Thomas Mückley

Arthroscopic Treatment of Osteochondral Lesions of the Ankle With Matrix-Associated Chondrocyte Implantation: Early Clinical and Magnetic Resonance Imaging Results

Background: Conventional autologous chondrocyte transplantation in the ankle often requires tibial or fibular osteotomies with potential morbidity for the patient. Advances in biotechnology and surgical techniques have resulted in the development of matrix-associated chondrocyte implantation (MACI). As the chondrocyte-loaded scaffold can be applied arthroscopically, this procedure is especially useful for the treatment of osteochondral defects in the ankle. Hypothesis: Arthroscopic MACI is a safe procedure in the ankle with good clinical and magnetic resonance imaging results. Study Design: Case series; Level of evidence, 4. Methods: The authors reviewed all patients (n = 18) who had arthroscopic MACI for osteochondral lesions of the ankle (n = 19) between February 2006 and May 2008 clinically and with magnetic resonance imaging. The pain and disability module of the Foot Function Index (FFI), the American Orthopaedic Foot & Ankle Society (AOFAS) clinical rating system, the Core Scale of the Foot and Ankle Module of the American Academy of Orthopaedic Surgeons (AAOS) Lower Limb Outcomes Assessment Instruments, and the Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score were used. The clinical results up to 3 years after MACI (mean follow-up, 24.5 months) were compared with preoperative data for 14 cases and the magnetic resonance imaging data for all 19. Results: A significant improvement (50.3% ± 13.2%) in all clinical scores was noted (FFI pain before MACI: 5.5 ± 2.0, after MACI: 2.8 ± 2.2; FFI disability before MACI: 5.0 ± 2.3, after MACI: 2.6 ± 2.2; AOFAS before MACI: 58.6 ± 16.1, after MACI: 80.4 ± 14.1; AAOS standardized mean before MACI: 59.9 ± 16.0, after MACI: 83.5 ± 13.2; AAOS normative score before MACI: 23.0 ± 13.0, after MACI: 42.2 ± 10.7). According to the AOFAS Hindfoot score, 64% were rated as excellent and good, whereas 36% were rated fair and poor. The results correlated with the age of the patient and the duration of symptoms, but not with the size of the lesion. Sixteen patients (89%) reported regular sports activities before the onset of symptoms; 13 of them (81%) returned to sports after the MACI, 56% (n = 9) to the same level. The mean MOCART score was 62.4 ± 15.8 points. In general, there was no relation between MOCART score and clinical outcome, although the filling of the defect showed some correlation with the AAOS score. Conclusion: Arthroscopic MACI is a safe procedure for the treatment of osteochondral lesions in the ankle with overall good clinical and magnetic resonance imaging results.

Short-Term Outcome of Retrograde Tibiotalocalcaneal Arthrodesis with a Curved Intramedullary Nail

Background: The aim of this study was to investigate the potential clinical benefit of tibiotalocalcaneal arthrodesis (TTCA) with an intramedullary nail with a valgus curve, two compression options, and angle-stable locking. Material and Methods: Patients who had undergone TTCA at two tertiary hospitals were eligible. Patients who had undergone TTCA before the beginning of the study were evaluated retrospectively, then all following patients were examined prospectively. There were 59 TTCAs; 55 patients were available for analysis. Twenty-eight were evaluated retrospectively, 27 prospectively. Main Outcome Measures were an SF-36, Mazur-, and AOFAS ankle-hindfoot rating scores and radiographic examination. Results: Bony union was obtained in 53 patients. Fifty-one patients were satisfied with the outcome. Fifty-one patients had marked subjective improvement in mobility. The mean AOFAS score of the 55 patients at the latest followup was 66.8 (range, 38 to 86). The mean Mazzur score was 68.0 (range, 30 to 83). In the prospective group, the scores were significantly improved: AOFAS score by an average of 39.6 points (p < 0.001); Mazur score by an average of 43 points (p < 0.001); SF-36 physical component summary score (p < 0.001) and mental component summary score also improved (p < 0.048). Radiology showed good hind-foot alignment. The complication rate was 25%. Conclusion: Compared with the literature, the data obtained in this study show a good outcome and a high rate of bony union, with comparable complication rates. Patient satisfaction was good. However, the patients still had limitations. The clinical benefit of the nail used was confirmed. Level of Evidence: IV, Case Series

