gms | German Medical Science

Objective: As population grows older, and patients receive primary joint replacements at younger age, the need for patient-specific surgery plans and implant designs increases. Most likely primary interventions will require revision surgery one day in a lifetime.

Challenging reconstructions of the acetabular bone, due to massive bone loss and/or multiple revisions, require a high-quality three-dimensional surgical planning.

Unfortunately, drawing up such a planning usually is demanding and time-consuming for both the clinician and the collaborating technician.

Ideally, the technician occupied which such planning, would be highly skilled to interpret and integrate the clinical constraints into the design. He would preferably accelerate the discussions by a patient-specific approach; allowing multiple and swift moments of interaction, fine-tuning and approval by the clinician; nevertheless making efficient use of the clinician’s time and effort.

Methods: A CT-based computer-supported methodology has been developed and validated to offer the user a biomechanically justified proposal for correction of a bone defect or malformation.

Based on this proposal, the personalized defect-filling implant is designed, in close collaboration with the surgeon, for unique fit and functionality. In the implant design, a porous structure fills the bone defect, while a thin porous layer is present at the interface between the implant and the bone. Inclination and anteversion angles are restored to their anatomical extent by analyzing planned cup orientation. Either press-fit or cemented liner fixation can be incorporated in the design.

The implant-bone system is evaluated in a fully patient-specific manner taken into account personal parameters such as patient weight, individualized muscle attachment and trajectories and bone properties.

Screw positions and lengths are pre-operatively and optimally planned based on the variable bone quality. Insertion of screws is transferred to surgery using jig guiding technology specifically fitting the implant surface.

Results and conclusions: To date, three clinical cases have benefited from the presented patient-specifically designed and evaluated acetabular implants, and other are presently in preparation. Personalized case documentation was provided for pre- and intra-operative referencing. Postoperative imaging with X-rays showed satisfying positioning and joint restoration. Short term follow-up (11 to 43 months) indicates good outcome for the patients treated.

Using the presented all-in-one solution which addresses both patient’s and surgeon’s needs, complex pelvic bone defects can be treated adequately and efficiently. Key to realization of this concept is the fusion of practical knowledge on reconstructive bone surgery, advanced biomechanical modelling, and medical imaging procedures of both hard and soft tissue.