Synthes Radial Head Replacement: A Surgical Guide

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Welcome to a comprehensive guide on the Synthes radial head replacement technique. This article is designed to provide surgeons and medical professionals with a detailed understanding of the procedure, including patient selection, surgical steps, potential complications, and post-operative care. Radial head replacement is a crucial intervention for patients with comminuted radial head fractures that are not amenable to repair, offering a chance to restore elbow function and alleviate pain. This guide aims to break down the complexities of the procedure into manageable segments, ensuring a clear and practical approach for practitioners at various levels of experience.

Understanding Radial Head Fractures

Before diving into the specifics of the Synthes radial head replacement, it's essential to understand the context of radial head fractures. These fractures are common injuries, often resulting from falls onto an outstretched arm. The radial head, located at the proximal end of the radius bone in the forearm, plays a vital role in elbow stability and forearm rotation. When this bone fractures, it can lead to significant pain, limited range of motion, and long-term complications if not properly addressed.

Types of Radial Head Fractures

Radial head fractures are classified using the Mason classification system, which helps determine the severity and guide treatment decisions:

  • Type I: Non-displaced fractures that are often treated non-operatively with a sling and early range of motion exercises.
  • Type II: Displaced fractures involving a single fragment. These may require open reduction and internal fixation (ORIF) if the displacement is significant.
  • Type III: Comminuted fractures, meaning the radial head is broken into multiple fragments. These fractures are often unstable and may require radial head replacement.
  • Type IV: Fractures associated with elbow dislocation. These are complex injuries that require careful assessment and management.

Indications for Radial Head Replacement

Radial head replacement is typically considered when the radial head is severely comminuted (Type III) or when ORIF is not feasible or has failed. Other indications include:

  • Irreparable fractures: When the bone fragments are too small or too numerous to be effectively reconstructed.
  • Associated injuries: In cases where there are concomitant injuries such as ligament damage or elbow instability.
  • Chronic pain and dysfunction: When conservative treatments have failed to relieve pain and restore function in patients with previous radial head fractures.

Patient Selection and Pre-operative Planning

Proper patient selection is paramount for the success of radial head replacement. Ideal candidates are those with severe radial head fractures that cannot be repaired and who have significant pain and functional limitations. A thorough pre-operative assessment is crucial to evaluate the patient’s overall health, the extent of the injury, and any associated conditions that may impact the surgical outcome.

Pre-operative Assessment

The pre-operative assessment typically includes:

  • Medical History: A detailed review of the patient’s medical history, including any pre-existing conditions, medications, and allergies.
  • Physical Examination: A comprehensive physical examination of the affected arm, focusing on range of motion, stability, and neurovascular status. Assess for any signs of nerve damage or vascular compromise.
  • Imaging Studies: X-rays are essential to visualize the fracture pattern and assess the degree of comminution. CT scans may be necessary to provide a more detailed view of the fracture and any associated injuries. MRI can be useful to evaluate ligamentous injuries.

Contraindications

While radial head replacement can be a life-changing procedure, it is not suitable for all patients. Contraindications include:

  • Active infection: Patients with active infections in or around the elbow joint are not candidates for radial head replacement until the infection is resolved.
  • Severe bone loss: Significant bone loss in the proximal radius or ulna may compromise the stability of the implant.
  • Neurological conditions: Patients with pre-existing neurological conditions that affect arm function may not benefit from radial head replacement.
  • Poor bone quality: Osteoporosis or other conditions that weaken the bone can increase the risk of implant failure.

Pre-operative Planning

Careful pre-operative planning is essential to ensure a smooth and successful surgery. This includes:

  • Implant Selection: Choosing the appropriate size and type of radial head prosthesis based on the patient’s anatomy and the extent of the injury. Synthes offers a range of radial head implants to accommodate different patient needs.
  • Surgical Approach: Determining the optimal surgical approach to access the radial head while minimizing the risk of nerve damage. The Kocher approach is commonly used for radial head replacement.
  • Instrumentation: Ensuring that all necessary surgical instruments are available and properly sterilized.

Surgical Technique: Step-by-Step Guide

The Synthes radial head replacement technique involves a series of precise steps to remove the damaged radial head and implant the prosthesis. This section provides a detailed guide to the surgical procedure.

Anesthesia and Positioning

The patient is typically placed in the supine position with the arm prepped and draped in a sterile manner. General or regional anesthesia may be used, depending on the patient’s preference and the surgeon’s recommendation. A tourniquet is applied to the upper arm to minimize bleeding during the procedure.

