Synthetic coracoclavicular ligament vs. coracoclavicular suspensory construct for treatment of acromioclavicular dislocation: a biomechanical study.

BACKGROUND: A synthetic ligament (LockDown, Worcestershire, England) has become available to treat complete acromioclavicular dislocation with promising clinical results and potential benefit to avoid postoperative loss of reduction. We investigated the biomechanics of this synthetic ligament in a simulated immediate postoperative rehabilitation setting, hypothesizing that the synthetic ligament would demonstrate less superior coracoclavicular displacement to cyclic loading and higher ultimate load-to-failure values than a coracoclavicular suspensory construct. METHODS: Seven matched-pair cadaveric shoulders (mean age at time of death, 79 years) were loaded cyclically and to failure. One specimen in each pair was randomly assigned to the synthetic ligament or coracoclavicular suspensory construct. Superiorly directed 70-N cyclic loading for 3000 cycles at 1.0 Hz was applied through the clavicle in a fixed scapula simulating physiologic states during immediate postoperative rehabilitation, followed by a load-to-failure test at 120 mm/min. RESULTS: After 3000 cycles, the superior displacement of the clavicle in the synthetic ligament (9.2 ± 1.1 mm) was 225% greater than in the coracoclavicular suspensory construct (2.8 ± 0.4 mm, 95% confidence interval [CI] 3.4, 8.3; P < .001). Average stiffness of the synthetic ligament (32.8 N/mm) was 60% lower than that of the coracoclavicular suspensory construct (81.9 N/mm, 95% CI 43.3, 54.9; P < .001). Ultimate load-to-failure of the synthetic ligament was 23% (95% CI 37.9, 301.5; P = .016) lower than the coracoclavicular suspensory construct (580.5 ± 85.1 N and 750.2 ± 135.5 N, respectively). CONCLUSION: In a simulated immediate postoperative cadaveric model, the synthetic ligament demonstrated poorer biomechanics than the coracoclavicular suspensory construct. These findings suggest that a coracoclavicular suspensory construct may be preferable to a synthetic ligament if early rehabilitation is intended.

Biomechanics of Biodegradable Subacromial Balloon Spacer for Irreparable Superior Rotator Cuff Tears: Study of a Cadaveric Model.

BACKGROUND: A subacromial balloon spacer is an option to treat irreparable rotator cuff tears. We hypothesized that the balloon would restore glenohumeral contact pressure, the acromion-humeral interval, and deltoid load to intact values after a simulated irreparable supraspinatus tear in a cadaveric model. METHODS: Fourteen cadaveric shoulders (mean age at the time of death, 67.9 years) were tested using a custom test frame. In this frame, glenohumeral contact pressure, the acromion-humeral interval, and deltoid load were measured using a digital sensor, a MicroScribe, and a spring scale, respectively. Test conditions included the intact shoulder, a small supraspinatus tear, supraspinatus repair, repair plus balloon, an irreparable supraspinatus tear (rotator cable-insufficient), and an irreparable tear plus balloon. Load was applied in a simulated neutral arm position (balanced) and active shoulder abduction (unbalanced). RESULTS: When the balloon was inflated over the irreparable supraspinatus tear in the balanced condition, glenohumeral contact pressure increased by 122% (p = 0.006) compared with that for the irreparable tear at 0° of abduction and by 94% (p = 0.046) at 60°. In the unbalanced condition, pressure decreased in the irreparable tear condition after the balloon was inflated, restoring pressure to close to that in the intact state. The balloon did not restore glenohumeral contact area to that in the intact shoulder in either the balanced or the unbalanced condition. The irreparable tear displaced the humeral head superiorly in the unbalanced condition, decreasing the acromion-humeral interval. The balloon moved the head inferiorly by a mean (and standard error of the mean) of 6.2 ± 1.3 mm (p < 0.001) at 0° of abduction, 4.4 ± 1.3 mm (p < 0.001) at 30°, and 3.0 ± 0.8 mm (p < 0.001) at 60°. The balloon increased the deltoid load after an irreparable tear by 8.2% (p = 0.022) at 0°, 12.6% (p = 0.002) at 30°, and 11.1% (p = 0.008) at 60°. CONCLUSIONS: In a cadaveric model of an irreparable supraspinatus tear, a balloon spacer restored intact-state glenohumeral contact pressures at most abduction angles, lowered the humeral head, and increased deltoid load at postoperative time 0. CLINICAL RELEVANCE: This study supports further investigation of the balloon spacer in comparative clinical studies of surgical options for irreparable rotator cuff tears, with clinically relevant evaluation measures and observation periods.

Outcomes following Peripheral Nerve Decompression with and without Associated Double Crush Syndrome: A Case Control Study.

BACKGROUND: Double crush syndrome, the association between proximal and distal nerve lesions, has been established. This investigation compares the outcomes of nerve surgery in patients with isolated peripheral compression versus those with double crush syndrome treated with peripheral nerve and cervical spine operations. METHODS: This case-controlled study enrolled 80 patients: 40 underwent carpal or cubital tunnel surgery and cervical spine surgery (double crush group); and 40 controls, matched by age and sex, underwent only peripheral nerve decompression (peripheral nerve group). A minimum of 18 months was required after peripheral nerve and cervical spine surgery for office assessment (mean, 4.9 years and 6.0 years, respectively). Statistical analysis compared postoperative function and symptom severity questionnaires, physical examination, and patient-reported satisfaction between groups. RESULTS: Patients in the double crush group reported significantly more disability and persistent symptoms on the QuickDASH questionnaire (29 versus 13) and Levine Katz symptom severity (2.0 versus 1.4) and functional status scales (1.9 versus 1.4). Double crush patients reported significantly lower satisfaction. The double crush group exhibited a greater frequency of persistent signs of nerve irritability and muscle weakness compared with the control group. CONCLUSIONS: At a minimum of 18 months after peripheral nerve surgery, patients with a history of cervical spine surgery are likely to have inferior patient-reported outcomes, persistent nerve dysfunction, and lower satisfaction after peripheral nerve release compared with patients following isolated peripheral nerve surgery. Double crush syndrome was associated with poorer outcome after peripheral nerve surgery despite treatment of cervical spine nerve compression. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.