Extensor pollicis longus (EPL) rupture after distal radius fractures is a well-recognized problem,4,7-9,11,12-14 occurring in 0.07% to 0.88% of patients.5-7 With the increasing use of volar plates for distal radius fractures, there are new possibilities for injury and rupture of the EPL in addition to previously reported etiologies.1,3,5-9,12-14 The two commonly accepted etiologies of EPL rupture after distal radius fractures are mechanical insults or vascular insults to the tendon. Mechanical etiologies include dorsal comminution or spurs, sharp bone edges, or entrapment of the tendon in the fracture site.12,13 Furthermore, Lister's tubercle can mask prominent screw tips dorsally with standard fluoroscopy. Using a Medline search, we found evidence of a new subset of mechanical injuries to the EPL tendon. Lee et al,9 Wong-Chung et al,14 and Failla et al4 described EPL injury secondary to drill-bit penetration or rupture from prominent dorsal screws. However, we could not find any data indicating a clear anatomic correlation between specific screw holes of given volar plate systems and the EPL tendon in the third extensor compartment.
We asked whether any of the holes in specific volar plate systems correlated to the third extensor compartment, therefore predisposing the EPL tendon to injury from drill-bit penetration or prominent screw tips. We then explored ways to identify a prominent screw tip during intraoperative fluoroscopy.
MATERIALS AND METHODS
We used three approaches to explore our questions. We first identified the potential for injury to the EPL tendon in two patients who presented with EPL ruptures after volar plate fixation of distal radius fractures. Next, we performed an anatomic study using six fresh-frozen below-the-elbow cadaver specimens to determine the specific drill hole corresponding to the undersur-face of the third extensor compartment in three commercially available volar plates. Last, in the clinical portion of the study, we performed limited dorsal incisions ulnar to Lister's tubercle in 10 nonconsecutive patients and recorded findings regarding screw tip prominence and dorsal bone fragments or gapping after reduction. Appropriate institutional review board approval was obtained.
Case reports for the two patients show the potential for injury to the EPL tendon after volar plate fixation of distal radius fractures.
Patient 1-Case Report
A 35-year-old woman sustained an extraarticular distal radius fracture of her right dominant wrist after a fall on her outstretched arm. The fracture was unstable and displaced, and after appropriate preoperative evaluation, the patient had open reduction internal fixation (ORIF) with a volar plate. Her immediate postoperative course was uneventful. However, 2 months later she had tenderness over the dorsum of the right wrist, and 2 days later she suddenly was unable to extend her right thumb. She was diagnosed with an EPL rupture and a tendon transfer was proposed. Preoperative radiographs showed protrusion of the screws dorsally (Fig 1A). Intraoperatively, a screw was seen protruding into the third extensor compartment (Fig 1B). The EPL was transected completely at the level of Lister's tubercle. The protruding screw was removed, and an extensor indicis proprius to EPL transfer was performed. The patient regained full extension of the thumb.
Patient 2-Case Report
A 52-year-old woman was run over by a car and sustained a left distal radius fracture. The fracture was displaced, and we performed surgical stabilization with a volar plate and three supplemental K wires. One month postoperatively, she noted pain and swelling in the dorsum of her wrist and was unable to extend her left thumb. She was diagnosed with an EPL rupture, and radio-graphs suggested slight protrusion of one of the screws dorsally (Fig 2A). Intraoperatively, two screws were protruding through the dorsal cortex. The most lateral screw was protruding into the third extensor compartment and the most medial screw was protruding into the fourth extensor compartment (Fig 2B). The EPL was transected, and after the screws were removed an extensor indicis proprius to EPL transfer was performed. Her postoperative course was uneventful.
