Nonstandard glenoid components for bone deficiencies in shoulder arthroplasty

BACKGROUND

Glenoid bone deficiencies may be addressed by specialized components. The purpose of this study is to evaluate the clinical and radiographic outcomes of 3 different types of nonstandard glenoid components.

MATERIALS AND METHODS

Thirty-eight patients with a mean age of 65 years (range, 34-84 years) underwent a primary or revision anatomic shoulder arthroplasty with one of 3 nonstandard glenoid components: a polyethylene component with an angled keel for posterior glenoid wear without posterior subluxation; a polyethylene component with 2 mm of extra thickness for central glenoid erosion; or a posteriorly augmented metal-backed glenoid component for posterior glenoid wear and posterior subluxation. Average clinical follow-up was 7.3 years (range, 2-19 years) or until revision surgery.

RESULTS

At the most recent follow-up, 24 patients had no, mild, or occasionally moderate pain. Mean elevation improved from 91° to 126°, and mean external rotation improved from 24° to 53°. Thirteen patients had moderate or severe subluxation preoperatively, and 11 had subluxation at follow-up. On radiographic evaluation, 3 glenoid components had loosened and 3 were at risk for loosening at an average 5.5 years of follow-up. Seven patients had revision surgery: 4 for instability, 1 for osteolysis, 1 for component loosening with osteolysis, and 1 for a periprosthetic fracture. Three additional patients had removal of glenoid components, 2 for infection and 1 for loosening. Ten-year survival rate free of revision or removal of the angled keel component was 73% (95% CI: 75.3-70.7); of the extra thick (+2 mm) component, 69% (95% CI: 65-73); and of the posteriorly augmented metal-backed glenoid component, 31% (95% CI: 35.6-26.4).

CONCLUSIONS

The effectiveness of nonstandard glenoid components in addressing glenoid bone deficiencies is compromised by an increased rate of component loosening and by only partial success in eliminating subluxation.

Two-year follow-up after microsurgical discectomy and dynamic percutaneous stabilization in degenerate and herniated lumbar disc: clinical and neuroradiological outcome

AIM

Lumbar disc herniation associated with back pain is often related to disc degeneration. Back pain after microdiscectomy often persists, prejudicing clinical outcome and quality of life. To this day, the evolution of disc degeneration after classical microdiscectomy has never been proven. Percutaneous dynamic stabilization after microdiscectomy has been proposed as a novel surgical strategy for treatment of back pain with herniated disc. However, clinical results are still debated and no evidences about the long-term evolution of back pain and relationships between neuroradiological imaging and clinical outcome have been provided. We report our preliminary observations concerning the clinical and neuroradiological outcome of 11 patients treated with microdiscectomy and dynamic percutaneous lumbo-sacral stabilization, after a long-term follow-up (2-years).

METHODS

This was an uncontrolled case series. The study included 11 patients (3 F, 8 M) with L5-S1 discal herniation and degeneration underwent microdiscectomy and percutaneous dynamic stabilization, from December 2008 to November 2009. All the patients were symptomatic with back and leg pain non-responsive to long-term (8-12 months) medical and physical treatments. VAS and Satisfaction Index were used, respectively, for evaluation of clinical outcome and general postoperative patients' satisfaction. Modic and Pfirrmann scores were used for evaluation of neuroradiological outcome. All the patients underwent to microdiscectomy and implantation of the same percutaneous device for dynamic stabilization of the middle vertebral column during the same surgery. Modic, Pfirrmann, VAS and Satisfaction Index scores were collected before surgery and over the follow-up (45 days, 1 and 2 years). MRI and dynamic X-Ray 2 years after surgery were compared to the preoperative imaging.

RESULTS

Motion preservation at the functional spinal unit after surgery was demonstrated in all the cases. All patients reported a reduction or complete resolution of back and leg pain, they were satisfied and came back to normal socio-professional life. No modification of the preoperative Pfirrmann was observed, even in those patients who experienced restoration of back pain. No surgical complications nor device failures were reported.

CONCLUSION

Percutaneous minimally invasive lumbo-sacral dynamic stabilization after microdiscectomy seems a reliable and effective technique in order to obtain a resolution of back pain and seems to prevent the Pfirrmann worsening, over a long-term follow-up.

