Corrective osteotomy knee joint is a proven method of surgical treatment of deformities of the tibia and femur. This operation reduces the load on the articular surfaces, eliminates existing pathologies and slows down the degeneration of the lower limb.

Schematic representation of the operation.

What is a knee osteotomy?

Corrective osteotomy of the knee joint is an operation that eliminates congenital and acquired bone deformities. During surgery, the doctor excises a pre-designated area of ​​bone tissue and connects the loose bone fragments with implants. As a result, the axis of mechanical load is transferred to the healthy area of ​​the joint. The operation is performed under complete or spinal anesthesia. After treatment, the orthopedist immobilizes the patient's lower limb with a plaster cast during recovery. Rehabilitation is underway.

The described correction method is traditionally compared with knee replacement. Osteotomy is a less traumatic treatment method. This medical procedure is perfect for young patients suffering from late stages of gonarthrosis. The choice of osteotomy as a method of restoring mobility of the lower limb makes it possible to delay endoprosthetics for a long time.

Osteotomy has been used for two centuries. After the discovery of replacement arthroplasty methods, this surgery faded into the background, but this method of treatment is still used today. At the beginning of the 21st century, they were developed modern methods fixation of bone areas, reducing the duration of rehabilitation.

Indications for surgery

The main indication for surgical intervention is gonarthrosis. This is a degenerative disease of the knee joint, manifested by the gradual destruction of cartilage tissue and deformation of the lower limb. In the later stages of gonarthrosis, patients develop valgus and varus deformities. The range of motion is limited, and chronic pain occurs.

Other indications:

• Congenital deformity of the lower limb.
• Curvature of bones after injury.
• Preparation for knee replacement surgery.
• Displacement of the axis of the lower limb in pathologies of the articular ligaments.
• Rickets, osteitis deformans and other bone diseases.

The intervention is recommended for satisfactory condition of the cartilaginous surface of the bones and isolated damage to one area of ​​the knee joint. This correction method makes it possible to maintain mobility of the lower limb in young patients.

In what cases will osteotomy not help?

The effectiveness of treatment depends on the age, gender and body weight of the patient. Unsatisfactory results of the operation may be due to the patient's advanced age, significant bone damage and destruction of hyaline cartilage.

Conditions in which intervention is inappropriate:

• osteoporosis;
• extra-articular pathologies;
• lack of blood supply to the lower limb;
• impaired bone growth;
• absence of meniscus;
• severe obesity (BMI: 40 and above).

If the indications are not properly assessed, osteotomy can accelerate degeneration of the knee joint. Before treatment, doctors conduct laboratory tests, take photographs of the lower limb along its length and prescribe additional diagnostic procedures.

Types of surgical techniques

Interventions are classified according to the location, method of tissue excision and the nature of bone grafting. The structure of the tibia or femur is corrected. Classification according to the nature of the plastic surgery includes open, closed, lateral and direct osteotomies. Tibial correction can be high or low. The specific surgical technique is selected by the doctor individually based on the results of a preliminary examination.

Main types of osteotomy:

• Wedge-shaped closed. A skin incision is made in the lateral or anterior region of the knee to access the superior epiphysis of the tibia or the inferior epiphysis of the femur. After excision of the tissue, the free surfaces of the bone are fixed with metal plates or staples.
• Wedge-shaped open. After a skin incision is made in the anterior or lateral area of ​​the knee, a partial osteotomy is performed. The end of the tibia separates into two parts to form a diastasis. Next, the bone areas are connected with a metal plate and an autograft from the patient’s pelvis.

Knee osteotomy: visual representation of the procedure.

Bone tissue is removed using an osteotome. To prevent damage to the vessels and nerves passing through the knee joint, the correction is carried out under the control of a fluoroscope or X-ray machine. After plastic surgery, the skin is stitched and the lower limb is fixed with a plaster cast or splint.

There is no single method of surgical intervention suitable for any indication. When choosing a surgical technique, the doctor takes into account the planned correction angle. Imaging methods help more accurately restore the axis of the lower limb. In modern orthopedics, an open wedge osteotomy of the tibia above the level of the tuberosity is most often performed.

Rehabilitation

Long-term treatment results depend on rehabilitation measures. After surgery, the doctor conducts follow-up examinations and selects methods for restoring mobility of the knee joint. The goals of rehabilitation include pain relief, prevention of postoperative complications, and restoration of the muscular system of the lower extremity.

