The Effect of Lower Limb Alignment on Tibiofemoral Joint Contact Biomechanics after Medial Meniscus Posterior Root Repair: A Finite-Element Analysis.

INTRODUCTION: The purpose of this study was to determine how variations in lower limb alignment affect tibiofemoral joint contact biomechanics in the setting of medial meniscus posterior root tear (MMPRT) and associated root repair. METHODS: A finite-element model of an intact knee joint was developed. Limb alignments ranging from 4° valgus to 8° varus were simulated under a 1,000 N compression load applied to the femoral head. For the intact, MMPRT, and root repair conditions, the peak contact pressure (PCP), total contact area, mean and maximum local contact pressure (LCP) elevation, and total area of LCP elevation of the medial tibiofemoral compartment were quantified. RESULTS: The PCP and total contact area of the medial compartment in the intact knee increased from 2.43 MPa and 361 mm 2 at 4° valgus to 9.09 MPa and 508 mm 2 at 8° of varus. Compared with the intact state, in the MMPRT condition, medial compartment PCP was greater and the total contact area smaller for all alignment conditions. Root repair roughly restored PCPs in the medial compartment; however, this ability was compromised in knees with increasing varus alignment. Specifically, elevations in PCP relative to the intact state increased with increasing varus, as did the total contact area with LCP elevation. After root repair, medial compartment PCP remained elevated above the intact state at all degrees tested, ranging from 0.05 MPa at 4° valgus to 0.27 MPa at 8° of varus, with overall PCP values increasing from 2.48 to 9.09 MPa. For varus alignment greater than 4°, root repair failed to reduce the total contact area with LCP elevation relative to the MMPRT state. DISCUSSION: Greater PCPs and areas of LCP elevation in varus knees may reduce the clinical effectiveness of root repair in delaying or preventing the development of tibiofemoral osteoarthritis.

Biomechanical Assessment of Bicortical Suspension Device Fixation for Proximal Tibiofibular Joint Instability: Single Versus Double Device.

BACKGROUND: Bicortical suspension device (BCSD) fixation treats proximal tibiofibular joint (PTFJ) instability in both the anterolateral and posteromedial directions. However, biomechanical data are lacking as to whether this technique restores the native stability and strength of the joint. PURPOSE: To test (1) if BCSD fixation restores the native stability and strength and (2) if using 2 devices is needed. STUDY DESIGN: Controlled laboratory study. METHODS: Sixteen pairs of fresh-frozen cadaveric specimens were obtained. Six pairs were assigned to the control group and 10 matched pairs assigned for transection to model PTFJ and subsequent BCSD fixation (one specimen with 1-device repair and the other with 2-device repair). Joint stability and strength were assessed by translating the fibular head relative to the fixed tibia either anterolaterally or posteromedially. Control specimens received 20 cycles of 0- to 2.5-mm joint displacement tests (subfailure) and then proceeded to load to failure (5 mm). For the experimental group, cyclic tests were repeated after ligament resection and after fixation. Forces and stiffness at 2.5- and 5-mm displacement were recorded for comparisons of joint strength and stability at subfailure and failure loads, respectively. RESULTS: After repair of anterolateral instability, both the single- and double-device fixations successfully restored near-native states, with no significant differences as compared with the intact group for forces at subfailure load (P = .410) or failure load (P = .397). Regarding posteromedial instability, single-device repair did not restore forces to the near-native state at subfailure load (intact: 92.9 N vs single: 37.4 N; P = .001) or failure load (intact: 170.7 N vs single: 70.4 N; P = .024). However, the double-device repair successfully restored near-native posteromedial forces at both subfailure load (P = .066) and failure load (P = .723). CONCLUSION: For treatment of the most common form of PTFJ instability (anterolateral), this cadaveric study suggests that 1 BCSD is sufficient to restore stability and strength. The current biomechanical results also suggest that 2 devices are needed for restoring PTFJ posteromedial stability and strength. Using 2 devices addresses both types of instability and provides more PTFJ posteromedial stability. CLINICAL RELEVANCE: The results suggest that 1 device should be used for treating anterolateral instability and 2 devices used for posteromedial instability based on the biomechanical study.

