Using a reverse engineering capability to quantify the factors that control the rigid body mechanics of the wrist, a mathematical forward animation capability and model of wrist motion that allows the carpus to move under its own rules is being developed. This characterises the isometric connections, from which was developed the Stable Central Column Theory of Carpal Mechanics - which incorporates the Law of Rules Based Motion. This work has now advanced to the ability to reapply the extracted rules to allow rules-based rigid body reanimation of an individual wrist. As each wrist is unique, there is a given reality that each reanimation must be based on an individual wrist's unique rules, and the aspiration to create a standard or normal wrist is unrealistic. Using In the preliminary application of this biomechanics environment, by using the reverse engineering / forward reanimation process, wrist motion can be recreated - based purely on the unique rules, extracted from individual wrists. Instability of the proximal scaphoid was evident in several of the animations, and there was confirmation that the spatial attachment points of the isometric constraints are very exacting. The actual attachment and specific morphology of the carpal bones varied between individual wrists. Using a reverse engineering and then forward reanimation process, we have been able to recreate wrist motion using the rigid body mechanics based on the Law of Rules Based Motion. Further work is required, but the potential to apply “what if” virtual surgery options to an individual injured wrist and more precisely characterise and test solutions to wrist dysfunction are becoming realised.
This study has developed a unifying theory of carpal motion based on computer derived isometric constraints which guides the movement of particular bones. This extends the previously reported concept of rules based animation which proposes that resultant motion is a net interplay of bone shape, isometric constraints, bone interaction, and applied load The positional relationship between bones of the proximal row and the radius at extremes of motion was assessed to identify isometric constraints, based on a computer derived analysis rather than by observation of carpal bone motion or ligamentous anatomy. Using 3-D surface rendering software, models were created from the CT scan data of 10 normal wrists taken in extremes of radial and ulna deviation as well as flexion and extension. Virtual lines were identified between specific points of the lunate and radius which corresponded to an isometric constraint through range. Similar pairs of points were found at the trapezium and scaphoid and dorsally at the scapho-lunate joint. There was a clear discrepancy (p <
.05) between those areas (typically either volar or dorsal depending on the bones) which remain isometric and those which did not and this corresponded to previous documented anatomical structures. Variability in the pattern of isometric lines correlated with variation in scaphoid motion, thus providing a correlation with previous carpal motion observations. The Carpus can be seen to function as a stable central column (lunate/capitate/hamate/trapezoid/trapezium), with a supporting lateral column (scaphoid). This functions more as a “crossed four bar linkage” than the traditionally described “slider crank”. On the medial side of the central column, the triquetrum acts principally as an ulna translation restraint. The “trapezoid” shaped trapezoid places the trapezium anterior to the transverse plane of the radius and ulna, and thus rotates the principal axis of the central column to correspond to that used in the “Dart Thrower Motion”. This model provides a unifying theory for understanding normal and abnormal wrist motion based on isometric constraints and more broadly rules based motion. The characterisation of isometric constraints within the proximal carpal row has allowed the quantitative analysis of carpal dynamics, which has as its core, a stable central carpal column – with a lateral column stabiliser, and medial column translation restraint key to safe administration of anaesthetic in the upright position.
We tested the hypothesis that it is possible to accelerate fracture healing by changing the mechanical environment used in current methods i.e., from initial rigidity or micromovement followed by dynamisation to initial macromovement followed by rigidity (micro-movement). It is accepted that callus formation requires movement at the fracture site and this callus response is limited to the first few weeks after fracture. Logically, early macromovement at the fracture site would be beneficial for callus formation. Additional callus is not produced by further movement. Indeed, it may be counter-productive, just as continuing movement around two ends of a wooden stick bonded with glue will retard and even prevent “union”. We postulate that continuing movement at the fracture site after the callus response has ceased will also delay union. As a result, rigidity rather than dynamisation is required in the later stage of fracture healing. After testing an animal model, we built an external fixator which allowed 5 mm of axial movement without “self-locking” and could be compressed at a later date in order to prevent further movement. A trial containing 15 patients with unilateral tibial shaft fractures (closed or grade 1 open) was undertaken after permission was obtained from the Helsinki Ethical Committee. So far, 13 patients have been entered into the trial. They have completed therapy and are at least one year post-fracture (12 months to 22 months). Age range is from 20 to 49. The group is composed of nine males and one female. Under general anaesthetic, an external fixator was applied and the fracture reduced. The patients started ankle exercises (active and passive) the following day, with as much weight-bearing on the fractured leg as possible on the day after. The patients were seen every two weeks and AP and lateral radiographs were taken. The fracture was compressed two to six weeks later. The percentage of body weight that the patient was able to tolerate through the fractured limb was measured by using the scales of Meggit’s step test. The fixators were removed when there was radiographic union and the patient could take at least 80% of body weight through the fractured limb. Mean time duration up to removal of the fixator was 10.8 weeks (range 7 to 15.4 weeks). We conclude that it is possible to increase the speed of bone healing by changing the mechanical environment to initial macromovement followed by elimination of movement.
