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PINNACLE® Shell Surgical Technique
PINNACLE® Shell Surgical Technique
Templating and Pre–Operative Planning
The radiographs should clearly demonstrate the acetabular configuration and the endosteal and periosteal contours of the femoral head, neck and proximal femur
Using the A/P radiograph, position the template 40° – 45° to the inter–teardrop or interischial line so that the inferomedial aspect of the cup abuts the teardrop and the superior–lateral cup is not excessively uncovered
The goal of acetabular reaming is to restore the centre of the original acetabulum. Initially employ a reamer 6 – 8 mm smaller than the anticipated acetabular component size to deepen the acetabulum to the level determined by pre–operative templating. Subsequent reaming should proceed in 1 – 2 mm increments. Centre the reamers in the acetabulum until the deepened socket becomes a true hemisphere. Use a curette to free all cysts of fibrous tissue. Pack any defects densely with cancellous bone.
Acetabular Cup Trialling and Positioning
- A 54 mm QUICKSET™ grater reams a 54 mm cavity
- A 54 mm trial cup os 54 mm in diameter
- A 54 mm PINNACLE Acetabular Cup is 54 mm in diameter as measured over the POROCOAT® Porous Coating
Trial cups in 1 mm incremental sizes are available to assess cup fit and orientation. Contingent on the quality of the prepared bone, select the acetabular trial equal to or 1 mm larger in diameter than the final reamer size. The size of the trial cup is as marked on the trial cup (54 mm measures 54 mm). Peripheral rim ridges on the trial cup enhance the stability of the trial cup through trial reduction. Even liner trials fit both even and smaller odd trial cups. For example, a 54 mm polyethylene liner trial fits both the 54 mm and the 53 mm trial cups. Using cup and liner trials in conjunction with the femoral component trials aids in ensuring optimum position of the components.
Peer reviewed publications highlight the importance of acetabular component positioning in relation to short and long term outcomes during total hip arthroplasty for all types of bearing materials.1-8
Cup positioning should be varied to optimise fixation, range of motion and dislocation resistance and minimise the likelihood of subluxation, impingement and edge loading. This may be assessed during pre-operative planning, acetabular preparation and cup trialling. Sub-optimal component positioning may lead to edge loading, dislocation, increased wear, elevated metal ion release, ceramic squeaking and polyethylene fracture.1-8
The target cup inclination (as measured on radiographs) should be 40-45° taking into account local soft tissue and anatomic landmarks. The target cup anteversion (as measured on radiographs) should be 15-20° taking into account local soft tissue and anatomic landmarks.
An alignment guide is provided to assist with cup positioning; however, cup orientation in the patient depends on patient position. The alignment guide does not allow for variation in patient position with respect to the operating table and it should be noted that patient orientation can vary throughout the procedure.
PINNACLE Alignment Guide System
The PINNACLE alignment guide system may be used to indicate an acceptable level of acetabular inclination and version. Once assembled, the inserter handle should be raised until the vertical bar is perpendicular to the plane of the operating table. With the patient in the lateral decubitus position and the version guide parallel to the floor.
The inserter handle should then be rotated until the horizontal bar is in line with the patient's longitudinal axis.
The extended arm of the version guide follows the long axis of the patient’s body, corresponding to the affected hip, to achieve appropriate anteversion.
Implanting a PINNACLE 100 Primary Acetabular Cup
Before implanting the final prosthesis, take the hip through a full range of motion and stability assessment with all trial components in position. Securely thread the permanent acetabular cup prosthesis onto the acetabular cup positioner. Use the PINNACLE external alignment guide to assist in component orientation.
After confirming alignment, impact the prosthesis into position. Given the nature of a hemispherical acetabular component, rim contact will occur before dome seating occurs. This may require additional impactionto ensure seating. Confirm seating by sighting through the apical hole or, if present, screw holes. An apical hole eliminator may be inserted with a standard hex head screwdriver following cup impaction.
Implanting a PINNACLE Sector Acetabular Cup with Screw Fixation
The PINNACLE Sector Cup has three screw holes and is designed for insertion with screws. Two medial hole alternatives are placed to enable screw placement up the posterior column in either the right or left hip. The single lateral screw provides additional access to the ilium.
The screw angle may vary by as much as 34˚.
Select holes where the prosthesis is to be anchored with cancellous screws so that the screws lie within a safe quadrant. The safe quadrant is defined by two lines from the anterior–inferior iliac spine through the centre of the acetabulum and posterior by a line from the sciatic notch to the centre of the acetabulum.
Implanting a PINNACLE 300 Acetabular Cup with Spikes
Spikes are placed along the radius of the PINNACLE 300 Series cup are coated and are for additional fixation. The spike height in the 300 Series cup ensures that the spike contacts bone on insertion at the same point that the cup contacts the rim of the prepared acetabulum. This gives the surgeon greater control when inserting the 300 Series cup and ensures the cup bottoms out in the dome of the acetabulum.
PINNACLE® Hip Solutions
- Learmonth ID, Young C, Rorabeck C. The operation of the century: total hip replacement. Lancet 2007;370:1508-19.
- Archbold HAP et al. The transverse acetabular ligament: an aid to orientation of the acetabular component during primary total hip replacement. J Bone Joint Surg. 2006;88B:883-6.
- Udomkiat P, Dorr LD, Wan Z. Cementless hemispheric porous-coated sockets implanted with press-fit technique without screws: average ten-year follow-up. J Bone Joint Surg. 2002;84A:1195-200.
- Schmalzried TP, Guttmann D, Grecula M, Amstutz H. The relationship between the design, position, and articular wear of acetabular components inserted without cement and the development of pelvic osteolysis. J Bone Joint Surg. 1994;76A:677-688.
- Kennedy JG, Rogers WB, Soffee KE, et al. Effect of acetabular component orientation on recurrent dislocation, pelvic osteolysis, polyethylene wear and component migration. J Arthroplasty 1998;13:530-534.
- Prudhommeaux F, Hamadouche M, Nevelos J, et al. Wear of alumina-on-alumina total hip arthroplasties at a mean 11-year followup. Clin Orthop Relat Res. 2000; 397:113-122.
- Walter WL, O’Toole GC, Walter WK, Ellis A, Zicat BA. Squeaking in ceramic-on‑ceramic hips: the importance of acetabular component orientation. J Arthroplasty. 2007;22:496-503.
- Tower SS, Currier JH, Currier BH, Lyford KA, Van Citters DW, Mayor MB. Rim cracking of the cross-linked longevity polyethylene acetabular liner after total hip arthroplasty. J Bone Joint Surg. 2007;89A(10):2212-7.
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