Midterm Outcomes of Ultrasound-guided Local Treatment for Infrapatellar Saphenous Neuroma Following Total Knee Arthroplasty

Case report: A case of injury to the infrapatellar branch of the saphenous nerve caused by medial approach in knee arthroscopy

We present the case of a 72-year-old man who was referred to our department for treatment of pain on the anteromedial infrapatellar side of the right knee with sensory disturbance that began 2 years earlier. The patient previously underwent right knee arthroscopy at another hospital for a meniscus injury 2 years earlier, which relieved his knee pain, but pain and discomfort near the incision of the medial portal persisted. Given this situation, various physical treatments, such as ice compress, were administered postoperatively. However, the symptom was only partially relieved before discharge. Subsequently, the patient visited two other hospitals and began taking oral pregabalin and duloxetine for treatment of the pain based on a diagnosis of right common peroneal nerve injury. The pain in the same dermatomal distribution was slightly relieved, but a withdrawal reaction was observed. However, the results of an ultrasound at our hospital indicated that the right medial quadriceps femoris tendon showed a hypoechoic area suggesting inflammatory changes. Physical examination of the right knee detected atrophy of the quadriceps femoris muscle, decreased muscle strength (M4), obvious tenderness in the medial side, radiating pain along the anterior tibia, and sensory disturbance (S3+); the results of a drawer test, McMurray test, pivot shift test, and lateral stress test were negative. Based on the aforementioned evidence, a diagnosis was made of injury to the infrapatellar branch of the saphenous nerve, after which neurolysis of the nerve in question was carried out. An enlarged incision was made along the original medial approach. Scar hyperplasia was observed after careful separation of the subcutaneous tissue. During neurolysis, branches were found wrapped in the scar; their continuity and integrity were confirmed after relief. The released nerve was placed in a physiological position. The patient's pain was clearly relieved, and numbness disappeared on the first postoperative day. At 1-month follow-up, all symptoms were found to have resolved.

Surgical treatment outcome of painful traumatic neuroma of the infrapatellar branch of the saphenous nerve during total knee arthroplasty

BACKGROUND

Development of infrapatellar saphenous neuroma (ISN) is a well-recognized reason for knee pain following total knee arthroplasty (TKA). So far, very few studies have addressed the development of painful ISN after TKA and its impact on functional outcome and patient satisfaction.

AIM

To present the results of surgical treatment for ISN after primary TKA, the level of pain relief, and the improvement of knee motion and function.

METHODS

Fifteen patients (13 women, 2 men) with persistent medial pain for more than six months after primary TKA, due to osteoarthritis, underwent surgical excision of ISN. ISN diagnosis was confirmed with the presence of Tinel’s sign along the course of the infrapatellar branch of the saphenous nerve and with pain relief after selective nerve block using local anesthetic. Component loosening, malalignment, instability and infection were excluded systematically in all patients as a source of pain. Pain relief in terms of visual analog scale (VAS), active knee range of motion (ROM), and the Knee Society Score (KSS) for pain and function were evaluated preoperatively and at least six months postoperatively.

RESULTS

The mean patients’ age was 71.3 ± 5.4 years old. The mean interval between TKA and neuroma excision was 10 mo (range, 6 to 14 mo), while the mean follow-up was 8 mo (range: 6 to 11 mo). All 15 patients experienced almost complete immediate pain relief and resolution of allodynia and hyperesthesia after surgery. Pain on the VAS scale improved from 8.6 ± 1.3 preoperatively to 0.8 ± 0.9 at the final follow-up (P = 0.001). KSS pain and function scores were improved from 49.3 ± 5.9 and 62.7 ± 12.8 before surgery to 91.8 ± 4.2 and 75.3 ± 11.3 after surgery, respectively (P = 0.001 and P = 0.015). Active knee ROM was also increased postoperatively from 96 ± 4 to 105 ± 6 degrees (P = 0.001). There were no complications and no further operations required.

CONCLUSION

ISN should be considered a potential cause of persistent pain following TKA. Neuroma excision not only provides immediate pain relief and resolution of symptoms but may also improve the knee range of motion.