How to Perform Total hip arthroplasty (uncemented) - posterior approach

Step 4. Opening the fascia and placing the Charnley retractor

The fascia lata is incised in line and through the entire length of the skin incision, using scissors, a scalpel, and/or diathermy.

• Proximally, the fascial incision should follow the line of fibers in the gluteus maximus.

• The gluteus maximus is split bluntly in the line with its fibers.

• The bursal tissue is incised along with possible bursal adhesions.

• Before placing the Charnley retractor it’s important to locate the sciatic nerve coursing posterior to the external rotators.  3D

• The retractor is placed at the level of the trochanteric tip, typically around the midpoint of the incision, grasping only the fascia and muscle layer, making sure to not to catch the sciatic nerve under the retractor or even too close to it to prevent iatrogenic sciatic nerve injury.

• After placing the retractor it should be checked that the sciatic nerve runs freely.

• The exposure to the short external rotator area should be sufficient proximally and distally.

• If not, widen the incision by opening all the layers: skin, subcutis and fascia to avoid any constriction in the area.

Step 5. Detaching the short external rotators and opening the joint capsule

Exposure to the short external rotators and posterior capsule area is enhanced by placing the patient's foot on a Mayo stand and internally rotating the hip.

• The posterior border of the gluteus medius muscle is identified.

• A Hohmann retractor is used to retract the gluteus medius muscle anteriorly,

• enhances the visibility of the surgical area and protects the muscle.

• Any remaining bursal tissue or fat is incised near the attachment site of the short external rotators.

• Short external rotators of the hip should then be identified: piriformis, superior & inferior gemellus, obturator internus and quadratus femoris.

• The tendinous proportion of these muscles may vary a lot as well as the extent of fatty atrophy.

• For improved exposure and later reattachment, tagging sutures can be placed on the piriformis tendon and other short external rotators before or after detaching them.

• The short external rotators and the posterior capsule beneath them are detached from their insertions with scalpel or electrocautery as close the greater trochanter surface as possible.

• Incision is done from the piriformis level to the lesser trochanter.

• Detaching the rotators too far from the bone might lead to difficulties in re-attaching them during closure step.

• This could potentially result in compromised muscle function and elevate the risk of post-operative dislocation.

• The joint capsule underneath the rotators can be incised simultaneously with the rotators or using a separate incision.

• Distally the incision should reveal the lesser trochanter.

• Proximally the incision curves postero-superiorly along the piriformis tendon making sure not to damage gluteus minimus.

• The incision is continued until the bony acetabular rim is reached, with the labrum also being incised in the same direction as the incision.

• The capsulotomy is now sufficient to allow for the dislocation of the femoral head.

Step 6. Dislocating the joint

The hip is flexed to relax the surrounding ligaments and muscles.

• Next the femur is adducted and internally rotated to dislocate the hip. Gentle traction can be applied if needed.

• The use of excessive force might lead to fractures or soft tissue damage.

• If there is resistance when dislocating, it may indicate the need for further capsular release or removal of possible obstructing osteophytes.

Step 7. Femoral neck resection

A Hohmann retractor is placed under the femoral neck to protect the soft tissues.

• The position of the limb is checked: the heel should be directed upwards towards the ceiling.

• This gives good access to the dislocated neck and stabilizes the limb.

• The correct level of the resection is determined from preoperative plan.

• The reference point can be the lesser trochanter or other bony landmark such as piriformis fossa.

• Consider also the saw angle in respect to the neck of the femur.

• The aim is to have the porous surface on the prosthesis inside the femoral bone.

• An oscillating saw is used to perform the initial cut along the planned line.

• Ensure the saw is held at the correct angle and that the cut is straight.

• The resection can be completed with a chisel (osteotome). The chisel should be directed away from the greater trochanter.

• Leverage towards the greater trochanter with the instrument should also be avoided to prevent iatrogenic fracture of the greater trochanter.

• The femoral head is removed with forceps by twisting the head and cutting the remaining anterior capsule adhesions.

• Once the femoral head has been removed, it's important to assess the anteversion of the femoral neck.

• Typically, the anteversion angle ranges between 10 and 15 degrees.

• If the observed angle deviates from this range, this variation should be taken into consideration when determining the placement of the cup component in the acetabulum.

Step 8. Preparing the acetabulum

The limb position is adjusted to improve access to the acetabulum by flexing the hip and introducing some internal rotation.

• The foot can be lifted onto a Mayo stand to facilitate the position.

• A long curved Hohmann retractor is placed behind the anterior column (typically at the 1-2 o'clock position in a right hip) and the femur is retracted anteriorly with it.

