These authors sought to determine whether humeral bone resorption was associated with inferior outcomes or higher rates of radiographic loosening in 171 TSA patients with average clinical and radiographic followup periods of 50 and 46 months, respectively.
A press-fit technique was used for humeral stem insertion in all cases. Humeral stem size was based on the first sequential broach that obtained rotational stability, typically achieving metaphyseal fixation rather than diaphyseal fixation. Morsalized bone graft from the humeral head was placed into the prepared humeral canal shortly before impaction of the final stem. The glenoid was prepared using standard noncannulated reamers, creating a concentrically matched surface for the glenoid component, often partially correcting glenoid version. The glenoid component was cemented in all cases, with pressurization of cement into the prepared glenoid surface and placement of cement behind the component prior to impaction.
Calcar resorption was identified in 110 patients (64.3%).
No significant overall differences were observed between the patient characteristics or outcomes with and without calcar resorption.
Subgroup analysis showed that patients with grade 3 resorption had a higher incidence of glenoid radiolucencies (50%, P ..001) and patients with a progression from grade 1 to grade 3 had higher incidences of glenoid (50%, P . .003) radiolucencies.
3 months post op
88 months post op
Comment: These authors point out that other risk factors for calcar osteolysis may be more important that stress-shielding. For example, third body wear related to polyethylene and/or cement debris contributes directly to debris-induced osteolysis. The cement technique used in this series included placement of cement onto the backside of the glenoid component. While this has been shown to improve initial glenoid fixation, the thin cement mantles that results could have led to cracks in the cement and resulting wear particles. Patients with quick progression to grade 3 were found to have significantly greater glenoid and humeral radiolucent lines. They also mention that postoperative infection may also result in both medial calcar resorption and glenoid component loosening.
They used a impaction autograft humeral fixation technique with low filling ratios to minimize the risk of stress-shielding. Filling ratios assessed using the initial postoperative radiographs showed metaphyseal filling ratios pf 0.43±0.1 (maximum, 0.66; minimum, 0.21) while the filling ratio at the diaphyseal region was 0.41± 0.08 (maximum, 0.59; minimum, 0.22). These are lower than many studies and consistent with those in another recently described article that showed low levels of adaptive changes with a standard length impaction grafted stem (see below).
Radiographic outcomes of impaction-grafted standard-length humeral components in total shoulder and ream-and-run arthroplasty: is stress shielding an issue?
These authors evaluated humeral stress shielding after shoulder arthroplasty performed with a smooth, standard-length humeral stem fixed with impaction autografting.
Prior to placement of the final component, cancellous autograft harvested from the humeral head was placed in the humeral canal and pressed into place using a humeral impactor with the same stem geometry as the implant. Autograft was progressively inserted until the impactor fit tightly within the humerus. The final uncoated, smooth, stemmed, fixed-angle humeral component with the desired head geometry was then driven into the prepared canal.
At two years after surgery, the radiographic appearances were evaluated by an independent experienced shoulder surgeon from another institution not involved in the care of these patients. The metaphysical and diaphysial filling ratios were measured as shown below.
The filling ratios were small, showing a substantial preservation of bone stock.
The Simple Shoulder Test score improved from 3.9±2.5 to 9.9±2.4.
Humeral component subsidence or component shift was observed in 3 ream-and-run procedures (6%) and in 8 TSAs (10%). These radiographic findings were not significantly associated with patient demographic characteristics, canal-filling ratios, or clinical outcomes.
The authors concluded that this independent assessment of the 2-year radiographic and clinical outcomes of a conventional smooth humeral stem inserted with impaction autografting demonstrates the clinical utility of this bone-preserving approach to humeral component fixation with minimal complications; good clinical outcomes; and low rates of bone loss, component subsidence, and shift in position.
Comment: After three decades of use, impaction autografting of a smooth standard-length stem remains our preferred method for bone-preserving humeral component fixation.
Impaction allografting remains our preferred method for addressing failed prior humeral component fixation.
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