Clinical and Sonographic Evaluation of Bicortical Button for Proximal Biceps Tenodesis
Use of a cortical button for proximal biceps tenodesis has demonstrated strength comparable to that of other types of fixation in biomechanical models, but few studies have evaluated the clinical outcome of such fixation.
In the study reported here, 18 patients who underwent open subpectoral biceps tenodesis with a bicortical button were assessed, at minimum 12-month follow-up, with the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, a pain scale, physical examination, biceps supination strength testing, and ultrasonographic evaluation (to determine tenodesis integrity and proximity of the button to the axillary nerve). No patient had symptoms of axillary nerve damage, clinical deformity, or tenodesis failure.
Mean DASH score was 15.15 (scale range: 0, none to 100, extreme difficulty), and mean pain score was 12.6 (scale range: 0, none to 100, worst pain). Seventy-eight percent of patients had no bicipital groove tenderness, 89% had full elbow range of motion, and 94% had full shoulder range of motion. Mean forearm supination strength of the operated arm (125.04 lb) was significantly (P = .01) less than that of the nonoperated arm (134.39 lb). Mean (SD) distance from button to posterior circumflex humeral artery was 18.17 (9.0) mm.
The study results suggest that subpectoral biceps tenodesis with a bicortical button is a safe, stable procedure that results in excellent functional outcomes.
Functional strength of forearm supination, shoulder ROM, and elbow ROM are objective measures of patient performance after fixation. On Cybex testing, Phillips and colleagues29 found no difference in forearm supination strength or elbow flexion (compared with contralateral arm) after biceps tenodesis or conservative treatment for proximal biceps ruptures. Shank and colleagues30 compared elbow flexion and supination strength of the affected and unaffected arms after suture anchor subpectoral biceps tenodesis. There was no significant difference in Cybex results, but there was a 14% to 15% loss of average strength in the tenodesed versus nonsurgical arm. In the present study, we found a significant difference in forearm supination strength between the operated and nonoperated arms, but with only a 7% loss of average strength in the operated arms. The difference in strength ranged from 1.59 to 17.11 pounds, which may not be clinically significant, as supination strength ranged from 60 to 270 pounds.
Of the 18 patients in this study, 9 had surgery on the dominant arm, and the other 9 had surgery on the nondominant arm. Examining the effect of arm dominance on results revealed that patients with surgery on the nondominant arm tended to have substantially reduced supination strength in that arm vs the dominant arm. There was an 11% loss of average strength for nondominant vs dominant arms that had surgery. Examining nondominant arms only revealed a 13% loss of strength for operated vs nonoperated arms. There was no difference in forearm supination strengths between nonoperated arms (dominant vs nondominant) or between dominant arms (operated vs nonoperated). This suggests that, though hand dominance may not play a significant role in control patients’ forearm supination strength,30 it may have a substantial effect on surgical patients’ ability to regain strength when the nondominant arm is the surgical arm. One objective of this study was to measure the distance between the biceps cortical button on the posterior humeral cortex and the AN/PCHA neurovascular bundle. The AN bundles with the PCHA posterior to the humeral neck.31-33 As the AN travels with the PCHA, and the PCHA has been reliably identified with Doppler ultrasonography,34-36 the PCHA was used as a marker for the AN in this study. Our bicortical button technique places the button on the posterior aspect of the humerus, making AN and PCHA the nearest at-risk neurovascular structures. None of our patients had symptoms of AN damage. However, 2 patients indicated pain in the posterior aspect of the humerus during deltoid activation. Distance from the neurovascular structures to the button was 48 mm in one patient and 13.6 mm in the other. DASH scores were 43 and 27, respectively. Both patients’ 1-year pain score was 30. The first patient underwent arthroscopic acromioplasty, distal clavicle resection, and microfracture of the glenoid surface in addition to the subpectoral biceps tenodesis; the second underwent subacromial decompression and distal clavicle resection in addition to the subpectoral biceps tenodesis. Whether the associated pathology contributed to their persistent pain is unknown. However, given the distance from AN/PCHA to button, it is unlikely that their pain was a result of neurovascular compromise from the procedure.
Advantages of the cortical button include the ability to drill a smaller hole in the humerus for fixation, compared with the hole drilled for an interference screw. Despite the biomechanical strength of the screw, large (8 mm) cortical violations have been associated with increased fracture risk of the proximal humerus.37,38 The tendon may experience less trauma than that caused by being twisted against an interference screw, the most common location of failure of which is the tendon–screw interface.39 In addition, tendon healing may be improved through circumferential healing in the cortical button tunnel.
A concern of using a bicortical button for fixation is drilling through the posterior cortex, because of the proximity of the posterior neurovascular structures. In a case in which the posterior cord was injured, Rhee and colleagues40 used a suture pullout technique whereby a Beath pin was passed out of the posterior humerus and soft tissues to then hold tension on the biceps tendon during the tenodesis. The radial nerve potentially could have been injured by pin overpenetration or by becoming wrapped up in the soft tissues as the pin was spinning through them. In our technique, the posterior humeral cortex is drilled cautiously to avoid overpenetration and possibly getting the posterior soft tissues wrapped up in the guide pin. No AN injuries have been reported with this technique. Mean distance from AN to posterior cortical button in this study was 18.17 mm. In 2 cadaver studies of bicortical drilling for subpectoral biceps tenodesis, the ANs were 25.1 mm and 36.7 mm from the posterior drill hole.41,21
Limitations of this study included its design (case series) and limited number of follow-up patients. Of the 28 consecutive patients identified for the study, 10 did not undergo the clinical examination, as they either lived more than 3 hours away (8 patients) or could not be contacted (2 patients). Another study limitation was the inability to directly image ANs with ultrasound. Therefore, measurements of the distance from the PCHA to the button were used to estimate the distance from the AN/PCHA neurovascular bundle to the button.
In this study, functional outcomes were excellent, and there were no tenodesis failures or neurovascular complications. These preliminary findings indicate that subpectoral biceps tenodesis with a bicortical button is a viable treatment option for patients with the appropriate indications for this procedure.
