Fibulocalcaneal Impingement in a Growing Child With Otherwise Asymptomatic Talocalcaneal Coalition.

Subfibular impingement has been described in patients with flatfoot. It possibly occurs with valgus deformity associated with talocalcaneal coalition. We observed symptomatic unilateral fibular impingement initially on the left foot of an 11-year-old female with an otherwise asymptomatic bilateral talocalcaneal coalition. From the age of 8 years, she had complained of pain around the left fibular tip. Magnetic resonance imaging showed a partial talocalcaneal coalition. At 10 years of age, it was questioned whether the pain was related to the coalition. However, imaging of the asymptomatic right foot also showed a talocalcaneal coalition, with the coalition in both feet appearing equal. Additionally, the peroneal trochlea appeared particularly prominent, more so on the left than on the right foot. Therefore, the symptoms were suspected to have been caused only by fibulocalcaneal impingement owing to a relatively long fibula. Subperiosteal shortening of the fibula was performed at when she was 11 years old. A bed for the peroneal tendons was created around the remaining epiphysis of the fibula, and the fibular ligaments were reattached with Arthrex® anchors (Arthrex, Naples, FL). At 14 months postoperatively, the patient was free of pain with unrestricted movement, although the follow-up imaging studies showed complete bony fusion on the medial aspect of the coalition between the talus and calcaneus. Approximately 1.5 years after surgery, our female patient at 12.5 years old complained of the same problems on her right foot, definitely occurring only around the fibula. The same procedure was performed as she had undergone on the left foot. At the last follow-up examination, she was asymptomatic 2.5 years after the initial surgery of the left foot and 11 months after surgery on the right. Talocalcaneal coalition can cause moderate to severe hindfoot deformity, leading to fibulocalcaneal impingement. Hence, treatment should be determined accordingly.

The Thrust Plate Hip Prosthesis: A Follow-Up of 15-20 Years With 102 Implants.

BACKGROUND: Between November 1992 and January 1999, a cohort of 102 thrust plate hip prostheses was implanted. METHODS: We now clinically and radiologically evaluate the remaining 73 prostheses with a mean follow-up of 17.2 years. RESULTS: The Harris Hip Score increased from 51.4 points preoperatively to 94.3 points at the time of this follow-up. No further changes in the radiologic findings occurred since the first follow-up, published in 2005, conducted 2-8 years after implantation. Within 15 to 20 years after primary implantation of the 102 prostheses, 6 aseptic loosenings occurred, which correspond to a cumulated survival rate of 94.7% at 17 and 91.8% at 18 years. CONCLUSION: Although the thrust plate hip prostheses is no longer marketed, the biomechanical behaviour of this unique, clinically successful prosthesis deserves attention.

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.

Evolution of open-wedge high-tibial osteotomy: experience with a special angular stable device for internal fixation without interposition material.

Surgical correction of bowed legs should be performed as early as possible. Overload osteoarthritis, even without significant varus deformity of the knee, is a further indication for open-wedge high-tibial osteotomy. Progression of damage to the joint surfaces due to overloading can be significantly retarded by realigning the extremity with the aim to, at least, reduce overload on the medial compartment to a value close to physiological. Significant improvement to open-wedge high-tibial osteotomy (OWHTO) has been made on two fronts: (a) by the use of a more appropriate surgical technique and (b) by promoting osteogenesis through an angular-stable fixation device with just the correct amount of elasticity. A retrospective study of 53 consecutive cases in which no interposition material was used to fill the wedge, with gap openings between 5 mm and 20 mm, showed that ossification of the gap always progressed from the lateral hinge towards the medial side. Standard radiographs showed 75% of the gap filled in with new bone within 6-18 months. In conclusion, we believe that open-wedge high-tibial osteotomy using the TomoFix plate has proved to be successful in treating unicompartmental gonarthrosis, even without bone grafts or bone-substitute material.

Assessment of isometricity before and after total knee arthroplasty: a cadaver study.

