The use of tantalum porous metal implants for Paprosky 3A and 3B defects

[Reconstruction of large acetabular defects using trabecular metal augments]

OBJECTIVE

Revision of cup and reconstruction of original center of rotation. High primary and secondary stability. Prevention of additional bone loss.

INDICATIONS

Osseous defects at the anterior-cranial, cranial and posterior-cranial rim of acetabulum. Larger cavitary, medial or oval defects (Paprosky IIb-IIIb). Segmental defects (anterior column up to half of host bone, posterior column up to one third of host bone).

CONTRAINDICATIONS

Infection of total hip arthroplasty. Pelvic discontinuity (Paprosky IV).

SURGICAL TECHNIQUE

Exposure of acetabulum and detection of defects. Complete removal of soft tissue from acetabulum, reaming of sclerotic bone, if necessary. Adaptation of trial augments to close an oval defect to a round defect and to reach an uncontained defect, respectively. Adaptation of trial cup. In case of sufficient stability, fixation of final augment with two or three screws in cranial bone stock. The screws should be directed to iliosacral joint. Augmentation with allogenic bone chips is possible in the region of wedge and acetabulum as well. Sealing of rough augment surface with bone cement. Implantation of cup, fixation with screws. Application of insert.

POSTOPERATIVE MANAGEMENT

Depending on bone defects, full weight bearing is possible. In cases of severe bone defects, reduction of weight bearing to 20 kg for 6 weeks is recommended. Postoperative physiotherapy is possible in most cases.

RESULTS

Between 2005 and 2007, 38 patients with acetabular defects type IIIa und IIIb according to Paprosky underwent reconstruction using the TMT system (Trabecular Metal Technology). After 25 months, a significant functional improvement was seen in all patients. The Merle d'Aubigné Score increased from 6 points preoperatively to 13 points postoperatively, the Harris Hip Score from 29 to 78 points. Two revisions were necessary because of loosening or migration of the cup.

Massive acetabular bone loss: Limits of trabecular metal cages

Massive acetabular bone loss (more than 50% of the acetabular area) can result in insufficient native bone for stable fixation and long-term bone ingrowth of conventional porous cups. The development of trabecular metal cages with osteoconductive properties may allow a more biological and versatile approach that will help restore bone loss, thus reducing the frequency of implant failure in the short-to-medium term. We report a case of massive bone loss affecting the dome of the acetabulum and the ilium, which was treated with a trabecular metal cage and particulate allograft. Although the trabecular metal components had no intrinsic stability, they did enhance osseointegration and incorporation of a non-impacted particulate graft, thus preventing failure of the reconstruction. The minimum 50% contact area between the native bone and the cup required for osseointegration with the use of porous cups may not hold for new trabecular metal cups, thus reducing the need for antiprotrusio cages. The osteoconductive properties of trabecular metal enhanced allograft incorportation and iliac bone rebuilding without the need to fill the defect with multiple wedges nor protect the reconstruction with an antiprotrusio cage.

Long-term results for minor column allografts in revision hip arthroplasty

BACKGROUND

While acetabular structural allografts provide an important alternative for reconstructions, concerns remain with long-term graft resorption, collapse, and failure. Midterm studies of minor column (shelf) allograft suggest reasonable survival but long-term survival is unknown.

QUESTIONS/PURPOSES

We therefore assessed long-term graft/cup survivorship, functional scores, radiographic resorption, and complications associated with minor column allograft.

METHODS

We retrospectively reviewed 74 patients (85 hips) with a mean age of 54 years (range, 28-83 years) undergoing acetabular cup revision using a minor column allograft. A minor column allograft was used in uncontained acetabular bone defects sized between 30% and 50% of the acetabulum. Graft failure was considered to occur when the graft required revision with another graft, metal augment, reconstruction cage, or excision arthroplasty. The minimum followup was 5 years (mean, 16 years; range, 5.3-25 years).

RESULTS

Twenty-three patients (27 hips) had rerevision for all causes at a mean time to rerevision of 6.9 years (range, 0.1-23). Fifteen grafts failed at a mean time-to-rerevision of 6.1 years (range, 0.5-23.2). The 15- and 20-year Kaplan-Meier survivorships were 61% and 55% for cups and 78% for grafts with rerevision for all causes as end point. With rerevision for aseptic loosening as end point, survivorships were 67% and 61% for cups and 81% for grafts. The mean modified Harris hip scores were 41 (range, 20-60) preoperatively, 73 (range, 40-95) at 1 year postoperatively and 73 (range, 26-93) at last followup.

