Three-dimensional transfer of the tibial tuberosity for patellar instability with patella alta

Normal values of the axial patellotrochlear overlap on MRI: Good correlation with patellotrochlear index in patients with no patellofemoral pathology

BACKGROUND

There are several imaging-based measurements for patellofemoral height, which are obtained from sagittal images. However, these methods can be misleading with sagittal oblique slices and when the patella is tilted and/or chronically subluxated. This study aimed to describe a simple method of measuring patellar height using axial patellotrochlear overlap (APTO) on MRI.

METHODS

A retrospective observational study of 97 knees from 251 patients, excluding those with fractures, massive effusion, or patellofemoral conditions. APTO was measured as follows: (1) patellar length (P) - expressed as the number of axial images showing patellar articular cartilage; (2) trochlear overlap (T) - the number of axial images showing the overlap between patellar articular cartilage and articular cartilage of the lateral trochlea. APTO is the ratio T/P. All measurements were performed independently by six raters on two separate occasions. The raters were two orthopaedic consultants, one knee surgery fellow, two consultant musculoskeletal radiologists, and one radiology fellow. The conventional patellotrochlear index (PTI) was measured as a control for all patients by a senior musculoskeletal radiologist.

RESULTS

The mean APTO value was 36.7% (range 14.2-66.6; standard deviation 11.4). There was a positive correlation with the PTI, Pearson correlation coefficient: 0.76, P < 0.001. Intra-observer reliability was good (intraclass correlation coefficient(ICC): 0.66, 95% confidence interval (CI) 0.54, 0.76, P < 0.001). Inter-observer reliability was fair (ICC: 0.51, 95% CI 0.41, 0.6, P < 0.001).

CONCLUSIONS

APTO was shown to be a reliable measurement of patellar height and correlated with existing PTI for patellar height. Measurement of APTO on MRI could be a reliable alternative for the evaluation of patellar height. However, further studies are required to assess its validity in patients with patellofemoral pathology.

Three-dimensional transfer of tibial tuberosity for patellar instability with patella alta preserves patellar position and clinical outcomes: A minimum 3-year follow-up study

BACKGROUND

The three-dimensional (3D) transfer of tibial tuberosity has been reported to improve patellofemoral congruity and showed good clinical outcomes during the short follow-up, however, little is known about whether the patellar position and clinical outcomes are preserved at longer follow-ups and the risk factors for poor clinical outcomes.

HYPOTHESIS

We hypothesized that patellar position and clinical outcomes would be preserved and the predisposing factors were associated with poor clinical outcomes after the 3D transfer of tibial tuberosity.

PATIENTS AND METHODS

Thirty-nine patients, with a mean age of 27.9 (15-52) years, who underwent the 3D transfer of the tibial tuberosity were enrolled. Patellar position was evaluated using the Caton-Deschamps index and patellar tilt. Clinical outcomes were evaluated with Lysholm and Kujala scores pre- and postoperatively. Age, body mass index (BMI), radiographic measurements, and range of motion (ROM) were compared between the poor group (defined as <80 points on Kujala score) and the good group (≥80 points). The mean follow-up period was 54.1 (36-100) months.

RESULTS

Patellar position decreased from 1.32 (1.21-1.53) preoperatively to 0.99 (0.84-1.07) at the final follow-up, according to the Caton-Deschamps index (p < 0.01). The mean patellar tilt decreased from 26.0° (21-40°) to 15.1° (5-28°) (p < 0.01). Kujala and Lysholm scales improved from 59.1 to 54.2 to 90.1 and 91.8 at final follow-up, respectively (p < 0.01). Increased BMI, lower femorotibial angle, limited ROM, and poor preoperative clinical outcomes were the predicting factors for poor postoperative clinical outcomes (p < 0.05).

CONCLUSION

The 3D transfer for patellar instability with patella alta preserved the patellar position and clinical outcomes for at least 3 years. Predisposing factors that may potentially affect postoperative clinical outcomes of the 3D transfer of tibial tuberosity include an increased BMI, valgus knee, limited ROM, and poor preoperative clinical outcomes.

