Individualized Stem-positioning in Calcar-guided Short-stem Total Hip Arthroplasty

The overall goal of this individualized surgical stem-positioning technique, using Calcar-guided short-stems is to individually reconstruct various hip anatomies and femoral offsets through the application of an appropriate stem alignment. This method facilitates the individual positioning of a Calcar-guided short-stem, according to the patient's anatomy. The main advantage of this technique is that it allows the reconstruction of various offsets.

Even extensive varus or valgus alignments can be reconstructed using a single type of femoral implant. To perform a total hip arthroplasty using the minimally invasive anterolateral approach, place the patient in the supine position on a standard operating table, with the legs on two separate leg supports. Apply standard sterile coverage suitable for the anterolateral approach in the supine position, and use a knee role to slightly flex the ipsilateral side.

Palpate the tip of the greater trochanter, as well as the anterior superior iliac spine, and use a surgical blade to make a six to 12 centimeter long skin incision from the tip of the greater trochanter to the anterior superior iliac spine above the intermuscular septum between the gluteus medius and the tensor fasciae latae. Place one skin retractor anteriorly and one skin retractor posteriorly to make a secondary incision through the underlying subcutaneous fat tissue. Then, open the fascia without causing damage to the tensor fasciae latae.

Next, use an index finger to gently and posteriorly blunt dissect the gluteal muscles. Then, use three retractors to expose the joint capsule, and perform a capsulectomy alongside the femoral neck. After removing the anterior joint capsule, place two facing curved intracapsular retractors around the femoral neck and palpate the fossa piriformis and the lesser trochanter.

Implementing the right level of the osteotomy is crucial to being able to position the stem in the intended alignment. Landmarks such as the lesser trochanter and the fossa piriformis should be carefully located to serve as our annotation points. If the hip is aligned in a valgus position, resect most of the femoral neck distally.

To align the stem in a varus position, resect proximally to retain most of the femoral neck. Preoperative planning should also always be performed to ensure accurate presurgical definition of the level of the osteotomy. When the femoral offset, leg length, and level of osteotomy have been reconciled with the preoperative plan, use a long, stiff bladed, oscillating saw to perform the osteotomy in a slight external rotation of the ipsilateral leg.

Use a femoral head extractor to remove the femoral head from the acetabulum. Place a langenbeck retractor medially, pulling proximally, to protect the gluteus medius. Insert a steinman pin in the proximal end of the acetabulum if needed.

Then, use two extractors to expose the acetabulum. And implant the acetabular component according to the patient's individual anatomy. For the femoral preparation, remove the knee roll and hyper-extend the contralateral leg about 15 degrees.

Then, externally rotate the knee joint 90 degrees with a maximal 90 degree flexion and have an assistant hold the patient's leg at a maximal adduction of about 40 degrees. Position two retractors, one on the medial side of the proximal femoral neck, and one proximally at the posterior medial cortical end of the femoral neck. Using the round the corner technique, open the proximal femur alongside the Calcar, with the curved opening all.

And use a hammer to gently drive in specially curved implant shaped rasps in ascending sizes, until the cortical contact and a stable fit and feel are reached. Insert a trial cone and a trial head and perform a trial reduction to compare the positioning of the trial implant to the preoperative implantation plan, and use a digital image intensifier to obtain anterior, posterior, and axial view radiographs to assess the trail and plan positioning. After making any necessary adjustments to the implants, use a special implant impactor to replace the trial implants with the definitive implant containing the appropriate offset version.

The original stem aligns exactly as the trial rasp. To complete the implantation, insert the original head. Then apply axial tension in combination with internal rotation to perform the final reduction.

And complete the procedure by standard wound closure. Here, representative preoperative planning templates of the Calcar-guided short-stem and cementless cup are shown. Allowing determination of the required level for the osteotomy.

Intraoperatively, the lateral shoulder height of the planned implant serves as an orientation point for the leg length and determines the osteotomy. The cortical contact point is used to adjust the stem upsizing. In this image, the stem is aligned in the valgus position following a low osteotomy.

Whereas here, the stem is aligned in the varus position, following a high osteotomy. In the case of a varus anatomy, the high resection results in a large femoral offset with three-point anchoring. In the case of a valgus anatomy, a low resection results in a diaphyseal anchorage, and causes a small femoral offset.

In the case of a neutral alignment, an intermediate resection level should be attempted. In all cases, achieving cortical contact to the distal lateral cortex is critical for primary stability of the stem. Preoperative planning for this varus hip revealed that conventional implants requiring a diaphyseal anchorage would not allow achievement of the offset reconstruction.

A varus alignment with the Calcar-guided short-stem, however, accomplished an exact reconstruction of the offset. Short-stems will position themselves almost automatically along the anteversion and anterior tilt of the preexisting proximal femoral bone, facilitates restoration of the anterior offset, as well. Calcar-guided short-stem implantation is a safe, reliable, soft tissue sparing technique with implementation of the correct level of the osteotomy key to the success of the procedure.

Undersizing has been found to be the main cause for impaired implant stability. Therefore, the use of intraoperative fluoroscopy is highly recommended to allow any necessary adjustments, and to make sure that the implant always reaches to the distal lateral cortex. Surgeons new to this surgical implantation technique may struggle because the technique differs from conventional straights and total hip arthroplasty and has a distinct learning curve for beginners.

After watching this video, you should have a good understanding of how to individually and safely position a Calcar-guided short-stem within various hip anatomies.