Resurfacing of the humeral head: An analysis of the bone stock and osseous integration under the implant

In vitro and in vivo evaluation of the osseointegration capacity of a polycarbonate-urethane zirconium-oxide composite material for application in a focal knee resurfacing implant

Currently available focal knee resurfacing implants (FKRIs) are fully or partially composed of metals, which show a large disparity in elastic modulus relative to bone and cartilage tissue. Although titanium is known for its excellent osseointegration, the application in FKRIs can lead to potential stress-shielding and metal implants can cause degeneration of the opposing articulating cartilage due to the high resulting contact stresses. Furthermore, metal implants do not allow for follow-up using magnetic resonance imaging (MRI).To overcome the drawbacks of using metal based FKRIs, a biomimetic and MRI compatible bi-layered non-resorbable thermoplastic polycarbonate-urethane (PCU)-based FKRI was developed. The objective of this preclinical study was to evaluate the mechanical properties, biocompatibility and osteoconduction of a novel Bionate® 75D - zirconium oxide (B75D-ZrO2 ) composite material in vitro and the osseointegration of a B75D-ZrO2 composite stem PCU implant in a caprine animal model. The tensile strength and elastic modulus of the B75D-ZrO2 composite were characterized through in vitro mechanical tests under ambient and physiological conditions. In vitro biocompatibility and osteoconductivity were evaluated by exposing human mesenchymal stem cells to the B75D-ZrO2 composite and culturing the cells under osteogenic conditions. Cell activity and mineralization were assessed and compared to Bionate® 75D (B75D) and titanium disks. The in vivo osseointegration of implants containing a B75D-ZrO2 stem was compared to implants with a B75D stem and titanium stem in a caprine large animal model. After a follow-up of 6 months, bone histomorphometry was performed to assess the bone-to-implant contact area (BIC). Mechanical testing showed that the B75D-ZrO2 composite material possesses an elastic modulus in the range of the elastic modulus reported for trabecular bone. The B75D-ZrO2 composite material facilitated cell mediated mineralization to a comparable extent as titanium. A significantly higher bone-to-implant contact (BIC) score was observed in the B75D-ZrO2 implants compared to the B75D implants. The BIC of B75D-ZrO2 implants was not significantly different compared to titanium implants. A biocompatible B75D-ZrO2 composite approximating the elastic modulus of trabecular bone was developed by compounding B75D with zirconium oxide. In vivo evaluation showed an significant increase of osseointegration for B75D-ZrO2 composite stem implants compared to B75D polymer stem PCU implants. The osseointegration of B75D-ZrO2 composite stem PCU implants was not significantly different in comparison to analogous titanium stem metal implants.

Poor evidence is used to support commercial payers' coverage policies for shoulder arthroplasty

BACKGROUND

The incidence of shoulder arthroplasty has continued to increase over the past decade. In response, commercial payers have implemented strategies to control the medical requirement of these surgeries in attempt to contain the growing costs. For example, most payers require a prolonged trial of conservative management prior to shoulder arthroplasty for patients who may otherwise be surgical candidates. However, little is known regarding the evidence used to support these indications. The purpose of this study was to analyze the references used by commercial payers to substantiate their coverage policies for shoulder arthroplasty.

METHODS

Ten of the leading commercial payers for total shoulder arthroplasty were identified. Publicly available coverage policies were searched on the internet or requested directly from the payer via email or telephone. Cited references were reviewed independently by two authors for type of document, level of evidence, and mention of the efficacy of conservative management.

RESULTS

A total of 5 coverage policies were obtained with 118 references. The most common reference type was primary journal article (n = 70; 59.3%) followed by review or expert opinion articles (n = 35; 29.7%). Most references were of level IV evidence (n = 60; 52.2%), with only 6 (5.2%) of level I or II evidence. Only 4 (3.5%) references mentioned the efficacy of conservative management in patients who may be candidates for shoulder arthroplasty.

CONCLUSION

The majority of references used to substantiate the coverage policies for shoulder arthroplasty among major commercial payers within the United States are of low scientific evidence and fail to demonstrate the success of required nonoperative intervention strategies. Our study underscores the need for high-quality, comparative trials that evaluate the outcomes of conservative management vs. shoulder arthroplasty in end-stage glenohumeral osteoarthritis patients in order to determine the most cost-effective treatment algorithm.

