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BACKGROUND: In difficult ankle arthrodesis situations, intramedullary (IM) arthrodesis nails and external fixation are often considered in lieu of standard fusion techniques. The purpose of this study was to compare the amount of micromotion measured across an ankle fusion site stabilized with either an IM nail or with the Ilizarov external fixator. MATERIALS AND METHODS: The relative bone mineral density of 8 pairs of human cadaveric lower legs was measured by DEXA scanning. One specimen from each pair was randomly assigned to be stabilized with a new generation IM nail and the other with an Ilizarov external fixator. Specimens were tested in compression, rotation, and dorsiflexion. Optical motion capture was used to measure the direct motion occurring at the fusion site. RESULTS: No significant difference was found between the axial displacements (p = 0.94), torsional displacement (p = 0.07), or the dorsiflexion angular displacement (p = 0.28) for the IM rod group and the external fixation group. A weak correlation was found between BMD and displacement. CONCLUSION: Both the new generation IM nail and the Ilizarov external fixator imparted excellent stability to the fusion site despite a wide range of bone mineral densities. Medialization of the talus, the ability to compress the nail, and the addition of a posterior-to-anterior locking screw were thought to improve the performance of the nail. CLINICAL RELEVANCE: Both IM nail and Ilizarov external fixation provided excellent fusion site stability. The decision of which implant to use for complex arthrodesis should be dictated by the clinical needs. [ABSTRACT FROM AUTHOR]

Background: Dislocation after total hip arthroplasty (THA) is a primary reason for THA revision. During THA through the direct anterior approach (DAA), the iliofemoral ligament, which provides the main resistance to external rotation (ER) of the hip, is commonly partially transected. We asked: (1) what is the contribution of the medial iliofemoral ligament to resisting ER after DAA THA? and (2) how much resistance to ER can be restored by repairing the ligament?, Methods: A fellowship-trained surgeon performed DAA THA on 9 cadaveric specimens. The specimens were computed tomography scanned before and after implantation. Prior to testing, the ER range of motion of each specimen to impingement in neutral and 10° of extension was computationally predicted. Each specimen was tested on a 6-degrees-of-freedom robotic manipulator. The pelvis was placed in neutral and 10° of extension. The femur was externally rotated until it reached the specimen's impingement target. Total ER torque was recorded with the medial iliofemoral ligament intact, after transecting the ligament, and after repair. Torque at extremes of motion was calculated for each condition. To isolate the contribution of the native ligament, the torque for the transected state was subtracted from both the native and repaired conditions., Results: The medial iliofemoral ligament contributed an average of 68% (range, 34 to 87) of the total torque at the extreme of motion in neutral and 80% (58 to 97) in 10⁰ of extension. The repaired ligament contributed 17% (1 to 54) of the total torque at the extreme of motion in neutral and 14% (5 to 38) in 10⁰ of extension, restoring on average 18 to 25% of the native resistance against ER., Conclusions: The medial iliofemoral ligament was an important contributor to the hip torque at the extreme of motion during ER. Repairing the ligament restored a fraction of its ability to generate torque to resist ER., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Anterior cervical discectomy and fusion (ACDF) is known to elicit adverse biomechanical effects on immediately adjacent segments; however, its impact on the kinematics of the remaining nonadjacent cervical levels has not been understood. This study aimed to explore the biomechanical impact of ACDF on kinematics beyond the immediate fusion site. We hypothesized that compensatory motion following single-level ACDF is not predictably distributed to adjacent segments due to compensation from noncontiguous levels., Methods: Six fresh-frozen cervical spines (C2-T1) underwent fluoroscopic screening and sagittal and coronal reformats from computed tomography scans and were utilized to grade segmental degeneration. Each specimen was tested to 30° of flexion and extension intact and following single-level ACDF at the C5-C6 level. The motions of each vertebral body were tracked using 3-dimensional (3D) motion capture into an inverse kinematics model, facilitating correlations between the 3D reconstruction from computed tomography images and the 3D motion capture data. This model was used to calculate each level's flexion/extension range of motion (ROM)., Results: Single-level fusion at the C5-C6 level across all specimens resulted in a significant motion reduction of -6.8° ( P = 0.002). No significant change in ROM occurred in the immediate adjacent segments C4-C5 ( P = 0.07) or C6-C7 ( P = 0.15). Hypermobility was observed in 2 specimens (33%) exclusively in adjacent segments. In contrast, the other 4 spines (66%) displayed hypermobility at noncontiguous segments. Hypermobility occurred in 42% (5/12) of the adjacent segments, 28% (5/18) of the noncontiguous segments, and 50% (3/6) of the cervicothoracic segments., Conclusion: Single-level ACDF impacts ROM beyond adjacent segments, extending to noncontiguous levels. Compensatory motion, not limited to adjacent levels, may be influenced by degenerative changes in noncontiguous segments. Surprisingly, hypermobility may not occur in adjacent segments after ACDF., Clinical Relevance: Overall, the multifaceted biomechanical effects of ACDF underscore the need for a comprehensive understanding of cervical spine dynamics beyond immediate adjacency, and it needs to be taken into consideration when planning single-level ACDF., Competing Interests: Declaration of Conflicting Interests : The authors report no conflicts of interest in this work., (This manuscript is generously published free of charge by ISASS, the International Society for the Advancement of Spine Surgery. Copyright © 2024 ISASS. To see more or order reprints or permissions, see http://ijssurgery.com.)

Background: Multiple animal models have previously been utilized to investigate anterior fusion techniques, but a mouse model has yet to be developed. The purpose of this study was to develop murine anterior interbody and posterolateral fusion techniques., Methods: Mice underwent either anterior interbody or posterolateral spinal fusion. A protocol was developed for both procedures, including a description of the relevant anatomy. Samples were subjected to micro-computed tomography to assess fusion success and underwent biomechanical testing with use of 4-point bending. Lastly, samples were fixed and embedded for histologic evaluation., Results: Surgical techniques for anterior interbody and posterolateral fusion were developed. The fusion rate was 83.3% in the anterior interbody model and 100% in the posterolateral model. Compared with a control, the posterolateral model exhibited a greater elastic modulus. Histologic analysis demonstrated endochondral ossification between bridging segments, further confirming the fusion efficacy in both models., Conclusions: The murine anterior interbody and posterolateral fusion models are efficacious and provide an ideal platform for studying the molecular and cellular mechanisms mediating spinal fusion., Clinical Relevance: Given the extensive genetic tools available in murine disease models, use of fusion models such as ours can enable determination of the underlying genetic pathways involved in spinal fusion., Competing Interests: Disclosure: This study was supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health (NIH) under award number T32-AR078751 (K.W.M.) and by NIH awards DP5OD021351 and R01AR075585 (M.B.G.). This study is also based on research supported by Pershing Square Sohn Cancer Research Alliance and Pershing Square Foundation MIND Prize awards to M.B.G. M.B.G. holds a Career Award for Medical Scientists from the Burroughs Welcome Fund. S.I. is supported by the Kellen Scholar Award. J.S. is supported by a Children’s Tumor Foundation Young Investigator Award (CTF-2023-01-005; https://doi.org/10.48105/CTF.CTF-2023-01-005.pc.gr.172007 ). A.R.Y. is supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health under award number T32-AR071302-07. S.B. is supported by a National Research Foundation of Korea award funded by the Ministry of Education (NRF-2021R1A6A3A14038667), the Arthritis Grant Program from the Arthritis National Research Foundation (1065843), and Weill Cornell Medicine JumpStart Awards (Year 2022). S.D. is supported by an NIH K99 grant (DE031819-01), a Department of Defense grant (W81XWH-22-PRMRP-DA), and Weill Cornell Medicine JumpStart Awards (Year 2019). The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article ( http://links.lww.com/JBJS/H833 )., (Copyright © 2024 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: Tissue-engineered intervertebral disc (TE-IVD) constructs are an attractive therapy for treating degenerative disc disease and have previously been investigated in vivo in both large and small animal models. The mechanical environment of the spine is notably challenging, in part due to its complex anatomy, and implants may require additional mechanical support to avoid failure in the early stages of implantation. As such, the design of suitable support implants requires rigorous validation., Methods: We created a FE model to simulate the behavior of the IVD cages under compression specific to the anatomy of the porcine cervical spine, validated the FE model using an animal model, and predicted the effects of implant location and vertebral angle of the motion segment on implant behavior. Specifically, we tested anatomical positioning of the superior vertebra and placement of the implant. We analyzed corresponding stress and strain distributions., Results: Results demonstrated that the anatomical geometry of the porcine cervical spine led to concentrated stress and strain on the posterior side of the cage. This stress concentration was associated with the location of failure of the cages reported in vivo, despite superior mechanical properties of the implant. Furthermore, placement of the cage was found to have profound effects on migration, while the angle of the superior vertebra affected stress concentration of the cage., Conclusions: This model can be utilized both to inform surgical procedures and provide insight on future cage designs and can be adopted to models without the use of in vivo animal models., Competing Interests: Lawrence J. Bonassar, Ibrahim Hussain, and Roger Härtl are consultants for 3DBio Therapeutics Corp., Lawrence J. Bonassar is co‐founder of 3DBio Therapeutics Corp. Remaining authors declare no conflict of interests. This work was partially funded by the Daedulus Fund., (© 2023 The Authors. JOR Spine published by Wiley Periodicals LLC on behalf of Orthopaedic Research Society.)

