Jeremiah Clinton

Glenoid Component Failure in Total Shoulder Arthroplasty

Glenoid component failure is the most common complication of total shoulder arthroplasty. Glenoid components fail as a result of their inability to replicate essential properties of the normal glenoid articular surface to achieve durable fixation to the underlying bone, to withstand repeated eccentric loads and glenohumeral translation, and to resist wear and deformation. The possibility of glenoid component failure should be considered whenever a total shoulder arthroplasty has an unsatisfactory result. High-quality radiographs made in the plane of the scapula and in the axillary projection are usually sufficient to evaluate the status of the glenoid component. Failures of prosthetic glenoid arthroplasty can be understood in terms of failure of the component itself, failure of seating, failure of fixation, failure of the glenoid bone, and failure to effectively manage eccentric loading. An understanding of these modes of failure leads to strategies to minimize complications related to prosthetic glenoid arthroplasty.

Treatment of osseous defects associated with anterior shoulder instability.

Bone loss of the glenoid and/or humerus is a common consequence of traumatic anterior shoulder instability and can be a cause of recurrent instability after a Bankart repair. Accurate characterization of the size and location of osseous defects associated with traumatic instability is important when planning treatment. Open or arthroscopic soft tissue repairs are usually sufficient when less than 25% of the width of the glenoid bone has been lost. Bone replacement techniques may be necessary when glenoid bone loss is greater than 25% of the glenoid width. Glenoid bone restoration techniques include the use of a tricortical iliac crest graft or the transfer of the coracoid process to the area of glenoid deficiency. Bone grafting becomes a strong consideration when soft tissue repairs have failed to restore stability. Treatment of these severe defects may be followed by osteoarthritis. The destabilizing effects of anterior glenoid bone defects are compounded by concurrent defects of the posterior-lateral humeral head, commonly known as Hill-Sachs lesions, which can engage the glenoid defect. Large humeral head defects can be treated by transhumeral bone grafting techniques or osteoarticular allograft reconstruction. Prosthetic replacement of the proximal humerus is considered for humeral head defects involving more than 40% of the articular surface. Understanding the importance of humeral and glenoid bone deficiencies may help guide the treatment of recurrent anterior glenohumeral instability.

Proximal Humeral Fracture as a Risk Factor for Subsequent Hip Fractures

BACKGROUND With the aging of the worlds population, the social and economic implications of osteoporotic fractures are at epidemic proportions. This study was performed to test the hypothesis that a proximal humeral fracture is an independent risk factor for a subsequent hip fracture and that the risk of the subsequent hip fracture is highest within the first five years after the humeral fracture. METHODS A cohort of 8049 older white women with no history of a hip or humeral fracture who were enrolled in the Study of Osteoporotic Fractures was followed for a mean of 9.8 years. The risk of hip fracture after an incident humeral fracture was estimated with use of age-adjusted Cox proportional hazards regression analysis with time-varying variables; women without a humeral fracture were the reference group. Cox regression analysis was used to evaluate the timing between the proximal humeral and subsequent hip fracture. Risk factors were determined on the basis of a review of the current literature, and we chose the variables that were most predictive and easily ascertained in a clinical setting. RESULTS Three hundred and twenty-one women sustained a proximal humeral fracture, and forty-four of them sustained a subsequent hip fracture. After adjustment for age and bone mineral density, the hazard ratio for hip fracture for subjects with a proximal humeral fracture relative to those without a proximal humeral fracture was 1.83 (95% confidence interval = 1.32 to 2.53). After multivariate adjustment, this risk appeared attenuated but was still significant (hazard ratio = 1.57; 95% confidence interval = 1.12 to 2.19). The risk of a subsequent hip fracture after a proximal humeral fracture was highest within one year after the proximal humeral fracture, with a hazard ratio of 5.68 (95% confidence interval = 3.70 to 8.73). This association between humeral and hip fracture was not significant after the first year, with hazard ratios of 0.87 (95% confidence interval = 0.48 to 1.59) between one and five years after the humeral fracture and 0.58 (95% confidence interval = 0.22 to 1.56) after five years. CONCLUSIONS In this cohort of older white women, a proximal humeral fracture independently increased the risk of a subsequent hip fracture more than five times in the first year after the humeral fracture but was not associated with a significant increase in the hip fracture risk in subsequent years.

Glenohumeral chondrolysis: A systematic review of 100 cases from the English language literature

HYPOTHESIS Chondrolysis can be a devastating complication of shoulder arthroscopy. We undertook a review of the 100 cases reported in the English language to test the hypothesis that common factors could be identified and that the identification of these factors could suggest strategies for avoiding this complication. MATERIALS AND METHODS We systematically reviewed the English language literature and identified 16 articles reporting 100 shoulders in which postsurgical glenohumeral chondrolysis had developed. RESULTS The average reported patient age was 27 +/- 11 years at the time of surgery; 35 were women. The most common indications for surgery were instability (n = 68) and superior labrum anteroposterior lesions (n = 17). In 59 cases, chondrolysis was reported to be associated with the use of intra-articular pain pumps. The infusate was known to include bupivacaine in 50 shoulders and lidocaine in 2. Radiofrequency capsulorrhaphy was performed in 2 shoulders. DISCUSSION Fifty-nine percent of the reported cases of glenohumeral chondrolysis occurred with the combination of arthroscopic surgery and postarthroscopy infusion of local anesthetic. The arthroscopic operations observed with chondrolysis were not limited to stabilization procedures, and the infused anesthetic was not limited to bupivacaine. CONCLUSION In that postoperative infusion of local anesthetic and radiofrequency may not be essential to the success of shoulder arthroscopy, surgeons may wish to consider the possible risks of their use.

