Accessibility of osteochondral lesion at the capitellum during elbow arthroscopy: an anatomical study.

INTRODUCTION: Osteochondrosis dissecans (OCD) at the capitellum is a common pathology in young patients. Although arthroscopic interventions are commonly used, there is a lack of information about the accessibility of the defects during elbow arthroscopy by using standard portals. MATERIALS AND METHODS: An elbow arthroscopy using the standard portals was performed in seven fresh frozen specimens. At the capitellum, the most posterior and anterior cartilage surface reachable was marked with K-wires. Using a newly described measuring method, we constructed a circular sector around the rotational center of the capitellum. The intersection of K-wire "A" and "B" with the circular sector was marked, and the angles between the K-wires and the Rogers line, alpha angle for K-Wire "A" and beta angle for K-wire "B", and the corridor not accessible during arthroscopy was digitally measured. RESULTS: On average, we found an alpha angle of 53° and a beta angle of 104°. Leaving a sector of 51° which was not accessible via the standard portals during elbow arthroscopy. CONCLUSION: Non-accessible capitellar lesions during elbow arthroscopy should be considered preoperatively, and the informed consent discussion should always include the possibility of open procedures or the use of flexible instruments.

Anatomic evaluation of the triceps tendon insertion at the proximal olecranon regarding placement of fracture fixation devices.

PURPOSE: Olecranon fractures, especially with a small proximal fragment, remain a surgical challenge. Soft tissue irritation and affection of the triceps muscle bear a risk of complications. In order to find an area for a soft-tissue sparing placement of implants in the treatment of olecranon fractures, we aimed to define and measure the segments of the proximal olecranon and evaluate them regarding possible plate placement. METHODS: We investigated 82 elbow joints. Ethical approval was obtained from the local ethics committee, After positioning in an arm holder and a posterior approach we described the morphology of the triceps footprint, evaluated and measured the surface area of the triceps and posterior capsule and correlated the results to easily measurable anatomical landmarks. RESULTS: We found a bipartite insertional footprint with a superficial tendinous triceps insertion of 218.2 mm2 (± 41.2, range 124.7-343.2), a capsular insertion of 159.3 mm2 (± 30.2, range 99.0-232.1) and a deep, muscular triceps insertion area of 138.1 mm2 (± 30.2, range 79.9-227.5). Olecranon height was 26.7 mm (± 2.3, range 20.5-32.2), and olecranon width was 25.3 mm (± 2.4, range 20.9-30.4). Average correlation between the size of the deep insertion and ulnar (r = 0.314) and radial length (r = 0.298) was obtained. CONCLUSIONS: We demonstrated the bipartite morphology of the distal triceps footprint and that the deep muscular triceps insertion area by its measured size could be a possible site for the placement of fracture fixations devices. The size correlates with ulnar and radial length.

Overlengthening of the radial column in radial head replacement: a review of the literature and presentation of a classification system.

BACKGROUND: Radial head arthroplasty is a common procedure in elbow surgery. It has been shown to be of benefit for the patients, but there also are relevant complications that should be prevented if possible. One significant complication is overlengthening of the radial head prosthesis. In overlengthening, the head of the prosthesis overextends the physiological level of the native radial head and leads to overcompression in the radiohumeral joint. Rapid erosion and arthritic changes may then impede the clinical outcome. The incidence of overlengthening is not precisely known, but estimations range to up to 20% of all implanted prostheses. METHODS: The present review discusses the available body of literature on overlengthening and lines out a classification system that may be used to guide treatment algorithms. The classification is based on the personal experiences of the author during their clinical practice. RESULTS: In low-grade overlengthening (type I) conservative treatment can be an option. In Types II-IV usually revision surgery is needed. Depending on the state of the capitulum and joint stability, it is possible re-implant a prosthesis, or rely on implant removal alone. DISCUSSION: The present review aimed at shedding light into overlengthening as a complication radial head replacement and to help identify and treat it.

Inducing pilon fractures in human cadaveric specimens depending on the injury mechanism: a fracture simulation.

