Subjects and clinical protocol on admission
This was a prospective study, designed to follow patients for 12 months following a distal radius fracture, during which patient-related outcome and bone mineral density (BMD) were evaluated. Adult men from 20 years of age who presented to the Department of Orthopedics, Skåne University Hospital, Malmö, with an acute distal radius fracture were eligible for inclusion in the study. Exclusion criteria were the diagnosis of multiple fractures (including bilateral radius fracture), residency outside the hospital’s catchment area, cognitive disorder or insufficiently understanding Swedish to complete the questionnaires [7]. The specific study assessments (BMD, DASH and SF-36) were additions to the regular clinical management. This study was granted ethical approval from Lund University ethical review board and was conducted in compliance with the Helsinki Declaration. Participants provided written and informed consent at enrollment.
In total, 457 men who presented with distal radius fracture were identified and 99 were excluded (non-acute fractures 42; multiple fractures 26; died 1; non-residents 12; non-Swedish speaking 18). All the remaining 358 eligible recruits were invited to participate in the prospective study and 133 accepted and provided written and informed consent. Eight were not contactable after the initial visit to the emergency department. Reasons given for non-participation were primarily unwillingness (143, 40%) and illness (59, 16%); 15 (4%) declining participation had known active substance abuse. Non-participants did not differ from participants in terms of age distribution, however, no additional information was available for them.
All participants were assessed and managed following routine clinical practice at their initial presentation. The established treatment protocol at the clinic was evaluated in 2008 and showed good final subjective outcome [23]. Briefly, undisplaced or minimally displaced fractures were treated in a short arm cast for 4–5 weeks; displaced fractures with closed reduction and cast, and highly unstable fractures with surgery. Displacement is defined as dorsal tilt > 10° and/or ulnar variance > 2 mm. The preferred method of surgery at the time of investigation was closed reduction and external fixation. Chronological and biological age, patients’ treatment preferences and physical demands are taken into consideration. All displaced fractures were imaged at a follow-up appointment 7–10 days following the initial presentation and treatment. Thereafter, radiographs were not routine unless there were signs of a possible complication. Patients were referred to a physiotherapist who initiated rehabilitation within 1 week after removal of the cast or external, and made a final review 3–4 weeks later.
At the initial presentation, standard postero-anterior (PA) and lateral radiographs were recorded [24]. If the fracture was totally undisplaced (20 patients), no further radiographic evaluation was performed. For all other participants, PA and lateral radiographs were recorded 7–10 days after the initial presentation and treatment. Two experienced radiologists (NE and JB) digitally evaluated all radiographs separately and the mean value of the two measurements was used in the analysis (Sectra IDS7 version 18.2.18.4066, Linkoping Sweden). Fractures were classified according to the AO-system: Type A - extra-articular; B - partial articular and C - complete intra-articular [18]. The severity and level of comminution was also recorded (subgroup AO type 3). The radiographic parameters measured were dorsal tilt (degrees), ulnar variance (mm), intra-articular gap and step-off (mm), see Fig. 1. Intra-observer reliability, assessed with the intraclass correlation coefficient (ICC) and 95% confidence intervals (CI) was 0.87(0.81–0.91) for ulnar variance and 0.90 (0.86–0.93) for sagittal tilt, indicating good reliability.
Data collection and patient-related outcome measures
Participants were assessed 1 week, 6–8 weeks and 12 months after fracture. At the initial assessment a comprehensive questionnaire on health, medication and lifestyle was completed. Subsequently, the Charlson Comorbidity Index (CCI) was calculated as a measure of pre-existing comorbidity [26]. The fracture was classified as being due to a low level or high level of energy i.e. falling from less or more than a standing height, respectively. Any complication (tendon/ligament rupture, infection, carpal tunnel syndrome, complex regional pain syndrome, hardware failure etc) within the 12-month period following the fracture were determined by a retrospective chart review.
