Normal stress pattern of the pubic symphysis.

THE PELVIC RING IS STRESSED BY EXTERNAL FORCES: by partial body weight, by ligament tension, and by muscles forces stabilizing the hip joints. For the symphysis ossis pubis there exist data concerning the type and magnitude of stresses. In one-leg-standing pressure, shear forces are predominant, and in both-leg-standing tensile forces are acting on the pelvic ring. Rupture of the symphysis is problematic due to the variety of its movements. Most literature descriptions of stress in the symphysis reflect only the frontal plane. Our intention was to make morphological as well as experimental investigations on the symphysis ossis pubis to delineate how it will be stressed in the horizontal plane. Twenty pubic bones taken from embalmed adult human cadavers (12 male, 8 female) were used. Horizontal and frontal slices (3 mm thick) of the symphyseal part of the os pubis were made. X-rays and densitometric analysis were performed. The width of the symphysis cartilage in the dorsal and the ventral regions was measured on 15 whole skeleton specimens coming from adult human cadavers. For experimental study an embalmed pelvic ring which had no abnormality was used. The symphysis pubis was cut completely in the midsagittal plane and then the ring was stressed via the cranial sacrum. Our results demonstrate that the symphysis is stressed by bending in the horizontal plane in one-leg-standing. In both-leg-standing the symphysis is stressed by tensile forces.

Anatomical variations between the sciatic nerve and the piriformis muscle: a contribution to surgical anatomy in piriformis syndrome.

PURPOSE: To detect the variable relationship between sciatic nerve and piriformis muscle and make surgeons aware of certain anatomical features of each variation that may be useful for the surgical treatment of the piriformis syndrome. METHODS: The gluteal region of 147 Caucasian cadavers (294 limbs) was dissected. The anatomical relationship between the sciatic nerve and the piriformis muscle was recorded and classified according to the Beaton and Anson classification. The literature was reviewed to summarize the incidence of each variation. RESULTS: The sciatic nerve and piriformis muscle relationship followed the typical anatomical pattern in 275 limbs (93.6 %). In 12 limbs (4.1 %) the common peroneal nerve passed through and the tibial nerve below a double piriformis. In one limb (0.3 %) the common peroneal nerve coursed superior and the tibial nerve below the piriformis. In one limb (0.3 %) both nerves penetrated the piriformis. In one limb (0.3 %) both nerves passed above the piriformis. Four limbs (1.4 %) presented non-classified anatomical variations. When a double piriformis muscle was present, two different arrangements of the two heads were observed. CONCLUSIONS: Anatomical variations of the sciatic nerve around the piriformis muscle were present in 6.4 % of the limbs examined. When dissection of the entire piriformis is necessary for adequate sciatic nerve decompression, the surgeon should explore for the possible existence of a second tendon, which may be found either inferior or deep to the first one. Some rare, unclassified variations of the sciatic nerve should be expected during surgical intervention of the region.

Does the hypopharyngeal cavernous body protect the development of Zenker's diverticulum?

OBJECTIVE: The aim of this study was to examine the morphology of the cavernous body at the pharyngoesophageal segment. METHODS: In 47 cadavers the submucosal vascular plexus of the pharyngoesophageal segment and the cricopharyngeal muscle were examined. RESULTS: A vascular plexus which was macroscopically non visible or slightly identified was observed in the majority of the specimens (28 or 59.6%). Fourteen of the cadavers (29.8%) exhibited macroscopically lightly observable blood vessels which were covering a discontinuous area of the hypopharyngeal wall. In the other five specimens (10.6%) the vascular plexus was covering a large part of the dorsal wall of the pharyngoesophageal segment as a compact mass. The grade of dilation of the vascular plexus corresponded to the degree of protrusion of the cricopharyngeal muscle. CONCLUSIONS: In the case of a persistent constricted cricopharyngeal muscle, the dilation of the hypopharyngeal cavernous body may protect from developing a Zenker's diverticulum by reinforcing the Killian's dehiscence.

The interspinous spacer: a clinicoanatomical investigation using plastination.