• Placing the retractor directly medially (at 3 o’clock) should be avoided as it might cause an acetabular fracture due to thinner bone.

• When placing the retractor it should be introduced carefully close to bone surface, not to cause damage to adjacent tissues (medially located femoral nerve, artery and vein). 3D

• To retract posterior structures out of the way, the inferior capsule is split with diathermy/scalpel. Cauterize any bleeding.

• Placing a Steinmann pin to the ischium (between the capsule and the labrum) keeps the posterior soft tissues retracted.

• When using a Steinmann pin, it's important to position it within the ischium to ensure sufficient bone support for stability

• being cautious to avoid damage to nearby structures.

• If achieving sufficient visibility for reaming proves challenging, the following things might help:  - Checking if the limb’s rotation/flexion needs adjusting. - Checking if superior capsule needs more detaching from superior acetabular rim. - If tension at the gluteus maximus insertion exists

• 1-2 cm of the superior tendon can be incised but this needs to also to be closed later on during closure.

• The labrum is removed along the bony rim of the acetabulum using a scalpel directed inside of the acetabulum.

• Retained labrum may interpose bone and the cup and prevent the cup from stabilizing.

• The true (anatomical) floor of the acetabulum (acetabular fossa) is identified to determine the right depth of reaming.

• The soft tissue and possible osteophytes are removed to visualize the true floor.

• Osteophytes are resected using a chisel and rongeur.

• Particularly, anterior osteophytes can cause levering against the neck of the femoral component and thus increase the risk of posterior dislocation.

• Preoperative images often provide information about the presence of osteophytes.

• The sufficient exposure and visibility have been achieved when the bony landmarks of acetabulum (the transverse acetabular ligament (TAL), acetabular fossa and the anterior and posterior walls of the acetabulum and the superior acetabular dome) are visible, and the soft tissues have been cleared for the reaming.

Step 9. Acetabular reaming

Before starting the reaming, the preoperative plan should be checked: the planned cup size and the planned reaming depth,

• gives a rough idea of how much bone needs to be removed.

• Usually, the desired depth of reaming is the “tear drop” seen in the x-ray.

• Commonly, underreaming by 1mm (compared to the final implant size) is desirable, but in the case of sclerotic bone,

• is denser and less compressible, line-to-line reaming may be preferable to ensure an optimal fit of the implant.

• The important landmarks for reaming and cup placement are identified: the transverse acetabular ligament (TAL), acetabular fossa and the anterior and posterior walls of the acetabulum and the superior dome.

• The reaming is started with approximately 2-6mm smaller reamer than the planned cup.

• The direction of the first reamer is medially and towards the acetabular fossa (depending on the plan: sometimes medialization is not desirable and in such situation the reamer should be aimed at the desired target).

• Ream carefully until just shy of the desired depth i.e. the floor has been reached and the edges of the fossa are no longer visible.

• It's crucial not to advance too deep medially.

• Perforating the medial wall could potentially lead to significant complications such as pelvic fractures, prosthetic loosening, neurovascular damage and increased risk of dislocation.

• The reamer size is then increased, typically in 1-2 mm steps,

• helps to ensure the maintaining of the desired shape and not removing too much bone.

• The direction of reamer should be adjusted to follow the desired cup position (typically 40-45 degree of inclination and 20-25 degree anteversion).

• The acetabulum should be frequently assessed during reaming, both visually and by palpation, to ensure the correct direction and depth.

• The pre-operative plan serves as an initial guide for the cup size, but ultimately, the anatomical landmarks will dictate the final size.

• When increasing the reamer diameter, the anterior or posterior walls must be assessed to prevent over-reaming.

• The final reamer size achieves a peripheral rim fit, removing bone uniformly around the socket.

• This typically results in an increase in resistance during the reaming process, accompanied by a change in sound.

• It creates a round socket, where no cartilage remains, and with a bleeding bony cancellous bed to allow for osseointegration between the host bone and porous surface of the cup.

Step 10. Trialing the acetabular component

The trial acetabular component is tapped into the reamed acetabulum using a surgical mallet.

• The goal is to seat the trial component, not to force it.

• The position is assessed by using the bony landmarks and the Transverse acetabular ligament (TAL) as references to aim for an inclination of 40-45 degrees and an anteversion of 20-25 degrees.

• The position of the cup can also be evaluated using alignment guides (guide whiskers).

• However, it's important to comprehend the influence of pelvis position, when utilizing these guides.

• Stability is tested by slightly turning and rotating the trial shell.

• The soft tissue and labrum have to be completely removed from the acetabular edges as they might prevent cup stabilizing.

• If the trial cup feels loose and there is still enough bone on the medial wall of acetabulum, increasing contact surface of bone and the implant might be considered.

