Fracture Care

Overview
Total ankle replacement (also known as “total ankle arthroplasty”) is a surgical procedure for patients with arthritis of the ankle. Arthritis causes wear and tear of the ankle joint, leading to bone-on-bone contact with limited motion and activity. TAR surgery can relieve pain while maintaining motion in the ankle joint and is a viable alternative to an ankle fusion (arthrodesis) which can relieve pain but completely eliminates motion in the joint.

Characteristics of the Ankle
The ankle joint is a hinge type joint comprising the three bones of the lower leg. The first bone in the ankle is the talus which contacts the second bone called the tibia, forming the tibiotalar joint. The third bone is the fibula and is the small bone on the outside part of the ankle. Held together with ligaments, the ankle joint contains cartilage that absorbs shock and allows the ankle to move. Pain-free motion and full function of the ankle joint require coordination of the ankle bones as well as the soft tissue surrounding the joint. The joint can lose its cartilage covering through post-traumatic damage, infection, or daily wear and tear. Radiographs (X-rays) will show a narrowed joint with other arthritic changes the surgeon will evaluate. Typically, advanced imaging will be ordered to determine specific characteristics of the arthritic ankle joint.

Alternatives to TAR Surgery
Treatment approaches for an arthritic ankle are based on how long the pathology has been present and the amount of pathology to the soft tissue as well as arthritic conditions to the joint. Conservative treatment options are explored prior to surgical intervention.

Incidence

A fracture is a partial or complete break in a bone. Fractures in the ankle can range from stable  less severe injuries to unstable injuries involving the tibia and/or fibula. Fractures include: Distal fibula or tibia avulsion fractures (typically treated non-operatively), Stable fibula fractures (typically treated non-operatively), Bimalleolar fractures (typically treated with surgery), trimalleolar fractures (typically treated with surgery), Dislocated fractures (typically treated with surgery), Tibia plafond fractures (typically treated with surgery).

Ankle fractures are the most common bone fractures and are often caused an indirect injury by the ankle rolling inward or outward or by direct trauma (i.e. motor vehicle accident, motorcycle crash, industrial injury)

Symptoms

  • Pain at the site of the fracture
  • Significant swelling, which may occur along the length of the leg or may be more localized
  • Blisters may occur over the fracture site
  • Bruising that develops soon after the injury
  • Inability to walk (it is possible to walk with less severe breaks)
  • Change in the appearance of the ankle

Diagnosis

Following evaluation by the emergency department or urgent care it is important to have the ankle evaluated by a foot and ankle surgeon for proper diagnosis and treatment.

The affected limb will be examined by the foot and ankle surgeon by touching specific areas to evaluate the injury. In addition, the surgeon may order additional x-rays and other imaging studies (i.e. CT scan, MRI), as necessary to further delineate the fracture pattern or for operative planning.

Non-Surgical Treatment

Treatment of ankle fractures depends upon the type and severity of the injury: If your surgeon has determined that your ankle fracture is stable and does not require surgery you will be placed in a removable boot with weight as tolerated in the boot.

  • Rest: Stay off the injured ankle during the acute phase.
  • Ice: Apply an ice pack to the injured area as well as behind the knee placing a thin towel between the ice and the skin. Use ice for 20 minutes and then wait at least 40 minutes before icing again.
  • Compression: An elastic wrap may be recommended by your surgeon to control swelling.
  • Elevation: The ankle should be raised slightly above the level of your heart to reduce swelling.
  • Medications: To help relieve the pain, the surgeon may prescribe pain medications or anti-inflammatory drugs for non-operative ankle fractures.

Surgery

After your surgeon has determined the severity of your fracture through the clinical exam and diagnostic modalities surgery may be required to anatomically stabilize the ankle joint. The surgeon will select and discuss the necessary procedure that is appropriate for your injury.

Surgery is typically scheduled 6-14 days following the injury to allow the soft tissue swelling to subside.

A splint will be placed on your injured ankle until your surgery date. No weight to the injured ankle is advised.

The overall structure of the foot is complex, consisting of bones and an intricate network of soft tissue attachments to make the joints move smoothly throughout foot function and motion. There are 28 bones in the foot, 19 of the bones are toe bones (phalanges) and metatarsal bones (the long bones in the midfoot that connect the toes to the foot). Fractures of the toe and metatarsal bones are very common and usually require evaluation by a specialist.

