The effect of femoral offset modification on gait after total hip arthroplasty

Figures & data

Figure 1. A subject carrying the Physilog system. The data logger (weighing 300 g) can be fixed around the waist. Sensors (gyroscopes) are attached by elastic strips to each shank and thigh, and also to the pelvis, and connected to the data logger by a thin cable.

Table 1. Epidemiologic characteristics of the three groups

Group	Age	BMI	Sex ratio
	Mean [SD] (range)	Mean [SD] (range)	M/F
Decreased	65.6 [10.7] (46–77)	24.7 [4.9] (19–33)	2/7
Restored	67.3 [8.2] (54–78)	25.5 [3.3] (21–34)	3/11
Increased	72.4 [8.9] (61–83)	27.7 [4.4] (21–33)	1/4

Table 2. The clinical scores in the groups before surgery and at 1 year follow up: Harris hip score (HHS), Postel Merle d’Aubigné (PMA), WOMAC, HOOS. Values are mean [SD] and (range)

Group	HHS		PMA		WOMAC		HOOS
	Before	1-year FU	Before	1-year FU	Before	1-year FU	Before	1-year FU
Decreased	46.6 [21.1]	87.9 [12.9]	10.7 [2.1]	16.3 [1.7]	53.0 [8.1]	7.4 [9.0]	36.5 [11.0]	86.2 [12.0]
	(12–87)	(69–100)	(8–15)	(14–18)	(43–69)	(0–28)	(23–52)	(64–100)
Restored	36.6 [8.3]	92.4 [6.1]	10.6 [1.2]	16.8 [0.9]	54.0 [8.6]	8.2 [11.8]	33.1 [7.6]	90.9 [8.8]
	(29–53)	(79–100)	(9–13)	(15–18)	(34–65)	(0–37)	(18–45)	(70–99)
Increased	34.3 [7.3]	92.7 [5.1]	9.4 [0.9]	16.8 [1.3]	54.4 [17.2]	4.0 [2.5]	29.0 [11.8]	94.2 [6.3]
	(27–47)	(88–100)	(8–10)	(15–18)	(35–73)	(0–6)	(20–45)	(85–99)

Table 3. Femoral offset alteration in the three groups

Group	Femoral offset alteration
	(%)	(mm)
	Mean [SD] (range)	Mean [SD] (range)
Decreased	-17.9 [3.1] (-25 to -15)	-7.6 [1.8] (-12 to -6)
Restored	0.7 [1.4] (0–4)	0.3 [0.7] (0–2)
Average	18.1 [1.4] (15–22)	6.0 [0.7] (5–7)

Figure 2. Difference in knee range of motion and maximal swing speed between the operated side and the healthy limb. In contrast to the 2 other groups, in the “decreased” group there was a statistically significant decrease in the knee range of motion and the maximal swing speed during the gait cycle.

Figure 3. Passive range of motion in the 3 groups. Compared to the “restored” FO group, there was a significant decrease in adduction mobility in the “decreased” FO group.

Figure 4. In some cases of dysplastic acetabula, the center of rotation has to be shifted medially. The FO may be increased in order to compensate for the decrease in acetabular offset and to avoid instability.