Kaveh Sajadi, MD
The volume of shoulder replacements performed has grown exponentially in the last decade due to its success in relieving pain and improving function with modern techniques and implants, but concerns regarding its longevity remain. The most common reason for failure in the long-term is loosening of the glenoid component. Progression of radiolucent lines is a worrisome sign that may suggest glenoid component loosening. However, the presence of radiolucent lines, as noted in the article, have been reported between 0-100% of the time with the lines frequently present on immediate postoperative radiographs. The presence of lines does appear to increase with longer follow up. The significance of these lines, aside from concern for loosening, is debated.
The authors of this study performed a retrospective review of all total shoulder arthroplasties (TSAs) over an 11-year period with all-polyethylene pegged or keeled glenoid components with a minimum 2-year followup. A multi-center research database was utilized. Glenoid lines were graded by the Lazarus scale, which grades lines on a scale from 0 (no lucency) to 5 (gross loosening or shift in component position). Demographic data was collected as well as patient-reported outcome (PRO) measures, including ASES score, Constant score, UCLA score, Simple Shoulder Test score, and Shoulder Pain and Disability Index score. Patients’ active range of motion was recorded as well. The authors only examined traditional all-polyethylene cemented implants, specifically excluding patients with a central in-growth peg as a previous study by Grey SG, et al, showed significantly reduced radiolucent lines with this prosthesis. This was recently confirmed in the study by Friedman RJ, et al, which showed a rate of lucent lines in 9% of patients with the hybrid cage glenoid versus 37.6% in all polyethylene pegged glenoids (p < .0001).
A total of 492 arthroplasties were included. Three-hundred and six (306) were pegged, and 186 were keeled. At a most recent follow up, 308 glenoids (63%) showed no lucencies and therefore composed Group 0. Group 1 was the group with lucencies, and pegs were more common than keeled. Of the 184 glenoids with lucencies, 64 were grade 1 by the Lazarus scale (35%), 47 were grade 2 (26%), 38 were grade 3 (21%), 18 were grade 4 (10%), and 17 were grade 5 (9%). Those with lucencies had significantly longer follow-up than those without (5.9 v 5.1 years).
Postoperatively, range of motion in all planes improved significantly in both groups compared to preoperatively, though those with lucent lines had significantly lower forward elevation and a trend toward less external rotation than those without lines. PROs also improved in both groups compared to before surgery, but all PROs were significantly worse in those with lucent lines on the glenoid. All range of motion and PRO improvements remained greater than the minimum clinically-important differences. Complications and re-operations were more common in group 1 (lucent lines). Forward elevation and PROs declined as the Lazarus grade increased.
The authors of this study have done an excellent job clearly showing that radiolucent lines on the glenoid, seen with a high prevalence in shoulder arthroplasty, are associated with less forward elevation and worse PROs. Re-operation rates are also higher in this group, generally for glenoid component loosening. Several techniques have been described to reduce the presence of radiolucent lines, including the use of suction through the bone, careful hemostasis and cleaning of the peg or keel vault, pressurization techniques, and hybrid implants that utilize a press-fit/in-growth part in conjunction with cement. The previously mentioned studies conducted by Grey SG, et al, and Friedman RJ, et al, demonstrated a reduction in radiolucent lines that they found with the use of a central in-growth peg. In addition, the Friedman RJ, et al, study showed that this type of implant was also associated with a reduction in humeral lucent lines. As seen in the literature, a system that allows a central in-growth component will reduce radiolucent lines, which in turn could lead to better range of motion and PROs.
- Schoch BS, et al. Glenoid component lucencies are associated with poorer patient-reported outcomes following anatomic shoulder arthroplasty. J Shoulder Elbow Surg. 2019 Oct;28(10):1956-1963. doi: 10.1016/j.jse.2019.03.011. Epub 2019 Jun 13
- Grey SG, et al. Preliminary Results of a Novel Hybrid Cage Glenoid Compared to an All-Polyethylene Glenoid in Total Shoulder Arthroplasty. Bull Hosp Jt Dis (2013). 2015 Dec;73 Suppl 1:S86-91.
- Lazarus MD, et al. The radiographic evaluation of keeled and pegged glenoid component insertion. J Bone Joint Surg Am. 2002 Jul;84(7):1174-82.
- Friedman RJ, et al. Clinical and radiographic comparison of a hybridcage glenoid to a cemented polyethylene glenoid in anatomic total shoulder arthroplasty. J Shoulder Elbow Surg. 2019 Jul 16. pii: S1058-2746(19)30319-2. doi: 10.1016/j.jse.2019.04.049. [Epub ahead of print].
Kaveh Sajadi, MD, practices orthopaedics with Kentucky Bone and Joint Surgeons and is an instructor in the University of Kentucky’s residency program. He completed his residency at the Campbell Clinic and his fellowship at the NYU Langone Hospital for Joint Diseases. Dr. Sajadi is a frequent instructor at Exactech domestic and international shoulder courses.