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External validity of a randomized controlled trial in patients with femoral neck fracture
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Background: Randomized clinical trials (RCT) are the most reliable way to evaluate theeffect of treatments by comparing them to previously accepted treatment regimes. The resultsobtained from a RCT are extrapolated from the study environment to the general health caresystem. This parameter is called external validity. The present study we sought to evaluatethe external validity of an RCT comparing the results of total hip arthroplasty tohemiarthroplasty in displaced femoral neck fracture in patients 80 years of age and above.

Methods: In a prospective cohort study, 267 patients (76% females, mean age 87 [SD] 4.7years) were included in the cohort study. All were screened according to the inclusion andexclusion criteria to be included in a RCT comparing total hip arthroplasty andhemiarthoplasty. Those who gave their informed consent and were randomized (RCT group,92 patients), those that were asked to participate in the RCT but would not give theirinformed consent (Non-consenters group, 54 patients) and all patients missed in the screeningprocess (Missed screening group, 121 patients). The primary end point was hip functionevaluated with Harris hip score at 1 year. Secondary end points included quality-of-lifeevaluated with EQ-5D mortality and hip re-operations. Follow up was performed at 1 yearpostoperatively by a mailed survey including patient reported outcome.

Results: We did not find any difference between the groups regarding HHS and EQ-5D, alsowhen adjusting for confounders. There was a statistically significant difference between thethree groups (p=0.047) as the Non-consenter group had a higher risk of death than thoseincluded (HR 2.06, 95% Cl 1.13 to 3.75). The rate of reoperation was lower in the MS groupcompared to the RCT and NC groups (4.1% vs 7.6% vs 9.3%). This difference did not reachstatistical significance when adjusting for confounders

Interpretation: This cohort study indicates a higher mortality rate but comparable hip functionand quality-of-life among eligible non-consenters compared to eligible consenters whenevaluating the external validity of a RCT patients with femoral neck fracture age 80 andabove.

National Category
URN: urn:nbn:se:umu:diva-108602OAI: diva2:853674
Available from: 2015-09-14 Created: 2015-09-14 Last updated: 2015-09-14
In thesis
1. Aspects on treatment of femoral neck fractures: studies on treatment methods, surgical approach and external validity
Open this publication in new window or tab >>Aspects on treatment of femoral neck fractures: studies on treatment methods, surgical approach and external validity
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Aspekter på behandling av lårbensfrakturer
Abstract [en]

Femoral neck fracture (FNF) is a great challenge for today´s health care and is associated with high mortality and morbidity in the elderly.  In the short term several studies in the literature have demonstrated improved hip function, quality of life and fewer re-operations in elderly patients treated with total hip arthroplasty (THA) instead of internal fixation (IF). There are few reports on the long-term outcome comparing IF and THA. The vast majority of orthopaedic departments in Sweden use the direct lateral (DL) or posteriolateral (PL) approaches for hip arthroplasty. The PL approach has been linked to an increased risk of dislocation of the prosthesis and a higher rate of revision surgery in comparison to the DL approach. There are few reports focusing on radiological risk factors for prosthetic dislocation and patient reported hip function comparing the two surgical approaches for hip arthroplasty in FNF.

The randomized controlled trial (RCT) is the gold standard for evaluating medical or surgical interventions. An RCT of high quality has to be internally and externally valid. Internal validity refers to a correct study design to avoid bias skewing the results. External validity (EV) refers to whether the results will be clinically relevant to a definable group of patients and can be extrapolated to the general health care situation. There are only a few reports in the orthopaedic literature focusing on the EV of published studies and none in the field of hip fractures.

Study I: This is a RCT of 100 patients with a displaced FNF comparing THA and IF. Follow-up evaluations were performed at three months and 1, 2, 4, 11 and 17 years. It was found that the Harris hip score (HHS) was higher and the rate of reoperations lower for patients treated with THA.

Study II: This is a prospective cohort study of 185 hips, comparing the DL and the PL approaches in patients treated with a hemiarthroplasty (HA) for a displaced FNF. Follow-up was after 1 year. There was no difference in patient reported outcome between the groups measured with the HHS and WOMAC index. The PL approach resulted in a higher re-operation rate while the DL approach in a higher incidence of limping.

Study III: This is a retrospective cohort study of 373 patients with a cemented bipolar HA using a PL approach for a FNF with a follow-up ranging from 6 months to 7 years. Radiographs and all surgical records were reviewed regarding femoral offset (FO), leg length discrepancy (LLD) and Wiberg angle. Patients with recurrent dislocations had a decreased postoperative FO, LLD and shallower acetabulum on the operated side compared with their controls.

Study IV: This is a prospective cohort study of 840 hips comparing patients included in a RCT with those that did not give their informed consent (NC) or did not fulfill the criteria for participating in the trial (MS). Patients in the NC and MS groups had an increased mortality rate in comparison to those included in the study. We did not find any differences in hip function between these groups.

