Hybrid Transtibial Femoral Preparation for Transphyseal Anterior Cruciate Ligament Reconstruction: A Radiographic Comparison With the Transtibial and Anteromedial Portal Techniques

Background: Transphyseal anterior cruciate ligament (ACL) reconstruction remains the most commonly used technique for pubescent patients. The transtibial (TT) drilling technique creates vertical and central femoral tunnels to minimize the physeal area of injury at the expense of a nonanatomic femoral tunnel. The hybrid TT (HTT) technique offers the potential of an anatomic femoral position with tunnel geometry similar to that using the TT technique. Purpose/Hypothesis: The purpose was to perform a radiographic comparison of the HTT technique with TT and anteromedial portal (AM) techniques in adolescent patients undergoing transphyseal ACL reconstruction. It was hypothesized that femoral tunnels created during HTT would be similar to TT tunnels but significantly more vertical and central than AM tunnels. Study Design: Cohort study; Level of evidence, 3. Methods: We retrospectively screened primary transphyseal ACL reconstructions performed in adolescents at our institution between 2013 and 2019. The youngest 20 eligible patients were selected from each technique cohort: TT, AM, and HTT. Postoperative radiographs were assessed for the coronal femoral tunnel angle, as well as the location of the tunnel-physis penetration on the anteroposterior and lateral views. Physeal lesion surface area was calculated. Data were compared among the 3 groups using 1-way analysis of variance followed by pairwise comparisons. Results: Included were 47 patients with a mean ± SD age of 14.3 ± 1.2 years (n = 9 with TT, 18 with AM, and 20 with HTT techniques). The coronal tunnel angle was significantly more vertical in the TT (60.7° ± 7.2°) and HTT (54.4° ± 5.7) groups as compared with the AM group (48.8° ± 5.9; P = .0037 and P = .02, respectively). There was no significant difference between the TT and HTT groups ( P = .066). The only significant finding regarding femoral tunnel location was that the HTT tunnels (28.9% ± 4.8%) penetrated the physis more centrally than did the AM tunnels (20.0% ± 5.1%; P = .00002) on lateral radiographs. Conclusion: The HTT technique presents an option for transphyseal ACL reconstruction, with femoral tunnel obliquity and estimated physeal disruption similar to that of the TT technique and significantly less than that of the AM technique. The HTT technique also results in the most central physeal perforation of all techniques, predominantly in the sagittal plane.

Crayfish chimneys function as burrow-ventilation structures

Most crayfish species are capable of constructing underground burrows. Burrow construction provides crayfishes the potential to actively engineer microhabitat and optimize local environmental conditions. Little attention, however, has been paid to quantifying the environmental outcomes of burrow morphology. We examined the potential of chimneys to ventilate burrows via wind-assisted buoyancy ventilation. We first conducted proof-of-concept trials in the field using smoke tracers. We then used a wind tunnel to quantify effects of wind velocity, chimney height, burrow orientation, and tunnel angle on model burrow ventilation rates. We developed a predictive model to predict burrow airflow based on endogenous and exogenous factors, and proofed the model with field measurements from a natural burrow. Proof-of-concept trials showed that during breezy conditions (i.e., 8–16 km−h wind gusts), smoke generated near a natural burrow was rapidly drawn into the non-chimney entry, through the burrow, and out the chimney. Wind-tunnel trials revealed significant effects of chimney height and wind velocity on burrow airflow, but no significant effects of burrow orientation towards the prevailing wind direction, nor of the angle of the burrow beneath the chimney. A model developed from wind-tunnel trials predicted air velocities exiting a theoretical chimney that were within 85% of observed velocities exiting natural chimney-burrow complexes. We conclude that crayfish chimneys can serve as passive ventilation systems for crayfish burrows, with chimney height and wind velocity exerting particularly strong effects on airflow. Costs and benefits associated with chimney construction and ventilation are still speculative but should comprise a productive line of research for future studies focused on burrowing crayfish ecology and conservation.

