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The purpose of this study was to examine the medium-term outcomes of patients undergoing proximal interphalangeal (PIP) joint arthroplasty using a pyrocarbon implant.
The study comprised an analysis of 170 PIP joint pyrocarbon arthroplasties in 99 patients with a minimum 2-year clinical follow-up. Diagnoses included inflammatory arthritis (n = 49), posttraumatic arthritis (n = 29), and osteoarthritis (n = 92). Univariate logistic regression and Kaplan-Meier survival analyses were performed.
At an average follow-up of 6 years (range, 2–14 years), 58 reoperations (34%) were required, including 36 (21%) involving implant revision surgery. The majority of revisions were performed for either dislocations (n = 16) or pain and stiffness (n = 14). The 5- and 10-year survival-free of revision surgery rates were 79% and 77%, respectively. The risk for revision surgery was higher in patients with posttraumatic arthritis. There were 15 intraoperative complications involving a fracture and 26 postoperative complications, including 21 dislocations. In unrevised implants, patients had significant improvements in their preoperative to postoperative pain levels, with no change in their PIP joint total arc of motion. At a mean radiographic follow-up of 5.4 years, there were 28% with grade 3+ loosening and 36% with progressive implant instability. Implant loosening or progressive instability was not associated with worse pain or PIP joint total arc of motion.
Approximately 1 in 5 PIP joint arthroplasties with a pyrocarbon implant will require revision surgery by 5 years, and 1 in 3 will undergo more than 1 operation. Furthermore, 1 in 4 PIP joint arthroplasties will have grade 3+ radiographic loosening and 1 in 3 will have progressive loosening or subsidence by 5 years. These results are particularly concerning in young patients and those with posttraumatic arthritis. Overall, in patients that do not require revision surgery, pain relief was improved and motion maintained.
Although variable outcomes have been reported, most reports show that proximal interphalangeal (PIP) joint arthroplasty can reliably relieve pain and maintain useful motion in the treatment of advanced arthritis of the PIP joint.
Despite these findings, revision surgery and complication rates following arthroplasty at this joint are relatively high, in part owing to the high propensity for joint instability and implant fracture or loosening.
However, given the silicone prosthesis propensity for implant fracture, coronal plane instability, and potential for silicone synovitis, other materials have been developed in recent decades to overcome some of these deficiencies.
The pyrocarbon implant was developed as a nonconstrained joint surface replacement to provide patients with an alternative to silicone. Although the initial results were promising, more recent investigations have suggested high rates of complications and revision surgery,
This variability is in part due to small samples sizes, short-term follow-up times, and variable outcome reporting all biasing the results and making it difficult to understand the true role in PIP joint arthroplasty.
Currently, there remains a paucity of large comprehensive studies examining the use of pyrocarbon in PIP joint arthroplasty. Therefore, the purpose of this study was to examine a large number of patients who underwent PIP joint arthroplasty using a pyrocarbon implant, focusing specifically on implant survival, complications, and clinical and radiographic outcomes.
After obtaining institutional review board approval, our institutional Joint Registry Database and electronic medical records were utilized to review all PIP joint arthroplasties performed over a 14-year period.
Briefly, the total joints registry collects information pertaining to patients, surgeries, and surgical outcomes after total joint arthroplasty. We utilized the electronic medical record to capture data not recorded by this registry. Variables collected included patient demographics, comorbidities, surgical indications, clinical outcomes, complications, and joint survival. Pain scores were collected as part of the total joints registry in the electronic medical record, and graded as none, mild, moderate, or severe. Range of motion was determined utilizing a goniometer by the examining clinician at the preoperative and postoperative visits. Revision surgery was defined as removal of the implant, and reoperation was any procedure involving or affecting the PIP joint after surgery (including revision). A PIP joint dislocation or instability episode was defined as a radiographically confirmed dislocation. Patients were excluded if they had less than 2 years of clinical follow-up (n = 14). Patients were followed up in clinic at 2, 5, and/or 10 years after surgery, unless they had a complication or another reason for returning for follow-up.
Demographics and operative details
From January 1, 1998, to December 31, 2012, we performed 184 primary PIP total joint arthroplasties in 109 patients. Six different surgeons carried out the surgery, utilizing the same second-generation pyrocarbon implant. Fourteen of these arthroplasties were lost to follow-up (< 2 years of clinical follow-up), leaving 170 PIP joint arthroplasties in 99 patients. The demographic characteristics of the study sample are summarized in Table 1. Of note, of the 49 patients with inflammatory arthritis, 11 were actively taking prednisone and 9 patients were taking methotrexate during the perioperative period.
