Periprosthetic Loss of Bone Mineral Density After Cementless Porous Tantalum and Cemented Total Knee Arthroplasties: A Mean of 11-Year Concise Follow-Up of a Previous Report

BackgroundOur previous study showed that the decrease in relative change of bone mineral density (BMD) in the lateral part of the tibia was significantly less in the group treated with the cementless porous tantalum component than in the group treated with the cemented cobalt-chromium tibial component up to 5 years after the operation. However, the long-term benefits of porous tantalum tibial component on BMD have not been proven. The aim of this study was to update a matched cohort study at a minimum of 6 years' follow-up period.MethodsTwenty patients with a porous tantalum tibial component and 18 patients with a cemented cobalt-chromium-alloy tibial component were investigated for more than 6 years in the present study. The mean follow-up period was 11.4 years. Dual X-ray absorptiometry was used to measure the BMD.ResultsThe decrease in relative change of BMD in the lateral aspect of the tibia was significantly less with the porous tantalum tibial component than that with the cemented cobalt-chromium tibial component up to 5 years. However, at the final follow-up period, no significant difference was observed in the relative change of BMD between the 2 groups. No prosthetic migration or periprosthetic fracture was detected in either group.ConclusionThe present study is one of the studies with the longest follow-up period on BMD after total knee arthroplasty. Porous tantalum tibial component did not have a favorable effect on the BMD of the proximal tibia after total knee arthroplasty for long term.     

Mechanical Stability of Novel Highly Porous Metal Acetabular Components in Revision Total Hip Arthroplasty

Highly porous metal acetabular components have emerged for revision hip arthroplasty. However, superior mechanical stability over traditional cementless components has not been demonstrated. Three different cementless acetabular components, including 2 highly porous tantalum designs, were inserted into hemipelvis specimens with a superolateral defect. Mechanical testing was performed to failure using a servohydraulic testing machine. The porous tantalum designs exhibited superior stability over the traditional cementless implant (P < .05). There was no difference in mechanical stability between the rigid modular tantalum shell and the more flexible revision tantalum shell (P > .46). In acetabular revision, highly porous tantalum acetabular components provide superior mechanical stability. However, these results suggest that improved frictional resistance is a more important design feature over implant flexibility with this particular implant.     

颗粒骨打压植骨结合多孔非骨水泥臼杯在AAOSⅢ型髋臼大面积骨缺损翻修中的应用

背景：颗粒骨打压植骨是修复髋臼骨缺损的重要方法,对大面积髋臼骨缺损采用打压植骨结合非骨水泥臼杯重建仍然存在争议。目的：探讨同种异体颗粒骨打压植骨结合多孔非骨水泥臼杯髋臼重建术修复AAOSⅢ型髋臼大面积骨缺损的方法及近期疗效。方法：随访2005年6月至2010年4月收治的28例（28髋）AA0SⅢ型髋臼大面积骨缺损患者。男18例,女10例,年龄34-74岁,平均53．8岁。髋关节置换术后感染醐翻修9例,骨溶解及髋臼假体松动翻修19例。本组AAOSⅢ型髋臼骨缺损面积大,术中见髋臼骨缺损超过髋臼关节面的50％。全部采用同种异体颗粒骨打压植骨结合多孔非骨水泥臼杯髋臼重建术。术后定期随访,观察臼杯有无松动、植入骨与宿主骨整合情况,髋关节功能评分采用Harris评分。结果：28例均获得随访,术后随访时间为13-70个月,平均43个月。Harris评分由术前32-48分,平均41分,提高至末次随访时86-95分,平均90分。28例髋臼假体均固定牢固无松动征象,植入骨逐渐与宿主骨整合,无感染及坐骨神经损伤。结论：在获得臼杯初始稳定固定的情况下,大面积颗粒骨打压植骨（臼杯与宿主骨接触面积〈50％）结合多孔非骨水泥臼杯髋臼重建术修复AAOSⅢ型髋臼大面积骨缺损近期疗效较好,远期疗效尚待进一步随访。     

Cancellous and cortical bone mineral density around an elastic press-fit socket in total hip arthroplasty

Background and purpose — The acetabular component has remained the weakest link in hip arthroplasty for achievement of long-term survival. One of the possible explanatory factors for acetabular failure has been acetabular stress shielding. For this, we investigated the effects of a cementless elastic socket on acetabular bone mineral density (BMD).

Patients and methods — During 2008–2009, we performed a single-center prospective cohort trial on 25 patients (mean age 64 (SD 4), 18 females) in whom we implanted a cementless elastic press-fit socket. Using quantitative BMD measurements on CT, we determined the change in BMD surrounding the acetabular component over a 2-year follow-up period.

