The critical size of a defect in the glenoid causing anterior instability of the shoulder after a Bankart repair, under physiological joint loading

Aims

Patients with recurrent anterior dislocation of the shoulder commonly have an anterior osseous defect of the glenoid. Once the defect reaches a critical size, stability may be restored by bone grafting. The critical size of this defect under non-physiological loading conditions has previously been identified as 20% of the length of the glenoid. As the stability of the shoulder is load-dependent, with higher joint forces leading to a loss of stability, the aim of this study was to determine the critical size of an osseous defect that leads to further anterior instability of the shoulder under physiological loading despite a Bankart repair.

Patients and Methods

Two finite element (FE) models were used to determine the risk of dislocation of the shoulder during 30 activities of daily living (ADLs) for the intact glenoid and after creating anterior osseous defects of increasing magnitudes. A Bankart repair was simulated for each size of defect, and the shoulder was tested under loading conditions that replicate in vivo forces during these ADLs. The critical size of a defect was defined as the smallest osseous defect that leads to dislocation.

Results

The FE models showed a high risk of dislocation during ADLs after a Bankart repair for anterior defects corresponding to 16% of the length of the glenoid.

Conclusion

This computational study suggests that bone grafting should be undertaken for an anterior osseous defect in the glenoid of more than 16% of its length rather than a solely soft-tissue procedure, in order to optimize stability by restoring the concavity of the glenoid.

[Evaluation of shoulder arthroplasty in treatment of four-fragment fractures of the proximal humerus]

The dislocated four-fragment fracture of the proximal humerus is a problematic fracture. In this study we evaluated shoulder function after implantation of a shoulder hemiprosthesis of the anatomical generation. The evaluation was based on a case-control study in which the following information was gathered: epidemiology, Constant-Murley score, compliance score, radiological results, and a summary of complications. Twenty shoulder prostheses were implanted between September 2000 and August 2002. After an average follow-up time of 14 months, the average Constant score was 52. The score for the opposite shoulder was 91 points. The function found to be most limited was shoulder movement. The subjective estimation of shoulder function had a mean value of 49% and correlated with the Constant score. Fourteen of the patients exhibited a postoperative defect in the tuberculum majus. Implantation of shoulder hemiprostheses allows treatment of four-fragment fractures of the humerus head in older patients, whereby limitations of mobility and function are to be expected.

Die komplexe Beckenverletzung im Kindesalter

Pelvic disruptions are rare in children caused by the flexible anchoring of bony parts associated with a high elasticity of the skeleton. Portion of pelvic fractures in infants is lower than 5% even when reviewing cases of specialized centers. The part of complex pelvic injuries and multiple injured patients in infants is higher when compared to adults, a fact caused by the more intense forces that are necessary to lead to pelvic disruption in children. Combination of a rare injury and the capability of children to compensate blood loss for a long time may implicate a wrong security and prolong diagnostic and therapeutic procedures--a problem that definitely should be avoided. Three cases were analyzed and established algorithms for treatment of patients matching these special injury-features demonstrated. A good outcome may only be achieved when all components of injury pattern get recognized and treatment is organized following the hierarchy of necessity. Therefore in the time table first life-saving steps have to be taken and then accompanying injuries can be treated that often decisively influence life quality. As seen in our cases unstable and dislocated fractures require open reduction and internal fixation ensuring nerval decompression, stop of hemorrhage and realizing the prerequisite for effective treatment of soft tissue damage. The acute hemorrhagic shock is one of the leading causes of death following severe pelvic injuries. After stabilization of fracture, surgical treatment of soft tissue injuries and intraabdominal bleeding sources the immediate diagnostic angiography possibly in combination with a therapeutic selective embolization is a well established part of the treatment. The aim of complete restitution can only be accomplished by cooperation of several different specialists and consultants in a trauma center.

[Tissue engineering with mesenchymal stem cells for cartilage and bone regeneration]

Tissue engineering offers the possibility to fabricate living substitutes for tissues and organs by combining histogenic cells and biocompatible carrier materials. Pluripotent mesenchymal stem cells are isolated and subcultured ex vivo and then their histogenic differentiation is induced by external factors. The fabrication of bone and cartilage constructs, their combinations and gene therapeutic approaches are demonstrated. Advantages and disadvantages of these methods are described by in vitro and in vitro testing. The proof of histotypical function after implantation in vivo is essential. The use of autologous cells and tissue engineering methods offers the possibility to overcome the disadvantages of classical tissue reconstruction--donor site morbidity of autologous grafts, immunogenicity of allogenic grafts and loosening of alloplastic implants. Furthermore, tissue engineering widens the spectrum of surgical indications in bone and cartilage reconstruction.

Migratory activity of blood polymorphonuclear leukocytes during juvenile rheumatoid arthritis, demonstrated with a new whole-blood membrane filter assay

Polymorphonuclear leukocyte (PMN) migration is measured in whole blood in a migration chamber consisting of a membrane filter (3-microns pores, 140 microns thick) with an integrated chemoattractant depot (FMLP in solid form) attached to a plastic container. Control chambers lack FMLP (blanks). One test unit requires 300 microliters blood. Numbers and distribution of the PMN immigrants into the filters are determined microscopically. Altogether 26 measurements of PMN migration in five juvenile rheumatoid arthritis (JRA) patients with varying disease activity were compared with the reactions of a healthy control group (N = 32). Correlations were calculated with conventional laboratory parameters (WBC, PLT, BSR, CRP, Hgb, serum Fe) and disease activity. In comparison with healthy controls, PMNs of JRA patients generally show a markedly increased penetration depth into the filters irrespective the presence of the chemoattractant or the disease activity. Increased migratory reactions to FMLP in comparison to blanks were found during high disease activity only. The PMN penetration depth correlates positively with the CRP, and reciprocally with the Hgb blood levels. The migration assay combines fast and simple processing with good preservation of the genuine PMN activation state.