TGF-b1 or hypoxia enhance glucose metabolism and lactate production via HIF1A signaling in tendon cells.

Purpose/Aim of the study: Healthy tendons are maintained in homeostasis through controlled usage of glucose for energy and redox equilibrium. Tendon cell stress imposed by overuse injury or vascular insufficiency is accompanied by activation of wound healing pathways which facilitate an adaptive response and the restoration of homeostasis. To understand this response at the gene expression level we have studied the in vivo effects of injected TGF-ß1 in a murine model of tendinopathy, as well as treatment of murine tendon explants with either TGF-ß1 or hypoxia in vitro. METHODS AND RESULTS: We provide evidence (from expression patterns and immunohistochemistry) that both in vivo and in vitro, the stress response in tendon cells may be metabolically controlled in part by glycolytic reprogramming. A major feature of the response to TGF-ß1 or hypoxia is activation of the Warburg pathway which generates lactate from glucose under normoxia and thereby inhibits mitochondrial energy production. CONCLUSIONS: We discuss the likely outcome of this major metabolic shift in terms of the potential benefits and damage to tendon and suggest how incorporation of this metabolic response into our understanding of initiation and progression of tendinopathies may offer new opportunities for diagnosis and the monitoring of therapies.

Biomechanical Performance of Medial Row Suture Placement Relative to the Musculotendinous Junction in Transosseous Equivalent Suture Bridge Double-Row Rotator Cuff Repair.

PURPOSE: To compare the biomechanical performance of medial row suture placement relative to the musculotendinous junction (MTJ) in a cadaveric transosseous equivalent suture bridge (TOE-SB) double-row (DR) rotator cuff repair (RCR) model. METHODS: A TOE-SB DR technique was used to reattach experimentally created supraspinatus tendon tears in 9 pairs of human cadaveric shoulders. The medial row sutures were passed either near the MTJ (MTJ group) or 10 mm lateral to the MTJ (rotator cuff tendon [RCT] group). After the supraspinatus repair, the specimens underwent cyclic loading and load to failure tests. The localized displacement of the markers affixed to the tendon surface was measured with an optical tracking system. RESULTS: The MTJ group showed a significantly higher (P = .03) medial row failure (5/9; 3 during cyclic testing and 2 during load to failure testing) compared with the RCT group (0/9). The mean number of cycles completed during cyclic testing was lower in the MTJ group (77) compared with the RCT group (100; P = .07) because 3 specimens failed in the MTJ group during cyclic loading. There were no significant differences between the 2 study groups with respect to biomechanical properties during the load to failure testing. CONCLUSIONS: In a cadaveric TOE-SB DR RCR model, medial row sutures through the MTJ results in a significantly higher rate of medial row failure. CLINICAL RELEVANCE: In rotator cuff tears with tendon tissue loss, passage of medial row sutures through the MTJ should be avoided in a TOE-SB RCR technique because of the risk of medial row failure.

Assessment of glenoid chondral healing: comparison of microfracture to autologous matrix-induced chondrogenesis in a novel rabbit shoulder model.

BACKGROUND: Management of glenohumeral arthrosis in young patients is a considerable challenge, with a growing need for non-arthroplasty alternatives. The objectives of this study were to develop an animal model to study glenoid cartilage repair and to compare surgical repair strategies to promote glenoid chondral healing. METHODS: Forty-five rabbits underwent unilateral removal of the entire glenoid articular surface and were divided into 3 groups--untreated defect (UD), microfracture (MFx), and MFx plus type I/III collagen scaffold (autologous matrix-induced chondrogenesis [AMIC])--for the evaluation of healing at 8 weeks (12 rabbits) and 32 weeks (33 rabbits) after injury. Contralateral shoulders served as unoperated controls. Tissue assessments included 11.7-T magnetic resonance imaging (long-term healing group only), equilibrium partitioning of an ionic contrast agent via micro-computed tomography (EPIC-µCT), and histologic investigation (grades on International Cartilage Repair Society II scoring system). RESULTS: At 8 weeks, x-ray attenuation, thickness, and volume did not differ by treatment group. At 32 weeks, the T2 index (ratio of T2 values of healing to intact glenoids) was significantly lower for the MFx group relative to the AMIC group (P = .01) whereas the T1ρ index was significantly lower for AMIC relative to MFx (P = .01). The micro-computed tomography-derived repair tissue volume was significantly higher for MFx than for UD. Histologic investigation generally suggested inferior healing in the AMIC and UD groups relative to the MFx group, which exhibited improvements in both integration of repair tissue with subchondral bone and tidemark formation over time. DISCUSSION: Improvements conferred by AMIC were limited to magnetic resonance imaging outcomes, whereas MFx appeared to promote increased fibrous tissue deposition via micro-computed tomography and more hyaline-like repair histologically. The findings from this novel model suggest that MFx promotes biologic resurfacing of full-thickness glenoid articular injury.

