Comparison of long-term clinical and radiological outcomes for cemented keel, cemented peg, and hybrid cage glenoids with anatomical total shoulder arthroplasty using the same humeral component.

Aims: The aim of this study was to longitudinally compare the clinical and radiological outcomes of anatomical total shoulder arthroplasty (aTSA) up to long-term follow-up, when using cemented keel, cemented peg, and hybrid cage peg glenoid components and the same humeral system. Methods: We retrospectively analyzed a multicentre, international clinical database of a single platform shoulder system to compare the short-, mid-, and long-term clinical outcomes associated with three designs of aTSA glenoid components: 294 cemented keel, 527 cemented peg, and 981 hybrid cage glenoids. Outcomes were evaluated at 4,746 postoperative timepoints for 1,802 primary aTSA, with a mean follow-up of 65 months (24 to 217). Results: Relative to their preoperative condition, each glenoid cohort had significant improvements in clinical outcomes from two years to ten years after surgery. Patients with cage glenoids had significantly better clinical outcomes, with higher patient-reported outcome scores and significantly increased active range of motion, compared with those with keel and peg glenoids. Those with cage glenoids also had significantly fewer complications (keel: 13.3%, peg: 13.1%, cage: 7.4%), revisions (keel: 7.1%, peg 9.7%, cage 3.5%), and aseptic glenoid loosening and failure (keel: 4.7%, peg: 5.8%, cage: 2.5%). Regarding radiological outcomes, 70 patients (11.2%) with cage glenoids had glenoid radiolucent lines (RLLs). The cage glenoid RLL rate was 3.3-times (p < 0.001) less than those with keel glenoids (37.3%) and 4.6-times (p < 0.001) less than those with peg glenoids (51.2%). Conclusion: These findings show that good long-term clinical and radiological outcomes can be achieved with each of the three aTSA designs of glenoid component analyzed in this study. However, there were some differences in clinical and radiological outcomes: generally, cage glenoids performed best, followed by cemented keel glenoids, and finally cemented peg glenoids.

Comparison of Reverse and Anatomic Total Shoulder Arthroplasty in Patients With an Intact Rotator Cuff and No Previous Surgery.

INTRODUCTION: This study's purpose is to compare clinical and radiographic outcomes of primary anatomic total shoulder arthroplasty (aTSA) and primary reverse total shoulder arthroplasty (rTSA) patients with osteoarthritis (OA) and an intact rotator cuff with no previous history of shoulder surgery using a single platform TSA system at a minimum follow-up of 2 years. METHODS: A total of 370 aTSA patients and 370 rTSA patients matched for age, sex, and length of follow-up from an international multi-institutional Western Institutional Review Board approved registry with a minimum 2-year follow-up were reviewed for this study. All patients had a diagnosis of OA, an intact rotator cuff, and no previous shoulder surgery. All patients were evaluated and scored preoperatively and at latest follow-up using six outcome scoring metrics and four active range of motion measurements. RESULTS: Mean follow-up was 41 months, and the mean age was 73 years. Preoperatively, the rTSA patients had lower outcome metrics and less motion. Postoperatively, aTSA and rTSA patients had similar clinical outcomes, motion, and function, with the only exception being greater external rotation in aTSA exceeding the minimal clinically important difference. Pain relief was excellent, and patient satisfaction was high in both groups. Humeral radiolucent lines were similar in both groups (8%). Complications were significantly higher with aTSA (aTSA = 4.9%; rTSA = 2.2%; P = 0.045), but revisions were similar (aTSA = 3.2%; rTSA = 1.4%; P = 0.086). CONCLUSION: At a mean of 41 month follow-up, primary aTSA and rTSA patients with OA and an intact rotator cuff with no previous history of shoulder surgery had similar clinical and radiographic outcomes. Greater external rotation was noted in aTSA patients at follow-up. However, aTSA patients had a significantly greater rate of complications compared with rTSA patients. rTSA is a viable treatment option in patients with an intact rotator cuff and no previous shoulder surgery, offering similar clinical outcomes with a lower complication rate. LEVEL OF EVIDENCE: Level III.

