Outcomes of Ulnar Shortening Osteotomy with an Intramedullary Bone Graft for Idiopathic Ulnar Impaction Syndrome.

Background: Although several techniques for the treatment of ulnar impaction syndrome (UIS) have been introduced, there have still been reports on various complications such as delayed union, nonunion, refracture, wrist pain, plate irritation, and chronic regional pain syndrome. This study aimed to compare the differences in radiological and clinical outcomes of patients in which intramedullary bone grafting was performed in addition to plate stabilization with those without additional bone grafting during ulnar shortening osteotomies (USOs). Methods: Between November 2014 and June 2021, 53 wrists of 50 patients with idiopathic UIS were retrospectively reviewed. Patients were divided into 2 groups according to whether intramedullary bone grafting was performed. Among the 53 wrists, USO with an intramedullary bone graft was performed in 21 wrists and USO without an intramedullary bone graft was performed in 32 wrists. Demographic data and factors potentially associated with bone union time were analyzed. Results: There was no significant difference between the 2 groups when comparing postoperative radioulnar distance, postoperative ulnar variance, amount of ulnar shortening, and postoperative Disabilities of the Arm, Shoulder and Hand score. Compared to the without-intramedullary bone graft group, bone union time of the osteotomy site was significantly shortened, from 8.8 ± 3.0 weeks to 6.7 ± 1.3 weeks in the with-intramedullary bone graft group. Moreover, there were no cases of nonunion or plate-induced symptoms. Both in univariable and multivariable analyses, intramedullary bone grafting was associated with shorter bone union time. Conclusions: USO with an intramedullary bone graft for idiopathic UIS has favorable radiological and clinical outcomes. The advantage of this technique is the significant shortening of bone union time.

Osteoid osteoma of the distal radius presenting as an inconspicuous swelling in a young child.

Osteoid osteoma is a benign osteoblastic tumour with a predilection for the lower extremity that rarely affects the forearm. It is commonly seen in adolescents and young adults, and is seldom diagnosed in the paediatric age group. We report a boy in his early childhood who presented with a swelling over the distal forearm, which was incidentally noted by the mother 3 months ago. Plain radiographs showed diffuse sclerosis of the dorsal cortex of the distal radius. CT scan showed a central lucent nidus in the intramedullary region and surrounding sclerosis in the radial metaphysis, confirming the diagnosis of osteoid osteoma. The patient was successfully treated by surgical en bloc resection of the nidus and was asymptomatic at 1-year follow-up. Non-specific symptoms at presentation make it a challenge to diagnose osteoid osteoma in children and it needs to be considered in the differential diagnosis when radiographs show lytic lesions in the bone.

Digital smart internal fixation surgery for coronal process basal fracture with normal joint spaces or radius-shortening: Occult factor of radius-ulna load sharing.

BACKGROUND: Reasonable postoperative humeroradial and humeroulnar joint spaces maybe an important indicator in biomechanical stability of smart internal fixation surgery for coronoid process basal fractures (CPBF). The aim of this study is to compare elbow articular stresses and elbow-forearm stability under smart internal fixations for the CPBF between normal elbow joint spaces and radius-shortening, and to determine the occult factor of radius-ulna load sharing. METHODS: CT images of 70 volunteers with intact elbow joints were retrospectively collected for accurate three-dimensional reconstruction to measure the longitudinal and transverse joint spaces. Two groups of ten finite element (FE) models were established prospectively between normal joint space and radius-shortening with 2.0 mm, including intact elbow joint and forearm, elbow-forearm with CPBF trauma, anterior or posterior double screws-cancellous bone fixation, mini-plate-cancellous bone fixation. Three sets of physiological loads (compression, valgus, varus) were used for FE intelligent calculation, FE model verification, and biomechanical and motion analysis. RESULTS: The stress distribution between coronoid process and radial head, compression displacements and valgus angles of elbow-forearm in the three smart fixation models of the normal joint spaces were close to those of corresponding intact elbow model, but were significantly different from those of preoperative CPBF models and fixed radius-shortening models. The maximum stresses of three smart fixation instrument models of normal joint spaces were significantly smaller than those of the corresponding fixed radius-shortening models. CONCLUSIONS: On the basis of the existing trauma of the elbow-forearm system in clinical practice, which is a dominant factor affecting radius-ulna load sharing, the elbow joint longitudinal space has been found to be the occult factor affecting radius-ulna load sharing. The stability and load sharing of radius and ulna after three kinds of smart fixations of the CPBF is not only related to the anatomical and biomechanical stability principles of smart internal fixations, but also closely related to postoperative elbow joint longitudinal space.

