Table 1.

Balance on pre-operative characteristics, means and % standardised mean differences.

Covariate	Mean hybrid (n = 631)	Mean cementless (n = 2952)	SMD (%)
Age	69.7	69.3	15.98
Oxford hip scorea	20.2	19.9	2.83
Pre-operative EQ-5Da	0.401	0.399	0.63
Index of deprivationa	3.26	3.03	15.92
ASA grade 1 (%)a	0.0903	0.120	9.55
ASA grade 2 (%)	0.740	0.738	0.52
Disability score	0.617	0.596	4.19
Obesea	0.270	0.266	0.69
Morbidly obesea	0.104	0.111	4.30
Number of comorbidities	1.00	0.96	4.14
Comorbidities
Heart disease	0.176	0.15	7.86
High bp	0.399	0.422	4.55
Stroke	0.0285	0.0169	7.78
Circulation	0.0777	0.0671	4.08
Lung disease	0.0555	0.0640	3.61
Diabetes	0.130	0.123	2.20
Kidney disease	0.0127	0.0207	6.24
Nervous system	0.00634	0.0118	5.20
Liver disease	0.0951	0.00339	7.65
Cancer	0.0602	0.0515	3.80
Depression	0.0491	0.0373	5.84
Consultant	0.803	0.869	17.64
Treatment centre	0.0491	0.122	26.16

Note: SMD: standardised mean difference. SMD was calculated as $d=100*\frac{|{\overline{x}}_h-{\overline{x}}_c|}{\sqrt{\frac{s_h^2+s_c^2}{2}}}$, where ${\overline{\text{x}}}_{\text{h}}$ and ${\overline{\text{x}}}_{\text{c}}$ are the means for the hybrid and cementless group, while the denominator includes the pooled standard deviation of the two groups, for a given covariate. Variables are dichotomous, with the exception of age, Oxford hip score, pre-operative EQ-5D-3L score, index of deprivation and number of comorbidities.

^aVariables with missing values. Here, SMDs were combined using Rubin’s formulae.