The Effect of PAO Followed by Progressive Resistance Training Versus Progressive Resistance Training in Patients With Hip Dysplasia. A Randomized Controlled Trial
Phase: NA
Conditions: Hip Dysplasia
Sponsor: University of Aarhus

Efficacy of periacetabular osteotomy followed by progressive resistance 
training compared to progressive resistance training as non-surgical 
treatment in patients with hip dysplasia (PreserveHip) – statistical 
analysis plan 
Lisa Cecilie Urup Reimerab, Stig Storgaard Jakobsena, Ulrik Dalgasc, Troels Kjeldsenabd, Julie Sandell 
Jacobsene, Kjeld Soballea, Tone Beref, Jan Erik Madsenf, Lars Nordslettenfg, May Arna Risbergf, Inger 
Mechlenburgabc and Bo Martin Bibbyh. 
Affiliation 
aDepartment of Orthopedic Surgery, Aarhus University Hospital, Denmark.  
bDepartment of Clinical Medicine, Aarhus University, Denmark 
cDepartment of Public Health – Sport, Aarhus University, Denmark 
dThe Research unit PROgrez, Department of Physiotherapy and Occupational Therapy, Næstved-Slagelse-
Ringsted Hospitals, Region Zealand, Denmark  
ePhysiotherapy & Research Centre for Health and Welfare Technology, Programme for Rehabilitation, VIA 
University College, Denmark 
fDepartment of Orthopedic Surgery, Oslo University Hospital, Norway 
gFaculty of Medicine, University of Oslo, Norway 
hDepartment of Biostatistics, Aarhus University, Denmark 
Corresponding author 
Lisa Cecilie Urup Reimer 
Department of Orthopedic Surgery, Aarhus University Hospital 
Palle Juul-Jensens Boulevard 99, 8200 Aarhus, Denmark 
E-mail: lisareimer@clin.au.dk 
Telephone: +4526474080 
Trial registration, version of statistical analysis plan and protocol 
This trial is registered at www.ClinicalTrials.gov with the number NCT03941171 and the Statistical Analysis 
Plan is version 1. The protocol has been published in BMJ Open and this version is used in the SAP (1). 
Signatures 
Role 
Name 
Date 
Signature                   
Person writing the SAP 
Lisa Cecilie Urup Reimer 17.01.2022                                          
Senior statistician responsible Bo Martin Bibby 
 
 
Chief investigator/clinical leas Inger Mechlenburg 
 
 
 
 
 
17.01.2022
17/1-2022

INTRODUCTION 
Background 
Hip dysplasia (HD) is characterised by a shallow and steep acetabulum that does not cover the femoral 
head sufficiently (2). The periacetabular osteotomy (PAO) is the surgical treatment of choice for patients 
suffering from HD (3). In short, the osteotomized acetabular fragment is reoriented in an adducted, 
extended and rotated position, and fixated with screws (4). The aim of PAO is to relieve symptoms, improve 
physical function and prevent development of hip osteoarthritis. Even though PAO has been found to 
improve self-reported outcomes (5,6), muscle-tendon pain (6), muscle strength (7) and walking pattern (8), 
the patients do not reach a level equal to healthy volunteers one year after PAO (6,7). In other related hip 
conditions including hip osteoarthritis (9) and femoroacetabular impingement syndrome (10), non-surgical 
treatment is considered “first-line treatment”. The role of non-surgical treatment for patients with HD is 
still to be investigated and the efficacy of PAO has not been investigated in a randomised controlled trial 
(RCT) previously.  
 
Objectives 
The primary aim of this trial is to examine the efficacy of PAO followed by 4 months of usual care followed 
by 8 months of Progressive Resistance Training (PRT) compared to 12 months of a PRT only, in patients with 
hip dysplasia eligible for PAO, in terms of patient-reported pain measured by the Copenhagen Hip and 
Groin Outcome Score (HAGOS). We hypothesise that PAO followed by usual care and PRT results in 
significantly less pain at 12 months follow-up compared to PRT only. 
 
