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®Surgical TechniqueTotal knee replacement

Surgical Technique : SummaryThe knees 1/ Tibial tray Page 1s 2/ Mobile bearing Page 1s 3/ Femoral component Page 2s 4/ Patella Page 2Surgical Techniques Important recommendations Page 3s Preoperative planning Page 31 - Distal femur resection Page 42 - Tibial resection Page 43 - Extension gap Page 4s Distal femoral resection Page 5s Tibial resection Page 61 - Centromedullary guiding Page 62 - Extramedullary guiding Page 83 - Combined guiding Page 8s Extension gap Page 9s Flexion gap Page 9s Femoral component size selection Page 10s Chamfer cutting procedure Page 11s Femoral component test Page 12s Tray size selection Page 12s Tibial preparation: Drilling Page 12s Fin imprint Page 13s S keel implantation Page 13s Patella preparation Page 14s Tests Page 14s Placement of final components Page 151 - Tibial tray Page 152 - Femoral component Page 163 - Mobile bearing placement Page 164 - Patella sealing Page 16

®The kneeis a highly congruent prosthesis for tri-compartmental resurfacing of the knee. Bearing mobility isexclusively rotatory.There is no medio-lateral or antero-posterior mobility to interfere with the kinematics induced by the prosthesis design.The mobile bearing was designed to offer optimal safety against the risk of dislocation.Intrinsic flexion range, determined by the design and position of the posterior-stabilised cam, and by the design of theprosthetic posterior condyle is greater than 130°.s 1/ Tibial trayIt is of anatomic shape and is able to adapt to the resected surface of the tibia, without it being necessary to use a rightor left component.The thickness of the tray has been reduced using a keel with two fins, playing the role of a prop. The keel is cone-shapedand can be prepared by drilling or piercing, and is hollow in the centre to accommodate the mobile bearing rivet.The tibial tray is made of cobalt chrome, a material of which the behaviour under friction is known. The characteristicsof friction are optimized by rectification of the bearing and high-level polishing.s 2/ Mobile bearingThe mobile bearing, made of ultra high molecular weight polyethylene (UHMWPE), to minimize wear phenomena hastwo lateral surfaces, in perfect congruence with the femur.The lower rivet, which joins with the tibial keel, has a 10 mm cylinder part, and ends with a 14.5 mm cone segment(total height = 24.5 mm).The cylindrical portion is required to stabilise the mobile bearing should it lift from the tray, a situation observed if thelateral ligaments are stretched, or distracted during walking.If the rivet was fully cone-shaped, lifting of the mobile bearing would lead to detrimental front or sagittal movements,which may encourage wear and creep of the polyethylene.To the front, the mobile bearing has been significantly indented to avoid all contact with the patella tendon or the tipof the patella during hyperflexion.The size of the mobile bearing with respect to the tibial tray was studied to allow for considerable rotation (over 15°),while avoiding contact with the soft parts (lateral ligaments, patella tendon and popliteal tendon).For a number of prosthesis models with mobile bearings, rotatory range, if it is not controlled by a stop device, is limitedby friction of the mobile bearing with the soft parts; Friction may cause anterior (ligamentum patellae), lateral (MCL/LCL)or postero-lateral (popliteal tendon) pain.1

s 3/ Femoral componentLike the tibial tray, the femoral component derives from a chrome cobalt casting process, and is rectified and highly polished.Like the posterior condyle, the distal condyle is 9 mm thick.The cutting angle of the trochlea is 6°. The sharp skew is used for anterior resection while preventing the risk of stair gaitThe design of the femoral component aimed to lighten this part.Recessing of the lateral condyles in the femur reduces mass by 30%.Posterior resection according to a 4.5° angle to the inside ensures good posterior release in favour of flexion.Ribs guarantee correct positioning of the implant, and ensure adjustment to the bone sections.The trochlea is deep, wide and its recess is continued as distally as possible so as to offer the prosthetic patella goodcongruence during flexion.s 4/ PatellaThis is a sphere portion, cut according to an oval contour for better adjustment to the edge of the patella section.It has two sealing rivets.2

