Outcome of surgery for recurrent patellar dislocation based on the distance of the tibial tuberosity to the trochlear groove

Incidence of Complications After Tibial Tubercle Osteotomy and Tibial Tubercle Osteotomy With Distalization

BACKGROUND

Tibial tubercle osteotomy (TTO) is a well-established surgical treatment option for patellofemoral instability and pain. TTO with distalization (TTO-D) is indicated for patients with patellofemoral instability, patellar malalignment, and patella alta. The current literature demonstrates several complications that may be associated with TTO, with reportedly higher rates of complications associated with TTO-D.

PURPOSE

To analyze and compare complication rates after TTO without distalization (TTO-ND) and TTO-D and assess risk factors associated with complications.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

All skeletally mature patients who underwent TTO with or without distalization by a single surgeon between September 2014 and May 2023 with a minimum of 6 months of clinical follow-up were retrospectively reviewed. Patient factors, surgical indications, perioperative data, and complications were collected via a retrospective review of electronic medical records. Concomitant procedures were categorized as intra-articular, extra-articular, and osteotomies.

RESULTS

A total of 251 TTOs (117 TTO-D, 134 TTO-ND) were included in the study group. Postoperative complications were observed in 15 operations (6%), with arthrofibrosis as the most common complication (10 operations [4%]). TTO-D and TTO-ND had similar rates of complication (5% vs 7%; P = .793). Clinical nonunion was observed in 3 operations (3%) in the TTO-D cohort and 1 operation (1%) in the TTO-ND cohort. In the TTO-D cohort, concomitant intra-articular procedures were significantly associated with an increased likelihood of complications in a univariate model. In the TTO-ND cohort, an increased tourniquet time was significantly associated with an increased likelihood of complications in a univariate model. For all TTOs as well as the TTO-D and TTO-ND cohorts, there were no significant associations between patient or surgical variables in a multivariate model.

CONCLUSION

TTO with and without distalization is a safe procedure with low rates of complication. TTO-D was not associated with a higher rate of complications compared with TTO-ND. There was no association between complications and surgical variables for TTO procedures.

Comparison of four different screw configurations for the fixation of Fulkerson osteotomy: a finite element analysis

BACKGROUND

Conventionally, two 4.5 mm cortical screws inserted toward the posterior tibial cortex are usually advocated for the fixation of Fulkerson osteotomy. This finite element analysis aimed to compare the biomechanical behavior of four different screw configurations to fix the Fulkerson osteotomy.

MATERIALS AND METHODS

Fulkerson osteotomy was modeled using computerized tomography (CT) data of a patient with patellofemoral instability and fixed with four different screw configurations using two 4.5 mm cortical screws in the axial plane. The configurations were as follows: (1) two screws perpendicular to the osteotomy plane, (2) two screws perpendicular to the posterior cortex of the tibia, (3) the upper screw perpendicular to the osteotomy plane, but the lower screw is perpendicular to the posterior cortex of the tibia, and (4) the reverse position of the screw configuration in the third scenario. Gap formation, sliding, displacement, frictional stress, and deformation of the components were calculated and reported.

RESULTS

The osteotomy fragment moved superiorly after loading the models with 1654 N patellar tendon traction force. Since the proximal cut is sloped (bevel-cut osteotomy), the osteotomy fragment slid and rested on the upper tibial surface. Afterward, the upper surface of the osteotomy fragment acted as a fulcrum, and the distal part of the fragment began to separate from the tibia while the screws resisted the displacement. The resultant total displacement was 0.319 mm, 0.307 mm, 0.333 mm, and 0.245 mm from the first scenario to the fourth scenario, respectively. The minimum displacement was detected in the fourth scenario (upper screw perpendicular to the osteotomy plane and lower screw perpendicular to the posterior tibial cortex). Maximum frictional stress and maximum pressure between components on both surfaces were highest in the first scenario (both screws perpendicular to the osteotomy plane).

CONCLUSIONS

A divergent screw configuration in which the upper screw is inserted perpendicular to the osteotomy plane and the lower screw is inserted perpendicular to the posterior tibial cortex might be a better option for the fixation of Fulkerson osteotomy. Level of evidence Level V, mechanism-based reasoning.

How to fix a tibial tubercle osteotomy with distalisation: A finite element analysis

BACKGROUND

Antero-medialisation osteotomy combined with a distalisation procedure may require a more stable fixation as the osteotomy fragment loses both proximal and distal support. This finite element analysis aimed to compare the mechanical behaviour of different fixation techniques in tibial tubercle antero-medialisation osteotomy combined with distalisation procedure.

METHODS

Tibial tubercle osteotomy combined with distalisation was modelled based on computerised tomography data, which were acquired from a patient with patellar instability requiring this procedure. Six different fixation configurations with two 3.5-mm cortical screws (1), two 4.5-mm cortical screws (2), three 3.5-mm cortical screws (3), three 4.5-mm cortical screws (4), three 3.5-mm screws with 1/3 tubular plate (5), and four 3.5-mm screws with 1/3 tubular plate (6) were created. A total of 1654 N of force was applied to the patellar tendon footprint on the tibial tubercle. Sliding, gap formation, and total deformation between the osteotomy components were analyzed.

RESULTS

Maximum sliding (0.660 mm), gap formation (0.661 mm), and displacement (1.267 mm) were seen with two 3.5-mm screw fixation, followed by two 4.5-mm screws, three 3.5-mm screws, and three 4.5-mm screws, respectively, in the screw-only group. Overall, the minimum displacement was observed with the four 3.5-mm screws with 1/3 tubular plate fixation model.

CONCLUSIONS

Plate fixation might be recommended for tibial tubercle antero-medialisation osteotomy combined with distalisation procedure because it might allow early active range of motion exercises and weight-bearing.

Outcomes and reoperation rates after tibial tubercle transfer and medial patellofemoral ligament reconstruction: higher revision stabilization in patients with trochlear dysplasia and patella alta

PURPOSE

To determine the reoperation rate, risk factors for reoperation, and patient-reported outcomes after isolated or combined tibial tubercle transfer and medial patellofemoral ligament reconstruction, for patellofemoral instability surgery.

METHODS

Patient's records who underwent medial patellofemoral ligament reconstruction and/or tibial tubercle transfer for patellar instability by 35 surgeons from 2002 to 2018 at a single academic institution were retrospectively reviewed using CPT codes. Four-hundred-and-eighty-six patients were identified. Radiographic measurements, demographic parameters, and subsequent revision procedures and their indications were identified. A modified anterior knee pain survey was conducted by mail and with follow-up phone survey.

RESULTS

The overall rate of reoperation was 120/486 (24.7%). The most common cause for reoperation was removal of hardware 42/486 (8.6%). The rate of reoperation for isolated medial patellofemoral ligament reconstruction 43/226 (19%) was lower than that of isolated tibial tubercle transfer 45/133 (33.8%) or a combined procedure 32/127 (25.2%) (P = 0.007). Woman had a higher rate of reoperation (29.4%) compared to men (15.9%) (P = 0.002). Patients at risk for a revision stabilization procedure included those with severe trochlear morphology (C or D) (6.1%) and those with Caton-Deschamps index > 1.3 (7.3%). Patients who underwent reoperation of any kind had poorer patient-reported outcomes.

CONCLUSION

The overall reoperation rate after patellofemoral instability surgery remains high, and any reoperation portends worse patient-reported outcomes. Re-operations for instability are more likely in patients with trochlear dysplasia and patella alta and may benefit from more aggressive initial treatment, such as medial patellofemoral ligament reconstruction and tibial tubercle transfer in combination. Using the results of this study, surgeons will be able to engage in meaningful discussion with patients to counsel patients on expectations postoperatively.

LEVEL OF EVIDENCE

IV.

Extensor mechanism tendinopathy in patients with lateral patellar maltracking

OBJECTIVE

Patellar maltracking is an important subset of patellofemoral pain syndrome. We hypothesize that maltracking patients have an increased incidence of extensor mechanism dysfunction due to repetitive attempts at stabilization of the patella. Our purpose is to delineate imaging features to identify maltracking patients at risk for extensor mechanism tendinopathy.

MATERIALS AND METHODS

Retrospective review of knee MRIs performed for anterior knee pain over a year was conducted to identify 218 studies with imaging findings of maltracking. The cases were evaluated for the presence and degree of patellar and quadriceps tendinopathy, tibial tuberosity-trochlear groove distance (TT-TG) and the distribution and grade of patellofemoral chondrosis. Cases were compared to 100 healthy, age-matched control knee MRIs.

RESULTS

The mean age of maltracking patients with either patellar or quadriceps tendinosis was 41.2 years versus 48.2 years in the control population (p = 0.037). The TT-TG was significantly higher in maltracking patients with either patellar or quadriceps tendinosis at 16.49 mm versus 14.99 mm (p = 0.006). Maltrackers with isolated lateral patellofemoral chondrosis had a higher mean TT-TG at 17.4 mm versus 15.4 mm (p = 0.007). Extensor mechanism tendinosis was increased in the maltracking population compared to the controls at 57.8% versus 27.3% (p = 0.004).

CONCLUSION

Extensor mechanism tendinosis is more common in the maltracking population and occurs at a younger age. TT-TG distance is significantly increased in patients with extensor mechanism dysfunction and in patients with isolated lateral patellofemoral chondrosis. TT-TG measurement can be used independently to identifying maltrackers who may be at risk for future complications.

Clinical Comparison of Medial Patellofemoral Ligament Reconstruction With or Without Tibial Tuberosity Transfer for Recurrent Patellar Instability

BACKGROUND

No clear guidelines or widespread consensus has defined a threshold value of tibial tuberosity-trochlear groove (TT-TG) distance for choosing the appropriate surgical procedures when additional tibial tuberosity osteotomy (TTO) should be added to augment medial patellofemoral ligament (MPFL) reconstruction for recurrent patellar instability.

