Does Resurfacing the Patella Increase the Risk of Extensor Mechanism Injury within the First 2 Years after Total Knee Arthroplasty?

Abstract

Extensor mechanism injury (EMI) following total knee arthroplasty (TKA) is a potentially catastrophic complication and may lead to significant morbidity or need for revision reconstructive procedures. Patellar resurfacing (PR), while commonly performed during TKA, reduces overall patella bone stock and may increase the risk of EMI after TKA. The purpose of this study was to assess if PR in elderly patients raises the risk for subsequent EMI.

The American Joint Replacement Registry (AJRR) was queried to identify Medicare patients ≥65 years old undergoing primary elective TKA for osteoarthritis between January 2012 and March 2020. Patient age, sex, and Charlson Comorbidity Index (CCI) were collected. Records were subsequently merged with Medicare claims records and evaluated for the occurrence of patella fracture, quadriceps tendon rupture, or patellar tendon rupture based on International Classification of Diseases 9 and 10 (ICD 9/10) diagnosis codes within 2 years of TKA. Patients were stratified based on whether PR occurred or not (NR). Logistic regression was used to determine the association between PR and EMI.

A total of 453,828 TKA were eligible for inclusion and 428,644 (94.45%) underwent PR. The incidence of PR decreased from 96.06% in 2012 to 92.35% in 2022 (p < 0.001). Patients undergoing PR were more often female (60.93 vs. 58.50%, p < 0.001) and had a lower mean CCI (3.09 [1.10] vs. 3.16 [1.20], p < 0.001). Odds for EMI did not differ based on whether PR was performed (odds ratio [OR]: 0.85, 95% confidence interval [CI]: 0.65–1.11, p = 0.2246). Increasing age (OR: 1.06, 95% CI: 1.05–1.07, p < 0.0001]) and CCI (OR: 1.06, 95% CI: 0.95–1.19, p = 0.0009) were associated with EMI.

PR is commonly performed during TKA in the United States and was not found to increase odds for EMI within 2 years of TKA in patients ≥65 years old. Increased age and medical comorbidity were associated with higher odds for subsequent EMI.

Keywords

total knee arthroplasty - patellar resurfacing - extensor mechanism injury - American Joint Replacement Registry - TKA complications

Demand for primary total knee arthroplasty (TKA) in the United States continues to increase and it is estimated that 1.26 million procedures will be performed annually by 2030.[1] As more procedures are performed, it is essential to consider methods to both improve the value and reduce the potential burden for complications and associated revision TKA (rTKA).[2] Patellar resurfacing (PR) has become a controversial aspect of TKA surgery, with rates ranging from over 93% in the United States to ∼3% in Sweden and Norway.[3] While PR can improve patella tracking and has been associated with lower reoperation rates in large studies, PR has not been found to consistently improve functional outcomes and may not be cost-effective.[4] [5] [6] [7] [8] [9] Additionally, PR introduces an additional opportunity for technical error, such as overresection, asymmetric resection, or iatrogenic tendon injury, which may lead to an increased risk for patella fracture.[10] [11] [12]

Maintenance of the integrity of the extensor mechanism is of paramount importance both during and after TKA. The incidence of patella fracture after PR has been reported between 0.2 and 21%, and fracture of the nonresurfaced patella (NR) was reported at 0.05%.[13] [14] [15] However, these studies are dated and there have been improvements in implant design and surgical technique that may have reduced the incidence of periprosthetic patella fracture after TKA. The incidences of quadriceps or patellar tendon rupture after TKA are 0.10 and 0.17%, respectively.[16] [17] Once injured, reparative techniques for extensor mechanism injury (EMI), such as open reduction and internal fixation of patella fractures or primary tendon repair or reconstruction of the extensor mechanism, may be performed. The complexity of these reparative procedures may be increased, and the success of repair diminished, when PR has been performed, due to decreased bone stock, suboptimal blood supply, and the presence of a patellar button. Tendinous EMIs often require reconstruction of the extensor mechanism using tissue allograft or synthetic mesh, possibly with revision arthroplasty. Recovery from these procedures has substantial patient morbidity, as patients are subjected to restricted weight-bearing and knee range of motion for several weeks.

The purpose of this study was to determine whether PR in patients undergoing primary TKA was associated with an increased risk of early EMI using a large national joint registry. Our hypothesis was that the risk for EMI is not increased by PR at the time of TKA.

