Long-term assessment of Swanson implant arthroplasty in the proximal interphalangeal joint of the hand

PURPOSE: The purpose of this study was to evaluate the clinical results of Swanson silicone implant arthroplasty of the proximal interphalangeal (PIP) joint, specifically evaluating clinical results with long-term assessment. METHODS: A retrospective review of 70 silicone implants of the PIP joint in 48 patients was performed with an average follow-up period of 6.5 years (range, 3-20 y). Clinical assessment included motion, stability, and alignment. Radiographic assessment included implant fracture, deformity, and cystic bone resorption. The pathology consisted of degenerative joint disease in 14, posttraumatic arthritis (TA) in 11, rheumatoid arthritis (RA) in 13, and idiopathic arthritis (IA) associated with collagen disease in 12 patients. Swan neck and boutonniere deformities were assessed separately. Statistical analysis of preoperative risk factors was compared with the postoperative assessment of pain, motion, and function (return to work). RESULTS: There was no significant change in the active range of motion (ROM) before and after PIP arthroplasty (26 degrees vs 30 degrees ). Correction of swan neck and boutonniere deformities was difficult, usually leading to poor results. There was improvement in maximum active extension before surgery lacking 32 degrees to after surgery lacking 18 degrees . From a statistical standpoint rheumatoid joint involvement with PIP arthroplasty had poorer results than degenerative or posttraumatic arthritis with respect to pain relief and ROM. Pain relief was present in 70% of replaced PIP joints with residual pain and loss of strength in 30%. Radiographic analysis showed abnormal bone formation (cystic changes) in 45%. There were 11 implant fractures and 9 joints that required revision surgery. CONCLUSIONS: Silicone replacement of the PIP joint is effective in providing relief of pain from arthritis but does not provide improvement in motion or correction of deformity. It provided a poorer outcome in rheumatoid disease in comparison with degenerative, posttraumatic, or idiopathic arthritis.     

Geschichte der Endoprothetik der Fingergelenke

The history of joint prostheses does not begin before the end of the 19th century. Prior to that, resection arthroplasty of functionally impaired joints was attempted with results sometimes allowing flexion or straightening of a previously immobile joint. These operative methods developed into interposition arthroplasty, which in its turn represents the predecessor of joint implantation. Lower extremity joint implantation is nowadays a well established and rewarding strong hold of orthopaedic and trauma surgeons. Due to certain obstacles specific to the hand, a similar success story for prostheses of the finger joints is still awaited.Although there have been many different designs of finger joint prostheses over the last 50 years, there is still no implant which offers satisfactory and reliable long-term results such as those that we have become accustomed to expect from lower extremity joint allo-arthroplasty. Only recently are we able to speak of an acknowledged standard of PIP-joint allo-arthroplasty. Using the library of the German historical museum of orthopaedic surgery as well as the relevant sources of international medical literature, a survey of the development of finger joint implantation is made.     

Pyrocarbon proximal interphalangeal joint arthroplasty: outcomes of a cohort study

Pyrocarbon arthroplasty of the proximal interphalangeal joint is a relatively new concept. Early studies have been encouraging, reporting improved pain and function, but a largely unchanged arc of motion. Subsidence of the implant is common, but how it relates to outcome has not been analyzed. This study was performed to review the results of 57 pyrocarbon proximal interphalangeal implanted joints. Results showed a statistically significant increase in the arc of motion, excellent pain relief, and improved function. Subsidence was observed on radiographs in 40% of joints, but no correlation was found compared with arc of motion or function. The incidence of complications is fairly high and usually related to the peri-articular soft tissues, but they are usually minor and do not require further treatment. From this review, we can recommend the use of this implant for treatment of arthritis of the proximal interphalangeal joint.     

A long-term follow-up of silicone-rubber interposition arthroplasty for osteoarthritis of the thumb carpometacarpal joint.

There are several surgical options for osteoarthritis (OA) of the thumb carpometacarpal (CMC) joint. This paper presents our long-term clinical and radiographic review of 12 thumbs in ten patients treated by partial trapezial excision and silicone-rubber interposition arthroplasty. The follow-up period averaged 15; three years with a ten-year minimum. Although the procedure provided early pain relief in most thumbs, all but two had mild to severe pain at follow-up. The average range of post-operative palmar abduction was 23 degrees. The average post-operative grip strength was 9.5 kg. Both tip and key pinch between thumb and index finger averaged about 50% that of normal subjects. Dislocation of the implant occurred in two joints and breakages in five. Bony erosions around the implant, which we attributed silicone synovitis, were found in four thumbs. The indications for silicone-rubber interposition arthroplasty for OA of the thumb CMC joint should be severely restricted as these produced unsatisfactory long-term results.     