Rehabilitation methods:

• Physiotherapy: electrical stimulation, cryotherapy and heat. Physical therapy relieves pain and reduces tissue swelling in the postoperative period.
• Massotherapy. Manual therapy improves blood flow in tissues, relieves pain and normalizes muscle tone.
• Physiotherapy . Exercises can be done at home. The main task is to restore flexion and extension movements in the knee joint.
• Orthopedic rehabilitation to prevent relapse of the disease. The patient is advised to wear a knee brace or elastic bandage to secure the joint. For the first time after surgery, it is necessary to use a cane and wear shoes with orthopedic insoles to reduce the load on the articular surfaces.

The rehabilitation plan is drawn up by an orthopedist and a physical therapy doctor. Drug therapy is selected. Full restoration of motor activity occurs within a year.

Life after treatment

The prognosis is determined by the initial diagnosis, the chosen surgical treatment technique, the surgeon’s qualifications, the patient’s age and other criteria. According to the G. A. Ilizarov Medical Center, positive results were noted in 95% of patients after the intervention. For 10 years after bone grafting, there is no pain or other symptoms of gonarthrosis. Young people who have undergone osteotomy return to a full life after rehabilitation. Subsequent replacement arthroplasty is facilitated.

The long-term results of the correction are difficult to predict. Patients are advised to regularly visit an orthopedist and undergo examinations to monitor the condition of the joint. Osteotomy as an independent treatment method does not completely eliminate arthrosis, but only slows down the development of degenerative processes. In some patients, relapse occurs as early as 4 years after the intervention.

Prices for knee osteotomy

The cost of treatment depends on the qualifications of the doctor, surgical technique and diagnosis.

Average prices:

• Moscow: from 7 to 22 thousand rubles.
• St. Petersburg: from 10 to 23 thousand rubles.
• The average price in Russia is 15 thousand rubles.

Information on prices must be clarified in a specific clinic.

What is better - plates, pins or devices?

Change the shape of the legs, i.e. restoring the normal position of the mechanical axis of the lower limb can be done in various ways.

Which method is better, more convenient, safer?

The general principle for correcting deformities is that the bone is divided and fused into the desired position. The intersection of a bone (artificial fracture) is called osteotomy. Bone fixation is called osteosynthesis. There are dozens of osteotomy methods and hundreds of osteosynthesis methods. In modern traumatology and orthopedics, 3 main types of osteosynthesis are used to correct the shape of the lower extremities: plates, rods, and devices. In principle, each of these methods can change the position of the axis.

Despite the apparent identity of the results, each of these methods has its own pros and cons, advantages and disadvantages. There are complications specific to each of these methods. Let's talk about this in more detail.

Osteosynthesis with plates.

Looking ahead, let's say that the main and almost only advantage of the plates is that they are not visible from the outside. Despite the fact that this operation is used quite often abroad to correct deformities, it has a large number of disadvantages, limitations and complications. The operation itself is quite complex and traumatic, i.e. A large incision is required to perform osteotomy and osteosynthesis.

We can name such complications as: fracture of the tibial plateau; peroneal nerve damage; suppuration in the area of ​​surgery; overcorrection or, conversely, insufficient correction; unstable fixation and secondary displacements; deep vein thrombosis and much more.

In addition, the plate does not provide stable fixation. After surgery, a restrictive regimen of 2-3 months is recommended. For the same reason, they try not to operate on both legs. Thus, two surgeries spaced several months apart will be required to correct both legs. Taking into account the fact that the plates may have to be removed, we are already talking about at least three operations. There are serious limitations on the amount of correction (usually no more than 12 degrees); it is impossible to simultaneously correct varus (valgus) deformity and lengthen the limb, as well as apply additional correction elements (medialization, rotation, etc.). A significant drawback is that the shape of the leg after surgery cannot be somehow changed or “corrected”. Overcorrection or, conversely, insufficient correction, asymmetry of the legs with bilateral correction is possible.

It is difficult to understand the reason for the popularity of this technique. Most likely, this has historical roots, traditions of foreign medical schools, and interest in the sale of expensive medical products and technologies. In addition, in many countries the Ilizarov apparatus has not become widespread, and orthopedists simply cannot appreciate its advantages and benefits.

