Mandatory NPO status for at least 8 hours, preoperative antibiotic prophylaxis, complete blood count, coagulation profile, type and cross-match for blood transfusion, cardiac clearance for anesthesia, and deep vein thrombosis prophylaxis assessment.
Post-operative monitoring in the recovery unit, pain management via multimodal analgesia, early mobilization within 24 hours with physical therapy, anticoagulant therapy to prevent thromboembolism, suture removal in 10-14 days, and hip precautions to prevent dislocation.
1. Comprehensive Introduction & Overview
Hemiarthroplasty of the hip is a specialized surgical procedure designed to address specific fractures of the proximal femur, primarily involving the femoral head and neck, while sparing the acetabulum (the hip socket). Unlike a Total Hip Arthroplasty (THA), which replaces both the femoral head and the acetabular cartilage, hemiarthroplasty involves the replacement of only the femoral component.
This procedure is most commonly reserved for elderly, physiologically frail patients who have sustained a displaced femoral neck fracture. The primary clinical objective is to restore mobility, alleviate pain, and facilitate early weight-bearing, thereby minimizing the systemic complications associated with prolonged immobilization in geriatric populations. By replacing the fractured femoral head with a metallic prosthesis, the surgeon creates a new articulating surface that fits into the patient’s native, preserved acetabulum.
2. Deep-Dive: Technical Specifications and Mechanisms
The mechanism of hemiarthroplasty relies on the structural integrity of the patient’s original acetabular cartilage. If the cartilage is healthy, there is no clinical requirement to replace it, making hemiarthroplasty a more conservative approach than a total hip replacement.
Types of Prosthetic Designs
There are two primary classifications of hemiarthroplasty implants:
| Feature | Unipolar Hemiarthroplasty | Bipolar Hemiarthroplasty |
|---|---|---|
| Design | Single-piece head attached to the stem. | Two-part design: an inner head within an outer shell. |
| Articulation | Articulates directly against the acetabulum. | Articulates at the inner bearing and the acetabulum. |
| Friction | Higher friction on acetabular cartilage. | Lower friction; reduced wear on native bone. |
| Stability | Generally high, but prone to migration. | High; designed to reduce acetabular erosion. |
Fixation Methods
- Cemented Fixation: Utilizing bone cement (polymethylmethacrylate - PMMA). This is preferred for osteoporotic bone, as it provides immediate stability and allows for immediate full weight-bearing.
- Cementless (Press-fit) Fixation: Relies on biological fixation where bone grows into a porous coating on the stem. This is typically reserved for younger, healthier bone stock.
3. Extensive Clinical Indications & Usage
Hemiarthroplasty is not a universal solution for hip pathology; it is highly specific to geriatric trauma.
Primary Indications
- Displaced Femoral Neck Fractures: The most common indication. In older patients, the blood supply to the femoral head is often compromised by the fracture, leading to a high risk of avascular necrosis (AVN).
- Pathological Fractures: Fractures resulting from metastatic bone disease in the proximal femur.
- Failed Internal Fixation: If a previous attempt to pin the fracture (ORIF) has failed.
Contraindications
- Acetabular Pathology: Pre-existing osteoarthritis, rheumatoid arthritis, or acetabular dysplasia. In these cases, a Total Hip Arthroplasty (THA) is mandatory.
- Active Infection: Systemic sepsis or localized hip infection.
- Patient Physiology: Patients with high functional demands or long life expectancies are generally better candidates for THA.
4. Pre-Operative Preparation
Preparation is critical to mitigating risks in an often-vulnerable patient population.
- Clinical Assessment: Evaluation of comorbidities (cardiac, pulmonary, renal) via the ASA (American Society of Anesthesiologists) classification.
- Imaging: High-resolution radiographs of the pelvis and lateral hip. CT scans may be used to assess bone quality or occult fractures.
- Medical Optimization: Management of anticoagulants (e.g., stopping Warfarin/Clopidogrel), blood glucose control, and nutritional assessment to ensure adequate wound healing.
- Consent: Discussion regarding the differences between hemi- and total hip replacement, specifically regarding the risk of future acetabular wear.
5. Detailed Procedure Steps
The procedure is typically performed under spinal or general anesthesia via an anterolateral (Watson-Jones) or posterior (Moore/Southern) approach.
- Exposure: The hip joint is accessed through a muscle-sparing or muscle-splitting incision. The capsule is incised to expose the femoral neck fracture.
