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All Posts in Category: Doctor’s Articles

Hip, Knee Replacements Tied to Heart Attack Risk

Hip, Knee Replacements Tied to Heart Attack Risk

This article reports a well-known fact which doctors call perioperative risks. Remember that we are talking about the elderly who undergo a major elective operation which is a replacement of a major part of the anatomy. This involves the implantation of large foreign metallic material, often with the inclusion of liquid cement to weld the metal to the bone. Let me explain the technicalities.

The metal is made usually of an alloy-mix which has cobalt, chrome, titanium, zinc and nickel. There is a 2-3% incidence of metal allergy to one or more components of this alloy. Fortunately it is rare and may occur sometime after implantation and of a mild severity. In rare cases the patient may develop a hypersensitivity reaction which may mimic a heart attack.

The liquid cement is often used in osteoporotic bone to fill the gap between metal and porous bone in order to reduce the risk of loosening over the years. This cement is a combination of a volatile material (poly methyl methacrylate) by mixing a powder with a liquid. Think of a two-part epoxy glue. In fact the odour during mixing is similar. The main difference is that cyanoacrylate is poisonous and not used in body cement. During injection of the liquid cement into the bony canal, small molecules may enter the blood stream and cause the heart to slow down (bradycardia) which may result in loss of pumping power thus resulting in a heart attack. This is a well-known but rare risk and the surgeon usually waits for the cement to polymerise so that small molecules are minimised. The anaesthetist is also warned of the impending injection so he can monitor the patient more closely and prevent this fall in blood pressure. This may happen in 1-in-20 to 1-in-40 patients and is part of the pre-op counselling given by the surgeon and anaesthetist.

Acute myocardial infarcts (AMI, or heart attacks) are an expected risk especially for elderly with heart disease. For the patient this risk must be outweighed by the benefits of a pain-free mobile knee joint before agreeing to surgery. It is a curious fact that heart disease patients who need to undergo treadmill stress test cannot do so because of knee or hip arthritis and heart patients who need exercise rehabilitation also cannot complete the regimes for the same reason. Joint replacement actually improves their function so they can recover from heart disease.

Another relevant factor is deep vein thrombosis (DVT, or clots in the leg blood vessels) and pulmonary embolism (PE, or loose clots plugging up critical lung vessels). DVT may occur in 15-20% of patients undergoing hip and knee replacements but only 1% develops into PE, which mimics a heart attack. Standard precautions include the use of special long stockings, pneumatic foot pumps, anti-clotting drugs and routine vein ultrasound scans before each patient is discharged. Early physiotherapy and walking within 1-2 days also reduces the clot-forming rates, so lying immobile in bed after surgery is not a good thing, both for veins and the heart.

Finally the study was conducted from 1999-2007 and is thus more than 10 years old. Although it involved a large number of patients, this reflects a state-of-the-art a decade ago. AMI risks have been significantly lowered nowadays by earlier diagnosis, better-managed disease and evolution of regional anaesthesia. Regional anaesthesia and moderate sedation is far safer than general anaesthesia in most cases where hip and knee replacement. This comes in the form of spinal and nerve blocks which leaves the heart and lungs free of powerful inhaled drugs. These blocks can be made to last into the second and third post-op days by leaving a catheter in place for drug infusion, thereby providing complete pain relief in the conscious patient. They can start talking and eating when they “wake up” from surgery. Stress, being a significant factor in the causation of heart attacks, is effectively reduced for someone who expect much pain after such a major operation.

In summary, the decision for elective surgery must always weigh the factors of pre-existing disease state, need for the surgery, and the type of anaesthesia administered. The patient and family should ask the surgeon about the risks and precautions as stated above and satisfy themselves that all will be done that can be done to make hip and knee replacements a lower-risk operation which clearly improves the quality of life for the older folks who can and wish to remain mobile and independent in their silver years.

Written by Dr. Khong Kok-Sun.

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Numbness and Feeling of Pins and Needles in the Palm

Numbness and Feeling of Pins and Needles in the Palm

Qns: I am a 56-year-old woman. I began experiencing numbness in both hands after taking care of my grandson who is 10 months old.

The most likely problem is carpal tunnel syndrome (CTS). This is a condition in which one of the main nerves supplying the hand is compressed as it passes through a bony-ligamentous tunnel in the wrist, resulting in the nerve not functioning normally, causing numbness, and in the more severe cases, weakness. The nerve concerned is the median nerve, which supplies sensation to the thumb, index and middle fingers and half of the ring finger, and the muscles that move the thumb.

