Stems improve the mechanical stability of tibial
components in total knee replacement (TKR), but come at a cost of stress
shielding along their length. Their advantages include resistance
to shear, reduced tibial lift-off and increased stability by reducing
micromotion. Longer stems may have disadvantages including stress
shielding along the length of the stem with associated reduction
in bone density and a theoretical risk of subsidence and loosening, peri-prosthetic
fracture and end-of-stem pain. These features make long stems unattractive
in the primary TKR setting, but often desirable in revision surgery
with bone loss and instability. In the revision scenario, stems
are beneficial in order to convey structural stability to the construct
and protect the reconstruction of bony defects. Cemented and uncemented
long stemmed implants have different roles depending on the nature
of the bone loss involved. This review discusses the biomechanics of the design of tibial
components and stems to inform the selection of the component and
the technique of implantation.
Patient expectations and their fulfilment are
an important factor in determining patient-reported outcome and satisfaction
of hip (THR) and knee replacement (TKR). The aim of this prospective
cohort study was to examine the expectations of patients undergoing
THR and TKR, and to identify differences in expectations, predictors
of high expectations and the relationship between the fulfilment
of expectations and patient-reported outcome measures. During the
study period, patients who underwent 346 THRs and 323 TKRs completed
an expectation questionnaire, Oxford score and Short-Form 12 (SF-12)
score pre-operatively. At one year post-operatively, the Oxford
score, SF-12, patient satisfaction and expectation fulfilment were
assessed. Univariable and multivariable analysis were performed.
Improvements in mobility and daytime pain were the most important
expectations in both groups. Expectation level did not differ between
THR and TKR. Poor Oxford score, younger age and male gender significantly
predicted high pre-operative expectations (p <
0.001). The level
of pre-operative expectation was not significantly associated with
the fulfilment of expectations or outcome. THR better met the expectations
identified as important by patients. TKR failed to meet expectations
of kneeling, squatting and stair climbing. High fulfilment of expectation
in both THR and TKR was significantly predicted by young age, greater
improvements in Oxford score and high pre-operative mental health
scores. The fulfilment of expectations was highly correlated with satisfaction.
Up to 20% of patients are not satisfied with the outcome following total knee replacement (TKR). This study investigated the pre- and post-operative predictors of dissatisfaction in a large cohort of patients undergoing TKR. We assessed 1217 consecutive patients between 2006 and 2008 both before operation and six months after, using the Short-form (SF)-12 health questionnaire and the Oxford Knee Score. Detailed information concerning comorbidity was also gathered. Satisfaction was measured at one year when 18.6% (226 of 1217) of patients were unsure or dissatisfied with their replacement and 81.4% (911 of 1217) were satisfied or very satisfied. Multivariate regression analysis was performed to identify independent predictors of dissatisfaction. Significant (p <
0.001) predictors at one year included the pre-operative SF-12 mental component score, depression and pain in other joints, the six-month SF-12 score and poorer improvement in the pain element of the Oxford Knee Score. Patient expectations were highly correlated with satisfaction. Satisfaction following TKR is multifactorial. Managing the expectations and mental health of the patients may reduce dissatisfaction. However, the most significant predictor of dissatisfaction is a painful total knee replacement.