scholarly journals Postoperative Recurrence of Instability After Arthroscopic Bankart Repair for Shoulders With Primary Instability Compared With Recurrent Instability: Influence of Bipolar Bone Defect Size

2019 ◽  
Vol 48 (1) ◽  
pp. 48-55
Author(s):  
Shigeto Nakagawa ◽  
Takehito Hirose ◽  
Ryohei Uchida ◽  
Makoto Tanaka ◽  
Tatsuo Mae
Keyword(s):  
Recurrence Rate ◽  
Bone Defect ◽  
Bone Defects ◽  
Postoperative Recurrence ◽  
Defect Size ◽  
Bankart Repair ◽  
Recurrent Instability ◽  
Important Indicator ◽  
Arthroscopic Bankart Repair ◽  
Primary Instability

Background: In shoulders with traumatic anterior instability, a bipolar bone defect has recently been recognized as an important indicator of the prognosis. Purpose: To investigate the influence of bipolar bone defects on postoperative recurrence after arthroscopic Bankart repair performed at primary instability. Study Design: Cohort study; Level of evidence, 3. Methods: The study group consisted of 45 patients (45 shoulders) who underwent arthroscopic Bankart repair at primary instability before recurrence and were followed for at least 2 years. The control group consisted of 95 patients (95 shoulders) with recurrent instability who underwent Bankart repair and were followed for at least 2 years. Glenoid defects and Hill-Sachs lesions were classified into 5 size categories on 3-dimensional computed tomography and were allocated scores ranging from 0 for no defect to 4 for the largest defect. The shoulders were classified according to the total score for both lesions (0-8 points). The postoperative recurrence rate was investigated for each score of bipolar bone defects and was compared between patients with primary instability and patients with recurrent instability. The same analysis was performed for the age at operation (<20 years, 20-29 years, or ≥30 years) and for the presence of an off-track Hill-Sachs lesion. Results: Bipolar bone defects were smaller in shoulders with primary instability (mean ± SD defect score, 1.4 ± 1.5 points) than in those with recurrent instability (3.6 ± 1.9 points) and were larger in older patients than in younger patients at the time of primary instability. The postoperative recurrence rate was low (6.7%) in shoulders with primary instability regardless of the size of the bipolar bone defect and the patient’s age, whereas the postoperative recurrence rate was high (23.2%) in shoulders with recurrent instability, especially among patients younger than 20 years with bipolar bone defects of 2 points or greater. An off-track Hill-Sachs lesion was found in only 1 patient in the oldest age group (2.2%) at primary instability, but it was found in 19 patients (20%) at recurrent instability, including 14 patients younger than 30 years. Among patients with an off-track lesion, the postoperative recurrence rate was significantly higher in patients younger than 20 years with recurrent instability (recurrence rates: <20 years, 71.4%; 20-29 years, 14.3%; ≥30 years, 0%). Conclusion: The recurrence rate was consistently low in patients with primary instability and was significantly influenced by bipolar bone defect size and patient age in patients with recurrent instability.

scholarly journals Changes of Bipolar Bone Defect Size After Arthroscopic Bankart Repair for Traumatic Anterior Shoulder Instability: Evaluation Using a Scoring System and Influence on Postoperative Recurrence

2019 ◽  
Vol 7 (11) ◽  
pp. 232596711988534
Author(s):  
Shigeto Nakagawa ◽  
Ryohei Uchida ◽  
Hiroyuki Yokoi ◽  
Wataru Sahara ◽  
Tatsuo Mae
Keyword(s):  
Recurrence Rate ◽  
Bone Defect ◽  
Bone Defects ◽  
Postoperative Recurrence ◽  
Defect Size ◽  
Bone Union ◽  
Bankart Repair ◽  
Glenoid Defect ◽  
Arthroscopic Bankart Repair ◽  
Glenoid Erosion

