Recognized anatomic variations that lead to patella instability include patella alta and trochlea dysplasia. Lateralization of the extensor mechanism relative to the trochlea is often considered to be a contributing factor; however, controversy remains as to the degree this contributes to instability and how this should be measured. As the tibial tuberosity-trochlear groove (TT-TG) is one of most common imaging measurements to assess lateralization of the extensor mechanism, it is important to understand its strengths and weaknesses. Care needs to be taken while interpreting the TT-TG value as it is affected by many factors. Medializing tibial tubercle osteotomy is sometimes used to correct the TT-TG, but may not truly address the underlying anatomical problem. This review set out to determine whether the TT-TG distance sufficiently summarizes the pathoanatomy, and if this assists with planning of surgery in patellar instability. Cite this article: Bone Jt Open 2022;3(3):268–274

Evaluating musculoskeletal conditions of the lower limb and understanding the pathophysiology of complex bone kinematics is challenging. Static images do not take into account the dynamic component of relative bone motion and muscle activation. Fluoroscopy and dynamic MRI have important limitations. Dynamic CT (4D-CT) is an emerging alternative that combines high spatial and temporal resolution, with an increased availability in clinical practice. 4D-CT allows simultaneous visualization of bone morphology and joint kinematics. This unique combination makes it an ideal tool to evaluate functional disorders of the musculoskeletal system. In the lower limb, 4D-CT has been used to diagnose femoroacetabular impingement, patellofemoral, ankle and subtalar joint instability, or reduced range of motion. 4D-CT has also been used to demonstrate the effect of surgery, mainly on patellar instability. 4D-CT will need further research and validation before it can be widely used in clinical practice. We believe, however, it is here to stay, and will become a reference in the diagnosis of lower limb conditions and the evaluation of treatment options.

Cite this article: Bone Joint J 2021;103-B(5):822–827.

Aims

The Oswestry-Bristol Classification (OBC) was recently described as an MRI-based classification tool for the femoral trochlear. The authors demonstrated better inter- and intraobserver agreement compared to the Dejour classification. As the OBC could potentially provide a very useful MRI-based grading system for trochlear dysplasia, it was the aim to determine the inter- and intraobserver reliability of the classification system from the perspective of the non-founder.

Aims

The purpose of this study was to explore the correlation between femoral torsion and morphology of the distal femoral condyle in patients with trochlear dysplasia and lateral patellar instability.

Aims. The Bereiter trochleoplasty has been used in our unit for 12 years to manage recurrent patellar instability in patients with severe trochlea dysplasia. The aim of this study was to document the outcome of a large consecutive cohort of patients who have undergone this operation. Patients and Methods. Between June 2002 and August 2013, 214 consecutive trochleoplasties were carried out in 185 patients. There were 133 women and 52 men with a mean age of 21.3 years (14 to 38). All patients were offered yearly clinical and radiological follow-up. They completed the following patient reported outcome scores (PROMs): International Knee Documentation Committee subjective scale, the Kujala score, the Western Ontario and McMaster Universities Arthritis Index score and the short-form (SF)-12. . Results. Outcomes were available for 199 trochleoplasties in 173 patients giving a 93% follow-up rate at a mean of 4.43 years (1 to 12). There were no infections or deep vein thromboses. In total, 16 patients reported further patella dislocation, giving an 8.3% rate of recurrence. There were 27 re-operations, giving a rate of re-operation of 14%. Overall, 88% were satisfied with the operation and 90% felt that their symptoms had been improved. . Conclusion. All PROMs improved significantly post-operatively except for the mental component score of the SF-12. Trochleoplasty performed using a flexible osteochondral flap is an effective treatment for recurrent patellar instability in patients with severe trochlea dysplasia and gives good results in the medium term. Cite this article: Bone Joint J 2017;99-B:344–50

