Median Nerve Compression Secondary to 35 Fractures of the Distal Radius

Fractures of the distal radius and carpal tunnel syn- drome are both commonly occurring entities seen in the wrist. The latter condition is an occasional compli- cation that should be well recognized as a result of the former traumatic condition. While treatment of distal radius fractures is currently undergoing a treatment revolution, the complication of carpal tunnel syn- drome should be similarly recognized and given the re- spect that it deserves. Once significant median nerve injury or compression occurs as a result of a fracture of the distal radius, it can be much more difficult to treat, and the final outcome may be much less predictable than its idiopathic counterpart.

Abraham Colles first described the fracture of the distal radius in 1814 but maintained that functional de- ficiency or complications were surprisingly rare after this common traumatic injury [6]. Similarly, carpal tunnel syndrome associated with this fracture was giv- en little attention and initially felt to be a rare sequela. Early textbooks discussing complications of Colles fractures rarely mentioned this nerve compression, and it was not until the classic paper by Abbott and Saunders in 1933 that this complication was clearly rec- ognized as being not as rare as initially thought [1].
The first case report was actually a direct traumatic injury to the median nerve as recognized by Gensoul in 1836 where he had performed an autopsy on a young girl who died of tetanus following an open fracture of the distal forearm [12]. It was found that the median nerve was caught in the fracture site of the radius. Many of these early reports focused on the direct compres- sion or contusion of the median nerve as a result of bo- ny impalement or stretching of the nerve, rather than the more commonly seen secondary compression as a result of edema and swelling from this fracture.
It was not until the review by Abbott and Saunders that the popular Cotton-Loder position for immobili- zation of distal radius fractures was discredited. They first recognized the anatomical course of the median nerve at the wrist, noting that the flexed position of the wrist will lead to direct compression of the median nerve by the proximal edge of the transverse carpal lig- ament. They also recognized that the median nerve car- ries with it the majority of sympathetic nerve innervation to the hand and that this can cause the other com- monly recognized complication of carpal tunnel syn- drome: Complex Regional Pain Syndrome Type I. This was the first time it was recommended that conserva- tive treatment of Colles fracture allow for immobiliza- tion of the wrist in a neutral position, mainly to avoid median nerve entrapment. However, despite elucidat- ing this important concept, they went on to say that if median nerve symptoms persist even after 4 months of closed treatment, surgical exploration of the median nerve is warranted. This underscored the prevailing concept that median nerve compression should not be treated as aggressively as we now recognize. Hence, more aggressive treatment of displaced distal radius fractures should go hand-in-hand with decompression of the median nerve.

Meadoff wrote in 1949 that injuries of the median nerve in fractures about the wrist are not uncommon and that good reduction and immobilization of the wrist in the neutral position are the best means of pre- venting median nerve injury [17]. He also felt that the majority of patients with median nerve injury recover completely without surgery. In 1952, Mark Mason re- viewed 100 cases of Colles fractures requiring closed reduction and found only one case developing a carpal tunnel syndrome [16]. However, his study had an aver- age follow-up period of only 22 months since the time of the fracture, which this supports the notion that per- haps many carpal tunnel syndrome complications may occur years after the initial fracture event. Much like Abraham Colles, he found only five patients had any complications whatsoever and supported the existing belief that complications were exceedingly rare after this common fracture. Later studies countered this popular belief.
It was not until 1963 that Lynch and Lipscomb re- ported 3.3% of their patients with distal radius frac- tures developing carpal tunnel syndrome [14]. In a ret- rospective review of 600 distal radius fractures seen over 10 years at the Mayo Clinic, they found that 20 wrists developed this complication in 19 of their pa- tients. Hence, they concluded that carpal tunnel syn- drome is indeed frequently associated with a Colles fracture, and they supported the notion that this often occurs after immobilization in the Cotton-Loder posi- tion. They also emphasized that carpal tunnel syn- drome following a Colles fracture can be classified as primary, when the median nerve is actually caught or directly contused between the fracture ends of the radi- us, and secondary when edema, hand position, and te- nosynovitis lead to secondary compression within the carpal tunnel. Phalen himself noted in 1951 that a tardy median palsy might be associated with Colles fractures [22]. He stated that any condition which either in- creased the volume of structures within the tunnel or anatomic factors that decreased the diameter of the tunnel would lead to compression of the median nerve. Therefore, it is only logical that carpal tunnel syn- drome would be a commonly seen complication after fracture of the distal radius, and it is an entity that should have a low threshold for consideration in post- fracture management.
Smaill from New Zealand continued to reiterate Col- les’ belief that patients would regain full, painless func- tion irrespective of how the fracture was treated [24]. He felt operative treatment or aggressive manipulation was unwarranted and only reported two complications in his series, both ruptures of the extensor pollicis lon- gus, and no carpal tunnel syndrome. It is apparent in reviewing his treatise that many authors shared an ac- ceptance of relatively poor outcomes after these frac- tures. Cole and Obletz in 1966 reviewed the end results of 33 cases of distal radius fractures treated by pins- and-plaster technique [5]. They found only one case of a transient median “neuritis,” but the longest follow-up in their study was 5 years, with the shortest being only 18 months. They did recognize, however, that many of their patients had poor functional outcomes, and they agreed with Gartland and Werley, who determined that closed immobilization led to inadequate results in their 60 patients treated for Colles fractures [8].
During these years, carpal tunnel syndrome was fre- quently thought of as a chronic condition. It was not until 1970, when Adamson presented his paper, “The Acute Carpal Tunnel Syndrome,” it was generally ac- cepted that this condition can occur acutely [2]. They reported nine cases of acute carpal tunnel syndrome, of which one was after a severe Colles fracture from a fall on the wrist while ice skating. They concluded that acute carpal tunnel syndrome was much more com- mon than ordinarily thought and, therefore, one can conclude that the Colles fractures would likely play a role in the etiology of this acute nerve compression. A similar report on acute carpal tunnel syndrome was written by McClain and Wissinger in 1976 [18]. They too presented nine different case reports; but in their study, four of the nine cases occurred from fractures of the distal radius. Two of these were classic, extra-artic- ular Colles fractures; one was a Salter-Harris II fracture of the distal radius in an adolescent, and the last report involved an intra-articular fracture of the distal radius. They concluded that immediate surgical decompres- sion was the most favored option. Bauman and Gelber- man also published a paper entitled, “The Acute Carpal Tunnel Syndrome,” and they presented five different cases of acute carpal tunnel syndrome in 1981 [3]. Of these, four cases involved distal radius fractures, and their review of the literature concluded that fractures of the distal radius were the leading cause of acute median nerve compression.

