A procedure for quantification of precipitate microstructures from three-dimensional atom probe data.

New analysis software for selecting and quantifying particles in three-dimensional atom maps has been designed. The selection of solute-rich regions is performed by connecting solute atoms which lie within a fixed distance (d), and taking clusters above a certain minimum number of solute atoms (N(min)). Other atoms within some distance L greater than d are taken to belong to the cluster. However, this results in the inclusion of a shell of matrix atoms, which must be removed through an erosion step, to define the final cluster. Data filtered in this way can be used for subsequent quantification of parameters such as size, shape, composition, number density and volume fraction with better accuracy than by manual selection. The choice of d, N(min) and L values is discussed and some methods of evaluation of these parameters are proposed. Examples are presented on the application of this new software to the analysis of early stage clustering in an Al-Mg-Si-Cu alloy and a copper-containing steel.

Transfemoral implantation of the Wagner SL stem. The abolition of subsidence and enhancement of osteotomy union rate using Dall-Miles cables.

BACKGROUND: The Wagner SL uncemented revision stem has been utilised successfully for revision hip surgery where marked loss of proximal bone stock co-exists or where there is a periprosthetic fracture. Implanted via the transfemoral approach, one significant difficulty appears to be a tendency for implant subsidence, which in some cases has been troublesome enough to necessitate early revision (usually to a larger prosthesis). METHODS: A change in our operative practice allowed us to review the effects of using either wire cerclages or 2.0 mm Dall-Miles cables for prophylactic wiring of the distal femur. Seventeen Wagner SL stems, inserted via the transfemoral approach, were studied in 16 patients. RESULTS: We found those patients prophylactically wired with Dall-Miles cables demonstrated no subsidence in comparison with those in whom heavy wire cerclage had been utilised (mean subsidence 6 mm; p=0.001). In addition, we found that closure of the proximal osteotomy with wires conferred a more reliable rate of union in comparison with those closed with heavy sutures. CONCLUSION: We recommend the use of Dall-Miles cables for distal cerclage and osteotomy closure for the Wagner prosthesis.

The Marchetti-Vincenzi humeral nail--a useful device in fresh fractures.

Whilst most humeral fractures may be treated by closed methods, humeral nailing has gained popularity where a surgical option is indicated. Concern has been expressed regarding placement of proximal and distal locking screws whilst the efficiency of the ingenious intra-medullary locking device of the Seidel nail has also been questioned. The Marchetti-Vincenzi nail, which "locks" proximally with the spreading of intra-medullary pins and distally with a single screw inserted via the surgical wound, apparently avoids potential neurovascular and tendon injury. Prospectively recorded data was analysed in 19 "fresh" fractures, i.e. within 3 weeks of injury, and in 13 "late" fractures (total of 32 humeral fractures) treated with the Marchetti nail. All fresh fractures thus treated progressed to union, whilst in the late fracture group there were three non-unions all of whom were in osteoprotic females. Whilst we commend the use of the Marchetti humeral nail in fresh fractures, we have reservations about its use in "late" fractures particularly where the patient is female and osteoporotic.

Effect of warming up on knee proprioception before sporting activity.

BACKGROUND: It is now generally accepted that the ligamentous structures of the knee not only act as mechanical restraints but also have a neurophysiological role in joint function and protection. A report that knee joint laxity increases with exercise raised the question as to whether there is any compensatory change in joint position appreciation. OBJECTIVE: To test whether there is a compensatory mechanism for increased ligamentous laxity during normal levels of activity. METHODS: Joint position appreciation was measured, using a previously reported technique, in the knees of sportsmen at rest and after warm up. RESULTS: Joint position appreciation was found to be significantly more sensitive after warm up (p = 0.005). CONCLUSIONS: These findings indicate that joint position appreciation within the knee accommodates physiological changes within the ligaments and muscles after exercise.

Delayed presentation of compartment syndrome following gastrocnemius tear.

The authors describe a case of acute compartment syndrome occurring twenty days following a tear of gastrocnemius. To their knowledge, this is the only such case reported where the onset of compartment syndrome was so long since of index injury.

Sural nerve injury associated with neglected tendo Achilles ruptures.

Two patients are described with delayed presentation of a ruptured tendo Achilles, each exhibiting signs of sural nerve dysfunction. Recovery occurred in each case after operative repair.

Ultrasonically driven instruments in the transfemoral approach--an aid to preservation of bone stock and reduction of implant length.

The transfemoral approach to the femur with implantation of the Wagner SL stem provides a means of dealing with the difficult revision problems of extensive endosteolysis and with peri-prosthetic fractures. This surgical approach has been modified such that with the aid of an ultrasonically driven cement removal instrument (OSCAR) the length of the osteotomy is reduced, preserving bone stock, and it is possible to implant a shorter prosthesis in approximately 60% of cases.

Complications following the use of the Marchetti flexible intramedullary nail.

Twenty-seven patients, with eight femoral and 20 tibial fractures, were treated with the Marchetti/Vincenzi flexible intramedullary nail between March 1993 and May 1994 in a District General Hospital. Clinical and radiological reviews were performed on all patients except for one who died. There was a high complication rate in both groups (63.5 per cent femoral and 43 per cent tibial). Particularly common was coronal mal-alignment. Other complications included non-union, external rotation, and fracture shortening with proximal migration of the nail. These data suggest that flexible intramedullary nails do not give adequate stability to either femoral or tibial fractures. We believe they should not be used in the lower limb without external support or delayed weight bearing.