Materials and Methods

This study was reviewed and approved by our Institutional Review Board. The American Joint Replacement Registry (AJRR) was queried to identify Medicare patients ≥65 years old undergoing primary, elective TKA between January 2012 and March 2020. The AJRR has the world's largest annual procedural volume, and full details regarding data collection are available on its Web site. The query was limited to those undergoing TKA for a diagnosis of primary osteoarthritis and all TKA prosthesis types were included. Patients aged <65 years were excluded for concurrent EMI at the time of TKA, rTKA, and TKA performed for rheumatoid arthritis or posttraumatic arthritis. Patient data were correlated with supplemental Medicare claims data through the Center for Medicare and Medicaid Services (CMS) to facilitate the inclusion of all potential EMIs, and therefore, patients without a valid CMS record were also excluded. The primary outcome was the occurrence of an EMI, defined as quadriceps tendon rupture, patella fracture, or patellar tendon rupture, within 2 years of the index operation, as determined by the associated International Classification of Diseases 9 and 10 (ICD 9/10) diagnosis codes within the AJRR or CMS claims database. A full listing of included ICD 9/10 diagnosis codes is provided in [Appendix 1].

Patients were stratified based on whether PR was or was not (NR) performed at the time of TKA. Patient age, sex, and Charlson Comorbidity Index (CCI) were collected for each patient. Statistical analysis was performed using SAS version 9.4 statistical software through the AJRR in accordance with their current data utilization practices. Chi-square and Fisher's exact were utilized for categorical variables and t-tests were performed for continuous variables. Mixed effects logistic regression models were utilized to determine odds ratios (ORs) for EMI. This method was also selected due to its ability to control for random variation or clustering effects between surgeons and hospitals seen in large registry datasets.

Results

A total of 1,124,236 primary TKAs were identified within the AJRR during the study period. After exclusion criteria were applied, there were 453,828 TKAs eligible for inclusion in the study and, of those, 428,644 (94.45%) underwent PR ([Fig. 1]). The incidence of PR decreased from 96.06% in 2012 to 92.35% in 2020 (p < 0.001). There was no difference in age between the PR (72.90 y, standard deviation [SD]: 5.90) and NR (79.95 y, SD: 5.85) groups (p = 0.13). The PR group had a larger proportion of females (60.93 vs. 58.50%, p < 0.001) and a lower mean CCI (3.09 [1.10] vs. 3.16 [1.20], p < 0.001) compared with those in the NR group. There was no difference in the incidence of EMI between the PR (0.28%) and NR (0.30%) groups (p = 0.54). Characteristics of the two groups are summarized in [Table 1].

Fig. 1 Diagram depicting TKA patient exclusions from AJRR cohort to define study population. AJRR, American Joint Replacement Registry; TKA, total knee arthroplasty; OA, osteoarthritis.

Table 1 Demographics by patellar resurfacing in primary TKA

	Resurfacing
	No (N = 25,184)	Yes (N = 428,644)	Total (N = 453,828)	p-Value
Age
Mean (SD)	72.90 (5.90)	72.95 (5.85)	72.95 (5.85)	0.13
N	25184	428644	453828
Charlson comorbidity index (CCI)
Mean (SD)	3.16 (1.20)	3.09 (1.10)	3.09 (1.11)	<0.001
N	25184	428644	453828
Sex
Female	014,732 (58.50%)	261,178 (60.93%)	275,910 (60.80%)	<0.001
Male	010,452 (41.50%)	167,466 (39.07%)	177,918 (39.20%)
Extensor mechanism injury
No	025,109 (99.70%)	427,458 (99.72%)	452,567 (99.72%)	0.54
Yes	0000075 (00.30%)	001,186 (00.28%)	001,261 (00.28%)
Injury type
Tendon rupture	0000059 (78.67%)	0000877 (73.95%)	0000936 (74.23%)	0.36
Patella bone fracture	0000016 (21.33%)	0000309 (26.05%)	0000325 (25.77%)
Missing	025,109 (99.70%)	427,458 (99.72%)	452,567 (99.72%)
Year
2012	000346 (03.94%)	08,429 (96.06%)	08,775 (01.93%)	<0.001
2013	000892 (04.14%)	20,676 (95.86%)	21,568 (04.75%)
2014	01,759 (04.71%)	35,555 (95.29%)	37,314 (08.22%)
2015	02,517 (04.53%)	53,104 (95.47%)	55,621 (12.26%)
2016	03,833 (04.97%)	73,338 (95.03%)	77,171 (17.00%)
2017	05,033 (05.75%)	82,422 (94.25%)	87,455 (19.27%)
2018	04,500 (05.82%)	72,836 (94.18%)	77,336 (17.04%)
2019	04,954 (06.98%)	65,980 (93.02%)	70,934 (15.63%)
2020	01,350 (07.65%)	16,304 (92.35%)	17,654 (03.89%)

Abbreviations: SD, standard deviation; TKA, total knee arthroplasty; LCL, lower confidence level; UCL, upper confidence level.

