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Year : 2020  |  Volume : 4  |  Issue : 3  |  Page : 125-128

Infrapatellar neuralgia due to bullous morphea in postknee arthroplasty patients treated with radiofrequency

Department of Anaesthesia and Pain Relief Service, Tata Motors Hospital, Jamshedpur, Jharkhand, India

Date of Submission23-Mar-2020
Date of Decision20-Apr-2020
Date of Acceptance02-May-2020
Date of Web Publication18-Jul-2020

Correspondence Address:
Dr. Ashok Jadon
Duplex-63, Vijaya Heritage Phase-6, Kadma, Jamshedpur - 831 005, Jharkhand
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/BJOA.BJOA_36_20

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Injury or entrapment of the infrapatellar branch of the saphenous nerve (IPS) can cause persistent anterior and medial knee pain. However, IPS neuralgia because of bullous morphea is rare and not reported earlier. We present a case of IPS neuralgia after total knee replacement where the pain was attributed to local skin lesion of bullous morphea (BM). After a successful diagnostic block, radiofrequency treatment was done to provide prolonged relief. We have discussed the possible pathogenesis of nerve entrapment and pain by BM in our case and the basis of treatment by radiofrequency ablation.

Keywords: Bullous morphea, infrapatellar saphenous nerve, knee pain, nerve injury, peripheral nerve entrapment, saphenous neuralgia, total knee replacement

How to cite this article:
Jadon A, Sinha N. Infrapatellar neuralgia due to bullous morphea in postknee arthroplasty patients treated with radiofrequency. Bali J Anaesthesiol 2020;4:125-8

How to cite this URL:
Jadon A, Sinha N. Infrapatellar neuralgia due to bullous morphea in postknee arthroplasty patients treated with radiofrequency. Bali J Anaesthesiol [serial online] 2020 [cited 2021 Mar 9];4:125-8. Available from: https://www.bjoaonline.com/text.asp?2020/4/3/125/290093

  Introduction Top

Infrapatellar neuralgia is caused by direct injury or entrapment neuropathy of the infrapatellar branch of the saphenous nerve (IPS). Anterior and medial knee pain due to IPS neuralgia is often mistaken for other causes of pain such as knee joint arthritis, meniscal injury, and collateral ligament injury.[1] We present a case of anteromedial knee pain due to IPS entrapment caused by bullous morphea (BM). Morphea or localized scleroderma (LS) is not a rare condition as the reported incidence of LS is around 0.3–3 cases/100,000 inhabitants/year,[2] and in about 2.4% of patients, LS may coexist with systemic sclerosis.[3] However, BM is a rare variant of LS as only limited cases have been reported in literature.[4],[5]

In this case, lesions of BM caused fibrosis of subcutaneous tissue on the medial side of the knee, leading to entrapment of IPS and neuralgic pain. Initially, the pain was managed with oral analgesics and neuropathic drugs. However, interventional pain management was done when pain could not be controlled, and the patient developed other features of neuropathic pain such as sleep disturbance. At first, the diagnostic block was given to confirm the diagnosis, and later, radiofrequency ablation (RFA) was done to provide sustained relief with neuralgic pain due to IPS neuralgia.

  Case Report Top

A 72-year-old female presented with severe burning pain for 4 months on the medial side of the left knee below the joint line. Initially, the pain was intermittent but became continuous and burning in nature with increased severity during night time. She had undergone bilateral total knee replacement (TKR) 4 years ago and was asymptomatic after surgery. She developed scleroderma of the left lower limb 1½ years back and was treated with local and systemic steroids and methotrexate. However, the disease progressed to BM (diagnosis was confirmed by histopathology).

Her pain was managed with etoricoxib 90 mg/day, pregabalin 150 mg/day, amitriptyline 10 mg, and a combination tablet of tramadol 50 mg and paracetamol 375 mg. However, when the pain became severe (continuous burning) and the patient developed sleep disturbances, she was referred to our pain clinic. On examination, scarring of the skin and subcutaneous tissue with a bullous lesion was seen along the medial side of the left lower limb. An area of severe pain (visual analog scale/[VAS] = 9/10), with hypersensitivity and tenderness, was present below the medial epicondyle of the femur, medial to the tibial tuberosity. IPS neuralgia was suspected due to excessive tissue scarring [Figure 1].
Figure 1: Medial side of the left thigh showing excessive scarring and bullous formation due to bullous morphea

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After informed consent regarding sensory loss in the area of pain, ultrasound-guided diagnostic block was decided. In the operation theater, noninvasive basic monitors were attached, and necessary aseptic preparation was done. The patient was positioned in supine, and the affected limb was flexed at the knee. Using a high-frequency linear ultrasound probe (6–13 MHz, (FUJIFILM SonoSite, Gurugram, India Pvt. Ltd.)), the saphenous nerve (SN) was localized at the lateral border of the sartorius muscle (probable origin of the infrapatellar branch) [Figure 2] and was further confirmed by sensory stimulation at 0.5 mA. Once confirmed, injection of 10 ml mixture of bupivacaine 0.25% and 40 mg triamcinolone was given using the in-plane technique. The block provided excellent pain relief (VAS 0/10) for 15 days, however slowly the pain returned to almost the previous intensity.
Figure 2: Sonoanatomy of the left lower medial thigh. SM: Sartorius muscle, SN: Saphenous nerve, IPS: Infrapatellar branch of saphenous nerve

