The hip

Question 1

What is fibrous dysplasia?

Answer 1

Fibrous dysplasia is a bone condition in which abnormal fibrous tissue develops in place of normal bone.

As these areas of fibrous tissue grow and expand over time, they can weaken bone – causing it to fracture or become deformed.

e.g facial bones, skull and femur

Question 2

What causes fibrous dysplasia?

Answer 2

The cause of this disease is unknown. It is believed to be due to a chemical defect in specific bone protein. This defect may be due to a gene mutation at birth, although the condition is not generally passed through generations of family members.

Question 3

What are the 2 types of fibrous dysplasia?

Answer 3

• Monostotic fibrous dysplasia — Only a single bone is affected. This is the most common form of the condition.
• Polyostotic fibrous dysplasia — More than one bone is involved. It can affect more than one bone within the same limb or multiple bones throughout the body. This form of the condition is usually more severe. For this reason, it is typically discovered earlier in life.

Question 4

What are the symptoms of fibrous dysplasia?

Answer 4

Pain
As fibrous bone tissue grows and expands, the affected area can become weak and painful. Pain is more likely to occur if the bone affected is one of the weight-bearing bones of the leg or pelvis.

Pain caused by fibrous dysplasia generally begins as a dull ache that worsens with activity and lessens with rest. It can get progressively worse over time.

Question 5

How can fibrous dysplasia cause fractures?

Answer 5

Fibrous bone is very weak when compared to normal bone. It can sometimes break or fracture through the weakened area causing sudden and severe pain. A fracture often occurs after a period of dull pain — although it may also happen suddenly with no prior pain at all.

Question 6

How can fibrous dysplasia cause bone deformity?

Answer 6

In patients who experience repeated fractures, poor healing can lead to bone deformity. If this deformity occurs in the facial bones or results in curving of the leg bones, it can become very noticeable.

If the legs or pelvis are involved, the patient may have trouble walking or may develop arthritis in nearby joints.
• Can cause malunion between bones, chronic lower back pain, leg length discrepancy and sitting imbalance
• Malignant transformations in 5-10%

Question 7

What is Developmental dysplasia?

How can this be tested for?

Answer 7

• spectrum of disorders
• In DHH the hip does not form well, the acetabulum of the hip is usually shallow and the roof slopes too steeply. Sometimes the femoral head my slide in and out of the hip socket
• Maturation of the acetabulum and femoral head is retarded
• Shallow socket, vertebral hip
• Barlows test (dislocate the abducted hip), Ortolanis test (relocating in abducted position)

Question 8

What imaging can be used for Developmental dysplasia?

Answer 8

Imaging:
• X-ray – no calcification
• Shenton’s line – broken line indicates a loss of symmetry with the neck of femur
• Ultrasound scan – shows bony rim and cartilage roof

All newborns are to be screened by physical examination. This examination includes an Ortolani or Barlow test.

If these tests are negative but the provocation test is positive, an ultrasonography is recommended. Ultrasound is the modality of choice prior to the ossification of the proximal femoral epiphysis. Once there is a significant ossification then an x-ray examination is required.

Other signs of hip dysplasia are asymmetric gluteus folds and an apparent limb-length inequality.

Question 9

What is the treatment for Developmental dysplasia?

Answer 9

Bracing – the brace most used is the Pavlik harness. It puts the leg into a position that guides the ball of the hip joint into the socket

Closed reduction or casting – for a closed reduction, a doctor will inject a contrast dye into the hip joint to see the cartilage of the joint. They will move the head of the femur so the femur aligns into the acetabulum. A hip spica cast then holds it in place

Open reduction and casting – the doctor will cut an incision in the skin, move muscles out of the way to see the hhip joint directly, place the head of the femur back into place. Closes the surgical cut with stitches. They will then put on a hip spica cast to hold it in place

Peri-acetabular osteotomy - The PAO preserves the integrity of the pelvic ring, but allows precise and full correction of even severe hip dysplasia. It involves cutting the pelvis around the entire acetabulum, which is then repositioned into a position that better covers the femoral head. Usually, 3 or 4 screws are used to hold the acetabulum in its new position. Over time, new bone will grow where the cuts are made, fusing the acetabulum to the rest of the pelvis.

Question 10

What is perthes disease?