Wrist arthroplasty--a systematic review

INTRODUCTION

Severely painful or dysfunctional destroyed wrists can be reconstructed by fusion, interposition of soft-tissue or by arthroplasty using artificial materials. Total and partial wrist arthroplasty (T/PWA) has been used on a regular basis since the 1960's. The objective of this study was to review the literature on second, third and fourth generation implants.

METHODS

The review was conducted according to the PRISMA-guidelines. A search was made using a protocolled strategy and well-defined criteria in PubMed, in the Cochrane Library and by screening reference lists.

RESULTS

37 publications describing a total of 18 implants were selected for analysis. 16 of the publications were useful for the evaluation of implant longevity. Despite methodological shortcomings in many of the source documents, a summary estimate was possible.

CONCLUSION

It seems that T/PWA has a good potential to improve function through pain reduction and preservation of mobility. The risk of severe complications - deep infection and instability problems - is small with the available implants. Implant survival of 90-100% at five years are reported in most series - if not all - using newer second generation and third generation implants, but declines from five to eight years. Periprosthetic osteolysis/radiolucency is frequently reported. Its causes and consequences are not clarified.

[Options and limits of stemless shoulder prostheses]

Currently there are five manufacturers offering stemless implants for shoulder joint replacement. A total number of almost 10,000 stemless implants have been used in shoulder arthroplasty since 2004. There are two different types of metaphyseal anchorage, one obtained by impaction of a fin system and in the other implant system cage screw fixation is used. Regarding revision surgery the different types of implants show varying advantages and disadvantages in terms of secondary approach to the glenoid and the metaphyseal component. Because of the small number of cases and short period of observation at the present time none of the implant systems show a decisive superiority. In sclerotic bone the cage screw system seems to be advantageous whereas impaction using the fin system seems to be preferable in osteoporotic bone and conditions with defects of the bone. A prerequisite for all types of stemless shoulder implants is good quality bone. There should not be bony defects under the surface of the area of head resection. Stemless implants are not indicated for acute fractures.

Bacterial biofilms and periprosthetic infections

In the past, diagnosing and treating periprosthetic infections in joint arthroplasty have often been challenging for orthopaedic surgeons. Certain diagnostic criteria and different treatment strategies can be better directed if these infections are placed in the context of microbial biofilms. An understanding of the biofilm mode of microbial infection can help explain the phenomenon of culture-negative infection and provide an understanding of why certain treatment modalities often fail. Continued basic research into the role of biofilms in infection will likely provide improved strategies for the clinical diagnosis and treatment of periprosthetic joint infections.

Computed tomography quantification of bone density adjacent to cemented pegged polyethylene glenoid components in shoulder arthroplasty

BACKGROUND

Cemented polyethylene devices are the prostheses implanted more frequently, but there is no agreement on the optimal glenoid component design. In this study, bone mineral density (BMD) adjacent to cemented all-polyethylene glenoid components was assessed to gain insights into the characteristics of glenoid bone as a potential risk factor implicated in the failure of shoulder arthroplasty.

PATIENTS AND METHODS

Twenty-two subjects were examined at an average follow-up of 31 months using the Constant-Murley score (CS) and multi-detector computed tomography. BMD was measured in 5 regions of interest (ROIs) at the sites where radiolucent lines are usually detected. BMD differences among the ROIs were tested. The relationship between BMD and a number of variables (CS subscores, age, gender, follow-up duration) was explored.

RESULTS

There was a significant increase in CS scores (p<0.05). Significantly different BMD (p=0.0039) was found in the 5 ROIs, especially between ROIs 2 and 5 (p=0.016, Bonferroni's test) and between ROIs 3 and 5 (p=0.005, Bonferroni's test). BMD was lower in ROI 1 than ROI 3 and in ROI 2 than ROI 4, but the difference was not significant.

DISCUSSION

The heterogeneous BMD distribution may be related to: (1) an interindividual variability in glenoid BMD; (2) the fixation technique; or (3) the different bone response to eccentric loading of the prosthetic head on the glenoid component.

CONCLUSIONS

BMD analysis may contribute to extent our knowledge on glenoid component loosening and encourage further techniques of glenoid fixation.

Human pose recovery for rehabilitation using ambulatory sensors

In this paper, an approach for lower-leg pose recovery from ambulatory sensors is implemented and validated in a clinical setting. Inertial measurement units are attached to patients undergoing physiotherapy. The sensor data is combined with a kinematic model within an extended Kalman filter framework to perform joint angle estimation. Anthropometric joint limits and process noise adaptation are employed to improve the quality of the joint angle estimation. The proposed approach is tested on 7 patients following total hip or knee joint replacement surgery. The proposed approach achieves an average root-mean-square error of 0.12 radians at key poses.