Effects of a new shape‐memory alloy interspinous process device on pressure distribution of the intervertebral disc and zygapophyseal joints in vitro

Objective: To quantify the pressure distribution of lumbar intervertebral discs and zygapophyseal joints with different degrees of distraction of the interspinous processes by using a new shape‐memory interspinous process stabilization device, and to research the relationship between changing disc and zygapophyseal joint loads and the degree of distraction of interspinous processes, and thus optimize usage of the implant. Methods: Six cadaver lumbar specimens (L₂–L₅) were loaded. The loads in disc and zygapophyseal joints were recorded at each L_3‐4 disc level. Implants with different spacer heights were then placed by turn and the pressure measurements repeated. Results: An implant with 10 mm spacer height does not significantly share the load. A 12 mm implant reduces the posterior annulus load, and meanwhile decreases the zygapophyseal joints pressure, but only in extension. A 14 mm implant shares the loads of posterior annulus, nucleus, and zygapophyseal joints in extension and the neutral position, but slightly increases the anterior annulus' load. Though 16–20 mm implants do decrease the loads in the posterior annulus and zygapophyseal joints, the anterior annulus' load was apparently increased. Conclusion: Different degrees of distraction of the interspinous processes lead to different load distribution on the intervertebral disc. The implant tested is not appropriate in cases of serious spinal stenosis because of the contradiction that, while over‐distraction of the interspinous processes decreases the posterior annulus and the zygapophyseal joints load and distracts the intervertebral foramina, it leads to a marked increase in the load of the anterior annulus, which is recognized to accelerate disc degeneration.     

Long-term results of cemented Steffee arthroplasty of the thumb metacarpophalangeal joint

A retrospective evaluation of the Steffee metacarpophalangeal (MCP) thumb joint prostheses was performed to determine the long-term outcome and survivorship of the prosthesis. Fifty-four primary thumb arthroplasties (49 patients) were performed for pain, weakness, or instability involving the thumb MCP joint secondary to arthritis. Underlying etiology included rheumatoid (49 thumbs), psoriatic (1 thumb), scleroderma (2 thumbs), and degenerative (2 thumbs) arthritis. Thirty-one thumbs had concomitant interphalangeal joint instability and underwent interphalangeal joint fusions. At an average follow-up period of 57 months, the average motion of the MCP joint was 21 degrees (range, 0 degrees to 40 degrees ), with a significant improvement in position and stability. Thumb axis length was maintained or increased in 98%. Although there was not a consistent long-term improvement in grip or pinch strength, 87% of the patients reported subjective improvement in strength and function as a result of surgery. Pain was relieved in all thumbs with preoperative pain. Complications included a periprosthetic fracture, 2 late infections, and 1 gross loosening of the implant. The survivorship of the implant was 93% survivorship at 5 years and 89% survivorship at 10 years, with only 4 failures in 54 thumbs. The Steffee thumb MCP arthroplasty resulted in excellent long-term survivorship, patient satisfaction, and functional outcome.     

Die Belastung orthopädischer Implantate

The loads measured at instrumented joint replacements and other orthopaedic implants allow the optimization of their stability, wear properties, fixation stability and kinematic properties prior to clinical applications. The data obtained also indicate which activities cause very high loads and should be avoided by the patients in order not to endanger the long-term success of the implant. In addition, physiotherapy after joint arthroplasty and fractures can be further improved on the basis of these data. The technical principles for such measurements are summarized and examples for the design of load measuring instrumented implants are presented. The most important results are presented based on the measurements taken at the hip and shoulder joints, internal spinal fixation devices, vertebral body replacements and knee joints. Using this data, many practical conclusions are drawn. Due to the huge amount of data obtained from the hip, most practical advise can be provided to patients with replacement or disorders involving this joint.     

