Modifying techniques can prevent neurovascular injury during THA

Preoperatively assess anatomy and risk factors in order to minimize neurovascular complications.

ORLANDO, Fla. — Performing preoperative assessment and modifying techniques based on a patient’s relative anatomy and risk factors can minimize the risk of neurovascular injury during total hip arthroplasty, according to Robert L. Barrack, MD, of the Washington University School of Medicine in St. Louis.

“Complications cannot be eliminated, but they can be minimized by preoperative assessment, judicious use of preop tests, such as MR angiograms or CT scans, appropriate modification and technique and, most importantly, good knowledge of the quadrant system,” Barrack explains.

Patients at risk for injury

Neurovascular injury is the least common injury in total hip arthroplasty (THA), occurring in just 1% to 2% of cases, Barrack said. However, it is the most distressing complication for both the patient and the surgeon and “the most common cause of litigation in hip replacement: number one for number of claims and number nine for amount of indemnity payouts,” he said.

In 25,000 cases from 28 studies, researchers found just 243 injuries: 79% to the sciatic nerve, 13.2% femoral nerve, 5.8% sciatic and femoral nerves and 1.6% obturator.

High-risk groups include women, revision cases, developmental dysplasia of the hip (DDH) patients and patients with history of peripheral neuropathy or lumbar spine disease, Barrack said. Intraoperative risk factors include previous trauma, open reduction internal fixation (ORIF), particularly of a posterior column fracture, and an absent posterior wall with plating or bone grafting.

Further, “if you’re going to be excising heterotopic ossification, it’s a good idea to get a CT scan and look for the proximity of the bone to the nerve,” Barrack said.

During THA, Barrack said to identify the nerve and protect it throughout the case. “You need to visualize the nerve in these cases, protect it with soft tissue, flex the knee and avoid extreme positions,” he said. “Don’t remove hardware unless it’s necessary.”

How to treat nerve palsy

If a patient develops a nerve palsy, it’s important that the surgeon recognizes it early, assesses the injury in the recovery room, obtains early neurological consultation, counsels the patient and family and begins early bracing and skin care, Barrack said. Skin breakdown is common with tibial nerve involvement.

“Our routine is to get an EMG at four to six weeks and treat the [injury] medically,” he said.

Surgery is used only in cases with hematoma, overlengthening, profound palsy, impingement from a screw or large structural graft or transsection. “There are three or four things you have to think about acutely, because those conditions are reversible at least for the first 24 hours,” Barrack said.

Outcome in patients treated for nerve palsy is generally positive. In another 21 studies with 228 neuropalsies, 80% of patients treated had a good outcome: 41% were asymptomatic, 44% had a mild deficit and only 15% had a major deficit.

“Good signs [for recovery] are incomplete injury, if you have some motor function and if you have early signs of return, particularly in the first week or two. Bad signs are painful dysesthesia or a complete lesion,” Barrack said in his presentation at the 22nd Annual Current Concepts in Joint Replacement Winter 2005 Meeting.

Much less common than sciatic nerve injuries, femoral nerve injuries are easier to overlook. These are usually associated with anterior approaches and anterior bone deficits. For example, “if you had a prior psoas release, it’s important to be careful when placing these anterior retractors, because you hit the nerve first, then the artery, then the vein,” Barrack said.

Surgeons can test for femoral nerve palsy by instructing the patient to press down on the popliteal space, while observing the quads for contraction. “The prognosis is generally better than sciatic or peroneal,” Barrack said.

General treatment is nonoperative and involves temporary bracing, except in those cases with direct impingement from hematoma, a screw or a graft.

Another nerve at risk during THA is the superior gluteal nerve, usually caused by the direct lateral approach. Barrack indicated the safe zone to avoid superior gluteal nerve injury is located 3 cm to 5 cm proximal to the greater trochanter.

Less common than both sciatic and femoral nerve palsy, obturator nerve palsy may present late with symptoms, such as groin or inguinal pain. Surgeons can confirm diagnosis by the response to a local block, Barrack said. Neurectomy and cement excision may be effective treatments.

Vascular injuries

Vascular injuries are even less common than the previously mentioned neurovascular injuries, but are more immediately life-threatening. However, these injuries may become more common, because surgeons are now using screws and other devices that protrude into the pelvis, Barrack said.

“You can get an occlusion or embolization and the operative approach or component removal can cause a problem,” he said. At-risk patients have dysvascular limbs, prior bypass surgery or absent pulses, while the most major risk is acetabular screw use.

To avoid vascular injuries, surgeons should stay away from the anterior superior zone. Posterior superior quadrants are safest and have the thickest bone; the anterior quadrant should only be used with extreme caution.

“You don’t want to plunge through medially. Be very aware of the quandrant system,” Barrack said. “If you’re removing the components, be aware that anything that goes medial to Kohler’s line could be impeding on a vascular structure ... . If you’re medial to the teardrop by even a centimeter, that can be a serious problem.”

For more information:
Barrack R. Neurovascular injury: Avoiding catastrophe. #36. Presented at 22nd Annual Current Concepts in Joint Replacement Winter 2005 Meeting. Dec. 14-17, 2005. Orlando, Fla.