Cervical arthroplasty with the Bryan disc

Cervical arthroplasty is a promising nonfusion alternative for the treatment of degenerative disc disease. After anterior cervical discectomy for neurological decompression, the intervertebral space is reconstructed by use of a metal and polymer prosthesis, allowing semiconstrained motion in multiple planes. This approach allows for preservation of cervical motion, potentially reducing the risk of transitional-level disease.

Total disc arthroplasty: consequences for sagittal balance and lumbar spine movement

This in vivo biomechanical study was undertaken to analyze the consequences for sagittal balance and lumbar spine movement in three different lumbar disc prostheses. A total of 105 patients underwent total disc replacement in three different centers. The Maverick prosthesis was used in 46 patients, the SB Charité device was used in 49 patients and the Prodisc device was utilized in 10 patients. The analysis was computer assisted, using Spineview and Matlab softwares. The intra and inter-observer reliability and measurement uncertainty was performed. The analysis of lateral X-ray films in flexion-extension allowed to measure the prosthesis positioning, the range of motion (ROM), the localization of the mean center of rotation (MCR), the vertebral translation and the disc height, for each prosthesis device. The sagittal balance was analyzed on a full spine film. The parameters studied were described by Duval-Beaupère. The results were compared to the data found in literature, and compared to 18 asymptomatic volunteers, and 61 asymptomatic subjects, concerning the sagittal balance. The prostheses allowed an improvement of the ROM of less than 2 degrees. The ROM of L5-S1 prostheses ranged from 11.6 to 15.6% of the total lumbar motion during flexion-extension. At L4-L5 level, the ROM decreased when there was an arthrodesis associated at the L5-S1 level. There was no difference of ROM between the three prostheses devices. The MCR was linked to the ROM, but did not depend on the prosthesis offcentering. The disc height improved for any prosthesis, and decreased in flexion or in extension, when the prosthesis was offcentered. An increase of translation indicated a minor increase of the ROM at L4-L5 level after Maverick or SB Charité implantation. The L5-S1 arthrodesis was linked with an increase of the pelvic tilt. The lumbar lordosis curvature increased between L4 and S1, even more when a prosthesis was placed at the L3-L4 level. Total disc arthroplasty is useful in the surgical management of discogenic spinal pathology. The three prostheses studied allowed to retorate the disc height, the ROM, without disrupting the sagittal balance, but induced modification of the lumbar curvature.

Exposure of the head of the radius using the Wrightington approach

Surgical access to the head of the radius is usually performed through a lateral approach. We present an alternative technique through a modified posterior approach which was developed following dissections of 22 human cadavers. An osteotomy of the supinator tuberosity was performed and reflected as a single unit with the attached annular ligament. Excellent exposure of the head of the radius was achieved, replacement of the head was undertaken and the osteotomy site repaired. The elbows were stable and had a full range of movement. The approach was then carried out on 13 patients for elective replacement of the head and was found to be safe and reproducible. In the patient group all osteotomies united, the elbows were stable and had an improved range of supination and pronation. There was no change in flexion and extension of the elbow. Complications included a haematoma and a reflex sympathetic dystrophy.

The modified posterior approach provides excellent access to the head and neck of the radius, gives good stability of the elbow and allows early mobilisation of the joint.

Motion preservation technologies: alternatives to spinal fusion

Spinal arthrodesis is a versatile and effective option in the management of instabilities, deformities, and painful spinal conditions. An increasing body of biomechanical and clinical evidence suggests that the relative immobility of fused spinal segments alters stress transfer, leading to adjacent-level degeneration. The development of nonfusion spinal prostheses has been driven by increasing concerns regarding these arthrodesis-related morbidities, including graft-site harvest, pseudarthrosis, and adjacent-level degeneration. Motion-sparing implants offer some theoretical advantages over fusion; however, judicious use of these products with careful patient selection is warranted until outcome studies can demonstrate their efficacy. In this article, we review the 3 major categories of nonfusion technologies: total disc replacement, prosthetic nuclear implants, and posterior stabilization devices.

