Total shoulder arthroplasty (TSA) is an effective treatment for end-stage glenohumeral arthritis. The use of high modulus uncemented stems causes stress shielding and induces bone resorption of up to 63% of patients following TSA. Shorter length stems with smaller overall dimensions have been studied to reduce stress shielding, however the effect of humeral short stem varus-valgus positioning on bone stress is not known. The purpose of this study was to quantify the effect of humeral short stem varus-valgus angulation on bone stresses after TSA. Three dimensional models of eight male cadaveric humeri (mean±SD age:68±6 years) were created from computed tomography data using MIMICS (Materialise, Belgium). Separate cortical and trabecular bone sections were created, and the resulting bone models were virtually reconstructed three times by an orthopaedic surgeon using an optimally sized short stem
Total shoulder arthroplasty results in excellent outcomes for most patients who suffer from osteoarthritis of the shoulder. Current trends within the field reflect a desire to minimise stem lengths in contemporary prosthetic designs. The movement towards short-stem
Shoulder arthroplasty humeral stem design has evolved to accommodate patient anatomy characteristics. As a result, stems are available in numerous shapes, coatings, lengths, sizes, and vary by fixation method. This abundance of stem options creates a surgical paradox of choice. Metrics describing stem stability, including a stem's resistance to subsidence and micromotion, are important factors that should influence stem selection, but have yet to be assessed in response to the diametral (i.e., thickness) sizing of short stem
The reverse total shoulder replacement (rTSR) has excellent clinical outcomes and prosthesis longevity, and thus, the indications have expanded to a younger age group. The use of a stemless
Introduction. Total shoulder arthroplasty (TSA) is an effective treatment to restore shoulder function and alleviate pain in the case of glenohumeral arthritis [1]. Stress shielding, which occurs when bone stress is reduced due to the replacement of bone with a stiffer metallic implant, causes bone resorption of up to 9% of the humeral cortical thickness following TSA [2]. Shorter length stems and smaller overall geometries may reduce stress shielding [3], however the effect of humeral head backside contact with the resection plane has not yet been fully investigated on bone stress. Therefore, the purpose of this study was to quantify the effect of humeral head contact conditions on bone stresses following TSA. Methods. 3D models of eight male left cadaveric humeri (68±6 years) were generated from CT data using MIMICS. These were then virtually prepared for reconstruction by an orthopaedic surgeon to accept a short-stem
Background. Scapular notching is a complication after reverse shoulder arthroplasty with a high incidence up to 100%. Its clinical relevance remains uncertain; however, some studies have reported that scapular notching is associated with an inferior clinical outcome. There have been no published articles that studied positional relationship between the scapular neck and polyethylene insert in vivo. The purpose of this study was to measure the distance between the scapular neck and polyethylene insert in shoulders with Grammont type reverse shoulder arthroplasty during active external rotation at the side. Methods. Eighteen shoulders with Grammont type prosthesis (Aequalis Reverse, Tornier) were enrolled in this study. There were 13 males and 5 female, and the mean age at surgery was 74 years (range, 63–91). All shoulders used a glenosphere with 36mm diameter, and retroversion of the
Total shoulder arthroplasty implants have evolved to include more anatomically shaped components that replicate the native state. The geometry of the humeral head is non-spherical, with the sagittal diameter of the base of the head being up to 6% (or 2.1-3.9 mm) larger than the frontal diameter. Despite this, many TSA
Patient Specific Instruments (PSIs) are becoming increasingly common in arthroplasty but have only been used with highly invasive surgical approaches that can result in significant complications. We have previously described a novel PSI for minimally invasive total shoulder arthroplasty and shown that it can accurately guide the creation of guide holes in the humerus and scapula. However, conducting shoulder replacement in a minimally invasive environment precludes the use of traditional instruments. In this work, we describe and evaluate the efficacy of a set of novel instruments that, in conjunction with our PSIs, enable accurate minimally invasive total shoulder arthroplasty to be achieved for the first time. The key components of this surgical procedure are: 1) a new minimally invasive posterior surgical approach that avoids the need for muscle transection; 2) a novel PSI that enables accurate guide tunnels to be simultaneously created in the humerus and scapula using a c- shaped drill guide that mates to the PSI; 3) a custom humeral head resection guide that uses the humeral guide tunnel; 4) a novel reamer and 3D metal printed gear mechanism for radial displaced drilling both powered by a central driver placed through the humeral head; and 5) custom impactors for glenoid and
Total elbow arthroplasty (TEA) usage is increasing owing to expanded surgical indications, better implant designs, and improved long-term survival. Correct
