Poly-ϵ-caprolactone scaffold as staple-line reinforcement of rectal anastomosis: an experimental piglet study.

PURPOSE: Rectal anastomoses have a persisting high incidence of anastomotic leakage. This study aimed to assess whether the use of a poly-ϵ-caprolactone (PCL) scaffold as reinforcement of a circular stapled rectal anastomosis could increase tensile strength and improve healing compared to a control in a piglet model. METHOD: Twenty weaned female piglets received a stapled rectal anastomosis and were randomised to either reinforcement with PCL scaffold (intervention) or no reinforcement (control). On postoperative day five the anastomosis was subjected to a tensile strength test followed by a histological examination to evaluate the wound healing according to the Verhofstad scoring. RESULTS: The tensile strength test showed no significant difference between the two groups, but histological evaluation revealed significant impaired wound healing in the intervention group. CONCLUSION: The incorporation of a PCL scaffold into a circular stapled rectal anastomosis did not increase anastomotic tensile strength in piglets and indicated an impaired histologically assessed wound healing.

Elastic stable intramedullary nailing versus submuscular plating in pediatric diaphyseal femur fractures: a randomized controlled trial among children in South India.

Elastic stable intramedullary nailing (ESIN) is the current preferred method for treating diaphyseal femur fractures in children. Introduction of the submuscular locked plate (SMP) fixation construct has opened the debate on treatment options for pediatric diaphyseal femur fractures in the older children and adolescents. A randomized controlled trial (RCT) protocol was designed to compare ESIN and SMP for diaphyseal femur fractures in children. An open-labelled RCT comparing SMP with ESIN was conducted from January 2013 to June 2016, for children aged 6-15 years with closed, acute femoral diaphyseal fractures. Randomization was done through computer-generated randomization sequence and opaque-sealed envelopes. Rate of adverse surgical events including unplanned re-operations was assessed as the primary outcome and secondary analysis was done for time to union, degree of malunion, limb length discrepancy, functional outcome at 2 years, surgical duration and blood loss, radiation exposure, hospital stay, cost incurred and secondary implant removal procedure. Forty children were randomized with allocation concealment. There were three adverse events in the SMP arm and five in the ESIN arm. Fifteen children with SMP underwent routine implant removal compared to only three children with ESIN (P < 0.001). Both ESIN and SMP are equally safe, viable and effective options for treating pediatric diaphyseal femoral fractures. However, the additional cost of secondary surgery for implant removal in the SMP group proved to be a deterrent factor, which led to ESIN being the preferred option in our resource-limited setting.

Effects of Upper Extremity Elevation on Intra-Cast Pressure and Digital Perfusion in a Fiberglass Short-Arm Cast Model.

The goal of this study was to determine the relationship of digital artery pressure to arm position and forearm skin surface pressure using a short-arm cast experimental setup, to ascertain the safest position for the injured casted upper extremity. A total of 27 volunteers were placed in bilateral short-arm fiber-glass casts with an empty 50-mL bladder bag under the cast and attached to a pressure transducer. Digital systolic pressure (Pdig), and skin surface pressure under the cast (Pskin) were assessed in 4 positions. Measurements were taken with and without 50 mL air in the bladder bag. A total of 54 forearms were evaluated. Both arm position and Pskin had a significant effect on Pdig (P<.001 for both), with increasing elevation leading to a decrease in Pdig (r=-0.50). The effect size of position on Pdig was large, whereas that of Pskin was small (partial eta-squared=0.371 and 0.028, respectively). Linear regression analysis of Pskin and Pdig with air in the neutral position yielded a moderate negative relationship with body mass index (r=-0.64, P<.001 for Pskin; r=0.49, P<.001 for Pdig) and wrist circumference (r=-0.66, P<.001 for Pskin; r=0.52, P<.001 for Pdig), without significant association with forearm length. For volunteers with short-arm fiberglass casts, increasing arm elevation had a large effect size on digital arterial pressure, whereas 50 mL simulated swelling had only a small effect size. Decreasing body mass index and forearm circumference correlated with increased skin surface pressure and decreased digital arterial pressure. These findings show that aggressive elevation of the injured limb may not be as desirable as previously believed. [Orthopedics. 2021;44(4):e487-e492.].

Genetic and QTL mapping in African bermudagrass.