Surgical Techniques General informationThe surgical technique aims to guarantee alignment of the knee and to obtain balanced ligament tension.This technique is based on the consensus philosophy of the Insall extension and flexion gaps.Ligament gaps and tension are evaluated using a system of spacers and wedges.This system is used to guide ligament release, and to create a rectangular extension gap, and also to achieve equaltension in the internal and external lateral formations.Ligament balance during flexion is obtained by unequal resection of the posterior condyles, based on ligamenttension during flexion. It is also possible to take the bone markings into account (biepicondylar line or Whiteside’s line).In any case, it is not necessary to alter ligament tension during flexion when setting extension.The instrumentation was designed to be the simplest and most reliable possible.Excessive modularity may be the cause of inaccuracy, due to accumulation of manufacturing limits, or due to clearancerelating to wear of the various parts.The instrumentation was designed to be volume- and weight-saving. The same instrumentation is used for distalfemoral resection and tibial resection.In the same way, only one resection block is used for posterior resection (identical for all sizes), and trochlear cut(5 slits on the same block).For distal femoral resection and tibial resection, and where per-operative observations are not compliant withpreoperative planning, and where per-operative navigation is used to optimize the degree of angular precision of thecuts, it is possible to proceed with extemporaneous correction, degree by degree.Either distal femoral resection or tibial resection can be performed first.Important recommendations :•The blades used to place theprosthesis must be 1.27 mm thick for insertion in thecutting block slots.•Different femoral component and tibial tray sizes can be combined.•However, the size of the mobile bearing must be identical to that of the femoral component.•It is recommended using a patella implant of the same size as the femoral component, but the patella canbe under (or over) sized by one size with respect to the femoral part.s Preoperative planningThis is fundamental, as it determines the angle of the femoral valgus, and the entry points of the centromedullary stemin the cavity of the femur and of the tibia.Planning is based on the principle of goniometry.The mechanical axis of the femur must be drawn, joining the centre of the femoral head to the tip of the intercondylar notch.The mechanical axis of the tibia joins the centre of the base of the eminence in the middle of the talus.3

1/ Distal femur resectionPlace the transparent template showing the outline of the centromedullary stems.Determine the centromedullary stem entry point, which may be slightly medialised if the femur is curved.Select the most appropriate diameter (8 or 10 mm).Decide which length to sink in (at least 20 cm for the femur, 30 cm for the tibia).Measure the angle formed between the reamer and the mechanical axis of the femur.Usually, this angle is between 5 and 7°. It may vary by up to 3° in long-legged subjects, or up to 11° in the case of curved femurs.Distal femoral resection can be viewed, enabling per-operative verification (angle correction may be necessary during theoperation in the event of discordance with the planning).2/ Tibial resectionPlace the transparent template (centromedullary stem) on the tibia.If the tibia is curved, and centromedullary guiding is only possible over an insufficient length (less than 30 cm), then optfor extramedullary guiding.If the tibia is straight, determine the entry point of the reamer, which is usually median, and its diameter (the 10 mm stemshould be preferred to the 8 mm stem).In intermediate cases, when the tibia is slightly curved, the centromedullary system can be used.To determine the entry point, move the transparent template while remaining parallel with the mechanical axis of the tibia,until the outline of the reamer is well marked, throughout the entire length of the centromedullary cavity. Measure thespace between the reamer entry point and the centre of the tibial eminence (e.g.: 6 mm lateralisation).To determine the entry point, move the transparent template while remaining parallel with the mechanical axis of the tibia, until the outlineof the reamer is well marked, throughout the entire length of the centromedullary cavity. Measure the space between the reamer entry pointand the centre of the tibial eminence (e.g.: 6 mm lateralisation).3/ Extension gapPreoperative planning makes it possible to view both cuts (distal femoral and tibial) and therefore the extension gap.Attention : the gap viewed does not take into account ligament tension and depends on the conditions ofimplementation of goniometry : It is therefore not recommended basing one’s decision as to which ligamentrelease procedure to use on planning only.By taking into account the clinical evaluation of ligament tension (reducibility of the deformation, laxity of convexity, retractionof concavity) it is possible to presuppose which release procedures should be used.E.g. : In cases of osteoarthritis of the knee with a varus of 12°, trapezoidal extension gap, retracted MCL (non-reduciblevarus), and distended LCL (varus laxity), extended release of the MCL will be necessary.In this specific case, if the angle of the femoral valgus is for example 7°, the cutting angle can be reduced by 1 or 2° (e.g. 6 or 5°) in orderto minimize ligament release procedures. In this case, a femoral varus of 1 or 2° must be accepted. However, it is strongly advisedagainst to not respect the principle of orthogonality of the tibial cut, as incorrect positioning in varus or in valgus of the tibialtray leads to high strain on the PE, and in the mid-term leads to mobilisation of the tibial implant.4