Table 1Demographics and Surgical Considerations (n = 170)
A dorsal incision is generally utilized including either a Chamay or a tendon-splitting approach is performed to expose the joint. The Chamay approach is preferred in cases of significant concavity of the base of the middle phalanx. Care is taken to try to preserve the collateral ligaments. However, if there is preoperative coronal plane deformity, plication on the tension side and release on the compression side may be necessary to balance the soft tissues. After surgery, motion is generally initiated in 3 to 7 days. The patient is instructed regarding edema control and 2 orthoses are fabricated: an extension orthosis for nighttime use and a second orthosis, prebent at 30° of flexion to help initiate a short arc protocol. Sutures are removed at 2 weeks. The orthosis is flexed further weekly at increments of 10° to 15°. Once the orthosis reaches 90° of flexion, it can be discontinued. Nighttime extension orthosis wear continues for 3 months.
The Kaplan-Meier model was used to construct implant survival curves and regression analysis was performed for different complications. Comparisons using this model were performed with the Cox proportional hazard regression log-rank test. In addition, categorical variables were examined using Fisher exact test, and continuous variables were analyzed using the paired (when comparing preoperative with postoperative outcomes) or unpaired Student t tests. A power analysis for most end points was not performed given the retrospective nature of this study. For the clinical outcomes, a sample size of 16 is required to detect a 10° difference in motion with a power of 0.80 and alpha of 0.05. A P value less than .05 was statistically significant.
Revisions, reoperations, and complications
At a median follow-up of 5.2 years (range, 2–14 years), there were 58 reoperations (34%), including 36 revision surgeries (21%) and 22 surgeries to improve PIP joint function (13%) not involving implant revision. The etiologies underlying the revision surgeries were dislocation (n = 16), pain and stiffness (n = 14), recurrent subluxation (n = 3), implant loosening (n = 2), and infection (n = 1). Kaplan-Meier survival analysis demonstrated 2-, 5-, and 10-year revision-free survival rates were 84% (at risk n = 145), 79% (at risk n = 91), and 77% (at risk n = 21), respectively.
Cox proportional hazard regression analysis demonstrated risk for revision surgery was increased in patients with posttraumatic arthritis (P < .05), whereas it was decreased in older patients (P < 05). When comparing those with posttraumatic arthritis with osteoarthritis or inflammatory arthritis, the 2- and 5- year survival rates were 66% and 57%, compared with 87% and 83% in osteoarthritis, and 90% and 83% in inflammatory arthritis, respectively (Fig. 1). Of note, the need for impaction bone grafting or the need for a size mismatch of the components did not increase revision rates.
In addition to the 36 revision surgeries, there were 22 reoperations (13%) not requiring a revision surgery, including 11 tenolysis procedures for stiffness, 3 for heterotopic ossification excision and tenolysis for impingement, 5 soft tissue stabilization procedures for hyperextension or subluxation, 1 closed reduction and percutaneous pinning of a proximal phalanx periprosthetic fracture, 1 excision of a painful suture granuloma, and 1 repair of a ruptured flexor digitorum profundus at 3 weeks after surgery. The reoperation-free survival at 2, 5, and 10 years was 75% (at risk n = 129), 67% (at risk n = 77), and 61% (at risk n = 17), respectively.
Overall, there were 41 complications (24%) out of 170 joints, including 15 intraoperative fractures (9%) and 26 postoperative complications (15%). The occurrence of an intraoperative fracture did not worsen the postoperative implant revision-free survival. The postoperative complications included 21 PIP joint dislocations, 4 infections, and 1 fracture. Younger patients (P < .05), patients with posttraumatic arthritis (P < .05), and patients with inflammatory arthritis requiring prednisone at the time of surgery (P < .05) had higher rates of dislocations, whereas those not taking prednisone did not have an increased risk. No other factor had an increased risk of dislocation.
At a mean follow-up of 5.2 years (range, 2–13 years), patients who did not require revision surgery at last follow-up (n = 134) had a significant improvement in their postoperative pain levels compared with before surgery, with 88% reporting moderate or severe pain before surgery compared with 13% after surgery (P < .05) (Table 2). There was no significant difference between preoperative and postoperative grip strength (P = .25). Furthermore, there was no significant difference in the patients preoperative (40°) to postoperative (41°) PIP joint total arc of motion. Worse preoperative PIP joint total arc of motion was associated with worse postoperative motion (P < .05). Of note, patients with inflammatory arthritis had worse grip strength (P < .05), and PIP joint total arc of motion than the remaining groups (P < .05).
