Hydroxyapatite (HA) is a bioactive material with a high affinity for bone. Ti-6Al-4V is lightweight and less biotoxic. Using these materials, a cementless hip prosthesis has been clinically used, consisting mainly of a Ti femoral stem coated with plasma-sprayed biocompatible HA. However, this type of stem entails several disadvantages: HA is likely to decompose at the coating; long term HA coating layer bonding to Ti is unstable and optimal HA thickness is unfeasible. In many actual cases, debonding of HA coating layer from the Ti surface was found upon removal of stems.

To resolve these concerns, we started developing a new hip prosthesis using composite materials comprised of Ti-6Al-4V and HA containing bioinactive and highly stable glass in 1985. The cementless hip prosthesis, named HAPG-Profile, unites the bioactive stem surface with the surrounding bone via adhesive glass. In basic experiments, the glass-coated HAPG-Profile has been demonstrated to possess much higher bonding stability than the plasma-sprayed HA, with bone affinity and safety not compromised. On the basis of these results, we manufactured the HAPG-Profile jointly with DePuy International, UK, and initiated a clinical trial in January 1997 in the teaching Hospital, Nagoya University School of Medicine, and Tokyo Kosei Nenkin Hospital. A total of 63 patients were followed up for more than two year and evaluated according to the Japanese Orthopedic Association Score and Harris Hip Score (HHS) clinically, functionally and radiographically. The results of the two-year follow-up study indicated success of early fixation associated with favorable outcomes.

We observed the healing process under rigid external fixation after Salter-Harris type-1 or type-2 physeal separation at the proximal tibia in immature rabbits.

Metaphyseal vessels grew across the gap with little delay; the site of separation then came to lie in the metaphysis and was bridged by endochondral ossification. Union was achieved within two days in all rabbits.

Progression of endochondral ossification repaired the separated physis, thus showing ‘primary healing of physeal separation’. This depends on accurate reduction and stable fixation to allow the survival of vessels across the gap.

We studied degenerative changes in the cervical intervertebral discs of 497 asymptomatic subjects by MRI and evaluated disc degeneration by loss of signal intensity, posterior and anterior disc protrusion, narrowing of the disc space and foraminal stenosis. In each subject, five disc levels from C2–C3 to C6–C7 were evaluated.

The frequency of all degenerative findings increased linearly with age. Disc degeneration was the most common observation, being present in 17% of discs of men and 12% of those of women in their twenties, and 86% and 89% of discs of both men and women over 60 years of age. We found significant differences in frequency between genders for posterior disc protrusion and foraminal stenosis. The former, with demonstrable compression of the spinal cord, was observed in 7.6% of subjects, mostly over 50 years of age.

Our results should be taken into account when interpreting the MRI findings in patients with symptomatic disorders of the cervical spine.

We used magnetic resonance (MR) myelography in ten patients with injuries to the brachial plexus and compared the findings with those obtained by conventional myelography and postmyelographic CT (CTM). In the presence of complete nerve-root avulsion (seven cases), a post-traumatic meningocele was detected by MR myelography. In injuries to the upper roots (three cases) MR myelography showed abnormal findings with a high signal intensity in the nerve root, obliteration of the damaged nerve root, or enlargement and obliteration of the root sleeve. No pseudomeningoceles were detected in these upper-root injuries by MR myelography and CTM. The overall accuracy of detection of damaged nerve roots or root sleeves was better with MR myelography than with conventional myelography and was similar to that of CTM.

MR myelography is non-invasive, relatively quick, requires no contrast medium, provides imaging in multiple projections, and is comparable in diagnostic ability to the more invasive, time-consuming techniques of conventional myelography and CTM.

A new method of replacement for the paralysed anterior deltoid is described. The latissimus dorsi with its neurovascular pedicle is freed and rotated, and then placed over the anterior part of the paralysed muscle. The lever arm of the transposed muscle is as long as that of the deltoid, and the muscle volume is enough to restore the natural contour of the shoulder. We report operations on 10 patients with shoulder palsy, eight caused by brachial plexus injury and two by resection of a neurilemmoma of the plexus. In six cases, active flexion to over 90 degrees was achieved. At least one of the rotator cuff muscles or the long head of biceps should have some active function if good results are to be obtained.