Purpose of the study: Reversed prostheses provide improved active anterior elevation in shoulders free of cuff tears by lengthening the deltoid and increasing is lever arm. The purpose of this work was to search for a correlation between arm lengthening and postoperative active anterior elevation.

Material and methods: One hundred eighty-three reversed prostheses were reviewed with minimum one year follow-up for a complete clinical and radiographic work-up. Using a previously validated protocol, arm lengthening was assessed either in comparison with the contralateral side or with preoperative measurements. A statistical analysis was performed to search for a correlation between lengthening of the humerus and the arm with active anterior elevation.

Results: Considering the entire series, mean lengthening of the humerus was 0.2±1.4 cm (range −4.7 to +5.4). Postoperative active anterior elevation was 141±27 (range 30–180). There was no correlation between humerus lengthening or shortening and active anterior elevation (p=0.169). A shorter arm produced an active anterior elevation at 121 and 0 – 1 cm lengthening an active anterior elevation at 140; lengthening 1 – 2.5 cm gave active anterior elevation at 144 and beyond 2.5 cm 147. The difference in active anterior elevation was statistically significant (p< 0.001) between patients with a shortening and those with a lengthening.

Discussion: Arm lengthening corresponds to a lengthening of the humerus plus a lengthening of the infra-acromial space. We found a statistically negative correlation between arm shortening (and thus deltoid shortening) and active anterior elevation and a positive trend between lengthening and active anterior elevation. Our measurement did not take into account the increased lever arm of the deltoid and thus only partially expresses the improvement in deltoid function. Nevertheless, our study shows that objective evaluation of deltoid lengthening is possible pre- intra- and postoperatively and that this measurement can be correlated with postoperative functional outcome.

Purpose of the study: Four elements differentiate myotendinous tears of the infraspinatus from other rotator cuff tears: the tendon insertion on the trochiter and the joint capsule are spared; the onset in characterized by intense muscle oedema followed at 6 to 12 months by severe and definitive fatty degeneration.

Material and method: Fifty-nine myotendinous tears of the infraspinatus were collected prospectively from 1993 to 2007. Female gender predominated (58%); trauma was noted at onset in 22% of the shoulders and the mean age of discovery was 48.9 years. Twenty-nine shoulders were seen at the acute phase with significant muscle oedema recognized on the MRI T2 Fat Sat sequence. A second group of 30 patients had grade 4 fatty infiltration of the infraspinatus without full thickness cuff tears. The EMG was available for 23 shoulders and was normal in all, ruling out a neurological cause. Associated lesions of the supraspinatus and infraspinatus tendons were: tendon calcification (61%) and partial tears at the acute phase (21%) and chronic phase (70%) suggesting a degenerative cause.

Results: Twenty-four patients underwent surgery and 35 had a medical treatment. At mean 46 months follow-up (range 12–125) the Constant score improved from 51.7 to 69.4 points (p< 0.0001). There was no different statistically between the operated and non-operated patients (p=0.325). All patients seen at the acute phase of the oedema progressed to complete grade 4 fatty degeneration of the muscle, irrespective of the treatment delivered.

Discussion: Early diagnosis of this lesion can be achieved with T2 Fat Sat MRI sequences. Arthroscopic repair to tighten the infraspinatus muscle could avoid the irremediable degeneration with total loss of muscle function.

Introduction: Clinically evident neurological injury of the operated limb after total shoulder arthroplasty is not uncommon. The purpose of this prospective study was to determine the incidence of subclinical neurological lesions after reverse shoulder arthroplasty and anatomic shoulder arthroplasty (group control), and to correlate its occurrence to postoperative lengthening of the arm.

Method: We included all patients needing a total shoulder arthroplasty either anatomic or reversed. Each patient underwent a pre- and postoperative electromyography (EMG). This study focused on the clinical, radiological and EMG evaluation, with a measure of the lengthening of the arm in case of reversed shoulder arthroplasty according to a protocol previously validated.

Result: Between November 2007 and February 2009, we collected 41 patients (42 prostheses), including 23 anatomic (group 1) and 19 reverse (group 2) primary shoulder arthroplasties. The 2 groups were similar according to mean age, comorbidity, male/female ratio and nerve conduction abnormalities on EMG performed on an average of 10 days before surgery. Control EMG realized at an average of 3.6 weeks postoperatively showed in group 1, a plexus lesion due to an intra-operative complication. In group 2, we noticed 9 recent neurological damages (45% of cases) involving mainly the axillary nerve; 8 were rapidly regressive. The incidence of recent injury was significantly more frequent in group 2 (p=0.003) with a risk 10.4 times higher (95% CI 1.4, 74.8). Mean lengthening of the arm after a reverse was 3.1 cm ± 1.8 (range 0.2 to 5.9) compared to preoperative measurement and 2.4 cm ± 2.1 (range −0.5 to 5.8) compared with the normal contra-lateral side.

Discussion: The occurrence of peripheral neurological lesion following a reverse shoulder arthroplasty is common but usually transient. These lesions may cause postoperative pain, alter rehabilitation and can theoretically induce prosthetic instability. Lengthening of the arm is considered as one of the major factors responsible for this neurologic damage. Indeed, surgical dissection, compression phenomena by use of retractors or presence of hematoma, vascular injury, mobilization of the upper limb and possibly interscalene block are similar for the two types of prosthesis. Arm lengthening is thus a compromise between necessary retensionning of the deltoid for good mobility and instability avoidance, and lengthening which may be responsible for neurological lesions, acromial fractures and permanent arm abduction.