Type of toe and metatarsal fractures

Traumatic fractures are caused by a direct blow or impact (stubbing toe, dropping a heavy item on the middle part of your foot). If the fracture is displaced, the bone has moved in a way that changes its position (malposition) and anatomical alignment which further jeopardizes the biomechanics of gate and ambulation.

Symptoms of a traumatic fracture include:

  • Hear a crack or pop at the time of the break.
  • Direct pain over the fracture.
  • Crooked/deviated or abnormal appearance of the toe.
  • Bruising and swelling the next day.

Stress fractures are small, hairline breaks that are usually caused by repetitive micro stress. Stress fractures often occur in athletes that increase their training; however, the can also occur in patients with abnormal foot structures, foot/ankle deformities, and/or osteoporosis/Vitamin D deficiency. Improper footwear can also lead to stress fractures.

Symptoms of stress fractures include:

  • Pain during or after normal activity
  • Pain that goes away when resting and then returns when standing or during activity
  • Pain at the site of the fracture
  • Swelling but no bruising

Treatment of Toe Fractures

Fractures of the toe bones are most often always traumatic fractures. Treatment for traumatic fractures depends on the characteristics of the fracture may include these options:

  • Rest. Stay off the injured toe during the acute phase. Only necessary activities are advised
    Splinting. The toe may be fitted with a splint to keep it in a fixed position to avoid further displacement.
  • Rigid/Stiff-soled shoe. Wearing a stiff-soled shoe protects the toe and helps keep it in the proper alignment.
  • CAM Walker/Post Op Shoe. At times a walker or post op shoe can offer protection and comfort.
  • Buddy taping. Applying the fractured toe to another toe is sometimes is appropriate, but in other cases it may be harmful. Your surgeon will advise if this is necessary.
  • Toe Fracture Surgery. If the break is severely displaced or if the joint is affected, surgery may be necessary. Surgery often involves the use of small fixation devices, such as pins or small screws.

Treatment of Metatarsal Fractures

Breaks in the metatarsal bones may be either stress or traumatic fractures. Certain types of fractures of the metatarsal bones present unique challenges. Treatment of metatarsal fractures depends on the type and extent of the fracture, and may include:

  • Rest. Stay off the injured foot during the acute phase. Only necessary activities are advised
  • Ice: Apply an ice pack to the injured area as well as behind the knee placing a thin towel between the ice and the skin. Use ice for 20 minutes and then wait at least 40 minutes before icing again.
  • Compression. An elastic wrap may be recommended by your surgeon to control swelling. Elevation: The foot/ankle should be raised slightly above the level of your heart to reduce swelling.
  • Medications. To help relieve the pain, the surgeon may prescribe pain medications.
  • Avoid certain activity. Because stress fractures result from repetitive stress, it is important to avoid activity that led to the fracture. Crutches/knee scooter/wheelchair are at times required to offload weight from the foot to give it time to heal.
  • Immobilization/casting/rigid shoe. A stiff-soled shoe, Cam walker, or short leg cast may be used to protect the fractured bone while it is healing.
  • Metatarsal Fracture Surgery. Some traumatic fractures of the metatarsal bones that are displaced or malpositioned require surgery, especially if the break is badly displaced.

Surgery

After your surgeon has determined the severity of your fracture through the clinical exam and diagnostic modalities surgery may be required to anatomically stabilize the fifth metatarsal fracture. The surgeon will select and discuss the necessary procedure that is appropriate for your injury.

Surgery is typically scheduled 6-14 days following the injury to allow the soft tissue swelling to subside.

A splint or non weight bearing removable boot will be placed on your injured foot until your surgery date. No weight to the injured foot is advised.

Consequences of Improper or Delayed Treatment

  • A deformity in the architecture of the bone and arch which may limit the ability to move the foot or cause difficulty in fitting in certain shoes.
  • Arthritis, which may be caused by a fracture in or adjacent to a joint (where two bones come together to allow movement).
  • Angular deformities that develop when a displaced fracture is severe or hasn’t been properly corrected.
  • Chronic pain and deformity.
  • Non-union, or delay in healing can lead to surgery or chronic pain.

