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Preliminary traction and the use of under-thigh pillows to prevent avascular necrosis of the femoral head in Pavlik harness treatment of developmental dysplasia of the hip
J Orthop Sci (2000) 5:540–545
Preliminary traction and the use of under-thigh pillows to prevent avascular necrosis of the femoral head in Pavlik harness treatment of developmental dysplasia of the hip Shigeo Suzuki, Yoichi Seto, Tohru Futami, and Naoya Kashiwagi Department of Orthopaedic Surgery, Shiga Medical Center for Children, 5-7-30 Moriyama, Moriyama, Shiga 524-0022, Japan
Abstract One hundred and sixty-one hips of 145 patients were treated with the Pavlik harness for developmental dysplasia of the hip. The patients were divided into two groups. Group A consisted of 65 patients (70 hips) who were treated between 1980 and 1987. The harness was applied immediately after the diagnosis. Group B consisted of 80 patients (91 hips) who were treated between 1988 and 1992. These patients received preliminary traction, and small pillows supported the lower extremities from just above the knee to the foot to prevent extreme abduction when the harness was applied. When the distance from the middle point of the proximal metaphyseal border of the femur to the Y-line (distance “a”) was 8 mm or more on the initial X-ray picture, the rate of avascular necrosis in group A was 11% and that in group B was 0%; the difference was significant. However, when distance “a” was less than 8 mm, the rate of avascular necrosis in group A was 13% and that in group B was 12%, and there was no significant difference. Thus, we suggest that the Pavlik harness is indicated for developmental dysplasia of the hip in which distance “a” is 8 mm or more. Traction should precede application of the harness, and pillows placed under the thigh must be used during application. Key words Pavlik harness · Developmental dysplasia of the hip · Preliminary traction · Under-thigh pillows · Avascular necrosis
Introduction Avascular necrosis of the femoral head, as a complication of treatment of developmental dysplasia of the hip (DDH) with the Pavlik harness, can lead to a serious condition resulting in early osteoarthrosis. It is impossible to predict whether avascular necrosis will occur, and a definite means to prevent it does not exist.
Offprint requests to: S. Suzuki Received: November 15, 1999 / Accepted: June 5, 2000
At the Shiga Medical Center for Children, the Pavlik harness had been used in the outpatient clinic between 1980 and 1987. In 1988, according to Iwasaki’s suggestion,6 we introduced two measures in order to reduce avascular necrosis; preliminary skin traction and the use of pillows placed under the thighs during application of the harness to prevent extreme abduction. We compared the results of the treatment used during the period between 1980 and 1987 and that in the period 1988 to 1992.
Patients and methods Between 1980 and 1992, 161 hips in 145 patients (13 boys and 132 girls) were treated with the Pavlik harness at Shiga Medical Center for Children, and these patients were followed-up for at least 1 year after application of the harness. Patients who had had previous treatment elsewhere or who were treated initially with a different method were excluded from the study. A dislocation was diagnosed when the hip was felt to have relocated with abduction, as described by Ortolani. If the hip could not be reduced but there was limited abduction, asymmetry of the thigh folds, or shortening of the affected extremity, a dislocation was suspected. The diagnosis was made radiographically. The radiograph was taken with the infant in the supine position, with both lower extremities maintained in a neutral position. The focus of the tube was adjusted to the center of the triangle that is formed bilaterally by the iliac crests and the symphysis, and the focal distance was 1 m. The diagnosis was established when there was lateral and cephalad displacement of the proximal end of the femur accompanied by interruption of the Shenton line. The amount of dislocation was measured on anteroposterior radiographs according to the method of
S. Suzuki et al.: Prevention of AVN in DDH treatment
541
Fig. 1. Distance a is the length from the middle point of the proximal metaphyseal border of the femur (point O) to the Y-line
Yamamuro and Chene18 (Fig. 1). The distance from the middle point of the proximal metaphyseal border of the femur (point O in Fig. 1) to the Y-line was termed distance “a”. The patients were divided into two groups. Group A consisted of 70 hips in 65 patients (6 boys and 59 girls) who were treated in the outpatient clinic between 1980 and 1987. The ages of the patients at the beginning of treatment ranged from 2 to 8 months (Table 1). The harness was applied with the hip in 100° of flexion immediately after DDH was diagnosed. If the hip was clinically stable 2–3 months after reduction, the harness was removed for 2 hours a day. Gradually, the time during which the harness was removed increased if the radiograph of the hip in neutral position revealed concentric reduction. If the dislocation persisted for more than 2 weeks, the harness was removed, and the patient received longitudinal traction followed by closed manual reduction. The results for hips which could not be reduced with the use of the Pavlik harness in the outpatient clinic were excluded from this study. Group B patients consisted of 91 hips in 80 patients (7 boys and 73 girls) who were treated in the inpatient clinic between 1988 and 1992. The ages of the patients at the beginning of treatment ranged from 1 week to 10 months (Table 1). These patients were admitted to the hospital after the diagnosis was made and received traction with the hip in 10° of abduction and 30° of flexion. Skin traction was applied with non-adhesive tape, and the skin was inspected at regular intervals
Fig. 2. Under-thigh pillows. These were placed under the thighs, supporting the knees and ankles
by the nursing staff. The weight was usually 2 kg and this was gradually increased according to the child’s tolerance. Radiographs were taken every second week to assess the position of the femoral head. The traction was continued until radiographs showed that distance “a” was equal to or more than 8 mm,12,18 and until the hip could be abducted in flexion up to 70°. After the skin traction, the harness was applied by the same method as that used in group A. When a child was placed in the supine position after Pavlik harness application, small pillows were put under his or her thighs. The height of the pillows was adjusted so that the amount of hip abduction did not exceed 75°. Attention was paid to the position of the pillows; these pillows supported the lower extremities from just above the knee to the foot (Fig. 2). If the pillows were placed more medially, they forcibly pushed up the femoral head. The position of the pillows was regularly checked by the nursing staff. After reduction, the patients were discharged from the hospital and were managed in the same way as those in group A. If the dislocation persisted for more than 2 weeks, the patient received closed manual reduction. The results of hips which could not be reduced with the use of the Pavlik harness in the inpatient clinic were excluded from this study. The average total time that the harness was worn was approximately 2 months after reduction in both groups.
