Size of cup affects the anterior capsular distance in total hip arthroplasty, as measured with ultrasound.
BACKGROUND
Previously was found that sonography is a reliable method to measure a capsular distance in total hip arthroplasty hips. The aim of our current study was to investigate the relation between the implanted size of the cup and the anterior capsular distance, as measured with ultrasound one year after THA.


METHODS
50 osteoarthritis (OA) patients operated on with total hip arthroplasty one year before were included in the study and the anterior capsular distance was measured sonographically. Patients were grouped with respect to cup size. The correlation between the implanted cup size and capsular distance was determined.


RESULTS
The mean capsular distance in the whole group was 1.37 (SD 0.19) cm. The mean capsular distance in the group with small cups was 1.27 (SD 0.13) cm, in large cups it was 1.45 (SD 0.20) cm, p = 0.02. Spearman correlation analysis showed a statistically significant correlation between a greater capsular distance and the larger size of the cup (r = 0.5, p < 0.0001).


CONCLUSIONS
The greater capsular distance in successful THA hips is affected by cup size. We propose that this should be considered when evaluating sonography of the anterior capsular distance after THA.
Department of Orthopedics, Lund University Hospital, Getingevagen 4, Lund 22185, Sweden. sarunas.tarasevicius@med.lu.se.
Sarunas
S
Tarasevicius
Valdemaras
V
Loiba
Justinas
J
Stucinskas
Otto
O
Robertsson
Hans
H
Wingstrand
D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging* / Q000601:surgery*; D011474:Prosthesis Design; D013997:Time Factors; D016896:Treatment Outcome; D014463:Ultrasonography