The talus is second largest bones in the foot. The talus is directly under the ankle joint. This bone is responsible for transitioning the motion/movement of the ankle joint to the remainder of the foot. Similar to the hip for leg motion, the talus is the center point for rotation for the foot. The talus connects the the ankle, the calcaneus, and the navicular and works in sync with these bones for smooth motion during ambulation. The joints involved are ankle joint (up and down motion), the subtalar joint (side to side motion of the rearfoot) and the talonavicular joint (inward and outward motion of the foot).

The talus is a strong/hard bone due to the the majority of bone covered in cartilage (joint connective tissue). Additionally the talus has no muscle/tendon connections and only ligament attachments. Due to the anatomy of the bone, the attachments, and the coverage of cartilage, the blood supply is often at risk with these fractures leading to necrosis of the bone. If the fracture of the talus involves the surrounding joints, there can be potential long-term consequences to include arthritis, difficulty in walking, and chronic pain.

Incidence/Mechanism

Talus fractures are the result of a traumatic event. Commonly, falling from a height, or a motor vehicle accident where the front part of the bone is wedged against the front of the ankle or where the body of the bone is wedged between the heel and the ankle joint. Talus fractures can also occur with other types of injuries, such as an ankle fracture or ankle sprain.

Types of Talus Fractures

Fractures of the calcaneus may or may not involve the ankle, subtalar, or talonavicular joint.

  • Head Fractures. Usually involve the talonavicular joint, at times include damage to the cartilage.
  • Neck Fractures. Most severe depending on the degree and displacement of the fracture due to the blood supply to the remainder of the bone
  • Body Fractures. Usually involve the ankle joint, at times include damage to the cartilage.
  • Posterior Process Fractures. Involve the back of the talus and may get wedged against the back of the ankle joint. The tendon to the big toe courses next to this area and damage to the tendon or surrounding structures may occur.
  • Lateral Process Fractures. Involve the outside of the talus and at times includes damage to the subtalar joint (side to side joint under the ankle). This fracture is associated with ankle sprains.

The treatment and severity of these fractures depend on their size and location.

Symptoms

  • Pain at the site of the fracture
  • Significant swelling, which may occur around the ankle or in the foot
  • Blisters may occur over the fracture site
  • Bruising that develops soon after the injury
  • Inability to walk
  • Change in the appearance of the ankle and heel

Diagnosis

In order to determine the diagnosis your surgeon will will ask how the injury occurred. The foot will be examined, with the surgeon gently pressing on different areas of the foot to locate the pain.

X-rays are necessary to evaluate the extent of the injury. Typically a CT scan will be ordered for further evaluation of the talus as well as for surgical planning if surgery is needed.

Treatment

Treatment of the talus fractures depends upon the type and severity of the injury: If your surgeon has determined that your talus fracture is stable with minimal displacement or minimal joint involvement and does not require surgery you will be placed in a short leg cast or a removable boot to restrict motion and allow the fracture to heal as weight can cause further displacement and possible surgical intervention.

  • Rest: Stay off the injured foot.
  • Ice: Apply an ice pack to the injured area as well as behind the knee placing a thin towel between the ice and the skin. Use ice for 20 minutes and then wait at least 40 minutes before icing again.
  • Compression: An elastic wrap may be recommended by your surgeon to control swelling.
  • Elevation: The ankle should be raised slightly above the level of your heart to reduce swelling.
  • Medications: To help relieve the pain, the surgeon may prescribe pain medications or anti-inflammatory drugs for non-operative talus fractures.

Please note: Due to limited ambulatory status, severe medical conditions, or noncompliance your surgeon may recommend non surgical treatment even though surgery would be indicated for your fracture. If this is the case you may require a surgical fusion of the ankle joint, subtalar joint and/or talonavicular joint once your medical status changes and/or you receive medical clearance for medical conditions. Arthritis may occur without surgical intervention.

Surgery

After your surgeon has determined the severity of your fracture through the clinical exam and diagnostic modalities surgery may be required to anatomically stabilize the talus and to reconstruct the ankle joint, subtalar joint, and/or talonavicular joint. The surgeon will select and discuss the necessary procedure that is appropriate for your injury.

Surgery is typically scheduled 6-14 days following the injury to allow the soft tissue swelling to subside.

A splint will be placed on your injured foot until your surgery date. No weight to the injured foot is advised.

