Postmortem analysis of consecutively retrieved asymmetric porous-coated tibial components

The objective of this investigation was to conduct a postmortem analysis of 8 porous-coated asymmetric tibial components to measure the extent of radiolucencies and bone ingrowth. With the use of radiographic, electron microscope, and histologic analysis techniques, a quantitative postmortem study of 8 consecutively retrieved porous-coated tibial components was conducted. Time in situ averaged 47 ± 36 months. The components were secured with 4 pegs and 2 screws. Autograft bone chips were applied to the resected tibia during implantation. Contact radiographs of an average of 8 3-mm sections from each implant revealed that 73% ± 17% of the porous coating had no apparent radiolucencies present between the host bone and porous coating for the series. Backscattered electron imaging showed that the bone ingrowth averaged 6% ± 2%. Histologic analysis was unable to demonstrate any adverse cellular response. The analysis suggested that this asymmetric implant design is stable and biocompatible and has potential for long-term clinical durability.     

Uncemented acetabular components: Histologic analysis of retrieved hydroxyapatite-coated and porous implants

Histologic sections of five hydroxyapatite-coated acetabular components retrieved at autopsy (2 dual geometry and 3 threaded cup designs) were analyzed, and the extent and pattern of bone apposition were compared with that of an uncoated, porous (beaded) dual geometry acetabular cup that had been removed for repeated dislocations. The results show hydroxyapatite and bone apposition most prominent in areas of likely load transmission, primarily around the peripheral rim of the dualgeometry cups and at the peaks of the threads of the screw cups. Hydroxyapatite and bone may have been removed by remodeling from the grooves between the threads. Although no significant wear debris was identified, the screw holes were incompletely covered by bone. The dual-geometry designs generally showed somewhat more bone apposition than the threaded cups, but all implants demonstrated less bone than might have been predicted from radiographs.     

Bone ingrowth into a porous-coated total shoulder component retrieved postmortem

An uncemented porous-coated humeral component, which functioned in vivo for over 2 1/2 years, was retrieved postmortem and examined histologically. Radiographs of the specimen revealed close approximation to the endosteal cortex medially and laterally. Apposition was limited or absent anteriorly and posteriorly. The overall extent of bone ingrowth was approximately 11% of the available pore volume with over 95% of ingrowth occurring in the medial and lateral quadrants. Bone ingrowth was limited anteriorly and posteriorly to regions in which spot welds were identified radiographically. There were no loose beads or coating failure observed.     

Analysis of retrieved uncemented porous-coated acetabular components in patients with and without pelvic osteolysis

Retrieved polyethylene liners and femoral heads from a consecutive series of revision components of one design were examined. All patients had Long-Term Stable Fixation (OsteoTechnology International, Timonium, Md) total hip arthroplasties (THAs) implanted between 1987 and 1992. The retrieved femoral heads and liners from patients with osteolysis were compared to those without osteolysis. Patients with osteolysis had significantly thinner polyethylene (5.1 mm versus 7.4 mm, P<.01 ) and a higher linear wear rate (0.5 mm/y versus 0.3 mm/y, P=.05). The average femoral head surface roughness also was significantly greater in patients with osteolysis (67 nm versus 35 nm, P<.05). Patients with osteolysis had more total volumetric wear, total linear wear, and volumetric wear rate compared to patients without osteolysis. Age, obesity index, time in situ, and cup inclination were not different between the two groups. Excessive polyethylene wear, probably accelerated by surface roughness of the femoral heads, was associated with pelvic osteolysis in these patients.     

