summary Flexor Tendon Injuries are traumatic injuries to the flexor digitorum superficialis and flexor digitorum profundus tendons that can be caused by laceration or trauma. Diagnosis is made clinically by observing the resting posture of the hand to assess the digital cascade and the absence of the tenodesis effect. Treatment is usually direct end-to-end tendon repair. Epidemiology Incidence rare occurs in 4.83 per 100,000 Etiology Pathophysiology mechanism of injury commonly results from volar lacerations and may have concomitant neurovascular injury pathophysiology tendon healing occurs via 2 pathways intrinsic produced by tenocytes within the tendon extrinsic stimulated by surrounding synovial fluid and inflammatory cells implicated in the formation of scarring and adhesions occurs in 3 phases Phases of Tendon Healing Phase Days Histology Strength Inflammatory 0-5 Cellular proliferation None Fibroblastic 5-28 Fibroblastic proliferation with disorganized collagen Increasing Remodeling >28 days Linear collagen organization Will tolerate active range of motion Anatomy Muscles flexor digitorum profundus (FDP) functions as a flexor of the DIP joint assists with PIP and MCP flexion shares a common muscle belly in the forearm has dual innervation index and long fingers are innervated by the AIN of the median nerve ring and small fingers are innervated by the ulnar nerve flexor digitorum superficialis (FDS) functions as a flexor of the PIP joint assists with MCP flexion individual muscle bellies exist in the forearm FDS to the small finger is absent in 25% of people innervated by the median nerve flexor pollicis longus (FPL) located within the carpal tunnel as the most radial structure innervated by the AIN of the median nerve flexor carpi radialis (FCR) primary wrist flexor inserts on the base of the second metacarpal closest flexor tendon to the median nerve innervated by the median nerve flexor carpi ulnaris (FCU) primary wrist flexor inserts on the pisiform, hook of hamate, and the base of the 5th metacarpal innervated by the ulnar nerve Camper chiasm located at the level of the proximal phalanx where FDP splits FDS Pulley system digits 2-5 contain 5 annular pulleys (A1 to A5) thicker and stiffer than cruciate pulleys A2 and A4 arise from the periosteum most important pulleys to prevent flexor tendon bowstringing A1, A3, and A5 arise from the volar plate 3 cruciate pulleys (C1 to C3) collapsible and flexible allows the annular pulleys to approximate each other during digital flexion thumb contains 3 annular pulleys (A1, Av, A2) A2 contributes least to arc of motion of thumb 1 interposed oblique pulley most important pulley to prevent flexor tendon bowstringing (along with A1 pulley) Blood supply 2 sources exist diffusion through synovial sheaths occurs when flexor tendons are located within a sheath it is the more important source distal to the MCP joint direct vascular perfusion nourishes flexor tendons located outside of synovial sheaths supplied by vincular systemosseous bony insertions, reflected vessels from the tendon sheath, and longitudinal vessels from the palm osseous bony insertionsreflected vessels from the tendon sheath, and longitudinal vessels from the palm reflected vessels from the tendon sheath longitudinal vessels from the palm Classification Flexor Zones of Injury Zone Definition Characteristics Treatment I Distal to FDS insertion Jersey finger Direct tendon repair II FDS insertion to distal palmar crease/proximal A1 pulley Zone is unique in that FDP and FDS in same tendon sheath (both can be injured within the flexor retinaculum). Tendons can retract if vincula are disrupted. Direct tendon repair followed by early ROM (Duran, Kleinert). This zone historically had very poor results but results have improved due to advances in postoperative motion protocols. III Palm (A1 pulley to distal aspect of carpal ligament) Often associated with neurovascular injury which carries a worse prognosis. Direct tendon repair. Good results from direct repair can be expected due to absence of retinacular structures (if no neurovascular injury). May require A1 pulley release to avoid impingement of the repaired tendon on the pulley. IV Carpal tunnel Often complicated by postoperative adhesions due to close quarters and synovial sheath of the carpal tunnel. Direct tendon repair. Transverse carpal ligament should be repaired in a lengthened fashion if tendon bowstringing is present. V Carpel tunnel to forearm Often associated with neurovascular injury which carries a worse prognosis. Direct tendon repair Thumb TI, TII, TIII Outcomes different than fingers. Early motion protocols do not improve long-term results and there is a higher re-rupture rate than flexor tendon repair in fingers. Direct