[Short-term effectiveness of Swanson artificial joint replacement in treating posttraumatic metacarpophalangeal joint stiffness]

OBJECTIVE

To investigate the short-term effectiveness of Swanson artificial joint replacement in treating post-traumatic metacarpophalangeal joint stiffness.

METHODS

Between August 2007 and May 2010, 11 cases (13 fingers) of metacarpophalangeal joint stiffness with soft tissue defects underwent Swanson artificial joint replacement. There were 7 males (9 fingers) and 4 females (4 fingers), aged 43 to 65 years with an average of 49 years. The involved fingers included 4 thumbs, 4 index fingers, 3 middle fingers, and 2 ring fingers. The types of injury included open and crush injury in 8 fingers, fracture of the metacarpophalangeal joint in 3 fingers, metacarpophalangeal joint severing in 2 fingers. The time from joint stiffness to hospitalization was 12 to 48 weeks (mean, 24 weeks). The joint activity was (136.82 +/- 28.96) degrees. According to total active motion (TAM) assessment, included good in 1 finger, fair in 6 fingers, and poor in 6 fingers before operation. The activities of daily living were assessed by Sollerman score, which was 45.64 +/- 11.04. The X-ray films and CT scan showed traumatic arthritis of the metacarpophalangeal joint.

RESULTS

The incision healed by first intention. All patients were followed up 12 to 34 months (mean, 24.1 months). At last follow-up, the joint activity was (194.64 +/- 28.86) degrees, showing significant difference when compared with preoperative value (t = 25.214, P = 0.000). According to TAM assessment, including excellent in 1 finger, good in 4 fingers, fair in 7 fingers, and poor in 1 finger. The Sollerman score was 67.45 +/- 8.20 postoperatively, showing significant difference when compared with the preoperative score (t = -10.470, P = 0.000). X-ray examination showed no prosthesis fracture, periprosthetic fracture, or joint dislocation occurred at last follow-up.

CONCLUSION

Swanson artificial joint replacement can be applied to treat post-traumatic metacarpophalangeal joint stiffness, which can improve the joint activity and has satisfactory short-term effectiveness.

Do less medialized reverse shoulder prostheses increase motion and reduce notching?

BACKGROUND

Cuff tear arthropathy is the primary indication for total reverse shoulder arthroplasty. In patients with pseudoparalytic shoulders secondary to irreparable rotator cuff tear, reverse shoulder arthroplasty allows restoration of active anterior elevation and painless shoulder. High rates of glenoid notching have also been reported. We designed a new reverse shoulder arthroplasty with a center of rotation more lateral than the Delta prosthesis to address this problem.

QUESTIONS/PURPOSES

Does reduced medialization of reverse shoulder arthroplasty improve shoulder motion, decrease glenoid notching, or increase the risk of glenoid loosening?

PATIENTS AND METHODS

We retrospectively reviewed 76 patients with 76 less medialized reverse shoulder prostheses implanted for pseudoparalytic shoulder with rotator cuff deficiency between October 2003 and May 2006. Shoulder motion, Constant-Murley score, and plain radiographs were analyzed. Minimum followup was 24 months (mean, 44 months; range, 24-60 months).

RESULTS

The absolute Constant-Murley score increased from 24 to 59, representing an increase of 35 points. The range of active anterior elevation increased by 61°, and the improvement in pain was 10 points. The gain in external rotation with elbow at the side was 15°, while external rotation with 90° abduction increased by 30°. Followup showed no glenoid notching and no glenoid loosening with these less medialized reverse prostheses.

CONCLUSIONS

Less medialization of reverse shoulder arthroplasty improves external and medial rotation, thus facilitating the activities of daily living of older patients. The absence of glenoid notching and glenoid loosening hopefully reflects longer prosthesis survival, but longer followup is necessary to confirm these preliminary observations.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

A history of reverse total shoulder arthroplasty

BACKGROUND

Management of the cuff-deficient arthritic shoulder has long been challenging. Early unconstrained shoulder arthroplasty systems were associated with high complication and implant failure rates. The evolution toward the modern reverse shoulder arthroplasty includes many variables of constrained shoulder arthroplasty designs.

QUESTIONS/PURPOSES

This review explores the development of reverse shoulder arthroplasty, specifically describing (1) the evolution of reverse shoulder arthroplasty designs, (2) the biomechanical variations in the evolution of this arthroplasty, and (3) the current issues relevant to reverse shoulder arthroplasty today.

