Evaluation of A2 and A4 Hand Pulley Repair Using Tendon Graft Rings.

PURPOSE: To compare the mechanical characteristics of A2 and combined A2-A4 pulley repair in the intact and damaged flexor pulley system. METHODS: After control testing, we recorded tendon excursion and flexion of 11 cadaveric fingers after several interventions: (1) complete excision of A2 and A4, (2) repair of the A2 with one ring of tendon graft, (3) repair of the A2 with 2 rings of tendon graft, and (4) repair of the A2 with 2 rings combined with repair the A4 with one ring. RESULTS: At the proximal interphalangeal (PIP) joint, the maximum rotational angle decreased by an average of 30% after complete excision of the A2 and A4 pulleys. This angle was still decreased compared with the control by an average of 25% after one-ring repair at A2, 23% after 2-ring repair at A2, and 17% after 2-ring repair at A2 combined with one-ring repair at A4. At the metacarpophalangeal joint, the average maximum rotational angle decreased by an average of 17% after complete excision of the A2 and A4 pulleys. This angle was still decreased compared with the control by an average of 11% after one-ring repair at A2, 7% after 2-ring repair at A2, and 4% after 2-ring repair at A2 combined with one-ring repair at A4. Kinematic behavior at the PIP joint with an intact pulley system was most closely approximated by the 3-loop repair. The least similar behavior was with a 2-ring construct at A2. CONCLUSIONS: All repairs increased average flexion at the PIP and metacarpophalangeal joints compared with the unrepaired samples. The 3-ring configuration exhibited a higher recovery of PIP flexion compared with the other repairs. CLINICAL RELEVANCE: Although each repair restored flexion, clinical studies are necessary to evaluate the clinical relevance of the mechanical results of this study.

Achievable pin spanning angulation in anterosuperior pelvic external fixation.

INTRODUCTION: Pelvic external fixation using anterosuperior pins provides a quick method of stabilization without necessitating fluoroscopic guidance. Various locations, depths, and inclinations have been cited for external fixator pins; however, the existing literature lacks clear indications for the angular difference between pins. Thus, we aimed to determine the greatest degree of sagittal pin spanning angulation (SPSA) between two iliac crest pins and how intraosseous depth (ID) affects these angulations. MATERIALS AND METHODS: A newly developed computer algorithm produced cross sections of 3D pelvic reconstructions in the sagittal plane in 5° increments. Computer-generated pins with IDs of 60, 75, and 90 mm were positioned in 5° increments transversely. Pins were assessed for cortical containment to define values for SPSA and transverse pin spanning angulation (TPSA). RESULTS: A bimodal distribution revealed varying degrees of insertion frequency and SPSA, cranially and caudally. The caudal distribution exhibited greater cortical containment with larger values for SPSA and TPSA. The highest insertion frequency (85.7%) and largest SPSA (155°) were observed for the 60-mm ID. Increasing ID resulted in further bony penetration and smaller values for SPSA and TPSA. CONCLUSIONS: Expanding the degree of SPSA between inserted pins in anterosuperior pelvic external fixation can be challenging due to the thinning of the iliac wing, which affords a narrow corridor for intraosseous pin containment. An ID of 60 mm allows larger degrees of SPSA while maintaining higher rates of cortical pin containment when compared to pins with greater IDs.

Segmental acetabular rim defects, bone loss, oversizing, and press fit cup in total hip arthroplasty evaluated with a probabilistic finite element analysis.

