[Cuff tear arthropathy – long-term results of reverse total shoulder arthroplasty]

Primary stability of fixation methods for periprosthetic fractures of the humerus: a biomechanical investigation

BACKGROUND

The incidence of periprosthetic fractures of the proximal humerus is gradually increasing, following an increase in reverse shoulder arthroplasties in recent years. Locking plate fixation and revision arthroplasty are both valuable treatment methods. However, the primary stability of fixation methods for periprosthetic fractures has not been investigated in detail. The aim of this study was to analyze and compare the primary stability of the common treatment measures.

MATERIALS AND METHODS

Cemented reverse total shoulder arthroplasty (Delta Xtend; DePuy Synthes, Warsaw, IN, USA) was performed in 5 shoulders, and a distal, mid-diaphysis humeral fracture (Wright and Cofield type B) was induced. The implant was left in place, and 3 distinct fixation scenarios were tested: osteosynthesis using 4.5-mm locking plate fixation (subgroup A), 4.5-mm locking plate fixation with an additional 3.5-mm locking plate (subgroup B), and 4.5-mm locking plate fixation with an additional K-wire cerclage (subgroup C). The specimens were tested in a biomechanical setup simulating activities of daily living including rotation. Strain gauges (4-wire strain at 120 Ω; Vishay Measurements Group, Chartres, France) mounted on the 4.5-mm locking plates were used to evaluate the strain of the fixation and to give an estimate of primary stability.

RESULTS

Regarding the simulation of activities of daily living, no statistically significant differences were found in the measured strains on the locking plate between subgroups A, B, and C. A maximum measured strain of 216.85 μm/m in subgroup A resulted in bending of the locking plate (length, 134 mm) of 0.03 mm. In subgroup B (277.01 μm/m), the plate strained 0.04 mm compared with a strain measurement of 0.01 mm in subgroup C (75.93 μm/m).

CONCLUSION

Additional K-wire cerclages or additional 3.5-mm locked plating did not increase primary stability. With a stable prosthetic implant in place, 4.5-mm locked plating is sufficient to address periprosthetic humeral shaft fractures in the present in vitro setup.

Reversed shoulder arthroplasty leads to significant histological changes of the deltoid muscle: a prospective intervention trial

INTRODUCTION

Reverse shoulder arthroplasty (RSA) shows promising short- and mid-term results in cuff tear arthropathy. However, functional impairments are described in long-term findings. Micromorphological changes in the periarticular musculature could be in part responsible for this, but have not yet been analysed. Thus, histological changes of the deltoid muscle and their association to the functional outcome were evaluated in this study.

MATERIAL AND METHODS

A total of 15 patients treated with RSA were included in this prospective study. Functional outcome was assessed using the Constant Score (CS) and the DASH (disabilities of the arm, shoulder and hand) Score before RSA and after a mean follow-up of 12 months. Deltoid muscle biopsies were harvested intraoperatively and 12 months postoperatively. Mean deltoid muscle fibre area (MMFA) was calculated histologically after haematoxylin-eosin staining.

RESULTS

Postoperative shoulder function significantly improved within 12 months (CS: Δ 37.4 ± 22.6, p = 0.001; DASH: Δ 27.1 ± 29.1, p = 0.006). The MMFA significantly decreased (p = 0.02), comparing the results from the intraoperative biopsy (MMFA: 8435.8 µm², SD ± 5995.9 µm²) to the 12 months biopsy (MMFA: 5792. µm², SD ± 3223.6 µm²). No correlation could be found between the functional score results and MMFA.

CONCLUSION

Signs of deltoid muscle changes in terms of a reduced MMFA can be detected 1 year after RSA and thus already a long time before long-term functional impairments become apparent. Further studies with larger patient series and longer follow-up periods as well as extended histological assessments and simultaneous radiological examinations are required.

Factors associated with poor active anterior elevation after reverse total shoulder arthroplasty

BACKGROUND

Although reverse total shoulder arthroplasty (RTSA) has been shown to reduce pain and to improve function in most patients, some still suffer from functional limitations. This study aimed to investigate the incidence of poor motion recovery after RTSA and to identify factors that may cause poor outcomes.

METHODS

Seventy-six patients who underwent primary RTSA with a reverse-type Aequalis prosthesis (Tornier, Montbonnot, France) were allocated to a satisfactory or unsatisfactory group on the basis of their postoperative active anterior elevation. The average age of the patients was 69 ± 8 years (range, 42-82 years); average follow-up period was 34 ± 12 months (range, 24-93 months).

RESULTS

Fifty-eight patients had a satisfactory outcome (satisfactory group) and 18 had an unsatisfactory outcome (unsatisfactory group). Twenty-seven patients (46.6%) in the satisfactory group and 10 (55.6%) in the unsatisfactory group had preoperative pseudoparalysis (P = .504). Pre-existing medical comorbidities, such as thyroid disease, hypertension, diabetes, and smoking, showed no significant differences. Anterior deltoid muscle belly volume also did not significantly differ between the satisfactory and unsatisfactory groups. However, mean postoperative lateral humeral offset (LHO) was -2 ± 6 mm in the satisfactory group and 3 ± 5 mm in the unsatisfactory group (P = .001).

CONCLUSION

Satisfactory improvement of active anterior elevation was achieved in three-quarters of patients who underwent RTSA using a prosthesis designed to be medialized. Of the factors we investigated, only postoperative LHO was found to be a significant risk factor for poor postoperative active anterior elevation. Therefore, surgeons should attempt to avoid increasing postoperative LHO when performing RTSA using an implant designed to be medialized.

