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

Axial radiographs were obtained under valgus and external rotation stress at 45° of knee flexion with and without contraction of the quadriceps muscle in order to assess the dynamics of patellar subluxation or dislocation. The radiography was performed on 82 knees in 61 patients with patellofemoral instability, and on 44 normal knees. The lateral patellofemoral angle and the congruence angle were measured and compared with the conventional Merchant views. Both parameters showed greater differences between symptomatic and normal knees on the stress radiographs obtained without quadriceps contraction. There was a major difference in the lateral patellofemoral angles between the groups, which clearly distinguished symptomatic knees from normal controls. Congruence angles on stress radiography had a significant correlation with the functional scores obtained after a period of conservative treatment and a positive correlation with the frequency of patellar subluxation. When the quadriceps contracted, two patterns of patellar shift were observed. While the patella reduced into the trochlear groove in all normal knees and about 70% of the symptomatic knees, contraction of the quadriceps caused further subluxation of the patella in the remaining symptomatic knees. All the knee joints which showed this displacement failed to respond to conservative treatment and eventually required surgical treatment. Thus, this technique of stress radiography is a simple, cost-effective and useful method of evaluating patellar instability and predicting the prognosis

The June 2024 Children’s orthopaedics Roundup. 360. looks at: Proximal femoral unicameral bone cysts: is ESIN the answer?; Hybrid-mesh casts in the conservative management of paediatric supracondylar humeral fractures: a randomized controlled trial; Rate and risk factors for contralateral slippage in adolescents treated for slipped capital femoral epiphysis; CRP predicts the need to escalate care after initial debridement for musculoskeletal infection; Genu valgum in paediatric patients presenting with patellofemoral instability; Nusinersen therapy changed the natural course of spinal muscular atrophy type 1: what about spine and hip?; The necessity of ulnar nerve exploration and translocation in open reduction of medial humeral epicondyle fractures in children

Aims. Classifying trochlear dysplasia (TD) is useful to determine the treatment options for patients suffering from patellofemoral instability (PFI). There is no consensus on which classification system is more reliable and reproducible for the purpose of guiding clinicians’ management of PFI. There are also concerns about the validity of the Dejour Classification (DJC), which is the most widely used classification for TD, having only a fair reliability score. The Oswestry-Bristol Classification (OBC) is a recently proposed system of classification of TD, and the authors report a fair-to-good interobserver agreement and good-to-excellent intraobserver agreement in the assessment of TD. The aim of this study was to compare the reliability and reproducibility of these two classifications. Methods. In all, six assessors (four consultants and two registrars) independently evaluated 100 axial MRIs of the patellofemoral joint (PFJ) for TD and classified them according to OBC and DJC. These assessments were again repeated by all raters after four weeks. The inter- and intraobserver reliability scores were calculated using Cohen’s kappa and Cronbach’s α. Results. Both classifications showed good to excellent interobserver reliability with high α scores. The OBC classification showed a substantial intraobserver agreement (mean kappa 0.628; p < 0.005) whereas the DJC showed a moderate agreement (mean kappa 0.572; p < 0.005). There was no significant difference in the kappa values when comparing the assessments by consultants with those by registrars, in either classification system. Conclusion. This large study from a non-founding institute shows both classification systems to be reliable for classifying TD based on axial MRIs of the PFJ, with the simple-to-use OBC having a higher intraobserver reliability score than that of the DJC. Cite this article: Bone Jt Open 2023;4(7):532–538

Aims. Trochlear dysplasia is a significant risk factor for patellofemoral instability. The Dejour classification is currently considered the standard for classifying trochlear dysplasia, but numerous studies have reported poor reliability on both plain radiography and MRI. The severity of trochlear dysplasia is important to establish in order to guide surgical management. We have developed an MRI-specific classification system to assess the severity of trochlear dysplasia, the Oswestry-Bristol Classification (OBC). This is a four-part classification system comprising normal, mild, moderate, and severe to represent a normal, shallow, flat, and convex trochlear, respectively. The purpose of this study was to assess the inter- and intraobserver reliability of the OBC and compare it with that of the Dejour classification. Methods. Four observers (two senior and two junior orthopaedic surgeons) independently assessed 32 CT and axial MRI scans for trochlear dysplasia and classified each according to the OBC and the Dejour classification systems. Assessments were repeated following a four-week interval. The inter- and intraobserver agreement was determined by using Fleiss’ generalization of Cohen’s kappa statistic and S-statistic nominal and linear weights. Results. The OBC showed fair-to-good interobserver agreement and good-to-excellent intraobserver agreement (mean kappa 0.68). The Dejour classification showed poor interobserver agreement and fair-to-good intraobserver agreement (mean kappa 0.52). Conclusion. The OBC can be used to assess the severity of trochlear dysplasia. It can be applied in clinical practice to simplify and standardize surgical decision-making in patients with recurrent patella instability. Cite this article: Bone Joint J 2020;102-B(1):102–107

Trochlear dysplasia is a developmental condition characterised by an abnormally flat or dome-shaped trochlea and is an important contributory factor to patellofemoral instability and recurrent dislocation. We studied prospectively a series of 54 consecutive patients (59 knees) with patellofemoral instability secondary to trochlear dysplasia, who were treated by a trochleoplasty by a single surgeon between June 2002 and June 2007. Pre- and post-operative scores were assessed by the patients and a satisfaction questionnaire was completed. Of the 54 patients (59 knees) in the series, 39 (44 knees) were female and 15 (15 knees) were male. Their mean age at surgery was 21 years and 6 months (14 years 4 months to 33 years 11 months). In 40 patients (42 knees) the mean follow-up was for 24 months (12 to 58). One patient was unable to attend for follow-up. An analysis of the results of those patients followed up for at least 12 months showed a statistically significant improvement in outcome (p < 0.001 for all scores). Overall, 50 patients (92.6%) were satisfied with the outcome of their procedure. The early results of trochleoplasty are encouraging in this challenging group of patients

