Backside polyethylene wear in reverse shoulder arthroplasty.

BACKGROUND: Aseptic loosening from implant-associated osteolysis in reverse shoulder arthroplasty (RSA) may contribute to premature implant failure. Although articular side polyethylene (PE) damage has been well documented in the literature, no studies to date have investigated backside wear in RSA. The aims of this investigation were to (1) document and compare the damage between the backside and articular surface in explanted RSA components, (2) assess whether certain quadrants have a greater propensity for damage, and (3) report the most common mode(s) of backside PE damage. METHODS: Twenty-one RSA humeral liners retrieved during revision procedures between 2005 and 2014 were included for analysis. The mean time between implantation and extraction was 16 months (10 days-88 months). Diagnoses at the time of revision included dislocation (10), infection (4), mechanical failure (3), loosening (2), and unknown (2). Liners were examined under light microscopy (×10-30 magnification) and damage on the articular and backside of the liner surface was graded using the modified Hood score. The location and damage modality were compared between the articular side and backside of the implant. RESULTS: Damage was noted on the articular surfaces of all 21 liners and on the backside surface of 20 liners. The total damage in all the quadrants was higher on the articular surface than on the backside of the component, with a mean difference in total quadrant damage scores of 11.74 ± 3.53 (P < .001). There was no difference in damage among the quadrants on the backside (P = .44) or the articular surface (P = .08). The articular side exhibited greater scratching, abrasion, and surface deformation than the backside (P < .001). CONCLUSIONS: This short-term retrieval study demonstrated that backside PE damage occurs on the humeral component of RSA implants. There was greater damage to the articular side of the liner but wear to the backside was present in almost all liners. The clinical importance of backside wear in RSA and its overall contribution to PE particulate disease and osteolysis needs further investigation.

No differences in early results of a hybrid glenoid compared with a pegged implant.

BACKGROUND: Glenoid component loosening after total shoulder arthroplasty is one of the most common causes of failure. A hybrid glenoid that uses peripherally cemented pegs and a central press-fit post may improve implant longevity. QUESTIONS/PURPOSES: We asked, compared with polyethylene pegged glenoid implants, do hybrid glenoid implants with a titanium post provide (1) better ingrowth with fewer radiolucencies, (2) better outcome and pain scores, and (3) lower risk of complications and revisions? METHODS: Between 2009 and 2010, 126 patients underwent primary total shoulder arthroplasty for osteoarthritis. Patients were included in this retrospective study if they consented for inclusion in a shoulder arthroplasty registry, had complete baseline and 2-year data, and had complete radiographs. Eighty-three (67%) were available at an average followup of 3.2 years (range, 24-45 months). Forty received a conventional all-polyethylene pegged glenoid and 43 received a hybrid component. During the period in question, four of the participating surgeons used only one implant, and four used only the other; there was one high-volume surgeon in each of the study groups. Radiographs were taken at the 2-year followup and analyzed for radiolucent lines. CT scans were obtained randomly for 10 patients with hybrid glenoid implants to assess bone ongrowth. American Shoulder and Elbow Surgeons score, VAS score, complications and revisions were recorded. RESULTS: At final followup, radiolucent lines between the two study groups were not different (hybrid, 1.0 ± 0.4; pegged, 1.6 ± 0.3; mean difference, 0.6; 95% CI, 0.85-1.72; p = 0.323). Final VAS pain scores were not different (hybrid, 1.2 ± 0.2; pegged, 1.5 ± 0.3; p = 0.056). Change in American Shoulder and Elbow Surgeons scores were not different (hybrid, 33.7 ± 7.3; pegged, 35.5 ± 8.2; p = 0.283). There were no differences in complication risk (hybrid, one of 43 [2.3%]; pegged, three of 40 [7.5%]; relative risk, 2.3; 95% CI, 0.82-3.12; p = 0.061). CONCLUSIONS: With the numbers available and at early followup, there were no differences between the hybrid and pegged glenoids in terms of fixation, functional outcome, pain scores, and complications. CT scans confirmed bone ongrowth on the porous titanium post in a small subcohort of patients. Further studies are needed to determine how this new implant will perform with time. Until then, its use should be initiated with caution. LEVEL OF EVIDENCE: Level III, therapeutic study.