Surgical Approach

The Kocher approach is commonly used for radial head replacement. This involves making an incision along the lateral aspect of the elbow, centered over the radial head. The interval between the anconeus and extensor carpi ulnaris muscles is identified and developed to access the radial head. Care is taken to protect the posterior interosseous nerve (PIN), which lies close to the surgical field.

Radial Head Resection

Once the radial head is exposed, it is carefully resected using a saw or osteotome. The amount of bone removed should be sufficient to allow for proper seating of the prosthesis, but excessive resection should be avoided to maintain elbow stability. The resected radial head is sent for pathological examination to rule out any underlying conditions.

Trial Reduction

After resecting the radial head, a trial prosthesis is inserted to assess the fit and stability of the implant. The elbow is moved through a full range of motion to ensure that there is no impingement or instability. The size of the trial prosthesis may be adjusted as needed to achieve optimal results.

Implant Insertion

Once the appropriate size of the prosthesis is determined, the definitive implant is inserted. The implant is typically secured to the radial neck using bone cement or a press-fit technique, depending on the type of prosthesis used. The implant should be carefully positioned to ensure proper alignment and stability.

Closure

After the implant is securely in place, the wound is closed in layers. The extensor carpi ulnaris and anconeus muscles are reapproximated, and the subcutaneous tissue and skin are closed with sutures or staples. A sterile dressing is applied, and the arm is placed in a splint or cast to immobilize the elbow.

Potential Complications

As with any surgical procedure, radial head replacement carries the risk of complications. While these are relatively rare, it is important for surgeons and patients to be aware of them.

Nerve Injury

The posterior interosseous nerve (PIN) is particularly vulnerable during radial head replacement due to its proximity to the surgical field. Nerve injury can result in weakness or paralysis of the muscles that extend the fingers and wrist. Careful surgical technique and meticulous dissection are essential to minimize the risk of nerve injury.

Infection

Infection is a potential complication of any surgical procedure. To minimize the risk of infection, strict sterile technique is essential. Patients may be given prophylactic antibiotics before surgery and after surgery. Signs of infection include redness, swelling, pain, and drainage from the surgical site.

Instability

Elbow instability can occur if the radial head prosthesis is not properly sized or positioned. Instability can result in pain, limited range of motion, and a feeling of the elbow giving way. Revision surgery may be necessary to address instability.

Implant Loosening

Over time, the radial head prosthesis may loosen from the bone. This can occur due to wear and tear, infection, or poor bone quality. Implant loosening can cause pain and instability, and may require revision surgery.

Stiffness

Elbow stiffness is a common complication after radial head replacement. This can be caused by scar tissue formation, muscle contractures, or inflammation. Early range of motion exercises and physical therapy are essential to prevent stiffness and restore function.

Post-operative Care and Rehabilitation

Post-operative care is crucial for optimizing the outcome of radial head replacement. This includes pain management, wound care, and rehabilitation.

Pain Management

Pain is typically managed with a combination of oral pain medications and local anesthetics. The goal is to keep the patient comfortable while allowing them to participate in rehabilitation exercises.

Wound Care

The surgical wound should be kept clean and dry. The dressing is typically changed regularly, and the wound is inspected for signs of infection. Sutures or staples are usually removed after 10-14 days.

Rehabilitation

Rehabilitation is a critical component of post-operative care. A physical therapist will guide the patient through a series of exercises to restore range of motion, strength, and function. Early range of motion exercises are initiated to prevent stiffness and promote healing. Strengthening exercises are gradually introduced as the patient progresses.

Recovery Timeline

The recovery timeline after radial head replacement can vary depending on the individual patient and the extent of the injury. However, a general timeline is as follows:

  • 0-6 weeks: Immobilization in a splint or cast, with gentle range of motion exercises.
  • 6-12 weeks: Gradual increase in range of motion and strengthening exercises.
  • 3-6 months: Return to normal activities, with continued physical therapy as needed.

Conclusion

The Synthes radial head replacement technique is a valuable surgical option for patients with severe radial head fractures that are not amenable to repair. By following a systematic approach to patient selection, pre-operative planning, surgical technique, and post-operative care, surgeons can achieve excellent results and restore function to the elbow. While complications can occur, they are relatively rare and can be minimized with careful technique and meticulous attention to detail. This guide provides a comprehensive overview of the procedure, empowering surgeons and medical professionals to provide the best possible care for their patients.

For more in-depth information, you might find the resources available at the American Academy of Orthopaedic Surgeons (AAOS) helpful.