Narrow Results

The purpose of this study was to compare the outcomes of volar plating using two different implants for distal radius fractures. Fifty-two patients with AO type C fractures were placed in either of two groups: the AO LDRS group (26 patients) or the Acu-Loc group (26 patients). Radiological parameters including radial length, radial inclination, volar tilt, and intra-articular step-off were significantly improved after surgery. The mean Mayo Wrist Performance Score was 84.6 in the AO LDRS group and 81.1 in the Acu-Loc group. The mean Subjective Wrist Value was 86.7% in the AO LDRS group and 86.3% in the Acu-Loc group. There were no significant differences between the two groups with respect to both radiological and clinical outcomes at the final follow-up evaluation. Volar fixed-angle plating for unstable distal radius fractures had satisfactory radiological and clinical outcomes. The difference of implant design did not influence overall final outcomes.

This in vitro biomechanical study reports on a new implant, called an intravertebral expandable pillar (IVEP). The implant is aimed at restoring the height and strength of collapsed vertebra after fracture in an osteoporotic patient. The hypothesis is that the IVEP can effectively restore the body height of the compressed vertebra and provide proper stiffness for the collapsed vertebra. Although the reported complication rate of percutaneous vertebroplasty by injection of polymethylmethacrylate (PMMA) is low, the sequelae are severe; other potential adverse effects of PMMA injection into the vertebral body include thermal necrosis of the surrounding tissue caused by a high polymerization temperature, and lack of long-term biocompatibility. We test the mechanical properties before and after fracture of 14 human cadaver lumbar vertebrae by a material testing system. The fractured vertebra was implanted with the IVEP, and its mechanical properties tested. The vertebral body height at each stage was evaluated by a digital caliper and radiographic films. After IVEP implantation, the vertebral body height restoration rate was 97.8%. The vertebral body height lost 12.7% after the same loading to create fracture. The vertebra lost half of its strength after compressed fracture, while IVEP implantation restored 86.4% of intact vertebra strength. The stiffness of intact vertebrae was significantly greater than that of untreated vertebrae after fracture and fractured vertebrae with IVEP treatment, while the stiffness of fractured vertebrae after IVEP treatment was significantly greater than that of untreated vertebrae after fracture. The bipedicularly implanted IVEP restores the initial height and strength of the vertebral body following an induced compression fracture, and could be used by a minimally invasive procedure to treat lumbar vertebra compression factures and avoid the disadvantage of using bone cement in vertebroplasty or kyphoplasty.

Rough surface height distribution can be nonsymmetric, depending on the process of surface preparation. The prevalent processes for implant surface involve turning and milling, both resulting in surface height distributions of nonsymmetric nature. Asymmetry in a surface height distribution is manifested through a parameter known as skewness. Unlike Gaussian distribution, Weibull distribution permits characteristics such as skewness and kurtosis in data to be included in the mathematical description of a height distribution. This paper develops hip implant contact model based on Weibull distribution of surface heights. The elastic–plastic interaction of implant surfaces are considered as macroscopically spherical surfaces containing micron-scale roughness. Symmetric and asymmetric roughness height distribution are compared. The total contact force is related to the minimum mean surface separation of the contacting rough surfaces. The force is obtained using statistical integral function of the asperity heights over the possible region of interaction of the roughness of surfaces. Approximate equations are obtained that relate the contact force to the minimum mean surface separation explicitly. The approximate equations are used to derive hysteretic energy loss per load–unload sequence, contact frequency, and damping. It is shown that energy loss per cycle, contact frequency, and damping are lower for asymmetric surface roughness distribution.

Background: This study evaluated the feasibility of using a low-profile titanium (Ti) plate implant, also known as the Ti-button, for Zone II flexor tendon repair. We hypothesize that the use of the Ti-button can distribute the tensile force on the digital flexor tendons to achieve better biomechanical performance.

Methods: Twenty lacerated porcine flexor tendons were randomly divided into two groups and repaired using Ti-button or 6-strand modified Lim-Tsai technique. Ultimate tensile strength, load to 2 mm gap force, and mode of failure were recorded during a single cycle loading test. We also harvested twelve fingers with lacerated flexor digitorum profundus tendons from six fresh-frozen cadaver hands and repaired the tendons using either Ti-button method or modified Lim-Tsai technique. A custom-made bio-friction measurement jig was used to measure the gliding resistance and coefficient of friction of the tendon sheath interface at the A2 pulley.

