Iatrogenic open humeral shaft fractures following functional bracing.

INTRODUCTION: The treatment of closed humeral shaft fractures tends to be successful with functional bracing. Treatment failure due to iatrogenic conversion to an open fracture has not been described in the literature. We present a case series of patients that experienced open humeral shaft fractures after initially being treated with functional bracing for closed humeral shaft fractures and describe what factors are associated with this complication. MATERIALS AND METHODS: This was a retrospective case series performed at three level 1 trauma centers across North America. All nonoperatively treated humeral shaft fractures were reviewed from 2001 to 2023. Patients were included if they sustained a humeral shaft fracture, > 18 years old, were initially treated non-operatively with functional bracing which subsequently converted to an open fracture. Eight patients met inclusion criteria. All included patients were eventually treated with irrigation, debridement, and open reduction and internal fixation. Outcomes assessed included mortality rate, time until the fracture converted from closed to open, need for further surgery, and bony union. Descriptive statistics were used in analysis. RESULTS: The eight included patients on average were 65 ± 21.4 years old and had a body mass index (BMI) of 25.6 ± 5.2. Six patients were initially injured due to a fall. Time until the fractures became open on average was 5.2 ± 3.6 weeks. Three patients (37.5%) died within 1.8 ± 0.6 years after initial injury. The average Charlson Comorbidity Index (CCI) score was 4.5 ± 3.4. Three patients (37.5%) had dementia. Common characteristics among this cohort included a history of visual disturbances (50.0%), cerebrovascular accident (50.0%), smoking (50.0%), and alcohol abuse (50.0%). CONCLUSION: Conversion from a closed to open humeral shaft fracture after functional bracing is a potentially devastating complication. Physicians should be especially cognizant of patients with a low BMI, history of falling or visual disturbance, dementia, age ≥ 65, decreased sensorimotor protection, and significant smoking or alcohol history when choosing to use functional bracing as the final treatment modality. LEVEL OF EVIDENCE: IV.

Preoperative Patient Reported Outcomes Predict Postoperative Clinical Outcomes Following Rotator Cuff Repair.

PURPOSE: The purpose of this study was to determine whether preoperative patient-reported outcomes (PROs) predict postoperative PROs and satisfaction following rotator cuff repair. METHODS: We retrospectively identified patients who underwent a primary rotator cuff repair at a single institution. A receiver operating characteristics (ROC) analysis was used to reach a preoperative American Shoulder and Elbow Surgeons (ASES) score threshold predictive of postoperative ASES and satisfaction scores. We evaluated patients above and below the ROC threshold by comparing their final ASES scores, ASES change (Δ) from baseline, percent maximum outcome improvement (%MOI), and achievement of minimum clinically important differences (MCID), substantial clinical benefit (SCB), and patient-acceptable symptom state (PASS). Fischer exact tests were used to analyze categorical data, while continuous data were analyzed using t-test. RESULTS: A total of 348 patients who underwent rotator cuff repair were included in this study. The preop ASES value predictive of achieving SCB was 63 (area under the curve [AUC], 0.75; 95% confidence interval: 58-67; P < .001). Patients with preoperative ASES less than 63 were significantly more likely to achieve MCID (odds ratio [OR]: 4.7, P < .001) and SCB (OR:6.1, P < .001) and had significantly higher %MOI (63% vs 41%; P = 0.003) and Δ ASES scores (36 vs 12; P < .001). However, patients with preop ASES scores above 63 had significantly higher final ASES scores (86 vs 79; P = .003), were more likely to achieve PASS (59% vs 48%; P = .045), and had higher satisfaction scores (7.4 vs 6.7; P = .024). CONCLUSIONS: Patients with high preop ASES scores achieve less relative improvement; however, these patients may be more likely to achieve PASS and may have higher satisfaction scores postoperatively. LEVEL OF EVIDENCE: Level III, retrospective comparative prognostic trial.

