MORE THAN JUST LOOSENING AND INFECTION: PERIPROSTHETIC STRESS FRACTURES.

Abstract

It is well appreciated that thigh pain following recent arthroplasty surgery is likely to be due to prosthetic loosening or infection. Both these sequelae can lead to periprosthetic fracture presenting complex challenges to even experienced surgeons.

Revision arthroplasty patients are prone to both fatigue and insufficiency fractures as they may have reduced bone stock after previous surgery and reduced bone density secondary to medical and immobility reasons. The post operative painfree condition will frequently permit early load bearing leading to a relatively rapid increase in activity and load bearing.

Fatigue fractures occur in bone of normal quality subject to abnormal cyclical overloading, leading to resorption and eventual failure, before adequate time has passed to permit adaptive remodelling. Insufficiency fractures occur when normal physiological loads are applied to bone of abnormal quality.

Surprisingly few periprosthetic stress fractures are reported in the literature but a series notes lateral tensile stress fractures associated with varus prosthetic alignment. These all occurred near the tip of the prosthesis.

The case of an unusual Gruen Zone 2, Vancouver B1 stress fracture, 9 months following revision arthroplasty is reported. Initially loosening was suspected due to the development of load bearing thigh pain. Plain radiography revealed the development of a dreaded black line, consistent with a stress fracture. Bone scintigraphy revealed the typical appearance of a stress fracture in the absence of loosening or infection.

The unusual location of this stress fracture allowed consideration of conservative non weight bearing management which lead to the alleviation of symptoms rather than further revision surgery.

This report illustrates this unusual stress fracture and highlights the importance of careful loading practises to permit adequate remodelling following complex revision surgery.