• This is achieved by reaming a bit deeper by taking a 1mm smaller reamer than the last one used and reaming 1-2mm deeper.

• Then the 1mm larger reamer is used again and reamed to the new depth and trialed again.

• Sometimes it’s possible to increase the reamer diameter to get better stability, but more often the answer is to go bit deeper, not wider.

• It’s crucially important to assess the anterior and posterior walls if decided to go wider.

• If the initial press-fit stability is not satisfactory after these steps or if the bone quality is poor (e.g. osteoporotic) the stability could be enhanced by screws

• help to secure the cup in place, preventing it from moving or loosening before bony ingrowth can occur.

• The trialing is considered done when satisfactory trialing is achieved, meaning, stability of the trial cup is sufficient in the correct cup position.

Step 11. Placing the acetabular components

The final component of the correct size can be implanted by holding the cup to the rim and adjusting the inclination and anteversion, and rotation if a cluster hole cup is selected.

• These adjustments should be maintained while the component is implanted through carefully controlled mallet blows.

• Confirmation of the implant reaching the correct depth can be obtained by noting a sound change as the shell settles and by verifying it through the screw holes.

• Verification of the correct positioning of the cup is done by referencing it to the anatomical landmarks and possibly with the external alignment guide.

• While individual circumstances may vary based on the surgical plan, the following points typically indicate that the cup is well positioned: - The anteroinferior edge of the cup aligns with the Transverse acetabular ligament (TAL) or is slightly more anteverted. - The anterior edge of the shell is flush with the anterior wall edge, or the bone slightly protrudes.

• Note

• Osteophytes may obscure the true anterior rim edge, so they should be carefully removed.  - The posterosuperior edge of the shell slightly protrudes beyond the posterosuperior acetabulum.

• If screws are necessary for achieving stability, their alignment with the acetabular safe zones, specifically the superoposterior region, should be ensured before proceeding with drilling.

• Wrong screw placement might lead to neurovascular injury.   3D Once the screw placement has been confirmed, holes should be drilled, and screws should be inserted based on the measurements.

• Note that the primary goal is to achieve stable fixation, and this can usually be accomplished without the screws penetrating the far cortex.

• Any remaining osteophytes should be removed, especially from the anterior wall to prevent impingement and thus reduce the risk of dislocation.

• The liner is inserted, and it should be ensured that no soft tissue remains between the liner and the cup.

• The manufacturer's instructions should be followed to ensure optimal fit and function.

• Improper liner placement or selection could potentially lead to complications such as dislocation, wear, or loosening.

Step 12. Femoral preparation

Before starting the preparation, the preoperative plan should be reviewed: the size of the femoral implant and the planned depth of implantation (with the lesser trochanter serving as a typical landmark) should be checked.

• For an accurate determination of the anteversion of the femoral component, the limb should be positioned in such a way that the femur is flexed and internally rotated, and the knee is flexed more than 90 degrees,

• positions the heel upwards.

• A curved Hohmann retractor or Mueller retractor is placed under the calcar area and the lesser trochanter to gain clear visualization of the calcar and for protecting the soft tissues.

• Any residual soft tissue should be cleared from the piriformis fossa to ensure an unobstructed area to locate the correct starting point of the femoral canal preparation.

• Also, any residual femoral neck should be carefully resected, as incomplete removal of the lateral neck could lead to varus mispositioning of the femoral component.

• The femoral canal is opened using a box osteotome.

• The starting point is posterolaterally, close to the greater trochanter which prevents the varus malalignment.

• Anteversion angle is also important to concider.

• A canal finder is used to open the femoral canal in line with the shaft.

• It’s important to follow the manufacturer’s instructions when using reamers and broaches for the canal enlargement and shaping.

• The smallest size is typically used first to minimize the risk of fracturing the bone.

• The planned degree of anteversion should be established from the smallest broach onwards, using the cortical bone as a reference.

• As progression is made through larger broach sizes, maintaining awareness of the correct anteversion is crucial.

• Each broach is used only to the intended depth.

• The depth can be verified by referencing the lesser trochanter and/or the piriformis fossa, as well as the tip of the greater trochanter when the trial neck is in position.

• Caution should be exercised when removing the broach to avoid striking the greater trochanter, as this could lead to an iatrogenic fracture.

• The broach size should be continuously increased until secure rotational stability is achieved at the planned depth level.

• While the pre-operative plan should be kept in mind, it's not uncommon to end up with a stem that is 1-2 sizes larger than originally planned.

• In cementless stems, your aim is not to remove all the cancellous bone but to pack it tight.

