Alexander Bertelsen

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.

Prognostic Factors for Bacterial Cultures Positive for Propionibacterium acnes and Other Organisms in a Large Series of Revision Shoulder Arthroplasties Performed for Stiffness, Pain, or Loosening

BACKGROUND Propionibacterium acnes has been grown on culture in half of the reported cases of chronic infection associated with shoulder arthroplasty. The presence of this organism can be overlooked because its subtle presentation may not suggest the need for culture or because, in contrast to many orthopaedic infections, multiple tissue samples and weeks of culture incubation are often necessary to recover this organism. Surgical decisions regarding implant revision and antibiotic therapy must be made before the results of intraoperative cultures are known. In the present study, we sought clinically relevant prognostic evidence that could help to guide treatment decisions. METHODS We statistically correlated preoperative and intraoperative observations on 193 shoulder arthroplasty revisions that were performed because of pain, loosening, or stiffness with the results of a Propionibacterium acnes-specific culture protocol. Regression models were used to identify factors predictive of a positive culture for Propionibacterium acnes. RESULTS One hundred and eight of the 193 revision arthroplasties were associated with positive cultures; 70% of the positive cultures demonstrated growth of Propionibacterium acnes. The rate of positive cultures per shoulder increased with the number of culture specimens obtained from each shoulder. Fifty-five percent of the positive cultures required observation for more than one week. Male sex, humeral osteolysis, and cloudy fluid were each associated with significant increases of ≥ 600% in the likelihood of obtaining a positive Propionibacterium acnes culture. Humeral loosening, glenoid wear, and membrane formation were associated with significant increases of >300% in the likelihood of obtaining a positive Propionibacterium acnes culture. CONCLUSIONS Preoperative and intraoperative factors can be used to help to predict the risk of a positive culture for Propionibacterium acnes. This evidence is clinically relevant to decisions regarding prosthesis removal or retention and the need for immediate antibiotic therapy at the time of revision shoulder arthroplasty before the culture results become available. LEVEL OF EVIDENCE Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Origin of Propionibacterium in Surgical Wounds and Evidence-Based Approach for Culturing Propionibacterium from Surgical Sites

BACKGROUND To explore the origin of Propionibacterium in surgical wounds and to suggest an optimized strategy for culturing this organism at the time of revision surgery, we studied the presence of this organism on the skin and in the surgical wounds of patients who underwent revision arthroplasty for reasons other than apparent infection. METHODS Specimens were cultured in broth and on aerobic and anaerobic media. The presence and degree of positivity of Propionibacterium cultures were correlated with sex. The results of dermal and deep cultures were correlated. Times to positivity and the yields of each media type and specimen source were investigated. RESULTS Propionibacterium grew in twenty-three of thirty cultures of specimens obtained preoperatively from the unprepared epidermis over the area where a skin incision was going to be made for a shoulder arthroplasty; males had a greater average degree of positivity than females (p < 0.002). Twelve of twenty-one male subjects and zero of twenty female subjects who had cultures of dermal specimens obtained during revision shoulder arthroplasty had positive findings for Propionibacterium (p = 0.0001). Twelve of twenty male subjects and only one of twenty female subjects had positive deep cultures (p = 0.0004). The positivity of dermal cultures for Propionibacterium was significantly associated with the positivity of deep cultures for this organism (p = 0.0001). If Propionibacterium was present in deep tissues, it was likely that it would be recovered by culture if four different specimens were obtained and cultured for a minimum of seventeen days on three different media: aerobic, anaerobic, and broth. CONCLUSIONS Because the surgical incision of dermal sebaceous glands may be a source of Propionibacterium in deep wounds, strategies for minimizing the risk of Propionibacterium infections may need to be directed at minimizing the contamination of surgical wounds from these bacteria residing in rather than on the skin. Obtaining at least four specimens, observing them for seventeen days, and using three types of culture media optimize the recovery of Propionibacterium at the time of revision surgery.

