Kinematic evaluation of isolated and combined medial patellofemoral and patellotibial ligament reconstruction to address lateral patellar instability

Objectives: The roles of the medial patellofemoral and patellotibial ligaments in patellofemoral kinematics have been previously reported. However, the effect of isolated and combined surgical reconstruction of these ligaments to restore native patellofemoral kinematics is not well understood. The purpose of this study was to determine the isolated and combined effects of medial patellofemoral and patellotibial ligament deficiency and reconstruction on patellofemoral kinematics. Methods: Sixteen matched-paired female, fresh-frozen, cadaveric knee specimens with a mean age of 53.5 years (range, 26-65) were used. Specimens were tested in five conditions; 1) intact, 2) MPFL or MPTL cut, 3) MPFL and MPTL combined cut, 4) MPFL or MPTL reconstruction, and 5) MPFL and MPTL combined reconstruction. Dynamic testing was performed by taking the knees through range of motion from 0° to 90° of knee flexion at 60 mm/min using a dynamic tensile testing machine by applying a force through the quadricep tendon. Following dynamic testing, knees were tested statically using a lateral load of 45 N applied to the patella at 0°, 30°, 60°, and 90° of flexion. In both dynamic and static loading tests, a motion capture system detected patellar position for each testing state to distinguish changes in patellar kinematics. Linear mixed effects modeling was performed to compare testing states. Results: Isolated MPFL deficiency created the greatest lateral translation of the patella at all knee flexion angles (p<0.001). MPTL deficiency alone did not create significant patella instability (p=0.68 or greater), but further increased instability when the MPFL was deficient (p<0.001). Isolated MPFL and combined MPFL and MPTL reconstruction decreased lateral patella translation (p<0.001). Native patella tracking was best recreated with combined ligament reconstruction while MPFL reconstruction alone over constrained the patella in extension and under constrained in flexion. Conclusions: The MPFL plays the greatest role in medial patellar stability, but the MPTL appears to have a large influence on patella tracking. The MPTL may be most important in preventing patellofemoral osteoarthritis following patella dislocation. Further investigation is needed to evaluate patellofemoral contact pressure following medial patellar ligament reconstruction.

Enhanced patella tracking in rotating platform total knee replacements, friend or foe? A case of iliotibial band impingement by rotating polyethylene insert

Rotating platform total knee replacement implants have been marketed to allow more precise approximation of normal knee kinematics and enhance patella tracking. At liberty of rotation, the distinct mobile polyethylene insert design does have its pitfalls in spite of purported merits. We report a case of lateral knee pain following rotating platform total knee replacement, attributable to iliotibial band impingement by the rotating polyethylene insert. Prompt treatment via arthroscopic release circumvented a traumatic and costly revision procedure.

Evaluation of the Effect of the Sulcus Angle and Lateral to Medial Facet Ratio of the Patellar Groove on Patella Tracking in Aging Subjects with Stable Knee Joint

Purpose.To determine whether the sulcus angle and the lateral to medial facet ratio correlate with patella lateral displacement and tilt in patients without patella instability.Methods.Computed tomography images of the lower limb of 64 patients without known arthropathy were collected. Three-dimensional models of the lower limb with a unified coordinate system were rebuilt by using Mimics software. The sulcus angle, lateral to medial facet ratio, lateral trochlear inclination of the patellar groove, tibial tuberosity-trochlear groove (TT-TG) distance, bisect offset index, and lateral tilt of the patella were measured. Pearson’s correlation test was used to determine the relationship between the aforementioned parameters.Results.Data from 51 patients were analyzed. The sulcus angle was negatively correlated with lateral tilt inclination (p<0.001,r=0.8406) and positively correlated with the bisect offset index (p=0.003,r=0.634) and patellar tilt (p=0.03,r=0.551); the lateral to medial facet ratio was positively correlated with TT-TG distance (p=0.003,r=0.643) and bisect offset index (p=0.026,r=0.559).Conclusion.The sulcus angle and lateral to medial facet ratio of the patellar groove can influence patella tracking in patients with stable knee joints.

Treatment of Symptomatic Bipartite Patella by Fragment Excision, Capsular Repair and Novel ITB Release

Objectives: The aim of this paper is to present the mid-term results of a novel technique used to treat symptomatic bipartite patella. Methods: Diagnosis of symptomatic bipartite patella was made by history, examination, Xray, MRI and/or bone scan. Patients with typical localised pain, pain on manually stressing the fragment, a positive ITB tightness test, a typical Xray and either, a hot bone scan or bone oedema on MRI were considered for treatment. All patients had a pre-op Kujala and Lysholm score recorded. Surgical Technique: Under GA and tourniquet a 4 part procedure was performed: Routine arthroscopy to assess patella tracking and fragment stability A 2 cm incision was made on the distal thigh 10-12 cm above the joint line over the ITB. A zig-zag incision was made across the ITB/IPB from anteriorly to the corner of the intermuscular septum. A 4 cm incision was made over the edge of the lateral patella. A longitudinal capsular incision was made at the edge of the patella. The capsule was reflected off the dorsal patella by sharp dissection and the bipartite fragment was excised through the synchondrosis. A watertight repair of the lateral capsule was performed with absorbable suture. Routine closures were performed. Comment: The author considers the ITB/IPB to be an important factor in the development and progression of the disorder. The addition of the novel release allows a tension-free capsular repair, reducing lateral facet loads, improving patella tracking without affecting patella stability Results: Over an 11 year period twenty patients underwent the procedure. 15 were available with a minimum 2 year and mean 6.35 year follow-up. Pre-op and post-op Kujala and Lysholm scores were compared. Patients were predominantly male (14:1) between ages 10-54 years. A clear history of trauma was present in 6 patients while in 9 symptoms were related to overuse. The pre-op Kujala score ranged from 28-90 with an average of 59. Post-op scores improved markedly with range 70-100 with 12 patients (80%) scoring >90 and an average improvement of 32 pts. Lysholm scores similarly improved significantly, with an average 32 pts improvement (range 1-66). Complications were minimal. Conclusion: Fragment excision, capsular repair and novel ITB release resulted in significant reproducible improvements in both objective and subjective outcome measures. Resolution of symptoms occurred in all patients suggesting the technique is a useful option in the treatment of symptomatic bipartite patella.