The initiation of failure in cemented femoral components of hip arthroplasties

We studied 16 femora retrieved at post-mortem from symptomless patients who had a satisfactory cemented total hip arthroplasty from two weeks to 17 years earlier, with the aim of delineating the initial mechanisms involved in loosening. Only one specimen showed radiographic evidence of loosening; the other 15 were stable to mechanical testing at 17.0 Nm of torque. In all 16 specimens, the cement-bone interface was intact with little fibrous tissue formation. By contrast, separation at the cement-prosthesis interface and fractures in the cement mantle were frequent. The most common early feature was debonding of the cement from the metal, seen at the proximal and distal ends of the prosthesis. Specimens which had been in place for longer also showed circumferential fractures in the cement, near the cement-metal interface, and radial fractures extending from this interface into the cement and sometimes to the bony interface. The most extensive cement fractures appeared to have started at or near sharp corners in the metal, or where the cement mantle was thin or incomplete. Fractures were also related to voids in the cement. The time relationship in this series suggested that long-term failure of the fixation of cemented femoral components was primarily mechanical, starting with debonding at the interface between the cement and the prosthesis, and continuing as slowly developing fractures in the cement mantle.     

Metallic debris in femoral endosteolysis in failed cemented total hip arthroplasties.

A prospective study was undertaken to quantitate metallic and cement debris in 12 consecutive patients with femoral endosteolysis (FE) and aseptic loosening of a cemented total hip arthroplasty. The mean interval between primary and revision surgery was 9.6 years. The average time to onset of FE was 8.9 years. There were four stems each of cobalt-chromium (Co-Cr), stainless steel (SS), and titanium alloy. At revision, tissue was retrieved from FE, the femoral bone-cement pseudomembrane, and the joint pseudocapsule. Histology of these tissues was studied using light and polarized microscopy. Metal and barium levels were measured by atomic absorption spectrophotometry. A histiocytic reaction and particulate cement debris were seen in every case. Polyethylene wear debris was noted in 11 of 12 cases (92%), and metallic debris in four cases (33%). Detectable metal levels were found in the FE in all cases. Metal levels were on average 2.5 times higher in FE than in femoral pseudomembrane, and 4.2 times higher than in joint pseudocapsule. This difference was statistically significant for the Co-Cr and SS groups. Barium levels in areas of FE were on average 1.7 times and 42.4 times higher than in femoral pseudomembrane and joint pseudocapsule, respectively. The difference seen between the FE and the joint pseudocapsule tissue was significant for all three alloy groups. The authors' data demonstrated higher metal and barium levels in FE than in the other tissue sites. Polyethylene and cement debris were noted in nearly every case. Cement, polyethylene, and metallic particulate wear debris may contribute to the pathogenesis and progression of FE.     

Radiological factors influencing femoral and acetabular failure in cemented Charnley total hip arthroplasties

We have made a retrospective review of 185 cemented Charnley total hip arthroplasties performed between 1970 and 1974 to determine the relationships between radiological variables and failure of the femoral and acetabular components. We measured the acetabular wear, the orientation of the cup, the thickness and consistency of acetabular and femoral cement mantles, radiolucency and femoral alignment. The mean follow-up was for 11.7 years. Femoral loosening was demonstrable radiologically in 15 hips (8.1%), ten (5.4%) of which were revised during the period of follow-up. Only when the first postoperative radiograph showed a thin cement mantle in Gruen zone 5 was there a significant association with failure of the femoral component. There were 12 loose acetabular components (6.5%), nine (4.8%) of which were revised. When the initial radiograph after operation showed radiolucency in DeLee and Charnley zone 1, the incidence of acetabular loosening was 28.21%. If such radiolucency was not present, the incidence of acetabular loosening was only 0.69%. Our findings emphasise the importance of careful cementing.     