植入体内多孔涂层假体界面研究

目的：研究翻修取出的假体柄多孔涂层内骨长入情况，评定Ｘ线平片判断假体稳定的应用价值。方法假体编号后经丙酮脱水固定，低温塑料包埋，切割出３ｍｍ厚片及１００μｍ以下薄片。厚片用软Ｘ射线高清晰度胶片显微拍照，薄片甲苯胺蓝染色后光镜下观察。结果显微镜摄片显示：临床Ｘ线片认为骨长入稳定型假体有的部分涂层内无骨长入，有的则是纤维稳定型。光镜发现骨未长入部位有纤维组织间隔，骨长入比例大小在各个假体不尽相同。有的     

Inflammatory response in retrieved noncemented porous-coated implants

One hundred forty-six noncemented porous-coated hip and knee implants retrieved from 97 patients were evaluated histologically for the type, amount, and anatomic distribution of tissue ingrowth. The degree of inflammatory cell infiltrate present was also evaluated and the predominant cell type was identified. An inflammatory infiltrate was present in the components of 21 of 97 patients (22%). In 16 of the 21 cases the infiltrate was lymphocytes and histiocytes with a minor population of plasma cells. One of the remaining five cases had a predominately plasma cell reaction, and the other four had significant populations of plasma cells. Vascular proliferation was observed in nine of the 21 cases. Bone ingrowth was present in ten of the 21 cases. A 38% incidence of removal for persistent pain was present in cases with an inflammatory infiltrate. Seventeen of 87 patients (20%) with cobalt-chromium devices and four of ten patients (40%) with titanium devices were identified as having an inflammatory infiltrate. The origin of the inflammatory infiltrate is unclear. All patients with inflammatory infiltrates had noninfected implants, which were not loose roentgenographically or clinically at the time of removal. Hypersensitivity and allergic responses to metal ions may produce such infiltrates. It is impossible, however, in the present study to definitively determine the etiology of the infiltrates.     

Histologic, biochemical, and ion analysis of tissue and fluids retrieved during total hip arthroplasty

Large amounts of metal and polyethylene debris and high ion readings are found in capsule and fibrous membranes of both loose titanium and cobalt-chromium stems. Prostaglandin E2, interleukin-1, and collagenase levels are elevated when compared to control values with collagenase having the highest and most consistent elevations. Synovial fluid and blood ion readings were elevated in loose cemented and cementless stems made from both materials. Blood ion readings were not elevated in fixed stems. Fixed stems had much less particulate debris in soft tissues. The data showed that failure of most metal hip stems was initially due to a mechanical cause, with high debris and ion counts occurring secondarily in capsule and fibrous membranes. Particulate debris and high ion readings are primarily a focal problem contained by the periprosthetic fibrous connective-tissue encapsulation within the femoral canal and joint capsules. No systemic problems were manifest in any of the patients examined and followed in this study.     

Histologic analysis of a retrieved hydroxyapatite-coated femoral prosthesis.

A hydroxyapatite-coated hip hemi-prosthesis was retrieved from a 98-year-old osteoporotic woman 12 weeks after implantation. Histologic analysis revealed bone and fibrous tissue almost evenly distributed around the surface of the implant circumference. Quantitative histologic analysis showed that 48% of the hydroxyapatite surface was covered by bone. Fibrous tissue covered 30% of the prosthetic surface, and 20% of the surface had no tissue coverage. Scanning electron microscopy showed direct contact without any clear boundary between the newly formed bone and the hydroxyapatite ceramic.     

Retrieval analysis of porous-coated components for total knee arthroplasty. A report of two cases

Retrieval analysis of two total knee replacements incorporating porous-coated components for biologic fixation was performed. The significant finding in a 63-year-old woman was fracture of the porous-coated metal backing of the tibial component, secondary to aseptic loosening. The significant findings at the time of revision surgery in an 82-year-old woman were nonuniform bone ingrowth (primarily around fixation pegs) and fracture of metal beads from the metal backing of the patellar component.     

