Modular Polyethylene Liner Research Articles

Polyethylene liner dissociation in cementless total hip arthroplasty: Ensuring accurate diagnosis.

Uncemented acetabular components are widely used in modern total hip arthroplasty (THA). Modularity has numerous advantages including the ability to use supplementary screw fixation for the shell, and allow to switch from ceramic to polyethylene (PE) bearings and vice versa, and the use of lipped and face-changing liners. Despite these advantages, a problem with modular PE liners is dissociation. This is a rare complication in modern implants. The rate of liner dissociation is reported to be very low between 0.17% and 0.8%. Typical symptoms are sudden onset of groin pain in a previously well-functioning hip joint, followed by grinding or clicking sensations during hip joint motions indicating, that the femoral head is articulating with the metal acetabular shell rather than with the PE liner. Any newly observed noise or squeaking from a THA should undergo radiographic investigation to exclude liner dissociation. We present the case of an 88-yearold male patient who developed PE liner dissociation in a cementless THA with a Pinnacle acetabular component six years after the index operation. We recommended revision of the left hip, which was performed two days later. In the interim, the patient was advised to use a pair of crutches. During revision surgery, it was observed that the metal head made contact with the cementless cup shell without damaging it from a macroscopic standpoint. Consequently, a simple exchange of the PE liner was conducted, and a 36 mm metal head was implanted due to scratches on the original head. Early diagnosis facilitates a straightforward exchange of the liner along with the head, potentially preserving the osseous integrated cup shell and stem integrity. Routine radiologic follow-up allows to distinguish between PE liner dissociation and severe PE wear.

Disengagement of Polyethylene Insert Locking Mechanism in Modular Tibial Components for Knee Arthroplasty: A Case Report

Background. Modular tibial components for knee arthroplasty are used in the majority of modern knee replacement systems. Despite a number of limitations, there are many aspects that make these types of implants indispensable for orthopedic surgeons.
 Aim — to demonstrate possible risks associated with a modular polyethylene liner with metal locking clip using a clinical case as an example.
 Case description. We present a case of primary total knee arthroplasty in a 70-year-old female patient. The surgery was performed by an experienced surgical team and resulted in good early radiologic and functional treatment outcome. After discharge, approximately 10 days after surgery, the patient developed knee pain. Control X-rays showed migration of the metal pin locking the polyethylene insert. The patient underwent an emergency revision surgery with replacement of the clip. The authors analyze possible causes of this complication and ways of its prevention.
 Conclusion. Migration of the insert locking element and dislocation of the insert in locked systems are quite rare complications of the knee arthroplasty. Their causes are soft tissue imbalance of the knee joint during arthroplasty and a number of technical errors. The very fact of using modular components of the joint is a predisposing factor for the disassociation of these modules.

Is There Harm in Debridement, Antibiotics, and Implant Retention Versus Two-Stage Revision in the Treatment of Periprosthetic Knee Infection? Experiences Within a Large US Health Care System

BackgroundWhen faced with a periprosthetic joint infection (PJI) following total knee arthroplasty, the treating surgeon must determine whether 2-stage revision or “liner exchange,” aka debridement, antibiotics, exchange of the modular polyethylene liner, and retention of fixed implants (DAIR), offers the best balance of infection eradication versus treatment morbidity. We sought to determine septic re-revision risk following DAIR compared to initial 2-stage revision. MethodsWe conducted a cohort study using data from Kaiser Permanente's total joint replacement registry. Primary total knee arthroplasty patients who went on to have a PJI treated by DAIR or 2-stage revision were included (2005-2018). Propensity score–weighted Cox regression was used to evaluate risk for septic re-revision. ResultsIn total, 1,410 PJIs were included, 1,000 (70.9%) treated with DAIR. Applying propensity score weights, patients undergoing DAIR had a higher risk for septic re-revision compared to initial 2-stage procedures (hazard ratio 3.09, 95% CI 2.22-4.42). Of DAIR procedures, 150 failed (15%) and went on to subsequent 2-stage revision (DAIR-F). When compared to patients undergoing an initial 2-stage revision, we failed to observe a difference in septic re-revision risk following DAIR-F (hazard ratio 1.11, 95% CI 0.58-2.12). ConclusionAlthough DAIR had a higher risk of septic re-revision, we failed to observe a difference in risk following DAIR-F when compared to those who initially underwent 2-stage revision. Functional outcome, patient, and organism factors are important to consider when discussing PJI management options. Level of EvidenceLevel III.

