Risk of dislocation using large- vs. small-diameter femoral heads in total hip arthroplasty

Large Femoral Heads With Small Acetabular Components: An Examination of 10-Year Polyethylene Wear

Highly cross-linked polyethylene (HXLPE) has improved polyethylene (PE) wear rates while decreasing osteolysis and aseptic loosening. However, concerns exist regarding the risk of mechanical failure with thin HXLPE liners in total hip arthroplasty (THA). Our purpose was to evaluate long-term outcomes and PE wear rates in primary THAs pairing large femoral heads with small acetabular components and thin HXLPE liners. We retrospectively reviewed 29 patients who underwent 33 primary THAs using large femoral heads (32 or 36 mm) with small acetabular components (48 or 50 mm) and thin HXLPE liners (3.9 or 5.9 mm) at minimum 10-year follow-up. PE liner wear was measured using a validated radiographic technique. Mean age was 66 years, 97% of the patients were women, and mean body mass index was 26.3 kg/m2. Thirty hips (90.9%) had ceramic femoral heads, and 13 hips (39%) had 36-mm femoral heads with 3.9-mm HXLPE liners. All cases used a neutral PE design. Mean linear wear rate and volumetric wear rate were 0.04 mm/year and 39.6 mm3/year, respectively, at mean 10.9-year follow-up. There were no instances of liner fracture, liner dissociation, or revision. Mean Hip disability and Osteoarthritis Outcome Score for Joint Replacement (HOOS, JR) was 92.1. In the largest long-term study of primary THAs using large femoral heads with small acetabular components and thin HXLPE liners, we found low linear and volumetric wear rates and no cases of liner mechanical failures. Thin HXLPE liners are a safe and viable option for THA surgeons. [Orthopedics. 2024;47(2):118-122.].

Global mapping of institutional and hospital-based (Level II-IV) arthroplasty registries: a scoping review

PURPOSE

Four joint arthroplasty registries (JARs) levels exist based on the recorded data type. Level I JARs are national registries that record primary data. Hospital or institutional JARs (Level II-IV) document further data (patient-reported outcomes, demographic, radiographic). A worldwide list of Level II-IV JARs must be created to effectively assess and categorize these data.

METHODS

Our study is a systematic scoping review that followed the PRISMA guidelines and included 648 studies. Based on their publications, the study aimed to map the existing Level II-IV JARs worldwide. The secondary aim was to record their lifetime, publications' number and frequency and recognise differences with national JARs.

RESULTS

One hundred five Level II-IV JARs were identified. Forty-eight hospital-based, 45 institutional, and 12 regional JARs. Fifty JARs were found in America, 39 in Europe, nine in Asia, six in Oceania and one in Africa. They have published 485 cohorts, 91 case-series, 49 case-control, nine cross-sectional studies, eight registry protocols and six randomized trials. Most cohort studies were retrospective. Twenty-three per cent of papers studied patient-reported outcomes, 21.45% surgical complications, 13.73% postoperative clinical and 5.25% radiographic outcomes, and 11.88% were survival analyses. Forty-four JARs have published only one paper. Level I JARs primarily publish implant revision risk annual reports, while Level IV JARs collect comprehensive data to conduct retrospective cohort studies.

CONCLUSIONS

This is the first study mapping all Level II-IV JARs worldwide. Most JARs are found in Europe and America, reporting on retrospective cohorts, but only a few report on studies systematically.

Survival Analysis and Failure Modes of Total Hip Arthroplasty Using a Cemented Semi-Retentive Acetabular Cup

To reduce the incidence of total hip revisions, there have been continuous efforts to enhance prosthetic materials and designs to optimize implant survival. A primary implant with a constrained acetabular component is often used to minimize the risk of dislocations even though this approach has some drawbacks as reported in the literature. To address these concerns, this study aimed to assess the survivorship and dislocation rate of a semi-retentive cemented acetabular cup when used as a primary implant. The specific cemented cup that we studied was not present in any study that we consulted, so to fill this gap, we conducted a retrospective examination of 527 cemented hip prostheses that utilized the semi-retentive cup between the years 2005 and 2012. We employed Cox multiple regression models for our statistical analysis. The revision due to dislocation occurred in 12.8% of all cases, with a lower incidence of 5% (14 cases) in age groups >70 years than in age groups <70 years (14%-32 cases) (p < 0.001). The survival rates of the semi-retentive cemented acetabular cup were 98.6% (520 cases) at 5 years and 92.2% (487 cases) at 10 years. The survival rates were significantly lower in women than men, with 1.9% (7 cases) toward 0% at 5 years and 8.1% (30 cases) toward 5% (7 cases) at 10 years (p = 0.002). The difference in failure rates between age groups over 70 years (2.3%-10 cases) and age groups under 70 years (11.5%-34 cases) was also statistically significant (p < 0.001). Our study indicates that the semi-constrained design may cause frequent damage to the polyethylene liner due to impingement and wear, which are the primary factors for failure. Also, this implant has a similar risk of revision due to dislocation as reported in studies and may be beneficial as a primary implant in elderly patients with low-demanding lifestyles, muscular insufficiency, and low compliance regarding hip prosthetic behavior, without a major effect on survivorship.

The Use of a High Offset Fully Coated Collarless Cementless Stem Does Not Result in Early Failures in Total Hip Arthroplasty

INTRODUCTION

The Corail femoral stem has excellent long-term survivorship in total hip arthroplasty (THA). However, there remains a paucity of information on the specific performance of the high offset collarless stem in relation to subsidence, loosening, offset, and failure rates.