Proximal Humerus Fractures: Leave It Alone, Fix It, Replace It?

Proximal humerus fractures are common injuries that account for 10% of all fractures in the elderly. Several options are available for the management of proximal humerus fractures. Optimal treatment is based on the fracture pattern and the patient characteristics. Most of these fractures are minimally displaced and managed nonsurgically. Approximately 15% of proximal humerus fractures are comminuted, head-split, fracture-dislocation, or severely displaced, which make the best treatment option more challenging. Hemiarthroplasty is still a viable option in selected patients of these groups; however, advancements in locking plate designs and introduction of reverse total shoulder arthroplasty have led to better clinical outcome in meticulously selected patients. Nonetheless, the debate continues regarding the best management. It is important to discuss the best treatment options based on current literature.

Compartment Syndrome: The Issues and Solutions You Need to Know About.

The diagnosis and management of compartment syndrome remains challenging and controversial. There continues to be a significant burden of disease and substantial resource implications associated with fractures complicated by compartment syndrome. Achieving consensus opinions regarding the diagnosis and treatment of this problem has important implications given the profound effect on patient outcomes.

Elbow Trauma: An Evidence-Based Approach to Improving Outcomes.

The management of elbow fractures remains difficult and controversial. The failure rate of surgical intervention in elbow fractures remains higher than that seen with other fractures, and there remains significant room for improvement in the care of these injuries. Evidence-based management strategies for elbow fractures and how to prevent and manage complications following elbow fracture surgery have been described.

Decreasing Trend in Complications for Patients With Obesity and Metabolic Syndrome Undergoing Total Knee Arthroplasty From 2006 to 2017.

BACKGROUND: To describe longitudinal trends in patients with obesity and Metabolic Syndrome (MetS) undergoing total knee arthroplasty (TKA) and the impact on complications. METHODS: We identified primary TKA patients between 2006 and 2017 within the National Surgical Quality Improvement Program database. We recorded patient demographics and 30-day complications. We labeled those with an obese Body Mass Index (BMI ≥30), hypertension, and diabetes as having MetS. We used regression to evaluate trends in BMI and complications over time and variables associated with the odds of complication. RESULTS: We identified 270,846 TKA patients, 63.71% of which were obese (n = 172,333), 15.21% morbidly obese (n = 41,130), and 12.37% met the criteria for MetS (n = 33,470). Mean BMI increased by 0.03 per year (0.02-0.05). Despite this, the odds of adverse events in obese patients decreased: major complications by 0.94 (0.93-0.96) and minor complications by 0.94 (0.93-0.95). The proportion of patients with MetS remained stable; however, we found improvements in major (0.94 [0.91-0.97]) and minor complications (0.97 [0.94-1.00]) over time. MetS components (hypertension, diabetes, and BMI ≥40) were associated with major and minor complications in obese patients, while neuraxial anesthesia lowered the odds of major complications in obese patients (0.87 [0.81-0.92]). CONCLUSION: Mean BMI in primary TKA patients increased from 2006 to 2017. MetS components diabetes and hypertension elevated the odds of complications in obese patients. Rates of complications in patients with obesity and MetS exhibited a longitudinal decline. These findings may reflect increased awareness and improved management of these patients.

Clavicle Trauma: From Acromioclavicular Joint Injuries to Distal Clavicle Fractures and Midshaft Fractures in Contact Athletes.

Injuries to the clavicle and its articulations (the acromioclavicular and sternoclavicular joints) are becoming increasingly common. Conventional treatment has been dominated by nonsurgical techniques; however, the active patient was often left with substantial residual disability that was underreported. It is now recognized that surgical intervention may be advantageous in specific patients, especially athletes. Surgeons should consider pathophysiology, indications, and surgical techniques to best manage these injuries.

Open Reduction and Internal Fixation Versus Acute Arthroplasty for the Management of Common Extremity Injuries: Evidence-Based Decision Making.