Results — We found a statistically significant decrease in cancellous BMD (?14% to ?35%) and a stable level of cortical BMD (5% to ?5%) surrounding the elastic press-fit cup during the follow-up period. The main decrease was seen during the first 6 months after implantation. During the second year, cancellous BMD showed a further decrease in the medial and lower acetabular regions.

Interpretation — We found no evidence that an elastic press-fit socket would prevent acetabular stress shielding during a 2-year follow-up.     

Cementless total hip arthroplasty with femoral head bone grafting for hip dysplasia

Femoral head bone grafting was required to augment acetabular bone stock in 19 cases of hip dysplasia treated with cementless total hip arthroplasty. All acetabular grafts provided mechanical support for the cementless acetabular component. Radiographic evaluation of the fixation of the femoral components at an average of 3 years after surgery revealed an optimum appearance in all cases. All porous-coated acetabular components remained stable, but only one of six (17%) nonporous threaded acetabular components maintained stability. One threaded acetabular component has been revised for symptomatic loosening. Acetabular graft healing was suspected in 18 of 19 cases (95%). Significant graft resorption was observed only in the cases with unstable threaded acetabular components. The clinical scores were high. Cementless total hip arthroplasty with structural acetabular grafting and porous acetabular components appears to produce satisfactory short-term results.     

Matched-pair analysis of cemented and cementless acetabular reconstruction in primary total hip arthroplasty

In a matched-pair study of primary total hip arthroplasty, 45 all-polyethylene cemented acetabular components were compared with 45 cementless, hemispheric, titanium acetabular components. At 9 to 12 years, 1 of the cemented acetabular components was revised for aseptic loosening, and 14 (31%) were radiographically loose. Nine (20%) cemented acetabular components had pelvic osteolysis. In the cementless acetabular component group, 2 well-fixed components were revised. No components were radiographically loose, and 3 (7%) had pelvic osteolysis. Thirty-eight (97%) of the patients in each group were satisfied with the surgery. The clinical results of the cemented and cementless components were excellent. The cementless components had less loosening (P <.001) than the cemented components.     

Pelvic Periprosthetic Bone Mineral Density Measurement Around Cemented vs Cementless Acetabular Prostheses

We compared the short-term precision of pelvic periprosthetic bone mineral density (BMD) measurement around a cementless acetabular prosthesis (n = 29) vs a cemented all-polyethylene acetabular prosthesis (n = 19) in patients after total hip arthroplasty. Two dual-energy x-ray absorptiometry scans of the pelvis were made on the same day in each subject with subject repositioning between scans and analyzed independently with a 4-region of interest model. Precision was expressed as coefficient of variation (CV%). The measured BMD around the cemented prostheses was greater than the cementless prostheses p < 0.004, all analyses). The net CV for pelvic BMD measurements around the cementless prosthesis was 1.9% vs 3.6% around the cemented prosthesis (F-test p < 0.001). The CVs of individual regions of interest was between 2.8% and 4.8% for the cementless prosthesis vs 4.4% to 8.4% for the cemented prosthesis (F-test; p < 0.05, all comparisons). Prospective studies would require 57 subjects to detect a 10% change in net pelvic BMD around a cementless prosthesis and 122 to detect a similar change around a cemented prosthesis with 90% power and with an alpha error of 0.05. In conclusion, the precision of pelvic BMD measurements made around cementless prostheses are better vs those for cemented prostheses. Dual-energy x-ray absorptiometry studies of cemented prosthesis require approximately double the number of subjects vs cementless prostheses to achieve a similar level of power.     

Highly Porous Tantalum Acetabular Components Without Ancillary Screws Have Similar Migration to Porous Titanium Acetabular Components With Screws at 2 Years: A Randomized Controlled Trial

BackgroundIt is proposed that highly porous coatings on acetabular components, such as a porous tantalum coating, provide adequate fixation without ancillary screw fixation in primary total hip arthroplasty (THA). However, tantalum acetabular components have been associated with higher rates of revision than other uncemented components in national registries. The aim of this randomized controlled trial is to determine whether the early migration of a solid-backed tantalum acetabular component was no greater than that of a titanium acetabular component with ancillary screw fixation that has proven good clinical results.MethodsSixty-six patients aged 40 to 64 years, with osteoarthritis and Charnley grade A or B activity grade and who underwent primary THA, were recruited into the trial. Patients were randomized intraoperatively to receive either the tantalum or titanium acetabular component. All patients received the same cemented polished tapered femoral stem, 28-mm cobalt-chromium femoral head, and highly cross-linked polyethylene liner. Acetabular component migration was measured using radiostereometric analysis at 4-6 days postoperatively and at 6 weeks, 3 months, 1 and 2 years following THA.ResultsThe mean proximal migration at 2 years for the tantalum cohort was 0.17 mm (95% confidence interval, 0.09-0.24) which was no greater than that of the titanium cohort which was 0.19 mm (0.07-0.32). Harris hip scores and functional activity scores were similar between groups.ConclusionThese results demonstrate that early stability can be achieved without ancillary screw fixation through the use of a highly porous high friction coating on a solid-backed modular acetabular component.Level of EvidenceLevel I.     

