Patellofemoral Contact Pressures and Lateral Patellar Translation After Medial Patellofemoral Ligament Reconstruction
ABSTRACT Overtensioning of medial patellofemoral ligament reconstructions may lead to adverse surgical outcomes.
Increasing tension on a medial patellofemoral ligament graft will increase patellofemoral contact forces and decrease lateral patellar translation.
Controlled laboratory study.
Patellofemoral contact pressures were measured in 8 fresh-frozen cadaveric knees before and after transection of the medial patellofemoral ligament and after a standardized reconstruction surgery. Contact pressures were measured at 3 knee angles (30 degrees , 60 degrees , and 90 degrees ) and under 3 levels of tension applied to the graft (2, 10, and 40 N). For each condition, patellar translation was measured at 30 degrees of knee flexion as a 22-N lateral force was applied.
Graft tension of 2 N restored normal translation, but 10 N and 40 N significantly restricted motion (5.2 mm and 1.9 mm, respectively). Compared with the intact knee, medial patellofemoral contact pressures significantly increased (P < .05) when 40 N of tension was applied to the reconstruction. Medial contact pressures were restored to normal with 2 N of graft tension. Lateral patellar translation was significantly greater (P < .05) after the medial patellofemoral ligament was cut (16.3 mm) compared with intact (7.7 mm).
Low (2-N) tension applied to a medial patellofemoral ligament reconstruction stabilized the patella and did not increase medial patellofemoral contact pressures. Higher loads (10 N and 40 N) progressively restricted lateral patellar translation and inappropriately redistributed patellofemoral contact pressures.
Overtensioning can be avoided by applying low loads to medial patellofemoral ligament reconstructions, which reestablished normal translation and patellofemoral contact pressures.
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- "Fixation of graft with femur was done with a screw, between 20° and 60° of knee flexion, depending on where the patella was engaging in the groove, while applying low tension pull over the graft (2 N). Overtensioning could be avoided by applying low loads (2 N) to MPFL reconstructions, which reestablished normal translation and patellofemoral contact.37 "
ABSTRACT: Disruption of the capsule, medial patellar retinaculum, and/or vastus medialis obliqus has been associated with recurrent patellar instability. Biomechanical studies have shown that the medial patellofemoral ligament (MPFL) is the main restraint against lateral patella displacement and reconstruction of the MPFL has become an accepted surgical technique to restore patellofemoral stability in patients having recurrent patellar dislocation. We report a prospective series of patients of chronic patellar instability treated by reconstruction of medial patellofemoral ligament. Twelve patients (15 knees) with recurrent dislocation of patella, were operated between January 2006 and December 2008. All patients had generalised ligament laxity with none had severe grade of patella alta or trochlear dysplasia. The MPFL was reconstructed with doubled semitendinosus tendon. Patients were followed up with subjective criteria, patellar inclination angle, and Kujala score. The mean duration of followup after the operative procedures was an average of 42 months (range 24-60 months) 10 knees showed excellent results, 3 knees gave good results, and 2 knees had a fair result. The average patellar inclination angle decreased from 34.3° to 18.6°. The average preoperative Kujala functional score was 44.8 and the average postoperative score was 91.9. MPFL reconstruction using the semitendinosus tendon gives good results in patients with chronic patellar instability without predisposing factors like severe patella alta and high-grade trochlear dysplasia, and for revision cases.Indian Journal of Orthopaedics 07/2012; 46(4):447-54. DOI:10.4103/0019-5413.97259 · 0.64 Impact Factor
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- "At present there is no consensus about the isometric points or the tension to be applied to these reconstructions although this is an important aspect of these ligamentoplasties . Consequently abnormal tracking of the patella due either to anisometric or over tightened medial reconstruction has been shown to overload the patellofemoral joint, exposing the patient to premature patellofemoral secondary arthritis  . In an attempt to avoid overcorrection of either distal alignment or MPFL reconstruction and to address the different components of this pathology, we propose a procedure that combines distal tibial tubercle alignment with a gracilis tendon transfer to the patella. "