Purpose: To characterize the ability of the intact medial patellofemoral ligament (MPFL) and the adductor transfer and adductor sling MPFL reconstruction techniques to resist subluxation and dislocation in a cadaveric model., Methods: Nine fresh-frozen cadaveric knees were placed on a custom testing fixture with the femur fixed parallel to the floor, the tibia placed in 20° of flexion, and the patella attached to a load cell. The patella was displaced laterally, and subluxation load (in newtons), dislocation load (in newtons), maximum failure load (in newtons), patellar displacement at failure, and mode of failure were recorded. Testing was conducted with the MPFL intact and after the adductor sling and adductor transfer reconstruction techniques. Statistical analysis was completed using 1-way repeated-measures analysis of variance with the Holm-Šidák post hoc test., Results: The subluxation load was not significantly different between groups. The native MPFL dislocation load was significantly higher than the dislocation loads of both reconstruction techniques, but no significant difference between the dislocation loads of the 2 reconstruction techniques occurred. The native MPFL failure load was significantly higher than the failure loads of both reconstruction techniques. The adductor sling failure load was significantly higher than the adductor transfer failure load. The mode of failure varied across groups. The native MPFL failed by femoral avulsion, patellar avulsion, and midsubstance tear. The main mode of failure for adductor transfer was pullout, whereas failure for the adductor sling technique most often occurred at the sutures. Most of the native MPFLs and all adductor sling reconstructions failed after dislocation. The adductor transfer reconstructions were much more variable, with failures spanning from before subluxation through dislocation., Conclusions: Our cadaveric model showed that neither the adductor transfer technique nor the adductor sling technique restored failure load to that of the native condition. There was no significant difference in the subluxation or dislocation loads between the 2 MPFL reconstructions, but the adductor sling technique resulted in a higher load to failure. The adductor transfer technique frequently failed before subluxation or dislocation when compared with the adductor sling technique and the native MPFL., Clinical Relevance: The best technique for MPFL reconstruction in patients with open physes is a topic of debate. Given the long-term consequences of MPFL injury and potential for growth plate disturbance, it is important to study MPFL reconstruction techniques thoroughly, including in the laboratory setting., (© 2023 The Authors.)

Purpose: To quantify the maximum load to fracture in patellae from which bone-patellar tendon-bone (BPTB) and bone-quadriceps tendon (BQT) autografts have been harvested for anterior cruciate ligament reconstruction in a cadaveric model., Methods: Forty-six fresh-frozen patellae were isolated and divided into the BPTB harvest and BQT harvest groups with matching based on donor age and sex. Computed tomography scans were obtained to calculate bone mineral density (BMD) and patellar height, width, and thickness. BPTB and BQT grafts were harvested from the inferior patella and superior patella, respectively, and then ramped to failure in a 3-point bend test configuration to simulate a postoperative fracture produced by a direct impact after a fall. The presence of fracture, fracture pattern, and maximum load to fracture were recorded. Donor demographic characteristics; patellar height, width, and thickness; and maximum load were compared by the Student t test. Pearson correlations were used to determine whether maximum load was affected by BMD or patellar morphology. The level of significance was set at P < .05., Results: Maximum load to fracture was not significantly different ( P  = .91) between the BPTB (5.0 ± 2.3 kN) and BQT (5.1 ± 2.6 kN) groups. Maximum load to fracture in the BPTB group did not correlate with BMD ( P  = .57) or patellar measurements ( P  = .57 for thickness, P  = .43 for width, and P  = .45 for height). Maximum load to fracture in the BQT group positively correlated with BMD and negatively correlated with patellar height. Maximum load to fracture in the BQT group did not correlate with patellar thickness or width. Fracture through the harvest site was observed in 87% of BPTB specimens and 78% of BQT specimens., Conclusions: The location of the BPTB or BQT autograft harvest site did not significantly affect patellar load to fracture in a cadaveric model., Clinical Relevance: It is important to understand patellar morphology and the effect of BPTB and BQT graft harvest-site locations on the biomechanical strength of the patella after anterior cruciate ligament reconstruction., Competing Interests: The authors report the following potential conflicts of interest or sources of funding: S.S.B. receives personal fees from Exactech and grant support from Peerless Surgical, 10.13039/100009026Smith & Nephew, and 10.13039/100008894Stryker, outside the submitted work. G.E.O. receives personal fees from Exactech and grant support from Peerless Surgical, outside the submitted work. S.A.M. is an equity holder in AGelity Biomechanics, outside the submitted work. K.S. receives personal fees from Medical Device Business Services and DePuy and grant support from 10.13039/100007307Arthrex and Gotham Surgical Solutions & Devices, outside the submitted work. All other authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Full ICMJE author disclosure forms are available for this article online, as supplementary material., (© 2023 The Authors.)

Background: Patellofemoral (PF) dysplasia is common in patients with recurrent patellar instability. Tibial tubercle osteotomy (TTO) is performed with goals of correcting patellar maltracking and redistributing contact forces across the PF joint. The biomechanical effects of TTO in the setting of PF dysplasia have not been quantified., Purpose/hypothesis: To quantify patellar contact mechanics and kinematics after TTO in the setting of PF dysplasia. We hypothesized that a simulated anteromedialization (AMZ) TTO would improve PF contact mechanics as compared with a pure medialization TTO., Study Design: Controlled laboratory study., Methods: PF dysplasia with Dejour type D classification was simulated in 7 cadaveric knees by replacing the native patellar and trochlear surfaces with synthetic polymeric patellar and trochlear implants. On each specimen, a flat TTO was fixed in 3 distinct positions simulating a pathologic lateralized tubercle (pathologic condition), a medialized tubercle (Elmslie Trillat), and an AMZ tubercle. The sum of forces acting on the medial and lateral patellar facet and patellar kinematics was computed for each knee for each condition from 0° to 70° of flexion at 10° increments., Results: Relative to the pathologic condition, AMZ TTO decreased contact forces across the lateral facet (20°-50° and 70° of flexion). Relative to the pathologic condition, Elmslie Trillat TTO had no effect on contact forces on either compartment. Relative to the Elmslie Trillat TTO, the AMZ TTO had significantly decreased contact forces across the medial facet (at 40°, 60°, and 70° of flexion). No significant differences in joint kinematics occurred across any groups., Conclusion: Of all groups studied, AMZ TTO resulted in significantly decreased patellar contact forces in simulated dysplastic PF joints. AMZ may be considered in certain patients with PF dysplasia to avoid medial compartment PF chondral overload., Clinical Relevance: PF dysplasia is common in patients with recurrent patellar instability who warrant surgical intervention to prevent subsequent recurrence. Numerous interventions to treat this condition, including various TTOs, have been proposed without a clear consensus. This cadaveric biomechanical study demonstrates that AMZ TTO resulted in more favorable PF contact mechanics than Elmslie Trillat TTO in a model representing PF dysplasia. AMZ TTO may be considered for patients in the setting of recurrent instability with PF dysplasia to avoid cartilage overload on the medial compartment of the PF joint.

