Mineralisation patterns in the subchondral bone plate of the humeral head

CT Osteoabsorptiometry Assessment of Subchondral Bone Density Predicts Intervertebral Implant Subsidence in a Human ACDF Cadaver Model

STUDY DESIGN

Cadaveric biomechanics study.

OBJECTIVE

Subchondral bone mineral density (sBMD) reflects the long-term mineralization and distribution of stress on joints. The use of 3-dimensional (3-D) methods to evaluate sBMD, including computed tomography osteoabsorptiometry (CT-OAM), enables the assessment of density distribution with emphasis on subchondral bone. This study sought to measure the sBMD of cervical endplates using CT-OAM and correlate it to mechanical implant subsidence in a cadaveric model.

METHODS

Fourteen fresh human cadaveric cervical spines were subjected to dynamic testing after single level discectomy and instrumentation using a PEEK interbody spacer. Specimens were imaged with CT 3 times: 1st) whole intact cervical spine, 2nd) after implantation, and 3 rd) after testing. These images were used to assess sBMD distributions using CT-OAM directly underneath the spacer. Subsidence was defined as the displacement of the device into the endplates.

RESULTS

The observed "failure mode" was consistently recorded as subsidence, with a mean of 0.45 ± 0.36 mm and 0.40 ± 0.18 mm for the C4-5 and C6-7 levels, respectively. There were no differences by level. The experimental cyclic test showed that denser endplates experienced less deformation under the same load.

CONCLUSIONS

This study achieved its stated aim of validating the use of CT-OAM as a method to analyze the sBMD of the cervical endplates. Studies such as this are providing new information on available technology such as CT-OAM, providing new tools for clinicians treating spinal conditions in need of augmentation and stabilization via interbody devices.

Lumbar facet joint subchondral bone density in low back pain and asymptomatic subjects

OBJECTIVE

To report in vivo measurements of lumbar facet joint subchondral bone mineral density used in the description of facet joint loading patterns and to interrogate if low back pain is associated with changes in subchondral bone mineral density.

MATERIALS AND METHODS

In vivo measurements of lumbar facet joint subchondral bone mineral density (L1/2 to L5/S1) in Hounsfield units were performed on 89 volunteers (56 controls and 33 with low back pain) by computed tomography osteoabsorptiometry at subchondral regions between 1.5 mm and 2.5 mm below the joint surface. The facet surface was divided into five topographic zones: cranial, lateral, caudal, medial, and central.

RESULTS

We analyzed 1780 facet joint surfaces. Facets were denser (p < 0.0001) both in superior facets and in low back pain subjects (p < 0.0001). For the entire cohort, the facet center zone subchondral bone mineral density was higher (p < 0.0001) than that of the peripheral zones. The analyses indicate that subchondral bone mineral density is highest in patients with low back pain, the superior facets, and the center zone of the facets.

CONCLUSIONS

Subchondral bone mineral density is thought to reflect cumulative, long-term distribution of stress acting on a joint. This work shows that higher subchondral bone mineral density values in the center zone indicate predominant stress transmission through the center of the facet joints. Finally, the greater subchondral bone mineral density in patients with low back pain may reflect both increased load bearing by the facets secondary to disc degeneration and misdistribution of loading within the joint.

An assessment of proximal humerus density with reference to stemless implants

BACKGROUND

Shoulder arthroplasty humeral components have undergone several generational changes, with systems now offering shorter stems and stemless options. The stemless humeral implants obtain fixation in the trabecular bone of the proximal humerus through elaborate fixation features. To optimize implant design, the regional variations in bone density within the proximal humerus should be determined. As such, the purpose of this computed tomography-based study was to map the regional variations in bone density of the proximal humerus.

METHODS

The trabecular-canal of the proximal humerus was extracted from computed tomography scans of 98 subjects and divided into 13 slices and 5 subsections (central, anterior, posterior, medial, and lateral). The average apparent density (ρ_AVG) was then quantified in each subsection of the trabecular-canal.

RESULTS

Slice depth, subsection, and gender were all significant main effects, with additional significant interactions between slice depth, subsection, and osteoarthritic condition. The slices above the resection plane had the greatest ρ_AVG, with densities decreasing down the canal. The central subsection had significantly lower ρ_AVG than the peripheral sections, and the medial subsection tended to have the highest ρ_AVG (P < .001). Furthermore, the ρ_AVG of male subjects was significantly greater than that of female subjects (P < .001).

CONCLUSIONS

The apparent density of the proximal humerus' trabecular-canal is nonuniform. This has implications for the design of stemless implants, indicating that implants seeking purchase in higher density bone should take advantage of the peripheral regions of the trabecular-canal within the first 15-20 mm beneath the humeral head resection plane.