Internal Fixation of Type-C Distal Femoral Fractures in Osteoporotic Bone

BACKGROUND Fixation of distal femoral fractures remains a challenge, especially in osteoporotic bone. This study was performed to investigate the biomechanical stability of four different fixation devices for the treatment of comminuted distal femoral fractures in osteoporotic bone. METHODS Four fixation devices were investigated biomechanically under torsional and axial loading. Three intramedullary nails, differing in the mechanism of distal locking (with two lateral-to-medial screws in one construct, one screw and one spiral blade in another construct, and four screws [two oblique and two lateral-to-medial with medial nuts] in the third), and one angular stable plate were used. All constructs were tested in an osteoporotic synthetic bone model of an AO/ASIF type 33-C2 fracture. Two nail constructs (the one-screw and spiral blade construct and the four-screw construct) were also compared under axial loading in eight pairs of fresh-frozen human cadaveric femora. RESULTS The angular stable plate constructs had significantly higher torsional stiffness than the other constructs; the intramedullary nail with four-screw distal locking achieved nearly comparable results. Furthermore, the four-screw distal locking construct had the greatest torsional strength. Axial stiffness was also the highest for the four-screw distal locking device; the lowest values were achieved with the angular stable plate. The ranking of the constructs for axial cycles to failure was the four-screw locking construct, with the highest number of cycles, followed by the angular stable plate, the spiral blade construct, and two-screw fixation. The findings in the human cadaveric bone were comparable with those in the synthetic bone model. Failure modes under cyclic axial load were comparable for the synthetic and human bone models. CONCLUSIONS The findings of this study support the concept that, for intramedullary nails, the kind of distal interlocking pattern affects the stabilization of distal femoral fractures. Four-screw distal locking provides the highest axial stability and nearly comparable torsional stability to that of the angular stable plate; the four-screw distal interlocking construct was found to have the best combined (torsional and axial) biomechanical stability.

Biomechanical Evaluation of Primary Stiffness of Tibiotalocalcaneal Fusion with Intramedullary Nails

Background: Intramedullary implants are being used with increasing frequency for tibiotalocalcaneal fusion (TTCF). Clinically, the question arises whether intramedullary (IM) nails should have a compression mode to enhance biomechanical stiffness and fusion-site compression. This biomechanical study compared the primary stability of TTCF constructs using compressed and uncompressed retrograde IM nails and a screw technique in a bone model. Methods: For each technique, three composite bone models were used. The implants were a Biomet nail (static locking mode and compressed mode), a T2™ femoral nail (compressed mode); a prototype IM nail 1 (PT1, compressed mode), a prototype IM nail 2 (PT2, dynamic locking mode and compressed mode), and a three-screw construct. The compressed contact surface of each construct was measured with pressure-sensitive film and expressed as percent of the available fusion-site area. Stiffness was tested in dorsiflexion and plantarflexion (D/P), varus and valgus (V/V), and internal rotation and external rotation (I/E) (20 load cycles per loading mode). Results: Mean contact surfaces were 84.0 ± 6.0% for the Biomet nail, 84.0 ± 13.0% for the T2 nail, 70.0 ± 7.2% for the PTI nail, and 83.5 ± 5.5% for the compressed PT2 nail. The greatest primary stiffness in D/P was obtained with the compressed PT2, followed by the compressed Biomet nail. The dynamically locked PT2 produced the least primary stiffness. In V/V, PT1 had the (significantly) greatest primary stiffness, followed by the compressed PT2. The statically locked Biomet nail and the dynamically locked PT2 had the least primary stiffness in V/V. In I/E, the compressed PT2 had the greatest primary stiffness, followed by the PT1 and the T2™ nails, which did not differ significantly from each other. The dynamically locked PT2 produced the least primary stiffness. The screw constructs contact surface and stiffness were intermediate. Conclusions: The IM nails with compression used for TTCF produced good contact surfaces and primary stiffness. They were significantly superior in these respects to the uncompressed nails and the screw construct. The large contact surfaces and great primary stiffness provided by the IM nails in a bone model may translate into improved union rates in patients who have TTCF.

Distal femur fractures of the elderly--different treatment options in a biomechanical comparison.

BACKGROUND Fractures of the distal femur, especially in the elderly patient, are an unsolved problem in orthopaedic and trauma surgery. Poor bone stock quality caused by osteoporosis often results in bad implant anchorage in the distal part with a high risk of secondary failures such as cutout. This study investigates the biomechanical characteristics of four implants with different distal locking options under quasi-static torsional and cyclic axial loading. Therefore, an osteoporotic bone model simulating severe osteoporotic conditions was used. METHODS Four different implants (T2 intramedullary nail, supracondylar nail (SCN), distal femoral nail (DFN) and the AxSOS angular stable plate) with different distal locking options were instrumented using an osteoporotic bone model. Five specimens per implant and per loading type (torsional and axial) were used. Mechanical testing was performed under physiologic loading conditions. First, a torsional test was performed in internal and external rotation (10 Nm), with a new specimen; a stepwise cyclic axial loading was conducted until failure of the construct. FINDINGS For torsional loading, the lowest range of motion (ROM) and neutral zone (NZ) was found for the AxSOS plate construct. The SCN and T2 constructs showed similar results, and the highest ROM and NZ were found for the constructs treated with the DFN. Axial stiffness was highest for SCN constructs and in the same range for DFN and T2. The lowest stiffness showed in the AxSOS plate constructs with 47% of SCN stiffness. Under cyclic axial loading, the SCN constructs showed the highest number of cycles to failure, followed by AxSOS (70%), DFN (69%) and T2 (48%). INTERPRETATION In conclusion of this biomechanical study, we can clinically suggest that, if, in general, torsional stability is required (e.g., for bedridden patients) the AxSOS plate will be sufficient. By contrast, the findings of this study support the fact that the SCN should be considered for mobile patients where early postoperative mobilisation for rehabilitation is desired.

