title: Medial patellofemoral ligament reconstruction: fixation strength of 5 different techniques for graft fixation at the patella.
abstract: OBJECTIVE
  To compare the structural properties of 5 different fixation strategies for a free tendon graft at the patella in medial patellofemoral ligament (MPFL) reconstruction under cyclic loading and load to failure testing.
  
  
  METHODS
  We used porcine patella and flexor tendons. We tested the following fixation techniques: 3.5-mm titanium anchor, transosseous 1-mm braided polyester suture, interference screw fixation, medial bone bridge, and transpatellar tunnels. We preconditioned each graft between 5 and 20 Nm before cyclic loading with 100 Nm for 1,000 cycles was started, and then performed load to failure testing. We recorded maximum load, stiffness, and elongation.
  
  
  RESULTS
  In the bone bridge group, 60% of all specimens failed during cyclic testing. Fixation by transosseous sutures showed significantly less stiffness compared with all other techniques (P < .05). The bone bridge technique showed significantly lower load to failure compared with all other techniques (P < .05). Differences between the other groups were not significant.
  
  
  CONCLUSIONS
  Fixation of a free tendon graft by transosseous sutures provides similar load to failure and elongation but less stiffness compared with fixation by anchors, interference screws, or transverse tunnels. Load to failure for the bone bridge technique was significantly lower than that for all other techniques. Furthermore, this fixation technique had a lower load to failure than that of the native MPFL.
  
  
  CONCLUSIONS
  Fixation of soft tissue grafts at the patella by 1-mm braided polyester suture provides adequate fixation strength without implants in the patella, which might cause soft tissue irritation. Further studies will have to show if the lesser stiffness of this technique causes problems in the clinical setting or if this laxity might even be an advantage because it makes this reconstruction more forgiving concerning overtensioning the graft. Significantly lower load to failure of the bone bridge technique should be considered in postoperative treatment.
authors: Department of Trauma, Hand and Reconstructive Surgery, Wilhelms University, Muenster, Germany. simon.lenschow@ukmuenster.de
authors: Simon
authors: S
authors: Lenschow
authors: Benedikt
authors: B
authors: Schliemann
authors: Jens
authors: J
authors: Gestring
authors: Mirco
authors: M
authors: Herbort
authors: Martin
authors: M
authors: Schulze
authors: Clemens
authors: C
authors: Kösters
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D008023:Ligaments, Articular / Q000293:injuries / Q000601:surgery*; D023421:Models, Animal; D010329:Patella / Q000601:surgery*; D057071:Patellofemoral Joint / Q000293:injuries* / Q000601:surgery*; D019651:Plastic Surgery Procedures / Q000379:methods*; D013536:Suture Techniques; D013552:Swine; D013710:Tendons / Q000503:physiopathology / Q000637:transplantation*