Percutaneous fixation of scaphoid fractures has become popular in recent years, mainly due to its reduced complexity compared to open surgical approaches. Fluoroscopy is currently used as guidance for this percutaneous approach, however, as a projective imaging modality, it provides only a 2D view of the complex 3D anatomy of the wrist during surgery, and exposes both patient and physician to harmful X-ray radiation. To avoid these drawbacks, 3D ultrasound has been suggested to provide imaging for guidance as a widely available, real-time, radiation-free and low-cost modality. However, the blurred, disconnected, weak and noisy bone responses render interpretation of the US data difficult so far. In this work, we present the integration of 3D ultrasound with a statistical wrist model to allow development of an improved ultrasound-based guidance procedure. For enhancement of bone responses in ultrasound, a phase symmetry based approach is used to exploit the symmetry of the ultrasound signal around the expected bone location. We propose an improved estimation of the local phase symmetry by using the local spectrum variation of the ultrasound image. The statistical wrist model is developed through a group-wise registration based framework in order to capture the major modes of shape and pose variations across 30 subjects at different wrist positions. Finally, the statistical wrist model is registered to the enhanced ultrasound bone surfaces using a probabilistic registration approach. Feasibility experiments are performed using two volunteer wrists, and the results are promising and warrant further development and validation to enable ultrasound guided percutaneous scaphoid fracture reduction.

1. Synovectomy of the elbow affected by rheumatoid arthritis is a worthwhile procedure even in the presence of advanced radiological changes.

2. Relief of pain is good (93 per cent) and movement is retained (87 per cent).

3. Although the follow-up in this series was short, averaging nineteen months, the results seem to be maintained.

4. Good access to the joint may be had through medial and lateral incisions, and division of the olecranon is unnecessary. A lateral incision alone is not recommended.

5. The ulnar nerve should be preserved during dissection. Anterior transposition is needed only if there are neurological symptoms before operation.

1. Twenty-two feet injured at the tarso-metatarsal level are reviewed.

2. Experiments with eleven cadaveric feet are reported.

3. The injuries are caused by forced plantar-flexion combined with rotation in most cases. Crushing of the foot alone often does not produce dislocation.

4. A classification is suggested.

5. The results of various treatments in this small series are presented. It is concluded that anatomical reduction is important, achieved if necessary by operation and internal fixation.