Postresurfacing periprosthetic femoral neck fractures: nonoperative treatment

Risk assessment of resurfacing implant loosening and femur fracture under low-energy impacts taking into account degenerative changes in bone tissues. Computer simulation

BACKGROUND AND OBJECTIVE

Degenerative diseases of the musculoskeletal system significantly reduce the quality of human life. Hip resurfacing is used to treat degenerative diseases in the later stages. After surgery, there is a risk of endoprosthesis loosening and low-energy fracture during daily physical activity. Computer modeling is a promising way to predict the optimal low-energy loads that do not lead to bone destruction. This paper aims to study numerically the mechanical behavior of the proximal femur, amenable to degenerative changes and subjected to hip resurfacing under low-energy impact equivalent to physiological loads.

METHODS

A numerical model of the mechanical behavior of the femur after hip resurfacing arthroplasty under low-energy impacts equivalent to physiological loads is presented. The model is based on the movable cellular automaton method (discrete elements), where the mechanical behavior of bone tissue is described using the Biot poroelasticity accounting for the presence and transfer of interstitial biological fluid.

RESULTS

For the first time, it is shown that a poroelastic model allows predicting the service life of endoprostheses, taking into account the individual characteristics of the bone tissues amenable to various degenerative diseases. The obtained results indicate that the changes in the bone properties have a significant influence on the critical forces corresponding to the first appearance of microcracks and the fracture formation. At the same time, their effect on the type of fracture is negligible. A much more impact on the type of fracture has the kinematic and dynamic conditions of the exposure.

CONCLUSIONS

The obtained results show the promise of using the proposed model for predicting the operational resource of resurfacing endoprostheses, taking into account the physiological features of the structure of the patient's bone tissues.

Bilateral fixation of a periprosthetic intertrochanteric hip fracture below Birmingham hip resurfacing

This case report involves a 59-year-old woman with a traumatic right intertrochanteric hip fracture below a previous Birmingham hip resurfacing (BHR). This woman had almost an identical fracture on the left hip 3 years before which was treated with a proximal femoral locking compression plate. Of note periprosthetic fractures following hip resurfacing are usually subcapital and treated with a revision or conservative management. We present an unusual surgical problem that has occurred twice in the same patient and has been treated effectively on both occasions using proximal femoral plating. To the best of our knowledge, there have been no other reports of bilateral periprosthetic fractures being treated in this way.

Fixation of a Periprosthetic Intertrochanteric Hip Fracture below a Birmingham Hip Resurfacing

This case report involves a 56-year-old female (Mrs X) with a traumatic intertrochanteric hip fracture with subtrochanteric extension below a previous Birmingham hip resurfacing. Periprosthetic fractures following hip resurfacing are usually subcapital and treated with a revision or conservative management. We present an unusual surgical problem with an interesting solution stabilising the fracture using a proximal femoral locking compression plate (LCP). Eight months following surgery the patient is able to walk pain free and there is good fixation and stability.