Clinical results and 10-year survivorship of the Synthes Epoca resurfacing total shoulder arthroplasty

Aims

This prospective cohort study reports the 10-year survivorship, patient-reported outcome measures and radiographic outcomes of the first series of the Epoca resurfacing head total shoulder arthroplasty.

Methods

From July 2008 to July 2014, 59 Epoca resurfacing head total shoulder arthroplasties were implanted in 50 patients by a single surgeon. Minimum 4.8 year and maximum 11.3 year follow-up (mean: 7.9 years) was analysed using the latest available Oxford Shoulder Score. Kaplan-Meier survivorship analysis was performed with revision as the end point. Most recent radiographs were reviewed for component radiolucency, osteolysis and proximal humeral migration.

Results

Two shoulders underwent revision (3.4%); one for pain with posterior subluxation following a fall, the other for pain with failure of the glenoid. Kaplan-Meier analysis revealed 10-year survivorship of 98.2% (95% confidence intervals: 88.0%-99.8%). Mean Oxford Shoulder Score improved significantly compared to pre-operative values from 18.2 (5-45) to 46.6 (36-48) (p < 0.001). Fifty-three shoulders underwent radiographic analysis (89.8%). This revealed humeral radiolucency in two cases (3.8%), glenoid radiolucency in three cases (5.7%) and radiographic rotator cuff failure in eight cases (15.1%).

Conclusion

This prospective cohort study shows excellent 10-year survivorship, medium to long-term clinical and radiological results and for the Synthes Epoca resurfacing head total shoulder arthroplasty.

Evidence level

IV.

Early offset-increasing migration predicts later revision for humeral head resurfacing implants. A randomized controlled radiostereometry trial with 10-year clinical follow-up

In a randomized controlled setting, medium-term implant migration and long-term clinical outcomes were compared for the Copeland and the Global C.A.P. humeral head resurfacing implants (HHRI). Thirty-two patients (mean age 63 years) were randomly allocated to a Copeland (n = 14) or Global C.A.P. (n = 18) HHRI. Patients were followed for 5 years with radiostereometry, Constant Shoulder Score, and the Western Ontario Osteoarthritis of the Shoulder Index (WOOS). WOOS and revision status were also obtained cross-sectionally at a mean 10-year follow-up. At the 5-year follow-up, total translation (TT) was 0.75 mm (95% confidence interval [CI]: 0.53-0.97) for the Copeland HHRIs and 1.15 mm (95% CI: 0.85-1.46) for the Global C.A.P. HHRIs (p = 0.04), but the clinical scores were similar at all follow-ups. The cumulative risks of revision at 5 and 10 years were 29% and 43% for Copeland and 35% and 41% for Global C.A.P HHRIs (p > 0.7). No implants were loose at revision, but HHRIs that were later revised followed an early offset-increasing migration pattern with medial translation and lift-off resulting in a mean 0.53 mm (95% CI: 0.18-0.88) higher TT at the 1-year follow-up compared to non-revised HHRIs. In conclusion, the Global C.A.P. HHRI had higher TT compared with the Copeland HHRI, but clinical scores and revision rates were similar. Nonetheless, revision rates were high and challenge the use of HHRIs. Interestingly, an early radiostereometry evaluated HHRI migration pattern with increased off-set predicted later implant revision.

Long-term results of the uncemented resurfacing shoulder hemiarthroplasty (Global Conservative Anatomic Prosthesis)

BACKGROUND

Treatment with uncemented resurfacing shoulder hemiarthroplasty has proved to be viable for patients with end-stage osteoarthritis at short- and mid-term follow-up. This study was essential to determine whether those outcomes will endure. This study presents the long-term results of the Global Conservative Anatomic Prosthesis (CAP) uncemented resurfacing shoulder hemiarthroplasty (DePuy Synthes, Warsaw, IN, USA).

METHODS

All patients with a diagnosis of glenohumeral osteoarthritis and an intact and clinically sufficient rotator cuff who underwent uncemented resurfacing shoulder hemiarthroplasty between 2007 and 2009 were included. The data of all patients who completed the 10-year follow-up assessments were used for analysis. The visual analog scale pain score, Dutch version of the Simple Shoulder Test score, Constant score, Short Form 12 scores, and physical examination findings were evaluated preoperatively and postoperatively on an annual basis. All complications and revisions were documented. Radiographs were evaluated for loosening, luxation or subluxation, migration, and glenoid erosion.

