Zimmer Biomet NexGen MIS LPS-Flex Surgical Technique Manual Download Page 4

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NexGen MIS LPS-Flex Mobile Implant System

Surgical Technique

Successful total knee arthroplasty (TKA) depends in
part on re-establishment of normal lower extremity
alignment, proper implant design and orientation,
secure implant fixation, adequate soft tissue balancing
and stability.

Introduction

Summary of Contents for NexGen MIS LPS-Flex

Page 1: ...NexGen MIS LPS Flex Mobile Implant System Surgical Technique ...

Page 2: ...S Medial Parapatellar Arthrotomy 8 MIS Midvastus Approach 9 MIS Subvastus Approach 11 MIS Quad Sparing Arthrotomy 12 Soft Tissue Releases 12 Varus Release 13 Valgus Release 14 Step One Resect Proximal Tibia 15 Assemble the Guide Position the Guide Set the Final Resection Level Resect the Proximal Tibia Step Two Establish Femoral Alignment 22 Step Three Cut the Distal Femur 24 Step Four Check Exten...

Page 3: ...ertion of Femoral Provisional Using Optional MIS Femoral Inserter Extractor Removal of Femoral Provisional using Optional MIS Femoral Inserter Extractor Step Eleven Finish the Tibia 48 Step Twelve Prepare the Patella 51 Resect the Patella Finish the Patella Optional Patella Protectors Surgeon Notes and Tips Step Thirteen Perform a Final Trial Reduction 59 Step Fourteen Implant Components 61 Tibial...

Page 4: ...rgical Technique Successful total knee arthroplasty TKA depends in part on re establishment of normal lower extremity alignment proper implant design and orientation secure implant fixation adequate soft tissue balancing and stability Introduction ...

Page 5: ...ees For example the interaction of the posterior condyles on the articular surface was carefully studied As a result efforts have been made to optimize the contact area as the posterior condyles roll back to flexion angles up to 155 degrees Figure 1 This is addressed by thickening the posterior condyles thereby extending the radius The tibial articular surface was also considered in the design In ...

Page 6: ...90 Patients with varus deformities greater than 17 or valgus deformities greater than 13 are typically not candidates for the MIS technique A common view among orthopaedic surgeons is that certain patients have greater potential for achieving higher flexion after knee replacement Patients with good flexion preoperatively tend to get better range of motion postoperatively The NexGen LPS Flex implan...

Page 7: ...is usually about 6 but may vary depending on morphology and patient size is important for choosing the appropriate femoral angle bushing and therefore a correct positioning of the distal femoral cut By lengthening the line of the anatomical axis of the femur it can be shown that the entry point for the intramedullary alignment guide does not necessarily lie in the center of the femoral condyle but...

Page 8: ...if the selected femoral component is smaller than the A P dimension of the femur The alteration of the joint line can be minimized by accurately measuring for the femoral component size and performing a posterior capsulotomy to correct flexion contractures Patient Preparation To prepare the limb for total knee arthroplasty adequate muscle relaxation is required This will facilitate the eversion of...

Page 9: ...ltaneously improving mobility of the skin and reducing tension on the skin flaps during minimally invasive exposure The estimated size of the femoral component influences the length of the incision Although the goal of a less invasive technique is to complete the surgery with an approximately 10 cm 14 cm incision it may be necessary to extend the incision if visualization is inadequate or if there...

Page 10: ...d avoidance of excess skin tension Skin under the appropriate tension should form a V at the apices If the skin forms a U the incision should be lengthened Following subcutaneous dissection develop full thickness medial and lateral flaps to expose the extensor mechanism Release of the deep fascia proximally beneath the skin and superficial to the quadriceps tendon facilitates mobilization of the s...

Page 11: ... make the exposure more like a subvastus approach and may make subluxation of the patella more difficult It is very important to carry the capsular incision all the way to the superior border of the patella before incising the muscle belly of the VMO After identifying the characteristics of the VMO insertion the vastus medialis obliquus muscle belly is split by sharp dissection approximately 1 5 c...

