Capitate Proximal Fragment Migration Compressing the Median Nerve in Scaphocapitate Fracture: A Case Report

Introduction

The wrist consists of the distal radius and ulna, the 8 carpal bones, and the 5 proximal bases of the metacarpals [1]. The proximal carpal row, comprising the scaphoid, lunate, triquetrum, and pisiform, has no tendinous insertion. In contrast, the distal carpal row, consisting of the trapezium, trapezoid, capitate, and hamate, is connected tightly, and motion between the bones is considered negligible, with the capitate being the largest carpal bone situated in the center of the carpus [1].

Scaphoid fractures comprise 2% of all fractures and 90% of carpal fractures, being a high-incidence injury [2]. In contrast, isolated capitate fractures are rare injuries accounting for 1% of carpal bone fractures, but a much higher incidence is reported as part of multiple carpal bone fracture injuries [3]. The combined fracture of scaphoid and capitate, along with 90- or 180-degrees rotation of the proximal capitate fragment, is described as scaphocapitate syndrome in the literature, a special case of perilunate fracture-dislocation, and was first described by Fenton in 1956 [4,5]. We present a severe case of scaphocapitate syndrome, where the proximal capitate fragment did not rotate, but migrated deep to the median nerve. Few scaphocapitate syndrome cases have been reported, and only 1 like ours has been described in the literature [6].

Case Report

A 25-year-old left-handed man presented to the Emergency Department (E.R) of our University Hospital after being transferred from a rural hospital following a motor-vehicle collision driving a motorcycle. He had a left-hand injury with severe edema and pain and he reported paresthesia at the first 3 fingers. X-rays revealed a dislocated osseus fragment volarly at the level of the distal radius, but no clear diagnosis could be made (Figure 1). Consultation by a fellowship-trained hand surgeon was acquired immediately. A CT scan was ordered and revealed a scaphoid distal pole unstable A1 Herbert fracture, along with a transverse proximal capitate fracture (Figure 2). The dislocated fragment was attributed to the capitate.

Surgery was performed within 4 hours after the patient’s entry to the hospital on an emergent basis. Careful physical examination along with CT scan revealed skin tenting volarly proximal to the proximal wrist crease at the midline. The Esmarch bandage technique was utilized and a tourniquet was inflated. A 2-cm longitudinal volar incision at the distal forearm was performed and the median nerve was immediately revealed. After retracting the flexor tendons, the osseous fragment was revealed to be deep and radially to the median nerve and it was retrieved (Figure 3). The volar incision was closed and the wrist was incised dorsally, extending from the Lister’s tubercle to the base of the second metacarpal through the third dorsal compartment. Inspection revealed a capitate and scaphoid fracture, in accordance to CT scan. A Herbert screw was put through the scaphoid to hold the dislocated fragment compressed into place. An open reduction of the capitate using the fragment that was retrieved earlier was performed and 3 Kirschner wires were drilled to transfix all the carpal bones under fluoroscopic control with C-arm (Figure 4). The scapholunate and lunotriquetrum ligaments were examined and were found intact, and both the proximal and distal row were functioning as a unit. Lateral radiographs revealed normal scapholunate angle after the trans-fixation. Immediately post-operatively, the patient reported that the paresthesias had subsided.

The patient presented to our outpatient clinic 1 year after the operation, showing a painless passive and active ROM, with no flexion or extension deficits. Functionally, the patient recorded a DASH score of 0/100. Postoperative X-rays revealed good fracture healing with no scaphoid pseudarthrosis and good carpal bones alignment (Figure 5). The patient was an amateur boxer and he has returned to full-time heavy-bag training and sparring as well as weight-lifting and calisthenic exercises, including pushups, with no functional limitations. He refused a CT scan examination 1 year post-operatively and the X-rays are not conclusive for AVN, but his excellent functional status along with the X-ray suggest a good fracture healing.