Background: The combination of a glenoid defect and a Hill-Sachs lesion in shoulders with traumatic anterior instability has been termed bipolar bone loss, and the preoperative size of these lesions has been reported to influence postoperative recurrence of instability after arthroscopic Bankart repair. Purpose: To investigate the influence of postoperative bipolar bone defect size on postoperative recurrence of instability. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 64 male collision/contact athletes (69 shoulders) were evaluated for a minimum of 2 years after surgery, and the pre- and postoperative sizes of both lesions (glenoid defect and Hill-Sachs) were evaluated retrospectively with 3-dimensional computed tomography. The sports played by the athletes included rugby (n = 28 shoulders), American football (n = 24 shoulders), and other collision/contact sports (n = 17 shoulders). Glenoid defects and Hill-Sachs lesions were classified into 5 size categories and assigned scores from 0 (no defect) to 4 (very large defect). Patients were then classified according to the total score (sum of the scores for both lesions). The influence of pre- and postoperative bipolar bone defect sizes on recurrence of instability was investigated by using the total scores for bipolar bone defects. The influence of postoperative glenoid morphology (normal preoperative glenoid, preoperative glenoid erosion, bone union after arthroscopic bony Bankart repair [ABBR], or nonunion after ABBR) was also investigated, as well as changes in shoulders with a preoperative off-track Hill-Sachs lesion. Results: Of 69 shoulders, 15 (21.7%) developed recurrent instability after surgery. The postoperative recurrence rate was 0% in shoulders with a total score ≤1, while the recurrence rate was consistently higher in shoulders with a total score ≥2 at both pre- and postoperative evaluation (mean, 28.8% and 32.6%, respectively). Postoperative recurrence was uncommon when there was a normal preoperative glenoid or bone union after ABBR, while it was frequent in shoulders with preoperative glenoid erosion or shoulders with nonunion after ABBR and a total score ≥2. An off-track lesion was recognized in 9 shoulders preoperatively. It was transformed to on-track lesions in 4 of the 5 shoulders showing bone union after ABBR, and there was no recurrence in the 5 shoulders with bone union. In contrast, postoperative recurrence of instability occurred in 3 of the 4 shoulders without bone union. Conclusion: Postoperative recurrence was influenced by the pre- and postoperative size of bipolar bone defects. Recurrence was uncommon if bone union was achieved after ABBR, even if there had been an off-track lesion preoperatively.

scholarly journals Bipolar Bone Defects in Shoulders With Primary Instability: Dislocation Versus Subluxation

2021 ◽  
Vol 9 (5) ◽  
pp. 232596712110035
Author(s):  
Shigeto Nakagawa ◽  
Wataru Sahara ◽  
Kazutaka Kinugasa ◽  
Ryohei Uchida ◽  
Tatsuo Mae
Keyword(s):  
Bone Defect ◽  
Older Patients ◽  
Bone Defects ◽  
Defect Size ◽  
Level Of Evidence ◽  
Glenoid Defect ◽  
Large Defect ◽  
Important Indicator ◽  
Defect Score ◽  
Primary Instability