Total knee arthroplasty (TKA) relies on soft tissue to regulate joint stability after surgery. In practice, the exact balance of the gaps can be difficult to measure, and various methods including intra-operative spreaders or distraction devices have been proposed. While individual ligament strain patterns have been measured, no data exist on the isometricity of the soft tissue envelope as a whole. In this study, a novel device was developed and validated to compare isometricity in the entire soft tissue envelope for both the intact and TKA knee. A spring-loaded rod was inserted in six cadaver knee joints between the tibial shaft and the tibial plateau or tibial tray after removing a 7 mm slice of bone. The displacement of the rod during passive flexion represented variation in tissue tension around the joint. The rod position in the intact knee remained within 1 mm of its initial position between 15 degrees and 135 degrees of flexion, and within 2 mm (+/-1.2 mm) throughout the entire range of motion (0-150 degrees). After insertion of a mobile-bearing TKA, the rod was displaced a mean of 6 mm at 150 degrees (p<0.001). The results were validated using a force transducer implanted in the tibial baseplate of the TKA, which showed increased tibiofemoral force in the parts of the flexion range where the rod was most displaced. The force measurements were highly correlated with the displacement pattern of the spring-loaded rod (r=-0.338; p=0.006). A simple device has been validated to measure isometricity in the soft tissue envelope around the knee joint. Isometricity measurements may be used in the future to improve implantation techniques during TKA surgery.

Changes in shoulder muscle function with humeral position: a graphical description.

A graphical description of the change in the role played by each of the scapulohumeral muscles with respect to spatial joint position is presented. Moment arms were collected from a biomechanical model using the tendon travel method. Data cover elevation and flexion in a space between the frontal plane and a plane of elevation 60 degrees anterior to this. Segments of a given muscle were seen possibly to exhibit antagonistic moment components in relation to others, emphasizing the importance of muscle segmentation in biomechanical models. Graphical description of muscle function in conjunction with electromyographic studies enables a more complete assessment of active muscle function in relation to arm motion and position. In cases of attenuated muscular function, this also offers a means of detecting which muscle is involved and which other muscles possess compensating potential. Two examples illustrate the use of this data, particularly to clarify clinical issues.

The contralateral foot in children with unilateral clubfoot: a study of pressures and forces involved in gait.

The unaffected contralateral side of patients with unilateral clubfeet has sometimes been taken as control in foot pressure measurement studies. However, it has never been shown that the pressure pattern under the contralateral foot is similar to a normal foot. Sixteen patients with unilateral clubfoot and 110 normal subjects took part in this study. All participants were aged from 4 to 8 years. Studies comprised clinical examination and foot pressure measurements in barefoot walking. Evaluations of the measurements were completed by the calculation of forces acting under 10 anatomical foot areas normalized to ground reaction force at foot-flat and push-off. Significant differences in peak pressure were observed between the control group and the contralateral foot of patients under the heel and the metatarsals 1 to 4. Significant differences in the forces at foot-flat and push-off are seen especially in the midfoot. Both sides of the patients with unilateral clubfeet exert significantly less ground reaction force than normal subjects. Different pressure and force distributions of clubfoot children on their contralateral side compared with the normal feet of the control group may indicate differences in the general control pattern generated by the central nervous system. Differences can still be observed after normalization of the forces. We therefore conclude that when foot pressure measurements are made with clubfeet, it might be advisable to use a collective of normal feet, instead of the contralateral foot, for comparison.

The biomechanical role of the subscapularis in latissimus dorsi transfer for the treatment of irreparable rotator cuff tears.

Inferior functional results of latissimus tendon transfer for the treatment of irreparable rotator cuff tears have been reported in the presence of a subscapularis tendon tear. A biomechanical or experimental explanation for the necessity of an intact subscapularis is unavailable. It was, therefore, the purpose of this investigation to study the biomechanical role of the subscapularis in the treatment of a posterosuperior rotator cuff tear with latissimus dorsi transfer. A biomechanical cadaveric model was developed to reproduce glenohumeral motion patterns created by loading of the transferred latissimus dorsi tendon with and without simultaneous action of the subscapularis muscle. Significant differences could be demonstrated not only for translation but also for rotation of the humeral head depending on subscapularis action. In the neutral and in the abducted/externally rotated position of the arm, anterior translation and dislocation of the joint were encountered without subscapularis action. Our results provide evidence that motion patterns of the humeral head are significantly altered in the absence of the stabilizing effect of the subscapularis muscle. The inferior functional results of latissimus dorsi transfer in the presence of subscapularis dysfunction are explained by the loss of centering of the humeral head upon abduction and elevation if subscapularis function is deficient.

