing through the pin clamp block (p). Tighten the pin clamp block knob (t) with a spanner after you have finger tightened it initially.

P – pelvic array attachment clamp.
t – tightening knob
paa – pelvic array attachment point

Apply the pelvic array to the pin clamp block at its attachment siteApply the pelvic array to the pin clamp block.

Mobilise the pelvic array so that it is aligned to the camera.Point the discs of the array at the camera. The aim now is to allow the computer to see the array using its camera. The camera is placed approximately 1 to 1.5m away out of the sterile field. Typically in the 11 o’clock or 1 o’clock position relative to the the patients head.
The computer screen will inform you when the array is visible to the camera, by displaying a green dot (representing the array) in a grey parallelogram representing the area the camera can see.
Once the array is “visible” to the camera tighten. Avoid knocking the array during the procedure as this step will have to be repeated to recalibrate the position of the array in relation to the patient’s anatomy.

The skin incision for the posterior approach is centred over the tip of the greater trochanter, distally running straight and in line with the vastus lateralis fibres and proximally curving towards the posterior iliosacral joint.Now start the posterior approach to the hip joint.

Incise through the skin into the fat. Cut perpendicular to the skin, if the dermis is not cut perpendicular the skin edges are harder to close.

The fascia lata is identified and a fasciotomy is made with a scalpel or scissors, extending both distally and proximally in the line of the skin incision.Make an incision into the fascia lata with a scapel, centered over the greater trochanter. Incise the fascia lata for the length of the wound.
Proximally the fibres of gluteus maximus under the fascia lata are split in the direction of its fibres using blunt dissection until you can completely visualise the greater trochanter of the hip when the muscle belly is retracted. Distally the fascia lata is free of muscle fibre attachments.

Excise the trochanteric bursaThe trochanteric bursa overlying the greater trochanter is seen. As I am using a posterior approach the sciatic nerve is at risk. Do not delve deeply and blindly with the retractors, instruments or your hands.
The sciatic nerve exits the pelvis through the lower part of the sciatic notch. It is particularly at risk during the posterior approach to the hip. Identify the nerve in the posterior fatty tissue to the greater trochanter before proceeding, if it looks small it may have divided into its tibial and common peroneal branches before piriformis. The nerve appears below the piriformis muscle and lies over superior gemellus, obturator internus, inferior gemellus and finally the ischial spine.

A Charnley bow retractor has been applied, placing one leaf anteriorly and one posteriorly under the tensor fasica lata.
Do not place the posterior leaf to deeply, you could inadvertently catch the sciatic nerve.

Insert the MAKO proximal femoral check pointThe next step in the express MAKO workflow procedure is to place a proximal femoral check point in the lateral aspect of the greater trochanter.
The check point is shown mounted and ready to drill into position.

The proximal femoral check point is drilled into the lateral aspect of the greater trochanter.It should be inserted perpendicularly to the long axis of the trochanter.

Capture proximal femoral check pointWith the leg resting on the contralateral limb, and the knee flexed at 90 degrees, capture the proximal checkpoint, using the blue probe.
To do this place the blue probe into the central divot of the checkpoint. Capture this point by pointing the probes array (a) at the camera. Allow the camera to “read” the position of the probe, it will be visible again on the computer screen, once it has been recognised by the camera.
The final process to capture this point is to tell the computer that you are happy with its recognition of the point identified. This is achieved by pressing the a foot pedal which is attached to the computer.

Capture distal femoral check pointWith the leg in the same position next capture the distal femoral landmark, by placing the blue probe on the ECG dot previously placed on the inferior pole of the patella.
Again, once the array is recognised by the computer you capture the point by pressing the foot pedal.

Internally rotate the femur to lengthen the piriformis tendon and aid its identification.Once the landmarks have been captured continue with the posterior approach to the hip joint.

The piriformis tendon can be found by palpating the greater trochanter and when you feel a small “nipple” of bone the tendon is adjacent to this. Once the fat is swept/dissected off the tendon it is readily seen.
The piriformis tendon is identified as shown. A Langenbach has been placed under the gluteal muscle to aid its identification.
The scissors have now been passed over the piriformis tendon superiorly.