Purpose. The relatively new and less-invasive therapeutic alternative "interspinous process decompression device (IPD)" is expected to result in improved symptoms of neurogenic intermittent claudication (NIC) caused by lumbar spinal stenosis. The aim of the study was to analyze IPD position particularly regarding damage originating from surgical implantation. Methods. Anatomic assessments were performed on a fresh human cadaver. For the anatomic examination, the lumbar spine was plastinated after implantation of the IPDs. After radiographic control, serial 4 mm thick sections of the block plastinate were cut in the sagittal (L1-L3) and horizontal (L3-L5) planes. The macroanatomical positioning of the implants was then analyzed. The insertion procedure caused only little injury to osteoligamentous or muscular structures. The supraspinous ligament was completely intact, and the interspinous ligaments were not torn as was initially presupposed. No osseous changes at the spinal processes were apparent. Contact of the IPD with the spinous processes was visible, so that sufficient biomechanical limitation of the spinal extension seems likely. Conclusions. Minimally invasive IPD implantation with accurate positioning in the anterior portion of the interspinous place is possible without severe surgical trauma.

Morphology of the first metatarsal head and hallux rigidus: a cadaveric study.

PURPOSE: Treatment options for hallux rigidus include several conservative and surgical measures. The aetiology leading to the disease has not sufficiently been examined so far. MATERIALS AND METHODS: We analysed the anatomical configuration of the first metatarsal head of 120 metatarsal bones of different collectives aiming to find a possible correlation between the geometry of the first metatarsophalangeal joint and manifestation of hallux rigidus. Wet human cadaveric specimens and macerated dry specimens served as material. The relevant parameters used for analysis were an axis running through the metatarsal head, the anatomical longitudinal axis, and the radius of curvature of the first metatarsal bone. RESULTS: A significant difference was found in the radius of curvature of osteoarthritic and healthy subjects. Using the binary logistic regression, we were able to predict the probability of an occurrence of hallux rigidus in dependence of the radius of curvature. Furthermore, we were enabled to calculate a correct prediction for the appearance of osteoarthritis in 85 % of the healthy subjects, and 73 % of the osteoarthritic subjects. CONCLUSIONS: A consolidated view of the factors indicates that persons with a high risk for the appearance of hallux rigidus should be identified by measuring the radius of curvature in conventional radiographs and preventive measures to postpone the occurrence of clinically relevant hallux rigidus considered.

Topographic description of an alternative insertion technique for percutaneous approach of cricopharyngeus muscle electromyography: a cadaveric and clinical study.

BACKGROUND: Cricopharyngeus is the only muscle for which electromyography is used in the differential diagnosis of swallowing disorders. Because of some practical difficulties, electrophysiologic tests for this muscle are not performed routinely. Thus we aimed to describe an alternative topographic way to reach the muscle easily. METHODS: On 10 cadavers, a spinal needle (20 G) and on 37 patients a concentric needle electrode (26 G) were used. The needle was inserted percutaneous at the level of the superior border of the cricoid cartilage, anterior to the anterior border of the sternocleidomastoid muscle at 60 degrees angle to the frontal plane in the posteromedial direction. RESULTS: We reached the muscle in all cadavers. In all of the patients, the needle entered the muscle on the first attempt; that was confirmed by electromyographic responses. CONCLUSION: Our results show that this method can be useful for the practical application of cricopharyngeus muscle electromyography.

The cadaver of a Caucasian man with a supernumerary fourth dorsal interosseous muscle in the right hand: a case report.

INTRODUCTION: The human hand is a complex anatomic entity consisting of many muscles, nerves, and vessels, thus providing a special ability to perform accurate and meticulous movements. In this group of muscles are the four dorsal interosseous muscles. CASE PRESENTATION: A distinct supernumerary fourth dorsal interosseous muscle was found in the right hand of the cadaver of a 76-year-old Caucasian man without any other concomitant abnormality. CONCLUSIONS: The presence of such an additional muscle in the hand should be considered in the management of hand deformities, whether the treatment is conservative or surgical.

The relationship between the medial collateral ligament and the medial meniscus: a topographical and biomechanical study.

