|Year : 2015 | Volume
| Issue : 3 | Page : 320-325
Ultrasound evaluation of carpal tunnel and median nerve in malunited Colles' fracture
Jaganath Kamath, Rejith Mathews, Ashish Wagmare, Amarnath Savur, Nikil Jayasheelan
Department of Orthopaedics, Kasturba Medical College, Manipal University, Manipal, Mangalore, Karnataka, India
|Date of Web Publication||15-May-2015|
Department of Orthopaedics, Kasturba Medical College, Manipal University, Manipal, Mangalore - 575 001, Karnataka
Source of Support: None, Conflict of Interest: None
Introduction: Colles' fractures continue to be one of the most common skeletal injuries of middle aged and elderly population. Compressive neuropathy is one of the most important complications of Colles' fractures and usually involves the median nerve. The objective of our study was to investigate the impact of malunion of Colles' fracture on the anatomy and dimensions of the carpal tunnel and the median nerve. Materials and Methods: Fifty cases of Colles' fracture were included in this study, which was conducted for a period of 2 years. Radiographic and ultrasonographic evaluation was done in all patients. Nerve conduction studies were done in four patients diagnosed with carpal tunnel syndrome (CTS). Results: From our study, it was seen that there was a significant decrease in the dimensions of the carpal tunnel and median nerve in Colles' fracture based on ultrasonographic evaluation and the loss of radial length and volar shift were the two parameters significant in patients suffering from a CTS, based on radiographic evaluation. There was also an increase in the motor and sensory nerve conduction latency on nerve conduction studies of the median nerve. Conclusion: The loss of radial length and presence of a volar shift of the distal radius are the two deformities when left uncorrected may predispose to a CTS.
Keywords: Carpal tunnel syndrome, malunited Colles′ fracture, radiographic evaluation, ultrasonographic evaluation
|How to cite this article:|
Kamath J, Mathews R, Wagmare A, Savur A, Jayasheelan N. Ultrasound evaluation of carpal tunnel and median nerve in malunited Colles' fracture. Med J DY Patil Univ 2015;8:320-5
|How to cite this URL:|
Kamath J, Mathews R, Wagmare A, Savur A, Jayasheelan N. Ultrasound evaluation of carpal tunnel and median nerve in malunited Colles' fracture. Med J DY Patil Univ [serial online] 2015 [cited 2020 Apr 9];8:320-5. Available from: http://www.mjdrdypu.org/text.asp?2015/8/3/320/157075
| Introduction|| |
Colles' fractures remain one of the most challenging of fractures that can be treated nonoperatively. Compressive neuropathy is one of the most important complications of distal radius fractures involving the median nerve. The reported prevalence of median neuropathy after Colles' fracture has ranged from 0.2% to 7.9%. ,, Onset of neuropathy may occur several years after fracture, producing "tardy median nerve palsy." Phalen had stated that any condition that might increase the volume of structures within the carpal tunnel, such as tenosynovitis or conversely decrease the size of the tunnel, would compress the median nerve.  Abbot and Saunders' classified median nerve injuries accompanying fractures of the distal part of the radius into four groups:
- Primary injuries, apparently immediately at the time of injury.
- Secondary injuries, following unstable or partial reduction and malunion.
- Late or delayed injuries, occurring months or years after fracture healing.
- Injuries following forced manipulation and immobilization in pronounced palmar flexion and ulnar deviation. 
Clinical features include numbness in the thumb, index, middle finger and radial half of the ring finger, dull aching or burning in nature type of pain along the distribution of the median nerve in the hand, weakness of pinch and grasp, skin and nail changes, motor weakness characterized by wasting of the thenar muscles and loss of thumb abduction and sensory changes like hypoesthesia in the lateral three digits of the hand and less commonly an alteration in two point discrimination and pin prick tests when compared with the opposite unaffected hand. In many studies function is reflected by grip strength and endurance was impaired when the fracture healed with a dorsal angulation of the distal articular surface of >20° with shortening defined as a loss of radial height more than 5 mm, radial inclination of <15° and with radial shift of the distal fragment beyond 2 mm. 
| Materials and Methods|| |
Fifty cases of malunited distal radius fractures that came to this hospital for treatment from March 2013 to March 2014 were included in the study. All skeletally mature patients of age more than 16 years were included in the study and fulfilled the Graham Hastings criteria. 
- More than 5 mm of radial shortening
- Less than 15° of radial inclination
- More than 15° dorsal tilt or more than 20° volar tilt
- More than 2 mm articular incongruity
Patients who were diagnosed with pathological fractures, diabetes, rheumatoid arthritis, tuberculosis and thyroid disorders were excluded from the study.
Bilaterally affected wrist cases were excluded. All cases of distal radius fractures that were operated, either using open reduction internal fixation or external fixators were excluded.