The key secondary aims are: 
1. To investigate the mean difference from baseline to 12 months after surgery or first 
training session, between the two groups regarding the remaining subscales of HAGOS: 
patient-reported symptoms, physical function in daily living, physical function in sport 
and recreation, hip and/or groin-related quality of life. 
2. To investigate the mean difference from baseline to 12 months after surgery or first 
training session in hip function, measured with the single leg hop for a distance test.  
3. To investigate the difference in number of adverse and serious adverse events within the 
12 months study period, between the two groups.  
4. To investigate the mean difference from baseline to 12 months after surgery or first 
training session, between the two groups regarding the usage of painkillers (yes/no) and 
the type of analgesics. 
5. To investigate the difference in the anchor question (a patient-reported question to 
evaluate to which extent the a priori hip problems have been addressed) at each 
assessment point, between the two groups. 
 
 
 

STUDY METHODS 
Trial design 
This trial is a multicentre randomised controlled and assessor blinded trial, following the Consolidated 
Standards of Reporting Trials (CONSORT) guidelines (11). The statistical Analysis Plan (SAP) is reported in 
accordance with the Guidelines for the Content of Statistical Analysis Plans in Clinical Trials (12). Change in 
primary outcome will be measured from baseline to 12 months follow-up, while change in secondary 
outcomes will be measured from baseline to four and 12-months follow-up. In addition, five year and 10 
year follow-up with questionnaires is planned. The trial has been registered at www.ClinicalTrials.gov with 
the number NCT03941171. The Central Denmark Region Committee on Biomedical Research Ethics (Journal 
No 1-10-72-234-18), the Danish Data Protection Agency (Journal No 1-16-02-120-19) and The Regional 
Committee for Medical and Health Research Ethics Region South-East Norway (Ref. 2018/1603) has 
approved the trial. 
 
Randomisation 
After baseline assessment, the patients will be randomized in a 1:1 ratio to either PAO followed by usual 
care and PRT (PAO-group) or PRT only (PRT-group). A computer-generated list of random numbers will be 
set up in the Research Electronic Data Capture (REDCap) randomize tool. The randomisation will be done 
separately for each recruitment site in blocks of varying sizes with half of the patients in each block 
receiving each treatment in a random permutation. This ensures that close to half of the patients receive 
each of the two treatments in each block (and exactly half if all blocks are filled). Administrators of the 
randomisation procedure will be blinded to block sizes and randomisation sequence at all times during the 
trial period. Allocation concealment will be ensured, as the randomisation will not be performed and 
revealed before the patient has been irreversibly included in the trial. After randomisation a secretary or 
project coordinator, will refer patients to surgery or to the treating physiotherapist/physiotherapy student 
who contacts the patient to arrange an appointment for the first exercise session. 
 
Sample size 
The minimal clinically relevant difference of the HAGOS pain subscale has been reported to be 9.7 points 
(28). Based on a previous pilot trial the SD of HAGOS pain in PAO patients is 16.2 points (15). Given a power 
of 0.80 and two-sided significance level α=0.05, the estimated sample size of each intervention group is 44 
patients. Allowing for possible crossovers and loss to follow-up, the number of included patients in each 
intervention group will be 48 patients. The sample size calculation has been performed on the minimal 
clinically relevant difference of the primary outcome (HAGOS pain) at 12 months follow-up. This has been 
done due to lack of knowledge on the expected improvements standard deviation within the 12-month 
period. The estimation is thus based on an assumption that the two groups will not have very different 
mean scores at baseline, due to randomisation.  
 
 
 

Statistical interim analysis and stopping guidance 
No formal interim analysis has been planned for the PreserveHip trial. The final deadline for recruitment of 
participants were originally set to be June 1st 2022, however due to the circumstances and lockdowns 
following the COVID-19, the inclusion period was prolonged to Marts 1st 2024.  
 
 
Timing of final analysis 
The final analysis of the primary outcome, the mean difference in pain assessed by the HAGOS subscale 
pain, will be performed after the last follow-up test. If a participant decides to drop out of the study, they 
are still encouraged to attend the follow-up test. In addition, papers on five and 10-year follow-up will be 
performed, when these follow-up tests have been performed.  
 