Augmented versus non-augmented locking-plate fixation in proximal humeral fractures.

Aims: Proximal humeral fractures are the third most common fracture among the elderly. Complications associated with fixation include screw perforation, varus collapse, and avascular necrosis of the humeral head. To address these challenges, various augmentation techniques to increase medial column support have been developed. There are currently no recent studies that definitively establish the superiority of augmented fixation over non-augmented implants in the surgical treatment of proximal humeral fractures. The aim of this systematic review and meta-analysis was to compare the outcomes of patients who underwent locking-plate fixation with cement augmentation or bone-graft augmentation versus those who underwent locking-plate fixation without augmentation for proximal humeral fractures. Methods: The search was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Articles involving patients with complex proximal humeral fractures treated using open reduction with locking-plate fixation, with or without augmentation, were considered. A meta-analysis of comparative studies comparing locking-plate fixation with cement augmentation or with bone-graft augmentation versus locking-plate fixation without augmentation was performed. Results: A total of 19 studies were included in the qualitative synthesis, and six comparative studies were included in the meta-analysis. Overall, 120 patients received locking-plate fixation with bone-graft augmentation, 179 patients received locking-plate fixation with cement augmentation, and 336 patients received locking-plate fixation without augmentation. No statistically relevant differences between the augmented and non-augmented cohorts were found in terms of the Disabilities of the Arm, Shoulder and Hand questionnaire score and Constant-Murley Score. The cement-augmented group had a significantly lower rate of complications compared to the non-augmented group. Conclusion: While locking-plate fixation with cement augmentation appears to produce a lower complication rate compared to locking-plate fixation alone, functional outcomes seem comparable between augmented and non-augmented techniques.

Evaluation of tumor necrosis factor α blockade on early tendon-to-bone healing in a rat rotator cuff repair model.

PURPOSE: The purpose was to determine whether systemic tumor necrosis factor α (TNF-α) blockade can improve rotator cuff healing in a rat model. METHODS: One hundred twenty Lewis rats underwent unilateral detachment and repair of the supraspinatus. Rats were randomized into 2 groups. The experimental group received injections of pegylated soluble tumor necrosis factor receptor type I (3.0 mg/kg every other day for 3 doses). The control group received saline solution on the same dosing schedule. At 2, 4, and 8 weeks, 20 animals in each group were killed (4 for histologic assessment and 16 for biomechanical testing). Outcomes included qualitative histologic assessment to determine new fibrocartilage formation and collagen fiber organization. Immunohistochemical staining was performed to localize TNF-α, ED1 and ED2 macrophages, and tartrate-resistant acidic phosphatase. Biomechanical testing was performed to determine the ultimate load to failure, stiffness, cross-sectional area, and ultimate stress to failure. RESULTS: Qualitative assessments of histology showed that the experimental group had more cartilage formation at 4 weeks but not at 2 or 8 weeks. There was less TNF-α staining in the experimental group at 4 and 8 weeks, and there were fewer ED1 macrophages at 4 weeks compared with controls. The ultimate load to failure was greater in the experimental group compared with controls at 2 weeks (13.3 ± 2.6 N v 11.2 ± 2.7 N, P = .05) and at 4 weeks (21.7 ± 4.6 N v 18.5 ± 2.1 N, P = .04). The experimental group also had a higher stiffness at 2 weeks (7.2 ± 2.3 N/mm v 5.8 ± 1.4 N/mm, P = .04) and at 4 weeks (10.5 ± 2.7 N/mm v 8.4 ± 1.7 N/mm, P = .01). There were no differences in any biomechanical variable at 8 weeks. CONCLUSIONS: TNF-α blockade can improve the biomechanical strength of tendon-bone healing in a rat rotator cuff model at early time points, which corresponded with modest qualitative improvements in histology. However, these differences were not maintained at 8 weeks. CLINICAL RELEVANCE: TNF-α blockade may influence rotator cuff tendon healing.

