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K-Wire Fixation of Metacarpal and Phalangeal Fractures: Association Between Superficial Landmarks and Penetration of Structures Surrounding the Metacarpophalangeal Joint

Open AccessPublished:August 16, 2019DOI:https://doi.org/10.1016/j.jhsg.2019.06.002

      Purpose

      There is little information regarding the starting points for intramedullary K-wires and their effect on the soft tissues surrounding the metacarpophalangeal (MCP) joint. This study attempted to identify starting points for intramedullary K-wire fixation and determine the effect of these K-wires on soft tissues surrounding the MCP joint.

      Methods

      We placed intramedullary K-wires in the index, middle, and little finger metacarpals and proximal phalanges in 6 cadaveric specimens. We measured the starting points of the K-wires and performed dissection to evaluate which structures were penetrated. A Fisher exact test determined statistical significance between K-wire penetration of soft tissue structures and the starting point for K-wires.

      Results

      Metacarpal K-wires started 8.5 ± 1.5 mm volar to the dorsal aspect of the metacarpal head, 19.1 ± 4.6 mm proximal to the digital palmar crease, and 8.6 ± 1.2 mm from the metacarpal head midline. All MCP K-wires crossed at least one soft tissue structure about the MCP joint; the most commonly the sagittal band. Proximal phalanx K-wires started 8.9 ± 2.9 mm proximal to the distal aspect of the metacarpal head, 25.5 ± 5.9 mm proximal to the digital palmar crease, and 9.9 ± 1.5 mm from metacarpal head midline. All proximal phalanx K-wires crossed at least one soft tissue structure about the MCP, most commonly the joint capsule. No relation was established between K-wire start point and penetration of soft tissue structures.

      Conclusions

      Use of these measurements may aid the physician in placing intramedullary K-wires into the proximal phalanges and metacarpals. Starting points that decrease the rate of penetration of soft tissue structures around the MCP joint have not been described, and all pins crossed at least one soft tissue structure adjacent to the MCP joint.

      Type of study/level of evidence

      Therapeutic IV

      Key words

      Metacarpal and proximal phalanx fractures represent a large proportion of orthopedic injuries. Depending on the finger, the deformity, and the amount of instability, operative management may be indicated. In the 1950s, Lord
      • Lord R.E.
      Intramedullary fixation of metacarpal fractures.
      and Vom Saal
      • Vom Saal F.H.
      Intramedullary fixation in fractures of the hand and fingers.
      described using K-wires to achieve intramedullary fixation for metacarpal (MC) and proximal phalanx (PP) fractures, respectively. Crossed intramedullary K-wire fixation is reliable and has demonstrated good results when operative treatment is necessary; however, complications can occur including pin site infection, joint stiffness, loss of reduction, and residual deformity.
      • Edwards G.S.
      • O’Brien E.T.
      • Heckman M.M.
      Retrograde cross-pinning of transverse metacarpal and phalangeal fractures.
      Furthermore, standardized start sites have not been defined that minimize penetration and/or tethering of nearby soft tissue structures. The current study aimed to describe standardized pin start sites based on consistent surface anatomy for PP and MC fracture K-wire fixation using a cadaver model. After placement of K-wires, we sought to determine the periarticular structures that were penetrated by the K-wires and to evaluate whether the start point was correlated with penetration of peri-articular soft tissue structures.

