Mineralisation and mechanical strength of the subchondral bone plate of the inferior tibial facies

Computed tomography Osteoabsorptiometry: Review of bone density, mechanical strength of material and clinical application

Computed Tomography (CT) imaging is an effective non-invasive examination. It is widely used in the diagnosis of fractures, arthritis, tumor, and some anatomical characteristics of patients. The density value (Hounsfield unit, HU) of a material in computed tomography can be the same for materials with varying elemental compositions. This value depends on the mass density of the material and the degree of X-ray attenuation. Computed Tomography Osteoabsorptiometry (CTOAM) imaging technology is developed on the basis of CT imaging technology. By applying pseudo-color image processing to the articular surface, it is used to analyze the distribution of bone mineralization under the articular cartilage, evaluate the position of prosthesis implantation, track the progression of osteoarthritis, and determine the joint injury prognosis. Furthermore, this technique was combined with indentation testing to discuss the relationship between the high bone density area of the articular surface, the mechanical strength of the bone, and the anchorage stability of the implant, in addition to the study of the relationship between mechanical strength and bone density. This narrative study discusses the pre- and postoperative evaluation of medical device implantation position, orthopedic surgery, and the clinical treatment of bone injury and degeneration. It also discusses the research status of CTOAM technology in image post-processing engineering and the relationship between bone material and mechanical strength.

Computed tomography osteoabsorptiometry for imaging of degenerative disc disease

Background

Lower back pain is a common condition with significant morbidity and economic impact. The pathophysiology is poorly understood but is in part attributable to degenerative disc disease (DDD). The healthy intervertebral disc ensures spine functionality by transferring the perceived load to the caudally adjacent vertebrae. The exposure to recurring mechanical load is mirrored in the mineralization pattern of the subchondral bone plate (SBP), where increased bone density is a sign of repetitive localized high stress. Computed tomography -osteoabsorptiometry (CT-OAM) is a technique based on conventional CT scans that displays the mineral density distribution in the SBP as a surface-color map. The objective of this study was to measure and analyze the SBP mineral density patterns of healthy lumbar intervertebral disc (IVDs) and those suffering DDD using CT-OAM densitograms. These findings should provide in vitro insight into the long-term morphological properties of the IVD and how these differ in the state of disc degeneration.

Methods

The CT-data sets of spines from 17 healthy individuals and 18 patients displaying DDD in the lumbar spine were acquired. Individual vertebrae of both cohorts were 3D reconstructed, processed using image analysis software, and compared to one another. Maximum intensity projection of the subchondral mineralization provided surface densitograms of the SBP. The relative calcium concentration, the local maxima of mineralization, and a mean surface projection of level-defined SBPs were calculated from the densitogram and statistically compared.

Results

The inferior SBP, adjacent to degenerating disc, display an 18-41 % higher relative calcium concentration than their healthy counterparts. In the opposing superior SBPs the relative calcium content is significantly increased. Whereas it is reasonably consistent for L1-L3 (L1: 132 %, L2: 127 %, L3: 120 %), the increase grows in caudal direction (L4: 131 %, L5: 148 %, S1: 152 %). Furthermore, a change in the areal distribution of excessive mineralization can be differentiated between healthy and diseased motion segments.

Conclusions

The acquired data provide in vitro proof of the mechanical and anatomical properties of the SBP in relation to the state of disc degeneration. In conjunction with the diagnostic use of CT-osteoabsorptiometry, our data provide a basis for a non-invasive and sensitive technique that correlates with disc functionality. This could be promising in various cases, from early identification of early stages of DDD, tracking disease progression, and assessing the repercussions of surgical procedures or experimental therapies.

