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23

Extramedullary (EM) Surgical Procedure

Rationale

The basic goals of unicompartmental 
knee arthroplasty are to improve 
limb alignment and function, and 
to reduce pain. Routinely, an effort 
is made to minimize disruption of 
the surrounding soft tissue during 
the procedure. The development of 
instruments specifically designed to be 
used through a smaller exposure has 
had a significant impact on this effort. 
Accurate limb alignment is described 
by the mechanical axis of the lower 
extremity, which is a straight line 
running from the center of the femoral 
head to the center of the ankle. When 
the center of the knee lies on this 
mechanical axis, the knee is said to be 
in neutral alignment. Unicompartmental 
knee disease typically reduces the joint 
space in the affected compartment, 
causing a malalignment of the joint.  
Full correction of the malalignment 
would return the knee to neutral 
alignment. (Fig.1).

Preop

Neutral Alignment

(Fully Corrected)

Mecha

ni

ca

l Axis

Transverse 

Axis

Malalignment

Fig. 1

Introduction

Unicompartmental knee arthroplasty 
(UKA) has been shown to be an 
effective treatment for isolated 
osteoarthritis affecting the 
medial or lateral compartment. 
The MIS Instruments for the ZUK 
Unicompartmental High Flex Knee 
System are designed to provide 
accurate, reproducible results using 
a minimally invasive technique. The 
goals of a minimally invasive surgical 
procedure are to:

•  Facilitate the patient’s recovery

•  Provide less pain

•  Provide earlier mobilization

•  Provide shorter hospital stay

This instrumentation allows the surgeon  
to operate without everting the patella.

The system offers three MIS 
instrumentation options:

•  Intramedullary Instrumentation 

System (IM)

•  Spacer Block Option

•  Extramedullary Instrumentation 

System (EM)

The same tibial assembly is used for 
all three options. However, the distal 
femoral resection instruments are 
unique to each of the three techniques.

This guide to the surgical technique  
is a step-by-step procedure written for 
a medial compartment UKA. Many of 
the same principles can be applied  
to the lateral compartment but it may 
be necessary to extend the incision a 
few centimeters given the proximity of 
the patella to the lateral condyle.

Combined with surgeon judgment, 
proper patient selection, and 
appropriate use of the device, this  
guide offers a comprehensive technique 
that discusses the procedure for 
component selection, bone preparation, 
trial reduction, cementing techniques, 
and component implantation. It is 
strongly recommended that the  
surgeon read the complete procedure 
for details, notes, and technique tips.

The alignment goals for 
unicompartmental  
arthroplasty differ from those that are 
customary in high tibial osteotomy 
(HTO) where overcorrection is desirable 
to displace the weight-bearing forces 
away from the diseased compartment. 
In contrast, when adjusting limb 
alignment in a unicompartmental 
procedure, 

it is particularly important 

to avoid overcorrection of the 
limb as this may increase the stress 
in the contralateral compartment 
and heighten the potential for 
cartilaginous breakdown. Studies of 
unicompartmental procedures have 
shown that slight undercorrection  
of the limb alignment correlates to 
long-term survivorship.

2

It is important to recognize that the 
methods used to adjust alignment  
in TKA are very different from those 
used in unicompartmental arthroplasty. 
In TKA, the angle of the femoral and 
tibial cuts determine the postoperative 
varus/valgus alignment. In UKA, the 
angle of the cuts does not affect 
varus/valgus alignment. 

Instead, 

postoperative varus/valgus  
alignment is determined by  
the composite thickness of the 
prosthetic unicompartmental 
components.
When using the extramedullary 
instruments, the angle between the 
anatomic and mechanical axes of the 
femur does not need to be measured. 
In the EM technique, the leg is 
manually aligned in extension, allowing 
the surgeon to visualize and adjust the 
alignment to the desired slight degree 
of undercorrection. The desired soft 
tissue tension is determined by the 
surgeon during this passive correction 
of limb alignment. As the distal 
femoral cut and proximal tibial cut are 
linked in extension, limb alignment is 
determined and set before committing 
to any cuts. Thus, 

alignment is 

achieved first, and the instruments will 
adjust to accommodate the appropriate 
implant sizing and positioning.

Содержание ZUK

Страница 1: ...Minimally Invasive Surgical Techniques for the Medial Compartment Intramedullary Spacer Block and Extramedullary techniques ...

