iPACK block for ACL repair: Clinical evidence and postoperative insights

The iPACK block for ACL repair offers no added benefit over femoral triangle block in reducing pain or opioid use post-surgery.

Managing pain effectively after anterior cruciate ligament (ACL) reconstruction is essential for recovery, rehabilitation and long-term knee function. In this article, we review the findings of a recent clinical trial entitled “Comparison of femoral triangle plus iPACK blocks with femoral triangle block alone for anterior cruciate ligament reconstruction: a randomised controlled clinical trial on postoperative pain and knee function.” This study, led by Professor Étienne Cavaignac and colleagues, provides valuable evidence on the true effectiveness of the iPACK block for knee surgery.

For more insights into knee surgery and pain management, explore the other clinical studies conducted by Professor Cavaignac.

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Comparing femoral triangle and iPACK knee blocks in ACL reconstruction

The study investigated whether adding an iPACK knee block for ACL repair to a femoral triangle block (FTB) and local infiltration analgesia would reduce postoperative morphine consumption and pain.

A total of 90 patients scheduled for ACL reconstruction were randomly assigned to two groups:

• One received a femoral triangle block alone, combined with local infiltration.

• The other received both the femoral triangle block and iPACK block injection.

The iPACK block, or "interspace between the popliteal artery and the capsule of the posterior knee", is designed to provide posterior analgesia of the knee without affecting motor function. It aims to complement anterior regional blocks like the FTB by targeting sensory fibres from the tibial, common peroneal and obturator nerves that innervate the posterior capsule of the knee.

Despite its theoretical advantages, the trial showed that the iPACK block for ACL did not provide significant clinical benefit when added to the standard analgesic regimen.

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iPACK Block for Knee Surgery: Postoperative pain relief and morphine consumption

The iPACK block for knee surgery has been proposed to improve postoperative pain management, but its actual impact on opioid consumption required objective evaluation.

The study’s primary outcome was the cumulative oral morphine equivalent (OME) consumed in the first 48 hours after surgery. Both groups received standard general anaesthesia and multimodal postoperative analgesia, including acetaminophen, NSAIDs and local infiltration.

Here are the key findings:

• Median cumulative OME consumption was 50 mg in the FTB group and 60 mg in the FTB+iPACK group.

• Pain scores measured at rest were similar at all time points: in the post-anaesthesia care unit (PACU), at 24 hours and at 48 hours.

• The difference in morphine consumption between the two groups (5 mg) was not statistically significant (p=0.49).

In simple terms, the iPACK block for knee arthroscopy did not significantly reduce the need for opioids compared to using FTB alone.

Morphine-related side effects

Adding an iPACK nerve block for knee surgery also did not reduce opioid-related side effects. Rates of nausea, vomiting, drowsiness and other adverse effects were similar between the two groups. These findings reinforce the idea that the additional injection, while safe, does not improve the overall analgesic profile in primary ACL surgery.

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iPACK block for total knee replacement and functional recovery after ACL reconstruction

Although the iPACK block for total knee replacement has demonstrated benefits for posterior knee analgesia, its use in ACL reconstruction showed no improvement in long-term functional recovery.

Long-term outcomes are just as important as immediate postoperative comfort. The study followed patients for 9 months using validated outcome measures, including:

• KOOS (Knee injury and Osteoarthritis Outcome Score)

• IKDC (International Knee Documentation Committee)

• Lysholm Knee Scoring Scale

No significant differences were observed between the groups at 3, 6 or 9 months in any of these scores. This suggests that the iPACK for ACL technique does not affect knee function or quality of life after ACL reconstruction.

Interestingly, patients with lower morphine use (<50 mg OME) during the first 48 hours tended to have slightly better KOOS and IKDC scores at 9 months. However, these differences did not reach the minimum threshold to be considered clinically significant. It remains unclear whether acute pain levels have a meaningful long-term impact on functional recovery.

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Why the iPACK block for ACL repair may not be effective?

The iPACK block for ACL repair appears to have a limited application. Several factors may explain this outcome:

1. Adequate anterior coverage by FTB
   The femoral triangle block alone provides strong anterior knee analgesia while preserving quadriceps strength, which is key for early mobilisation.

2. Effective local infiltration
   In this study, all patients received 20 mL of ropivacaine via targeted surgical infiltration at key pain sources (e.g., tendon harvest site), which may have rendered the additional iPACK block redundant.

3. Limited posterior knee pain in ACL surgery
   Unlike total knee arthroplasty, ACL reconstruction does not typically involve significant posterior capsule manipulation. Thus, targeting posterior sensory branches via iPACK may not offer added value.

4. Overlap of local anaesthetic effects
   Injecting multiple blocks may cause overlapping zones of anaesthesia, without increasing overall benefit. In this context, more is not necessarily better.

Conclusion: Clinical recommendations and surgical implications

This clinical trial supports the continued use of the femoral triangle block as the standard regional technique for ACL reconstruction, in combination with surgical local infiltration.

There is no evidence to support the routine addition of an iPACK block for ACL repair under these conditions. Avoiding unnecessary blocks can save time, reduce patient discomfort and streamline the anaesthetic protocol.

Moreover, sparing the iPACK injection allows teams to focus on optimising rehabilitation, which remains the cornerstone of ACL recovery. Professor Cavaignac’s approach to postoperative care includes:

• Early mobilisation and pain control

• Individualised physiotherapy programmes

• Digital follow-up tools such as Orthense for remote guidance

The decision to use any additional block should be made based on individual patient characteristics and surgical context.

Findings and outcomes

This large, randomised clinical trial demonstrates that the iPACK block for ACL repair does not reduce pain or opioid consumption when combined with a femoral triangle block and local infiltration. Functional outcomes at 9 months are also unaffected.

In ACL reconstruction performed under general anaesthesia with multimodal analgesia, adding an iPACK block does not offer additional clinical value. Surgical teams can confidently rely on FTB and infiltration alone, streamlining care while maintaining excellent outcomes.

Patients seeking reliable, evidence-based care for ACL injuries can place their trust in Professor Étienne Cavaignac’s expertise.