Bone lysis in well-fixed cemented femoral components

We have reviewed 25 cases of focal femoral osteolysis in radiographically stable, cemented femoral implants. In three hips retrieved at post-mortem from two patients, we have been able to make a detailed biomechanical and histological analysis. The interval between arthroplasty and the appearance of focal osteolysis on clinical radiographs ranged from 40 to 168 months, and in over 70% of the cases this did not appear until after five or more years. Few had significant pain and there was no relation to age, sex or original diagnosis. The most common site for osteolysis were Gruen zones 2 and 3 on the anteroposterior radiograph and zones 5 and 6 on the lateral radiograph. In 15 cases (60%), the area of osteolysis corresponded to either a defect in the cement mantle or an area of very thin cement. The rate of progression of these lesions was variable, but to date only one has progressed to gross loosening of the femoral component. The back-scatter scanning electron microscopic examination of serial sections and biomechanical testing of the post-mortem specimens demonstrated focal cement fracture around implants that were otherwise rigidly fixed. In eight cases from which tissue was available, histology showed a histiocytic reaction with evidence of particulate polymethylmethacrylate. We consider that this local fragmentation was the stimulus for local osteolysis in an otherwise stable cemented femoral component.     

Radiographic analysis of a bone plug in 275 primary cemented total hip arthroplasties

Various designs of cement restrictors for total hip arthroplasty have shown a variability in resistance to intramedullary pressure and migration. The performance of a conical bone plug was studied in 275 cemented total hip arthroplasties with a followup between 5 and 19 years. In a radiographic analysis the relation between the plug position and the cement mantle quality was investigated. The results were compared to the performance of other cement restrictors as reported in the literature. Good to excellent cement mantles were observed in 80% of the femurs. A significant correlation between the stability of the plug and the quality of the cement mantle was found. Forty-nine percent of the plugs were within 1 to 3 centimetres of the Exeter stem hollow centraliser. We also demonstrated that bone plugs performed almost always better than polyethylene or gelatine restrictors reported in other studies.     

Ten-year results of cemented Weller-type total hip arthroplasties

The first 100 consecutive cemented Weller-type total hip arthroplasties carried out between 1976 and 1977 were reexamined. Clinical analysis of 43 implants with more than 10 years follow-up showed that results were excellent in 21 patients (49%), good in 13 (30%), fair in 7 (16%) and poor in 2 (5%). Radiographic analysis revealed 33 (87%) stable femoral and 31 (81%) stable acetabular components. Statistical survivorship analysis of all 100 implants produced a probability of reoperation of 6.2%, a probability of radiographic implant loosening of 28.2% and a probability of radiographic loosening with clinical symptoms of 7.6%. The definition of failure should be radiographic loosening of the prosthesis with clinical symptoms because this evaluation seems to have the best clinical relevance. Concerning the fact that the cement fixation was not performed to today's standard, the results after more than 10 years with this total hip system (Weller long stem) are sufficient.     

Revision total hip replacement using cemented collarless double-taper femoral components

We investigated 219 revisions of total hip replacement (THR) in 211 patients using a collarless double-taper cemented femoral component. The mean age of the patients was 72 years (30 to 90). The 137 long and 82 standard length stems were analysed separately. The mean follow-up was six years (2 to 18), and no patient was lost to follow-up. Survival of the long stems to re-revision for aseptic loosening at nine years was 98% (95% confidence interval (CI) 94 to 100), and for the standard stems was 93% (95% CI 85 to 100). At five years, one long stem was definitely loose radiologically and one standard stem was probably loose. Pre-operative femoral bone deficiency did not influence the results for the long stems, and corrective femoral osteotomy was avoided, as were significant subsidence, major stress shielding and persistent thigh pain. Because of these reliable results, cemented long collarless double-taper femoral components are recommended for routine revision THR in older patients.     

Cup containment and orientation in cemented total hip arthroplasties

We reviewed the radiographs of 864 Charnley and STH (Zimmer) cemented total hip arthroplasties with a mean follow-up of seven years (maximum 16 years). Survivorship analysis was used to assess the correlation between radiographic performance and the bony containment or the coronal orientation of the acetabular cup. The cup orientation and containment were interrelated; all vertically oriented cups were completely contained, whereas 25% of more horizontal cups were only partially contained. Completely contained cups had significantly lower incidences of complete cement-bone radiolucency (p = 0.02) and of wear (p = 0.09). Vertically oriented cups had a lower incidence of continuous radiolucency than neutrally oriented cups, but this was not statistically significant (p = 0.25). Our results confirm the importance of complete bony containment, and also indicate that it is better to accept vertical orientation and obtain full bony coverage than to have a more horizontal orientation with partial containment.     