Once the piriformis tendon (p) is identified an incision is made in line with its superior border.Due to difficulties with photography due to the position of the robot. Slides from a posterior approach which has been previously documented are used below. Their orientation is the same, ie both are for a right sided THR.

The piriformis tendon can be found by palpating the greater trochanter and when you feel a small “nipple” of bone the tendon is adjacent to this. Once the fat is swept/dissected off the tendon it is readily seen.
The piriformis tendon is identified as shown. Gluteus medius (A) is superior to the piriformis tendon. Gluteus maximus (B).

Insert Hohmann above piriformis tendon
A sharp Hohmann is placed superior to the piriformis tendon, under gluteus minimus muscle. To achieve this pass the curved dissecting scissors into the incision you have made with them superior to the piriformis tendon, then place the Hohmann retractor over the scissors into the same space, removing the scissors.
A- Gluteus Maximus fibres fascia lata
B- Tip of greater trochanter

Insert Hohmann proximal to quadratus femorisTo insert the distal Hohmann retractor use the curved dissecting scissors to enter the space between the joint capsule superiorly and the quadratus femoris muscle inferiorly. A blunt Hohmann is then placed in the same tract made by the scissors and the scissors removed. By placing the two Hohmann retractors in this fashion the piriformis tendon and the posterior capsule of the hip are exposed.

Place a stay suture to the piriformis tendon and then release it from its trochanteric insertion.A 2 Vicryl stay suture (s) is applied to the piriformis tendon using 2 “throws” of the suture into the tendon as close to its insertion on the greater trochanter as possible.
Maintain as much length of the tendon as you can.
This is not shown clearly but the vicryl suture is shown leading away from the posterior aspect of the hip joint.
The priformis tendon is now released from its distal insertion on the greater trochanter, control of the tendon is achieved by tension placed on the stay suture.

Now an arthrotomy of the hip capsule is made as an L-shaped limb starting proximally (p) at the edge of the acetabulum heading towards the tip of the greater trochanter.
The arthrotomy is then continued distally (d) along the edge femoral neck until the quadratus femoris muscle is reached. Inferiorly and distally there is often a venous vessel which bleeds – this will require diathermy.

A second stay suture is been applied to the joint capsule along its free edge after the arthrotomy has been performed.
Using the two stay sutures that are now in place reflect the tissues (t- piriformis tendon and posterior capsule) posteriorly to protect the sciatic nerve throughout the rest of the operation.

A ruler with a clip mounted is used to mark the femoral necks predetermined resection level (in this case 15mm).
With the MAKO package this distance can be measured during the femoral stem planning prior to surgery.
Apply the ruler to the top of the lesser trochanter and measure the 15mm superiorly, marking the femoral neck resection line.
In the enhanced workflow for MAKO this line can be derived from the computer. Using a hand held array the exact point can be identified on the screen as the array tip is moved on the femoral neck.

The femoral neck osteotomy is made with the sagittal saw at the level of the neck cut as marked.

The osteotomised femoral head is removed. Sometimes the foveal ligament may hindered removal of the femoral head this can be incised with curved scissors, place them under the curve of the femoral head and release the ligament.

Place a posterior acetabular Judd pin into the ischium. To insert this Judd pin place the tip of the pin inside the acetabulum gradually walk it back until you go over the acetabulum margin posteriorly in the space before the short external rotators are and then aiming for the ischium hammer the pin insitu this acts as a retractor.

Place a Judd pin, A, superior to the acetabulum under the gluteal musculature aiming to retract the gluteal muscles with the pin once it has been hammered into the ilium.A curved retractor,B, is now also placed anteriorly on the acetabular margin to mobilise the femur anteriorly and out of the way of the acetabulum.

The labrum and soft tissues are excised by sharp dissection around the acetabulum margin to expose the acetabulum 360o.
Sometimes you might need to release the reflected head of rectus femoris to allow the femur to mobilise forward to gain better exposure of the acetabulum. The reflected head is extra-articular on the superior and anterior margin of the acetabulum – release the fibres by sharp dissection onto the bone.
The transverse acetabular ligament is identified. This is a valuable landmark for cup positioning (Archibold et al’s paper (J Bone Joint Surg Br. 2006 Jul;88(7):883-6.).
Aligning your acetabular component with the transverse acetabular ligament seems to be the optimal cup position for specifically reducing dislocation rates to the region of 0.6%.

