Are Suture Tape Knots as Secure as Standard Suture? A Biomechanical Study.

BACKGROUND: Few studies have investigated the biomechanical performance of flat-braided suture tapes versus round-braided sutures after being knotted. PURPOSE: To compare the loop security and knot strength of a standard round-braided suture with 3 commercially available flat-braided suture tapes using 2 types of arthroscopic knots. STUDY DESIGN: Controlled laboratory study. METHODS: One standard suture (SS) and 3 suture tapes (T1, T2, and T3) were tied with the surgeon's knot (SK) and the Tennessee slider (TS), 25 times each, by a single surgeon. Each combination of knots and sutures underwent a preload, cyclic loading, and load to failure. Outcomes were loop security (defined by loop stretch after a 5-N preload), load at clinical failure (3 mm of displacement), and load at ultimate failure (suture rupture or knot slippage). Two-way analysis of variance was used for analysis. RESULTS: Overall, the SK group had greater overall loop security than that of the TS group (0.4 ± 0.3 vs 0.5 ± 0.3 mm of stretch, respectively; P = .020). The clinical failure load varied by suture type (P < .001) but not knot type (P = .106). For both knot types, the SS had the lowest mean ± SD clinical failure load (SK, 171 ± 49 N; TS, 176 ± 37 N), which was significantly less than that of T2 (247 ± 85 N; P < .001) and T3 (251 ± 96 N; P < .001) for the SK type and T2 (231 ± 67 N; P = .023) for the TS type. T2 sutures had the greatest ultimate failure load for both knot types (SK, 418 ± 45 N; TS, 461 ± 57 N), which was significantly greater than SS, T1, and T3 (P < .001 for all). The TS knot had greater overall ultimate failure load than the SK (375 ± 64 vs 350 ± 66 N; P < .001). CONCLUSION: Not all suture tape knots had the same biomechanical properties, although knot security and strength appeared to be adequate for all suture tapes as well as for SS. There was no evidence that suture tape knots are lower profile than SS knots. CLINICAL RELEVANCE: Surgeons should not use suture tape based only on the assumption that it has superior biomechanical properties to a standard round-braided suture.

Biomechanical properties of the repaired and non-repaired rat supraspinatus tendon in the acute postoperative period.

PURPOSE: The rat rotator cuff (RC) model is used to study RC pathology and potential treatment; however, native scar-mediated healing allows the rat RC to recover at 4-6 weeks but little is known about acute healing. This study characterized the properties of the repaired and non-repaired rat RC following surgical detachment. MATERIALS AND METHODS: Forty-eight rats underwent surgical RC detachment and received surgical repair (Repair) or left unrepaired (Defect) to either 12 or 19 days. Healthy controls were obtained from contralateral limbs. Biomechanical properties were assessed using stress relaxation and failure testing and mechanical modeling performed using quasilinear viscoelastic (QLV) and structurally based elastic models. Histology and micro-magnetic resonance imaging were used to qualitatively grade tendon-to-bone healing. RESULTS: Repair and Defect exhibited significantly inferior mechanical properties compared to Healthy at both time points. Repair had significant increases in peak, equilibrium, and ultimate stress, modulus, and stiffness and significant decreases in cross-sectional area, % relaxation, and QLV constant "C" between 12 and 19 days, whereas Defect showed no change. CONCLUSIONS: This study demonstrates acute differences in mechanical properties of the rat supraspinatus tendon in the presence and absence of surgical repair. Understanding the longitudinal recovery of mechanical properties can facilitate more accurate characterization of RC pathology or future treatments.

Characterization of doxycycline-loaded calcium phosphate cement: implications for treatment of aneurysmal bone cysts.

