Stem Size Research Articles

Planning Accuracy and Stem Offset Assessment in Digital Two-Dimensional Versus Three-Dimensional Planning in Cementless Hip Arthroplasty: A Systematic Review and Meta-Analysis

Background/Objectives: Total hip arthroplasty (THA) planning is crucial for restoring hip function and minimizing complications. The present systematic review and meta-analysis aimed to assess and compare the accuracy of 2D versus 3D preoperative planning in THA. Methods: The inclusion criteria were randomized controlled trials (RCTs) and observational studies (ROSs) published in English comparing the accuracy of 2D and 3D preoperative planning for total hip arthroplasty. We excluded review articles, registers, studies not written in English, studies that did not report the cup sizing accuracy or stem sizing accuracy or give a description of the preoperative planning method used, and non-comparative studies. In June 2024, following the PRISMA 2020 statement, a systematic review and a meta-analysis of the literature were conducted in PubMed, Scopus, and the Cochrane Library. The statistical analysis software Review Manager (RevMan) version 5.4 was used to perform the meta-analysis to compare the accuracy of 2D and 3D planning, and to assess the risk of bias, the ROBINS-I tool was used. Results: The analysis included 777 patients from six studies. The analysis showed that 3D planning offers superior precision compared to 2D planning, both for the cup (96.92% vs. 87.14%) and the stem (94.72% vs. 86.28%). The forest plots assessed a better trend for 3D planning in terms of exact size prediction and accuracy within ±1 size. Conclusions: The three-dimensional method was more precise and accurate than two-dimensional planning, both for the stem and the cup. It offered a detailed three-dimensional view of the patient’s anatomy. The main limitation was the challenge in finding homogeneous data regarding biomechanical parameters, surgical approaches, and different planning systems for both three-dimensional and two-dimensional methods.

Foliar Spray Treatment for Exogenous Application of Hormones in Maize.

Exogenous application of hormones in plants is a valuable technique for studying and manipulating plant growth, development, and responses to environmental stimuli. The foliar spray method is one of the most common approaches for the exogenous application of hormones in plants due to its ease of use on aerial organs (such as leaves and inflorescences) and the rapid absorption of the treated tissue, facilitating subsequent analyses. Here, we provide a protocol to implement this method in maize. The approach consists of preparing dilutions of the hormones or plant growth regulators (PGRs) of interest, usually in an aqueous solution and at low concentrations, followed by application by foliar spraying using a defined treatment regimen. Users can then evaluate effects by measuring different parameters, such as stem size, flowering time, seed production, or others. The foliar spray method can easily be scaled up and automated in greenhouse and field settings, and can be used to treat plants at all developmental stages.

Fruit growth and water use of two pear cultivars grown in South Africa: implications for precision irrigation scheduling

In South Africa, as in other semi-arid countries, sustainable production of high-value crops requires precise management of limited water resources. We investigated daily and seasonal changes in stem and fruit growth as indicators of water stress in pear (Pyrus communis L.) trees, in the Western Cape Province. Stem and fruit growth data were collected hourly throughout the 2022–2023 growing season on 2 cultivars commonly planted in South Africa – Packham’s Triumph and Forelle. Soil water content, tree sap flow, and orchard microclimate were also monitored. Fruit maximum daily shrinkage (MDS) was highly sensitive to soil water deficit and more sensitive than stem size changes. However, the patterns of fruit MDS for both cultivars changed as the season progressed. Early in the season (October–December), there was a strong correlation between fruit MDS and soil water deficit (R2 ~ 0.72). The fruit shrunk with increasing soil water deficit as water loss through transpiration exceeded gains through xylem and phloem inflows. In contrast, daytime fruit size swelled from late December until harvest (February/March), likely because of the dominance of phloem inflows and decreased peel transpiration as the fruit matured. Correlation between fruit expansion and soil water deficit was weaker (R2 ~ 0.32) during the later stage even though fruit growth continued until harvest. Stem MDS consistently showed midday shrinkage throughout the season in response to soil water deficit, but with more scatter (R2~ 0.37). Seasonal total transpiration was greater for Forelle (733 mm) than Packham’s Triumph (539 mm) because of the higher leaf area index of the Forelle and the longer growing season. This study suggests that pear fruit growth data can provide accurate estimates of tree water status, but only during the early stages of growth. Towards maturity, fruit size changes respond indirectly to water deficit, possibly through reductions in photosynthesis.

