Joint replacement- Stryker SR Metal on Poly PIP joint

Dorso-lateral skin incision marked on ulnar border of PIPJ.
With the limb anaesthetised, prepped and drapped on an arm board and tourniquet inflated the skin incision is marked.
The line of the incision is on the dorso-ulnar border (dorso-radial in the little finger). It roughly lies over the junction of the lateral bands and the central tendon. It extends from mid-proximal phalanx to mid-middle phalanx.

Skin is incised and then blunt dissection performed down to the extensor hood.Once the skin is incised the skin, fat and dorsal branches of the digital nerves are elevated as one layer to the level of the extensor tendon to maintain skin vascularity and protection of the nerves.
The junction between the lateral band (interossei tendons) and central tendon is marked.

The extensor hood is incised between the lateral band and the central tendon.The capsule will be incised as a separate layer.

The capsule is incised.The capsule is incised in line with the tendon incision and is then released from the middle phalanx starting on the ulnar border working gradually volar to the insertion of the true collateral ligament which is attached to the volar 30-40% of the lateral border of the middle phalanx.

The capsule is reflected radially as is part of the insertion of the central slip.The central slip which is also partially elevated with the periosteum of the middle phalanx.
Occasionally the central slip may completely detach at this point, if this occurs it will need to be reattached at the end of the procedure. NB – a bony suture must be inserted before cementing if this is the case.

The scissors are pointing to the ulna collateral ligament of the PIPJ travelling from the centre of rotation of the proximal phalanx head to the volar 30-40% of the middle phalanx.

The true and accessory ulnar collateral ligaments and volar plate are released.The ligaments are sharply dissected off the middle phalanx as a sheet continuous with the periosteum, the ulnar two thirds of volar plate is also released. The release is made easier by pronating the middle phalanx as the dissection proceeds dorsal to volar as this keep the tension on the tissues for a cleaner dissection.
The collateral ligaments are elevated in a sheet in this way to allow them to stick back down and provide lateral stability in the post operative period without the need for a formal repair.

The joint is shotgunned radially.Once the joint is released as described the lateral shotgun of the joint is attempted. It often takes a few attempts to complete this manoeuvre with a little further release required between each attempt. In joints which have marked erosion of the joint the whole volar plate may need to be released to shotgun the joint.

The joint is now shotgunned revealling a clear view of both articular surfaces.
MP – Middle phalanx
PP – Proximal phalanx

Be aware that the lateral bands seperated of the central tendon in the initial dissection can be under tension on the ulnar side of the joint (shown by the scissors) and therefore are at risk of iatrogenic damage if care is not taken.

The proximal phalanx head is cut perpendicular to the diaphysis just distal to the collateral ligament insertion.This cut can be difficult execute correctly if the phalanx condyle are unevenly worn therefor it is best to firstly remove and large dorsal osteophytes, clear soft tissue around the head allowing both origins of the collateral ligaments to be clearly identified and drawing a line along the long axis of the bone as seen in the image. Following this a cut line on the distal edge of the collateral insertions and perpendicular to the long axis is drawn (also shown).
It can be seen that on this image the radial condyle (highlighted by the metal pointer) is less eroded and therefore relatively more bone will be cut from this side.

The bone cut is undertaken with the appropriate size saw and the collateral are protected.

The cut is made. Often is the cut is at the level of the collaterals the insertion of the the ligaments can be seen indenting into the bone at the cut level.

The starter awl is inserted centrally in both radio-ulnar and volar-dorsal directions.

A 45 degree volar bone cut is performed at the lower level of the awl entry point. The cut is easiest to perform with the proximal phalanx vertical and the blade at 45 degrees to the table.
The collateral ligaments and lateral bands are protected with skin hooks.

The starter awl is then used on the middle phalanx.The awl is inserted centrally from radial to ulnar and slightly dorsal of central in the volar-dorsal direction.

The middle phalanx is cut perpendicular to the diaphysis.The site of the starter awl entry can be seen.
A sliver of bone is removed with the saw from the ulnar aspect of the middle phalanx where the collateral was excised from. This bone sliver aims to create enough space for the implant and its thickness will depend on the severity of erosion of the base of the phalanx.
If still attached the central slip should be protected also at this point.

