The rate and associated risk factors for acute carpal tunnel syndrome complicating a fracture of the distal radius

Acute carpal tunnel syndrome (ACTS) is a recognised complication following a fracture of the distal radius and is due to elevated compartment pressure within the carpal tunnel [1‐3]. ACTS associated with a distal radial fracture has a reported incidence of between 3 and 17% [4‐9] and could result in permanent median nerve dysfunction or complex regional pain syndrome (CRPS) if left unrecognised or untreated [10‐12]. Although the condition can be treated with surgical decompression of the carpal tunnel, the diagnosis of ACTS and subsequent selection of patients to be treated surgically can be challenging [13]. Symptoms are often non-specific, which leads to a wide range in the reported incidence of ACTS following distal radius fractures [4‐9].

The Carpal Tunnel Syndrome-6 (CTS-6) is a six-item clinical diagnostic algorithm that takes into consideration two symptoms (paraesthesia in the median nerve distribution and nocturnal symptoms), two signs of advanced disease (atrophy of thenar muscles and reduced 2-point discrimination) and two positive provocation tests (Tinel’s test and Phalen’s test) [14]. However, it is intended for cases of chronic carpal tunnel syndrome, as the provocative tests do not exhibit good sensitivity and are difficult to perform in ACTS. Clinical diagnostic algorithms can aid in stratifying the probability of carpal tunnel syndrome rather than in making a definitive diagnosis [15].

There is a paucity of evidence that defines the epidemiology, presenting signs and symptoms and management of patients presenting with ACTS following a distal radius fracture. Studies have shown that AO Type-C fractures, open fractures, fracture translation and diabetes mellitus are risk factors for developing ACTS [16, 17]. However, these studies investigated patients who developed ACTS following open reduction internal fixation (ORIF), which may represent a confounding factor for development of ACTS [18, 19]. Distal radius fractures are one of the commonest types of fractures and a majority of them can be treated conservatively [20‐22]. Therefore, knowledge of the epidemiology and risk factors associated with developing ACTS from a general fracture population could help surgeons in the diagnosis and subsequent planning of management.

The primary aim of this study was to describe the prevalence and demographics of patients that developed ACTS in association with a fracture of the distal radius from a defined population. The secondary aim was to determine risk factors associated with development of ACTS following a distal radius fracture.

A consecutive series of 1189 patients with an acute fracture of the distal radius who presented to the study centre over a period of 12 months were recorded. The study was reviewed by the local NHS Research Ethics Service (NR/1411AB8) and was registered with the local musculoskeletal quality improvement committee.

There were 51(4.3%) patients in the study cohort of 1189 patients with a distal radius fracture who developed ACTS. The mean age of these patients was 56 years (range 16-89 years; SD 18.9) and the most common age group to present with ACTS was 60–70 years (n = 14/52, 27%; Fig. 1). The majority (n = 36,73%) of ACTS cases were female (Table 1). The median time of onset post-injury was one week (range, 1–12 weeks). The most commonly sustained fracture among the CTS group were type-A extra-articular fractures (n = 26, 51%), followed by type-C complete articular fractures (n = 22, 43%) and finally type-B partially articular fractures (n = 3, 6%).

This study has defined the epidemiology, symptoms and signs, and management of patients presenting with ACTS complicating a fracture of the distal radius. The classical predisposing factors for idiopathic CTS were not associated with the development of ACTS. AO-OTA Type-C fractures was the most important risk factor associated with development of ACTS.

ACTS was shown to complicate 4.3% of distal radius fractures with a preponderance for females, similar to the results reported by Dyer et al [16]. All of the patients presented with paraesthesia in any of the fingers within the median nerve distribution. There were 14% of patients who experienced pain on top of paraesthesia, which is not a classical symptom of CTS. However, intense paraesthesia may often be misinterpreted as pain [28] and it can be difficult to distinguish between pain caused by the fracture and true carpal tunnel syndrome pain. In our series, signs of advanced disease including wasting of the thenar eminence and reduced two-point discrimination only presented after 5 weeks. This suggests that in the acute setting, the diagnosis of ACTS remains clinical and almost exclusive to paraesthesia in the median nerve distribution.

Documented risk factors in the literature that predispose to idiopathic CTS include diabetes, thyroid disease, pregnancy, BMI, smoking status, alcohol excess, SIMD and occupation [6, 7, 29‐31]. However, no significant difference was demonstrated for these parameters in our study. Thyroid disease showed a trend towards the development of ACTS, and it is a known risk factor for idiopathic CTS. Patients with known thyroid disease should be counselled to recognise the symptoms and signs of developing CTS.

Although none of the ‘intrinsic’ factors seem to predispose patients to carpal tunnel syndrome, it appears that the fracture configuration does. Patients who sustained an AO-OTA type C fracture were more likely to experience ACTS. The results corroborate the findings from other studies, which showed that ACTS was more common in AO-OTA type C fractures [16]. However, no association was found with the mechanism of injury. The median nerve passes under the flexor retinaculum very close to the articular surface between the radius and the carpal bones and any injury involving the articular surface is more likely to cause median neuropathy. Patients with an AO-OTA type C fracture should undergo careful assessment of median nerve function during the acute presentation to ensure early intervention and prevent the morbidity associated with neglected carpal tunnel syndrome.

There is no high-level evidence on the optimal management of ACTS following a distal radius fracture. Studies have recommended that patients presenting with signs and symptoms of ACTS and gross deformity in the wrist should be reduced and/or stabilised expeditiously [13, 32]. Patients who do not present with symptoms of ACTS should not undergo prophylactic CTD at the time of fixation [33]. If surgical fixation is carried out, a carpal tunnel decompression should be performed through a separate incision [13]. A number of patients in our cohort did not undergo CTD at the time of surgical fixation. The signs and symptoms of ACTS can result from a median nerve contusion and these cases can be treated with observation alone initially [32]. However, we would recommend a CTD should be performed if there is any uncertainty regarding the diagnosis or if the clinical picture has not improved or resolved. Kwasny et al [34, 35] reported that carpal tunnel syndrome after malunion of distal radius fractures can be treated with corrective osteotomy to reduce pressure of the transverse carpal ligament on the median nerve without a concomitant carpal tunnel decompression. Due to the acute nature of presentation, the published management of ACTS has been predominantly limited to case series and based on traditional teaching. In Fig. 2, the authors present a suggested treatment algorithm for these patients.

The main strength of our study is that it represents a large series of patients from a well-defined population that were prospectively recorded. Despite this, studies including a larger sample size are likely required to further investigate these associations. The primary limitation of this study is with the definition of ACTS. We believe that patients who have median nerve contusion cannot be reliably distinguished from progressive ACTS in the acute setting and have used the definition of paraesthesia in any of the fingers within the median nerve distribution as a diagnosis of ACTS. The retrospective nature of the study also meant that information including the exact onset of symptoms, nature of symptoms and two-point discrimination test were not recorded or retrievable. We have excluded cases of chronic carpal tunnel syndrome in our study. Although patients with chronic carpal tunnel syndrome may be more susceptible to acute exacerbations of their condition following a distal radius fracture, we believe that including patients with chronic CTS represents a confounding factor for development of ACTS secondary to a distal radius fracture. We also acknowledge that the treatment decision in our series was at the discretion of the treating surgeon, which it a clear limitation of retrospective work such as this and limits any firm conclusions regarding the optimal management algorithm for these patients. Future studies should incorporate prospective outcome data of patients who had carpal tunnel syndrome complicating a fracture of their distal radius. This could be used to investigate if this group of patients have inferior outcomes compared to those without CTS.