A considerable burden of disease is associated with the management of periarticular fractures. Increasingly, evidence-based medicine is used to define the standard of clinical care. The role of internal fixation in the management of periarticular fractures, particularly in elderly patients, has been questioned. Currently available evidence-based medicine studies may help surgeons decide whether open reduction and internal fixation or arthroplasty is appropriate for the management of common periarticular injuries. The management of periarticular injuries about the shoulder, elbow, hip, and knee is controversial. The long-term outcomes of patients with a periarticular upper or lower extremity injury who undergo open reduction and internal fixation are limited by high complication and revision surgery rates and poor functional outcomes. Despite evidence-based medicine decision making and the substantial number of prospective clinical trials available in the literature, a lack of consensus with regard to best practices for the surgical management of periarticular injuries exists. This lack of consensus has substantial implications given that proximal humerus, elbow, hip, and knee fractures are common and that the role of acute arthroplasty in the management of periarticular injuries is changing.

Orthopaedic surgeons' opinions surrounding the management of proximal humerus fractures: an international survey.

PURPOSE: The purpose of this study was to survey surgeons' preferences surrounding the management and evaluation of proximal humerus fractures internationally. METHODS: A questionnaire was developed using previous literature and input from practicing orthopaedic surgeon opinion leaders. Between November 13, 2014 and December 31, 2014, the questionnaire was posted on the membership section of three major orthopaedic and shoulder surgery association websites. Survey responses were anonymous. RESULTS: The survey was completed by 134 unique practicing orthopaedic surgeons. The majority of respondents (72%) practiced in North America while 28% practiced internationally. For displaced two-part fractures, a preference for open reduction and internal fixation (ORIF) with locking plates was identified (75%). No consensus was reached for preferred treatment of three- and four- part fractures: 37% chose ORIF with locking plates, 26% chose hemi-arthroplasty (HA), and 29% chose reverse shoulder arthroplasty (RSA). Preferred treatment types for three- and four-part fractures were marginally significantly different depending on place of practice (North America vs. international, p = 0.058). A significantly larger proportion of surgeons who had completed an upper extremity fellowship (35%) chose RSA for the treatment of three and four-part fractures, compared to those who had not (9%, p = 0.002). No consensus was observed regarding what outcome measure is best to assess function following proximal humerus fractures. CONCLUSIONS: The management of more complex, displaced proximal humerus fractures remains controversial. Additionally, there are conflicting opinions on what outcome measure is best to assess function following the treatment of proximal humerus fractures.

Total Hip Arthroplasty After Acetabular Fracture Is Associated With Lower Survivorship and More Complications.

BACKGROUND: Despite modern fracture management techniques allowing for near anatomic reduction of acetabular fractures, there continues to be a risk of posttraumatic arthritis and need for total hip arthroplasty (THA). Few well-controlled studies have compared THA after acetabular fractures with THAs performed for other indications in terms of survivorship or complications, and none, to our knowledge, present 10-year survivorship data in this setting. QUESTIONS/PURPOSES: (1) How does the 10-year survival of THA compare between those patients who underwent THA after an acetabular fracture and those who underwent THA for primary arthritis or avascular necrosis (AVN)? (2) Is there an increased risk of serious complications like infection, dislocation, and aseptic loosening as well as heterotopic ossification associated with a THA performed after a previous acetabular fracture? METHODS: This retrospective case-control study compared findings of patients who underwent THA after acetabular fracture versus a matched cohort of patients who had received a primary THA for primary osteoarthritis or AVN. Between 1987 and 2011, we performed 95 THAs after acetabular fracture; of those, 74 (78%) met inclusion criteria and had documented followup beyond 2 years in our institutional registry. We selected 74 matched patients based on an algorithm that matched patients based on preoperative diagnosis, date of operation, age, gender, and type of prosthesis. During this time, we performed approximately 8000 THAs that were potentially available for matching based on complete followup beyond 2 years. We compared cases and control subjects using the Kaplan-Meier survivorship estimator as well as a comparison of the proportions in each group that developed major complications (including infection, dislocation, loosening, and heterotopic ossification) based a retrospective chart review. RESULTS: The 10-year survivorship after THA was lower in patients with a previous acetabular fracture than in the matched cohort (70%, 95% confidence interval [CI], 64%-78%, versus 90%, 95% CI, 86-95%; p < 0.001). There was no difference in the 10-year survival rate for those patients whose acetabular fracture was initially treated conservatively and those treated by open reduction and internal fixation. Patients with previous acetabular fracture had a higher likelihood of developing infection (7% [five of 74] versus 0% [zero of 74]; odds ratio [OR], 11.79; p = 0.028), dislocation (11% [eight of 74] versus 3% [two of 74]; OR, 4.36; p = 0.048), or heterotopic ossification (43% [32 of 74] versus 16% [12 of 74]; OR, 3.93; p < 0.001). CONCLUSIONS: In this case-control study, patients with a prior acetabular fracture had markedly inferior 10-year survivorship and more frequent serious complications when compared with patients undergoing THA for primary osteoarthritis or AVN. Given these findings, management of these complex cases should be in highly specialized units where the expertise of arthroplasty and trauma reconstruction is available. LEVEL OF EVIDENCE: Level III, therapeutic study.

