Associated Anatomic Abnormalities in Patients Undergoing Rotational Tibial Osteotomies for Patellofemoral Pathology and Implications for the Level of Correction

Abstract

Purpose

Tibial rotational deformity is a known risk factor for patellofemoral joint (PFJ) disorders. However, it is commonly associated with other abnormalities which affect the PFJ. The purpose of this study was to describe the prevalence of associated factors known to affect PFJ in patients undergoing rotational tibial osteotomy and their implication for the correction level.

Methods

All patients with PFJ disorder, who underwent rotational tibial osteotomy between July 2009 and February 2020, were included. Patients were excluded if there were no preoperative computed tomography (CT)/magnetic resonance imaging (MRI). Scans were analyzed by 2 observers. Parameters of interest were femoral version, tibial torsion, trochlear dysplasia, lateral trochlear inclination (LTI), tibial tuberosity–trochlear groove (TT-TG) distance, Insall-Salvati (IS), and Caton Deschamps Index (CDI).

Results

The search resulted in 80 knees, which had a mean femoral version of 21.0 ± 11.7, tibial torsion of 45.9 ± 9.1, TT-TG of 18.3 ± 5.5, and LTI of 11.4 ± 14.7. In total, 42.5% had TT-TG value of ≥ 20 mm. Patella alta/baja was found in 54% based on CDI or IS >1.2 and <0.8. High-grade trochlear dysplasia was found in 25%. In total, 29% had a tibial torsion abnormality but normal TT-TG and patella height. In total, 18% had abnormal TT-TG but normal patellar height.

Conclusion

Based on the associated abnormalities of patella height and tubercle lateralization, 18% of the population were suitable for supratubercle osteotomy, and 29% of patients were suitable for diaphyseal or distal tibial osteotomy. A tibial tubercle osteotomy was required in 54% of patients, making a through-tubercle approach the most appropriate option for most patients.

Level of evidence:

Radiological cross-sectional study.

Keywords

patellofemoral pathology rotational tibial osteotomy level derotational osteotomy patellofemoral instability anterior knee pain

Introduction

Rotational deformities of the tibia and femur are known to be associated with patellofemoral (PFJ) disorders.^1-5 Tibial extorsion leads to an increased foot progression angle, which is compensated for by internal rotation of the hip.⁶ This results in an inward-pointing knee and creates a dynamic valgus with a resultant valgus vector on the patella, facilitating pain and instability.⁶ It also potentially creates a lateralized tibial tubercle, leading to a lateral rotation of the patella with increased lateral trochlea contact forces.⁷

The etiology of PFJ disorders is usually multifactorial and rotational abnormalities rarely occur in isolation. They are commonly associated with other anatomical abnormalities which affect the PFJ mechanics such as patella alta, increased tibial tuberosity–trochlear groove (TT-TG) distance, and trochlea dysplasia.^3,8 The association between some of these rotational anatomical risk factors has been previously highlighted in the literature.^3,8,9 Thakrar et al.¹⁰ reported a significant higher mean value for the knee joint rotational angle (KJRA) in patients with a pathological TT-TG distance ≥20 mm. They concluded that an increase in the TT-TG distance can be as a result of a lateralized tibial tubercle in isolation or in combination with a coexisting lower limb rotational malalignment. Imhoff et al.⁸ reported that patients with high-grade trochlear dysplasia showed significantly higher values for femoral torsion and significantly higher values for TT-TG distance. They also found a significant correlation between femoral torsion and tibial torsion, femoral torsion and TT-TG distance, femoral torsion and frontal mechanical axis, and tibial torsion and TT-TG distance. This reflects the complexity of bony malalignment in PFJ disorders and reinforces the need for a comprehensive patient evaluation of all anatomical abnormalities that influence the PFJ. Failure to address all significant pathology simultaneously will likely compromise clinical outcomes, and the correction of associated pathology has the potential to influence surgical approach. In addition, it is important to be aware of the impact of surgical approach on the tubercle position in order to avoid iatrogenic malposition.

