Corail Pinnacle (De Puy)Total Hip replacement ( Midi-posterior approach)

The incision is based on the posterior aspect of the greater trochanter, is about 10cm in length with one third distal to tip of G.Trochanter and two thirds proximal.

A Charnley bow retractor is placed wirh the horizotal arm distal. The Fascia Lata is retracted enough to expose the external rotators, but not under too much tension.
A skin marker suture is inserted into the skin just proximal to the apex of the incision and a cautery mark is made over the greater trochanter.
The amount of hip flexion is noted and also the position of the upper knee to the unoperated knee is assessed.

A nail is placed in the ilium between G.minimus and Piriformis and cutting diathermy used to cut the external rotators from their femoral insertion distally to the G.max tendon. Initially finger pressure with a dry swab is helpful to tension the tissues.

The external rotators course from piriformis proximally to gluteus maximus distall; internal rotation of the femur puts them under tension allowing length to be preserved when cutting them close transversely to the femur.
At this time the sciatic nerve can be identified and protected by sweeping back the bursal fat.

Up til now, the assistant has been internally rotating the femur enough to tension the rotators; once they are cut, and posterior capsule is divided transversely,the operating surgeon must take responsibility to dislocate the hip. This can NEVER be a two man manoeuvre. Only a single pair of hands can detect the force required to dislocate. Failure to adhere to this rule can result in spiral fractures of the femur.
Once the head is dislocated an appreciation of femoral neck anteversion can be made by visualising the neck angle compared with the vertical tibia. This is important for hip stability. A very anteverted femoral neck may indicate a more neutral version of the cup.
The final decision on cup version is made after trial stem impaction as some native version influence persists into the metaphysis: it is for this reason I always tend to trial the femoral component prior to acetabular reaming.

With the tibia vertical, a small Hohman retractor is placed inferior to the neck of femur and a further protective retractor can be placed in the trochanteric notch.
The neck is then resected with an oscillating saw parallel with the base of the head but usually 1-1.5 cm distal according to preoperative templating which may be relative to the lesser trochanter or base of head.

The femoral head is removed, assessed for wear and measured to give an indication of size for acetabular reaming and cup size.

With the tibia, still vertical any soft tissue is removed from around the trochanteric notch. Although a minor step- everything that follows is consequent to this. Failure to perform this step can result in a varus and undersized stem.
A starter box chisel is used to expand the neck shaft junction. Be careful that this box chisel is not oversized- this can lead to splitting of the calcar. It is important to irritate your representative to make a sufficiently small size available !

The femoral canal is entered with an initial rasp, attempting to keep as lateral as possible. It is helpful to consciously keep the rasp at 10-20 degrees of anteversion but be aware if the stem is forced into an abnormal version position- this may affect your chosen cup version.

The Corail technique is based on sequential cancellous impaction/compression. This relies on millimetre increases in sequential rasps up to the templated size. Assessment is made of a secure scratch fit with longitudinal and rotational stability.
Before detaching the rasp handle, an assessment of femoral anteversion is made. If the rasp is rotationally deviated by internal bony buttresses, this is accentuated at the last reamer; it is essential to know femoral anteversion before acetabular reaming.

The acetabulum is now addressed.
The leg is brought back to the neutral position and a small retractor placed in the anterior acetabulum levering the residual femoral neck – with trial in situ – forwards.
The anterior retractor is placed in the 10 o’clock position for a left hip and 2 o’clock for a right.
Two nails are place posteriorly; the first superior towards the ilium protecting soft tissues. The inferior nail is angled posteriorly in the ischium.
A broad Hohman retractor is placed beneath the Transverse Acetabular Ligament (TAL) and secured in place with a swab tied to the Charnley retractor.
The labrum is completely excised.
Circumferential control and visualisation of the acetabulum is thus obtained.