RESULTS

Of 48 shoulders, 23 (48%, 18 women and 5 men) were available for the 10-year follow-up assessments and their data were used for analysis. The main reasons for dropout were revision (27%) and death (10%). The mean follow-up period of the remaining patients was 10.9 years (range, 9-13 years). The visual analog scale pain score (from 6.5 ± 2.1 to 0.7 ± 1.6, P < .001), Simple Shoulder Test (Dutch version) score (from 22% ± 22% to 79% ± 22%, P < .001), Constant score (from 40 ± 29 to 70 ± 8, P < .001), and Short Form 12 physical score (from 36 ± 7 to 41 ± 12, P = .001) improved significantly compared with preoperative scores. Revision surgery was performed in 13 of the initial 48 shoulders (27%). Most revisions were seen within 7 years postoperatively.

CONCLUSION

Two revisions have been performed in the mid-term to long term because of increased functional outcome scores and the absence of signs of loosening. Nevertheless, the high overall revision rate of 27% between short- and long-term follow-up reflects the need to limit the use of uncemented resurfacing shoulder hemiarthroplasty for the treatment of glenohumeral osteoarthritis.

Stemless Total Shoulder: A Review of Biomechanical Fixation and Recent Results

Introduction: Anatomic total shoulder arthroplasty is the replacement of the humeral head and glenoid surfaces with the goal of replicating normal anatomy. It is commonly utilized for patients with osteoarthritis, rheumatoid arthritis, and osteonecrosis, who have decreased range of motion (ROM), persistent pain, and loss of strength. Total shoulder Arthroplasty (TSA) is the third most common joint replacement in the United States. The incidence of TSA has been increasing, some data suggest that by the year 2025, TSA incidence may rise to 439,206 operations per year. In recent years, stemless total shoulder implants have become available. Results: These implants preserve bone stock while decreasing complications such as osteolysis, stress shielding and periprosthetic fracture. Stemless implants improve anatomic reconstruction and biomechanical function of the shoulder joint. Conclusion: Increasing amounts of data suggest stemless TSA to be a safe and effective technology that will become more common in the coming year.

Revision shoulder arthroplasty for failed humeral head resurfacing hemiarthroplasty

BACKGROUND

The purpose of the present study was to analyze and report the clinical outcomes following revision shoulder arthroplasty for failed humeral head resurfacing hemiarthroplasty (HHRH).

METHODS

All patients who underwent revision shoulder arthroplasty for failed HHRH at our institution were retrospectively reviewed. Twenty-two shoulders in 20 patients were available for analysis. Mean age at the time of HHRH was 60 years (range 42 years to 75 years). The cohort consisted of 17 females and three males.

RESULTS

The mean time from HHRH to revision was 5 years (range 1 year to 8 years). Mean age at the time of revision surgery was 62 years (range 44 years to 80 years). Patients were followed-up for a mean of 3.3 years (range 2 years to 4 years) after revision. Following revision surgery, there was an increase in forward elevation from 67° (range 0° to 130°) to 97° (range 40° to 160°) (p = 0.04). This was accompanied by an improvement in both the Oxford Shoulder Score and the subjective shoulder value, which increased from 13 (range 2 to 28) to 39 (range 24 to 48) (p = 0.000) and from 23 (range 0 to 65) to 79 (range 25 to 100) (p = 0.000) respectively.

CONCLUSIONS

Revision shoulder arthroplasty for failed HHRH improves functional outcome.

Preoperative Comorbidities and Postoperative Complications Do Not Influence Patient-Reported Satisfaction Following Humeral Head Resurfacing: Mid- to Long-term Follow-up of 106 Patients

Background

Humeral head resurfacing (HHR) has emerged as an alternative treatment for glenohumeral osteoarthritis. We investigated the outcomes of HHR using validated patient-reported outcome (PRO) measures.

Methods

A retrospective review was performed on 213 patients who underwent HHR. A PRO follow-up was performed by administering a questionnaire including the American Shoulder and Elbow Society (ASES) score, Brophy activity survey, short form of the Disabilities of the Arm, Shoulder and Hand (quickDASH) survey, and general shoulder function. PRO scores were stratified by comorbidities and complications.

