Ingrowth Surface Research Articles

Does the Ingrowth Surface Make a Difference? A Retrieval Study of 423 Cementless Acetabular Components

The effect of factors such as design, alloy and coating type on bony or fibrous tissue ingrowth was evaluated in a study of 423 retrieved cementless acetabular shells representing 16 shell designs. Small-beaded (250μm) porous coatings, either with or without hydroxyapatite (HA) coatings, proved to be the superior porous surface for bone ingrowth. Small-beaded shells that were Duofix coated had predominantly fibrous tissue ingrowth. In addition to bead size, alloy type and surface type have significant effect on bone ingrowth. In contrast, there is no significant association between bone ingrowth and time in situ, with most bone ingrowth occurring early. Although roughened, press-fit shells have acceptable clinical and Registry data, they showed some of the lowest ingrowth/ongrowth scores of all the shells tested.

The jumbo cup: Curtain calls and caveats

Use of an oversized “jumbo cup” is an effective technique for revision of most failed acetabular components. The jumbo cup is prepared with hemispherical reamers and provides a large porous ingrowth surface area in direct contact with the host bone. However, since the oversized cup is larger than the native acetabulum, the hip center can be raised, which may require use of a longer femoral head to maintain soft tissue tension and leg length. The anterior edge of the cup may also protrude through the anterior wall, which could be a cause of iliopsoas tendonitis resulting in groin pain.

Removal of a well-fixed femoral stem: Tour de force

Revision total hip arthroplasty often requires removal of a well-fixed femoral implant. Ease of implant removal is dependent on the stem design, geometry, and location/extent of porous ingrowth surface. In an effort to preserve the proximal femoral bone, many different surgical exposures and techniques are available. The intent of this review article is to briefly review the most popular techniques and their indications for use revision total hip, well-fixed femoral stem, femoral stem design.

Long-Term Outcome of a Metal-on-Polyethylene Cementless Hip Resurfacing

Due to the well-documented problems surrounding metal-on-metal bearings, the use of hip resurfacing has declined. Since the potential benefits of hip resurfacing remain desirable, it may be beneficial to investigate the long-term outcome of hip resurfacings using metal-on-polyethylene in the 1980’s. We report the long-term survivorship and modes of failure of a cementless metal-on-polyethylene resurfacing (n=178) with different porous ingrowth surfaces. While acetabular loosening was absent, a high incidence of femoral failures (femoral loosening=18.1%, osteolytic neck fracture=21%) occurred despite using the same ingrowth surface for both components. Ongoing developments using the lessons learned from these previous generation components and utilizing modern low wear materials, e.g., cross-linked polyethylene, may lead to improved implants for future hip resurfacings.

A Randomized Trial Comparing Acetabular Component Fixation of Two Porous Ingrowth Surfaces Using RSA

Several new porous ingrowth surfaces for acetabular component fixation have recently been developed. The purpose of this study was to compare the in vivo fixation achieved by two different porosity ingrowth surfaces using radiostereometric analysis (RSA). Sixty-two patients undergoing primary total hip arthroplasty (THA) were randomized to receive a cementless acetabular component with either a 61% high porosity asymmetric titanium porous surface (StikTite, Smith and Nephew, TN, USA) or a 45% low porosity sintered bead porous surface (Roughcoat, Smith and Nephew, TN, USA). RSA and clinical follow-up examinations were done post-operatively, 6-weeks, 3-months, 6-months, 1-year and 2-years. Both the high porosity StikTite and lower porosity Roughcoat surfaces provided excellent biologic fixation.

Cemented versus cementless fixation in total knee arthroplasty

The question of whether to use cemented or cement-less fixation for a total knee arthroplasty (TKA) is still debated. Discouraging preliminary results of cement-less TKAs have determined the worldwide use of cemented implants. However, with the development of biotechnologies and new biomaterials with high osteoconductive properties, biological fixation is now becoming an attractive option for improving the longevity of TKAs, especially in young patients. There is no evidence in the current literature to support the use of one method of fixation. The extensive clinical experience with cemented implants gathered over the years justifies their widespread use. New randomized clinical trials are necessary to compare cementless fixation based on the new ingrowth surfaces with standard cemented implants.

