Fernando Pena

Comparison of Failure Strength Between Metallic and Absorbable Interference Screws Influence of Insertion Torque, Tunnel-Bone Block Gap, Bone Mineral Density, and Interference

Because of the good initial fixation strength of interfer ence screws used in anterior cruciate ligament recon struction, metal interference screws have become the standard method for fixation of bone-patellar tendon- bone grafts. To avoid some of the complications with metal screws, a bioabsorbable interference screw was developed. Data on fixation strength in older human cadavers indicate a similar failure strength between bioabsorbable and metal screws. We studied the fail ure mechanisms, insertion torques, and fixation strengths of absorbable and metal interference screws in cadaveric knees from young and middle-aged do nors. With identical gap and screw size, the mean insertion torque for the metal screws (mean, 1.5 N-m; SD, 0.8) was significantly higher than for the absorb able screws (mean, 0.3 N-m; SD, 0.19). The mean failure load for the metal screws (mean 640 N; SD, 201) was also significantly higher than for the absorb able screws (mean, 418 N; SD, 118).

Fixation strength of interference screw fixation in bovine, young human, and elderly human cadaver knees: Influence of insertion torque, tunnel-bone block gap, and interference

A failure analysis of interference screw fixation was performed to test the hypothesis that bovine and/or elderly human cadavers are appropriate models for bonepatellar tendon-bone anterior cruciate ligament (ACL) reconstruction fixation studies. Failure mode is an important criterion for validating experimental models. The bovine, young human, and elderly human failure loads were 799±261 N, 655±186 N, and 382±118 N, respectively, and the failure modes were 75%, 69%, and 30% tissue failures, respectively. The similarities between the bovine and young human models in failure loads and failure modes indicate that bovine models are appropriate for ACL reconstruction fixation studies. The statistically significant differences between the young human and elderly human models in failure loads and failure modes indicate that elderly human cadavers are not an appropriate model for ACL reconstruction fixation studies. The differences in failure modes are consistent with previous studies using elderly human cadavers in which the predominant failure mode was bone block pullout. The tissue failures observed in the bovine and young human models contradict previous studies suggesting fixation strength is the weakest link in bone-patellar tendon-bone ACL reconstruction. Results of linear regression modeling showed statistically significant correlations between insertion torque and failure load (R2=0.44,P<0.0001) and interference (defined as the screw outer thread diameter minus the tunnel-bone block gap) and insertion torque (R2=0.18,P=0.003) when data from all models was combined. Results for the bovine model multiple regression showed a statistically significant regression of insertion torque (linear) and interference (quadritic) versus failure load (R2=0.56,P=0.02). Regression slopes for screw diameter (P=0.52) and gap size (P=1.00) were not statistically significant. These results indicate that insertion torque and interference are independent predictors of failure load and should be included in future interference screw studies in addition to bone block dimensions, tunnel size, gap size, and screw diameter. Clinicians may consider using insertion torque and interference as indicators of postoperative graft fixation regarding rehabilitation decisions.

Biomechanics of Ankle Ligament Reconstruction An In Vitro Comparison of the Broström Repair, Watson-Jones Reconstruction, and a New Anatomic Reconstruction Technique

We wanted to use biomechanical testing in a cadaveric model to compare the Broström repair, the Watson- Jones reconstruction, and a new anatomic reconstruc tion method. Eight specimens were held in a specially designed testing apparatus in which the ankle position (dorsiflexion-plantar flexion and supination-pronation) could be varied in a controlled manner. Testing was done with intact ligaments and was repeated after sectioning of the anterior talofibular ligament and the calcaneofibular ligament and after a Broström repair, a Watson-Jones reconstruction, and a new anatomic re construction were performed. An anterior drawer test was performed using an anterior translating force of 10 to 50 N, and a talar tilt test was performed using a supination torque of 1.1 to 3.4 N-m. The forces in the anterior talofibular ligament and calcaneofibular liga ment were measured with buckle transducers, and tibiotalar motion and total ankle joint motion were meas ured with an instrumented spatial linkage. The in crease in ankle joint laxity observed after sectioning of both the anterior talofibular and calcaneofibular liga ments was significantly reduced by the three recon structive techniques, although not always to the level of the intact ankle. Joint motion was restricted after the Watson-Jones procedure compared with that in the intact ankle. Unlike the Watson-Jones procedure, the ligament or graft force patterns observed during load ing after the Broström repair and the new anatomic technique resembled those observed in the intact ankle.