Complications of Talus Fractures

Talus fractures can be serious injuries that may produce lifelong problems. Arthritis, stiffness, and pain in the joints frequently develop. Sometimes the fractured bone fails to heal in the proper position. Other possible long-term consequences of talus fractures are avascular necrosis (dead bone) due to the limited blood supply to the talus. This may cause decreased ankle, subtalar, and talonavicular motion and walking with a limp due to collapse of bone and loss of length in the leg. Patients often require additional surgery and/or long term or permanent use of a brace and/or an orthotic device to help manage these complications.

Fractures of the fifth metatarsal involve the long bone on the outside of the foot that connects to the little toe. Several types of fractures occur.

  • Avulsion fracture. A small piece of bone is pulled (avulsed) off the main portion of the bone by a tendon or ligament. This type of fracture is usually secondary to ankle sprains. Non-operative treatment is usually due to the small size of the avulsion. At times your surgeon may recommend excising the fragment to relieve any pain.  
  • Base fracture. At times avulsion fractures are much larger involving the styloid of the fifth metatarsal. Surgery is dependent on how large the fragment is as well as how much displacement is involved.
  • Jones fracture. Jones fractures occur in a small area of the fifth metatarsal that receives less blood (watershed area) and is therefore more prone to delayed healing. A Jones fracture can be occur through repetitive stress (i.e. stress fracture) or an acute traumatic event. Surgery is typically advised to provide stability and promote healing even with minimal displacement of this fracture; however, at times Jones fractures may be treated non operatively pending other injuries, medical conditions, or compliance.
  • Intra-articular fracture. An intra-articular fracture of the fifth metatarsal involves the base of the metatarsal and the joint adjacent to this bone (tarsalmetatarsal). This type of fracture can be a simple fracture (one part) or more complex (involving several fracture pieces). Surgery is advised if there is a displacement of the joint and if anatomical alignment of the fracture is needed.
  • Shaft fracture. Fractures involving the shaft of the metatarsal are usually involved with a traumatic twisting even of the foot. Surgery is recommended if displacement is involved as well as shortening of the bone in order to restore the anatomy of the fifth metatarsal.
  • Neck fracture. Neck fractures are usually secondary to a direct trauma (i.e. dropping an item on the foot). If this fracture is displaced and affects the joint next to the little toe surgery is warranted to restore the biomechanics of the joint.
  • Head fracture. Head fractures involve the joint adjacent to the little toe. Surgery is advised if the fracture is displaced and affect the biomechanics of the joint.

Symptoms

Pain, swelling, bruising, and tenderness (typically directly over the fracture) on the outside of the foot, Difficulty walking.

Diagnosis

In order to determine the diagnosis your surgeon will will ask how the injury occurred or when the pain started. The foot will be examined, with the surgeon gently pressing on different areas of the foot to locate the pain.

X-rays will be ordered. If the surgeon is concerned with a stress fracture (hairline fracture) or comminution of the joint complex additional imaging may be needed.

Non-surgical Treatment

Treatment of fifth metatarsal fractures depends upon the type and severity of the injury: If your surgeon has determined that your fifth metatarsal fracture is stable and does not require surgery you will be placed in a removable boot with the ability to weight bear as tolerated in the boot.

  • Rest. Stay off the injured foot during the acute phase. Only necessary activities are advised
  • Ice. Apply an ice pack to the injured area as well as behind the knee placing a thin towel between the ice and the skin. Use ice for 20 minutes and then wait at least 40 minutes before icing again.
  • Compression. An elastic wrap may be recommended by your surgeon to control swelling.
  • Elevation. The foot/ankle should be raised slightly above the level of your heart to reduce swelling.
  • Medications. To help relieve the pain, the surgeon may prescribe pain medications for non-operative fifth metatarsal fractures.
  • Immobilization. At times due to other medical conditions or fracture patterns. The surgeon may recommend immobilization with the removable boot or a short leg cast. Crutches/walker/knee scooter/wheel chair may also be needed to avoid placing weight on the injured foot until healing is noted radiographically and clinically.
  • Bone stimulation. A pain-free external bone stimulator device is used to speed the healing of some fractures. Bone stimulation, is typically reserved for Jones fractures that are treated non operatively due to medical conditions. This is determined if delayed or non healing is noted radiographically and clinically.