See text for explanation of groups I to IV
2 7 16 14 26 16 5 3 0 0 2 91
,1 1 2 3 4 5 6 7 8 9 10 Total
Group B
a
14 24 20 6 4 0 2 70
2 3 4 5 6 7 8 Total
Treated hips (number)
Group A
Age at beginning of treatment (months)
54
25 5 18 12 19 14 12 17
Duration of traction (days)
1 7 11 12 24 16 5 2 0 0 0 78
13 22 13 5 3 0 2 58
Reduced hips (number)
0 86
50 100 69 86 92 100 100 67
100 83
93 92 65 83 75
%
0 0 1 0 2 0 0 0 0 0 0 3
3 2 2 0 0 0 0 7
Reduced hips that had avascular necrosis
Table 1. Rate of reduction and avascular necrosis according to age at the beginning of treatment
4
0 0 9 0 8 0 0 0
0 12
23 9 15 0 0
%
0 0 1 0 1 0 0 0 0 0 0 2
3 2 2 0 0 0 0 7
Group Ia
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
Group IIa
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
Group IIIa
0 0 0 0 0 1 0 0 0 0 0 1
0 0 0 0 0 0 0 0
Group IVa
Classification of avascular necrosis Number of hips
542 S. Suzuki et al.: Prevention of AVN in DDH treatment
S. Suzuki et al.: Prevention of AVN in DDH treatment
543
Table 2. Rate of reduction and avascular necrosis according to distance “a”
Distance “a” (mm)a
Treated
Reduced
%
Reduced hips that had avascular necrosis
Group A
$8 ,8 Total
33 37 70
28 30 58
85 81 83
3 4 7
11* 13 12
3 4 7
0 0 0
0 0 0
0 0 0
Group B
$8 ,8 Total
55 36 91
53 25 78
96 69 86
0 3 3
0* 12 4
0 2 2
0 0 0
0 0 0
0 1 1
Number of hips
Classification of avascular necrosis Number of hips %
Group I
Group II
Group III
Group IV
* P , 0.05 a See text for explanation of distance “a”
The diagnosis of avascular necrosis was established according to the criteria of Salter et al.:10 (1) failure of appearance of the ossific nucleus of the femoral head for 1 year or longer after reduction, (2) failure of growth of an existing ossific nucleus for 1 year or longer after reduction, (3) broadening of the femoral neck during the year after reduction, (4) increased radiographic density of the femoral head followed by the radiographic appearance of fragmentation, and (5) residual deformity of the femoral head and neck when reossification was complete. Hips that had temporary irregular ossification were not considered to have avascular necrosis. The hips that had avascular necrosis were divided into four groups according to the classification of Kalamchi and MacEwen:7 group I hips had changes affecting the ossific nucleus, group II hips had lateral physeal damage, group III hips had central physeal damage, and group IV hips had damage to the entire femoral head and physis. Comparisons between groups were performed by Fisher’s exact probability test. Correlations between the duration of traction and patient’s age or distance “a” on the initial X-ray picture were examined by the Cochran and Cox test. Statistical significance was set at P , 0.05.