METHODS

Retrospective data were collected on all consecutive high offset collarless Corail stems implanted at a single centre in the UK. Data included patient demographics, femoral Dorr classification, radiographic analysis for radiolucent lines, and stem subsidence. The postoperative femoral offset was measured against the native offset of the contralateral hip. Any early failures, re-operations, or requirements for revision surgery were recorded.

RESULTS

We identified 162 stems for inclusion in the study. Ninety-five patients were male. The mean age was 60.5 (40 to 78) years, and the mean BMI was 29.8 (21 to 50) kg/m2. The mean length of follow-up was 84.5 (12-130) months. Subsidence was recorded on 113 (69.7%) stems. The mean amount of total stem subsidence in the whole cohort was 1.62mm (0 to 3.9mm). There was no correlation between the amount of subsidence and the preoperative Dorr classification, age, sex, BMI, or indication for surgery. Radiolucent lines were exclusively seen in stems paired with a large-diameter 36-mm femoral head. The high offset stem accurately reproduced native femoral offset; the mean difference in offset was -1.21mm (-24mm to +21mm). There were no early failures, re-operations, or revision surgeries.

CONCLUSION

The use of a high offset stem can accurately reproduce native femoral offset when chosen for THA. The high offset collarless Corail stem does not result in early failures in THA, and we support its use.

The 45-year evolution of the Mathys RM monoblock cups: have the paradigm shifts been worthwhile?

INTRODUCTION

The Robert Mathys (RM) monoblock uncemented cup is a design less commonly used in primary total hip replacement. It's purported advantages over modular cemented cups are: (1) its modulus of elasticity approximating bone, thus mimicking load transmission and the biomechanical behaviour of the cup to better match stresses on the acetabulum, leading to bone-preservation; and (2) as a 1-piece cup there is absence of a mobile interface between a liner and shell, preventing backside wear. Since its inception in 1983 there have been 3 major design changes: the RM Classic, the RM Pressfit, and the RM Vitamys with the most modern polyethylene (vitamin E).

METHODS

In a retrospective cohort study of the New Zealand Joint Registry, all designs of RM acetabular cup were reviewed. Data were included from1998 to 2018. All-cause revision rates, reasons for revision and the Oxford Hip Score (OHS) were assessed.

RESULTS

In total 13,272 acetabular cups were included. The all-cause revision rates did not differ between the designs. Revision rates for aseptic loosening in the RM Vitamys were lower, but the follow-up was shorter and more larger heads were used. There was no difference in the OHS.

CONCLUSION

All implant designs were safe. The use of larger heads led to a decrease in revisions due to dislocation. It has to be waited out whether the RM Vitamys performs superior in the long-term due to the highly cross-linked polyethylene.

Influence of Accelerated Aging on the Wear Behavior of Cross-Linked Polyethylene Liners—A Hip Simulator Study

Sequential cross-linked and annealed ultra-high-molecular-weight polyethylene (SX-PE) is known as a low-wear articulating partner, especially for total hip endoprostheses. Aging of polymeric materials, irrespective of if induced by shelf or in vivo life, can degrade their tribological and mechanical properties. However, changes in wear behavior of aged SX-PE liners have not been not quantified so far. An accelerated aging procedure, to simulate shelf and in vivo aging, was performed on thin SX-PE liners after five million load cycles using a simulator (“worn-aged”) as well as on new SX-PE liners (“new-aged”). A subsequent hip simulator test was performed with both thin SX-PE liner sets in combination with large-diameter ceramic femoral head, representing a combination known as advantageous for treatment after revision because of dislocation. Oxidation indices were measured on the liners after each step of the procedure. SX-PE liners after accelerated aging show bedding-in phases during simulator test, which was a characteristic only known from clinical investigations. Hence, the wear rates of the “new-aged” ((1.71 ± 0.49) mg/million cycles) and of the “worn-aged” ((9.32 ± 0.09) mg/million cycles) SX-PE were increased in the first period compared to new unaged SX-PE liners. Subsequently, the wear rates decreased for “new-aged” and “worn-aged” inserts to (0.44 ± 0.48) mg/million cycles and (2.72 ± 0.05) mg/million cycles, respectively. In conclusion, the results show promising effects of accelerated aging on SX-PE liners in simulator testing and for potential long-term use in clinical applications.

Outcome and risk factors of failures associated with revision total hip arthroplasty for recurrent dislocation

INTRODUCTION

Recurrent dislocation represents the third most common cause of revision surgery after total hip arthroplasty (THA). However, there is a paucity of information on the outcome of revision total hip arthroplasty for recurrent dislocation. In this study, we investigated (1) clinical outcomes of patients that underwent revision THA for recurrent dislocation, and (2) potential risk factors associated with treatment failure in patients who underwent revision total hip arthroplasty for recurrent dislocation.

METHODS

We retrospectively reviewed 211 consecutive cases of revision total hip arthroplasty for recurrent dislocation, 81 implanted with a constrained liner and 130 with a non-constrained liner with a large-diameter femoral head (> 32 mm). Patient- and implant-related risk factors were analyzed in multivariate regression analysis.

RESULTS

At 4.6-year follow-up, 32 of 211 patients (15.1%) underwent re-revision surgery. The most common causes for re-revision included infection (14 patients) and dislocation (10 patients). Kaplan-Meier analysis demonstrates a 5-year survival probability of 77% for patients that underwent revision THA for recurrent dislocation. Osteoporosis, obesity (BMI ≥ 40), spine disease and abductor deficiency are independent risk factors for failure of revision surgery for recurrent dislocation. Liner type (constrained vs. non-constrained) was found not to be associated with failure of revision THA for recurrent dislocation (p = 0.44).

CONCLUSION

This study suggests that THA revision for recurrent dislocation is associated with a high re-revision rate of 15% at mid-term follow-up. Osteoporosis, obesity (BMI ≥ 40) spine disease and abductor deficiency were demonstrated to be independent risk factors for failure of revision THA for recurrent dislocation.

