Modular implant design affects metal ion release following metal-on-metal hip arthroplasty: a retrospective study on 75 cases.

Metal-on-Metal (MoM) total hip arthroplasty (THA) has been associated to wear and metal-ions release, controversially related to a variety of clinical complications. Little is known about the relevant design-dependent parameters involved in this process. The present study investigated the correlation between metal ion release in blood and revision rate as a function of: (i) specific MoM implant modular design parameters, (i.e. acetabular cup and femoral head diameters, taper adapter material and size, femoral neck material and modularity and stem size); (ii) MoM bilaterality. Co and Cr ions concentration levels in blood of 75 patients were retrospectively-evaluated with a mean follow-up of 4.8 years (range: 1.8-6.3). Patients were divided in a unilateral and a bilateral group. Statistical analysis was performed to find any significant difference related to acetabular cup diameter, femoral head diameter, taper adapter material/size, neck material/size and stem size. The bilateral MoM group had 4-times higher metal ion levels in blood than the unilateral one (p=0.017 only Cr), related to a higher revision rate (30% vs 20%): differences were 10-times higher particularly with a 48 mm femoral head diameter (p=0.012) and a Ti-alloy neck (p=0.041). Within the monolateral group using a shorter taper adapter and a shorter neutrally-oriented neck demonstrated higher ion levels (p=0.038 only Cr and p=0.008 only Co, respectively). The aforementioned design-features and MoM bilaterality are important risk-factors for metal-ion release in modular MoM THA.

The use of dual-mobility bearings in patients at high risk of dislocation.

AIMS: Instability continues to be a troublesome complication after total hip arthroplasty (THA). Patient-related risk factors associated with a higher dislocation risk include the preoperative diagnosis, an age of 75 years or older, high body mass index (BMI), a history of alcohol abuse, and neurodegenerative diseases. The goal of this study was to assess the dislocation rate, radiographic outcomes, and complications of patients stratified as high-risk for dislocation who received a dual mobility (DM) bearing in a primary THA at a minimum follow-up of two years. MATERIALS AND METHODS: We performed a retrospective review of a consecutive series of DM THA performed between 2010 and 2014 at our institution (Hospital for Special Surgery, New York, New York) by a single, high-volume orthopaedic surgeon employing a single prosthesis design (Anatomic Dual Mobility (ADM) Stryker, Mahwah, New Jersey). Patient medical records and radiographs were reviewed to confirm the type of implant used, to identify any preoperative risk factors for dislocation, and any complications. Radiographic analysis was performed to assess for signs of osteolysis or remodelling of the acetabulum. RESULTS: There were 151 patients who met the classification of high-risk according to the inclusion criteria and received DM THA during the study period. Mean age was 82 years old (73 to 95) and 114 patients (77.5%) were female. Mean follow-up was 3.6 years (1.9 to 6.1), with five patients lost to follow-up and one patient who died (for a reason unrelated to the index procedure). One patient (0.66%) sustained an intraprosthetic dislocation; there were no other dislocations. CONCLUSION: At mid-term follow-up, the use of a DM bearing for primary THA in patients at high risk of dislocation provided a stable reconstruction option with excellent radiographic results. Longer follow-up is needed to confirm the durability of these reconstructions.

Total hip arthroplasty in rapidly progressive osteoarthritis of the hip: clinical and radiological outcome of a consecutive series of patients.

Rapidly progressive osteoarthritis (RPOA) is an uncommon subset of osteoarthritis (OA) characterized by rapid joint degeneration and destruction. The treatment of choice for these patients has traditionally been total hip arthroplasty (THA) because nonoperative treatments modalities are not effective. RPOA can lead to acetabular bone loss and consequently intraoperative technical difficulties making joint reconstruction in such patients a challenge for the surgeon. The purpose of this study was to determine the clinical and radiological results of patients suffering from RPOA and treated with hybrid or cementless THA at a single institution. We retrospectively review of all patients who underwent THA for RPOA from January 2011 to December 2016. Twenty-three hips in twenty-one patients were included in this study, with a mean age at surgery of 74 years (range, 41-82) and a mean follow-up of 30 months (range, 24-60). In all patients an uncemented cup, either plasma-spray or trabecular titanium, was implanted. In eighteen cases a cemented femoral stem was used. In eight cases autologous bone graft was used to replace the acetabular defect. Radiographic and clinical follow-up was performed at six months postoperatively, twelve months and yearly thereafter. At radiographic follow-up, no signs of prosthetic loosening or migration were seen. Harris Hip Score improved from 65.3 preoperatively to 89.2 at latest follow-up. The use of both hybrid and uncemented THA in the treatment of RPOA was found to be successful in our patients with a mean 30 months follow-up. Hemispherical cementless cups with both plasma spray and high porosity outer surface (used in the worse cases) were effective in getting primary stability and bone ingrowth.

Evaluation of accuracy of bone cuts and implant positioning in total knee arthroplasty using patient specific instrumentation.

