Recommendations on prevention and screening for colorectal cancer in Hong Kong.

Colorectal cancer is the commonest cancer in Hong Kong. The Cancer Expert Working Group on Cancer Prevention and Screening was established in 2002 under the Cancer Coordinating Committee to review local and international scientific evidence, assess and formulate local recommendations on cancer prevention and screening. At present, the Cancer Expert Working Group recommends that average-risk individuals aged 50 to 75 years and without significant family history consult their doctors to consider screening by: (1) annual or biennial faecal occult blood test, (2) sigmoidoscopy every 5 years, or (3) colonoscopy every 10 years. Increased-risk individuals with significant family history such as those with a first-degree relative diagnosed with colorectal cancer at age ≤60 years; those who have more than one first-degree relative diagnosed with colorectal cancer irrespective of age at diagnosis; or carriers of genetic mutations associated with familial adenomatous polyposis or Lynch syndrome should start colonoscopy screening earlier in life and repeat it at shorter intervals.

Recommendations on prevention and screening for breast cancer in Hong Kong.

In Hong Kong, breast cancer is the most common cancer among women and poses a significant health care burden. The Cancer Expert Working Group on Cancer Prevention and Screening (CEWG) was set up in 2002 by the Cancer Coordinating Committee to review and assess local and international scientific evidence, and to formulate recommendations for cancer prevention and screening. After considering the local epidemiology, emerging scientific evidence, and local and overseas screening practices, the CEWG concluded that it was unclear whether population-based breast cancer screening did more harm than good in local asymptomatic women at average risk. The CEWG considers that there is insufficient evidence to recommend for or against population-based mammography screening for such individuals. Women who consider breast cancer screening should be adequately informed about the benefits and harms. The CEWG recommends that all women adopt primary preventive measures, be breast aware, and seek timely medical attention for suspicious symptoms. For women at high risk of breast cancer, such as carriers of confirmed BRCA1/2 deleterious mutations and those with a family history of breast cancer, the CEWG recommends that they seek doctor's advice for annual mammography screening and the age at which the process should commence. Additional annual screening by magnetic resonance imaging is recommended for confirmed BRCA1/2 mutation carriers or women who have undergone radiation therapy to the chest between the age of 10 and 30 years. Women at moderate risk of breast cancer should discuss with doctors the pros and cons of breast cancer screening before making an informed decision about mammography screening every 2 to 3 years.

Combined phacoemulsification and nonpenetrating deep sclerectomy in the treatment of chronic angle-closure glaucoma with cataract.

PURPOSE: To review the result of nonpenetrating deep sclerectomy (NPDS) combined with phacoemulsification in the treatment of chronic angle-closure glaucoma (CACG) with coexisting cataract. METHODS: This is a retrospective review of 29 eyes of 26 patients who had undergone combined NPDS and phacoemulsification for cataract and CACG between January 2001 and June 2003. The visual acuity, intraocular pressure (IOP), and complications were analyzed. RESULTS: The mean follow-up period was 33.8 months (range 23.3 to 54.0 months). Postoperative visual acuity improved in 21 eyes (72%) and remained the same in 6 eyes (21%). The IOP was reduced significantly from 20.3+/-3.9 mmHg (mean +/- SD) preoperatively to 15.9+/-3.1 mmHg postoperatively at last follow-up visit (p<0.001). The number of antiglaucoma medications was also reduced significantly from 2.9+/-0.8 (mean +/- SD) preoperatively to 1.0+/-1.2 at last follow-up (p<0.001). Fifteen eyes (52%) achieved complete success with IOP < or = 21 mmHg without antiglaucoma medications and 25 eyes (86%) achieved qualified success with IOP < or = 21 mmHg with or without medications at the last follow-up visit. Of the 25 eyes achieving qualified success, 24 (96%) had a reduction in the number of medications. There were 4 failures, defined as uncontrolled IOP requiring further filtering operation or oral drug treatment. Intraoperative complications included one accidental anterior chamber puncture and one iris plug intraoperatively. Postoperative complications included one choroidal effusion, three wound leaks requiring repair, and two punctate epithelial erosions. There was no shallowing of the anterior chamber, hyphema, hypotony, or infection encountered. CONCLUSIONS: Combined NPDS and phacoemulsification could be a safe and effective surgical option for the management of CACG with cataract.