Laxity and function in knee replacements. A comparative study of three prosthetic designs.

This study was designed to determine the influence of laxity on clinical function after knee replacement. Using a recently developed computerized method, anteroposterior laxities were measured in 29 Insall-Burstein posterior stabilized, 25 Kinemax Condylar (posterior cruciate retaining), and 10 Oxford bicompartmental (anterior and posterior cruciate retaining) knee replacements. Laxities of less than 5 min, irrespective of implant design, was associated with an impaired range of passive motion and an increased likelihood of incurring a flexion deformity in excess of 4 degrees. Clinical function, as reflected by the American Knee Society Clinical Rating system, demonstrated a particular sensitivity in the Oxford knee to anteroposterior laxity. It was concluded that anteroposterior laxity in excess of 5 mm in prosthetic knees is desirable for unimpaired joint function, although an upper limit of acceptable anteroposterior laxity could not be identified. These findings, which emphasize the need for attention to ligamentous tensions at the time of surgery, also indicate the need for appropriate weighting of anteroposterior laxity in the continuing evolution of clinical rating systems.

Proprioception after knee arthroplasty. The influence of prosthetic design.

It is recognized that awareness of joint position in the knee deteriorates because of aging, anterior cruciate injury, or osteoarthrosis. Proprioception was studied in osteoarthritic and prosthetic knees, including both posterior cruciate ligament (PCL)-retaining and PCL-sacrificing designs. An improvement in proprioception was observed after knee arthroplasty. A PCL-retaining prosthesis was found to confer a greater improvement than a PCL-sacrificing design.

Colles' fractures: the use of the metacarpal index as a prognostic indicator investigated.

The radiographs of 25 patients who presented to the Whittington Hospital with Colles' fractures were studied. Measurements of dorsal angulation and radial shortening were made on radiographs taken at presentation, following reduction (where performed) and 5 weeks after injury. The presence, and degree, of osteoporosis was assessed using the metacarpal index. There was a strong correlation between the degree of osteoporosis and age. There was no correlation between the degree of osteoporosis, as determined by the metacarpal index, and either the severity of the injury or the final result. Thus, the metacarpal index is not a useful prognostic indicator as to the radiological outcome of Colles' fractures. The single most important factor influencing the radiological result was the quality of the initial reduction.

Limb exsanguination. II. The leg: effect of angle of elevation.

Although limb exsanguination prior to tourniquet inflation is usually accomplished using mechanical devices, elevation alone may still be employed under circumstances where mechanical means are contraindicated. The rather confusing advice within the literature as to duration of elevation, stimulated a study in the arm which revealed the optimal duration of elevation to be 5 min, a period somewhat longer than generally advised. Because the pattern of venous drainage within the leg is slightly different to that of the arm, we undertook a similar study to ascertain if our findings for the arm also held true for the leg. Volume changes in the calves of seven male volunteers during elevation at 45 degrees and 90 degrees were assessed using strain gauge plethysmography. To achieve maximal exsanguination it is recommended that the leg should be elevated at an angle of 45 degrees for 5 min. Higher angles of elevation produce slower and less complete exsanguination.

Limb exsanguination. I. The arm: effect of angle of elevation and arterial compression.

Limb exsanguination before tourniquet inflation is usually accomplished using mechanical devices although, where their use is contraindicated, exsanguination by elevation alone may be employed. Advice regarding duration of elevation within the literature is a little confusing with recommendations ranging from 20 s to 5 min. Volume changes, during elevation at 45 degrees and 90 degrees, were measured using strain gauge plethysmography in seven male volunteers. In addition, the superimposed effect of brachial arterial compression on elevation at 90 degrees was investigated. To achieve maximal exsanguination it is recommended that the arm should be elevated for 5 min at 90 degrees before tourniquet inflation. Supplementary brachial arterial compression is not recommended as this tends to attenuate changes in volume.

Accuracy and completeness of orthopaedic computer audit.

The completeness of data contained in a microcomputerized audit system has been compared with the operating theatre record book. The computerized audit system contained details of only 63% of the operations performed. Of the missing patients, 52% had never been completed. There were no failures of the computer system itself. Serious deficiencies in the methods of data entry were found and methods are described to overcome these deficits. The collection of audit information requires a disciplined approach and close supervision by a designated member of the surgical team.

Technical aspects of the use of the Russell-Taylor reconstruction nail.

The introduction of the reconstruction nail has broadened the indications for the intramedullary fixation of difficult femoral fractures. The operative technique is, however, complicated. Some technical difficulties encountered during its use are presented, together with guidance to allow these problems to be avoided.

Tension-band fixation of olecranon fractures. A cadaver study of elbow extension.

The loss of extension produced by tension-band wiring was studied using cadaveric elbows. Extension loss was found to be due to impingement of the longitudinal wires against the humerus independent of the tension band. Reducing the size of the bent end of the longitudinal wire is recommended, and bending the wire into a loop achieves this. In addition, passing the tension band through the loops prevents the wire from backing out.

Fixation of a fracture of the femoral head with preservation of remaining soft-tissue attachments.

Residual soft-tissue attachments may provide a blood supply to femoral head fragments after fractures associated with traumatic dislocation of the hip. Screw fixation of these fractures without sacrifice of the attachments can prove to be difficult. A case is presented using a method of fixation--not, to my knowledge, previously reported--that preserves these attachments and facilitates subsequent removal of metalware.