Cynodon transvaalensis Burtt-Davy is frequently used to cross with C. dactylon Pers. in the creation of F1 hybrid cultivars that are some of the most widely used in the worldwide turf industry. However, molecular resource development in this species is limited. Accordingly, the objectives of this study were to construct a high-density genetic map, and to identify genomic regions associated with establishment rate. In this study, we constructed the first high-density linkage map for African bermudagrass using a genotyping by sequencing approach based on 109 S1 progenies. A total of 1,246 single nucleotide polymorphisms and 32 simple sequence repeat markers were integrated in the linkage map. The total length of nine linkage groups was 882.3 cM, with an average distance of 0.69 cM per interval. Four genomic regions were identified to be associated with sod establishment rate. The results provide important genetic resources towards understanding the genome as well as marker-assisted selection for improving the establishment rate in bermudagrass breeding.

Sequence-based genetic mapping of Cynodon dactylon Pers. reveals new insights into genome evolution in Poaceae.

Bermudagrass (Cynodon dactylon Pers.) is an important warm-season perennial used extensively for turf, forage, soil conservation and remediation worldwide. However, limited genomic information has hindered the application of molecular tools towards understanding genome evolution and in breeding new cultivars. We genotype a first-generation selfed population derived from the tetraploid (4x = 36) 'A12359' using genotyping-by-sequencing. A high-density genetic map of 18 linkage groups (LGs) is constructed with 3,544 markers. Comparative genomic analyses reveal that each of nine homeologous LG pairs of C. dactylon corresponds to one of the first nine chromosomes of Oropetium thomaeum. Two nested paleo-ancestor chromosome fusions (ρ6-ρ9-ρ6, ρ2-ρ10-ρ2) may have resulted in a 12-to-10 chromosome reduction. A segmental dissemination of the paleo-chromosome ρ12 (ρ1-ρ12-ρ1, ρ6-ρ12-ρ6) leads to the 10-to-9 chromosome reduction in C. dactylon genome. The genetic map will assist in an ongoing whole genome sequence assembly and facilitate marker-assisted selection (MAS) in developing new cultivars.

Do sounds near the hand facilitate tactile reaction times? Four experiments and a meta-analysis provide mixed support and suggest a small effect size.

The brain represents the space immediately surrounding the body differently to more distant parts of space. Direct evidence for this 'peripersonal space' representation comes from neurophysiological studies in monkeys, which show distance-dependent responses to visual stimuli in neurons with spatially coincident tactile responses. Most evidence for peripersonal space in humans is indirect: spatial- and distance-dependent modulations of reaction times and error rates in behavioural tasks. In one task often used to assess peripersonal space, sounds near the body have been argued to speed reactions to tactile stimuli. We conducted four experiments attempting to measure this distance-dependent audiotactile interaction. We found no distance-dependent enhancement of tactile processing in error rates or task performance, but found some evidence for a general speeding of reaction times by 9.5 ms when sounds were presented near the hand. A systematic review revealed an overestimation of reported effect sizes, lack of control conditions, a wide variety of methods, post hoc removal of data, and flexible methods of data analysis. After correcting for the speed of sound, removing biased or inconclusive studies, correcting for temporal expectancy, and using the trim-and-fill method to correct for publication bias, meta-analysis revealed an overall benefit of 15.2 ms when tactile stimuli are accompanied by near sounds compared to sounds further away. While this effect may be due to peripersonal space, response probability and the number of trials per condition explained significant proportions of variance in this near versus far benefit. These confounds need to be addressed, and alternative explanations ruled out by future, ideally pre-registered, studies.

Biomechanical Comparison of Titanium Locking Fragment-Specific and Volar Locking Plates for AO B1 and B2 Fractures of the Distal Radius.