BACKGROUND: Operative management of pilon fractures, especially high-energy compression injuries, is a challenge. Operative education is of vital importance to handle these entities. Not rarely, it is cut by economics and staff shortage. As public awareness toward operative competence rises, surgical cadaver courses that provide pre-fractured specimens can improve realism of teaching scenarios. The aim of this study is to introduce a realistic pilon fracture simulation setup regarding the injury mechanism. MATERIALS AND METHODS: 8 cadaveric specimens (two left, six right) were fixed onto a custom drop-test bench in dorsiflexion (20°) and light supination (10°). The proximal part of the lower leg was potted, and the specimen was exposed to a high energetic impulse via an axial impactor. CT imaging was performed after fracture simulation to detect the exact fracture patterns and to classify the achieved fractures by two independent trauma surgeons. (AO/OTA recommendations and the Rüedi/Allgöwer). RESULTS: All cadaveric specimens could be successfully fractured: 6 (75%) were identified as a 43-C fracture and 2 (25%) as 43-B fracture type. Regardless of the identical mechanism two different kinds of fracture types were reported. In five cases (62.5%), the fibula was also fractured and in three specimens, a talus fracture was described. There was no statistically significant correlation found regarding Hounsfield Units (HU) and age as well as HU and required kinetic energy. CONCLUSION: A high energetic axial impulse on a fixed ankle specimen in light dorsiflexion (20°) and supination (10°) induced by a custom-made drop-test bench can successfully simulate realistic pilon fractures in cadaveric specimens with intact soft tissue envelope. Although six out of eight fractures (75%) were classified as a 43-C fracture and despite putting a lot of effort into the mechanical setup, we could not achieve an absolute level of precision. Therefore, we suggest that the injury mechanism is most likely a combination of axial loading, shear and rotation. LEVEL OF EVIDENCE: III.

[Radial head fractures : Epidemiology, diagnosis, treatment and outcome]. / Radiuskopffrakturen : Epidemiologie, Diagnose, Behandlung und Outcome.

Radial head fractures account for the majority of bony injuries to the elbow. The usual clinical signs include hemarthrosis, pain and limitations in movement. The standard diagnostic tool is radiological imaging using X­rays and for more complex fractures, computed tomography (CT). Concomitant ligamentous injuries occur more frequently than expected and must be reliably excluded. The classification is based on the modified Mason classification. Mason type I fractures are usually treated conservatively with immobilization and early functional aftercare. Mason type II fractures can be well-addressed by screw osteosynthesis but higher grade fractures (Mason types III-IV) can necessitate a prosthetic radial head replacement. In this case, prosthesis implantation is to be preferred to a radial head resection. The outcome after treatment of radial head fractures can be described as good to very good if all accompanying injuries are adequately addressed.

[Lower leg, ankle and foot]. / Distaler Unterschenkel, Sprunggelenk und Fuß.

CLINICAL/METHODICAL ISSUE: Bipedal locomotion means high mechanical stress on the lower extremities and susceptibility to fractures. On the one hand, these can be the result of a one-time traumatic stress in the context of high speed traumas or falls, but can also result from repetitive microtraumas with subsequent stress fractures. STANDARD RADIOLOGICAL METHODS: For all fracture entities and localizations, X­ray diagnostics is the basic modality. METHODICAL INNOVATIONS: For optimal surgical reconstruction of intra-articular fractures or in complex fracture configurations, computed tomography should be generously used to improve postoperative outcome. PERFORMANCE: The classification of the individual fractures should enable standardised further therapy planning, especially with regard to conventional or surgical treatment. ACHIEVEMENTS: The combination of X­ray, magnetic resonance imaging and computed tomography makes a reliable diagnosis regarding foot fractures possible. PRACTICAL RECOMMENDATIONS: Important for the use of individual classification systems is always, in addition to clinical relevance, the safe and equal understanding of the individual types and degrees by the radiologist and the referring colleague.

Laparoscopic pectopexy: a follow-up cyclic biomechanical analysis determining time to functional stability.

