1. Thirty-four patients with severe lumbo-sacral subluxation have been studied. Twenty-nine of these came for advice between the ages of nine and nineteen, and of these, twenty-five developed symptoms and signs of a characteristic syndrome.

2. The details of the syndrome are described: the essential features are spinal stiffness, a lordotic gait, resistance to straight leg raising, and in some cases evidence of interference with cauda equina or nerve root.

3. The danger of attempted reduction by traction is stressed, as well as the difficulties to be encountered during posterior lumbo-sacral fusion.

4. The reasons for operating are given; the results of spinal fusion were satisfactory.

5. The traditional apprehension concerning the effect of severe subluxation on childbirth has probably been over-stressed.

6. The tendency to slip was almost completely arrested by spinal fusion.

1. During a fifteen-year period a clinical, radiological and in some cases a surgical study has been made of 319 patients suffering from spondylolisthesis–that is, forward slipping of one lumbar vertebra on another or forward sagging of the whole lumbar spine in relation to the sacrum.

2. The five etiological factors are described, and the cases are assigned to five groups according to the factor responsible for the slip. In every case slipping is permitted by a lesion of the apparatus which normally resists the forward thrust of the lower lumbar spine–that is, the hook of the neural arch composed of the pedicle, the pars interarticularis and the inferior articular facet engaging caudally over the superior articular facet of the vertebra below.

3. In Group I (congenital spondylolisthesis–sixty-six cases) the lesion is a congenital defect of the facets. In Group II (spondylolytic spondylolisthesis–164 cases) the lesion occurs in the region of the pars interarticularis and is either an elongation of the bone or a break in continuity. There are reasons for thinking that the lesion is caused by stress over a long period rather than by acute injury or by a congenital anomaly of ossification. In Group IV (degenerative spondylolisthesis–eighty cases) the lesion of the facets is degenerative. There are no good grounds for thinking that an abnormality of the angle between the facets and the pedicles is the primary lesion behind the degenerative change.

4. Group III and V comprise few cases. In the former (traumatic spondylolisthesis–three cases) the lesion–a fracture of the neural arch–is caused by a single severe injury. In Group V (pathological spondylolisthesis–six cases) the slipping is caused by weakness of bone from various causes.

5. A full description is given of the etiological and biomechanical features of each group. A special investigation has been made into the etiological factors in degenerative spondylolisthesis.

6. The incidence of involvement of nerve tissues is highest in degenerative spondylolisthesis; the most severe degrees of slip are found in congenital spondylolisthesis.

Simple pinning to fix the epiphysis in those patients in whom the position is acceptable is a valuable surgical procedure. It is safe and gives good results. It eliminates the danger of further displacement, promotes fusion of the epiphysial plate and allows the patient to return to full activity within one month, thus avoiding joint stiffness, muscle atrophy, osteoporosis and interference with growth at other sites.

Fixation by small pins is preferable to the use of the trifin nail, the latter giving excessive trauma and predisposing to subtrochanteric fracture. Gentle replacement of the epiphysis, when loose, into an acceptable position is a valuable method of treatment. It is essential that replacement is not undertaken by force.

The problem of major displacement of the epiphysis which cannot be so replaced is unsolved. Conservative treatment in this group is useless and harmful. Intra-articular osteotomy can give good results in most cases but is risky and may cause stiffening of the hip. Subtrochanteric osteotomy does not give a good anatomical result but in most cases the function of the hip is satisfactory.

Slipping of the upper femoral epiphysis, however slight, should be regarded as a surgical emergency.

Sprung back is one of the commonest causes of low back pain. Its characteristic features are described. It is caused by rupture of the posterior ligaments of the spine, including sometimes the posterior longitudinal ligament and annulus fibrosus. The manner in which it is produced and its mechanical effects are discussed in detail.

In addition to its orthopaedic interest, this case illustrates the special behaviour of fine particles of a synthetic material when implanted in the human body. These results may interest those engaged in the control of dusts in the plastics industry, for the inhalation of such dusts may well result in "implantation" of the material in the lung, with consequent histological changes.

1. Fat embolism occurs in a high percentage of all cases of injury and it is a relatively frequent complication of fractures of the long bones in civilian accidents as well as battle casualties.

2. The diagnosis can usually be established by the clinical features together with certain physical signs which must however be sought deliberately.

3. Important clinical features are the mental disturbance, alternation of coma with full consciousness, petechial haemorrhages in the conjunctiva and skin, and typical changes in the retina.

4. Evidence is still conflicting as to whether the fat arises by embolism from an injured bone, or by general metabolic disturbance.

5. The fat is harmful not so much by reason of mechanical obstruction of vessels as by erosion and rupture of the vessel wall clue to the liberation of fatty acids.

6. Preventive treatment appears to be of some value but no satisfactory specific treatment is yet available for the established case.

7. Ligation of the profunda vein has been tried in two patients, one of whom recovered and the other died.