Long-term results of total joint arthroplasty and phalangeal hemiarthroplasty of the first metatarsophalangeal joint using the ToeFit Plus™ system.

BACKGROUND: This paper compares long term success rate of MTP joint replacement for hallux rigidus. We provide long term results of MTP joint replacement with the use of the ToeFit Plus™ System. MATERIALS AND METHODS: Our group consisted of 19 total joint replacements and 12 hemiarthroplasties in 18 and 11 patients respectively, performed between 2005-2009. The average follow-up period was 12.2 years (range 9.8-13.7, SD 1.1) for total arthroplasty group and 11.1 years (range 9.5-13.9, SD 1.7) for hemiarthroplasty group. In all followed patients AOFAS score was calculated along with the range of motion assessment. RESULTS: Average AOFAS score improved from 37 preoperatively to 79 at the time of last follow-up in total arthroplasty group and from 45 to 86 in the hemiarthroplasty group, with consideration to the statistically considerable difference of both groups. The total range of motion improved on average from 14° to the current 32° in patients with total arthroplasty and from 15° to 32° with hemiarthroplasty. The total number of cases that required surgical revision was 7 (37%) in total arthroplasty group and 2 (17%) in hemiarthroplasty group. CONCLUSION: Due to the high percentage of failure that was shown in our long term results, we no longer utilise the ToeFit Plus™ System.

Stemless Hemiarthroplasty of the Shoulder Using the SMR® System: Summary of Six-Year Experience and Surgical Technique.

PURPOSE OF THE STUDY In the last number of years, the anatomic hemiarthoplasty has gradually been pushed out of clinical practice by modern reverse shoulder arthroplasty (RSA) designs. This is due to the clear excellent functional results of RSAs in a wide spectrum of indication criteria. Nevertheless, RSAs have several possible complications that cannot occur in an anatomic hemiarthroplasty. In anatomic hemiarthoplasty, the importance of correct indication criteria and observing correct operative technique including soft tissue reconstruction is much more important than in RSA. Furthermore, there is a clear recent trend of increased use of humeral components fixed only in the proximal metaphyseal cancellous bone. Our aim was to summarise our six-year experience with the SMR® Stemless (LimaCorporate, Italy) system which is one of the most modern ones. MATERIAL AND METHODS Twenty cases of SMR® Stemless anatomic shoulder hemiarthroplasty performed between 2016 and 2021 were included in the study. All patients were followed up prospectively. The function was evaluated preoperatively and at the last follow-up. We evaluated the range of active elevation, classic Constant Score (CS) and pain level according to the visual analogue scale (VAS). Statistical evaluation was performed by using basic statistical methods and the statistical significance of the results was assessed with a paired t-test. Level of statistical significance was set at p= 0.01. RESULTS The mean follow-up in our cohort was 3.01 years (range 0.32-5.69, Median 2.82, SD 1.56) All cases were indicated for surgery due to primary osteoarthritis with a limitation of movement and pain. The mean postoperative CS was 85.7 (range 70-96, Median 86, SD 6.83). The mean active elevation postoperatively was 143° (range 100-170°, Median 150°, SD 20.76). Mean postoperative pain according to VAS was 1.05 (range 0-4, Median 1, SD 1.02). The mean preoperative elevation was 60.5° (range 30-100°, Median 65°, SD 18.83). After surgery the mean elevation increased to 143° (range 100-170°, Median 150°, SD 20.76). Statistical evaluation showed a statistically significant increase in the CS (41.7 preoperatively to 85.7 postoperatively), range of active elevation (60.5° preoperatively to 143° postoperatively) and a statistically significant decrease in pain (VAS 6.95 preoperatively to 1.05 postoperatively). We observed no cases of failure or loosening of the implant. A statistically significant increase in post-operative range of motion was demonstrated. DISCUSSION Most modern shoulder arthroplasty designs now include implants allowing for proximal humerus metaphyseal fixation in hemiarthroplasty and even RSA designs. The advantage of metaphyseal fixation without the use of a longer stem is clear. Notably, treatment of periprosthetic humeral fractures is simpler, extraction of the implant for any reason is easier and the preoperative anatomic position of the humeral head can be respected. As with any anatomic shoulder arthroplasty, the functional result is dependent on correct indication criteria, precise surgical technique, correct humeral head position and soft tissue reconstruction - primarily the rotator cuff. CONCLUSIONS Between 2016 and 2021, we performed 20 SMR® stemless shoulder hemiarthroplasties for primary osteoarthritis. The mean follow up was 3 years. The shoulder function improved significantly post-operatively in all patients. There were no cases of implant loosening or failure. Radiographic evaluation showed no implant loosening or change in implant position in the humeral metaphysis. Key words: shoulder joint replacement, reverse shoulder arthroplasty, SMR, stemless, total shoulder arthroplasty, shoulder hemiarthroplasty, EPOCA, wear.

