Exploiting plant transcriptomic databases: Resources, tools, and approaches

There are now more than 300 000 RNA sequencing samples available, stemming from thousands of experiments capturing gene expression in organs, tissues, developmental stages, and experimental treatments for hundreds of plant species. The expression data have great value, as they can be re-analyzed by others to ask and answer questions that go beyond the aims of the study that generated the data. Because gene expression provides essential clues to where and when a gene is active, the data provide powerful tools for predicting gene function, and comparative analyses allow us to study plant evolution from a new perspective. This review describes how we can gain new knowledge from gene expression profiles, expression specificities, co-expression networks, differential gene expression, and experiment correlation. We also introduce and demonstrate databases that provide user-friendly access to these tools.

Submammary placement of implantable cardioverter defibrillators: a Singapore plastic surgeon experience

The use of implantable cardioverter defibrillators (ICDs) in young women has been increasing in recent years owing to greater awareness about inherited cardiac conditions that increase the risk of sudden death. Traditional placement of ICDs in the infraclavicular region among young women often leads to visible scars, a constant prominence that causes irritation from purse or bra straps and can result in body image concerns and device-related emotional distress. In this case series, two women with long QT syndrome required placement of ICDs for prevention of sudden cardiac death. Submammary placement of ICDs was performed in collaboration with electrophysiologists. We describe our local experience and technique in submammary placement of ICDs as well as the challenges faced.

Progression-free and overall survival in ovarian cancer patients treated with CVac, a mucin 1 dendritic cell therapy in a randomized phase 2 trial

Background

CAN-003 was a randomized, open-label, Phase 2 trial evaluating the safety, efficacy and immune outcomes of CVac, a mucin 1 targeted-dendritic cell (DC) treatment as a maintenance therapy to patients with epithelial ovarian cancer (EOC).

Methods

Patients (n = 56) in first (CR1) or second clinical remission (CR2) were randomized (1:1) to standard of care (SOC) observation or CVac maintenance treatment. Ten doses were administered over 56 weeks. Both groups were followed for progression-free survival (PFS) and overall survival (OS).

Results

Fifty-six patients were randomized: 27 to SOC and 29 to CVac. Therapy was safe with only seven patients with Grade 3–4 treatment-emergent adverse events. A variable but measurable mucin 1 T cell-specific response was induced in all CVac-treated and some standard of care (SOC) patients. Progression free survival (PFS) was not significantly longer in the treated group compared to SOC group (13 vs. 9 months, p = 0.36, hazard ratio [HR] = 0.73). Analysis by remission status showed in the CR1 subgroup a median PFS of 18 months (SOC) vs. 13 months (CVac); p = 0.69 (HR = 1.18; CI 0.52–2.71). However CR2 patients showed a longer median PFS in the CVac-treated group (median PFS not yet reached, >13 vs. 5 months; p = 0.04, HR = 0.32 CI). OS for CR2 patients at 42 months of follow-up showed a difference of 26 months for SOC vs. > 42 months for CVac-treated (as median OS had not been reached; HR = 0.17 (CI 0.02–1.4) with a p = 0.07).

Conclusions

CVac, a mucin 1-dendritic cell maintenance treatment was safe and well tolerated in ovarian cancer patients. A variable but observed CVac-derived, mucin 1-specific T cell response was measured. Notably, CR2 patients showed an improved PFS and lengthened OS. Further studies in CR2 ovarian cancer patients are warranted (NCT01068509).

Trial registration

NCT01068509. Study Initiation Date (first patient screened): 20 July 2010. Study Completion Date (last patient observation): 20 August 2013, the last patient observation for progression-free survival; 29 April 2015, the last patient was documented regarding overall survival.

Biomechanical Strength of Large Diaphyseal Deep-frozen Allografts

The aim of this paper is to study the biomechanical strength of deep-frozen allografts as they heal. Twenty-eight adult cats were used with the tibia as the experimental model site. Deep-frozen allografts stored at -80 degrees C were used to reconstruct a large tibial defect (at least two-thirds of the diaphysis). An intra-medullary rod was used for fixation. The healing was studied by X-ray at observation periods of 4, 6, 8, 12, 16, 24 and 36 weeks. Post-transplantation biomechanical testing was performed using the Shimadzu Universal Testing Machine DCS series with a torsion test device of 50 kg force metre. Parameters studied included maximum torque, torsional stiffness and energy of absorption. The transplanted grafts were compared to the mechanical properties of the internal controls of the normal opposite tibia of each cat. The results of the mechanical tests demonstrated that deep-frozen allografts did not regain normal strength. At nine months, only about 60% of normal torque strength and about 80% of normal torsional stiffness was achieved. Clinically, it is important to employ strong and rigid internal fixation using intra-medullary nailing rather than plating to allow for immediate mobilisation and reduce the rate of graft fracture.

Optimization of stacked half-hitch knots for arthroscopic surgery

PURPOSE

This study was conducted to determine the optimal configuration of stacked half-hitch knots that would give the maximum knot-holding capacity (KHC).

TYPE OF STUDY

Mechanical testing study.

METHODS

The 2 types of suture materials tested were No. 1 PDS II monofilament and No. 2 Ethibond braided (Ethicon, Somerville, NJ) because these are the 2 most commonly used sutures in arthroscopic surgery. Twelve configurations of stacked half-hitch knots including 2 versions of the Revo knot were tested. Knots were tied between 2 steel hooks 7 mm apart on a manual knot-testing machine. The steel hooks were spread apart to break the knot and the KHC was determined by the peak load recorded on the digital force transducer. Maximum KHC was achieved for No. 1 PDS II sutures by locking the knot with 2 RHAPs (reversing half-hitch on alternate post) and, for No. 2 Ethibond sutures, by locking the knot with 3 RHAPs. Because of the possibility of PDS II sutures unraveling, it is recommended for both No. 1 PDS II and No. 2 Ethibond sutures, that all stacked half-hitches be locked with 3 RHAPs. By adding 1 RHAP to the Revo knot, failure by slippage can be eliminated.

RESULTS

The recommended knots tied with braided No. 2 Ethibond sutures were 1.5 times stronger than knots tied with No. 1 PDS II sutures. Although there was variability in the KHC of the recommended knots tied by different surgeons using different knot tiers, the greatest difference in the mean KHC was less than 10%.

