A new arthroscopic technique to determine anterior-inferior glenoid bone loss: validation of the secant chord theory in a cadaveric model.
OBJECTIVE
The accuracy of a previously described method using the glenoid bare spot (GBS) as a reference point was compared with a new method using the secant chord theory (SCT), which relies on the circular geometry of the inferior glenoid to calculate bone loss.


METHODS
In 7 embalmed cadaveric shoulders a digital image of the glenoid face was used to calculate the area of the best-fit circle of the inferior glenoid. Osteotomy templates from the 3-o'clock to 6-o'clock position were created to make a simulated anterior-inferior bone defect of 12.5% and 25% of the area of the circle. Measurements were taken with an arthroscopic probe from 2 simulated posterior portal positions (9 and 10 o'clock) by use of 2 techniques-SCT and GBS-in the intact, 12.5% loss, and 25% loss states.


RESULTS
In the intact state, measurements showed a mean SCT loss of 4.1% and GBS loss of 4.4%. In the 12.5% loss state, mean percent bone loss with GBS was 23.1% compared with 14.8% with SCT (P = .0001) at the 10-o'clock portal and 22.2% compared with 15.9% (P = .006) at the 9-o'clock portal. In the 25% loss state, mean percent bone loss with GBS was 31.5% compared with 26.6% with SCT (P = .002) at the 10-o'clock portal and 30.4% compared with 28.9% (P = .48) at the 9-o'clock portal.


CONCLUSIONS
The SCT is shown to be a more accurate method of determining glenoid bone loss in an arthroscopic model; however, additional mathematic calculations are necessary. As shown in the intact state, there is an inherent small error of approximately 4% when arthroscopically determining bone loss.


CONCLUSIONS
The technique may aid the clinician in quantifying glenoid bone loss and help determine when bone augmentation may be advisable.
Detterline
Alvin J
AJ
Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, USA. adetterlinemd@gmail.com
Provencher
Matthew T
MT
Ghodadra
Neil
N
Bach
Bernard R
BR
Romeo
Anthony A
AA
Verma
Nikhil N
NN
D000368:Aged; D000369:Aged, 80 and over; D001182:Arthroscopy / Q000379:methods*; D001862:Bone Resorption / Q000175:diagnosis*; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D012785:Shoulder Joint / Q000601:surgery*