Uncemented Hemiarthroplasty, Radiological Features Comparing Lateral Versus Anterolateral Approach: A Follow-up of a Randomized Controlled Trial.
Phase: NA
Conditions: Femoral Neck Fractures, Hemiarthroplasty, Heterotopic Ossification
Sponsor: Sorlandet Hospital HF

 
 
 
 
 
 
 
 
 
 
 
28.05.2019 
 
Title:  
Uncemented Hemiarthroplasty, Radiological features comparing Lateral versus Anterolateral 
approach: A follow-up of a randomized controlled trial.  
 
 

Study Protocol  
 
 
The following protocol is an extension of the project: Surgical treatment of displaced femoral 
neck fractures in patients between 70 and 90 years. A prospective, randomized study, comparing 
the lateral approach to the anterior muscle sparing approach. 
 
Project title: Uncemented Hemiarthroplasty, Radiological features comparing Lateral versus 
Anterolateral approach: A follow-up of a randomized controlled trial.  
Hypothesis: There is no difference in component positioning or heterotopic ossification in 
uncemented hemiarthroplasty operated in lateral (Hardinge) or anterolateral (modified Watson-
Jones/Röttinger) approach. 
 
The study's main objective:  
To compare leg length, femoral offset, valgus/varus position, canal fill ratio and heterotopic 
ossification between the two approaches, and to investigate the morphology of the proximal femur 
with canal flare index, Dorr classification and femoral cortical thickness index. If a difference exists, 
we will compare the results to existing clinical findings (Harris Hips score, PROM data and Timed Up 
and Go test).  
 
Background: 
In Norway approximately 9,000 persons are operated every year for a fracture of the proximal femur. 
Of these, 38% are displaced femoral neck fractures(1). The mortality rate is approximately 25% the 
first year(2-5). Hemiarthroplasty is a universally accepted method for the treatment of displaced 
femoral neck fractures in patients over 70 years(6, 7). Several studies have compared the posterior 
approach to either anterior or lateral approach, and dislocation is often the primary outcome(8). Due to 
the risk of dislocation following the posterior approach, there is increased popularity of the muscle 
preserving approaches(9). Concerns about component positioning is relevant because for limited 
exposure(10, 11). In total hip replacement, geometrical restoration of leg length and femoral offset is 
important for patient satisfaction and postoperative function. These patients often perceives leg length 
discrepancy of 10mm(12) and a 15% reduction of offset is associated with increased frequency of gate 
disorders(12). A decrease in femoral offset can cause impaired function in terms of reduced abduction 
strength(13), induce instability(12) and a limp(14). Valgus/varus position may influence early 
loosening, especially in cemented stems, the reports on cementless stems is varying(15). Surgical 
approach is expected to effect the clinical outcome in this fragile population(8). In the current 
literature, lateral- and anterior approaches have comparable results. The effect of hemiarthroplasties 
inserted through the muscle preserving approach on femoral neck fractures is still unclear, but may be 
beneficial in terms of less pain and earlier mobilisation (9, 16-18). 
Heterotopic ossification (HO) is a common complication following total hip arthroplasty, the 
incidence vary widely in the literature(19) and surgical approach is shown to affect the incidence(20). 
The Brooker classification is the most widely used grading system(21). For most patients the presence 
of HO is not clinically significant, but it may correlate with limitations in range of motion. Kocic et al 
found that only higher grades of HO is related to poorer clinical outcome(22). HO is possibly less 
common in cementless hemiarthroplasty. Corrigan et al found that the overall rates of HO in 
hemiarthroplasty patients did not vary with the surgical approach, but in patients who develop HO, the 
anterior and anterolateral approaches is associated with higher ossification rates.  

Is there a difference in component positioning or heterotopic ossification in uncemented 
hemiarthroplasty operated in lateral (Hardinge) or anterolateral (modified Watson-
Jones/Röttinger) approach? 
 