Does the ulnohumeral angle have a role in the aetiopathogenesis of lateral epicondylitis?

The pathophysiology of lateral epicondylitis (LE) remains not fully elucidated, as it involves a complex interaction of anatomical structures. The primary objective of the research is to identify a potential relationship between LE and the ulnohumeral angle (UHA), which demonstrates the coronal alignment of the elbow. Patients diagnosed with LE between September 1st, 2020, and September 1st, 2023, were retrospectively examined. Demographic information and UHA measurements of patients meeting the inclusion criteria and a control group with similar criteria were collected. Measurements were independently conducted by 2 orthopedists at a 2-week interval and compared. Among 413 patients meeting the inclusion criteria and the control group comprising 420 patients, there were no significant differences in age, gender, and side (P = .447, P = .288, P = .159, respectively). The mean UHA for the LE group was 13.49 ±â€…4.24, while for the control group, it was 12.82 ±â€…9.19, showing a significant difference (P = .026). The inter-observer and intraobserver reliability of the angle measurements were both above 0.80. We hypothesize that the increase in UHA in patients with LE reflects an adaptive change secondary to compressive forces acting on the lateral aspect of the elbow. This study is the first to describe the relationship between LE and UHA based on anatomical-biomechanical foundations, suggesting a cause-and-effect relationship. Further studies are warranted to delve deeper into this relationship.

Considerable variation in current coronoid height and fracture measurement techniques: a systematic review.

BACKGROUND: Coronoid fractures usually occur in the presence of a significant osseoligamentous injury to the elbow. Fracture size and location correlate with degree of instability and many authors have attempted to analyze the effect of fracture variation on decision making and outcome. There remains no standardized technique for measuring coronoid height or fracture size. The aim of this study was to appraise the literature regarding techniques for coronoid height measurement in order to understand variation. METHODS: Preferred Reporting Items of Systematic Reviews and Meta-Analyses guidelines were followed. A search was performed to identify studies with either a description of coronoid height, fracture size, or bone loss using the terms (Coronoid) AND (Measurement) OR (Size) OR (Height). Articles were shortlisted by screening for topic relevance based on title, abstract and, if required, full-text review. Exclusion criteria were non-English articles, those on nonhuman species or parts other than the ulna coronoid process, and studies that included patients with pre-existing elbow pathology. Shortlisted articles were grouped based on study type, imaging modality, measurement technique, and measurement parameter as well as its location along the coronoid. RESULTS: Thirty out of the initially identified 494 articles met the inclusion criteria. Twenty-one articles were clinical studies, 8 were cadaveric studies, and 1 combined patients as well as cadavers. A variety of imaging modalities (plain radiographs, 2-dimensional computed tomography [CT], 3-dimensional CT, magnetic resonance imaging or a combination of these) were used with CT scan (either 2-dimensional images or 3-dimensional reconstructions or both) being the most common modality used by 21 studies. Measurement technique also varied from uniplanar linear measurements in 15 studies to multiplanar area and volumetric measurements in 6 studies to techniques describing various angles and indices as an indirect measure of coronoid height in 8 studies. Across the 30 shortlisted studies, 19 different measurement techniques were identified. Fifteen studies measured normal coronoid height while the other 15 measured intact coronoid and/or fracture fragment height. The location of this measurement was also variable between studies with measurements at the apex of the coronoid in 24/30 (80%) of studies. Measurement accuracy was assessed by only 1 study. A total of 12/30 (40%) studies reported on the interobserver and intraobserver reliability of their measurement technique. CONCLUSION: The systemic review demonstrated considerable variability between studies that report coronoid height or fracture size measurements. This variability makes comparison of coronoid height or fracture measurements and recommendations based on these between studies unreliable. There is need for development of a consistent, easy to use, and reproducible technique for coronoid height and bone loss.

Resection Arthroplasty Is a Valuable Strategy for Humeroradial Synostosis - A Case Report.

