The effect of hip reconstruction on gross motor function levels in children with cerebral palsy

Objective

The aim of this study was to determine whether the hip reconstruction has an effect on gross motor function classification system (GMFCS) levels in patients with hip instability in cerebral palsy (CP).

Head-shaft angle is a risk factor for hip displacement in children with cerebral palsy

Background and purpose — Hip dislocation in children with cerebral palsy (CP) is a common and severe problem. The Swedish follow-up program for CP (CPUP) includes standardized monitoring of the hips. Migration percentage (MP) is a widely accepted measure of hip displacement. Coxa valga and valgus of the femoral head in relation to the femoral neck can be measured as the head-shaft angle (HSA). We assessed HSA as a risk factor for hip displacement in CP.

Patients and methods — We analyzed radiographs of children within CPUP from selected regions of Sweden. Inclusion criteria were children with Gross Motor Function Classification System (GMFCS) levels III–V, MP of < 40% in both hips at the first radiograph, and a follow-up period of 5 years or until development of MP > 40% of either hip within 5 years. Risk ratio between children who differed in HSA by 1 degree was calculated and corrected for age, MP, and GMFCS level using multiple Poisson regression.

Results — 145 children (73 boys) with a mean age of 3.5 (0.6–9.7) years at the initial radiograph were included. 51 children developed hip displacement whereas 94 children maintained a MP of < 40%. The risk ratio for hip displacement was 1.05 (p < 0.001; 95% CI 1.02–1.08). When comparing 2 children of the same age, GMFCS level, and MP, a 10-degree difference in HSA results in a 1.6-times higher risk of hip displacement in the child with the higher HSA.

Interpretation — A high HSA appears to be a risk factor for hip displacement in children with CP.     

The prognostic value of the head-shaft angle on hip displacement in children with cerebral palsy

BackgroundHip displacement is the second most common deformity in cerebral palsy (CP). The risk for hip displacement is related to the Gross Motor Function Classification System (GMFCS). Recently, the head-shaft angle (HSA) has been identified as a predictor for hip displacement and the aim of this study is to assess the predictive value of the HSA for hip displacement in CP.MethodsIn this retrospective cohort, we performed radiological measurements in 50 children on both hips. In children with GMFCS level II (30 hips), III (30 hips), IV (20 hips) and V (20 hips), we measured the HSA and migration percentage (MP) in three age intervals: age two years (T1), age four years (T2) and age seven years (T3).ResultsAt T1, the HSA was larger (more valgus) in hips that will displace than in hips that will not displace (174° vs. 166°; p = 0.001) and was also larger in higher GMFCS levels (IV–V vs. II–III) (172° vs. 165°; p < 0.001). At T1, GMFCS [odds ratio (OR) 14.7; p = 0.001] and HSA (OR 1.102; p = 0.043) were predictors for hip displacement at T3, but at T2, MP (OR 1.071; p = 0.010) was the only predictor for hip displacement at T3.ConclusionsThe HSA at two years is larger in hips that will displace and larger in children with higher GMFCS levels (IV–V). At age two years, GMFCS and HSA are valuable predictors for hip displacement, but at the age of four years, only MP should be used in the prediction of hip displacement.

Level of evidence

Prognostic study, level II.     

A balanced approach for stable hips in children with cerebral palsy: a combination of moderate VDRO and pelvic osteotomy

Background

Hip reconstructive surgery in cerebral palsy (CP) patients necessitates either femoral varus derotational osteotomy (VDRO) or pelvic osteotomy, or both. The purpose of this study is to review the results of a moderate varisation [planned neck shaft angle (NSA) of 130°] in combination with pelvic osteotomy for a consecutive series of patients.

Methods

Patients with CP who had been treated at our institution for hip dysplasia, subluxation or dislocation with VDRO in combination with pelvic osteotomy between 2005 and 2010 were reviewed.

Results

Forty patients with a mean follow-up of 5.4 years were included. The mean age at the time of operation was 8.9 years. The majority were non-ambulant children [GMFCS I–III: n = 11 (27.5 %); GMFCS IV–V: n = 29 (72.5 %)]. In total, 57 hips were treated with both femoral and pelvic osteotomy. The mean pre-operative NSA angle of 152.3° was reduced to 132.6° post-operatively. Additional adductor tenotomy was performed in nine hips (16 %) at initial operation. Reimers’ migration percentage (MP) was improved from 63.6 % pre-operatively to 2.7 % post-operatively and showed a mean of 9.7 % at the final review. The results were good in 96.5 % (n = 55) with centred, stable hips (MP <33 %), fair in one with a subluxated hip (MP 42 %) and poor in one requiring revision pelvic osteotomy for ventral instability.