Study Design: Prospective randomized placebo controlled animal trial., Objective: Determine the effect of daily subcutaneous abaloparatide injection on the intervertebral fusion rate in rabbits undergoing posterolateral fusion., Study of Background Data: Despite the wide utilization of spine fusion, pseudarthrosis remains prevalent, and results in increased morbidity. Abaloparatide is a novel analog of parathyroid hormone-related peptide (1-34) and has shown efficacy in a rat posterolateral spine fusion model to increase fusion rates. The effect of abaloparatide on the fusion rate in a larger animal model remains unknown., Materials and Methods: A total of 24 skeletally mature New Zealand White male rabbits underwent bilateral posterolateral spine fusion. Following surgery, the rabbits were randomized to receive either saline as control or abaloparatide subcutaneous injection daily. Specimens underwent manual assessment of fusion, radiographic analysis with both x-ray and high-resolution peripheral quantitative computed tomography, and biomechanical assessment., Results: Rabbits that received abaloparatide had a 100% (10/10) fusion rate compared with 45% (5/11) for controls ( P <0.02) as assessed by manual palpation. Radiographic analysis determined an overall mean fusion score of 4.17±1.03 in the abaloparatide group versus 3.39±1.21 for controls ( P <0.001). The abaloparatide group also had a greater volume of bone formed with a bone volume of 1209±543 mm 3 compared with 551±152 mm 3 ( P <0.001) for controls. The abaloparatide group had significantly greater trabecular bone volume fraction and trabecular thickness and lower specific bone surface and connectivity density in the adjacent levels when compared with controls. Abaloparatide treatment did not impact trabecular number or separation. There were no differences in biomechanical testing in flexion, extension, or lateral bending ( P >0.05) between groups., Conclusions: Abaloparatide significantly increased the fusion rate in a rabbit posterolateral fusion model as assessed by manual palpation. In addition, there were marked increases in the radiographic evaluation of fusion., Competing Interests: The authors report no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Background: An extended trochanteric osteotomy (ETO) safely addresses femoral component removal during challenging revision total hip arthroplasty. However, no prior study has evaluated whether a difference in axial stability exists between ETO closure performed before (reconstitution) or after (scaffolding) canal preparation and stem impaction. We hypothesized that given the absence of clinical reports of outcome differences despite the wide use of both practices, no significant difference in the initial axial stability would exist between the 2 fixation techniques., Methods: ETOs were performed and repaired using the reconstitution technique for the 6 right-sided femora and the scaffolding technique for the six left-sided femora. The 195-mm long, 3.5°-tapered splined titanium monobloc stems were impacted into 6 matched pairs of human fresh cadaveric femora. Three beaded cables were placed in a standardized fashion on each specimen, 1 for prophylaxis against osteotomy propagation during reaming/impaction and 2 to close the ETO. Stepwise axial loading was performed to 2600 N or until failure, which was defined as subsidence >5 mm or femoral/cable fracture., Results: All specimens successfully resisted axial testing, with no stem in either ETO repair group subsiding >2 mm. The mean subsidence for the reconstitution group was 0.9 ± 0.4 mm, compared to 1.2 ± 0.5 mm for the scaffolding group (P = .2)., Conclusion: In this cadaveric model with satisfactory proximal bone stock, no difference existed between the reconstitution and scaffolding ETO repair techniques, and both provide sufficient immediate axial stability in a simulated revision total hip arthroplasty setting under physiologic loads., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Current reconstruction techniques do not re-create the distal ulnar collateral ligament (UCL) insertion. Reconstructing the distal extension of the anterior band ulnar footprint may increase elbow stability and resistance against valgus stress after UCL reconstruction (UCLR)., Purpose/hypothesis: The purpose was to test a new technique for UCLR, a modification of the docking technique, aimed at re-creating the distal ulnar footprint anatomy of the anterior band. We hypothesize that this novel "anatomic" technique will provide greater resistance to valgus stress after UCLR when compared with the docking technique., Study Design: Descriptive laboratory study., Methods: Eighteen unpaired cadaveric arms were dissected to capsuloligamentous elbow structures and potted. With use of a servohydraulic load frame, 5 Nċm of valgus stress was placed on the UCL-intact elbows at 30°, 60°, 90°, and 120° of flexion. UCLR was performed on each elbow, randomized to either the docking technique or the anatomic technique. After UCLR, the elbow was again tested at 30°, 60°, 90°, and 120° of flexion. Ulnohumeral joint gapping was calculated using a 3-dimensional motion capture system applied to markers attached to the ulna and humerus. Differences in gapping among the intact state and docking and anatomic techniques were compared using a 2-way analysis of variance with significance set to P < .05., Results: There was no significant difference in gapping between the anatomic and docking technique groups regardless of elbow flexion angle. All reconstructed groups showed increased gapping relative to intact, but all increases were below the clinically relevant level of 1 mm., Conclusion: Ulnohumeral joint gapping and resistance to valgus stress were similar between the anatomic technique and the docking technique for UCLR., Clinical Relevance: This study provides evidence that the anatomic technique is a viable alternative UCLR method as compared with the docking technique in a cadaveric model.

Purpose: To compare the kinematic effects of the dorsal fiber-splitting approach for scapholunate ligament repair to a dorsal "window" approach that spares all ligaments., Methods: We randomized 24 fresh-frozen paired cadaveric forearms to either the dorsal fiber-splitting capsulotomy approach (FSC) or the dorsal window approach (window) following scapholunate interosseous ligament (SLIL) division. Loaded fluoroscopic radiographs were obtained after each of the 4 testing conditions following cyclic loading (200 cycles; 71 N): (1) intact SLIL, (2) SLIL-division, (3) surgical approach, and (4) closure. FSC specimens were randomly allocated to 2 subgroups for closure with either a suture anchor (n = 6) or a simple running suture closure (n = 6). Radiographic parameter measurements included the scapholunate gap, radiolunate angle, scapholunate angle, and dorsal scaphoid translation., Results: Following the FSC, there were significant alterations in all radiographic parameters when compared with the intact and SLIL-division conditions. The window approach did not result in significant changes in any radiographic parameter. When compared to the window approach, all radiographic parameters of the FSC approach were significantly altered. Following closure with suture anchors in the FSC group, radiographic parameters improved, whereas with standard closure they failed to do so. Despite anchor closure, dorsal scaphoid translation, radiolunate angle, and scapholunate angle all remained elevated compared with scapholunate-divided wrists., Conclusions: The FSC produced significant changes in carpal posture under load, including scapholunate diastasis, dorsal intercalated segment instability, and dorsal scaphoid translation in SLIL-deficient wrists. The window approach preserved the critical dorsal ligament stabilizers and did not produce changes in carpal posture., Clinical Relevance: The FSC may create iatrogenic changes in carpal posture that cannot be fully corrected with standard or anchor closure. The window approach does not alter carpal posture and should be considered when performing surgical procedures on the scaphoid or lunate., (Copyright © 2021 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

Purpose: The study was to determine the effect of locking hole inserts and their insertion torque on the fatigue life of a large fragment Locking Compression Plate (LCP) under bending forces., Methods: Fatigue strength of the LCP was examined using cyclic three-point bend testing at 80% yield strength of the construct. Locking hole inserts were used in 2, 4, and 6-hole of a 12-hole plate to simulate three different working lengths. Within each working length, plates were tested without locking inserts serving as the control group. In the experimental groups, inserts were tightened to manufacturer recommendations (4 Nm) and using overtorque (8 Nm)., Results: Significantly fewer cycles to failure were observed in control groups versus the locking hole insert groups for all working lengths (2-hole: 4 Nm p = 0.003, 8 Nm p = 0.003; 4-hole: 4 Nm p = 0.02, 8 Nm p < 0.001; 6-hole: 4 Nm p = 0.004, 8 Nm p < 0.001). There was a statistically significant increase in fatigue strength when using overtorque in the 4-hole (p = 0.04) and 6-hole (p = 0.01) defect groups. This was not shown in the 2-hole defect group (p = 0.99)., Conclusions: By placing locking inserts in the empty locking regions of Combi holes along the working length, the number of cycles to failure was increased. Tightening inserts to twice the recommended insertion torque further increased cycles to failure in longer working length models. A longer fatigue life has the potential to decease the incidence of plate failure especially in the setting of delayed union due to poor intrinsic healing capacity, fractures in the geriatric population, osteoporosis and periprosthetic fractures., (© 2021. The Author(s).)

Background: Satisfactory management of bone defects is important to achieve an adequate reconstruction in revision TKA. Metaphyseal cones to address such defects in the proximal tibia are increasingly being used; however, the biomechanical superiority of cones over traditional techniques like fully cementing the implant into the defect has not yet been demonstrated. Moreover, although long stems are often used to bypass the defects, the biomechanical efficacy of long stems compared with short, cemented stems when combined with metaphyseal cones remains unclear., Questions/purposes: We developed and validated finite-element models of nine cadaveric specimens to determine: (1) whether using cones for addressing moderate metaphyseal tibial defects in revision TKA reduces the risk of implant-cement debonding compared with cementing the implant alone, and (2) when using metaphyseal cones, whether long, uncemented stems (or diaphyseal-engaging stems) reduce the risk of implant-cement debonding and the cone-bone micromotions compared with short, cemented stems., Methods: We divided nine cadaveric specimens (six male, three female, aged 57 to 73 years, BMI 24 to 47 kg/m2) with standardized tibial metaphyseal defects into three study groups: no cone with short (50-mm) cemented stem, in which the defect was filled with cement; cone with short (50-mm) cemented stem, in which a metaphyseal cone was implanted before cementing the implant; and cone with long, diaphyseal-engaging stem, which received a metaphyseal cone and the largest 150-mm stem that could fit the diaphyseal canal. The specimens were implanted and mechanically tested. Then, we developed and validated finite-element models to investigate the interaction between the implant and the bone during the demanding activity of stair ascent. We quantified the risk of implant debonding from the cement mantle by comparing the axial and shear stress at the cement-implant interface against an experimentally derived interface failure index criterion that has been previously used to quantify the risk of cement debonding. We considered the risk of debonding to be minimal when the failure index was below 10% of the strength of the interface (or failure index < 0.1). We also quantified the micromotion between the cone and the bone, as a guide to the likelihood of fixation by bone ingrowth. To this end, we assumed bone ingrowth for micromotion values below the most restrictive reported threshold for bone ingrowth, 20 µm., Results: When using a short, 50-mm cemented stem and cement alone to fill the defect, 77% to 86% of the cement-implant interface had minimal risk of debonding (failure index < 0.1). When using a short, 50-mm cemented stem with a cone, 87% to 93% of the cement-implant interface had minimal debonding risk. When combining a cone with a long (150-mm) uncemented stem, 92% to 94% of the cement-implant interface had minimal debonding risk. The differences in cone-bone micromotion between short, cemented stems and long, uncemented stems were minimal and, for both configurations, most cones had micromotions below the most restrictive 20-µm threshold for ingrowth. However, the maximum micromotion between the cone and the bone was in general smaller when using a long, uncemented stem (13-23 µm) than when using a short, cemented stem (11-31 µm)., Conclusion: Although the risk of debonding was low in all cases, metaphyseal cones help reduce the biomechanical burden on the implant-cement interface of short-stemmed implants in high-demand activities such as stair ascent. When using cones in revision TKA, long, diaphyseal-engaging stems did not provide a clear biomechanical advantage over short stems. Future studies should explore additional loading conditions, quantify the interspecimen variability, consider more critical defects, and evaluate the behavior of the reconstructive techniques under repetitive loads., Clinical Relevance: Cones and stems are routinely used to address tibial defects in revision TKA. Despite our finding that metaphyseal cones may help reduce the risk of implant-cement debonding and allow using shorter stems with comparable biomechanical behavior to longer stems, either cones or cement alone can provide comparable results in contained metaphyseal defects. However, longer term clinical studies are needed to compare these techniques over time., Competing Interests: All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request., (Copyright © 2021 by the Association of Bone and Joint Surgeons.)