Effects of glenoid component version on humeral head displacement and joint reaction forces: an experimental study.

The purpose of this study was to determine whether changes in glenoid version are associated with humeral head displacement and changes in the joint reaction forces, as these might contribute to instability or loosening in total shoulder replacement. A total shoulder prosthesis was implanted in neutral version in 6 cadaveric shoulders. Glenoid version was then changed in steps of 4 degrees toward more anteversion and retroversion. An increase in anteversion resulted in anterior translation of the humeral head and in eccentric loading of the anterior part of the glenoid. Retroversion was associated with posterior displacement and posterior loading of the glenoid. A change in rotation of the humeral component did not compensate for altered version of the glenoid component. These results suggest that both instability and glenoid component loosening may be related to the version of the glenoid component. Therefore, assessment of loosening and instability justifies precise assessment of glenoid component version.

Forces involved in lower limb lengthening: an in vivo biomechanical study.

Despite improvements in surgical techniques for limb-lengthening procedures, the complication rate remains high. Bone fixators must cope with the forces involved during treatment, providing sufficient strength to maintain integrity of the limb in the course of lengthening, while permitting some "micromotion" across the bone gap that could enhance healing during the final phase of bone consolidation. This study reports on the forces generated during limb lengthening in the distraction and consolidation phases. Forces were measured on 19 patients between 6 and 22 years of age with 10 femoral and 11 tibial lengthenings of 1 mm/day by means of a monotube external fixator, fitted diaphysially, and modified to measure tension and weight-bearing forces. Peak force measured during the lengthening period amounted to about 14 N/kg of body mass. Generally, distraction forces leveled off at between 8 and 10 N/kg of body mass. During the consolidation period, the average force carried by the fixator dropped from 55% initially to about 10% of the force transmitted to the ground, consistent with increased load carrying capacity of the bone as healing progressed. Studying the forces involved in limb lengthening is important to gain knowledge of the forces required to overcome the resistance offered by the tissues that bridge the osteotomy site, to understand the biology of distraction osteogenesis and histiogenesis across the regenerate over time, and to provide scientific guidelines for frame removal.

Moment arms of forearm rotators.

BACKGROUND: Rotation about a longitudinal axis of the forearm has been a matter of investigation for over 100 years. However, most studies were limited to only a few muscles and to their action in specific set positions of elbow and forearm rotation. This investigation aims at determining the moment arms of muscles that contribute to pronation and supination at three different angles of elbow flexion throughout the entire range of forearm rotation. METHODS: Muscle moment arms were derived from tendon excursions that were recorded on a full-size epoxy model of the radioulnar complex. The results were verified on a fresh cadaver specimen. FINDINGS: Moment arms of all major supinators exhibit peak values in 40-50 degrees of pronation, for all three positions of the elbow. These peak values vary with elbow position, the biceps muscle showing the highest dependency with its greatest moment arm in 90 degrees of elbow flexion. The pronators show a maximum of moment arm about the neutral position, with little dependency on elbow flexion. Brachioradialis brings the pronated, or supinated forearm into the neutral position. The bow of the radius is in function comparable to the 'throw' of a crankshaft, forming a greater lever arm between the point of insertion of the muscles and the axis of rotation of the radius. INTERPRETATION: The observations drawn from this study could be of eminent value in planning rotator muscle transplantation, in understanding functional disorders after injury, and in the physical treatment of forearm rotator muscle deficiency. Reconstruction of the physiological anatomical arrangement in the treatment of injuries is strongly recommended for restoration of function.