In the last years new surgical techniques are developing to improve prosthesis positioning, increasing clinical and functional results and reducing invasiveness. In this scenario patient-specific instrumentations have been introduced in order to enhance surgical accuracy and ease of implantation. The purpose of this study was to assess the compliance of the pre-operative planning data with bone resections measured intraoperatively and to evaluate prosthesis positioning in patients undergoing total knee arthroplasty (TKA) using an MRI-based pin-guides instrumentation. Thirty consecutive patients (20 women and 10 men) undergoing 30 total knee replacements (20 right- and 10 left-sided knees) were included in this study. The same cemented cruciate ligament sacrificing prosthesis (NexGen LPS, Zimmer, Warsaw, Indiana, USA) was implanted in all patients by a single surgeon using Patient-Specific Instruments (PSI, Zimmer, Warsaw, Indiana, USA). Femoral and tibial bone resections were measured using a manual caliper intra-operatively and compared with the corresponding pre-operative values. Each patient underwent A CT examination following surgery in order to investigate individual component positioning. None of the cases was converted from PSI technique to conventional TKA and adequate femoral and tibial bone cuts were performed without the need for intraoperative adjustments. Two outliers were detected among the intra-operative bone cuts measurements. In all patients the size of femoral and tibial prosthetic components, hypothesized at preoperative planning, was confirmed intra-operatively. Two outliers were detected among post-operative CT measurements as for components positioning. PSI system can assist in obtaining good component positioning with reduction of outliers. Despite the small number of patients, our data demonstrate the validity of this patient-specific pin-guides system in TKA and may support repeatable improvements in surgical accuracy. Level of evidence: IV.

Dislocation following total hip arthroplasty using dual mobility acetabular components: a systematic review.

AIMS: The aim of this systematic review was to report the rate of dislocation following the use of dual mobility (DM) acetabular components in primary and revision total hip arthroplasty (THA). MATERIALS AND METHODS: A systematic review of the literature according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines was performed. A comprehensive search of Pubmed/Medline, Cochrane Library and Embase (Scopus) was conducted for English articles between January 1974 and March 2016 using various combinations of the keywords "dual mobility", "dual-mobility", "tripolar", "double-mobility", "double mobility", "hip", "cup", "socket". The following data were extracted by two investigators independently: demographics, whether the operation was a primary or revision THA, length of follow-up, the design of the components, diameter of the femoral head, and type of fixation of the acetabular component. RESULTS: In all, 59 articles met our inclusion criteria. These included a total of 17 908 THAs which were divided into two groups: studies dealing with DM components in primary THA and those dealing with these components in revision THA. The mean rate of dislocation was 0.9% in the primary THA group, and 3.0% in the revision THA group. The mean rate of intraprosthetic dislocation was 0.7% in primary and 1.3% in revision THAs. CONCLUSION: Based on the current data, the use of DM acetabular components are effective in minimising the risk of instability after both primary and revision THA. This benefit must be balanced against continuing concerns about the additional modularity, and the new mode of failure of intraprosthetic dislocation. Longer term studies are needed to assess the function of these newer materials compared with previous generations. Cite this article: Bone Joint J 2017;99-B(1 Supple A):18-24.

The Synergy cementless femoral stem in primary total hip arthroplasty at a minimum follow-up of 15 years.

AIMS: We report on the outcome of the Synergy cementless femoral stem with a minimum follow-up of 15 years (15 to 17). PATIENTS AND METHODS: A retrospective review was undertaken of a consecutive series of 112 routine primary cementless total hip arthroplasties (THAs) in 102 patients (112 hips). There were 60 female and 42 male patients with a mean age of 61 years (18 to 82) at the time of surgery. A total of 78 hips in the 69 patients remain in situ; nine hips in eight patients died before 15 years, and 16 hips in 16 patients were revised. Clinical outcome scores and radiographs were available for 94 hips in 85 patients. RESULTS: In all, four stems were revised. One stem was revised for aseptic loosening; two stems because of deep infection; and one because of periprosthetic femoral fracture. There was a significant improvement in all components of the Western Ontario and McMaster Universities Osteoarthritis Index score at the final follow-up (total: p < 0.001, pain: p < 0.001, stiffness: p < 0.001, function: p < 0.001). The mean Harris Hip Scores improved from 47 points (27 to 59) pre-operatively to 89 points (65 to 100) at the latest follow-up (p < 0.001). Kaplan-Meier survivorship, with stem revision for aseptic loosening as the endpoint, was 98.9% at 15 years (95% confidence interval (CI) 96.9 to 100, number at risk at 15 years: 90) and with stem revision for any reason was 95.7% (95% CI 91.7 to 99.8, number at risk at 15 years: 90). CONCLUSION: The Synergy cementless femoral stem demonstrates excellent survivorship and functional outcomes at 15 years. Cite this article: Bone Joint J 2017;99-B:29-36.