[Efficacy evaluation of treating cervical spondylopathy with the Discover artificial cervical disc prosthesis]

OBJECTIVE

To explore the clinical and radiological outcomes of Discover artificial cervical disc arthroplasty and the range of motion status on adjacent segments for cervical spondylosis causing radiculopathy or myelopathy.

METHODS

A total of 18 consecutive patients underwent cervical arthroplasty with the Discover artificial cervical disc at our hospital. Clinical and radiological follow-ups were conducted. Their radiographic parameters of treatment and adjacent segments were evaluated at Month 1, 3, 6, 12, 18 post-operation. And the Japanese Orthopedic Association (JOA) score, visual analog scale (VAS) pain score and Odom's scale were recorded and analyzed.

RESULTS

During follow-ups over an average of 15 months, there was no occurrence of vascular injury, severe complications or prosthesis displacement and loosening. The score of JOA was 7.2±1.8 at preoperation and 16.7±4.5 at postoperation. And the score of VAS was 8.15±1.65 at preoperation and 2.03±1.12 at postoperation.

CONCLUSION

Discover artificial cervical disc arthroplasty is efficacious and the patients recover quickly. Targeted cervical segments may be stabilized and their physiological ranges of motion preserved.

Bone graft materials in fixation of orthopaedic implants in sheep

Bone graft is widely used within orthopaedic surgery especially in revision joint arthroplasty and spine fusion. The early implant fixation in the revision situation of loose joint prostheses is important for the long-term survival. Bone autograft has been considered as gold standard in many orthopaedic procedures, whereas allograft is the gold standard by replacement of extensive bone loss. However, the use of autograft is associated with donor site morbidity, especially chronic pain. In addition, the limited supply is a significant clinical challenge. Limitations in the use of allograft include the risk of bacterial contamination and disease transmission as well as non-union and poor bone quality. Other bone graft and substitutes have been considered as alternative in order to improve implant fixation. Hydroxyapatite and collagen type I composite (HA/Collagen) have the potential in mimicking skeletal bones. The osteoconductive properties of the composite might be improved by adding bone marrow aspirate (BMA), which can be harvested during surgery. Other alternatives to bone graft are demineralised bone matrix (DBM) and human cancellous bone (CB). DBM is prepared by acid extraction of human bone and includes bone collagen, morphogenetic proteins and growth factors. The combination of DBM with CB and with allograft might improve the healing potential of these grafts around non-cemented orthopaedic implants and thereby the implant fixation. Study I investigates the effect of HA/Collagen composite alone and in combination with BMA on the early fixation of porous coated titanium implants. In addition, the study compares also the effect of autograft with the gold standard allograft. By using a sheep model, the implants were inserted in the trabecular bone of femoral condyles. The test biomaterials were placed in a well defined peri-implant gap. After the observation period, the bone-implant specimens were harvested and evaluated mechanically by a destructive push-out test and analyzed histologically qualitatively and quantitatively. Study II investigates the effect of DBM alone and in combination with CB or allograft. The control group in study I and II was allograft. Study III is a methodological study and investigates the potential systematic bias by applying the traditional sampling method, which includes evaluating the mechanical fixation by using the superficial part and the histological analysis by using the profound part of the implant. The implants in this study were inserted in the proximal humerus and only allograft was used in the peri-implant gap. In study I, the mechanical testing showed failure by the preloading in the composite group with and without BMA. There were no bone ongrowth and sparely bone formation in the gap by the composite group. Adding BMA to the composite has no beneficial effect on implant fixation. No significant difference between autograft and allograft on mechanical fixation, bone ongrowth and bone formation. In study II the combination of DBM with CB or allograft showed no significant differences on the mechanical testing and histological analysis to the control group, whereas DBM alone showed significant low mechanical fixation, low bone ongrowth and low bone formation. Study III showed no significant difference between the sampling methods. In conclusion, HA/Collagen composite alone or in combination with BMA has no effect on the early fixation of porous coated titanium implants. Autograft has comparable effect on allograft with regard to early implant fixation. The combination of DBM with CB may represent an alternative to allograft. In study III, mechanical testing and histological analysis can be applied either from the superficial or the profound part of the implant. By applying the histological analysis from the superficial part and the mechanical testing from the profound part, an extra section is required.