METHODS

Using a PubMed search, the literature was explored for articles addressing reverse shoulder arthroplasty, focusing on those papers with historical context.

RESULTS

Results of the early designs were apparently poor, although they were not subjected to rigorous clinical research and usually reported only in secondary literature. We identified a trend of glenoid component failure in the early reverse designs. This trend was recognized and reported by authors as the reverse shoulder evolved. Authors reported greater pain relief and better function in reverse shoulder arthroplasty with the fundamental change of Grammont's design (moving the center of rotation medially and distally). However, current reports suggest lingering concerns and challenges with today's designs.

CONCLUSIONS

The history of reverse shoulder arthroplasty involves the designs of many forward-thinking surgeons. Many of these highly constrained systems failed, although more recent designs have demonstrated improved longevity and implant performance. Reverse shoulder arthroplasty requires ongoing study, with challenges and controversies remaining around present-day designs.

Surgical technique: the anterosuperior approach for reverse shoulder arthroplasty

BACKGROUND

The anterosuperior approach used for reverse shoulder arthroplasty is an intermediate between the transacromial approach originally proposed by Paul Grammont and the anterosuperior approach described by D. B. Mackenzie for shoulder arthroplasty. As an alternative to the deltopectoral approach, the anterosuperior approach has the advantages of simplicity and postoperative stability.

DESCRIPTION OF TECHNIQUE

The anterior deltoid is divided from the anterior edge of the acromioclavicular arch, allowing exposure to the glenoid for glenosphere implantation.

PATIENTS AND METHODS

We used the findings of published studies to assess instability, function and pain scores, scapular notching, and complications after this approach.

RESULTS

In a comparison of the deltopectoral and anterosuperior approaches in 527 reverse arthroplasties with a minimum 2-year followup, postoperative instability rate was greater with the deltopectoral (5.1%) than with the anterosuperior (0.8%) approach. Other published studies confirm this finding. No differences in Constant-Murley score or active mobility were found. Scapular notching occurred at similar rates after the anterosuperior (74%) and deltopectoral (63%) approaches. Humeral diaphyseal fracture rates were similar, whereas the acromial fracture rate was higher using the deltopectoral approach. Loosening tended to occur more often with the anterosuperior approach.

CONCLUSIONS

The anterosuperior approach can be used in primary and revision reverse shoulder arthroplasty, as well as in acute humeral head fracture. Its main apparent advantages are simplicity, ease of axial humerus preparation, quality of frontal exposure of the glenoid, and due to subscapularis tendon preservation, a low risk of postoperative instability. Its drawbacks are risk of inaccurate glenoid positioning, axillary nerve palsy, and deltoid weakening.

Can reverse shoulder arthroplasty be used with few complications in rheumatoid arthritis?

BACKGROUND

Many patients with rheumatoid arthritis develop superior migration of the humeral head because of massive cuff tears, causing loss of active motion. Reverse shoulder arthroplasty could potentially restore biomechanical balance but a high incidence of glenoid failure has been reported. These studies do not, however, typically include many patients with rheumatoid arthritis (RA) and it is unclear whether the failure rates are similar.

QUESTIONS/PURPOSES

We therefore (1) evaluated pain relief and shoulder function after reverse arthroplasty in RA; (2) compared results between primary and revision procedures; (3) determined the incidence of scapular notching; and (4) determined the complication rate.

METHODS

We identified 29 patients with RA who had 33 reverse arthroplasties from among 412 patients having the surgery. Six patients were lost to followup. Twenty three patients (27 shoulders) were evaluated after a minimum followup of 18 months (mean, 56 months; range, 18-143 months), including 18 primary and nine revision arthroplasties. All patients were evaluated preoperatively and 23 shoulders postoperatively by an independent physiotherapist and four were assessed postoperatively by phone. Level of pain, range of motion, and Constant-Murley score were recorded and new radiographs taken.

RESULTS

Visual Analog Scale score for pain decreased from 8.0 to 1.0. Constant-Murley score increased from 13 to 52. Primary procedures had higher scores compared with revisions. Three patients had revision surgery. Notching occurred in 52% of shoulders but no loosening was seen.

