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Diaphyseal tibia fractures may require plate fixation for proper healing to occur. Currently, there is no consensus on the number of screws required for proper fixation or the optimal placement of the screws within the plate. Mechanical stability of the construct is a leading criterion for choosing plate and screws configuration. However, number and location of screws have implications on the mechanical environment at the fracture site and, consequently, on bone healing response: The interfragmentary motion attained with a specific plate and screw construct may elicit mechano-transduction signals influencing cell-type differentiation, which in turn affects how well the fracture heals. This study investigated how different screw configurations affect mechanical performance of a tibia plate fixation construct. Three configurations of an eight-hole plate were considered with the fracture in the center of the plate: eight screws-screws at first, fourth, fifth and eighth hole and screws at first, third, sixth and eighth hole. Constructs' stiffness was compared through biomechanical tests on bone surrogates. A finite element model of tibia diaphyseal fracture was used to conduct a stress analysis on the implanted hardware. Finally, the potential for bone regeneration of each screw configuration was assessed via the computational model through the evaluation of the magnitude of mechano-transduction signals at the bone callus. The results of this study indicate that having screws at fourth and fifth holes represents a preferable configuration since it provides mechanical properties similar to those attained by the stiffest construct (eight screws), and elicits an ideal bone regenerative response.

Human cadavers currently represent the gold standard for spine biomechanical testing, but limitations such as costs, storage, handling, and high interspecimen variance motivate the development of alternatives. A commercially available synthetic surrogate for the human spine, the Sawbones spine model (SBSM), has been developed. The equivalence of SBSM to a human cadaver in terms of biomechanical behavior has not been fully assessed. The objective of this study is to compare the biomechanics of a lumbar tract of SBSM to that of a cadaver under physiologically relevant mechanical loads. An L3-S1 SBSM and 39 comparable human cadaver lumbar spine tracts were used. Each sample was loaded in pure flexion-extension or torsion. Gravity and follower loads were also included. The movement of each vertebral body was tracked via motion capture. The range of motion (ROM) of each spine segment was recorded, as well as the overall stiffness of each L3-S1 sample. The ROM of SBSM L3-L4 was larger than that found in cadavers in flexion-extension and torsion. For the other spine levels, the ROMs of SBSM were within one standard deviation from the mean values measured in cadavers. The values of structural stiffness for L3-S1 of SBSM were comparable to those of cadaveric specimens for both flexion and torsion. In extension, SBSM was more compliant than cadavers. In conclusion, most of the biomechanical properties of an L3-S1 SBSM model were comparable to those of human cadaveric specimens, supporting the use of this synthetic surrogate for testing applications.

A nonbridging external fixation (NBX) system with 1.6-mm diameter pins provided excellent stability for distal radius fractures in cadavers. For the present study, all patients with distal radius fractures were seen by the surgeon authors. Fractures that were displaced and unstable, including Orthopaedic Trauma Association (OTA) types 23-A2.3 to C3.3, were reduced and fixed with the NBX system. The Western Institutional Review Board granted approval (296864) for this retrospective study. Fractures numbered five OTA-A2, eight OTA-A3, two OTA-B3, one OTA-C1, two OTA-C2, and eight OTA-C3. In total, the study included 26 patients. At fixator removal, average dorsiflexion was 37.0° ± 17.8°; volar flexion, 39.4° ± 17.2°; pronation, 80.6° ± 16.1°; and supination, 48.1° ± 24.2°. Follow-up averaged 11.7 mo ± 19.2 mo. At final follow-up, average dorsiflexion was 52.9° ± 25.0°; volar flexion, 53.1° ± 23.7°; pronation, 80.8° ± 14.5°; and supination, 67.7° ± 30.3°. Average radial tilt at the time of injury was 11.6° ± 8.3°; post op to 23.9° ± 5.0°; and at last follow-up, 23.1° ± 5.0°. Average radial styloid length at the time of injury was 4.1 mm ± 3.7 mm; post op to 11.4 mm ± 3.0 mm; and at last follow-up, 10.5 mm ± 3.1 mm. Volar tilt at the time of injury averaged -19.6° ± 14.8°; reduced to 9.8° ± 6.3°; and at last follow-up, 7.5° ± 6.5°. This form of nonbridging fixation is safe and effective at maintaining reduced, extra- and intra-articular, distal radius fractures and allows functional range of motion with minimal complications.

Study Design-Biomechanical cadaveric study. Objective-Long anterior cervical plate and cage (APC) constructs have a risk of pseudarthrosis with minor bone resorption. Stand-alone cages (SACs) allow settling. The biomechanics of SAC have been investigated, but not multilevel, compression screw SAC. The purpose of this study is to evaluate the biomechanical safety of three-level SAC versus APC. Methods-Discectomies at three levels of five human cadaver spines (T1-C3) were fixed with SAC. A 0.18 mm thick shim was interposed between the cage and the superior endplate, and a pressure transducer map was placed between the cage and the inferior endplate. Tests were performed in flexion-extension and then repeated after removing the shims to simulate minor bone resorption. Subsequently, APC was applied and experiments were repeated. The pressure between each cage and endplate and motion of the implants were measured. Results-The range of motion (ROM) of SAC and APC constructs were comparable. The contact area and pressure between cage and endplate did not significantly change during motion with SAC. Shim removal did not significantly affect ROM, contact area, or average pressure measures. For APC, both contact area and pressure decreased from extension to flexion. Shim removal caused a significant loss of contact area and pressure. Conclusions-SAC provided comparable rigidity to the conventional APC construct while maintaining compression at the endplate-cage interface throughout flexion-extension and after minor bone resorption.

The etiology of bone refractures after screw removal can be attributed to residual drill hole defects. This biomechanical study compared the torsional strength of bones containing various sized cortical drill defects in a tibia model.Bicortical drill hole defects of 3 mm, 4 mm, and 5 mm diameters were tested in 26 composite tibias versus intact controls without a drill defect. Each tibia was secured in alignment with the rotational axis of a materials testing system and the proximal end rotated internally at a rate of 1 deg./s until mechanical failure.All defect test groups were significantly lower (P 0.01) in torque-to-failure than the intact group (82.80 ± 3.70 Nm). The 4 mm drill hole group was characterized by a significantly lower (P = 0.021) torque-to-failure (51.00 ± 3.27 Nm) when compared to the 3 mm drill hole (59.00 ± 5.48 Nm) group, but not different than the 5 mm hole group (55.71 ± 5.71 Nm). All bones failed through spiral fractures, bones with defects also exhibited posterior butterfly fragments.All the tested drill hole sizes in this study significantly reduced the torque-to-failure from intact by a range of 28.4% to 38.4%, in agreement with previous similar studies. The 5 mm drill hole represented a 22.7% diameter defect, the 4 mm drill hole a 18.2% diameter defect, and the 3 mm drill hole a 13.6% diameter defect. Clinicians should be cognizant of this diminution of long bone strength after a residual bone defect in their creation and management of patient rehabilitation programs.