High infection rate outcomes in long-bone tumor surgery with endoprosthetic reconstruction in adults: a systematic review

BACKGROUND

Limb salvage surgery (LSS) with endoprosthetic replacement is the most common method of reconstruction following bone tumor resection in the adult population. The risk of a postoperative infection developing is high when compared with conventional arthroplasty and there are no appropriate guidelines for antibiotic prophylaxis.

QUESTIONS/PURPOSES

We sought to answer the following questions: (1) What is the overall risk of deep infection and the causative organism in lower-extremity long-bone tumor surgery with endoprosthetic reconstruction? (2) What antibiotic regimens are used with endoprosthetic reconstruction? (3) Is there a correlation between infection and either duration of postoperative antibiotics or sample size?

METHODS

We conducted a systematic review of the literature for clinical studies that reported infection rates in adults with primary bony malignancies of the lower extremity treated with surgery and endoprosthetic reconstruction. The search included articles published in English between 1980 and July 2011.

RESULTS

The systematic literature review yielded 48 studies reporting on a total of 4838 patients. The overall pooled weighted infection rate for lower-extremity LSS with endoprosthetic reconstruction was approximately 10% (95% CI, 8%-11%), with the most common causative organism reported to be Gram-positive bacteria in the majority of cases. The pooled weighted infection rate was 13% after short-term postoperative antibiotics and 8% after long-term postoperative antibiotics. There was no correlation between sample size and infection rate.

CONCLUSIONS

Infection rates of 10% are high when compared with rates for conventional arthroplasty. Our results suggest that long-term antibiotic prophylaxis decreases the risk of deep infection. However, the data should be interpreted with caution owing to the retrospective nature of the studies.

Risk of thromboembolism in shoulder arthroplasty: effect of implant type and traumatic indication

BACKGROUND

Prior research about symptomatic venous thromboembolism (VTE) after shoulder arthroplasty has not determined whether procedure type (hemiarthroplasty, total shoulder arthroplasty, or reverse shoulder arthroplasty) or surgical indication (traumatic or elective) represent risk factors for VTE after shoulder replacement.

QUESTIONS/PURPOSES

We therefore asked whether the risk of symptomatic VTE events and mortality within 90 days of shoulder arthroplasty was influenced by (1) procedure type, and (2) surgical indication (traumatic or elective).

METHODS

We performed a retrospective database review of symptomatic VTE events and mortality within 90 days of shoulder arthroplasty in a large (30-hospital) integrated healthcare system over a 5-year period, from January 2005 to December 2009. We compared the likelihood of VTE and death in patients undergoing reverse shoulder arthroplasties (RSAs), total shoulder arthroplasties (TSAs), and hemiarthroplasties (HAs), and we compared the likelihood of VTE and death in patients who underwent elective shoulder arthroplasties with those who underwent shoulder arthroplasty in the setting of acute trauma.

RESULTS

In the 2574 eligible shoulder arthroplasties identified during the study period, VTE developed in 1.01% of patients (deep vein thrombosis 0.51% and pulmonary embolism 0.54%). With the numbers available, no differences were observed in rates of VTE or mortality by procedure type. A trend toward increased VTE occurred more frequently in patients having surgery for traumatic indications than after elective surgery (1.71% versus 0.80%; p = 0.055). A higher likelihood of 90-day mortality was observed in trauma patients compared with elective (odds ratio = 7.4; 95% CI, 2.4-25.2).

CONCLUSIONS

VTE occurred infrequently in this study sample. These data support future risk and benefit assessment of routine pharmacologic VTE prophylaxis in the perioperative treatment of patients undergoing shoulder arthroplasty, especially in all RSA and traumatic HA subsets, where the risk of VTE may be higher.

Equally good fixation of cemented and uncemented cups in total trapeziometacarpal joint prostheses. A randomized clinical RSA study with 2-year follow-up

BACKGROUND AND PURPOSE

Cup failure is a recognized problem in total trapeziometacarpal (TM) joint prostheses; it may be related to poor fixation, which can be revealed by radiostereometric analysis (RSA). We compared the early implant migration of cemented trapezium cups to that of uncemented screw cups.