Answer 10

This is a disorder that generally occurs in young children between 4-10 years of age. The hip is made up of the femur, part of the proximal region of the femur and the acetabulum, the cup that fits around the femoral head.

In Perthes disease, the blood supply to the head of femur is interrupted. The femoral head then necroses, or loses blood supply which weakens the bone and can lead to multiple fractures. Next, the bone is taken by the body, or resorbed which can lead to complete collapse of the femoral head. The blood supply does eventually return and the bone will re-form, or re-ossify.

However, the bone may re-form with a different shape than it had before. Because of this, degenerative joint disease (osteoarthritis) can develop later in life. It can cause avascular necrosis of nucleus of proximal femoral epiphysis and abnormal growth characteristics. It can cause chrondrolysis where the cartilage begins to fall away that can lead to pain and collapse.
Individuals with the conditions will have a noticeable limp, they may experience stiffness of the hip or complain of mild pain in the groin, thigh or knee area. The pain is usually worse with activity and better with rest.

Question 11

What are the 4 stages of perthes disease?

Answer 11

1. Initial / necrosis. In this stage of the disease, the blood supply to the femoral head is disrupted and bone cells die. The area becomes intensely inflamed and irritated and your child may begin to show signs of the disease, such as a limp or different way of walking. This initial stage may last for several months.
2. Fragmentation. Over a period of 1 to 2 years, the body removes the dead bone beneath the articular cartilage and quickly replaces it with an initial, softer bone (“woven bone”). It is during this phase that the bone is in a weaker state and the head of the femur is more likely to collapse into a flatter position.
3. Reossification. New, stronger bone develops and begins to take shape in the head of the femur. The reossification stage is often the longest stage of the disease and can last a few years.
4. Healed. In this stage, the bone regrowth is complete and the femoral head has reached its final shape. How close the shape is to round will depend on several factors, including the extent of damage that took place during the fragmentation phase, as well as the child’s age at the onset of disease, which affects the potential for bone regrowth.

Question 12

What is the treatment for perthes disease?

Answer 12

Nonoperative Treatment

It is very important to keep the joint moving. This is because the cartilage on the femoral head depends on the liquid in the joint, called the synovial fluid, for its nutrition. Moving the hip helps to supply the cartilage with this fluid.
It is also important to keep the head in the hip socket so that when the bone does re-form, it has the best and most round shape possible. Sometimes, the child’s hip becomes stiff and may need help to keep the ball in the cup. Your doctor may recommend a period of casting, bracing and/or physical therapy to help achieve this.

Surgical Treatment

Surgery may be warranted to treat Legg-Calve-Perthes disease, but is often not recommended for children under the age of 6. The goal of surgery is containment. The idea is to keep the femoral head within the acetabulum. To do this, the paediatric orthopaedic surgeon may alter the angle of the bones of the femur and/or acetabulum and fix them in a more anatomically correct position. This procedure, called an osteotomy, allows the femoral head to grow in its normal spherical fashion.

Question 13

What is SUFE?

Answer 13

A slipped upper femoral epiphysis (SUFE) is a condition involving the hip joint. The hip joint works as a ball and socket. The very top of the femur (thigh bone) forms the ball (also called femoral head), and beneath this ball lies a growth plate (an area of growing tissue that allows the bones to lengthen, also called the epiphyseal plate).

With a SUFE, this growth plate suffers a form of fracture, and the head of the femur slips out of position.
A SUFE is characterised by the displacement of the capital femoral physis from the metaphysis.

Question 14

How is SUFE classified?

Answer 14

• ability to weight bear
o Stable - the patient is able to weight bear on the affected leg
o Unstable - the patient is unable to weight bear on the affected leg, even with crutches
• duration of symptoms
o Acute - sudden onset of severe symptoms and inability to weight bear
o Chronic - gradual onset and progression of symptoms for more than 3 weeks, without sudden exacerbation. This is the most common presentation (85% of patients with SUFE)
o Acute on chronic - sudden exacerbation of symptoms due to acute displacement of a chronically slipped epiphysis

Question 15

What are the signs and symptoms of SUFE?

Answer 15

• The symptoms often develop slowly over several months, but can also occur suddenly. If your child has a SUFE, they may have:
• pain in their groin, hip, thigh and/or knee – some children only have knee pain, even though the condition affects the hip
• a limp, or holding their leg in an unusual resting position
• reduced movement of their hip joint
• a slight shortening of the affected leg.

