Advances in the processing, sterilization, and crosslinking of ultra-high molecular weight polyethylene for total joint arthroplasty.

Recent studies have generated considerable information that reveals substantial support for major change in the understanding of total hip arthroplasty and its current state. Although some of these observations appear unrelated at first glance, they can be drawn together to support the thesis that osteolysis is the dominant problem in total hip arthroplasty. These observations are as follows: (1) Five-year followup data are required for a minimum assessment of a new concept in total hip design and material because osteolysis is uncommon before that time. (2) Excellent fixation can be achieved on the femoral side with good cementing and good cementless techniques. Thus, femoral component loosening is less of an issue currently. (3) Many acetabular components become loose because of the ingress of particulate debris that leads to linear bone loss at the interface with the pelvis, a process that is biologically akin to the more florid forms of osteolysis. Thus, much acetabular component loosening represents a form of osteolysis. (4) Many cementless femoral reconstructions have developed a high incidence of femoral osteolysis. (5) Many cementless sockets have developed a high incidence of pelvic osteolysis. Taken in conjunction, these observations suggest that periprosthetic osteolysis is the leading problem in contemporary total hip replacement.

The problem is osteolysis

http://www.ibmc.up.pt/projectos/FJMonteiro/Researchers/AHDeAza/08_AHdeAza_Biomaterials_23%203%20937-945%202002.pdf

Crack growth resistance of alumina, zirconia and zirconia toughened alumina ceramics for joint prostheses.

Today, aseptic loosening is the most common cause of revision of major arthroplasties. Aseptic loosening accounts for more than two-thirds of hip revisions and almost one-half of knee revisions in Sweden. Several theories on the cause of aseptic loosening have been proposed. Most of these theories, however, are based on empiric observations, experimental animal models or anecdotal cases. In this review, we discuss the most common theories concerning aseptic loosening. It emerges from this review that aseptic loosening has a multifactorial etiology and cannot be explained by a single theory.

https://www.tandfonline.com/doi/pdf/10.1080/17453670610045902

Aseptic loosening, not only a question of wear: a review of different theories.

Background: The purpose of this retrospective study was to report the results, after a minimum of 18.5 years of follow-up, in a consecutive series of total hip arthroplasties performed with an alumina-on-alumina combination.

Methods: One hundred and eighteen consecutive total hip arthroplasties were performed in 106 patients between 1979 and 1980. The prostheses combined a 32-mm alumina head and an all-alumina socket. Both components were cemented in eighty-five hips, both components were implanted without cement in twenty-nine, and only the stem was cemented in four. The mean age of the patients at the time of the index arthroplasty was 62.2 years (range, thirty-two to eighty-nine years).

Results: At the 18.5 to 20.5-year follow-up evaluation, forty-five patients (fifty-one hips) were alive and had not had a revision, twenty-five patients (twenty-five hips) had undergone revision of one or both components, twenty-seven patients (thirty hips) had died, and nine patients (twelve hips) had been lost to follow-up. The mean Merle d’Aubigne hip score (and standard deviation) was 16.2 ± 1.8 points at the latest follow-up evaluation. The rate of survival at twenty years, with revision for any reason as the end-point, was 85.6% for the cementless cups compared with 61.2% for the cemented cups and 84.9% for the cementless stems compared with 87.3% for the cemented stems. Wear of the prosthetic components was undetectable on plain radiographs. Periprosthetic cystic or scalloped lesions requiring the use of allograft bone during revision were present in three of the twenty-five revised hips. In addition, seven hips had moderate acetabular osteolysis treated with a 4-mm-larger cup. No fracture of the alumina socket or head was recorded. The mean acetabular wear rate in this series was <0.025 mm/yr.

Conclusion: With the alumina-on-alumina total hip arthroplasty, minimal wear rates and limited osteolysis can be expected up to twenty years after the operation, provided that sound acetabular component fixation is obtained.

Alumina-on-alumina total hip arthroplasty: a minimum 18.5-year follow-up study.

Late aseptic loosening of cemented acetabular components is governed by the progressive, three-dimensional resorption of the bone immediately adjacent to the cement mantle. This process begins circumferentially at the intraarticular margin and progresses toward the dome of the implant. Evidence of bone resorption at the cement-bone interface was present even in the most well-fixed implants before the appearance of lucent lines on standard roentgenographic views. The mechanical stability of the implant was determined by the three-dimensional extent of bone resorption and membrane formation at the cement-bone interface. The leading edge of the membrane is a transition zone from regions of membrane interposition between the cement and the bone to regions of intimate cement-bone contact. Histologic analysis revealed that progressive bone resorption is fueled by small particles of high density polyethylene (HDP) migrating along the cement-bone interface and bone resorption occurs as a result of the macrophage inflammatory response to the particulate HDP. Evidence in support of a mechanical basis for failure of fixation was lacking. The mechanism of late aseptic loosening of a cemented acetabular component is therefore biologic in nature, not mechanical. This is exactly opposite to the mechanism of loosening on the femoral side of a cemented total hip replacement, which is mechanical in nature.

Kabo Jm

Papers

The mechanism of loosening of cemented acetabular components in total hip arthroplasty : analysis of specimens retrieved at autopsy