Clinical and radiographic outcomes following reverse total shoulder arthroplasty in patients 60 years of age and younger.

BACKGROUND: Although initially indicated for use in older patients, reverse total shoulder arthroplasty (rTSA) is being increasingly used in younger patients. The purpose of this study is to compare the clinical and radiographic outcomes of patients aged <60 years to those aged 60-79 years following primary rTSA. METHODS: 154 patients aged <60 years and 1763 patients aged 60-79 years were identified from an international multi-institutional Western Institutional Review Board-approved registry with a minimum 2 years' follow-up. All patients were evaluated and scored preoperatively and at latest follow-up using 5 outcome scoring metrics and 4 active range of motion (ROM) measurements. RESULTS: Patients aged <60 years were more often male (P = .023), had a higher body mass index (P = .001), higher rates of previous surgery (57% vs. 27%, P < .001), higher rates of post-traumatic arthritis (11% vs. 5%, P < .001) and inflammatory arthropathy (13% vs. 4%, P < .001), and lower rates of rotator cuff tear arthropathy (25% vs. 38%, P = .006). There were no differences in ROM between the groups but patients aged <60 years had significantly lower function and outcome metric scores and higher pain scores at latest follow-up. Adverse event rates were similar between the 2 groups, but patients aged <60 years were more likely to require revision (5.2% vs. 1.8%, P = .004). Patients aged <60 years also had lower satisfaction scores (much better/better 86% vs. 92%, P = .006). CONCLUSION: At a mean follow-up of 47 months, primary rTSA patients aged <60 years had worse clinical outcomes compared with those aged 60-79 years, with lower outcome scores, increased pain, lower function scores, and less patient satisfaction. Patients aged <60 years had higher rates of previous surgery, inflammatory arthropathy, and post-traumatic arthritis, whereas those aged 60-79 years had higher rates of rotator cuff tear arthropathy. Although complications were similar, younger patients had 3 times the risk of revision rTSA.

Effects of freezing and short-term fixation on muscle mass, volume, and density.

Preventing postmortem deterioration of soft-tissues is an important requisite of anatomical research. In order to provide corrections for potential myological distortions, this study quantifies the acute effects of freezing, formalin fixation and ethanol storage using muscles from (n = 46) rabbits (Oryctolagus cuniculus). Bilateral dissections of specific muscles were performed and each side was assigned to a different preparation group (fresh, formalin fixation only, fixation followed by short duration ethanol storage, and freezing once or twice). We demonstrate that short-term freezing at -20C and thawing have no significant effect on muscle mass, volume, and density while short-term formalin fixation and ethanol storage significantly reduces mass and volume (density remains relatively constant.) Although freezing may have less of an effect on the gross morphometric characteristics of the musculature than ethanol storage, slow freezing damages muscle microanatomy, and therefore, faster freezing and other modes of preservation such as formalin fixation and ethanol storage may be preferable. Based on our results, we derived the following correction factors for each preparation: the mass of specimens stored in 70% ethanol should be multiplied by 1.69 to approximate fresh muscle mass, and specimens fixed in 10% formalin multiplied by 1.32. Although not significant, specimens frozen-once were slightly less massive and could be multiplied by 1.03 (frozen-twice ×1.09). The volumetric corrections are: ethanol 1.64; 10% formalin 1.32; frozen-once 1.03; frozen-twice 1.10. While the density of ethanol preserved specimens is slightly less than that of fresh ones (correction: 1.03), those preserved in formalin and frozen maintain nearly the same density.

Effects of long-term ethanol storage on muscle architecture.