Question 16

What is the treatment for SUFE?

Answer 16

• In all cases, children with a SUFE need surgery. It is very important that your child avoids standing up and placing weight on their leg until the SUFE is corrected surgically, so until then they will need to use a wheelchair or have bed rest.
• The type of operation will depend on the how far the head of the femur has slipped, but most operations will involve screws being put into the head of the femur to make sure it is stable.
• The operation will take place while your child is asleep under a general anaesthetic. After the surgery, an X-ray is taken to make sure the screws are in the right place.
• Your child may need to have their unaffected side treated as well, to prevent that side slipping in the future. Your orthopaedic surgeon will discuss this with you.
• Your child will need to stay at least one to two nights in hospital. They will be able to go home once they feel comfortable and safe using crutches or a wheelchair. The hospital staff will teach you and your child how to use the crutches or wheelchair safely.

Question 17

Describe the arterial supply to the femoral head

Answer 17

The blood supply to the neck of the femur is retrograde meaning there is supply in the early days of life from the ligamentum arteriosum, which lies within the ligamentum teres, however this dramatically reduces in size in later life and is of negligible importance in adults.

There is a very extensive blood supply to the neck of the femur. At the base of the femoral neck there is the extracapsular ring. Ascending cervical or retinacular branches run on the femoral neck subcapsular. At the junction of the articular surface of the femoral head with neck is the sub synovial intracapsular ring and through the fovea capitis is the artery of the ligamentum teres.

The extracapsular ring is made of four main arteries: the medial circumflex femoral artery (MCFA), the lateral circumflex femoral artery (LCFA), the superior gluteal artery (SGA) and inferior gluteal artery (IGA). The SGA and IGA form a minor contribution to the extracapsular ring. These circumflex arteries arise from the profunda femoris artery that arises from the femoral artery. The MFCA wraps around the posterior side of the femur, supplying its neck and head. It also supplies posteroinferior reticular vessels. The LFCA wraps around the anterior side of the femur, supplying muscles on the lateral aspect of the thigh.

The ascending cervical arteries or reticular branches arise from the extracapsular arterial ring. They run up the femoral neck beneath the capsule and give rise to the metaphyseal arteries. There are three groups of cervical arteries or reticular branches. Firstly the anterior (arises from LCFA) supplies the femoral neck rather than the femoral head. Secondly, the postero-superior (arises from the deep branch of MFCA). 80% of foramina are located in postero-superior and antero-superior quadrant of femoral head from where poster-superior group of arteries enter. Finally the postero-inferior arises from the MFCA.

The subsynovial intracapsular ring – the deep branch of the MFCA gives rise to the lateral epiphyseal artery which supplies the majority of the femoral head including the weight bearing surface which is important and particularly prone to injury

The artery of ligamentum teres arises from the obturator artery and occasionally the MFCA. It continues as the medial epiphyseal artery.

Question 18

What is an intracapsular fracture?

Answer 18

Intracapsular fractures
Intracapsular fractures occur between the subcapital region of the femoral head to basocervical region of the femoral neck, immediately proximal to the trochanters.

A fracture in the intracapsular region has poor prognosis due to interrupting the main blood supply to the femoral head and neck by the medial femoral circumflex artery. This leads to worse healing due to reduced blood supply and oxygen to the fracture site and can lead to avascular necrosis of the femoral head, a potentially fatal condition if infection and sepsis occur. Moreover, the femoral head is intracapsular and does not have a periosteal layer hence callouses do not form quickly leading to slow healing

Question 19

What is an extracapsular fracture?

Answer 19

Extracapsular fractures
Extracapsular fractures occur outside the capsule. They are subdivided into: inter-trochanteric, which are between the greater trochanter and the lesser trochanter and sub-trochanteric which are from the lesser trochanter to 5cm distal to this point.

The blood supply to the neck of the femur is retrograde*, passing from distal to proximal along the femoral neck to the femoral head. This is predominantly through the medial circumflex femoral artery, which lies directly on the intra-capsular femoral neck.