Subchondral bone strength of the sacroiliac joint-a combined approach using computed tomography osteoabsorptiometry (CT-OAM) imaging and biomechanical validation

Bone mineral density distribution patterns at the sacroiliac joint (SIJ) may reflect long-term adaptation patterns to the loading the joint endures. This study aims to display bone mineralisation patterns of the articular SIJ subchondral lamella using computed tomography (CT) osteoabsorptiometry and mechanical indenting, to determine whether a relationship exists between mineralisation and mechanical strength. Twenty hemipelves were CT-scanned before osteoabsorptiometry densitograms were derived. Each articular side of eleven SIJs was mechanically indented following a 10-mm grid scheme. The sacral surface displayed lower Hounsfield unit (HU) values (≤ 700 HU) than the iliac side (> 700 HU). The apex, superior corner and borders yielded the highest HU scores (> 700 HU). Penetration strength was significantly higher on the iliac side (p < 0.04). Mineral density correlated positively with penetration strength of the subchondral bone layer (p < 0.05). No correlations were found between the HU values, nor between penetration strength of corresponding sides of the same SIJ in the majority of cases (p > 0.05). The iliac subchondral lamella is mechanically denser than the sacral aspect. The non-correlation between density and bone strength of articulating sides indicates biomechanical non-conformity. Loading throughout the SIJ may follow a complex distribution pattern involving the surrounding soft tissues, suspending the sacrum between the ilia.

Raman microspectroscopy demonstrates reduced mineralization of subchondral bone marrow lesions in knee osteoarthritis patients

INTRODUCTION

Bone marrow lesions (BMLs) are frequently identified by MRI in the subchondral bone in knee osteoarthritis (KOA). BMLs are known to be closely associated with joint pain, loss of the cartilage and structural changes in the subchondral trabecular bone (SCTB). Despite this, understanding of the nature of BMLs at the trabecular tissue level is incomplete. Thus, we used Raman microspectroscopy to examine the biochemical properties of SCTB from KOA patients with presence or absence of BMLs (OA-BML, OA No-BML; respectively), in comparison with age-matched cadaveric non-symptomatic controls (Non-OA CTL).

METHODS

Tibial plateau (TP) specimens were collected from 19 KOA arthroplasty patients (6-Male, 13-Female; aged 56-74 years). BMLs were identified ex-vivo by MRI, using PDFS- and T1-weighted sequences. The KOA specimens were then categorized into an OA-BML group (n = 12; containing a BML within the medial condyle only) and an OA No-BML group (n = 7; with no BMLs identified in the TP). The control (CTL) group consisted of Non-OA cadaveric TP samples with no BMLs and no macroscopic or microscopic evidence of OA-related changes (n = 8; 5-Male, 3-Female; aged 44-80 years). Confocal Raman microspectroscopy, with high spatial resolution, was used to quantify the biochemical properties of SCTB tissue of both the medial and the lateral condyle in each group.

RESULTS

The ratios of peak intensity and integrated area of bone matrix mineral (Phosphate (v1), Phosphate (v2) and Phosphate (v4)), to surrogates of the organic phase of bone matrix (Amide I, Proline and Amide III), were calculated. Within the medial compartment, the mineral:organic matrix ratios were significantly lower for OA-BML, compared to Non-OA CTL. These ratios were also significantly lower for the OA-BML medial compartment, compared to the OA-BML lateral compartment. There were no group or compartmental differences for Carbonate:Phosphate (v1, v2 and v4), Amide III (α-helix):Amide III (random-coil), Hydroxyproline:Proline, or Crystallinity.

CONCLUSION

As measured by Raman microspectroscopy, SCTB tissue in BML zones in KOA is significantly less mineralized than the corresponding zones in individuals without OA. These data are consistent with those obtained using other methods (e.g. Fourier transform infrared spectroscopy; FTIR) and with the increased rate of bone remodeling observed in BML zones. Reduced mineralization may change the biomechanical properties of the trabecular bone in BMLs and the mechanical interaction between subchondral bone and its overlying cartilage, with potential implications for the development and progression of OA.

Does the relative density of periarticular bone influence the failure pattern of intra-articular fractures?

INTRODUCTION

The architecture of joints almost certainly influences the nature of intra-articular fractures, and the concavity is much more likely to fail than the associated convexity. However, local differences in periarticular bone density potentially also plays a critical role. The purpose of this study was to investigate if there was any difference in periarticular bone density in intra-articular fractures between the two opposing joint surfaces, comparing the convexity to the concavity.

