Internal lengthening devices in the femur lengthen
along the anatomical axis, potentially creating lateral shift of
the mechanical axis. We aimed to determine whether femoral lengthening
along the anatomical axis has an inadvertent effect on lower limb
alignment. Isolated femoral lengthening using the Intramedullary
Skeletal Kinetic Distractor was performed in 27 femora in 24 patients
(mean age 32 years (16 to 57)). Patients who underwent simultaneous realignment
procedures or concurrent tibial lengthening, or who developed mal-
or nonunion, were excluded. Pre-operative and six-month post-operative
radiographs were used to measure lower limb alignment. The mean lengthening
achieved was 4.4 cm (1.5 to 8.0). In 26 of 27 limbs, the mechanical
axis shifted laterally by a mean of 1.0 mm/cm of lengthening (0
to 3.5). In one femur that was initially in varus, a 3 mm medial
shift occurred during a lengthening of 2.2 cm. In a normally aligned limb, intramedullary lengthening along
the anatomical axis of the femur results in a lateral shift of the
mechanical axis by approximately 1 mm for each 1 cm of lengthening.
The lateral compartment is predominantly affected
in approximately 10% of patients with osteoarthritis of the knee. The
anatomy, kinematics and loading during movement differ considerably
between medial and lateral compartments of the knee. This in the
main explains the relative protection of the lateral compartment
compared with the medial compartment in the development of osteoarthritis.
The aetiology of lateral compartment osteoarthritis can be idiopathic,
usually affecting the femur, or secondary to trauma commonly affecting
the tibia. Surgical management of lateral compartment osteoarthritis
can include osteotomy, unicompartmental knee replacement and total
knee replacement. This review discusses the biomechanics, pathogenesis
and development of lateral compartment osteoarthritis and its management. Cite this article:
We present a retrospective study of 27 patients treated by callus distraction using a unilateral external fixator of our own design for nonunion with bone loss and shortening of the femur caused by suppurative osteomyelitis. The unilateral external fixator was used either alone or in combination with an intramedullary nail. The mean age of the patients was 13.6 years (8 to 18). The fixator was used alone in 13 patients and with an intramedullary nail in 14. The bone results at a mean follow-up of 88 months (37 to 144) were excellent in 16 patients and good in 11. The functional results were excellent in 18 patients and good in nine. However, four patients still had draining sinuses at the latest follow-up. A residual deformity greater than 7° was present in seven femora, but this did not adversely affect function or require further treatment.