CONCLUSIONS

Reverse arthroplasty in rheumatoid arthritis improved shoulder function with a low incidence of complications. We believe it should be considered in elderly patients with rheumatoid arthritis with pain and poor active range of motion resulting from massive cuff tears.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Grammont's idea: The story of Paul Grammont's functional surgery concept and the development of the reverse principle

BACKGROUND

The increased use of the reverse prosthesis over the last 10 years is due to a large series of publications using the reverse prosthesis developed by Paul Grammont. However, there is no article reporting the story of the concepts developed by Grammont.

QUESTIONS/PURPOSES

The purposes of this review are to describe the principles developed by Grammont, the chronology of development, and the biomechanical concepts and studies that led to the current design of the reverse prosthesis.

METHODS

We selectively reviewed literature and provide personal observations.

RESULTS

From phylogenetic observations, Grammont developed the principle of functional surgery applied to the rotator cuff tears. To increase the deltoid lever arm, he imagined two possibilities: the lateralization of the acromion, which facilitates the action of the rotator cuff, and the medialization of the center of rotation, which has been developed to respond to situations of rotator cuff deficiency. Grammont proposed the use of an acromiohumeral prosthesis, which was quickly abandoned due to problems of acromial loosening. Finally, Grammont used the principle of reverse prosthesis developed in the 1970s, but made a major change by medializing the center of rotation in a nonanatomic location. In 1985, Grammont validated the concept by an experimental study and the first model using a cemented sphere was implanted.

CONCLUSIONS

The development of the modern reverse prosthesis is the result of the intellectual and experimental work conducted by Grammont and his team for 20 years. Knowledge of this history is essential to envision future developments.

Effects of tilt and glenosphere eccentricity on baseplate/bone interface forces in a computational model, validated by a mechanical model, of reverse shoulder arthroplasty

HYPOTHESIS/BACKGROUND

Reverse shoulder arthroplasty is being used with greater frequency for patients with severe rotator cuff deficiency. There are several commercially available reverse shoulder devices, each with different glenosphere options. The purpose of this study was to determine: (1) forces at the baseplate-bone interface in glenospheres with centers of rotation located concentrically and eccentrically to the center of the baseplate; and (2) if baseplate-bone forces can be optimized by altering tilt of the baseplate.

METHODS

A validated computer model was used to compare concentric glenospheres with neutral offset to eccentrically offset glenospheres (6 mm inferior or 6 mm lateral) in 3 baseplate tilts: 15° inferior, neutral, or 15° superior. A baseplate, simulated bone, screws, and humeral component were modeled, and forces underneath the baseplate were calculated as the arm was abducted through 90° of glenohumeral motion.

RESULTS

For lateral and concentric glenospheres, inferior tilt provides the most even distribution of forces (mean difference in force between superior and inferior portions of baseplate: 11.3 N and 24.7 N, respectively) and superior tilt provides the most uneven distribution of forces (109.3 N and 78.7 N, respectively). For inferior eccentric glenospheres, inferior tilt provides the most uneven distribution of forces (58.7 N) and neutral tilt provides the most even distribution of forces (27.7 N).

CONCLUSION

This is the first study to investigate force distribution under the baseplate in inferior eccentric glenospheres. Although inferior tilting of the baseplate is recommended for concentric and laterally offset glenospheres, this same recommendation may be detrimental to inferiorly offset glenospheres and warrants further investigation.

Recommendations of the OARSI FDA Osteoarthritis Devices Working Group

Osteoarthritis (OA) is the most common type of arthritis and a major cause of chronic musculoskeletal pain and functional disability. While both pharmacologic and non-pharmacologic modalities are recommended in the management of OA, when patients with hip or knee OA do not obtain adequate pain relief and/or functional improvement, joint replacement surgery or other surgical interventions should be considered. Total joint arthroplasties are reliable and cost-effective treatments for patients with significant OA of the hip and knee. Evidence from cohort and observational studies has confirmed substantial improvements in pain relief with cumulative revision rates at 10 years following total hip (THA) and total knee arthroplasties (TKA) at 7% and 10%, respectively. Joint replacements have been used in most every synovial joint, although results for joints other than hip and knee replacement have not been as successful. The evolution of new device designs and surgical techniques highlights the need to better understand the risk to benefit ratio for different joint replacements and to identify the appropriate methodology for evaluating the efficacy and optimal outcomes of these new devices, designed to treat OA joints.

Current concepts for clean air and total joint arthroplasty: laminar airflow and ultraviolet radiation: a systematic review

BACKGROUND

With the trend toward pay-for-performance standards plus the increasing incidence and prevalence of periprosthetic joint infection (PJI), orthopaedic surgeons must reconsider all potential infection control measures. Both airborne and nonairborne bacterial contamination must be reduced in the operating room.

