Total hip replacement (THR) is a common orthopedic procedure performed to alleviate pain and restore mobility. While generally safe, the operation carries a small risk of complication, including injury to the nerves surrounding the hip joint. Understanding the signs of nerve damage is important for patients, as early identification aids recovery. The incidence of nerve injury after a primary THR is relatively low, occurring in less than 2% of procedures, though it is slightly higher in complex or revision surgeries. This article explores the specific nerves at risk and the symptoms that can indicate damage.
Nerves Commonly Affected
The proximity of major nerves to the hip joint makes them vulnerable to injury during surgery. The sciatic nerve is the most frequently affected, accounting for the vast majority of nerve injuries following THR. It passes directly behind the hip joint and is susceptible to tension, compression, or direct trauma.
The femoral nerve is also at risk, particularly with the anterior surgical approach. This nerve runs along the front of the hip and can be compressed by surgical retractors used for implant placement. Injury mechanisms often involve stretching due to excessive limb lengthening, compression, or localized damage during fixation.
The common peroneal nerve, a branch of the sciatic nerve, is often compromised. Other less frequently injured nerves include the obturator nerve, the lateral femoral cutaneous nerve, and the superior gluteal nerve.
Recognizing Specific Symptoms of Nerve Damage
Symptoms of nerve damage are categorized into sensory and motor deficits. Sciatic nerve injury often presents as pain radiating from the buttocks down the back of the leg, commonly called sciatica. This damage also causes altered sensation, described as tingling, numbness, or a burning feeling along the back of the thigh, calf, and foot.
Motor symptoms are specific, with damage to the common peroneal division of the sciatic nerve leading to “foot drop.” This involves difficulty or inability to lift the front part of the foot and toes, causing the foot to drag when walking.
Injury to the femoral nerve primarily affects the muscles on the front of the thigh. This typically results in weakness when attempting to straighten the knee or flex the hip. Patients may experience a feeling that the knee is going to give out or buckle. Sensory changes are usually localized to the front of the thigh, the knee, and the inner part of the lower leg.
Less common injuries, such as to the lateral femoral cutaneous nerve, cause meralgia paresthetica. This sensory-only neuropathy results in burning pain, numbness, or an intense tingling sensation on the outer side of the thigh. It does not affect a person’s ability to move the leg.
Immediate Steps and Medical Consultation
If a patient notices new or worsening sensory changes or muscle weakness in the operated leg after a total hip replacement, they should immediately contact their surgical team or physician. Delayed onset of symptoms can occasionally occur, sometimes caused by hardware or a developing hematoma, requiring ongoing vigilance.
The medical team will perform a physical examination to assess muscle strength, reflexes, and sensation patterns to pinpoint the injured nerve. To confirm the diagnosis and assess the extent of the damage, the doctor may order electrodiagnostic studies, including nerve conduction velocity (NCV) tests and electromyography (EMG).
These tests are often performed several weeks after the injury to allow for measurable changes in the nerve and muscle. The results help distinguish between a mild, temporary injury and a more severe structural one.
Recovery Timeline and Prognosis
The prognosis for nerve injuries following total hip replacement depends on the type and severity of the damage. A mild injury, known as neurapraxia, involves a temporary block of nerve signaling without structural damage. These injuries often resolve spontaneously, with function returning within a few weeks to several months.
More severe injuries, called axonotmesis, involve damage to the nerve fibers while the outer sheath remains intact. These require a longer recovery period as the nerve must physically regrow. Recovery can take many months, with nerve fibers regenerating at a rate of approximately one inch per month. Not all patients achieve full recovery, particularly those with severe initial deficits.
Management strategies focus on supporting the patient during recovery and preventing secondary complications. Physical therapy is a primary component, involving targeted exercises to maintain muscle strength and joint mobility while the nerve heals. Pain management, utilizing specific medications, is used to control discomfort. In rare cases where compression from a hematoma or hardware is identified, or if no improvement is seen, surgical exploration and nerve repair may be considered.