Computed tomography osteoabsorptiometry is reliable for the determination of the subchondral bone mineralization distribution in the rabbit knee

Rabbits are among the most frequently used animals in osteoarthritis research. It is meanwhile accepted that the subchondral bone plate (SBP) plays a key role in the development of osteoarthritis. The most suitable technique for analyzing subchondral bone mineralization is computed tomography osteoabsorptiometry (CT-OAM). Because CT-OAM has not yet been applied to smaller animals, the purpose of this study is to test the reliability of CT-OAM in the rabbit knee. Another important task in animal experiments is the intra- and interindividual difference of the measurement parameters. Our hypothesis is that there is no difference regarding both the position of the density maxima and the bone mineral density (BMD) of the SBP comparing right and left tibial plateaus of rabbits. For evaluating the reliability, a rabbit knee was examined by computed tomography 6 times at weekly intervals. The subchondral mineralization distribution was measured by means of CT-OAM. Positions of the density maxima and BMD of the SBP were determined in a standardized procedure. Furthermore, both parameters were evaluated in 6 female White New Zealand rabbits. Positions of density maxima and BMD in the SBP in left tibial plateaus were compared with right tibial plateaus. The relative coefficient of variation as a parameter for reproducibility was 1.6% for determining the position of the density maxima and 1.2% for measuring the BMD. The positions of density maxima and relative BMD between right and left tibial plateaus varied only about 2% intraindividually, whereas interindividual variance was about 10%. In conclusion, determination of the position of density maxima as well as BMD of the SBP by means of CT-OAM is reliable and reproducible in the rabbit knee. We recommend using the contralateral limb as control, because intraindividual accordance of the mineralization patterns and of the BMD of the SBP was higher than interindividual accordance

Mineralisation patterns in the subchondral bone plate of the humeral head

PURPOSE: Pathologic changes of the glenohumeral joint, like a long-standing overloading or an accident often lead to severe glenohumeral osteoarthritis, and a glenohumeral joint replacement could be necessary. Joint instability and glenoid loosening are the most common post-operative complications, which can be caused by eccentric loading of the glenoid, if the humeral head is malcentered. If these malcentered cases could be identified pre-operatively, the pathologic position of the humeral head could be fixed intra-operatively and complication may be prevented. Computed tomography osteoabsorptiometry (CT-OAM) is a useful method to determine the distribution of mineralisation in the subchondral bone as a marker for the long-term loading history of a joint. The objective of this study was to gain information about the mineralisation distribution in the subchondral bone plate of the humeral head. METHODS: By the use of CT-OAM, the distribution of the subchondral mineralisation of 69 humeral heads was investigated and groups of mineralisation patterns were built. To evaluate if differences in age exist, the mean values of the two groups were compared using t test. RESULTS: 49 humeral heads (71% of 69 specimens) showed bicentric subchondral mineralisation patterns with ventral and dorsal maxima, 20 humeral heads (29% of 69 specimens) could be classified as monocentric with a centro-dorsal maximum. We found no statistical significant difference between the age of the monocentric and the bicentric group on a significance level of 95%. CONCLUSION: We could show that stress distribution at the humeral head is typically bicentric with a ventral and dorsal maximum. However, other mineralisation patterns may occur under pathologic circumstances. The pre-operative identification of such cases by the use of CT-OAM could help to improve the post-operative results in shoulder surgery

A comparison of subchondral bone mineralization between the glenoid cavity and the humeral head on 57 cadaverous shoulder joints

PURPOSE: Mineralization distribution of the subchondral bone plate can be used as a marker for long-term stress distribution in diarthrodial joints. Severe injuries or pathological changes of the glenohumeral joint often end in osteoarthritis, where shoulder arthroplasty has become the treatment of choice. The computed tomography osteoabsorptiometry (CT-OAM) is a non-invasive method to determine the distribution of the mineralization of the subchondral bone plate in vivo, which is an important factor concerning the implantation of orthopedic endoprostheses. The aim of this study was to investigate the mineralization of both joint partners of the glenohumeral joint and to compare them with each other. METHODS: The distribution of the mineralization of the subchondral bone plate of 57 shoulder specimens was determined by means of CT-OAM. To evaluate a correlation between age and localization of subchondral mineralization maxima, the Chi-square test correlation test was applied. RESULTS: Forty-nine glenoid cavities (86 %) showed a bicentric mineralization distribution pattern with anterior and posterior maxima, only 8 glenoid cavities (14 %) revealed a monocentric mineralization pattern with anterior maxima. Forty-five humeral heads (79 %) showed a bicentric distribution pattern with anterior and posterior maxima, 12 humeral heads (21 %) could be classified as monocentric with a centro-posterior pronounced maximum. CONCLUSIONS: We could demonstrate that stress distribution in both joint partners of the glenohumeral joint is inhomogeneous and characteristically bicentric due to the physiological incongruity. Monocentric mineralization patterns can result as a cause of age-related loss of incongruity