Results

Survey responses were received from 106 patients (51%), with a mean follow-up of 5.6 ± 1.8 years (range: 9 months to 6.1 years). Preoperative comorbidities were associated with significantly higher quickDASH scores. Postoperative complications were associated with significantly higher rates of current pain, higher visual analog scale scores, night pain, lower subjective shoulder values, and lower ASES pain and total scores. No differences in patient satisfaction were identified between the cohorts with and without preoperative comorbidities and between the cohorts with and without postoperative complications.

Conclusion

In our cross-sectional analysis of mid- to long-term outcomes following HHR, preoperative comorbidities, or postoperative complications had no impact on patient-perceived postoperative satisfaction or most PROs. HHR is clinically viable in a wide variety of patients. Future work is necessary to compare the efficacy of HHR compared with more traditional total shoulder arthroplasty and stemmed hemiarthroplasty regarding long-term outcomes and appropriate indications.

Revision of Failed Resurfacing Hemiarthroplasty: Midterm Results, Survival, and Group Comparison

Shoulder arthroplasty is a valuable option for treating glenohumeral osteoarthritis. Revision surgery for a failed shoulder arthroplasty is associated with difficult procedures, complications, and worse outcomes. Compared with a total joint arthroplasty, a resurfacing prosthesis has the supposed advantages of limited perioperative complications and little bone loss during revision. The aim of this study was to describe patient-reported outcome measures of revision surgery from failed uncemented Global CAP (DePuy, Warsaw, Indiana) resurfacing hemiarthroplasty to total shoulder or reverse shoulder arthroplasty. Eleven patients from 2 collaborating institutes had a failed resurfacing prosthesis. Revision surgery was performed to total shoulder prosthesis in 7 patients and to reverse shoulder prosthesis in 3 patients. Data were missing for 1 patient. Outcomes were monitored using the Constant-Murley score, Dutch Simple Shoulder Test, Short Form-12, visual analog scale for pain, and physical examination. Mean time to revision was 54 months (SD, 15.6 months). No perioperative complications occurred. At 42 months of follow-up (SD, 15.9 months), clinical and patient-reported outcomes were excellent. The Constant-Murley score improved a significant 29 points (P<.01). The visual analog scale pain score decreased from 55 to 5 points (P<.01), and the Dutch Simple Shoulder Test and Short Form-12 scores improved significantly (P≤.02). Five-year survival was 82.6% (95% confidence interval, 71.6%-93.6%). At 3.5-year follow-up, clinical and patient-reported outcome measures had satisfying results. [Orthopedics. 2019; 42(1):e111-e117.].

Bone remodelling of the humerus after a resurfacing and a stemless shoulder arthroplasty

BACKGROUND

New implant designs, such as resurfacing and stemless implants, have been developed to improve the long-term outcomes of the shoulder arthroplasty. However, it is not yet fully understood if their influence on the bone load distribution can compromise the long-term stability of the implant due to bone mass changes. Using three-dimensional finite element models, the aim of the present study was to analyse the bone remodelling process of the humerus after the introduction of resurfacing and stemless implants based on the Global C.A.P. and Sidus Stem-Free designs, respectively.

METHODS

The 3D geometric model of the humerus was generated from the CT data of the Visible Human Project and the resurfacing and stemless implants were modelled in Solidworks. Considering a native humerus model, a humerus model with the resurfacing implant, and a humerus model with the stemless implant, three finite element models were developed in Abaqus. Bone remodelling simulations were performed considering healthy and poor bone quality conditions. The loading condition considered comprised 6 load cases of standard shoulder movements, including muscle and joint reaction forces estimated by a multibody model of the upper limb.

FINDINGS

The results showed similar levels of bone resorption for the resurfacing and stemless implants for common humeral regions. The regions underneath the head of the resurfacing implant, unique to this design, showed the largest bone loss. For both implants, bone resorption was more pronounced for the poor bone quality condition than for the healthy bone quality condition.

INTERPRETATION

The stemless implant lost less density at the fixation site, which might suggest that these implants may be better supported in the long-term than the resurfacing implants. However, further investigation is necessary to allow definite recommendations.