Muscle excursion and force potential can be estimated from architectural variables, including mass, volume, fascicle length, and density. These have been collected from fresh specimens, preserved specimens, and sometimes mixed samples of both. However, preservation alters the gross morphology of muscles. This study aims to quantify the effects of long-term storage on myological properties across a sample of fresh and ethanol preserved Mus musculus specimens ranging in storage time from 16 to 130 years. Masses, volumes, and densities of biceps femoris, quadriceps femoris, and triceps surae were measured, and histological cross-sections of some specimens were used to evaluate the microscale effects of long-term fluid preservation. For the remainder of the sample, chemically dissected fascicle lengths were measured to evaluate the fixation effects on the linear dimensions of muscle architecture. Relative muscle mass, volume, fascicle length, average fiber area, and density, and percent fiber area were regressed against years stored in ethanol. Muscle size dropped steeply between fresh and stored samples, ultimately decreasing by 62 and 60%, respectively. These losses correlate with histologically measured shrinking of average muscle fiber area. Density of stored specimens plateaued 5% below that of fresh ones. Although muscles lost mass and volume during ethanol storage, fascicle lengths did not shorten significantly (presumably because they were preserved attached on either end to bone). This study demonstrates that muscle mass, volume, and density of specimens stored long-term in ethanol should be corrected by factors of 2.64, 2.49, and 1.054 respectively for comparability to fresh specimens.

Clinical and radiographic outcomes after reverse total shoulder arthroplasty in patients 80 years of age and older.

BACKGROUND: Previous studies have found less favorable outcomes for patients aged 80 years and older after primary reverse total shoulder arthroplasty (rTSA). However, they are based on small sample sizes with no control group for comparison. The purpose of this study is to compare the clinical, functional, and radiographic outcomes after primary rTSA in patients aged 80 years and older with a younger cohort of patients aged 60-79 years. METHODS: Patients undergoing primary rTSA between 2004 and 2018 were identified within a multi-institutional database with a minimum of 2 years of follow-up. All patients received the same platform prosthesis. Patients were divided into 2 groups based on age: 80 years and older (n = 369) and 60-79 years (n = 1764). Statistical analyses were performed to compare the 2 age cohorts based on pre- and postoperative function and range of motion (ROM) scores, adverse event rates, pain scores, and patient satisfaction. RESULTS: Patients aged 80 years and older had lower preoperative functional and ROM scores relative to patients aged 60-79 years. The differences observed in active abduction, active forward elevation, and Constant scores exceed the minimal clinically important difference (MCID). The evaluation of function and ROM at latest follow-up showed that patients in both age cohorts had significant improvements that exceeded both the MCID and substantial clinical benefit, but older patients still scored lower relative to younger patients, with the differences in active abduction and Constant scores exceeding the MCID. Despite the lower scores observed in older patients, both groups report similar satisfaction (93% in older patients vs. 92% in younger patients, P = .379). There were no differences between the 2 age cohorts with regard to humeral radiolucent lines (9.2% vs. 8.7%, P = .765), scapular notching (11.0% vs. 10.3%, P = .727), adverse events (3.5% vs. 3.3%, P = .863), and revisions (0.8% vs. 1.8%, P = .188). CONCLUSIONS: Patients aged 80 years and older can expect significant improvements in function and ROM after primary rTSA, with satisfaction similar to that of patients aged 60-79 years. Patients in both age cohorts have similar rates of adverse events and revisions, and the rates observed in patients 80 years and older are much lower than what has previously been reported in the literature. rTSA in patients age 80 years and older is a beneficial surgery with outcomes similar to those found in younger patients, and age should not be a limiting factor when considering rTSA.

Myological variation in the forearm anatomy of Callitrichidae and Lemuridae.