Ten-Year Outcome of Serum Metal Ion Levels After Primary Total Hip Arthroplasty

We previously reported on the metal ion concentrations of cobalt, chromium, and titanium that were found in the serum of patients three years after they had undergone primary total hip arthroplasty as compared with the concentrations found in the serum of control patients who did not have an implant. This study is a concise update on the serum metal levels found in a cohort of these patients ten years after the time of hip implantation. Of the original seventy-five subjects, metal ion levels were available for forty patients (53%). Ten patients (hybrid group) had received a hybrid total hip replacement that consisted of a modular cobalt-alloy femoral stem with a cobalt-alloy femoral head that had been inserted with cement and a titanium acetabular socket that had been inserted without cement. Nine patients (cobalt-chromium [CoCr] group) had received an implant with an extensively porous-coated modular cobalt-alloy femoral stem and femoral head along with a titanium acetabular socket; the femoral and acetabular components had each been inserted without cement. Eight patients (titanium group) had undergone insertion of a proximally porous-coated modular titanium-alloy femoral stem with a cobalt-alloy femoral head and a titanium acetabular socket; the femoral and acetabular components had each been inserted without cement. Thirteen patients (control group) from the original control group of patients who had not received an implant served as control subjects. Serum metal levels were measured with use of high-resolution sector field inductively coupled plasma mass spectrometry. The hybrid total hip arthroplasty group had mean cobalt levels that were 3.2 times higher at 120 months than they were at baseline, and the cobalt levels in that group were significantly higher than those in the titanium total hip arthroplasty group at thirty-six, sixty, eighty-four, ninety-six, and 120 months (p < 0.01). The hybrid group had mean chromium levels that were 3.9 times higher at 120 months than they were at baseline, and the CoCr total hip arthroplasty group had chromium levels that were 3.6 times higher at 120 months than they were at baseline. The serum titanium levels were higher in the titanium group at all follow-up time intervals as compared with the levels in all other groups, and the level in the titanium group at 120 months was eighteen times higher than it was at baseline (p < 0.01). Patients with well-functioning primary metal-on-polyethylene total hip replacements had elevated serum metal levels for as many as ten years postoperatively. Furthermore, metal release at the modular femoral head-neck junctions, rather than passive dissolution from porous ingrowth surfaces, was likely the dominant source of serum cobalt and chromium.

Custom Reconstruction of the Distal Part of the Humerus Using Compressive Osseointegration: A Report of Three Cases.

Reconstruction of the elbow with extensive humeral bone loss presents substantial challenges. Options include the use of allografts with standard elbow prostheses, modular devices, and custom implants1-4. Failure of allograft incorporation as well as implant failure can complicate attempts at such reconstruction. Prestressed osseointegration implants (Compress; Biomet, Warsaw, Indiana) have been successfully used to reconstruct massive segments of bone loss in the lower extremity5. To our knowledge, the use of such techniques in the upper extremity is limited to a single case report6. We describe three patients who underwent elbow arthroplasty for humeral reconstruction and who were managed with a Compress implant (Fig. 1). We received the approval of our Institutional Review Board for this case report. Fig. 1 This schematic shows the elements of the custom fabricated implants used in our three patients. The anchor plug is secured with five bicortical pins after bone preparation. The spindle, with its bone ingrowth surface, was inserted and tensioned. A force of 400 lb was chosen for all three implants, based on the manufacturer’s recommendation for a cortical thickness of 2.5 to 3.9 mm20. The humeral body and components of the distal part of the humerus were then sequentially impacted in place. A second humeral body component was used in Case 1 because of the extensive length that was required. Case 1. A sixty-five-year-old woman had incurred a comminuted fracture of the distal part of the humerus seven years prior to presentation. Previous treatment had included open reduction and internal fixation (ORIF) as well as subsequent total elbow arthroplasty (TEA) with triceps reconstruction (Table I). Two years after the TEA, the pain had returned. View this table: TABLE I History of Elbow Surgery and Year of Surgery On presentation to us, pain on the visual analog score (VAS) …

Implant Choices, Technique, and Results in Revision Acetabular Surgery: A Review

Acetabular reconstruction in revision total hip arthroplasty can successfully be achieved with hemispherical components featuring a porous or roughened ingrowth surface and options for placement of multiple screws. Most defects can be reconstructed with large hemispherical or "jumbo" cups. Achieving component stability and sufficient contact area on adequate host bone is mandatory. Defects with greater bony loss or compromised columns require either the use of modular augments combined with a hemispherical shell, reconstruction cages, structural allografts, or custom triflange acetabular components. This paper will detail the necessary pre-operative evaluation, the intra-operative details, and the reported results of these acetabular revisions.