Conclusions

This approach maintains good hip abduction and reduces soft-tissue surgery. Moderate varisation in VDRO in combination with pelvic osteotomy leads to good mid-term results with stable, pain-free hips, even in patients with severe spastic quadriplegia.

     

Annual changes in radiographic indices of the spine in cerebral palsy patients

Purpose

We estimated the annual changes in radiographic indices of the spine in cerebral palsy (CP) patients and analyzed the factors that influence its progression rate.

Methods

We included CP patients who had undergone whole-spine radiography more than twice and were followed for at least 1 year. The scoliosis Cobb angle, coronal balance, apical vertebral translation, apical rotation, and pelvic obliquity were measured on anteroposterior (AP) radiographs; thoracic kyphosis and lumbar lordosis angles, and sagittal balance was measured on lateral radiographs; and migration percentage was measured on AP hip radiographs to determine hip instability. For each gross motor function classification system (GMFCS) level, the Cobb angles, apical vertebral translation, coronal and sagittal balance, and pelvic obliquity were adjusted by multiple factors with a linear mixed model.

Results

A total of 184 patients (774 radiographs) were included in this study. There was no significant annual change in scoliosis Cobb, thoracic kyphosis, and lumbar lordosis angles in the GMFCS level I–II and III groups. In the GMFCS level IV–V group, there was an annual increase of 3.4° in the scoliosis Cobb angle (p = 0.020). The thoracic kyphosis angle increased by 2.2° (p = 0.018) annually in the GMFCS level IV–V group. Apical vertebral translation increased by 5.4 mm (p = 0.029) annually in the GMFCS level IV–V group. Progression of coronal and sagittal balance and pelvic obliquity with aging were not statistically significant. Sex, hip instability, hip surgery, and triradiate cartilage did not affect the progression of scoliosis and the balance of the spine and pelvis.

Conclusions

The scoliosis Cobb angle, thoracic kyphosis angle, and apical vertebral translation in the GMFCS level IV–V CP patients progressed with age. These findings can predict radiographic progression of scoliosis in CP patients.

     

Systematic review on outcomes of acetabular revisions with highly-porous metals

Purpose

The purpose of this study was to systematically review the literature and report the clinical and radiographic outcomes of highly-porous acetabular cups in revision settings.

Method

A literature search of four electronic databases of EMBASE, CINAHL-plus, PubMed, and SCOPUS yielded 25 studies reporting the outcomes of 2,083 revision procedures with highly-porous acetabular components. There was lack of high quality evidence (level I and level II studies) and only two studies with level III evidence, while the remainder were all level IV studies. In addition, a majority of the studies had small sample sizes and had short to mid-term follow-up. The mean age of the patients was 65 years (range, 58–72 years) and the mean follow-up was 3.6 years (range, two to six years). Outcomes evaluated were aseptic survivorship, Harris hip scores, migration rates, incidence of peri-acetabular radiolucencies and radiographic restoration of the hip centre.

Results

The mean aseptic survivorship was 97.2 % (range, 80–100 %). The Harris hip scores improved from a mean pre-operative score of 42 points, (range, 29–75 points), to a mean postoperative score of 79 points (range, 69–94 points). The mean incidence of cup migration and prevalence of peri-acetabular radiolucencies was 2.4 % (range, 0–8.8 %) and 4.6 % (range, 0–19 %), respectively, at final follow-up. The vertical hip centre-of-rotation was restored significantly from a mean of 39.2 mm (range, 27.6–50 mm) pre-operatively, to a mean of 24.1 mm (range, 7.4–47 mm), postoperatively.

Conclusion

The short-term clinical and radiographic results of highly-porous metals in revision hip arthroplasty are excellent with a low rate of loosening in the presence of both major and minor bone loss.     

Results and complications of percutaneous pelvic osteotomy and intertrochanteric varus shortening osteotomy in 54 consecutively operated GMFCS level IV and V cerebral palsy patients

Purpose

This retrospective study evaluated mid-to-long-term outcome of a minimally invasive percutaneous pelvic osteotomy (PPO) approach combined with varus derotational shortening osteotomy (VDRSO) and soft tissue release in children with severe CP.