Long‐Term Impacts of Selective Logging in a Tropical Rainforest in the East Region of Cameroon

ABSTRACTAlthough selective logging has become the primary cause of degradation in many African countries, little is known about its long‐term effects. This study investigated the long‐term effects of selective logging on forest tree species diversity and dynamics in the East Region of Cameroon. Six permanent monitoring plots of 1 ha each in unlogged and logged forests were established in 2005 and a recensus in 2011. Each 1 ha plot was divided into 25, 20 × 20 m quadrats. Each 20 × 20 m quadrat was further divided into 16, 5 × 5 m subquadrats, where the diameter at breast height (DBH) of all trees ≥ 2 cm was measured. There was a decrease in plant species density and richness in all forest types. Sloetiopsis usambarensis was the most important species in the unlogged forests and forests logged 21 years ago. The most important family was Putrangivaceae, Euphorbiaceae and Violaceae in the unlogged forests and forests logged 11 and 21 years ago, respectively. The frequency distribution of stem size classes indicated a reversed J‐shape of tropical forests. The above ground biomass (AGB) recovered more than 50% in all forests, and the unlogged forest had the highest AGB (961.8 Mg/ha). Larger stems indicated a forest at a stage of recovery from disturbance. Silvicultural management should be considered.

How does the position of the pelvis and femur influence the selection of prosthesis size during 2D preoperative planning for total hip arthroplasty?

PurposeTotal Hip Arthroplasty (THA) is the primary treatment for hip diseases today. Nevertheless, total hip arthroplasty has its challenges, and one of these challenges is the potential for incorrect execution of the preoperative planning process. Such errors can lead to complications such as loosening and instability of the prosthesis and leg length discrepancy. In this study, we used human phantoms to investigate the influence of pelvic and femoral factors on prosthesis size selection in the preoperative planning of total hip arthroplasty and to provide a reference standard for clinical imaging in preoperative planning of total hip arthroplasty.MethodsIn this experiment, we utilised a custom-made experimental device that enabled us to manipulate the movement of the pelvis and femur in various directions. The device also incorporated sensors to control the angle of movement. By obtaining X-rays from different positions and angles, we were able to determine the size of the prosthesis based on the 2D preoperative planning generated by the mediCAD software.ResultsWhen the pelvis was in a nonneutral position, the size of the acetabular cup varied within a range of three sizes. Similarly, when the femur was in a nonneutral position, the size of the femoral stem varied within a range of two sizes. The movement of the pelvis and femur in the coronal plane, relative to the neutral position, did not impact the selection of the prosthesis size. However, the motion of the pelvis and femur in the sagittal and transverse planes had a notable effect.ConclusionThe selection of the prosthesis size for preoperative planning can be significantly influenced by specific positions of the pelvis and femur. It is crucial for the radiographer to ensure that the pelvis and femur maintain a standard neutral position, particularly in the sagittal and transverse planes, during the image acquisition process.

Influence of proximal femoral morphology on osteointegration of the AMIS uncemented femoral stem in modern hip arthroplasty

BackgroundIndications for total hip arthroplasty (THA) have evolved over recent decades, with a growing trend toward operating on younger and more active patients. With this shift in patient demographics, there has been a change in femoral stem designs and proximal femoral morphology encountered. This study aimed to evaluate the potential correlation between femoral stem osteointegration and proximal femoral morphology using the Dorr and Noble classifications.Materials and methodsWe conducted a retrospective review of 122 uncemented femoral stems (AMIstem Medacta, triple tapered). The demographic data analyzed included sex, age, stem size, and surgical indications. Preoperative radiographs were reviewed to determine the Dorr classification as well as the canal-to-calcar isthmus ratio, cortical index, and canal flare index. Postoperative radiographs were carefully reviewed to identify the presence of potential postoperative radiolucencies. Inter- and intra-observer agreements for these parameters were also analyzed.ResultsSignificant radiolucencies (> 2 mm) were found in 19.5% of the patients. Of all the variables analyzed, the cortical index was the only parameter significantly associated with the appearance of clinically significant radiolucency, with a threshold value of 0.62.ConclusionsThe appearance of radiolucencies is multi-factorial. Nevertheless, in this study, a high cortical index (> 0.62), representing the champagne flute morphology, was found to be associated with the development of significant radiolucencies.