Micro-CT Imaging and Mechanical Properties of Ovine Ribs.

The use of ovine animal models in the study of injury biomechanics and modeling is increasing, due to their favorable size and other physiological characteristics. Along with this increase, there has also been increased interest in the development of in silico ovine models for computational studies to compliment physical experiments. However, there remains a gap in the literature characterizing the morphological and mechanical characteristics of ovine ribs. The objective of this study therefore is to report anatomical and mechanical properties of the ovine ribs using microtomography (micro-CT) and two types of mechanical testing (quasi-static bending and dynamic tension). Using microtomography, young ovine rib samples obtained from a local abattoir were cut into approximately fourteen 38 mm sections and scanned. From these scans, the cortical bone thickness and cross-sectional area were measured, and the moment of inertia was calculated to enhance the mechanical testing data. Based on a standard least squares statistical model, the cortical bone thickness varied depending on the region of the cross-section and the position along the length of the rib (p < 0.05), whereas the cross-sectional area remained consistent (p > 0.05). Quasi-static three-point bend testing was completed on ovine rib samples, and the resulting force-displacement data was analyzed to obtain the stiffness (44.67 ± 17.65 N/mm), maximum load (170.54 ± 48.28 N) and displacement at maximum load (7.19 ± 2.75 mm), yield load (167.81 ± 48.12 N) and displacement at yield (6.10 ± 2.25 mm), and the failure load (110.90 ± 39.30 N) and displacement at failure (18.43 ± 2.10 mm). The resulting properties were not significantly affected by the rib (p > 0.05), but by the animal they originated from (p < 0.05). For the dynamic testing, samples were cut into coupons and tested in tension with an average strain rate of 18.9 strain/sec. The resulting dynamic testing properties of elastic modulus (5.16 ± 2.03 GPa), failure stress (63.29 ± 14.02 MPa), and failure strain (0.0201 ± 0.0052) did not vary based on loading rate (p > 0.05).

Biomechanical comparison of Tibial-sided supplemental fixation techniques in Bone-Patellar Tendon-Bone anterior cruciate ligament reconstruction.

PURPOSE: The purpose of this study was to compare the biomechanical properties of a commercially available suture anchor and a screw post for supplemental tibial fixation of a bone-patellar tendon-bone (BTB) graft at time zero. We hypothesized that supplemental fixation using a suture anchor would demonstrate similar biomechanical performance in comparison with a screw post. METHODS: Sixteen fresh frozen, healthy human cadaveric knees underwent BTB autograft harvest, placement, and primary tibial-sided interference screw fixation using a standardized technique performed by a single surgeon. Specimens were randomly assigned to one of two tibial-sided supplemental fixation groups (suture anchor or screw post), yielding eight specimens in each group. Each specimen was affixed to a custom loading apparatus, with the tibial tunnel aligned in a vertical position that allowed for parallel "worst-case scenario" loading and eliminated loading variation due to tibial tunnel angle. Grafts were pretensioned to 30 N and biomechanical performance was compared with respect to cyclical loading between 50-250 N for 500 cycles at 0.5 Hz and pull-to-failure loading at 60 mm/min. RESULTS: The suture anchor and screw post supplemental constructs demonstrated similar performance with respect to all biomechanical parameters assessed, including yield strength (294.0 N [IQR 267.2-304.2 N] versus 332.1 N [IQR 313.8-350.4 N]; P = 0.079) and ultimate strength (330.1 N [IQR 306.9-418.7 N] versus 374.7 N [IQR 362.0-387.3 N]; P = 0.3798). However, of the eight original specimens in each group, one suture anchor specimen (12.5%) and six metallic screw post specimens (75%) failed during cyclical testing and were unable to undergo displacement and load to failure testing. CONCLUSION: This study provides preliminary evidence that supplemental tibial-sided fixation of a BTB ACL graft with a suture anchor has similar loading characteristics or load-to-failure strength when compared to supplemental fixation with a screw post construct. STUDY DESIGN: Laboratory Controlled Study. LEVEL OF EVIDENCE: Basic Science Study.

External Validation of Natural Language Processing Algorithms to Extract Common Data Elements in THA Operative Notes.