Background: In shoulders with traumatic anterior instability, a bipolar bone defect has been recognized as an important indicator of the prognosis. Purpose: To investigate bipolar bone defects at primary instability and compare the difference between dislocation and subluxation. Study Design: Cohort study; Level of evidence, 3. Methods: There were 156 shoulders (156 patients) including 91 shoulders with dislocation and 65 shoulders with subluxation. Glenoid defects and Hill-Sachs lesions were classified into 5 size categories on 3-dimensional computed tomography (CT) scans and were allocated scores ranging from 0 (no defect) to 4 points (very large defect). To assess the combined size of the glenoid defect and Hill-Sachs lesion, the scores for both lesions were summed (range, 0-8 points). Patients in the dislocation and subluxation groups were compared regarding the prevalence of a glenoid defect, a bone fragment of bony Bankart lesion, a Hill-Sachs lesion, a bipolar bone defect, and an off-track Hill-Sachs lesion. Then, the combined size of the bipolar bone defects was compared between the dislocation and subluxation groups and among patients stratified by age at the time of CT scanning (<20, 20-29, and ≥30 years). Results: Hill-Sachs lesions were observed more frequently in the dislocation group (75.8%) compared with the subluxation group (27.7%; P < .001), whereas the prevalence of glenoid defects was not significantly different between groups (36.3% vs 29.2%, respectively; P = .393). The combined defect size was significantly larger in the dislocation versus subluxation group (mean ± SD combined defect score, 2.1 ± 1.6 vs 0.8 ± 0.9 points, respectively; P < .001) due to a larger Hill-Sachs lesion at dislocation than subluxation (glenoid defect score, 0.5 ± 0.9 vs 0.3 ± 0.6 points [ P = .112]; Hill-Sachs lesion score, 1.6 ± 1.2 vs 0.4 ± 0.7 points [ P < .001]). Combined defect size was larger in older patients than younger patients in the setting of dislocation (combined defect score, <20 years, 1.6 ± 1.2 points; 20-29 years, 1.9 ± 1.5 points; ≥30 years, 3.4 ± 1.6 points; P < .001) but was not different in the setting of subluxation (0.8 ± 1.0, 0.7 ± 0.9, and 0.8 ± 0.8 points, respectively; P = .885). An off-track Hill-Sachs lesion was observed in 2 older patients with dislocation but was not observed in shoulders with subluxation. Conclusion: The bipolar bone defect was significantly more frequent, and the combined size was greater in shoulders with primary dislocation and in older patients (≥30 years).

scholarly journals Outcomes of arthroscopic capsulolabral reconstruction for anterior instability with greater than 20% glenoid bone defects: are Latarjet procedures absolutely indicated for these patients?

2020 ◽  
Vol 23 (2) ◽  
pp. 62-70 ◽  
Author(s):  
Sae Hoon Kim ◽  
Whanik Jung ◽  
Sung-Min Rhee ◽  
Ji Un Kim ◽  
Joo Han Oh
Keyword(s):  
Bone Defect ◽  
Shoulder Instability ◽  
Bone Defects ◽  
Defect Size ◽  
Anterior Shoulder Instability ◽  
Return To Sports ◽  
Anterior Instability ◽  
Recurrent Instability ◽  
Capsulolabral Reconstruction

Background: Recent studies have reported high rates of recurrence of shoulder instability in patients with glenoid bone defects greater than 20% after capsulolabral reconstruction. The purpose of the present study was to evaluate the failure rate of arthroscopic capsulolabral reconstruction for the treatment of anterior instability in the presence of glenoid bone deficits >20%. Methods: Retrospective analyses were conducted among cases with anterior shoulder instability and glenoid bone defects of >20% that were treated by arthroscopic capsulolabral reconstruction with a minimum 2-year follow-up (30 cases). We included the following variables: age, bone defect size, instability severity index score (ISIS), on-/off-track assessment, incidence recurrent instability, and return to sports. Results: The mean glenoid bone defect size was 25.8% ± 4.2% (range, 20.4%–37.2%), and 18 cases (60%) had defects of >25%. Bony Bankart lesions were identified in 11 cases (36.7%). Eleven cases (36.7%) had ISIS scores >6 points and 21 cases (70%) had off-track lesions. No cases of recurrent instability were identified over a mean follow-up of 39.9 months (range, 24–86 months), but a sense of subluxation was reported by three patients. Return to sports at the preinjury level was possible in 24 cases (80%), and the average satisfaction rating was 92%. Conclusions: Arthroscopic soft tissue reconstruction was successful for treating anterior shoulder instability among patients with glenoid bone defects >20%, even enabling return to sports. Future studies should focus on determining the range of bone defect sizes that can be successfully managed by soft tissue repair.

