Dislocation after total hip arthroplasty: does head size really matter?

The Use of Large Metal Heads in Thin Vitamin E-Doped Cross-Linked Polyethylene Inserts Does Not Increase Polyethylene Wear in Total Hip Arthroplasty: 5-Year Results From a Randomized Controlled Trial

BACKGROUND

Vitamin E-doped cross-linked polyethylene (VEPE) has encouraged the use of larger heads in thinner liners in total hip arthroplasty (THA). However, there are concerns about wear and mechanical failure of the thin liner, especially when metal heads are used. The aim of this randomized controlled trial was to investigate if the use of a large metal head in thin VEPE liner would increase polyethylene wear compared with a standard 32-mm metal head and to compare periacetabular radiolucencies and patient-reported outcomes in THA.

METHODS

There were 96 candidates for uncemented THA who were randomly allocated to either the largest possible metal head (36 to 44 mm) that could be fitted in the thinnest available VEPE liner (intervention group) or a standard 32-mm metal head (control group). The primary outcome was proximal head penetration, measured with a model-based radiostereometric analysis. Secondary outcomes were periacetabular radiolucencies and patient-reported outcomes. The midterm results of the trial at 5 years are presented.

RESULTS

The median total proximal head penetration (interquartile range) was -0.04 mm (-0.12 to 0.02) in the intervention group and -0.03 mm (-0.14 to 0.05) in the control group (P = .691). The rates of periacetabular radiolucencies were 1 of 44 and 4 of 42 (P = .197), respectively. Patient-reported hip function and health-related quality of life did not differ between the groups, but participants in the intervention group reported a higher level of activity (median University of California Level of Activity score 7 versus 6, P = .020). There were 5 revisions caused by dislocations (2), periprosthetic fracture (1), stem subsidence (1), or iliopsoas impingement (1).

CONCLUSIONS

Large metal heads in thin VEPE liners did not increase liner wear and were not associated with liner failure 5 years after THA.

Head, acetabular liner composition, and rate of revision and wear in total hip arthroplasty: a Bayesian network meta-analysis

Total hip arthroplasty (THA) is a common procedure for patients suffering from hip pain e.g. from osteoarthritis, osteonecrosis, or hip fractures. The satisfaction of patients undergoing THA is influenced by the choice of implant type and material, with one key factor being the selection of the appropriate material combination for the bearing surface. In this Bayesian network meta-analysis, we investigated the impact of material combinations for the bearing surface on the longevity of hip implants. The wear penetration rate per year and the total wear penetration in the liner resulting from different material combinations, as well as the survival rate at last follow-up, were examined. We analyzed a total of 663,038 THAs, with 55% of patients being women. Mean patient age was 59.0 ± 8.1 years and mean BMI 27.6 ± 2.6 kg/m2. The combination of an aluminium oxide (Al2O3) head and an Al2O3 liner demonstrated the lowest wear penetration at last follow-up and the lowest rate of wear penetration per year. Additionally, the combination of a crosslinked polyethylene (XLPE) liner and a zircon oxide (ZrO2) head demonstrated the lowest rate of revision at last follow-up. These findings underscore the importance of careful material selection for hip implant bearing surfaces to optimize their longevity and patient satisfaction after THA.

Comparing outcomes of total hip arthroplasty versus hemiarthroplasty in neck of femur fracture patients: an Australian registry study

PURPOSE

To determine discharge outcomes of displaced subcapital NOF patients who were from home, with intact pre-operative cognition, ASA 1 or 2 and independent walkers treated with either THA or hemiarthroplasty.

METHODS

A retrospective registry study was performed using data from the Australia and New Zealand Hip Fracture Registry (ANZHFR). Institutional ethics approval was obtained prior to commencement. Hip fracture registry records between 1st January 2016 and 31st January 2020 were reviewed.

RESULTS

A total of 930 patients with complete records were identified and included. There were 602 THA and 328 hemiarthroplasty patients. Using multivariate analysis, pre-operative factors associated with THA include younger age (OR = 0.90 for every year older, p < 0.001), females (p = 0.043), private admissions (OR = 1.62, p = 0.028) and receiving pre-operative geriatric assessment (OR = 1.89, p = 0.002). Delay to theatre due to not being fit for surgery was associated with not receiving THA (OR = 0.21, p < 0.001). THA resulted in a shorter total hospital length of stay (MD = 7.24, p < 0.001), higher likelihood of being discharged home (OR = 1.88, p < 0.001) and lower likelihood of being discharged to a residential aged care facility (OR = 0.32, p = 0.019).