BACKGROUND: Natural language processing (NLP) systems are distinctive in their ability to extract critical information from raw text in electronic health records (EHR). We previously developed three algorithms for total hip arthroplasty (THA) operative notes with rules aimed at capturing (1) operative approach, (2) fixation method, and (3) bearing surface using inputs from a single institution. The purpose of this study was to externally validate and improve these algorithms as a prerequisite for broader adoption in automated registry data curation. METHODS: The previous NLP algorithms developed at Mayo Clinic were deployed and refined on EHRs from OrthoCarolina, evaluating 39 randomly selected primary THA operative reports from 2018 to 2021. Operative reports were available only in PDF format, requiring conversion to "readable" text with Adobe software. Accuracy statistics were calculated against manual chart review. RESULTS: The operative approach, fixation technique, and bearing surface algorithms all demonstrated perfect accuracy of 100%. By comparison, validated performance at the developing center yielded an accuracy of 99.2% for operative approach, 90.7% for fixation technique, and 95.8% for bearing surface. CONCLUSION: NLP algorithms applied to data from an external center demonstrated excellent accuracy in delineating common elements in THA operative notes. Notably, the algorithms had no functional problems evaluating scanned PDFs that were converted to "readable" text by common software. Taken together, these findings provide promise for NLP applied to scanned PDFs as a source to develop large registries by reliably extracting data of interest from very large unstructured data sets in an expeditious and cost-effective manner.

The Hybrid Transtibial Technique for Femoral Tunnel Drilling in Anterior Cruciate Ligament Reconstruction: A Finite Element Analysis Model of Graft Bending Angles and Peak Graft Stresses in Comparison With Transtibial and Anteromedial Portal Techniques.

PURPOSE: The purpose of this finite element analysis was to compare femoral tunnel length; anterior cruciate ligament reconstruction graft bending angle; and peak graft stress, contact force, and contact area created by the transtibial, anteromedial portal (AMP), and hybrid transtibial techniques. METHODS: Finite element analysis modeling was used to examine anterior cruciate ligament reconstruction models based on transtibial, AMP, and hybrid transtibial femoral tunnel drilling techniques. An evaluation of femoral tunnel length, graft bending angle, peak graft stress, contact force, and contact area was done in comparison of these techniques. RESULTS: The femoral tunnel created with the hybrid transtibial technique was 45.3 mm, which was 13.3% longer than that achieved with the AMP technique but 15.2% shorter than that with the transtibial technique. The femoral graft bending angle with the hybrid transtibial technique (105°) was less acute than that with the AMP technique (102°), but more acute than that with the transtibial technique (109°). At 11° knee flexion, the hybrid transtibial technique had 22% less femoral contact force, 21% less tibial contact force, 21% less graft tension than the AMP technique. Yet, the hybrid transtibial technique had 41% greater femoral contact force, 39% greater tibial contact force, 33% greater graft tension, and 6% greater graft von Mises stress than the transtibial technique. A similar trend was found for the anterior knee drawer test. At both 6-mm anterior tibial displacement and 11° knee flexion, the hybrid transtibial and AMP techniques had at least 51% more femoral contact area than the transtibial technique. CONCLUSION: This finite element analysis highlights that the hybrid transtibial technique is a true hybrid between the AMP and transtibial techniques for femoral tunnel drilling regarding femoral tunnel length, graft bending angle, and peak graft stress.

Cyclic and Load-to-Failure Properties of All-Suture Anchors in Human Cadaveric Shoulder Greater Tuberosities.