Страница 2: ...se refer to the product s label and the Instructions for Use packaged with the product Indications Unicompartmental knee implants are indicated for restoring either compartment of a knee that has been affected by the following 1 Noninflammatory degenerative joint disease including osteoarthritis traumatic arthritis or avascular necrosis 2 Correction of functional deformity 3 Revision procedures wh...

Страница 3: ...l Reduction 18 Step Nine Implant Final Components 19 Closure 20 Spacer Block Surgical Technique 21 Spacer Block Option 21 Extramedullary EM Surgical Technique 23 Introduction 23 Rationale 23 Preoperative Planning 24 Patient Preparation 24 Exposure 25 Step One Assemble Apply the Instrumentation 26 Step Two Align the Joint 30 Step Three Resect the Distal Femoral Condyle 32 Step Four Resect the Proxi...

Страница 4: ...ystem IM Extramedullary Instrumentation System EM The same tibial assembly is used for all three options However the distal femoral resection instruments are unique to each of the three techniques This guide to the surgical technique is a step by step procedure written for a medial compartment UKA Many of the same principles can be applied to the lateral compartment but it may be necessary to exte...

Страница 5: ... that the methods used to adjust alignment in TKA are very different from those used in unicompartmental arthroplasty In TKA the angle of the femoral and tibial cuts determines the postoperative varus valgus alignment In UKA the angle of the cuts does not affect varus valgus alignment Instead postoperative varus valgus alignment is determined by the composite thickness of the prosthetic unicompart...

Страница 6: ...ver if preferred the tibia can be resected first To resect the tibia first begin with Step 3 Resect the Proximal Tibia Then continue with Step 1 Resect the Distal Femur For the Spacer Block technique the tibia must be resected first as the femoral resection is based off the tibial cut If the surgeon prefers to use the Spacer Block technique begin with Step Three Resect the Proximal Tibia Then go t...

Страница 7: ...remove peripheral osteophytes that interfere with the collateral ligaments and capsule With medial compartment disease osteophytes are commonly found on the lateral aspect of the medial tibial eminence and anterior to the origin of the ACL Final debridement will be performed before component implantation Careful osteophyte removal may be important in achieving full extension Fig 4 7 12cm Skin Inci...

Страница 8: ...e the site for inserting the IM Femoral Resection Guide approximately 1cm anterior to the origin of the posterior cruciate ligament and just anterior to the intercondylar notch in the distal femur Use the 8mm Femoral IM Drill or an awl to create the hole for the guide Hold the drill parallel to the shaft of the femur in both the A P and lateral projections Fig 6 Drill only the cancellous bone of t...

Страница 9: ...lock Note If a pin is used for fixation of the IM guide to the distal femur impingement may occur with the saw blade The distal cut may be started with the pin in place but the pin should be removed before contact with the blade occurs Use a narrow 1 27mm 0 050 inch oscillating or reciprocating blade to cut the distal portion of the condyle through the slot of the Distal Femoral Resector Block Fig...

Страница 10: ...nt that allows M L positioning Secure the distal portion of the assembly by placing the spring arms of the Ankle Clamp around the ankle proximal to the malleoli Fig 13 Loosen the knob at the top of the Distal Telescoping Rod position the Tibial Resector proximal to the tibial tubercle with the cutting slot at the approximate desired level of resection then retighten the knob While holding the prox...

Страница 11: ...of resection with the Resection Guide Fig 16 Fig 15 Secure the assembly to the proximal tibia by inserting a 48mm Headed Screw or predrilling and inserting a Holding Pin through the hole in the fixation arm of the Tibial Resector Base Fig 16 Do not completely seat the screw pin until the final adjustments have been made to the position of the Tibial Resector Use the 2mm tip of the Tibial Depth Res...

Страница 12: ...Fig 18 Fig 19 Insert a retractor medially to protect the medial collateral ligament Use 1 27mm 0 050 inch oscillating saw blade through the slot in the cutting guide to make the transverse cut The Tibial Resector must remain against the bone during resection Note Do not use a saw blade with a thickness of less than 1 27mm to avoid inaccurate cuts With the knee flexed use the reciprocating blade at...

Страница 13: ...g the thin end of the selected Flexion Extension Gap Spacer into the joint Fig 21 If in both flexion and extension the joint space is too tight to insert the 8mm Flexion Extension Gap Spacer then more tibial bone must be removed Then use the Flexion Extension Gap Spacers to recheck the gaps If in both flexion and extension the joint space is too loose insert progressively thicker Flexion Extension...