Successful bony integration of a porous tantalum implant despite longlasting and ongoing infection: Histologic workup of an explanted shoulder prosthesis

Infection associated with an implant is a complication feared in surgery, as it leads to loosening and dysfunction. This report documents an unexpected good bony integration of a porous tantalum shoulder prosthesis despite infection. A shoulder prosthesis with a porous tantalum glenoidal base plate was retrieved after 3 years of ongoing infection with Staphylococcus spp. Methyl-methacrylate embedded sections of the retrieved glenoidal component were analyzed by optical and scanning electron beam microscopy (SEM). Bone ongrowth and ingrowth were quantified. Bone had formed at the implant surface and within the open cell structure of the porous tantalum. The bone implant contact index was 32%. The bone ingrowth or relative bone area within the open structure was 8.2%, respectively 11.9% in the outer 50% of the thickness. Due to the section thickness, bone ongrowth could best be documented in SEM. Despite long-lasting and ongoing infection, the glenoidal base plate of the prosthesis showed good bony integration upon removal. The bone ingrowth into the porous tantalum was comparable to the values previously reported for the undersurface of retrieved proximal humerus resurfacing implants. Good integration of the implant however did not solve the problem of infection, and related morbidity. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2924-2931, 2018.

Radiolucency in stemless shoulder arthroplasty is associated with an imaging phenomenon

Stemless humeral implants show comparable midterm clinical results compared to stemmed components. Recently, radiolucencies around the metaphyseal seating of humeral stemless implants were reported on postoperative radiographs. It is controversial whether they are attributable to bone resorption. We hypothesized these radiolucencies result from imaging artifacts. Seven cadaveric specimens (three male and four female) were first radiographed and then scanned with CT. A stemless humeral component of current design was implanted in each specimen. After implantation, all specimens were radiographed with different exposure settings. The implant was removed, and the specimens were scanned with CT again. Pre- and post-implantation radiographs and CT scans were compared. The mean Hounsfield units (HU) at the humeral resection plane from the pre-implantation CT were correlated with the diameter of the radiolucent halo on the post-implantation radiographs. A symmetric radiolucent halo of variable diameters occurred on all radiographs after implantation when an automatic exposure control was used. The halo disappeared in all specimens when the tube voltage was reduced. Lower CT-values (HU) before the implantation resulted in greater halos on the radiograph after implantation. Symmetric radiolucent halos can result from imaging artifacts, which is most likely due to radiation scatter. The halos can be minimized by reducing the tube voltage. The halo effect appears to be pronounced in bones with decreased density. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2040-2050, 2017.

Clinical and radiological results 7 years after Copeland shoulder resurfacing arthroplasty in patients with primary glenohumeral osteoarthritis: an independent multicentre retrospective study

PURPOSE

The aim of this multicentre cohort study was to evaluate the midterm outcomes and survival after cementless stemless resurfacing arthroplasty (CSRA) in a series of 33 shoulders in 27 patients with primary osteoarthritis.

METHODS

Clinical outcome assessment included: Constant-Murley score (CMS); Simple Shoulder Test (SST); Disability of Arm, Shoulder, Hand (DASH); EuroQol-5D (EQ-5D) utility scores; Numerous Rating Scale (NRS) for pain. Radiographs were assessed by two independent observers for oversizing, radiolucency, glenohumeral subluxation, glenoid erosion and subsidence. Correlations between the clinical and radiological outcomes were calculated. Complications were registered, and revision and survival rates were calculated.

RESULTS

Mean age at time of surgery and mean follow-up time were, respectively, 67.7 (range 50.2-85.1) and 7.2 years (range 5.7-9.3 years). Means (SD) for CMS, age- and gender-adjusted CMS, SST, DASH and EQ-5D utility scores were: 56.4 (20.2), 76.5 (25.0), 54.0 (29.8), 37.6 (23.3) and 0.8 (0.1), respectively. NRS for pain was 2.0 and 3.8, respectively, in rest and during activities. Radiographic assessment of the CSRAs showed oversizing in 54.5%; radiolucency in 18.2%; superior glenohumeral subluxation in 33.3%; glenoid erosion in 45.5%; and subsidence in 3.0%. Perioperative complications did not occur. Revision surgery was performed in one patient (3.0%).

CONCLUSION

For primary osteoarthritis, the CSRA showed good clinical but poor radiological outcomes at midterm follow-up.