Osteosynthesis with rods (pins)

This technique is the least widespread compared to the other two (plates and devices). An undoubted advantage is stable fixation, which allows you to operate on both limbs at once and ensures early function and feeding ability. The essence of the technique is that after preliminary drilling of the medullary canal of the femur or tibia, a pin of the appropriate diameter is inserted into it.

Despite the fact that the pins are inserted through a small incision, this technique cannot be considered low-traumatic. There is a risk of developing serious complications. If, for example, when using the Ilizarov apparatus, inflammation or suppuration is local, superficial and easily curable, then with intramedullary osteosynthesis, suppuration threatens to spread the process throughout the medullary canal. It is also very difficult to achieve symmetrical correction of both legs, which is important in cosmetic surgery.

Considering the risk of developing serious complications, I would not like to recommend this technique for aesthetic correction of the shape of the legs. It is advisable to use pins during lengthening, when long periods of fixation with the Ilizarov apparatus significantly reduce the quality of life of patients.

Osteosynthesis using the Ilizarov apparatus

The Ilizarov apparatus is the most common method for correcting severe and complex limb deformities. There are no restrictions on the amount of correction or correction of deformation in other planes. Simultaneously with the elimination of angular deformity, it is possible to perform medialization, rotation, eliminate subluxation of the head of the fibula, and also lengthen the legs. Full weight bearing on the limbs is possible in the coming days after surgery.

The main complication that occurs with external osteosynthesis is inflammation at the sites where the wires exit. They are not difficult to treat. The incidence of wire osteomyelitis does not exceed 1.5%. Despite the fact that the bone is already involved in the inflammatory process, this process is local in nature and is completely cured.

The main disadvantage of Ilizarov apparatuses is their very presence and limitations in the selection of clothing and shoes. The solution to this problem is the transition from ring supports to monolateral mini-fixators located along the anterior surface of the shin. They are significantly smaller in volume and do not impede the full function of the knee joint.

The transition from Ilizarov ring devices to mini-fixators is advisable 1.5-2 months after surgery, when signs of regenerate formation in the osteotomy area have already appeared. During operations on both limbs, mini-fixators allow you to close the legs in the area of ​​the knee joints and evaluate the final shape of the legs even before complete fusion occurs.

Corrective osteotomy of the knee joint is a surgical intervention aimed at eliminating bone deformation. When planning such an operation, you should prepare to artificially break a small section of bone in order to correct the malunion. There are different osteotomy techniques, differing in the level of complexity depending on the presence or absence of concomitant pathologies and the general condition of the patient.

Indications and contraindications

Knee osteotomy is most often performed when there is degradation of the cartilage and parts of the knee joints, when it is necessary to preserve healthy tissue.

Contraindications for surgery:

• rheumatoid arthritis;
• local and general infectious diseases;
• diseases of the veins and blood vessels of the legs;
• heart and lung diseases in the stage of decompensation;
• kidney and liver failure;
• obesity or dystrophy;
• diabetes;
• increased bone fragility.

People who do not fall into the 40-60 age group may be denied surgery due to the low likelihood of a positive outcome or the possibility of a more gentle treatment.

Correction of the knee joint using osteotomy is recommended for patients who meet the following characteristics:

• mild to moderate arthritis that affects only one knee;
• middle age category;
• optimal weight;
• high mobility of the knee joint: ability to straighten – bend at least 90 degrees;
• the presence of pain caused by arthritis and manifesting itself only during periods of activity or prolonged standing;
• consent to long-term rehabilitation;
• consent to walk with crutches for 6–8 weeks after surgery.

If the operation is performed correctly, the positive result will last for a long time.

Preparing for surgery

MRI of the knee joint

Before osteotomy, confirmation of the diagnosis and determination of the volume of bone tissue to be removed is required. Required research:

• radiography;
• MRI, which uses special magnetic waves to create a picture of the structure inside the knees;

A comprehensive examination allows you to understand how high the level of effectiveness of the planned procedure will be.

Before performing an osteotomy, it is recommended to consult a doctor regarding the medications used. You may need to temporarily stop taking certain medications, such as anti-inflammatory drugs and blood thinners, for about a week. This measure increases the effectiveness of surgical intervention.

The operation is performed exclusively on an empty stomach, so you must abstain from eating at least 8 hours before and from drinks 3 hours before.

