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Minerva Ortopedica e Traumatologica 2020 March;71(1):1-7

DOI: 10.23736/S0394-3410.19.03946-8


language: English

Preoperative patellar positioning as a prognostic factor in the knee replacement patient: a longitudinal prospective study

Sergio RIGONI , Mario SCAPIN, Andrea DEIDONÈ

Department of Recovery and Functional Rehabilitation, Health Units 7, Hospital of Asiago, Asiago, Vicenza, Italy

BACKGROUND: The measurement of postsurgery patellar positioning has been the subject of several studies in literature to confirm the influence of the patella alignment on the outcome of knee replacement procedures, considering that malalignment is one of the possible reasons for failure of the prosthesis itself. However, postoperative assessment does not give an accurate picture of the soft tissue tensions prior to surgery, as these are then masked by the new joint structure. This paper aims to assess whether the alteration of patellar positioning and patellofemoral biomechanics in the preoperative stage may be a prognostic factor for the development of knee rigidity in subjects undergoing total knee arthroplasty (TKA).
METHODS: This is a prospective, monocentric and randomized observational study. 36 subjects who underwent total knee arthroplasty were randomly selected from the complete patient list by simple computerized randomization. The radiological condition was evaluated in the preoperative stage (time T0, corresponding to 2 months before surgery) by using the Insall-Salvati Index, the Laurin angle and the Merchant angle to assess the positioning of the patella in relation to the femur-tibia joint and by measuring at the same time the Range of Movement (ROM) during flexion. In the postoperative period we checked the changes in ROM and muscle strength using the MRC Scale at T1 (one week after surgery) and T2 (4 weeks after surgery).
RESULTS: The patient sample consisted of 26 females and 10 males. The average age was 74.36 years, with a standard deviation of 6.62 years. We found statistically significant correlations between ROM at T1 and T2 (P value 0.0001), and between ROM at T0 and the Merchant angle (P value 0.086). The correlations between ROM at T0 and T1 (directly proportional), and between ROM at T1 and the Laurin angle (inversely proportional) showed interesting albeit not significant trends.
CONCLUSIONS: The influence of preoperative ROM on the postoperative level, endorsed by literature, was not significant in our work; however, given the observed trend, it is possible that the result will show positive changes with an increase of the sample size. The preoperative positioning of the patella does not seem to play an important role on postsurgical outcomes: according to our study, a surgical approach to the patella is justified only in extreme cases; much more important seems to be the control of inflammatory factors in the first postsurgical period.

KEY WORDS: Range of motion, articular; Arthroplasty, replacement, knee; Prognosis; Patella

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