Correction of malformative patellar instability in patients with nail-patella syndrome: a case report and review of the literature

"Knee-Ding" a Diagnosis: A Case of Nail Patella Syndrome

Nail Patella Syndrome (NPS) is a rare genetic disorder with pathognomonic signs including dystrophic fingernails, iliac horns, and limb abnormalities, which commonly include hypoplastic development of the patellae, causing patients to experience patellar instability. This resulting patellar instability increases susceptibility to recurrent subluxations or dislocations in NPS patients. Since these anatomical abnormalities are present at birth or in childhood, early recognition may prevent the need for surgical intervention if appropriate preventive measures are taken. This case report describes a 54-year-old woman with a history of NPS, diagnosed later in adulthood, with a prior patellectomy at age 18 secondary to an unspecified left knee injury that occurred at age 4. A combination of radiographic and clinical findings are presented, which support the diagnosis of NPS, including dystrophic nails, left knee x-ray consistent with prior patellectomy, and right knee x-ray showing inferolateral subluxation of a hypoplastic patella. Additional signs associated with NPS are also discussed, including mood disorders, Raynaud's, and a high hairline which may assist in early diagnosis. This case report emphasizes earlier identification of NPS by clinicians through recognition of signs and symptoms while also considering proactive measures to lessen recurrent subluxations or dislocations to preserve patellar integrity and reduce the need for surgical intervention.

Nail-Patella Syndrome: A Case Series From Northern India

The nail-patella syndrome (NPS) is an uncommon entity with a characteristic set of anomalies. The presence of classical tetrad of hypoplastic or absent fingernails, hypoplastic or absent patellae, bilateral iliac horns and varying grades of elbow deformities are well elucidated in the literature. The spectrum of clinical manifestation varies, resulting in very few cases presenting to the healthcare facility or being diagnosed appropriately. We, hereby, describe our experience of three separate cases of the NPS, diagnosed on clinical and radiological basis. All cases were diagnosed incidentally and none presented to us for consultation regarding the anomalies due to this disorder. In one of the cases, a young girl was managed medically for an associated abdominal complaint. Her father was also found with the clinical features of the disorder thus making the father-daughter duo, part of our series. One case presenting with a femur fracture was managed with fracture fixation surgery leading to an uneventful healing of fracture. There was neither a history of any other family member having similar anomalies nor other systemic disorders in all three cases. Knowledge of the condition may help in improving the diagnosis of NPS and enrich the medical literature.

Robotic-Assisted Lateral Unicompartmental Knee Arthroplasty in a Patient With Nail-Patella Syndrome

A 59-year-old woman with nail patella syndrome (NPS) presented with progressive and severe right knee pain for the past 3 years. Imaging demonstrated laterally dislocated patella, with asymmetric femoral trochlea, and advanced lateral compartment arthritis. The patient underwent robotic-assisted lateral unicompartmental knee arthroplasty (RAUKA). The patient saw marked improvements in patient-reported outcome measurements from her initial visit to the last follow-up visit. While treatment of knee osteoarthritis in patients with NPS can be difficult, especially with attempts of patellar realignment, we present a case of a patient who underwent RAUKA, with sustained improvements in patient outcomes and range of motion, at the 2-year follow-up visit. This study is the first of its kind to demonstrate the use of a novel technology in a rare condition.

Genetics of patella hypoplasia/agenesis

The patella is a sesamoid bone, crucial for knee stability. When absent or hypoplastic, recurrent knee subluxations, patellofemoral dysfunction and early gonarthrosis may occur. Patella hypoplasia/agenesis may be isolated or observed in syndromic conditions, either as the main clinical feature (Nail-patella syndrome, small patella syndrome), as a clue feature which can help diagnosis assessment, or as a background feature that may be disregarded. Even in the latter, the identification of patella anomalies is important for an appropriate patient management. We review the clinical characteristics of these rare diseases, provide guidance to facilitate the diagnosis and discuss how the genes involved could affect patella development.

Management of patellar problems in skeletally mature patients with nail-patella syndrome

PURPOSE

Nail-patella syndrome (NPS) or hereditary onychoosteodysplasia is a rare autosomal dominant disease, characterized by a tetrad of findings, which include fingernail abnormalities, hypoplasia of the patellae, radial head dislocation and prominent iliac horns. Most of the literature on the treatment of patellar problems in NPS concerns paediatric patients, and there is no standard treatment algorithm for adult patients.

METHODS

We reviewed the charts of skeletally mature patients with NPS who presented to our clinic. We reviewed the presenting complaints, the physical examination findings and the radiographic imaging.

RESULTS

We identified seven skeletally mature patients with NPS who presented with patellofemoral complaints. Their symptoms were instability, pain, or a combination of the two. Examination and imaging revealed a wide range of severity but included patellar instability and patellar arthritis. In our series, milder forms of the disease were treated with non-operative measures, but the majority of our patients required surgery including medial patellofemoral ligament reconstruction, tibial tuberosity transposition, patellofemoral and total knee arthroplasty. At midterm follow-up, most patients had good results.

CONCLUSION

Nail-patella syndrome has a wide range of presentations and severity in skeletally mature patients. Knee surgeons should be familiar with the spectrum of clinical presentation and the range of treatment options available in order to provide optimum treatment for patients with this disorder.

LEVEL OF EVIDENCE

IV.

Nail-patella-syndrome in a young patient followed up over 10 years: relevance of the sagittal trochlear septum for patellofemoral pathology

INTRODUCTION

Nail-patella-syndrome (NPS) is a rare autosomal-dominant inherited disease with pathologies of nails, skeleton, kidneys, and eyes. Linkage to a mutated gene was found. It codes for the transcription-factor LMX1B. In most cases knees are symptomatic. Patients have hypoplastic patellae, which are laterally subluxated. In those individuals a sagittal trochlear fibrous septum was found, dividing the anterior knee-joint-space. In the literature the etiology and clinical significance of this anatomic abnormality is unclear. Based on clinical and intraoperative findings we developed a theory regarding knee pathology in nail-patella-syndrome. Successful treatment via early resection of the septum with sustained good outcome is presented.

METHODS

In a symptomatic six-year-old boy with nail-patella-syndrome we resected the fibrous sagittal septum adherent to the trochlea femoris and we balanced the patella via lateral release and medial plication in both knee joints. We analyzed the clinical outcome of this procedure prospectively over 10 years.

RESULTS

Postoperatively the hypoplastic patellae stayed centered and stable during further skeletal development. The patient was still pain free with normal range of motion of both operated knee joints after 10 years of follow-up.

DISCUSSION

In patients with nail-patella-syndrome and a subluxated or dislocated patella we recommend diagnostics with magnetic-resonance-imaging and early surgical treatment via resection of the trochlear septum and soft-tissue-balancing of the patella. When the septum displaces the patella and prevents physiological articulation of the patella with the trochlea femoris, early septum resection is likely to be important for a good functional outcome and proper development of the patellofemoral joint during growth.