Effect of interference screw depth on fixation strength in biceps tenodesis.

PURPOSE: The purpose of this study was to assess the biomechanical performance of the long head of the biceps tenodesis with an interference screw with respect to screw depth. METHODS: Twenty-one human cadaveric shoulders were randomized into 3 treatment groups (7 each): interference screw placed flush to the humeral cortex, 50% proud, or fully recessed. Bone density was determined, and subpectoral biceps tenodesis was performed with 8 × 12 mm Bio-Tenodesis screws (Arthrex, Naples, FL). Each construct was cyclically loaded from 5 to 70 N for 500 cycles at 1 Hz and then pulled to failure at 1 mm/s. Relative actuator displacement was calculated from cyclic testing. Maximum load, elongation, linear stiffness, and failure mode were recorded from pull-to-failure testing. Because of numerous failures during cyclic testing, the final load data from the fully recessed group were not statistically analyzed. The remaining groups were compared by use of a 2-tailed, Student unpaired t test and χ(2) analysis. RESULTS: There was no significant difference in displacement among groups during cyclic testing. Five specimens in the recessed group failed during cyclic testing, whereas 2 specimens and 0 specimens failed in the proud and flush groups, respectively. The maximum loads sustained were 281.6 ± 77.8 N, 184.5 ± 56.3 N, and 209.1 ± 57.0 N for the flush group, 50% proud group, and recessed group (in those specimens surviving cyclical loading), respectively. CONCLUSIONS: Placement of a Bio-Tenodesis screw flush to the humeral cortex is preferred for maximum fixation strength in subpectoral biceps tenodesis. A screw placed to 50% depth may be effective in the laboratory setting, but recessed placement is more variable and requires additional fixation. The fully recessed group resulted in 5 of 7 failures during cyclical loading, with no specimens failing in the flush group. CLINICAL RELEVANCE: This study shows the importance of determining the optimal depth of interference screw placement during biceps tenodesis to obtain optimal biomechanical performance and reduce the risk of fixation failure.

Role of the superior labrum after biceps tenodesis in glenohumeral stability.

BACKGROUND: Little is known about the role that a torn superior labrum (SLAP) plays in glenohumeral stability after biceps tenodesis. This biomechanical study evaluated the contribution of a type II SLAP lesion to glenohumeral translation in the presence of biceps tenodesis. The authors hypothesize that subsequent to biceps tenodesis, a torn superior labrum does not affect glenohumeral stability and therefore does not require anatomic repair in an overhead throwing athlete. METHODS: Baseline anterior, posterior, and abduction and maximal external rotation glenohumeral translation data were collected from 20 cadaveric shoulders. Translation testing was repeated after the creation of anterior (n = 10) and posterior (n = 10) type II SLAP lesions. Translation re-evaluation after biceps tenodesis was performed for each specimen. Finally, anatomic SLAP lesion repair and testing were performed. RESULTS: Anterior and posterior SLAP lesions led to significant increases in glenohumeral translation in all directions (P < .0125). Biceps tenodesis showed no significance in stability compared with SLAP alone (P > .0125). Arthroscopic repair of anterior SLAP lesions did not restore anterior translation compared with the baseline state (P = .0011) but did restore posterior (P = .823) and abduction and maximal external rotation (P = .806) translations. Repair of posterior SLAP lesions demonstrated no statistical difference compared with the baseline state (P > .0125). CONCLUSIONS: With no detrimental effect on glenohumeral stability in the presence of a SLAP lesion, biceps tenodesis may be considered a valid primary or revision surgery for patients suffering from symptomatic type II SLAP tears. However, biceps tenodesis should be considered with caution as the primary treatment of SLAP lesions in overhead throwing athletes secondary to its inability to completely restore translational stability.

