Total shoulder prosthesis with humeral resurfacing: Impact on lateral offset and short-term clinical consequences

Humeral and glenoid component malposition in patients requiring revision shoulder arthroplasty: a retrospective, cross-sectional study

BACKGROUND

The purpose of this study was to assess the incidence of glenoid and humeral component malposition in failed primary shoulder arthroplasty requiring revision. We hypothesized that glenoid and humeral component malposition would be a prevalent feature in cases requiring revision arthroplasty for primary anatomic total shoulder arthroplasty (TSA), primary reverse shoulder arthroplasty (RSA), and primary hemiarthroplasty procedures.

METHODS

A retrospective cross-sectional study was performed focusing on identifying the incidence of malpositioned components in shoulder arthroplasty in quantitative and qualitative reviews. A total of 234 consecutive cases from 3 institutions were included in the study. Past surgical and radiographic data relative to the primary and revision surgeries were collected by each of the 3 investigative institutions, and radiographs were reviewed by an independent reviewer. Descriptive data are summarized as means, ± standard deviations, or frequency (%). An Exact McNemar's test was used to compare frequencies between the independent reviewer and the institutions when appropriate, with significance set at P = .05.

RESULTS

Quantitative analysis demonstrated that the majority of glenoid components in these revision cases were malpositioned in both TSA (51%) and RSA (93%) when all measures were considered. Similarly, there was humeral component malposition in 57% of TSA cases, 62% of RSA cases, and 54% of hemiarthroplasty cases when all measures were considered. When asked if there was glenoid component malposition, the independent reviewer considered 17% of glenoid components to be malpositioned in TSA cases and 54% in RSA cases. The investigative institutions reported similar rates (P = .585). For the humeral side, the independent reviewer felt that 71% of TSA cases, 24% of RSA cases, and 74% of hemiarthroplasty implants were malpositioned in some direction. The investigative institutions reported similar rates (P = .087).

DISCUSSION AND CONCLUSION

The data from this study suggest that component malposition is frequently present among patients requiring revision arthroplasty. Component malposition was not just frequently present, but also occurred in consistent patterns. Moreover, while significant attention has been placed on the impact of glenoid malposition, this study highlights the previously underappreciated high incidence of humeral component malposition in cases requiring revision arthroplasty.

Shoulder Physiological Offset Parameters in Asian Populations-A Magnetic Resonance Imaging Study

Background/Objectives: Physical shoulder offset parameters (SOPs) play important roles in the diagnosis and treatment of shoulder diseases. However, there is little research analyzing SOPs in healthy shoulders using cross-sectional MRI images, especially in Asians. Therefore, this study aimed to establish physiological reference values of shoulder parameters for Asian populations. Methods: This was a retrospective imaging study using MRI images of the shoulder joints of 500 patients (mean age: 55.9 ± 14.0 years). We measured the following SOPs of the normal joint: HO, GO, lateral glenoidal humeral offset (LGHO), humeral shaft axis offset (HAO), and cortical offset (CO). In addition, the offset parameters were examined for associations with age, gender, side, and osteoarthritis. Results: The mean HO was 22.9 (±2.4) mm, the mean GO was 62.3 (±6.6) mm, the mean LGHO was 48.9 (±4.2) mm, the mean HAO was 25.2 (±2.8) mm, and the mean CO was 15.7 (±2.7) mm. Male patients exhibited significantly higher values across all SOPs compared to female patients. In addition, there was a significantly lower mean value for HAO in left shoulders (HAO: 24.7± 2.8 mm vs. 25.5 ± 2.8 mm, p = 0.011). There was a negatively significant correlation between age and all SOPs. No significant difference in mean values was noted between shoulders with osteoarthritis and non-osteoarthritis in any SOPs. Conclusions: Significant gender- and age-specific differences were noted for all measured SOPs. In addition, right shoulders did not show higher mean SOP values than left shoulders, except for HAO, suggesting that the contralateral joint is a reliable reference for surgical planning. These findings should be considered in shoulder surgery planning.

Fixed- vs. variable-angle humeral neck cut in anatomic total shoulder arthroplasty: a randomized controlled trial

BACKGROUND

Variable neck-shaft angle (NSA) stemmed humeral components have been incorporated into certain implant designs to better re-create normal anatomy in total shoulder arthroplasty (TSA). The purpose of this study was to determine if premorbid glenohumeral joint anatomy is better restored with a fixed- vs. variable-NSA prosthesis.

METHODS

A randomized controlled trial was performed including 50 patients with osteoarthritis indicated for primary anatomic TSA. Patients were randomized preoperatively to receive either a variable- (n = 26) or fixed-NSA (n = 24) prosthesis. Humeral neck cut in the variable-NSA group matched the patient's anatomic neck, with prosthetic NSA of 127.5°, 132.5°, and 137.5° available. Fixed-NSA cuts were made with an intramedullary guide of 132.5°. Preoperative and postoperative radiographs were evaluated for specific radiographic anatomic variables: NSA, head thickness, tuberosity-to-head height, head offset, articular arc, greater tuberosity offset, and center of rotation (COR). Postoperative radiographic criteria were compared between groups.

RESULTS

No differences were found between groups in demographics or preoperative radiographic measures. When comparing average difference in preoperative and postoperative measurements in the fixed-NSA group, the humeral head offset from the humeral shaft axis significantly decreased by 1.4 mm (P = .046), and the COR moved superiorly (3.0 mm, P = .002) without significant medialization or lateralization. In the variable angle group, humeral head offset decreased but did not reach significance (1.2 mm, P = .091), and the COR also moved superiorly (2.9 mm, P < .001) without significant medialization or lateralization. All remaining radiographic parameters did not significantly change from pre- to postoperative imaging. In comparing the fixed- and variable-NSA groups' net change from the premorbid measurements, no significant differences were found in tuberosity-to-head height, head offset, or COR position in both the horizontal and vertical planes.