Background: The distribution of contact forces across the dysplastic patellofemoral joint has not been adequately quantified because models cannot easily mimic the dysplasia of both the trochlea and the patella. Thus, the mechanical consequences of surgical treatments to correct dysplasia cannot be established., Purpose/hypothesis: The objective of this study was to quantify the contact mechanics and kinematics of normal, mild, and severely dysplastic patellofemoral joints using synthetic mimics of the articulating surfaces on cadavers. We tested the hypothesis that severely dysplastic joints would result in significantly increased patellofemoral contact forces and abnormal kinematics., Study Design: Controlled laboratory study., Method: Patellofemoral dysplasia was simulated in 9 cadaveric knees by replacing the native patellar and trochlear surfaces with synthetic patellar and trochlear implants. For each knee, 3 synthetic surface geometries (normal, showing no signs of dysplasia; mild, exemplifying Dejour type A; and severe, exemplifying Dejour type B) were randomized for implantation and testing. Patellar kinematics and the sum of forces acting on the medial and lateral patellar facets were computed for each knee and for each condition at 10° increments from 0° to 70° of flexion., Results: A pronounced lateral shift in the weighted center of contact of the lateral facet occurred for severely dysplastic knees from 20° to 70° of flexion. Compared with normal geometries, lateral patellar facet forces exhibited a significant increase only with mild dysplasia from 50° to 70° of flexion and with severe dysplasia at 70° of flexion. No measurable differences in medial patellar facet mechanics or joint kinematics occurred., Conclusion: Our hypothesis was rejected: Severely dysplastic joints did not result in significantly increased patellofemoral contact forces and abnormal kinematics in our cadaveric simulation. Rather, severe dysplasia resulted in a pronounced lateral shift in contact forces across the lateral patellar facet, while changes in kinematics and the magnitude of contact forces were not significant., Clinical Relevance: Including dysplasia of both the patella and trochlea is required to fully capture the mechanics of this complex joint. The pronounced lateralization of contact force in severely dysplastic patellofemoral joints should be considered to avoid cartilage overload with surgical manipulation.

Background: Titanium tapered stems (TTS) achieve fixation in the femoral diaphysis and are commonly used in revision total hip arthroplasty. The initial stability of a TTS is critical, but the minimum contact length needed and impact of implant-specific taper angles on axial stability are unknown. This biomechanical study was performed to better guide operative decision-making by addressing these clinical questions., Methods: Two TTS with varying conical taper angles (2° spline taper vs 3.5° spline taper) were implanted in 9 right and left matched fresh human femora. The proximal femur was removed, and the remaining femoral diaphysis was prepared to allow for either a 2 cm (n = 6), 3 cm (n = 6), or 4 cm (n = 6) cortical contact length with each implanted stem. Stepwise axial load was then applied to a maximum of 2600N or until the femur fractured. Failure was defined as either subsidence >5 mm or femur fracture., Results: All 6 femora with 2 cm of stem-cortical contact length failed axial testing, a significantly higher failure rate (P < .02) than the 4 out of 6 femora and all 6 femora that passed testing at 3 cm and 4 cm, respectively, which were not statistically different from each other (P = .12). Taper angle did not influence success rates, as each matched pair either succeeded or failed at the tested contact length., Conclusion: 4 cm of cortical contact length with a TTS demonstrates reliable initial axial stability, while 2 cm is insufficient regardless of taper angle. For 3 cm of cortical contact, successful initial fixation can be achieved in most cases with both taper angle designs., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Previous studies have utilized ultrashort echo (UTE) magnetic resonance imaging (MRI), and derived T2* maps, to evaluate structures with highly ordered collagen structures such as tendon. T2* maps may provide a noninvasive means to assess tendon damage and healing. This pilot study evaluated the longitudinal relationship of an induced mechanical strain on the patellar tendon with corresponding UTE T2* metrics, histologic and biomechanical evaluation at two post-operative time points., Methods: A total of 27 patellar tendons in male Beagles were surgically subjected to stretching by a small diameter (SmD) or a large diameter (LgD) diameter rod to induce damage due to strain, and evaluated at 4- and 8-week intervals using quantitative MRI (qMRI), biomechanical testing, and histology. A separate set of 16 limbs were used as controls., Results: The tendons experienced a 67% and 17% prolongation of short T2* values as compared to controls at 4 and 8 weeks post-operatively, respectively. Histologic analysis displayed a trend of increased collagen disruption at 4 weeks followed by presence of greater organization at 8 weeks. Biomechanical evaluation found a reduction of tendon modulus and failure strain at both time points, and an increase in cross-sectional area at 4 weeks as compared to controls., Conclusions: These findings display tendon healing in response to an imposed strain and present the utility of qMRI to evaluate longitudinal differences of patellar tendon T2* values in a model of induced subclinical tendon damage. The qMRI technique of UTE provides a means to non-invasively evaluate the healing process of a mechanically damaged tendon., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/qims-20-684). Dr. SLP and Dr. REB report other from GE Healthcare, outside the submitted work. Dr. MFK reports other from GE Healthcare, other from GE/NBA, grants from NIH, grants from NIH NIAMS, outside the submitted work. Dr. HGP reports other from GE Healthcare, other from GE/NBA, grants from National Institutes of Health (NIAMS/NICHD), personal fees from Ortho RTI, personal fees from Stryker, outside the submitted work, and Member of Editorial or Governing boards of: AOSSM, Imaging in Sports Health, Journal of Hip Preservation Surgery, Journal of Orthopaedic Research, Osteoarthritis and Cartilage; owns stock or stock options in: Imagen. The other authors have no conflicts of interest to declare., (2021 Quantitative Imaging in Medicine and Surgery. All rights reserved.)

Background Context: Annular repair devices offer a solution to recurrent disc herniations by closing an annular defect and lowering the risk of reherniation. Given the significant risk of neurologic injury from device failure it is imperative that a reliable preclinical model exists to demonstrate a high load to failure for the disc repair devices., Purpose: To establish a preclinical model for disc herniation and demonstrate how changes in species, intervertebral disc height and Pfirrmann classification impacts failure load on an injured disc. We hypothesized that: (1) The force required for disc herniation would be variable across disc morphologies and species, and (2) for human discs the force to herniation would inversely correlate with the degree of disc degeneration., Study Design: Animal and human cadaveric biomechanical model of disc herniation., Methods: We tested calf lumbar spines, bovine tail segments and human lumbar spines. We first divided individual lumbar or tail segments to include the vertebral bodies and disc. We then hydrated the specimens by placing them in a saline bath overnight. A magnetic resonance images were acquired from human specimens and a Pfirrmann classification was made. A stab incision measuring 25% of the diameter of the disc was then done to each specimen along the posterior intervertebral disc space. Each specimen was placed in custom test fixtures on a servo-hydraulic test frame (MTS, Eden Prarie, MN) such that the superior body was attached to a 10,000 lb load cell and the inferior body was supported on the piston. A compressive ramping load was placed on the specimen in load control at 4 MPa/sec stopping at 75% of the disc height. Load was recorded throughout the test and failure load calculated. Once the test was completed each specimen was sliced through the center of the disc and photos were taken of the cut surface., Results: Fifteen each of calf, human, and bovine tail segments were tested. The failure load varied significantly between specimens (p<.001) with human specimens having the highest average failure load (8154±2049 N). Disc height was higher for lumbar/bovine tail segments as compared to calf specimens (p<.001) with bovine tails having the highest disc height (7.1±1.7 mm). Similarly, human lumbar discs had a cross sectional area that was greater than both bovine tail/calf lumbar spines (p<.001). There was no correlation between disc height and failure load within each individual species (p>.05). Cross sectional area and failure load did not correlate with failure load for human lumbar spine and bovine tails (p>.05) but did correlate with calf spine (r=0.53, p=.04). There was a statistically significant inverse correlation between disc height and Pfirrmann classification for human lumbar spines (r=-0.84, p<.001). There was also a statistically significant inverse relationship between Pfirrmann classification and failure load (r=-0.58, p=.02)., Conclusions: We have established a model for disc herniation and have shown how results of this model vary between species, disc morphology, and Pfirrmann classification. Both hypotheses were accepted: The force required for disc herniation was variable across species, and the force to herniation for human spines was inversely correlated with the degree of disc degeneration. We recommend that models using human intervertebral discs should include data on Pfirrmann classification, while biomechanical models using calf spines should report cross sectional area. Failure loads do not vary based on dimensions for bovine tails., Clinical Significance: Our analysis of models for disc herniation will allow for quicker, reliable comparisons of failure forces required to induce a disc herniation. Future work with these models may facilitate rapid testing of devices to repair a torn/ruptured annulus., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Adult medial patellofemoral ligament (MPFL) reconstruction techniques are not appropriate for the skeletally immature patient given the proximity of the distal femoral physis. Biomechanical consequences of reconstructions aimed at avoiding the physis have not been adequately studied., Purpose: To quantify the biomechanical effects of MPFL reconstruction techniques intended for skeletally immature patients., Study Design: Controlled laboratory study., Methods: Four MPFL reconstruction techniques were evaluated using a computationally augmented cadaveric model: (1) Schoettle point: adult-type reconstruction; (2) epiphyseal: socket distal to the femoral physis; (3) adductor sling: graft wrapped around the adductor tendon; (4) adductor transfer: adductor tendon transferred to patella. A custom testing frame was used to cycle 8 knees for each technique from 10° to 110° of flexion. Patellofemoral kinematics were recorded using a motion camera system, contact stresses were recorded using Tekscan pressure sensors, and MPFL length was computed using an inverse kinematics computational model. Change in MPFL length, patellar facet forces, and patellar kinematics were compared using generalized estimating equation modeling., Results: Schoettle point reconstruction was the most isometric, demonstrating isometry from 10° to 100°. The epiphyseal technique was isometric until 60°, after which the graft loosened with increasing flexion. The adductor sling and adductor transfer techniques were significantly more anisometric from 40° to 110°. Both grafts tightened with knee flexion and resulted in significantly more lateral patellar tilt versus the intact state in early flexion and significantly higher contact forces on the medial facet versus the epiphyseal technique in late flexion., Conclusion: In this cadaveric simulation, the epiphyseal technique allowed for a more isometric ligament until midflexion, when the patella engaged within the trochlear groove. The adductor sling and adductor transfer grafts became tighter in flexion, resulting in potential loss of motion, pain, graft stretching, and failure. Marginal between-condition differences in patellofemoral contact mechanics and patellar kinematics were observed in late flexion., Clinical Relevance: In the skeletally immature patient, using an epiphyseal type MPFL reconstruction with the femoral attachment site distal to the physis results in a more isometric graft compared with techniques with attachment sites proximal to the physis.