There were 131 PIP joint arthroplasties with radiographic follow-up greater than 1 year. At a mean follow-up of 4.9 years (range, 1–14 years), 84 pyrocarbon implants (64%) were determined to be stable (no progressive migration or loosening over radiographs spaced greater than 6 months apart) (Table 3). We modified the radiographic classification previously described by Sweets and Stern
to differentiate implants that migrate against but not into the cortex (grade 2) versus those that breach the cortical bone, but not out of the cortex (grade 3) (Fig. 2). There were 37 patients (28%) with grade 3 or higher implant loosening at final follow-up (Fig. 3). The majority of these implants demonstrated loosening proximally (n = 26) or both proximally and distally (n = 7), usually in the sagittal plane (n = 24) or both sagittal and coronal planes (n = 11). The most common grade 3 or higher loosening pattern was proximal volar (n = 24) and/or proximal radial (n = 10) (Table 3). Although 67 patients (51%) demonstrated signs of implant subsidence, many of these were not progressive. Overall, 47 pyrocarbon arthroplasties (36%) demonstrated progressive implant instability (progressive subsidence of grade 3 or higher implant loosening). The survival “free of grade 3 or 4 implant loosening” at 2, 5 and 10 years were 96%, 80%, and 53%, respectively (Figs. 4, 5). The 2-, 5-, and 10-year survival-free rates of progressive implant instability were 95%, 76%, and 46%, respectively. There were 7 (4%) fingers with postoperative ulnar deviation greater than 10°. The 2-, 5-, and 10-year survival-free rates of ulnar deviation greater than 10° were 98%, 95%, and 80%, respectively.
A diagnosis of inflammatory arthritis was not associated with worse radiographic outcomes, including evidence for grade 3 or higher implant loosening (P = .17), progressive implant instability (P = .34), subsidence (P = .17), or ulnar deviation (P = .42). Grade 3 or higher implant loosening was associated with female sex (P < .05), diabetes mellitus (P < .05), and intraoperative fractures (P < .05) (Table 3). The number of progressively unstable implants was increased in female patients (P < .05) and diabetes mellitus (P < .05). Subsidence rates were increased by older age (P < .05) and the need for impaction bone grafting (P < .05). No factors influenced the rate of ulnar deviation.
When examining the effect of these radiographic parameters on clinical outcomes, implant subsidence was associated with a decreased PIP joint total arc of motion (33° vs 44°; P < .05), while progressive implant instability (36° vs 41°; P = .41) and grade 3 or higher implant loosening (35° vs 41°; P = .33) did not statistically decrease PIP joint total arc of motion. Progressive implant loosening was also associated with worse grip strength (P < .05). Of note, patients with Sweets and Stern grade 3 or higher radiographic findings did not report worse pain.
Pyrocarbon arthroplasty was introduced as an alternative to silicone and metal-plastic resurfacing implants. The material properties of pyrocarbon offer favorable characteristics in the setting of small joint arthroplasty. The pyrocarbon-pyrocarbon articulation generates little or no particulate debris. Its elastic modulus is similar to cortical bone and thus has potential to serve as an excellent load-sharing device, minimizing the risk of stress shielding. Because it is biologically inert, pyrocarbon does not generate an inflammatory reaction.
However, these implants fail to develop osseous ingrowth and thus are vulnerable to loosening and implant migration. Previous reports have documented problems of postoperative instability and implant loosening, leading some authors to question or even abandon its use in PIP joint arthroplasty.
In this series of 170 pyrocarbon implants performed over a 14-year period, 79% of implants were retained. However, 34% of fingers required reoperations. Patients with posttraumatic arthritis fared worse, with 57% survivorship. The patients who did not require a second revision surgery experienced improvement of pain, with maintenance of their grip strengths as well as PIP joint arc of motion.
The radiographic findings are worrisome. Of those with greater than 1 year of radiographic follow-up, 1 in 4 had grade 3 or higher implant loosening, and 1 in 3 had experienced progressive loosening or subsidence by 5 years. Despite the fact that not all patients with grade 3 or 4 loosening have undergone revision surgery, these radiographic findings are important in that they are essentially failures and are more likely to require further surgery. It is important to appreciate that a patient who has not undergone reoperation does not always equate to a satisfied patient or surgeon. Acknowledging the limitations of the joint registry data measures, implant loosening or progressive implant instability did not differ clinically from stable implants with respect to pain and range of motion. In addition, 13% of patients reported moderate/severe pain who did not undergo revision surgery, potentially increasing the need for further surgery and number of “failed” arthroplasties.