Страница 14: ...tour of the Femoral Sizer Finishing Guides matches the contour of the corresponding implant Insert the prongs on the Insertion Handle into the corresponding holes of the appropriate left or right Femoral Sizer Finishing Guide Fig 22 Then thread the handle into the guide and tighten it securely Fig 23 2 to 3mm Note Be sure that there is no soft tissue or remaining osteophytes between the Femoral Si...

Страница 15: ...l Sizer Finishing Guide does not overhang 2 Insert one 33mm Headed Screw gold head into the angled anterior pin hole which is parallel to the chamfer cut Fig 28 For best fixation seat the screw head slowly This should stabilize the guide sufficiently to finish the femur For additional stability insert a 48mm Headed Screw or predrill and insert a Short Head Holding Pin into the middle hole closest ...

Страница 16: ...ional stability 4 Drill the posterior post hole in the same manner This hole is angled the same as the anterior post hole Fig 30 5 Remove the anterior Femoral Holding Peg and cut the posterior chamfer through the cutting slot in the guide If a screw pin was inserted into a middle hole either remove the screw pin or cut around it The remaining island of bone can then be resected after removing the ...

Страница 17: ...ebride the joint and inspect the posterior condyle If any prominent spurs or osteophytes are present especially in the area of the superior posterior femoral condyle remove them with an oscillating saw or an osteotome as they could inhibit flexion or extension Fig 33 Technique Tip The Femoral Provisional may be put in place and the knee flexed This would aid in identifying and removing any residua...

Страница 18: ... tibia in both the A P and M L dimensions If desired use the resected tibial bone fragment as an aid in sizing If necessary a second sagittal cut can be made to allow for optimal coverage with the next larger size tibial base plate The Tibial Sizer has a sliding ruler which facilitates measuring in the A P dimension Fig 35 Be sure that the head of the sizer rests on cortical bone near the edge of ...

Страница 19: ...bial Fixation Plate Provisional in place on the bone There are a number of indicators on the Tibial Sizer If the slider is used without the sizer the etch marks 1 through 6 on the slider indicate the A P length of the corresponding implant If the slider is used with the sizer the A P length is indicated on the sizer handle Fig 37 An additional measurement on the slider at the tip of the sizer hand...

Страница 20: ... correct prosthesis should allow the joint space to be opened approximately 2mm when a stress is applied with the knee in full extension and without soft tissue release The knee must also be tested in 90 of flexion to allow a 2mm flexion gap Excessive flexion tightness will prevent postoperative flexion and may cause the tibial prosthesis to lift up anteriorly as the femoral component rolls poster...

Страница 21: ...an opened and slightly moist sterile gauze sponge behind the tibia before implanting the components to help collect excess cement behind the tibia Apply cement and press the tibial base plate or the all polyethylene tibial component onto the tibia Position and press down the posterior portion of the component first Then press the anterior portion of the component expressing excess cement anteriorl...

Страница 22: ...ticular Surface After the cement has cured remove any remaining excess cement before the final placement of the tibial articular surface Do not proceed with locking the final articular surface component until cement has fully cured With the engraved side down slide the edge of the polyethylene component under the posterior lip of the base plate Then insert the tab on the lower jaw of the Tibial Ar...

Страница 23: ... not fit into the joint remove an additional 2mm from the proximal tibia If the 8mm Spacer Block is too loose use a thicker Spacer Block Insert a 48mm Headed Screw or predrill and insert a Short head Holding Pin into the anteromedial angled hole in the Spacer Block Fig 2 Attach the Alignment Tower to the Spacer Block Fig 3 and insert the Alignment Rod through the Alignment Tower Then insert the Ta...

Страница 24: ... 5 Then secure the guide by inserting a 48mm Headed Screw or predrill and insert a Holding Pin through the hole Fig 6 Use a 1 27mm 0 050 inch oscillating saw blade to resect the distal femur Fig 7 Do not extend the saw blade posteriorly past the distal femur to avoid damaging the posterior popliteal area If desired the femoral cut can be started in extension and finished in flexion Before flexing ...

Страница 25: ... it may be necessary to extend the incision a few centimeters given the proximity of the patella to the lateral condyle Combined with surgeon judgment proper patient selection and appropriate use of the device this guide offers a comprehensive technique that discusses the procedure for component selection bone preparation trial reduction cementing techniques and component implantation It is strong...

