The inverted pear glenoid: an indicator of significant glenoid bone loss

PurposeThe purpose of this study was to determine the amount of glenoid bone loss required to produce an inverted pear glenoid.Type of studyTwo-part anatomic study involving live subjects and cadaveric specimens.MethodsFrom June 2000 to April 2002, 53 patients (mean age, 30 ± 13 years) underwent arthroscopic evaluation and treatment with a diagnosis of anterior instability by the senior author (S.S.B.). Each of these patients underwent a 3-portal diagnostic arthroscopy to determine the morphology of the glenoid. Glenoids were classified as either inverted pear or non-inverted pear glenoids based on the visual appearance. The amount of glenoid bone loss was then quantified arthroscopically using a validated methodology. In addition, 6 fresh-frozen cadaveric specimens (mean age, 74.1 ± 7.4 years) were dissected and evaluated to determine the minimum amount of bone loss required to produce an inverted pear glenoid.ResultsForty-two patients were classified as having non-inverted pear glenoids and 11 patients were classified as having inverted pear glenoids. The mean amount of bone loss anteriorly was significantly more (P < .000006) in the inverted pear glenoid group (mean, 8.6 mm; range, 6 to 12 mm) than the non-inverted pear glenoid group (mean, 1.5 mm; range, 0 to 3.0 mm). The percentage of loss of glenoid width was also significantly different (inverted pear mean, 36%; range, 25% to 45% versus non-inverted pear mean, 6.2%; range, 0% to 12.5%; P < .000006). The mean amount of bone loss required in cadaveric specimens to convert a normal pear-shaped glenoid into an inverted pear glenoid was 7.5 mm (range, 6.5 to 9.0 mm), representing 28.8% of the glenoid width (range, 27% to 30%).ConclusionsThe results of this study show that the majority of patients with the diagnosis of anterior instability show some bone loss anteriorly. However, the inverted pear glenoid represents a significant amount of bone loss, at least 25% to 27% of the width of the inferior glenoid. In patients with an inverted pear glenoid, a bone grafting procedure to restore the normal articular arc of the glenoid should be strongly considered to re-establish normal stability to the shoulder.     

Superior glenoid inclination and glenoid bone loss

Correct anatomical alignment of the glenoid component is of central importance for wear and loosening in shoulder endoprostheses. The aim of this article is to review and clarify the biomechanical and clinical effects of incorrect glenoid inclination in reverse and anatomical joint replacements. Based on the literature and on our own work, statements are made about the following: (1) the glenoid inclination of a normal glenoid, a degenerative glenoid and a glenoid implant, and the consequences if superior inclination is too large, and (2) the surgical technique as well as tips and tricks for correct adjustment of the inclination. The inclination of the glenoid plane is a morphological parameter of the scapula with high individual variation and is best measured using reformatted computed tomography using three-dimensional software for reconstruction and evaluation. The standard value is between 0 and 10°. Excessive superior inclination promotes translation of the humeral head and the formation of rotator cuff tears—in a degenerative glenoid, to superior wear. The correct amount of superior inclination of the glenoid component is essential for the survival of the implant. Positioning without excessive superior inclination is therefore mandatory. Precise preoperative determination of glenoid inclination and wear is important in order to correctly plan the positioning of an implant. This serves as the basis for deciding whether a bone graft or patient-specific instrumentation is necessary. Thus, the surgeon also has prognostic parameters for the anticipation of possible complications as a result of the bone defect and abnormal orientation. However, the evaluation must always include the position of the scapula in these considerations.     

Focal cortical bone loss at the inferior aspect of the glenoid: A new radiographic sign of anterior shoulder instability

This report describes the detection of localized cortical bone loss at the inferior glenoid with the use of anteroposterior radiographs of the shoulder. This bone loss was noticed in two of 100 patients who had recurrent anterior instability of traumatic origin. Double-contrast arthrography and the operative findings disclosed that this lesion coincided anatomically with the scapular insertion of the detached anterior capsule. A survey of 544 radiographs from patients who had various other shoulder disorders did not detect any similar bony changes. Thus this pattern of bone loss, although small and uncommon, appears to be a new radiographic sign of damage to the anterior capsular mechanism.     