A quantitative study of bone and soft tissues in cementless porous-coated acetabular components retrieved at autopsy

The authors examined 11 cementless acetabular components of one design retrieved at autopsy and made observations concerning tissue ingrowth and local tissue reaction, radiographic-histologic correlation, and the distribution of particulate wear debris. The cups were hemispherical in design with a commercially pure titanium fibermetal porous coating. All of the prostheses were implanted with screws. The implants were in place for an average of 41 months (range, 5 weeks to 75 months). Ten of the cups had bone ingrowth, with the average volume fraction being 12.1±8.2%. There were no differences in the amount of bone ingrowth when the component was partitioned into nine anatomic regions. However, there was more bone adjacent to screw holes through which screws were inserted compared with empty screw holes. As the number of radiolucent zones increased on the clinical radiographs less bone ingrowth was observed histologically. The amount of metal debris in holes with screws and holes without screws was similar. In the longest term cases, polyethylene debris was noted within empty screw holes, but no granulomatous reactions or osteolytic processes were observed.     

Mechanical stability of porous-coated acetabular components in total hip arthroplasty.

Five different porous-coated acetabular prosthetic configurations underwent in vitro testing to assess mechanical stability in embalmed cadaver hemipelves: Harris Galante II cup with three cancellous screws, Biomet Universal cup, Whiteside cup with peripheral pegs, Whiteside cup with two cancellous screws, and plain Whiteside cup. Following implantation in a neutral frame, cyclic load testing was done using 33 specimens at 100-kg load for 100,000 cycles using an MTS machine (MTS Systems Corp., Minneapolis, MN). Subsequently, static load-to-failure testing was done in all specimens. Subsidence and micromovement were determined for each specimen using linear variable differential transformers. With cyclic testing, overall cup subsidence revealed a significant increase, from 500 to 100,000 cycles. Overall cup micromovement revealed a significant decrease, and all cup groups demonstrated less than 125 microns (.125 mm) of average mean micromotion at the completion of cyclic testing. The best cup configuration was a 1-mm, oversized, press-fit cup using two 6.5 cancellous screws for additional fixation, which revealed an average mean of 60 microns (.06 mm) of micromovement. Static load testing revealed unacceptable micromovement over 150 microns (.150 mm) in most cups with 300-kg loads.     

Revision of failed total hip arthroplasties with uncemented porous-coated anatomic components

This series represents a relatively short follow-up study of patients who were treated with cementless revisions for failed previous arthroplasties. Many of these cases required extensive bone grafting to the acetabulum and often to the femur. Despite extensive bone grafting, there were no infections. There has been but a single graft resorption after a hemiarthroplasty conversion for recurrent dislocations. To date, all other grafts have remained intact and have shown signs of union. Even though the acetabular components were not anchored in place by adjuvant fixation devices such as screws, migration of the acetabular component has not been a problem. All other components have remained stable, and the supporting grafts appear to have united successfully. Femoral revision has been more technically demanding because the largest stem possible should be placed within the femur to prevent subsidence and provide good stabilization in the proximal metaphyseal area. These short-term results compared favorably with similar series of cemented revisions. Patient selection is important and there are definite candidates for cemented femoral components, particularly with first-time revisions in elderly patients. If there is massive osteolysis in the femur, cemented revision is probably not indicated. Long stems should not be used unless necessary. Cortical defects at the tip of the standard stem obviously would require bypassing the stress riser with a longer stem. If, however, the cortex is intact in this region and stability can be achieved, revision should be carried out with a relatively short stem. Techniques for cementless revision are demanding, but with meticulous attention to detail and technical perfection, the method has a most encouraging prognosis. Longer follow-up evaluations will be necessary to make an accurate evaluation of graft incorporation, but short-term results are encouraging to both surgeons and patients.     

High placement of porous-coated acetabular components in complex total hip arthroplasty