A lower Instability Severity Index score threshold may better predict recurrent anterior shoulder instability after arthroscopic Bankart repair: a systematic review

2021 ◽  
pp. jisakos-2020-000584
Author(s):  
Samuel I Rosenberg ◽  
Simon J Padanilam ◽  
Brandon Alec Pagni ◽  
Vehniah K Tjong ◽  
Ujash Sheth
Keyword(s):  
Shoulder Instability ◽  
Severity Index ◽  
Postoperative Recurrence ◽  
Bankart Repair ◽  
Anterior Shoulder Instability ◽  
Recurrence Rates ◽  
Recurrent Instability ◽  
Arthroscopic Bankart Repair ◽  
Score Threshold ◽  
Recurrent Anterior Shoulder Instability

ImportanceThe Instability Severity Index (ISI) score was developed to evaluate a patient’s risk of recurrent shoulder instability following arthroscopic Bankart repair. While patients with an ISI score of >6 were originally recommended to undergo an open procedure (ie, Latarjet) to minimise the risk of recurrence, recent literature has called into question the utility of the ISI score.ObjectiveThe purpose of this systematic review was to evaluate the efficacy of the ISI score as a tool to predict postoperative recurrence among patients undergoing arthroscopic Bankart procedures.Evidence reviewArticles were included if study participants underwent arthroscopic Bankart repair for anterior shoulder instability and reported postoperative recurrence by ISI score at a minimum of 2 years of follow-up. Methodological study quality was assessed using the Methodological Index for Non-Randomized Studies criteria. Pearson’s χ2 test was used to compare recurrence rates among patients above and below an ISI score of 4. Sensitivity, specificity, mean ISI scores and predictive value of individual factors of the ISI score were qualitatively reviewed.FindingsFour studies concluded the ISI score was effective in predicting postoperative recurrence following arthroscopic Bankart repair; however, these studies found threshold values lower than the previously proposed score of >6 may be more predictive of recurrent instability. A pooled analysis of these studies found patients with an ISI score <4 to experience significantly lower recurrence rates when compared with patients with a score ≥4 (6.3% vs 26.0%, p<0.0001). The mean ISI score among patients who experienced recurrent instability was also significantly higher than those who did not.Conclusions and relevanceThe ISI score as constructed by Balg and Boileau may have clinical utility to help predict recurrent anterior shoulder instability following arthroscopic Bankart repair. However, this review found the threshold values published in their seminal article to be insufficient predictors of recurrent instability. Instead, a lower score threshold may provide as a better predictor of failure. The paucity of level I and II investigations limits the strength of these conclusions, suggesting a need for further large, prospective studies evaluating the predictive ability of the ISI score.Level of evidenceIV.

A Prospective, Randomized Evaluation of Arthroscopic Stabilization versus Nonoperative Treatment in Patients with Acute, Traumatic, First-Time Shoulder Dislocations

2002 ◽  
Vol 30 (4) ◽  
pp. 576-580 ◽  
Author(s):  
Craig R. Bottoni ◽  
John H. Wilckens ◽  
Thomas M. DeBerardino ◽  
Jean-Claude G. D'Alleyrand ◽  
Richard C. Rooney ◽  
...  
Keyword(s):  
Recurrence Rate ◽  
Nonoperative Treatment ◽  
High Rate ◽  
Bankart Repair ◽  
Arthroscopic Stabilization ◽  
Young Athletes ◽  
Recurrent Instability ◽  
Arthroscopic Bankart Repair ◽  
First Time

Background Nonoperative treatment of traumatic shoulder dislocations leads to a high rate of recurrent dislocations. Hypothesis Early arthroscopic treatment for shoulder dislocation will result in a lower recurrence rate than nonoperative treatment. Study Design Prospective, randomized clinical trial. Methods Two groups of patients were studied to compare nonoperative treatment with arthroscopic Bankart repair for acute, traumatic shoulder dislocations in young athletes. Fourteen nonoperatively treated patients underwent 4 weeks of immobilization followed by a supervised rehabilitation program. Ten operatively treated patients underwent arthroscopic Bankart repair with a bioabsorbable tack followed by the same rehabilitation protocol as the nonoperatively treated patients. The average follow-up was 36 months. Results Three patients were lost to follow-up. Twelve nonoperatively treated patients remained for follow-up. Nine of these (75%) developed recurrent instability. Six of the nine have required subsequent open Bankart repair for recurrent instability. Of the nine operatively treated patients available for follow-up, only one (11.1%) developed recurrent instability. Conclusions Arthroscopic stabilization of traumatic, first-time anterior shoulder dislocations is an effective and safe treatment that significantly reduces the recurrence rate of shoulder dislocations in young athletes when compared with conventional, nonoperative treatment.