The aim of this study is to document the outcome of a large cohort of patients treated with the Bereiter trochleoplasty with between 1 and 12 years of follow up. 215 consecutive cases in 186 patients were recorded prospectively. All patients were offered yearly clinical and radiological review. PROMs were recorded including the IKDC, OKS, Kujala and SF-12. Patients unable to attend clinic were assessed with PROMS and radiographs from their local institutions where possible. There were 133 females and 53 males, with a mean age of 21 (14–38). There were no infections and only 6 patients reported further dislocations. There was one flap breakdown and no identified cases of secondary osteoarthritis. PROMs were available for 194 cases in 167 patients (90% follow up). 84% of patients were satisfied, 87% felt their symptoms had improved and 69% had gone back to sport. All scores improved (all p<0.001) except for the SF-12 mental score (p=0.42), with averages comparable to the results of MPFL reconstruction. Good outcomes were observed despite the difficult patient population in which these cases were performed. The Bereiter trochleoplasty is an effective method of treating recurrent patella instability in patients with severe trochlea dysplasia

Introduction. Patellofemoral pain and instability can be quantified by using the tibial tuberosity to trochlea groove (TT-TG) distance with more than or equal to 20mm considered pathological requiring surgical correction. Aim of this study is to determine if knee joint rotation angle is predictive of a pathological TT-TG. Methods. One hundred limbs were imaged from the pelvis to the foot using Computer Tomography (CT) scans in 50 patients with patellofemoral pain and instability. The TT-TG distance, femoral version, tibial torsion and knee joint rotation angle ((KJRA) were measured. Limbs were separated into pathological and non-pathological TT-TG. Significant differences in the measured angles between the pathological and non-pathological groups were estimated using the t test. The inter- and intraobserver variability of the measurement was performed. Logistic regression analysis was used to find the best combination of rotational angle predictors for a pathological TT-TG. Results. The intraclass correlation coefficients for inter- and intraobserver variability of the measured parameters was higher than 0.94 for all measurements. A statistically significant difference (P=0.024) was found between the KJRA between the pathological (mean=10.6, SD=7.79 degrees) and the non-pathological group (mean=6.99, SD=5.06 degrees). Logistic regression analysis showed that both femoral version (P=0.03, OR = 0.95) and KJRA (P=0.004, OR=1.15) were, in combination, significant predictors of an abnormal TT-TG. Tibial torsion was not a significant predictor. Conclusion. The KJRA can be used as an alternative measurement when the TT-TG distance cannot be measured as in cases of severe trochlea dysplasia and may act as a surrogate for pathological TT-TG

This study is a prospective analysis of clinical outcome in 201 consecutive patients treated with medial patellofemoral ligament reconstruction using an autologous semitendinosus graft between October 2005 and January 2011. Patients received pre and post-operative clinical evaluation, radiological assessment and outcome scoring systems. 193 patients (92 male, 119 female) underwent 211 procedures, with mean age 26 (16–49) and follow-up 16 months (6–42 months). Indications were atraumatic recurrent patella dislocation (68%), traumatic recurrent dislocation (22.8%), instability (5%), single dislocation (2.7%) and anterior knee pain (1.4%). Trochlea dysplasia was moderate in 57% and mild in 35%. There have been no recurrent dislocations/ subluxations. 10 patients have required further surgery. The mean pre-op Kujala Scores were 55 (SE 5.21) and post-op scores improved to mean 82 (31–100) (SE 1.18)(p < 0.001). This improvement and significance is mirrored with Oxford (27 to 41), WOMAC (76 to 93), Fulkerson (53 to 83), IKDC (46 to 75), Tegner (4.1 to 5.3) and SF12 (38 to 51) scores (p < 0.005). 93% of patients were satisfied with their operation. History of prior realignment surgery was associated with significantly worse outcomes compared to patients where MPFL reconstruction was their first realignment procedure (p < 0.05). This series is the largest reported in the literature for any technique of MPFL surgery. This technique allows for objective intra-operative evaluation of the required graft tension to optimise patella tracking