The pelvic checkpoint (A) needs to be inserted into the bone superior to the acetabulum and far enough over the acetabular margin that it does not protrude into the acetabulum.Some surgeons place this before the posterior approach to the hip joint, but I find it easier after the femoral neck cut and acetabulum has been fully exposed.

Insertion of pelvic checkpoint is in a perpendicular fashion and well seated.
Make sure it is flush with the bone with no interposed soft tissue.

Capture the pelvic checkpoint with the blue mobile array.Once the Checkpoint is recognised by the camera press the foot pedal to register it.

Place the array in such a way so that it faces the camera to be captured.

Once the pelvic checkpoint has been registered, the neck step is too perform the acetabular registration process.
This involves placing the hand held array tip onto the landmarks requested by the MAKO computer. They follow a set sequence.
When capturing points the probe must be on bone and not soft tissue. If there are host cartilage remnants present at the capture point in question push the probe through the cartilage until it touches bone.

The first three landmarks to be identified are the posterior acetabulum, anterior acetabulum, and superior rim of the acetabulum.
These larger blue bubbles represent the area that the computer needs to register. Pictured is the posterior landmark.
Place the array probe tip into the acetabulum and identify this blue bubble. Once you are in the correct place the bubble changes colour and you capture it by pressing a foot peddle.
You must match the registration points as closely as possible to the virtual model, to allow for accurate alignment of the patient’s bone with the virtual model .

Once the three initial points have been captured, you proceed to capture a further 32 points inside and outside the acetabulum. The system automatically moves you onto the next registration point. Spread registration points out as much as possible and ensure those requested peripherally are truly peripheral. This screen shot shows the outcome of capturing these points, those marked green are optimally captured, <0.5mm those in yellow are out by 0.5 to 1.5mm. If they appear red the capture point is >1.5mm out and can be recaptured. An overall accuracy of all the points and must be within 0.5mm.
A further 8 verification points are finally captured (large white bubbles in this screen shot).

Once registration is complete the haptic arm can be moved into position. Move the acetabular reamer into the mouth of the acetabulum. Once close the MAKO arm will adjust itself to the desired acetabular inclination and version angle. Once this has been achieved the arm will lock in this position.

The correctly sized acetabular reamer is mounted on the haptic arm, reaming for a Tritanium cup being 1mm under or line to line dependent on surgeon preference and the quality of the bone. Hard bone may require line to line reaming. Mount the size reamer you require ie 55mm for a 56mm cup.
Surgeons not familiar with the MAKO procedure can start with a smaller reamer first and ream sequentially with increasing sizes until the correct size is reached. However, once confident with the MAKO technique there is no need to do this, simply ream with correctly planned reamer.

A clear and unimpeded view of the acetabulum should have been achieved by previous preparative steps.

Using the free arm mode, move the acetabular reamer into the mouth of the acetabulum and into the planned orientation then change from free arm mode to engage the robotic-arm guidance.
Begin reaming once you happy the reamer is in correct position.

Now ream observing the computer sceen aiming to ream until the superior, lateral, and posterior values read 0 .
On the screen the acetabular model when reading green (as shown) indicates more bone should be resected, when it turns white the bone resection is “to plan”, and if it is red it indicates resection has exceeded the plan by 1mm.
The haptic arm should protect you from over-reaming. It will stop and not allow you to ream too deep, or incorrectly.
Once reaming is complete, remove the power equipment and reamer handle from the robotic-arm .

Visually inspect the reamed acetabulum to confirm the level of preparation.

Once reaming has been finished mount the acetabular introducer onto the haptic arm.
Next mount the correctly sized acetabular shell onto the introducer as shown.

Move the haptic arm, with cup mounted, into the acetabulum.Move the haptic arm into the wound and towards the mouth of the acetabulum in the free arm mode.

Once the acetabular component is in this position change from free arm to robotic arm guidance mode. The robotic arm will adjust itself to allow for the cup to be placed into the correct version and inclination as planned.