- Femoral Head Extraction: The fractured femoral head is removed from the acetabulum.
- Preparation of the Femoral Canal: The medullary canal is reamed and broached to the appropriate size to accept the prosthetic stem.
- Trialing: A trial prosthesis is inserted to check leg length, offset, and stability.
- Implantation:
- If Cemented: The canal is cleaned, a restrictor is placed, and cement is injected under pressure before the stem is inserted.
- If Cementless: The stem is impacted into place for a "press-fit."
- Closure: The soft tissues, fascia, and skin are closed in layers. A drain may be used depending on surgeon preference.
6. Post-Operative Recovery Protocol
The "Fast-Track" recovery model is the standard of care for hemiarthroplasty.
- Immediate Post-Op: Mobilization often begins within 6–24 hours post-surgery.
- Weight-Bearing: Usually weight-bearing as tolerated (WBAT), unless the bone quality is extremely poor.
- Physical Therapy (PT): Focus on gait training, transfer mechanics, and hip abductor strengthening.
- Precautions (Posterior Approach): To prevent dislocation, patients are often instructed to avoid:
- Flexion beyond 90 degrees.
- Adduction past the midline.
- Internal rotation of the hip.
7. Potential Complications
While highly effective, hemiarthroplasty carries inherent surgical and physiological risks:
- Dislocation: Occurs more frequently in the posterior approach.
- Acetabular Erosion: The prosthetic head slowly wears down the natural cartilage of the socket over several years.
- Periprosthetic Fracture: Fractures occurring around the femoral stem during or after surgery.
- Infection: Deep prosthetic infection is a catastrophic complication often requiring two-stage revision.
- Leg Length Discrepancy: Ensuring equal length is challenging and requires precise intraoperative measurement.
- Systemic Risks: Deep vein thrombosis (DVT), pulmonary embolism (PE), and cardiac events due to the age of the patient demographic.
8. Alternative Treatments
- ORIF (Open Reduction Internal Fixation): Using screws or a sliding hip screw. Best for non-displaced fractures or younger patients to preserve the native femoral head.
- Total Hip Arthroplasty (THA): Replacing both the ball and socket. Recommended for patients with pre-existing arthritis or those with higher physical demands.
- Non-Operative Management: Reserved only for patients with prohibitive surgical risk who are not expected to survive or gain function from surgery.
9. Frequently Asked Questions (FAQ)
1. What is the difference between Hemiarthroplasty and Total Hip Replacement?
Hemiarthroplasty replaces only the ball of the hip joint. Total Hip Arthroplasty replaces both the ball and the socket.
2. How long does a hemiarthroplasty implant last?
In the typical geriatric patient, the implant usually lasts for the remainder of the patient's life, as the activity level is generally lower.
3. Will I need physical therapy?
Yes, PT is essential for regaining strength and learning how to navigate daily activities safely while protecting the hip.
4. How long is the hospital stay?
Most patients stay 2 to 4 days, depending on their ability to perform basic mobility tasks.
5. Can I sleep on my side?
Usually, side-sleeping is restricted for the first 6 weeks, particularly on the operative side, to prevent dislocation.
6. What are the signs of a complication?
Increased redness, drainage from the incision, sudden severe pain, or a "giving way" sensation should be reported to your surgeon immediately.
7. Is the procedure painful?
Post-operative pain is managed with a multimodal approach including nerve blocks, anti-inflammatories, and analgesics.
8. Will I set off airport metal detectors?
Yes, the metallic stem will likely trigger security scanners. Always carry your implant ID card.
9. What is "acetabular erosion"?
This is the wearing away of the natural hip socket cartilage caused by the constant friction of the metal prosthesis head.
10. Can I return to sports?
Low-impact activities like walking or swimming are encouraged. High-impact sports are generally discouraged to protect the implant.
10. Conclusion and Clinical Outlook
Hemiarthroplasty remains a cornerstone procedure in orthopedic trauma. Its success is defined not by the achievement of "perfect" anatomy, but by the rapid restoration of function and the prevention of morbidity in the elderly. By carefully selecting candidates and adhering to established surgical techniques and post-operative protocols, surgeons can significantly improve the quality of life for patients facing the challenge of a proximal femoral fracture. As implant technology continues to evolve, specifically in bipolar designs, the incidence of long-term acetabular wear is expected to decrease, further cementing the role of hemiarthroplasty in the orthopedic armamentarium.