A number of studies have reported good results following rotational osteotomy of the tibia at various levels for PFJ disorders.^11-13 Server et al.¹⁴ reported on 35 supratubercle tibial rotational osteotomies in patients with chronic PFJ subluxation secondary to lateral tibial torsion. The results were good or excellent in 88.5%, fair in 5.7%, and poor in 5.7%. Similarly, Drexler et al.¹⁵ reported a satisfactory outcome in 15 knees with recurrent patella subluxation and excessive external tibial torsion who underwent tibial derotational osteotomy at the level of tibial tubercle. However, these studies do not describe any associated anatomical risk factors which may contribute to the pathology and influence the surgical planning. Tibial derotational osteotomies can be performed at the level of the tibial tubercle, but also above or below the tubercle (in the tibial shaft or the supramalleolar region). Osteotomy above the tibial tubercle changes the TT-TG as the tibial tubercle moves medially when the distal tibia is internally rotated. This must be considered and planned, in order to avoid pathological negative values of the TT-TG. On the contrary, osteotomy below the tibial tubercle does not change the TT-TG or patellar height. Osteotomy at the level of the tibial tubercle removes the tubercle and enables correction of patellar height with additional consideration of the TT-TG, whether normal or pathological.

The purpose of this study was to comprehensively describe the prevalence of associated anatomical risk factors known to affect PFJ mechanics in a cohort of patients with significant rotational malalignment of the tibia undergoing corrective osteotomy and determine how the incidence of associated abnormalities could impact the surgical level of tibial correction.

Methods and Materials

Study Population

This study involved a retrospective analysis of diagnostic imaging in a cohort of patients with PFJ pain and/or instability. The study was approved by the internal institutional review board. All patients who underwent rotational osteotomy of the tibia by the senior author between July 2009 and February 2020 were included. Patients were excluded if they had undergone any prior realignment surgery, had a history of previous fracture of the involved limb, and if there were no preoperative computed tomography (CT) and magnetic resonance imaging (MRI) scans available on the hospital PACS for assessment. This resulted in a final study population of 86 patients.

All patients presented to our institution with PFJ pain and/or instability and had failed a minimum of 6 months of conservative treatment, which included a structured physiotherapy program. All patients prior to surgical intervention underwent a rotational CT of the lower limbs to assess tibial and femoral torsion in addition to TT-TG distance. The decision to proceed with tibial rotational correction was made by the senior author based on the assessment of the “combined torsional profile.” The torsional malalignment was considered significant if the tangent line at the posterior aspect of the distal femoral condyles relative to the distal transtibial axis was greater than 50°.⁶ The individual torsional alignment of the femur and tibia was then measured, and the site of correction was chosen based on the relative magnitude of the deformity in each bone compared to normal values. The normal values used, given a largely European population, are 15° (±8°) for femoral anteversion and 23° (±8°) for tibial torsion.

Radiological Evaluation

The preoperative CT/MRI scans were analyzed by 2 independent fellowship-trained surgeons. Parameters of interest were the femoral torsion, the tibial torsion, the grade of trochlear dysplasia, the lateral trochlear inclination (LTI) angle, the TT-TG distance, the Insalle-Salvati (IS),¹⁶ and the Catone Deschamps Index (CDI).¹⁷ Interclass correlation coefficients (ICCs) and Cohen’s kappa statistics were used to determine the interobserver reliability between the observers for different parameters.

The femoral torsion

This was determined on CT by Hernandez et al.¹⁸ technique, measuring the angle between the tangent line at the posterior aspect of the distal femoral condyles and the line that passes through the centers of the femoral head and femoral neck using 2 images for better evaluation of the femoral neck axis and reliability, as recommended by Kaiser et al.¹⁹ ( Fig. 1A-C ).^10,18,20

Figure 1.

Axial CT scan of right hip (A and B) and knee (C). Femoral torsion measurement: The center of the femoral head was defined by drawing a circle around the femoral head where it is most rounded (A). The center of femoral head was copied into the section, where the femoral head, isthmus of the femoral neck, and superior border of the greater trochanter are evident (yellow arrow). A line from the femoral head center passing through the center of femoral neck was drawn on the same section and the angle between it and the horizontal was measured (B). The angle apex was lateral (femoral neck is anteverted relative to horizontal), so it was given a positive value (+1.1). On the slice showing the most prominent femoral condyles, a tangent line at the posterior aspect of the condyles was drawn and the angle between it and the horizontal was measured (C). The angle apex was medial (condyles were internally rotated relative to horizontal), so it was given a positive value +20. The femoral version is calculated by adding measurements. Femoral torsion = +1.1 + 20 = +21.1° anteversion in this example.