Radiographic and Clinical Outcomes After Tibial Tubercle Osteotomy for the Treatment of Patella Alta: A Systematic Review and Meta-analysis

BACKGROUND

Patella alta is a known risk factor for patellar instability and, in the setting of recurrent patellar instability with significant patella alta, correction of patellar height with a tibial tubercle osteotomy (TTO) may help decrease the failure of soft tissue-based stabilization.

PURPOSE

To perform a systematic review and meta-analysis of radiographic and clinical outcomes after TTO for patella alta.

STUDY DESIGN

Systematic review and meta-analysis; Level of evidence, 4.

METHODS

PubMed, OVID/Medline, and Cochrane databases were queried in June 2020 for studies reporting outcomes of TTO for patella alta. Data pertaining to study characteristics and design, radiographic and clinical outcome values, and incidence of complications and reoperations were extracted. DerSimonian-Laird continuous and binary random-effects models were constructed to (1) perform subgroup-based analysis of mean changes in radiographic indices after TTO and (2) quantify the pooled incidence of complications and reoperations.

RESULTS

Eight studies including 340 patients (420 knees) with a mean age of 24.7 ± 8.4 years were included. The mean follow-up was 53.1 months (range, 3-120 months), with 1 study reporting a mean follow-up of less than 2 years. The pooled mean anterior transfer was 5.6 mm; the mean medial transfer was 8.7 ± 1.3 mm; and the pooled mean distalization of the tibial tubercle was 12.2 ± 4.5 mm. Continuous random-effects meta-analysis determined that significant reductions in the mean Insall-Salvati ratio (1.40 vs 0.98, P < .001), Caton-Deschamps index (1.26 vs 0.97, P < .001), and tibial tubercle to trochlear groove ratio (18.27 vs 10.69, P < .001) were observed after TTO. The overall incidence of complications was 7.6% (95% CI, 4.8%-10.5%), while the overall incidence of reoperations was 14.3% (95% CI 6.2%-22.4%).

CONCLUSION

TTO for patellar instability in the setting of patella alta results in a significant decrease in patellar height with varying degrees of medialization depending on the utilized technique. A mean postoperative complication rate of 7.6% was reported with a reoperation incidence of 14.3%, related primarily to hardware removal.

Distalization of the Tibial Tubercle for Patellar Stabilization Combined With Medial Patellofemoral Ligament Reconstruction: Length of Distalization or Residual Patella Alta and its Affect on Outcome

BACKGROUND

Previous research supports that distal translation of the tibial tubercle osteotomy (dTTO) for patients with recurrent lateral patellar dislocation (R-LPD) and patella alta is effective for surgical patellar stabilization.

HYPOTHESIS/PURPOSE

The main purpose of this article is to evaluate (1) the results of modifying the surgical threshold and postoperative goal of patellar height measurements for surgical stabilization originated in the "menu à la carte" approach to patellar surgical stabilization and (2) the relationship between the distance distalized in millimeters and postoperative complications. Our hypothesis was that dTTO with medial patellofemoral ligament reconstruction (MPFL-R) will successfully stabilize the patella with improvement in outcome scores and few complications, using a modification of the original menu à la carte as our surgical algorithm.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 68 consecutive patients with R-LPD underwent dTTO and MPFL-R for surgical patellar stabilization by a single surgeon between May 2009 and September 2015. Surgical indications were R-LPD combined with patella alta. The surgical threshold for dTTO was Caton-Deschamps index (CDI) or Insall-Salvati ratio ≥1.4 and/or a patellar trochlear index <0.15. The postoperative surgical goal for patellar height was a CDI of 1.1 to 1.2. Length of the distalization was computed by using the CDI measurement as the primary intraoperative guide and measured intraoperatively with a ruler. Clinical, radiographic, and patient outcome measures were reviewed.