Evaluation of Tibial Tunnel Location with the Femoral Tunnel Created Behind the Resident's Ridge in Transtibial Anterior Cruciate Ligament Reconstruction

Few studies have determined whether a femoral bone tunnel could be created behind the resident's ridge by using a transtibial (TT) technique-single bundle (SB)-anterior cruciate ligament (ACL) reconstruction. The aim of this study was to clarify (1) whether it is possible to create a femoral bone tunnel behind the resident's ridge by using the TT technique with SB ACL reconstruction, (2) to define the mean tibial and femoral tunnel angles during anatomic SB ACL reconstruction, and (3) to clarify the tibial tunnel inlet location when the femoral tunnel is created behind resident's ridge. Arthroscopic TT-SB ACL reconstruction was performed on 36 patients with ACL injuries. The point where 2.4-mm guide pin was inserted was confirmed, via anteromedial portal, to consider a location behind the resident's ridge. Then, an 8-mm diameter femoral tunnel with a 4.5-mm socket was created. Tunnel positions were evaluated by using three-dimensional computed tomography (3D-CT) 1 week postoperatively. Quadrant method and the resident's ridge on 3D-CT were evaluated to determine whether femoral tunnel position was anatomical. Radiological evaluations of tunnel positions yielded mean ( ± standard deviation) X- and Y-axis values for the tunnel centers: femoral tunnel, 25.2% ± 5.1% and 41.6% ± 10.2%; tibial tunnel, 49.2% ± 3.5%, and 31.5% ± 7.7%. The bone tunnels were anatomically positioned in all cases. The femoral tunnel angle relative to femoral axis was 29.4 ± 5.5 degrees in the coronal view and 43.5 ± 8.0 degrees in the sagittal view. The tibial tunnel angle relative to tibial axis was 25.5 ± 5.3 degrees in the coronal view and 52.3 ± 4.6 degrees in the sagittal view. The created tibial bone tunnel inlet had an average distance of 13.4 ± 2.7 mm from the medial tibial joint line and 9.7 ± 1.7 mm medial from the axis of the tibia. Femoral bone tunnel could be created behind the resident's ridge with TT-SB ACL reconstruction. The tibial bone tunnel inlet averaged 13.4 mm from the medial tibial joint line and 9.7 mm medial from the tibia axis.

Is Arthroscopic Transosseous Rotator Cuff Repair Strength Dependent on the Tunnel Angle?

Background: Previous studies have aimed to biomechanically improve the transosseous tunnel technique of rotator cuff repair. However, no previous work has addressed tunnel inclination at the time of surgery as an influence on the strength of the repair construct. Hypothesis: We hypothesized that the tunnel angle and entry point would influence the biomechanical strength of the transosseous tunnel in rotator cuff repair. Additionally, we investigated how tunnel length and bone quality affect the strength of the repair construct. Study Design: Controlled laboratory study. Methods: Mechanical testing was performed on 10 cadaveric humeri. Variations in the bone tunnel angle were imposed in the supraspinatus footprint to create lateral tunnels with inclinations of 30°, 45°, and 90° relative to the longitudinal axis of the humeral shaft. A closed loop of suture was passed through the bone tunnel, and cyclic loading was applied until failure of the construct. Load to failure and distance between entry points were the dependent variables. Analysis of variance, post hoc paired t tests, and the Bonferroni correction were used to analyze the relationship between the tunnel angle and failure load. The Pearson correlation coefficient was then used to evaluate the correlation of the distance between entry points to the ultimate failure load, and t tests were used to compare failure loads between healthy and osteoporotic bone. Results: Tunnels drilled perpendicularly to the longitudinal axis (90°) achieved the highest mean failure load (167.51 ± 48.35 N). However, there were no significant differences in the failure load among the 3 tested inclinations. Tunnels drilled perpendicularly to the longitudinal axis (90°) measured 13.86 ± 1.35 mm between entry points and were significantly longer ( P = .03) than the tunnels drilled at 30° and 45°. We found no correlation of the distance between entry points and the ultimate failure load. Within the scope of this study, we could not identify a significant effect of bone quality on failure load. Conclusion: The tunnel angle does not influence the strength of the bone-suture interface in the transosseous rotator cuff repair construct. Clinical Relevance: The transosseous technique has gained popularity in recent years, given its arthroscopic use. These findings suggest that surgeons should not focus on the tunnel angle as they seek to maximize repair strength.

