Implants are medical devices that are surgically placed inside the body to replace or enhance a biological structure. Some common examples of implants include hip and knee replacements, dental implants, breast implants, and pacemakers. While implants are designed to last for many years, it is possible for them to become damaged over time. There are several factors that can contribute to implant damage.
What Can Cause Damage to an Implant?
Normal Wear and Tear
Even though implants are made from durable materials like titanium, ceramics, or plastic, they still undergo normal wear and tear inside the body. The constant movement and forces exerted on the implant over months and years can cause the materials to slowly degrade. This is especially true for joint replacement implants. The repetitive impact and motion gradually wears down the bearing surfaces of the implant components, leading to increased friction. This process is known as osteolysis. Tiny particles also break off from the implant and accumulate around it, causing inflammation and bone loss. While all implants are subject to wear, damage accumulates more quickly in younger, active patients.
Poor Surgical Technique
The way an implant is positioned and fixed during surgery can affect its long-term survival. If the implant or bone is not prepared properly, the implant components may loosen or become misaligned over time. For example, under-reaming the femur during hip replacement surgery can lead to inadequate cement fixation of the femoral stem. This allows micromotion of the implant and premature loosening. Poor surgical technique can also result in soft tissue imbalance or impingement that places extra strain on the implant.
Trauma and Falls
Since implants lack the natural shock-absorbing qualities of bone and cartilage, trauma from falls or accidents can easily damage them. The impact may fracture part of the implant or disrupt its fixation to bone. Dislocation of modular components is also a risk. Knee and hip implants are particularly prone to damage from trauma because of their exposure to external forces. The rate of damage depends on factors like implant design and position, bone quality, and the direction and severity of impact.
Infection
One of the most serious complications that can lead to implant damage or failure is infection. Bacteria can be introduced during surgery or sometimes seed the implant area later via the bloodstream. The presence of a foreign object makes infections more difficult to treat with antibiotics alone. In some cases, the immune system attacks the implant components, causing surrounding tissue damage and loss of fixation. Removing the implant is often necessary to cure the infection.
Biological Complications
The body’s response to an implant can also contribute to its breakdown in certain situations. In some patients, overly exuberant scar tissue formation occurs around the implant, constricting nearby nerves and muscles. An autoimmune reaction to metal ions released from joint implants may trigger inflammation and bone loss as well. Risk factors like smoking, diabetes, and steroid use can impair healing and osseointegration after implant surgery, setting the stage for failure.
Mechanical Issues
Problems intrinsic to the implant itself, such as fractured components, disconnection at modular junctions, and loosening at the implant-bone interface can lead to accelerated damage. Early generation designs with suboptimal materials and engineering are more prone to these types of mechanical issues. Manufacturing defects that compromise the structural integrity of the implant may not manifest until months or years later.
Wear and Tear from Adjacent Joints
Damage to other biological structures near an implant can indirectly contribute to implant failure. For example, advanced arthritis in adjacent joints like the patellofemoral knee compartment or lumbar spine can cause added stress on a hip or knee replacement. This leads to premature loosening, even when the implant components themselves are intact.
How Does Implant Damage Occur?
Implants can be damaged in a variety of ways depending on the underlying cause. Here are some of the common modes of damage:
Fractures
Repeated stress may cause tiny cracks or fissures to form in the implant material, which can expand over time into major fractures. Brittle materials like ceramics are prone to fractures.
Wear and Fatigue Failure
Wear generates debris particles from the bearing surfaces while fatigue failure happens after critical loading cycles are exceeded. Both wear and fatigue can lead to breakage or loss of function.
Corrosion and Fretting
Chemical degradation from corrosion and micromotion from fretting gradually weaken metal implants. Oxide layers form on the surface and metal ions are released into the surrounding tissue.
Loosening and Lysis
Chronic inflammation around the implant-bone interface causes resorption of the supporting bone. This leads to loosening, subsidence, and eventual failure of the fixation.
Dislocation and Subluxation
Trauma or instability from poor surgical technique can displace implants from their normal alignment. Recurrent dislocations accelerate wear and cause further tissue damage.
Creep and Deformation
Some plastic components slowly deform and elongate over years of use. This creep deformation leads to joint laxity and altered biomechanics.
How is Implant Damage Detected?
Routine follow-up exams with imaging tests are important to monitor implants for signs of damage before major complications occur. Here are some ways doctors diagnose implant damage:
Patient History and Physical Exam
Increased pain, swelling, feeling of instability, catching or clicking with joint motion can indicate a problem with the implant. Exam findings like tenderness, reduced range of motion, and strength deficits provide clues as well.
Radiographs
X-rays are routinely used to assess the integrity and position of implants. Signs of damage like fractures, wear, loosening, and osteolysis are often visible on radiographs before symptoms appear. Serial images are analyzed to detect progressive changes.
CT Scans
CT provides detailed 3D views of bone and implant components. It is helpful for further evaluating damage found on x-ray or diagnosing subtle hairline fractures not visible on regular radiographs.
Metal Ion Testing
Blood levels of metal ions released from joint implants are measured to monitor abnormal wear rates. Elevated cobalt and chromium levels indicate wear of metal-on-metal implants.
Joint Aspiration
Analysis of synovial fluid can detect infection, wear particles, and inflammation in a painful or dysfunctional joint with an implant. Cultures identify pathogens while cell count and chemistry reflect the degree of inflammation.
Bone Scans
Nuclear medicine bone scans look for abnormal areas of increased metabolic activity around implants. This helps identify regions of loosening or osteolysis before changes become evident on radiographs.
What are the Consequences of Implant Damage?
Depending on the cause and extent of damage, complications from implant failure can range from mild to severe. Some potential consequences include:
Pain and Functional Loss
A damaged implant results in increased pain and stiffness that limits activity and function. Everyday tasks become more challenging.
