Wren V. McCallister

Central Placement Of The Screw In Simulated Fractures Of The Scaphoid Waist: A Biomechanical Study

Background: Recent reports on internal fixation of acute fractures of the scaphoid waist have demonstrated higher rates of central placement of the screw when cannulated screws were used than when noncannulated screws were used. This cadaveric study was designed to determine whether central placement in the proximal fragment of the scaphoid offers a biomechanical advantage.Methods: Eleven matched pairs of scaphoids were removed from fresh cadaveric wrists. Each scaphoid was placed in a custom manufactured jig that was used to create reproducible central and eccentric positioning of the guidewire. Then a linear osteotomy was made followed by placement of a Herbert-Whipple cannulated screw to fix the osteotomy. The specimen was then potted in a holder with use of polymethylmethacrylate with a Kirschner wire passed through the proximal end of the scaphoid and placed into a fixture with a pneumatically driven plunger resting on the surface of the distal pole. The load acting through the plunger was measured with use of a load-cell, and its excursion was measured with use of a linear variable differential transformer. Stiffness, load at 2 mm of displacement, load at failure, and mechanism of failure were measured, and the two groups were compared with regard to stiffness and strength.Results: Central placement of the screw in the proximal fragment of the scaphoid had superior results compared with those after eccentric positioning of the screw. Fixation with central placement of the screw demonstrated 43% greater stiffness (12.7 N per mm compared with 8.9 N per mm; p < 0.01), 113% greater load at 2 mm of displacement (126 N compared with 59.1 N; p < 0.01), and 39% greater load at failure (712 N compared with 513 N; p > 0.05).Conclusions and Clinical Relevance: Central placement of the screw in the proximal fragment of the scaphoid offers a biomechanical advantage in the internal fixation of an osteotomy of the scaphoid waist. Clinical efforts and techniques that facilitate central placement of the screw in the fixation of fractures of the scaphoid waist should be encouraged.

Displaced Scaphoid Fractures Treated with Open Reduction and Internal Fixation with a Cannulated Screw

Background: This study was performed to determine if the accuracy of screw placement was improved with use of the Herbert-Whipple cannulated screw compared with use of the AO/ASIF cannulated screw and also to evaluate the functional results in patients with an acute displaced fracture of the waist of the scaphoid treated with open reduction and internal fixation with a cannulated screw. Methods: We retrospectively reviewed the results for thirty-five patients in whom an acute displaced fracture of the waist of the scaphoid had been treated with internal fixation with use of a cannulated screw. The patients were divided into two groups; Group 1 consisted of nineteen patients managed with a 3.5-millimeter cannulated AO/ASIF screw from 1990 through 1997, and Group 2 consisted of sixteen patients managed with a Herbert-Whipple screw from 1993 through 1997. Results: There were no clinical or radiographic differences between the two groups. The average time to union (and standard deviation), confirmed with tomography, was 4.2 ± 1.2 months for Group 1 and 4.0 ± 1.2 months for Group 2. Both screws significantly improved the alignment of the scaphoid and decreased carpal collapse (p < 0.01). Importantly, the use of either cannulated screw improved the height-to-length ratio and the lateral intrascaphoid angle, which were correlated with an increase in the range of motion of the wrist (r = 0.584 and 0.625). In addition, both screws allowed for accurate placement in the central portion of the proximal pole. Regardless of the type of screw used, the time to union increased with increasing age of the patient (r = 0.665) and with increasing initial displacement of the fracture (r = 0.541). Within both groups, the time to union was longer for the patients who smoked (p < 0.01). Conclusions: Within both groups, cannulated screw fixation maintained the corrected fracture alignment and promoted healing and return of function. Our study shows cannulated screws to be a safe and effective method of treatment.

Open rotator cuff repair without acromioplasty.

Background: In most clinical reports on rotator cuff repair, acromioplasty was done as part of the procedure. In this prospective study, we evaluated the hypothesis that rotator cuff repair without acromioplasty would result in a substantial improvement in shoulder comfort and function. Methods: Ninety-six consecutive primary repairs of full-thickness tears of the rotator cuff were performed through a deltoid-muscle-splitting incision that preserved the integrity of the coracoacromial arch and the deltoid insertion. All patients were invited to participate in a prospective study involving periodic self-assessment of shoulder function with the Simple Shoulder Test and general health status with the Short Form-36 (SF-36) questionnaire, both of which are validated instruments. Sixty-one patients provided follow-up information for at least two years postoperatively, and the average duration of follow-up was five years. Thirty-four of the tears involved the supraspinatus tendon alone; sixteen involved the supraspinatus and infraspinatus tendons; and eleven involved the supraspinatus, infraspinatus, and subscapularis tendons. Results: The percentage of shoulders that could be used to perform each of the twelve functions on the Simple Shoulder Test was significantly increased postoperatively (p < 0.002). Men and women had different degrees of function preoperatively (p < 0.00000001) and postoperatively (p < 0.001), but the improvement in function was essentially identical for the two genders. The mean improvement in the number of shoulder tests that could be performed was best for the patients with one-tendon tears (4.9 tests), next best for those with two-tendon tears (3.6 tests), and worst for those with three-tendon tears (3.3 tests). SF-36 scores for physical role (p < 0.003) and comfort (p < 0.0001) were significantly improved postoperatively. Conclusions: Significant improvement in self-assessed shoulder comfort and in each of the twelve shoulder functions was observed after rotator cuff repairs performed without acromioplasty. The technique that we used is very similar to that described by Codman almost seventy years ago. Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.