Computed tomographic analysis of curved and straight guides for placement of suture anchors for acetabular labral refixation.

PURPOSE: The purpose of this study was to compare suture anchor placement in the acetabular rim between straight and curved drill guides regarding angle and distance of the suture anchor tip from the articular cartilage during labral refixation. METHODS: A total of 14 fresh-frozen cadaveric hips underwent arthroscopic labral incision from the 12 to 3 o'clock positions and subsequent repair with either a curved drill guide or a straight drill guide. These hips were then compared by computed tomographic imaging analysis by measuring the angle of suture anchor insertion and the distance of the tip of the suture anchor to the articular cartilage at the 1 o'clock, 2 o'clock, and 3 o'clock positions. RESULTS: The curved suture anchor (CSA) guide significantly increased the insertion angle (P = .009) and distance from the articular cartilage to anchor (P = .003) at the 1 o'clock position on the acetabulum. The angle of insertion at the 2 and 3 o'clock positions was greater for the CSA guide compared with the straight suture anchor (SSA) guide but did not reach statistical significance. CONCLUSIONS: A CSA guide was shown to be significantly more effective in increasing the angle of insertion of suture anchors and increased the distance of the suture anchor tip to the articular cartilage surface at the 1 o'clock position but not at the 2 or 3 o'clock position. CLINICAL RELEVANCE: The use of SSA guides can be difficult because of the osseous morphologic characteristics of the acetabular rim, leading to placement of the suture anchor away from the acetabular rim and therefore resulting in a nonanatomical refixation of the acetabular labrum. The use of a curved guide, flexible drill, and flexible suture anchor inserter may provide more precise placement of suture anchors in the acetabular rim.

Rotator cuff healing after continuous subacromial bupivacaine infusion: an in vivo rabbit study.

BACKGROUND: The objective of this study was to evaluate the effects of continuous subacromial bupivacaine infusion on supraspinatus muscle and rotator cuff tendon healing using gross, biomechanical, and histologic analyses. MATERIALS AND METHODS: Thirty-three New Zealand White rabbits underwent unilateral supraspinatus transection and rotator cuff repair (RCR). Rabbits were assigned to 1 of 3 groups: (1) RCR only, (2) RCR with continuous saline infusion for 48 hours, or (3) RCR with continuous 0.25% bupivacaine with epinephrine (1:200,000) infusion for 48 hours. Rabbits were euthanized postoperatively at 2 weeks (for histologic assessment) or 8 weeks (for biomechanical and histologic assessment). RESULTS: Tensile testing showed a significantly higher load to failure in intact tendons compared with repaired tendons (P < .01); however, no statistical differences were detected among RCR only, RCR saline, and RCR bupivacaine groups. Histologically, the enthesis of repaired tendons showed increased cellularity and disorganized collagen fibers compared with intact tendons, with no differences between treatment groups. Muscle histology demonstrated scattered degenerative muscle fibers at 2 weeks in RCR saline and RCR bupivacaine groups, but no degeneration was noted at 8 weeks. CONCLUSIONS: The healing supraspinatus tendons exposed to bupivacaine infusion showed similar histologic and biomechanical characteristics compared with untreated and saline-infused RCR groups. Muscle histology showed fiber damage at 2 weeks for the saline and bupivacaine-treated groups, with no apparent disruption at 8 weeks, suggesting a recovery process. Therefore, subacromial bupivacaine infusion in this rabbit rotator cuff model does not appear to impair muscle or tendon after acute injury and repair.

Guidelines for ex vivo mechanical testing of tendon.

Tendons are critical for the biomechanical function of joints. Tendons connect muscles to bones and allow for the transmission of muscle forces to facilitate joint motion. Therefore, characterizing the tensile mechanical properties of tendons is important for the assessment of functional tendon health and efficacy of treatments for acute and chronic injuries. In this guidelines paper, we review methodological considerations, testing protocols, and key outcome measures for mechanical testing of tendons. The goal of the paper is to present a simple set of guidelines to the nonexpert seeking to perform tendon mechanical tests. The suggested approaches provide rigorous and consistent methodologies for standardized biomechanical characterization of tendon and reporting requirements across laboratories.