LEVEL OF EVIDENCE

Level III, case-control retrospective analysis.

The relationship between patellar volume and trochlear volume in patients with patellofemoral instability

AIM

To investigate a possible relationship between both the volume and morphology of the patella and the volume of the trochlea in trochlear dysplasia (TD).

MATERIALS AND METHODS

Eighteen patients with TD and 18 controls were evaluated retrospectively in two groups using computed tomography (CT). Patellar morphology was evaluated with the standard measurement methods described in the literature. Additionally trochlear sulcus volume (TV) and patellar volume (PV) were measured quantitatively using the three-dimensional volume-rendering method. The relationship between patella dimensions and volume and trochlea volume was evaluated.

RESULTS

The length of the medial patellar facet (lMP), patellar width (PW), TV and PV were significantly lower in the patient group. When compared according to Dejour types, PW was statistically significantly lower than the control group in those with high-grade and those with low-grade dysplasia. A positive correlation was found between the TV and PV in both groups (patient group: r=0.583 p=0.011; control group: r=0.485 p=0.042). CONCLUSİONS: PV and the TV are related. Therefore, PV can be used as a determining parameter in the evaluation of TD. This technique can also be used for prosthesis construction and more accurate surgical planning.

Implant factors that might influence components' survival in primary total hip arthroplasty

Primary total hip arthroplasty (THA) is an invaluable surgical procedure that has revolutionised the treatment of various end-stage hip pathologies. Aseptic loosening of either acetabular cup and/or femoral stem as well as components' dislocation are well-known post-operative complications due to so many factors: environmental, surgeon, patient related, disease related or implant design. The aim of this literature review is to look at some relevant implant designs that might influence acetabular and femoral components' survival for primary cementless THA using revision for aseptic loosening and dislocation as criteria for failure. This may also assist the surgeon in making an informed choice of using appropriate implants to match the demographic and disease-specific need of the patients undergoing the surgical procedure. This review article was performed using an online literature search on relevant publications.

Dual Mobility hip replacement in hip fractures offer functional equivalence and a stability advantage - A case-controlled study

BACKGROUND

Hip fracture is a common and serious injury in the elderly. Hip arthroplasty is the most frequently performed procedure for patients with an  intracapsular hip fracture. The majority of national guidelines recommend total hip arthroplasty (THA) for more active patients. Literature indicates significant stability advantages for dual mobility (DM) acetabular components in non-emergent scenarios. Evidence supporting the use of DM in hip fracture patients is limited.

AIM

We set out to ascertain if DM implants offer stability and/or functional advantages over standard THA in patients with hip fracture.

METHODS

We utilised our local National Hip Fracture Database to identify all patients undergoing either a standard or DM THA for hip fracture (n=477) We matched cohorts based on age, AMTS, mobility status pre-operatively, gender, ASA and source of admission. Our primary outcome of interest was functional status using the oxford hip score (OHS). Secondary outcome measures included  dislocation, fracture and deep infection requiring further surgery.

RESULTS

62 patient pairs were available for this study. Mean OHS for DM THA was 41.5 and for standard THA this was 42.7 (p=0.58). There were 4 dislocations in the standard THA group and 0 with DM THA. No difference was seen with infection or peri-prosthetic fracture.

CONCLUSION

This study demonstrates functional equivalence between DM and standard THA. In addition it shows a trend towards less dislocation with DM THA. Cost savings from less instability may outweigh initial prosthesis costs. This study suggests a suitably powered RCT using instability as the primary outcome measure is indicated.

Evaluation of Dislocation Risk Factors With Total Hip Arthroplasty in Developmental Hip Dysplasia Patients: A Multivariate Analysis

BACKGROUND

This study aimed to investigate the risk factors for dislocation in patients diagnosed with developmental dysplasia of the hip (DDH) who underwent total hip arthroplasty.

METHODS

We retrospectively reviewed 40 patients who developed dislocation and compared them with 400 patients in the control group without hip instability. Patients-, surgery-, and implant-related factors were investigated. Risk factors were evaluated using multivariate logistic regression.

RESULTS

The mean follow-up period was 32.3 months. The mean time to dislocation was 4.4 months. There were 7 men (17.5%) and 33 women (82.5%) in the dislocation group and 83 men (20.7%) and 317 women (79.3%) in the control group (P = .627). Diabetes mellitus (DM; P = .032) and history of previous hip surgery for DDH were associated with dislocation (P < .001). The subtrochanteric shortening osteotomy (P = .001), acetabular inclination (P = .037), acetabular anteversion (P < .001), femoral head size (P < .001), and postoperative infection (P = .003) were associated with dislocation. Major predictors of hip dislocation after total hip arthroplasty in patients with DDH were previous hip surgery (odds ratio [OR], 6.76; 95% confidence interval [CI], 1.86-24.6; P = .004), high hip center (OR, 2.90; 95% CI, 1.31-6.38; P = .008), DM (OR, 2.68; 95% CI, 1.06-6.80; P = .037), and acetabular inclination (OR, 2.62; 95% CI, 1.09-6.26; P = .03).

CONCLUSION

Patients with DM and previous hip surgery should be informed about increased dislocation rates. Using a larger head diameter and restoration of the true hip rotation center are essential to prevent hip dislocation in these patients. Furthermore, accurate positioning of the acetabular inclination and anteversion are also important.

