2015 ISAKOS Biennial Congress ePoster #1118
Length Change Patterns of Lateral Extra-Articular Structures of the Knee and Related Reconstructions
Christoph Kittl, MD, Muenster GERMANY
Camilla Halewood, MEng, MBiomedE, London UNITED KINGDOM
Joanna M. Stephen, PhD, London UNITED KINGDOM
Chim Gupte, PhD, FRCS(Tr&Orth), London, Middlesex UNITED KINGDOM
Andreas Weiler, MD, PhD, Berlin GERMANY
Andy Williams, MBBS, FRCS(Orth), FFSEM(UK), London UNITED KINGDOM
Andrew A. Amis, PhD, FREng, DSc, London UNITED KINGDOM
Department of Mechanical Engineering Imperial College London, London, UNITED KINGDOM
FDA Status Not Applicable
Summary: Extra-articular soft tissue reconstructions with a femoral attachment proximal to the lateral epicondyle and a graft course deep to the lateral collateral ligament (LCL) showed desirable length changes for restraining anterior subluxation of the lateral tibial plateau.
Anterolateral rotatory instability (ALRI) may follow combined anterior cruciate ligament (ACL) and anterolateral capsulo-ligamentous injury. These anterolateral structures include the iliotibial tract (ITT), midthird lateral capsular ligament, and the recently found anterolateral ligament (ALL).
The treatment of ALRI involves an intra-articular (IA) ACL reconstruction and an additional extra-articular (EA) lateral soft-tissue reconstruction. This prevents the lateral tibial plateau from subluxing anteriorly, during the pivot-shift test. Although isolated EA reconstructions showed unsatisfactory results in the past, recent studies of combined IA plus EA reconstruction have presented excellent clinical results.
Various femoral attachment points of the recently found ALL and EA lateral soft tissue reconstructions have been suggested to restrain the anterior subluxation of the lateral tibial plateau. However, only few studies regarding isometry have been published, therefore the goal of the present study was to examine length change patterns and total strain range (TSR) of these tibio-femoral point combinations for anatomical structures and reconstructions.
Eight fresh frozen knees were used. After removal of skin and fat, tibial pins were positioned at the tip of Gerdy’s tubercle and another midway between Gerdy’s tubercle and the fibula head (site of the Segond fracture). Six femoral eyelets were positioned according to femoral attachment sites of native anterolateral structures (anterior ITT, posterior ITT, ALL) and lateral EA soft tissue reconstructions (MacIntosh, Losee, Lemaire, Rowe-Zarins). A monofilament suture was fixed at a tibial pin, guided through a femoral eyelet, and connected to a length change transducer. All possible tibio-femoral point combinations were tested using a rig, which loaded the quadriceps muscles and the ITT according to their fibre direction. Length changes were measured from 0° to 90° knee flexion. Statistical analysis used repeated-measures ANOVA.
The ALL combination with the femoral attachment point posterior and proximal to the lateral femoral epicondyle (Dodds et al.) showed the most isometric behaviour (TSR=9±6%) among the tested native ligaments and was tight near knee extension. The ALL combination attached anterior/distal to the lateral femoral epicondyle (Claes et al., Helito et al.) slackened from 90°to 10° flexion, with TSR=20±8%.
All tested EA reconstructions with a femoral attachment proximal to the lateral epicondyle and graft path deep to the LCL showed similar length change patterns (tendency to tighten towards knee extension) and significantly closer to isometry (Lemaire, Rowe-Zarins, MacIntosh: p<0.025) than the reconstruction anterior to the lateral epicondyle (anterior part of the Losee reconstruction).
All tested reconstructions with a femoral insertion proximal to the lateral epicondyle and a graft course deep to the LCL showed preferable results regarding length change patterns (tightening towards knee extension) and total strain range (high degree of isometry) to inhibit the lateral tibial plateau from subluxing anteriorly.