PURPOSE: This biomechanical study compared the stability of volar locking plates (VLPs) and locking fragment-specific (LFS) dorsal and radial styloid plates for the fixation of dorsal (AO 23-B2) and radial styloid (AO 23-B1) shear fractures of the distal radius, respectively. METHODS: Two groups of 6 composite radii were fixed with a VLP or an LFS dorsal plate over a simulated dorsal shear fracture. Two additional groups of 6 radii received the same VLP or an LFS radial plate to fix a radial styloid fracture. Each plated radius was tested under cyclic axial compression by a servohydraulic testing machine that recorded axial displacement per cycle. Construct stiffness was calculated from the slope of the force-displacement curve. RESULTS: In the dorsal shear fracture model, the dorsal LFS plate exhibited less displacement than the VLP (0.32 ± 0.04 vs 0.43 ± 0.07 mm, respectively) and showed greater average stiffness (645 ± 64 vs 433 ± 88 N/mm, respectively). Plate type was responsible for 53.1% of the variation in displacement and 68.6% of the variation in stiffness. In the radial styloid fracture model, variations due to number of cycles elapsed and plate type were similar for displacement and stiffness in both groups. The average stiffness during cyclical nondestructive testing was 566 ± 45 and 573 ± 60 N/mm for VLP and LFS radial plating groups, respectively. CONCLUSIONS: For AO 23-B2 (dorsal rim) fractures, the dorsal LFS plates exhibited significantly less displacement and greater stiffness in axial loading than VLPs. For AO 23-B1 (radial styloid) fractures, the VLP displayed similar displacement and stiffness to the radial LFS plates. CLINICAL RELEVANCE: All constructs tested could be expected to withstand axial compressive forces typical of early postoperative rehabilitation.

Surgical Loupes Worn by Orthopaedic Surgeons Are a Reservoir for Microorganisms.

BACKGROUND: Surgeons frequently use optical loupes to magnify the surgical field; they are typically unprotected when positioned directly over the wound, where particulate shedding containing microorganisms could potentially lead to surgical site infections (SSIs). SSIs are rare in some orthopaedic subspecialties such as hand surgery; however, in other subspecialties, for example, the spine, where surgeons often use loupes, SSIs can have devastating consequences. QUESTIONS/PURPOSES: (1) What is the degree of bacterial and fungi organism colonization of surgical loupes and storage cases? (2) Is there a difference in the degree of colonization at the beginning and the end of a surgery day? (3) Does an alcohol swab reduce bacterial colonization of surgical loupes? METHODS: The surgical loupes of 21 orthopaedic surgeons from a large, regional orthopaedic practice were cultured over a 3-month period and form the basis of this study. Five loupe storage cases were also cultured. In two different subgroup comparisons, the presence of microorganisms was evaluated just before the start and immediately after the end of the surgical day (n = 9) and before and 1 minute after cleaning with an alcohol swab (n = 6). A total of 36 cultures were evaluated. Surgeons who declined to participate in the study were excluded. The number of loupes selected for all of the analyses were samples of convenience and limited by surgeon availability. The degree of bacterial and fungal presence was graded using a point system: 0 = no growth; 1 = limited growth (meaning few scattered colonies); 2 = moderate growth; 3 = extensive but scattered growth; and 4 = growth consuming the entire plate. Demographic data were assessed using descriptive statistics. Additionally, the Student's t and Wilcoxon signed-rank tests were used to detect differences in categorical bacterial growth between paired samples. A p value of 0.05 represented statistical significance. Kappa statistics of reliability were performed to evaluate interobserver agreement of microorganism growth in the culture plates. RESULTS: Bacteria were present in 19 of 21 (90%) sets of loupes. Five species of bacteria were noted. Fungi were present in 10 of 21 (48%) sets of loupes. Bacterial contamination was identified in two storage cases (40%) and fungi were present in five cases (100%). In a subset of nine loupes tested, the degree of bacterial presence had a median of 2 (range, 1-4; 95% confidence interval [CI], 1.0-2.6) in samples collected before starting the surgical day compared with 3 (range, 2-4; 95% CI, 2.0-3.3) at the end of the day (p = 0.004). In a separate study arm comprised of six loupes, 1 minute after being cleaned with an alcohol swab, bacterial presence on loupes decreased from a median of 2 (range, 2-3; 95% CI, 1.9-2.5) to a median of 1 (range, 0-2; 95% CI, 0.5-1.5; p = 0.012). CONCLUSIONS: Loupes are a common reservoir for bacteria and fungi. Given the use of loupes directly over the surgical field and the lack of a barrier, care should be taken to decrease the bacterial load by cleaning loupes and airing out storage cases, which may decrease the risk of surgical field contamination and iatrogenic wound infections. CLINICAL RELEVANCE: Routine cleaning and disinfecting of optical loupes with alcohol pads can reduce microorganism colonization and should be implemented by surgeons who regularly use loupes in the operating room. Theoretically, particulate shedding from the loupes into the surgical field containing microorganisms could increase the risk of SSI, although this has not been proven clinically.

