A biomechanical comparison of steel screws versus PLLA and magnesium screws for the Latarjet procedure.

INTRODUCTION: The fixation of the coracoid process onto the glenoid is an important step of the Latarjet procedure, and implant-associated complications are a relevant and severe problem. This study compares the fixation strength and failure mode of two biodegradable materials with stainless-steel screws. METHODS: 24 Fresh-frozen cadaveric scapulae were divided into three groups of equal size and received a coracoid transfer. Cadavers were matched according to their bone mineral density (BMD). In group 1, small-fragment screws made of stainless steel were used. In the second group, magnesium screws were used, and in the third group, screws consisted of polylactic acid (PLLA). A continuously increasing sinusoidal cyclic compression force was applied until failure occurred, which was defined as graft displacement relative to its initial position of more than 5 mm. RESULTS: At 5-mm displacement, the axial force values showed a mean of 374 ± 92 N (range 219-479 N) in group 1 (steel). The force values in group 2 (magnesium) had a mean of 299 ± 57 N (range 190-357 N). In group 3 (PLLA), failure occurred at 231 ± 83 N (range 109-355 N). The difference between group 1 (steel) and group 2 (magnesium) was not statistically significant (P = 0.212), while the difference between group 1 (steel) and group 3 (PLLA) was significant (P = 0.005). CONCLUSION: Stainless-Steel screws showed the highest stability. However, all three screw types showed axial force values of more than 200 N. Stainless steel screws and PLLA screws showed screw cut-out as the most common failure mode, while magnesium screws showed screw breakage in the majority of cases. EVIDENCE: Controlled laboratory study.

[Arthroscopic soft tissue stabilization of posttraumatic anterior shoulder instability : Techniques, limitations and long-term results]. / Arthroskopische Weichteilstabilisierung der posttraumatischen ventralen Schulterinstabilität : Techniken, Limitationen und Langzeitergebnisse.

Arthroscopic soft tissue stabilization is a well-established and broadly accepted procedure to treat posttraumatic shoulder instability. Advantages in comparison to open stabilization procedures include improved visualization of the structural damage and a less invasive approach. Technical developments in recent years have led to further improvement of the arthroscopic technique for shoulder instability. This article presents a description of principles and new developments as it contains basic techniques including patient positioning, access portals, preparation of the glenoid bone, soft tissue handling and shuttle techniques. Modern suture anchor systems to achieve arthroscopic stabilization with the corresponding advantages and disadvantages are also presented. Furthermore, the limitations and long-term results of arthroscopic soft tissue stabilization are discussed.

[Arthroscopic rotator cuff construction : Current state of refixation techniques]. / Arthroskopische Rotatorenmanschettenrekonstruktion : Aktueller Stand der Refixationstechniken.

The treatment of rotator cuff tears is affected by numerous factors. In addition to the patient's age, quality of blood supply, age and size of the tear and fatty infiltration, the refixation technique is important to ensure successful treatment. In recent years a trend towards arthroscopic operation techniques has been observed due to new developments in the field.The most important principles of arthroscopic refixation techniques currently used are presented. Special attention is paid to the type of suture, suture anchors and anchor arrangements used. Biomechanics and footprint coverage of double row constructions are superior to single row but clinical results do not show any clear advantages. If feasible, double row rotator cuff repair with lateral suture bridging seems to represent presently a useful technique with a superior rate of tendon healing.

[Pathomorphology of shoulder instability]. / Pathomorphologie der Schulterinstabilität.

In cases of a traumatic anterior first-time dislocation of the shoulder, pathomorphological changes may initially occur at three different sites: at the capsule itself, at its origin or at its insertion. The typical injury is an avulsion of the labrum and the capsule from the glenoid and is called a Bankart lesion. There is a tendency to underestimate the amount of plastic deformation of the capsule and alternative injuries, such as avulsion of the capsule from the humeral head (HAGL lesion). Bony deformities at the humeral head or at the glenoid are of utmost importance for the prognosis of shoulder instability. In the dislocated position the anterior glenoid rim may notch the posterior surface of the humeral head (Hill-Sachs lesion). Bony defects of the glenoid may be caused by a fracture or due to chronic wear (fracture or erosion type). If bony defects exceed a certain size, isolated reconstruction of soft tissues does not guarantee stability of the shoulder.

On the applicability of two different stimulation techniques for intra-operative peroneal nerve conduction testing.