The functional influence of the medial collateral ligament on the medial meniscus is still discussed controversially. Commonly, a strong fixation of the meniscus by the collateral ligament is described. Injury to the medial meniscus is explained by its reduced mobility due to its strong adherence to the medial collateral ligament. The analysis of 10 plastinated series of the medial femorotibial compartment prove that only few fibres of the ligament radiate into the meniscus. To define the possible contribution of these fibers to the stability of the medial meniscus, experiments on two fresh frozen knee joints were performed. The distal femur was separated by cutting the capsule. The medial collateral ligament was detached carefully from its femoral insertion. The tibial head with both menisci was fixed in a clamping system. A translucent, exact acrylic glass copy of the femoral component to which the medial collateral ligament was reinserted, allowed studying the behaviour of the medial meniscus under axial compression (500 N). Firstly, stress was applied while the collateral ligament was proximally fixed and under tension; then the same experiment was performed after femoral detachment of collateral ligament. All plastinated series revealed only some deep and tender fibrous bundles of the medial collateral ligament radiating into the medial meniscus proximally and posteriorly. The behaviour of medial meniscus was exactly the same in both stress experiment series. The conclusion is that there is no relevant influence of the medial collateral ligament on the stability of the medial meniscus.

In vitro comparison of the pullout strength of 3 anterior double-screw fixation techniques with different screw angulations.

OBJECT: The pullout resistance of double-screw fixation systems in anterior spine surgery has been shown to be dependent on screw length as well as on screw angulation. The objective of the study was to evaluate the pullout strength of anterior double-screw systems with different angulations. METHODS: The authors conducted a comparative pullout test of converging, parallel, and diverging angulations of double-screw systems in human cadavers. Twenty-four human vertebral bodies from T-11 to L-1 were harvested from 8 donors, dissected from surrounding tissue, and matched to 3 different fixation groups. Three systems were tested: VentroFix, with near parallel screw direction; the Hopf Anterior Fixation System (HAFS), with converging screw angulation; and the ART anterior system, with diverging screw angulation. RESULTS: The mean (± SD) pullout strength of the VentroFix system was 699 ± 214 N, whereas the HAFS resisted to 591 ± 372 N. The ART anterior system with diverging screws demonstrated a pullout resistance of 810 ± 273 N. There was no significant difference amongst the pullout forces of the 3 groups (p > 0.05). In the HAFS and the ART anterior group, a weak correlation of pullout strength and bone mineral density measured by quantitative CT was found (r = 0.59 and r = 0.62, respectively), whereas the pullout force of the VentroFix system was not correlated with bone mineral density (r = 0.33). CONCLUSIONS: The in vitro pullout resistance of anterior double-screw systems does not appear to depend on screw angulation.

Influence of cementing the pin on resistance to fracture in hip resurfacing.

BACKGROUND: Since the introduction of modern hip resurfacing systems, there has been a controversy regarding the fixation of the centering pin in the femoral component. It has been suggested that cementing the pin may increase strength of the femoral neck. This in-vitro analysis investigated the influence of a cemented, femoral pin on resistance to fracture in the resurfaced hip. METHODS: Five pairs of cadaveric, fresh-frozen femora underwent hip resurfacing (ASR™) using a high viscosity cementing technique. In one side of each pair only the inner surface of the implant was cemented, in the other side, cement was additionally hand-pressurized down the pinhole prior to implantation of the femoral component. Specimen were then mounted on a material testing machine and cyclic loading with increasing load steps was applied until fracture of the femoral neck. FINDINGS: Fracture load was increased (P = 0.013) in the cemented pin group (Median = 4200 N) when compared with the cementless pin group (Median = 2800 N). The number of cycles to failure in the group with the cemented pin (Median = 8072) was likewise higher (P = 0.01) when compared to the group, in which the pin was not cemented (Median = 5906). INTERPRETATION: Cementing the pin may provide additional fixation in hips with low bone mineral density or osteonecrotic lesions, as resistance to fracture could be improved in the presented in-vitro scenario. Although this was shown for a specific hip resurfacing system, this effect might be extrapolated to other, similar implant designs.