PURPOSE: Management of segmental rim defects and bone mineral density (BMD) loss in the elderly prior to total hip replacement is unclear within classification systems for acetabular bone loss. In this study, our objectives were (1) to understand how a reduction in BMD in the elderly affects the oversizing of a press-fit cup for primary fixation and (2) to evaluate whether the location of the segmental defect affected cup fixation. METHODS: A finite element (FE) model was used to simulate and evaluate cup insertion and fixation in the context of segmental rim defects. We focused on the distribution of patients over age 70 and used BMD (estimated from CT) as a proxy for aging's implications on THR and used probabilistic FE analysis to understand how BMD loss affects oversizing of a press-fit cup. RESULTS: A cup oversized by 1.10 ± 0.28 mm provides sufficient fixation and lower stresses at the cup-bone interface for elderly patients. Defects in the anterior column and posterior column both required the same mean insertion force for cup seating of 84% (taken as an average of 2 anterior column and 2 posterior column defects) compared to the control configuration, which was 5% greater than the insertion force for a superior rim defect and 12% greater than the insertion force for an inferior rim defect. CONCLUSIONS: A defect along the superior or inferior rim had a minimal effect on cup fixation, while a defect in the columns created cup instability and increased stress at the defect location.

Biomechanical evaluation of distal biceps tendon repair using tension slide technique and knotless fixation technique.

BACKGROUND: Acute distal biceps tendon ruptures are uncommon injuries that often affect young active males, typically resulting from an eccentric load on their dominant extremity. The purpose of this study was to compare pullout strength and tendon gapping in the tension slide technique (TST) versus a knotless fixation technique (KFT). METHODS: Two sets of experiments were performed using cadaveric elbow specimens. In the first experiment, eight elbows from different cadavers were tested to compare TST with a standard locking whipstitch with KFT, four elbows in each group, using a standard locking whipstitch. In the second experiment, 12 elbows were used to study the differences between TST with a standard locking whipstitch with KFT using suture tape reinforced whipstitch (RKFT), using the TST data from the first and second experiment. Each experiment evaluated gapping after cyclic loading and the second experiment also tested the construct to load to failure. RESULTS: Gapping for KFT with a standard locking whipstitch was 10.64 mm versus 2.69 mm for the TST after 1000 cycles (P = 0.016). A reinforced whipstitch significantly improved the failure to gap on the KFT with no significant difference in gapping when compared to TST after 3000 cycles (P = 0.36). The resultant gapping for TST and KST was 2.08 mm and 2.99 mm (P = 0.91), respectively. Load to failure for TST and KFT were 282 Nm and 328 Nm (P = 0.20), respectively. CONCLUSION: Bone-tendon gap resistance of a KFT repair of a torn distal biceps tendon is limited by suture technique. Using a tape reinforced locking whipstitch, the repair is as strong as TST repair. LEVELS OF EVIDENCE: Basic Science.

Validating a Modified Circle Theorem Method for the Measurement of Acetabular Cup Anteversion on Plain Radiography with Intra-Operative Data from Robotic Assisted Total Hip Arthroplasty.

This study aims to validate a modified circle theorem method for the calculation of true version of the acetabular component on anteroposterior x-rays with intra-operative version data derived from robotic assisted total hip arthroplasty (THA). Planar anteversion measurements recorded intraoperatively in 80 THAs were correlated to measurements on anteroposterior radiographs. The mean anteversion of the cohort measured by the robotic system and on plain radiography was 21.2° ± 2.0° and 19.9° ± 3.4° respectively and 97.5% of cases were in a 30% relative error. The correlation between the true and planar measurements of anteversion on plain radiographs was strong (Pearson correlation coefficient of 0.9422). We conclude that the circle theorem method can be validated with data from robotic guided THA.

Can high-friction intraannular material increase screw pullout strength in osteoporotic bone?