CONCLUSIONS

Stacked half-hitch knots locked with 3 RHAPs are unlikely to fail by slippage.

Paired cylindrical interbody cage fit and facetectomy in posterior lumbar interbody fusion in an Asian population

STUDY DESIGN

The intervertebral disc heights and interfacetal distances of normal lower lumbar segments were measured from MRI scans of 150 male subjects.

OBJECTIVES

To investigate the probabilities of paired cylindrical interbody cage placement across the facet joints of the lower lumbar spine in an Asian population with respect to the spinal segmental level, facetectomy, and the restoration of normal intervertebral height.

SUMMARY OF BACKGROUND DATA

Cylindrical interbody cage devices often require extensive facetectomy for insertion through a posterior approach in a posterior lumbar interbody fusion (PLIF) procedure. This is because the transverse dimension of a pair of cages could far exceed the interfacetal interval of the lumbar segment.

METHODS

One hundred and fifty MRI scans of the lumbosacral spine of male patients between the ages of 18 and 55 years undergoing investigation for low back pain were collected for this study. The interfacetal distances and intervertebral disc heights were measured from transverse and sagittal images, respectively, at L3/L4, L4/L5 and L5/S1. Degenerated discs were not measured. The inner, mid, and outer interfacetal distances were compared with the dimensions of paired cages of 13, 15, and 17 mm in diameter to obtain the proportion of lumbar segments at a particular spinal level that would accommodate paired cages of different diameters and under conditions of varying degrees of facetectomy.

RESULTS

Without facetectomy, there was no lumbar segment that could accommodate paired cages as well as restore intervertebral height. With hemi-facetectomy, very few segments at L3/L4 and L4/L5 could fit paired cages. At L5/S1, fewer than 9% of segments could fit paired cages and restore intervertebral heights. The proportion of segments that could accommodate paired cages increased with near-total facetectomy: 25% of L5/S1 segments could accommodate 15-mm cages with restoration of intervertebral heights.

CONCLUSIONS

Paired cylindrical cage installation in the majority of patients is likely to require near-total or total facetectomy, with implications for potential segmental instability. Among the three lumbar segments studied, L5/S1 had the highest proportion of segments that could accommodate paired cages and at the same time restore intervertebral height.

An introduction to biodegradable materials for tissue engineering applications

Tissue generation by autogenous cell transplantation is one of the most promising treatment concepts being developed as it eliminates problems of donor site scarcity, immune rejection and pathogen transfer. Cultured cells are seeded onto a three-dimensional biocompatible scaffold that will slowly degrade and resorb as the soft and hard structures grow and assimilate in vitro and/or in vivo. The 3-D scaffold provides the necessary template for cells to proliferate and maintain their differentiated state. Ultimately, it defines the overall shape of the tissue-engineered transplant. The aim of this review is to describe and discuss the scaffold materials of natural and synthetic origin that are of specific interest to tissue engineers. This review is based on previous publications and our own experience in the use of biomaterials of natural and synthetic origin for tissue engineering applications. Biodegradable polymers which have been used for tissue engineering applications are mainly based on clinically established medical devices and implants. In the group of macromolecules of natural origin collagen, alginate, agarose, hyaluronic acid derivatives, chitosan, and fibrin glue have been used as scaffolds. Man-made polymers such as polyglycolide (PGA), polylactides (PLLA, PDLA), poly(caprolactone) (PCL), and poly(dioxanone) (PDS) have been studied as matrix material to guide the differentiation and proliferation of cells into the targeted functional premature and/or mature tissue. Appropriate selection of scaffold material with respect to the targeted tissue is essential. Today, biomaterials of choice remain to be those approved by the US Food and Drug Administration. In spite of that, novel biomaterials should be developed specifically designed for tissue engineering applications.

Linear correlation between axial and lateral bone mineral density of lumbar vertebrae

The placement of most spinal interbody devices is above the cancellous region of the vertebral bodies. Dual X-ray absorptiometry (DXA) scans of patients are usually taken from the anterior-posterior or the lateral projection. DXA scans taken in vitro from the axial direction would most closely indicate the bone mineral density (BMD) of the bone at this region. So far, in vitro studies have not been conducted to determine the correlation between axial and lateral scans. Because lateral DXA BMD scans are noninvasive and have low radiation dosage, they could be used as a predictive tool to determine the quality of cancellous bone at the centrum of the vertebral bodies, where spinal interbody devices are commonly placed.

Biomechanical study on the effect of twisted human patellar tendon

OBJECTIVE

To compare the stiffness and maximum strength between the untwisted and twisted free-tendon.

DESIGN

22 twisted and untwisted sectioned-specimens of human cadaver patellar tendons were used and pulled to failure to obtain load-deformation profiles from which stiffness, maximum load to failure and elastic elongation limit were derived.

BACKGROUND

In the reconstruction of the deficient anterior cruciate ligament, the use of the central one-third of the patellar tendon is a well-established procedure in which, prior to insertion, the tendon graft may be twisted to mimic the natural orientation of the anterior cruciate ligament in the knee joint.

RESULTS

The untwisted tendons had a mean stiffness of 36.5 kg/mm (SD, 16.6 kg/mm) and maximum load of 165.9 kg (SD, 86.8 kg). With a 90 degrees twist, the average stiffness of the twisted tendon was 66.5 kg/mm (SD, 25.4 kg/mm), with maximum load at 364.5 kg (SD, 109.9 kg), an increase of over 100%. The elastic elongation limit, or allowable elongation before permanent deformation or failure, was significantly larger in twisted tendons by 35%.

CONCLUSION

Twisting increased the resistance to deformation of the tendon in this study. Relevance The finding supports the surgical practice of pre-twisting tendon grafts for anterior cruciate ligament reconstruction, based on the premise that a stronger and stiffer graft provides a more favourable outcome.

Principal structural testing of trans-tibial prosthetic assemblies: specimen preparation

A simple alignment apparatus and the method of transferring the offset test load to the prosthetic assembly through an aligned mandrel for the principal structural tests in accordance with ISO 10328 is presented. The new alignment apparatus was used to prepare test specimens consisting of traditional laminated prosthetic sockets, adaptors, shanks and foot blocks. The alignment apparatus proved useful in ensuring proper orientation and positioning of the components relative to one another as well as to the loading coordinate axes. The sockets and the other components achieved the maximum load specifications during the static failure tests and no failure of components was observed in the cyclic tests.

