Surgical Techniquefor the

CMICarpo Metacarpal Implant

CMI Trapezio-MetacarpalRessurfacing Implant

TheThe CMI CMI resurfacingresurfacing implant implant isis designeddesigned to restore to restore strengthstrength, , mobilitymobility, , andand longlong--termterm stabilitystability to to thethe failedfailed or or deficientdeficienttrapeziotrapezio--MetacarpalMetacarpal joint.joint.

UnlikeUnlike thethe TrapezioTrapezio--MetacarpalMetacarpal prosthesisprosthesis, , itsits unipolarunipolar design design andandstraightstraight--forwardforward surgicalsurgical procedureprocedure allowallow thethe surgeon to surgeon to achieveachieve a a nearnear anatomicalanatomical joint joint functionfunction..

INDICATIONS

• TMC degenerative arthritis

• (TMC prosthesis revision)

• (Trapezectomy revision)

FEATURESAVANTAGES

1. Anatomical stem for better stability

2. Angled and off-set head for better stability

3. Unipolar prosthesis - no trapezium insert

4. Short metacarpal bone resection

5. Non cemented

6. Very accurate instrumentation

ANATOMICAL STEMANATOMICAL STEM

TigeTige anatomiqueanatomique

��The The PyrocarbonPyrocarbon Stem fits and fulfills perfectly the first metacarpal thanks toStem fits and fulfills perfectly the first metacarpal thanks to its its anatomical designanatomical design��The shape of the The shape of the PyrocarbonPyrocarbon Stem is ovoidStem is ovoid

��The CMI implant is stable. It does not rotate inside the The CMI implant is stable. It does not rotate inside the diaphysisdiaphysis��Optimal partition of load inside the first metacarpal Optimal partition of load inside the first metacarpal diaphysisdiaphysis

ANGLED and off-set HEAD

��The CMI Head is angled to respect the Metacarpal anatomyThe CMI Head is angled to respect the Metacarpal anatomy

��The CMI implant is stable. It does not rotate inside the The CMI implant is stable. It does not rotate inside the diaphysisdiaphysis��Maximum congruence between the trapezium and the CMI implantMaximum congruence between the trapezium and the CMI implant��Prevents the metacarpal Prevents the metacarpal subluxationsubluxation

15°15°

TrapeziumMetacarpal

UNIPOLAR PROSTHESIS

� No trapezium insert

� There is no dislocation of the trapezium insert� The CMI procedure is easy. The precise and difficult placement and fixation of the

trapezium insert is not necessary anymore. The only piece to be implanted is the metacarpal part.

� Small trapezium is not contra-indication for the CMI implant

� Metacarpal resurfacing only

� Anatomical design

BONE SAVINGMetacarpal preparation

� Minimal resection of the first metacarpal

� Bone saving compared to a Trapezio-Metarcarpal prosthesis. We establish a 3,5 mm resection of the first Metacarpal for CMI implant (from 7 to 10 mm for a trapezio-metacarpal prosthesis)

� This technique allows other surgical alternatives in case of failure� Conservation of the thumb height

� The trapezium is not resected but milledThe procedure leads to the local milling of the arthrosic part of the trapezium only (1 - 2 mm depth)

� Bone saving compared to a Trapezio-Metarcarpal prosthesis. � No risk of trapezium fracture � Conservation of the thumb height� Maximal congruence of Trapezio-Metacarpal joint� Optimal partition of load on the trapezium

BONE SAVINGTrapezium preparation

CEMENTLESS IMPLANTImplant sans ciment

� The Pyrocarbon Stem is impacted in the first metacarpal without any ciment addition

� The Pyrocarbon Stem has an extremely low friction coefficient and an elasticity modulussimilar to that of the bone

� The stem is not osteointegrated but stable

TrapeziumMetacarpal

Instrumentation

SURGICAL TECHNIQUE CONTENTS

1. Surgical approach

2. Metacarpal preparation

3. Trapezium preparation

4. Implant selection

5. Ligamentoplasty

6. Wound closure

SURGICAL APPROACH

• A dorsal or dorso-radial approach is used. The trapezio-metacarpal joint isexposed. Care must be taken to avoid the palmar cutaneous branch of the mediannerve and of the extensor pollicis brevis.

• The superficial branches of the median nerve are then gently dissected and the tendons are retracted to identify the joint line.

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• The capsule is incisedlongitudinally, while preservingas possible the articularcapsule, scraping the 1st

metacarpal basis with a periosteal elevator.

• Osteophytes that may be present are removed.

• The first metacarpal cutting guide is used to establish a 3,5 mm resection.The first metacarpal is maintained in compression against the cutting guide. Any osteophytes should be removed.The joint is irrigated and cleared of debris.

•

METACARPAL PREPARATION

Prepare the metacarpal bone shaft using the broaches. A mark on the instrument indicates the dorsal side and permits to correctly orientate the implant inclination. The metacarpal broach is introduced in line with the center of the bone, with its dorsal mark facing the dorsal side of the diaphysis. The aim is to correctly fill in the diaphysis using the biggest size that fits the bone shaft.

This will prepare the shape of the implant and will ensure a press-fit when the final implant will be impacted in the diaphysis.

To make the impaction and extraction of the broaches in the bone shaft easier, use the extractor screwed on the broach handle.

METACARPAL PREPARATION

• With a sharp awl, locate the trapezium centre.

TRAPEZIUM PREPARATION

• Prepare the implant place by milling the trapezium arthrosic part using the powered CMC reamer : a good axial compression will be maintained with the CMC reamer handle, and also a good pression on the trapezium, which should be strongly maintained.

The joint is irrigated and cleared of debris.

IMPLANT SELECTION• The metacarpal trial corresponding to the

broach is introduced, ensuring its correct position thanks to its dorsal mark.

• Control by X-rays.

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• A distal insertion of the abductor pollicis longus is reinserted dorsally. The insertion must be advanced distally on the metacarpal and strongly anchored through the bone on the middle of the 1st metacarpal.

This transposition is not under tension already in order to enable the definitive implant to be inserted.

LIGAMENTOPLASTY

• The trial is extracted and the joint space is irrigated and cleared of debris.

The definitive implant is then implanted insuring its correct orientation thanks to the implant holder.

• Impact the final implant with the plastic impactor.

• Be careful:

• no other instrument should be used for this operation because the implant may

be damaged.

• Pull to apply some tension on the dorsalized APL.

LIGAMENTOPLASTY

LIGAMENTOPLASTY

Take a strip of the extensor carpi radialislongus, preserving its distal insertion ; transfer the strip beneath the radial bundle and the extensor pollicis longus. Thus this strip comes to double the capsule over the abductor pollicis longus.

LIGAMENTOPLASTY

TransferedTransfered APLAPLECRL ECRL stripstrip

This ECRL strip is finally inserted with some tension on the radial side of the 1st metacarpal, trying to insert it as palmar as possible in order to favour thumb pronation.

Closure over to a suction drain and immobilization in a "resting position".

WOUND CLOSURE