Bioreconstructive joint scaffold implant arthroplasty in metacarpophalangeal joints: short-term results of a new treatment concept in rheumatoid arthritis patients

Structural assessment of pre-flexion in silicone implants for arthroplasty of the first metatarsophalangeal joint

The development of numerical models to analyze pathologies and implants related to the first metatarsophalangeal joint of the foot remains an issue for attention. The structural effects of implants pre-flexion have been discarded in several finite elements analyses due to complexities to achieve these positions. This work aims to evaluate if the pre-flexion stress state should be included or could be discarded when only flexion is applied in two different silicone commercial implants, Swanson and Tornier, during a gait cycle. Finite element models were created for silicone implants. Both models were discretized using high-order finite elements. The hyperelasticity constitutive material model of Arruda-Boyce was used, based on experimental data; its behavior was compared with linear elastic models reported and used frequently assuming small and large deformations and applying to the Swanson and Tornier implants a flexion angle of 64°, which corresponds to in vivo measurements reported after implantation. Comparison between models, regarding hyperelastic model, showed mean variations of up to 32.5% for stresses and 14.01% for bending moment in Swanson implant, while for Tornier implant mean variations of 29.73% and 632.55% was obtained for stress and bending moment respectively. The maximum stress value obtained for the hyperelastic model in the Swanson implant reached a value of 22.82% of the tensile strength of the implant material while in the Tornier implant reached a value of 25.92%, the above values were evaluated at a flexion angle of 64°. The results suggest considering in finite element analyses not only the stress state generated to achieve critical flexion position in pleflexed implants models but also the hyperelastic material behavior of silicone for implants to avoid dismissing the non-linear structural behavior of hyperelastic materials.

Retrospective Review of Long-term Outcomes of Patients Undergoing CMC Arthroplasty With Interposition Scaffold

Background: The treatment of rhizarthritis involves several surgical techniques; among them, bioabsorbable scaffolds have begun to be proposed to avoid the use of other biological tissues or artificial permanent devices. Methods: In this study, we evaluated the long-term outcomes of poly-ld-lactic acid scaffold in interposition arthroplasty in a series of patients treated in our department. Results: Strength, range of motion, and pain improved after the intervention and lasted over the years; nonetheless, most of the radiographs showed a progressive collapse of the first metacarpal. Conclusions: Despite radiological findings, we believe that poly-ld-lactic acid scaffold can be considered a good alternative to traditional trapeziectomy with tendon interposition and suspensionplasty, with long-lasting satisfactory clinical results.

Interpositional Arthroplasty of the First Metatarsophalangeal Joint with Bioresorbable Pldla Implant in the Treatment of Hallux Rigidus and Arthritic Hallux Valgus: A 9-Year Case Series Follow-Up

BACKGROUND AND AIMS

The interpositional arthroplasty was developed to retain foot function and to relieve pain due to the arthritis of the first metatarsophalangeal joint. The bioabsorbable poly-L-D-lactic acid RegJoint^® interpositional implant provides temporary support to the joint, and the implant is subsequently replaced by the patient's own tissue. In this study, we retrospectively examined the results of the poly-L-D-lactic acid interpositional arthroplasty in a 9-year follow-up study among patients with hallux valgus with end-stage arthrosis or hallux rigidus.

MATERIAL AND METHODS

Eighteen patients and 21 joints underwent interpositional arthroplasty using the poly-L-D-lactic acid implant between February 1997 and October 2002 at Tampere University Hospital. Of these, 15 (83.3%) (21 joints) patients were compliant with clinical examination and radiographic examination in long-term (average 9.4 years) follow-up. The mean age of the patients was 48.3 (from 28 to 67) years at the time of the operation. Six patients underwent the operation due to arthritic hallux valgus and nine patients due to hallux rigidus.

RESULTS

The mean Ankle Society Hallux Metatarsophalangeal-Interphalangeal Scale and visual analogue scale (VAS) for pain scores improved after the operation in all patients. The decrease of pain (visual analogue scale) after the operation was statistically significant (77.5 vs 10.0; p < 0.001). Postoperative complications were observed in 3 (14.3%) joints of two hallux rigidus patients. For these patients, surgery had only temporarily relieved the pain, and they underwent reoperation with arthrodesis.

