A systematic approach to managing complications after proximal tibial osteotomies of the knee.

Proximal tibial osteotomy (PTO) is an effective procedure for active and young adult patients with symptomatic unicompartmental osteoarthritis and malalignment. They were considered technically demanding and prone to various complications related to the surgical technique, biomechanical or biological origin. Among the most important are hinge fractures and delayed or non-healing, neurovascular complications, loss of correction, implant-related problems, patellofemoral complaints, biological complications and changes in limb length. Being aware of these problems can help minimizing their prevalence and improve the results of the procedure.The aim of this narrative review is to discuss the potential complications that may occur during and after proximal tibial osteotomies, their origin and ways to prevent them.

The portal of Neviaser: a valid option for antegrade nailing of humerus fractures.

INTRODUCTION: The objective of this retrospective non-randomized study was to evaluate the portal of Neviaser (PN) as an alternative approach in antegrade humeral nailing. METHODS: The surgical approach for the straight antegrade intramedullary nail (SAIN) was either the anterolateral delta-split (group 2, n = 79) or the portal of Neviaser (group 3, n = 27). Length of surgery and time of radiation were extracted from charts. Patients stabilized using the PN were followed for a clinical and radiological exam. At follow-up we evaluated the DASH (Disability of the Arm, Shoulder and Hand) and CMS (Constant-Murley Score). RESULTS: Between 10.2015 and 12.2018 191 proximal and diaphyseal humeral fractures were operated using either an angular stable extramedullary device (group 1, PHILOS®, n = 85) or a straight humeral nail (MultiLoc®, n = 106). Time of radiation and intervention followed a normal distribution. The mean length of surgery was 172.9 min (SD 91.5) in group 1, 121.5 min (SD 54.1) in group 2 and 96.4 min (SD 33.7) in group 3 (p < 0.01). Time of radiation was significantly different with 1.1 min (SD 0.6: group 1), 3.1 min (SD 1.6: group 2) and 2.9 min (SD 1.7: group 3) (p < 0.01). After a mean interval of 21.5 months (range 6-43 months) 14 / 27 patients of group 3 were available for a clinical and radiological follow-up. The mean DASH in group 3 was 25, the CMS reached 70. The age and sex weighted CMS mean value was 96%. Forward flexion was 131°, abduction 125°. The ratio of strength affected versus non-affected side was 4.4: 6.2 kg. CONCLUSIONS: The portal of Neviaser is a feasible and safe approach and is an alternative to the anterolateral delta-split. Length of surgery and time of radiation were significantly shorter. LEVEL OF EVIDENCE: IV.

Ramp lesions of the medial meniscus are associated with a higher grade of dynamic rotatory laxity in ACL-injured patients in comparison to patients with an isolated injury.

PURPOSE: The purpose of this study was to compare preoperative knee laxity between two groups of patients with primary or revision ACL reconstruction with or without an associated ramp lesion of the medial meniscus. METHODS: Two-hundred and seventy-five patients with an ACL reconstruction (243 primaries; 32 revisions) were prospectively screened using direct arthroscopic visualisation and divided into a ramp lesion group (RLG) and a control group (CG) regardless of the presence of other associated meniscal tears. All patients were clinically examined under anaesthesia before surgery by grading the Lachman and pivot shift tests. RESULTS: Fifty-eight patients were included in the RLG. The CG included 217 patients. With all meniscus lesions included, there were no significant differences between the two groups. After excluding all other meniscus lesions in both groups except for ramp lesions in the RLG, the prevalence of a grade III pivot shift was higher in the RLG (32 remaining patients; 47% grade III) compared to the CG (91 remaining patients; 24% grade III, p = 0.02). The difference of patients with a grade III pivot shift between the CG and RLG remained significant after removal of revision ACL reconstructions (CG, 85 remaining patients; 25% grade III-RLG, 27 remaining patients; 44% grade III, p = 0.05). CONCLUSION: Patients with an isolated ramp lesion of the medial meniscus in association with an ACL injury displayed a higher amount of dynamic rotational laxity as expressed by the pivot shift test in comparison to patients with isolated ACL injury and no ramp lesion. The association between ramp lesions of the medial meniscus and increased pivot shift grading suggests that it is important to diagnose and repair them during ACL reconstruction surgery. LEVEL OF EVIDENCE: III.

