Aims. Computer hexapod assisted orthopaedic surgery (CHAOS), is a method
to achieve the intra-operative correction of long bone deformities
using a hexapod external fixator before definitive internal fixation
with minimally invasive stabilisation techniques. The aims of this study were to determine the reliability of this
method in a consecutive case series of patients undergoing femoral
deformity correction, with a minimum six-month follow-up, to assess
the complications and to define the ideal group of patients for
whom this treatment is appropriate. Patients and Methods. The medical records and radiographs of all patients who underwent
CHAOS for femoral deformity at our institution between 2005 and
2011 were retrospectively reviewed. Records were available for all
55 consecutive procedures undertaken in 49 patients with a mean
age of 35.6 years (10.9 to 75.3) at the time of surgery. Results. Patients were assessed at a mean interval of 44 months (6 to
90) following surgery. The indications were broad; the most common
were vitamin D resistant rickets (n = 10), growth plate arrest (n
= 6) and post-traumatic deformity (n = 20). Multi-planar correction was required in 33 cases. A single level
osteotomy was performed in 43 cases. Locking plates were used to
stabilise the osteotomy in 33 cases and intramedullary nails in
the remainder. Complications included two nonunions, one death,
one below-knee deep vein thrombosis, one deep infection and one
revision procedure due to initial under-correction. There were no
neurovascular injuries or incidence of compartment syndrome. Conclusion. This is the largest reported series of femoral deformity corrections
using the CHAOS technique. This series demonstrates that precise
intra-operative