Loads acting on orthopaedic implants. Measurements and practical applications

The loads measured at instrumented joint replacements and other orthopaedic implants allow the optimization of their stability, wear properties, fixation stability and kinematic properties prior to clinical applications. The data obtained also indicate which activities cause very high loads and should be avoided by the patients in order not to endanger the long-term success of the implant. In addition, physiotherapy after joint arthroplasty and fractures can be further improved on the basis of these data. The technical principles for such measurements are summarized and examples for the design of load measuring instrumented implants are presented. The most important results are presented based on the measurements taken at the hip and shoulder joints, internal spinal fixation devices, vertebral body replacements and knee joints. Using this data, many practical conclusions are drawn. Due to the huge amount of data obtained from the hip, most practical advise can be provided to patients with replacement or disorders involving this joint.     

First metatarsophalangeal joint replacement: Long-term results of a double stemmed flexible silicone prosthesis

Background

The aim of this retrospective study was to evaluate the long-term results of a Swanson type silicone prosthesis used for the first metatarsophalangeal (FMTP) joint replacement. It compares implants with and without the use of grommets.

Methods

Fifty-nine FMTP joints were replaced. The average follow-up period was 9 years. Subjective and clinical findings were scored according to the AOFAS-HMI (American Orthopedic Foot and Ankle Society-Hallux Metatarsophalangeal-Interphalangeal) score. X-ray examination was carried out by evaluation of the presence of reactive bone areas around the implant.

Results

Ninety-five percent of patients had relief of pain. Clinical findings showed a reasonable function (range of motion >30°) in 77% of the FMTP joints. A trend for decrease in radiolucency and lytic bone was seen in areas around the implant with the use of grommets.

Conclusion

The prosthesis shows good results concerning pain relief and a reasonable to good function (>30° range of motion) of the FMTP joint in most patients. Reactive bone areas around the implant decreased by the use of grommets.     

Metacarpophalangeal joint arthroplasty in rheumatoid arthritis. A long-term assessment

BACKGROUND: The long-term results of silicone metacarpophalangeal arthroplasty in patients with rheumatoid arthritis are uncertain. The purpose of this investigation was to evaluate the subjective, objective, and radiographic outcomes at the time of long-term follow-up. METHODS: Patients with rheumatoid arthritis who underwent simultaneous silicone metacarpophalangeal joint arthroplasties of all four fingers by one surgeon were eligible for inclusion in the study. The results of a total of 208 arthroplasties in fifty-two hands of thirty-six patients were evaluated at an average of fourteen years postoperatively. Active metacarpophalangeal joint motion, ulnar drift, and radiographs were assessed. The radiographs were reviewed for changes in bone length, erosions, and implant fractures. The Michigan Hand Outcomes Questionnaire (MHQ) was administered to the patients. RESULTS: The mean arc of motion of the metacarpophalangeal joints improved from 30 degrees preoperatively to 46 degrees immediately after the surgery but decreased to 36 degrees at the time of final follow-up. The mean extension deficit of the metacarpophalangeal joints improved from 57 degrees preoperatively to 11 degrees immediately after the surgery but worsened to 23 degrees at the time of final follow-up. The mean ulnar drift improved from 26 degrees preoperatively to <5 degrees in the immediate postoperative period and then recurred to an average of 16 degrees at the time of final follow-up. Implant fractures were associated with increased ulnar drift (p < 0.001). Bone reaction adjacent to the implant was demonstrated by bone-shortening in most patients and by erosions in 29% of the patients. One hundred and thirty implants (63%) were broken and forty-five (22%) more were deformed at the time of final follow-up. The MHQ score averaged 48 of 100 points. The patients expressed satisfaction with the function of only 38% of the hands, and only 27% of the hands were pain-free at the time of final follow-up. A greater degree of ulnar drift was associated with decreased patient satisfaction and a decreased score for the cosmetic appearance (p 相似文献   