Influence of PLIF cage size on lumbar spine stability

STUDY DESIGN

In vitro biomechanical testing on functional spine units with posterior lumbar interbody fusion cage implants of progressively larger sizes.

OBJECTIVES

To determine the influence of increasing cage size on the restoration of spine stability after total facetectomy.

SUMMARY OF BACKGROUND DATA

Bilateral insertion of cages in posterior lumbar interbody fusion commonly involves facetectomy. To restore stability with no additional instrumentation, the cages must provide sufficient distraction of the vertebrae and adequate tension in the anulus. The size of cages is therefore an important consideration in posterior lumbar interbody fusion.

METHODS

Eight human lumbar functional spine units were obtained and divided into two equal groups; one group underwent bending tests and the other twisting. The functional spinal units were tested intact, after total bilateral facetectomy and with three sets of cages that were progressively larger in size.

RESULTS

After facetectomy, the functional spine unit's stiffness reduced significantly from that of the intact spine in extension (48% of intact), lateral bending (25%), and torsion (39%). With the posterior insertion of small cages into the facetectomized functional spine units, only extension stiffness was restored to the intact level, whereas flexion stiffness reduced significantly (41% of intact). The medium cages restored the lateral bending stiffness of the facetectomized functional spine units; only the large cages managed to restore the torsional stiffness. Flexion stiffness of the facetectomized functional spine units with cages remained significantly less than that of the intact spine, regardless of cage size.

CONCLUSION

In the facetectomized lumbar spine unit, cage size influences lateral bending and torsional stability.

Postoperative vomiting (POV) in the paediatric outpatient general surgical population

AIM

To determine the incidence of postoperative vomiting (POV) in the paediatric outpatient general surgical population, the factors affecting POV and the incidence of unplanned admissions contributed by POV.

METHOD

One hundred and ninety-nine children below 13 yeas of age undergoing elective outpatient general surgical procedures were enrolled into this prospective study. Anaesthesia was induced either intravenously or via the inhalational route. It was then maintained with nitrous oxide, oxygen and isoflurane or halothane. The age, sex, body weight, duration of fasting, administration of trimeprazine, type of general surgical procedure, maintenance technique for general anaesthesia, duration of general anaesthesia, the administration of opiods or local anaesthetics and the incidence of POV were noted. The results were analysed initially with chi-squared test and subsequently subjected to multivariate logistic regression analysis and stepwise variable selection method.

RESULTS

The incidence of POV was 8.5%. Duration of general anaesthesia greater than one hour was associated with a significantly higher incidence of POV. Postoperative emesis did not contribute to unplanned admissions in these day surgical patients.

Difficult pulmonary artery catheterization in a patient with persistent left superior vena cava

A persistent left superior vena cava is an uncommon congenital abnormality. It arises when the left anterior cardinal vein fails to regress during the embryonic period. Although such patients are usually asymptomatic, they may have associated cardiovascular abnormalities. The anaesthetist may encounter difficulty in the insertion of pulmonary artery catheters. Other implications in the management of these patients in the operating theatre or intensive care unit are discussed.

Biomechanical study of tibialis anterior tendon transfer

The tibialis anterior tendon transfer has been used in the treatment of recurrent congenital clubfoot and paralytic equinovarus foot deformities in cerebral palsy. This study attempts to determine the optimal site of tibialis anterior tendon insertion for ankle and foot motion and to compare the split and whole tendon transfer. Ten fresh normal anatomic leg specimens were used. The lateral half of the tibialis anterior tendon was detached from its insertion, passed beneath the extensor retinaculum, and anchored to the appropriate tarsal bone by a barbed staple. Tension was applied, and ankle and foot motions were measured. The experiment was done by anchoring the tendon to the tarsal bones along the axis of the second metatarsal and serially through to the axis of the fifth' metatarsal. The entire experiment was repeated using the whole tibialis anterior tendon. For split tendon transfer, insertion onto the fourth metatarsal axis was the most effective route; it produced maximal dorsiflexion with minimal supination and pronation. For whole tendon transfer, the ideal site of insertion was along the third metatarsal axis. However, the difference between the average maximum dorsiflexion achieved by the split tendon transfer and that of total tendon transfer is not statistically significant.

Periprosthetic bone remodelling after cementless total hip replacement. A prospective comparison of two different implant designs

In a prospective study of 14 patients undergoing total hip replacement we have used dual-energy X-ray absorptiometry (DEXA) to investigate remodelling of the bone around two different designs of cementless femoral prosthesis. The bone mineral density (BMD) was measured at 12-weekly intervals for a year. Eight patients (group A) had a stiff, collarless implant and six (group B) a flexible isoelastic implant. Patients in group A showed a decrease in BMD from 14 weeks after operation. By 12 months, the mean loss in BMD was 27%, both medially and laterally to the proximal part of the implant. Those in group B showed an overall increase in BMD which reached a mean of 12.6% on the lateral side of the distal portion of the implant. Our results support the current concepts of the effects of stem stiffness and flexibility on periprosthetic remodelling.

Pattern of fall and bone mineral density measurement in hip fractures

The objectives of this study were to determine the pattern of fall and the bone mineral density distribution in hip fracture patients. The study was carried out on 260 patients (204 females and 56 males) with hip fractures over a period of three years (i.e. 1991 to 1993). The patients were all above 50 years old and the average age was 77.7 years for women and 76.8 years for men. Information relating to their falls and subsequent hip fractures were collected. Bone mineral density of the contralateral intact femoral neck was measured using dual energy X-ray absorptiometry (Model XR26, Norland Corporation, USA). Bone mineral density in the patients with hip fracture (mean value 0.55 g/cm2) was significantly lower than the fracture threshold value of 0.64 g/cm2. Falls which would result in direct impact on the hip such as sideways, backwards and straight down formed 95.6% of the cohort. Forty-six (17.7%) of the patients fell from a seated or lying position and their bone mineral density were significantly lower (i.e. 0.45 g/cm2). Two hundred and twenty-three (85.7%) of the patients fell on hard surfaces such as ceramic, marble and concrete. Two hundred and twelve (81.5%) of the falls occurred indoors and 153 (58.8%) while walking. Low bone mineral density and falls are important risk factors in hip fracture in the elderly population. Patients with low bone mineral density can sustain a hip fracture from mild trauma such as falling from a seated or lying position. It is therefore necessary to monitor bone mineral density values as well as to prevent or minimise the risk of falling.

