| Background and subject：Both flexor digitorum profundus (FDP) tendon injuries in Zone I andII require reattaching a tendon to the distal phalanx.Regardless of thepostoperative rehabilitation protocol used, the tendon attachments mustbe strong enough to withstand any forces generated during therapy whilepermitting strong tendon-to-bone healing. Bunnell initially described thepullout button suture5which is commonly used clinically for tendonattachment between tendon and bone interfaces and has subsequentlybeen modified using different suture techniques and materials. Recently, abone suture anchor has been employed to increase the pullout force,allowing for a repair to bone without externalizing the suture and for astronger locking suture repair technique. The anchor provides a strongertendon to bone repair than a pullout button in an vitro biomechanicalstudy, and the anchor is worth consideration as an alternative method toplace the distal flexor tendon into bone. However, the strength of thetendon/suture interface, which is considered as the weak point, can stillfail by suture rupture or anchor pullout, especially if a small anchor isused in the distal phalanx. A more recent report has described the use of a plantaris tendon with a fragment of its bony attachment fixed with ascrew to the distal phalanx to allow immediate active motion and earlyuse of the involved hand,the plantaris tendon is an extrasynovial tendon,and experimental data have shown poorer outcomes when extrasynovialtendons are used to replace intrasynovial flexor tendons such as the FDP.While intrasynovial autografts are difficult to obtain, intrasynovial tendonallografts with a fragment of bone are readily available, and arefrequently used for anterior cruciate ligament (ACL) reconstruction.Acomparable tendon allograft with a fragment of bone could also be usedto reconstruct the FDP tendon. A recent in vivo animal studydemonstrated that FDP tendon reconstruction with allograft FDP tendongraft had fewer adhesions and better digit function compared to anautologous extrasynovial tendon graft. However, the distaltendon-to-bone repair showed a higher rupture rate for the FDPallografts.10In that study, FDP allografts were fashioned without anattached bone fragment. The purpose of this study was to investigate thebiomechanical properties of a technique using an intrasynovial flexortendon graft with a fragment of bone at its distal end for bone-to-boneattachment, using a suture button technique in a human cadaver model.MATERIALS AND METHODS：Were harvested from12fresh-frozen human cadaveric hands (meanage,74years; range,64-94years). None of the human cadaveric donors were known to have a history of musculoskeletal abnormalities or illnessrelated to the finger tendons.36distal phalanges (Since the tendon in thebony attachment group was harvested with its bony attachment, the distalphalanx in this digit could not be used as a recipient) including3differentrepair techniques, using a random number table.8index fingers,8longfingers,8ring fingers, and12thumbs were randomly assigned to the3different repair techniques.（1）pullout button group：a bone tunnel was created with a3-mmdiameter drill to a depth of5mm for the tendon insertion. Then, twoneedle holes were made into the distal phalanx just distal to the nail bedmatrix. Each suture strand was brought through a drill hole in the distalphalanx and tied over a1.1-cm polypropylene button on the fingernail.（2）suture anchor group：The body of the anchor measured2.2mmin diameter and4.0mm in length. The anchor was inserted according tothe manufacturer’s specifications, using an insertion device provided bythe manufacturer, at a45°angle toward the DIP joint in a distalvolar–proximal dorsal direction.（3）bony attachment group：tendons with their bony attachment wereattached to the distal phalanges that had been prepared with a bony tunnelas described for the pullout button group. The bone fragment of the FDPtendon graft was trimmed to fit the3mm tunnelThe finger was suspended in a fixture that resisted the Kirschner wire inserted through the tuft of each distal phalanx anterior-posteriorlywithout contacting the finger. After tendon attachment, a1.6-mmKirschner wire (3cm in length) was inserted through the tuft of each distalphalanx anterior-posteriorly for the purpose of mounting the distalphalanx onto a materials testing machineThe proximal end of the graft tendon was clamped using acustom-made vice clamp, attached to the test machine actuator,maintaining a constant distance to its attachment. The FDP tendons weredistracted at a rate of20mm/min until complete rupture of the repairoccurred. Load and displacement were recorded continuously. The failuremode was also noted during testing and confirmed after testing.Throughout the preparation and testing, tendons were kept moist withsaline mist. The slope of the linear region of the load-displacement curvewas calculated to determine the tensile stiffness of the repair. Maximumfailure load and tendon repair stiffness were used for data analyses.RESULTS：There was no significant difference in failure force and stiffnessbetween the pullout button and suture anchor groups. All failures in thepullout button group occurred by suture pullout from the graft tendon. Inthe suture anchor group,7specimens failed by suture pullout from thetendon, and5failed by anchor pullout from distal phalanx. In the bonyattachment group,8specimens failed by suture pullout from the bony attachment, and4specimens failed by suture rupture at the bonyattachment.conclusion：Our findings indicate that an intrasynovial flexor tendon graft with itsbony attachment preserved substantially improves the initial tensileproperties when compared with a typical tendon-to-bone attachment witha button or suture anchor. This improvement in the tensile properties mayfacilitate early postoperative rehabilitation after tendon graft, therebyleading to better clinical results. |
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