Evaluation of the glenoid implant survival using a biomechanical finite element analysis: influence of the implant design, bone properties, and loading location

Total shoulder arthroplasty has become a successful surgical procedure through design improvements. However, lucent lines around the glenoid component are of major concern for leading to component loosening. To better understand the mechanism causing loosening, a finite element biomechanical model of an in vivo scapula was developed. The effect of eccentric loading was analyzed on a keel glenoid and a peg glenoid implant. Results indicated that eccentric loading greatly increases stresses in the cement mantle at the bone-cement interface, and no significant difference was predicted between keel and peg implants. The results suggested that eccentric loading is a likely cause for initiation of cracks in the cement layer especially on the posterior side. Moreover, these results, compared with other studies, indicate that geometric and bone properties of the scapula may be more important factors in the success of shoulder arthroplasty than implant design.

Cementless hemiarthroplasty in femoral neck fractures: evaluation of clinical results and measurement of migration by EBRA-FCA

Aim of the present study was to evaluate migration rates of cementless primary hemiarthroplasty in acute femoral neck fractures. In a longitudinal, prospective study 46 patients were treated by cementless hemiarthroplasty. Clinical follow up was correlated with the EBRA-FCA method. In 30% of all patients stem migration amounted to more than 2 mm; further, these patients were seen to have a high level of activity. A high degree of migration in more than 30% of all patients requires critical scepticism toward further use of the investigated cementless stem as hemiarthroplasty. According to literature, migration of more than 2 mm suggests a high probability of early aseptic loosening. In patients with a low degree of activity good results could be observed; nevertheless, in patients with a high level of activity the combination of the investigated cementless stem with a solid fracture head cannot be recommended.

A Comparison of Retraction Pressure During Anterior Cervical Plate Surgery and Cervical Disc Replacement

BACKGROUND CONTEXT

Dysphagia is a well-recognized complication after anterior cervical discectomy and fusion, observed in as high as 50% of cases by videofluoroscopic evaluation postoperatively. Esophageal injury due to surgical retraction is a complication due to which swallowing difficulties may ensue. There are limited published data evaluating the effect of soft tissue retraction on intraesophageal pressures during anterior cervical instrumentation procedures.

PURPOSE

The purpose of this study was to (a) measure the intraesophageal pressure secondary to retraction during anterior instrumentation, (b) determine whether any pressure differences exist between plating and cervical disc replacement, and (c) determine whether the surgical level or length of the plate influences the magnitude of intraesophageal pressure during retraction.

STUDY DESIGN

An analysis of soft tissue retraction pressure was performed for anterior single-level and 3-level cervical plating and cervical disc replacement procedures.

METHODS

Using a 4-cm transverse incision, a Smith-Robinson anterior approach to the cervical spine was performed on 7 fresh, frozen cadavers. The correct placement of an esophageal pressure-transducing catheter was confirmed by laryngoscopy, manual palpation of the esophagus, and fluoroscopic imaging. Three surgical instrumentation groups were used for comparisons: (a) single-level plate (b) single-level Porous Coated Motion cervical disc replacement, and (c) 3-level plate. Hand-held appendiceal retractors were used to retract the soft tissues during screw insertion into the plate and during application of the disc prosthesis into the interspace. Care was taken to exert just enough force on the retractors to allow the surgeon to move the desired implant into the correct position. In addition the individual performing the retraction was blinded to the procedure being performed-1-level plating, 3-level plating, or disk replacement. Fluoroscopy confirmed that the pressure sensors were directly behind the retractors during data acquisition.

RESULTS

Significantly greater intraesophageal pressures were demonstrated for single-level cervical plating at C5-6 compared to that at C3-4 (P=0.036). Similarly, significantly greater pressures were recorded at C5-6 versus C3-4 for the 3-level plating group (P<0.001). In contrast, there was no statistically significant difference in pressures observed during disk replacement at C5-6 compared to that at C3-4 (P=0.084). Significantly greater pressures were recorded during single-level plating compared to disc replacement at both C3-4 (P=0.016) and C5-6 (P=0.016). Three-level plating demonstrated significantly greater pressures at C5-6 compared to disk replacement (P<0.001) but no statistically significant difference compared to disk replacement at C3-4 (P=0.333). The highest mean pressure, 154.5+/-49.5 mm Hg, was recorded at C5-6 level during insertion of the 3-level plates.