Once the haptic arm is in the correct position and you have confirmed that you are happy with the cup inclination and version displayed on the computer screen hammer the cup into position.
As the cup is impacted, realtime feedback about its depth and remaining distance to go in mm is displayed on the screen.
Once the shell is fully seated capture the final values of its position. A further check of acetabular shell orientation can be made by capturing points on the rim of the cup using the handheld array. (not shown). Confirm clinically that the cup is seated correctly, check it has bottomed out by observing the host bone through its handle attachment hole.
If the cup is not stable once impacted augment its stability with cancellous bone screws through its cluster holes. In this case the cup was stable and no screws were required. Screw holes are drilled with a 3.3mm drill bit and the screw depth is then measured. Screws are 6.5mm in diameter and the lengths available are 16mm, 20,25,30,35,40,45,50,55 and 60mm.

Impact the liner into the acetabular component and ensure the liner is correctly seated.Check 360 degrees around the cup to confirm liner seating.

Start with a box chisel in the postero-lateral margin of the femoral canal to gain access to the femoral canal.Aim to remove enough cancellous bone with the box chisel to enable easy entry into the femoral canal for the pencil reamer.
Next pass a pencil reamer down the femoral canal. This will pass easily if you have got the box chisel entry position correct. The amount of resistance feedback during passage of the pencil reamer will act as guide to how tight the femoral canal is.

The smallest femoral stem broach applied to its handle which is hammered until the correct broach is seated fully.
Start with the smallest broach and increase in size incrementally. Once you have reached the planned femoral stem size, ensure there is no further movement of the broach and that it has rotational stability.

Broach in femoral canal, confirm you are happy with its seating.

Apply the trial neck and head to the trial stem in the femur. Now test the stability of the hip replacement.
For a description and pictures of stability testing refer to
https://www.orthoracle.com/lib/bone-soft-tissue-tumour/lower-limb/bone-tumour-reconstruction-lower-limb/exeter-stem-stryker-and-gap-ii-restoration-acetabular-cage-stryker-for-acetabular-metastases/operation/#slide-55
When using the express workflow, you can capture the values after implantation in the reduction results page by capturing the proximal and distal femoral checkpoints. Leg length and hip offset are accurately measured by the computer check if conform to your plan.

Definitive femoral stem insertionOnce you are happy with the constructs stability insert the femoral stem prostheses. Impact the femoral stem with controlled hammer blows. Allow the stem to seat into the same version and depth as the trial. As the stem finally engages into the femoral canal the audible pitch of hammer blows will change.
Test the stability of the uncemented stem with simple hand rotation of the impactor – it should be solid with no movement. The stem should not subside any further with repeated hammer blows after it has come to stop as per the trialling level.

Stem finally impacted into the patient’s femur.
Apply a trial head to the stem and repeat your tests of stability and leg length.

Remove pelvis arrayRemove the pelvic array and its clamp from the three iliac pins. Remove the three pelvic iliac crest pins with the reverse function on the drill.

DONT FORGET TO REMOVE THE INTERNAL CHECKPOINTS ONE ON THE FEMUR AND ONE ON SUPERIOR ACETABULAR MARGIN.

Apply the femoral head, impact it and reduce the hip.The definitive ceramic head is applied to the trunnion of the Accolade II stem.
When applying the femoral head ensure the trunnion of the stem is clean and dried. Apply the femoral head with a twisting motion to the trunnion. Once it is seated use one hammer blow to the femoral head only ever imparted through the purpose designed impactor.
One sufficient blow is better than multiple blows to engage the ceramic femoral head tightly on the trunnion.
Lavage the joint thoroughly and ensure haemostasis before proceeding to closure.

Finally test the hips stability and the leg length then reattach the short external rotatorsUsing 2 drill holes through the lateral aspect of the greater trochanter make two passages for the superior and inferior limbs of the stay sutures attached to the short external rotators and piriformis tendon.
The closure technique is documented in C-stem/Elite THR technique at https://www.orthoracle.com/library/total-hip-replacementc-stem-amt-elite-depuy-cemented-hip-femur-first/operation/#slide-61

Close the wound and iliac pin sitesThe pin sites have been closed with interrupted 3/o Ethilon sutures – horizontal mattress suture in each stab incision.
Dressings applied to both the hip replacement incision and the pelvic array site.

AP Postoperative radiograph. Showing satisfactory leg length, component alignment and offset.