Influence of Acetabular Shell Position and Component Design on Hip Dynamic Dislocation

BackgroundDislocation is a major complication following total hip arthroplasty, with risk factors such as surgical technique, implant positioning, and implant design. Literature has suggested the distance the femoral head must travel before dislocation to be a predictive factor of dislocation where smaller travel distance has increased dislocation risk. The purpose of this study was to compare 3 designs (hemispherical, metal-on-metal, and dual mobility [DM]) in terms of the dynamic dislocation distance and force required to dislocate. MethodsThis dynamic dislocation distance model used a material testing system that defined acetabular component inclination (30°, 45°, and 60°), anteversion angles (0°, 15°, and 30°), and pelvic tilt (5° [standing] and 26° [chair rise]). Testing groups included a hemispherical shell with a modular polyethylene liner and 32-mm head, a metal-on-metal hip resurfacing cup design with a 40-mm CoCr head, and a DM design with a 42-mm outside diameter articulating liner and an inner 28-mm articulating head. ResultsThe dynamic dislocation distance of the DM hip was greater than that of the other designs for all inclination, anteversion, and pelvic tilt angles tested with the exception of 60° inclination/0° anteversion. At 26° pelvic tilt, it was observed that dislocation distance increased with greater anteversion and decreased with larger inclination. ConclusionClinical results have shown the DM design may reduce dislocation. These data support those findings and suggest that if instability is a concern preoperatively or intraoperatively, using a DM implant increases the dynamic dislocation distance.

Oral Antibiotic Therapy

Oral Antibiotic Therapy

Minimal Backside Surface Changes Observed in Retrieved Acetabular Liners

Modular polyethylene liners offer versatility in total hip arthroplasty, but the locking mechanism may allow micromotion and backside wear. We evaluated the backside surface of 56 retrieved acetabular liners (mean 5.54 years in vivo, range 0.003-13.1 years) to determine whether damage correlated with liner age in vivo, patient factors associated with higher activity, and polyethylene quality. Half of the liners exhibited minimal damage, half exhibited no damage and none exhibited severe damage. Backside damage significantly correlated only to liner age in vivo. Ten of the 28 liners revised for osteolysis exhibited no backside damage, but the osteolytic cysts were peripheral and did not originate from screw holes. The results suggest that modular polyethylene liners in a porous titanium-coated shell with screw holes can be designed such that clinically significant backside wear is minimal.

Management of massive acetabular defects in revision total hip arthroplasty

Twenty-four cases of massive periacetabular bone loss (Paprosky Type 3B) were reconstructed using custom triflanged acetabular components (CTAC). Fixation is obtained by the creation of a triflanged component that is anchored to the ilium, ishium, and pubis with multiple fixation screws. Acetabular defects are grafted with large amounts of cancellous allograft. Modular polyethylene liners are then locked into the CTAC. Twenty-one of 24 cases (87.5%) were considered clinically successful at short-term follow-up (average, 48 months; maximum, 78 months), with stable fixation and reconstruction of periacetabular bone. Three failures occurred from loss of fixation in patients with a preoperative dissociation of the hemipelvis and severe osteopenia. Presently, these devices should be used with caution in cases with a preoperative dissociation of the hemipelvis, unless additional column plating is performed. © 2003 Elsevier Inc. All rights reserved.

