Hilaire A.C. Jacob

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.

Mechanical strength of arthroscopic rotator cuff repair techniques: an in vitro study.

Background: Retears after rotator cuff repairs occur relatively frequently and may compromise the functional result. The goal of this study was to analyze the mechanical properties following arthroscopic techniques for rotator cuff repair and to evaluate possible alternative techniques.Methods: In the first part, five different bone anchors (the Revo screw; Mitek Rotator Cuff anchor, 5.0-mm Statak, PANALOK RC absorbable anchor, and 5.0-mm Bio-Statak) were tested in vitro under cyclic loading on five pairs of cadaveric shoulders. Then five types of arthroscopic tendon suturing instruments were tested on rotator cuff tendons. Finally, the arthroscopically performed mattress and modified Mason-Allen stitches, fixed with either the Revo screw or the Bio-Statak, were evaluated on ten pairs of human cadaveric shoulders.Results: The holding strengths of the various anchors were similar, ranging from 130 to 180 N, and approximated the holding strength of knotted number-2 suture materials. The fixation of the tested anchors yielded comparable values of stiffness except for one anchor, which showed significantly greater subsidence under cyclic load (p = 0.003). All tested, commercially available arthroscopic suturing devices were unsuitable for performing a modified Mason-Allen stitch on normal supraspinatus tendons. Modification of a commercially available suture punch with a longer needle allowed us to consistently perform a modified Mason-Allen stitch. The modified Mason-Allen stitch, which has shown favorable mechanical properties in open repairs of the rotator cuff, was not found to be stronger than the mattress stitch when performed arthroscopically and used with bone anchors. When the modified Mason-Allen stitch was fixed to one anchor, it was even weaker than a mattress stitch repaired with another anchor (168 versus 228 N). Unequal loading of the two suture branches due to the more rigid modified Mason-Allen stitch may be the reason for this difference.Conclusions: Arthroscopic techniques for rotator cuff repair with use of the mattress stitch and bone anchors allow for a relatively solid fixation. The holding strength is not improved with use of the modified Mason-Allen stitch. Although a direct comparison with previous in vitro studies is not possible, the holding strength of open fixation techniques seems to be stronger. If rotator cuffs are subjected to high postoperative loading, open repair might be preferred to reduce the risk of a retear, until stronger arthroscopic fixation techniques are developed.

Patient-controlled interscalene analgesia with ropivacaine 0.2% versus bupivacaine 0.15% after major open shoulder surgery: the effects on hand motor function.

We compared the effects of patient-controlled interscalene analgesia with ropivacaine 0.2% and patient-controlled interscalene analgesia (PCIA) with bupivacaine 0.15% on hand grip strength after major open shoulder surgery. Sixty patients scheduled for elective major shoulder surgery were prospectively randomized to receive in a double-blinded fashion either ropivacaine or bupivacaine through an interscalene catheter. Before surgery, all patients received an interscalene block (ISB) with either 40 mL of 0.6% ropivacaine or 40 mL of 0.5% bupivacaine. Six h after ISB, the patients received a continuous infusion of either 0.2% ropivacaine or 0.15% bupivacaine for 48 h. In both groups, the PCIA infusion rate was 5 mL/h plus a bolus of 4 mL with a lockout time of 20 min. Strength in the hand was assessed preoperatively, 24 h, and 48 h after ISB and 6 h after stopping the infusion of local anesthetic. The presence of paresthesia in the fingers was checked. Pain relief was assessed using a visual analog scale; side effects were noted, and the patients rated their satisfaction 54 h after the block. A significant decrease of strength in the hand was observed in the Bupivacaine group 24, 48, and 54 h after ISB (P < 0.05). Paresthesia was more frequently reported in the Bupivacaine group for the second and third fingers 48 h after ISB (P < 0.05) and in the first three fingers 6 h after discontinuation of the local anesthetic infusion (P < 0.05). The pain score was similar in the two groups at all times, and patient satisfaction was comparable between the two groups. We conclude that the use of the PCIA technique with ropivacaine 0.2% or bupivacaine 0.15% provides a similar pain relief after major shoulder surgery. However, ropivacaine 0.2% is associated with better preservation of strength in the hand and less paresthesia in the fingers. Implications We compared the patient-controlled interscalene analgesia technique with ropivacaine 0.2% and bupivacaine 0.15% after major open shoulder surgery. For similar pain control ropivacaine is associated with better preservation of strength in the hand and less paresthesia in the fingers.

Forces acting in the forefoot during normal gait – an estimate

OBJECTIVE To estimate forces acting along tendons and across the joints of the first and second rays of the forefoot during gait. DESIGN Using recently published data on force distribution under the forefoot and relevant anthropometrical data, internal forces are calculated. BACKGROUND It is of paramount importance to know the magnitude and direction of the forces acting within the most heavily loaded structures of the forefoot, especially when surgical treatment is envisaged. It can also be of major value in understanding the pathomechanics of certain disorders of the foot. As far as the author is aware, there is no such information presently available. METHODS The ground force distribution during the second force peak of the stance phase was used with anthropometrical data (including lengths of lever arms of the tendons that cross the joints investigated) to determine conditions of equilibrium in the sagittal plane for each joint of the first and second rays. RESULTS The flexor hallucis longus and brevis tendons exert about 52% and 36% body weight, respectively, and the peroneus longus muscle more than 58% body weight. The resultant force on the first metatarsal head amounts to about 119% body weight. The second metatarsal bone is subjected to a high bending moment with a resultant force of about 45% body weight acting on its head. The flexor digitorum longus and brevis forces are about 9% and 13% body weight, respectively. CONCLUSIONS The high forces acting along the flexor tendons of the heavily loaded first ray support the so-called longitudinal arch of the foot. The second metatarsal bone is also heavily loaded, but more in bending. If the first ray with its powerful toe be deprived of its function, be it through muscular fatigue, disease, or trauma, the second metatarsal bone will probably also fail. RELEVANCE Such information is necessary to understand the physiological function of the foot. It might also explain the development and manifestation of certain foot pathologies. Furthermore, it is of importance when considering surgical procedures in the treatment of forefoot disorders.