BACKGROUND: Osteoporotic bone brings unique challenges to orthopaedic surgery, including a higher likelihood of problematic screw stripping in cancellous bone. Currently, there are limited options to satisfactorily repair stripped screws. Additionally, nonstripped screws hold with less purchase in osteoporotic bone. QUESTIONS/PURPOSES: This study attempts to answer the following questions: (1) Does high-friction intraannular (HFIA) augmentation increase pullout strength in osteoporotic and in severely osteoporotic bone; and (2) can HFIA repair stripped bone thread in osteoporotic and severely osteoporotic bone? METHODS: We measured screw pullout strength using a synthetic bone model in three groups: (1) predrilled nonstripped control holes as controls; (2) predrilled nonstripped augmented with HFIA; and (3) predrilled stripped holes repaired with HFIA. We tested this in osteoporotic and severely osteoporotic synthetic bone for a total of six test groups. We measured screw pullout force using an electromechanical tensile-testing machine comparing pullout force between the test groups and controls. RESULTS: HFIA augmentation did not increase pullout force compared with the control group in the osteoporotic bone model (489 ± 175 versus 607 ± 76, respectively; effect size = 0.94 [95% confidence interval {CI}, -1.75 to 0.08], p = 0.06). However, in severely osteoporotic cancellous bone that was augmented, the HFIA material generated more pullout force than the control (51 ± 18 versus 35 ± 16, respectively; effect size = 0.94 [95% CI, -0.02 to 1.82], p = 0.05). In stripped holes, HFIA partially restored pullout strength but remained weaker than controls in both osteoporotic and severely osteoporotic bone models (osteoporotic: 320 ± 59 versus 607 ± 76, respectively; effect size = -4.28 [95% CI, -5.57 to -2.51], p < 0.001; severely osteoporotic: 21 ± 8 versus 35 ± 16, respectively; effect size = -1.13 [95% CI, -2.0 to 0.12], p = 0.027). CONCLUSIONS: HFIA effectively augmented severely osteoporotic bone for screw purchase, but this effect was not seen for osteoporotic bone. In a model simulating both osteoporotic and severely osteoporotic bone, we found that HFIA can be used to repair stripped screw holes, but the resulting construct remains weaker than nonstripped controls. CLINICAL RELEVANCE: The HFIA material looks promising as a potential solution to stripped screws in osteoporotic bone. However, this material has yet to be tested in human bone. Furthermore, the fine mesh material could be damaged by autoclaving and could break off in vivo causing unknown tissue reactions. We recommend additional testing in a living animal model to better understand how living bone will react to the HFIA material.

Biomechanical Comparison of Perpendicular Versus Oblique In Situ Screw Fixation of Slipped Capital Femoral Epiphysis.

BACKGROUND: Percutaneous in situ single screw fixation is the preferred treatment for stable and unstable slipped capital femoral epiphysis (SCFE). The recommended screw placement is in the center of the epiphysis and perpendicular to the physis, which necessitates an anterior starting point for most SCFEs. A recent clinical study has shown good clinical results with a laterally based screw for SCFE, which is oblique to the physis. We sought to biomechanically compare these 2 techniques for load to failure and hypothesized that the laterally based oblique screw is equivalent or superior to an anteriorly based perpendicular screw. METHODS: Twenty-two paired immature porcine femurs were used to compare the techniques. A SCFE model was created in all femurs using a previously published technique by performing a 30-degree posterior closing wedge osteotomy through the proximal physis. In the control group, a screw was placed perpendicular to the slip with an anterior starting point. In the experimental group, the screw was started as close to the mid-lateral cortex of the proximal femur as possible while maintaining the screw anterior to the posterior cortex of the femoral neck and ending at the apex of the epiphysis ignoring the resultant angle to the physis for the experimental group. The specimens were then potted and loaded in a physiologically relevant posteroinferior direction (30 degrees posterior from vertical) to determine load to failure (N) and stiffness (N/mm). RESULTS: No statistical difference was found between the 2 groups in maximum load to failure or stiffness (P>0.05). CONCLUSIONS: A laterally based screw oblique to the physis for in situ fixation in mild SCFE is not significantly different than an anteriorly based screw perpendicular to the physis in load to failure and stiffness in our study model. CLINICAL RELEVANCE: In light of no difference in load to failure of these 2 constructs, surgeons may be more comfortable with the traditional lateral entry point while still aiming for screw placement in the center of head.

Comparative Study of Alternative Methods for Measuring Leg Length Discrepancy after Robot-Assisted Total Hip Arthroplasty.