Results The mean duration of traction in group B patients was 16 days, varying from 0 to 54 days (Table 1). It was correlated with the patient’s age, and the younger the patient, the shorter the duration of traction (P , 0.05). When the duration of traction was considered in relation to distance “a” on the initial X-ray picture, the lower distance “a”, the longer the duration of traction required, and there was a high correlation between these factors (P , 0.01). When distance “a” was 10 mm
or more, the mean duration of traction was 11 days, and the mean duration of traction was 23 days when distance “a” was 3 mm or less. The overall rate of reduction in group A was 83% (58 of 70 hips) and that in group B was 86% (78 of 91 hips), and there was no significant difference between the groups (Table 1). When distance “a” was less than 8 mm on the initial radiograph, the rate of reduction in group A was 81% (30 of 37 hips) and that in group B was 69% (25 of 36 hips), and there was no significant difference (Table 2). When distance “a” was 8 mm or more, the rate of reduction in group A was 85% (28 of 33 hips) and that in group B was 96% (53 of 55 hips), and there was no significant difference. Thus, the rate of reduction with the use of the Pavlik harness did not change after the treatments of preliminary traction and under-thigh pillows were introduced. The overall rate of occurrence of avascular necrosis in group A was 12% (7 of 58 reduced hips) and that in group B was 4% (3 of 78 reduced hips), and there was no significant difference between the groups (Table 1). But, when distance “a” was 8 mm or more, the rate of avascular necrosis in group A was 11% (3 of 28 reduced hips) and that in group B was 0% (none of 53 reduced hips), and this difference was significant (P , 0.05). When distance “a” was less than 8 mm on the initial radiograph, the rate of avascular necrosis in group A was 13% (4 of 30 reduced hips) and that in group B was 12% (3 of 25 reduced hips), and there was no significant difference (Table 2). Thus, the rate of avascular necrosis decreased after preliminary traction and avoidance of extreme abduction when distance “a” was 8 mm or more, but the rate of avascular necrosis was not decreased when distance “a” was less than 8 mm. The classification of avascular necrosis is shown in Tables 1, 2. In group A, all hips with avascular necrosis were group I. In group B, two hips were group I and one was group IV.
544
Discussion Treatment of DDH using the Pavlik harness has gained widespread acceptance in Japan. However, this treatment does not always produce an excellent result, because avascular necrosis can occur as a complication of using the Pavlik harness, and the involved hip will develop osteoarthrosis if the physis is damaged. The reported rate of avascular necrosis with the use of the Pavlik harness has ranged from 1% to 30%,3–5,6,8,12,14–16 The more severe the dislocation, the higher the rate of occurrence of avascular necrosis.4,5,12,13,16 Grill et al.4 demonstrated that the rate of avascular necrosis was 1.28% in grade Tönnis 1, 2.12% in grade Tönnis 2, 3.1% in grade Tönnis 3, and 16.4% in grade Tönnis 4. Suzuki and Yamamuro12 reported that the rate of avascular necrosis was 13% when distance “a” was 8 to 10 mm, 17% when “a” was 6 to 8 mm, 21% when “a” was 4 to 6 mm, and 27% when “a” was less than 4 mm. Thus, avascular necrosis tends to occur in the hip that has higher proximal migration of the femoral head. One of the important causes of avascular necrosis may be extreme abduction after reduction. Ogden9 showed that retinacular vessels are occluded due to a tight interlocking of the acetabular labrum to the intertrochanteric notch of the proximal femur in extreme hip abduction. Salter et al.10 found that the combination of tight muscles around the hip at the time of reduction, and immobilization of the hip in extreme abduction tended to produce avascular necrosis of the femoral head, as the tight adductors are stretched further and they strongly compress the femoral head into the acetabulum. When the dislocation is treated with the Pavlik harness, immobilization can occur in extreme abduction. When awake, the child can move the hip joint, but after he or she goes to sleep and the active adduction disappears, the hip is forced to abduct by the weight of the extremities because the child cannot extend his or her hips.6 When the hip is immobilized in extreme abduction after reduction, the already contracted muscles are stretched and they compress the femoral head into the acetabulum. In severe dislocations, the contractions of muscles around the hip joint are greater. The compression force will be stronger due to the contracted muscles in extreme abduction after reduction, and this could be one of the reasons for the higher rate of avascular necrosis in the hip that has higher proximal migration of the femoral head. In order to prevent avascular necrosis, both preliminary traction to relax the tight muscles, and immobilization in the human position after reduction have been widely accepted among orthopedic surgeons.1,2,17 We tried to reduce avascular necrosis by introducing a combination of preliminary traction and
S. Suzuki et al.: Prevention of AVN in DDH treatment