Effect of Selective Capsulorrhaphy on the Passive Range of Motion of the Glenohumeral Joint

Background: Capsulorrhaphy of the glenohumeral joint is a common surgical procedure for the treatment of instability caused by increased capsular laxity. The effect of capsulorrhaphy on the range of motion of the shoulder is poorly understood.Methods: We simulated localized capsular contractures by selective capsular plications in eight human cadaveric shoulders and studied the effect of such plications on the passive range of glenohumeral abduction, flexion, and external and internal rotation in different degrees of abduction. A 0.5 or 1-N-m torque was applied to the humerus, and the range of glenohumeral motion was measured with electronic goniometers in three planes and compared with those of the intact shoulder.Results: Anterosuperior capsular plication most markedly affected external rotation of the adducted arm, decreasing it by a mean of 30.1° (p < 0.0001). Anteroinferior plication significantly reduced abduction by a mean of 19.4° (p < 0.0001) and external rotation by a mean of 20.6° (p = 0.0046). Posterosuperior plication mostly limited internal rotation of the adducted arm (mean decrease, 16.1°, p = 0.0045). On the average, total anterior and total posterior plication each limited flexion by approximately 20° (p = 0.005) and abduction by ≥15° (p < 0.005), whereas total anterior plication limited external rotation by >30° (p £ 0.0002) and total posterior plication limited internal rotation by >20° (p < 0.0001). Total inferior capsular plication restricted abduction (by a mean of 27.7°, p = 0.0001), flexion, and rotation. Total superior plication restricted external rotation and flexion.Conclusions and Clinical Relevance: Localized plications of the glenohumeral joint capsule lead to predictable patterns of loss of glenohumeral mobility. If plication is planned, losses of movement can be anticipated. The findings of this study may assist surgeons in identifying the parts of the capsule that are contracted and that may need lengthening.

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 mobility of the sacroiliac joints in healthy volunteers between 20 and 50 years of age

The nature and amplitude of movement in the sacroiliac joint (SIJ) is still open to controversy. Whereas some authors using modern measuring techniques have reported on the range of motion in the SIJ of patients and in embalmed elderly humans, the following is a presentation of our observations related to healthy individuals between 20 and 50 years of age. Using a three-dimensional stereophotogrammetric method, the motion in the joints of 15 males and nine females was investigated with change in posture from the upright standing position. The general description of spatial motion, as obtained through the helical axis concept, has been used. For comparison of the results obtained, the motion is also specified as components of rotation about vertical, anteroposterior and transverse axes, or in horizontal, frontal and sagittal planes respectively. The average values for total rotation and translation were low, being 1.7 degrees and 0.7 mm respectively. One of the test subjects who was known to have occasional trouble with his sacroiliac joints exhibited more than 6 degrees rotation. No statistically significant differences could be demonstrated with respect to sex, age, or parturition. RELEVANCE:--No data are available in the literature on the motion of the sacroiliac joints of healthy men and women in the age group 20-50 years. Measurements were carried out with the aid of percutaneously introduced external markers, using conventional light photography. This is a definite advantage over the use of X-rays and radio-opaque markers that would probably remain implanted in the bone indefinitely. Therefore this method might also be considered for future use in clinical research involving the mobility of the SIJ in patients.

Is Impingement the Cause of Jumper’s Knee? Dynamic and Static Magnetic Resonance Imaging of Patellar Tendinitis in an Open-Configuration System

Background Chronic overload is considered the main cause of patellar tendinitis, but it has been postulated that impingement of the inferior patellar pole against the patellar tendon during knee flexion could be responsible. Hypothesis The role of the patellar pole in patellar tendinitis can be determined by dynamic magnetic resonance imaging. Study Design Case-control study. Methods We compared 19 knees with patellar tendinitis and 32 asymptomatic knees of age-matched subjects using an open-configuration magnetic resonance imaging system. Dynamic sagittal images were obtained from full extension to 100° of flexion with and without activation of the quadriceps muscle. The following measurements were made from the images: tendon-patella angle, anteroposterior diameter of the tendon, signal difference-to-noise ratio, the shape of the inferior patellar pole, and the location of the patellar tendon insertion. Results The tendon-patella angle was not significantly different between groups at any flexion angle, with or without quadriceps muscle activation. The insertion site of the patellar tendon differed significantly but not the shape of the inferior pole of the patella. The volume and the signal difference-to-noise ratio of zones of increased intratendinous signal as well as the anteroposterior diameter of the proximal patellar tendon were increased in symptomatic knees. Conclusions The relationship between the patella and the patellar tendon was identical in both groups; therefore, chronic overload seems to be a major cause of patellar tendinitis.

The effect of capsular tightening on humeral head translations.

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.

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.