Mechanics of the anterior drawer and talar tilt tests: A cadaveric study of lateral ligament injuries of the ankle

We analyzed the changes in lateral ligament forces during anterior drawer and talar tilt testing and examined ankle joint motion during testing, following an isolated lesion of the anterior talofibular ligament (ATFL) or a combined lesion of the ATFL and calcaneofibular ligament (CFL). 8 cadaver specimens were held in a specially designed testing apparatus in which the ankle position (dorsiflexion-plantarflexion and supination-pronation) could be varied in a controlled manner. Ligament forces were measured with buckle transducers, and joint motion was measured with an instrumented spatial linkage. An anterior drawer test was performed using an 80 N anterior translating force, and a talar tilt test was performed using a 5.7 Nm supination torque with intact ligaments, after sectioning of the ATFL, and again after sectioning of the CFL. The tests were repeated at 10 degrees dorsiflexion, neutral, and 10 degrees and 20 degrees plantarflexion. In the intact ankle, the largest increases in ATFL force were observed during testing in plantarflexion, whereas the largest increases in CFL force were observed in dorsiflexion. Isolated ATFL injury caused only small laxity changes, but a pronounced increase in laxity was observed after a combined CFL and ATFL injury.

All-inside arthroscopic lateral collateral ligament repair for ankle instability with a knotless suture anchor technique.

Background: Recently, arthroscopic-assisted techniques have been described to treat lateral ankle instability with excellent results. However, complications including neuritis of the superficial peroneal or sural nerve, and pain or discomfort due to a prominent anchor or suture knot have been reported. The aim of this study was to describe a novel technique, the “all-inside arthroscopic lateral collateral ankle ligament repair,” and its results for treating patients with ankle instability. Methods: Sixteen patients (10 men and 6 women, mean age 29.3 years, 17-46) with lateral ankle instability were treated with an arthroscopic procedure. Using a suture passer and a knotless anchor, the ligaments were repaired with an all-inside technique. The right ankle was affected in 10 cases. Mean follow-up was 22.3 (12-35) months. Results: On arthroscopic examination, 13 patients had an isolated anterior talofibular ligament (ATFL) injury, and in 3 patients, both the ATFL and calcaneofibular ligament (CFL) were affected. All-inside arthroscopic anatomic repair of the lateral collateral ligament complex was performed in all cases. All patients reported subjective improvement of their ankle instability. The mean AOFAS score increased from 67 preoperatively to 97 at final follow-up. No major complications were reported. Conclusion: The all-inside arthroscopic ligament repair was a safe, reliable, and reproducible technique that both provided an anatomic repair of the lateral collateral ligament complex and restored ankle stability while preserving all the advantages of an arthroscopic technique. Level of Evidence: Level IV, retrospective case series.

Ligament force and joint motion in the intact ankle: a cadaveric study

Abstract The aims of this study were to measure the forces in the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL) and the motion in the tibiotalar and subtalar joints during simulated weight-bearing in eight cadaver ankle specimens. An MTS test machine was used to apply compressive loads to specimens held in a specially designed testing apparatus in which the ankle position (dorsiflexion-plantarflexion and supination-pronation) could be varied in a controlled manner. The forces in the ATFL and CFL were measured with buckle transducers. Tibiotalar motion and total ankle joint motion were measured with an instrumented spatial linkage. The specimens were positioned sequentially at 10° dorsiflexion, neutral, and 10° and 20° plantarflexion, and this sequence was repeated at 15° supination, neutral pronation/supination, and 15° pronation. Force and motion measurements were recorded in each of these positions with and without a 375 N compressive load simulating weight-bearing. From 10° dorsiflexion to 20° plantarflexion, all motion occurred in the tibiotalar joint. In contrast, the ratio of subtalar motion to tibiotalar motion was 3:1 for supination-pronation and 4:1 for internal-external rotation. Inverse loading patterns were observed for the ATFL and CFL from plantarflexion to dorsiflexion. Compressive loading did not affect CFL tension, but it magnified the pattern of increasing ATFL tension with plantarflexion. The largest increase in ATFL force was observed in supination and plantarflexion with a compressive load (76 ± 23 N), whereas CFL tension mainly increased in supination and dorsiflexion with a compressive load (109 ± 28 N). In conclusion, the results showed that the ATFL acted as a primary restraint in inversion, where injuries typically occur (combined plantarflexion, supination and internal rotation). Also, the subtalar joint was of primary importance for normal supination-pronation and internal-external rotation.

Comparison of the MFA to the AOFAS outcome tool in a population undergoing total ankle replacement.

Background Little information is available on the American Orthopaedic Foot and Ankle Society (AOFAS) outcome tool and its capacity to show changes and improvement in function of patients without a floor or ceiling effect. The purpose of the study was to compare results from the Musculoskeletal Functional Assessment (MFA) and AOFAS outcome tools in a population undergoing a total ankle replacement. Methods Prospective data was collected on 154 patients preoperatively and at 6, 12, and 24 months after surgery. An analysis was performed between both and within each tool across the time of followup. Results No ceiling or floor effect was noticed on the AOFAS outcome tool. Its capacity for discrimination and to observe changes in pain and function are acceptable. No correlation between the AOFAS categories of pain and function and the MFA domain of well being could be found. Both outcome tools presented similar responses. Conclusions Though the AOFAS outcome tool seems to have enough sensitivity to analyze pain and function during a postoperative period, the authors strongly recommend the use of an alternative outcome tool to better understand and delineate the patients level of function and effect of treatment on their quality of life. Clinical Relevance These data improve the understanding of and indications for the AOFAS outcome tool. They confirm the AOFAS questionnaire as a tool with enough discriminatory capacity to assess patient improvement and also point out the weaknesses of the questionnaire and the importance of collecting parallel data with other available outcome tools to better understand patient function and quality of life.

