When you step onto a modern jet airliner, you typically do not dwell on the tens of thousands of parts that have to work correctly in order to fly you across the country. In fact, if you really knew in detail the thousands of things that could go wrong, you might feel daunted about getting on the airliner in the first place. Yet at any given moment, there are thousands of jets in the air, and we rarely hear about crashes.
The same scenario holds true for major surgery. The vast majority of patients undergoing orthopaedic joint surgery every day do quite well, with an estimated 95% to 98% of patients having a good outcome, but it is a complex effort made by a team of professionals working together. Sometimes complications can and do occur despite all of the modern technology and herculean efforts made to prevent them.
For this reason, we always re-iterate in our practice that joint surgery is elective and should not be undertaken until patients are completely willing to accept the risks of surgery in order to get better. For most patients, pain and disability generally reach this point after conservative options no longer provide adequate relief. This chapter goes into detail about the more common complications that can occur after major orthopaedic joint surgery, but it is not possible to list every potential complication. Rare complications can occur that are outside the scope of this discussion, but complications themselves are uncommon and this list discusses the ones that are seen most often. The complications here are broadly grouped into categories of anesthesia complications, medical complications, and surgical complications.
Airway problems can occur if a patient needs to be intubated (i.e., have a breathing tube placed) during surgery but has a swollen or abnormal airway. In severe cases, this may necessitate an emergency tracheotomy. Sometimes the breathing tube may not be properly placed into the airway and is instead in the esophagus, but there are multiple checks to prevent this, including electronic monitoring of carbon dioxide (which should be seen with exhalation) and listening with a stethoscope. A mild sore throat may result from intubation, although most patients do not recall the intubation because the tube is placed after sedation and removed before awakening.
If a patient has loose teeth, these may be further knocked loose during intubation, the process of placing a breathing tube for general anesthesia. Loose teeth should be addressed by a dentist prior to surgery if present. Cracked teeth can rarely occur from the intubation process. Dentures can get in the way, and these should be removed prior to surgery in case intubation is necessary.
This is a rare but potentially serious reaction to some anesthetics in which the patient's body temperature raises rapidly after induction of general anesthesia. It usually is determined by a genetic predisposition that runs in families, so the anesthesiologist may often ask about any prior problems with anesthesia in yourself or any family members. This is not usually a concern with spinal anesthesia.
Some patients may have a severe headache after spinal anesthesia. This is because of a pressure change in the cerebrospinal fluid. It is usually not dangerous, but it can be uncomfortable. It is usually treated with caffeine and resting flat. If the headache is severe and prolonged, sometimes an anesthesiologist may administer a blood patch. A blood patch is a spinal injection with a minute quantity of the patient's own blood, in order to produce a clot over the site of spinal fluid leakage. This usually resolves the problem.
Heart Attack / Stroke
These complications are rare during or right after elective joint surgery, in part because most patients are "tuned up" for surgery and optimized after obtaining presurgical medical clearance. A small percentage of patients may experience these complications as a result of low blood pressure (hypotension) during or right after surgery.
Some patients can spontaneously develop a cardiac arrhythmia after surgery, often for reasons that are unclear. This may require monitoring in the telemetry unit until the symptoms disappear. Rarely, this may require treatment with either blood thinners or electric cardioversion by the cardiologist.
Congestive Heart Failure (CHF)
Patients who have preexisting heart disease may have decreased pumping ability of the heart (often measured preoperatively by the cardiologist as an ejection fraction). Sometimes the heart has difficulty keeping up with the pumping demands, and fluid begins to back up into the lungs because the heart is not pumping as strongly as it should. This is usually treated with fluid restrictions, diuretics ("water pills"), and cardiac medications prescribed by the cardiologist to help the heart pump more strongly.
Blood Clots (Thromboembolic Disease)
An entire chapter is devoted to this topic, but after major surgery in the lower extremities, clots can form in the deep veins of the leg or pelvis (deep venous thromboses, or DVT). The DVT may cause swelling in the leg and calf that may be uncomfortable, but is not usually dangerous by itself. The principal concern is that a portion of the clot may break away into the blood stream and travel back to the heart, through the right side of the heart, and then to the lungs and lodge there. That event is called a pulmonary embolism, and it can be immediately fatal. In our published series, we documented one case of fatal pulmonary embolism in over 2000 consecutive anterior approach total hip replacements.
