3D-Printed Guide for Thumb Carpometacarpal Prosthesis in Low Bone Stock

Abstract

Background

Thumb carpometacarpal (CMC) joint arthritis is a common and limiting condition of the hand in the elderly population. This can often lead to Z-deformity and compromised grip strength. While prosthetic arthroplasty has improved treatment outcomes, patients with low bone stock still present technical challenges. Standard techniques may risk poor implant positioning, fracture, and loosening. This case report describes the use of a novel technique with the use of a patent-specific three-dimensional (3D)-printed guide to enhance surgical precision.

Case Description

A 77-year-old female with Eaton stage IV CMC arthritis presented with advanced trapezium collapse, adduction, and Z-deformity of her left thumb. Preoperative computed tomography scan revealed a severely compromised trapezium with a medium height of 7 mm. A custom 3D-printed polylactic acid guide was designed to optimize cup positioning for MAÏA prothesis implantation. Accurate guidewire placement was obtained through the use of the 3D-printed guide, reducing the risk of malposition. Postoperative imaging confirmed correct implant alignment without lucency at 12 weeks' postoperative.

Literature Review

In previous studies, the use of 3D-printed guides show reduced intraoperative time and errors. However, challenge remains on the widespread adoption of the method, due to increased cost and high production time outside the operating room.

Clinical Relevance

This case illustrates that 3D-printed patient-specific guides may enhance implant placement accuracy in CMC arthroplasty, particularly in patients with compromised bony anatomy. The guide facilitated safer reaming of the trapezium and optimized long-term implant stability. Despite concerns about cost, production time, and required technical expertise, such technology holds promise for select, high-risk cases.

Carpometacarpal (CMC) joint arthritis is a debilitating health condition that mostly affects the elderly population. It is highly prevalent in individuals over 75 years of age, with an incidence of around 33%. ¹ Its typical progression results in less pain, due to severe ankylosis of the CMC joint, however, at the cost of hand function and progression to Z-deformity of the thumb. The base of the first metacarpal dislocates as it slowly falls into an adduction contracture; the metacarpophalangeal joint hyperextends in order to compensate for a contracted first web space. ²

Conservative treatment aims to improve thumb function, pain relief, mobility, and grip strength. Commonly used options include nonsteroid anti-inflammatory drugs, occupational therapy, and injections. ³ However, cases with advanced metacarpophalangeal deformity tend to perform poorly under conservative treatment. ⁴ For a long time, trapeziectomy was the sole option for surgical treatment of CMC joint arthritis. Recently, the treatment has evolved with the addition of new techniques, including trapeziometacarpal arthroplasty. ⁵ One commonly used prosthesis is the MAÏA implant (Lépine group, France). This implant has undergone various studies with follow-up of 9 to 12 years in regard to its safety and efficacy in the medium to long term. ^{6 7}

However, patients with low bone stock still represent a unique challenge, as standard surgical techniques may not provide sufficient precision for optimal implant positioning on the trapezium. Malpositioning in these cases can lead to intraoperative fracture, implant instability, and loosening. ⁸ It may be possible to overcome such challenges with the use of three-dimensional (3D)-printed patient-specific guides, in order to optimize implant positioning and guiding osteotomies. ^{9 10 11}

For the purpose of this study, we demonstrate a novel technique, highlighting the use of a 3D-printed patient-specific guide in polylactic acid (PLA) for a CMC arthroplasty with a MAÏA implant in a patient with low bone stock.

Case Report

A 77-year-old female with thumb basal joint arthritis with adduction deformity and hyperextension of the metacarpophalangeal joint presented to the clinic, with failure of conservative treatment such as physical therapy, hyaluronate injection, and orthosis. Radiographs show trapeziometacarpal joint arthritis, Eaton's stage IV ( Fig. 1 ), with advanced trapezium collapse. A CMC arthroplasty was proposed to better correct the Z-deformity, improve grip strength, and address the adduction contracture. Importantly, despite scaphotrapezial joint involvement, the patient had previously undergone diagnostic and therapeutic injections and remained clinically painless.

Fig. 1.

Preoperative radiographs in anteroposterior (AP) oblique views of the left hand, demonstrating severe compromise of the trapezium.

A computed tomography scan was obtained, given the patient's low bone stock. It was observed that the height of the trapezium averaged 7 mm ( Fig. 2 ). A decision was made to supplement our technique with a 3D-printed patient-specific guide to optimize implant positioning.

Fig. 2.

Computed tomography (CT) scan of the trapezium. Various height measures were obtained in order to determine medium height of the trapezium and guide manufacture.