Younger age and hamstring tendon graft are associated with higher IKDC 2000 and KOOS scores during the first year after ACL reconstruction.

PURPOSE: Although reference values in healthy subjects have been published for both the International Knee Documentation Committee 2000 subjective knee form (IKDC 2000) and the Knee injury and Osteoarthritis Outcome Score (KOOS), data obtained during the first year after anterior cruciate ligament reconstruction (ACL-R) are sparse. The aim was to establish patient reference values for both questionnaires at different time points and depending on nine individual patient characteristics during the first year after ACL-R. METHODS: Prospectively recorded data from a hospital-based registry were retrospectively extracted from the database. IKDC 2000 and KOOS questionnaires were self-administered pre-operatively and 6 weeks, 3 months, and 6 and 12 months following primary ACL-R. Score values were compared according to nine individual patient criteria: gender, age, body mass index, level of activity, involvement in competition, previous contralateral knee injury and/or surgery, graft type, meniscal repair and/or cartilage lesions. The feature which had a significant and consistent impact on the outcomes was considered as main reference. RESULTS: Two-hundred and nighty-eight patients met the inclusion criteria. Overall, the score values increased over time after ACL-R. At 12 months, they were significantly greater than at any other time point (p < 0.05). The main individual feature influencing the IKDC 2000 score was age. Patients below 30 years of age had up to 9 points higher IKDC 2000 score values at all time points (p < 0.05). The main individual characteristic influencing the KOOS score was graft type. Patients with hamstring tendon grafts (STGR) had up to 15 points higher KOOS score values than patients with bone-patellar tendon-bone (BPTB) grafts during the first months after ACL-R (p < 0.05). At 12 months, no differences in KOOS score values could be identified anymore. CONCLUSIONS: Younger age (< 30 years) and STGR grafts were related to higher IKDC 2000 and KOOS score values within the first year after primary ACL-R. The patient reference values adjusted to age and graft provided in this study may help to identify patients with lower outcomes within the first year after ACL-R. LEVEL OF EVIDENCE: Level III.

Advances in modern osteotomies around the knee : Report on the Association of Sports Traumatology, Arthroscopy, Orthopaedic surgery, Rehabilitation (ASTAOR) Moscow International Osteotomy Congress 2017.

Corrective lower limb osteotomies are innovative and efficient therapeutic procedures for restoring axial alignment and managing unicompartmental knee osteoarthritis. This review presents critical insights into the up-dated clinical knowledge on osteotomies for complex posttraumatic or congenital lower limb deformities with a focus on high tibial osteotomies, including a comprehensive overview of basic principles of osteotomy planning, biomechanical considerations of different implants for osteotomies and insights in specific bone deformity correction techniques. Emphasis is placed on complex cases of lower limb osteotomies associated with ligament and multiaxial instability including pediatric cases, computer-assisted navigation, external fixation for long bone deformity correction and return to sport after such osteotomies. Altogether, these advances in the experimental and clinical knowledge of complex lower limb osteotomies allow generating improved, adapted therapeutic regimens to treat congenital and acquired lower limb deformities.

Anterior buttress plate is successful for treating posterior sterno-clavicular dislocation.

PURPOSE: Traumatic posterior instability of the sternoclavicular joint is a potentially life-threatening injury. In contrast to the low incidence there is a plethora of different strategies to treat this lesion. It was the objective of this retrospective analysis to evaluate and further develop current strategies. METHODS: In this retrospective analysis all posterior dislocations that were diagnosed and treated between 2011 and 2018 were included. In this 7 year period, eight male patients (median age 32 years) were operated. RESULTS: Three patients were not diagnosed at the primary institution and were referred later. Five patients were treated with an anterior buttress plate with clavicular stabilisation only. One patient was stabilized with a temporary sternoclavicular arthrodesis. Two patients were operated using an autologous tendon graft. All of the patients underwent an immediate postoperative CT-scan that documented the anatomical articulation. All patients treated with a plate underwent implant removal. A final CT examination after removal documented the maintenance of the anatomic alignment. CONCLUSIONS: The buttress plate technique with clavicular screw fixation is a sufficient treatment to restore and preserve a normal sternoclavicular alignment. The technique finds its indication in unidirectional posterior instability. LEVEL OF EVIDENCE: IV.