Are patients willing to pay for total shoulder arthroplasty? Evidence from a discrete choice experiment.

BACKGROUND: Total shoulder arthroplasty (TSA) is a common treatment to decrease pain and improve shoulder function in patients with severe osteoarthritis (OA). In Canada, patients requiring this procedure often wait a year or more. Our objective was to determine patient preferences related to accessing TSA, specifically comparing out-of-pocket payments for treatment, travel time to hospital, the surgeon's level of experience and wait times. METHODS: We administered a discrete choice experiment among patients with endstage shoulder OA currently waiting for TSA. Respondents were presented with 14 different choice sets, each with 3 options, and they were asked to choose their preferred scenario. A conditional logit regression model was used to estimate the relative preference and willingness to pay for each attribute. RESULTS: Sixty-two respondents completed the questionnaire. Three of the 4 attributes significantly influenced treatment preferences. Respondents had a strong preference for an experienced surgeon (mean 0.89 ± standard error [SE] 0.11), while reductions in travel time (-0.07 ± 0.04) or wait time (-0.04 ± 0.01) were of less importance. Respondents were found to be strongly averse (-1.44 ± 0.18) to surgical treatment by a less experienced surgeon and to paying out-of-pocket for their surgical treatment (-0.56 ± 0.05). CONCLUSION: Our results suggest that patients waiting for TSA to treat severe shoulder OA have minimal willingness to pay for a reduction in wait time or travel time for surgery, yet will pay higher amounts for treatment by an experienced surgeon.

CONTEXTE: L'arthroplastie totale de l'épaule est un traitement courant visant à atténuer la douleur et à augmenter la fonction de l'épaule chez les patients atteints d'arthrose grave. Au Canada, l'attente est souvent d'un an ou plus pour cette intervention. Notre objectif était de cerner les préférences des patients concernant l'accès à l'arthroplastie, particulièrement en ce qui a trait aux déboursés personnels pour le traitement, à la durée du trajet vers l'hôpital, à l'expérience du chirurgien et au temps d'attente. MÉTHODES: Nous avons mené une expérience avec choix discrets auprès de patients atteints d'arthrose de l'épaule au stade terminal actuellement en attente d'une arthroplastie totale. Les répondants ont reçu 14 ensembles de choix différents, comportant chacun 3 options, et devaient choisir leur scénario préféré. Nous avons utilisé un modèle de régression logit conditionnelle pour estimer la préférence relative et la disposition à payer pour chaque caractéristique. RÉSULTATS: En tout, 62 répondants ont rempli le questionnaire. Trois des 4 caractéristiques ont significativement influencé les préférences de traitement. Les répondants avaient une forte préférence pour un chirurgien expérimenté (moyenne de 0,89 ± écart-type de 0,11), alors que la réduction de la durée du trajet (­0,07 ± 0,04) ou du temps d'attente (­0,04 ± 0,01) était moins importante. Les répondants se sont révélés très réfractaires (­1,44 ± 0,18) à se faire opérer par un chirurgien peu expérimenté et à payer de leur poche leur traitement chirurgical (­0,56 ± 0,05). CONCLUSION: Nos résultats semblent indiquer que les patients en attente d'une arthroplastie totale de l'épaule pour traiter une arthrose grave sont très peu disposés à payer pour réduire le temps d'attente ou la durée du trajet, mais qu'ils sont prêts à desserrer les cordons de leur bourse pour être opérés par un chirurgien chevronné.