Fat emboli result when fat from the bone marrow enters the circulation and causes damage to small blood vessels elsewhere. It is not usually serious, but can result in mental status changes and respiratory problems (sometimes major respiratory failure in the case of trauma patients). Rarely, it can cause coagulation problems. Fat embolism is seen more often with fracture care than with elective joint replacement surgeries, particularly with surgeries that require reaming and rodding through the marrow of the long bones.
Disseminated Intravascular Coagulation
Disseminated Intravascular Coagulation (DIC) is a rare complication in which blood starts to coagulate throughout the entire body. Because the body uses up all of the platelets and other materials that it normally uses for clotting, patients paradoxically have simultaneous problems of hemorrhage and clotting at the same time. This potentially fatal condition is usually only seen in critically ill patients and patients who have had massive trauma, very extensive surgeries with massive transfusions, cancer, liver disease, or sepsis (systemic infection in the blood).
Pneumonia / Atelectasis
Small sacs within the lungs (called alveoli) may close down, particularly if a general anesthesia is used instead of a spinal. This is called atelectasis, and by itself this can reduce oxygen exchange and also lead to low-grade fever. This is why deep breathing and use of incentive spirometers is encouraged after surgery. For frail or ill patients, a post-operative pneumonia can occur (this is more of a concern for hip fracture patients than for elective joint replacement patients).
Sometimes patients have difficulty voiding on their own after surgery and anesthesia. If this occurs, it usually is the result of anesthesia and narcotics, and resolves shortly on its own but may require catheterization for a day or two. For men, an already enlarged prostate can sometimes be the culprit, and this can sometimes be treated with medications. If it remains a problem after a short period of time, then a urology consultation is usually obtained and the patient may rarely go home with a catheter until the underlying problem has resolved.
Urinary Tract Infection
Many elderly patients, particularly women, may be prone to urinary tract infections even without surgery. However, if a urinary catheter is needed, there is some chance of introducing a urinary tract infection. This is not usually serious but may require antibiotics. For this reason, catheters are discontinued as soon as possible after surgery.
Clostridium Difficile (C. Diff)Colitis
Prolonged use of antibiotics can lead to the destruction of the "good" bacteria that normally inhabit the gut and overgrowth of the "bad" bacteria, namely a particular bacteria called clostridium difficile. This usually presents as intractable diarrhea. It can be treated with special antibiotics, but it is best to prevent it by only using antibiotics when needed. It can be fatal, particularly in frail or elderly patients (such as hip fracture patients).
It is normal for the gastrointestinal system to slow down for a few days after anesthesia and surgery, and most patients do not have a bowel movement for at least a couple of days. However, sometimes the gut can stop moving entirely, particularly in obese patients and/or those patients taking heavy doses of narcotics, resulting in bloating and abdominal pain that is termed an ileus. This normally resolves by stopping all oral intake of food and liquids, mobilizing out of bed and walking, giving IV fluids to prevent dehydration, and sometimes placing a nasogastric tube to suction that keeps the stomach empty until the condition resolves.
It is not uncommon for elderly patients (particularly the very elderly and patients who already demonstrate some mild evidence of early Alzheimer's dementia) to have post-operative confusion and mental status changes. It is usually worse at night, hence the common term "sundowning." This can last for days, and in uncommon instances, the confusion can last for weeks. It usually resolves as narcotics are discontinued and the patient returns to more familiar surroundings, but it can be distressing for other family members.
The DT's occur as a result of alcohol withdrawal. Heavy drinkers cannot simply stop their usual intake; otherwise, mental status changes and tremors can occur that in some cases can actually be life threatening. Treatment usually involves tranquilizers, folate and potassium, and in severe cases resuming regular dosage with alcohol. It is important to tell your doctor if you drink on a daily basis so that they can be prepared for this possibility and try to prevent it.
Some patients may react to receiving donated volunteer blood from the blood bank. It is rare to have a serious reaction, although such reactions have been well described. Usually a transfusion reaction results in fever and itching, and the transfusion is simply stopped. Most transfusions are run very slowly, over several hours, so that when a reaction is observed it can be stopped immediately. The symptoms usually resolve with benadryl and fluids.
