Regaining Gait Using an Early Postoperative Hip Prosthesis: A Case Report of an Elderly Woman

Design and optimization of a new integrated hip and knee prosthesis structure

BACKGROUND

Conventional hip disarticulation prostheses (HDPs) are passive devices with separate joint structures, limiting amputees' ability to control and resulting in abnormal gait patterns. This study introduces a new HDP integrating the hip and knee joints for amputees' natural gait.

METHODS

The new HDP restores the physiological rotation center of the hip with a remote center of motion (RCM) structure, and simulates the knee motion with a four-bar structure. Nonlinear programming was employed to optimize the hip-knee joint structure. A hybrid multi-objective drive structure with a series-parallel connection was also designed to ensure motion synergy between the hip and knee joints. Finally, a prototype of the prosthesis was tested using the HDP test system.

RESULTS

The optimization results demonstrate that the new HDP accurately restores the rotation center of the femur in amputees, with the knee's instantaneous center of rotation (ICR) trajectory closely resembling that of the human knee (Pearson correlation coefficient is 0.999). The study shows that the new HDP achieves a motion reproduction accuracy of over 95% for the human hip joint at walking speeds above 1.5 km/h, 38% higher than conventional prosthesis. Similarly, at the same walking speed, the new HDP replicates the motion of the human knee at 82.89%, surpassing conventional prosthesis by 57.85%.

CONCLUSIONS

The new HDP restores symmetry and replicates synergistic movement in amputees' lower limbs, exhibiting superior movement characteristics compared to conventional prostheses. This innovative HDP has the potential to enhance the quality of life for amputees.

Hip Disarticulation in Wound Care: A Case Series

BACKGROUND

Hip disarticulation (HD) is a radical lower extremity amputation performed by carefully transecting all muscles and nerves surrounding the hip joint and separating the leg at the joint capsule. It is considered a last resort to be used as a life-preserving measure under emergent circumstances due to high rates of morbidity and mortality.

METHODS

This case series presents 4 patients who underwent HD. The procedure was performed due to various indications including necrotizing fasciitis, gangrene, stump necrosis from previous above-the-knee amputation, and septic joint secondary to chronic osteomyelitis, 3 of which were planned and 1 was emergent.

RESULTS

The procedure was performed successfully in all 4 patients. Furthermore, all patients were eventually discharged to home or to a long-term care facility for wound care or rehabilitation.

CONCLUSIONS

Overall, HD should be reserved as a life-saving treatment for various indications including infections that fail other modalities, limb ischemia, trauma, and malignancy. Ideally, this procedure would be planned and performed on proper candidates; however, HD should still be a consideration in the emergent setting regardless of most optimal patients due to its life-saving potential.