Single vs double headless compression screw fixation for scaphoid nonunion

Table 1 Baseline demographics and clinical characteristics, n (%)/mean ± SD

Variable	1-screw group (n = 15)	2-screw group (n = 8)	Test statistic	P value
Age (years)	32.80 ± 9.41	23.88 ± 7.30	t = 2.326	0.030a
BMI (kg/m2)	28.84 ± 4.15	25.84 ± 2.18	t = 1.894	0.072
Dominant hand			N/A	1.000
Right	14 (93.3)	7 (87.5)
Left	1 (6.7)	1 (12.5)
Comorbidities			N/A	0.558
None (free)	13 (86.7)	8 (100.0)
DM + UC	1 (6.7)	0 (0.0)
Hyperlipidemia	1 (6.7)	0 (0.0)
Pre-operative DISI	7 (46.7)	7 (87.5)	N/A	0.086

^aP < 0.05.

Continuous variables (age, body mass index) were analyzed using an independent samples t-test. Categorical variables (Dominant Hand, Comorbidities, Pre-Operative dorsal intercalated segment instability) were analyzed using Fisher’s exact test. N/A indicates Fisher’s exact test was used, which computes exact probability directly without generating a standardized test statistic. BMI: Body mass index; DM: Diabetes mellitus; UC: Ulcerative colitis; DISI: Dorsal intercalated segment instability; N/A: Not applicable.

Table 2 Post-operative radiographic changes and deformity correction

Variable	1-screw group (n = 15)	2-screw group (n = 8)	Test statistic	P value
∆H/L, median (range)	0.01 (-0.07 to 0.13)	0.02 (-0.09 to 0.34)	U = 49.00	0.476
∆SL (degrees), mean ± SD	-7.27 ± 20.31	-11.75 ± 23.66	t = 0.477	0.639
DISI successfully corrected, n (%)	5 (71.4)	2 (28.6)	N/A	0.286

Change in height-to-length ratio was analyzed using the Mann-Whitney U test. Change in scapholunate angle was analyzed using an independent samples t-test. Dorsal intercalated segment instability correction rates were analyzed using Fisher’s exact test. N/A indicates Fisher’s exact test was used, which computes exact probability directly without generating a standardized test statistic. ∆H/L: Change in height-to-length ratio; ∆SL: Change in scapholunate angle; DISI: Dorsal intercalated segment instability; N/A: Not applicable.

Table 3 Post-operative clinical and functional outcomes, mean ± SD

Outcome measure	1-screw group (n = 15)	2-screw group (n = 8)	Test statistic	P value
Time to union (weeks)	11.47 ± 3.38	11.13 ± 5.11	t = 0.193	0.849
Final DASH score	44.53 ± 21.39	23.13 ± 11.40	t = 2.620	0.016a
Final grip strength, mean rank	11.20	13.50	U = 48.0	0.186
Final ROM, mean rank	10.67	14.50	U = 40.0	0.074

^aP < 0.05.

Continuous parametric variables (time to union, final Disabilities of the Arm, Shoulder, and Hand) were analyzed using an independent samples t-test. Ordinal variables (final grip strength, final range of motion) were analyzed using the Mann-Whitney U test and are reported as mean ranks. DASH: Disabilities of the Arm, Shoulder, and Hand; ROM: Range of motion.