Patellar Options in Revision Total Knee Arthroplasty


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Patellar Options in Revision Total Knee Arthroplasty


Jesse Wolfstadt MD MSc FRCSC1 and Paul Zalzal MASc MD FRCSC2


1Division of Orthopaedic Surgery, Department of Surgery, McMaster University, Hamilton, ON, Canada


2Oakville Trafalgar Memorial Hospital, Oakville, ON, Canada


Clinical scenario



  • A 65‐year‐old woman with rheumatoid arthritis presents with a painful right total knee arthroplasty (TKA) five years after index surgery.
  • She notes anterior knee pain, difficulty ascending and descending stairs, and pain when standing up from a seated position.
  • X‐rays, bone scan, and inflammatory markers suggest aseptic loosening of her cemented, metal‐backed patellar component.

Top three questions



  1. In patients with deficient patellar bone stock, does the use of bone grafting or trabecular metal‐backed components improve outcomes compared to patellectomy?
  2. In patients with anterior knee pain following TKA with an unresurfaced patella, does secondary resurfacing reduce anterior knee pain compared to conservative management?
  3. When revising a femoral component for aseptic loosening, does retaining a well‐fixed patellar component improve outcome compared to revision to compatible patellar and femoral components?

Question 1: In patients with deficient patellar bone stock, does the use of bone grafting or trabecular metal‐backed components improve outcomes compared to patellectomy?


Rationale


Patellofemoral complications are the most common cause of re‐operation after a TKA. Poor patellar bone stock presents a challenging technical problem during revision TKA, as there is a high risk of fracture, osteonecrosis, and difficulty achieving stable fixation.


Clinical comment


Poor patellar bone stock may be encountered at the time of revision TKA. Historically, patellectomy has been associated with unfavorable outcomes due to poor quadriceps strength and abnormal knee function, and is considered a last resort for compromised patellar bone stock. Patellar resection arthroplasty (patelloplasty) may result in improvements in function when no options are available for resurfacing the deficient patella. More recently, options such as gull‐wing osteotomy, bone graft augmentation, cemented all‐polyethylene biconvex prostheses, and trabecular metal prostheses have been introduced to address poor patellar bone stock at the time of revision TKA.


Available literature and quality of the evidence


We found one study with level III evidence, 20 studies with level IV evidence, and one study with level V evidence. Most evidence is drawn from small case series from single institutions with short‐ to medium‐term follow‐up.


Findings


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,38 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


Resolution of clinical scenario



  • Patellar components should be retained during revision TKA unless they are metal‐backed or show evidence of loosening or maltracking.
  • Patellectomy and patelloplasty have poor outcomes in revision TKA and should be avoided in lieu of novel options for managing the deficient patella.
  • Bone grafting, osteotomy, biconvex cemented patella, and porous metal components offer good short‐ and medium‐term results for deficient patellae in revision TKA.

Question 2: In patients with anterior knee pain following TKA with an unresurfaced patella, does secondary resurfacing reduce anterior knee pain compared to conservative management?


Rationale


Surgeons must understand the current evidence before offering a secondary resurfacing to patients with anterior knee pain and an unresurfaced patella.


Clinical comment

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Nov 28, 2021 | Posted by in ORTHOPEDIC | Comments Off on Patellar Options in Revision Total Knee Arthroplasty
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