PURPOSE

To compare the clinical outcomes between MPFL reconstruction and MPFL reconstruction with TTO for patients who have patellar instability with a TT-TG distance of 15 to 25 mm.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

We retrospectively analyzed 81 patients who underwent surgical treatment using either MPFL reconstruction or MPFL reconstruction with TTO for recurrent patellar instability with a TT-TG distance of 15 to 25 mm; the mean follow-up was 25.2 months (range, 12.0-53.0 months). The patients were divided into 2 groups: isolated MPFL reconstruction (iMPFL group; n = 36) performed by 2 surgeons and MPFL reconstruction with TTO (TTO group; n = 45) performed by another 2 surgeons. Clinical outcomes were assessed using the Kujala score, Knee injury and Osteoarthritis Outcome Score, and Tegner activity score. Radiological parameters, including patellar height, TT-TG distance, patellar tilt, and congruence angle were compared between the 2 groups. Functional failure based on clinical apprehension sign, repeat subluxation or dislocation, and subjective instability and complications was assessed at the final follow-up. We also compared clinical outcomes based on subgroups of preoperative TT-TG distance (15 mm ≤ TT-TG ≤ 20 mm vs 20 mm < TT-TG ≤ 25 mm).

RESULTS

All of the clinical outcome parameters significantly improved in both groups at the final follow-up (P < .001), with no significant differences between groups. The radiological parameters also showed no significant differences between the 2 groups. The incidence of functional failure was similar between the 2 groups (3 failures in the TTO group and 2 failures in the iMPFL group; P = .42). In the TTO group, 1 patient experienced a repeat dislocation postoperatively and 2 patients had subjective instability; in the iMPFL group, 2 patients had subjective instability. The prevalence of complications did not differ between the 2 groups (P = .410). In the subgroup analysis based on TT-TG distance, we did not note any differences in clinical outcomes between iMPFL and TTO groups in subgroups of 15 mm ≤ TT-TG ≤ 20 mm and 20 mm < TT-TG ≤ 25 mm.

CONCLUSION

MPFL reconstruction with and without TTO provided similar, satisfactory clinical outcomes and low redislocation rates for patients who had patellar instability with a TT-TG distance of 15 to 25 mm, without statistical difference. Thus, our findings suggest that iMPFL reconstruction is a safe and reliable treatment for patients with recurrent patellar dislocation with a TT-TG distance of 15 to 25 mm, without the disadvantages derived from TTO.

Clinical outcomes and predictive factors for failure with MPFL reconstruction combined with tibial tubercle osteotomy and lateral retinacular release for recurrent patellar instability

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction combined with tibial tubercle osteotomy (TTO) and lateral retinacular release (LRR) is one of the main treatment methods for patellar instability. So far, few studies have evaluated the clinical effectiveness and assessed potential risk factors for recurrent patellar instability.

PURPOSE

To report the clinical outcomes of MPFL reconstruction combined with TTO and LRR at least three years after operation and to identify potential risk factors for recurrent patellar instability.

METHODS

A retrospective analysis of medical records for patients treated with MPFL, TTO and LRR from 2013 to 2017 was performed. Preoperative assessment for imaging examination included trochlear dysplasia according to Dejour classification, patella alta with the Caton-Deschamps index (CDI), tibial tubercle-trochlear groove distance. Postoperative assessment for knee function included Kujala, IKDC and Tegner scores. Failure rate which was defined by a postoperative dislocation was also reported.

RESULTS

A total of 108 knees in 98 patients were included in the study. The mean age at operation was 19.2 ± 6.1 years (range, 13-40 years), and the mean follow-up was 61.3 ± 15.4 months (range, 36-92 months). All patients included had trochlear dysplasia (A, 24%; B, 17%; C, 35%; D, 24%), and 67% had patellar alta. The mean postoperative scores of Tegner, Kujala and IKDC were 5.3 ± 1.3 (2-8), 90.5 ± 15.5 (24-100) and 72.7 ± 12.1 (26-86). Postoperative dislocation happened in 6 patients (5.6%). Female gender was a risk factor for lower IKDC (70.7 vs 78.1, P = 0.006), Tegner (5.1 vs 6.0, P = 0.006) and Kujala (88.2 vs 96.6, P = 0.008). Age (p = 0.011) and trochlear dysplasia (p = 0.016) were considered to be two failure factors for MPFL combined with TTO and LRR.

CONCLUSION

As a surgical method, MPFL combined with TTO and LRR would be a reliable choice with a low failure rate (5.6%). Female gender was a risk factor for worse postoperative outcomes. Preoperative failure risk factors in this study were age and trochlear dysplasia.

LEVEL OF EVIDENCE

Level IV; Case series.

Isolated medial patellofemoral ligament reconstruction for recurrent patellofemoral instability: analysis of outcomes and risk factors

Background

The medial patellofemoral ligament (MPFL) is always damaged after patellar dislocation. In selected patients, MPFL reconstruction is necessary to restore a correct patellar tracking. Despite the large number of different techniques reported to reconstruct the MPFL, there is no consensus concerning the optimal procedure, and debates is still ongoing. The present study analysed the results after isolated MPFL reconstruction in patients with patellofemoral instability. Furthermore, a subgroup analysis of patients presenting pathoanatomical risk factors was made.

Methods

In November 2020, the main electronic databases were accessed. All articles reporting the results of primary isolated MPFL reconstruction for recurrent patellofemoral instability were considered for inclusion. Only articles reporting a minimum 12-month follow-up were eligible.

Results

Data from a total of 1777 knees were collected. The mean age of the patients involved was 22.8 ± 3.4 years. The mean follow-up was 40.7 ± 25.8 months. Overall, the range of motion (+ 27.74; P < 0.0001) and all the other scores of interests improved at last follow-up: Kujala (+ 12.76; P = 0.0003), Lysholm (+ 15.69; P < 0.0001), Tegner score (+ 2.86; P = 0.006). Seventy-three of 1780 patients (4.1%) showed a positive apprehension test. Thirty of 1765 patients (1.7%) experienced re-dislocations, while 56 of 1778 patients (3.2%) showed persisting joint instability. Twenty-five of 1786 patients (1.4%) underwent revision surgeries.

Conclusion

Isolated MPFL reconstruction for recurrent patellofemoral instability provides reliable surgical outcomes. Patients with pathoanatomical predisposing factors reported worse surgical outcomes.

Measurement of tibial tuberosity-trochlear groove distance by MRI: assessment and correction of knee positioning errors

OBJECTIVE

The tibial tuberosity-trochlear groove (TTTG) distance varies with the position of the knee in the MR or CT scanner. We present and assess a simple method for adjustment of adduction or abduction of the knee.

MATERIALS AND METHODS

MRI of the knee encompassing a three-dimensional (3D) sagittal sequence including ≥ 8 cm of the proximal tibia was analyzed (29 females, 17 males; median age 45 years). Using 3D visualization software, the central longitudinal axis of the proximal tibia (TA) was constructed, and the TTTG distance was measured before and after alignment of the TA. Observer reliability was assessed with inter- and intra-class correlation coefficient (ICC) and Bland-Altman plots.

RESULTS

Adduction of the knee occurred in 26 examinations, mean 2.7° (range 0.0° to 9.4°), and abduction in 20 examinations, mean 2.6° (range 0.0° to 7.2°). Following adjustment, the mean TTTG distance increased 2.4 mm (range 0.0 to 6.7 mm) in the knees positioned in adduction and decreased 2.3 mm when in abduction (range 0.0 to 5.5 mm). The correlation coefficient (r²) between the deviation in adduction and abduction and the difference between TTTG unadjusted and adjusted was r² = 0.96. ICCs were excellent, but limits of agreement were close to ± 3 mm.

CONCLUSION

Measurement of the TTTG distance by MRI is influenced by a systematic technique-dependent error caused by knee positioning in adduction or abduction. We suggest a simple method for adjusting the positioning.

Tibial tubercle transfer leads to clinically relevant improvement in patients with patellar maltracking without instability: a systematic review and meta-analysis

PURPOSE

To assess the different surgical techniques and their outcomes following tibial tubercle transfer (TTT) in patients with patellar maltracking.

METHODS

A systematic search of the literature was performed in PubMed, EMBASE and Cochrane Library. Studies reporting patient-reported outcome measures (PROMs) or clinical outcome following: TTT in patients with patellar maltracking were included. Collected PROMs were Lysholm, Kujala, IKDC score, and VAS pain. Clinical outcome included reported clinical success, patient satisfaction, complications and removal of hardware (ROH). Overall pre-, post-operative and change scores were estimated using random-effects meta-analysis models. Results were reported as overall mean and per transfer direction.

RESULTS

A total of 26 studies and 761 patients (818 knees, mean age 35 years, mean follow-up 5.0 years) were included. In 73% of the studies, surgery was performed after failed conservative treatment. Transfer direction was anteromedial in 76% of all procedures. Overall Lysholm score improved from 61 to 91, Kujala from 52 to 85, IKDC from 53 to 81, and VAS from 6.2 to 2.5, respectively. Clinical success was reported in 79% of patients, and 80% of patients reported to have satisfactory results. Rates of complications and ROH were 13% and 29%, respectively.

CONCLUSIONS

TTT for management of patellar maltracking can lead to good results with clinically meaningful improvement, an overall clinical success of 79% and overall patient satisfaction of 80% when appreciating the underlying anatomic condition and using appropriate technique. The level of evidence was low, and large-scale prospective, comparative cohort studies with uniform outcome scales are needed to confirm these findings.

LEVEL OF EVIDENCE

IV.

Return-to-Play Guidelines After Patellar Instability Surgery Requiring Bony Realignment: A Systematic Review

Background

Recurrent patellar instability can be treated nonoperatively or surgically, and surgical management may vary based on the causative pathology in the structures surrounding the patella. Although isolated soft tissue reconstruction is among the most common operative treatments, certain patient populations require bony realignment for adequate stabilization.

Purpose

To evaluate postoperative guidelines, including return to play and rehabilitation, after bony procedures involving the tibial tubercle for patellar instability.

Study Design

Systematic review; Level of evidence, 4.

Methods

A systematic review on return-to-play guidelines was conducted with studies published from 1997 to 2019 that detailed procedures involving bony realignment by tibial tubercle osteotomies and tibial tubercle transfers with or without soft tissue reconstruction. Exclusion criteria included animal or cadaveric studies, basic science articles, nonsurgical rehabilitation protocols, and patients with mean age <18 years. Studies were assessed for return-to-play criteria, rehabilitation protocols, and bias.