®s Distal femoral resectionAfter having exposed the joint, resected the synovial membrane andthe osteophytes, and having released the ligament to a minimum extent.Drill the femur at approximately 10 mm above the notches, in thecentre, or (according to preoperative planning) slightly inside the centre.Choose the 8 or 10 mm centromedullary stem according to thepatient’s size and preoperative x-ray study.Place the 8 or 10 mm centromedullary stem, pre-assembled on a Thandle, and which will be sunk in to the length determined in the preoperativestudy, taking into account the curve of the femur, or the presenceof an underlying femoral stem.Remove the handle. Insert the pre-set angle cursor (e.g.: 5°) until itcomes into contact with one of the femoral condyles.Check that the intra-operative observations are compliant withthe planning (e.g. contact with the internal condyle, 2 mm space withrespect to the external condyle for a 5° valgus angle).Where this is not the case the femoral valgus angle can be correctedin situ, by unlocking the angle cursor.Pre-assemble the FT cutting block on the bevel gear.Slide the two bevel gear rivets into holes made in the angle cursor,until the cutting block comes into contact with the trochlea5

Detach the FT cutting block from the bevel gear.Remove the centromedullary stem and the bevel gear.If necessary, move the FT cutting block to + 2 (previous and/or nonreduciblepreoperative flexum) or to – 2 (preoperative laxity and/or severewear of the distal condyles).Resect, using a 1.27 mm blade sufficiently long for resecting in one step only.It is strongly advised against to use thinner blades as they maydistort the cut.s Tibial resectionAfter having excised the menisci and cruciate ligaments, the tibia isdislocated to the front.It is possible to perform tibial resection with the centromedullarysystem or the extramedullary system.1) Centromedullary guidingDrill the entry point for the centromedullary stem at the centre ofthe tibial eminence (insertion of the ACL).If the tibia is slightly curved, preoperative planning may have providedfor a slightly lateralised (or medialised) entry point.Insert the centromedullary stem pre-assembled on the handleand sink it in as far as possible in the centromedullary cavitySlide the angle cursor preset to 0°, and place the FT cutting blockpre-assembled on the T bevel gear.6

®To determine the tibia resection level, raise the FT cutting block to a height.- Use the paddle to set resection height.- Using the probe : It is advisable to base the resection level with respectto the tray the most frequently used (internal tibial tray in genu varum).Preset the probe at the desired resection level (e.g. 3mm) and lower theassembly until it comes into contact with the tibial tray (base of the cup).The probe can also be used unlocked.Fixe the FT cutting block using 2 nails at markings 0 (drill first).Move the cutting block nearer to the tibia, and fix again using oneor two oblique nailsPerform tibial resection using a long, 1.27 mm thick blade.If resection is insufficient, the block can be moved to marking + 2 or + 4,for further trimming by 2 or 4 mm.7

E.g. : 3°Centre of the ankleor2 nd intermetatarsal space2) Extramedullary guidingThis technique is recommended in curved tibias, wherethere is malunion or in any other situation in whichthe intramedullary system is not reliable.Insert the 8 (or 10 mm) centromedullary stem into thetibia, over a length sufficient for stabilising it.Slide the angle cursor and position the FT cuttingblock assembled on the T bevel gear.Insert the extramedullary stem into the bevel gear.Check that it is centred at ankle level.Set the angle cursor so that the distal end of theextramedullary stem extends into the middle of thetalocrural joint (the talus more specifically) or of the2 nd intermetatarsal space.Fix the FT cutting block and resect (after having removedthe centromedullary stem).3) Combined guidingWhere centromedullary guiding is applied, the extramedullary stem can beused: To vary the varus/valgus angle by referring to the projection of the endof the stem in the ankle and foot.8

