A cruciate ligament injury produces considerable, permanent osteoporosis in the affected knee

Changes in Bone Mineral Density of the Femur and Tibia Before Injury to 2 Years After Anterior Cruciate Ligament Reconstruction in Division I Collegiate Athletes

BACKGROUND

Osteoarthritis (OA) is a significant long term concern after anterior cruciate ligament (ACL) reconstruction (ACLR). A low bone mineral density (BMD), particularly in the subchondral region, has been associated with the development of OA and is evident at the knee in patients long after ACLR. It is unknown if persistent BMD deficits are present in high level collegiate athletes.

PURPOSE/HYPOTHESIS

The purpose of this study was to evaluate bilateral changes in the BMD of the femur and tibia from before the injury to 24 months after ACLR in collegiate athletes. We hypothesized that the BMD of both the distal femur and the proximal tibia would be significantly reduced within the surgical limb initially postoperatively but return to preinjury levels by 24 months after ACLR.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 33 Division I collegiate athletes were identified between 2010 and 2021 (13 female) who underwent total body dual-energy X-ray absorptiometry (DXA) before sustaining an ACL injury. DXA was repeated at 6, 12, and 24 months after ACLR. Linear mixed effects models assessed differences in the BMD at 5%, 15%, and 50% of the femur's length (F₅, F₁₅, F₅₀) and at 5%, 15%, and 50% of the tibia's length (T₅, T₁₅, T₅₀) within each limb from before the injury to 24 months after ACLR, reported as Tukey-adjusted P values.

RESULTS

Compared with before the injury, the BMD at F₅ of the surgical limb was reduced by 0.15 g/cm² (SE, 0.02 g/cm²) at 6 months (P < .001). The BMD at F₁₅ of the surgical limb was reduced by 0.06 g/cm² (SE, 0.01 g/cm²), 0.09 g/cm² (SE, 0.01 g/cm²), and 0.09 g/cm² (SE, 0.01 g/cm²) at 6, 12, and 24 months, respectively (all P < .001). The BMD at T₅ of the nonsurgical limb was reduced by 0.07 g/cm² (SE, 0.02 g/cm²) at 12 months (P = .02) and 0.10 g/cm² (SE, 0.02 g/cm²) at 24 months (P = .001). The BMD at T₁₅ of the surgical limb was reduced by 0.07 g/cm² (SE, 0.01 g/cm²) at 6 months and 0.08 g/cm² (SE, 0.02 g/cm²) at 12 months (P < .001).

CONCLUSION

BMD deficits at F₁₅ of the surgical limb persisted out to 24 months (-7.1%) after ACLR compared with before the injury in collegiate athletes. The BMD at F₅ and T₁₅ of the surgical limb was reduced at 6 and 12 months but not at 24 months compared with preinjury levels. For the nonsurgical limb, no significant differences were detected, except for the T₅ region at 12 months (-5.1%) and 24 months (-7.2%). The BMD at F₅₀ and T₅₀ of both limbs was not significantly different than preinjury levels at any time after ACLR.

The Proximal Tibia Loses Bone Mineral Density After Anterior Cruciate Ligament Injury: Measurement Technique and Validation of a Quantitative Computed Tomography Method

Purpose

Results

Conclusions

Level of Evidence

Contribution of glycosaminoglycans to the structural and mechanical properties of tendons - A multiscale study

Tendinopathy of the Achilles tendon contributes to a large range of disorders, including mechanical damage and degenerative diseases. Glycosaminoglycans (GAGs), are thought to play a role in the mechanical strength of tendons by forming cross-links between collagen molecules and allowing the transmission of forces between fibrils. This study assessed the response of GAG-depleted tendons to damage induced by fatigue loading, investigating the mechanical damage (stiffness, hysteresis and maximum load), macrostructural changes (tenocyte morphology, fiber anisotropy and waviness) assessed by confocal imaging and nanostructural changes (fibril D-periodicity length) within the same non-viable intact tendons. Changes in fiber waviness and tenocyte shape are strongly correlated to mechanical and nano-structural (D-periodicity elongation) properties in both Control and GAG-depleted tendons. This study supports firstly, the vital role GAGs play as mechanical connectors facilitating the load transfer between the fibrils and their hydrophilic role in facilitating fibril sliding. Secondly, that observed changes in tenocyte shape and fiber waviness correlate with tendon stiffness and other mechanical profiles.

Traumatic joint injury induces acute catabolic bone turnover concurrent with articular cartilage damage in a rat model of posttraumatic osteoarthritis

Assess acute alterations in bone turnover, microstructure, and histomorphometry following noninvasive anterior cruciate ligament rupture (ACLR). Twelve female Lewis rats were randomized to receive noninvasive ACLR or Sham loading (n = 6/group). In vivo μCT was performed at 3, 7, 10, and 14 days postinjury to quantify compartment-dependent subchondral (SCB) and epiphyseal trabecular bone remodeling. Near-infrared (NIR) molecular imaging was used to measure in vivo bone anabolism (800 CW BoneTag) and catabolism (Cat K 680 FAST). Metaphyseal bone remodeling and articular cartilage morphology was quantified using ex vivo μCT and contrast-enhanced µCT, respectively. Calcein-based dynamic histomorphometry was used to quantify bone formation. OARSI scoring was used to assess joint degeneration, and osteoclast number was quantified on TRAP stained-sections. ACLR induced acute catabolic bone remodeling in subchondral, epiphyseal, and metaphyseal compartments. Thinning of medial femoral condyle (MFC) SCB was observed as early as 7 days postinjury, while lateral femoral condyles (LFCs) exhibited SCB gains. Trabecular thinning was observed in MFC epiphyseal bone, with minimal changes to LFC. NIR imaging demonstrated immediate and sustained reduction of bone anabolism (~15%-20%), and a ~32% increase in bone catabolism at 14 days, compared to contralateral limbs. These findings were corroborated by reduced bone formation rate and increased osteoclast numbers, observed histologically. ACLR-injured femora had significantly elevated OARSI score, cartilage thickness, and cartilage surface deviation. ACL rupture induces immediate and sustained reduction of bone anabolism and overactivation of bone catabolism, with mild-to-moderate articular cartilage damage at 14 days postinjury.

Structural Consequences of a Partial Anterior Cruciate Ligament Injury on Remaining Joint Integrity: Evidence for Ligament and Bone Changes Over Time in an Ovine Model

BACKGROUND

Severe injury to the knee joint often results in accelerated posttraumatic osteoarthritis (PTOA). In an ovine knee injury model, altered kinematics and degradation of the cartilage have been observed at 20 and 40 weeks after partial anterior cruciate ligament (ACL) transection (p-ACL Tx) surgery. However, changes to the integrity of the remaining intact intra-articular ligaments (posterolateral [PL] band and posterior cruciate ligament [PCL]) as well as the subchondral bone after anteromedial (AM) band Tx remain to be characterized.

PURPOSE

(1) To investigate histological alterations to the remaining intact intra-articular ligaments, the synovium, and the infrapatellar fat pad (IPFP) and (2) to quantify subchondral bone changes at the contact surfaces of the proximal tibia at 20 and 40 weeks after AM band Tx.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Mature female Suffolk cross sheep were allocated into 3 groups: nonoperative controls (n = 6), 20 weeks after partial ACL transection (p-ACL Tx; n = 5), and 40 weeks after p-ACL Tx (n = 6). Ligament, synovium, and IPFP sections were stained and graded. Tibial subchondral bone microarchitecture was assessed using high-resolution peripheral quantitative computed tomography.

RESULTS

p-ACL Tx of the AM band led to significant change in histological scores of the PL band and the PCL at 20 weeks after p-ACL Tx (P = .031 and P = .033, respectively) and 40 weeks after p-ACL Tx (P = .011 and P = .029) as compared with nonoperative controls. Alterations in inflammatory cells and collagen fiber orientation contributed to the greatest extent of the combined histological score in the PL band and PCL. p-ACL Tx did not lead to chronic activation of the synovium or IPFP. Trabecular bone mineral density was strongly inversely correlated with combined gross morphological damage in the top and middle layers of the subchondral bone in the lateral tibial plateau for animals at 40 weeks after p-ACL Tx.

CONCLUSION

p-ACL Tx influences the integrity (biology and structure) of remaining intact intra-articular ligaments and bone microarchitecture in a partial knee injury ovine model.

CLINICAL RELEVANCE

p-ACL Tx leads to alterations in structural integrity of the remaining intact ligaments and degenerative changes in the trabecular bone mineral density, which may be detrimental to the injured athlete's knee joint in the long term.