Identification and subsequent treatment of these two patients prompted us to investigate this potential set of problems with volar plate fixation. This led us to the anatomic component of our study in which we analyzed six fresh-frozen below-the-elbow cadaver specimens. The distal radius was exposed through a standard flexor carpi radialis (FCR) approach, and a volar plate was applied using the techniques recommended by each manufacturer. The implants used included the Hand Innovations (Miami, FL) four-hole standard and five-hole wide plates and the standard Acumed (Hillsboro, OR) plate (Fig 3). Each of the three plates was studied in two separate cadaver specimens. In each plate hole, the drill was allowed to pass through the dorsal cortex into soft tissue, and screws then were placed in standard fashion. We obtained fluoroscopic images to ensure correct plate placement after which we exposed the third extensor compartment through a dorsal approach to the distal radius and the findings were recorded.
During this portion of the cadaveric study, after recording the location of the screw tips relative to the third extensor compartment for each plate hole, we exchanged the screws such that they were 2 mm and 4 mm prominent at the dorsal cortex. We then checked lateral fluoroscopic images to ascertain at what length screw penetration into the third extensor compartment could be determined at the level of Lister's tubercle.
In the clinical component of our study, we identified 10 nonconsecutive patients based on surgical indication (unstable distal radius fracture pattern) and included patients with dorsal comminution or bone fragments or with dorsal bone gaps after reduction. In patients who met these criteria, after reduction and volar plate fixation through a standard volar approach to the distal radius, we made limited dorsal incisions ulnar to Lister's tubercle. Our dorsal incision was 2 cm in length, we identified the third extensor compartment and incised the overlying retinaculum, and then we gently retracted the EPL tendon to observe the floor of the compartment. This allowed us to record the findings with respect to possible etiologies of EPL injury.
Specific plate holes corresponded to the third extensor compartment with all three plates studied. In the Acumed plate, the targeting guide-set screw hole and the hole just distal to this correspond to the fibroosseous canal of the third extensor compartment (Fig 4). In both Hand Innovations plates, the third hole in the proximal row, counting from the radial side of the plate, directs the drill bit and/or screw into the third extensor compartment (Figs 5 and 6).
In the clinical portion of this study, examination of the third extensor compartment through our limited dorsal incision identified two worrisome possibilities for EPL injury after volar plate fixation of dorsally comminuted distal radius fractures. These included postreduction bone spurs or dorsal gapping of the fracture site and prominent screw tips in the third extensor compartment. Eight patients had either bone spurs on the floor of the third extensor compartment or a bony ledge abutting the EPL tendon. One patient had a hematoma of the third extensor fibroosseous canal. One had screw penetration of the third extensor compartment not identified on fluoroscopic imaging before the limited dorsal approach.
Screws at least 4 mm longer than measured using the depth gauges provided with each system were necessary to observe penetration into the third extensor compartment by radiographic or fluoroscan examination. Screws only 2 mm longer than the measured depth were masked by Lister's tubercle on lateral images.
After finding EPL tendon ruptures in two patients who presented to our clinic between 1 and 2 months after volar plate fixation of distal radius fractures, and observing screw tip penetration into the third extensor compartment in both patients, we designed cadaveric and clinical components of a study to further investigate this problem.
The numbers of cadaveric specimens and clinical subjects in this study are small. However, given the reproducibility in application of the Hand Innovations and Acumed volar plates, we think that the consistent results shown with two cadaveric specimens per plate adequately and reproducibly identified the plate holes that correspond to the third extensor compartment. Similarly, the 10 patients in the clinical component of the study, although a small number, were sufficient to identify, intraoperatively, the problems we sought to address: postreduction bone fragments or dorsal gapping and a prominent screw tip in the third extensor compartment.