Elevated Radiation Exposure Associated With Above Surface Flat Detector Mini C-Arm Use.

Background: This study aims to test the hypothesis that: (1) radiation exposure is increased with the intended use of Flat Surface Image Intensifier (FSII) units above the operative surface compared with the traditional below-table configuration; (2) this differential increases in a dose-dependent manner; and (3) radiation exposure varies with body part and proximity to the radiation source. Methods: A surgeon mannequin was seated at a radiolucent hand table, positioned for volar distal radius plating. Thermoluminescent dosimeters measured exposure to the eyes, thyroid, chest, hand, and groin, for 1- and 15-minute trials from a mini C-arm FSII unit positioned above and below the operating surface. Background radiation was measured by control dosimeters placed within the operating theater. Results: At 1-minute of exposure, hand and eye dosages were significantly greater with the flat detector positioned above the table. At 15-minutes of exposure, hand radiation dosage exceeded that of all other anatomic sites with the FSII in both positions. Hand exposure was increased in a dose-dependent manner with the flat detector in either position, whereas groin exposure saw a dose-dependent only with the flat detector beneath the operating table. Conclusions: These findings suggest that the surgeon's hands and eyes may incur greater radiation exposure compared with other body parts, during routine mini C-arm FSII utilization in its intended position above the operating table. The clinical impact of these findings remains unclear, and future long-term radiation safety investigation is warranted. Surgeons should take precautions to protect critical body parts, particularly when using FSII technology above the operating with prolonged exposure time.

Reliability of Metacarpal Subsidence Measurements after Thumb Carpometacarpal Joint Arthroplasty.

BACKGROUND: Thumb metacarpal subsidence after trapeziectomy can affect clinical function over time. Methods for measuring subsidence after trapeziectomy have been described, and they rely on an intact thumb metacarpal or proximal phalanx for measurement. The authors evaluated the reliability and reproducibility of measuring the trapezial space ratio, using previously described methods. In addition, the authors evaluated a new method that measures trapezial space on a posteroanterior (PA) hand/wrist radiograph that does not rely on an intact thumb metacarpal or proximal phalanx for measurement, which can often be altered by degenerative changes or in cases in which metacarpophalangeal arthrodesis is performed during carpometacarpal (CMC) joint arthroplasty to correct excessive hyperextension. The authors hypothesized that a new method of calculating trapezial space would have comparable reliability and reproducibility to previously proposed methods. METHODS: Thirty-seven PA hand/wrist radiographs from patients who had trapeziectomy with ligament reconstruction and tendon interposition were evaluated. Trapezial space was measured using PACS (Picture Archiving and Communication System) digital tools as the distance perpendicular to the tangents of the scaphoid and first metacarpal joint surfaces. All X-rays were evaluated individually by five fellowship-trained hand surgeons, twice, 4 weeks apart. The reviewers calculated trapezial space ratios, using three different methods, two previously described and a novel one: (1) trapezial space relative to first metacarpal length (classic 1); (2) trapezial space relative to proximal phalanx length (classic 2); and (3) trapezial space relative to capitate height (novel). Inter- and intraobserver reliabilities were measured using intraclass correlation coefficients (ICC) and limits of agreement for each method. RESULTS: The authors identified excellent agreement between the classic 1, classic 2, and novel methods with an ICC greater than 0.8, indicating excellent agreement. The average trapezial space ratios for the thumb proximal phalanx, thumb metacarpal, and capitate methods were measured as 0.19, 0.12, and 0.24, respectively. The upper and lower limits of the 95% confidence intervals for both the inter- and intraobserver agreements of the aforementioned trapezial space ratios were (0.17-0.26), (0.11-0.17), and (0.21-0.34) for the interobserver rates and (0.11-0.25), (0.06-0.16), and (0.12-0.33) for the intraobserver rates, respectively. CONCLUSION: Measuring trapezial space is an important diagnostic tool to assess postoperative changes in thumb length. The trapezial space indexed to the capitate height method (novel) provides a simple and similarly reliable method for calculating the trapezial space ratio on a PA radiograph of the hand/wrist when other measurement techniques are unavailable and when the thumb metacarpal or proximal phalanx is not intact. The authors found a high degree of reproducibility and inter- and intraobserver reliability as measured by the ICC and the 95% limits of agreement that compare with previous agreements in the literature.