CONCLUSION

In conclusion, interpositional arthroplasty using a poly-L-D-lactic acid implant yielded good results. This study indicates that the poly-L-D-lactic acid interpositional implant may be a good alternative for arthrodesis for treatment of end-stage degeneration of the first metatarsophalangeal joint.

Short-Term Results after Total Trapeziectomy with a Poly-L/D-Lactide Spacer

Background  Proximal migration of the first metacarpal can be seen after total trapeziectomy and various techniques have been described to prevent this subsidence. Purpose  We hypothesized the insertion of a poly-L/D-lactide spacer to prevent proximal migration of the first metacarpal without the need of an additional ligament reconstruction, allowing early mobilization and less demanding rehabilitation. Patients and Methods  Ten thumbs were treated with a total trapeziectomy and insertion of a poly-L/D-lactide scaffold. Clinical and radiological evaluation was performed after 6 months and 1 year. Patient satisfaction, pain, Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) score, mobility of the thumb, and strength were assessed. Results  Pain according to the visual analog scale decreased ( p  = 0.01) and QuickDASH score decreased ( p  = 0.02) significantly after 1 year. Radiological evaluation after 12 months showed a collapse of the scaphometacarpal distance of 45% ( p  = 0.01). Osteolysis of the distal scaphoid pole and/or proximal metacarpal was seen in 6 out of 10 cases. Because of the osteolysis, the use of the poly-L/D-lactide scaffold was discontinued in our practice. Conclusion  In this limited series, total trapeziectomy with the use of the poly-L/D-lactide scaffold provides significant pain reduction and improvement of overall function. Radiographic evaluation shows significant collapse of the scaphometacarpal distance after 1 year and frequent signs of osteolysis. We do not encourage the use of the poly-L/D-lactide scaffold with total trapeziectomy before long-term clinical and radiological follow-ups of the osteolysis are available.

Bioabsorbable poly-L/D-lactide (96/4) scaffold arthroplasty (RegJoint™) for trapeziometacarpal osteoarthritis: a 3-year follow-up study

The poly-L/D-lactide joint scaffold (RegJoint™) has recently been associated with adverse tissue reactions and osteolysis after partial trapeziectomy for trapeziometacarpal osteoarthritis. Twenty-two of 23 patients previously operated on with this scaffold were re-examined at a mean follow-up of 3.3 years (range 36-53 months). Overall, the results showed an unacceptably high rate of adverse tissue reactions related to the degradation process of the implant, resulting in a revision procedure in three patients. At final follow-up, at which point the implant had completely degraded, there were no signs of ongoing adverse tissue reactions. There was a significant decrease in pain, increase in strength and subjective improvement in function at final follow-up compared with the pre-operative results in patients who had not undergone revision surgery. However, owing to the high incidence of adverse tissue reactions, the use of the implant has been discontinued in the treatment of trapeziometacarpal osteoarthritis.

LEVEL OF EVIDENCE

IV.

Histomorphometric Analysis of Poly-L/D-Lactide 96/4 Sutures in the Gastrocnemius Tendon of Rabbits

Background

Common Achilles tendon ruptures are not usually fixed by bioabsorbable sutures due to limitations in their strength retention properties. Modern technology has made it possible to develop bioabsorbable sutures with prolonged strength retention.

Aims

To evaluate histologically tissue reactions of poly-L/D-lactide (PLDLA) sutures implanted in Achilles tendon of rabbits.

Material and Methods

Fifteen rabbits were evaluated at 2, 6 and 12 weeks postoperatively, with five rabbits in each follow-up group. PLDLA monofilament sutures were implanted into the medial gastrocnemius tendon. Polyglyconate monofilament sutures with similar diameter (Maxon® 4–0, Cyanamid of Great Britain Ltd., Gosport, UK) were implanted in the contralateral gastrocnemius tendon. The histology was studied in hard-resin embedded samples. The thickness of the formed fibrous tissue capsule was determined histomorphometrically.

Results

PLDLA led to formation of significantly thinner fibrous tissue capsule than Maxon® sutures of the same diameter. Median thickness (PLDLA vs. Maxon®) at two weeks was 5.26 vs. 13.22μm, at six weeks 11.66 vs. 80.97μm, and at 12 weeks 10.63 vs. 17.59μm (p<0.01).