PURPOSE: The purpose of this study was to evaluate the cyclic displacement, stiffness, and ultimate load to failure of 3 all-suture anchors in human cadaveric greater tuberosities. METHODS: Three all-suture anchors indicated for rotator cuff repair were tested in 14 matched pairs of human cadaver fresh-frozen humeri. Anchors were inserted at 3 locations from anterior to posterior along the greater tuberosity and placed 5 mm from the articular margin. The constructs were cycled from 10 to 60 N at 1 Hz for 200 cycles. The anchors that survived cycling were then subjected to a single pull to failure test. A Kruskal-Wallis 1-way analysis of variance on ranks was performed to compare the displacement, stiffness, and ultimate load to failure of the different anchors tested. RESULTS: One matched pair was excluded because of poor bone quality; therefore, 13 matched pairs were included in the study. After 20, 100, and 200 cycles, there was no difference in median displacement between the anchors tested (P = .23, P = .21, P = .18, respectively). The median ultimate load-to-failure between the Iconix (295.2 N, 95% confidence interval [CI], 125-762.2), JuggerKnot (287.6 N, 95% CI, 152.9-584.4), and Q-fix (333.3 N, 95% CI, 165.0-671.9) showed no statistically significant difference (P = .58). After 20, 100, and 200 cycles, there was no difference in median stiffness between the anchors tested (P = .41, P = .19, P = .26 respectively). Displacement greater than 5 mm occurred in 0 Iconix anchors (0%), 1 JuggerKnot anchor (3.64%), and 2 Q-fix anchors (7.69%). One JuggerKnot anchor failed by anchor pullout during cyclic loading. CONCLUSIONS: When tested in human cadaveric humeral greater tuberosities 3 all-suture anchors, the 2.9-mm JuggerKnot, the 2.8-mm Q-fix, and the 2.3-mm Iconix, showed no significant differences in median displacement or stiffness after 20, 100, or 200 cycles or in median ultimate load to failure. Although not statistically significant, the Iconix was the only anchor tested to have no failures, whereas the JuggerKnot had both a clinical and catastrophic failure and the Q-fix had 2 clinical failures. LEVEL OF EVIDENCE: Level V, Controlled Laboratory Study.

Biomechanical Evaluation of an All-Inside Posterior Medial Meniscal Root Repair Technique Via Suture Fixation to the Posterior Cruciate Ligament.

PURPOSE: To evaluate the tibiofemoral contact mechanics of an all-inside posterior medial meniscal root repair technique via suture fixation to the posterior cruciate ligament (PCL) and to compare with that of the intact knee and the knee with a root tear. METHODS: Tibiofemoral contact mechanics were recorded in 8 human cadaveric knee specimens using pressure sensors. Each knee underwent 3 testing conditions related to the posterior medial meniscal root: (1) intact knee; (2) root tear; and (3) all-inside repair via suture fixation to the PCL. Knees were loaded with a 1000-N axial compressive force at 4 knee flexion angles (0°, 30°, 60°, 90°). Calculations were performed for contact area, mean contact pressure, and peak contact pressure. A generalized linear model with a Tukey adjusted least square means test was used to determine differences between testing conditions. RESULTS: Across all knee flexion angles, there was an overall mean 26.3% reduction in contact area with root tear (211.34 mm2 vs intact 286.64 mm2, P = .0002), and a 31.6% increase from root tear to repair (277.61 mm2, P = .0297). Across all knee flexion angles, there was an overall mean 24.3% increase in contact pressure with root tear (1849.12 N/mm2 vs. intact 1487.52 N/mm2, P < .0001), and a 31.1% decrease from root tear to repair (1410.7 N/mm2, P = .0037). Across all knee flexion angles, there was an overall mean 10.6% increase in peak contact pressure with root tear (4083.55 N/mm2 vs. intact 3693.68 N/mm2, P < .0001), and a 12.4% decrease from root tear to repair (3632.13 N/mm2, P = .531). CONCLUSIONS: In most testing conditions and with overall averaging across knee flexion angles, the all-inside posterior medial meniscal root repair with suture fixation to the adjacent PCL fibers restored contact area (from 26.3% reduction with root tear to 31.6% increase with repair), contact pressures (from 24.3% increase with root tear to 31.1% decrease with repair), and peak contact pressures (from 10.6% increase with root tear to 12.4% decrease with repair) to that of the intact knee This may be a future potential technique to limit complications associated with the traditional transtibial pull-out method of repair. CLINICAL RELEVANCE: This technique may provide a posterior medial meniscal root repair construct that restores most tibiofemoral contact mechanics and offers theoretical benefits of technical ease and potential for an acceptable, less "anatomic" repair location.

Use of an instrumented dual-task timed up and go test in children with traumatic brain injury.