Human knee joint anatomy revisited: morphometry in the light of sex-specific total knee arthroplasty.

This study investigates differences in the anatomy of male and female knee joints to contribute to the current debate on sex-specific total knee implants. Morphometric data were obtained from 60 human cadaver knees, and sex differences were calculated. All data were corrected for height, and male and female specimens presenting with an identical length of the femur were analyzed as matched pairs. Male linear knee joint dimensions were significantly larger when compared with females. When corrected for differences in height, medial-lateral dimensions of male knees were significantly larger than female; however, matched paired analysis did not prove these differences to be consistent. Although implant design should focus interindividual variations in knee joint anatomy, our data do not support the concept of a female-specific implant design.

In-vitro comparison of the pullout strength of 3 different thoracic screw fixation techniques.

SUMMARY OF BACKGROUND DATA: Dvorak et al in 1993 and Husted et al in 2003 reported 2 different screw fixation techniques at the thoracic spine as alternatives to transpedicular screws. So far, there is no investigation comparing the pullout stability of all 3 possible screw fixation techniques. OBJECTIVE: To evaluate the stability of possible alternatives for transpedicular screw fixation. STUDY DESIGN: A biomechanical human cadaver investigation of the transpedicular and 2 different extrapedicular techniques was performed in the form of a comparative pullout test. MATERIALS AND METHODS: Eighteen human vertebral bodies from Th7 to Th9 were harvested from 6 donors, dissected from surrounding tissue, and matched to 3 different fixation groups. As alternatives for transpedicular screw fixation, an extrapedicular supratransverse screw insertion from posterolateral and a tricortical screw fixation technique, penetrating the transverse process and reentering the vertebral body at the pedicle base were evaluated biomechanically. A unilateral screw fixation was performed in one of the described techniques. Axial pullout strength was measured using a Zwick Z50 servoelectric testing machine. RESULTS: The average pullout strength of the pedicle screws was 400 N, whereas the supratransverse and the pertransverse screw fixation resisted 370 N pullout force on average. There was neither a statistic significant difference between the pullout forces of the 3 groups nor a significant correlation of pullout strength and bone mineral density measured by quantitative computed tomography. CONCLUSIONS: In-vitro pullout resistance of thoracic screw fixation does not differ significantly in intrapedicular and extrapedicular insertion techniques.

Nasal, sellar, and sphenoid sinus measurements in relation to pituitary surgery.

A study of 24 adult Caucasian cadavers was undertaken to assess and document the anatomical measurements within the nasal cavity and sphenoid sinus as routes of instrumentation utilized in sublabial transsphenoidal and endonasal endoscopic approaches. Five measurements were performed. The mean thickness of the anterior sellar wall was 0.8 +/- 0.3 mm for both the sellar and presellar types of sinuses, respectively. Also, the mean thickness of the bony floor of the sellar type of sinus was 0.9 +/- 0.4 mm. In addition, the mean depth of the sphenoid sinus was 13.6 +/- 5.1 mm for the sellar type and 13.2 +/- 3.9 mm for the presellar type of sinus. Furthermore, the mean distance between the suspinale (inferior-posterior edge of the anterior nasal spine) and the anterior sphenoid wall was 62.3 +/- 4.6 mm for the sellar type of sinus (P < 0.05) and 60.6 +/- 2.9 mm for the presellar type of sinus, while the distance between the subspinale and the anterior sellar wall had a mean value of 75.9 +/- 6.3 mm for the sellar type of sinus (P < 0.05) and 73.8 +/- 4.2 mm for the presellar type of sinus, with the distance of the sellar type sinus being greater for male specimens. Sphenoid sinus pneumatization was of a conchal type in 4%, presellar type in 28%, and sellar type in 68% of subjects examined. The results of the current study expand upon current anatomical knowledge and may be beneficial in the future refinement of surgical instrument design.

Morphometric and anthropometric analysis of Killian's triangle.