An algorithm for estimation of shoulder muscle forces for clinical use.

BACKGROUND: The shoulder joint represents an indeterminate mechanical system, making it difficult to predict individual muscle forces required to equilibrate a given arbitrary external force. Although considerable work has been published on this matter, no model exhibits the adaptability required for the analysis involving different positions of the humerus and for any external load. An algorithm involving decision-making loops is developed to predict forces exerted by muscles that cross the shoulder joint in equilibrating a given external force acting in an arbitrary direction, with the humerus in any one of 12 selected positions. METHODS: Muscle lever arms and directions of action collected from a full-size epoxy model of the shoulder joint are used together with the external force as input. The algorithm selects an appropriate group of muscles and step by step attributes small force increments to withstand the external moment while aiming at minimising the forces involved. Each muscle force increment is stored after every loop and eventually summed up. Stability of the glenohumeral joint is the final determining factor. FINDINGS: Six worked-out examples show interesting features of probable muscular activity. Muscle segmentation is of paramount importance for spatial control. Although stability can be achieved by increasing the overall rotator cuff activity (co-contraction), this is rarely necessary. INTERPRETATION: The strategy of force sharing among the muscles opens up the possibility to examine the outcome of muscle deficiencies and to investigate causes of joint instability as encountered in clinical practice. Further validation of the model is still needed, but certain clinical observations can be explained.

Radiological findings and clinical results of 102 thrust-plate femoral hip prostheses: a follow-up of 2 to 8 years.

We report the radiological and clinical outcome of 102 consecutive femoral hip arthroplasty we prospectively followed up in 84 patients using the third generation of the thrust-plate prosthesis with a mean period of follow-up of 58 (range, 26-100) months. Four implants were revised: 2 because of an infection and 2 because of aseptic loosening. The thrust-plate prosthesis, which allows preservation of part of the femoral neck, was used in younger patients, 80% were younger than 60 years. In 95 implants, contact was maintained between thrust plate and underlying bone, and in only 3 instances, without any clinical manifestation, did the bone retract from the thrust plate to the extent that a gap appeared. The extent of radiologically evident bone contact with the flat surface of the thrust plate, as a consequence of the bone remodeling behavior, is described and retrospectively classified. The average Harris hip score increased from 51 points preoperatively to 96 points postoperatively at the last follow-up. Survivorship analysis according to Kaplan-Meier showed a survival rate of 98% after 6 years, with no further losses up to the end of the 8-year follow-up period.

In vitro comparison of standard and Knotless metal suture anchors.

PURPOSE: Clinical experience after failed Knotless suture anchor (Mitek, Westwood, MA) fixations suggested that the Knotless anchor provides considerably less fixation stability than a standard metal anchor. The purpose of this study was to analyze soft tissue fixation to bone comparing a standard and a Knotless metal suture anchor. TYPE OF STUDY: In vitro study. METHODS: The Mitek GII and Mitek Knotless suture anchors were tested on 7 human cadaveric fresh-frozen glenoids. The anchors were inserted into the glenoid rims, and the sutures of the anchors were fixed to a metal hook attached to the cross-head of a testing machine. Cyclic loading was performed. The gap formation between the metal hook and the glenoid rim, the ultimate failure loads and the modes of failure were determined. RESULTS: The mean gap formation was significantly greater for the Knotless anchor (3.8 +/- 1.4 mm) than for the GII anchor (2.4 +/- 0.5 mm) after 25 cycles with 50 N repeated load (P =.04). The largest gap of a Knotless fixation was 5.3 mm compared with 3.0 mm for the GII. The ultimate failure load was not significantly different for the Knotless anchor (179 N) and for the GII anchor (129 N). Both anchors failed by either rupture of the suture material or by pullout of the anchors. CONCLUSIONS: The GII anchor allows significantly less displacement than the Knotless anchor. Ultimate tensile strength and mode of failure are similar. Greater displacement results in larger gap formation between the soft tissue and the bone. This might weaken and jeopardize the repair. CLINICAL RELEVANCE: If reattached soft tissues are subjected to postoperative loading, gap formation may result when using the Knotless anchor. For these conditions, suture fixation with knots may be used instead.