Endocrine cell hyperplasia of the uterine cervix. A precursor of neuroendocrine carcinoma of the cervix?

A 33-year-old woman who presented with vaginal bleeding was diagnosed to have neuroendocrine small cell carcinoma based on cervical smear and biopsy. Hysterectomy was performed, and a tumor measuring 5.5 X 2 mm was found at the squamocolumnar junction of the uterine cervix. In the immediate vicinity of the tumor, there was proliferation of cytologically benign endocrine cells in the normal endocervical glands and in the glands showing intraepithelial glandular neoplasia. Both the hyperplastic endocrine cells and the invasive tumor cells showed argyrophilia and immunostaining for neuron-specific enolase, neurofilament, and chromogranin. The topographical relationship suggests that endocrine cell hyperplasia may represent a precursor of neuroendocrine carcinoma of the cervix.

Comparison of residual stability in thoracolumbar spine fractures using neutral zone measurements.

Because treatment algorithms for spinal injuries depend largely on the clinical assessment of stability after injury, this study both quantified and compared the mechanical stability after three different patterns of injury in the thoracolumbar spine. We created compression fractures, burst fractures, and flexion-distraction injuries in 26 thoracolumbar specimens from human cadavers in order to compare residual stability as a function of type of injury. Spinal stability was evaluated using measurements of the boundaries of the neutral zone, which provide a measure of spinal laxity in various directions of motion. An increase after injury was indicative of greater spinal laxity and hence reduced residual stability. Geometric characteristics (or parameters) of the neutral zone boundaries were used for statistical comparison between the types of injury. Of the three groups, burst fractures retained the least residual stability and compression fractures, the greatest. The angular ranges of motion in the neutral zone for burst fractures demonstrated increases (compared with average values for intact specimens) of 154% in flexion-extension, 134% in lateral bending, and 108% in torsion after injury. The results for flexion-distraction injuries were similar to those for burst fractures in flexion-extension (126%) and torsion (62%); however, more residual stability was retained in lateral bending than was seen for burst fractures (48%). Compression fractures retained the most residual stability, with increases in motion of 40% in flexion-extension, 56% in lateral bending, and 3% in torsion. These findings may be useful in determining the necessity for surgical stabilization of the spine and selection of the appropriate system of fixation.

Subluxation of the talocalcaneal joint in adults who have symptomatic flatfoot.

BACKGROUND: When flatfoot is acquired during adulthood, the shape of the foot changes. In addition to a decreased arch, there may be valgus angulation of the hindfoot or abduction of the forefoot, or both. However, there is little objective information to provide a better understanding of the anatomical or morphological changes that occur in acquired adult flatfoot. We wondered if such an understanding of the three-dimensional anatomy might shed light on the pathway by which these changes occur. We designed this study to measure the three-dimensional position of the talocalcaneal joint in patients who have painful flatfoot. METHODS: Computed tomography scans of the feet of eight patients who had symptomatic flatfoot were used to construct a model of the talocalcaneal articulation. The scans were performed on a custom loading frame developed to simulate weight-bearing with the foot in a neutral position while a seventy-five-newton axial compressive load was applied. The digital data from the scans were used to make three-dimensional computer models of the articular surfaces of the talus and calcaneus of each foot. These models then were used to calculate the percentage of the articular surface that was in contact and, conversely, the percentage that was subluxated. Two surfaces were modeled for each bone; the posterior facet formed one surface, and the anterior and middle facets were combined to form the second surface. The data were compared, with use of Mann-Whitney nonparametric U analysis, with those derived from scans of the feet of four patients without a deformity of the hindfoot who served as controls. RESULTS: A mean (and standard deviation) of 68+/-9 percent of the posterior facet of the calcaneus was in contact with the talus in the patients who had flatfoot compared with 92+/-2 percent in the controls, and a mean of 51+/-23 percent of the anterior and middle facets of the calcaneus was in contact with the talus in the patients who had flatfoot compared with 95+/-6 percent in the controls. These differences were significant (p = 0.0066 for both). CONCLUSIONS: Marked subluxation of the talocalcaneal joint occurs in some patients who have symptomatic planoabductovalgus deformity.

Geometric changes in the cervical spinal canal during impact.