Percutaneous doxycycline for treatment for aneurysmal bone cysts (ABCs) has been shown to decrease recurrence rates, however, this requires multiple procedures, includes the risks soft tissue necrosis, and does not provide structural support. We propose utilizing curettage with doxycycline-loaded calcium phosphate cement. This study aimed to evaluate the elution profile of doxycycline from calcium phosphate cement. Calcium phosphate cement underwent an in vitro elution protocol evaluating doxycycline concentrations of 0, 5, 10, and 15 mg/mL. Eluted concentrations were quantified utilizing high performance liquid chromatography at predetermined time points over 96 h. Compressive strength was evaluated both pre- and post-elution and micro-computed tomography was utilized to assess changes in cement porosity. Cement with 15 mg/mL of doxycycline maintained a higher average concentration (mean, 95% confidence intervals) (14.5 µg/mL [9.2-19.9 µg/mL]) compared to both 5 mg/mL (5.8 µg/mL [3.1-8.6 µg/mL]; P < 0.001) and 10 mg/mL (8.4 ± µg/mL [6.0-10.9 µg/mL]; P < 0.001). Ultimate stress significantly decreased between pre- and post-elution samples for 10 mg/mL (P= 0.001) and 15 mg/mL (P = 0.004) groups. This study demonstrated a dose-dependent response in ultimate strength and compressive modulus with addition of doxycycline to calcium phosphate cement.

Intraoperative Psoas Compartment Block vs Preoperative Fascia Iliaca Block for Pain Control After Direct Anterior Total Hip Arthroplasty: A Randomized Controlled Trial.

BACKGROUND: Modern joint arthroplasty protocols place an emphasis on minimizing patient-reported postoperative pain while minimizing opioid consumption. The use of multimodal pain management protocols has been reported to improve patient outcomes and satisfaction after total hip arthroplasty. METHODS: In a prospective, single-surgeon trial, 50 patients undergoing primary direct anterior approach total hip arthroplasty were randomized to receive a preoperative fascia iliaca compartment block (FICB) or an intraoperative surgeon-delivered psoas compartment block (PCB). Patient-reported pain was recorded in the postanesthesia care unit, recovery floor and 3 weeks postoperatively. Opioid use was recorded during the hospital stay. RESULTS: Average visual analog scale pain scores in the postanesthesia care unit were 38.7 ± 8.7 vs 35.6 ± 8.3 (P = .502) for the preoperative FICB and intraoperative PCB groups, respectively. No significant difference was found between groups at the 3-week visit for postoperative pain (FICB: 2.9 ± 1.4; PCB: 3.2 ± 2.0; P = .970) and patient-reported pain satisfaction (FICB: 8.8 ± 2.2; PCB: 9.7 ± 0.6; P = .110). CONCLUSION: During the direct anterior approach for total hip arthroplasty, PCB is an effective and efficient regional anesthesia technique. It may be used to obtain satisfactory postoperative pain control and patient satisfaction while decreasing hospital resources.

Psoas Compartment Block vs Periarticular Local Anesthetic Infiltration for Pain Management After Anterior Total Hip Arthroplasty: A Prospective, Randomized Study.

BACKGROUND: The psoas compartment block (PCB) or periarticular soft-tissue local anesthetic injection are forms of regional anesthesia often used as one of the components in multimodal anesthesia applied during total hip arthroplasty (THA). The most efficacious form of regional anesthesia for THA has yet to be determined. METHODS: In a single-surgeon, prospective, clinical trial, patients undergoing THA via direct anterior approach were randomized to receive an intraoperative periarticular local anesthetic infiltration (periarticular injection) or a PCB. Postoperative pain scores, narcotic consumption, and complications were recorded. RESULTS: Forty-nine patients were randomized to the PCB and 50 were randomized to the periarticular injection. The resting pain score 3 hours postoperatively was statistically significantly lower in the periarticular injection group by 1.1 point (2.9 ± 2.2 vs 4.0 ± 2.2, P = .036). No difference was found in resting pain scores or ambulatory pain scores in the morning or evening of postoperative day 1, 2, or at the 3-week follow-up visit. There was no difference in in-hospital narcotic consumption between groups (P = 1.0). There were no major complications directly related to the block in either group. A total of 6 patients reported complaints of transient numbness, 5 in the PCB group (5/49, 10.2%), and one in the periarticular injection group (1/50, 2%, P = .087). CONCLUSION: These results demonstrate similarity between the 2 methods. We prefer periarticular anesthetic infiltration over PCB due to improved immediate postoperative pain scores and avoidance of potential symptoms associated with nerve blockade.