CONCLUSION

The data may provide a long-term benchmark by which future treatments for Type III defects can be measured.

Porous metal augments: big hopes for big holes

The majority of acetabular defects can be reconstructed with a hemispherical acetabular component alone. However, severe bone loss encountered at the time of revision acetabular surgery can result in compromised initial fixation leading to component micromotion, failure of bone ingrowth, and mechanical failure. Porous acetabular augments offer a potential solution to enhance initial component fixation while maximizing the area for biologic ingrowth. Premanufactured metal augments can be placed independent of the acetabular component. This feature provides surgeons the flexibility to place the hemispherical acetabular component in the optimal orientation at the anatomic hip center. The augment is initially secured to the hemipelvis with multiple screws before it is then secured to the hemispherical acetabular component with the use of polymethylmethacrylate bone cement. The modularity of the augments effectively allows a custom implant to be designed intraoperatively. Porous acetabular augments offer the potential advantages of a nonresorbable material that can be inserted without extensive soft tissue stripping. Additionally, these metal augments do not carry the risk of disease transmission associated with bulk structural allograft and are manufactured in a variety of shapes and sizes. The early clinical and radiographic results of porous acetabular augments are promising, yet there remains a paucity of long-term data.

Revision of failed total hip arthroplasty acetabular cups to porous tantalum components: a 5-year follow-up study

We reviewed 263 consecutive patients with failed acetabular components after total hip arthroplasty that were revised using porous tantalum acetabular components and augments when necessary. The mean follow-up was 73.6 months (range, 60-84 months). The improvement of mean Harris hip score, Western Ontario and McMaster Osteoarthritis Index, and University of California Los Angeles activity scales were statistically significant (P < .001). Subjective assessments showed that 87.3% of patients reported "improvement" and 85.9% were "very or fairly pleased" with the results. At the most recent follow-up, all acetabular components were radiographically stable and none required rerevision for loosening. The acetabular revision was considered successful in 87% of cases. From this study, we conclude that the acetabular component used was reliable in creating a durable composite without failure for a minimum of 5 years.

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.

Early results of a new highly porous modular acetabular cup in revision arthroplasty

BACKGROUND

The 'Tritanium' (Stryker, New Jersey, USA) highly porous acetabular cup is a new implant used in revision hip arthroplasty.

AIM

To determine the early results of this device.

METHODS

A prospective study of 43 acetabular component revisions performed using the implant between March 2007 and February 2008 was undertaken. All procedures were performed at a single centre with standard approach and follow up.

RESULTS

The mean age of patients at surgery was 66 years. Mean follow up was 18.2 months. AAOS classification revealed 17% Type 1, 49% Type 2, 24% Type 3 and 5% Type 4 defects at surgery. 5% had no bone defect. Bone graft was used to in 73% of patients. Mean Harris Hip Score improved from 68 pre-operatively to 86 at the last follow-up. Cup integration was seen in 95% of patients by 6 weeks. One patient with pelvic discontinuity had symptomatic aseptic loosening which was revised.

CONCLUSION

The 'Tritanium'acetabular cup has been successful in achieving rapid osseointegration with few complications. The management of pelvic discontinuity continues to be a challenge.

Tantalum components in difficult acetabular revisions

Although porous-coated hemispherical components are usually successful in acetabular revisions, the rate of failure is increased in hips with severe bone loss. Tantalum acetabular implants are characterized by higher friction, higher porosity, and greater osteoconductivity than titanium mesh or chrome-cobalt beads. We asked whether these components would provide stable short-term fixation without radiographic loosening in revisions at higher risk for failure. We prospectively followed 37 patients (39 hips) who had an acetabular revision with tantalum acetabular components. The minimum followup time was 2 years (mean, 3.3 years; range, 2-7 years). The acetabular defects were classified as Paprosky et al. Type 3 in 26, Type 2 in 11, and Type 1 in two hips. The mean postoperative Harris hip score was 86. Thirty-eight of the 39 (97%) tantalum components were radiographically well fixed. There was one mechanical failure at 6 months, rerevised with a larger tantalum component. Bone ingrowth was apparent in 38 hips and four hips had a radiolucent line. There were six other reoperations, three recurrent dislocations (constrained liners leaving the shell in place), two infections that seeded to the hip from elsewhere and treated with drainage, and one supracondylar femur fracture, but the tantalum component was left in place. Tantalum acetabular components provide stable fixation in difficult acetabular revisions.

LEVEL OF EVIDENCE

Level IV, case series. See Guidelines for Authors for a complete description of levels of evidence.

