Tension Band for Patella Frx     

- Discussion:
    - theory of tension band wiring:
    - modified anterior tension band technique is indicated for both transverse and comminuted fractures of the patella;
    - for maximal strength, wires are placed on tension surface of bone (anterior surface), as compared to circumferential cerclage wiring;
    - frx fragments are opposed from tension of the figure of 8 wire passed thru insertions of the quadriceps tendon and patellar ligament;
           - remember Sharpey's fibers provide the strongest site of fixation;
    - two K wires or 4 mm cancellous lag scres are incorporated into figure of 8 wire to augment anchorage of cerclage wire;
    - if there is too much comminution for secure ORIF, but a major (usually superior) fragment with a substantial amount of normal articular
           cartilage is present, partial patellectomy is the appropriate approach;

- PreOp Planning:
    - position patient supine w/ bump under knee;
    - equipement: several large towel clamps, 14 gauge needle, 20 and 22 gauge wire, and K wires;
    - be sure to explain to the patient that eventual hardware removal may be necessary due to pain;

- Incision:
    - approached via a midline longitudinal incision or a transverse incision;
    - transverse incision gives more cosmetic result, esp in young patients;
    - be careful to avoid areas of contused skin or abrasions;
    - soft tissue overlying patella is often injured from direct compression or abrasion at the time of the fracture;
         - large frx hematoma frequently develops, further compromising soft tissues;

- Exposure:
    - expose entire anterior surface of patella, and the quadriceps and patellar tendon;
    - expose frx & identify any defect in the extensor mechanism;
    - defects in retinaculum will extend several cm medially or laterally, or both;
    - therefore extend exposure with a medial parapatellar capsular incision for a short distance proximally and medially.
    - need enough release to allow adequate palpation & partial visualization of frx site to ensure anatomical reduction of the articular surface;
         - look for osteochondral fragments, esp in trochlear groove;
         - it is not necessary to create a large medial arthrotomy, such as would be necessary for eversion and full visualization of the articular 
                 surface - small arthrotomy can be closed after fixation;
    * before proceding, place simple sutures in the torn retinaculum on either side of the fracture, and clamp the suture ends (do not tie);
             - the sutures are not tied at this point, becuase this would interfere w/ visualization of the fracture fragments;
             - placing sutures across the torn retinaculum will facilitate their repair, after the fracture has been fixed;

- Reduction:
    - integrity of the fragments is evaluated;
    - often there is comminution that was not recognized on the radiographs;
    - decision regarding whether to proceed with an ORIF, partial patellectomy, or total patellectomy is then re-evaluated;
           - ORIF of transverse fractures with little or no comminution are most amenable to treatment with open reduction and internal fixation;
    - two large towel clips may assist w/ the reduction;
    - frx w/ small amount of comminution can often be first converted to a simple transverse frx by lag-screw fixation of comminuted portion;
    - provisional stabilization of the fracture can usually be obtained with one or two bone-reduction forceps or with K wires;
    - once articular reduction is assured, procede w/ hardware insertion;

- Tension Band Wiring w/ Cannulated Screws:
    - main disadvantage is that there may be only a limited amount of bone to accomodate 2 cannulated screws;
          - if hardware failure occurs, there may not be a good back up plan;

- K Wire Technique: (Modified Tension Band Technique);
    - insert two parallel 2.0-millimeter smooth K wires from an inferior to superior direction (w/ ends left long to accomodate the tension band wire);
          - K wires must be parallel for compression to take place;
          - knee flexion is helpful during K wire insertion;
    - alternatively, parallel longitudinal Kirschner wires can be inserted retrograde thru the frx site, which assures that the wires
          will be inserted slightly anterior to the mid-point;
          - it is important that the K wires be inserted slightly anteriorly in the patella in order for the tension band to function properly;
          - further, posterior placement of K wires will leave the K wires deeply imbeded in the substance of the quadriceps and patellar tendons,
                  which will make future hardware removal difficult;
          - attempt to insert the wires so that both wire tips are parallel to the anterior patellar surface (and therefore neither pin tip is excessively deep to the tendon surface);

- Passage of 18 gauge Wire:
    - an 18-gauge wire is then passed across the anterior surface of the patella (either cross or not crossed) and passed directly behind the K wires;
          - no soft tissue (quad or patellar tendon) should intervene between the the K wires or bone surface and the tensioned wire;
          - hence, the tensioned wires are placed directly adjacent to the patellar surface and directly against the K wires;
          - wire passage is facilitated w/ 14 gauge needle or angiocath;
          - the wires will pass thru the anterior portions of the quadriceps and patellar tendons (just posterior to the K wires);
          - circle configuration: arms of the wires are brought anteriorly over surface of patella, and each medial and lateral side is twisted and tightened;
          - figure of 8 configuration: the wire is passed over the K wires in figure of eight configuration, anteriorly over the surface of the patella;
                 - note that wires placed in a figure of 8 fashion over the anterior patellar surface may end up causing excessive tenderness;
          - consider using the standard circle configuration supplemented with the figure of 8 configuration, the later using a No 5 suture (to reduce tenderness);

- Twist and Cut the Wires:
    - it is important to avoid having sharp protruding wires inferiorly as these can cause signficant pain or even lead to patellar tendon laceration;
    - inferiorly, bend each end of the K wires 180 deg, cut short, and impact into the patellar bony surface;
    - superiorly twist the K wires 180 degs and cut them short, but do not impact them (leaving the superior K wire tips slightly prominent will cause
          less symptoms than leaving the inferior K wire tips prominent);
          - cut the inferior protruding ends of the K wire short (3-4 mm from the bony surface so the K wires will not dislodge;
    - some authors recommend, bending both the superior and inferior ends of the K wires inorder to prevent K wire migration;
          - in the report by Wu CC, et al, the authors report 100% (62/62 fractures) and a union period of 2.5 ± 0.5 months;
                 - skin irritation was noted in 2 patients (3%)
          - ref: Patellar tension band wiring: a revised technique

- Wound Closure:
    - following hardware insertion, the extensor retinaculum is repaired;
    - be sure to close the superficial retinaculum inorder to maximize coverage over the hardware;

- Post Operative Care:
    - patient is immobilized for 2-3 weeks;
    - begin prone hang exercises at 2-3 weeks;
    - crutches are discontinued after 6 weeks

 Patellar tension band wiring: a revised technique
 Comparison of the mechanical properties of different tension band materials and suture techniques.

 Experimental investigation of the tension band in fractures of the patella.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Wednesday, May 30, 2012 11:38 am