Endoprothetik an der Hand

In 1890, the German surgeon T. Gluck was the first to implant an ivory arthroplasty into a wrist which was being destroyed by tuberculosis. The finger joints were first replaced with endoprostheses in 1940 by Burman. Indications for the procedure are degenerative, posttraumatic or arthritis related destruction of the joints of the hand.Nowadays, several more or less comparable prosthetic designs are available. The replacement of single bones of the wrist has not been of lasting success. Occasionally, an indication for arthroplasty of the trapezium-metacarpal joint of the thumb may exist. The metacarpophalangeal joint of the thumb should, in our experience, be fused when the need arises. Up until the present, the silastic spacer of Swanson for the metacarpophalangeal and proximal interphalangeal joints has not shown any substantial development, although a variety of designs have been introduced. Questions related to the complicated biomechanics of these articulations in combination with problems concerning the material to be used, intraosseous fixation, the articulation of the prosthesis components and the design of the stems have not yet been solved convincingly.The Swanson spacers in mid- to long-term follow-ups show little active range of motion, although the subjective patient satisfaction is very high and the potential for removal at its best. We do not see an indication for arthroplasty in the distal interphalangeal finger joints.     

Implantation eines Femurteilersatzes nach periprothetischer Femurfraktur

The development of modular prostheses is becoming increasingly important in revision surgery due to the rising need of arthroplasty in knee and hip joints. The demand for suitable prostheses is high because of the desire for a higher mobility and a good postoperative functionality, whereby preliminary experience with megaprostheses using modular implant systems in orthopedic oncology have already been obtained. Considering the clinical outcome of our 58-year-old patient (obesity III, BMI 58) and the third revision operation after two periprosthetic fractures, a megaprosthesis was implanted (Mega C-system, co. Link, Hamburg). We aimed both at good clinical functionality and good stability of the knee joint. After the implant, a good functional result was observed at the beginning; however, there were some indices for prosthesis loosening. During the fourth revision we implanted a total femoral replacement. Postoperatively, a good clinical outcome after intensive physiotherapy was observed. Nevertheless, the use of megaprostheses has to be judged cautiously because of a lack of long-term results. In addition, it should not be used as a standard implant in periprosthetic joint surgery because of the risk of aseptic loosening during its course.     

Long-term results of digital arthrodesis with the Harrison-Nicolle peg

This study determined the long-term success of digital arthrodesis with the Harrison-Nicolle peg. We reviewed 90 digital joints in 60 patients fused with the peg between 1986 and 1998 at a mean follow-up of 6 (range 2-11) years. The prime indication for surgery was rheumatoid arthritis. The early complication rate was 8%. At 1 month 89% of joints were pain-free and stable. In the long-term follow up, 96% of the joints were pain-free and stable, with the original angle of fusion. 85% achieved bony fusion, with no clinical difference between bony and fibrous fusion. Overall there was a significantly higher complication rate in the distal interphalangeal joint. We conclude that, with the exception of the distal interphalangeal joint, the Harrison-Nicolle peg is extremely effective for digital arthrodesis in the rheumatoid patient.     

Pyrolytic carbon proximal interphalangeal joint arthroplasty: results with minimum two-year follow-up evaluation

PURPOSE: To retrospectively review the surgical technique, postoperative therapy/splinting protocols, and clinical and radiographic outcomes of patients who had pyrolytic carbon proximal interphalangeal (PIP) joint arthroplasty. METHODS: A total of 50 PIP joint replacements in 35 patients were performed with a minimum follow-up period of 27 months. Indications for surgery included pain, decreased range of motion, instability, and/or deformity. The preoperative diagnosis was osteoarthritis in 14, rheumatoid arthritis in 11, and posttraumatic arthritis in 10. There were 20 women and 15 men affected. The average age at the time of surgery was 53 years. The fingers replaced included the index (15), middle (18), ring (10), and small (7). The preoperative arc of motion averaged 40 degrees (0 degrees-60 degrees ), and the pinch and grip measurements averaged 3 and 19 kg, respectively. The preoperative pain scores averaged 6 (scale, of 0-10) on a visual analog space scale. RESULTS: The arc of motion was 47 degrees after surgery, and the average pinch and grip measurements were 4 and 25 kg, respectively. Pain scores improved to 1. At the final follow-up evaluation the overall patient satisfaction was nearly 80%. The results of index finger PIP replacements are compatible with other digits. Fourteen joints (in 14 patients) to date have required additional procedures to improve or maintain joint motion/function or pain; 5 for minor reasons and 9 for major complications. The revision arthroplasty rate was 8%. No infections were noted. Although not medically necessary, 2 patients requested and had an amputation. Radiographic subsidence and subsequent settling (in accordance with Wolff's law) without apparent loosening occurred in 20 joints. CONCLUSIONS: Our 2-year minimum follow-up evaluation of pyrolytic carbon implant arthroplasty showed improved pain relief and good overall patient satisfaction. Twenty-eight percent of patients required a second procedure and 8% required a revision arthroplasty. Radiographs showed gross changes in implant and eventual settling to a stable position in 40% of the joints. A longer follow-up period will help to better determine the efficacy of this implant. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic, Level IV.     