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We then performed pulsed radiofrequency (PRF) treatment of distal SN (at 42° and 50 V, two cycles for 3 min each), which provided relief for 6 weeks only. After the recurrence of pain, conventional RFA was decided to provide long-term relief. After informed consent regarding loss of sensation in the area of IPS nerve, RFA (at 70° for 90 s, two cycles) was done (using a similar technique of localization as used during the diagnostic block) [Figure 3], which provided sustained pain relief for more than 6 months (the patient is still symptom free). There was no complication except sensory loss in the infrapatellar area, which was acceptable to the patient.
Figure 3: Ultrasound image during radiofrequency ablation procedure. Arrows showing needle entering from the lateral side through in-plane approach. SM: Sartorius muscle, VM: Vastus medialis muscle, IPS: Infrapatellar branch of saphenous nerve

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  Discussion Top

IPS is a pure sensory nerve that innervates the skin below the patella.[6] IPS neuralgia resulting in persistent knee pain, especially after TKR surgery, is known, yet, the diagnosis is often delayed.[7] Because the clinical presentation is vague, it is often misdiagnosed and underdiagnosed.[8] In our case, IPS neuralgia due to TKR surgery was unlikely as the patient was asymptomatic for 4 years and pain occurred only after the bullous transformation of existing morphea.

Could morphea be the cause of neuropathic pain? Morphea, also known as LS, is a distinctive inflammatory disease usually asymptomatic and regresses spontaneously over time.[9] However, BM involving the skin and the subcutaneous tissue may cause excessive collagen deposition that ultimately leads to fibrosis.[4] This fibrosis is secondary to a series of events that occur in the skin, starting with an influx of mononuclear cells which infiltrate the dermis and surround the blood vessels.

This is followed by a vascular injury resulting in functional and structural changes in the vessels, especially the vessels underlying the epidermis. There is also upregulation of intercellular adhesion molecule and vascular cell adhesion molecule in response to cytokines such as interferon gamma, interleukin (IL)-1, and tumor necrosis factors. IL-4 produced by the CD4+ Th2 lymphocytes upregulates the production of transforming growth factor-beta (TGF-β). The fibrosis is induced by excessive TGF-β and IL-4 activity.[10] The deep tissue destruction and fibrosis can cause nerve entrapment syndromes.[9]

The pain in morphea could be multifactorial and could be correlated with the type of lesion.[11] A patient with morphea presented with debilitating pain in skin plaque and managed successfully with methotrexate has been reported.[12] However, in our patient, pain was not localized to lesion only, rather, it was distal to the lesion, did not respond to methotrexate, and manifested only after bullae formation. BM is a rare variant of morphea; only <100 cases have been reported till 2013 and three more cases have been reported in 2015.[4],[5]

Although lymphangiectasis has been suggested as the most likely mechanism for the development of the bullae in cases of morphea, many other theories such as local injury, vasculitis, and autoimmune response have been suggested. The exact pathogenesis of BM is not known, however, it is accepted that subepidermal bullae develop due to the sclerodermatous process.[13]

Nagai et al.[14] hypothesized that autoimmune background in LS-induced anti-Cu/Zn superoxide dismutase (SOD) autoantibodies and inhibited SOD activity contribute to fibrosis by increasing reactive oxygen species. Although BM is a rare disease, in our patient, the working diagnosis of IPS neuralgia due to BM was made because the patient was asymptomatic for many years after TKR surgery and pain occurred only after progression to BM. Moreover, the patient had symptomatic relief after the diagnostic block.[15]

We used nerve stimulation for localization and confirmation of IPS because the use of nerve stimulator increases the success of nerve localization during IPS block.[16] As far as the management of IPS neuralgia is concerned, it can be managed surgically or by interventional pain management techniques such as cryoneuroablation and PRF.[17],[18],[19] Both radiofrequency techniques, PRF and RFA, interrupt pain transmission; PRF causes neuromodulation and RFA causes heat destruction of pain carrying axons by  Wallerian degeneration More Details. There are two proposed mechanisms of action by which RFA controls the pain transmission. First, there is heat generation (when high-voltage current passes through a thin electrode) leading to thermos-coagulation and destruction of neural tissue if the temperature is above 45°C. Second, neuromodulation due to ionic movement induced by current.

The neuromodulating effect of PRF gives short-lasting effect, but the regeneration of neurons after RFA takes long time, therefore, the effect also lasts longer.[20] In our case, initial management with local anesthetic and steroid injection and PRF provided only short-term relief. Therefore, RFA of IPS was done as the last resort which provided sustained pain relief.