Effect of femoral rotation on bone mineral density measurements with dual energy X-ray absorptiometry

Precision in femoral neck scans with dual energy X-ray absorptiometry (DXA) is affected by variability in positioning and subsequent repositioning of the femur for repeated scans. To study the in vitro effect of femoral rotation on the bone mineral density (BMD), four fresh-frozen cadaveric femurs were fixed in a specially designed jig which allows for rotation of the femurs. BMD measurements of the femurs were done in neutral position (0 degrees) i.e., with the femoral neck axis parallel to the surface of the couch and at 15 degrees, 30 degrees, and 45 degrees of internal and external rotation. In vivo precision of the femoral neck scan was determined in five normal male subjects. The scans were first done with the legs positioned using the manufacturer's foot block. Five scans were performed, with repositioning, on the left hip of each subject. The procedure was then repeated with the legs positioned using a custom-designed positioning jig to minimize the rotation of the hips during a scan. In the in vitro study, the femoral neck BMD value was minimum at neutral position (0 degrees) and increased when the femur was rotated internally or externally. In vivo precision error of the femoral neck scan was reduced by almost 50% with the use of the positioning jig when compared with the manufacturer's foot block. Femoral rotation was shown to have a significant effect on BMD measurements, and proper positioning of the femur during a scan can improve precision significantly.

Biomechanical study on tibialis posterior tendon transfers

Two methods are used to route the tibialis posterior tendon anteriorly to achieve dorsiflexion: (1) around the medial side of the tibia, or the subcutaneous route; and (2) through the interosseous membrane, or the interosseous route. This study determined the effect of site of tendon insertion on ankle and foot motions and compared the efficacy of both routes. Eleven fresh normal cadaveric legs were used. The detached tibialis posterior tendon was transferred anteriorly through the interosseous membrane and anchored to the first cuneiform along the first metatarsal axis by a barbed staple. The specimen was mounted on a mechanical testing machine. Tension was applied to the tendon and ankle and foot motions were measured. The experimental procedure was repeated with tendon insertion along the second metatarsal axis and serially through to the fifth metatarsal axis. The entire experiment was repeated using the subcutaneous route. The interosseous route was more effective in achieving maximum dorsiflexion with minimal pronation. Shifting the insertion medially caused supination, whereas a more lateral insertion caused pronation.

A cadaver study of the function of the oblique part of vastus medialis

Six normal cadaver lower limbs were mounted on a specially designed loading apparatus. Wires were used to simulate the five muscle bellies of the quadriceps, the ratio of their tensions having been determined from that of the anatomical cross-sectional areas of the muscles. A three-camera system was used to track the patella during knee movements from flexion to extension. The patellofemoral contact area was determined by pressure-sensitive film. The limb was loaded with and without tension on the wire which simulated the oblique part of the vastus medialis (VMO). Absence of VMO tension caused the patella to displace laterally (4.2 mm) and increased the load on the lateral patellar facet throughout the range of knee motion. When the tension on the wire simulating vastus lateralis was reduced by 40% to simulate the effect of a lateral release procedure, the abnormal kinematics caused by the absent VMO returned to normal.

A cadaver study of the function of the oblique part of vastus medialis

Six normal cadaver lower limbs were mounted on a specially designed loading apparatus. Wires were used to simulate the five muscle bellies of the quadriceps, the ratio of their tensions having been determined from that of the anatomical cross-sectional areas of the muscles. A three-camera system was used to track the patella during knee movements from flexion to extension. The patellofemoral contact area was determined by pressure-sensitive film. The limb was loaded with and without tension on the wire which simulated the oblique part of the vastus medialis (VMO). Absence of VMO tension caused the patella to displace laterally (4.2 mm) and increased the load on the lateral patellar facet throughout the range of knee motion. When the tension on the wire simulating vastus lateralis was reduced by 40% to simulate the effect of a lateral release procedure, the abnormal kinematics caused by the absent VMO returned to normal.

Cold extrusion deformation of UHMWPE in total knee replacement prostheses

The use of metal-backed tibial plates in total knee replacement prostheses can result in the flow of ultra-high molecular weight polyethylene (UHMWPE) from the tibial insert into a cavity on the metal tray surface. A study of the relationship between the thickness of UHMWPE inserts and the amount of cold extrusion is reported here. An attempt was made to correlate the occurrence of cold extrusion with computer-aided analysis. UHMWPE samples of varying thickness, from 3 mm to 10 mm, were placed over cobalt-chrome (Co-Cr) discs. The Co-Cr discs had a 5 mm diameter hole placed centrally to simulate a tibial tray cavity. A cyclic load was applied at 20 Hz through a Co-Cr spherical indentor for a million cycles. The application of cyclic loading on UHMWPE samples resulted in cold-extrusion values comparable to those reported for retrieval analysis studies. Results after fatigue loading show that the samples do not suffer any gross surface damage. A shiny depression was visible at the load application site and the surface roughness value was decreased. The amount of cold extrusion increased with decreasing UHMWPE sample thickness. From the results, a minimum UHMWPE thickness of 12 mm is required if cold extrusion of UHMWPE is to be eliminated.

Effect of decalcification on bone mineral content and bending strength of feline femur

The relationships between bone mineral content (BMC), bone calcium, and bone strength were studied in fractionally demineralized feline femurs. In 44 pairs of cat femurs, the right bones were decalcified in ethylene diaminetetra acetic acid (EDTA) to 20%, 40%, 60%, 80%, and 100% of the mineral content of the intact left bone (= control). The bones were then loaded to failure, and maximum strength values were recorded. The data were then used to calculate the percentage strength of the right relative to the left femurs. A correlation coefficient (r) of 0.970 was found between the percentage decalcification and percentage bending strength. A direct relationship (r = 0.876) was also observed between the total calcium extracted and total loss in BMC. The EDTA solutions were spot checked for protein content to determine if the organic matrices had been altered by demineralization. Protein was never detected. Nor did the demineralized tissues display histologic evidence of gross microscopic damage. This study has shown that in cat femurs, 20% decalcification led to about 35% loss in bending strength, and 60% decalcification caused 75% loss in strength. These values are significant as they highlight the importance of calcium to the strength of osteopenic bone.