Longitudinal Effects of Acute Anterior Cruciate Ligament Tears on Peri-Articular Bone in Human Knees Within the First Year of Injury

Anterior cruciate ligament (ACL) tears are common sports-related knee injuries that increase the risk of developing post-traumatic osteoarthritis. ACL tears are rarely an isolated injury but are often associated with traumatic bone marrow lesions (BMLs). While early loss of bone mass following the ACL injury has been previously described, to date, microarchitectural information has not been reported due to the limited resolution of clinical imaging systems. In this study, we provide the first evidence of detailed bone mass and microarchitectural changes in the first 10 months following an acute ACL tear, and localized to traumatic BMLs. Fifteen participants with an acute unilateral ACL tear were assessed at four-time points using dual-energy X-ray absorptiometry and high-resolution peripheral quantitative computed tomography, and traumatic BMLs were identified with magnetic resonance imaging. Loss of bone mass was localized to the injured knee (-4.6% to -15.8%, depending on bone and depth) and was accelerated immediately following the injury before suggesting a recovery phase. This loss of bone was accelerated even greater in traumatic BMLs (-18.2% to -20.6%, depending on bone). Bone loss was accompanied by microstructural degeneration of trabecular bone. For example, in the lateral femur of the injured knee, the subchondral bone plate decreased in thickness (-9.0%). This study confirmed loss of bone mass in the months following ACL tears and described the underlying bone microstructural changes. The presented bone changes were accelerated in regions of traumatic BMLs. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2325-2336, 2019.

A study of the relationship between meniscal injury and bone microarchitecture in ACL reconstructed knees

BACKGROUND

Anterior cruciate ligament (ACL) tears increase the risk of developing knee osteoarthritis. This risk increases further with concurrent meniscus injury. The role of bone changes during knee osteoarthritis development are not well-understood, but may be important to its etiology.

PURPOSE

To explore the effects of ACL tears on bone mineral density (BMD) and bone microarchitecture at five years post-op and their relationship to meniscal pathology, using high-resolution peripheral quantitative computed tomography (HR-pQCT).

METHODS

Twenty-eight participants with unilateral ACL reconstructions five years prior and no evidence of clinical or radiographic osteoarthritis were recruited. All participants represented one of three meniscus statuses: meniscus intact, meniscus repair, or meniscectomy. BMD and bone microarchitecture of the subchondral bone plate and adjacent trabecular bone were assessed using HR-pQCT, and percent-differences between the injured and contralateral knee were determined.

RESULTS

Subchondral bone plate thickness in the lateral femoral condyle was higher in the reconstructed knee (9.0%, p = 0.002), driven by the meniscus repair and meniscectomy groups (15.2% to 15.4%, p < 0.05). Trabecular BMD was lower in the reconstructed knee in the medial femoral condyle (-4.8% to -7.6%, p < 0.05), driven by all meniscus statuses. In the lateral compartments, few differences in trabecular bone were found. However, accounting for meniscus status, the meniscus intact group had lower trabecular BMD throughout both femur and tibia.

CONCLUSIONS

Five years post-op, reconstructed knees demonstrated detectable differences in BMD and bone microarchitecture, despite having normal radiographs. Meniscus damage affected primarily the lateral compartment, warranting further investigation to determine if these changes relate to osteoarthritis development.

Subchondral bone microarchitecture in ACL reconstructed knees of young women: A comparison with contralateral and uninjured control knees

Anterior cruciate ligament (ACL) tears are a common sports-related knee injury that increases the risk of developing post-traumatic osteoarthritis (OA). During OA progression bone microarchitecture changes in the affected knee, however, little is known about bone microarchitecture in knees with early stage OA. The purpose of this study is to investigate in a cohort of females predisposed to develop OA how bone microarchitecture in ACL reconstructed knees differs from uninjured contralateral knees as well as healthy control knees and how this relates to early changes in OA. Bone microarchitecture was directly assessed in ACL reconstructed knees of injured female participants (n=15) with a median age of 25.4years (age range: 22.5-28.5) and compared to their uninjured contralateral knees, as well as to a healthy age-matched female control sample (n=14) with a median age of 25.2years (age range: 22.2-27.1). ACL reconstructed knees had lower trabecular bone mineral density (compared to contralateral: -7.7% to -10.4%, p<0.05; control knees: -7.1% to -13.9%, p<0.05) and altered trabecular bone microarchitecture in the medial femur compared to contralateral and control knees. The subchondral bone plate in the lateral femur was thicker in ACL reconstructed knees compared to contralateral (29.6%, p=0.009) and control knees (47.9% to 53.7%, p<0.05). Contralateral knees did not differ from control knees. Loss of trabecular bone and increased subchondral bone plate thickness in the ACL-reconstructed knees are consistent with changes associated with OA progression. Most differences in bone microarchitecture were found in the femur, with few differences in the tibia. The bone microarchitecture of contralateral knees did not differ from control knees in our participants, suggesting the potential to use them as control references in future longitudinal studies.

What Role Does Low Bone Mineral Density Play in the "Killer Turn" Effect after Transtibial Posterior Cruciate Ligament Reconstruction?

OBJECTIVE

To explore the mechanism of the "killer turn", which is reported to be a reason for postoperative residual laxity after transtibial posterior cruciate ligament (PCL) reconstruction, in a low bone mineral density (BMD) condition.

METHODS

A total of 80 skeletally mature female New Zealand white rabbits were included for biomechanical evaluation after transtibial PCL reconstructions. The subjects were equally divided into low BMD (n = 40) and control groups (n = 40). Rabbits in the low BMD group were treated with surgery and drug injection to establish an osteoporotic model. Rabbits in the control group received sham surgeries and no injection. All assignments were conducted randomly according to random numbers generated by a computer. All grafts were then subjected to biomechanical testing with an MTS model-858 Mini Bionix servohydraulic materials testing machine (MTS Systems, Minneapolis, Minnesota, USA). The experimental outcomes were the increment of total graft displacement, tunnel inlet enlargement, graft elongation, stiffness and failure load of the two groups, and the comparison between them.

RESULTS

Among the 80 subjects, 1 subject of the low BMD group failed at the 30th cycle by proximal tibial fracture and 1 subject of the control group failed at the 20th cycle for the same reason. As a result, 39 subjects of the low BMD group and 39 subjects of the control group survived the cyclic loading test. Compared with the control group, the low BMD group demonstrated significantly larger total graft displacement ( P = 0.006) and tunnel inlet enlargement ( P = 0.041) than the control group. The number of subjects with less than 10% enlargement was significantly greater (57.1%) in the control group than in the low BMD group ( P = 0.004). In the load-to-failure test, 26 (66.7%) subjects in the low BMD group failed by proximal tibial fracture (around the tunnel), 6 (15.4%) at the mounting site, 5 (12.8%) at the fixation site, and only 2 (5.1%) failed at the "killer turn." In the control group, 20 (51.3%) failed at the "killer turn," 9 (23.1%) at the proximal tibia (around the tunnel), 5 (12.8%) at the mounting site, and 5 (12.8%) at the fixation site. There were significantly fewer failures (10.0%) at the "killer turn" ( P = 0.000) and 155.6% more for the para-tunnel fracture ( P = 0.000) in the low BMD group compared with the control group.

CONCLUSIONS

The low BMD group demonstrated an inferior biomechanical outcome to the control group with the transtibial technique. With low BMD, the "killer turn" effect compromises the posterior tibial cortex by enlarging the tunnel inlet.

Measurement of regional trabecular bone attenuation of the knee following anterior cruciate ligament rupture

INTRODUCTION

The purpose of this study was to determine regional trabecular bone attenuation changes of the knee using computed tomography after anterior cruciate ligament rupture.

MATERIALS AND METHODS

Thirty one patients'-computed tomography images of the injured knees were used to measure trabecular bone attenuation in seven predetermined regions.

RESULTS

Trabecular bone attenuation at four of seven regions (anteromedial area of the proximal tibia, anterolateral area of the proximal tibia, posteromedial area of the proximal tibia, and posterocentral area of the proximal tibia) was negatively correlated with the duration after injury. Independent negative correlation between the duration after injury and the density in anteromedial area of the proximal tibia was detected.

CONCLUSIONS

After anterior cruciate ligament injury, trabecular bone attenuation of the knee decreases by time in certain regions of proximal tibia. Anteromedial region is the most significantly effected of all, which it is the anterior cruciate ligament fixation area.

Subchondral and epiphyseal bone remodeling following surgical transection and noninvasive rupture of the anterior cruciate ligament as models of post-traumatic osteoarthritis

OBJECTIVE

Animal models are frequently used to study post-traumatic osteoarthritis (PTOA). A common anterior cruciate ligament (ACL) injury model is surgical transection, which may introduce confounding factors from surgery. Noninvasive models could model human injury more closely. The purpose of this study was to compare subchondral and epiphyseal trabecular bone remodeling after surgical transection and noninvasive rupture of the ACL.

METHODS

Thirty-six rats were randomized to an uninjured control, surgical transection (Transection), or noninvasive rupture (Rupture). Animals were randomized to 4 or 10 week time points (n = 6 per group). Micro computed tomography (μCT) imaging was performed with an isotropic voxel size of 12 μm. Subchondral and epiphyseal bone was segmented semi-automatically, and morphometric analysis was performed.