BACKGROUND: Our study addresses the lack of consensus on measuring leg length discrepancy (LLD) after total hip arthroplasty (THA). We will assess the inter-observer variability and correlation between the five most commonly used LLD methods and investigate the use of trigonometric principles in overcoming the limitations of current techniques. METHODS: LLD was measured on postoperative AP pelvic radiographs using five conventional methods. CT images created a 3D computer model of the pelvis and femur. The resulting models were projected onto a 2D, used to measure LLD by the five methods. The measurements were evaluated via Taguchi analysis, a statistical method identifying the process's most influential factors. The approach was used to assess the new trigonometric method. RESULTS: Conventional methods demonstrated poor correlation. Methods referenced to the centers of the femoral heads were insensitive to LLD originating outside the acetabular cup. Methods referencing either the inter-ischial line or the inter-obturator foramina to the lesser trochanter were sensitive to acetabular and femoral components. Trigonometry-based measurements showed a higher correlation. CONCLUSIONS: Our results underscore clinicians' need to specify the methods used to assess LLD. Applying trigonometric principles was shown to be accurate and reliable, but it was contingent on proper radiographic alignment.

Suture Tying Force for Cut-Out during Radial Meniscus Tear Repair: A Biomechanical Evaluation of Failure Loads during the Knot-Tying Process.

OBJECTIVE: The purpose of the study was to determine average tensile forces resulting in suture failure while tying a knot during repair of complete radial meniscus tears and to compare the failure tensile force based on meniscus tissue location: the peripheral (red-red) versus inner (white-white). DESIGN: This study was designed as a cadaveric biomechanical study using 24 menisci harvested from fresh frozen cadaveric knees with midbody radial tears. Tears were repaired using 2-0 nonabsorbable suture in both the inner meniscus and the peripheral meniscus. A force gauge was used to measure the tension of a surgeon's knot until failure of either the suture or the meniscus tissue. Statistical analysis was performed comparing suture failure tensile forces between inner and peripheral sutures using 2-sample t test. RESULTS: Suture repairs primarily failed due to meniscal tissue cut-out after suture tensioning (96%). There was no statistical difference in failure mode between medial and lateral meniscus for both the inner (100% cut-out) and the peripheral (92% cut-out; P = 0.703) sutures. The peripheral sutures failed as significantly higher loads (54 ± 26 N) than the inner sutures (36 ± 11 N, P = 0.006). The peripheral meniscus tissue tolerated significantly higher tension at failure (36 ± 7 N) than the inner meniscus (26 ± 7 N, P < 0.001). CONCLUSION: When tying parallel sutures to repair a radial meniscus tear, suture tensile forces above 30 N may tear through meniscus tissue. Surgeons should not use suture tying forces above 30 N when repairing radial meniscus tears with parallel sutures. The peripheral meniscus can withstand higher knot-tying forces than the inner meniscus, so surgeons should consider tying the peripheral suture before the inner suture.

Biomechanical evaluation of the modified lasso technique.

BACKGROUND: The Terrible Triad of the elbow is a constellation of elbow dislocation, radial head fracture and coronoid process fracture. A common type of coronoid fracture documented with this triad is type II Regan-Morrey coronoid fractures. The preferred fixation method for this fracture type is the lasso technique, medial-lateral tunnel orientation being the traditional approach. Considering elbow anatomy, we saw an opportunity to potentially improve fixation by altering the suture lasso tunnel orientation to a proximal-distal orientation. HYPOTHESIS: Two tunnels in the proximal-distal direction would result in greater biomechanical stability as compared to the traditional lasso technique. MATERIAL AND METHODS: A type 2 Regan-Morrey fracture was created in 12 fresh frozen cadaveric elbows at 50% of the coronoid height using an oscillating saw. The humero-ulnar joint was placed in 0 degrees flexion then loaded at a rate of 10mm/min to failure. RESULTS: The control technique (medio-lateral tunnels) showed failure load of 150±81N that was not significantly different (p=0.825) than the 134±116N measured for the modified technique (distal-proximal tunnels). The portion of the load-displacement curve used to calculate stiffness was linear (R^2=0.94±0.04) with determination coefficients that did not differ between the two groups (p=0.351). For stiffness, we measured 17±13N/mm and 14±12N/mm respectively for control and modified techniques that did not result in a significant difference (p=0.674). CONCLUSION: In this attempt to improve the shortcomings of the lasso technique, we found that changing from medio-lateral to proximal-distal drilling directions did not result in an appreciable biomechanical benefit. LEVEL OF EVIDENCE: Basic science study; Biomechanics.