CONCLUSIONS

On the basis of the data presented here, anterior cervical plating results in significantly greater intraesophageal pressures when performed at C5-6 compared to C3-4. This holds regardless of whether the plate spans the distance from C3 to C6 (3-level plate) or the single C5-6 level. In addition, the insertion of the cervical disc replacement seems to require less esophageal retraction and hence reduced intraesophageal pressures when compared to anterior cervical plating.

Cement and press-fit humeral stem fixation provides similar results in rheumatoid patients

It is unclear whether humeral stems should be fixed with or without cement. We question whether press-fit fixation would provide similar results to cemented stem fixation. We prospectively randomized 26 shoulders in 24 patients with rheumatoid arthritis (20 women, 4 men) to have either a cemented or press-fit stem. In the press-fit group, stems were matched to the medullary canal, while lavage, pressurizing and distal plugging were used in the cemented group. We followed patients with conventional radiographs and radiostereometric analysis (RSA) at 5 to 7 days, 4 months, 1 year, and 2 years after surgery. One patient died from unrelated causes before the 1-year followup, while the remaining patients were followed according to the protocol. All but two patients were very satisfied or satisfied at 2 years. No stem was radiographically loose. There was no difference in micromotion between groups. The average rotation for all axes was less than 0.25 degrees for both groups and the average translation was less than 0.32 mm for all three axes including subsidence, which was less than 0.1 mm for the uncemented stems. We concluded at 2 years these stems provided similar fixation in rheumatoid shoulders.

LEVEL OF EVIDENCE

Therapeutic Level I. See the Guidelines for Authors for a complete description of levels of evidence.

Kudo type-5 total elbow arthroplasty in mutilating rheumatoid arthritis

We studied 11 patients (14 elbows) with gross rheumatoid deformity of the elbow, treated by total arthroplasty using the Kudo type-5 unlinked prosthesis, and who were evaluated between five and 11 years after operation. Massive bone defects were augmented by autogenous bone grafts. There were no major complications such as infection, subluxation or loosening. In most elbows relief from pain and stability were achieved. The results, according to the Mayo Elbow Performance Score, were excellent in eight, good in five and fair in one. In most elbows there was minimal or no resorption of the grafted bone. There were no radiolucent lines around the stems of the cementless components. This study shows that even highly unstable rheumatoid elbows can be replaced successfully using an unlinked prosthesis, with augmentation by grafting for major defects of bone.

Alterations in surface geometry in retrieved polyethylene glenoid component

This study characterized and quantified the changes found in retrieved glenoid polyethylene components found at revision total shoulder arthroplasty (TSA). Twenty components obtained at revision TSA were evaluated, all from a system (Global, DePuy, Warsaw, IN) with a glenoid radius of curvature 3 mm greater than that of the humeral head. Laser surface scanning provided three-dimensional analysis of the surface of the glenoid component. Scans of unused components of similar sizes enabled determination of the changes occurring after implantation. Alterations in radius of curvature were noted in every glenoid. All showed loss of the balance stability angle (BSA, the maximal angle that the net humeral joint reaction force can make with the glenoid center line before the humeral head would dislocate) of at least 5 degrees in one or more directions. Increase in BSA in one direction was seen in 11 of the components. In five of these, the increase was associated with a reduction of the local radius to match that of the humeral component. Glenoid surface morphology and stability can be changed by in vivo use. While correlation with clinical instability in the patients from whom the implants were obtained was not possible, many of the observed changes in surface morphology are of sufficient magnitude to compromise the contribution of the glenoid surface to shoulder stability. Three patterns of wear were identified: "humeral" that showed loss of the mismatch between the humeral and glenoid radii of curvature (5 of 20 components), "diffuse" that showed broad surface irregularity (18 of 20), and "rim" wear with loss of the polyethylene rim of the component (14 of 20). More than one type of wear was possible within a single glenoid.