Results

Included in the review were 39 studies with a total of 1477 patients and 1598 knees. Mean patient age ranged from 17.5 to 34.0 years, and mean follow-up ranged from 23 to 161 months. All 39 studies described postoperative rehabilitation; however, only 16 studies specifically outlined return-to-play criteria. The most commonly cited return-to-play criterion was quadriceps strength (62.5%). Range of motion (50.0%), physical therapy protocols (18.8%), and radiographic evidence of healing (18.8%) were other cited objective criteria for return-to-play. Four of 16 (25.0%) studies described subjective criteria for return to play, including pain, swelling, and patient comfort and confidence. Of the 11 studies that described a timeline for return to play, the range was between 2 and 6 months.

Conclusion

The results revealed that 100% of papers evaluated lacked adequate return-to-play guidelines. Moreover, timelines significantly varied among studies. More clearly defined return-to-play guidelines after tibial tubercle transfer for patellar instability are required.

[Patellar dislocation : Causes and treatment]

The causes of patellofemoral instability (PFI) are complex. In accordance with the current literature a classification was developed which clearly weights all entities and derives diagnostic and therapeutic consequences. It considers patellar instability and patellar maltracking or the complete loss of patellar tracking and differentiates into 5 types. Type 1: patellar dislocation without maltracking or instability with a low risk of redislocation. Type 2: high risk of redislocation, no maltracking. Type 3: instability and maltracking; reasons for maltracking are a) soft tissue contracture, b) patella alta, c) pathological tibial tuberosity trochlear groove (TTTG) distance, c) valgus deformities and e) torsional deformities. Type 4: massively unstable floating patella, which is based on a high-grade trochlear dysplasia. Type 5: maltracking without instability.

Tibial Tubercle-Midepicondyle Distance Can Be a Better Index to Predict the Outcome of Medial Patellofemoral Ligament Reconstruction Than Tibial Tubercle-Trochlear Groove Distance

Purpose

To compare the clinical utility of tibial tubercle-midepicondyle (TT-ME) and tibial tubercle-trochlear groove (TT-TG) distances in predicting the risk for recurrent instability after isolated MPFL reconstruction.

Methods

A consecutive series of patients with recurrent patellar dislocation who underwent isolated MPFL reconstruction made up the study population. The patients were followed for a minimum of 2 years. In assessment of surgical outcome, the patient was deemed to exhibit “postoperative recurrent patellar instability” when ≥1 of the following 3 conditions was identified: redislocation, positive apprehension sign, and positive J-sign (manifestation of abnormal patellar tracking). As for radiological parameters for position of the tibial tubercle, TT-ME distance (transverse distance between the tibial tubercle and midpoint of the transepicondylar line) and TT-TG distance were measured on axial computed tomography images. The clinical utility as a factor to predict the outcome of MPFL reconstruction was compared between the 2 distances using receiver operating characteristic (ROC) analysis. In addition, various radiological indices potentially influencing the surgical outcome were subjected to multivariable logistic regression analysis.

Results

We examined 38 knees in 38 patients with a mean age at surgery of 17.6 years. Postoperative recurrent patellar instability was encountered in 8 of the 38 knees. The ROC curve analysis showed the TT-ME distance to be a significantly better indicator in predicting surgical outcome than the TT-TG distance (P = .001). The univariate analysis for radiological factors demonstrated that the TT-ME distance was significantly associated with postoperative recurrent patellar instability (odds ratio 1.42, P = .012) whereas all other factors including the TT-TG distance did not correlate with recurrent instability. The multivariable logistic regression analysis revealed that only the TT-ME distance was significantly associated with recurrent instability (P = .035).

Conclusions

Analysis of our patient population undergoing isolated MPFL reconstruction showed that the TT-ME distance was a significantly better indicator than the TT-TG distance to predict the risk for recurrent instability after isolated MPFL reconstruction performed for patellar instability.

Level of Evidence

Level IV, therapeutic case series.

The Outcomes of Isolated Lateral Release in Patellofemoral Instability: A Systematic Review and Meta-Analysis

There have been conflicting reports regarding the outcomes of lateral release when used in the management of patellofemoral instability. This systematic review and meta-analysis therefore aims to evaluate the outcomes of isolated lateral release in the management of patellofemoral instability. The review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All studies that reported the outcomes of isolated lateral release for recurrent patellofemoral dislocations were included. A total of 10 publications were included, with 204 knees. All studies consistently reported a decrease in the rates of patellofemoral dislocation (odds ratio [OR] < 0.01; 95% confidence interval [CI]: <0.01-0.01) and an increase in the odds of having a good outcome (OR 0.01; 95% CI: <0.01-0.02) after lateral release. All studies also consistently reported a similar number of patients participating in sports postoperatively as compared with preinjury (OR 2.78; 95% CI: 0.53-14.68). A total of 28 (14.1%) out of 198 patients had postoperative dislocation. Of these patients, 15 required a secondary procedure for patellofemoral realignment; however, all patients who had their eventual outcomes reported still had a good outcome postoperatively. Isolated lateral release can lead to good short- to middle-term outcomes when used in the management of recurrent patellofemoral dislocations. The procedure can lead to a significantly decreased rate of recurrence of patellofemoral dislocations, a significantly increased rate of good outcomes, and a similar number of patients being able to participate in sports as compared with the number of patients participating in sports prior to having patellofemoral dislocations. An isolated lateral release could therefore potentially serve as a simple and relatively low-risk procedure that could be performed as a first-line surgical management in selected patients with patellofemoral instability, allowing them to possibly avoid a more complex and major operation. This is a Level IV study.

New standardization method of tibial tubercle-posterior cruciate ligament distance according to patient size in patients with patellofemoral instability

BACKGROUND

Large differences in tibial tubercle-posterior cruciate ligament (TT-PCL) distance were described in several reports between countries, suggesting that abnormal TT-PCL distance is variable due to individual patient size. This study aimed to clarify the relationship between TT-PCL distance and patient size, and to determine a method for describing individualized TT lateralization.

METHODS

We analyzed 41 patients with recurrent patellar dislocation (RPD) and 41 age-matched patients without patellar instability who underwent primary anterior cruciate ligament reconstruction (control). TT-PCL distance and tibia width (TW) were measured based on preoperative T2-weighted magnetic resonance imaging. Then, TT-PCL distance was standardized based on TW (TT-PCL ratio), and TT-PCL distance and ratio were compared between groups. Correlations were investigated among TT-PCL distance, TT-PCL ratio and each measurement (patient height, weight, TW).

RESULTS

Strong positive correlations were observed between TW and patient height, and weak or moderate positive correlations were found between TT-PCL distance and each parameter. The mean TT-PCL distance was 21.2 and 20.6 mm (P = .39), while the mean TT-PCL ratio was 31.6% and 29.0% (P = .0093) in the RPD and control groups, respectively. The TT-PCL ratio was <34% in 39 of 41 knees (95.1%) in the control group. No correlation was indicated between the TT-PCL ratio and patient size.

CONCLUSIONS

Our findings demonstrate that the TT-PCL ratio is not affected by patient size, although the TT-PCL distance is associated with knee size and patient height. The TT-PCL ratio could be an important index for identifying patients for whom distal realignment surgery should be considered.

Highly variable tibial tubercle-trochlear groove distance (TT-TG) in osteoarthritic knees should be considered when performing TKA

PURPOSE

The tibial tubercle-trochlear groove distance (TT-TG) is an established measurement to assist diagnosis and treatment of patellofemoral instability. However, little is known about the distribution of TT-TG in osteoarthritic knees. The purpose of the current study is to investigate the TT-TG in a large cohort of osteoarthritic knees and to analyse, in particular, the association of knee alignment and TT-TG.

METHODS

Data from 962 consecutive patients [455 male, 507 female; mean age ± SD 70.8 ± 9.3 (37-96)] who had undergone 3D-CT and preoperative knee planning with validated commercial 3D planning software before total knee arthroplasty (TKA) were collected prospectively. The TT-TG, coronal hip knee ankle angle (HKA), femoral anteversion (AVF), external tibial torsion (ETT), and femorotibial rotation (Rot FT) were analysed. Pearson correlations were performed to assess correlations between TT-TG, mechanical axis, and rotational parameters (p < 0.05).

RESULTS

HKA showed a strong correlation with TT-TG (r = 0.488; p < 0.001) with 98 (67.1%) and 45 (30.8%) of valgus knees having respective abnormal and pathological TT-TG values. There were no significant correlations between parameters of rotational alignment (AVF, ETT, Rot FT) and TT-TG. Mean TT-TG was 12.9 ± 5.6 mm, ranging from 0.0 to 33.7 mm. 325 (33.8%) of all patients had abnormal (> 15 mm) and 101 (10.5%) had pathological (> 20 mm) values. A varus alignment was present in 716 (74.4%) of the cases (HKA < - 1.5°), a neutral alignment in 100 (10.4%), and a valgus alignment in 146 (15.2%) (HKA > 1.5°).

CONCLUSION

A wide variation of TT-TG values in osteoarthritic knees was shown by our results. There was a relevant influence of coronal limb alignment on the TT-TG-the more valgus the higher and more pathological the TT-TG. With the aim of having a more personalised TKA, the individual TT-TG should be taken into account to improve the outcome.

LEVEL OF CLINICAL EVIDENCE

III. Retrospective cohort study.

No Difference in Outcome Between Femoral Soft-Tissue and Screw Graft Fixation for Reconstruction of the Medial Patellofemoral Ligament: A Randomized Controlled Trial

PURPOSE

The aim of the present randomized controlled trial was to compare 2 different medial patellofemoral ligament reconstruction (MPFL-R) techniques that utilize different femoral fixation principles, which could affect subjective clinical outcomes and surgical morbidity.

METHODS

Sixty patients were randomly assigned to 2 MPFL-R techniques: bone or soft-tissue fixation of the graft at the femoral condyle. Patients had operations performed between 2010 and 2015 at a single center. Indication for surgery was 2 or more patellar dislocations. When the bone fixation technique was used, the gracilis tendon was fixed with the use of an interference screw. When the soft-tissue fixation technique was used, the gracilis tendon was looped around the adductor magnus tendon. Both techniques used patella-graft fixation with drill holes in the medial patellar edge. Clinical outcomes were evaluated by means of Kujala, knee injury and osteoarthritis outcome, and pain scores before the operation and at 1- and 2-year follow-up examinations. Surgical morbidity was evaluated by pain on palpation along the reconstruction site.