THE X-RAY CALIBRATION PROJECT

Increasing the accuracy of information provided through X-Rays maximises pre-operative planning. Aim of this project is to determine the necessity of calibration probes that would improve the accuracy of pre-operative templating. This is a retrospective study involving leg length and pelvis X-Rays performed across the NHS Lanarkshire from 01/03/2023 until 31/04/2024.A total of 87 leg length X-Rays were identified, 18 had a calibration probe present. Leg length was measured on each and the X-Rays were calibrated against the existing probe. In 66.7% of cases there was a major leg length discrepancy of over 2cm between the pre-calibrated and post-calibrated X-Rays. Pelvic X-Rays of 80 patients that underwent total hip replacement were reviewed. Preoperative templating was compared to the implants inserted. An average of 1.94 discrepancy in the size of the acetabular implant was identified whilst in 30 cases the size of the femoral stem was incorrect by at least 1 size. Magnification of 119.7% on X-Rays was found to provide the most accurate templating. Seventy seven cases of pelvic X-Rays before and after hip hemiarthroplasty were also reviewed. The implant head was templated incorrectly in 74% of cases and the stem in 51%. It was identified that pelvic X-Ray magnification of 121.7% would provide the most accurate results.X-Rays with no calibration probes provide inaccurate measurements leading to faulty preoperative planning. Standardised use of a calibration sphere is strongly suggested and whenever that is not available, we suggest magnification of 121%.

Identification of Essential Features in Developing a Novel Femoral Stem Reflecting Anatomical Features of East Asian Population: A Morphological Study.

Background: Recent advancements in hip arthroplasty aim to enhance the stability, longevity, and functionality of femoral implants. However, the distal fitting of femoral stems, often caused by metaphyseal-diaphyseal mismatch, remains a significant issue, particularly in patients with Dorr type A femora. Such mismatches can result in suboptimal implant performance, leading to potential complications. This study focuses on evaluating the anatomical compatibility of five representative single-tapered wedge mid-short stems with the mediolateral (ML) anatomy of the proximal femur in an East Asian population, where these mismatches are often more pronounced. Methods: A total of 742 patients from two hospitals, all of whom underwent unilateral primary total hip arthroplasty, were included in the study. The contralateral proximal femur was confirmed to have normal anatomy in each patient. Hip anteroposterior radiographs were used for measurements, which were standardized in conjunction with CT images. Key anatomical parameters were measured, including proximal and distal medial-lateral canal dimensions, vertical offset, and medial offset. Five femoral stem designs-Tri-lock®, Taperloc®, Anthology®, Accolade II®, and Fit®-were evaluated. R programming was employed for a detailed fit analysis to match stem sizes with patient anatomy, categorizing the fit as proximal, simultaneous proximal-distal, or distal engagement. Results: Among the femoral stems analyzed, the Fit® stem demonstrated the closest alignment with the regression line for ML widths in the study population (slope = 0.69; population ML slope = 0.38). This was followed by Accolade II®, which had a slope of 0.83. In terms of offset options, the Accolade II® offered the largest offset coverage, making it particularly suitable for this population. The fit analysis revealed that the Fit® stem had the highest suitable fit rate (90.56%), followed by Accolade II® (73.04%). Taperloc®, Anthology®, and Tri-lock® had similar fit rates of approximately 59%. Overall, optimal results were obtained for 92.05% of the population in the automated fitting trial, regardless of the product type. Conclusions: When designing modern cementless femoral stems intended for press-fit fixation, it is crucial to account for the anatomical variations specific to the target population. In this study, Fit® and Accolade II® femoral components demonstrated superior compatibility with the femoral anatomy of the East Asian population, particularly in those with a higher incidence of Dorr type A femora. These stems, characterized by slimmer distal dimensions and high-offset options, appear to minimize metaphyseal-diaphyseal mismatch and associated complications.

Does the calcar femorale affect the position of uncemented short stems?

