Midterm results of 506 solid trispiked reflection cementless acetabular components for primary total hip arthroplasty

The purpose of this prospective study was to evaluate the outcomes and survivorship of a trispiked, sintered bead-coated titanium shell with a polished inner surface, no screw holes, and an improved locking mechanism. A total of 506 total hip arthroplasties with a minimum 5-year follow-up were available for review at a mean of 7 years (range, 5-11 years). Three sockets (0.6%) were revised for reasons other than aseptic loosening, and 14 (2.8%) polyethylene liners were exchanged. There was no difference in revision rate between non-cross-linked and highly cross-linked liners (P = .4). There were no cases of radiographic loosening. Retroacetabular osteolysis was identified in 2%. The overall 5-year and 10-year Kaplan-Meier survivorship was 97.5% and 97.4%, respectively, whereas survivorship of the shell was 99.8%.     

A novel technique for the removal of well-fixed cementless, large-diameter metal-on-metal acetabular components

Removing well-fixed cementless acetabular components can be a challenge for every orthopedic surgeon involved in revision hip arthroplasty. Forceful removal of such components often leads to acetabular bone loss and compromises reimplantation of a new socket. Instruments like the Explant Acetabular Cup Removal System (Zimmer, Warsaw, Ind) are developed to avoid such issues. We report a novel technique, cementing a polyethylene liner inside the uncemented metal-on-metal shell and using systems such as the Explant to safely extract it without the need for matching large-diameter heads. We successfully used this technique on 3 occasions and recommend its use.     

Multidirectional deformation in fully congruent acetabular components

Most clinical studies have used femoral head migration as an index of acetabular wear, but a previous study showed multiple wear vectors in 30% of retrieved acetabular components with noncongruent liners. The origin of multiple wear vectors is unclear, and it has been suggested that polyethylene creep in a noncongruent shell might influence deformation on the articular surface. We used shadowgraph and volumetric methods to evaluate the extent and direction of surface deformation of 37 retrieved polyethylene liners that were fully congruent to a single design of metal backing. The results show that multiple deformation vectors are relatively common in retrieved acetabular cups (27% in this study) and are independent of congruency between liner and metal backing, rim impingement, and backside creep. Polyethylene liners with multiple wear vectors were significantly thinner than those of cups with a single vector. The origin of multiple vectors is still unclear, but clinical and laboratory studies measuring linear wear alone without recognizing multiple vectors underestimate total in vivo volumetric wear.     

The pumping of fluid in cementless cups with holes

Ten patients who were scheduled for revision for pelvic osteolysis were studied. All had bone-ingrown metal-backed cups with holes and polyethylene liners. Pressures were measured in the osteolytic lesion and in the hip joint while applying cyclic forces across the artificial joint. In 4 cases with lesions that were fully contained by bone, loading of the hip produced a pressure wave in the osteolytic lesion. Cyclic forces, such as those that occur in normal gait, can act on the polyethylene liner, the metal shell, and the supporting bone to pump fluid in the retroacetabular osteolytic lesion. This pumping action may contribute to the pathogenesis of osteolysis by the mechanisms of fluid pressure, fluid flow, or the transportation of wear particles.     

The minimum 10-year results of a second-generation cementless acetabular shell with a polished inner surface

The purpose of this prospective study was to evaluate the minimum 10-year outcomes and survivorship of the Reflection shell with a polished inner surface and an improved locking mechanism. Three hundred sixty-three total hip replacements with a mean follow-up of 11.6 years (range, 10.0-15.1) were evaluated. The mean Harris Hip and WOMAC scores at last follow-up were 87 and 77, respectively. Four cups were revised: 2 for infection and 2 for aseptic loosening. Thirteen cases underwent liner exchange for wear. Radiographic review of remaining cups identified 8.8% with identifiable peri-acetabular osteolysis and no cases of loosening. The overall 10- and 15-year Kaplan-Meier survivorship was 94% and 90% for the total hip arthroplasty system while the survivorship of the shell remained 99.4% at 15 years.     

Revision of failure acetabular components with cementless acetabular components

Outcomes of cemented acetabular components show unacceptably high rates of loosening over the short-term, and increased failure over the long term. The use of uncemented acetabular components with porous coatings and supplemental screw fixation has improved the success rates of revision surgery with bone loss. Intermediate follow-up results of uncemented acetabular components for revision surgery suggest excellent outcomes with superior fixation compared with cemented components. Use of large components that rely on the posterior column and acetabular dome for fixation appear to function satisfactorily, even in a significantly bone deficient acetabulum.     