Ramp lesions associated with ACL injuries are more likely to be present in contact injuries and complete ACL tears.

PURPOSE: The purpose of this study was to analyse patient and injury characteristics as well as arthroscopic findings in a prospective cohort of ACL-injured patients with or without an associated ramp lesion. METHODS: Two hundred and twenty-four patients undergoing a primary (n = 196) or revision (n = 28) ACL reconstruction were included. The presence of a ramp lesion was determined by a systematic arthroscopic inspection of the posteromedial compartment. Chi-square tests were used to compare the population of ACL-injured patients with and without a ramp lesion regarding sex, age, body mass index, previous ACL injuries, sport before injury, and injury characteristics. Significance was set at p < 0.05. RESULTS: Fifty-three out of 224 patients had a ramp lesion (24%). The presence of the latter was not related to any of the analysed patient characteristics. The prevalence of the lesion was higher in contact injuries (n = 19; 41%) compared with non-contact injures (n = 34; 19%; p < 0.001). It was higher in patients with complete ACL ruptures (n = 49; 27%) as opposed to partial ruptures (n = 1; 4%; p = 0.01). A patient was 2.98 [95% CI 1.49-5.98] times more likely to have a ramp lesion if the ACL injury was declared to have been caused by direct contact and 8.71 [95% CI 1.15-66.12] times more likely if the ACL tear was complete. CONCLUSION: Ramp lesions may be anticipated in almost one out of four patients undergoing ACL reconstruction, especially if a patient sustained a contact injury and in the presence of a complete ACL tear. LEVEL OF EVIDENCE: III.

The Impact of Osseous Malalignment and Realignment Procedures in Knee Ligament Surgery: A Systematic Review of the Clinical Evidence.

BACKGROUND: Failure rates of knee ligament surgery may be high, and the impact of osseous alignment on surgical outcome remains controversial. Basic science studies have demonstrated that osseous malalignment can negatively affect ligament strain and that realignment procedures may improve knee joint stability. HYPOTHESIS/PURPOSE: The purpose of this review was to summarize the clinical evidence concerning the impact of osseous malalignment and realignment procedures in knee ligament surgery. The hypotheses were that lower extremity malalignment would be an important contributor to knee ligament surgery failure and that realignment surgery would contribute to increased knee stability and improved outcome in select cases. STUDY DESIGN: Systematic review; Level of evidence, 4. METHODS: According to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a systematic electronic search of the PubMed database was performed in November 2015 to identify clinical studies investigating (A) the influence of osseous alignment on postoperative stability and/or failure rates after knee ligament surgery and (B) the impact of osseous realignment procedures in unstable knees with or without additional knee ligament surgery on postoperative knee function and stability. Methodological quality of the studies was assessed using the Oxford Centre for Evidence-Based Medicine Levels of Evidence and the Coleman Methodological Score (CMS). RESULTS: Of the 1466 potentially relevant articles, 28 studies fulfilled the inclusion and exclusion criteria. Average study quality was poor (CMS, 40). For part A, studies showed increased rerupture rate after anterior cruciate ligament (ACL) replacement in patients with increased tibial slope. Concerning the posterior cruciate ligament (PCL)/posterolateral corner (PLC)/lateral collateral ligament (LCL), varus malalignment was considered a significant risk factor for failure. For part B, studies showed decreased anterior tibial translation after slope-decreasing high tibial osteotomy in ACL-deficient knees. Correcting varus malalignment in PCL/PLC/LCL instability also showed increased stability and better outcomes. CONCLUSION: In cases of complex knee instability, the 3-dimensional osseous alignment of the knee should be considered (eg, mechanical weightbearing line and tibial slope). In cases of failed ACL reconstruction, the tibial slope should be considered, and slope-reducing osteotomies are often helpful in the patient revised multiple times. In cases of chronic PCL and/or PLC instability, osseous correction of the varus alignment may reduce the failure rate and is often the first step in treatment. Changes in the mechanical axis should be considered in all cases of instability accompanied by early unicompartmental osteoarthritis.

Surgical anatomy of medial open-wedge high tibial osteotomy: crucial steps and pitfalls.