Blood glucose levels may be elevated in diabetics and pre-diabetics after surgery or trauma for a number of reasons. Some diabetics who normally are controlled with oral medications may require insulin for a short period of time. Some patients who have never been diagnosed as diabetic may require treatment during their hospitalization; it does not necessarily mean that they are diabetic and often can just be a stress reaction. This usually resolves fairly quickly as the body re-adjusts from the stress of surgery.
Numerous metabolic disturbances can cause individual electrolytes to become off-balance, namely sodium (hyponatremia or hypernatremia), potassium (hypokalemia or hyperkalemia), magnesium, and other electrolytes. Some of these derangements can potentially cause serious problems such as cardiac arrhythmias, but most are not serious and are corrected as needed by administering or restricting the appropriate element.
It is normal for the lower extremities to have some degree of swelling after orthopaedic surgery, often for many months. In unusual cases, it can sometimes be quite pronounced. There can be many underlying reasons for this, but it usually resolves with elevation and time. Some male patients who have had very extensive pelvic trauma or surgery may notice scrotal edema, which can be alarming but usually resolves on its own without any significant problems.
Failure of the kidneys to filter the blood adequately is uncommon in healthy patients, but patients with severely low blood pressure (as seen after a major trauma, for example) or with preexisting renal insufficiency (as with many diabetics) may see significant decreases in the functioning of the kidneys. This is usually temporary. Some medications may contribute to this problem (e.g., nonsteroidal antiinflammatory medications or NSAIDs) and may need to be discontinued. Rarely, temporary hemodialysis may be needed in severe cases.
There is some overlap between medical and surgical complications, but surgical complications are generally related to the incision and joint replacement itself. Some specific risks to each type of surgery are also discussed in the this section.
Although very uncommon, with any major surgery there is the risk of uncontrolled bleeding during (or even after) surgery. It does not happen often, but sometimes a blood vessel can be injured and may be difficult to clamp or cauterize, leading to increased blood loss. If this occurs, the outcome is usually the need for a blood transfusion during or after the surgery, but on rare occasions the blood loss can be more serious. Unlike surgeries within the chest or abdomen, however, there are few vessels in the hip or extremities large enough to produce bleeding that is fast enough to be a serious danger, allowing surgeons time to control the bleeding.
Deep infection of the joint (sepsis) is probably one of the worst surgical complications that can occur. Despite all of the efforts made to prevent it and use of perioperative prophylactic antibiotics, rates of deep infection in joint replacement surgeries still are reported at about 1 per 100 patients.
In some cases, this may necessitate additional surgery to "wash out" the joint, or possibly even remove all artificial components and treat with antibiotics for several months until re-implantation can be considered after clearing the infection. Infection is an increased risk for patients who are obese, smoke, have problems with their immune system, are on immunosuppressive drugs (such as transplant patients or some patients with autoimmune diseases), diabetics, or patients who have had previous surgeries in the same location.
An infection that involves the bone itself is termed osteomyelitis. This usually only develops in chronic infections that have been present for a long time. Many cases of osteomyelitis which do not involve artificial implants can be treated with antibiotics that travel to the bones, but sometimes surgical intervention is required if this fails.
Today there is increasing awareness about MRSA, or methicillin-resistant staphylococcus aureus, a particularly nasty bug that has become problematic in hospitals around the country in the past fifteen years as bacterial resistance to modern antibiotics increases. If a patient has ever had MRSA, in most hospitals they will be kept in private rooms and isolated from other patients because of the potential risk that they may still harbor the resistant bacteria and could pass it to other patients.
Cellulitis refers to a superficial infection that occurs in the skin, usually a patch of red, warm, tender skin over the surgical site (some redness and warmth is normal, however). This is not usually a serious problem and resolves quickly with treatment, but surgeons take it seriously because it can sometimes spread to deeper tissues or into the joint if left untreated. Most cases of cellulitis are treated with elevation, antibiotics, warm compresses, and marking out the area involved and observing it.
Dehiscence means a breakdown of the wound. A wound may break down and open up for several reasons, including infection, poor wound healing ability (e.g., a malnourished elderly patient, patient who has had chemotherapy or radiation, or diabetic), or pressure from below the incision due to a fluid collection. Superficial dehiscence is usually not serious, but merits close observation. The wound usually fills in on its own over time, usually a period of weeks. Rarely, it may need to be packed with a gauze dressing or a vacuum dressing until it fills in.