PATIENTS AND METHODS

In a prospective, parallel-group, randomized patient-blinded clinical trial, we included 32 hands in 28 patients (5 males) with a mean age of 58 (40-77) years and with Eaton stage-2 or -3 osteoarthritis of the trapeziometacarpal joint. Patients were randomized to surgery with a cemented DLC all-polyethylene cup (C) (n = 16) or an uncemented hydroxyapatite-coated chrome-cobalt Elektra screw cup (UC) (n = 16). Uncemented cups were inserted without threading of the bone. Stereoradiographs for evaluation of cup migration (primary effect size) and DASH and pain scores were obtained during 2 years of follow-up.

RESULTS

The 2-year total translation (TT) was similar (p = 0.2): 0.24 mm (SD 0.10) for the C (n = 11) and 0.19 mm (SD 0.16) for the UC (n = 11). Variances were similar (p = 0.4). Judged by RSA, 2 UC cups and 1 C cup became loose (TT > 1 mm). Both UC cups were found to be loose at revision. Grip strength, pain, and DASH scores were similar between groups at all measurement points.

INTERPRETATION

Early implant fixation and clinical outcome were equally good with both cup designs. This is the first clinical RSA study on trapezium cups, and the method appears to be clinically useful for detection of loose implants.

Reverse shoulder glenoid loosening: an evaluation of the initial fixation associated with six different reverse shoulder designs

INTRODUCTION

This study quantified glenoid fixation before and after cyclic loading of six reverse shoulder prosthesis designs when secured to low and high density bone substitute blocks.

METHODS

A displacement test quantified fixation of six reverse shoulder designs: 38 mm Equinoxe standard offset (EQ), 38 mm Equinoxe lateral offset (EQL), 36 mm Depuy Delta III (DRS), 36 mm Zimmer (ZRS), 32 mm DJO RSP (DJO), and a 36 mm Tornier BIO-RSA (BIO), secured to 0.24 and 0.48 g/cm 3 polyurethane blocks as a shear (357 N) and compressive (50 N) load were applied before and after cyclic loading. Displacement was measured with a dial indicator in the directions of the applied loads along the superior/inferior axis. A cyclic test rotated each glenosphere (N= 7) at 0.5 Hz for 10 k cycles as 750 N was constantly applied. A two-tailed Student's unpaired t-test compared mean displacements.

RESULTS

The average displacement of the EQ, EQL, ZRS, DJO, DRS, and BIO-RSA devices in the low density substrate was 182, 137, 431, 321, 190, and 256 microns, respectively. The average displacement of the EQ, EQL, ZRS, DRS, and BIO-RSA devices in the high density substrate was 102, 95, 244, 138, and 173 microns, respectively. Pre- and post-cyclic displacement was significantly less in the high density bone substitutes than in the low density bone substitutes for the majority of implant comparisons. During the cyclic test, six of seven ZRS devices failed at an average of 2,603 cycles, one of seven 32 mm DJO failed at 7,342 cycles, and four of seven BIO devices failed at an average of 2,926 cycles. All seven of the EQ, EQL, and DRS devices remained well fixed throughout cyclic loading.

DISCUSSION AND CONCLUSIONS

This study quantified glenoid fixation of six reverse shoulder designs; significant differences in fixation were observed between nearly every implant design tested.

Muscle force and excursion requirements and moment arm analysis of a posterior-superior offset reverse total shoulder prosthesis

Current reverse total shoulder arthroplasty prosthesis designs do not permit offset of the humerus in the sagittal plane. Posteriorly shifting the humerus has the theoretical benefit of lengthening the infraspinatus and teres minor muscles and their external rotation moment arms, thereby improving the tension and efficiency of each external rotator and subsequently requiring each muscle to produce less force to rotate the arm. A cadaveric shoulder controller was used to quantify the impact of a novel posterior-superior offset reverse shoulder prosthesis on muscle length, moment arms, and muscle forces relative to a non-offset reverse shoulder design during two different motions: scapular plane abduction and internal/external rotation. The results of this study demonstrate that both the non-offset and offset reverse shoulder designs had similar force and excursion demands of the infraspinatus and teres minor muscles during both scapular abduction and internal and external rotation. Additionally, the offset reverse shoulder design was associated with significantly less over-tensioning of the middle and posterior deltoid and significantly more anatomic tensioning of the teres minor than the non-offset design. However, the offset reverse shoulder was observed to have more impingement than the non-offset design. These findings support the feasibility of this design: by restoring a more anatomic resting length to the deltoid and teres minor, the posterior-superior offset rTSA design may provide better teres minor function and rotational strength and may decrease the incidence of acromial stress fractures relative to the non-offset design. Clinical follow-up is required to confirm these findings.