PURPOSE: To give an overview of the basic knowledge of the functional surgical anatomy of the proximal lower leg and the popliteal region relevant to medial high tibial osteotomy (HTO) as key anatomical structures in spatial relation to the popliteal region and the proximal tibiofibular joint are usually not directly visible and thus escape a direct inspection. METHODS: The surgical anatomy of the human proximal lower leg and its relevance for HTO are illustrated with a special emphasis on the individual steps of the operation involving creation of the osteotomy planes and plate fixation. RESULTS: The posteriorly located popliteal neurovascular bundle, but also lateral structures such as the peroneal nerve, the head of the fibula and the lateral collateral ligament must be protected from the instruments used for osteotomy. Neither positioning the knee joint in flexion, nor the posterior thin muscle layer of the popliteal muscle offers adequate protection of the popliteal neurovascular bundle when performing the osteotomy. Tactile feedback through a loss-of-resistance when the opposite cortex is perforated is only possible when sawing and drilling is performed in a pounding fashion. Kirschner wires with a proximal thread, therefore, always need to be introduced under fluoroscopic control. Due to anatomy of the tibial head, the tibial slope may increase inadvertently. CONCLUSIONS: Enhanced surgical knowledge of anatomical structures that are at a potential risk during the different steps of osteotomy or plate fixation will help to avoid possible injuries. LEVEL OF EVIDENCE: Expert opinion, Level V.

Large animal models in experimental knee sports surgery: focus on clinical translation.

Large animal models play a crucial role in sports surgery of the knee, as they are critical for the exploration of new experimental strategies and the clinical translation of novel techniques. The purpose of this contribution is to provide critical aspects of relevant animal models in this field, with a focus on paediatric anterior cruciate ligament (ACL) reconstruction, high tibial osteotomy, and articular cartilage repair. Although there is no single large animal model strictly replicating the human knee joint, the sheep stifle joint shares strong similarities. Studies in large animal models of paediatric ACL reconstruction identified specific risk factors associated with the different surgical techniques. The sheep model of high tibial osteotomy is a powerful new tool to advance the understanding of the effect of axial alignment on the lower extremity on specific issues of the knee joint. Large animal models of both focal chondral and osteochondral defects and of osteoarthritis have brought new findings about the mechanisms of cartilage repair and treatment options. The clinical application of a magnetic device for targeted cell delivery serves as a suitable example of how data from such animal models are directly translated into in clinical cartilage repair. As novel insights from studies in these translational models will advance the basic science, close cooperation in this important field of clinical translation will improve current reconstructive surgical options and open novel avenues for regenerative therapies of musculoskeletal disorders.

Surgical-experimental principles of anterior cruciate ligament (ACL) reconstruction with open growth plates.

OBJECTIVE: To review surgical and animal experimental studies performed with open growth plates in relation with pediatric anterior cruciate ligament (ACL) reconstruction. BACKROUND: When it comes to the treatment of ACL injured children, there is a lack of current international guidelines, leaving the treating physicians with a therapeutic dilemma. A variety of surgical and animal experimental studies have been undertaken over the last decades in relation with open growth plates and ACL-reconstruction. METHOD: Based on our own previous animal experimental data, we highlighted 15 specific points concerning pediatric ACL-reconstruction and reviewed additional literature concerning these individual items. RESULTS: Pediatric ACL-reconstruction could be proven to be safe in animal models. Growth abnormalities, risk factors and factors, which were specifically related to biological healing processes in children, were identified. From them surgical principles for safe pediatric ACL replacements can be deducted. Applying these principles through a correct technical execution of surgery may prevent clinically significant growth changes. CONCLUSION: Over the last 2 decades it has been shown that a technically correct pediatric ACL reconstruction has little risk in creating clinically significant growth abnormalities. Animal experiments support this hypothesis despite the fact that the gained knowledge cannot be fully generalized to humans. More long time follow-up is needed to fully understand the complete risk factors related to ACL surgery with open growth plates.

Effect of open wedge high tibial osteotomy on the lateral tibiofemoral compartment in sheep. Part III: analysis of the microstructure of the subchondral bone and correlations with the articular cartilage and meniscus.