Gelberman went on to look at carpal tunnel pres- sures and wrist positions in patients with Colles frac- tures and stated that an awareness of the magnitude of increased interstitial fluid pressure should lead to an al- ternate method of treatment in many cases of distal ra- dius fractures [4]. They found that intracarpal canal in- terstitial fluid pressures were highest in extreme flexion after Colles fractures. In contrast, similar studies in pa- tients with no fractures have demonstrated that ex- treme extension actually produces the most intracarpal pressure [9, 15]. This underscores the importance of maintaining the wrist in a relatively neutral position during immobilization for this injury.

Besides causative factors such as hyperflexion of the wrist and direct entrapment of the median nerve at the time of fracture, a third cause of median nerve compres- sion can occur by volarly displaced fragments. Paley and McMurtry first described compression of the medi- an nerve against the proximal edge of the transverse carpal ligament by a volarly displaced fragment in this fracture pattern [21]. They concluded that not only was reduction of this fragment necessary, but that carpal tunnel decompression is also necessary. They presented nine patients with markedly displaced volar fragments in a distal radius fracture, with eight of these patients developing either acute or delayed carpal tunnel syn- drome. They first described the concept that median neuropathy can occur acutely, subacutely, or late after Colles fractures. They further noted that compression from a volar displaced fragment was a much less com- mon phenomenon but, nevertheless, should be recog- nized. Other authors have described late median nerve symptoms after displaced volar fragments with Lewis and Miller describing a case where a carpal tunnel syn- drome developed 18 years after a Smith fracture [13]. Watson-Jones described a similar case [26], while Coo- ney reported that six out of 565 patients reviewed at the Mayo Clinic developed a late carpal tunnel syndrome directly attributed to a volar fragment compression [7]. Although this fracture pattern necessitates an open re- duction, it should also be done for the reason of decom- pressing the median nerve since any attempt at closed reduction can cause further injury to the nerve due to the presence of this fragment against the nerve itself.
Secondary carpal tunnel syndrome is not limited to adults as Binfield from London described three cases of Salter-Harris type II fractures of the distal radius lead- ing to median nerve complaints [4]. As often done in children, the fractures were treated closed and once re- duction was obtained, the symptoms quickly resolved. They were quick to conclude that adult management of a median nerve palsy associated with distal radius frac- ture usually necessitated exploration and decompres- sion of the carpal canal. However, with children this de- cision is more controversial, and they supported the concept of closed reduction and close follow-up of the clinical symptoms over time.

