Modes of failure of hip hemiarthroplasty for femoral neck fracture.

BACKGROUND: Hemiarthroplasty is a common treatment for displaced femoral neck fractures, but limited Canadian data are available about hemiarthroplasty failure. We evaluated the frequency and predictors of hemiarthroplasty failure in Manitoba. METHODS: In this retrospective multicentre province-wide study, billing and joint registry databases showed 4693 patients who had hemiarthroplasty for treatment of femoral neck fracture in Manitoba over an 11-year period (2005-2015), including 155 hips with subsequent reoperations (open or closed) for treatment of hemiarthroplasty failure. Hospital records were reviewed to identify modes of hemiarthroplasty failure, comorbidities and reoperations. Data were analyzed using χ2 test and Poisson and γ regression models. RESULTS: During our study period, 155 hips (154 patients [3%]) underwent 230 reoperations. Of these, 131 hips (85%) initially had an uncemented unipolar modular implant. Indications for first-time reoperation included periprosthetic femur fracture (49 hips [32%]), dislocation (45 hips [29%]), acetabular wear (28 hips [18%]) and infection (26 hips [17%]). There were 46 hips (30%) that had 2 or more reoperations. Reoperation for dislocation was associated with presence of dementia; acetabular wear was associated with absence of dementia. Time from hemiarthroplasty to reoperation was associated inversely with age at hemiarthroplasty, dislocation and dementia and was directly associated with acetabular wear. The risk of having 2 or more reoperations was associated independently with dislocation, infection, and alcohol abuse. CONCLUSION: Hemiarthroplasty for femoral neck fracture in Manitoba had a low frequency of failure. Risk factors for multiple reoperations included dislocation, infection and alcohol abuse.

Midterm Results of a Contemporary, Porous-Coated Acetabular System in Patients Undergoing Primary Total Hip Replacement for Degenerative Hip Disease: A Prospective, Multicenter Study.

BACKGROUND: A contemporary, porous-coated acetabular implant designed for uncemented insertion was introduced in Europe and Australia in 2007. A similar previous acetabular system was found in several studies at 10 to 15-year follow-up to demonstrate accelerated polyethylene wear, osteolysis, and early failure. The current study was conducted to determine the midterm safety and effectiveness of this contemporary acetabular system using highly crosslinked polyethylene and ceramic liners at 5-year follow-up. METHODS: A prospective, nonrandomized study was conducted at 8 sites in Canada and the United States. All 148 study participants received a contemporary acetabular shell with proprietary porous coating. The primary outcome was the requirement for revision surgery at 5 years postoperatively. Secondary outcomes included a survival analysis, patient-reported outcome measures, radiographic failure, and postoperative adverse events. RESULTS: At 5-year follow-up there was 1 cup revised for deep infection. No cups were revised for loosening and none were found to be radiographically loose. The overall survival rate with reoperation for any reason was 97.1%. The success rate was 96.8% for polyethylene and 100% for ceramic with no difference in the success rate between either bearing surface (P = 1.0). The mean patient-reported outcome measures all improved significantly between preoperative and 5-year postoperative scores (P < .001). CONCLUSION: Results from this 5-year, multicenter, prospective study indicate excellent survivorship for this acetabular system when used with crosslinked polyethylene or ceramic bearing surfaces.

Retrieval Analysis of Large-Head Modular Metal-on-Metal Hip Replacements of a Single Design.

BACKGROUND: There are limited publications examining modular metal-on-metal (MoM) total hip implants in which a comprehensive analysis of retrieved components is performed. This study examines 24 retrieved modular MoM implants from a single manufacturer and compares retrieval analytics; bearing surface damage, wear, and modular taper corrosion against patient, surgical and implant characteristics to elucidate significant associations. METHODS: Clinical, patient, and surgical data were collected including age, body mass index, blood metal ion levels, and cup inclination. Damage assessment was performed visually in addition to surface profilometry. Acetabular liners and femoral heads were measured for volumetric wear. Femoral head taper bores were similarly measured for material removal due to corrosion and fretting. RESULTS: Patients with MoM-related reasons for revision showed significantly higher levels of blood metal ion levels. Bearing wear was strongly associated with blood metal ion levels and was significantly increased in cups placed more vertically. Younger patients tended to have higher body mass indices as well as poorer cup placement. CONCLUSION: This work details a broad range of analyses on a series of modular MoM total hip implants from a single manufacturer of which there are few published studies. Acetabular cup inclination angle was deemed a primary cause of revision surgery through increased MoM wear, high metal ion levels in the blood, and subsequent adverse local tissue reactions. Heavy patients can increase the surgical difficulty which was shown to be related to poor cup placement in this cohort.

