Ultrasound-guided lateral-medial transmuscular quadratus lumborum block for analgesia following anterior iliac crest bone graft harvesting: a clinical and anatomical study.

Background: The anterior iliac crest (AIC) is one of the most common sites for harvesting autologous bone, but the associated postoperative pain can result in significant morbidity. Recently, the transmuscular quadratus lumborum block (TQL) has been described to anesthetize the thoraco-lumbar nerves. This study utilizes a combination of cadaveric models and clinical case studies to evaluate the dermatomal coverage and analgesic utility of TQL for AIC bone graft donor site analgesia.

Methods: Ten ultrasound-guided TQL injections were performed in five cadaver specimens using a lateral-to-medial transmuscular approach. Twenty mL of 0.5% methylcellulose was injected on each side after ultrasound confirmation of the needle tip ventral to the quadratus lumborum muscle (QLM). Cranio-caudal and medial-lateral extent of the dye spread in relation to musculoskeletal anatomy and direct staining of the thoraco-lumbar nerves were recorded. Following the anatomical findings, continuous catheter TQL blocks were performed in four patients undergoing ankle surgery with autologous AIC bone graft. The dermatomal anesthesia and postoperative analgesic consumption were recorded.

Results: In the anatomical component of the study, 9/10 specimens showed a lateral spread anterior to the transversalis fascia and medially between the QLM and psoas major muscle. Direct staining of the branches of the T12, L1, and L2 nerves was noted ventral to the QLM, while variable staining of the T9-T11 nerves was seen laterally in the transversus abdominis plane and the transversalis fascia. The vertical spread of injectate anterior to the QLM was T12 to the iliac crest (n = 5/10) and L1 to the iliac crest (n = 4/10). In the four patients who received TQL, the T9-L2 dermatomal anesthesia correlated with the injectate spread seen in the cadavers and provided effective analgesia at the bone graft donor site.

Conclusion: Ultrasound-guided TQL injections consistently cover the thoraco-lumbar innervation relevant to the AIC graft donor site. The injectate spread seen in anatomical dissections correlated with the dermatomal anesthesia clinically. The TQL has the potential to provide reliable analgesia for patients undergoing AIC bone graft harvesting.