Conclusions

During the 12 week follow-up period, PLDLA sutures implanted intratendineously formed thinner fibrous capsule than Maxon® sutures of the same diameter. The suture materials were not totally absorbed by 12 weeks.

Grading of Radiographic Osteolytic Changes after Silastic Metacarpophalangeal Arthroplasty and a Prospective Trial of Osteolysis Following Use of Swanson and Sutter Prostheses

The purpose of this study was to compare the incidence of radiographic osteolysis following insertion of 89 Swanson and 126 Sutter metacarpophalangeal implants in rheumatoid arthritis patients. The mean follow-up time in the two groups of patients was 57 (40–80) and 55 (36–79) months, respectively. This paper proposes a new method of classifying radiographic osteolysis. The remarkable number of osteolytic changes seen in the bones adjacent to MCP prostheses in this study would suggest that silastic prostheses should only be used when other surgical alternatives cannot be used and that long-term control by radiography be maintained after implantation of silicone prostheses into the MCP joint. In all grades of our classification, osteolysis was more frequent in the Sutter than in the Swanson group in this study, suggesting that use of the Sutter rather than the Swanson implant is questionable.

Synthesis and Characterization of Polyamide of Trans-4-hydroxy-L-proline used as Porogen Filler in Acrylic Bone Cement

The aim of this study was to synthesize on a larger scale, an experimental polyamide based on an amino acid of trans-4-hydroxy-L-proline. The polyamide of trans-4-hydroxy-L-proline has been used as porogen filler (i.e., a hydrophilic pore generating material) in nondegradable acrylic bone cement. In in vitro studies, this hydrophilic filling component has been shown to form porosity within the acrylic bone cement in an aqueous environment. The formation of in situ porosity in the acrylic polymer matrix is believed to improve the fixation between the cement and the living bone. Namely, a porous structure can support bone ingrowth and strengthen the mechanical connection between the acrylic bone cement and the bone. The monomer, trans-4-hydroxy-L-proline methyl ester, was prepared from trans-4-hydroxy-L-proline by means of two steps, and the monomer was then polymerized to polyamide of trans-4-hydroxy-L-proline. The polymerization was carried out using a melt polycondensation method. The molecular weights (Mψ) of the produced polyamides were between 1800 and 3600. The products were characterized by FTIR and 1H-NMR spectroscopy.

Unfavourable short-term outcomes of a poly-L/D-lactide scaffold for thumb trapeziometacarpal arthroplasty

The bioabsorbable poly-L-D-lactide joint scaffold arthroplasty is a recent attempt in the reconstruction of small joints in rheumatoid patients. In this study, we analysed the 1-year clinical, functional and radiologic results of partial trapeziectomy with the poly-L-D-lactide (96/4) joint scaffold in 23 patients with isolated trapeziometacarpal osteoarthritis. The results showed that the procedure provided pain relief and improvement in overall function according to the Quick Disabilities of the Arm, Shoulder and Hand score in most patients. However, radiographs demonstrated a high frequency of osteolysis around the implant. Seven patients developed clinically manifested foreign-body reactions 6 months to 1 year after surgery. The reason for the unexpected tissue reactions may relate to excessive mechanical cyclic loading of the implant. The outcomes of this implant in our patients have not been sufficiently beneficial and we have discontinued use of this implant in isolated trapeziometacarpal osteoarthritis.

Textile cell-free scaffolds for in situ tissue engineering applications

In this article, the benefits offered by micro-fibrous scaffold architectures fabricated by textile manufacturing techniques are discussed: How can established and novel fiber-processing techniques be exploited in order to generate templates matching the demands of the target cell niche? The problems related to the development of biomaterial fibers (especially from nature-derived materials) ready for textile manufacturing are addressed. Attention is also paid on how biological cues may be incorporated into micro-fibrous scaffold architectures by hybrid manufacturing approaches (e.g. nanofiber or hydrogel functionalization). After a critical review of exemplary recent research works on cell-free fiber based scaffolds for in situ TE, including clinical studies, we conclude that in order to make use of the whole range of favors which may be provided by engineered fibrous scaffold systems, there are four main issues which need to be addressed: (1) Logical combination of manufacturing techniques and materials. (2) Biomaterial fiber development. (3) Adaption of textile manufacturing techniques to the demands of scaffolds for regenerative medicine. (4) Incorporation of biological cues (e.g. stem cell homing factors).