Cementless acetabular fixation in total hip arthroplasty using polyglycolide-lactide screws: an in vivo canine study

Bone ingrowth into cementless acetabular components was evaluated in a canine total hip arthroplasty model, comparing components initially stabilized with polyglycolide-lactide screws with those initially stabilized with titanium screws. The acetabular shell was anchored with 2 polyglycolide-lactide screws in 16 dogs and with 2 titanium screws in 12 dogs. The dogs were followed and sacrificed at 7 weeks, 14 weeks, 10 months, or 15 months. Histomorphometric analysis of bone ingrowth into the weight-bearing dome of the acetabular shell was conducted. No difference was detected in mean bone ingrowth into the acetabular shell comparing the 2 screw groups. The results of this study do not support a significant advantage to the use of biodegradable screws for the initial stabilization of cementless acetabular components in canine total hip arthroplasty.     

Second-generation cementless total hip arthroplasty. Eight to eleven-year results.

BACKGROUND: Second-generation cementless femoral components were designed to provide more reliable ingrowth and to limit distal osteolysis by incorporating circumferential proximal ingrowth surfaces. We examined the eight to eleven-year results of total hip arthroplasty with a cementless, anatomically designed femoral component and a cementless hemispheric acetabular component. METHODS: Ninety-two consecutive primary total hip arthroplasties with implantation of a femoral component with a circumferential proximal porous coating (Anatomic Hip) and a cementless hemispheric porous-coated acetabular component (Harris-Galante II) were performed in eighty-five patients. These patients were prospectively followed clinically and radiographically. Six patients (seven hips) died and five patients (seven hips) were lost to follow-up, leaving seventy-four patients (seventy-eight hips) who had been followed for a mean of ten years (range, eight to eleven years). The mean age at the time of the arthroplasty was fifty-two years. RESULTS: The mean preoperative Harris hip score of 51 points improved to 94 points at the time of final follow-up; 86% of the hips had a good or excellent result. Thigh pain was reported as mild to severe after seven hip arthroplasties. No femoral component was revised for any reason, and none were loose radiographically at the time of the last follow-up. Two hips underwent acetabular revision (one because of dislocation and one because of loosening). Kaplan-Meier survivorship analysis was performed with revision or loosening of any component as the end point. The ten-year survival rate was 96.4% +/- 2.1% for the total hip prosthesis, 100% for the femoral component, and 96.4% +/- 2.1% for the acetabular component. Radiolucencies adjacent to the nonporous portion of the femoral component were seen in sixty-eight (93%) of the -seventy-three hips with complete radiographic follow-up. Femoral osteolysis proximal to the lesser trochanter was noted in four hips (5%). No osteolysis was identified distal to the lesser trochanter. Periacetabular osteolysis was identified in twelve hips (16%). Five patients underwent exchange of the acetabular liner because of polyethylene wear. CONCLUSIONS: This second-generation cementless, anatomically designed femoral component provided excellent clinical and radiographic results with a 100% survival rate at ten years. The circumferential porous coating of this implant improved ingrowth and prevented distal osteolysis at a mean of ten years after the arthroplasty.     

Comparison of Bone Removed During Total Hip Arthroplasty With a Resurfacing or Conventional Femoral Component : A Cadaveric Study

We sought to examine the amount of bone removed during total hip arthroplasty with a resurfacing femoral component, compared to with a conventional, stemmed femoral component, by using 6 male and 4 female cadaveric pelves with attached bilateral proximal femora. Using randomized assignment and order, a total hip arthroplasty with a resurfacing femoral implant was performed on one side, and total hip arthroplasty with a cementless, stemmed femoral implant was performed on the contralateral side. The relationship between native femoral head diameter and the implanted acetabular socket was on average within 2 mm for both procedures. No significant difference was observed in the amount of acetabular bone removed (9.8 g for hip resurfacing vs 8.8 g). However, a resurfacing component resulted in approximated 3 × less bone removal from the femur (25.8 g vs 75.1 g). This study shows that the preservation of femoral bone with a resurfacing femoral component does not result in an increased removal of acetabular bone when compared to the use of a conventional, stemmed femoral component.     