Page 12: ...xternally rotating the tibia while applying gentle pressure on the patella An excessively thick patella may make exposure more difficult and it may help to make a standard patellar cut to decrease the thickness of the patella If this is necessary the patella must be protected from retraction forces with an appropriate patellar protection device Once the patella is subluxed one or two standard size...

Page 13: ...culum tendon to a point on the patella corresponding to 10 o clock on a left knee or 2 o clock on a right knee Then continue the incision obliquely 1 cm 2 cm just below and in line with the VMO fibers Figure 8 Do not extend the oblique incision beyond this point as it creates further muscle invasion without providing additional exposure Perform a medial release according to surgeon judgment depend...

Page 14: ... implant stability The basic principle for ligament release entails that the tight contracted concave side is lengthened to match the convex side The goal is to maintain a consistent and rectangular not rhomboidal flexion and extension gap After accessing the knee joint balancing of the soft tissue structures and removal of osteophytes is initiated Osteophytes may tent the medial capsule and ligam...

Page 15: ...om the proximal medial tibia including the deep medial collateral ligament superficial medial collateral ligament and insertion of the pes anserinus tendons Continue the elevation with a periosteal elevator to free the posterior fibers To improve exposure during the release retract this subperiosteal sleeve using a Hohmann retractor Release the insertion of the semimembranosus muscle from the post...

Page 16: ...imally above the joint and distally within the joint Following the multiple punctures use a laminar spreader to stretch the lateral side This should elongate the lateral side and create a rectangular extension space Use spacer blocks to confirm ligament balance in flexion and extension For a severe fixed valgus deformity it may be necessary to perform a complete release of the lateral supporting s...

Page 17: ...cle anchor left or right MIS tibial adjustable rod MIS distal telescoping rod ankle bar ankle clamp or spring Attach the ankle clamp or optional spring to the ankle bar Then slide the ankle bar onto the dovetail at the bottom of the MIS distal telescoping rod Turn the knob opposite the dovetail to temporarily hold the bar in place Arrows are etched onto both the MIS tibial adjustable rod and the M...

Page 18: ... stem of the tibial cut guide represent 2 mm increments Figure 1c Attach the correct right or left tubercle anchor onto the corresponding side of the adjustable rod For a left knee the left anchor is inserted into the right hole For a right knee the right anchor is inserted into the left hole Be sure that the etched line on the side of the tubercle anchor aligns with the corresponding etched line ...

Page 19: ...imal end of the adjustable rod so it is centered below the intercondylar eminence The tibial cut guide will contact the tibia at an oblique angle and the low profile portion of the cutting head should fit under the patellar tendon Figure 1f The tubercle anchor is shaped to fit between the patellar tendon and the base of the cutting head Note Be sure that only the low profile portion of the cutting...

Page 20: ...kle bar Loosen the knob on the side of the distal end of the MIS distal telescoping rod Then use the slide adjustment to align the rod in the sagittal plane so it is parallel to the anterior tibial shaft This will create a 7 posterior tibial slope If more or less slope is desired use the slide adjustment to obtain the desired slope Then tighten the knob If there is a bulky bandage around the ankle...

Page 21: ...e up or down by rotating the thumb wheel until the tip of the 2 mm stylus rests on the surface of the condyle Figure 1j This will position the tibial cut guide to remove 2 mm of bone below the tip of the stylus Alternatively swing the 10 mm arm of the MIS tibial depth resection stylus over the least involved tibial condyle Adjust the tibial cut guide until the tip of the 10 mm arm rests on the sur...

Page 22: ...lity and the type of prosthetic fixation planned Insert an MIS screw through the medial oblong hole on the cutting head Figure 1l This hole is angled to facilitate screw insertion Remove the MIS tibial depth resection stylus Place another MIS screw through the central anterior hole on the cutting head Figure 1m Note The MIS depth resection stylus must be removed before inserting a pin or screw int...

Page 23: ...rough the medial side and as far as possible into the lateral side remove the cut guide assembly Extend the knee and retract soft tissue on the lateral side Then use an osteotome to complete the cut Note Be careful to avoid cutting the patellar tendon when cutting the lateral side Use a Kocher clamp to remove the tibial bone fragment Then trim any remaining bone spikes on the posterior and lateral...