Purpose To compare the time-zero load to failure of a quadrupled, single-tendon, all-inside anterior cruciate ligament (ACL) reconstruction graft construct with (supplemented) and without the incorporation of inner-limb whipstitch sutures (control) into a tibial suspensory fixation button. Methods Eight matched pairs of peroneus longus tendons were prepared according to a quadrupled, all-inside ACL soft-tissue graft technique with 1 side serving as a control and the contralateral side supplemented. The constructs were biomechanically tested for strain in the inner and outer limbs during a preconditioning protocol, single-cycle load to failure, and elongation of the whole construct. Results Ultimate load to failure was significantly higher in the supplemented group: 797.5 ± 49.6 N (95% confidence interval [CI], 763.13-831.87 N) versus 719.6 ± 69.6 N (95% CI, 671.38-767.82 N; P = .044). Less graft elongation at failure was observed in the supplemented group (3.1 ± 1.5 mm; 95% CI, 2.07-4.17 mm) versus the control group (21.0 ± 21.2 mm; 95% CI, 6.31-35.69 mm; P = .052). The number of grafts undergoing a 5-mm or greater change in length at failure was 1 of 8 in the supplemented group versus 5 of 8 in the control group (P = .038). Conclusions Inner-limb supplemental tibial fixation results in higher time-zero load to failure and decreased graft elongation in a quadrupled, single-tendon, all-inside ACL reconstruction graft construct. Clinical Relevance The weak point of a single-tendon, quadrupled, all-inside ACL graft construct is the tendon-to-tendon suturing to secure the inner limbs of the graft. Adding supplemental fixation by incorporating the sutures from the inner limb to the tibial suspensory fixation button leads to a higher time-zero load to failure and decreased graft elongation.

Introduction Surgical navigation technology has recently become more prevalent for total knee arthroplasty. Surgical navigation typically requires pin placement in the proximal tibia diaphysis to stabilize the bone-tracking hardware, and there have been several recent reports of fractures through these residual navigation pin holes. The objective of this biomechanical study was to determine whether a difference exists in the torsional bone strength of a 5-mm navigation pin hole drilled at a single location in three different orientations: unicortical, bicortical, and transcortical. Methods Biomechanical composite sawbone tibias were used to test four conditions: the intact condition with no holes, a unicortical hole, a bicortical hole, and a transcortical hole through the proximal diaphysis. Seven specimens from each group were tested in external rotation to failure at 1 deg/sec. Torque-to-failure, absorbed energy-to-failure, and rotational angle-to-failure were statistically compared across the four groups. Results All specimens failed proximally by spiral oblique fractures. No statistical differences were found between unicortical and bicortical groups in torque-to-failure, energy-to-failure, and angle-to-failure. However, both unicortical and bicortical groups were markedly lower in all measures than the intact group. The transcortical group was markedly lower in all measures than the intact group and both unicortical and bicortical groups. Discussion An appropriately placed navigation residual pin hole, either unicortical or bicortical, markedly decreases the torque-to-failure, energy-to-failure, and angle-to-failure of the tibia compared with the intact condition in a synthetic sawbones model. No notable difference was detected between the unicortical and bicortical holes; however, an errant transcortical residual navigation pin hole markedly decreases all measures compared with an appropriately placed unicortical or bicortical hole.

Intra-articular distal radius fractures are difficult to reduce and maintain by nonoperative means. ORIF leaves implants in the patient long after the fracture is healed. External fixation can stabilize the reduced fracture and leaves no long-term implants. The nonbridging fixator (NBX) will provide better reduction and comparable rigidity of fixation to a volar plate for a 5-fragment, OTA 23 C3.2 distal radius fracture. A 5-part distal radius fracture was created in 5 pairs of cadaver arms. One arm was randomly fixed with the NBX fixator; the matched pair was fixed with a volar plate (VPS). Fluoroscopic images recorded the extremes of passive volar-dorsiflexion range of motion (ROM) and radial-ulnar deviation ROM. Each arm was loaded with an axial force at a constant displacement rate until failure. The average reduction of radial tilt achieved for the NBX group was 13.8 ± 4.8° and 6.3 ± 4.7° for VPS; radial length: 3.4 ± 3.7 mm for NBX and 1.9 ± 1.0 mm for VPS; volar tilt: 26.3 ± 12.4° for NBX and 14.0 ± 13.5° for VPS. For NBX, ROM was slightly less after fixation than before fracture. ROM with volar plating was greater after fracture. The peak axial load for NBX was 925 ± 445 N; for VPS, 2,152 ± 1023 N. NBX had minimal effect on ROM and provided adequate strength and restoration of alignment at least as good as VPS for this 5-part fracture model.

Mechanical properties and morphological features of the vertebral cancellous bone are related to resistance to fracture and capability of withstanding surgical treatments. In particular, vertebral strength is related to its elastic properties, whereas the ease of fluid motion, related to the success of incorporation orthopedic materials (eg, bone cement), is regulated by the hydraulic permeability (K). It has been shown that both elastic modulus and permeability of a material are affected by its morphology. The objective of this study was to establish relations between local values of K and the aggregate modulus (H), and parameters descriptive of the bone morphology. We hypothesized that multivariate statistical models, by including the contribution of several morphology parameters at once, would provide a strong correlation with K and H of the vertebral cancellous bone. Hence, μCT scans of human lumbar vertebra were used to determine a set of bone morphology descriptors. Subsequently, indentation tests on the bone samples were conducted to determine local values of K and H. Finally, a multivariate approach supported by principal component analysis was adopted to develop predictive statistical models of bone permeability and aggregate modulus as a function of bone morphology descriptors. It was found that linear combinations of bone volume fraction, trabecular thickness, trabecular spacing, structure model index, connectivity density, and degree of anisotropy provide a strong correlation (R2 ~ 76%) with K and a weaker correlation (R2 ~ 47%) with H. The results of this study can be exploited in computational mechanics frameworks for investigating the potential mechanical behavior of human vertebra and to develop strategies to treat or prevent pathological conditions such as osteoporosis, age‐related bone loss, and vertebral compression fractures. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Background:. It is unclear whether the sacroiliac joint is vulnerable to adjacent segment disease. Clinical studies have suggested that many patients who have undergone lumbar arthrodesis will develop adjacent segment disease, which may contribute to sacroiliac joint degeneration. The purpose of the present study was to examine whether arthrodesis in the lumbar spine results in altered biomechanics at the sacroiliac joint that could contribute to adjacent segment disease within the joint. Methods:. With use of human cadavers in a biomechanical laboratory study, the effects of lower-lumbar arthrodesis and sacroiliac screws on the biomechanics of the sacroiliac joint were assessed. Human cadaveric pelves with lumbar spines were biomechanically tested in flexion-extension, rotation about the vertical axis, and compression along the vertical axis with single and double-leg support. Four conditions were compared: (1) intact, (2) L4-L5 arthrodesis, (3) L4-S1 arthrodesis, and (4) left sacroiliac screw. Construct vertical and horizontal motions at the anterior and posterior surfaces of the sacroiliac joint were measured. Results:. Significant measurable increases in motion of the sacroiliac joint related to arthrodesis of the lumbar spine occurred with flexion-extension loading (p < 0.05). No significant changes were observed for rotation about the vertical axis or compression along the vertical axis with single and double-leg support. Conclusions:. After 360°, 1 or 2-level lumbosacral spine arthrodesis, the sacroiliac joint showed a significant increase in rotational motion with flexion-extension loading. Increases in horizontal translation with axial rotation loading and vertical translation with axial compression loading were not significant. Clinical Relevance:. The risk of significant alteration of normal sacroiliac kinematics should be considered in all patients undergoing 360° lumbosacral arthrodesis.