Consequently, displaced intra-capsular fractures disrupt the blood supply to the femoral head and, therefore, the femoral head will undergo avascular necrosis (even if the hip is fixed). Patients with a displaced intra-capsular fracture therefore require joint replacement (arthroplasty), rather than fixation. Extracapsular fractures are highly vascularised but not at risk from AVN due to collateral circulation from the lateral femoral circumflex artery and no injury to the medial circumflex artery. Hence these fractures have a better prognosis.

Question 20

What happens to the leg during a neck of femur fracture?

Answer 20

• A fractured neck of femur can cause apparent shortening and lateral rotation of the effected leg
• The head of the femur is vital for anchoring the femur to the pelvis
• A fracture in the neck causes this support to be lost and the femur can move more easily as a result of surrounding muscles of the hip
• The gluteus maximus inserts into the gluteal tuberosity of the femur and the iliotibial band. In the case of a neck of femur fracture, the gluteus maximus causes unopposed lateral rotation of the femur and if the muscle spasms it will exacerbate the external rotation
• The iliopsoas that inserts into the lesser trochanter of the femur acts to cause external rotation and flexion. As the femoral neck is fractures and detached the iliopsoas muscle pulls the distal portion of the femur superiorly causing an apparent shorting of the leg
• Other muscles exacerbating the condition the lateral rotation of the hip are the superior and inferior gemellus obturator externus and internus, quadratus femoris and piriformis
• If medial circumflex artery is damaged it can lead to AVN

Question 21

What is osteoarthritis of the hip?

Answer 21

Osteoarthritis (OA) is a degenerative joint disease characterised by loss of articular cartilage. This is associated with periarticular bone response, the features of which are seen on the radiographs.

Question 22

What are the risk factors of osteoarthritis?

Answer 22

Systemic – Increasing age (>45 yrs), obesity, female gender, genetic factors*, vitamin D deficiency

Local – History of trauma to the hip, anatomic abnormalities, muscle weakness or joint laxity, participation in high impact sports

Question 23

What are the clinical features of hip OA?

Answer 23

Pain is the leading feature, most commonly felt in the groin, however can also present over the lateral hip or even deep in the buttock. Pain is aggravated by weight-bearing and improved with rest. It is invariably worse towards the end of the day and better in the mornings.

Other symptoms include stiffness, which improves with mobility, or an associated grinding or crunching sensation.

On examination, they will have an antalgic gait and may walk with a mobility aid. There is very little to find on palpation.

Passive movement is painful and, in severe OA, the range of motion is reduced. In end stage disease, the patient may have a fixed flexion deformity and walk with a Trendelenburg gait.

Question 24

How is Hip OA investigated?

Answer 24

Hip osteoarthritis is demonstrated readily on plain radiographs (Fig. 2). The features* include:

Narrowing of the joint space
Osteophyte formation
Sclerosis of the subchondral bone
Subchondral bone cysts

Question 25

What are the management options for hip OA?:

Conservative, surgical

What are the surgical issues?

What are the surgical approaches?

Answer 25

Initial Management
Adequate pain control is important, using the WHO analgesic ladder, to ensure ongoing mobility and quality of life. Lifestyle modifications are also essential in aiming to improve self-management, including weight loss, regular exercise, and smoking cessation.

Physiotherapy is essential and should be provided for all individuals with hip OA, aiming to slow disease progression and improve joint mechanics.

Long-Term Management
If conservative management efforts do not work, surgical intervention is warranted.

Definitive treatment is with a hip replacement, either as a total hip replacement or a hemiarthroplasty. Several surgical approaches for these procedures are available (see below)

Common post-operative complications include thromboembolic disease, bleeding, dislocation, infection, loosening of the prosthesis, and leg length discrepancy.

Surgical Approaches
There are a number of different approaches to hip replacement surgery that can be taken, defined by their relation to gluteus medius:

Posterior Approach – The most common approach, as rehabilitation is often fast due to preservation of the abductor mechanism, minimising the risk of abductor dysfunction post-operatively
There is the greatest risk of causing damage to the sciatic nerve and of dislocation

Anterolateral Approach (Modified Hardinge approach) – The abductor mechanism is detached to allow excessive adduction and thus full exposure of the acetabulum

A merit of this method is that the superior retinacular vessels are not interrupted lowering the risk of avascular necrosis, however there is a risk of damage to the superior gluteal nerve

Anterior Approach (Smith-Petersen approach) – This approach is rarely used in adult arthroplasty in the UK, most commonly used in open washouts of infected native hips