Metaphyseal-stabilised short stems rely on sufficient metaphyseal fixation and are inserted by following the medial cortex. This type of stem is used extensively in our institution, and we observed on occasion unintended implant positioning with an increased distance between the implant and the medial cortex. A bony structure within the proximal femur which was first described in 1874 and named the calcar femorale, coincides with this phenomenon.The aim of this study was to investigate the impact of the calcar femorale on the position of a metaphyseal-stabilised short stem. The frequency of cases with an increased distance between medial cortex and the implanted short stem was analysed in 52 consecutive patients. Additionally, we performed an anatomical CT study with 60 cadaveric femora to obtain more detailed information on the anatomy of the calcar femorale. Detailed measurements regarding the calcar femorale and its relationship to the proximal femur were obtained. From this, we derived implications for the implantation of a short stem prosthesis. In 50% of all cases, we found an increased gap between the stem and the medial cortex. An increased gap did not significantly affect stem size, position, or subsidence rate, but in cases with an increased gap we found fewer stems with a radiologically optimum fit. The calcar could be identified in all 60 cadavers. The calcar femorale angle showed a high correlation with the mechanical antetorsion (0.87, p = 0.02) and the functional antetorsion (0.86, p = 0.05) of the femur. The calcar femorale is a consistent anatomical structure which may be the cause for an increased gap medial to the short stem in 50% of our cases. It limits the intramedullary space and influences both stem size and orientation. The CF angle which correlates with femoral antetorsion may influence the anteversion of the stem.

Mixed stands of black spruce (Picea mariana) and tamarack (Larix laricina) offer high secondary growth in eastern boreal forests of Canada

The Canadian boreal forest is still lacking investigation into compatible species mixtures that can lead to higher growth rates than monospecific or pure stands. The effect of species mixtures on stand productivity can vary with stem density, species proportion, site characteristics, and climate variation. We investigated mixed stands of black spruce (Picea mariana) and tamarack (Larix laricina) in eastern Canadian boreal forests. Using modern forest survey data, we analyzed stand basal area variation in 756 mature stands exclusively composed of these two species over a study area spanning 535,000 km². We generated a linear relationship between mixed stand basal area and stem density, and the residual of this relation was used as response variable named ‘residual basal area’. Positive and negative deviations of residual basal area were analysed with generalized additive models and quantile regressions with tamarack basal area, climate, and site characteristics as explanatory variables. The selected model included tamarack basal area, mean seasonal precipitation, degree days, mean annual temperature, stand age, latitude, longitude, and the type of surficial deposit. Tamarack exhibited a linear positive effect on predicted residual basal area. The most significant effect was observed from the interaction between tamarack basal area and stand age, predicting positive residual basal area of 16 m² ha−1 when stand aged was 150 years old and tamarack basal area was between 12 and 17 m² ha−1. Quantile regressions revealed that tamarack could enhance basal area while increasing black spruce stem size and density. Landscape managers may consider the establishment of mixed black spruce and tamarack stands to favor secondary growth in eastern Canadian boreal forests.

How stem size variations in forest stands influence harvester productivity and the use of productivity models

ABSTRACT Stem size has the greatest effect on harvester productivity, and stem sizes vary in a forest stand. How these within-stand variations influence harvester productivity is normally not considered in studies or predictions of productivity. This study suggests reasons as to why the current production and/or application of productivity models are prone to bias from stem size variations in a stand, irrespective of whether models were developed from tree-based or stand-based studies. Moreover, it also provides empirical data on the stand stem size variation’s influence on stand-based modeling of harvester productivity. Data from 11 harvesters in 347 final fellings and four harvesters in 80 thinnings were used. The mean productivity was 26.7 and 11.0 m3/PMh5 in final felling and thinning, respectively, and the mean stem size explained most of the observed variation. The productivity in final felling decreased with increased levels of stand stem size variation, as well as with increases in the proportion of broadleaf trees in the stand. For thinnings, productivity increased with increases in the proportion of pine trees in the stand, but there was no significant effect of stand stem size variation or other tested factors. The results show that stand stem size variation is a relevant factor to consider when modeling and predicting harvester productivity.

Diel and annual rhythms of tropical stem size changes in the Mayombe forest, Congo Basin

Diel and annual rhythms of tropical stem size changes in the Mayombe forest, Congo Basin

A new species of Neocalamites from the Upper Buntsandstein (Anisian) of Üdingen (Rur Eifel, Germany)

Well preserved Early-Middle Triassic plant fossils from Northwest Europe are relatively rare due to the environmental conditions within the Germanic basin during this time period. The only sphenophyte species commonly described in the floras that are found in the area, is Equisetites mougeotii. However, only stems without leaf sheaths were ever reported. Here, we describe sphenophyte stems with free standing leaves from the Upper Buntsandstein of Üdingen, Germany, which we attribute to the genus Neocalamites based on this characteristic and the difference, mainly in stem size, of the Üdingen material to E. mougeotii. Most of the material consists of internodal, infertile stems that are unbranched and vary in width. A few of these stems are three-dimensionally preserved. Due to the difference of the material to the other, rarely present, Neocalamites species reported from the Anisian of Western Europe, we propose the plant fossils from Üdingen to be a new species called Neocalamites vanderburghii n.sp.