Damage Assessment of Retrieved Birmingham Monoblock Cups: Is Conversion to Dual-Mobility Head a Viable Revision Option?

BACKGROUND: A novel revision technique for failed hip resurfacings involves retention of the acetabular cup, if well-fixed, which is mated to dual-mobility (DM) prosthesis in a traditional hip replacement configuration. It is unknown whether existing damage on the retained cup will result in unacceptable wear of the DM prosthesis. METHODS: Thirty retrieved Birmingham (Smith & Nephew) monoblock cups were visually scored for damage features and area of coverage. Surface roughness measurements were obtained within each damage feature as well as reference points on each cup. Analysis of prior metal-on-metal wear was also performed to determine the maximum change in diameter of the cup. RESULTS: Scratching and grooving (deep, singular scratches) were the most common damage features. Overall bearing surface roughness was estimated as 0.059 µm (±0.030 µm) based on percent area coverage of each damage feature. Dimensional change of the bearing surface was negligible for most cups (18 of 30) but ranged from 0.20 to 0.38 mm for the most severely worn samples (5 of 30). CONCLUSION: Average surface roughness of the retrieved Birmingham cups was low, suggesting an expected 10%-20% increase in DM prosthesis wear. Similarly, dimensional change of the cup due to prior wear is not believed to significantly affect wear. Our findings support the use of a DM head in appropriate scenarios but suggest caution when applied to younger, more active patients whom may be adversely affected by increased prosthesis wear in the long term.

Radiostereometric analysis of keeled versus pegged glenoid components in total shoulder arthroplasty: a randomized feasibility study.

BACKGROUND: This study aimed to assess differences in the fixation and functional outcomes between pegged and keeled all-polyethylene glenoid components for standard total shoulder arthroplasty. METHODS: Patients were randomized to receive a keeled or pegged all-polyethylene glenoid component. We used model-based radiostereometric analysis (RSA) to assess glenoid fixation and subjective outcome measures to assess patient function. Follow-up examinations were completed at 6 weeks and 6, 12 and 24 months after surgery. Modifications to the RSA surgical, imaging and analytical techniques were required throughout the study to improve the viability of the data. RESULTS: Stymied enrolment resulted in only 16 patients being included in our analyses. The RSA data indicated statistically greater coronal plane migration in the keeled glenoid group than in the pegged group at 12 and 24 months. Functional outcome scores did not differ significantly between the groups at any follow-up. One patient with a keeled glenoid showed high component migration after 24 months and subsequently required revision surgery 7 years postoperatively. CONCLUSION: Despite a small sample size, we found significant differences in migration between glenoid device designs. Although clinically these findings are not robust, we have shown the feasibility of RSA in total shoulder arthroplasty as well as the value of a high-precision metric to achieve objective results in a small group of patients.