A biomechanical comparison of repair techniques for complete gluteus medius tears.

PURPOSE: The purpose of this study was to compare the biomechanical fixation stability conferred by 2 specific arthroscopic repair techniques for complete gluteus medius tendon tears. METHODS: Twelve fresh-frozen human cadaveric hemi-pelves were tested. Six received double-row repair with massive cuff stitches (DR-MCS), whereas the remaining 6 underwent double-row repair with knotless lateral anchors (DR-KLA). Constructs were preloaded to 10 N, tested from 10 N to 125 N at 90 N/s for 150 cycles, and then loaded to failure at 1 mm/s. Markers were placed on the tissue for video tracking. RESULTS: No significant differences in cyclic outcomes were observed. The DR-KLA construct showed a significantly higher normalized yield load than the DR-MCS construct. Post-yield extension for the DR-MCS construct was significantly higher than that for the DR-KLA construct. At yield load, the optically measured soft-tissue elongation of the DR-KLA construct was significantly higher than that of the DR-MCS construct. CONCLUSIONS: This study strongly suggests that the biomechanical stability conferred by DR-MCS and DR-KLA constructs for gluteus medius tendon repair is similar. Because the failure load of the DR-KLA construct is strongly correlated to bone mineral density (BMD), clinical considerations of bone quality may be particularly important for gluteus medius repairs. CLINICAL RELEVANCE: Maximum load was strongly correlated to BMD in the DR-KLA group. On the basis of this analysis, BMD should be considered during surgical planning.

Looking Back on Graduate BME Admissions Data: Lessons Learned and Implications for Holistic Review and Diversity.

Graduate school applications in Biomedical Engineering (BME) are steadily rising, making competition stiffer, applications more complex, and reviews more resource intensive. Holistic reviews are being increasingly adopted to support increased diversity, equity, and inclusion in graduate student BME admissions, but which application metrics are the strongest predictors of admission and enrollment into BME programs remains unclear. In this perspectives article, we aim to shed light on some of the key predictors of student acceptance in graduate school. We share data from a three-year retrospective review of our own institution's graduate BME applications and admission rates and review the influence of grade point averages (GPA), standardized test scores (e.g., GRE), and prior research experience on graduate school admission rates. We also examine how the waiver of GRE requirements has changed the landscape of BME graduate applications in recent years. Finally, we discuss efforts taken by our institution and others to develop and implement holistic reviews of graduate applications that encourage students from underrepresented backgrounds to apply and successfully gain admission to graduate school. We share five key lessons we learned by performing the retrospective review and encourage other institutions to "self-reflect" and examine their historical graduate admissions data and past practices. Efforts aimed at engaging faculty to overcome their own implicit biases, engaging with underrepresented students in hands-on, research-intensive programs, and networking with diverse student populations have strong potential to enhance the diversity of BME graduate programs and our STEM workforce. Supplementary Information: The online version contains supplementary material available at 10.1007/s43683-022-00080-5.

Biceps tenodesis with interference screw fixation: a biomechanical comparison of screw length and diameter.

PURPOSE: To evaluate the effect of screw length and diameter on the mechanical properties of biceps tenodesis (BT) with an interference screw in 2 different locations (proximal and distal). METHODS: We randomized 42 fresh-frozen human cadaveric shoulders (mean age, 65 ± 8 years) into 6 groups (n = 7): arthroscopic proximal BT using 7 × 15-, 7 × 25-, 8 × 15-, or 8 × 25-mm interference screws or distal subpectoral BT with 7 × 15- or 8 × 15-mm interference screws. Each repaired specimen was mounted onto a materials testing machine, preloaded to 5 N for 2 minutes, cycled from 5 to 70 N for 500 cycles (1 Hz), and loaded to failure (1 mm/s). Displacement during cyclical loading, pullout stiffness, and ultimate load to failure were computed, and the mechanism of failure was noted. RESULTS: All failures occurred at the tendon-screw interface. There was no statistically significant difference in ultimate displacement among all groups in the ultimate load to failure, displacement at peak load, and stiffness. CONCLUSIONS: There is no difference in ultimate load to failure, displacement at peak load, and stiffness of BT with regard to screw length or diameter at both proximal and distal tenodesis locations. These data would support use of a smaller-diameter and shorter implant for BT both proximally and distally. CLINICAL RELEVANCE: The results may serve as a guide to the orthopaedic surgeon performing proximal BT in selecting the appropriate interference screw. When possible, we recommend using the smallest screw size available to minimize risk of stress fracture at the tenodesis site.

