Abstract
Introduction:
Subsidence of cementless femoral stems in total hip arthroplasty (THA) has been associated with poor initial fixation and subsequent risk of aspectic loosening. There is limited literature on how subsidence of cementless, proximally porous coated, tapered wedge femoral stems impacts the patient clinically. The aim of our study was to assess whether subsidence with these stems is associated with a decline in clinical function.
Method:
A review of a prospectively collected database of THAs performed by a single surgeon at one institution using two cementless, tapered wedge stem designs from January 2006 to June 2010 was performed. Radiographic analysis using Picture Archiving and Communications System (PACS) was used to identify patients with greater than 1.5 mm of subsidence, and to document osseointegration. Preoperative and postoperative pain and Harris hip scores were recorded; and analyzed to identify if the clinical recovery pattern of the subsidence versus no subsidence groups differed. Protected weight bearing was recommended to all patients with subsidence.
Results:
264 hips were reviewed clinically and radiographically at a mean follow-up of 29 months. 10 hips had subsidence greater than 1.5 mm at last follow up. There were 6 males and 3 females with a mean age of 62.1 years in the subsidence group. Subsidence was noted at the 6 week visits in all 10 patients. Mean Harris Hip scores and pain scores were significantly diminished at 6 weeks in the subsidence group (Mean 67.6) as compared to the none subsidence group (82.2) (Figure 1). The two groups had similar scores preoperatively, at 1 year and 2 years postoperatively. In the subsidence group 9 of 10 hips had no further progression of subsidence, and showed radiographic evidence of osseointegration. Persistent thigh pain was noted in 2 patients in the subsidence group. One underwent successful femoral revision for failure of osseointegration and the other continues to have pain with radiographic signs of osseointegration. All 254 hips in the control group had evidence of osseointegration.
Conclusion:
Subsidence of tapered wedge stems which occurs at the 6 week mark may be associated with a transient decline in clinical function. Early modification in the rehabilitation regimen may help improve clinical outcome scores in these patients.