Timing of outcome assessments 
The trial consists of five tests timepoints; baseline, four month, 12 months, five years and 10 years after 
surgery or first exercise session. A table of the assessments and procedures has been presented in the 
protocol (Table 2).   
 
STATISTICAL PRINCIPLES 
Confidence intervals and P values 
All confidence intervals will be two-sided and based upon 95% (9% CI). Consistent with contemporary 
statistical guidelines, the use of p values for secondary and other comparisons will be toned down when 
interpreting the results of this study (i.e. p values will be included but not in the conventional, dichotomous 
way) (13). For the primary aim, a significance level of 0.05 will be used, meaning that a result with a p value 
less than 0.05 will be considered as statistically significant. 
 
Adherence and protocol deviations 
Adherence is defined as the ability to follow the allocated treatment and will be compared between the 
groups as the number of supervised sessions that patients showed up for, the number of sessions were all 
exercises were completed and the number of self-reported training sessions during the study period. In 
addition good adherence has been predefined as participation in at least 70% of the supervised training 
sessions within the first four months of training. There are three predefined protocol deviations within the 
trial: a patient randomised to PRT undergoing PAO during the study period, a patient withdrawing from the 
trial after being randomised to PAO and a patient withdrawing from the trial after being randomised to 
PRT. In addition, a fourth protocol deviation has been detected after initiating the study: a patient receiving 
additional surgery after PAO (i.e. hip arthroscopy or removal of screws) within the study period 

Analysis populations 
The primary efficacy analysis will be assessment of the between-group difference in change in the HAGOS 
pain subscale from baseline to 12 months after initiating the treatment (primary endpoint). The primary 
analysis will follow the intention-to-treat principle and a mixed effects model will be used (see the section 
“Analysis method”). Sensitivity and exploratory analysis will be performed with the purposes to test the 
robustness of the results per-protocol with good compliance (defined as participation in ≥70% of the 
training sessions) and as-treated analysis, in which patients will be analysed based on their adherence to 
the randomised treatment expecting three groups: patients randomised to PAO, patients randomised to 
PRT without undergoing PAO in the follow-up period and patients randomised to PRT undergoing PAO in 
the follow-up period. The patients that cross over to PAO after being randomised to PRT, will most likely be 
a very heterogeneous group of patients because of differences in times of cross over, however due to the 
expected small sample in this group, the group will be treated as one group.  
 
TRIAL POPULATION 
Screening data 
At both hospitals all patients eligible for PAO will be screened for the inclusion and exclusion criteria in the 
trial and invited to participate if they fulfil the criteria. The number of patients who did not meet the 
inclusion criteria as well as the number of patients who did not the exclusion criteria will be presented in a 
flow chart (see figure 1).  
 
Eligibility 
Patients who meet the inclusion and exclusion criteria presented below and are willing to participate are 
eligible for the PreserveHip study. The inclusion criteria are: (1) patients aged 18 to 40 years and diagnosed 
with hip dysplasia referred from primary care to the Department of Orthopaedic Surgery at one of the two 
participating Hospitals, (2) considered eligible for PAO by a surgeon, (3) radiographically verified hip 
dysplasia (Wiberg's centre-edge angle <25 degrees and Acetabular Index angle >10 degrees) and clinical 
symptoms, (4) range of motion: internal rotation >15 degrees, external rotation >15 degrees, hip flexion 
>110 degrees and (5) able to drive or commute to training sessions. The exclusion criteria are: (1) OA 
degree >1 on classification of Tönnis, (2) CE-angle <10 degrees, (3) previous pelvic surgery for hip dysplasia 
(affected side), (4) Legg–Calvé–Perthes or epiphysiolysis, (5) simultaneous bilateral PAO, (6) previous 
surgery for herniated disc, spondylodesis, arthroplasty of hip, knee or ankle, (7) previous surgery of the hip 
(tenotomy of iliopsoas tendon, z-plastic of the iliotibial tract or hip arthroscopy) in index leg, (8) 
neurological or rheumatoid diseases that affect the hip function, (9) inadequacy in written and spoken 
Danish or Norwegian and (10) Body Mass Index (BMI) >25. 
 
