The Journal of Bone and Joint Surgery

Image Quiz

Pain and Weakness Following Total Hip Arthroplasty¹
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Answer: Obturator nerve palsy due to fixation of an acetabular reinforcement ring with transacetabular screws

The radiograph shows that two of the four screws that had been used for fixation of the acetabular reinforcement ring had perforated the medial pelvic wall. The possibility that the obturator nerve has been damaged should be considered when a patient has pain as well as anesthesia or hypoesthesia in the medial aspect of the thigh, weakness of the adductors, and a gait disturbance. Electromyography may help to confirm the diagnosis. Although clinically evident lesions of the obturator nerve rarely have been reported after total hip arthroplasty, such lesions have occurred as a result of excessive retraction during the operation² or intrapelvic extrusion of cement through the anchoring holes of the acetabular component³. Anatomical studies have demonstrated that, in addition to the risk of serious hemorrhage due to lesions of the external iliac vein, tributaries of the internal iliac vein, and the obturator vessels, there also is the risk of an injury of the obturator nerve when screws in the anterior and central regions of the acetabulum⁴ or the anterior-inferior quadrant of the acetabulum⁵ perforate the inner pelvic cortex.

References

1. Fricker RM, Troeger H, Pfeiffer KM. Obturator nerve palsy due to fixation of an acetabular reinforcement ring with transacetabular screws. A case report. J Bone Joint Surg Am. 1997;79:444-6.
2. Weber ER, Daube JR, Coventry MB. Peripheral neuropathies associated with total hip arthroplasty. J Bone Joint Surg Am. 1976;58:66-9.
3. Siliski JM, Scott RD. Obturator-nerve palsy resulting from intrapelvic extrusion of cement during total hip replacement. Report of four cases. J Bone Joint Surg Am. 1985;67:1225-8.
4. Keating EM, Ritter MA, Faris PM. Structures at risk from medially placed acetabular screws. J Bone Joint Surg Am. 1990;72:509-11.
5. Wasielewski RC, Cooperstein LA, Kruger MP, Rubash HE. Acetabular anatomy and the transacetabular fixation of screws in total hip arthroplasty. J Bone Joint Surg Am. 1990;72:501-8.