Does the Femoral CCD Angle Measurement in a Standard AP Projection Correlate with the True Anatomical Shape of the Femur?

PURPOSE OF THE STUDY This study aims to ascertain whether a high anteversion of the femoral neck can influence the measurement of the caputcollum-diaphyseal (CCD) angle on a plain anteroposterior (AP) radiograph of the proximal femur. MATERIAL AND METHODS We developed a new method of measuring the CCD angle and femoral neck version of the femur. This was done with the use of a computer program that utilised the measurement of the entire visualised area of femoral neck and shaft to calculate their long axis. Using this method, we measured the CCD angle and femoral neck version (FNV) of 100 photographed cadaveric femurs in two projections: The condylar line (CL) projection and the femoral neck (FN) projection. The same method was applied to 50 radiographs of the same femurs. The femurs were divided into three groups depending on the femoral neck version: Retro (FNV of <0°), Normal (FNV of 0-15°) and Ante (FNV of >15°) RESULTS We found a statistically significant difference in the CCD angle measured in the FN and CL projections in the Normal and Ante groups but not in the Retro group. There is a significant correlation between the increase in FNV and the difference between the measured CCD values in the FL and CL projections. The femoral neck version of our cadaveric femurs varied from -14. 4° to 31. 5° which is a range of more than 35°. CONCLUSIONS From the results, it is clear that with an increase in femoral neck anteversion, there is a statistically significant difference in the CCD angle measured between the two projections. This difference can be up to almost 10°. Surgeons should be aware of the limitation of the AP projection when planning for surgery on the hip. Key words: femoral neck anteversion, CCD angle, templating, preoperative planning.

[Mid-Term Results of Proxima Ultra-Short Anatomical Stem: Analysis of 130 Cases]. / Strednedobé výsledky ultra-krátkeho anatomického drieku Proxima: analýza 130 prípadov.

PURPOSE OF THE STUDY The aim of this study is to assess the mid-term results of this specific ultra-short, cementless stem in patients younger than 60 years with regard to clinical and radiographic outcomes, survivorship, complication rate and revisions. MATERIAL AND METHODS A consecutive series of one hundred and twenty-one patients (130 hips) younger than 60 years at the time of surgery was enrolled in the study. Primary arthritis (33.8%) and dysplastic hips (30%) were the most common diagnoses. The patients used crutches for 6 weeks to protect femoral components against subsidence and rotational stress. The mean follow-up was 118 months (range 96-156 months). RESULTS At the final evaluation, the mean Harris Hip Score was 98.8. A perioperative periprosthetic fracture occurred in two hips and a perioperative ceramic insert breakage was observed in one hip. One hip had ceramic insert fracture 3.5 years postoperatively. In one hip a dislocation occurred. These two hips (1.5%) were revised due to reasons not associated with the stem. One hip has aseptic asymptomatic polyethylene inlay wear. In two hips squeezing was reported. There were two cases of loosening and migration of stems (1.5%) with osteolysis all around the stems. These patients have moderate thigh pain. The radiological survival is 98.5% and the clinical survival is 100% after 10 years on average. DISCUSSION Although improved clinical results were reported in younger patients with standard cementless stems, some problems still prevail: thigh pain, proximal stress shielding, difficult removal of the stem. In an effort to reduce these problems, Proxima ultra-short anatomical cementless stem was developed. Several studies show that this stem design provides good short- and mid- term results, but only in a limited number of patients and relatively short follow-up. Furthermore, the initial fears of early aseptic loosening due to the absence of diaphyseal fixation were not confirmed. CONCLUSIONS Proxima ultra-short anatomical cementless stem provided excellent mid-term clinical and radiographic results in patients younger than 60 years. Key words: total hip arthroplasty, ultra-short cementless anatomical stem.

