Marko Kraljević

Mineralisation and mechanical strength of the glenoid cavity subchondral bone plate

PurposeFailures 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.MethodsA 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).ConclusionsLong-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.

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).

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

PurposeAmong 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.MethodsTo 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.ResultsResults 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.ConclusionWe 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.

Glenohumeral relationships: Subchondral mineralization patterns, thickness of cartilage, and radii of curvature

Subchondral mineralization represents the loading history of a joint and can be measured in vivo using computed tomography osteoabsorptiometry. Different mineralization patterns in the glenohumeral joint have been explained by the principle of physiologic incongruence. We sought to support this explanation by measurement of mineralization, radii, and cartilage thickness in 18 fresh shoulder specimens. We found three mineralization patterns: bicentric, monocentric anterior, and monocentric central. Mean radii of the glenoids were 27.4 mm for bicentric glenoids, 27.3 mm for monocentric anterior, and 24.8 mm for monocentric central glenoids. Cartilage thickness measurement revealed the highest values in anterior parts; the thinnest cartilage was found centrally. Our findings support the principle of a physiologic incongruence in the glenohumeral joint. Bicentric mineralization patterns exist in joints consisting of more flat glenoids compared to the corresponding humeral head. Monocentric distribution with a central maximum was found in specimens with glenoids being more curved, indicating higher degrees of congruence, which might represent an early stage of degenerative disease. The obtained information might also be important for implant fixation in resurfacing procedures or to achieve the best possible fit of an osteochondral allograft in the repair of cartilage defects.

Timing of surgical antimicrobial prophylaxis: a phase 3 randomised controlled trial

BACKGROUND Based on observational studies, administration of surgical antimicrobial prophylaxis (SAP) for the prevention of surgical site infection (SSI) is recommended within 60 min before incision. However, the precise optimum timing is unknown. This trial compared early versus late administration of SAP before surgery. METHODS In this phase 3 randomised controlled superiority trial, we included general surgery adult inpatients (age ≥18 years) at two Swiss hospitals in Basel and Aarau. Patients were randomised centrally and stratified by hospital according to a pre-existing computer-generated list in a 1:1 ratio to receive SAP early in the anaesthesia room or late in the operating room. Patients and the outcome assessment team were blinded to group assignment. SAP consisted of single-shot, intravenous infusion of 1·5 g of cefuroxime, a commonly used cephalosporin with a short half-life, over 2-5 min (combined with 500 mg metronidazole in colorectal surgery). The primary endpoint was the occurrence of SSI within 30 days of surgery. The main analyses were by intention to treat. The trial is registered with ClinicalTrials.gov, number NCT01790529. FINDINGS Between Feb 21, 2013, and Aug 3, 2015, 5580 patients were randomly assigned to receive SAP early (2798 patients) or late (2782 patients). 5175 patients (2589 in the early group and 2586 in the late group) were analysed. Median administration time was 42 min before incision in the early group (IQR 30-55) and 16 min before incision in the late group (IQR 10-25). Inpatient follow-up rate was 100% (5175 of 5175 patients); outpatient 30-day follow-up rate was 88·8% (4596 of 5175), with an overall SSI rate of 5·1% (234 of 4596). Early administration of SAP did not significantly reduce the risk of SSI compared with late administration (odds ratio 0·93, 95% CI 0·72-1·21, p=0·601). INTERPRETATION Our findings do not support any narrowing of the 60-min window for the administration of a cephalosporin with a short half-life, thereby obviating the need for increasingly challenging SAP timing recommendations. FUNDING Swiss National Science Foundation, Hospital of Aarau, University of Basel, Gottfried und Julia Bangerter-Rhyner Foundation, Hippocrate Foundation, and Nora van Meeuwen-Häfliger Foundation.

Mineralisation patterns in the subchondral bone plate of the humeral head

PurposePathologic 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.MethodsBy 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.Results49 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%.ConclusionWe 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.

Obstructing adenocarcinoma of the descending colon in a 31-year-old pregnant woman.

INTRODUCTION Colon cancer in pregnant women is rare and tends to produce unspecific symptoms until advanced stage. Therefore common manifestations during pregnancy must be properly evaluated to avoid delayed diagnosis. PRESENTATION OF CASE A 31-year-old pregnant woman presented with nausea, vomiting and obstipation. An obtained magnetic resonance imaging (MRI) showed distended colon and the consecutive colonoscopy with biopsies confirmed the diagnosis of stenosing carcinoma of the descending colon. Left sided hemicolectomy was performed 10 days after initial presentation. Tumor histology confirmed the diagnosis of adenocarcinoma of the descendo-sigmoidal junction. Adjuvant chemotherapy with 5-fluorouracil was started in the 29th gestational week. The patient had an uneventful delivery of a healthy baby in her 39th gestational week. DISCUSSION Colorectal carcinoma during pregnancy is a rare event and its diagnosis is often delayed because symptoms are unspecific until the disease is advanced. Although constipation in pregnancy is a common symptom differential diagnosis of a mechanical stenosis should always be contemplated, especially when conservative treatment of constipation fails. MRI is the imaging tool of choice as abdominal computed tomography (CT) is contraindicated in pregnancy. Endoscopic confirmation should be obtained to gain pathological diagnosis of colorectal carcinoma. Surgery is the gold standard of treatment. In relation to the stage of the disease chemotherapy is of great importance. CONCLUSION Obstructing colorectal cancer can be a rare reason for the common problem of constipation in pregnancy. Beside clinical examination, MRI scan and colonoscopy will reveal the tumor in most cases and should be followed by surgical treatment and chemotherapy according to the stage of disease.