Retrieval Analysis of Porous Titanium Glenoid Posts: An Evaluation of Osteointegration.

Glenoid component loosening is a commonly encountered complication of total shoulder replacements. Therefore, focus has been placed on glenoid fixation. Porous metal implants, which promote biological fixation through osteointegration, have provided an uncemented alternative to the traditional cemented implant. In this explantation study, the authors examined the bone ingrowth and ongrowth of a specific porous titanium glenoid peg. Six explanted polyethylene glenoid components with porous titanium-coated central pegs were identified in the authors' implant retrieval program via retrospective review. The retrieved implants were sectioned into thirds with a precision saw and underwent scanning electron microscopy for analysis of bone ingrowth and ongrowth. Bone ingrowth was calculated as bone volume fraction, or the fraction of available pore space filled with bone, whereas ongrowth was the percentage of the perimeter of the implant covered with bone. The 6 total shoulders included in the study were revised at an average of 16.3 months (range, 5-48 months) for instability secondary to subscapularis rupture, subscapularis rupture plus infection, or other rotator cuff tear. All glenoid components were grossly stable on retrieval and had an average of 23% bone ingrowth and 54% ongrowth. The preliminary results show that osteointegration into a porous titanium ingrowth glenoid component is possible in the short-term, even in the presence of an unfavorable biomechanical environment, such as instability and rotator cuff dysfunction, as well as infection. [Orthopedics. 2017; 40(4):e703-e707.].

Augmentation of tendon-to-bone healing with a magnesium-based bone adhesive.

BACKGROUND: Healing of an anterior cruciate ligament graft in a bone tunnel occurs by formation of fibrous scar tissue, which is weaker than the normal fibrocartilaginous insertion. HYPOTHESIS: We hypothesized that a magnesium-based bone adhesive would improve tendon-to-bone healing in a rabbit anterior cruciate ligament reconstruction model. STUDY DESIGN: Controlled laboratory study. METHODS: Thirty-five New Zealand White rabbits underwent bilateral anterior cruciate ligament reconstructions with semitendinosus autografts. A total of 12.5 g of bone adhesive was placed in the intraosseous tunnel around the graft in one limb, while the tunnels in the contralateral limb received no implant. Sixteen animals each were sacrificed at 3 weeks and at 6 weeks (12 biomechanical testing/4 histology). Outcomes included semiquantitative histologic analyses for new cartilage formation and fibrous tissue formation in the tendon-bone interface, microcomputed tomography to quantify new bone formation along the bone tunnel, and biomechanical testing of load-to-failure and stiffness. Three animals were sacrificed at time 0 to confirm adequate tunnel fill with the bone adhesive on microcomputed tomography. RESULTS: All specimens had adequate tunnel fill with the bone adhesive at time 0. Application of the bone adhesive resulted in more cartilage formation and less fibrous tissue formation at the tendon-bone interface at 6 weeks compared with controls (P < .05). There was significantly more bone formation in the tibia of the treated limbs at 6 weeks (P = .01). The load-to-failure was significantly higher in the treated group at 6 weeks (71.8 +/- 31.8 N vs 43.4 +/- 14.8 N; P = .04). There were no differences in stiffness at either time point, and there were no differences at 3 weeks in any outcome variable. CONCLUSION: The magnesium-based bone adhesive improves tendon-to-bone healing based on histologic and biomechanical testing at 6 weeks in a rabbit model of anterior cruciate ligament reconstruction. CLINICAL RELEVANCE: Further studies are needed to investigate the clinical potential of this bone adhesive to enhance healing and decrease recovery time in soft-tissue ligament reconstruction.