This prospective, observational cohort study evaluates the long-term outcomes of Regenerative Peripheral Nerve Interface (RPNI) surgery in patients with major lower extremity amputations suffering from symptomatic neuromas. RPNI is a surgical technique where the transected nerve end is implanted into a free autologous muscle graft to serve as a physiological target for reinnervation. The study aims to objectively assess the reduction in mechanical hypersensitivity using Pressure Pain Threshold (PPT) measurements via a digital algometer. Additionally, it monitors subjective neuropathic pain levels, functional mobility, and prosthesis satisfaction over a 24-month follow-up period compared to pre-operative baselines.
Age: Adults aged 18 to 70 years.
Amputation Status: Unilateral major lower extremity amputation (Transtibial, Transfemoral, or Knee Disarticulation).
Radiological Baseline: Absence of Heterotopic Ossification (HO) in the residual limb, confirmed by pre-operative X-rays (Walter Reed Classification Grade 0).
Neuropathic Pain: DN4 Questionnaire score ≥ 4.
CRPS: Diagnosis of Complex Regional Pain Syndrome (CRPS Type 1 or 2).
Concurrent Bone Surgery: Patients requiring simultaneous stump revision surgery (e.g., bone shortening, osteotomy, spur excision) or having existing HO (Walter Reed Grade > 0).
Systemic Conditions: Uncontrolled diabetes mellitus (HbA1c > 8.5%) or severe peripheral arterial disease compromising wound healing.
Cognitive Status: Cognitive impairment or psychiatric conditions preventing reliable completion of patient-reported outcome measures (PEQ, DN4).
Adult patients with major lower extremity amputations presenting to the tertiary Orthopedics and Traumatology clinic with complaints of chronic residual limb pain, phantom limb pain, and prosthesis intolerance, who are diagnosed with symptomatic neuroma and scheduled for surgical intervention.
Cohort
Prospective
Regenerative Peripheral Nerve Interface (RPNI) Surgery
Procedure/SurgeryThe surgical procedure is standardized as follows to preserve the residual limb (stump) anatomy: * Approach: An 8-10 cm incision is made on the lateral thigh. For transtibial (below-knee) amputees, the incision is placed approximately 15 cm proximal to the knee joint. For transfemoral (above-knee) amputees, it is placed 5-10 cm proximal to the distal end of the residual limb. * Nerve Dissection: The sciatic nerve is isolated, dissected, and transected at its most distal point. Subsequently, it is separated into the Common Peroneal and Tibial divisions. * Fascicular Separation: Based on nerve thickness, intraneural dissection is performed to split the Common Peroneal nerve into 1 or 2 fascicles, and the Tibial nerve into 2 to 4 fascicles. * Graft Harvesting: Autologous muscle grafts are harvested to wrap these created fascicles. The donor site is standardized by amputation level: Vastus Lateralis muscle for transtibial amputees and Biceps Femoris muscle for transfemoral amputees.
Change in Pressure Pain Threshold (PPT)
Objective measurement of mechanical hypersensitivity at the neuroma site using a digital pressure algometer. The device applies increasing pressure in kg/cm² until the patient reports pain. Measurements are taken from the most tender point of the neuroma and a control point. Higher values indicate higher pain tolerance (improvement).
Change in Pain Intensity (NRS)
Self-reported pain intensity measured by the Numeric Rating Scale (NRS). Scale ranges from 0 (No pain) to 10 (Worst possible pain).
Change in Neuropathic Pain Characteristics (DN4 Score)
Assessment using the Douleur Neuropathique 4 (DN4) questionnaire. Total score ranges from 0 to 10. A score of 4 or higher indicates neuropathic pain.
Prosthesis Satisfaction and Quality of Life (PEQ)
Evaluation using the Turkish validated version of the Prosthesis Evaluation Questionnaire (PEQ). Scores are normalized to a 0-100 scale (Higher scores indicate better outcome).
Change in Functional Mobility (TUG Test)
Timed Up and Go (TUG) test measuring the time (in seconds) required to stand, walk 3 meters, turn, walk back, and sit down. Lower time indicates better mobility.
Charlson Comorbidity Index (CCI)
Weighted index to predict risk of death from comorbidities. Used to standardize baseline health status.
Elixhauser Comorbidity Index (ECI)
Index categorizing comorbidities based on ICD diagnosis codes to adjust for confounding factors.
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