The findings from the mixed effects logistic regression model are provided in [Table 2]. There was no difference in OR for EMI based on whether PR was performed (OR: 0.85, 95% confidence interval [CI]: 0.65–1.11, p = 0.2246). Female sex also did not significantly increase the odds for an EMI. Both increasing age (OR: 1.06, 95% CI: 1.05–1.07, p < 0.0001]) and CCI (OR: 1.06, 95% CI: 0.95–1.19, p = 0.0009) were associated with greater odds of EMI.

Table 2 Results of mixed effects logistic regression model for odds of extensor mechanism injury

Mixed effects logistic regression. Assessing extensor mechanism injury within 2 y as an outcome of TKA. N = 453,828
Parameter	Odds ratio	95% LCL	95% UCL	p-Value
Resurfacing (yes/no)	0.85	0.654	1.105	0.2246
Age (continuous)	1.057	1.045	1.07	<0001
Sex (female/male)	0.875	0.808	0.947	0.2996
CCI (continuous)	1.063	0.947	1.193	0.0009

Abbreviation: TKA, total knee arthroplasty.

Discussion

This study found PR continues to be performed at a high rate in the United States, with over 94% of patients undergoing PR at the time of primary TKA. PR was not found to be associated with an increased odds for EMI within 2 years of primary TKA in patients ≥65 years old. These findings suggest PR can safely be performed in elderly patients without increasing the rate of early EMI. However, without a large-scale prospective study to evaluate these differences, readers should not interpret these findings as definitive.

Technical factors related to PR have been previously implicated in increasing the risk for subsequent EMI. Asymmetric or overresection of the patella to a thickness <12 mm results in greater stresses and increases the risk for fracture.[10] [11] Conversely, underresection with overstuffing, malrotation of the tibia or femoral components with maltracking, or repeated activities of excessive flexion can increase shear forces, patellar strain, and subsequent injury.[18] [19] [20] Need for lateral release has also been associated with EMI, most likely due to compromise of blood supply or strain from component malalignment.[12] [20] [21] [22] Femoral component geometry and design of patella prostheses have also been associated with having increased fracture risk, particularly those with a single central peg.[12] [21] [22] [23] [24] [25] Eversion of the patella during preparation may put the tendonous insertions under excessive force, leading to diminished strength and later injury. These patients or surgical factors could not be directly assessed in this study, as they were not variables collected by the AJRR or may have gone unrecognized at the time of TKA. The incidence of PR was found to decrease during the study period. It is possible that concern for EMI contributed to a lower rate of PR; however, recent studies have demonstrated that similar results may be obtained from primary TKA regardless of how the patella is managed.[26] [27] [28] [29]

Both increased age and CCI were found to have significantly higher odds for early EMI; however, sex was not found to have significantly different odds. Male sex has previously been associated with an increased risk for patella fracture after TKA.[19] [21] [24] Other patient factors, such as obesity and higher activity levels, have also been associated with EMI; however, the association varies between studies.[23] [30]

EMI was uncommon in this study, occurring in 0.30 and 0.28% in the PR and NR groups, respectively. Previous reports have varied widely, ranging from 0.2 to 21%.[14] [15] [31] [32] [33] [34] Some of these reports were with particular designs, such as hinges, that have been associated with higher failure rates. Contemporary rates may be lower due to improvements in implant design and surgical techniques. There is limited data on the incidence of EMI with NR patella. One study reported an incidence of 0.05%.[14] Modern rates may differ due to changes in patient demographics and activity expectations for those undergoing TKA.[35]

This study is not without limitations. The study was performed using the AJRR and the findings are dependent on accurate coding. While not all U.S. hospitals participate in the AJRR, the registry does have high annual procedure volumes and includes both community and academic centers, which may increase the generalizability of the findings. Representativeness of AJRR patients and procedural characteristics have also been found to be consistent with national trends compared with the National Inpatient Sample (NIS) dataset.[36] We did limit the study to patients ≥65 years of age with CMS claims records to reduce the impact of uncaptured outcome data. Only variables collected by the registry were able to be included in the study, and other potential patient factors of interest such as bone quality or native patella thickness were unable to be evaluated. Similarly, intrinsic surgical errors, such as overresection of the patella or component malalignment in either group, could not be accounted for. The reasons why PR was or was not performed, whether risk for EMI is associated with preoperative patellar arthritis, and the mechanism or location of EMI was unable to be determined using registry data. Patellar avascular necrosis, a complication of PR and risk factor for fracture, was unable to be assessed as there are no ICD 9/10 codes specific to this diagnosis. Additionally, this study was limited to 2 years following primary TKA, and it is unknown whether the risk profile EMI after PR changes with longer follow-up. Patients with systemic inflammatory diseases were excluded and may have a different risk profile for EMI with PR.

