Purpose: The purpose of this study is to evaluate the biomechanical properties and the stability between locking clavicle plate, dynamic compression plate and external fixation systems on an unstable displaced fracture model under torsional and 3 point bending loading.

Materials and Methods: Forty eight human adult formalin fixed clavicles were paired according to their BMD (DEXA) homogeneously into three groups; Group 1: Locking clavicle plate, Group 2: Dynamic compression plate and Group 3: External fixator. Each specimen was then osteotomized in the midshaft; and a 5mm bone segment was removed in order to stimulate a displaced fracture model. Biomechanical tests were applied in a cyclic loading model in MTS, Bionix 2. Torsional and three point bending forces were performed for 1000 cycles in all subgroups, stiffness was recorded at 10 cycles (initial) and periodic every 100 cyclic intervals. Failure load and moment were obtained after 1000 cycles. Initial stiffness, failure loads and the percentage of initial stiffness for each subgroup were compared across each group. One-way ANOVA and Bonferoni post- hoc tests were utilized to determine which were significantly different from one another with the significance level set as p< 0.05.

Results: The mean initial stiffness(Nmm/deg) - mean failure moments(Nmm) for torsional tests were 703.2 – 7671.7 (locking plate), 448.1 – 4370.3 (compression plate), 365.2 – 2999.7 (ex-fix) and the mean initial stiffness(Nmm) – mean failure loads(N) for bending tests were 32.6 – 213.2 (locking plate), 23.4 – 131.1 (compression plate), 20.6 – 102.7 (ex-fix) respectively. ANOVA test confirmed an overall significant difference between the three constructs in terms of both failure loads and a significant difference only between locking plate and others in terms of initial stiffness. At all cyclic intervals after 100 cycles there was significant difference of percentage of initial stiffness between locking plate and others in bending and torsion. There was a significant difference between compression plate and ex-fix after 700 cycles in torsional group and no difference found in bending group between (any of) them at any cyclic interval.

Conclusions: Locking anatomic clavicle plate is significantly more stable than unlocked dynamic compression plate and external fixator under torsional and bending cyclic loading in an unstable displaced fracture or non-union clavicle model.

Introduction: Identifying normal ranges for calcaneal angles is important for the assessment of morbidity after calcaneal fractures. We have evaluated the distribution and normal ranges of calcaneal angles.

Method: A retrospective study was performed to review 105 lateral radiographs of 87 patients (62 female, 43 male). Radiographs with fractures, deformities and fusion were excluded. The mean age was 42.6 (18–79). Böhler and Gissane angles were measured by the same surgeon with the macros of the Hipax program. T test and Pearson correlation coefficients were used for statistical analysis with SPSS software with a significance level of P< 0.05.

Results: The mean Böhler angle was 34.4±4.12º (range 23–44), the Gissane angle was 116.4±6.23º (range 103–133). There was no statistically significant difference between the mean Böhler angles of women (34.9º±4.5) and men (33.9º±3.79) (t test: p> 0.05). There was no correlation between the two angles (r=−0.044; p> 0.05). There was a negative correlation between the Böhler angle and age (R=−0.36; P< 0.01). The regression equation of this correlation was y=−0.01x+38.51. There was no significant correlation between the Gissane angle and age (r=−0.046; p> 0.05).

Discussion: The reported ranges for Böhler and Gissane angles are widely spread (14–50 and 95–130, respectively). Our results were consistent with 4 (Hauser; Loucks; Didia; Igbigbi) of the 5 previous studies. However, unlike the other studies Böhler angle results did not show sex dimorphism and revealed a negative correlation with aging. Posterior facet collapse may be the cause of this correlation.

We compared time-dependent changes in the biomechanical properties of single-and double-row repair of a simulated acute tear of the rotator cuff in rabbits to determine the effect of the fixation techniques on the healing process.

A tear of the supraspinatus tendon was created in 80 rabbits which were separated into two equal groups. A single-row repair with two suture anchors was conducted in group 1 and a double-row repair with four suture anchors in group 2. A total of ten intact contralateral shoulder joints was used as a control group. Biomechanical testing was performed immediately post-operatively and at four and eight weeks, and histological analysis at four and eight weeks.

The mean load to failure in group 2 animals was greater than in group 1, but both groups remained lower than the control group at all intervals. Histological analysis showed similar healing properties at four and eight weeks in both groups, but a significantly larger number of healed tendon-bone interfaces were identified in group 2 than in group 1 at eight weeks (p < 0.012).

The ultimate load to failure increased with the number of suture anchors used immediately post-operatively, and at four and eight weeks. The increased load to failure at eight weeks seemed to be related to the increase in the surface area of healed tendon-to-bone in the double-row repair group.