CTS is more common in females over 40 years of age. It may also be associated with frequent use of the hand and use of vibration tools.

In the mild stage, there may be intermittent numbness with tingling (pins and needles sensation) to the involved digits. This comes with certain activities that stress the hands and wrist, as in your case of having to take care of your grandson. The numbness and tingling may also occur at night, usually in the early hours of the morning, when a patient wakes up, having to shake the hands and wrist before feeling better.

In the moderate stage, there will be constant numbness, even when at rest. There may also be occasional dropping of things which the patient is holding, such as a cup, handphone, or newspapers.

In the severe stage, there will be associated weakness of the thumb and shrinkage (wasting) of the thumb muscles in the palm.

Treatment involves avoidance of activities that precipitate the symptoms, and wearing of a wrist splint at night to prevent bending of the wrist during sleeping as this increases the pressure on the nerves. Certain medication may also help. Steroid injections are usually temporary, and are not recommended as a standard method of treatment.

Nerve conduction studies can help to confirm the diagnosis, but is not always necessary.

If non-surgical treatment fails, surgery to release the ligament that compresses the nerve can be done. This may be done in the conventional open technique, or using minimally invasive techniques such as the scope-assisted release, as a day surgery procedure.

Recovery from surgery usually takes up to 6 weeks after surgery, whilst the wound takes 1-2 weeks to heal.

Written by Dr Winston Chew Yoon Chong, Hand Surgeon.

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Guidelines may help prevent re-injury after knee surgery

Guidelines may help prevent re-injury after knee surgery – A surgeon’s point of view


This is a sobering article for those who unfortunately suffered a “game-ending” knee injury either to the meniscus or cruciate ligaments, which is a rather common occurrence amongst the young. Fortunately surgical reconstruction is often successful in restoring the knee to its normal function, but at a price. In almost all cases of first-time injuries to the anterior cruciate ligament, a substitute ligament is taken from the same knee, either a patellar ligament or a hamstring tendon. It is like “borrowing from Peter to pay Paul”. Hence the injured knee is never the same as before. It goes without saying that intensive rehabilitation is the key to restoring as much function as can be obtained from a doubly–damaged knee. In the young, there is undoubtedly a lot of reserve and good potential for recovery.

So what are the issues to understand for those who have sustained such injuries?

Firstly, a torn meniscus which is repairable should be repaired, but there is a 20-30% chance of reinjury increasing to 50-70% if associated with an unstable ligament injury. An irrepairable torn meniscus will leave the knee compartment with a lack of cushioning that is almost impossible to restore, thus starting the downhill slide to post-traumatic arthritis. Such people should refrain from high-impact and twisting or pivoting sports if they want to preserve their knee-life. Swimming and cycling are appropriate sports to engage in.

Secondly, a torn anterior cruciate ligament (ACL) is very amenable to surgical repair except for the fact that another donor tissue is necessary to replace it. In rare instances, an allograft (tissue taken from a tissue bank) may be used, but their results are not as good, and this is reserved for repeat reconstructions. As the article states, it will be around 9 months of intensive rehabilitation before patients are returned to their pre-injury sporting status.

Thirdly, in 30-60% of young individuals who sustain complete ACL tears there is potential to avoid surgery and yet allow them to return to contact sports or those requiring pivoting. Why is this so?

The key to preventing re-injury is a combination of normal muscle strength and proprioceptive feedback, together with a dose of common sense. Knee function depends a balance of quadriceps and hamstring function. After surgery, one or the other is disadvantaged and there is imbalance of strength causing the knee to buckle and at risk of injuring the repaired structures.

Proprioception (sensation of knee position by the brain) is an automatic process allowing split-second adjustments to body posture to prevent abnormal knee joint distortion. Intact structures provide this feedback and surgery disrupts this positional sense through loss of sensory nerves. Rehabilitation for injury to joints must always incorporate proprioceptive feedback so the body can sense imbalance and activate the right muscles to counteract this. In simple terms, one cannot afford time to think about rebalancing, as it must be instinctive. This explains why those who do not undergo surgery for torn ligaments can return to sports at the same level in spite of a clearly unstable knee. The learnt to re-institute bio-feedback in their proprioceptive systems. They are also more conducive and diligent in rehabilitation as they chose to avoid surgery.