Long-term clinical results of cemented revision of primary cemented total hip arthroplasties

Seventy-six patients who had undergone revision of a cemented total hip replacement were reviewed with an average follow-up of almost ten years. The average age at primary total hip replacement (PTHR) was 63.3 years. The average time between primary total hip replacement and revision was 62.5 months. Revision surgery was performed without using special techniques such as acetabulum reconstruction or femoral bone grafting. We evaluated patients pre- and postoperatively using the Merle d'Aubigné-Postel(M d'A) hip score. Clinically we observed an improvement of the hip score after total hip revision, particularly regarding pain. Thirty hips required a second, and six a third revision. If re-revision is used as an end-point, our results are unsatisfactory, as we had a cumulative failure rate of 54% after 12 years. This is mainly due to not using special techniques adapted to revision situations.     

In vivo surface wear mechanisms of femoral components of cemented total hip arthroplasties: the influence of wear mechanism on clinical outcome

The appearance and mechanism of femoral stem wear was studied in 172 retrieved femoral components, of which 74 stems had been stable in vivo. Macroscopic, microscopic, and nano-level scales of examination were used. Loss of stem surface in response to micromotion (wear) was found to affect 93% of stems. However, changes were frequently difficult to see with the naked eye, and in 19% of cases they would have been missed completely without the use of light microscopy. The surface finish of the prosthesis determined the mechanism of stem wear. Matte surfaces showed typical abrasive processes that also damage the cement, releasing particulate debris from the cement and metal surfaces. This may destabilize the stem within the cement. Polished stems showed a typical fretting appearance with retention of debris on the stem surface and without significant damage to the cement. These differences in wear mechanism between matte and polished stems have significant effects on stem function.     

Autopsy studies of the bone-cement interface in well-fixed cemented total hip arthroplasties

Although knowledge of the clinical status of the implant is important, only instrumented mechanical testing of retrieved specimens provides quantitative assessment of implant fixation. This measurement allows placement of the implant along a continuum of loosening and is the foundation for the interpretation of subsequent findings. Analysis of implants that have been proven to be well fixed by instrumented testing reveals significant differences in the initial events in the loosening of femoral and acetabular components. Although radiolucencies were observed around all of these well-fixed femoral and acetabular components, the histology (and therefore the etiology) of the radiolucency is different and variable on the two sides of the articulation. The majority of femoral radiolucencies appear to be due to age and stress-related remodeling while particulate-induced bone resorption plays an important role in acetabular radiolucencies. A finding common to both sides of the articulation in these stable components, however, was intimate contact of bone with cement without any interposed soft tissue even after 17.5 years of service. Primary incompatibility and/or failure of the cement was not identified as a factor in initiating either femoral or acetabular component loosening. These studies document the long-term compatibility of bone with cement in bulk form. Improvements in cemented femoral component fixation should focus on stem design and cementing technique. Long-term acetabular component fixation can be improved by reduction or elimination of polyethylene wear and optimization of the bone-implant interface.     

The relative cost of cemented and uncemented total hip arthroplasties

The use of uncemented femoral stems in primary total hip arthroplasty (THA) has been slow to develop in the UK because of the lack of encouraging published long-term follow-up data, the continued success of the cemented primary THA, and the perceived excessive relative cost of the uncemented THA. In this article, we argue that the total costs of 3 "proven" uncemented stems are comparable with commonly used cemented femoral components, when all necessary materials are taken into consideration. In addition, we will also discuss other potential benefits and drawbacks for considering the use of uncemented stems.     

