Minimally invasive anatomic reconstruction of the anterolateral ligament with ipsilateral gracilis tendon: a kinematic in-vitro study

Purpose The anterolateral ligament (ALL) has been defined as a key stabilizer of internal tibial rotation at 35 degrees or more of knee flexion, with a minimal primary or secondary stabilizing role in the AP direction. This study aimed to demonstrate that anatomical reconstruction of the ALL confers rotational stability equal to that of the uninjured knee. Hypothesis: anteroposterior (AP) and rotatory laxity will significantly vary after ALL tenotomy and ALL reconstruction with the author's previously described technique. Methods After ultrasound (US) ALL identification, different kinematic measurements were performed with an image-less Computer-Assisted Navigation System with dedicated software for Laxity Analysis in 5 knee specimens. Anteroposterior (AP) translations and varus/valgus (VV) and Internal-External (IE) rotations were evaluated by two trained orthopedic surgeons before ALL section, after ALL section, and after ALL anatomical reconstruction with doubled ipsilateral autologous gracilis tendon. Results ALL resection significantly increased laxity in IE rotations with knee 90 degrees flexed (IE90) and AP translation with tibia internally rotated and the knee 30 degrees flexed (APlat) (p < 0.05). ALL reconstruction significantly reduced laxity in IE90 and APlat (p < 0.05) and reduced VV rotations at 30 degrees of flexion (VV30) (p < 0.05). There were no statistically significant elongation differences between native ALL and reconstructed ALL (graft) during laxity tests. The inter-operator repeatability of the tests was excellent for each measurement. Conclusions ALL acted as an important internal tibial rotation restrain at 90 degrees and a significant (secondary) AP stabilizer at 30 degrees of knee flexion. The presented ALL reconstruction technique significantly restored the increase of knee laxity produced by the ALL section. Scientific level Case-Controlled Laboratory Study, Level III

Description and validation of a navigation system for intra-operative evaluation of knee laxity

This paper describes the features of KIN-nav, a navigation system specifically dedicated to intra-operative evaluation of knee laxity, and assesses the reliability of the system during surgery. The acquisition protocol for its intra-operative use, the original user interface, and the computational methods for elaboration of kinematic data are described in detail. Moreover, an extensive and specific validation of the system was performed in order to evaluate its intra-operative performance and usability. KIN-nav's reliability and accuracy were analyzed in a series of 79 patients undergoing ACL reconstruction. The intra-surgeon repeatability computed for ACL-deficient and reconstructed knees at different flexion angles was less than 0.6 degrees for varus-valgus (VV) rotation, less than 1 mm for AP translation, and less than 1.6 degrees for IE rotation. The inter-surgeon repeatability is less than 2 degrees for VV rotation, 5 degrees for internal-external rotation, and less than 3 mm for AP translation. The proposed method was fast (requiring an additional 10 minutes of surgical time on average), required only a short learning period (5 cases), was minimally invasive, and was robust from the numerical perspective. Our system clearly shows that the use of navigation systems for kinematic evaluation provides useful and complete information on the knee state and test performance, and is simple and reliable to use. The good repeatability in manual kinematic tests is an improvement on the present ability to discriminate knee kinematics intra-operatively, and thus offers the possibility of better discrimination between knee pathologies and the prospect of new surgical applications

Does patellofemoral geometry in TKA affect patellar position in mid-flexion?

PURPOSE: This study aimed to compare the position of the patella at 90° of flexion before and after implantation of two TKA models with identical tibiofemoral geometry but different trochlear and patellar designs. The hypothesis was that the design with the deeper 'anatomic' trochlea could produce more natural patellar positions. METHODS: Intra-operative navigation data were collected from 22 consecutive cases that received two TKA designs (9 HLS Noetos(®) and 13 HLS KneeTec(®)). Both implants were cemented postero-stabilised TKAs with mobile tibial inserts and patellar resurfacing. Operations were guided by a non-image-based system that recorded relative femoral, tibial and patellar positions pre- and post-operatively. RESULTS: The two groups exhibited little difference in femoral internal-external rotation and anterior-posterior translation during knee flexion. The two groups exhibited significant differences in patellar position at 90° of flexion. Post-operatively, the patella was similarly shifted medially relative to the femur (Noetos 6.9 mm, KneeTec 6.0 mm, n.s.). Patellar flexion was equivalent in native knees (Noetos 18.3°, KneeTec 20.5°, n.s.), but in implanted knees, it was considerably different (Noetos 6.3°, KneeTec 23.5°, p = 0.031). CONCLUSIONS: The present study compared intra-operative navigation data from two patient series that received TKA implants with identical tibiofemoral articular geometry but different patellofemoral designs. The results confirm that tibiofemoral kinematics are unchanged, but that patellar positions at 90° of flexion offer greater mechanical advantage to the quadriceps using the KneeTec than using the Noetos. The findings raise awareness of influence of patellofemoral geometry on mid-flexion kinematics and help surgeons select the most suitable implant for patients with weak quadriceps muscles or with history of patellar instability. LEVEL OF EVIDENCE: Comparative study, Level III