Prospective Study Showing Results of Large-Diameter Femoral Heads After Cementless Total Hip Replacement

Introduction Large-diameter femoral heads (≥36 mm) were introduced to decrease instability and improve the range of motion of the hip. We hypothesized regarding the clinical outcome and complications (dislocation, implant survivorship, and functional scores) following total hip replacement (THR) surgery in an Indian population who have smaller acetabulum compared to the western population. Methodology A prospective study was conducted at a tertiary hospital from November 2011 to July 2013. A total of 70 patients with hip pathology were operated by a senior surgeon for THR using the anterolateral approach. The Harris Hip Scores were recorded pre and postoperatively in all patients. Postoperatively, radiographs were taken to check for evidence of implant loosening or osteolysis. The patients were followed up till a mean follow-up of 86.52 months (range: 74 to 108 months) in our cohort. Detailed clinical and radiographic results were available for 59 patients, while six died (three died of myocardial infarction (MI), two had cerebrovascular accident (CVA), and one patient died of pulmonary embolism) and five patients were lost to follow-up. Results Of the 59 hips, majority (76%) had acetabular inclination of 46-55 degrees. Ninety percent of the stems were in the central position and 10% were in the varus position. The average preoperative Harris Hip Score was 38.8 ± 5.7 (range: 24-46), which increased to 90.4 ± 7.3 (range: 78-94) at the last follow-up. A total of six patients died (four died of MI and two of CVA) and two patients had infection which was treated with antibiotics. Three cases of dislocation were observed; one following a fall one year after surgery and revision total hip arthroplasty was done and two cases while getting up from the bed which were managed with closed reduction and abduction brace for six weeks. Two cases of periprosthetic fracture were observed which were managed with plating. Conclusion Lower dislocation rate and better range of movement reinforces the advantage of large-diameter femoral head during THR in the Indian population.

Return to sports after hip resurfacing versus total hip arthroplasty: a mid-term case control study

BACKGROUND

Hip resurfacing (HR) is an alternative to conventional total hip arthroplasty (THA) for the treatment of osteoarthritis (OA) in very active, young male patients. However, there is no study in the literature that has proven its benefits for high-impact sport over standard primary THA. The aim of the current study was to investigate the return to sport and function level of male patients after THA vs. HR.

MATERIALS AND METHODS

This prospective study is based on a telephone questionnaire for general health and sports activities. 40 HRs were matched with 40 THAs based on preoperative University of California Arthroplasty Score (UCLA), BMI, age at time of surgery and age at follow-up. The mean follow-up period was 56 months (range 24-87 months).

RESULTS

HR patients showed a significantly higher High-activity arthroplasty score (HAAS) (14.9 vs. 12.9, p < 0.001) and Lower extremity activity scale (LEAS) (15.9 vs. 14.1, p < 0.001) and reached significantly higher values in the Hip cycle score (HCS) (44.7 vs. 35.7 p = 0.037) and Impact score (IS) (40.9 vs. 29.6, p < 0.002) than THA patients. No significant differences were found in the HOOS function section (91.4 vs. 90.3, p = 0.803) and the Pain numeric rating scale (NRS)-11 (0.6 vs. 0.9 p = 0.169). Patients with HR had a slightly higher Harris hip score (HHS) (97.8 vs. 95.6, p = 0.015) CONCLUSION: The current study suggests that young male patients are able to engage in higher activity levels after HR compared to standard THA.

Conversion of Failed Hip Hemiarthroplasty to Low Friction Arthroplasty (LFA)

Purpose: We aimed to study clinical and radiological outcomes of conversion from hemiarthroplasty to Charnley hip replacement (CHR) with a particular concern over reported increased dislocation rate and literature review. Conversion of hip hemiarthroplasty to total hip replacement (THR) is a procedure reported to have high rates of complications. In the literature, there is no specific study on small head conversion. The purpose of this study was to evaluate the conversion of failed hip hemiarthroplasty to CHR with the use of modern implants. Methods: The study included 42 patients, who underwent the above procedure. The operations were carried out using a modern Charnley-type THR with a 22-mm diameter of femoral head and a trans-trochanteric approach. The mean follow-up was 75.7 months (range 25–171). Radiographs from the last follow up were evaluated for loosening and other reasons of failure. Clinical outcome was assessed using postoperative pain, function scores, complications and implant survivorship as well as radiological evaluation. Charnley’s modified pain and mobility scoring system were used for clinical and Hodgkinson and Harris’ criteria were used for radiological assessment. Results: Functionally, all of the patients showed improvement. Mean improvement in the pain level was by average of 2.4. On mobility assessment, 38 patients (90.4%) improved. Three patients (7.1%) had recurrent infections and three (4.8%) cases were treated with revision surgery and pseudarthrosis. Further complications occurred in 19.1%, not requiring operative treatment. On radiological evaluation, one (2.4%) case showed cup demarcation without bone loss, two (4.8%) cup migration, and one (2.4%) stem demarcation. Kaplan Meier survival analysis showed a survival of 90% at 96 months of follow up (95% CI (confidence interval), 60–90). Conclusion: Larger head might not be the answer to decrease the dislocation rate. Complication rates during revision of hip hemiarthroplasty to modern CHR with 22.225-mm head diameter were comparable to first-time THR revision despite having a smaller head.

Low failure rate at short term for 40 mm heads and second generation triple annealed HCLPE liners in hybrid hip replacements

INTRODUCTION

40 mm large diameter heads offer the advantages of lesser dislocation rates and better stability while highly cross linked polyethylene have lower wear rates than ultra high molecular weight polyethylene. Studies of the survivorship of 40 mm heads in hybrid hip replacements with Exeter stem and second generation highly cross linked polyethylene are limited. The purpose of the study is to report the short term of survivorship of the large diameter heads (40 mm) with Exeter stem with the secondary aim being the survival analysis of the thinnest second generation highly cross linked polyethylene.