      Materials and Methods

      Six human cadaver upper extremities (5 males and 1 female), average age 78 years (range, 61–92 years), were used in the study. Three right and 3 left hands were used. Cadavers were evaluated radiographically to ensure there was no evidence of prior trauma or osseous defects. Using fluoroscopic guidance and trochar-tipped 1.4-mm (0.045-in) K-wires (MicroAire, Charlottesville, VA), a board-certified hand surgeon pinned the second, third, and fifth MC and PP on the radial and ulnar side using a crossed-pin configuration. The hands were bound to a block with the metacarpophalangeal (MCP) joint centered over the corner apex so the MCP joint would remain flexed in 90° with the phalanges extended. The MC pins were placed in a retrograde fashion beginning at the collateral recess to avoid placing the pin within the MCP joint. The pins were then advanced proximally within the intramedullary space until the subchondral bone was reached at the base of the MC. The PP pins were placed antegrade starting on each side of the PP base until they contacted the subchondral bone of the PP head. All pin placements were confirmed using orthogonal fluoroscopic images. The second, third, and fifth MC and PP were pinned in each specimen such that each specimen contained 6 PP pins and 6 MC pins (Fig. 1A, B).
      Figure thumbnail gr1
      Figure 1A Fluoroscopic images demonstrating PP K-wire placement. B Fluoroscopy demonstrating MC K-wire placement.
      Pin start sites were measured with digital calipers using measurements from reproducible surface landmarks. With the MCP joints in 90° flexion, we defined 3 measurements (Fig. 2A–D). The distance from the PP K-wire to the distal aspect of the MC head was defined as measurement-1 (M-1). The distance from the PP K-wire to the level of the digital palmar crease marked dorsally was defined as measurement-2 (M-2). The distance of the radial or ulnar pin from the MC diaphysis midline was defined as lateral-1 (L-1). Similarly, the starting points for the MC K-wires were measured using the distance from the K-wire to the most dorsal part of the MC head (M-1) and the same landmarks as those used for the PP were applied to the MC for M-2 and L-1 measurements. All measurements were performed using digital calipers with an accuracy of 0.025 mm (Mitutoyo, Aurora, IL) by a single fellowship-trained hand surgeon.
      Figure thumbnail gr2
      Figure 2A, B M-1 and M-2 measurements for PP and MC pins, respectively. C, D L-1 measurement from PP or MC diaphyseal midline to K-wire skin penetration point for PP and MC pins, respectively.
      After measurements were obtained, each hand was dissected to determine soft tissue involvement (Fig. 3). Penetration of the joint, joint capsule, collateral ligament, extensor tendon, dorsal expansion, sagittal band, collateral recess, juncturae tendinum, or intermetacarpal ligaments was documented. The average location of each K-wire origin and the frequency with which structures were penetrated were recorded. Fisher exact test was used to determine the statistical significance of penetration frequency in relation to the K-wire position.
      Figure thumbnail gr3
      Figure 3A, B Dissection of overlying skin demonstrating adjacent soft tissues and K-wires.

      Results

      Metacarpal K-wire pin measurements were M-1: 8.5 ± 1.5 mm; M-2: 19.1 ± 4.6 mm; and L-1: 8.6 ± 1.2 mm. All MC K-wires crossed at least one structure; the most common were the sagittal band (n = 28 of 36; 78%), collateral recess (n = 25 of 36; 69%), and joint capsule without intra-articular extension (n = 13 of 36; 36%) (Table 1). On average, K-wires penetrated at least 2 structures. There was no statistical relation between the MC pin starting point defined by surface anatomy and critical structure avoidance (M-1: P = .317; M-2: P = .337; L-1: P = .386). The PP K-wire measurements were M-1 = 8.9 ± 2.9 mm; L-1 = 9.9 ± 1.5 mm; and M-2 = 25.5 ± 5.9 mm. Every K-wire crossed at least one structure, most commonly the joint capsule without intra-articular involvement (n = 23 of 36; 64%), the sagittal band (n = 21 of 36; 58%), and the collateral ligament (n = 14 of 36; 39%) (Table 2). Metacarpal K-wires penetrated an average of 2.4 structures, whereas PP K-wires penetrated an average of 2.3 structures. There was no statistical significance between penetration frequency and starting location as measured by M-1 (P = .417), M-2 (P = .063), and L-1 (P = .230). Among all MC and PP pins, only 8% of K-wires entered the joint space.
      Table 1Metacarpal K-Wires (n = 36)
      Metacarpal PinsJuncturae TendinumExtensor TendonDorsal ExpansionSagittal BandCollateral RecessCollateral LigamentIntermetacarpal LigamentJoint CapsuleIntra-Articular
      Pins, n (%)02 (6)7 (19)28 (78)25 (69)6 (17)013 (36)4 (11)
      Table 2Proximal Phalanx K-Wires (n = 36)
      Proximal Phalanx PinsJuncturae TendinumExtensor TendonDorsal ExpansionSagittal BandCollateral LigamentIntermetacarpal LigamentJoint CapsuleIntra-Articular
      Pins, n (%)7 (19)1 (3)8 (22)21 (58)14 (39)023 (64)2 (6)