BACKGROUND: Wearable sensors have allowed researchers to instrument tests of gait-related mobility, including the widely used timed 'up-and-go' test (TUG). Currently, there is a lack of instrumented test data on whether children with moderate to severe traumatic brain injury (TBI) perform differently on the TUG compared to typically developed (TD) controls during a cognitive-motor task. RESEARCH QUESTION: The aim was to explore the effects of a cognitive-motor task on TUG subcomponents among children with TBI compared to TD children. METHODS: This observational cross-sectional study included 12 children with moderate to severe TBI (6 males and 6 females, age 10.5 ±â€¯1.5 years of age) and 10 age and sex-matched TD controls (5 males and 5 females, 10.4 ±â€¯1.3 years of age). Each participant completed 6 trials of the TUG wearing a single inertial measurement unit sensor at a self-selected walking pace while listening to an array of 10 randomly presented single digits during each TUG trial. RESULTS: Total time to complete the TUG was not significantly different between groups. The cognitive-motor task led to significantly lower mean turn and peak turn angular velocity values during the turn-around-the-cone and turn-before-sitting TUG subcomponents in children with TBI compared to the TD controls (p ≤ 0.05). Additionally, the cognitive-motor task led to significantly lower values for maximum torso flexion to extension angle, peak flexion and extension angular velocity and peak vertical acceleration for the sit-to-stand subcomponent (p < 0.05). Peak flexion angular velocity during the stand-to-sit subcomponent was lower for the TBI group compared to the children with TD (p < 0.05). SIGNIFICANCE: The study provides new insights into the performance of complex gait-related mobility tasks in the context of an instrumented TUG among children with moderate to severe TBI. Our results highlight the potential benefits of outfitting pediatric inpatients with an IMU while completing the TUG.

Cyclic and Load-to-Failure Properties of All-Suture Anchors in Human Cadaveric Shoulder Glenoid Bone.

PURPOSE: To evaluate the cyclic displacement and ultimate load to failure of 4 all-suture anchors in human cadaveric shoulder glenoid bone. METHODS: Four all-suture anchors indicated for glenoid labral repair were tested in 14 matched pairs of human cadaveric fresh-frozen glenoids. Anchors were inserted at 4 different locations for a total of 112 tests (12-, 3-, 6-, and 9-o'clock positions for right glenoids). Cyclic loading (10 to 60 N at 1 Hz for 200 cycles) and single pull-to-failure testing (33 mm/s) were performed. A Kruskal-Wallis 1-way analysis of variance with the Dunn multiple-comparison post hoc test was used for statistical analysis. RESULTS: One matched pair was excluded because of poor bone quality. Thus, 13 matched pairs were included in the study, and a total of 104 tests were performed. The Q-Fix anchors showed significantly less displacement after 100 cycles (mean ± standard deviation, 1.40 ± 0.97 mm; P < .001) and 200 cycles (1.53 ± 1.00 mm, P < .001) than all other anchors tested. The Q-Fix (191.3 ± 65.8 N), Suturefix (188.3 ± 61.4 N), and JuggerKnot (183.6 ± 63.5 N) anchors had significantly greater ultimate loads to failure than the Iconix anchors (143.5 ± 54.1 N) (P = .01, P = .012, and P = .021, respectively). Displacement greater than 5 mm occurred in 6 Iconix anchors (22.1%), 5 Suturefix anchors (19.2%), 4 JuggerKnot anchors (15.4%), and 0 Q-Fix anchors (0%). CONCLUSIONS: The Q-Fix anchors showed less displacement with cyclic loading than the Iconix, JuggerKnot, and Suturefix anchors. The Iconix anchors had a lower ultimate load to failure than the Q-Fix, Suturefix, and JuggerKnot anchors. Only the Q-Fix group had no anchors displace greater than 5 mm with cyclic loading. CLINICAL RELEVANCE: All-suture anchors vary in their deployment mechanism, which may alter their strength and performance. Operators must be aware of these anchors' propensity to displace while deploying them.

Greater Tuberosity Decortication Decreases Load to Failure of All-Suture Anchor Constructs in Rotator Cuff Repair.