Knitted polylactide 96/4 L/D structures and scaffolds for tissue engineering: shelf life, in vitro and in vivo studies

This study covers the whole production cycle, from biodegradable polymer processing to an in vivo tissue engineered construct. Six different biodegradable polylactide 96/4 L/D single jersey knits were manufactured using either four or eight multifilament fiber batches. The properties of those were studied in vitro for 42 weeks and in 0- to 3-year shelf life studies. Three types (Ø 12, 15 and 19 mm) of cylindrical scaffolds were manufactured from the knit, and the properties of those were studied in vitro for 48 weeks. For the Ø 15 mm scaffold type, mechanical properties were also studied in a one-year in vivo experiment. The scaffolds were implanted in the rat subcutis. All the scaffolds were γ-irradiated prior to the studies. In vitro, all the knits lost 99% of their mechanical strength in 30 weeks. In the three-year follow up of shelf life properties, there was no decrease in the mechanical properties due to the storage time and only a 12% decrease in molecular weight. The in vitro and in vivo scaffolds lost their mechanical properties after 1 week. In the case of the in vivo samples, the mechanical properties were restored again, stepwise, by the presence of growing/maturing tissue between weeks 3 and 12. Faster degradation was observed with in vitro scaffolds compared to in vivo scaffolds during the one-year follow up.

Bioabsorbable fixation devices in trauma and bone surgery: current clinical standing

Bioabsorbable fixation devices are increasingly used in trauma, orthopedic and craniomaxillofacial surgery. The devices are essentially made of polylactic acid and/or polyglycolic acid polymers. Ultra-high-strength implants are manufactured from such polymers using self-reinforcing techniques. Implants are available for stabilization of fractures, osteotomies, bone grafts and fusions, as well as for reattachment of ligaments, tendons, meniscal tears and other soft tissue structures. As these implants are completely absorbed, the need for a removal operation is overcome and long-term interference with tendons, nerves and the growing skeleton is avoided. The risk of implant-associated stress shielding, peri-implant osteoporosis and infections is reduced. Implants do not interfere with clinical imaging. Current clinical use of bioabsorbable devices is reviewed.

The application of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) scaffolds for tendon repair in the rat model

Tendon injuries and defects present a substantial burden to global healthcare economies. There are no synthetic/biosynthesised implants available which can restore full function or match the mechanical properties of native tendon. Therefore, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) was investigated for its utility as a scaffold in a rat Achilles tendon repair model. Porous PHBHHx tubes and fibres were prepared with particle leaching and extrusion methods, respectively. Collagen gels reinforced by polymer fibres were inserted into the lumen of scaffold tubes to create the operational scaffold unit. Mechanical testing demonstrated that PHBHHx scaffolds had comparable mechanical properties to rat tendon, with maximal loads of 23.73 ± 1.08 N, compared to 17.35 ± 1.76 N in undamaged rat Achilles tendon. Sprague-Dawley (SD) rats were split into four experimental groups: control, PHBHHx scaffold only, PHBHHx scaffold and collagen, PHBHHx scaffold, collagen and tenocyte compositions for implantation to repair an induced Achilles tendon defect. No secondary immune response to PHBHHx was observed over a 40 days period of implantation. Movement was restored in PHBHHx scaffold-collagen-tenocyte recipient rats at an earlier time point than in other experimental groups, with complete load-bearing and function returning 20 days post-surgery as determined by the Achilles Functional Index. In vitro testing of tendon constructs after 40 days demonstrated reductions in PHBHHx molecular weight and polydispersity index accompanied by an increase in mean chain length indicating degradation of smaller polymer chain subunits. Similarly a reduction in PHBHHx tube ultimate tensile strength and elastic modulus was observed. Histological analysis provided evidence of tissue remodelling and cell alignment. In summary, PHBHHx scaffolds have been successfully applied in an in vivo tendon repair model raising promise for future utility in tissue engineering applications.