METHODS

Retrospective case series of survivorship of patients with hybrid hip replacements of Exeter stems with 40 mm heads articulating with second generation triple annealed highly cross linked polyethylene liner on a uncemented acetabular shell was performed. As a subset, survival of thinnest second generation highly cross linked polyethylene survival (3.8 mm) at short term was assessed. Survival of the implants was confirmed from the hospital records and National joint registry as of 2015. Revision for any cause was taken as end point.

RESULTS

324 hybrid hip replacements with 40 mm heads had been performed for primary hip osteoarthritis. Of the 324 hip replacements, 154 hip replacements had thinnest second generation highly cross linked polyethylene (3.8 mm). Two patients had revision of components, one for periprosthetic fracture and one for deep infection. Mean age of the patients was 70.5 years (range 42-88 years, median 71, SD 8.3 years). None of the patients had revision due to trunion wear or loosening of components. The overall 5-year implant survival probability of hips with 40 mm heads was 99.4% (95% CI 98 to 100%) while the subset group of hip replacements with thinnest second generation highly cross linked polyethylene (3.8 mm) had 5-year implant survival probability of 99.3% (95% CI 97.1 to 100%).

CONCLUSION

Short term survivorship does not show significant evidence of early failure or higher rate of revision in our series of hybrid hip replacements with large diameter heads and second generation triple annealed highly cross linked polyethylene. Dislocation rate at the short term is none. Results from this series have to be carefully interpreted due to the relatively short follow up but so far results are encouraging. Long term follow up is required to conclude whether there is early or higher rate of failure. It is our intention to follow up this cohort and further publish our results at longer term.

Five Hundred Fifty-five Retrieved Metal-on-metal Hip Replacements of a Single Design Show a Wide Range of Wear, Surface Features, and Histopathologic Reactions

BACKGROUND

In 2010, a widely used metal-on-metal hip implant design was voluntarily recalled by the manufacturer because of higher than anticipated failure rates at 5 years. Although there was a large published range of revision rates, numerous studies had reported a higher risk of revision for excessive wear and associated adverse tissue reactions when compared with other metal-on-metal total hips. The reasons for this were suggested by some to be related to cup design features.

QUESTIONS/PURPOSES

From retrievals of ASR metal-on-metal implants and tissue samples obtained at revision surgery, we asked the following questions: (1) What were the common and uncommon surface features? (2) What were the common and uncommon linear and volumetric wear characteristics? (3) Were there common taper corrosion characteristics? (4) What aseptic lymphocytic vasculitis-associated lesion (ALVAL) features were present in the tissues?

METHODS

Five hundred fifty-five ASRs, including 23 resurfacings, were studied at one academic research center. Features of wear (eg, light and moderate scratching), damage (eg, deposits, gouges), and bone attachment on the porous coating were semiquantitatively ranked from 0 (none) to 3 (> 75%) based on the amount of a feature in each region of interest by the same experienced observer throughout the study. Visible features of head taper corrosion were ranked (Goldberg score) from 1 (none) to 4 (severe) by the same observer using a previously published scoring method. An experienced tribologist measured component wear depth using a coordinate measuring machine and quantified wear volume using previously validated methods. All available tissues were sampled and examined for features of ALVAL and scored from 0 to 10 by a single observer using a method they previously developed and published. A score from 0 to 4 is considered low, 5 to 8 is considered moderate, and 9 or 10 is considered high with regard to the risk of metal hypersensitivity features in the tissues.

RESULTS

The most common bearing surface features were light and moderate scratches and removal or postremoval damage. Discoloration and deposits were commonly observed on femoral heads (55% [305 of 553]) and less commonly on cups (30% [165 of 546]). There was no evidence of impingement or dislocation damage. There was typically a small amount of bone attachment in at least one of eight designated regions of interest (84% [460 of 546]); extensive or no bone attachment was uncommon. Edge wear was highly prevalent. The maximum wear of 469 cups (88%) occurred near the edge, whereas the maximum wear of 508 femoral heads (94%) occurred between the pole and 45° from the pole. The median combined head-cup wear volume was 14 mm (range, 1-636 mm). One hundred sixty-nine pairs (32%) had a combined wear volume of < 10 mm, 42 pairs (8%) had volumetric wear of > 100 mm, and 319 pairs (60%) had wear volume between 10 and 100 mm³. Seventy-four percent of tapers (390 of 530) received a Goldberg score of 4, 22% (116 of 530) a score of 3, < 5% (24 of 530) a score of 2, and none received a score of 1. The most frequent ALVAL score was 5 out of 10 (35 of 144 hips [24%]) and ranged from 2 (one hip) to 10 (nine hips); 92 of 144 (64%) had a moderate score, 17 of 144 (12%) had a high score, and 35 (24%) had a low score.

CONCLUSIONS

Although edge wear was prevalent, in most cases, this was not associated with high wear. The increased diameter and decreased coverage angle of the ASR design may have resulted in the observed high incidence of edge wear while perhaps decreasing the risk for impingement and dislocation.

CLINICAL RELEVANCE

The role of bearing wear in the revisions of metal-on-metal implants is controversial, because it is known that there is a large range of in vivo wear rates even within the same implant type and that patient variability affects local tissue responses to wear debris. The observations from our study of 555 retrieved ASR implant sets indicate that there was a wide range of wear including a subset with very high wear. The results suggested that the failure of the ASR and ASR XL was multifactorial, and the failure of different subgroups such as those with low wear may be the result of mechanisms other than reaction to wear debris.

Three-dimensional friction measurement during hip simulation

Objectives

Wear of total hip replacements has been the focus of many studies. However, frictional effects, such as high loading on intramodular connections or the interface to the bone, as well as friction associated squeaking have recently increased interest about the amount of friction that is generated during daily activities. The aim of this study was thus to establish and validate a three-dimensional friction setup under standardized conditions.