RESULTS

Transection caused a greater decrease in subchondral bone volume fraction (BV/TV) than Rupture in the femur and tibia. Rupture had greater subchondral bone tissue mineral density (TMD) at 4 and 10 weeks in the femur and tibia. Subchondral bone thickness (SCB.Th) was decreased in the femur in Transection only. Epiphyseal BV/TV was decreased in Transection only, and Rupture exhibited increased femoral epiphyseal TMD compared to both Control and Transection. Rupture exhibited greater femoral epiphyseal trabecular thickness (Tb.Th.) compared to Control and Transection at 4 weeks, and both Rupture and Transection had increased femoral epiphyseal Tb.Th. at 10 weeks. Epiphyseal trabecular number (Tb.N) was decreased in both injury groups at both time points. Femoral and tibial epiphyseal structure model index (SMI) increased in both groups.

CONCLUSIONS

The two injury models cause differences in post-injury bone morphometry, and surgical transection may be introducing confounding factors that affect downstream bony remodeling.

Femoral fixation strength following soft-tissue posterolateral corner reconstruction using fibular-based technique: Biomechanical analysis of four techniques in normal and low-density synthetic bone

BACKGROUND

Optimal femoral fixation of soft-tissue grafts has been described for anterior cruciate ligament reconstruction. Posterolateral corner reconstruction differs from ACL reconstruction in two ways: (a) soft-tissue fixation into the femur requires two tails and (b) the line of force is different. Our purpose was to determine the optimal femoral fixation of soft-tissue grafts during posterolateral corner reconstructions. We hypothesized that interference screw fixation is the strongest technique in normal-density lateral femoral condyle, whereas, cortically-based fixation techniques are stronger methods in low-density lateral femoral condyle.

METHODS

We evaluated elongation during cyclic loading, yield load, peak load-to-failure, and stiffness of four soft-tissue graft femoral fixation methods during posterolateral corner reconstruction. Our model included bovine flexor tendons and contoured synthetic bones. Grafts were secured to the lateral epicondyle in normal- or low-density bone models using spiked washer, button, interference screw, or button and interference screw. Five specimens for each were tested in each bone density. Analysis of variance using Tukey-Kramer adjustment for multiple hypothesis testing was used. Six cadaver bones whose density was analyzed using computerized tomography scan quantitation were tested using interference screw fixation.

RESULTS

No method produced significantly stronger yield load or peak load-to-failure in normal-density bone. In low-density bone, cortically-based methods produced significantly higher yield load or peak load-to-failure. Yield load or peak load-to-failure was significantly higher in normal-density bone when using spiked washer or interference screw fixation.

CONCLUSION

No femoral fixation method tested produced superior yield load or peak load-to-failure. Spiked washer and interference screw fixation are inferior fixation methods in low-density bone.

CLINICAL RELEVANCE

For fibular-based posterolateral corner reconstructions, all fixation methods tested are acceptable in high-density bone, while cortical fixation methods should be considered in low-density bone.

Peri-tunnel bone loss: does it affect early tendon graft to bone tunnel healing after ACL reconstruction?

PURPOSE

The clinical relevance and mechanisms of local bone loss early post-anterior cruciate ligament (ACL) reconstruction remain unclear. The early spatial and temporal changes of peri-tunnel bone, its molecular mechanisms and its relationships with graft-bone tunnel healing were investigated in a 12-week-old rat model.

METHODS

At various times, the reconstructed ACL complex was harvested for vivaCT imaging, biomechanical test, histology and immunohistochemical staining of CD68+ cells (a monocyte-macrophage lineage marker), MMP1 and MMP13.

RESULTS

The peri-tunnel bone resorbed simultaneously with improvement of graft-bone tunnel healing. There were 30.1 ± 17.4, 46.8 ± 10.5 and 81.5 ± 12.3 % loss of peri-tunnel BMD as well as 43.2 ± 21.7, 78.7 ± 8.5 and 92.4 ± 17.7 % loss of peri-tunnel bone volume/total volume (BV/TV) at week 6 at the distal femur, epiphysis and metaphysis of tibia, respectively. MMP1, MMP13 and CD68+ cells were expressed at the graft-bone tunnel interface and peri-tunnel bone and increased with time post-reconstruction at the tibia. The ultimate load and stiffness of the healing complex positively correlated with tibial tunnel bone formation and negatively correlated with tibial peri-tunnel bone. Tunnel BV/TV at the tibial metaphysis and epiphysis showed the highest correlation with ultimate load (ρ = 0.591; p = 0.001) and stiffness (ρ = 0.427; p = 0.026) of the complex, respectively.

CONCLUSION

There was time-dependent loss of peri-tunnel bone early post-reconstruction, with the greatest loss occurring at the tibial metaphysis. This was consistent with high expression of MMP1, MMP13 and CD68+ cells at the graft-bone tunnel interface and the peri-tunnel region. The significant loss of peri-tunnel bone, though not critically affecting early tunnel healing, suggested the need to protect the knee joint early post-reconstruction.

Effects of glucosamine and risedronate alone or in combination in an experimental rabbit model of osteoarthritis

Background

The osteoarthritis (OA) treatment in humans and in animals is a major orthopaedic challenge because there is not an ideal drug for preserving the joint structure and function. The aim of this study was to assess the effects of the treatment with oral glucosamine and risedronate alone or in combination on articular cartilage, synovial membrane and subchondral bone in an experimental rabbit model of OA. Osteoarthritis was surgically induced on one knee of 32 New Zealand White rabbits using the contralateral as healthy controls. Three weeks later treatments were started and lasted 8 weeks. Animal were divided in four groups of oral treatment: the first group received only saline, the second 21.5 mg/kg/day of glucosamine sulfate, the third 0.07 mg/kg/day of risedronate; and the fourth group both drugs simultaneously at the same dosages. Following sacrifice femurs were removed and osteochondral cylinders and synovial membrane were obtained for its histological and micro-CT evaluation.

Results

Sample analysis revealed that the model induced osteoarthritic changes in operated knees. OA placebo group showed a significant increase in cartilage thickness respect to the control and inflammatory changes in synovial membrane; whereas subchondral bone structure and volumetric bone mineral density remained unchanged. All the treated animals showed an improvement of the cartilage swelling independent of the drug used. Treatment with glucosamine alone seemed to have no effect in the progression of cartilage pathology while risedronate treatment had better results in superficial fibrillation and in resolving the inflammatory changes of the tissues, as well as modifying the orientation of trabecular lattice. The combination of both compounds seemed to have additive effects showing better results than those treated with only one drug.

Conclusions

The results of this animal study suggested that glucosamine sulfate and risedronate treatment alone or in combination may be able to stop cartilage swelling. The risedronate treatment could partially stop the fibrillation and the inflammation of synovial membrane as well as modify the orientation of trabeculae in healthy and in osteoarthritic knees.

Bone mineral density changes in the knee following anterior cruciate ligament rupture

OBJECTIVE

The pathophysiology of anterior cruciate ligament (ACL) rupture leading to knee osteoarthritis (OA) remains largely unknown. It seems that bone loss occurs after ACL rupture. The purpose of our study was to determine bone mineral density (BMD) changes in the knee after ACL rupture during 2-year follow-up period and to compare BMD changes between the injured and healthy contralateral knee.

DESIGN

Patients were included in an observational prospective follow-up study within 6 months after ACL trauma and evaluated for 2 years. Patients were treated operatively or non-operatively. At baseline and at the one- and 2-year follow-ups, BMD was measured in six regions of the tibia and femur for both knees (medial, central, lateral) using a Dual-energy X-ray Absorptiometry (DXA) scanner.

RESULTS

One hundred forty-one patients were included, with the following characteristics: 66% were male, median age at baseline was 25.3 (inter-quartile range 11.3) years, and 63% were treated operatively. After 1 year, BMD was significantly lower in all regions of the injured knee of the operatively treated patients compared to baseline. After 2 years, BMD was significantly increased, but remained lower than the baseline levels. In all regions for all measurements, the mean BMD was significantly lower in the injured knee than in the healthy contralateral knee.

CONCLUSIONS

During a 2-year follow-up period after ACL rupture, the BMD level in the injured knee was found to be lower than in the healthy contralateral knee. In operatively treated patients, the BMD decreased in the first year and increased in the second follow-up year.

Anterior cruciate ligament reconstruction reduces bone mineral areal mass

PURPOSE

The aim of this study was to prospectively follow bone mineral areal mass (BMA) changes in the calcaneii, hips, and lumbar spine after anterior cruciate ligament (ACL) reconstruction using hamstring tendon autografts.

METHODS

Patients with a unilateral ACL injury scheduled for reconstruction were included in the study. The BMA mass was measured in both calcaneii, the hips, and the lumbar spine using the dual-energy x-ray absorptiometry (DEXA) technique. Quality of life was estimated using the EQ-5D questionnaire, and activity was measured using the Tegner activity score. The patients were assessed before surgery and after 6, 18, 36, and 60 months.

