Introduction
A vital component of the femoral nerve, the infrapatellar branch of the saphenous nerve (IBSN), courses along the medial aspect of the leg and knee. Incidents of its injury are commonplace during total knee arthroplasty, a procedure involving substituting the knee joint with an artificial counterpart.
Consequently, neuromas (nerve tissue tumors that do not spread to other areas) may develop due to nerve trauma, leading to discomfort and restricted mobility. The advent of these neuromas poses a substantial obstacle to postoperative pain control and functional rehabilitation, underscoring the necessity for a thorough comprehension of their origins, clinical presentation, diagnostic modalities, and therapeutic interventions.
What Is Saphenous Nerve Neuroma in Total Knee Arthroplasty?
The development of a saphenous nerve neuroma entails the benign proliferation of tissue along this sensory nerve, the principal branch of the femoral nerve traversing the inner thigh and leg. Typically arising from skin incisions, the formation of this infrapatellar branch of the saphenous nerve neuroma is often precipitated by the entrapment of nerve endings during incision closure, provoking irritation and, ultimately, neuroma formation.
Instances of saphenous nerve neuroma have been documented following procedures such as tibial nailing (a surgical intervention involving the stabilization of tibial fractures through the utilization of screws or metal rods), anterior cruciate ligament (ACL) reconstruction, and arthroscopy (a minimally invasive diagnostic and therapeutic procedure utilized for addressing joint issues, employing a narrow tube equipped with a camera for visualization and treatment guidance), further highlighting its multifaceted etiology and clinical associations.
What Is the Cause of Saphenous Nerve Neuroma After Total Knee Arthroplasty?
Following total knee arthroplasty, it is not uncommon for the infrapatellar branch of the femoral nerve to undergo injury. This can result from factors such as compression, surgical trauma, infection, needle injections, or entrapment of the nerve, leading to irritation and, eventually, the development of neuroma. Several studies indicate a broad range in injuries to the infrapatellar branch of the femoral nerve post-surgery, with reported rates ranging from 0.5 percent to 53 percent in certain cases.
What Are the Symptoms of Saphenous Nerve Neuroma?
Symptoms of saphenous nerve neuroma following total knee arthroplasty present a spectrum of discomfort and dysfunction, including:
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Pain and Discomfort: Patients often report varying degrees of pain and discomfort in the knee that underwent surgery. This discomfort may manifest as localized or radiating, affecting mobility and overall comfort.
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Stiffness in the Knee Joint: A notable symptom is the development of stiffness within the knee joint.
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Positive Tinel's Sign: During this diagnostic test, tapping the affected nerve elicits a tingling sensation, confirming nerve irritation and potential neuroma formation.
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Limited Knee Movement: Patients may notice a decreased range of motion in the affected knee.
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Heightened Sensitivity: Sensitivity in the inner part of the knee may become heightened, leading to increased discomfort.
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Inflammation or Swelling: In some cases, inflammation or swelling may develop near the site of the saphenous nerve neuroma.
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Tenderness to Touch: The area surrounding the saphenous nerve neuroma may become tender.
What Is the Diagnosis of Saphenous Nerve Neuroma After Total Knee Arthroplasty?
The diagnostic process involves a thorough evaluation conducted by a healthcare professional, which encompasses various components:
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Evaluation of the patient's medical history, particularly focusing on prior knee surgeries or procedures and any existing nerve-related conditions, is imperative.
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A comprehensive physical examination is essential, specifically targeting the knee joint and its neurological function. This examination aims to detect sensory disturbances and signs of nerve irritation, often utilizing Tinel's sign (a tingling sensation that often accompanies the tapping of an irritated nerve) as an indicator of nerve damage.
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Simple X-ray imaging is crucial in confirming the knee replacement device's correct positioning and secure attachment. These images also help rule out fractures around the implant, bone damage, or any implant loosening.
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Relief of pain and stiffness following local anesthetic injections near the nerve injury can provide valuable insights into nerve-related symptoms.
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High-resolution ultrasound emerges as a valuable tool for accurately measuring nerve size and early identifying neuromas. Additionally, techniques such as MRI (magnetic resonance imaging), ultrasound-guided needle procedures, and peripheral nerve stimulators are instrumental in precisely targeting the affected nerve.
What Is the Histopathology of a Saphenous Nerve Neuroma?
In the histopathological analysis of saphenous nerve neuroma, examination of the tissue reveals a distinctive composition. Elements such as fat, blood vessels, collagen, and nerve tissue are identified within the neuroma tissue. Notably, disorganized nerve fiber bundles are observed, a characteristic often associated with traumatic neuromas.
How Can the Injury to the Sapneous Nerve Be Avoided?
Avoiding injury to the infrapatellar branch of the saphenous nerve (IBSN) during total knee arthroplasty poses a significant challenge for surgeons. While ideally, the surgical incision should align parallel to the IBSN, its precise location can vary among individuals, complicating efforts to establish a definitive safe zone preoperatively. Recent research has highlighted that a standard midline approach in TKA may not consistently prevent IBSN injury. Therefore, educating patients about this potential risk is paramount to ensure informed decision-making regarding their surgical procedure.
What Is the Management of Saphenous Nerve Neuroma?
In the management of saphenous nerve neuroma, a multifaceted approach is employed, encompassing both conservative and surgical treatments:
A. Conservative Treatment: Initially, conservative measures such as injections and physical therapy alleviate symptoms. However, surgical intervention may be considered if these conservative approaches fail to provide adequate relief.
B. Surgical Treatment: These include:
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IBSN Neurolysis: This surgical procedure involves the meticulous dissection of the infrapatellar branch of the saphenous nerve and the interruption of nerve fibers.
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Cryoneurolysis: Cryoneurolysis is a medical procedure that utilizes extreme cold to temporarily disrupt the function of target nerves.
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Neurectomy: Neurectomy is a surgical procedure involving the removal or cutting of the affected nerve. Some studies suggest that neurectomy may offer superior pain relief compared to neurolysis.
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Selective Knee Denervation: This includes delicately targeting the specific pain-conducting nerves within the knee joint while safeguarding the integrity of surrounding sensory nerves.
In addition to these surgical interventions, preventative measures may be taken to mitigate the risk of neuroma recurrence. Nerve end cauterizing using electrocautery is one such preventative measure that may be employed during surgical intervention.
What Is the Prognosis of Saphenous Nerve Neuroma?
Patients who develop a neuroma following total knee arthroplasty can expect a considerably improved outlook if early diagnosis and treatment are pursued. Beyond merely requiring subcutaneous neurectomy, addressing the condition entails thoroughly removing proliferating fibrous tissue and replacing the knee spacer, ensuring comprehensive management and enhancing the overall prognosis.
Conclusion
Surgeons must maintain a high index of suspicion for neuroma as a potential etiology of knee pain in post-TKA patients, particularly when pain symptoms are pronounced. Timely diagnosis and intervention are paramount to optimizing patient outcomes. Diagnostic measures such as Tinel's test, which assesses nerve sensitivity and changes in the range of motion following local anesthesia injections, are invaluable in distinguishing between IBSN injury and alternative knee pathologies. If conservative treatments such as injections or therapy fail to yield satisfactory results, surgeons should contemplate the implementation of surgical interventions to address the underlying issue effectively.