Die intraoperative 3D-C-Bogen-Anwendung

Mobile C-arms with the option of 3D imaging like the Iso-C(3D) allow for intraoperative 3D visualization of anatomical areas with complex three-dimensional structures like articular surfaces. In an 8-year period we performed 1,841 intraoperative control scans following osteosynthesis. Among these patients we registered the number of intraoperative adjustments of fracture reduction and implant position in correlation to the area of surgery. The majority of intraoperative examinations in 1,841 patients was performed in fractures of the calcaneus (20.5%) and the upper ankle joint (13.2%). Altogether we improved the reduction or the implant position intraoperatively in 21.5%. The majority of intraoperative revisions was seen in osteosynthesis of the calcaneus (40.3%), the upper ankle joint (30.9%) and fractures of the distal tibia (29%). The rate of revisions over the time was very stable. Intraoperative need for revision of reduction or implant position is not a rare phenomenon in our experience. Intraoperative 3D imaging is a valid tool to recognize and adjust suboptimal reduction or implant positioning. Intraoperative 3D imaging can improve the quality of osteosynthesis especially in fractures of joints and complex anatomical areas.     

Long term results of the Toefit-Plus replacement for first metatarsophalangeal joint arthritis

Hallux rigidus is osteoarthritis affecting the metatarsophalangeal joint of the first toe. Patients often complain of pain and stiffness with pain being aggravated by walking, particularly during toe-off in the gait cycle. Osteoarthritis of the metatarsophalangeal joint is commonly treated with arthrodesis or resection arthroplasty. Metallic replacement of this joint is used sometimes but is not widely accepted. The use of silastic joints has problems with synovitis and implant failure. The authors used titanium implants, which can be screwed into the metatarsal and phalanx, allowing good fixation without the use of bone cement. Release of the tight plantar capsule and tissues is necessary to achieve better range of movement and correct implant positioning.Fifty five cases of arthritis of the first metatarsophalangeal joint were treated surgically with Toefit-Plus™ joint replacement. The implant consists of both metatarsal and phalangal components and a fixed-bearing polyethylene insert. All patients had a release of tight soft tissues on the plantar side. Follow up occurred at 84 to 144 months after surgery (mean of 134 months), and the results showed increasing numbers of implant failures and revisions (21%) of Toefit-Plus™ implants. 47 patients were available for review. Twenty four (51%) out of 47 patients reported satisfactory results with Toefit-Plus™ arthroplasty. Ten of these patients (21%) had removal of implants and further surgical procedures were needed due to implant failure. Eleven (23%) out of 47 patients still complained of pain despite having joint replacement with the Toefit-Plus ™ implant.There is a high rate of complications with the Toefit-Plus™ implant resulting in revision surgery. Patients should have the risks associated with arthroplasty clearly explained, including the risk of revision, and the option of arthrodesis should be discussed when planning surgery. Further trials and redesign of implants may help to improve results. The authors would not recommend the Toefit-Plus™ implant due to poor results seen in one third of patients.     

Flexible implant arthroplasty of the radiocarpal joint. Surgical technique and long-term study

The wrist joint is frequently impaired in rheumatoid, post-traumatic, and degenerative arthritis. Stable radiocarpal motion, even limited, can improve functional hand adaptations, especially if the proximal or distal joints are disabled. A flexible silicone intramedullary stemmed hinged implant was developed in 1967 to be used as an adjunct to resection arthroplasty of the radiocarpal joint while at the same time maintaining the radiocarpal relation and allowing wrist motion in all planes. The surgical technique includes proper contracture release, bone preparation, extensor tendon repair and balancing, and dorsal and palmar capsuloligamentous repair to allow only 60 degrees of total passive flexion/extension and 10 degrees radial/ulnar deviation. This procedure can be combined with ulnar head capping. Metal bone liners (grommets) may be used to protect the radiocarpal implant from sharp bone edges. From January 1970 to April 1983, 181 wrist implant procedures had been performed in 139 patients, most of whom had rheumatoid arthritis. Stable, pain-free functional motion was obtained in the majority of cases. Roentgenograms showed the implants to be well tolerated by bone. Complications were infrequent. Because this procedure does not require cementing or significant bone resection, revision or arthrodesis procedures are facilitated.     