Category: Hindfoot Introduction/Purpose: Lateral column lengthening calcaneus osteotomy has been used widely in treating Stage IIB flexible flatfoot deformity in order to shift the anterior segment of the calcaneus forwards, which improves the coverage of the talonavicular joint by forefoot adduction. The premise of this investigation is that in addition to shifting the forefoot anteriorly around the axis of the talar head, there is also a posterior translation of the tuberosity of the calcaneus which is detrimental in that the angle of Gissane then impinges upon the posterior facet of the subtalar joint causing pain. Our hypothesis is that in addition to anterior translation of the calcaneus, posterior shift of the calcaneal tuberosity occurs with lengthening osteotomy of the calcaneus. Methods: An acute cadaveric flatfoot model was created on 5 fresh frozen cadaver feet with no previous foot and ankle deformity. In order to simulate the surgical scenario, the study was performed with no external load on the limb. A vertical osteotomy was performed 1 cm posterior of the calcaneocuboid joint. Commercially available precut wedges of 6 mm, 8 mm, 10 mm, and 12 mm were used for lateral column lengthening. After the insertion of the bone grafts, positional changes in sagittal plane of both the anterior and posterior calcaneus segments were monitored on lateral views under both fluoroscopy and a 3D digital high-resolution motion capture system. Results were calculated in percentage change from the base line horizontal distance between the talar and both anterior and posterior calcaneus markers before insertion of the wedges. Results: According to fluoroscopic measurements, the anterior translation of the anterior calcaneus segment was 7.27%+/-0.06 for 6 mm wedge, 16.11%+/-0.06 for 8 mm wedge, 20.81%+/- 0.08 for 10 mm wedge and 18.16%+/-0.07 for 12 mm wedge. The posterior translation of the posterior calcaneus segment was 9.85%+/-0.09 for 6 mm wedge, 13.15%+/-0.09 for 8 mm wedge, 12.04+/-0.09 for 10 mm wedge, and 14.06%+/-0.10 for 12 mm wedge. Statistical analysis showed that: 6 mm wedges did not cause significant changes in the translation of both anterior and posterior calcaneus segments with respect to the talus. 8 mm, 10 mm and 12 mm wedges caused significant translations both anteriorly and posteriorly. There was no statistically significant difference in the amount of either anterior or posterior translation caused by 8 mm, 10 mm or 12 mm wedges. These results were corroborated by 3D measurements. Conclusion: Of interest is that a 6 mm graft did not cause any significant anterior or posterior shift of the calcaneus. Lateral column lengthening with the 8,10, and 12 mm grafts however caused forward shifting of the anterior calcaneus, but also statistically significant posterior translation of the tuberosity, causing impingement of the posterior facet which was visible in each cadaver tested. There was no statistical difference between the sizes of the wedge above 6 mm and the translations they caused either anteriorly or posteriorly. Surgeons should be aware of the potential for painful impingement with the lateral column lengthening osteotomy.

Christopher M Aguila,1 Gaëtan J-R Delcroix,2–5 David N Kaimrajh,6 Edward L Milne,6 H Thomas Temple,5,7 Loren L Latta2,6 1Department of Biological Sciences, Florida International University, Miami, FL, USA; 2Department of Orthopaedics, Miller School of Medicine, University of Miami, Miami, FL, USA; 3Research Service & Geriatric Research, Education, and Clinical Center, Bruce W. Carter Veterans Affairs Medical Center, Miami, FL, USA; 4Interdisciplinary Stem Cell Institute, University of Miami, Miami, FL, USA; 5Vivex Biomedical Inc., Marietta, GA, USA; 6Max Biedermann Institute for Biomechanics, Miami Beach, FL, USA; 7Translational Research and Economic Development, Nova Southeastern University, Fort-Lauderdale, FL, USA Purpose: This study was designed to investigate the biomechanical properties of nonirradiated (NI) and irradiated (IR) peroneus tendons to determine if they would be suitable allografts, in regards to biomechanical properties, for anterior cruciate ligament reconstruction after a dose of 1.5–2.5 Mrad.Methods: Seven pairs of peroneus longus (PL) and ten pairs of peroneus brevis (PB) tendons were procured from human cadavers. The diameter of each allograft was measured. The left side of each allograft was IR at 1.5–2.5 Mrad, whereas the right side was kept aseptic and NI. The allografts were thawed, kept wet with saline, and attached in a single-strand fashion to custom freeze grips using liquid nitrogen. A preload of 10 N was then applied and, after it had reached steady state, the allografts were pulled at 4 cm/sec. The parameters recorded were the displacement and force.Results: The elongation at the peak load was 10.3±2.3 mm for the PB NI side and 13.5±3.3mm for the PB IR side. The elongation at the peak load was 17.4±5.3 mm for the PL NI side and 16.3±2.0 mm for the PL IR side. For PL, the ultimate load was 2,091.6±148.7 N for NIand 2,122.8±380.0 N for IR. The ultimate load for the PB tendons was 1,485.7±209.3 N for NI and 1,318.4±296.9 N for the IR group. The ultimate stress calculations for PL were 90.3±11.3 MPa for NI and 94.8±21.0 MPa for IR. For the PB, the ultimate stress was 82.4±19.0 MPa for NI and 72.5±16.6 MPa for the IR group. The structural stiffness was 216.1±59.0 N/mm for the NI PL and 195.7±51.4 N/mm for the IR side. None of these measures were significantly different between the NI and IR groups. The structural stiffness was 232.1±45.7 N/mm for the NI PB and 161.9±74.0 N/mm for the IR side, and this was the only statistically significant difference found in this study (P=0.034).Conclusion: Our statistical comparisons found no significant differences in terms of elongation, ultimate load, or ultimate stress between IR and NI PB and PL tendons. Only the PB structural stiffness was affected by irradiation. Thus, sterilizing allografts at 1.5–2.5 Mrad of gamma irradiation does not cause major alterations in the tendons’ biomechanical properties while still providing a suitable amount of sterilization for anterior cruciate ligament reconstruction. Keywords: ACL reconstruction, allograft, sterilization, tissue banking

Background: The objective of this study was to define the volume (mLs) needed for a positive saline load challenge test in anterolateral (AL), anteromedial (AM), posterolateral (PL), or posteromedial (PM) ankle arthrotomy wounds using normal saline (NS) and methylene blue (MB). Another objective was to evaluate the use of fluoroscopy and iodinated contrast in the diagnosis of ankle arthrotomies. Methods: Four cadaveric ankle specimens underwent standardized arthrotomy creation in either the AL, AM, PL, or PM portion of each specimen. An 18-gauge needle was used to inject fluid into each ankle, and the volumes needed for positive fluid challenges were recorded. All 4 ankles were tested 10 times (n = 40) with NS and 10 times using MB (n = 40). A fifth cadaveric ankle was injected with radiopaque contrast solution, and an arthrotomy was simulated and imaged with fluoroscopy.Statistical analyses compared the volumes of NS and MB needed for a positive test. In addition, the 25th, 50th, 75th, 90th, and 95th percentiles of volumes needed for a positive test was calculated. Results: The volume of fluid necessary to detect 25%, 50%, 75%, 90%, and 95% of ankle arthrotomies from any site was 2.0 mL, 4.5 mL, 9.0 mL, 10 mL, and 10 mL, respectively. Anterior arthrotomies required less fluid (2.1 mL ± 0.5) than posterior arthrotomies (9.0 mL ± 1.2) for a positive test ( P < .0001). There was no difference between the amount of NS (5.5 mL ± 3.6) vs MB (5.6 mL ± 3.7) needed for a positive challenge test ( P = .739). Conclusion: Ninety-five percent of ankle arthrotomies could be diagnosed with 10 mL of injected fluid; there was no difference between the volume of NS vs MB needed. Fluoroscopy assisted with needle placement and can be combined with radiopaque contrast solution to diagnose ankle arthrotomies. Clinical Relevance: The findings of this study may improve sensitivity and efficiency in the diagnosis of traumatic ankle arthrotomies, for which there is currently a paucity of literature.