Reverse Total Shoulder Arthroplasty: 14-Year Clinical Experience with 496 Performed Arthroplasties.

PURPOSE OF THE STUDY Reverse total shoulder arthroplasty (RSA) can be considered a proven method for the treatment of the most severe shoulder joint affections. In this study, we present 14-year experiences of the authors with the LimaCorporate SMR® RSA system in 496 cases. MATERIAL AND METHODS Included in the study are 496 RSAs performed between 2007 and 2020. We successfully followed up 368 shoulders in 358 patients. This was a prospective study with function being evaluated preoperatively and at the last follow-up in 2020. We evaluated the range of motion in active elevation and the classic Constant Score (CS). According to this score, the pain level was also evaluated. Standard statistical methods were used with a paired t-test used for comparisons of values. RESULTS The mean follow-up in our group was 5.5 years (0.7-13.6, SD 3.22, median 4.96). Indications were: primary osteoarthritis (84), acute trauma (69), posttraumatic sequelae (79), cuff tear arthropathy (37), RA (29), chronic dislocations (18), final treatment of infectious complications (7), avascular necrosis (6), tumours (4) and TSA revisions (9). The mean post-operative CS of all patients was 71.9 (2-94, SD 11.26, median 73). The mean post-operative active elevation was 127.35° (30°-180°, SD 28.36, median 130°). The mean pain level at final follow-up was 0.65 (0-3, SD 0.65, median 1). There was a statistically significant improvement In the CS (26.9 to 71) and the final achieved elevation (48.5° to 127.35°) in all groups except acute traumas for obvious reasons. A significant decrease in pain (2.8 to 0.65) was observed in all groups. We saw no implant failures or UHMWPE component wear. DISCUSSION We compared our results with those published by other authors. When considering the functional outcomes, our results are comparable with those published previously. Compared to other studies, an interesting result is the low incidence of scapular notching. In our cohort of patients, it was only present in 10 (2.7%) cases. We attribute this to the design of the SMR® implant which meets the main criterium of a modern shoulder arthroplasty system: modularity of both glenoid components. The glenospheres are available in 36, 40 and 44mm sizes with standard and distalised options. Furthermore, the system also contains the Axioma® revision glenoid component. Humeral stems are available in a range of sizes and lengths including revision stems. The humeral body is also available in two sizes. The short variant is optimal for revision with hemiarthroplasty to reverse conversion. CONCLUSIONS During a period of 14 years, we performed 496 implantations of RSAs using the SMR® system. We evaluated 368 cases with an average follow-up of 5.5 years. During long-term follow-up we experienced no implant failures or complications indicative of any constructional insufficiencies. We saw no signs of UHMWPE liner wear. The SMR® system allows for treatment of even the most complex shoulder affections due to its high modularity. Key words: shoulder joint replacement, reverse shoulder arthroplasty, SMR®, Axioma®, outcomes, ROM, scapular notching, complication, polyethylene wear, UHMWPE.

[Revision of Infected Total Knee Arthroplasties with DAIR Method - Factors Affecting the Two-Year Survival Rate]. / Revize infektu totální náhrady kolenního kloubu metodou DAIR ­ faktory ovlivnující dvouleté prezití.