长期随访下全髋关节置换术采用不同关节界面Meta分析

目的：比较陶瓷-陶瓷（ceramic on ceramic,CoC）界面与聚乙烯-陶瓷（ceramic on polyethylene,CoP）界面在初次全髋关节置换术中的长期随访效果及并发症,提供临床依据。方法：检索PubMed、EMBase、CoChrane图书馆、Web of science、万方数据库和中国知网,检索时间2000年1月至2021年9月,筛选纳入关于比较陶瓷-陶瓷界面和聚乙烯-陶瓷界面在全髋关节置换长期疗效和并发症的随机对照试验的随机临床研究（randomized controlled trial,RCTs）,根据纳入与排除标准进行文献筛选、质量评价及数据提取,采用Review Manager 5.3统计学软件对采用CoC或CoP术后关节功能、翻修、假体骨折、脱位、关节异响及假体磨损率进行统计分析。结果：纳入7个RCTs研究,其中CoC人工关节390髋,CoP人工关节384髋。CoC和CoP人工关节长期关节功能改善相近,差异无统计学意义[MD=0.63,95%CI(-1.81,3.07)],P=0.61;在术后并发症方面CoC人工关节有着较高的关节异响发生率[OR...     

Experimental investigation of finger dynamics before and after metacarpophalangeal joint arthroplasty

PURPOSE: The purpose of this study was to quantify the changes in the arc of digital flexion before and after metacarpophalangeal (MCP) silicone arthroplasty with a 30 degrees preflexed design. METHODS: Index, middle, and ring fingers of 4 fresh-frozen cadaver hands were used. Each hand was attached (palmar side up) to a custom test apparatus. The tendon was drawn by a small winch-type servomotor. Micropotentiometers that were attached to the centers of rotation of the MCP, distal interphalangeal, and proximal interphalangeal joints measured angular displacement before and after MCP arthroplasty as a function of tendon excursion. The data were analyzed comparing the angle of flexion initiation and the angular displacement as a function of tendon excursion before and after joint arthroplasty. RESULTS: There were no statistical differences in the angles of the MCP joints at rest, the order of initiation of joint flexion, and the overall degree of flexion between the unoperated fingers and the fingers that had surgery. There was, however, a trend toward delay in flexion initiation, an increase in the MCP angle at rest, and a decrease in torque after implant arthroplasty. CONCLUSIONS: The decrease in initiation of flexion of the MCP joint, although not statistically significant, probably was related to the 30 degrees of preflexion built into the implant. We also noted a trend of decreased flexion at the MCP joint and increased flexion at the proximal interphalangeal and distal interphalangeal joints. This trend may be advantageous in the reconstruction of hands that initially have an MCP joint flexion deformity. TYPE OF STUDY/LEVEL OF EVIDENCE: to come.     

No adverse effects of bone compaction on implant fixation after resorption of compacted bone in dogs

BACKGROUND: A new bone preparation technique, compaction, has been shown to enhance initial implant fixation. However, short-term compaction has resulted in more non-vital bone being in contact with the implant. Also, compaction may result in inferior long-term implant fixation as the compacted non-vital bone at the bone-implant interface is resorbed. METHODS: We tested the hypothesis that compaction would result in inferior implant fixation after 10 weeks of weight bearing. We compared compaction with the conventional bone removal technique (drilling) for (1) porous coated titanium (Ti) implants inserted exact-fit into medial femoral condyles, and for (2) hydroxy-apatite (HA) porous coated implants inserted press-fit into lateral femoral condyles. In each of 8 dogs, we prepared the implant cavities of one knee joint with drilling, and the other with compaction. Implants were tested mechanically to failure by push-out test, and histomorphometry was done. RESULTS: For all specimens, non-vital bone implant contact contributed very little to the total bone implant contact. Inferior mechanical or histological implant fixation with compaction was not found for either Ti implants or HA implants. INTERPRETATION: Compaction does not appear to result in inferior implant fixation as the compacted bone at the bone implant interface is resorbed.