Stability of Medial Locking Plate and Compression Screw Versus Two Crossed Screws for Lapidus Arthrodesis

Background: Lapidus (first metatarsocuneiform joint) arthrodesis is an established procedure for the management of hallux valgus. This study investigated the utility of fixation with a medial locking plate with adjunct compression screw versus fixation with two crossed screws. Materials and Methods: Eight pairs of fresh-frozen human specimens were used in a matched pair test. Bone mineral density (BMD) was measured with peripheral quantitative computed tomography (pQCT). Fixation with two 4-mm-diameter crossed screws was compared versus a medial locking plate (X-Locking Plate 2.4/2.7; Synthes, Solothurn, Switzerland) with adjunct 4-mm-diameter compression screw. The specimens were tested in a four-point bending test. Parameters obtained were initial stiffness; plantar joint-line gapping after one cycle, 100 and 1000 cycles; and number of cycles to failure. Failure was defined as more than or equal to 3 mm plantar gapping. Results: The groups did not differ significantly with regard to BMD (p = 0.866) and initial stiffness (p = 0.889). The plate-and-screw construct showed significantly less movement during testing, and significantly (p = 0.001) more cycles to failure than did the crossed-screw construct. There was a significant correlation (crossed-screw construct: p = 0.014; plate-and-screw construct: p = 0.010) between BMD and the number of cycles to failure. Conclusion: Under cyclic loading conditions, the construct using a medial locking plate with adjunct compression screw was superior to the construct using two crossed screws. Clinical Relevance: The medial locking-plate technique described could help shorten the period of nonweightbearing and reduce the risk of non-union.

2D-fluoroscopic navigated percutaneous screw fixation of pelvic ring injuries - a case series

BackgroundScrew fixation of pelvic ring fractures is a common, but demanding procedure and navigation techniques were introduced to increase the precision of screw placement. The purpose of this case series was the evaluation of screw misplacement rate and functional outcome of percutaneous screw fixation of pelvic ring disruptions using a 2D navigation system.MethodsBetween August 2004 and December 2007, 44 of 442 patients with pelvic injuries were included for closed reduction and percutaneous screw fixation of disrupted pelvic ring lesions using an optoelectronic 2D-fluoroscopic based navigation system. Operating and fluoroscopy time were measured, as well as peri- and postoperative complications documented. Screw position was assessed by postoperative CT scans. Quality of live was evaluated by SF 36-questionnaire in 40 of 44 patients at mean follow up 15.5 ± 1.2 month.Results56 iliosacral- and 29 ramus pubic-screws were inserted (mean operation time per screw 62 ± 4 minutes, mean fluoroscopy time per screw 123 ± 12 seconds). In post-operative CT-scans the screw position was assessed and graded as follows: I. secure positioning, completely in the cancellous bone (80%); II. secure positioning, but contacting cortical bone structures (14%); III. malplaced positioning, penetrating the cortical bone (6%). The malplacements predominantly occurred in bilateral overlapping screw fixation. No wound infection or iatrogenic neurovascular damage were observed. Four re-operations were performed, two of them due to implant-misplacement and two of them due to implant-failure.Conclusion2D-fluoroscopic navigation is a safe tool providing high accuracy of percutaneous screw placement for pelvic ring fractures, but in cases of a bilateral iliosacral screw fixation an increased risk for screw misplacement was observed. If additional ramus pubic screw fixations are performed, the retrograde inserted screws have to pass the iliopubic eminence to prevent an axial screw loosening.

