2017 ISAKOS Biennial Congress ePoster #1261

 

Total Knee Replacement: Is There An Alternative Technique To Mechanical Or Kinematic Alignment?

Ponky Firer, Prof., Johannesburg SOUTH AFRICA
Linksfield Clinic, Johannesburg, SOUTH AFRICA

FDA Status Cleared

Summary

Total Knee Replacements accurately balanced within 2°-3° throughout range of movement, without soft tissue releases and accepting constitutional alignment, may give improved patient satisfaction and outcomes.

Abstract

Introduction

Mechanical Alignment (MA) (0°±3°) is the accepted standard for Total Knee Replacements (TKR). Perfect soft tissue balance is often not achieved and 15% of patients are unsatisfied mostly because of pain. Kinematic Alignment (KA) aims to achieve normal kinematics and soft tissue balance.Improved outcomes have been reported. However the alignments of the tibial component are reported to be in “excessive” varus Perfect balance (within 2°-3°) is not always achieved by KA, and soft tissue releases or boney adjustments are required in some cases. Postulate: Improved satisfaction and outcomes may be achieved by balancing the soft tissues accurately (within 2°), throughout range of movement without soft tissue releases. Constitutional alignment is accepted and the tibial prosthesis is placed within 3°.
Material and Methods: Surgical technique: The tibial cut is at 0° except for severe proximal tibial varus, in which cases up to 3° varus is chosen. Classic flexion gap balancing is done to set femoral rotation. A preliminary extension cut 4mm less than expected is made at the measured valgus angle. The flexion and extension gaps are assessed for balance and size with a tensiometer, The final extension cut is then made at a changed valgus angle and position to give ideal balance (<3°) and an extension gap size equal to the flexion gap. 255 consecutive, single surgeon, osteoarthritic TKRs were prospectively studied. Long leg pre and postoperative X-rays were taken. Mean follow up = 32months (24-41) Outcomes assesments: 1) Patient satisfaction [question and VAS score] and correlated pain VAS score 2) Oxford Knee Scores (OKS) and 3) WOMAC scores. Outcomes were compared with reported MA and KA studies. Results of the neutrally “aligned” ( Mechanical axis = 0°±3°) knees and “outlier” (>±3°) knees in this series were compared.
Results: 234 knees (91.7%) had satisfactory x-rays and fully completed outcome scores. 218 (93.1%) of these patients were satisfied. The mean VAS score (range) was: Satisfied = 9.53 (7.2-10) (10 = totally satisfied), and unsatisfied = 3.78 (0-6.3). The VAS pain scores (0 = no pain; 10 = most pain) were: satisfied = 0.33(0-4.6) and unsatisfied = 5.8 (1.5-10). These differences were significant (P< 0.05). Ninety two percent of unsatisfied patients complained of pain whilst 36% had stiffness. Mean OKS=41.8 (38-48) and WOMAC=21.3 (5-42). Reported outcomes for MA knees: Satisfaction= 75-89%; OKS= 37.5 to 41; WOMAC (0 is best)=24.5-26.0. Outcomes for KA knees: Satisfaction (not reported) OKS=42; WOMAC (100 is best) =85.
Postoperative alignment: 201 (86%) were “aligned” TKRs and 33 (14%) “outliers”. The distribution of coronal mechnical aligment matches that of the normal popuation. There was no difference in Satisfaction, OKS or WOMAC scores between these groups (p=0.859) . (93.2%vs 92.9%; 41.7 vs 42.5; 21.3 vs 21.3 respectively). Mean tibial component alignment = -1.4° (+1° to -4°). There was 1 mechanical failure (an aligned knee )
Conclusion: Perfectly balanced TKRs may be an alternate method of TKR, enabling higher patient satisfaction than previously reported. This is thought to be due to decreased pain related to decreased soft tissue imbalances. The OKS and WOMAC scores were at least as good as reported for both MA and KA TKRs. Coronal mechanical algnment made no difference to satisfaction or outcome scores.