CONTEXTE: Cette étude avait pour objet d'évaluer les différences sur le plan de la fixation et des résultats fonctionnels entre les composants glénoïdiens à plots et à quille, tous deux en polyéthylène, dans une arthroplastie totale traditionnelle de l'épaule. MÉTHODES: La répartition des composants glénoïdiens en polyéthylène à plots et à quille a été faite de façon aléatoire. Nous nous sommes servis de modèles d'analyses radiostéréométriques (ARS) pour évaluer la fixation glénoïdienne et les indicateurs de résultats subjectifs, ce qui nous a ainsi permis d'évaluer les résultats fonctionnels des patients. Quatre examens de suivi ont été réalisés après la chirurgie : à 6 semaines, puis à 6 mois, à 12 mois et à 24 mois. Tout au long de l'étude, des ajustements ont été apportés aux modèles d'ARS de la chirurgie, de l'imagerie et des analyses afin d'améliorer la viabilité des données. RÉSULTATS: Des problèmes liés au recrutement ont fait en sorte que nous n'avons retenu que 16 patients dans le cadre de nos analyses. Les données d'ARS ont montré une migration statistiquement plus grande du plan frontal dans le groupe quille que dans le groupe plots à 12 et à 24 mois. Les résultats fonctionnels étaient sensiblement les mêmes d'un groupe à l'autre, peu importe le moment du suivi. Un patient du groupe quille a présenté une migration très importante du composant après 24 mois; il a dû subir une chirurgie de révision 7 ans après la chirurgie initiale. CONCLUSION: Malgré la petite taille de l'échantillon, nous avons observé des différences significatives dans la migration des composants, selon le type utilisé. Même si ces observations ne permettent pas d'arriver à des conclusions robustes d'un point de vue clinique, nous avons montré qu'il est possible d'avoir recours aux ARS en contexte d'arthroplastie totale de l'épaule et démontré la valeur associée à l'utilisation de mesures de haute précision pour l'obtention de résultats objectifs chez un petit groupe de patients.

In Vivo Wear Performance of Cobalt-Chromium Versus Oxidized Zirconium Femoral Total Knee Replacements.

This study examines the damage and wear on the polyethylene (PE) inserts from 52 retrieved Genesis II total knee replacements to identify differences in tribological performance between matched pairs of cobalt-chromium (CoCr) and oxidized zirconium (OxZr) femoral components. Observer damage scoring and microcomputed tomography were used to quantify PE damage and wear, respectively. No significant differences were found between CoCr and OxZr groups in terms of PE insert damage, surface penetration, or wear. No severe damage such as cracking or delamination was noted on any of the 52 PE inserts. Observer damage scoring did not correlate with penetrative or volumetric PE wear. The more costly OxZr femoral component does not demonstrate clear tribological benefit over the standard CoCr component in the short term with this total knee replacement design.

Corrosion on the acetabular liner taper from retrieved modular metal-on-metal total hip replacements.

Eight retrieved metal-on-metal total hip replacements displayed corrosion damage along the cobalt-chromium alloy liner taper junction with the Ti alloy acetabular shell. Scanning electron microscopy indicated the primary mechanism of corrosion to be grain boundary and associated crevice corrosion, which was likely accelerated through mechanical micromotion and galvanic corrosion resulting from dissimilar alloys. Coordinate measurements revealed up to 4.3mm(3) of the cobalt-chromium alloy taper surface was removed due to corrosion, which is comparable to previous reports of corrosion damage on head-neck tapers. The acetabular liner-shell taper appears to be an additional source of metal corrosion products in modular total hip replacements. Patients with these prostheses should be closely monitored for signs of adverse reaction towards corrosion by-products.

Wear of a sequentially annealed polyethylene acetabular liner.

BACKGROUND AND PURPOSE: We previously reported on a randomized controlled trial (RCT) that examined the effect of adding tobramycin to bone cement after femoral stem migration. The present study examined femoral head penetration into both conventional and highly crosslinked polyethylene acetabular liners in the same group of RCT patients, with a minimum of 5 years of postoperative follow-up. PATIENTS AND METHODS: Linear penetration of the femoral head into an X3 (Stryker) crosslinked polyethylene (XLPE) liner was measured in 18 patients (19 hips) using radiostereometric analysis (RSA). Femoral head penetration was also measured in 6 patients (6 hips) with a conventional polyethylene liner (CPE), which served as a control group. RESULTS: The median proximal femoral head penetration in the XLPE group after 5.5 years was 0.025 mm with a steady-state penetration rate of 0.001 mm/year between year 1 and year 5. The CPE liner showed a median proximal head penetration of 0.274 mm after 7.2 years, at a rate of 0.037 mm/year. INTERPRETATION: The Trident X3 sequentially annealed XLPE liner shows excellent in vivo wear resistance compared to non-crosslinked CPE liners at medium-term implantation. The rate of linear head penetration in the XLPE liners after > 5 years of follow-up was 0.001 mm/year, which is in close agreement with the results of previous studies.

Comparison of two hydroxyapatite-coated femoral components: a randomized clinical trial using radiostereometric analysis.