end-to-end repair of FPL is advocated. Try to avoid Zone III to avoid injury to the recurrent motor branch of the median nerve. Oblique pulley is more important than the A1 pulley; however both may be incised if necessary. Attempt to leave one pulley intact to prevent bowstringing Presentation Symptoms loss of active flexion strength or motion of the involved digit(s) Physical exam inspection observe resting posture of the hand and assess the digital cascade evidence of malalignment or malrotation may indicate an underlying fracture assess skin integrity to help localize potential sites of tendon injury look for evidence of traumatic arthrotomy motion passive wrist flexion and extension allows for assessment of the tenodesis effect normally wrist extension causes passive flexion of the digits at the MCP, PIP, and DIP joints maintenance of extension at the PIP or DIP joints with wrist extension indicates flexor tendon discontinuity active PIP and DIP flexion is tested in isolation for each digit neurovascular important given the close proximity of flexor tendons to the digital neurovascular bundles Imaging Radiographs may have associated fracture Ultrasound used to assess suspected lacerations Treatment Nonoperative wound care and early range of motion indications partial lacerations < 60% of tendon width outcomes may be associated with gap formation or triggering Operative flexor tendon repair and controlled mobilization indications lacerations > 60% of tendon width flexor tendon reconstruction and intensive postoperative rehabilitation indications failed primary repair chronic untreated injuries FDS4 transfer to thumb single stage procedure indications chronic FPL rupture Techniques Flexor tendon repair indications > 75% laceration ≥ 50-60% laceration with triggering epitendinous suture at the laceration site is sufficient no benefit of adding core suture fundamentals of repair easy placement of sutures in the tendon secure suture knots smooth juncture of the tendon ends minimal gapping at the repair site minimal interference with tendon vascularity sufficient strength throughout healing to permit application of early motion stress to the tendon timing of repair perform repair within three weeks of injury (2 weeks is ideal) delayed treatment leads to difficulty due to tendon retraction approach incisions should always cross flexion creases transversely or obliquely to avoid contractures (never longitudinal) meticulous atraumatic tendon handling minimizes adhesions technique core sutures # of suture strands that cross the repair site is more important than the number of grasping loops linear relationship between strength of repair and # of sutures crossing repair 4-6 strands provide adequate strength for early active motion high-caliber suture material increases strength and stiffness and decreases gap formation locking-loops decrease gap formation ideal suture purchase is 10mm from cut edge core sutures placed dorsally are stronger circumferential epitendinous suture improves tendon gliding by reducing the cross-sectional area improves strength of repair (adds 20% to tensile strength) allows for less gap formation (first step in repair failure) simple running suture is recommended produces less gliding resistance than other techniques sheath repair theoretically improves tendon nutrition through synovial pathway controversial clinical studies show no difference with or without sheath repair most surgeons will repair if it is easy to do pulley management historically believed to be critical to preserve A2 pulleys in digits A4 pulleys in digits oblique pulley in thumb however recent biomechanical studies have shown 25% of A2 can be incised with little resulting functional deficit 100% of A4 can be incised with little resulting functional deficit FDS repair in zone 2 injuries, repair of one slip alone improves gliding compared to repair of both slips outcomes repair failure tendon repairs are weakest between postoperative day 6 and 12 repair usually fails at suture knots repair site gaps > 3mm are associated with an increased risk of repair failure adhesion formation increased risk with zone 2 injuries Wide-awake flexor tendon repair anesthesia performed under tumescent local anesthesia using lidocaine with epinephrine dosing usually epinephrine 1:100,000 and 7mg/kg lidocaine from 1:400,000 to 1:1000 is safe if < 50cc is needed 1% lidocaine with 1:100,000 epi for a 70kg person if 50-100cc is needed dilute with saline (50:50) to get 0.5% lidocaine, 1:200,000 epi if 100-200cc is needed for large fields (tendon transfer, spaghetti wrist) dilute with 150cc saline to get 0.25% lidocaine and 1:400,000 epi for longer surgery > 2 hours add 10cc of 0.5% bupivacaine with 1:200,000 epi location