Biomechanical evaluation of a high tibial osteotomy with a meniscal transplant.

This study determines the biomechanical advantage and the optimal configuration of a high tibial osteotomy (HTO) and meniscus transplantation performed concurrently. Six cadaver knees were placed in a spatial frame, and an HTO was completed. Loading points between a mechanical 6 degrees of varus and 8 degrees ofvalgus were loaded to 800 N for medial meniscal intact, meniscectomized, and transplanted states. Posterior slope was also increased by 3 degrees in these specimens. Contact data was recorded. Peak pressures significantly increased in the meniscectomized state in every degree of varus/valgus (p < 0.05). For both peak and total medial compartment pressures, there was a significant drop (p < 0.001) between neutral and 3 degrees of valgus. Lateral compartment pressures linearly increased from varus to valgus orientation. There was no significant change in the pressure profile of the knee with a 3-degree increase in posterior slope. This biomechanical study confirms the hypothesis that an HTO improves the peak pressures in the medial compartment at all degrees of varus/valgus alignment in the setting of meniscal transplantation. Furthermore, the largest decrease in medial pressures was between neutral and 3 degrees of valgus, suggesting that perhaps neutral aligned knees could benefit from an HTO.

A novel murine muscle loading model to investigate Achilles musculotendinous adaptation.

Achilles tendinopathy is a debilitating condition affecting the entire spectrum of society and a condition that increases the risk of tendon rupture. Effective therapies remain elusive, as anti-inflammatory drugs and surgical interventions show poor long-term outcomes. Eccentric loading of the Achilles muscle-tendon unit is an effective physical therapy for treatment of symptomatic human tendinopathy. Here, we introduce a novel mouse model of hindlimb muscle loading designed to achieve a tissue-targeted therapeutic exercise. This model includes the application of tissue (muscle and tendon)-loading "doses," coupled with ankle dorsiflexion and plantarflexion, inspired by human clinical protocols. Under computer control, the foot was rotated through the entire ankle joint range of motion while the plantar flexors simultaneously contracted to simulate body mass loading, consistent with human therapeutic exercises. This approach achieved two key components of the heel drop and raise movement: ankle range of motion coupled with body mass loading. Model development entailed the tuning of parameters such as footplate speed, number of repetitions, number of sets of repetitions, treatment frequency, treatment duration, and treatment timing. Initial model development was carried out on uninjured mice to define a protocol that was well tolerated and nondeleterious to tendon biomechanical function. When applied to a murine Achilles tendinopathy model, muscle loading led to a significant improvement in biomechanical outcome measures, with a decrease in cross-sectional area and an increase in material properties, compared with untreated animals. Our model facilitates the future investigation of mechanisms whereby rehabilitative muscle loading promotes healing of Achilles tendon injuries.NEW & NOTEWORTHY We introduce a novel mouse model of hindlimb muscle loading designed to achieve a tissue-targeted therapeutic exercise. This innovative model allows for application of muscle loading "doses," coupled with ankle dorsiflexion and plantarflexion, inspired by human loading clinical treatment. Our model facilitates future investigation of mechanisms whereby rehabilitative muscle loading promotes healing of Achilles tendon injuries.

Restoring the labral height for treatment of Bankart lesions: a comparison of suture anchor constructs.