A biomechanical model to determine lumbosacral loads during single stance phase in normal gait

A dynamic biomechanical model to determine loads (joint forces) attained at the lumbosacral joint-centre during the stance phase of normal level walking was developed. The biomechanical model was based on rigid free body-segments; namely, the foot, shank, thigh, pelvis and head, arms and trunk (HAT) segments. In this biomechanical model, the forces and moments acting on the lumbar spine are derived from body-segment mass and movements of the trunk. These external forces and their moments must be equilibrated by internal forces, that is, contributions from the erector spinae or rectus abdominus muscle group, and abdominal pressures from within the trunk together with spine forces. Three-dimensional co-ordinate and ground-reaction force data were captured from five healthy young male subjects performing normal level walking in the motion analysis laboratory of the Department of Orthopaedic Surgery, National University of Singapore. These data were captured using the VICON motion analysis system. Both of these data sets were pre-processed, and together with relevant anthropometric parameters and physical measurements of the subject, were passed into the biomechanical model to compute the resultant loads at the lumbosacral joint-centre. The results of this study showed that the peak resultant loads at the lumbosacral joint-centre were between 1.45 and 2.07 times body-weight.

Vertebral body index and bone mineral density in women with spinal fractures. 66 probands compared with controls

The bone mineral density (BMD) was measured in 61 women with compression fractures of the spine and 66 normal pre-menopausal women. Radiographs of the lateral spine were also obtained and the vertebral body index (VBI) was measured in the region L2-L4. Women with spinal fractures had lower BMD and VBI values. Using both BMD and VBI, 3 regions of fracture risk were defined. All but 2 of the fracture patients were in the moderate- or high-risk region for fracture.

A comparison of lumbosacral loads during static and dynamic activities

A biomechanical model to determine the loads at the lumbosacral joint was developed. This model was used to determine the lumbosacral loads during two specific activities--a stable standing posture representing a static activity, and a normal level walk representing a dynamic activity. This study involved ten healthy and young male subjects. The results obtained indicated that the lumbosacral loads during a stable standing posture was in the range of 0.82 to 1.18 times body-weight, with a mean of 1.03 (+/- 0.11) times body-weight. In comparison, during a normal level walk the lumbosacral loads were in the range between 1.41 and 2.07 times body-weight, with a mean of 1.61 (+/- 0.24) times body-weight. The walking speed of these subjects varied between 0.96 and 1.48 ms-1, with a mean of 1.25 (+ 0.18) ms-1. Results in this study indicated that there was a significant difference (p < 0.005) between the means of the lumbosacral loads of these two specified activities. An increase of 56.3% between means of the static to the dynamic case was observed.

Fatigue testing of energy storing prosthetic feet

This paper describes a simple approach to the fatigue testing of prosthetic feet. A fatigue testing machine for prosthetic feet was designed as part of the programme to develop an energy storing prosthetic foot (ESPF). The fatigue tester does not simulate the loading pattern on the foot during normal walking. However, cyclic vertical loads are applied to the heel and forefoot during heel-strike and toe-off respectively, for 500,000 cycles. The maximum load applied was chosen to be 1.5 times that applied by the bodyweight of the amputee and the test frequency was chosen to be 2 Hz to shorten the test duration. Four prosthetic feet were tested: two Lambda feet (a newly developed ESPF), a Kingsley SACH foot and a Proteor SACH foot. It was found that the Lambda feet have very good fatigue properties. The Kingsley SACH foot performed better than the Proteor model, with no signs of wear at the heel. The results obtained using the simple approach was found to be comparable to the results from more complex fatigue machines which simulate the load pattern during normal walking. This suggests that simple load simulating machines, which are less costly and require less maintenance, are useful substitutes in studying the fatigue properties of prosthetic feet.

Molecular characterization of a variant Ph1 translocation t(9;22;11) (q34;q11;q13) in chronic myelogenous leukemia (CML) reveals the translocation of the 3'-part of BCR gene to the chromosome band 11q13

We performed cloning and sequence analysis of translocation junctions at 11q- and 22q- (Ph1) chromosomes and the corresponding germline DNAs of a variant Ph1-positive CML with t(9;22;11)(q34;q11;q13). Southern blot analysis using probes for different regions of bcr mapped the translocation break near the 5'-side of bcr exon 4. Cloning, Southern blot analysis and restriction map analysis of both bcr fragments showed that the part of bcr 3'- to the translocation break moved to 11q13. Sequence analysis of the translocation junction on the Ph1 chromosome showed that the translocation break occurred 63 bp upstream of exon 4. Compared to the germline sequence, bcr sequence from the translocated partners showed deletion of seven basepairs at the site of translocation. A probe derived from the 5'-region of the clone isolated from the 11q- chromosome identified clonal rearrangements in the leukemic DNA. Restriction map and sequence analysis showed that this clone consisted of the 3'-half of the glutathione S-transferase Pi (GST-Pi) gene and the 3'-part of bcr. We identified two point mutations in the GST-Pi allele involved in translocation. Northern blot analysis showed that the GST-Pi gene was expressed in the leukemic cells at blast crisis but not at chronic phase; however, no fusion mRNA between GST-Pi and bcr was identified. We did not find any sequence homology between 11q13 DNA and 22q11 DNA around the translocation breakpoints; however, sequences homologous to ALU repeats were identified close to the sites of translocation breaks at 22q11 and 11q13. This study supports our hypothesis that variant Ph1 translocations may occur as primary cytogenetic changes similar to the classical Ph1 translocations.

Serial phenotypic, cytogenetic and molecular genetic studies in Richter's syndrome: demonstration of lymphoma development from the chronic lymphocytic leukaemia cells

In this report we describe a unique longitudinal study on the clinical, phenotypic, cytogenetic and molecular genetic features of malignant cells from diagnosis of chronic lymphocytic leukaemia (CLL) to the development of lymphoma and lymphomatous meningitis. CLL cells at diagnosis were CD5+, CD19+, surface IgG+, kappa+, were karyotypically abnormal and showed clonal rearrangements in the immunoglobulin heavy (IgH) and kappa light chain genes. Phenotypically leukaemic cells and lymphoma cells at RS resembled CLL at diagnosis, but showed cytogenetic evolution. Geometrically leukaemic cells and lymphoma cells retained the initial clonal rearrangements in IGH and kappa genes, but showed additional supervening clonal rearrangements in both of these genes as the disease progressed to RS. Furthermore, the c-lambda DNA showed clonal rearrangements in the leukaemic cells and lymphoma cells at RS. This complete phenotypic and genotypic analysis of tumour cells during the course of the disease demonstrates the origin of lymphoma from CLL cells through progressive cytogenetic and molecular genetic changes in CLL cells.