The human hip joint and its long-term load intake - how x-ray density distribution mirrors bone strength

The aim of this study was to gain information about the topographical distribution of the mechanical strength of the subchondral bone plate of the hip joint and evaluate the correlation to its density distribution. Our intention was to describe a method of visualising and monitoring the long-term load intake of the hip using conventional CT-data in a way which might be applied in clinical practice. We examined the lunate surface of the acetabulum (facies lunata) and femoral head in 25 cases, looking at the density of the subchondral bone plate by computed tomography osteoabsorptiometry (CT-OAM) and determined its mechanical strength by indentation testing using an osteo-penetrometer. The resulting distribution patterns were matched and statistically analysed, showing an inhomogeneous but regular and reproducible distribution of mineralisation and mechanical strength throughout the joint surface. Maximal density was found anterosuperiorly and near the rim of the facies lunata and in the superior area of the femoral head. For each specimen a correlation of density and strength (r2 = 0.77 - 0.97) was found (p>0.01). The density distribution pattern shown by CT-OAM allows conclusions to be drawn about the distribution of strength and therefore the long term load intake within the subchondral bone plate of the hip. Using conventional CT-data, the method can be used in the clinical setting for evaluation and monitoring

Mineralisation and mechanical strength of the glenoid cavity subchondral bone plate

PURPOSE: Failures in total shoulder replacements are often due to aseptic loosening of the glenoid component; the subchondral bone plate is an important factor governing primary fixation of implant materials. Therefore, we investigated characteristic mineralisation patterns of the subchondral bone plate, which demonstrate long-term stress on articular surfaces, age-related changes, postsurgical biomechanical situations and regions of fixation. Using computed tomography osteo-absorptiometry (CT-OAM), these distribution patterns can be demonstrated in vivo. The aim of this study was to investigate the relationship between subchondral bone-plate mineralisation measured with CT-OAM and the mechanical strength measured by indentation. METHODS: A total of 32 cadaverous glenoid cavities were evaluated by CT-OAM and indentation testing. Linear regression was used to compare mineralisation and strength of the subchondral bone plate. RESULTS: Results showed two patterns of mineralisation distribution. Twenty-eight cavities were related to bicentric distribution pattern and four showed a single maximum. The correlation coefficient between CT-OAM density and subchondral bone-plate strength was determined to be between 0.62 and 0.96 (P > 0.02). CONCLUSIONS: Long-term stress affects not only the subchondral but also the underlying cancellous bone. It therefore can be assumed that mineralisation patterns of the subchondral bone plate continue in cancellous bone. Areas of high density could serve as anchoring locations for orthopaedic implants in resurfacing the glenoid cavity

Thickness distribution of the glenohumeral joint cartilage : a quantitative study using computed tomography

PURPOSE: Among late signs like sclerosis, cysts and osteophytes, alteration of cartilage is a common problem in osteoarthritis. To detect abnormal states in the glenohumeral joint, the physiologic distribution of the cartilage thickness must be known, which will allow physicians to better advise patients. High-resolution computed tomography (CT) data in soft tissue kernel provide highly accurate quantitative results and are a useful method to determine the geometrical situation of the glenohumeral joint. The objective of this study was to characterize the distribution of the thickness of the glenohumeral joint cartilage using CT. METHODS: To investigate the distribution of thickness of the joint cartilage, CT images in soft tissue kernel of nine specimens were analyzed using image visualization software. Statistical analysis of the obtained data was performed using the ANOVA test. RESULTS: Results showed different patterns in the glenoid cavity than in humeral head. Cartilage thickness in all glenoids showed maxima in the inferior and anterior portion, whereas central areas are covered with the thinnest cartilage layer. Maximum cartilage thickness in the humeral head was found in the central and superior parts. CONCLUSION: We could show that the distribution of cartilage thickness in the glenohumeral joint is not homogenous and that there exist several reproducible patterns. Evaluation of cartilage thickness in the glenohumeral joint is of high interest in basic and clinical research

Correlation between mineralization and mechanical strength of the subchondral bone plate of the humeral head