Aims: The primary aim of this trial was to compare the subsidence of two similar hydroxyapatite-coated titanium femoral components from different manufacturers. Secondary aims were to compare rotational migration (anteversion/retroversion and varus/valgus tilt) and patient-reported outcome measures between both femoral components. Methods: Patients were randomized to receive one of the two femoral components (Avenir or Corail) during their primary total hip arthroplasty between August 2018 and September 2020. Radiostereometric analysis examinations at six, 12, and 24 months were used to assess the migration of each implanted femoral component compared to a baseline assessment. Patient-reported outcome measures were also recorded for these same timepoints. Overall, 50 patients were enrolled (62% male (n = 31), with a mean age of 65.7 years (SD 7.3), and mean BMI of 30.2 kg/m2 (SD 5.2)). Results: The two-year subsidence was similar for Avenir (-0.018 mm (95% confidence interval (CI) -0.053 to 0.018) and Corail (0.000 mm (95% CI -0.027 to 0.026; p = 0.428). Both anteversion/retroversion (Avenir 0.139° (95% CI -0.204 to 0.481°); Corail -0.196° (95% CI -0.445 to 0.053°; p = 0.110) and varus/valgus tilt (Avenir -0.024° (95% CI -0.077 to 0.028); Corail -0.049° (95% CI -0.098 to 0.000°; p = 0.473) were not statistically significantly different. After two years, patients reported similar improvements in EuroQol five-dimension five-level health questionnaire (Avenir 0.22 (SD 0.2); Corail 0.22 (SD 0.18); p = 0.965) and other outcomes scores. Patient satisfaction on a five-point Likert scale was also similar between both groups after two years (Avenir 1.38 (SD 0.88); Corail 1.33 (SD 0.57); p = 0.846). Conclusion: The performance of both femoral components was similar in terms of stability and patient outcomes.

Survivorship of constrained polyethylene inserts in primary total knee replacements.

BACKGROUND: Varus-valgus constrained (VVC) inserts are used in primary total knee arthroplasty (TKA) when stability cannot be achieved with a traditional insert. Concern has been raised regarding premature loosening and failure of these primary TKAs due to the increased load transfer through the prosthesis. This study seeks to assess the survival, clinical outcomes and radiographic assessment of VVC total knee inserts used in a single primary TKA system without diaphyseal stem extensions. METHODS: A consecutive cohort of 74 primary TKAs with VVC inserts was identified from an institutional database. A two-to-one matched group of 136 posterior-stabilized (PS) primary TKAs was generated from the same database. Survival analysis was assessed for all-cause revision surgery. Patient outcome measures were the Oxford Knee Score (OKS) and patient reported satisfaction. Radiographs were assessed in accordance with the Knee Society radiographic scoring system for radiolucency. RESULTS: Survival rates at three and five years were 98.1% and 95.1% for the VVC liner group and 98.1% and 98.1% for the PS liner group, respectively. OKS improved from pre-op to post-op for both groups (p < .001). OKS was reduced in the VVC liner group compared to the PS liner group at latest available follow-up (p = .012). However, clinical satisfaction rates did not differ between the two groups. Small, non-progressive radiolucent lines existed on several radiographs; however, no components in either group were deemed radiographically loose. CONCLUSION: The survivorship, clinical, and radiographic outcomes of VVC knees were similar to the PS comparison group at short- to mid-term follow-up.

Clinical and radiographic outcomes of a hybrid fixation revision total knee arthroplasty system at short to mid-term follow-up.

BACKGROUND: Despite the extensive study of primary arthroplasty, revision surgery is rarely discussed due to the reduced frequency and variability between patients. A new revision knee system was introduced to build off the geometry of a successful knee replacement system. This study seeks to assess the survival, clinical outcomes and radiographic assessment of this revision system at the early to mid-term. METHODS: A consecutive cohort of 234 rTKAs was identified from an institutional database. Survival analysis was assessed for aseptic loosening and any-cause failure. Patient outcome measures were the Oxford Knee Score (OKS) and patient reported satisfaction. Radiographs were assessed in accordance with the Knee Society radiographic scoring system. Mechanical alignment was assessed on three-foot standing radiographs. RESULTS: Aseptic survivorship at one year, two years, and five years was 100%, 100%, and 99.1%, respectively. Any-cause survival at one, two, and five years was 99.6%, 98.7%, and 92.3%, respectively. OKS improved from pre-op (average 18.8) to one year (average 31.7), two years (average 30.7), and mid-term (average 30.6) follow-up (p < 0.001 for all). At all intervals, patient satisfaction exceeded 70%. One component (0.4%) failed radiographically and was later revised. Neutral mechanical alignment was achieved in 83% of cases. In the remaining cases, alignment was in varus (10%) or valgus (seven percent). No consistent relationship between radiographs or mechanical alignment and clinical outcomes was noted. CONCLUSION: The survivorship, clinical, and radiographic outcomes of the single rTKA system studied are equivalent or superior to other hybrid fixation rTKA systems reviewed in the literature at similar follow-up intervals.

