Radiolucency in stemless shoulder arthroplasty is associated with an imaging phenomenon

Stemless humeral implants show comparable midterm clinical results compared to stemmed components. Recently, radiolucencies around the metaphyseal seating of humeral stemless implants were reported on postoperative radiographs. It is controversial whether they are attributable to bone resorption. We hypothesized these radiolucencies result from imaging artifacts. Seven cadaveric specimens (three male and four female) were first radiographed and then scanned with CT. A stemless humeral component of current design was implanted in each specimen. After implantation, all specimens were radiographed with different exposure settings. The implant was removed, and the specimens were scanned with CT again. Pre‐ and post‐implantation radiographs and CT scans were compared. The mean Hounsfield units (HU) at the humeral resection plane from the pre‐implantation CT were correlated with the diameter of the radiolucent halo on the post‐implantation radiographs. A symmetric radiolucent halo of variable diameters occurred on all radiographs after implantation when an automatic exposure control was used. The halo disappeared in all specimens when the tube voltage was reduced. Lower CT‐values (HU) before the implantation resulted in greater halos on the radiograph after implantation. Symmetric radiolucent halos can result from imaging artifacts, which is most likely due to radiation scatter. The halos can be minimized by reducing the tube voltage. The halo effect appears to be pronounced in bones with decreased density. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2040–2050, 2017.

     

Food and Drug Administration–reported complications of anatomic stemless total shoulder arthroplasty vary with implant model

BackgroundStemless shoulder arthroplasty not only allows for shorter operative time and less blood loss but also for placement of the humeral head independent of the diaphysis, thereby preserving bone that may be needed for further revisions. The purpose of this study was to evaluate the current adverse event profile for anatomic stemless shoulder arthroplasty using the Manufacturer and User Facility Device database.MethodsThe adverse event reports mandated by the US Food and Drug Administration for all hospitals housed in the Manufacturer and User Facility Device database were screened for mention of anatomic stemless total shoulder arthroplasty (TSA). Each applicable report was then characterized by implant design and failure mode.ResultsThe most commonly reported stemless implants were the Zimmer Biomet Sidus, Zimmer Biomet Nano, and Arthrex Eclipse. The most common complications were pain/stiffness (16.8%), glenoid component loosening (12%), glenoid component failure (11%), and problems with attachment onto the humeral insert (9.9%).ConclusionsBecause of the benefits of increased bone preservation with less operative time and decreased blood loss compared with anatomic stemmed TSA, stemless implants are becoming increasingly popular in clinical practice. There were no findings that discourage the use of stemless TSA in the right candidate.Level of evidenceLevel III; Database Case Series Treatment Study     

Short stem shoulder replacement

Context:

It is agreed that it is important to anatomically reproduce the proximal humeral anatomy when performing a prosthetic shoulder replacement. This can be difficult with a long stemmed prosthesis, in particular if there is little relationship of the metaphysis to the humeral shaft. The ‘short stem’ prosthesis can deal with this problem.

Aims:

A prospective study assessed the results of total shoulder arthroplasty using a short stem humeral prosthesis, a ceramic humeral head, and a pegged cemented polyethylene glenoid.

Materials and methods:

Patients with primary shoulder osteoarthritis were recruited into this prospective trial and pre-operatively had the ASES, Constant, SPADI, and DASH scores recorded. The patients were clinically reviewed at the two weeks, eight weeks, one year, and two year mark with completion of a data form. Radiological evaluation was at the eight week, one year and two year follow-up. At the one and two year follow-up the satisfaction rating, the range of passive and active motion, Constant, ASES, SPADI, DASH and pain results were recorded and analysed with SPPS 20.

Results:

During the study period 97 short stem, ceramic head total shoulder replacements were carried out. At the time of follow-up 12 were two years from operation and 38 one year from operation. Active elevation was overall mean 160 degrees. Constant scores were 76 at 1 year, and 86 at 2 years, ASES 88 and 93, and satisfaction 96% and 98% respectively at one and 2 year follow up. There were no problems during insertion of the humeral prosthesis, or any radiolucent lines or movement of the prosthesis on later radiographs.

Conclusion:

The short stem prosthesis had no complications, and on follow up radiographs good bone fixation. These fairly short term clinical results were overall good.     

Bone mineral density,mechanical properties,and trabecular orientation of cancellous bone within humeral heads affected by advanced shoulder arthropathy

The mechanical properties of cancellous bone in the humeral head are increasingly interesting due to the increased popularity of stemless prosthetic fixation in the cancellous bone of the metaphysis. Age or pathology-related systemic osteoporosis, inactivity, or pathology of the shoulder joint may influence the primary bonding of implants that rely on good cancellous bone quality. We assessed the bone mineral density (BMD) and anisotropy using micro-computed tomography (micro-CT) (0.04 mm voxel size) and correlated the results with indentation load/displacement response. Resected parts of humeral heads (from patients undergoing total shoulder replacement, n = 18) were used as probes. The region of interest was defined as 2 mm medial from the resection plane, presuming that it mirrored the bone quality lateral to the resection plane. The indentation tests were performed with a large probe (diameter 10 mm) in a single destructive loading procedure. The BMD and trabecular orientation were determined by micro-CT. Our results showed a correlation between the BMD and the slope of the load/displacement curve. Furthermore, the trabeculae were predominantly oriented orthogonal to the joint surface. In conclusion, the predominant factor determining the bone quality and mechanical resistance to pressure appears to be the BMD, while trabecular orientation could not be related to load/displacement response. Statement of clinical significance: Bone quality predominately determines the mechanical properties of cancellous bone. This might be crucial when prosthetic implants need to be anchored in metaphyseal bone. Therefore, clinical decision-making processes should also include local BMD measurements.