PURPOSE OF THE STUDY Periprosthetic joint infections in total knee arthroplasty (TKA) represent one of the most limiting factors of implantation. Frequency of this complication is up to 2.5% in primary implantation. Revision TKA with the use of DAIR (Debridement, Antibiotics and Implant Retention) procedure is a widely accepted method in treating infection, but the indication criteria have not been clearly defined as yet. The lack of uniformity prevails also with respect to the surgical technique and the importance of respective techniques for successful treatment. The purpose of this study was to evaluate the factors affecting the twoyear survival of TKA after treating the infection by DAIR. MATERIAL AND METHODS We conducted a monocentric retrospective analysis involving 52 cases of infected TKA managed with DAIR in the period between 2007 and 2016. The evaluation took into account such factors as the sex, age, history of revision surgery for aseptic or septic reasons, and pathogens. The patients were divided into groups based on the McPherson criteria. As to the procedure, we monitored the effect of administered antibiotics, time interval between the manifestation of symptoms of TKA infection and surgery, exchange of modular parts, and use of pulse lavage, continual lavage, local antibiotic carrier, or combination of these techniques. Treatment failure was defined as persistent infection and transition to chronic suppressive antibiotic therapy or need for revision surgery of the respective joint due to recurrent infection of TKA, or death directly associated with the treatment of infected TKA in the follow-up period of 2 years after DAIR. The R software (Team Development Core, 2017) was used to carry out the statistical analysis. The target variable was the failure at two years after surgery. The Generalized Linear Model (GLM) was used for the binary dependent variable - the socalled logistic model with a logit link function. RESULTS 32 of 52 patients (61.5%) were successfully treated, of whom 18 women (62.1%) and 14 men (60.9%). The effect of causative agent, administered antibiotics, polyethylene insert exchange, McPherson score or history of revision surgery of the respective joint for aseptic reasons was not confirmed. The history of revision surgery for infection of the affected joint had a strong negative impact on treatment success, 10 of 13 (76.9%) implants failed as against 10 of 39 (25.6%) implants with negative history of infection. The mean time from surgery to the manifestation of infection was 5.9 weeks (0.5-47.5). When surgery was performed within 2 weeks from the manifestation of infection, 1 of 15 (6.7%) cases failed. In case of a later surgery, 19 of 37 (51.4%) cases failed. As concerns the used surgical technique, 60% (9/15) failure was reported in case of the combination of pulse lavage and continual lavage, 36.4% (4/11) in case of the combination of pulse lavage and local antibiotic carrier, 25% (4/16) in case of separate continual lavage, and 66.7% (2/3) in case of continual lavage with local antibiotic carrier. DISCUSSION The importance of individual factors in revision surgery of periprosthetic joint infections of TKA remains unclear. The world literature indicates as a major negative effect the time factor, the positive history of infection of the affected implant, or other previous revision surgery for aseptic reasons. Ambiguous results are achieved in assessing the effect of the pathogen, administered antibiotics or presence of fistula, the statistical significance of which has not been confirmed in our study. Questionable is also the importance of individual surgical techniques. CONCLUSIONS DAIR is a suitable method in treating infections of stable TKA without the history of revision surgery for infection. The surgery should be performed within 2 weeks from the manifestation of symptoms. Key words: debridement, antibiotics, infection, implant retention, total knee arthroplasty.

Rare case of osteomyelitis of tibial shaft caused by Nocardia cyriacigeorgica.

Nocardiosis is a rare infection caused by the aerobic actinomycete of the Nocardia genus. In most cases, nocardiosis manifests as a lung infection or a bone lesion. Due to the nonspecific and mild clinical manifestations of nocardiosis, the establishment of definite diagnosis can be difficult. When antibiotic therapy is incorrectly targeted, only the symptoms of the disease are suppressed. The mainstay in the treatment of Nocardia osteomyelitis has so far been the combined surgical debridement with long-term, initially intravenous, antibiotic administration. We present the successful conservative treatment of a nocardiosis osteomyelitis of the tibia caused by the Nocardia cyriacigeorgica species in an 81-year-old female patient that manifested itself as a secondary affection on top of a primary nocardiosis infection of the lung. From microbiological examination, N. cyriacigeorgica was discovered; the identification was made using matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) with an identification score of 1.9. The sensitivity was evaluated using E test. Sensitivity to trimethoprim/sulfamethoxazole, amikacin, imipenem, and linezolid was demonstrated. The bacteria were shown to be resistant to ciprofloxacin. For treatment, trimethoprim/sulfamethoxazole was used due to the value of minimum inhibitory concentration, which was 0.25 mg/L. The initial dose of 960 mg of trimethoprim/sulfamethoxazole every 8 h was reduced to 960 mg every 12 h after 3 months. The total duration of treatment was 7.5 months. Under the established treatment, the bone and lung lesions healed. Nocardiosis of the long bone is considered a rare disease and its precise diagnosis has not yet been standardized. We used the MALDI-TOF MS method for the identification of the causal organism which is a fast and reliable method according to current world literature even when compared with the rRNA genetic sequencing reference method. Our case study presents a rare case of osteomyelitis of tibial shaft caused by N. cyriacigeorgica and its successful conservative treatment.

No alignment of cattle along geomagnetic field lines found.