Cementless acetabular revision for aseptic failure of cemented hip arthroplasty

This study is a 5- to 11-year retrospective followup of 40 hips in 33 patients with cementless acetabular revision for aseptic failure of a cemented total hip arthroplasty. A porous coated, Harris-Galante acetabular component was used in all revisions. Thirty-eight of the 40 hips received acetabular bone grafting at revision. The mean Harris Hip Score improved from 51 points just before the index cementless revision to 87 points at the most recent followup. Twenty-nine of 40 (73%) hips were classified as having a good or excellent result. Radiolucencies were observed in seven of the 40 (18%) hips at the most recent followup, but none of these radiolucencies were complete or progressive. Five of the 40 (13%) hips were rated as failures and required repeat revision. Two (5%) of these failures were caused by aseptic loosening, with both hips having severe acetabular bone damage at the time of the index revision. This failure rate for aseptic loosening was less than that reported for cemented acetabular revision, thereby confirming the efficacy of cementless acetabular components in revision hip surgery in the intermediate term.     

A quantitative in vitro assessment of fit and screw fixation on the stability of a cementless hemispherical acetabular component

This investigation quantifies in vitro the effect of component fit, as well as the effect of adjuvant screw fixation, on the initial stability of cementless hemispherical titanium acetabular total hip arthroplasty components and assesses apposition of the acetabular components to bone. Six, fresh human hemipelvi (3 matched pairs) were harvested at autopsy. Titanium alloy acetabular components with a porous surface of commercially pure titanium fiber mesh (Harris Galante Porous acetabular components, Zimmer, Warsaw, IN) were used for implantation. Initially, each acetabulum was underreamed to achieve a 2 mm press-fit with the acetabular component. Pressuresensitive film had been placed along the dome and medial wall at the bone-implant interface to assess the completeness of seating. After the implant was impacted into the acetabular cavity, relative motion between the implant and bone was measured during simulated single leg stance. Adjuvant fixation of the implant was then obtained with the insertion of four 6.5 mm cancellous screws. High-contrast roentgenograms of the specimens in multiple views were obtained after initial cup insertion and again after screw insertion. The stability of each implant under load was measured with four, three, two, one, and no screws in place. Further reaming of the bone was done to create a 1 mm press-fit. The sequence was then repeated. Further reaming was done to create an exact-fit and the sequence was repeated again. Under these conditions, 1 mm press-fit with or without screws provided the optimum combination of fit and stability. With the 2 mm press-fit, incomplete seating of the implant was found in every case, resulting in gaps between the dome of the implant and the bone. This reduced the area of the porous surface in contact with bone, and resulted in an increase in micromotion with the dome of the implant. The addition of supplemental screws did not significantly enhance stability of the implant under press-fit conditions. Exact-fit reaming with the use of two, three, or four screws yielded acetabular component stability at the dome equal to 1 mm press-fit, but at the rim the acetabular component was less stable than 1 mm press-fit. The optimum combination might be a press-fit introduction of the acetabular component, and the advantage of screws must be weighed against possible particulate debris and vascular damage.     

Clinical applications of Trabecular Metal

Trabecular Metal (porous tantalum) offers a viable solution to several challenges in orthopedic reconstructive surgery, including monoblock acetabular cups, avascular necrosis intervention devices, and total hip reconstruction in situations of massive femoral bone loss. Porous tantalum approaches the ideal biomaterial: it is porous, strong, flexible, and biocompatible. For use in components for total hip arthroplasty, porous tantalum provides a substitute for lost bone, immediate bone loading, bone ingrowth, and soft-tissue attachment. It can be machine-shaped into custom designs in situations of massive bone loss.     

金属骨小梁杯在髋臼翻修中的应用及随访

目的探讨设计新颖的组配式骨小梁金属杯在髋臼翻修中的早期效果。方法自2006年4月至2007年2月期间对24例髋臼假体翻修患者使用了骨小梁金属杯,共计25髋,女13例,男11例,平均年龄73．5岁。每个患者术前及术后6个月,1、2、3年,作X线拍片影像学随访,以及进行Harris髋关节（HHS）评分和（UCLA）活动评分。所有患者随访的临床及影像学资料完整。结果术后随访30—40个月（平均36个月）。Harris评分由翻修前的5～57分（平均33．6分）提高到术后的69～95分（平均92．4分）（t=3．943,P〈0．01）,UCLA评分由翻修前的2～5分（平均3．7）提高到术后的7～9分（平均8．6分）（t=3．910,P〈0．01）。影像学随访未见假体移位、下沉等不稳和松动迹象,骨小梁金属杯周围骨质向内长人。结论对于全髋置换手术（THA）中,初次用骨水泥固定的髋臼杯失败的患者,若无骨缺损,翻修时使用骨小梁金属杯可以获得良好的早期效果。     

Treatment of High-Grade Acetabular Defects: Do Porous Titanium Cups Provide Better Stability Than Traditional Titanium Cups When Combined With an Augment?