Methods

A retrospective review was performed of all patients presenting with a diagnosis of CP with hip subluxation or dislocation treated surgically by simultaneous soft tissue release, VDRSO, and PPO between 2002 and 2015. Eligible patients included those with a diagnosis of spastic quadriplegia or CP GMFCS level IV or V with unilateral or bilateral hip subluxation or dislocation and surgical treatment of the deformity by simultaneous soft tissue release, VDRSO and PPO. All anterior–posterior (AP) radiographs of the pelvis were reviewed and Reimers migration percentage (MP) and acetabular angle (AA) were measured.

Results

In total, 54 children and adolescents (34 boys, 20 girls) with CP GMFCS level IV and V were treated during study period: 38 (70.4%) classified GMFCS level IV and 16 (29.6%) classified GMFCS level V. A total of 64 consecutive hips underwent simultaneous PPO associated with VDRSO. Overall, at the time of chart and radiograph review, mean age was 9.1 ± 3.3 years (range 4–16.5) and mean follow-up was 43.9 ± 19.5 months (range 3–72). Mean migration percentage improved from 66.8 ± 19.8% (range 33–100) preoperatively to 8.1 ± 16.5% (range 0–70) at last follow-up. Mean acetabular angle improved from 32.7° ± 7.1° (range 20–50) preoperatively to 14° ± 6.7° (range 0–27) at last follow-up. Only one case of bone graft dislodgment was observed. We did not observe any cases of avascular necrosis of the femoral head. All operated hips were pain free at the time of last follow-up.

Conclusion

PPO through a less invasive surgical approach offers a valuable alternative to standard techniques as it gives similar outcome but with less muscle stripping and less time in surgery.

Level of evidence

III.

     

Risk factors and complications in hip reconstruction for nonambulatory patients with cerebral palsy

Background

Hip dysplasia is prevalent in nonambulatory children with cerebral palsy, and may contribute to a decreased quality of life (Lonstein in J Pediatr Orthop 6:521–526, 1). Reconstructive procedures such as a femoral varus derotation osteotomy with or without a pelvic osteotomy are commonly employed with the goal of achieving and maintaining well reduced hips.

Purposes

The goals of this study are both to characterize the complications of reconstructive procedures and to identify risk factors that may contribute to these complications.

Patients and methods

A retrospective analysis was conducted among 61 nonambulatory children (93 hips) with cerebral palsy who underwent a femoral varus derotation osteotomy, with or without an open reduction and/or pelvic osteotomy, from 1992 through 2008 at our institution. The average patient age was 8.1 years (2.6–14.7) and the mean follow-up time was 5.9 years (2.1–15.9).

Results

The cumulative complication rate per patient including failures to cure was 47.6 %. Spica casting was found to be a risk factor for all complications (P = 0.023); whereas patients younger than 6 years old (P = 0.013) and children with a tracheostomy (P = 0.004) were found to be risk factors for resubluxation following surgery.

Conclusions

Although reported complication rates of hip reconstructive procedures performed upon children with cerebral palsy have varied considerably, those with more severe disease have experienced more complications. We report our tertiary referral center’s complication rate and our institutional experiences with risk factors for complications and failures to cure.

Level of evidence

IV, Retrospective case series.     

Unilateral varus osteotomy of the proximal femur in children with cerebral palsy: a five-year follow-up of the development of both hips

Background  

Varus osteotomy of the proximal femur (VOPF) is one treatment option to prevent hip dislocation in children with cerebral palsy (CP). It is questioned whether the osteotomy should be performed in the displaced hip only, or if it should be performed bilaterally to prevent later displacement of the contralateral hip. CPUP is a register and healthcare programme for children with CP that was initiated in 1994 in southern Sweden. In the programme, range-of-motion and radiographic examination of the hips is performed regularly. These data have been analysed preoperatively and for 5 years postoperatively in children treated with unilateral VOPF.     

Windswept hip deformity in children with cerebral palsy: a population-based prospective follow-up

Purpose

To analyze the development of windswept hip deformity (WS) in a total population of children with cerebral palsy (CP) up to 20 years of age, the association between WS and hip dislocation, and femoral varus osteotomy and scoliosis, and the impact of a hip surveillance program on the subsequent incidence of WS.

