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

What Factors Are Associated With Patella Baja After Internal Fixation of Patellar Fractures?

BACKGROUND

Patellar fractures represent approximately 0.5% to 1.5% of all trauma-related fractures, and patella baja, or an abnormally low-lying patella, may be a result of treatment. This complication is underappreciated, and although patella baja may result in patient discomfort, stiffness, and later degenerative changes, the association between fracture type, operative treatment, and this complication is not well described.

QUESTIONS/PURPOSES

(1) What percentage of patients treated surgically for patellar fractures developed patella baja, and which fracture patterns were more likely to demonstrate postoperative patella baja? (2) What was the association between postoperative patella baja and functional outcomes as measured by ROM and Böstman score? (3) What complications were associated with the development of patella baja?

METHODS

Between January 2018 and January 2021, we treated 3244 patients for patellar fractures at the National Center for Orthopaedics in Shanghai, PR China. The average age of the patients was 53.4 ± 12.0 years, and the male-to-female ratio was 1:1.34. After accounting for exclusion and inclusion criteria, 11% (259 of 2370) of patients were lost to follow-up before 2 years, leaving 2111 patients for review in this retrospective study at a mean of 32 ± 9 months after injury. During this time, we generally recommended surgery for patellar fractures when the fracture demonstrated an articular surface step-off exceeding 2 mm or there was loss of knee extension function. According to the AO/OTA (Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association) classification systems, the fractures were divided into eight subtypes: A1, B1, B2, C1.1, C1.2, C1.3, C2, and C3. All of these patients had CT scans and clinical data collected in our longitudinally maintained institutional database. Two independent observers classified the fractures based on the preoperative CT scan and recorded the Insall-Salvati index (ISI) on plain radiographs at the 2-year follow-up visit. An ISI of < 0.8 determined the presence of patella baja. Patient demographics, ROM, Böstman functional scores, complications, and implant removal rates were assessed. Binary logistic regression and linear regression models were employed to analyze risk factors for patella baja, associations, and treatment outcomes. Under the AO/OTA classification, the most common fracture patterns were C1.1 (30% [634 of 2111]) and C3 (25% [538 of 2111]).

RESULTS

Overall, 25% (527 of 2111) of patients had postoperative patella baja, and those with type A1 (OR 6.44 [95% confidence interval (CI) 4.57 to 9.10]), C1.3 (OR 4.96 [95% CI 3.68 to 7.10]), and C3 (OR 2.61 [95% CI 1.93 to 3.52]) fractures displayed a higher odds of developing patella baja. Patients with patella baja had poorer ROM in flexion than did patients without patella baja (116° ± 12° versus 125° ± 11° [95% CI 8.17° to 10.41°]; p < 0.01), and patients with patella baja did not have poorer Böstman scores at minimum 2-year follow-up (26.0 ± 3.2 versus 26.0 ± 3.2; p = 0.90). After controlling for potentially confounding variables such as sex, age, BMI, fracture classification, and complications, we found that fracture classification-specifically A1 (OR 6.7 [95% CI 4.8 to 9.5]), C1.3 (OR 5.0 [95% CI 3.6 to 6.9]), and C3 (OR 2.5 [95% CI 1.9 to 3.4])-deep infection (OR 10.5 [95% CI 4.2 to 26.5]; p < 0.001), and superficial infection (OR 2.4 [95% CI 1.4 to 4.4]; p = 0.003) were associated with the development of postoperative patella baja, whereas sex, BMI, and age were not. Postoperative infection was the only complication associated with patella baja.

CONCLUSION

The findings of this study underscore the importance for surgeons to be vigilant about the occurrence of patella baja after patellar fractures. In cases of the specific fracture types identified here, surgeons are encouraged to actively explore and adopt more suitable internal fixation techniques. By doing so, the incidence of postoperative patella baja may be effectively reduced, leading to better ROM and functional outcomes for patients.

LEVEL OF EVIDENCE

Level III, therapeutic study.

The effect of surgery for multipleligament knee injuries on patellar position and patellofemoral function: a retrospective study

BACKGROUND

Patients who undergo reconstruction for multiligament knee injuries (MLKIs) often exhibit knee instability and poor overall knee function during postoperative follow-up. This may be related to the changes in patellar position and decline in patellofemoral function after surgery.

OBJECTIVE

To evaluate the outcomes following reconstruction of MLKIs through the assessment of: (1) changes in patellar height; (2) anatomical changes in patellofemoral alignment, such as tilt or displacement; and (3) functional outcomes of the patellofemoral joint.