Materials and methods

A standard hip simulator was modified to allow for high precision measurements of small frictional effects in the hip during three-dimensional hip articulation. The setup was verified by an ideal hydrostatic bearing and validated with a static-load physical pendulum and an extension-flexion rotation with a dynamic load profile. Additionally, a pendulum model was proposed for screening measurement of frictional effects based on the damping behavior of the angular oscillation without the need for any force/moment transducer. Finally, three-dimensional friction measurements have been realized for ceramic-on-polyethylene bearings of three different sizes (28, 36 and 40 mm).

Results

A precision of less than 0.2 Nm during three-dimensional friction measurements was reported, while increased frictional torque (resultant as well as taper torque) was measured for larger head diameters. These effects have been confirmed by simple pendulum tests and the theoretical model. A comparison with current literature about friction measurements is presented.

Conclusions

This investigation of friction is able to provide more information about a field that has been dominated by the reduction of wear. It should be considered in future pre-clinical testing protocols given by international organizations of standardization.

A Single-Center Experience With a Titanium Modular Neck Total Hip Arthroplasty

BACKGROUND

Added modular junction has been associated with implant-related failures. We report our experience with a titanium-titanium modular neck-stem interface to assess complications, possible clinical factors influencing use of neck modularity, and whether modularity reduced the incidence of dislocation.

METHODS

A total of 809 total hip arthroplasties completed between 2005 and 2012 from a prospectively collected database were reviewed. The mean follow-up interval was 5.7 years (3.3-10.3 years). Forty-five percent were male (360 of 809), and 55% were female (449 of 809). All stems were uncemented PROFEMUR TL (titanium, flat-tapered, wedge) or PROFEMUR Z (titanium, rectangular, dual-tapered) with a titanium neck.

RESULTS

Increased modularity (anteverted/retroverted and anteverted/retroverted varus/valgus (anteverted/retroverted + anteverted/retroverted varus/valgus) was used in 39.4% (135 of 343) of cases using the posterior approach compared with 6.8% (20 of 293) of anterior and 23.7% (41 of 173) of lateral approaches. Four males sustained neck fractures at a mean of 95.5 months (69.3-115.6 months) after primary surgery. Overall dislocation rate was 1.1% (9 of 809). The posterior approach had both the highest utilization of increased modularity and the highest dislocation rate (2.3%), of which the most were recurrent. The anterior (0.3%) and lateral (0%) approaches had lower dislocation rates with no recurrences.

CONCLUSION

At a mean 5.7 years, our experience demonstrates a low neck fracture (0.5%) and a low dislocation rate (1.1%). Use of increased modularity may not improve dislocation risk for the posterior approach. Continued surveillance of this group will be necessary to determine long term survivorship of this modular titanium implant.

A Comparison of Blood Metal Ions in Total Hip Arthroplasty Using Metal and Ceramic Heads

BACKGROUND

In recent time, metal ion debris and adverse local tissue reaction have reemerged as an area of clinical concern with the use of large femoral heads after total hip arthroplasty (THA).

METHODS

Between June 2014 and January 2015, 60 patients with a noncemented THA using a titanium (titanium, molybdenum, zirconium, and iron alloy) femoral stem and a V40 trunnion were identified with a minimum 5-year follow-up. All THAs had a 32- or 36-mm metal (n = 30) or ceramic (n = 30) femoral head coupled with highly cross-linked polyethylene. Cobalt, chromium, and nickel ions were measured.

RESULTS

Patients with metal heads had detectable cobalt and chromium levels. Cobalt levels were detectable in 17 (56.7%) patients with a mean of 2.0 μg/L (range: <1.0-10.8 μg/L). Chromium levels were detectable in 5 (16.7%) patients with a mean of 0.3 μg/L (range: <1.0-2.2 μg/L). All patients with a ceramic head had nondetectable cobalt and chromium levels. Cobalt and chromium levels were significantly higher with metal heads compared to ceramic heads (P < .01). Cobalt levels were significantly higher with 36-mm metal heads compared with 32-mm heads (P < .01). Seven patients with metal femoral heads had mild hip symptoms, 4 of whom had positive findings of early adverse local tissue reaction on magnetic resonance imaging. All ceramic THA was asymptomatic.

CONCLUSION

The incidence and magnitude of cobalt and chromium levels is higher in metal heads compared to ceramic heads with this implant system (P < .01). Thirty-six millimeter metal femoral heads result in larger levels of cobalt compared with 32-mm metal heads.

[Larger heads compensate for an increased risk of THA dislocation in high-risk patients]

BACKGROUND

Dislocation is a devastating complication after total hip arthroplasty (THA) and occurs in 2-5% of primary THA cases and 5-10% of revision THA cases. Assuming correct implantation, dislocation risk can be reduced primarily by capsular repair and the use of larger prosthetic heads. However, larger heads are also associated with risks like accelerated wear or implant loosening, which is why heads with a maximum diameter of 36 mm are currently standard in primary THA. In cases with high dislocation risk, the use of 40 mm and 44 mm heads should be considered.

OBJECTIVES

This study aimed to quantify THA dislocation risk and retrospectively analyze the course of disease in high-risk patients treated with 40 mm or 44 mm femoral heads after primary or revision THA, concerning dislocation and other complications suffered.

MATERIALS AND METHODS

All patients with increased THA dislocation risk, treated from 2009-2014, were evaluated regarding dislocations. The cases with installation of 40 mm or 44 mm prosthetic heads were classified using a self-developed 5-level risk score and retrospectively analyzed.

