Expression of Signaling Molecules Involved in Embryonic Development of the Insertion Site Is Inadequate for Reformation of the Native Enthesis: Evaluation in a Novel Murine ACL Reconstruction Model.

BACKGROUND: Since healing of anterior cruciate ligament (ACL) grafts occurs by formation of a fibrovascular scar-tissue interface rather than by reformation of the native fibrocartilage transition zone, the purpose of our study was to examine expression of various signaling molecules and transcription factors that are known to be involved in embryologic insertion-site development following ACL reconstruction. We also aimed to characterize a murine model of ACL reconstruction to allow future study of the molecular mechanisms of healing. METHODS: Seventy-nine mice underwent reconstruction of the ACL with autograft. Healing was assessed using histology in 12 mice and quantitative real-time polymerase chain reaction (qRT-PCR) gene-expression analysis in 3 mice at 1 week postoperatively (Group-1 mice) and by biomechanical analysis in 7, histological analysis in 7, immunohistochemical analysis in 5, microcomputed tomography analysis in 5, and qRT-PCR analyses in 8 at 2 weeks (Group-2 mice) and 4 weeks (Group-3 mice) postoperatively. Fifteen additional mice did not undergo surgery and were used for biomechanical (7 mice), qRT-PCR (3 mice), and immunohistochemical (5 mice) analyses to obtain baseline data for the native ACL. RESULTS: Histological analysis demonstrated healing by formation of fibrovascular tissue at the tendon-bone interface. Immunohistochemical analysis showed a positive expression of proteins in the Indian hedgehog, Wnt, and parathyroid hormone-related protein (PTHrP) pathways. There was minimal Sox-9 expression. Gene-expression analysis showed an initial increase in markers of tissue repair and turnover, followed by a subsequent decline. Mean failure force and stiffness of the native ACL were 5.60 N and 3.44 N/mm, respectively. Mean failure force and stiffness were 1.29 N and 2.28 N/mm, respectively, in Group 2 and were 1.79 N and 2.59 N/mm, respectively, in Group 3, with 12 of 14 failures in these study groups occurring by tunnel pull-out. CONCLUSIONS: The spatial and temporal pattern of expression of signaling molecules that direct embryologic insertion-site formation was not adequate to restore the structure and composition of the native insertion site. CLINICAL RELEVANCE: Development of a murine model to study ACL reconstruction will allow the use of transgenic animals to investigate the cellular, molecular, and biomechanical aspects of tendon-to-bone healing following ACL reconstruction, ultimately suggesting methods to improve healing in patients.

Outcomes of Patellofemoral Osteochondral Lesions Treated With Structural Grafts in Patients Older Than 40 Years.

Background Chondral lesions in the patellofemoral compartment represent a difficult entity to treat among active patients, with no clear consensus on the optimal treatment strategy. The purpose of this study was to review the functional outcomes of patients >40 years old with primary patellofemoral osteochondral lesions who underwent a cartilage restoration procedure with a structural graft. Methods Following institutional review board approval, 35 patients >40 years treated for patellofemoral chondral or osteochondral injuries were retrospectively identified. Seventeen (47%) had prior surgery (mean 1.4 procedures, range 1-4). Average follow-up was 3.6 ± 1.6 years. Average patient age was 51.5 years (range 40-72 years); 54% were male. Twenty-six (74%) had isolated trochlear lesions, 7 had isolated patellar lesions (20%), while 2 (6%) had bipolar lesions. Twenty patients (57%) were treated with synthetic biphasic scaffold plugs (SS), 9 (26%) with fresh osteochondral allograft (OCA) and 6 (17%) with osteochondral autograft transfer (OAT). Outcomes were measured with validated measures: Activity of Daily Living Score (ADL), International Knee Documentation Committee (IKDC) Subjective Evaluation form, and Marx Activity Scale (MAS). Results The average lesion size for the entire cohort was 3.1 ± 1.7 cm2. Average defect size was 2.6 ± 1.7 cm2 for the SS group, 4.3±1.5 cm2 for the OCA group, and 2.9 ± 0.8 cm2 for the OAT group ( P > 0.051). Outcome scores for the entire population demonstrated significant improvement in ADL ( P = 0.002) and IKDC scores ( P = 0.004) between baseline and final follow-up, while MAS scores were maintained ( P = 0.51). Conclusion Structural grafts are a viable treatment option for symptomatic focal osteochondral lesions of the patellofemoral joint in patients 40 years and older, with anticipated improvements in pain and function and maintenance of preoperative activity levels.

Outcomes following Structural Grafting of Distal Femoral Osteochondral Injuries in Patients Aged 40 Years and Older.