Phenotypic and genotypic characterization of Hodgkin's disease

Although a few studies have reported clonal cytogenetic changes in Hodgkin's disease (HD), their correlation with histologic groups is poorly defined. This is because of insufficient numbers of clonally abnormal cases ascertained in each of these studies, an inherent problem associated with the cytogenetic studies of HD. In this report we present results of pathologic, phenotypic, and genetic studies on 29 HD tumors consecutively ascertained by us and the results of a comprehensive analysis of the cytogenetic data available in the literature. In our series 75% of the tumors were positive for Epstein-Barr virus (EBV) by polymerase chain reaction (PCR) assay. A higher frequency of EBV-positive tumors showed clonal karyotypic abnormalities than the EBV-negative tumors. Unlike the case in the previous reports, none of the 24 tumors studied by PCR showed the presence of t(14;18) (q32;q21)-carrying cells. From the comprehensive analysis of the literature, we identified recurring nonrandom numerical changes, deletions, and chromosome breaks in HD. Some of these are associated either with nodular sclerosis or with mixed cellular histologies. A comparison of the pattern of these nonrandom cytogenetic changes in HD and those reported for non-Hodgkin's lymphomas (NHL) identified common deletions and breaks between them. These common genetic lesions probably play a role in disease evolution.

Gait analysis study on patients with varus osteoarthrosis of the knee

Biomechanical changes that occur after high tibial osteotomy (HTO) was investigated in 30 patients with osteoarthrosis (OA) of the knee and 11 age-matched normal subjects. Of the 37 knees with varus OA evaluated, 21 were analyzed before and after surgery (average follow-up evaluation, two years). The mean age of the patient group was 58.2 years. Clinical assessment was based on the Hospital for Special Surgery (HSS) knee scoring system. Full-length weight-bearing radiograms were taken for the measurement of the mechanical axis of the lower limb. Results from clinical assessment showed that 90% of the patients had good or excellent postoperative clinical results, as opposed to 9.5% before surgery. An overall improvement in the gait parameters was evident in the group evaluated after surgery, although control levels were not attained. Further analysis based on moments about the knee showed that 57% of the surgically treated knees with good or excellent clinical results had abnormal load distribution. This may lead to deterioration in the future, and further surgery may be required. The abnormal loading was also reflected in the ground-reaction force vector diagram. Therefore, the force vector diagram can be used as a quick screening method to detect abnormal joint loading.

Parametric modelling of a knee joint prosthesis

This paper presents an approach for the establishment of a parametric model of knee joint prosthesis. Four different sizes of a commercial prosthesis are used as an example in the study. A reverse engineering technique was employed to reconstruct the prosthesis on CATIA, a CAD (computer aided design) system. Parametric models were established as a result of the analysis. Using the parametric model established and the knee data obtained from a clinical study on 21 pairs of cadaveric Asian knees, the development of a prototype prosthesis that suits a patient with a very small knee joint is presented. However, it was found that modification to certain parameters may be inevitable due to the uniqueness of the Asian knee. An avenue for rapid modelling and eventually economical production of a customized knee joint prosthesis for patients is proposed and discussed.

Effect of pore sizes and cholesterol-lipid solution on the fracture toughness of pure titanium sintered compacts

Commercial pure titanium has been widely used as an implant material because of its excellent biocompatibility and good ductility. To determine the effect of pore size on the fracture resistance of porous titanium compacts, a series of fracture toughness (KQ) tests were performed on commercial pure titanium powder compacted to 0.17 and 0.62 GPa. Pore sizes ranged from 25 to 103 microns, with porosity between 8.5 and 35%. Two sets of fracture toughness tests using disc-shaped compacts (ASTM E 399-90) were performed, the first in air at 37 degrees C and the second with compacts treated in cholesterol-lipid solution at 37 degrees C. The KQ value of compacts with a smaller mean pore size (ca. 50 microns) was approximately twice that of the compacts with a larger mean pore size (100 microns). The effect of cholesterol-lipid solution treatment was detrimental, perhaps due to preferential lipid absorption by the titanium oxide and/or the presence of chlorides. For the smaller pore size compacts, the KQ values decreased by up to 20%. For the larger pore size compacts, the effect of cholesterol-lipid solution was less significant. Morphologically, compacts with smaller pore size had a predominantly ductile fracture with significantly higher dimple density than the larger pore size compacts.

Hodgkin's disease and non-Hodgkin's lymphoma in an HIV positive patient

The occurrence of HIV associated non-Hodgkin's lymphoma (NHL) is a well recognized event. HIV associated Hodgkin's disease (HD) has also been observed. A unique patient with both entities is described. The patient was a 29 year old homosexual male who developed clinical IIA nodular sclerosis HD in 1985. He was HIV + with CD4/CD8 = 0.2 and his sister had HD 20 years earlier. He received MOPP and had a complete response. In October 1988 he developed weight loss with an abdominal mass and biopsy revealed diffuse small non-cleaved NHL, with bone marrow involvement. This was his first AIDS associated illness. Probes identified clonally rearranged DNA fragments in the J region of IgH chains and clonal rearrangements in the c-myc gene were also observed but EBV sequences could not be demonstrated. He was treated with m-BACOD but died in March 1989. His course was not complicated by opportunistic infection. Possible etiologies for the HD include his HIV status or shared sibling environment. The development of the NHL may have resulted from HIV infection and/or secondary to his treatment for HD. The relationship between the two lymphomas is uncertain and factors other than HIV exposure and its immune dysfunction may have been causal.

Value of gait analysis in the assessment of surgery in cerebral palsy

Twenty-three ambulatory children with cerebral palsy were assessed preoperatively by a detailed clinical examination and by gait analysis using a video-based gait analysis system (VICON). Surgery was then performed based on either the clinical assessment alone or a combination of clinical evaluation and gait analysis. About one year after surgery, a postoperative clinical and gait analysis assessment was performed. Sixteen children had improved and seven children had not improved after surgery. Most of the children who had not improved were found to have had operations that differed from those recommended by gait analysis. Dynamic EMG studies were found to be useful in preoperative planning but did not show any consistent improvement even in the children with good results. The combination of a careful clinical assessment and gait analysis can produce better results in surgery for children with cerebral palsy.

