SLR - May 2014 - Jacqueline Donovan

Popliteal Blocks for Foot and Ankle Surgery: Success Rate and Contributing Factors

Reference: Hegewald K., McCann K., Elizaga A, and Hutchinson BL. Popliteal Blocks for Foot and Ankle Surgery: Success Rate and Contributing Factors. Journal of Foot and Ankle Surgery.  53 (2014) 176-178.

Scientific Literature Review

Reviewed By: Jacqueline Donovan, DPM
Residency Program: Grant Medical Center, Columbus, Ohio

Podiatric Relevance: The post-operative period following foot and ankle surgery is often associated with moderate to severe pain. The popliteal nerve block has well-documented safety and efficacy for post-operative pain control. In the foot and ankle literature, contributing factors and the assessment of a learning curve has yet to be studied. The authors analyzed the variables influencing the success rate of popliteal blocks utilizing two different approaches by podiatric surgical residents in various stages of training.
 
Methods: In the retrospective study, 143 popliteal nerve blocks performed from August 1, 2009 to August 1, 2011 were reviewed. All blocks were performed at a single institution, utilizing a nerve stimulator by podiatric surgical residents within their first three years of training. Data collected included patient age, body mass index (BMI), a pre-versus immediately postoperative block, surgical procedure type and patient reported postoperative pain intensity in the postanesthesia care unit. All blocks were performed in an operating room setting with the patient under general anesthesia. The blocks were performed in standardized fashion using either a lateral or modified posterior approach, using 0.5 percent bupivicaine and 1:200,000 ephinephrine. Lateral blocks were performed using a trans-biceps approach. Modified posterior popliteal blocks were performed using a double injection technique that targeted the tibial nerve within the popliteal fossa and the common peroneal nerve at the level of the fibular neck. The nerve stimulator was introduced perpendicular to the skin at the popliteal crease, 1 cm lateral to the midline. The current was set at 5.0 mA and the needle was advanced until a plantar flexion response was noted at the ankle joint. The current was then decreased until stimulation was lost at 0.6 to 1.0 mA. An injection of 15 mL of local anesthetic was administered near the tibial nerve. The second injection was performed at the level of the fibular neck to target the common peroneal nerve consisting of 10 mL of anesthetic. In all patients, 5 mL of anesthetic was injected along the saphenous nerve distribution. The patients were categorized based on block success (designated by an NRS score of 0 to 4) or failure (NRS score of 5 to 10). 

Results: A total of 143 blocks were performed on 77 female and 66 male patients by residents with 1 to 26 months of training. Eighty-six percent were performed for rearfoot or ankle reconstructive procedures, 13 percent for midfoot surgical procedures and 1 percent for forefoot procedures. Of the 143 blocks that were performed, 109 were successful and 34 failed for an overall success rate of 76 percent. An independent variable analysis showed significant differences in the patients BMI and age between success and failure groups. No significant difference was observed for the variables of block approach or resident months of training. 

Conclusions: Of the 143 blocks that were performed, an overall success rate of 76 percent was noted. The data demonstrated that patient age and BMI contribute to the differences in overall block outcome with more successful blocks observed in older patients and patients with a lower BMI. The present study is the first to report on the performance of popliteal nerve blocks by podiatric residents for foot and ankle surgery. The amount of experience of the resident did not result in any difference in the likelihood of block success.  

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