The authors retrospectively evaluated the results of 56 hips in 51 patients with an acetabular deficiency who had a total hip arthroplasty with a porous-coated, cementless acetabular component implanted at a high hip center. Forty-nine cases were revisions and seven were primary operations. The mean height of the hip center was 43 mm above the interteardrop line compared to 14 mm for the anatomic center, threefold higher than normal. In contrast, the mean horizontal locus was reduced compared to normal (33 vs 37 mm for the anatomic center). Sixteen acetabular components were small (46–48 mm o.d.) and eight were miniature (40–44 mm o.d.). Despite superior placement of the acetabular component, 32 limbs were lengthened by the procedure. The mean preoperative Harris hip score was 51 (range, 28–93). At a mean follow-up period of 40 months (range, 24–64 months), the mean Harris hip score was 86 (range, 36–100). In 23 hips no radiolucent lines were present at the interface of the bone to the porous mesh, and 33 hips had a thin (0.5 mm), nonprogressive radiolucent line in one or more zones. No acetabular component had migrated and no problems occurred with the screws. Four hips (3 revisions and 1 primary operation) had a complete radiolucent line on one oblique view of the acetabulum. No acetabular component has been revised for loosening. These short-term data suggest that under circumstances in which the acetabulum cannot be reconstructed at the anatomic level without a major structural bone-graft, superior placement of the porous-coated acetabular component against viable host-bone at a higher level than normal may be an acceptable alternative.     

广泛微孔涂层非骨水泥假体在股骨翻修的应用

目的报告采用广泛微孔涂层非骨水泥股骨假体对失败的骨水泥固定股骨假体翻修的近期效果。方法1998年至2003年,对20例骨水泥固定型人工髋关节置换后无菌性松动的股骨假体采用广泛微孔涂层假体进行翻修。翻修前使用国产假体18例,进口假体2例;全髋关节置换14例,人工股骨头置换6例。所有假体均为骨水泥固定,早期骨水泥技术固定18例,第二代骨水泥技术固定2例。原始疾病为股骨头无菌性坏死14例,股骨颈骨折6例。从初次关节置换到翻修手术的时间最短5年,最长17年,平均11.5年。其中4例患者为再次翻修。根据Paprosky分型,Ⅰ型3髋,Ⅱ型6髋,ⅢA型11髋。翻修假体,AML(DePuy)5髋,Solution(DePuy)7髋,Full-coated(Zimmer)6髋,Perfecta延长柄(WrightMed)2髋。翻修时患者平均年龄64岁(41～77岁),术后平均随访时间40个月(18～60个月)。结果Harris评分从术前平均34分改善为术后平均85分。根据Engh骨长入分级标准评定,术后X线表现骨性固定17例,稳定性纤维固定3例。无一例因松动需要再翻修的病例,骨皮质密度和厚度均明显增加。结论广泛微孔涂层假体在股骨干骺端和股骨髓腔同时存在缺损时,可以在相对正常的股骨远端髓腔获得轴向及抗旋转初始稳定,为骨长入和生物学固定创造条件。     

A radiographic and histological analysis of 17 retrieved ultrahigh-molecular-weight polyethylene porous-coated femoral stems

Radiographic and histological and evaluation for failure of 17 retrieved implants was performed. The implants consisted of a titanium stem with a 3-mm ultrahigh-molecular-weight polyethylene coating and an outer 1.5-mm ultrahigh-molecular-weight polyethylene fiber layer. Particular attention was paid to osteolysis, subsidence, debris, and foreign body reaction. Radiographic analysis showed subsidence (14 of 17), osteolytic lesions (9 of 14), and unique posterior medial exostoses (8 of 14). Histological analysis showed no significant evidence of acrylic bone cement either as debris or reactive tissue. There was an intense foreign body reaction directly related to the amount and size of polyethylene debris.     

Loss of hydroxyapatite coating on retrieved,total hip components

The goal of this study was to examine the early retrievals of hydroxyapatite-(HA) coated hip prostheses to assess evidence of osteoconductivity, resorption of HA, and the integrity of the HA/implant bond. Six retrieved HA-coated hip prostheses (3 femoral hip stems, 3 acetabular cups) were analyzed for the amount of bone ongrowth or ingrowth of the HA-coated surface and the extent to which the coating was still present after in vivo service. The examination of these six HA-coated prostheses indicates that HA appeared to be osteoconductive. There was evidence of debonding of HA from the smooth-surfaced femoral prosthesis, although that may have been a result of the extraction process. The five plasma-spray surfaced, HA-coated prostheses showed evidence of considerable loss of the HA coating at the time of receipt in the authors' laboratory, although it is was not possible to determine the cause of the loss of coating.