These key surgical steps are highlights only and may not be used for training purposes. For the detailed procedure, please refer to the PINNACLE Surgical Technique Brochure (9068-80-050)
Polyethylene Liner Configurations
In the PINNACLE Hip Solutions, a variety of polyethylene liner designs are available. Each design has specific benefits. It is important for the surgeon to understand the geometry of the various liner alternatives and their impact on joint biomechanics and range of motion.1
The neutral liner provides 180° of head coverage. The wide face chamfer is optimised for range of motion. The range of motion measured is 119° with a DePuy AMT 12/14 Taper Stem and a 28 mm +5 head. The femoral head’s centre of rotation is concentric with the outer diameter of the cup.
+4 Neutral Liner
Like the neutral liner, the +4 mm neutral liner provides 180° of head coverage. The wide face chamfer is optimised for range of motion. The range of motion measured is 121° with a DePuy AMT 12/14 Taper Stem and a 28 mm +5 head. This liner provides a 4 mm lateralisation of the femoral head’s centre of rotation. This 4 mm offset both increases soft tissue tensioning and provides 4 mm of increased polyethylene thickness in the cup’s dome region. This lateralised liner can be used as an alternative to a longer neck and may enable the surgeon to avoid using a skirted head. A +4 mm lateralised liner will result in about 3 mm of leg length and about 3 mm of offset if the cup is inserted at a 45° abduction angle.
+4 10° Face–Changing Liner
Like the other liners, the +4 10° liner provides 180° of head coverage and the wide chamfer is optimised for range of motion. The range of motion measured is 115° with a DePuy AMT 12/14 Taper Stem and a 28 mm +5 head. This liner lateralises the femoral head 4 mm and a 10° face change alters inclination/version dependent upon placement of the liner.
Range of motion is measured at 106° maximum, with a DePuy AMT 12/14 Taper Stem and a 28 mm +5 head. The lip on this liner can provide additional stability; however, the impact on range of motion and early impingement must be understood.
Constrained liners are available for the PINNACLE cup and are described in brochure 9068-84-052.
Polyethylene Liner Insertion and Impaction
Following insertion of the final acetabular cup and femoral component, the trial liners can be used in the cup to confirm liner selection and evaluate joint stability and range of motion. Prior to inserting the final acetabular liner, thoroughly irrigate and clean the cup. It is important to check the cup/liner locking groove to ensure it is clear of any debris.
Prior to insertion/impaction, mate the liner anti-rotational device (ARD) tabs with the ARD scallops on the cup. There are six ARD tabs on the liners and 12 ARD scallops for cup diameters 48 mm – 72 mm. Also, there are four ARD tabs and eight ARD scallops in cup diameters 38 mm – 46 mm. This allows the liner to be rotated in 30° increments for cups 48 mm – 80 mm and 45° increments for 38 mm – 46 mm.
Seat the liner using the ID impactor that corresponds to the selected implant. Because the locking mechanism is tapered, it is important to impact the liner directly into the cup with multiple medium blows.
Impacting the liner in a tilted position may prevent complete seating. Seating of the liner is visually confirmed when the liner ARDs are flush with the face of the acetabular cup; however, the liner face will remain proud in relation to the cup face by approximately 1 mm for a neutral liner to 4 mm for a laterlised liner
Polyethylene Liner Extraction
A polyethylene liner extractor is available to aid in polyethylene liner extraction and to help ensure the PINNACLE Acetabular Cup is not damaged during polyethylene liner extraction.
Open the extractor jaws and extend the ARD pin from the extractor tip. Place the ARD pin into an empty ARD and tightly close the jaws of the extractor. The teeth of the extractor should dig into the inner diameter of the polyethylene.
Once the ARD tip and teeth are secure on the polyethylene, advance the extraction knob clockwise until the polyethylene is removed
It is important to note that an extracted polyethylene insert cannot be reused.