This paper presents a study of the body orientation of domestic cattle on free pastures in several European states, based on the Google satellite photographs. In sum, 232 herds with 3,412 individuals were evaluated. Two independent groups participated in our study and came to the same conclusion that in contradiction to the recent findings of other researchers, no alignment of the animals and of their herds along geomagnetic field lines could be found. Several possible reasons for this discrepancy should be taken into consideration: poor quality of Google satellite photographs, difficulties in determining the body axis, selection of herds or animals within herds, lack of blinding in the evaluation, possible subconscious bias, and, most importantly, high sensitivity of the calculated main directions of the Rayleigh vectors to some kind of bias or to some overlooked or ignored confounder. This factor could easily have led to an unsubstantiated positive conclusion about the existence of magnetoreception.

[Meniscoids of the intervertebral joints]. / Meniskoidy meziobratlových kloubu.

PURPOSE OF THE STUDY: A large amount of material was used to study the distribution, location and shape of meniscoids in intervertebral joints of the human spine, from the atlanto-occipital joint to the sacrum, in order to find out how many of intervertebral joints had mobile meniscoids. These might be regarded as possible causes of spinal blockade or other vertebrogenous complaints. MATERIAL: The materials provided by the Department of Anatomy and Department of Forensic Medicine at the Faculty of Medicine of Charles University in Pilznen included 20 cadaverous spines from humans aged 20 to 80 years. METHODS: Access to each joint was provided by dissection of the articular capsule from the lower articular processes of the vertebra situated above. In the orthograde view, all meniscoids were described in terms of shape, size, consistence and location. Their structure was ascertained by histological examination of cross sections stained with haematoxylin and eosin. RESULTS: Meniscoids varying in shape and size were found in all of the intervertebral joints. They were classified by their histological structure as synovial, fat and fibrous meniscoids. The first category was observed frequently, the last only rarely. A total of 29 mobile meniscoids were recorded, most of them in the lumbar spine. Most of the meniscoids present in the cervical spine were of synovial and less frequently of fat types. Meniscoids found in the thoracic spine were poorly developed synovial ones and those present in the lumbar spine were of all types and were also largest in size. The most conspicuous meniscoids were seen in the spines that showed degenerative changes in intervertebral joints. Large fat pads were found in atlanto-occipital and atlanto-axial joints. Mobile meniscoids, most of them present in the lumbar spine (6.4% of all joints.), were connected with the capsule by a thin pedicle and it was possible to move them over a half of the articular surface. Some inter-individual changes were also found; in some spines, the most developed meniscoids were fat pads, in the others, these were synovial meniscoids. Spines of younger individuals showed a predominance of synovial meniscoids with smooth surfaces that arched against the articular cavity. In spines of elderly individuals, meniscoids were rough, in some cases fibrous in structure, and had a lobulated or frayed edge. DISCUSSION: The shape, location of meniscoids and their presence in every joint indicate their definite role for the spine: they compensate the incongruence of articular surfaces, fill in empty spaces and facilitate spread of synovial fluid during translation movements. Variability in shape, size and location of meniscoids give support to the view that meniscoids developed secondarily in relation to the morphogenesis of articular surfaces and that they are fully adapted to the shape and function of the joint. Mobile meniscoids, particularly fibrous ones, can get wedged between articular surfaces due to a sudden, rush movement (entrapment theory) or can be caught between the edge of an articular surface and the articular capsule attachment (extrapment theory). This situation may result in either mechanical or functional blockade of the spine and a subsequent painful condition due to compression of nerves and reflex contraction of muscles. Direct evidence of such blockade and the validity of either hypothesis can today be provided by magnetic resonance imaging. CONCLUSIONS: All intervertebral joints, along the length of spine, possess capsule processes, i.e., meniscoids, which can be classified as synovial, fat and fibrous. Meniscoids are most developed in the lumbar and cervical spine. They serve to compensate for the incongruence of articular surfaces and to fill in empty spaces. Mobile, peduncular meniscoids can, at sudden or non-physiological movements, be caught between articular surfaces and cause spinal blockade and painful conditions. Manipulative treatment is, therefore, justified in indicated cases.

[Mechanical loading of the human femoral neck]. / Mechanické namáhání krcku femuru cloveka.