RESULTS

The mean CDI preoperatively was 1.40 and postoperatively it was 1.09. The mean distalization was 9.9 mm (range, 4-15 mm). Three patients (4.4%) had frank R-LPD postoperatively. Ten patients had residual patella alta (CDI >1.2), with 1 redislocation. Mean postoperative CDI in the recurrent dislocation group was 1.13 (range, 1.06-1.25) as compared with 1.09 (range, 0.92-1.35) in the nonrecurrent group (P = 0.65). Complications included 3 tibial fractures (4.4%) and postoperative knee arthrofibrosis in 6 patients (8.8%), with mean distalization greater in the arthrofibrosis group (P = .04). Knee injury and Osteoarthritis Outcome Score (KOOS) values improved in all domains, including a 31-point increase in Quality of Life.

CONCLUSION

dTTO with MPFL-R for patients with patella alta leads to a high rate of normalization of patellar height measurements (87%) and patellar stabilization (95.6%). Residual patella alta is not associated with an increased risk of recurrence. The length of dTTO up to 15 mm is not associated with an increase in postoperative complications, except for an increased prevalence of arthrofibrosis (8.8%).

[Osteotomy in patellofemoral malalignment]

Anterior knee pain and patellofemoral instability are the two major symptoms of patellofemoral dysbalance. Various pathologies can cause these symptoms. In recent years, axis deviations have been increasingly discussed as a cause of patellofemoral dysbalance. In the frontal axis, valgus deformities are a major risk factor, but torsional deformities may be a cause as well. Increased femoral internal rotation or increased tibial external rotation are the key pathologies. Osteotomy is the treatment of choice. Valgus deformities require varisation osteotomy, which is either performed on the femur or tibia depending on the location of the deformity. Torsional deformities are treated by external femoral or internal tibial torsional osteotomy. Femoral osteotomies are located above the femoral condyles, tibial osteotomies above the tibial tuberosity. Tibial internal torsional correction must not exceed 15° because this would jeopardise structures such as the peroneal nerve. Rehabilitation includes partial weight-bearing for four to six weeks. Hardware removal can be performed half a year after osteotomy. The relevance of axis deviations and treatment by osteotomy in patellofemoral dysbalance has been highlighted in recent reviews. Several publications report promising results after osteotomy, including significant pain relief and achievement of patellofemoral stability.

Surgical Management of Patella Alta in Patellofemoral Instability: A Systematic Review and Meta-analysis

Background

Proximal, distal, and combined proximal and distal procedures have been performed for patellofemoral instability in the presence of patella alta. No consensus exists regarding the accepted surgical management for this condition.

Purpose

To pool the outcomes of surgical management for patellofemoral instability in the presence of patella alta and to determine whether the outcomes differ for different surgical techniques.

Study Design

Systematic review; Level of evidence, 4.

Methods

This systematic review was conducted using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. All studies that reported surgical outcomes for patellofemoral instability in the presence of patella alta were included. The random-effects model was used to analyze pooled estimates of preoperative and postoperative differences for outcomes that were reported in ≥3 studies. If heterogeneity existed among the studies, further analysis was performed using random-effects meta-regression analysis, which allowed for the identification of moderators.

Results

A total of 11 studies with 546 knees were included. The pooled relative risk (RR) of having no patellofemoral dislocation and no patellofemoral apprehension or subjective instability postoperatively was 51.80 (95% CI, 20.75-129.31) and 48.70 (95% CI, 17.22-137.71), respectively. The pooled weighted mean improvement (WMI) for the Kujala and Lysholm scores postoperatively was 31.98 (95% CI, 28.66-35.30) and 35.93 (95% CI, 30.12-41.74), respectively. The pooled WMI for patellar tilt angles postoperatively was 10.94 (95% CI, 7.87-14.01). These outcomes were homogeneous across all studies. The pooled WMI for Insall-Salvati ratio, Caton-Deschamps index, and tibial tubercle-trochlear groove distance postoperatively was 0.31 (95% CI, 0.17-0.45), 0.24 (95% CI, 0.12-0.36), and 6.77 (95% CI, 1.96-11.58), respectively. These outcomes were heterogeneous across the studies, with the presence of distal procedures being a significant moderator. The presence of distal procedures had a significantly higher unweighted RR of 38.07 (95% CI, 2.37-613.09) for major complications compared with proximal procedures alone, although the incidence of minor complications was comparable (unweighted RR, 1.25; 95% CI, 0.35-4.48).

