Is Modular Prosthesis Superior to Monoblock Variant in Hemiarthroplasty for Fracture Neck of Femur?

Background: The incidence of hip fractures is increasing every year worldwide. Even though hemiarthroplasty is one of the most common procedures performed for a fractured neck of the femur, there is very little research comparing the outcomes of monoblock and modular systems, the two most commonly used prostheses in neck of the femur fractures. It was hypothesized that in narrow femoral canals, the single-size monoblock stem would be more difficult to insert and lead to complications like limb lengthening and intra-operative calcar fractures. The objective of our study was to compare the outcomes of a modular prosthesis with that of a monoblock prosthesis in a fractured neck of the femur.

Materials And Methods: This study analyzed the surgical outcomes of 192 cases of hemiarthroplasties performed over a 4-year period using a modular system and compared it to 192 cases performed using a single-sized monoblock system.

Results: The monoblock systems were more likely to cause post-operative limb lengthening compared to their modular counterparts (P = 0.01). The incidence of intra-operative fractures was also more in the monoblock system, although it was not statistically significant. Up to 45% of patients required a femoral stem size smaller than the single-sized monoblock system as the optimum size for their femoral canals, which was available only in the modular system.

Conclusions: Modular prosthesis was found to have lower chances of post-operative limb lengthening and lower chances of intraoperative calcar fractures compared to monoblock prosthesis. Careful pre-operative radiologic planning is essential in cases where monoblock systems are used, and the modular system might serve as a viable solution in such scenarios.