Scapular notching in reverse shoulder arthroplasty: validation of a computer impingement model

PURPOSE

The purpose of this study is to validate a reverse shoulder computer impingement model and quantify the impact of implant position on scapular impingement by comparing it to that of a radiographic analysis of 256 patients who received the same prosthesis and were followed postoperatively for an average of 22.2 months.

METHODS

A geometric computer analysis quantified anterior and posterior scapular impingement as the humerus was internally and externally rotated at varying levels of abduction and adduction relative to a fixed scapula at defined glenoid implant positions. These impingement results were compared to radiographic study of 256 patients who were analyzed for notching, glenoid baseplate position, and glenosphere overhang.

RESULTS

The computer model predicted no impingement at 0° humeral abduction in the scapular plane for the 38 mm, 42 mm, and 46 mm devices when the glenoid baseplate cage peg is positioned 18.6 mm, 20.4 mm, and 22.7 mm from the inferior glenoid rim (of the reamed glenoid) or when glenosphere overhang of 4.6 mm, 4.7 mm, and 4.5 mm was obtained with each size glenosphere, respectively. When compared to the radiographic analysis, the computer model correctly predicted impingement based upon glenoid base- plate position in 18 of 26 patients with scapular notching and based upon glenosphere overhang in 15 of 26 patients with scapular notching.

CONCLUSIONS

Reverse shoulder implant positioning plays an important role in scapular notching. The results of this study demonstrate that the computer impingement model can effectively predict impingement based upon implant positioning in a majority of patients who developed scapular notching clinically. This computer analysis provides guidance to surgeons on implant positions that reduce scapular notching, a well-documented complication of reverse shoulder arthroplasty.

New design of a cementless glenoid component in unconstrained shoulder arthroplasty: a prospective medium-term analysis of 143 cases

The uncemented glenoid implants in total anatomical shoulder arthroplasty are likely to be accused of problems like dissociations, secondary rotator cuff tear, and wear of polyethylene (PE). This work is a clinical and radiological prospective review of 143 cases of anatomical total shoulder arthroplasty using a new metal back uncemented glenoid implant (MB) in order to see if this new implant induces those complications. A total of 143 cases were operated between 2003 and 2011. In a first part, the whole series of 143 cases was radiologically studied in order to quantify the lateralisation induced by the MB implant. In a second study, 37 cases had a mean follow-up of 38 months (24-75, mean 32) and served for the clinical and radiological final study. Pre- and postoperative clinical evaluation was done using the Constant-Murley score and the simple shoulder test from Matsen. The final X-rays served to detect an eventual secondary narrowing of the joint space and to analyse the frequency of radio lucent lines (RLL) and loosenings. Despite a small radiological lateralisation in comparison with the normal contralateral side (0.36 cm, p = 0.02), the clinical results after 2 years were similar to the published cemented glenoid implants series but without any RLL, glenoid loosening or joint narrowing. Some dissociations occured in the beginning and definitely eliminated by a design modification of the PE tray. The discussion tried to show that, despite a still short follow-up, this series is encouraging to continue to use this new MB implant. Different applications of the concept of universality and conversion are discussed, this tray been also the support of a glenosphere in reverse arthroplasty.

Comparison of bone removed with reverse total shoulder arthroplasty

INTRODUCTION

A computer model quantified glenoid base - plate surface contact area and the amount of humeral and glenoid bone removed by three different reverse shoulder prosthesis designs when implanted with various techniques.

METHODS

The computer model quantified differences in glenoid baseplate contact area and the cortical and cancellous humeral and glenoid bone removed to implant the 36 mm Depuy Delta III, 32 mm neutral DJO RSP, and the 38 mm Exactech Equinoxe reverse shoulders when each was implanted along the inferior glenoid rim of a normal and 10 mm medially eroded scapula in 20° of humeral retroversion. The impact of inferior glenoid tilt was also quantified.

RESULTS

The Delta III resected the most overall humeral bone (47.4 cm 3 ), the 32 mm RSP the second most (38.0 cm 3 ), and the Equinoxe the least (31.7 cm 3 ). The 32 mm RSP reamed away the most glenoid bone (3.7 cm 3 ), the Delta III the second most (3.6 cm 3 ), and the Equinoxe the least (3.3 cm 3 ), with greater bone removed with inferior tilt. The Equinoxe had the most glenoid baseplate surface contact (501.3 mm 2 ), the RSP had the second most (386.0 mm 2 ), and the Delta III had the least (360.6 mm 2 ), with less surface contact occurring with medial wear.