Geriatric trauma: the role of immediate arthroplasty.

Periarticular fractures in elderly patients are challenging to manage because the fractures are typically comminuted and the bone is osteopenic, which often result in the failure of internal fixation. Patients who sustain these fractures demand immediate mobilization or they often do not recover their preinjury level of function. In geriatric patients, immediate arthroplasty provides an alternative to internal fixation for many periarticular fractures of the shoulder, elbow, and hip.

Use of a Continuous Intracompartmental Pressure Monitoring Device During Fasciotomy.

A 52-year-old man presented with a bicondylar tibial plateau fracture and acute compartment syndrome. Continuous compartment pressure monitoring was used while the patient was treated with fasciotomies and application of an external fixator. The intraoperative pressure reading in the anterior compartment decreased from 105 mm Hg to 50 mm Hg after skin and subcutaneous tissue incision. Pressure continued to decrease to 10 mm Hg after all 4 compartments were released. The patient underwent staged open reduction and internal fixation and healed both fracture and fasciotomy incisions without complication. To our knowledge, this is the first report of continuous pressure changes during the different stages of a compartment release. Future studies could expand on use of this technology to gain information on compartment pressures during release and how single release affects pressures in other compartments. [Orthopedics. 2024;47(2):e98-e101.].

Distal femur fractures: basic science and international perspectives.

Distal femur fractures are challenging injuries to manage, and complication rates remain high. This article summarizes the international and basic science perspectives regarding distal femoral fractures that were presented at the 2022 Orthopaedic Trauma Association Annual Meeting. We review a number of critical concepts that can be considered to optimize the treatment of these difficult fractures. These include biomechanical considerations for distal femur fixation constructs, emerging treatments to prevent post-traumatic arthritis, both systemic and local biologic treatments to optimize nonunion management, the relative advantages and disadvantages of plate versus nail versus dual-implant constructs, and finally important factors which determine outcomes. A robust understanding of these principles can significantly improve success rates and minimize complications in the treatment of these challenging injuries.

The radiographic quantification of scapular malalignment after malunion of displaced clavicular shaft fractures.

BACKGROUND: Malunion after displaced fractures of the clavicle can result in varying degrees of scapular malalignment and potentially scapular winging. The purpose of our study was to quantify the scapular malalignment in patients with midshaft clavicle malunions showing scapular winging. METHODS: Eighteen patients with symptomatic midshaft clavicle malunions showing scapular winging were identified and underwent standardized computed tomography scanning of the thorax. Specific bony landmarks on the clavicle and scapula were digitized, allowing generation of 3-dimensional points. These points were acquired bilaterally so that relative translations comparing the malunited side with the contralateral side could be obtained. Statistical analysis using a paired t test was performed. RESULTS: The mean time from fracture to examination was 42.9 months. There were 15 men and 3 women with a mean age of 41.6 years. The mean clavicular shortening was 21.1 mm (P = .0000004). The acromion of the affected scapula on average translated 24.3 mm. The components of this translation were medial, 11.9 mm (P = .00008); inferior, 20.7 mm (P = .0009); and anterior, 4.6 mm (P = .02). Posterior bony landmarks on the scapula including the superior and inferior angles of the scapula translated a total of 9.9 mm and 5.9 mm, respectively. CONCLUSION: This is the first study to document the degree of scapular malalignment in patients with symptomatic clavicle malunions showing scapular winging. The acromion closely follows the distal clavicular fragment and translates medially, inferiorly, and anteriorly. The translations of the superior and inferior angles of the scapula are quite variable in magnitude and direction, and on average, these angles translate substantially less than the acromion.

