Proponents of artificial hand joints have suggested that these protheses reduce pain, increase mobility and improve function compared with alternative treatments. Numerous total joint devices have been developed to reconstruct the MCP and PIP joints. However, regardless of design, these devices usually fail due to difficulties in restoring the biomechanics of the joint. In 1970, Swanson developed the silicone interpositional arthroplasty implant. Although this device is a joint spacer and not a total joint replacement, it provides good pain relief. Despite its numerous shortcomings (e.g., implant fracture, bone reaction adjacent to the implant, implant dislocation, silicone synovitis, and little active range of motion), the silicone spacer remains the preferred choice for the prosthetic reconstruction of the MCP and PIP joints (Hilker et al, 2007; Garcia-Moral, 2009).
Takigawa et al (2004) evaluated the Swanson silicone implant arthroplasty of the PIP joint, specifically evaluating clinical results with long-term assessment. A retrospective review of 70 silicone implants of the PIP joint in 48 patients was performed with an average follow-up period of 6.5 years (range of 3 to 20 years). Clinical assessment included motion, stability, and alignment. Radiographic assessment included implant fracture, deformity, and cystic bone resorption. The pathology consisted of degenerative joint disease in 14, post-traumatic arthritis in 11, rheumatoid arthritis in 13, and idiopathic arthritis associated with collagen disease in 12 patients. Swan neck and boutonniere deformities were assessed separately. Statistical analysis of pre-operative risk factors was compared with the post-operative assessment of pain, motion, and function (return to work). There was no significant change in the active range-of-motion (ROM) before and after PIP arthroplasty (26 degrees versus 30 degrees). Correction of swan neck and boutonniere deformities was difficult, usually leading to poor results. There was improvement in maximum active extension before surgery lacking 32 degrees to after surgery lacking 18 degrees. From a statistical standpoint rheumatoid joint involvement with PIP arthroplasty had poorer results than degenerative or post-traumatic arthritis with respect to pain relief and ROM. Pain relief was present in 70 % of replaced PIP joints with residual pain and loss of strength in 30 %. Radiographic analysis showed abnormal bone formation (cystic changes) in 45 %. There were 11 implant fractures and 9 joints that required revision surgery. The authors concluded that silicone replacement of the PIP joint is effective in providing pain relief from arthritis but does not provide improvement in motion or correction of deformity. It provided a poorer outcome in rheumatoid disease in comparison with degenerative, post-traumatic, or idiopathic arthritis.
Individuals who are very active and use their hands for heavy labor may not be good candidates for the silicone rubber spacer. Due to the shortcomings of the silicone implant, other materials have been investigated in the hopes of improving long-term outcomes of finger joint implants. Pyrocarbon, a form of pyrolytic carbon, is a strong, durable, ceramic-like material that has proven its biocompatibility and durability in artificial heart valves and is being used in artificial hand joints as an alternative to silicone implants for end-stage arthritis.
The Ascension MCP (Ascension Orthopedics, Inc., Austin, TX) received pre-market approval (PMA) from the U.S. Food and Drug Administration (FDA) in 2001. It is indicated for use as a total joint replacement of the index, long, ring, and small finger MCP joints that exhibit symptoms of pain, limited motion, or inadequate body alignment (i.e., subluxation/dislocation) secondary to articular destruction or degenerative disease related to rheumatoid arthritis, systemic lupus erythematosus, osteoarthritis, or post-traumatic arthritis where soft tissue reconstruction can provide adequate stabilization. In the approval letter, the FDA stated that Ascension Orthopedics, Inc. is required to conduct a post-approval study to obtain 12 months of post-operative data on each Ascension MCP device implanted in a minimum of 100 patients at 4 sites.
The Ascension PIP (Ascension Orthopedics, Inc., Austin, TX) pyrocarbon total joint is a bicondylar, anatomically shaped, articulating implant that allows joint flexion-extension, while providing some restriction of adduction-abduction motion. The FDA granted a humanitarian use device approval for the Ascension PIP joint implant on March 22, 2002 for use in arthroplasty of the PIP joint when the patient has soft tissue and bone that can provide adequate stabilization and fixation under high-demand loading conditions after reconstruction and needs a revision of a failed PIP prosthesis, or has pain, limited motion, or joint subluxation/dislocation secondary to damage or destruction of the articular cartilage. The FDA noted that compared to current treatment alternatives, such as arthrodesis or resection arthroplasty with a silicone spacer, the Ascension PIP may provide the potential benefits of increased motion and function, and may be used on patients whose strength and motion demands would exceed the capabilities of the currently available 1-piece silicone spacers. The FDA concluded that pre-clinical testing of the Ascension PIP device demonstrated that the wear resistance, fracture strength, fatigue resistance, and resistance to articulating surface contact damage is acceptable for its intended use.