Conclusion

Surgical management for patellofemoral instability in the presence of patella alta consistently led to improvement in clinical and functional outcomes, regardless of the type of procedure performed. Distal procedures were better able to correct the patellar height and tibial tubercle-trochlear groove distance, although these procedures also posed a higher RR of subsequent surgery compared with proximal procedures alone.

Hybrid high tibial osteotomy is superior to medial opening high tibial osteotomy for the treatment of varus knee with patellofemoral osteoarthritis

PURPOSE

To evaluate patellofemoral congruity after opening wedge high tibial osteotomy (OWHTO) and hybrid HTO.

METHODS

Twenty-four knees with hybrid HTO and 24 with OWHTO were evaluated in this study. The Caton-Deschamps and modified Miura-Kawamura indices were used to evaluate pre- and post-operative patellar heights for both types of surgery. Tibial tuberosity-trochlear groove (TT-TG) distance, patellar tilt, and medial and lateral joint space at the patellofemoral joint were compared. Anterior knee pain was assessed using the Kujala anterior knee pain scale.

RESULTS

There was no significant difference between the correction angles of the hybrid HTO and OWHTO. Pre- and post-operative values for the Caton-Deschamps and modified Miura-Kawamura indices in patients who underwent hybrid HTO changed from 0.90 to 0.94 and from 0.95 to 1.03, respectively, with no significant differences noted. Following OWHTO, these values decreased significantly from 0.91 to 0.73 and from 1.06 to 0.84, respectively (p < 0.01). The post-operative patellar height after OWHTO was significantly lower than that after hybrid HTO (p < 0.01). After hybrid HTO, the TT-TG distance decreased significantly from 11.4 to 7.4 (p < 0.01), but it did not change significantly after OWHTO. Although pre- and post-operative patellar tilt were not altered significantly in either group, the medial joint space of the patellofemoral joint was significantly increased post-operatively following hybrid HTO (p = 0.035). The pre-operative Kujala scores were significantly lower in the hybrid HTO group, but post-operative scores improved in both groups.

CONCLUSIONS

Hybrid HTO provides a better post-operative patellofemoral joint than does OWHTO with regard to patellar position and reduction of the TT-TG distance, as well as improved clinical outcomes. Hybrid HTO, rather than OWHTO, is the preferred technique for the treatment of varus knees combined with patellofemoral osteoarthritis.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Distalization and Medialization of Tibial Tuberosity for the Treatment of Potential Patellar Instability with Patella Alta

Purpose  The aim of the study was to test the distalization and medialization of the tibial tuberosity (DMTT) for the treatment of patellar instability associated with patella alta, focusing on residual instability and pain. Methods  Twenty-four consecutive patients (26 knees) suffering from patellofemoral instability and patella alta were treated by DMTT. Two groups were identified, which differed for documented history of frank patella dislocation. The groups were named objective patellar instability (OPI) (history of dislocation) and potential patella instability (PPI) (no dislocation). Outcome was measured with visual analogue scale (VAS), Kujala score, and Tegner score. Comparison between groups was performed using Student's t -test, Wilcoxon rank score, and Fisher's exact test (significance at p  < 0.05). Results  At 50 ± 18 and 41 ± 18 months of follow-up, respectively, both PPI and OPI groups obtained a significant pain reduction and functional improvement. The PPI group showed a significant decrease of the subjective instability. No procedure-related complications were reported. Conclusion  This study suggests that DMTT is a viable option for PPI patients with patella alta. The outcome was comparable between PPI and OPI cases; however, decrease in subjective instability was significantly greater in PPI patients. Level of Evidence  Level III, retrospective comparative study.

