Anterior cruciate ligament repair and peripheral nerve blocks: time to change our practice?

Effective pain control after anterior cruciate ligament repair (ACLR) is vital for recovery and rehabilitation¹ and to reduce the need for potent analgesics such as opioids. In the past 30 yr the analgesic care of these patients has evolved from a model predominantly focused on opioids, subsequently complemented by peripheral nerve blocks such as femoral nerve block (FNB)2, 3 and then adductor canal block (ACB),⁴ all in the context of a multimodal analgesic regimen.5, 6, 7, 8 Although these regional anaesthesia techniques can provide very effective pain control, their use has to be balanced against the time, expertise, and resources required for their placement in addition to potential adverse effects such as motor block and longer-term, albeit much less common, complications such as nerve injury, persistent motor weakness, and myotoxicity.⁹

More recently, local instillation analgesia (LIA) during ACL surgery has been used in addition to, or as a replacement for, peripheral nerve blocks. Recent studies and subsequent systematic reviews have shown that FNB or ACB may not produce additional analgesic advantage when compared with multi-modal analgesia (MMA) alone,5, 10 whereas LIA can provide effective analgesia compared with placebo for ACLR.¹¹ Although previous studies have compared FNB with LIA,12, 13, 14 until now a direct comparison between ACB and LIA for ACLR has not been reported.

In this issue of the British Journal of Anaesthesia, Stebler and colleagues¹⁵ add to our knowledge of this area with a randomised study comparing ACB and LIA for ACLR. The authors used a triple-blinded approach randomising 104 patients to either ACB or LIA for hamstring graft ACLR under general anaesthesia. Both regional techniques were performed with 0.5% ropivacaine (20 ml) with the LIA technique applied during surgery and the ACB placed at the end of the operation. The strengths of the current study include its use of high-quality methods, use of a multimodal analgesic regimen, and inclusion of a number of functional outcome assessments including quadriceps strength and other tests of balance. Overall, the authors found no difference in early or late outcomes including pain control, analgesic consumption, or functional outcomes up to 8 months after surgery.

On the one hand, these results will be seen as disappointing by proponents of regional anaesthesia because of the lack of superiority of ACB compared with LIA. Conversely, this result can be seen as a ‘win’ for patients who should have effective analgesia using a peripheral local anaesthetic technique that does not require a separate injection with all of the attendant risks.

Given these results, we should accept that LIA provides effective analgesia for ambulatory knee surgery cases such as ACLR. The efficacy of LIA for TKA corroborates these findings. However, the combination of LIA and ACB appears to have a synergistic effect in TKA and may provide better analgesia than either modality alone.16, 17 A similar synergistic effect will need to be studied for ACLR. However, large-scale pragmatic studies should be performed to further evaluate the many patients often excluded from randomised trials—those with opioid tolerance, chronic pain, obesity, and paediatric patients. Further focus on how to optimise functional outcome and limit long-term use of opioid analgesics is required.

In practical terms for patients with ACLR, we should use MMA in combination with LIA, while reserving ACB for those patients with opioid tolerance, chronic pain, or those in whom LIA is not possible. Consideration should also be provided for the type of graft being used (i.e. hamstring or quadriceps graft vs bone–patellar tendon–bone autograft).

A future focus should be on longer-term outcomes and provision of MMA across a broad range of patients since for many interventions the application in practice is varied and limited across all centres. This will ensure high-quality pain control immediately after surgery, and limit the need for opioid analgesics and prescription of these drugs.¹⁸

Regional anaesthesia should be provided as peripherally as possible without sacrificing effectiveness. It is now becoming apparent that for certain types of peripheral surgery, LIA is the most practical and effective option and likely to be easiest to implement in practise. Stebler and colleagues¹⁵ have taken us forward in our knowledge of how to provide optimal pain control and functional recovery after ACLR.

Authors' contributions

Conception and writing of the editorial: RR, CJLM. Critical intellectual content: ST. All authors reviewed and approved the final version of the manuscript.

Declaration of interest

CJLM is a member of the BJA associate editorial board.