Avulsion Injuries

J. A. Bertelli and M. F. Ghizoni, Brachial plexus avulsion injury repairs with nerve transfers and nerve grafts directly implanted into the spinal cord yield partial recovery of shoulder and elbow movements, Neurosurgery, 52 (2003) 1385-1389, diseussion 1389-1390. 

The force generated by muscle contraction is transmitted to bone by tendons, with the muscle-tendon-bone combination forming a functional unit which can be referred to as the musculoskeletal chain. There are important differences between the child, the young adult and the mature adult which account for the different injury patterns that are encountered (Harris 1981). In children, the weak links in the musculoskeletal chain are at the bone-tendon interface and at the growth plate, which accounts for the high occurrence of apophyseal avulsion injuries... 

Sleeve avulsion fractures are a particular form of avulsion injury seen in the unossified skeleton which differs from avulsions in adults because the sleeve of periosteum which is pulled off can continue to form bone if not treated. The typical location is at the lower pole of the patella, but the upper pole of the patella, the olecranon and the medial epicondyle can also be affected. Ultrasound demonstrates a sleeve of cartilage that has been avulsed usually with a small fragment of bone (Hunt and Somashekar 2005). In some cases a double cortical sign may be present, indicating elevation of a superficial layer of cortex from the underlying bone. There maybe associated haemarthrosis and patella alta (Fig. 4.14). 

MRI is ideally suited to the assessment of avulsion injuries as it can provide detail about the marrow oedema, cartilage damage and associated soft tissue or ligament damage. Unossified cartilage... 

Various secondary ossification centres develop in the pelvis at different ages. Accessory ossification centres may develop at the tip of the ischial spine and the rim of the acetabulum between 14 and 18 years of age (Fig. 7.26). The normal apophyseal centres on the inferior border of the ischium (Fig. 7.27) should not be mistaken for avulsion injuries, although they may be separated by violent hamstring contraction. The fusing ischiopubic synchondroses maybe mistaken for healing fractures, particularly... 

Pelvic trauma in children can result in a wide variety of different fractures and soft tissue injuries these range from isolated, relatively henign avulsion injuries to very complex multiple pelvic fractures and joint dissociations. The type of injury will depend on the causative mechanism as well as the age and development of the child. Compared with adults, pelvic fractures are relatively uncommon in children (ScHLiCKWEi and Keck 2005) and indicate a significant high energy impact. 

At the site of many of the muscle attachments are a number of apophyses which are separated from the bone by growth cartilage. An apophysis is essentially a centre of ossification which does not lead to longitudinal growth. In children, avulsion injuries are more common at these sites, which is a reflection of the presence of the relatively weaker cartilage in these regions. 

Fig. 12.17. Widening of the pubic symphysis with a fracture of the superior pubic ramus and avulsion injury from the iliac spine on the right...

Torode and Zeig classification of pelvic fractures. Type I avulsion injuries. Type II Iliac wing fractures (stability of the ligament complex). 

Fig. 12.24. Sites of pelvic avulsion injuries. A, iliac crest (abdominal muscle insertion). B, anterior superior iliac spine (sartorious muscle origin). C, anterior inferior iliac spine (rectus femoris origin). D, greater trochanter (gluteal insertions). Ey Lesser trochanter (illiopsoas). F, ischial tuberosity (hamstring muscle). G, body of pubis and inferior pubic ramus (adductors and gracillis)...

Dalai SA, Burgess AR, et al. (1989) Pelvic fracture in multiple trauma classification by mechanism is key to pattern of organ injury, resuscitative requirements, and outcome. J Trauma 29 981-1000 discussion 1000-1002 Demetriades D, Karaiskakis M, et al. (2003) Pelvic fractures in pediatric and adult trauma patients are they different injuries J Trauma 54 1146-1151 discussion 1151 El-Khoury GY, Daniel WW, et al. (1997) Acute and chronic avulsive injuries. Radiol Clin North Am 35 747-766 Ersoy G, Karcioglu O, et al. (1995) Should all patients with blunt trauma undergo routine pelvic X-ray Eur J Emerg Med 2 65-68... 

Apophyseal avulsion injuries are common around the hip and pelvis, with about 90% occurring in boys whilst playing sport. The apophysis is avulsed by strong muscle contraction. Once avulsed, the... 