Category: Sports Introduction/Purpose: Lateral ankle pain persists in 10%-20% of patients following severe ankle sprains treated non-operatively. The authors hypothesize that the peroneal tendons may become interposed between the ruptured ends of the calcaneofibular ligament (CFL). Though previously visualized and noted in the literature, no studies have evaluated this lesion biomechanically and anatomically. The purpose of this study is to demonstrate that following a severe lateral ankle sprain that the interposition of the peroneal tendons between the ruptured ends of the CFL can occur. Methods: Eight fresh-frozen cadaveric lower extremity specimens (defrosted) were secured by the foot to a wooden board in the method of Lauge-Hansen. A manual inversion force was then applied to the ankle, both with the ankle in plantar flexion and also in a neutral position to approximate a severe ankle sprain. Magnetic resonance imaging (MRI) was then performed on each ankle. Each specimen was then dissected to observe the integrity and relationship of the lateral ankle structures. Results: Four of the eight specimens sustained CFL tears as viewed by MRI and confirmed through anatomic dissection. One of the four specimens with a CFL tear had a mid substance ligament rupture with the proximal half of the ligament positioned superficial to the peroneal tendon complex. This relationship was observed using the MRI. Conclusion: Creating severe lateral ankle sprain produced ruptures of the CFL with interposition of the peroneal tendon complex between the torn ends of the ligament was seen and identified. This phenomenon may prevent primary ligament healing of the CFL and may be a contributing factor in the chronic ankle pain of non-surgically treated lateral ankle sprains. Perhaps surgical intervention should be considered if clinical suspicion exists, such as with a Stener lesion of the hand.

Cup position is crucial for optimal outcomes in total hip arthroplasty. Radiographic assessment of component position is routinely performed in the early postoperative period.The aims of this study were to determine in a controlled environment if routine radiographic methods accurately and reliably assess the acetabular cup position and to assess if there is a statistical difference related to the rater's level of training.A pelvic model was mounted in a spatial frame. An acetabular cup was fixed in different degrees of version and inclination. Standardized radiographs were obtained. Ten observers including five fellowship-trained orthopaedic surgeons and five orthopaedic residents performed a blind assessment of cup position. Inclination was assessed from anteroposterior radiographs of the pelvis and version from cross-table lateral radiographs of the hip.The radiographic methods used showed to be imprecise specially when the cup was positioned at the extremes of version and inclination. An excellent inter-observer reliability (Intra-class coefficient0,9) was evidenced. There were no differences related to the level of training of the raters.These widely used radiographic methods should be interpreted cautiously and computed tomography should be utilized in cases when further intervention is contemplated.

Purpose: The purpose of this study was to thoroughly characterize the fan-folded iliotibial band (FITB) allograft and compare it with anterior tibialis tendons (ATs) and native anterior cruciate ligaments (ACLs) to determine whether it measures up to those tissues. Methods: We compared the histologic structure, tensile strength to failure, creep, and stress-relaxation properties of FITBs with those of ATs and ACLs. In vitro cytotoxicity and biocompatibility of FITBs were also compared with ATs. Results: No structural difference was observed between the tissues studied. FITB ultimate tensile strength (3,459 � 939 N) was not significantly different (P > .9999) from ultimate tensile strength of ATs (3,357 � 111 N) and was significantly greater (P ¼ .0005) than that of ACLs (886 � 254 N). No significant difference (P > .9999) was observed in the increase in length resulting from creep testing between FITBs (9.5 � 3.0 mm) and ATs (9.7 � 4.0 mm). During stress-relaxation testing, FITBs reached 181 � 46 N, which was not significantly different (P > .9999) from ATs (166 � 40 N). Finally, we showed that cytotoxicity of FITBs and ATs was negligible. In vitro biocompatibility of FITBs and ATs was very good, whereas FITBs had a higher propensity to favor the attachment and infiltration of cells that proliferated for at least 4 weeks on their contact. Conclusions: We found that FITBs, ACLs, and ATs shared a similar structure made of aligned collagen fibers. No significant difference was observed between FITB and AT ultimate tensile strength, creep, and stress-relaxation viscoelastic properties. Ultimate tensile strength to failure of ACLs was lower than that of FITBs and ATs, whereas ACLs were superior to both FITBs and ATs during creep and stress-relaxation testing. FITBs and ATs showed low cytotoxicity and excellent biocompatibility in vitro, with a somewhat higher propensity of FITBs to favor cell attachment and infiltration over time. Clinical Relevance: This study suggests that FITBs have the potential to perform as well as ATs for ACL reconstruction.

Physical testing is commonly performed to answer important biomechanical questions in the treatment of patients with fractures and other orthopaedic conditions. However, a variety of mistakes that are made in performing such investigations can severely limit their impact. The goal of this article is to discuss important aspects of study design to consider when planning for biomechanical investigations so that the studies can provide maximal benefit to the field. The best mechanical investigations begin with a good research question, one that comes out of patient care experience, is clearly defined, and can be stated concisely. The first practical issue to be considered is often choosing the type of physical specimens to be tested to address the research question. A related issue involves determining how many specimens will be needed to answer the posed mechanical question. Cadavers are generally still the closest to the actual clinical situation, but they are limited by interspecimen variability, which often requires a matched pair design that can address only one question. Simulated bone specimens limit variability and can replicate normal and osteoporotic bone. In planning the physical testing, the critical mechanical variables involved in answering the research question must be identified and due consideration given to deciding how best to measure them. Another important issue that arises relates to whether or not single static loadings will suffice in the testing (eg, to study construct stiffness) or whether cyclic dynamic testing is necessary (eg, to study late failure likely attributable to fatigue). To summarize, experimental design should be carefully planned before initiating mechanical testing. Sample size calculations should be performed to ensure adequate power and that clinically relevant differences can be detected. This pregame analysis can save significant time and cost and greatly increase the likelihood that the results will advance knowledge.