PURPOSE OF THE STUDY: The aim of the study is to explain what is the actual loading of human proximal femur. MATERIAL: Measuring of stress is based on 5 femurs of normal shape (bones obtained from dissection and ossuary). In order to determine the direction of the resultant force the authors used 30 ossuary bones of different age but of analogical shape. METHODS: By means of their own graphic method the authors identified the direction of appositional growth of femoral neck which contains with the longitudinal diaphyseal axis the angle of 26 degrees (alpha angle). The value of the angle is identical with the direction of the resultant force acting on the femoral head in vivo. Tensometric method was used for the measuring of stress on the medial and lateral surfaces of femoral neck during loading in direction of the determined resultant force. Linear strain gauges of Hottinger type were used for the measuring and Instron apparatus was applied for biomechanical analysis in which femoral heads were loaded by a standard force of 50 kg, first in the direction of femoral diaphyseal axis and then gradually (always by 5 degrees) in the divergence from the diaphyseal axis up to 50 degrees. RESULTS: Appositional growth of femoral neck with regard to the longitudinal diaphyseal axis is progressing under the alpha angle (alpha = 26 degrees), which corresponds to the direction of the resultant force. The value of the compression stress on the medial surface of the neck ranged between--165 and -300 microstrain (mean value -239 microstrain). On the lateral surface there is a tension stress ranging between +20 up to +140 microstrain (main value +64 microstrain). The ratio of stress on both sides (surfaces) was 3.8:1. The point of zero stress is located in the lateral part of the neck, i.e. in the area of lateral trajectorial system of cancellous bone. DISCUSSION: The method of measuring of the direction of the resultant force on the basis of the bone development (on the basis of superposition of successive growth stages) is despite certain inaccuracies a correct procedure. The alpha angle (alpha = 26 degrees) identified by the authors corresponds with Pauwels' calculation (24 degrees) and Bergman's findings (22 degrees up to 27 degrees). The identified values of stress show that the opinion on a purely axial loading of the neck is wrong and has to be corrected. Femur is not exposed in the frontal plane to the action of the resultant force only in one direction as supposed e.g. by Pauwels but the direction of the resultant force oscillates within a limited extent from different directions. It means that the lateral wall of femoral neck is exposed to alternating both tensile and compression loading. CONCLUSION: The presented work allows to specify the opinions on the way of loading of human proximal femur. Our experiments have shown that apart from axial pressure the femoral neck is exposed also to bending forces. This way of loading also corresponds with the oval shape and thickened medial wall of the neck.

["Tension" and "pressure" osteons - reality or myth?]. / "Tahové" a "tlakové" osteony - realita nebo mýtus?

The underlying study tests the hypothesis on the existence of two types of osteons, the "tension" and the "pressure" ones. Osteons of the first type should be built under the influence of tension and should manifest greater strength in tension. The contrary applies to the "pressure" osteons. The ultimate strength of the bone tissue in tension and compression was studied on samples from the medial wall of the femoral diaphysis, subjected in vivo to compression, and on samples from the lateral wall, subjected to tension. All samples were manufactured with the long axis corresponding to the orientation of osteons, arranged in two helical antirotary systems situated in the contralateral walls of the diaphysis. The osteon orientation was ascertained after filling vascular canals with India-ink. The bone samples were tested using the Schenk Trebel RM 10-K machine. Tension tests found no difference in bone strength between samples from the lateral and from the medial walls. In compression tests, three cases manifested greater strength in samples from the medial wall, two cases in samples from the lateral wall. Such results speak against the hypothesis of the existence of two functional types of osteons. A complementary series of experiments showed that the tension strength is greatest in samples having a longitudinal orientation of osteons and that it decreases rapidly with growing inclination of osteons from the axis of loading. The dominant factor, responsible for the bone strength, is therefore the osteon orientation and not the mode of mechanical loading in vivo or the orientation of collagen fibres. Key words: haversian bone, osteons, strength of bone.

[Dependence of mechanical strength on the architecture of the compact bone of human shaft.]. / Závislost mechanické pevnosti na architektonice kompaktní kosti diafýzy u cloveka.