Angle-stable and Compressed Angle-stable Locking for Tibiotalocalcaneal Arthrodesis with Retrograde Intramedullary Nails: Biomechanical Evaluation

BACKGROUND Retrograde intramedullary nailing is an established procedure for tibiotalocalcaneal arthrodesis. The goal of this study was to evaluate the effects of angle-stable locking or compressed angle-stable locking on the initial stability of the nails and on the behavior of the constructs under cyclic loading conditions. METHODS Tibiotalocalcaneal arthrodesis was performed in fifteen third-generation synthetic bones and twenty-four fresh-frozen cadaver legs with use of retrograde intramedullary nailing with three different locking modes: a Stryker nail with compressed angle-stable locking, a Stryker nail with angle-stable locking, and a statically locked Biomet nail. Analyses were performed of the initial stability of the specimens (range of motion) and the laxity of the constructs (neutral zone) in dorsiflexion/plantar flexion, varus/valgus, and external rotation/internal rotation. Cyclic testing up to 100,000 cycles was also performed. The range of motion and the neutral zone in dorsiflexion/plantar flexion at specific cycle increments were determined. RESULTS In both bone models, the intramedullary nails with compressed angle-stable locking and those with angle-stable locking were significantly superior, in terms of a smaller range of motion and neutral zone, to the statically locked nails. The compressed angle-stable nails were superior to the angle-stable nails only in the synthetic bone model, in external/internal rotation. Cyclic testing showed the nails with angle-stable locking and those with compressed angle-stable locking to have greater stability in both models. In the synthetic bone model, compressed angle-stable locking was significantly better than angle-stable locking; in the cadaver bone model, there was no significant difference between these two locking modes. During cyclic testing, five statically locked nails in the cadaver bone model failed, whereas one nail with angle-stable locking and one with compressed angle-stable locking failed. CONCLUSIONS Regardless of the bone model, the nails with angle-stable or compressed angle-stable locking had better initial stability and better stability following cycling than did the nails with static locking.

Outcome of allogeneic vascularized knee transplants

Transplantation of vascularized knee joints is a novel approach in Composite Tissue Allotransplantation (CTA). In 1996 our group started a clinical knee transplantation project and six transplantations have been performed since. Key problems identified early were the monitoring of acute rejection and choice of an immunosuppressive regime. One graft was lost due to postoperative infection and one due to of noncompliance where the patient discontinued the immunosuppressant regime. In three cases late rejection lead to necrosis and graft dysfunction after 15, 16 and 24 months, respectively. Exit‐strategies were arthrodesis in one patient and Above Knee Amputation in two cases. With retrospective analysis after initial five cases the treatment protocol was improved. The immunosuppressive drug regime was altered, femoral diaphysis and knee joint grafting was combined and a vascularized block of donor skin and subcutaneous tissue was harvested with the graft (sentinel skin graft). The sentinel skin graft enabled us to monitor acute rejection by clinical and histological examination and avoid late rejection by rapid treatment with high dose steroids. In summary, over a four‐year period, one of six allogeneic vascularized knee transplants has survived, one was lost from a surgical site infection, one by noncompliance and three by late rejection. Analysis of our data leads us to suggest that knee transplantation should be limited to a combined injury consisting of extensive loss of cartilage and bone, deficient extensor mechanism and soft tissue and skin defects without any signs of infection. Transplantation should only be taken into consideration as last option before Above Knee Amputation in an otherwise healthy patient under 35 years of age.

Comparison of Two Intramedullary Nails for Tibiotalocalcaneal Fusion: Anatomic and Radiographic Considerations:

Background: Retrograde intramedullary nailing is an established procedure for tibiotalocalcaneal arthrodesis. This study was conducted to see whether, and if so to what extent, nail design modifications would influence the risk to anatomic structures and the bony coverage of the nail base. Methods: Six pairs of thawed fresh-frozen cadaver legs received two different intramedullary nails (N1: straight nail, lateral-medial tip locking; N2: valgus-curved nail, medial-lateral tip locking) under simulated operative conditions. The specimens were dissected; distances between the at-risk structures and the hardware were measured. The hindfoot axis and the volume of the intracalcaneal nail portion were determined with CT. Results: At the plantar entry site, N2 was significantly farther from the flexor hallucis longus tendon (p = 0.047), the medial plantar artery (p = 0.026), and the lateral plantar nerve (p = 0.026) than N1. The lateral-medial calcaneal locking screw of N1 damaged significantly more often the peroneus brevis tendon (p = 0.03) than N2. The proximal tip-locking screw, N2, was significantly farther from the anterior tibial artery (p = 0.075) and the deep (p = 0.047) and superficial peroneal nerves (p = 0.009) than N1; N1 was significantly farther from the great saphenous vein (p = 0.075) than N2. The distal tip-locking screw, N1. damaged significantly more often the extensor digitorum longus (p = 0.007), the anterior tibial artery(p = 0.04), and the deep and superficial peroneal nerves (p = 0.03) than N2. CT did not show any significant changes in the hindfoot axis with either device; intracalcaneal nail volumes were similar. Conclusions: A curved nail can increase the distance to at-risk plantar structures. Medial-lateral nail-tip locking appears to have less risk to neurovascular structures. Clinical Relevance: Safer retrograde intramedullary nailing for tibiotalocalcaneal fusion requires knowledge of the structures at risk and appropriate operative technique.