Object Previous studies have demonstrated that patients with spinal fusion are at greater risk for adjacent-segment disease and require additional surgery. It has been postulated that excessive motion of a given motion segment unit (MSU) leads to an increased risk of disc degeneration. It is the authors' hypothesis that a greater increase in adjacent-segment motion will be observed following a 2-level versus a single-level anterior cervical discectomy and instrumented fusion (ACDF). Therefore, they undertook this study to determine the effect of single-level versus 2-level ACDF on the biomechanics of adjacent MSUs. Methods Ten fresh-frozen human cervical spines were used in this study. The specimens were potted at C-4 and T-1 and tested in flexion and extension. Range of motion (ROM) was 30° of flexion and 15° of extension at a maximum load of 50 N. The specimens were tested intact and then were randomized into 2 groups of 5 specimens each. Group 1 underwent a single-level ACDF at the C5–6 level first, and Group 2 underwent the procedure at the C6–7 level. After testing, both groups had the fusion extended to include the C5–7 levels, and the testing was repeated. Changes in overall ROM, stiffness, and segmental motion were calculated and statistically analyzed using a paired Student t-test. Results An increase in sagittal ROM of 31.30% above (p = 0.012) and 33.88% below (p = 0.066) the fused MSU was found comparing a 2-level with a 1-level ACDF. The overall stiffness of the entire spinal construct increased 37.34% (p = 0.051) in extension and 30.59% (p = 0.013) in flexion as the second fusion level was added. As expected, the overall sagittal ROM of the entire spinal construct decreased by 13.68% (p = 0.0014) with a 2-level compared with a 1-level fusion. Conclusions This study has shown that the biomechanics at adjacent levels to a cervical spine fusion are altered and that there is increased adjacent-segment motion at the levels above and below, after a 2-level compared with a 1-level ACDF.

This article is based on an invited presentation at the Biomechanics Session for the Basic Science Focus Forum held at the Orthopaedic Trauma Association meeting, 2010. It is not intended to be a scientific presentation of any specific investigation. It presented aspects of several types of investigations to illustrate the variety of biomechanical models that are used, and what value can be derived from those models. All models have limitations in what they try to portray. In order for any model to provide useful information, it must stand some type of validation of its ability to behave similar to real world experiences. The advantages and disadvantages of each model must be described to the best of the investigators ability-so that the readers can determine how the information may be used in the real world.

Purpose The purpose of this study was to evaluate the initial biomechanical properties of a fan-folded, single-loop construct of fan-folded fascia lata allograft in comparison to other graft tissues currently being used for anterior cruciate ligament (ACL) reconstruction. Methods Eighteen fascia lata specimens were harvested from 11 donors and fan folded through a proprietary process. Bone–patellar tendon–bone (BPTB), tibialis anterior, tibialis posterior, and peroneus longus tendons were harvested from 4 additional donors. All soft-tissue grafts were tested to failure in an MTS machine (MTS Systems, Eden Prairie, MN) in a single-looped fashion. BPTB grafts were similarly clamped in freeze grips. The ultimate load to failure and stiffness were calculated for each graft type tested. Results The mean ultimate load to failure was 3,266 N and stiffness was 414 N/mm for the single-looped fascia lata grafts (n = 18). There was no significant difference for ultimate load to failure and stiffness between the fascia lata and tibialis anterior (3,012 N and 342 N/mm, respectively), tibialis posterior (3,666 N and 392 N/mm, respectively), and peroneus longus (3,050 N and 346 N/mm, respectively) tendons. The fascia lata grafts performed significantly better ( P Conclusions A single-loop construct of fan-folded fascia lata allograft has, on biomechanical testing, initial ultimate tensile strength (3,266 N) and stiffness values equivalent to or better than several other graft tissues currently used in ACL reconstruction, including BPTB (1,403 N), tibialis anterior (3,012 N), tibialis posterior (3,666 N), and peroneus longus (3,050 N). Clinical Relevance In the face of potential allograft tissue shortages and increasing constraints on health care expenditures, the use of fascia lata has the potential to be a readily available graft for ACL reconstruction that performs as well as other grafts and at a comparable or lower cost.

This review summarizes symposium presentations from the OTA's Basic Science Focus Forum on care for osteoporotic fractures. The limitations of diaphyseal osteoporotic animal bone models are discussed, together with the potential benefits of using metaphyseal models to study osteoporotic fracture fixation constructs. Metaphyseal bone repair models provide better simulation of the most common osteoporotic fractures. Selection of an osteoporotic model for mechanical testing is also challenging. One should always thoroughly define the clinical problem to be addressed. The selected model should then be validated for behavior matched to known clinical behavior with known fixation configurations. The medical management of osteoporosis is directed at enhancing bone mass, improving bone quality, and lowering fracture risk. Medical strategies to achieve these goals are discussed. The medical strategy should include provision of an adequate calcium and vitamin D environment to facilitate well-mineralized bone and improve bone quality, prevent excessive bone resorption, and provide an anabolic stimulus to enhance bone formation. Atypical femur fractures continue to be a serious issue for the orthopaedic community. Risk factors, treatment modalities, and prevention strategies are discussed. A comprehensive strategy for the improved treatment of osteoporotic fractures must address both biological and mechanical issues and includes 4 specific approaches: (1) removal of inhibitors to bone healing; (2) introduction of bone healing stimulants; (3) modification of fracture fixation constructs; and (4) application of bone augmentation or substitutes. There is currently no optimal bone substitute. Substitutes should be chosen based on the most critical need when treating a particular fracture.

A B S T R A C T Introduction: Distal femur fractures proximal to total knee femoral component constitutes the most prevalent type of periprosthetic fracture, and plate fixation treatment is associated with a 7.7% incidence of refracture proximal to the plate. The primary objective of this study was to compare proximal fixation techniques of a periprosthetic distal femur fracture plate in an osteoporotic bone model. The secondary objective was to determine the subsequent periprosthetic plate fracture pattern and/or complexity associated with each proximal plate fixation configuration. Materials and methods: A segmental defect was created in 21 synthetic osteoporotic adult femurs 6 cm proximal to the distal femur and all specimens were stabilised with a 246 mm locking femur plate. Fixation in the most proximal hole was varied by use of either a cerclage cable, unicortical locking screw, or a bicortical locking screw. Specimens were tested to failure in simultaneous eccentric compression and torsion. Results: Proximal cerclage fixation demonstrated higher mean maximum axial force at failure (4142.67 178.71 N, p < 0.001), stiffness (443.8 61.64 N/mm), and maximum torque (20.9 0.93 N m, p < 0.001). Unicortical and bicortical screw refractures occurred at the screw, cerclage wire refractures occurred at the first proximal screw distal to the cerclage. Conclusions: In periprosthetic distal femur fracture locking plate fixation, proximal hole stabilization with a cerclage wire tolerates significantly higher failure forces while distributing forces distal to the area within the plate fixation. Cerclage wiring may be an option in distal femur periprosthetic fractures to alleviate stress risers in vulnerable bone.

