Is total knee replacement more painful than total hip replacement?

Area of Science:

• Orthopedic Surgery
• Pain Management
• Pharmacology

Background:

• Patient-controlled analgesia (PCA) devices allow self-administration of medication, enhancing patient safety and satisfaction.
• PCA enables objective measurement of analgesic use and pain intensity, facilitating comparisons between different surgical procedures.
• Morphine consumption via PCA serves as a reliable parameter for quantifying postoperative pain.

Purpose of the Study:

• To compare the intensity of postoperative pain between total hip replacement (THR) and total knee replacement (TKR) surgeries.
• To utilize patient-controlled analgesia (PCA) morphine consumption as an objective measure of pain intensity.
• To elucidate differences in pain experienced following THR versus TKR.

Main Methods:

• A prospective cohort study involving 50 patients (24 THR, 26 TKR) undergoing major orthopedic surgery.
• Intravenous morphine titration to achieve a VAS score ≤3, followed by 48 hours of morphine PCA (1 mg bolus, 6-minute lockout).
• Recording of pain scores, total morphine dose, demand/delivery data, and adverse effects for comparison between groups.

Main Results:

• Postoperative pain scores were similar between THR and TKR groups over 48 hours.
• Total morphine consumption was significantly higher in the TKR group compared to the THR group on both postoperative days 1 and 2 (P < 0.05).
• No significant differences were observed in the demand/delivery ratio or incidence of minor adverse effects between the two surgical groups.

Conclusions:

• PCA morphine consumption effectively distinguishes pain intensity between THR and TKR procedures.
• Contrary to assumptions, total knee replacement may involve greater postoperative pain intensity than total hip replacement.
• Further research is warranted to explore the underlying reasons for observed pain differences.