QUESTIONS/PURPOSES

Analysis of airborne bacterial reduction technologies includes evaluation of (1) the effectiveness of laminar air flow (LAF) and ultraviolet light (UVL); (2) the financial and potential health costs of each; and (3) an examination of current national and international standards, and guidelines.

METHODS

We systematically reviewed the literature from Ovid, PubMed (Medline), Cochrane DSR, ACP Journal Club, DARE, CCTR, CMR, HTA, NHSEED, CINAHLPLUS, and Google Scholar published until June 2010 focusing on ultraclean air, ultraviolet light, and laminar air.

RESULTS

High-level data demonstrating substantial PJI reduction of any infection control method may not be feasible as a result of the relatively low rates of occurrence and the expense and difficulty of conducting a large enough study with adequate power. UVL has potentially unacceptable health costs and the Centers for Disease Control and Prevention (CDC) recommends against its use. European countries have standardized LAF and it is used by the majority of American joint surgeons.

CONCLUSIONS

Both LAF and UVL reduce PJI. The absence of a high level of evidence from randomized trials is not proof of ineffectiveness. The historically high cost of LAF has decreased substantially. Only LAF has been standardized by several European countries. The CDC recommends further study of LAF but recommends UVL not be used secondary to documented potential health risks to personnel.

[Experimental study on stability of temporomandibular joint replacement]

OBJECTIVE

To discuss the stability and practicality of temporomandibular joint replacement by establishing goats artificial temporomandibular joint replacement model.

METHODS

Six healthy mature goats were selected, the male and female being half and weighing 35.3-37.0 kg. According to the parameters from X-ray films of goat's temporomandibular joint and the shape of the same kind goat's skull, the total temporomandibular joint prosthesis was prepared. The one side temporomandibular joints of six goats were replaced by prosthesis randomly as the experimental group (n = 6, fossa and condyle according to replacement location) and the other side by titanium plate as the control group (n = 6). At 4, 8, and 12 weeks, the histological observation, scanning electron microscope (SEM) observation were carried out for observing structural changes in the interface. The mechanical test and histochemistry test were used for observing the combination degree of interface and the alkaline phosphatase (ALP) activity.

RESULTS

All animals were alive to the end of experiment with normal open mouth, good recovery of masticatory function, and normal eating. At 4, 8, and 12 weeks, implants were stable in 2 groups without loosening. The histological observation and SEM observation showed the amount of osteoblasts in interface increased over times. There were significant differences in the shearing force and the ALP activity between fossa in experimental group and control group at 4 weeks (P < 0.05), but there was no significant difference between other groups (P > 0.05).

CONCLUSION

The total temporomandibular prosthesis has good stability in temporomandibular joint reconstruction of goat after replacement.

Prospective clinical and radiographic results of CHARITÉ III artificial total disc arthroplasty at 2- to 7-year follow-up: a Canadian experience

BACKGROUND

Early and intermediate results have shown that the SB CHARITÉ III total disc arthroplasty (TDA) favourably compares to spinal fusion, but is associated with fewer complications and higher levels of satisfaction. We sought to prospectively report the clinical and radiographic results of the CHARITÉ III TDA after an average of 55 months follow-up.

METHODS

We conducted a prospective study of patients receiving the CHARITÉ TDA at either L4-5 or L5-S1 between April 2001 and November 2006. The primary indication for surgery was discogenic low-back pain confirmed by provocative discography. Assessment included pre- and postoperative (3, 6 and 12 mo and yearly thereafter) validated patient outcome measures and radiographic review.

RESULTS

Fifty-seven of the potential 64 (89%) patients were available for complete follow-up. Their mean age was 39 (range 21-59) years. A statistically significant improvement was demonstrated between all the mean pre- and postoperative intervals for the Oswestry Disability Index, visual analogue scale for back and leg pain, and Short Form-36 health survey (p < 0.001). The mean sagittal rotation was 6.5° (range 0.5°-22.4°), and the mean intervertebral translation was 1.1 mm (range 0-2.4 mm). Subsidence of the implant was present in 44 of 53 (83%) patients with an L5-S1 disc arthroplasty. The mean subsidence was 1.7 mm (range 0-4.8 mm).