The main conclusions of this thesis are:

  • Healthy and lucid elderly patients with good hip function preoperatively, should be treated with THA for a displaced FNF.
  • The DL approach is favourable in treating displaced FNF with HA due to its decreased risk of reoperation but with an identical hip function outcome as the PL approach.
  • Care should be taken to restore the LLD and FO otherwise this may increase the risk of recurrent dislocation of a HA.
  • Our findings suggest that trial participants had a lower mortality rate than non-participants but the functional outcome of non-participants appeared to be satisfactory. This is important to take into consideration when extrapolating study results to a health care system.
Abstract [sv]

Lårbenshalsfrakturer (FNF) är en utmaning för dagens sjukvård och förknippad med hög mortalitet i den äldre befolkningen. FNF orsakas främst av lågenergitrauma efter fall i samma plan hos patienter med benskörhet. Total höftledsprotes (THA) har visat sig ge en bättre höftfunktion, livskvalitet med färre omoperationer hos äldre patienter än sluten reposition samt fixering med skruvar (IF) under de första två-fyra åren efter operation. Få studier har publicerats med långtidsuppföljning av THA jämfört med IF.

Vid behandling av felställd FNF med halv höftledsplastik (HA) eller THA finns olika kirurgiska metoder (snittföring) för implantation av protesen. Majoriteten av ortopedkliniker i Sverige använder direkt lateral (DL) eller posteriolateral (PL) snittföring. PL har kopplats till en ökad risk för luxation av protesen (urledsvridning), vilket i sin tur genererat en högre risk för omoperation jämfört med DL. Få studier har utvärderat höftfunktion med avseende på snittföring. Detsamma gäller vilka radiologiska faktorer som påverkar risken förprotesluxation. Det finns olika typer av studiedesigner för utvärdering av medicinska och kirurgiska behandlingsmetoder. Studiedesignen med högst bevisvärde anses vara den randomiserade kontrollerade studien (RCT). För att en RCT skall hålla hög kvalitet krävs intern och extern validitet. Intern validitet syftar på ett korrekt studieupplägg som mäter det som avses och undviker påverkan av icke önskvärda faktorer. Extern validitet (EV) innebär att erhållna resultat från studien är generaliserbara och kan extrapoleras till andra grupper än den studerade. Det inga rapporter i ortopediska litteraturen med fokus på EV med patienter som drabbats av FNF.

Studie I: Prospektiv randomiserad studie av 100 patienter med en felställd FNF jämförs THA med IF med avseende på höftfunktion och reoperationer. Uppföljning gjordes efter tre månader samt 1, 2, 4, 11 och 17 år. HHS som mått på höftfunktion var högre och andelen reoperationer lägre för patienter som behandlades med THA.

Studie II: Prospektiv kohortstudie med 183 patienter med felställd FNF behandlade med HA och antingen DL eller PL. Vi fann ingen skillnad i patientrapporterad höftfunktion utvärderat med HHS och WOMAC efter 1 år men en ökad förekomst av hälta vid DL.

Studie III: Retrospektiv kohortstudie av 373 patienter opererade med en cementerad bipolär HA och PL. Postoperativa röntgenbilder granskades avseende femoral offset (FO), postoperativ benlägdsskillnad (LLD) samt acetabulär Wibergvinkel och relaterades till återkommande protesluxationer. Detta relaterades till återkommande luxationer. Uppföljningstiden varierade mellan 6 månader och 7 år. Patienter med återkommande luxationer hade en minskad postoperativ global FO, förkortad LLD och grundare acetabulum på den opererade sidan jämfört med kontroller.

Studie IV: Prospektiv kohortstudie av 840 patienter med felställd FNF där patienter som ingick i en RCT jämförs med de som inte gav sitt samtycke för deltagande eller ej inkluderats i screeningprocessen. De patienterna som inte gav sitt samtycke hade ökad dödlighet, men ingen skillnad i höftfunktion jämfört med deltagare.


• Friska och kognitivt vitala äldre patienter med god höftfunktion innan en felställd lårbenshalsfraktur bör behandlas med total höftledsprotes.

• DLsnittföring ger ett lika bra patientrapporterad höftfunktion men en ökad förekomst av hälta jämfört med PL snitt vid behandling med halvprotes på grund av en felställd lårbenshalsfraktur.

• Ansträngning bör göras för att återställa benlängdsskillnad samtfemoral offset och därigenom minska risken för återkommande luxation.

• Våra resultat tyder på att patienter som deltar i en randomiserad studie har lägre dödlighet än patienter som avböjt att delta samt de som missats i screeningprocessen. Det är viktigt att ta hänsyn till när extrapolerar studieresultat till ett hälso-och sjukvårdssystem. Detta bör vägas in i värderingen av studieresultatens externa validitet.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2015. 97 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1737
Hip fracture, femoral neck fracture, treatment, total hip arthroplasty, hemiarthroplasty, internal fixation, surgical approach, outcome, dislocation, femoral offset, leg length discrepancy, external validity
National Category
Research subject
urn:nbn:se:umu:diva-108269 (URN)978-91-7601-305-2 (ISBN)
Public defence
2015-10-09, Aulan, Länssjukhuset Sundsvall-Härnösand, Lasarettsvägen 21, 856 43, Sundsvall, 09:00 (Swedish)
Available from: 2015-09-08 Created: 2015-09-07 Last updated: 2015-10-13Bibliographically approved

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