Tibial torsion

This was determined by the Waidelich²¹ technique measuring the angle between the posterior proximal tibial axes (PTA) and the distal transtibial axis (DTA) on CT. PTA was defined as the line joining the 2 most posterior points of the plateau just distal to the articular surface of the tibial plateau and proximal to the fibular head. DTA was defined by drawing a line on the distal articular surface of the tibia bisecting both the medial malleolus and incisura (fibular sulcus) ( Fig. 2 ).^6,22,23

Figure 2.

Axial CT scan of right knee (A) and ankle (B). Tibial torsion measurement: The cut just distal to the articular surface of the tibial plateau and proximal to the fibular head was selected. PTA was defined by drawing line joining the 2 most posterior points of the plateau and the angle between PTA and horizontal was calculated. The apex of the angle was medial (PTA is internally rotated), so it was assigned a positive value +13.1 (A). DTA is defined by drawing a line on the distal articular surface of the tibia connecting the tip of the medial malleolus to the mid-point of fibular sulcus. The angle between DTA and horizontal was calculated. The apex of the angle was lateral (DTA externally rotated), so it was assigned a positive value. Tibial torsion was calculated by adding measurements. Tibial torsion = +13.1 + 32.5 = 45.6 external torsion in this example.

The tibial tuberosity–trochlear groove distance

This was determined by measuring the distance between the most anterior point of the tibial tuberosity and the deepest bony point of the TG, parallel to the tangent to the posterior condyles on axial CT scans ( Fig. 3 ).²⁴ A pathological TT-TG was defined as ≥20 mm.

Figure 3.

Axial CT scan of right knee. The tibial tuberosity–trochlear groove (TT-TG) distance: The most anterior point of the tibial tuberosity was identified on axial CT scan (yellow arrow) (A). This point is transferred into the section where the deepest point of the trochlea was identified (blue arrow) (B). A line through the deepest point of the trochlea perpendicular to a tangent line to the posterior femoral condyles was drawn. The distance between the point and the vertical line, parallel to the posterior tangent line, was measured. TT-TG = 9.9 mm in this example.

The trochlear dysplasia

Qualitative assessment was performed on axial CT scan approximately at the level of the medial femoral physeal scar, with cross-reference to sagittal CT view, or CT scout view.²⁵ Trochlear dysplasia was graded according to the Oswestry–Bristol Classification (OBC),²⁶ which classifies dysplasia into 4 grades: normal, mild, moderate, and severe. Normal is defined when the sulcus angle is less than 145, shallow when the sulcus angle 145° or more, moderate is when the trochlea is flat, and severe when it is convex²⁷ ( Fig. 4 ). A 2-group grading system was made for statistical analysis—high-grade dysplasia (included moderate and severe) and low-grade dysplasia (included only mild grade).

Figure 4.

Axial CT scan right knees with cross-reference to sagittal CT view. Trochlear dysplasia grading: The assessment was performed o axial CT scan approximately at the level of the medial femoral physeal scar. Mild dysplasia if trochlea was shallow (sulcus angle = 145 or more) (A). Moderate dysplasia if trochlea was flat (B). Severe dysplasia if trochlea was convex (C).

The lateral trochlear inclination angle

This is defined on CT as the angle between a line parallel to the lateral trochlear facet and a line tangent to the posterior femoral condyles.⁹ It is used to quantitatively evaluate trochlear dysplasia as it indirectly reflects the TG depth and geometry. Measurement was performed according to the 2 image techniques as described by Joseph et al.²⁸ ( Fig. 5 ). According to Carrillon et al.,⁹ LTI of <11 is associated with a 95% specificity of having patellar instability secondary to trochlear dysplasia.

Figure 5.

