Lee Beom Koo Gachon university Gil Hospital Technique UKA Technique UKA

Pre-op measurement of tibia resection line & slope Lateral joint line 을 기준으로 joint 에 parallel 하게 선을 긋고 그선에서 7mm 하방으로 선을 그은 후 그선 과 tibia medial plateau 와 의 거리를 측정한 다 ( 대개 2-4 mm 이다 ) Lateral 사진을 보고 sagittal slope 측정하여 7 도 이하이면 natural slope 로,cutting line 을 정하고 7 도이상이면 slope 를 7 도 정도에 맞추어 자른 다

Approach AM arthrotomy 후 proximal tibia 의 medial soft tissue 를 elevation 하는 데 deep MCL 과 MCL tibia insertion 중 proximal insertion 은 elevate 한다 그후 The anterior part of medial meniscus 을 자르고 The medial spur 도 rongeur and osteotome 으로 자른 다

Evaluation of joint While the patella is retracted. Resistance of ACL and state of cartilage of lateral & patellofemoral joint is inspected

Exposure of medial compartment patella 를 retraction 후 MCL 을 MCL retractor 로 retract 하고 다리 를 slight external rotation of leg 하면 전체 적으로 좋은 시야가 나온 다

Guide 의 shaft 를 tibia crest 에 맞추어 coronal alignment 결정후 하나의 screw 를 박아서 coronal alignment 를 정한다 Guide 의 center 를 술전 tibia axis 맞나는 곳에 둔다. Adjustment and fixation of tibia guide

Sagittal slope 를 재고 distal 에서 guide 를 올려서 slope 를 정한다. The natural slope is preferred But slope greater than 7 is not recommended

Horizontal cut MCL retractor 로 MCL protection 요하며. 역시 너무 깊이 들어가 N_V 손상주지 않도록 조심 해야한다

The sagittal tibial cut 위치 ; The sagittal cutting line is marked at the medial edge of ACL Rotation; Sagittal cut line point toward the Femoral head in flexion,akaki line medial femoral condyle wall 방향 깊이 ; 너무 깊지 않게, 깊으면 후에 tibia fx 올수 있 다

Balance in extension Balance in extension After placement of sliding spacer block, the medial joint space should open up 1 or 2 mm when valgus stress is applied with the knee in full extension. It is very important to avoid overstuff & overcorrection

Balance in flexion, 2 to 3 mm laxity is suggested.in medial UKA after placing block For the balance in flexion, the thigh should be lifted with one arm to balance the flexion gap

If the flexion gap is too tight; first step 종종 pre-op tibia slope 가 7 도 이상이나 tibia 를 slope 를 7 도로 주고 하면 flexion gap 이 tight 해진 다 If the flexion gap is too tight, cartilage or bone should be removed from the posterior condyle of femur with rasp or saw

or The slope should be slightly increased

Marking of femoral rotation line Marking of femoral rotation line Next step for the Marking of femoral rotation line the center of the tibial spacer block is marked with a Bovie on the femoral condyle in different positions It should not be judged while the patella is everted or perpendicular line to the cut tibia bone can be chosen

Distal femoral cut the distal femoral cutting guide is slided in extension and fixed with two pin and resected. The knee should be flexed 5 if the resected posterior slope of tibia is 5 to avoid hyperextension. shim can be used to manage the bone defect. Distal cut 가 flex 해지면 flex gap 이 tight 해진다

Distal femoral cut

Finishing cutting guide placement. Femur finishing guide is inserted in 90 degree flexion

Finishing cut ;Size If the size is proper, 1 to 2 mm of exposed bone. At the anterior edge

Mediolateral dimension For the correct mediolateral position, The guide should be placed in the center of the femoral condyle,mediolaterally

Rotation femoral rotation may follow the previously Marked rotation line or This guide should also be rotationally set so that the posterior cutting surface of femoral condyle is parallel to the resected tibia

Fixation of finishing guide Posterior & Champer cut Finishing guide is fixed with two screw. at the Anterior margin of guide, bone is gouged slightly to accept the curved prosthesis While the MCL is protected with MCL retractor placed at femoral side, the posterior femur is resected and after anterior and posterior chamfer cut, two femoral peg hole is drilled

1 st alignment check

Post. Condyle trimming to avoid impingement posteriorly

The final preparation of the tibia; exposure The leg is externally exposed, while the MCL is retracted to expose the whole medial compartment

The size of the tibial tray Size 는 AP 길이를 보고 결정해야한다 종종 ACL 보다 떨어져서 sagittal cut 하는데 medial 크기가 작아진 다 그후 coronal plane 으로 크기 정하면 AP 상 적은 크기가 들어가고 cortical support 가 안 된다 ; tibia plate 가 cancelleous bone 에만 걸치므 로 조기 collapse 가 온 다

Tibia preparation; tibia guide 넣고 일시적으로 tensor 로 눌러서 고정후 the keel 을특 수한 osteotome 을 써서 하며 peg hole 을 drilled tibia 의 posterior margin 을 정확히 파악 후 하여야 하며 종종 tibia guide 가 뒤로 가는 경우가 많으니 anterior cortical shell 에 guide 의 margin 을 맞 추는 것 이 좋다

Alignment check

Tibia cement Tibia cement Staged cementing Avoid tilt of tibia plate especially posterior ( which result in tightness in flexion. adequate exposure of posteromedial tibia adequate sizing

tilt of tibia plate especially posterior Easily happen when simultaneous cementing because knee extension cause pressure anteriorly which result in tightness in flexion Cement defect posteriorly.

Cement is applied wholly to prosthesis and femoral cut surface except posterior condyle & prosthesis is inserted & impacted Femoral cement Argenson, Jean-Noel A MD; Parratte, corr 464 Nov 2007 P32

Liner insertion In flexion, the liner is inserted with hand

The ideal correction as measured on the postoperative full weightbearing view will probably consist of a tibiofemoral axis crossing the knee between the tibial spines and the medial third of the tibial plateau for a medial UKA alignment Kennedy WR, White RP. Unicompartmental arthroplasty of the knee; post-operative alignment and its influence on overall results. Clin Orthop Relat Res. 1987;221: Argenson, Jean-Noel A MD; Parratte, corr 464 Nov 2007 P32

Lateral Unicompartmental Replacement

unique tibial component positioning in 10° to 15° of internal rotation to compensate for the “screw-home” mechanism Transpatella tendon sagittal sawing or medial approach is helpful( AAOS 2012) Lateral Unicompartmental Knee Arthroplasty: Survivorship and Technical Considerations at an Average Follow-Up of 12.4 Years Pages Jan'06 J arthroplasty Donald W. Pennington, John J. Swienckowski, William B. Lutes and Gregory N. Drake

Trans patella tendon sag saw in lat UKA to achive IR in tibia resection, trans tibial axis rotation Femur ; trans tibia rotation Keith R. Berend Clin Orthop Relat Res (2012) 470:77–83

Balancing is similar to that for a medial UKA, but looser; play of 2 to 3 mm instead of 1 to 2 mm (medial UKA) is suggested. Flexion gap balancing Scott Insall 4 th edit P 1413

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