ABSTRACT: Many surgical techniques for the medial patellofemoral ligament have recently been suggested, all of which included problems identifying the femoral anchorage point and determining the proper extent of knee flexion for the transplant. P. Burdin proposed a different and original approach consisting in performing a gracilis muscle transfer to the medial edge of the patella, thus obtaining progressive tension of the transfer during knee flexion by means of the myotatic reflex. We report the results herein. We retrospectively assessed 17 knees treated for patellofemoral instability using this technique. Two cases presented subjective patellofemoral instability and 15 presented objective patellofemoral instability. The patients' mean age was 17.4 years (range, 8-47 years) during the first episode of dislocation. Two cases of instability were secondary to advanced neuromuscular disease. Two knees had already undergone two stabilization attempts. Fifteen knees presented trochlear dysplasia (four stage A, eight stage B, and three stage C). The mean age at surgery was 28.2 years (range, 16-47 years). In 15 cases, the gracilis transfer was associated with lowering the anterior tibial tuberosity (mean, 10mm). No patellar fracture occurred. A persistent sensory deficit of the anterior branch of the internal saphenous nerve was observed in 15 cases. One knee remained painful and retained subjective instability; total knee arthroplasty was performed 3 years after the intervention. The mean follow-up at revision was 5.5 years (range, 1.5-16.5 years). No recurrence of dislocation was reported. Eight cases retained subjective instability. The SF-36 and IKDC scores were good or excellent in 12 cases and the KOOS was good or excellent in 13 cases. Radiologically, patellar tilt persisted in six cases out of 14, translation persisted in two cases out of 14, and secondary patella baja was observed in one. Medial patellofemoral osteoarthritis was observed in five cases: one case IWANO stage I and four cases IWANO stage II. These satisfactory results seem stable over time and were acquired using a simple procedure with reduced morbidity, making it possible to avoid significant displacement of the anterior tibial tuberosity and stabilize the extensor apparatus. It can also be hoped that the onset of secondary patellofemoral osteoarthritis, undoubtedly inevitable, has been delayed.Orthopaedics & Traumatology Surgery & Research 06/2011; 97(4 Suppl):S5-11. DOI:10.1016/j.otsr.2011.03.013 · 1.26 Impact Factor
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- "provides an overview of the experimental conditions for the data shown in these figures. Model simulations were obtained using simultaneous quadriceps forces; 56 N for the combined effect of the RF and VI muscles, 20 N for the VM and 38 N for the VL. Figure 3b shows the mean peak contact stress (with standard deviation bars) for the medial patellar facet reported recently by Beck and colleagues (Beck et al., 2007) using a single quadriceps force of 178 N (see Table 1 for experimental description of the Beck et al study). "
ABSTRACT: Although variability in connective tissue parameters is widely reported and recognized, systematic examination of the effect of such parametric uncertainties on predictions derived from a full anatomical joint model is lacking. As such, a sensitivity analysis was performed to consider the behavior of a three-dimensional, non-linear, finite element knee model with connective tissue material parameters that varied within a given interval. The model included the coupled mechanics of the tibio-femoral and patello-femoral degrees of freedom. Seven primary connective tissues modeled as non-linear continua, articular cartilages described by a linear elastic model, and menisci modeled as transverse isotropic elastic materials were included. In this study, a multi-factorial global sensitivity analysis is proposed, which can detect the contribution of influential material parameters while maintaining the potential effect of parametric interactions. To illustrate the effect of material uncertainties on model predictions, exemplar loading conditions reported in a number of isolated experimental paradigms were used. Our findings illustrated that the inclusion of material uncertainties in a coupled tibio-femoral and patello-femoral model reveals biomechanical interactions that otherwise would remain unknown. For example, our analysis revealed that the effect of anterior cruciate ligament parameter variations on the patello-femoral kinematic and kinetic response sensitivities was significantly larger, over a range of flexion angles, when compared to variations associated with material parameters of tissues intrinsic to the patello-femoral joint. We argue that the systematic sensitivity framework presented herein will help identify key material uncertainties that merit further research and provide insight on those uncertainties that may not be as relative to a given response.Journal of Biomechanics 12/2010; 43(16):3118-25. DOI:10.1016/j.jbiomech.2010.08.005 · 2.75 Impact Factor