Axial knee CT scan with cross-reference to sagittal CT view. The lateral trochlear inclination angle (LTI): The section where the femoral condyles were most prominent and best defined was selected, and a line tangent to the posterior condyles was drawn (A). Next this line was copied into the previous section which was used to evaluate trochlear dysplasia at the level of physeal scar of medial femoral condyle. The lateral trochlear angle is calculated between the copied line and a line parallel to the lateral trochlear facet, and if the angle apex was medial, so it was assigned a + value (B). In a patient with a convex trochlea, a best-fit line between the most lateral part of lateral trochlea and the apex of the convexity was used to form an angle between the proximal trochlea and a tangent to posterior condyles; in this case, the angle apex was lateral, so it was assigned a −ve value (C).

Insall-Salvati¹⁶ and Caton Deschamps Index.¹⁷

These parameters were measured using CT or MRI on the midline sagittal section through the patella where the maximal length of the patella was visualized. Insall-Salvati (IS) was calculated as patellar tendon length divided by the patellar length ( Fig. 6 ).^29,30 In patients with significant lateralization or where initial measurements were normal, the measurement of patellar tendon length was repeated on a second slice where it shows its midline with max length, and the largest measurement taken. The Caton Deschamps Index (CDI) was calculated as the ratio between the distance from the lower pole patellar articular surface to the anterosuperior corner of the tibial joint surface and length of patellar articular surface ( Fig. 6 ).^29,30 These parameters were originally described on plain lateral radiographs but subsequently have been validated and used on CT and MRI scans.^29-33 The normal values used for IS and CDI are (0.8-1.2).

Figure 6.

Sagittal CT scan knee. Insalle-Salvati (IS) and Catone Deschamps Index (CDI): IS was calculated as the ratio between patellar tendon length (line a) and patellar length (line b) and CDI was calculated as the ratio between the distance from the lower pole patella articular surface to the upper limit of the tibia (line c) and the length of the patellar articular surface (line d).

Statistics

The data were analyzed using IBM SPSS software package version 20.0 (IBM Corp., Armonk, New York). Categorical data were represented as numbers and percentages. Continuous variables were calculated and presented as means ± standard deviation if it was normally distributed, and as median (range) if it was not normally distributed. Continuous data were tested for normality by the Kolmogorov–Smirnov test. Intraclass correlation coefficient was used for the evaluation of interobserver and intraobserver reliability for continuous variables in a random sample of 15 patients. The ICCs were classified using a system suggested by Koo and Li³⁴ as follows: less than 0.50 Z poor agreement; 0.50 to less than 0.75 Z moderate agreement; 0.75 to 0.90 Z good agreement; above 0.90 Z excellent agreement. The significance of the obtained results was judged at the 5% level. The interobserver and intraobserver agreement for trochlear dysplasia grade was determined using Cohen’s kappa statistics.

Results

Interobserver reliability was excellent for femoral version (0.942, P < 0.001) and IS (0.947, P < 0.001); good for tibial torsion (0.798, P < 0.001), TT-TG (0.811, P < 0.001), and LTI (0.792, P < 0.001); and moderate for CDI (0.742, P < 0.001). The interobserver agreement for trochlear dysplasia was fair (k = 0.400, P = 0.054).³⁵ Intraobserver reliability was good to excellent for all the radiographic measurements.

Following exclusions, a total of 80 knees were included for evaluation; the descriptive statistics of the demographical data and the main parameters are shown in Tables 1 and 2. A total of 34 knees (42.5%) had a pathological TT-TG value of ≥20 mm. Patella alta/baja was found in 43 knees (54%) based on CDI and/or IS >1.2 and <0.8. High-grade trochlear dysplasia was found in 20 knees (25%), whereas low-grade dysplasia was found in 44 (55%). A greater proportion of females 59 (73.8%) underwent correctional rotational osteotomy compared to males 21 (26.3%).

Table 1.

Distribution of the Studied Cases According to Different Parameters.

Parameter	No. (%)
Gender
Male	21 (26.2%)
Female	59 (73.8%)
Age (years)
Min.-Max	15.9-51.7
Mean ± SD	28.0 ± 9.8
Median (IQR)	26.0 (19.7-34.3)
Side
Right	46 (57.5%)
Left	34 (42.5%)

Table 2.

Distribution of the Studied Cases According to Different Parameters.