CONCLUSIONS

Both fixed- and variable-NSA anatomic TSA humeral components demonstrate adequate restoration of premorbid anatomy radiographically.

The value of lateral glenohumeral offset in predicting construct failure in proximal humerus fractures following internal fixation

BACKGROUND

Proximal humerus fractures are the third most common osteoporosis defining injury in the United States, yet operative fixation of these injuries remains technically challenging. Although several modifiable and nonmodifiable risk factors are correlated with failure of proximal humerus fixation, no study has investigated whether failure to restore glenohumeral offset plays a part in fixation failure. The goals of this study are: (1) to determine if lateral glenohumeral offset (LGHO) and humeral head diameter (HHD) can be measured radiographically with accuracy between observers, (2) to observe whether there is a correlation between failure to operatively restore an anatomic LGHO:HHD ratio and failure of fixation, and (3) if there is a correlation, can any recommendations be made in regard to the ideal LGHO:HHD ratio.

METHODS

Retrospective review found 183 patients meeting inclusion criteria who underwent operative fixation for proximal humerus fractures between 2005 and 2018. Patients suffering construct failure requiring reoperation were compared with clinically successful surgeries on the basis of age, sex, fracture morphology, head-shaft angle, smoking history, presence or absence of a calcar screw, and LGHO:HHD ratio. The groups were compared using a combination of Student t-tests, χ², and bivariate and multivariate logistic regression analyses where appropriate. The Student t-test and intraclass correlation coefficient were both used to assess interobserver reliability.

RESULTS

We found that LGHO and HHD can be measured by independent observers accurately (intraclass correlation coefficient = 0.80, 95% confidence interval: 0.65-0.89). Patients suffering implant failure had a significantly lower LGHO:HHD ratios compared with those who did not (0.94 vs. 1.03, P ≤ .001). The LGHO:HHD ratio was an independent predictor of implant failure even after controlling for other potential risk factors. Patients with an LGHO:HHD of 1.0 or above have a <10% chance of failure compared with a 20% risk with a ratio of 0.9 and a 40% risk at 0.8.

CONCLUSION

We found the LGHO:HHD ratio to be an independent predictor for construct failure after plate and screw fixation of proximal humerus fractures. Efforts should be made to restore an anatomic ratio of at least 1.0 to minimize the risk of failure.

Fracture of pyrocarbon humeral head resurfacing implant: a case report

We report a case of a pyrocarbon humeral head resurfacing implant fracture, occurring 6 years after its implantation, without any obvious trauma or dislocation. Initial radiographs showed a proud and oversized pyrocarbon resurfacing implant. On clinical examination, the patient had a painful and pseudoparalyzed shoulder with subscapularis insufficiency. Imaging studies confirmed implant fracture and severe fatty infiltration (Goutallier, grade 4) of the subscapularis muscle. Intraoperatively, the implant was found to be fractured with multiple pyrocarbon debris in the glenohumeral joint. The implant was loose, and gross inspection showed no visible bony adhesion or ongrowth. Histologic analysis showed multiple seats of metallosis in the synovial tissue and cancellous bone of the humeral head. Successful management of this complication was managed with a thorough débridement and irrigation and revision to reverse shoulder arthroplasty. Our observation put into question the use of pyrocarbon as a humeral head resurfacing implant. The material seems to be too fragile to be used as a resurfacing implant and cannot achieve fixation of the implant to bone.

Clinical and radiological outcomes of 17 reverse shoulder arthroplasty cases performed after failed humeral head resurfacing

INTRODUCTION

Despite the good outcomes with shoulder resurfacing procedures reported by some authors, our team has documented several failures caused by glenoid erosion and rotator cuff rupture, likely due to implant overstuffing. The aim of this study was to evaluate the clinical and radiological outcomes of reverse shoulder arthroplasty (RSA) performed after failed humeral head resurfacing (HHR).

MATERIAL AND METHODS

This was a retrospective, single-center study of 17 patients who underwent RSA after failed HHR between January 2011 and February 2016. The mean patient age was 69.4 years and the mean time between HHR and surgical revision was 41 months (14.7-73.5±18.8). Preoperative ultrasonography and CT were used to evaluate the condition of the rotator cuff, extent of glenoid erosion and to look for signs of humeral cup loosening. The clinical outcomes were evaluated pre- and postoperatively using the simple shoulder test (SST), DASH (Disabilities of the Arm, Shoulder and Hand) and the Constant-Murley score. Pain was estimated using a visual analog scale (VAS). The range of motion (ROM) was determined pre- and postoperatively. All patients had standard AP and lateral X-ray views of the shoulder taken as part of their postoperative follow-up protocol to look for implant loosening.

RESULTS

The mean follow-up was 35.9 months (24-59±10.7). There were no intraoperative or postoperative complications. All the functional scores were improved after RSA. The median weighted Constant score preoperatively was 46% (36; 62) while it was 92% postoperatively (78; 100) (p<0.0001). The active ROM improved by 65° in forward flexion (p=0.0003) and by 30° in external rotation (p=0.002). On X-rays, we identified one patient with Sirveaux stage 4 glenoid notching and one patient with a humeral periprosthetic radiolucent line less than 2mm thick in zone 6, with no clinical consequences.

CONCLUSION

The excellent outcomes after RSA for failed HHR in our study are similar to the ones reported when RSA is performed for cuff tear arthropathy.