The lowest morbidity at the time of revision TKA involves retaining a well‐fixed patellar component, but the surgeon must ensure there are no signs of loosening, wear, patellofemoral maltracking, or incompatibility between the femoral and patellar components.1,2 Most authors advocate revising a well‐fixed metal‐backed component due to high rates of failure,^3–8 although some small case series have shown high rates of complications and secondary surgery.^5,9 Several options have been proposed to address deficient patellar bone stock at the time of revision TKA.¹⁰ Patellectomy should be avoided because of poor outcomes, including persistent pain, quadriceps weakness, and extensor lag.^1,11,12 Patellar resection arthroplasty is a reasonable option and is preferred to patellectomy,¹³ although one‐third of patients have persistent anterior knee pain and there is a 15% complication rate.¹⁴ Barrack et al. found a higher level of satisfaction in patients with a retained patellar component compared to patellar resection arthroplasty (98% vs 79%, p <0.01).¹⁵ Of those studied, 47% of patients with a patellar resection arthroplasty had difficulty using stairs compared to 24% with a patellar component in place (p <0.05), and there was a higher rate of dissatisfaction, difficulty with stair climbing, and difficulty with squatting and kneeling. For cases with central bone loss with only 5–10 mm thickness remaining, an all‐polyethylene, biconvex, inlay‐type prosthesis can be used.¹ Biconvex patellar components for revision TKA with bone stock as thin as 5 mm have low complication rates at up to seven‐year follow‐up.^16,17

Hanssen described packing cancellous bone graft into a tissue flap to restore patellar bone stock, with significant improvements in Knee Society function and pain scores at a mean follow‐up of 36.7 months.¹⁸ Another group experimented with adding an Achilles tendon allograft to augment the Hanssen bone graft technique in three patients to allow early mobilization and protect against patellar fracture.¹⁹ These techniques are technically demanding and described by only a few authors. A sagittal gull‐wing osteotomy has been used with promising results in two studies.^20,21 A sagittal osteotomy is made through the articular surface followed by anterior displacement of the medial and lateral borders of the patella to create a gull‐wing or V pattern that articulates with the concave trochlear groove. Thirty knees in 28 patients with deficient patella during revision TKA (less than 8 mm thickness and cortical rim not intact) were treated with a novel technique involving an onlay prosthesis, cement, and transcortical wiring. At a mean follow‐up of 36.6 months, the Knee Society Score (KSS) improved significantly with only one complication (patellar fracture one week after surgery).²² Fisher described a rebar technique with threaded Kirschner wires (k‐wires) to create a buttress to prevent displacement of the pegs in 15 patients with deficient patellar bone stock.²³ Porous tantalum patellar components have demonstrated excellent survivorship. One study found 83% survivorship (19 of 23 patients) at a mean follow‐up of 7.7 years. Risk factors for failure were thin or avascular patellar bone and components that were secured directly to soft tissue.²⁴ Nasser and Poggie found no evidence of failure, excellent patient satisfaction, and improvements in function scores at 32‐month follow‐up for patients treated with a porous tantalum implant.²⁵