A secondarilly remodelled bone (the haversian bone) forming a wall of human shaft represents a significantly anisotropic material, which has different strengths in different directions. One of the factors influencing mechanical properties (strength in particular) of the bone is the architectonics of the compact bone. Osteons of the haversian bone are arranged in the direction of the dominant first principal stress and create two antirotational spiral systems in the opposite walls of the shaft. The aim of the work was to found out how the bone tensile strength depends on the orientation of osteons and check whether the premise applies that the architectonics of the haversian bone depends on the directions of the first principal stress and in what relation of strength moments the direction of the first principal stress corresponds to the actual orientation of osteons. The results of the tensile strength tests in wet samples from 10 femurs and the strength of the whole shaft in 9 pairs of femurs (cadaver material) have confirmed the premise that osteons are arranged in the directions of the dominant first principal stress and depend on the relation between bending and torsion moments. The strength of the femoral shaft is maximal in the physiological way of loading, i.e. in medial bending and outer rotation. The decisive motion on which the strength of the bone depends is torsion. In non-physiological loading the femoral shaft (by an opposite bending moment or opposite torsion moment in medial bending) the strength of the bone is significantly lower. From the biomechanical viewpoint the architecture of the haversian bone has an optimal and efficient structure. Key words: compact bone, bone strength, types of loading.

Spatial organization of the haversian bone in man.

The osteons in all human long bones are grouped in two helical antirotary systems of opposite oblique directions, situated in the contralateral walls of the diaphysis. Several arguments support the hypothesis that this special architecture arises from functional adaptations and that it depends on the orientation of the first principal stress. A new macroscopic method based on the filling of vascular canals of the undecalcified, polished bone with India-ink enabled us to study the spatial architecture of the haversian bone in the entire diaphysis. The osteon directions in normal and atypical femurs was compared with the direction of the first principal stresses, determined analytically in a cylindrical tube model of the diaphysis subjected to a combination of bending, torsion and compression. Under combined loading with the bending moment in the frontal plane to the medial side and with the torque moment in the sense of external rotation, the direction of the first principal stresses corresponded with the direction of osteons in the diaphysis of the femur. In both cases, the first principal stresses, as well as the osteons, were oriented in the opposite oblique direction in the medial and lateral walls of the model and of the bones. Between the two oblique fields a sharp boundary with an atypical organization of the principal stresses and osteons existed. In atypical femurs the osteonal orientation was longitudinal (likely unloaded femurs) or rotated 90 degrees (markedly anteriorly convex femurs). These observations support the hypothesis of a causal relation between the loading mode and the dominant osteonal direction. The organization of the haversian bone seems a typical example of functional adaptation.

Osteon orientation of the diaphysis of the long bones in man.

The orientation of osteons has been described in the long bones of man, using a special macroscopic method, which enabled the study of the osteonal architecture throughout the extent of the diaphysis. The osteons in all bones are arranged in two helical systems of opposite directions, which lie on the opposite sides of the diaphysis. The inclination of osteon direction from the bone axis in remarkably constant, varying between 5 degrees and 15 degrees. The boundary between the two fields is sharp. This special type of osteon orientation corresponds with the directions of the maximum principal stress and/or strain in the walls of the bones, which are exposed to both the bending and torque moments. The typical orientation of osteons reflects the history of loading of the bones in the course of physiological activity. The dominant stress state of every bone could be deduced from the osteon orientation and from the position of the pressure and tension fields on the surface of the bone.

A new attempt at the interpretation of the functional architecture of the cancellous bone.

The author's theory explains the development mechanisms of the functional structure of cancellous bone. Functional, secondary cancellous bone develops from the primary growth-dependent cancellous lattice under the influence of multidirectional loading. The primary cancellous bone is remodelled according to the general strain-dependent mechanism of the functional adaptation of bone. Oblique loading of the metaphysis in extreme positions in the joint evokes the greatest strain in the bone trabeculae oriented in these oblique directions, as demonstrated by calculation on a simple three-beam model. All trabeculae are therefore remodelled in these directions resulting in a typical picture of two crossed pressure systems. Each of them corresponds to one of the extreme loading directions. Tensile systems can be found only in places of ligament or tendon insertions or under concave joint surfaces.

Principal types of functional architecture of cancellous bone in man.