INTRODUCTION: Pectopexy, a laparoscopic method for prolapse surgery, showed promising results in previous transient testing by this group. It was shown that a single suture, yielding an ultimate load of 35 N, was equivalent to continuous suturing. This was demonstrated in an in vitro cadaver study. This transient data were used to establish an elastic stress-strain envelope. It was now possible to proceed to dynamic in vitro analysis of this surgical method to establish time to functional stability. METHODS: Cyclic testing of this fixation method was performed on human female embalmed cadaver (cohort 1) and fresh, non-embalmed cadaver (cohort 2) pelvises. The testing envelope was 5-25 N at a speed of 1 mm/s. 100 load regulated cycles were applied. RESULTS: 100 cycles were completed with each model; no overall system failure occurred. Steady state, i.e., functional stability was reached after 14.5 (± 2.9) cycles for the embalmed group and after 19.1 (± 7.2) cycles for the non-embalmed group. This difference was statistically significant p = 0.00025. CONCLUSION: This trial showed in an in vitro cyclic testing of the pectopexy method that functional stability may be achieved after no more than 19.1 cycles of load exposure. When remaining within the established load envelope of below 25 N, patients do not need to fear global fixation failure. Testing did demonstrate differences in non-embalmed and embalmed cadaver testing. Embalmed cadaver testing tends to underestimate time to steady state by 26.3%.

Peroneal nerve location at the fibular head: an anatomic study using 3D imaging.

INTRODUCTION: Injuries to the peroneal nerve are a common complication in operative treatment of proximal tibial or fibular fractures. To minimize the risk of iatrogenic injury to the nerve, detailed knowledge of the anatomy of the peroneal nerve is essential. Aim of this study was to present a detailed description of the position and branching of the peroneal nerve based on 3D-images to assist preparation for surgical approaches to the fibular head and the tibial plateau. METHODS: The common peroneal nerve, the deep and the superficial peroneal nerve were marked with a radiopaque thread in 18 formalin-embalmed specimens. Three-dimensional X-ray scans were then acquired from the knee and the proximal lower leg in full extension of the knee. In 3D-reconstructions of these scans, distances of the common peroneal nerve and its branches to clearly defined osseous landmarks were measured digitally. Furthermore, the height of the branching of the common peroneal nerve was measured in relation to the landmarks. RESULTS: The mean distance of the common peroneal nerve at the level of the tibial plateau to its posterior osseous limitation was 7.92 ± 2.42 mm, and 1.31 ± 2.63 mm to the lateral osseous limitation of the tibia. In a transversal plane, distance of the common peroneal nerve branching was 27.56 ± 3.98 mm relative to the level of the most proximal osseous extension of fibula and 11.77 ± 6.1 mm relative to the proximal extension of the tibial tuberosity. The deep peroneal nerve crossed the midline of the fibular shaft at a distance of 22.14 mm ± 4.35 distally to the most proximal extension of the fibula, the superficial peroneal nerve at a distance of 33.56 mm ± 6.68. CONCLUSION: As the course of the peroneal nerve is highly variable in between individuals, surgical dissection for operative treatment of proximal posterolateral tibial or fibular fractures has to be done carefully. We defined an area were the peroneal nerve and its branches are unlikely to be found. However, specific safe zones should not be utilized due to the individual anatomic variation.

[Elbow prostheses in rheumatic diseases]. / Ellenbogenprothese bei rheumatischen Erkrankungen.

When the elbow is destroyed due to rheumatic diseases, the joint can be replaced by a prosthesis and total arthroplasty. Improved pharmaceutical treatment for rheumatic diseases has, however, reduced the number of implantations in these patients. Reported 10-year survival rates of the implant currently achieve 81-90%.; however, due to limited long-term survival of the implant and high complication rates, total elbow arthroplasty should still be used with caution. Continuous technical improvements in the available prostheses and in surgical techniques could lead in the future to a decline in complications, such as aseptic loosening and infections.

[Olecranon fractures]. / Olekranonfrakturen.

