Abstract
Introduction
The Delta Motion device (developed by Finsbury Orthopaedics, Leatherhead, United Kingdom, now manufactured by DePuy, Leeds, United Kingdom) is a pre-assembled factory fitted cup. It has been introduced to overcome some of the concerns relating to intra-operative assembly with improper seating of the liner and chipping. This device has a thinner shell and liner in comparison with other cups, allowing the use of larger sized heads which should help reduce the risk of impingement and dislocation. A drawback of the pre-assembled design is the inability to use supplementary screws to achieve stability and the difficulty in obtaining primary stability compared with a thin titanium shell. To date we are not aware of any publications reviewing the outcomes of these devices.
Methods
206 DeltaMotion cups were implanted in 195 patients, between Dec 2008 to Dec 2009 by the three senior authors. All the hips had the same stem (Osteonics) and a ceramic head was used. Data was prospectively collected and we reflect on our two year results.
Results
A total of 206 cups (123 F: 83 M) were implanted in 195 patients. The mean age at implantation was 69 years (range 38–93). 11 patients had bilateral hips (6M:5F). Complications were 1 pulmonary embolism, 2 femoral stem subsidence, 1 dislocation, 2 femoral fractures, 13 squeaking hips (9F:4M). The squeaking hips had a mean age of 65 years.
Discussion
The main complication was ‘benign’ squeaking. This was more common in younger (mean age 64 years) females. This cohort has a squeaking rate of 6.3% which is higher than 3.1% previously reported by our unit. There was no squeaking when 36 mm heads were used. The risk of squeaking dramatically increased when cup sizes 60 mm and above were used with 48 mm heads. Although squeaking seems to have increased with this device, none of the patients required revision.