RESULTS

Forty-eight patients (21 female and 27 male patients), median age 31 years (17 to 64 years), participated in the study for 5 years. After 5 years, the female patients had lost 9.5% (P < .001) and 10.1% (P < .001) of their BMA in the calcaneus on the operated and nonoperated sides, respectively. Correspondingly, the male patients had lost 6.5% (P = .004) and 8.5% (P < .001) on the operated and nonoperated sides, respectively. In the hips, the female patients had lost 4.0% (P < .001) and 2.7% (P < .001) on the operated and the nonoperated sides, respectively. Among the male patients, the BMA loss was 3.4% (P = .002) and 4.8% (P < .001) in the hips on the operated and the nonoperated sides, respectively. The EQ-5D index was a mean (standard deviation [SD]) of 0.72 (0.23) before surgery and 0.86 (0.17) (P < .001) after 5 years. The preinjury Tegner activity level was a median (range) 7.5 (1 to 10). The preoperative Tegner activity level was 2.5 (0 to 9) and increased to 4 (1 to 9) (P = .002) after 5 years.

CONCLUSIONS

Both female and male patients had a significant decrease in BMA in both calcaneii and both hips during the 5-year study period compared with a reference population of Swedish healthy women and men. The patients increased their Tegner activity level and improved their EQ-5D index during the 5-year follow-up period.

LEVEL OF EVIDENCE

Level II, prognostic prospective study.

Effectiveness of low-profile supplemental fixation in anterior cruciate ligament reconstructions with decreased bone mineral density

PURPOSE

The purpose of this study was to compare anterior cruciate ligament (ACL) fixation using a bioabsorbable interference screw (BIS) and a supplemental low-profile suture anchor (PushLock 4.5-mm polyetheretherketone anchor; Arthrex, Naples, FL) with a standard BIS fixation to determine if fixation methods were dependent on tibial bone mineral density (BMD).

METHODS

Ten matched pairs of fresh-frozen human female knee specimens (20 total) were harvested with specimen ages ranging from 40 to 65 years. The BMD for each specimen was determined with a dual-energy x-ray absorptiometry scanner. The specimens were divided into 2 groups, 1 with a BIS and the other with a BIS plus a PushLock. Tibial-sided ACL fixation with hamstring tendon grafts was performed on all the specimens. Then, load to failure and stiffness were biomechanically tested.

RESULTS

The BIS-plus-PushLock specimens had a significantly higher mean yield load compared with specimens with the BIS alone (702 N v 517 N, P = .047). However, in samples with lower bone density, there was no statistically significant difference in failure loads between fixation techniques (P = .8566 at BMD of 0.5 g/cm(2)). As the bone density of the samples increased, the failure loads increased for both techniques (P < .0001 for PushLock and P = .0057 for BIS). This BMD-associated increase was greater for the PushLock (P = .0148), resulting in a statistically significant difference in failure load at the upper range tested (P = .0293 at BMD of 0.9 g/cm(2)).

CONCLUSIONS

Supplemental fixation of ACL reconstructions with a PushLock is beneficial in persons with a normal BMD of the proximal tibia, but at a lower BMD, there was no difference in our study.

CLINICAL RELEVANCE

Individuals with normal BMDs may benefit from this supplemental fixation. However, caution should be used in postmenopausal women or individuals with chronic ACL injuries when using this fixation strategy.

Consideration of growth factors and bio-scaffolds for treatment of combined grade II MCL and ACL injury

The literature suggests that a Grade II medial collateral ligament (MCL) injury in combination with anterior cruciate ligament (ACL) injury will heal naturally and not compromise patient outcome following ACL reconstruction. Evidence based on bone-patella tendon-bone autograft use is stronger than evidence supporting anatomically placed soft tissue graft use. Current ACL reconstruction practices make greater use of soft tissue grafts, differing fixation methods, and anatomically lower placement on the inner wall of the lateral femoral condyle. Anatomical graft placement aligns the femoral bone tunnel more directly with valgus knee loading forces. Differences in the soft tissue graft-bone tunnel integration and ligamentization timetable following ACL reconstruction also increase concerns regarding residual Grade II MCL laxity and functional deficiency during accelerated functional rehabilitation. MCL dysfunction may increase susceptibility to early ACL graft slippage, elongation, outright failure, and medial femoral condyle lift-off with valgus knee loading. This concept paper discusses the potential role of growth factors and bio-scaffolds for improving Grade II MCL injury healing and mechanical integrity when the injury occurs in combination with an ACL injury that is reconstructed with a soft tissue graft and an anatomical surgical approach.

Supplemental bio-tenodesis improves tibialis anterior allograft yield load in extremely low density tibiae

INTRODUCTION

Improved soft tissue tendon graft mechanical properties have led to their increased use for anterior cruciate ligament (ACL) reconstruction. Because they do not have an osseous component; however, there are greater concerns regarding tibial graft slippage during early postoperative rehabilitation and activities of daily living, particularly in patients with poor bone mineral density (BMD), such as older patients, women, smokers, and patients undergoing revision ACL reconstruction surgery.

METHODS

This in vitro biomechanical study attempted to determine the effectiveness of supplemental ACL graft fixation in low BMD tibiae. Eight paired knees (16 specimens) were harvested from female cadavers (mean age = 76, range = 60-88 years). Tibiae were assigned to either a combination bioabsorbable interference screw, bio-tenodesis screw group (Group 1, n = 8, apparent BMD = 0.44 ± 0.13 g/cm(2)) or a bioabsorbable interference screw group (Group 2, n = 8, apparent BMD = 0.44 ± 0.14 g/cm(2)). Double-strand (single loop) tibialis anterior tendon allografts were fixed in matched diameter tibial tunnels. Using a custom 6° of freedom jig, potted constructs were mounted on to a servo hydraulic device with the axial loading force aligned directly with the tibial tunnel. Constructs underwent progressive cyclic tensile loading from 10 to 150 N with a 25 N load increase every 20 cycles. This was followed by yield load to failure testing (20 mm/min).

RESULTS

Groups did not display displacement differences during progressive cyclic loading. Group 1 (312.7 ± 67.5 N) displayed 25% greater yield load at failure than Group 2 (235.0 ± 47.6 N), P = 0.045. Both groups displayed fixation levels well below the previously reported minimal safe threshold estimate for early unrestricted weight bearing, accelerated rehabilitation and activities of daily living.

CONCLUSION

Supplemental bio-tenodesis fixation may improve early tibial-soft tissue tendon graft fixation in patients that have poor tibial BMD, but study results suggest that both methods may require weightbearing, rehabilitation, and activity of daily living restrictions during the early postoperative period to prevent graft slippage.

Delta screw versus RetroScrew tibial fixation for ACL reconstruction

PURPOSE

The purpose of this study is to determine whether the RetroScrew tibial fixation system offers a biomechanical advantage over the Delta screw for anterior cruciate ligament (ACL) reconstruction in cadaveric tibias with low bone mineral density (BMD).

METHODS

Ten matched pairs of osteoporotic cadaveric tibiae underwent simulated ACL reconstruction using quadrupled hamstring grafts with one of the two tibial fixation constructs. Group 1 was fixed with the Delta screw (DS; 35-mm antegrade biointerference screw), and group 2 was fixed with the RetroScrew system (RSS; 20-mm retrograde and 17-mm antegrade biointerference screws). Each construct was cyclically loaded (50-200 N, 1 Hz, 500 cycles) and subsequently loaded to failure (20 mm/s).

RESULTS

All specimens were osteoporotic without significant segmental (proximal, middle, and distal) BMD differences between groups by quantitative computed tomography (P = n.s.). A trend was noted for more construct failures due to graft slippage in the DS group (n = 3) over the RSS group (n = 1). There were no significant differences in cyclic displacement (P = n.s.), maximum cyclic stiffness (P = n.s.), maximum load at failure (P = n.s.), or pullout stiffness (P = n.s.) between groups.

CONCLUSIONS

In an osteoporotic cadaveric model, there was no significant biomechanical advantage of the RetroScrew system versus the Delta screw for tibial fixation in soft tissue graft ACL reconstruction. However, a trend toward lower graft fixation failure to cyclic loading was noted with the RetroScrew system.

Osseous deficits after anterior cruciate ligament injury and reconstruction: a systematic literature review with suggestions to improve osseous homeostasis

PURPOSE

This systematic review was performed to improve our understanding of the current evidence regarding the influence of anterior cruciate ligament (ACL) injury and reconstruction on involved lower extremity apparent bone mineral density, bone content, or bone area mass (bone integrity).

METHODS

Two independent reviewers performed a Medline search from 1966 to January 2010 using the terms "anterior cruciate ligament" or "ACL" combined with "wound" or "injury" and "bone density" or "osteoporosis." Study inclusion criteria were English-language human studies. Reference sections of selected studies were also reviewed.

RESULTS

Ten studies were identified that met our inclusion criteria. Eight studies performed ACL reconstruction with bone-patellar tendon-bone autografts and interference screw fixation. One study performed ACL reconstruction by use of Achilles tendon allografts with interference screw and staple fixation. Two ACL injury studies either did not involve ACL reconstruction or attempted primary repair with sutures. All studies reported varying levels of decreased bone mineral density, bone content, or bone area mass (bone integrity) at the involved lower extremity after ACL injury that did not return to premorbid levels even with ACL reconstruction and rehabilitation. Sites of reduced bone integrity included the proximal and distal femur, proximal tibia, patella, and calcaneus. Bone loss was increased with limited weight bearing and prolonged disuse or immobilization; however, significant improvements were not observed with accelerated rehabilitation. Some studies reported relations between Lysholm, Tegner, International Knee Documentation Committee survey, or function scores and bone integrity, whereas others reported no or poor relations.