PURPOSE: First, to evaluate whether medial open wedge high tibial osteotomy (HTO) induces alterations of the microstructure of the lateral tibial subchondral bone plate of sheep. Second, to test the hypothesis that specific correlations exist between topographical structural alterations of the subchondral bone, the cartilage and the lateral meniscus. METHODS: Three experimental groups received biplanar osteotomies of the right proximal tibiae: (a) closing wedge HTO (4.5° of tibial varus), (b) opening wedge HTO (4.5° tibial valgus; standard correction) and (c) opening wedge HTO (9.5° of valgus; overcorrection), each of which was compared to the non-osteotomised contralateral proximal tibiae. After 6 months, subchondral bone structure indices were measured by computed tomography. Correlations between the subchondral bone, the articular cartilage and the lateral meniscus were determined. RESULTS: Increased loading by valgus overcorrection led to an enlarged specific bone surface (BS/BV) in the subarticular spongiosa compared with unloading by varisation. The subchondral bone plate was 3.9-fold thicker in the central region of the lateral tibial plateau than in the submeniscal periphery. Its thickness in the central region significantly correlated with the thickness of the articular cartilage. In the submeniscal region, such correlation did not exist. In general, a higher degree of osteoarthritis (OA) correlated with alterations of the subchondral bone plate microstructure. OA of the submeniscal articular cartilage also correlated with worse matrix staining of the lateral meniscus. CONCLUSION: Osteoarthritis changes are associated with alterations of the subchondral bone plate microstructure. Specific topographical relationships exist in the central region between the articular cartilage and subchondral bone plate thickness, and in the submeniscal periphery between and the articular cartilage and lateral meniscus. From a clinical perspective, the combined follow-up data from this and the previous two investigations suggest that open wedge valgus HTO is a safe procedure for the lateral compartment to manage medial osteoarthritis of the knee with varus malalignment in the short term.

Small subchondral drill holes improve marrow stimulation of articular cartilage defects.

BACKGROUND: Subchondral drilling is an established marrow stimulation technique. HYPOTHESIS: Osteochondral repair is improved when the subchondral bone is perforated with small drill holes, reflecting the physiological subchondral trabecular distance. STUDY DESIGN: Controlled laboratory study. METHODS: A rectangular full-thickness chondral defect was created in the trochlea of adult sheep (n = 13) and treated with 6 subchondral drillings of either 1.0 mm (reflective of the trabecular distance) or 1.8 mm in diameter. Osteochondral repair was assessed after 6 months in vivo by macroscopic, histological, and immunohistochemical analyses and by micro-computed tomography. RESULTS: The application of 1.0-mm subchondral drill holes led to significantly improved histological matrix staining, cellular morphological characteristics, subchondral bone reconstitution, and average total histological score as well as significantly higher immunoreactivity to type II collagen and reduced immunoreactivity to type I collagen in the repair tissue compared with 1.8-mm drill holes. Analysis of osteoarthritic changes in the cartilage adjacent to the defects revealed no significant differences between treatment groups. Restoration of the microstructure of the subchondral bone plate below the chondral defects was significantly improved after 1.0-mm compared to 1.8-mm drilling, as shown by higher bone volume and reduced thickening of the subchondral bone plate. Likewise, the microarchitecture of the drilled subarticular spongiosa was better restored after 1.0-mm drilling, indicated by significantly higher bone volume and more and thinner trabeculae. Moreover, the bone mineral density of the subchondral bone in 1.0-mm drill holes was similar to the adjacent subchondral bone, whereas it was significantly reduced in 1.8-mm drill holes. No significant correlations existed between cartilage and subchondral bone repair. CONCLUSION: Small subchondral drill holes that reflect the physiological trabecular distance improve osteochondral repair in a translational model more effectively than larger drill holes. CLINICAL RELEVANCE: These results have important implications for the use of subchondral drilling for marrow stimulation, as they support the use of small-diameter bone-cutting devices.

Effect of open wedge high tibial osteotomy on the lateral tibiofemoral compartment in sheep. Part II: standard and overcorrection do not cause articular cartilage degeneration.