Reaming is undertaken with cheesegrater reamers.
Reaming strategy is dependent on reamer sharpness and bone quality. If the reamers are sharp the reamer chosen can be close in size to the templated cup size: for instance with good reamers and an anticipated cup diameter of 52mm, I would ream 47mm, 49mm and 51mm. It is always best to check best fit with a cup trial.
My default reamer angle is 40 degrees of closure or abduction and 20 degrees of anteversion ie pointint forwards. Some use the TAL as a guide which is reasonable but beware it can just reproduce a pathologogical anomaly.
The cup version is also dependent on stem version. I regard 10-20 degrees of neck version as normal ; anything more than this, I err towards less version on the cup ie more neutral. Anything less, a little more version is required.

The cup is impacted into the desired position and assessed for stability: usually 1mm underreaming does not require screws. If stability is questionable, usually one peripheral 25-30mm screw will provide sufficient fixation.
A word on drill and screw length. Often I am in a situation wher I ask for an flexible drill and I am given a 50 or 60 mm long drill; this is fine if the drill guide is 30-40 mm long; if it is very short then a plunging drill can cause retroperitoneal bleeding. Additionally, excessively long screws should be avoided. The safe zone is straight up the aloacetabular bar. Anterior positioning jeopardises femoral vessels and posterior, the sciatic nerve.
Osteophytes should not be removed at this stage.

In younger patients, a hole eliminator can be used- but this may be adding unnecessary expense. Modern poly access disease is not the issue.

The poly insert is carefully impacted at this stage. It is essential that the liner is perfectly aligned and does not get impacted in a scewed position.
My preference is to use a lipped liner, although I do recognise potential for increased impingement and lip fracture, I prefer the benefit of early stability.
The liner is tested for stability in the shell by rocking the edge with an osteotome but being carful not to damage the plastic.
Once the liner has been inserted any protruding osteophytes can be taken.

The retractors are removed and the leg internally rotated to reveal the prepared femur. The modular neck/head trial is impacted and the hip reduced.
Preoperative templating gives a guide to offset choice and head length. My default head diameter is 32mm. This has increased over the years with outstanding clinical and simulator wear results with HXLPE. I remain a little uncomfortable about 36mm bearing couples in metal/poly with current trunnion design (debate is beyond the scope of this op technique).
My preference for the Corail stem is the collared variety; there may be some subsidence issues with the non collared alternative.

The hip is tested for stability in various rotational positions. Although traditionally with the posterior approach , the risk has been for posterior dislocation, my experience is that anterior dislocation is equally likey – probably due to over anteversion or too prominent a posterior lip.
Leg length is assessed using the relative lengths of the knees, the marker suture, a Schuck test and by observing the direction of insertion of the Piriformis tendon.
A recognition of limb length inequality or instability at this stage allows for component reconfiguration.

Once content that the trial leg lengths are correct, the selected stem is implanted. At this stage stability and leg length can be finally assessed with a trial head but this may be deemed unnecessary.
The stem is implanted with serial impactions to the shoulder of the implant- always being aware of failure of stem to progress or calcar fracture.

The head is impacted firmly ensuring that the trunnion is dry. The importance of trunnion care and its influence on taper tribocorrosion is increasing understood.
Reduction of the hip is effected using the head impactor with special attention to avoid head scratching on the cup.
A final assessment of leg length is made by;
1) assessing relative length of the operated and unoperated knee.
2) asssessing final position of leg marker suture.
3) assessing direction of repaired piriformis tendon.
4) assessing tension to reduce or Scuck test less reliable in posterior approach).
Stability is assessed by taking the leg through a functional range with particular note made of any impingement. Any residual impinging osteophytes should now be removed.

The wound is then closed in several layers. The tension in the retractor is reduced and if possible several non-absorbable sutures are placed to reconstitute the posterior capsule. The Piriformis tendon is individually repaired and the the rotators reattached in two layers from Piriformis down to G.Max tendonwith an absorbable looped monofilament looped suture preferred.

The Fascia Lata is repaired with a looped non absorbable suture and subcutaneous and sometimes subcuticular absorbable sutures are inserted.

Finally skin staples are used to close the skin and an assessment of the length of skin incision relative to femoral head size can be seen.