DOES ACL TUNNEL PLACEMENT AFFECT QUALITY OF LIFE IN ADOLESCENTS?

Purpose: The aim of this study was to evaluate the influence of surgical experience of an orthopaedic surgeon on femoral and tibial tunnel placement during anterior cruciate ligament (ACL) reconstruction, and the effect of tunnel angle on patient self-report outcomes. Methods: We retrospectively reviewed 115 consecutive ACL reconstruction surgeries by a single fellowship-trained orthopaedic surgeon over his first 5 years in practice. 70 patients with hamstring (HS) and 44 patients with bone-patellar tendon-bone (BTB) autografts were included, all epiphyseal approaches, graft hybrids or allografts were excluded. Posterior distal femoral angle (PDFA), femoral and tibial tunnel angulation were measured on AP and lateral radiographs by 2 independent raters with high inter-rater reliability (ICC >0.8 for all measures). Tunnel angulation was compared to recently reported ideal femoral angle of 33.5°±1.8 or ideal tibial angle of 62.5°±5 (Luthringer et al, 2016). Complications and self-report outcomes - pediIKDC, Tegner-Lysholm and KOOSChild - were recorded, as well as demographics, injury and surgery characteristics (e.g. concurrent meniscal repairs, chondroplasty, tourniquet time). Average follow-up was 1.14 years. Continuous variables were analyzed using unpaired t-test, Wilcoxon rank sum test and Spearman correlation. Categorical variables were analyzed using Fisher’s exact test. Results: ACL reconstruction was performed at an average age of 16.7 years (range, 11.8 to 20.4 years), 59% males. Figure 1 shows tunnel angles over case groups of N=15. For HS autografts, femoral tunnel angle and tibial tunnel angle improved toward the ideal angle after 15 cases (ANOVA, p=0.020 and p=0.031, respectively). For BTB autografts, femoral tunnel angle and tibial tunnel angle did not demonstrate a significant change over cases (Figure 1). The tibial tunnel angle in HS cases showed a negative weak correlation with the selected outcome scores at 6 months and 1 year after ACL reconstruction, whereas the tibial tunnel angle in BTB cases showed a weak positive correlation with KOOSChild pain scores 6 months after initial surgery (Table 1). For either graft type, femoral tunnel angle was not correlated with any outcome measure. Overall, self-report outcome scores were similar between patients with ideal and non-ideal tunnel angles (data not shown). Of the 70 patients with HS autografts, 5 (7%) required a secondary surgery: 2 revisions for graft tear, 1 revision for a non-functional graft, 1 for arthrofibrosis and 1 for a prominent tibial screw. PDFA, femoral and tibial tunnel angle were similar between patients needing secondary surgery and those who did not (Table 2). Patients needing revision surgery had significantly lower Tegner-Lysholm and KOOSChild Pain scores at 6 months after the initial ACL reconstruction. Of the 44 BTB patients, 3 (6.8%) had complications: 2 patients developed arthrofibrosis and subsequently underwent surgery, and 1 patient experienced neuropathy. In these patients, the PDFA was significantly higher, the femoral tunnel angle significantly lower and tibial tunnel angle similar compared to those without a complication (Table 2). Demographic factors, injury and surgical parameters (concurrent meniscal repairs, chondroplasty, tourniquet time, aso) were similar between HS patients with or without additional surgery and between BTB patients with and without complications. Conclusion/Significance: Femoral and tibial tunnel angle improved towards the reported ideal angle after 15 cases for HS autografts. PDFA, femoral and tibial tunnel angle were not associated with surgical complications in HS patients. For BTB autografts, no significant changes were seen in tunnel placement with surgical experience. Patients experiencing complications after BTB autografts had a low femoral tunnel angle and high PDFA. Overall, tibial tunnel angle, but not femoral tunnel angle, correlated with outcome scores of patients with BTB and HS autografts. [Figure: see text][Table: see text][Table: see text]