At 6–8 weeks after fracture, anthropometric characteristics were assessed at the time of bone mineral density measurement at the Osteoporosis Research unit. BMD (g/cm2) was assessed at the femoral neck, total hip and lumbar spine (L1-L4), using dual-energy X-ray absorptiometry (DXA), (Lunar Prodigy, GE Healthcare Lunar, Madison, Wisconsin, USA). Osteoporosis was defined as a T-score ≤ − 2.5 SD at the femoral neck, total hip and/or spine as previously reported [7, 27]. 10-year absolute fracture probability was estimated by Fracture Risk Assessment tool (FRAX®), for major osteoporotic fracture (MOF: hip, wrist, humerus and clinical spine) and for hip fracture; calculated with inclusion of femoral neck BMD [28].
Disabilities of the Arm, Shoulder and Hand (DASH) is a 30 item self-report instrument evaluating disability of the upper limb with a five likert-like response option for each item [29]. It provides a score ranging from 0 to 100 with higher scores indicating a greater level of disability. The Swedish version of the questionnaire [30] was mailed to participants at 6–8 weeks and 12 months after fracture. Pre-injury DASH score was not available. The minimum clinically relevant difference in DASH is considered to be 10 points [31].
As a measure of global health, participants completed the SF-36 health status questionnaire [32] 6–8 weeks, 12 weeks and 12 months after fracture. The instrument is compressible into the physical component score (PCS) and the mental component score (MCS), each normalized to a mean of 50 (SD 10) compared to the general population; higher scores indicating better quality of life [33].
Statistical analysis
Categorical variables are expressed as number (%), and continuous variables as mean with standard deviation (SD) and/or range. Quantitative data were normally distributed (Kolmogorov-Smirnov test). To compare groups independent unpaired t-test was used for continuous variables and chi-square for comparisons between categorical variables (age; displacement groups). DASH data are ordinal with skewed distribution; non-parametric analyses were used and, as recommended, data is therefore presented as median (interquartile range), although mean and SD are included for comparison with published studies. To compare age and displacement we used Mann-Whitney and for multiple groups, Kruskal-Wallis.
To determine the influence of age on self-reported outcome and fracture properties, participants were grouped into: ‘younger’ below age 65 and ‘older’ 65 and above. We used this definition to facilitate comparison with the majority of published studies and because, in men, osteoporosis is more frequent from age 60–70. Adjustment was made for displacement, fracture classification and treatment method.
Inter-observer reliability of the radiographic measurements of the two radiologists was analysed using a mixed effects model with absolute agreement and reported as intraclass correlation coefficient (ICC) and 95% confidence interval (CI).
We applied multiple linear regression to determine whether BMD was predictive of patient-related outcome using continuous DASH scores at 12 months including the covariates age, treatment method, complications, radiographic parameters and CCI in the model. Although there are no validated divisions to categorize DASH scores, based on the age-specific population norm (US adult population mean DASH 10) we dichotomized DASH scores into good (< 15) or poor (≥15) outcome, to enable comparison with existing studies [5, 34]. Logistic regression analysis was used to determine if BMD is an independent predictor of poor outcome, including age, treatment method, complications, radiographic parameters and CCI. Finally, we used a generalized estimating equations analysis to explore the potential impact of femoral neck BMD and displacement at follow up on the rate of recovery in terms of DASH at 6–8 weeks and 12 months.
The final analyses included the radiographic parameters dorsal tilt and ulnar variance since exploratory analyses indicated these affected DASH negatively at 12 months, whereas intra-articulate gap and/or step-off > 1 mm did not (Supplementary Table 1). Fractures were grouped as undisplaced or displaced (dorsal tilt > 10° and/or ulnar variance > 2 mm). In 20 patients with totally undisplaced fractures and no x-ray at follow-up, we assume the fracture remained undisplaced.
Analyses were performed using SPSS v25 (IBM Corp., NY, USA). A two-tailed p-value < 0.05 was considered nominally significant, acknowledging that correction for multiple testing has not been performed.