CONCLUSION

The 2- to 7-year follow-up of this cohort of patients demonstrated satisfactory clinical and radiographic results in a carefully selected patient population. The radiographic assessment confirmed preservation and maintenance of motion at the replaced disc during the period of follow-up.

Total ankle replacement compatible with ligament function produces mobility, good clinical scores, and low complication rates: an early clinical assessment

BACKGROUND

A three-part ankle replacement was developed to achieve compatibility with the natural ligaments by allowing fibers on the medial and lateral sides to remain isometric during passive motion. Unlike all current prostheses, the new design uses nonanatomically shaped components on the tibia and talus and a fully conforming interposed meniscal bearing.

QUESTIONS/PURPOSES

Does this new design restore ankle mobility, improve clinical score, and result in low complication and early revision rates?

PATIENTS AND METHODS

We reviewed 51 patients in whom 51 prostheses were implanted in a seven-center trial from July 2003 to July 2006. The mean age of the patients at surgery was 61.5 years (range, 35.1-82.5 years). We used the AOFAS score to assess clinical outcome. We used lateral radiographs to assess function. The minimum followup was 24 months (mean, 30 months; range, 24-48 months).

RESULTS

The mean preoperative AOFAS score of 38.5 increased to 76.9, 79.1, 76.4, and 79.0 at 12, 24, 36, and 48 months, respectively. We observed a correlation between meniscal bearing movement on the tibial component (mean, 3.4 mm; range, 2-12 mm) and range of flexion at the replaced ankle (mean, 27.4º; range, 16º-53º). We revised one arthroplasty in the second postoperative year for lateral impingement, providing a 3-year cumulative survival rate of 97% and performed one other secondary operation for hindfoot pain.

CONCLUSIONS

These data suggest the new prosthesis can provide short-term restoration of ankle mobility, a good clinical score, and low complication and failure rates. Longer followup with larger numbers is required.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Radial head arthroplasty

Radial head arthroplasty remains an encouraging treatment option for comminuted radial head fractures in an unstable elbow or forearm. This article discusses the surgical considerations related to radial head arthroplasty, including anatomy, indications, and surgical technique. Radial head arthroplasty outcomes literature and a review of current implant options are also discussed.

The endlock tumor prosthesis with short-length fixation: a clinical study

Anchorage of segmental replacement prostheses in diaphyseal bone remains a challenge in lower limb reconstructions. We developed and studied a new prosthesis design that features an intramedullary anchorage system for which finite element analysis predicted favorable bone remodeling. We retrospectively analyzed the cases of all patients who underwent implantation of the new stem. Their data were prospectively collected. Twenty-four patients (25 prosthetic reconstructions using diaphyseal fixation of the prosthesis) had 18 primary implantations and 7 revision cases. At a mean follow- up of 61 months, TESS (Toronto Extremity Salvage Score) and MSTS (Musculoskeletal Tumor Society Rating Scale score) were 80% and 65% that of a normal extremity, respectively. SF-36 (36-Item Short-Form Health Survey) Mental and Physical scores were 54 and 44 points, respectively. Minimum follow-up was 31 months (mean, 61 months; range, 31-107 months). Radiographic evaluation (1991 International Symposium of Limb Salvage [ISOLS] Radiological Implant Evaluation System) revealed 65% excellent and 35% good bone remodeling around the implant as a whole, 65% excellent and 35% good results for the anchorage proper, and 70% excellent and 30% good findings for lucencies at the bone-metal interface. Two patients (1 traumatic event) developed a loose stem. The results support the expectations as shown by finite element analysis - that the risk for loosening is reduced and that favorable bone remodeling occurs around the stem over time.

Incidence of early development of radiolucent lines in keeled polyethylene glenoid components after total shoulder arthroplasty

Glenoid loosening after total shoulder arthroplasty (TSA) remains a major concern. The purpose of this study was to determine the incidence of radiolucent lines (RLLs) after TSA performed with modern glenoid bone preparation and cement techniques for keeled-back glenoid components. One hundred ten consecutive patients with osteoarthritis were included in this study. Patients had undergone primary TSA with a keeled-back glenoid component. Mean age was 64.0 years (SD, 10.6 years; range, 27-91 years). Two independent, blinded observers assessed the initial postoperative radiographs for RLLs using the Molé, Torchia, and Franklin classification systems. On 93 (84.5%) of the 110 radiographs, there was no evidence of RLLs; on the other 17 radiographs (15.5%), there was evidence of RLLs. Mean Torchia score was 0.02 (SD, 0.13) on the anteroposterior view and 0.14 (SD, 0.34) on the axillary lateral view. Mean Franklin score was 0.02 (SD, 0.13) on the anteroposterior view and 0.21 (SD, 0.62) on the axillary lateral view. Incidence of early RLLs in keeled-back glenoid components prepared with modern cement and bone compaction techniques was 15.5%, similar to what other investigators have reported for pegged-back glenoid components.