Purpose: To investigate alterations in technique for medial patellofemoral ligament (MPFL) reconstruction in the setting of patella alta and describe the effect of these alterations on MPFL anatomometry., Methods: Ten cadaveric knees were used. Four candidate femoral attachment sites of MPFL were tested. The attachment sites were Schottle's point (SP), 5 mm distal to SP, 5 mm proximal to SP, and 10 mm proximal to SP. A suture anchor was placed at the upper 40% of the medial border of the patella with the emanating suture used to simulate the reconstructed ligament. MPFL maximum length change was calculated through a range of motion between 0° and 110°. Recordings at all 4 candidate femoral attachments sites were repeated after a flat tibial tubercle osteotomy and transfer to achieve alta as measured by the Caton-Deschamps Index (CDI) of 1.3, 1.4, and 1.5., Results: The 10 specimens had an average CDI of 0.99, range 0.87 to 1.16. In the native tibial tubercle condition, SP was more isometric through 20° to 70° range of motion, or anatomometric, than any other candidate femoral attachment location. With patella alta with a CDI of 1.3 and 1.4, attachment site 5 mm proximal to SP exhibited more anatomometry than SP. With patella alta with a CDI of 1.5, attachment site 10 mm proximal to SP exhibited more anatomometry than SP., Conclusions: Increased patella alta significantly alters MPFL anatomometry. With increasing degrees of patella alta, more proximal candidate femoral attachment sites demonstrate decreased change in length compared with SP. None of the varied femoral attachments produced anatomometry over the entirety of the flexion range from 20° to 70°, suggesting that in cases of significant patella alta, proximalization the femoral attachment site of MPFL reconstruction may be necessary to achieve an anatomometric MPFL reconstruction., Clinical Relevance: A standardized, isolated MPFL reconstruction may be prone to failure in the setting of patella alta, given the anisometry demonstrated. Alternative femoral attachment sites for MPFL reconstruction should be considered in these patients., (Copyright © 2020 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Background Context: A variety of solutions have been suggested as candidates for the repair of the annulus fibrosis (AF), with the ability to withstand physiological loads of paramount importance., Purpose: The objective of our study was to capture the scope of biomechanical test models of AF repairs. We hypothesized that common test parameters would emerge., Study Design: Systematic Review METHODS: PubMed and EMBASE databases were searched for studies in English including the keywords "disc repair AND animal models," "disc repair AND cadaver spines," "intervertebral disc AND biomechanics," and "disc repair AND biomechanics." This list was further limited to those studies which included biomechanical results from annular repair in animal or human spinal segments from the cervical, thoracic, lumbar and/or coccygeal (tail) segments. For each study, the method used to measure the biomechanical property and biomechanical test results were documented., Results: A total of 2,607 articles were included within our initial analysis. Twenty-two articles met our inclusion criteria. Significant variability in terms of species tested, measurements used to quantify annular repair strength, and the method/direction/magnitude that forces were applied to a repaired annulus were found. Bovine intervertebral disc was most commonly used model (6 of 22 studies) and the most common mechanical property reported was the force required for failure of the disc repair device (15 tests)., Conclusions: Our hypothesis was rejected; no common features were identified across AF biomechanical models and as a result it was not possible to compare results of preclinical testing of annular repair devices. Our analysis suggests that a standardized biomechanical model that can be repeatably executed across multiple laboratories is required for the mechanical screening of candidates for AF repair., Clinical Significance: This literature review provides a summary of preclinical testing of annular repair devices for clinicians to properly evaluate the safety/efficacy of developing technology designed to repair annular defects after disc herniations., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Blade plates are frequently used for internal fixation following proximal femoral varus rotational osteotomy to treat hip dysplasia in children with cerebral palsy. Recently, cannulated blade plates with the option for a proximal locking screw have demonstrated ease of insertion and low complication rates. Although there are two commonly used blade plates with a proximal screw option, no comparison of their biomechanical profiles has been undertaken., Questions/purposes: Our study sought to compare the structural properties under axial loading, as well as the biomechanical contribution of a proximal screw, of two different 90° cannulated blade plates designed for pediatric proximal femurs. Plate A has a hole distal to the blade designed to attach a plate inserter, through which a 3.5-mm non-locking cortical screw could be placed. Plate B has a threaded hole distal to the blade designed to accept a 3.5-mm locking screw., Methods: Plate A and plate B were inserted into 33 left pediatric synthetic proximal femurs. Axial loading to failure of plate A with and without a proximal screw was compared to that of plate B with and without a proximal screw. An additional 10 samples using plate B, with and without a proximal locking screw, were tested in tension to quantify the effect of the proximal screw on pullout strength., Results: Plate B failed at a higher axial load than plate A. The addition of a proximal screw did not affect the axial load to failure for either plate. Pullout testing revealed that blade plates fixed with the proximal screw failed in tension at a significantly higher load (856.3 ± 120.9 N) than those without proximal fixation (68.1 ± 9.3 N, p  < 0.001)., Conclusions: Plate B failed at a higher axial load in biomechanical testing, likely related to differences in its design. The addition of a proximal screw did not increase the axial loading properties of the blade plate construct but did increase the pullout strength by a factor of 12. These results may be used to influence implant selection and post-operative rehabilitation following proximal femoral osteotomies in children., Competing Interests: Conflict of InterestJoseph J. Ruzbarsky, MD, Ishaan Swarup, MD, Matthew R. Garner, MD, Kathleen Meyers, MS, Folorunsho Edobor-Osula, MD, Roger Widmann, MD, and David M. Scher, MD, report that OrthoPediatrics provided some of the blade plates used in this study. David M. Scher, MD, also reports receiving personal fees as a consultant from OrthoPediatrics, during the conduct of this study., (© Hospital for Special Surgery 2019.)

Background: Isolated injuries of the scapholunate interosseous ligament (SLIL) are insufficient to produce dorsal intercalated segment instability. There is no consensus about which additional ligamentous stabilizers are critical determinants of dorsal intercalated segment instability. The aim of this study was to evaluate the role of the long radiolunate (LRL), scaphotrapeziotrapezoid (STT), and dorsal intercarpal (DIC) ligaments in preventing dorsal intercalated segment instability., Methods: Thirty fresh-frozen forearms were randomized to 5 ligament section sequences to study the SLIL, LRL, STT, and DIC ligaments. The DIC-lunate insertion (DIC) and scaphoid insertion (DIC) were studied separately; the DIC insertions on the trapezium and triquetrum were left intact. Loaded posteroanterior and lateral fluoroscopic images were obtained at baseline and repeated after each ligament was sectioned. After each sequence, the wrists were loaded cyclically (71 N). The radiolunate angle was measured with load. Dorsal intercalated segment instability was defined as an increase of >15° in the radiolunate angle compared with baseline., Results: Division of the SLIL did not increase the radiolunate angle. Section of the SLIL+LRL or SLIL+DIC significantly increased the radiolunate angle but did not produce dorsal intercalated segment instability. Section of the SLIL+STT or SLIL+DIC+DIC produced dorsal intercalated segment instability., Conclusions: In order to produce dorsal intercalated segment instability, complete scapholunate injuries require the disruption of at least 1 critical ligament stabilizer of the scaphoid or lunate (the STT or DIC+DIC)., Clinical Relevance: When treating SLIL tears with dorsal intercalated segment instability, techniques to evaluate the volar and dorsal critical stabilizers of the proximal carpal row should be considered.

