Digital pre-operative planning for challenging surgical procedures can increase the chances of a successful outcome. Careful pre-operative planning not only helps the surgeon formulate the plan, but also prepares the OR team, provides intra-operative checks to ensure the procedure is going according to plan, and enables post-operative assessment of the outcome as compared to the pre-operative plan. Planning pre-operatively enhances preparedness and provides reassurance, two factors surgeons need in the operating room. Digital planning also allows the surgeon to create, visualize, and communicate the pre-operative plan effectively.
A 43 year-old female runner suffered a displaced right femoral neck stress fracture that failed to heal with conservative treatment. She was treated at an outside hospital with percutaneous reduction and internal fixation. At six months post-op, the patient was experiencing increasing pain, especially with walking, and limited, painful range of motion.
On physical examination, she has a discrepancy in her leg lengths - the affected side being shorter than the non-affected side. The AP pelvis x-ray shows a femoral neck non-union on the right and asymmetric hip joints. In addition, the patient’s hip is in varus, causing her leg length discrepancy.
While a hip replacement allows for immediate weight-bearing, and bone healing would not be an issue, the bearing surfaces may not be able to tolerate the patient’s lifestyle and desire to return to running. Also, if the hip replacement became infected, or she required a revision surgery, either would present a significant complication.
An osteotomy is more challenging technically but post-operatively, once healed, she would not have any limitations or restrictions to activities. The procedure is not done frequently, but if well planned (and executed), will restore the patient’s leg lengths, restore her alignment, allow her non-union to heal, and maintain her native femoral head.
Using the Materialise OrthoView digital pre-operative planning software enables pre-surgical visualization of a valgus-producing intertrochanteric osteotomy.
The Planning Stage
The right femoral neck angle was measured as 118 degrees and the left 132 degrees. The 14-degree difference results in a shorter right leg, changes the forces going across the hip, and does not allow the fracture to heal
The femoral neck and transischial line wizards in the planning software allow us to determine both the neck-shaft angle and the leg-length discrepancy of the right side versus the left.
The Reduction Stage
Using the planning tools to visualize how to optimize femoral neck healing, the angle of the non-union is determined relative to the angle of the affected femoral neck (right) and the normal femoral neck angle from the uninjured side (left). Part of the art is getting the femoral neck non-union to heal by making it perpendicular to the joint reactive forces along the femoral neck.
The location of the cut is determined by the x-rays and the desired correction, whereas the angle of the cut is determined by the necessary angle that will allow the femoral neck to heal. The length of the segment is determined by the cut location and angle. This measurement is used as a guide in the OR.
Visualizing the anticipated final x-ray with the cut made and head/next moved into it’s new position.
The osteotomy is performed digitally in the Materialise OrthoView software. The cut is made, and the head / neck is moved into its new position to visualize the anticipated final x-ray as a check and reference. The blade plate used to repair the osteotomy can then be templated.
A final check of the new neck-shaft angle is done. In addition, a final measurement of the hardware that will be used to fix the osteotomy is taken so that the appropriate equipment can be ordered, including the correct angle blade plate with the appropriately sized blade.
The final radiographs show that the femoral neck is now in an optimal position, the leg lengths are now equal and the neck shaft angle is no longer in varus.
The fact that the plan matches the technical execution is reassuring and provides some comfort that the patient should have a desirable outcome.