The joint gap is assessed in finger extension.Once both bone sections have been cut there should be an even joint space able to fit the implant when the finger is pulled straight. Clearly the joint gap will open more on the ulnar side if stressed as no collateral ligament is attached.

A burr is used to widen the awl hole if the bone is sclerotic.When reaming PIP joints the surgeon must be aware whether the implant being used can mix sizes of proximal and distal implants or whether one size is used, as in the case of this implant.
Where one size for both proximal and middle phalanx is used then the largest implant is used which fits the smallest bone.
As it can vary whether the canal of the middle or proximal phalanx is largest is is best to ream sequentially to avoid over reaming of one bone.
When starting reaming a burr may be required initially if the bone is sclerotic.

The initial reamer is sited in the middle phalanx.The initial reamer is sited in the middle phalanx.

A radiograph is taken to check central placement on the AP and lateral images.

It can be seen from this view that the reamer is slightly volar in its placement and therefore on subsequent reamer insertions a dorsal pressure can be applied to ream more dorsal than volar and correct the reaming position prior to trial insertion.

The initial reamer is placed in the proximal phalanx.

The initial reamer position is checked on the AP and lateral images.

Again the reamer is slightly volar in placement and therefore this should be corrected on subsequent reams prior to trial insertion.

Trial implants are inserted.Once both bones have been sequentially reamed up to the largest size of the smallest bone (if the proximal phalanx is reamed maximally to a size 2 and the middle phalanx could be easily reamed to a size 3 – stop at a size 2 in both bones so that the sizes match).
The trials (in this case size 2) can now be inserted.
The tension is tested to assess for over stuffing of the joint. If the correct size is inserted the PIPJ should fully extend with ease and flex without the trial being too unstable (if a significant preoperative flexion contracture was present this assessment may vary).

Range of movement assessed with trial implants in situ.The rotational alignment is also assessed. Make sure the shapes of the 2 components of the trial sea nicely and align with the pen line previously drawn down the proximal phalanx. Rotation can often look abnormal in this approach due to the one sided joint release. If there is any concern them place a tacking suture attaching the central slip to the lateral band and reassess – this will usually correct any abnormal rotation caused by the operative dissection.

Radiographs of the trials are taken.

The trial is removed and the bone washed and dried to prepare for cementing.At this point, if the central slip was completely lifted off the middle phalanx then two osseous tunnels can be drilled with a 1.2mm k-wire into the insertion on the middle phalanx and a suture passes through the holes before cementing enabling reattachment during closure.
The area is prepared with a clean drape or towel, change of gloves, implant (which has been checked and opened), implant impactors, forceps and Watson-Cheyne dissector for removal of excess cement.

An antibiotic impregnated cement is inserted.In this case a standard cement is used and after 2-3 mins when easy to handle the cement is rolled into a small sausage shape and pushed into the canal of both bones and the impacted it with a thumb.

The proximal phalanx implant is inserted.

The middle phalanx implant is inserted.

The appropriate impactor is used to firm in the two implants.

The excess cement is removed, the joint relocated and radiographs taken.

AP radiograph of the implant in situ

Manufacturers box showing the size 2 implant.

The ulnar collateral ligament is laid back into position and the capsule and tendon repaired.The collateral ligament is left to heal in place and is not formally sutured down.
The central slip is sutured back if necessary with the pre-prepared interosseous suture and the lateral band is sutured back to the central tendon with 4/0 PDS.
This will then correct any rotational deformity and instability seen following the initial dissection.
To note in this patient, the marked ulnar angulation of the DIPJ made intra-operative alignment (often referenced off the nailbed) more difficult and must be appreciated pre-operatively.

The skin is closed using a 4/0 vicryl rapide.

An occlusive dry dressing is applied.

A volar plaster slab, wool and crepe are applied in extension. This cast will be removed at 1 week in clinic.

Pre-operative AP radiograph showing marked erosion of the ulnar condyle of both the proximal and middle phalanges.

Pre-operative lateral radiograph revealing PIPJ and DIPJ arthritis.