avoidance of extreme abduction by using under-thigh pillows during the application of the Pavlik harness. We compared group A patients, in whom the Pavlik harness was applied immediately after diagnosis between 1980 and 1987, with group B patients, in whom preliminary traction and the prevention of extreme abduction during application of the harness were performed between 1988 and 1992. The results showed that the incidence of avascular necrosis was significantly less in group B than in group A when distance “a” was 8 mm or more. However, the rate of necrosis among those with distance “a” less than 8 mm was not significantly decreased in group B. Although the combination of preliminary traction and the use of under-thigh pillows was effective in reducing avascular necrosis in the slightly dislocated hips, this method alone was useless in severe dislocations that had proximal migration. In hips with proximally dislocated femoral head, in addition to the contraction of muscles around the hip and extreme abduction, other factors, such as the intraarticular interpositions of pulvinar, inverted labrum, hypertrophied round ligament, and elevated transverse ligament are thought to be involved in the occurrence of avascular necrosis. In hips in which the femoral head is dislocated proximally, large intra-articular interpositions, instead of the femoral head, may occupy the cavity in the acetabulum. Even after the use of the combination of preliminary traction and avoidance of extreme abduction with the under-thigh pillows, the muscles around the hip joint are strongly stretched as the intra-articular substances increase the distance between the origin and the insertion of muscles after reduction. As a result of this muscle stretching, strong pressure is exerted on the reduced femoral head. Moreover, excessive pressure is concentrated in one part of the femoral head soon after the reduction, as the contact area is limited when there is an obstacle. Somerville and Scott11 and Tönnis16 noted that an inverted labrum produced circumscribed pressure on the femoral head. The limited area in the femoral head appears to receive too much pressure in the course of reduction, which interrupts the blood flow in the femoral head. In this study, the combination of preliminary traction and the use of under-thigh pillows was ineffective in reducing avascular necrosis in hips with distance “a” less than 8 mm. If the duration of traction is prolonged for these hips until distance “a” is 10 mm or more, in order to minimize muscle contraction, the incidence of avascular necrosis may decrease after the reduction. In this study, the mean duration of traction in group B was 16 days. The lower distance “a”, the longer the duration of traction required, and the duration was 23 days when distance “a” was 3 mm or less. If the duration of traction is prolonged for hips in which distance “a” is 3 mm or
S. Suzuki et al.: Prevention of AVN in DDH treatment
less before reduction, the baby will have to stay in the hospital for some months until distance “a” is 10 mm or more. Longer stay in a hospital, however, is unfavorable for the baby. We suggest that the Pavlik harness is indicated for hips in which distance “a” is equal to or more than 8 mm. Preliminary traction should precede the application of the harness, and under-thigh pillows must be placed during the harness application. For hips in which distance “a” is less than 8 mm, avascular necrosis, as a complication of treatment with the Pavlik harness, cannot be prevented by this method alone. References 1. Fish DN, Herzenberg JE, Hensinger RN. Current practice in use of prereduction traction for congenital dislocation of the hip. J Pediatr Orthop 1991;11:149–53. 2. Gage JR, Winter RB. Avascular necrosis of the capital femoral epiphysis as a complication of closed reduction of congenital dislocation of the hip. J Bone Joint Surg Am 1972;54:373–88. 3. Gotoh E, Ando M, Ibayashi K, et al. Significance of screening by the Pavlik harness in congenital dislocation of the hip: for prevention of avascular necrosis. Rinsho Seikei Geka (Clin Orthop Surg) 1992;27:1331–5 (in Japanese). 4. Grill F, Bensahel H, Canadell J, et al. The Pavlik harness in the treatment of congenital dislocating hip: report on a multicenter study of the European Paediatric Orthopaedic Society. J Pediatr Orthop 1988;8:1–8. 5. Inoue T, Nakamura H. Factors for prediction of avascular necrosis after treatment with Pavlik’s harness. J Jpn Paediatr Orthop 1995;4:298–301 (in Japanese). 6. Iwasaki K. Treatment of congenital dislocation of the hip by the Pavlik harness. Mechanism of reduction and usage. J Bone Joint Surg Am 1983;65:760–7.
545 7. Kalamchi A, MacEwen GD. Avascular necrosis following treatment of congenital dislocation of the hip. J Bone Joint Surg Am 1980;62:876–88. 8. Kumazawa H, Yoshihashi Y. Long-term results of congenital dislocation of the hip treated with Pavlik harness. J Jpn Orthop Assoc 1991;65:851–61 (in Japanese). 9. Ogden JA. Treatment positions for congenital dysplasia of the hip. J Pediatr 1975;86:732–4. 10. Salter RB, Kostuik J, Dallas S. Avascular necrosis of the femoral head as a complication of treatment for congenital dislocation of the hip in young children: a clinical and experimental investigation. Can J Surg 1969;12:44–60. 11. Sommerville EW, Scott JC. The direct approach to congenital dislocation of the hip. J Bone Joint Surg Br 1957;39:623– 40. 12. Suzuki S, Yamamuro T. Avascular necrosis in patients treated with the Pavlik harness for congenital dislocation of the hip. J Bone Joint Surg Am 1990;72:1048–55. 13. Suzuki S, Kashiwagi N, Kasahara Y, et al. Avascular necrosis and the Pavlik harness. J Bone Joint Surg Br 1996;78:631– 5. 14. Takahashi I. Functional treatment of congenital dislocation of the hip using Pavlik harness (Riemenbügel). J Jpn Orthop Assoc 1985;59:973–84. 15. Takahashi M. A long-term follow-up study of the femoral heads presenting with Perthes-like abnormality after Pavlik harness treatment for congenital dislocation of the hip. Cent Jpn J Orthop Traumat 1992;35:327–37 (in Japanese). 16. Tönnis D. Ischemic necrosis of the femoral head in the treatment of congenital hip dislocation. In: Tönnis D, editor. Congenital dysplasia and dislocation of the hip in children and adults. Berlin Heidelberg New York Tokyo: Springer-Verlag; 1984. p. 268– 90. 17. Weiner DS, Hoyt WA, O’Dell HW. Congenital dislocation of the hip. The relationship of premanipulation traction and age to avascular necrosis of the femoral head. J Bone Joint Surg Am 1977;59:306–11. 18. Yamamuro T, Chene S-H. A radiological study on the development of the hip joint in normal infants. J Jpn Orthop Assoc 1975;49:421–39.