RESULTS

During the observation period, 288 THA interventions with increased dislocation risk were performed. In 278 cases with ball diameters ≤ 36 mm the dislocation rate was 15.1% (n=42). In 10 high dislocation-risk cases (3A to 4B according to recommended scoring system), 40 mm and 44 mm heads were used. After a 22.8 month mean follow-up, no THA dislocations were reported.

CONCLUSION

Our results with 40 and 44 mm heads and the existing literature confirm much higher joint stability and, thus, significantly reduced dislocation risk with larger prosthetic heads in THA. Their use is, therefore, justified in high-risk patients and should be considered in future THA.

Total Hip Arthroplasty for Failed Internal Fixation After Femoral Neck Fracture Versus That for Acute Displaced Femoral Neck Fracture: A Comparative Study

The outcome of total hip arthroplasty (THA) for failed internal fixation after femoral neck fracture (FNF) versus that for acute displaced femoral neck fracture is still controversial. This study retrospectively analyzed a consecutive series of 130 THAs for acute displaced FNF (64, group I) and for failed internal fixation (66, group II). Results showed THAs in group II were more technically demanding procedures with longer operative time and larger amounts of drainage compared to that in group I. Furthermore, multivariate analysis revealed that the associations between THAs (group II) and hip complications were notable (OR=4.15, P=0.017). These increased risks should be paid much attention to, not only for choosing the appropriate treatment option, but also for providing effective perioperative care.

Comparison of ceramic-on-ceramic to metal-on-polyethylene bearing surfaces in total hip arthroplasty: a meta-analysis of randomized controlled trials

Background

In recent years, the choice of ceramic-on-ceramic (COC) and metal-on-polyethylene (MOP) in primary total hip arthroplasty (THA) remains controversial. The purpose of this study was to compare the reliability and durability of COC with that of MOP bearing surfaces in THA.

Methods

Based on prospective randomized controlled trials (RCTs) searched from Pubmed, Embase, Web of Science, and Cochrane central database, we performed a meta-analysis for comparing clinical and radiographic outcomes of COC with those of MOP. Two investigators independently selected studies, extracted data, and assessed risk of bias. Relative risks and weighted mean differences from each trial were pooled using random-effect or fixed-effect models depending on the heterogeneity of the included studies.

Results

Five RCTs involving 897 patients with 974 hips met predetermined inclusion criteria. Our results demonstrated COC significantly decreased the risks of revision, osteolysis and radiolucent line, aseptic loosening, and dislocation and increased the risks of squeaking and intraoperative implant fracture compared with MOP. There was no significant difference between the two groups in postoperative hip function, deep infection, and heterotopic ossification.

Conclusions

Generally, despite more squeaking and intraoperative implant fracture, our findings support the use of COC bearing surface which has lower rates of revision, osteolysis and radiolucent line, aseptic loosening, and dislocation compared with MOP.

Large-diameter metal-on-metal total hip arthroplasty: dislocation infrequent but survivorship poor

BACKGROUND

Use of large-diameter metal-on-metal (MoM) articulations in THA increased, at least in part, because of the possibility of achieving improved joint stability and excellent wear characteristics in vitro. However, there have been subsequent concerning reports with adverse reactions to metal debris (ARMD), pseudotumors, and systemic complications related to metal ions.

QUESTIONS/PURPOSES

The purpose of this study was to determine at a minimum of 2 years' followup (1) the proportion of patients who experienced a dislocation; (2) the short-term survivorship obtained with these implants; (3) the causes of failure and the proportion of patients who developed ARMD; and (4) whether there were any identifiable risk factors for revision.

METHODS

We reviewed the results of 1235 patients who underwent 1440 large-diameter MoM primary THAs at our institution using two acetabular devices from a single manufacturer with minimum 2-year followup. Large-diameter MoM devices were used in 48% (1695 of 3567) of primary THAs during the study period. We generally used these implants in younger, more active, higher-demand patients, in patients considered at higher risk of instability, and in patients with adequate bone stock to achieve stable fixation without use of screws. Clinical records and radiographs were reviewed to determine the incidence and etiology of revision. Patients whose hips were revised were compared with those not revised to identify risk factors; Kaplan-Meier survivorship analysis was performed as was multivariate analysis to account for potential confounding variables when evaluating risk factors. Minimum followup was 2 years (average, 7 years; range, 2-12 years); complete followup was available in 85% of hips (1440 of 1695).

RESULTS

Dislocation occurred in one hip overall (<1%; one of 1440). Kaplan-Meier analysis revealed survival free of component revision was 87% at 12 years (95% confidence interval, 84%-90%). The two most common indications for revision were ARMD (48%; 47 of 108 hips revised) and loosening or failure of ingrowth (31%; 34 of 108). Risk factors for component revision were younger age at surgery (relative risk [RR] 0.98 per each increased year; p=0.02), higher cup angle of inclination (RR 1.03 per each increased degree; p=0.04), and female sex (RR 1.67; p=0.03).

CONCLUSIONS

Large-diameter MoM THAs are associated with a very low dislocation rate, but failure secondary to ARMD and loosening or lack of ingrowth occur frequently. Patients with MoM THA should be encouraged to return for clinical and radiographic followup, and clinicians should maintain a low threshold to perform a systematic evaluation. Early diagnosis and appropriate treatment are recommended to prevent the damaging effects of advanced ARMD.

LEVEL OF EVIDENCE

Level IV, Therapeutic study.

Revisions of monoblock metal-on-metal THAs have high early complication rates

BACKGROUND

A relatively high percentage of monoblock metal-on-metal total hip arthroplasties (THAs) undergo early revision. Revision of these THAs poses challenges unique to this implant type. The early complications after these revisions remain unreported as do the clinical and demographic factors associated with these complications.

QUESTIONS/PURPOSES

We describe (1) the frequency of early complications after revision of monoblock metal-on-metal THA; and (2) the clinical and demographic factors associated with complications.

