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.

[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.

Histological findings of tendon-bone healing following anterior cruciate ligament reconstruction with hamstring grafts.

BACKGROUND: The purpose of the study was the histological examination of tendon-bone healing of hamstring grafts after anterior cruciate ligament (ACL) reconstruction. METHODS: During five arthroscopies done 6-14 months after ACL reconstructions, biopsies of the wall of the former drilled femoral canal were obtained. Four patients were primarily operated on using a suspending device (Endobutton, Acufex Microsurgical, Mansfield, MA, USA, and Transfix, Arthrex, Naples, FL, USA) for femoral fixation, one patient was reconstructed with a biodegradable interference screw directly inserted between the tendon and the wall of the canal. Biopsies were obtained using a tube harvester during re-arthroscopy. Three grafts were stable, two grafts were unstable, and revision of the ACL was performed. RESULTS: Histologically, in the four cases of reconstruction with a button or a rectangular pin, biopsies resembled granulation tissue without insertion of fibers between the tendon tissue and the bony wall. A wide area of woven bone was noted adjacent to the pre-existing lamellar bone. In contrast, the tendon-bone junction in the knee reconstructed with a biodegradable interference screw resembled a zone of metaplastic fibrous cartilage between the tendon graft and the lamellar bone. Collagen fibers connecting the tendon-bone interface occurred under polarized light microscopy. CONCLUSION: We conclude that the use of hamstring grafts for ACL reconstruction can lead to different histological pattern of tendon-bone healing. Micromotion of the hamstring graft inside the drilled canal can be play a role in tendon-bone healing.

[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.

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.

Biomechanical properties of quadruple tendon and patellar tendon femoral fixation techniques.

Two femoral fixation techniques for quadruple hamstring tendon grafts were compared under cyclic loading with the patellar tendon: the rectangular inserted pin (TransFix) and biodegradable interference screw fixation of the quadruple tendon and titanium interference screw fixation of the middle third of the patellar tendon. Porcine specimens were mounted onto a tension load machine, and the tendon-fixation-femur-complex was tested for stiffness, displacement during 800 cycles of loading between 50 and 250 N and ultimate tension load. TransFix fixation showed the greatest stiffness at 183.6 N/mm ( P<0.05). The least displacement under cyclic loading was observed for the titanium interference screw followed by the TransFix and biodegradable interference screw ( P<0.01). The ultimate tension load was greatest for the TransFix fixation at 1303+/-282 N, followed by patellar tendon fixation with 763+/-103 N and the biodegradable interference screw fixation with 480+/-133 N ( P<0.001). To reduce initial elongation of the graft and displacement at the fixation site, preconditioning of both the tendon and tendon-fixation complex is especially important when using quadruple tendons. TransFix fixation provides better stability and greater stiffness and pull-out strength than the other techniques. This finding is of clinical relevance to surgeons of the anterior cruciate ligament.

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.

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.

[Semitendinosus tendon vs. patellar ligament. Results of a prospective randomized study after anterior cruciate ligament reconstruction]. / Semitendinosussehne vs. Ligamentum patellae. Klinische Ergebnisse einer prospektiven randomisierten Studie nach vorderer Kreuzbandplastik.

UNLABELLED: The aim of our prospective randomised study was to evaluate the clinical results after arthroscopical reconstruction of the ACL using the midthird patellar ligament or semitendinosus tendon. METHODS: Forty patients were followed up two years postoperatively. Twenty of them received either a patellar ligament graft (BTB-group) or doubled semiteninosus tendon (SET-group). The clinical evaluation included the preoperative and two years postoperative assessment, based on the IKDC-Score, Tegener-Score and Mc-Carroll-Score. The a.p.-translation was evaluated using the KT-1000. RESULTS: Sixteen (80%) patients of the SET-group and 10 (50%) patients of the BTB-group showed good and excellent results in the over all assessment with the IKDC-Score. The mean side to side KT-1000 difference yielded 1.6 mm (-2-4 mm) in the BTB-group and 2.7 mm (0-7 mm) in the SET-group (p < 0.05). The retropatellar pain syndrome based on the Mc-Caroll-Score showed 17.4 points in the BTB-group in comparison to 19.5 points in the SET-group (p < 0.05). The level of activity using the Tegner-score showed preoperatively for both the SET- and BTB-group 6.9 points and postoperatively for the SET-group 6.7 points and for the BTB-group 5.6 points. CONCLUSIONS: Despite the inferior a.p.-stability for the patients who received doubled semitendinosus tendon grafts they presented clinically superior results compared to the BTB-group. Therefore this technique seems to be the alternative method. In order to improve the stability we recommend the usage of three or four stranded grafts and an improved fixation technique.

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.

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.

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.

Rotationplasty as a salvage procedure in revision of tumor endoprosthesis of the distal femur--a report of two cases.

We performed two rotationplasties (type A1 and A2) as salvage procedures in cases of custom-made endoprosthetic replacements of the distal femur and knee joint. The patients suffered from malignant bone and soft-tissue tumors of the knee, respectively. One of them developed chronic osteomyelitis around both stems of the prosthesis, and three local revisions turned out to be ineffective. The other patient, suffering from parossal osteosarcoma of the distal femur, developed a local recurrence following endoprosthetic reconstruction. The functional abilities following the operation of these two patients suggested that rotationplasty was a viable alternative to above-the-knee amputation in failed or severely complicated total arthroplasty of the knee with massive bone loss.