Methods

This is a prospective study on children with CP in southern Sweden included in the Swedish follow-up programme and registry for CP (CPUP). All children born between 1990 and 1995 with CP were included; those born between 1990 and 1991 did not partake in the hip surveillance program until they were older (3–5 years of age) and served as a historic control group. Children born between 1992 and 1995 were included in the hip surveillance program from about 2 years of age and constituted the study group.

Results

In the control group, 12 of 68 children (18 %) developed WS. In the study group of 139 children, 13 (9 %) developed WS (p = 0.071). Of all 25 children with WS, 21 also developed scoliosis and 5 developed a hip dislocation. The number of children with WS starting in the lower extremities was significantly lower in the study group (p = 0.028). No difference between the two groups was seen regarding WS that started in combination with scoliosis.

Conclusion

With early inclusion in a hip surveillance program and early treatment of contractures, it appears possible to reduce the frequency of WS starting in the lower extremities.

     

Regional differences in hip bone mineral density levels in Norway: the NOREPOS study

Summary

Large regional differences in hip fracture rates within Norway have previously been shown. However, regional differences in hip bone mineral density (BMD) have not yet been assessed. In this study including 10,504 hip scans, there were significant regional differences in BMD. Further studies to address reasons for the regional differences in hip fracture risk are warranted.

Introduction

Bone mineral density (BMD) at the hip is an important determinant of hip fracture. While regional differences in Norwegian hip fracture rates have previously been shown, no comparative studies of hip BMD have been conducted.

Methods

Total hip BMD was measured by DXA in two population-based studies across Norway during 1997–2002. Valid hip scans with in vivo calibration were obtained from 5127 subjects in Tromsø (age 30–89 years) and 5377 subjects in Bergen (age 47–50 and 71–75 years).

Results

Women ≥60 years in Tromsø had 0.052 g/cm² higher age-adjusted BMD than women in Bergen, whereas BMD among women <60 years was similar in Tromsø and Bergen. Age-adjusted total hip BMD was 0.035 g/cm² lower in men ≥60 years in Bergen compared with Tromsø, and the corresponding figure for men <60 years was 0.028 g/cm². While adjustment for body mass index explained some, but not all of the differences, smoking, physical activity, diabetes prevalence, self-perceived health, intake of alcohol and estrogen use did not.

Conclusions

Regional differences in BMD at the hip were found in Norway. Reasons for this and potential impact on hip fracture rates should be explored in further studies.     

Utility of combined hip abduction angle for hip surveillance in children with cerebral palsy

Background:

Spontaneous hip lateralization complicates the management of non-ambulatory children with cerebral palsy (CP). It can be diagnosed early using radiographs, but it involves standardization of positioning and exposure to radiation. Hence, the aim of this study was to assess the utility of Combined hip abduction angle (CHAA) in the clinical setting to identify those children with CP who were at greater risk to develop spontaneous progressive hip lateralization.

Materials and Methods:

One hundred and three children (206 hips) with CP formed our study population. There were 48 boys and 55 girls aged 2–11 years (mean 5.03 years). 61 children were Gross Motor Function Classification System (GMFCS) level 5, while 42 were GMFCS level 4. Clinical measurements of CHAA were statistically correlated with radiographic measurements of Reimer''s migration percentage (MP) for bivariate associations using χ² and t tests.

Results:

CHAA is evaluated against MP which is considered as a reliable measure of hip subluxation. Thus, for CHAA, sensitivity was 74.07% and specificity was 67.35%. False-positive rate was 32.65% and false-negative rate was 25.93%.

Conclusions:

Our study shows that correlation exists between CHAA and MP, which has been proved to be useful for hip screening in CP children at risk of hip dislocation. CHAA is an easy, rapid, cost-effective clinical test which can be performed by paraclinical health practitioners (physiotherapists) and orthopedic surgeons.     

Comparative study on results of reconstructive surgery in 45 hip joints of 25 children with cerebral palsy

Purpose

Multilevel surgeries with hip reconstruction in children with cerebral palsy require low morbid surgical interventions. The aim of our study is to compare results of application of two locking plates in hip reconstructive surgeries in children with cerebral palsy (CP) from the point of view of efficiency and morbidity of the intervention.