Cementless Acetabular Fixation in Patients 50 Years and Younger at 10 to 18 Years of Follow-Up

The purpose of the study was to evaluate the 10- to 18-year follow-up of cementless acetabular fixation in patients 50 years and younger. We retrospectively reviewed a consecutive group of 118 patients (144 hips) in whom primary total hip arthroplasty had been performed by 2 surgeons using a cementless acetabular component. Two (1.4%) cementless acetabular components were revised because of aseptic loosening. Twenty-four hips (16.7%) were revised for any mechanical failure of the acetabular component mostly related to acetabular liner wear and osteolysis. The average linear wear rate was 0.19 mm per year, which was higher than our previous reports with cemented acetabular fixation. The fiber mesh ingrowth surface of the cementless acetabular component in this study was superior to cemented acetabular components in terms of fixation. However, the high rates of wear and osteolysis have led to poor overall acetabular component construct survivorship.

The Springback Characteristics of a Porous Tantalum Sheet-Metal

This study examines the elastic recovery (springback) of a porous tantalum foam after sheet forming operations. The foam and sheet-like form is applicable to bone ingrowth surfaces on orthopedic implants and is desirable due to its combination of high strength, low relative density, and excellent osteoconductive properties. Forming of the foam improves nestability during manufacture and is essential to have the material achieve the desired shape. Experimentally, bending about a single axis using a wiping die is studied by observing cracking and measuring springback. Die radius and clearance strongly affect the springback properties, while punch speed, embossing, die radius, and clearance all influence cracking. To study the effect of the foam microstructure, bending also is examined numerically. A horizontal hexagonal mesh comprised of beam elements is employed, which allows for the densification that occurs during forming. The flow strength of individual tantalum struts is directly measured in an atomic force microscope. The numerical results show that as the hexagonal cells are elongated along the sheet length, elastic springback decreases. By changing the material properties of the struts, the models can be modified for use with other open-cell metallic foams.

Acetabular Impaction Grafting in Total Hip Replacement

Acetabular impaction grafting has been shown to be very effective, but concerns regarding its suitability for larger defects have been highlighted. We report the use of this technique in a large cohort of patients, and address possible limitations of the technique. We investigated a consecutive group of 339 cases of impaction grafting of the cup with morcellised impacted allograft bone for survivorship and mechanisms for early failure. Kaplan Meier survival was 89.1% (95% CI 83.2 to 95.0%) at 5.8 years for revision for any reason, and 91.6% (95% CI 85.9 to 97.3%) for revision for aseptic loosening of the cup. Of the 15 cases revised for aseptic cup loosening, nine were large rim mesh reconstructions, two were fractured Kerboull-Postel plates, two were migrating cages, one was a medial wall mesh failure and one had been treated by impaction alone. In our series, results were disappointing where a large rim mesh or significant reconstruction was required. In light of these results, our technique has changed in that we now use predominantly larger chips of purely cancellous bone, 8-10 mm3 in size, to fill the cavity and larger diameter cups to better fill the aperture of the reconstructed acetabulum. In addition we now make greater use of i) implants made of a highly porous in-growth surface to constrain allograft chips and ii) bulk allografts combined with cages and morcellised chips in cases with very large segmental and cavitary defects.

Effects of Hydroxyapatite on Titanium Foam as a Bone Ingrowth Surface in Acetabular Shells: A Canine Study

This study investigated a highly porous titanium foam with and without a PeriApetite coating as an alternative surface for implant fixation. Twelve mongrel canines received staged total hip replacements under International Animal Care and Use Committee (IACUC) approval from our institution. Animals were randomly placed in three- or six-month groups for sacrifice. Seventeen total hips were available for evaluation. The area and depth of ingrowth was measured by SEM. At three months, PeriApetite Ti foam had 37% more depth and almost 10% more bone ingrowth. Both groups were found not to be different at the six-month mark with over 36% of ingrowth calculated on SEM. The results prove not only that titanium foam is a viable ingrowth surface but also that PA coating can enhance the time to bony incorporation.