Background

Revision total hip arthroplasty frequently faces challenges associated with deficient bone stock. Porous metal implants were developed to meet the challenge, but require rapid osseointegration for ultimate success. This study aims to assess relative motion as an indicator for primary stability and osseointegration of two different titanium cups each combined with a titanium augment.

Treatment options for chronic pelvic discontinuity

Chronic pelvic discontinuity is a distinct and unique challenge seen during revision total hip arthroplasty (THA) in which the superior ilium is separated from the inferior ischiopubic segment through the acetabulum, rendering the anterior and posterior columns discontinuous. The operative management of acetabular bone loss in revision THA is one of the most difficult challenges today. Common treatment options include cage reconstruction with bulk acetabular allograft, custom triflange acetabular component, a cup-cage construct, jumbo acetabular cup with porous metal augments, or acetabular distraction with a porous tantalum shell with or without modular porous augments.     

人工全髋关节置换术中髋臼骨缺损的重建

目的 探讨人工全髋关节置换术中各种髋臼骨缺损的特点与重建方法.方法 1998年5月至2008年8月对获得随访的行初次全髋关节置换或翻修的37例(37髋)髋臼缺损患者的临床资料进行回顾性分析,依据AAOS分型采取颗粒性或结构性植骨、生物或骨水泥髋臼假体以及钛网或加强环置入等方法对骨缺损进行重建.术前Harris评分(42±8)分.术后采用Harris评分判断髋关节的功能改善情况,复查X线片了解移植骨愈合及假体在位情况.结果 AAOS Ⅰ型9例,Ⅱ型13例,Ⅲ型15例.颗粒性植骨24例,结构性植骨6例,混合性植骨7例;生物型假体21例,骨水泥型假体16例.平均随访时间53.7个月.术后Harris评分(87±5)分,与术前比较,差异具有统计学意义(P<0.05).移植骨在最后一次复查时均已愈合或基本愈合.结论 对于AAOS Ⅰ型、Ⅱ型等简单的髋臼骨缺损,颗粒性或结构性植骨结合生物型髋臼假体就可以获得很好的初始稳定性,而对于AAOSⅢ型等较严重的缺损,则应行结构性植骨或附加钛网及加强环等重建髋臼.其短、中期疗效是令人满意的.     

Acetabular fracture associated with cementless acetabular component insertion: a report of 13 cases.

Acetabular fracture during insertion of a cementless acetabular component occurred in 13 patients. The preoperative diagnosis was osteoarthritis in 6 patients, rheumatoid arthritis in 2 patients, avascular necrosis in 3 patients, hip fracture nonunion in 1 patient, and developmental dysplasia of the hip in 1 patient. Several different components were used; however, the acetabulum was underreamed by 1 to 3 mm in all cases. The acetabular fracture was identified in 9 of 13 cases intraoperatively. The fracture was identified on postoperative radiographs for the other 4 cases. Fractures were treated by a variety of means, including the addition of augmentation screws in or around the cup, use of autograft bone at the fracture site, modified postoperative weight-bearing status, and immobilization. In 2 cases, the socket needed to be revised after it progressively migrated and failed. One patient had cup migration, and another had a radiolucent line about the cup but was not symptomatic enough to require revision. In 3 of these 4 cases, the fracture was not identified intraoperatively. Underreaming of the acetabulum and use of an oversized acetabular component has been recommended to improve the initial stability of the acetabular component during total hip arthroplasty. Impaction of an oversized component requires bone to undergo plastic deformation if the cup is to be fully seated. Theoretically, this technique provides improved component stability with enhanced osseous ingrowth into the cup. The 13 cases reported in this study demonstrate that acetabular fracture is a complication that may occur in association with uncemented hip arthroplasty, particularly if oversized components are used. The importance of recognizing acetabular fractures intraoperatively and the need to institute appropriate treatment to ensure a stable acetabular component is emphasized. In patients with osteoporotic bone, line-to-line reaming with use of a cementless acetabular component or insertion of a cemented socket may be considered to avoid this significant complication.