Frykmann type 5, type 6, type 7 and type 8 fractures of distal radius were not included in the study since many of these fractures were surgically treated.
All patients were assessed clinically, followed by which posteroanterior and lateral view X-rays of both wrist joints was done and classified based on the Frykmann classification system. All these patients were subjected to ultrasonographic evaluation and selected subjects underwent nerve conduction studies. A radiologist, sonologist and neurologist were part of the study team and they were all blinded to the study. Radiographic parameters were evaluated as follows:
- Radial length - the perpendicular distance between two lines, one at the level of the distal articular surface of the ulna and the other at the level of the radial styloid process was measured; normal range is 8-14 mm.
- Radial angulation or inclination: The angle formed by two lines that is, a line perpendicular to the center line of the radius at the level of the distal end of the ulna, not including the ulnar styloid process and another line drawn through the ulnar and radial margins of the radial articular surface was taken; normal range is 16-30°.
- Radial shift or radial width: This is measured on the posteroanterior view, which is the distance of displacement of the distal fragment in relation to radial shaft.
- Volar - dorsal or radial tilt - One line is drawn perpendicular to the center line of the radius on the lateral view in the region of the fracture and another line is drawn parallel to the distal radial articular surface. The angle formed by these two lines is the measure which is normally 10° of volar tilt.
- Dorsal shift or displacement: On the lateral view, it is the distance between the distal radial fragment in relation to the radial shaft.
Ultrasound evaluation of the carpal tunnel and median nerve was done on each patient on the affected and normal sides. Measurement was taken proximally at the inlet of carpal tunnel, at the level of the pisiform bone and distally at the level of the hook of hamate. A high-frequency linear-array probe, with operating frequencies of 12 MHz was used (Philips, manufactured-2010). The carpal tunnel and median nerve was visualized by transverse and longitudinal scans over the volar aspect of the wrist joint. The normal cross-section of the median nerve ranges from 9 to 12 mm. 
Finally nerve conduction studies of the median nerve were recorded bilaterally. It was calculated by measuring the distance between the surface electrode and the receiving electrode and the time it takes for electrical impulses to travel between the electrodes.
A radiologist, sonologist and neurologist were part of the study team and they were all blinded to the study.
Off the 50 patients included in the study, 29 were males and the rest females. The youngest patient in the study was 30 years and the oldest was 78 years with an average age group of 55.82 years [Table 1]. The mode of injury was fall on outstretched hands in 41 patients, direct injury in 3 patients, road traffic accidents in 2 and fall from height in 4 patients, which indicates that the majority (82%) had sustained a Colles' fracture due to fall on outstretched hands [Table 2]. Off these patients, 42 subjects were treated by closed reduction and cast application, 2 by immobilization using cast and 6 patients did not receive any treatment at all [Table 3]. Around 62%, that is, 31 patients, came with complaints of deformity, 22%, that is, 11 patients complained of stiffness and 16% (8) patients with pain in wrist [Table 4]. Out of 50 patients, 4 of them showed signs and symptoms of carpal tunnel syndrome (CTS) with 52%, that is, 26 patients on the right hand and the rest on the left side. Majority of the patients (38%) presented between 3 and 5 months after injury, whereas the rest 34% presented after 6-8 months.
Based on the Frykmann classification for distal radius fractures, 64%, that is, 32 patients sustained a type 1 fracture, 14 patients sustained a type 2 fracture, 2 patients had a type 3 and the remaining 2 patients had a type 4 fracture [Table 5].
Mean radial length of the affected side in these patients was 2.54 mm as compared to the normal side, which was 8.72 mm. Mean radial inclination on the affected side was 14.69 mm as compared to 24.1 mm on the normal side. The mean dorsal tilt on the affected side was 10.94° comparing to 10.88° of volar tilt on the normal side. There was a radial shift present in 28 patients with a maximum shift of 10 mm and a mean of 3.11 mm and standard deviation of 2.117 [Table 6]. Dorsal shift was present in 27 patients with a maximum shift of 11 mm and volar shift was present in 3 patients with a maximum shift of 5 mm. Mean shift on lateral radiograph was 1.74 mm dorsally with a standard deviation of 2.280 [Case 1 and Case 2 in [Figure 3]].
When all these parameters were compared in patients with CTS and without CTS, we found that radial length in patients with CTS had a mean value of −1.75 mm and in patients without CTS was 3.09 mm. This was statistically significant with a P = 0.041. Change in values of radial tilt, radial shift and dorsal tilt were not found to be statistically significant, in patients with or without CTS. There was a mean volar shift of 1.75 mm in patients with CTS when compared to dorsal shift of 1.17 mm in patients without CTS. This change in value of volar shift has a P = 0.010 and is significant.