Biomechanical study on the load-bearing characteristics of the fibula and the effects of fibular resection

The objective of this research was to investigate the load-bearing function of the fibula in relation to donor leg morbidity in patients who have had fibular resections. Biomechanical loading experiments were performed on ten anatomic specimens. Force transducers were mounted in place of resected tibial and fibular segments to allow load transmission to be measured. Load transmission through the fibula varied with ankle position. With the ankle at neutral position, the load distribution to the fibula averaged 7.12% of the total force transmitted through the tibia and fibula. Maximum loads occurred at full dorsiflexion and eversion. Resection of the proximal fibula results in a significant reduction of load through the distal fibular remnant. The values varied between 0.62% and 0.81% of the total force transmitted. When a cortex screw was introduced to anchor the distal fibula remnant to the tibia, the load distribution to the distal fibula remnant was partially restored with values ranging from 1.71% to 5.14% of the total force transmitted depending on the different ankle positions. These observations suggest that more consideration of the loading characteristics of the fibula should be taken into account in planning resection operations.

Biomechanical strength of non-vascularised and vascularised diaphyseal bone transplants. An experimental study

We studied the healing and torsional strength of non-vascularised (28) and vascularised (28) sections of tibial diaphyses in 56 cats. Both types of graft achieved fracture union in the same period of time, and at 12 and 16 weeks the non-vascularised grafts were as strong as the vascularised grafts.

Principles and applications of Computer-Aided Design and Computer-Aided Manufacturing (CAD/CAM) technology in orthopaedics

The principles involved in Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) technology is presented in this article. It also highlights the current advances and capability of this technology. Application of the CAD/CAM technology in orthopaedics is relatively new. Three broad areas of applications can be defined: (1) three-dimensional reconstructions of skeletal structure based on any of the imaging technique, i.e. CT scan, MRI or X-ray, to analyse, simulate, design and evaluate orthopaedic procedures without having to actually perform the surgery; (2) the production of plastic or wax models for surgeons to have global impressions and understanding of complex cases of bone and joint disorders and the possibility of using the physical models as templates to sculpt allograft pre-operatively; and (3) to design and manufacture geometrically optimal standard and customised implants. CAD/CAM technology is also rapidly developing in the field of prosthetics, orthotics and orthopaedics footwear. The advantages offered include shorter delivery time, more consistent design, quantifiable rectification and "modern" or remote manufacturing. Apart from these applied usage, the CAD/CAM technology is also an effective tool for education and training. The application of CAD/CAM technology in orthopaedics and its related fields has been shown to have tremendous potential, but may appear to be too esoteric, complex and costly at the present moment. However, with improved generality, simplicity and cost-effectiveness of the system, it will become more practical.

Donor site morbidity following resection of the fibula

Ten adults were studied two to seven years after resection of a fibula for use as a free vascularised bone graft. Six had no symptoms in the donor leg, four had some aching, weakness or paraesthesia and three had definite weakness of the long toe flexors and extensors. All knees and ankles were clinically and radiologically stable, but the distal fibular remnant was osteoporotic in nine patients. Gait analysis of the donor leg and the contralateral normal leg showed definite differences, which could be attributed to weakness of the deep muscles caused by loss of their normal origin and to the change in load transmission through the fibula.

The effect of submandibular gland removal on testicular and epididymal parameters

The effect of sialoadenectomy (submandibular gland removal) for four weeks duration was studied in five C3H mice and four sham-operated controls. This preliminary experiment using small numbers of animals indicated that sperm production parameters were lowered in sialoadenectomized animals although there were no significant differences between the sialodenectomized and sham-operated group. In a second experiment using larger numbers of animals, significant differences in testicular weights, epididymal weights, and testis weights were noted. These parameters were reduced only 10-14% from control levels. Epididymal sperm head counts were reduced 10% after sialoadenectomy but the two groups were not significantly different (P less than 0.05). No difference in testicular histology was observed. The present report contrasts to that of Tsutsumi et al. (1986) who indicate that submandibular removal with subsequent depletion of epidermal growth factor (EGF), is extremely deleterious (40-55% decreases in spermatid and sperm content) to the progress spermatogenesis.

Biofeedback device for patients on axillary crutches

The axillary crutch is commonly prescribed as an ambulatory aid to patients with temporal or permanent disability in the lower extremity. When fitting the axillary crutch, it is important that the user be instructed not to bear excessive weight on the axillary bar. Excessive weight bearing on the axillary bar can result in a sevenfold increase in the reaction force under the armpit. This force may be a contributory factor to crutch paralysis or thrombosis of the axillobrachial artery. In order to prevent this occurrence an electronic biofeedback device was designed and developed for use in the training of 3-point swing-through axillary crutch ambulation. It detects excessive weight bearing on the axillary bar during crutch ambulation and produces an audible signal which prompts the patient to make necessary adjustment to relieve load bearing on the axillary bar. The design and development of the biofeedback device is discussed in this paper.

Effect of preservation medium on the mechanical properties of cat bones

Mechanical properties of long cat bones after freezing at -20 degrees C and after storage in 10 percent buffered formalin were investigated. The right humeri and femora from 48 adult cats were divided into four groups: Groups 1 and 2 were stored in a freezer at -20 degrees C for 3 and 21 days, respectively, while Groups 3 and 4 were stored in 10 percent buffered formalin for 3 and 21 days, respectively. The control left bones were tested fresh. The humeri were subjected to a torsion test and the femora to a four-point bending test. Freezing had no effect on the mechanical properties evaluated, while formalin storage caused a 50 percent reduction in energy absorption and increased the brittleness of the bones.