A 15-year-old girl with humeroradial synostosis since birth underwent a resection arthroplasty. A trapezoidal resection osteotomy of approximately 2 cm was performed at the anterior part of the bone flexure. This resulted at 18 months in an elbow arc of motion of 60°-110° and forearm pronation/supination of 40° and 60° without postoperative complications and improved disabilities of the arm, shoulder and hand and Hand 20 scores. Radiographic analysis revealed a humeroradial joint with a maintained pseudarthrosis and hinged motion at the humeroulnar joint. When performed by an experienced surgeon, resection arthroplasty corrects humeroradial synostosis, resulting in improvement in range of motion and quality of life. Level of Evidence: Level V (Therapeutic).

Measurement of Radiological Parameters of Distal Radius Fracture Using the Ulnar Axis Compared with the Radial Axis.

Background: The long axis of the radius is a standard reference for measuring radiological parameters in distal radius fractures. However, in patients with severe comminution and anatomical variation with distal radius bowing, it is challenging to assess using the long axis of the radius. The long axis of the ulna can be used as an alternative reference. The aim of this study is to assess the reliability and level of agreement using the long axis of the ulna as an alternative reference in comparison to the long axis of the radius. Methods: Posteroanterior (PA) radiography of the wrist in patients with acute distal radius fractures was evaluated in two rounds by four observers. Radial height, radial inclination and ulnar variance were measured using radial and ulnar long axis as references. The intraobserver and interobserver reliability of the measurements with two reference axes was assessed using intraclass correlation coefficient (ICC). The level of agreement was determined using the Bland-Altman plot. Results: In total, 59 patients who underwent PA radiography of the wrist were included in this study. All parameters exhibited good agreement between the two methods, with a mean difference of nearly zero (radial height = -0.03 mm, radial inclination = -0.14° and ulnar variance = 0.03 mm). The limits of agreement in radial height (-2.87, 2.82 mm) and ulnar variance (-0.81, 0.87 mm) were narrow. However, for the radial inclination, it was wider (-6.21, 5.94°). Intraobserver reliability between the long axis of radius and ulna (ICC = 0.85-0.99 and 0.84-0.98, respectively) was good to excellent. The interobserver reliability of each parameter was excellent (ICC = 0.94-0.97). Conclusions: The ulnar long axis can be used as an alternative reference for measuring radial height, radial inclination and ulnar variance in PA radiography of the wrist in acute distal radius fracture, particularly if the radial long axis is distorted. Level of Evidence: Level III (Diagnostic).

Consolidation rate in ulnar shortening osteotomy with the APTUS Wrist plate.

INTRODUCTION: Ulnocarpal impaction syndrome causes pain on the ulnar side of the wrist. Various surgical techniques have been described. Ulnar shortening osteotomy is now a standard treatment. However, it is associated with complications such as non-union of the osteotomy site. The main study objective was to report the rate of radiographic consolidation after ulnar shortening osteotomy with a cutting guide. MATERIAL AND METHODS: This multicenter retrospective study of 30 cases reported clinical and radiographic criteria at a minimum 6 month's follow-up. RESULTS: The non-union rate was 3.4%. One case presented non-union of the osteotomy site. 87% of patients were satisfied or very satisfied with the procedure. Mean VAS pain rating was 2.7 ± 2.4. Mean QuickDASH and PRWE scores were 24.7 ± 19.2 and 28.6 ± 25. Mean strength on Jamar dynamometer was 27.4 ± 8.9 kg. One patient developed complex regional pain syndrome. Five patients required plate removal for hardware-related discomfort. DISCUSSION: Ulna shortening osteotomy with the Aptus Wrist plate provides a standardized approach to the surgical treatment of ulnocarpal impaction syndrome. Compared with other series in the literature, the procedure provided satisfactory consolidation and clinical results.

Synovial sarcoma of the dorsal aspect of the hand: a case report.

BACKGROUND: Synovial sarcoma is a rare soft tissue sarcoma, with incidences of 0.81/1,000,000 in children and 1.42/1,000,000 in adults. It is most commonly found in soft tissue and rarely in bone. It often has a slow growth pattern and a benign radiologic appearance. CASE PRESENTATION: This study reports a case of metacarpal synovial sarcoma occurring in the hand-wrist of a 32-year-old Iranian man presented with the chief complaint of a lump on the dorsal ulnar side of his left hand and wrist. Initially, the first physician suspected the case to be a ganglion cyst. After two months of conservative treatment, the size of the lesion gradually increased. Magnetic resonance imaging (MRI) was performed and after an excisional biopsy and a postoperative histological analysis, the tumor was identified as a synovial sarcoma. The patient underwent a scheduled surgical procedure. Unfortunately, he had poor follow-ups and brought the pathologic results two months later when, the tumor had incredible growth, which makes this presentation rare. CONCLUSIONS: Since early diagnosis can lead to higher survival rates, this report increases doctors' awareness of this extremely malignant tumor that is rarely seen.