Olecranon fractures represent a common elbow injury and they are usually treated operatively. Depending on fracture morphology conservative therapy can be considered in geriatric patients. When surgical treatment is performed the anatomical features of the proximal ulna have to be taken into consideration. Tension band wiring is considered a standard procedure for simple fractures and provides good clinical results. Plate osteosynthesis is indicated for more complex fracture patterns. Nowadays, many surgeons prefer plate fixation over tension band wiring even for simple fractures as it leads to a more stable fixation. Both methods frequently require hardware removal for persisting soft tissue irritation. The use of modern low-profile plates could reduce the need for implant removal due to better soft tissue coverage. The available clinical data regarding low-profile plates are promising but limited.

[Total elbow arthroplasty in traumatic and post-traumatic bone defects]. / Ellenbogentotalendoprothetik bei traumatischen und posttraumatischen Knochendefekten.

Total elbow arthroplasty is currently most commonly carried out due to acute trauma or post-traumatic conditions. Bone defects are often present and must be considered in the (pre-)operative workup. The use of semi-constrained prostheses with a systematic cementing technique through a triceps-on approach leads to satisfying clinical results, however, the outcome is worse when compared with rheumatic patients.Primary total elbow arthroplasty for complex distal humerus fractures in the elderly patient or secondary implantation following failed conservative treatment or osteosynthesis represent possible indications for (post­)traumatic joint replacement. The condyles do not have to be reconstructed and the humerus can be shortened by 2-3 cm without sacrificing the functionality of the extensor apparatus. In the case of post-traumatic joint destruction and pronounced chronic instability following complex fractures of the proximal forearm - especially following terrible triad or Monteggia-like injuries - total elbow arthroplasty can be considered as a treatment option. The extensor apparatus must be reconstructed, and the implantation of the prosthesis must thus be combined with plate osteosynthesis of the ulna - if necessary. Chronic deformity should only be corrected as much as needed in order to avoid early aseptic loosening due to increased shearing forces and polyethylene wear.Massive bone loss is problematic and can be compensated with allografts or tumor prostheses. The results of these salvage procedures are less predictable, and complication rates increase significantly.

Functional anatomy of the lateral collateral ligament of the elbow.

INTRODUCTION: The aim of this study was to analyze the functional anatomy of the lateral collateral ligament complex (LCLC) and the surrounding forearm extensors. MATERIALS AND METHODS: Using 81 human cadaveric upper extremities, the anatomy of the forearm extensors-especially the anconeus, supinator and extensor carpi ulnaris (ECU)-was analyzed. After removal of aforementioned extensors the functional anatomy of the LCLC was analyzed. The origin of the LCLC was evaluated for isometry. The insertion types of the lateral ulnar collateral ligament (LUCL) were analyzed and classified. RESULTS: The ECU runs parallel to the RCL to dynamically preserve varus stability. The supinator and anconeus muscle fibers coalesce with the LCLC and lengthen during pronation. The anconeus fibers run parallel to the LUCL in full flexion. The LCLC consists of the annular ligament (AL) and the isometric radial collateral ligament (RCL). During elbow flexion, its posterior branches (LUCL) tighten while the anterior branches loosen. When performing a pivot shift test, the loosened LUCL fibers do not fully tighten in full extension. The LUCL inserts along with the AL at the supinator crest. Three different insertion types could be observed. CONCLUSIONS: The LUCL represents the posterior branch of the RCL rather than a distinct ligament. It is non-isometric and lengthens during elbow flexion. The RCL was found to be of vital importance for neutralization of posterolateral rotatory forces. Pronation of the forearm actively stabilizes the elbow joint as the supinator, anconeus and biceps muscle work in unison to increase posterolateral rotatory stability.

[Chronic ligamentous instability of the elbow]. / Chronische Bandinstabilitäten des Ellenbogengelenks.