Other Wound Problems (Tape Blisters, Decubitus ulcers, etc.)
Patients can sometimes develop a variety of minor, superficial skin and wound problems. Tape blisters are common in patients with sensitive skin or thin skin (such as elderly patients or patients who have been on prednisone). These usually heal fine without any specific intervention once the dressings are removed.
Pressure sores, also known as decubitus ulcers, can occur if a patient is not getting up much, commonly on the back of the heel or buttocks. The principal treatment is to remove pressure from the affected skin area, by mobilizing, placing gel pads, rolled towels under the heel, and other similar measures.
Suture abscesses or "spitting sutures" are also common and usually harmless, but a patient may notice a tiny bit of exposed suture several weeks after the surgery. This is usually nothing to be concerned about and dissolves on its own.
A hematoma is a collection of blood. It can sometimes be quite large and cause pain and swelling around the surgical site. Some degree of hematoma is normal after all surgeries, but very large ones sometimes need to be drained. In rare cases, the hematoma expands to a large enough size that it can compress nearby nerves or blood vessels. This usually only occurs if a patient is on high dosage anticoagulants (blood thinners).
A related problem is a seroma, which is similar except the fluid collection contains serous (usually joint) fluid rather than blood. Obese patients are more prone to seroma formation as some of the underlying adipose tissue liquefies after surgery.
Sometimes a hematoma can spontaneously decompress on its own days or weeks after surgery. While it can be distressing to a patient who was not expecting it (it appears similar to menstruating from the wound, with old clots expressing from a small opening), it usually stops on its own in a day or two and the patient actually feels better. Usually a dressing is all that is required until the wound closes up again.
With most joint replacements and resurfacings, there always exists the possibility of fracturing the bone while placing the implants. This is one reason why we always obtain x-rays in the recovery room before starting physical therapy. This can vary from an incidental finding on x-rays to a serious problem that requires additional surgery or fixation, although when it occurs, most patients are simply treated with limited weightbearing for a few weeks until the fracture has healed. Some patients may not fully fracture until later, as they place weight on a weakened area of bone. It is a greater concern in frailer, older patients (such as elderly hip fracture patients), patients chronically on steroids (prednisone), or in complex revision surgeries.
Nerve injuries can occur with any surgery, and the specific nerves involved vary according to the region in which surgery occurs. Any superficial skin incision will often result in localized numbness, which is usually harmless and resolves over a period of months. Sometimes more serious injuries can occur, such as a peroneal nerve palsy which manifests as a foot drop. This is usually seen in posterior approach hip surgeries or when correcting a knee valgus (knock-kneed) deformity and the nerve is stretched. Rarely it can sometimes be seen after knee arthroscopy because of stretching the nerve while positioning the knee.
Foot drops (or peroneal or sciatic nerve palsy) frequently get better on their own but may require many months to do so. Sometimes an orthosis is required to keep the foot up and from dragging the ground.
Anterior approach hip surgery can result in rare injuries to the femoral nerve or the lateral femoral cutaneous nerve (meralgia parasthetica, which affects the skin area over the front of the thigh). Many nerve injuries are the result of stretching (as from retractors) rather than direct injury, a condition known as neuropraxia, and this often resolves over a period of months without the need for any additional intervention.
It is also possible to injure a nearby blood vessel with any invasive procedure, although it is rare with hip and knee surgeries. In the hip, one particular area of concern is injury to blood vessels inside the pelvis while placing screws into the socket (acetabulum), which may penetrate large vessels on the other side of the bone. In knee surgeries, the major arteries and vessels are in the very back of the knee, but these can rarely be injured by instruments, saws, or retractors. Major vessel injury in routine knee surgeries is exceedingly rare (it is more common in complex revision surgeries), but it can be a potentially devastating complication that may result in loss of the limb if the vessel damage cannot be repaired.
Sometimes the body can form "extra bone" or dense calcified scar tissue in the region of a joint in the months after surgery. This is typically seen around the hip, and it is more common in men and in larger, more complex surgeries. It can sometimes be prevented (at least to some degree) by immediate radiation therapy just before or after surgery (within 72 hours), or by starting medications right after surgery that prevent extra bone formation (such as indomethicin or celecoxib), but these treatments are not usually undertaken unless a patient has a prior history of heterotopic ossification. In some cases, the stiffness may limit range of motion enough to warrant surgery to remove the calcified tissue.