Conclusion

While PR incidence has decreased over the past decade, it is still widely implemented in the United States. We found that PR was not an independent risk factor for EMI in patients ≥65 years old undergoing primary TKA. Other factors such as older age and higher CCI could increase the risk of EMI and should be considered in this patient population.

Conflict of Interest

None declared.

• References

• 1 Sloan M, Premkumar A, Sheth NP. Projected volume of primary total joint arthroplasty in the U.S., 2014 to 2030. J Bone Joint Surg Am 2018; 100 (17) 1455-1460
• 2 Livshetz I, Sussman BH, Papas V. et al. Analyzing the burden of revision total knee arthroplasty in the United States between 2009 and 2016. J Knee Surg 2023; 36 (02) 121-131
• 3 Heckmann N, Ihn H, Stefl M. et al. Early results from the American Joint Replacement Registry: a comparison with other national registries. J Arthroplasty 2019; 34 (7S): S125-134.e1
• 4 Pavlou G, Meyer C, Leonidou A, As-Sultany M, West R, Tsiridis E. Patellar resurfacing in total knee arthroplasty: does design matter? A meta-analysis of 7075 cases. J Bone Joint Surg Am 2011; 93 (14) 1301-1309
• 5 Pilling RW, Moulder E, Allgar V, Messner J, Sun Z, Mohsen A. Patellar resurfacing in primary total knee replacement: a meta-analysis. J Bone Joint Surg Am 2012; 94 (24) 2270-2278
• 6 Maradit-Kremers H, Haque OJ, Kremers WK. et al. Is selectively not resurfacing the patella an acceptable practice in primary total knee arthroplasty?. J Arthroplasty 2017; 32 (04) 1143-1147
• 7 Longo UG, Ciuffreda M, Mannering N, D'Andrea V, Cimmino M, Denaro V. Patellar resurfacing in total knee arthroplasty: systematic review and meta-analysis. J Arthroplasty 2018; 33 (02) 620-632
• 8 Deroche E, Batailler C, Swan J. et al. No difference between resurfaced and non-resurfaced patellae with a modern prosthesis design: a prospective randomized study of 250 total knee arthroplasties. Knee Surg Sports Traumatol Arthrosc 2022; 30 (03) 1025-1038
• 9 Zmistowski BM, Fillingham YA, Salmons HI, Ward DT, Good RP, Lonner JH. Routine patellar resurfacing during total knee arthroplasty is not cost-effective in patients without patellar arthritis. J Arthroplasty 2019; 34 (09) 1963-1968
• 10 Fitzpatrick CK, Kim RH, Ali AA, Smoger LM, Rullkoetter PJ. Effects of resection thickness on mechanics of resurfaced patellae. J Biomech 2013; 46 (09) 1568-1575
• 11 Reuben JD, McDonald CL, Woodard PL, Hennington LJ. Effect of patella thickness on patella strain following total knee arthroplasty. J Arthroplasty 1991; 6 (03) 251-258
• 12 Meding JB, Fish MD, Berend ME, Ritter MA, Keating EM. Predicting patellar failure after total knee arthroplasty. Clin Orthop Relat Res 2008; 466 (11) 2769-2774
• 13 Chalidis BE, Tsiridis E, Tragas AA, Stavrou Z, Giannoudis PV. Management of periprosthetic patellar fractures. A systematic review of literature. Injury 2007; 38 (06) 714-724
• 14 Goldberg VM, Figgie III HE, Inglis AE. et al. Patellar fracture type and prognosis in condylar total knee arthroplasty. Clin Orthop Relat Res 1988; (236) 115-122
• 15 Sheth NP, Pedowitz DI, Lonner JH. Periprosthetic patellar fractures. J Bone Joint Surg Am 2007; 89 (10) 2285-2296
• 16 Dobbs RE, Hanssen AD, Lewallen DG, Pagnano MW. Quadriceps tendon rupture after total knee arthroplasty. Prevalence, complications, and outcomes. J Bone Joint Surg Am 2005; 87 (01) 37-45
• 17 Rand JA, Morrey BF, Bryan RS. Patellar tendon rupture after total knee arthroplasty. Clin Orthop Relat Res 1989; (244) 233-238