The anatomy of the primate forearm is frequently investigated in terms of locomotor mode, substrate use, and manual dexterity. Such studies typically rely upon broad, interspecific samples for which one or two representative taxa are used to characterize the anatomy of their genus or family. To interpret variation between distantly related taxa, however, it is necessary to contextualize these differences by quantifying variation at lower hierarchical levels, that is, more fine-grained representation within specific genera or families. In this study, we present a focused evaluation of the variation in muscle organization, integration, and architecture within two speciose primate families: the Callitrichidae and Lemuridae. We demonstrate that, within each lineage, several muscle functional groups exhibit substantial variation in muscle organization. Most notably, the digital extensors appear highly variable (particularly among callitrichids), with many unique configurations represented. In terms of architectural variables, both families are more conservative, with the exception of the genus Callimico-for which an increase is observed in forearm muscle mass and strength. We suggest this reflects the increased use of vertical climbing and trunk-to-trunk leaping within this genus relative to the more typically fine-branch substrate use of the other callitrichids. Overall, these data emphasize the underappreciated variation in forearm myology and suggest that overly generalized typification of a taxon's anatomy may conceal significant intraspecific and intrageneric variation therein. Thus, considerations of adaptation within the forearm musculature should endeavor to consider the full range of anatomical variation when making comparisons between multiple taxa within an evolutionary context.

Anatomical and ontogenetic influences on muscle density.

Physiological cross-sectional area (PCSA), an important biomechanical variable, is an estimate of a muscle's contractile force potential and is derived from dividing muscle mass by the product of a muscle's average fascicle length and a theoretical constant representing the density of mammalian skeletal muscle. This density constant is usually taken from experimental studies of small samples of several model taxa using tissues collected predominantly from the lower limbs of adult animals. The generalized application of this constant to broader analyses of mammalian myology assumes that muscle density (1) is consistent across anatomical regions and (2) is unaffected by the aging process. To investigate the validity of these assumptions, we studied muscles of rabbits (Oryctolagus cuniculus) in the largest sample heretofore investigated explicitly for these variables, and we did so from numerous anatomical regions and from three different age-cohorts. Differences in muscle density and histology as a consequence of age and anatomical region were evaluated using Tukey's HSD tests. Overall, we observed that older individuals tend to have denser muscles than younger individuals. Our findings also demonstrated significant differences in muscle density between anatomic regions within the older cohorts, though none in the youngest cohort. Approximately 50% of the variation in muscle density can be explained histologically by the average muscle fiber area and the average percent fiber area. That is, muscles with larger average fiber areas and a higher proportion of fiber area tend to be denser. Importantly, using the age and region dependent measurements of muscle density that we provide may increase the accuracy of PCSA estimations. Although we found statistically significant differences related to ontogeny and anatomical region, if density cannot be measured directly, the specific values presented herein should be used to improve accuracy. If a single muscle density constant that has been better validated than the ones presented in the previous literature is preferred, then 1.0558 and 1.0502 g/cm3 would be reasonable constants to use across all adult and juvenile muscles respectively.

The Forearm Musculature of the Gray Mouse Lemur (Microcebus murinus): An Ontogenetic Study.

Although studies have sought to characterize variation in forearm muscular anatomy across the primate order, none have attempted to quantify ontogenetic changes in forearm myology within a single taxon. Herein, we present muscle architecture data for the forearm musculature (flexors and extensors of the wrist and digits) of Microcebus murinus, a small Lemuroid that has been the focus of several developmental studies. A quadratic curvilinear model described ontogenetic changes in muscle mass and fascicle length; however, fascicle lengths reached peak levels at an earlier age and showed a stronger decline during senescence. Conversely, physiological cross-sectional area followed a more linear trend, increasing steadily throughout life. As previous studies into the functional role of the primate forelimb emphasize the importance of long muscle fascicles within arboreal taxa in order to maximize mobility and flexibility, the early attainment of peak fascicle lengths may consequently reflect the importance of agility within this mobile and highly arboreal species. Similarly, observed myological trends in forearm strength are supported by previous in vivo data on grip strength within M. murinus in which senescent individuals showed no decline in forearm force relative to prime age individuals. This trend is interpreted to reflect compensation for the previously reported decline in hind limb grip strength in the hind limb with age, such that older individuals are able to maintain arboreal stability. Interestingly, the ontogenetic trajectory of each architectural variable mirrored previous observations of the masticatory musculature in M. murinus, suggesting that ontogenetic trends are relatively conserved between anatomical regions. Anat Rec, 303:1354-1363, 2020. © 2019 American Association for Anatomy.