Retrieval analysis of a failed TriboFit polycarbonate urethane acetabular buffer.

The purpose of this research was to determine the failure mechanisms and damage features of a TriboFit acetabular buffer implanted directly against a native, prepared acetabulum which was revised after 11months. Retrieval analyses were carried out via light microscopy, gravimetric wear assessment, and observer scoring of visible damage features on the buffer. The volume of material abraded from the backside of the buffer was estimated via three-dimensional reconstruction using a laser scanner. Scanning electron microscopy was used to confirm damage features and mechanisms. Severe abrasion to the backside of the buffer was the primary damage feature, while stippling damage was seen on the articular surface of the buffer. Material loss due to backside abrasion was approximated to be between 0.13360.085 g (gravimetric analyses) and 0.19360.053 g (three-dimensional reconstruction). Implantation of the TriboFit buffer against the patient's native acetabulum without a metal backing allowed for significant movement of the buffer against the bone, resulting in the abrasion seen on this implant. The stippling damage on the articular surface indicates an adhesive wear mechanism which exacerbates movement of the buffer against the acetabulum, thereby increasing backside abrasion.

The effect of patient positioning on the precision of model-based radiostereometric analysis.

A repeatable method for in vivo and in vitro measurement of polyethylene wear in total knee replacement (TKA) is needed. This research examines the model-based radiostereometric analysis' (MBRSA) in vitro precision under different patient-radiograph orientations and flexion angles of the knee using a TKA phantom. Anterior-posterior and medial-lateral imaging orientations showed the highest precision; better than 0.036mm (3-dimensional translation) and 0.089° (3-dimensional rotation). Flexion of the knee did not affect MBRSA precision. Medial-lateral imaging is advantageous as it allows for flexion of the knee joint during an RSA examination, thus providing greater information for wear measurement.

Clinical failure analysis of contemporary ceramic-on-ceramic total hip replacements.

The present study investigates the performance of ceramic-on-ceramic total hip replacements by combining a retrieval analysis with a survivorship analysis to elucidate mechanisms that led to clinical failure. Semiquantitative surface damage assessment, contact profilometry, contour measurements, and scanning electron microscopy were performed to characterize the types and quantify the extent of surface damage on the retrieved ceramic components. The implantation period was positively correlated with both damage scores of the femoral heads (R = 0.573, p < 0.001) and the acetabular cups (R = 0.592, p < 0.001). Increased maximal out-of-roundness values of the femoral heads correlated with both increased metal transfer damage score (R = 0.384, p = 0.023) and increased stripe damage score (R = 0.729, p ≤ 0.001) of the acetabular liners. The damage rate (damage score/year) for both the retrieved heads and acetabular liners was at least 2.2-fold greater at inclination angles of >45° than the damage rate at inclination angles of ≤45°. For the retrieved femoral heads only, the linear wear rate of 25.5 ± 21.3 µm/year at inclination angles of >45° was 6-fold greater than the linear wear rate of 4.2 ± 2.3 µm/year at inclination angles of ≤45°. Metal transfer on the ceramic bearing surface could possibly contribute to fluid-film starvation and, in combination with an increased inclination angle, may facilitate an adhesive wear mechanism associated with stripe surface damage. At our institution, the clinical survivorship of ceramic-on-ceramic total hip replacements was 98.9% (a total of 9 out of 815 patients were revised within 10 years after total hip arthroplasty) with revision as the end point, suggesting their safe use in younger patients.