Dysfunction of the peroneal nerve is an important complication of knee surgery. We compared two monitoring procedures of peroneal nerve function during a standardized operation, a closing wedge high tibial osteotomy. For two types of stimulation the evoked compound motor unit action potentials (CMAPs) were recorded on the tibialis anterior muscle. We used direct perineural electrical stimulation of the common peroneal nerve distal to the cuff (dCMAPs) after nerve identification in the surgical field. Additionally, magnetic stimulation of the sacral plexus proximal to the cuff (pCMAPs) was performed. It was found that dCMAPs were recorded during almost one hour of tourniquet time whereas the pCMAPs were blocked after 25-30 min in 9 out of 11 cases. On the other hand, the CMAP obtained after proximal stimulation exhibited a latency shift with tourniquet yielding an indicator of ischaemic changes present beneath and distal to the tourniquet cuff. In conclusion, different applicabilities of both stimulation techniques under tourniquet conditions were demonstrated.

Bilateral deficit of voluntary quadriceps muscle activation after unilateral ACL tear.

PURPOSE: The inability to fully activate the quadriceps femoris muscle voluntarily is known to accompany several different knee-joint pathologies. The extent of a voluntary-activation deficit in patients after isolated rupture of the anterior cruciate ligament (ACL), however, has been reported to be small or nonexistent, making it questionable if a voluntary-activation deficit is a relevant factor for these patients at all. METHODS: In this study the ability to voluntarily activate the quadriceps femoris muscles was quantified in 22 male patients with arthroscopically-proven isolated ACL ruptures using an established highly sensitive twitch-interpolation technique. Furthermore, the maximal voluntary contraction force of the quadriceps muscle was obtained by isometric knee-joint torque measurements. The results were compared with an age-, gender-, and activity-matched control group. RESULTS: There was a moderate but significant mean reduction in maximal voluntary activation (VA) in both the injured (VA: 83.9 +/- 2.3%, mean +/- SEM) and uninjured side (VA: 84.7 +/- 2.2%) in comparison with controls (VA: 91.1 +/- 0.8%). However, of the patients the 23% who presented a considerably reduced voluntary-activation of less than 80% were mainly responsible for the significant mean deficit. CONCLUSIONS: The deficit of isometric muscle strength on the injured side compared with that of controls was explained by the voluntary-activation deficit and a true muscle weakness. On the other hand, the diminished muscle strength of the uninjured side was explained sufficiently by the voluntary-activation deficit alone. Considering the bilateral voluntary-activation deficit, functional muscle tests might not be valid when the uninjured extremity serves as reference.

Immunohistochemical analysis of several proteolytic enzymes as parameters of cartilage degradation.

Osteoarthritis is the most common joint disease in humans. It is characterized by a gradual loss of extracellular matrix components of articular cartilage such as collagen and proteoglycan. Presently, however, emphasis is placed on enzymes exerting a strong influence on cartilage degradation. These enzymes include matrix metalloproteinases (MMP), their specific inhibitors (TIMP) and the plasminogen activator/inhibitor system. We applied monoclonal antibodies against MMP-1, -2, -3, -9 and their inhibitors TIMP-1/-2, as well as against urokinase-plasminogen activator u-PA and its inhibitor PAI to investigate their influence on articular cartilage degradation in patients with varusgonarthritis. We examined the cartilage of the lateral and medial compartments of 20 tibia plateaus, which can present with slight and severe cartilage degradations at the same time. In doing so, we tried to show whether or not immunohistological detection of enzymes could serve as a parameter for chondral degradation. The strongest immunoreaction for all enzymes was noted in the superficial layer of articular cartilage both medially and laterally. Between medial and lateral compartments, however, there were striking differences in the immunoreaction intensity of chondrocytes for MMP-1 and -3 as well as for TIMP-1 and u-PA. We noted that in cartilage with more advanced degradation, the immunoreaction for these enzymes was significantly higher in medial than in lateral compartments (p < 0.05). At the immunohistological level, a direct correlation between the grade of cartilage degradation and immunoreaction intensity was found. Our results corroborate the assumption that the expression of certain matrix-degradating enzymes serves as a parameter for the grade of cartilage degradation.

Expression of stromelysin and urokinase type plasminogen activator protein in resection specimens and biopsies at different stages of osteoarthritis of the knee.

