investigator choice

The purpose of this study is to realize a cartography of the allodynic and hypoasthetic territories associated with a neuropathic pain appearing in patients who underwent a Total Knee Arthroplasty (TKA)

The occurrence of Post-surgical Pain depends on the surgical procedure performed, the surgical site and patients-dependents characteristics. Post surgical pain became chronic when it persist beyond two month.

Chronic post-surgical pain (CPSP) is one of the most common complications after surgery. Nerve injury during surgery has been implicated in the development of CPSP. Some patients with CPSP have neuropathic pain (NP). NP is pain cause by damage or disease affecting the somatosensory nervous system. It may be associated with abnormal cutaneous sensation such as hypoesthesia (partial loss of sensitivity to sensory stimuli) or allodynia (pain from normally non-painful stimuli)

Total Knee Arthroplasty (TKA) present a high risk of injury of the infrapatellar branch of the saphenous nerve, thus can cause the appearance of neuropathic post-surgical pain. Only few data are available concerning the skin areas affected after this surgery.

The goal of this study is to analyse the localization of allodynic or hypoasthetic territories that may appear after TKA. The investigators will include 200 patients undergoing TKA surgery at the CHU-Amiens-Picardie. Patient will be seen the day before their surgery, and at follow-up visits at 6 weeks, 6 months and one year postoperatively. A DN diagnostic test (DN4 test) will be performed at each visits. The cartography will be performed on each DN4-positive patients. In addition, patients will also complete questionnaires to assess the intensity of pain, quality of life and level of anxiety.

Thus, the knowledge of the localization of allodynic or hypoasthetic territories will allow a most efficient an faster detection and relief of post-surgical neuropathic pain.

Inclusion Criteria:

• major patient benefit from a first setting operation of TKA (total knee arthroplasty) by standard medial arthrotomy
• Patient signed an informed consent
• Patients receiving social coverage

Exclusion Criteria:

• Patient not wishing to be part of the study, or unable to consent,
• Patient under guardianship or deprived of his liberty
• Patients with neuropathic pain in the territory concerned preoperatively
• Patient who underwent TKA laying by a technique other than standard medial arthrotomy

adult patient who received a first setting operation of TKA (total knee arthroplasty)