Restoration of compressive loading properties of lumbar discs with a nucleus implant-a finite element analysis study

BACKGROUND CONTEXT

Discectomy is a common procedure for treating sciatica. However, both the operation and preceding herniated disc alter the biomechanical properties of the spinal segment. The disc mechanics are also altered in patients with chronic contained herniation. The biomechanical properties of the disc can potentially be restored with an elastomeric nucleus replacement implanted via minimally invasive surgery.

PURPOSE

The purpose of this study was to determine whether the compressive characteristics of the intervertebral disc after a nucleotomy can be restored with an elastomeric nucleus replacement.

STUDY DESIGN

A finite element model of the L4-L5 intervertebral disc was created to investigate the effect of the implantation of an elastomeric nucleus replacement on the biomechanical properties of the disc under axial loading.

METHOD

A L4-L5 physiologic intervertebral disc model was constructed and then modified to contain a range by volume of nucleotomies and nucleus replacements. The material properties of the nucleus replacement were based on experimental data for an elastomeric implant. The compressive stiffness, radial annular bulge, and stress distribution of the nucleotomy and nucleus replacement models were investigated under displacement-controlled loading.

RESULTS

Removal of nucleus pulposus from the physiologic disc reduced the force necessary to compress the disc 2 mm by 50%, altered the von Mises stress distribution, and reduced the outward radial annular bulge. Replacing the natural nucleus pulposus of the physiologic disc with an artificial nucleus reduced the force required to compress the disc 2 mm by 10%, indicating a restoration of disc compressive stiffness. The von Mises stress distribution and annular bulge observed in the disc with an artificial nucleus were similar to that observed in the physiologic disc.

CONCLUSION

This study demonstrates that despite having different material properties, a nucleus replacement implant can restore the axial compressive mechanical properties of a disc after a discectomy. The implant carries compressive load and transfers the load into annular hoop stress.

The metal-backed glenoid component in rheumatoid disease: eight- to fourteen-year follow-up

HYPOTHESIS

We believe the variable reported survivorship of the metal-backed glenoid is related to the design of the component. This study reports the outcome and survivorship of the uncemented glenoid in rheumatoid patients with an intact or repairable rotator cuff at surgery, and considers the key design features that may predict longevity of this component.

METHOD

Forty-six shoulders in 39 patients (31 women), with a mean age of 55 years (range, 35-86 years) received a total shoulder replacement with a screw-fixed porous coated metal-back glenoid. Twenty-nine patients (36 shoulders) were monitored for a mean of 132 months (96-168 months), and 10 were lost to follow-up or died before 8 years of follow-up. A Constant score was measured preoperatively and annually from the time of surgery. Radiographs were assessed for lucency, loosening, and superior subluxation of the humeral head.

RESULTS

The Constant score improved from a mean of 20.6 preoperatively to 33.5 at last follow-up (P < .001). Implant survivorship at 10 years was 89%. Five were revised: 3 for pain with associated superior subluxation, 1 for infection, and 1 for aseptic loosening. In the 4 patients with lucent zones around the glenoid, superior subluxation of the humeral head had occurred 2 to 4 years before the observed lucent lines.

DISCUSSION

The uncemented glenoid performs well in the rheumatoid shoulder, giving pain relief and improved functional outcome. The survivorship is comparable to previously reported studies.

CONCLUSION

We believe the key design features in the survivorship of the metal-backed glenoid are: a low-profile tray, with a fully coated bone ingrowth substance at the plate-bone interface, a conical stem, and secure screw fixation.

Medium term follow-up of the AES ankle prosthesis: High rate of asymptomatic osteolysis

BACKGROUND

The AES (Ankle Evolutive System) is a cobalt-chromium three-component ankle prosthesis with a hydroxyapatite coating, similar to the Buechel-Pappas ankle prosthesis, but with some modifications. Our objective was to assess its medium term follow-up results as well as its complications.