BACKGROUND: Chronic ligamentous instability of the elbow is an important pathology as it is accompanied with pronounced dysfunction. Moreover, it represents an established risk factor for the development of osteoarthritis. Posterolateral rotatory instability (PLRI) caused by insufficiency of the lateral collateral ligament (LCL) is the most common type of chronic elbow instability and is usually a sequel of traumatic elbow dislocation. Chronic overload can lead to insufficiency of the ulnar collateral ligament (UCL) with subsequent valgus instability, especially in overhead athletes. DIAGNOSTICS: Subjective instability and recurrent elbow dislocations are not always the main symptoms but elbow instability is instead often characterized by pain and secondary joint stiffness. Many clinical tests are available yet eliciting them can be difficult and inconclusive. A "drop sign" on lateral radiographs as well as the detection of collateral ligament injuries and joint incongruity on MRI scans can support the suspected diagnosis. In some cases, instability can only be verified by diagnostic arthroscopy. TREATMENT: Reconstruction of the lateral ulnar collateral ligament (LUCL) for treatment of PLRI generally leads to good clinical results, yet recurrent instability remains an issue and has been reported in 8 % of cases. UCL reconstruction for chronic valgus instability leads to a return-to-sports rate of about 86 % in the overhead athlete. Ulnar neuropathy, which is seen in approximately 6 % of patients, represents the most common complication. On the rare occasion of multidirectional instability, the box-loop technique can be used for simultaneous reconstruction of the LUCL and UCL with a circumferential graft. 15 cases with promising results have been reported in literature thus far.

[Lateral ulnar collateral ligament reconstruction : A biomechanical analysis of posterolateral rotatory instability of the elbow]. / Laterale ulnare Kollateralbandplastik : Biomechanische Untersuchung zur posterolateralen Rotationsinstabilität des Ellenbogens.

BACKGROUND: Chronic posterolateral rotatory instability (PLRI) of the elbow is the result of an insufficiency of the lateral collateral ligament (LCL). Lateral ulnar collateral ligament (LUCL) reconstruction represents a well-established treatment method for PLRI. However, recurrent instability remains a problem. OBJECTIVES: The goal of this in-vitro study was to evaluate the posterolateral rotatory stability of the intact elbow, after sectioning of the LCL and after LUCL reconstruction with a triceps tendon autograft and double BicepsButton(TM) fixation. MATERIALS AND METHODS: Posterolateral rotatory stability of 6 fresh-frozen elbow specimens at a torque of 3 Nm was analyzed at 0, 45, 90 and 120° of flexion for the intact LCL, after sectioning of the LCL and after LUCL reconstruction. Moreover, cyclic loading (1000 cycles) of the intact specimens and after LUCL reconstruction was performed. RESULTS: The intact LCL and the LUCL reconstruction provided equal primary stability (0.250 ≤ p ≤ 0.888). Sectioning of the LCL significantly increased PLRI (p < 0.001). The stability of the intact specimens and after LUCL reconstruction did not differ after cyclic loading (p = 0.218). During cyclic loading, posterolateral rotation increased significantly more after LUCL reconstruction (3.2 ± 0.8°) when compared to the native LCL (2.0 ± 0.7°, p = 0.020). CONCLUSIONS: LUCL reconstruction with BicepsButton(TM) fixation provides comparable stability to the native LCL. Further clinical results are necessary to evaluate whether this technique can decrease the complication rate.

[The bare area of the proximal ulna : An anatomical study on optimizing olecranon osteotomy]. / Die Bare Area der proximalen Ulna : Eine anatomische Studie zur Optimierung der Olekranonosteotomie.

BACKGROUND: Olecranon osteotomy is an established approach for the treatment of distal humerus fractures. It should be performed through the bare area of the proximal ulna to avoid iatrogenic cartilage lesions. OBJECTIVES: The goal of this study was to analyze the anatomy of the proximal ulna with regard to the bare area and, thereby, to optimize the hitting area of the bare area when performing olecranon osteotomy. MATERIALS AND METHODS: The bare areas of 30 embalmed forearm specimens were marked with a radiopaque wire and visualized three-dimensionally with a mobile C­arm. By means of 3D reconstructions of the data sets, the following measurements were obtained: height of the bare area; span of the bare area-hitting area in transverse osteotomy; ideal angle for olecranon osteotomy to maximize the hitting area of the bare area; distance of the posterior olecranon tip to the entry point of the transverse osteotomy and the ideal osteotomy. RESULTS: The height of the bare area was 4.92 ± 0.81 mm. The hitting area of the transverse osteotomy averaged 3.73 ± 0.89 mm. The "ideal" angle for olecranon osteotomy was 30.7° ± 4.19°. The distance of the posterior olecranon tip to the entry point was 14.08 ± 2.75 mm for the transverse osteotomy and 24.21 ± 3.15 mm for the ideal osteotomy. The hitting area of the bare area in the ideal osteotomy was enhanced significantly when compared to the transverse osteotomy (p < 0.0001). CONCLUSIONS: This study provides guide values for correct osteotomy of the olecranon. Moreover, a 30° angulation of the osteotomy can significantly increase the hitting area of the bare area.