Outcome and revision rate of uncemented glenohumeral resurfacing (C.A.P.) after 5-8 years

BACKGROUND

Resurfacing of the glenohumeral joint for patients with glenohumeral arthritis has gained popularity since the first introduction. We report the mid-term results of the Global C.A.P. uncemented resurfacing shoulder prosthesis (DePuy Synthes).

METHODS

From January 2007 to December 2009, 48 humeral cementless resurfacing prostheses in 46 patients were performed. All patients were diagnosed with primary glenohumeral osteoarthritis. Patients were contacted for review; the Constant Score, visual analog pain scale, Dutch Simple Shoulder Test, SF-12 scores and physical examination were assessed both preoperatively and yearly postoperatively. Complications and revision surgery were documented. Radiographs were evaluated for component size, offset, inclination, height, loosening and subluxation.

RESULTS

Forty-six patients (12 males) with a mean age of 72 years old (range 59-89) were included. At a mean 6.4-year follow-up (range 5-8), the Constant Score, visual analog pain scale and the Dutch Simple Shoulder Test scores improved significantly (p < 0.05) from baseline. Three patients were lost to follow-up. One patient died and two patients were not able to attend the follow-up appointments, due to other health-related issues. Eleven patients (23%) had a revision operation.

CONCLUSIONS

The most important findings of this study of the Global C.A.P. shoulder resurfacing arthroplasty were an increase of range of motion, a reduction of pain complaints, but a concerning high rate of revision after mid-term follow-up.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Changes of the bone structure after cap resurfacing arthroplasty of the humeral head

INTRODUCTION

Although humeral head resurfacing with a cap is relatively common in clinical practice, clinical studies about the changes of the bone are rare. The aim of this study was to analyse qualitative and quantitative changes of the bone after cup arthroplasty. Our hypothesis is that the implant leads to a new functional load with remarkable changes of the bone underneath the cap.

MATERIAL AND METHODS

Overall, 12 explanted caps with adherent bone tissues, retrieved at the revision surgery, were collected for histological examination. None of these implants were revised for loosening. Afterwards, there was a qualitative evaluation of the bone as well an assessment of established quantitative bone tissue parameters. Results were analyzed in correlation to the time to revision surgery, as well as to patient's age.

RESULTS

A significant decrease of the bone volume and trabecular architecture underneath the cap was already observed after a relatively short lifetime. The quantitatively measured bone loss does not depend on the patient's age, but correlates significantly with the lifetime of the implants. In contrast to these findings within the central areas, an increased bone remodeling with bone densifications and microcallus formations was noticed at the edge of the cap in most cases.

DISCUSSION

A significant reduction of the bone volume underneath the cap and remarkable changes of the trabecular architecture confirm our hypothesis. Even if these changes did not lead to a clinically relevant loosening in our series, they might influence revision surgeries. Thus, these findings might be of interest, especially when a non-stemmed reversed or anatomical revision arthroplasty with a central metaphyseal press-fit fixation is chosen.

LEVEL OF EVIDENCE

IV - retrospective or historical series.

Osteointegration of a modular metal-polyethylene surface gliding finger implant: a case report

INTRODUCTION

Primary press fit and secondary osteointegration is a precondition for component anchoring in articular surface replacements, also in the case of proximal interphalangeal (PIP) joint. Nevertheless, many existing prostheses for the PIP joint have failed to show sufficient osteointegration. CapFlex-PIP(©) implant is a modular metal-polyethylene surface replacement for the PIP joint consisting of a proximal and distal component each having a titanium pore backside, which allows secondary osteointegration at the bone-implant interface. To evaluate osseous integration of this implant, we report a histological analysis of an explantation of a CapFlex-PIP(©) finger implant.

CASE PRESENTATION

We present a case of a removed CapFlex-PIP(©) implant due to a soft tissue complication in an 84-year-old woman. The patient received bisphosphonate medication as treatment for osteoporosis. For the histological analysis, the bone-implant contact (BIC) was measured on all stained sections using a Zeiss Axioplan microscope. The summated BIC was 40.7 % for the proximal component and 46.5 % for the distal component of the implant. Histology showed that the implant was in direct contact with the bone at various locations, with no signs of wear or degradation.

CONCLUSIONS

This case demonstrates successful osteointegration of the CapFlex-PIP(©) implant. Both components of the investigated implant show osseous integration to an extent which is comparable to that of other load-bearing and articulating implants at different locations in the human body.