[Elbow arthroplasty]

Each year, about 80 elbow arthroplasties are performed in Denmark. Approximately two thirds are done due to rheumatoid arthritis, the others due to comminuted fractures of the elbow, especially in elderly patients. The prosthesis is fixed with or without bone cement, and there are two different types of elbow prostheses: linked, in which the humerus and ulna are connected by a sloppy hinge, and non-linked, in which stability is dependent on the soft tissues of the elbow. Good pain relief can be expected, but the range of motion will usually be permanently affected.

[Shoulder arthroplasty]

Every year, almost 500 shoulder arthroplasties are performed in Denmark. About two-thirds are done due to fractures of the proximal humerus. Other common indications are rheumatoid arthritis and primary or secondary arthrosis. The prosthesis is fixed with or without bone cement. If the rotator cuff is lacking, an inverse total arthroplasty can be used, and in arthrosis/arthritis with good bone stock, a resurfacing prosthesis can be used. Good pain relief can be expected, but shoulder movement will usually be permanently inhibited.

Design limitations of Bryan disc arthroplasty

BACKGROUND CONTEXT

Disc arthroplasty is gaining momentum as a surgical procedure in the treatment of spinal degenerative disease. Results must be carefully scrutinized to recognize benefits as well as limitations.

PURPOSE

The aim of this study was to investigate factors associated with segmental kyphosis after Bryan disc replacement.

STUDY DESIGN/SETTING

Prospective study of a consecutively enrolled cohort of 10 patients treated in a single center using the Bryan cervical disc prosthesis for single-level segmental reconstruction in the surgical treatment of cervical radiculopathy and/or myelopathy. Radiographic and quality of life outcome measures.

METHODS

Static and dynamic lateral radiographs were digitally analyzed in patients undergoing Bryan disc arthroplasty throughout a minimum 3-month follow-up period. Observations were compared with preoperative studies looking for predictive factors of postoperative spinal alignment.

RESULTS

Postoperative end plate angles through the Bryan disc in the neutral position were kyphotic in 9 of 10 patients. Compared with preoperative end plate angulation there was a mean change of -7 degrees (towards kyphosis) in postoperative end plate alignment (p=.007, 95% confidence interval [CI] -6 degrees to -13 degrees). This correlated significantly with postoperative reduction in posterior vertebral body height of the caudal segment (p=.011, r2=.575) and postoperative functional spine unit (FSU) kyphosis (p=.032, r2=.46). Despite intraoperative distraction, postoperative FSU height was significantly reduced, on average by 1.7 mm (p=.040, 95% CI 0.5-2.8 mm).

CONCLUSIONS

Asymmetrical end plate preparation occurs because of suboptimal coordinates to which the milling jig is referenced. Although segmental motion is preserved, Bryan disc arthroplasty demonstrates a propensity towards kyphotic orientation through the prosthesis likely as a result of intraoperative lordotic distraction. FSU angulation tends towards kyphosis and FSU height is decreased in the postoperative state from lack of anterior column support. Limitations of Bryan cervical disc arthroplasty should be carefully considered when reconstruction or maintenance of cervical lordosis is desirable.

Einfach- und doppeltbeschichtete STAR-Sprunggelenkprothesen

An up to 12-year follow-up of 51 single-coated STAR revealed that 15 ankles had undergone fusion. The mean time from primary surgery to the first revision was median 51 months. In a series of 58 double-coated STAR ankles followed up to 5 years only one ankle had to be revised for component loosening. In this series the clinical survival rate was 98% and the radiographic survival rate 94% at 5 years. The radiographic survival rate, with component loosening as endpoint, was significantly better for the last 31 cases in the series of the single-coated prostheses. However, the loosening rate did not differ when these latter 31 cases were compared with the cases operated on with a double-coated prosthesis. One may conclude that improvement of the anchoring surfaces has had a limited influence on the radiographic survival of the STAR ankle. However, from the clinical survivorship figures it is obvious that the learning process continues as the difference in revision rate between the 31 last implanted single-coated and the later on implanted double-coated prostheses approached significance.