PURPOSE: To evaluate the effect of greater tuberosity decortication on ultimate load to failure and displacement after cyclic loading with an all-suture anchor. METHODS: A 2.9-mm all-suture anchor was evaluated in decorticated and nondecorticated greater tuberosities of 10 matched pairs of human cadaveric shoulders. Greater tuberosity decortication was performed to a mean depth of 1.7 mm. Anchors were placed in the anterior, middle, and posterior tuberosity. Anchors were tested under cyclic loads followed by load-to-failure testing. Displacement after 20, 100, and 200 cycles and ultimate failure strength were determined. Clinical failure was defined as displacement greater than 5 mm during cyclic loading. RESULTS: After 20 and 100 cycles, there was no difference in mean displacement between the decorticated and nondecorticated cohorts (P = .139 and P = .127, respectively). The mean displacement after 200 cycles was greater in the decorticated cohort, although not significantly (3.4 vs 2.7 mm; P = .05). The mean ultimate load to failure was significantly lower in the decorticated cohort (314 vs 386 N, P = .049). There were 2 clinical failures in the decorticated specimens and 1 in the nondecorticated specimens. CONCLUSIONS: A minimal greater tuberosity decortication significantly decreases the ultimate load to failure of an all-suture anchor. However, decreased biomechanical strength may not necessitate actual clinical failure. CLINICAL RELEVANCE: A decrease in ultimate load to failure could increase the risk of catastrophic postoperative anchor failure. However, while this decrease in strength is statistically significant, the overall decrease in strength may not be sufficient in magnitude to translate to clinical failure.

Reliability of the sub-components of the instrumented timed up and go test in ambulatory children with traumatic brain injury and typically developed controls.

BACKGROUND: Studies have evaluated the test-re-test reliability of subcomponents of the timed up and-go test in adults by using body-worn inertial sensors. However, studies in children have not been reported in the literature. RESEARCH QUESTION: To evaluate the within-session reliability of subcomponents of a newly developed electronically augmented timed 'upand-go' test (EATUG) in ambulatory children with traumatic brain injury (TBI) and children with typical development (TD). METHOD: The timed up and go test was administered to twelve consecutive ambulatory children with moderate to severe TBI (6 males and 6 females, age 10.5 ±â€¯1.5 years, range 8-13 years, during inpatient rehabilitation at 27.0 ±â€¯11.8 days following injury) and 10 TD age and sex-matched children (5 males and 5 females, 10.4 ±â€¯1.3 years, range 8-11 years). Participants wore a single chest-mounted inertial measurement sensor package with custom software that measured angular and acceleration velocity and torso flexion and extension angles, while they performed 6 trials of the EATUG test. Measures were derived from the overall time to complete the TUG test, angular velocity and angular displacement data for torso flexion and extension during sit-to-stand and stand-to-sit segments and both mean and peak angular velocities for two turning segments (i.e. turning around a cone and turning-before-sitting). RESULTS: Within-session reliability of the subcomponents of the TUG test for children with TBI assessed by the intra-class correlation coefficient was ICC (1,1) = 0.84, (range 0.82-0.96), and for TD children ICC (1,1) = 0.73, (range 0.53-0.89). Scores on Total Time, maximum torso flexion/extension angle and peak flexion angular velocity during sit-tostand, and peak turn angular velocity for both turns around the cone and turns before sitting were lower for children with TBI than for TD children (p ≤ 0.05). SIGNIFICANCE: The EATUG test is a reliable measure of physical function in children with TBI who are being discharged from inpatient rehabilitation.

Cortical Button Fixation: A Better Patellar Tendon Repair?