scholarly journals Variability of Reporting Recurrence After Arthroscopic Bankart Repair: A Call for a Standardized Study Design

2019 ◽  
Vol 7 (5) ◽  
pp. 232596711984691 ◽  
Author(s):  
Mitchell I. Kennedy ◽  
Colin Murphy ◽  
Grant J. Dornan ◽  
Gilbert Moatshe ◽  
Jorge Chahla ◽  
...  
Keyword(s):  
Recurrence Rate ◽  
Study Design ◽  
Positive Association ◽  
Attrition Rate ◽  
Bankart Repair ◽  
Recurrent Instability ◽  
Level Of Evidence ◽  
Arthroscopic Bankart Repair ◽  
Meta Regression

Background: High recurrence rates have been reported after anterior shoulder dislocations, regardless of the treatment utilized. However, the definition of recurrent instability has been inconsistent, making a comparison between studies difficult. Purpose: To report on the nature with which the rate of recurrent instability is reported after arthroscopic Bankart repair, across all levels of evidence, and to analyze factors that may affect the reported rate of recurrence. Study Design: Systematic review; Level of evidence, 4. Methods: A systematic review of the literature was performed by searching PubMed, the Cochrane Central Register of Controlled Trials, Embase, and ClinicalTrials.gov for studies published within the dates of January 2008 and September 2018. Studies in English that reported on the recurrence of instability after arthroscopic Bankart repair for anterior shoulder instability were considered for inclusion in this review. A meta-regression was performed to test for a linear association between the reported recurrence rate and several continuous covariates, including mean age at surgery, mean length of follow-up, attrition rate (loss to follow-up percentage), and percentage of male patients. Results: A trim-and-fill meta-analysis yielded an estimated overall recurrence rate of 17.4% (95% CI, 14.3%-20.9%). There was a significant difference in the recurrence rate depending on the level of evidence (Q(3) = 10.98; P = .012). Significant associations were found with the recurrence rate through the meta-regression, including a negative association with mean age ( P = .009), a positive association with mean follow-up time ( P = .002), and a positive association with attrition rate ( P = .035). Conclusion: A call for standardization is necessary for reporting outcomes of anterior instability after arthroscopic Bankart repair, especially with regard to the reporting of recurrence/failure rates, with careful consideration of the effects that may occur from patient demographics and study design. With no current recommendations for deeming failure, we suggest that all forms of instability be accounted for when determining a failed treatment procedure, with future studies placing an emphasis on greater control of the study design.

Influence of Glenoid Defect Size and Bone Fragment Size on the Clinical Outcome After Arthroscopic Bankart Repair in Male Collision/Contact Athletes

2017 ◽  
Vol 45 (9) ◽  
pp. 1967-1974 ◽  
Author(s):  
Shigeto Nakagawa ◽  
Tatsuo Mae ◽  
Kenji Yoneda ◽  
Kazutaka Kinugasa ◽  
Hiroyuki Nakamura
Keyword(s):  
Clinical Outcome ◽  
Recurrence Rate ◽  
Fragment Size ◽  
Defect Size ◽  
American Football ◽  
Bone Union ◽  
Bankart Repair ◽  
Bone Fragment ◽  
Glenoid Defect ◽  
Arthroscopic Bankart Repair