CONCLUSION

Displaced subcapital NOF patients who were admitted from home, had intact pre-operative cognition, ASA 1 or 2, independent walkers and had THAs, had shorter total hospital length of stay, were more likely to be discharged home directly and less likely to end up in residential aged care facilities compared to those undergoing hemiarthroplasty.

Functional safe zone for THA considering the patient-specific pelvic tilts: An ultrasound-based approach

The usual Lewinnek orientation for cup positioning in total hip arthroplasty is not suitable for all patients as it does not consider the patient mobility. We propose an ultrasound-based approach to compute a Functional Safe Zone (FSZ) considering daily positions. Our goal was to validate it, and to evaluate how the input parameters impact the FSZ size and barycentre. The accuracy of the FSZ was first assessed by comparing the FSZ computed by the proposed approach and the true FSZ determined by 3D modelling. Then, the input parameters' impact on the FSZ was studied using a principal component analysis. The FSZ was estimated with errors below 0.5° for mean anteversion, mean inclination, and at edges. The pelvic tilts and the neck orientation were found correlated to the FSZ mean orientation, and the target ROM and the prosthesis dimensions to the FSZ size. Integrated into the clinical workflow, this non-ionising approach can be used to easily determine an optimal patient-specific cup orientation minimising the risks of dislocation.

Risk factors of dislocation after total hip arthroplasty in patients with developmental dysplasia of the hip

PURPOSE

Dislocation following total hip arthroplasty (THA) is a well-known complication. However, there is little data on its rate and predictors in patients with developmental dysplasia of the hip (DDH). The current study is aimed to determine the rate and specific risk factors of dislocation following THA in DDH patients.

METHODS

All the medico-surgical records of primary THAs from January 2014 to January 2019 were retrospectively reviewed. They were categorized into three main groups: primary OA, DDH, and others. Pre-operative and post-operative radiographs, past medical and surgical history, and surgical notes were reviewed in DDH cases.

RESULTS

In a total of 171 patients with DDH, 21 suffered from dislocation after THA (12%) which was significantly more frequent than those with primary OA. In univariate analysis, higher grade of dysplasia, smaller head size, intra-operative fracture, Wagner Cone stem, failure of offset restoration, and implanting the cup outside the Lewinnek's safe zone were identified as predictors of dislocation. In multiple regression analysis, however, only higher Crowe grade, intra-operative fracture, and post-operative acetabular offset less than 16 mm were independent predictors of dislocation.

CONCLUSION

Dysplastic hips can be more prone to post-THA dislocation than those with primary OA. Higher grades of dysplasia, failure of offset restoration, and intra-operative fracture can increase the rate of dislocation in this group of patients.

Ceramic-on-Ceramic Total Hip Arthroplasty with Large Diameter Heads: A Systematic Review

Ceramic-on-ceramic (COC) total hip arthroplasties (THAs) with large heads (>36 mm) were introduced to reduce dislocation rates and restore the hip anatomy as closely as possible to the native one. To date, the literature is scarce and fragmented; a review is desirable to point out the outcomes and the possible specific complications (noise, groin pain, and taperosis). A systematic review about large-diameter COC THAs was conducted according to the PRISMA guidelines. The PubMed and Cochrane databases were searched using the terms "large", "big", "head", "hip", and "ceramic." The methodological quality of the papers was assessed using the MINORS (Methodological Index for Nonrandomized Studies) score. Seven papers (level of evidence: 5 case series and 2 case-control studies) met the inclusion criteria. Clinical outcomes were excellent in >90% of the patients. Groin pain was reported in only 1 article (7%). Radiological outcomes were positive. Minimal revision rates (<2%) were reported at short- to mid-term follow-ups. Dislocation rates were usually <1%. No bearing surfaces failed. No case of trunnionitis was reported. Noise occurred in up to 30% of the patients, mostly squeaking. The noise did not influence clinical outcomes or patients' satisfaction. Noise was inconstantly associated with component positioning, younger age, high articular excursions, and larger sizes. Large-diameter heads in COC THAs (≥40 mm) showed promising clinical and radiological outcomes with minimal revision rates. Noise is a cause of concern and should be carefully evaluated at longer follow-ups and in larger, prospective, and specifically designed case series.