The cancellous bone architecture in man is locally specific. Several principal types can be distinguished, depending on the kind of loading and movement in the joint in one, two or more directions. Under multidirectional load the spongiosa trabeculae form spatial fans seen as two crossing systems on plane sections. Marked differences exist between the bone structure under concave joint surfaces and the convex ones. The analysis testifies the correctness of the author's own theory on the development of the cancellous bone architecture. According to this theory every trabecular system corresponds to other direction of maximal principal stress in the course of movement. Both crossing systems in the metaphysis are pressure systems, corresponding to opposite extreme positions in the joint. Tension systems can be found in sites of ligament or tendon insertions and closely under concave articular surfaces only.

[Structure of compact bone and types of stress in the long bones in humans]. / Struktura kompaktní kosti a zpusob namáhání dlouhých kostí cloveka.

The authors elaborated a new macroscopic method which made it possible to analyze the orientation of osteons in the entire diaphysis. All long bones of the human extremities were thus analyzed. In each bone the osteons are arranged in a specific pattern but according to a uniform plan. Most of them are oriented in an oblique direction and are arranged as two helices of opposite directions located on opposite sides of the bone. The two fields are separated by a sharp borderline. Biomechanical analysis revealed that the orientation of the osteons is consistent with the direction of the maximal principal stress which depends on the normal and torsional stress to which the bone is exposed. From the orientation of osteons the authors derived ex post the mode of dominant loading of all long bones: the femur is exposed to bending in the medial direction and to outer rotation, the tibia is exposed to bending in dorsal direction and to inner rotation. The humerus is bent in the medial direction, the radius in the dorsal one. Both these bones are exposed to loading in inner rotation. In the ulna and fibula the mode of stress could not be assessed by the authors' method. The results are summarized in two diagrams which indicate the orientation of osteons and the way in which the long bones in man are exposed to load. The authors discuss the theoretical and practical impact of these findings.

A new explanation of the cancellous bone architecture.

Various objections can be made to all the theories so far put forward in explanation of the architecture of cancellous bone. The author suggests another explanation, which takes into account the following points: 1) the structure of the secondary spongiosa is based on the pre-existent primary spongiosa, 2) the secondary spongiosa develops under alternating pressures from different directions, 3) oblique forces from marginal directions corresponding to extreme positions on the joint place the greatest strain on the spongiosa trabeculae, as demonstrated by means of a geometrical model. Oblique forces are therefore of decisive morphogenetic importance. 4) The spongiosa trabeculae are oriented in the direction of the oblique marginal forces, in accordance with the experimentally demonstrated mechanism of the strain-dependent reaction of the bone. Spatially, the secondary spongiosa assumes a fan-shaped structure. Two-dimensionally, the two intersecting systems are compression systems, each of which depends on another marginal loading direction. This pattern offers an optimum solution to the problem of the transmission of alternating forces to the diaphysis from various directions, using a minimum of material.

[Importance of vascular and mechanical factors for bone healing.]. / Význam cévních a mechanických faktoru pro hojení kosti.

The author submits a brief account of contemporary views on the importance of vascular and mechanical factors for healing of bones. Damage of the vascularization after fractures when using conservative treatment and intramedullary and external fixation, does not influence bone healing in a substantial way. In those instances the bone heals by forming a callus with newly formed ample vascularization. On the other hand, in case of osteosynthesis, using a splint with perfect stabilization, the bone heals very slowly by a process of direct healing by haver remodelling. The period of healing is proportional to the extent of bone necrosis. Therefore biological surgery with maximal sparing of periostal vessels is essential. The importance of mechanical factors depends also on the type of healing. The prerequisite of direct healing and healing in the cavity is mechanical rest. Mechanical influences become involved only in the osteoblastic, apposition stage of the remodelling process. During healing by means of a callus mechanical factors play a different role in different stages of development of the callus. In the proliferation stage the mechanical optimum is moderate, so far not accurately quantified motor activity. In the differentiation stage similar mechanisms are involved as during differentiation of the embryonic mesenchymal blastema: traction in the surface layers of the callus leads to desmogenesis, pressure inside the callus to chondrogenesis. The ossification stage calls for mechanical rest. In the final modelling and remodelling stage two basic mechanism of functional adaptation of bone are involved, apposition caused by deformation of the bone marrow and surface reabsorption caused by direct pressure of the adjacent periostium. In the conclusion the authors discuss the importance of mechanical factors in the stress shielding phenomenon, traction osteogenesis and dynamic compression. Key words: bone - healing, vascular and mechanical factors, mechanical factors - bone.