**6. Clinical presentations**

#### **6.1. Hip**

Femoral head osteonecrosis is the most common site affected by osteonecrosis and perhaps the best studied. About 20% of the cases are idiopathic. The rest are linked to alcoholism, corticosteroid therapy, and other factors already described in **Table 1**. Surgical treatment varies. In mild or moderate cases, there is the possibility of preserving the joint with techniques such as decompression, osteotomies, bone grafting, and new stem cell therapies. Severe cases should be treated with arthroplasties, which can vary in partial or total arthroplasties and resurfacing [6].

An important aspect related to osteonecrosis of the hip is the vascularization of the head of the femur and the changes that this vascularization presents throughout life. In this sense, Ismet Gavrankapetanović and co‐authors present us, in this book, a very interesting chapter on this topic, addressing an unexplored topic, which is the relationship between hip development disorder and osteonecrosis.

#### **6.2. Knee**

In addition to the traditional osteonecrosis itself, two other entities must be recognized: spontaneous osteonecrosis of the knee (SPONK) described by Ahlback in 1968 and postoperative osteonecrosis (ONPK) described by Brahme in 1991.

Patients with SPONK have a different epidemiological profile, since they affect women over 50 in only one joint, with a single small lesion, without the traditional risk factors (use of corticosteroids, alcoholism, etc.).

Similarly, ONPK has an epidemiological profile similar to SPONK, only occurring after a surgical intervention, which is most often an arthroscopic meniscectomy indicated for meniscal degenerative lesions. Anterior Cruciate Ligament (ACL) surgery and cartilage procedures also could predispose to ONPK.

The current trend is to consider SPONK and ONPK as subchondral bone insufficiency fractures, unlike osteonecrosis, which is caused by a bone infarct [7].

#### **6.3. Ankle**

The site most affected by osteonecrosis in the foot and ankle segment is the talus. The most frequent etiology is trauma (75%). Osteonecrosis is a complication well known and feared in the treatment of talus fractures because of the precarious vascular supply of this bone.

One of the ways to treat and prevent osteonecrosis of the talus is through early and accurate anatomic reduction. Once osteonecrosis is established, the first measure is limited weight bearing. In the failure of this treatment, the surgery is indicated, being basically divided into two groups: the arthrodesis and the ankle arthroplasty [8].

#### **6.4. Shoulder**

Osteonecrosis of the humeral head (ONHH) is an uncommon condition, but after the hip, it is the second most common site of nontraumatic osteonecrosis. The four‐part fracture is the most common cause of ONHH.

The most widely used classification is the Cruess classification system, which has five stages according to radiographic appearance as follows:

Stage I: normal X‐ray with altered MRI;

Stage II: sclerotic bone without collapse;

Stage III: crescent sign;

Stage IV: collapse of the humeral head;

Stage V: osteoarthritis.

Treatment could be divided as nonoperative, arthroscopic debridement, core decompression, bone grafting, and shoulder arthroplasty [9].

#### **6.5. Elbow**

The elbow is rarely affected by osteonecrosis. According to Le et al. [10], the most affected sites are the capitellum and the lateral epicondyles, being, therefore, a rare differential diagnosis of tennis elbow syndrome.

#### **6.6. Wrist**

Patients with SPONK have a different epidemiological profile, since they affect women over 50 in only one joint, with a single small lesion, without the traditional risk factors (use of cortico-

Similarly, ONPK has an epidemiological profile similar to SPONK, only occurring after a surgical intervention, which is most often an arthroscopic meniscectomy indicated for meniscal degenerative lesions. Anterior Cruciate Ligament (ACL) surgery and cartilage pro-

The current trend is to consider SPONK and ONPK as subchondral bone insufficiency frac-

The site most affected by osteonecrosis in the foot and ankle segment is the talus. The most frequent etiology is trauma (75%). Osteonecrosis is a complication well known and feared in

One of the ways to treat and prevent osteonecrosis of the talus is through early and accurate anatomic reduction. Once osteonecrosis is established, the first measure is limited weight bearing. In the failure of this treatment, the surgery is indicated, being basically divided into

Osteonecrosis of the humeral head (ONHH) is an uncommon condition, but after the hip, it is the second most common site of nontraumatic osteonecrosis. The four‐part fracture is the

The most widely used classification is the Cruess classification system, which has five stages

Treatment could be divided as nonoperative, arthroscopic debridement, core decompression,

The elbow is rarely affected by osteonecrosis. According to Le et al. [10], the most affected sites are the capitellum and the lateral epicondyles, being, therefore, a rare differential diag-

the treatment of talus fractures because of the precarious vascular supply of this bone.

steroids, alcoholism, etc.).

**6.3. Ankle**

6 Osteonecrosis

**6.4. Shoulder**

most common cause of ONHH.

Stage III: crescent sign;

Stage V: osteoarthritis.

**6.5. Elbow**

cedures also could predispose to ONPK.

tures, unlike osteonecrosis, which is caused by a bone infarct [7].

two groups: the arthrodesis and the ankle arthroplasty [8].

according to radiographic appearance as follows:

Stage I: normal X‐ray with altered MRI; Stage II: sclerotic bone without collapse;

Stage IV: collapse of the humeral head;

nosis of tennis elbow syndrome.

bone grafting, and shoulder arthroplasty [9].

Osteonecrosis of the wrist most commonly involves the scaphoid, lunate, and capitate. Scaphoid is the most frequently injured bone in the carpus. It is second only to the femoral head in the incidence of posttraumatic osteonecrosis. In the absence of trauma, it is known as Preiser's disease [11].

Osteonecrosis of the lunate is known as Kienbock's disease. It is associated with trauma, overuse, and negative ulnar variance [11].

Osteonecrosis of the capitate is a rare condition and often associated with trauma.

#### **6.7. Spine**

Osteonecrosis of the vertebral body is also known as Kummel's disease (KD), usually related to osteoporotic vertebral fractures. It is a rare and under diagnosed disease. Elizabeth Pérez Hernández and co‐authors gave us a rare chapter on this subject in this book.

#### **6.8. Jaw**

Unlike orthopedics, where the term osteonecrosis has been used for pathologies resulting from aseptic bone infarction, in dentistry, the term is used in its broadest sense, indicating the death of the bony tissue. Recently, the problem of osteonecrosis caused by the use of medicines, known by the abbreviation MRONJ, has gained much interest.

In this book, Kenji Yamagata and Mario Pérez‐Sayáns García present chapters that address in depth of this relevant and current topic.

#### **6.9. Multifocal osteonecrosis**

When three or more separate articulations are involved, concurrently or consecutively, it is called a multifocal osteonecrosis (MFON).

The most common cause of MFON is the use of corticosteroids [5]. It is therefore important to have a high degree of suspicion in patients on chronic use of this medication that present more than one site of involvement in X‐ray. Bone scintigraphy may be helpful in these cases, as some sites, such as the shoulders, may be little symptomatic at the beginning, when preservation strategies of the joint, such as decompression, have its indication.
