Similar range of motion and function after resurfacing large–head or standard total hip arthroplasty

Figures & data

Consort flow chart of the inclusion and follow–up. There is a discrepancy between the number of assessments in each department, as one of the departments screened the GP referrals prior to assignment to the project. If the referral mentioned one of the exclusion criteria, they were never assessed.

Table 1. Demographic data. Age and BMD are presented as median (range)

	RHA	Standard THA	Large–head THA
n	20	34	17
Age, years	57 (54–61)	56 (52–62)	63 (54–64)
Females, %	40	29	47
Charnley class I, %	80	69	59
BMI, kg/m ^2	28 (24–31)	27 (25–29)	28 (26–32)

Table 2. Surgery–related outcomes, presented as mean (SD). Surgery time for RHA and large–head THA patients included a mean 12–min (a) and 8–min (b) surgery time due to insertion of tantalum markers related to a radiostereometry study. Tantalum time was missing for two–thirds of the RHA patients, so adjusted surgery time is not reported. Subtraction of mean tantalum times for missing values also finds a group difference in adjusted surgery time with p–values < 0.001

	RHA	Standard THA	Large–head THA	p–value
n	20	34	17
Surgery time, min	113 (15) ^a	66 (11)	83 (12) ^b	< 0.001
Incision length, cm	24 (2.8)	14 (2.8)	15 ( 2.6)	< 0.001
Blood loss, mL	625 (467)	515 (216)	753 (315)	0.09
Hemoglobin decrease, mmol/L	1.7 (0.7)	1.8 (0.5)	2.2 (0.6)	0.5

Table 3. Hip movements compared by regression analysis adjusted for baseline values. The mean difference (95% CI) measured in degrees between standard THA and RHA, large–head THA and RHA, and large–head THA and standard THA was calculated

	A	B	C	D	E	F
Baseline
ROM, total	156 (31)	161 (44)	145 (29)	5	(–16 to 25)	–11	(–31 to 8)	–16	(–37 to 5)
Extension	–1 (3)	1 (4)	2 (4)	2	(–0 to 4)	2	( –0 to 4)	0	( –2 to 3)
Flexion	90 (12)	91 (13)	85 (13)	1	(–6 to 8)	–5	(–13 to 3)	–6	(–14 to 1)
Abduction	26 (12)	25 (11)	22 (8)	–1	(–8 to 5)	–5	(–11 to 2.0)	–3	( –9 to 2)
Adduction	14 (7)	14 (9)	13 (6)	–0	(–4 to 4)	–1	( –5 to 4)	–1	( –5 to 4)
Internal rotation	5 (9)	6 (14)	2 (10)	2	(–5 to 8)	–3	( –10 to 3)	–5	(–12 to 2)
External rotation	22 (8)	24 (12)	22 (9)	2	(–3 to 7)	0	( –5 to 6)	–2	( –8 to 4)
2 years
ROM, total	221 (35)	232 (36)	225 (30)	8	(–11 to 28)	9	(–12 to 31)	1	(–17 to 19)
Extension	7 (8)	5 (6)	3 (4)	–2	(–6 to 1)	–5	(–9 to –2) ^a	–3	(–6 to –0) ^a
Flexion	103 (12)	107 (14)	103 (10)	3	(–4 to 10)	2	(–6 to 9)	–1	(–8 to 6)
Abduction	31 (5)	36 (10)	36 (8)	4	(0 to 9) ^a	6	(1 to 10) ^a	2	(–3 to 6)
Adduction	24 (6)	24 (7)	24 (5)	0	(–4 to 4)	–0	(–4 to 4)	0	(–4 to 4)
Internal rotation°	25 (10)	25 (9)	24 (10)	–1	(–6 to 4)	1	(–5 to 8)	2	(–3 to 8)
External rotation°	30 (9)	35 (8)	35 (9)	5	(–0 to 9)	4	(–2 to 11)	0	(–6 to 5)

A RHA: Mean (SD)

B Standard THA: Mean (SD)

C Large-head THA: Mean (SD)

D Standard THA minus RHA: Mean difference (95% CI)

E Large-head THA minus RHA: Mean difference (95% CI)

F Large-head THA minus standard THA: Mean difference (95% CI)

^a CIs not including zero

Table 4. Clinical endpoints compared by regression analysis adjusted for baseline values. The mean difference (95% CI) between standard THA and RHA, large–head THA and RHA, and large–head THA and standard THA was calculated

	A	B	C	D	E	F
Baseline
HHS	63 (10)	56 (9)	59 (8)	–7	(–13 to –2) ^b	–4	(–10 to 2)	3	( –2 to 8)
WOMAC ^a	50 (21)	55 (16)	49 (20)	6	(–6 to 17)	–1	(–15 to 13)	–6	(–18 to 5)
UCLA activity	5.8 (2.2)	6.3 (1.8)	5.8 (1.6)	0.5	(–0.7 to 1.7)	0.0	(–1.2 to 1.3)	–0.5	(–1.5 to 0.5)
Steps, mill/y	1.8 (0.9)	2.3 (1.5)	1.6 (0.6)	0.5	(–0.2 to 1.2)	–0.2	(–0.7 to 0.4)	–0.7	(–1.3 to –0.0)
Eq–5d	0.6 (0.3)	0.6 (0.2)	0.6 (0.2)	0.1	(–0.1 to 0.2)	0.0	(–0.1 to 0.2)	–0.0	(–0.1 to 0.1)
2 years
HHS	93 (10)	91 (14)	95 (6)	2	(–3 to 8)	4	( –1 to 9)	2	(–3 to 7)
WOMAC ^a	8 (13)	10 (18)	5 (6)	1	(–8 to 10)	–4	(–11 to 3)	–5	(–11 to 2)
UCLA activity	7.3 (1.8)	7.0 (2.0)	7.8 (1.7)	–0.6	(–1.6 to 0.4)	0.4	(–0.8 to 1.6)	1.0	(–0.1 to 2.1)
Steps, mill/y	3.0 (2.0)	2.8 (1.4)	2.5 (1.2)	–0.1	(–0.8 to 0.5)	0.2	(–0.6 to 0.9)	0.3	(–0.6 to 1.2)
Eq–5d	0.8 (0.3)	0.9 (0.2)	1.0 (0.1)	0.0	(–0.1 to 0.2)	0.1	(–0.0 to 0.2)	0.1	(0.0 to 0.2) ^b

A–F: See Table 3

^a WOMAC can be reported from 0 to 100 and a low score represents minimal discomfort. A negative mean difference in the columns comparing large–head THA and standard THA or RHA indicates that large–head has less discomfort. For all other endpoints, a high score is optimal.

^b CIs not including zero