Minimial clinically important difference values in distal metaphyseal ulnar shortening for ulnar impaction syndrome and assessment of the relationship between level of the osteotomy and bone union time.

OBJECTIVE: We aimed to define minimal clinically important difference (MCID) values of patient-reported outcome measures (PROMs) for distal metaphyseal ulnar shortening and to assess the relationship between level of the osteotomy and time to bone union. METHODS: 20 patients who had distal metaphyseal ulnar shortening osteotomies due to ulnar impaction syndrome and had at least 6 months of follow-ups were included in this study. The mean follow-up period was 12.3 ± 7.01 months. The PROMs which consisted of patient-rated wrist evaluation (PRWE) and quick disabilities of arm, shoulder, and hand (QDASH) were recorded on the day before the surgery and at follow-up assessments. Grip strength and range of motion were recorded for operated and contralateral wrists at postoperative assessments. Postoperative radiological evaluations of distance of the osteotomy from the distal ulnar articular surface (osteotomy level), the union of osteotomy site; preoperative and postoperative evaluations of styloid-triquetral distance, and ulnar variance were performed using AP wrist x-rays. The MCID values for PRWE and QDASH were calculated using ROC curve analysis. RESULTS: Mean PRWE and QDASH scores decreased statistically significantly. The mean grip strength of contralateral wrists was higher. Mean ulnar variance decreased, whereas styloid-triquetral distance increased postoperatively. Patients with osteotomy levels of greater than 13.7 mm had a longer time from surgery to bone union. Furthermore, patients with time from surgery to bone union shorter than 7 weeks had an osteotomy closer to the ulnar articular surface. The MCID values for PRWE and QDASH were analyzed and calculated through the ROC curve as 22.25 and 20.45, respectively. CONCLUSION: This study has shown us that the osteotomy level affects the time to bone union and an osteotomy closer than 13.7 mm to the ulnar articular surface seems to result in shorter union time. Furthermore, MCID values were defined for PRWE and QDASH as 22.25 and 20.45, respectively. LEVEL OF EVIDENCE: Level IV, Therapeutic Study.

Malignant giant cell tumour of distal ulna.

Giant cell tumour (GCT) accounts for 5% of all primary bone tumours. GCT in the distal third of ulna is quite rare. We present a case of recurrent GCT in distal third of ulna with malignant features involving tenosynovium. The case was treated by wide resection of tumour and on follow up, patient recovered well with no evidence of further recurrence. Considering the features, according to the literature reviewed, is the first case of its type.

Assessment of 3.0 Tesla magnetic resonance imaging in Madelung's deformity: findings and implications.

OBJECTIVE: The aim of the study was to investigate the 3.0 Tesla magnetic resonance imaging (MRI) features of Madelung's deformity. MATERIALS AND METHODS: The wrist MRI scans of 19 patients clinically diagnosed with Madelung's deformity and 20 patients without deformity were consecutively selected from Beijing Jishuitan Hospital between April 2019 and December 2022 for observation, in the case group and control group, respectively. Multiple linear regression was used to analyze the factors affecting tilting angle and width of central disc (CD, also termed as triangular fibrocartilage, the main component of triangular fibrocartilage complex), while the chi-square test was used to compare the occurrences of CD (radial) attachment displacement, VL, and RTL. p < 0.05 indicated statistical significance. RESULTS: Madelung's deformity significantly contributed to the tilting and thickening of the CD. In the case group, the tilting angle and thickness of CD were (51.46 ± 1.33)° and (0.23 ± 0.01) cm, respectively, which was statistically significant (p < 0.05); the radial attachment of the CD significantly shifted away from the distal articular surface level (χ2 = 39.00, p < 0.001), with a mean displacement of (0.97 ± 0.38) cm. Furthermore, the cases demonstrated abnormally developed Vickers ligament (χ2 = 35.19, p < 0.001) and radiotriquetral ligament (χ2 = 25.66, p < 0.001). CONCLUSION: MRI provides a notable advantage in diagnosing Madelung's deformity. Compared with the control group, patients with Madelung's deformity exhibited tilting and thickening of the CD. Additionally, the radial attachment of the CD was significantly shifted proximally with abnormal development of Vickers and radiotriquetral ligaments.