PURPOSE: To evaluate whether medial open wedge high tibial osteotomy (HTO) results in structural changes in the articular cartilage in the lateral tibiofemoral compartment of adult sheep. METHODS: Three experimental groups received biplanar osteotomies of the right proximal tibiae: (a) closing wedge HTO (4.5° of tibial varus), (b) opening wedge HTO (4.5° tibial valgus; standard correction), and (c) opening wedge HTO (9.5° of valgus; overcorrection), each of which was compared to the contralateral knees that only received an arthrotomy. After 6 months, the macroscopic and microscopic characteristics of the articular cartilage of the lateral tibiofemoral compartment were assessed. RESULTS: The articular cartilage in the central region of the lateral tibial plateau in sheep had a higher safranin O staining intensity and was 4.6-fold thicker than in the periphery (covered by the lateral meniscus). No topographical variation in the type-II collagen immunoreactivity was seen. All lateral tibial plateaus showed osteoarthritic changes in regions not covered by the lateral meniscus. No osteoarthritis was seen in the peripheral submeniscal regions of the lateral tibial plateau and the lateral femoral condyle. Opening wedge HTO resulting in both standard and overcorrection was not associated with significant macroscopic and microscopic structural changes between groups in the articular cartilage of the lateral tibial plateau and femoral condyle after 6 months in vivo. CONCLUSION: Opening wedge HTO resulting in both standard and overcorrection is a safe procedure for the articular cartilage in an intact lateral tibiofemoral compartment of adult sheep at 6 months postoperatively.

Wedge volume and osteotomy surface depend on surgical technique for high tibial osteotomy.

PURPOSE: Biplanar open-wedge high tibial osteotomy (HTO) is thought to promote rapid bone healing due to the increased cancellous bone surface compared to other HTO techniques. However, precise data on the bone surface area and wedge volume resulting from both open- and closed-wedge HTO techniques remain unknown. We hypothesized that biplanar rather than uniplanar HTO better reflects the ideal geometrical requirements for bone healing, representing a large cancellous bone surface combined with a small wedge volume. METHODS: Tibial saw bones were assigned to 4 different groups of valgisation high tibial osteotomies: group 1: open-wedge uniplanar HTO; group 2: open-wedge biplanar HTO with ascending frontal cut; group 3: open-wedge biplanar HTO with descending frontal cut (retrotubercule osteotomy technique), and group 4: closed-wedge uniplanar HTO. Bone surface areas of all osteotomy planes were quantified. Wedge volumes were determined using a prism-based algorithm, applying standardized wedge heights of 5, 10, and 15 mm. RESULTS: The open-wedge biplanar osteotomy with a descending frontal cut (group 3) created significantly larger bone surfaces compared to the "classic" biplanar technique with an ascending frontal cut (group 2) and compared to all uniplanar techniques. Bone surfaces after the classic open-wedge technique (group 2) were slightly larger compared to all uniplanar techniques (group 1 and 4). No significant differences of wedge volumes were found between the retrotubercle (group 3) and classic open-wedge techniques (group 2). Wedge volumes were significantly higher in the uniplanar open-wedge technique (group 1) compared to the biplanar open-wedge techniques (group 2 and 3). CONCLUSION: Bone geometry following HTO suggests that the biplanar open-wedge techniques simultaneously create smaller wedge volumes and larger bone surface areas compared to the uniplanar open-wedge techniques. The relatively neglected closed-wedge technique still offers in theory the best healing potential, characterized by an almost absent wedge volume and a large bone-to-bone contact area. Although this idealized geometric view on bony geometry excludes all biologic factors that influence bone healing, the current data suggest a general rule for the applied standard osteotomy techniques and all of their surgical modifications: reducing the amount of slow gap healing and simultaneously increasing the area of faster contact healing may be beneficial for osteotomy healing. Thus, a biplanar rather than a uniplanar osteotomy may be performed for high tibial osteotomy in clinical practice.

Effect of open wedge high tibial osteotomy on the lateral compartment in sheep. Part I: Analysis of the lateral meniscus.

PURPOSE: To evaluate whether medial open wedge high tibial osteotomy (HTO) results in structural and biochemical changes in the lateral meniscus in adult sheep. METHODS: Three experimental groups with biplanar osteotomies of the right proximal tibiae were tested: (a) closing wedge HTO resulting in 4.5° of tibial varus, (b) open wedge HTO resulting in 4.5° of tibial valgus (standard correction) and (c) open wedge HTO resulting in 9.5° of valgus (overcorrection), each of which was compared to the contralateral knees with normal limb axes. After 6 months, the lateral menisci were macroscopically and microscopically evaluated. The proteoglycan and DNA contents of the red-red and white-white zones of the anterior, middle and posterior third were determined. RESULTS: Semiquantitative macroscopic and microscopic grading revealed no structural differences between groups. The red-red zone of the middle third of the lateral menisci of animals that underwent overcorrection exhibited a significant 0.7-fold decrease in mean DNA contents compared with the control knee without HTO (P = 0.012). Comparative estimation of the DNA and proteoglycan contents and proteoglycan/DNA ratios of all other parts and zones of the lateral menisci did not reveal significant differences between groups. CONCLUSION: Open wedge HTO does not lead to significant macroscopic and microscopic structural changes in the lateral meniscus after 6 months in vivo. Overcorrection significantly decreases the proliferative activity of the cells in the red-red zone of the middle third in the sheep model.

