Hip surgery to prevent hip dislocation in children with cerebral palsy

Background: Cerebral palsy (CP) refers to a group of disorders that primarily affect movement, muscle tone, and posture. It is caused by abnormal brain development or damage to the developing brain with an incidence of 2 to 3 per 1,000 births. The most affected children with CP (non-ambulatory) have a high risk (up to 90%) of hip dislocation. In Sweden, the Cerebral Pares UppföljningsProgram (CPUP) is a National Quality Register that includes all children diagnosed with CP born from 2003 onwards, involving around 4,000 children. The great advantage of this type of register is its extent, allowing the study of the entire population of children with CP. The primary purpose of this thesis was to study the outcome after hip surgery and a summary of different orthopedical surgical procedures.

Methods: All studies of this thesis are based on registry data from CPUP. In Study II, data from the National Patient Registry (NPR) were also used, and in Study IV, CPUP-data from only two regions were included. The data extracted from the CPUP register included age at operation and reoperation, gender, Gross Motor Function Classification System (GMFCS) level, CP subtype, and the radiographic variables Migration Percentage (MP), Acetabular Index (AI), and Head-Shaft Angle (HSA).

In study I we identified 186 children with CP who underwent either adductor/iliopsoas tenotomy (APT) or femoral osteotomy (FO) as the primary preventive surgery due to hip displacement. The cohort was followed for five years, regarding the hip migration (MP) and the need for revision surgery. Outcome failure was defined as either repeat surgery or MP>50%.

In the second study, using data from the CPUP and NPR registers, we followed 3,305 children and young adults to describe the risk of undergoing primary orthopedic surgical treatment in relation to age.

In study III we identified and followed for five years all 163 children who had been treated with FO or with combined femur and pelvic osteotomy (FPO) in the CPUP register, regarding reoperation rates or MP >50%, using the same definition of outcome failure as in study I In the fourth study, we described and analyzed the 5-year radiological follow-up regarding MP, AI, and HSA in 72 children who underwent reconstructive hip surgery with FO and/or FPO in two regions in Sweden.

Results: Out of the 129 children who had had adductor-iliopsoas tenotomy (APT), 56 (43%) had repeated surgery, and 2 children (2%) with MP>50% at the 5-year follow-up. Out of the 57 children who had had at least one proximal femur osteotomy with or without concomitant pelvic osteotomy (FO) as primary surgery, 22 children (39%) were reoperated within 5 years (24 hips, 30% of all hips) (Study I).

In study II, data for 3,311 orthopedic surgeries performed during 1,717 surgery sessions were collected. The percentage of children undergoing surgery before age 15 increased from 20% in GMFCS level I to 64% in level. Surgeries at the foot and lower leg level, dominated in GMFCS I and II. Hip and femur surgery was most common in GMFCS level IV or V, as was spine surgery. Repeated surgeries were more common for higher GMFCS levels.

In study III, two types of skeletal corrections were compared. Out of 63 combined proximal femur and pelvic osteotomies (FPO), only 2 hips were re- operated, and four hips had an MP>50% at the last follow-up. Out of 124 isolated proximal femur osteotomies FO, 25 hips had repeated orthopedic surgery, and 16 hips had an MP>50% at the last follow-up. Multivariate analysis showed that FPO reduced the risk of treatment failure by more than 60%.

In 72 children with radiological 5-year follow-up who underwent 103 reconstructive surgeries (FO or FPO), there was a statistically significant difference regarding only the AI parameter at the end of the follow-up (Study IV).

Conclusions: The high reoperation rates within 5 years after APT and FO as primary surgical treatment for hip displacement emphasizes the importance of continuous postoperative follow-up. The percentage of young individuals undergoing orthopedic surgery increased as GMFCS levels rose. Among ambulatory children and adolescents (GMFCS I), around 20% had undergone a surgical intervention before age 15 years, commonly involving the lower leg or foot, such as Achilles tendon lengthening. Among children needing support to ambulate (GMFCS level II or III), up to 30-35% had undergone similar surgery. For children reliant on a wheelchair for transport (GMFCS level IV or V), surgery at the hip and spine was more common. Approximately one-fourth of the children at GMFCS level V had undergone hip surgery before the age of 5, and about 50% of the children by the age of 12.

In the comparison between treatment with FO or FPO, the proportion of re- operated hips within five years was considerably lower for FPO than for FO. FPO lowered the risk of failure by more than 60% compared with FO. Despite more severe displacement preoperatively in the FPO group, the radiological results were similar at the end of the follow-up.

List of scientific papers

I. Kiapekos N, Broström E, Hägglund G, Åstrand P. Primary surgery to prevent hip dislocation in children with cerebral palsy in Sweden: a minimum 5-year follow-up by the national surveillance program (CPUP). Acta Orthop. 2019 Oct;90(5):495-500. https://doi.org/10.1080/17453674.2019.1627116

II. Telléus A, Kiapekos N, Von Heideken J, Wagner P, Broström E, Hägglund G, Åstrand P. Orthopedic surgical procedures in 3,305 children and young adults with cerebral palsy: a register-based cohort study. Acta Orthop. 2022 May 23;93:472-477. https://doi.org/10.2340/17453674.2022.2583

III. Kiapekos N, von Heideken J, Broström E, Hägglund G, Åstrand P. Treatment of Hip Displacement in Children With Cerebral Palsy: A 5-year Comparison of Proximal Femoral Osteotomy and Combined Femoral-Pelvic Osteotomy in 163 Children. J Pediatr Orthop. 2024 Jul 1;44(6):e536-e541. https://doi.org/10.1097/BPO.0000000000002674

IV. Kiapekos N, Broström E, Hägglund G, Åstrand P. Radiographical development after Hip osteotomy in Children with Cerebral Palsy: A Five-Year Population-Based Study. [Manuscript]