The preoperative computed tomography (CT) scans were used as a layout of the trapezium ( Fig. 3 ), and a 3D model was manufactured using PLA on top of the trapezium with a drill hole centered on the desired position of the cup component ( Fig. 4 ). Softwares utilized in its confection were Blender 4.0 version and SolidWorks V2023.

Fig. 3.

Initial CAD model design of the three-dimensional (3D)-printed guide/simulation of guide placement on the trapezius for accuracy.

Fig. 4.

Internal guide design.

Surgical Technique

Under regional anesthesia, a dorsoradial incision was performed on the patient's left CMC joint. Dissection was carried out with preservation of the metacarpal periosteum for later closure. The MAÏA implant was chosen for this procedure and prepping of the first metacarpal bone was carried out as per manufacturer's instructions. As for the trapezium, the 3D-printed guide was positioned on top of it, allowing for precise guidewire placement, managing to secure correct placement of the wire on the first attempt. We then removed the 3D-printed guide and left the guidewire on the trapezium as planned. We checked its position using fluoroscopy before starting the reaming of the trapezium. Afterward, the surgical steps were carried out as usual for the MAÏA joint prosthesis ( Fig. 5 ), and release of the thumb adductor was carried out at the end of the procedure. Total operative time was 56 minutes.

Fig. 5.

Step-by-step: three-dimensional (3D)-printed patient-specific guide placed over trapezium, positioning of the guide wire, guide removal, and reaming in the desired cup placement on the trapezium.

Postoperative care was maintained with an abduction orthosis during nighttime and a regular thumb spica orthosis during the day. The patient was reexamined in 1, 3, 6, and 12 weeks postoperatively. Occupational therapy was started on the third week, in order to achieve optimal thumb abduction. At 6 weeks, we removed the daytime orthosis and maintained the abduction orthosis at night. At 3 months, the patient achieved a decent correction of her adduction deformity, improved grip strength, and pain control ( Fig. 6 ).

Fig. 6.

Clinical aspect of the patient's left hand at 12 weeks' postoperative.

Radiographs at this moment demonstrate normal alignment of the implants and did not show any sign of lucency around the components ( Fig. 7 ). We also obtained CT scans to better demonstrate the postoperative positioning of the cup on the trapezium ( Fig. 8 ).

Fig. 7.

Postoperative radiographs at 12 weeks' postoperative.

Fig. 8.

Comparison of preoperative and postoperative computed tomography (CT) scan, demonstrating cup positioning in the trapezium.

Discussion

The use of a 3D-printed guide in this case facilitated precise trapezium preparation, mitigating the odds of potential complications such as intraoperative fracture of the trapezium and subsequent loosening of the implant. This approach yielded a positive functional outcome, with the patient demonstrating substantial improvement in pain and regaining 85% of prearthritic thumb mobility. These findings support previous studies on the manufacturing of 3D-printed guides in surgical assistance for orthopaedic procedures, reducing surgical times and intraoperative errors. ^{12 13 14}

This case report represents the first description of a 3D-printed patient-specific guide in CMC arthroplasty. The improved precision given by this novel technique allowed us to treat a patient with a severely compromised trapezium, as evidenced by her CT scan, showing a medium height of 7 mm at the center of the trapezium. Without this adjuvant method, such an approach would be otherwise considered nonadvisable. The guide provided optimal positioning of the cup on the trapezium, which is critical to ensure long-term stability and function. Additionally, this procedure was performed in a patient with pan-trapezial arthritis, to which some authors consider nonadvisable. We highlight that recent data demonstrate satisfactory outcomes even in patients with stage IV disease in the long-term follow-up; however, given divergence among studies, this topic may carry some controversy yet. ^{15 16}

On the other hand, challenges remain regarding the widespread adoption of 3D-printed guides. Some authors argue that the additional cost and production time associated with this technique may outweigh the potential benefits and limits the reproducibility of the technique, especially in health care systems with limited resources. ^{17 18}

Specialized software and skills required to design and manufacture such guides must also be considered before these technologies become standard practice. The integration of 3D-printed into surgical routine requires dedicated teamwork, continued training, and significant investment. Factors that may pose a barrier to its large-scale implementation. ^{19 20}

Despite such challenges, this case report highlights the importance of integrating 3D printing technology into a hand surgeon's routine, especially in such borderline and challenging scenarios. Further studies should explore large patient cohorts and trials in order to validate the efficiency of patient-specific guides in CMC arthroplasty and other upper extremity bone reconstruction procedures. We believe that establishing the cost-effectiveness of this approach, compared with traditional techniques, is paramount for its broader adoption.