Background: The usefulness of arthroscopic Bankart repair for collision/contact athletes has varied in previous reports. Purpose: To investigate the influence of glenoid rim morphologic characteristics on the clinical outcome after arthroscopic Bankart repair without additional reinforcement procedures in male collision/contact athletes, including athletes with a large glenoid defect. Study Design: Case-control study; Level of evidence, 3. Methods: Eighty-six athletes (93 shoulders) followed for a minimum of 2 years were retrospectively investigated. The sports were rugby (36 shoulders), American football (29 shoulders), and other collision/contact sports (28 shoulders). Preoperative glenoid defect size, bone fragment size, and bone union after bony Bankart repair were investigated regarding factors influencing postoperative recurrence. Postoperative changes in glenoid defect size and bone fragment size were investigated as well as their influence on the clinical outcome. Results: Postoperative recurrence of instability was noted in 22 shoulders (23.7%). The recurrence rate was 33.3% in rugby, 17.2% in American football, and 17.9% in other collision/contact sports. The recurrence rate was only 7.1% in 28 shoulders without a preoperative glenoid defect, but it increased to 43.8% in 16 shoulders that did not have a bone fragment even though there was a preoperative glenoid defect. Additionally, the recurrence rate was 7.7% in 26 shoulders with bone union after arthroscopic bony Bankart repair but rose to 45% in 20 shoulders without bone union. In the shoulders with bone union, the mean bone fragment size increased from 8.2% preoperatively to 15.2% postoperatively, while the mean glenoid defect size decreased from 18.0% to 2.8%, respectively. The recurrence rate was 8.3% in shoulders with a final glenoid defect 5% or less versus 38.1% in shoulders with a defect greater than 5%. While the recurrence rate was low among athletes other than rugby players with a final defect of 10% or less, it was low in only the rugby players with a defect of 0%. Conclusion: In male collision/contact athletes, while the overall clinical outcome was unsatisfactory, a favorable outcome was achieved in athletes without a preoperative glenoid defect and athletes with bone union. The glenoid defect decreased in size postoperatively due to remodeling of the united bone fragment, and the recurrence rate was low when the final glenoid defect size was 5% or less.

Clinical Outcome of Arthroscopic Bankart Repair Combined With Simultaneous Capsular Repair

2017 ◽  
Vol 45 (6) ◽  
pp. 1289-1296 ◽  
Author(s):  
Shigeto Nakagawa ◽  
Ryo Iuchi ◽  
Tatsuo Mae ◽  
Naoko Mizuno ◽  
Yasuhiro Take
Keyword(s):  
Postoperative Recurrence ◽  
Bankart Repair ◽  
Level Of Evidence ◽  
Old Patients ◽  
Glenohumeral Ligament ◽  
Capsular Repair ◽  
Arthroscopic Bankart Repair ◽  
Significant Difference ◽  
Competitive Athletes

Background: A capsular tear and humeral avulsion of the glenohumeral ligament lesion are not uncommon findings in association with a Bankart lesion. However, there have been few reports regarding the prevalence of such capsular lesions and the postoperative recurrence after capsular repair. Purpose/Hypothesis: This study investigated the prevalence of capsular lesions and clarified their influence on the postoperative recurrence of instability. In addition, factors were identified that were associated with the occurrence of capsular lesions and the postoperative recurrence of instability. We hypothesized that clinical outcomes would be improved by combining arthroscopic Bankart repair with simultaneous capsular repair. Study Design: Cohort study; Level of evidence, 3. Methods: Capsular lesions were retrospectively examined through operative records, still pictures, and videos in 172 shoulders with traumatic anterior instability. First, the prevalence of capsular lesions and their severity were investigated. Then, postoperative recurrence was determined in shoulders observed for a minimum of 2 years. Finally, factors were assessed that were associated with the occurrence of capsular lesions and the postoperative recurrence of instability. Results: A capsular lesion was recognized in 37 shoulders (21.5%), being severe and mild in 20 and 17, respectively. All were repaired simultaneously with the arthroscopic Bankart procedure. After follow-up for at least 2 years, recurrence of instability was detected in 10 of 34 shoulders (29.4%), including 6 (31.6%) with severe capsular lesions and 4 (26.7%) with mild lesions. The recurrence rate was significantly higher in shoulders with a capsular lesion than in shoulders without a capsular lesion (18 of 120, 15%; P = .013), but there was no significant difference between severe and mild lesions. Regardless of the sport played, capsular lesions were significantly more frequent in patients ≥30 years old, patients with complete dislocation, and patients with a coexisting Hill-Sachs lesion. Postoperative recurrence of instability was significantly more frequent in patients <30 years and competitive athletes. Conclusion: In shoulders undergoing arthroscopic Bankart repair, capsular lesions were often present and were associated with higher postoperative recurrence of instability. While these lesions were more frequent in older patients, postoperative recurrence of instability was more likely in young competitive athletes.