RESULTS

Kujala scores were 88 and 89 for bone and soft-tissue fixation groups, respectively, with no difference between groups (P = .73). No significant differences in knee injury osteoarthritis outcome or pain scores were found. Analysis of surgical morbidity, defined as femoral-based tenderness overlying the fixation site, demonstrated that 13% and 12% of patients had significant tenderness at the reconstruction site after bone and soft-tissue MPFL-R, respectively. No patellar re-dislocations were observed in either group.

CONCLUSIONS

MPFL-R with soft-tissue graft fixation at the femoral condyles resulted in findings for subjective clinical outcome, patellar stability, and pain level similar to those associated with MPFL-R with bone fixation. Surgical morbidity was also similar between patients who had soft-tissue and those who had bone fixation MPFL-R. Soft-tissue femoral graft fixation does not result in inferior clinical outcomes compared with screw fixation, and it can be used safely for MPFL-R.

Influence of patient-related factors on clinical outcome of tibial tubercle transfer combined with medial patellofemoral ligament reconstruction

BACKGROUND

Tibial tubercle transfer is frequently used for treating patellar instability. This study aimed to analyze the clinical results following tibial tuberosity transfer with medial patellofemoral ligament (MPFL) reconstruction in the treatment of patellar instability.

METHODS

Seventy-two cases presenting a lateralized tibial tubercle were treated with tibial tuberosity transfer and MPFL reconstruction. Pre-operative and postoperative pain levels and knee function were evaluated using common scoring systems. Cartilage status was assessed at the time of surgery, and the influence of patient-related factors was analyzed. Median and interquartile ranges were used to present the results.

RESULTS

After a mean of 27.6 (12 -76) months, a re-dislocation rate of 4.2% and significant improvement in knee function from a median of 48.0 (33 -70) to 83.0 (68 -94) and a median of 44.0 (24 -62) to 85.0 (69 -93), based on Kujala (P ≤ 0.001) and Lysholm (P ≤ 0.001) scores were observed. The Tegner score significantly increased from a median of 3.0 (2 -4) to 4.0 (4 -5) (P ≤ 0.001), while the pain level decreased from a median of 5.0 (3 -8) to 2.0 (0 -3) (P ≤ 0.001). Cartilage lesions were found in 55/72 (76.4%) knees. The likelihood of finding II° cartilage lesions was six times higher in cases of ≥ two previous operations.

CONCLUSION

Tibial tuberosity transfer with MPFL reconstruction allowed reliable patellar stabilization with a low re-dislocation rate. Patient age and unsuccessful attempts at surgical stabilization posed significant risk factors for cartilage lesions and may have limited postopertive outcomes.

Complications After Tibial Tuberosity Osteotomy: Association With Screw Size and Concomitant Distalization

Background:

Tibial tuberosity osteotomy (TTO) is a versatile procedure commonly used to treat patellar instability as well as to unload cartilage lesions. TTO with concomitant distalization (TTO-d) may be performed in patients with patella alta to stabilize the patella by helping it to engage in the trochlea earlier during flexion.

Purpose:

To identify and compare perioperative complications in patients who underwent TTO and those who underwent TTO-d and to analyze risk factors associated with these complications.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

We retrospectively identified perioperative complications and associated factors from medical records for 240 patients who underwent TTO with or without distalization performed by 2 surgeons at 2 institutions between 2009 and 2015. A musculoskeletal radiologist at each institution determined osteotomy union using a published grading system. Significance was set at P < .01.

Results:

Of the 240 patients, 153 (122 TTO, 31 TTO-d) had clinical and radiographic follow-up of at least 90 days or evidence of osseous union. Eighty-eight complications were identified in 71 of 153 (46%) patients: delayed union (n = 35); painful hardware (n = 32); deep vein thrombosis (n = 4); clinical nonunion, delayed range of motion, sensory deficit, and wound breakdown (n = 3 each); and broken screw, fascial hernia, hematoma, quadriceps dysfunction, and tibial fracture (n = 1 each). Thirteen of 35 delayed unions occurred in the TTO-d group (P = .005). Painful hardware was more frequent in patients who received 4.5-mm screws (31/115) than in those who received 3.5-mm screws (1/38) (P = .001). A reoperation was required in 38 of 153 patients (37 patients using 4.5-mm screws vs 1 patient using 3.5-mm screws; P < .001), primarily for screw removal (32/38).

Conclusion:

Minor complications, including delayed union and painful hardware, were common, but major complications such as tibial fracture, deep vein thrombosis, and clinical nonunion were rare. Delayed union was more frequent in the TTO-d group. The 3.5-mm screws were less painful and less likely to need removal than the 4.5-mm screws.

Lateralization of the Tibial Tubercle in Recurrent Patellar Dislocation: Verification Using Multiple Methods to Evaluate the Tibial Tubercle

BACKGROUND

The tibial tubercle deviation associated with recurrent patellar dislocation (RPD) has not been studied sufficiently. New methods of evaluation were used to verify the extent of tubercle deviation in a group with patellar dislocation compared with that in a control group, the frequency of patients who demonstrated a cutoff value indicating that tubercle transfer was warranted on the basis of the control group distribution, and the validity of these methods of evaluation for diagnosing RPD.

METHODS

Sixty-six patients with a history of patellar dislocation (single in 19 [SPD group] and recurrent in 47 [RPD group]) and 66 age and sex-matched controls were analyzed with the use of computed tomography (CT). The tibial tubercle-posterior cruciate ligament (TT-PCL) distance, TT-PCL ratio, and tibial tubercle lateralization (TTL) in the SPD and RPD groups were compared with those in the control group. Cutoff values to warrant 10 mm of transfer were based on either the minimum or -2SD (2 standard deviations below the mean) value in the control group, and the prevalences of patients in the RPD group with measurements above these cutoff values were calculated. The area under the curve (AUC) in receiver operating characteristic (ROC) curve analysis was used to assess the effectiveness of the measurements as predictors of RPD.

RESULTS

The mean TT-PCL distance, TT-PCL ratio, and TTL were all significantly greater in the RPD group than in the control group. The numbers of patients in the RPD group who satisfied the cutoff criteria when they were based on the minimum TT-PCL distance, TT-PCL ratio, and TTL in the control group were 11 (23%), 7 (15%), and 6 (13%), respectively. When the cutoff values were based on the -2SD values in the control group, the numbers of patients were 8 (17%), 6 (13%), and 0, respectively. The AUC of the ROC curve for TT-PCL distance, TT-PCL ratio, and TTL was 0.66, 0.72, and 0.72, respectively.

CONCLUSIONS

The extent of TTL in the RPD group was not substantial, and the percentages of patients for whom 10 mm of medial transfer was indicated were small.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Current clinical, radiological and treatment perspectives of patellofemoral pain syndrome

Anterior knee pain in active young adults is commonly related to patellofemoral pain syndrome, which can be broadly classified into patellar malalignment and patellar maltracking. Imaging is performed to further elucidate the exact malalignment and maltracking abnormalities and exclude other differentials. This article details the role of the stabilizers of the patellofemoral joint, findings on conventional and multimodality imaging aiding in patellofemoral pain syndrome diagnosis and characterization, and current perspectives of various treatment approaches.

Medial patellofemoral ligament reconstruction: patient selection and perspectives

Patellofemoral instability is a painful and often recurring disorder with many negative long-term consequences. After a period of failed nonoperative management, surgical intervention has been used to reduce the incidence of patellar subluxation and dislocations. Medial patellofemoral ligament (MPFL) reconstruction successfully addresses patellofemoral instability by restoring the deficient primary medial patellar soft tissue restraint. When planning MPFL reconstruction for instability, it is imperative to consider the patient's unique anatomy including the tibial tuberosity-trochlear groove (TT-TG) distance, trochlear dysplasia, and patella alta. Additionally, it is important to individualize surgical treatment in the skeletally immature, hypermobile, and athletic populations.

Evaluation of a modified knee rotation angle in MRI scans with and without trochlear dysplasia: a parameter independent of knee size and trochlear morphology

PURPOSE

Regarding TT-TG in knee realignment surgery, two aspects have to be considered: first, there might be flaws in using absolute values for TT-TG, ignoring the knee size of the individual. Second, in high-grade trochlear dysplasia with a dome-shaped trochlea, measurement of TT-TG has proven to lack precision and reliability. The purpose of this examination was to establish a knee rotation angle, independent of the size of the individual knee and unaffected by a dysplastic trochlea.

METHODS

A total of 114 consecutive MRI scans of knee joints were analysed by two observers, retrospectively. Of these, 59 were obtained from patients with trochlear dysplasia, and another 55 were obtained from patients presenting with a different pathology of the knee joint. Trochlear dysplasia was classified into low grade and high grade. TT-TG was measured according to the method described by Schoettle et al. In addition, a modified knee rotation angle was assessed. Interobserver reliability of the knee rotation angle and its correlation with TT-TG was calculated.

RESULTS

The knee rotation angle showed good correlation with TT-TG in the readings of observer 1 and observer 2. Interobserver correlation of the parameter showed excellent values for the scans with normal trochlea, low-grade and high-grade trochlear dysplasia, respectively. All calculations were statistically significant (p < 0.05).

CONCLUSION

The knee rotation angle might meet the requirements for precise diagnostics in knee realignment surgery. Unlike TT-TG, this parameter seems not to be affected by a dysplastic trochlea. In addition, the dimensionless parameter is independent of the knee size of the individual.

LEVEL OF EVIDENCE

II.

Upright weight-bearing CT of the knee during flexion: changes of the patellofemoral and tibiofemoral articulations between 0° and 120°

PURPOSE

To prospectively compare patellofemoral and tibiofemoral articulations in the upright weight-bearing position with different degrees of flexion using CT in order to gain a more thorough understanding of the development of diseases of the knee joint in a physiological position.