SUMMARY OF BACKGROUND DATA: Although the extent of injury after cervical spine fracture can be visualized by imaging, the deformations that occur in the spinal canal during injury are unknown. STUDY DESIGN: This study compared spinal canal occlusion and axial length changes occurring during a simulated compressive burst fracture with the residual deformations after the injury. METHODS: Canal occlusion was measured from changes in pressure in a flexible tube with fluid flowing through it, placed in the canal space after removal of the cord in cadaver specimens. To measure canal axial length, cables were fixed in C1 and led through the foramen transversarium from C2-T1, then out through the base, where they were connected to the core rods of linearly variable differential transformers (LVDT). Axial compressive burst fractures were created in each of ten cadaveric cervical spine specimens using a drop-weight, while force, distraction, and occlusion were monitored throughout the injury event. Pre- and post-injury radiographs and computed tomography scans compared transient and post-injury spinal canal geometry changes. RESULTS: In all cases, severe compressive injuries were produced. Three had an extension component in addition to compression of the vertebra and retropulsion of bone into the canal. The mean post-injury axial height loss measured from radiographs was only 35% of that measured transiently (3.1 mm post-injury, compared with 8.9 mm measured transiently), indicating significant recovery of axial height after impact. Post-injury and transient height loss were not significantly correlated (r2 = 0.230, P = 0.16) demonstrating that it is not a good measure of the extent of injury. Similarly, mean post injury canal area was 139% of the minimum area measured during impact, indicating recovery of canal space, and post-injury and transient values were not significantly correlated (r2 = 0.272, P = 0.12). Mean post-injury midsagittal diameter was 269% of the minimum transient diameter and showed a weak but significant correlation (r2 = 0.481, P = 0.03). CONCLUSIONS: Two potential spinal cord injury-causing mechanisms in axial bursting injuries of the cervical spine are occlusion and shortening of the canal. Post-injury radiographic measurements significantly underestimate the actual transient injury that occurs during impact.

The effect of post-injury spinal position on canal occlusion in a cervical spine burst fracture model.

STUDY DESIGN: The canal space of burst-fractured, human cervical spine specimens was monitored to determine the extent to which spinal position affected post-injury occlusion. OBJECTIVE: To test the null hypothesis that there is no difference in spinal canal occlusion as a function of spinal positioning for a burst-fractured cervical spine model. SUMMARY OF BACKGROUND DATA: Although previous studies have documented the effect of spinal positioning on canal geometry in intact cadaver spines, to the authors' knowledge, none has examined this relationship specifically in a burst fracture model. METHODS: Eight human cervical spine specimens (levels C1 to T3) were fractured by axial impact, and the resulting burst injuries were documented using post-injury radiographs and computed tomography scans. Canal occlusion was measured using a custom transducer in which water was circulated through a section of flexible tygon tubing that was passed through the spinal canal. Any impingement on the tubing produced a rise in fluid pressure that was monitored with a pressure transducer. Each spine was positioned in flexion, extension, lateral (and off-axis) bending, axial rotation, traction, and compression, while canal occlusion and angular position were monitored. Occlusion values for each position were compared with measurements taken with the spine in neutral position. RESULTS: Compared with neutral position, compression, extension, and extension combined with lateral bending significantly increased canal occlusion, whereas flexion decreased the extent of occlusion. In extension, the observed mechanism of occlusion was ligamentum flavum bulge caused by ligament laxity resulting from reduced vertebral body height. CONCLUSIONS: Increased compression of the spinal cord after injury may lead to more extensive neurologic loss. This study demonstrated that placing a burst-fractured cervical spine into either extension or compression significantly increased canal occlusion as compared with occlusion in a neutral position.

Canal geometry changes associated with axial compressive cervical spine fracture.

