Concave impressio ligamenti costoclavicularis ("rhomboid fossa") and its prevalence and relevance to clinical practice.

PURPOSE: The incidence of fossa rhomboidea (RF) and its relevance to clinical practice were retrospectively studied in 1,017 cases of patients who endured clavicle fractures. The aim of the study was to determine the frequency of different types of insertion areas of costoclavicular ligament (LCC) in our group, as well as gender distribution. Furthermore, we wanted to investigate whether the RF represents a weakened part of clavicle where the fracture occurred. Several of our findings in our control group were quite interesting and worth mentioning.
MATERIALS AND METHODS: 1,017 roentgenograms were analyzed from 1,027 clavicle fractures of patients from 2 to 90 years of age who were treated between 2007 and 2011.
RESULTS: Using the Allman classification system, 79% of the examined clavicle fractures were identified as type 1, 18.4% as type 2, and 2.6% as type 3. Statistical analysis did not demonstrate a difference in fractures of the clavicle between the right and the left side (47, 53%, respectively; p = 0.0570). There was a statistically significant difference in the incidence of fractures between the genders (males 71%, females 29 %; p < 0.0001). The results for the insertion attachment area were as follows for the given percent of cases: flat (75.2%); concave (21.1%); convex (3.7%). Those 21.1% of concave insertions represent RF. 5.3% of RF cases were between 2 to 10 mm in depth. One of the patients with RF had a deepend insertion of the LCC on the superior surface of the first rib analogous to RF. The bilateral RF was asymmetrical in its appearance. One of the patients suffered from LCC enthesopathy. The difference of the distribution of RF throughout the genders was 10.5% in females and 89.5% in males, marking a difference that is statistically significant (p < 0.0001). Only in 0.3%, the fracture line occurred in RF, which did not prove the RF to be a weakened point of the fracture (p < 0.0001).
CONCLUSIONS: RF represents a variety of LCC insertion that is predominantly found in male patients, which can be used in the determination of gender in forensic analysis. RF is not a weak point for fracture formation. Enthesopathy of the LCC together with RF can lead to suspicion concerning the osteolytic process. Biopsy of RF should be avoided. Insertion of LCC similar to RF can be exceptionally found on the first rib.