Coronoid process and radial head as posterolateral rotatory stabilizers of the elbow.

BACKGROUND: The purpose of this study was to evaluate the role of the radial head and the coronoid process as posterolateral rotatory stabilizers of the elbow and to determine the stabilizing effect of radial head replacement and coronoid reconstruction. METHODS: The posterolateral rotatory displacement of the ulna was measured after application of a valgus and supinating torque (1). in seven intact elbows, (2). after radial head excision, (3). after sequential resection of the coronoid process, (4). after subsequent insertion of each of two different types of metal radial head prostheses (a rigid implant and a bipolar implant with a floating cup), and (5). after subsequent reconstruction of the coronoid with each of two different techniques in the same cadaveric elbow. RESULTS: The posterolateral rotatory laxity averaged 5.4 degrees in the intact elbows. The surgical approach used in this study insignificantly increased the mean laxity to 9 degrees. Excision of the radial head in an elbow with intact collateral ligaments caused a mean posterolateral rotatory laxity of 18.6 degrees (p < 0.0001). Additional removal of 30% of the height of the coronoid fully destabilized the elbows, always resulting in ulnohumeral dislocation despite intact ligaments. Implantation of a rigid radial head prosthesis stabilized the elbows. However, a mean laxity of 16.9 degrees persisted after insertion of a floating prosthesis (p < 0.0001). The elbows with a defect of 50% or 70% of the coronoid, loss of the radial head, and intact ligaments could not be stabilized by radial head replacement alone, but additional coronoid reconstruction restored stability. CONCLUSIONS: The results of this study suggest that the coronoid and the radial head contribute significantly to posterolateral rotatory stability.

Influence of humeral prosthesis height on biomechanics of glenohumeral abduction. An in vitro study.

BACKGROUND: During shoulder replacement surgery, the normal height of the proximal part of the humerus relative to the tuberosities frequently is not restored because of differences in prosthetic geometry or problems with surgical technique. The purpose of the present study was to determine the effect of humeral prosthesis height on range of motion and on the moment arms of the rotator cuff muscles during glenohumeral abduction. METHODS: Tendon excursions and abduction angles were recorded simultaneously in six cadaveric specimens during passive glenohumeral abduction in the scapular plane. Moment arms were calculated for each muscle by computing the slope of the tendon excursion-versus-glenohumeral abduction angle relationship. The experiments were carried out with the intact joint and after replacement of the humeral head with a prosthesis that was inserted in an anatomically correct position as well as 5 and 10 mm too high. RESULTS: Insertion of the prosthesis in positions that were 5 and 10 mm too high resulted in significant and marked reductions of the maximum abduction angle of 10 degrees (range, 5 degrees to 18 degrees ) and 16 degrees (range, 12 degrees to 20 degrees ), respectively. In addition, the moment arms of the infraspinatus and subscapularis decreased by 4 to 10 mm. This corresponded to a 20% to 50% decrease of the abduction moment arms of the infraspinatus and an approximately 50% to 100% decrease of the abduction moment arms of the subscapularis, depending on the abduction angle and the part of the muscle being considered. CONCLUSIONS: If a humeral head prosthesis is placed too high relative to the tuberosities, shoulder function is impaired by two potential mechanisms: (1) the inferior capsule becomes tight at lower abduction angles and limits abduction, and (2) the center of rotation is displaced upward in relation to the line of action of the rotator cuff muscles, resulting in smaller moment arms and decreased abduction moments of the respective muscles. CLINICAL RELEVANCE: In patients managed with shoulder replacement surgery, limitation of range of motion, loss of abduction strength, and overload with long-term failure of the supraspinatus tendon are potential consequences of positioning the humeral head of the prosthesis proximal to the anatomic position.

The effect of capsular tightening on humeral head translations.

