There is conflicting evidence about the benefit
of using corticosteroid in periarticular injections for pain relief
after total knee arthroplasty (TKA). We carried out a double-blinded,
randomised controlled trial to assess the efficacy of using corticosteroid
in a periarticular injection to control pain after TKA. A total of 77 patients, 67 women and ten men, with a mean age
of 74 years (47 to 88) who were about to undergo unilateral TKA
were randomly assigned to have a periarticular injection with or
without corticosteroid. The primary outcome was post-operative pain
at rest during the first 24 hours after surgery, measured every
two hours using a visual analogue pain scale score. The cumulative
pain score was quantified using the area under the curve. The corticosteroid group had a significantly lower cumulative
pain score than the no-corticosteroid group during the first 24
hours after surgery (mean area under the curve 139, 0 to 560, and
264, 0 to 1460; p = 0.024). The rate of complications, including
surgical site infection, was not significantly different between
the two groups up to one year post-operatively. The addition of corticosteroid to the periarticular injection
significantly decreased early post-operative pain. Further studies
are needed to confirm the safety of corticosteroid in periarticular
injection.
Cite this article:
Evidence from recent trials has supported the efficacy of periarticular analgesic injection for pain control following total knee arthroplasty (TKA). However, no randomized controlled trial has compared the efficacy of periarticular analgesic injection with that of other regimens for simultaneous bilateral TKA. We conducted a randomized controlled trial in which patients scheduled for simultaneous bilateral TKA were randomly assigned to receive periarticular analgesic injection or epidural analgesia. In the periarticular analgesic injection group, the injection contained 7.5 mg/ml ropivacaine 40 ml, 10 mg/ml morphine hydrochloride hydrate 1.0 ml, 1.0 mg/ml epinephrine 0.6 ml, methylprednisolone 80 mg, and ketoprofen 50 mg. These agents were mixed with normal saline to a combined volume of 120 ml. The 60 ml of the cocktail was injected into each knee. In the epidural analgesia group, the catheter was placed at the L2–3 or L3–4 level, and connected to an infusion pump delivering continuous infusion (flow rate: 4 ml/h) of 100 ml of 2 mg/ml ropivacaine plus 1.0 ml of 10 mg/ml morphine hydrochloride hydrate. Surgery was managed under spinal anaesthesia. Surgical techniques and postoperative medication protocols were identical in both groups. The primary endpoint was postoperative pain at rest, quantified as the area under the curve (AUC) of the score on a visual analogue scale.Background
Methods
A biomechanical study has been carried out on 20 cadaveric knees to investigate their load-absorbing mechanism. The impact load was applied using a weight falling onto the transected proximal femur and the force transmitted through the knee was measured at the transected distal tibia using a load transducer. The peak force transmitted increased as, sequentially, meniscus, articular cartilage and subchondral bone were damaged or removed. The most striking result was found in an implanted knee replacement where the transmitted force reached 180% of that in the intact knee. The results show that the joint has an impact-absorbing property in each segment and that in the osteoarthritic knee there is less absorption of shock than in the normal knee. The high impact force in an implanted knee suggests that microfractures of the cancellous bone might be expected and may produce loosening.