Extensor pollicis longus tendon rupture after distal radius fractures has been well described in the orthopaedic literature dating to 1934.4,7-9,11-14 The generally accepted incidence of EPL ruptures after distal radius fractures is 0.07% to 0.88%,5,7 usually occurring 1 to 3 months after the injury and with a slightly increased incidence in patients prescribed systemic cortisone.1 Minimally or non-displaced fractures have an increased incidence of EPL ruptures compared with markedly displaced fractures.3,5-8
This may be because of the intact third extensor compartment which may, through increased fluid and hematoma pressure, prevent proper nutrition to the EPL.3,5-8
There seems to be an increased incidence of EPL ruptures after volar plating, although this observation requires additional clarification and analysis.2,9,10,14 Volar plating for distal radius fractures is being used more frequently,16 but as with any new method or technique, long-term complications are not known. Our interest in EPL ruptures after volar plating raised numerous questions concerning the possible causes and what can be done to prevent ruptures.
The anatomy of the EPL in the third extensor compartment on the dorsum of the distal radius has been described.3,8,15 The third extensor compartment with its contained EPL is located on the central aspect of the dorsal distal radius before turning toward the thumb around Lister's tubercle. A tight fibroosseous compartment of the third extensor compartment is present emanating from the dorsal aspect of the radius at the level where dorsally impacted and comminuted fractures occur.6 The EPL has three separate blood sources starting from its musculotendinous origin to its insertion point. The point of rupture in our patients at the level of Lister's tubercle is a watershed area with a marginal blood supply.3,8,15 A high stress or increased frictional area of the EPL occurs at the level of Lister's tubercle as it changes direction moving radially toward the thumb.3
There are two main proposals regarding the etiology of EPL tendon ruptures after distal radius fractures-mechanical versus vascular causes. The mechanical theories include: (1) bone spurs and/or dorsal bone edges protrude into the undersurface or into the third extensor compartment and into the EPL tendon; (2) mushrooming or protrusion of bone dorsally after a distal radius fracture along with a dorsal raw bone edge after reestablishment of the volar inclination of the joint surface may leave a sharp bone edge that causes attritional problems12; (3) screw and drill penetration into the third extensor compartment result in acute and ongoing damage to the EPL tendon9,14; and (4) entrapment of the EPL tendon into the fracture surface with volarly displaced fractures.13
The vascular theories include: (1) marginal blood supply in a high-stress area3,8; (2) decreased synovial perfusion of the third extensor compartment caused by a tight unyielding compartment secondary to pressure from fracture hematoma3,5-8; or (3) systemic factors that might alter blood flow to the EPL tendon such as rheumatoid arthritis or systemic corticosteroid use.1 Both theories may be partially correct in describing the pathophysiology.
We found dorsally impacted fractures may have a mass of bone protruding into the third extensor compartment that is not addressed by a volar approach. With correction of the dorsal inclination, a dorsal gap with a sharp bone edge underneath the third extensor compartment may exist. Also, after reduction of the dorsal impacted fracture, it may be difficult to sense the dorsal cortex with the commercially provided depth gauge with subsequent increased risk of a prominent screw or peg in the third extensor compartment. As most dorsally impacted fractures occur in osteoporotic bone, the normal feel of the dorsal cortex may be absent, therefore increasing the possibility of incorrect instrument placement. Lateral radiographs used to determine the depth of screw or peg placement may be difficult to evaluate as Lister's tubercle or dorsal bone fragments may screen peg or screw protrusion into the third extensor compartment.
When using volar plates for dorsally comminuted distal radius fractures, the surgeon should be aware of the specific screw holes that correspond to the third extensor compartment. The surgeon may consider using shorter screws in these specific plate holes, or potentially leaving these screw holes unfilled if adequate fixation can be obtained with the remaining screws or pegs. Certainly, making a dorsal incision ulnar to Lister's tubercle is not always warranted. In some patients, direct palpation alone may identify screw tip penetration into the third extensor compartment, although patient habitus, swelling, and other factors may make this unreliable. We suggest that a dorsal incision ulnar to Lister's tubercle be considered in patients with dorsal bone comminution or gaps after reduction and volar plate application to inspect the third extensor compartment for possible sources of injury to the EPL tendon.
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