108 A CRITICAL-SIZE CRANIOFACIAL BONE DEFECT MODEL IN THE YORKSHIRE PIG

2011 ◽  
Vol 23 (1) ◽  
pp. 159 ◽  
Author(s):  
A. J. Maki ◽  
S. G. Clark ◽  
J. R. Woodard ◽  
M. Goldwasser ◽  
M. B. Wheeler
Keyword(s):  
Bone Defect ◽  
Critical Size ◽  
Rapid Development ◽  
Bone Defects ◽  
Defect Size ◽  
Posterior Region ◽  
Primate Species ◽  
Large Animal ◽  
Mineral Density ◽  
Calcified Tissue

Substantial and innovative developments in the field of bone tissue engineering have prompted increased demand for suitable pre-clinical large animal models. The pig has several advantages over other non-primate species, including availability, rapid growth, large litters, and similar anatomy and physiology to humans. These characteristics make them ideal models for research in diverse applications such as cardiovascular disease, pharmacological activity testing, and organ transplantation. There has been an increased interest in the use of swine as a model for bone healing and grafting techniques. Maxillofacial surgeons strive to develop the best therapy for large bone defects in the face resulting from tumour resection, congenital abnormalities, and traumatic injuries. Creating a model to study a critical-sized bone defect in the mandible, which does not spontaneously heal without clinical intervention, would be a method to test growth factors and synthetic bone graft therapies. However, the size of bone defect required to create this condition has not been ascertained. In the current study, we examined the in vivo healing response for 4, 8, and 16 weeks of surgically created bone defects in the posterior region of the pig mandible. Yorkshire barrows (n = 12) 6–7 months of age were used for the study. All animal experiments conformed to the University of Illinois Institutional Animal Care and Use Committee (IACUC) guidelines. Animals were maintained under general anaesthesia and transcortical, circular defects with diameters of 6, 10, 16, or 25 mm were created on both sides of the mandible. The presence and amount of calcified tissue was assessed using radiographs and dual energy x-ray absorptiometry (DEXA). Tissue morphology was examined using hard-tissue histological methods and a light microscope. Defect diameters of 6, 10, and 16 mm had completed healing or were in the process of healing within the 16-week timeframe of the study. Compared to controls, average percent differences in bone mineral density, in order of increasing defect size, were 0.62%, 28.1%, and 54.5%, respectively. In contrast, 25 mm diameter defects displayed limited collagenous tissue ingrowth, and the presence of calcified tissue was not detected, as indicated by radiographs and histological staining. As the defect size increased, the time required to heal was prolonged until a critical size was determined and normal bone was not completely regenerated. In conclusion, circular defects in the posterior region of the pig mandible with diameters equal or greater than 25 mm will result in limited healing without additional medical intervention and can be termed critical-sized defects. This porcine model will allow for the rapid development and testing of new approaches for the repair of damaged bone, which is especially prevalent in the craniofacial area. This work was partially supported by the Carle Foundation Hospital (#2007-04072) and the Illinois Regenerative Medicine Institute (IDPH #63080017).

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