The Mean Seven Years' Results of the Use of Poly-L/D-Lactic Acid (PLDLA) Interposition Implant and Bone Packing in Revision Metacarpophalangeal Arthroplasty: A Prospective Cohort Study

Background and Aims:

Revision arthroplasty of metacarpophalangeal (MCP) joints in chronic inflammatory arthritis patients after silicone implants is challenging due of severe bone loss and soft tissue deficiencies. The aim of this study was to evaluate the outcome of revision MC Parthroplasty using poly-L/D-lactic acid 96:4 (PLDLA) interposition implant and morcelised allograft or autograft bone packing in patients with failed MCP arthroplasties and severe osteolysis.

Material and Methods:

The study group consisted of 15 patients (15 hands and 36 joints) at a mean follow-up of seven years (range 5–10 years). The radiographs were reviewed for osteolysis and incorporation of the grafted bone. The clinical assessments included active range of motion, evaluation of pain, subjective outcome and assessment of grip power.

Results:

PLDLA interposition arthroplasty combined with bone packing provided satisfactory pain relief, but function was limited. Radiographic analysis showed complete incorporation of the grafted bone to the diaphyseal portion of the host metacarpal and phalangeal bones in 30 of the 36 joints. All the patients had very limited grip strength, both on the operated and non-operated side.

Conclusions:

Due to soft tissue deficiencies long-term function and alignment problems can not be resolved with PLDLA interposition implant.

Using the Taguchi method to obtain more finesse to the biodegradable fibers

The Taguchi method together with Minitab software was used to optimize the melt spun PLLA multifilament fiber finesse. The aim was to minimize the number of spinning experiments to find optimal processing conditions and to maximize the quality of the fibers (thickness, strength, and smoothness). The optimization was performed in two parts. At first, the melt spinning process was optimized considering the drawing that followed and at second step the drawing was optimized. Fine (15 μm) fibers with feasible strength properties (730 MPa) for further processing were produced with the aid of Minitab software.

Biomechanical validation of finite element models for two silicone metacarpophalangeal joint implants

Silicone implants are used for prosthetic arthroplasty of metacarpophalangeal (MCP) joints severely damaged by rheumatoid arthritis. Different silicone elastomer MCP implant designs have been developed, including the Swanson and the NeuFlex implants. The goal of this study was to compare the in vitro mechanical behavior of Swanson and NeuFlex MCP joint implants. Three-dimensional (3D) finite element (FE) models of the silicone implants were modeled using the commercial software ANSYS and subjected to angular displacement from 0 deg to 90 deg. FE models were validated using mechanical tests of implants incrementally bent from 0 deg to 90 deg in a joint simulator. Swanson size 2 and 4 implants were compared with NeuFlex size 10 and 30 implants, respectively. Good agreement was observed throughout the range of motion for the flexion bending moment derived from 3D FE models and mechanical tests. From 30 deg to 90 deg, the Swanson 2 demonstrated a greater resistance to deformation than the NeuFlex 10 and required a greater bending moment for joint flexion. For larger implant sizes, the NeuFlex 30 had a steeper moment-displacement curve, but required a lower moment than the Swanson 4, due to implant preflexion. On average, the stress generated at the implant hinge from 30 deg to 90 deg was lower in the NeuFlex than in the Swanson. On average, starting from the neutral position of 30 deg for the preflexed NeuFlex implant, higher moments were required to extend the NeuFlex implants to 0 deg compared with the Swanson implants, which returned spontaneously to resting position. Implant toggling within the medullary canals was less in the NeuFlex than in the Swanson. The differential performance of these implants may be useful in implant selection based on the preoperative condition(s) of the joint and specific patient functional needs.

Bioreconstructive poly-L/D-lactide implant compared with Swanson prosthesis in metacarpophalangeal joint arthroplasty in rheumatoid patients: a randomized clinical trial

It was hypothesized that the bioresorbable interposition implant might offer a viable alternative to conventional silicone implant arthroplasty in rheumatoid metacarpophalangeal joint destruction. A randomized clinical study was performed to compare a stemless poly-L/D-lactide copolymer 96 : 4 (PLDLA) implant with the Swanson silicone implant. Results in 52 patients (53 hands and 175 joints) at a mean follow-up of 2 years (minimum 1 year) showed that the improvement in clinical assessments was comparable in both groups, except for better maintenance of palmar alignment in the Swanson group. The lack of implant fractures and intramedullary osteolysis were advantages of the PLDLA implant. The bioresorbable PLDLA interposition implant may offer an alternative tool for tailored reconstruction of rheumatoid metacarpophalangeal joints.