Osteochondral lesions of the distal femur represent a challenging clinical entity, particularly in patients > 40 years of age. Microfracture has demonstrated inferior results in this population with clinical deterioration beyond 1 to 2 years postoperatively. Limited evidence exists to support alternative cartilage restoration procedures. The purpose of this study was to report functional outcomes and activity levels following cartilage restoration procedures in patients > 40 years with symptomatic distal femoral osteochondral lesions. From 2000 to 2012, 61 patients with distal femoral osteochondral injuries were retrospectively identified. Mean follow-up was 3.6 ± 1.4 years; mean age was 51.6 years (range 40-71); 59% were male. Of 61 patients, 35 patients (57%) were treated with synthetic scaffold (SS) plugs (off-label), 14 (23%) with osteochondral allograft (OCA), and 12 (20%) with autologous osteochondral transfer (AOT). Validated outcome measures including activity of daily living (ADL) score, International Knee Documentation Committee (IKDC) subjective evaluation form, and Marx activity scale (MAS) were used. The average lesion size was 3.8 ± 2.1 cm2. Lesion size was significantly greater in the OCA group (5.8 ± 1.8 cm2), compared with the SS (3.2 ± 1.9 cm2) and AOT group (3.3 ± 1.8 cm2, p ≤ 0.0024). Collectively, outcome scores for the entire population demonstrated significant improvement in ADL (61.36 ± 17.76-76.81 ± 17.2, p < 0.0001) and IKDC scores (40.28 ± 13.28-61.84 ± 20.83, p < 0.001) from baseline to final follow-up, with no significant change in MAS (4.19 ± 5.13-2.59 ± 3.92, p = 0.07). Similarly, subgroup analysis identified that all treatment groups (SS, OCA, and AOT) demonstrated significant improvement in ADL and IKDC scores from preoperative to final postoperative visit (p ≤ 0.0361). MAS scores were maintained in the OCA and AOT groups (p ≥ 0.1704), but significantly decreased in the SS group (4.3 ± 5.2-2.7 ± 4.11, p = 0.0163). Ten patients (16.3%) required revision surgery at a mean of 4.4 years (range 0.3-13.4 years). Cartilage restoration procedures using structural grafts are successful in patients 40 years and older, with improved pain and functional outcome scores compared with preoperative baseline scores. OCA and AOT should primarily be used, given recent concerns with SS implants.

Restriction of Postoperative Joint Loading in a Murine Model of Anterior Cruciate Ligament Reconstruction: Botulinum Toxin Paralysis and External Fixation.

Control of knee motion in small animal models is necessary to study the effect of mechanical load on the healing process. This can be especially challenging in mice, which are being increasingly used for various orthopedic reconstruction models. We explored the feasibility of botulinum toxin (Botox; Allergan, Dublin, Ireland) paralysis and a newly designed external fixator to restrict motion of the knee in mice undergoing anterior cruciate ligament (ACL) reconstruction. Nineteen C57BL/6 mice were allocated to two groups: (1) Botox group (n = 9) and (2) external fixator group (n = 10). Mice in Botox group received two different doses of Botox: 0.25 unit (n = 3) and 0.5 unit (n = 6). Injection was performed 72 hours prior to ACL reconstruction into the quadriceps, hamstring, and calf muscles of the right hind leg. Mice in external fixator group received an external fixator following ACL reconstruction. Mice were monitored for survival, tolerance, and achievement of complete knee immobilization. All mice were meant for sacrifice on day 14 postoperatively. No perceptible change in gait was observed with 0.25 unit of Botox. All mice that received 0.5 unit of Botox had complete hind limb paralysis documented by footprint analysis 2 days after injection but failed to tolerate anesthesia and were euthanized 24 hours after operation due to their critical condition. In contrast, the external fixator was well tolerated and effectively immobilized the limb. There was a single occurrence of intraoperative technical error in the external fixator group that led to euthanasia. No mechanical failure or complication was observed. Botox paralysis was not a viable option for postoperative restriction of motion and joint loading in mice. However, external fixation was an effective method for complete knee immobilization and can be used in murine models requiring postoperative control of knee loading. This study introduces a robust research tool to allow control of postoperative joint loading in animal models such as ACL reconstruction, permitting study of the effects of mechanical load on the biologic aspects of tendon-to-bone healing.

Orthopaedic Residents Improve Confidence and Knot-Tying Speed With a Skills Course.