Quantitative evaluation of retrieved reverse total shoulder arthroplasty liner surface deviation and volumetric wear.

Polyethylene wear is a known complication in total joint arthroplasty, however, in vivo wear rates in reverse total shoulder arthroplasty (RTSA) remain largely unknown. This study aimed to quantify volumetric and surface deviation changes in retrieved RTSA humeral liners using a novel micro-computed tomography (µCT)-based technique. After IRB-approval, 32 humeral liners (single manufacturer and model) with term-of-service greater than 90 days were analyzed. Clinical demographics and surgical data were collected via chart review. Unworn liners were used as geometric controls. Retrieved and unworn liners underwent µCT scanning. Retrieved liner volumes were isolated, co-registered to controls of matching geometry, and surface deviations of the articulation surface and rim were computed. Differences in total volume loss (TVL), volumetric wear rate (VWR), and surface deviation were reported. Semi-quantitative grading evaluated rim damage presence and severity. Mean term-of-service for all liners was 2.07 ± 1.33 years (range: 0.30-4.73). Mean TVL and VWR were 181.3 ± 208.2 mm3 and 114.5 ± 160.3 mm3 /year, respectively. Mean articulation and rim surface deviations were 0.084 ± 0.065 and 0.177 ± 0.159 mm, respectively. Articulation surface deviation was positively correlated to term-of-service. Rim damage was present on 63% of liners and correlated significantly to rim surface deviation. This study reports in vivo wear rates of retrieved RTSA implants. Our results demonstrate volumetric and articulation surface wear in select RTSA liners that is correlated to term-of-service. Calculation of in vivo wear rates can help bridge the gap between clinical outcomes and experimental models such as wear simulations and computational models. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2007-2014, 2018.

Three-dimensional computed tomography measurement accuracy of varying Hill-Sachs lesion size.

BACKGROUND: The glenoid track concept has been proposed to correlate shoulder stability with bone loss. Accurate assessment of Hill-Sachs lesion size preoperatively may affect surgical planning and postoperative outcomes; however, no measurement method has been universally accepted. This study aimed to assess the accuracy and reliability of measuring Hill-Sachs lesion sizes using 3-dimensional (3D) computed tomography (CT). METHODS: Nine polyurethane humerus bone substitutes were used to create Hill-Sachs lesions of varying sizes with a combination of lesion depth (shallow, intermediate, and deep) and width (small, medium, and large). Specimens were scanned with a clinical CT scanner for size measurements and a micro-CT scanner for measurement of true lesion size. Six evaluators repeated measurements twice in a 2-week interval. Scans were measured by use of 3D CT reconstructions for length, width, and Hill-Sachs interval and with use of 2D CT for depth. The interclass correlation coefficient evaluated interobserver and intraobserver variability and percentage error, and Student t-tests assessed measurement accuracy. RESULTS: Interclass correlation coefficient reliability demonstrated strong agreement for all variables measured (0.856-0.975). Percentage error between measured length and measured depth and the true measurement significantly varied with respect to both lesion depth (P = .003 and P = .005, respectively) and lesion size (P = .049 and P = .004, respectively). DISCUSSION AND CONCLUSIONS: The 3D CT imaging is effective and reproducible in determining lesion size. Determination of Hill-Sachs interval width is also reliable when it is applied to the glenoid track concept. Measured values on 3D and 2-dimensional imaging using a conventional CT scanner may slightly underestimate true measurements.

Neer Award 2017: wear rates of 32-mm and 40-mm glenospheres in a reverse total shoulder arthroplasty wear simulation model.