All hip and knee joint surgery patients limp for at least a while. There can be many reasons for persistent limp, but the most common reason is weakness (atrophy) of the muscles around the affected joint from disuse prior to surgery. The joint can be replaced, but the muscles only get stronger through exercise and therapy. The muscles around hip and knee replacements get stronger for about a year after surgery.
Sciatica and Bursitis
Surgery does not usually cause sciatica or bursitis, but it can aggravate these problems if already present. Low back pain can sometimes flare up also right after surgery. Sometimes the prolonged period of lying down during surgery and convalescence can aggravate these problems. However, these issues usually resolve uneventfully with anti-inflammatory medications and/or physical therapy, just as they are treated in patients who have never had surgery. These problems usually resolve within a few weeks, although some patients who have had hip replacement may come back from time to time to get a steroid injection for bursitis.
These problems may also frequently be seen in patients before surgery, often as a result of an altered gait pattern due to a bad hip or knee.
Over a long enough period of time, all implants will eventually loosen from the bone. Cemented components will generally loosen before noncemented (porous-coated) components. Joints that contain polyethylene (plastic) bearing surfaces are also particularly prone to osteolysis, or reabsorption of the bone. There are a number of other factors, such as patient activity level, weight, and types of activities (e.g., impact activities such as running are more likely to loosen the components). Usually loosening is a slow, gradual process that leads to slowly progressive pain (often in the thigh for femoral loosening and in the groin for acetabular cup loosening) over months to years. A bone scan detects the process before it is visible on x-rays (although a scan will not be useful until at least a year after surgery because of normal bone uptake around a new prosthesis), and patients usually can plan on revision surgeries usually well before the time that loosening becomes debilitating.
A related longevity problem is wear of the bearing surfaces. Over time, the artificial joints simply wear out the surfaces, like brake pads in a car. Ceramic and metal bearings very rarely wear out and usually require decades before significant wear occurs, but polyethylene (plastic) bearings may wear out in the years after surgery. This usually manifests as pain in the affected joint, and often there is associated osteolysis (or re-absorption of the bone around the prosthesis) and loosening because of the wear particles. In fact, it is the loosening that usually necessitates revision surgery, although plastic liners are sometimes replaced in a smaller surgery if the wear is noted on xrays before osteolysis becomes a problem.
Noises (Pops, Clicks, etc.)
It is not uncommon to experience "noisy" joints after any surgery, particularly joint replacement or resurfacing. In fact, most patients experience popping, clicking, or other noises even before surgery. For the vast majority of patients, it is a harmless phenomenon that is probably more common than not after surgery. There are multiple reasons for noises after surgery.
The ligaments and soft tissues around a joint frequently are the culprits with painless noises. Artificial joints can often produce clicking when the hard surfaces of the components come together. Normal arthritic joints frequently crack and make crunching noises, called crepitus, which can persist after surgery.
Painful noises, on the other hand, may be a cause for further investigation. Tissue or loose bodies that become trapped in the joint, as is the case with the painful clicking from a meniscal tear, may need treatment. Ceramic surfaces have also been reported to uncommonly cause "squeaking" noises.
Complications Specific To Hip Replacements/ Resurfacings
A hip dislocation occurs when the ball slips out of the socket. It is typically quite painful and results in immediate shortening of the leg and inability to bear weight on it, similar to a fracture. It has to be put back into the socket in the emergency room or operating room under anesthesia. Rarely, surgery may be needed to put it back into the socket if there is muscle or other tissue blocking it from going back into place. However, once it is back in the socket, most patients immediately feel better and frequently are able to walk out of the emergency room and go home (with careful precautions so that it does not happen again).
If only one or two dislocations occur, the tissues usually will tighten up over time and no further treatment may be needed. However, if a patient continues to experience multiple dislocations, there may be an underlying problem that needs to be addressed with revision surgery (commonly from an acetabular socket that is too vertical or tilted forwards/backwards, impinging scar tissue or bone that allows the hip replacement to fulcrum out of the socket, increased tissue laxity that has occurred since the original surgery, or most commonly a patient who is noncompliant and does not follow instructions - they may need conversion to a more constrained hip replacement that is more difficult to dislocate).