We report a prospective analysis of clinical outcome in patients treated with medial patellofemoral ligament (MPFL) reconstruction using an autologous semitendinosus graft. The technique includes superolateral portal arthroscopic assessment before and after graft placement to ensure correct graft tension and patellar tracking before fixation. Between October 2005 and October 2010, a total of 201 consecutive patients underwent 219 procedures. Follow-up is presented for 211 procedures in 193 patients with a mean age of 26 years (16 to 49), and mean follow-up of 16 months (6 to 42). Indications were atraumatic recurrent patellar dislocation in 141 patients, traumatic recurrent dislocation in 50, pain with subluxation in 14 and a single dislocation with persistent instability in six. There have been no recurrent dislocations/subluxations. There was a statistically significant improvement between available pre- and post-operative outcome scores for 193 patients (all p < 0.001). Female patients with a history of atraumatic recurrent dislocation and all patients with history of previous surgery had a significantly worse outcome (all p < 0.05). The indication for surgery, degree of dysplasia, associated patella alta, time from primary dislocation to surgery and evidence of associated cartilage damage at operation did not result in any significant difference in outcome.

This series adds considerably to existing evidence that MPFL reconstruction is an effective surgical procedure for selected patients with patellofemoral instability.

Purpose of the study: The purpose of this retrospective work was to analyse a series of ten patients (11 osteotomies) who underwent closed rotation osteotomy of the femur performed with an endomedullary saw and stabilized with a centromedullar locked nail. We identified the proper indications, technical aspects, clinical and radiological outcome and describe the complications of this surgical technique. Material and method: The 11 osteotomies were performed in ten patients from January 1999 to July 2007 for post-trauma rotation defects or congenital deformity. On average the rotation defect was 33.5 (range 24–52), mainly internal rotation (10 cases versus 1 with external rotation). One female patient required a bilateral procedure in a context of congenital bilateral trochlea dysplasia. For two other patients the corrective osteotomy was associated with a lengthening procedure performed during the same operative time (totally closed operation). Clinical and radiological follow-up was available to 4 years 9 months on average (range 26–104 months). The angle corrections were determined on bone tomographs. Results: Ten of the 11 osteotomies yielded correction to ±4° physiological values (or controlateral values if the other side was healthy) for anteversion of the femoral neck. There were no infections (bone, joint, skin, soft tissue) and not late healing or non-union. There was one transient neurological complication involving the pudendal nerve during a rotation-lengthening procedure and one bilateral fracture of the femur during a bilateral osteotomy. All patients healed within 3 to 5 months. Subjective outcome was satisfactory very satisfactory for 8 of 9 patients (one lost to follow-up) in terms of functional recovery and aesthetic aspect of the scars. Discussion: The closed procedure for rotation osteotomy of the adult femur is a reliable, effective, safe and reproducible technique for the correction of rotation defects of the femur resulting from trauma or congenital disorders. These results can be obtained only with rigorous technique requiring experience and skill with centromedullary nailing

Purpose: Trochlea dysplasia is a developmental condition characterized by an abnormally flat or dome shaped trochlea. This predisposes to recurrent patella instability. This study prospectively reviews the early results of patients undergoing a trochleoplasty procedure which corrects the dysplastic anatomical abnormality. Patients and Methods: All patients were recruited from the senior author’s (JDJE) specialist knee clinic following the standard patellofemoral assessment. Patients were seen pre-operatively to collect epidemiological data, ensure completion of patient reported assessment forms and document clinical examination findings and investigations. Duration of instability and previous procedures performed for patella instability were recorded. Multiple patient-reported outcome measures were recorded. Outcome score assessments and clinical examinations were repeated post-operatively, along with a patient satisfaction questionnaire. All operations were carried out by the senior author with supplementary procedures based on pre-operative assessment. Results: 22 patients had a minimum of 12 months follow-up. The average age was 21 years and the average duration of instability symptoms (pre-trochleoplasty) was 7 years. There were 16 females and 6 males. Mean follow up was 18 months. Patients reported improvement in outcome when the pre and post-operative scores were compared (mean scores of Oxford 34 to 41, WOMAC 23 to 15, Kujula 62 to 79, IKDC 62 to 81, and Lysholm 57 to 77). The patient satisfaction questionnaire revealed just one patient not satisfied with the procedure despite good patient reported outcome scores. The majority of patients perceived improvement due to the surgery and agreed they would recommend the procedure to others despite some residual symptoms. Recurrent instability after trochleoplasty was rare (one subluxation) and range of movement was uniformly excellent. Conclusion: Early results of this trochleoplasty for patients with trochlea dysplasia and symptomatic recurrent patella instability are encouraging