Methods

We performed a prospective study on the results of 25 consecutive children with CP operated for hip reconstruction. The patients were divided into two groups according to the type of applied plate chosen at random. Group 1 (Synthes, LCP Pediatric Hip Plate) included 12 patients (22 hips) of an average age 6.2 years. Group 2 (Surfix, PSFE or PPSFE) included 13 patients (23 hips) of an average age 6.1 years. Thirteen acetabuloplasties were performed in group 1 and 15 acetabuloplasties in group 2. Duration of the procedure, amount of intraoperative blood loss, and hematogram indices before and in 24 h after surgery were compared. The following radiographic parameters were compared preoperatively and in 5–6 months of follow-up: acetabular index, projected neck shaft angle, Reimers index, and Wiberg angle.

Results

A statistically longer duration of surgery and more significant intraoperative blood loss were noted in group 1. Evaluation of radiograms did not reveal difference between the groups.

Conclusions

Results of hip reconstruction in children with severe forms of CP are satisfactory and reproducible in our series. Application of Surfix locking plates is associated with smaller volume of blood loss, and operation time is shorter.     

Management of spinal deformity in cerebral palsy: conservative treatment

Introduction

The incidence of scoliosis in Cerebral Palsy (CP) is directly related to the Gross Motor Function Classification System (GMFCS) level. The natural history of untreated scoliosis in patients with CP is one of progression and factors implicated in deterioration include type of involvement (quadriplegia), poor functional status (nonambulatory, GMFCS levels IV and V), and curve location (thoracolumbar). The generally accepted incidence in the overall CP population is 20–25 %.

Materials and methods

We recently published our short term results for 31 children treated with a short lumbar brace. In cases of a "positive hands up test" we recommend a short lumbar brace, and in patients with scoliosis with a Cobb angle >20° a double shelled brace.

Results

In our study, there was a correction of 37 % for the lumbar Cobb angle and 39 % for the thoracic Cobb angle at a mean follow-up of 28 months.

Conclusion

The incidence of scoliosis in the overall CP population is 20–25 % and is directly related to the GMFCS level. Therefore, we recommend early treatment and prescribe a short lumbar brace in patients with dynamic instability of the trunk, and in scoliosis with a Cobb angle >20° a double shelled brace.     

Correlation between the Gait Deviation Index and gross motor function (GMFCS level) in children with cerebral palsy

Aim

The Gait Deviation Index (GDI) is a score derived from three-dimensional gait analysis (3DGA). The GDI provides a numerical value that expresses overall gait pathology (ranging from 0 to 100, where 100 indicates the absence of gait pathology). The aim of this study was to investigate the association between the GDI and different levels of gross motor function [defined as the Gross Motor Function Classification System (GMFCS)] and to explore if age, height, weight, gender and cerebral palsy (CP) subclass (bilateral and unilateral CP) exert any influence on the GDI in children with unilateral and bilateral spastic CP.

Methods

We calculated the GDI of 109 children [73 % boys, mean age 9.7 years (standard deviation, SD 3.5)] with spastic CP, classified at GMFCS levels I, II and III. Twenty-three normally developing children were used as controls [61 % boys, mean age 9.9 years (SD 2.6)]. Multiple linear regression analysis was performed.

Results

The mean GDI in the control group was 100 (SD 7.5). The mean GDI in the GMFCS level I group was 81 (SD 11), in the GMFCS level II group 71 (SD 11) and in the GMFCS level III group 60 (SD 9). Multiple linear regression analysis showed that gender, age and CP subclass had no significant correlation with the GDI, whereas height and weight had a slight impact.

Conclusion

This study showed a strong correlation between the GDI and GMFCS levels. The present data indicate that calculation of the GDI is a useful tool to characterise walking difficulties in children with spastic CP.

     

Flexed-knee gait in children with cerebral palsy: a 10-year follow-up study

Background

While several studies have evaluated the short-term effectiveness of conservative and surgical treatment of flexed-knee gait in children with cerebral palsy (CP), few have explored the long-term outcomes using gait analysis. The purpose of this study was to examine, through gait analysis, the 10-year outcomes of flexed-knee gait in children with CP.

Methods

Ninety-seven children with spastic CP who walked with a flexed-knee gait underwent two gait evaluations [age 6.1 ± 2.1 and 16.2 ± 2.3 years, Gross Motor Function Classification System (GMFCS) I (12), II (45), III (37), IV (3)]. Limbs with knee flexion at initial contact >15° were considered walking with a flexed-knee gait and were included in the study (n = 185). Kinematic data were collected using an eight-camera motion analysis system (Motion Analysis, Santa Rosa, CA). Surgical and therapeutic interventions were not controlled.