Discussion

The scaphocapitate syndrome is associated with a high-energy mechanism of wrist hyperextension during motor-vehicle crashes or falls from heights. It is considered a special case of trans-scaphoid and trans-capitate perilunate fracture-dislocation, representing a greater arc injury, with a challenging prognosis [7–9]. Fenton proposed that the wrist is radially deviated and hyperextends as the radial styloid comes in contact first with the scaphoid and then with the capitate, fracturing both bones, whereas more hyperextension leads to the proximal capitate fragment rotation [4]. However, Stein and Siegel suggest that as the wrist extends, the capitate is compressed against the dorsal radius border [10]. Early recognition of all concomitant injuries is crucial, even utilizing CT scan in addition to X-rays, as a delay in diagnosis can lead to wrist instability and osteoarthritis. In our case, complete radiological control (CT and X-rays) was performed immediately and the patient was examined and treated within a few hours after the injury by a hand specialist, minimizing the risk of avascular necrosis. Open anatomical reduction utilizing compression screws or K-wires is suggested for both fractures when part of the scaphocapitate syndrome [11]. Intraoperatively, the scaphoid appeared to be A1 according to the Hebert classification and unstable, thus a Herbert screw was utilized, gaining adequate fixation [12]. The capitate fracture was classified as transverse-low and was fixed with a K-wire [13]. Two additional K-wires were employed to stabilize the carpal bones for direct bone and ligament healing. Capitate avascular necrosis (AVN) is one of the most common complications, as the capitate receives most of its blood supply retrogradely, but many capitates receive proximal pole vessels as well, explaining the low rates of proximal pole avascular necrosis among certain cohorts [14]. Despite the low transverse displaced fracture in our case being associated with the risk of AVN, the short time from injury to surgery created favorable circumstances for healing. Although not addressed here, in high-energy carpal injuries a high level of suspicion intraoperatively should be maintained, not only for osseus fractures, but for ligamentous injuries as well, as injuries such as scapholunate ligament rupture can lead to a progression of carpal instability, DISI, and SLAC, with potentially devastating results [15,16].

Searching the existing literature, Mugdal et al in 1995 is the only one who treated a same injury pattern as ours, with proximal migration of the capitate fragment and median nerve compression [6]. Their approach was slightly different, utilizing K-wires for osteosynthesis of the capitate and scaphoid fracture only, but a two-incision approach, volarly and dorsally, was also utilized [6]. Adjacent carpal bones were not stabilized with K-wires to facilitate ligament healing, and a scapholunate gap was seen in the postoperative static X-rays, indicating grade III scapholunate instability [6,17]. In addition, the comminuted scaphoid fracture was non-compressed, as a Herbert screw could not be used due to instrumentational restriction at the center, raising the question of scaphoid AVN at a later follow-up. However, the median nerve compression symptoms subsided at the end of the 9-month follow-up and they reported a good functional outcome [6]. To conclude, early literature supported conservative care for scaphocapitate syndrome with devastating results [2,11]. Daliana et al summarized the current evidence and supported it with their own 2 long follow-up cases, concluding that anatomical reduction with K-wires or compression screws should be the goal [11]. Favorable results can be expected in most cases, but bone grafting might be needed for the most challenging ones [11]. Pyrocarbon resurfacing of the capitate has been described in case of extreme capitate comminution [18]. In our case, a great functional outcome was achieved, including full ROM, excellent functional scores (0/100 DASH), and more importantly, return-to-play in very demanding activities for the hand including boxing, pushups, and karate, with absolutely no symptoms. His involvement with amateur boxing in the past might have benefited him, as in our study, boxers showed better functional status than the general population despite their injuries and the repetitive stress [19].

Conclusions

Although scaphocapitate syndrome is a high-energy fracture-dislocation injury, timely reduction and fixation in a specialized center can provide excellent results and avoid common adverse events. Reduction of the capitate fragment along with fixation using K-wires and a Herbert screw by a hand surgeon a few hours after the injury avoided the impeding median neuropathy, capitate AVN, and carpal instability in the 1-year follow-up.