Page 24: ...e IM alignment guide is available with two intramedullary rod lengths The rod on the standard instrument is 229 mm 9 in long and the rod on the short instrument is 165 mm 6 5 in Choose the length best suited to the length of the patient s leg which will provide the most accurate reproduction of the anatomic axis If the femoral anatomy has been altered as in a femur with a long stem hip prosthesis ...

Page 25: ...ments can be made using the 2 mm 2 mm holes on the mini distal cut guide Insert the IM guide into the hole in the distal femur If the epicondyles are visible the epicondylar axis may be used as a guide in setting the orientation of the adjustable IM alignment guide If desired add the threaded handles to the guide and position the handles relative to the epicondyles This does not set rotation of th...

Page 26: ...guide until the cutting guide rests on the anterior femoral cortex Figure 3b The mini distal femoral cutting guide is designed to help avoid soft tissue impingement Using the 3 2 mm drill bit drill holes through the two standard pin holes marked 0 in the anterior surface of the mini distal femoral cutting guide and place headless holding pins through the holes Figure 3c Additional 2 mm adjustments...

Page 27: ... 3e in the distal placement guide Then use the slaphammer extractor to remove the IM alignment guide and the distal placement guide Cut the distal femur through the cutting slot in the cutting guide using a 1 27 mm 0 050 in oscillating saw blade Figure 3f Then remove the cutting guide Check the flatness of the distal femoral cut with a flat surface If necessary modify the distal femoral surface so...

Page 28: ...de between the resected surfaces of the femur and tibia Figure 4a If necessary insert progressively thicker spacer alignment guides until the proper soft tissue tension is obtained Drop the alignment rod with coupler into the spacer alignment guide Check the flatness slope and alignment of the tibial cut Apply varus and valgus stress for optimal ligament balancing Ligament releases should be perfo...

Page 29: ...hort 3 2 mm 1 8 in Headed screw or predrill and insert a short head holding pin into the lateral hole in the lower portion of the guide Note Remove the threaded handle before using the screw inserter extractor Then remove the threaded handle and insert a 3 2 mm 1 8 in headed screw or predrill and insert a short head holding pin into the medial hole in the lower portion of the guide Do not over tig...

Page 30: ...s with a valgus deformity from 10 to 13 Attach the selected plate to the mini A P sizing guide Figure 5d Use a 3 2 mm drill to drill through the two holes that correspond to the desired external rotation Position two headless holding pins and impact them into the guide Figure 5e Leave the head of the pin proud If preferred the MIS headless screws may be used Note Do not impact the headless holding...

Page 31: ...ved from the posterior condyles when using the flex femoral finishing guide Place the finishing guide onto the distal femur over the headless pins Figure 6a This determines the A P position and rotation of the guide Remove any lateral osteophytes that may interfere with guide placement Position the finishing guide mediolaterally by sliding it on the headless pins The width of the MIS femoral finis...

Page 32: ...ral drill bit Figure 6c Then insert 6 5 mm x 35 mm periarticular bone screws through the post holes If desired predrill and insert two short head holding pins through the inferior holes on one or both sides of the guide Use the resection guide through the anterior cutting slot of the finishing guide and check the medial and lateral sides to be sure the cut will not notch the anterior femoral corte...

Page 33: ... sequence for optimal stability of the finishing guide Figure 6g 1 Anterior condyles 2 Posterior condyles 3 Posterior chamfer 4 Anterior chamfers Use the patellar femoral drill bit to drill the post holes if not done previously Use the 1 27 mm 0 050 in narrow reciprocating saw blade to cut the base of the trochlear recess Figure 6h and score the edges Figure 6i Remove the finishing guide to comple...

Page 34: ...echnique Tip If between sizes and you don t want to go to larger size you may shift the femoral cutting block 2 mm anterior using the 2 mm setting to reduce chance of notching the femur Place the finishing guide on the distal femur bringing the feet of the rotation guide flush against the posterior condyles of the femur Figure 6l Set the rotation of the finishing guide parallel to the epicondylar ...

