Does surgeon handedness affect the outcomes after primary total knee arthroplasty? A retrospective cohort study

Table 1 Basic characteristics of included patients, n (%)

Variables		Group D (n = 177)	Group N (n = 193)	P value
Age (years), mean ± SD (range)		57.87 ± 9.16 (29 to 77)	58.54 ± 8.50 (30 to 76)	0.2321
Gender	Male	32 (18.1)	46 (23.8)	0.1752
	Female	145 (81.9)	147 (76.2)
Diagnosis	OA	144 (82.4)	151 (78.2)	0.5152
	RA	33 (18.6)	42 (21.2)
BMI (kg/m2), mean ± SD (range)		24.7 ± 3.1 (18.9-34.1)	23.7 ± 3.3 (18.9-33.5)	0.2451

¹Students' t-test compares the mean difference between variables.

²χ² test compares proportions between both groups.

The level of significance was considered at a P value < 0.05. RA: Rheumatoid arthritis; OA: Osteoarthritis; BMI: Body mass index.

Table 2 Comparison of coronal alignment between both sides, n (%)

Radiographic parameters			Group D (n = 177)	Group N (n = 193)	P value	OR (95%CI)
HKA (degrees)	Preoperative, mean ± SD (range)		167.88 ± 9.34 (142 to 195)	167.94 ± 8.82 (141 to 195)	0.9561
	Postoperative, mean ± SD (range)		177.96 ± 3.13 (165 to 186)	178.55 ± 3.38 (170 to 187)	0.0821
	P value		< 0.0011	< 0.0011
	Safe zone (180° ± 3°)	Within	116 (65.5)	123 (63.7)	0.8032	1.08 (0.72-1.63)
		Outside	61 (34.5)	70 (36.3)
MPTA (degrees)	Measurement		88.90 ± 2.61 (78 to 95)	89.43 ± 2.71 (80 to 98)	0.0561
	Safe zone (90° to 87°)	Within	95 (53.7)	90 (41.4)	0.0222,a	1.63 (1.08-2.48)
		Outside	82 (46.3)	113 (58.5)
mLDFA (degrees)	Measurement, mean ± SD (range)		90.16 ± 2.54 (81 to 98)	89.76 ± 2.53 (82 to 101)	0.1401
	Safe zone (90° ± 3°), mean ± SD (range)	Within	139 (78.5)	154 (79.8)	0.7632	0.92 (0.55-1.53)
		Outside	38 (21.5)	39 (20.2)

¹Students' t-test compares the mean difference between variables.

²χ² test compares proportions between both groups.

^aP value < 0.05 was considered significance.

HKA: Hip-knee-ankle; MPTA: Medial proximal tibial angle; mLDFA: Mechanical lateral distal femoral angle; OR: Odds ratio; CI: Confidence interval.

Table 3 Comparing the methods used for tibial component insertion, n (%)

		IM (188 patients)		EM (182 patients)		P value	OR (95%CI)
Total number	Group D	88 (46.8)		89 (48.9)		0.6871
	Group N	100 (53.2)		93 (51.1)
MPTA (degrees), mean ± SD (range)	Group D	88.86 ± 3.26 (78 to 95)		88.93 ± 1.76 (84 to 93)		0.8621
	Group N	88.56 ± 3.00 (80 to 98)		90.38 ± 1.99 (84 to 95)		0.0011,a
Safe zone 90° to 87°		Within	Outside	Within	Outside
	Group D	32 (36.4)	56 (63.6)	63 (70.8)	26 (29.2)	0.0012,a	4.24 (2.26-7.96)
	Group N	43 (43)	57 (57)	37 (39.8)	56 (60.2)	0.6502	1.19 (0.68-2.09)
	P value	0.3532		0.0012,a
	OR (95%CI)	1.32 (0.73 to 2.38)		3.67 (1.98 to 6.80)

¹Students' t-test compares the mean difference between variables.

²χ² test compares proportions between both groups.

^aP value < 0.05 was considered significance.

IM: Intramedullary; EM: Extramedullary; MPTA: Medial proximal tibial angle; OR: Odds ratio; CI: Confidence interval.

Table 4 Summary of the results reported in the previous studies

Ref.	Number of patients (knees)	Dominant side	Non-dominant side	Number of surgeons	Surgeons’ handedness	Radiological (dominant vs non-dominant)			Functional (dominant vs non-dominant)
						HKA	MPTA	LDFA
Mehta and Lotke[27]	688 (728)	377	351	One	Right-handed	NR	NR	NR	Knee extension 1.25 vs 1.75 (P = 0.19), KS function 73.5 vs 70.5 (P = 0.03), KS pain 95 vs 87 (P = 0.029)
Liu et al[28]	86 (100)	50	50	One	Right-handed	1.9 ± 4.4 vs 2.3 ± 3.8 (P = 0.634)	90.0 ± 2.5 vs 90.1 ± 2.6 (P = 0.855)	88.6 ± 2.8 vs 88.4 ± 2.5 (P = 0.616)	HSS score was 87.2 ± 4.3 vs 86.8 ± 5.0 (P = 0.639).
Jaglarz et al[30]	200 (200)	102	98	Four	2 right-handed, and 2 left-handed1	For the right-handed surgeons: No difference in the radiological outcomes regardless of the side of surgery and regardless of their standing position during surgery. For the left-handed surgeons: A significant difference in the HKA [-1.5 (-2.6 to -1) vs -3 (-4.5 to -2), P = 0.01] for surgeon B. A significant difference in the MPTA [0 (-1 to 0.5) vs 1 (0-2), P < 0.01] for surgeon D			NR
Current study, (2025)	370 (370)	177	193	Five	Right-handed	177.96 ± 3.13 vs 178.55 ± 3.38, (P = 0.082)	88.90 ± 2.61 vs 89.43 ± 2.71, (P = 0.056)	90.16 ± 2.54 vs 89.76 ± 2.53, (P = 0.140)	KSS: 80.59 ± 14.73 vs 79.56 ± 15.64 (P = 0.628)

¹Details of involved surgeons: Surgeon A: Right-handed, stands always on the right side (left/right: 23/27), Surgeon B: Left-handed, stands always on the left side (left/right: 28/22), Surgeon C: Right-handed, stands at the side of the operated knee (left/right: 26/24), and Surgeon D: Left-handed, stands at the side of the operated knee (left/right: 23/27).

NR: Not reported; HKA: Hip to knee to ankle; MPTA: Medial proximal tibial angle; LDFA: Lateral distal femoral angle; HSS: Hospital of special surgery; KS: Knee society; KSS: Knee society score.