The Joystick Method: A Mini Open Technique for Repairing Patellar Osteochondral Fractures With Concomitant Medial Patellofemoral Ligament Reconstruction.

Fixation of osteochondral fractures after patellar dislocation is typically done using an open approach due to the location of the defect. This is traditionally performed through a medial parapatellar arthrotomy to allow adequate visualization. By using the joystick method, adequate visualization is achieved with a smaller arthrotomy. Careful placement of the joystick in the planned anchor site of the medial patellofemoral ligament reconstruction reduces the number of drill sites in the patella.

Biomechanical Comparison of All-Suture, All-Inside Meniscus Repair Devices in a Human Cadaveric Meniscus Model.

OBJECTIVE: Newer all-suture, all-inside meniscus repair devices utilize soft suture anchors. The purpose of this study was to compare the biomechanical performance of 4 meniscus repair devices in human cadaver menisci: the JuggerStitch (all-suture, all-inside), the FiberStitch (all-suture, all-inside), a polyether ether ketone (PEEK) all-inside, and an inside-out device. DESIGN: Forty human cadaver menisci were tested after creating 20 mm longitudinal tears in the posterior meniscus. Each knee was randomized to 1 of 4 meniscus repair groups: JuggerStitch (all-suture, all-inside), FiberStitch (all-suture, all-inside), FAST-FIX 360 (PEEK-based anchor all-inside), and inside-out (with BroadbandTM tape meniscus needles). For each meniscus, 2 devices were used to prepare vertical mattress repair construct. The specimens were tested by pre-conditioning 20 cycles between 5 N and 30 N and then the tear diastasis was measured, followed by distraction to failure phase after imposing a displacement at a rate of 0.5 mm/s. RESULTS: Ten menisci were tested in each of the 4 groups. After pre-conditioning, there was no significant difference in the gap formation among groups (P = 0.212). The average failure load for the JuggerStitch, FiberStitch, PEEK all-inside, and inside-out was 384 N, 311 N, 207 N, and 261 N, respectively, with a significant difference between groups (P = 0.034). Post hoc analysis showed the JuggerStitch failure load was higher than the PEEK all-inside and inside-out (P = 0.005, and P = 0.045, respectively). There was no significant difference between the failure load of the JuggerStitch and FiberStitch (P = 0.225). CONCLUSION: The JuggerStitch all-suture device, FiberStitch all-suture device, PEEK all-inside, and inside-out devices have similar biomechanical properties for gapping and stiffness. The JuggerStitch all-suture, all-inside device has superior failure load compared with the PEEK all-inside and inside-out repair for longitudinal meniscus tear repair.

Enhanced Manual Ventilation with a Handheld Audiovisual Device - BENGI - Insights from a Pilot Study in Special Operations Medicine.

BACKGROUND: In emergency casualty and evacuation situations, manual ventilation using self-inflating bags remains a critical skill; however, significant challenges exist in ensuring safety and effectiveness, since inaccurate manual ventilation is associated with life-threatening risks (e.g., gastric insufflation with aspiration, barotrauma, and reduced venous return). METHODS: This study assessed the impact of audiovisual feedback from the bag-valve-mask (BVM) emergency narration guided instrument (BENGI), a handheld manual ventilation guidance device, on improving performance and safety, immediately and 2 weeks after, with no additional manual ventilation training. In a crossover manikin simulation study with 20 participants, BENGI immediately and significantly improved tidal volume and respiratory rate accuracy. RESULTS: Intraand inter-participant variations were lower with BENGI, with Poincaré plot analysis showing improved performance that remained for at least 2 weeks following BENGI training. CONCLUSION: BENGI's audiovisual feedback improves manual immediately and persistently, making it invaluable for training and clinical use in diverse scenarios, from battlespace to civilian emergencies.

