The hand is one of the most intricate and complex structures of the human body. It is a complex structure made of bone and soft tissue. The structures work in a precise and extremely well coordinated way to produce well coordinated and precise movements. The hand can perform a wide variety of function and is capable of both strength and power or fine motor and sensory function. Any disruption to the anatomic structures can cause profound loss of function and disability to not only the hand, but the patient as a whole. The hand performs range of motion, strength and fine motor skills such as pinch.
The bones of the hand provide the scaffold that support all other structures of the hand. The hand bones include the metacarpals, proximal phalanges, middle phalanges and distal phalanges. The joints of the hand are the carpometacarpal, metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints. Each joint is stabilized by ligaments. Motion to the hand is provided by the gliding of a complex array of tendons. Each finger has two flexor tendons that bend the fingers and one or two extensor tendons that straighten the fingers. These tendons are in close proximity to the bone especially at the phalangeal level. The flexor tendons are held close to the bone by a sheath or tunnel. The extensor tendons extend over the phalanges and form a complex extensor mechanism to straighten the fingers.
The coordinated action of the flexor and extensor tendons provide flexion and extension for the fingers and full range of motion of the hand. When the extensor muscles in the forearm contract, they pull on the extensor tendons of the hand, and straighten the fingers. When the flexor muscles in the forearm contract, they pull the flexor tendons in the hand, which flex the fingers. In addition, intrinsic muscles in the hand contribute to hand motion and strength.
It is the coordinated effort of the muscles and tendons in the forearm and hand that provides hand function. If the skeletal system or the highly intricate soft tissue structures are disrupted the function of the hand is compromised.
Hand fractures are some of the most common fractures that occur. The mechanisms in which hand fractures occur are varied. The most common cause of hand fractures is due to trauma. Hand fractures can be in the form of simple fractures, resulting, e.g., from lower energy trauma such as ground level falls or punching mechanism, or complex fractures, resulting, e.g., from high energy mechanisms such as motor vehicle accidents or falls from a significant height. Other causes of hand fractures are pathologic from bone tumors.
Most fractures that occur in the hand are simple stable fractures that can be treated conservatively without surgery. Conservative treatment methods commonly used are casting or splints. Fractures treated with these methods heal the vast majority of the time with good results (Ref. 1, Ref. 2).
More severe fractures that occur, such as unstable fractures, comminuted fractures or open fractures of the hand, are more problematic to treat. Many times conservative cast or splint treatment does not provide enough stability to the fracture and the fracture heals in a mal-united or angled position. This causes loss of function of the hand.
For the more severe fractures surgical intervention is indicated. Presently, open reduction and internal fixation (ORIF) with plates and screws, or screws alone, are most commonly used (Ref. 3). The advantage of open reduction and internal fixation is that good anatomic alignment and stability can be obtained. The inherent anatomy of the hand and fingers demonstrates that the flexor and extensor tendons are in close proximity to the bone. They are separated from the bone surface by a thin soft tissue layer. It is paramount that to regain function of the hand, unimpeded gliding of the tendons occurs during fracture healing.
The disadvantage of open reduction and internal fixation is the disruption of the soft tissues and especially the extensor mechanism during surgical dissection. Once the soft tissue layer between the bone and tendon or tendon itself is disrupted, tendon adherence to the hardware or bone commonly occurs. This compromises tendon function and ultimately hand function.
This situation occurs most commonly when proximal and middle phalangeal fractures occur at the finger level. In this area the tendon structures are in very close proximity to the bone surface. Fractures and injury that occur in these regions either by trauma or surgery lead to a high incidence of tendon adherence and loss of finger motion. Many surgical exposures for open reduction and internal fixation of metacarpal, proximal and middle phalangeal fractures are through the dorsal aspects of the hand and fingers. Tendon adherence is less often an issue in the dorsal aspect of the hand for metacarpal fractures during open reduction and internal fixation surgery, due to the fact that the extensor tendons are not as close to the bone surface. There is a greater amount of soft tissue between the bone and the tendons. Also, extensor tendons over the metacarpal region of the hand have greater excursion and glide over a greater area.
The most problematic area for surgical intervention is for fractures of the proximal and middle phalangeal region. In these areas the extensor mechanism is only separated from the bone by a thin tissue layer. The placement of hardware on the dorsal aspect of the bone or radial or ulnar aspects, as most commonly done, leads to a high incidence of the extensor tendon adhering to the hardware due to the close proximity of the tendon. This leads to loss of tendon gliding and loss of motion of the finger. Most commonly extensor lag or drooping of the finger occurs. Later surgeries such as freeing up the tendon from scar and removal of the hardware have less than satisfactory results. Once the extensor mechanism is disrupted through trauma and scarring usually there is permanent damage.