Prior studies have noted that pyrocarbon PIP joint arthroplasty provides patients with predictable pain relief and maintenance of their range of motion, but implant survival and complications have been variable.
reported that out of 50 PIP joint arthroplasties, there was a relatively high rate of reoperation (28%), but only 8% of required actual implant revision surgery. Patients had excellent pain relief and maintenance of their PIP joint motion. In a retrospective review of 97 implants by Watts et al,
the patients had an 85% 5-year survival rate, with good pain relief and improvements in their range of motion. Similarly, a study of 89 arthroplasties found only 10 required a secondary procedure, whereas 19 of the 21 available at 5-year’ follow-up had complete pain relief.
in their early series of 31 pyrocarbon PIP joint arthroplasties, found that PIP joint motion decreased after surgery, with a high rate of revision surgery (n = 5), dislocations (n = 5), and implant fracture (n = 1). The authors reported that they no longer use this implant in their PIP joint arthroplasty practice. In a meta-analysis by Chan et al,
including 718 arthroplasties, there was a higher rate of complications associated with the use of pyrocarbon implants (30%) versus silicone implants (8%).
In this series, patients with the diagnosis of posttraumatic arthritis fared worse, suggesting that more caution should be taken when considering pyrocarbon PIP joint arthroplasty in this group. The most common complication noted in this series was dislocation (11%). The remainder of the complication rates was reasonably low. The most common indication for reoperation was limited motion (14 of 36). Unfortunately, our experience with reoperation to improve motion has been poor and we conclude that reoperation with this intention should proceed with caution. This is consistent with prior experiences with other implants as well.
progressive implant instability occurred at an unacceptably high rate (36%).
There are features of the implant and its design that may contribute to the difficulties encountered in this and other series—particularly as it pertains to the radiographic outcomes. The articulation is shallow compared with other designs, which may lead to translational motion, strain on the soft tissue stabilizers, and eccentric loading with use. In cases of more severe arthritis, placement of the implant becomes more challenging, more so with respect to the distal component placement. These situations often require free-hand drilling, with the use of a Swanson bur, to fit the components. Intuitively, these challenges increase the chances of imprecision in implant placement. Combined with the lack of bony ingrowth into the components, the patients are vulnerable to complications like subsidence and catastrophic loosening. Some surgeons have suggested impaction grafting as a means of preventing subsidence or implant migration; however, this technique did not improve these rates in our series. It may be that the implant and bone settle to a stable or unstable load-sharing joint. These unstable load-sharing constructs are associated with the subsidence and catastrophic loosening; whereas the stable constructs demonstrate longer-term stability consistent with that observed by Watts et al
in their experience in which the rates of failure levelled off significantly over time.
There are several limitations in this study. It is a retrospective study and we are limited in what we can analyze, including a lack of a validated outcome measure. It is a single-institution study and, although that has strengths, such as limiting confounding variables, it does invite limitations such as referral bias. In addition, the total joints registry is limited by the lack of a true patient-related outcome, such as the Michigan Hand Questionnaire, limiting the ability to truly assess patient satisfaction with this elective procedure. In addition, given the retrospective nature of this study, many minor complications are potentially missed because they are not recorded in the medical record or total joints registry. In addition, as mentioned previously, whereas registries can provide useful information, they do not always reflect the complete “story” because many patients may be dissatisfied or have evidence of radiographic failure and do not undergo further interventions.
However, this large series of PIP joint arthroplasties using the pyrocarbon implant provides surgeons with important data on this implant as an option when faced with a patient with PIP joint arthritis. With an average 5-year follow-up, motion was maintained and pain improved. Seventy-nine percent of patients maintained their original implant and 66% were free of reoperation. Whereas outcomes were similar between osteoarthritis and inflammatory arthritis, patients with posttraumatic arthritis fared worse. Radiographic outcomes remain worrisome with significant rates of implant loosening and subsidence. This experience should help surgeons to better counsel patients regarding expectations following pyrocarbon PIP joint arthroplasty.
S.L.M. is a consultant for Integra. Investigation performed at the Mayo Clinic, Rochester, MN.