The Ontario Ministry of Health (2004) conducted a systematic review to identify the subset of patients who might benefit from pyrocarbon finger joint implants and to compare the safety and effectiveness of the pyrocarbon finger joint implants with the most commonly used implants for MCP and PIP joint arthroplasty. The authors identified the following important considerations in patient selection: (i) the condition of associated soft tissues and ligaments, (ii) the activity level of the patient, and (iii) the age of the patient. The authors stated that "[p]yrobarbon can be considered for patients in whom soft tissues, capsules, and the collateral ligaments as the primary movers of the finger joints are better preserved. Therefore, it is indicated for young patients with post-traumatic arthritis or osteoarthritis. Patients with severe rheumatoid arthritis, in which adjacent ligaments and soft tissues are badly damaged, are not good candidates for pyrocarbon finger joint implants for the restoration of function. Silicone finger joint implants are not suitable for patients who are at risk of implant fracture due to high-demand loading conditions and frequent hand movements. For young patients, an implant made of a highly durable and resistant material such as pyrocarbon is expected to reduce the rate of implant fracture. The current evidence does not support the use of pyrocarbon finger joint implants for older patients and patients with severe rheumatoid arthritis. In these patients, silicone arthroplasty can be a final salvage procedure."
Based upon a systematic evidence review on artificial MCP and PIP joint replacement for end-stage arthritis, the National Institute for Health and Clinical Excellence (NICE, 2005) concluded that "[c]urrent evidence on the safety and efficacy of artificial MCP and interphalangeal (IP) joint replacement of the hand for end-stage arthritis appears adequate to support the use of this procedure provided that the normal arrangements are in place for consent, audit and clinical governance. Most of the evidence was based on a single type of joint prosthesis. The range of prostheses used is continually changing and clinicians are encouraged to submit their results to the appropriate joint-replacement registry for the evaluation of long-term outcomes of different types of prosthesis." The specialist advisors to the Institute's Interventional Procedures Advisory Committee noted the following potential adverse effects: stiffness, loosening of the prosthesis, generation of wear debris, bone resorption, nerve injury, wound hematoma, silicone synovitis, infection and prosthesis fatigue.
Stutz et al (2005) evaluated the pyrolytic carbon Ascension PIP implant for replacing the PIP joint in 13 patients and reported that at 1 year the ROM of the PIP joint improved from 0-28-51 pre-operatively to 0-22-77 post-operatively (average value), pain relief was achieved at rest and in motion of 80 % on the visual analog scale (VAS) (0: no pain, 10: incapacitating pain) and on the verbal analog scale an improvement of 62 % was achieved. The authors concluded that pyrolytic carbon implants reduce pain and are functionally superior to arthrodesis, however, a precise and individual post-operative protocol is necessary for beneficial results.
Schulz et al (2005) retrospectively reviewed the results of 20 out of 29 patients with idiopathic or post-traumatic arthritis who had been treated with the Ascension pyrolytic carbon PIP joint prosthesis from April 2002 to April 2004. Clinical, subjective and radiologic parameters were studied. On follow-up after 0.5 to 2.5 years the patients were satisfied with the pain relief; ROM varied. However, with an average ROM of 50 degrees it was equivalent to the results in the literature. Signs of periprosthetic cysts, osteophytes and loosening of the proximal as well as of the distal component could be seen in the radiograms of some patients. There was no correlation between these radiologic observations and ROM, pain or grip strength. In 3 cases the joint prosthesis had to be converted to an arthrodesis of the PIP joint. Bearing in mind the correct indications (intact collateral ligaments, stable bone stock and sufficient extensor and flexor tendons), pyrocarbon prostheses are a treatment option for idiopathic and post-traumatic arthritis preserving motion and reducing pain. Radiologic results seem to indicate an absence of osteointegration and tension forces at the prosthesis/bone interface. Further investigation will be necessary to improve surface and design to increase radiologic results in long-term follow-up. Additional surveys are required to improve indications, surgical approach and intra-operative control of correct component positioning.