Patellofemoral reconstruction for patellar instability with patella alta in middle-aged patients: Clinical outcomes

INTRODUCTION

Although several surgical treatments for patellar instability with patella alta have been reported, the clinical outcomes and optimal surgical procedures for patellar instability with patella alta in middle-aged patients are still controversial. We hypothesized that optimal surgical procedures for patellar instability with patella alta in middle-aged patients may induce good clinical outcomes with better patellofemoral geometry.

MATERIALS AND METHODS

Twelve middle-aged patients with a mean age of 44 years (range: 40-55 years), who presented with patellar instability and patella alta, were treated with a combination of several surgeries, such as medial patellofemoral ligament (MPFL) reconstruction, trochleoplasty, lateral release, and three-dimensional transfer of the tibial tuberosity, based on a surgical algorithm. Patellar position and clinical outcomes were evaluated postoperatively. The mean follow-up time was 41.5 months (range: 24-72 months).

RESULTS

Patellar position altered from 1.31 (1.21-1.53) preoperatively to 0.88 (0.69-1.06) postoperatively on the Caton-Deschamps Index (p<0.01). The tibial tuberosity-trochlear groove (TT-TG) distance altered from 21.8mm (20.1-25.8mm) to 10.3mm (5.1-14.7mm), and patellar tilt ranged from 28.1° (21-40°) to 14.6° (5-28°), respectively (p<0.01). Clinical outcomes on the Lysholm and Kujala scales improved from 43.1 and 38.4 to 86.7 and 78.3, respectively, at final follow-up (p<0.01). Surgical treatment that included trochleoplasty resulted in better outcomes than other surgical combinations without trochleoplasty (p<0.05). Sulcus angle and postoperative patellar tilt improved more in those who underwent trochleoplasty than in those who did not (p<0.05).

DISCUSSION

Surgical treatment for patellar instability with patella alta in middle-aged patients resulted in improved clinical outcomes. In particular, a combination surgery including trochleoplasty resulted in the greatest improvement in case of severe trochlear dysplasia.

LEVEL OF EVIDENCE

IV. Retrospective case series study.

Influence of age on clinical outcomes of three-dimensional transfer of the tibial tuberosity for patellar instability with patella alta

PURPOSE

To evaluate the clinical outcomes of three-dimensional (3D) transfer of the tibial tuberosity for patellar instability with patella alta, with a focus on the influence of age at initial surgery.

METHODS

Three-dimensional surgery was performed on 28 knees with a mean follow-up of 46 months. Patients were separated into three groups based on the age at initial surgery: group A, 10 knees and an average age of 16.3 ± 1.8 (14-19) years; group B, 10 knees and an average age of 22.1 ± 2.5 (20-28) years; and group C, eight knees and an average age of 44.0 ± 2.2 (40-46) years. Patellofemoral geometry improvement focused on patella alta by determining the Insall-Salvati ratio and Caton-Deschamps index, rotational malalignment by measuring the tibial tubercle-trochlear groove (TT-TG) distance, and lateral patellar subluxation by measuring the patellar tilt. Clinical outcomes were evaluated by the Lysholm and Kujala scores, which were compared before and after surgery. Cartilage degeneration was evaluated by the International Cartilage Repair Society grading system at initial arthroscopy.

RESULTS

The patellar height, TT-TG, and patellar tilt significantly improved in all groups postoperatively (p < 0.05). The Lysholm and Kujala scores also significantly improved postoperatively; however, both scores were lower in group C than in the other groups (p < 0.05). Particularly, pain scores were more severe in group C than in the other groups, and the severity of cartilage degeneration correlated with the pain scores (p < 0.05). Cartilage damage differed significantly between the groups at initial arthroscopy; particularly, group C included grades III and IV cartilage degeneration (p < 0.05).

CONCLUSIONS

Age at initial surgery may be the predicting factor for poor clinical outcomes of 3D transfer surgery. The clinical outcome may depend on the age at surgery, which correlated with cartilage damage; thus, surgeons should be given this information when patients are considered undergoing patella surgery.

LEVEL OF EVIDENCE

Therapeutic case series, Level IV.