Wedge volume and osteotomy surface depend on surgical technique for distal femoral osteotomy.

PURPOSE: Biplanar distal femoral osteotomy (DFO) is thought to promote rapid bone healing due to the increased cancellous bone surface compared to other DFO techniques. However, precise data on the bone surface area and wedge volume resulting from both open- and closed-wedge DFO techniques remain unknown. We hypothesized that biplanar rather than uniplanar DFO better reflects the ideal geometrical requirements for bone healing, representing a large cancellous bone surface combined with a small wedge volume. METHODS: Femoral saw bones were assigned to 4 different groups of varization distal femur osteotomies: group 1, lateral open-wedge uniplanar DFO; group 2, medial closed-wedge uniplanar DFO; group 3, lateral open-wedge biplanar DFO; and group 4, medial closed-wedge biplanar DFO. Bone surface areas of all osteotomy planes were quantified. Wedge volumes were determined using a prism-based algorithm, applying standardized wedge heights of 5, 10 and 15 mm. RESULTS: The biplanar osteotomy techniques (groups 3 and 4) created significantly larger femoral surface compared to the uniplanar groups (groups 1 and 2) (p = 0.036). Bone surfaces after the lateral biplanar open-wedge technique (group 3) were slightly larger than the medial biplanar closed-wedge technique (group 4) and biplane techniques significantly larger than the uniplanar techniques (groups 1 and 2). Wedge volumes were significantly higher in the lateral uniplanar open-wedge (group 1) and biplanar open-wedge (group 3) techniques compared to the closed-wedge techniques (groups 2 and 4) that have nearly absent wedge volumes. CONCLUSION: Bone geometry following DFO suggests that the medial biplanar closed-wedge technique simultaneously creates smaller wedge volume and larger bone surface areas compared to the lateral biplanar open-wedge and the uniplanar DFO techniques. The horizontal cuts of the biplane DFO techniques are positioned behind the trochlear area in better healing metaphysial bone, which further enhances bone healing potential. Although this idealized geometric view on bony geometry excludes all biological factors that influence bone healing, the current data confirm the general rule for osteotomy techniques: reducing the amount of slow gap healing and wedge volumes and simultaneously increasing the area of faster contact healing by larger bone surface areas may be beneficial for osteotomy healing.

The preclinical sheep model of high tibial osteotomy relating basic science to the clinics: standards, techniques and pitfalls.

PURPOSE: To develop a preclinical large animal model of high tibial osteotomy to study the effect of axial alignment on the lower extremity on specific issues of the knee joint, such as in articular cartilage repair, development of osteoarthritis and meniscal lesions. Preoperative planning, surgical procedure and postoperative care known from humans were adapted to develop a HTO model in the adult sheep. METHODS: Thirty-five healthy, skeletally mature, female Merino sheep between 2 and 4 years of age underwent a HTO of their right tibia in a medial open-wedge technique inducing a normal (group 1) and an excessive valgus alignment (group 2) and a closed-wedge technique (group 3) inducing a varus alignment with the aim of elucidating the effect of limb alignment on cartilage repair in vivo. Animals were followed up for 6 months. RESULTS: Solid bone healing and maintenance of correction are most likely if the following surgical principles are respected: (1) medial and longitudinal approach to the proximal tibia; (2) biplanar osteotomy to increase initial rotatory stability regardless of the direction of correction; (3) small, narrow but long implant with locking screws; (4) posterior plate placement to avoid slope changes; (5) use of bicortical screws to account for the brittle bone of the tibial head and to avoid tibial head displacement. CONCLUSION: Although successful high tibial osteotomy in sheep is complex, the sheep may--because of its similarities with humans--serve as an elegant model to induce axial malalignment in a clinically relevant environment, and osteotomy healing under challenging mechanical conditions.