• You don’t have to get cortical contact on the calcar (though you should get pretty close).

• If you do, the final implant of the same size tends to stick too high so you can’t get it to the planned depth.

Step 13. Trialing and implantation of femoral components

Once the final broach size has been determined, a trial neck and head are inserted according to the preoperative plan.

• The hip is reduced by external rotation, extension and slight traction.

• It’s important to verify that no soft tissue is interposed.

• The determination of the leg length, general laxity, offset, and stability is accomplished with the use of trial implants.

• The following tests are intended to be used together, supplementing each other.

• If all of them consistently show the same result, it can be relatively confirmed as accurate.

• However, if a discrepancy is found in one measure, an assessment should be made to determine the cause and to decide

• results are most trustworthy.

• Leg length

• The aim is to ensure that the leg lengths are equal, or as close to equal as possible, to prevent limping or discomfort post-surgery.  - Can the hip be fully extended?   - Does the knee kick to extension when extending hip?  - Are the patellas on the same level or how they were initially planned?

• Stability

• The aim is to ensure that the hip joint remains stable and doesn't dislocate during normal ranges of movement.  - How much flexion and internal rotation can the hip tolerate before dislocation occurs (posterior stability)?  - Additionally, external rotation should also be tested to evaluate anterior stability. - Combined anteversion

• The femur is placed in extension and internal rotation is performed until the femoral head is flush with the acetabular cup.

• The degree of internal rotation achieved (angle between tibia and horizontal line) equates to the combined anteversion.

• Approximately 40 (25-50) degrees is considered within the acceptable range.

• If the angle is significantly lower, indicating less internal rotation in the femur when the femoral head and the cup are aligned, it suggests an increased risk of posterior dislocation.

• Conversely, if the degree significantly exceeds 40, it indicates a higher risk for anterior dislocation.

• Range of motion

• The aim is to restore as much of the patient's natural range of motion as possible, ensuring the patient can move their hip joint freely and comfortably in daily activities post-surgery.

• General laxity/tightnesss

• The aim is to achieve a balance where the hip joint is neither too tight,

• can restrict movement and cause discomfort, nor too loose,

• can lead to instability.  - How was the reduction?   - Is there a lot of telescoping with a push-pull test?

• (usually several mm in flexion and none or minimal in extension) Offset

• The aim is to evaluate the distance from the center of rotation of the hip to the longitudinal axis of the femur.

• This is crucial for restoring the normal biomechanics of the hip joint.  - Can you set the posterior capsule and external rotators back to their place?

• Once satisfaction with the trial is achieved, the hip is dislocated, and the trial implants are removed.

• Many stems tend to protrude a couple of millimeters compared to the broach.

• In such situations, it is advisable to hit the broach a few more times before removal to position it 1-2mm deeper.

• This assists in aligning the final implant at the same level as the trial.

• Before proceeding with implantation, the calcar should be inspected to detect any potential fissures.

• Unlike, when cementing a stem, pulse lavage is not beneficial or recommended.

• Fixation of a cementless stem needs biological bone ingrowth and pulse lavage has been proposed to possibly wash away potentially beneficial components of bone tissue.

• The chosen stem is inserted using firm hammer blows.

• If it appears too high, it may be necessary to revert to broaching or remove some bone with a rasp.

• The final stem is once more trialed with the trial head to verify the correct positioning and level of the stem and the size of the head.

• Once the correct size of the trial head is confirmed, the final head component is implanted.

• The chosen head is positioned and secured with a mallet strike, followed by hip reduction.

• Again, care should be taken to ensure no tissue interferes between the cup and the head.

• Finally, the joint is irrigated to remove any debris.

Step 14. Closure

The closure process starts with securing the posterior capsule and piriformis tendon via two bony tunnels in the greater trochanter for anatomical alignment.

• Non-absorbable sutures are passed through the tunnels and tied together resulting in neatly aligned posterior structures.

• Verification of the sciatic nerve's free passage is essential.

• Care must be taken to ensure that the nerve is not inadvertently included in the closure sutures or that sutures are not positioned too close to it, as this could cause tension.

• The rest of the external rotators can also be reattached to their anatomical locations for additional support.

• The fascia and the muscular part of the gluteus maximus are closed with e.g. running sutures (e.g. Vicryl 2).

• Repositiong the limb by abducting it slightly can help to approximate the tissue layers together.

• The subcutaneous layer is closed with a running absorbable suture usually in two layers.

• Creating dead space should be avoided as it might lead to seroma or hematoma formation and potentially increase the risk of infection.

• The sutures in subcutis shouldn’t be too tight to prevent fat necrosis.

• The skin is closed with e.g. interrupted sutures or skin staples.