METHODS

A review of our institution's total joint registry identified 107 patients who underwent 114 revisions of monoblock metal-on-metal THAs. Mean patient age at revision was 60 years (range, 17-84 years), and 65% of the patients were women. Mean followup after revision was 14 months (range, 0-122 months). Revision diagnoses included metallosis (51%), aseptic loosening (27%), infection (7%), pain (6%), malposition (4%), instability (3%), iliopsoas impingement (2%), and periprosthetic fracture (1%). Major complications (instability, infection, aseptic loosening, and wound complications) were documented and included in the analysis. Minor postoperative complications such as urinary tract infection were excluded.

RESULTS

Twenty-three of 114 procedures (20%) involved at least one early complication after revision of monoblock metal-on-metal THA with 18 (16%) undergoing at least one additional subsequent surgery. The most common complications included aseptic loosening (6%), deep infection (6%), dislocation (4%), and acetabular fracture (3%). Patients who sustained a complication after revision surgery were older on average than those who did not (66 years versus 58 years, p=0.003). There were no differences in complication rate with respect to sex, time to revision, or revision diagnosis.

CONCLUSIONS

Complications and reoperations occur frequently after revision for failed monoblock metal-on-metal THA (20% and 16%, respectively), and older patients appear to be at greater risk for complications after these revisions. Aseptic loosening, deep infection, and instability are all of great concern after revision and surgeons should be aware of these potential complications when undertaking revision of these THAs.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Hip dislocations after 2,734 elective unilateral fast-track total hip arthroplasties: incidence, circumstances and predisposing factors

STUDY DESIGN

Retrospective review of prospectively collected data.

OBJECTIVE

To investigate the incidence of hip dislocation 90 days after total hip arthroplasty in relation to time after surgery, mechanism of dislocation and predisposing factors.

METHODS

Prospective data on preoperative patient characteristics from six Danish arthroplasty departments with similar fast-track approaches were cross-referenced with the Danish National Patient Registry for complete 90-day follow-up on readmissions, including emergency-room contacts. Complete patient files and postoperative radiographs were reviewed in case of dislocations. Unadjusted comparisons were made using t test/Chi-square analyses, while evaluation of risk factors potentially predisposing to dislocations was done using uni- and multivariate regression analysis.

RESULTS

A total of 2,734 consecutive unselected procedures were available for analysis, of which 65 (2.4 %) had dislocations. Of these, eight were during index admission and five were treated and discharged from the emergency room. Mechanisms of dislocation were most often movement while supine or sitting for the first 30 days and due to squatting/bending from day 31 to 90. The 65 patients with dislocations had suboptimal cup placement in 34 (52.3 %), and a femoral head size of <36 mm in 20 (30.8 %) cases. Predisposing factors of dislocation were age ≥75 [OR:1.96 (1.18-3.38)], pharmacologically treated psychiatric disease [OR:2.37 (1.29-4.36)] and department of surgery [OR:2.27 (1.31-3.40)] but not hospital stay of <4 days. Departments with recommendations for activity restrictions had fewer dislocations than a department without restrictions.

CONCLUSIONS

Patients ≥75 years and with pharmacologically treated psychiatric disease may be at increased risk of dislocations after fast-track total hip arthroplasty. Further studies including detailed information on patient and prosthesis characteristics, and activity restrictions are needed to reduce the risk of dislocation.

Ceramic on ceramic hip prostheses: a review of past and modern materials

Ceramic on ceramic hip prostheses are an increasingly popular choice for hip replacement. Modern manufacturing techniques and developments have increased the strength and reliability of ceramic materials. The alternative bearing couples such as metal-on-polyethylene and metal-on-metal are more inclined to wear and produce particulate debris. Despite reports of fractures and stripe wear, harder, more inert and more wear resistant, modern ceramic-ceramic hip replacements provide a strong alternative to traditional bearings.

Total hip arthroplasty for femoral neck fracture: comparing in-hospital mortality, complications, and disposition to an elective patient population

Patients treated with total hip arthroplasty (THA) for osteoarthritis (OA) and femoral neck fracture (FNF) between 1990-2007 were compared using the National Hospital Discharge Survey (NHDS). In-hospital, post-operative complications and disposition were compared at six-year intervals to establish trends over time. A total of 2,160,061 THAs were performed for OA, while 174,641 were performed for FNF. Peri-operative mortality and pulmonary embolism rates following elective THA were lower at each interval when compared to THA performed for FNF (P<0.001). Hematomas, infections, and dislocations were also higher in the traumatic group. The FNF group showed improvements with respect to mortality and rates of pulmonary embolism, infection, and dislocation over time. During the most recent interval, there was no difference in dislocation rates between the two groups. The length of stay and the percentage of patients discharging to a rehab facility were significantly higher in the FNF group at each time interval.

Reduced dislocation rates and excellent functional outcomes with large-diameter femoral heads

The purpose of this study was to compare the dislocation rates, functional outcomes, and radiographic results between large- and small-diameter femoral head components. A total of 225 patients (248-hips) who received total hip arthroplasties with large-diameter components (36mm or greater) were compared to 501 patients (559-hips) who received smaller diameter components (less than 36mm). Rates of dislocation and revision, Harris hip score, radiographic findings, and complications were compared between the groups. At a mean follow-up of approximately 5years, a significantly higher rate of dislocation was noted in the small-diameter group (10 of 559) compared to the large-diameter group (0 of 248). The overall implant survivorship, mean Harris hip scores, complication rates, and radiographic outcomes were similar for the two groups. The authors believe that large-diameter components significantly reduced the risk of dislocation in susceptible patients, while preserving good to excellent functional outcomes.