In a recent case discussion with Joshua Rozell MD (NYU Langone), we reviewed a patient with severe bilateral hip dysplasia and congenital hip dislocation. These cases present unique challenges that require advanced planning, precise execution, and thoughtful patient communication.
Understanding Hip Dysplasia in Adults
In severe dysplasia, the hip joint does not develop normally. Instead of sitting in the true acetabulum (native socket), the femoral head often migrates upward, forming a pseudoacetabulum.
This leads to:
- Abnormal joint mechanics
- Progressive cartilage wear
- Pain and loss of function
- Significant leg length discrepancy
In this case, the patient’s femoral head was positioned far above the native socket, making reconstruction significantly more complex than a standard hip replacement.
The Surgical Challenge: Restoring the “True Hip Center”
One of the most important goals in hip replacement for dysplasia is restoring the hip to its anatomic position.
This involves:
- Identifying the true acetabulum (which is often small and underdeveloped)
- Repositioning the implant into this location
- Reconstructing missing bone where needed
Restoring the hip center improves:
- Biomechanics
- Implant longevity
- Patient function
However, it also introduces one of the biggest risks in these cases…
Leg Length Correction and Sciatic Nerve Risk
When the hip is brought back down to its normal position, the leg is effectively lengthened.
This creates tension on the sciatic nerve, which can lead to:
- Nerve injury
- Weakness or foot drop
- Persistent neurologic symptoms
To manage this risk, surgeons must carefully plan:
- How much lengthening is safe
- Whether a femoral shortening osteotomy is required
Equally important is preoperative patient counseling.
One key principle:
“The difference between an explanation and an excuse is timing.”
Patients should understand ahead of time that:
- Leg lengths may temporarily differ
- A shoe lift may be needed
- A staged approach (operating on the second hip later) may be required
The Role of Robotic-Assisted Surgery
In complex anatomy like this, robotic technology plays a critical role.
With robotic planning, we can:
- Visualize the patient’s anatomy in 3D before surgery
- Accurately locate the true acetabulum
- Plan implant size, position, and orientation
- Map out screw trajectories into strong bone
- Simulate reconstruction before entering the operating room
During surgery, the robotic system helps execute this plan with a high level of precision.
This improves:
- Accuracy
- Reproducibility
- Surgeon confidence in complex cases
Why We Use Acetabular Augments
In dysplasia, there is often missing bone in the socket, particularly superiorly.
To address this, we use acetabular augments, which serve two key purposes:
1. Primary Fixation
If there is not enough native bone to support the implant, augments help recreate the structure needed for stability.
2. Secondary Stabilization
Even when the cup is stable, augments fill remaining defects to:
- Prevent implant migration
- Promote bone ingrowth
- Improve long-term durability
In this case, the augment was used to fill a superior defect and was unitized with the cup using bone cement, creating a single stable construct.
Surgical Workflow: Step-by-Step
The procedure followed a precise sequence:
- Identify the true acetabulum using anatomy, imaging, and robotic guidance
- Ream the socket to prepare for the implant
- Ream for the augment to match the defect
- Place the acetabular cup and secure with screws
- Insert the augment and fix it into position
- Use cement to unitize the construct
- Implant the femoral component (cemented in this case due to anatomy)
- Reduce the hip and confirm stability and leg length
Each step is carefully planned preoperatively and executed with intraoperative precision.
Anterior Approach in Complex Cases
This case was performed using the direct anterior approach, which offers:
- Supine positioning (helpful for assessing leg lengths)
- Use of fluoroscopy during surgery
- Familiarity for surgeons experienced with this technique
While some surgeons may prefer a posterior approach in complex reconstructions, the most important factor is surgeon experience and comfort.
Implant Strategy: Cemented vs Cementless
In complex dysplasia cases, flexibility is key.
Options include:
- Cementless stems for good bone quality
- Cemented stems for wider canals or poor bone
- Revision-style implants for added control and fixation
In this patient, a cemented femoral stem was used due to a capacious canal, allowing for better immediate stability.
Key Takeaways
This case highlights several important principles:
- Restoring the true hip center is critical for long-term success
- Leg length changes must be carefully managed to avoid nerve injury
- Patient education is essential before surgery
- Robotic planning enhances precision in complex anatomy
- Acetabular augments are powerful tools for reconstruction
- Having multiple implant options available is critical
Final Thoughts
Complex hip dysplasia cases represent some of the most technically demanding procedures in joint replacement.
With modern tools like robotic-assisted surgery, advanced implants, and thoughtful preoperative planning, we are able to:
- Improve accuracy
- Reduce complications
- Deliver more predictable outcomes
If you’re a patient dealing with hip dysplasia or a surgeon interested in advanced reconstruction techniques, this case highlights how far hip replacement technology has come.
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