Features of knee surgery

The joints should be corrected until the disease becomes more severe and does not lead to the patient being unable to work. For advanced pathologies, endoprosthetics is recommended, which involves replacing the affected joint or part of it.

The main goal of osteotomy is to normalize the relationships between the surfaces of the knee joints and improve blood circulation in bone tissue. It is possible to remove the load from the affected area, which is subsequently transferred to the healthy limb for full functionality. Stagnation of blood in nearby tissues is prevented, thereby eliminating the risk of destruction of the cartilage tissue of the knees.

Result of corrective osteotomy of the knee joint

The result of corrective osteotomy depends on the correct calculation of the deformity angle and further surgical adjustment. To prevent relapse, it is recommended to take 3-4 healthy degrees. Doctors use imaging technology to measure the part of the bone that needs to be removed. Careful control increases the effectiveness of the event.

A skin incision is made and thin wires are placed into the knee to facilitate bone removal. The doctor carefully removes part of the knee joint at a certain angle. The remaining parts are fastened with special medical screws. At the end of the procedure, the tissues are sutured in layers and treated with antiseptics.

Corrective knee osteotomy usually takes 1-3 hours and requires a 2-3 day hospital stay after surgery. In some cases, the doctor extends the length of hospital stay if he sees complications.

Features of rehabilitation

After corrective osteotomy of the knee joint, rehabilitation is mandatory for the full restoration of knee function. The set of measures includes:

1. Taking painkillers.
2. Cold compresses for 15–20 minutes four times a day.
3. During rest, position the operated leg above the body to eliminate swelling, improve blood circulation and lymph outflow.
4. Caring for seams to prevent inflammation, keeping them clean and dry.
5. Use of crutches or walkers at the initial stage. The duration of use of auxiliary products is determined by the doctor.

The knee after osteotomy should be developed under the supervision of a physiotherapist after 6–8 weeks. Therapy is based on gradually increasing the range of motion and includes strength training.

Osteotomy is a surgical procedure, the essence of which is to create an “artificial fracture.” During the operation, the bone is sawed into two parts. After this, the bone fragments are shifted in the desired direction and fixed in an anatomically advantageous position.

Osteotomy of the tibia.

Indications for surgery

In clinical practice, osteotomies are most often used to correct axial and torsional deformities of the lower extremities. Such operations are performed for hip dysplasia, leg length discrepancy, and flat feet., hallux valgus, curvature of the upper limbs and spine. During surgical interventions, surgeons may saw through long tubular bones, vertebrae, pelvis or foot bones.

The main purpose of osteotomy is to correct the distribution of load on the joints. With the help of surgical intervention, doctors can restore the normal functional state of joints or “unload” their damaged parts.

Advantages of corrective osteotomy

During the procedure, surgeons separate the bone into pieces using a saw, drill or chisel. They perform all manipulations in accordance with a clear preoperative plan. During preparation for surgery, doctors create an optimal scheme for correcting existing defects. Naturally, such tactics allow one to achieve good functional results.

The video is in English, but very informative:

During an osteotomy, surgeons do not touch healthy joints. This allows you to preserve their functions and avoid complications associated with opening the synovial cavity. If the joint is damaged, repositioning the bones will help slow down its destruction. For example, osteotomy can delay the development of deforming arthrosis and delay surgery on the joint by 10-15 years.

In the presence of severe osteoarthritis or ligamentous weakness, osteotomy alone is not enough. Therefore, to achieve the desired effect, doctors supplement it with reconstructive operations on ligaments, arthrodesis or other manipulations.

For example, in case of flat feet, corrective osteotomy of the foot is often combined with plastic surgery of the long plantar ligament and arthrodesis of the subtalar joint.

Preparing for surgery

During preoperative preparation, doctors examine the patient and select the optimal treatment plan for him. After this, specialists must coordinate it with the patient himself. Before surgery, each person undergoes a full examination.

List of necessary analyzes and studies:

• general blood and urine analysis;
• determination of blood group, Rh factor;
• blood tests for RW and HbAg;
• coagulogram;
• blood chemistry;
• radiography in 2 projections;
• magnetic resonance imaging (MRI) of the affected segment;
• consultations with a neurologist, cardiologist, endocrinologist, allergist and other necessary specialists.