MATERIALS AND METHODS

We retrospectively identified a series of 1003 intra-articular fractures of the hip, knee, and ankle; 129 of these patients had previously undergone CT scanning during their routine clinical assessment. Periarticular bone density was assessed using Hounsfield Units (HU) as a measure of the composite density of the adjacent bone. Bone density was compared between the opposite sides of each joint, to determine if a relationship exists between local bone density and the risk of articular surface fracture.

RESULTS

There was a statistically significant difference in density between the two opposing surfaces, with the convexity 19% more dense than the concavity (p=0.0001). The knee exhibited the largest difference (55%), followed by the hip (18%); in the ankle, an inverse relationship was observed, and the concave surface was paradoxically denser (5%). There was no significant difference between those cases where the concavity failed in isolation compared to those where the convexity also failed (p=0.28).

CONCLUSION

When the results were pooled for all three joints, there was a statistically significant higher local bone density demonstrated on the convex side of an intra-articular fracture. However, while this relationship was clearly exhibited in the knee, this was less evident in the other two joints; in the ankle the reverse was true, and the local bone adjacent to the concavity was found to have greater density. This suggests local bone density plays only a minor role in determining the nature of intra-articular fractures.

Medial malleolar osteotomy for the treatment of talar osteochondral lesions: anatomical and morbidity considerations

PURPOSE

Osteochondral lesions of the talus are often located posteromedially requiring open surgery to facilitate solid and complete osteochondral reconstruction. The aim of the study was to identify the optimal anatomical site for medial malleolar osteotomy based on the criteria of minimal cartilage damage (Study I) and to report on the morbidity in patients receiving osteotomy performed at the previously identified site (Study II).

METHODS

For Study I, cartilage coverage of the tibiofibular ankle joint facet was measured in 40 cadaveric ankles (20 cadaver specimens). In Study II, we assessed clinical (VAS pain score, AOFAS score, range of motion) and radiological outcome measures (SPECT-CT) in 17 patients (mean age, 36.8 ± 10.8 years) undergoing medial malleolar osteotomy.

RESULTS

The medial edge in the transition zone of the tibial plafond to the medial malleolus showed less than 75 % of cartilage coverage in 62.5 % of cadavers (Study I). Surgery resulted in lower pain levels (2.4 ± 2.6 compared with 6.3 ± 1.8 points; p < 0.001) and greater AOFAS scores (82.9 ± 14.1 compared with 43.5 ± 10.8 to points; p < 0.001) compared with baseline (Study II). No signs of intra-operative damage or mal- or non-union were found. Long-term morbidity was found in one patient. Implant removal was necessary in 12 of 17 patients (71 %).

CONCLUSION

Anatomically, there is an optimal location for the medial malleolar osteotomy at the medial ankle edge involving minimal cartilage damage. Clinical results using this location showed no short- or mid-term morbidity and little long-term morbidity. However, many patients required re-intervention for implant removal.

LEVEL OF EVIDENCE

IV.

Influence of Ankle Position and Radiographic Projection Angle on Measurement of Supramalleolar Alignment on the Anteroposterior and Hindfoot Alignment Views

BACKGROUND

Using digitally reconstructed radiographs (DRRs), we determined how changes in the x-ray beam projection angle from the horizon, tibiotalar joint angle, and axial rotation of the foot influenced measurements of the medial distal tibial angle (MDTA) on the anteroposterior (AP) and hindfoot alignment views (HAV).

METHODS

Seven cadaver foot-ankle specimens were scanned by computed tomography (CT) at fixed tibiotalar joint positions, ranging from 15 degrees of dorsiflexion to 25 degrees of plantarflexion. DRRs were created from each CT scan to simulate alterations in the horizontal projection angle (0 to 25 degrees) and foot axial rotation (-30 to 30 degrees). The MDTA was measured on each DRR and compared with that quantified on the baseline HAV and AP view.