BACKGROUND: Larger glenosphere diameters have been used recently to increase prosthesis stability and impingement-free range of motion in reverse total shoulder arthroplasty. The goal of this study was to evaluate the rate of polyethylene wear for 32-mm and 40-mm glenospheres. METHODS: Glenospheres (32 mm and 40 mm, n = 6/group) and conventional polyethylene humeral liners underwent a 5-million cycle (MC) wear simulation protocol. Abduction-adduction and flexion-extension motion profiles were alternated every 250,000 cycles. At each interval, mass loss was determined and converted to volume loss and wear rate. At 0, 2.5 MC, and 5 MC, liners were imaged using micro-computed tomography to determine surface deviation. White light interferometry was performed on liners and glenospheres at 0 and 5 MC to quantify surface roughness. Wear particle morphology was characterized by environmental scanning electron microscopy. RESULTS: Total volume loss was significantly higher in 40-mm liners from 1.5 MC onward (P < .05). Overall, volumetric wear rate was significantly higher in 40-mm liners compared with 32-mm glenospheres (81.7 ± 23.9 mm3/MC vs. 68.0 ± 18.9 mm3/MC; P < .001). However, micro-computed tomography surface deviation results demonstrated increased linear penetration on 32-mm glenospheres compared with 40-mm glenospheres (0.36 ± 0.03 µm vs. 0.28 ± 0.01 µm; P = .002). Surface roughness measurements showed no difference for liners; however, increased roughness was noted for 40-mm glenospheres at 5 MC compared with 32 mm (P < .05). CONCLUSION: Larger glenospheres underwent significantly greater polyethylene volume loss and volumetric wear rates, whereas smaller glenospheres underwent greater polyethylene surface deviations. The enhanced stability provided by larger glenospheres must be weighed against the potential for increased polyethylene wear.

Exposure of articular chondrocytes to wear particles induces phagocytosis, differential inflammatory gene expression, and reduced proliferation.

The production of wear debris particulate remains a concern due to its association with implant failure through complex biologic interactions. In the setting of unicompartmental knee arthroplasty (UKA), damage and wear of the components may introduce debris particulate into the adjacent, otherwise, healthy compartment. The purpose of this study was to investigate the in vitro effect of polymeric and metallic wear debris particles on cell proliferation, extracellular matrix regulation, and phagocytosis index of normal human articular chondrocytes (nHACs). In culture, nHACs were exposed to both cobalt-chromium-molybdenum (CoCrMo) and polymethyl-methacrylate (PMMA) wear debris particulate for 3 and 10 days. At 3 days, no significant difference in cell proliferation was found between control cells and cells exposed to both CoCrMo or PMMA particles. However, cell proliferation was significantly decreased for CoCrMo exposed nHACs at both 6 (P < 0.001) and 10 days (P < 0.001) and PMMA at 10 days (P < 0.001). Target gene expression displayed both a time- and material-dependent response to CoCrMo and PMMA particles. Significant differences in COL10A1, ACAN, VCAN, IL-1ß, TNF-α, MMP3, ADAMTS1, CASP3, and CASP9 regulation were found between CoCrMo and PMMA exposed nHACs at day 3 with gene regulation returning to near baseline at 10 days. Results from our study indicate a role of wear debris induced cartilage degeneration after exposure to polymeric and metallic wear debris particulate, suggesting an additional pathway of cartilage breakdown, potentially manifesting in traditional clinical symptoms.

The influence of testing angle on the biomechanical properties of the rat supraspinatus tendon.

Rotator cuff tears are a common shoulder pathology. The rat supraspinatus tendon model is commonly employed for preclinical assessment of rotator cuff pathology or regeneration. However, there is a lack of a standardized biomechanical testing protocol; previous studies have tested the tendon at abduction angles ranging from -15° to 90°. This study aimed to assess the effect of abduction/testing angle on the biomechanical properties of the rat supraspinatus tendon. Fourty-eight shoulders (n=12/group) from healthy Sprague-Dawley rats were randomized to 4 testing angle groups: 0° (corresponding to 90° abduction), 30°, 60°, and 90° (0° abduction). Biomechanical testing of the supraspinatus was performed, consisting of stress-relaxation and load-to-failure. Mechanical properties were calculated, and nonlinear tensile modeling was performed via the Quasilinear Viscoelastic (QLV) and Structurally Based Elastic (SBE) models. Results indicate that testing angle significantly affects supraspinatus tendon biomechanics. Stiffness and modulus significantly decreased with increasing testing angle (stiffness: 20.93±5.8N/mm at 0° vs. 6.12±1.0N/mm at 90°, P<.001; modulus: 59.51±34.0MPa at 0° vs. 22.37±7.4MPa at 90°, P=.002). Testing angle correlated significantly to ultimate strain, yield strain, and all coefficients of the SBE and QLV models, implying differences in collagen fiber crimp patterns and viscoelastic behavior as a function of testing angle. These results suggest that differences in testing methodology, in particular testing angle, significantly affect the measured mechanical properties of the supraspinatus tendon. Future studies may consider utilizing testing angles of 0°-30°, at which tendon stiffness is maximized, and full standardization of rat rotator cuff testing protocols is necessary.

