Key Surgical Steps
These key surgical steps are highlights only and may not be used for training purposes. For the detailed procedure, please refer to the CORAIL Upgrade Kit Surgical Technique (DSEM/JRC/0115/0236) pages 4-14.
The CORAIL Hip System provides pre-operative templates at three different magnifications (100%, 115% and 120%). The templates are placed over the AP and lateral radiographs to help determine the implant size in order to restore the patient’s natural anatomy.
When templating ensure that the prosthesis does not make cortical contact. Understand the difference between fit and fill and optimum fit.
The surgical objective is a 1-2 mm gap between the cortices and the implant. If in doubt template a size that contacts the cortex and then go down a size.
Templating should be done with a neutral +5 head centre so that the possibility to change to a short or a long neck still remains in order to adjust leg length. The pre-operative templating will indicate the level of neck resection.
Dorr Type A Femurs
In Dorr Type A (‘champagne flute’) femurs proper metaphyseal fit may require a larger size than the femoral canal can accommodate distally.
In these cases consideration should be given to distal reaming to enlarge the canal to accommodate a broach of the appropriate size.
Femoral Neck Resection
The level of the neck cut, defined during the pre-op planning, is achieved using anatomical landmarks (lesser trochanter, trochanteric fossa, greater trochanter) and a graduated ruler. A broach aligned with the femoral diaphyseal axis can enable the 45° slanting of the cutting plane to be visualised. If the resection is too high, it may result in a varus positioned stem.
The osteotomy can be performed in one or two steps depending on the surgeon’s preference.
Preparation of the entry point
It is important to select a point of entry posterolaterally to the Piriformis Fossa to avoid varus positioning. Use a curette or general instrument to indicate the direction of the canal.
To prevent under-sizing or varus positioning, the greater trochanter may be prepared with a Modular Box Osteotome (2598-07-530) to allow better insertion of the broaches.
Visualisation of the medullary canal axis
The medullary canal axis is determined using the femoral canal explorer. Its entry point must be postero-lateral, near the trochanteric fossa. The canal explorer comprises an 8 mm “bullet” end piece that enables the width of the distal femoral canal to be assessed. The tip of the canal explorer is larger than the distal AP part of the 8 stems.
At this stage, a Type A femur should be identified. In such cases, distal reaming could be carried out in principle followed by compaction broaching.
Cancellous Bone Compaction
Use the Modular Bone Impactor (L94013) to compact the cancellous bone proximally. This is an important step as the philosophy of the CORAIL stem is based on bone preservation.
The compaction of the cancellous bone is continued using specific atraumatic broaches. This process begins with the smallest size broach, along the axis provided by the femoral canal explorer. Ensure that broaching is started posterolaterally. The broach should run parallel to the posterior cortex following the natural anatomy of the femur. Begin with the smallest broach attached to the broach handle and increase the size of broach sequentially until longitudinal and rotational stability is achieved, broaching should then be stopped. Careful preoperative planning is key to help selection of the final broach size. The version will be determined by the natural version of the femur.
If concern around sizing still exists, intraoperative X-rays could be considered, where available.
In relation to the planned size, should vertical (subsiding) stability fail to be achieved, check for false route and/or calcar fracture.
Leave the last broach in place and use the Shielded Calcar Planer to achieve a flat resection surface. The calcar reaming should allow an optimised fit of the collar on the calcar.
The small shielded calcar reamer (940080007) is to be used for sizes from 8 to 12. The large shielded calcar reamer (L94010) is to be used for sizes 13 and above.
Ensure all soft tissue is clear before performing calcar reaming.
The trochometer is placed on the last broach inserted. Using the trochometer ruler, the level of the center of head is checked relative to the apex of the greater trochanter. The grooves correspond to the various implant styles (STD 125/135, KHO, KLA or SN) with a neutral (+5) head.
With the final broach in situ, attach the appropriate trial neck and trial head. Reduce the hip and assess what adjustments, if any, are required to ensure stability through a full range of motion.
Trial Implant Removal
The trial neck should then be removed. The broach stability including subsidence or rotation should be checked again using the handle to prove that it has not been affected by the previous test. This also confirms the reliability of the compacted cancellous bed. Should the broach seem to have lost its stability, the broach that is the next size up should be inserted.
The last femoral broach is then removed. The femoral canal should not be irrigated or dried in order to preserve the quality of the compacted cancellous bone and promote osteointegration of the stem. The surgeon can then request the selected implant size. The CORAIL stem can then be implanted.
Femoral Component Insertion
Important Note: The protective covers should be left on until the components are ready to be implanted. Before implanting a femoral head, the male taper on the femoral stem must be wiped clean of any blood, bone chips or other foreign materials. When implanting the definitive stem (that has the same size as the final broach) in the femoral canal, ensure that it is directed in by hand. It must be held by the taper protection sleeve. This will help avoid changing the version as a precautionary measure. You should not have more than a thumb’s breadth between the resection line and the top of the HA coating on the stem. If the stem does not readily go down this far, the surgeon should broach again. If the HA level of the stem sinks below the resection line, the surgeon should consider a larger stem or using a collar. Then lightly tap the stem impactor to fully seat the stem so the HA coating sits level with the milled femoral neck cut.
Once the femoral stem has been implanted, the calcar should be checked for possible damage such as cracks. If a crack is discovered, this should be wired into place.
The stem is slightly larger than the broach in order to ensure the press-fit function. This volume difference corresponds to the thickness of the HA coating, 155 µm on either face of the implant.
Once the CORAIL stem is fully seated, cancellous bone from the resected femoral head is added around the proximal part of the stem using the bone tamp to seal the femoral canal and to reduce the time for osteointegration which provides definitive stability.
Femoral Head Impaction
A final trial reduction is carried out to confirm joint stability and range of motion. A DePuy 12/14 head must be used. Clean and dry the stem taper carefully to remove any particulate debris. Place the femoral head onto the taper and lightly tap it (especially if a ceramic head is used) using the head impactor. Ensure bearing surfaces are clean and dry and finally reduce the hip.
Primary Intra-operative: Non Osteointegrated Stem Extraction
Warning: Please be aware that the Modular Non Osteo-Integrated Extractor is not in the CORAIL upgrade kit. Components which make up the Modular Non Osteo-Integrated Extractor can be ordered separately.
If the stem becomes blocked in an incorrect position, sits proud or subsides, it must be removed. This is carried out using a threaded pin screwed into the CORAIL stem and linked to the modular handle. The strike plate is screwed into the other side of the modular handle.
In order to optimise the use of the instrument, it is essential to ensure that the threaded rod is fully screwed into the CORAIL stem during the extraction. Once the stem is removed, broaching should be resumed with the last used broach to remove the blockage. The extractor is not to be used to extract osteo-ingrated stems.
The extractor screw (the one locking the plate to the handle) must be tightened regularly when extracting a stem (to prevent any loosening of the plate or the screw itself).