METHODS

This retrospective study included 45 patients who underwent reconstruction for MLKIs at our hospital between November 2015 and September 2022, with complete data and meeting the inclusion criteria. These patients formed the case group. An additional 20 outpatients without ligament injuries or patellar dislocation were selected as the normal control group. Patellar height changes in the case group were assessed preoperatively and postoperatively using the Caton-Deschamps (CD) and Insall-Salvati (IS) indices on lateral X-rays. Magnetic resonance imaging (MRI) was used to measure patellofemoral alignment parameters in both groups, including the sulcus angle (SA), patellar tilt angle (PTA), lateral patellofemoral angle (LPA), congruence angle (CA), and patellofemoral index (PI), to evaluate patellofemoral positioning. Additionally, the Kujala score questionnaire was used to assess the stability function of the patellofemoral joint.

RESULTS

Preoperative patellar height in the case group, measured by the CD and IS indices, was (1.07 ± 0.10, 1.10 ± 0.09), showing a statistically significant difference when compared to postoperative measurements (0.96 ± 0.13, 1.05 ± 0.10) (P < 0.05). However, postoperative patellofemoral alignment parameters, including SA, PTA, LPA, CA, and PI, in the case group showed no statistically significant differences compared to the control group (P > 0.05). At the latest follow-up, the patellofemoral function score in the case group was (89.0 ± 5.3), which was not significantly different from the control group (91.0 ± 2.9) (P > 0.05).

CONCLUSION

After reconstruction of MLKIs, patellar height decreased but remained within the normal range. Patellofemoral alignment was well-maintained, and patellofemoral function was maintained.

Dual tension band technique for patellar fractures involving articular surface and inferior pole: a retrospective cohort study and finite element analysis

Background

Fractures involving the inferior pole of the patella can lead to postoperative patella baja. For comminuted patellar fractures that affect both the articular surface and the inferior pole, we aim to explore a new fixation method that provides reliable internal stabilization while reducing the incidence of patella baja.

Methods

We conducted a finite element biomechanical study and a retrospective cohort clinical study. The finite element analysis compared the "dual tension band" technique to the traditional single tension band method using 3D models of patellar fractures. The clinical study included 66 patients with patellar fractures involving the articular surface and inferior pole, divided into two groups based on the fixation method. Outcomes were assessed using a range of motion (ROM), Böstman scores, and the Insall-Salvati Index (ISI).

Results

The finite element analysis revealed that the dual tension band technique resulted in lower maximum stress on the patella and lower displacement on the fixation devices compared to the single tension band. Clinically, patients treated with the dual tension band had significantly higher postoperative ISI values (0.93 ± 0.16 vs. 0.85 ± 0.17, p < 0.05), better ROM (123.75 ± 9.58 vs. 117.63 ± 12.28, p < 0.05), and a lower incidence of patella baja (17.86% vs. 34.21%). The Böstman scores showed no significant difference between the groups.

Conclusion

The dual tension band technique provides effective stabilization for patellar fractures involving the articular surface and inferior pole, reducing the incidence of postoperative patella baja and improving functional outcomes.

Fracture of the patella involving inferior pole is associated with postoperative patella baja - A retrospective multicenter study

BACKGROUND

The patella fracture involving of inferior pole fractures (IPF) may be associated with patella baja, However, the clinical impact of this condition remains unclear. This study aims to clarify 1) the incidence of patella baja following patellar fracture surgery, 2) the associated clinical outcomes with and without the presence of patella baja, and 3) the potential correlation between the detection of IPF on CT and the occurrence of patella baja.

METHODS

We conducted a retrospective multicenter study involving 251 patients who underwent surgical treatment for patellar fractures. Patients were divided into the patella baja (PB; n = 49) group and patella norma (PN; n = 202) group. Data collected included demographics, radiographic findings, surgical details, and postoperative complications. We compared these items between PB group and PN group. Logistic regression analyses were used to identify risk factors for patella baja.

RESULTS

Immediately following surgery, 36 (14.3%) patients presented with patella baja which increased to 49 cases (19.5%) at six months postoperatively. There is no statistically significant difference in the demographics, surgical details, clinical outcomes and complication between PB group and PN group. While, in the radiographical assessment, the prevalence of IPF on CT scan in the patella baja group was significantly higher than that in the patella norma group. By logistic regression analysis, IPFP on CT was identified as an independent risk factor for patella baja. (odds ratio 2.11, 95% confidence interval: 1.03-4.33, p = 0.042).

CONCLUSION

In patients with patellar fractures, the incidence of patella baja increased from 14.3% immediately post-surgery to 19.5% at the six-month check-up. No significant differences were observed in clinical outcomes between the patella baja group and the norma group. The patella fracture involving IPF on CT emerged as a predictive factor for patella baja.