Preliminary traction and the use of under-thigh pillows to prevent avascular necrosis of the femoral head in Pavlik harness treatment of developmental dysplasia of the hip Shigeo Suzuki, Yoichi Seto, Tohru Futami, and Naoya Kashiwagi Department of Orthopaedic Surgery, Shiga Medical Center for Children, 5-7-30 Moriyama, Moriyama, Shiga 524-0022, Japan
Abstract One hundred and sixty-one hips of 145 patients were treated with the Pavlik harness for developmental dysplasia of the hip. The patients were divided into two groups. Group A consisted of 65 patients (70 hips) who were treated between 1980 and 1987. The harness was applied immediately after the diagnosis. Group B consisted of 80 patients (91 hips) who were treated between 1988 and 1992. These patients received preliminary traction, and small pillows supported the lower extremities from just above the knee to the foot to prevent extreme abduction when the harness was applied. When the distance from the middle point of the proximal metaphyseal border of the femur to the Y-line (distance “a”) was 8 mm or more on the initial X-ray picture, the rate of avascular necrosis in group A was 11% and that in group B was 0%; the difference was significant. However, when distance “a” was less than 8 mm, the rate of avascular necrosis in group A was 13% and that in group B was 12%, and there was no significant difference. Thus, we suggest that the Pavlik harness is indicated for developmental dysplasia of the hip in which distance “a” is 8 mm or more. Traction should precede application of the harness, and pillows placed under the thigh must be used during application. Key words Pavlik harness · Developmental dysplasia of the hip · Preliminary traction · Under-thigh pillows · Avascular necrosis
Introduction Avascular necrosis of the femoral head, as a complication of treatment of developmental dysplasia of the hip (DDH) with the Pavlik harness, can lead to a serious condition resulting in early osteoarthrosis. It is impossible to predict whether avascular necrosis will occur, and a definite means to prevent it does not exist.
Offprint requests to: S. Suzuki Received: November 15, 1999 / Accepted: June 5, 2000
At the Shiga Medical Center for Children, the Pavlik harness had been used in the outpatient clinic between 1980 and 1987. In 1988, according to Iwasaki’s suggestion,6 we introduced two measures in order to reduce avascular necrosis; preliminary skin traction and the use of pillows placed under the thighs during application of the harness to prevent extreme abduction. We compared the results of the treatment used during the period between 1980 and 1987 and that in the period 1988 to 1992.
Patients and methods Between 1980 and 1992, 161 hips in 145 patients (13 boys and 132 girls) were treated with the Pavlik harness at Shiga Medical Center for Children, and these patients were followed-up for at least 1 year after application of the harness. Patients who had had previous treatment elsewhere or who were treated initially with a different method were excluded from the study. A dislocation was diagnosed when the hip was felt to have relocated with abduction, as described by Ortolani. If the hip could not be reduced but there was limited abduction, asymmetry of the thigh folds, or shortening of the affected extremity, a dislocation was suspected. The diagnosis was made radiographically. The radiograph was taken with the infant in the supine position, with both lower extremities maintained in a neutral position. The focus of the tube was adjusted to the center of the triangle that is formed bilaterally by the iliac crests and the symphysis, and the focal distance was 1 m. The diagnosis was established when there was lateral and cephalad displacement of the proximal end of the femur accompanied by interruption of the Shenton line. The amount of dislocation was measured on anteroposterior radiographs according to the method of
S. Suzuki et al.: Prevention of AVN in DDH treatment
541
Fig. 1. Distance a is the length from the middle point of the proximal metaphyseal border of the femur (point O) to the Y-line
Yamamuro and Chene18 (Fig. 1). The distance from the middle point of the proximal metaphyseal border of the femur (point O in Fig. 1) to the Y-line was termed distance “a”. The patients were divided into two groups. Group A consisted of 70 hips in 65 patients (6 boys and 59 girls) who were treated in the outpatient clinic between 1980 and 1987. The ages of the patients at the beginning of treatment ranged from 2 to 8 months (Table 1). The harness was applied with the hip in 100° of flexion immediately after DDH was diagnosed. If the hip was clinically stable 2–3 months after reduction, the harness was removed for 2 hours a day. Gradually, the time during which the harness was removed increased if the radiograph of the hip in neutral position revealed concentric reduction. If the dislocation persisted for more than 2 weeks, the harness was removed, and the patient received longitudinal traction followed by closed manual reduction. The results for hips which could not be reduced with the use of the Pavlik harness in the outpatient clinic were excluded from this study. Group B patients consisted of 91 hips in 80 patients (7 boys and 73 girls) who were treated in the inpatient clinic between 1988 and 1992. The ages of the patients at the beginning of treatment ranged from 1 week to 10 months (Table 1). These patients were admitted to the hospital after the diagnosis was made and received traction with the hip in 10° of abduction and 30° of flexion. Skin traction was applied with non-adhesive tape, and the skin was inspected at regular intervals
Fig. 2. Under-thigh pillows. These were placed under the thighs, supporting the knees and ankles
by the nursing staff. The weight was usually 2 kg and this was gradually increased according to the child’s tolerance. Radiographs were taken every second week to assess the position of the femoral head. The traction was continued until radiographs showed that distance “a” was equal to or more than 8 mm,12,18 and until the hip could be abducted in flexion up to 70°. After the skin traction, the harness was applied by the same method as that used in group A. When a child was placed in the supine position after Pavlik harness application, small pillows were put under his or her thighs. The height of the pillows was adjusted so that the amount of hip abduction did not exceed 75°. Attention was paid to the position of the pillows; these pillows supported the lower extremities from just above the knee to the foot (Fig. 2). If the pillows were placed more medially, they forcibly pushed up the femoral head. The position of the pillows was regularly checked by the nursing staff. After reduction, the patients were discharged from the hospital and were managed in the same way as those in group A. If the dislocation persisted for more than 2 weeks, the patient received closed manual reduction. The results of hips which could not be reduced with the use of the Pavlik harness in the inpatient clinic were excluded from this study. The average total time that the harness was worn was approximately 2 months after reduction in both groups.