Thumb Basal Joint Arthroplasty: Prospective Comparison of Perioperative Analgesia and Opioid Consumption.

Trapeziectomy alone or in combination with a suspensionplasty technique is a common surgical treatment for symptomatic thumb basal joint arthritis. The authors undertook a prospective comparative study to test the hypothesis that peripheral nerve blocks would provide better pain control than local anesthesia with bupivacaine or liposomal bupivacaine regarding pain scores and opioid pill consumption. Patients who elected to undergo basal joint arthroplasty were allocated to 1 of 3 postoperative pain management groups: (1) peripheral nerve block, (2) local anesthesia with bupivacaine, or (3) local anesthesia with liposomal bupivacaine. Total opioid pill consumption and visual analog scale pain scores were reported for the first 5 postoperative days (PODs). Seventy-eight patients were enrolled, with 27, 23, and 28 patients in the peripheral nerve block, bupivacaine, and liposomal bupivacaine groups, respectively. All groups experienced an increase in opioid pill consumption and visual analog scale pain scores from POD 0 to POD 1. Postoperative visual analog scale pain scores were lowest in group 3 from POD 0 to POD 2. Average visual analog scale pain scores were highest in group 1, except for on POD 0. After POD 2, visual analog scale pain scores normalized between all groups and decreased uniformly thereafter. Total opioid consumption was lowest in group 3 (average, 11 pills) compared with group 1 (average, 17 pills) and group 2 (average, 19 pills). Overall, these findings did not support the authors' hypothesis that peripheral nerve blocks are superior in terms of postoperative pain control and opioid consumption. Although there were advantages regarding opioid consumption and pain control with liposomal bupivacaine, these were limited to the first POD. The effectiveness of each modality, as well as potential risks and costs, should be considered when determining the optimal strategy. [Orthopedics. 2018; 41(3):e410-e415.].

Mini C-Arm Fluoroscopy: Does Its Configuration Matter for Radiation Exposure to the Surgeon?

BACKGROUND: The risk of occupational radiation exposure to the surgeon associated with the use of a mini C-arm has yet to reach a wide consensus. Using a distal radius fracture surgery model, we tested the hypothesis that radiation exposure to the surgeon's critical body parts is independent of mini C-arm configuration. METHODS: An anthropomorphic mannequin (representing the upper body of a 60" male surgeon) was seated at a hand table as if operating on a volar-plated wrist Sawbone model. Thermoluminescent dosimeters measured radiation exposure to the surgeon's eyes, thyroid, chest, hand, and groin from a mini C-arm fluoroscopy unit in 3 commonly used configurations: vertical (source above table), inverted (source below table), and horizontal (with beam parallel to table surface). The fluoroscope scanned the wrist model for 15 continuous minutes in triplicate for each orientation. RESULTS: Radiation to the hand was significantly greatest in all mini C-arm positions compared with all other anatomic sites irrespective of C-arm position. Hand radiation exposure was greatest in the horizontal position (2887.09 mrem), versus the vertical and inverted positions (59.79 mrem, 31.10 mrem, P < .001). Eye radiation exposure was significantly greater in the inverted position (2.33 mrem) compared with the vertical (0.67 mrem, P = .024), and horizontal positions (0.33 mrem, P = .012). No significant difference in radiation exposure was found at the thyroid, chest, and groin sites, at each of the 3 C-arm configurations. CONCLUSIONS: The model's hand received almost 1000 times more radiation exposure than all other anatomic sites with statistically greatest radiation exposure sustained in the horizontal position. Eye radiation exposure with the C-arm in the inverted position (below the table) was also significantly greater.

Incidence of Glove Perforation During Hand Surgical Procedures.