Comparison of bioreplaceable interposition arthroplasty with metatarsal head resection of the rheumatoid forefoot

BACKGROUND

Interposition arthroplasty with bioreplaceable poly-L/D-lactic acid (PLDLA) implants has been studied in Finland with promising results in reconstruction of the rheumatoid hand. We evaluated this material in a series of patients with rheumatoid forefoot deformities.

MATERIALS AND METHODS

Thirty-five patients were randomized to either PLDLA metatarsophalangeal joint interposition arthroplasty group (16 patients) or to conventional metatarsal head resection group (19 patients).

RESULTS

At 3 months after surgery, the function VAS was significantly better in the control group (p = 0.003). The difference disappeared by 12 months. Otherwise, comparison between the two groups did not reveal any statistically significant differences in the AOFAS scores or the pain VAS at 3 or 12 months.

CONCLUSION

Early results after PLDLA interposition arthroplasty of metatarsophalangeal joints were not as promising as previously reported with rheumatoid metacarpophalangeal reconstruction.

Tissue-engineered small-caliber vascular graft based on a novel biodegradable composite fibrin-polylactide scaffold

Small-caliber vascular grafts (< or =5 mm) constructed from synthetic materials for coronary bypass or peripheral vascular repair below the knee have poor patency rates, while autologous vessels may not be available for harvesting. The present study aimed to create a completely autologous small-caliber vascular graft by utilizing a bioabsorbable, macroporous poly(L/D)lactide 96/4 [P(L/D)LA 96/4] mesh as a support scaffold system combined with an autologous fibrin cell carrier material. A novel molding device was used to integrate a P(L/D)LA 96/4 mesh in the wall of a fibrin-based vascular graft, which was seeded with arterial smooth muscle cells (SMCs)/fibroblasts and subsequently lined with endothelial cells. The mold was connected to a bioreactor circuit for dynamic mechanical conditioning of the graft over a 21-day period. Graft cell phenotype, proliferation, extracellular matrix (ECM) content, and mechanical strength were analyzed. alpha-SMA-positive SMCs and fibroblasts deposited ECM proteins into the graft wall, with a significant increase in both cell number and collagen content over 21 days. A luminal endothelial cell lining was evidenced by vWf staining, while the grafts exhibited supraphysiological burst pressure (>460 mmHg) after dynamic cultivation. The results of our study demonstrated the successful production of an autologous, biodegradable small-caliber vascular graft in vitro, with remodeling capabilities and supraphysiological mechanical properties after 21 days in culture. The approach may be suitable for a variety of clinical applications, including coronary artery and peripheral artery bypass procedures.

A midterm follow-up study of bioreconstructive polylactide scaffold implants in metacarpophalangeal joint arthroplasty in rheumatoid arthritis patients

This paper presents the results of a prospective study of 80 metacarpophalangeal joint arthroplasties, in which biodegradable polylactide 96/4 copolymer scaffolds were used. Twenty-three rheumatoid arthritis patients were assessed at an average of 59 months after operation, which exceeds the resorption time of P(L/D)LA 96/4 according to animal experiments. Palmar subluxation exceeded half of the bone thickness in 39 joints before operation and in nine at the last follow-up. Ulnar deviation decreased from 25 degrees to 5 degrees , extension deficit from 32 degrees to 15 degrees and active flexion from 76 degrees to 63 degrees . The results are comparable with published data on silicone implant arthroplasties. Implant resorption did not induce any significant osteolysis in the medium term and the restoration of the structure and function of the hand was maintained after implant resorption, probably as the guided fibrous tissues had replaced the dissolved implant.