Increasing Liner Anteversion Decreases the Interfacial Strength of Polyethylene Liners Cemented Into Titanium-Alloy Acetabular Shells.

BACKGROUND: Acetabular component positioning during revision total hip arthroplasty can be suboptimal. Cementation of an acetabular liner into a well-fixed acetabular shell can allow surgeons to correct component version and inclination without the need for extensive revision surgery and progressive pelvic bone loss. However, to date, it is unknown what degree of version can be corrected without sacrificing fixation strength of the construct. In this study, cemented liners were biomechanically evaluated at increasing degrees of liner anteversion. METHODS: Twenty-five commercially available liners were cemented into acetabular shells at 0°, 10°, 20°, 30°, and 40° of liner anteversion, relative to the acetabular shell (n = 5 per group). Components were then fixed to a materials testing frame and evaluated via an established lever-out testing protocol. Test data were collected via test frame software for calculation of yield and maximum moments during biomechanical testing. RESULTS: When liners were cemented at 20°, 30°, and 40° of liner anteversion, a significant decrease in maximum fixation moment was found when compared liners cemented at both 0° and 10° (P < .05). A significant negative correlation was noted for both yield and maximum moments and increasing liner angle (r = -0.566; P = .011 and r = -0.604; P = .006, respectively). CONCLUSION: Biomechanical data from our study suggest that a threshold of acceptable anteversion during revision total hip arthroplasty is <20°. However, further studies are warranted to continue evaluation of the potential clinical impact and long-term device performance in this setting.

Biomechanical Evaluation of All-Polyethylene Pegged Bony Ingrowth Glenoid Fixation Techniques on Implant Micromotion.

Newer glenoid components that allow for hybrid cement fixation via traditional cementation of peripheral pegs and bony ingrowth into an interference-fit central peg introduce the possibility of long-term biological fixation. However, little biomechanical work has been done on the initial stability of these components and the various fixation options. We conducted a study in which all-polyethylene glenoid components with a centrally fluted peg were implanted in polyurethane blocks with interference-fit, hybrid cement, and fully cemented fixation (5 per fixation group). Biomechanical evaluation of glenoid loosening, according to ASTM Standard F-2028-12, subjected the glenoids to 50,000 cycles of rim loading, and glenoid component motion was recorded with 2 differential variable reluctance transducers fixed to each glenoid prosthesis. Fully cemented fixation exhibited significantly less mean distraction in comparison with interference-fit fixation (P < .001) and hybrid cement fixation (P < .001). Hybrid cement fixation exhibited significantly less distraction (P < .001), more compression (P < .001), and no significant difference in glenoid translation (P = .793) in comparison with interference-fit fixation. Fully cemented fixation exhibited the most resistance to glenoid motion in comparison with hybrid cement fixation and interference-fit fixation. However, hybrid cement fixation and interference-fit fixation exhibited equivocal motion. Given these results, cementation of peripheral pegs may confer no additional initial stability over that provided by uncemented interference-fit fixation.

Wear rates of retentive versus nonretentive reverse total shoulder arthroplasty liners in an in vitro wear simulation.