Effect of Hydroxyapatite on Bone Integration in a Rabbit Tibial Defect Model

BackgroundThe aim of the present study was to prepare hydroxyapatite (HA) and then characterize its effect on bone integration in a rabbit tibial defect model. The bone formation with different designs of HA was compared and the bony integration of several graft materials was investigated qualitatively by radiologic and histologic study.MethodsTen rabbits were included in this study; two holes were drilled bilaterally across the near cortex and the four holes in each rabbit were divided into four treatment groups (HAP, hydroxyapatite powder; HAC, hydroxyapatite cylinder; HA/TCP, hydroxyapatite/tri-calcium phosphate cylinder, and titanium cylinder). The volume of bone ingrowth and the change of bone mineral density were statistically calculated by computed tomography five times for each treatment group at 0, 2, 4, 6, and 8 weeks after grafting. Histologic analysis was performed at 8 weeks after grafting.ResultsThe HAP group showed the most pronounced effect on the bone ingrowth surface area, which seen at 4, 6, and 8 weeks after graft (p < 0.05). On comparing the change of bone mineral density the bone ingrowth surface area among the 4 groups, there were no statistically significant differences among the groups found for any period (p > 0.05). On histological examination, the HAP group revealed well-recovered cortical bone, but the bone was irregularly thickened and haphazardly admixed with powder. The HAC group showed similar histological features to those of the HA/TCP group; the cortical surface of the newly developed bone was smooth and the bone matrix on the surface of the cylinder was regularly arranged.ConclusionsWe concluded that both the hydroxyapatite powder and cylinder models investigated in our study may be suitable as a bone substitute in the rabbit tibial defect model, but their characteristic properties are quite different. In contrast to hydroxyapatite powder, which showed better results for the bone ingrowth surface, the hydroxyapatite cylinder showed better results for the sustained morphology.

Acetabular Options: Notes From the Other Side

The socket remains the weakest link of primary total hip arthroplasty (THA). The revision rates of the socket are higher than those of the stem, with aseptic loosening and polyethylene wear being the most frequent indications for revision THA. Both cemented all-polyethylene cups and cementless sockets have benefited from stepwise improvements in surgical techniques and designs. In many countries, cementless sockets have replaced cemented cups during primary THA, with >90% of the acetabular components using a cementless fixation mode. The long-term prospective data of cementless sockets from high-volume centers show excellent and equivalent survivorship to cemented implants, but the insertion technique is easier and quicker. In addition, cementless sockets are more versatile than cemented all-polyethylene cups. With cementless sockets there is a move to increased porosity of the ingrowth surface, tri-bearing options, and enhanced locking mechanisms. There is a role for well-conducted randomized controlled trials to assess these new designs because data from various national registries show that the socket remains the weakest link of primary THA. Factors like sex, age, diagnosis, and bearing couples have a different and significant influence on the intermediate to long-term survivorship of contemporary cemented and cementless THA.

Selective Laser Melting: A regular unit cell approach for the manufacture of porous, titanium, bone in‐growth constructs, suitable for orthopedic applications

In this study, a novel porous titanium structure for the purpose of bone in-growth has been designed, manufactured and evaluated. The structure was produced by Selective Laser Melting (SLM); a rapid manufacturing process capable of producing highly intricate, functionally graded parts. The technique described utilizes an approach based on a defined regular unit cell to design and produce structures with a large range of both physical and mechanical properties. These properties can be tailored to suit specific requirements; in particular, functionally graded structures with bone in-growth surfaces exhibiting properties comparable to those of human bone have been manufactured. The structures were manufactured and characterized by unit cell size, strand diameter, porosity, and compression strength. They exhibited a porosity (10-95%) dependant compression strength (0.5-350 Mpa) comparable to the typical naturally occurring range. It is also demonstrated that optimized structures have been produced that possesses ideal qualities for bone in-growth applications and that these structures can be applied in the production of orthopedic devices.