The use of lateral arthroscopy portals for the management of a fragmented lateral coronoid process in an English Bulldog.

OBJECTIVE: To report a case of unilateral lateral coronoid process fragmentation in a dog treated via lateral elbow arthroscopy portals. ANIMAL: A 9-month old male intact English Bulldog. STUDY DESIGN: Case report. METHODS: The dog presented with a history of intermittent right thoracic limb lameness. Orthopedic examination on presentation was unremarkable. Computed tomography of the right thoracic limb was pursued and revealed a mineralized focus along the lateral margin of the lateral coronoid process as well as sclerosis of the medial coronoid process and subtrochlear region of the ulna. Elbow arthroscopy was performed via a lateral approach and revealed chondromalacia of the entire lateral coronoid process. Abrasion arthroplasty of the lateral coronoid process was performed. RESULTS: Complete resolution of the lameness was achieved within two weeks of surgery. At 6 weeks postoperatively, the dog remained sound and a gradual return to normal activity was recommended. At the final follow up assessment, 5 months after surgery, no abnormalities were found on orthopedic examination and the owners reported excellent limb function with no observable lameness. CONCLUSION: Lateral coronoid disease can occur as a rare component of elbow dysplasia in dogs. Abrasion arthroplasty via lateral arthroscopic portals may have resulted in a successful outcome in this case and may form an effective treatment option for lateral coronoid disease in dogs.

Arthroscopic wafer procedure versus ulnar shortening osteotomy for ulnar impaction syndrome: a systematic review and meta-analysis.

PURPOSE: This study aimed to systematically compare the efficacy and safety of arthroscopic wafer procedure (AWP) versus ulnar shortening osteotomy (USO) for ulnar impaction syndrome (UIS) treatment. METHODS: All the studies included in this meta-analysis compared the efficacy of AWP to USO for UIS and were acquired through a comprehensive search across multiple databases. The meta-analysis was performed by calculating the effect sizes with the Cochrane Collaboration's RevMan 5.4 software. RESULTS: A total of 8 articles were included in this analysis, comprising 148 cases in the AWP group and 163 cases in the USO group. The pooled estimates indicated no significant differences in combined Darrow's Criteria or Modified Mayo Wrist Score, Modified Mayo Wrist Score, DASH scores, grip strength, VAS score, and postoperative ulnar variation. On the other hand, the patients in the AWP group exhibited fewer complications (OR = 0.17, 95%CI 0.05-0.54, P = 0.003) and a lower reoperation rate (OR = 0.12, 95%CI 0.05-0.28, P < 0.00001) than those in the USO group. CONCLUSIONS: The two surgical techniques were both effective in treating UIS but the AWP group showed fewer complications and a lower reoperation rate. Therefore, AWP may present a superior alternative for UIS treatment.

Effects of simulated radioulnar synostosis on supination and pronation in cats. A cadaveric study.

OBJECTIVE: To evaluate the effect of an induced synostosis with a screw on pronation and supination in cats. STUDY DESIGN: Ex vivo biomechanical study. SAMPLE POPULATION: A total of 58 feline forelimbs. METHODS: A total of 58 cadaveric feline thoracic limbs were mounted on a custom-built jig with the elbow and carpus flexed at a 90° angle. To exclude any orthopedic disease, radiographs of the forelimbs were performed prior to the mechanical tests. Radioulnar synostosis was imitated with a 2 mm cortical screw through the radius into the ulna in the proximal (Group P; n = 54), middle (Group M; n = 52), and distal (Group D; n = 53) radial diaphysis. The angles of pronation and supination were recorded after manually applying a two-finger tight rotational force to the metacarpus. Rotational tests were performed without a screw (Group N) and with a screw in each of the aforementioned positions. Pairwise comparisons between the groups were performed based on their angles of rotation with a paired t-test with the Benjamini-Hochberg procedure and a mixed model ANOVA. RESULTS: Mean angles of rotation decreased between Group N (129.5 ± 15.9°) and all groups with imitated radioulnar synostosis to a mean angle of 37.5 ± 14.5° (p < .0001). Mean angles of rotation did not differ between the groups with imitated radioulnar synostosis. CONCLUSION: Induced radioulnar synostosis decreases antebrachial rotation by more than two-thirds, regardless of location. CLINICAL SIGNIFICANCE: Implants fixating the radius to the ulna should be avoided in cats, regardless where they are located along the radial diaphysis.