Factors affecting fixation of the glenoid component of a reverse total shoulder prothesis

The semiconstrained design of the reverse arthroplasty allows loads from the humerus to challenge the fixation of the glenoid component to the scapula. We examined some of the factors affecting the quality of glenoid screw fixation, including the density of the material into which the screws are placed, the purchase of individual screws, and the direction of loading in relation to screw placement. Loads were applied by the humeral component to glenoid components with different conditions of fixation. The load to failure for each set of conditions was measured and compared statistically. Load to failure was less when the glenoid component was fixed to material of lesser density. Each screw contributed to the quality of fixation; the screw nearest the point of load application made the largest contribution. Load to failure was less when the load was colinear with a line through the nonlocking holes in the base plate compared to colinear with a line through the locking holes. In performing a reverse total shoulder, surgeons should emphasize secure intraosseous placement of the fixation screws in the best quality bone available. The placement of the inferior screw appears to be the most critical.

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.

Postsurgical Chondrolysis of the Shoulder

There are multiple reports in the literature of chondrolysis following arthroscopic shoulder surgery. Although the etiology of these cases is not known for certain, there has been speculation that radiofrequency devices, young patient age, instability surgery, intra-articular pain pumps, and type of anesthetic may be precipitating factors. This article describes a case of a 37-year-old law enforcement officer who injured both shoulders and ultimately underwent nearly identical bilateral procedures: arthroscopic superior labrum anteroposterior (SLAP) repair, Bankart repair, capsulorrhaphy, acromioplasty, and distal clavicle excision. Intra-articular pain catheters were placed following both procedures, but the right-sided catheter never functioned properly, as evidenced by continuous leakage outside of her body until it was removed. Subsequently she had an arthroscopic lysis of adhesions done for residual stiffness, in which the left humeral head and glenoid cavity were noted to be completely devoid of articular cartilage. Over the ensuing months, multiple cortisone injections, 5 viscosupplementation injections, physical therapy, and narcotics all failed to relieve her left shoulder pain. Radiographs showed significant left glenohumeral joint space narrowing and a normal-appearing joint space on the right. Our impression was postsurgical chondrolysis of the left shoulder. The patient has recently undergone humeral hemiarthroplasty with nonprosthetic glenoid arthroplasty. This case differs from others reported in the literature in that nearly identical bilateral procedures were performed by the same surgeon, yet chondrolysis only developed on the side that had a functioning postoperative pain catheter.

Comparison of Patients Undergoing Primary Shoulder Arthroplasty Before and After the Age of Fifty

BACKGROUND The reported outcomes of shoulder arthroplasty in patients under the age of fifty years are worse than those in patients over fifty. While there are several possible explanations for this finding, we explored the possibility that patients who had a primary shoulder arthroplasty when they were under fifty years of age differed from those who had the procedure when they were over fifty with respect to their pre-arthroplasty self-assessed comfort and function, sex distribution, and specific type of arthritis. METHODS The study group consisted of patients with glenohumeral arthritis who were treated with a primary shoulder arthroplasty by the same surgeon between 1990 and 2008. For each decade of age, the sex distribution, the pre-arthroplasty self-assessed shoulder comfort and function, and the prevalence of twelve different diagnoses were documented. We reviewed the series for three potential causes of worse outcomes in patients under fifty years of age as compared with those over fifty years of age: (1) a higher percentage of women, (2) a lower score for pre-arthroplasty self-assessed comfort and function, and (3) more complex pathological conditions. RESULTS Patients under the age of fifty years were not more likely than those over fifty to be female or to have a lower pre-arthroplasty self-assessed comfort and function score, but they did have more complex pathological conditions, such as capsulorrhaphy arthropathy, rheumatoid arthritis, and posttraumatic arthritis. Only 21% of the younger patients had primary degenerative joint disease, whereas 66% of the older patients had that diagnosis. This difference was significant (p < 0.000000001). CONCLUSIONS Surgeons performing shoulder arthroplasty in individuals under the age of fifty should be prepared to encounter pathological conditions such as capsulorrhaphy arthropathy, rheumatoid arthritis, and posttraumatic arthritis rather than primary osteoarthritis, which is more common in individuals older than fifty. The pathoanatomy in these younger patients may complicate the surgery, the rehabilitation, and the outcome of the shoulder arthroplasty.

Shoulder hemiarthroplasty with concentric glenoid reaming in patients 55 years old or less.