PURPOSE: The purpose of this study was to evaluate glenoid labral heights before injury and after repair with 2 suture anchors: (1) traditional suture anchor secured with knots and (2) knotless suture anchor. METHODS: Ten matched pairs of human cadaveric glenoids were examined. In each specimen the labrum was detached from the 3-o'clock position to the 6:30 clock position on the anteroinferior glenoid, and labral repair was performed with either (1) traditional Bio-SutureTak suture anchors (n = 10) (Arthrex, Naples, FL) or (2) knotless PushLock suture anchors (n = 10, contralateral side) (Arthrex). By use of a 3-dimensional digitizer, the labral height, measured from the deepest point of the glenoid articular surface to the highest tip of the labrum, was measured in all specimens before injury and after repair at the 3:30, 4:30, and 5:30 clock positions. The degree of labral height increase was computed as a percent increase in labral height from before injury to after repair. RESULTS: Labral height increased significantly for all specimens from before injury (5.35 mm) to after repair (8.05 mm) (159.1% +/- 13.7%, P < .0001). Increases in labral height from before injury to after repair were similar (P > .05) for Bio-SutureTak suture anchors (164.6% +/- 18.7%, P < .0001) and PushLock suture anchors (153.6% +/- 5.8%, P < .0001). The amount of labral height increase did not vary by anatomic location (157.0% +/- 50.2%, 168.9% +/- 51.0%, and 150.4% +/- 35.2% at 3:30, 4:30, and 5:30, respectively; P = .46). CONCLUSIONS: An increase in labral height can be achieved to create a significant height increase from before injury to after labral repair. The difference in labral height afforded by a traditional suture anchor and a knotless anchor is not statistically significant. CLINICAL RELEVANCE: Both traditional and knotless suture anchor constructs provide a reliable restoration of labral height in an acute Bankart model.

Biomechanical similarities among subscapularis repairs after shoulder arthroplasty.

HYPOTHESIS: Many authors suggest that subscapularis deficiency after shoulder arthroplasty has a negative effect on long-term outcomes. Thus, increasing emphasis has been placed on the technique for repair of the tendon. This study evaluated the biomechanical strength of 3 different repairs: osteotomy, tendon to bone, and a combined method. MATERIALS AND METHODS: Twenty-four paired shoulders from deceased donors were prepared for shoulder arthroplasty. The subscapularis tendon was removed/repaired with the lesser tuberosity in the osteotomy group, was removed periosteally in the bone-to-tendon group, and was tenotomized in the combined group. The tendon-to-bone repair used bone tunnels, and the combined construct added tendon-to-tendon fixation. A materials testing system machine was used for cycling. A digital motion analysis system with spatial markers was used for analysis. RESULTS: There were no significant differences (P > .05) in age, bone mineral density, or construct thickness. No statistically significant differences (P > .05) in elongation amplitude (P = .67) or cyclic elongation (P = .58) were detected within the constructs or between repair techniques. Failure testing revealed no differences in maximum load, stiffness, or mode of failure. DISCUSSION: There remains no consensus about the optimal method of repairing the subscapularis tendon during shoulder arthroplasty. Furthermore, the results of the current study do not support one technique over another with regard to initial fixation properties. All constructs investigated exhibited comparably robust biomechanical performance. Durability may, therefore, be more a result of healing potential than the specific construct chosen.

In-Vivo Efficacy of Recombinant Human Hyaluronidase (rHuPH20) Injection for Accelerated Healing of Murine Retrocalcaneal Bursitis and Tendinopathy.

The deposition of aggrecan/hyaluronan (HA)-rich matrix within the tendon body and surrounding peritenon impede tendon healing and result in compromised biomechanical properties. Hence, the development of novel strategies to achieve targeted removal of the aggrecan-HA pericellular matrix may be effective in treating tendinopathy. The current study examined the therapeutic potential of a recombinant human hyaluronidase, rHuPH20 (FDA approved for reducing HA accumulation in tumors) for treating murine Achilles tendinopathy. The 12-week-old C57Bl/6 male mice were injected with two doses of rHuTGF-ß1 into the retrocalcaneal bursa (RCB) to induce a combined bursitis and tendinopathy. Twenty-four hours following induction of injury, treatment groups were administered rHuPH20 Hyaluronidase (rHuPH20; Halozyme Therapeutics) into the RCB. At either 6 h (acute), 9 days, or 25 days following hyaluronidase treatment, Achilles tendons were analyzed for gene expression, histology and immunohistochemistry, fluorophore-assisted carbohydrate electrophoresis, and biomechanical properties. The rHuPH20 treatment was effective, particularly at the acute and 9-day time points, in (a) removing HA deposits from the Achilles tendon and surrounding tissues, (b) improving biomechanical properties of the healing tendon, and (c) eliciting targeted increases in expression of specific cell fate, extracellular matrix metabolism, and inflammatory genes. The potential of rHuPH20 to effectively clear the pro-inflammatory, HA-rich matrix within the RCB and tendon strongly supports the future refinement of injectable glycosidase preparations as potential treatments to protect or regenerate tendon tissue by reducing inflammation and scarring in the presence of bursitis or other inducers of damage such as mechanical overuse. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:59-69, 2020.