The more thorough the examination, the lower the risk of complications.

While waiting for surgery, doctors advise patients to perform special exercises. They help stretch and strengthen the muscles, which makes it possible to avoid the appearance of contractures in the postoperative period.

Some doctors refuse to operate on patients with severe obesity. The reason is high intraoperative risk, difficulties during rehabilitation and a high probability of complications. Such patients are usually operated on after they have lost weight.

The patient is hospitalized in the hospital 1 day before surgery. There he communicates with the attending physician, signs informed consent for anesthesia and surgical intervention. After this, the patient is prescribed the necessary medications, which he takes under the supervision of medical staff.

The evening before the operation, the person is prohibited from eating. In the morning he is asked to remove all jewelry. Immediately before surgery, the patient is changed into sterile clothing and taken to the operating room.

Progress of the operation

Osteotomy can be performed under general or local regional anesthesia. The choice of pain relief method depends on the extent of surgery, the person’s general health, and some other factors.

The operation begins with layer-by-layer dissection of soft tissues. Having gained access to the desired bone, the surgeon saws it. After this, he fixes the bone fragments using external (Ilizarov apparatus) or internal fixation systems (bone plates, screws). Before suturing a wound, doctors often conduct a control X-ray examination. It is necessary to confirm correct fixation of the bone.

The operation lasts from 60 to 120 minutes.

Rehabilitation after corrective osteotomy

After surgery, the person remains in the hospital for 3-7 days. In the postoperative period, he is regularly treated with wounds, given painkillers, antibiotic prophylaxis and prevention of thromboembolic complications. The medical staff also ensures that the patient begins to get out of bed as early as possible.

After discharge from the hospital, the patient goes home. There he continues to take the medications prescribed by the doctor. He gets around with the help of crutches. The patient's sutures are removed 10-14 days after surgery. After an osteotomy, a person must undergo full rehabilitation.

Most common complications

Sawing bones is a serious operation that involves considerable risk. Undesirable complications can develop during the manipulation or already during the recovery period. Many of them are difficult to treat.

Table 1. Possible complications

	Causes	Treatment and consequences
Non-union of bones	Smoking, poor blood supply to the bone, osteoporosis, severe concomitant diseases	If nonunion occurs, the patient requires reoperation and subsequent long-term rehabilitation.
Vicious union	Incorrect fixation of bone fragments during surgery	The defect can only be eliminated with another operation.
Dysfunction of nearby joints	Incorrect rehabilitation or its complete absence	In most cases, joint function can be restored through physical therapy.
Compartment syndrome	Compression of muscles with a hemostatic tourniquet during surgical procedures	The pathology is treated conservatively with the help of certain pharmaceuticals. In severe cases, the patient undergoes surgery - fasciotomy
Nerve damage	Inattentiveness of the surgeon or “non-standard” location of the nerve in a particular patient	It is impossible to restore the integrity and function of damaged nerves
Infectious complications	Infection during surgery or failure to follow the rules of postoperative wound care	Treated with antibiotics. In severe cases, the patient may require revision surgery
Thromboembolic complications	Inadequate prescription of anticoagulants, refusal to wear compression stockings, late mobilization	To treat thrombosis, large doses of anticoagulants and antiplatelet agents are used

Possible alternatives

Unfortunately, many diseases can only be cured with corrective osteotomy. This applies to congenital dysplasia of the hip joints, O- and X-shaped deformities of the lower extremities, severe kyphosis, lordosis, scoliosis. But in the treatment of flat feet and hallux valgus, osteotomy can be replaced by other types of interventions. The only problem is that they are likely to be less effective.

Osteotomy is the most effective method of surgical treatment of many diseases of the musculoskeletal system.

Corrective osteotomy is a type of surgical treatment during which the doctor dissects damaged bone structures. Often, osteoarthritis or another form of pathology is a direct indication for intervention. However, first, specialists will carry out treatment using other methods. But if there is no desired effect, the operation will still be prescribed for the patient. Only in this way will he be able to get rid of pain in the joint and restore its motor ability.

The duration of the intervention is within an hour, but sometimes the time can increase to one and a half hours, depending on the complexity of the clinical case. As for anesthesia, the use of both local and general anesthesia is acceptable, although the latter method is often preferred.