See text for explanation of groups I to IV
2 7 16 14 26 16 5 3 0 0 2 91
,1 1 2 3 4 5 6 7 8 9 10 Total
Group B
a
14 24 20 6 4 0 2 70
2 3 4 5 6 7 8 Total
Treated hips (number)
Group A
Age at beginning of treatment (months)
54
25 5 18 12 19 14 12 17
Duration of traction (days)
1 7 11 12 24 16 5 2 0 0 0 78
13 22 13 5 3 0 2 58
Reduced hips (number)
0 86
50 100 69 86 92 100 100 67
100 83
93 92 65 83 75
%
0 0 1 0 2 0 0 0 0 0 0 3
3 2 2 0 0 0 0 7
Reduced hips that had avascular necrosis
Table 1. Rate of reduction and avascular necrosis according to age at the beginning of treatment
4
0 0 9 0 8 0 0 0
0 12
23 9 15 0 0
%
0 0 1 0 1 0 0 0 0 0 0 2
3 2 2 0 0 0 0 7
Group Ia
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
Group IIa
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
Group IIIa
0 0 0 0 0 1 0 0 0 0 0 1
0 0 0 0 0 0 0 0
Group IVa
Classification of avascular necrosis Number of hips
542 S. Suzuki et al.: Prevention of AVN in DDH treatment
S. Suzuki et al.: Prevention of AVN in DDH treatment
543
Table 2. Rate of reduction and avascular necrosis according to distance “a”
Distance “a” (mm)a
Treated
Reduced
%
Reduced hips that had avascular necrosis
Group A
$8 ,8 Total
33 37 70
28 30 58
85 81 83
3 4 7
11* 13 12
3 4 7
0 0 0
0 0 0
0 0 0
Group B
$8 ,8 Total
55 36 91
53 25 78
96 69 86
0 3 3
0* 12 4
0 2 2
0 0 0
0 0 0
0 1 1
Number of hips
Classification of avascular necrosis Number of hips %
Group I
Group II
Group III
Group IV
* P , 0.05 a See text for explanation of distance “a”
The diagnosis of avascular necrosis was established according to the criteria of Salter et al.:10 (1) failure of appearance of the ossific nucleus of the femoral head for 1 year or longer after reduction, (2) failure of growth of an existing ossific nucleus for 1 year or longer after reduction, (3) broadening of the femoral neck during the year after reduction, (4) increased radiographic density of the femoral head followed by the radiographic appearance of fragmentation, and (5) residual deformity of the femoral head and neck when reossification was complete. Hips that had temporary irregular ossification were not considered to have avascular necrosis. The hips that had avascular necrosis were divided into four groups according to the classification of Kalamchi and MacEwen:7 group I hips had changes affecting the ossific nucleus, group II hips had lateral physeal damage, group III hips had central physeal damage, and group IV hips had damage to the entire femoral head and physis. Comparisons between groups were performed by Fisher’s exact probability test. Correlations between the duration of traction and patient’s age or distance “a” on the initial X-ray picture were examined by the Cochran and Cox test. Statistical significance was set at P , 0.05.