Fifteen patients who limped and had early fatigue on walking caused by ischaemic necrosis after treatment for congenital dislocation of the hip had distal and lateral transfer of the greater trochanter. Nine of them in whom the predicted leg-length discrepancy was more than 3 cm also had epiphysiodesis of the contralateral leg. At skeletal maturity the limp was eliminated and walking distance was significantly improved in them all. In those who had epiphysiodesis the average leg-length discrepancy was 0.7 cm at maturity. Two of those not treated by epiphysiodesis used a heel raise of 1.5 cm. In seven cases the two operations were performed simultaneously without serious complications. This procedure is recommended at about the age of 12 years.
In 30 patients in whom osteomyelitis was suspected fine-needle bone biopsies (FNBB) were taken at the same time as bone was aspirated for bacteriological examination. The diagnosis of osteomyelitis was eventually confirmed in 15 patients; the other 15 had myositis (3), arthritis (3), trauma (2), microgeodic phalangeal syndrome (2), haematoma in a non-ossifying fibroma (1), and Ewing's sarcoma (1). In three patients no pathology was found. The temperature, WBC and ESR at presentation did not help to distinguish osteomyelitis from other conditions. FNBB, however, proved to be a useful additional investigation with a sensitivity for osteomyelitis of 87% and a specificity of 93%.
We reviewed the ultrasound findings in 59 children suspected of having bone infection. Twenty-nine were eventually proved to have acute haematogenous osteomyelitis and 26 of these showed characteristic ultrasound findings. Such changes were rare in 30 patients with other clinically similar conditions. Ultrasound examination was also able to detect the presence of subperiosteal pus and thus indicate the need for surgical treatment.
We studied the ossific nuclei on radiographs of the feet of three stillborn infants, two with club feet, relating the size, position and alignment of each nucleus to the cartilaginous talus or calcaneum in which it lay. Anteroposterior projections of the nucleus of the talus show deformity of that bone as well as subtalar malalignment. Lateral projections of the calcaneal nucleus may underestimate the degree of hindfoot equinus.
We treated 63 club feet in 44 patients by a defined programme of strapping from birth followed by one of two operations performed at six weeks, either a simple calcaneal tendon lengthening or a subtalar realignment, and reviewed them prospectively. The decision as to which operation to perform was taken at four weeks after radiographic measurement of the talocalcaneal angle. All but eight patients (ten feet) were followed for a mean of 8.7 years. The overall results after calcaneal tendon lengthening were satisfactory. The re-operation rate after subtalar realignment was high (39%) due to over or undercorrection of the deformity.
We describe the results of a policy of highly selective splintage for CDH, using knee plasters. No child suffered because splintage was withheld. In those who were treated the results were satisfactory and the proportion who required a subsequent operation was extremely low. Avascular necrosis was not a significant problem. The method, although a little more time consuming, appears to offer significant advantages over current alternatives.
The tissue surrounding carbon fibre reinforced epoxy resin plates applied to forearm and tibial fractures was biopsied in 32 patients at the time the plates were removed. The reaction was minimal and was compared with that in a control group of 16 similar patients in whom stainless steel plates were used. No significant histological differences were found. A series of experiments on rats, in which the histology was studied from 2 to 78 weeks, also showed that there was very little reaction to carbon fibre reinforced plastic.
We have studied the natural history of spontaneous dislocation of the hip in cerebral palsy, with particular reference to the pattern of neurological involvement. In patients with bilateral hemiplegia and severe involvement of the upper limbs the incidence of dislocation was very high (59%), while in those with diplegia and little involvement of the upper limbs, only 6.5% were affected. There was no evidence of dysplasia or instability of the hip in any of the patients with unilateral hemiplegia. A strong correlation was found between the stability of the hip and the patients' ability to walk. These findings have a bearing on clinical surveillance and also on the indications for prophylactic surgery.
We have studied the use of filamentous polyglycolic acid (Dexon) for the induction of neotendon in the calcaneal tendon of sheep. Uniformly good results were obtained, with the formation of a thick neotendon. However, in a control group the power of spontaneous regeneration of the tendon was studied; it was found that, provided overlengthening of the gap was prevented, an equally good tendon resulted. It is concluded that this particular model is not an appropriate one for testing neotendon induction, despite its use for this purpose in the past. The favourable results of using filamentous polyglycolic acid as a tendon replacement suggest that it should be further investigated (in a more suitable model) since it may well have useful clinical applications.
Ruptures of the calcaneal tendon which present late may be repaired using carbon fibre to induce a neotendon. The operative technique is described and the results of five cases reviewed. The average muscle power obtained was 88% of normal, and the thickness of the neotendon was 148% of that of the normal side. It would appear that this tendon formation in man is comparable to that previously described in sheep.
Ten cases of a complication of Garden screw fixation of subcapital fracture, namely subtrochanteric fracture through the lower screw hole, are presented. Their possible aetiology, prevention and difficulties in management are discussed. It is recommended that, during the insertion of Garden screws, care should be taken to avoid multiple attempts at passing the guide wire. If subtrochanteric fracture occurs internal fixation with a nail plate or screw plate is advised. Ideally the nail or screw should be inserted along the track of one of the existing screws.