Parameter	Statistical description
Femoral version
Min.-Max	−1.0 to 51.0
Mean ± SD	21.0 ± 11.7
Median (IQR)	20.8 (13.0-27.5)
Tibial torsion
Min.-Max	37-62.7
Mean ± SD	45.9 ± 9.1
Median (IQR)	47.1 (43.0-50.5)
TT-TG (mm)
<20	46 (57.5%)
≥20	34 (42.5%)
Min.-Max	7.7-34.0
Mean ± SD	18.3 ± 5.5
Median (IQR)	18.3 (13.5-22.2)
Trochlear dysplasia CT
Normal	16 (20.0%)
Mild (low grade)	44 (55.0%)
Moderate (high grade)	9 (11.3%)
Severe (high grade)	11 (13.8%)
LTI/CT
Min.-Max	−43.0 to 30.0
Mean ± SD	11.4 ± 14.7
Median (IQR)	15.8 (10.0-20.3)
CDI
Min.-Max	0.583-1.68
Mean ± SD	1.17 ± 0.17
Median (IQR)	1.18 (1.1-1.3)
IS
Min.-Max	0.69 ± 1.5
Mean ± SD	1.19 ± 0.18
Median (IQR)	1.20 (1.1-1.3)
Patellar height
Normal	37 (46%)
Alta	42 (53%)
Baja	1 (1%)

IQR = interquartile range; SD = standard deviation.

A torsional abnormality with a normal TT-TG and patella height was found in 23 knees (29%). Of the 23 knees, 17 knees had trochlea dysplasia, leaving only 6 (7.5%) patients with isolated tibial torsion abnormalities. Fourteen knees (18%) had an abnormal TT-TG but normal patellar height.

A total of 20 knees (25%) had abnormal femoral version based on the normal reference value of 15 ± 8°. Eighteen knees (22.5%) had increased femoral anteversion (>23°) and 2 (2.5%) had femoral retroversion (<7°).

Discussion

The main findings of this study were that there was a high prevalence of additional anatomical risk factors in patients with tibial rotational abnormalities undergoing corrective tibial osteotomy. These include increased femoral anteversion (25%), increased pathological TT-TG distance (42.5%), trochlear dysplasia (80%), and patella alta/baja (54%). A greater number of females (73.3%) were treated compared to males (26.7%).

The median tibial torsion in the studied population was 47.1° with interquartile range (IQR) of 43.0 to 50.5. Although there is no well-defined cut-off value of tibial torsion to perform a derotational osteotomy, a recent systematic review by Ferreira et al.¹² has shown that correcting excessive tibial torsion >30° was associated with statistically significant clinical improvements and advocated correcting at this level. Although the indication for correction in this study was based on different criteria, all patients had a tibial torsion above 30°. Given that a reasonable reference range for tibial torsion in a European population is 23 ± 8°, this is a representative pathological population.⁶

There are a number of studies which have reported on the prevalence of anatomical risk factors in patients presenting with PFJ pain and/or instability symptoms.^3,8 To our knowledge, this is the first study to report on the prevalence of associated anatomic PFJ risk factors in a patient population with significant tibial rotational malalignment. Trochlear dysplasia is a known risk factor for PFJ disorders, in particular, recurrent instability.^3,36,37 Trochlear dysplasia was found in 80% of the current studied population (55% low grade, and 25% high grade). The median LTI of the studied population was 15.8 with IQR of 10.0 to 20.3. The LTI indirectly reflects the TG depth and geometry, and it was first proposed by Carrillon et al.⁹ as a quantitative evaluation of trochlear dysplasia. They found significant differences in LTI values between a patellar instability group and a normal control group and indicated a threshold value less than 11 as a diagnostic test of patellar instability. Imhoff et al. reported that increased grade of trochlear dysplasia was associated with higher mean values for TT-TG distance (low grade: 19.0 mm ± 5.0 mm, high grade: 21.9 mm ± 5.4 mm; P = 0.002). It has thus been suggested that trochlear dysplasia constitutes an element of groove medialization in addition to the previously described decreased groove depth and the supratrochlear prominence.³⁸ Correcting trochlea dysplasia without correcting the abnormal mechanics secondary to a rotational abnormality carries a potential increased risk of osteoarthritis, as the patella can be captured in trochlea.³⁹ In this study, 20 patients (25%) had high-grade trochlea dysplasia which would have been suitable for trochleoplasty.

