Biomechanics of internal fixation in Hoffa fractures - A comparison of four different constructs.

OBJECTIVE: Compare the biomechanical effectiveness of four different bone-implant constructs in preventing fracture displacement under axial loading. METHODS: Twenty artificial femora had a standardized coronally oriented fracture of the lateral femoral condyle, representing a Hoffa fracture classified as a Letenneur type I. Four different fixation constructs were applied to the synthetic bones for biomechanical testing. The constructs consisted of a posterolateral (PL) buttressing locking plate in conjunction with two cannulated lag screws inserted from posterior to anterior (PA) - Group 1; Two cannulated screws inserted from anterior to posterior (AP) without plating- Group 2; A posterolateral (PL) buttressing locking plate in isolation - Group 3; and a combination of two lag screws from anterior to posterior (AP) in addition to a horizontal one-third tubular locking plate - Group 4. An axial load was applied to the fracture site with a constant displacement speed of 20 mm/min, and the test was interrupted when a secondary displacement was detected determining a fixation failure. We recorded the maximum applied force and the maximum fracture displacement values. RESULTS: Group 1 demonstrated the highest overall bone-implant axial stiffness with the lowest secondary displacement under loading. Groups 3 and 4 showed equivalent mechanical behavior. Group 2 presented the lowest mechanical stiffness to axial loading. The combination of the one-third tubular locking plate with anterior-to-posterior lag screws (Group 4) resulted in 302 % increase in fixation stiffness when compared to anterior-to-posterior lag screws only (Group 2). CONCLUSIONS: This study confirms the mechanical superiority of having a plate applied parallel to the main fracture plane in the setting of coronally oriented femoral condyle fractures. The addition of a horizontal plate, perpendicular to the main fracture plane, significantly increased the resistance to shearing forces at the fracture site when compared to constructs adopting just cannulated screws. LEVEL OF EVIDENCE: Biomechanical study.

Distal radius fracture fixation using volar plate: A comparative study evaluating the biomechanical behavior of uni and bicortical distal screws.

Extensor tendon ruptures caused by bicortical screws impingement following distal radius fracture fixation with volar plates are extensively reported in the literature. Thus, a biomechanical study comparing unicortical and bicortical fixations in intra-articular distal radius fracture models is critical in decision-making regarding distal radius fracture management. Forty-two synthetic radius models were fixed using a variable angle volar distal locking plate with seven screws. They were divided into 6 groups (n = 7): G1/G3/G4 unicortical fixation (75% of anteroposterior distal radius lenght); G2/G4/G6 bicortical fixation. Each group underwent a different mechanical test: axial compression (G1/G2), dorsal flexion (G3/G4), and volar flexion (G5/G6). The load application rate was 5 mm/min and 1000 cycles of 50 to 250 N at 1 Hz were performed between both static tests. Comparative results in the first static test, in the second static test, and in failure generally showed a very similar behavior. Models depicted similar behavior in the second static test when cyclic load was performed. Therefore, one can realize that stiffness differed during dorsal flexion only in the first static test. Maximum force to break the model in axial compression was greater in bicortical than in unicortical construct. Since biomechanical properties are similar, we recommend using unicortical distal locking screws in distal radius fracture fixation with volar plates to prevent extensor tendon ruptures.

ELBOW ULNAR NEUROPATHY: TREATMENT BY ANTERIOR TRANSPOSITION OF THE ULNAR NERVE

ABSTRACT Objectives: Retrospective clinical evaluation of 31 patients who underwent ulnar nerve decompression at the elbow and subcutaneous anterior transposition. Methods: From January 2000 to December 2013, 71 patients underwent subcutaneous anterior transposition of the ulnar nerve. Thirty-one patients returned for evaluation. The mean follow-up period was 60 months. Patients were evaluated for the degree of satisfaction after surgery, paresthesia, pain, Tinel sign, Froment test and sensitivity test by esthesiometer, muscle strength of the intrinsic muscles and deep flexor of the fifth digit, visual analogic pain scale (VAS) and were subjected to the QuickDash questionnaire. Results: Thirty-nine per cent of patients had compression on the right side and 61% on the left side. Sixty-one percent were idiopathic, 35% post traumatic and 3% had Poems syndrome. Forty-eight per cent of patients were very much satisfied after surgery and 52% were satisfied. Forty-eight per cent had paresthesia after surgery and 52% did not. Conclusion: The ulnar neurolysis of the cubital tunnel with anterior subcutaneous transposition is a safe and effective technique for treating idiopathic or post-traumatic compressive neuropathy, with high success rate and excellent function for activities of daily living. Level of Evidence IV, Case Series.

Treatment of scaphoid nonunion with olecranon bone graft and compression screw

OBJECTIVE: To evaluate the outcome of olecranon bone graft and compression screw for the treatment of nonunion of the Lichtman type I scaphoid. METHOD: We evaluated 15 patients of 32 who underwent surgical treatment for nonunion of the Lichtman type I scaphoid with olecranon bone graft and screw compression. RESULTS: We obtained 100% consolidation in our sample. The mean flexion of the wrist on the affected side was 68° and 75° on the non-affected side. The average extension was 63° and 72°, respectively. The average grip strength was 35 kgf. This corresponds to 98% of the handgrip strength of the non-affected side, which was 37 kgf. The DASH score averaged 5 points. CONCLUSION: We believe that the use of bone graft obtained from the olecranon and secured with cannulated screw is a resolute technique for cases of linear nonunion of the Lichtmann type I scaphoid. It has the advantages of a new anesthesia for removal of the graft and the access is easy, providing a good exposure for removal and good aesthetic results. Level of evidence IV. Case series