Страница 26: ...f the femoral head Alternatively the surgeon may prefer to reference the anterior superior iliac spine Technique tip Place a marker such as an EKG electrode over the center of the femoral head Then confirm the location with an A P radiograph or fluoroscopy Preoperative Planning This technique is written with the distal femoral resection performed first However if preferred the tibia can be resecte...

Страница 27: ...eniscus The remainder of the meniscus will be removed after bone resection A subperiosteal dissection should be carried out towards the midline ending at the patellar tendon insertion This will facilitate positioning of the tibial cutting guide Debride the joint and inspect it carefully Remove intercondylar osteophytes to avoid impingement with the tibial spine or cruciate ligament Also remove per...

Страница 28: ...nsists of an Ankle Clamp a Distal Telescoping Rod a Tibial Resector Stem a Tibial Resector Base a Tibial Resector and a Distal Femoral Resector Fig 5 Positioning of the Tibial Resector and Distal Femoral Resector is crucial Assemble the Instrument Slide the Ankle Clamp onto the dovetail at the bottom of the Distal Telescoping Rod and tighten the knob opposite the dovetail to temporarily hold the c...

Страница 29: ...sector into the affected compartment Fig 7 Be sure that the paddle abuts the most distal aspect of the femoral condyle and that the Tibial Resector engages the anterior tibia Then retighten the knob at the top of the Distal Telescoping Rod Technique tip If the Distal Femoral Resector will not fit into the joint while attached to the assembly remove the holding peg and resector Then place the Tibia...

Страница 30: ...tal portion and therefore parallel to the mechanical axis of the tibia Use the M L slide adjustment at the midshaft of the assembly to position the fixation arm of the Tibial Resector Base and Tibial Resector so it lies just medial to the midpoint of the tibial tubercle and is in line with the center of the intercondylar eminence Fig 8 In the sagittal plane align the assembly so it is parallel to ...

Страница 31: ... opening the extension gap more relative to the flexion gap This can be accomplished by moving the assembly closer to the leg distally Then check the depth and angle of resection with the Resection Guide Secure the assembly to the proximal tibia by inserting a 48mm Headed Screw or predrilling and inserting a Holding Pin through the hole in the fixation arm of the Tibial Resector Base Fig 10 ...

Страница 32: ...e guide near the femoral head Fig 11 While maintaining this corrected position use the thumb screw on the Tibial Resector Base to move the cutting guides superiorly until the paddle on the Distal Femoral Resector contacts the distal femoral condyle It is important to manually hold the joint open and raise the paddle to meet the condyle rather than using the paddle to open the joint Once the paddle...

Страница 33: ... Screws through the two holes Fig 13 Use electrocautery or the reciprocating saw to score the tibial surface where the sagittal cut will be made Check this point both in extension and flexion If desired the depth of both the femoral and tibial cuts can be verified by inserting the Resection Guide through the cutting slots Fig 14 Fig 13 Fig 14 ...

Страница 34: ...osterior margin of the femoral condyle while the knee is in extension Begin the femoral cut with the knee in extension Before flexing the knee use the Removal Hook to remove the Distal Femoral Resector Fig 16 by sliding it over the headless pins or screws or by removing the headed pins or screws Note If completing the distal femoral cut after removing the Distal Femoral Resector the cut must be fi...

Страница 35: ...nst the bone during resection Make the sagittal cut with the knee flexed Position the reciprocating saw blade at the base of the tibial eminence and parallel to the eminence in the A P plane Cut along the edge of the ACL down to but not beyond the intended level of the transverse cut Fig 17 Be careful to avoid the ACL attachment When the tibial preparation is complete remove the tibial assembly ...

Страница 36: ...hin end of the selected Flexion Extension Gap Spacer into the joint Fig 19 If in both flexion and extension the joint space is too tight to insert the 8mm Flexion Extension Gap Spacer then more tibial bone must be removed Then use the Flexion Extension Gap Spacers to recheck the gaps Fig 18 Fig 19 If in both flexion and extension the joint space is too loose insert progressively thicker Flexion Ex...

Страница 37: ...e Femoral Sizer Finishing Guides matches the contour of the corresponding implant Insert the prongs on the Insertion Handle into the corresponding holes of the appropriate left or right Femoral Sizer Finishing Guide Fig 20 Then thread the handle into the guide and tighten it securely Fig 21 Step Six Size the Femur Fig 20 Fig 21 ...