Background. Medical advances and an ageing population mean that more people than ever rely on artificial joints. In the past years, shoulder joint replacement has developed rapidly and the numbers of shoulder prostheses implanted increased dramatically. Wear is one of the main contributors to the failure of shoulder implants. It is therefore important to measure the wear properties of the articulating surfaces within the joint in vitro. Investigation of wear characteristics through a comprehensive range of motion using a sophisticated shoulder simulator would reveal the durability of the material, the performance of component design and the safety analyses of prostheses. The purpose of the work was to develop and validate a multi-station shoulder simulator, which could accurately simulate physiological gleno-humeral forces and displacements during activities of daily living. Materials and Methods. Imperial shoulder simulator was designed with six articulating stations and one loaded soak control station for anatomical shoulder system wear simulation. It gives an adduction-abduction (AA) range of-15° to 55°, flexion-extension (FE) range of −90° to 90° and internal external rotation (IER) range of 15° to −90°. The rotations are applied simultaneously to the
The modern humeral head resurfacing was developed by Stephen Copeland, M.D. and introduced in 1986 as an alternative to stemmed
Introduction. A common phenomenon occurring as a result of reverse total shoulder arthroplasties (RSA) is scapular notching. While bone loss of the scapula may be quantified using radiographic techniques,[1] the material loss on the humeral bearing has not been quantified. Depending on their functional biological activity, a high volume of polyethylene wear particles has been shown to be related to osteolysis, bone loss and ultimately, loosening of implants in other joints.[2] In order to understand the threshold for osteolysis in the shoulder, it is important to have a method that can accurately quantify the amount of material loss. The aim of this research was to (I) create and validate a method for quantifying material loss from a single
Introduction. Reverse total shoulder arthroplasty (RTSA) can partially restore lost range of motion (ROM). Active motion restoration is largely a function of RTSA joint constraint, limiting impingement, and muscle recruitment; however, it may also be a function of implant design. The aim of this computational study was to examine the effects of implant design parameters, such as neck-shaft (N-S) angle and glenoid lateralization, on impingement-free global circumduction range of motion (GC-ROM). GC-ROM summarizes the characteristically complex, wide-ranging envelope of glenohumeral motion into a single quantity for ease of comparison. Methods. Nine computational models were used to investigate implant parameters. The parameters examined were N-S angles of 135°, 145°, and 155° in combination with glenoid lateralizations (0, 5, and 10 mm). Static positioning of the humerus was defined by an elevation direction angle, elevation angle, and rotation. The humerus was rotated from the neutral position (0° of rotation and elevation), and then elevated in different elevation directions until impingement was detected. Abduction occurred at an elevation direction angle of 0°, while flexion and extension occurred at elevation direction angles of 90° and −90°, respectively. Elevation direction angles ranged from −180° to 180°. Elevation ranged from 0° and 180°. Rotations ranged from −45° to 90°, where negative and positive rotations represented external and internal rotation, respectively. For each rotation angle, a plot of maximum elevation in each elevation plane was created using polar coordinates (radius = elevation, angle = elevation direction). The area enclosed by the resulting points, normalized with respect to the implant with a 145° N-S angle and 5 mm lateralization, was calculated. The sum of these areas defined the GC-ROM. Results. Figure 1 depicts the maximum ROM curves at each angle of rotation for a 145° N-S angle
EPRs are the treatment of choice following resection of tumours. These have been used for 39 years in our institution. There has been concern regarding the long term survival of endoprosthesis; this study investigates the fate of the reconstruction. Methods. Between 1966 and 1995, 3716 patients were seen with a suspected neoplasm and 776 patients underwent EPRs. Patients receiving growing endoprostheses were excluded from the study as they invariably require revision, leaving 667 replacements. Insufficient data was available in 6 cases, leaving 661 patients in the study group. Information was reviewed concerning the diagnosis, survival of implant and patient, subsequent surgery, complications and functional outcome. Kaplan-Meier survival analysis was used for implant survival with end points defined as revision for mechanical failure (aseptic loosening, implant fracture, instability, avascular necrosis, periprosthetic fracture, pain and stiffness) and revision for any cause (infection, local recurrence and mechanical failure). Results. Mean age at diagnosis was 34 years. Overall patient survival was 52.7% at 10 years and 45.7% at 20 years. The mean follow-up for all patients was 9 years, and for those patients who survived their original disease, the mean follow-up was 15 years. 227 (34%) patients underwent revision surgery, 75 patients for infection (33%), 36 patients for locally recurrent disease (16%) and mechanical failure in 116 patients (51%). With revision for mechanical failure as the end-point, implant survival was 75% at 10 years and 52% at 20 years. With revision any cause as an end-point implant survival was 58% at 10 years and 38% at 20 years. Overall limb salvage was maintained in 91% of patients at 10 years from reconstruction and 79% at 20 years. There was a significant difference between survival of implant between implantation sites, with the proximal
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