Page 35: ...ial side of the femoral finishing guide Figure 6m Then secure the lateral side in the same manner For additional fixation drill the post holes using the patellar femoral drill bit Figure 6n Then insert 6 5 mm x 35 mm periarticular bone screws through the post holes If desired predrill and insert two short head holding pins through the inferior holes on one or both sides of the guide Use the resect...

Page 36: ...xit the bone Use a 1 27 mm 0 050 in narrow oscillating saw blade to cut the femoral profile in the following sequence for optimal stability of the finishing guide Figure 6q 1 Anterior condyles 2 Posterior condyles 3 Posterior chamfer 4 Anterior chamfers Use the patellar femoral drill bit to drill the post holes if not done previously Use the 1 27 mm 0 050 in narrow reciprocating saw blade to cut t...

Page 37: ...ld equal the extension gap If the MIS flex femoral finishing guide is used then the flexion gap will be approximately 2 mm greater For an LPS Flex implant use an MIS spacer block with the MIS LPS Flex spacer block adapter to check flexion gap An oscillating saw with a narrow blade may also be used or a reciprocating blade may be used to cut the sides and a chisel or osteotome used to cut the base ...

Page 38: ...size MIS notch chamfer guide onto the femur so it is flush against the resected surfaces both distally and anteriorly Ensure that no soft tissue or osteophytes interfere with instrument positioning Position the guide mediolaterally Figure 7a Note The distal mediolateral profile of the MIS notch chamfer guides anterior to the tabs can be used to position the guide referencing the lateral condyle In...

Page 39: ...ndyle cuts are made using the appropriate size MIS flex femoral finishing guide and the LPS Flex femur peg drill Then use an oscillating saw to cut the anterior chamfer and the posterior chamfer Figure 7e Apply the matching size MIS trochlear guide to the MIS notch chamfer guide with the holes in the trochlear guide aligned with the threaded holes in the notch chamfer guide Figure 7f Thread the MI...

Page 40: ...MIS trochlear guides cannot be used for downsizing Select the preferred size notch chamfer guide and pin to the distal femur with two short spring screws or 3 2 mm 1 8 in headed screws 48 mm length Alternatively insert two hex headed pins Ensure that the guide is seated on the anterior and distal femur Use a reciprocating saw to recut the sides of the intercondylar box Use an oscillating saw to re...

Page 41: ... prepared trochlear recess and or the femoral post holes to position the MIS QS notch guide mediolaterally Use the recut guide modular peg with MIS QS notch guides sizes C G for mediolateral positioning Secure the MIS QS notch guide to the femur with two 3 2 mm 1 8 in headed screws or predrill and insert two 3 2 mm 1 8 in holding pins Figure 7i Use a reciprocating saw to cut the sides and the base...

Page 42: ...Technique Option Two MIS QS Notch Guide cont With the knee in flexion remove posterior osteophytes with a 3 4 in curve on flat osteotome Figure 7l Use a laminar spreader and the posterior femoral retractor to improve exposure Figure 7m Figure 7l Figure 7m ...

Page 43: ...r on top of the spacer block to simulate the LPS Flex component posterior condyle dimension for sizes C G Note Do not use the CR Flex spacer block adapter since it simulates the CR Flex component posterior condyle dimension and will result in inaccurate representation of the LPS Flex flexion gap Balance Flexion Extension Gaps Knee in extension Attach the alignment rod to the alignment rod with cou...

Page 44: ...moral and tibial component sizes will be compatible If there is a femoral tibial mismatch consider using the fixed bearing system Assemble the LPS Flex mobile broach and trialing plate Position the trialing plate onto the broach plate Figure 9b so that the peg on the under side of the trialing plate mates with the anterior hole on the proximal surface of the broach plate Align the peg and hole to ...

Page 45: ...g plate assembly is positioned as far posteriorly as possible on the lateral side without overhanging the tibia This position may leave some bone exposed on the posteromedial tibia when the plate lines up with the posterolateral cortex Insert a small head holding pin into the lateral pin hole on the top face of the broach plate Figure 9f Only the small head holding pins may be used through the top...

