Significant reduction of patellar height affected lower clinical outcomes and knee flexion over five-year follow-up after total knee arthroplasty

Aims This study aimed to investigate the relationship between changes in patellar height and clinical outcomes at a mean follow-up of 7.7 years (5 to 10) after fixed-bearing posterior-stabilized total knee arthroplasty (PS-TKA). Methods We retrospectively evaluated knee radiographs of 165 knees, which underwent fixed-bearing PS-TKA with patella resurfacing. The incidence of patella baja and changes in patellar height over a minimum of five years of follow-up were determined using Insall-Salvati ratio (ISR) measurement. We examined whether patella baja (ISR < 0.8) at final follow-up affected clinical outcomes, knee joint range of motion (ROM), and Knee Society Score (KSS). We also assessed inter- and intrarater reliability of ISR measurements and focused on the relationship between patellar height reduction beyond measurement error and clinical outcomes. Results The ISR gradually decreased over five years after TKA, and finally 33 patients (20.0%) had patella baja. Patella baja at the final follow-up was not related to passive knee ROM or KSS. Interestingly, when we divided into two groups - patella baja and patella normal-alta (ISR ≥ 0.8) - the patella baja group already had a lower patellar height before surgery, compared with the patella normal-alta group. The ISR measurement error in this study was 0.17. Both passive knee flexion and KSS were significantly decreased in the group with a decrease in ISR of ≥ 0.17 at final follow-up. Conclusion Patellar height gradually decreased over five years of follow-up after TKA. The reduction in patellar height beyond measurement error following TKA was associated with lower clinical outcomes. Cite this article: Bone Jt Open 2021;2(12):1075–1081.

Patella baja after intramedullary nailing of tibial fractures, using an infrapatellar/transtendinous approach, predicts worse patient reported outcome

Purpose After intramedullary nailing of tibial shaft fractures using an infrapatellar/transtendinous approach, several patients suffer anterior knee pain. We suspect that the approach is associated with soft tissue scars and the development of a postoperative patella baja. The goal of the study is to investigate whether the development of patella baja is associated with worse subjective outcomes. Methods We retrospectively analyzed all patients in our orthopedic trauma department between 2011 and 2020 who underwent tibial fracture fixation via intramedullary nailing via an infrapatellar/transtendinous approach. Pre- and postoperative lateral knee x-rays were evaluated by measurement of the Insall-Salvati Index, and nail tip position. All patients were asked to answer the self-assessment Kujala questionnaire and Lysholm questionnaire. Results We included 78 patients (age: 44 ± 18 years) with a minimum follow-up of 12 months. Mean follow up was 59 ± 25 months. We included 50 male and 28 female patients. Patella baja detected by Insall-Salvati Index could be observed in 8 (10.3%) patients. Patients with patella baja showed significant worse function measured by the Kujala score 54 ± 18 vs. 80 ± 14 (p < 0.01). Likewise, Lysholm score did show significant differences between both groups (60 ± 24 vs. 86 ± 11; p < 0.01). Nail tip position was not associated with worse subjective function. Conclusions Patella baja in patients after tibial intramedullary nailing via an infrapatellar/transtendinous approach, is associated with worse subjective function and increased pain.

Fracture of the inferior pole of the patella: tension band wiring versus transosseous reattachment

Background The optimal surgical technique for the fixation of inferior pole patellar fracture remains controversial. The aims of this study were (1) to compare clinical and radiological outcomes following fixation of inferior pole patellar fracture by using tension band wire (TBW) and transosseous reattachment (TOR) without excision of the bony fragment and (2) to determine the risk factors for postoperative radiological loss of reduction. Methods For this retrospective cohort study, consecutive patients with inferior pole patellar fracture between January 2010 and December 2017 were recruited. The patients were grouped according to their fixation method (TBW or TOR), and demographic data, clinical outcomes, and postoperative Insall–Salvati (IS) ratio were analyzed. Then, the patients were grouped according to radiological loss of reduction, the possible risk factors for loss of reduction were identified, and odds ratios were calculated. Result This study included 55 patients with inferior pole patellar fracture; 30 patients were treated using TBW and 25 were treated using TOR. Clinical failure occurred in two patients in the TBW group (7%) and three in the TOR group (12%). The rate of radiological loss of reduction was significant higher in the TOR group, whereas removal of implants was significantly more common in the TBW group. Patella baja was noted immediately after surgery in the TOR group, but the IS ratios of the two groups were similar after 3 months. Fracture displacement of more than 30 mm was the only independent risk factor for postoperative radiological loss of reduction. Conclusion For treating inferior pole patellar fracture, both TWB and TOR were effective and had a low clinical failure rate. In 60% of patients undergoing TBW fixation, however, additional surgery was required to remove the implants. Patella baja occurred immediately following TOR, but the patellar height was similar to that in the TBW group after 3 months. Surgeons should be aware of the high risk of postoperative radiological loss of reduction, especially when the fracture displacement is more than 30 mm.