MATERIALS AND METHODS

CT scans of the knee in 0°, 30°, 60° flexion in the upright weight-bearing position and in 120° flexion upright without weight-bearing were obtained of 10 volunteers (mean age 33.7 ± 6.1 years; range 24-41) using a cone-beam extremity-CT. Two independent readers quantified tibiofemoral and patellofemoral rotation, tibial tuberosity-trochlear groove distance (TTTG) and patellofemoral distance. Tibiofemoral contact points were assessed in relation to the anteroposterior distance of the tibial plateau. Significant differences between degrees of flexion were sought using Wilcoxon signed-rank test (P < 0.05).

RESULTS

With higher degrees of flexion, internal tibiofemoral rotation increased (0°/120° flexion; mean, 0.5° ± 4.5/22.4° ± 7.6); external patellofemoral rotation decreased (10.6° ± 7.6/1.6° ± 4.2); TTTG decreased (11.1 mm ±3.7/-2.4 mm ±6.4) and patellofemoral distance decreased (38.7 mm ±3.0/21.0 mm ±7.0). The CP shifted posterior, more pronounced laterally. Significant differences were found for all measurements at all degrees of flexion (P = 0.005-0.037), except between 30° and 60°. ICC was almost perfect (0.80-0.99), except for the assessment of the CP (0.20-0.96).

CONCLUSION

Knee joint articulations change significantly during flexion using upright weight-bearing CT. Progressive internal tibiofemoral rotation leads to a decrease in the TTTG and a posterior shift of the contact points in higher degrees of flexion. This elucidates patellar malalignment predominantly close to extension and meniscal tears commonly affecting the posterior horns.

The outcomes of the modified Fulkerson osteotomy procedure to treat habitual patellar dislocation associated with high-grade trochlear dysplasia

BACKGROUND

Habitual patellar dislocation is not common in clinical practice, but it has a deep impact on the patient's lifestyle and movement. There has been no large case-control study on habitual patellar dislocation, and the management of it is still controversial. The aim of this study was to observe the efficacy of the modified Fulkerson procedure on patients with habitual patellar dislocation with high-grade trochlear dysplasia without trochleoplasty and to evaluate the results of this procedure.

METHODS

A total of 25 patients who were admitted to our hospital from April 2007 to October 2013 were included: 7 males and 18 females, aged 17-28 years old, with an average age of 21.5 years old, including 21 cases of unilateral dislocation and 4 cases of bilateral dislocation. The tibial tuberosity transfer procedure (internal rotation, medial transfer and elevation osteotomy) and medial patellofemoral ligament (MPFL) reconstruction were performed in all cases of habitual patellar dislocation that were accompanied by trochlea dysplasia.

RESULTS

The mean follow-up duration was 36.8 months (range, 25-68 months). A CT scan was performed to compare the tibial tuberosity-trochlear groove distance (TT-TG), the patellar tilt angle (PTA), and the mean Kujala and Lysholm scores before surgery and at follow-up and to measure the angle of internal rotation of the tibial tubercle after surgery. The mean Kujala and Lysholm scores improved significantly (P < 0.05) from 55.65 ± 6.10 and 50.34 ± 6.54 preoperatively to89.24 ± 4.66 and 88.53 ± 4.75, respectively, at follow-up. The tibial tuberosity-trochlear groove distance (TT-TG) decreased significantly (P < 0.05) from 20.24 ± 2.80 mm to 10.50 ± 4.50 mm, and the patellar tilt angle (PTA) decreased significantly (P < 0.05) from28.58 ± 3.28to7.54 ± 5.56. No recurrence was observed, and only one patient had a mild skin infection after surgery. The mean angle of internal rotation of the tibial tubercle was 10 ± 4° after surgery. There were no cases of stiffness.

CONCLUSIONS

The modified procedure of tibial tubercle transfer, especially the internal rotation, which can improve the patella stability and knee function, is an effective surgical procedure for the treatment of habitual patellar dislocation associated with high-grade trochlear dysplasia without trochleoplasty.

LEVEL OF EVIDENCE

III.

Does tibial tuberosity-trochlear groove distance (TT-TG) correlate with knee size or body height?

PURPOSE

Since excessive tibial tuberosity-trochlear groove distance (TT-TG) is one of the major risk factors for patellofemoral instability, TT-TG is an often-used parameter in knee realignment surgery. Up to date, TT-TG is measured and interpreted using absolute values, disregarding the knee size of the individual. It was hypothesized that there is a relation between TT-TG and knee size and body height, respectively.

METHODS

Consecutive MRI scans of 120 knee joints were analysed retrospectively. Of these, 60 MRI scans were obtained from patients with trochlear dysplasia and another 60 MRI scans were acquired from patients presenting with a different pathology of the knee joint. TT-TG was measured and TD was classified into low and high grade. Interepicondylar distance as an expression of knee size was measured on transverse MRI slices presenting the maximal distance from the medial to the lateral epicondylus. TT-TG was correlated with interepicondylar distance and body height.

RESULTS

Interepicondylar distance as an expression of knee size correlated highly with body height in the control group with normal trochlea (r = 0.78) as well as in the TD group (r = 0.69). Correlation of TT-TG with interepicondylar distance or body height in the control group as well as in the TD group showed poor values with r < 0.30 (range r = 0.072-0.28).

CONCLUSION

TT-TG seems associated neither with the size of the individual knee, nor with body height. For this reason, TT-TG has to be considered as very individual parameter in knee realignment surgery.

A new classification system of patellar instability and patellar maltracking

To date there is no classification of patellar dislocations considering clinical and radiological pathologies. As a result many studies mingle the dislocation's underlying pathologies, so that there are no consistent therapy recommendations. It is this article's objective to introduce a patellar dislocation classification based on the current literature to allow for the application of a structured diagnosis and treatment algorithm. The classification is based on instability criteria as well as on clinical and radiological analyses of maltracking and on loss of patellar tracking. There are five types of patellar instability and maltracking. The rare type 1 is a simple (traumatic) patellar dislocation without maltracking and instability with a low risk of redislocation. Type 2 has a high risk of redislocation after primary dislocation; there is no maltracking. Here, a stabilising operation (in most cases MPFL reconstruction) is indicated and sufficient. Type 3 shows both instability and maltracking. Maltracking is mainly caused by: (a) soft tissue contracture, (b) patella alta, (c) pathological tibial tuberosity-trochlea groove distance, (d) valgus deviations and (e) torsional deformities. Stabilisation by means of isolated MPFL reconstruction is not sufficient in these types and additional osseous corrective surgeries are required to achieve physiological patellar tracking and to prevent redislocation. Type 4 features a highly unstable "floating patella" with complete loss of tracking caused by severe trochlear dysplasia. Therapy of choice is trochleoplasty, and if necessary combined with bony and soft-tissue procedures. Type 5 shows a patellar maltracking without instability. Maltracking can only be fixed by means of corrective osteotomy. The classification is referenced to current literature and each type is introduced by a case example. The resulting treatment consequence is also presented.

An Algorithmic Approach to the Management of Recurrent Lateral Patellar Dislocation

High-level evidence supports nonoperative treatment for first-time lateral acute patellar dislocations. Surgical intervention is often indicated for recurrent dislocations. Recurrent instability is often multifactorial and can be the result of a combination of coronal limb malalignment, patella alta, malrotation secondary to internal femoral or external tibial torsion, a dysplastic trochlea, or disrupted and weakened medial soft tissue, including the medial patellofemoral ligament (MPFL) and the vastus medialis obliquus. MPFL reconstruction requires precise graft placement for restoration of anatomy and minimal graft tension. MPFL reconstruction is safe to perform in skeletally immature patients and in revision surgical settings. Distal realignment procedures should be implemented in recurrent instability associated with patella alta, increased tibial tubercle-trochlear groove distances, and lateral and distal patellar chondrosis. Groove-deepening trochleoplasty for Dejour type-B and type-D dysplasia or a lateral elevation or proximal recession trochleoplasty for Dejour type-C dysplasia may be a component of the treatment algorithm; however, clinical outcome data are lacking. In addition, trochleoplasty is technically challenging and has a risk of substantial complications.

Reconstructive surgery for patellofemoral joint incongruency

PURPOSE

A retrospective analysis of a heterogeneous patient cohort was performed to determine the outcome and eligibility of a combined trochleaplasty and soft tissue-balancing technique for repair of patellofemoral joint disorders.

METHODS

A strict surgical treatment algorithm including trochleaplasty and reconstruction of the medial patellofemoral ligament and vastus medialis oblique muscle was implemented to restore the patellofemoral joint. A heterogeneous patient cohort including 46 consecutively treated symptomatic knees was reviewed. The median follow-up period was 4.7 years (range 24-109 months).

RESULTS

No patellar redislocation occurred post-operatively, and the median Kujala score improved from 62 (9-96) to 88 (47-100) points (p < 0.001) at follow-up. Radiological signs of trochlear dysplasia were corrected, and both patellar height and trochlear depth were significantly restored after surgery. In total, 16% of affected patients with pre-existing patellofemoral degenerative changes showed progression of osteoarthrosis according to the Kellgren and Lawrence classification.

CONCLUSION

The surgical combination of trochleaplasty and reconstruction of the medial patellofemoral ligament and vastus medialis oblique muscle offers excellent clinical and radiological results. The overall results of the present study showed significant improvement of the Kujala score in patients with Dejour grades C and D dysplasia. These results outline the clinical relevance of trochleaplasty with additional soft tissue balancing as an effective joint-preserving method with satisfying results in patients with pre-existing degenerative changes.

LEVEL OF EVIDENCE

IV.

The Relationship Between Tibial Tuberosity-Trochlear Groove Distance and Abnormal Patellar Tracking in Patients With Unilateral Patellar Instability

PURPOSE

To evaluate the role of tibial tuberosity-trochlear groove (TT-TG) distance in patellofemoral kinematics by retrospectively reviewing the dynamic computed tomography scans of patients with unilateral patellofemoral instability and comparing unstable and contralateral asymptomatic knees.

METHODS

We reviewed all dynamic computed tomography scans obtained at one tertiary care hospital from 2008 through 2013 and identified 25 patients with a history of recurrent unilateral patellofemoral instability. During the scans, subjects performed active knee extension against gravity. Both knees were imaged simultaneously. Lateral patellar tilt (LPT) and bisect offset (BO) were measured to assess tracking. TT-TG distance was measured to assess alignment. Measurements were made in full extension, maximum flexion, and approximately 10° increments in between. The significance level was set at P < .05.