Previous studies have shown that the TT-TG was significantly higher in patients with PFJ pain and instability compared to a normal control group and defined a 20-mm value as a pathologic threshold.^3,40,41 In the current studied population, with significant tibial rotational malalignment, 42.5% of the knees had a TT-TG ≥ 20 mm which required tibial tubercle medialization. The associations between TT-TG and femoral/tibial torsion have been previously investigated in the literature. Imhoff et al.⁸ reported a significant correlation between femoral torsion and TT-TG distance (r = 0.328, P < 0.001) and tibial torsion and TT-TG distance (r = 0.182, P = 0.026). However, Xu et al.⁴² found that increased TT-TG distance was significantly positively correlated with femoral anteversion but not tibial torsion in 80 patients with recurrent lateral patellar dislocation versus 80 controls. Similarly, Xu Z et al.⁴³ found that TT-TG distance was significantly correlated with diaphyseal femoral and distal femoral version but not tibial torsion. The majority of patients in this study had a normal TT-TG; this is important to be aware of and identify, as tubercle position has a significant influence on surgical technique.

Previous studies have reported an increased prevalence of patella alta in patients with PFJ problems and highlighted patella alta as a risk factor for recurrent patellar instability.^3,37,44 However, the association of patella alta and rotational malalignment remains underreported in the literature. IS and CDI are the most commonly used measurements for evaluation of patellar height with cut-off value >1.2 for diagnosing patella alta.⁴⁵ Patella alta was found in 42 patients (53%) patients and baja in 1 patient (1%) of the current cohort. Patella alta is associated with decreased bony stability secondary to the delayed entry of the patella into the trochlear groove; thus, there is a greater arc of knee motion in early flexion in which the patella is potentially subjected to lateral forces leading to a patellar instability.⁴⁵ Patella alta increases the quadriceps moment arm, resulting in greater compression forces and a decrease in the PFJ contact area between 0° and 60° of flexion, leading to a higher risk of cartilage degeneration and subsequent PFJ pain.³⁸ Rotational osteotomy of either the tibia or femur will not correct for patellar height, and so consideration needs to be given to undertaking a tubercle distalization in parallel if thought to be significant.

Tibial derotational osteotomies can be performed above (supratubercle), at the level, or below the tibial tubercle (at the tibial shaft or at the supramalleolar region). Osteotomy above the tibial tubercle changes the TT-TG, as the tibial tubercle moves medially when the distal tibia is internally rotated. The effect on TT-TG following supratubercle tibial osteotomy has been investigated using finite element analysis, and it has been calculated that a 0.6-mm TT-TG correction occurs for every 1° of tibial correction.⁴⁶ Ferner et al.⁴⁷ similarly reported that with 1° of torsional correction, the TT-TG decreases 0.45 mm using the surgical technique. Consequently, a 20° tibial correction will reduce the TT-TG between 9 and 12 mm. Supratubercle osteotomy should thus only be performed in individuals with abnormal TT-TG and normal patella height in order to avoid the risk of overmedialization and the potential for pain and medial instability. In the current study, only 14 knees (17.5%) had abnormal TT-TG and normal patellar height and thus could be considered suitable for osteotomy at this level. Osteotomy distal to the tibial tubercle does not change the TT-TG or patellar height and so would only be appropriate for patients with isolated tibial torsion deformity. In the current study, only 23 knees (28.75%) would have been considered suitable for osteotomy at this level.

An osteotomy at the level of the tibial tubercle involves removal of the tubercle, which has the benefit of improving the surgical exposure. Tubercle osteotomy in addition enables correction of patella height, which was present in 54% of the study population. Patella alta, however, can occur in the presence of both a normal and abnormal TT-TG. In the situation of an abnormal TT-TG, the tubercle can be placed on the medialized bed of the distal tibia. Conversely, in the situation where the TT-TG is normal, the tubercle can be lateralized in order to prevent iatrogenic deformity. In theory, a through-tubercle osteotomy can be performed in 100% of cases, as long as attention is paid to the preoperative patella height and TT-TG distance, and the surgical technique is adjusted accordingly. Given the volume of rotational osteotomies performed per year by surgeons, even with a specialist interest, is generally low, a through-tubercle osteotomy may be the preferable osteotomy level in order to maintain competency and minimize surgical risk.