Surgery

After your surgeon has determined the severity of your fracture through the clinical exam and diagnostic modalities surgery may be required to anatomically stabilize the fifth metatarsal fracture. The surgeon will select and discuss the necessary procedure that is appropriate for your injury.

Surgery is typically scheduled 6-14 days following the injury to allow the soft tissue swelling to subside.

A splint or boot will be placed on your injured foot until your surgery date. No weight to the injured foot is advised.

The calcaneus (heel bone) is one of the largest bones in the foot. This bone is responsible for absorbing the weight during walking/running and forms the foundation of the rear part of the foot. The calcaneus connects with the talus and cuboid bones. The connection between the talus and calcaneus forms the subtalar joint. This joint is important for side to side motion and works in sync with other joints during the ambulation process.

The calcaneus can be compared to a hard boiled egg (hard shell on the outside and softer, spongy bone on the inside.) When the outer shell is broken, the bone tends to collapse and become fragmented. Also, if the fracture involves the joints, there can be potential long-term consequences to include arthritis, difficulty in walking, and chronic pain.

Incidence/Mechanism

Calcaneal fractures are the result of a traumatic event. Commonly, falling from a height (ladder), or a motor vehicle accident where the heel is crushed against the floorboard. Calcaneal fractures can also occur with other types of injuries, such as an ankle sprain. A smaller number of calcaneal fractures are stress fractures, caused by overuse or repetitive stress on the heel bone.

Types of Calcaneal Fractures

Fractures of the calcaneus may or may not involve the subtalar and surrounding joints.

Fractures involving the joints (intra-articular fractures) are the most severe calcaneal fractures, and at times include damage to the cartilage (joint connective tissue that allows the joints to move).

Fractures that don’t involve the joint (extra-articular fractures) include:

Those caused by trauma, such as avulsion fractures (piece of calcaneus is pulled off with the achilles tendon) or crush injuries resulting in multiple fracture fragments

Stress fractures, caused by overuse or mild injury.

The treatment and severity of extra-articular fractures depend on their location and size.

Signs and Symptoms

Calcaneal fractures produce variable signs and symptoms, depending on whether they are traumatic or stress fractures.

The signs and symptoms of traumatic fractures may include:

  • Sudden pain in the heel
  • Inability to bear weight on that foot
  • Swelling in the heel area
  • Bruising of the heel and ankle

The signs and symptoms of stress fractures may include:

  • Generalized pain in the heel area that usually develops slowly (over several days to weeks)
  • Swelling in the heel area

Diagnosis

In order to determine the diagnosis your surgeon will will ask how the injury occurred or when the pain started. The foot will be examined, with the surgeon gently pressing on different areas of the foot to locate the pain.

X-rays are necessary to evaluate the extent of the injury. Typically a CT scan will be ordered for further evaluation of the calcaneus as well as for surgical planning if surgery is needed.

Treatment

Treatment of the calcaneus fractures depends upon the type and severity of the injury: If your surgeon has determined that your calcaneus fracture is stable with minimal displacement or minimal joint involvement and does not require surgery you will be placed in a short leg cast or a removable boot to restrict motion and allow the fracture to heal as weight can cause further displacement and possible surgical intervention.

  • Rest: Stay off the injured foot.
  • Ice: Apply an ice pack to the injured area as well as behind the knee placing a thin towel between the ice and the skin. Use ice for 20 minutes and then wait at least 40 minutes before icing again.
  • Compression: An elastic wrap may be recommended by your surgeon to control swelling.
  • Elevation: The ankle should be raised slightly above the level of your heart to reduce swelling.
  • Medications: To help relieve the pain, the surgeon may prescribe pain medications or anti-inflammatory drugs for non-operative calcaneal fractures.

Please note: Due to limited ambulatory status, severe medical conditions, or noncompliance your surgeon may recommend non surgical treatment even though surgery would be indicated for your fracture. If this is the case you may require a surgical fusion of the subtalar joint once your medical status changes and/or you receive medical clearance for medical conditions. Arthritis, heel widening, limb length may occur without surgical intervention.

Surgery

After your surgeon has determined the severity of your fracture through the clinical exam and diagnostic modalities surgery may be required to anatomically stabilize the calcaneus and to reconstruct the subtalar joint. The surgeon will select and discuss the necessary procedure that is appropriate for your injury.