METHODS

21 patients (mean age of 57.6 years) were operated by a total ankle arthroplasty (TAA), using the AES implant, according to the standard technique. Only 18 patients were included. The other three patients were excluded from the study: two had been revised for avascular talar necrosis and one patient was happy with her outcome but could not present for logistic reasons at the last follow-up. Indications for surgery included posttraumatic osteoarthritis, primary osteoarthritis, hemochromatosis, rheumatic arthritis and osteoarthritis as a sequel of ankle instability. All patients were analyzed clinically and radiologically. Special attention was given to the presence or not of areas of osteolysis around the implants as well on conventional radiography as on CT-scan imaging, according to a specific protocol.

RESULTS

The mean follow-up was 39.4 months. Average American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score improved from 52.2 preoperatively to 86.6 postoperatively. No intra-operative complications or early complications have been noted. Delayed complications were the following: one valgus malalignment, one recurrent painful anterior heterotrophic bone formation. Above all, we noted on conventional X-ray the presence of osteolysis in 77% (14) of our patients, with a size of 0.5-1cm or greater on conventional X-ray. The most vulnerable area seemed to be the posterior tibial plafond. The four remaining patients did not show any cyst formation on X-ray but did also, just as the other 14 patients, on the CT-scan. CT-scan, on the contrary, found more osteolysis in the body of the talus, underneath the implant, an area masked on conventional X-ray. Only one patient was revised with allograft bone filling of a symptomatic osteolysis, without the need for implant removal.

CONCLUSIONS

This retrospective study shows a high frequency of delayed appearance of osteolysis (77%) in 18 AES total ankle arthroplasties. Fortunately at this moment and considering one revision, this considerable amount of asymptomatic osteolysis could not warrant a durable uncomplicated outcome.

Reverse shoulder arthroplasty as a salvage procedure for failed conventional shoulder replacement due to cuff failure--midterm results

Our goal was to evaluate the objective and subjective midterm outcome after revision of a failed shoulder arthroplasty with a reverse design prosthesis. Twenty consecutive patients with 21 revisions of a primary shoulder arthroplasty using reverse shoulder prosthesis Delta III(®) were followed up postoperatively for a mean of 46 months including clinical and radiological examination. Complications were recorded and Constant score, DASH and SF36 were assessed. With the numbers given a significant reduction of pain was achieved from 8.7 to 3.0 (p < 0.001). There was a significant improvement of active flexion from 43° to 97° (p < 0.001) and active abduction from 44° to 90° (p < 0.001). However, at the same time, active external rotation with an adducted humerus decreased significantly from 26° to 12° (p = 0.012). The constant score improved significantly from 16.7 to 55.9 (p < 0.001). Sixteen patients (84%) rated their shoulder better or much better than before. In 43% an intraoperative and in 38% a postoperative complication occurred including two late stage infections which required prosthesis removal. Our results support the use of the reverse prosthesis as revision prosthesis. The reverse design helps to compensate functional deficits due to severe soft-tissue damage except active external rotation. Nevertheless, the revision is a technically demanding procedure reflected in a high rate of intraoperative complications. The rate of secondary infections of 10% remains a special concern.

[Mechanisms, prevention, and treatments of prosthetic aseptic loosening]

OBJECTIVE

To introduce the occurrence mechanisms, prevention, and treatment measures of prosthetic aseptic loosening.

METHODS

The recent original articles about prosthetic aseptic loosening were extensively reviewed and analyzed.

RESULTS

Prosthetic aseptic loosening was a very complex process involving many mechanical and biological aspects. The main mechanical factors included prosthetic materials, shapes and sizes, implant fixation methods (including surface treatments), clinical installation, interface micromotion, stress shielding, implant wear, interface integrity, and peri prosthetic high hydraulic pressure, etc.; the main biological factors included the types and sizes of wear particles, cell-activated responses, cytokine release, enzyme activation and allergic reactions to wear particles, etc.. Many measures should be adopted to effectively prevent and treat it, including improving materials and designs of prostheses, fixation techniques, surgical techniques, and drug treatments.

CONCLUSION

Prosthetic aseptic loosening is still a troublesome complication after joint replacements in orthopaedics, and more attention should be paid for its effective prevention and treatment.