      Discussion

      Closed reduction percutaneous pinning is an accepted fixation method for MC and PP fractures.
      • Edwards G.S.
      • O’Brien E.T.
      • Heckman M.M.
      Retrograde cross-pinning of transverse metacarpal and phalangeal fractures.
      • Rhee S.H.
      • Lee S.K.
      • Lee S.L.
      • Kim J.
      • Baek G.H.
      • Lee Y.H.
      Prospective multicenter trial of modified retrograde percutaneous intramedullary Kirschner wire fixation for displaced metacarpal neck and shaft fractures.
      • Hornbach E.E.
      • Cohen M.S.
      Closed reduction and percutaneous pinning of fractures of the proximal phalanx.
      Several different fixation strategies and starting points have been described over the past several decades starting in the 1950s. Lord
      • Lord R.E.
      Intramedullary fixation of metacarpal fractures.
      described retrograde MC pinning in 30 military patients using K-wires passed through the center of the MC head. Few complications were reported, and loss of motion resolved once the pin was removed after bony healing. Rhee et al
      • Rhee S.H.
      • Lee S.K.
      • Lee S.L.
      • Kim J.
      • Baek G.H.
      • Lee Y.H.
      Prospective multicenter trial of modified retrograde percutaneous intramedullary Kirschner wire fixation for displaced metacarpal neck and shaft fractures.
      in 2012 provided a more complete description of the starting site used for retrograde MC fixation. Those authors started K-wires at the “MC head” and the “dorsal third in the sagittal plane,” advancing in a “slightly dorsal direction to emerge at the carpometacarpal joint without penetrating the carpal bone.” They reported that almost 9% of patients developed an extensor lag, which was ascribed to wire irritation using this method. More recently, Akinleye et al
      • Akinleye S.D.
      • Garofolo-Gonzalez G.
      • Culbertson M.D.
      • Choueka J.
      Iatrogenic injuries in percutaneous pinning techniques for fifth metacarpal neck fractures.
      performed a cadaveric comparison among antegrade, retrograde, transverse, and cross-pin fixation for fifth MC neck fractures. The authors described penetration of various soft tissue structures but did not suggest a detailed method for possibly avoiding these structures.
      Regarding PP fractures, Vom Saal
      • Vom Saal F.H.
      Intramedullary fixation in fractures of the hand and fingers.
      offered an early description for PP intramedullary fixation in 1953 that was deemed useful when encountering a high degree of angulation, shortening, or rotational instability. Later, in 1984, Belsky et al
      • Belsky M.R.
      • Eaton R.G.
      • Lane L.B.
      Closed reduction and internal fixation of proximal phalangeal fractures.
      described a transarticular intramedullary approach using a single K-wire in 45 patients. The authors noted that the Eaton–Belsky method resulted in good to excellent results in 90% of patients. Hornbach and Cohen
      • Hornbach E.E.
      • Cohen M.S.
      Closed reduction and percutaneous pinning of fractures of the proximal phalanx.
      later reassessed the Eaton–Belsky method in 2001 and found an increased complication rate compared with the original Eaton–Belsky study; however, the authors concluded that the transarticular approach was still appropriate if surgeons restored coronal and sagittal alignment. Faruqui et al
      • Faruqui S.
      • Stern P.J.
      • Kiefhaber T.R.
      Percutaneous pinning of fractures in the proximal third of the proximal phalanx: complications and outcomes.
      compared transarticular pinning and cross-pinning of PP fractures and noted equivalent regarding complication rates. Sela et al
      • Sela Y.
      • Peterson C.
      • Baratz M.E.
      Tethering the extensor apparatus limits PIP flexion following K-wire placement for pinning extra-articular fractures at the base of the proximal phalanx.
      evaluated 3 different pin start sites. The authors noted no difference in proximal interphalangeal joint flexion between pins placed through the sagittal band and adjacent to the extensor tendon avoiding soft tissue structures completely. The authors noted that flexion deficits occurred when the pins were placed directly through the extensor tendon before penetrating the PP.
      The current study sought to identify reproducible surface anatomical landmarks that determine K-wire start sites for retrograde MC and antegrade PP cross-pinning. A single technique for multiple MC and PP K-wire placement was used and meticulous dissection was performed to record soft tissue structures penetrated by K-wires, which previous articles described in limited fashion. Weaknesses of the current study include the limited applicability of starting points in the presence of swelling, injuries to the dermis, and/or shortening or other deformities associated with MC and PP fractures. Furthermore, we did not record whether multiple attempts were required in pin placement. Whereas the starting points themselves may have limited applicability in practice, understanding the frequency with which underlying soft tissue structures may be penetrated by crossed, intramedullary fixation of MC and PP fractures remains pertinent.
      The most common structures affected were the sagittal band, collateral ligament, and MCP joint capsule. Proximal phalanx pins penetrated the MCP joint capsule, the sagittal band, and the collateral ligament. Restricting the mechanical actions of each structure could easily cause the postoperative stiffness described by patients and previous studies. Unfortunately, a pin start site that reduces the penetration of these soft tissue structures could not be determined.

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