Die AGILITY-Sprunggelenkprothese

The AGILITY ankle has been clinically used for over 20 years and between the two authors, a total of 1,075 AGILITY ankles have been inserted. Beside concept and design of this unique ankle prosthesis, specific follow-up data will be presented on 775 implants performed by the first author (FGA). The AGILITY Ankle System can give reliable and predictable results if the surgeon is aware of the complexity of this operation and the need for careful postoperative monitoring. Many of the failures that have occurred in the Agility System can be prevented by early detection (i.e., syndesmotic nonunion, hindfoot valgus, fractures, etc.) and if the problem is corrected, the implant can be maintained. The new LP System will also add another dimension to the overall adaptability of the prosthesis for an additional broader base of patients.

Die TNK-Sprunggelenkprothese

Total ankle replacement has been introduced in the last 30 years. The TNK ankle is build from ceramics, and it was continuously improved. This prosthesis has the longest fellow-up times. Seventy ankle prostheses of the newest generation has been implanted between 1991 and 2001. Of these, 67 prostheses were assessed clinically and radiographically after 62 months (range, 24 to 132 months). Three ankles have been revised. The clinical score improved for the patients with primary or posttraumatic arthritis from 34 to 86, and for the patients with rheumatoid arthritis from 45 to 74. Loosening was found in 4 ankles with non-rheumatoid arthritis, and in 17 ankles with rheumatoid ankles. Total ankle replacement has emerged to a valuable alternative to ankle arthrodesis, and satisfactory results have been achieved with the current implants. The bone-implant interphase might play a most important factor for success. There is evidence that the biologic advantages of ceramics may help to improve long-lasting success in total ankle replacement.

Dreidimensionale Fußanalyse nach Implantation einer HINTEGRA-Sprunggelenkendoprothese

Detailed foot kinematics after total ankle replacement has not yet been investigated. In this study 11 patients with unilateral Hintegra ankle prosthesis were analysed with the Heidelberg Foot Model. This model measures the kinematics of the fore-, mid- and hindfoot in three clinical planes. Moreover, the kinetics of the hip, knee and ankle was captured. A diminished ROM was found in all foot segments investigated. The timing of the kinematics between sound and involved side appeared similar. A limitation in the hindfoot mobility, as experienced after ankle arthrodesis, was not observed. However, a careful hindfoot alignment is essential for optimal foot function, and previous malalignments should be corrected. Concerning the kinetics, the replaced ankle showed a decreased power generation compensated by an increase in power in the ipsilateral knee. For a more detailed evaluation, further studies are required which include pre- and postoperative data and also take into account different types of prostheses.

Lumbar total disc arthroplasty utilizing the ProDisc prosthesis in smokers versus nonsmokers: a prospective study with 2-year minimum follow-up

STUDY DESIGN

Prospective nonrandomized clinical series.

OBJECTIVES

To evaluate the efficacy of ProDisc lumbar artificial disc replacement (ADR) in smokers versus nonsmokers.

SUMMARY OF BACKGROUND DATA

Smoking is a negative predictor in fusion surgery. To date, a prospective study of the treatment of incapacitating discogenic low back pain using ADR in smokers versus nonsmokers has not been described.

METHODS

A prospective analysis was performed on 104 patients with disabling discogenic low back pain treated with single-level lumbar ProDisc total disc arthroplasty. Smokers and nonsmokers were assessed before surgery and after surgery using patient satisfaction, Oswestry, and Visual Analog Scores. Additionally, preoperative and postoperative neurologic, radiographic, and pain medication assessments were performed at similar postoperative intervals.

RESULTS

Oswestry, Visual Analog Scores, and patient satisfaction scores revealed statistical improvement beginning 3 months after surgery and were maintained at minimum 2-year follow-up. Patient satisfaction scores were higher in smokers (94%) than in nonsmokers (87%) at 2-year follow-up (P = 0.07). Radiographic analysis revealed an affected disc height increase from 4 mm to 13 mm (P < 0.05) and an affected disc motion from 3 degrees to 7 degrees (P < 0.05). No cases of loosening, dislodgment, mechanical failure, infection, or fusion of the affected segment occurred.

CONCLUSIONS

The results of our study indicate that smokers do equally well compared with nonsmokers when ProDisc ADR is used in the treatment of debilitating lumbar spondylosis. Patient outcome and radiographic scores showed significant improvement compared with preoperative levels. Although not evident in our series, additional surveillance for intraoperative and postoperative vascular spasm and occlusion may be warranted in smokers.