Results The mean duration of traction in group B patients was 16 days, varying from 0 to 54 days (Table 1). It was correlated with the patient’s age, and the younger the patient, the shorter the duration of traction (P , 0.05). When the duration of traction was considered in relation to distance “a” on the initial X-ray picture, the lower distance “a”, the longer the duration of traction required, and there was a high correlation between these factors (P , 0.01). When distance “a” was 10 mm
or more, the mean duration of traction was 11 days, and the mean duration of traction was 23 days when distance “a” was 3 mm or less. The overall rate of reduction in group A was 83% (58 of 70 hips) and that in group B was 86% (78 of 91 hips), and there was no significant difference between the groups (Table 1). When distance “a” was less than 8 mm on the initial radiograph, the rate of reduction in group A was 81% (30 of 37 hips) and that in group B was 69% (25 of 36 hips), and there was no significant difference (Table 2). When distance “a” was 8 mm or more, the rate of reduction in group A was 85% (28 of 33 hips) and that in group B was 96% (53 of 55 hips), and there was no significant difference. Thus, the rate of reduction with the use of the Pavlik harness did not change after the treatments of preliminary traction and under-thigh pillows were introduced. The overall rate of occurrence of avascular necrosis in group A was 12% (7 of 58 reduced hips) and that in group B was 4% (3 of 78 reduced hips), and there was no significant difference between the groups (Table 1). But, when distance “a” was 8 mm or more, the rate of avascular necrosis in group A was 11% (3 of 28 reduced hips) and that in group B was 0% (none of 53 reduced hips), and this difference was significant (P , 0.05). When distance “a” was less than 8 mm on the initial radiograph, the rate of avascular necrosis in group A was 13% (4 of 30 reduced hips) and that in group B was 12% (3 of 25 reduced hips), and there was no significant difference (Table 2). Thus, the rate of avascular necrosis decreased after preliminary traction and avoidance of extreme abduction when distance “a” was 8 mm or more, but the rate of avascular necrosis was not decreased when distance “a” was less than 8 mm. The classification of avascular necrosis is shown in Tables 1, 2. In group A, all hips with avascular necrosis were group I. In group B, two hips were group I and one was group IV.
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Discussion Treatment of DDH using the Pavlik harness has gained widespread acceptance in Japan. However, this treatment does not always produce an excellent result, because avascular necrosis can occur as a complication of using the Pavlik harness, and the involved hip will develop osteoarthrosis if the physis is damaged. The reported rate of avascular necrosis with the use of the Pavlik harness has ranged from 1% to 30%,3–5,6,8,12,14–16 The more severe the dislocation, the higher the rate of occurrence of avascular necrosis.4,5,12,13,16 Grill et al.4 demonstrated that the rate of avascular necrosis was 1.28% in grade Tönnis 1, 2.12% in grade Tönnis 2, 3.1% in grade Tönnis 3, and 16.4% in grade Tönnis 4. Suzuki and Yamamuro12 reported that the rate of avascular necrosis was 13% when distance “a” was 8 to 10 mm, 17% when “a” was 6 to 8 mm, 21% when “a” was 4 to 6 mm, and 27% when “a” was less than 4 mm. Thus, avascular necrosis tends to occur in the hip that has higher proximal migration of the femoral head. One of the important causes of avascular necrosis may be extreme abduction after reduction. Ogden9 showed that retinacular vessels are occluded due to a tight interlocking of the acetabular labrum to the intertrochanteric notch of the proximal femur in extreme hip abduction. Salter et al.10 found that the combination of tight muscles around the hip at the time of reduction, and immobilization of the hip in extreme abduction tended to produce avascular necrosis of the femoral head, as the tight adductors are stretched further and they strongly compress the femoral head into the acetabulum. When the dislocation is treated with the Pavlik harness, immobilization can occur in extreme abduction. When awake, the child can move the hip joint, but after he or she goes to sleep and the active adduction disappears, the hip is forced to abduct by the weight of the extremities because the child cannot extend his or her hips.6 When the hip is immobilized in extreme abduction after reduction, the already contracted muscles are stretched and they compress the femoral head into the acetabulum. In severe dislocations, the contractions of muscles around the hip joint are greater. The compression force will be stronger due to the contracted muscles in extreme abduction after reduction, and this could be one of the reasons for the higher rate of avascular necrosis in the hip that has higher proximal migration of the femoral head. In order to prevent avascular necrosis, both preliminary traction to relax the tight muscles, and immobilization in the human position after reduction have been widely accepted among orthopedic surgeons.1,2,17 We tried to reduce avascular necrosis by introducing a combination of preliminary traction and
S. Suzuki et al.: Prevention of AVN in DDH treatment