Thermal Effects of Glenoid Reaming During Shoulder Arthroplasty in Vivo

BACKGROUND Glenoid component loosening is a common cause of failure of total shoulder arthroplasty. It has been proposed that the heat generated during glenoid preparation may reach temperatures capable of producing osteonecrosis at the bone-implant interface. We hypothesized that temperatures sufficient to induce thermal necrosis can be produced with routine drilling and reaming during glenoid preparation for shoulder arthroplasty in vivo. Furthermore, we hypothesized that irrigation of the glenoid during reaming can reduce this temperature increase. METHODS Real-time, high-definition, infrared thermal video imaging was used to determine the temperatures produced by drilling and reaming during glenoid preparation in ten consecutive patients undergoing total shoulder arthroplasty. The maximum temperature and the duration of temperatures greater than the established thresholds for thermal necrosis were documented. The first five arthroplasties were performed without irrigation and were compared with the second five arthroplasties, in which continuous bulb irrigation was used during drilling and reaming. A one-dimensional finite element model was developed to estimate the depth of penetration of critical temperatures into the bone of the glenoid on the basis of recorded surface temperatures. RESULTS Our first hypothesis was supported by the recording of maximum surface temperatures above the 56°C threshold during reaming in four of the five arthroplasties done without irrigation and during drilling in two of the five arthroplasties without irrigation. The estimated depth of penetration of the critical temperature (56°C) to produce instantaneous osteonecrosis was beyond 1 mm (range, 1.97 to 5.12 mm) in four of these patients during reaming and one of these patients during drilling, and two had estimated temperatures above 56°C at 3 mm. Our second hypothesis was supported by the observation that, in the group receiving irrigation, the temperature exceeded the critical threshold in only one specimen during reaming and in two during drilling. The estimated depth of penetration for the critical temperature (56°C) did not reach a depth of 1 mm in any of these patients (range, 0.07 to 0.19 mm). CONCLUSIONS Temperatures sufficient to induce thermal necrosis of glenoid bone can be generated by glenoid preparation in shoulder arthroplasty in vivo. Frequent irrigation may be effective in preventing temperatures from reaching the threshold for bone necrosis during glenoid preparation.

Rab23 Regulates Differentiation of ATDC5 Chondroprogenitor Cells

Insulin treatment of mouse ATDC5 chondroprogenitors induces these cells to differentiate into mature chondrocytes. To identify novel factors that are involved in this process, we carried out mutagenesis of ATDC5 cells through retroviral insertion and isolated two mutant clones incapable of differentiation. Inverse PCR analysis of these clones revealed that the retroviral DNA was inserted into the promoter region of the Rab23 gene, resulting in increased Rab23 expression. To investigate whether an elevated level of Rab23 protein led to inhibition of chondrogenic differentiation, we characterized ATDC5 cells that either overexpress endogenous Rab23 or stably express ectopic Rab23. Our results revealed that up-regulation of Rab23 can indeed inhibit chondrogenic differentiation with a concomitant down-regulation of matrix genes such as type II collagen and aggrecan. In addition, stable small interfering RNA knockdown of Rab23 also resulted in inhibition of chondrogenic differentiation as well as down-regulation of Sox9, a master regulator of chondrogenesis. Interestingly, Sox9 expression has recently been linked to Gli1, and we found that Rab23 knockdown decreased Gli1 expression in chondrocytes. Because the phenotypes of Rab23 mutations in mice and humans include defects in cartilage and bone development, our study suggests that Rab23 is involved in the control of Sox9 expression via Gli1 protein.

Shoulder Hemiarthroplasty With Nonprosthetic Glenoid Arthroplasty: The Ream and Run

Shoulder arthroplasty offers patients with glenohumeral arthritis the opportunity to regain comfort and function. Current approaches to the humeral side of the arthritic shoulder offer the patient and the surgeon robust and durable methods for anatomic positioning and fixation of a smooth and unwearing joint surface. Although humeral hemiarthroplasty can provide good results, there is some evidence that the comfort and function is less than a successful total shoulder arthroplasty. Problems with prosthetic glenoid components are loosening and wear; which now represent the dominant modes of failure of total shoulder arthroplasty. Attempts to solve the glenoid problem with interposed autograft or allograft materials have yet to provide satisfactory results in most cases. For these reasons, there has been an interest in combining a humeral hemiarthroplasty with a nonprosthetic approach to the glenoid side of the arthritic shoulder avoiding the risks associated with glenoid components and allowing unrestricted activity. In this approach, the arthritic glenoid is contoured by reaming to a concavity slightly larger in diameter than that of the humeral component. The purpose of this paper is to document the refinements in patient selection, surgical technique, and postoperative care that appear to optimize the results of this procedure.