In our published review of over 2000 hip replacements with the anterior approach, dislocation rates were around 1%. These typically occurred within the first 6 weeks of surgery, before the muscles and tissue has "tightened up" after surgery. For this reason, there are some precautions that we advise total hip replacement patients to follow during this period. As of the time of this writing, we have yet to see any dislocations from hip resurfacing, although it is still technically possible and these surgeries have only been performed on a routine basis for a relatively short period of time.
While ceramics have the potential to last a very long time (decades), there are some downsides other than being very expensive. Ceramic balls and liners can on rare occasions fracture. For this reason, impact activities like running or basketball are not recommended for ceramic bearings. In most of the rare cases we have seen, there has often been a trauma that required equivalent energy to breaking a bone or a manufacturing defect in the ceramic. For most patients, the risk of ceramic fracture is far out-weighed by the benefits of a long-lasting bearing surface.
Ceramics can also be the culprit for audible noises, such as squeaking or clicking. While not usually harmful, these problems can be annoying for the rare patient in which they occur (generally estimated at about 1 in 400 ceramic hip replacements).
Metal on Metal Problems
Metal on metal bearings are another bearing surface that has the potential to last significantly longer than a traditional metal on polyethylene (plastic) joint replacement, but these also have some specific drawbacks. Metal ions accumulate over time in the body, particularly in the lymph nodes, liver, spleen, and other tissues. Metal on metal bearings have been used for decades in tens of thousands of patients, and while increased metal ion levels can be measured in the blood and urine of these patients, there has not to date been convincing evidence that this presents a danger except to those patients who have metal ion allergies or those who have kidney disease (because this is how the metal ions are normally excreted). We typically do advise patients that while these are very tough and long-lasting bearings, there may be a small chance of problems with metal ion accumulation in the future. Women who may become pregnant are also typically advised to consider alternatives such as ceramic hip replacements because of the potential for metal ion accumulation.
Although this is not as much of a problem as it was several decades ago, before the engineering of joint replacement devices advanced to where it is today, on rare occasions the implant itself can break. We typically see this today with breakage of implants that were placed many years ago, and we do not expect to see it as much in the future as high performance implant designs have improved. However, it does usually necessitate revision surgery when it happens.
Leg Length Discrepancy
Nearly all hip replacement patients will at least feel as though one leg is longer than other for several months after surgery. This is because of the muscles on the affected side that are healing after surgery. Sometimes it is because of pelvic obliquity, in which the lower lumbar spine tilts (somewhat like scoliosis, but located at the very lower part of the spine where it meets the pelvis). This results in an apparent leg length difference.
However, true leg differences do occur in hip replacement surgery. Surgeons are careful to try to match the length as much as possible by a number of different techniques during surgery (in our practice, we use an anterior approach with the patient lying flat, so it is simpler to check that the knee caps are at the same level). However, the most frequent reason for a true length discrepancy is stability. At the time of surgery, the hip is held in the socket by muscle and soft tissues; if there is inadequate tension, the hip may dislocate. Most surgeons test the stability with trial components of different sizes before implanting the final components, and if the hip dislocates too easily, the surgeon must decide if extra length is necessary (there can be other reasons for dislocation, too, such as suboptimal positioning of the acetabular cup). By making the leg a little longer, the tension is increased and the hip is more stable.
Relatively few patients have a length difference significant enough to require a shoe lift, but some do. All patients undergoing hip replacement must be willing to accept that it is a possibility and potential trade-off for hip stability. It is significantly more likely with complex revision surgeries.
The femoral stem can sometimes "sink" further into the upper portion of the femur in the weeks after surgery, leading to shortening of the leg and sometimes resulting in instability or dislocations. This can occur in soft bone or with noncemented prostheses that are not fully seated. This is one of the reasons post-operative x-rays are taken a month or two after surgery.
There are several potential causes for thigh pain after hip surgery, with the most common being trochanteric bursitis. Within the first month few months after surgery, occasional thigh pain is normal and expected. Some patients may experience thigh pain in the first 18 to 24 months after surgery, especially after a cementless hip replacement, as the bone grows into the porous coating of the prosthesis. It is usually not constant or severe and resolves once bone growth is adequate.