Impact of inferior glenoid tilt, humeral retroversion, bone grafting, and design parameters on muscle length and deltoid wrapping in reverse shoulder arthroplasty

PURPOSE

This study quantifies the ability of humeral retroversion, glenoid tilt, bone graft, and varying prosthesis design parameters to restore anatomic muscle length and deltoid wrapping with reverse shoulder arthroplasty.

METHODS

A computer model simulated abduction and internal and external rotation for a normal shoulder, the RSP reverse shoulder, the Equinoxe reverse shoulder, and the Grammont reverse shoulder when implanted using various implantation methods. The length of eight different muscles and the deltoid wrapping angle were quantified to evaluate the ability of each implantation method and design to restore anatomic muscle tensioning.

RESULTS

Each reverse shoulder shifted the center of rotation medially and inferiorly relative to the normal shoulder and caused a corresponding shift in the position of the humerus. Each reverse shoulder elongated each head of the deltoid and shortened the internal and external rotators relative to the normal shoulder. The surgical techniques and prosthesis designs, which resulted in a more lateral humeral position, were associated with more deltoid wrapping and better tensioning of the anterior and posterior shoulder muscles.

CONCLUSIONS

Muscle tensioning and deltoid wrapping can be substantially altered by surgical implantation meth- ods using the Grammont reverse shoulder. However, the results of this study demonstrate that more anatomic muscle tensioning and improved deltoid wrapping are achieved using alternative prosthesis designs that better restore the lateral position of the humerus.

Histological ex vivo analysis of retrieved human tantalum augmentations

PURPOSE

The characteristics of tantalum augment osseointegration in human ex vivo specimens from re-revision procedures are unknown and limited data in this regard is available. The purpose of this study was to investigate the osseointegration pattern into porous tantalum augmentations harvested during re-revision procedures.

METHODS

Between 2007 and 2010 a total of 324 hip and knee revisions with a tantalum augmentation were performed in our institution. Out of this cohort, seven patients (2.2 %) had to be re-revised. To analyse the status of trabecular ingrowth in the retrieved cases (four hips, three knees), all specimens were analysed by contact radiography, subjected to undecalcified processing, histology, thin-section analysis and backscattered electron imaging.

RESULTS

Trabecular and vascular ingrowth could be found along the bone-augment-interface in two of seven revised specimens, respectively. The depth of bone ingrowth reached up to 2.6 mm. However, the analysis of the remaining cases revealed no bony ingrowth into trabecular metal. Rather, large parts of the implants were embedded in cement or pores were filled with autologous bone.

CONCLUSIONS

Although the cause for the missing bony ingrowth seems to be multifactorial, some fundamental conditions, such as the provision of the greatest possible interface between the tantalum implant and the host bone, should be met and thus, bone cement and autologous bone grafts should be used with caution.

Amandys(®) implant: novel pyrocarbon arthroplasty for the wrist

OBJECTIVES

Post-traumatic, arthritic or degenerative destruction of the midcarpal and radiocarpal joints are difficult to treat. A new arthroplasty with a free interposition pyrocarbon implant, Amandys(®), is proposed for the treatment of extensive destruction of midcarpal and radiocarpal joints. Preliminary results are reported.

METHODS

The prospective series included 25 patients, 15 males and 10 females with a mean age of 60. The indications were degenerative, post-traumatic or rheumatoid destruction of the wrist. Sixty percent of the patients had already had surgery on their wrist before the operation. The mean follow-up was 24months.

RESULTS

Three patients had a reoperation: two for a repositioning of the implant and one for a styloidectomy. At the last follow-up, the mean grip strength was 16kg (51% of the contralateral side), the mean range of motion in flexion-extension was 68°. Mean strength and range of motion did not change significantly with the operation. Pain and function showed significant improvement. The mean pain score decreased from 6.7/10 to 3.7/10 postoperatively. The mean PRWE score decreased from 61/100 to 32/100.The mean QuickDash score decreased from 63/100 to 36/100. Ninety-six percent of the patients were satisfied or very satisfied. No dislocation or subsidence of the implant was noticed.

CONCLUSIONS

This minimally invasive pyrocarbon interposition increases the possibilities for the treatment of extensive articular destructions of the wrist. Indications must be limited to a well-aligned wrist with competent capsuloligamentous structure. This new arthroplasty is a reliable alternative to other surgical options, which are more radical or invasive such as total arthrodesis or total wrist prosthesis.