STUDY DESIGN: A laboratory study using isolated ligamentous human cadaveric cervical spines to investigate canal occlusion during (transient) and after (steady-state) axial compressive fracture. OBJECTIVES: To determine whether differences exist between transient and postinjury canal occlusion under axial compressive loading, and to examine the effect of loading rate on canal occlusion. SUMMARY OF BACKGROUND DATA: Prior studies have shown no correlation between neurologic deficit and canal occlusion measurements made on radiographs and computed tomography scans. The authors hypothesized that postinjury radiographic assessment does not provide an appreciation for the transient occlusion that occurs during the traumatic fracture event, which may significantly affect the neurologic outcome. METHODS: Twelve human cervical spines were instrumented with a specially designed canal occlusion transducer, which dynamically monitored canal occlusion during axial compressive impact. Six specimens were subjected to a fast-loading rate (time to peak load, approximately 20 msec), and the other six were subjected to a slow-loading rate (time to peak load, approximately 250 msec). After impact, two different postinjury canal occlusion measurements were performed. RESULTS: Each of the six specimens subjected to the fast-loading rate incurred burst fractures, whereas the slow-loading rate produced six wedge-compression fractures. For the fast-rate group, the postinjury occlusion-measurements were significantly smaller than the transient occlusion. In contrast, transient occlusion was not found to be significantly different from postinjury occlusion in the slow-rate group. All of the comparisons between loading rate groups showed significant differences, with the fast-rate fractures producing larger amounts of canal occlusion in every category. CONCLUSIONS: The findings indicate that even if canal occlusion could be measured immediately after axial compressive trauma, the measurement would underestimate the maximal amount of transient canal occlusion. Therefore, postinjury measurement of canal occlusion may indicate a smaller degree of neurologic deficit than what might be expected if the transient occlusion could be measured.

Mechanism of the burst fracture in the thoracolumbar spine. The effect of loading rate.

STUDY DESIGN: Calf lumbar spine motion segments were randomly assigned to two groups. After insertion of a transducer capable of measuring transient occlusion of the spinal canal during impact, a low rate axial impact was applied in one group and a high rate load in the other. Post-injury computed tomography scans and peak canal occlusions were measured to determine the effect of rate of load application on occlusion of the spinal canal. OBJECTIVES: This study was designed to determine if for the same direction of impact and total energy delivered, occlusion of the spinal canal postvertebral fracture was related to the rate at which the impact was delivered (time from zero to peak load). SUMMARY OF BACKGROUND DATA: Several reports based on clinical observations have hypothesized that axial burst fractures, which displace bone fragments into the canal, occur because of internal pressurization and explosion of the vertebral body. The extent of bursting of the vertebra may depend on the rate of pressurization of the body, which could be related to the rate at which the load is applied. METHOD: Using calf lumbar spines, a transducer was placed within the spinal canal, after removal of the cord, to measure canal occlusion during impact. One group received axial compressive impacts at a mean loading rate of 400 msec (zero to peak load) using a materials-testing machine. The energy of failure was determined and used to select a drop weight and distance for the high loading rate tests, which would yield equivalent impact energy. The second group received impacts at a loading rate of of 20 msec. The post-injury radiographs and canal occlusion measurements were compared. RESULTS: The same mean energy of impact was used in the fractures for both groups. Post-injury radiographs of the low loading rate group showed compressive fractures with a mean canal occlusion of 6.84%, whereas the high loading rate group had burst fractures with mean canal encroachment of 47.6% (P = 0.0007). CONCLUSIONS: For the same energy and direction of impact, a high impact loading rate produces fractures with significant canal encroachment, whereas minimal encroachment is seen for fractures produced at a low loading rate.

Compartmentation of glycogen metabolism in the liver.

The incorporation of radioactivity into liver glycogen has been shown not only to be a metabolically inhomogeneous process but also to depend critically on the nature of the precursor. D-Galactose is incorporated into glycogen by a mechanism which is separate from that associated with the incorporation of D-glucose. D-Galactose is favoured for incorporation into high-molecular-weight glycogen and consequently is affected more by treatment of the animal with the antibiotic tunicamycin, since high-molecular-weight glycogen is preferentially found in the lysosomal compartment.

Joint motion and surface contact area related to component position in total hip arthroplasty.

A three-dimensional computer model of a total hip replacement was used to examine the relationship between the position of the components, the range of motion and the prosthetic joint contact area. Horizontal acetabular positions with small amounts of acetabular and femoral anteversion provide the largest contact areas, but result in limited joint movement. These data will allow surgeons to select implant positions that will provide the largest possible joint contact area for a given joint range of motion although these are conflicting goals. In some component positions a truncated spherical prosthetic head resulted in smaller contact areas than a completely spherical head.

Damage to bicycle helmets involved with crashes.