The Harris-Galante Porous Acetabular Component at Intermediate Follow-Up

Outcome of the acetabular component in 90 consecutive primary noncemented total hip arthroplasties (THAs) was prospectively studied. The acetabular cup consisted of a hemispherical titanium alloy shell with a titanium fiber-mesh porous coating and a modular polyethylene liner (Harris-Galante Porous-1, Zimmer, Warsaw, Ind). The cup was implanted using line-to-line reaming with adjunctive dome screw fixation. The femoral component consisted of a titanium alloy stem with titanium fiber-mesh porous coating and a 28-mm cobalt-chrome modular head. Mean patient age was 53 years (range: 27-75 years); male:female ratio was 48:42; and mean follow-up was 6 years (range: 4.5-8 years). One acetabular component was revised for aseptic loosening. Of 81 unrevised hips available for follow-up, mean Harris hip score was 57 preoperatively and 96 at final follow-up (72% excellent, 15% good, 1 3% fair, and none poor). Of 61 unrevised hips with adequate radiographic follow-up, radiographic failure (complete periprosthetic radiolucency) was evident in 3 (4.9%) and periacetabular osteolysis in none. Radiographic failure did not correlate with poor clinical outcome. Linear polyethylene wear rate (mean: 0.13 mm/year) did not correlate with age, gender, weight, outcome, or cup abduction angle, but did correlate with the presence of femoral periprosthetic osteolysis (0.18 mm/year with femoral osteolysis versus 0.11 mm/year without; P= .01). This series of porous-coated hemispherical cups demonstrated excellent intermediate-term clinical and radiographic outcome, comparable with similarly favorable results reported by the prosthesis designers. A potentially adverse effect of polyethylene wear on the longevity of a THA was supported by a positive correlation between polyethylene wear rate and femoral osteolysis.

Wear-Through of a Modular Polyethylene Liner

Four patients in whom the S-ROM Total Hip System Polydial polyethylene liner was used illustrate the importance of, and difficulties in, detecting polyethylene wear-through before a complete acetabular revision is necessary. The patients in these cases had full thickness polyethylene wear-through 11 or more years after total hip arthroplasties. Dorr and Livermore wear measurements from radiographs of the patients underestimated the actual wear and did not indicate wear-through. Because excessive head penetration was not evident radiographically with the S-ROM components, the cases showed the necessity of using additional measures to diagnose wear-through, particularly with these components. Repeat radiographs at a higher kilovoltage were used to better visualize the outline of the femoral head, and hip aspiration was used to diagnose metallosis. These cases also showed the importance of yearly followup evaluations, especially 10 or more years after surgery for patients with the S-ROM Polydial locking mechanism.

Motion at the Modular Acetabular Shell and Liner Interface A Comparative Study

Excessive polyethylene debris generated from a total hip arthroplasty can lead to osteolysis and premature revision. Most of this polyethylene debris comes from the concave articulation. However, abrasive wear on the convex side of a modular polyethylene component also may play a role in this problem. Motion of a modular polyethylene liner with respect to its shell can lead to such abrasive wear. Six samples of modular acetabular components from eight manufacturers were tested for motion between the shell and the liner. Motion at the shell liner interface was detected by five fiberoptic sensors in the x, y, and z planes. Micromotion occurred at the shell liner interface in all designs tested. The magnitude of motion varied between manufacturers, ranging from 5 to 311 microns. Design features that limit motion may be advantageous in limiting the amount of polyethylene debris.