PURPOSE: To determine the effect of a knot-tying module, within an arthroscopic training course, on resident speed, resident confidence, and biomechanical quality of arthroscopically tied knots. METHODS: Sixty-four participants (8 postgraduate year [PGY]-3 and 8 PGY-4 orthopaedic residents annually for 4 years) were enrolled in a 5-day training course, which included a daily knot-tying module. Self-assessed confidence was obtained by pre-course (day 1) and post-course (day 5) questionnaire. Each participant tied 5 sequential knots using an arthroscopic knot-tying station. Time per knot was recorded in seconds. Knots were later preloaded, cycled, and tested for peak load to failure and displacement change. Mean peak load to failure, displacement change, speed, and confidence were compared before and after training. RESULTS: The mean time to complete 5 knots was significantly faster after training (12.8 minutes before the course [day 1] v 9.39 minutes after the course [day 5]) (P < .0001). Confidence improved from pre-course (mean, 3.3) to post-course (mean, 7.8) questionnaires (P < .0001). No statistically significant difference was found between peak force for pre-course (mean, 136 N) and post-course (mean, 138 N) knots (P = .076). No statistically significant difference was detected in mean displacement change (mean, 3.51 mm before the course v 3.57 mm after the course) (P = .61). Comparison of PGY-3 and PGY-4 residents was significant only for a higher pre-course confidence in PGY-4 residents (P = .02). CONCLUSIONS: Participation in an arthroscopic knot-tying module improves resident speed and confidence in tying arthroscopic knots. Our data did not show a significant change in peak load to failure or loop security with training. These findings suggest that participation in a knot-tying module improves efficiency regarding arthroscopic knot tying by residents. CLINICAL RELEVANCE: Residents who practice arthroscopic knot tying 5 days per year as part of an arthroscopic training course may be more efficient in the operating room.

Subtalar joint axis in patients with symptomatic peritalar subluxation compared to normal controls.

BACKGROUND: The etiology of peritalar subluxation (PTS) is poorly understood and likely mutifactorial. An anatomic predisposition for posterolateral subluxation of the hindfoot has not been previously described or investigated. The aim of the current study was to describe the morphology of the subtalar joint axis (STJA) in patients with symptomatic PTS compared to normal controls. METHODS: We identified patients with symptomatic PTS who had undergone operative correction from hospital records. The angle of the axis of the posterior facet of the subtalar joint was made on simulated weight-bearing CT (SWBCT) scans. A control group of patients who had no foot deformity on standing films was used for comparison. The STJA was defined as the angle between the superior talar dome and the posterior facet of the talus on coronal CT scan. The mean, maximum, and minimum STJAs were calculated for each cut from anterior to posterior across the posterior facet. The trend in progression across the posterior facet was also examined. RESULTS: After exclusions, 22 feet in 20 patients were included in the study group and compared to 20 control subjects. It was seen that patients with PTS had an increased valgus orientation of the subtalar joint. In patients with PTS the STJA began in valgus and progressed to even greater valgus from anterior to posterior across the posterior facet. The STJA in control subjects was seen instead to begin in slight varus and transition to valgus at the junction of the anterior and middle third and then increase in valgus as the joint progressed posteriorly. CONCLUSIONS: The valgus orientation of the coronal plane of the subtalar joint may represent an anatomic contribution to the etiology of PTS. LEVEL OF EVIDENCE: Level III, comparative series.

Anatomical variance in acetabular anteversion does not predict hip fracture patterns in the elderly: a retrospective study in 135 patients.

It has been suggested that variances in the anatomy of the acetabulum determine the type of hip fracture in elderly patients. Based on this concept, an overly anteverted acetabulum would lead to impingement of the femoral neck against the posterior rim of the acetabulum, causing a femoral neck fracture, whereas with a retroverted acetabulum, external rotation of the hip would be limited by the capsular tissues attached to the trochanteric region, causing a trochanteric fracture. To test the hypothesis that acetabular version predicts hip fracture type in elderly patients, we measured acetabular version using computed tomography scans for 135 patients with hip fracture. Logistic regression analysis was used to check for an association between version angle and fracture type. No significant relationship between acetabular version and fracture type was found. Therefore, we conclude that acetabular version angle does not predict hip fracture type in the elderly, and our data do not support the impingement concept as the mechanism of hip fractures.

Bone density and cortical thickness in normal, osteopenic, and osteoporotic sacra.

It is unclear if a decrease in cancellous bone density or cortical bone thickness is related to sacral insufficiency fractures. We hypothesized that reduction in overall bone density leads to local reductions in bone density and cortical thickness in cadaveric sacra that match clinically observed fracture patterns in patients with sacral insufficiency fractures. We used quantitative computed tomography to measure cancellous density and cortical thickness in multiple areas of normal, osteopenic, and osteoporotic sacra. Cancellous bone density was significantly lower in osteoporotic specimens in the central and anterior regions of the sacral ala compared with other regions of these specimens. Cortical thickness decreased uniformly in all regions of osteopenic and osteoporotic specimens. These results support our hypothesis that areas of the sacrum where sacral insufficiency fractures often occur have significantly larger decreases in cancellous bone density; however, they do not support the hypothesis that these areas have local reduction of cortical bone thickness.