This study aimed at assessing the possible diagnostic value of cartilage biopsies as a convenient marker for cartilage matrix degradation. We therefore examined cartilage specimens from 56 patients with primary osteoarthritis (OA) of the knee. Resection and biopsy cartilage specimens obtained during joint replacement surgery were used for this study. In addition to histomorphology, immunohistochemistry (ICH) was performed to determine the expression levels and distribution patterns of stromelysin and u-PA protein. The latter data were compared with the degree of histomorphological changes in osteoarthritic cartilage samples, based on a modified version of Mankin's grading score. Compared to the cartilage resection specimens, the biopsies showed comparable expression patterns for both proteinases: the strongest signals were noted in the superficial zone and, as matrix destruction increased, also in the chondrocytes of the transition and deep zones. The strongest signals were ascertained in cell clusters beneath deep matrix fissures. At the immunohistochemical level, we found a direct correlation in the expression of MMP-3 and u-PA between resection specimens and biopsies. Furthermore, in both types of cartilage samples, we noticed a positive relationship between the expression of both proteins and the Mankin score. Analysis of the expression levels revealed significant differences between deep, transition and superficial zones. Histomorphological and immunohistochemical examinations of MMP-3 and u-PA in biopsies of osteoarthritic cartilage turned out to be useful for estimating the pathological changes within osteoarthritic knee joints. Therefore, in future, cartilage biopsies from osteoarthritic knee joints might serve as a diagnostic tool and thus have an influence on further therapeutic strategies.

Radiographic findings in osteoarthritis of the knee joint are not correlated with cartilage histomorphology or immunohistochemistry.

The purpose of this study was to investigate whether radiographic joint space narrowing (JSN) of the lateral knee compartment predicts the histomorphological or immunhistochemical grading in cases of osteoarthritis of the knee joint. The lateral joint space was measured on weight-bearing radiographs. Femoral osteochondral plugs of 29 patients undergoing total knee replacement were obtained from lateral condyles. All these patients had severe osteoarthritis of the medial compartment, with the lateral compartment showing different stages of osteoarthritis. The specimens were histomorphologically evaluated with the Mankin score, and the expression of the cartilage-degrading enzymes MMP1 and MMP3 was measured. There was no correlation between the joint space and histomorphological or immunohistochemical data, whereas the enzyme expression was correlated with histomorphological grading. We conclude that radiographic assessment alone is not sufficient to evaluate the cartilage damage of the lateral condyle.

Effects of reconstruction of the anterior cruciate ligament on voluntary activation of quadriceps femoris a prospective twitch interpolation study.

The loss of full muscle activation contributes to weakness of the quadriceps muscle in patients with deficiency of the anterior cruciate ligament (ACL). We examined whether a deficit of voluntary activation (VA) of the quadriceps muscle can be reversed by reconstruction of the ACL and assessed its influence on muscle strength and clinical parameters. We evaluated 12 male subjects with an isolated tear of the ACL and 12 matched control subjects before operation and two years after reconstruction of the ACL. Assessment included measurements of isometric knee-extension torque at maximal voluntary contraction (MVC force), knee stability tests, the International Knee Ligament Standard Evaluation Form and the Tegner activity score. A sensitive method of twitch interpolation was used to quantify the VA and to calculate true muscle force. Before operation we found a deficit of VA on both the injured (mean +/- SEM 74.9 +/- 3.5%) and the uninjured side (74.6 +/- 3.0%) in comparison with the control group (91 +/- 0.9%). Two years after reconstruction of the ACL the VA improved significantly on both sides but remained less than that of the controls. Correlation analysis revealed an improvement of the VA in patients who returned to a higher level of activity. The deficit of true muscle force, however, persisted regardless of the clinical outcome and ligament stability.

Detailed analysis of proprioception in normal and ACL-deficient knees.

We assessed proprioception using threshold levels for the perception of knee movement at slow angular velocities (0.1 degrees/s to 0.85 degrees/s) in 20 patients with unilateral tears of the anterior cruciate ligament (ACL) and 15 age-related control subjects. Failure to detect movement was also analysed. The threshold levels of detection did not differ between the damaged and undamaged knees in the patients or between the patients and the control group. Failure to appreciate movement, however, was significantly greater in knees with ACL loss compared with the undamaged knees of patients and the control group. Our findings show a proprioceptive deficit in the absence of the ACL. Measurements of threshold levels of detection of passive movement alone are not suitable for the evaluation of proprioceptive loss in ACL deficiency; assessment of failure to appreciate movement is essential.

A new technique of arthroscopic capsular shift in anterior shoulder instability.