Effects of A2 Pulley Venting on Bowstringing and Tendon Slack: A Biomechanical Investigation.

BACKGROUND: A2 pulley release is often needed for exposure of the lacerated tendon, retrieval of retracted tendons, placement of core sutures, or to permit full motion and gliding of the repaired and edematous tendon. However, there is no agreement in the literature on the specific quantity of pulley venting that can be performed and recommendations are limited to an undefined "judicious release" of the pulleys when necessary. METHODS: Following a previously developed testing protocols, finger kinematics, tendon excursion, and bowstringing were evaluated on cadaveric hands for venting in increments of 20% of the pulley length. RESULTS: In our study, we found a statistically significant influence of venting on bowstringing, although no difference was found between fingers, and a significant difference in tendon slack, which was variable depending on the finger. Bowstringing started increasing at 20% of A2 venting and peaked at full release. Tendon slack did not start until 40% of A2 venting on the index finger, but started at 20% on the middle, ring, and small fingers. CONCLUSIONS: Venting of the A2 pulley leads to an incremental increase in tendon bowstringing and tendon slack. However, differences in metacarpophalangeal flexion angle were not observed until full A2 pulley release, and only observed in the index finger, and no differences were observed in proximal interphalangeal flexion angles. Therefore, the benefit of releasing the A2 pulley when clinically necessary will likely outweigh the risks of loss of motion or strength.

Impact of bone density and integrated screw configuration on standalone anterior lumbar interbody construct strength.

Background: In anterior lumbar interbody fusion (ALIF), the use of integrated screws is attractive to surgeons because of the ease of implantation and no additional profile. However, the number and length of screws necessary for safe and stable implantation in various bone densities is not yet fully understood. The current study aims to determine how important both length and number of screws are for stability of ALIFs. Methods: Three bone models with densities of 10, 15, and 20 pounds per cubic foot (PCF) were chosen as surrogates. These were instrumented using the Z-Link lumbar interbody system with either 2, 3, or 4 integrated 4.5 × 20 mm screws or 4.5 × 25 mm screws (Zavation, LLC, Flowood, MS). The bone surrogates were tested with loading conditions resulting in spine extension to measure construct stiffness and peak force. Results: The failure load of the construct was influenced by the length of screws (p=.01) and density of the bone surrogate (p<.01). There was no difference in failure load between using 2 screws and 3 screws (p=.32) or when using four 20 mm screws versus three 25 mm screws (p=.295). Conclusion: In our study, both bone density and length of screws significantly affected the construct's load to failure. In certain cases where a greater number of screws are unable to be implanted, the same stability can potentially be conferred with use of longer screws. Future clinical studies should be performed to test these biomechanical results.

Histologic Analysis of 'Distraction Vaginogenesis' in a Rat Model.

Vaginal agenesis (VA) is frequently associated with mullerian agenesis. VA treatments include mechanical dilation and surgical vaginoplasty. We created a vaginal expansion sleeve (VES) as a novel device to progressively lengthen the vaginal canal. This study evaluated the histologic effects of the VES on rat vaginal tissue. The VES is a spring-like device made of proprietary woven cylindrical material and flat resin caps. The VESs were constructed as 25-30 mm, pre-contracted springs, which were secured into the vaginas of six Sprague Dawley rats and allowed to re-expand post-surgically. After one week, the VESs were removed, and the vaginas were harvested and measured in length. Test (n = 6) and control (n = 4) formalin-fixed paraffin-embedded tissues were stained with hematoxylin and eosin (H&E), Masson's trichrome, and anti-Desmin antibodies. The VESs achieved significant vaginal lengthening. The mean vaginal canal length increased from 20.0 ± 2.4 mm to 23.8 ± 1.2 mm after removal of the VESs (n = 6, p < 0.001), a 19% increase. There was a positive correlation between the expander/tension generated in the vagina and the amount of acute and chronic inflammation. H&E staining revealed increased submucosal eosinophilia in five of the six test tissues. One VES sample that was lengthened to 30 mm long showed evidence of lymphocytic and neutrophilic inflammation. Desmin immunostaining and Masson's trichrome stain revealed a thinner muscularis with more infiltrative fibrous tissue between muscle fibers in the test tissue compared to the control tissue. Although effective, the VES may provoke at least a transient increase in eosinophils consistent with a localized immune reaction during muscularis remodeling.