Median nerve dimensions [Figure 1]
The mean cross-sectional area of median nerve was found to be 8.53 mm 2 on the affected side as compared to 10.22 mm 2 on the normal side, proximally at the level of the distal wrist crease. Distally in the carpal tunnel, the cross-sectional area of the median nerve was 8.24 mm 2 on the affected side when compared to 9.58 mm 2 on the normal side. This change in the area of the median nerve is statically significant with a P > 0.000.
Carpal tunnel dimensions [Figure 2]
The mean cross-sectional area of carpal tunnel on the affected side proximally was found to be 159.16 mm 2 when compared to 174.86 mm 2 on the normal side. Distally the cross-sectional area of the median nerve was 172.40 mm 2 in the affected side and 180.12 mm 2 on the normal side. Change in the cross-sectional area proximally was statically significant with a P = 0.16. Change in the cross-sectional area distally was not significant.
Co-relation of the radiographic and ultrasonographic parameters with the presence of carpal tunnel syndrome
When data from 4 patients with CTS were compared to patients without CTS, it was found that the mean radial length in patients with CTS was-1.75 mm and in patients without CTS, it was 3.09 mm. There was a mean volar shift of 1.75 mm in patients with CTS as compared to mean dorsal shift of 1.17 mm in patients without CTS. These two values are statistically significant. There were no significant changes in the values of radial tilt, radial shift, dorsal tilt and cross-sectional area of median nerve and carpal tunnel seen [Table 7].
|Table 7: Significance of radiographic and ultrasound parameters to patients with CTS|
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In nerve conduction studies, average motor nerve conduction latency was 6.3 ms while average sensory nerve conduction latency was 5.05 ms in the four patients diagnosed with CTS. A co relation between dimensions of the median nerve on ultrasound scanning and median nerve conduction study could not be established since the sample size was small [Table 8].
|Table 8: Nerve conduction study values in patients with carpal tunnel syndrome|
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| Discussion|| |
Identification of neurological deficits secondary to fracture distal radius, necessitates alternative treatment methods to enhance neurological recovery and to improve functional results.
The close proximity of the median nerve to the distal part of the radius and its confinement within the carpal tunnel, predisposes it to injury. Anatomical studies have demonstrated the nerve to be located 3 mm from the distal radius.  Following simulated Colle's fracture, the nerve was seen to lie within 2 mm of the distal fragment of the radius and to be angulated over the proximal fragment. Incidence of median nerve compression following Colle's fracture varies from 0.2% to 7.9%. ,,, Incidence of late median neuropathy was found to be <1% by Frykmann. , Cooney et al.  in his study of 565 patients with Colle's fracture found late median nerve compression in 41 patients (7.2%). In 4 patients, median neuropathy was combined with ulnar neuropathy. There was no late radial neuropathy. Stewart et al. found a rate of 12% of late median nerve compression.  Aro et al.  in a study of 166 patients of Colle's fracture treated conservatively found 12% rate of late compression neuropathies and revealed that anatomic derangement play a role in the development of late compression neuropathies following Colle's fracture. Compression of median nerve (8%) was twice as common as ulnar nerve compression (4%). 85% of patients with median nerve compression had malunion with radial collapse with or without deformities (dorsal angulation/radial displacement). According to our observation, we found that a loss of radial length and the presence of a volar shift could probably cause an overcrowding of soft tissues in the carpal tunnel precipitating the syndrome. In our ultrasound study of patients with malunited Colles' fractures treated conservatively, we found 8% of late median compressive neuropathy. Our study shows that median nerve cross-sectional area decreases significantly proximally in the carpal tunnel at the level of the distal wrist crease, as well as distally at the level of the hamate. Dimensions of carpal tunnel too decrease significantly at the proximal level, but distally the change is not significant.
When the data of patients with CTS was compared with patients without CTS, it was found that there was significant loss of radial length on anteroposterior radiograph and uncorrected volar or dorsal shift in lateral radiographs in patients who manifested with signs and symptoms of CTS [Table 7].
When nerve conduction studies of patients with CTS were evaluated, it was seen that there was an increase in the motor conduction and sensory conduction latency as compared to the contralateral wrist in four patients. For those patients who were diagnosed to be asymptomatic for CTS both clinically and sonographically, we decided not to subject them for an invasive procedure like nerve conduction study which is also costly, rather to do it for patients who were symptomatic both clinically as well as radiologicaly. Since the sample size was small, a co relation between increased nerve conduction latency and dimensions of the median nerve on ultrasonographic evaluation could not be established.
The shortcomings of this study was the small sample size and the limitation of doing nerve conduction studies in only four patients keeping in mind the invasiveness and the cost of the procedure, which would have thrown more light into this study.
| Conclusion|| |
Malunion of distal radius fractures cause a significant decrease in dimensions of the carpal tunnel and median nerve. This change in dimensions need not produce manifestation of CTS in all the patients. Radial length and volar shift are the two deformities, which if left uncorrected, may give rise to a CTS later.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]