High revision and reoperation rates using the Agility™ Total Ankle System

BACKGROUND

Total ankle arthroplasty (TAA) is an evolving treatment for end-stage ankle arthritis, however, there is controversy regarding its longevity.

QUESTIONS/PURPOSES

We determined survival of the Agility™ TAA, the overall reoperation rate, and function in patients who retained their implant.

METHODS

We retrospectively reviewed 64 patients who had 65 TAAs between June 1999 and May 2001. Information was gathered through chart reviews, mailed-in questionnaires, and telephone interviews. Nine patients had died; data were available for 41 of the remaining 55 patients. Survival was based on revision as an end point. The minimum followup was 0.5 years (median, 8 years; range, 0.5-11 years).

RESULTS

Sixteen of the 41 patients (39%) needed revisions. The average time to revision surgery was 4 years with six of the revisions (38%) occurring within 1 year of the TAA. Of the 25 patients who retained their implants, 12 required secondary surgery for an overall reoperation rate of 28 of 41 (68%) at an average of 8 years followup. The average VAS pain score was 4, the average Foot and Ankle Ability Measure (FAAM) sports subscale score was 33, and the average FAAM activities of daily living subscale score was 57.

CONCLUSION

TAA had high revision and reoperation rates. Patients who retained their implant had only moderate pain relief and function. TAA must be approached with caution. More research is needed to elucidate the role of contemporary TAA.

[Early effectiveness of discover cervical artificial disc replacement in treatment of cervical spondylosis]

OBJECTIVE

To investigate the early effectiveness of the Discover cervical artificial disc replacement in treating cervical spondylosis.

METHODS

Qualified for the selective standard, 24 patients with cervical spondylosis were treated between March 2010 and March 2011. Of 24 patients, 13 patients underwent anterior cervical decompression and fusion (ACDF) (ACDF group, between March 2010 and September 2010) and 11 patients underwent Discover cervical artificial disc replacement (CADR group, between September 2010 and March 2011). There was no significant difference in gender, age, disease duration, lesions typing, and affected segments between 2 groups (P > 0.05). The operative time, blood loss, and complications were recorded. Japanese Orthopaedic Association (JOA) scores, Neck Disability Index (NDI) scores, and Odom's scores were used to evaluate the postoperative effectiveness. In CADR group, the cervical range of motion (ROM) in all directions, and prosthesis eccentricity were measured before and after operation.

RESULTS

Symptoms disappeared and no complication occurred after operation in the patients of 2 groups. The patients were followed up 12 to 18 months (mean, 15.3 months) in ACDF group and 6 to 12 months (mean, 9.6 months) in CADR group. The NDI scores in CADR group were significantly higher than those in ACDF group at 1, 3, and 6 months (P < 0.05), but no significant difference was observed in JOA score improvement rate between 2 groups (P > 0.05). According to Odom's score at last follow-up, the results were excellent in 6 cases, good in 4 cases, and fair in 3 cases with an excellent and good rate of 76.92% in ACDF group, and were excellent in 9 cases, good in 1 case, and poor in 1 case with an excellent and good rate of 90.91% in CADR group, showing no significant difference (chi2 = 3.000, P = 0.223). The patients in CADR group had significant limit of cervical joint ROM in flexion and extension and right bending at 1 month (P < 0.05), but cervical joint ROM restored after 3 months. The ROMs of left bending at 3 months and 6 months were bigger than preoperative value (P < 0.05). Meanwhile, ROM in left bending were bigger than that in right bending in replaced segment and upper segment (P < 0.05), and the ROM difference between left bending and right bending in upper segment was 2 times higher than that in the replaced segment; a marked linear correlation (P < 0.05) existed between the ROM difference and prosthesis eccentricity, and prosthesis bias had bigger ROM in lateral bending.

CONCLUSION

Discover cervical artificial disc replacement for treatment of cervical spondylosis can provide a good effectiveness and cervical postoperative movement function. As a new prosthesis, it has some merits such as simple operative steps and less complications.

[The artificial joint failure types and analysis]

This paper focused on the joint prosthesis failure event, through survey and investigation in different kinds of case studies, generalized and analyzed the failure reason of joint prosthesis. The failure reason been categorized according to the failure occurring time: short-term, medium-term and long-term, and for each category, the characteristics and root causes are discussed, and the corresponding countermeasures put forward.