BACKGROUND: One of the main problems in shoulder arthroplasty is the fixation of the prosthesis, where the subchondral bone plate plays an important role. Subchondral mineralization patterns represent the loading history of a joint and give information about the individual biomechanical situation. The objective of this study was to determine if a correlation between subchondral mineralization and mechanical strength in the humeral head exists. MATERIALS AND METHODS: Subchondral mineralization of 32 shoulder specimens was investigated by use of computed tomography (CT) osteoabsorptiometry. The previously dissected specimens were scanned axially in a CT scanner, and the obtained data sets were transferred into an image analyzing system. Maximum intensity projection was used to evaluate the density distribution of the subchondral bone plate. To get information about mechanical strength of the subchondral bone, each specimen was investigated at 29 predefined points by means of an indentation-testing machine. RESULTS: The maximum strength was mostly detected in the center (monocentric pattern) or in anterior and posterior areas of the articular surface (bicentric pattern). The distribution of mineralization showed the same 2 reproducible patterns. The coefficient of correlation between mechanical strength and mineralization shown on CT was between 0.59 and 0.96. The obtained information was statistically significant (P > .01). CONCLUSION: Mechanical strength and subchondral mineralization in the humeral head are significantly associated (P > .01). As a consequence of these findings, CT osteoabsorptiometry can be indirectly used to give information about bone quality in vivo. Our findings could be useful for the development of new fixation methods in shoulder surgery (eg, humeral resurfacing arthroplasty)

Can clinical examination cause a Stener lesion in patients with skier's thumb? : a cadaveric study

Approximately one-third of all injuries of the upper limb and 7% of all injuries in skiing affect the ulnar collateral ligaments of the thumb metacarpophalangeal joint (skier's thumb). In some patients the collateral ligaments are displaced proximally over the adductor aponeurosis, resulting in a so-called Stener lesion. In these cases surgical treatment is indicated. We hypothesized that a Stener lesion could be provoked by clinical stability testing in patients with a skiers thumb and performed a cadaveric study on 10 Thiel fixated cadaver hands. For clinical stability testing, the thumb was manually deviated in radial direction in both 30 degrees flexion and extension of the MP-joint. It was performed with maximum strength by two hand surgeons after sequential detachment of the ulnar collateral ligaments. After every sequence, it was assessed if the clinical stability testing had caused a Stener lesion. All of the 10 cadavers showed identical results while testing the clinical stability. A decreased stability was only found after cutting both parts of the ulnar collateral ligaments. A Stener lesion could not be provoked in any of the cadavers at any time by clinical stability testing. Summarizing our findings we conclude that a proper performed clinical stability testing of the thumb MP joint is a safe maneuver, which does not lead to a Stener lesion in patients with skier's thumb

Simultaneous and multisite measure of micromotion, subsidence and gap to evaluate femoral stem stability

The initial stability of cementless femoral components is crucial for the long-term success of total hip arthroplasty. This has been reported in animal and clinical studies. Until now, the stability was evaluated by the measurement of relative micromotion on a few simultaneous locations around the stem in cadaveric experiments. This paper presents an extended experimental setup to measure simultaneously local micromotion, subsidence and gap on hundreds of points at the bone-stem interface. This technique we applied to anatomical and straight stems in three pairs of cadaveric femurs. Measurements were in agreement with typically reported values. Conversely to other methods, which measure micromotion between implant and bone anchoring points of the measuring device, our method provides local micromotion between stem surface and adjacent bone surface. The observed variation of micromotion at the peri-implant surface confirms the importance of this simultaneous measure on a lot of points around the implant

Micro CT analysis of the subarticular bone structure in the area of the talar trochlea

PURPOSE: Certain regions of the talar trochlea are recognized as exhibiting varying cartilage thickness and degrees of subchondral bone mineralization. These changes have been attributed to the long-term loading history. For the current study, we accepted the hypothesis that stress-induced alterations of the joint surface include not only varying degrees of subchondral lamellar mineralization, but also structural changes of the subarticular cancellous bone. METHODS: In order to examine the structure of the subarticular cancellous bone, ten formalin-fixed talar trochleae were analyzed using micro CT. Sixteen measurement zones were defined and then evaluated in five layers each of 1-mm thickness, enabling assessment of the cancellous architecture extending 5 mm below the trochlear surface using numerical and structural parameters. RESULTS: As with mineralization patterns in the subchondral lamella, large variation was observed regarding bone volume, trabecular quantity, thickness, and spacing, as well as for structure model index and degree of anisotropy, depending on localization. In addition, like previous reports examining mineralization of the subchondral lamella, two distinct groups could be identified as "bicentric" or "monocentric". CONCLUSIONS: These results show that structural tissue adaptation probably due to loading history is also evident within the subarticular cancellous bone