Different techniques have been described in the literature to measure the femoral torsion including Hernandez et al.,¹⁸ Yoshioka and Cooke,⁴⁸ Murphy et al.,^49,50 Waidelich et al.,²¹ Jarrett et al.,⁵¹ and Weiner et al.⁵² The measured femoral torsion values showed significant differences among different techniques,¹⁹ and the need to use standard values for each measurement technique has been advocated. In a comparison study by Liodakis et al.,⁵⁰ the Hernandez technique achieved greater intraobserver and interobserver reliability than the method described by Weiner et al. Abnormal femoral version was present in 20 knees (25%) within the study population. Tibial derotation osteotomy was performed in this group, as the tibia had the largest percentage deviation from the norm and/or the deformity was equivalent, but there was the presence of associated patella alta and/or pathological TT-TG. Currently, there is limited evidence to suggest that double-level rotational correction is appropriate. Fouilleron et al.⁵³ found no difference in the satisfaction index, PFJ score, or The International Knee Society (IKS) score between patients with a femoral torsion above or below 20°. Consequently, they concluded in patients with combined deformity, patellar recentering can be successfully obtained by an isolated tibial derotation osteotomy procedure alone. Manilov et al.¹³ have also reported similar results in their series when including patients with increased femoral anteversion up to 25°.

There are several limitations in the current study. CT scan imaging was only used in the current study for the descriptions of trochlear dysplasia and so are based on bony anatomy rather than cartilage. Previous studies have shown that there is a cartilage-bone mismatch in the dysplastic trochlea, which may lead to some variation in the results.⁵⁴ However, Thakkar et al.⁵⁵ have demonstrated that either MRI or CT can be used for the measurement of trochlear angle and trochlear depth with excellent interobserver reliability. Inclusion of only patients undergoing surgery may not reflect the incidence of associated abnormalities in all patients with rotational issues, but the aim of this study was to determine how the associated abnormalities affect the surgical level of correction. Outcome scores were not recorded in all patients and are consequently not presented, and so the correlation between the effect of associated abnormalities is not possible.

Conclusion

Within this geographical population of patients undergoing tibial rotational osteotomy for PFJ pain and/or instability, 25% had increased femoral anteversion, 42.5% had a high TT-TG distance, 54% had abnormal patella height, and 80% of patients had trochlea dysplasia. Based on the associated abnormalities of patella height and tubercle lateralization, 18% of the population were suitable for supratubercle osteotomy (had abnormal TT-TG but normal patellar height) and 29% of patients were suitable for diaphyseal or distal tibial osteotomy (had normal TT-TG and patellar height). A tibial tubercle osteotomy was required in 54% of patients (had abnormal patellar height) making a through-tubercle approach the most appropriate option for the majority of patients.

Footnotes

Acknowledgments and Funding

M.H. was funded by a full scholarship (ID: NMJ10/20) from the Ministry of Higher Education of the Arab Republic of Egypt for 1-year clinical research fellowship at the Royal Orthopaedic Hospital, UK.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethical Approval

Ethical approval was not required for the current study, as this was a retrospective analysis of investigations which had already been performed. It was registered with internal research governance as an audit project.

ORCID iDs

Mohammad Haikal

Renjit Issac

Martyn Snow

Data Availability

The data that support the findings of this study are available from the corresponding author upon reasonable request and are not openly available due to reasons of sensitivity.

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Associated Anatomic Abnormalities in Patients Undergoing Rotational Tibial Osteotomies for Patellofemoral Pathology and Implications for the Level of Correction

Abstract

Purpose

Methods

Results

Conclusion

Level of evidence:

Keywords

Introduction

Methods and Materials

Study Population

Radiological Evaluation

The femoral torsion

Tibial torsion

The tibial tuberosity–trochlear groove distance

The trochlear dysplasia

The lateral trochlear inclination angle

Insall-Salvati 16 and Caton Deschamps Index. 17

Statistics

Results

Discussion

Conclusion

Footnotes

Acknowledgments and Funding

Declaration of Conflicting Interests

Ethical Approval

ORCID iDs

Data Availability

References

Insall-Salvati¹⁶ and Caton Deschamps Index.¹⁷