Medial UKA

Sohrab Keyhani MDAssociate professor of orthopedic surgery of SBUMSAkhtar Hospital-Knee fellowship

Esfahan 8 jan 2015

Patient selection

one more indication

• Irrepairable medial meniscal root avulsion in normal alignment knee in pateints more than 50

years old• We can accept small lateral chondral lesion in

Medial UKA

Female 62 years old

TKA or UKA• final decision for UKA or TKA before of the surgery

• Standing PA standing views in ext and flex (Rosenberg views)

• Standing lateral x-ray helps to identify an ant-med wear pattern to predict whether the ACL is intact

• overall knee alignment should be restored to the alignment that was present before cartilage loss occurred and should not be corrected to a fixed amount

• In UKA final limb alignment is determined by the thickness of the implant relative to the bone excised

• A formal medial ligament release is never recommended

Deschamps G, Chol C. Fixed-bearing unicompartmental knee arthroplasty. Patients' selection and operative technique.

Orthop Traumatol Surg Res 2011;97:648–61.

The ideal correction, tibiofemoral axis crossing the knee between the tibial spines and third of

the tibial plateau for a medial UKA Implant- bone interface will be directly compressed

Small SR, Berend ME, Rogge RD, Archer DB, Kingman AL, Ritter MA. Tibial loading

after UKA: evaluation of tibial slope, resection depth, medial shift and component rotation. J Arthroplasty 2013;28(9 Suppl.):179–83

Preserving the PTEA and avoiding excessive or insufficient corrections of the pre-operative limb alignment are predictors of a successful UKA

M. Vasso et al. / The Knee 22 (2015) 117–121

Personalized preoperative planning may facilitate surgical techniques for osteophyte removal

Be careful to not move the femoral compo- nent too far laterally to prevent patellar impingement

Marie-Antoinette effect

Fewer fixation pins decrease the risk of medial tibial plateau fracture

Total space

Tibia 8 + Femur 6 = 14 Play space of 1-2 mm in Flex or Ext

Between two sizes

Femur :choose smaller size

Tibia : choose bigger size if there is no overhang to have rim contact to prevent subsidence

Flexion of the femoral component may cause patellofemoral impingement

• Preserve posterior rim

• Post first for prevention of cement extrusion

Tibial component position has direct relation with clinical performance

• Sagittal tilt has been correlated with early UKA revision due to medial collapse

• Excessive component overhang has led to less satisfactory outcomes at 5 years after surgery

S.R. Small et al. / The Journal of Arthroplasty 28 Suppl. 2 (2013) 179–183

Tibial component factors that affect load sharing across the medial proximal tibia :

• sagittal tilt : ant or post tibial collaps• Rotational alignment• Distal resection depth • Medial–lateral positioning

S.R. Small et al. / The Journal of Arthroplasty 28 Suppl. 2 (2013) 179–183

No difference in clinical outcome when sagittal tilt was within ± 5° of a neutral 7°

slope

• Excessive posterior slope should be avoided to minimize bone stress, as they saw an 18% increase in stress area with increased slope

• Especially in mobile bearing UKA

Guliati A, Chau R, Simpson DJ, et al. Influence of component alignment on outcome for unicompartmental knee replacement. Knee

2009;16:196.

increase in anteromedial strain with increased distal resection

Simpson DJ, Price AJ, Gulati A, et al. Elevated proximal tibial strains following unicompartmental knee replacement—a

possible cause of pain. Med Eng Phys 2009;31:752.

Tibial component coverage

• Reaches or slightly overhangs less than 3 mm

• Medial shift was paired with decreased component size to maintain cortical rim contact that decrease contact area

Goodfellow J, O'Connor J, Dodd C, et al. Unicompartmental arthroplasty with theOxford knee. Oxford, UK: Oxford University Press;

2006

coronal alignment

• Sawatari et al [16] found that slight valgus inclination should be preferred to square alignment since it should reduce loosening of the tibial component

• But some other surgeon prefer slighty varus

Sawatari T, Tsumura H, Iesaka K, et al. Three-dimensional finite element analysis of unicompartmental knee arthroplasty

—the influence of tibial component inclina-tion. J Orthop Res 2005;23:549.

vertical cut A deep vertical cut should be avoided as it

creates a stress concentration in the tibia and may increase risk of postoperative fracture

Simpson DJ, Kendrick BJL, Dodd CAF, et al. Load transfer in the proximal tibial following implantation

with a unicompartmental knee replacement: a static snapshot. Proc Inst Mech Eng H

2011;225(5):521.

Chang T, Yang C, Liu Y, et al. Biomechanical evaluation of proximal tibial behavior following

unicondylar knee arthroplasty: modified resected surface with corre- sponding surgical technique.

Med Eng Phys 2011;33(10):1175.

Component rotation Component rotation was not

independently observed to show a great influence on proximal load

distribution

S.R. Small et al. / The Journal of Arthroplasty 28 Suppl. 2 (2013) 179–183

metaphyseal varus deformity of the proximal tibia (>7 degrees) because, in these rare cases, combined

or staged HTO-UKA surgery can be considered

Female 62 years old

Male 58 years old

Take home message

correct three dimensional placement of the tibial component is too important for

uniform load distribution in unicompartmental knee arthroplasty and

good success

Thank you