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

Aims. The aim of this study was to determine and compare the congruency of the articular surface contact area of the patellofemoral joint (PFJ) during both active and passive movement of the knee with the use of an MRI mapping technique in both the stable and unstable PFJ. Patients and Methods. A prospective case-control MRI imaging study of patients with a history of PFJ instability and a control group of volunteers without knee symptoms was performed. The PFJs were imaged with the use of an MRI scan during both passive and active movement from 0° through to 40° of flexion. The congruency through measurement of the contact surface area was mapped in 5-mm intervals on axial slices. In all, 40 patients were studied. The case group included 31 patients with symptomatic patellofemoral instability and the control group of nine asymptomatic volunteers. The ages were well matched between the case and control groups. The mean age was 25 years (16 to 42; . sd. 6.9) in the case group and 26 years (19 to 32; . sd. 5.1) in the control group. There were 19 female and 12 male patients in the case group. Results. The unstable PFJs were demonstrably less congruent than the stable PFJs throughout the range of knee movement. The greatest mean differences in congruency between unstable and stable PFJ’s were observed between 11° and 20° flexion (1.73 cm. 2. vs 4.00 cm. 2. ; p < 0.005). . Conclusion. The unstable PFJ is less congruent than the stable PFJ throughout the range of knee movement studied. This approach to mapping PFJ congruency produces a measurable outcome and will allow the assessment of pre- and postoperative results following surgical intervention. This may facilitate the design of new procedures for patients with PFJ instability. If a single axial series is to be obtained on MRI scan, the authors recommend 11° to 20° of tibiofemoral flexion, as this was shown to have the greatest difference in contact surface area between the case and control groups. Cite this article: Bone Joint J 2019;101-B:552–558

Aims

The aim of this study was to evaluate medium- to long-term outcomes and complications of the Stanmore Modular Individualised Lower Extremity System (SMILES) rotating hinge implant in revision total knee arthroplasty (rTKA) at a tertiary unit. It is hypothesized that this fully cemented construct leads to satisfactory clinical outcomes.

Aims

This study aimed to evaluate if total knee arthroplasty (TKA) femoral components aligned in either mechanical alignment (MA) or kinematic alignment (KA) are more biomimetic concerning trochlear sulcus orientation and restoration of trochlear height.

The February 2024 Knee Roundup³⁶⁰ looks at: Do patients with hypoallergenic total knee arthroplasty implants for metal allergy do worse? An analysis of healthcare utilizations and patient-reported outcome measures; Defining a successful total knee arthroplasty; Incidence, microbiological studies, and factors associated with periprosthetic joint infection after total knee arthroplasty; A modified Delphi consensus statement on patellar instability; Cause for concern? Significant cement coverage in retrieved metaphyseal cones after revision total knee arthroplasty; Prevalence of post-traumatic osteoarthritis after anterior cruciate ligament injury remains high despite advances in surgical techniques; Cost-effectiveness of arthroscopic partial meniscectomy versus physical therapy for traumatic meniscal tears in patients aged under 45 years.

Advanced 3D imaging and CT-based navigation have emerged as valuable tools to use in total knee arthroplasty (TKA), for both preoperative planning and the intraoperative execution of different philosophies of alignment. Preoperative planning using CT-based 3D imaging enables more accurate prediction of the size of components, enhancing surgical workflow and optimizing the precision of the positioning of components. Surgeons can assess alignment, osteophytes, and arthritic changes better. These scans provide improved insights into the patellofemoral joint and facilitate tibial sizing and the evaluation of implant-bone contact area in cementless TKA. Preoperative CT imaging is also required for the development of patient-specific instrumentation cutting guides, aiming to reduce intraoperative blood loss and improve the surgical technique in complex cases. Intraoperative CT-based navigation and haptic guidance facilitates precise execution of the preoperative plan, aiming for optimal positioning of the components and accurate alignment, as determined by the surgeon’s philosophy. It also helps reduce iatrogenic injury to the periarticular soft-tissue structures with subsequent reduction in the local and systemic inflammatory response, enhancing early outcomes. Despite the increased costs and radiation exposure associated with CT-based navigation, these many benefits have facilitated the adoption of imaged based robotic surgery into routine practice. Further research on ultra-low-dose CT scans and exploration of the possible translation of the use of 3D imaging into improved clinical outcomes are required to justify its broader implementation.

Cite this article: Bone Joint J 2024;106-B(9):892–897.

Aims

Tibial tubercle osteotomy (TTO) facilitates surgical exposure and protects the extensor mechanism during revision total knee arthroplasty (rTKA). The purpose of this study was to determine the rates of bony union, complications, and reoperations following TTO during rTKA, to assess the functional outcomes of rTKA with TTO at two years’ minimum follow-up, and to identify the risk factors of failure.

Aims

The Oswestry-Bristol Classification (OBC) is an MRI-specific assessment tool to grade trochlear dysplasia. The aim of this study is to validate clinically the OBC by demonstrating its use in selecting treatments that are safe and effective.

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.

Measurements of tibial torsion using a tropometer were made in more than 1200 consecutive patients attending an adult knee clinic. In total 1672 readings from 836 patients in 11 diagnostic categories were analysed. Patients with either patellofemoral instability or Osgood-Schlatter disease had a significant increase in lateral tibial torsion. The most important finding was a significant reduction in this torsion in patients with panarticular disease

Aims

The aim of this study was to evaluate medium-term outcomes and complications of the S-ROM NOILES Rotating Hinge Knee System (DePuy, USA) in revision total knee arthroplasty (rTKA) at a tertiary unit.