CT provides excellent images of bone anatomy (Fig. 27.1) and can be used to supply three-dimensional images to help in the reconstruction of complex fractures. The thin axial slices are particularly useful as a guide for obtaining biopsy specimens

Fig. 27.1 A three dimensional CT showing a iliac wing fracture.

Magnetic resonance imaging (MRI)

MRI (Fig. 27.2) provides excellent images of soft tissue, joint and bone pathology without exposure to radiation. It is widely used in virtually all branches of orthopaedics for diagnosis and preoperative planning.

Fig. 27.2 An MRI scan of a shoulder through the level of the acromioclavicular joint and the glenohumeral joint.

Bone scans

These can be used to assess a number of bone conditions, including infection and tumours (Fig. 27.3).

Fig. 27.3 An example of a bone scan showing increased uptake of radioactive tracer in the clavicle: in this case, indicative of infection.

There are also increased areas of uptake in the shoulders and sternum.

Description of deformity

With patients in the anatomical position (i.e. lying on their back with their palms pointing up to the ceiling), limb deformities are described relative to the midline (away = valgus, towards = varus) and to the alignment of the limb below the joint or deformity. For example, with respect to the knees, bowleggedness is a varus deformity, while knock-knees are a valgus deformity (Fig. 27.4). With the patient viewed from the side, there is a range of descriptive terms available. For example, hyperextension of the knee joint is known as recurvatum (Fig. 27.5). The three types of spinal deformity are:

• kyphosis: forward flexion (‘the kyphotic kisses his knees’).

• lordosis: the opposite, extension, or bent-over-backwards deformity; this represents the normal alignment of the lumbar and cervical spine.

• scoliosis: a sideward deformity that is normally associated with a degree of rotation (Fig. 27.6).

Fig. 27.4 Historical slide of children, showing deformities of the knees.

All the children show valgus knee, i.e. knock-kneed, deformities.

Fig. 27.5 A recurvatum deformity of the knees with hyperextension.

Fig. 27.6 An X-ray of the thoracic and lumbar spine, showing gross scoliosis of both.

Osteoarthritis: degenerative disease of the joints

Osteoarthritis (OA) of a joint may occur as a primary idiopathic condition or secondary to problems such as malalignment, intra-articular fractures or over-stressing (obesity, overuse). In some patients, there is a strong genetic component. OA may occur in any joint (shoulder, elbow, wrist and hands) but predominantly affects those that are weight-bearing (hip and knee) (Figs 27.7 and 27.8). Idiopathic OA is generally of slow onset and affects the elderly. Secondary OA can affect the young and may develop quite rapidly when a joint injury leads to loss of articular cartilage. On plain X-ray, OA is associated with:

• joint space loss due to thinning of articular cartilage

• sclerosis of the joint surface, with the development of increased density of the bone just under the joint space

• osteophytes

• cystic change.

Fig. 27.7 Bilateral knee osteoarthritis.

The left knee (on the right-hand side in the illustration) shows predominantly lateral wear and has a valgus deformity. The right knee has osteoarthritis of both medial and lateral compartments.

Fig. 27.8 Osteoarthritis can affect any joint.

A Here, the first toe metatarsophalangeal joint is clearly arthritic. B Similarly, the carpometacarpal joint at the base of the thumb can also be affected.

The treatment of OA may be conservative or operative (Table 27.2). The former focuses on the use of drugs and physical methods of pain and stress relief to the joint.

Table 27.2 Management options for osteoarthritis

Non-operative	Operative
Analgesia Physiotherapy Orthotics Injections Lifestyle modifications	Osteotomy Joint debridement Excisional osteotomy Joint replacement (arthroplasty) Joint fusion (arthroplasty)

Medical management of OA

Drug therapy

Simple analgesics, such as paracetamol, with or without the inclusion of nonsteroidal anti-inflammatory drugs (NSAIDs), are the mainstay of treatment. More powerful analgesic combinations may be introduced such as codeine or morphine, if simple analgesics prove inadequate.

Off-loading

This involves the use of aids, such as a walking stick and weight loss, aimed at reducing the forces passing through the joint. In the obese, weight loss is helpful as the load across a joint is three to six times body weight. Various insoles and splints are commonly used in orthopaedics to offload joints and are fitted by an orthotist.

Injections

Introducing a mix of a corticosteroid and local anaesthetic into the joint may reduce inflammation and ease pain. Injections of compounds of hyaluronic acid are increasingly used and are designed to supplement the natural joint levels of hyaluronic acid essential to normal functioning of articular cartilage. They work best in early OA but have little, if any, effect in late-stage disease.

Other conservative treatments

Physiotherapy and hydrotherapy both have a part to play in the control of symptoms, especially in early disease. Building up lost muscle bulk (frequently lost due to reduced activity) provides the joint with an increased degree of muscular control and may lead to considerable symptom improvement. Other treatment modalities, such as acupuncture, are recognized to have a role in the management of pain associated with OA. Failure of conservative methods normally leads to consideration of surgical intervention; in the patient unfit for surgery, benefit may be gained from referral to a pain therapist.

Surgical management of OA

The main operative interventions include osteotomy, replacement and fusion. Certain joints, particularly the knee, may benefit from a more minimal approach, such as arthroscopic debridement. This may help when a patient complains of physical symptoms indicative of underlying mechanical problems, such as locking or discomfort related to meniscal problems. However in well established OA this intervention can have a limited affect.

Osteotomy

This is useful in the younger patient, in whom joint replacement may not be advisable. The aim is to change the axis of the joint, so that a portion of the joint surface that has thus far been protected from wear and tear now forms the weight-bearing area. For example, with respect to the knee, although there may be severe OA of the medial compartment in conjunction with a varus deformity, the lateral compartment may have well-preserved articular cartilage. Over-correcting the varus deformity by means of osteotomy (removing wedges of bone from the tibia), so that body weight is now largely transmitted through the lateral compartment, may lead to significant improvement in symptoms, thus delaying the need for joint replacement (Fig. 27.9). Osteotomies generally use opening wedges (adding bone), closing wedges (removing bone) or may be translational or rotational.

Fig. 27.9 An example of an osteotomy to the proximal tibia.

A The osteotomy site has been fixed by a plate and screws. B The cut of the osteotomy lies between the top two screws and the bottom three screws.

Joint replacement

The hip, knee, ankle and shoulder, and indeed almost any joint, can now be partially or completely replaced in a number of different ways with varying degrees of success.

Hemi-arthroplasty

In this operation, only one-half of the joint is replaced, leaving half of the joint intact. It is normally the natural socket – for example, the acetabulum – that is left untouched. The most common example is following fracture of the femoral neck in the elderly. Such patients usually have low demand on the joint, and the hemi-arthroplasty (Fig. 27.10) gives adequate function without risking many of the complexities of a total hip replacement.

Fig. 27.10 An example of a hemi-arthroplasty of the hip, where only the femoral part of the hip joint has been replaced.

This type of procedure is commonly used after a displaced intracapsular fracture of the hip.

Total joint replacement

This entails resurfacing of both sides of a joint (Fig. 27.11). The choice of materials for the weight-bearing surfaces varies, depending on the joint and prosthesis in question. Currently, metal against a high-density polyethylene is the most common, although new prostheses involving metal and ceramics surfaces have been developed for use in young people (Fig. 27.12). Fixation of the implants may be with cement, or by encouraging bone to grow into or onto the surface of the implant. In small joints, such as those of the hand in patients with rheumatoid arthritis, silastic may be used as a buffer or spacer between the two joint surfaces.