Consideration of natural history of the injury – characteristics of the injury and existing knowledge of healing times. The appearance of remodelling bridging callus (often endosteal) on anteroposterior and lateral radiographs. Clinical behaviour of the injured limb within a dynamised frame – after 1 and 2 are met, rods connecting the rings stabilising the fracture are loosened. The frame is removed when the patient can stand on the affected limb and dynamised frame without pain, and after weightbearing without pain on the dynamised frame for 3–4 weeks.
It is said “It is better to leave a frame on one month too long than to remove it a day too soon”, but this merely emphasises that timing of frame removal remains an art rather than an exact science. Marsh and Montgomery have previously suggested use of CT scanning to assess union in peri-articular fractures. We recommend that in high energy tibial fractures whose fracture pattern geometry lies outwith the antero-posterior and lateral radiograph views, a CT scan should be considered to detect stiff non-union and avoid premature frame removal.