CAN COMPOSITE FEMURS BE USED TO ASSESS PERIPROSTHETIC FRACTURE MECHANICS USING AN ESTABLISHED ROTATIONAL PROTOCOL? REPRODUCTION OF PUBLISHED RESULTS COMPARING COLLARED AND COLLARLESS CEMENTLESS FEMORAL STEMS IN A SIMULATED PERIPROSTHETIC FRACTURE MODEL

Jonathan Lamb; Oliver Coltart; Isaiah Adekanmbi; Todd Stewart; Hemant Pandit

doi:10.1302/1358-992X.2021.2.020

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CAN COMPOSITE FEMURS BE USED TO ASSESS PERIPROSTHETIC FRACTURE MECHANICS USING AN ESTABLISHED ROTATIONAL PROTOCOL? REPRODUCTION OF PUBLISHED RESULTS COMPARING COLLARED AND COLLARLESS CEMENTLESS FEMORAL STEMS IN A SIMULATED PERIPROSTHETIC FRACTURE MODEL

The British Orthopaedic Research Society (BORS) Annual Meeting 2020, held online, 7–8 September 2020.

Jonathan Lamb
Oliver Coltart
Isaiah Adekanmbi
Todd Stewart
Hemant Pandit

CAN COMPOSITE FEMURS BE USED TO ASSESS PERIPROSTHETIC FRACTURE MECHANICS USING AN ESTABLISHED ROTATIONAL PROTOCOL? REPRODUCTION OF PUBLISHED RESULTS COMPARING COLLARED AND COLLARLESS CEMENTLESS FEMORAL STEMS IN A SIMULATED PERIPROSTHETIC FRACTURE MODEL

Lamb J, Coltart O, Adekanmbi I, Stewart T, Pandit H. CAN COMPOSITE FEMURS BE USED TO ASSESS PERIPROSTHETIC FRACTURE MECHANICS USING AN ESTABLISHED ROTATIONAL PROTOCOL? REPRODUCTION OF PUBLISHED RESULTS COMPARING COLLARED AND COLLARLESS CEMENTLESS FEMORAL STEMS IN A SIMULATED PERIPROSTHETIC FRACTURE MODEL. Orthop Procs. 2021;103-B(SUPP_2):20-20. doi:10.1302/1358-992X.2021.2.020

Lamb, Jonathan, et al. “CAN COMPOSITE FEMURS BE USED TO ASSESS PERIPROSTHETIC FRACTURE MECHANICS USING AN ESTABLISHED ROTATIONAL PROTOCOL? REPRODUCTION OF PUBLISHED RESULTS COMPARING COLLARED AND COLLARLESS CEMENTLESS FEMORAL STEMS IN A SIMULATED PERIPROSTHETIC FRACTURE MODEL.” Orthopaedic Proceedings, vol. 103-B, no. SUPP_2, 2021, pp. 20-20., https://doi.org/10.1302/1358-992X.2021.2.020

Lamb, J., Coltart, O., Adekanmbi, I., Stewart, T., & Pandit, H. (2021). CAN COMPOSITE FEMURS BE USED TO ASSESS PERIPROSTHETIC FRACTURE MECHANICS USING AN ESTABLISHED ROTATIONAL PROTOCOL? REPRODUCTION OF PUBLISHED RESULTS COMPARING COLLARED AND COLLARLESS CEMENTLESS FEMORAL STEMS IN A SIMULATED PERIPROSTHETIC FRACTURE MODEL. Orthopaedic Proceedings, 103-B(SUPP_2), 20-20. https://doi.org/10.1302/1358-992X.2021.2.020

Lamb, J., Coltart, O., Adekanmbi, I., Stewart, T. and Pandit, H. (2021) “CAN COMPOSITE FEMURS BE USED TO ASSESS PERIPROSTHETIC FRACTURE MECHANICS USING AN ESTABLISHED ROTATIONAL PROTOCOL? REPRODUCTION OF PUBLISHED RESULTS COMPARING COLLARED AND COLLARLESS CEMENTLESS FEMORAL STEMS IN A SIMULATED PERIPROSTHETIC FRACTURE MODEL.” Orthopaedic Proceedings, 103-B(SUPP_2), pp. 20-20. Available at: https://doi.org/10.1302/1358-992X.2021.2.020

Lamb, Jonathan, Oliver Coltart, Isaiah Adekanmbi, Todd Stewart, and Hemant Pandit. “CAN COMPOSITE FEMURS BE USED TO ASSESS PERIPROSTHETIC FRACTURE MECHANICS USING AN ESTABLISHED ROTATIONAL PROTOCOL? REPRODUCTION OF PUBLISHED RESULTS COMPARING COLLARED AND COLLARLESS CEMENTLESS FEMORAL STEMS IN A SIMULATED PERIPROSTHETIC FRACTURE MODEL.” Orthopaedic Proceedings 103-B, no. SUPP_2 (2021): 20-20. https://doi.org/10.1302/1358-992X.2021.2.020

Lamb J, Coltart O, Adekanmbi I, Stewart T, Pandit H. CAN COMPOSITE FEMURS BE USED TO ASSESS PERIPROSTHETIC FRACTURE MECHANICS USING AN ESTABLISHED ROTATIONAL PROTOCOL? REPRODUCTION OF PUBLISHED RESULTS COMPARING COLLARED AND COLLARLESS CEMENTLESS FEMORAL STEMS IN A SIMULATED PERIPROSTHETIC FRACTURE MODEL. Orthop Procs. 2021 Mar 1;103-B(SUPP_2):20-20. https://doi.org/10.1302/1358-992X.2021.2.020

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Abstract

Objective

To compare the periprosthetic fracture mechanics between a collared and collarless fully coated cementless femoral stem in a composite femur.

Methods

Two groups of six composite femurs (‘Osteoporotic femur’, SawBones, WA USA) were implanted with either a collared (collared group) or collarless (collarless group) cementless femoral stem which was otherwise identical by a single experienced surgeon. Periprosthetic fractures of the femur were simulated using a previously published technique. High speed video recording was used to identify fracture mechanism. Fracture torque and angular displacement were measured and rotational work and system stiffness were estimated for each trial. Results were compared between collared and collarless group and the comparison was evaluated against previously published work using fresh frozen femurs and the same protocol.

Results

In composite femur testing median fracture torque (IQR) was greater with a collared versus collarless implant (48.41 [42.60 to 50.27] Nm versus 45.12 [39.13 to 48.09] Nm, p= 0.4). Median rotational displacement (IQR) was less with a collared versus collarless implant (0.29 [0.27 to 0.31] radians versus 0.33 [0.32 to 0.34] radians, p= 0.07). Estimated rotary work was similar between groups (5.76 [4.92 to 6.64] J versus 5.21 [4.25 to 6.04] J, p= 0.4). Torsional stiffness was greater with a collared versus collarless implant (158.36 [152.61, 163.54] Nm per radian versus 138.79 [122.53, 140.59] Nm per radian, p= 0.5). Collarless stems were seen to move independently of the femur and fracture patterns originated at the calcar.

Conclusions

Testing with composite femurs using an established protocol produced similar results to previously published studies using human femurs, but the difference between collared and collarless stems was smaller. The internal homogenous foam material in composite femurs does not accurately represent the heterogeneous cancellous bone which supports a femoral stem in vivo and may lead to overestimation of implant stability.