BACKGROUND Glenohumeral arthritis in younger individuals is challenging because of the complex pathology, need for extended durability, and high expectations of the patients. Humeral hemiarthroplasty combined with concentric glenoid reaming is a surgical option for the management of glenohumeral arthritis that avoids the risks of glenoid component failure and avoids the challenges of tissue interposition. The results of this procedure in young patients have not been previously reported. METHODS Sixty-five shoulders in patients who were 55 years old or less at the time of surgery underwent humeral hemiarthroplasty combined with concentric glenoid reaming and were followed for a minimum of 2 years or until the time of revision surgery. Patient self-assessments of shoulder comfort and function were compared before and after surgery. For 22 of these shoulders, standardized radiographs were available for follow-up evaluation. RESULTS Nine shoulders required revision surgery. These shoulders had 3 ± 3 prior surgeries, in comparison to 1 ± 1 prior surgeries for the unrevised group. For the 56 unrevised shoulders, the number of Simple Shoulder Test functions that could be performed improved from a mean of 4.1 before surgery to a mean of 9.5 at an average follow-up of 43 months (range, 24-85) (P < .001). For the 22 shoulders with radiographic follow-up, medial glenoid erosion averaged 1.1 mm (range, 0.0-6.3 mm) at an average of 44 months after the procedure. CONCLUSION In selected patients 55 years or younger with glenohumeral arthritis, this procedure can provide significant improvement in self-assessed shoulder comfort and function.

Propionibacterium can be isolated from deep cultures obtained at primary arthroplasty despite intravenous antimicrobial prophylaxis

BACKGROUND Propionibacterium organisms are commonly recovered from deep cultures obtained at the time of revision arthroplasty. This study sought to determine whether deep cultures obtained at the time of primary arthroplasty can be substantially positive for Propionibacterium despite thorough skin preparation and preoperative intravenous antibiotic prophylaxis. METHODS After timely administration of preoperative antibiotics chosen specifically for their activity against Propionibacterium and after double skin preparation, specimens from the dermis, fascia, capsule, synovium, and glenoid tissue were sterilely harvested from 10 male patients undergoing primary shoulder arthroplasty and were submitted for culture for Propionibacterium. RESULTS Of the 50 specimens, 7 were positive for Propionibacterium: 3 in each of 2 patients and 1 in 1 patient. The specimen sources having positive anaerobic cultures were the dermis (1 of 10), fascia (2 of 10), synovium (1 of 10), and glenoid tissue (3 of 10). None of these patients had evidence of infection at the time of the arthroplasty. DISCUSSION AND CONCLUSION Preoperative antibiotics and skin preparation do not always eliminate Propionibacterium from the surgical field of primary shoulder arthroplasty. The presence of these bacteria in the arthroplasty wound may pose a risk of delayed shoulder arthroplasty failure from the subtle type of periprosthetic infection typically associated with Propionibacterium.

A quantitative method for determining medial migration of the humeral head after shoulder arthroplasty: preliminary results in assessing glenoid wear at a minimum of two years after hemiarthroplasty with concentric glenoid reaming

HYPOTHESIS Glenoid erosion and medial migration of the humeral head prosthesis have been observed after most types of shoulder arthroplasty. A method of measuring the change in humeral head position with time after shoulder prosthetic arthroplasty was applied it to 14 shoulders that underwent humeral hemiarthroplasty with concentric glenoid reaming. We hypothesized that the measurement technique would be reproducible and that the rate of wear would be small in the series of shoulders studied. MATERIALS AND METHODS Standardized anteroposterior and axillary radiographs were obtained after surgery. Two examiners measured the position of the humeral head center in relation to scapular reference coordinates for the anteroposterior and axillary projections and plotted these values against time after surgery. The change in position was characterized as the slope of this plot. Shoulders were included if there were at least 3 sets of postoperative films, the last being at least 2 years after surgery. RESULTS The slopes measured by the 2 examiners agreed within 0.5 mm/y for the anteroposterior and the axillary projections. For the series of shoulder arthroplasties, the rate of movement of the head center toward the scapula was less than 0.4 mm/y for either examiner in either projection. DISCUSSION Medial migration is a concern after any type of shoulder arthroplasty, whether a hemiarthroplasty, a biological interpositional arthroplasty, or a total shoulder arthroplasty. Quantifying the rate of medial migration over time after shoulder arthroplasty is an important element of clinical follow-up. CONCLUSIONS This is an inexpensive, practical, and reproducible method that can be used to determine the rate of medial migration of the humeral head on plain radiographs after shoulder arthroplasty. The average rate of medial migration in the shoulders in this study was small.