Results: The ultimate tensile strength, load to 2 mm gap force, stiffness, and gliding resistance of the Ti-button repairs were 101.5 N, 25.7 N, 7.8 N/mm, and 2.2 N respectively. Ti-button repairs had significantly higher ultimate tensile strength and stiffness than the modified Lim-Tsai repair. However, Ti-button also increased the gliding resistance and coefficient of friction but there was no significant difference between the two repair techniques.

Conclusions: Ti-button repair displayed comparable mechanical properties to the traditional repair in terms of 2-mm gap formation and gliding resistance, but with a stronger repair construct. Thus, this deepened our interest to further investigate the potential of using Ti-button implant in Zone II flexor tendon repair by studying both the mechanical and biochemical (tendon healing) properties in more in-depth.

Background: Proximal interphalangeal joint (PIPJ) arthroplasty using a Swanson implant is commonly used for the treatment of PIPJ arthritis despite newer implants being available. Many patients develop arthritis in more than one digit and some tend to have multiple digits operated on in their lifetime. There is paucity of literature on the outcomes of multiple PIPJ arthroplasty in one sitting. The aim of this study is to determine the outcomes of PIPJ arthroplasty using a Swanson implant done for multiple digits at one sitting.

Methods: We retrospectively reviewed the outcomes of multiple Swanson PIPJ arthroplasty during a single operation from 2008 to 2018 in 13 patients (43 arthroplasties). We compared pre- and post-operative results of flexion/extension arcs, grip and pinch strength and questionnaires subsequently compared QuickDASH (Disabilities of Arm, Shoulder and Hand), Patient Evaluation Measure (PEM) and Visual Analogue Score (VAS) scores. Data were analysed with a Mann–Whitney U test.

Results: Patients on average attended 5.6 hand therapy sessions over 5.1 months post-operatively. Average flexion/extension arc improved from 31.9° pre-operatively to 37.2° post-operatively. Average grip strength increased from 7.2 kg to 10.2 kg. The QuickDASH, PEM and VAS scores improved in keeping with the reported literature. There were no implant failures.

Conclusion: We demonstrate similar outcomes for multi-digit Swanson PIPJ arthroplasty compared to the literature for single digit Swanson PIPJ arthroplasty. We conclude that multi-digit arthroplasty in a single operation is safe and effective.

Level of Evidence: Level IV (Therapeutic)

Background: Wrist arthroplasties have not achieved clinical outcomes comparable to those of shoulders and knees, being offered low-demand patients due to a high failure rate. In the 90s, there were no wrist arthroplasties available for high-demand patients. An experimental setup for the development of a new wrist arthroplasty intended for all wrist patients were done. A long-term final follow-up to evaluate the performance of the experimental arthroplasty was performed.

Methods: A novel uncemented modular wrist prosthesis with conical threaded fixation, metal-on-metal coupling and ball-and-socket articulation was developed. In an experimental study, eight patients (7 men, 53 years of age) were operated between 2001 and 2003, to treat non-inflammatory primary or secondary osteoarthritis. Published mid-term results (7–9 years) demonstrated satisfactory function, but two arthroplasties were converted to arthrodesis due to infection.

Results: At final follow-up 15–20 years after primary surgery, the remaining six patients still had a wrist arthroplasty (in three the original) in situ. The clinical results were good. Low pain (median = 0), Quick Disability of Arm, Shoulder and Hand (QDASH median 11) and Patient Rated Wrist and Hand Evaluation (PRWHE median = 14) scores were reported. Wrist active range of motion (AROM) was 64% and grip strength 86% compared to the opposite side. None regretted choosing arthroplasty knowing the outcome.

Conclusions: Despite technical errors and the implementation of an incomplete prototype, this new concept for arthroplasty has demonstrated promising long-term fixation, a stable articulation with good range of motion, satisfactory function and pain reduction in high-demand patients.