CONCLUSIONS

Involved lower extremity bone integrity is decreased after ACL injury. Current evidence suggests that premorbid bone integrity is not re-established after ACL reconstruction even when accelerated rehabilitation is performed. Recommendations to improve osseous homeostasis and bone health after ACL injury and reconstruction are provided.

Biology and augmentation of tendon-bone insertion repair

Surgical reattachment of tendon and bone such as in rotator cuff repair, patellar-patella tendon repair and anterior cruciate ligament (ACL) reconstruction often fails due to the failure of regeneration of the specialized tissue ("enthesis") which connects tendon to bone. Tendon-to-bone healing taking place between inhomogenous tissues is a slow process compared to healing within homogenous tissue, such as tendon to tendon or bone to bone healing. Therefore special attention must be paid to augment tendon to bone insertion (TBI) healing. Apart from surgical fixation, biological and biophysical interventions have been studied aiming at regeneration of TBI healing complex, especially the regeneration of interpositioned fibrocartilage and new bone at the healing junction. This paper described the biology and the factors influencing TBI healing using patella-patellar tendon (PPT) healing and tendon graft to bone tunnel healing in ACL reconstruction as examples. Recent development in the improvement of TBI healing and directions for future studies were also reviewed and discussed.

Inferior tendon graft to bone tunnel healing at the tibia compared to that at the femur after anterior cruciate ligament reconstruction

BACKGROUND

Tunnel widening after anterior cruciate ligament (ACL) reconstruction (ACLR) is commonly reported without a clear understanding of the mechanism. This study aimed to quantify the spatiotemporal change of the newly formed bone mass, bone tunnel diameter, and area along both bone tunnels using micro-computed tomography (microCT) and correlated the result with histology.

METHODS

ACLR was performed in 24 rabbits. At baseline and weeks 2, 6, and 12, the juxta-articular, middle, and exit segments of both tunnels were harvested for microCT and histological evaluation.

RESULTS

microCT and histology revealed significant bone tunnel and graft-bone tunnel healing, respectively, only at week 6 after reconstruction. Despite this, the mean tunnel diameter and area remained relatively unchanged with time. The newly formed bone mass [new bone volume/total bone volume (BV/TV) ratio] and its bone mineral density (BMD) were both higher, whereas the mean tunnel diameter and area were significantly smaller at the femoral tunnel compared to those at the tibial tunnel at weeks 6 and 12 and at week 12, respectively. These were consistent with histological findings, which showed inferior graft remodeling and integration at the tibial tunnel at weeks 6 and 12. The BV/TV increased, whereas the mean tunnel diameter and area decreased toward the exit segment of both tunnels. However, whereas better histological healing occurred at the femoral exit segment, poorer graft remodeling and Sharpey's fiber formation occurred at the tibial exit segment.

CONCLUSIONS

Poor healing was observed during the initial 6 weeks, particularly that of the tibia, after ACLR. Bone resorption was rapid during healing, resulting in unchanged tunnel diameter and area with time.

The relation between tunnel widening and bone mineral density after anterior cruciate ligament reconstruction: an experimental study in sheep

PURPOSE

The aim of this study was to analyze the relation between bone mineral density (BMD) and femoral tunnel enlargement (TE) in a previously validated sheep model of soft-tissue anterior cruciate ligament (ACL) reconstruction.

METHODS

Thirty sheep underwent ACL reconstruction by use of a soft-tissue graft at the age of 4 months. Graft fixation was achieved with the EndoButton (Smith & Nephew Endoscopy, Andover, MA) and Suture Washer (Smith & Nephew Endoscopy). Six animals were killed at 0, 3, 6, 12, and 24 weeks postoperatively. Each ACL-reconstructed knee was examined both by computed tomography to analyze the bone tunnel cross-sectional area and by dual-energy x-ray absorptiometry to analyze BMD.

RESULTS

There was a significant increase in tunnel cross-sectional area. BMD decreased significantly within the first 3 weeks after surgery and increased thereafter. A positive correlation between TE and BMD was found. However, a subgroup analysis showed that there is no influence of BMD on the development of a tunnel widening.

CONCLUSIONS

The hypothesis that a TE would be associated with a loss in BMD was not confirmed. Tunnel widening during the first 6 months after ACL reconstruction is not affected by the transient changes in BMD.

CLINICAL RELEVANCE

There is no correlation between TE and BMD in an experimental sheep model of ACL reconstruction. Translational investigations will determine whether this is also true in humans.

Cancellous bone properties and matrix content of TGF-beta2 and IGF-I in human tibia: a pilot study

Transforming and insulin-like growth factors are important in regulating bone mass. Thus, one would anticipate correlations between matrix concentrations of growth factors and functional properties of bone. We therefore investigated the relationships of (1) TGF-beta2 and (2) IGF-I matrix concentrations with the trabecular microstructure, stress distribution, and mechanical properties of tibial cancellous bone from six male human cadavers. Trabecular stress amplification (VMExp/sigma(app)) and variability (VMCOV) were calculated using microcomputed tomography (muCT)-based finite element simulations. Bone volume fraction (BV/TV), surface/volume ratio (BS/BV), trabecular thickness (Tb.Th), number (Tb.N) and separation (Tb.Sp), connectivity (Eu.N), and anisotropy (DA) were measured using 3-D morphometry. Bone stiffness and strength were measured by mechanical testing. Matrix concentrations of TGF-beta2 and IGF-I were measured by ELISA. We found higher matrix concentrations of TGF-beta2 were associated with higher Tb.Sp and VMExp/sigma(app) for pooled data and within subjects. Similarly, a higher matrix concentration of IGF-I was associated with lower stiffness, strength, BV/TV and Tb.Th and with higher BS/BV, Tb.Sp, VMExp/sigma(app) and VMCOV for pooled data and within subjects. IGF-I and Tb.N were negatively associated within subjects. It appears variations of the stress distribution in cancellous bone correlate with the variation of the concentrations of TGF-beta2 and IGF-I in bone matrix: increased local matrix concentrations of growth factors are associated with poor biomechanical and architectural properties of tibial cancellous bone.

Influence of bone adaptation on tendon-to-bone healing in bone tunnel after anterior cruciate ligament reconstruction in a rabbit model

Anterior cruciate ligament (ACL) reconstruction with placement of grafted tendon in bone tunnel is a common surgical procedure. Bone tunnel creation may result in stress shielding of postero-lateral regions of tibial tunnel. The present study was designed to characterize the changes of peri-graft bone and compare with tendon-to-bone (T-B) healing in spatial and temporal manners after ACL reconstruction in rabbit. Surgical reconstruction using digital extensor tendon in bone tunnel was performed on 48 rabbits. Twelve rabbits were sacrificed at 0, 2, 6, and 12 weeks postoperatively for radiological and histological examinations. Bone mass and microarchitecture at the anterior, posterior, medial, and lateral regions of tunnel wall at distal femur and proximal tibia were evaluated. Using peripheral quantitative computed tomography, a 26, 22, and 42% decrease in bone mineral density (BMD) relative to baseline was present in the medial region of the femoral tunnel and the posterior and lateral regions of the tibial tunnel, respectively, at week 12 postoperatively (p < 0.05). It was accompanied by a decrease in trabecular number and increase in trabecular spacing, the shift of platelike to rodlike trabeculae, and loss of anisotropy under micro-computed tomography evaluation. This finding was echoed by histology showing increased osteoclastic activities and poor T-B healing in these regions. In conclusion, the postoperative bone loss and associated poor T-B healing was region-dependent, which may result from adaptive changes after tunnel creation.

Meniscectomy leads to an early increase in subchondral bone plate thickness in the rabbit knee

We evaluated morphological changes in the tibial bone after meniscectomy in a rabbit model. 15 rabbits subjected to a medial meniscectomy in the right knee and a sham-operation in the left. Histomorphometric parameters were evaluated in the subchondral bone plate and the underlying trabecular bone, 13, 25 and 40 weeks after surgery. 5 rabbits were used as unoperated controls. Meniscectomized knees had a thicker subchondral bone plate than sham-operated contralateral ones in 13 of the 15 rabbits (p = 0.01), but the trabecular bone showed no morphological differences. The meniscectomized knees of these rabbits developed mild osteoarthrosis, described elsewhere, which may have been partly due to a change in the mechanical properties of the thickened subchondral bone plate. Our findings suggest that the first bony response after meniscectomy occurs in the subchondral bone plate rather than in the trabecular bone.