Does Patella Tendon Tenodesis Improve Tibial Tubercle Distalization in Treating Patella Alta? A Computational Study

BACKGROUND

Patellofemoral malalignment associated with patella alta may cause pain and arthritis; because of this, the condition sometimes is treated surgically. Two common procedures are tibial tubercle distalization with or without patellar tendon tenodesis. However, the biomechanical consequences of these interventions for patella alta are not clearly understood.

QUESTIONS/PURPOSES

We evaluated changes in patellofemoral joint contact mechanics after tibial tubercle distalization and tibial tubercle distalization combined with patella tendon tenodesis. Specifically, we asked: (1) Are there biomechanical differences between these two types of procedures? (2) Is there an ideal range to distalize the patella?

METHODS

Subject-specific finite-element models were created for 10 individuals with patella alta (mean Insall-Salvati ratio of 1.34 ± 0.05). Input parameters for the finite-element models included subject-specific joint geometry, quadriceps muscle forces, and weightbearing patellofemoral joint kinematics. Virtual operations were conducted to simulate the two procedures. For distalization, the tibial tubercle and patella were displaced distally 4 mm to 20 mm in 4-mm increments based on the original model. At each level of distalization, the patella tendon was attached back to its original insertion to simulate the additional tenodesis procedure. Cartilage stress, contact area, and contact forces were quantified and compared between procedures and distalization levels.

RESULTS

Distalization and distalization + tenodesis reduced patellofemoral joint stress compared with the baseline of 1.02 ± 0.11 MPa. Distalization led to lower cartilage stress than distalization + tenodesis, and the effect size was relatively large (0.88 ± 0.10 MPa vs 0.92 ± 0.10 MPa; mean difference, 0.04 MPa [95% CI, 0.02 MPa-0.05 MPa], p < 0.01; effect size of 1.64 [Cohen's d], with Insall-Salvati ratio decreased to 0.95). For both procedures, the trend of stress reduction plateaued when the Install-Salvati ratio approached 0.95.

CONCLUSIONS

Cartilage stress appears lower using distalization as opposed to distalization + tenodesis in this finite-element analysis simulation. An Insall-Salvati ratio of 0.95 may be an ideal level for distalization; further distalization does not show additional benefits.

CLINICAL RELEVANCE

This study suggests that distalization may result in less stress than distalization + tenodesis, therefore future clinical research might be preferentially directed toward evaluating isolated distalization procedures.

Variations in kinematics and function following patellar stabilization including tibial tuberosity realignment

PURPOSE

The current study was performed to characterize the influence of patellar stabilization procedures on patellofemoral and tibiofemoral dynamic motion.

METHODS

Six knees were evaluated pre-operatively and 1 year or longer following stabilization via tibial tuberosity realignment, with simultaneous medial patellofemoral ligament reconstruction performed for five knees. Knees were imaged during extension against gravity using a dynamic CT scanner. Models representing each knee at several positions of extension were reconstructed from the images. Local coordinate systems were created within one femur, patella and tibia for each knee, with shape matching of the bones used to transfer the coordinate axes to the other models. The patellar lateral shift and tilt and tibial external rotation were quantified based on the reference axes and interpolated to flexion angles from 5° to 40°. Pre-operative and post-operative data were compared with the paired t tests.

RESULTS

Surgical realignment significantly decreased the average patellar lateral shift and tilt at low flexion angles. At 5°, surgical realignment decreased the average lateral shift from 15.5 (6.3) to 8.5 (4.7) mm and decreased the average lateral tilt from 20.8 (9.4)° to 13.8 (6.4)°. The changes were statistically significant (p<0.05) at 5° and 10° of flexion, as well as 20° for lateral shift. The average tibial external rotation also increased significantly at 30° and 40° following surgery.

CONCLUSION

Patellar stabilization including a component of tuberosity realignment reduces patellar lateral shift and tilt at low flexion angles, but the long-term influence of increased tibial external rotation on tibiofemoral function is currently unknown.

LEVEL OF EVIDENCE

Prospective comparative study, Level II.