The decision to undergo a hip replacement, or total hip arthroplasty, is often made to relieve severe joint pain and restore mobility. While this surgery is highly successful, the recovery process involves managing post-operative pain, which can sometimes include nerve pain. Severe nerve injury resulting in permanent damage is an infrequent complication, with reported incidences ranging between 0.6% and 3.7% in primary surgeries. However, milder, temporary nerve irritation or neuropathic pain symptoms are more commonly reported during the initial recovery phase.
Understanding the Frequency of Nerve Pain
The overall risk of experiencing severe, permanent nerve damage following a primary hip replacement is low, with some institutions reporting an incidence as low as 0.21%. The risk is notably higher in revision surgery, where the incidence can increase to 7.6%. Studies find that 3.1% to 5.5% of patients report persistent neuropathic pain symptoms two months to two years after the operation.
The nerve most commonly implicated in injury after hip replacement is the sciatic nerve, accounting for over 90% of all reported nerve injuries. Damage to the sciatic nerve can result in “foot drop”—the inability to lift the foot and ankle—along with numbness and tingling (paresthesias) that radiate down the posterior thigh and leg.
The femoral nerve is another major nerve that can be affected, though this occurs much less frequently, with an incidence ranging from 0.04% to 7.6%. Injury to the femoral nerve manifests as weakness in the quadriceps muscle, making it difficult to straighten the knee or manage stairs. It may also cause abnormal sensations in the medial pelvic or anterior thigh region.
A third nerve, the lateral femoral cutaneous nerve (LFCN), is a sensory nerve susceptible to injury when an anterior surgical approach is used. Injury to the LFCN does not cause muscle weakness but results in meralgia paresthetica, characterized by burning pain or persistent numbness and tingling on the outer side of the thigh. Although this sensory disturbance can be intense, the symptoms are often temporary and resolve spontaneously within a few months.
How Nerve Pain Occurs and What It Feels Like
Nerve irritation or injury during hip replacement surgery arises from several mechanical processes within the operative field. Primary causes include direct trauma, such as laceration or contusion from a surgical tool, and compression from retractors used to hold tissues aside. Compression can also be caused by a developing hematoma or the extrusion of bone cement near the nerve.
Another mechanism is traction, or stretching of the nerve, which occurs due to positioning the limb or when the leg is lengthened during the procedure. Leg lengthening of more than 2.7 centimeters, for example, significantly increases the risk of injury to the peroneal division of the sciatic nerve. Nerves can also suffer from ischemia (restriction of blood supply) or from thermal damage caused by the heat generated when the bone cement sets.
The sensation of nerve pain, known as neuropathic pain, is distinctly different from the typical musculoskeletal pain felt after surgery. Musculoskeletal pain is usually a deep, aching sensation localized to the incision and surrounding soft tissues. Neuropathic pain, conversely, is described as burning, electrical shock sensations, a pins-and-needles feeling, or intense tingling.
Patients may describe the pain as feeling like battery acid or fire ants gnawing at the leg due to the hypersensitivity of the damaged nerve. When a motor nerve is involved, such as the sciatic or femoral nerve, the patient will also experience muscle weakness or paralysis. This motor dysfunction indicates that the pain is originating from the nervous system rather than the healing joint itself.
Treating Nerve Pain and Long-Term Outlook
The initial management for most cases of nerve irritation involves observation and expectant waiting, as many temporary nerve dysfunctions resolve spontaneously. The recovery timeline varies, with improvement often seen within weeks or months as post-operative swelling subsides and the nerve begins to regenerate. Most patients achieve a full or near-full recovery, with approximately 41% experiencing complete recovery and 44% retaining only a mild, non-disabling deficit.
Medical management for persistent neuropathic pain involves specific pharmacological interventions designed to calm irritated nerves. Medications like gabapentin, pregabalin, or amitriptyline may be prescribed to manage the burning, tingling, and electrical sensations. Steroid injections can also be used to reduce localized inflammation around the nerve.
Physical therapy is a fundamental component of recovery, focusing on mobility exercises and strengthening muscles weakened by the nerve injury. For significant motor deficits like foot drop, an extended brace may be used to assist with walking and prevent further injury. If significant compression from a hematoma or cement is identified, a surgical procedure to decompress the nerve may be necessary.
The long-term outlook for nerve pain after hip replacement is generally favorable, especially for less severe injuries. Femoral nerve palsies, for example, tend to follow a more predictable and positive recovery course than sciatic nerve injuries. Recovery can continue for a long period, with some patients achieving further improvement in nerve function beyond two years after the initial surgery.