A comparison of normal and osteoarthritic humeral head size and morphology

BACKGROUND

The purpose of this study was to evaluate and to compare the size and morphologic patterns among normal and osteoarthritic (OA) humeral heads.

METHODS

This comparative anatomic imaging study evaluated 150 humeral heads that were separated into 3 cohorts: normal, OA with symmetric glenoid erosion, and OA with asymmetric (type B2) glenoid erosion. Three-dimensional models were created of the humeral head from computed tomography data, and point coordinates were extracted for evaluation. Parameters measured were diameter (sphere fit and circle fit), chord distance (superoinferior and anteroposterior), and humeral head height.

RESULTS

The sphere-fit diameter of the humeral head for the entire OA cohort (100 patients; mean diameter, 59 ± 9 mm) was significantly greater (P < .001) than that of the normal cohort (50 patients; mean diameter, 49 ± 5 mm). Similarly, the humeral head circle-fit diameters in the superoinferior and anteroposterior planes were significantly greater (P < .001) in the combined OA cohorts (59 ± 9 mm and 56 ± 10 mm, respectively) compared with the normal cohort (51 ± 5 mm and 47 ± 5 mm, respectively). However, there were no significant differences (P ≥ .099) between the symmetric and asymmetric OA cohorts in sphere-fit or circle-fit diameters. The mean values of humeral head heights were not significantly different (P = .382) between cohorts, 19 ± 2 mm, 18 ± 2 mm, and 18 ± 2 mm for the normal, symmetric, and asymmetric cohorts, respectively.

DISCUSSION

Although OA humeral head morphology varies significantly from normal, it does not vary as a function of the Walch classification between symmetric and asymmetric glenoids. Understanding of the morphologic variability of the pathologic humeral head may provide insight into the pathoanatomy of osteoarthritis and the development of various erosion patterns.

Radiologic assessment of glenohumeral relationship: reliability and reproducibility of lateral humeral offset

BACKGROUND

It has been shown that anatomical reconstruction is an important step in achieving good function after shoulder arthroplasty. It is essential to reconstruct the distance between the coracoid process and greater tubercle as this relates to the moment arm of the deltoid and rotator cuff muscles. This study evaluated the reliability of measurement of the lateral humeral offset (LHO) on plain radiographs and on computed tomography (CT).

METHODS

Four independent observers performed measurements of LHO on radiographs and CT from 26 patients awaiting shoulder reconstruction. The interobserver reliability and intraobserver reproducibility were assessed.

RESULTS

Interobserver reliability and intraobserver reproducibility of LHO in axial CT scans were excellent. Plain radiography showed fair to excellent interobserver reliability and variable intraobserver reproducibility.

CONCLUSION

CT is a reliable tool to measure LHO supporting its use in preoperative planning. When AP radiography is used for preoperative planning the examiner should be aware of its limitations and standardisation protocols should be considered.

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.

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.

Glenoid stress distribution in baseball players using computed tomography osteoabsorptiometry: a pilot study

BACKGROUND

It is important to understand the loading conditions when considering the pathology of shoulder disorders in overhead athletes. However, because throwing is a complicated motion and methods to directly determine stress distribution are complex, direct measurement of the stress distribution across the glenohumeral joint has not been attempted. Subchondral bone density reportedly reflects the cumulative stress acting on a joint surface under actual loading conditions.

QUESTIONS/PURPOSES

To assess alterations in stress distribution across the glenoid cavity caused by pitching, we investigated the distribution of subchondral bone density in nonathletic volunteers and asymptomatic baseball players, including fielders and pitchers.

METHODS

We collected CT imaging data from the dominant-side shoulder of 10 nonathletic volunteers (controls), 10 fielders, and 10 pitchers in a competitive college baseball league (all men aged 19–24 years, mean 20.7 years). We measured the distribution of subchondral bone density of the glenoid cavity using CT osteoabsorptiometry. The obtained stress distribution map was divided into four segments: anterosuperior, anteroinferior, posteroinferior, and posterosuperior regions. We quantitatively analyzed the location and percentages of high-density regions on the articular surface.

RESULTS

The percentages of high-density regions, including the anteroinferior and posterior segments, were greater in pitchers and fielders than in controls. The percentages of high-density regions did not differ between pitchers and fielders.

CONCLUSIONS

The bicentric density patterns indicated that the cumulative force of pitching activity affected the long-term stress distribution across the glenoid cavity.

CLINICAL RELEVANCE

Our data should be useful for analyzing pitching activity and clarifying the pathology of shoulder disorders associated with throwing.