Results

A comparison between the two gait studies showed an overall improvement in gait at 10 years follow-up. Significant improvements were seen in knee flexion at initial contact, Gait Deviation Index (GDI), Gross Motor Function Measure (GMFM), and gait speed (P < 0.01 for all). Outcome was also evaluated based on the severity of flexed-knee gait at the initial visit, with functional skills and overall gait (GDI) improving in all groups (P < 0.01 for all). The group with a severe flexed-knee gait exhibited the most improvement, while subjects with a mild flexed-knee improved the least.

Conclusions

Children at a specialty hospital whose orthopedic care included gait analysis and multi-level surgery showed improvement of flexed-knee gait and gross motor function over a 10-year course, regardless of the initial severity.     

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)

Background and purpose — Children with cerebral palsy (CP) have an increased risk of hip dislocation. Outcome studies after surgery to prevent hip dislocation in children with CP are usually retrospective series from single tertiary referral centers. According to the national CP surveillance program in Sweden (CPUP), hip surgery should preferably be performed at an early age to prevent hip dislocation. Preventive operations are performed in 12 different Swedish hospitals. We compared the outcomes between soft tissue release and femoral osteotomy in children with CP treated in these hospitals.

Patients and methods — 186 children with CP underwent either adductor–iliopsoas tenotomy (APT) or femoral osteotomy (FO) as the primary, preventive surgery because of hip displacement. They were followed for a minimum of 5 years (mean 8 years) regarding revision surgery and hip migration. A good outcome was defined as the absence of revision surgery and a migration percentage (MP) < 50% at the latest follow-up. Logistic and Cox regression analysis were used to investigate the influence of age, sex, preoperative MP, Gross Motor Function Classification System (GMFCS) level, and CP subtype.

Results — APT was performed in 129 (69%) children. After 5 years, the reoperation rate was 43%, and 2 children (2%) had an MP > 50%. For the 57 children who underwent FO, the corresponding figures were 39% and 9%. Of the potential risk factors studied, the outcome was statistically significantly associated with preoperative MP only in children who underwent APT, but not in those who underwent FO. None of the other factors were significantly associated with the outcome in the 2 procedure groups.

Interpretation — Reoperation rates after preventive surgery are high and indicate the importance of continued postoperative follow-up. Age, sex, GMFCS level, and CP subtype did not influence the outcome significantly.     

Hip surveillance and management of the displaced hip in cerebral palsy

Introduction

This article provides an overview of the management of a displaced hip in children with cerebral palsy and considers surveillance programmes, principles of surgical reconstruction and options for the salvage of an unreconstructable hip in these children.

Conclusion

Hip dislocation in CP is potentially preventable if children are included from an early age in a surveillance programme that includes repeat radiographic and clinical examinations, and preventive treatment for hips that are displacing. A surveillance programme should be based on the child’s age, GMFCS level and migration percentage (MP), and surgical prevention may be considered in children with a MP exceeding 33 %.     

Dislocation after total hip arthroplasty with 28 and 32-mm femoral head

Background

Dislocation after primary total hip arthroplasty (THA) is a significant complication that occurs in 2–5% of patients. It has been postulated that increasing the femoral head diameter may reduce the risk of dislocation. The purpose of this paper is to report our experiences with a change from a 28 to a 32-mm femoral head.

Materials and methods

The retrospective cohort study includes 2572 primary THA performed with a 28 or 32 mm diameter femoral head in the period February 2002 to July 2009. All patients were operated with a posterolateral approach, and all except 18 were operated because of osteoarthritis. Cemented stems were used in 1991 cases and uncemented stems in 581 cases. Cemented cups were used in 2,230 cases and uncemented cups in 342 cases. The patients have been routinely followed for 1–8 years in the 28-mm femoral head group and from 0.5–7.5 years in the 32 femoral head group. We defined a dislocation as an event in which the hip required reduction by a physician.

Results

Dislocation occurred in 49 hips with a 28-mm femoral head and in 4 hips with a 32-mm femoral head with an odds ratio of 6.06 (95% CI = 2.05–17.8) (P < 0.001). Otherwise, there were no significant associations between sex, age, diagnosis and type of prosthesis.

Conclusions

Multivariate analyses of patients operated at our hospital indicate a significant association between femoral head diameter and dislocation after THA. There were no significant associations between dislocation and sex, age, diagnosis, or type of prosthesis.