OBJECTIVES/HYPOTHESIS: To determine the prevalence and the morphometric characteristics of Killian's triangle and to examine their relationship with the anthropometric features of the person. STUDY DESIGN: Prospective. METHODS: The hypopharyngeal wall was examined on 47 human cadavers. After a standardized method of dissection, the muscular structures of the hypopharyngeal wall were demonstrated and the existence or absence of Killian's triangle was determined. The triangle was examined in regard to its morphometric characteristics. In addition, anthropometric examinations of the whole body and of the head and neck regions on these cadavers were done, and the results were compared with the features of Killian's dehiscence. RESULTS: A triangle of Killian was present on 60% (9/15) of the males and on 34% (11/32) of the females. The mean height for the males was 7 mm and for the females 4 mm, and the width was on average 16 mm and 12 mm, respectively. The dimensions of the triangle were correlated significantly with the dimensions of the body and with the length and the descensus of the larynx. CONCLUSIONS: The frequency and the dimensions of Killian's triangle appear to be greater in males than in females. Furthermore, the morphometric characteristics of the dehiscence show a correlation with the anthropometric features of the person. These findings can be an explanation for the higher incidence of Zenker's diverticulum with men and for the geographical differences of the diverticulum's frequency.

Arterial anatomy of the hallucal sesamoids.

The aim of this study was to analyze the arterial supply of the sesamoid bones of the hallux. Twenty-two feet from adult cadavers were injected with epoxide resin or an acrylic polymer in methyl methacrylate (Acrifix) and subsequently processed by two slice plastination methods and the enzyme maceration technique. Afterwards, the arterial supply of the sesamoid bones was studied. The first plantar metatarsal artery provided a medial branch to the medial sesamoid bone. The main branch of the first plantar metatarsal artery continued its course distally along the lateral side of the lateral sesamoid and supplied it. The supplying arteries penetrated the sesamoid bones on the proximal, plantar, and distal sides. The analysis and cataloging of the microvascular anatomy of the sesamoids revealed the first plantar metatarsal artery as the main arterial source to the medial and lateral sesamoid bones. In addition, the first plantar metatarsal artery ran along the lateral plantar side of the lateral sesamoid bone, suggesting that this artery is at increased risk during soft-tissue procedures such as hallux valgus surgery.

Olecranon fracture fixation with a new implant: biomechanical and clinical considerations.

UNLABELLED: This study aims to describe the first clinical results in the treatment of dislocated olecranon fractures with 2.2-mm, fine-threaded wires with a washer. Furthermore, in the second part of the article, the stability of these new implants has been compared to standard tension band wiring in a sawbone model. PATIENTS: The radiological and clinical outcomes in 24 patients (mean age: 53.6 years) with 24 isolated Mayo type I and II fractures of the olecranon were evaluated in a prospective study after open reduction and internal fixation (ORIF) with a new fixation device (FFS; Orthofix). The quality of reduction with the implementation of 24 FFS constructions was compared with 24 tension band-wiring procedures performed by six different surgeons in a standard sawbone Mayo type IIa fracture model. Stability was tested in all constructs using a single cycle load to failure protocol (group I), cyclic loading for 300 cycles between 10 and 500 N (group II) and incremental sinusoidal loading from 10 to 200 N with an incremental increase of 10 N per cycle (group III) in a laboratory study. RESULTS: The Morrey elbow score was excellent in 23 patients and good in one patient, with mean DASH score of 1.6. No implant migration, secondary dislocation or nonunion was observed. In the sawbone model, the quality of reduction was the same with the FFS implants compared to the tension band wiring in the sawbone model. Here, bending moments in all three groups showed no significant difference, whereas displacement at failure was significantly greater in the tension band-wiring group at a single cycle load (p=0.017). CONCLUSION: Clinical results were comparable to tension band wiring and stability of the implants in the sawbone model was the same; thus, we conclude that the FFS technique can serve as an alternative treatment option for isolated olecranon fractures.

Anatomy of the clavicle and the intramedullary nailing of midclavicular fractures.