Design and development of a computer assisted glenoid implantation technique for shoulder replacement surgery

OBJECTIVE

Replacement of the diseased shoulder joint with implants is a procedure whose frequency is rapidly increasing. However, glenoid replacement remains challenging due to the difficult joint exposure and visualization of anatomical reference landmarks during the procedure. Improper positioning of the glenoid component can lead to early failure. The objective of this study was to develop and evaluate a Computer Assisted Glenoid Implantation (CAGI) technique to achieve a more accurate and reliable placement of the glenoid component.

MATERIALS AND METHODS

Twenty cadaveric scapulae were imaged with CT. The accuracy of an electromagnetic tracking system and 3D surface modeling for the measurement of glenoid position was compared to that of the standard CT-based method. Custom jigs were then developed to track instruments and to correct for scapular motion during in vitro trials. A standardized protocol for determining, in real time, the glenoid position and placement was developed and validated.

RESULTS

The version angles measured by the tracking system, CT, and the 3D modeling software were 0.0 +/- 1.2 degrees , -1.3 +/- 1.0 degrees , and -1.1 +/- 1.1 degrees , respectively. The magnitudes for inclination angles were 0.7 +/- 0.7 degrees , 0.9 +/- 0.8 degrees , and 1.0 +/- 0.7 degrees , respectively. A statistically significant difference was found only between measurements made with the tracking system and with CT (p < 0.05). Testing of the CAGI system in a cadaveric trial resulted in an accuracy of 1.17 degrees of version and 0.60 degrees of inclination. The procedure was readily performed with excellent feedback and guidance for the surgeon.

CONCLUSIONS

Preoperative planning using CT imaging with 3D modeling and intraoperative tracking were combined to produce improved accuracy and reliability of glenoid implantation in the setting of total shoulder arthroplasty.

Total ankle replacement systems available in the United States

Ankle replacement continues to be a viable option for treating patients with ankle arthritis. Over the past 10 years, there has been a significant increase in the number of ankle replacement systems available for use. Current controversy centers on whether fixed- or mobile-bearing devices are most advantageous. Most total ankle systems used outside the United States are mobile-bearing devices, whereas ankle replacement systems used in the United States are all essentially fixed-bearing devices. Not all ankles with degenerative changes are amenable to replacement surgery, and several exclusion criteria are well documented. Ankle replacement is especially complicated because of the ankle's proximity to the foot and the important role that the balance and alignment of the foot play in the success of the ankle replacement. Foot deformities should be treated before or at the time of ankle replacement surgery. Ignoring foot deformities can lead to failure of the ankle replacement. It is also of paramount importance to consider the stability of the ankle ligaments. An unstable ankle with a varus or valgus deformity of more than 20 degrees is probably not amenable to ankle replacement. There are currently no reliable options to predictably reconstruct the lateral or medial ligaments in these severe deformities. It is important to be aware of the ankle replacement systems currently available in the United States and understand the key features of each design. Devices approved by the US Food and Drug Administration, a device that is awaiting approval, and a device that is being evaluated by the Food and Drug Administration in a prospective randomized clinical trial are discussed, along with an objective comparison of fixed- and mobile-bearing devices.

Analysis of reverse total shoulder joint forces and glenoid fixation

Reverse total shoulder arthroplasty (rTSA) implants are intended to restore stability and function to shoulders with rotator cuff deficiency. The implant consists of a glenosphere projecting from a glenoid baseplate and articulating in a socket at the proximal end of a humeral component. Despite the demonstrated clinical efficacy, little information is available regarding the joint forces about this construct and the stability of the glenoid component against these forces. Our hypotheses were that the joint forces about the rTSA were comparable to that about a normal shoulder joint, and that the micromotion between the baseplate and the scapula against these loads would be sufficiently low to induce bone ingrowth. To investigate this, a custom testing rig was constructed to simulate active shoulder elevation in fresh-frozen shoulder specimens. The forces about the rTSA were calculated and found to include compressive and shear forces up to 0.7 and 0.4 BW, respectively. In contrast to a normal shoulder, where the joint forces peak at 90° of abduction, forces about the rTSA were highest at about 60° of abduction. These forces were then applied in cyclic loading conditions to the glenoid baseplate, and the micromotion of the implant relative to the bone was measured in the four quadrants of the component. For two different rTSA designs (DePuy Delta III® and Encore RSP®) and in the entire range of the fixation testing, the cyclical micromotions were always less than 62 µm. Thus, under loading conditions similar to physiological shoulder elevation, micromotion of the glenoid component was sufficiently low and within previously published limits to induce bone ingrowth.