Bone remodelling and integration of two different types of short stem: a dual-energy X-ray - absorptiometry study.

PURPOSE: Different kinds of bone preserving hip stems have been created to assure a more physiological distribution of the strengths on the femur. The aim of this research is to evaluate the density reaction of the periprosthetic bone while changing the conformation of the prosthetic implant on dual-energy X-ray - absorptiometry (DXA). METHODS: This is a prospective, single-centre study assessing bone remodelling changes after implantation of two short hip stems, dividing the patients in two groups according to the implant used: 20 in group A, Metha (B-Braun), and 16 in group B, SMF (Smith and Nephew). All participants had a pre-operative and a post-operative (24 months) DXA evaluating the changes in bone mass density (BMD) occurred in the five Gruen's zones. RESULTS: Compared to the pre-operative value, differences in BMD percentage were statistically significant only in ROI 4 (p < 0.05), with an increase in both groups (9 and 18%, respectively). The average increase in BMD was of 7.3% and 7.2% in the 2 groups. CONCLUSION: According to our study, both stems have proved able to provide good load distribution across the metaphyseal region favouring proper system integration. Nonetheless, is certainly needed to perform other studies with longer follow-up and bigger populations to give strength to these conclusions.

Contamination of revision procedures in patients with adverse tissues reaction to metal on metal implant.

OBJECTIVE: The aim of this study is to evaluate the incidence of infections in MoM total hip replacement revisions and to propose a therapeutic algorithm that can reduce the onset of this complication. Total hip arthroplasty is one of the most successful procedures performed annually in the world. As the population ages, the number of primary arthroplasty procedures performed each year is rising in conjunction with an increasing revision burden. Metal on Metal (MoM) total hip arthroplasties were reintroduced in over the last fifteen years to meet these needs, larger diameters, improved lubrication, better stability, increased ROM and wear properties of the bearing couple. These advantageous features have led to an exponential diffusion of MoM. Since over last decade, it has become evident that hip replacements with MoM bearing have significantly higher revision rates compared to those with Metal on Polyethylene. The common pathway for this failure mode appears to be increased wear or corrosion with excessive release of metal ions and nanoparticles. Complications such as elevated serum metal ion levels, aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) and pseudotumours have all been well documented, but recent studies suggest increased risk of infection with MoM bearing surfaces. PATIENTS AND METHODS: We collect data from a cohort of 44 patients who underwent revision of total hip arthroplasty between 2014 and 2017 for the complication of MoM bearing. Studied by radiological images, blood tests, and intraoperative clinical status, part of the population was treated with one stage revision, while the other was treated with a two-stage revision. RESULTS: Results showed a difference in the occurrence of infections in the two populations. CONCLUSIONS: We consider it appropriate to perform two-stage revision in all case of failure of MoM replacement so as to allow to minimize the likelihood of infection in patients with damaged tissues by ALVAL, pseudotumour, and necrosis that could create an ideal environment for bacterial development.

Low complication rates in Minimally Invasive Plate Osteosynthesis (MIPO) for proximal humeral fractures at 5 years of follow-up.

INTRODUCTION: Purpose of this study was to analyse the medium term follow-up of minimally invasive plate osteosynthesis (MIPO) for proximal humeral fractures in terms of postoperative shoulder function, radiological outcome and complications. METHODS: 76 consecutive patients with unstable proximal humeral fractures were treated using locking plate with a minimally invasive antero-lateral approach in two surgical centers. Constant score and radiographic evaluation of 74 patients were available at mean follow up of 5 years (minimum 4 years). RESULTS: Mean Constant score was 74 (range to 28-100). Results were comparable in the two centers. Younger patients registered significantly higher scores (p < 0.05). 20 patients (27%) developed complications. Subacromial impingement occurred in 16,2% of cases for varus malreduction (6,7%) and for too proximal plate positioning (9,5%). Primary screws perforation (2,7%), secondary perforation due to cut-out (1,4%), avascular necrosis (AVN) of humeral head (1,4%), partial resorption of greater tuberosity (2,7%), secondary displacement of the greater tuberosity (2,7%) and stiffness (2,7%) were observed. DISCUSSION AND CONCLUSIONS: Even at a medium term follow-up, MIPO for proximal humeral fractures ensured good and reproducible results for most common pattern of fractures. Major complications were lower respect to open procedures, because of soft tissue, deltoid muscle and circumflex vessels sparing.

