The Bernese periacetabular osteotomy: clinical, radiographic and mechanical 7–15-year follow-up of 26 hips

Figures & data

Clinical, radiographic and mechanical results for the 26 hips, stratified into 3 subgroups according to clinical outcome

	Conversion to total hip arthroplasty (n = 4)^a	Progressive arthrosis to grade 3, or decrease in WOMAC > 20 (n = 8)^b	No total hip arthroplasty, no or mild arthrosis (n = 14) c
Mean duration of follow−up (years)	4.5^d	9.9	11.6
Mean age at operation (years)	42.3	37.4	28.7
Mean lateral center-edge angle (°)
preoperatively	17	14	16
postoperatively	34	32	41
Mean vertical-center-anterior angle (°)
preoperatively	13	20	27
postoperatively	22	41	40
Postoperative lateralization of the center ofrotation (mm)	+6	+4	+5
Mean resultant hip force, normalized to the body weight, R/WB (−)
preoperatively	3.0	3.0	2.9
postoperatively	3.2	3.5	3.2
Mean peak contact stress on the weight−bearing surface, normalized to the body weight, pmax/WB (kPa/N)
preoperatively	5.8	5.2	5.0
postoperatively	3.8	3.1	2.7
Mean WOMAC score (points; 0 = worst, 96 = best)
preoperatively	50	72	67
at follow−up	N/A	35	80
Severity of osteoarthritis (no. of hips with Tönnis grade 0 /grade 1 / grade 2 / grade 3)
preoperatively	0 / 0 / 3 / 1	1 / 6 / 1 / 0	11 / 3 / 0 / 0
at follow−up	N/A	0 / 0 / 6 / 2	4 / 9 / 1 / 0
Patients satisfied or partially satisfied (no. of hips)	0	2	14

^a False profile radiographs were missing for 1 hip preoperatively and two hips postoperatively.

^b Postoperative radiographs were missing for 1 hip. False profile radiographs were missing for 3 hips preoperatively and 6 hips postoperatively.

^c False profile radiographs were missing for 5 hips preoperatively and 8 hips postoperatively.

^d Mean time interval between the index operation and conversion to total hip arthroplasty.

N/A: not applicable.

Simulation of the contact stress distribution in the hip joint before and after a periacetabular osteotomy in a single patient. In dysplastic hip, the contact stress increases drastically towards the lateral edge where the peak of the contact stress is located (A). Increase in lateral center-edge angle reduces the magnitude and shifts the location of the peak contact stress, even if the resultant hip force remains unchanged (B). Lateralization or medialization of the periacetabular fragment increases or reduces the peak contact stress due to the change in magnitude/direction of the resultant hip force, even if the lateral center-edge angle is the same (C and D). The location of the peak stress, p_max, on the weight bearing surface is marked with a dot. R denotes the resultant hip force, ϑ_CEis the lateral center-edge angle of Wiberg, and ϑ_Ris the vertical inclination of the resultant hip force (adapted from Srakar et al. 1992, Iglic et al. 1993b).

Srakar F, Iglič A, Antolič V, Herman S. Computer simulation of the periacetabular osteotomy. Acta Orthop Scand 1992; 63: 411–2

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