Anatomy of the Infrapatellar Branch in Relation to Skin Incisions and as the Basis to Treat Neuropathic Pain by Percutaneous Cryodenervation

Background: Neuropathic knee pain, particularly of the infrapatellar branch, is an importantcomplication of knee replacement surgery, with an incidence as high as 70%. The increasingnumber of elderly patients requiring knee surgery, including total knee arthroplasty (TKA), hascontributed to an increase in the number of patients with this pathology. Treatment includesneurectomy, infiltration therapy, and cryodenervation. Percutaneous cryodenervation of theinfrapatellar branch is a promising option.Objective: To provide the necessary anatomical analysis to optimize percutaneous cryodenervationof the infrapatellar branch by defining sections of the unbranched ramus infrapatellaris todemonstrate the risk of nerve injury through 3 different skin incisions typically used during TKA.Study Design: Anatomical study.Methods: Cadavers were used for assessment. Exclusion criteria were scars from knee surgery,deep wounds, and a flexion angle of no more than 90°. We compared 3 frequently used skinincisions with the course of the infrapatellar branch and identified sections of the unbranchednerves that were suitable for percutaneous cryodenervation.Results: In total, 18 formalin-fixed cadavers (mean age, 78.9 years) contributed 30 knees (15 pairs)for dissection. We identified the following 4 anatomical variations of the ramus infrapatellaris inrelation to the sartorius muscle: anterior, posterior, penetrating, and pes anserinus types. Sectionswere then found to treat the nerve branch types. The nerve sections were localized using themedial pole of the patella as a palpable landmark and varied in length between 15 mm and 40mm. The medial parapatellar skin incision showed the highest risk of lesions to the infrapatellarbranch (53.3%) followed by the midline skin incision (46.7%) and the lateral parapatellar skinincision (30.0%).Limitations: This was an observational study, performed using a limited number of cadavers.This therefore precluded generalization and statistical analysis. Significantly more female (13)cadavers were examined compared to male (5). Further studies in human populations, and withlarger samples, are necessary to confirm these results.Conclusion: Based on our findings, the surgeon can localize the unbranched main nerve.Compared with the current practice, our approach should allow for a lower impact on tissues andshould facilitate complete pain relief through a single cryodenervation. Furthermore, we proposethat the lateral parapatellar skin incision is an acceptable alternative surgical approach in kneereplacement surgery because it is associated with the lowest risk of damage to the infrapatellarbranch.Key words: Percutaneous cryodenervation, infrapatellar branch, neuropathic knee pain, kneesurgery, skin incisions knee surgery, total knee arthroplasty