Threaded Intramedullary Nails Are Biomechanically Superior to Crossed K-wires for Metacarpal Neck Fractures.

BACKGROUND: Intramedullary nail (IMN) fixation of metacarpal fractures is an alternative to Kirschner wire (K-wire) fixation. The goal of this study was to compare the biomechanical properties of K-wire fixation with a threaded IMN (InNate; ExsoMed, Aliso Viejo, California). METHODS: The study design was based on previously described biomechanical models for evaluating metacarpal fractures. Sixteen fresh frozen small finger-matched and ring finger-matched pairs were randomized to either IMN or 0.045 in K-wire fixation after receiving a standardized neck osteotomy. Proper implant placement was confirmed with plain radiographs. Specimens then underwent loading in a 3-point bend configuration. Load to failure (LTF), stiffness, and fracture displacement were recorded. Mechanical failure was defined by a sharp change in the load-displacement curve. RESULTS: Age, sex, sidedness (left or right), and digit (ring or small finger) were evenly distributed between groups. The IMN had a significantly higher LTF than K-wires (546 N vs 154 N, P < .001). The K-wire fixation demonstrated plastic deformation between 75 and 150 N. Intramedullary nail stiffness was higher than that of K-wires (155.89 N/mm vs 59.28 N/mm, P < .001). CONCLUSIONS: When surgical fixation is indicated for metacarpal neck and shaft fractures, the threaded IMN is biomechanically superior to crossed K-wires with the application of 3-point bend.

Clavicular Fractures in the Adolescent.

➤: Current evidence suggests that the majority of clavicular fractures in adolescents can and should be treated nonoperatively. ➤: Although rare, in certain patients or fracture patterns, nonoperative management may be associated with delayed healing, prolonged disability, and/or poor functional outcome requiring secondary reconstruction. ➤: When warranted, primary open reduction and internal fixation with plate and screw application has consistently good outcomes with a low complication rate, with the most common complication being implant-related symptoms requiring a secondary surgical procedure for implant removal. ➤: Prospective, comparative studies examining operative and nonoperative treatment, including measures of early return to function, injury burden, return to athletic activity, complication and reoperation rates, and shoulder-girdle-specific, long-term outcome measures are warranted to further elucidate which fractures may benefit from primary fixation.

Humerus fractures: selecting fixation for a successful outcome.

Current evidence suggests at least one-third of humeral shaft fractures initially managed nonoperatively will fail closed treatment, and this review highlights surgical considerations in those circumstances. Although operative indications are well-defined, certain fracture patterns and patient cohorts are at greater risk of failure. When operative intervention is necessary, internal fixation through an anterolateral approach is a safe and sensible alternative. Determining which patients will benefit most involves shared decision-making and careful patient selection. The fracture characteristics, bone quality, and adequacy of the reduction need to be carefully evaluated for the specific operative risks for individuals with certain comorbid conditions, inevitably balancing the patient's expectations and demands against the probability of infection, nerve injury, or nonunion. As our understanding of the etiology and risk of nonunion and symptomatic malunion of the humeral diaphysis matures, adhering to the principles of diagnosis and treatment becomes increasingly important. In the event of nonunion, respect for the various contributing biological and mechanical factors enhances the likelihood that all aspects will be addressed successfully through a comprehensive solution. This review further explores specific strategies to definitively restore function of the upper extremity with the ultimate objective of an uninfected, stable union.