®s Extension gapPlace the knee in extension, and exert traction according to the axis.View the space created in the two compartments.Position the detachable femoral wedge and 9 mm spacer assembly.This thickness matches the added thickness of the tibial tray and thethinnest part of the polyethylene at the base of the cup.The detachable wedge is equivalent to the thickness of the posterior condyles(9mm) of the femoral implant.If it is not possible to insert the assembly, trim the tibia (or the femurif there is severe preoperative flexum). To do this, adjust the cutting blockby 2 or 4 mm.Once the assembly is in place, it must be ensured that complete extensionof the knee has been achieved and that the knee is aligned correctly.If the knee is also taut in extension and in flexion (varus and valgus movements) and thegap is perfectly rectangular, it will not be necessary to perform any further release.If one of the compartments is wider (external compartment in genu varum), it willbe necessary to release the ligament on the retracted side (MCL in this case).If frontal laxity is both internal and external, thickness must be increased, byadding a 2 mm spacer, representing the 11 mm mobile bearing.Add another spacer where required until total stability in the two compartments is achieved.The gap and ligament balance in extension having been achieved,the spacer-wedge assembly can be removed.s Flexion gapPlace the knee in flexion.Insert the spacer assembly used during balancing in extension(without the 9 mm femoral wedge).Place the knee at 120° flexion to make insertion of the spacer easier.Bring the joint back to 90° and test laxity.External laxity is observed the most often, requiring addition of a wedge(1, 2, 3, 4 or 5 mm).In cases of genu varum, it is usual to insert a 1 or 2 mm wedge in theexternal compartment, which leads to positioning of the femoral part inexternal rotation.The external degree of rotation depends on the wedge used and on bone size. E.g. foran average sized knee (size 3), a difference of 1 mm is equivalent to 1°30’ externalrotation, 2 mm = 3°, 3 mm = 4°30’, 4 mm = 6° and 5 mm = 7°30’.9

In cases of genu valgum, it is often necessary to insert a thicker wedge (up to 5 mm) in the external compartment,which places the femoral component in external rotation.Attention : it is highly unadvisable to insert a wedge thicker than that in the external compartment in the internalcompartment, as it would place the femoral component in internal rotation, and would be harmful to patello-femoral trackingIf it is possible to insert very thick wedges during flexion (e.g.: 4 mm external, 2 mm internal), return to the previous stepand check the extension gap as it has probably been under-evaluated. Add one or several spacers in extension and bringinto flexion; this will reduce the wedge thickness during flexion. If such correction is not made, it would lead to ligamentimbalance (knee stable in flexion but with the axis in extension) and to implantation of an oversized femoral component,as determination of the size takes the total anteroposterior size of the femur and wedges in flexion into account.Ligament setting in flexion may also take into account the epicondylar markings or the posteriorbiepicondylar (Whiteside’s) line.s Femoral component size selectionAnterior and posterior resectionThis is a decisive stage :- An oversized femoral component loses its press-fit effect as the trochlearbearing surface is reduced. Over sizing may lead to pain (patella retinaculumoverload) and limited flexion (overload of the extensor system andlateral ligaments in flexion).- An undersized femoral component leads to the opposite effects: Weakeningof the anterior cortical (risk of supracondylar fracture if trochlear cutcreates stair gait), and laxity in flexion.Slide the APM block until it comes into contact with the distal section. Varyknee flexion, which must be 90°, so that the block is flat against the bone.Fix the cutting block using 2 flange screws 2 oblique nails.Apply the stylus to the anterior cortical and read the size.Where the reading is between 2 sizes (e.g.: T3 T4), follow the procedurebelow:10

®- Cut on the next size up (T4) and evaluate cut surface.If it is insufficient, select the next size down (T3) and trim (by inserting theblade in the lower slot). The resected thickness will be 3.5 mm (includingblade thickness).The thickness of the posterior condylar cut does not vary with size (constantand equivalent to 9 mm), and it will not be necessary to rework it.Anterior cutEvaluation of trochlear trimming prior to resection may appear to be toosignificant. In this case, remove the nails and position 1 or 2 mm wedgesin the 2 compartments (internal and external). Anterior trimming will not be3.5 mm, but 2.5 mm (where there are two 1 mm wedges), or 1.5 mm (wherethere are two 2 mm wedges). Posterior resection will not be 9 mm asin standard cases but 8 mm (1 mm wedge), or 7 mm (2 mm wedge).This leads to slight ligament overload in flexion.Posterior cuts Chamfer cutting procedureFurther to posterior resection and anterior resection, position the chamfercutting block of the size described in the previous stage.Medio-lateral sizing of the CC block should match implant width.Check that the chamfer cutting block is well set against the distal cutand the anterior cut. Fix the block using 4 nails (2 straight nails at thetop, and 2 oblique nails on the sides).Carry out the section of the posterior chamfers and then the anteriorchamfers.These sections are carried out with a wide blade for greater comfort (20 mm).11