BACKGROUND: Although short-term outcomes of reverse total shoulder arthroplasty (rTSA) remain promising, the most commonly cited complication remains prosthetic instability. A retentive rTSA liner is commonly used to increase system constraint; however, no studies have evaluated the rate of polyethylene wear. Our hypothesis was that more constrained retentive liners would have higher wear rates than nonretentive liners. METHODS: Six nonretentive and six retentive rTSA non-cross-linked polyethylene liners were subjected to 4.5 million cycles of alternating cycles of abduction-adduction and flexion-extension motion loading profiles. The rTSA liners were assessed for gravimetric wear loss, 3-dimensional volumetric loss by novel micro-computed tomography analysis, and particulate wear debris analysis. RESULTS: Volumetric wear rates were significant at 7 specific time points (1.0, 2.0, 2.5, 3.25, 3.75, 4.0, and 4.5 million cycles) throughout testing between nonretentive and retentive liners; however, overall mean volumetric wear rate was not statistically significant (P = .076). Total volume loss between liner test groups was found to be significant starting after 3.5 million cycles of testing. Maximum and mean surface deviations were found to be larger for retentive liners vs. nonretentive liners by micro-computed tomography analysis across the entire articulation surface. DISCUSSION AND CONCLUSION: Retentive liners undergo significantly greater volume loss and greater surface deviation compared with nonretentive liners, most notably at later time points representing extended implantation times. Additional stability afforded by retentive liners should be balanced against the potential for increased wear and potential for subsequent polyethylene wear-induced aseptic loosening.

The impact of rotator cuff deficiency on structure, mechanical properties, and gene expression profiles of the long head of the biceps tendon (LHBT): Implications for management of the LHBT during primary shoulder arthroplasty.

The long head of the biceps tendon (LHBT) occupies a unique proximal intra-articular and distal extra-articular position within the human shoulder. In the presence of a rotator cuff (RC) tear, the LHBT is recruited into an accelerated role undergoing potential mechanical and biochemical degeneration. Intra-articular sections of the LHBT were harvested during primary shoulder arthroplasty from patients with an intact or deficient RC. LHBTs were stained (H&E, Alcian Blue) and subjected to histologic analysis using the semiquantitative Bonar scale and measurement of collagen orientation. LHBTs (n = 12 per group) were also subjected to gene-expression analyses via an RT(2) -PCR Profiler Array quantifying 84 genes associated with cell-cell and cell-matrix interactions. LHBTs (n = 18 per group) were biomechanically tested with both stress-relaxation and load-to-failure protocols and subsequently modeled with the Quasilinear Viscoelastic (QLV) and Structural-Based Elastic (SBE) models. While no histologic differences were observed, significant differences in mechanical testing, and viscoelastic modeling parameters were found. PCR arrays identified five genes that were differentially expressed between RC-intact and RC-deficient LHBT groups. LHBTs display signs of pathology regardless of RC status in the arthroplasty population, which may be secondary to both glenohumeral joint arthritis and the additional mechanical role of the LHBT in this population.

Biomechanical Characterization of a Model of Noninvasive, Traumatic Anterior Cruciate Ligament Injury in the Rat.

The onset of post-traumatic osteoarthritis (PTOA) remains prevalent following traumatic joint injury such as anterior cruciate ligament (ACL) rupture, and animal models are important for studying the pathomechanisms of PTOA. Noninvasive ACL injury using the tibial compression model in the rat has not been characterized, and it may represent a more clinically relevant model than the common surgical ACL transection model. This study employed four loading profiles to induce ACL injury, in which motion capture analysis was performed, followed by quantitative joint laxity testing. High-speed, high-displacement loading repeatedly induces complete ACL injury, which causes significant increases in anterior-posterior and varus laxity. No loading protocol induced valgus laxity. Tibial internal rotation and anterior subluxation occurs up to the point of ACL failure, after which the tibia rotates externally as it subluxes over the femoral condyles. High displacement was more determinative of ACL injury compared to high speed. Low-speed protocols induced ACL avulsion from the femoral footprint whereas high-speed protocols caused either midsubstance rupture, avulsion, or a combination injury of avulsion and midsubstance rupture. This repeatable, noninvasive ACL injury protocol can be utilized in studies assessing PTOA or ACL reconstruction in the rat.

Glenohumeral mismatch affects micromotion of cemented glenoid components in total shoulder arthroplasty.