Recruitment 
The number of patients screened for the PreserveHip trial, as well as the number of patients not meeting 
the inclusion and exclusion criteria will be presented in a flow chart (see figure 1). For patients fulfilling the 

inclusion criteria but not the exclusion criteria the precise number for each exclusion criteria will be 
presented. In addition, the number of patients allocated to PAO and PRT will be presented, with a note of 
how many patients received the allocated intervention and the number of patients who decided to leave 
the study based on allocation. For the two follow-up assessments the number of patients lost to follow-up 
and number of patients who discontinued the intervention will be presented. The last part of the flow chart 
will be the presentation of the number of participants who will be analysed.  
 
Withdrawal  
Throughout the trial period the participants are always allowed to withdraw from the study. Participants 
who decide to withdraw will be encouraged to complete the follow-up assessments as if they had received 
the intervention. Withdrawal will thus be divided in to two: withdrawal from intervention with completion 
of assessments and withdrawal from intervention with no further assessments. The number of participants 
who decide to withdraw, as well as the timing of the withdrawal, will be presented in the flow chart. The 
baseline characteristics age and gender, HAGOS results and single-leg-hop test result will be presented for 
the four groups (PAO, PRT, Cross-over and Drop-out) as illustrated I table 7. 
 
Baseline patient characteristics 
Baseline characteristics will be presented as seen in Table 1. Continuous variables will be presented as 
mean with standard deviation if normally distributed and as median with interquartile range if not normally 
distributed. Categorical variables will be presented as number and percentages. Baseline variables for the 
primary and secondary outcomes will be presented as part of the analysis, as seen in Table 2. 
 
ANALYSIS 
Outcome definitions 
The prespecified primary outcome is the difference from baseline to 12 months follow-up in the subscale 
pain of the Copenhagen Hip and Groin Outcome Score (HAGOS) (14). The subscale consists of 10 items 
related to pain. Each item has five possible categories, ranging from 0-4 point. In accordance with the 
HAGOS protocol, the points will be converted to a score from 0-100, where 0 indicates severe problems 
and 100 indicates no problems. The minimal clinically relevant difference of HAGOS pain has been found to 
be 9.7 points (15). HAGOS is a valid and reliable questionnaire to collect patient reported outcome 
regarding hip and groin pain among young to middle-age patients (15,16). In addition, five key secondary 
outcomes will also be obtained. For the other five subscales of HAGOS (symptoms, physical function in daily 
living, physical function in sport and recreation, participation in physical activities and hip and groin related 
quality of life) and the single leg hop for a distance test, the outcome will be the difference from baseline to 
12 months follow-up. In addition, the number of adverse and serious adverse events will be presented as 
the between group difference at 12 months follow-up. Usage of analgesics will be presented as the number 
of patients using analgesics at each assessment (yes/no). In addition, the patients who reported using 
analgesics will further be asked to report type of analgesics and frequency of use. The study has no 

information on exact dose of various analgesics. The “Anchor question” will be presented as the number of 
participants in each group defining their hip at the assessment point compared to before the intervention, 
as much better, slightly better, the same, slightly worse, or much worse. 
 
Analysis methods 
Descriptive statistics will be presented as means with standard deviations (SD) for all normally distributed 
continuous variables and as median with interquartile ranges for all continuous variables that do not follow 
a normal distribution. Normal distribution will be determined by visual inspection of quantile plots and 
histograms. Categorical outcomes will be presented as numbers with percentage.  
The difference between the two intervention groups, regarding the primary outcome and the continuous 
secondary outcomes, will be determined based on the intention-to-treat principle and thus includes all 
randomized patients regardless of actual treatment received. For the primary outcome, HAGOS pain, mixed 
effect models will be used with the patient as the random effect and assessment time, and intervention 
group along with the interaction between them as fixed effects. Patients who drops out will contribute with 
data to their respective groups until they drop out (i.e. imputations will not be applied). The intention-to-
treat analysis will be adjusted for inclusion site and the time that the patients waits from baseline 
assessment to initiation of the intervention. This has been decided a priori since the waiting period for 
surgery could vary throughout the study period. 
The categorical secondary outcomes will only be presented and thus not analysed, to tone down the use of 
p-values. Table 4, 5 and 6 illustrate this. 
 