The Ontogeny of Masticatory Muscle Architecture in Microcebus murinus.

The masticatory apparatus has been the focus of many studies in comparative anatomy-especially analyses of skulls and teeth, but also of the mandibular adductor muscles which are responsible for the production of bite force and the movements of the mandible during food processing and transport. The fiber architecture of these muscles has been correlated to specific diets (e.g., prey size in felids) and modes of foraging (e.g., tree gouging in marmosets). Despite the well-elucidated functional implications of this architecture, little is known about its ontogeny. To characterize age-related myological changes, we studied the masticatory muscles in a large (n = 33) intraspecific sample of a small, Malagasy primate, Microcebus murinus including neonatal through geriatric individuals. We removed each of the mandibular adductors and recorded its mass as well as other linear measurements. We then chemically dissected each muscle to study its architecture-fascicle length and physiological cross-sectional area (PCSA) which relate to stretch (gape) and force capabilities, respectively. We observed PCSA and muscle mass to increase rapidly and plateau in adulthood through senescence. Fascicle lengths remained relatively constant once maximal length was reached, which occurred early in life, suggesting that subsequent changes in PCSA are driven by changes in muscle mass. Quadratic curvilinear models of each of the architectural variables of all adductors combined as well as individual muscles regressed against age were all significant. Anat Rec, 303:1364-1373, 2020. © 2019 American Association for Anatomy.

A primate with a Panda's thumb: The anatomy of the pseudothumb of Daubentonia madagascariensis.

OBJECTIVES: Accessory digits have evolved independently within several mammalian lineages. Most notable among these is the pseudothumb of the giant panda, which has long been considered one of the most extraordinary examples of contingent evolution. To date, no primate has been documented to possess such an adaptation. Here, we investigate the presence of this structure within the aye-aye (Daubentonia madagascariensis), a species renowned for several other specialized morphological adaptations in the hand, including a morphologically unique third digit. MATERIALS AND METHODS: We combine physical dissection techniques with digital imaging processes across a sample of seven individuals (six adults and one immature individual) to describe and visualize the anatomy of the wrist and hand within the aye-aye. RESULTS: A distinct pseudothumb, which consists of both a bony component (an expanded radial sesamoid) and a dense cartilaginous extension (the "prepollex") was observed in all specimens. We demonstrate that this pseudodigit receives muscular attachments from three muscles, which collectively have the potential to enable abduction, adduction, and opposition. Finally, we demonstrate that the pseudothumb possesses its own distinct pad within the palm, complete with independent dermatoglyphs. DISCUSSION: Pseudothumbs have been suggested to improve palmar dexterity in taxa with overly -generalized first digits (e.g., pandas) and to widen the hand for digging (e.g., some fossorial moles), but the aye-aye's pseudothumb represents what we believe is a heretofore unrecognized third functional role: its accessory digit compensates for overspecialization of its fingers for non-gripping functions (in this case, the aye-aye's unique "tap foraging" practices).

Extraordinary grip strength and specialized myology in the hyper-derived hand of Perodicticus potto?

Previous behavioral reports of the African lorisid, Perodicticus potto, have speculated that these animals have an extraordinary grip strength. This ability is hypothesized to be facilitated by a range of anatomical features within the forelimb, ranging from the presence of a retia mirabilia in its wrist to the hyper-abduction of its pollex. Despite numerous behavioral reports, however, this claim of extraordinary grip strength has not been empirically substantiated. This study quantifies the physiological cross-sectional area of the digital flexor muscles within P. potto. These data are compared with a broad primate sample, including several similarly sized strepsirrhines. Contrary to expectation, we found that P. potto actually has relatively below-average digital flexor PCSA. However, we identified other myological characteristics in the upper limb of P. potto that were unexpected, including the largest brachioradialis muscle (an elbow flexor) among our primate sample, and - despite P. potto having only a vestigial second digit - an independent digital extensor indicis that is absent in almost a quarter of our primate sample.