At-Risk Median Motor Branch to the Thenar Musculature Crossing Under the Flexor Carpi Radialis in the Forearm: A Case Report.

CASE: A 77-year-old woman who sustained a distal radius and ulna fracture underwent open reduction internal fixation through a standard flexor carpi radialis (FCR) approach. On dissection, a proximal division of the median nerve was identified, with an aberrant motor branch crossing radial to ulnar deep to FCR and superficial to flexor pollicis longus. CONCLUSION: Although many anatomic variants of the median nerve have been described, the current case demonstrates a particularly important median motor branch variant, imposing a substantial risk of iatrogenic injury during a standard FCR approach.

Homozygous SMAD6 variants in two unrelated patients with craniosynostosis and radioulnar synostosis.

BACKGROUND: SMAD6 encodes an intracellular inhibitor of the bone morphogenetic protein (BMP) signalling pathway. Until now, rare heterozygous loss-of-function variants in SMAD6 were demonstrated to increase the risk of disparate clinical disorders including cardiovascular disease, craniosynostosis and radioulnar synostosis. Only two unrelated patients harbouring biallelic SMAD6 variants presenting a complex cardiovascular phenotype and facial dysmorphism have been described. CASES: Here, we present the first two patients with craniosynostosis harbouring homozygous SMAD6 variants. The male probands, both born to healthy consanguineous parents, were diagnosed with metopic synostosis and bilateral or unilateral radioulnar synostosis. Additionally, one proband had global developmental delay. Echocardiographic evaluation did not reveal cardiac or outflow tract abnormalities. MOLECULAR ANALYSES: The novel missense (c.[584T>G];[584T>G], p.[(Val195Gly)];[(Val195Gly)]) and missense/splice-site variant (c.[817G>A];[817G>A], r.[(817g>a,817delins[a;817+2_817+228])];[(817g>a,817delins[a;817+2_817+228])], p.[(Glu273Lys,Glu273Serfs*72)];[(Glu273Lys,Glu273Serfs*72)]) both locate in the functional MH1 domain of the protein and have not been reported in gnomAD database. Functional analyses of the variants showed reduced inhibition of BMP signalling or abnormal splicing, respectively, consistent with a hypomorphic mechanism of action. CONCLUSION: Our data expand the spectrum of variants and phenotypic spectrum associated with homozygous variants of SMAD6 to include craniosynostosis.

Zoledronate reduces loading-induced microdamage in cortical ulna of ovariectomized rats.

As a daily physiological mechanism in bone, microdamage accumulation dissipates energy and helps to prevent fractures. However, excessive damage accumulation might bring adverse effects to bone mechanical properties, which is especially problematic among the osteoporotic and osteopenic patients treated by bisphosphonates. Some pre-clinical studies in the literature applied forelimb loading models to produce well-controlled microdamage in cortical bone. Ovariectomized animals were also extensively studied to assimilate human conditions of estrogen-related bone loss. In the present study, we combined both experimental models to investigate microdamage accumulation in the context of osteopenia and zoledronate treatment. Three-month-old normal and ovariectomized rats treated by saline or zoledronate underwent controlled compressive loading on their right forelimb to create in vivo microdamage, which was then quantified by barium sulfate contrast-enhanced micro-CT imaging. Weekly in vivo micro-CT scans were taken to evaluate bone (re)modeling and to capture microstructural changes over time. After sacrifice, three-point-bending tests were performed to assess bone mechanical properties. Results show that the zoledronate treatment can reduce cortical microdamage accumulation in ovariectomized rats, which might be explained by the enhancement of several bone structural properties such as ultimate force, yield force, cortical bone area and volume. The rats showed increased bone formation volume and surface after the generation of microdamage, especially for the normal and the ovariectomized groups. Woven bone formation was also observed in loaded ulnae, which was most significant in ovariectomized rats. Although all the rats showed strong correlations between periosteal bone formation and microdamage accumulation, the correlation levels were lower for the zoledronate-treated groups, potentially because of their lower levels of microdamage. The present study provides insights to further investigations of pharmaceutical treatments for osteoporosis and osteopenia. The same experimental concept can be applied in future studies on microdamage and drug testing.