Bone loss in the lower leg during 35 days of bed rest is predominantly from the cortical compartment

Immobilization-induced bone loss is usually greater in the epiphyses than in the diaphyses. The larger fraction of trabecular bone in the epiphyses than in the diaphyses offers an intuitive explanation to account for this phenomenon. However, recent evidence contradicts this notion and suggests that immobilization-induced bone loss from the distal tibia epiphysis is mainly from the cortical compartment. The aim of this study was to establish whether this pattern of bone loss was a general rule during immobilization. We monitored various skeletal sites with different tissue composition during 5 weeks of immobilization. Ten healthy male volunteers with mean age of 24.3 years (SD 2.6 years) underwent strict horizontal bed rest. Bone scans were obtained during baseline data collection, at the end of bed rest and after 14 days of recovery by peripheral Quantitative Computed Tomography (pQCT). Sectional images were obtained from the distal tibia epiphysis (at 4% of the tibia's length), from the diaphysis (at 38%), from the proximal metaphysis (at 93%) and from the proximal epiphysis (at 98%), as well as from the distal femur epiphysis (at 4% of the femur's length) and from the patella. Relative bone losses were largest at the patella, where they amounted to -3.2% (SD 1.8%, p<0.001) of the baseline values, and smallest at the tibia diaphysis, where they amounted to -0.7% (SD 1.0%, p=0.019). The relative losses were generally larger from cortical than from trabecular compartments (p=0.004), and whilst all skeletal sites depicted such cortical losses, substantial trabecular losses were found only from the proximal tibia epiphysis. Results confirm that the differential losses from the various skeletal sites cannot be explained on the basis of trabecular vs. cortical tissue composition differences, but that endocortical circumference can account for the different amounts of bone loss in the tibia. The present study therefore supports the suggestion of the subendocortical layer as a transitional zone, which can readily be transformed into trabecular bone in response to immobilization. The latter will lead to cortical thinning, a factor that has been associated with the risk of fracture and with osteoarthritis.

Recovery of muscle atrophy and bone loss from 90 days bed rest: results from a one-year follow-up

Earlier studies found the recovery of bone loss after clinical immobilization to be incomplete. It has been argued that this is due to the human skeleton's inability to accrue bone mass once peak bone mass has been attained. However, recent studies suggest that bone losses can fully recover when complete functional rehabilitation is achieved. Accordingly, we hypothesized that bone losses by experimental bed rest would recover within one-year of follow-up. Twenty-five men (mean age 32 years, SD 4.2) were randomly assigned to either bed rest only (Ctrl), resistive flywheel exercise (FW), or to a group receiving 60 mg. i.v pamidronate prior to bed rest (Pam). Calf muscle cross sectional area and bone mineral content of the tibia was measured by peripheral quantitative computed tomography. Calcium, PTH and alkaline phosphatase blood levels were assessed along with urinary desoxypyridinoline excretion. Physical activity was assessed by the Freiburg questionnaire. In Pam and FW, diaphyseal bone losses were completely recovered at a 180-day follow-up, and there was even a small surplus after 1 year (p=0.016). Epiphyseal bone losses were largely, although not completely recovered after 1 year, when they still amounted to -0.6% (SD 1.3%, p=0.034, averaged over all groups). Bone formation and resorption markers had returned to baseline values at this time. However, epiphyseal recovery may still have been on-going, and fitting an exponential model yielded full recovery of the epiphysis within 2 years. Importantly, recovery of calf muscle cross-section and resumption of impact sport activities seemed to precede bone recovery, and bone accrual was closely matching the prior losses on an individual basis. No relationship was found between the epiphyseal BMC deficit at one-year follow-up and the participants' age. Results demonstrate recovery of bed rest induced bone losses in healthy adults. The initial re-accrual rate was remarkably high and is comparable to the accrual of bone mass during the pubertal growth spurt. This and the fact that the recovery of bone appeared to be tightly regulated, and generally followed neuromuscular recovery underline the adult skeleton's capability to adapt to mechanical stimuli.

Regional bone density changes in anterior cruciate ligament deficient knees: a DEXA study

Bone mineral density (BMD) loss is one of the secondary problems occurring in knee joint after injury of anterior cruciate ligament (ACL). The effect of this injury on BMDs of specific regions is not clear. The aim of this study was to investigate BMD changes in unreconstructed ACL-deficient knees with subregion analysis of dual energy X-ray absorptiometry (DEXA). Precision and reliability studies of DEXA revealed that two region of interests (ROI) in medial condyle, two ROIs in lateral femoral condyle (LFC) and one ROI in medial tibial plateau (MTP) in anteroposterior (AP) DXA view and one ROI for each of distal femur, proximal tibia and patella in lateral view had high reproducibility and reliability. Thirty-two patients with complete ACL ruptures were collected for the study and uninjured sides served as the control. All the patients were male with a mean age of 30 years. Mean duration of ACL rupture was 24 months. There were significant BMD losses in both ROIs of LFC and ROI of MTP in AP view and all three ROIs of lateral view. Greatest BMD losses in AP and lateral views were at MTP and patella respectively. There was a significant association between patellar BMD loss and duration after trauma. Bone bruises in lateral condyle might be the cause of selective involvement of LFC. Periarticular bone mineral loss in ACL-deficient knees has a predilection for the specified region of interest rather than uniform periarticular loss. This may be important for graft fixation or a factor in tunnel enlargement.

Biomechanical comparison between CentraLoc and Intrafix fixation of quadrupled semitendinosus-gracilis allografts in cadaveric tibiae with low bone mineral density

Supplementary or back-up tibial tunnel fixation of a quadruple semitendinosus-gracilis (STG) graft is often performed when the knee surgeon questions the integrity of intra-tunnel fixation. Back-up fixation devices such as staples however may contribute to increased knee pain and dysfunction. Both primary extra-tunnel and intra-tunnel fixation devices may provide sufficient quadruple STG graft fixation in a tibial tunnel to preclude the need for back-up fixation. This biomechanical study compared the fixation of quadruple STG allografts in standard drilled tunnels prepared in low apparent bone mineral density (BMD) cadaveric tibiae using either an Intrafix device with primary intra-tunnel fixation in a region of predominantly cancellous trabecular bone, or a CentraLoc device with primary extra-tunnel fixation in a region of predominantly cortical bone. The study hypothesis was that the CentraLoc device would display superior fixation in these low apparent BMD cadaveric tibiae. Matched pair tibiae and quadruple STG allografts were divided into two groups of seven specimens each. Extraction drilled tunnels matched allograft diameter. Constructs were pretensioned on a servo hydraulic device between 10 and 50 N for 10 cycles and isometric pretensioned at 50 N for 1 min prior to undergoing 500 loading cycles (50-250 N) and load to failure testing (20 mm/min). The CentraLoc group displayed superior load at failure (448.4+/-171 N vs. 338.4+/-119 N, P=0.04) and survived more loading cycles (410+/-154 cycles vs. 196+/-230 cycles, P=0.04) than the Intrafix group. Most CentraLoc group specimens (6/7, 85.7%) failed by device pullout with intact quadruple STG allograft strands while all Intrafix group specimens (7/7, 100%) failed by slippage of one or more strands (P=0.005).

Unilateral chronic insufficiency of anterior cruciate ligament decreases bone mineral content and lean mass of the injured lower extremity

We studied the effects of unilateral chronic anterior cruciate ligament (ACL) injury on bone size, bone mineral content (BMC), bone mineral density (BMD), soft tissue composition and muscle strength of the injured lower extremity in Japanese 21 men and 12 women aged 15 to 39 years. Bone area, BMD, BMC, lean mass and fat mass of lower extremity were measured using dual energy X-ray absorptiometry. The isometric and isokinetic muscle strength was assessed by an isokinetic machine.BMC, lean mass, circumference of the thigh and circumference of the lower leg of the injured lower extremity were significantly smaller than those of the intact lower extremity (p=0.0002, p<0.0001, p<0.0001, p=0.0131). In contrast, fat mass and %Fat of the injured lower extremity was significantly greater than that of the intact lower extremity (p=0.0301, p<0.0001). Bone area and BMD did not produce significant difference. These findings suggest that chronic insufficiency of ACL decreases BMC and lean mass of the injured lower extremity.

Interlimb differences in lower extremity bone mineral density following anterior cruciate ligament reconstruction

STUDY DESIGN

Prospective descriptive study.

OBJECTIVE

To determine the extent of bone mineral density (BMD) interlimb differences at several hip locations in the involved versus noninvolved lower extremity following anterior cruciate ligament (ACL) surgery.

BACKGROUND

Disuse following ACL reconstruction can be extensive. This disuse not only affects the soft tissue, but may also affect the skeletal structure. The extent of this disuse specific to the proximal femur has not been previously determined.

METHODS AND MEASURES

BMD was assessed in 15 subjects, 17 to 51 years old, who were between 6 and 32 months post-ACL reconstruction surgery. Bone mineral content (BMC) and BMD of the femoral neck, trochanteric region, intertrochanteric region, and entire hip were measured as a primary emphasis of this study. BMD and BMC of the entire lower extremities were also measured bilaterally.

