Table 5. Summary of Recent Studies Comparing the Patellofemoral Outcomes of Attune and PFC Sigma Prostheses.

Study	Study design and patients	Patellofemoral outcome				Other outcome	Remark
		Outcome	Attune (%)	PFC Sigma (%)	p-value
Current study	Prospective	AKP	1.4	1.4	1.000	No significant difference in ROM, questionnaire-based outcomes	Single surgeon study, who had substantial experience with PFC Sigma; these were his first cases of Attune. Groups were comparable
	72 matched pairs	Painful crepitus	1.4	1.4	1.000
		Patellar clunk surgery	-	-	-
		Manipulation	-	-	-
Indelli et al. (2016)8)	Prospective	AKP	2	9	0.006	Significantly better ROM in Attune group	PFC Sigma surgeries done by two surgeons, whereas Attune surgeries done by a third surgeon
	100 matched pairs	Painful crepitus	1	5	0.007
		Patellar clunk surgery	-	2
Ranawat et al. (2017)7)	Prospective	AKP	13	26	0.02	No significant difference in function, ROM, and satisfaction between groups	PFC Sigma surgeries done by two surgeons; the groups were not comparable with respect to distribution of mobile-bearing and fixedbearing tibial components
	100 matched pairs	Painless crepitus	18	31	0.03
		Painful crepitus	1	4	0.37
		Manipulation	2	2	-
		Peripatellar scar excision	1	-	-
Martin et al. (2017)6)	Retrospective	Total crepitus	0.5	6.3	0.001	Significantly better ROM but lower KSS in Attune	Two surgeon-based study; groups not comparable in sex, BMI, follow-up, and preoperative scores
	1,165 PFC Sigma; 728 Attune	Symptomatic crepitus	0.1	2.7	0.001
		Patellar clunk surgery	0.1	1.6	0.002
Webb et al. (2017)5)	Retrospective	Significantly higher chances of lateral release in PFC and Sigma as compared to Attune (odds ratio of 6.3 and 2, respectively)			< 0.001	No other outcome measure investigated	Surgeries were done over a period of 30 years, hence introducing variations in techniques and instruments
	397 PFC; 1,403 Sigma; 191 Attune

AKP: anterior knee pain, ROM: range of motion, KSS: Knee Society Score, BMI: body mass index.