Finally, a dose of common sense is required for those who return to sports whether or not they had surgery to repair their ligaments. In other words they must choose to avoid heavy contact during a game understanding that further injury can mean total cessation of their favourite recreation.

Written by Dr. Khong Kok-Sun, General Orthopaedic Surgeon.

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Amputation of the Hand

Amputation of the Hand

On Tuesday, 13 October 2015, 85 year-old Mdm Khoo had her hand amputated in a lift accident in Tah Ching Road. In this article, our Hand and Microsurgery specialist, Dr Winston Chew shares on the Types of amputation and Reattachment options to give a better understanding of this type of devastating injuries.

What is Amputation of the Hand?

Amputation is a type of injury in which the hand is severed. This results in cutting off the blood supply to the hand, resulting in death of the tissues after several hours. It also results in loss of function as the bones are broken, the muscles or tendons are disconnected and hence cannot control movements in the hand, and the nerves are disrupted so they cannot perform the function of transmitting sensation or control the movements of the muscles. Complete amputation is when the part is completely detached from the body. Incomplete amputation is when certain parts may still be attached. In the case of Mdm Khoo, it was a complete amputation.

What are the Types of Amputation?  

Amputation can be categorized into Major and Minor amputation.

When the amputated part contains significant muscle tissues (hand, forearm, or arm), it is considered a Major amputation. The importance of the presence of muscles is that muscles cannot withstand loss of blood supply for more than 4-6 hours. After which, muscle tissue will start to die making reattachment not possible. This muscle survival can be prolonged by cooling the amputated hand with ice. The higher the level of amputation in the arm, the worse the function after eventual recovery. The best outcome for a major amputation is for those at the level of the wrist.

Minor amputations are so called when it involves the fingers. As they do not contain muscles, the fingers can survive for a longer period of time. Typically, it can survive beyond 12 hours, especially when cooled.

In the case of Mdm Khoo, it is likely to be an extensive crush if the hand was severed by the lift door, or an avulsion type if the hand was pulled off by the leash of the dog caught in the lift door. In either case, the damage would be expected to be severe. It is considered a major amputation, as the hand contains significant amount of muscle.


Diagrams show possible amputation mechanisms for Mdm Khoo’s injuries.

How can one render First aid?  

1.  Remove victim from danger (if possible)

2.  Stop the bleeding: Apply pressure on wound using a clean cloth or compression bandage. Elevate the arm to stop bleeding.

3.  Preserve the amputated part: Rinse part with clean water and put it into a clean plastic bag, then into another plastic bag with ice. Cooling prolongs survival of amputated part while double plastic bag prevents soaking severed part in water.

What are the Procedure risks?

In general, doctors will try to reattach all major limb amputation, such as that of the hand. The reason is that current technology is not able to recreate a hand substitute. As reattachment is a complex and long surgery, there are important factors to consider:

  • Patient factors

Medical conditions such as diabetes, hypertension and heart conditions increase the risk of complications. Risk also increases with age of the patient.

  • Extent of damage

The more severe the injury, the lower the success of replantation. The higher the amputation level, the worse the function after surgery.

  • Timing

A delay of more than 6 hours makes reattachment less feasible due to multi-organ failure. When muscle tissue dies, the wound may result in infection.

  • Surgeon and Surgery Facility

In Singapore, most hospitals are equipped with the capability to perform reattachment surgery.

In the case of Mdm Khoo, at 85 years of age, she is at higher risk for such a surgery. As mentioned above, Mdm Khoo’s injury may most likely be the extensive crush or the avulsion type, which are less likely to be replantable.

What is the outcome of Hand Replantation?

The best recovery of hand replantation (reattachment) is at the level of the wrist. The higher the amputation level, the worse the function. Nerve regeneration is a major limiting factor as most of the functions require the nerve to work well.

The younger the child, the better the recovery. This is because nerve regeneration in the young is good, and recovery is much better, especially for those below 10 years of age.

In general, it has been found that a replanted hand can function better than an artificial hand (prosthesis). But a long period of therapy is required before recovery, which may take up to a year or more, depending on the level. Follow-up surgery often need to be done, the average being about 3 additional procedures after the replantation surgery.

Written by Dr Winston Chew Yoon Chong, Hand & General Orthopaedic surgeon

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