The objective was to evaluate the relationship between helmet damage and head injuries in helmeted bicyclists in a sub-study of a large case-control study of bicycle injuries and helmet effectiveness. The setting consisted of seven hospital emergency departments in Seattle, WA. Hospitalized patients and medical examiners cases were included. The participants in the study were helmeted bicyclists who suffered a head injury or who damaged or hit their helmet in a crash. The Snell Memorial Foundation laboratory evaluated the helmets, blinded to crash circumstance and injury diagnosis. Damage was scored on a five-point scale (0 = none to 4 = destroyed). The damage location for each helmet was coded into regions (six longitudinal and three latitudinal) and mapped onto a three-dimensional CAD (computer-aided design) model of a helmet. The same procedure was also followed for injury location, which was mapped onto a three-dimensional ISO (International Organization for Standardization) headform for visualization of head-injury distribution. 785 helmeted subjects met the criteria for inclusion in the sub-study, and 527 helmets were purchased and evaluated (67%). 316 (60%) of the helmets had no or minimal damage, and 209 (39.7%) had significant damage (score 2, 3 or 4). Helmet types were 49.7% hard shell, 34.2% thin shell and 16.1% no shell. The risk of head and brain injury increased if the helmet was destroyed: OR = 5.3 (95% CI 2.9, 9.9) and OR = 11.2 (95% CI 3.5, 37.9), respectively. A high proportion of helmet impacts were along the front edge of the helmet, with a preponderance of head injuries in the same region. The large number of impacts to the front rim of the helmet, combined with the substantial number of riders with injuries to the forehead, indicate that some helmets, because of poor fit or wearing style, expose the forehead to injury. In addition, the data indicate that for a small proportion of injuries, the energy to the helmet may exceed design limits.

Relationship of mechanical factors to the strength of proximal femur fractures fixed with cancellous screws.

The decision of whether to attempt screw fixation of a femoral neck fracture is based partly on the estimated strength of the fixed bone/implant construct in relation to the loads it will be required to bear. The goal of this study was to determine in vitro the relation of the following biomechanical factors to the strength of internally fixed femoral neck fractures subjected to cyclic and failure loading: (a) square of the density of cancellous bone in the femoral head, (b) percent comminution of the inferior fracture surface, (c) moment arm of the joint force, or distance from the axis of the joint force to the fracture surface, and (d) orientation angle of the fracture surface in the medial/lateral plane relative to the axis of the femoral shaft. Femoral neck fractures were created in each of 38 fresh cadaveric proximal femora using a dropweight or with a materials testing machine. After sustaining a displaced fracture, fixation was achieved using three cannulated cancellous bone screws. The fixed femur was then subjected to 10,000 cycles of a sinusoidially varying load acting on the femoral head, parallel to the femoral shaft, with an initial peak magnitude of 2.2 times body weight, while the hip was flexed, extended, and rotated to mimic some motions of gait. Muscle loading was not simulated. The magnitude of the peak load decreased as the femoral head displaced during cycling. The mean of the peak load for each cycle over the duration of the test was defined as the average load. Following cycling, the bone/screw construct was loaded to failure in the same direction, and this measurement was termed the maximum load. Average and maximum load were then correlated to the four biomechanical factors using a multiple regression analysis. These factors correlated to a high degree with average force (R2 = 0.771; p < 0.0001) and to a lesser but still significant degree with maximum force (R2 = 0.458; p = 0.012), demonstrating that they can be used to estimate the strength of fixation under these loading conditions. The strongest correlation for average force was with fracture angle (p = 0.005) and for failure force was with moment arm length (p = 0.072).

Glenohumeral kinematics and capsulo-ligamentous strain resulting from laxity exams.

OBJECTIVE: Identification and quantification of strain in shoulder capsular-ligamentous structures during clinical exams and validation of this testing on cadavers. METHODS: Mercury strain gauges were sutured in seven locations on shoulders from cadavers. An electromagnetic tracker quantified humeral head translations during laxity exams. Strain and humeral position were acquired during performance of Sulcus, Feagin, Apprehension, Load and Shift, Drawer, and Hawkins tests. RESULTS: Anterior humeral head translation in neutral position was primarily constrained by the coracohumeral ligament. With the arm abducted, anterior middle and inferior ligaments also became active. External rotation and abduction activated inferior and middle capsules. Posterior capsule constrained motion for posterior tests in neutral and abduction. Superior and inferior capsular ligaments were active during inferior tests in neutral position. With abduction, inferior ligaments provided primary translation constraint. CONCLUSION: Study of kinematics and strain evaluation on cadavers can yield useful information on mechanisms of glenohumeral instability. Relevance This study clarifies the contribution of specific structures of the shoulder to strain in the joint capsule. It also identifies which structures are challenged by provocative laxity exams commonly used by orthopaedic physicians.