Midterm radiographic comparison of cementless acetabular shells containing lateralized and nonlateralized liners

This retrospective study assessed the effect of lateralized acetabular inserts on polyethylene wear rates, radiographic loosening, and hip stability. Fifty-six 4-mm lateralized liners and 39 neutral liners were compared at a mean follow-up of 7.1 years. Multivariate regression analysis demonstrated a significant increase of 0.04 mm/y in polyethylene wear rate with use of lateralized liners. However, predictable cementless fixation was obtained without screws in both liner groups with no migration or radiographic signs of loosening observed for any cup. The dislocation rate for hips with lateralized liners (3.6%) was less than that for hip with neutral liners (10.3%), although the difference was not significant with the numbers available. Despite the increase in wear rate, hips with lateralized liners performed as well as those with neutral liners with regard to loosening and stability.     

Press-fit cementless acetabular fixation with and without screws

Purpose

Cementless acetabular fixation for total hip arthroplasty (THA) is widely used. The question of using screws for a better primary and secondary acetabular fixation has been discussed in the literature in recent years. The aim of this meta-analysis was to compare fixation of acetabular cups with and without screws in total hip arthroplasty.

Methods

Electronic databases Embase, PubMed and Cochrane Library were used to search for randomised controlled trials reported through May 2013 of cementless acetabular fixation for THA with and without screws. Two independent reviewers assessed the trials for eligibility and quality. All related data matching our standards were abstracted for meta-analysis by RevMan 5.0. Evaluation criteria included revisions, migration and osteolysis.

Results

A total of 1,130 THAs enrolled into five trials were included in this meta-analysis. All studies compared fixation of acetabular cups with and without screws, and our pooled data showed no statistical significance between the two surgical methods in revision, migration and osteolysis.

Conclusion

There is no significant difference between cementless acetabular fixation for THA with and without screws in revisions, migration or osteolysis.     

Revision total hip: a novel modular cementless acetabular system for reconstruction of severe acetabular bone loss

Severe acetabular bone loss remains a challenge at the time of revision hip arthroplasty. A novel modular system is available to aid in the reconstruction of these challenging cases. This technique can provide support for an uncemented acetabular shell. By using the augments in combination with the revision acetabular component, the following goals of revision surgery on the acetabular side can be achieved at the time of surgery: initial stable fixation, restoration of the center of rotation, and maximization of host bone contact.     

Screw-augmented fixation of acetabular components: A mechanical model to determine optimal screw placement

Sixteen embalmed hemipelves were used to determine the optimal acetabular screw placement to provide maximal screw pull-out strength in unicortical and bicortical screw fixation. The anterior column, superior ilium, posterior column, ischium, and pubis regions of the pelvis were tested using 6.5-mm titanium alloy screws and a hydraulic servo-controlled 1321 Instron testing machine. Force vs displacement data were acquired. Bicortical fixation was stronger than unicortical fixation in the four zones compared. This difference was significant in the superior ilium, posterior column, and ischium. The anterior column could not accept unicortical screws due to inadequate bone depth, which ranged between only 6 mm and 10 mm. Bicortical fixation was significantly greater in the superior ilium, posterior column, and ischium than in the anterior column or pubis. Unicortical fixation was greatest in the superior ilium. This information may aid decisions concerning the positioning of screws to augment acetabular component fixation.     

The combined anteversion technique for acetabular component anteversion

The combined anteversion technique for acetabular component placement of total hip arthroplasty is beneficial because of the surgeons' limited ability to control the anteversion of a cementless femoral stem. Our data show that the cementless stem anteversion can be 15 degrees different than anticipated. By determining femoral stem anteversion before positioning cup anteversion, the cup anteversion can be adjusted for the stem anteversion. The combined anteversion technique should provide a mean near 35 degrees with a safe zone of 25 degrees to 50 degrees.     

Selective screw fixation is associated with early failure of primary acetabular components for aseptic loosening

Selective supplementation of acetabular component fixation with a screw during primary total hip arthroplasty (THA) assumes that the surgeon can detect when an acetabular component needs additional stability. In contrast, nonselective screw users do not alter their practice based on their interpretation of stability and either use screws all or none of the time. We aimed to determine the effect of selective screw use on aseptic acetabular component loosening. We retrospectively reviewed aseptic failures of acetabular components after primaty THA. We compared the survivorship of selective and nonselective supplementation of acetabular fixation with respect to time to revision, obesity, and screw use. Selective screw use (n = 16) was associated with earlier acetabular component aseptic loosening (median: 1.9 years; interquartile range [IQR]: 1.1-5.0) compared to nonselective screw use (n = 22; median: 5.6 years; IQR: 2.0-15.3; P = .010). Selective screw use was independently associated with earlier revision after adjusting for patient obesity. Obesity was associated with selective screw use in 50% of the cases vs 14% of nonselective cases (odds ratio: 6.3; confidence interval: 1.2-25.2; P = .028), possibly reflecting the increased difficulty in achieving acetabular component stability in this and other settings with compromised bone. Surgeons should carefully assess component stability at time of primary THA. If the acetabulum is not stable, the addition of screws alone may not be sufficient for acetabular component stability.     