[Prosthetics of metacarpophalangeal joints]

Only a few of the large number of implants developed during the last decades for replacement of the metacarpophalangeal (MCP) joint have proven to be reliable. The rates of loosening and mechanical failure of almost all types of constrained prostheses are so high that their use cannot be recommended at present. For more than 40 years silicone arthroplasty according to Swanson has been regarded as the gold standard in the prosthetic replacement of the MCP joint. In long-term studies this device provided good pain relief and a lasting correction of preoperative ulnar deviation. The degree of patient satisfaction continues to be high after more than 10 years. With the NeuFlex spacer, a modification of the original Swanson implant, a better range of motion and a reduction of wear-related problems is expected. In this study the results of 130 NeuFlex spacers after a mean time of 3.6 years were examined and 82% of the patients were completely pain free. The mobility of the joints improved from 40 degrees preoperatively to 54 degrees after 3.6 years. Radiologically periprosthetic erosions or osteolyses were seen in approximately 15% of implants. A minimal sinking of the stems developed in 24%, a massive one in 6% and 13% of the spacers were broken. Thus the use of the NeuFlex implant resulted in a better range of motion compared to the Swanson spacer, but the problem of radiological appearance remained unchanged. For unlinked prostheses sufficient soft tissue stability is mandatory as well as wear-resistant surface materials. The pyrocarbon prosthesis according to Beckenbaugh is the only implant for which long-term results are available. In a prospective study we evaluated 28 Ascension pyrocarbon prostheses with a mean follow-up of 4 years. Stability was not found to be a problem. Subjective results were satisfactory, the range of motion remained unchanged, however 46% of prosthesis stems exhibited radiolucent seams, 7 prostheses (25%) were rated as loose and 5 of those had to be replaced by a silicone implant. Use of the implant was abandoned, as it was unreliable regarding bony fixation. There are promising concepts in some new prostheses but independent data are still lacking.

One-year results of use of poly-L/D-lactic acid joint scaffolds and bone packing in revision metacarpophalangeal arthroplasty

Revision metacarpophalangeal arthroplasty after silicone implant arthroplasty is frequently complicated by severe bone loss, osteolysis and diaphyseal perforations. Impacted, morselised allografts are frequently used to treat bone loss in revision surgery. A new method of treatment using bioreconstructive poly-L/D-lactic acid (PLDLA) joint scaffold and allograft bone packing, after complete removal of the original silicone implants, allows recovery of bony deficiencies, correction of malalignment and improves function of the hand. This article presents the one-year results of a prospective, non-randomised clinical and radiographic follow-up study of 21 patients with 52 revision metacarpophalangeal arthroplasties using the PLDLA implants and allograft bone packing.

Studies of P(L/D)LA 96/4 non-woven scaffolds and fibres; properties, wettability and cell spreading before and after intrusive treatment methods

Poly(L/D)lactide 96/4 fibres with diameters of 50 and 80 microm were produced. The smaller diameter fibres were carded and needle punched to form a non-woven mat. Fibres and non-woven mats were hydrolysed for a period of 20 weeks. Fibres and pressed non-woven discs were treated with low-temperature oxygen plasma and alkaline KOH hydrolysis and ethanol washing was used as a reference treatment. The non-wovens lost 50% of their tear strength after 8 weeks in vitro while the fibres still retained 65% tensile strength after 20 weeks. Hydrolysation time in KOH, treatment time and power settings of the oxygen plasma were all directly proportional to the mechanical properties of the fibres. Increasing time (and power) resulted in lower tensile properties. Rapid wetting of the scaffolds was achieved by oxygen plasma, KOH hydrolysation and ethanol washing. Cell culturing using fibroblast cell line was carried out for the treated and non-treated non-woven scaffolds. In terms of adhesion and the spreading of the cells into the scaffold, best results after 3-day culturing were obtained for the oxygen plasma treated scaffolds.

Challenges in tissue engineering

Almost 30 years have passed since a term 'tissue engineering' was created to represent a new concept that focuses on regeneration of neotissues from cells with the support of biomaterials and growth factors. This interdisciplinary engineering has attracted much attention as a new therapeutic means that may overcome the drawbacks involved in the current artificial organs and organ transplantation that have been also aiming at replacing lost or severely damaged tissues or organs. However, the tissues regenerated by this tissue engineering and widely applied to patients are still very limited, including skin, bone, cartilage, capillary and periodontal tissues. What are the reasons for such slow advances in clinical applications of tissue engineering? This article gives the brief overview on the current tissue engineering, covering the fundamentals and applications. The fundamentals of tissue engineering involve the cell sources, scaffolds for cell expansion and differentiation and carriers for growth factors. Animal and human trials are the major part of the applications. Based on these results, some critical problems to be resolved for the advances of tissue engineering are addressed from the engineering point of view, emphasizing the close collaboration between medical doctors and biomaterials scientists.