Intramedullary fixation is used increasingly to treat clavicular fractures. Anatomical variations in the clavicle of relevance to this procedure are analyzed. The length, diameters and curvature of the clavicle were measured in 196 specimens from the dissecting room. The calcium bone density was analyzed in 300 cross-sectional samples of 100 specimens. The thickness of cortical and medullary bone of 70 slices was analyzed from freshly plastinated clavicles with implants in place. The female clavicle was shorter, less curved, and had a lower concentration of calcium than the male clavicle. Measurement of cortical thickness showed a mean value of 1.05 +/- 0.23 mm at the most sternal measuring point, 2.05 +/- 0.29 mm at the midpoint of the clavicle, and 0.95 +/- 0.35 mm at the acromial end. The thinnest regions were the medial ventral cortex and the dorsal acromial cortex. These measurements explain clinical observations on nail perforation. The diameter of the medullary canal measured 6.7 +/- 2.6 mm at its narrowest part, so that reaming (i.e., predrilling the medullary canal) prior to 3.5 mm titanium nail insertion is not necessary. The main difficulties encountered when placing a nail are secondary to the S-curvature of the clavicle. In 80% of fractures, the break is located at the narrowest diameter of the medullary canal. Thus, the clavicle displays definite gender- and side-specific anatomical features in terms of length, diameter, curvature, and calcium concentration. These should be considered when performing intramedullary fixation.

Malunion of the clavicle causes significant glenoid malposition: a quantitative anatomic investigation.

OBJECTIVE: An experimental cadaver model was used to assess the effects of a malunited fracture of the middle third of the clavicle on the functional anatomy of the shoulder joint. METHOD: Anatomic samples were prepared with simulated shortening and axial malposition of the clavicle. From these, alterations in glenoid fossa position were measured and depicted graphically. RESULTS: Healing of clavicle fractures with bony shortening leads to a ventromedialcaudal shift in glenoid fossa position. The following malpositions of the clavicle lead to the respective glenoid fossa positional changes: caudal deviation leads to a mediocaudal shift, cranial deviation leads to a dorsolateral shift of the glenoid fossa, ventral deviation causes a ventrolateral shift, dorsal deviation leads to mediocaudal shift of the fossa, cranial rotation leads to ventrolateral shift in fossa position, and caudal rotation leads to a dorsomedial shift in glenoid fossa position. CONCLUSION: Clinical implication of these data is that bony shortening in combination with caudal displacement leads to distinct functional deficits in abduction, particularly overhead motion. Using the above data, a vector model was created to calculate position of the glenoid fossa dependent on clavicle position/malposition. The model is a valuable tool to be used for planning open reduction and fixation of clavicular fractures or malunions.

Morphometric side-to-side differences in human cruciate ligament insertions.

Graft placement in cruciate ligament reconstruction is known to significantly influence postoperative knee stability and range of motion. Improvement of bone tunnel positioning has been advocated by computer-assisted surgical procedures that require reliable input and reference data. This study validates the hypothesis that morphometric reference data can be obtained from the uninjured controlateral knee for accurate bone tunnel and graft positioning. Thirty pairs of human cadaver knees were dissected and the femoral and tibial footprints of the anterior and posterior cruciate ligaments (PCL) were radiopaquely marked. Radiographs were taken of the corresponding left- and right-sided femora and tibiae, and digitally processed. Controlateral specimens were mirrored and overlapped precisely, the areas and intersections of ligament insertion were digitally determined. There were no significant differences in the total area of cruciate ligament insertion between left and right knee specimens or between female and male specimens. Intersection areas (IAs) in femoral and tibial anterior cruciate ligament (ACL) insertions averaged 31.3 and 33.4% of the total insertion area, respectively. The center of gravity for the femoral and tibial ACL footprint differed by 4.7 and 4.5 mm between left and right knees, respectively. IAs in femoral and tibial PCL insertions averaged 46.1 and 61.3% of the total insertion area, respectively. The center of gravity for the femoral and tibial PCL footprint differed by 4.5 and 2.4 mm between left and right knees, respectively. Our study does not support the concept of obtaining morphologic reference data from the uninjured controlateral knee for individual bone tunnel placement.