gms | German Medical Science

Objectives: Functional demands of patients undergoing knee arthroplasty are increasing. Which factors are predictive for higher postoperative activity and whether there is a difference between total and unicompartmental knee arthroplasties (TKA/UKA) remains unclear. Furthermore,it has been suggested that high activity might reduce implant survival and many surgeons advise their patients against high physical activity. To date, there is no sufficient evidence on whether such restraints are necessary to assure longevity of TKA and UKA.

Methods: This retrospective study analyzed 1,907 knees with TKA (1,746) or UKA (161), implanted for primary osteoarthritis in patients aged 45–75 years. Lower extremity activity scale (LEAS) was assessed at a 2 year follow. Cases were grouped in low (LEAS maximum 6), moderate (LEAS 7–13) and high activity (LEAS minimum 14). Revisions were assessed by chart review. Cohorts were compared with Kruskal-Wallis- or Pearson-Chi²-Test. Univariate logistic regression was conducted to test for association between activity level at a two years and later revisions. Odds ratio was reported and converted to predicted probability. A Kaplan-Meier curve was plotted to predict implant survival. A Generalized Least Squares model was used to predict LEAS scores between UKA and TKA adjusted for age, sex, BMI, Charlson Comorbidity Index, ASA score and preoperative LEAS.

Results and conclusion: UKA and TKA had similar preoperative LEAS (p=0.994), both groups showed significant (p<0.001, respectively) and similar improvement postoperative (p=0.068). When adjusted for preoperative LEAS, age, sex, BMI, CCI and ASA, the postoperative LEAS did not differ between UKA and TKA (p=0.225). Male sex, lower BMI, higher preoperative LEAS and younger age were associated with higher postoperative LEAS (p<0.001, respectively). The predicted implant survival for UKA was 98.1% at 5 years and for TKA 98.1% at 5 years. The difference was not significant (p=0.410). Differences in revision rates between moderate and high active UKA were not significant (p=0.292). The revision rate in the high activity TKA group was lower than in the low and moderate active cases (p=0.008). A higher LEAS 2 years after surgery was associated with a lower risk for future revision (p=0.001). A 1 point increase in postoperative LEAS lowered the odds for revision surgery by 19%.

Patients can achieve a high level of activity following both TKA and UKA. The patients' postoperative activity level does not depend on the type of procedure but is predominantly influenced by age, sex, BMI and preoperative activity level. Participating in sports activity following both UKA and TKA is not a risk factor for revision surgery at a mid-term follow-up.Patients should not be prevented from an active lifestyle following knee replacement.