The Scandinavian total ankle replacement (STAR)

Ankle joint arthritis is a condition that affects many people. Initial conservative treatment includes nonsteroidal antiinflammatory drugs, soft bracing, and ankle foot orthosis. When conservative management fails, surgical intervention is often considered. Previously an ankle joint fusion has been considered the "gold standard" to treat disabling ankle joint arthritis because early total ankle joint replacements had unacceptably high complication rates. However, early and midterm data have demonstrated that the Scandinavian Total Ankle Replacement (STAR) or Agility Total Ankle may be a reasonable alternative to an ankle joint fusion.

[Muscle biomechanics in total ankle replacement]

The purpose of this orthopaedic-biomechanical study was to evaluate the muscle function in total ankle replacement (TAR) patients 1 year after surgery. Ten patients underwent a combined clinical and muscle biomechanical assessment prior to implantation and at the 1-year follow-up. Pain score, American Orthopaedic Foot and Ankle Society (AOFAS) ankle score, ankle range of motion (ROM), and calf circumference difference between the affected leg and contralateral healthy leg were assessed. Biomechanically, isometric maximal voluntary torque for ankle dorsiflexion and plantar flexion was measured simultaneously with surface electromyography of four lower leg muscles. At follow-up, a significant improvement of the pain score (from 6.7 to 0.8 points), AOFAS ankle score (from 35.6 to 92.3 points), and ROM could be shown. Not significantly, the mean calf circumference difference between legs decreased from 2.2 to 1.4 cm. However, a significant increase was seen in the mean dorsiflexion (from 17.0 to 25.8 Nm) and plantar flexion torque (15.7 to 24.6 Nm) of the TAR-treated ankle. The mean EMG frequency content of the affected lower leg at TAR follow-up was lower than in the muscles of the contralateral healthy side. In contrast, the mean EMG intensity at TAR follow-up in side-comparison was statistically the same for all muscles. Ankle OA patients have better muscle function with TAR than under the arthritic condition, but they do not reach the normal level of the contralateral healthy leg 1 year after surgery.

Comparison of two types of ulnar component in type-5 Kudo total elbow arthroplasty in patients with rheumatoid arthritis

The purpose of this study was to assess the long-term results (more than ten years) of two types of cemented ulnar component with type-5 Kudo total elbow arthroplasty in a consecutive series of 56 patients (60 elbows) with rheumatoid arthritis, and to compare the results in elbows above and below a Larsen grade IV.

There was no radiolucency around the humeral component. Patients in whom a metal-backed ulnar component and a porous-coated stem were used had better clinical results and significantly less progression of radiolucent line formation around the ulnar component. They also had a significantly better long-term survival than patients with an all-polyethylene ulnar component. The clinical results of arthroplasty using all-polyethylene ulnar components were inferior, regardless of the degree of joint destruction.

We conclude that the type-5 Kudo total elbow arthroplasty with cementless fixation of the porous-coated humeral component and cemented fixation of a metal-backed ulnar component is acceptable and well-tolerated by rheumatoid patients.

Glenoid replacement in total shoulder arthroplasty

Advances in glenoid replacement have contributed to improved patient outcomes and satisfaction while decreasing complications following total shoulder arthroplasty.

Influence of the design of the prosthesis on the outcome after hemiarthroplasty of the shoulder in displaced fractures of the head of the humerus

We reviewed 39 patients with displaced three- and four-part fractures of the humerus. In 21 patients (group A) we had used an anatomical prosthesis for the humeral head and in 18 (group B) an implant designed for fractures.

When followed up at a mean of 29.3 months after surgery the overall Constant score was 51.9 points; in group A it was 51.5 and in group B 52.4 points. The subjective satisfaction of the patients was assessed using a numerical rating scale and was similar in both groups. In group A complete healing of the tuberosities was found in 29% and 50% in group B. Partial integration was seen in 29% of group A and in only one patient in group B, while resorption was noted in 43% of group A and 44% of group B. The functional outcome was significantly better in patients with complete or partial healing of the tuberosities (p = 0.022). The specific trauma prosthesis did not lead to better healing of the tuberosities. The difference in clinical outcome obtained by the two designs did not reach statistical significance.