TKR INSTABILITY OF THE KNEE – DIAGNOSIS/CAUSES/TREATME NT
Jose A Rodriguez, MD Center for Joint Preservation and Reconstruction Lenox Hill Hospital NYC Most successful surgery with best long term survivorship
Up to 20% of patients are not satisfied with the outcome following total knee replacement – Predicting dissatisfaction following total knee replacement: a prospective study of 1217 patients. Scott CE et al JBJS Br 2010 Early Revision
TKR 3% revised in first 24 months Heck DA, Melfi CA, Mamlin LA, Katz BP, Arthur DS, Dittus RS: Revision rates after knee replacement in the United States. Med Care 1998;36:661-669.
Up to 22% of Revision TKR for instability Sharkey PF, Hozack WJ, Rothman RH, Shastri S, Jacoby SM: Why are total knee arthroplasties failing today? Clin Orthop Relat Res 2002;404:7- 13 Laxity ≠ Instability
Some patients can tolerate a wide variety of laxity states with no symptoms
Instability
Functional Pathology related to Laxity, Ligament imbalance or incompetence Soft Tissue Tension - Balance
Stiffness ------Instability
/---Good Function---/
Judgment Black / White
Grey Judgement – soft tissue tension
Differing requirements
70 yo Woman, 140 lb, Anxiety, pre-op 90 deg
55 yo Man, 240 lb, Tennis Pro, 130 deg Instability
Related to Composition of Gaps
Goal Rectangular -- Symmetrical
Balanced Flexion gap = Extension Gap Gap imbalance
Flexion loose / tight
Extension Loose tight
Asymmetric gaps / rotation Gaps
Trapezoidal --- Asymmetrical
Related to Bony cut alignment Soft tissue Contracture Soft Tissue Stretching Gaps – filled by implants
Femoral and Tibial contributions
Alignment – sagital
Rotation – Coronal
Implant (poly) thickness Symmetrical Extension Instability
Extension gap rectangular >> Flexion gap Imbalance Hyperextension
Over resection of distal femur Symmetrical Extension Instability
Management Distal femoral augment to lower joint line
Larger polyethylene - create flexion tightness Asymmetrical Extension Instability
Trapezoidal Ext gap
Sagital Alignment Soft Tissue Contracture Soft tissue Stretching Excessive release MCL incompetence
Flexion Instability
Excessive laxity of flexion gap Aberrant movement PCL Insufficiency – posterior tibial translation Diagnosis Pagnano MW, Hanssen AD, Lewallen DG, Stuart MJ: Flexion instability after primary posterior cruciate retaining total knee arthroplasty. Clin Orthop Relat Res 1998;356:39- 46
25 PCL Retaining TKR – Revised
Instability without giving way Swelling, Hemarthrosis/effusion Diffuse Tenderness Posterior sag / drawer @ 90 degrees 10 pts Revised 95 – 02
Sense of Instability without giving way 8/10 Difficulty with stairs 7/10 Recurring effusion 7/10 Anterior knee pain or diffuse soft tissue pain 7/10 Tenderness: Pes Anserinus, peripatellar, Hamstring insertions
Tibial Posterior Slope Avg 7 degrees ( 3 – 11) Physical Exam
Post Sag
Tenderness
Ant Drawer
Sulcus sign
Rotational Laxity Ant Drawer Sulcus sign Loss of Posterior Femoral Offset Causes-
Anteriorizing the femoral component to avoid notching
poor restoration of post condylar offset Causes-
Excessive tibial slope- as most PS designs are built in with no / minimal tibial slope Causes-
Asymmentric flexion space – femoral component internal rotation with/without tibial varus Isolated Flexion Instability In Posterior Stabilized Total Knee Replacements Deshmane P, Deshmukh A, Scuderi G, Rodriguez J
18 knees 05 – 10 Revised for Instability
Well fixed, reasonably aligned > 5 mm anterior Translation 3 – 5 mm Condylar Lift-off with rotation Sulcus sign Isolated Flexion Instability In Posterior Stabilized Total Knee Replacements Deshmane P, Deshmukh A, Scuderi G, Rodriguez J
16/18 Recurrent Effusions 18/18 Difficulty with Stair Descent 18/18 Sense of knee feeling loose or unstable 9/ 18 Interface Lucency / Erosion Treatment Understand criteria for evaluation of stability Well aligned / rotated bony cuts Soft tissue tension balance in extension Flexion Extension Gap Balancing Operative Options