Distraction Enterogenesis in Rats: A Novel Approach for the Treatment of Short Bowel Syndrome.

BACKGROUND: Surgeons often encounter patients with intestinal failure due to inadequate intestinal length ("short bowel syndrome"/SBS). Treatment in these patients remains challenging and the process of physiologic adaptation may take years to complete, which frequently requires parenteral nutrition. We propose a proof-of-concept mechanical bowel elongation approach using a self-expanding prototype of an intestinal expansion sleeve (IES) for use in SBS to accelerate the adaptation process. METHODS: IESs were deployed in the small intestines of Sprague Dawley rats. Mechanical characterization of these prototypes was performed. IES length-tension relationships and post-implant bowel expansion were measured ex vivo. Bowel histology before and after implantation was evaluated. RESULTS: IES mechanical studies demonstrated decreasing expansive force with elongation. The deployment of IES devices produced an immediate 21 ± 8% increase in bowel length (p < 0.001, n = 11). Mechanical load testing data showed that the IESs expressed maximum expansive forces at 50% compression of the initial pre-contracted length. The small-intestine failure load in the rats was 1.88 ± 21 N. Intestinal histology post deployment of the IES showed significant expansive changes compared to unstretched bowel tissue. CONCLUSIONS: IES devices were scalable to the rat intestinal model in our study. The failure load of the rat small intestine was many times higher than the force exerted by the contraction of the IES. Histology demonstrated preservation of intestinal structure with some mucosal erosion. Future in vivo rat studies on distraction enterogenesis with this IES should help to define this organogenesis phenomenon.

Investigating the effect of autograft diameter for quadriceps and patellar tendons use in anterior cruciate ligament reconstruction: a biomechanical analysis using a simulated Lachman test.

Introduction: Current clinical practice suggests using patellar and quadriceps tendon autografts with a 10 mm diameter for ACL reconstruction. This can be problematic for patients with smaller body frames. Our study objective was to determine the minimum diameter required for these grafts. We hypothesize that given the strength and stiffness of these respective tissues, they can withstand a significant decrease in diameter before demonstrating mechanical strength unviable for recreating the knee's stability. Methods: We created a finite element model of the human knee with boundary conditions characteristic of the Lachman test, a passive accessory movement test of the knee performed to identify the integrity of the anterior cruciate ligament (ACL). The Mechanical properties of the model's grafts were directly obtained from cadaveric testing and the literature. Our model estimated the forces required to displace the tibia from the femur with varying graft diameters. Results: The 7 mm diameter patellar and quadriceps tendon grafts could withstand 55-60 N of force before induced tibial displacement. However, grafts of 5.34- and 3.76-mm diameters could only withstand upwards of 47 N and 40 N, respectively. Additionally, at a graft diameter of 3.76 mm, the patellar tendon experienced 234% greater stiffness than the quadriceps tendon, with similar excesses of stiffness demonstrated for the 5.34- and 7-mm diameter grafts. Conclusions: The patellar tendon provided a stronger graft for knee reconstruction at all diameter sizes. Additionally, it experienced higher maximum stress, meaning it dissociates force better across the graft than the quadriceps tendon. Significantly lower amounts of force were required to displace the tibia for the patellar and quadriceps tendon grafts at 3.76- and 5.34-mm graft diameters. Based on this point, we conclude that grafts below the 7 mm diameter have a higher chance of failure regardless of graft selection.