Herren et al (2006) reported problematic bone fixation with the use of pyrocarbon implants in PIP joints. Seventeen pyrocarbon PIP prostheses were implanted into 14 patients, followed prospectively and reviewed clinically. The patients were assessed after a mean follow-up of 20.5 months subjectively by a VAS and radiographically. Significant pain relief was noted in all patients from a mean of 7.6 pre-operatively to 1.3 at final follow-up. Migration of one, or both, components was observed radiographically in 8 joints and radiolucent lines were evident in 3 more cases. The clinical results of the implants that had migrated were less favorable for ROM and grip strength than the stable joints of this series, although statistically the results were not significant. The number of possibly unstable prostheses in this series raises the question as to whether pyrocarbon is suitable for uncemented pressfit fixation in combination with early functional rehabilitation.
Nunley et al (2006) prospectively evaluated the subjective and objective functional outcome of patients treated with a pyrolytic carbon PIP joint arthroplasty for post-traumatic arthritis. Five patients (7 joints) with traumatic injuries to the PIP joint were followed-up for more than 1 year after pyrolytic carbon arthroplasty. All patients were treated with surgical reduction and stabilization at the time of the initial injury, but at a minimum of 6 months after the initial injury they had persistent pain, loss of motion, and functional limitations. All patients had a stable PIP joint with a satisfactory extensor mechanism but had radiographic evidence of post-traumatic arthritis. Patients were evaluated before and after arthroplasty with the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire and VAS and by radiographic and physical examination. At an average of 17 months, the mean DASH questionnaire score was unchanged. The pain rating on the VAS was 6 out of 10 before surgery and 4 out of 10 after surgery; this change was not statistically significant. The average ROM of the PIP joint decreased by 10 degrees at the last evaluation. Grip strength improved from an average of 47 lb to 63 lb after surgery. The authors concluded that the subjective and objective functional outcomes in 5 patients more than 1 year after pyrolytic carbon PIP joint arthroplasty for PIP joint trauma were disappointing and for post-traumatic patients, they no longer use pyrolytic carbon PIP joint arthroplasty.
In a prospective study, Hilker et al (2007) evaluated 28 Ascension pyrocarbon prostheses with a mean follow-up of 4 years and reported that stability was not a problem, subjective results were satisfactory, and the ROM 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.
Bravo et al (2007) retrospectively reviewed the surgical technique, post-operative therapy/splinting protocols, and clinical and radiographic outcomes of patients who had pyrolytic carbon PIP joint arthroplasty. A total of 50 PIP joint replacements in 35 patients were performed with a minimum follow-up period of 27 months. Indications for surgery included pain, decreased ROM, instability, and/or deformity. The pre-operative diagnosis was osteoarthritis in 14, rheumatoid arthritis in 11, and post-traumatic arthritis in 10. There were 20 women and 15 men affected. The average age at the time of surgery was 53 years. The fingers replaced included the index (n = 15), middle (n = 18), ring (n = 10), and small (n = 7). The pre-operative arc of motion averaged 40 degrees (0 degrees to 60 degrees), and the pinch and grip measurements averaged 3 and 19 kg, respectively. The pre-operative pain scores averaged 6 (scale 0 to 10) on a VAS. The arc of motion was 47 degrees after surgery, and the average pinch and grip measurements were 4 and 25 kg, respectively. Pain scores improved to 1. At the final follow-up evaluation the overall patient satisfaction was nearly 80 %. The results of index finger PIP replacements are compatible with other digits. Fourteen joints (in 14 patients) to date have required additional procedures to improve or maintain joint motion/function or pain; 5 for minor reasons and 9 for major complications. No infections were noted. Although not medically necessary, 2 patients requested and had an amputation. Radiographic subsidence and subsequent settling (in accordance with Wolff's law) without apparent loosening occurred in 20 joints. Twenty-eight percent of patients required a second procedure and 8 % required a revision arthroplasty. Radiographs showed gross changes in implant and eventual settling to a stable position in 40 % of the joints. The authors concluded that the pyrolytic carbon implant arthroplasty showed improved pain relief and good overall patient satisfaction at the 2-year minimum follow-up evaluation, however, a longer follow-up period will help to better determine the efficacy of this implant.
Meier et al (2007) reported outcomes of PIP replacement with the pyrolytic carbon prostheses. Indications included symptomatic arthritis of the proximal interphalangeal joint with preservation of the collateral ligaments, sufficient bone support, and intact or at least reconstructable extensor tendons. Contraindications included: lack of stability (e.g., as a result of rheumatoid arthritis or destruction of the ligaments caused by an accident), non-reconstructable extensor tendons, florid or chronic infection, and lack of patient compliance. Twenty patients were treated for post-traumatic or idiopathic arthritis with 24 pyrolytic carbon PIP prostheses, and a follow-up examination was carried out after an average of 15 months (6-30 months). Surgical management was changed from arthroplasty to arthrodesis in 3 cases. For the remaining prostheses, an average ROM of 50 degrees was achieved for the PIP joint. On the VAS (0: no pain, 10: incapacitating pain), the patients suffered few symptoms (0 to 3). Eighty percent of patients said they were satisfied with the outcome of the operation. In 3 cases (1 infection, 2 dislocations) the prostheses had to be removed and arthrodesis performed. Migration of the distal components was observed on the radiographs in 5 cases, and of the proximal components in 4 cases, although this did not have any effect on the functional parameters. The development of a painless noise ("squeaking") was noticed in 9 out of 21 prostheses. However, as with prosthetic migration, this did not cause any functional deficits.
