Complex Primary THA

Courtesy: Dr Amar Ranawat, Dr Ashok Shyam, Ortho TV

Introduction

• Complex hip reconstruction may be required in conditions such as acetabular protrusion, acetabular fractures, post traumatic arthritis, and failed fixation around the hip.
• These procedures are technically demanding and require careful planning, adequate exposure, and appropriate implant selection.
• Surgeons must be prepared to address difficulties related to bone defects, previous implants, and soft tissue imbalance.

Management of Hip Protrusion During Total Hip Arthroplasty

Surgical Exposure

• Adequate exposure is essential because the hip is often stiff and difficult to dislocate.
• In many cases, the hip cannot be dislocated easily due to deformity or soft tissue tightness.
• A femoral neck osteotomy may need to be performed before dislocation.

Posterior Approach

• The posterior approach is commonly used.
• Surgeons should remain close to the bone while dissecting to protect surrounding structures.
• The sciatic nerve lies close to the greater trochanter and must be protected throughout the procedure.

Anterolateral Approach

• Some surgeons prefer the anterolateral approach.
• This approach allows clear identification of the greater trochanter and femoral neck.
• A retractor can be placed over the femoral neck to help expose the surgical field.

Identifying the Femoral Neck and Acetabulum

• During exposure, it is important to clearly differentiate the femoral neck from the acetabulum.
• Gentle movement of the femur can help identify the femoral neck because it moves with manipulation.
• The acetabulum remains stationary during these movements.
• In uncertain situations, intraoperative imaging can be used to confirm anatomical landmarks.

Techniques to Improve Exposure

• Wide exposure should be obtained in these cases rather than attempting minimally invasive techniques.
• Osteophytes around the acetabulum may need to be removed to improve visualization.
• Removal of a small portion of the posterior acetabular wall may provide better access to the femoral neck and facilitate dislocation.

Acetabular Preparation

Reaming Strategy

• The acetabular rim is usually intact even in protrusion deformities.
• The mouth of the acetabulum may appear constricted and should be widened carefully.
• Peripheral reaming should be performed while preserving the medial wall.

Cleaning the Medial Defect

• The deepest portion of the defect should not be aggressively reamed.
• Soft tissues and cartilage remnants should be removed using curettes.
• If a reamer is used, it should be small and used gently.

Bone Grafting

• The resected femoral head can be used as a bone graft.
• The graft is placed into the medial defect to restore bone stock.
• This approach helps reconstruct the acetabular floor and supports the acetabular component.

Acetabular Component Stability

• The acetabular component must achieve strong contact with the peripheral host bone.
• Adequate host bone contact should ideally exceed half of the cup surface.
• If host bone contact is insufficient, additional reconstruction techniques such as cages or reinforcement devices may be required.

Cup Orientation

• Proper cup positioning is essential to restore the natural center of rotation of the hip.
• In protrusion cases, slightly reducing the inclination angle may help direct load toward the superior acetabular roof rather than the medial wall.
• Stability of the rim support remains more important than exact cup inclination.

Implant Selection

• Highly porous revision type acetabular components are often preferred.
• These implants provide improved fixation to host bone.
• Screw fixation is commonly used to enhance initial stability.

Reduction Challenges After Cup Placement

• After the acetabular component is placed, reduction of the hip can sometimes be difficult.
• This difficulty occurs particularly in long standing deformities where soft tissues have shortened.
• Extensive soft tissue release may be necessary.

Strategies to Facilitate Reduction

• Adjusting femoral stem position
• Using stems with shorter neck lengths
• Selecting appropriate offset options
• Ensuring balanced cup and stem positioning

Total Hip Arthroplasty in Acute Acetabular Fractures

Indications

Total hip replacement may be considered in selected situations such as:

• Elderly patients with poor bone quality
• Associated femoral neck fracture
• Severe damage to the femoral head
• Irreparable acetabular fractures
• Thin or non reconstructable posterior wall

Surgical Considerations

• Detailed imaging including computed tomography scans may be helpful to understand fracture patterns.
• Stabilization of the acetabular columns may be required before inserting the cup.
• Limited plating can sometimes provide adequate column stability for cup fixation.

