Periprosthetic Stress Shielding of the Humerus after Reconstruction with Modular Shoulder Megaprostheses in Patients with Sarcoma

Abstract

(1) Background: Modular megaprosthetic reconstruction using a proximal humerus replacement has emerged as a commonly chosen approach after bone tumor resection. However, the long-term risk for revision surgery is relatively high. One factor that might be associated with mechanical failures is periprosthetic osteolysis around the stem, also known as stress shielding. The frequency, potential risk factors, and the effect on implant survival are unknown. (2) Methods: A retrospective single-center study of 65 patients with sarcoma who underwent resection of the proximal humerus and subsequent reconstruction with a modular endoprosthesis. Stress shielding was defined as the development of bone resorption around the prosthesis stem beginning at the bone/prosthesis interface. The extent of stress shielding was measured with a new method quantifying bone resorption in relation to the intramedullary stem length. All patients had a minimum follow-up of 12 months with conventional radiographs available and the median follow-up amounted to 36 months. (3) Results: Stress shielding was observed in 92% of patients (60/65). The median longitudinal extent of stress shielding amounted to 14% at last follow-up. Fifteen percent (10/65) showed bone resorption of greater than 50%. The median time to the first radiographic signs of stress shielding was 6 months (IQR 3–9). Patients who underwent chemotherapy (43/65) showed a greater extent of stress shielding compared to those without chemotherapy. Three percent (2/65) of patients were revised for aseptic loosening, and one patient had a periprosthetic fracture (1/65, 1.5%). All these cases had >20% extent of stress shielding (23–57%). (4) Conclusions: Stress shielding of the proximal humerus after shoulder reconstruction with modular megaprosthesis is common. It occurs within the first year of follow-up and might be self-limiting in many patients; however, about one third of patients shows progression beyond the first year. Still, mechanical complications were rare, but stress shielding might be clinically relevant in individual cases. The extent of stress shielding was increased in patients who underwent perioperative chemotherapy. Stress shielding can be quantified with an easy method using the stem length as a reference.

Effect of implant length variations on stress shielding in proximal humeral replacement after tumor excision under torsion: Finite element study

“…Nevertheless, a quantitative understanding of the role of peri‐implant bone stresses in response to varying endoprosthesis length in implant stability is still lacking in the current literature. Implant failure due to peri‐prosthetic osteolysis around the stem caused by stress shielding as well as implant loosening are common modes of failure in proximal humeral replacement as previously described 2,4,12 . Better solutions are required to improve existing surgical procedures.…”

“…Implant failure due to peri-prosthetic osteolysis around the stem caused by stress shielding as well as implant loosening are common modes of failure in proximal humeral replacement as previously described. 2,4,12 Better solutions are required to improve existing surgical procedures. Computational modeling can be considered for investigating the loading of the whole bone system and its resultant stability in response to changes in PAREATUMBEE ET AL.…”

“…Aseptic loosening is a common problem associated with custom mega‐protheses according to a study involving 57 patients with malignant and aggressive benign tumors in the proximal humerus 4 . Additionally, modular megaprosthetic replacement of the proximal humerus was also found to be highly susceptible to revision surgery owing to mechanical failure of the implant and peri‐prosthetic osteolysis around the stem caused by stress shielding, observed in 92% of patients studied 12 . Failure among the younger population which has a higher life expectancy has ignited the search for more durable and alternative solutions.…”

Implant Survival, Clinical Outcome and Complications of Megaprosthetic Reconstructions Following Sarcoma Resection

“…However, considering the expanding usage of reverse shoulder arthroplasties and improved patient survival as well as potentially increasing functional demand in long-term survivors [ 6 ], it is possible that glenoid loosening, as it has been reported for non-oncological shoulder arthroplasty [ 36 ], may also become more relevant in orthopedic oncology [ 28 ]. Furthermore, the radiological phenomenon of stress shielding around a humeral prosthetic stem has most recently also been reported for cemented and uncemented megaprostheses [ 37 , 38 ] and was found to be quite frequent. Nonetheless, in both studies, mechanical complications were rare and stress shielding might only play a role in individual cases.…”

Computer‐aided Design and 3D‐printed Personalized Stem‐plate Composite for Precision Revision of the Proximal Humerus Endoprosthetic Replacement: A Technique Note

“…[7][8][9] Soft tissue failure is the most common failure mode, while aseptic loosening is considered to be rather uncommon. 10,11 However, patients with aseptic loosening often suffer bone loss, which poses a great challenge in following revision. 12 Bone rarefaction or osteolysis around prosthetic stems results in a poor implantation environment for revision endoprosthesis.…”