Surgery is typically scheduled 6-14 days following the injury to allow the soft tissue swelling to subside.

A splint will be placed on your injured foot until your surgery date. No weight to the injured foot is advised.

Complications of Calcaneal Fractures

Calcaneal fractures can be serious injuries that may produce lifelong problems. Arthritis, stiffness, and pain in the joint frequently develop. Sometimes the fractured bone fails to heal in the proper position. Other possible long-term consequences of calcaneal fractures are decreased ankle motion and walking with a limp due to collapse of the heel bone and loss of length in the leg. Patients often require additional surgery and/or long term or permanent use of a brace or an orthotic device (arch support) to help manage these complications.

The Lisfranc joint is a general term for injuries in the mid foot involving the metatarsal bones (long bones that connect to the toes) and the tarsal bones (bones in the arch).

The Lisfranc ligament is a tough band of tissue that joins two of these bones. This is the most important ligament in the midfoot and is involved with maintaining proper alignment and strength of the arch.

Incidence

Injuries to the Lisfranc joint most commonly occur in motor vehicle accidents, motorcycle crashes, runners, horseback riders, contact sports, and at times something as simple as missing a a curb or step.

Lisfranc injuries occur as a result of direct or indirect forces to the foot. A direct force often involves something heavy falling on the foot. Indirect force commonly involves twisting the foot.

Types of Lisfranc Injuries

There are three types of Lisfranc injuries, which sometimes occur together:

  • Sprains. The Lisfranc ligament and other ligaments on the bottom of the midfoot are stronger than those on the top of the midfoot. Therefore, when they are weakened through a sprain (a stretching or tearing of the ligament), you may experience instability of the middle part of the foot.
  • Fractures. A break in a bone in the Lisfranc joint can be either an avulsion fracture (small piece of bone that is pulled off) or a break through the bone or multiple bones of the midfoot typically involving the joints.
  • Dislocations. The bones of the Lisfranc joint may be forced from their normal positions resulting in multiple fractures or purely ligament injuries causing the one part of the foot to go to the inside or outside.

Symptoms

  • Swelling of the foot
  • Pain throughout the midfoot when standing or when pressure is applied
  • Inability to place weight on the injured foot.
  • Bruising on the bottom part of the arch or blistering on the top of the foot.
  • Abnormal widening of the foot.

Diagnosis

Lisfranc injuries are sometimes mistaken for ankle sprains or minor sprains of the foot and can commonly be missed. In order to determine the diagnosis your surgeon will will ask how the injury occurred or when the pain started. The foot will be examined, with the surgeon gently pressing on different areas of the foot to locate the pain. A stress exam may be needed to determine if the source of pain is over the Lisfranc complex.

X-rays are necessary to evaluate the extent of the injury. At times a stress x-ray will be ordered by the surgeon to determine instability of the midfoot and see if the joints move (typically these do not move unless provoked by injury). Typically a CT scan will be ordered for further evaluation of the small midfoot bones as well as for surgical planning if surgery is needed.

Non-surgical Treatment

Treatment of Lisfranc injuries depends upon the type and severity of the injury: If your surgeon has determined that your Lisfranc injury/fracture is stable and does not require surgery you will be placed in a removable boot with the ability to weight bear as tolerated in the boot.

  • Rest: Stay off the injured foot during the acute phase. Only necessary activities are advised
  • Ice: Apply an ice pack to the injured area as well as behind the knee placing a thin towel between the ice and the skin. Use ice for 20 minutes and then wait at least 40 minutes before icing again.
  • Compression: An elastic wrap may be recommended by your surgeon to control swelling.
  • Elevation: The foot/ankle should be raised slightly above the level of your heart to reduce swelling.
  • Medications: To help relieve the pain, the surgeon may prescribe pain medications or anti-inflammatory drugs for non-operative Lisfranc fractures.
  • Immobilization: At times due to other medical conditions or fracture patterns. The surgeon may recommend immobilization with the removable boot or a short leg cast. Crutches/walker/knee scooter/wheel chair may also be needed to avoid placing weight on the injured foot until healing is noted radiographically and clinically.

Surgery

After your surgeon has determined the severity of your fracture through the clinical exam and diagnostic modalities surgery may be required to anatomically stabilize the Lisfranc injury/fracture pattern. The surgeon will select and discuss the necessary procedure that is appropriate for your injury.