Over the past three decades, additive manufacturing has changed from an innovative technology to an increasingly accessible tool in all aspects of different medical practices, including orthopedics. Although 3D-printing technology offers a relatively inexpensive, rapid and less risky route of manufacturing, it is still quite limited for the fabrication of more complex objects. Over the last few years, stable 3D-printed objects have been converted to smart objects or implants using novel 4D-printing systems. Four-dimensional printing is an advanced process that creates the final object by adding smart materials. Human bones are curved along their axes, a morphological characteristic that augments the mechanical strain caused by external forces. Instead of the three axes used in 4D printing, 5D-printing technology uses five axes, creating curved and more complex objects. Nowadays, 6D-printing technology marries the concepts of 4D- and 5D-printing technology to produce objects that change shape over time in response to external stimuli. In future research, it is obvious that printing technology will include a combination of multi-dimensional printing technology and smart materials. Multi-dimensional additive manufacturing technology will drive the printing dimension to higher levels of structural freedom and printing efficacy, offering promising properties for various orthopedic applications.

The authors report a case of a 47-year-old professional driver with an acute, simultaneous tear of patellar tendon and anterior cruciate ligament (ACL). The patient was treated in two stages. Acute patellar tendon repair and delayed (6-month postinjury) ACL reconstruction was performed. The authors discuss the possible mechanism of injury and the rationality of the two-stage surgical treatment.

Ring-shaped lateral meniscus is a rare clinical entity that is usually asymptomatic. Moreover, diagnosis is always based on arthroscopic exploration of lateral meniscus. MRI has not been proven useful so far because the inner portion of the ring-shaped lateral meniscus is usually misinterpreted as a bucket-handle tear. The authors report a case of a 16-year-old girl with ring-shaped lateral meniscus in combination with a meniscal cyst. MRI demonstrated a cyst arising from lateral meniscus and meniscal tissue into the inner portion of the lateral compartment mimicking displaced meniscal fragment. Bucket-handle tears have not been reported to cause or accompany meniscal cysts. As a result the diagnosis of a ring-shaped lateral meniscus along with meniscal cyst was assumed based on MRI and confirmed during arthroscopy. The patient was treated with arthroscopic partial lateral meniscectomy and intra-articular cyst debridement.

The meniscus is a critical component of a healthy knee joint. It is a complex and vital fibrocartilaginous tissue that maintains appropriate biomechanics. Injuries of the meniscus, particularly in the inner region, rarely heal and usually progress into structural breakdown, followed by meniscus deterioration and initiation of osteoarthritis. Conventional therapies range from conservative treatment, to partial meniscectomy and even meniscus transplantation. All the above have high long-term failure rates, with recurrence of symptoms. This communication presents a brief account of in vitro and in vivo studies and describes recent developments in the field of 3D-printed scaffolds for meniscus tissue engineering. Current research in meniscal tissue engineering tries to combine polymeric biomaterials, cell-based therapy, growth factors, and 3D-printed scaffolds to promote the healing of meniscal defects. Today, 3D-printing technology represents a big opportunity in the orthopaedic world to create more specific implants, enabling the rapid production of meniscal scaffolds and changing the way that orthopaedic surgeons plan procedures. In the future, 3D-printed meniscal scaffolds are likely to be available and will also be suitable substitutes in clinical applications, in an attempt to imitate the complexity of the native meniscus.

The authors report the case of a 38-year-old male who presented to the accident and emergency department with a locked knee after falling from a height. The knee was locked at 35° of flexion without any signs of instability in clinical examination. The patient was operated within 6 h from injury. During arthroscopy bucket-handle tears of both medial and lateral menisci were found. The bucket-handle fragments were displaced into the intercondylar notch causing the knee to lock. Additionally, tears of the anterior cruciate ligament (ACL) and the medial collateral ligament (MCL) were also found. The patient underwent ACL reconstruction with hamstrings autograft, medial subtotal meniscectomy and lateral meniscus repair. The MCL was treated conservatively. The postoperative period was uneventful and the patient returned to the preinjury level of activity within 8 months. The patient remains asymptomatic 2 years postoperatively.