Performance of a sterile meniscal allograft in an ovine model.

Meniscus transplantation is indicated for persistent pain in a meniscectomized knee. Currently, grafts are prepared aseptically, which provides limited protection against donor-derived infection. The performance of a novel, sterilized meniscus was compared with an aseptically prepared one in an experimental model. Twenty-two sheep were divided into three groups: aseptic meniscal allograft, sterile meniscal allograft, and medial meniscectomy. Animals were euthanized 2 and 4 months after surgery. Meniscal assessments included cell viability, histology, and biomechanical testing. Articular cartilage was evaluated through histology and Outerbridge scoring. Aseptic and sterile allografts had cell viabilities of 59.7% and 58.7%, respectively, at 4 months, which was less than native controls. Grafts had decreased compressive strength at 4 months compared with their preimplantation moduli and were weaker than native menisci. In operated knees, the tibial plateau had more severe degenerative changes, although Outerbridge scores were similar between operated groups. Overall, the allografts were similar in their cellularity and biomechanical properties but were inferior to the native tissue at these end points. The severity of chondral damage in the allograft knees could not be distinguished from meniscectomized joints. The sterilization process does not appear to compromise tissue integrity and provides additional allograft safety.

Biomechanical comparison of subscapularis peel and lesser tuberosity osteotomy for double-row subscapularis repair technique in a cadaveric arthroplasty model.

INTRODUCTION: Management of the subscapularis during shoulder arthroplasty is controversial. The purpose of this study was to compare the biomechanical performance of subscapularis peel (SP) and lesser tuberosity osteotomy (LTO) in a cadaveric model. METHODS: The subscapularis and proximal humerus were dissected from all soft tissues in 21 fresh-frozen human cadaveric shoulders and randomized to undergo SP, LTO, or standard subscapularis tenotomy (ST, control). For SP and LTO, six #5 sutures were passed through eyelets in the implant (on lateral border and through drill holes in bicipital groove [2] and under trunion [4]). Double-row repair was performed using two lateral row transosseous sutures and four medial row sutures through the tendon (SP) or osseotendinous junction (LTO). Biomechanical properties and mode of failure were tested. RESULTS: There were no significant differences in elongation amplitude, cyclic elongation, or maximum load to failure between the three groups (P > 0.05). Mean stiffness was significantly higher in LTO (P = 0.009 vs. SP and ST). In the ST group, 7/7 specimens failed at the tendon-suture interface. For SP, 4/7 failed at the tendon-suture interface, one at the suture-bone interface, one fractured around the implant stem, and one at the knots. For LTO, 3/7 failed at the tendon-suture interface, two at the suture-bone interface and two fractured around the implant stem. CONCLUSIONS: In this cadaveric model, subscapularis repair via ST, SP, and LTO techniques was biomechanically equivalent. Additional studies are needed to confirm these findings and determine the influence of biologic healing on healing rates and clinical outcomes. LEVEL OF EVIDENCE: N/a, biomechanical laboratory study.

Biceps tendinitis in chronic rotator cuff tears: a histologic perspective.

Patients with chronic rotator cuff tears frequently have anterior shoulder pain attributed to the long head of the biceps brachii (LHBB) tendon. In this study, tenodesis or tenotomy samples and cadaveric controls were assessed by use of immunohistochemical and histologic methods to quantify inflammation, vascularity, and neuronal plasticity. Patients had moderate pain and positive results on at least 1 clinical test of shoulder function. The number of axons in the distal LHBB was significantly less in patients with biceps tendinitis. Calcitonin gene-related peptide and substance P immunostaining was predominantly within nerve roots and blood vessels. A moderate correlation (R = 0.5) was identified between LHBB vascularity and pain scores. On the basis of these results, we conclude that, in the context of rotator cuff disease, the etiology of anterior shoulder pain with macroscopic changes in the biceps tendon is related to the complex interaction of the tendon and surrounding soft tissues, rather than a single entity.