RESULTS

BMD was significantly less in the involved lower extremity compared to noninvolved lower extremity at several hip sites: 6.6% less (P<.001) for the trochanteric region, 4.0% less (P<.001) for the entire hip, and 3.4% less (P = .004) for the intertrochanteric region. No significant differences were noted comparing the entire lower extremities for either BMD (0.9%, P = .48) or BMC (3.7%, P= .09).

CONCLUSION

BMD differences at the hip are significant in patient's postoperative ACL reconstruction, especially in the trochanteric region.

Bone mineral density in the proximal tibia and calcaneus before and after arthroscopic reconstruction of the anterior cruciate ligament

PURPOSE

To monitor changes in bone mineral density (BMD) of the proximal tibia and the calcaneus in patients with anterior cruciate ligament (ACL) rupture before and after arthroscopic reconstruction of the ligament, related to clinical data.

TYPE OF STUDY

A 2-year prospective cohort study with assessment of patient evaluation of knee performance, clinical scoring of surgical results, and measurement of BMD in the tibia and calcaneus.

METHODS

Eighteen patients with a unilateral ACL rupture underwent an autogenous bone-patellar tendon-bone graft ACL reconstruction. The patients were examined before surgery and after 4, 12, and 24 months. BMD was assessed bilaterally in the proximal tibia and calcaneus using dual-photon absorptiometry and converted to a Z-score by use of BMD values from a group of healthy controls. Clinical evaluation included determination of Lysholm score, quantitative Lachman test, pivot-shift test, and the patients' self-reported highest level of activity and knee performance in sports and daily activities.

RESULTS

There were significant declines in Z-score of the proximal tibia of the operated leg during the first year after surgery, whereas there was no change in the calcaneus and contralateral leg. In the lateral tibia, the Z-score was significantly lower at 24 months follow-up, compared with both controls and the noninjured side, whereas BMD of the medial tibia had returned to near normal levels. There were significant improvements in Lysholm score, highest level of activity, and knee performance in daily activities and sports. The patients' evaluation of improvement in knee performance in sports activities at 24 months follow-up was associated with an increase in Z-score of the injured leg.

CONCLUSIONS

We found a partially reversible decline in BMD of the proximal tibia after arthroscopic ACL reconstruction. Improvement in knee performance in sports activities was associated with an increase in BMD of the injured leg. BMD of the calcaneus remained unaffected in both legs.

LEVEL OF EVIDENCE

Level III, therapeutic case control study.

Reconstruction of the anterior cruciate ligament with a patella-tendon-bone graft may lead to a permanent loss of bone mineral content due to decreased patellar tendon stiffness

Immobilisation induces bone loss. Evidence from studies in animals and healthy humans that were immobilised for a limited time indicates that, in general, bone mass may be restored even in adults. Following conservative management of partial tears of the anterior cruciate ligament (ACL), bone loss is often negligible (2-3%). After surgical reconstruction, however, there is greater bone loss (15-20%), with little or no recovery. Bones adapt to the stresses they experience. Also, the largest forces in the musculoskeletal system arise from muscle pull. Tendons transmit these forces. Many surgical techniques for ACL reconstruction use autologous tendon grafts. We hypothesise that tissue harvesting causes weakening of the formerly intact tendon, which, in turn, leads to reduced muscle pull and subsequent bone loss in those parts of the bone that are loaded by the tendon. If our hypothesis holds true, it may change patients' and surgeons' choice of management. Clinical follow-up should assess the functional result with greater scrutiny, possibly including the assessment of bone mineral content. This may be particularly important since there is accumulating evidence that a decrease in bone mineral density (BMD) preceedes, and hence may be a cause of, osteoarthritis.

Ultrasonographic examination of the normal and injured posterior cruciate ligament

PURPOSE

The purpose of the study was to determine the echogenicity and thickness of both the normal and injured posterior cruciate ligament (PCL).

METHODS

Eight patients with anterior cruciate ligament injury received ultrasonographic evaluation during arthroscopic examination. With the aid of the comet-tail artifact produced by the metal hook during arthroscopic examination, the normal PCL was located on sonograms. Thereafter, 11 patients with PCL injury were examined. In all subjects, the PCL thickness was measured at 2.0 cm proximal from posterior end of the distal PCL inserting onto the tibia.

RESULTS

The normal PCL was located just posterior to the posterior tibial intercondylar area. It was hypo-echoic and was thickened proximally and tapered distally. The mean thickness of the injured PCL was 0.71 +/- 0.12 cm, which was significantly (p < 0.05) greater than that of the normal ligament (0.52 +/- 0.08 cm). Different appearances could be observed, including ligamental rupture and avulsion fracture of the tibial insertion of the PCL.

CONCLUSIONS

The normal PCL appears on longitudinal sonograms as a hypoechoic fan-shape structure. Sonographic examination can identify different types of PCL lesions.

Increased concentrations of neuro-excitatory amino acids in rat anterior cruciate ligament-transected knee joint dialysates: a microdialysis study

Changes in excitatory amino acid (EAA) levels were examined in the knee joint dialysates of rats with early osteoarthritis (OA). Early OA was induced by anterior cruciate ligament (ACL) transection in one knee and the contralateral knee was used as the sham-operated control, the side for ACL transection being assigned randomly. Twenty weeks after operation, knee joint dialysates were collected by microdialysis and assayed for EAAs by high performance liquid chromatography. The rats were then sacrificed for histopathological examination. Hematoxylin/eosin and Safranin-O staining showed cartilage fibrillation, clustering of chondrocytes, and a reduction in matrix proteoglycans at week 20 in the ACL-transected knee, but not in the sham-operated knee. Levels of glutamate and aspartate in dialysates from the ACL-transected knee were significantly increased by 92 +/- 20.3% or 57 +/- 17.5%, respectively, compared to those in the contralateral sham-operated knee. This increase may contribute to the pathogenesis of early OA.

Long-term periarticular bone adaptation in a feline knee injury model for post-traumatic experimental osteoarthritis

OBJECTIVES

This study investigates the long-term changes of the periarticular bone, including cancellous bone and the subchondral plate, in an anterior cruciate ligament (ACL)-transected cat for post-traumatic osteoarthritis (OA). These periarticular bone changes are related to the health of all knee tissues including articular cartilage degeneration and may be a key component of osteoarthritic development.

METHODS

Thirteen cats (mean mass 4.9+/-1.9 kg) were divided into three experimental groups: (1) normal controls, (2) 16 week, and (3) 5 year post unilateral ACL-transection (ACLT). Micro-computed tomography was used to scan the three-dimensional (3D) bone architecture of the proximal tibia, and analysis was performed on the subchondral plate and cancellous bone in the epiphyseal and metaphyseal regions of each bone.

RESULTS

A decrease in cancellous bone mass (BV/TV) and subchondral plate thickness (Ct.Th) was observed 16 week post-ACLT, and the trend was statistically significant for the long-term animals (>5 year post-ACLT: BV/TV decreased 16.8%, P<0.003; Ct.Th decreased 36.8%, P<0.03). A decrease in bone mass was also observed as a function of animal age by comparing the young and aged normal control animals, however ACLT intensified those changes, particularly Ct.Th (P<0.009) and anisotropy (P<0.045). It was speculated that decreased internal joint loading despite normal kinematics may play an important role in the long-term reduction of cancellous bone volume and subchondral plate thinning.

CONCLUSIONS

The periarticular bone changes measured in this study were concurrent with articular cartilage degeneration, and suggest that bone may be a contributing factor in the aetiology of post-traumatic OA development.

Antiresorptive therapy conserves some periarticular bone and ligament mechanical properties after anterior cruciate ligament disruption in the rabbit knee

The purpose of this study was to assess, in an osteoarthritic (OA) model, whether bisphosphonate (BP) antiresorptive therapy altered periarticular bone and bone-ligament biomechanics and OA progression. We surgically transected the anterior cruciate ligament (ACLX) in two groups of rabbits; the first group was dosed with BP (risedronate, 0.01 mg/kg s.c. daily for 6 wk), the second group remained untreated, and a third group of normal (unoperated) control rabbits was also evaluated. We measured distal femoral bone mineral density (BMD, Dual Energy X-ray Absorptiometry [DEXA]), medial collateral ligament (MCL) laxity, and bone mechanical function (bone cores mechanically tested in compression). These measures were related to cartilage/joint gross morphology, histology, and measures of vascular volume (gelatin-dye perfusion) for evidence of inflammatory angiogenesis and early OA. BMD by DEXA in 6 wk ACLX animals was 18% less than normal controls (p<0.05). In contrast, BP dosing conserved periarticular BMD; risedronate-treated rabbits had distal femoral BMD only 5% less and not significantly different than normal controls. When the same bone cores were compressed to failure, both ACLX and BP-dosed animals were significantly weaker than normal controls (p<0.05). However, the bone energy to failure and elastic modulus of BP-dosed animals was conserved and not significantly different from normal controls 6 wk after ACLX. Blocking bone resorption with BP also resulted in a significantly improved bone-ligament structural complex. MCL-complex laxity was significantly less in BP-dosed animals (1.2 times that of normal controls) compared to untreated ACLX animals (1.7 times that of normal controls; p<0.05). Blocking bone resorption with risedronate did not suppress osteophytosis and inflammatory angiogenesis, which were significantly increased in the periarticular bone of both untreated and BP treated ACLX animals. Thus, administering BP immediately after ACL loss conserved some periarticular bone and MCL-complex properties in an early OA model.