Fig. 14.9. Classification of tibial tuberosity avulsion injuries 1A,1B, separation of the distal portion of the physis 2A,2By the separation involves the ossification centres of the tibial tubercles and tibial epiphysis 3A,3B, fracture/separation of the entire tubercle. In addition, there may be fracturing through the avulsed fragment (type B)...

Radiographs can identify associated avulsion injuries, such as Pelegrini-Stieda lesions (avulsion of the medial femoral condyle at the origin of the medial collateral ligament) and Segond lesion (avulsion fracture of the lateral tihial plateau). Segond fractures are associated with LCL, ACL and meniscal tears (Sferopoulos et al. 2006). 

Associated signs of ACL injury are common in children and include lipohaemarthrosis (this may indicate bony injury and a tibial avulsion injury should be exduded), contusion in the lateral femoral condyle and posterior tihial plateau, depression within the lateral condylopatellar sulcus (secondary to impaction of the lateral condyle on the tihial plateau) and Segond fractures (Prince et al. 2005). 

This is an avulsion injury caused by an external rotation force. It accounts for 2% of distal tibial physeal fractures (Spiegel et al. 1978). It tends to occur at a... 

Epiphyseal avulsion injuries Comminuted tibial epiphyseal (Type V) fractures... 

Fractures of the scapula are rare and are typically the result of high energy trauma. Immediate concern is therefore with regard to associated rib fractures, pulmonary or cardiac contusion and mediastinal injury. The presence of tenderness and swelling around the shoulder indicates the possibility of a scapular fracture, which can be evaluated by CT. Indirect trauma leads to avulsion injuries (Goss 1996). 

Radiologically the Hill-Sachs compression lesion maybe evident. The Hill-Sachs lesion is a compressive fracture of the humeral head and is an important bony sign of previous anterior shoulder dislocation and instability and is significant more common in adult patients. There may also be an avulsion injury to the glenoid rim indicative of an associated Bankart lesion (detachment of the anteroinferior capsule from the glenoid neck). 

Isolated fractures of the lesser tuberosity are rare. They are avulsion injuries of the apophysis and are likely to present with chronic shoulder pain following a sporting injury (Levine et al. 2005). If associated with instability reconstruction of subscapularis is indicated. Fractures of the greater tuberosity have been described in association with luxatio erecta. 

The ossific nucleus of the scaphoid appears around 4-6 years of age, and ossification is complete at 13-15 years. As in adults, the scaphoid is the most frequently injured carpal hone. The incidence of fractures is extremely low in the first decade, thereafter rising to a peak in the late teens to mid twenties (Grad 1986). Unlike adults, fractures of the distal pole are more common than of the waist (Fig. 19.34). These fractures represent ligamentous avulsion injuries, with failure through the bone rather than the stronger soft tissues. Middle third fractures occur in older children and adolescents, whilst proximal pole fractures are rare. Many fractures are the result of direct trauma to the wrist rather than a fall on the outstretched hand (Vahvanen and Westerlund 1980). 

In a degenerative setting, intense muscle contraction or abnormal stress forces exerted on healthy tendons may lead to avulsions at their sites of insertion into bone. These tears often lead to detachment and retraction of a bony fragment which remains embedded in the tendon. Avulsion injuries typically involve the supraspinatus tendon, causing retraction of a fleck of bone from the greater tuberosity, the peroneus brevis, leading to avulsion of the base of the fifth metatarsal, the flexor and extensor digi-... 

Fig. 12.32a,b. Combined acute avulsion injury of the adductor longus and brevis. Long-axis 12-5 MHz US images obtained over the insertion of the adductor muscles on the pubis (P) reveals discontinuity with bell-clapper retraction of the proximal tendon (white arrows) of the adductor longus muscle (Add Lg). The torn tendon end is separated from the pubis by a hypoechoic hematoma (asterisks). On a deeper plane, note a hypoechoic cleft (open arrows) at the insertion of the adductor brevis (Add Br) indicating a combined tear of both muscles... 

Due to the anatomic complexity of the hip, some undisplaced fractures or bone avulsion injuries at the tendon attachments on the bone may go unnoticed on plain films, even when additional projections are performed. In these cases, the patient may be submitted to US examination of the hip due to persistent pain and disability in order to rule out soft-tissue abnormalities. With careful scanning technique, US is able to identify occult fractures around the hip based on detection of either a step-off deformity or focal discontinuity or fragmentation of the hyperechoic cortical line (Fig. 12.69). In these instances, additional radiographic or CT studies should always be obtained to confirm the US diagnosis. 

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