Review Question - QID 4866

This patient is presenting with foot drop after a THA for hip dysplasia (Crowe 4). The most appropriate treatment at this stage would be providing her with an ankle foot orthosis (AFO) for mobility.

Sciatic nerve injury after THA is an uncommon and difficult situation to manage. Patients with DDH that have undergone a large limb-lengthening procedure are at a greater risk due to the significant stretch of the sciatic nerve. Intra-operative procedures that have been shown to prevent this outcome include good pre-operative planning, limb lengthening <3 cm, subtrochanteric osteotomy, intra-operative wake-up test, and downsizing implant components if presenting with deficits peri-operatively. An ankle-foot orthosis may be used for foot drop when surgery is not warranted or during neurologic recovery.

Prahinski et al. reviewed the Bridle transfer for paresis of the anterior and lateral compartment musculature. Indications for the procedure include no neurological recovery for at least 18 months after injury or 18 months after the most recent attempt at exploration or repair of the nerve. Electrodiagnostic changes must indicate permanent damage. In addition, there must be good passive range of motion, with at least 90° of dorsiflexion.

Edwards et al. reported on twenty-three peroneal and sciatic nerve palsies that occurred in patients following total hip arthroplasty. They showed that peroneal nerve palsy occurred with an average lengthening of 2.7 cm (1.9 cm-3.7 cm) in comparison with 4.4 cm (4.0 cm-5.1 cm) for sciatic nerve palsies.

Figure A and B show pre- and post-operative images of a patient with severe hip dysplasia treated with primary total hip arthroplasty.

Incorrect Answers:
Answer 1: MRI is often not useful due to the signal artifact from the implants around the hip.
Answer 2: There would be no indication for revision surgery of well positioned implants after 4 weeks.
Answer 4: Tendon transfer procedures would be considered in chronic paresis situations.
Answer 5: Neurology consult would be appropriate, but not the most appropriate next treatment option. The primary objective is to help the patient regain function. Neurological consult would be important if concerned of some underlying neurological disease process. Referral would be most appropriate after 3-6 months if no return of function.