Finite element analysis of a novel patellar fracture fixation method

BACKGROUND

Patellar fractures present challenges in treatment, with traditional methods often leading to complications such as loss of reduction and implant failure. This study aimed to compare a novel suture fixation technique with the traditional tension band method using finite element analysis.

METHODS

CT images of a healthy 35-year-old male were used to construct 3D patellar models. Two fixation methods were modeled: the novel suture technique using polyester sutures and traditional tension band fixation with Kirschner wires and cerclage wires. Finite element analysis was conducted to compare stress and pressure distribution under varying force angles.

RESULTS

The novel suture fixation method demonstrated superior stress dispersion and more uniform pressure distribution compared to the traditional tension band technique. Stress concentration was notably reduced, indicating potential for enhanced fracture stability and healing. Tensile testing confirmed the mechanical properties of the sutures, further validating the proposed method.

CONCLUSIONS

Finite element analysis revealed that the novel suture technique for patellar fractures provides better stress and pressure distribution compared to traditional methods. This approach offers promise for improved fracture stability and reduced complications. Clinical validation and long-term follow-up studies are warranted to confirm these findings and assess patient-specific outcomes.

Early Postoperative Rapid Rehabilitation Yields More Favorable Short-term Outcomes in Patients Undergoing Patellar Realignment Surgery for Recurrent Patellar Dislocation: A Prospective Randomized Controlled Study

BACKGROUND

Use of a rapid rehabilitation protocol for postoperative recovery after recurrent patellar dislocation (RPD) has gradually gained attention; nonetheless, evidence of its safety and effectiveness is lacking.

PURPOSE

To compare the short-term postoperative outcomes of early rapid rehabilitation with those of conservative rehabilitation in patients with RPD.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

A total of 50 patients with RPD who underwent tibial tubercle osteotomy combined with medial patellofemoral ligament reconstruction were enrolled between January 2018 and February 2019. Postoperatively, the patients were randomly assigned to either the early rapid group (rapid group; n = 25 patients) or the conservative group (control group; n = 25 patients) for rehabilitation training. The rapid group underwent faster progression in weightbearing and range of motion (ROM) training. Knee joint functional scores, ROM, bilateral thigh circumference differences, and imaging data were recorded preoperatively and at 6 weeks and 3, 6, 12, and 24 months postoperatively for comparison. Postoperative complications were recorded over the 24-month follow-up period.

RESULTS

The baseline data did not significantly differ between the 2 groups. Postoperatively, compared with the control group, the rapid group had higher Tegner scores at 6 weeks and 3 months; higher Lysholm scores at 3 and 6 months; higher International Knee Documentation Committee scores at 6 weeks, 3 months, and 12 months; better ROM; and smaller bilateral thigh circumference differences at 24 months (P < .05 for all). However, no differences were observed in the Tegner, Lysholm, and International Knee Documentation Committee scores at 24 months postoperatively. At the 6-week and subsequent follow-up visits, the Caton and Insall indices were lower in the control group than in the rapid group (P < .01 for all). Moreover, compared with the control group, the rapid group had a lower incidence of patella baja at 24 months (0% vs 17%) and fewer complications during the whole follow-up period (P < .01).

CONCLUSION

Early rapid postoperative rehabilitation appears to be safe and effective for patients who undergo tibial tubercle osteotomy combined with medial patellofemoral ligament reconstruction to treat RPD. In the short term, this approach was shown to be more advantageous than conservative rehabilitation in improving functional scores, allowing an earlier return to daily activities, although the lack of difference at 24 months implies no long-term benefits. In addition, it potentially helped to prevent the occurrence of complications, including patella baja.

REGISTRATION

ChiCTR1800014648 (ClinicalTrials.gov identifier).

Serial Change in Patellar Height after Tension Band Wiring of Patellar Fractures

Background and Objectives: Patella baja is a common complication after operative treatment for patellar fracture. This study aimed to investigate (1) the serial changes in patellar height and (2) the potential predictive factors for patellar height changes after tension band wiring (TBW) for patellar fractures. Materials and Methods: Forty-one patients who underwent TBW for patellar fracture between March 2019 and September 2022 were enrolled. To identify serial changes in patellar height, modified Blackburne-Peel index (mBPI) was assessed at just after surgery, at 3 months, at 6 months, at 1 year and at the final follow-up. Multiple regression analysis was conducted to identify factors correlated with mBPI difference between the contralateral side (considered as preoperative status) and injured side. Results: The postoperative mBPI exhibited a decline over time (mean mBPI immediately post operation/3 months/6 months/1 year/final follow-up: 0.69/0.63/0.63/0.62/0.61) Specifically, mBPI showed a significant reduction immediately post operation to 3 months (p < 0.001), although comparisons at other time points did not reveal significant differences. A lower position of the fracture was associated with a decrease in patellar height after surgery. Conclusions: Patellar height was mainly decreased from immediately post operation to 3 months. A fracture in a lower position of associated with decreased patellar height after the TBW of the transverse patellar fracture.