UNLABELLED: Idiopathic or surgical tightening of the glenohumeral joint capsule may cause displacement of the humeral head relative to the glenoid fossa and favor the development of instability and/or osteoarthritis. In the present investigation the relative position of the humerus to the glenoid fossa was determined at the end of the ranges of eight different passive movements before and after selective capsular plication in eight cadaveric shoulders to study the effects of selective capsular plications on the kinematics of the shoulder. While the capsule was in its unaltered state, translation of the humeral head was 3.8 mm superiorly in abduction, 7.3 mm antero-superiorly in flexion. In internal rotation in 0 degrees, 45 degrees and 90 degrees of abduction the head moved 6.1, 8.0 and 12.0 mm antero-inferiorly. In external rotation at 0 degrees of abduction the translation was 0.9 mm antero-inferiorly, at 45 degrees and 90 degrees of abduction it was 4.3 and 5.6 mm postero-inferiorly, respectively. Plications of the anterior part of the capsule reproducibly and significantly either increased or decreased translations during flexion (up to 5.9 mm anteriorly and up to 3.8 mm inferiorly), external rotation (up to 2.9 mm posteriorly and 1 mm inferiorly) and internal rotation (from 5.5 mm posteriorly to 2 mm anteriorly and up to 2.2 mm superiorly). Posterior plications had only little effect on translations (mainly a decrease of anterior translation during flexion of 2.8 mm). CLINICAL RELEVANCE: The 'obligate' glenohumeral translations which occur towards the end of passive shoulder movements are altered in a reproducible fashion by tightening specific parts of the glenohumeral joint capsule, as often carried out in treatment of shoulder instability. These alterations of the kinematics of the glenohumeral joint may be relevant for the development of static subluxation and osteoarthitis as seen after too tight plication in the treatment of instability [Int. Orthop. (SICOT) 67-B (1985) 709; J. Bone Joint Surg. Am. 72 (1990) 1193; J. Bone Joint Surg. Am. 66-A (1984) 169; J. Bone Joint Surg. Am. 65 (1983) 456].

Fluoroscopically assisted stress radiography for varus-valgus stability assessment in flexion after total knee arthroplasty.

A radiographic technique to quantify varus and valgus joint laxity in flexion after total knee arthroplasty (TKA) was evaluated by means of inter-rater assessment in 12 patients. The test was shown to have good reliability. The simple method helps to detect instability in knee flexion that might be overlooked in a conventional clinical examination.

Mechanical testing of absorbable suture anchors.

PURPOSE: Absorbable suture anchors offer great advantages but are made of mechanically weak material. The weakest link in the fixation of soft tissue to bone may therefore be the anchor itself. In this study, several commercially available anchors were mechanically tested in vitro. TYPE OF STUDY: Biomechanical bench study. METHODS: Twelve absorbable suture anchor models were implanted into an artificial test bone according to the recommended technique. Testing temperature was 37 degrees C +/- 1 degrees C. The anchors were loaded with an Instron testing machine with the suture material (USP No. 2, Ethibond, Ethicon, Somerville, NJ) in line with the anchor axis, with and without previous abrasion of the suture at the eyelet. Tensile load at failure and failure mode were recorded. To test creep behavior, a permanent load of 100 N was applied to the anchors, and time to failure was recorded. Suture anchor weight and crystallinity were analyzed. RESULTS: Mean failure load on tensile testing using a cross-head speed of 60 mm/min ranged from 124 to 244 N. Failure modes were eyelet failure in 5 cases, suture failure in 6 cases, and anchor pullout in 1 case. In creep testing, eyelet failure occurred in 8 anchor models after a mean duration of 0.5 to 99 hours; 3 anchor models remained intact after 300 hours, and 1 anchor model failed by pullout of the test sample. Crystallinity ranged from 0% (amorphous) to 57.2%; anchor weight ranged from 0.036 to 0.161 g. Mechanical properties did not correlate with crystallinity but with anchor weight. Abrasion of the suture material at the eyelet had little effect on failure load. CONCLUSIONS: At 37 degrees C, structural failure (breaking) of absorbable suture anchors may occur if loaded to the mechanical limit. Absorbable anchors are particularly sensitive to static, long-term loading.