BACKGROUND: The "rocking horse" phenomenon is considered the main cause of glenoid component loosening by eccentric loading of the glenoid rim. This study aimed to investigate the influence of increasing glenohumeral implant mismatch on bone-implant interface micromotion in a cemented all-polyethylene pegged glenoid biomechanical model. METHODS: Five glenoid sizes, 40 mm, 44 mm, 48 mm, 52 mm, and 56 mm, representing +2 mm, +6 mm, +10 mm, +14 mm, and +18 mm glenohumeral mismatch, respectively, were cyclically loaded according to ASTM Standard F2028-08 at a constant frequency of 2 Hz to a size-dependent humeral head subluxation translation. Additional glenoid components were cyclically loaded to their subluxation translations at a constant humeral head rate of 4.4 mm/s. Component micromotion was characterized as compression, distraction, and superior-inferior translation measured by differential variable reluctance transducers. RESULTS: During constant frequency tests, 52-mm and 56-mm glenoids were unable to complete cyclic testing because of catastrophic failure of the glenoid-implant interface and permanent glenoid deformation, probably due to increasing severity of testing parameters. When tested at a constant humeral head speed, 48-mm, 52-mm, and 56-mm glenoids had significantly increased glenoid distraction and glenoid translation at cycle 50,000 compared with cycle 1. Distraction and translation measurements for 52-mm and 56-mm glenoids were significantly greater compared with 40-mm, 44-mm, and 48-mm glenoids at 50,000 cycles. CONCLUSIONS: In a biomechanical model, optimal glenohumeral mismatch in cemented pegged glenoid implants is multifactorial and has not been definitively established. However, our data suggest that a radial mismatch of less than +10 mm may decrease the risk of glenoid micromotion.

Wear rates of highly cross-linked polyethylene humeral liners subjected to alternating cycles of glenohumeral flexion and abduction.

BACKGROUND: Although short-term outcomes of reverse total shoulder arthroplasty have been promising, long-term success may be limited due to device-specific complications, including scapular notching. Scapular notching has been explained primarily as mechanical erosion; however, the generation of wear debris may lead to further biologic changes contributing to the severity of scapular notching. METHODS: A 12-station hip simulator was converted to a reverse total shoulder arthroplasty wear simulator subjecting conventional and highly cross-linked ultra-high-molecular-weight polyethylene humeral liners to 5 million cycles of alternating abduction-adduction and flexion-extension loading profiles. RESULTS: Highly cross-linked polyethylene liners (36.5 ± 10.0 mm(3)/million cycle) exhibited significantly lower volumetric wear rates compared with conventional polyethylene liners (83.6 ± 20.6 mm(3)/million cycle; P < .001). The flexion-extension loading profile exhibited significantly higher wear rates for conventional (P < .001) and highly cross-linked polyethylene (P < .001) compared with the abduction-adduction loading profile. Highly cross-linked wear particles had an equivalent circle diameter significantly smaller than wear particles from conventional polyethylene (P < .001). CONCLUSIONS: Highly cross-linked polyethylene liners significantly reduced polyethylene wear and subsequent particle generation. More favorable wear properties with the use of highly cross-linked polyethylene may lead to increased device longevity and fewer complications but must be weighed against the effect of reduced mechanical properties.

Extensive Lower-Extremity Deep Venous Thrombosis Following Arthroscopic Anterior Cruciate Ligament Reconstruction Related to May-Thurner Syndrome: A Case Report.

CASE: An extensive iliofemoral-popliteal deep venous thrombosis following arthroscopic anterior cruciate ligament reconstruction presented on the ninth postoperative day as the result of underlying May-Thurner syndrome. The patient was managed with therapeutic anticoagulation and mechanical disruption of the thrombus. The focal stenosis of the left common iliac vein was addressed with angioplasty and stent placement. Repeat venography demonstrated no residual stenosis of the vein. CONCLUSION: A multidisciplinary approach remains necessary for treating and reducing the risk of post-thrombotic syndrome. The present case further emphasizes the need for aggressive workup and response when a patient presents with left-sided deep venous thrombosis associated with underlying May-Thurner syndrome.

Biomechanical testing of small versus large lesser tuberosity osteotomies: effect on gap formation and ultimate failure load.

