Objective: Notwithstanding the increasing recognition of occult hip fracture the diagnosis is not suspected in some patients who present later with displaced hip fracture. We wished to investigate if the “missed occult fracture” group had any distinct demographic or clinical details and the eventual outcome of delayed diagnosis and treatment.

Methods: Over a three year period we followed all patients admitted with fracture neck of femur to identify patients where the diagnosis was initially missed and compared them with patients admitted over the same period with a correct suspicion of occult hip fracture.

Results: Out of 797 patients with hip fractures there were 24 occult hip fractures, the diagnosis was initially missed in 9 of them. In the correctly identified occult fracture patients 8/15 were independently mobile and 9/15 were living in own home compared to 0/9 independently mobile and 2/9 living in own home with missed occult fracture (both p< 0.001, Fisher exact test).7/9 patients with a missed diagnosis had mental confusion but none in the rest (p< 0.001). All patients presented within 10 days from the index visit (range 3–10). There was no obvious history of a fall in 2 patients. 4 patients had restricted straight leg raise ability on initial examination but were dismissed. 8/9 had intra-capsular fracture of which 6 had displaced at repeat presentation and required hemiarthroplasty. Maximum follow-up is 18 months (range 13–18 months) and 1 year mortality rate is 33%.

Discussion: Patients with a missed diagnosis of occult hip fracture appear physiologically less robust compared to the patients who are correctly suspected and investigated for occult fracture. The patients with missed diagnosis have higher ASA grade and their mental confusion, restricted mobility and dependence for activities of daily living are statistically significantly different compared to patients where the diagnosis is correctly suspected. Most of them have sub-capital femoral neck fractures and will most likely return with a displaced fracture within a week. We suggest a low threshold for investigation for occult hip fracture in the elderly, infirm and mentally confused.