The OST and non-OST groups in our study had similar characteristics in regard to patient and surgical variables, even the casting duration and length of rehabilitation. They only differed in age and sex, perhaps as a result of the fact that these variables are both intimately linked to osteoporosis.
In this study, the OST group had a worse result on the DASH questionnaire than the non-OST group (p = .003). This is in line with the results of the work by Fitzpatrick et al. . Their work studied the effect of osteoporosis on functional outcomes after wrist fracture surgery. Like our study, they found a relationship between osteoporosis and outcomes, though unlike in our work, they diagnosed osteoporosis using DEXA and we did so by evaluating HU values in CT scans.
Fitzpatrick et al. also found that osteoporosis negatively affected PROs regardless of age. However, their group comprised 64 women over 50 years of age. In contrast, our study group consisted of patients with an identical diagnosis (intra-articular distal radius fractures (DRF)) and though age differed between our groups, 89% of patients in the OST group were over 50 years of age (p = .001). Bone mineral density has been shown to decline after age 50 and therefore, age is a key factor in patients with fragility fractures .
There is controversy on the use of CT scans to detect osteoporosis by measuring the HU values of trabecular bone. The International Society for Clinical Densitometry states it is possible only if validated machines are used and scanner stability has been established. In current clinical practice, these are difficult conditions to meet. Some authors have proposed a correlation between wrist CT scan HU values and DEXA scan values , but some of these works include non-enhanced and enhanced scans, which could affect the HU values measured . All of our patients underwent non-enhanced scans and therefore possible differences as a result of enhancement or non-enhancement were not present in our results.
We chose the trabecular bone of the capitate for HU measurements, as did Johnson et al. , because the capitate is located away from the DRF site and there are few direct contusions in this type of trauma. This is important because it reduces the risk of presence of edema, which is not visible on the CT scan and which could alter HU values by increasing the mean value of bone marrow. In addition, fatty marrow conversion in the capitate is evident from an early age and is probably very similar in both sexes. This is in contrast to the lumbar spine—an area where HU are frequently measured—as it is part of the axial skeleton, which shows greater variability of composition as individuals age.
Some authors have measured HU values in the trabecular bone of the distal radius and ulna after DRF [6, 8, 16]. However, it is likely that fatty marrow embedded between the trabeculae is infiltrated by blood and edema, which could cause the HU value to rise. As the capitate has fewer degenerative changes than the spine, its use also avoids the distortion of true values by sclerosis, which produces degenerative changes.
Our measurements of the capitate showed that the central coronal slice had a significantly greater HU value than the more volar and dorsal slices. There is most likely denser trabecular bone in this part of the capitate, however no other authors have described similar findings. In fact, Schreiber et al. found very similar HU values in each slice and even proposed that just one measurement could be enough .
To obtain the threshold HU value, we used the 26 patients (41%) in our cohort who had DEXA scan results. The work by Johnson et al. found a correlation between the HU values and DEXA; we reproduced their technique for measuring the capitate HU value . Our cut-off value of 323 HU differs from that of Johnson et al., which was 307, but the differences could be explained by the fact that the study populations were different: our group included both men and women, instead of just women, and all our patients had wrist fractures instead of other wrist pathologies.
Different voltages are related to different HU values in the same patient when assessing vertebral bodies or when using phantoms . It has been demonstrated that the mean HU decreases as tube voltage increases , though to our knowledge, this has not been confirmed in the appendicular skeleton. Our study’s findings were in line with this observation and found that there was a slight but statistically significant difference between tube voltages used and HU values obtained (p = .049). This is one of the limitations of the study and indeed further research should stratify patients by the kVp used in light of the differences in HU measurements obtained. Furthermore, the results reported in this work must be considered with caution, given that patients whose measurements were taken with different tube voltages were analyzed jointly. To our knowledge, most studies include patients with CT scans performed with a tube voltage of 120 kVp. Some authors do not specify the tube current used, which can be considered a limitation in their works.
Another limitation of this study is its retrospective nature. However, the two groups were similar in terms of almost all the independent variables assessed in this study, including all surgical and postoperative variables.
In regard to the secondary outcomes, no significant difference among the PRWE-total and SF-12 questionnaires were found, but the results of the PRWE-function subgroup were significantly different. This could indicate a possible limitation of sample size.
One of the strengths of our study was the long follow-up period. A systematic review of DRF outcomes by Diaz-Garcia et al., which used the Structured Effectiveness Quality Evaluation Scale (SEQES) to evaluate the quality of the articles, indicated that a minimum follow-up period of approximately 12 months should be used . Our work only included patients with a follow-up period of at least one year, in accordance with Díaz-García et al.’s recommendations.
We did not include range of motion, strength, or radiographic outcomes as part of this work due to the extensive amount of literature describing how measured impairments are not directly linked to self-reported functional outcomes, which cover a different aspect of health. Indeed, Goldhahn et al. recommend a core set of domains for reporting outcomes in DRFs that include function and pain outcomes rather than radiological or wrist motion parameters, which are considered optional outcomes for analysis .
All major complications observed in this work (articular collapse that required additional surgery) occurred in the OST group. However, to date, the link between osteoporosis and postoperative complication remains controversial [14, 21].
As a minority of the wrist fractures cases in our study had a CT scan performed for surgical management (26%), it is unknown whether our cohort is truly representative of the larger DRF cohort. Our work analyzed preoperative wrist CT scans that were carried out mainly in complex fractures with comminution. Therefore, we cannot extrapolate our results to other types of wrist fracture and as such, broader prospective studies are necessary to definitively establish the relationship between HU values and wrist fracture surgery outcomes.
In conclusion, we assert that measuring HU in a preoperative wrist CT scan offers valuable information for the diagnosis of distal radius bone quality prior to surgery. It is especially useful in patients over 50 years of age and may modify the treatment strategy or even the relevance of surgery in these cases.