Purpose: To investigate whether the location of distal radius osteotomy/shortening relative to the radial insertion of the distal interosseous membrane (DIOM) is correlated with distal radioulnar joint (DRUJ) instability. We hypothesized that distal radius osteotomy and shortening proximal to the DIOM insertion would result in increased DRUJ instability because of induced laxity in the DIOM., Methods: Osteotomies of the distal radius were performed proximal and distal to the DIOM insertion in 14 fresh-frozen cadaveric specimens. Using a volar plate, 5 conditions were tested: anatomical radius alignment; 2- and 4-mm shortening at the proximal osteotomy site; and 2- and 4-mm shortening at the distal osteotomy site. Basilar ulnar styloid osteotomy was performed to simulate triangular fibrocartilage complex (TFCC) detachment-specimens were tested with the ulnar styloid detached and the ulnar styloid fixed (to restore normal anatomy). The DRUJ stability was quantified using dorsal-volar displacement of the radius in response to 20 N of force using a force-displacement probe in neutral, pronation, and supination. Posttesting specimen dissections assessed DIOM and distal oblique bundle (DOB) anatomy. The DRUJ stability in each experimental condition was compared with a multifactor repeated measures analysis of variance with the specimen treated as the repeated factor., Results: There were no significant differences in dorsal-volar translation of the radius (ie, DRUJ stability) between radial osteotomy/shortening proximal and distal to the DIOM insertion, regardless of forearm rotational position or magnitude of shortening. Five (36%) of the 14 specimens had a DOB present. There was a significant increase in DRUJ instability in the setting of TFCC detachment (via basilar ulnar styloid osteotomy)., Conclusions: No difference in DRUJ stability was observed between distal radius osteotomy/shortening proximal and distal to the DIOM radial insertion, regardless of forearm rotation, magnitude of shortening, and/or TFCC detachment., Clinical Relevance: Distal radius osteotomy and shortening did not affect DRUJ stability regardless of location relative to the DIOM insertion., (Copyright © 2019 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

Purpose: The purposes of this study were (1) to evaluate the percentage of gluteus medius and minimus tendon footprint restoration that can be achieved with fixation using single-row repair versus double-row repair and (2) to evaluate the yield load of a repair of the gluteus medius and minimus tendon using single-row versus double-row repair techniques., Methods: Twelve human fresh-frozen cadaveric hip specimens (6 matched pairs, 4 female, mean age 47.5 ± 14.5 years) were tested. Specimens were excluded if they had any prior hip surgery or injury, if any abnormality of the tendon was noted on dissection, or if they had a body mass index <20 or >35 or a T-score <2.0 on dual-energy x-ray absorptiometry scanning. Matched pairs were randomized to receive either double-row repair with 2 standard suture anchors and 2 knotless anchor devices or a single-row repair with suture anchors only. The percentage of the footprint area covered after repair was determined using a computer-assisted digitization algorithm. With a mechanical testing system, each repaired specimen was tested for mechanical strength first with cyclic loading and then load to failure testing., Results: Footprint coverage of the lateral facet was significantly greater for double-row repair (mean 76.6%) compared with single-row repair (mean 50.3%) (P = .03). There was no significant difference between single- and double-row repair for posterior-superior or anterior facet coverage. Mechanical testing showed a higher mean yield load for double-row anchor repair (197.6 ± 61.7 N vs 163.5 ± 35.4 N for single-row repair), but this did not reach statistical significance (P = .15). The predominant mode of failure was suture pullout through the musculotendinous unit (9/12 specimens: 5 double-row and 4 single-row)., Conclusions: For hip abductor tears, double-row suture repair yields improved footprint coverage compared with single-row repair. Although it did not reach statistical significance, there was a higher mean yield load in the double-row group., Clinical Relevance: Double-row suture fixation technique for hip abductor tears maximizes strength and footprint coverage of the repair., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Background: In knee arthroplasty with preoperative varus deformity, medial collateral ligament (MCL) release may be needed to achieve balance. Pie-crusting allows for controlled release, but questions remain regarding its ability to obtain predictable results. We compared 16- vs18-gauge needle punctures and determined the number of punctures required to (1) lengthen the MCL by 1 mm and (2) cause ligament failure., Methods: Thirteen knees were dissected, leaving the femur and tibia with an isolated MCL, and randomly assigned to 16- or 18-gauge groups. Initial stiffness was assessed by cycling the ligament to 300 N for 5 cycles. The selected needle was used to make 10 punctures centered over the area of greatest tension. Cyclic testing was repeated after each set of punctures. Changes in MCL length and stiffness were measured. This process was repeated until failure., Results: No differences occurred between the 16- and 18-gauge groups in cross-sectional area, initial stiffness, number of punctures to lengthen the MCL by 1 mm, or number of punctures to failure. As the number of punctures increased, a linear increase in elongation and decrease in stiffness occurred., Conclusion: Needle size was not the influencing factor. Variability in number of punctures, regardless of needle size, to elongate or fail the MCL shows the difficulty in developing a reproducible pie-crusting technique. This suggests that a standard number of punctures do not achieve controlled MCL lengthening for all patients, but that the number of punctures needed can be calculated for an individual knee based on the initial elongation after 10 punctures., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Purpose: To use a CT-based approach with 3D modeling to determine novel radiographic views of the scaphotrapezial (STl) and scaphotrapezoid (STd) joints., Materials and Methods: Consecutive wrist CT scans excluding those with pathology of the distal radius, scaphoid, trapezium, or trapezoid of subjects between ages 18 and 60 years were retrospectively reviewed. Three-dimensional reconstructions of CT scans were created and best-fit planes of the STl and STd joints were generated. Angles of these planes relative to a distal radial coordinate system were calculated to determine tilt of the wrist and the X-ray beam for novel radiographic views of these joints., Results: Fifty eligible wrist CT scans were identified. The mean age was 38 years (range, 18 to 59). For the novel STl PA view, the wrist is supinated 17° from the standard PA view and the X-ray beam is canted 6° caudad. In the STl lateral view, the wrist is pronated 17° from the standard lateral view, and the X-ray beam is canted 20° caudad. In the STd PA tilt view, the wrist is supinated 28° from the standard PA view, and the X-ray beam is canted 13° caudad. In the STd joint lateral tilt view, the wrist is pronated 28° from the standard lateral view, and the X-ray beam is canted 29° caudad., Conclusion: We describe novel radiographic views of the STl and STd joints based on 3D modeling of wrist CT scans. Further studies are required to assess the efficacy of these views in detecting joint pathology., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Purpose: To assess the impact elevated tibial tubercle-trochlear groove (TT-TG) distance and patella height, as measured by the Caton-Deschamps Index (CDI), have on the isometry of a reconstructed medial patellofemoral ligament (MPFL)., Methods: Nine fresh-frozen cadaveric knees were placed on a custom testing fixture, with a fixed femur and a mobile tibia. A suture fixed to the MPFL origin on the patella and free to move at the Schöttle point on the femur represented a reconstructed MPFL. A local coordinate system was established, and retroreflective markers attached to the suture quantified MPFL length changes by use of a 3-dimensional motion capture system. The tubercle was transferred to create TT-TG distances of 20 mm and 25 mm and CDIs of 1.2 and 1.4 (patella alta). Recordings of the MPFL suture length change as the knee was brought through a range of motion were made using all combinations of tubercle anatomy in a randomized order for each specimen. A generalized estimating equation modeling technique was used to analyze and control for the clustered nature of the data., Results: Knees with native tibial tubercle anatomy showed MPFL isometry through 20° to 70° range of motion. Tibial tubercle lateralization (increased TT-TG distance) significantly altered MPFL isometry with a TT-TG distance of 20 mm (P < .0001). Patella alta significantly altered MPFL isometry with a CDI of 1.2 (P = .0182). The interaction of tibial tubercle lateralization combined with patella alta significantly increased the amount of anisometry seen in the reconstructed MPFL (P < .001)., Conclusions: Increased tibial tubercle lateralization and patella alta produce anisometry in an MPFL reconstruction using currently recommended landmarks, leading to potentially increased graft tension and potential failure., Clinical Relevance: Tibial tubercle transfer should be considered when performing an MPFL reconstruction for recurrent patellofemoral instability in the setting of significant patella alta and an elevated TT-TG distance-especially when both are present-because an isolated MPFL reconstruction will be prone to failure given the anisometry shown in this study., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Background: We sought to evaluate clinical and biomechanical outcomes of dual mini-fragment plate fixation for clavicle fractures. We hypothesized that this technique would produce an anatomical reduction with good clinical outcomes, be well tolerated by patients, and demonstrate equivalent biomechanics to single plating., Methods: Dual mini-fragment plating was performed for 17 isolated, displaced midshaft clavicle fractures. Functional outcomes and complications were retrospectively reviewed. A sawbones model compared dual plating biomechanics to a (1) superior 3.5-mm locking reconstruction plate, or (2) antero-inferior 3.5-mm locking reconstruction plate., Results: On biomechanical testing, with anterior loading, dual plating was significantly more rigid than single locked anterior-plating (p = 0.02) but less rigid than single locked superior-plating (p = 0.001). With superior loading, dual plating trended toward higher rigidity versus single locked superior-plating (p = 0.07) but was less rigid than single locked anterior-plating (p = 0.03). No statistically significant differences in axial loading (p = 0.27) or torsion (p = 0.23) were detected. Average patient follow-up was 16.1 months (12-38). Anatomic reduction was achieved and maintained through final healing (average 14.7 weeks). No patient underwent hardware removal. Average 1-year DASH score was 4.0 (completed in 88 %)., Conclusions: Displaced midshaft clavicle fractures can be effectively managed with dual mini-fragment plating. This technique results in high union rates and excellent clinical outcomes. Compared to single plating, dual plating is biomechanically equivalent in axial loading and torsion, yet offers better multi-planar bending stiffness despite the use of smaller plates. This technique may decrease the need for secondary surgery due to implant prominence and may aid in fracture reduction by buttressing butterfly fragments in two planes.