HISTOLOGIC ANALYSIS OF BIOABSORBABLE SCLERAL BUCKLING IMPLANTS

PURPOSE

To analyze histologically tissue reactions to bioabsorbable PLA96 in rabbit eyes.

METHODS

Scleral buckling operations were carried out in 48 rabbits. Two materials were used: bioabsorbable PLA96 (polylactide 96/4; L/D molar ratio 96/4) and silicone sponge. One eye of each rabbit was operated on and the other eye served as a nonoperated control. After follow-up times of 1, 3, 5, and 12 months, the rabbits were killed and the eyes enucleated for histology.

RESULTS

All rabbits recovered well. Histologically, tissue reactions were very localized; implant fragments were not seen within the sclera. The amounts of fibrous tissue and inflammatory cells (mainly macrophages) inside the implant area increased over time. One rabbit from the silicone group was killed 4 months postoperatively owing to refusal to eat. In the PLA96 group, acute or chronic infections occurred in four rabbits. The bioabsorbable implant was macroscopically easily detectable at 12 months postoperatively.

CONCLUSIONS

The PLA96 material used for scleral buckling in rabbits showed good biocompatibility. The material did not undergo biodegradation during the follow-up period of 12 months. PLA96 implants were associated with thicker fibrous tissue encapsulation and more inflammatory cells compared with silicone sponge implants.

Comparison of Swanson and Sutter metacarpophalangeal arthroplasties in patients with rheumatoid arthritis: a prospective and randomized trial

PURPOSE

To perform a prospective and randomized comparison of the clinical outcome of patients with rheumatoid arthritis who had Swanson or Sutter implant replacement arthroplasty of the metacarpophalangeal joints.

METHODS

There were 45 patients (3 men, 42 women) and 49 hands; a total of 75 Swanson and 99 Sutter implants were inserted. The mean time between surgery and the final follow-up control visit was 58 months (range, 37-80 mo). Preoperative and postoperative measurements were performed including active extension and flexion, correction of ulnar deviation, and strength.

RESULTS

There was no statistically significant difference between groups with regard to active extension deficit correction. Mean active flexion decreased less in the Sutter group than in the Swanson group but difference between the groups was statistically significant in only the index finger. At the final follow-up examination no significant differences existed between the groups in the correction of ulnar deviation or arc of motion. Grip strengths, chuck pinch, and thump-to-fingertip grip strengths did not improve in either of the groups.

CONCLUSIONS

In this study clinical results showed no significant difference between the groups with the single exception of the amount of index finger metacarpophalangeal joint flexion.

Hand surgery in rheumatoid arthritis: state of the art and suggestions for research

OBJECTIVE

The role of surgery in the clinical management of patients with rheumatoid arthritis (RA)-associated hand dysfunction is still a subject of controversy. The efficacy of surgery in RA-associated hand dysfunction is assessed through an exhaustive review of published studies.

METHODS

A high-sensitivity search strategy was used to identify in MedLine and CENTRAL original studies related to hand and wrist surgery in RA patients. We selected articles including at least two adult RA patients which evaluated clinical outcomes through an observational or experimental design. Eligible studies were evaluated by standardized criteria. Two investigators independently used a pre-defined form to extract data about patient population, intervention, follow-up and clinical outcomes. Disagreements were discussed and resolved.

RESULTS

One hundred and ninety-six papers met inclusion criteria. Only five were randomized trials, while most studies followed an observational design, often of poor quality. As such, we could not pool data for statistical analysis; however, we were still able to provide a best evidence synthesis. A positive trend suggesting the efficacy of total carpal arthrodesis and metacarpophalangeal arthroplasty in reducing pain and improving function seemed to emerge from the published studies.

CONCLUSIONS

Despite recent advances in medical treatment, surgery still plays a role in the clinical management of RA-associated hand dysfunction. However, the majority of the available studies showed methodological flaws that prevented a clear definition of both surgical indications and criteria for choosing any specific procedure. Suggestions for further investigations are also provided.