After the doctor has administered the selected type of anesthesia to the patient, the limb is treated with special antiseptic solutions, which helps avoid infection of the wound. Next, the doctor clearly determines which element of the bone and to what extent he will excise it. This process is carried out under radiographic control. Or using computer three-dimensional modeling.

When the order of work is determined and the removal is carried out, the diseased joint should receive maximum unloading from the injured cartilage tissue. Weight is transferred to a greater extent to the healthy zone.

Also, corrective osteotomy is indicated for patients diagnosed with varus or valgus curvature of the femur or rectus femoris muscle after poliomyelitis. The area for the operation is the supracondylar region.

Kinds

As already mentioned, direct indications for prescribing an osteotomy are deformations of bone structures, for example, if the patient was diagnosed with joints in a strong position. If the doctor believes that the best therapeutic effect can be achieved by performing an operation by shortening or shortening a limb, then so be it.

There are three main types of corrective osteotomy:

1. Linear. The doctor will make an incision into the bone structures, after which a bone graft will be placed in them, which will lead to the alignment of the limbs.
2. Wedge-shaped. To align the bone structures, a wedge-shaped excision of a certain area is performed.
3. Angular. Thanks to corrective manipulations and angular cuts of bone structures on both sides, the doctor can achieve the installation of bones in the correct position.

Most often, such an operation is prescribed to patients who have ever received, but it did not heal properly. In this case, the duration of the procedure will be maximum, and specialists will also use general anesthesia. will also take a long period of time.

Indications

An osteotomy procedure is an operation in which a bone is cut.

The main pathologies for which treatment is prescribed in this way are:

• deformations of congenital and acquired bones (if they have a shape that does not comply with the rules of anatomy), located on the hip, shoulder or lower leg;
• adhesions in the joints of the bone and fibrous type, which provokes impaired motor activity and the development of ankylosis;
• , and its complications;
• other metabolic pathologies of skeletal bones;
• accumulation of purulent exudate in tissues and organs.

Thanks to modern technologies in surgical medicine, tissue dissection is now performed not only with a scalpel, but also with the help of ultrasonic waves, radio waves and lasers.

After the operation is performed, the hip and its component parts are fixed in the required position using medical instruments, including: nails, plates, bone grafts, plaster casts, and traction.

Peculiarities

Corrective osteotomy is performed to restore or improve the functions of the musculoskeletal system. That is why it is most often done on the femur, which allows you to create a fulcrum in the proximal part. Depending on which area is injured, whether it is a congenital dislocation of the hip or in its neck, the procedure is performed both on the bone itself and in the pelvic area.

If a patient is diagnosed with ankylosis, that is, he suffers from a sharp limitation of motor abilities in the hip joint, the operation is performed based on the individual characteristics of the deformity presented in a particular clinical case.

When the patient progresses to the second stage, or the disease was detected at the very beginning, that is, it is classified as coxarthrosis of the first degree, or pseudarthrosis of the femoral neck, intervertical osteotomy according to McMurry is indicated.

In this case, with coxarthrosis of the first or second degree, the goal is to immerse the femoral head deeper into the acetabulum, and in the second case, the goal is to shift the load that the joint receives when performing movements.

It should be understood that such complex operations may be associated with the risk of developing all sorts of complications. For example, a piece of bone may break off or suppuration may occur. But during the rehabilitation process, there is a possibility of the formation of a false joint and slow fusion.

Rehabilitation

Corrective osteotomy has long been used by surgeons to treat pathologies of the hip joints. Therefore, there is a general plan of rehabilitation measures that the patient must carry out. After surgery, recovery time ranges from one to six months. It all depends on the complexity of the procedure itself and the age of the patient.

Recently, doctors began to practice only the use of special bone fixators, and decided to avoid plaster casts as much as possible. In some cases, casting is performed for only a few days after surgery. However, if the procedure was complex, and many restorative actions were performed on a small area, then such a step is extremely necessary. The patient will have to wear the cast from several weeks to a month.

It is important to strictly adhere to medical recommendations during the rehabilitation process. And if a specialist said that it is necessary to undergo a course of physiotherapy, massage and exercise therapy, then they should not be neglected, because otherwise a false joint may form.

You should also control your own. No need to eat junk food. The diet should be balanced and rich in fresh fruits and vegetables. This approach will help compensate for the lack of vitamins and also prevent excess weight gain.