Branam et al (2007) compared the outcomes of silicone PIP arthroplasties to pyrolytic carbon implants in patients with osteoarthritis in a retrospective review of 41 arthroplasties in 22 patients with severe PIP joint osteoarthritis performed by a single surgeon. There were 13 patients and 22 joints in the silicone group with an average follow-up of 45 months. There were 9 patients and 19 joints in the pyrolytic carbon group with an average follow-up of 19 months. Clinical assessment included ROM, grip strength, and deformity. Radiographs were evaluated for alignment, subsidence, and implant fracture. Patients filled out a subjective questionnaire with respect to pain, appearance of the finger, and satisfaction. Complications were recorded. In the silicone group, the average pre-operative PIP joint ROM was 11 degrees/64 degrees (extension/flexion) and the average post-operative ROM was 13 degrees/62 degrees. In the pyrolytic carbon group, the average pre-operative PIP joint ROM was 11 degrees/63 degrees and the average post-operative ROM was 13 degrees/66 degrees. Eleven of 20 joints in the silicone group and 4 of 19 joints in the pyrolytic carbon group had a coronal plane deformity as defined by angulation of the PIP joint greater than or equal to10 degrees. The average coronal plane deformity was 12 degrees in the silicone group and 2 degrees in the pyrolytic carbon group. The difference was statistically significant. In the silicone group, 3 of 22 joints required additional surgery. Two implants in 1 patient were removed and the PIP joint fused, and 1 implant was permanently removed for sepsis. In the pyrolytic carbon group, 8 of 19 joints squeaked, and there were 2 early post-operative dislocations and 2 implants with radiographic loosening. To date, there has been no revision surgery. Both groups had good pain relief. Patients were generally satisfied with the appearance of their joints in the pyrolytic carbon arm; however, satisfaction with appearance was variable in the silicone group. Nine of 13 patients in the silicone group and 6 of 7 patients in the pyrolytic carbon group would have the procedure again. The authors reported that both implants provide excellent pain relief and comparable post-operative ROM. Complications were implant specific. The authors concluded that the results of this series show promise for the pyrolytic carbon PIP joint resurfacing arthroplasty but did not clearly demonstrate superiority compared with the silicone implant.
The Avanta MCP and PIP joint finger implants (Avanta Orthopaedics, Inc., San Diego, CA) received humanitarian use device approval from the FDA for use in arthroplasty of the MCP or PIP joints when the patient is in need of a revision of failed MCP or PIP prosthesis(es); or the patient expects to place his/her hands under loading situations which preclude the use of an alternative implant in the painful osteo-arthritic and post-traumatic MCP or PIP joint. The distal components are made of an ultra-high molecular weight polyethylene and the proximal components consists of a cobalt chromiun-molybdenum articulating surface.
Moller and colleagues (2005) compared the results of the Avanta versus Swanson silicone implants in the MCP joint in a prospective, randomized comparison of 30 patients (120 implants). At 2-year follow-up, grip strength was measured, hand function was assessed with the Sollerman test and the subjective outcome was determined with VAS. With both implants ulnar deviation and flexion deformities decreased, and there was no difference between the groups. The increase in ROM was 7 degrees greater with Avanta implants than with Swanson implants. Grip strength and hand function were unaltered but the VAS showed decreased pain levels and subjective improvements in hand function, grip strength and cosmesis. Twenty-four of 30 patients were satisfied. Fracture of the silicone spacer occurred with 12 Avanta (20 %) and 8 Swanson implants (13 %), with a higher fracture frequency in men.