We describe a new arthroscopic technique to reinforce the torn inferior glenohumeral ligament (IGHL) and the elongated capsule to the glenoid rim. The arthroscope is inserted over the superior portal and, after the insertion of a suture anchor, both limbs are pulled out over the posterior portal. The IGHL is grasped and pulled upward onto the glenoid rim using a suture retriever clamp inserted over the posterior portal. A 45 degrees curved blunt clamp (Sidewinder; Arthrex, Naples, FL) coming from the anterior penetrates the IGHL, and 1 end of the suture limb is given into the branches of the clamp and pulled out anteriorly. After a second perforation of the capsule, a horizontal suture creating a neolabrum can be placed. This technique allows a suitable reinforcement of the capsule without intraoperative complications. In cases of capsular elongation, especially a torn IGHL, the capsular instability can be addressed by the described Sidewinder technique. More sophisticated arthroscopic techniques such as this will increase the indication for arthroscopic shoulder stabilization.

Biomechanical investigations of different meniscal repair implants in comparison with horizontal sutures on human meniscus.

PURPOSE: The use of biodegradable implants for arthroscopic repair of meniscal lesions is becoming increasingly popular. The aim of this study was to test the biomechanical stability and the mode of failure of these implants. TYPE OF STUDY: Biomechanical testing study. METHODS: Biomechanical investigations were performed on human menisci using 6 commonly used biodegradable implants for meniscal repair to compare them with horizontal mattress suture using 2/0 Ethibond (Ethicon, Norderstedt, Germany). Included in this study were the Meniscus Arrow (Bionx, Tampere, Finland), Dart (Arthrex, Naples, FL), Stinger (Linvatec, Largo, FL), Meniscal Screw (Innovasive, Marlborough, MA), T-Fix (Acufex, Mansfield, MA), and the Fastener (Mitek, Westwood, MA). The tests were carried out using a material testing machine at a loading rate of 10 N/second. The ultimate tension load (UTL), elongation, and stiffness were evaluated for each implant technique. RESULTS: The highest UTL was shown by Ethibond (62 +/- 7.91 N) and the T-Fix (51.35 +/- 16.31 N), followed by the Fastener (32.67 +/- 2.97 N). All other implants had a significantly lower UTL (P =.001). Less elongation under a load of 5 N was noted for Ethibond (0.64 +/- 0.25 mm) and for T-Fix (0.43 +/- 0.32 mm) compared with the other implants. The greatest elongation was found for the Fastener (2.239 +/- 0.581 mm). The stiffness of the fixation was similar in all implants, except for the Dart and Fastener, which were significantly inferior (P <.05). CONCLUSIONS: All of the biodegradable implants had lower UTL than the suture techniques. Therefore, when using the implants, they should be inserted close together to provide sufficient stability. In cases of an extended lesion, there might even be an option to combine the implant and suturing techniques.

Vertebral collapse and normal peripheral blood cell count at the onset of acute lymphatic leukemia in childhood.

Acute lymphatic leukemia presenting with bone pain and spine involvement is a recognized clinicopathologic complex that can mimic a wide range of orthopaedic conditions. Bone pain as the presenting complaint is common, with a reported incidence of 27% to 50%. Radiologic abnormalities associated with leukemia in children has been described previously. In the literature, the incidence of spinal involvement is controversial, but there is agreement that the spine is less commonly involved than are the long bones. At the onset of the disease, only 10% of children have normal peripheral blood counts. If the patient has spinal involvement and a normal leukocyte count, the diagnosis is often unclear. Only three of these patients have been described in the literature; this article adds one more patient with acute lymphatic leukemia with back pain as the main symptom, vertebral collapse, and a normal peripheral blood cell count at the time of initial presentation. It illustrates that delay in diagnosis frequently occurs, with the classic features of the disease being uniformly absent.

[Intraoperative monitoring of the function of the peroneal nerve in knee joint operations]. / Intraoperatives Monitoring der Funktion des Nervus peroneus bei Kniegelenkoperationen.

Operations on the knee are known to be associated with postoperative neurological complications. There is no consensus opinion on the causes of these complications. The aim of the present study was to develop a method for the intraoperative monitoring of the function of the common peroneal nerve. This was done as to identify intraoperative factors that might be responsible for reversible and irreversible neurological deficits. Computer-aided neuromonitoring is based on online digitizing of the surface EMG of the anterior tibial muscle. An algorithm continuously modifies the amplitude to determine the motor threshold. The method described has been used in 18 patients undergoing high tibial osteotomy. In 10 of the 18 patients, the nerve is rendered completely non-excitable after an average tourniquet application time of 59 min. This non-excitability was reversed on release of the tourniquet. In the remaining 8 patients, excitability was maintained throughout the ischaemic period, which did not exceed 60 minutes in any of the cases. Our method enables accurate quantification of the neural function throughout the entire operation, and convincingly documents the influence of ischaemia on peripheral nerve block.

[Frozen shoulder. Diagnosis and therapy]. / Die eingesteifte Schulter. Diagnose und Therapie.

