358 Acta Orthopaedica 2011; 82 (3): 356–359 The degree of radial shortening measured on bilateral wrist radiographs, categorized by fracture complexity according to the Mason classification Mason classification Age, years median (range) Radial shortening, mm median (range) I II III 39 (19–78) 54 (38–79) 31 (NA) 2.0 (2–3) 2.5 (2–3.5) 4 (NA) type-I fractures, 8 type-II fractures, and 1 type-III fracture. The degree of radial shortening varied with increasing fracture severity (p = 0.04) (Table). There were no fractures associated with a dislocation of the elbow. Nonoperative management was employed in 21 patients. Operative management was employed in 1 patient due to sub- stantial comminution and displacement of the radial head—the one Mason type-III fracture with suspected forearm instability that was confirmed intraoperatively. This patient underwent acute radial head replacement with no complications. Of the 22 patients who were diagnosed with ≥ 2 mm of radial shortening suggestive of an Essex-Lopresti type lesion, 21 attended a follow-up examination (10 radial head and 11 radial neck; 12 Mason type-I, 8 Mason type-II, and 1 Mason type-III). The mean follow-up was 6 (1.5–12) months. The mean MES at final evaluation was excellent: 90 (70– 100), with a mean flexion arc of 136 (90–154) degrees and a mean forearm rotation arc of 175 (90–180) degrees. The mean SMFA at final evaluation was 4.8 (0–26). 18 patients achieved excellent or good functional results as measured on the MES (Figure 2). Of the 3 patients who did not achieve excellent or good functional results, all had MES values of 70, with 2 patients being treated nonoperatively. 1 patient who was lost to follow-up at 3 months had mild elbow stiffness, but had a flexion arc of 144 degrees and a rotation arc of 180 degrees. 1 patient developed shoulder capsulitis secondarily, delaying recovery. The patient who underwent operative intervention with radial head replacement had a final MES of 70, with notable elbow stiffness. Discussion In this paper, we describe a range of radial shortening sug- gestive of an Essex-Lopresti lesion following a fracture of the radial head or neck. Due to the small numbers in our study, we were unable to determine the degree of radial shortening found on radiographs that would be indicative of an unstable Essex-Lopresti lesion. However, all patients treated as having a stable lesion had less than 4 mm of radial shortening. Our findings indicate that stable lesions need no treatment. For the unstable Essex-Lopresti injuries, the treatment algorithm described by Edwards and Jupiter (1988) is commonly used. Figure 2. Initial presentation AP and lateral radiographs of a 27-year- old male who sustained a Mason type-I fracture of the left elbow while playing sport. An Essex-Lopresti lesion was diagnosed at 2 weeks when bilateral wrist radiographs were taken. Management was con- servative, using collar and cuff immobilization for 1 week followed by supervised physiotherapy. At 6 months, the patient had a flexion arc of 152 degrees and a forearm rotation arc of 180 degrees, with an excel- lent MES (100). Recent studies have examined the less complex fractures of the proximal radius and the possible association with Essex- Lopresti lesions (Hausmann et al. 2009, Helmerhorst and Ring 2009). A study examining low-energy Mason type-I radial head fractures with MRI of the forearm revealed partial rup- tures of the distal interosseous membrane without disruption of the interosseous ligament (Hausmann et al. 2009). How- ever, they reported that none of their patients had abnormali- ties on wrist examination or imaging diagnostic for an Essex- Lopresti lesion, which was present in all of our patients. Fur- thermore, Essex-Lopresti injuries have been described with minimally displaced partial fractures (Mason type-II) of the proximal radius (Helmerhorst and Ring 2009). We found that as the complexity of the fracture increases, the degree of radial shortening also increases; thus, the index of suspicion for instability should increase. As with isolated proximal radial fractures, the most common mechanism of injury we found was a fall onto an outstretched arm, and no association was found between the mechanism of injury and the degree of radial shortening. The original paper by Essex-Lopresti suggested that the injury was sustained following a “violent longitudinal compression force in the long axis of the radius”, and the mechanism of injury and the force required to cause it has been the focus of many studies since (Essex-Lopresti 1951, McDougall and White 1957). Essex-Lopresti lesions are often suspected following high-energy falls onto an outstretched hand, e.g. a fall from a