In Vitro Evaluation of Lateral Femur Condyle Free Chondral Fragment Swelling after Soaking in Normal Saline.

OBJECTIVE: After traumatic knee injuries, chondral fragments can avulse off bone with the progeny fragment becoming a loose body. The loose fragment may be larger than expected when trying to surgically repair the fragment back to its original site. The purpose of this study was to determine whether a loose chondral fragment from the lateral femur condyle would increase in size and weight after soaking in normal saline (NS) for 14 days. DESIGN: Twelve 6-mm OAT (osteoarticular transfer) plugs were harvested from 6 cadaver knees on the lateral femoral condyle to simulate a chondral fragment. The chondral fragments were then placed inside an airtight specimen container with NS (0.9% sodium chloride) and were measured over 14 days. RESULTS: After 14 days, the chondral fragments showed no increase in diameter as they measured an average of 5.567 ± 0.448 mm on Day 1 and 5.702 ± 0.253 mm on Day 14 (P = 0.183). The chondral fragments showed an increase in mass from an average of 0.058 ± 0.012 g on Day 1 to 0.073 ± 0.012 g on Day 14 (P < 0.001) and an increase in thickness from an average of 2.038 ± 0.346 mm on Day 1 to 2.229 ± 0.297 mm on Day 14 (P = 0.033). CONCLUSIONS: Chondral fragments in NS increase in mass and thickness over time, but do not change in diameter. When surgeons are evaluating loose chondral fragments for fixation, they should consider that these fragments may appear thicker than the recipient location.

Compressibility of Osteochondral Autograft Transfer Donor Grafts: A Comparison of Different Donor Regions and How Much Shortening Occurs of Plugs After Impaction.

Background: Osteochondral autograft transfer (OAT) is a useful technique for full-thickness cartilage lesions of the distal femur. Various techniques recommend harvesting a plug 2 mm longer than the recipient hole to allow for graft impaction. Grafts with limited compressibility may not sit flush when impacted. Purpose: To compare the compressibility/shortening of OAT donor plug regions from the distal femur of human cadaveric knees after impaction. Study Design: Controlled laboratory study. Methods: A total of 20 cadaveric knees (mean age, 70.3 ± 8.4 years) were divided into 4 donor regions: medial intercondylar (IC) notch, lateral IC notch, medial trochlea, and lateral trochlea. Each region was subdivided into 4 zones: far superior (FSZ), middle superior (MSZ), middle inferior (MIZ), and far inferior (FIZ). A total of 320 grafts (6-mm diameter, 15-mm depth) were extracted, and a custom-built machine was used to strike the graft 5 times using a predetermined energy of 0.11 J. The graft length was measured initially and after each impact. Statistical analysis of the compressibility for each of the 4 regions and all 16 zones was performed utilizing analysis of variance, with post hoc testing using the Fisher's least significant difference. Results: Compression in the lateral IC notch, medial IC notch, medial trochlea, and lateral trochlea was 2.4 ± 1.5, 2.1 ± 0.7, 3.1 ± 2.2, and 2.1 ± 0.6 mm, respectively, with significant differences between the 4 regions (P < .01) and the most compression in the medial trochlea (P < .01). Subgroup analysis showed that the lateral trochlea had higher compressibility for FIZ versus MIZ (P = .02) and the lateral IC notch had higher compressibility for FSZ versus FIZ and MIZ (P < .05 for both). Conclusion: Compressibility varied between OAT donor sites in the distal femur. OAT donor grafts showed the highest compressibility in the medial trochlea (3.1 mm) and lateral IC notch FSZ (3.0 mm). Clinical Relevance: The lateral trochlea, medial IC notch, and the lower zones of the lateral IC notch grafts should not be oversized more than 2 mm in length, as these grafts may not compress adequately.