Anterior Glenoid Reconstruction With Distal Tibial Allograft: Biomechanical Impact of Fixation and Presence of a Retained Lateral Cortex.

BACKGROUND: Glenoid reconstruction with distal tibial allograft (DTA) is a known surgical option for treating recurrent glenohumeral instability with anterior glenoid bone loss; however, biomechanical analysis has yet to determine how graft variability and fixation options alter the torque of screw insertion and load to failure. HYPOTHESIS: It was hypothesized that retention of the lateral cortex of the DTA graft and the presence of a washer with the screw will significantly increase the maximum screw placement torque as well as the load to failure. STUDY DESIGN: Controlled laboratory study. METHODS: Whole, fresh distal tibias were used to harvest 28 DTA grafts, half of which had the lateral cortex removed and half of which had the lateral cortex intact. The grafts were secured to polyurethane solid foam blocks with a 2-mm epoxy laminate to simulate a glenoid with an intact posterior glenoid cortex. Grafts underwent fixation with 4.0-mm cannulated drills, and screws and washers were used for half of each group of grafts while screws alone were used for the other half, creating 4 equal groups of 7 samples each. A digital torque-measuring screwdriver recorded peak torque for screw insertion. Constructs were then tested in compression with a uniaxial materials testing system and loaded in displacement control at 100 mm/min until at least 3 mm of displacement occurred. Ultimate load was defined as the load sustained at clinical failure. RESULTS: The use of a washer significantly improved the ultimate torque that could be applied to the screws (+cortex and +washer = 12.42 N·m [SE, 0.82]; -cortex and +washer = 10.54 N·m [SE, 0.59]) (P < .0001), whereas the presence of the native bone cortex did not have a significant effect (+cortex and -washer = 7.83 N·m [SE, 0.40]; -cortex and -washer = 8.03 N·m [SE, 0.56]) (P = .181). CONCLUSION: In a hybrid construct of fresh cadaveric DTA grafts secured to a foam block glenoid model, the addition of washers was more effective than the retention of the lateral distal tibial cortex for both load to failure and peak torque during screw insertion. CLINICAL RELEVANCE: This biomechanical study is relevant to the surgeon when choosing a graft and selecting fixation options during glenoid reconstruction with a DTA graft.

Utility of Allograft Talus as a Source for Grafting of Concurrent Humeral and Glenoid Defects Associated With Anterior Glenohumeral Instability: An Anthropometric Analysis.

PURPOSE: To compare morphologic data of the talus using magnetic resonance images with previously reported values of the humeral head and the glenoid as a potential graft source for both the humeral head as well as glenoid reconstruction in the setting of concomitant glenoid and humeral head defects. METHODS: All magnetic resonance images of the ankle were reviewed for assessment of the morphology and variation of the talus among individuals. Patients with post-traumatic, osteoarthritic, or surgical changes to the distal tibia about the mid- or hind- foot, or patients with incomplete medical records were excluded. Radiographic parameters that were measured included the maximum vertical height (MVH), the height to the talar neck, the radius of curvature (ROC) of the talar dome, ROC of the subtalar joint, and the maximum medial-to-lateral width of the talar dome. Demographic data also were collected on each individual. Statistical analysis was performed via a linear regression model with backwards elimination to determine which demographic data correlated most strongly with talar anthropometric values. RESULTS: A total of 82 study patients met inclusion criteria (59 male, 23 female; mean age 40.91 ± 14.69 years). Sex was found have a positive correlation of the following talar dimensions: MVH (P = .039), talar dome ROC (P < .001), and subtalar joint ROC (p = 0.001). Height was the most positive correlation for medial-to-lateral width (P < .001), height to the talar neck (P = .004), and also correlate for MVH (P = .004). Body mass index was found to have multicollinearity and was therefore not used as a variable. CONCLUSIONS: Allograft talus appears to be a viable graft, as demonstrated in this anthropometric study for both reconstruction of the glenoid and humeral head when cases of bipolar glenohumeral bone loss are present. CLINICAL RELEVANCE: This study aims to further evaluate potential allograft donor sites for bipolar lesions.

Use of the Contralateral Glenoid for Calculation of Glenoid Bone Loss: A Cadaveric Anthropometric Study.

PURPOSE: The purpose of this study was to determine if there are significant side-to-side anthropometric differences between paired glenoids. METHODS: Forty-six matched-pair cadaver glenoids were harvested, and their glenoid heights (GHs) and glenoid widths (GWs) were measured with digital calipers. The glenoid surface area was calculated using the standard assumption that the inferior two-thirds of the glenoid is a perfect circle. RESULTS: There was a statistically significant difference between matched-pair GHs of 0.96 ± 3.07 mm (P = .020) and GWs of 0.46 ± 1.64 mm (P = .033). There was a significant difference of glenoid cavity area of 20.30 ± 81.53 mm2 (P = .044), or a difference of ∼3%. A total of 4 of 46 pairs of glenoids (8.6%) showed a difference in width >3 mm. CONCLUSIONS: This study demonstrates the fallacy of use of the contralateral glenoid in measuring glenoid bone loss. Although many paired samples exhibited similar side-to-side glenoid measurements, the number of cadaveric pairs that showed differences of >3 mm was substantial. Caution should be taken when using calculation methods that include this assumption for surgical decision making, as surface area, GW, and GH were all shown to have statistically significant side-to-side differences in their measurements. CLINICAL RELEVANCE: Many methods exist for measuring glenoid bone loss after anterior shoulder dislocation, but some of the current methods may be inaccurate and lead to unreliable estimations.

Intradural extramedullary metastasis: a review of literature and case report.

Introduction: Intradural extramedullary (IDEM) metastatic disease is infrequently encountered by spine surgeons and consequently poorly understood. Discovery often corresponds with the onset of neurologic symptoms and no consensus exists regarding the importance of complete resection or anticipated postoperative outcome. We aim to elucidate treatment methodologies that exist in the literature. Case presentation: We present a unique case of a 57-year-old male with a known history of esophageal adenocarcinoma, including brain and visceral metastases, who presented with cauda equina syndrome. An IDEM metastatic esophageal adenocarcinoma lesion was identified on advanced imaging and biopsy. This was treated operatively without return of neurologic function. Discussion: We reviewed and summarized the existing literature. Trends are highlighted to further guide surgeons treating this unusual metastatic phenomenon. Conclusion: Intradural metastasis is a harbinger of advanced disease with a poor prognosis regardless of the etiology of the primary lesion. There are a number of proposed mechanisms for metastatic spread with little available literature for surgeon guidance. Most authors are advocates of a palliative, decompressive approach.