Page 46: ...g seating In extension apply a valgus stress to view or palpate the lateral side of the tibia to check broach plate fit laterally Be sure that the component is properly positioned rotationally Broach plate rotation and varus valgus alignment can be checked by inserting the alignment rod through the hole or slot in the handle of the MIS sizing plate handle Figure 9h There are two options available ...

Page 47: ...roper soft tissue balancing complete the tibial component tends to seat itself in the position where it best articulates with the femur After this process has occurred mark the position of the component with methylene blue electrocautery or by placing a pin or MIS screw in the sizing plate anteriorly Pin the broach plate in place with small head holding pins It is recommended to use one anterior p...

Page 48: ...of the instrument labeled PS or CR see A B which corresponds with the implant or provisional type Figure 10a Initially adjust the femoral rotation setting and tension setting For the femoral rotation setting a good starting point is between the lines of the implant type A For the tension setting start with the two lines aligned B Open the locking handle G to attach the implant or provisional Attac...

Page 49: ...al provisional laterally until the lateral peg of the provisional aligns with the drill hole in the lateral femoral condyle Push the provisional in place beginning laterally then medially Be sure that soft tissue is not trapped beneath the provisional component Knee in extension Check to ensure that the femoral provisional is flush against the resected surface on the medial condyle Then retract th...

Page 50: ...provisional F Figure 10f Turn the tension adjustment knob D to tighten or loosen as needed Close the locking handle G Attach the slaphammer H and extract Step Eleven Finish the Tibia Use the slaphammer extractor or small osteotome to remove the trialing plate leaving the broach plate in place on the tibia Figure 11a Avoid torquing the trialing plate during removal as this could damage the peg on t...

Page 51: ...line on the cemented drill Figure 11c This depth will prepare for the length of the keel Note Make sure detents are engaged and bushing remains in full contact with the sizing plate during drilling Assemble the proper size MIS cemented broach to the MIS tibial broach impactor Figure 11d Seat the MIS tibial broach impactor assembly in the corresponding broach plate holes Figure 11e During broaching...

Page 52: ...ly Broaching is complete when the impactor knob is fully seated against the MIS broach impactor Impact and the instrument bottoms out on the handle stop Figure 11g Remove the tibial broach impactor assembly and bone plug Figure 11h Gently tapping the undersurface of the impaction head can facilitate removal The tibial bone plug may not be fully removed by the hollow broach A Kocher or small rongeu...

Page 53: ...la Sharply dissect through the prepatellar bursa to expose the anterior surface of the patella This will provide exposure for affixing the anterior surface into the patellar clamp Remove all osteophytes and synovial insertions from around the patella Be careful not to damage tendon insertions on the bone Use the patellar caliper to measure the thickness of the patella Figure 12a Subtract the impla...

Page 54: ... the lateral side Set the mediolateral position of the guide so that the patella ridge sits in the deepest part of the v shape on the posterior clamp Use the engraved lines to visualize the position of the patella by looking through the underside of the instrument Figure 12c When orientation and position are set clamp tightly Note Take care to avoid any tilting of the patella relative to the cut s...

Page 55: ...scale Read the measurement between the engraved lines Figure 12e This scale indicates the thickness of the bone that will remain after resecting the posterior patella Note When releasing the buttons at the desired resection level be sure both buttons withdraw and lock fully If they do not engage the posts fully the cut guide may become loose during cutting Check resection depth and orientation wit...

Page 56: ...the patella as it is rotated this indicates that at least 10 mm of bone stock will remain after the cut Figure 12h Cut the patella flat so that a smooth surface remains Figure 12i Patellar Reamer Technique Total Surfacing Procedure Use the patellar reamer surfacing guides as templates to determine the appropriate size guide and reamer Choose the guide which fits snugly around the patella using the...

Page 57: ...amer clamp to the proper indication for the correct amount of bone that is to remain after reaming Figure 12m Attach the appropriate size patellar reamer blade to the appropriate size patellar reamer shaft Figure 12n Use only moderate hand pressure to tighten the blade Do not overtighten the blade Insert the patellar reamer shaft into a drill reamer Insert the reamer assembly into the patellar rea...

