What did the study look at?
Controlling pain after total knee replacement (total knee arthroplasty) is a prerequisite for starting early rehabilitation. Because the knee is supplied by many nerves, pain management is difficult. An adductor canal block (ACB) in the thigh is used for pain at the front of the knee, while several methods have been described for the back of the knee.
This study compared two methods for the back of the knee: the iPACK block (an injection into the space between the popliteal artery and the back of the knee capsule), given by an anaesthetist under ultrasound guidance after surgery, and posterior capsule infiltration (PCI), an injection into the back of the knee capsule given by the surgeon during the operation.
How was it done?
This was a double-blind, prospective, randomised controlled trial (registration NCT05943080). A total of 195 patients undergoing primary total knee replacement for end-stage osteoarthritis were randomly assigned to three groups of 65:
- Group 1: ACB + iPACK
- Group 2: ACB + PCI
- Group 3 (control): ACB only
One surgeon performed all the operations and one anaesthetist performed all the ultrasound-guided blocks. Pain was measured on the Visual Analogue Scale (VAS) before surgery and at set times afterwards, on day 10 and at week 12. Opioid consumption, knee range of motion, continuous passive motion device values and knee function scores (KSS, Oxford Knee Score) were also recorded.
What did it find?
- The groups were similar in age, sex, body mass index and side of surgery.
- Three hours after surgery, the mean VAS pain score was 4.72 in the iPACK group, 5.00 in the PCI group and 7.06 in the control group. At 6 and 12 hours, pain was also significantly lower in both combination groups than in the control group.
- The lowest pain scores were seen in the iPACK group, but the difference between iPACK and PCI was not statistically significant.
- From 24 hours onwards there was no significant difference in pain between the groups.
- Opioid use on day one, day two and in total was significantly lower in both combination groups than in the control group (total: 3.60 and 3.54 versus 4.34 ampoules). Patients in the control group needed pain relief earlier.
- Knee function scores at week 12 did not differ between the groups.
- Active range of motion on day 3 and passive motion values in the first days were better in the PCI group; the authors note that these small differences are hard to observe clinically and diminish by day 10.
- No participant showed evidence of nerve or blood vessel injury.
The authors' conclusion
The authors regard iPACK as a reliable technique that reduces pain in the first 12 hours and significantly lowers opioid consumption, but they found that PCI combined with ACB was not inferior to iPACK. They believe these combinations can be used according to the surgeon's experience and preference, and they point out that PCI is quicker and easier to perform without ultrasound.
Limitations
- Pain was not scored separately for different regions of the knee; the authors state this would have made participant compliance difficult.
- No allergy testing for local anaesthetics was carried out.
- VAS measurement relies on participant compliance.
Reference
Cakmak MF, Bayram S, Horoz L, Arslan FN, Demir OU, Gürsoy S. (2025). No superior method for analgesia after total knee arthroplasty: randomised controlled comparison of adductor canal block combined with iPACK block versus posterior capsule block. Archives of Orthopaedic and Trauma Surgery, 145(1):222. Licence: CC BY 4.0.
DOI: 10.1007/s00402-025-05845-5
Free full text: PMC11972175
This article summarises a published scientific paper for general information; it does not replace an examination or a personal medical assessment. Please consult your doctor about your symptoms.