Chronic patellofemoral instability can be a disabling condition. Management of patients with this condition has improved owing to our increased knowledge of the functional anatomy of the patellofemoral joint. Accurate assessment of the underlying pathology in the unstable joint enables the formulation of appropriate treatment. The surgical technique employed in patients for whom non-operative management has failed should address the diagnosed abnormality. We have reviewed the literature on the stabilising features of the patellofemoral joint, the recommended investigations and the appropriate forms of treatment.

An abnormal lateral position of the tibial tuberosity causes distal malalignment of the extensor mechanism of the knee and can lead to lateral tracking of the patella causing anterior knee pain or objective patellar instability, characterised by recurrent dislocation. Computer tomography is used for a precise pre-operative assessment of the tibial tubercle-trochlear groove distance. A distance of more than 15 mm is considered to be pathological and an indication for surgery in symptomatic patients.

In a prospective study we performed a subtle transfer of the tibial tuberosity according to the information gained from the pre-operative CT scan. This method was applied to two groups of patients, those with painful lateral tracking of the patella, and those with objective patellar instability. We evaluated the clinical results in 30 patients in each group. The outcome was documented at 3, 12 and 24 months using the Lysholm scale, the Kujala score, and a visual analogue pain score.

Post-operatively, all but one patient in the instability group who had a patellar dislocation requiring further surgery reported good improvement with no further subluxation or dislocation. All patients in both groups had a marked improvement in pain and functional score. Two patients sustained a tibial fracture six and seven weeks after surgery. One patient suffered a per-operative fracture of the tibial tubercle which later required further fixation.

If carefully performed, this type of transfer of the tibial tubercle appears to be a satisfactory technique for the treatment of patients with an increased tibial tubercle-trochlear groove distance and who present with symptoms related to lateral maltracking of the patella.

Purpose: We performed a biometric evaluation of the femoral trochlea in the human foetus and compared measurements with those observed in the adult in order to search for correlations with other biometric parameters of the human femur. Material: Twenty-two foetuses with no orthopaedic anomalies were preserved in formol. The 44 knees were studied. Fœtal age varied from 26 to 40 weeks. Method: After anatomic dissection, digital photographic documents were analysed using angular measurement software. The following dimensions were measured on the distal epiphysis: anteroposterior thickness of the condyles, protrusions of the lateral and medial trochleal edges, the difference in condyle height, the trochlear opening angle alpha, trochlear slope. Femoral anteversion, length of the femoral neck, and the neck-shaft angle were measured on the AP view of the femur. Spearman’s test was used to search for correlations. Results were compared with those measured under the same conditions in a series of 32 adult knees published by Wanner. Results: The alpha angle of trochlear opening was 148° with a coefficient of variability of 4%. The alpha angle was greater than 150° in 18 trochleae. The lateral edge of the trochlea was higher than the medial edge in 37/44 trochleae. There was no correlation by age and sex. The femoral measurements showed 27.01° anteversion with very wide variability (coefficient 46%) and no correlation with trochlear opening. No significant differences were observed between the fœtal and adult measurements. Discussion: Our data are the first reporting anatomic measurements of the fœtal trochlea. The morphology of the lower extremity of the femur during the third trimester of pregnancy is globally the same as in adult femurs. Morphological changes of the proximal femur occurring during growth do not appear to modify the morphology of the distal femur. The deep and asymmetrical engagement of the patella onto the trochlea is a characteristic of modern man and is considered to be a consequence of bipedal stance. Our study would appear to confirm that the anatomic characteristics of the human trochlea have been integrated into the genome in the course of evolution. This suggests that a genetic origin of trochlea dysplasia, as suggested by Dejour, is a reasonable hypothesis