Humeral stress shielding following cemented endoprosthetic reconstruction: An under‐reported complication?

Abstract

IntroductionThe proximal humerus is a common location for primary and non‐primary tumors. Reconstruction of the proximal humerus is commonly performed with an endoprosthesis with low rates of structural failure. The incidence and risk factors for stress shielding are under reported.MethodsThirty‐nine (19 male, 20 female) patients underwent resection of the proximal humerus and reconstruction with a cemented modular endoprosthesis between 2000 and 2018. The mean resection length was 12 ± 4 cm and was most commonly performed for metastatic disease (n = 26, 67%).ResultsStress shielding was observed in 9 (23%) patients at a mean of 29 (6–132) months postoperatively. Patients with stress shielding were noted to have shorter intramedullary stem length (87 vs. 107 mm, p < .001), longer extramedullary implant length (16 vs. 14 cm, p = .01) and a higher extramedullary implant to stem length ratio (2.1 vs. 1.1, p < .001). The incidence of stress shielding was higher (p = .003) in patients reconstructed with 75 mm stem (n = 6, 67%) lengths.ConclusionStress shielding of the humerus was associated with the use of shorter stems and long extramedullary implants. The long‐term ramifications of stress shielding on implant stability, complications at the time of revision surgery, and overall patient outcomes remain unknown.

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

“…On the other hand, there was no correlation between extent of stress shielding and the duration of follow-up (p = 0.17). With the numbers available, there was no difference regarding the extent of stress shielding between patients with extra-articular resections compared to intra-articular resections (17% (8-24 vs. 12% (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26), p = 0.43) and with respect to the use of reverse total shoulder arthroplasty compared to anatomical hemiprostheses (14% (IQR 10-29) vs. 12% (6-21), p = 0.47). Additionally, the ratio of stem length to the length of extramedullary reconstruction was not higher in patients with an extent of stress shielding > 50% (1.93 (IQR 1.61-2.43) vs. 2.26 (IQR 1.87-2.53), p = 0.46).…”

“…However, considering that this procedure is still relatively rare, there are few studies that investigate individual failure modes, particularly aseptic loosening or failure of the bone–implant interface [ 11 , 27 , 28 ]. To our knowledge, only one study by Braig et al analyzed stress shielding after implantation of modular endoprosthesis of the humerus [ 18 ]. This study included 39 patients (metastatic disease n = 26; primary sarcoma n = 7; hematological disease n = 5) after proximal humerus resection and reconstruction with cemented modular endoprosthesis focusing on stress shielding, associated risk factors, and perioperative complications.…”

“…However, only one study has most recently drawn attention to this phenomenon. Braig et al reported stress shielding around cemented stems in 23% of cases including 39 patients of whom 67% had PHR due to bone metastases [ 18 ]. To our knowledge, there are no studies on stress shielding around uncemented PHR and no studies that focus on primary sarcoma patients despite the fact that for long-term surviving patients, implant survival and associated revision surgeries become more important [ 19 , 20 ].…”

Reducing the prosthesis modulus by inclusion of an open space lattice improves osteogenic response in a sheep model of extraarticular defect

“…Moreover, the engineered porosity (if substantial) reduces device’s elastic modulus, which has been suggested to result in enhanced osteogenesis and reduced stress shielding of the periprosthetic bone ( Huiskes et al, 1992 ; Sumner and Galante, 1992 ; Nouri and Hodgson, 2010 ; Moghaddam et al, 2016 ; Caffrey et al, 2018 ). Stress shielding is a common complication of endoprosthetic reconstruction surgery and is significant not only because of associated surgical failure, but also due to the resulting periprosthetic osteopenia, which significantly limits future treatment options ( Nagels et al, 2003 ; Tagliero et al, 2020 ; Braig et al, 2021 ; Cho et al, 2021 ; Bendich et al, 2022 ). Selecting an appropriate prosthesis modulus is crucial to achieving the best possible functional and long-term outcomes for patients with medical implants because it ensures that the mechanical properties of the artificial implant closely match those of the surrounding natural tissues and bones, preventing issues like stress shielding and subsequent implant loosening, or implant failure that may arise if the prosthesis is too rigid or too flexible compared to the natural tissue.…”

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.…”