RESULTS

Altering the horizontal projection angle by ≥5 degrees and >10 degrees significantly altered the MDTA for the AP view and the HAV, respectively. Shifting dorsiflexion and plantarflexion caused minor changes in the MDTA that were only statistically significant for the HAV. Axial rotation significantly changed the MDTA on both views, but deviations were more pronounced for the HAV.

CONCLUSIONS

Compared with the HAV, the MDTA on the AP view was less sensitive to changes in foot-ankle position. However, increasing the tilt of the x-ray beam from the horizon altered the MDTA on the AP view substantially.

CLINICAL RELEVANCE

To avoid misinterpretation of the MDTA, we recommend using the AP view to quantify supramalleolar alignment as it is less sensitive to changes in positioning of the foot-ankle. When acquiring an AP film, the x-ray beam should be directed along the horizon to ensure consistent assessment of the MDTA across patients.

Mineral density and penetration strength of the subchondral bone plate of the talar dome: high correlation and specific distribution patterns

The subchondral bone plate plays an important role in stabilizing the osteochondral joint unit and in the pathomechanism of osteochondral lesions and osteoarthritis. The objective of the present study was to measure the mineral density distribution and subchondral bone plate penetration strength of the talar dome joint facet to display and compare the specific distribution patterns. Ten cadaver specimens were used for computed tomography (CT) scans, from which densitograms were derived using CT-osteoabsorptiometry, and for mechanical indentation testing from which the penetration strength was obtained. Our results showed 2 different distribution patterns for mineral density and penetration strength. Of the 10 specimens, 6 (60%) showed bicentric maxima (anteromedially and anterolaterally), and 4 (40%) showed a monocentric maximum (either anteromedially or anterolaterally). A highly significant correlation (p < .0001) for both methods confirmed that the mineral density relied on local load characteristics. In conclusion, the biomechanical properties of the subchondral bone plate of the talar dome joint facet showed specific distribution patterns. CT-osteoabsorptiometry is a reliable method to display the mineral density distribution noninvasively. We recommend CT-osteoabsorptiometry for noninvasive analysis of the biomechanical properties of the subchondral bone plate in osteochondral joint reconstruction and the prevention and treatment of osteoarthritis and osteochondral lesions.

Changes of density distribution of the subchondral bone plate after supramalleolar osteotomy for valgus ankle osteoarthritis

CT-osteoabsorptiometry (CT-OAM) has been used to visualize subchondral bone plate density distribution regarding to its mineralization. The purpose of this study was to display and analyze the density distribution of the subchondral bone plate before and after supramalleolar realignment osteotomies. We retrospectively analysed pre- and postoperative CT images of nine consecutive patients with post-traumatic unilateral valgus ankle OA. The distribution charts of CT-OAM scans were quantitatively analyzed for subchondral bone plate density distribution. VAS for pain and the Tegner activity scale were used to assess clinical outcome. At a mean follow-up of 20 ± 5.6 months (range 13-27), we observed a significant pre- to postoperative decrease of the mean high-density area ratio in tibia (lateral and posterior area) (p ≤ 0.05) and the talus (lateral area) (p ≤ 0.05). Pairwise comparison between the pre- and postoperative mineralization at the articular surface showed a significant decrease of the high-density area ratio for the tibia and the talus. The VAS decreased from 6.2 ± 0.9 pre- to 2.8 ± 0.9 postoperatively (p = 0.027), and the Tegner score inclined from 4.5 ± 1.1 preoperatively to 5.3 ± 0.7 after surgery (p = 0.082). The tibial and talar subchondral bone plate density, regarding to its mineralization, decreased after supramalleolar medial closing wedge osteotomy in patients with valgus ankle OA. The results of this study suggest that realignment surgery may decrease peak bone density areas corresponding to the alignment correction and contribute to a homogenization of the subchondral bone plate mineralization.

The subtalar and talonavicular joints: a way to access the long-term load intake using conventional CT-data

PURPOSE

The aim of this study was to investigate the distribution of density of the subchondral bone plate within the articular surfaces of the subtalar and talonavicular joint regarding to its mineralisation and to verify whether a correlation to the mechanical bone strength exists.