In this study we wanted to compare the radiological features and stem positioning in two well 
described approaches operated by experienced surgeons. Experienced surgeons defined as having done 
more than 50 arthroplasties for each approach, hopefully minimizing poorer results due to longer 
learning curve and restricted visibility in the modified Watson-Jones approach (23).  
In our study we defined leg length as the perpendicular distance between a horizontal line passing 
through the lower edge of the teardrop to the ipsilateral center of the femoral head(24).  
Femoral offset/Global offset was defined according to Lecerf et al as the distance between the 
longitudinal axis of the femur to the centre of the femoral head and the distance from the centre of the 
femoral head to a perpendicular line passing through the medial edge of the teardrop(25). 
Valgus/varus position was measured on the AP and lateral view in relation to the femoral axis. 
Canal fill ratio was evaluated at the following points; 2 cm above the lower trochanter, at the tip of the 
lower trochanter, 2 cm and 7 cm below the tip of lesser trochanter(26).  
Heterotopic ossification was classified as type 1-4 according to Brooker classification(27). 
The proximal femur morphology evaluated by canal flare index(CFI)(28), Dorr classification(29) and 
cortical thickness index (CTI)(30). CFI defined as the ratio of the intracortical width of the femur at 20 
mm proximal to the tip of lesser trochanter and isthmus at 10 cm distally. CTI defined as the ratio of 
cortical width minus endosteal width, to cortical width at 10 cm below the tip of lesser trochanter. 
Two of the authors blinded to the surgical approach do the radiological measurement. 
Primary outcome: 
Leg length 
 
Secondary outcome: 
Femoral offset 
Valgus/Varus position 
Canal fill ratio 
Heterotopic ossification 
Canal flare index 
Dorr classification 
Cortical thickness index 
Radiographic evaluation: 
Included an AP view of the pelvis and lateral view of the hip. The parameters was measured on pre 
and post operative x-rays, and at 12 months postoperative.  
Inclusion/Exclusion criteria: 
In addition to the existing criteria defined in the original protocol, we excluded patients with 
arthroplasty, history of fracture or fracture implants in the contralateral hip. 
The handling and analysis of data  
The data is entered into the statistical program SPSS (SPSS Inc, Chicago, Illinois). 

Sample size and and power calculation: 
Based on the sample size and power calculation already done in the primary project. The sample size 
would be sufficient to detect a mean difference between two groups of approximately half their SD, 
both continuous and normally distributed outcome variables with a statistical power of 80%.  
Statistical method: 
Data were examined for normal distribution using histograms, Q-Q plots and the Shapiro–Wilks test. 
The groups were compared with the Student's independent samples t-test for continuous data, whereas 
categorical variables were analyzed using Pearson's chi-square test. The Student's paired samples t-test 
was conducted to compare changes from baseline to follow-ups. The Wilcoxon signed-rank test / 
Mann-Whitney U-test was performed when the normal distribution- assumptions of the Student's t-test 
were not met. The strength of the association between primary and secondary continuous outcomes 
was assessed with the Pearson correlation coefficient. Binary outcomes were assessed using logistic 
regression or Pearson Chi-Square test. We plan to do an intraclass correlation analysis on the 
measured results and a Bland-Altman plot. We plan to perform several sensitivity analysis to assess 
the robustness of our results and possibly do a correction for repeated measurements. 
A p-value of < 0.05 was considered statistically significant. We used IBM SPSS Statistics version 25 
for Windows. All statistical analysis was conducted using IBM SPSS statistics 21 for Windows (SPSS 
Inc., Chicago, Illinois). 
 
Ethics  
The trial was approved by the regional ethics committee Regional Committees for Medical and Health 
Research Ethics (REC) and registered with ClinicalTrials.gov. The trial was reported based on the 
guidelines of the CONSORT Statement(31) and in compliance with the Helsinki Declaration. 
Informed consent was obtained from all individual participants included in the study. 
 
Publication:  
Results will be published in international Orthopaedic journals with referee evaluation.  

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