To assess ulnocarpal joint stability after treatment of a peripheral triangular fibrocartilage complex (TFCC) injury with all-inside arthroscopic suture repair (SR), extensor retinaculum capsulorrhaphy with the Herbert sling (HS), and a combination of both (SR+HS).Twelve fresh-frozen, age-matched, upper-extremity specimens intact from the distal humerus were prepared. Nondestructive mechanical testing was performed to assess native ulnocarpal joint stability and load-displacement curves were recorded. A peripheral, ulnar-sided TFCC injury was created with arthroscopic assistance, and mechanical testing was performed. Each specimen was treated with SR or HS and testing was repeated. The 6 specimens treated with SR were then treated with HS (SR+HS), and testing was repeated. We used paired Student t tests for statistical analysis within cohorts.For all cohorts, there was an average increase in ulnar translation after the creation of a peripheral TFCC injury and an average decrease after repair. Herbert sling decreased translation by 21%, SR decreased translation by 12%, and SR+HS decreased translation by 26%.Suture repair plus HS and HS reduce ulnar translation the most after a peripheral TFCC injury, followed by SR alone.Ulnocarpal joint stability should be assessed clinically in patients with peripheral TFCC injury, and consideration should be made for using extensor capsulorrhaphy in isolation or as an adjunct to SR as a treatment option.

© 2015 Wolters Kluwer Health, Inc. All rights reserved. Geriatric hip fractures continue to increase in frequency as the population ages, and intertrochanteric femur fractures are a significant part of these injuries. Plate fixation for intertrochanteric fractures of the proximal femur has been in use for many years, and application of the sliding hip screw has also been a mainstay of treatment. Recent data suggest there may be a benefit to using implants that add rotational stability to the proximal intertrochanteric fragment. Although preliminary data are promising, there is need for improved investigation to demonstrate the benefit of these new implant designs. In this era of increasing emphasis on cost, quality, and value, better data are needed to help clinicians determine the best therapy for their patients.

Surgeries for Lumbar Spinal Stenosis (LSS) aim at decompressing spinal nerves and relieving symptoms of radiculopathy or myelopathy. Frequently after surgery, stenosis may progress in adjacent spinal segments, but the etiology of adjacent segment degeneration is still unclear. It is hypothesized that surgical approaches for LSS may alter the normal biomechanics of adjacent segments, eventually contributing to the development of stenosis. This study investigated implications of established decompressive surgical approaches on adjacent segments biomechanics. A realistic finite element model of a L1-L5 human lumbar spine was used for assessing changes in spine segments’ biomechanics due to laminotomy and laminectomy surgeries. First, the model was validated by comparing its predictions to previously reported spine kinematic data obtained after multi-level laminotomy and laminectomy. Subsequently, using a hybrid loading protocol, segments’ kinematics, intradiscal pressure, and stress in flexionextension were investigated simulating single level (L4-L5) laminotomy and laminectomy procedures. Alterations of spine segments biomechanics due to laminotomy were minimal. In contrast, after laminectomy, the L3-L4 range of motion, intradiscal pressure, and stress increased up to 50%, 20%, and 120%, respectively. These results suggest that laminotomy represents a better approach than laminectomy for reducing risks of spine instability or mechanically-accelerated disc degeneration in adjacent segments.

Bei allen schweren Motorradunfallen besteht – bis zum Beweis des Gegenteils in der Klinik – immer der Verdacht auf das Vorliegen einer instabilen Halswirbelsaulenverletzung. Um eine adaquate Notfallversorgung zu ermoglichen, muss der Motorradhelm jedoch bereits am Unfallort entfernt werden. Aus den bisherigen klinischen und experimentellen Daten in der Literatur ist nicht abzuschatzen, welche Effekte die zur Helmabnahme erforderlichen Manipulationen auf eine instabile Verletzung der Halswirbelsaule haben konnen. An 10 humanen Kadavern mit intakten Weichteilen wurde durch Osteotomie des Dens axis eine standardisierte experimentelle Instabilitat der oberen Halswirbelsaule geschaffen. Unter Bildwandlerdurchleuchtung wurden die bei der Helmabnahme auftretenden Bewegungen in den Segmenten C1–2 und C2–3 registriert und dokumentiert. Nach Osteotomie des Dens axis zeigten sich bei den gefuhrten physiologischen Bewegungen der Halswirbelsaulen ohne Helm eine durchschnittliche Beweglichkeit von 23,7° im verletzten Segment in der Sagittalebene ohne Auftreten von Subluxationen oder Luxationen. Mit Motorradhelm kam es in Neutralposition am liegenden Praparat in einem Fall zu einer Subluxation im Segment C1–2,bei der Helmabnahme in 2weiteren Fallen.Die durchschnittlich im verletzten Segment C1–2 gemessene Bewegung beim Helmabnehmen betrug 19,0° (2–25°),Median 18,0°. Um die auch beim vorsichtigen Entfernen des Motorradhelm an der instabilen oberen Halswirbelsaule auftretenden Bewegungen zu vermeiden,sollte der Helm am Unfallort mit geeignetem Gerat aufgeschnitten werden.Auf der Basis der Ergebnisse muss zudem ein Dialog mit den Herstellern von Motorradhelmen aufgenommen werden,um Veranderungen des Konstruktionsprinzips zu diskutieren, die es ermoglichen,den Helm so zu zerlegen, dass eine Entfernung ohne Manipulationen am Kopf moglich wird.

This biomechanical study was performed to evaluate a new modular, tibial testing system developed for analysis of tibial nails and their locking screws.A new testing system, consisting of five modules, was designed to simulate a tibia. For this study one module was removed to simulate a 55-mm distal tibial defect inducing maximum loading on the distal portion of the implant and locking bolts. The tibial load offsets were 23 mm proximally and 10 mm distally medial to the centreline of the tibial shaft to simulate the location of the expected resultant load during the peak loading and inversion torque on the ankle during the gait cycle. Four solid tibial nails (STN, Stryker-Howmedica-Osteonics, Kiel, Germany) were tested to static failure and 15 nails were tested dynamically. Our results showed that the solid tibial nails fractured in the testing device in the same manner and location as they do in clinical series. Evaluation of the results showed the mean fatigue limit of the STN to be 1.4 kN for 500,000 cycles with a standard deviation (S.D.) of 0.33 kN. This biomechanical study establishes a standard technique for the biomechanical testing of tibial nails, in a clinically relevant manner, avoiding the inconsistency of cadaver bone tests. As it is a standardised test set-up this new modular testing system could serve as a standard by which small diameter tibial nails and other devices could be evaluated and compared with other systems currently in use.

All of the current modalities have a place in the treatment of diaphyseal humeral fractures. Functional bracing renders a high rate of union and seems to be a safe method of treatment for most closed fractures. Type II and III open fractures seem to respond best to plate fixation or external fixation, particularly when there are associated neural or vascular pathologic findings. Patients with polytrauma who are unable to walk are also best treated with plate fixation. Plate fixation is also the best method of treatment when adequate alignment cannot be obtained with nonsurgical methods. Intramedullary nailing remains controversial because its complication rate is higher than that associated with either plate fixation or functional bracing. None of the treatments described is a panacea, and complications may occur with each one of them. An appropriate appreciation of the biologic response to the three modalities; an understanding of the indications, contraindications, and possible complications of the treatments; and a mastery of the techniques of application are essential for the attainment of satisfactory clinical results.

The authors present a prospective randomized blinded cadaver study designed to evaluate the engineering concept of a squeeze film effect and the effect of cement viscosity on cement penetration in total knee arthroplasty. This was done in response to an earlier clinical study demonstrating inferior tibial cement penetration using early, often liquid, phase cement. Paired cadaver tibias were implanted with the tibial component using either liquid or dough phase cement. Based on an AP fluoroscopic image, the dough phase cement penetrated deeper than liquid in all four zones. This was statistically significant in zones 1, 2 and 3. Deeper cement penetration has been shown to provide a stronger cement–bone interphase. As a result dough phase cement is recommended to obtain optimal cement penetration.