RESULTS

LPT, BO, and TT-TG distance were highest in extension and decreased with flexion. Measurements were higher in symptomatic than in asymptomatic knees, with significant differences identified for LPT, BO, and TT-TG distance at 5° and 15° and for TT-TG distance at 25° and 35° (P < .05). TT-TG distance was associated with LPT and BO, with r(2) values in symptomatic knees of 0.55 for TT-TG distance and LPT and of 0.45 for TT-TG distance and BO.

CONCLUSIONS

In patients with unilateral patellar instability, LPT, BO, and TT-TG distance are higher on the unstable side. An association exists between TT-TG distance and the tracking parameters studied, suggesting that TT-TG distance relates to patellar tracking, and a laterally positioned tibial tuberosity may predispose to instability episodes.

LEVEL OF EVIDENCE

Level IV, diagnostic study.

What Components Comprise the Measurement of the Tibial Tuberosity-Trochlear Groove Distance in a Patellar Dislocation Population?

BACKGROUND

The tibial tuberosity-trochlear groove distance is used as an indicator for medial tibial tubercle transfer; however, to our knowledge, no studies have verified whether this distance is strongly affected by tubercle lateralization at the proximal part of the tibia. We hypothesized that the tibial tuberosity-trochlear groove distance is mainly affected by tibial tubercle lateralization at the proximal part of the tibia.

METHODS

Forty-four patients with a history of patellar dislocation and forty-four age and sex-matched controls were analyzed with use of computed tomography. The tibial tuberosity-trochlear groove distance, tibial tubercle lateralization, trochlear groove medialization, and knee rotation were measured and were compared between the patellar dislocation group and the control group. The association between the tibial tuberosity-trochlear groove distance and three other parameters was calculated with use of the Pearson correlation coefficient and partial correlation analysis.

RESULTS

There were significant differences in the tibial tuberosity-trochlear groove distance (p < 0.001) and knee rotation (p < 0.001), but there was no difference in the tibial tubercle lateralization (p = 0.13) and trochlear groove medialization (p = 0.08) between the patellar dislocation group and the control group. The tibial tuberosity-trochlear groove distance had no linear correlation with tubercle lateralization (r = 0.21) or groove medialization (r = -0.15); however, knee rotation had a good positive correlation in the patellar dislocation group (r = 0.62). After adjusting for the remaining parameters, knee rotation strongly correlated with the tibial tuberosity-trochlear groove distance (r = 0.69, p < 0.001), whereas tubercle lateralization showed moderate significant correlations in the patellar dislocation group (r = 0.42; p = 0.005).

CONCLUSIONS

Because the tibial tuberosity-trochlear groove distance is affected more by knee rotation than by tubercle malposition, its use as an indicator for tibial tubercle transfer may not be appropriate.

CLINICAL RELEVANCE

Surgical decisions of tibial tubercle transfer should be made after the careful analysis of several underlying factors of patellar dislocation.

The ability of medial patellofemoral ligament reconstruction to correct patellar kinematics and contact mechanics in the presence of a lateralized tibial tubercle

BACKGROUND

Tibial tubercle (TT) transfer and medial patellofemoral ligament (MPFL) reconstruction are used after patellar dislocations. However, there is no objective evidence to guide surgical decision making, such as the ability of MPFL reconstruction to restore normal behavior in the presence of a lateralized TT.

HYPOTHESIS

MPFL reconstruction will only restore joint contact mechanics and patellar kinematics for TT-trochlear groove (TG) distances up to an identifiable limit.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight fresh-frozen cadaveric knees (mean TT-TG distance, 10.4 mm) were placed on a testing rig. Individual quadriceps heads and the iliotibial band were loaded with 205 N in physiological directions using a weighted pulley system. Patellofemoral contact pressures and patellar tracking were measured at 0°, 10°, 20°, 30°, 60°, and 90° of flexion using pressure-sensitive film and an optical tracking system. The MPFL attachments were marked. TT osteotomy was performed, and a metal T-plate was fixed to the anterior tibia with holes at 5-mm intervals for TT fixation. The anatomic TT position was restored after plate insertion. The TT was lateralized in 5-mm intervals up to 15 mm, with pressure and tracking measurements recorded. The MPFL was transected and all measurements repeated before and after MPFL reconstruction using a double-stranded gracilis tendon graft. Data were analyzed using repeated-measures ANOVA, Bonferroni post hoc analysis, and paired t tests.

RESULTS

MPFL transection significantly elevated lateral patellar tilt and translation and reduced mean medial contact pressures during early knee flexion. These effects increased significantly with TT lateralization. MPFL reconstruction restored patellar translation and mean medial contact pressures to the intact state when the TT was in anatomic or 5-mm lateralized positions. However, these were not restored when the TT was lateralized by 10 mm or 15 mm. Patellar tilt was restored after 5-mm TT lateralization but not after 10-mm or 15-mm lateralization.

CONCLUSION

Considering the mean TT-TG distance in this study (10.4 mm), findings suggest that in patients with TT-TG distances up to 15 mm, patellofemoral kinematics and contact mechanics can be restored with MPFL reconstruction. However, for TT-TG distances greater than 15 mm, more aggressive surgery such as TT transfer may be indicated.

CLINICAL RELEVANCE

This provides guidance to surgeons as to the threshold at which MPFL reconstruction may satisfactorily restore patellofemoral mechanics, beyond which more invasive surgery such as TT transfer may be indicated.

The Incidence of Complications of Tibial Tubercle Osteotomy: A Systematic Review

PURPOSE

The goal of this review was to quantify the risk of perioperative and early postoperative complications of tibial tubercle osteotomy (TTO) with different techniques.

METHODS

A systematic review of multiple databases was performed to identify studies that reported complications of TTO. Complications were defined as any adverse outcome, including osteotomy site nonunion, fracture, infection, wound complications, neurovascular complications, deep vein thrombosis (DVT), and pulmonary embolism (PE). Major complications were defined as nonunion, fracture, infections/wound complications requiring return to the operating room, and DVT or PE. The risk of subsequent hardware removal was also quantified.

RESULTS

The 19 identified studies included a total of 787 TTOs: 472 direct medialization procedures (Elmslie-Trillat technique), 193 anteromedialization procedures (Fulkerson technique), and 102 procedures in which the tibial tubercle was completely detached for medialization or distalization, or a combination. The overall complication risk was 4.6%. The risk of complications was higher when the tibial tubercle was completely detached (10.7%) than with Elmslie-Trillat (3.3%) or Fulkerson (3.7%) procedures (P = .004). The overall risk of major complications was 3.0%. Hardware removal was performed in 36.7% of osteotomies and was less frequent with the Elmslie-Trillat technique (26.8%) than with the Fulkerson technique (49.0%) or complete tubercle detachment (48.3%) (P < .001).

CONCLUSIONS

Tibial tubercle osteotomy is a complex surgical procedure with a significant risk of complications. Osteotomies that involve complete detachment of the tubercle have an increased risk of complications compared with those in which a distal cortical hinge is maintained.

LEVEL OF EVIDENCE

Level IV, systematic review of Level IV studies.

The effect of tibial tuberosity medialization and lateralization on patellofemoral joint kinematics, contact mechanics, and stability

BACKGROUND

Tibial tuberosity (TT) transfer is a common procedure to treat patellofemoral instability in patients with elevated TT-trochlear groove (TG) distances. However, the effects of TT lateralization or medialization on patellar stability, kinematics, and contact mechanics remain unclear.

HYPOTHESIS

Progressive medialization and lateralization will have increasingly adverse effects on patellofemoral joint kinematics, contact mechanics, and stability.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight fresh-frozen cadaveric knees were placed on a testing rig, with a fixed femur and tibia mobile through 90° of flexion. Individual quadriceps heads and the iliotibial band were separated and loaded with 205 N in anatomic directions using a weighted pulley system. Patellofemoral contact pressures and patellar tracking were measured at 0°, 10°, 20°, 30°, 60°, and 90° of flexion using pressure-sensitive film behind the patella and an optical tracking system. The intact knee was measured with and without a 10-N patellar lateral displacement load, and recordings were repeated after TT transfer of 5, 10, and 15 mm medially and laterally. Statistical analysis used repeated-measures analysis of variance, Bonferroni post hoc analysis, and Pearson correlations.

RESULTS

Tibial tuberosity lateralization significantly elevated lateral joint contact pressures, increased lateral patellar tracking, and reduced patellar stability (P<.048). There was a significant correlation between mean lateral contact pressure and the TT position (r=0.810, P<.001) at 10°. Tibial tuberosity medialization reduced lateral contact pressures (P<.002) and did not elevate peak medial contact pressures (P>.11).

CONCLUSION

Progressive TT lateralization elevated lateral contact pressures, increased lateral patellar tracking, and reduced patellar stability. Medial contact pressure and tracking did alter with progressive TT medialization, but the changes were smaller.

CLINICAL RELEVANCE

Lateral patellofemoral joint contact pressures increased with progressive lateralization of the TT; medialization of the TT reduced these effects, restoring patellar stability, and did not cause excessive peak pressures. These data provide a rationale for medial TT transfer surgery in patients with elevated TT-TG distances.

Tibial rotational osteotomy and distal tuberosity transfer for patella subluxation secondary to excessive external tibial torsion: surgical technique and clinical outcome

PURPOSE

Recurrent patella subluxation may be secondary to excessive external tibial torsion. The purpose of this study is to evaluate the clinical and radiographic outcome of patients undergoing tibial derotation osteotomy and tibial tuberosity transfer for recurrent patella subluxation in association with excessive external tibial torsion.

METHODS

A combined tibial derotation osteotomy and tibial tuberosity transfer was performed in 15 knees (12 patients) with recurrent patella subluxation secondary to excessive external tibial torsion. Clinical evaluation was carried out using preoperative and post-operative Knee Society Score (KSS), Kujala Patellofemoral score, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire, the short form-12 (SF-12) and a visual analogue score (VAS) pain scale.