Mechanical properties of the scapholunate ligament correlate with bone mineral density measurements of the hand

The mechanical properties of the scapholunate ligament have been previously examined in small sample sizes, with ultimate load and occasionally stiffness reported. The present study examined 16 scapholunate ligaments in uniaxial extension at two rates and determined stiffness, ultimate load, and stress relaxation properties. Mean stiffness values of 66.4+/-28.6 N/mm at an elongation rate of 50 mm/min and 94.5+/-44.4 N/mm at an elongation rate of 100 mm/min were found. Relaxation behavior, determined by the percent load remaining after 100 s, was found to be 68.1+/-12%. Mean ligament ultimate loads were 357+/-110 N (n = 8). In eight specimens, failure occurred in bone. Positive correlations were observed between bone mineral density of the hand and ligament stiffness, ligament ultimate load, and bone ultimate load. No correlation was observed between bone mineral density and ligament load relaxation behavior. The results provide a comprehensive understanding of scapholunate ligament biomechanics and demonstrate a relationship between bone and ligament properties.

The effect of anterior cruciate ligament surgery on bone mineral in the calcaneus: a prospective study with a 2-year follow-up evaluation

PURPOSE

The goal of this study was to evaluate the effect of anterior cruciate ligament (ACL) reconstruction on the bone mineral area mass (BMA) in the calcaneus on the injured and noninjured sides.

TYPE OF STUDY

A prospective cohort study with sequential assessments of bone mineral in the calcaneus before and after ACL reconstruction.

METHODS

Thirty-four consecutive patients with a unilateral ACL rupture underwent arthroscopic reconstruction using patellar tendon autografts. The BMA was assessed bilaterally in the calcaneus using a gamma camera according to the dual-energy photon absorptiometry technique, before surgery and after 6 and 26 months.

RESULTS

Thirty-one of 34 patients (20 men and 11 women) underwent all BMA measurements. The median age at index surgery was 27 (16 to 50) years, and the reconstruction was performed 12 (2 to 192) months after the injury. The median preoperative Tegner activity level increased from 3 (2 to 8) to 7 (2 to 9) at 26 months (P <.0001). The BMA in the calcaneus on both the injured and noninjured side decreased by 16% and 17% respectively from the preoperative measurement to the 26-month control (P =.0014; P =.0006). On all occasions, the BMA was lower on the injured side than on the noninjured side (P =.012).

CONCLUSIONS

Patients with a unilateral ACL rupture had a lower BMA in the calcaneus on the injured side compared with the noninjured side. Although patients increased activity levels after reconstruction, the BMA in the calcaneus decreased on both the injured and the noninjured side up to 2 years after surgery.

LEVEL OF EVIDENCE

Level II-1, prospective cohort study.

Bone loss following tendon laceration, repair and passive mobilization

Little is known about the localized changes in bone mass that occur following tendon or ligament injury. Interruption of normal load transfer at the insertion site will presumably lead to a localized loss of bone, although few data exist to support this claim. To test this hypothesis, we transected the canine flexor digitorum profundus (FDP) tendon from its insertion, and either repaired it using a trans-osseous suture technique or left it unrepaired (laceration only). Post-operatively, forelimbs in the repair group were cast immobilized except for 10 min of daily passive mobilization rehabilitation, whereas in the laceration only group dogs were allowed full weight bearing. At 5-42 days post-injury, we assessed bone mineral density (BMD) using pQCT and osteoclast surface by histomorphometry. We measured significant bone loss in the distal phalanx after combined FDP tendon laceration, repair, and post-operative passive mobilization, with BMD decreases of 20%, 40%, and 41% at 10, 21, and 42 days (p<0.01). Moreover, we observed that passive mobilization and tendon laceration each contributed independently to the observed bone loss. At 42 days, BMD was reduced by 21% in bones that were not injured but were subjected to the post-operative passive mobilization protocol, while BMD was reduced by 28% in bones subjected to tendon laceration and full weight bearing (p<0.01). In both the passive mobilization and laceration specimens, we counted significantly increased osteoclasts after only 7-10 days, and these increases persisted through 42 days (p<0.05). We conclude that rapid and sustained bone resorption leads to significant bone loss in the 6-week period following flexor tendon injury and repair. This bone loss may impact healing by impeding the restoration of a strong tendon-bone interface.

Loss of bone mineral of the hip and proximal tibia following rupture of the Achilles tendon

In a prospective uncontrolled study 12 patients suffering from a rupture of the Achilles tendon treated operatively with surgical repair and post-operative immobilization in a short plaster cast for 6 weeks had bilateral measurements of bone mineral content (BMC) of the proximal tibia and bone mineral density (BMD) of the femoral neck and greater trochanter. The measurements were performed by dual energy X-ray absorptiometry (DEXA) and scans were performed post-operatively within 7 days after the operation and with follow up after 6 weeks, 3, 6, and 12 months. In the operated legs, BMC of the proximal tibia showed a progressive decrease reaching a total bone loss of 6.4% (95%-CL: -10.6%; -2.3%) 1 year after the injury. Bone mineral density at the hip of the operated legs also decreased significantly and 1 year after the injury BMD was 2.5% (95%-CL: -5.5%; 0.5%) and 6.8% (95%-CL: -9.8%; -3.7%) below the initial value in, respectively, the femoral neck and greater trochanter. Patients with a previous Achilles tendon rupture must be considered to be some years ahead in their natural osteoporotic process of the bones of the affected legs, and an increased risk of osteoporotic fractures must be considered not to be only theoretical.

Limited bone loss in the hip and heel after reamed intramedullary fixation and early weight-bearing of tibial fractures

OBJECTIVE

To determine changes in bone mineral density at the hip and calcaneus in the injured and uninjured sides after surgery for tibial fractures.

DESIGN

Prospective, longitudinal study.

SETTING

University hospital.

PATIENTS AND METHODS

Twenty-six patients with a tibial fracture were treated with a reamed and statically locked intramedullary nail with early weight-bearing. Dual-energy x-ray absorptiometry at the proximal femur and quantitative ultrasonography at the calcaneus were performed bilaterally after surgery and after three, six, and twelve months.

RESULTS

At three months, the bone mineral density in the trochanteric region in the injured limb had decreased almost 4 percent (p < 0.007), a reduction still present at twelve months, whereas in the femoral neck, the reduction was approximately 2.5 percent at twelve months (p < 0.03). The stiffness index and speed of sound at the calcaneus on the injured side decreased (p < 0.03 and p < 0.008, respectively) during the first three months, whereas at twelve months, there was no significant difference when compared with those measured directly after surgery. There were no significant changes at any time in the proximal femur or calcaneus of the uninjured limb.

CONCLUSION

Treatment with a reamed statically locked intramedullary nail and early weight-bearing resulted in limited bone loss in the proximal femur and calcaneus of the injured limb. After twelve months, the bone properties at the heel were restored, whereas there was still a small reduction at the hip. Compared with previous studies of patients with similar fractures treated with casts and restricted weight-bearing, the loss in bone mineral density was less and not as longstanding.

Early morphometric and anisotropic change in periarticular cancellous bone in a model of experimental knee osteoarthritis quantified using microcomputed tomography

OBJECTIVE

To quantify early stage microstructural changes of periarticular cancellous bone in a canine anterior cruciate ligament transection model for experimental osteoarthritis.

DESIGN

Unilateral transection of the anterior cruciate ligament was performed in 10 animals. Bone structure changes were quantified in five animals at 3-week post-transection and five animals at 12-week post-transection. An additional two non-operated animals were used as controls.

BACKGROUND

Changes in trabecular architecture of the periarticular cancellous bone in early stage post-traumatic osteoarthritis is not well understood. Previous studies have found alterations in bone mineral density in experimental osteoarthritis suggesting adaptation of the trabecular structure. Early change of the periarticular bone following a ligament injury may contribute to the long-term development of osteoarthritis.

METHODS

++. Bone cores from the medial condyles of the femoral and tibial pairs were scanned with a three-dimensional microtomographic system. Structural indices were quantified including bone volume ratio, bone surface ratio, trabecular thickness, trabecular separation, trabecular number, as well as structural anisotropy determined by the mean-intercept-length method.Results. Significant structural changes were observed at 3-week post-transection, and were more prominent at 12-week post-transection. These changes were accompanied by decreasing anisotropy.

CONCLUSIONS

Periarticular cancellous bone microstructure is significantly altered in experimental osteoarthritis. These changes occurred as early as 3-week post-transection, and were large at 12-week post-transection.

RELEVANCE

The pathogenesis of post-traumatic osteoarthritis is poorly understood, but it is clear that this disease involves the entire organ system of the joint, including the cartilages, synovium, ligaments, and bones. This study focuses on the changes that occur in the bones during the early stages following a joint injury, and contributes to a better overall understanding of the disease aetiology.