Purpose: To evaluate the biomechanical properties of 3 scapholunate repair techniques., Methods: In 51 cadavers, the scapholunate ligament was exposed through a dorsal approach, incised at its scaphoid insertion, and repaired using 1 of 3 techniques: 2 single-loaded suture anchors, 2 double-loaded suture anchors, or 2 transosseous sutures. Twenty-four repaired specimens underwent load to failure (LTF) testing using tensile distraction on a servo-hydraulic machine. Twenty-seven specimens underwent cyclical testing to measure gap formation at the scapholunate joint., Results: The mode of failure was suture pullout through the substance of the ligament in 22 specimens, failure at the bone suture interface in 1, and anchor pullout in 1. Double-loaded anchor repairs demonstrated a significantly higher mean ultimate LTF compared with single-loaded anchor (91 N vs 35 N) and transosseous (91 N vs 60 N) repairs. Transosseous repairs demonstrated a higher mean ultimate LTF compared with single-loaded suture repairs (60 N vs 35 N). After 300 cycles, the average gap for the transosseous repair group was double that for the single- and double-loaded repairs, although not statistically significant., Conclusions: Primary scapholunate ligament repairs using double-loaded suture anchors demonstrated significantly higher strength compared with single-loaded anchors and transosseous repairs. On cyclic loading, transosseous repairs demonstrated the greatest gap formation with no measurable difference between single- and double-loaded repairs., Clinical Relevance: In a cadaveric model for primary repairs, double-loaded suture anchors demonstrated the highest LTF and offer a similar but unproven performance in vivo., (Copyright © 2015 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

Background: Backside damage of the polyethylene in TKA is a potential source of debris. The location of the tibial post in posterior-stabilized implants may influence micromotion, and thus affect backside damage, as may surface roughness., Questions: We used implant retrieval analysis to (1) examine if there were differences in backside damage among three modern posterior-stabilized implants attributable to variable surface roughness; (2) determine if the location of damage on the tibial post affected the pattern of backside damage; and (3) determine if demographics influenced backside damage., Methods: We identified 403 posterior-stabilized tibial retrieved inserts (147 NexGen(®), 152 Optetrak(®), 104 Genesis(®) II). The damage on the surfaces of the tibial posts was previously graded. The backside of the inserts (divided into quadrants) were scored for evidence of damage. The total quadrant damage was compared for each implant group, the relationship between post face damage and location of damage on the backside was determined for each implant group, and total backside damage was compared among the three implant groups., Results: No correlation was found between the location of damage on the post and location of damage on the backside of the implant for any of the three groups. The Genesis(®) II polyethylene implants, which articulate with a highly polished tibial tray, showed a significantly lower total backside damage score (p < 0.01) when compared with the other two implant groups. The Genesis(®) II and Optetrak(®) showed significantly more damage in the posterior quadrants of the implants (p < 0.01) when compared with the anterior quadrants. A linear regression analysis revealed that lower tibial tray surface roughness was correlated with decreased damage., Conclusions: An implant design with a highly polished tibial tray was associated with decreased backside damage. However, tibial post design and location did not influence the location of backside damage., Clinical Relevance: Our study showed that a highly polished tibial tray was associated with decreased damage to the backside of polyethylene inserts independent of post design and location. These findings should be taken into consideration when new generations of implants are designed.

Purpose: Shift of the distal fragment of a distal radius fracture (DRF) in the coronal plane (coronal shift) may compromise the contributions of the distal oblique bundle (DOB) of the interosseous membrane to distal radioulnar joint (DRUJ) stability. The purpose of the study was to test our hypothesis that coronal shift of the distal fragment would increase dorsal-volar DRUJ displacement in response to applied load., Methods: A distal radius osteotomy was performed proximal to the sigmoid notch base and the ulnar styloid was cut (to simulate triangular fibrocartilage complex detachment) in 10 cadaveric specimens. A volarly placed plate was used to shift the distal radius fragment radially in 2-mm increments. A mechanical testing apparatus applied a 20 N load to the distal fragment perpendicular to the volar cortex with the forearm in neutral, 60° pronation, and 60° supination. Dorsal-volar displacement of the radius relative to the fixed ulna was measured in the control state (DRF and ulnar styloid anatomically fixed) and in 3 positions (anatomical reduction, 2-mm coronal shift, 4-mm coronal shift) with ulnar styloid displacement. The specimens were dissected post hoc to evaluate for a distinct DOB (thickness, > 0.5 mm). Dorsal-volar DRUJ displacement was compared among testing and control states using analysis of variance., Results: In specimens with a distinct DOB, 2-mm coronal shift significantly increased dorsal-volar DRUJ displacement. However, there was no difference in DRUJ displacement between 4-mm coronal shift and control state. Coronal shift did not affect dorsal-volar DRUJ displacement in specimens without a distinct DOB., Conclusions: In the setting of an ulnar styloid fracture, a 2-mm (but not a 4-mm) coronal shift of the DRF is associated with increased dorsal-volar DRUJ displacement in specimens with a distinct DOB, but not in specimens without a distinct DOB., Clinical Relevance: Awareness of the importance of coronal shift may aid in prevention of DRUJ instability associated with DRF, especially in patients with a DOB., (Copyright © 2014 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

Background: The success of ankle distraction arthroplasty relies on the separation of the tibiotalar articular surfaces., Question/purpose: The purpose of this study was to find the minimum distraction gap needed to ensure that the tibiotalar joint surfaces would not contact each other with full weight-bearing while under distraction., Methods: Circular external fixators were mounted to nine cadaver ankle specimens. Each specimen was then placed into a custom-designed load chamber. Loads of 0, 350, and 700N were applied to the specimen. Radiographic joint space was measured and joint contact pressure was monitored under each load. The external fixator was then sequentially distracted, and the radiographic joint space was measured under the three different loads. The experiment was stopped when there was no joint contact under 700N of load. The radiographic joint space was measured and the initial (undistracted) radiographic joint space was subtracted from it yielding the distraction gap. The minimum distraction gap (mDG) that would provide total unloading was calculated., Results: The average mDG was 2.4 mm (range, 1.6 to 4.0 mm) at 700N of load, 4.4 mm (range, 3.7 to 5.8 mm) at 350N of load, and 4.9 mm (range, 3.7 to 7.0 mm) at 0N of load., Conclusion: These results suggest that if the radiographic joint space of on a standing X-ray of an ankle undergoing distraction arthroplasty shows a minimum of 5.8 mm of DG, then there will be no contact between joint surfaces during full weight-bearing. Therefore, 5 mm of radiographic joint space, as recommended historically, may not be adequate to prevent contact of the articular surfaces during weight-bearing.

Background: Safely permitting early range of motion after a destabilizing injury to the elbow is believed to optimize return of function. However, the range-of-motion exercises must be balanced against the risk of re-dislocation or subluxation. The goal of this study was to describe the position of the upper limb that permitted the greatest motion while minimizing the risk of re-dislocation or subluxation., Methods: Seven cadaveric elbows were affixed with a 3-dimensional motion capture system. Ulnohumeral distraction was recorded at flexion angles from 10° to 90° for intact, approach only (sham procedure), and LCL-sectioned. Ulnohumeral separation was recorded in 3 distinct positions of the upper limb that are frequently used in a clinical setting: 1) trunk seated upright with arm at the side; 2) trunk seated upright with elbow in hinged-brace; and 3) trunk supine with shoulder flexed and internally rotated - "gravity-assisted overhead motion" protocol., Results: A significant ulnohumeral distraction difference was found between the supine and the upright protocols. Upon direct comparison, 104% more displacement occurred across the ulnohumeral joint in the upright LCL-sectioned condition compared to the supine LCL-sectioned condition (P = .001). The greatest ulnohumeral distraction occurred in the seated upright range of motion with a hinged elbow brace (range, 2.5-5.6 mm)., Conclusion: The overhead motion protocol is a safe protocol for unstable elbows. The supine position results in the least amount of ulnohumeral distraction across flexion angles from 10° to 90°. The upright protocols, especially with the hinged elbow brace, exhibited ulnohumeral distraction that may result in dislocation., (Copyright © 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.)