The management of severe acetabular bone defects in revision hip arthroplasty using modular porous metal components

We investigated the early results of modular porous metal components used in 23 acetabular reconstructions associated with major bone loss. The series included seven men and 15 women with a mean age of 67 years (38 to 81), who had undergone a mean of two previous revisions (1 to 7). Based on Paprosky's classification, there were 17 type 3A and six type 3B defects. Pelvic discontinuity was noted in one case. Augments were used in 21 hips to support the shell and an acetabular component-cage construct was implanted in one case. At a mean follow-up of 41 months (24 to 62), 22 components remained well fixed. Two patients required rerevision of the liners for prosthetic joint instability. Clinically, the mean Harris Hip Score improved from 43.0 pre-operatively (14 to 86) to 75.7 post-operatively (53 to 100). The mean pre-operative Merle d'Aubigné score was 8.2 (3 to 15) and improved to a mean of 13.7 (11 to 18) post-operatively. These short-term results suggest that modular porous metal components are a viable option in the reconstruction of Paprosky type 3 acetabular defects. More data are needed to determine whether the system yields greater long-term success than more traditional methods, such as reconstruction cages and structural allografts.

Photoactivated chemotherapy (PACT): the potential of excited-state d-block metals in medicine

The fields of phototherapy and of inorganic chemotherapy both have long histories. Inorganic photoactivated chemotherapy (PACT) offers both temporal and spatial control over drug activation and has remarkable potential for the treatment of cancer. Following photoexcitation, a number of different decay pathways (both photophysical and photochemical) are available to a metal complex. These pathways can result in radiative energy release, loss of ligands or transfer of energy to another species, such as triplet oxygen. We discuss the features which need to be considered when developing a metal-based anticancer drug, and the common mechanisms by which the current complexes are believed to operate. We then provide a comprehensive overview of PACT developments for complexes of the different d-block metals for the treatment of cancer, detailing the more established areas concerning Ti, V, Cr, Mn, Re, Fe, Ru, Os, Co, Rh, Pt, and Cu and also highlighting areas where there is potential for greater exploration. Nanoparticles (Ag, Au) and quantum dots (Cd) are also discussed for their photothermal destructive potential. We also discuss the potential held in particular by mixed-metal systems and Ru complexes.

[Acetabular defect reconstruction in revision surgery of the hip. Autologous, homologous or metal?]

The treatment of periprosthetic bone defects of the acetabulum is a therapeutic challenge in hip revision surgery. The aims are the biological reconstruction of osseous acetabular defects and the restoration of a load-bearing acetabular bone stock as well as restoring the physiological joint biomechanics and achieving primary and load-stable fixation of the revision graft in the vital pelvic bone. The biological reconstruction of the acetabular bone stock should include what is referred to as "down-grading" of the acetabular defect situation in case a repeat revision procedure becomes necessary.Nowadays, a large variety of grafts and reconstruction procedures are available for the reconstruction of acetabular defects. The choice of suitable materials (osseous or metallic) for the restoration of a load-bearing acetabular bone stock is currently the subject of controversial discussion.This article reviews the various options for the reconstruction of acetabular bone defects taking into consideration the current findings in the scientific literature.

Total hip arthroplasty revision in elderly people with cement and Burch-Schneider anti-protrusio cage

Total hip arthroplasty revision is increasingly becoming a common procedure, but the acetabular bone loss and the advanced age of the patients make revision procedures extremely complex and technically demanding. The aim of the present work is to examine the clinical and radiological results of the Burch-Schneider anti-protrusio cage (APC) implanted in revision hip arthroplasty with severe acetabular bone deficiency in elderly people. Between February 1994 and November 2005, a total of 60 revision operations of acetabular components were performed in 60 select patients (42 females and 18 males), using the Burch-Schneider APC. The indication for the Burch-Schneider APC use was massive pelvic bone loss with migration of the prosthesis cup and high-grade acetabular defects (type III or IV AAOS). The mean age at the time of surgery was 82 years (range 78-85 years). Polymethylmetacrylate cement (PMMA) was used to fill bony deficiencies in all the procedures. No graft was used. The average Harris Hip Score had improved from 28.2 preoperatively to 82.5 points at the time of follow-up. According to the classification of Gill et al., we have seen no Burch-Schneider cages definitely loose or probably. Only one acetabular component has been revised (for recurrent dislocation). Acetabular reconstruction with the use of cement and an acetabular support ring appears to have a useful role in the treatment of severe acetabular bony deficiency in elderly patients and may provide a definitive reconstruction.