Tibia 90 deg – Proper rotation Femur – posteriorize – augment / metaph sleeve Femur – joint line raise lower Femur – rotation, lat augment
Poly exchange Surgical Management Flexion Instab Create Stable Tibial base, well aligned, no slope
Assess Gaps
Posteriorize Femur – posterior augments Offset stem vs short cemented stem Assure proper rotation Fehring TK, Odum S, Griffin WL, Mason JB: Outcome comparison of partial and full component revision TKA. Clin Orthop Relat Res 2005; 44
Full component revision was more successful than partial revision, especially for a diagnosis of instability (P = 0.0001).0:131-134 Mayo Series combined
9 / 10 knees successfully stabilized 19/22
Femoral and tibial revision Fill flexion space 70 Rev TKR for Instability 50 both Comp, 10 one Comp, 11 poly only
Avg 39 mo 17 (24%) cont instability sx
Both Comp rev, Fem Augments assoc with good outcome Poly alone – poor outcome 27 Knees Instability Poly exchange 12 Failed avg 3 yrs 5 Instab 1 tib loose 1 stiff 1 inf
15 survived avg KSS 80 Flexion stability assessment
Reduction appearance Anterior Drawer 2 – 5 mm Rotation – Condylar lift off Translation in traction – simulated sulcus sign Ant Drawer y Posterior Stabilized Total Knee Replacements Deshmane P, Deshmukh A, Scuderi G, Rodriguez 12 Femoral and Tibial Revision Femoral augment posteriorly No tibial slope Gap Balance Proper rotation
6 Poly exchange – Constrained Case
Varus, Neutral femoral rotation, Lig laxity Cumulative Error
3 degrees of tibial varus
Slight Fem Ext Rot – Condylar liftoff
5 degrees Tibial slope
Condylar Liftoff
y Posterior Stabilized Total Knee Replacements Deshmane P, Deshmukh A, Scuderi G, Rodriguez 18 / 18 Instability symptoms improved
KSS clinical 53.5 to 81.2 functional 50.5 to 79.1
Ant Drawer 2 – 5mm No Condylar liftoff Instability
Complicated 3 dimensional problem Understand component parts Address each anatomic variable
Many are preventable Most are treatable Prevention
Proper bony cuts – coronal alignment Proper rotation Gap balancing Stability testing
Thank You
Poly xchange
Criteria to evaluate stability
Apply criteria to make decision
Post capsular release will only get you so much extension
Engh22 reported on eight patients with flexion instability who were managed with placement of a thicker tibial insert. Only four knees were stabilized, and one knee was rerevised.
Engh GA. Tibiofemoral instability. In: Proceedings of the 67th Annual Meeting of the American Academy of Orthopaedic Surgeons; 2000 Mar 15-19; Orlando, FL. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2000. p 32-4. Medial-Lateral Stability Post Total Knee Arthroplasty Affects Function: Results From A Joint Registry Seah et al, Singapore AAOS 2011 Incorrect placement of the femoral component too anteriorly and proximally, as well as compensating for that position with a thicker tibial insert, can cause medial-lateral instability only in midflexion. Martin JW, Whiteside LA: The influence of joint line position on knee stability after condylar knee arthroplasty. Clin Orthop 1990;259:146– 156. Causes of asymmetric extension instability include collateral ligament injury and inadequate collateral ligament release. Iatrogenic collateral ligament injury can occur by complete disruption during bone cuts, by vigorous knee exposure, or by ligament overrelease
MCL Repair Leopold SS, McStay C, Klafeta K, Jacobs JJ, Berger RA, Rosenberg AG: Primary repair of intraoperative disruption of the medial collateral ligament during total knee arthroplasty. J Bone Joint Surg Am 2001;83:86-91 Assessment
Collat Lig Ext mech Alignment Foot / Hip deformities Berend ME, Ritter MA, Meding JB, et al: Tibial component failure mechanisms in total knee arthroplasty. Clin Orthop Relat Res 2004;428:26- 34
Valgus Tibial Cuts Varus Tibial Cuts Excessive tibial slope
Associated with early failure Vince KG, Abdeen A, Sugimori T: The unstable total knee arthroplasty: Causes and cures. J Arthroplasty 2006;21:44-49.
Plano-valgus hindfoot – associated with instability with PCL sparing TKR