Страница 38: ...maller size This helps prevent the patella from impinging on the prosthesis Note Be sure that there is no soft tissue or remaining osteophytes between the Femoral Sizer Finishing Guide and the cut distal condyle It is important that the Femoral Sizer Finishing Guide sits flush against the bone Any gaps between the guide and the bone will compromise the accuracy of the cuts and subsequently compone...

Страница 39: ...nish the Femur 2 Insert one 33mm Headed Screw gold head into the angled anterior pin hole which is parallel to the chamfer cut Fig 26 For best fixation seat the screw head slowly This should stabilize the guide sufficiently to finish the femur For additional stability insert a 48mm Headed Screw or predrill and insert a Short Head Holding Pin into the middle hole closest to the intercondylar notch ...

Страница 40: ...ional stability 4 Drill the posterior post hole in the same manner This hole is angled the same as the anterior post hole Fig 28 5 Remove the anterior Femoral Holding Peg and cut the posterior chamfer through the cutting slot in the guide If a screw pin was inserted into a middle hole either remove the screw pin or cut around it The remaining island of bone can then be resected after removing the ...

Страница 41: ...ebride the joint and inspect the posterior condyle If any prominent spurs or osteophytes are present especially in the area of the superior posterior femoral condyle remove them with an oscillating saw or an osteotome as they could inhibit flexion or extension Fig 31 Technique Tip The Femoral Provisional may be put in place and the knee flexed This would aid in identifying and removing any residua...

Страница 42: ... tibia in both the A P and M L dimensions If desired use the resected tibial bone fragment as an aid in sizing If necessary a second sagittal cut can be made to allow for optimal coverage with the next larger size tibial base plate The Tibial Sizer has a sliding ruler which facilitates measuring in the A P dimension Fig 33 Be sure that the head of the sizer rests on cortical bone near the edge of ...

Страница 43: ...bial Fixation Plate Provisional in place on the bone There are a number of indicators on the Tibial Sizer If the slider is used without the sizer the etch marks 1 through 6 on the slider indicate the A P length of the corresponding implant If the slider is used with the sizer the A P length is indicated on the sizer handle Fig 35 An additional measurement on the slider at the tip of the sizer hand...

Страница 44: ...correct prosthesis should allow the joint space to be opened approximately 2mm when a stress is applied with the knee in full extension and without soft tissue release The knee must also be tested in 90 of flexion to allow a 2mm flexion gap Excessive flexion tightness will prevent postoperative flexion and may cause the tibial prosthesis to lift up anteriorly as the femoral component rolls posteri...

Страница 45: ...an opened and slightly moist sterile gauze sponge behind the tibia before implanting the components to help collect excess cement behind the tibia Apply cement and press the tibial base plate or the all polyethylene tibial component onto the tibia Position and press down the posterior portion of the component first Then press the anterior portion of the component expressing excess cement anteriorl...

Страница 46: ...ticular Surface After the cement has cured remove any remaining excess cement before the final placement of the tibial articular surface Do not proceed with locking the final articular surface component until cement has fully cured With the engraved side down slide the edge of the polyethylene component under the posterior lip of the base plate Then insert the tab on the lower jaw of the Tibial Ar...

Страница 47: ...7220 4149 Dyonics Single sided Tibia Resector 5 Spacer Block 5 Spacer Block Femoral Resector Femoral Sizer Finishing Guide 7401 3401 30mm Rimmed SPEED PIN 00 5791 044 00 Headed Screw 33mm 7401 3471 45mm Rimmed SPEED PIN 00 5791 041 00 Headed Screw 48mm 2mm Recut Block 7401 3471 45mm Rimmed SPEED PIN 00 5791 041 00 Headed Screw 48mm EM Femoral Resector 7401 3471 45mm Rimmed SPEED PIN 00 5791 041 00...

Страница 48: ...8 www smith nephew com The color Pantone 151 Orange for medical instruments is a U S registered trademark of Smith Nephew Trademark of Smith Nephew All Trademarks acknowledged Supporting healthcare professionals for over 150 years References 1 Cartier P Seinouiller JL Grelsamer RP Unicompartmental knee arthroplasty 10 year minimum follow up period J Arthroplasty 1996 11 7 782 788 ...

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