Three-dimensional evaluation of cyclic displacement in single-row and double-row rotator cuff reconstructions under static external rotation.

BACKGROUND: The double-row suture bridge repair was recently introduced and has demonstrated superior biomechanical results and higher yield load compared with the traditional double-row technique. It therefore seemed reasonable to compare this second generation of double-row constructs to the modified single-row double mattress reconstruction. HYPOTHESIS: The repair technique, initial tear size, and tendon subregion will have a significant effect on 3-dimensional (3D) cyclic displacement under additional static external rotation of a modified single-row compared with a double-row rotator cuff repair. STUDY DESIGN: Controlled laboratory study. METHODS: Rotator cuff tears (small to medium: 25 mm; medium to large: 35 mm) were created in 24 human cadaveric shoulders. Rotator cuff repairs were performed as modified single-row or double-row repairs, and cyclic loading (10-60 N, 10-100 N) was applied under 20° of external rotation. Radiostereometric analysis was used to calculate cyclic displacement in the anteroposterior (x), craniocaudal (y), and mediolateral (z) planes with a focus on the repair constructs and the initial tear size. Moreover, differences in cyclic displacement of the anterior compared with the posterior tendon subregions were calculated. RESULTS: Significantly lower cyclic displacement was seen in small to medium tears for the single-row compared with double-row repair at 60 and 100 N in the x plane (P = .001) and y plane (P = .001). The results were similar in medium to large tears at 100 N in the x plane (P = .004). Comparison of 25-mm versus 35-mm tears did not show any statistically significant differences for the single-row repairs. In the double-row repairs, lower gap formation was found for the 35-mm tears (P ≤ .05). Comparison of the anterior versus posterior tendon subregions revealed a trend toward higher anterior gap formation, although this was statistically not significant. CONCLUSION: The tested single-row reconstruction achieved superior results in 3D cyclic displacement to the tested double-row repair. Extension of the initial rupture size did not have a negative effect on the biomechanical results of the tested constructs. CLINICAL RELEVANCE: Single-row repairs with modified suture configurations provide comparable biomechanical strength to double-row repairs. Furthermore, as increased gap formation in the early postoperative period might lead to failure of the construct, a strong anterior fixation and restricted external rotation protocol might be considered in rotator cuff repairs to avoid this problem.

Effect of subchondral drilling on the microarchitecture of subchondral bone: analysis in a large animal model at 6 months.

BACKGROUND: Marrow stimulation techniques such as subchondral drilling are clinically important treatment options for symptomatic small cartilage defects. Little is known about whether they induce deleterious changes in the subchondral bone. HYPOTHESIS: Subchondral drilling induces substantial alterations of the microarchitecture of the subchondral bone that persist for a clinically relevant postoperative period in a preclinical large animal model. STUDY DESIGN: Controlled laboratory study. METHODS: Standardized full-thickness chondral defects in the medial femoral condyles of 19 sheep were treated by subchondral drilling. Six months postoperatively, the formation of cysts and intralesional osteophytes was evaluated. A standardized methodology was developed to segment the ovine subchondral unit into reproducible volumes of interest (VOIs). Indices of bone structure were determined by micro-computed tomography (micro-CT). RESULTS: Analysis of the microarchitecture revealed the absence of zonal stratification in the ovine subarticular spongiosa, permitting an unimpeded and simultaneous analysis of the entire subchondral trabecular network. Subchondral drilling led to the formation of subchondral bone cysts (63%) and intralesional osteophytes (26%). Compared with the adjacent unaffected subchondral bone, drilling induced significant alterations in nearly all parameters for the microarchitecture of the subchondral bone plate and the subarticular spongiosa, most importantly in bone volume, bone surface/volume ratio, trabecular thickness, separation, pattern factor, and bone mineral density (BMD) (all P ≤ .01). CONCLUSION: The data show that the ovine subchondral bone can be reliably evaluated using micro-CT with standardized VOIs. We report that subchondral drilling deteriorates the microarchitecture both of the subchondral bone plate and subarticular spongiosa and decreases BMD. These results suggest that the entire osteochondral unit is altered after drilling for an extended postoperative period. CLINICAL RELEVANCE: The subchondral bone remains fragile after subchondral drilling for longer durations than previously expected. Further evaluations of structural subchondral bone parameters of patients undergoing marrow stimulation are warranted.