Polyethylene Wear After Total Hip Arthroplasty

The use of modular components in total hip arthroplasty has been thought to contribute to accelerated polyethylene wear. Specifically, a modular femoral head with a flange extension and a longer neck may cause increased wear. The purpose of the current study was to evaluate the effect of a flange extension on polyethylene wear. Ninety-one patients who had had a total of 100 primary total hip arthroplasties were evaluated after an intermediate duration of follow-up. All of the acetabular components consisted of a hemispherical titanium-alloy fiber-mesh porous-coated shell with a nonelevated modular polyethylene liner; they were inserted without cement and with use of supplemental screws through the dome after so-called line-to-line reaming. All of the femoral components consisted of a modular head with a diameter of twenty-eight millimeters and either a long neck (with a flange extension) or a short or medium neck (without a flange extension). The study group comprised sixty-two patients (sixty-six hips) who had had radiographic evaluation that was adequate to allow the valid measurement of polyethylene wear. Thirty-two hips were in men, and thirty-four were in women. The mean age of the patients was fifty-six years, the mean weight was seventy-three kilograms, and the mean duration of follow-up was 6.1 years (range, four to eight years). The rate of polyethylene wear in the eleven hips in which the femoral component had a flange extension was significantly greater than that in the fifty-five in which the femoral component did not have a flange extension (mean, 0.17 compared with 0.11 millimeter per year; p = 0.009). Multivariate analysis showed that the presence of a flange extension was associated with increased polyethylene wear to a greater degree (F = 2.86) than were all other variables that were measured, including a younger age (F = 1.72), a more vertical angle of the acetabular component (F = 0.49), a heavier weight (F = 0.14), male gender (F = 0.11), and a smaller initial thickness of the polyethylene (F = 0.02). These data support an association between the presence of a modular femoral head with a flange extension and an accelerated rate of polyethylene wear. The presumed mechanism is an increase in peripheral, or so-called rim, impingement of the flange-reinforced neck on the acetabulum due to a decrease in the ratio between the diameters of the femoral head and neck.

Fracture of the femoral head after ceramic-on-polyethylene total hip arthroplasty

Four of 184 ceramic femoral heads that the authors used in total hip arthroplasty fractured from 5 to 9 months after surgery. A polyethylene-lined acetabular component was used in all cases. The fracture rate, 2.2%, was much higher than previously reported for ceramic head fractures when used with a polyethylene cup. The fractures occurred during normal daily activities. Possible causes included manufacturing defects, neck length (short in all cases), bearing diameter (28 mm in all cases), cone-trunnion mismatch, excess hoop stresses from impaction, or material deterioration. All patients were treated by removal of debris, wide excision of capsular tissue containing tiny abrasive fragments, exchange of the modular polyethylene liner, and implantation of a cobalt—chrome femoral head. The trunnion had been somewhat damaged by relatively brief exposure to the ceramic particles in every case. The authors' experience suggests that ceramic femoral heads be used with caution.

Modularity of Prosthetic Implants.

The vast majority of total-joint-replacement components currently utilized are modular to some degree. Modularity reduces inventory and increases the surgeon's options in both primary and revision total-joint arthroplasty. Use of a modular interface, however, increases the risk of fretting, wear debris, and dissociation and mismatching of components. The use of modular heads in total hip replacement is firmly established. The occurrence of corrosion and fretting has been recognized, and most manufacturers have improved the quality of the interface to minimize these problems. Modular polyethylene liners also offer advantages, particularly in revision procedures, where the option of additional screw fixation remains important. Many uncemented acetabular components are inserted without screws, which may generate renewed interest in one-piece factory-preassembled components. The conformity, locking mechanism, and nonarticular interface of modular acetabular components have all been studied and improved. Modular tibial components offer additional flexibility in the performance of total knee replacement but introduce the risk of dissociation and increased polyethylene wear; in revision procedures, modularity provides a valuable option for dealing with bone loss and an additional method of fixation by means of press-fit stems. Modular humeral components offer a significant advantage with limited apparent risk; however, longer clinical experience is required to assess potential problems.

Complications related to modularity of total hip components.

We report complications from the use of modular components in 20 hip replacements in 18 patients. Fifteen complications (in 13 patients) were related to failure of a modular interface after operation. Femoral head detachment from its trunnion was seen in 6 hips from trauma (3), reduction of a dislocation (2), and normal activity (1). In one case the base of the trunnion fractured below an extra-long modular head. In seven other hips the modular polyethylene liner dislodged from its shell, causing severe damage to the shell in four cases with extensive metallosis. In one other hip an asymmetrical polyethylene liner rotated, resulting in impingement of the femoral component and recurrent dislocation. Operative errors were seen in five cases: implantation of a trial acetabular component in one; and mismatching between the size of the femoral head and the acetabular component in the others. Surgeons who use hip replacements with modular components should be aware of the potential for operative error and of the importance of early treatment for postoperative mechanical failure.