Philipp Moroder1, Lukas Ernstbrunner2, Werner Pomwenger3, Florian Oberhauser4, Wolfgang Hitzl5, Mark Tauber6, Herbert Resch2, Rudi Moroder7. 1. Department of Traumatology and Sports Injuries, Paracelsus Medical University, Salzburg, Austria. Electronic address: philipp.moroder@pmu.ac.at. 2. Department of Traumatology and Sports Injuries, Paracelsus Medical University, Salzburg, Austria. 3. Department of Information Technology, Salzburg University of Applied Science, Salzburg, Austria. 4. gbd ZT, Dornbirn, Austria. 5. Research Office for Biostatistics, Paracelsus Medical University, Salzburg, Austria. 6. Department of Traumatology and Sports Injuries, Paracelsus Medical University, Salzburg, Austria; Department of Shoulder and Elbow Surgery, ATOS Clinic, Munich, Germany. 7. Thomas Lorenz ZT, Graz, Austria.
Abstract
PURPOSE: To determine whether anterior shoulder instability is associated with an inherent deficiency of the bony glenoid concavity, which results in a reduced bony shoulder stability ratio (BSSR). METHODS: In this case-control study, we searched the institutional database for patients treated for unilateral recurrent anterior shoulder instability. We included 30 consecutive patients with atraumatic instability, 30 consecutive patients with traumatic instability, and 36 matched healthy controls, for a total of 96 shoulders. Computed tomography images of the unaffected shoulders of the instability patients were compared with images of the ipsilateral shoulders of age- and sex-matched healthy controls for differences in glenoid morphology. By use of a mathematical formula based on Pythagorean trigonometric identities, the mean BSSRs of the different groups were calculated and compared. Validation of the formula was accomplished by finite element analysis. RESULTS: The mean BSSR of atraumatic instability patients was 17.9% ± 8.5% and therefore significantly lower than the mean BSSR of 31.1% ± 7.5% of the control group (13.2%; 95% confidence interval [CI], 9.1% to 17.4%; P < .001). The mean BSSR of the traumatic instability group was higher, at 23.9% ± 8.5% (P = .007), but still showed a deficit of 7.2% (95% CI, 2.8% to 11.7%; P = .002) compared with controls. The atraumatic instability group showed a mean reduction of 0.9 mm (95% CI, 0.6 to 1.1 mm; P < .001) in concavity depth and a decrease of 2.9° (95% CI, 0.4° to 5.3°; P = .021) in concavity retroversion, whereas the traumatic instability patients had a reduction of 0.4 mm (95% CI, 0.1 to 0.8 mm; P = .006) in concavity depth. Neither of the instability groups differed significantly from their respective controls in terms of glenoid concavity diameter, head radius, or glenoid vault morphology. CONCLUSIONS: Anterior shoulder instability is associated with an inherent flattening of the bony glenoid concavity, which significantly decreases the BSSR. The deficiency appears to be more pronounced in patients with atraumatic instability than in patients with traumatic instability. LEVEL OF EVIDENCE: Level III, case-control study.
PURPOSE: To determine whether anterior shoulder instability is associated with an inherent deficiency of the bony glenoid concavity, which results in a reduced bony shoulder stability ratio (BSSR). METHODS: In this case-control study, we searched the institutional database for patients treated for unilateral recurrent anterior shoulder instability. We included 30 consecutive patients with atraumatic instability, 30 consecutive patients with traumatic instability, and 36 matched healthy controls, for a total of 96 shoulders. Computed tomography images of the unaffected shoulders of the instability patients were compared with images of the ipsilateral shoulders of age- and sex-matched healthy controls for differences in glenoid morphology. By use of a mathematical formula based on Pythagorean trigonometric identities, the mean BSSRs of the different groups were calculated and compared. Validation of the formula was accomplished by finite element analysis. RESULTS: The mean BSSR of atraumatic instabilitypatients was 17.9% ± 8.5% and therefore significantly lower than the mean BSSR of 31.1% ± 7.5% of the control group (13.2%; 95% confidence interval [CI], 9.1% to 17.4%; P < .001). The mean BSSR of the traumatic instability group was higher, at 23.9% ± 8.5% (P = .007), but still showed a deficit of 7.2% (95% CI, 2.8% to 11.7%; P = .002) compared with controls. The atraumatic instability group showed a mean reduction of 0.9 mm (95% CI, 0.6 to 1.1 mm; P < .001) in concavity depth and a decrease of 2.9° (95% CI, 0.4° to 5.3°; P = .021) in concavity retroversion, whereas the traumatic instabilitypatients had a reduction of 0.4 mm (95% CI, 0.1 to 0.8 mm; P = .006) in concavity depth. Neither of the instability groups differed significantly from their respective controls in terms of glenoid concavity diameter, head radius, or glenoid vault morphology. CONCLUSIONS: Anterior shoulder instability is associated with an inherent flattening of the bony glenoid concavity, which significantly decreases the BSSR. The deficiency appears to be more pronounced in patients with atraumatic instability than in patients with traumatic instability. LEVEL OF EVIDENCE: Level III, case-control study.
Authors: Matthijs Jacxsens; Shireen Y Elhabian; Sarah E Brady; Peter N Chalmers; Robert Z Tashjian; Heath B Henninger Journal: J Shoulder Elbow Surg Date: 2019-03-28 Impact factor: 3.019
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Authors: Philipp Moroder; Franziska Haniel; Michael Quirchmayr; Eva Schulz; Manfred Eppel; Nicholas Matis; Alexander Auffarth; Herbert Resch Journal: BMC Musculoskelet Disord Date: 2016-08-22 Impact factor: 2.362