Hip resurfacing: why does it fail? Early results and critical analysis of our first 60 cases.

Resurfacing replacement represents the most conservative solution available for total arthroplasty of the hip. However, despite the excellent results reported by highly experienced surgeons, a small but not insignificant body of literature has been published on the more controversial aspects of this approach, mainly those related to the biological and mechanical vulnerability of the retained epiphysis. We report here our evaluation of most of the variables inherent to this procedure (surgical exposure, implant design, technical steps). Based on our results, we conclude that the short-term outcome is strongly related to the surgical approach and the relationship between implant design and cementing technique. Even if posterior approaches are currently widely accepted for resurfacing replacement, the ability to preserve the medial circumflex artery has been questioned, and an alternative exposure has been proposed with good results (antero-lateral, lateral and digastric trochanteric osteotomy). Moreover, a minimally invasive posterior approach could increase the risks of vascular damage. Alternatively, inner implant geometry could affect the distribution of cement over the epiphysis when other variables (direct or indirect cementing technique, viscosity) are not properly selected.

Perspectives on metaphyseal conservative stems.

Total hip replacement is showing, during the last decades, a progressive evolution toward principles of reduced bone and soft tissue aggression. These principles have become the basis of a new philosophy, tissue sparing surgery. Regarding hip implants, new conservative components have been proposed and developed as an alternative to conventional stems. Technical and biomechanical characteristics of metaphyseal bone-stock-preserving stems are analyzed on the basis of the available literature and our personal experience. Mayo, Nanos and Metha stems represent, under certain aspects, a design evolution starting from shared concepts: reduced femoral violation, non-anatomic geometry, proximal calcar loading and lateral alignment. However, consistent differences are level of neck preservation, cross-sectional geometry and surface finishing. The Mayo component is the most time-tested component and, in our hands, it showed an excellent survivorship at the mid-term follow-up, with an extremely reduced incidence of aseptic loosening (partially reduced by the association with last generation acetabular couplings). For 160 implants followed for a mean of 4.7 years, survivorship was 97.5% with 4 failed implants: one fracture with unstable stem, 1 septic loosening and 2 aseptic mobilizations. DEXA analysis, performed on 15 cases, showed a good calcar loading and stimulation, but there was significant lateral load transfer to R3-R4 zones, giving to the distal part of the stem a function not simply limited to alignment. Metaphyseal conservative stems demonstrated a wide applicability with an essential surgical technique. Moreover, they offer the options of a "conservative revision" with a conventional primary component in case of failure and a "conservative revision" for failed resurfacing implants.

Non-union in an unnoticed neck fracture in resurfacing total hip arthroplasty.

The renewed popularity of resurfacing hip arthroplasty (RHA) in the last five years has generated a remarkable quantity of scientific contributions based on mid- and short-term follow-up. In spite of some large series with extremely low complication rates, more than one paper has reported a consistent early revision rate as a consequence of biological or biomechanical failure. Two major complications are commonly described with resurfacing implants: avascular necrosis and neck fracture. A close relationship between these two events has been suggested, but not firmly demonstrated, while surgical exposure and implant positioning seem to be better understood as potential causes of failure. However, it may happen that neither avascular necrosis nor neck fracture can be clearly recognised in a failed resurfacing implant: it is what we have directly experienced, with a missed fracture at the head-neck junction, evolved in non-union, beneath the dome of the femoral component. The present report, besides a brief clinical history, tries to give a possible interpretation of such an unusual complication.