Cup Fixation in Fracture Cases

• Rim fit fixation remains the goal.
• Multiple screws are typically required to secure the acetabular component.
• Screw placement into the pubis or ischium can significantly increase construct stability.

Technical Challenge of Pubic Screw Placement

• The direction of screw holes in the cup may not always align with the pubic bone.
• One technique is to insert a guide wire into the pubis before cup insertion.
• The cup is then positioned relative to this wire to allow screw placement along the desired trajectory.

Challenges of Acute Reconstruction

• Performing total hip replacement in the presence of an acute acetabular fracture is more complex than routine hip replacement.
• These procedures have higher rates of complications including instability and fixation failure.
• When possible, fracture fixation alone may be preferred, followed by delayed hip replacement if arthritis develops.

Total Hip Arthroplasty After Healed Acetabular Fractures

Preoperative Considerations

• Previous internal fixation hardware may be present.
• Surgeons should evaluate for possible infection before performing hip replacement.
• Complications such as nerve injury and heterotopic bone formation are more common in these cases.

Hardware Management

• Complete removal of previous implants is not always necessary.
• Only screws or plates that interfere with acetabular preparation need to be removed.
• Attempting to remove all hardware can increase surgical risk.

Acetabular Preparation

• Previous fracture fixation may alter the orientation of the acetabulum.
• Careful evaluation of acetabular anatomy is necessary before cup placement.
• Standard principles of rim fixation and screw augmentation still apply.

Total Hip Arthroplasty for Intertrochanteric Fractures

Indications

Total hip replacement is rarely performed for intertrochanteric fractures but may be considered when:

• The patient is elderly with poor bone quality
• The fracture is severely comminuted
• Early mobilization is essential

Surgical Challenges

• Trochanteric fractures create instability around the hip.
• Reconstruction of the greater trochanter is necessary to restore abductor function.
• Failure to adequately stabilize the trochanter can lead to dislocation.

Surgical Techniques

• Trochanteric fixation can be achieved using sutures, wires, or cables.
• High offset femoral stems may be required to restore soft tissue tension.
• Some surgeons utilize the fracture line as part of the surgical exposure.

Conversion of Failed Internal Fixation to Total Hip Arthroplasty

Common Scenario

• Patients may present with failed fixation devices such as intramedullary nails or dynamic hip screws.

Steps in Hardware Removal

Initial Surgical Steps

• Exposure is performed using the posterior approach in many cases.
• The hip should first be dislocated before attempting hardware removal.
• Releasing soft tissue adhesions helps facilitate dislocation.

Removal Sequence

• Distal locking screws should generally remain in place until the extraction device is engaged.
• Once the extraction device is secured, distal screws can be removed.

Removal of Lag Screws

• The lag screw may be removed using the original extraction instruments if available.
• If standard instruments are not available, the screw can sometimes be removed after femoral head resection.
• Fragmentation of the femoral head can expose the screw and allow it to be driven out in the opposite direction.

Key Surgical Principles for Complex Hip Reconstruction

• Achieve adequate surgical exposure.
• Protect critical neurovascular structures.
• Preserve host bone whenever possible.
• Restore the anatomical center of rotation of the hip.
• Ensure strong peripheral fixation of the acetabular component.
• Use bone grafts when needed to reconstruct bone defects.
• Select implants based on bone quality and defect type.
• Anticipate technical challenges and plan accordingly.

Summary

• Complex total hip arthroplasty cases require meticulous surgical planning and execution.
• Conditions such as acetabular protrusion, fractures, and failed internal fixation significantly increase operative complexity.
• Successful outcomes depend on careful exposure, stable implant fixation, appropriate reconstruction of bone defects, and proper management of previous hardware.
• With thorough planning and adherence to surgical principles, satisfactory functional outcomes can be achieved even in challenging cases