• 18 Abolghasemian M, Samiezadeh S, Sternheim A, Bougherara H, Barnes CL, Backstein DJ. Effect of patellar thickness on knee flexion in total knee arthroplasty: a biomechanical and experimental study. J Arthroplasty 2014; 29 (01) 80-84
• 19 Ortiguera CJ, Berry DJ. Patellar fracture after total knee arthroplasty. J Bone Joint Surg Am 2002; 84 (04) 532-540
• 20 Berger RA, Crossett LS, Jacobs JJ, Rubash HE. Malrotation causing patellofemoral complications after total knee arthroplasty. Clin Orthop Relat Res 1998; (356) 144-153
• 21 Ritter MA, Herbst SA, Keating EM, Faris PM, Meding JB. Patellofemoral complications following total knee arthroplasty. Effect of a lateral release and sacrifice of the superior lateral geniculate artery. J Arthroplasty 1996; 11 (04) 368-372
• 22 Boyd Jr AD, Ewald FC, Thomas WH, Poss R, Sledge CB. Long-term complications after total knee arthroplasty with or without resurfacing of the patella. J Bone Joint Surg Am 1993; 75 (05) 674-681
• 23 Rosenberg AG, Andriacchi TP, Barden R, Galante JO. Patellar component failure in cementless total knee arthroplasty. Clin Orthop Relat Res 1988; (236) 106-114
• 24 Stulberg SD, Stulberg BN, Hamati Y, Tsao A. Failure mechanisms of metal-backed patellar components. Clin Orthop Relat Res 1988; (236) 88-105
• 25 Keating EM, Haas G, Meding JB. Patella fracture after post total knee replacements. Clin Orthop Relat Res 2003; (416) 93-97
• 26 Burnett RSJ, Boone JL, Rosenzweig SD, Steger-May K, Barrack RL. Patellar resurfacing compared with nonresurfacing in total knee arthroplasty. A concise follow-up of a randomized trial. J Bone Joint Surg Am 2009; 91 (11) 2562-2567
• 27 Ali A, Lindstrand A, Nilsdotter A, Sundberg M. Similar patient-reported outcomes and performance after total knee arthroplasty with or without patellar resurfacing. Acta Orthop 2016; 87 (03) 274-279
• 28 Shon O-J, Kim GB. Does the degree of intraoperatively identified cartilage loss affect the outcomes of primary total knee arthroplasty without patella resurfacing? A prospective comparative cohort study. Knee Surg Relat Res 2022; 34 (01) 36
• 29 Choi KY, In Y, Kim MS, Sohn S, Koh IJ. Is the patient aware of the difference between resurfaced and nonresurfaced patella after bilateral total knee arthroplasty? A systematic review of simultaneous bilateral randomized trials. Knee Surg Relat Res 2022; 34 (01) 4
• 30 Deans J, Scuderi GR. Classification and management of periprosthetic patella fractures. Orthop Clin North Am 2021; 52 (04) 347-355
• 31 Berry DJ. Epidemiology: hip and knee. Orthop Clin North Am 1999; 30 (02) 183-190
• 32 Grace JN, Sim FH. Fracture of the patella after total knee arthroplasty. Clin Orthop Relat Res 1988; (230) 168-175
• 33 Tria Jr AJ, Harwood DA, Alicea JA, Cody RP. Patellar fractures in posterior stabilized knee arthroplasties. Clin Orthop Relat Res 1994; (299) 131-138
• 34 Windsor RE, Scuderi GR, Insall JN. Patellar fractures in total knee arthroplasty. J Arthroplasty 1989; 4: S63-S67
• 35 Derman PB, Fabricant PD, David G. The role of overweight and obesity in relation to the more rapid growth of total knee arthroplasty volume compared with total hip arthroplasty volume. J Bone Joint Surg Am 2014; 96 (11) 922-928
• 36 Porter KR, Illgen RL, Springer BD. et al. Is American Joint Replacement Registry data representative of national data? A comparative analysis. J Am Acad Orthop Surg 2022; 30 (01) e124-e130

Publication History

Received: 12 April 2024

Accepted: 09 September 2024

Accepted Manuscript online:
11 September 2024

Article published online:
04 October 2024