Postnatal development of the Sertoli cell barrier, tubular lumen, and cytoskeleton of Sertoli and myoid cells in the rat, and their relationship to tubular fluid secretion and flow

The postnatal development of the Sertoli cell barrier, tubular lumen, fluid flow, and cytoskeletal elements in Sertoli and myoid cells was investigated in the Sprague-Dawley rat. With the aid of hypertonic fixatives, a barrier to the rapid entry of fluid was noted in the majority of tubules on the 15th and 16th postnatal (p.n.) days and was completely formed in all tubules prior to p.n. day 18. The actin forming the ectoplasmic specialization (ES), a cytoskeletal complex related to the occluding junctions composing the barrier, began its development during the period of initial barrier formation (16 p.n. day) and progressively attained its adult prominence. The ES developed its characteristic adult pattern and adult fluorescent intensity at about p.n. day 22. Some seminiferous tubules showed very small lumina as early as p.n. day 10. All tubules were not open until p.n. day 30. The size (diameter) of the lumen increased slowly from p.n. day 10 until p.n. day 30 when it started to increase rapidly until about p.n. day 50. Fluid flow in seminiferous tubules was detected as early as p.n. day 20 and increased in amount thereafter. Myoid cell actin filament bundles, running in parallel, were present at p.n. day 10. Actin formed a meshwork pattern characteristic of the adult on, or slightly prior to, p.n. day 22. These data indicate that there is a temporal relationship between the development of the actin cytoskeleton within the Sertoli cell and initial formation of the Sertoli cell barrier. Similarly, there is a temporal relationship between the development of the actin cytoskeleton of myoid cells and tubular fluid flow. The rapid increase in tubular lumen diameter, however, does not correlate with the initial development of Sertoli and myoid cytoskeletal elements.

The consequences of actin disruption at Sertoli ectoplasmic specialization sites facing spermatids after in vivo exposure of rat testis to cytochalasin D

Cytochalasin D (CD) was used to perturb actin filaments of the Sertoli ectoplasmic specialization (ES)--a cytoskeletal complex of the Sertoli cell related to spermatids. CD (500 microM for 6 h) produced a loss of 88% of the ES facing the head region of early (Step 8) elongating spermatids as compared to vehicle (dimethylsulfoxide:saline) controls. Nitrobenzoxadiazole-phallacidin staining of F-actin revealed a CD-related loss of uniform fluorescence over the head of elongated spermatids. To examine for a possible relationship between the presence of actin and cell attachment at ES sites, hypertonic fixatives were introduced to provoke cell shrinkage and stress ES-associated junctions. After osmotic stress, cell-to-cell adhesion at ES sites remained intact in vehicle-treated animals. CD treatment caused Sertoli cells to separate from elongating spermatids at sites where ES had been lost from the Sertoli cell surface. It is suggested that actin of the ES plays a role in cell-to-cell interaction analogous to its possible role at the Sertoli cell barrier. In CD-treated animals, structures resembling tubulobulbar complexes frequently developed at sites where ES was lost, suggesting that the loss of ES has a facilitatory role in tubulobulbar complex formation. It is hypothesized that tubulobulbar complexes are devices that rid the cells of ES-associated junctional links to effect dissociation of the spermatid from the Sertoli cell during spermiation. Spermatids at Step 8 of development are known to become oriented with their acrosomes facing the base of the Sertoli cell. After CD treatment, a 5.8-fold increase in malorientation of Step 8 spermatids was noted. A role for the ES cytoskeletal complex in orienting the spermatid acrosome toward the basal aspect of the Sertoli cell is also suggested.

Effects of electrical stimulation on the biomechanical properties of fracture healing in rabbits

One hundred fifteen white rabbits with an average weight of 2.0 kg were used to study the influence of electrical stimulation on osteogenesis. They were divided into three groups: Group I was electrically stimulated with a constant direct current of 20 microamperes delivered to the fracture site; Group II was the control group having the same protocol as Group I except that the stimulator was not switched on; and Group III was the normal fracture healing group (no introduction of electrodes to the fracture site). Roentgenologic and histologic assessment showed that new bone formation in the electrical stimulation group was more exuberant than those in the other two groups in observation periods from three to eight weeks. However, at 12 weeks no difference was observed among the three groups. Biomechanical analysis showed definite increases in the breaking strength and bending stiffness of the fracture healing tibia in Group I, especially at six weeks after surgery. However, at 12 weeks no significant difference was observed among the three groups. Therefore, electrical stimulation of fracture healing has a positive effect only at the midphase of the healing process, and it does not lead to faster fracture healing.

Biomechanical study on axillary crutches during single-leg swing-through gait

This paper describes a kinetic and kinematic study on axillary crutches during one-leg swing-through gait. The primary objective is to evaluate the interplay of forces at the crutch and body interfaces and to relate them in the understanding of problems associated with the use of axillary crutches. Ten normal adult male subjects with simulated left leg impairment participated in the study. For data acquisition, the VICON kinematic system, a Kistler force plate and an instrumented crutch (with force transducers at the two upper struts close to the axillary bar and one near the crutch tip) were used. Results showed that the peak ground reaction force on the weight-bearing leg during lower limb stance increased by 21.6 percent bodyweight. The peak reaction force transmitted to the arm during crutch stance was 44.4 percent bodyweight. These increased loadings could be detrimental to patients with unsound weight-bearing leg and upper extremities respectively. When the crutches were used incorrectly, 34 percent bodyweight was carried by the underarm. This could cause undue pressure over the neurovascular structures at the axillary region.

Surface morphology of Asian cadaveric hips

The joint surfaces of 60 hips obtained from the cadavers of elderly Asians were studied to determine the incidence, the grade and the distribution of both non-progressive (age-related) and progressive degenerative changes. It was observed that in the Asian population of 40 to 90 years of age, non-progressive changes were common, being seen in 66% of the acetabular specimens and 50% of the femoral heads. Only one specimen of the 60 showed unexplained progressive degenerative change. We conclude that primary osteoarthritis of the hip is rare in Asians.

Biomechanical evaluation of SACH and uniaxial feet

A review of prosthetic prescription practice reveals that in the United Kingdom about 85% of below and above-knee amputees are fitted with uniaxial feet, whereas in the United States about 80% are fitted with SACH feet. An evaluation method was developed to assess the performance of these two different types of feet. This included a subjective assessment procedure and a biomechanical evaluation of the function of the two feet and their effects on whole body gait kinematics and lower limb kinetics. Data were acquired by three Bolex H16 cine cameras and two Kistler force plates. This set-up allowed three-dimensional analysis on the prosthetic and contralateral sides of the subject. Investigations were undertaken in which an experimental prosthesis permitted the interchange of the ankle/foot while keeping the rest of the components the same. Altogether, six below knee and five above knee amputees were tested. No clear trend for preference for either type of foot was evident from the subjective survey; in general the patients showed a preference for the foot that they were accustomed to. Kinematic and kinetic analysis showed some differences in the function between the two prosthetic feet. It is the purpose of this paper to discuss these differences and their significance.