Occasionally, thigh pain that is severe and worsening over time can be indicative of more serious problems. These can include early loosening, stress fractures, or infections. Fortunately, these problems are quite rare in comparison to the routine thigh pain or bursitis pain above, but for this reason it is important to let your surgeon know if thigh pain develops and persists or worsens in the years after surgery.
Not so much a complication as a phenomenon, stress shielding occurs because bone will sometimes reabsorb around an implant if the implant is so mechanically solid and "stiff" that the body decides the bone above it is no longer needed. This is typically seen with certain types of noncemented femoral stems that become very solidly fixed in the thigh, and the body reabsorbs the bone around the upper portion of the stem over a period of years. This is one reason that femoral stems are often made from titanium, which is strong but allows some bending. Other designs have a "clothespin" design at the bottom so that the implant is not so mechanically stiff. Stress shielding is not usually a problem in itself, although it makes revision surgery tougher if the implant ever needs to be taken out and replaced because there is less bone left to work with for reconstruction.
Complications Specific To Knee Replacements
There are a number of problems that are primarily associated with knee replacements and surgeries. These are more likely with joint replacements than with minor procedures such as arthroscopy, and total knee replacements in general are somewhat more likely to have complications than partial knee replacements.
Any joint can become stiff after injury or surgery. Generally, elbows and knees are more concerning for this problem, which is why physical therapy starts so soon after surgery and focuses on aggressive range of motion. Sometimes additional manipulations or other interventions are required for stiffness that does not adequately improve with physical therapy. In knee replacement surgeries in particular, a patient who develops significant stiffness (particularly obese patients, diabetics, or patients who are slow to mobilize) may require manipulation under anesthesia in which the scar tissue is broken up by manipulating the knee under light anesthesia for a few minutes. There is a small chance of fracturing the bones or dislodging the prosthesis when manipulating the knee under anesthesia, usually in frail, older patients with osteoporosis. In a few cases, arthrofibrosis may require surgical debridement by arthroscopy or an open procedure (arthrotomy).
Sometimes a knee can be unstable after surgery. There can be many reasons for this; typically, it is after total knee replacement when one of the ligaments surrounding the knee is either stretched, cut, injured, or improperly balanced. Knee replacements are more difficult to balance than hip replacements, primarily because the joint is more complex. The knee is not a simple hinge mechanism, but actually swings like a four-bar linkage. Additionally, it has some rotational movement as well (the "screw-home" mechanism). Most knee replacement designs rely on keeping some or most of the knee's ligaments intact (except for true hinge designs, but these do not work as well as designs that keep the patient's ligaments). If a knee is initially unstable and gives way in a particular direction (often from side to side), it will usually improve with time as the ligaments heal and readjust to the knee replacement. Sometimes a knee brace may be needed if the knee tends to buckle after surgery.
Extensor Mechanism Disruption
This is one of the more serious mechanical complications of knee replacement. The quadriceps attach to the patella, which in turn attaches to the patella tendon, which is anchored on the front of the tibia. This entire assembly is commonly referred to as the extensor mechanism; if this is disrupted - for instance, the patella tendon pulls away from the tibia during or after surgery - then there is no power to the extensor mechanism.Thus, the knee will have no ability to extend and the quadriceps cannot do its work. This is a serious complication that requires revision surgery to repair the extensor mechanism at whichever point it has failed, sometimes even requiring tendon grafts to strengthen the failed mechanism.
There are times when the knee is so stiff or tight that the extensor mechanism has to be surgically taken apart in order to perform the knee replacement. This is usually only seen during complex revisions or when there has been previous knee surgery and scarring, but occasionally a stoic patient will put off surgery until the knee is so stiff that this step is required just to perform the knee replacement. In this circumstance, the disruption is planned and surgically repaired at the end of the case, typically by detaching the bony anchor at the tibia and then wiring it back or by cutting the quadriceps tendon and then suturing it back together at the end of the case (I much prefer the former technique as patients seem to recover faster). However, either technique will necessitate walking in a knee immobilizer and not bending the knee for at least 4 to 6 weeks after surgery and result in some residual stiffness.
Because the knee does not move as a true hinge, it is a challenge to correct the many different variables that are necessary for optimal stability and ligamentous balancing. Commonly, many knees may be tight in flexion but loose in extension, or loose in flexion but tight in extension. These issues usually arise because of the depth of chamfer cuts on the end of the femur or the depth, slope, and tilt of the tibial bone cuts. Typically these issues, if present, will improve or resolve over time as the knee strengthens and regains mobility.