Rehart and Kerschbaumer (2003) noted that finger joints were first replaced with endo-prostheses in 1940 by Burman. Indications for the procedure are degenerative, post-traumatic or arthritis related destruction of the joints of the hand. Nowadays, several more or less comparable prosthetic designs are available. The replacement of single bones of the wrist has not been of lasting success. Occasionally, an indication for arthroplasty of the trapezium-metacarpal joint of the thumb may exist. The MCP joint of the thumb should, in the authors' experience, be fused when the need arises. Up until the present, the silastic spacer of Swanson for the MCP and PIP joints has not shown any substantial development, although a variety of designs have been introduced. Questions related to the complicated biomechanics of these articulations in combination with problems concerning the material to be used, intra-osseous fixation, the articulation of the prosthesis components and the design of the stems have not yet been solved convincingly. The Swanson spacers in mid-term to long-term follow-ups show little active ROM, although the subjective patient satisfaction is very high and the potential for removal at its best. The authors stated that they do not see an indication for arthroplasty in the distal interphalangeal (DIP) finger joints.
Drake and Segalman (2010) noted that arthritis in the small joints of the hand can be treated with arthrodesis or arthroplasty. Arthrodesis has known risks of infection, pain, and nonunion. Distal interphalangeal arthroplasty has been successful in preserving motion and alleviating pain for distal DIP, PIP, and MCP joints. Unfortunately, complications arise that limit the success of surgery. Silicone implants have been reliable for many years but still present with the risks of infection, implant breakage, stiffness, and pain. Newer implant designs may limit some of these complications, but present with unique problems such as dislocations and loosening. It is not yet clear as to which type of implant provides the most reliable results, although implant arthroplasty appears to give better function than arthrodesis. Silicone arthroplasty does not lead to silicone synovitis and is a reliable procedure. Pyrocarbon implants are showing some promise, particularly in the osteoarthritic patient.
Ikeda et al (2010) examined the usefulness of a custom-made splint for treatment of painful osteoarthritis of the DIP joints. The splint was designed to be easily detachable so as not to diminish finger pad sensation or interfere with PIP joint motion. These researchers enrolled 25 patients (24 women and 1 man, mean age of 58 years) with painful osteoarthritis of the DIP joints of the fingers and thumbs in this cohort study. Nineteen patients had multiple affected digits in one or both hands. Splints were applied to protect and immobilize the DIP joints. These investigators assessed the outcome of this treatment using the VAS pain score and the Quick Disabilities of the Arm, Shoulder, and Hand score for subjective assessment of symptoms. The mean follow-up period after wearing the splint until assessment was 6 months. Subjects were assessed 6 months after they started wearing the splint. Pain decreased from 100 % at pre-treatment to 34 % at final follow-up. So, the average improvement ratio was 66 %. The Quick Disabilities of the Arm, Shoulder, and Hand disability/symptom score changes were not statistically significant (28 points pre-treatment and 17 points at final follow-up). The authors concluded that this splint reduced pain from DIP osteoarthritis according to the VAS; however, this does not enable the patient to obtain completely satisfactory function of the upper extremities.
In a randomized prospective trial, Escott et al (2010) compared post-operative ROM and function of Swanson and NeuFlex MCP joint implants. A total of 33 patients who had rheumatoid arthritis underwent primary MCP arthroplasty of all 4 fingers in 40 hands; 20 received Swanson implants and 20 received NeuFlex implants. Exclusion criteria included diagnosis of other connective tissue disorders and previous MCP joint surgery. All participants followed the same post-operative rehabilitation protocol. The primary outcome measure was active MCP flexion. Secondary outcomes included active MCP extension, arc of motion, ulnar drift, function (Jamar grip strength and Sollerman hand function test), and the Michigan Hand Questionnaire. Patients were assessed pre-operatively and 12 months post-operatively. Patients' mean age was 62.5 years (Swanson) and 58.1 years (NeuFlex) (p = 0.03). A total of 19 of 20 hands (Swanson) and 14 of 20 hands (NeuFlex) were from female patients. Pre-operative active ROM was not significantly different. At follow-up, both groups demonstrated increased active extension and arc of motion (p < 0.001), reduced active flexion and improved ulnar deviation (p < 0.001), increased mean Sollerman and Michigan Hand Questionnaire domain scores (p < 0.001), and improved grip strength (p = 0.03). Active MCP flexion was significantly greater in all 4 digits of hands with NeuFlex implants compared with Swanson implants. The NeuFlex group demonstrated a greater total arc of motion in the little finger. Implant groups were not significantly different by individual digit for active MCP extension, ulnar drift, and composite flexion. Functional outcomes did not differ between groups. Patients with Swanson implants reported higher Michigan Hand Questionnaire scores in the function and aesthetics domains. The authors concluded that both implant groups obtained satisfactory clinical improvement after MCP reconstruction of the hand. The NeuFlex group demonstrated superior ROM, whereas the Swanson group had better self-reported function and aesthetics, but not objectively measured function.