  Conclusion Top

IPS neuralgia due to BM after TKR surgery is a rare condition. RFA of IPS provided sustained and long-term relief. No serious complication was noticed except the loss of sensation in the area inverted by IPS.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Morganti CM, McFarland EG, Cosgarea AJ. Saphenous neuritis: A poorly understood cause of medial knee pain. J Am Acad Orthop Surg 2002;10:130-7.  Back to cited text no. 1
Peterson LS, Nelson AM, Su WP, Mason T, O'Fallon WM, Gabriel SE. The epidemiology of morphea (localized scleroderma) in Olmsted County 1960-1993. J Rheumatol 1997;24:73-80.  Back to cited text no. 2
Giuggioli D, Colaci M, Cocchiara E, Spinella A, Lumetti F, Ferri C. From localized scleroderma to systemic sclerosis: Coexistence or possible evolution. Dermatol Res Pract 2018;2018;1284687.  Back to cited text no. 3
Rosato E, Veneziano ML, Di Mario A, Molinaro I, Pisarri S, Salsano F. Ulcers caused by bullous morphea: Successful therapy with N-acetylcysteine and topical wound care. Int J Immunopathol Pharmacol 2013;26:259-62.  Back to cited text no. 4
Fernandez-Flores A, Gatica-Torres M, Tinoco-Fragoso F, García-Hidalgo L, Monroy E, Saeb-Lima M. Three cases of bullous morphea: Histopathologic findings with implications regarding pathogenesis. J Cutan Pathol 2015;42:144-9.  Back to cited text no. 5
Horner G, Dellon AL. Innervation of the human knee joint and implications for surgery. Clin Orthop Relat Res 1994;301:221-6.  Back to cited text no. 6
Mistry D, O'Meeghan C. Fate of the infrapatellar branch of the saphenous nerve post total knee arthroplasty. ANZ J Surg 2005;75:822-4.  Back to cited text no. 7
Trescot AM, Brown MN, Karl HW. Infrapatellar saphenous neuralgia – Diagnosis and treatment. Pain Physician 2013;16:E315-24.  Back to cited text no. 8
Careta MF, Romiti R. Localized scleroderma: Clinical spectrum and therapeutic update. An Bras Dermatol 2015;90:62-73.  Back to cited text no. 9
Badea I, Taylor M, Rosenberg A, Foldvari M. Pathogenesis and therapeutic approaches for improved topical treatment in localized scleroderma and systemic sclerosis. Rheumatology (Oxford) 2009;48:213-21.  Back to cited text no. 10
Walker D, Susa JS, Currimbhoy S, Jacobe H. Histopathological changes in morphea and their clinical correlates: Results from the Morphea in Adults and Children Cohort V. J Am Acad Dermatol 2017;76:1124-30.  Back to cited text no. 11
Jeon H, Kim C. Letter: Methotrexate for localized morphea with severe pain: A case report. Dermatol Online J 2011;17:12.  Back to cited text no. 12
Fett N, Werth VP. Update on morphea: Part I. Epidemiology, clinical presentation, and pathogenesis. J Am Acad Dermatol 2011;64:217-28.  Back to cited text no. 13
Nagai M, Hasegawa M, Takehara K, Sato S. Novel autoantibody to Cu/Zn superoxide dismutase in patients with localized scleroderma. J Invest Dermatol 2004;122:594-601.  Back to cited text no. 14
Lundblad M, Kapral S, Marhofer P, Lönnqvist PA. Ultrasound-guided infrapatellar nerve block in human volunteers: Description of a novel technique. Br J Anaesth 2006;97:710-4.  Back to cited text no. 15
Montgomery SH, Shamji CM, Yi GS, Yarnold CH, Head SJ, Bell SC, et al. Effect of nerve stimulation use on the success rate of ultrasound-guided sub sartorial saphenous nerve block: A randomized controlled trial. Reg Anesth Pain Med 2017;42:25-31.  Back to cited text no. 16
Hosahalli G, Sierakowski A, Venkatramani H, Sabapathy SR. Entrapment neuropathy of the infrapatellar branch of the saphenous nerve: Treated by partial division of Sartorius. Indian J Orthop 2017;51:474-6.  Back to cited text no. 17
[PUBMED]  [Full text]  
Trescot AM. Cryoanalgesia in interventional pain management. Pain Physician 2003;6:345-60.  Back to cited text no. 18
Han BR, Choi HJ, Kim MK, Cho YJ. Pulsed radiofrequency neuromodulation for the treatment of saphenous neuralgia. J Korean Neurosurg Soc 2013;54:136-8.  Back to cited text no. 19
Cabrera RG, Barajas MS, Fraga TC, Acevedo MAE. Radiofrequency ablation: a review of current knowledge, therapeutic perspectives, complications, and contraindications. Int J Biosen Bioelectron. 2018;4:56–8. DOI: 10.15406/ijbsbe.2018.04.00098.  Back to cited text no. 20


  [Figure 1], [Figure 2], [Figure 3]


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