Varus describes a knee that is "bow-legged," and valgus describes a knee that is "knock-kneed." Both terms are used to describe a leg that is not in anatomical alignment. Most knees prior to surgery have worn one side of the knee away faster than the other, resulting in a bowing of the leg (most of the time, it is in varus, or "bow-legged).
At the time of surgery, we try to correct this angle back to an anatomic alignment. However, this is not always possible to do for a number of reasons. If a patient has a severe angular deformity or bow prior to surgery, chances are good that there will still be at least some deformity after surgery. Sometimes surgery can result in an overcorrection. As with most mechanical complications, patients must be willing to accept that possibility before surgery.
Just as the knee can have angular problems with bowing from side to side, it can also have rotational issues. Sometimes the foot is rotated outward or inward ("pigeon-toed") after surgery. This may result after attempting to fix balance and angular problems. It is usually a more cosmetic problem than functional unless the rotation causes problems with the tracking of the patella.
Patella Tracking Problems
The patella, or knee cap, has to glide up and down in the groove over the femur. This can be a problem even in many patients who have never had surgery, and sometimes can lead to the patella jumping out of its track (dislocating) or having pain. Some patients in fact have surgeries to correct this problem (and there are a number of alternative surgeries to try to fix this).
However, this problem can also appear after knee replacement. It is most commonly associated with patellas that have been resurfaced with a plastic button, which may cause the patella to track differently or catch and "clunk" as it passes over the metal flange of the knee replacement. In some cases, the tracking problem may be severe enough to warrant revision surgery.
Some knees have problems with catching and locking after surgery. Typically, this develops months or years later, and is often associated with scar tissue or meniscal remnants that are getting caught in the hinge of the joint. Sometimes it can be caused by a loose body, such as a small bit of cement that has become loose and is floating about in the knee. If symptoms are severe enough, arthroscopic surgery is sometimes used to take a look inside the knee.
Some patients can have persistent effusions (or collections of fluid) in the knee joint after surgery. Some effusion is normal for at least a month or two, but persistent, large amounts of fluid that accumulate in the knee may need to be drained. The most common reason for a fluid accumulation is that the patient has been very active and "overdid it," such as the patient who decides to try to walk several miles at the beach 6 weeks after surgery. The fluid accumulation itself is not too concerning, but there is always the potential that the underlying cause may be infection, crystalline disease (gout or pseudogout - more on that in a moment), or other causes. Fluid aspirated from a knee replacement will usually be sent to the laboratory for analysis.
Pseudogout is the accumulation of calcium pyrophosphate crystals within a joint. This can occur even without ever having knee surgery, and it looks similar to gout or an infection in the knee with redness, swelling, and pain. Surgery can sometimes trigger a pseudogout attack in the months after surgery. This is diagnosed by examining the joint fluid under a microscope and special light, identifying the characteristic crystals (gout can also affect the knee with a similar appearance, except the crystals are from uric acid in this case).
Compartment syndrome occurs when there is swelling within the muscles and soft tissues within an anatomic compartment that is so severe that it constricts blood flow, possibly enough to lead to death of the muscles and tissues. It is exceedingly rare to see after joint replacement surgeries and is in fact seen more often with traumas, particularly crush injuries to the lower leg in which there is extensive damage. It can occur rarely from other causes, such as a tourniquet that has been placed for too long around the leg during surgery with constricted blood flow. Another rare cause is from having saline that is normally pumped through the knee during arthroscopy leak out of the knee capsule into the tissues of the calf or thigh.
This is one of the reasons that we do not use tourniquets routinely for knee and ankle surgeries in our practice, but across the country there are many surgeons who do in order to decrease bleeding at the time of surgery. There is some debate as to whether the blood loss is really decreased, however, given that cut blood vessels will bleed after surgery, since the surgeon did not see them and cauterize them at the time of surgery. The high pressure tourniquet also can cause significant thigh pain after the surgery. However, it remains an accepted difference of opinion among surgeons and both techniques are accepted in the orthopaedic community.
Please remember the information on this site is for educational purposes only and should not be used to make a decision on a condition or a procedure. All decisions should be made in conjunction with your surgeon and your primary care provider.