Identification of overlengthening after replacement of the radial head with a bipolar prosthesis.

INTRODUCTION: Overlengthening of the radial column leads to insufficient functionality and increased capitellar wear. Methods to detect or prevent overlengthening have been described for monopolar prostheses. The aim of this study was to evaluate whether one such method described by Athwal et al. is also applicable for a bipolar prosthesis. MATERIALS AND METHODS: The radial heads of six fresh frozen upper extremities were resected. A bipolar radial head prosthesis was implanted in each, and the effects of sequential overlengthening on the alignment of the radiocapitellar and ulnohumeral joint line were recorded by fluoroscopic images. Digital image analysis and estimation of overlengthening followed according to the method described by Athwal et al. RESULTS: Statistical analysis of the estimated and actual differences between the native state and bipolar replacement of the radial head with stepwise overlengthening of 1.5, 3, 4.5, and 6 mm showed a specificity of 86 % but consistently underestimated the amount of overlengthening with a sensitivity of only 61 %. DISCUSSION: The method described by Athwal et al. for the identification of overlengthening by a monopolar prosthesis was not found to be reliable for ruling out or quantifying overlengthening of the tested bipolar prosthesis. However, the use of the method to detect (rule in) overlengthening may be acceptable in certain circumstances. A reliable method for postoperative quantification of overlengthening by bipolar prostheses has still to be found.

[Locking plate osteosynthesis of the radial head fractures : clinical and radiological results]. / Winkelstabile Plattenosteosynthese des Radiuskopfes : Klinische und radiologische Ergebnisse.

BACKGROUND: Therapy of radial head fractures is still controversially discussed. Especially comminuted fractures are at risk of complications such as radial head necrosis, nonunion and secondary loss of reduction after open reduction and internal fixation. The aim of this study was to evaluate clinical and radiographic results of ORIF (open reduction internal fixation) of radial head fractures using a new radial head-specific locking plate system. PATIENTS AND METHODS: A total of 21 patients (13 men and 8 women) were treated with locking plate osteosynthesis of radial head fractures. Mean age was 50 years (range 29-67 years). According to the Mason classification, 15 were type III and 6 type IV. Mean time between trauma and surgery was 5.6 days (range 0-23 days). These patients were reexamined using the Mayo Elbow Performance Score and x-rays in two planes. RESULTS: In all, 21 patients were reexamined with a mean follow-up of 12.1 months (range 5-23 months). The mean Mayo Elbow Performance Score was 87.1. Excellent results were obtained in 12 patients, good results in 6 patients, and fair results in 3 patients. Mean extension deficit was 12.1°, mean flexion 135.2°, mean pronation 70.9°, and mean supination 63.6°. All fractures healed uneventfully. There was no complete radial head necrosis but one partial. Four cases of heterotopic ossification were detected: Hastings classification I (n = 2), IIb (n = 1), IIIb (n = 1). CONCLUSION: ORIF of radial head fractures using locking plates can lead to good and excellent results. Modern implants may allow for reconstruction of comminuted fractures avoiding arthroplasty in these young patients.

[Mason I fracture - a simple injury?]. / Mason-I-Fraktur - eine harmlose Verletzung?