Influence of patella height after patella fracture on clinical outcome: a 13-year period

Introduction The incidence of patella fracture is statistically low (0.5–1.5%) compared to other fractures of the extremities [Patella fractures 76(10):987–997, 2005]. In the latter research, patella fractures if treated surgically present an overall inferior functional outcome. Little is known about the influence of the postoperative patella height on the clinical outcome. Therefore, the aim of our study was to analyse the influence of the patella height on the patients’ functional outcome after surgery. Methods In this retrospective study the in-house trauma register of our level I University trauma center was screened for patients suffering patella fractures treated surgically. Patella height of the same patients was evaluated on lateral X-rays using the Insall–Salvati Ratio (ISR). The patients’ X-rays were analyzed at two time points for the ISR, whereas group A presents ISR data right after surgery and group B data at the latest follow up (minimum 6 weeks). The change of mean ISR at both time points was tested for significance. The functional outcome was measured by the “Munich Knee Questionaire” (MKQ). These MKQ results of different patella heights and fracture types were compared. Results The screening of our in-house trauma register revealed 375 patients between the years 2003 and 2016. Out of these 54 patients (34f, 20 m) were enrolled. In detail the follow-up time for ISR between group A and B accounted for a mean of 503.8 ± 655.7 days. The MKQ was assessed at a mean of 1367.0 ± 1042.8 days after surgery. According to the AO-classification 10% AO.34 type B and 90% AO.34 type C fractures were found. Group A showed in 9.1% a patella baja and in 27.3% a patella alta compared to group B presenting 20.0% patella baja and 14.5% patella alta. There was no significant difference in functional outcome referring to the MKQ in patella alta (MKQ 69.0% ± 18.2) or baja (MKQ 67.1% ± 17.9) (p = 0.9). No significant functional difference between AO34.type B (MKQ 74.5% ± 11.0) and AO34.type C fractures (MKQ 64.0% ± 15.0) resulted (p = 0.1). Conclusion Our results demonstrate that different postoperative patella heights apparently do not influence the functional outcome in the short follow-up.

Variables affecting patellar height in patients undergoing primary total knee replacement

Background Alteration of patellar height is commonly encountered in total knee arthroplasty (TKA), and failure to address patella baja can result in suboptimal functional outcomes. It may therefore be prudent to evaluate pre-operative patellar height (PPH) and to seek risk factors for patella baja. Methods Two hundred eighty-five patients who underwent TKA were included. Patient’s age, gender, body mass index (BMI), and history of prior arthroscopy were recorded. PPH was measured using plateau-patella angle (PPA) as well as the Blackburn-Peel (BP), Caton-Deschamps (CD), and Insall-Salvati (IS) ratios. Results The average patients’ age was 71 years with a mean BMI of 30.45. There were 191 female and 94 male patients. One-fourth of the cases had at least one prior knee arthroscopy. Multivariate linear regression analysis identified gender and BMI as variables significantly affecting the IS ratio (p: < 0.05). Gender also had a significant correlation with PPA. Male patients were likely to have lower PPA (p: < 0.03). Though increasing age had a positive correlation with patellar height, this was not statistically significant. History of prior arthroscopy had no significant effect on any of the four PPH measurements. Conclusion Lower patellar height is significantly correlated to male gender and high BMI. We suggest that obese male patients be screened for pre-operative patella baja. This can help in surgical planning and optimizing results in TKA.