BACKGROUND: Subscapularis muscle dysfunction after total shoulder arthroplasty (TSA) can be a devastating complication. Recent biomechanical and clinical results suggest the superiority of lesser tuberosity osteotomy (LTO) over subscapularis tenotomy; however, disagreement over the best repair technique remains. This study aimed to characterize the strength of 2 novel repair techniques for LTO fixation compared with standard tenotomy and dual-row tuberosity osteotomies during TSA. METHODS: Twenty fresh frozen cadaveric shoulders were dissected of all soft tissues except the humeri and attached subscapularis myotendinous unit. Humeri and subscapularis muscle belly were secured to a materials testing frame and subjected to cyclic loading, followed by load to failure for characterization of gap formation, ultimate failure load, and mechanism of failure. Repair techniques investigated were traditional subscapularis tenotomy and dual-row fleck LTO compared with novel techniques of single-cable and 2-suture large LTO repairs. RESULTS: No significant difference in ultimate failure load was noted among the repair techniques (P = .565). The tenotomy repair (6.0 ± 3.9 mm) displayed significantly greater gapping in response to increasing load than LTO repair techniques (P < .05). No significant difference was noted between any LTO repairs at specific loads during cyclic testing (P > .05). CONCLUSION: Our study displayed superior repair integrity of LTO vs tenotomy repairs. The advantages of the 2-suture large LTO technique over other LTO techniques include its simple technique, with a minimum amount of suture, avoidance of metallic hardware, and greater access to the glenoid, while providing comparable repair stability. Further research is warranted to fully evaluate these new techniques.

The GraftLink ulnar collateral ligament reconstruction: biomechanical comparison with the docking technique in both kinematics and failure tests.

BACKGROUND: Ulnar collateral ligament (UCL) reconstruction aims to restore valgus stability, and numerous techniques have been described in the literature. HYPOTHESIS/ PURPOSE: To biomechanically compare the GraftLink (GL) technique with traditional bone tunnels used in the docking (DO) technique. It is hypothesized that the GL method will offer a stiffer, less lax construct compared with the DO. STUDY DESIGN: Controlled laboratory study. METHODS: Native and reconstructed states were tested in 7 matched pairs of cadaveric arms. To test kinematics, a 1.5-N·m valgus torque was applied and the resultant displacement at 15° to 90° of flexion was measured. Dissipated energy and the torque at the peak of the 10th cycle of preconditioning were analyzed during kinematic tests. Failure testing was performed by internal rotation of the humerus at 4.5 deg/s in 70° of flexion. Ulnotrochlear joint (UTJ) gapping was quantified during failure tests by use of video tracking. RESULTS: Kinematics testing revealed no differences between the native state and the reconstructed state in either the DO or the GL group at any flexion angle. Stiffness was lower in the reconstructed specimens in both the DO (39.92 N·m/rad) and GL (50.74 N·m/rad) groups compared with their matched native states (DO Native, 71.41 N·m/rad, P = .005; GL Native, 86.36 N·m/rad, P = .002). There was no difference in stiffness between DO and GL. Reconstructed specimens in the GL group had lower torque at failure compared with native specimens (17.404 N·m vs 24.63 N·m, P = .038), but there was no difference in the DO group at failure. There was no difference in torque at failure between DO and GL. The DO exhibited higher angular displacement at failure compared with the native state (34.21° vs 21.79°, P = .010) and compared with the GL when normalized (1.58-fold vs 1.19-fold, P = .039). Compared with their native states, both DO and GL had significantly higher UTJ gapping at 3 N·m and at failure. The DO had significantly higher normalized UTJ gapping than the GL at 3 N·m (P = .037) and at failure (P = .043). CONCLUSION: The DO and GL both restored joint kinematics under low loading conditions. Although less stiff, the GL exhibited lower joint gapping and laxity than did the DO. CLINICAL RELEVANCE: Understanding the biomechanics of UCL reconstruction has significant implications for postoperative management as it relates to early rehabilitation. Biomechanically inferior constructs could risk graft failure or early loosening during rehabilitation, and comparing the biomechanics of new techniques to established, widely used procedures such as the docking technique can provide important information about the immediate postoperative performance.