s Femoral component testTake the test femoral component using the pliers.Position and impact the test component.Position the knee in hyper flexion and proceed if necessary with resectionof the posterior osteophytes.To optimise flexion, it is advisable to resect all bone overlappingfrom the prosthetic posterior condyles.If the test femoral component does not fit perfectly on the distal femoralcut, the angle may need to be broken using a bone file on the internal sideof the trochlea.s Tray size selectionA tibial tray of any size can be implanted, as thefemoral component and mobile bearing mustmatch in size, but not the tibial tray and themobile bearing.Select the tray size which will the most effectively cover the tibia cut surface.In the event of osteoporosis, it is advisable to widen coverage by overlappingonto the corticals by 1 mm if necessary.Set the rotation of the test tray with respect to the axis of the foot.Accurate setting is not necessary as it is a mobile bearing and accuratepositioning in rotation of the tibial tray is not essential.Fix the test tibial tray with the two flange screws.Position the tower, of which the role is to guide drilling and keel sinkingin the three planes.Position the two handles which will be used to hold the tibial tray by flatteningit against the bone during bone preparation.s Tibial preparation : DrillingA tapered drill is used for drilling.Depending on the size of the keel, adjust the depth of the drill :• For sizes 1 and 2, upper mark• For sizes 3, 4 et 5 , lower mark12

®s Fin imprintXSThe fin imprint is made in this stage: impact the router using the hammerattached to the universal handle.The router can be used with all sizes.The depth is controlled by the laser marking lines (same marking as for the drill).If the bone is particularly hard (sclerous bone of an internal tibial tray ongenu varum), the bone should be prepared using the oscillating saw.Where an XS keel is implanted, tibialpreparation should be completes S keel implantationS keel implantation requires preparation withthe reamer.Position the jig bushing matching the diameterof the keel selected on the test tibial tray.Match the top of the teeth of the reamer withthe top of the jig bushing.S13

s Patella preparationEvert the patellaResect the synovial membrane in the suprapatellar region, and remove the lower perimeter of the patellafrom the fatty tissue.Determine the thickness to be resected. Where the patella is little worn, 8 mm bone should ideally be resected.Take the patella with the forceps.Place the forceps at a height using the probe, which determines resection depth.Proceed with resection.s TestsInsert the bush in the test tibial tray. This will stabilise the stray for thetests. The bush is the size of an XS keel.When an S keel is implanted, the trial keel need to be fixed on modular bush :Fix the test keel to the modular bush, and insert the assembly inthe test tray.Ensure that the test bush/modular keel assembly is in close contact withthe test tibial tray.Position the mobile bearing matching the size of the femoralcomponent and of which the thickness was determined duringthe extension and flexion gap setting phase.Test the knee in flexion and extension- If the knee is aligned and tight both in extension and flexion, the mobilebearing thickness used for the tests can be adopted.- If the knee appears to be too taut in extension and in flexion, test the nextthickness down.If the knee is lax in extension and flexion, test the next mobile bearingthickness up.14

®When the tests are considered tobe satisfactory, the centring rivetholes for the femoral componentmust be prepared.Using the stop drill, prepare thetwo impaction rivet holes.Ensure that the drill descends andthen stops against the test femoralcomponent.s Placement of final componentsWash the joint thoroughly to remove any bone debris.Proceed as follow :1) Tibial trayDislocate the tibia to the front, and place the knee in hyperflexionCarefully wash then dry the bone surfacee.Assemble the extension keel with the tibial tray by impact the assemblytaper, then solidarize the keel with the screw packed into the conditioningof the tibial tray. Use the tibial impactor mounted on the universalhandle for impaction.15

2) Femoral componentImpact the femoral component.If a cemented femur is implanted, ensure that a little cement is applied tothe posterior condyles.Remove any excess cement around the edges and from the chamber.3/ Mobile bearing placementWhen the tibia is in hyper flexion and anterior draw position, insertthe mobile bearing.Place the knee in extension, in order to place the cement undercompression where sealing is applied.4/ Patella sealingHold the patella during sealing using the patella forceps.16

®TO 07 EN-BConception & impression : Imprimerie du Petit-Cloître - Chaumont•Langres - 114519 T - 06 / 2010Z.I. Rue Lavoisier - B.P. 10 - 52800 NOGENT - Tél : +33 (0)3 25 02 72 89 - Fax : +33 (0)3 25 31 29 99 - Info@c2f-implants.com