Long-term Periprosthetic Remodeling in THA Shows Structural Preservation

Abstract

Although periprosthetic changes after THA have been well documented in short-term studies of less than 5 years, little is known about long-term changes. Long-term mineral changes must be evaluated against an unaffected limb control and for regional differences about a prosthesis. This study evaluated long-term periprosthetic remodeling using dual-energy xray absorptiometry in a prospective study of patients who had noncemented THAs with a modular titanium alloy proximal-loading prosthesis. In 15 randomly selected patients, bone mineral content was measured within 15 months of surgery and then at late mean followup of 13 years. In the affected femur, there was a major decrease in periprosthetic bone mineral content in Zones 1, 2, 6, and 7 (Gruen et al.) over the course of the study. The overall decrease in Zone 7 was 39% in bone mineral content. Estimates made after controlling for the contralateral unaffected femur indicate a major loss only in Zone 7 and preservation of mineral content in Zones 3, 4, and 5 of the proximal femur. The data suggest bone remodeling maintains the overall structural integrity of the upper femoral shaft.

Bone remodeling around stable uncemented titanium stems during the second decade after total hip arthroplasty: a DXA study at 12 and 17 years

“…This confirms previous observations that proximal loading cannot be normalized with the use of certain stem designs that aim for a proximal intertrochanteric fixation [10]. Moreover, this finding is consistent with the hypothesis based on previous studies suggesting that bone loss will be greatest in areas in which physiologic loading is reduced by the implant.…”

“…In the literature, data on changes in BMD after 10 years is only available for selected stems and small patient numbers [7][8][9][10]. To our knowledge, there is no study that investigates bony remodeling in periprosthetic BMD within the second decade after THA comparing potential differences between male and female patients.…”

Prospective 5-year study with 96 short curved Fitmore™ hip stems shows a high incidence of cortical hypertrophy with no clinical relevance

“…Stress-shielding of the proximal femur has been observed in a number of conventional cementless implants used in THA [5, 30, 39, 40]. Short femoral-neck implants were originally invented to reduce interference with the biomechanics of the proximal femur [12, 41].…”

Effect of bone type on clinical and radiographic outcomes of a proximally-coated cementless stem in primary total hip arthroplasties

“…At a mean follow‐up of 17 years, they noted no overall change in bone mineral density from initial DEXA scans taken 1‐year after surgery, although scattered regions of bone loss from stress shielding were noted, suggesting a decrease in remodeling at long‐term follow‐up. Stiehl evaluated the long‐term effects of periprosthetic remodeling in 15 patients who had a mean age of 61 years and underwent cementless THA. At a mean follow‐up of 13 years (range: 12–13 years), significant change in bone mineral density occurred only in Gruen zone 7 (near the calcar) after controlling for aging‐related resorption in the non‐operative leg.…”

“…The reported effects of patient variables, such as age, sex, body‐mass index (BMI), race, activity level, and nutritional status, are disparate . Implant design and stiffness determine the location and magnitude of stress transferred from implant to bone, while the surface coating, surgical approach, and fixation technique affect the strength of the bone‐implant interface and the degree of adjacent bone mineralization. Pre‐operative femoral bone quality was previously classified by Dorr et al into types A, B, and C based on the cortical thickness and proximal taper visualized on radiographs.…”