PURPOSE: To determine the rate of glove perforation during hand surgery. METHODS: We prospectively examined the rate of glove perforations among 10 fellowship-trained hand surgeons at our institution during a 6 week period. Gloves were tested for perforation using a water-fill technique at the conclusion of each surgical procedure. Surgeons recorded the presence of any glove perforations. RESULTS: Eleven perforations were identified in 10 gloves among 600 surgical procedures during the study period. The perforation rate per case was 1.5% (95% confidence interval, 0.78% to 2.8%). Forty percent of perforations (n = 4) occurred during fracture surgery. Other holes occurred during isolated carpal tunnel release (n = 3) or combined carpal tunnel and trigger finger release (n = 3). The perforation was noticed intraoperatively in only 2 gloves. The difference in perforation rate between single- and double-gloved procedures was not significant. There were no perforations in the inner glove of surgeons who double gloved. A total of 73% of holes (8 of 11) occurred on surgeons' index finger; 75% of these were on the dominant hand. The dominant thumb, non-dominant ring and nondominant little fingers each had a single perforation. CONCLUSIONS: The rate of glove perforation during hand surgery is low. Holes can occur even during soft tissue procedures of short duration. The dominant index finger appears to be at greatest risk for perforation. When they do occur, most often holes are not noticed by the operating surgeon. The baseline glove perforation rate is unknown. CLINICAL RELEVANCE: A high level of vigilance is required to maintain sterile technique.

Ground level air convection produces frost damage patterns in turfgrass.

Frost injury patterns are commonly observed on the warm-season turfgrass species bermudagrass (Cynodon species Rich.), zoysiagrass (Zoysia species Willd.), and buffalograss [Bouteloua dactyloides (Nutt.) J.T. Columbus] in cool-temperate and subtropical zones. Qualitative observations of these injury patterns are presented and discussed. A model for the formation of such patterns based on thermal instability and convection of air is presented. The characteristic length scale of the observed frost pattern injury requires a temperature profile that decreases with height from the soil to the turfgrass canopy surface followed by an increase in temperature with height above the turfgrass canopy. This is justified by extending the earth temperature theory to include a turf layer with atmosphere above it. Then the theory for a thermally unstable layer beneath a stable region by Ogura and Kondo is adapted to a turf layer to include different parameter values for pure air, as well as for turf, which is treated as a porous medium. The earlier porous medium model of Thompson and Daniels proposed to explain frost injury patterns is modified to give reasonable agreement with observed patterns.

Development and characterization of genomic SSR markers in Cynodon transvaalensis Burtt-Davy.

Simple sequence repeat (SSR) markers are a major molecular tool for genetic and genomic research that have been extensively developed and used in major crops. However, few are available in African bermudagrass (Cynodon transvaalensis Burtt-Davy), an economically important warm-season turfgrass species. African bermudagrass is mainly used for hybridizations with common bermudagrass [C. dactylon var. dactylon (L.) Pers.] in the development of superior interspecific hybrid turfgrass cultivars. Accordingly, the major objective of this study was to develop and characterize a large set of SSR markers. Genomic DNA of C. transvaalensis '4200TN 24-2' from an Oklahoma State University (OSU) turf nursery was extracted for construction of four SSR genomic libraries enriched with [CA](n), [GA](n), [AAG](n), and [AAT](n) as core repeat motifs. A total of 3,064 clones were sequenced at the OSU core facility. The sequences were categorized into singletons and contiguous sequences to exclude redundancy. From the two sequence categories, 1,795 SSR loci were identified. After excluding duplicate SSRs by comparison with previously developed SSR markers using a nucleotide basic local alignment tool, 1,426 unique primer pairs (PPs) were designed. Out of the 1,426 designed PPs, 981 (68.8 %) amplified alleles of the expected size in the donor DNA. Polymorphisms of the SSR PPs tested in eight C. transvaalensis plants were 93 % polymorphic with 544 markers effective in all genotypes. Inheritance of the SSRs was examined in six F(1) progeny of African parents 'T577' × 'Uganda', indicating 917 markers amplified heritable alleles. The SSR markers developed in the study are the first large set of co-dominant markers in African bermudagrass and should be highly valuable for molecular and traditional breeding research.

Development of the adult pelage in normal and hormone-injected spiny mice (Acomys cahirinus).

The dorsal pelage of the adult Egyptian spiny mouse (Acomys cahirinus) consists primarily of coarse brittle spines which differ from those of the juvenile pelage. The development of the adult pelage in juvenile spiny mice was examined in normal and estradiol- or testosterone-injected animals. Females complete the development of their adult pelage significantly faster than males. Both estradiol and testosterone injections speed pelage development in males. Testosterone causes a significant delay in the completion of the female's pelage. Studies of replacement of adult spines show that spine replacement is mosaic and slower than in other murid rodents.