METHODS

A total of 21 cadaverous lower leg specimens were investigated. Computed tomography osteo-absorptiometry (CT-OAM) was used to display the mineralisation of the subchondral bone plate analysing its density. The mechanical strength was measured by means of indentation testing. The distribution pattern was analysed regarding their dissemination with the main focus on number and location of their maxima. The correlation of both parameters was evaluated by linear regression.

RESULTS

The mineralisation and the mechanical strength were not distributed homogenously throughout the articular surfaces but showed unique and reproducible patterns. The range of absolute values for density and strength varied in between the samples and joint surfaces, but the number and location of the maxima evaluated by both methods showed to be concurring. The coefficient of correlation of both datasets ranged from 0.76 to 0.95 (median 0.88) and showed a linear dependency.

CONCLUSIONS

Density distribution and mechanical strength of the subchondral bone plate are significantly associated and can be seen as a mirror of the long-term load intake of a joint. It can be concluded that CT-OAM as a tool to visualize subchondral bone plate density distribution regarding to its mineralisation can be used to indirectly gain information about joint biomechanics in vivo by the use of conventional CT-data.

Computed tomography osteoabsorptiometry for assessing the density distribution of subchondral bone as a measure of long-term mechanical stress in the "rugby shoulder"

BACKGROUND

Rugby is a collision sport with a high risk of shoulder injury. Although traumatic anterior shoulder instability is common, the long-term effects of rugby and joint instability on the shoulder have not been described; thus, this study assessed the effects of rugby itself, and joint instability, on the glenoid cavity.

MATERIALS AND METHODS

Both sides of the shoulders from 25 rugby players and 17 control patients with unilateral shoulder instability were prospectively evaluated by means of computed tomography osteoabsorptiometry, which represents the distribution of mineralization in subchondral bone plate (DMSB) as a marker of the long-term loading history of a joint. For the quantitative analysis, intergroup differences of maximum Hounsfield unit (HU) values in 7 areas on the glenoid were assessed in the uninjured intact shoulder to characterize the influence of rugby. Side-to-side differences of the HUs in each area were assessed in each participant to characterize the effects of shoulder instability. For the qualitative analysis, associations between the patterns of each DMSB and each group were assessed by means of correspondence analysis.

RESULTS

All examined areas on the glenoid had a significantly higher HUs in rugby players. Shoulder instability affected the HUs in both groups. A qualitative analysis demonstrated that the maximum HU tended to be shifted more inferiorly in rugby players and in the unstable shoulders.

CONCLUSIONS

Rugby affects the shoulder joint, regardless of any history of instability, suggesting that "rugby shoulder" tends to involve degenerative changes, such as osteoarthritis or labral tears.

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).

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.

Importance of the dome and posterior wall as evidenced by bone density mapping in the acetabulum

BACKGROUND

Characterizing the distribution of bone density in the acetabulum is of importance in better understanding and guiding treatment for both osteoarthritis and trauma of the hip joint. This study aims to develop a highly automated method to quantify the pattern of subchondral bone density in the acetabulum using clinically identifiable regions.

METHODS

Subchondral acetabular bone density distribution maps were created bilaterally from 30 non-pathologic pelvic CT scans. The density maps were aligned orthogonal to the acetabular rim plane and divided into twelve zones. Average bone density was calculated in each of these zones and compared to investigate differences between regions within each acetabulum and between right and left sides in a given patient.

FINDINGS

In all patients, the zones corresponding to the dome and posterior wall of the acetabulum demonstrated significantly higher average bone densities than all other regions (P<0.01). Significant correlations (R=0.4 to 0.76, P<0.05) were found between corresponding regions of the left and right sides in 10 of the 12 zones.

INTERPRETATION

The pattern of subchondral bone density distribution found in this study is consistent with previously observed bone density patterns in the acetabulum. Correspondence of right and left sides suggests that the distribution of loading on the acetabulum is similar on both sides in healthy individuals, though differences may exist in load sharing. Quantifying bone density patterns using zonal density map analysis may lead to a better understanding of the impact of traumatic injuries and progression of pathologic conditions in the hip joint.