The effect of posterior tibial tendon dysfunction on hindfoot kinematics.

This biomechanical study investigated the functional role of the posterior tibial tendon (PTT) in acquired flatfoot mechanics. Acquired flatfoot deformity has been attributed to PTT dysfunction; however, the progression from acute dysfunction to end-stage deformity has not been fully demonstrated. Eight human cadaver lower leg and foot specimens were used in two phases of experimental testing. In Phase 1, intact (normal) specimens were loaded to simulate (a) heel strike, (b) stance, and (c) heel rise both with and without PTT function. Then, each specimen was subjected to a procedure designed to create a simulated flatfoot deformity. The resulting flattened feet were used in Phase 2 to examine the effect of restoring PTT function to a flatfoot model. During both phases of testing, the 3-D kinematic orientation of the hindfoot complex was recorded. Small but statistically significant changes in the angular orientation of the hindfoot complex were observed, during both Phase 1 and 2 testing, when comparing the effects of a functional and dysfunctional PTT. The greatest angular changes were recorded during heel rise. For the normal foot, the small changes observed in the orientation of the hindfoot complex following release of the PTT load suggest that the intact osteo-ligamentous structure of the hindfoot is initially able to maintain normal alignment following acute PTT dysfunction. Once the soft tissues have been weakened, as in our flatfoot model, the PTT had little effect in overcoming the soft tissue laxity to correct the position of the foot.

Effect of variations in calcaneocuboid fusion technique on kinematics of the normal hindfoot.

Calcaneocuboid fusion with lengthening of the lateral column of the foot has been advocated as a method of treating flatfoot deformity. This study was designed to determine how the length of the lateral column chosen or the position of the foot selected when performing this fusion affect hindfoot kinematics in normal cadaver feet. An electromagnetic tracking system was used to monitor the positions of the talus, calcaneus, navicular, and cuboid while the intact cadaver feet were moved passively and then under reproducible loads. Calcaneocuboid fusion was then performed on these feet first with the feet in neutral position and the lateral column of normal length, then lengthened 10 mm or shortened 5 mm, and then with the lateral column lengthened 10 mm and the feet positioned in plantar flexion and eversion or dorsiflexion and inversion. Kinematic measurements were made at each stage using the same loads. Fusing the calcaneocuboid joint with lengthening or shortening the lateral column and the feet in neutral position did not affect hindfoot joint motion compared with intact. Changing the position of the foot for fusion, however, resulted in significant decreases in motion in the talocalcaneal and talonavicular joints. Tibiotalar joint motion was unaffected. This study, therefore, demonstrates that when fusing the calcaneocuboid joint, attention should be paid to maintaining a neutral position of the foot.

Alterations in talar morphology associated with adult flatfoot.

To gain a better understanding on the anatomy of the factors contributing to symptomatic flatfoot, we compared the shape of the talus in feet that were flat to that in control tali from feet with a normal arch. Computed tomographic (CT) scans were performed on 9 adult patients with 10 symptomatic flatfoot deformities. CT scans of 10 feet being evaluated for acute trauma not involving the talus were randomly selected as controls. Flatfoot tali tended to be of greater overall length than the control tali, and this difference was not statistically significant. Statistically significant differences were found when comparing ratios of talar length with talar width (P = 0.011), talar length with talar height (P = 0.001) (they were long relative to their height and width), and head length with head width (P = 0.001) for individual tali from the two groups. The tali from the flatfoot group were narrower in width and shorter in height when compared with overall length and had heads that were more elongated in the transverse plane than tali in feet with a normal appearance. CLINICAL CORRELATION: When performing surgical correction of a flatfoot in an adult, appearance of the foot rather than standard radiographic parameters should be used to judge the reduction. The altered shape of the bone may alter the standard radiographic parameters.