Читать книгу Fractures in the Horse - Группа авторов - Страница 103

One of the most obvious but salient requirements of follow‐up radiographs is that the images must be comparable to those taken previously. Small changes in position can result in the X‐ray photon beam not being parallel to the fracture plane. Endosteal and periosteal new bone formation can also appear to be reducing or increasing. Both errors lead to incorrect conclusions which in turn can compromise case management.

Healing and remodelling of fracture margins occur simultaneously. Even with internal fixation and primary healing (Chapter 6), there is often initial resorption along the fracture line. It is important to establish an expected time frame for uncomplicated fracture healing for individual sites. For example, bone in and adjacent to the proximal subchondral bone plate can take the longest to heal in parasagittal proximal phalangeal fractures [42]. Awareness of common accompanying features is also needed. For example, periosteal new bone formation on the dorsal proximal aspect of the proximal phalanx frequently extends further distad than radiographically identifiable fracture lines [43].

Surgical implants are examined carefully for evidence of migration, bending, breakage or adjacent osseous lucency, which may suggest instability or infection (Figure 14.5c). Care must be taken to differentiate abnormality from Uberschwinger artefact. With healing, adjacent soft tissues should exhibit reduced swelling and more clearly defined fascial planes. Persistent swelling whether generalized or focally over an implant generally warrants further scrutiny (see Figure 14.5a).

In articular fractures, the cartilage space, articular margins, subchondral bone and entheses are evaluated for evidence of reactive or degenerative changes. Resolution or persistence of intra‐articular fat pad effacement in applicable joints provides a guide to joint distension.

In the first week or two of second intention healing (Chapter 6), there is an initial loss of mineral density adjacent to the fracture resulting in reduced sharpness of the margins and a possible increase in the fracture gap. It usually takes 10–12 days for endosteal and periosteal new bone formation to become evident. Within 30 days, the fracture line should be less distinct and callus demonstrate increased radiopacity. By three months, the callus should have remodelled with an appearance close to the bone's original conformation [44]. The time frames will vary according to intrinsic factors, e.g. degree of osseous compromise and patient age, and extrinsic factors, e.g. external coaptation and loading.

A delayed union is a clinical rather than a radiographic diagnosis since the radiographic features mirror those of second intention healing. Appearance of callus in non‐union fractures provides the radiographic descriptors, hypertrophic, oligotrophic or atrophic (Chapter 6).