Treatment of Avulsion Fractures of the Second Metacarpal Base With a Miniplate and Screws

First-generation porous coated acetabular cups have achieved durable biologic fixation, although liner dissociation and wear were common failure mechanisms. Second-generation modular acetabular cups retained the successful ingrowth surfaces used in earlier cup designs and incorporated congruent contact between the liner and shell. However, impingement-related fractures of highly cross-linked ultra-high-molecular-weight-polyethylene (UHMWPE) used in second-generation cup designs have occurred. Third-generation cup designs that eliminate UHMWPE protruding above the metal rim and minimize sharp corners at the liner-locking mechanism would be expected to reduce the risk of liner fracture in modular acetabular cups used with highly crosslinked UHMWPE.

Trabecular Metal in Hip Reconstructive Surgery

Biological ingrowth surfaces have become a standard prosthetic element in reconstructive hip surgery. A material's properties, three-dimensional architecture, and surface texture all play integral parts in its biological performance. Trabecular metal is an important new biomaterial that has been introduced to enhance the potential of biological ingrowth as well as provide a structural scaffold in cases of severe bone deficit. Initial clinical applications have focused on bone restoration in tumor and salvage cases and in primary and revision reconstructive cases where the increased biological fixation would be of clinical benefit. The bone ingrowth potential and mechanical integrity of this material offer exciting options for orthopedic reconstructive surgeons.

Simulation of Fretting Wear at Orthopaedic Implant Interfaces

Osteolysis due to wear debris is a primary cause of failure of total joint replacements. Although debris produced by the joint articulating surfaces has been studied and simulated extensively, fretting wear debris, produced at nonarticulating surfaces, has not received adequate attention. We developed a three-station fretting wear simulator to reproduce in vivo motion and stresses at the interfaces of total joint replacements. The simulator is based on the beam bending theory and is capable of producing cyclic displacement from 3 to 1000 microns, under varying magnitudes of contact stresses. The simulator offers three potential advantages over previous studies: The ability to control the displacement by load, the ability to produce very small displacements, and dynamic normal loads as opposed to static. A pilot study was designed to test the functionality of the simulator, and verify that calculated displacements and loads produced the predicted differences between two commonly used porous ingrowth titanium alloy surfaces fretting against cortical bone. After 1.5 million cycles, the simulator functioned as designed, producing greater wear of bone against the rougher plasma-sprayed surface compared to the fiber-mesh surface, as predicted. A novel pin-on-disk apparatus for simulating fretting wear at orthopaedic implant interfaces due to micromotion is introduced. The test parameters measured with the fretting wear simulator were as predicted by design calculations, and were sufficient to measure differences in the height and weight of cortical bone pins rubbing against two porous ingrowth surfaces, plasma-sprayed titanium and titanium fiber mesh.

Bone mineral density of the distal femur following uncemented total knee arthroplasty: a two-year follow-up of 11 knees using dual energy X-ray absorptiometry

In a prospective study, we evaluated the adaptive bone remodelling pattern of the distal femur using dual energy X-ray absorptiometry (DEXA) after total knee arthroplasty (TKA). Eleven patients underwent TKA with insertion of an Interax total knee system (Howmedica) because of primary osteoarthrosis of the knee. All patients received an uncemented femoral component with an uncoated cast-mesh ingrowth surface. The components had a 20-mm long central peg placed anteriorly just behind the anterior flange. DEXA scans were performed postoperatively at 2 weeks and at 3, 6, 12 and 24 months in the mediolateral plane of the distal femur and in the anteroposterior plane of the distal tibia and fibula. Compared to the immediate 2-week postoperative bone mineral density (BMD) value, we found no significant changes in BMD in 4 regions of interest (ROI) in the distal femur during the 2-year follow-up at 3 months. A temporary but significant decrease in BMD of 11.2% (95% CL, -17.3% to -5.0%) was observed in the most distal ROI just posterior to the fixation peg. Bone mineral content (BMC) of the distal tibia and fibula showed no significant changes in the operated and contralateral legs during the follow-up. The adaptive bone remodelling of the distal femur after TKA using an uncemented femoral component not previously examined by DEXA induced only a very limited and temporary loss of bone mineral.