Purpose: This study biomechanically evaluated a technically easy variation of anatomical reconstruction of the thumb metacarpophalangeal (MCP) joint ulnar (UCL) and radial (RCL) collateral ligaments. Based on previous work describing the anatomical origin and insertion of these ligaments, we hypothesized that, using these attachment points, joint stability would be restored without significant loss of MCP flexion., Methods: The collateral ligaments were isolated in 30 cadaveric thumbs (15 UCLs and 15 RCLs). A cyclical load was applied to the MCP joint to assess flexion, radial/ulnar deviation in neutral, and radial/ulnar deviation in 30° of flexion. The collateral ligaments were detached from the bone while their origin and insertion points were marked. Using these sites, anatomical ligament reconstruction was performed with a palmaris longus tendon graft and interference screw fixation. Cyclical testing was repeated on the reconstructed ligaments., Results: No significant difference was found between intact and reconstructed UCLs when tested for radial deviation in neutral, radial deviation in 30° of flexion, or total MCP flexion. No significant difference was found between intact and reconstructed RCLs when tested for ulnar deviation in neutral, ulnar deviation in 30° of flexion, or total MCP flexion., Conclusions: Our anatomical reconstruction is simple and restores UCL and RCL anatomy as compared with current techniques in the literature by placing the origin and insertion at their anatomical points with use of an interference screw. Using these anatomical origins and insertions, we were able to restore the MCP flexion and stability seen in an intact ligament., Clinical Relevance: Our anatomical reconstruction offers a technically easy option for reconstruction of thumb MCP collateral ligament injuries, restoring joint stability without sacrificing flexion., (Copyright © 2013 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

Dorsal instability of the metatarsophalangeal joint (MTPJ) of the lesser toes is an important cause of forefoot pain. Both conservative and surgical treatment options have been proposed. However, the role of each static stabilizing structure has not been elucidated. We hypothesized that isolated sectioning of the plantar plate (PP) would result in greater dorsal translation compared to isolated sectioning of the medial collateral ligaments (MCL) or lateral (LCL) collateral ligaments, or the extensor hood (EH), and that combined injury to two or more structures would result in greater dorsal translation compared to isolated PP injury. Fifty-four cadaveric lesser toe specimens were randomized into groups for individual and combined sectioning of the PP, EH, and LCL and MCL. A 30 N axial load was applied to each specimen in the plantar-dorsal direction and dorsal translation of the phalanx was measured for each condition. ANOVA was used to compare groups. A 19% change in MTP translation was found from intact after sectioning the PP. No significant difference in translation was seen after individual sectioning of the EH, MCL, or LCL. A significant increase in translation occurred from intact with the following sectioning combinations: MCL + LCL, 37%; EH + MCL + LCL, 45%; and PP + MCL + LCL, 63%. Thus, the PP is the main restraint for dorsal MTPJ translation. MCL and LCL have important partial contribution to MTPJ stability. Injury to the PP, individually, or combined injuries to the PP, EH, MCL, or LCL, appear to cause significant instability that may warrant more aggressive treatment., (Copyright © 2012 Orthopaedic Research Society.)

Purpose: To describe the origin and insertion of the ulnar (UCL) and radial collateral ligaments (RCL) of the thumb metacarpophalangeal (MCP) joint., Methods: We dissected 18 UCLs and 18 RCLs from fresh-frozen human cadaveric thumbs. We removed all soft tissue overlying the MCP joint, isolating the proper collateral ligaments. We detached the collateral ligaments from the bone while marking their origin and insertion points and measured these attachment sites in relation to bony landmarks by digital photo analysis., Results: The center of the UCL origin at the metacarpal was 4.2 mm from the dorsal surface and 5.3 mm from the articular surface. The dorsal aspect of the metacarpal origin site was 2.1 mm from the dorsal edge of the metacarpal. The center of the phalangeal insertion was 2.8 mm from the volar surface and 3.4 mm from the articular surface. The volar aspect of the phalangeal insertion site was 0.7 mm from the volar edge of the phalanx. The center of the RCL origin at the metacarpal was 3.5 mm from the dorsal surface and 3.3 mm from the articular surface. The dorsal aspect of the metacarpal origin site was 1.5 mm from the dorsal edge of the metacarpal. The center of the phalangeal insertion was 2.8 mm from the volar surface and 2.6 mm from the articular surface. The volar aspect of the phalangeal insertion site was 0.5 mm from the volar edge of the phalanx., Conclusions: Our study accurately defined the origin and insertion sites of the UCL and RCL of the thumb MCP joint., Clinical Relevance: An accurate definition of the anatomical origin and insertion points of the thumb MCP UCL and RCL may allow for more successful surgical repair and reconstruction., (Copyright © 2012 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

Avoidance of patellar eversion during total knee arthroplasty may help to prevent injury to the patellar tendon. The purpose of this study was to compare the load-to-failure of the everted versus the noneverted patella in a cadaveric model. Fourteen cadaver knees (seven pairs) were loaded to failure with the patella everted in one knee and not everted in the other. Mean load-at-ultimate failure in the patella-everted group was 1,111 ± 572 N, and in the patella-noneverted group was 1,621 ± 683 N (p = 0.01). Additionally, loads-at-initial-partial failure were lower (p = 0.04) in the patella-everted compared to the patella-noneverted group, 573 ± 302 N versus 1,115 ± 358 N, respectively. A partial failure of the patellar tendon occurred in 100% of the everted specimens, whereas only 57% of the noneverted specimens had partial failure. These findings suggest patella eversion may lead to failure of the patellar insertion at lower loads than when the patella is not everted.

Background: In difficult ankle arthrodesis situations, intramedullary (IM) arthrodesis nails and external fixation are often considered in lieu of standard fusion techniques. The purpose of this study was to compare the amount of micromotion measured across an ankle fusion site stabilized with either an IM nail or with the Ilizarov external fixator., Materials and Methods: The relative bone mineral density of 8 pairs of human cadaveric lower legs was measured by DEXA scanning. One specimen from each pair was randomly assigned to be stabilized with a new generation IM nail and the other with an Ilizarov external fixator. Specimens were tested in compression, rotation, and dorsiflexion. Optical motion capture was used to measure the direct motion occurring at the fusion site., Results: No significant difference was found between the axial displacements (p = 0.94), torsional displacement (p = 0.07), or the dorsiflexion angular displacement (p = 0.28) for the IM rod group and the external fixation group. A weak correlation was found between BMD and displacement., Conclusion: Both the new generation IM nail and the Ilizarov external fixator imparted excellent stability to the fusion site despite a wide range of bone mineral densities. Medialization of the talus, the ability to compress the nail, and the addition of a posterior-to-anterior locking screw were thought to improve the performance of the nail., Clinical Relevance: Both IM nail and Ilizarov external fixation provided excellent fusion site stability. The decision of which implant to use for complex arthrodesis should be dictated by the clinical needs.

The amount of axial rotation in the tibia caused by high tibial osteotomy is relatively unknown. The authors hypothesize that the coronal plane high tibial osteotomy, a novel technique used to treat varus malalignment, alters the axial rotation of the tibia less than the opening wedge high tibial osteotomy. Eight, embalmed, stripped cadaveric tibia-fibula constructs with intact interosseous membranes were randomized to either opening wedge or coronal plane high tibial osteotomies. Sequential valgus corrections of 5 degrees, 10 degrees, and 15 degrees were performed. The Qualisys Track Manager motion capture system was used to measure axial rotation. Student's t test was used to compare axial rotation between the two groups. A p value of 0.05 was determined to be significant. The coronal plane technique produced rotations about the tibial axis that were statistically significantly smaller than those of the opening wedge technique for all correction angles (1.2 degrees internal rotation (IR) vs 16 degrees external rotation (ER), respectively, at 5 degrees correction; p = 0.02) (3.5 degrees IR vs 21.2 degrees ER at 10 degrees correction; p = 0.04) (4.5 degrees IR vs 23.0 degrees ER at 15 degrees correction; p = 0.01). The coronal plane high tibial osteotomy alters axial rotation of the tibia significantly less than the opening wedge high tibial osteotomy.

Low-back pain is a common, disabling medical condition, and one of the major causes is disc degeneration. Total disc replacements are intended to treat back pain by restoring disc height and re-establishing functional motion and stability at the index level. The objective of this study was to determine the effect on range of motion (ROM) and stiffness after implantation of the ProDisc-L device in comparison to the intact state. Twelve L5-S1 lumbar spine segments were tested in flexion/extension, lateral bending, and axial rotation with axial compressive loads of 600 N and 1,200 N. Specimens were tested in the intact state and after implantation with the ProDisc-L device. ROM was not significantly different in the implanted spines when compared to their intact state in flexion/extension and axial rotation but increased in lateral bending. Increased compressive load did not affect ROM in flexion/extension or axial rotation but did result in decreased ROM in lateral bending and increased stiffness in both intact and implanted spine segments. The ProDisc-L successfully restored or maintained normal spine segment motion.