RESULTS

The median follow-up period was 84 months (range 15-156) and median patient age was 34 years (range 19-57 years). The median preoperative external tibial torsion was 62° (range 55°-70°), with a median rotational correction of 36° (range 30°-45°) after surgery. Significant improvement (p < 0.05) was found in the KSS part I (37 ± 14 to 89 ± 11 points), KSS part II (25 ± 26 to 85 ± 14 points), Kujala score, the SF-12 outcome, WOMAC score and VAS score (8.8 ± 1.9 to 2.4 ± 1.5). Two patients had a nonunion of the tibial osteotomy site; one patient required bone grafting, while another patient required revision to total knee arthroplasty.

CONCLUSION

Patients presenting with recurrent patella subluxation secondary to excessive external tibial torsion >45° who underwent tibial derotation osteotomy and tibial tuberosity transfer achieved a satisfactory outcome in terms of pain relief and improved function. A significant complication was seen in 2/15 patients.

LEVEL OF EVIDENCE

Case series, Level IV.

Arthroscopic evaluation of trochlear dysplasia as an aid in decision making for the treatment of patellofemoral instability

PURPOSE

Trochlear dysplasia is an important aetiological factor for the development of patellofemoral instability (PFI). The aim of the study was to identify the arthroscopic morphology of trochlear dysplasia that can be helpful when planning operative treatment for PFI.

METHODS

Magnetic resonance imaging (MRI) scans and strict lateral radiographs of 46 patients treated for PFI were assigned according to Dejour and matched with arthroscopic views from the lateral superior arthroscopic portal. On arthroscopy, signs of trochlear dysplasia were identified and classified into two types. Intra- and inter-observer agreements of the arthroscopic evaluation were assessed.

RESULTS

Arthroscopically, 2 major types of trochlear dysplasia could be distinguished. Type I shows a flat trochlear groove with an elevated trochlear floor in relation to the anterior femoral cortex. In type II, the proximal trochlea was convex with a lateral trochlear bump. Arthroscopic evaluation was not consistent with the Dejour's radiographic and axial MRI classification. Arthroscopic grading showed excellent intra- and inter-observer agreements (81-92%).

CONCLUSION

Arthroscopic evaluation can give additional information about the severity of trochlear dysplasia. This additional information can be used as an aid in decision making for the treatment of PFI.

LEVEL OF EVIDENCE

II.

Clinical outcome after reconstruction of the medial patellofemoral ligament in patients with recurrent patella instability

PURPOSE

We present the clinical results of a large consecutive, prospective, single-clinic series of patients treated with medial patellofemoral ligament (MPFL) reconstruction for recurrent patellar instability.

METHODS

The study included 224 patients undergoing MPFL reconstruction in a total of 240 knees between 2008 and 2011. Indication for surgery was two or more patellar dislocations and ADL limitations due to patella instability.

SURGICAL PROCEDURE

A gracilis tendon autograft was fixed in drill holes in the medial edge of the patella and with screws at the femoral MPFL insertion point. Outcomes were evaluated with the Kujala Anterior Knee Pain Score and pain scores preoperatively and at follow-up (12-60 months). Furthermore, incidences of re-dislocations, subluxations and revision surgery were evaluated.

RESULTS

The Kujala score improved from 62.5 (17) to 80.4 (18) (p<0.001) at the 1-year follow-up. Pain during activity improved from 3.2 (2.6) to 1.3 (2.7) at 1 year (p<0.001). The revision rate was 2.8%. Some degree of pain at the medial femoral condyle was seen in 30% of the patients. The reconstruction was supplemented with a tibial tuberosity osteotomy in 23% of cases. The outcome for these patients did not differ from that of patients with isolated MPFL reconstruction. Female gender BMI>30, age>30 years and grade 3-4 cartilage injury predisposed a poor subjective outcome.

CONCLUSIONS

The present study is the largest MPFL reconstruction patient material reported to date. MPFL reconstruction with a gracilis tendon autograft consistently normalised the patella stability and improved knee function. Moderate medial pain was seen. Age above 30, obesity, cartilage injury and female gender are predictors of a poor subjective outcome.

LEVEL OF EVIDENCE

Level IV.

Medial patellofemoral ligament reconstruction as an isolated or combined procedure for recurrent patellar instability

PURPOSE

The principal aim of this study was to report the outcomes of medial patellofemoral ligament (MPFL) reconstruction, used as either an isolated procedure or in combination with another stabilization procedure, for the primary treatment of recurrent patellar instability.

METHODS

Between 2007 and 2012, 45 patients with recurrent patellar instability and no prior stabilization surgery had an MPFL reconstruction by a single surgeon, either as an isolated procedure or in combination with another stabilization procedure. Questionnaires detailing patellar instability since surgery, knee pain, ability to negotiate stairs, and sports participation were completed, and data regarding examination and radiological findings were collected from the medical record.

RESULTS

A total of 36 (80%) patients completed the questionnaire at a mean of 3.1 years (minimum 1 year), whilst a further 11% had clinical follow-up of greater than 1 year. Four patients were excluded due to lack of adequate follow-up. Thirty-one patients had an isolated MPFL reconstruction and none had further patellar instability. Of the ten patients who had a combined procedure, one experienced recurrent instability. Return to sport rates were 81 and 57% for the isolated and combined groups, respectively, with the majority returning to strenuous sport (81 and 57%, respectively). Most patients (96 and 80%) could negotiate stairs without difficulty, whilst 38 and 40% reported some degree of anterior knee pain.

CONCLUSIONS

This study shows that satisfactory results can be obtained using MPFL reconstruction either in isolation or in combination to treat recurrent patellar instability. Whether the indications for an isolated MPFL can be extended further remains unclear.

LEVEL OF EVIDENCE

III.

Measurement of tibial tuberosity-trochlear groove distance: evaluation of inter- and intraobserver correlation dependent on the severity of trochlear dysplasia

PURPOSE

Excessive tibial tuberosity-trochlear groove distance (TT-TG) is considered as one of the major risk factors in patellofemoral instability (PFI). TT-TG characterises the lateralisation of the tibial tuberosity and the medialisation of the trochlear groove in the case of trochlear dysplasia. The aim of this study was to assess the inter- and intraobserver reliability of the measurement of TT-TG dependent on the grade of trochlear dysplasia.

METHODS

Magnetic resonance imaging (MRI) scans of 99 consecutive knee joints were analysed retrospectively. Hereof, 61 knee joints presented with a history of PFI and 38 had no symptoms of PFI. After synopsis of the axial MRI scans with true lateral radiographs of the knee, the 61 knees presenting with PFI were assessed in terms of trochlear dysplasia. The knees were distributed according to the four-type classification system described by Dejour.

RESULTS

Regarding interobserver correlation for the measurements of TT-TG in trochlear dysplasia, we found r=0.89 (type A), r=0.90 (type B), r=0.74 (type C) and 0.62 (type D) for Pearson's correlation coefficient. Regarding intraobserver correlation, we calculated r=0.89 (type A), r=0.91 (type B), r=0.77 (type C) and r=0.71 (type D), respectively. Pearson's correlation coefficient for the measurement of TT-TG in normal knees resulted in r=0.87 for interobserver correlation and r=0.90 for intraobserver correlation.

CONCLUSION

Decreasing inter- and intraobserver correlation for the measurement of TT-TG with increasing severity of trochlear dysplasia was detected. In our opinion, the measurement of TT-TG is of significance in low-grade trochlear dysplasia. The final decision to perform a distal realignment procedure based on a pathological TT-TG in the presence of high-grade trochlear dysplasia should be reassessed properly.

LEVEL OF EVIDENCE

Retrospective study, Level II.

Clinical outcomes of medial patellofemoral ligament reconstruction in patients with an increased tibial tuberosity-trochlear groove distance

PURPOSE

Medial patellofemoral ligament (MPFL) reconstruction is performed to treat recurrent patellar dislocation (RPD). However, the effectiveness of MPFL reconstruction in patients with a severely lateralised tibial tuberosity remains unknown. In this study, the clinical outcomes of MPFL reconstruction in patients with an increased tibial tuberosity-trochlear groove (TT-TG) distance were examined.

METHODS

A total of thirty-four patients who underwent MPFL reconstruction for RPD were retrospectively examined. Nineteen patients with a TT-TG distance of >20 mm (increased TT-TG distance group) were compared with 15 patients with a TT-TG distance of <20 mm (control group). Clinical outcomes of MPFL reconstruction were evaluated by occurrence of re-dislocation, Crosby and Insall grading system, apprehension sign, and Kujala and Lysholm scores.

RESULTS

None of the patients reported re-dislocation. Apprehension sign remained in three patients in the increased TT-TG distance group and in one patient in the control group. According to the Crosby and Insall grading system, 9 patients (47%) were excellent, 9 (47%) were good, and 1 (5%) was fair to poor in the increased TT-TG distance group, while 6 (40%) were excellent and 9 (60%) were good in the control group. Kujala and Lysholm scores were significantly improved post-operatively in both groups. No significant correlations were observed between TT-TG distance and post-operative Kujala or Lysholm score.

CONCLUSION

Overall clinical outcomes of MPFL reconstruction were favourable even in patients with an increased TT-TG distance. TT-TG distance of >20 mm may not be an absolute indication for medialisation of the tibial tuberosity when performing MPFL reconstruction.

LEVEL OF EVIDENCE

Case-control study, Level III.

MRI performed on dedicated knee coils is inaccurate for the measurement of tibial tubercle trochlear groove distance

OBJECTIVE

Tibial tubercle trochlear groove distance (TTD) is a significant factor in patello-femoral instability. Initially described on CT scans with the knee in full extension, the measurement has been validated on MR scans. Dedicated knee MRI coils have subsequently superseded both CT and MRI body coils for knee imaging. However, the knee rests in partial flexion within the dedicated knee coil. The objective of this study is to investigate whether images from dedicated knee MRI coils produce different TTD measurements from MR body coils.

MATERIALS AND METHODS

Thirty-two symptomatic knees (27 patients) had simultaneous knee MR scans performed in both a dedicated knee coil and a body coil. TTD measurements were independently compared to assess whether the coil type used affected TTD.

RESULTS

Patients' ages ranged from 10 to 27 years (mean 15 years). Mean TTD in the dedicated knee coil (partially flexed knee) was 11.3 mm compared with 19.9 mm in the body coil (that permits full knee extension). The mean difference was 8.6 mm, which was highly significant (p < 0.0001, unpaired t test). Inter-rater correlation co-efficient was 96 %. Of the knees that recorded a "normal" TTD on the dedicated knee coil, 60-100 % recorded a "pathological" TTD on body coil images, depending on which diagnostic value for "normal" cut-off was used.