Productivity benchmarks for unguyed excavator-based tower yarders

ABSTRACT Detailed productivity studies were conducted on three distinct crews, all operating the modern version of the EMS Harvestline excavator-based yarder working with a motorized grapple carriage for harvesting radiata pine from plantation forests in New Zealand. Data were collected from over 1000 cycles and used to estimate robust productivity benchmarks and models. Mean productivity neared 100 t per productive machine hour (PMH) on short distances (100 m) and decreased to <70 t PMH−1 on longer ones (>200 m). In addition to very fast cycle times, only 1.5 min on average at 100 m, large stem size contributed to those very high productivity figures. Utilization ranged from 50% to 63%, with line-shifts and yarder relocation being a common delay type given the short corridors and quick extraction cycles. Productivity was 40–60 t per scheduled machine hour. This productivity range is comparable with those obtained by heavier and more expensive purpose-built swing yarders, showing great potential for cost-effective future applications.

Artificial Intelligence Machine Learning Algorithms Versus Standard Linear Demographic Analysis in Predicting Implant Size of Anatomic and Reverse Total Shoulder Arthroplasty.

Accurate and precise templating is paramount for anatomic total shoulder arthroplasty (TSA) and reverse total shoulder arthroplasty (RSA) to enhance preoperative planning, streamline surgery, and improve implant positioning. We aimed to evaluate the predictive potential of readily available patient demographic data in TSA and RSA implant sizing, independent of implant design. A total of 578 consecutive, primary, noncemented shoulder arthroplasty cases were retrospectively reviewed. Demographic variables and implant characteristics were recorded. Multivariate linear regressions were conducted to predict implant sizes using patient demographic variables. Linear models accurately predict TSA implant sizes within 2 millimeters of humerus stem sizes 75.3% of the time, head diameter 82.1%, head height 82.1%, and RSA glenosphere diameter 77.6% of the time. Linear models predict glenoid implant sizes accurately 68.2% and polyethylene thickness 76.6% of the time and within one size 100% and 95.7% of the time, respectively. Linear models accurately predict shoulder arthroplasty implant sizes from demographic data. No significant statistical differences were observed between linear models and machine learning algorithms, although the analysis was underpowered. Future sufficiently powered studies are required for more robust assessment of machine learning models in predicting primary shoulder arthroplasty implant sizes based on patient demographics.

Evaluating the transferability of airborne laser scanning derived stem size prediction models for Pinus taeda L. stem size estimation to two different locations and acquisition specifications

ABSTRACT Airborne laser scanning (ALS) datasets are used widely for estimating forest biometrics. The transferability of predictive models among ALS acquisitions is a topic of research due to differences in timing, flight parameters, equipment specifications, environmental conditions, and processing methods. The transferability of predictive models therefore is subject to uncertainty. This paper presents an evaluation of the transferability of models for the estimation of stem volume and diameter at breast height (DBH) based on individual tree crown size and competitive neighbourhood metrics derived for managed loblolly pine (Pinus taeda) and slash pine (Pinus elliottii) forest in the Southern USA. Two predictive models types were tested: multiple linear regression (MLR) and Rand Forest (RF). We also evaluated the inclusion of additional training data to model development. Models were able to be transferred to other locations with similar structural and management conditions as the original training dataset with little decrease in accuracy, specifically unthinned stands, despite different ALS acquisitions (Plot stem volume: R2 0.7–0.8; NRMSE 10–12%; mean DBH: R2 0.4–0.7; NRMSE 10–17%; plot basal area: R2 0.7–0.8; NRMSE 12%). Increases in structural differences between the training and test data, driven by age or thinning status, introduced unacceptable levels of uncertainty (Stem volume: R2 0.4–0.7; NRMSE 12–16%; mean DBH: R2 0.4–0.5; NRMSE 18–20%; plot basal area: R2 0.5–0.6; NRMSE 22–40%). Generally, RF models most accuracy estimated DBH, and MLR for stem volume. Improvements to estimate accuracy can be achieved through the addition of relatively small datasets, representing features which were not present in the original data. ALS’s ability to provide accurate and near-complete inventories of forests hold a great deal of potential for forest management. The existence of a transferable model that can be used across different acquisitions represents a saving in terms of cost and time, we would argue that future research is therefore warranted.