Missing data 
As stated above, imputations will not be applied in this study. Instead each randomised patient will be 
included in the intention-to-treat analysis with the data collected. An attempt to collect data from all 
randomised patients will be made, see the section on withdrawing. 
 
Additional analysis 
A per-protocol analysis using the same analysis will be conducted. A priory “good compliance to the 
protocol” has been defined as a participation in at least 70% of the training sessions (1). Patients who do 
not comply with the randomised treatment will be excluded from this analysis. As-treated analysis will also 
be applied, using the same mixed effect model as described for the intention-to-treat, however the 
patients randomized to the exercise group (PRT) will further be divided into those who decides to cross-
over to surgery and those who do not. Table 2 and 3 illustrates this. 
In 2020-2021 the two countries were under lockdown in periods due to the COVID-19 pandemic. This 
resulted in postponed surgeries and amendments to the exercise protocol. A sensitivity analysis, excluding 

all patients included before 2022 will therefore be made to assess the potential impact of the pandemic on 
the study.  
 
Harms 
Adverse and serious adverse events as defined by Biederman et al. (17) will be presented as number and 
percentage for each event. Depending on the number of adverse and serious adverse events during the 
trial the events will either be presented as illustrated in Table 5 or as text in the results section. 
 
Statistical software  
All statistical analyses will be performed in Stata version 17.0 (StataCorp LLC, College Station, TX, USA). 
 
 
 

FIGURES 
Figure 1. Flow chart of the participants in the PreserveHip trial randomised to either Periacetabular 
Osteotomy (PAO) or Progressive Resistance Training (PRT). 
 
 
 
 
 
 
 
 
 
 
 
 
Assessed for eligibility (n=) 
Excluded (n=) 

Not meeting inclusion criteria (n=) 

Declined to participate (n=) 

Osteoarthrosis>0 (n=) 

CE-angle<10o (n=) 

Previous surgery in the affected hip (n=) 

Legg-Clavé-Perthes or epiphysiolysis (n=) 

Simultaneous bilateral PAO (n=) 

Previous surgery for herniated disc, 
spondylodesis, hip-, knee- or ankle 
arthroplasty (n=) 

Neurological or rheumatoid disease (n=) 

Inadequacy in written and spoken Danish 
or Norwegian (n=) 

BMI>25 (n=) 
Lost to follow-up (give reasons) (n=) 
Discontinued intervention (give reasons) (n=) 
Lost to follow-up due to allocation (n=) 
Discontinued intervention (give reasons) (n=) 
Allocated to PAO (n=) 

Received allocated intervention (n=) 

Dropout due to allocation (n=) 
Lost to follow-up due to allocation (n=) 
Discontinued intervention due to cross over (n=) 
Allocated to PRT (n=) 

Received allocated intervention (n=) 

Drop out due to allocation (n=) 
Lost to follow-up due to allocation (n= ) 
Discontinued intervention due to pregnancy (n=) 
Allocation 
Follow-up 12 month 
Follow-up four month 
Randomised (n=) 
Enrollment 
Analysed (n=) 

Excluded from analysis (give reasons) (n=) 
Analysed (n=) 

Excluded from analysis (give reasons) (n=) 
Analysis 

Figure 2: HAGOS pain change over time (baseline, 4 months, and 12 months after intervention). This figure 
is an example and is based on results from two trials reporting HAGOS Pain in a group of patients with hip 
dysplasia receiving PAO (6) and a group of patients with hip dysplasia receiving PRT (18). 
 
 
 
 

TABLES 
 
Table 1. Baseline characteristics for the two intervention groups. 
 