Reliability of Current Classification Systems for Periprosthetic Fractures of the Humerus.

OBJECTIVE: Numerous classification systems exist to evaluate periprosthetic humerus fractures, although most are based on limited patient numbers. The Wright and Cofield system is the most widely used classification system. We sought to evaluate the interobserver and intraobserver reliabilities of this system compared with the Unified Classification System (UCS) using the largest patient sample to date. METHODS: This retrospective study identified patients between December 2011 and January 2021 with a periprosthetic fracture of the humerus around the stem of a shoulder arthroplasty component. Three upper extremity fellowship-trained surgeons evaluated all radiographs for stem stability, evidence of preinjury stem loosening, Wright and Cofield classification, UCS classification, and recommended treatment for each case at 2 timepoints separated by 2 months. The kappa statistic for interobserver and intraobserver reliability was calculated. RESULTS: Seventy-six patients were included. There was moderate interobserver (kappa 0.53) and substantial intraobserver (kappa 0.69) agreement when classifying stem stability after fracture. There was moderate interobserver (kappa 0.48) and intraobserver (kappa 0.60) agreement when evaluating for stem loosening before fracture. There was fair interobserver (kappa 0.29) and moderate intraobserver (kappa 0.51) agreement regarding the UCS class. There was moderate interobserver (kappa 0.41) and intraobserver (kappa 0.57) agreement regarding the proposed treatment. There was slight interobserver (kappa 0.04) and moderate intraobserver (kappa 0.44) agreement regarding the Wright and Cofield classification. CONCLUSION: The Wright and Cofield system is less reliable than the UCS classification. A more reliable and clinically relevant classification system is needed to standardize discussion of periprosthetic proximal humerus fractures.

A preliminary biomechanical study of cyclic preconditioning effects on canine cadaveric whole femurs.

Biomechanical preconditioning of biological specimens by cyclic loading is routinely done presumably to stabilize properties prior to the main phase of a study. However, no prior studies have actually measured these effects for whole bone of any kind. The aim of this study, therefore, was to quantify these effects for whole bones. Fourteen matched pairs of fresh-frozen intact cadaveric canine femurs were sinusoidally loaded in 4-point bending from 50 N to 300 N at 1 Hz for 25 cycles. All femurs were tested in both anteroposterior (AP) and mediolateral (ML) bending planes. Bending stiffness (i.e., slope of the force-vs-displacement curve) and linearity R(2) (i.e., coefficient of determination) of each loading cycle were measured and compared statistically to determine the effect of limb side, cycle number, and bending plane. Stiffnesses rose from 809.7 to 867.7 N/mm (AP, left), 847.3 to 915.6 N/mm (AP, right), 829.2 to 892.5 N/mm (AP, combined), 538.7 to 580.4 N/mm (ML, left), 568.9 to 613.8 N/mm (ML, right), and 553.8 to 597.1 N/mm (ML, combined). Linearity R(2) rose from 0.96 to 0.99 (AP, left), 0.97 to 0.99 (AP, right), 0.96 to 0.99 (AP, combined), 0.95 to 0.98 (ML, left), 0.94 to 0.98 (ML, right), and 0.95 to 0.98 (ML, combined). Stiffness and linearity R(2) versus cycle number were well-described by exponential curves whose values leveled off, respectively, starting at 12 and 5 cycles. For stiffness, there were no statistical differences for left versus right femurs (p = 0.166), but there were effects due to cycle number (p < 0.0001) and AP versus ML bending plane (p < 0.0001). Similarly, for linearity, no statistical differences were noted due to limb side (p = 0.533), but there were effects due to cycle number (p < 0.0001) and AP versus ML bending plane (p = 0.006). A minimum of 12 preconditioning cycles was needed to fully stabilize both the stiffness and linearity of the canine femurs. This is the first study to measure the effects of mechanical preconditioning on whole bones, having some practical implications on research practices.