avoidance of extreme abduction by using under-thigh pillows during the application of the Pavlik harness. We compared group A patients, in whom the Pavlik harness was applied immediately after diagnosis between 1980 and 1987, with group B patients, in whom preliminary traction and the prevention of extreme abduction during application of the harness were performed between 1988 and 1992. The results showed that the incidence of avascular necrosis was significantly less in group B than in group A when distance “a” was 8 mm or more. However, the rate of necrosis among those with distance “a” less than 8 mm was not significantly decreased in group B. Although the combination of preliminary traction and the use of under-thigh pillows was effective in reducing avascular necrosis in the slightly dislocated hips, this method alone was useless in severe dislocations that had proximal migration. In hips with proximally dislocated femoral head, in addition to the contraction of muscles around the hip and extreme abduction, other factors, such as the intraarticular interpositions of pulvinar, inverted labrum, hypertrophied round ligament, and elevated transverse ligament are thought to be involved in the occurrence of avascular necrosis. In hips in which the femoral head is dislocated proximally, large intra-articular interpositions, instead of the femoral head, may occupy the cavity in the acetabulum. Even after the use of the combination of preliminary traction and avoidance of extreme abduction with the under-thigh pillows, the muscles around the hip joint are strongly stretched as the intra-articular substances increase the distance between the origin and the insertion of muscles after reduction. As a result of this muscle stretching, strong pressure is exerted on the reduced femoral head. Moreover, excessive pressure is concentrated in one part of the femoral head soon after the reduction, as the contact area is limited when there is an obstacle. Somerville and Scott11 and Tönnis16 noted that an inverted labrum produced circumscribed pressure on the femoral head. The limited area in the femoral head appears to receive too much pressure in the course of reduction, which interrupts the blood flow in the femoral head. In this study, the combination of preliminary traction and the use of under-thigh pillows was ineffective in reducing avascular necrosis in hips with distance “a” less than 8 mm. If the duration of traction is prolonged for these hips until distance “a” is 10 mm or more, in order to minimize muscle contraction, the incidence of avascular necrosis may decrease after the reduction. In this study, the mean duration of traction in group B was 16 days. The lower distance “a”, the longer the duration of traction required, and the duration was 23 days when distance “a” was 3 mm or less. If the duration of traction is prolonged for hips in which distance “a” is 3 mm or
S. Suzuki et al.: Prevention of AVN in DDH treatment
less before reduction, the baby will have to stay in the hospital for some months until distance “a” is 10 mm or more. Longer stay in a hospital, however, is unfavorable for the baby. We suggest that the Pavlik harness is indicated for hips in which distance “a” is equal to or more than 8 mm. Preliminary traction should precede the application of the harness, and under-thigh pillows must be placed during the harness application. For hips in which distance “a” is less than 8 mm, avascular necrosis, as a complication of treatment with the Pavlik harness, cannot be prevented by this method alone. References 1. Fish DN, Herzenberg JE, Hensinger RN. Current practice in use of prereduction traction for congenital dislocation of the hip. J Pediatr Orthop 1991;11:149–53. 2. Gage JR, Winter RB. Avascular necrosis of the capital femoral epiphysis as a complication of closed reduction of congenital dislocation of the hip. J Bone Joint Surg Am 1972;54:373–88. 3. Gotoh E, Ando M, Ibayashi K, et al. Significance of screening by the Pavlik harness in congenital dislocation of the hip: for prevention of avascular necrosis. Rinsho Seikei Geka (Clin Orthop Surg) 1992;27:1331–5 (in Japanese). 4. Grill F, Bensahel H, Canadell J, et al. The Pavlik harness in the treatment of congenital dislocating hip: report on a multicenter study of the European Paediatric Orthopaedic Society. J Pediatr Orthop 1988;8:1–8. 5. Inoue T, Nakamura H. Factors for prediction of avascular necrosis after treatment with Pavlik’s harness. J Jpn Paediatr Orthop 1995;4:298–301 (in Japanese). 6. Iwasaki K. Treatment of congenital dislocation of the hip by the Pavlik harness. Mechanism of reduction and usage. J Bone Joint Surg Am 1983;65:760–7.
545 7. Kalamchi A, MacEwen GD. Avascular necrosis following treatment of congenital dislocation of the hip. J Bone Joint Surg Am 1980;62:876–88. 8. Kumazawa H, Yoshihashi Y. Long-term results of congenital dislocation of the hip treated with Pavlik harness. J Jpn Orthop Assoc 1991;65:851–61 (in Japanese). 9. Ogden JA. Treatment positions for congenital dysplasia of the hip. J Pediatr 1975;86:732–4. 10. Salter RB, Kostuik J, Dallas S. Avascular necrosis of the femoral head as a complication of treatment for congenital dislocation of the hip in young children: a clinical and experimental investigation. Can J Surg 1969;12:44–60. 11. Sommerville EW, Scott JC. The direct approach to congenital dislocation of the hip. J Bone Joint Surg Br 1957;39:623– 40. 12. Suzuki S, Yamamuro T. Avascular necrosis in patients treated with the Pavlik harness for congenital dislocation of the hip. J Bone Joint Surg Am 1990;72:1048–55. 13. Suzuki S, Kashiwagi N, Kasahara Y, et al. Avascular necrosis and the Pavlik harness. J Bone Joint Surg Br 1996;78:631– 5. 14. Takahashi I. Functional treatment of congenital dislocation of the hip using Pavlik harness (Riemenbügel). J Jpn Orthop Assoc 1985;59:973–84. 15. Takahashi M. A long-term follow-up study of the femoral heads presenting with Perthes-like abnormality after Pavlik harness treatment for congenital dislocation of the hip. Cent Jpn J Orthop Traumat 1992;35:327–37 (in Japanese). 16. Tönnis D. Ischemic necrosis of the femoral head in the treatment of congenital hip dislocation. In: Tönnis D, editor. Congenital dysplasia and dislocation of the hip in children and adults. Berlin Heidelberg New York Tokyo: Springer-Verlag; 1984. p. 268– 90. 17. Weiner DS, Hoyt WA, O’Dell HW. Congenital dislocation of the hip. The relationship of premanipulation traction and age to avascular necrosis of the femoral head. J Bone Joint Surg Am 1977;59:306–11. 18. Yamamuro T, Chene S-H. A radiological study on the development of the hip joint in normal infants. J Jpn Orthop Assoc 1975;49:421–39.