Background: Nonoperatively treated fractures of the humeral diaphysis have a high rate of union with good functional results. However, there are clinical situations in which operative treatment is more appropriate, and, though interest in plate osteosynthesis has decreased, intramedullary nailing has gained popularity in recent years. We report the results of treating fractures of the humeral diaphysis with a prefabricated brace that permits full motion of all joints and progressive use of the injured extremity. Methods: Between 1978 and 1990, 922 patients who had a fracture of the humeral diaphysis were treated with a prefabricated brace that permitted motion of adjacent joints. The injured extremities were initially stabilized in an above-the-elbow cast or a coaptation splint for an average of nine days (range, zero to thirty-five days) prior to the application of the prefabricated brace. Orthopaedic residents, supervised by teaching staff, provided follow-up care in a special outpatient clinic. Radiographs were made at each follow-up visit until the fracture healed. Results: We were able to follow 620 (67 percent) of the 922 patients. Four hundred and sixty-five (75 percent) of the fractures were closed, and 155 (25 percent) were open. Nine patients (6 percent) who had an open fracture and seven (less than 2 percent) who had a closed fracture had a nonunion after bracing. In 87 percent of the 565 patients for whom anteroposterior radiographs were available, the fracture healed in less than 16 degrees of varus angulation, and in 81 percent of the 546 for whom lateral radiographs were available, it healed in less than 16 degrees of anterior angulation. At the time of brace removal, 98 percent of the patients had limitation of shoulder motion of 25 degrees or less. We were unable to follow most of the patients long-term, as they did not return to the clinic once the fracture had united and use of the brace had been discontinued. Conclusions: Functional bracing for the treatment of fractures of the humeral diaphysis is associated with a high rate of union, particularly when used for closed fractures. The residual angular deformities are usually functionally and aesthetically acceptable. The present study illustrates the difficulties encountered in carrying out long-term follow-up of indigent patients treated in charity hospitals that are affiliated with teaching institutions. These difficulties are also becoming common with patients insured under managed-care organizations and are frequent in our peripatetic population.

Functional bracing is an effective therapeutic modality in the management of selected fractures of the tibia, humerus, and ulna, particularly low-energy injuries. In the case of tibial fractures, it is applicable only to reduced transverse fractures and to axially unstable fractures with an acceptable degree of shortening. The rate of union of tibial fractures after functional bracing is approximately 97%. The initial shortening noted with closed tibial fractures rarely increases with weight bearing. Shortening has been reported to be as little as 12 mm in 95% of patients, with angulation of 8 degrees in 90%. Such minimal shortening and angulation do not affect functional results. In closed and type I open diaphyseal humeral fractures treated with functional braces, the nonunion rate is approximately 3%. Most of the reported residual angular deformities have been functionally and cosmetically acceptable. For isolated ulnar fractures, the nonunion rate is approximately 2%. Functional fracture bracing is predicated on the premise that motion at the fracture site encourages osteogenesis. The method is applicable only to selected fractures, and it is necessary to have a clear understanding of its rationale, indications, and technique.

A reconstruction of the anterior bundle of the ulnar collateral ligament of the elbow using bone anchors was compared regarding strain and valgus load strength with the intact ulnar collateral ligament and the reconstructed ulnar collateral ligament using bone tunnels. In both normal and reconstructed elbows, the anterior band and posterior band were tight during only a portion of the range of motion. Toward extension, the mean peak strain in the anterior band was tight for the normal and bone anchor groups, but lax in the bone tunnel group. Toward extension, the mean peak strain in the posterior band was lax in all elbows. Toward flexion, the strain in the anterior band was lax in the normal and bone anchor groups, but tight in the bone tunnel group. The mean of the peak strains for the posterior band toward flexion was tight for all elbows. Mean valgus load strength of normal elbows was 22.7 9.0 N m. The bone tunnel and bone anchor mean strengths were 76.3% and 63.5%, respectively, of normal elbow strength. We concluded that the bone anchor reproduced the normal anatomy and mechanical function of the ulnar collateral ligament more closely than the bone tunnel, and that both reconstruction methods were significantly weaker than the normal ulnar collateral ligament. However, we found no significant difference in reconstruction strength between bone anchor and bone tunnel.

Conventionally, short-segment fusion involves instrumentation of one healthy vertebra above and below the injured vertebra, skipping the injured level. This short-segment construct places less surgical burden on the patient compared with long-segment constructs, but is less stable biomechanically, and thus has resulted in clinical failures. The addition of two screws placed in the fractured vertebral body represents an attempt to improve the construct stiffness without sacrificing the benefits of short-segment fusion.To determine the biomechanical differences between four- and six-screw short-segment constructs for the operative management of an unstable L1 fracture.Biomechanical study of instrumentation in vertebral body cadaveric models simulating an L1 axial load injury pattern.Thirteen intact spinal segments from T12 to L2 were prepared from fresh-frozen cadaver spines. An axial load fracture of at least 50% vertebral body height was produced at L1 and then instrumented with pedicle screws. Specimens were evaluated in terms of construct stiffness, motion, and rod strain. Two conditions were tested: a four-screw construct with no screws at the L1 fractured body (4S) and a six-screw construct with screws at all levels (6S). The two groups were compared statistically by paired Student t test.The mean stiffness in flexion-extension was increased 31% (p.03) with the addition of the two pedicle screws in L1. Relative motion in terms of vertical and axial rotations was not significantly different between the two groups. The L1-L2 rod strain was significantly increased in the six-screw construct compared with the four-screw construct (p.001).In a cadaveric L1 axial load fracture model, a six-screw construct with screws in the fractured level is more rigid than a four-screw construct that skips the injured vertebral body.

To the authors’ knowledge, no published studies have examined the use of locking plates on injuries of the anterior pelvic ring. The purpose of this study was to determine whether locked plates provide enhanced stability in the treatment of pubic symphyseal disruptions. Completely unstable pelvic injuries were simulated in pelvic Sawbones (model 1301; Pacific Research Laboratories, Vashon, Washington) and 2 different fixation constructs used for anterior fixation (4-hole, 3.5-mm pubic symphysis plate with all locked or all unlocked screws). Adjunctive sacroiliac screw fixation with a single 7.3-mm screw placed into S1 was used in all specimens. Specimens were analyzed for motion at the pubic symphysis and sacroiliac joints using a Material Testing System (MTS Systems Corporation, Eden Prairie, Minnesota). Each specimen was subjected to compressive loading in a single-limb stance. Side loading was also examined. The main outcome measurement was motion at the pubic symphysis and sacroiliac joints and overall construct stiffness. No significant difference existed in overall construct stiffness between the 2 methods of pubic symphysis fixation. The motions at the pubic symphysis or injured sacroiliac joints were not significantly different. In addition, motion at the pubic symphysis joint with lateral load was not improved with a locking construct. No significant difference existed between 4-hole locked or unlocked constructs used for fixation of the pubic symphysis. No apparent advantage of locking screws exists for disruptions of the pubic symphysis, and recent reports have questioned the possibility of catastrophic failure.