Accuracy of femoral tunnel placement and resulting graft force using one- or two-incision drill guides. A cadaver study on ten paired knees

Recently, one-incision drill guides introduced through predrilled tibial tunnels have become popular in anterior cruciate ligament (ACL) reconstruction. No data are available on the reproducibility of the tunnel placement when this drill guide is used. The primary goal of this study was to compare accuracy of tunnel placement using the one-incision (all-inside) and the conventional two-incision drill guide (outside-in) to the location of the center of the normal ACL attachment. Furthermore, our goal was to measure the forces seen by the normal ACL during extension from 90 degrees of flexion, when the tibia is subjected to 100 N anterior load (22.7 lbs), and compare these with the forces measured in the reconstructions performed with the two drill guides. The center of the tunnel on the lateral femoral condyle using the two different drill guides was measured with a three-dimensional pointer and compared with the center of the normal ACL insertion site. Forces in the normal ACl and the reconstructed ligament were measured with a buckle transducer in a loaded and an unloaded state at four different flexion angles. The one-incision drill guide led to a statistically more proximal placement of the graft than both the conventional drill guide and the center of the normal ACL. Both drill guides led to an anterior placement compared with the normal ACL. There was no difference in the graft forces after reconstruction with the two drill guides, but the forces in the loaded grafts were twice those of the normal ACL.

Arch Height and First Metatarsal Joint Axis Orientation as Related Variables in Foot Structure and Function

Background: This study investigated the association of arch height combined with first metatarsal joint axis vertical (V) orientation to the size of the 1–2 intermetatarsal angle (IMA) and first metatarsal adduction/abduction position simulating foot postures during gait, kinematics commonly affected by bunion. Materials and Methods: Nine cadaver specimens were mounted in a loading frame. Measures of arch height ratio and IMA were made. With the foot placed in positions seen during normal gait cycle an electromagnetic device measured displacement of the relative angle of rotations between the first metatarsal and navicular, and helical axis (HA) parameters. Canonical correlation analysis assessed the relationship among the variables. Results: A negative relationship (r = −0.73) was found between arch height and first metatarsal HA V-orientation. When considered as combined variables, arch height and metatarsal HA V-orientation accounted for 69% of the variance of IMA and change in first metatarsal adduction/abduction position. Conclusion: Orientation of the first metatarsal joint axis was highly variable between specimens but correlated with arch height. The conjoined factors of arch height and first metatarsal HA V-orientation accounted for most of the variance of IMA and change in first metatarsal adduction/abduction position during the sequence of foot position during simulated gait. Clinical Relevance: These findings suggest that orthotic arch support could reorient the metatarsal joint axis out-of-vertical and in effect, limit the first metatarsal from displacing into an adducted bunion deformity. These findings could help to explain the pathogenesis of bunions.

An Image-Based Gait Simulation Study of Tarsal Kinematics in Women With Hallux Valgus

Background Although not well understood, foot kinematics are changed with hallux valgus. Objective The purpose of this study was to examine tarsal kinematics in women with hallux valgus deformity. Design A prospective, cross-sectional design was used. Methods Twenty women with (n=10) and without (n=10) deformity participated. Data were acquired with the use of a magnetic resonance scanner. Participants were posed standing to simulate gait, with images reconstructed into virtual bone datasets. Measures taken described foot posture (hallux angle, intermetatarsal angle, arch angle). With the use of additional computer processes, the image sequence was then registered across gait conditions to compute relative tarsal position angles, first-ray angles, and helical axis parameters decomposed into X, Y, and Z components. An analysis of variance model compared kinematics between groups and across conditions. Multiple regression analysis assessed the relationship of arch angle, navicular position, and inclination of the first-ray axis. Results Both the hallux and intermetatarsal angles were larger with deformity; arch angle was not different between groups. The calcaneus was everted by ≥6.6 degrees, and the first ray adducted (F=44.17) by ≥9.3 degrees across conditions with deformity. There was an interaction (F=5.06) for the first-ray axis. Follow-up comparisons detected increased inclination of the first-ray axis over middle stance compared with late stance in the group with deformity. Limitations Gait was simulated, kinetics were not measured, and sample size was small. Conclusions There were group differences. Eversion of the calcaneus and adduction of the first ray were increased, and the first-ray axis was inclined 24 degrees over middle stance in women with deformity compared with 6 degrees in control participants. Results may identify risk factors of hallux valgus and inform nonoperative treatment (orthoses, exercise) strategies.