Instability and Dislocations
Implants that are fractured, worn, or loosened no longer provide adequate joint stability. This leads to a feeling that the joint will give way or recurrent dislocations.
Bone and Soft Tissue Injury
Abnormal stresses on bone and tissues surrounding a damaged implant result in further injury. This can be painful and difficult to treat.
Particle Debris and Inflammation
Tiny fragments from implant wear and corrosion incite a chronic inflammatory response that can damage local bone and tissues.
Infection
Implant damage creates surfaces where bacteria can adhere and biofilm can develop. Infection may spread to the joint space, bone, and bloodstream.
Loss of Function
Severe implant damage may result in complete failure where no or minimal function remains in the joint. Damaged beyond repair, the only option is removal.
Revision Surgery
Most damaged implants require one or more complex revision surgeries to extract and replace the failed components. This entails significant cost, risk, and rehabilitation.
| Type of Damage | Early Signs | Consequences if Undetected |
|---|---|---|
| Fracture | Audible clicking or popping, pain with weightbearing | Sudden joint instability, severe pain, detached fragments |
| Wear and fatigue | Increase in pain or swelling, feeling of “grinding” | Progression of damage, accelerated joint degeneration |
| Corrosion | Color change around implant, elevated metal ions | More rapid corrosion, metallosis, tissue toxicity |
| Loosening | Dull ache around implant, subsidence on x-ray | Worsening instability, severe bone loss, failure |
| Dislocation | Sudden joint instability, immediate pain | Recurrent dislocations, tissue stretching, arthritis |
| Infection | Fever, swelling, wound drainage | Joint/bone destruction, abscess, sepsis |
Can Implant Damage Be Prevented?
While some degree of gradual wear is inevitable, certain precautions can help prevent premature or catastrophic implant damage:
Choose an Experienced Surgeon
Proper surgical technique including precise implant positioning greatly reduces the risk of future complications. Orthopedic surgeons who regularly perform implant procedures tend to have better outcomes.
Follow Activity Restrictions
Avoiding high impact activities protects implants from excessive wear and traumatic loading. Activity guidelines vary by implant type but limiting certain motions prevents damage.
Get Regular Follow-Up
Routine x-rays, exams, and bloodwork allow early detection of abnormal implant wear, corrosion, or loosening so that corrective action can be taken before failure occurs.
Maintain a Healthy Weight
Carrying excessive body weight increases forces across implants, contributing to accelerated damage over time. Keeping weight within a normal range extends implant longevity.
Control Other Health Issues
Medical problems like diabetes, osteoporosis, and vascular disease negatively affect implant outcomes. Meticulous control of these conditions promotes proper osseointegration and healing.
Report Any New Symptoms
Promptly report any concerning implant-related symptoms like increasing pain, swelling or sensations of instability to your doctor for evaluation rather than waiting until the next routine visit.
Avoid Falls and Trauma
Be especially cautious to avoid falls and accidents that could result in damage to an implant through sudden impact or twisting forces. Use recommended assistive devices.
How is Damaged Implant Treated?
The main treatment options for a significantly damaged, dysfunctional implant include:
Revision Surgery
This involves surgically removing all or part of the original implant and replacing it with a new one. Extracting well-fixed components can be challenging and bone loss may require grafting.
Partial Revision
If the damage is confined to just one section, such as a broken femoral stem, sometimes only that component needs replacement while retaining other intact parts.
Complete Removal
If the implant cannot be salvaged, the entire device may need complete extraction. A new implant can be placed after some delay to allow for treatment of infection or bone healing.
Spacers
Static or articulating antibiotic spacers help deliver high doses of medication when infection must be cleared before a revision implant. They also maintain joint mobility.
Debridement and Washout
Loose fragments are extracted while remaining well-fixed components are thoroughly cleansed and irrigated to remove all debris and bacteria.
Resection Arthroplasty
If bone loss is too severe, the joint may need to be fused or converted to a non-articulating pseudarthrosis to stabilize it. This retains some function.
Amputation
In rare cases of catastrophic implant failure with uncontrollable infection or extensive tissue destruction, amputation of the limb may be the only option.
What is the Outlook After Implant Damage?
The prognosis after implant damage varies substantially based on multiple factors:
– Cause and extent of damage
– Bone quality and degree of loosening
– Infection or other complicating conditions
– Patient age, activity level and comorbidities
– Surgical technique and implant choice for revision
While many patients have good pain relief and restoration of function from component exchange revision, the new implant is still subject to the same wear and failure processes as the original. Multiple revision procedures are often required over a lifetime. With each successive surgery, complications increase and outcomes worsen.
In general, the earlier implant damage is recognized, the better the results from revision surgery. Mild to moderate damage has a more favorable outlook compared to extensive damage with severe pain, bone loss, and instability. Meticulous surgical technique, advanced component materials, and optimal patient selection maximize the probability of a durable revision implant.
Despite the best efforts of patient and surgeon, however, there are no guarantees when it comes to repairing a damaged implant. Some degree of persistent pain, limited mobility, and activity restriction is likely. Though imperfect, revision surgery remains the best option for most patients with a failed implant. Realistic expectations are important. Prevention of damage through regular monitoring and protecting implants from undue stress can help extend their lifespan.
Conclusion
While originally designed to last for decades, joint replacement implants can occasionally become damaged and fail prematurely. Contributing factors range from normal wear and tear to trauma, infection, and mechanical issues. Damage modes include fractures, loosening, instability, and excessive wear. Routine follow-up and imaging studies allow early detection before catastrophic failure occurs. Revising the damaged components, or sometimes the entire implant, is usually necessary to restore function. However, preventing damage in the first place through proper implant selection and patient education offers the best chance for a durable result.