Background Instability at the ulnocarpal joint has many causes, but the common thread among these causes is the presence of abnormalities in the triangular fibrocartilage complex (TFCC). However, the biomechanical consequences at the ulnocarpal joint after detachment of the TFCC from the ulnar styloid are not clearly defined. Better delineation of whether peripheral TFCC detachments cause ulnocarpal instability will help to design surgical treatments.

Clinical experience led us to the hypothesis that in the proximal humerus cancellous bone beneath the top part of the head is the strongest and the bone of the humeral neck is the weakest. This hypothesis was examined on dissected proximal humeri with bone mineral densitometry and an indention test. Both dual photon absorptiometry and bone mineral analyses confirmed that the top part of the humeral head was the region with the greatest amount of bone mineral. The humeral neck had approximately one half the bone mineral density of the humeral head. The cancellous bone of the neck had only one third the mechanical strength of the humeral head on the indention test. The high degree of osteoporosis of the neck region increases the difficulty of surgical treatment for displaced humeral neck fractures.

We present the results of a cadaveric study of 2 forearm reconstructions with radial head replacement for longitudinal radioulnar dissociation injuries.We created a simulated longitudinal radioulnar dissociation injury in 8 cadaver forearms. Two reconstructions were performed alternately on each arm: patellar tendon interosseous ligament complex reconstruction and the Herbert sling extensor retinaculum plication. We performed mechanical testing in a materials testing machine with and without a radial head replacement, and measured ulnocarpal impaction force through 2 distal ulna strain gauges. We determined relative radioulnar displacement using live fluoroscopic analysis of implanted stainless-steel beads.Relative radioulnar longitudinal displacement in the destabilized forearms was 10.7 compared with 0.7 mm before creating the injury. A prosthetic radial head replacement alone decreased the displacement by 75% to 2.7 mm. Interosseous ligament reconstruction alone reduced the displacement to 5.1 mm and to 1.3 mm when combined with a radial head implant. The Herbert sling alone did not improve longitudinal stability. The distal ulna force in the native arm was 17 N, or 17% of the force across the wrist. The interosseous ligament reconstruction restored the force to 21 N, whereas the Herbert sling only marginally decreased the ulna impaction force to 45 N. Adding a radial head decreased the distal ulna force to 7 N for the patellar tendon interosseous ligament reconstruction, and 2 N for the Herbert sling.In longitudinal radioulnar dissociation injuries, the radial head is an important stabilizer and should be repaired or replaced to minimize radial shortening and ulnar impaction force. Patellar tendon interosseous ligament reconstruction effectively restores the ulnocarpal force distribution and markedly reduces longitudinal instability at the distal radioulnar joint. Combined with radial head arthroplasty, the construct has stability similar to an intact forearm. The Herbert sling did not improve longitudinal stability in this testing construct.Treatment of longitudinal radioulnar dissociation may benefit from radial head replacement and interosseous ligament reconstruction using a patellar tendon graft.

♦ Inexpensive♦ Avoids complications of internal fixation♦ Allows mobilization of joints♦ Weight bearing and movement as tolerated, guided by pain.

Longitudinal radioulnar dissociation is a triad of injuries consisting of distal radioulnar joint disruption, interosseous ligament complex (IOLC) tear, and radial head fracture. This renders the forearm longitudinally unstable, resulting in proximal migration of the radius and ulnar-sided wrist degeneration. We hypothesized that reconstruction of the central band of the IOLC in cadaver forearms using a Mini-TightRope suture-button construct would restore native forearm stability.We implanted 8 fresh-frozen cadaver arms with steel beads into the distal radius and ulna, mounted them on an MTS machine, and cyclically loaded them from 13 N distraction to 130 N compression. Bead motion was recorded fluoroscopically and analyzed using Image-Pro Express software. We measured distal ulnar forces using strain gauge transducers. Longitudinal radioulnar dissociation injuries were created by radial head excision and complete IOLC and triangular fibrocartilage complex disruption. At each stage, arms were tested with and without a radial head implant. We reconstructed the central band of the IOLC using a Mini-TightRope and tightened until the distal radioulnar joint was reduced fluoroscopically. We used multiple-comparison analysis of variance with Tukey's Honestly Significant Difference test for statistical analysis.The intact arms had an average radioulnar axial displacement of 0.7 ± 0.8 mm and distal ulnar impaction force of 16.7 ± 11.1 N (per 100 N of axial load on the forearm). After destabilization, the radioulnar displacement increased to 10.7 ± 3.9 mm (p.001) and ulnar load increased 312%, to an average of 52.2 ± 25.7 N (p.001). After IOLC reconstruction, average displacement decreased to 2.2 ± 0.9 mm with a distal ulnar load of 19.05 ± 13.5 N (not significantly different from intact arms).In this cadaveric study, Mini-TightRope IOLC reconstruction with or without a radial head prosthesis significantly reduced distal ulnar impaction forces to that of the native forearm, while limiting radioulnar displacement to near-anatomic levels.

Objective: To evaluate the use of a Na+/H+ exchanger (NHE-1) inhibitor as a cardioprotective adjunct therapy to low-volume resuscitation in two different rat models of traumatic hemorrhagic shock. Design: Experimental, prospective study. Setting: Medical center research laboratory. Subjects: Sprague Dawley male rats. Interventions: Series 1: femur fracture was induced in anesthetized rats, followed by pressure-controlled hemorrhage (40 mm Hg for 20 minutes) and resuscitation. Groups: 1) no therapy; 2) 15 mL/kg hetastarch; and 3) 3 mg/kg benzamide, N-(aminoiminomethyl)-4-[4-(2-furanylcarbonyl)-1-piperazinyl]-3-(methylsulfonyl), methanesulfonate (BIIB513) (NHE-1 inhibitor) + 15 mL/kg hetastarch infusion over 40 minutes. The experiment was terminated at 6 hours after resuscitation. Series 2: the rats received laparotomy and closure under anesthesia and subsequently remained conscious for the rest of the study. The rats were subjected to volume-controlled hemorrhage (2.5 mL/100 g) followed by resuscitation as described in series 1. The experiment was terminated at 24 hours after resuscitation. Measurements and Main Results: Series 1: all animals in the no-therapy group died within 2 hours. Compared with hetastarch infusion alone, the addition of NHE-1 inhibitor improved the hemodynamic response to fluid resuscitation, increased blood oxygen content, prevented metabolic acidosis, and improved 6-hour survival (42% in hetastarch group vs. 80% in BIIB513 + hetastarch group). NHE-1 inhibition also resulted in reduced plasma levels of tumor necrosis factor-α, intercellular adhesion molecule-1, and C-reactive protein, and attenuated neutrophil infiltration in the liver. Series 2: all animals in the no-therapy group died within 4 hours after hemorrhage. Compared with hetastarch infusion alone, the addition of BIIB513 improved 24-hour survival (44% in hetastarch group vs. 78% in BIIB513 + hetastarch group). NHE-1 inhibition also reduced plasma levels alanine aminotransferase at 24 hours after resuscitation. Conclusions: NHE-1 inhibition facilitated the hemodynamic response to fluid resuscitation, attenuated tissue inflammatory injury, and organ dysfunction, but most importantly improved survival.