Effects of stem size and age on resprouting ability of different tree species after clear-cutting in a warm temperate secondary forest

ABSTRACT Understanding the resprouting abilities of various tree species provides valuable insights into managing coppice forests and predicting forest dynamics. Clear-cutting was conducted in a secondary forest comprising warm-temperate broadleaf trees, and the stump size, age, and traits of the resprouts were measured to study their effects on resprouting ability. The number of resprouts that emerged from a stump was not significantly different when comparing different tree forms (canopy and shrub) or leaf longevity (evergreen and deciduous). Taller species generated taller and fast-growing resprouts. The ability to generate more resprouts with age was more important for species dominance than the ability to generate more resprouts with increase in stem size. Most shrub layer species exhibited age-related reductions in resprouting ability. Evergreen canopy species tended to have a larger number of resprouts and higher stump survival rate. The results suggest that the diversity of the resprouting traits among tree species could largely influence the stand dynamics and contribute to the coexistence of tree species.

Innovative Seed Treatment for Cassia siamea Lam. Germination and Carbon Stock Analysis in Varied Stem Sizes for Sustainable Land Management and Climate Change Mitigation

Innovative Seed Treatment for Cassia siamea Lam. Germination and Carbon Stock Analysis in Varied Stem Sizes for Sustainable Land Management and Climate Change Mitigation

Finite element analysis part 1 of 2: Influence of short stem implant polyethylene configuration on glenohumeral joint biomechanics

AbstractPurposeStress shielding in short‐stem arthroplasty can cause critical metaphyseal bone loss. If the size and shape of the humeral shaft are important factors, it is unknown whether the shape of the polyethylene component in reverse shoulder arthroplasty (RSA) affects bone stress around or within the stem. We explored the impact of polyethylene shape on humeral and scapular stress distribution using a finite element model.MethodsWe developed a shoulder‐specific finite element model. A defined set of muscle forces was applied to simulate movements. An intact rotator cuff state and a superior deficient rotator cuff state were modelled. We used the FX V135 short stem in three conditions: total shoulder arthroplasty (TSA), and RSA with symmetrical and asymmetrical polyethylene (145°/135°). We measured biomechanical markers related to bone stress for different implant sizes. Joint kinematics and the mechanical behaviour of the implant were compared.ResultsRupture of the supraspinatus muscle produced a functionally limited shoulder. The placement of an anatomic TSA with an intact rotator cuff restored function similar to that of a healthy shoulder. RSA in the rotator cuff‐deficient shoulder restored function regardless of stem size and polyethylene shape. While stem size had an impact on the stress distribution in the bone and implant, it did not show significant potential for increasing or decreasing overall stress. For the same stem, stress distribution at the humerus is different between TSA and RSA. Polyethylene shape did not alter the transmission of stress to the bone in RSA. Asymmetric polyethylene produced a greater abduction range of motion.ConclusionsIn terms of bone stress distribution, smaller stems seemed more appropriate for TSA, while larger stems may be more appropriate for RSA. Polyethylene shape resulted in different ranges of motion but did not influence bone stress.Level of EvidenceDiagnostic Tests or Criteria; Level IV.

A Case for Old Frisian Vowel Balance as Prosodically-driven Vowel Reduction

Abstract Drawing on data from the Old Frisian Riustring manuscripts, modern Frisian dialects, as well as older and more modern Scandinavian dialects and languages, this article argues for two points: first, that Vowel Balance is ultimately a reduction process, and second, that a foot-based analysis can account for Vowel Balance. In Old Frisian, i and u appear after light stems while e and o are found after heavy and polysyllabic stems; in some other languages and dialects, vowels after heavy and polysyllabic stems are reduced supporting an interpretation of e and o as reduced allophonic variants of i and u respectively. Two caveats can be made for arguments in favour of interpreting Vowel Balance as a reduction process, namely the case of trimoraic Vowel Balance in disyllabic words, and the reinterpretation of the contrast between i~e in Old Frisian as a means of marking the prosodic contrast between stem size. These caveats help clarify how prosody can shape stems both in terms of additional manifestations of Vowel Balance, and extending the vowel alternations based on light-heavy stem contrast to words which would not have otherwise undergone Vowel Balance.