Treatment of glenoid loosening and bone loss due to osteolysis with glenoid bone grafting

Twenty-four patients underwent conversion of a total shoulder replacement to a humeral head replacement with glenoid bone grafting for glenoid loosening due to osteolysis. Of the 24 patients, 18 (75%) had satisfactory pain relief at a mean follow-up of 33.4 months (range, 24-63 months). Four had good pain relief with conversion back to total shoulder replacement at a mean of 11 months (range, 9-15 months) after the index procedure, thus bringing the rate of overall satisfactory pain relief to 92%. Two patients continued to report significant pain and were not satisfied with the procedure. Significant functional motion improvements were not seen (P > .05). Graft subsidence was seen in 10 of 20 cases (50%). Bone grafting of glenoid defects in revision arthroplasty provides satisfactory improvement in terms of pain relief and, by improving bone stock, allows for placement of a glenoid component at a later date if there is persistent pain. However, high rates of graft subsidence are concerning.     

Classifications of glenoid dysplasia, glenoid bone loss and glenoid loosening: a review of the literature

So far, glenoid implantation still remains a challenge and is technically demanding even for an experienced shoulder surgeon. Each shoulder pathology has its own evolution. In primary glenohumeral osteoarthritis, glenoid involvement and proper morphology vary considerably. Erosion is more posterior and inferior. In rheumatoid arthritis, glenoid erosion is more medial with a very weak and soft bone. In eccentric arthritis, glenoid erosion is most of the time superior. Glenoid component loosening has been recognized as one of the common indications for revision surgery after total shoulder arthroplasty. Scapular notching is specific to the reverse shoulder arthroplasty. Moreover, there is concern about the high frequency of glenoid components that demonstrate radiographic periprosthetic lucencies. There is little information available to guide clinical decision making regarding glenoid surgery. Placement or replacement with a standard glenoid component is usually possible. In some instances, bone graft reconstruction or the use of augmented or custom components can be an option. The purpose of this study is to evaluate the main glenoid erosion classifications.     

Recognizing anterior metaphyseal femoral bone loss during uncemented total hip arthroplasty: the skylight sign

During preparation for uncemented femoral arthroplasty, a phenomenon has been observed that indicates thinning of anterior metaphyseal bone to a critical level. Light can be seen from within the canal passing through the anterior cortex. This skylight sign alerts the surgeon that a cortical defect or fracture can occur on reaming, broaching, or component insertion. In 420 consecutive arthroplasties, a skylight sign was noted in 97 (23%) hips. In 5 of those hips an oval cortical defect was created and in 3 hips a fracture occurred during broaching or insertion. Loosening developed in 1 hip with fracture. No fractures or defects occurred in hips without a skylight sign. If a skylight sign is present, the femur is at risk and preventive measures should be taken.     

Cortical ultrasound velocity as an indicator of bone status

Normative population data are reported here for velocity of ultrasound in tibial cortical bone in a population-based sample of both men and women (n=371). The cortical measurement is highly precise with reproducibility of the order of 0.5%. As with heel and patellar trabecular velocity, tibial cortical velocity declines with age from the fourth through the ninth decades. The rate is 1.7 m/s per year in men and 4.1 m/s per year in women. Tibial cortical velocity values correlate with patellar velocity and with forearm mineral, with correlation coefficients ranging from + 0.46 to +0.54 in women and +0.27 to +0.43 in men (P<0.002 for all). Tibial velocity averaged 77–104 m/s lower (2–3%: equal to about 1 SD of the young adult normal distribution) in individuals with a history of low-energy appendicular fractures (P<0.05), and the difference remained significant after adjusting for age. However, there were no perceptible differences in tibial velocity for those with and without vertebral fractures. Odds ratios derived from logistic regression showed an approximate twofold increase in likelihood of low-energy appendicular fracture for every standard deviation decrement in velocity. Comparison of tibial velocity with patellar velocity and forearm density in the same individuals revealed tibial velocity to be more strongly associated with appendicular fractures than patellar velocity for women and about the same for men, and less strongly associated than patellar velocity for vertebral fractures. We conclude that tibial cortical velocity provides useful information about bone status in populations at risk for osteoporosis, and seems particularly well suited for assessing appendicular fracture risk.     

Managing glenoid bone loss virtual surgery—A software solution

Inaccurate placement of glenoid prosthesis in shoulder arthroplasty can lead to early loosening, instability, and failure. To address difficult glenoid morphology, patient-specific instrumentation and navigation techniques have been developed. Advanced imaging data has demonstrated utility in preoperative decision making. Cadaveric studies have subsequently shown that the application of advancing imaging and navigation can lead towards increased accuracy with prosthesis placement. Clinical trials have also shown increased accuracy with navigation and advanced imaging, but data demonstrating improved long-term outcomes and decreased complication rates is not yet available. This technology continues to evolve as a method to address glenoid bone loss and abnormal morphology.