Level of Evidence: Level IV (Therapeutic)

Wrist arthroplasty is becoming more commonplace, with various implant choices available. The Motec (Swemac Orthopaedics AB, Linköping, Sweden) cementless ball-and-socket system is being increasingly utilised and is designed for the distal component to be implanted into the third metacarpal. However, distal component failure is a recognised complication. We outline our experience with the revision of this component into the second metacarpal. This technical note is presented through our experience of two patients who underwent revision arthroplasty for the management of peri-prosthetic fracture of the third metacarpal. This technique has demonstrated a safe and viable solution to this complication, achieving good anatomical centre of rotation, function, range of movement and patient satisfaction.

Level of Evidence: Level V (Therapeutic)

Background: Wrist arthroplasty is increasingly offered to patients with symptomatic wrist arthritis as an alternative to wrist arthrodesis. The purpose of this study was to present our outcomes with the ReMotion™ wrist arthroplasty in a consecutive series of patients with wrist arthritis from non-inflammatory conditions.

Methods: Thirteen (eight women, nine dominant wrists) patients, 68 (44–85) years of age with advanced radiocarpal arthritis due to SLAC/SNAC (11) and Kienbock disease (2) had a ReMotion™ (Stryker, Michigan, USA) wrist arthroplasty implanted, and were prospectively followed for 7 (4–9) years. The outcome measures included patient-rated wrist and hand evaluation (PRWHE) score, disabilities of the arm, shoulder and hand questionnaire (QuickDASH) score, visual analogue pain score (0–10) on the radial and ulnar aspect of the wrist at rest (VASrR/VASuR) and activity (VASrA/VASuA), active wrist range of motion (AROM) including flexion, extension, ulnar and radial deviation, pronation and supination and grip and key-pinch strength measured preoperatively and at yearly follow-ups by independent hand therapists.

Results: Six patients had ten re-operations during the follow-up including four revisions to a new arthroplasty. Four were considered loose at follow-up. A significant reduction in PRWHE (63 to 12), radial pain at activity (6 to 1) and increased pronation (85° v 90°) was observed.

Conclusions: We found a high complication and reoperation rate, two out of 13 had no complications or reoperations. The ReMotion™ arthroplasty should be used with caution in non-inflammatory wrist patients and the patients followed closely. A high reoperation and revision rate can be expected, and surgeons familiar with revision arthroplasty procedures should perform the surgery.

Level of Evidence: Level II (Therapeutic)

Arthroplasty of the small joints of the hand and fingers is a complex problem facing the hand surgeon. Pyrocarbon implants have been available for several decades. They were originally thought to provide better functional outcomes than silicone implants in patients, mostly due to recreation of the joint anatomy. In a recent publication, pyrocarbon proximal interphalangeal joint (PIPJ) arthroplasty was found to have a higher complication and revision rate. We present a patient with pyrocarbon metallosis of the PIPJ in a revision arthroplasty procedure.

Level of Evidence: Level V (Therapeutic)

Nondestructive three-dimensional (3D) micro-computed tomography (CT) image analysis used in orthopedic research needs to be accompanied by adequate tools for the numerical assessment of experimental systems. Such quantitative tools should be user-friendly and intuitive, not too complex for the orthopedic researcher to implement, as well as accurate and repeatable in order to be suitable for laboratory application. Here, two experimental systems are examined and straightforward micro-CT analysis methods are described, allowing the experimental outcomes to be accurately quantified in a flexible and multidimensional manner. These systems include the study of osteointegration around a metal implant in bone, and the study of porosity of a biocompatible scaffold matrix for tissue engineering (specifically, the study of scaffolds for permeability to cellular ingrowth) Both studies involve a number of standard image analysis techniques applied in a 3D manner, such as erosion and dilation (applied flexibly to both the image and the region of interest), distance transforms, and novel techniques like “shrink wrap”. Applied in combination in an easily programmable “task list” (otherwise known as “scripting”), these functions provide a powerful and versatile range of 3D structural analyses.

Implants (hemitrochlea) were prepared from nacre (mother of pearl) and implanted in the knees of sheep. Cartilage formed at the endoarticular surfaces of the implant, and new endochondral bone was also formed at the interface between the host cancellous bone and nacre. These phenomena resulted in the total integration of the implant.