BACKGROUND: Mason I fractures of the radial head are judged to be simple injuries that can generally be treated nonoperatively. According to the current literature mainly good and excellent results can be expected. We present a case series of patients presenting to us due to complications of Mason I fractures. PATIENTS AND METHODS: We reviewed all cases of patients that were treated because of complaints following Mason I radial head fractures. In all, 16 patients (10 men and 6 women) were identified. Mean age was 37 years (range 16-59 years). Mean time between trauma and surgery was 25 months (range 1-108 months). RESULTS: Ten patients developed painful osteoarthritis with elbow stiffness and loose bodies, 4 patients suffered a posterolateral rotatory instability that had to be treated with ligament reconstruction, 1 patient presented with a combined medial and lateral instability, and 1 patient with a symptomatic hypertophic plica posterolateralis. Diagnotics and therapeutic concepts of these complications will be presented. CONCLUSION: In light of the complications, Mason I fractures must be reevaluated. They remain the domain of conservative treatment but close follow-up is recommended to recognize possible complications early in order to prevent stiffness, chronic instabilities, and osteoarthritis.

Tibia segment deformation in response to simulated muscle forces: a cadaveric study with a novel optical segment tracking (OST) approach.

OBJECTIVES: A novel optical segment tracking (OST) approach reliant upon motion capturing was previously proposed to assess human tibia segment deformation. The purposes of the present study were to validate the OST approach and assess the contribution of muscular forces to the bone deformation in a well-defined ex vivo human model. METHODS: A custom-made Lower Extremity Loading Device (LELD) was developed to simulate physiological muscle contractions in six human cadaveric lower extremities. Tibia segment deformation was measured by tracking the relative movement between two marker clusters which were affixed into the proximal and distal tibia, respectively. RESULTS: Compared to the physiological norms, the simulated muscle forces remained at a low level. When quadriceps muscle was loaded with forces from 198 N to 505 N, posterior bending (0.12°-0.25°) and lateral bending (0.06°-0.21°) of the tibia segment were found. Large tibia bending angles were found when simulating the co-contraction of upper leg muscles and plantar flexors, and of all leg muscles, respectively. The standard deviations of the deformation angles between the repetitions remained at a low level. CONCLUSIONS: We conclude that the OST approach has the potential to be applied in vivo and quantify muscle-induced bone deformations.

Correlation of reduction and clinical outcome in patients with degenerative spondylolisthesis.

STUDY DESIGN: Prospective cohort study. INTRODUCTION: Operative treatment is increasingly implemented for the treatment of degenerative lumbar listhesis, with lumbar fusion the most common intervention. Prediction of clinical outcomes after such procedures is of ongoing relevance, and the correlation of radiologic parameters with clinical outcome remains controversial. In particular, clinical studies have not determined conclusively whether reduction of slipped vertebrae is beneficial. METHODS: We performed a monocenter prospective analysis of a comprehensive set of quality of life scores (QLS) (Core Outcome Measure Index, Oswestry Low Back Pain Disability Index, SF-36) of 40 patients, who underwent a standardized PLIF procedure for symptomatic, Spondylolisthesis. Follow-up was 24 months. The correlations between the radiologic parameters (degree of slippage, sagittal rotation) and the clinical scores before surgery as well as 12 and 24 months post-operatively were examined. RESULTS: All QLS showed a statistically significant improvement after 12 and 24 months post-operatively (p < 0.05). The mean amount of the anterior slippage was 34.2 ± 14.7 % (minimum 12 %, maximum 78 %). After 12 months, there was an average 19.1 % decrease to 15.1 ± 8.3 % (minimum 2 %, maximum 38 %, p < 0.000) and after 24 months it was decreased by 18.0-16.2 ± 9.0 % (minimum 2.9 %, maximum 40 %, p < 0.000). Average sagittal rotation measured 67.3° ± 16.6° initially (minimum 35°, maximum 118) and decreased by 4.3° to an average of 63.0° ± 15.2° at 12 months post-surgery (minimum 15°, maximum 101°, p = 0.065,), and by 5.7° to an average of 61.6° ± 13.0° at 24 months (minimum 15°, maximum 90°, p = 0.044). The data show positive correlations between the amount of reduction of the slipped vertebra as well as the amount of correction of the sagittal rotation and the improvement of the clinical outcomes(r = 0.31-0.54, p < 0.05). CONCLUSION: The current study indicates a modest advantage for the best possible reposition in respect of the clinical outcome.