Early polyethylene wear and osteolysis in cementless total hip arthroplasty: the influence of femoral head size and polyethylene thickness

We examined initial polyethylene thickness, early polyethylene liner wear, and osteolysis in 350 primary, cementless total hip arthroplasties (THAs). All of the prostheses were of identical design and used Omnifit components. In the 32-mm head group, the mean liner wear correlated significantly with polyethylene thickness (P<.001) and increased rapidly with initial thinner polyethylene following a logarithmic model, although this increase was not statistically significant (r = -.633). Inadequate polyethylene thickness in the 32-mm head group was implicated as the major cause of higher liner wear. A minimal polyethylene thickness of 7 mm is recommended in cementless metal-backed THAs. The use of a large head combined with poor prosthetic design appeared to be responsible for the unacceptably high incidence of femoral osteolysis.     

Use of an anatomical acetabular component for treatment of iliopsoas impingement

Iliopsoas impingement is a known cause of pain after total hip arthroplasty. The author reports on a patient with iliopsoas impingement due to prominence of the anterior aspect of her acetabular hip arthroplasty component successfully treated with revision to an anatomically designed acetabular implant. Use of such an anatomically designed acetabular implant may prove to be beneficial in selected patients with iliopsoas impingement.     

Revision of well-fixed cementless acetabular components for polyethylene failure

The results of revision of well-fixed Porous Coated Anatomic cementless acetabular components for polyethylene failure or periacetabular osteolysis in 18 hips (14 patients) are reported. Revisions were done with larger diameter cementless acetabular components replacing one-piece Porous Coated Anatomic devices for which no replacement liner was available. The objective was to determine the increase in size of the revision acetabular component and to assess clinical and radiographic outcomes. The Porous Coated Anatomic components were in place for an average of 7.8 years. At an average followup of 68 months, all revision components remain in place. Preoperatively, 12 hips in 10 patients had radiographic osteolysis, and 25 osteolytic lesions in 17 patients were grafted at revision. All grafted lesions showed partial or complete evidence of bone graft consolidation. The average revision component size increased 8.5 mm in diameter (range, 3-14 mm) compared with the primary component size. This corresponded to an average 6.5-mm increase in the acetabular cavitary diameter. When locking mechanism failure in a well-fixed cementless acetabular component prevents polyethylene liner replacement, acetabular component revision can provide good clinical and radiographic results with acceptable bone loss and improved access to osteolytic areas for debridement and grafting.     

Reconstruction of major segmental acetabular defects with an oblong-shaped cementless prosthesis: a long-term outcomes study

A retrospective outcomes study was performed on 25 consecutive acetabular reconstructions of major segmental defects by using an oblong-shaped cementless implant. All patients had combined acetabular defects (type III) as defined by the American Academy of Orthopaedic Surgeons classification of acetabular bone deficiency. Long-term follow-up was performed at an average of 11 years postoperatively. Clinical and radiographic outcomes were measured. Failures were defined by component revision or clear radiographic evidence of loosening. Six patients died before final evaluation, and 4 patients did not have complete radiographic data, leaving 14 patients (15 hips) for final analysis. At final follow-up, only 3 of the implants had failed and were revised. There was 1 case of a well-functioning implant with circumferential radiolucency; otherwise, there was no evidence of loosening among the remaining implants.     

Acetabular preparation and insertion of cementless acetabular components

acetabular preparation is of critical importance for the long term success of cernentless acetabular components.The goals of this preparation are to provide intimate bony prosthesis contact and initial component stability. Technical aspects of the procedure including osteophyte removal, component positioning, controversies concerning on line versus underrearning of the acetabulum, and screw and component insertion are outlined.     

The relationship between increased hip range of motion, wear, and locking mechanism failure in the Harris-Galante acetabular component

We performed both clinical and radiographic evaluations of 178 patients (190 hips) who had undergone cementless total hip arthroplasties using Harris-Galante I/II porous cups after an average 12-year follow-up period (range, 8-18 years). We revised 15 Harris-Galante I/II porous cups (7.8%), and the locking mechanism was broken in 10 revised cups (67%). There was a significant association between locking mechanism failure and linear polyethylene wear. We observed a significant positive correlation between linear polyethylene wear and increased ranges of motion such as flexion, adduction, and external rotation at the last follow-up visit after the primary operation. Increased ranges of motion seen in Asians induced higher linear polyethylene wear and locking mechanism failure due to impingement of the neck and cup.     

Periprosthetic acetabular bone loss using a constrained acetabular component

We describe two patients with a constrained acetabular component who required treatment for recurrent dislocation showing postoperative periprosthetic acetabular bone loss. These hips required revision surgery and demonstrated considerable bone loss caused by the migrated acetabular component. Impingement may have occurred with increased stress at the bone-prosthesis interface, and the sharp ends of screws with a metal shell may have gradually plowed up the acetabular bone. These failures illustrate the potential risk of using a constrained acetabular component.