The condition of shoulder stiffness is often called adhesive capsulitis or frozen shoulder. It is regarded as a distinct clinical entity showing a benign and regular course. The major clinical feature is significant reduction in both active and passive range of motion (ROM) accompanied by stage-dependent pain, allowing for a clinical diagnosis. There are primary and secondary forms, the former having an unknown etiology and increased occurrence in patients with metabolic disorders and the latter being seen with prior injury or operation. Three stages, each lasting 4-6 months, mark the clinical course. The progression of the disease is self-limiting and may occasionally resolve in partial restitution. In the first stage ("freezing"), the shoulder continuously loses passive motion and causes worsening pain. Continuing stiffness and improvements in pain and inflammation are characteristic of the second stage ("frozen"). In the third stage ("thawing"), restriction of shoulder motion decreases, and ROM increases. Treatment should be adjusted to these stages. Recommendations include analgesics and joint injections in the first stage and physiotherapy in combination with manual therapy in the second and third stages. In cases of failure, passive exercise under interscalene block, manipulation under general anesthesia, or arthroscopic arthrolysis should be considered.

Rationales of arthroscopic shoulder stabilization.

Arthroscopic reconstruction of glenohumeral instability has become more common during the past decade. Compared with open reconstruction, which is still the gold standard in the treatment of shoulder instability, arthroscopic techniques allow for improved diagnosis of numerous intraarticular findings. This review presents an appropriate system for the arthroscopic classification of most pathological findings in patients with anterior shoulder instability. Based on the presented classification, a rationale for arthroscopic reconstruction under special conditions is given. Several operative techniques and implants are discussed and their use in certain circumstances analyzed. Special emphasis is targeted on techniques of realizing sufficient capsular shift or plication. Arthroscopic procedures remain technically demanding and require skills to address the great variety of possible situations. On the other hand, arthroscopic techniques in shoulder reconstruction benefit patients by avoiding the morbidity of open surgery. However, the surgeon must be prepared to address numerous conditions beyond a mere Bankart lesion, especially those involving capsular laxity, rotator interval lesions, and SLAP (superior labrum lesions from anterior to posterior) lesions. Nowadays, considering all the new technical possibilities of arthroscopic shoulder reconstruction including capsular shift procedures, most cases of anterior shoulder instability are suitable for arthroscopic reconstruction. Further studies are necessary to validate the continued efficacy of arthroscopic stabilization.

[Anterior cruciate ligament reconstruction - graft options and fixation techniques]. / Die vordere Kreuzbandplastik - Transplantatwahl und Verankerungstechniken.

With the introduction of arthroscopy most of the surgeon have changed their technique in ACL-reconstruction from open to arthroscopically performed techniques. Several new techniques have been developed in the past, including new fixation devices and different grafts. The cruciate ligament reconstruction comprises a composition of both, the graft and the fixation to the bone. Well accepted autografts are the patellar midthird, the semitendinosus/gracilis or the quadriceps tendon. In special cases allografts are alternatives. The fixation can cause failure due to overstrain or creep during the postoperative period of healing. Considering their biomechanical properties, cruciate ligament reconstruction should aim for a graft behavior comparable with the native cruciate ligament. Results gained from basic science and clinical studies are reviewed in the following article.

[Intraoperative computer-assisted measurement of stimulation threshold of the common peroneal nerve in osteotomy of the head of the tibia]. / Intraoperative computergestützte Reizschwellenmessung (Neuromonitoring) des N. peroneus communis bei Tibiakopfosteotomien.

Using a computer-assisted threshold hunting paradigm the motoric threshold of the common peroneal nerve was monitored in 18 patients during a high tibial osteotomy (HTO). The exposed nerve (lateral approach) was stimulated proximal to the osteotomy area and the surface EMG of the M. tibialis anterior was used to guide a threshold hunting device. Motoric threshold as a sensitive indicator of nerve function was found to be almost unaffected by several surgical steps of HTO. Only forceful rotation of a subperiostal Hohmann device during high peroneal osteotomy evoked a slight threshold shift that was fully reversible with device repositioning. The tourniquet, however, affected the threshold significantly. In 10 of the 18 patients the nerve became completely inexcitable after an average time of 59 min. The inexcitability was reversible after opening of the tourniquet. On the other hand, the eight patients maintaining an excitability throughout the entire ischemic period had tourniquet times that did not exceed 60 min. There are several factors that may be responsible for the observed inexcitability after long ischemic periods and we conclude that tourniquet time minimization appears appropriate to avoid neurological deficits during a high tibial osteotomy.