松动人工髋关节周围组织中聚乙烯磨损颗粒观察

为探讨聚乙烯磨损及其与人工髋关节松动的关系,作者对６例因人工髋关节臼侧假体松动而行翻修术病例的假体周围软组织、软组织中聚乙烯碎屑及臼杯内表面进行了肉眼、偏光交易及扫描电镜观察,分析了聚乙烯内杯员颗粒的产生机制及其在假体周围纤维膜形成、假体松动发生过程中的意义。研究结果显示,假体松动时,在聚乙烯内杯磨损式中,夹有第三体粒（如骨块、骨水泥或金属碎屑）的二个负重面磨擦（三体磨损）占有主要地位。表现为表面     

骨水泥与非骨水泥股骨柄在初次全髋关节置换术后疗效的Meta分析

目的：系统评价骨水泥与非骨水泥股骨柄在初次全髋关节置换术后的疗效。方法计算机检索PubMed、EMBASE、OVID、Highwire、SpringerLink、ScienceDirect、Cochrane 图书馆、中国知网、中国生物医学文献数据库文献及手工检索相关文献,收集有关骨水泥与非骨水泥股骨柄在初次全髋关节置换术的随机对照试验,根据考克兰协作组织标准评价纳入试验质量,用Revman5.2软件进行Meta分析。结果纳入11篇文献,共1651例患者,骨水泥髋801例、非骨水泥髋850例。 Meta分析结果示：不限年龄和随访年限,术后翻修率骨水泥固定和非骨水泥固定差异无统计学意义[ OR＝3.20,95％CI （0.72,14.22）, P＞0.05],5年以内随访术后翻修率两种固定方式差异无统计学意义[OR＝0.41,95％CI （0.15,1.16）, P＞0.05],5年以上随访术后翻修率骨水泥固定较非水泥固定股骨柄高,差异有统计学意义[OR＝5.92,95％CI （2.68,13.07）, P＜0.01],术后大腿痛发生率骨水泥固定较非骨水泥固定低,差异有统计学意义[OR＝0.51,95％CI （0.28,0.94）, P＜0.05],术后Harris评分[MD ＝0.6,95％CI （-0.79,1.99）, P＞0.05],松动率[OR ＝1.31,95％CI （0.27,6.30）, P＞0.05]、骨折发生率[OR＝0.91,95％CI （0.3,2.7）, P＞0.05]、感染率[OR＝2.46,95％CI （0.7,8.58）, P＞0.05]、异位骨化发生率[OR＝0.91,95％CI （0.63,1.33）, P＞0.05]和脱位率[OR＝3.11,95％CI （0.6,16.10）, P＞0.05]二者差异无统计学差异。结论骨水泥与非骨水泥固定股骨柄在初次全髋关节置换术后均有满意的效果,非骨水泥固定股骨柄5年以上稳定性较骨水泥好,但术后大腿痛的发生率较骨水泥固定柄高。     

Pre-heating of components in cemented total hip arthroplasty

Fatigue fractures which originate at stress-concentrating voids located at the implant-cement interface are a potential cause of septic loosening of cemented femoral components. Heating of the component to 44 degrees C is known to reduce the porosity of the cement-prosthesis interface. The temperature of the cement-bone interface was recorded intra-operatively as 32.3 degrees C. A simulated femoral model was devised to study the effect of heating of the component on the implant-cement interface. Heating of the implant and vacuum mixing have a synergistic effect on the porosity of the implant-cement interface, and heating also reverses the gradients of microhardness in the mantle. Heating of the implant also reduces porosity at the interface depending on the temperature. A minimum difference in temperature between the implant and the bone of 3 degrees C was required to produce this effect. The optimal difference was 7 degrees C, representing a balance between maximal reduction of porosity and an increased risk of thermal injury. Using contemporary cementing techniques, heating the implant to 40 degrees C is recommended to produce an optimum effect.     

Comparison of cemented and cementless total hip arthroplasty in patients with bilateral hip arthroplasties

A consecutive series of 36 patients underwent primary cemented total hip arthroplasty followed by primary cementless total hip arthroplasty of the contralateral hip. Clinical pain scores between the cementless and cemented hips were not different. Subjectively, patients either had no preference or preferred the cementless side. Comparison of results in the same patient eliminates variability introduced by differences in sex, weight, comorbidities, bone quality, and activity level. Control of these factors permits more meaningful comparison of the type of fixation.