PAO group  
Exercise group 
 
n = 
n = 
Gender 
 
 
Age 
 
 
Height 
 
 
Weight 
 
 
CE-angle 
 
 
AI-angle 
 
 
Duration of hip symptoms 
 
 
 
0-6 months 
 
 
 
6-12 months 
 
 
 
1-2 years 
 
 
 
2-5 years 
 
 
 
5-10 years 
 
 
 
More than 10 years 
 
 
Civil status 
 
 
 
Married 
 
 
 
Cohabiting 
 
 
 
Single 
 
 
 
Divorced 
 
 
 
Widow/widower 
 
 
 
Not informed 
 
 
Educational level 
 
 
 
Primary school 
 
 
 
Vocational education 
 
 
 
High school or similar 
 
 
 
Short higher education 
 
 
 
Medium higher education 
 
 
 
Long higher education 
 
 
 
Other education 
 
 
Employment status 
 
 
 
During education 
 
 
 
In work 
 
 
 
In activation, sick leave, available, etc. 
 
 
 
Outside the labor market 
 
 
 
Other 
 
 
Alcohol consumption 
 
 
 
Under 2 items per week 
  
 
 
2-7 items per week 
 
 
 
8-14 items per week 
 
 
 
15-21 items per week 
 
 
 
22-30 items per week 
 
 
 
Over 30 items per week 
 
 
Smoking behaviour 
 
 
 
Never smoked 
 
 
 
Quit smoking 
 
 
 
Sometimes 
 
 
 
Daily 
 
 
Co-morbidities 
 
 
PAO = Periacetabular osteotomy. CE-angle = Wibergs centre edge angle. AI-angle = Acetabular Index angle 
 
 
 

Table 2. Intention-to-treat and per-protocol analysis of the difference between the PAO group and the exercise group in improvement from 
baseline to one year after intervention. 
Intention-to-treat analysis 
 
PAO 
Exercise 
Improvements between the 
two groups 
 
Baseline 
Four month 
One year 
Baseline 
Four month 
One year 
Crude 
Adjusted 
HAGOS 
 
 
 
 
 
 
 
 
Pain 
 
 
 
 
 
 
 
 
Symptoms 
 
 
 
 
 
 
 
 
Activities of daily living 
 
 
 
 
 
 
 
 
Sport and recreation 
 
 
 
 
 
 
 
 
Participation in activity 
 
 
 
 
 
 
 
 
Hip and groin related quality of 
life 
 
 
 
 
 
 
 
 
Single leg hop for distance 
 
 
 
 
 
 
 
 
Per-protocol analysis 
 
PAO 
Exercise 
Improvements between the 
two groups 
 
Baseline 
Four month 
One year 
Baseline 
Four month 
One year 
Crude 
Adjusted 
HAGOS 
 
 
 
 
 
 
 
 
Pain 
 
 
 
 
 
 
 
 
Symptoms 
 
 
 
 
 
 
 
 
Activities of daily living 
 
 
 
 
 
 
 
 
Sport and recreation 
 
 
 
 
 
 
 
 
Participation in activity 
 
 
 
 
 
 
 
 
Hip and groin related quality of 
life 
 
 
 
 
 
 
 
 
Single leg hop for distance 
 
 
 
 
 
 
 
 
Outcomes presented as mean with 95% confidence interval. PAO = Periacetabular osteotomy. Adjusted: the analysis was adjusted for inclusion site 
and time from baseline assessment to intervention. 
 
 
 
Table 3. As treated analysis of the difference between the PAO group, the exercise group and cross-over patients in improvement from 
baseline to one year after intervention. 
 
PAO 
Exercise 
Cross-over 
Improvements between 
the three groups 
 
Baseline 
Four 
month 
One 
year 
Baseline 
Four 
month 
One 
year 
Baseline 
Four 
month 
One 
year 
Crude 
Adjusted 
HAGOS 
 
 
 
 
 
 
 
 
 
 
 
Pain 
 
 
 
 
 
 
 
 
 
 
 
Symptoms 
 
 
 
 
 
 
 
 
 
 
 
Activities of daily 
living 
 
 
 
 
 
 
 
 
 
 
 
Sport and recreation 
 
 
 
 
 
 
 
 
 
 
 
Participation in 
activity 
 
 
 
 
 
 
 
 
 
 
 
Hip and groin 
related quality of life 
 
 
 
 
 
 
 
 
 
 
 
Single leg hop for 
distance 
 
 
 
 
 
 
 
 
 
 
 
Outcomes presented as mean with 95% confidence interval. PAO = Periacetabular osteotomy. Adjusted: the analysis was adjusted for inclusion site 
and time from baseline assessment to intervention. 
 