proximal and middle phalanges, use 2ml distal phalanx, use 1ml palm, use 10-15ml no tourniquet, no sedation 4 advantages allows intraoperative assessment for repair gaps by getting awake patient to actively flex digit reduces need for postop tenolysis by allowing intraoperative assessment of whether repair will fit through pulleys allows on-the-spot debulking of bunched repairs allows division of A4 pulley and venting (partial division) of A2 pulleys allows repair of tendons inside tendon sheaths as patients can demonstrate that the inside of the sheath has not been inadvertently caught facilitates postop early active motion immobilize for 3 days begin active midrange motion after day 3 (form a partial fist with 45 degree flexion at MP, PIP and DIP joints, or "half a fist 45/45/45 regime") Flexor tendon reconstruction requirements supple skin sensate digit adequate vascularity full passive range of motion of adjacent joints techniques single-stage procedures only perform if the flexor sheath is pristine and the digit has full ROM two-stage procedures Hunter-Salisbury Stage I - SR is placed to create a favorable tendon bed Stage II (3-4 months) - SR is retrieved and a tendon graft is placed through the mesothelium-lined pseudosheath pulvertaft weave proximally and end-to-end tenorrhaphy distally Paneva-Holevich Stage I SR is placed in the flexor sheath, pulleys are reconstructed (as needed), and a loop between the proximal stumps of FDS and FDP is created in the palm Stage II SR is retrieved, FDS is cut proximally and reflected distally through the pseudosheath and either attached directly to FDP stump or secured with a button advantages graft (FDS) size is known at the time of silicone rod selection less graft diameter-rod diameter mismatch FDS graft is intrasynovial fewer adhesions than extrasynovial grafts relies on only 1 tenorrhaphy site (distal or proximal) to heal at any one time (vs. Hunter technique where 2 tennoprhaphy sites are healing simultaneously) disadvantages graft tensioning is at the distal end during stage II the proximal end has already healed after stage I graft selection palmaris longus (absent in 15% of population) most common plantaris (absent in 19%) indicated if longer graft is needed extensor digitorum longus to 2nd-4th toes extensor indicis proprius flexor digitorum longus to 2nd toe FDS pulley reconstruction one pulley should be reconstructed proximal and distal to each joint pulley reconstruction should occur first if a tendon graft is being used methods belt loop method FDS tail method outcomes subsequent tenolysis is required more than 50% of the time Tenolysis indications localized tendon adhesions with minimal to no joint contracture and full passive digital motion may be required if a discrepancy between active and passive motion exists after therapy timing of procedure wait for soft tissue stabilization (> 3 months) and full passive motion of all joints technique careful technique to preserve A2 and A4 pulleys postoperative care follow with extensive therapy Postoperative Rehabilitation Postoperative controlled mobilization has been the major reason for improved results with tendon repair especially in zone II leads to improved tendon healing biology limits restrictive adhesions and leads to increased tendon excursion Protocols Immobilization indicated for children and non-compliant patients casts/splints are applied with the wrist and MCP joints positioned in flexion and the IP joints in extension Early passive motion Duran protocol low force and low excursion active finger extension with patient-assisted passive finger flexion and static splint Kleinert protocol low force and low excursion active finger extension with dynamic splint-assisted passive finger flexion Mayo synergistic splint low force and high tendon excursion adds active wrist motion which increases flexor tendon excursion the most Early active motion moderate force and potentially high excursion dorsal blocking splint limiting wrist extension perform “place and hold” exercises with digits Complications Tendon adhesions most common complication following flexor tendon repair higher risk with zone 2 injuries treatment physical therapy tenolysis perform if 4-6 months after tendon repair and significant loss of excursion Rerupture 15-25% rerupture rate treatment if < 1cm of scar is present, resect the scar and perform primary repair if > 1cm of scar is present, perform tendon graft if the sheath is intact and allows passage of a pediatric urethral catheter or vascular dilator, perform primary tendon grafting if the sheath is collapsed, place Hunter rod and perform staged grafting Joint contracture rates as high as 17% Swan-neck deformity Trigger finger Lumbrical plus finger Quadrigia