Just as median nerve compression has been managed with increasing vigilance, we have also gradually come to a point where the distal radius fracture is treated much more aggressively. Due to the relative frequency of median nerve compression in these fractures, as we have seen with literature review, we might also conclude that perhaps median nerve compression should be im- plied once distal radius surgical management is under- taken. It is only in recent years that distal radius frac- tures are commonly being treated by open means due to the accepted notion that a more anatomic reduction will lead to a better clinical result [11]. Although there is still a role for the use of external fixation, it is becoming in- creasingly accepted that an open reduction with plates and screws is indicated. During this open reduction, it is often prudent to release the median nerve in that same sitting. This becomes even more intuitive when the ap- proach for the fracture is performed in a volar fashion. Recent papers indicate that the distal radius anatomy and biomechanics dictate that a plate be placed on the volar side [19]. Consequently, this allows for a median nerve decompression since it can be done through the same volar side and perhaps even the same incision if it is approached in a more extensile manner.

Internal fixation of the distal radius through a volar approach is usually performed through a more distal Henry approach between the flexor carpi radialis (FCR) and the radial artery. In complex fractures, this approach can be extended more distally to better allow reduction of the articular surface, and the incision can be extended directly over the carpal tunnel to allow for open release of the transverse carpal ligament. This ex- tension should be done in a zig-zag manner to avoid a longitudinal scar over the volar wrist creases. More complex fractures (Fig. 35.1) that require articular ele- vation may be approached through the extended FCR approach [20]. This was first described by Orbay and allows one to reduce the fracture through an intrafocal approach. This way the critical volar ligaments are not violated in reducing the articular surface. I also recom- mend arthroscopic assistance in many of these articu- lar fractures in the younger, high-demand patient. Be- cause of the amount of postoperative swelling that may occur after this aggressive approach, it may also be pru- dent to decompress the median nerve as a consequence of the surgical technique itself. It is my preference to perform the carpal tunnel release endoscopically. Hence, I make a separate, small, transverse incision in the midline to the wrist directly over or just ulnar to the palmaris longus tendon (Fig. 35.2). This tends to be several centimeters ulnar to the distal extent of the ap- proach for distal radius volar open reduction. The en- doscopic technique obviously results in less surgical trauma being a minimally invasive approach and is ad- equate in cases where reduction of associated fractures in the carpus are not necessary.

My personal preference is to decompress the median nerve first in fractures of mild-to-moderate displace- ment, and then perform the open reduction through the previously described volar approach through a sep- arate longitudinal incision. More severely displaced fractures should be reduced first, prior to the median nerve decompression, since the severity of fracture dis- placement may place the median nerve in a much less predictable position, making endoscopic release more technically challenging. In these markedly displaced cases, I perform volar plating first, and then once the anatomy has been restored, it is much easier to release the transverse carpal ligament through the endoscopic approach (Fig. 35.3). I have frequently noted that the carpal tunnel is not tight once the fracture is reduced, although there is almost always blood within the carpal canal. Irrigating this out can also minimize neuritis from the effect of blood around the nerve. Despite the obvious advantages of decompressing the median nerve at the time of surgery, I have also found there to be other direct benefits. Besides preventing or revers- ing the effects of median nerve compression from the fracture, I also find that postoperative rehabilitation is much easier once the transverse carpal ligament is di- vided. This is because of the empiric observation that the patient can flex and extend the fingers much easier once the confines of the carpal tunnel are decompres- sed. We must realize that not only does the median nerve run within the carpal tunnel, but nine flexor ten- dons pass through this very narrow canal as well. Due to either anatomic variation in the carpal tunnel due to the fracture or the effects of swelling from interstitial edema or direct bleeding, the flexor tendons are nar- rowly constricted within the tunnel. Once the ligament is divided, the flexor restriction, and this allows for the patient to fully ex- tend and flex the fingers immediately in the recovery room after open reduction/internal fixation. This has not only the advantage of allowing improved and less painful rehabilitation, but likely diminishes the possi- bility of developing a complex regional pain syndrome.
It is my current practice to perform an endoscopic carpal tunnel release in all patients who undergo open reduction/internal fixation for displaced distal radius fractures (Fig. 35.4). The vast majority of these patients undergo volar fixation using a subchondral peg sup- port, but on rare occasions a shear articular fracture of the distal radius may require the application of an exter- nal fixator and concomitant arthroscopic reduction of the articular surface for management of this fracture. In these cases, once the external fixator is placed, a sepa- rate incision is made for endoscopic carpal tunnel re- lease at that time. It has been my experience that these patients have much less pain and better digital function in the postoperative period as a direct result of median nerve decompression at the initial time of surgery.
In conclusion, it is now a well-accepted fact that car- pal tunnel syndrome is a frequently seen complication of distal radius fractures, either in the acute period or delayed as a consequence of the swelling and deformity of the wrist. It might also be concluded that decompres- sion of the median nerve should be done in conjunc- tion with the ever-increasing operative treatment of displaced distal radius fractures. This has many bene- fits besides avoiding carpal tunnel syndrome which al- lows our patient with this common fracture to rehabili- tate the hand in a more rapid and less painful fashion.tendons can glide free of relative