 
 

Table 4. Usage of painkillers. 
 
PAO group 
Exercise group 
 
Baseline 
Four month 
One year 
Baseline 
Four month 
One year 
Use of painkillers, n (%) 
 
 
 
 
 
 
Type of painkillers, n (%) 
 
 
 
 
 
 
Paracetamol 
 
 
 
 
 
 
NSAID 
 
 
 
 
 
 
Morfin/opiods 
 
 
 
 
 
 
Other painkillers 
 
 
 
 
 
 
Usage of painkillers, n (%) 
 
 
 
 
 
 
Never 
  
 
 
 
 
 
Monthly 
 
 
 
 
 
 
Weekly 
 
 
 
 
 
 
Daily 
 
 
 
 
 
 
Outcomes presented as numbers and percentages. PAO = Periacetabular osteotomy. 
 
 
Table 5. Adverse and seriouse adverse events. 
 
PAO group  
Exercise group 
Adverse events n (%) 
 
 
Haematoma 
 
 
Delayed wound closure 
 
 
Dysaethesia of lateral femoral cutaneous nerve 
 
 
Malpositioning 
 
 
Heterotopic ossifications (Brooker I and II) 
 
 
Urinary tract infections 
 
 
Infection not requiring surgical revision 
 
 
Injuries related to the training interventions 
 
 
Seriouse adverse events, n (%) 
 
 
Avascular necrosis of the femoral head or acetabulum 
 
 
Nerve palsy 
 
 
Major bleeding 
 
 
Peroneal and femoral neurapraxia 
 
 
Deep vein thrombosis 
 
 
Pulmonary embolism 
 
 
Stress fracture of ischial bone and posterior column 
 
 
Intraarticular osteotomy 
 
 
Heterotopic ossifications (Brooker III and IV) 
 
 
Infection requiring surgical revision 
 
 
Loss of fixation/loss of reorientation 
 
 
Delayed or non-union of pubic, ischial or iliac bone 
 
 
PAO = Periacetabular osteotomy. Malpositioning; retroversion or insufficient reorientation (CE-angle not between 30o-40o or AI-angle not between 
0o-10o). Major bleeding: administration of more than five blood units intraoperatively and postoperatively. 
 
 
 
 

Table 6. Treatment related information within the study period measured at one-year follow-up 
 
PAO group  
Exercise group 
Training adherence 
 
 
Showed up for supervised sessions, mean (SD) 
 
 
Completion of all exercises during supervised sessions, mean (SD) 
 
 
Participated in at least 70% of supervised sessions within the first four months of PRT, n (%) 
 
 
Number of self-reported training sessions, mean (SD) 
 
 
Received other treatment in the hip, n (%) 
 
 
Type of other treatment in the hip, n (%) 
 
 
Work out 
 
 
Physiotherapy 
 
 
Chiropractor 
 
 
Osteopathy 
 
 
Painkillers 
 
 
Blockade 
 
 
Other surgery than PAO 
 
 
Else 
 
 
PAO = Periacetabular osteotomy. 
 
 
Table 7. Presentation of baseline results among the included patients, stratified in four groups; PAO, exercise, cross-over and drop-out. 
 
PAO groupa 
(n=) 
Exercise groupa 
(n=) 
Cross over 
(n=) 
Drop out  
(n=) 
Gender 
 
 
 
 
Age 
 
 
 
 
HAGOS 
 
 
 
 
Pain 
 
 
 
 
Symptoms 
 
 
 
 
Activities of daily living 
 
 
 
 
Sport and recreation 
 
 
 
 
Participation in activity 
 
 
 
 
Hip and groin related quality of life 
 
 
 
 
Single leg hop for distance 
 
 
 
 
Outcomes presented as mean with standard deviation. PAO = Periacetabular osteotomy. aWithout cross-over and drop out patients. 
 
 
 
 

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