For decades, the advantages of rapid prototyping for clinical use have been recognized. However, demonstrations of potential solutions to treat spinal problems that cannot be solved otherwise are scarce. In this paper, we describe the development, regulatory process, and clinical application of two types of patient specific 3D-printed devices that were developed at an in-house 3D point-of-care facility. This 3D lab made it possible to elegantly treat patients with spinal problems that could not have been treated in a conventional manner. The first device, applied in three patients, is a printed nylon drill guide, with such accuracy that it can be used for insertion of cervical pedicle screws in very young children, which has been applied even in semi-acute settings. The other is a 3D-printed titanium spinal column prosthesis that was used to treat progressive and severe deformities due to lysis of the anterior column in three patients. The unique opportunity to control size, shape, and material characteristics allowed a relatively easy solution for these patients, who were developing paraplegia. In this paper, we discuss the pathway toward the design and final application, including technical file creation for dossier building and challenges within a point-of-care lab.

Hip dysplasia (HD) is a common orthopedic problem in young dogs. To decrease the laxity of the hip joint related to HD, the surgical treatments are recommended to increase femoral head coverage. ACEtabular rim eXtension (ACE-X) using a personalized 3-dimensional printed titanium shelf implant is a new surgical treatment to increase femoral head coverage and decrease laxity of the dysplastic hip joint, however, the efficacy is less know. Client-owned dogs older than 6 months with clinical signs of coxofemoral joint subluxation and radiographic evidence of HD with no or mild osteoarthritis (OA) were included. The Norberg angle (NA), linear percentage of femoral head overlap (LFO), and percentage of femoral head coverage (PC) were investigated radiographically and with computed tomography (CT) before and after surgery. OA was graded (scores 0–3) according to the maximum osteophyte size measured on CT. In addition, joint laxity (Ortolani) test results, gait analysis, and the Helsinki chronic pain index (HCPI) questionnaire were obtained at preoperative, immediately postoperative and at 1.5- and 3-month evaluations. Acetabular rim extension was performed in 61 hips of 34 dogs; NA, LFO, and PC were significantly higher immediately postoperatively and at the 1.5- and 3-month follow-up examinations compared with preoperative values (p < 0.05). Osteophyte size gradually increased over time (p < 0.05). The OA score significantly increased between preoperatively and directly postoperatively, and between preoperatively and at 3-month follow-up (p < 0.05). The laxity test normalized in 59 out of 61 hips after surgery, and the HCPI questionnaire showed that the pain score decreased significantly at 1.5 and 3 months, postoperatively. The force plate showed no significant improvement during the 3 months follow-up. Although pain reduction by the implant was unclear in short-term results, a personalized shelf implant significantly increased femoral head coverage and eliminated subluxation of the dysplastic hip joint. Further studies are required to study the long-term efficacy of gait, chronic pain, and progression of osteoarthritis.

Custom-made triflange acetabular implants are increasingly used in complex revision surgery where supporting bone stock is diminished. In most cases these triflange cups induce stress-shielding. A new concept for the triflange is introduced that uses deformable porous titanium to redirect forces from the acetabular rim to the bone stock behind the implant and thereby reduces further stress-shielding. This concept is tested for deformability and primary stability.Three different designs of highly porous titanium cylinders were tested under compression to determine their mechanical properties. The most promising design was used to design five acetabular implants either by incorporating a deformable layer at the back of the implant or by adding a separate generic deformable mesh behind the implant. All implants were inserted into sawbones with acetabular defects followed by a cyclic compression test of 1800N for 1000 cycles.The design with a cell size of 4 mm and 0.2 mm strut thickness performed the best and was applied for the design of the acetabular implants. An immediate primary fixation was realized in all three implants with an incorporated deformable layer. One of the two implants with a separate deformable mesh needed fixation with screws. Cyclic tests revealed an average additional implant subsidence of 0.25 mm that occurred in the first 1000 cycles with minimal further subsidence thereafter.It is possible to realize primary implant fixation and stability in simulated large acetabular revision surgery using a deformable titanium layer behind the cup. Additional research is needed for further implementation of such implants in the clinic.

Recent developments in the medical field of additive manufacturing (AM) have allowed the creation of patient-specific porous titanium implants for use in the medical field. With correct pore size such scaffolds are able to be integrated into surrounding bone.Two dogs were presented with atrophic non-union of the proximal ulna involving the elbow joint due to previous orthopaedic procedures with severe complications that led to segmental bone defects that were not expected to heal without a secondary intervention. Computed tomography (CT) was performed and porous scaffolds and saw guides were designed in silico and printed by AM. Osteotomies in adjacent healthy bone were guided by patient-specific three-dimensional (3D)-printed nylon saw guides allowing a perfect fit for the 3D-printed implant. In one case the scaffold was filled with bone morphogenic protein and held in place by two plates. In the other case the scaffold was filled with cancellous bone graft and held in place by a titanium plate that was part of the scaffold design. Both cases regained function and weight-bearing without lameness. Osseointegration of the implant was shown in both cases on follow-up CT and radiographs and macroscopically evident in the pores of the 3D implant after plate removal. One dog was euthanatized for unrelated disease and micro-CT revealed solid bone bridging through the inner scaffold tunnel.This study showed the successful application of the design, fabrication and clinical use of a patient-specific 3D-printed titanium implant to repair segmental bone defects of the antebrachium in two dogs.

Study Design. Cross-sectional Objective. To describe morphological changes of the annulus fibrosus (AF) and nucleus pulposus (NP) in children during growth using magnetic resonance imaging (MRI). Summary of Background Data. Little is known of intervertebral disc (IVD) maturation as opposed to degeneration, such as changes in relative AF/NP proportions and orientation during growth. Studies suggest the IVD plays a role in the etiology of pediatric spinal deformities. Therefore, understanding the morphological development of the AF and NP during growth is key. Methods. An existing database of children aged 0-18 that had magnetic resonance imaging (MRI) for indications unrelated to the spine were analyzed. The AF/NP were segmented semi-automatically from T1-L5. The parameters: mean IVD height, cross-sectional area, slenderness (height/width ratio), volume (ratio) and relative position of the centroid of the NP within the IVD in three directions (x,y,z) were extracted, and compared between age, sex and spinal level. Results. IVD height increased modestly and predominantly in the low-thoracic and lumbar spine during the first 5-10 years of life. Cross-sectional area and thus volume increased steadily at all levels throughout growth. IVD slenderness decreased sharply the first years of life and remains relatively stable throughout the remainder of growth. IVDs were smaller and more slender in females, especially in the mid-thoracic spine at early adolescence. In the upper- and mid-thoracic spine the NP comprises 10-12% of total IVD volume during growth, this percentage increases in the low-thoracic and lumbar spine towards 20-25%. In the anterior-posterior direction, the position of the nucleus increasingly shifts with age, possibly in line with the developing sagittal profile of the spine. Conclusion. This study describes the development of thoracic and lumbar IVDs during growth and may be used as a reference for future studies on the IVD its role in the etiology of disc related disorders.