A novel patella fracture fixation technique: finite element analysis

INTRODUCTION

Patella fractures account for approximately 1% of all bone fractures. The tension band wiring technique has been used in surgical treatment. However, there is no clear information about the location of the K-wires in sagittal plane. Thus, a transverse fracture line was created in the patella finite element model and fixed with Kirchner (k) wires and cerclage at different angles and compared with two different standard tension band models.

MATERIALS AND METHODS

A total of 10 finite element models were created to study AO/OTA 34-C1 patella fractures. Two models used the classical tension band method with either circumferential or 8-shaped cerclage wire. The other 8 models used K-wires placed at 45° or 60°, either alone or combination with cerclage wire. A force of 200 N, 400 N, and 800 N were applied at 45° knee angle and the resulting data fracture line opening, surface pressure and stress in the implants were analyzed through finite element analysis.

RESULTS

When all the results are considered, it was determined that the K-wires 60° crossing at the fracture line and with cerclage modeling was superior to the other models. The diagonal placement of the K-wires with cerclage (could be 45° or 60° medium) was superior to the reference models.

CONCLUSIONS

This study has shown that the new fixation method we propose could come to the fore as an alternative method to be used successfully in transverse patella fractures and lower complications. In transverse patellar fractures, the use of K-wires crossed at 60° may be a good alternative to the standard method.

Surgical Treatment of Iatrogenic Patella Baja

PURPOSE OF REVIEW

Patella baja is characterized by a loss of patellar height and can develop as either an acute or chronic complication following a knee injury or surgical procedure. The purpose of this review is to describe the diagnosis and management of patella baja and highlight the senior author's surgical technique.

RECENT FINDINGS

The pathogenesis of patella baja involves a complex interaction between quadriceps dysfunction, immobilization, and inflammation leading to infrapatellar scarring and adhesions. It is associated with fractures about the knee and can result as a complication of surgical procedures such as anterior cruciate ligament (ACL) reconstruction, particularly bone-patellar tedon-bone autografts, high tibial osteotomies (HTOs), tibial tubercle osteotomies (TTOs), and total knee arthroplasties (TKAs). Patients with patella baja can have limited knee range of motion, anterior knee pain, significant weakness with active knee extension, and an extensor lag. Surgical intervention is indicated in cases of symptomatic patella baja. Treatment strategies include tibial tubercle proximalization, patellar tendon lengthening, and patellar tendon reconstruction. Allografts and autografts can be utilized to augment tendon lengthening or reconstructive procedures. Various small case series have reported favorable outcomes for these procedures. The treatment of patella baja is challenging and little consensus exists on optimal management, as much of the literature is limited to small case series. The preferred surgical technique of the senior author involves an end-to-end patellar tendon lengthening with hamstring autograft augmentation.

"Fishing net" suture augmenting tension-band wiring fixation in the treatment of inferior pole fracture of the patella

INTRODUCTION

Inferior pole fracture of the patella (IPFP) is difficult to repair and stabilize clinically. Although various fixation techniques have been developed, fixation strength and mobility remain daunting challenges to orthopedic surgeons. The goal of this research is to evaluate the biomechanical strength and clinical outcomes of a novel "fishing net" suture fixation procedure.

MATERIALS AND METHODS

Four finite element models, modified tension-band wiring fixation, anchor suture fixation, basket plate fixation and "fishing net" suture fixation were built to compare the fixing efficacy of "fishing net" suture fixation with three other fixation methods during IPFP fixation. From January 2018 to February 2019, 17 patients who suffered IPFP and treated by "fishing net" suture (FNS) fixation were compared with 20 patients treated by tension-band wiring (TBW) fixation in database and the two groups were evaluated postoperatively using the modified Cincinnati knee rating system.

RESULTS

Biomechanical evaluation showed that the relative displacement values of proximal patella measured by three pairs of points on both sides of the fracture line were the lowest using the "fishing net" suture fixation, while fixation using tension-band wiring and basket plate showed similar levels of stability that were less desirable than the "fishing net" method. As to clinical outcomes, there were 17 (100%) patients exhibited excellent or good results with no internal fixation failures in the FNS group compared to three internal fixation failures in the TBW group.

CONCLUSION

The biomechanical and clinical results suggest that the "fishing net" suture fixation is a viable candidate for fixation of IPFP.