Effect of lesser tuberosity osteotomy size and repair construct during total shoulder arthroplasty.

BACKGROUND: Lesser tuberosity osteotomy has been shown to decrease postoperative subscapularis dysfunction. The purpose of this study was to determine the effect of osteotomy thickness and suture configuration on repair integrity. MATERIALS AND METHODS: One side of 12 matched-pair cadaveric shoulders was randomly assigned to either a thick osteotomy (100% of lesser tuberosity height) or a thin osteotomy (50% of height). Both sides of the matched pairs were given the same repair, either (1) compression sutures or (2) compression sutures plus 1 tension suture. This created 4 groups of 6 paired specimens. Computed tomography imaging was used to measure tuberosity dimensions before and after osteotomy to validate fragment height and area. The repairs were loaded cyclically and then loaded to failure. A video system measured fragment displacement. The percent area of osteotomy contact was calculated from the computed tomography and displacement data. RESULTS: The average initial displacement was less in the thin osteotomy groups (P = .011). Adding a tension suture negated this difference. A significant number of thin repair sites compared with thick repair sites remained intact during load-to-failure testing (P = .001). No difference occurred because of maximum load between the repair groups (P = .401), and construct stiffness was greater when a tension suture was used (P = .032). The percent area of osteotomy contact showed no differences between the osteotomy (P = .431) and repair (P = .251) groups. CONCLUSION: The study showed that thin osteotomies displaced less than thick osteotomies. Adding a tension band improved construct stability and eliminated some failure modes. Our ideal repair was a thin wafer with both tension and compression sutures. This construct had smaller total displacement, a high osteotomy percent contact area, and a high maximum load.

Repaired distal biceps magnetic resonance imaging anatomy compared with outcome.

BACKGROUND: This study examined the magnetic resonance imaging (MRI) appearance of an anterior incision distal biceps tendon repair and evaluated the association between appearance and outcome. MATERIALS AND METHODS: Nineteen patients were randomly recruited to undergo an elbow MRI from a single-surgeon series of distal biceps repairs using an anterior approach. Tendon healing was evaluated by the integrity of the repair, the amount of heterogeneity within the tendon substance, and the presence of heterotopic bone. The angle of tendon insertion on the tuberosity was used to quantify the tendon location from the MRI in the patients and in 10 healthy volunteers. All patients completed the Disabilities of Arm, Shoulder and Hand (DASH) and a visual analog pain scale (VAPS), and 17 patients underwent isometric supination strength testing. MRI findings were statistically compared with the outcome scores. RESULTS: All of the repairs healed to cortical bone. High intrasubstance heterogeneity or heterotopic bone was present in 11 patients (58%). The insertion site angle of the repaired tendons was 73° more anterior than the uninjured controls (P < .001). Average DASH was 7.7 (range, 0-49.2) and VAPS was 0.7 (range, 0-5). At 60° of forearm supination, supination strength was 67% of the uninjured side (P < .01). No significant differences in DASH or VAPS scores were found between groups based on tendon appearance. CONCLUSIONS: The distal biceps tendon predictably heals to cortical bone but demonstrates a wide variability in overall morphology that does not influence DASH or VAPS scores. A significant decrease in strength at 60° of supination appears to be an effect of an anterior tendon reattachment location.

Anatomic and biomechanical analysis of the short and long head components of the distal biceps tendon.

HYPOTHESIS: The short head bundle of the distal biceps tendon is more efficient at elbow flexion, and the long head is more efficient at forearm supination. METHODS: The short and long head bundles of the distal biceps tendon were separated to the bicipital tuberosity in 6 cadavers. The area and centroid of each bundle insertion were computed from surface points measured within each footprint. Each bundle was individually loaded. The supination torque and flexion load generated were recorded at 90° of elbow flexion. The slope of the torque generated versus biceps load was used to define the supination moment arm. The ratio of the flexion load generated to biceps load applied was used to define the relative flexion efficiency. RESULTS: The short head insertion was positioned distal and anterior relative to the long head and typically included the apex of the tuberosity. The areas of the long and short heads were 59 ± 15 and 94 ± 44 mm(2) (P = .07), respectively. The long head moment arm was significantly higher in supination. The short head had a significantly higher moment arm in neutral and pronation. The ratio of the flexion load to biceps load was 15% higher for the short head. CONCLUSION: The short and long heads of the biceps have distinct insertions. The short head's insertion allows it to be relatively more efficient at elbow flexion at 90°. In the neutral and pronated forearm, the short head is the relatively more efficient supinator. In the supinated forearm, the long head becomes relatively more efficient at supination.

The effect of biceps reattachment site.

BACKGROUND: We hypothesize that an anatomic repair of the distal biceps tendon would recreate native tendon moment arm and forearm rotation, while a nonanatomic insertion would compromise moment arm and forearm rotation. METHODS: Isometric supination torque was measured at 60° of pronation, neutral, and 60° of supination for the native distal biceps tendon and 4 repair points in 6 cadaveric specimens using a computer controlled elbow simulator. The slope of the regression line fitted to the torque versus biceps load data was used to define the moment arm for each attachment location. Range of motion testing was performed by incrementally loading the biceps, while measuring the supination motion generated using a digital goniometer. RESULTS: Tendon location and forearm position significantly affected the moment arm of the biceps (P < .05). Anatomic repair in all forearm positions showed no significant difference from the native insertion. Moment arm for an anterior center repair was significantly lower in supination (-97%) and neutral (-27%) and also produced significantly less supination motion. No difference was observed between all tendon locations in pronation. CONCLUSIONS: Reattachment of the biceps to its anatomic location, as opposed to a more anterior central position, is critical in reestablishing native tendon biomechanics. Clinically, these findings would suggest that patients with a biceps repair might experience the most weakness in a supinated position without experiencing a deficit in the pronated forearm.