Page 58: ...ns and contact the fixation plate Turn the clamp wing to the inset position Attach the appropriate size patellar reamer blade to the appropriate size patellar reamer shaft Figure 12p Use only moderate hand pressure to tighten the blade Do not overtighten the blade Insert the patellar reamer shaft into a drill reamer Use the patellar reamer depth stops to control the amount of bone to be removed ba...

Page 59: ...ill guide sits flat on the bone surface Figure 12q Drill the peg hole making sure the drill stop collar contacts the top of the drill guide Figure 12r Note The primary porous patellar clamp may be used to fully seat the drill guide on hard sclerotic bone surfaces For the NexGen All Polyethylene Patella Center the appropriate patellar drill guide over the patella with the handle on the medial side ...

Page 60: ...terial Leave an adequate amount of suture material to position the hemostat away from the incision After the initial patella cut is completed use thumb pressure to press the patella protector against the bone If the bone is particularly hard apply the patellar clamp against the patella protector Squeeze the clamp until the patella protector is fully seated against the bone The patella protector sh...

Page 61: ...al and impact until completely seated Figure 13c Use the femoral inserter extractor and align the femoral provisional onto the prepared bone and impact If preferred the femoral provisional may be positioned by hand Translate the femoral provisional laterally until the lateral peg of the provisional aligns with the drill hole in the lateral femoral condyle Push the provisional in place beginning la...

Page 62: ...Attach the articular surface provisional Figures 13d 13e Flex and extend the knee again to ensure proper soft tissue balancing Insert the appropriate tibial articular surface provisional and perform a trial reduction Check ligament stability in extension and in 30 60 and 90 flexion Attempt to distract the joint in flexion to ensure that it will not distract Hyperflex the knee and check to make sur...

Page 63: ...ment The cement should have a doughy consistency when ready for use Tibial Base Plate Position the PCL retractor posteriorly the collateral soft tissue protector laterally and the collateral retractor medially Sublux the tibia anteriorly Place a layer of cement on the underside of the tibial base plate and on the resected tibial surface Position the tibial base plate onto the tibia and use the Tib...

Page 64: ...ateral femoral condyle Take care to avoid scratching the implant component surfaces Disposable plastic tibial plate protectors may be temporarily inserted onto the tibial base plate to protect the implant surfaces during insertion of the femoral component Remove the tibial plate protector after the femur is seated Be sure that soft tissue is not trapped beneath the implant Use a mallet to impact t...

Page 65: ...surface Implant against the distal portion of the femoral component with the spine of the articular surface fitting into the intercondylar notch of the femoral component The distal condyles of the femoral component will be in contact with the articular surface Figure 14c Next bring the tibia into extension while the articular surface is held in place against the femoral component Axial rotation an...

Page 66: ... stop on the tibial plate Figure 14f Tighten the MIS counter torque wrench by turning the knob clockwise Ensure that the hooks are flush with the top surface of the tibial plate Do not over tighten Alternatively the LCCK tibial plate wrench that matches the size of the implant may be used Place the end of the wrench over the tibial base plate Ensure that the wrench is in line with the base of the ...

Page 67: ...face Recheck the ROM and stability of the knee NexGen All polyethylene Patella Knee in 70 90 flexion Apply cement to the anterior surface and pegs of the patellar component while in a doughy consistency Locate the drilled peg holes and use the patellar clamp to insert and secure the patella in place Fully open the jaws of the clamp and align the teeth to the anterior surface of the patella and the...

Page 68: ... a chair or a car Those patients undergoing TKA who are able and willing to flex and wish to maintain preoperative flexibility may be better off with earlier and or relatively more aggressive rehabilitation exercises Closure Freely irrigate the wound with the solution of choice A drain may be placed within the capsule Proceed with wound closure Please refer to package insert for complete product i...

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Page 70: ...68 NexGen MIS LPS Flex Mobile Implant System Surgical Technique Notes ...

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Page 72: ...8 Insall JN Surgery of the Knee 3rd ed New York NY Churchill Livingston 2001 1553 This documentation is intended exclusively for physicians and is not intended for laypersons Information on the products and procedures contained in this document is of a general nature and does not represent and does not constitute medical advice or recommendations Because this information does not purport to consti...

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