BACKGROUND: Patellar tendon ruptures require surgical repair to optimize outcomes, but no consensus exists regarding the ideal repair technique. Cortical button fixation is a secure method for tendon repair that has not been studied in patellar tendons. HYPOTHESIS: Cortical button repair is biomechanically superior to the standard transpatellar repair and biomechanically equivalent to suture anchor repair. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-three fresh-frozen cadaveric knees were used to compare 3 techniques of patellar tendon repair after a simulated rupture at the inferior pole of the patella. Repairs were performed at 45° of flexion using a standard transpatellar suture repair (n = 7), polyetheretherketone (PEEK) suture anchor repair (n = 8), or cortical button repair (n = 8). All specimens were tested on a custom apparatus to simulate cyclic open kinetic chain quadriceps contraction from extension to 90o of flexion. Outcomes of gap formation up to 250 cycles, maximum load to failure, and mode of failure were evaluated. RESULTS: Cortical button repair had significantly less gap formation than anchor repair after 1 cycle (P < .001) and 20 cycles (P < .01) and significantly less gap formation than suture repair from 1 to 250 cycles (P < .05). Cortical button repair sustained significantly higher loads to failure than anchor repair and suture repair (P < .001). All suture repairs failed through the suture. Anchor repairs failed at the suture-anchor eyelet interface (n = 4) or by anchor pullout (n = 3). Cortical button repairs either failed through the suture (n = 5), secondary failure of the patellar tendon (n = 2), or subsidence of the button through the anterior cortex of the patella (n = 1). CONCLUSION: Patellar tendon repair using cortical button fixation demonstrated mechanical advantages over suture repair and anchor repair in cadaveric specimens. Cortical button fixation showed less cyclic gap formation and withstood at least twice the load to failure of the construct. CLINICAL RELEVANCE: The biomechanical superiority of cortical button fixation may impart clinical advantages in accelerating postoperative rehabilitation.

Deformation of 1-piece metal acetabular components.

The success of metal bearings is dependent on several parameters. The effects of in vivo forces on the deformation of monoblock acetabular components have yet to be determined. The purpose of our study was to assess the amount of deformation with press-fit fixation of 1-piece metal acetabular components. Four manufacturers provided 1-piece metal acetabular components in each size (30 cups). Testing was conducted using a custom vise to simulate press-fit fixation, and measurements were performed with a Mitutoyo Test device (Aurora, Ill). Previously determined in vivo forces were used in the press-fit simulation. All components deformed under simulated in vivo applied loads. Component deformation ranged from 15 to 300 µm. Larger cups with thinner walls to accommodate larger heads had the greatest deformation and often exceeded the range of reported clearances from the manufacturers (76-227 µm).

A biomechanical evaluation of ulnar collateral ligament reconstruction using a novel technique for ulnar-sided fixation.

BACKGROUND: Techniques for ulnar collateral ligament (UCL) reconstruction have evolved since its original description. HYPOTHESIS: Ulnar collateral ligament reconstruction using the ZipLoop for ulnar-sided fixation, as combined with the humeral docking technique supplemented with an interference screw, will restore valgus stability similar to that of the Jobe technique and the native ligament. STUDY DESIGN: Controlled laboratory study. METHODS: Kinematic testing was performed on 8 matched pairs of cadaver elbows with an electromagnetic tracking system through an arc of motion for the intact, disrupted, and reconstructed states of the UCL in an unloaded and loaded condition. From each pair, the docking technique using the ZipLoop for ulnar fixation and humeral docking technique supplemented with an interference screw and the traditional Jobe technique were performed with matched gracilis allograft tendons. After kinematic testing, both reconstruction groups were tested to failure at 70 degrees of flexion. RESULTS: Kinematic results for the unloaded condition showed that both reconstruction techniques significantly overcorrected (less valgus angulation) the specimens between 40 degrees and 120 degrees of flexion when compared with the intact ligament (all P values < .027). Under loaded conditions, the ulnar trajectories for both reconstruction techniques exhibited significantly greater valgus angulation (undercorrection) at 20 degrees of flexion (Jobe, P = .0084; ZipLoop, P = .0289) when compared with the intact ligament but were not significantly different over the remaining arc of motion. Failure testing resulted in no significant statistical difference between the 2 reconstruction groups. Failure testing demonstrated that humeral tunnel egress, midsubstance elongation, and ulnar tunnel egress of the ligament were similar between the reconstruction techniques. CONCLUSION: The docking technique using the ZipLoop for ulnar-sided fixation is biomechanically equivalent to the Jobe technique for UCL reconstruction. Both reconstruction techniques restore valgus stability similar to that of the native UCL ligament. CLINICAL RELEVANCE: This modification in the docking technique restores elbow kinematics while eliminating the risk of ulnar bone bridge fracture, and it allows for retensioning of the graft after cortical fixation.