Techniques to avoid the problem of tendon adherence include placement of percutaneous Kirschner wires (K wires) through the skin to hold the fracture in place. Percutaneous placement of screws alone to join bone fragments has also been advocated. These techniques can be technically demanding and require indirect reduction, and typically provide less stable fixation than obtained with plates and screws in many instances.
To decrease soft tissue trauma during surgery, intramedullary devices and rods have been developed for stabilization of other fractures such as the femur, tibia and humerus and have become a mainstay of treatment. They provide stable internal fixation with less trauma to the soft tissues (Ref. 4, Ref. 5, Ref. 6). Locking screws employed with such conventional intramedullary devices typically comprise headed screws, wherein in use the head of the screw extends beyond the exterior surface of the bone.
Intramedullary devices have been developed for hand fractures (Ref. 3, Ref. 7, Ref. 8, Ref. 9). Orbay U.S. Pat. No. 6,533,378 discloses an intramedullary rod system with a proximal locking device for treatment of simple fractures of the metacarpal and proximal phalanx. The rod provided good translational control, but does not control rotation adequately (Ref. 9).
Gonzalez et al. (Ref. 10, Ref. 11, Ref. 12) reported using intramedullary rods for both proximal phalanx and metacarpal fractures. The implants were indicated for transverse and short oblique fractures only. They also reported metacarpal rod system for comminuted fractures resulting from gunshot wounds that had locking capability, but open reduction and internal fixation was necessary to place the implant. Locking screws employed appear to be conventional screws with heads extending beyond the external surface of the bone.
Bio-absorbable rods have also been used for metacarpal and phalangeal fractures. The advantages of these implants are that they give stability to the fracture and are later absorbed, precluding hardware complications or removal. Disadvantages of these implants are that they have higher implant failure due to resorption of the implant, implant inflammatory reaction during resorption, and less rotational control (Ref. 13, Ref. 14).
References referred to above are:    Ref. 1: Stern P J. Fractures of the Metacarpals and Phalanges. In Green Operative Hand Surgery, 4th edition. 1999, pp 711-771;    Ref. 2: Tavassoli J, Ruland R T, Hogan C J, Cannon D L. Three Cast Techniques for the Treatment of Extra-articular Metacarpal Fractures. Comparison of short term Outcomes and Final Fracture Alignments. J Bone Joint Surg., Am (87-10) October 2005, pp. 2196-2201;    Ref. 3: Ozerk K, Gillani S, Williams A, Peterson S L, Morgan S. Comparison of Intramedullary Nailing versus Plate-Screw Fixation of Extra-articular Metacarpal fractures. J Hand Surg, Am. (33-10) December 2008, 1724-1731;    Ref. 4: Kreder H J, Schemitsch E H, Conlan L B, Wild L, McKee M D. Femoral Intramedullary Nailing: Comparison of Fracture Table and Manual Traction. A Prospective Randomized Study. J Bone Joint Surg. Am, 84-A, (9) pp. 1514-1521;    Ref. 5: Tornetta P, Tiburzi. Antegrade or Retrograde Reamed Femoral Nailing: A Prospective Randomized Trial. J Bone Joint Surg, Br., (82) 2000, pp. 652-654;    Ref. 6: Brumback R J. The Rational of Interlocking Nailing of the Femur, Tibia and Humerus. Clin Orthop Rel Res. (324) March 1996, pp. 292-320;    Ref. 7: Mockford B J, Thompson N S, Nolan P C, Calderwood J W. Antegrade Intramedullary Fixation of Displaced Metacarpal Fractures: A New Technique. Plastic Recon Surg. (111-1) January 2003, pp. 351-354;    Ref. 8: Downing N D, Davis T R. Intramedullary Fixation of Unstable Metacarpal Fractures. Hand Clinic, 22(3) August 2006, pp. 269-277;    Ref. 9: Depew Small Bone fixation System. Technique manual;    Ref. 10: Gonzalez M H, Igram C M, Hall R F. Intramedullary nailing of Proximal Phalanx Fractures. J Hand Surg (20-5) September 1995, pp 808-812;    Ref. 11: Gonzalez M H, Hall R F. Intramedullary Fixation of Metacarpal and Proximal Phalanx Fractures of the Hand. Clin Orth Rel Res. (327) June 1996, pp. 47-54;    Ref. 12: Busch H G, Gonzalez M H, Hall R F. Locked Intramedullary Nailing of Metacarpal Fractures Secondary to Gunshot wounds. J Hand Surg, Am (31-7) September 2006, pp. 1083-1087;    Ref. 13: Hughes T B. Bioabsorbable Implants in the Treatment of Hand Fractures: An Update. Clin Ortho Rel Res. (445) April 2006, pp. 169-174;    Ref. 14: Kumpta S M, Spinner R, Leung P C. Absorbable Intramedullary Implants for Hand Fractures. Animal Experiment and Clinical Trial. J Bone Joint Surg, Br., (74-4) July 1992, pp. 563-566.