Improved external rotation with concomitant reverse total shoulder arthroplasty and latissimus dorsi tendon transfer: A systematic review

BACKGROUND

In conjunction with reverse total shoulder arthroplasty (RSA), latissimus dorsi and teres major (LD-TM) transfer has been advocated in the setting of combined loss of elevation and external rotation. The purpose of this systematic review is to summarize the clinical outcomes following RSA with LD-TM transfer.

METHODS

A search of PubMed, EMBASE, CINAHL, Medline, and Cochrane databases was performed between January 1, 1990 and March 1, 2016 and included articles related to outcomes following RSA with LD-TM transfer. Primary outcomes of interest were constant score, shoulder range of motion, and patient satisfaction. Secondary outcomes of interest included subjective shoulder value, simple shoulder test, activities of daily living requiring external rotation, and visual analog pain score. Additional outcomes evaluated included complications and reoperations. Frequency-weighted values of outcome data were utilized.

RESULTS

Five level IV studies involving 98 shoulders met the inclusion criteria. The mean age of the cohort was 69.1 ± 5.19 years (range 47-85). RSA with LD-TM transfer was performed for rotator cuff arthropathy (94%) or proximal humerus fracture (6%). The average follow-up was 44.5 ± 10.38 months (range 12-105 months). The constant score improved from 28 to 65 ( p < 0.0005). Active external rotation improved from -7.4° to 22.9° ( p < 0.0005). There was a 22.4% overall complication rate, including dislocation (5.1%), infection (5.1%), and transient nerve palsy (3.4%).

CONCLUSION

Patients undergoing RSA with LD-TM transfer in the setting of loss of external rotation demonstrate reliable clinical improvements in shoulder function with complication rates which are comparable to RSA alone.

[Shoulder endoprosthesis in the elderly : Hemiarthroplasty or total shoulder arthroplasty? Anatomic or reverse?]

Implantation of reverse shoulder endoprostheses is becoming more popular for elderly patients besides the well-established standard anatomic endoprostheses. The reasons for this are the increased life expectancy, age-dependent degeneration of the rotator cuff leading to cuff tear arthropathy, posttraumatic disability after failed osteosynthesis and primary reverse fracture arthroplasty. Stemless implants are more frequently used for primary osteoarthritis with the bone quality being the limiting factor. Modern implant systems allow the stepwise extension from bone preserving primary implants to modular and convertible revision implants that allow a partial exchange of components. Revision surgery, especially that of reverse arthroplasty, has limited potential for secondary treatment options and therefore implantation and revision should be performed in specialized treatment facilities.

Patients With Impingement Syndrome With and Without Rotator Cuff Tears Do Well 20 Years After Arthroscopic Subacromial Decompression

PURPOSE

To present the long-term outcome of arthroscopic subacromial decompression (ASD) for patients with impingement syndrome with or without rotator cuff tears as well as with or without calcific tendinitis in a follow-up of 20 years.

METHODS

We included 95 patients after a mean follow-up of 19.9 (19.5 to 20.5) years. All patients underwent ASD, including acromioplasty, resection of the coracoacromial ligament, and coplaning without cuff repair. The Constant score was used to assess the functioning of the shoulder. In addition, we defined a combined failure end point of a poor Constant score and revision surgery.

RESULTS

Revision surgery was performed in14.7% of the patients. The combined end point showed successful results in 78.8% of all cases. All patients with isolated impingement syndrome achieved successful results. Those with partial-thickness tears had successful outcomes in 90.9% of all cases, and patients with full-thickness tears had successful outcomes in 70.6% of all cases. The tendinitis calcarea group showed the poorest results, with a 65.2% success rate.

CONCLUSIONS

Our long-term results show that patients with impingement syndrome who received ASD, including acromioplasty, resection of the coracoacromial ligament, and coplaning do well 20 years after the index surgery. ASD without cuff repair even appears to be a safe, efficacious, and sustainable procedure for patients with partial rotator cuff tears.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Stress-shielding induced bone remodeling in cementless shoulder resurfacing arthroplasty: a finite element analysis and in vivo results

Cementless surface replacement arthroplasty (CSRA) of the shoulder was designed to preserve the individual anatomy and humeral bone stock. A matter of concern in resurfacing implants remains the stress shielding and bone remodeling processes. The bone remodeling processes of two different CSRA fixation designs, conical-crown (Epoca RH) and central-stem (Copeland), were studied by three-dimensional (3-D) finite element analysis (FEA) as well as evaluation of contact radiographs from human CSRA retrievals. FEA included one native humerus model with a normal and one with a reduced bone stock quality. Compressive strains were evaluated before and after virtual CSRA implantation and the results were then compared to the bone remodeling and stress-shielding pattern of eight human CSRA retrievals (Epoca RH n=4 and Copeland n=4). FEA revealed for both bone stock models increased compressive strains at the stem and outer implant rim for both CSRA designs indicating an increased bone formation at those locations. Unloading of the bone was seen for both designs under the central implant shell (conical-crown 50-85%, central-stem 31-93%) indicating high bone resorption. Those effects appeared more pronounced for the reduced than for the normal bone stock model. The assumptions of the FEA were confirmed in the CSRA retrieval analysis which showed bone apposition at the outer implant rim and stems with highly reduced bone stock below the central implant shell. Overall, clear signs of stress shielding were observed for both CSRAs designs in the in vitro FEA and human retrieval analysis. Especially in the central part of both implant designs the bone stock was highly resorbed. The impact of these bone remodeling processes on the clinical outcome as well as long-term stability requires further evaluation.