CONCLUSION

This study has identified a highly significant difference in TTD measurement when knees are scanned in a dedicated knee coil with the knee partially flexed, compared with an MR body coil. It is critical for surgeons and radiologists managing patello-femoral instability to appreciate this profound difference. TTD measurement taken from knees scanned in dedicated knee coils may lead to patients being falsely re-assured or erroneously denied surgery.

End-stage extension of the knee and its influence on tibial tuberosity-trochlear groove distance (TTTG) in asymptomatic volunteers

PURPOSE

Increased tibial tuberosity-trochlear groove distance (TTTG) is one potential correcting parameter in patients suffering from lateral patellar instability. It was hypothesized that end-stage extension of the knee might influence the TTTG distance on MR images.

METHODS

Transverse T1-weighted MR images of the knee were acquired at full extension, 15° and 30° flexion of the knee in 30 asymptomatic volunteers. MRI parameters: slice thickness: 3 mm, matrix: 256 × 384, FOV: 150 × 150 mm. Two observers independently measured the TTTG at all positions.

RESULTS

Mean TTTG for observer 1 was 15.1 ± 3.2 mm at full extension, 10.0 ± 3.5 mm at 15° flexion and 8.1 ± 3.4 mm at 30° flexion. Mean TTTG for observer 2: 14.8 ± 3.3 mm at full extension, 9.4 ± 3.0 mm at 15° flexion, 8.6 ± 3.4 mm at 30° flexion. Mean values were significantly different (p < 0.001) between full extension and 15° as well as 30° flexion for both observers. Mean values were significantly different (p < 0.001) between 15° and 30° for observer 1, but not for observer 2 (n.s.). Interobserver agreement was very good (intraclass correlation coefficient: 0.87-0.88; p < 0.001).

CONCLUSIONS

The TTTG increases significantly at the end-stage extension of the knee. Therefore, the comparability of published TTTG values measured on radiographs, CT and MRI at various flexion/extension angles of the knee are limited.

Evaluation of trochlear dysplasia using MRI: correlation between the classification system of Dejour and objective parameters of trochlear dysplasia

PURPOSE

Trochlear dysplasia is considered to be one of the major factors causing patellofemoral instability (PFI). Dejour's classification is widely used to assess the severity of trochlear dysplasia. Additionally, in current literature, different quantitative parameters are recommended to distinguish between a normal trochlea and a dysplastic trochlea. In order to achieve a more objective evaluation of the trochlea, the aim of this study was to evaluate whether specific measurements of the femoral trochlea can be assigned to the qualitative classification system of Dejour.

METHODS

Transverse MRI T2-weighted scans of 80 knees with symptomatic PFI and varying severity of trochlear dysplasia were classified according to Dejour (type A to D). For all MRI scans, quantitative measurements with parameters as described in the literature were applied. The values were then allocated to Dejour's classification. In addition to the four-grade analysis, two-grade analysis was also performed (Dejour type A against type BCD). Dependent on the cut-off values, specificity, sensitivity and Youden index for each parameter was defined.

RESULTS

The allocation resulted in the following distribution: type A trochlear dysplasia n = 25, type B n = 23, type C n = 18 and type D n = 14. In descriptive statistics, none of the measurements proposed in the literature could be assigned to the four-grade classification system of Dejour. For the two-grade analysis at the cut-off, sensitivity ranged from 75 to 86 % and specificity from 76 to 84 % for lateral trochlear inclination, trochlear facet asymmetry and depth of trochlear groove. All other measurements showed a poor sensitivity ranging from 49 to 67 % and specificity from 40 to 72 %. Interobserver and intraobserver repeatability for the measured parameters was fair to moderate (ICC values 0.34-0.58) in high-grade dysplasia (type BCD) and substantial to almost perfect (ICC values 0.71-0.88) in low-grade trochlear dysplasia (type A).

CONCLUSION

Quantitative measurements of the femoral trochlea have shown to be of limited value for the assessment of trochlear dysplasia. None of the quantitative measurements of the trochlea on transverse images could be assigned to the four-grade descriptive classification of trochlear dysplasia of Dejour. Additionally, measurements could not be reliably performed in high-grade trochlear dysplasia. However, trochlear inclination, trochlear facet asymmetry and depth of trochlear groove may help to distinguish between low-grade and high-grade dysplasia.

The contemporary management of anterior knee pain and patellofemoral instability

In this review the evidence for the management of patients with patellofemoral disorders is presented confined to anterior knee pain and patellar dislocation (excluding patellofemoral arthritis). Patients present along a spectrum of these two problems and are best managed with both problems considered. The key to managing these patients is by improving muscle function, the patient losing weight (if overweight), and judicious use of analgesics if pain is an important feature. Hypermobility syndrome should always be looked for since this is a prognostic indicator for a poor operative outcome. Operations should be reserved for those with correctable anatomical abnormalities that have failed conservative therapy. The current dominant operation is a medial patellofemoral ligament reconstruction.

Influence of rupture patterns of the medial patellofemoral ligament (MPFL) on the outcome after operative treatment of traumatic patellar dislocation

PURPOSE

Patellar dislocation usually occurs to the lateral side, leading to ruptures of the medial patellofemoral ligament (MPFL) in about 90 % of all cases. Reliable prognostic factors for the stability of the patellofemoral joint after MPFL surgery and satisfaction of the patient have not been established as yet.

METHODS

This multicentric study retrospectively included 40 patients with a mean age of 22.4 ± 8.1 years (range 9-48) from 5 German Trauma Departments with first-time traumatic patellar dislocation and operative treatment. Surgery was limited to soft tissue repairs, and a preoperative magnetic resonance imaging (MRI) was performed in all cases. Evaluation of the MRI included sulcus angle, dysplasia of the trochlea, depth and facet asymmetry of the trochlea, Insall-Salvati index, Tibial tuberosity to trochlear groove (TTTG) distance, and rupture patterns of the MPFL. Patients were interrogated after 2 years about recurrent dislocation, satisfaction, and the Kujala score.

RESULTS

Trochlea facet asymmetry was significantly lower in patients with redislocation (23.5 ± 18.8) than in patients without redislocation (43.1 ± 16.5, p = 0.03). Patients with a patellar-based rupture were significantly younger (19.5 ± 7.2 years) than patients without patellar-based rupture (25.4 ± 8.1 years, p < 0.02). Patients with femoral-based ruptures were significantly older (25.7 ± 9.2 years) than patients without femoral-based rupture (19.7 ± 6.1 years, p < 0.02), and had a significantly higher TTTG distance (10.2 ± 6.9 vs. 4.5 ± 5.5, p < 0.02). Patients with incomplete ruptures of the MPFL had a significantly lower Insall-Salvati index (1.2 ± 0.2 vs. 1.4 ± 0.2, p = 0.05). The Kujala score in patients with redislocations was significantly lower (81.0 ± 10.5 points) than in patients without redislocation (91.9 ± 9.2 points, p < 0.02).

CONCLUSION

Younger patients more often sustain patellar-based ruptures following first-time traumatic patella dislocation, while older patients more often sustain femoral-based ruptures of the MPFL. Incomplete MPFL ruptures are correlated with lower Insall-Salvati indices. Low trochlear facet asymmetry is correlated with higher rates of redislocation. These results may be of relevance for the operative and postoperative treatment in the future.

LEVEL OF EVIDENCE

Prognostic study, Level IV.

Distal realignment (tibial tuberosity transfer)

Although tibial tuberosity (TT) transfer has for many years been the basis of many protocols for the management of patellar instability, the role of pure medial transfer in particular appears to be declining. In contrast, the greater recognition of the importance of patella alta as a predisposing factor to recurrent patellar dislocation has resulted in a resurgence in the popularity of distal TT transfer. When TT transfer is performed, the direction and amount of transfer is based on the patellar height and the lateralization of the TT relative to the trochlear groove. Patellar height is best assessed on a lateral radiograph with the knee in flexion using a ratio that uses the articular surface of the patella in relation to the height above the tibia. Assessment of lateralization of the TT relative to the trochlear groove can be made using either computed tomography or magnetic resonance imaging scans.

Incidence and radiologic predictor of postoperative patellar instability after Fulkerson procedure of the tibial tuberosity for recurrent patellar dislocation

PURPOSE

Excellent results of anteromedialization of the tibial tuberosity for recurrent patellar dislocation have been reported; however, the contribution of the preoperative anatomic factors to postoperative patellar instability has not been well established. The purpose of this study was to investigate the mid-term results and the incidence of postoperative patellar instability after Fulkerson procedure for recurrent patella dislocation, and to determine the radiologic predictor of the postoperative patellar instability.

METHODS

Sixty-two knees of 41 patients underwent Fulkerson procedure with or without lateral retinacular release for recurrent patellar dislocation and were followed-up for 85-155 months. Predisposing anatomic factors for recurrent patellar dislocation were evaluated preoperatively, including valgus knee alignment (femorotibial angle), patella alta (Insall-Salvati ratio), trochlear dysplasia (trochlear depth), lateral patellar displacement (congruence angle) and lateral malposition of the tibial tuberosity (tibial tuberosity-trochlear groove distance). The relationship between the measurements of anatomic factors and postoperative patellar instability, which was defined by the patellar re-dislocation or residual apprehension after surgery, was analyzed.

RESULTS

The Fulkerson score and the Kujala score were significantly improved from the median of 65 (35-80) points and 68 (36-82) points preoperatively to 95 (60-100) points and 92 (57-100) points at the final follow-up, respectively. Three knees (4.8%) experienced postoperative patellar re-dislocation and 4 knees (6.5%) showed the positive apprehension sign at the final follow-up. The statistical analysis showed that the postoperative patellar instability correlated with only patella alta.

CONCLUSION

Patella alta was the only predictor of postoperative patellar instability after Fulkerson procedure. These results indicated that isolated Fulkerson procedure should not be indicated for recurrent patellar dislocation with severe patella alta.

LEVEL OF EVIDENCE

Case-control study, Level III.