This multicenter parallel randomized controlled trial included patients with a displaced femoral neck fracture. The study was approved by the Regional Ethics Committee (NL19200.098.07, METC07 –118). The trial was registered in the Netherlands Trial Registry NTR 1508 (http://www.trialregister.nl). The protocol was published before start of the study [14].
All patients were admitted to one of the participating hospitals (Reinier de Graaf hospital, Delft; Rijnstate hospital, Arnhem and Canisius Wilhelmina hospital, Nijmegen), large district hospitals in the Netherlands. Inclusion was between August 2008 and June 2012. Included were patients aged 70 years or older, with a displaced femoral neck fracture (Garden type III or IV) suitable for hemiarthroplasty. Excluded were patients with a pathological fracture, a fracture older than seven days or ASA-IV or V classification. Orthopedic residents, trained for this study, performed inclusion.
All patients gave informed consent. In case of (mental) incompetence of the patient, his or her legal representative was consulted to obtain informed consent. Patients were randomized following a simple randomization procedure in the operation theatre by the orthopedic surgeon through opaque sealed envelopes. These were prepared by A.J.V. and kept at the operation theatre of each of the three hospitals. 200 opaque sealed envelopes were prepared. However, 16 patients could not be included in our trial due to variable reasons (Fig. 1), which forced us to prepare another 16 envelopes.
The patients were blinded for the type hemiarthroplasty they received, although we acknowledge the possibility that they might be able to tell after seeing their radiographs during the outpatient clinic visits. Surgeons and outcome assessors were aware of the allocated arm.
Patients received a cemented hemiarthroplasty, type Müller Straight Stem (Zimmer - Biomet, 1800 West Center St. Warsaw, Indiana, USA) or an uncemented hemiarthroplasty, type DB-10 (Zimmer- Biomet, 1800 West Center St. Warsaw, Indiana, USA). The cemented hemiarthroplasty, the Muller straight stem has a small proximal collar and two longitudinal grooves to enable good cement adhesion. The non-cemented DB-10 is a straight collared stem with metaphyseal anchoring and on the surface full hydroxyapatite coating on macro-structured titanium and grooves. If complications occurred during the procedure, the surgeon could change the procedure to ensure best medical practice. Operating technique was according to the manufacturer instruction. In the participating hospitals there was experience with both cemented and uncemented hip arthroplasty. Either an orthopedic surgeon or registrar performed the operation. Cementing technique involved vacuum mixing, cement plug, saline pulsed lavage and retrograde introduction of cement with a cement gun. The approach was up to the surgeon’s preference, as Parker’s Cochrane analysis has shown that insufficient evidence is available for superiority of either approach [3].
Each patient received physiotherapy therapy, analgesia and trombo-embolic prophylaxis according to the protocol of the hospital in which they were treated.
Preoperatively, social demographic data (age, sex, place of residence), ASA— (American Society of Anesthesiologists) classification [15], Body Mass Index (BMI), Minimal Mental State Examination (MMSE) [16] were obtained. Patients were asked to score their pre-fracture mobility and Health Related Quality of Life (HRQoL) using the New Mobility Score (NMS) [17], Groningen Activity Restriction Scale (GARS) [18] and the SF-12 [19]. Patients were asked if they mobilized with an aid indoors and outdoors with or without aid and whether they received homecare. The baseline hemoglobin level was measured. The surgical approach, the type of surgeon (consultant or registrar) and kind of anesthesia were registered.
Outcomes measured during operation were operation time (defined as skin-to-skin surgical time, measured in minutes) and blood loss (in centiliter, estimated by the surgeon).
Length of stay, decrease in hemoglobin level and transfusion rate were measured postoperatively.
All patients were invited for follow up at six, 12 and 52 weeks postoperatively. When the patient was not able to visit the outpatient clinic, the questionnaires were mailed to the patient or its relatives. During follow-up functional outcome was measured using Timed-Up and- Go (TUG) score [20], GARS [18] and NMS [17]. HRQoL, expressed in the SF-12 [19], was measured. The SF-12 was divided in a Physical Component summary Score (PCS) and a Mental Component summary Score (MCS). Mid-thigh pain (defined as pain explicitly in the front and mid part of the femur) pain and place of residence were registered. Complications during surgery, hospital stay and the year thereafter were recorded. The complications were defined and ranked in the modified Elixhauser mode, as described by Parvizi [21]. Mortality was scored meticulously by repeated consultation of the population registers of the counties in the region of the hospital as well as the hospital’s patient registration systems for the full length of follow-up.
A radiograph was obtained on the first postoperative day and after six weeks, 12 weeks and 1 year. Adequate positioning of the stem was defined as within 10° varus or valgus position with respect to the femoral axis. Fissures, fractures, subsidence and loosening were noted.
Analysis
Primary outcomes were complications, operation time, functional outcome and post-operative mid-thigh pain. A Bonferroni correction was applied for the eight primary outcome measures (4 types of complications, operation time, GARS, TUG and mid-thigh pain at 1 year) making p < 0.006 significant. Secondary outcomes were return to place of residence as percentage of pre-fracture situation, HRQoL and adequate radiological positioning of the hemiarthroplasty [14].
Determination of sample size
The complete power calculation is published in our protocol [14] We expected (based on the literature in 2008) that midthigh pain in uncemented prosthesis would be 30% and in cemented prosthesis 7.5%.
$$ \uppi 1=30\%,\uppi\ 2=7.5\%,\uppi =\left(30\%+7.5\%\right)/2=18.75\% $$
$$ \mathrm{n}1=\mathrm{n}2\ge 21\ast \left(0,1875\ast \left(1-0,1875\right)\right)/\left(0,225\right)2=\mathrm{63.2.} $$
While we expected 25% 1-year mortality and 10% lost-to follow-up we raised this number by 35%. Thus a total of 86 patients a group were needed. The calculations for the other three primary outcome measures (duration of surgery, functional outcome and complications) produced lower patients numbers [14]. From a practical point of view we choose a total of 100 patient per group.
Statistical analysis
All analyses were performed using SPSS software (SPSS Inc., Chicago, IL, USA). The differences in outcome measures were analyzed using an independent sample student T-test (for continuous data) and Chi-Square Test (for categorical data), setting the level of significance at p < 0.05 for secondary outcomes. All outcomes analyses were done twice: both for as treated analysis and for intention to treat. The numbers given in the results section represent the intention to treat analysis. We will report explicitly if differences exist between as treated analysis and intention to treat analysis.